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Sample records for anomalous small angle

  1. Anomalous small angle x-ray scattering studies of amorphous metal-germanium alloys

    SciTech Connect

    Rice, M.

    1993-12-01

    This dissertation addresses the issue of composition modulation in sputtered amorphous metal-germanium thin films with the aim of understanding the intermediate range structure of these films as a function of composition. The investigative tool used in this work is anomalous small-angle X-ray scattering (ASAXS). The primary focus of this investigation is the amorphous iron-germanium (a-Fe{sub x}Ge{sub 100-x}) system with particular emphasis on the semiconductor-rich regime. Brief excursions are made into the amorphous tungsten-germanium (a-W{sub x}Ge{sub 100-x}) and the amorphous molybdenum-germanium (a-Mo{sub x}Ge{sub 100-x}) systems. All three systems exhibit an amorphous structure over a broad composition range extending from pure amorphous germanium to approximately 70 atomic percent metal when prepared as sputtered films. Across this composition range the structures change from the open, covalently bonded, tetrahedral network of pure a-Ge to densely packed metals. The structural changes are accompanied by a semiconductor-metal transition in all three systems as well as a ferromagnetic transition in the a-Fe{sub x}Ge{sub 100-x} system and a superconducting transition in the a-Mo{sub x}Ge{sub 100-x} system. A long standing question, particularly in the a-Fe{sub x}Ge{sub 100-x} and the a-Mo{sub x}Ge{sub 100-x} systems, has been whether the structural changes (and therefore the accompanying electrical and magnetic transitions) are accomplished by homogeneous alloy formation or phase separation. The application of ASAXS to this problem proves unambiguously that fine scale composition modulations, as distinct from the simple density fluctuations that arise from cracks and voids, are present in the a-Fe{sub x}Ge{sub 100-x}, a-W{sub x}Ge{sub 100-x}, and a-Mo{sub x}Ge{sub 100-x} systems in the semiconductor-metal transition region. Furthermore, ASAXS shows that germanium is distributed uniformly throughout each sample in the x<25 regime of all three systems.

  2. New method for analyzing the periodic structure of multilayer by differential anomalous small-angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Kato, K.; Matsubara, E.; Saito, M.; Kosaka, T.; Waseda, Y.; Inomata, K.

    1995-03-01

    A new method has been proposed for analyzing the periodic structure of a multilayered sample by the differential anomalous small-angle X-ray scattering method in the reflection geometry. The scattering peaks due to the periodically layered structure in the small angle region are often observed with a large background intensity. These peak intensities strongly depend upon the anomalous dispersion terms of the constituent element near its absorption edge. Thus, by taking a difference of these peak intensities observed at two energies near the edge, the scattering intensity attributed to various causes can be accurately eliminated except the periodically layered structure. Namely, only the intrinsic peak intensities are precisely determined by this method. Furthermore, this method is the most effective for analyzing the periodic structures of multilayers composed of the next neighboring elements in the periodic table. The experimental details and the usefulness of the present new method have been presented by obtaining the concentration profile of a Cu/Co multilayer using the peak intensity variation arising from the anomalous dispersion terms of Cu and Co near their K absorption edges.

  3. Anomalous small-angle X-ray scattering of nanoporous two-phase atomistic models for amorphous silicon–germanium alloys

    SciTech Connect

    Chehaidar, A.

    2015-09-15

    The present work deals with a detailed analysis of the anomalous small-angle X-ray scattering in amorphous silicon–germanium alloy using the simulation technique. We envisage the nanoporous two-phase alloy model consisting in a mixture of Ge-rich and Ge-poor domains and voids at the nanoscale. By substituting Ge atoms for Si atoms in nanoporous amorphous silicon network, compositionally heterogeneous alloys are generated with various composition-contrasts between the two phases. After relaxing the as-generated structure, we compute its radial distribution function, and then we deduce by the Fourier transform technique its anomalous X-ray scattering pattern. Using a smoothing procedure, the computed X-ray scattering patterns are corrected for the termination errors due to the finite size of the model, allowing so a rigorous quantitative analysis of the anomalous small-angle scattering. Our simulation shows that, as expected, the anomalous small-angle X-ray scattering technique is a tool of choice for characterizing compositional heterogeneities coexisting with structural inhomogeneities in an amorphous alloy. Furthermore, the sizes of the compositional nanoheterogeneities, as measured by anomalous small-angle X-ray scattering technique, are X-ray energy independent. A quantitative analysis of the separated reduced anomalous small-angle X-ray scattering, as defined in this work, provided a good estimate of their size.

  4. Anomalous small angle x-ray scattering studies of heavy metal ion solvation behavior in clay minerals

    SciTech Connect

    Carrado, K.A.; Thiyagarajan, P.; Winans, R.E.; Song, Kang

    1997-09-01

    The authors have exploited anomalous small angle x-ray scattering (ASAXS) to monitor the solvation behavior of Cu(II), Er(III) and Yb(III) ions within the interlayers of the natural aluminosilicate clay mineral montmorillonite. The ASAXS technique can reveal the distribution of specific metallic species within a heterogeneous and disordered matrix. The variations of signal intensity as a function of absorption energy were monitored for all of the metal-clays as a function of hydration. Two different hydration levels were probed: as prepared at ambient conditions, or so-called {open_quotes}dry{close_quotes} powders, and {open_quotes}wet{close_quotes} pastes. ASAXS intensities should increase with absorption energy if the metal ion is associated with the interlayer solvent (water in this case), and decrease if the metal ion is associated with the solid matrix. The results show that: (1) Cu(II) is solvated within the interlayers of the wet sample, as expected, and (2) Er(III) and Yb(III) decrease in ASAXS intensity with increased hydration. This latter result was not expected and there is speculation that these ions have associated as hydrolyzed products with the clay surface. The basic principles underlying SAXS and ASAXS will also be presented in this paper.

  5. Copper and copper oxide nanoparticles in a cellulose support studied using anomalous small-angle X-ray scattering

    NASA Astrophysics Data System (ADS)

    Vainio, U.; Pirkkalainen, K.; Kisko, K.; Goerigk, G.; Kotelnikova, N. E.; Serimaa, R.

    2007-04-01

    Microcrystalline cellulose is a porous natural material which can be used both as a support for nanoparticles and as a reducer of metal ions. Cellulose supported nanoparticles can act as catalysts in many reactions. Cu, CuO, and Cu2O particles were prepared in microcrystalline cellulose by adding a solution of copper salt to the insoluble cellulose matrix and by reducing the copper ions with several reducers. The porous nanocomposites were studied using anomalous small angle X-ray scattering (ASAXS), X-ray absorption spectroscopy, and X-ray diffraction. Reduction of Cu2+ with cellulose in ammonium hydrate medium yielded crystalline CuO nanoparticles and the crystallite size was about 6-20 nm irrespective of the copper concentration. The size distribution of the CuO particles was determined with ASAXS measurements and coincided with the crystallite sizes. Using sodium borohydrate or hydrazine sulfate as a reducer both metallic Cu and Cu2O nanoparticles were obtained and the crystallite size and the oxidation state depended on the amount of reducer.

  6. Trends in anomalous small-angle X-ray scattering in grazing incidence for supported nanoalloyed and core-shell metallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Andreazza, P.; Khelfane, H.; Lyon, O.; Andreazza-Vignolle, C.; Ramos, A. Y.; Samah, M.

    2012-06-01

    As atomic structure and morphology of particles are directly correlated to their functional properties, experimental methods probing local and average features of particles at the nanoscale elicit a growing interest. Anomalous small-angle X-ray scattering (ASAXS) is a very attractive technique to investigate the size, shape and spatial distribution of nanoobjects embedded in a homogeneous matrix or in porous media. The anomalous variation of the scattering factor close to an absorption edge enables element specific investigations. In the case of supported nano-objects, the use of grazing incidence is necessary to limit the probed depth. The combination of grazing incidence with the anomalous technique provides a powerful new method, anomalous grazing incidence small-angle X-ray scattering (AGISAXS), to disentangle complex chemical patterns in supported multi-component nano-structures. Nevertheless, a proper data analysis requires accurate quantitative measurements associated to an adapted theoretical framework. This paper presents anomalous methods applied to nanoalloys phase separation in the 1-10 nm size range, and focuses on the application of AGISAXS in bimetallic systems: nanocomposite films and core-shell supported nanoparticles.

  7. In-situ study of precipitates in Al–Zn–Mg–Cu alloys using anomalous small-angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Chun-Ming, Yang; Feng-Gang, Bian; Bai-Qing, Xiong; Dong-Mei, Liu; Yi-Wen, Li; Wen-Qiang, Hua; Jie, Wang

    2016-06-01

    In the present work, the precipitate compositions and precipitate amounts of these elements (including the size distribution, volume fraction, and inter-precipitate distance) on the Cu-containing 7000 series aluminum alloys (7150 and 7085 Al alloys), are investigated by anomalous small-angle x-ray scattering (ASAXS) at various energies. The scattering intensity of 7150 alloy with T6 aging treatment decreases as the incident x-ray energy approaches the Zn absorption edge from the lower energy side, while scattering intensity does not show a noticeable energy dependence near the Cu absorption edge. Similar results are observed in the 7085 alloy in an aging process (120 °C) by employing in-situ ASAXS measurements, indicating that the precipitate compositions should include Zn element and should not be strongly related to Cu element at the early stage after 10 min. In the aging process, the precipitate particles with an initial average size of ∼ 8 Å increase with aging time at an energy of 9.60 keV, while the increase with a slower rate is observed at an energy of 9.65 keV as near the Zn absorption edge. Project supported by the National Natural Science Foundation of China (Grant Nos. 11005143, 11405259, and 51274046) and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry of China (Grant No. [2014]1685).

  8. Small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Cousin, Fabrice

    2015-10-01

    Small Angle Neutron Scattering (SANS) is a technique that enables to probe the 3-D structure of materials on a typical size range lying from ˜ 1 nm up to ˜ a few 100 nm, the obtained information being statistically averaged on a sample whose volume is ˜ 1 cm3. This very rich technique enables to make a full structural characterization of a given object of nanometric dimensions (radius of gyration, shape, volume or mass, fractal dimension, specific area…) through the determination of the form factor as well as the determination of the way objects are organized within in a continuous media, and therefore to describe interactions between them, through the determination of the structure factor. The specific properties of neutrons (possibility of tuning the scattering intensity by using the isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons) make it particularly interesting in the fields of soft matter, biophysics, magnetic materials and metallurgy. In particular, the contrast variation methods allow to extract some informations that cannot be obtained by any other experimental techniques. This course is divided in two parts. The first one is devoted to the description of the principle of SANS: basics (formalism, coherent scattering/incoherent scattering, notion of elementary scatterer), form factor analysis (I(q→0), Guinier regime, intermediate regime, Porod regime, polydisperse system), structure factor analysis (2nd Virial coefficient, integral equations, characterization of aggregates), and contrast variation methods (how to create contrast in an homogeneous system, matching in ternary systems, extrapolation to zero concentration, Zero Averaged Contrast). It is illustrated by some representative examples. The second one describes the experimental aspects of SANS to guide user in its future experiments: description of SANS spectrometer, resolution of the spectrometer, optimization of spectrometer

  9. Anomalous incident-angle and elliptical-polarization rotation of an elastically refracted P-wave

    NASA Astrophysics Data System (ADS)

    Fa, Lin; Fa, Yuxiao; Zhang, Yandong; Ding, Pengfei; Gong, Jiamin; Li, Guohui; Li, Lijun; Tang, Shaojie; Zhao, Meishan

    2015-08-01

    We report a newly discovered anomalous incident-angle of an elastically refracted P-wave, arising from a P-wave impinging on an interface between two VTI media with strong anisotropy. This anomalous incident-angle is found to be located in the post-critical incident-angle region corresponding to a refracted P-wave. Invoking Snell’s law for a refracted P-wave provides two distinctive solutions before and after the anomalous incident-angle. For an inhomogeneously refracted and elliptically polarized P-wave at the anomalous incident-angle, its rotational direction experiences an acute variation, from left-hand elliptical to right-hand elliptical polarization. The new findings provide us an enhanced understanding of acoustical-wave scattering and lead potentially to widespread and novel applications.

  10. Anomalous incident-angle and elliptical-polarization rotation of an elastically refracted P-wave

    PubMed Central

    Fa, Lin; Fa, Yuxiao; Zhang, Yandong; Ding, Pengfei; Gong, Jiamin; Li, Guohui; Li, Lijun; Tang, Shaojie; Zhao, Meishan

    2015-01-01

    We report a newly discovered anomalous incident-angle of an elastically refracted P-wave, arising from a P-wave impinging on an interface between two VTI media with strong anisotropy. This anomalous incident-angle is found to be located in the post-critical incident-angle region corresponding to a refracted P-wave. Invoking Snell’s law for a refracted P-wave provides two distinctive solutions before and after the anomalous incident-angle. For an inhomogeneously refracted and elliptically polarized P-wave at the anomalous incident-angle, its rotational direction experiences an acute variation, from left-hand elliptical to right-hand elliptical polarization. The new findings provide us an enhanced understanding of acoustical-wave scattering and lead potentially to widespread and novel applications. PMID:26244284

  11. Multi-wavelength anomalous diffraction using medium-angle X-ray solution scattering (MADMAX).

    PubMed

    Makowski, L; Bardhan, J; Gore, D; Rodi, D J; Fischetti, R F

    2012-02-22

    Proteins are dynamic molecules whose function in virtually all biological processes requires conformational motion. Direct experimental probes of protein structure in solution are needed to characterize these motions. Anomalous scattering from proteins in solution has the potential to act as a precise molecular ruler to determine the positions of specific chemical groups or atoms within proteins under conditions in which structural changes can take place free from the constraints of crystal contacts. In solution, anomalous diffraction has two components: a set of cross-terms that depend on the relative location of the anomalous centers and the rest of the protein, and a set of pure anomalous terms that depend on the distances between the anomalous centers. The cross-terms are demonstrated here to be observable and to provide direct information about the distance between the anomalous center and the center of mass of the protein. The second set of terms appears immeasurably small in the context of current experimental capabilities. Here, we outline the theory underlying anomalous scattering from proteins in solution, predict the anomalous differences expected on the basis of atomic coordinate sets, and demonstrate the measurement of anomalous differences at the iron edge for solutions of myoglobin and hemoglobin. PMID:22385864

  12. Fractal Approach in Petrology: Combining Ultra-Small Angle (USANA) and Small Angle Neutron Scattering (SANS)

    SciTech Connect

    LoCelso, F.; Triolo, F.; Triolo, A.; Lin, J.S.; Lucido, G.; Triolo, R.

    1999-10-14

    Ultra small angle neutron scattering instruments have recently covered the gap between the size resolution available with conventional intermediate angle neutron scattering and small angle neutron scattering instruments on one side and optical microscopy on the other side. Rocks showing fractal behavior in over two decades of momentum transfer and seven orders of magnitude of intensity are examined and fractal parameters are extracted from the combined USANS and SANS curves.

  13. Emerging applications of small angle solution scattering in structural biology

    PubMed Central

    Chaudhuri, Barnali N

    2015-01-01

    Small angle solution X-ray and neutron scattering recently resurfaced as powerful tools to address an array of biological problems including folding, intrinsic disorder, conformational transitions, macromolecular crowding, and self or hetero-assembling of biomacromolecules. In addition, small angle solution scattering complements crystallography, nuclear magnetic resonance spectroscopy, and other structural methods to aid in the structure determinations of multidomain or multicomponent proteins or nucleoprotein assemblies. Neutron scattering with hydrogen/deuterium contrast variation, or X-ray scattering with sucrose contrast variation to a certain extent, is a convenient tool for characterizing the organizations of two-component systems such as a nucleoprotein or a lipid-protein assembly. Time-resolved small and wide-angle solution scattering to study biological processes in real time, and the use of localized heavy-atom labeling and anomalous solution scattering for applications as FRET-like molecular rulers, are amongst promising newer developments. Despite the challenges in data analysis and interpretation, these X-ray/neutron solution scattering based approaches hold great promise for understanding a wide variety of complex processes prevalent in the biological milieu. PMID:25516491

  14. The Pluto System At Small Phase Angles

    NASA Astrophysics Data System (ADS)

    Verbiscer, Anne J.; Buie, Marc W.; Binzel, Richard; Ennico, Kimberly; Grundy, William M.; Olkin, Catherine B.; Showalter, Mark Robert; Spencer, John R.; Stern, S. Alan; Weaver, Harold A.; Young, Leslie; New Horizons Science Team

    2016-10-01

    Hubble Space Telescope observations of the Pluto system acquired during the New Horizons encounter epoch (HST Program 13667, M. Buie, PI) span the phase angle range from 0.06 to 1.7 degrees, enabling the measurement and characterization of the opposition effect for Pluto and its satellites at 0.58 microns using HST WFC3/UVIS with the F350LP filter, which has a broadband response and a pivot wavelength of 0.58 microns. At these small phase angles, differences in the opposition effect width and amplitude appear. The small satellites Nix and Hydra both exhibit a very narrow opposition surge, while the considerably larger moon Charon has a broader opposition surge. Microtextural surface properties derived from the shape and magnitude of the opposition surge of each surface contain a record of the collisional history of the system. We combine these small phase angle observations with those made at larger phase angles by the New Horizons Long Range Reconnaissance Imager (LORRI), which also has a broadband response with a pivot wavelength of 0.61 microns, to produce the most complete disk-integrated solar phase curves that we will have for decades to come. Modeling these disk-integrated phase curves generates sets of photometric parameters that will inform spectral modeling of the satellite surfaces as well as terrains on Pluto from spatially resolved New Horizons Ralph Linear Etalon Imaging Spectral Array (LEISA) data from 1.2 to 2.5 microns. Rotationally resolved phase curves of Pluto reveal opposition effects that only appear at phase angles less than 0.1 degree and have widths and amplitudes that are highly dependent on longitude and therefore on Pluto's diverse terrains. The high albedo region informally known as Sputnik Planum dominates the disk-integrated reflectance of Pluto on the New Horizons encounter hemisphere. These results lay the groundwork for observations at true opposition in 2018, when the Pluto system will be observable at phase angles so small that

  15. Small Angle X-Ray Scattering Detector

    DOEpatents

    Hessler, Jan P.

    2004-06-15

    A detector for time-resolved small-angle x-ray scattering includes a nearly constant diameter, evacuated linear tube having an end plate detector with a first fluorescent screen and concentric rings of first fiber optic bundles for low angle scattering detection and an annular detector having a second fluorescent screen and second fiber optic bundles concentrically disposed about the tube for higher angle scattering detection. With the scattering source, i.e., the specimen under investigation, located outside of the evacuated tube on the tube's longitudinal axis, scattered x-rays are detected by the fiber optic bundles, to each of which is coupled a respective photodetector, to provide a measurement resolution, i.e., dq/q, where q is the momentum transferred from an incident x-ray to an x-ray scattering specimen, of 2% over two (2) orders of magnitude in reciprocal space, i.e., q.sub.max /q.sub.min.congruent.100.

  16. Impedance Scaling for Small Angle Transitions

    SciTech Connect

    Stupakov, G.; Bane, Karl; Zagorodnov, I.; /DESY

    2010-10-27

    Based on the parabolic equation approach to Maxwell's equations we have derived scaling properties of the high frequency impedance/short bunch wakefields of structures. For the special case of small angle transitions we have shown the scaling properties are valid for all frequencies. Using these scaling properties one can greatly reduce the calculation time of the wakefield/impedance of long, small angle, beam pipe transitions, like one often finds in insertion regions of storage rings. We have tested the scaling with wakefield simulations of 2D and 3D models of such transitions, and found that the scaling works well. In modern ring-based light sources one often finds insertion devices having extremely small vertical apertures (on the order of millimeters) to allow for maximal undulator fields reaching the beam. Such insertion devices require that there be beam pipe transitions from these small apertures to the larger cross-sections (normally on the order of centimeters) found in the rest of the ring. The fact that there may be many such transitions, and that these transitions introduce beam pipe discontinuities very close to the beam path, means that their impedance will be large and, in fact, may dominate the impedance budget of the entire ring. To reduce their impact on impedance, the transitions are normally tapered gradually over a long distance. The accurate calculation of the impedance or wakefield of these long transitions, which are typically 3D objects (i.e. they do not have cylindrical symmetry), can be quite a challenging numerical task. In this report we present a method of obtaining the impedance of a long, small angle transition from the calculation of a scaled, shorter one. Normally, the actual calculation is obtained from a time domain simulation of the wakefield in the structure, where the impedance can be obtained by performing a Fourier transform. We shall see that the scaled calculation reduces the computer time and memory requirements

  17. Soller collimators for small angle neutron scattering

    SciTech Connect

    Crawford, R.K.; Epperson, J.E.; Thiyagarajan, P.

    1988-09-30

    Small angle diffractometers at pulsed sources need to have fairly short flight paths if they are to make use of the long-wavelength portion of the spectrum without encountering problems from frame overlap or sacrificing intensity with band-limiting or pulse-removing choppers. With such short flight paths, achieving the necessary angular collimation in the incident beam while utilizing the full source size (/approximately/10 cm diameter) and a reasonable sample size (/approximately/1 cm diameter) requires the use of converging multiple-aperture collimation. If the collimation channels are all focused to the same point on the detector then the large sample size will not affect Q/sub min/ or the Q-resolution, even if the sample-to-detector distance is short. The Small Angle Diffractometer (SAD) at IPNS uses crossed converging soller collimators to provide focusing multiple-aperture collimation having /approximately/400 converging beam channels with essentially no ''dead'' space between them. This entire collimator system occupies a distance of only /approximately/60 cm along the incident flight path, while providing angular collimation of 0.003 radians FWHM. The dimensions for the SAD upstream collimator are L/sub c/ = 32.8 cm, d/sub 1/ = 0.974 mm, d/sub 2/ = 0.851 mm, while for the SAD downstream collimator L/sub c/ = 25.0 cm, d/sub 1/ - 0.844 mm, d/sub 2/ = 0.750 mm. Each of these collimators has 20 blades defining 21 horizontal or vertical channels. 4 refs., 6 figs.

  18. Small-angle scattering from fat fractals

    NASA Astrophysics Data System (ADS)

    Anitas, Eugen M.

    2014-06-01

    A number of experimental small-angle scattering (SAS) data are characterized by a succession of power-law decays with arbitrarily decreasing values of scattering exponents. To describe such data, here we develop a new theoretical model based on 3D fat fractals (sets with fractal structure, but nonzero volume) and show how one can extract structural information about the underlying fractal structure. We calculate analytically the monodisperse and polydisperse SAS intensity (fractal form factor and structure factor) of a newly introduced model of fat fractals and study its properties in momentum space. The system is a 3D deterministic mass fractal built on an extension of the well-known Cantor fractal. The model allows us to explain a succession of power-law decays and respectively, of generalized power-law decays (GPLD; superposition of maxima and minima on a power-law decay) with arbitrarily decreasing scattering exponents in the range from zero to three. We show that within the model, the present analysis allows us to obtain the edges of all the fractal regions in the momentum space, the number of fractal iteration and the fractal dimensions and scaling factors at each structural level in the fractal. We applied our model to calculate an analytical expression for the radius of gyration of the fractal. The obtained quantities characterizing the fat fractal are correlated to variation of scaling factor with the iteration number.

  19. Nucleation of small-angle boundaries

    SciTech Connect

    Nabarro, F.R.N. |; Wilsdorf, D.K.

    1996-12-01

    The internal stresses induced by the strain gradients in an array of lattice cells delineated by low-angle dislocation boundaries are partially relieved by the creation of new low-angle boundaries. This is shown to be a first-order transition, the new boundaries having finite misorientations. The calculated misorientations both of the new boundaries and of the existing boundaries which provoke the transition agree well with observations.

  20. Small Explorers - Small is beautiful. [Solar, Anomalous, and Magnetospheric Particles Explorer (SAMPEX)

    NASA Technical Reports Server (NTRS)

    Gilman, David

    1990-01-01

    NASA's Small Explorer Program aims to achieve a flight rate of one mission per year in a program of small scientific satellites launched from small expendable launch vehicles. The Program is developing 3 missions for launch in the early 1990's: the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX), the Submillimeter Wave Astronomy Satellite (SWAS), and the Fast Auroral Snapshot Explorer (FAST). This paper gives an overview of the program, a description of the selected missions, the approach to developing the missions and the plans for the next Announcement of Opportunity.

  1. Small angle neutron scattering from nanometer grain sized materials

    SciTech Connect

    Epperson, J.E.; Siegel, R.W.

    1991-11-01

    Small angie neutron scattering has been utilized, along with a number of complementary characterization methods suitable to the nanometer size scale, to investigate the structures of cluster-assembled nanophase materials. Results of these investigations are described and problems and opportunities in using small angle scattering for elucidating nanostructures are discussed.

  2. Small-angle neutron scattering from samples of expanded carbon

    SciTech Connect

    Bogdanov, S. G. Valiev, E. Z.; Dorofeev, Yu. A.; Pirogov, A. N.; Skryabin, Yu. N.; Makotchenko, V. G.; Nazarov, A. S.; Fedorov, V. E.

    2006-12-15

    The subatomic structure of expanded graphite has been investigated by small-angle neutron scattering. Samples were synthesized during quick thermal decomposition of intercalated compounds based on oxidized graphite. They had a low bulk density (up to 0.1 g/cm{sup 3}) and were characterized by considerable small-angle scattering. It has been established that majority of the volume of expanded graphite samples is occupied by participles with characteristic sizes in two ranges: from 6 to 8 nm and from 20 to 30 nm. Small particles have properties of a surface fractal with the dimension D{sub s} = 2.4-2.6, whereas the larger particles are mainly smooth and have the dimension D{sub s} = 2.0-2.1. The specific surface of the samples studied was determined from the small-angle scattering data.

  3. Impedance Scaling for Small-angle Tapers and Collimators

    SciTech Connect

    Stupakov, G.; /SLAC

    2010-02-11

    In this note I will prove that the impedance calculated for a small-angle collimator or taper, of arbitrary 3D profile, has a scaling property that can greatly simplify numerical calculations. This proof is based on the parabolic equation approach to solving Maxwell's equation developed in Refs. [1, 2]. We start from the parabolic equation formulated in [3]. As discussed in [1], in general case this equation is valid for frequencies {omega} >> c/a where a is a characteristic dimension of the obstacle. However, for small-angle tapers and collimators, the region of validity of this equation extends toward smaller frequencies and includes {omega} {approx} c/a.

  4. SMALL ANGLE CRAB COMPENSATION FOR LHC IR UPGRADE

    SciTech Connect

    CALAGA,R.; DORDA, U.; OHMI, D.; OIDE, K.; TOMAS, R.; ZIMMERMANN, F.

    2007-06-25

    A small angle (< 1 mrad) crab scheme is an attractive option for the LHC luminosity upgrade to recover the geometric luminosity loss from the finite crossing angle [I]. The luminosity loss increases steeply to unacceptable levels as the IP beta function is reduced below its nominal value (see Fig. 1 in Ref. [2]). The crab compensation in the LHC can be accomplished using only two sets of deflecting RF cavities, placed in collision-free straight sections of the LHC to nullify the effective crossing angles at IPI & IP5. We also explore a 400 MHz superconducting cavity design and discuss the pertinent RF challenges. We present IR optics configurations with low-angle crab crossing, study the beam-beam performance and proton-beam emittance growth in the presence of crab compensation, lattice errors, and crab RF noise sources.

  5. Ultra Small-Angle Neutron Scattering Study of Porous Glass

    SciTech Connect

    Desai, Reshma R.; Desa, J. A. Erwin; Sen, D.; Mazumder, S.

    2011-07-15

    Compacts of silica micro-spheres prepared for different times at sintering temperatures of 640 deg. C and 740 deg. C have been studied by Ultra Small-Angle Neutron Scattering (USANS) and Scanning Electron Microscopy (SEM). Stress versus strain measurements display several breakage points related to a range of nearest neighbour coordination around each microsphere.

  6. Substrate size and heterogeneity control anomalous transport in small streams

    NASA Astrophysics Data System (ADS)

    Aubeneau, A. F.; Hanrahan, Brittany; Bolster, Diogo; Tank, Jennifer L.

    2014-12-01

    In alluvial systems, substrate characteristics play a critical role in slowing downstream transport of both water and solutes. We present results from solute injection experiments testing the influence of sediment size (pea gravel versus coarse gravel) and heterogeneity (alternating sections versus well-mixed reaches) on solute transport dynamics in four experimental streams at the Notre Dame Linked Experimental Ecosystem Facility. The stream with pea gravel resulted in more long-term retention than the stream with coarse gravel, whereas both streams with heterogeneous substrate (alternated and mixed) fell between with similar late-time scaling. Inverse modeling of solute breakthrough curves suggested that residence times were distributed according to a truncated power law. While conservative solute transport in all four streams was anomalous, truncation times were influenced by sediment size, with the smaller pea gravel exhibiting a later truncation time than the coarse gravel, and the two streams with heterogeneous substrate having an intermediate cutoff. These results uniquely associate transport scaling with substrate characteristics in fluvial systems, revealing truncation time scales that had been previously predicted but not observed and quantified in field conditions. Because both benthic (i.e., substrate-water interface) and subsurface hyporheic regions are known biogeochemical hot spots, relating physical characteristics to the macroscopic transport behavior could be crucial to improve our estimates of solute export from fluvial systems.

  7. Implications of the small aspect angles of equatorial spread F

    SciTech Connect

    Hysell, D.L.; Farley, D.T.

    1996-03-01

    Small-scale equatorial spread F irregularities are almost perfectly aligned with the geomagnetic field. The authors develop here an analytic plasma kinetic theory of small-scale, quasi-field-aligned irregularities that include ion viscosity and finite Larmor radius effects. They conclude, for one thing, that the measured aspect angles are too small to be consistent with a dissipative drift wave source of 3-m irregularities. Nonlinearly driven flute modes appear to be the only available mechanism. The authors compare the relative influence of parallel and perpendicular dissipation and conclude that the aspect width depends only weakly on any single geophysical parameters, such as collision frequency, gradient length, temperature, etc. This finding is consistent with their observation that the measured aspect angles vary little with altitude and only weakly with instability level. 29 refs., 5 figs.

  8. The activity and radial dependence of anomalous diffusion by pitch angle scattering on split magnetic drift shells

    NASA Astrophysics Data System (ADS)

    O'Brien, T. P.

    2015-01-01

    in the magnetospheric magnetic field produce drift shell splitting, which causes the radial (drift shell) invariant to sometimes depend on pitch angle. Where drift shell splitting is significant, pitch angle scattering leads to diffusion in all three invariants of the particle's motion, including cross diffusion. We examine the magnitude of drift shell splitting-related anomalous diffusion for outer zone electrons compared to conventional diffusion in the absence of drift shell splitting. We assume that the primary local scattering process is wave-particle interactions with chorus. We find that anomalous radial diffusion can exceed that of conventional drift-resonant radial diffusion for particles with energies near 0.1 MeV at all radial distances outside the plasmasphere during quiet to moderate geomagnetic activity, and it is significant at 0.5 MeV. Cross diffusion involving the radial invariant can exceed the geometric mean of the corresponding pure diffusion coefficients at 0.1 MeV, and that such cross diffusion is significant even at 0.5-1 MeV. At 1 MeV, cross diffusion is often significant. The highest radial distances and magnetic activity levels in our study do not always exhibit as much significant anomalous diffusion as moderate radial distances and activity levels. This can be explained by (a) stronger dependence of conventional diffusion on magnetic activity and radius, and (b) strongest drift shell splitting at moderate magnetic activity. Simulation codes that neglect the possibility for cross terms will likely systematically underperform, especially for 0.1-0.5 MeV electrons, for much of the outer zone for quiet to moderate levels of magnetic activity.

  9. A SMALL-ANGLE DRILL-HOLE WHIPSTOCK

    DOEpatents

    Nielsen, D.E.; Olsen, J.L.; Bennett, W.P.

    1963-01-29

    A small angle whipstock is described for accurately correcting or deviating a drill hole by a very small angle. The whipstock is primarily utilized when drilling extremely accurate, line-of-slight test holes as required for diagnostic studies related to underground nuclear test shots. The invention is constructed of a length of cylindrical pipe or casing, with a whipstock seating spike extending from the lower end. A wedge-shaped segment is secured to the outer circumference of the upper end of the cylinder at a position diametrically opposite the circumferential position of the spike. Pin means are provided for affixing the whipstock to a directional drill bit and stem to alloy orienting and setting the whipstock properly in the drill hole. (AEC)

  10. SANS (small-angle neutron scattering) from polymers and colloids

    SciTech Connect

    Hayter, J.B.

    1987-01-01

    Small-angle neutron scattering (SANS) has been remarkably successful in providing detailed quantitative structural information on complex everyday materials, such as polymers and colloids, which are often of considerable industrial as well as academic interest. This paper reviews some recent SANS experiments on polymers and colloids, including ferrofluids, and discusses the use of these apparently complex systems as general physical models of the liquid or solid state.

  11. The small angle neutron spectrometer at the HANARO reactor, Korea

    NASA Astrophysics Data System (ADS)

    Seong, B.-S.; Han, Y.-S.; Lee, C.-H.; Lee, J.-S.; Hong, K.-P.; Park, K.-N.; Kim, H.-J.

    A new small angle neutron spectrometer (SANS) has been installed on the CN beam tube at the 30 MW HANARO Research Reactor in the Korea Atomic Energy Research Institute (KAERI). The SANS is to be used for the study of microstructural inhomogeneities in materials in the 1 nm to 100 nm size range. In this paper, the design characteristics of the spectrometer are presented in detail, and several SANS results for standard samples are presented which illustrate its performance.

  12. Persistence of small-scale anisotropies and anomalous scaling in a model of magnetohydrodynamics turbulence

    PubMed

    Antonov; Lanotte; Mazzino

    2000-06-01

    The problem of anomalous scaling in magnetohydrodynamics turbulence is considered within the framework of the kinematic approximation, in the presence of a large-scale background magnetic field. The velocity field is Gaussian, delta-correlated in time, and scales with a positive exponent xi. Explicit inertial-range expressions for the magnetic correlation functions are obtained; they are represented by superpositions of power laws with nonuniversal amplitudes and universal (independent of the anisotropy and forcing) anomalous exponents. The complete set of anomalous exponents for the pair correlation function is found nonperturbatively, in any space dimension d, using the zero-mode technique. For higher-order correlation functions, the anomalous exponents are calculated to O(xi) using the renormalization group. The exponents exhibit a hierarchy related to the degree of anisotropy; the leading contributions to the even correlation functions are given by the exponents from the isotropic shell, in agreement with the idea of restored small-scale isotropy. Conversely, the small-scale anisotropy reveals itself in the odd correlation functions: the skewness factor is slowly decreasing going down to small scales and higher odd dimensionless ratios (hyperskewness, etc.) dramatically increase, thus diverging in the r-->0 limit. PMID:11088340

  13. Uncertainties in Small-Angle Measurement Systems Used to Calibrate Angle Artifacts.

    PubMed

    Stone, Jack A; Amer, Mohamed; Faust, Bryon; Zimmerman, Jay

    2004-01-01

    We have studied a number of effects that can give rise to errors in small-angle measurement systems when they are used to calibrate artifacts such as optical polygons. Of these sources of uncertainty, the most difficult to quantify are errors associated with the measurement of imperfect, non-flat faces of the artifact, causing the instrument to misinterpret the average orientation of the surface. In an attempt to shed some light on these errors, we have compared autocollimator measurements to angle measurements made with a Fizeau phase-shifting interferometer. These two instruments have very different operating principles and implement different definitions of the orientation of a surface, but (surprisingly) we have not yet seen any clear differences between results obtained with the autocollimator and with the interferometer. The interferometer is in some respects an attractive alternative to an autocollimator for small-angle measurement; it implements an unambiguous and robust definition of surface orientation in terms of the tilt of a best-fit plane, and it is easier to quantify likely errors of the interferometer measurements than to evaluate autocollimator uncertainty.

  14. Uncertainties in Small-Angle Measurement Systems Used to Calibrate Angle Artifacts

    PubMed Central

    Stone, Jack A.; Amer, Mohamed; Faust, Bryon; Zimmerman, Jay

    2004-01-01

    We have studied a number of effects that can give rise to errors in small-angle measurement systems when they are used to calibrate artifacts such as optical polygons. Of these sources of uncertainty, the most difficult to quantify are errors associated with the measurement of imperfect, non-flat faces of the artifact, causing the instrument to misinterpret the average orientation of the surface. In an attempt to shed some light on these errors, we have compared autocollimator measurements to angle measurements made with a Fizeau phase-shifting interferometer. These two instruments have very different operating principles and implement different definitions of the orientation of a surface, but (surprisingly) we have not yet seen any clear differences between results obtained with the autocollimator and with the interferometer. The interferometer is in some respects an attractive alternative to an autocollimator for small-angle measurement; it implements an unambiguous and robust definition of surface orientation in terms of the tilt of a best-fit plane, and it is easier to quantify likely errors of the interferometer measurements than to evaluate autocollimator uncertainty. PMID:27366616

  15. Determining Equilibrium Lamellar Thickness by Small Angle Light Scattering

    NASA Astrophysics Data System (ADS)

    Li, Ying; Akpalu, Yvonne

    2002-03-01

    The crystallization and melting behavior of homogeneous copolymers of ethylene with butene and hexene is studied by small angle light scattering (SALS). We show that the final melting temperature (T_m^f), which corresponds to equilibrium between a melt with an overall ethylene sequence concentration (equal to the mole fraction of crystallizable units) and the thickest lamellar crystals can be determined from the SALS melting measurements. The T_m^f values, determined from the temperature at which the SALS HV or VV invariant vanishes during the melting, are substantially higher (7 to 10 °C) than those obtained from small angle x-ray (SAXS), wide angle x-ray scattering (WAXS) and differential scanning calorimetry (DSC). Thus our measurements indicate that SAXS, WAXS and DSC underestimate the lamellar thickness (l_f) of the largest crystals, a parameter necessary for estimating thermodynamic and kinetic parameters for ethylene copolymers. We also investigate T_m^f as a function of crystallization time (ranging from 1 hr to 72 hr) and heating rate. We discuss the implications of our SALS approach for estimating T_m^f, lf and lamellar morphological parameters from x-ray scattering.

