To better understand radiation-matter interaction at the surface, we perform grazing incidence x-ray diffraction (GIXRD) measurements of a deuterium-ion (D-ion) plasma-irradiated bulk zinc oxide (ZnO) single crystal. The D-ion-irradiated crystal exhibits the (100) reflection of hexagonal wurtzite ZnO similar to the non-irradiated sample but with an asymmetric and shifted peak, broader rocking curve, larger a-axis lattice constant, and positive Cauchy strain along the a-axis. These structural properties are attributed to the presence of a strained lattice on the irradiated surface of the bulk crystal. D-ion irradiation of the ZnO (100) surface leads to a lattice expansion along the crystals a-axis and in-plane compression along the c-axis. Our results show the specific effects of D-ion plasma irradiation on the ZnO crystal lattice along with the interaction of D-ions with the ZnO surface.. ...
In this study, x-ray diffraction measurements of liquid water are reported at pressures up to 360 MPa corresponding to a density of 0.0373 molecules per Å 3. The measurements were conducted at a spatial resolution corresponding to Q max = 16 Å -1. The method of data analysis and measurement in this study follows the earlier benchmark results reported for water under ambient conditions having a density of 0.0333 molecules per Å 3 and Q max = 20 Å -1 [J. Chem. Phys. 138, 074506 (2013)] and at 70°C having a density of 0.0327 molecules per Å 3 and Q max = 20 Å -1 [J. Chem. Phys. 141, 214507 (2014)]. The structure of water is very different at these three different T and P state points and thus they provide the basis for evaluating the fidelity of molecular simulation. Measurements show that at 360 MPa, the 4 waters residing in the region between 2.3 and 3 Å are nearly unchanged: the peak position, shape, and coordination number are nearly identical to their values under ambient conditions. ...
Changes in the molecular structure of striated muscle during contraction can be determined owing to corresponding changes in X-ray diffraction data. The work presented in this thesis analyses X-ray diffraction patterns obtained from frog sartorius muscles using Synchrotron Radiation at two distinctly different stages of the contractile cycle; rest and peak of isometric plateau.;Two-dimensional theoretical diffraction patterns were produced from a three-dimensional computer model of striated muscle and compared with experimental X-ray diffraction data. Modifications were made to both the thick and thin filaments situated within a hexagonal lattice, within the model, however the emphasis of the work was upon the protein myosin. In particular, the configuration, orientation and axial distribution of the myosin heads were analysed until the meridional intensity profile was comparable with experiment. Additionally, the dominant equatorial and row line reflections were modelled to fully define the ...
Using grazing incidence geometry and a thin layer cell, x-ray scattering has been used to study the structure of electrochemically deposited monolayers of lead on silver (111) and gold (111) electrodes in-situ. For the lead monolayer deposited on sliver, the lead was found to order in a hexagonoal closed packed (hcp) geometry with the lead lattice compresssed 1.2% relative to bulk lead. A rotational epitaxy angle of 4.4 deg was observed. From the width of the first order diffraction peak, the domain size of the lead was determined to be 300 A indicating that even when deposited from a solution, the lead forms a well ordered two-dimensional solid. On a gold (111) substrate, the lead monolayer was again found to order into a hcp layer, incommensurate with the gold. The lead was compressed 0.7% relative to bulk lead, with a domain size 200 A. Keywords: X-ray electrode; Lead(Metal); Gold electrode; Interface structure; Electrodeposition.*ELECTRODES
A century has passed since the first X-ray diffraction experiment (Friedrich et al. 1912). During this time, X-ray diffraction has become a commonly used technique for the identification and characterization of materials and the field has seen continuous development. Advances in the theory of diffraction, in the generation of X-rays, in techniques and data analysis tools changed the ways X-ray diffraction is performed, the quality of the data analysis, and expanded the range of samples and problems that can be addressed. X-ray diffraction was first applied exclusively to crystalline structures idealized as perfect, rigid, space and time averaged.... ...