  16. Bibliography on Small Systems: Nonequilibrium Phenomena and Anomalous Behavior

    NASA Astrophysics Data System (ADS)

    LIU, Fei; Lamberto, Rondoni; TANG, Lei-Han; ZHOU, Hai-Jun; WANG, Yan-Ting

    2014-10-01

    The workshop and satellite conference held in July 2013 at the Kavli Institute for Theoretical Physics China (KITPC) of the Chinese Academy of Sciences (CAS) brought together experts of a variety of different fields, and constituted a unique opportunity to share ideas and breed new ones in a strongly interdisciplinary fashion. At the same time, the breadth of the scope of these two meetings was so wide that the need for a collection of reference books and papers was pointed out, in order to help the interested professionals, as well as graduate students, both to tackle the technically advanced issues and to bridge the gaps, necessarily present in each other's background. Therefore, we invited some of the participants to produce a bibliography containing the most relevant works in their own fields, and to complement this bibliography with a short explanation of the content of those books and papers. We are thus very grateful to Igor Goychuk, David Lacoste, Annick Lesne, Andrea Puglisi, Hong Qian and Hugo Touchette for having accepted our invitation and for having produced what we consider a very useful tool for all those who want to learn or to understand more deeply the current theories concerning small and nonequilibrium systems.

  17. Structural analysis of Fe–Mn–O nanoparticles in glass ceramics by small angle scattering

    SciTech Connect

    Raghuwanshi, Vikram Singh; Harizanova, Ruzha; Tatchev, Dragomir; Hoell, Armin; Rüssel, Christian

    2015-02-15

    Magnetic nanocrystals containing Fe and Mn were obtained by annealing of silicate glasses with the composition 13.6Na{sub 2}O–62.9SiO{sub 2}–8.5MnO–15.0Fe{sub 2}O{sub 3−x} (mol%) at 580 °C for different periods of time. Here, we present Small Angle Neutron Scattering using Polarized neutrons (SANSPOL) and Anomalous Small Angle X-ray Scattering (ASAXS) investigation on these glass ceramic samples. Analysis of scattering data from both methods reveals the formation of spherical core–shell type of nanoparticles with mean sizes between 10 nm and 100 nm. ASAXS investigation shows the particles have higher concentration of iron atoms and the shell like region surrounding the particles is enriched in SiO{sub 2}. SANSPOL investigation shows the particles are found to be magnetic and are surrounded by a non-magnetic shell-like region. - Graphical abstract: Magnetic spherical core–shell nanoparticles in glass ceramics: SANSPOL and ASAXS investigations. - Highlights: • Formation and growth mechanisms of magnetic nanoparticles in silicate glass. • SANSPOL and ASAXS methods employed to evaluate quantitative information. • Analyses showed formation of nanoparticles with spherical core–shell structures. • Core of the particle is magnetic and surrounded by weak magnetic shell like region.

  18. Modified small angle magnetization rotation method in multilayer magnetic microwires

    NASA Astrophysics Data System (ADS)

    Torrejón, J.; Badini, G.; Pirota, K.; Vázquez, M.

    2007-09-01

    The small angle magnetization rotation (SAMR) technique is a widely used method to quantify magnetostriction in elongated ultrasoft magnetic materials. In the present work, we introduce significant optimization of the method, particularly simplification of the required equipment, profiting of the very peculiar characteristics of a recently introduced family of multilayer magnetic microwires consisting of a soft magnetic core, insulating intermediate layer and a hard magnetic outer layer. The introduced modified SAMR method is used not only to determine the saturation magnetostriction constant of the soft magnetic nucleus but also the magnetoelastic and magnetostatic coupling. This new method has a great potential in multifunctional sensor applications.

  19. Calculations of transonic boattail flow at small angle of attack

    NASA Technical Reports Server (NTRS)

    Nakayama, A.; Chow, W. L.

    1979-01-01

    A transonic flow past a boattailed afterbody under a small angle of attack was examined. It is known that the viscous effect offers significant modifications of the pressure distribution on the afterbody. Thus, the formulation for the inviscid flow was based on the consideration of a flow past a nonaxisymmetric body. The full three dimensional potential equation was solved through numerical relaxation, and quasi-axisymmetric boundary layer calculations were performed to estimate the displacement effect. It was observed again that the viscous effects were not negligible. The trend of the final results agreed well with the experimental data.

  20. Small-angle scattering model for multilamellar vesicles

    SciTech Connect

    Frielinghaus, Henrich

    2007-11-15

    A small-angle neutron-x-ray-light-scattering model for multilamellar vesicles is developed on the basis of a simple geometry. N spherical shells with radii of an arithmetic series are allowed for displacements {delta}R which are limited by {delta}Rsmall displacements {delta}R, but no second order peak is predicted. Only for rather large displacements the correlation peak widens up and shifts to smaller scattering angles. Then the important bilayer spacing is larger. The predictive power of the model lies in the connection of the compactness with N and in the maximum correlation peak sharpness. This model considers many length scales at a time while existing theories focus on length scales of the bilayer spacing and the bilayer itself.

  1. Azimuthal angle probe of anomalous HWW couplings at a high energy ep collider.

    PubMed

    Biswal, Sudhansu S; Godbole, Rohini M; Mellado, Bruce; Raychaudhuri, Sreerup

    2012-12-28

    A high energy ep collider, such as the proposed LHeC, possesses the unique facility of permitting direct measurement of the HWW coupling without contamination from the HZZ coupling. At such a machine, the fusion of two W bosons through the HWW vertex would give rise to typical charged current events accompanied by a Higgs boson. We demonstrate that azimuthal angle correlations between the observable charged current final states could then be a sensitive probe of the nature of the HWW vertex and hence of the CP properties of the Higgs boson.

  2. Small-angle neutron scattering at pulsed spallation sources

    SciTech Connect

    Seeger, P.A.; Hjelm, R.P. Jr.

    1990-01-01

    The importance of small-angle neutron scattering (SANS) in biological, chemical, physical, and engineering research mandates that all intense neutron sources be equipped with SANS instruments. Four existing instruments are described, and the general differences between pulsed-source and reactor-based instrument designs are discussed. The basic geometries are identical, but dynamic range is achieved by using a broad band of wavelengths (with time-of-flight analysis) rather than by moving the detector. This allows a more optimized collimation system. Data acquisition requirements at a pulsed source are more severe, requiring large, fast histogramming memories. Data reduction is also more complex, as all wave length-dependent and angle-dependent backgrounds and non-linearities must be accounted for before data can be transformed to intensity vs Q. A comparison is shown between the Los Alamos pulsed instrument and D-11 (Institute Laue-Langevin), and examples from the four major topics of the conference are shown. The general conclusion is that reactor-based instruments remain superior at very low Q or if only a narrow range of Q is required, but that the current generation of pulsed-source instruments is competitive at moderate Q and may be faster when a wide range of Q is required. In principle, a user should choose which facility to use on the basis of optimizing the experiment; in practice the tradeoffs are not severe and the choice is usually made on the basis of availability.

  3. Structural investigations of fat fractals using small-angle scattering

    NASA Astrophysics Data System (ADS)

    Anitas, Eugen M.

    2015-01-01

    Experimental small-angle scattering (SAS) data characterized, on a double logarithmic scale, by a succession of power-law decays with decreasing values of scattering exponents, can be described in terms of fractal structures with positive Lebesgue measure (fat fractals). Here we present a theoretical model for fat fractals and show how one can extract structural information about the underlying fractal using SAS method, for the well known fractals existing in the literature: Vicsek and Menger sponge. We calculate analytically the fractal structure factor and study its properties in momentum space. The models allow us to obtain the fractal dimension at each structural level inside the fractal, the number of particles inside the fractal and about the most common distances between the center of mass of the particles.

  4. Small angle neutron scattering studies of vesicle stability

    SciTech Connect

    Mang, J.T.; Hjelm, R.P.

    1997-10-01

    Small angle neutron scattering (SANS) was used to investigate the structure of mixed colloids of egg yolk phosphatidylcholine (EYPC) with the bile salt, cholylglycine (CG), in D{sub 2}O as a function of pressure (P) and temperature (T). At atmospheric pressure, the system forms an isotropic phase of mixed, single bilayer vesicles (SLV`s). Increasing the external hydrostatic pressure brought about significant changes in particle morphology. At T = 25 C, application of a pressure of 3.5 MPa resulted in the collapse of the SLV`s. Further increase of P, up to 51.8 MPa, resulted in a transition from a phase of ordered (stacked), collapsed vesicles to one of stacked, ribbon-like particles. A similar collapse of the vesicles was observed at higher temperature (T = 37 C) with increasing P, but at this temperature, no ribbon phase was found at the highest pressure explored.

  5. Small-angle scattering study of Aspergillus awamori glycoprotein glucoamylase

    NASA Astrophysics Data System (ADS)

    Schmidt, A. E.; Shvetsov, A. V.; Kuklin, A. I.; Lebedev, D. V.; Surzhik, M. A.; Sergeev, V. R.; Isaev-Ivanov, V. V.

    2016-01-01

    Glucoamylase from fungus Aspergillus awamori is glycoside hydrolase that catalyzes the hydrolysis of α-1,4- and α-1,6-glucosidic bonds in glucose polymers and oligomers. This glycoprotein consists of a catalytic domain and a starch-binding domain connected by an O-glycosylated polypeptide chain. The conformation of the linker, the relative arrangement of the domains, and the structure of the full-length enzyme are unknown. The structure of the recombinant glucoamylase GA1 was studied by molecular modelling and small-angle neutron scattering (SANS) methods. The experimental SANS data provide evidence that glucoamylase exists as a monomer in solution and contains a glycoside component, which makes a substantial contribution to the scattering. The model of full-length glucoamylase, which was calculated without taking into account the effect of glycosylation, is consistent with the experimental data and has a radius of gyration of 33.4 ± 0.6 Å.

  6. A novel small-angle neutron scattering detector geometry.

    PubMed

    Kanaki, Kalliopi; Jackson, Andrew; Hall-Wilton, Richard; Piscitelli, Francesco; Kirstein, Oliver; Andersen, Ken H

    2013-08-01

    A novel 2π detector geometry for small-angle neutron scattering (SANS) applications is presented and its theoretical performance evaluated. Such a novel geometry is ideally suited for a SANS instrument at the European Spallation Source (ESS). Motivated by the low availability and high price of (3)He, the new concept utilizes gaseous detectors with (10)B as the neutron converter. The shape of the detector is inspired by an optimization process based on the properties of the conversion material. Advantages over the detector geometry traditionally used on SANS instruments are discussed. The angular and time resolutions of the proposed detector concept are shown to satisfy the requirements of the particular SANS instrument.

  7. A novel small-angle neutron scattering detector geometry

    PubMed Central

    Kanaki, Kalliopi; Jackson, Andrew; Hall-Wilton, Richard; Piscitelli, Francesco; Kirstein, Oliver; Andersen, Ken H.

    2013-01-01

    A novel 2π detector geometry for small-angle neutron scattering (SANS) applications is presented and its theoretical performance evaluated. Such a novel geometry is ideally suited for a SANS instrument at the European Spallation Source (ESS). Motivated by the low availability and high price of 3He, the new concept utilizes gaseous detectors with 10B as the neutron converter. The shape of the detector is inspired by an optimization process based on the properties of the conversion material. Advantages over the detector geometry traditionally used on SANS instruments are discussed. The angular and time resolutions of the proposed detector concept are shown to satisfy the requirements of the particular SANS instrument. PMID:24046504

  8. Small angle scattering from protein/sugar conjugates

    NASA Astrophysics Data System (ADS)

    Jackson, Andrew; White, John

    2006-11-01

    The Maillard reaction between free amine groups on proteins and sugars is well known. We have examined the effect of the reaction of the casein group of milk proteins with sugars on their nanoscale structure and aggregation. The small angle neutron scattering from beta casein and sodium caseinate and their sugar conjugates have been studied as a function of solution concentration. At high conjugate concentration (greater than ca. 5 mg/ml) the addition of sugar reduces supra-micellar aggregation of the protein whilst at lower concentration, where the protein is expected to be deaggregated already, little effect is seen. Guinier analysis of the scattering data show a radius of gyration of around 75 A˚ for beta casein in solution and around 80 A˚ for the sucrose conjugate.

  9. Small Angle Neutron Scattering of Solutions of Arborescent Graft Polymers

    NASA Astrophysics Data System (ADS)

    Choi, Sangwook; Briber, R. M.; Bauer, B. J.; Topp, Andreas; Gauthier, Mario

    1998-03-01

    Arborescent graft polymers are branched macromolecules resulting from successive cycles of chloromethylation and anionic grafting reactions. Small angle neutron scattering (SANS) was used to measure the size and shape of arborescent graft polymers in solution. Guinier plots were used to analyze the data at small q. The radius of gyration of arborescent graft polymers was found to be almost independent of temperature as the solution was cooled towards the phase separation temperature. The optical cloud point temperature was found to be 15 ^0C. At the phase separation temperature two peaks were observed in the I versus q SANS data. The first peak is due to the interference between molecules while the second peak comes from the single particle form factor. The value of q at the peak from the form factor was almost constant as temperature was changed from 40 ^0C to 20 ^0C. The peak position shifted to higher q at the phase separation temperature. This indicates that the size of molecules decreased as the molecules began to aggregate below the phase separation temperature. The value of A2 for arborescent graft polymers was found to be independent of temperature and close to zero.

  10. Anomalously-dense firn in an ice-shelf channel revealed by wide-angle radar

    NASA Astrophysics Data System (ADS)

    Drews, R.; Brown, J.; Matsuoka, K.; Witrant, E.; Philippe, M.; Hubbard, B.; Pattyn, F.

    2015-10-01

    The thickness of ice shelves, a basic parameter for mass balance estimates, is typically inferred using hydrostatic equilibrium for which knowledge of the depth-averaged density is essential. The densification from snow to ice depends on a number of local factors (e.g. temperature and surface mass balance) causing spatial and temporal variations in density-depth profiles. However, direct measurements of firn density are sparse, requiring substantial logistical effort. Here, we infer density from radio-wave propagation speed using ground-based wide-angle radar datasets (10 MHz) collected at five sites on Roi Baudouin Ice Shelf (RBIS), Dronning Maud Land, Antarctica. Using a novel algorithm including traveltime inversion and raytracing with a prescribed shape of the depth-density relationship, we show that the depth to internal reflectors, the local ice thickness and depth-averaged densities can reliably be reconstructed. For the particular case of an ice-shelf channel, where ice thickness and surface slope change substantially over a few kilometers, the radar data suggests that firn inside the channel is about 5 % denser than outside the channel. Although this density difference is at the detection limit of the radar, it is consistent with a similar density anomaly reconstructed from optical televiewing, which reveals 10 % denser firn inside compared to outside the channel. The denser firn in the ice-shelf channel should be accounted for when using the hydrostatic ice thickness for determining basal melt rates. The radar method presented here is robust and can easily be adapted to different radar frequencies and data-acquisition geometries.

  11. Practical applications of small-angle neutron scattering.

    PubMed

    Hollamby, Martin J

    2013-07-14

    Recent improvements in beam-line accessibility and technology have led to small-angle neutron scattering (SANS) becoming more frequently applied to materials problems. SANS has been used to study the assembly, dispersion, alignment and mixing of nanoscale condensed matter, as well as to characterise the internal structure of organic thin films, porous structures and inclusions within steel. Using time-resolved SANS, growth mechanisms in materials systems and soft matter phase transitions can also be explored. This review is intended for newcomers to SANS as well as experts. Therefore, the basic knowledge required for its use is first summarised. After this introduction, various examples are given of the types of soft and hard matter that have been studied by SANS. The information that can be extracted from the data is highlighted, alongside the methods used to obtain it. In addition to presenting the findings, explanations are provided on how the SANS measurements were optimised, such as the use of contrast variation to highlight specific parts of a structure. Emphasis is placed on the use of complementary techniques to improve data quality (e.g. using other scattering methods) and the accuracy of data analysis (e.g. using microscopy to separately determine shape and size). This is done with a view to providing guidance on how best to design and analyse future SANS measurements on materials not listed below. PMID:23552189

  12. Small Angle X-ray Scattering for Nanoparticle Research.

    PubMed

    Li, Tao; Senesi, Andrew J; Lee, Byeongdu

    2016-09-28

    X-ray scattering is a structural characterization tool that has impacted diverse fields of study. It is unique in its ability to examine materials in real time and under realistic sample environments, enabling researchers to understand morphology at nanometer and angstrom length scales using complementary small and wide angle X-ray scattering (SAXS, WAXS), respectively. Herein, we focus on the use of SAXS to examine nanoscale particulate systems. We provide a theoretical foundation for X-ray scattering, considering both form factor and structure factor, as well as the use of correlation functions, which may be used to determine a particle's size, size distribution, shape, and organization into hierarchical structures. The theory is expanded upon with contemporary use cases. Both transmission and reflection (grazing incidence) geometries are addressed, as well as the combination of SAXS with other X-ray and non-X-ray characterization tools. We conclude with an examination of several key areas of research where X-ray scattering has played a pivotal role, including in situ nanoparticle synthesis, nanoparticle assembly, and operando studies of catalysts and energy storage materials. Throughout this review we highlight the unique capabilities of X-ray scattering for structural characterization of materials in their native environment.

  13. Small angle x-ray scattering with edge-illumination

    PubMed Central

    Modregger, Peter; Cremona, Tiziana P.; Benarafa, Charaf; Schittny, Johannes C.; Olivo, Alessandro; Endrizzi, Marco

    2016-01-01

    Sensitivity to sub-pixel sample features has been demonstrated as a valuable capability of phase contrast x-ray imaging. Here, we report on a method to obtain angular-resolved small angle x-ray scattering distributions with edge-illumination- based imaging utilizing incoherent illumination from an x-ray tube. Our approach provides both the three established image modalities (absorption, differential phase and scatter strength), plus a number of additional contrasts related to unresolved sample features. The complementarity of these contrasts is experimentally validated by using different materials in powder form. As a significant application example we show that the extended complementary contrasts could allow the diagnosis of pulmonary emphysema in a murine model. In support of this, we demonstrate that the properties of the retrieved scattering distributions are consistent with the expectation of increased feature sizes related to pulmonary emphysema. Combined with the simplicity of implementation of edge-illumination, these findings suggest a high potential for exploiting extended sub-pixel contrasts in the diagnosis of lung diseases and beyond. PMID:27491917

  14. New Very Small Angle Neutron Scattering (VSANS) Instrument

    NASA Astrophysics Data System (ADS)

    Van Every, E.; Deyhim, A.; Kulesza, J.

    2016-09-01

    The design of a new Very Small Angle Neutron Scattering (VSANS) Instrument for use in National Institute of Standards And Technology (NIST) will be discussed. This instrument is similar to a shorter instrument we designed and delivered to ANSTO in Australia called the Bilby SANS instrument. The NIST VSANS and the ANSTO Bilby SANS instruments have very similar dimensions for length and diameter and have similar requirements for internal detector motion, top access port, walkway supports, and ports; however, the Bilby SANS instrument vacuum requirement was lower (7.5×10-5 Torr) and the entire (60,000 pound) vessel was required to move 1.5 meters on external rails with a repeatability of 100 um, which ADC achieved. The NIST VSANS length is 24 meter, internal diameter 2.3 meter with three internal carriages. The NIST VSANS instrument, which covers the usual SANS range will also allow configuration to cover the range between q ∼⃒ 10-4 A-1 to 10-3 A-1 with a sample beam current of (104 neutrons/s). The key requirements are a second position-sensitive detector system having a 1 mm pixel size and a longer sample-detector flight path of 20 m (i.e., a 40 m instrument).

  15. Magnetic small-angle neutron scattering of bulk ferromagnets.

    PubMed

    Michels, Andreas

    2014-09-24

    We summarize recent theoretical and experimental work in the field of magnetic small-angle neutron scattering (SANS) of bulk ferromagnets. The response of the magnetization to spatially inhomogeneous magnetic anisotropy and magnetostatic stray fields is computed using linearized micromagnetic theory, and the ensuing spin-misalignment SANS is deduced. Analysis of experimental magnetic-field-dependent SANS data of various nanocrystalline ferromagnets corroborates the usefulness of the approach, which provides important quantitative information on the magnetic-interaction parameters such as the exchange-stiffness constant, the mean magnetic anisotropy field, and the mean magnetostatic field due to jumps ΔM of the magnetization at internal interfaces. Besides the value of the applied magnetic field, it turns out to be the ratio of the magnetic anisotropy field Hp to ΔM, which determines the properties of the magnetic SANS cross-section of bulk ferromagnets; specifically, the angular anisotropy on a two-dimensional detector, the asymptotic power-law exponent, and the characteristic decay length of spin-misalignment fluctuations. For the two most often employed scattering geometries where the externally applied magnetic field H0 is either perpendicular or parallel to the wave vector k0 of the incoming neutron beam, we provide a compilation of the various unpolarized, half-polarized (SANSPOL), and uniaxial fully-polarized (POLARIS) SANS cross-sections of magnetic materials. PMID:25180625

  16. Ultra-small-angle neutron scattering with azimuthal asymmetry

    PubMed Central

    Gu, X.; Mildner, D. F. R.

    2016-01-01

    Small-angle neutron scattering (SANS) measurements from thin sections of rock samples such as shales demand as great a scattering vector range as possible because the pores cover a wide range of sizes. The limitation of the scattering vector range for pinhole SANS requires slit-smeared ultra-SANS (USANS) measurements that need to be converted to pinhole geometry. The desmearing algorithm is only successful for azimuthally symmetric data. Scattering from samples cut parallel to the plane of bedding is symmetric, exhibiting circular contours on a two-dimensional detector. Samples cut perpendicular to the bedding show elliptically dependent contours with the long axis corresponding to the normal to the bedding plane. A method is given for converting such asymmetric data collected on a double-crystal diffractometer for concatenation with the usual pinhole-geometry SANS data. The aspect ratio from the SANS data is used to modify the slit-smeared USANS data to produce quasi-symmetric contours. Rotation of the sample about the incident beam may result in symmetric data but cannot extract the same information as obtained from pinhole geometry. PMID:27275140

  17. Small angle elastic scattering of protons off of spinless nuclei

    SciTech Connect

    Ling, A.G.

    1988-07-01

    Elastic differential cross sections and analyzing powers for 800 MeV protons incident on /sup 12/C, /sup 40/Ca, and /sup 208/Pb in the momentum transfer range 20 MeV/c < q < 130 MeV/c have been measured. The data was taken with the High Resolution Spectrometer (HRS) at the Los Alamos Meson Physics Facility. Special delay-line drift chambers with dead regions for the beam to pass through them were used to obtain the data. Through the interference of the Coulomb and nuclear contributions to the differential cross section in the small angle region, the ratio of the real to imaginary part of the forward nuclear amplitude ..cap alpha../sub n/(0) = Ref/sub n/(0)/Imf/sub n/(0) is extracted. The importance of knowing this quantity at lower energies in order to study the differences between relativistic and non-relativistic scattering theories is discussed. 130 refs., 60 figs., 12 tabs.

  18. Small angle x-ray scattering with edge-illumination

    NASA Astrophysics Data System (ADS)

    Modregger, Peter; Cremona, Tiziana P.; Benarafa, Charaf; Schittny, Johannes C.; Olivo, Alessandro; Endrizzi, Marco

    2016-08-01

    Sensitivity to sub-pixel sample features has been demonstrated as a valuable capability of phase contrast x-ray imaging. Here, we report on a method to obtain angular-resolved small angle x-ray scattering distributions with edge-illumination- based imaging utilizing incoherent illumination from an x-ray tube. Our approach provides both the three established image modalities (absorption, differential phase and scatter strength), plus a number of additional contrasts related to unresolved sample features. The complementarity of these contrasts is experimentally validated by using different materials in powder form. As a significant application example we show that the extended complementary contrasts could allow the diagnosis of pulmonary emphysema in a murine model. In support of this, we demonstrate that the properties of the retrieved scattering distributions are consistent with the expectation of increased feature sizes related to pulmonary emphysema. Combined with the simplicity of implementation of edge-illumination, these findings suggest a high potential for exploiting extended sub-pixel contrasts in the diagnosis of lung diseases and beyond.

  19. Characterization of photosynthetic supramolecular assemblies using small angle neutron scattering

    SciTech Connect

    Tiede, D.M.; Marone, P.; Wagner, A.M.; Thiyagarajan, P.

    1995-12-31

    We are using small angle neutron scattering (SANS) to resolve structural features of supramolecular assemblies of photosynthetic proteins in liquid and frozen solutions. SANS resolves the size, shape, and structural homogeneity of macromolecular assemblies in samples identical to those used for spectroscopic assays of photosynthetic function. Likely molecular structures of the supramolecular assemblies can be identified by comparing experimental scattering data with scattering profiles calculated for model supramolecular assemblies built from crystal structures of the individual proteins. SANS studies of the Rhodobacter sphaeroides reaction center, RC, presented here, show that the detergent solubilized RC exists in a variety of monomeric and aggregation states. The distribution between monomer and aggregate was found to depend strongly upon detergent, temperature and nature of additives, such as ethylene glycol used for low temperature spectroscopy and polyethylene glycol used for crystallization. Likely aggregate structures are being identified by fitting the experimental scattering profiles with those calculated for model aggregates built-up using the RC crystal structure. This work establishes the foundation for using SANS to identify intermediates in the RC crystallization pathways, and for determining likely structures of complexes formed between the RC and its physiological reaction partners, cytochrome c, and the LHI antenna complex.

  20. Small angle x-ray scattering with edge-illumination.

    PubMed

    Modregger, Peter; Cremona, Tiziana P; Benarafa, Charaf; Schittny, Johannes C; Olivo, Alessandro; Endrizzi, Marco

    2016-01-01

    Sensitivity to sub-pixel sample features has been demonstrated as a valuable capability of phase contrast x-ray imaging. Here, we report on a method to obtain angular-resolved small angle x-ray scattering distributions with edge-illumination- based imaging utilizing incoherent illumination from an x-ray tube. Our approach provides both the three established image modalities (absorption, differential phase and scatter strength), plus a number of additional contrasts related to unresolved sample features. The complementarity of these contrasts is experimentally validated by using different materials in powder form. As a significant application example we show that the extended complementary contrasts could allow the diagnosis of pulmonary emphysema in a murine model. In support of this, we demonstrate that the properties of the retrieved scattering distributions are consistent with the expectation of increased feature sizes related to pulmonary emphysema. Combined with the simplicity of implementation of edge-illumination, these findings suggest a high potential for exploiting extended sub-pixel contrasts in the diagnosis of lung diseases and beyond. PMID:27491917

  1. Physical characteristics of human transferrin from small angle neutron scattering.

    PubMed Central

    Martel, P; Kim, S M; Powell, B M

    1980-01-01

    The technique of small angle neutron scattering has been used to determine the molecular shape, the volume, and the molecular weight of pooled human transferrin in an aqueous solution isotonic with blood. Analysis of the measurements assuming a spheroidal molecular shape indicates that an oblate spheroid with semi-axes of length 46.6 +/- 1.4, 46.6 +/- 1.4 and 15.8 +/- 3.8 A, and a molecular volume of (144 +/- 45) X 10(3) A3 is the best simple approximation to the shape of the transferrin molecule. The radius of gyration, Rg, determined from a Guinier plot is 30.25 +/- 0.49 A, in agreement with Rg calculated for the oblate spheroidal shape. The molecular weight is determined to be (75 +/- 5) X 10(3). The shape-independent molecular volume is found to be (98 +/- 10) X 10(3) A3. The difference in the two volumes suggests that transferrin is not a uniform spheroid but may have a more complex shape. PMID:7260293

  2. Cryocup - Compact spherical neutron polarimetry device for small angle measurement

    NASA Astrophysics Data System (ADS)

    Wang, Tianhao

    In my thesis I describe my research work of developing a compact device for Spherical Neutron Polarimetry (SNP) measurements at small neutron scattering angles. The thesis first introduced the purpose of this research project, which is developing an easy to use and maintain version of an advanced neutron experiment technique (SNP). After the introduction, the design principle and construction detail of the prototype device is demonstrated. The design principle is based on our finite element simulation of the device's magnetic field profile, and is later verified by the performance test experiment. The prototype device is tested at the SESAME neutron beamline at Indiana University and the HB-2D beamline at Oak Ridge National laboratory. The performance test data are analyzed and proof that the design is successful and the prototype is capable of perform accurate SNP measurement. Based on the test result, the prototype device is utilized to perform SNP measurement on two types of magnetic film sample: Permalloy and Metglas. Combined with other characterization method such as SQUID and MFM, I study the magnetization of these two samples both at zero magnetic field environment and in external field. The SNP data provided by the prototype device is discussed in the thesis and provide detailed information about the magnetization, which is also not accessible through other method. In the end, the possible improvement and the future application of the device is discussed.

  3. Practical applications of small-angle neutron scattering.

    PubMed

    Hollamby, Martin J

    2013-07-14

    Recent improvements in beam-line accessibility and technology have led to small-angle neutron scattering (SANS) becoming more frequently applied to materials problems. SANS has been used to study the assembly, dispersion, alignment and mixing of nanoscale condensed matter, as well as to characterise the internal structure of organic thin films, porous structures and inclusions within steel. Using time-resolved SANS, growth mechanisms in materials systems and soft matter phase transitions can also be explored. This review is intended for newcomers to SANS as well as experts. Therefore, the basic knowledge required for its use is first summarised. After this introduction, various examples are given of the types of soft and hard matter that have been studied by SANS. The information that can be extracted from the data is highlighted, alongside the methods used to obtain it. In addition to presenting the findings, explanations are provided on how the SANS measurements were optimised, such as the use of contrast variation to highlight specific parts of a structure. Emphasis is placed on the use of complementary techniques to improve data quality (e.g. using other scattering methods) and the accuracy of data analysis (e.g. using microscopy to separately determine shape and size). This is done with a view to providing guidance on how best to design and analyse future SANS measurements on materials not listed below.

  4. Comparative analysis of the nucleosome structure of cell nuclei by small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Isaev-Ivanov, V. V.; Lebedev, D. V.; Lauter, H.; Pantina, R. A.; Kuklin, A. I.; Islamov, A. Kh.; Filatov, M. V.

    2010-05-01

    The nucleosome structure in native nuclei of normal (chicken erythrocyte and rat leukocyte nuclei) and anomalously proliferating (the human cervical adenocarcinoma cell line HeLa and the Chinese hamster fibroblast cell line A238) cells has been investigated using small-angle neutron scattering. The experimental results obtained allow one to make the inference that the parameters of the nucleosome structure for the chicken erythrocyte and rat leukocyte nuclei (on average over the nucleus) are close to the universally accepted values and that the distance distribution function is bimodal. The bimodality of the distance distribution function reflects a narrow distribution of distances between nucleosomes (on average over the nucleus) at the fibril level of the chromatin organization. The histone core of the nucleosome structure in the nuclei of the HeLa and A238 cells (on average over the nucleus) is considerably less compact than that in the chicken erythrocyte and rat leukocyte nuclei, and the distance distribution function does not exhibit indications of the bimodality.

  5. Counterion Distribution Around Protein-SNAs probed by Small-angle X-ray scattering

    NASA Astrophysics Data System (ADS)

    Krishnamoorthy, Kurinji; Bedzyk, Michael; Kewalramani, Sumit; Moreau, Liane; Mirkin, Chad

    Protein-DNA conjugates couple the advanced cell transfection capabilities of spherical DNA architecture and the biocompatible enzymatic activity of a protein core to potentially create therapeutic agents with dual functionality. An understanding of their stabilizing ionic environment is crucial to better understand and predict their properties. Here, we use Small-angle X-ray scattering techniques to decipher the structure of the counterion cloud surrounding these DNA coated nanoparticles. Through the use of anomalous scattering techniques we have mapped the local concentrations of Rb+ ions in the region around the Protein-DNA constructs. These results are further corroborated with simulations using a geometric model for the excess charge density as function of radial distance from the protein core. Further, we investigate the influence of solution ionic strength on the structure of the DNA corona and demonstrate a reduction in the extension of the DNA corona with increasing concentration of NaCl in solution for the case of both single and double stranded DNA shells. Our work reveals the distribution of counterions in the vicinity of Protein-DNA conjugates and decouples the effect of solution ionic strength on the thickness of the DNA layer.

  6. Automated small tilt-angle measurement using Lau interferometry

    SciTech Connect

    Prakash, Shashi; Singh, Sumitra; Rana, Santosh

    2005-10-01

    A technique for a tilt-angle measurement of reflecting objects based on the Lau interferometry coupled with the moire readout has been proposed. A white-light incoherent source illuminates a set of two gratings, resulting in the generation of the Fresnel image due to the Lau effect. The Fresnel image is projected onto a reflecting object. The image reflected from the object is superimposed onto an identical grating, which results in the formation of a moire fringe pattern. The inclination angle of moire fringes is a function of tilt angle of the object. Theory and experimental arrangement of the proposed technique is presented and results of the investigation are reported.

  7. Small roll angle measurement based on auto-collimation and moiré fringe

    NASA Astrophysics Data System (ADS)

    Bai, Xu-guang; Cai, Sheng; Qiao, Yan-feng; Dai, Ming

    2009-11-01

    A novel method for small roll angle measurement based on auto-collimation and moiré fringe is presented. A right-angle prism is used as an indicator of small roll angle around the optical axis, and a CCD is used to collect moiré fringes that are generated by scale grating image which is reflected by prism and index grating. Any small roll angle of the prism will change the include angle of the grating pair and meanwhile induce a change in the moiré fringe period. The relationship between roll angle and period of moiré fringes is established. The period data is obtained by image processing. The experimental result certifies that the principle of small angle measurement method based on auto-collimation and moiré fringe is correct and feasible. The measuring error is smaller than 0.2" within 7' range compared with 0.2" autocollimator.

  8. Predictability of the appearance of anomalous waves at sufficiently small Benjamin-Feir indices

    NASA Astrophysics Data System (ADS)

    Ruban, V. P.

    2016-05-01

    The numerical simulation of the nonlinear dynamics of random sea waves at sufficiently small Benjamin-Feir indices and its comparison with the linear dynamics (at the coincidence of spatial Fourier harmonics near a spectral peak at a certain time t p) indicate that the appearance of a rogue wave can be predicted in advance. If the linear approximation shows the presence of a sufficiently extensive and/or high group of waves in the near future after t p, an anomalous wave is almost necessarily formed in the nonlinear model. The interval of reliable forecasting covers several hundred wave periods, which can be quite sufficient in practice for, e.g., avoiding the meeting of a ship with a giant wave.

  9. Anomalous uptake and circulatory characteristics of the plant-based small RNA MIR2911

    PubMed Central

    Yang, Jian; Hotz, Tremearne; Broadnax, LaCassidy; Yarmarkovich, Mark; Elbaz-Younes, Ismail; Hirschi, Kendal D.

    2016-01-01

    Inconsistent detection of plant-based dietary small RNAs in circulation has thwarted the use of dietary RNA therapeutics. Here we demonstrate mice consuming diets rich in vegetables displayed enhanced serum levels of the plant specific small RNA MIR2911. Differential centrifugation, size-exclusion chromatography, and proteinase K treatment of plant extracts suggest this RNA resides within a proteinase K-sensitive complex. Plant derived MIR2911 was more bioavailable than the synthetic RNA. Furthermore, MIR2911 exhibited unusual digestive stability compared with other synthetic plant microRNAs. The characteristics of circulating MIR2911 were also unusual as it was not associated with exosomes and fractionated as a soluble complex that was insensitive to proteinase K treatment, consistent with MIR2911 being stabilized by modifications conferred by the host. These results indicate that intrinsic stability and plant-based modifications orchestrate consumer uptake of this anomalous plant based small RNA and invite revisiting plant-based microRNA therapeutic approaches. PMID:27251858

  10. Versatile wide angle diffraction setup for simultaneous wide and small angle x-ray scattering measurements with synchrotron radiation

    SciTech Connect

    Rueda, D.R.; Garcia-Gutierrez, M.C.; Nogales, A.; Capitan, M.J.; Ezquerra, T.A.; Labrador, A.; Fraga, E.; Beltran, D.; Juanhuix, J.; Herranz, J.F.; Bordas, J.

    2006-03-15

    Here we present a novel, simple, and versatile experimental setup aimed to perform wide angle x-ray scattering (WAXS) measurements alone or in simultaneous combination with small angle x-ray scattering measurements. The design of the WAXS goniometer allows one to obtain high resolution diffraction patterns in a broad angular range. The setup can incorporate a hot stage in order to evaluate temperature resolved experiments. The performance of the equipment has been verified in the BM16 beam line of the European Synchrotron Radiation Facility with different well known samples such as alumina, isotropic film of high density polyethylene (HDPE), and oriented HPDE fiber.

  11. Asymmetric Domain Walls of Small Angle in Soft Ferromagnetic Films

    NASA Astrophysics Data System (ADS)

    Döring, Lukas; Ignat, Radu

    2016-05-01

    We focus on a special type of domain wall appearing in the Landau-Lifshitz theory for soft ferromagnetic films. These domain walls are divergence-free S^2-valued transition layers that connect two directions {m_θ^± in S^2} (differing by an angle {2θ}) and minimize the Dirichlet energy. Our main result is the rigorous derivation of the asymptotic structure and energy of such "asymmetric" domain walls in the limit {θ downarrow 0}. As an application, we deduce that a supercritical bifurcation causes the transition from symmetric to asymmetric walls in the full micromagnetic model.

  12. A new approach to quantification of metamorphism using ultra-small and small angle neutron scattering.

    SciTech Connect

    Anovitz, Lawrence {Larry} M; Lynn, Gary W; Cole, David R

    2009-12-01

    In this paper we report the results of a study using small angle and ultra-small angle neutron scattering techniques (SANS and USANS) to examine the evolution of carbonates during contact metamorphism. Data were obtained from samples collected along two transects in the metamorphosed Hueco limestone at the Marble Canyon, Texas, contact aureole. These samples were collected from the igneous contact out to {approx}1700 m. Scattering curves obtained from these samples show mass fractal behavior at low scattering vectors, and surface fractal behavior at high scattering vectors. Significant changes are observed in the surface and mass fractal dimensions as well as the correlation lengths (pore and grain sizes), surface area to volume ratio and surface Gibbs Free energy as a function of distance, including regions of the aureole outside the range of classic metamorphic petrology. A change from mass-fractal to non-fractal behavior is observed at larger scales near the outer boundary of the aureole that implies significant reorganization of pore distributions early in the metamorphic history. Surface fractal results suggest significant smoothing of grain boundaries, coupled with changes in pore sizes. A section of the scattering curve with a slope less than -4 appears at low-Q in metamorphosed samples, which is not present in unmetamorphosed samples. A strong spike in the surface area to volume ratio is observed in rocks near the mapped metamorphic limit, which is associated with reaction of small amounts of organic material to graphite. It may also represent an increase in pore volume or permeability, suggesting that a high permeability zone forms at the boundary of the aureole and moves outwards as metamorphism progresses. Neutron scattering data also correlate well with transmission electron microscopic (TEM) observations, which show formation of micro- and nanopores and microfractures during metamorphism. The scattering data are, however, quantifiable for a bulk rock

  13. A new approach to quantification of metamorphism using ultra-small and small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Anovitz, Lawrence M.; Lynn, Gary W.; Cole, David R.; Rother, Gernot; Allard, Lawrence F.; Hamilton, William A.; Porcar, Lionel; Kim, Man-Ho

    2009-12-01

    In this paper we report the results of a study using small angle and ultra-small angle neutron scattering techniques (SANS and USANS) to examine the evolution of carbonates during contact metamorphism. Data were obtained from samples collected along two transects in the metamorphosed Hueco limestone at the Marble Canyon, Texas, contact aureole. These samples were collected from the igneous contact out to ˜1700 m. Scattering curves obtained from these samples show mass fractal behavior at low scattering vectors, and surface fractal behavior at high scattering vectors. Significant changes are observed in the surface and mass fractal dimensions as well as the correlation lengths (pore and grain sizes), surface area to volume ratio and surface Gibbs Free energy as a function of distance, including regions of the aureole outside the range of classic metamorphic petrology. A change from mass-fractal to non-fractal behavior is observed at larger scales near the outer boundary of the aureole that implies significant reorganization of pore distributions early in the metamorphic history. Surface fractal results suggest significant smoothing of grain boundaries, coupled with changes in pore sizes. A section of the scattering curve with a slope less than -4 appears at low- Q in metamorphosed samples, which is not present in unmetamorphosed samples. A strong spike in the surface area to volume ratio is observed in rocks near the mapped metamorphic limit, which is associated with reaction of small amounts of organic material to graphite. It may also represent an increase in pore volume or permeability, suggesting that a high permeability zone forms at the boundary of the aureole and moves outwards as metamorphism progresses. Neutron scattering data also correlate well with transmission electron microscopic (TEM) observations, which show formation of micro- and nanopores and microfractures during metamorphism. The scattering data are, however, quantifiable for a bulk rock in a

  14. Mapping the local nanostructure inside a specimen by tomographic small-angle x-ray scattering

    SciTech Connect

    Schroer, C.G.; Kuhlmann, M.; Roth, S.V.; Gehrke, R.; Stribeck, N.; Almendarez-Camarillo, A.; Lengeler, B.

    2006-04-17

    Small-angle x-ray scattering is combined with scanning microtomography to reconstruct the small-angle diffraction pattern in the direction of the tomographic rotation axis at each location on a virtual section through a specimen. These data yield information about the local nanoscale structure of the sample. With rotational symmetry present in the diffraction patterns, e.g., for isotropic or fiber-textured scatterers, the full reciprocal space information in the small-angle scattering regime can be reconstructed at each location inside the specimen. The method is illustrated investigating a polymer rod made by injection molding.

  15. Simulation-guided optimization of small-angle analyzer geometry in the neutron backscattering spectrometer SPHERES.

    PubMed

    Wuttke, Joachim; Zamponi, Michaela

    2013-11-01

    The resolution of neutron backscattering spectrometers deteriorates at small scattering angles where analyzers deviate from exact backscattering. By reducing the azimuth angle range of the analyzers, the resolution can be improved with little loss of peak intensity. Measurements at the spectrometer SPHERES are in excellent agreement with simulations, which proves the dominance of geometric effects.

  16. Simulation-guided optimization of small-angle analyzer geometry in the neutron backscattering spectrometer SPHERES

    SciTech Connect

    Wuttke, Joachim; Zamponi, Michaela

    2013-11-15

    The resolution of neutron backscattering spectrometers deteriorates at small scattering angles where analyzers deviate from exact backscattering. By reducing the azimuth angle range of the analyzers, the resolution can be improved with little loss of peak intensity. Measurements at the spectrometer SPHERES are in excellent agreement with simulations, which proves the dominance of geometric effects.

  17. Small-angle x-ray scattering/diffraction system for studies of biological and other materials at the Stanford Synchrotron Radiation Laboratorya)

    NASA Astrophysics Data System (ADS)

    Wakatsuki, S.; Hodgson, K. O.; Eliezer, D.; Rice, M.; Hubbard, S.; Gillis, N.; Doniach, S.; Spann, U.

    1992-02-01

    A versatile small-angle x-ray diffraction/scattering system has been developed at Stanford Synchrotron Radiation Laboratory for studies of biological and other materials. The system includes two sets of collimation slits separated by an ionization chamber, a sample holder cooled by a circulation bath, a vacuum/He scattering path after the sample holder and a detector, either a linear one-dimensional position-sensitive proportional counter or a position-sensitive quadrant detector. Data aquisition is controlled by a VAXstation through a CAMAC interface. Menu-driven data acquisition and on-line analysis software has been developed. The system can be used to collect small- to intermediate-angle x-ray scattering and diffraction data. Monochromatic, anomalous, and time-resolved scattering/diffraction experiments are possible. A time-resolved spectrophotometer using photodiode arrays has also been developed for simultaneous measurements of optical absorption spectra and x-ray scattering/diffraction.

  18. Small-angle x-ray scattering/diffraction system for studies of biological and other materials at the Stanford Synchrotron Radiation Laboratory (abstract)a)

    NASA Astrophysics Data System (ADS)

    Wakatsuki, S.; Hodgson, K. O.; Eliezer, D.; Rice, M.; Hubbard, S.; Gillis, N.; Doniach, S.; Spann, U.

    1992-01-01

    A versatile small-angle x-ray diffraction/scattering system has been developed at Stanford Synchrotron Radiation Laboratory for studies of biological and other materials. The system includes two sets of collimation slits separated by an ionization chamber, a sample holder cooled by a circulation bath, a vacuum/He scattering path after the sample holder and a detector, either a linear one-dimensional position-sensitive proportional counter or a position-sensitive quadrant detector. Data aquisition is controlled by a VAXstation through a CAMAC interface. Menu-driven data acquisition and on-line analysis software has been developed. The system can be used to collect small- to intermediate-angle x-ray scattering and diffraction data. Monochromatic, anomalous, and time-resolved diffraction/scattering experiments are possible. A time-resolved spectrophotometer using photodiode arrays has also been developed for simultaneous measurements of optical absorption spectra and x-ray scattering/diffraction.

  19. Accurate small and wide angle x-ray scattering profiles from atomic models of proteins and nucleic acids

    SciTech Connect

    Nguyen, Hung T.; Pabit, Suzette A.; Meisburger, Steve P.; Pollack, Lois; Case, David A.

    2014-12-14

    A new method is introduced to compute X-ray solution scattering profiles from atomic models of macromolecules. The three-dimensional version of the Reference Interaction Site Model (RISM) from liquid-state statistical mechanics is employed to compute the solvent distribution around the solute, including both water and ions. X-ray scattering profiles are computed from this distribution together with the solute geometry. We describe an efficient procedure for performing this calculation employing a Lebedev grid for the angular averaging. The intensity profiles (which involve no adjustable parameters) match experiment and molecular dynamics simulations up to wide angle for two proteins (lysozyme and myoglobin) in water, as well as the small-angle profiles for a dozen biomolecules taken from the BioIsis.net database. The RISM model is especially well-suited for studies of nucleic acids in salt solution. Use of fiber-diffraction models for the structure of duplex DNA in solution yields close agreement with the observed scattering profiles in both the small and wide angle scattering (SAXS and WAXS) regimes. In addition, computed profiles of anomalous SAXS signals (for Rb{sup +} and Sr{sup 2+}) emphasize the ionic contribution to scattering and are in reasonable agreement with experiment. In cases where an absolute calibration of the experimental data at q = 0 is available, one can extract a count of the excess number of waters and ions; computed values depend on the closure that is assumed in the solution of the Ornstein–Zernike equations, with results from the Kovalenko–Hirata closure being closest to experiment for the cases studied here.

  20. Accurate small and wide angle x-ray scattering profiles from atomic models of proteins and nucleic acids.

    PubMed

    Nguyen, Hung T; Pabit, Suzette A; Meisburger, Steve P; Pollack, Lois; Case, David A

    2014-12-14

    A new method is introduced to compute X-ray solution scattering profiles from atomic models of macromolecules. The three-dimensional version of the Reference Interaction Site Model (RISM) from liquid-state statistical mechanics is employed to compute the solvent distribution around the solute, including both water and ions. X-ray scattering profiles are computed from this distribution together with the solute geometry. We describe an efficient procedure for performing this calculation employing a Lebedev grid for the angular averaging. The intensity profiles (which involve no adjustable parameters) match experiment and molecular dynamics simulations up to wide angle for two proteins (lysozyme and myoglobin) in water, as well as the small-angle profiles for a dozen biomolecules taken from the BioIsis.net database. The RISM model is especially well-suited for studies of nucleic acids in salt solution. Use of fiber-diffraction models for the structure of duplex DNA in solution yields close agreement with the observed scattering profiles in both the small and wide angle scattering (SAXS and WAXS) regimes. In addition, computed profiles of anomalous SAXS signals (for Rb(+) and Sr(2+)) emphasize the ionic contribution to scattering and are in reasonable agreement with experiment. In cases where an absolute calibration of the experimental data at q = 0 is available, one can extract a count of the excess number of waters and ions; computed values depend on the closure that is assumed in the solution of the Ornstein-Zernike equations, with results from the Kovalenko-Hirata closure being closest to experiment for the cases studied here.

  1. Accurate small and wide angle x-ray scattering profiles from atomic models of proteins and nucleic acids

    NASA Astrophysics Data System (ADS)

    Nguyen, Hung T.; Pabit, Suzette A.; Meisburger, Steve P.; Pollack, Lois; Case, David A.

    2014-12-01

    A new method is introduced to compute X-ray solution scattering profiles from atomic models of macromolecules. The three-dimensional version of the Reference Interaction Site Model (RISM) from liquid-state statistical mechanics is employed to compute the solvent distribution around the solute, including both water and ions. X-ray scattering profiles are computed from this distribution together with the solute geometry. We describe an efficient procedure for performing this calculation employing a Lebedev grid for the angular averaging. The intensity profiles (which involve no adjustable parameters) match experiment and molecular dynamics simulations up to wide angle for two proteins (lysozyme and myoglobin) in water, as well as the small-angle profiles for a dozen biomolecules taken from the BioIsis.net database. The RISM model is especially well-suited for studies of nucleic acids in salt solution. Use of fiber-diffraction models for the structure of duplex DNA in solution yields close agreement with the observed scattering profiles in both the small and wide angle scattering (SAXS and WAXS) regimes. In addition, computed profiles of anomalous SAXS signals (for Rb+ and Sr2+) emphasize the ionic contribution to scattering and are in reasonable agreement with experiment. In cases where an absolute calibration of the experimental data at q = 0 is available, one can extract a count of the excess number of waters and ions; computed values depend on the closure that is assumed in the solution of the Ornstein-Zernike equations, with results from the Kovalenko-Hirata closure being closest to experiment for the cases studied here.

  2. Small-angle approximation to the transfer of narrow laser beams in anisotropic scattering media

    NASA Technical Reports Server (NTRS)

    Box, M. A.; Deepak, A.

    1981-01-01

    The broadening and the signal power detected of a laser beam traversing an anisotropic scattering medium were examined using the small-angle approximation to the radiative transfer equation in which photons suffering large-angle deflections are neglected. To obtain tractable answers, simple Gaussian and non-Gaussian functions for the scattering phase functions are assumed. Two other approximate approaches employed in the field to further simplify the small-angle approximation solutions are described, and the results obtained by one of them are compared with those obtained using small-angle approximation. An exact method for obtaining the contribution of each higher order scattering to the radiance field is examined but no results are presented.

  3. Measuring the distribution of cellulose microfibril angles in primary cell walls by small angle X-ray scattering

    PubMed Central

    2014-01-01

    Background X-ray scattering is a well-established method for measuring cellulose microfibril angles in secondary cell walls. However, little data is available on the much thinner primary cell walls. Here, we show that microfibril orientation distributions can be determined by small angle X-ray scattering (SAXS) even in primary cell walls. The technique offers a number of advantages: samples can be analyzed in the native hydrated state without any preparation which minimizes the risk of artifacts and allows for fast data acquisition. The method provides data averaged over a specimen region, determined by the size of the used X-ray beam and, thus, yields the microfibril orientation distribution within this region. Results Cellulose microfibril orientation distributions were obtained for single cells of the alga Chara corallina, as well as for the multicellular hypocotyl of Arabidopsis thaliana. In both, Chara and Arabidopsis, distributions with a broad scattering around mean microfibril angles of approximately 0° and 90° towards the longitudinal axis of the cells were found. Conclusions With SAXS, the structure of primary cell walls can be analysed in their native state and new insights into the cellulose microfibril orientation of primary cell walls can be gained. The data shows that SAXS can serve as a valuable tool for the analysis of cellulose microfibril orientation in primary cell walls and, in consequence, add to the understanding of its mechanical behaviour and the intriguing mechanisms behind cell growth. PMID:25170343

  4. Small-angle Compton Scattering to Determine the Depth of a Radioactive Source in Matter

    SciTech Connect

    Oberer, R. B.; Gunn, C. A.; Chiang, L. G.; Valiga, R. E.; Cantrell, J. A.

    2011-04-01

    A gamma-ray peak in a spectrum is often accompanied by a discontinuity in the Compton continuum at the peak. The Compton continuum results from Compton scattering in the detector. The discontinuity at a peak results from small-angle Compton scattering by the gamma rays in matter situated directly between the gamma-ray source and the detector. The magnitude of this discontinuity with respect to the gamma-ray peak is therefore an indicator of the amount of material or shielding between the gamma-ray source and the detector. This small-angle scattering was used to determine the depth of highly-enriched uranium (HEU) solution standards in a concrete floor mockup. The empirical results of the use of this small-angle scattering discontinuity in a concrete floor experiment will be described. A Monte Carlo calculation of the experiment will also be described. In addition, the depth determined from small-angle scattering was used in conjunction with differential attenuation to more accurately measure the uranium content of the mockup. Following these empirical results, the theory of small-angle scattering will be discussed. The magnitude of the discontinuity compared to the peak count rate is directly related to the depth of the gamma-ray source in matter. This relation can be described by relatively simple mathematical expressions. This is the first instance that we are aware of in which the small-angle Compton scattering has been used to determine the depth of a radioactive source. Furthermore this is the first development of the theoretical expressions for the magnitude of the small-angle scattering discontinuity.

  5. Using small angle solution scattering data in Xplor-NIH structure calculations.

    PubMed

    Schwieters, Charles D; Clore, G Marius

    2014-07-01

    This contribution describes the use of small and wide angle X-ray and small angle neutron scattering for biomolecular structure calculation using the program Xplor-NIH, both with and without NMR data. The current algorithms used for calculating scattering curves are described, and the use of scattering data as a structural restraint is given concrete form as a fragment of an Xplor-NIH structure calculation script. We review five examples of the use of scattering data in structure calculation, including the treatment of single domain proteins, nucleic acids, structure determination of large proteins, and the use of ensemble representations to characterize small and large amplitude motions.

  6. Reflection of X-rays from a rough surface at extremely small grazing angles.

    PubMed

    Wen, Mingwu; Kozhevnikov, Igor V; Wang, Zhanshan

    2015-09-21

    Peculiarities of X-ray diffraction from a rough surface at an extremely small grazing angle of an incident beam are theoretically studied. The interrelation of four diffraction channels (coherent reflectance, coherent transmittance, diffuse scattering in vacuum, and scattering into the matter depth) is analyzed for different limiting cases (large and small correlation length of roughness and large and extremely small grazing angle of incident radiation). Both the Debye-Waller and the Nevot-Croce factors are demonstrated to describe improperly the features of X-ray diffraction at extremely small grazing angles. More appropriate simple analytic expressions for the specular reflectivity and total integrated scattering in vacuum are obtained instead. Transformation of one limiting diffraction regime into another one with variation in the correlation length of roughness is discussed.

  7. Measurement of two-dimensional small angle deviation with a prism interferometer

    SciTech Connect

    Chatterjee, Sanjib; Kumar, Y. Pavan

    2008-09-20

    A new technique for the measurement of two-dimensional small angular deviation is presented. A compound prism, which effectively produces a combination of two right-angled prisms in orthogonal directions, and plane reference surfaces have been utilized for the measurement of the orthogonal components of the angular tilt of an incident plane wavefront. Each orthogonal component of the angular tilt is separately measured from the angular rotation of the resultant wedge fringes between two plane wavefronts generated due to splitting of the incident plane wavefront by the corresponding set of right-angled prism and plane reference surface. The technique is shown to have high sensitivity for the measurement of small angle deviation. A monolithic prism interferometer, which is practically insensitive to vibration, is also proposed. Results obtained for the measurement of a known tilt angle are presented.

  8. A modified laminar optical tomography system with small dip-angle and the initial validation

    NASA Astrophysics Data System (ADS)

    Zhao, Huijuan; Wang, Shuang; Jia, Mengyu; Chen, Xueying; Qi, Jin; Tian, Jing; Ma, Wenjuan; Li, Jiao; Gao, Feng

    2016-03-01

    In a typical laminar optical tomography (LOT) system, the dip-angle between the incident light (or the emitting light) and the normal of the detection plane randomly changes during raster-scanning. The inconstant dip-angle causes consistency between the measurement and the light transportation model where a fixed dip-angle of the incident light is generally required. To eliminate the effect from this dip angle, methods such as keeping the angle unchangeable by moving the phantom instead of scanning the light were investigated. In this paper, a LOT system with small dip-angle over the whole detection range is developed. Simulation and experimental evaluation show that the dip-angle of the modified system is much smaller than that of the traditional system. For example, the relative angle between the two incident light at (x=0mm, y=0mm) and (x=0mm, y=2.5mm) on the image plane is about 0.7° for the traditional system while that is only about 0.02° for the modified system. The main parameters of the system are also evaluated and an image reconstruction algorithm is developed based on Monte Carlo simulation. The reconstructed images show that the spatial resolution and quantitative ratio is improved by the modified system without loss of the scanning speed.

  9. Hierarchical O(N) computation of small-angle scattering profiles and their associated derivatives

    PubMed Central

    Berlin, Konstantin; Gumerov, Nail A.; Fushman, David; Duraiswami, Ramani

    2014-01-01

    The need for fast approximate algorithms for Debye summation arises in computations performed in crystallography, small/wide-angle X-ray scattering and small-angle neutron scattering. When integrated into structure refinement protocols these algorithms can provide significant speed up over direct all-atom-to-all-atom computation. However, these protocols often employ an iterative gradient-based optimization procedure, which then requires derivatives of the profile with respect to atomic coordinates. This article presents an accurate, O(N) cost algorithm for the computation of scattering profile derivatives. The results reported here show orders of magnitude improvement in computational efficiency, while maintaining the prescribed accuracy. This opens the possibility to efficiently integrate small-angle scattering data into the structure determination and refinement of macromolecular systems. PMID:24701198

  10. Small angle x-ray scattering with a beryllium compound refractive lens as focusing optic

    SciTech Connect

    Timmann, Andreas; Doehrmann, Ralph; Schubert, Tom; Schulte-Schrepping, Horst; Hahn, Ulrich; Kuhlmann, Marion; Gehrke, Rainer; Roth, Stephan Volkher; Schropp, Andreas; Schroer, Christian; Lengeler, Bruno

    2009-04-15

    At BW4 at HASYLAB a beryllium compound refractive lens (Be-CRL) is used for the focusing in small-angle x-ray scattering experiments. Using it provides the advantages of higher long-term stability and a much easier alignment compared to a setup with focusing mirrors. In our investigations presented here, we show the advantages of using a Be-CRL in small-angle and also ultra small-angle x-ray scattering. We investigated the beam characteristics at the sample position with respect to spot size and photon flux. The spot size is comparable to that of a setup with focusing mirrors but with a gain in flux and better long-term stability. It is also shown that plane mirrors are still necessary to suppress higher order energies passing the monochromator.

  11. A more informative approach for characterization of polymer monolithic phases: small angle neutron scattering/ultrasmall angle neutron scattering.

    PubMed

    Ford, Kathleen M; Konzman, Brian G; Rubinson, Judith F

    2011-12-15

    Neutron scattering techniques have been used frequently to characterize geological specimens and to determine the structures of glasses and of polymers as solutions, suspensions, or melts. Little work has been reported on their application in determining polymers' structural properties relevant to separations. Here, we present a comparison of characterization results from nitrogen porosimetry and from combined small angle neutron scattering (SANS) and ultrasmall angle neutron scattering (USANS) experiments. We show that SANS is extremely sensitive to the pore characteristics. Both approaches can provide information about porosity and pore characteristics, but the neutron scattering techniques provide additional information in the form of the surface characteristics of the pores and their length scales. Fits of the scattering data show that cylindrical pores are present with diameters down to 0.6 μm and that, for length scales down to approxmately 20 Å, the material shows self-similar (fractal) slopes of -3.4 to -3.6. Comparison of these characteristics with other examples from the scattering literature indicate that further investigation of their meaning for chromatographic media is required. PMID:22066706

  12. Experimental methods in the study of neutron scattering at small angles

    SciTech Connect

    Dragolici, Cristian A.

    2014-11-24

    Small angle scattering (SAS) is the collective name given to the techniques of small angle neutron (SANS) and X-ray (SAXS) scattering. They offer the possibility to analyze particles without disturbing their natural environment. In each of these techniques radiation is elastically scattered by a sample and the resulting scattering pattern is analyzed to provide information about the size, shape and orientation of some component of the sample. Accordingly, a large number of methods and experimental patterns have been developed to ease the investigation of condensed matter by use of these techniques. Some of them are the discussed in this paper.

  13. High-resolution angle-resolved measurements of light scattered at small angles by red blood cells in suspension.

    PubMed

    Turcu, Ioan; Pop, Cristian V L; Neamtu, Silvia

    2006-03-20

    Red blood cells (RBCs) scatter light mainly in the forward direction, where the scattering phase function has a narrow peak. We performed an experimental investigation into the angular distribution of light scattered by blood in the small-angle domain. A highly diluted suspension of RBCs (hematocrits in the range 5 x 10(-5)-10(-2)) was illuminated with a He-Ne laser with 633 nm wavelength. We focused our research on two main topics: the scattering efficiency of the RBCs given by the mean scattering cross section and the scattering anisotropy obtained from the angular distribution of the scattered photons. The collimated beam transmission and the angular distribution of scattered light were measured and compared with the predictions of the effective phase function model. The RBCs' mean scattering cross section and scattering anisotropy were obtained by fitting of the experimental data. PMID:16579566

  14. Angle correction for small animal tumor imaging with spatial frequency domain imaging (SFDI).

    PubMed

    Zhao, Yanyu; Tabassum, Syeda; Piracha, Shaheer; Nandhu, Mohan Sobhana; Viapiano, Mariano; Roblyer, Darren

    2016-06-01

    Spatial frequency domain imaging (SFDI) is a widefield imaging technique that allows for the quantitative extraction of tissue optical properties. SFDI is currently being explored for small animal tumor imaging, but severe imaging artifacts occur for highly curved surfaces (e.g. the tumor edge). We propose a modified Lambertian angle correction, adapted from the Minnaert correction method for satellite imagery, to account for tissue surface angles up to 75°. The method was tested in a hemisphere phantom study as well as a small animal tumor model. The proposed method reduced µa and µs` extraction errors by an average of 64% and 16% respectively compared to performing no angle correction, and provided more physiologically agreeable optical property and chromophore values on tumors. PMID:27375952

  15. Angle correction for small animal tumor imaging with spatial frequency domain imaging (SFDI)

    PubMed Central

    Zhao, Yanyu; Tabassum, Syeda; Piracha, Shaheer; Nandhu, Mohan Sobhana; Viapiano, Mariano; Roblyer, Darren

    2016-01-01

    Spatial frequency domain imaging (SFDI) is a widefield imaging technique that allows for the quantitative extraction of tissue optical properties. SFDI is currently being explored for small animal tumor imaging, but severe imaging artifacts occur for highly curved surfaces (e.g. the tumor edge). We propose a modified Lambertian angle correction, adapted from the Minnaert correction method for satellite imagery, to account for tissue surface angles up to 75°. The method was tested in a hemisphere phantom study as well as a small animal tumor model. The proposed method reduced µa and µs` extraction errors by an average of 64% and 16% respectively compared to performing no angle correction, and provided more physiologically agreeable optical property and chromophore values on tumors. PMID:27375952

  16. Small-angle neutron scattering of nanocrystalline terbium with random paramagnetic susceptibility.

    PubMed

    Balaji, G; Ghosh, S; Döbrich, F; Eckerlebe, H; Weissmüller, J

    2008-06-01

    We report magnetic small-angle neutron scattering (SANS) data for the nanocrystalline rare earth metal Terbium in its paramagnetic state. Whereas critical scattering dominates at large momentum transfer, q, the (magnetic-) field response of the scattering at small q arises from the spatial nonuniformity of the paramagnetic susceptibility tensor. The finding of an interrelation between SANS and the susceptibility suggests a way for characterizing the nonuniform magnetic interactions in hard magnets by neutron scattering. PMID:18643454

  17. Irena : tool suite for modeling and analysis of small-angle scattering.

    SciTech Connect

    Ilavsky, J.; Jemian, P.

    2009-04-01

    Irena, a tool suite for analysis of both X-ray and neutron small-angle scattering (SAS) data within the commercial Igor Pro application, brings together a comprehensive suite of tools useful for investigations in materials science, physics, chemistry, polymer science and other fields. In addition to Guinier and Porod fits, the suite combines a variety of advanced SAS data evaluation tools for the modeling of size distribution in the dilute limit using maximum entropy and other methods, dilute limit small-angle scattering from multiple non-interacting populations of scatterers, the pair-distance distribution function, a unified fit, the Debye-Bueche model, the reflectivity (X-ray and neutron) using Parratt's formalism, and small-angle diffraction. There are also a number of support tools, such as a data import/export tool supporting a broad sampling of common data formats, a data modification tool, a presentation-quality graphics tool optimized for small-angle scattering data, and a neutron and X-ray scattering contrast calculator. These tools are brought together into one suite with consistent interfaces and functionality. The suite allows robust automated note recording and saving of parameters during export.

  18. Studying fractal geometry on submicron length scales by small-angle scattering

    SciTech Connect

    Wong, P.; Lin, J.

    1988-08-01

    Recent studies have shown that internal surfaces of porous geological materials, such as rocks and lignite coals, can be described by fractals down to atomic length scales. In this paper, the basic properties of self-similar and self-affine fractals are reviewed and how fractal dimensions can be measured by small-angle scattering experiments are discussed.

  19. Structure of unilamellar vesicles: Numerical analysis based on small-angle neutron scattering data

    SciTech Connect

    Zemlyanaya, E. V. Kiselev, M. A.; Zbytovska, J.; Almasy, L.; Aswal, V. K.; Strunz, P.; Wartewig, S.; Neubert, R.

    2006-12-15

    The structure of polydispersed populations of unilamellar vesicles is studied by small-angle neutron scattering for three types of lipid systems, namely, single-, two-and four-component vesicular systems. Results of the numerical analysis based on the separated-form-factor model are reported.

  20. Design and use of a 6 meter neutron small-angle scattering spectrometer at KUR

    NASA Astrophysics Data System (ADS)

    Komura, S.; Takeda, T.; Fujii, H.; Osamura, K.; Mochiki, K.; Hasegawa, K.

    1983-05-01

    A 6 meter neutron small-angle scattering spectrometer has been constructed at the Kyoto University Reactor (KUR) and has been used successfully in various fields of application. The design principles and the characteristics of the spectrometer are described briefly. Some examples of the scattering measurements are presented.

  1. Drag measurements on long thin cylinders at small angles and high Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Keith, William L.; Cipolla, Kimberly M.; Hart, David R.; Furey, Deborah A.

    2005-06-01

    Measurements of the drag caused by turbulent boundary layer mean wall shear stress on cylinders at small angles of attack and high length Reynolds numbers (8×106angles, resulting in linear cylinder geometry for tow speeds ranging from 2.6 m/s to 20.7 m/s and angles between 0° and 12°. Towing angles were measured with digital photography, and streamwise drag was measured with a strut-mounted load cell at the tow point. The measured tangential drag was very sensitive to small increases in angle at all tow speeds. A momentum thickness length scale is proposed to scale the tangential drag coefficient. The effects of the cross-flow resulting from the small angles of tow have a significant effect on the tangential drag coefficient values. A scaling for the orthogonal force on the cylinders was determined and provides a correction to published normal drag coefficient values for pure cross-flow. The presence of the axial turbulent boundary layer has a significant effect on these orthogonal forces.

  2. A preliminary study of breast cancer diagnosis using laboratory based small angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Round, A. R.; Wilkinson, S. J.; Hall, C. J.; Rogers, K. D.; Glatter, O.; Wess, T.; Ellis, I. O.

    2005-09-01

    Breast tissue collected from tumour samples and normal tissue from bi-lateral mastectomy procedures were examined using small angle x-ray scattering. Previous work has indicated that breast tissue disease diagnosis could be performed using small angle x-ray scattering (SAXS) from a synchrotron radiation source. The technique would be more useful to health services if it could be made to work using a conventional x-ray source. Consistent and reliable differences in x-ray scatter distributions were observed between samples from normal and tumour tissue samples using the laboratory based 'SAXSess' system. Albeit from a small number of samples, a sensitivity of 100% was obtained. This result encourages us to pursue the implementation of SAXS as a laboratory based diagnosis technique.

  3. Anomalous Separation of Small Y-Chromosomal DNA Fragments on Microchip Electrophoresis

    PubMed Central

    Jabasini, Mohammad; Ewis, Ashraf; Sato, Youichi; Nakahori, Yutaka; Baba, Yoshinobu

    2016-01-01

    We investigated an anomalous DNA separation where two DNA fragments from the human Y-chromosome sY638 (64 bp) and sY592 (65 bp), with only one base pair difference, were separated. This result is abnormal since in a previous study, we found that 5 bp was the minimum difference between two DNA fragments that the microchip electrophoresis system can separate. The formation of a mini-loop in the structure of the DNA fragment of sY638 (64 bp) was strongly expected to be the reason. To investigate this, we synthesized three modified DNA fragments for sY638 (64 bp), and the modifications were in two expected locations for possible mini-loop formation. Later, the separation between sY592 (65 bp) and the three modified fragments of sY638 (64 bp) was not possible. Thus, we conclude that the formation of a mini-loop in the structure of the DNA is the reason behind this anomalous separation.

  4. Molecular theory for the phase equilibria and cluster distribution of associating fluids with small bond angles.

    PubMed

    Marshall, Bennett D; Chapman, Walter G

    2013-08-01

    We develop a new theory for associating fluids with multiple association sites. The theory accounts for small bond angle effects such as steric hindrance, ring formation, and double bonding. The theory is validated against Monte Carlo simulations for the case of a fluid of patchy colloid particles with three patches and is found to be very accurate. Once validated, the theory is applied to study the phase diagram of a fluid composed of three patch colloids. It is found that bond angle has a significant effect on the phase diagram and the very existence of a liquid-vapor transition.

  5. Hierarchical Pore Morphology of Cretaceous Shale: A Small-Angle Neutron Scattering and Ultrasmall-Angle Neutron Scattering Study

    SciTech Connect

    Bahadur, J.; Melnichenko, Y. B.; Mastalerz, Maria; Furmann, Agnieszka; Clarkson, Chris R.

    2014-09-25

    Shale reservoirs are becoming an increasingly important source of oil and natural gas supply and a potential candidate for CO2 sequestration. Understanding the pore morphology in shale may provide clues to making gas extraction more efficient and cost-effective. The porosity of Cretaceous shale samples from Alberta, Canada, collected from different depths with varying mineralogical compositions, has been investigated by small- and ultrasmall-angle neutron scattering. Moreover these samples come from the Second White Specks and Belle Fourche formations, and their organic matter content ranges between 2 and 3%. The scattering length density of the shale specimens has been estimated using the chemical composition of the different mineral components. Scattering experiments reveal the presence of fractal and non-fractal pores. It has been shown that the porosity and specific surface area are dominated by the contribution from meso- and micropores. The fraction of closed porosity has been calculated by comparing the porosities estimated by He pycnometry and scattering techniques. There is no correlation between total porosity and mineral components, a strong correlation has been observed between closed porosity and major mineral components in the studied specimens.

  6. Hierarchical Pore Morphology of Cretaceous Shale: A Small-Angle Neutron Scattering and Ultrasmall-Angle Neutron Scattering Study

    DOE PAGES

    Bahadur, J.; Melnichenko, Y. B.; Mastalerz, Maria; Furmann, Agnieszka; Clarkson, Chris R.

    2014-09-25

    Shale reservoirs are becoming an increasingly important source of oil and natural gas supply and a potential candidate for CO2 sequestration. Understanding the pore morphology in shale may provide clues to making gas extraction more efficient and cost-effective. The porosity of Cretaceous shale samples from Alberta, Canada, collected from different depths with varying mineralogical compositions, has been investigated by small- and ultrasmall-angle neutron scattering. Moreover these samples come from the Second White Specks and Belle Fourche formations, and their organic matter content ranges between 2 and 3%. The scattering length density of the shale specimens has been estimated using themore » chemical composition of the different mineral components. Scattering experiments reveal the presence of fractal and non-fractal pores. It has been shown that the porosity and specific surface area are dominated by the contribution from meso- and micropores. The fraction of closed porosity has been calculated by comparing the porosities estimated by He pycnometry and scattering techniques. There is no correlation between total porosity and mineral components, a strong correlation has been observed between closed porosity and major mineral components in the studied specimens.« less

  7. Angle-resolved photoemission spectroscopy observation of anomalous electronic states in EuFe2As(2-x)P(x).

    PubMed

    Richard, P; Capan, C; Ma, J; Zhang, P; Xu, N; Qian, T; Denlinger, J D; Chen, G-F; Sefat, A S; Fisk, Z; Ding, H

    2014-01-22

    We used angle-resolved photoemission spectroscopy to investigate the electronic structure and the Fermi surface of EuFe2As2, EuFe2As1.4P0.6 and EuFe2P2. We observed doubled core level peaks associated with the pnictide atoms. Using K atoms evaporated at the surface to affect the surface quality, we show that one component of these doubled peaks is related to a surface state. Nevertheless, strong electronic dispersion along the c-axis, especially pronounced in EuFe2P2, is observed for at least one band, thus indicating that the Fe states, albeit probably affected at the surface, do not form pure two-dimensional surface states. We determine the evolution of the Fermi surface as a function of the P content and reveal that the hole Fermi surface pockets enlarge with increasing P content. We also show that the spectral weight near the Fermi level of EuFe2P2 is reduced as compared to that of EuFe2As2 and EuFe2As1.4P0.6. Finally, we identify the electronic states associated with the Eu(2+) f states and show an anomalous jump in EuFe2P2. PMID:24351570

  8. Tilt Angle and Footpoint Separation of Small and Large Bipolar Sunspot Regions Observed with HMI

    NASA Astrophysics Data System (ADS)

    McClintock, B. H.; Norton, A. A.

    2016-02-01

    We investigate bipolar sunspot regions and how tilt angle and footpoint separation vary during emergence and decay. The Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory collects data at a higher cadence than historical records and allows for a detailed analysis of regions over their lifetimes. We sample the umbral tilt angle, footpoint separation, and umbral area of 235 bipolar sunspot regions in Helioseismic and Magnetic Imager—Debrecen Data with an hourly cadence. We use the time when the umbral area peaks as time zero to distinguish between the emergence and decay periods of each region and we limit our analysis of tilt and separation behavior over time to within ±96 hr of time zero. Tilt angle evolution is distinctly different for regions with small (≈30 MSH), midsize (≈50 MSH), and large (≈110 MSH) maximum umbral areas, with 45 and 90 MSH being useful divisions for separating the groups. At the peak umbral area, we determine median tilt angles for small (7.°6), midsize (5.°9), and large (9.°3) regions. Within ±48 hr of the time of peak umbral area, large regions steadily increase in tilt angle, midsize regions are nearly constant, and small regions show evidence of negative tilt during emergence. A period of growth in footpoint separation occurs over a 72-hr period for all of the regions from roughly 40 to 70 Mm. The smallest bipoles (<9 MSH) are outliers in that they do not obey Joy's law and have a much smaller footpoint separation. We confirm the Muñoz-Jaramillo et al. (2015) results that the sunspots appear to be two distinct populations.