Real-time synchrotron diffraction has been used to monitor the phase transformations of highly exothermic, fast self-propagating solid combustion reactions on a subsecond time scale down to 100 milliseconds and in some instances to 10 milliseconds. Three systems were investigated: Ti + C → TiC; Ti + C + xNi → TiC + Ni-Ti alloy; and Al + Ni → AlNi. In all three reactions, the first step was the melting of the metal reactants. Formation of TiC in the first two reactions was completed within 400 milliseconds of the melting of the Ti metal, indicating that the formation of TiC took place during the passage of the combustion wave front. In the Al + Ni reaction, however, passage of the wave front was followed by the appearance and disappearance of at least one intermediate in the afterburn region. The final AlNi was formed some 5 seconds later and exhibited a delayed appearance of the (210) reflection, which tends to support a phase transformation from a disordered AlNi phase at high temperature ...
TY - JOUR. T1 - Grazing incidence X-ray absorption characterization of amorphous Zn-Sn-O thin film. AU - Moffitt, S. L.. AU - Ma, Q.. AU - Buchholz, D. B.. AU - Chang, R. P.H.. AU - Bedzyk, M. J.. AU - Mason, T. O.. PY - 2016/1/1. Y1 - 2016/1/1. N2 - We report a surface structure study of an amorphous Zn-Sn-O (a-ZTO) transparent conducting film using the grazing incidence X-ray absorption spectroscopy technique. By setting the measuring angles far below the critical angle at which the total external reflection occurs, the details of the surface structure of a film or bulk can be successfully accessed. The results show that unlike in the film where Zn is severely under coordinated (N , 4), it is fully coordinated (N = 4) near the surface while the coordination number around Sn is slightly smaller near the surface than in the film. Despite a 30% Zn doping, the local structure in the film is rutile-like.. AB - We report a surface structure study of an amorphous Zn-Sn-O (a-ZTO) transparent ...
An X-ray diffraction method has been developed which was able to describe the diffusion zone produced by annealing nickel plated copper specimens at 750 degrees and 850 degrees. The experimental X-ray diffraction data were first corrected for instrumental broadening and then used to compute concentration-penetration curves across the diffusion zone. the experimental curves are in general agreement with a new mathematical analysis and also the diffusion coefficients reported in the literature ...
This thesis is composed of two parts. In part I the x-ray structural analyses of two sesquiterpenoids and two derivatives of 2-naphthol are reported, while in part II the results from molecular mechanics calculations are used to investigate the conformational processes occurring in a series of cyclo-octa-1,5-dienes and to interpret some of the stereochemical peculiarities of germacrane based sesquiterpenoids. The crystal structure analysis of the germacranolide, costunolide, was undertaken to determine its structure and stereochemistry. An incomplete structure was available at the commencement of this study, derived partially from x-ray diffraction measurements using Mo - Ka radiation and partially from synthetic and spectral observations. The diffraction data were recollected using Cu - Ka radiation in order to obtain more accurate measurements of the weaker reflexions. This technique was completely successful and allowed the structure and stereochemistry to be determined. Crystals of the ...
In the absorption edge region of metals the photoelectron is excited to the first unoccupied level above the Fermi level. Therefore its w:mean free path in a pure single crystal at zero temperature is as large as infinite, and it remains very large increasing the energy of the final state up to about 5 eV above the Fermi level. Beyond the role of the unoccupied density of states and matrix elements in single electron excitations, many-body effects appear as an "infrared singularity" at the absorption threshold in metals.. In the absorption edge region of insulators the photoelectron is excited to the first unoccupied level above the chemical potential but the unscreened core hole forms a localized bound state called core exciton.. ...
In this study, the course of myofibrillogenesis in Drosophila pupae was followed by means of conventional X-ray diffraction and end-on microdiffraction. Owing to the high transmission of X-ray beams, the diffraction technique is suitable for detecting overall regularity in molecular arrangement in bulk specimens such as the thoraces of insects. With the wavelength of the X-ray used here (0.1 nm), this technique will be applicable to larger insects, including honeybees and silkworm moths. In the conventional X-ray diffraction recordings, in which the beamsize is comparable to the size of a Drosophila thorax (approx. 1 mm), the extent of development of thoracic musculature can be diagnosed with a single shot of chest X-ray. This is a non-invasive method requiring relatively low doses of X-rays and may be incorporated for routine checks of developmental status and/or quick assessment of effect of mutations on flight muscle-related genes. On the other hand, the end-on microdiffraction recording is ...