  9. EDITORIAL Proceedings of the XIV International Conference on Small-Angle Scattering, SAS-2009

    NASA Astrophysics Data System (ADS)

    Ungar, Goran; Heenan, Richard

    2010-10-01

    There are 52 papers in these Proceedings. The papers are divided into 10 thematic sections and a section for invited papers and reviews. The sections and the respective section editors are given below. Section Editor(s) Invited Papers and Reviews Peter Griffiths, Wim Bras, Rudolf Winter Beamlines and Instrumentation Elliot Gilbert, Wim Bras, Nigel Rhodes Theory, Data processing and Modelling Jan Skov Pedersen, Carlo Knupp Biological Systems and Membranes Richard Heenan, Cameron Neylon Ceramics, Glasses and Porous Materials Rudolf Winter Colloids and Solutions Peter Griffiths Hierarchical Structures and Fibres Steve Eichhorn, Karen Edler Metallic and Magnetic Systems Armin Hoell Polymers Patrick Fairclough Time resolved Diffraction, Kinetic and Dynamical Studies João Cabral, Christoph Rau We are grateful to all section editors and the many anonymous referees for their invaluable effort which made the publication of the Proceedings possible. The refereeing process was strict and thorough, some papers were rejected and most were improved. The resulting compendium gives a good overview of recent developments in small-angle X-ray and neutron scattering theory, application, methods of analysis and instrumentation. Thus it should be a useful source of reference for a number of years to come. The papers are a good reflection of the material presented at the meeting. Because of the general high quality of the articles, it was difficult to decide which to highlight and be fair to all contributors. The following in particular have caught the attention of the editors. Highlighted papers A statistical survey of publications reporting the application of SAXS and SANS by Aldo Craievich (paper 012003) is recommended reading for anyone needing convincing about the vibrancy of this scientific field and the ever expanding use of these techniques. Two aspects of coherent X-ray scattering, made available by the advent of the 3rd generation synchrotron sources, are discussed in the

  10. EDITORIAL Proceedings of the XIV International Conference on Small-Angle Scattering, SAS-2009

    NASA Astrophysics Data System (ADS)

    Ungar, Goran; Heenan, Richard

    2010-10-01

    There are 52 papers in these Proceedings. The papers are divided into 10 thematic sections and a section for invited papers and reviews. The sections and the respective section editors are given below. Section Editor(s) Invited Papers and Reviews Peter Griffiths, Wim Bras, Rudolf Winter Beamlines and Instrumentation Elliot Gilbert, Wim Bras, Nigel Rhodes Theory, Data processing and Modelling Jan Skov Pedersen, Carlo Knupp Biological Systems and Membranes Richard Heenan, Cameron Neylon Ceramics, Glasses and Porous Materials Rudolf Winter Colloids and Solutions Peter Griffiths Hierarchical Structures and Fibres Steve Eichhorn, Karen Edler Metallic and Magnetic Systems Armin Hoell Polymers Patrick Fairclough Time resolved Diffraction, Kinetic and Dynamical Studies João Cabral, Christoph Rau We are grateful to all section editors and the many anonymous referees for their invaluable effort which made the publication of the Proceedings possible. The refereeing process was strict and thorough, some papers were rejected and most were improved. The resulting compendium gives a good overview of recent developments in small-angle X-ray and neutron scattering theory, application, methods of analysis and instrumentation. Thus it should be a useful source of reference for a number of years to come. The papers are a good reflection of the material presented at the meeting. Because of the general high quality of the articles, it was difficult to decide which to highlight and be fair to all contributors. The following in particular have caught the attention of the editors. Highlighted papers A statistical survey of publications reporting the application of SAXS and SANS by Aldo Craievich (paper 012003) is recommended reading for anyone needing convincing about the vibrancy of this scientific field and the ever expanding use of these techniques. Two aspects of coherent X-ray scattering, made available by the advent of the 3rd generation synchrotron sources, are discussed in the

  11. Performance of silicon pixel detectors at small track incidence angles for the ATLAS Inner Tracker upgrade

    NASA Astrophysics Data System (ADS)

    Viel, Simon; Banerjee, Swagato; Brandt, Gerhard; Carney, Rebecca; Garcia-Sciveres, Maurice; Hard, Andrew Straiton; Kaplan, Laser Seymour; Kashif, Lashkar; Pranko, Aliaksandr; Rieger, Julia; Wolf, Julian; Wu, Sau Lan; Yang, Hongtao

    2016-09-01

    In order to enable the ATLAS experiment to successfully track charged particles produced in high-energy collisions at the High-Luminosity Large Hadron Collider, the current ATLAS Inner Detector will be replaced by the Inner Tracker (ITk), entirely composed of silicon pixel and strip detectors. An extension of the tracking coverage of the ITk to very forward pseudorapidity values is proposed, using pixel modules placed in a long cylindrical layer around the beam pipe. The measurement of long pixel clusters, detected when charged particles cross the silicon sensor at small incidence angles, has potential to significantly improve the tracking efficiency, fake track rejection, and resolution of the ITk in the very forward region. The performance of state-of-the-art pixel modules at small track incidence angles is studied using test beam data collected at SLAC and CERN.

  12. Small-angle neutron scattering studies from solutions of bovine nasal cartilage proteoglycan

    SciTech Connect

    Patel, A.; Stivala, S.S.; Damle, S.P.; Gregory, J.D.; Bunick, G.J.; Uberbacher, E.C.

    1985-08-01

    Small-angle neutron scattering, SANS, of the proteoglycan subunit of bovine nasal cartilage in 0.15N LiCl at 25/sup 0/C yielded the radius of gyration, R/sub g/, radius of gyration of the cross-section, R/sub q/, persistence length, a, and the molecular weight, M. The following values were obtained: M = 3.9 x 10/sup 6/, R/sub g/ = 745 A, R/sub q/ = 34.6 A and a = 35.2 A. These values compare favorably with those that were obtained from small angle x-ray scattering, SAXS, of a similar extract. The scattering curve of the proteoglycan subunit in D/sub 2/O showed a characteristic broad peak in the specified angular range similar to that observed from SAXS, thus confirming the polyelectrolyte nature of the proteoglycan. 15 refs., 3 figs., 1 tab. (DT)

  13. BIOISIS: Biological Macromolecules by Small Angle X-ray Scattering (SAXS)

    DOE Data Explorer

    Tainer, John [Scripps Research Institute; Hura, Greg [LBNL; Rambo, Robert P. [LBNL

    BIOISIS is an open access database dedicated to the study of biological macromolecules by small angle X-ray scattering (SAXS). BIOISIS aims to become the complete source for the deposition, distribution and maintenance of small angle X-ray scattering data and technologies. The database is designed around the concept of an ôexperimentö and relates a specific experiment to a set of genes, organisms, computational models and experimental data. As of May 2012, BIOSIS contains 7,118 genes covering four different organisms. Forty-two modeled structures are available. Clicking on a structures reveals scattering curves, experimental conditions, and experimental values. The data are collected at Beamline 12.3.1 of the Advanced Light Source (ALS).[Copied with editing from http://www.bioisis.net/about

  14. Characterization of porous materials using combined small-angle X-ray and neutron scattering techniques

    SciTech Connect

    Hu, Naiping; Borkar, Neha; Kohls, Doug; Schaefer, Dale W.

    2014-09-24

    A combination of ultra small angle X-ray scattering (USAXS) and ultra small angle neutron scattering (USANS) is used to characterize porous materials. The analysis methods yield quantitative information, including the mean skeletal chord length, mean pore chord length, skeletal density, and composition. A mixed cellulose ester (MCE) membrane with a manufacturer-labeled pore size of 0.1 {mu}m was used as a model to elucidate the specifics of the method. Four approaches describing four specific scenarios (different known parameters and form of the scattering data) are compared. Pore chords determined using all four approaches are in good agreement with the scanning electron microscopy estimates but are larger than the manufacturer's nominal pore size. Our approach also gives the average chord of the skeletal solid (struts) of the membrane, which is also consistent for all four approaches. Combined data from USAXS and USANS gives the skeletal density and the strut composition.

  15. Development and prospects of Very Small Angle Neutron Scattering (VSANS) techniques

    NASA Astrophysics Data System (ADS)

    Xuo, Tai-Sen; Cheng, He; Chen, Yuan-Bo; Wang, Fang-Wei

    2016-07-01

    Very Small Angle Neutron Scattering (VSANS) is an upgrade of the traditional Small Angle Neutron Scattering (SANS) technique which can cover three orders of magnitude of length scale from one nanometer to one micrometer. It is a powerful tool for structure calibration in polymer science, biology, material science and condensed matter physics. Since the first VSANS instrument, D11 in Grenoble, was built in 1972, new collimation techniques, focusing optics (multi-beam converging apertures, material or magnetic lenses, and focusing mirrors) and higher resolution detectors combined with the long flight paths and long incident neutron wavelengths have been developed. In this paper, a detailed review is given of the development, principles and application conditions of various VSANS techniques. Then, beam current gain factors are calculated to evaluate those techniques. A VSANS design for the China Spallation Neutron Source (CSNS) is thereby presented. Supported by National Natural Science Foundation of China (21474119, 11305191)

  16. Small-angle X-ray scattering method to characterize molecular interactions: Proof of concept.

    PubMed

    Allec, Nicholas; Choi, Mina; Yesupriya, Nikhil; Szychowski, Brian; White, Michael R; Kann, Maricel G; Garcin, Elsa D; Daniel, Marie-Christine; Badano, Aldo

    2015-01-01

    Characterizing biomolecular interactions is crucial to the understanding of biological processes. Existing characterization methods have low spatial resolution, poor specificity, and some lack the capability for deep tissue imaging. We describe a novel technique that relies on small-angle X-ray scattering signatures from high-contrast molecular probes that correlate with the presence of biomolecular interactions. We describe a proof-of-concept study that uses a model system consisting of mixtures of monomer solutions of gold nanoparticles (GNPs) as the non-interacting species and solutions of GNP dimers linked with an organic molecule (dimethyl suberimidate) as the interacting species. We report estimates of the interaction fraction obtained with the proposed small-angle X-ray scattering characterization method exhibiting strong correlation with the known relative concentration of interacting and non-interacting species. PMID:26160052

  17. New analysis of the small-angle-magnetization-rotation method for magnetostriction measurements on amorphous ribbons

    NASA Astrophysics Data System (ADS)

    Severino, A. M.; Missell, F. P.

    1987-09-01

    The small-angle-magnetization-rotation (SAMR) method for measuring the saturation magnetostrictin λ s has been reanalyzed, taking into account the underlying domain structure of the amorphous ribbon. Although the condition for determining λ s reamins unchenged, the modifications introduced allow one to understand many additional features of the experimental data. With the appropriate modifications, the SAMR method can be used to study stress relaxation in amorphous alloys. Examples are given Fe-based and Co-based alloys.

  18. X-ray small-angle scattering from sputtered CeO{sub 2}/C bilayers

    SciTech Connect

    Haviar, S.; Dubau, M.; Khalakhan, I.; Vorokhta, M.; Matolinova, I.; Matolin, V.; Vales, V.; Endres, J.; Holy, V.; Buljan, M.; Bernstorff, S.

    2013-01-14

    Surface and interface morphology of cerium oxide/carbon bilayers used as thin-film catalysts is studied by grazing-incidence small-angle x-ray scattering, scanning electron microscopy, and atomic-force microscopy, and the dependence of the structural parameters on the thicknesses of the constituting layers is investigated. The applicability of x-ray scattering and its advantages over standard analytical methods are discussed.

  19. Small-angle x-ray scattering of intercalation compounds of graphite, fluorographite, and graphite oxide

    SciTech Connect

    Perevozkin, V.Yu.; Yur'ev, G.S.; Nazarov, A.S.; Danilenko, A.M.; Lisitsa, V.V.; Makotchenko, V.G.; Paasonen, V.M.; Yakovlev, I.I.

    1988-05-01

    Graphite intercalation compounds are interesting as cathode materials in chemical current sources and catalysts and are good conductors of electricity. Small-angle x-ray scattering was studied on natural graphite, intercalation compounds of fluorinated graphite, graphite oxide, and the products of reduction of the compounds. It was shown that scattering takes place in regions with a lower density and the size of the density inhomogeneities was determined.

  20. Two-dimensional position-sensitive detectors for small-angle neutron scattering

    SciTech Connect

    McElhaney, S.A.; Vandermolen, R.I.

    1990-05-01

    In this paper, various detectors available for small angle neutron scattering (SANS) are discussed, along with some current developments being actively pursued. A section has been included to outline the various methodologies of position encoding/decoding with discussions on trends and limitations. Computer software/hardware vary greatly from institute and experiment and only a general discussion is given to this area. 85 refs., 33 figs.

  1. A 6-Meter Neutron Small-Angle Scattering Spectrometer at KUR

    NASA Astrophysics Data System (ADS)

    Komura, Shigehiro; Takeda, Takayoshi; Fujii, Hironobu; Toyoshima, Yoshinori; Osamura, Kozo; Mochiki, Koichi; Hasegawa, Ken'ichi

    1983-02-01

    A 6-meter neutron small-angle scattering spectrometer has been constructed at Kyoto University Reactor (KUR) and has been used successfully for various fields of application in these three years. This paper describes overall design principles and the characteristics of the various parts of the spectrometers which can be assembled and disassembled easily at KUR. Some examples of scattering measurements are presented to show the performance of the spectrometer.

  2. Pore size distribution of shaley rock by small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Hall, P. L.; Mildner, D. F. R.; Borst, R. L.

    1983-08-01

    Information concerning pore microstructure of shaly rocks is of considerable relevance to petroleum exploration and production. Pore sizes and distributions within shaly samples have been determined by small angle neutron scattering. The data are indicative of a considerable spread of pore dimension, showing inhomogeneities with a range from 20 Å and greater. The cumulative pore volumes are compared with those derived from mercury intrusion porosimetry and nitrogen adsorption and desorption isotherms.

  3. Pore size distribution of shaly rock by small angle neutron scattering

    SciTech Connect

    Hall, P.L.; Mildner, D.F.R.; Borst, R.L.

    1983-08-01

    Information concerning pore microstructure of shaly rocks is of considerable relevance to petroleum exploration and production. Pore sizes and distributions within shaly samples have been determined by small angle neutron scattering. The data are indicative of a considerable spread of pore dimension, showing inhomogeneities with a range from 20 A and greater. The cumulative pore volumes are compared with those derived from mercury intrusion porosimetry and nitrogen adsorption and desorption isotherms.

  4. Monte Carlo-based rigid body modelling of large protein complexes against small angle scattering data.

    PubMed

    Meesters, Christian; Pairet, Bruno; Rabenhorst, Anja; Decker, Heinz; Jaenicke, Elmar

    2010-06-01

    We present a modular, collaborative, open-source architecture for rigid body modelling based upon small angle scattering data, named sas_rigid. It is designed to provide a fast and extensible scripting interface using the easy-to-learn Python programming language. Features include rigid body modelling to result in static structures and three-dimensional probability densities using two different algorithms. PMID:20598639

  5. Study of High-Frequency Impedance of Small-Angle Tapers and Collimators

    SciTech Connect

    Stupakov, Gennady; Podobedov, B.; /Brookhaven

    2010-06-04

    Collimators and transitions in accelerator vacuum chambers often include small-angle tapering to lower the wakefields generated by the beam. While the low-frequency impedance is well described by Yokoya's formula (for axisymmetric geometry), much less is known about the behavior of the impedance in the high frequency limit. In this paper we develop an analytical approach to the highfrequency regime for round collimators and tapers. Our analytical results are compared with computer simulations using the code ECHO.

  6. Effect of the concentration of inhomogeneities on the multiple small-angle neutron scattering

    SciTech Connect

    Abov, Yu. G.; Dzheparov, F. S.; Elyutin, N. O.; Lvov, D. V. Tyulyusov, A. N.

    2013-03-15

    The interference effects manifested during multiple small-angle neutron scattering (MSANS) on a chaotically arranged close-packed ensemble of scatterers have been studied. MSANS measurements have been performed for mixtures of Al and Ti-Zr alloy powders. It is shown that the results can be satisfactorily described based on a theory that takes into account spatial correlations in the arrangement of powder grains.

  7. SFF analysis of the small angle scattering data for investigation of a vesicle systems structure

    NASA Astrophysics Data System (ADS)

    Zemlyanaya, E. V.; Kiselev, M. A.; Zhabitskaya, E. I.; Gruzinov, A. Yu.; Aksenov, V. L.; Ipatova, O. M.; Druzhilovskaya, O. S.

    2016-06-01

    Experimental data on the small angle synchrotron X-ray scattering (SAXS) are analyzed on a basis of Separated form factors method (SFF) for a study of the drug delivery Phospholipid Transport Nano System (PTNS). Basic parameters of polydispersed population of PTNS nanoparticles (average radius of PTNS-particles, polydispersity of radius, thickness of membrane) have been determined. The results are discussed in comparison with the SFF results for the “classical” vesicular system of dimyristoylphosphocholine (DMPC).

  8. Using a Hexagonal Mirror for Varying Light Intensity in the Measurement of Small-Angle Variation.

    PubMed

    Hsieh, Meng-Chang; Lin, Jiun-You; Chang, Chia-Ou

    2016-08-16

    Precision positioning and control are critical to industrial-use processing machines. In order to have components fabricated with excellent precision, the measurement of small-angle variations must be as accurate as possible. To achieve this goal, this study provides a new and simple optical mechanism by varying light intensity. A He-Ne laser beam was passed through an attenuator and into a beam splitter. The reflected light was used as an intensity reference for calibrating the measurement. The transmitted light as a test light entered the optical mechanism hexagonal mirror, the optical mechanism of which was created by us, and then it entered the power detector after four consecutive reflections inside the mirror. When the hexagonal mirror was rotated by a small angle, the laser beam was parallel shifted. Once the laser beam was shifted, the hitting area on the detector was changed; it might be partially outside the sensing zone and would cause the variation of detection intensity. This variation of light intensity can be employed to measure small-angle variations. The experimental results demonstrate the feasibility of this method. The resolution and sensitivity are 3 × 10(-40) and 4 mW/° in the angular range of 0.6°, respectively, and 9.3 × 10(-50) and 13 mW/° in the angular range of 0.25°.

  9. Using a Hexagonal Mirror for Varying Light Intensity in the Measurement of Small-Angle Variation.

    PubMed

    Hsieh, Meng-Chang; Lin, Jiun-You; Chang, Chia-Ou

    2016-01-01

    Precision positioning and control are critical to industrial-use processing machines. In order to have components fabricated with excellent precision, the measurement of small-angle variations must be as accurate as possible. To achieve this goal, this study provides a new and simple optical mechanism by varying light intensity. A He-Ne laser beam was passed through an attenuator and into a beam splitter. The reflected light was used as an intensity reference for calibrating the measurement. The transmitted light as a test light entered the optical mechanism hexagonal mirror, the optical mechanism of which was created by us, and then it entered the power detector after four consecutive reflections inside the mirror. When the hexagonal mirror was rotated by a small angle, the laser beam was parallel shifted. Once the laser beam was shifted, the hitting area on the detector was changed; it might be partially outside the sensing zone and would cause the variation of detection intensity. This variation of light intensity can be employed to measure small-angle variations. The experimental results demonstrate the feasibility of this method. The resolution and sensitivity are 3 × 10(-40) and 4 mW/° in the angular range of 0.6°, respectively, and 9.3 × 10(-50) and 13 mW/° in the angular range of 0.25°. PMID:27537893

  10. A Hierarchical Algorithm for Fast Debye Summation with Applications to Small Angle Scattering

    PubMed Central

    Gumerov, Nail A.; Berlin, Konstantin; Fushman, David; Duraiswami, Ramani

    2012-01-01

    Debye summation, which involves the summation of sinc functions of distances between all pair of atoms in three dimensional space, arises in computations performed in crystallography, small/wide angle X-ray scattering (SAXS/WAXS) and small angle neutron scattering (SANS). Direct evaluation of Debye summation has quadratic complexity, which results in computational bottleneck when determining crystal properties, or running structure refinement protocols that involve SAXS or SANS, even for moderately sized molecules. We present a fast approximation algorithm that efficiently computes the summation to any prescribed accuracy ε in linear time. The algorithm is similar to the fast multipole method (FMM), and is based on a hierarchical spatial decomposition of the molecule coupled with local harmonic expansions and translation of these expansions. An even more efficient implementation is possible when the scattering profile is all that is required, as in small angle scattering reconstruction (SAS) of macromolecules. We examine the relationship of the proposed algorithm to existing approximate methods for profile computations, and show that these methods may result in inaccurate profile computations, unless an error bound derived in this paper is used. Our theoretical and computational results show orders of magnitude improvement in computation complexity over existing methods, while maintaining prescribed accuracy. PMID:22707386

  11. Using a Hexagonal Mirror for Varying Light Intensity in the Measurement of Small-Angle Variation

    PubMed Central

    Hsieh, Meng-Chang; Lin, Jiun-You; Chang, Chia-Ou

    2016-01-01

    Precision positioning and control are critical to industrial-use processing machines. In order to have components fabricated with excellent precision, the measurement of small-angle variations must be as accurate as possible. To achieve this goal, this study provides a new and simple optical mechanism by varying light intensity. A He-Ne laser beam was passed through an attenuator and into a beam splitter. The reflected light was used as an intensity reference for calibrating the measurement. The transmitted light as a test light entered the optical mechanism hexagonal mirror, the optical mechanism of which was created by us, and then it entered the power detector after four consecutive reflections inside the mirror. When the hexagonal mirror was rotated by a small angle, the laser beam was parallel shifted. Once the laser beam was shifted, the hitting area on the detector was changed; it might be partially outside the sensing zone and would cause the variation of detection intensity. This variation of light intensity can be employed to measure small-angle variations. The experimental results demonstrate the feasibility of this method. The resolution and sensitivity are 3 × 10−40 and 4 mW/° in the angular range of 0.6°, respectively, and 9.3 × 10−50 and 13 mW/° in the angular range of 0.25°. PMID:27537893

  12. Small-angle scatter tomography with a photon-counting detector array

    NASA Astrophysics Data System (ADS)

    Pang, Shuo; Zhu, Zheyuan; Wang, Ge; Cong, Wenxiang

    2016-05-01

    Small-angle x-ray scatter imaging has a high intrinsic contrast in cancer research and other applications, and provides information on molecular composition and micro-structure of the tissue. In general, the implementations of small-angle coherent scatter imaging can be divided into two main categories: direct tomography and angular dispersive computerized tomography. Based on the recent development of energy-discriminative photon-counting detector array, here we propose a computerized tomography setup based on energy-dispersive measurement with a photon-counting detector array. To show merits of the energy-dispersive approach, we have performed numerical tests with a phantom containing various tissue types, in comparison with the existing imaging approaches. The results show that with an energy resolution of ~6 keV, the energy dispersive tomography system with a broadband tabletop x-ray would outperform the angular dispersive system, which makes the x-ray small-angle scatter tomography promising for high-specificity tissue imaging.

  13. Anomalous uptake and circulatory characteristics of the plant-based small RNA MIR2911

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Inconsistent detection of plant-based dietary small RNAs in circulation has thwarted the use of dietary RNA therapeutics. Here we demonstrate mice consuming diets rich in vegetables displayed enhanced serum levels of the plant specific small RNA MIR2911. Differential centrifugation, size-exclusion c...

  14. Nanostructure surveys of macroscopic specimens by small-angle scattering tensor tomography

    NASA Astrophysics Data System (ADS)

    Liebi, Marianne; Georgiadis, Marios; Menzel, Andreas; Schneider, Philipp; Kohlbrecher, Joachim; Bunk, Oliver; Guizar-Sicairos, Manuel

    2015-11-01

    The mechanical properties of many materials are based on the macroscopic arrangement and orientation of their nanostructure. This nanostructure can be ordered over a range of length scales. In biology, the principle of hierarchical ordering is often used to maximize functionality, such as strength and robustness of the material, while minimizing weight and energy cost. Methods for nanoscale imaging provide direct visual access to the ultrastructure (nanoscale structure that is too small to be imaged using light microscopy), but the field of view is limited and does not easily allow a full correlative study of changes in the ultrastructure over a macroscopic sample. Other methods of probing ultrastructure ordering, such as small-angle scattering of X-rays or neutrons, can be applied to macroscopic samples; however, these scattering methods remain constrained to two-dimensional specimens or to isotropically oriented ultrastructures. These constraints limit the use of these methods for studying nanostructures with more complex orientation patterns, which are abundant in nature and materials science. Here, we introduce an imaging method that combines small-angle scattering with tensor tomography to probe nanoscale structures in three-dimensional macroscopic samples in a non-destructive way. We demonstrate the method by measuring the main orientation and the degree of orientation of nanoscale mineralized collagen fibrils in a human trabecula bone sample with a spatial resolution of 25 micrometres. Symmetries within the sample, such as the cylindrical symmetry commonly observed for mineralized collagen fibrils in bone, allow for tractable sampling requirements and numerical efficiency. Small-angle scattering tensor tomography is applicable to both biological and materials science specimens, and may be useful for understanding and characterizing smart or bio-inspired materials. Moreover, because the method is non-destructive, it is appropriate for in situ measurements and

  15. Small-angle scattering studies of meso-scopic structures with synchrotron X-rays

    NASA Astrophysics Data System (ADS)

    Dore, J. C.; North, A. N.; Rigden, J. S.

    1995-03-01

    The use of small-angle X-ray scattering techniques for the study of spatial inhomogeneities over the range 20 Å to 2 μm is reviewed. The basic formalism for scattering by an inhomogeneous medium is developed with particular reference to liquid suspensions, porous solids and solid aggregates. The instrumentation available on the Synchrotron Radiation Source at the Daresbury Laboratory is briefly presented and the use of the Bonse-Hart method for studies at ultra-low scattering angles described. The extraction of structural information for a range of natural and synthetic materials is presented with particular reference to microemulsions, porous silicas, clays and composites. The complementarity of X-ray and neutron techniques is critically reviewed and prospects for future developments, particularly for the study of anisotropic systems, are discussed.

  16. Focusing of Gaussian beam passed under small angle to optical axis of uniaxial crystal

    NASA Astrophysics Data System (ADS)

    Ivanov, M. O.; Shostka, N. V.

    2016-07-01

    We showed both experimentally and analytically, the effect of focusing of a Gaussian beam propagated under small angle ϕ with respect to the optical axis of a uniaxial crystal, on the generation of a bottle beam. At ϕ = 0° two foci that correspond to ordinary and extraordinary parts of a beam form a closed 3D structure of a bottle beam. At this point, the beam, in the foci points, has radially and azimuthally aligned polarizations. Increasing the value of ϕ leads to dramatic changes in the intensity and polarization structure of a bottle beam. Starting from the value of ϕ = ±2° the closed 3D symmetric structure of a bottle beam breaks down. At ϕ = ±5° both beams are focused at the same transverse plane, while its polarization evolves to x- and y-linear. With a further increase in angle ϕ two foci ‘switch’ their spatial positions and move further away.

  17. Cylindrical aggregates of chlorophylls studied by small-angle neutron scatter

    SciTech Connect

    Worcester, D.L.; Katz, J.J.

    1994-12-31

    Neutron small-angle scattering has demonstrated tubular chlorophyll aggregates formed by self-assembly of a variety of chlorophyll types in nonpolar solvents. The size and other properties of the tubular aggregates can be accounted for by stereochemical properties of the chlorophyll molecules. Features of some of the structures are remarkably similar to light harvesting chlorophyll complexes in vivo, particularly for photosynthetic bacteria. These nanotube chlorophyll structures may have applications as light harvesting biomaterials where efficient energy transfer occurs from an excited state which is highly delocalized.

  18. Analysis of C-S-H gel and cement paste by small-angle neutron scattering

    SciTech Connect

    Allen, Andrew J. . E-mail: andrew.allen@nist.gov; Thomas, Jeffrey J. . E-mail: jthomas@northwestern.edu

    2007-03-15

    The role of small-angle X-ray and neutron scattering (SAXS and SANS) in the characterization of cement is briefly reviewed. The unique information obtainable from SANS analysis of C-S-H gel in hydrating cement is compared with that obtainable by other neutron methods. Implications for the nature of C-S-H gel, as detected by SANS, are considered in relation to current models. Finally, the application of the SANS method to cement paste is demonstrated by analyzing the effects of calcium chloride acceleration and sucrose retardation on the resulting hydrated microstructure.

  19. Direct Observation Of Nanoparticle-Surfactant Interactions Using Small Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Kumar, Sugam; Aswal, V. K.

    2010-12-01

    Interactions of anionic silica nanoparticles with anionic, cationic and nonionic surfactants have directly been studied by contrast variation small angle neutron scattering (SANS). The measurements are performed on 1 wt% of both silica nanoparticles and surfactants of anionic sodium dodecyle sulphate (SDS), cationic dodecyltrimethyl ammonium bromide (DTAB) and non-ionic polyoxyethylene 10 lauryl ether (C12E10) in aqueous solution. We show that there is no direct interaction in the case of SDS with silica particles, whereas strong interaction for DTAB leads to the aggregation of silica particles. The interaction of C12E10 is found through the micelles adsorbed on the silica particles.

  20. From small angle x-ray scattering to reflectivity: Instrumentation and sample study

    SciTech Connect

    Hua, D.W.; Beaucage, G.; Kent, M.S.

    1996-02-01

    In this study, we described the first results from an x-ray reflectometer which has been modified from an existing Kratky small angle x-ray scattering (SAXS) camera at the UNM/Sandia scattering center. Typically, seven orders of magnitude of reflectivity can be obtained over a range of 0.02 to 0.5 A{sup {minus}1} in {ital q}. This allows the resolution of surface features of 10 to 1000 A. The conversion to reflectometer is reversible and can be achieved in a short time, allowing for dual use of an existing Kratky camera. {copyright} {ital 1996 Materials Research Society.}

  1. Correlation between fractal dimension and surface characterization by small angle X-ray scattering in marble.

    PubMed

    Salinas-Nolasco, Manlio Favio; Méndez-Vivar, Juan

    2010-03-16

    Among several analysis techniques applied to the study of surface passivation using dicarboxylic acids, small angle X-ray scattering (SAXS) has proved to be relevant in the physicochemical interpretation of the surface association resulting between calcium carbonate and the molecular structure of malonic acid. It is possible to establish chemical affinity principles through bidimensional geometric analysis in terms of the fractal dimension obtained experimentally by SAXS. In this Article, we present results about the adsorption of malonic acid on calcite, using theoretical and mathematical principles of the fractal dimension.

  2. Effect of Dzyaloshinski-Moriya interaction on elastic small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Michels, Andreas; Mettus, Denis; Honecker, Dirk; Metlov, Konstantin L.

    2016-08-01

    For magnetic materials containing many lattice imperfections (e.g., nanocrystalline magnets), the relativistic Dzyaloshinski-Moriya (DM) interaction may result in nonuniform spin textures due to the lack of inversion symmetry at interfaces. Within the framework of the continuum theory of micromagnetics, we explore the impact of the DM interaction on the elastic magnetic small-angle neutron scattering (SANS) cross section. It is shown that the DM interaction gives rise to a polarization-dependent asymmetric term in the spin-flip SANS cross section. Analysis of this feature may provide a means to determine the DM constant.

  3. Small-angle and surface scattering from porous and fractal materials.

    SciTech Connect

    Sinha, S. K.

    1998-09-18

    We review the basic theoretical methods used to treat small-angle scattering from porous materials, treated as general two-phase systems, and also the basic experimental techniques for carrying out such experiments. We discuss the special forms of the scattering when the materials exhibit mass or surface fractal behavior, and review the results of recent experiments on several types of porous media and also SANS experiments probing the phase behavior of binary fluid mixtures or polymer solutions confined in porous materials. Finally, we discuss the analogous technique of off-specular scattering from surfaces and interfaces which is used to study surface roughness of various kinds.

  4. Small Angle Neutron Scattering Observation of Chain Retraction after a Large Step Deformation

    SciTech Connect

    Blanchard, A.; Heinrich, M.; Pyckhout-Hintzen, W.; Richter, D.; Graham, R.S.; Likhtman, A.E.; McLeish, T.C.B.; Read, D.J.; Straube, E.; Kohlbrecher, J.

    2005-10-14

    The process of retraction in entangled linear chains after a fast nonlinear stretch was detected from time-resolved but quenched small angle neutron scattering (SANS) experiments on long, well-entangled polyisoprene chains. The statically obtained SANS data cover the relevant time regime for retraction, and they provide a direct, microscopic verification of this nonlinear process as predicted by the tube model. Clear, quantitative agreement is found with recent theories of contour length fluctuations and convective constraint release, using parameters obtained mainly from linear rheology. The theory captures the full range of scattering vectors once the crossover to fluctuations on length scales below the tube diameter is accounted for.

  5. Sample environments and techniques combined with small angle X-ray scattering.

    PubMed

    Bras, W; Ryan, A J

    1998-03-31

    The number of synchrotron radiation-based Small Angle X-ray Scattering beamlines has increased considerably over the last decade. With the high X-ray flux and collimation of these beamlines it not only has become possible to perform time-resolved experiments on time scales down to the millisecond/frame range, but also it allows experimenters to utilise new sample environments and use simultaneous several experimental techniques on one sample. An overview of recent developments in this field is given.

  6. Characterising density fluctuations in liquid yttria aluminates with small angle x-ray scattering

    SciTech Connect

    Greaves, G. Neville; Wilding, Martin C.; Vu Van, Quang; Majerus, Odile; Hennet, Louis

    2009-01-29

    Small angle x-ray scattering (SAXS) has been measured in the wavevector range 0.01

  7. Study of Nano-Precipitates Using Small-Angle Neutron Scattering

    SciTech Connect

    Chen, Wei-Ren

    2008-01-01

    Small-Angle-Neutron-Scattering (SANS) experiments were performed on a Ni-based nano-precipitate strengthened superalloy. A theoretical model for SANS absolute intensity distribution, I(Q), was developed to extract the structural properties. During the deformation process, a change in the morphology of precipitates was discovered. However, the average inter-precipitate distance and the average volume of precipitate were found to remain invariant. This microstructural information resolved by SANS is in good agreement with the results obtained from the quantitative transmission-electron-microscopy (TEM) image analysis.

  8. Small angle X-ray and neutron scattering on cadmium sulfide nanoparticles in silicate glass

    NASA Astrophysics Data System (ADS)

    Kuznetsova, Yu. V.; Rempel, A. A.; Meyer, M.; Pipich, V.; Gerth, S.; Magerl, A.

    2016-08-01

    Small angle X-ray and neutron scattering on Cd and S doped glass annealed at 600 °C shows after the first 12 h nucleation and growth of spherical CdS nanoparticles with a radius of up to 34±4 Å. After the nucleation is completed after 24 h, further growth in this amorphous environment is governed by oriented particle attachment mechanism as found for a liquid medium. Towards 48 h the particle shape has changed into spheroidal with short and long axis of 40±2 Å and 120±2 Å, respectively.

  9. DAMMIF, a program for rapid ab-initio shape determination in small-angle scattering

    PubMed Central

    Franke, Daniel; Svergun, Dmitri I.

    2009-01-01

    DAMMIF, a revised implementation of the ab-initio shape-determination program DAMMIN for small-angle scattering data, is presented. The program was fully rewritten, and its algorithm was optimized for speed of execution and modified to avoid limitations due to the finite search volume. Symmetry and anisometry constraints can be imposed on the particle shape, similar to DAMMIN. In equivalent conditions, DAMMIF is 25–40 times faster than DAMMIN on a single CPU. The possibility to utilize multiple CPUs is added to DAMMIF. The application is available in binary form for major platforms.

  10. Study of chemically unfolded β-casein by means of small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Aschi, Adel; Gharbi, Abdelhafidh; Daoud, Mohamed; Douillard, Roger; Calmettes, Patrick

    2007-01-01

    β-casein is a flexible amphiphilic milk protein which forms an unfolded conformation in presence of very high denaturant concentrations. The structure of β-casein formed at the bulk was studied by small-angle neutron scattering (SANS). The value of the second virial coefficient of the protein solutions indicates that the interactions between the polypeptide chain and solvent are repulsive. The protein conformation is similar to an excluded volume chain. The corresponding values of the contour length, L, the statistical length, b and the apparent radius of the chain cross-section, Rc are given.

  11. Small angle neutron scattering from nanocrystalline Pd and Co compacted at elevated temperatures

    SciTech Connect

    Sanders, P.G.; Weertman, J.R.; Barker, J.G.; Siegel, R.W.

    1994-05-01

    Nanocrystalline (n-) Cu and Pd, prepared by inert gas condensation and in situ room temperature (RT) and elevated temperature (warm) compactions, have been studied by small angle neutron scattering (SANS). Previous work on RT compacted and subsequently annealed n-Pd seemed to show that all the scattering could be accounted for by a distribution of pores. Analysis of more extensive SANS measurements, together with results of prompt gamma activation analysis, indicates that the SANS can be explained by the presence of pores and hydrogen. Warm compaction reduces the hydrogen impurity level, while increasing the bulk density and decreasing the pore size. This can lead to a dramatic hardness increase in these materials.

  12. Investigation of the tripoli porous structure by small-angle neutron scattering

    SciTech Connect

    Avdeev, M. V.; Blagoveshchenskii, N. M.; Garamus, V. M.; Novikov, A. G. Puchkov, A. V.

    2011-12-15

    The characteristics of the tripoli porous structure have been investigated by small-angle neutron scattering (SANS). Tripoli is a finely porous sedimentary rock formed by small spherical opal particles. Its main component is aqueous silica SiO{sub 2} {center_dot} nH{sub 2}O (80-90%). Tripoli is widely used in practice as a working medium for sorption filters and in some other commercial and construction technologies. The shape of the experimental SANS curves indicates the presence of small and large pores in tripoli. The small-pore size was estimated to be {approx}100 Angstrom-Sign . The size of large pores turned out to be beyond the range of neutron wave vector transfers Q that are available for the instrument used; however, their size was indirectly estimated to be {approx}(2000-2500) Angstrom-Sign . The pores of both groups behave as surfacetype fractal scatterers with the fractal dimension D {approx} 2.2-2.6. The densities of pores of these two groups differ by approximately three orders of magnitude ({approx}10{sup 16} and {approx}10{sup 13} cm{sup -3} for small and large pores, respectively); the fraction of large pores amounts to 70-80% of the total pore volume. The found pore characteristics (their densities, sizes, and relative volumes) are in satisfactory agreement (when a comparison is possible) with the absorption data.

  13. Comparison of tibial plateau angles in small and large breed dogs

    PubMed Central

    Su, Lillian; Townsend, Katy L.; Au, Jennifer; Wittum, Thomas E.

    2015-01-01

    Cranial cruciate ligament (CCL) disease can affect dogs of all sizes. The literature describing tibial plateau angle (TPA) in small breed dogs is limited. A retrospective study was conducted in unselected dogs presented for stifle or tibial examination to compare TPA in small breed dogs (n = 146 dogs, 185 stifles) versus large breed dogs (n = 200 dogs, 265 stifles). Small breed dogs had a mean TPA 3.1° ± 0.6° higher than large breed dogs. There were higher TPAs in spayed females and castrated males for all dogs compared with intact males (3.6° ± 1.0° and 2.7° ± 1.0°, respectively). Dogs with unilateral and bilateral CCL disease had higher TPAs compared to dogs with intact CCLs (2.0° ± 0.7° and 2.5° ± 0.8°, respectively). Tibial morphology differs between large and small breed dogs; however, the significance of the impact of TPA on CCL disease in small breed dogs is unknown. PMID:26028684

  14. Comparison of tibial plateau angles in small and large breed dogs.

    PubMed

    Su, Lillian; Townsend, Katy L; Au, Jennifer; Wittum, Thomas E

    2015-06-01

    Cranial cruciate ligament (CCL) disease can affect dogs of all sizes. The literature describing tibial plateau angle (TPA) in small breed dogs is limited. A retrospective study was conducted in unselected dogs presented for stifle or tibial examination to compare TPA in small breed dogs (n = 146 dogs, 185 stifles) versus large breed dogs (n = 200 dogs, 265 stifles). Small breed dogs had a mean TPA 3.1° ± 0.6° higher than large breed dogs. There were higher TPAs in spayed females and castrated males for all dogs compared with intact males (3.6° ± 1.0° and 2.7° ± 1.0°, respectively). Dogs with unilateral and bilateral CCL disease had higher TPAs compared to dogs with intact CCLs (2.0° ± 0.7° and 2.5° ± 0.8°, respectively). Tibial morphology differs between large and small breed dogs; however, the significance of the impact of TPA on CCL disease in small breed dogs is unknown.

  15. Optical and Geometric Properties of Free Silica Nanoparticles Studied by Small-Angle X-Ray Scattering

    NASA Astrophysics Data System (ADS)

    Langer, Burkhard; Raschpichler, Christopher; Gruner, Mathias; Antonsson, Egill; Goroncy, Christian; Graf, Christina; Rühl, Eckart

    2016-09-01

    Elastic small-angle X-ray scattering (SAXS) of free silica (SiO2) nanoparticles is reported (d = 100-180 nm). The particles were prepared by a modified Stöber synthesis in narrow size distributions with controlled surface roughness and functionalization. Angle-resolved small-angle X-ray scattering patterns are shown to be sensitive to these changes in particle properties. It is reported that there is an exponential decrease in scattered X-ray intensity towards larger scattering angles as well as distinct oscillations, which is fully explained by Mie theory. Small-angle X-ray scattering of mesoporous nanoparticles with rough surfaces is compared to that of microporous nanoparticles with smooth surfaces, revealing distinct differences that are rationalized by diffuse scattering from nanoparticle pores in addition to the dominating contribution of Mie scattering. Furthermore, results from small-angle X-ray scattering experiments on functionalized silica nanoparticles are presented, where the incorporation of the dye fluorescein isothiocyanate is found to cause changes in the optical properties of the nanoparticles, as compared to non-functionalized samples. Small, but distinct deviations in particle size derived from electron microscopy and from small-angle X-ray scattering are observed. These are rationalized by particle shrinking occurring in electron microscopy as well as slight changes in optical properties of the nanoparticle samples.

  16. Structure-property relationships in Waspaloy via small angle scattering and electrical resistivity measurements

    SciTech Connect

    Whelchel, R.; Gerhardt, Dr. Rosario; Littrell, Ken

    2010-01-01

    The mechanical properties in superalloys are controlled by the distribution of the {gamma}{prime} precipitate phase. Electrical measurements have been shown to be sensitive to certain aspects of the precipitation process and show promise for predicting the evolving microstructural state in superalloys. Aging experiments were conducted on Waspaloy samples for temperatures between 600 and 950 C for times ranging from 2min to 500h. Particle size distributions were obtained by modeling of small angle scattering (SAS) data, whereas, small precipitate size information, strain, and lattice mismatch data were obtained from X-ray diffraction. The microstructural information was then used to create a figure of merit of electron scattering intended to correlate electrical properties to the precipitate microstructure. The proposed figure of merit shows an empirical correlation with the electrical resistivity data, demonstrating the sensitivity of the resistivity measurements to the precipitation process and coarsening behavior.

  17. Time resolved small angle x-ray scattering reactivity studies on coals, asphaltenes, and polymers.

    SciTech Connect

    Seifert, S.; Thiyagarajan, P.; Winans, R. E.

    1999-07-02

    The objective of this study is to examine changes in the structures of coals, asphaltenes, and polymers in situ with small angle X-ray scattering (SAXS) during thermal treatments. We have built a SAXS instrument at the Basic Energy Sciences Synchrotrons Radiation Center at the Advanced Photon Source that allows us to obtain scattering data on very small samples and in the millisecond time domain. The Argonne Premium Coal samples, petroleum derived asphaltenes, and polymers with functionality to model fossil fuels were used in this study. The information that can be derived from these experiments includes: changes in fractal dimensionality, surface topology, and size and type of porosity. The information is correlated with other methods on the same samples.

  18. Sample holder for small-angle x-ray scattering static and flow cell measurements

    SciTech Connect

    Lipfert, Jan; Millett, Ian S.; Seifert, Soenke; Doniach, Sebastian

    2006-04-15

    We present the design of a sample holder for small-angle x-ray scattering (SAXS) that can be used for both static and flow cell measurements, allowing to switch between these two types of measurement without having to realign the detector and camera geometry. The device makes possible high signal-to-noise experiments with sample volumes as small as 16 {mu}l and can be thermocontrolled using a standard circulating water bath. The setup has been used successfully for a range of biological SAXS measurements, including peptides, detergent micelles, membrane proteins, and nucleic acids. As a performance test, we present scattering data for horse heart cytochrome c, collected at the BESSRC CAT beam line 12-ID of the Advanced Photon Source. The design drawings are provided in the supplementary material.

  19. Micelle structural studies on oil solubilization by a small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Putra, Edy Giri Rachman; Seong, Baek Seok; Ikram, Abarrul

    2009-02-01

    A small-angle neutron scattering (SANS) technique was applied to reveal the micelle structural changes. The micelle structural changes of 0.3 M sodium dodecyl sulfate (SDS) concentration by addition of various oil, i.e. n-hexane, n-octane, and n-decane up to 60% (v/v) have been investigated. It was found that the size, aggregation number and the structures of the micelles changed exhibiting that the effective charge on the micelle decreases with an addition of oil. There was a small increase in minor axis of micelle while the correlation peak shifted to a lower momentum transfer Q and then to higher Q by a further oil addition.

  20. On the effect of emergence angle on emissivity spectra: application to small bodies

    NASA Astrophysics Data System (ADS)

    Maturilli, Alessandro; Helbert, Jörn; Ferrari, Sabrina; D'Amore, Mario

    2016-05-01

    Dependence of laboratory-measured emissivity spectra from the emergence angle is a subject that still needs a lot of investigations to be fully understood. Most of the previous work is based on reflectance measurements in the VIS-NIR spectral region and on emissivity measurements of flat, solid surfaces (mainly metals), which are not directly applicable to the analysis of remote sensing data. Small bodies in particular (c.f. asteroids Itokawa and 1999JU3, the respective targets of JAXA Hayabusa and Hayabusa 2 missions) have a very irregular surface; hence, the spectra from those rough surfaces are difficult to compare with laboratory spectra, where the observing geometry is always close to "nadir." At the Planetary Emissivity Laboratory of the German Aerospace Center (DLR), we have set up a series of spectral measurements to investigate this problem in the 1- to 16-µm spectral region. We measured the emissivity for two asteroid analogue materials (meteorite Millbillillie and a synthetic enstatite) in vacuum and under purged air, at surface temperature of 100 °C, for emergence angles of 0°, 5°, 10°, 20°, 30°, 40°, 50°, and 60°. Emissivity of a serpentinite slab, already used as calibration target for the MARA instrument on Hayabusa 2 MASCOT lander and for the thermal infrared imager spectrometer on Hayabusa 2 orbiter, was measured under the same conditions. Additionally, a second basalt slab was measured. Both slabs were not measured at 5° inclination. Complementary reflectance measurements of the four samples were taken. For all the samples measured, we found that for calibrated emissivity, significant variations from values obtained at nadir (0° emergence angle) appear only for emergence angles ≥40°. Reflectance measurements confirmed this finding, showing the same trend of variations.

  1. Wavelength-independent constant period spin-echo modulated small angle neutron scattering.

    PubMed

    Sales, Morten; Plomp, Jeroen; Habicht, Klaus; Tremsin, Anton; Bouwman, Wim; Strobl, Markus

    2016-06-01

    Spin-Echo Modulated Small Angle Neutron Scattering (SEMSANS) in Time-of-Flight (ToF) mode has been shown to be a promising technique for measuring (very) small angle neutron scattering (SANS) signals and performing quantitative Dark-Field Imaging (DFI), i.e., SANS with 2D spatial resolution. However, the wavelength dependence of the modulation period in the ToF spin-echo mode has so far limited the useful modulation periods to those resolvable with the limited spatial resolution of the detectors available. Here we present our results of an approach to keep the period of the induced modulation constant for the wavelengths utilised in ToF. This is achieved by ramping the magnetic fields in the coils responsible for creating the spatially modulated beam in synchronisation with the neutron pulse, thus keeping the modulation period constant for all wavelengths. Such a setup enables the decoupling of the spatial detector resolution from the resolution of the modulation period by the use of slits or gratings in analogy to the approach in grating-based neutron DFI.

  2. Small-angle neutron and dynamic light scattering study of gelatin coacervates

    NASA Astrophysics Data System (ADS)

    Mohanty, B.; Aswal, V. K.; Goyal, P. S.; Bohidar, H. B.

    2004-08-01

    The state of intermolecular aggregates and that of folded gelatin molecules could be characterized by dynamic laser light and small-angle neutron scattering experiments, which implied spontaneous segregation of particle sizes preceding coacervation, which is a liquid-liquid phase transition phenomenon. Dynamic light scattering (DLS) data analysis revealed two particle sizes until precipitation was reached. The smaller particles having a diameter of 50 nm (stable nanoparticles prepared by coacervation method) were detected in the supernatant, whereas the inter-molecular aggregates having a diameter of 400 nm gave rise to coacervation. Small-angle neutron scattering (SANS) experiments revealed that typical mesh size of the networks exist in polymer dense phase (coacervates) [1]. Analysis of the SANS structure factor showed the presence of two length scales associated with this system that were identified as the correlation length or mesh size, xi = 10.6 Å of the network and the other is the size of inhomogeneities = 21.4 Å. Observations were discussed based on the results obtained from SANS experiments performed in 5% (w/v) gelatin solution at 60oC (xi = 50 Å, zeta = 113 Å) and 5% (w/v) gel at 28oC (xi = 47 Å, zeta = 115 Å) in aqueous phase [2] indicating smaller length scales in coacervate as compared to sol and gel.

  3. SASfit: a tool for small-angle scattering data analysis using a library of analytical expressions

    PubMed Central

    Breßler, Ingo; Kohlbrecher, Joachim; Thünemann, Andreas F.

    2015-01-01

    SASfit is one of the mature programs for small-angle scattering data analysis and has been available for many years. This article describes the basic data processing and analysis workflow along with recent developments in the SASfit program package (version 0.94.6). They include (i) advanced algorithms for reduction of oversampled data sets, (ii) improved confidence assessment in the optimized model parameters and (iii) a flexible plug-in system for custom user-provided models. A scattering function of a mass fractal model of branched polymers in solution is provided as an example for implementing a plug-in. The new SASfit release is available for major platforms such as Windows, Linux and MacOS. To facilitate usage, it includes comprehensive indexed documentation as well as a web-based wiki for peer collaboration and online videos demonstrating basic usage. The use of SASfit is illustrated by interpretation of the small-angle X-ray scattering curves of monomodal gold nanoparticles (NIST reference material 8011) and bimodal silica nanoparticles (EU reference material ERM-FD-102). PMID:26500467

  4. Small-angle neutron and X-ray scattering reveal conformational changes in rhodopsin activation

    NASA Astrophysics Data System (ADS)

    Shrestha, Utsab R.; Bhowmik, Debsindhu; Perera, Suchitrhanga M. C. D.; Chawla, Udeep; Struts, Andrey V.; Graziono, Vito; Pingali, Sai Venkatesh; Heller, William T.; Qian, Shuo; Brown, Michael F.; Chu, Xiang-Qiang

    2015-03-01

    Understanding G-protein-coupled receptor (GPCR) activation plays a crucial role in the development of novel improved molecular drugs. During photo-activation, the retinal chromophore of the visual GPCR rhodopsin isomerizes from 11-cis to all-trans conformation, yielding an equilibrium between inactive Meta-I and active Meta-II states. The principal goals of this work are to address whether the activation of rhodopsin leads to a single state or a conformational ensemble, and how protein organizational structure changes with detergent environment in solution. We use both small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) techniques to answer the above questions. For the first time we observe the change in protein conformational ensemble upon photo-activation by SANS with contrast variation, which enables the separate study of the protein structure within the detergent assembly. In addition, SAXS study of protein structure within detergent assembly suggests that the detergent molecules form a belt of monolayer (micelle) around protein with different geometrical shapes to keep the protein in folded state.

  5. Two-dimensional granular flow in a vibrated small-angle funnel

    PubMed

    Lindemann; Dimon

    2000-10-01

    We have studied the flow of a single layer of uniform balls in a small-angle funnel when it is vibrated parallel to the flow. Generally, we measured the flow rate as a function of a dimensionless acceleration Gamma. However, for sufficiently small outlet widths, the flow can jam so we also measured the elapsed times between balls and their correlations to study jam dynamics. In particular, we found that when the funnel angle beta was larger than approximately 4 degrees, a stable jam always formed for Gamma<1 and the flow stopped. For Gamma approximately 1-4, jams still occurred, but now they broke and reformed, although they could last approximately 100 s, resulting in long-time correlations in the flow. The elapsed time distributions in this case show distinct, possibly algebraic, tails. Beyond Gamma approximately 4, the flow no longer jammed and the flow rate became constant. The general behavior has been mapped out in a rough phase diagram.

  6. Small-angle scattering for structural biology—Expanding the frontier while avoiding the pitfalls

    PubMed Central

    Jacques, David A; Trewhella, Jill

    2010-01-01

    The last decade has seen a dramatic increase in the use of small-angle scattering for the study of biological macromolecules in solution. The drive for more complete structural characterization of proteins and their interactions, coupled with the increasing availability of instrumentation and easy-to-use software for data analysis and interpretation, is expanding the utility of the technique beyond the domain of the biophysicist and into the realm of the protein scientist. However, the absence of publication standards and the ease with which 3D models can be calculated against the inherently 1D scattering data means that an understanding of sample quality, data quality, and modeling assumptions is essential to have confidence in the results. This review is intended to provide a road map through the small-angle scattering experiment, while also providing a set of guidelines for the critical evaluation of scattering data. Examples of current best practice are given that also demonstrate the power of the technique to advance our understanding of protein structure and function. PMID:20120026

  7. A small-angle x-ray scattering system with a vertical layout

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Chen, Xiaowei; Meng, Lingpu; Cui, Kunpeng; Wu, Lihui; Li, Liangbin

    2014-12-01

    A small-angle x-ray scattering (SAXS) system with a vertical layout (V-SAXS) has been designed and constructed for in situ detection on nanostructures, which is well suitable for in situ study on self-assembly of nanoparticles at liquid interface and polymer processing. A steel-tower frame on a reinforced basement is built as the supporting skeleton for scattering beam path and detector platform, ensuring the system a high working stability and a high operating accuracy. A micro-focus x-ray source combining parabolic three-dimensional multi-layer mirror and scatteringless collimation system provides a highly parallel beam, which allows us to detect the very small angle range. With a sample-to-detector distance of 7 m, the largest measurable length scale is 420 nm in real space. With a large sample zone, it is possible to install different experimental setups such as film stretching machine, which makes the system perfect to follow the microstructures evolution of materials during processing. The capability of the V-SAXS on in situ study is tested with a drying experiment of a free latex droplet, which confirms our initial design.

  8. Laser desorption mass spectrometry and small angle neutron scattering of heavy fossil materials

    SciTech Connect

    Hunt, J.E.; Winans, R.E.; Thiyagarajan, P.

    1997-09-01

    The determination of the structural building blocks and the molecular weight range of heavy hydrocarbon materials is of crucial importance in research on their reactivity and for their processing. The chemically and physically heterogenous nature of heavy hydrocarbon materials, such as coals, heavy petroleum fractions, and residues, dictates that their structure and reactivity patterns be complicated. The problem is further complicated by the fact that the molecular structure and molecular weight distribution of these materials is not dependent on a single molecule, but on a complex mixture of molecules which vary among coals and heavy petroleum samples. Laser Desorption mass spectrometry (LDMS) is emerging as a technique for molecular weight determination having found widespread use in biological polymer research, but is still a relatively new technique in the fossil fuel area. Small angle neutron scattering (SANS) provides information on the size and shape of heavy fossil materials. SANS offers the advantages of high penetration power even in thick cells at high temperatures and high contrast for hydrocarbon systems dispersed in deuterated solvents. LDMS coupled with time of flight has the advantages of high sensitivity and transmission and high mass range. We have used LDMS to examine various heavy fossil-derived materials including: long chain hydrocarbons, asphaltenes from petroleum vacuum resids, and coals. This paper describes the application of laser desorption and small angle neutron scattering techniques to the analysis of components in coals, petroleum resids and unsaturated polymers.

  9. A small-angle x-ray scattering system with a vertical layout.

    PubMed

    Wang, Zhen; Chen, Xiaowei; Meng, Lingpu; Cui, Kunpeng; Wu, Lihui; Li, Liangbin

    2014-12-01

    A small-angle x-ray scattering (SAXS) system with a vertical layout (V-SAXS) has been designed and constructed for in situ detection on nanostructures, which is well suitable for in situ study on self-assembly of nanoparticles at liquid interface and polymer processing. A steel-tower frame on a reinforced basement is built as the supporting skeleton for scattering beam path and detector platform, ensuring the system a high working stability and a high operating accuracy. A micro-focus x-ray source combining parabolic three-dimensional multi-layer mirror and scatteringless collimation system provides a highly parallel beam, which allows us to detect the very small angle range. With a sample-to-detector distance of 7 m, the largest measurable length scale is 420 nm in real space. With a large sample zone, it is possible to install different experimental setups such as film stretching machine, which makes the system perfect to follow the microstructures evolution of materials during processing. The capability of the V-SAXS on in situ study is tested with a drying experiment of a free latex droplet, which confirms our initial design.

  10. Small angle scattering methods to study porous materials under high uniaxial strain

    SciTech Connect

    Le Floch, Sylvie Balima, Félix; Pischedda, Vittoria; Legrand, Franck; San-Miguel, Alfonso

    2015-02-15

    We developed a high pressure cell for the in situ study of the porosity of solids under high uniaxial strain using neutron small angle scattering. The cell comprises a hydraulically actioned piston and a main body equipped with two single-crystal sapphire windows allowing for the neutron scattering of the sample. The sample cavity is designed to allow for a large volume variation as expected when compressing highly porous materials. We also implemented a loading protocol to adapt an existing diamond anvil cell for the study of porous materials by X-ray small angle scattering under high pressure. The two techniques are complementary as the radiation beam and the applied pressure are in one case perpendicular to each other (neutron cell) and in the other case parallel (X-ray cell). We will illustrate the use of these two techniques in the study of lamellar porous systems up to a maximum pressure of 0.1 GPa and 0.3 GPa for the neutron and X-ray cells, respectively. These devices allow obtaining information on the evolution of porosity with pressure in the pore dimension subdomain defined by the wave-numbers explored in the scattering process. The evolution with the applied load of such parameters as the fractal dimension of the pore-matrix interface or the apparent specific surface in expanded graphite and in expanded vermiculite is used to illustrate the use of the high pressure cells.

  11. Small-Angle Neutron Scattering for Structural Biology of Protein-RNA Complexes.

    PubMed

    Gabel, Frank

    2015-01-01

    This chapter deals with the applications of small-angle neutron scattering (SANS) for the structural study of protein-RNA complexes in solution. After a brief historical introduction, the basic theory and practical requirements (e.g., sample state) for SANS experiments will be treated. Next, model-free parameters, such as the molecular mass and the radius of gyration, which can be obtained without a priori structural information, will be introduced. A more detailed section on the specific properties of SANS (with respect to its sister technique, small-angle X-ray scattering), and their implications on possibilities and limits of model building and interpretation will be discussed with a focus on protein-RNA systems. A practical illustration of the information content of SANS data will be given by applying ab initio modeling to a tRNA-synthetase system of known high-resolution structure. Finally, two present state-of-the-art examples that combine SANS data with complementary structural biology techniques (NMR and crystallography) will be presented and possible future developments and applications will be discussed.

  12. Wavelength-independent constant period spin-echo modulated small angle neutron scattering.

    PubMed

    Sales, Morten; Plomp, Jeroen; Habicht, Klaus; Tremsin, Anton; Bouwman, Wim; Strobl, Markus

    2016-06-01

    Spin-Echo Modulated Small Angle Neutron Scattering (SEMSANS) in Time-of-Flight (ToF) mode has been shown to be a promising technique for measuring (very) small angle neutron scattering (SANS) signals and performing quantitative Dark-Field Imaging (DFI), i.e., SANS with 2D spatial resolution. However, the wavelength dependence of the modulation period in the ToF spin-echo mode has so far limited the useful modulation periods to those resolvable with the limited spatial resolution of the detectors available. Here we present our results of an approach to keep the period of the induced modulation constant for the wavelengths utilised in ToF. This is achieved by ramping the magnetic fields in the coils responsible for creating the spatially modulated beam in synchronisation with the neutron pulse, thus keeping the modulation period constant for all wavelengths. Such a setup enables the decoupling of the spatial detector resolution from the resolution of the modulation period by the use of slits or gratings in analogy to the approach in grating-based neutron DFI. PMID:27370470

  13. A small-angle x-ray scattering system with a vertical layout

    SciTech Connect

    Wang, Zhen; Chen, Xiaowei; Meng, Lingpu; Cui, Kunpeng; Wu, Lihui; Li, Liangbin

    2014-12-15

    A small-angle x-ray scattering (SAXS) system with a vertical layout (V-SAXS) has been designed and constructed for in situ detection on nanostructures, which is well suitable for in situ study on self-assembly of nanoparticles at liquid interface and polymer processing. A steel-tower frame on a reinforced basement is built as the supporting skeleton for scattering beam path and detector platform, ensuring the system a high working stability and a high operating accuracy. A micro-focus x-ray source combining parabolic three-dimensional multi-layer mirror and scatteringless collimation system provides a highly parallel beam, which allows us to detect the very small angle range. With a sample-to-detector distance of 7 m, the largest measurable length scale is 420 nm in real space. With a large sample zone, it is possible to install different experimental setups such as film stretching machine, which makes the system perfect to follow the microstructures evolution of materials during processing. The capability of the V-SAXS on in situ study is tested with a drying experiment of a free latex droplet, which confirms our initial design.

  14. Morphological characterization of carbon-nanofiber-reinforced epoxy nanocomposites using ultra-small angle scattering

    SciTech Connect

    Justice, R.S.; Anderson, D.P.; Brown, J.M.; Arlen, M.J.; Colleary, A.J.; Lafdi, K.; Schaefer, D.W.

    2010-07-01

    Studies of the properties of nanocomposites reinforced with vapor-grown carbon nanofibers (VGCFs) can be found throughout the literature. Electrical, mechanical, viscoelastic, and rheological properties are just a few of the characteristics that have been well discussed. Although these properties depend on morphology, morphological characterization is rare. Due to its 2-dimensional nature, microscopy is of limited value when analyzing network morphologies. This work will show how the characterization of the three-dimensional geometry and network formation of VGCFs can be determined using ultra-small angle scattering techniques. Ultra-small angle x-ray and neutron scattering (USAXS and USANS) were used to characterize the morphology of carbon nanofibers suspended in epoxy. Using a simplified tube model, we estimate the dimensions of suspended fibers. The assumption of tubular fibers accounts for the increased surface area observed with USAXS that is not accounted for using a solid rod model. Furthermore, USANS was used to search for a structural signature associated with the electrical percolation threshold. USANS extends to longer dimensional scales than USAXS, which measures a smaller range of momentum transfer. To determine the electrical percolation threshold, AC impedance spectroscopy was employed to verify that an electrically conductive, percolated network forms at VGCNF loadings of 0.8% < CNF wt% < 1.2%. These values correlate with the USANS data, where a morphological transition is seen at {approx}1.2% loading.

  15. Wavelength-independent constant period spin-echo modulated small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Sales, Morten; Plomp, Jeroen; Habicht, Klaus; Tremsin, Anton; Bouwman, Wim; Strobl, Markus

    2016-06-01

    Spin-Echo Modulated Small Angle Neutron Scattering (SEMSANS) in Time-of-Flight (ToF) mode has been shown to be a promising technique for measuring (very) small angle neutron scattering (SANS) signals and performing quantitative Dark-Field Imaging (DFI), i.e., SANS with 2D spatial resolution. However, the wavelength dependence of the modulation period in the ToF spin-echo mode has so far limited the useful modulation periods to those resolvable with the limited spatial resolution of the detectors available. Here we present our results of an approach to keep the period of the induced modulation constant for the wavelengths utilised in ToF. This is achieved by ramping the magnetic fields in the coils responsible for creating the spatially modulated beam in synchronisation with the neutron pulse, thus keeping the modulation period constant for all wavelengths. Such a setup enables the decoupling of the spatial detector resolution from the resolution of the modulation period by the use of slits or gratings in analogy to the approach in grating-based neutron DFI.

  16. Small angle scattering methods to study porous materials under high uniaxial strain.

    PubMed

    Le Floch, Sylvie; Balima, Félix; Pischedda, Vittoria; Legrand, Franck; San-Miguel, Alfonso

    2015-02-01

    We developed a high pressure cell for the in situ study of the porosity of solids under high uniaxial strain using neutron small angle scattering. The cell comprises a hydraulically actioned piston and a main body equipped with two single-crystal sapphire windows allowing for the neutron scattering of the sample. The sample cavity is designed to allow for a large volume variation as expected when compressing highly porous materials. We also implemented a loading protocol to adapt an existing diamond anvil cell for the study of porous materials by X-ray small angle scattering under high pressure. The two techniques are complementary as the radiation beam and the applied pressure are in one case perpendicular to each other (neutron cell) and in the other case parallel (X-ray cell). We will illustrate the use of these two techniques in the study of lamellar porous systems up to a maximum pressure of 0.1 GPa and 0.3 GPa for the neutron and X-ray cells, respectively. These devices allow obtaining information on the evolution of porosity with pressure in the pore dimension subdomain defined by the wave-numbers explored in the scattering process. The evolution with the applied load of such parameters as the fractal dimension of the pore-matrix interface or the apparent specific surface in expanded graphite and in expanded vermiculite is used to illustrate the use of the high pressure cells.

  17. Irradiation Induced Defect Characterization in Reactor Pressure Vessel Steel by Small Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Han, Yougn-Soo; Shin, Eun-Joo; Lee, Chang-Hee; Park, Duck-Gun

    The degradation of the mechanical properties of the RPV (Reactor Pressure Vessel) steel during an irradiation in a nuclear power plant is closely related to the irradiation induced defects. The size of these defects is known to be a few nanometer, and the small angle neutron scattering technique is regarded as the best non destructive technique to characterize the nano sized inhomogeneities in bulk samples. The investigated the RPV steel has been used in YeongKwang nuclear power plant at Korea and the Cu content of the RPV steel is 0.06 wt%. The RPV steel was irradiated in the HANARO reactor at KAERI. The small angle neutron scattering experiments were performed by the SANS instrument in the HANARO reactor. The nano sized irradiation induced defects were quantitatively analyzed by SANS and the type of the irradiation induced defects was discussed in detail. The relation between irradiation induced defects and the yield strength was investigated. The characteristics of irradiation induced defects in low Cu containing RPV steel were discussed.

  18. Anomalous current-voltage characteristics due to macroscopic resonant tunneling in a small Josephson junction

    SciTech Connect

    Hatakenaka, N.; Kurihara, S. ); Takayanagi, H. )

    1990-09-01

    Current-voltage characteristics of a small Josephson junction are studied, taking into account quantized energy levels in the Josephson potential. In the energy regions where the Josephson coupling energy is greater than the charging energy at zero temperature, it is predicted that voltage spikes in a usual zero-voltage state branch will appear due to resonant phase slips by macroscopic quantum tunneling. These spikes are very different from those expected by the Bloch oscillation mechanism based on the band motion of the macroscopic variable.

  19. Pinhole-type two-dimensional ultra-small-angle X-ray scattering on the micrometer scale.

    PubMed

    Kishimoto, Hiroyuki; Shinohara, Yuya; Suzuki, Yoshio; Takeuchi, Akihisa; Yagi, Naoto; Amemiya, Yoshiyuki

    2014-01-01

    A pinhole-type two-dimensional ultra-small-angle X-ray scattering set-up at a so-called medium-length beamline at SPring-8 is reported. A long sample-to-detector distance, 160.5 m, can be used at this beamline and a small-angle resolution of 0.25 µm(-1) was thereby achieved at an X-ray energy of 8 keV. PMID:24365910

  20. Pinhole-type two-dimensional ultra-small-angle X-ray scattering on the micrometer scale

    PubMed Central

    Kishimoto, Hiroyuki; Shinohara, Yuya; Suzuki, Yoshio; Takeuchi, Akihisa; Yagi, Naoto; Amemiya, Yoshiyuki

    2014-01-01

    A pinhole-type two-dimensional ultra-small-angle X-ray scattering set-up at a so-called medium-length beamline at SPring-8 is reported. A long sample-to-detector distance, 160.5 m, can be used at this beamline and a small-angle resolution of 0.25 µm−1 was thereby achieved at an X-ray energy of 8 keV. PMID:24365910

  1. Probing the conformation of FhaC with small-angle neutron scattering and molecular modeling.

    PubMed

    Gabel, Frank; Lensink, Marc F; Clantin, Bernard; Jacob-Dubuisson, Françoise; Villeret, Vincent; Ebel, Christine

    2014-07-01

    Probing the solution structure of membrane proteins represents a formidable challenge, particularly when using small-angle scattering. Detergent molecules often present residual scattering contributions even at their match point in small-angle neutron scattering (SANS) measurements. Here, we studied the conformation of FhaC, the outer-membrane, β-barrel transporter of the Bordetella pertussis filamentous hemagglutinin adhesin. SANS measurements were performed on homogeneous solutions of FhaC solubilized in n-octyl-d17-βD-glucoside and on a variant devoid of the α helix H1, which critically obstructs the FhaC pore, in two solvent conditions corresponding to the match points of the protein and the detergent, respectively. Protein-bound detergent amounted to 142 ± 10 mol/mol as determined by analytical ultracentrifugation. By using molecular modeling and starting from three distinct conformations of FhaC and its variant embedded in lipid bilayers, we generated ensembles of protein-detergent arrangement models with 120-160 detergent molecules. The scattered curves were back-calculated for each model and compared with experimental data. Good fits were obtained for relatively compact, connected detergent belts, which occasionally displayed small detergent-free patches on the outer surface of the β barrel. The combination of SANS and modeling clearly enabled us to infer the solution structure of FhaC, with H1 inside the pore as in the crystal structure. We believe that our strategy of combining explicit atomic detergent modeling with SANS measurements has significant potential for structural studies of other detergent-solubilized membrane proteins. PMID:24988353

  2. Probing the Conformation of FhaC with Small-Angle Neutron Scattering and Molecular Modeling

    PubMed Central

    Gabel, Frank; Lensink, Marc F.; Clantin, Bernard; Jacob-Dubuisson, Françoise; Villeret, Vincent; Ebel, Christine

    2014-01-01

    Probing the solution structure of membrane proteins represents a formidable challenge, particularly when using small-angle scattering. Detergent molecules often present residual scattering contributions even at their match point in small-angle neutron scattering (SANS) measurements. Here, we studied the conformation of FhaC, the outer-membrane, β-barrel transporter of the Bordetella pertussis filamentous hemagglutinin adhesin. SANS measurements were performed on homogeneous solutions of FhaC solubilized in n-octyl-d17-βD-glucoside and on a variant devoid of the α helix H1, which critically obstructs the FhaC pore, in two solvent conditions corresponding to the match points of the protein and the detergent, respectively. Protein-bound detergent amounted to 142 ± 10 mol/mol as determined by analytical ultracentrifugation. By using molecular modeling and starting from three distinct conformations of FhaC and its variant embedded in lipid bilayers, we generated ensembles of protein-detergent arrangement models with 120–160 detergent molecules. The scattered curves were back-calculated for each model and compared with experimental data. Good fits were obtained for relatively compact, connected detergent belts, which occasionally displayed small detergent-free patches on the outer surface of the β barrel. The combination of SANS and modeling clearly enabled us to infer the solution structure of FhaC, with H1 inside the pore as in the crystal structure. We believe that our strategy of combining explicit atomic detergent modeling with SANS measurements has significant potential for structural studies of other detergent-solubilized membrane proteins. PMID:24988353

  3. NanoARPES of twisted bilayer graphene on SiC: absence of velocity renormalization for small angles.

    PubMed

    Razado-Colambo, I; Avila, J; Nys, J-P; Chen, C; Wallart, X; Asensio, M-C; Vignaud, D

    2016-01-01

    The structural and electronic properties of twisted bilayer graphene (TBG) on SiC(000) grown by Si flux-assisted molecular beam epitaxy were investigated using scanning tunneling microscopy (STM) and angle-resolved photoelectron spectroscopy with nanometric spatial resolution. STM images revealed a wide distribution of twist angles between the two graphene layers. The electronic structure recorded in single TBG grains showed two closely-spaced Dirac π bands associated to the two stacked layers with respective twist angles in the range 1-3°. The renormalization of velocity predicted in previous theoretical calculations for small twist angles was not observed. PMID:27264791

  4. NanoARPES of twisted bilayer graphene on SiC: absence of velocity renormalization for small angles

    PubMed Central

    Razado-Colambo, I.; Avila, J.; Nys, J.-P.; Chen, C.; Wallart, X.; Asensio, M.-C.; Vignaud, D.

    2016-01-01

    The structural and electronic properties of twisted bilayer graphene (TBG) on SiC(000) grown by Si flux-assisted molecular beam epitaxy were investigated using scanning tunneling microscopy (STM) and angle-resolved photoelectron spectroscopy with nanometric spatial resolution. STM images revealed a wide distribution of twist angles between the two graphene layers. The electronic structure recorded in single TBG grains showed two closely-spaced Dirac π bands associated to the two stacked layers with respective twist angles in the range 1–3°. The renormalization of velocity predicted in previous theoretical calculations for small twist angles was not observed. PMID:27264791

  5. Anomalously small resistivity and thermopower of strongly compensated semiconductors and topological insulators

    NASA Astrophysics Data System (ADS)

    Chen, Tianran; Shklovskii, B. I.

    2013-04-01

    In the recent paper, we explained why the maximum bulk resistivity of topological insulators (TIs) such as Bi2Se3 is so small [B. Skinner, T. Chen, and B. I. Shklovskii, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.109.176801 109, 176801 (2012)]. Using the model of completely compensated semiconductor we showed that when the Fermi level is pinned in the middle of the gap the activation energy of resistivity is Δ=0.3(Eg/2), where Eg is the semiconductor gap. In this paper, we consider a strongly compensated n-type semiconductor. We find the position of the Fermi level μ calculated from the bottom of the conduction band Ec and the activation energy of resistivity Δ as a function of compensation K, and show that Δ=0.3(Ec-μ) holds at any 0<1-K≪1. In the same range of relatively high temperatures, the Peltier energy (heat) Π is even smaller: Π≃Δ/2=0.15(Ec-μ). We also show that at low temperatures, the activated conductivity crosses over to variable range hopping (VRH) and find the characteristic temperature of VRH, TES, as a function of K.