In-situ X-ray diffraction study of hydrogen absorption and desorption processes in Pd thin films: Hydrogen composition dependent anisotropic expansion and its quantitative descriptionIn-situ X-ray diffraction study of hydrogen absorption and desorption processes in Pd thin films: Hydrogen composition dependent anisotropic expansion and its quantitative description ...
X-ray Diffraction Patterns of Activated Carbons Prepared under Various Conditions - Activated carbon;$H_3PO_4$-activation;steam pyrolysis;graphite structure;X-ray diffraction;
Wertz, D. L. (1992). X-Ray Diffraction Analysis of the Argonne Premium Coals: Descriptors of the Near Diffraction Peak. Abstracts of Papers of the American Chemical Society, 204, 37-Fuel ...
High- and low-angle X-ray diffraction studies of hard α -keratin have been studied, and various models have been proposed over the last 70 years. Most of these studies have been confined to one or two forms of alpha keratin. This high- and low-angle synchrotron fibre diffraction study extends the study to cover all available data for all known forms of hard α -keratin including hairs, fingernails, hooves, horn, and quills from mammals, marsupials, and a monotreme, and it confirms that the model proposed is universally acceptable for all mammals. A complete Bragg analysis of the meridional diffraction patterns, including multiple-time exposures to verify any weak reflections, verified the existence of a superlattice consisting of two infinite lattices and three finite lattices. An analysis of the equatorial patterns establishes the radii of the oligomeric levels of dimers, tetramers, and intermediate filaments (IFs) together with the centre to centre distance for the IFs, thus confirming the ...
FOR some time X-ray diffraction techniques have been used to study living muscle in the resting state1-4. Using a modified Frankss type of small-angle camera5,6 and a Hilger microfocus X-ray generator, it has been possible for the first time to record equatorial and meridional X-ray reflexions from striated muscle during contraction as well as during rest.
The structure of the synthetic deoxyoctamer d(GGIGCTCC) has been determined by single crystal X-ray diffraction techniques to a resolution of 1.7A. The sequence crystallises in space group P6(1), with unit cell dimensions a = b = 45.07, c = 45.49A. The refinement converged with a crystallographic residual R = 0.14 and the location of 81 solvent molecules. The octamer forms an A-DNA duplex with 6 Watson-Crick (G.C) base pairs and 2 inosine-thymine (I.T) pairs. Refinement of the structure shows it to be essentially isomorphous with that reported for d(GGGGCTCC) with the mispairs adopting a "wobble" conformation. Conformational parameters and base stacking interactions are compared to those for the native duplex d(GGGGCCCC) and other similar sequences. A rationale for the apparent increased crystal packing efficiency and lattice stability of the I.T octamer is given. Refined crystal structure of an octanucleotide duplex with I.T. mismatched base pairs.,Cruse WB, Aymani J, Kennard O, Brown T, Jack ...
Coherent X-ray Diffraction patterns of collagen in soft tissues have been measured for the first time by Dr Felisa Berenguer at the London Centre for Nanotechnology with her colleagues.
We performed the solution-phase synthesis of a set of model peptides, including homo-oligomers, based on the 2-aminoadamantane-2-carboxylic acid (Adm) residue, an extremely bulky, highly lipophilic, tricyclic, achiral, Ca-tetrasubstituted a-amino acid. In particular, for the difficult peptide coupling reaction between two Adm residues, we took advantage of the Meldals a-azidoacyl chloride approach. Most of the synthesized Adm peptides were characterized by single-crystal X-ray diffraction analyses. The results indicate a significant propensity for the Adm residue to adopt ¿-turn and ¿-turn-like conformations. Interestingly, we found that a -CO-(Adm)2-NH- sequence is folded in the crystal state into a regular, incipient ¿-helix, at variance with the behavior of all of the homo-dipeptides from Ca-tetrasubstituted a-amino acids already investigated, which tend to adopt either the ß-turn or the fully extended conformation. Our density functional theory conformational energy calculations on the ...
The first hard X-ray laser, the Linac Coherent Light Source (LCLS), produces 120 shots per second. Particles injected into the X-ray beam are hit randomly and in unknown orientations by the extremely intense X-ray pulses, where the femtosecond-duration X-ray pulses diffract from the sample before the particle structure is significantly changed even though the sample is ultimately destroyed by the deposited X-ray energy. Single particle X-ray diffraction experiments generate data at the FEL repetition rate, resulting in more than 400,000 detector readouts in an hour, the data stream during an experiment contains blank frames mixed with hits on single particles, clusters and contaminants. The diffraction signal is generally weak and it is superimposed on a low but continually fluctuating background signal, originating from photon noise in the beam line and electronic noise from the detector. Meanwhile, explosion of the sample creates fragments with a characteristic signature. Here, we describe ...
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RapiData 2017 at SSRL - Data Collection and Structure Solving: A Practical Course in Macromolecular X-ray Diffraction Measurement, April 16-21, 2017, Menlo Park, CA The announcement, agenda, registration and additional information are now available at the RapiData 2017 website canSAS-IX Meeting, June 5-7, 2017, San Francisco, CA. Please join us in San Francisco for canSAS-IX Meeting from June 5-7, 2017. The meeting will be hosted jointly between the Advanced Light Source at Lawrence Berkeley National Laboratory and Stanford Synchrotron Radiation Lightsource at SLAC National Accelerator Laboratory. The collective action for nomadic materials science small angle scatterers (canSAS) is an ongoing activity to provide the small-angle scattering user community with shared tools and information. For more information please visit both canSAS and the meeting website. 7th International Conferences on Hard X-ray Photoelectron Spectroscopy, September 11-15, 2017, Berkeley, CA. The 7th International ...
An optical pick-up device comprising an optical system including a light source and an optical diffraction grating element and a light receiving element, wherein the optical diffraction grating element guides the 0th-order diffracted lights of a light beam emitted from the light source onto a recording medium and guides the first-order diffracted lights of a reflected light from the recording medium onto the light receiving element to produce a plurality of focused light spots having the same light amount, wherein the optical diffraction grating element includes diffraction gratings having a configuration in which grooves and flat lands each positioned between the adjacent grooves are successively alternately formed, wherein the diffraction gratings have the same groove depth, groove width and groove tilt angle in order to obtain a constant 0th-order diffraction efficiency and first-order diffraction efficiency in the optical diffraction grating element while the pitches of the diffraction gratings are
We consider the problem of phase determination for continuous diffraction patterns obtained from a beam of identical, aligned large molecules (such as proteins), each coated with a layer of water or vitreous ice. Many laser-aligned molecules are assumed to lie within a wide continuous x-ray beam at any instant. An iterative phasing method is developed to extract the common target structure in three dimensions from diffraction patterns of these doped ice balls. Several measurements of the diffraction intensity in reciprocal space are needed. We found iteratively two boundaries (supports) (between protein and ice and the outer iceball support) by using the charge-flipping and multiple hybrid input-output algorithms, working with multiple sets of measured data. The approach is applied to simulated data from hydrated lysozyme proteins generated by the serial crystallography method of laser-aligned protein-beam diffraction proposed by Spence and Doak [Phys. Rev. Lett. 92, 198102 (2004) ]. We consider ...