  6. Anomalous glass transition behavior of SBR-Al₂O₃ nanocomposites at small filler concentrations.

    PubMed

    Sushko, Rymma; Filimon, Marlena; Dannert, Rick; Elens, Patrick; Sanctuary, Roland; Baller, Jörg

    2014-10-24

    Elastomers filled with hard nanoparticles are of great technical importance for the rubber industry. In general, fillers improve mechanical properties of polymer materials, e.g. elastic moduli, tensile strength etc. The smaller the size of the particles, the larger is the interface where interactions between polymer molecules and fillers can generate new properties. Using temperature-modulated differential scanning calorimetry and dynamic mechanical analysis, we investigated the properties of pure styrene-butadiene rubber (SBR) and SBR/alumina nanoparticles. Beside a reinforcement effect seen in the complex elastic moduli, small amounts of nanoparticles of about 2 wt% interestingly lead to an acceleration of the relaxation modes responsible for the thermal glass transition. This leads to a minimum in the glass transition temperature as a function of nanoparticle content in the vicinity of this critical concentration. The frequency dependent elastic moduli are used to discuss the possible reduction of the entanglement of rubber molecules as one cause for this unexpected behavior. PMID:25277754

  7. Magnetization processes in nanostructured metals and small-angle neutron scattering

    SciTech Connect

    Loeffler, J.F.; Braun, H.B.; Wagner, W.; Kostorz, G.; Wiedenmann, A.

    2005-04-01

    The magnetization process in nanostructured (n-) Fe and Co was investigated via small-angle neutron scattering (SANS). In a zero field, the magnetization exhibits correlations extending over several grains. In intermediate applied magnetic fields around 1 kOe, n-Fe and n-Co samples with small grain sizes exhibit an anisotropic scattering profile with an unusual intensity enhancement for scattering vectors parallel to the field direction. Comparing the experimental data with a modeled granular microstructure containing magnetic domains of arbitrary size and orientation, we conclude that magnetic domains extending over several grains are tilted considerably out of the external field direction in intermediate fields. Since the domain size does not change significantly with the magnitude of the external field, we conclude that the magnetization process does not proceed via domain-wall motion. Together with theoretical arguments showing the existence of marginally stable domains within the random-anisotropy model, our SANS data suggests that the magnetization process proceeds by simultaneous reversal of a few adjacent domains, presumably in the form of small avalanches. This resembles the magnetization process predicted for random-field Ising magnets. Our theoretical analysis of SANS data is general and applies to other systems consisting of magnetic nanoclusters embedded in a nonmagnetic matrix.

  8. Monomeric Amyloid Beta Peptide in Hexafluoroisopropanol Detected by Small Angle Neutron Scattering

    PubMed Central

    Zhang-Haagen, Bo; Biehl, Ralf; Nagel-Steger, Luitgard; Radulescu, Aurel; Richter, Dieter; Willbold, Dieter

    2016-01-01

    Small proteins like amyloid beta (Aβ) monomers are related to neurodegenerative disorders by aggregation to insoluble fibrils. Small angle neutron scattering (SANS) is a nondestructive method to observe the aggregation process in solution. We show that SANS is able to resolve monomers of small molecular weight like Aβ for aggregation studies. We examine Aβ monomers after prolonged storing in d-hexafluoroisopropanol (dHFIP) by using SANS and dynamic light scattering (DLS). We determined the radius of gyration from SANS as 1.0±0.1 nm for Aβ1–40 and 1.6±0.1 nm for Aβ1–42 in agreement with 3D NMR structures in similar solvents suggesting a solvent surface layer with 5% increased density. After initial dissolution in dHFIP Aβ aggregates sediment with a major component of pure monomers showing a hydrodynamic radius of 1.8±0.3 nm for Aβ1–40 and 3.2±0.4 nm for Aβ1–42 including a surface layer of dHFIP solvent molecules. PMID:26919121

  9. MISLIFT- AERODYNAMIC LIFT ON WING-BODY COMBINATIONS AT SMALL ANGLES OF ATTACK IN SUPERSONIC FLOW

    NASA Technical Reports Server (NTRS)

    Sawyer, W. C.

    1994-01-01

    Two separate and distinct theories are incorporated in this computer program to estimate the lift-induced pressures existent on a wing-body combination. These are (1) the second-order shock-expansion theory, which is used to obtain the lifting pressures on the body alone at small angles of attack, and (2) the linear-theory integral equations, which is used to evaluate the lifting pressures induced by the wing. These equations relate the local surface slope at a point on the lifting surface to the pressure differential at the point and the influence of the pressures upstream of the point. The numerical solution of these equations is effected by treating the wing-planform as a composite of elemental rectangles and applying summation techniques to satisfy the necessary integral relations. Most of the input required by this program is involved with the description of the missile planform geometry. The output consists of the computed value of the lifting pressure slope (the differential pressure coefficient per degree angle of attack) for each of the elements in the planform array. A force and moment summary is presented for the configuration under consideration.

  10. Kinetic small angle neutron scattering of the skyrmion lattice in MnSi

    NASA Astrophysics Data System (ADS)

    Mühlbauer, S.; Kindervater, J.; Adams, T.; Bauer, A.; Keiderling, U.; Pfleiderer, C.

    2016-07-01

    We report a kinetic small angle neutron scattering (SANS) study of the skyrmion lattice (SL) in MnSi. Induced by an oscillatory tilting of the magnetic field direction, the elasticity and relaxation of the SL along the magnetic field direction have been measured with microsecond resolution. For the excitation frequency of 325 {{Hz}} the SL begins to track the tilting motion of the applied magnetic field under tilting angles exceeding {α }{{c}}≳ 0.4^\\circ . Empirically the associated angular velocity of the tilting connects quantitatively with the critical charge carrier velocity of ∼ 0.1 {{mm}} {{{s}}}-1 under current driven spin transfer torques, for which the SL unpins. In addition, a pronounced temperature dependence of the skyrmion motion is attributed to the variation of the skyrmion stiffness. Taken together our study highlights the power of kinetic SANS as a new experimental tool to explore, in a rather general manner, the elasticity and impurity pinning of magnetic textures across a wide parameter space without parasitic signal interferences due to ohmic heating or Oersted magnetic fields.

  11. Glassy carbon as an absolute intensity calibration standard for small-angle scattering.

    SciTech Connect

    Zhang, F.; Ilavsky, J.; Long, G.; Allen, A.; Quintana, J.; Jemian, P.; NIST

    2010-05-01

    Absolute calibration of small-angle scattering (SAS) intensity data (measured in terms of the differential scattering cross section per unit sample volume per unit solid angle) is essential for many important aspects of quantitative SAS analysis, such as obtaining the number density, volume fraction, and specific surface area of the scatterers. It also enables scattering data from different instruments (light, X-ray, or neutron scattering) to be combined, and it can even be useful to detect the existence of artifacts in the experimental data. Different primary or secondary calibration methods are available. In the latter case, absolute intensity calibration requires a stable artifact with the necessary scattering profile. Glassy carbon has sometimes been selected as this intensity calibration standard. Here we review the spatial homogeneity and temporal stability of one type of commercially available glassy carbon that is being used as an intensity calibration standard at a number of SAS facilities. We demonstrate that glassy carbon is sufficiently homogeneous and stable during routine use to be relied upon as a suitable standard for absolute intensity calibration of SAS data.

  12. On the small angle twist sub-grain boundaries in Ti3AlC2

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Zhang, Chao; Hu, Tao; Zhan, Xun; Wang, Xiaohui; Zhou, Yanchun

    2016-04-01

    Tilt-dominated grain boundaries have been investigated in depth in the deformation of MAX phases. In stark contrast, another important type of grain boundaries, twist grain boundaries, have long been overlooked. Here, we report on the observation of small angle twist sub-grain boundaries in a typical MAX phase Ti3AlC2 compressed at 1200 °C, which comprise hexagonal screw dislocation networks formed by basal dislocation reactions. By first-principles investigations on atomic-scale deformation and general stacking fault energy landscapes, it is unequivocally demonstrated that the twist sub-grain boundaries are most likely located between Al and Ti4f (Ti located at the 4f Wyckoff sites of P63/mmc) layers, with breaking of the weakly bonded Al–Ti4f. The twist angle increases with the increase of deformation and is estimated to be around 0.5° for a deformation of 26%. This work may shed light on sub-grain boundaries of MAX phases, and provide fundamental information for future atomic-scale simulations.

  13. On the small angle twist sub-grain boundaries in Ti3AlC2

    PubMed Central

    Zhang, Hui; Zhang, Chao; Hu, Tao; Zhan, Xun; Wang, Xiaohui; Zhou, Yanchun

    2016-01-01

    Tilt-dominated grain boundaries have been investigated in depth in the deformation of MAX phases. In stark contrast, another important type of grain boundaries, twist grain boundaries, have long been overlooked. Here, we report on the observation of small angle twist sub-grain boundaries in a typical MAX phase Ti3AlC2 compressed at 1200 °C, which comprise hexagonal screw dislocation networks formed by basal dislocation reactions. By first-principles investigations on atomic-scale deformation and general stacking fault energy landscapes, it is unequivocally demonstrated that the twist sub-grain boundaries are most likely located between Al and Ti4f (Ti located at the 4f Wyckoff sites of P63/mmc) layers, with breaking of the weakly bonded Al–Ti4f. The twist angle increases with the increase of deformation and is estimated to be around 0.5° for a deformation of 26%. This work may shed light on sub-grain boundaries of MAX phases, and provide fundamental information for future atomic-scale simulations. PMID:27034075

  14. Small-angle x-ray scattering studies of the manganese stabilizing subunit in photosystem II.

    SciTech Connect

    Svensson, B.; Tiede, D. M.; Barry, B. A.; Univ. of Minnesota

    2002-08-29

    Small-angle X-ray scattering studies (SAXS) were used to determine the size, shape, and oligomeric composition of the manganese stabilizing protein (MSP) of photosystem II. This extrinsic protein subunit plays an important role in photosynthetic oxygen evolution. As its name implies, MSP stabilizes the tetranuclear Mn cluster of the water oxidation complex. Removal of MSP lowers activity and decreases the stability of active-site manganese. Reconstitution of MSP reverses these effects. In this study, MSP was extracted from spinach PSII membranes using CaCl{sub 2} or urea. Through the use of MALDI-TOF mass spectrometry, the molecular weight of MSP was determined to be 26.53 kDa. X-ray scattering results show that both samples display a monodisperse scattering pattern; this pattern is consistent with a homogeneous protein solution. The CaCl{sub 2} extracted and urea extracted MSP samples have radii of gyration of 25.9 {+-} 0.4 and 27.0 {+-} 0.01 {angstrom}, respectively. MSP is shown to be monomeric in solution. This was determined using a cytochrome c standard and the scattering intensity, extrapolated to zero scattering angle, which is proportional to the molecular weight. This SAXS study suggests that, in solution, MSP is a monomeric, elongated prolate ellipsoid with dimensions, 112 x 23 x 23 {angstrom}{sup 3} and an axial ratio of 4.8.

  15. Convex and concave successions of power-law decays in small-angle scattering

    NASA Astrophysics Data System (ADS)

    Anitas, E. M.

    2016-08-01

    The small-angle scattering (SAS) structure factor from a new model of a 3D deterministic fractal in which the relative positions and the number of structural units vary with fractal iteration number is calculated. It is shown that, depending on the relative positions of scattering units inside the fractal, we can obtain various types of power-law successions, such as: convex/concave - when the absolute value of the scattering exponent of the first power-law decay is higher/smaller than that of the subsequent power- law decay, or any combination of them (i.e. convex-concave or concave-convex). The obtained results can explain experimental SAS (neutron or X-rays) data which are characterized by a succession of power-law decays of arbitrary length.

  16. Small-Angle X-Ray Scattering From RNA, Proteins, And Protein Complexes

    SciTech Connect

    Lipfert, Jan; Doniach, Sebastian; /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept. /SLAC, SSRL

    2007-09-18

    Small-angle X-ray scattering (SAXS) is increasingly used to characterize the structure and interactions of biological macromolecules and their complexes in solution. Although still a low-resolution technique, the advent of high-flux synchrotron sources and the development of algorithms for the reconstruction of 3-D electron density maps from 1-D scattering profiles have made possible the generation of useful low-resolution molecular models from SAXS data. Furthermore, SAXS is well suited for the study of unfolded or partially folded conformational ensembles as a function of time or solution conditions. Here, we review recently developed algorithms for 3-D structure modeling and applications to protein complexes. Furthermore, we discuss the emerging use of SAXS as a tool to study membrane protein-detergent complexes. SAXS is proving useful to study the folding of functional RNA molecules, and finally we discuss uses of SAXS to study ensembles of denatured proteins.

  17. Clustering of water molecules in ultramicroporous carbon: In-situ small-angle neutron scattering

    DOE PAGES

    Bahadur, Jitendra; Contescu, Cristian I.; Rai, Durgesh K.; Gallego, Nidia C.; Melnichenko, Yuri B.

    2016-10-19

    The adsorption of water is central to most of the applications of microporous carbon as adsorbent material. We report early kinetics of water adsorption in the microporous carbon using in-situ small-angle neutron scattering. It is observed that adsorption of water occurs via cluster formation of molecules. Interestingly, the cluster size remains constant throughout the adsorption process whereas number density of clusters increases with time. The role of surface chemistry of microporous carbon on the early kinetics of adsorption process was also investigated. Lastly, the present study provides direct experimental evidence for cluster assisted adsorption of water molecules in microporous carbonmore » (Do-Do model).« less

  18. Nanopores in track-etched polymer membranes characterized by small-angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Cornelius, T. W.; Schiedt, B.; Severin, D.; Pépy, G.; Toulemonde, M.; Apel, P. Yu; Boesecke, P.; Trautmann, C.

    2010-04-01

    Nanochannels and nanowires with diameters ranging from 30 to 400 nm were produced by etching ion tracks in thin polyarylate and polycarbonate foils. The shape and the size distribution of dry and wet nanochannels, as well as of nanowires grown therein, were examined by small-angle x-ray scattering. The x-ray intensity as a function of the scattering vector exhibits pronounced oscillations showing that both the channels and the wires have a highly cylindrical geometry and a very narrow size distribution. UV exposure before chemical etching significantly improves the monodispersity of the nanopores. For fixed etching conditions, the scattering patterns provide evidence that the diameter of dry and water-filled channels as well as for embedded nanowires are identical, demonstrating that the pores in the polymer are completely filled.

  19. Robust, high-throughput solution structural analyses by small angle X-ray scattering (SAXS)

    SciTech Connect

    Hura, Greg L.; Menon, Angeli L.; Hammel, Michal; Rambo, Robert P.; Poole II, Farris L.; Tsutakawa, Susan E.; Jenney Jr, Francis E.; Classen, Scott; Frankel, Kenneth A.; Hopkins, Robert C.; Yang, Sungjae; Scott, Joseph W.; Dillard, Bret D.; Adams, Michael W. W.; Tainer, John A.

    2009-07-20

    We present an efficient pipeline enabling high-throughput analysis of protein structure in solution with small angle X-ray scattering (SAXS). Our SAXS pipeline combines automated sample handling of microliter volumes, temperature and anaerobic control, rapid data collection and data analysis, and couples structural analysis with automated archiving. We subjected 50 representative proteins, mostly from Pyrococcus furiosus, to this pipeline and found that 30 were multimeric structures in solution. SAXS analysis allowed us to distinguish aggregated and unfolded proteins, define global structural parameters and oligomeric states for most samples, identify shapes and similar structures for 25 unknown structures, and determine envelopes for 41 proteins. We believe that high-throughput SAXS is an enabling technology that may change the way that structural genomics research is done.

  20. The crystallization of hectorite clays as monitored by small angle X-ray scattering and NMR

    SciTech Connect

    Carrado, K. A.; Xu, L.; Seifert, S.; Gregory, D.; Song, K.; Botto, R. E.

    1999-12-13

    The authors have probed the 48-hr crystallization of a magnesium silicate clay called hectorite. Small angle X-ray scattering (SAXS) at the Advanced Photon Source using aliquots ex situ has revealed that data is consistent with ex situ XRD, TGA, AFM, and IR data in that all these techniques see clay crystallite beginning to form in the first few hours of reaction. Tetraethylammonium (TEA) ions are used to aid crystallization and become incorporated as the exchange cations within the interlayers. {sup 13}C NMR shows that 80% of the final TEA loading is accomplished in the first 10 hrs. {sup 29}Si NMR displays a visible clay silicate peak after just 1 hr. In addition, the first in situ study of clay crystallization of any kind was performed by in situ SAXS. Results are consistent with the ex situ data as well as showing the sensitivity of SAXS to sol gel reactions occurring on the order of minutes.

  1. Small-angle neutron scattering and molecular dynamics structural study of gelling DNA nanostars.

    PubMed

    Fernandez-Castanon, J; Bomboi, F; Rovigatti, L; Zanatta, M; Paciaroni, A; Comez, L; Porcar, L; Jafta, C J; Fadda, G C; Bellini, T; Sciortino, F

    2016-08-28

    DNA oligomers with properly designed sequences self-assemble into well defined constructs. Here, we exploit this methodology to produce bulk quantities of tetravalent DNA nanostars (each one composed of 196 nucleotides) and to explore the structural signatures of their aggregation process. We report small-angle neutron scattering experiments focused on the evaluation of both the form factor and the temperature evolution of the scattered intensity at a nanostar concentration where the system forms a tetravalent equilibrium gel. We also perform molecular dynamics simulations of one isolated tetramer to evaluate the form factor numerically, without resorting to any approximate shape. The numerical form factor is found to be in very good agreement with the experimental one. Simulations predict an essentially temperature-independent form factor, offering the possibility to extract the effective structure factor and its evolution during the equilibrium gelation. PMID:27586949

  2. Small angle x-ray diffraction studies of mucopolysaccharides in collagen.

    PubMed Central

    Lam, R; Claffey, W J; Geil, P H

    1978-01-01

    Small angle X-ray diffraction (SAXD) was used to locate mucopolysaccharides (MPS) at regular intervals along the collagen axis under physiological conditions. Ruthenium red was used to stain the MPS specifically. The difference in electron density between ruthenium red-stained and unstained moist native rat tail tendon should correspond to the position of the MPS. This difference was calculated from the SAXD intensity data by using difference Fourier transform calculations. Phases calculated independently from the amino acid sequence of collagen by two laboratories were used in this calculation, and the results were compared. At least four to seven bands of MPS per 660 A were found at regular intervals along the collagen axis. Some of these bands match in position to the cross-striations observed by freeze-etching. Electron micrographs of ruthenium red-stained native fibrils also showed bands close in position to the ones calculated. Images FIGURE 3 FIGURE 4 FIGURE 6 FIGURE 7 PMID:83884

  3. A microstructural comparison of two nuclear-grade martensitic steels using small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Coppola, R.; Fiori, F.; Little, E. A.; Magnani, M.

    1997-06-01

    Results are presented of a small-angle neutron scattering (SANS) study on two 10-13% Cr martensitic stainless steels of interest for nuclear applications, viz. DIN 1.4914 (MANET specification, for fusion reactors) and AISI 410. The investigation has focussed principally on microstructural effects associated with the differences in chromium content between the two alloys. The size distribution functions determined from nuclear and magnetic SANS components for the two steels given identical heat treatments are in accord with an interpretation based on the presence of ˜ 1 nm size CCr aggregates in the microstructure. Much larger (˜ 10 nm) scattering inhomogeneities with different magnetic contrast are also present and tentatively identified as carbides.

  4. Toward a Taxonomy of the Denatured State: Small Angle Scattering Studies of Unfolded Proteins

    SciTech Connect

    Millett, I.S.; Doniach, S.; Plaxco, K.W.

    2005-02-15

    Despite the critical role the unfolded state plays in defining protein folding kinetics and thermodynamics (Berg et al., 2002; Dunker, 2002; Shortle, 2002; Wright and Dyson, 2002), our understanding of its detailed structure remains rather rudimentary; the heterogeneity of the unfolded ensemble renders difficult or impossible its study by traditional, atomic-level structural methods. Consequently, recent years have seen a significant expansion of small-angle X-ray and neutron scattering (SAXS and SANS, respectively) techniques that provide direct, albeit rotationally and time-averaged, measures of the geometric properties of the unfolded ensemble. These studies have reached a critical mass, allowing us for the first time to define general observations regarding the nature of the geometry - and possibly the chemistry and physics - of unfolded proteins.

  5. Small Angle X-ray Scattering in Structural Investigation of Selected Biological Systems

    SciTech Connect

    Kozak, Maciej

    2007-11-26

    Small angle X-ray scattering method (SAXS) is a technique complementary to the protein crystallography, allowing determination of the structural parameters such as the radius of gyration or the maximum size characterizing the macromolecules, and providing information on the conformational changes taking place in solution. The use of SAXS method enables a comparison of the protein crystal structure with the data collected in solution. Recent development of the measurement techniques (mainly those based on synchrotron radiation) and calculation methods has permitted introduction of advanced techniques also in the field of structural analysis of biomolecules (e.g. for determination of the shape of the protein molecule in solution). The paper presents a few selected methods of structural analysis of biological systems based on the SAXS data and illustrates their performance on the example of xylanase from Trichoderma longibrachiatum and a model phospholipid system.

  6. Small Angle X-ray Scattering in Structural Investigation of Selected Biological Systems

    NASA Astrophysics Data System (ADS)

    Kozak, Maciej

    2007-11-01

    Small angle X-ray scattering method (SAXS) is a technique complementary to the protein crystallography, allowing determination of the structural parameters such as the radius of gyration or the maximum size characterizing the macromolecules, and providing information on the conformational changes taking place in solution. The use of SAXS method enables a comparison of the protein crystal structure with the data collected in solution. Recent development of the measurement techniques (mainly those based on synchrotron radiation) and calculation methods has permitted introduction of advanced techniques also in the field of structural analysis of biomolecules (e.g. for determination of the shape of the protein molecule in solution). The paper presents a few selected methods of structural analysis of biological systems based on the SAXS data and illustrates their performance on the example of xylanase from Trichoderma longibrachiatum and a model phospholipid system.

  7. A new small-angle neutron scattering spectrometer at China Mianyang research reactor

    NASA Astrophysics Data System (ADS)

    Peng, Mei; Sun, Liangwei; Chen, Liang; Sun, Guangai; Chen, Bo; Xie, Chaomei; Xia, Qingzhong; Yan, Guanyun; Tian, Qiang; Huang, Chaoqiang; Pang, Beibei; Zhang, Ying; Wang, Yun; Liu, Yaoguang; Kang, Wu; Gong, Jian

    2016-02-01

    A new pinhole small-angle neutron scattering (SANS) spectrometer, installed at the cold neutron source of the 20 MW China Mianyang Research Reactor (CMRR) in the Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, has been put into use since 2014. The spectrometer is equipped with a multi-blade mechanical velocity selector, a multi-beam collimation system, and a two-dimensional He-3 position sensitive neutron detector. The q-range of the spectrometer covers from 0.01 nm-1 to 5.0 nm-1. In this paper, the design and characteristics of the SANS spectrometer are described. The q-resolution calculations, together with calibration measurements of silver behenate and a dispersion of nearly monodisperse poly-methyl-methacrylate nanoparticles indicate that our SANS spectrometer has a good performance and is now in routine service.

  8. Structure of nanocrystalline palladium and copper studied by small angle neutron scattering

    SciTech Connect

    Sanders, P.G.; Weertman, J.R.; Barker, J.G.

    1996-12-01

    The structure of nanocrystalline palladium and copper, made by inert gas condensation and compaction, was studied using small angle neutron scattering (SANS), optical microscopy, and scanning electron microscopy. The effects of annealing and warm compaction were also examined with these techniques. The SANS results were interpreted using a maximum entropy routine, combined with knowledge of the Archimedes density and hydrogen concentration determined by prompt gamma activation analysis (PGAA). Similar hydrogen concentrations were detected by SANS and PGAA. This hydrogen content, which was approximately 5 at.{percent} in samples compacted at room temperature, was reduced by both annealing and warm compaction. Defects in several size classes were observed, including missing grain pores ({approx_equal}1{endash}50 nm diameter) and defects of micrometer size. Warm compaction produced a lower number density of pores in nanocrystalline palladium, which led to increased density. The observed structure was correlated with Vickers microhardness and fracture surface morphology. {copyright} {ital 1996 Materials Research Society.}

  9. Polyhydroxyalkanoate-based natural synthetic hybrid copolymer films: A small-angle neutron scattering study

    NASA Astrophysics Data System (ADS)

    Foster, L. John R.; Knott, Robert; Sanguanchaipaiwong, Vorapat; Holden, Peter J.

    2006-11-01

    Polyhydroxyalkanoates have attracted attention as biodegradable alternatives to conventional thermoplastics and as biomaterials. Through modification of their biosynthesis using Pseudomonas oleovorans, we have manipulated the material properties of these biopolyesters and produced a natural-synthetic hybrid copolymer of polyhydroxyoctanoate- block-diethylene glycol (PHO- b-DEG). A mixture of PHO and PHO-DEG were solvent cast from analytical grade chloroform and analysed using small-angle neutron scattering. A scattering pattern, easily distinguished above the background, was displayed by the films with a diffraction ring at q∼0.12 Å -1. This narrow ring of intensity is suggestive of a highly ordered system. Analysis of the diffraction pattern supported this concept and showed a d-spacing of approximately 50 Å. In addition, conformation of the hybrid polymer chains can be manipulated to support their self-assembly into ordered microporous films.

  10. Mixed micelles of alkyltrimethylammonium halides A small-angle neutron-scattering study

    NASA Astrophysics Data System (ADS)

    Aswal, V. K.; Goyal, P. S.

    1998-01-01

    Mixed micelles of alkyltrimethylammonium halides have been studied using small-angle neutron scattering (SANS). The experiments were carried out on mixed micellar solutions (CTAB + DTAB, CTAB + TTAB and TTAB + DTAB) of surfactants with the same head group but different chain lengths. The measurements were also made from the mixture of surfactants with the same chain length but different head groups of CTAB + CDAB and CTAB + CTAC. The surfactant components were mixed in the molar proportions of 1:1 and the total concentration was kept 0.2 M. It is found that size, aggregation number and the fractional charge on the micelle in the mixed systems have values in between those for the pure-component systems.

  11. Tackiness of pressure-sensitive adhesives: An ultra-small-angle X-ray scattering investigation

    NASA Astrophysics Data System (ADS)

    Müller-Buschbaum, P.; Ittner, T.; Petry, W.

    2004-05-01

    The debonding of a model pressure-sensitive adhesive (PSA) poly-n-buthylacrylate is investigated by a combination of the mechanical tack test, optical microscopy and in situ ultra-small-angle X-ray scattering. From the mechanical test, macroscopic values such as force-distance curves are determined. The force-distance curve exhibits the typical non-linear behavior. With microscopy the macroscopic cavitation structure is observed. Scattering addresses the structure of the PSA on a microscopic level for the first time. As a new feature, a sub-structure of the usual optically resolvable macroscopic fibrils between the PSA surface and the probe punch is detected. The sub-structure exists over a large distance between the PSA and the probe surface and remains constant in diameter. This behavior of the sub-structure as well as the dependence of the force plateau on the film thickness are compared with theoretical predictions.

  12. Small angle x-ray scattering studies of carbon anodes used in lithium rechargeable batteries.

    SciTech Connect

    Sandi, G.; Carrado, K. A.; Winans, R. E.; Seifert, S.; Johnson, C. S.

    1999-11-16

    In ANL laboratories, disordered carbons with predictable surface area and porosity properties have been prepared using inorganic templates containing well defined pore sizes. The carbons have been tested in electrochemical cells as anodes in lithium secondary batteries. They deliver high specific capacity and display excellent performance in terms of the number of cycles run. In situ small angle X-ray scattering (SAXS) during electrochemical cycling was carried out at the Advanced Photon Source, at ANL. In order to monitor the carbon electrode structural changes upon cycling, an electrochemical cell was specially designed to allow for the application of electrical current and the collection of SAXS data at the same time. Results show that upon cycling the structure of the carbon remains unchanged, which is desirable in reversible systems.

  13. Small angle neutron and X-ray scattering studies of carbons prepared using inorganic templates

    SciTech Connect

    Sandi, G.; Thiyagarajan, P.; Winans, R.E.; Carrado, K.A.

    1997-09-01

    Small angle neutron (SANS) and X-ray (SAXS) scattering analyses of carbons derived from organic-loaded inorganic template materials, used as anodes in lithium ion cells, have been performed. Two clays were used as templates to load the organic precursors, pillared montmorrillonite (PILC), a layered silicate clay whose sheets have been permanently propped open by sets of thermally stable molecular props, and sepiolite, a natural channeled clay. Five different organic precursors were used to load the PILC: pyrene, styrene, pyrene/trioxane copolymer, ethylene and propylene, whereas only propylene and ethylene were used to load sepiolite. Pyrolysis took place at 700{degrees}C under nitrogen. Values such as hole radius, fractal dimension, cutoff length and density of the final carbons will be compared as a function of the clay and carbon precursors.

  14. Small angle neutron scattering analysis of novel carbons for lithium secondary batteries.

    SciTech Connect

    Sandi, G.; Thiyagarajan, P.; Winans, R.; Carrado, K.

    1998-01-14

    Small angle neutron scattering analyses of carbonaceous materials used as anodes in lithium ion cells have been performed. The carbons have been synthesized using pillared clays (PILCs) as inorganic templates. Pillared clays are layered silicates whose sheets have been permanently propped open by sets of thermally stable molecular props. The calcined PILC was loaded with five different organic precursors and heated at 700 C under nitrogen. When the inorganic pillars were removed by acid treatment, carbon sheets are produced with holes. The fitting of the data in the high q region suggested that the carbon sheets have voids with radii ranging from 4 to 8 {angstrom}. Similar radii were obtained for the PILC and PILC/organic precursor, which suggests that the carbon was well distributed in the clay prior to pyrolysis.

  15. Multiple magnetic scattering in small-angle neutron scattering of Nd–Fe–B nanocrystalline magnet

    PubMed Central

    Ueno, Tetsuro; Saito, Kotaro; Yano, Masao; Ito, Masaaki; Shoji, Tetsuya; Sakuma, Noritsugu; Kato, Akira; Manabe, Akira; Hashimoto, Ai; Gilbert, Elliot P.; Keiderling, Uwe; Ono, Kanta

    2016-01-01

    We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd–Fe–B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd–Fe–B nanocrystalline magnet. It is considered that the mean free path of the neutrons for magnetic scattering is rather short in Nd–Fe–B magnets. We analysed the SANS data by the phenomenological magnetic correlation model considering the magnetic microstructures and obtained the microstructural parameters. PMID:27321149

  16. The complete VS ribozyme in solution studied by small-angle X-ray scattering

    SciTech Connect

    Lipfert, Jan; Ouellet, Jonathan; Norman, David G.; Doniach, Sebastian; Lilley, David M.J.

    2008-10-06

    We have used small-angle X-ray solution scattering to obtain ab initio shape reconstructions of the complete VS ribozyme. The ribozyme occupies an electron density envelope with an irregular shape, into which helical sections have been fitted. The ribozyme is built around a core comprising a near-coaxial stack of three helices, organized by two three-way helical junctions. An additional three-way junction formed by an auxiliary helix directs the substrate stem-loop, juxtaposing the cleavage site with an internal loop to create the active complex. This is consistent with the current view of the probable mechanism of trans-esterification in which adenine and guanine nucleobases contributed by the interacting loops combine in general acid-base catalysis.

  17. Characterization of Nanocomposite filler Morphology using Ultra Small-Angle X-ray Scattering

    SciTech Connect

    Justice, Ryan S.; Schaefer, Dale W.

    2010-10-22

    Loading polymer matrices with nanoscale fillers is widely believed to have the potential to push polymer properties to extreme values. Realization of anticipated properties, however, has proven elusive. Recent nanocomposite research suggests better characterization of the large-scale morphology will provide insight explaining these shortfalls. This work will present ultra-small angle X-ray scattering as a viable tool for elucidating the hierarchical filler morphology that exists within polymer nanocomposites. Scattering analysis tools developed by our group will be applied to scattering data from nanocomposites filled with carbon nanotubes, layered silicates, and colloidal silica. The relationship between imaging data and scattering data will be discussed in the context of filler dispersion. Finally, the impact of large-scale filler morphology on mechanical and electrical properties will be discussed.

  18. The complete VS ribozyme in solution studied by small-angle X-ray scattering

    PubMed Central

    Lipfert, Jan; Ouellet, Jonathan; Norman, David G.; Doniach, Sebastian; Lilley, David M.J.

    2010-01-01

    SUMMARY We have used small-angle X-ray solution scattering to obtain ab initio shape reconstructions of the complete VS ribozyme. The ribozyme occupies an electron density envelope with an irregular shape, into which helical sections have been fitted. The ribozyme is built around a core comprising a near-coaxial stack of three helices, organized by two three-way helical junctions. An additional three-way junction formed by an auxiliary helix directs the substrate stem-loop, juxtaposing the cleavage site with an internal loop to create the active complex. This is consistent with the current view of the probable mechanism of transesterification in which adenine and guanine nucleobases contributed by the interacting loops combine together in general acid-base catalysis. PMID:18786398

  19. Small-angle neutron scattering and molecular dynamics structural study of gelling DNA nanostars

    NASA Astrophysics Data System (ADS)

    Fernandez-Castanon, J.; Bomboi, F.; Rovigatti, L.; Zanatta, M.; Paciaroni, A.; Comez, L.; Porcar, L.; Jafta, C. J.; Fadda, G. C.; Bellini, T.; Sciortino, F.

    2016-08-01

    DNA oligomers with properly designed sequences self-assemble into well defined constructs. Here, we exploit this methodology to produce bulk quantities of tetravalent DNA nanostars (each one composed of 196 nucleotides) and to explore the structural signatures of their aggregation process. We report small-angle neutron scattering experiments focused on the evaluation of both the form factor and the temperature evolution of the scattered intensity at a nanostar concentration where the system forms a tetravalent equilibrium gel. We also perform molecular dynamics simulations of one isolated tetramer to evaluate the form factor numerically, without resorting to any approximate shape. The numerical form factor is found to be in very good agreement with the experimental one. Simulations predict an essentially temperature-independent form factor, offering the possibility to extract the effective structure factor and its evolution during the equilibrium gelation.

  20. Small-angle scattering instruments on a 1 MW long pulse spallation source

    SciTech Connect

    Olah, G.A.; Hjelm, R.P.; Seeger, P.A.

    1995-12-01

    Two small-angle neutron scattering instruments have been designed and optimized for installation at a 1 MW long pulse spallation source. The first of these instruments allows access to length scales in materials from 10 to 400 {angstrom}, and the second instrument from 40 to 1200 {angstrom}. Design characteristics were determined and optimization was done using the MCLIB Monte Carlo instrument simulation package. The code has been {open_quote}benchmarked{close_quote} by simulating the {open_quote}as-built{close_quote} D11 spectrometer at ILL and a performance comparison of the three instruments was made. Comparisons were made by evaluating the scattered intensity for {delta} scatterers at different Q values for various instrument configurations needed to span a Q-range of 0.0007 - 0.44 {angstrom}{sup {minus}1}.

  1. Multiple magnetic scattering in small-angle neutron scattering of Nd-Fe-B nanocrystalline magnet.

    PubMed

    Ueno, Tetsuro; Saito, Kotaro; Yano, Masao; Ito, Masaaki; Shoji, Tetsuya; Sakuma, Noritsugu; Kato, Akira; Manabe, Akira; Hashimoto, Ai; Gilbert, Elliot P; Keiderling, Uwe; Ono, Kanta

    2016-06-20

    We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd-Fe-B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd-Fe-B nanocrystalline magnet. It is considered that the mean free path of the neutrons for magnetic scattering is rather short in Nd-Fe-B magnets. We analysed the SANS data by the phenomenological magnetic correlation model considering the magnetic microstructures and obtained the microstructural parameters.

  2. Periodic blade loads of a high speed propeller at small angle of attack

    NASA Technical Reports Server (NTRS)

    Takallu, M. A.; Lessard, V. R.

    1991-01-01

    A code has been developed to predict the periodic aerodynamic loads of an advanced turboprop propeller. The analytical formulation accounts for flow three-dimensionality and flow periodicity due to the propeller inclination. The flow past the blade sections is computed using a thin layer Navier-Stokes solver. An iterative procedure is used to account for the induced axial and rotational velocities. The viscous periodic results are obtained for an eight-bladed Hamilton Standard SR-7L advanced propeller at a cruise Mach number of 0.813 and 35,000 ft. altitude. The results are shown for flow field quantities and performance parameters during the blade passage in the plane of rotation illustrating the periodic nature of blade flow separation and shocks. The time averaged coefficients of thrust and power are computed and compared with available flight test data. The results obtained show excellent agreement at cruise conditions for small nacelle angles of attack.

  3. Study of the enzyme ascorbate oxidase by small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Maritano, S.; Carsughi, F.; Fontana, M. P.; Marchesini, A.

    1996-09-01

    We report a study of the large scale structure of the "blue" copper enzyme ascorbate oxidase by small angle neutron scattering. The enzyme has been extracted from zucchini and studied in solutions of two different preparations. Contrast variation method was used by performing the measurements in water, heavy water and mixtures of H 2OD 2O. Our data show that, at least at the concentrations used here, the gyration radius of the enzyme is about 34 Å; with such a value our analysis is most consistent with a value of 70 KDa for the molecular weight of ascorbate oxidase in the conditions of our experiment. This is in contrast to the generally accepted value of 140 KDa, obtained by other techniques at high concentrations (e.g. greater than 2 mg ml -1). The possible origins of such a discrepancy are discussed.