TY - JOUR. T1 - Specimen preparation for cryogenic coherent X-ray diffraction imaging of biological cells and cellular organelles by using the X-ray free-electron laser at SACLA. AU - Kobayashi, Amane. AU - Sekiguchi, Yuki. AU - Oroguchi, Tomotaka. AU - Okajima, Koji. AU - Fukuda, Asahi. AU - Oide, Mao. AU - Yamamoto, Masaki. AU - Nakasako, Masayoshi. PY - 2016/7/1. Y1 - 2016/7/1. N2 - Coherent X-ray diffraction imaging (CXDI) allows internal structures of biological cells and cellular organelles to be analyzed. CXDI experiments have been conducted at 66 K for frozen-hydrated biological specimens at the SPring-8 Angstrom Compact Free-Electron Laser facility (SACLA). In these cryogenic CXDI experiments using X-ray free-electron laser (XFEL) pulses, specimen particles dispersed on thin membranes of specimen disks are transferred into the vacuum chamber of a diffraction apparatus. Because focused single XFEL pulses destroy specimen particles at the atomic level, diffraction patterns are collected ...
Dilauroylglycerol arginine conjugates constitute a novel class of specific biocompatible surfactants, which can be considered analogues of partial glycerides and phospholipids. During their preparation, spontaneous intramolecular acyl-migration reactions are observed and both possible regioisomers are obtained: 1,2-dilauroyl-rac-glycero-3-(Nα-acetyl-l-arginine) (1212RAc) and 1,3-dilauroylglycero-2-(Nα-acetyl-l-arginine) (12RAc12). To study the influence of the presence of both regioisomers on the physicochemical properties, the phase behavior in the dry state of pure 1,2-dilauroyl-rac-glycero-3-(Nα-acetyl-l-arginine) and two mixtures of both regioisomers were studied by differential scanning calorimetry and small-angle X-ray diffraction complemented by polarized light microscopy. The experiments were performed for a sequence of heating, cooling and reheating scans. The results have shown that all samples investigated display thermotropic liquid crystallinity. The transition temperatures have ...
Denis Andrault, Guillaume Fiquet, Jean-Paul Itie, Pascal Richet, Philippe Gillet, Daniel Haeusermann, Michael Hanfland; Thermal pressure in the laser-heated diamond-anvil cell; an X-ray diffraction study. European Journal of Mineralogy ; 10 (5): 931-940. doi: Download citation file:. ...
The first goal of the platform is to provide research teams working in the field of macromolecular crystallography at the Institut Pasteur with the expertise and technology required for automated crystallogenesis, X-ray diffraction measurements, and crystallographic computing as a core facility. The platform has obtained significant funding from the Institut Pasteur and from external sources such as the National Genopole Network (RNG-France), and from GIS-IBISA allowing us to upgrade or to acquire new equipment. Our crystallogenesis pipeline today is the most fully automated in academic institutions in France. Each year more than 900 different protein samples are submitted to automated crystallization assays. Most of these samples (about 80%) originated from crystallographic research groups within the department of Structural Biology & Chemistry and the department of Virology at Pasteur. The remaining 20% originated from outside Pasteur (Institut de biologie physico-chimique, CEA-Saclay, and ...
After producing a recombinant form of AqpZ in E. coli, the proteins were crystallized--capturing five water molecules inside--and then analyzed by state-of-the-art high-resolution X-ray diffraction techniques. The architecture of aquaporin Z is typical of aquaporins, with a spiral of eight oxygens providing water-binding sites inside the channel. The outer membrane and cytoplasmic ends of the channel are wider than the interior, which is long and narrow. This structure demonstrates that aquaporin selectivity arises in part from erecting a physical barrier: small molecules, like water, can easily pass, but larger ones simply cant fit. And the strategic positioning of amino acid residues with hydrophilic or hydrophobic properties along the channel helps police the influx of molecules based on their affinity for water. While it seems two amino acid chains located in the middle of the channel also provide a water-friendly surface, Stroud et al. say they play a more intriguing role. Noting that the ...
EuTe is a magnetic semiconductor with potential applications in prototype optoelectronic and spintronic devices. In this work, we investigated the structural properties of EuTe grown on BaF2(111) substrates by molecular beam epitaxy. X-ray diffraction measurements were performed on two series of samples with different growth times and temperatures. The growth occurs in the Volmer-Webber mode, with initial formation of islands that then coalesce to form thin films. The islands size, mosaic spread, and strain state are deduced as a function of growth conditions. Surprisingly, the EuTe islands exhibit in-plane tensile strain, while compressive strain is expected for structures grown over a substrate with smaller lattice parameter. The islands tensile strain relaxes with increasing deposition times and substrate temperature, and it tends to zero for thick EuTe films. We propose that the EuTe/BaF2 lattice mismatch is compensated by the formation of interfacial misfit dislocations. The growth ...
Tutorial-like scientific monograph on X-ray diffraction analysis Summarizes the complete knowledge on X-Ray diffraction crystallography and structure
A homologous series of novel λ-shaped mesogenic compounds in which three mesogenic groups are connected to 3, 4-dihydroxybenzoic acid has been prepared and their physical properties investigated by means of optical microscopy, differential scanning calorimetry and X-ray diffraction measurements. The λ-shaped
We report the growth of Mn-doped wurtzite GaN epilayers by nitrogen plasma-assisted molecular beam epitaxy, with a systematic attention to the dependence on the growth conditions. The addition of Mn modifies the growth diagram related to the Ga/N flux ratio. In particular, the stable Ga-bilayer coverage on the growth surface for the Ga-rich condition is destabilized in the presence of Mn. Mn incorporation in the epilayers is found to strongly depend on the Ga/N flux ratio: it varies by two orders of magnitude between the Ga-rich and the N-rich growth conditions. X-ray diffraction measurements on epilayers grown in the stoichiometric condition reveal a clear contrast between the precipitation of perovskite GaMn[sub 3]N clusters at Mn compositions higher than 1.7%, and the single phase of wurtzite Ga[sub 1-x]Mn[sub x]N at lower Mn compositions. © 2003 American Institute of Physics ...
Ligation of 2,6-diphenylbenzenethiol (DppSH) onto Au clusters stabilized by poly(N-vinyl-2-pyrrolidone) and subsequent core etching yielded a single cluster Au25(SDpp)11. High-energy X-ray diffraction measurement showed that Au25 constitutes a core in Au25(SDpp)11. We propose a bi-icosahedral Au25 core whose
1 Properties of X-rays 2 Geometry of Crystals 3 Diffraction I: Directions of Diffracted Beams 4 Diffraction II: Intensities of Diffracted Beams 5 Diffraction III: Non-Ideal Samples 6 Laure Photographs 7 Powder Photographs 8 Diffractometer and Spectrometer 9 Orientation and Quality of Single Crystals 10 Structure of Polycrystalline Aggregates 11 Determination of Crystal Structure 12 Precise Parameter Measurements 13 Phase-Diagram Determination 14 Order-Disorder Transformation 15 Chemical Analysis of X-ray Diffraction 16 Chemical Analysis by X-ray Spectrometry 17 Measurements of Residual Stress 18 Polymers 19 Small Angle Scatters 20 Transmission Electron Microscope
Lecture 16 Diffraction Chp. 36. Topics Youngs double slit interference experiment Diffraction and the wave theory Single slit diffraction Intensity of single slit diffraction Circular aperture and double slit diffraction Diffraction grating Dispersion and resolving power Demos Slideshow 1282984 by Ava
We report experimental results on x-ray diffraction of quantum-state- selected and strongly aligned ensembles of the prototypical asymmetric rotor molecule 2,5-diiodobenzonitrile using the Linac Coherent Light Source. The experiments demonstrate first steps toward a new approach to diffractive imaging of distinct structures of individual, isolated gas-phase molecules. We confirm several key ingredients of single molecule diffraction experiments: the abilities to detect and count individual scattered x-ray photons in single shot diffraction data, to deliver state-selected, e.g., structural-isomer-selected, ensembles of molecules to the x-ray interaction volume, and to strongly align the scattering molecules. Our approach, using ultrashort x-ray pulses, is suitable to study ultrafast dynamics of isolated molecules ...