  4. Multiple magnetic scattering in small-angle neutron scattering of Nd-Fe-B nanocrystalline magnet.

    PubMed

    Ueno, Tetsuro; Saito, Kotaro; Yano, Masao; Ito, Masaaki; Shoji, Tetsuya; Sakuma, Noritsugu; Kato, Akira; Manabe, Akira; Hashimoto, Ai; Gilbert, Elliot P; Keiderling, Uwe; Ono, Kanta

    2016-01-01

    We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd-Fe-B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd-Fe-B nanocrystalline magnet. It is considered that the mean free path of the neutrons for magnetic scattering is rather short in Nd-Fe-B magnets. We analysed the SANS data by the phenomenological magnetic correlation model considering the magnetic microstructures and obtained the microstructural parameters. PMID:27321149

  5. Small-angle scattering as a tool to study the thermal denaturation of DNA

    NASA Astrophysics Data System (ADS)

    Wood, Kathleen; Knott, Robert; Tonchev, Ognyan; Angelov, Dimitar; Theodorakopoulos, Nikos; Peyrard, Michel

    2014-10-01

    DNA thermal denaturation is the breaking of the base pairs, leading to a splitting of the two strands of the double helix. While it is easy to measure the fraction of open base pairs (f) vs. temperature, determining the fraction (p) of fully open molecules is much harder. Previously, the simultaneous recording of f and p could only be achieved for special sequences. We show that small-angle scattering of X-rays or neutrons allows the measurement of p for any sequence. We illustrate the method with a SAXS investigation of two sequences designed to exhibit different melting profiles and compare the SAXS data with nano-calorimetric measurements of the melting curve.

  6. Probing coal reactivity by time-resolved small angle x-ray scattering.

    SciTech Connect

    Winans, R. E.

    1999-01-22

    The objective of this study is to observe changes in coal structure in situ with small angle X-ray scattering (SAXS) during solvent swelling and during pyrolysis. We have built a SAXS instrument at the Basic Energy Sciences Synchrotrons Research Center at the Advanced Photon Source that allows us to obtain scattering patterns in the millisecond time domain. The eight Argonne Premium Coal samples were used in this study. The information that can be derived from these experiments, such as changes in fractal dimensionality and in size and type of porosity, was found to be very rank-dependent. In the swelling experiments, it was noted that for certain coals, structural changes occurred in just a few minutes.

  7. Spin echo small angle neutron scattering using a continuously pumped {sup 3}He neutron polarisation analyser

    SciTech Connect

    Parnell, S. R.; Li, K.; Yan, H.; Stonaha, P.; Li, F.; Wang, T.; Baxter, D. V.; Snow, W. M.; Washington, A. L.; Walsh, A.; Chen, W. C.; Parnell, A. J.; Fairclough, J. P. A.; Pynn, R.

    2015-02-15

    We present a new instrument for spin echo small angle neutron scattering (SESANS) developed at the Low Energy Neutron Source at Indiana University. A description of the various instrument components is given along with the performance of these components. At the heart of the instrument are a series of resistive coils to encode the neutron trajectory into the neutron polarisation. These are shown to work well over a broad range of neutron wavelengths. Neutron polarisation analysis is accomplished using a continuously operating neutron spin filter polarised by Rb spin-exchange optical pumping of {sup 3}He. We describe the performance of the analyser along with a study of the {sup 3}He polarisation stability and its implications for SESANS measurements. Scattering from silica Stöber particles is investigated and agrees with samples run on similar instruments.

  8. Small-angle neutron scattering from polymer hydrogels with memory effect for medicine immobilization

    SciTech Connect

    Kulvelis, Yu. V. Lebedev, V. T.; Trunov, V. A.; Pavlyuchenko, V. N.; Ivanchev, S. S.; Primachenko, O. N.; Khaikin, S. Ya.

    2011-12-15

    Hydrogels synthesized based on cross-linked copolymers of 2-hydroxyethyl methacrylate and functional monomers (acrylic acid or dimethylaminoethyl methacrylate), having a memory effect with respect to target medicine (cefazolin), have been investigated by small-angle neutron scattering. The hydrogels are found to have a two-level structural organization: large (up to 100 nm) aggregates filled with network cells (4-7 nm in size). The structural differences in the anionic, cationic, and amphiphilic hydrogels and the relationship between their structure and the ability of hydrogels to absorb moisture are shown. A relationship between the memory effect during cefazolin immobilization and the internal structure of hydrogels, depending on their composition and type of functional groups, is established.

  9. Beyond the small-angle approximation for MBR anisotropy from seeds

    NASA Astrophysics Data System (ADS)

    Stebbins, Albert; Veeraraghavan, Shoba

    1995-02-01

    In this paper we give a general expression for the energy shift of massless particles traveling through the gravitational field of an arbitrary matter distribution as calculated in the weak field limit in an asymptotically flat space-time. It is not assumed that matter is nonrelativistic. We demonstrate the surprising result that if the matter is illuminated by a uniform brightness background that the brightness pattern observed at a given point in space-time (modulo a term dependent on the observer's velocity) depends only on the matter distribution on the observer's past light cone. These results apply directly to the cosmological MBR anisotropy pattern generated in the immediate vicinity of an object such as a cosmic string or global texture. We apply these results to cosmic strings, finding a correction to previously published results in the small-angle approximation. We also derive the full-sky anisotropy pattern of a collapsing texture knot.

  10. Adsorption of CO2 in porous MCM-41 and MCM-48 using small angle scattering

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Das, Narayan; Warren, Garfield; Rupp, John; Mastalerz, Maria; Prisk, Timothy; Sokol, Paul

    2012-02-01

    Adsorption of CO2 onto the surface of nanopores in organic rich materials, such as shale and coals, is of great interest for understanding the processes associated with geological sequestration. These natural materials have complex pore structures which make the interpretation of experimental sorption measurements complicated. MCMs are synthetic materials with a well-defined regular porous structure that provides an ideal substrate to evaluate the models for the adsorption of gases (CO2) into nanopores. Samples of MCM-41 and MCM-48 were synthesized at Indiana University and were characterized by nitrogen adsorption isotherms and Small Angle X-ray Scattering (SAXS). SANS studies were carried out on MCMs with different pore sizes as a function of pore filling and the results are interpreted in terms of layer growth models.

  11. Online ion-exchange chromatography for small-angle X-ray scattering

    PubMed Central

    Hutin, Stephanie; Brennich, Martha; Maillot, Benoit; Round, Adam

    2016-01-01

    Biological small-angle X-ray scattering (BioSAXS) is a powerful technique to determine the solution structure, particle size, shape and surface-to-volume ratio of macromolecules. However, a drawback is that the sample needs to be monodisperse. To ensure this, size-exclusion chromatography (SEC) has been implemented on many BioSAXS beamlines. Here, the integration of ion-exchange chromatography (IEC) using both continuous linear and step gradients on a beamline is described. Background subtraction for continuous gradients by shifting a reference measurement and two different approaches for step gradients, which are based on interpolating between two background measurements, are discussed. The results presented here serve as a proof of principle for online IEC and subsequent data treatment. PMID:27710930

  12. Elucidating the Molecular Deformation Mechanism of Entangled Polymers in Fast Flow by Small Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Wang, Yangyang; Sanchez-Diaz, Luis; Cheng, Shiwang; Hong, Kunlun; Chen, Wei-Ren; Liu, Jianning; Lin, Panpan; Wang, Shi-Qing

    Understanding the viscoelastic properties of polymers is of fundamental and practical importance because of the vast and ever expanding demand of polymeric materials in daily life. Our current theoretical framework for describing the nonlinear flow behavior of entangled polymers is built upon the tube model pioneered by de Gennes, Doi, and Edwards. In this work, we critically examine the central hypothesis of the tube model for nonlinear rheology using small angle neutron scattering (SANS). While the tube model envisions a unique non-affine elastic deformation mechanism for entangled polymers, our SANS measurements show that the evolution of chain conformation of a well-entangled polystyrene melt closely follows the affine deformation mechanism in uniaxial extension, even when the Rouse Weissenberg number is much smaller than unity. This result provides a key clue for understanding the molecular deformation mechanism of entangled polymers in fast flow. Several implications from our analysis will be discussed in this talk.

  13. PREFACE Proceedings of the XIV International Conference on Small-Angle Scattering, SAS-2009

    NASA Astrophysics Data System (ADS)

    King, Stephen; Terrill, Nicholas

    2010-10-01

    The XIV International Conference on Small-Angle Scattering, SAS-2009, was held in Oxford UK, 13-18 September 2009, and was jointly organised under the auspices of the International Union of Crystallography Commission on SAS by a team from the Diamond Light Source and the ISIS Pulsed Neutron Source - their first such joint venture - with help from the UK Science and Technology Facilities Council. It was the first time that this long running and successful series of conferences on the application, science and technology of small-angle scattering techniques had been staged in the UK. The UK has a proud heritage in small-angle scattering: as home to one of the world's first SANS instruments (at AERE Harwell), as the site of the world's first 2nd generation X-ray Synchrotron (the SRS at Daresbury with its suite of SAXS beamlines), and latterly as the location of the world's most successful pulsed source SANS instrument. Indeed, 2009 also marked the 25th Anniversary of neutron operations at ISIS and the opening of a Second Target Station. Whilst the SRS ceased operations in 2008, its mantle has been inherited by the Diamond synchrotron. Many delegates took the opportunity to visit both Diamond and ISIS during a conference excursion. Despite the prevailing global economic downturn, we were delighted that 434 delegates from 32 different countries were able to attend SAS-2009; two-thirds were drawn from the UK, Germany, Japan, the USA and France, but there were also sizeable contingents from Australia, Korea, Taiwan and South America. In many ways this geographical spread reflects the present and emerging distribution, respectively, of 3rd generation X-ray synchrotrons and high-flux neutron sources, although the scope of the conference was not solely limited to these probes. Financial support from the IUCr enabled us to grant bursaries to attend SAS-2009 to 12 delegates from emerging countries (Algeria, Argentina, Brazil, India, Nepal, Romania, Russia and the Ukraine). The

  14. Enhanced small-angle scattering connected to the Widom line in simulations of supercooled water

    NASA Astrophysics Data System (ADS)

    Wikfeldt, K. T.; Huang, C.; Nilsson, A.; Pettersson, L. G. M.

    2011-06-01

    We present extensive simulations on the TIP4P/2005 water model showing significantly enhanced small-angle scattering (SAS) in the supercooled regime. The SAS is related to the presence of a Widom line (TW) characterized by maxima in thermodynamic response functions and Ornstein-Zernike correlation length. Recent experimental small-angle x-ray scattering data [Huang et al., J. Chem. Phys. 133, 134504 (2010)], 10.1063/1.3495974 are excellently reproduced, albeit with an increasing temperature offset at lower temperatures. Assuming the same origin of the SAS in experiment and model this suggests the existence of a Widom line also in real supercooled water. Simulations performed at 1000 bar show an increased abruptness of a crossover from dominating high-density (HDL) to dominating low-density (LDL) liquid and strongly enhanced SAS associated with crossing TW, consistent with a recent determination of the critical pressure of TIP4P/2005 at 1350 bar. Furthermore, good agreement with experimental isothermal compressibilities at 1000, 1500, and 2000 bar shows that the high pressure supercooled thermodynamic behavior of water is well described by TIP4P/2005. Analysis of the tetrahedrality parameter Q reveals that the HDL-LDL structural transition is very sharp at 1000 bar, and that structural fluctuations become strongly coupled to density fluctuations upon approaching TW. Furthermore, the tetrahedrality distribution becomes bimodal at ambient temperatures, an observation that possibly provides a link between HDL-LDL fluctuations and the structural bimodality in liquid water indicated by x-ray spectroscopic techniques. Computed x-ray absorption spectra are indeed found to show sensitivity to the tetrahedrality parameter.

  15. Structural and Thermodynamic Properties of Septin 3 Investigated by Small-Angle X-Ray Scattering

    PubMed Central

    Ortore, Maria Grazia; Macedo, Joci N.A.; Araujo, Ana Paula U.; Ferrero, Claudio; Mariani, Paolo; Spinozzi, Francesco; Itri, Rosangela

    2015-01-01

    Septins comprise a family of proteins involved in a variety of cellular processes and related to several human pathologies. They are constituted by three structural domains: the N- and C-terminal domains, highly variable in length and composition, and the central domain, involved in the guanine nucleotide (GTP) binding. Thirteen different human septins are known to form heterogeneous complexes or homofilaments, which are stabilized by specific interactions between the different interfaces present in the domains. In this work, we have investigated by in-solution small-angle x-ray scattering the structural and thermodynamic properties of a human septin 3 construct, SEPT3-GC, which contains both of both interfaces (G and NC) responsible for septin-septin interactions. In order to shed light on the role of these interactions, small-angle x-ray scattering measurements were performed in a wide range of temperatures, from 2 up to 56°C, both with and without a nonhydrolysable form of GTP (GTPγS). The acquired data show a temperature-dependent coexistence of monomers, dimers, and higher-order aggregates that were analyzed using a global fitting approach, taking into account the crystallographic structure of the recently reported SEPT3 dimer, PDB:3SOP. As a result, the enthalpy, entropy, and heat capacity variations that control the dimer-monomer dissociation equilibrium in solution were derived and GTPγS was detected to increase the enthalpic stability of the dimeric species. Moreover, a temperature increase was observed to induce dissociation of SEPT3-GC dimers into monomers just preceding their reassembling into amyloid aggregates, as revealed by the Thioflavin-T fluorescence assays. PMID:26083929

  16. Nanostructural features in silica-polyvinyl acetate nanocomposites characterized by small-angle scattering.

    SciTech Connect

    Narayanan, R. A.; Thiyagarajan, P.; Zhu, A. J.; Ash, J.; Shofner, M. L.; Schadler, L. S.; Kumar, S. K.; Sternstein, S. S.; ORNL; Rensselaer Polytechnic Inst.

    2007-09-10

    Small-angle scattering (SAS) experiments were carried out on nanocomposites of poly(vinyl acetate) (PVAc) and fumed silica nanoparticles with different surface areas and chemical treatment, in the wave-vector (Q) range: 0.0002-1 Angstrom{sup -1}. SAS data on composites with matrices of two different molecular weights indicate that the particle aggregation is independent of the molecular weight of the matrix for a fixed filler concentration and surface treatment. Particle size distributions derived from the SAS data suggest that particle aggregation is reduced when the native surface hydroxyl groups are blocked by various surface treatments, which also reduce the bonding strength to the polymer matrix. The unified exponential/power-law analysis of the SAS data shows three levels of hierarchy in the organization of silica particles. The first level consists of small aggregates of silica particles. At the second level we observe polydispersed aggregates resembling mass-fractal objects that is corroborated by TEM. The polydispersed aggregates further associate to form agglomerates at the third level. The relevance of these findings to the mechanism of nanofiller reinforcement of linear amorphous polymers above T{sub g} is discussed.

  17. Nanostructural Features in Silica-polyvinyl Acetate Nanocomposites Characterized by Small-Angle Scattering

    SciTech Connect

    Raghavan, Aravinda N; Thiyagarajan, P.; Zhu, Dr. Ai-Jun; Ash, Dr. Benjamin J.; Shofner, M. L.; Schadler, Linda; Kumar, Sanat K; Sternstein, S. S.

    2007-01-01

    Small-angle scattering (SAS) experiments were carried out on nanocomposites of poly(vinyl acetate) (PVAc) and fumed silica nanoparticles with different surface areas and chemical treatment, in the wave-vector (Q) range: 0.0002-1 A-1 . SAS data on composites with matrices of two different molecular weights indicate that the particle aggregation is independent of the molecular weight of the matrix for a fixed filler concentration and surface treatment. Particle size distributions derived from the SAS data suggest that particle aggregation is reduced when the native surface hydroxyl groups are blocked by various surface treatments, which also reduce the bonding strength to the polymer matrix. The unified exponential/power-law analysis of the SAS data shows three levels of hierarchy in the organization of silica particles. The first level consists of small aggregates of silica particles. At the second level we observe polydispersed aggregates resembling mass-fractal objects that is corroborated by TEM. The polydispersed aggregates further associate to form agglomerates at the third level. The relevance of these findings to the mechanism of nanofiller reinforcement of linear amorphous polymers above Tg is discussed.

  18. Glycerol monooleate reverse micelles in nonpolar solvents: computer simulations and small-angle neutron scattering.

    PubMed

    Bradley-Shaw, Joshua L; Camp, Philip J; Dowding, Peter J; Lewtas, Ken

    2015-03-19

    The formation of glycerol monooleate reverse micelles in n-heptane and toluene at room temperature is studied using molecular-dynamics simulations and small-angle neutron scattering. The glycerol monooleate concentrations under consideration are in the range of 5-20 wt %. Under these conditions, spontaneous reverse-micelle formation is observed on the simulation timescale (up to 30 ns). From simulations, the typical dimensions (semiaxes) of the equivalent ellipsoids with the same masses and moments of inertia are in the range of 15-23 Å, with instantaneous shapes that are slightly nonspherical. By analyzing the scattering form factors from simulation and experiment, the radii of gyration of the reverse micelles are determined to be approximately 15 Å. The number of glycerol monooleate molecules in a reverse micelle is smaller in toluene (∼20) than in n-heptane (∼30), but the overall dimensions are similar due to greater penetration of the toluene in to the reverse micelle. The effects of low concentrations (1 wt %) of water, acetic acid, and ethanol on the reverse-micelle dimensions are determined. The overall structural effects are small, but the distributions of the molecules within the reverse micelles are shown to be sensitive to the molecular polarity.

  19. Structural formation of huntingtin-like aggregates probed by small-angle neutron scattering

    SciTech Connect

    Stanley, Christopher B; Perevozchikova, Tatiana; Berthelier-Jung, Valerie M

    2011-01-01

    In several neurodegenerative disorders, including Huntington s disease (HD), aspects concerning the earliest of protein structures that form along the aggregation pathway have increasingly gained attention since these particular species are likely to be neurotoxic. We used time-resolved small-angle neutron scattering (SANS) to probe in solution these transient structures formed by peptides having the N-terminal sequence context of mutant huntingtin (Htt) exon 1. We obtained snapshots of the formed aggregates as the kinetic reaction ensued to yield quantitative information on their size and mass. At the early stage, small precursor species with an initial radius of gyration (Rg) of 16.1 5.9 and average mass of a dimer to trimer were monitored. Structural growth was treated as two modes with a transition from three-dimensional early aggregate formation to two-dimensional fibril growth and association. Our SANS results on the internal structure of the mature fibrils demonstrate loose packing with about 1 peptide per 4.75 -sheet repeat distance, which is shown to be quantitatively consistent with a -helix model. This research provides new insights into the structures forming along the pathway of Htt exon 1 aggregation and should assist in determining the role that precursors play in neuronal toxicity.

  20. Characterization of Physically and Chemically Separated Athabasca Asphaltenes Using Small-Angle X-ray Scattering

    SciTech Connect

    Amundaraín Hurtado, Jesús Leonardo; Chodakowski, Martin; Long, Bingwen; Shaw, John M.

    2012-02-07

    Athabasca asphaltenes were characterized using small-angle X-ray scattering (SAXS). Two methods were used to separate asphaltenes from the Athabasca bitumen: namely, chemical separation by precipitation with n-pentane and physical separation by nanofiltration using a zirconia membrane with a 20 nm average pore size. The permeate and chemically separated samples were diluted in 1-methylnaphtalene and n-dodecane prior to SAXS measurements. The temperature and asphaltene concentration ranges were 50-310 C and 1-10.4 wt %, respectively. Model-independent analysis of SAXS data provided the radius of gyration and the scattering coefficients. Model-dependent fits provided size distributions for asphaltenes assuming that they are dense and spherical. Model-independent analysis for physically and chemically separated asphaltenes showed significant differences in nominal size and structure, and the temperature dependence of structural properties. The results challenge the merits of using chemically separated asphaltene properties as a basis for asphaltene property prediction in hydrocarbon resources. While the residuals for model-dependent fits are small, the results are inconsistent with the structural parameters obtained from model-independent analysis.

  1. Pore distributions in nanocrystalline metals from small-angle neutron scattering

    SciTech Connect

    Sanders, P.G.; Weertman, J.R.; Eastman, J.A.

    1998-07-24

    Recent upgrades in inert-gas condensation processing equipment have produced nanocrystalline metal samples with high densities and low-impurity levels. Typical Cu and Pd samples have densities {ge}98% of theoretical and oxygen and hydrogen impurity concentrations {le}0.5 at. %. Lower porosity and impurity levels may make it difficult to produce and maintain samples with the smallest nanocrystalline grain sizes. These improved samples were studied by small-angle neutron scattering (SANS) to determine the volume fraction and size distribution of pores. Excellent correlation was obtained between the total volume fraction of pores and the Archimedes density for Pd, signifying that most of the pores were relatively small and in the detectability range of SANS ({approx}1--100 nm). Nanocrystalline Cu is shown to exhibit a wider pore size distribution. For Pd, the average pore sizes were slightly smaller than the average grain size, while for Cu the pore size and grain size were about the same. Both materials exhibited a trend of increasing pore size with increasing grain size. In terms of processing prerequisites, the principal condition for the production of high-density nanocrystalline Cu is an exceptionally clean synthesis environment, while nanocrystalline Pd requires compaction at elevated temperatures. These differences are the result of Cu having both a lower melting point and a greater susceptibility to contamination by gaseous impurities such as oxygen.

  2. The accurate assessment of small-angle X-ray scattering data

    DOE PAGES

    Grant, Thomas D.; Luft, Joseph R.; Carter, Lester G.; Matsui, Tsutomu; Weiss, Thomas M.; Martel, Anne; Snell, Edward H.

    2015-01-23

    Small-angle X-ray scattering (SAXS) has grown in popularity in recent times with the advent of bright synchrotron X-ray sources, powerful computational resources and algorithms enabling the calculation of increasingly complex models. However, the lack of standardized data-quality metrics presents difficulties for the growing user community in accurately assessing the quality of experimental SAXS data. Here, a series of metrics to quantitatively describe SAXS data in an objective manner using statistical evaluations are defined. These metrics are applied to identify the effects of radiation damage, concentration dependence and interparticle interactions on SAXS data from a set of 27 previously described targetsmore » for which high-resolution structures have been determined via X-ray crystallography or nuclear magnetic resonance (NMR) spectroscopy. Studies show that these metrics are sufficient to characterize SAXS data quality on a small sample set with statistical rigor and sensitivity similar to or better than manual analysis. The development of data-quality analysis strategies such as these initial efforts is needed to enable the accurate and unbiased assessment of SAXS data quality.« less

  3. The accurate assessment of small-angle X-ray scattering data

    SciTech Connect

    Grant, Thomas D.; Luft, Joseph R.; Carter, Lester G.; Matsui, Tsutomu; Weiss, Thomas M.; Martel, Anne; Snell, Edward H.

    2015-01-23

    Small-angle X-ray scattering (SAXS) has grown in popularity in recent times with the advent of bright synchrotron X-ray sources, powerful computational resources and algorithms enabling the calculation of increasingly complex models. However, the lack of standardized data-quality metrics presents difficulties for the growing user community in accurately assessing the quality of experimental SAXS data. Here, a series of metrics to quantitatively describe SAXS data in an objective manner using statistical evaluations are defined. These metrics are applied to identify the effects of radiation damage, concentration dependence and interparticle interactions on SAXS data from a set of 27 previously described targets for which high-resolution structures have been determined via X-ray crystallography or nuclear magnetic resonance (NMR) spectroscopy. Studies show that these metrics are sufficient to characterize SAXS data quality on a small sample set with statistical rigor and sensitivity similar to or better than manual analysis. The development of data-quality analysis strategies such as these initial efforts is needed to enable the accurate and unbiased assessment of SAXS data quality.

  4. Improving small-angle X-ray scattering data for structural analyses of the RNA world

    PubMed Central

    Rambo, Robert P.; Tainer, John A.

    2010-01-01

    Defining the shape, conformation, or assembly state of an RNA in solution often requires multiple investigative tools ranging from nucleotide analog interference mapping to X-ray crystallography. A key addition to this toolbox is small-angle X-ray scattering (SAXS). SAXS provides direct structural information regarding the size, shape, and flexibility of the particle in solution and has proven powerful for analyses of RNA structures with minimal requirements for sample concentration and volumes. In principle, SAXS can provide reliable data on small and large RNA molecules. In practice, SAXS investigations of RNA samples can show inconsistencies that suggest limitations in the SAXS experimental analyses or problems with the samples. Here, we show through investigations on the SAM-I riboswitch, the Group I intron P4-P6 domain, 30S ribosomal subunit from Sulfolobus solfataricus (30S), brome mosaic virus tRNA-like structure (BMV TLS), Thermotoga maritima asd lysine riboswitch, the recombinant tRNAval, and yeast tRNAphe that many problems with SAXS experiments on RNA samples derive from heterogeneity of the folded RNA. Furthermore, we propose and test a general approach to reducing these sample limitations for accurate SAXS analyses of RNA. Together our method and results show that SAXS with synchrotron radiation has great potential to provide accurate RNA shapes, conformations, and assembly states in solution that inform RNA biological functions in fundamental ways. PMID:20106957

  5. The accurate assessment of small-angle X-ray scattering data

    SciTech Connect

    Grant, Thomas D.; Luft, Joseph R.; Carter, Lester G.; Matsui, Tsutomu; Weiss, Thomas M.; Martel, Anne; Snell, Edward H.

    2015-01-01

    A set of quantitative techniques is suggested for assessing SAXS data quality. These are applied in the form of a script, SAXStats, to a test set of 27 proteins, showing that these techniques are more sensitive than manual assessment of data quality. Small-angle X-ray scattering (SAXS) has grown in popularity in recent times with the advent of bright synchrotron X-ray sources, powerful computational resources and algorithms enabling the calculation of increasingly complex models. However, the lack of standardized data-quality metrics presents difficulties for the growing user community in accurately assessing the quality of experimental SAXS data. Here, a series of metrics to quantitatively describe SAXS data in an objective manner using statistical evaluations are defined. These metrics are applied to identify the effects of radiation damage, concentration dependence and interparticle interactions on SAXS data from a set of 27 previously described targets for which high-resolution structures have been determined via X-ray crystallography or nuclear magnetic resonance (NMR) spectroscopy. The studies show that these metrics are sufficient to characterize SAXS data quality on a small sample set with statistical rigor and sensitivity similar to or better than manual analysis. The development of data-quality analysis strategies such as these initial efforts is needed to enable the accurate and unbiased assessment of SAXS data quality.

  6. In situ small angle neutron scattering revealing ion sorption in microporous carbon electrical double layer capacitors.

    PubMed

    Boukhalfa, Sofiane; Gordon, Daniel; He, Lilin; Melnichenko, Yuri B; Nitta, Naoki; Magasinski, Alexandre; Yushin, Gleb

    2014-03-25

    Experimental studies showed the impact of the electrolyte solvents on both the ion transport and the specific capacitance of microporous carbons. However, the related structure-property relationships remain largely unclear and the reported results are inconsistent. The details of the interactions of the charged carbon pore walls with electrolyte ions and solvent molecules at a subnanometer scale are still largely unknown. Here for the first time we utilize in situ small angle neutron scattering (SANS) to reveal the electroadsorption of organic electrolyte ions in carbon pores of different sizes. A 1 M solution of tetraethylammonium tetrafluoroborate (TEATFB) salt in deuterated acetonitrile (d-AN) was used in an activated carbon with the pore size distribution similar to that of the carbons used in commercial double layer capacitors. In spite of the incomplete wetting of the smallest carbon pores by the d-AN, we observed enhanced ion sorption in subnanometer pores under the applied potential. Such results suggest the visible impact of electrowetting phenomena counterbalancing the high energy of the carbon/electrolyte interface in small pores. This behavior may explain the characteristic butterfly wing shape of the cyclic voltammetry curve that demonstrates higher specific capacitance at higher applied potentials, when the smallest pores become more accessible to electrolyte. Our study outlines a general methodology for studying various organic salts-solvent-carbon combinations.

  7. Small angle light scattering characterization of single micrometric particles in microfluidic flows

    NASA Astrophysics Data System (ADS)

    Dannhauser, David; Romeo, Giovanni; Causa, Filippo; Netti, Paolo A.

    2013-04-01

    A CCD-camera based small angle light scattering (SALS) apparatus has been used to characterize single micrometric particles flowing in a micro-channel. The measured scattering vector spans the range 2x10-2 - 6:8x101μm-1. The incident laser light is collimated to a spot of about 50 μm in diameter at the sample position with a divergence lower than 0.045 rad. Such small collimated laser beam opens the possibility to perform on-line SALS of micron-sized particles flowing in micro-channels. By properly designing the micro-channel and using a viscoelastic liquid as suspending medium we are able to realize a precise 3D focusing of the target particles. The forward scattering emitted from the particle is collected by a lens with high numerical aperture. At the focal point of that lens a homemade beam stop is blocking the incident light. Finally, a second lens maps the scattered light on the CCD sensor, allowing to obtain far field images on short distances. Measurements with mono-disperse polystyrene particles, both in quiescent and in-flow conditions have been realized. Experiments in-flow allow to measure the single particle scattering. Results are validated by comparison with calculations based on the Lorenz-Mie theory. The quality of the measured intensity profiles confirms the possibility to use our apparatus in real multiplex applications, with particles down to 1 μm in radius.

  8. Study of nanoscale structures in hydrated biomaterials using small-angle neutron scattering

    PubMed Central

    Luk, Arnold; Murthy, N. Sanjeeva; Wang, Wenjie; Rojas, Ramiro; Kohn, Joachim

    2012-01-01

    Distribution of water in three classes of biomedically relevant and degradable polymers was investigated using small-angle neutron scattering. In semicrystalline polymers, such as poly(lactic acid) and poly(glycolic acid), water was found to diffuse preferentially into the noncrystalline regions. In amorphous polymers, such as poly(D,L-lactic acid) and poly(lactic-co-glycolic acid), the scattering after 7-days of incubation was attributed to water in microvoids that form following the hydrolytic degradation of the polymer. In amorphous copolymers containing hydrophobic segments (desaminotyrosyl-tyrosine ethyl ester) and hydrophilic blocks (poly(ethylene glycol) PEG), a sequence of distinct regimes of hydration were observed: homogeneous distribution (~ 10 Å length scales) at <13 wt% PEG (~ 1 water per EG), clusters of hydrated domains (~50 Å radius) separated at 24 wt% PEG (1 to 2 water per EG), uniformly distributed hydrated domains at 41 wt% PEG (~ 4 water per EG), and phase inversion at > 50 wt% PEG ( > 6 water per EG ). Increasing PEG content increased the number of these domains with only a small decrease in distance between the domains. These discrete domains appeared to coalesce to form submicron droplets at ~60 °C, above the melting temperature of crystalline PEG. Significance of such observations on the evolution of μm size channels that form during hydrolytic erosion is discussed. PMID:22227373

  9. Phase separation and ordering process in Al-Li alloys studied by small-angle neutron scattering and neutron diffraction

    SciTech Connect

    Furusaka, M.; Fujikawa, S.I.; Tranquada, J.M.

    1993-07-01

    To study phase separation kinetics of Al-9.5at.%Li polycrystalline alloys in which precipitates have ordered Al{sub 3}Li ({delta}{prime}) structure, profile analysis of small-angle neutron scattering and superlattice reflections (100) and (110) were done. A small-angle scattering instrument and a triple-axis spectrometer in elastic mode were used in the measurements. Strong texture was observed in the reflections. Therefore, measurements were done using the crystal orientation where the intensity of the reflection was at the maximum. Profiles of small-angle scattering and superlattice reflections were almost identical at higher momentum transfer side. At lower momentum transfer side, small-angle scattering showed interference effects, but superlattice reflection did not show any sign of interference. Integrated intensities of superlattice reflections were obtained and compared with small-angle scattering intensity. The order parameter was not saturated in the {delta}{prime} precipitates at the early stage of the phase separation process.

  10. Primary Open Angle Glaucoma is Associated with MR Biomarkers of Cerebral Small Vessel Disease

    PubMed Central

    Mercieca, Karl; Cain, John; Hansen, Thomas; Steeples, Laura; Watkins, Amy; Spencer, Fiona; Jackson, Alan

    2016-01-01

    This prospective study tests the hypotheses that: 1) glaucoma is associated with evidence of cerebral small vessel disease; 2) that imaging biomarkers of cerebral small vessel disease in POAG and NTG will show different characteristics. 12 normal controls, 7 patients with primary open angle glaucoma (POAG) and 9 patients with normal tension glaucoma (NTG) were recruited. Ophthalmological clinical assessment and MR imaging of the brain were performed. MR imaging was used to quantify white matter lesion load, frequency of dilated perivascular spaces (PVS) and abnormalities in cerebral hydrodynamics. Patients with POAG had significantly greater white matter lesion load (p < 0.05), more PVS in the centrum semiovale (p < 0.05) and had higher overall PVS scores than controls (p < 0.05). In the POAG group, optic cup-to-disc ratio (CDR) was positively correlated with deep white matter hyperintensities (R2 = 0.928, p < 0.01). Mean deviation on the Humphrey visual field assessment was negatively correlated with deep white matter lesion load (R2 = −0.840, p < 0.01), total white matter lesion load (R2 = −0.928, p < 0.01) and total PVS (R2 = −0.820, p < 0.01). MR evidence of cerebral small vessel disease is strongly associated with a diagnosis of POAG and with the severity of abnormalities in CDR and visual field. PMID:26923106

  11. Parameterization of structures in HE composites using surrogate materials: A small angle neutron scattering investigation

    SciTech Connect

    Mang, J.T.; Hjelm, R.P.; Skidmore, C.B.; Howe, P.M.

    1996-07-01

    High explosive materials used in the nuclear stockpile are composites of crystalline high explosives (HE) with binder materials, such as Estane. In such materials, there are naturally occurring density fluctuations (defects) due to cracks, internal (in the HE) and external (in the binder) voids and other artifacts of preparation. Changes in such defects due to material aging can affect the response of explosives due to shock, impact and thermal loading. Modeling efforts are attempting to provide quantitative descriptions of explosive response from the lowest ignition thresholds to the development of full blown detonations and explosions, however, adequate descriptions of these processes require accurate measurements of a number of structural parameters of the HE composite. Since different defects are believed to affect explosive sensitivity in different ways it is necessary to quantitatively differentiate between defect types. The authors report here preliminary results of SANS measurements on surrogates for HE materials. The objective of these measurements was to develop methodologies using SANS techniques to parameterize internal void size distributions in a surrogate material, sugar, to simulate an HE used in the stockpile, HMX. Sugar is a natural choice as a surrogate material, as it has the same crystal structure, has similar intragranular voids and has similar mechanical properties as HMX. It is used extensively as a mock material for explosives. Samples were used with two void size distributions: one with a sufficiently small mean particle size that only small occluded voids are present in significant concentrations, and one where the void sizes could be larger. By using methods in small-angle neutron scattering, they were able to isolate the scattering arising from particle-liquid interfaces and internal voids.

  12. Structural characterization of a polymer substituted fullerene (flagellene) by small angle neutron scattering

    SciTech Connect

    Affholter, K.A.; Bunick, G.J.; Wignall, G.D.; Desimone, J.M.; Hunt, M.O. Jr.; Menceloglu, Y.Z.; Samulski, E.T.

    1994-12-31

    Small-angle neutron scattering (SANS) can structurally characterize fullerenes in solvents with strong SANS contrast (e.g. CS{sub 2}). Deuterated solvents (e.g. toluene-d{sub 8}) have a high scattering length density (SLD), which is close to that of C{sub 60} and C{sub 70} moieties. Hence, there is virtually no SANS contrast with the solvent and these particles are practically ``invisible`` in such media. On the other hand, the negative scattering length of hydrogen means that the SLD of H{sup 1}-containing materials is much lower, so they have strong contrast with toluene-d{sub 8}. Thus, SANS makes it possible to study the size and shapes of modified buckyballs such as the polymer-substituted fullerenes, or flagellenes. These consist of C{sub 60} cores to which 1-4 polystryene chains (with a molecular weight, MW {approx_equal} 2000) are attached. The extrapolated cross section at zero angle of scatter [d{Sigma}/d{Omega}(0)] is a function of the number of pendant chains, so SANS can be used to assess the number of ``arms`` which are covalently attached to the fullerene ``sphere.`` Close agreement ({plus_minus}4%) between measured and calculated values of d{Sigma}/d{Omega}(0) along with independent estimates of the radius of gyration (R{sub g}) and second virial coefficient (A{sub 2}) for a calibration linear polystyrene sample serves as a cross check on the validity of this methodology.

  13. A triple axis double crystal multiple reflection camera for ultra small angle X-ray scattering

    NASA Astrophysics Data System (ADS)

    Lambard, Jacques; Lesieur, Pierre; Zemb, Thomas

    1992-06-01

    To extend the domain of small angle X-ray scattering requires multiple reflection crystals to collimate the beam. A double crystal, triple axis X-ray camera using multiple reflection channel cut crystals is described. Procedures for measuring the desmeared scattering cross-section on absolute scale are described as well as the measurement from several typical samples : fibrils of collagen, 0.3 μm diameter silica spheres, 0.16 μm diameter interacting latex spheres, porous lignite coal, liquid crystals in a surfactant-water system, colloidal crystal of 0.32 μm diameter silica spheres. L'extension du domaine de diffusion des rayons-X vers les petits angles demande l'emploi de cristaux à réflexions multiples pour collimater le faisceau. Nous décrivons une caméra à rayons-X à trois axes où les réflexions multiples sont réalisées dans deux cristaux à gorge. Nous donnons ensuite les procédures de déconvolution pour obtenir la section efficace de diffusion en échelle absolue, ainsi que les résultats des mesures effectuées avec plusieurs échantillons typiques : fibres de collagène, sphères de silice de 0,3 μm de diamètre, sphères de latex de 0,16 μm de diamètre en interaction, charbon lignite poreux, cristaux liquides formés dans un système eau-tensioactif, solution colloïdale de sphères de silice de 0,32 μm de diamètre.