High-pressure single-crystal diffraction experiments often suffer from the crushing of single crystals due to the application of high pressure. Consequently, only diffraction data resulting from several particles in random orientations is available, which cannot be routinely indexed by commonly used methods designed for single-crystal data. A protocol is proposed to index such diffraction data. The techniques of powder pattern indexing are first used to propose the possible lattice parameters, and then a genetic algorithm is applied to determine the orientation of the reciprocal lattice for each of the particles. This protocol has been verified experimentally ...
White blood cell. X-ray crystallography diffraction pattern for a white blood cell, obtained as part of research on biochemical structures. This image was produced by British physicist and molecular biologist Maurice Wilkins (1916-2004) while working at the MRC Biophysics Research Unit at Kings College London, UK. It was here in the early 1950s that Wilkins, Rosalind Franklin, and other crystallographers obtained X-ray diffraction patterns for DNA that led to James Watson and Francis Cricks DNA double helix model. As well as DNA, the Kings College researchers investigated other materials, cells, and biological tissues. - Stock Image C020/9044
In this work, 100 ps time-resolved liquid diffraction experiments on the photoreactions of diiodomercury (HgI2) dissolved in methanol (10 mM) were performed at beamline ID09B, using the optical pump and X-ray probe method. This molecular system has been investigated using the same technique as before, but the transient pathway and subsequent structural dynamics have not been elucidated due to the poor signal-to-noise ratio and limited data analysis method [2]. An optical pulse (267 nm, 2 ps, 986 Hz) triggers impulsive photodissociation of HgI2, followed by subsequent reactions and then the X-ray pulse (100 ps, 0.067 nm, 986 Hz) interrogates the reacting sample by making the diffraction patterns on the CCD detector in a stroboscopic manner for the different time-delays spanning from 100 picosecond to 1 microsecond. The difference diffraction and corresponding radial intensities were extracted from the diffraction pattern and analysed using the so-called "global-fitting method" which considers ...
Recent studies on the interference fringes in the myosin meridional reflections provide a new source of structural information on cross-bridge movement during mechanical transients and steady shortening. Many observations can be interpreted satisfactorily by the tilting lever-arm model, with some assumptions, including the presence of fixed repeating structures contributing to the M3 and higher-order meridional reflections. In isometric contraction, the lever arms are oriented near the start of the working stroke, with a dispersion of ca +−20-25°. Upon a rapid release of 10-12 nm, they move to the end of the stroke, with a well-known T2 delay of 1-2 ms. This delay must represent additional processes, which have to occur even in tension-generating heads, or activation of attached heads, which initially do not develop force. Surprisingly, in muscles shortening at moderate loads (0.5-0.6 P0), the mean position of the heads moves only 2-3 nm closer to the M-line than in the isometric case, ...
As a member of the wwPDB, the RCSB PDB curates and annotates PDB data according to agreed upon standards. The RCSB PDB also provides a variety of tools and resources. Users can perform simple and advanced searches based on annotations relating to sequence, structure and function. These molecules are visualized, downloaded, and analyzed by users who range from students to specialized scientists.
Titanium aluminides find application in modern light-weight, high-temperature turbines, such as aircraft engines, but suffer from poor plasticity during manufacturing and processing. Huge forging presses enable materials processing in the 10-GPa range, and hence, it is necessary to investigate the phase diagrams of candidate materials under these extreme conditions. Here, we report on an in situ synchrotron X-ray diffraction study in a large-volume press of a modern (α2 + γ) two-phase material, Ti-45Al-7.5Nb-0.25C, under pressures up to 9.6 GPa and temperatures up to 1686 K. At room temperature, the volume response to pressure is accommodated by the transformation γ → α2, rather than volumetric strain, expressed by the apparently high bulk moduli of both constituent phases. Crystallographic aspects, specifically lattice strain and atomic order, are discussed in detail. It is interesting to note that this transformation takes place despite an increase in atomic volume, which is due to the high
Grazing incidence X-ray diffraction (GI-XRD) is used to characterize the crystallographic dynamics of low molecular weight (LMW) and high molecular weight (HMW) poly(3-hexylselenophene) (P3HS) films and blend films of P3HS with [6-6-]-phenyl-C61-butyric acid methyl ester (PCBM) as a function of step-by-step thermal annealing, from room temperature to 250 °C. The temperature-dependent GIXRD data show how the melting point of P3HS crystallites is decreased by the presence of PCBM. P3HS crystallite domain sizes dramatically increase upon annealing to the P3HS melting temperature. The formation of well-oriented HMW P3HS crystallites with the (100) plane parallel to the substrate (edge-on orientation), when cooled from melt, are observed. We compare the behaviour of P3HS pure and blend films with that of poly(3-hexyl)thiophene (P3HT) pure and PCBM blended films and suggest that the similar temperature dependent behaviour we observe may be a common to polythiophene and related polymers and their ...
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Read chapter 2 Science and Policy Context: Mitochondrial replacement techniques (MRTs) are designed to prevent the transmission of mitochondrial DNA (mtDN...
TY - JOUR. T1 - Effects of thermal annealing upon the nanomorphology of poly(3-hexylselenophene)-PCBM blends. AU - Lilliu, Samuele. AU - Agostinelli, Tiziano. AU - Verploegen, Eric. AU - Pires, Ellis. AU - Hampton, Mark. AU - Al-Hashimi, Mohammed. AU - Heeney, Martin J.. AU - Toney, Michael F.. AU - Nelson, Jenny. AU - MacDonald, J. Emyr. PY - 2011/9/15. Y1 - 2011/9/15. N2 - Grazing incidence X-ray diffraction (GI-XRD) is used to characterize the crystallographic dynamics of low molecular weight (LMW) and high molecular weight (HMW) poly(3-hexylselenophene) (P3HS) films and blend films of P3HS with [6-6-]-phenyl-C 61-butyric acid methyl ester (PCBM) as a function of step-by-step thermal annealing, from room temperature to 250 °C. The temperature-dependent GIXRD data show how the melting point of P3HS crystallites is decreased by the presence of PCBM. P3HS crystallite domain sizes dramatically increase upon annealing to the P3HS melting temperature. The formation of well-oriented HMW P3HS ...
Under constant volume muscle contraction myofilament overlap increases and muscle expands radially. While myofilament overlap is considered a major factor in force generation, considerably less is known about the role of myofilament expansion accompanying shortening during contraction. Recent theoretical evidence suggests that the spacing between filaments will indeed be an important determinant of force generation at any level of filament overlap, however, there are scant data that show the extent to which filament overlap changes in intact muscles. To address this issue we performed work loops on intact Manduca sexta flight muscles while simultaneously measuring myofilament spacing, force, and length using time resolved small angle x-ray diffraction imaging. Muscles were stimulated at 25 Hz and held at a temperature of 35C while simultaneously measuring length and force. Five x-ray images were taken during each wingbeat cycle for 100 contractions. These images were averaged over all cycles, ...
Schamper, Christian; Dornisch, D.; Moritz, Wolfgang; Schulz, H.; Feidenhansl, Robert; Nielsen, Morten; Grey, F. und Johnson, Robert L. (1992): Au Adsorption on Si(111). Studied by Grazing Incidence X-Ray Diffraction. Proceedings of the 2nd International Conference, June 25 - 28, 1991, Physik-Zentrum, Bad Honnef, Fed. Rep. of Germany. [PDF, 797kB] ...
Protein crystallography uses X-ray diffraction techniques to determine the three-dimensional structures of proteins. Proteins are molecules with complex structure, and the diversity of the biological functions they express is determined by, and is dependent upon, the diversity of the tertiary structures they adopt, and upon the abilities of these structures to respond to other molecules by changes in shape and chemistry. At the present time, protein crystallography is the most widely applicable method of acquiring significant new structural data, and the detail it provides is unequalled by any other technique. Together with biochemical and chemical studies, the structural information acquired provides information upon which proposals concerning the molecular basis of biological activity can be based. The goal of the project described in this thesis is to optimize methods for crystallizing a copperhead phospholipase A2 enzyme both in its free state and complexed with an inhibitor. This thesis presents a