  14. PREFACE Proceedings of the XIV International Conference on Small-Angle Scattering, SAS-2009

    NASA Astrophysics Data System (ADS)

    King, Stephen; Terrill, Nicholas

    2010-10-01

    The XIV International Conference on Small-Angle Scattering, SAS-2009, was held in Oxford UK, 13-18 September 2009, and was jointly organised under the auspices of the International Union of Crystallography Commission on SAS by a team from the Diamond Light Source and the ISIS Pulsed Neutron Source - their first such joint venture - with help from the UK Science and Technology Facilities Council. It was the first time that this long running and successful series of conferences on the application, science and technology of small-angle scattering techniques had been staged in the UK. The UK has a proud heritage in small-angle scattering: as home to one of the world's first SANS instruments (at AERE Harwell), as the site of the world's first 2nd generation X-ray Synchrotron (the SRS at Daresbury with its suite of SAXS beamlines), and latterly as the location of the world's most successful pulsed source SANS instrument. Indeed, 2009 also marked the 25th Anniversary of neutron operations at ISIS and the opening of a Second Target Station. Whilst the SRS ceased operations in 2008, its mantle has been inherited by the Diamond synchrotron. Many delegates took the opportunity to visit both Diamond and ISIS during a conference excursion. Despite the prevailing global economic downturn, we were delighted that 434 delegates from 32 different countries were able to attend SAS-2009; two-thirds were drawn from the UK, Germany, Japan, the USA and France, but there were also sizeable contingents from Australia, Korea, Taiwan and South America. In many ways this geographical spread reflects the present and emerging distribution, respectively, of 3rd generation X-ray synchrotrons and high-flux neutron sources, although the scope of the conference was not solely limited to these probes. Financial support from the IUCr enabled us to grant bursaries to attend SAS-2009 to 12 delegates from emerging countries (Algeria, Argentina, Brazil, India, Nepal, Romania, Russia and the Ukraine). The

  15. Small-angle x-ray scattering study of crazing in bulk thermoplastic polymers

    NASA Astrophysics Data System (ADS)

    Salomons, Gregory John

    Crazing is a form of tension-induced deformation consisting of microscopic cracks spanned by load-bearing fibrils. This is generally considered to be the primary source of plastic strain response of rubber-modified thermoplastics subjected to applied tensile stress. An understanding of the mechanisms involved in crazing is, therefore, valuable as a means of identifying structure-property relationships. Extensive studies on single crazes in thin films have been done,sp{1-6} however, experiments on crazing in bulk materials have been fraught with problems, such as difficulties with the production of uniform crazes and accurate temperature control.sp7 A new apparatus has been designed to overcome many of these problems; a symmetric tensile stretching mechanism and a radiant heating technique combined with real-time small-angle x-ray scattering (RTSAXS) is used to examine craze fibril structure. The analysis of small-angle x-ray scattering (SAXS) data is highly model-dependent requiring precise structural models to ensure accurate interpretation. Recently, improved measurement techniques have called into question some aspects of the long accepted models applied to SAXS interpretation of craze structures.sp{8,9} A detailed examination of the models applicable to craze fibril structure is presented here, including a newly proposed model involving power-law density distributions within the fibrils. It is shown that the best description of craze fibrils comes from a Gaussian density distribution. This is in contrast to the traditional models which describe the fibrils as having uniform density with sharp boundaries.sp{1,2} RTSAXS studies of High Impact Polystyrene (HIPS) and Polystyrene (PS) blended with 2 wt.% Polybutadiene (PB) were performed using a constant strain rate of 5 × 10sp{-4} ssp{-1} and temperatures from 30 to 70sp°C. Crazing deformation modes were identified and the macroscopic deformation characteristics for the two materials were compared revealing a

  16. Multiaxial deformation of polyethylene and polyethylene/clay nanocomposites: In situ synchrotron small angle and wide angle X-ray scattering study

    SciTech Connect

    Gurun, Bilge; Bucknall, David G.; Thio, Yonathan S.; Teoh, Chin Ching; Harkin-Jones, Eileen

    2013-01-10

    A unique in situ multiaxial deformation device has been designed and built specifically for simultaneous synchrotron small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS) measurements. SAXS and WAXS patterns of high-density polyethylene (HDPE) and HDPE/clay nanocomposites were measured in real time during in situ multiaxial deformation at room temperature and at 55 C. It was observed that the morphological evolution of polyethylene is affected by the existence of clay platelets as well as the deformation temperature and strain rate. Martensitic transformation of orthorhombic into monoclinic crystal phases was observed under strain in HDPE, which is delayed and hindered in the presence of clay nanoplatelets. From the SAXS measurements, it was observed that the thickness of the interlamellar amorphous region increased with increasing strain, which is due to elongation of the amorphous chains. The increase in amorphous layer thickness is slightly higher for the nanocomposites compared to the neat polymer.

  17. Research on ship wake detection by optical method of small angle forward scattering

    NASA Astrophysics Data System (ADS)

    Zhu, Donghua; Rao, Jionghui; Zhang, Xiaohui; Sun, ChunSheng

    2008-03-01

    A ship wake in the ocean contains lots of microsize air bubbles with diameter of 10μm~200μm. When a beam of light propagates through the ship wake, it leads to attenuation of the light energy and change of its spatial distribution due to absorption and scattering caused by ocean water and bubble mass together, but they don't share the same scattering mechanism, leaving absorption out of account. Scattering from micro bubbles can usually be explained by Mie scattering theory. In this paper, a method based on optical scattering theory is proposed for detecting the target of ship wake in the ocean, and an experimental system is built up according to the Lambert-Beer law. In the experiment, a semiconductor laser with wavelength about 532nm was employed as the light source, an experimental device which modeled the target of a ship wake to generate bubble mass in water, and a high-speed PIN photodiode as the detector. Besides, the optical receiving system included a set of optical lens and apertures, which were employed to limit the field of view(FOV) of the receiver detector. After measurement of the small angle forward scattering rays scattered from bubble mass with a small FOV, the target signals was got and processed. Then adjustments were made to the optical receiving system and experiments were implemented with varying the FOV to find out the influence of FOV on target signal SNR and obtain the optimum FOV. The results showed that adjusting the FOV according to different microbubble size density could improve SNR.

  18. SCT: a suite of programs for comparing atomistic models with small-angle scattering data

    PubMed Central

    Wright, David W.; Perkins, Stephen J.

    2015-01-01

    Small-angle X-ray and neutron scattering techniques characterize proteins in solution and complement high-resolution structural studies. They are of particular utility when large proteins cannot be crystallized or when the structure is altered by solution conditions. Atomistic models of the averaged structure can be generated through constrained modelling, a technique in which known domain or subunit structures are combined with linker models to produce candidate global conformations. By randomizing the configuration adopted by the different elements of the model, thousands of candidate structures are produced. Next, theoretical scattering curves are generated for each model for trial-and-error fits to the experimental data. From these, a small family of best-fit models is identified. In order to facilitate both the computation of theoretical scattering curves from atomistic models and their comparison with experiment, the SCT suite of tools was developed. SCT also includes programs that provide sequence-based estimates of protein volume (either incorporating hydration or not) and add a hydration layer to models for X-ray scattering modelling. The original SCT software, written in Fortran, resulted in the first atomistic scattering structures to be deposited in the Protein Data Bank, and 77 structures for antibodies, complement proteins and anionic oligosaccharides were determined between 1998 and 2014. For the first time, this software is publicly available, alongside an easier-to-use reimplementation of the same algorithms in Python. Both versions of SCT have been released as open-source software under the Apache 2 license and are available for download from https://github.com/dww100/sct. PMID:26089768

  19. Nano-Scale Morphology of Melanosomes Revealed by Small-Angle X-Ray Scattering

    PubMed Central

    Gorniak, Thomas; Haraszti, Tamas; Garamus, Vasyl M.; Buck, Andreas R.; Senkbeil, Tobias; Priebe, Marius; Hedberg-Buenz, Adam; Koehn, Demelza; Salditt, Tim; Grunze, Michael; Anderson, Michael G.; Rosenhahn, Axel

    2014-01-01

    Melanosomes are highly specialized organelles that produce and store the pigment melanin, thereby fulfilling essential functions within their host organism. Besides having obvious cosmetic consequences – determining the color of skin, hair and the iris – they contribute to photochemical protection from ultraviolet radiation, as well as to vision (by defining how much light enters the eye). Though melanosomes can be beneficial for health, abnormalities in their structure can lead to adverse effects. Knowledge of their ultrastructure will be crucial to gaining insight into the mechanisms that ultimately lead to melanosome-related diseases. However, due to their small size and electron-dense content, physiologically intact melanosomes are recalcitrant to study by common imaging techniques such as light and transmission electron microscopy. In contrast, X-ray-based methodologies offer both high spatial resolution and powerful penetrating capabilities, and thus are well suited to study the ultrastructure of electron-dense organelles in their natural, hydrated form. Here, we report on the application of small-angle X-ray scattering – a method effective in determining the three-dimensional structures of biomolecules – to whole, hydrated murine melanosomes. The use of complementary information from the scattering signal of a large ensemble of suspended organelles and from single, vitrified specimens revealed a melanosomal sub-structure whose surface and bulk properties differ in two commonly used inbred strains of laboratory mice. Whereas melanosomes in C57BL/6J mice have a well-defined surface and are densely packed with 40-nm units, their counterparts in DBA/2J mice feature a rough surface, are more granular and consist of 60-nm building blocks. The fact that these strains have different coat colors and distinct susceptibilities to pigment-related eye disease suggest that these differences in size and packing are of biological significance. PMID:24621581

  20. Small Angle Neutron-Scattering Studies of the Core Structure of Intact Neurosecretory Vesicles.

    NASA Astrophysics Data System (ADS)

    Krueger, Susan Takacs

    Small angle neutron scattering (SANS) was used to study the state of the dense cores within intact neurosecretory vesicles. These vesicles transport the neurophysin proteins, along with their associated hormones, oxytocin or vasopressin, from the posterior pituitary gland to the bloodstream, where the entire vesicle contents are released. Knowledge of the vesicle core structure is important in developing an understanding of this release mechanism. Since the core constituents exist in a dense state at concentrations which cannot be reproduced (in solution) in the laboratory, a new method was developed to determine the core structure from SANS experiments performed on intact neurosecretory vesicles. These studies were complemented by biochemical assays performed to determine the role, if any, played by phospholipids in the interactions between the core constituents. H_2O/D_2 O ratio in the solvent can be adjusted, using the method of contrast variation, such that the scattering due to the vesicle membranes is minimized, thus emphasizing the scattering originating from the cores. The applicability of this method for examining the interior of biological vesicles was tested by performing an initial study on human red blood cells, which are similar in structure to other biological vesicles. Changes in intermolecular hemoglobin interactions, occurring when the ionic strength of the solvent was varied or when the cells were deoxygenated, were examined. The results agreed with those expected for dense protein solutions, indicating that the method developed was suitable for the study of hemoglobin within the cells. Similar SANS studies were then performed on intact neurosecretory vesicles. The experimental results were inconsistent with model calculations which assumed that the cores consisted of small, densely-packed particles or large, globular aggregates. Although a unique model could not be determined, the data suggest that the core constituents form long aggregates of

  1. Small-angle Neutron Scattering and Contrast Variation: A Powerful Combination for Studying Biological Structures

    SciTech Connect

    Heller, William T

    2010-01-01

    The use of small-angle scattering (SAS) in the biological sciences continues to increase, driven as much by the need to study increasingly complex systems that are often resistant to crystallization or are too large for NMR as by the availability of user facilities and advancements in the modelling of biological structures from SAS data. SAS, whether with neutrons (SANS) or X-rays (SAXS), is a structural probe of length scales ranging from 10 to 10,000 {angstrom}. When applied to biological complexes in dilute solution, it provides size and shape information that can be used to produce structural models that can provide insight into function. SANS enables the use of contrast-variation methods through the unique interaction of neutrons with hydrogen and its isotope deuterium. SANS with contrast variation enables the visualization of components within multisubunit complexes, making it a powerful tool for probing protein-protein and protein-nucleic acid complexes, as well as the interaction of proteins with lipids and detergents.

  2. Collagen Orientation and Crystallite Size in Human Dentin: A Small Angle X-ray Scattering Study

    SciTech Connect

    Pople, John A.

    2001-03-29

    The mechanical properties of dentin are largely determined by the intertubular dentin matrix, which is a complex composite of type I collagen fibers and a carbonate-rich apatite mineral phase. The authors perform a small angle x-ray scattering (SAXS) study on fully mineralized human dentin to quantify this fiber/mineral composite architecture from the nanoscopic through continuum length scales. The SAXS results were consistent with nucleation and growth of the apatite phase within periodic gaps in the collagen fibers. These mineralized fibers were perpendicular to the dentinal tubules and parallel with the mineralization growth front. Within the plane of the mineralization front, the mineralized collagen fibers were isotropic near the pulp, but became mildly anisotropic in the mid-dentin. Analysis of the data also indicated that near the pulp the mineral crystallites were approximately needle-like, and progressed to a more plate-like shape near the dentino-enamel junction. The thickness of these crystallites, {approx} 5 nm, did not vary significantly with position in the tooth. These results were considered within the context of dentinogenesis and maturation.

  3. Structural modeling of proteins by integrating small-angle x-ray scattering data

    NASA Astrophysics Data System (ADS)

    Zhang, Yong-Hui; Peng, Jun-Hui; Zhang, Zhi-Yong

    2015-12-01

    Elucidating the structure of large biomolecules such as multi-domain proteins or protein complexes is challenging due to their high flexibility in solution. Recently, an “integrative structural biology” approach has been proposed, which aims to determine the protein structure and characterize protein flexibility by combining complementary high- and low-resolution experimental data using computer simulations. Small-angle x-ray scattering (SAXS) is an efficient technique that can yield low-resolution structural information, including protein size and shape. Here, we review computational methods that integrate SAXS with other experimental datasets for structural modeling. Finally, we provide a case study of determination of the structure of a protein complex formed between the tandem SH3 domains in c-Cb1-associated protein and the proline-rich loop in human vinculin. Project supported by the National Key Basic Research Program of China (Grant Nos. 2013CB910203 and 2011CB911104), the National Natural Science Foundation of China (Grant No. 31270760), the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB08030102), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20113402120013).

  4. Using Small Angle Neutron Scattering on Glucose Oxidase immobilized on Single Layer Graphene

    NASA Astrophysics Data System (ADS)

    Rai, Durgesh; Gurusaran, M.; Qian, S.; Weiss, K.; Urban, V.; Li, P.; Ma, L.; Ajayan, P.; Narayanan, T.; Sekar, K.; Viswanathan, S.; Renugopalakrishanan, V.

    2015-03-01

    Reliable blood glucose monitoring using biosensors is valuable for health evaluations and medication in wake of chronic diabetic issues accompanying deviations from evolutionary human lifestyle. Glucose oxidase (GOx) is an ideal enzyme because of its specificity and the ability to electrochemically transduce from the enzymatic reaction. We use graphene-based electrode with GOx sensor matrix so that the emitted electrons from sensor matrix can flow across graphene nearly without scattering; crucial for constructing ultrasensitive-sensors. Thereafter, establishing a structure-property based relationships to tune the sensor topology with electrochemically output forms the main focus of the device development process. We have developed a methodology to obtain low-resolution hierarchical models of the aggregate matrix using Small Angle Neutron Scattering (SANS) technique. A Unified Fit model is used in tandem with GNOM, DAMMIN and DAMAVER to construct low-resolution models for GOx matrices. A detailed explanation of a general methodology for obtaining quantitative details aggregate structures along with qualitative models will be presented.

  5. Interactive graphical system for small-angle scattering analysis of polydisperse systems

    NASA Astrophysics Data System (ADS)

    Konarev, P. V.; Volkov, V. V.; Svergun, D. I.

    2016-09-01

    A program suite for one-dimensional small-angle scattering analysis of polydisperse systems and multiple data sets is presented. The main program, POLYSAS, has a menu-driven graphical user interface calling computational modules from ATSAS package to perform data treatment and analysis. The graphical menu interface allows one to process multiple (time, concentration or temperature-dependent) data sets and interactively change the parameters for the data modelling using sliders. The graphical representation of the data is done via the Winteracter-based program SASPLOT. The package is designed for the analysis of polydisperse systems and mixtures, and permits one to obtain size distributions and evaluate the volume fractions of the components using linear and non-linear fitting algorithms as well as model-independent singular value decomposition. The use of the POLYSAS package is illustrated by the recent examples of its application to study concentration-dependent oligomeric states of proteins and time kinetics of polymer micelles for anticancer drug delivery.

  6. Ensemble Activation of G-Protein -Coupled Receptors Revealed by Small-Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Chu, Xiang-Qiang; Perera, Suchithranga; Shrestha, Utsab; Chawla, Udeep; Struts, Andrey; Qian, Shuo; Brown, Michael

    2014-03-01

    Rhodopsin is a G-protein -coupled receptor (GPCR) involved in visual light perception and occurs naturally in a membrane lipid environment. Rhodopsin photoactivation yields cis-trans isomerization of retinal giving equilibrium between inactive Meta-I and active Meta-II states. Does photoactivation lead to a single Meta-II conformation, or do substates exist as described by an ensemble-activation mechanism (EAM)? We use small-angle neutron scattering (SANS) to investigate conformational changes in rhodopsin-detergent and rhodopsin-lipid complexes upon photoactivation. Meta-I state is stabilized in CHAPS-solubilized rhodopsin, while Meta-II is trapped in DDM-solubilized rhodopsin. SANS data are acquired from 80% D2O solutions and at contrast-matching points for both DDM and CHAPS samples. Our experiments demonstrate that for detergent-solubilized rhodopsin, SANS with contrast variation can detect structural differences between the rhodopsin dark-state, Meta-I, Meta-II, and ligand-free opsin states. Dark-state rhodopsin has more conformational flexibility in DDM micelles compared to CHAPS, which is consistent with an ensemble of activated Meta-II states. Furthermore, time-resolved SANS enables study of the time-dependent structural transitions between Meta-I and Meta-II, which is crucial to understanding the ensemble-based activation.

  7. Density of hydrophobically confined deeply cooled water investigated by small angle X-ray scattering

    SciTech Connect

    Liu, Kao-Hsiang; Zhang, Yang; Jeng, U-Ser; Mou, Chung-Yuan

    2015-09-07

    Water’s behavior near hydrophobic surfaces has attracted great attention due to chemical and geological applications. Here, we report small angle X-ray scattering (SAXS) studies of water confined in the hydrophobic nanoporous carbon material, CMK-1-14, from ambient to deeply cooled temperatures. By monitoring the scattering intensity of the first Bragg peak, which is directly related to the scattering length density contrast between the carbon matrix and the confined water, the average density of the hydrophobically confined water was determined from 300 K to 150 K at ambient pressure. Furthermore, differential scanning calorimetry and X-ray diffraction measurements showed that the majority of such hydrophobically confined water did not crystallize in the investigated temperature range. By exploiting the fast speed of SAXS measurements and the continuous temperature ramping, the average density profile and the deduced thermal expansion coefficient (α{sub p}) were obtained. We found that the well-known density maximum of water at 277 K downshifted to 260 K, and the density minimum which has been observed in hydrophilic confinement disappeared. In addition, the previously measured large density decreasing of 18% at low temperature was recalibrated to a more reasonable 10% instead. Consequently, the recalculated α{sub p} peak was found to be quite similar to that of the water confined in hydrophilic MCM-41-S-15 suggesting an intrinsic property of water, which does not sensitively depend on the confinement surface.

  8. Structural Studies of Bleached Melanin by Synchrotron Small-angle X-ray Scattering¶

    SciTech Connect

    Littrell, Kenneth C.; Gallas, James M.; Zajac, Gerry W.; Thiyagarajan, Pappannan

    2003-01-01

    Small-angle X-ray scattering was used to measure the effects of chemical bleaching on the size and morphology of tyrosine-derived synthetic melanin dispersed in aqueous media. The average size as measured by the radius of gyration of the melanin particles in solution, at neutral to mildly basic pH, decreases from 16.5 to 12.5 angstroms with increased bleaching. The melanin particles exhibit scattering characteristic of sheet-like structures with a thickness of approximately 11 angstroms at all but the highest levels of bleaching. The scattering data are well described by the form factor for scattering from a pancake-like circular cylinder. These data are consistent with the hypothesis that unbleached melanin, at neutral to mildly basic pH, is a planar aggregate of 6- to 10-nm-sized melanin protomolecules, hydrogen bonded through their quinone and phenolic perimeters. The observed decrease in melanin particle size with increased bleaching is interpreted as evidence for deaggregation, most probably the result of oxidative disruption of hydrogen bonds and an increase in the number of charged, carboxylic acid groups, whereby the melanin aggregates disassociate into units composed of decreasing numbers of protomolecules.

  9. Preliminary analysis of the distribution of water in human hair by small-angle neutron scattering.

    PubMed

    Kamath, Yash; Murthy, N Sanjeeva; Ramaprasad, Ram

    2014-01-01

    Diffusion and distribution of water in hair can reveal the internal structure of hair that determines the penetration of various products used to treat hair. The distribution of water into different morphological components in unmodified hair, cuticle-free hair, and hair saturated with oil at various levels of humidity was examined using small-angle neutron scattering (SANS) by substituting water with deuterium oxide (D(2)O). Infrared spectroscopy was used to follow hydrogen-deuterium exchange. Water present in hair gives basically two types of responses in SANS: (i) interference patterns, and (ii) central diffuse scattering (CDS) around the beam stop. The amount of water in the matrix between the intermediate filaments that gives rise to interference patterns remained essentially constant over the 50-98% humidity range without swelling this region of the fiber extensively. This observation suggests that a significant fraction of water in the hair, which contributes to the CDS, is likely located in a different morphological region of hair that is more like pores in a fibrous structure, which leads to significant additional swelling of the fiber. Comparison of the scattering of hair treated with oil shows that soybean oil, which diffuses less into hair, allows more water into hair than coconut oil. These preliminary results illustrate the utility of SANS for evaluating and understanding the diffusion of deuterated liquids into different morphological structures in hair.

  10. Measuring Material Microstructure Under Flow Using 1-2 Plane Flow-Small Angle Neutron Scattering

    PubMed Central

    Gurnon, A. Kate; Godfrin, P. Douglas; Wagner, Norman J.; Eberle, Aaron P. R.; Butler, Paul; Porcar, Lionel

    2014-01-01

    A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is presented. The SANS shear cell consists of a concentric cylinder Couette geometry that is sealed and rotating about a horizontal axis so that the vorticity direction of the flow field is aligned with the neutron beam enabling scattering from the 1-2 plane of shear (velocity-velocity gradient, respectively). This approach is an advance over previous shear cell sample environments as there is a strong coupling between the bulk rheology and microstructural features in the 1-2 plane of shear. Flow-instabilities, such as shear banding, can also be studied by spatially resolved measurements. This is accomplished in this sample environment by using a narrow aperture for the neutron beam and scanning along the velocity gradient direction. Time resolved experiments, such as flow start-ups and large amplitude oscillatory shear flow are also possible by synchronization of the shear motion and time-resolved detection of scattered neutrons. Representative results using the methods outlined here demonstrate the useful nature of spatial resolution for measuring the microstructure of a wormlike micelle solution that exhibits shear banding, a phenomenon that can only be investigated by resolving the structure along the velocity gradient direction. Finally, potential improvements to the current design are discussed along with suggestions for supplementary experiments as motivation for future experiments on a broad range of complex fluids in a variety of shear motions. PMID:24561395

  11. Location of two antioxidants in oriented model membranes. Small-angle x-ray diffraction study.

    PubMed Central

    Katsaras, J; Stinson, R H; Davis, J H; Kendall, E J

    1991-01-01

    Small-angle x-ray diffraction has been applied in locating either butylated hydroxytoluene (BHT) or delta-tocopherol and their brominated analogues at a concentration of 40 mol% in oriented bilayers of dipalmitoylphosphatidylcholine (DPPC) or DPPC + 15 mol% cholesterol at 20 degrees C. Phases were determined using swelling experiments with structure factors plotted in reciprocal space, creating a relatively smooth curve as the amount of water between the bilayers was changed. Continuous Fourier transforms were also calculated using sampling theory (Shannon, C. E. 1949. Proc. Inst. Radio Engrs. NY. 37:10-21) to further test the consistency of the phase assignments. Fourier synthesis of structure factors resulted in absolute electron density profiles for different bilayers to a resolution of 5-6 A. In addition, difference Patterson maps were constructed to confirm the positions of the bromine atoms in the unit cell. Analysis of the data indicates the following: (a) The BHT molecules are dispersed throughout the alkyl-chain region in DPPC samples with and without cholesterol. (b) The chromanol ring of delta-tocopherol is in the vicinity of the glycerol backbone-headgroup region in samples of DPPC or DPPC + 15 mol% cholesterol. (c) Difference Patterson maps confirm the localization of bromine atoms in the various delta-tocopherol samples and lack of bromine localization in the various BHT samples. PMID:2049525

  12. Small-Angle Neutron Scattering by the Magnetic Microstructure of Nanocrystalline Ferromagnets Near Saturation

    PubMed Central

    Weissmüller, J.; McMichael, R. D.; Michels, A.; Shull, R. D.

    1999-01-01

    The paper presents a theoretical analysis of elastic magnetic small-angle neutron scattering (SANS) due to the nonuniform magnetic microstructure in nanocrystalline ferromagnets. The reaction of the magnetization to the magnetocrystalline and magnetoelastic anisotropy fields is derived using the theory of micromagnetics. In the limit where the scattering volume is a single magnetic domain, and the magnetization is nearly aligned with the direction of the magnetic field, closed form solutions are given for the differential scattering cross-section as a function of the scattering vector and of the magnetic field. These expressions involve an anisotropy field scattering function, that depends only on the Fourier components of the anisotropy field microstructure, not on the applied field, and a micromagnetic response function for SANS, that can be computed from tabulated values of the materials parameters saturation magnetization and exchange stiffness constant or spin wave stiffness constant. Based on these results, it is suggested that the anisotropy field scattering function SH can be extracted from experimental SANS data. A sum rule for SH suggests measurement of the volumetric mean square anisotropy field. When magnetocrystalline anisotropy is dominant, then a mean grain size or the grain size distribution may be determined by analysis of SH.

  13. Synchrotron Small-Angle X-ray Scattering Study of Cross-Linked Polymeric Micelles.

    PubMed

    Kim, Hyun-Chul; Jin, Kyeong Sik; Lee, Se Guen; Kim, Eunjoo; Lee, Sung Jun; Jeong, Sang Won; Lee, Seung Woo; Kim, Kwang-Woo

    2016-06-01

    Polymeric micelles of methoxypoly(ethylene glycol)-b-poly(lactide) containing lysine units (mPEG-PLA-Lys4) were cross-linked by reacting of lysine moieties with a bifunctional bis(N-hydroxy-succinimide ester). The micelles were characterized in aqueous solution using dynamic light scattering, transmission electron microscopy, and synchrotron small-angle X-ray scattering. The mPEG-PLA-Lys4 was synthesized through the ring-opening polymerization of N6-carbobenzyloxy-L-lysine N-carboxyanhydride with amine-terminated mPEG-PLA and subsequent deprotection. The polymeric micelles showed enhanced micelle stability after cross-linking, which was confirmed by adding sodium dodecyl sulfate as a destabilizing agent. The average diameters measured via dynamic light scattering were 19.1 nm and 29.2 nm for non-cross-linked polymeric micelles (NCPMs) and cross-linked polymeric micelles (CPMs), respectively. The transmission electron microscopy images showed that the size of the polymeric micelles increased slightly due to cross-linking, which was in good agreement with the DLS measurements. The overall structures and internal structural changes of NCPMs and CPMs in aqueous solution were studied in detail using synchrotron X-ray scattering method. According to the structural parameters of X-ray scattering analysis, CPMs with a more densely packed core structure were formed by reacting bifunctional cross-linking agents with lysine amino groups located in the innermost core of the polymeric micelles. PMID:27427731

  14. Scanning of Adsorption Hysteresis In Situ with Small Angle X-Ray Scattering

    PubMed Central

    Mitropoulos, Athanasios Ch.; Favvas, Evangelos P.; Stefanopoulos, Konstantinos L.; Vansant, Etienne F.

    2016-01-01

    Everett’s theorem-6 of the domain theory was examined by conducting adsorption in situ with small angle x-ray scattering (SAXS) supplemented by the contrast matching technique. The study focuses on the spectrum differences of a point to which the system arrives from different scanning paths. It is noted that according to this theorem at a common point the system has similar macroscopic properties. Furthermore it was examined the memory string of the system. We concluded that opposite to theorem-6: a) at a common point the system can reach in a finite (not an infinite) number of ways, b) a correction for the thickness of the adsorbed film prior to capillary condensation is necessary, and c) the scattering curves although at high-Q values coincide, at low-Q values are different indicating different microscopic states. That is, at a common point the system holds different metastable states sustained by hysteresis effects. These metastable states are the ones which highlight the way of a system back to a return point memory (RPM). Entering the hysteresis loop from different RPMs different histories are implanted to the paths toward the common point. Although in general the memory points refer to relaxation phenomena, they also constitute a characteristic feature of capillary condensation. Analogies of the no-passing rule and the adiabaticity assumption in the frame of adsorption hysteresis are discussed. PMID:27741263

  15. Using Small-Angle Neutron Scattering to Detect Nanoscopic Lipid Domains

    SciTech Connect

    Pan, Jianjun; Heberle, Frederick A; Petruzielo, Robin S; Katsaras, John

    2013-01-01

    The cell plasma membrane is a complex system, which is thought to be capable of exhibiting non-random lateral organization. Studies of live cells and model membranes have yielded mechanisms responsible for the formation, growth, and maintenance of nanoscopic heterogeneities, although the existence and mechanisms that give rise to these heterogeneities remain controversial. Small-angle neutron scattering (SANS) is a tool ideally suited to interrogate lateral heterogeneity in model membranes, primarily due to its unique spatial resolution (i.e., "5 100 nm) and its ability to resolve structure with minimal perturbation to the membrane. In this review we examine several methods used to analyze the SANS signal arising from freely suspended unilamellar vesicles containing lateral heterogeneity. Specifically, we discuss an analytical model for a single, round domain on a spherical vesicle. We then discuss a numerical method that uses Monte Carlo simulation to describe systems with multiple domains and/or more complicated morphologies. Also discussed are several model-independent approaches that are sensitive to membrane heterogeneity. The review concludes with several recent applications of SANS to the study of membrane raft mixtures.

  16. Small angle neutron scattering contrast variation reveals heterogeneities of interactions in protein gels.

    PubMed

    Banc, A; Charbonneau, C; Dahesh, M; Appavou, M-S; Fu, Z; Morel, M-H; Ramos, L

    2016-06-28

    We propose a quantitative approach to probe the spatial heterogeneities of interactions in macromolecular gels, based on a combination of small angle X-ray (SAXS) and neutrons (SANS) scattering. We investigate the structure of model gluten protein gels and show that the gels display radically different SAXS and SANS profiles when the solvent is (at least partially) deuterated. The detailed analysis of the SANS signal as a function of the solvent deuteration demonstrates heterogeneities of sample deuteration at different length scales. The progressive exchange between the protons (H) of the proteins and the deuteriums (D) of the solvent is inhomogeneous and 60 nm large zones that are enriched in H are evidenced. In addition, at low protein concentration, in the sol state, solvent deuteration induces a liquid/liquid phase separation. Complementary biochemical and structure analyses show that the denser protein phase is more protonated and specifically enriched in glutenin, the polymeric fraction of gluten proteins. These findings suggest that the presence of H-rich zones in gluten gels would arise from the preferential interaction of glutenin polymers through a tight network of non-exchangeable intermolecular hydrogen bonds. PMID:27198847

  17. Survey of background scattering from materials found in small-angle neutron scattering

    PubMed Central

    Barker, J. G.; Mildner, D. F. R.

    2015-01-01

    Measurements and calculations of beam attenuation and background scattering for common materials placed in a neutron beam are presented over the temperature range of 300–700 K. Time-of-flight (TOF) measurements have also been made, to determine the fraction of the background that is either inelastic or quasi-elastic scattering as measured with a 3He detector. Other background sources considered include double Bragg diffraction from windows or samples, scattering from gases, and phonon scattering from solids. Background from the residual air in detector vacuum vessels and scattering from the 3He detector dome are presented. The thickness dependence of the multiple scattering correction for forward scattering from water is calculated. Inelastic phonon background scattering at small angles for crystalline solids is both modeled and compared with measurements. Methods of maximizing the signal-to-noise ratio by material selection, choice of sample thickness and wavelength, removal of inelastic background by TOF or Be filters, and removal of spin-flip scattering with polarized beam analysis are discussed. PMID:26306088

  18. Deterministic fractals: extracting additional information from small-angle scattering data.

    PubMed

    Cherny, A Yu; Anitas, E M; Osipov, V A; Kuklin, A I

    2011-09-01

    The small-angle scattering curves of deterministic mass fractals are studied and analyzed in momentum space. In the fractal region, the curve I(q)q(D) is found to be log-periodic with good accuracy, and the period is equal to the scaling factor of the fractal. Here, D and I(q) are the fractal dimension and the scattering intensity, respectively. The number of periods of this curve coincides with the number of fractal iterations. We show that the log-periodicity of I(q)q(D) in the momentum space is related to the log-periodicity of the quantity g(r)r(3-D) in the real space, where g(r) is the pair distribution function. The minima and maxima positions of the scattering intensity are estimated explicitly by relating them to the pair distance distribution in real space. It is shown that the minima and maxima are damped with increasing polydispersity of the fractal sets; however, they remain quite pronounced even at sufficiently large values of polydispersity. A generalized self-similar Vicsek fractal with controllable fractal dimension is introduced, and its scattering properties are studied to illustrate the above findings. In contrast with the usual methods, the present analysis allows us to obtain not only the fractal dimension and the edges of the fractal region, but also the fractal iteration number, the scaling factor, and the number of structural units from which the fractal is composed.

  19. Synchrotron-based small-angle X-ray scattering (SAXS) of proteins in solution

    PubMed Central

    Skou, Soren; Gillilan, Richard E

    2015-01-01

    Summary With recent advances in data analysis algorithms, X-ray detectors, and synchrotron sources, small-angle X-ray scattering (SAXS) has become much more accessible to the structural biology community than ever before. Although limited to ~10 Å resolution, SAXS can provide a wealth of structural information on biomolecules in solution and is compatible with a wide range of experimental conditions. SAXS is thus an attractive alternative when crystallography is not possible. Moreover, advanced usage of SAXS can provide unique insight into biomolecular behavior that can only be observed in solution, such as large conformational changes and transient protein-protein interactions. Unlike crystal diffraction data, however, solution scattering data are subtle in appearance, highly sensitive to sample quality and experimental errors, and easily misinterpreted. In addition, synchrotron beamlines that are dedicated to SAXS are often unfamiliar to the non-specialist. Here, we present a series of procedures that can be used for SAXS data collection and basic cross-checks designed to detect and avoid aggregation, concentration effects, radiation damage, buffer mismatch, and other common problems. The protein, human serum albumin (HSA), serves as a convenient and easily replicated example of just how subtle these problems can sometimes be, but also of how proper technique can yield pristine data even in problematic cases. Because typical data collection times at a synchrotron are only one to several days, we recommend that the sample purity, homogeneity, and solubility be extensively optimized prior to the experiment. PMID:24967622

  20. Density of hydrophobically confined deeply cooled water investigated by small angle X-ray scattering

    SciTech Connect

    Liu, Kao-Hsiang; Zhang, Yang; Jeng, U-Ser; Mou, Chung-Yuan

    2015-09-07

    The behavior of water near hydrophobic surfaces has attracted great attention due to chemical and geological applications. Here, we report small angle X-ray scattering (SAXS) studies of water confined in the hydrophobic nanoporous carbon material, CMK-1-14, from ambient to deeply cooled temperatures. Moreover, by monitoring the scattering intensity of the first Bragg peak, which is directly related to the scattering length density contrast between the carbon matrix and the confined water, the average density of the hydrophobically confined water was determined from 300 K to 150 K at ambient pressure. Furthermore, differential scanning calorimetry and X-ray diffraction measurements showed that the majority of such hydrophobically confined water did not crystallize in the investigated temperature range. By exploiting the fast speed of SAXS measurements and the continuous temperature ramping, the average density profile and the deduced thermal expansion coefficient (alpha(p)) were obtained. We found that the well-known density maximum of water at 277 K downshifted to 260 K, and the density minimum which has been observed in hydrophilic confinement disappeared. Additionally, the previously measured large density decreasing of 18% at low temperature was recalibrated to a more reasonable 10% instead. Consequently, the recalculated ap peak was found to be quite similar to that of the water confined in hydrophilic MCM-41-S-15 suggesting an intrinsic property of water, which does not sensitively depend on the confinement surface.

  1. Density of hydrophobically confined deeply cooled water investigated by small angle X-ray scattering

    DOE PAGES

    Liu, Kao-Hsiang; Zhang, Yang; Jeng, U-Ser; Mou, Chung-Yuan

    2015-09-07

    The behavior of water near hydrophobic surfaces has attracted great attention due to chemical and geological applications. Here, we report small angle X-ray scattering (SAXS) studies of water confined in the hydrophobic nanoporous carbon material, CMK-1-14, from ambient to deeply cooled temperatures. Moreover, by monitoring the scattering intensity of the first Bragg peak, which is directly related to the scattering length density contrast between the carbon matrix and the confined water, the average density of the hydrophobically confined water was determined from 300 K to 150 K at ambient pressure. Furthermore, differential scanning calorimetry and X-ray diffraction measurements showed thatmore » the majority of such hydrophobically confined water did not crystallize in the investigated temperature range. By exploiting the fast speed of SAXS measurements and the continuous temperature ramping, the average density profile and the deduced thermal expansion coefficient (alpha(p)) were obtained. We found that the well-known density maximum of water at 277 K downshifted to 260 K, and the density minimum which has been observed in hydrophilic confinement disappeared. Additionally, the previously measured large density decreasing of 18% at low temperature was recalibrated to a more reasonable 10% instead. Consequently, the recalculated ap peak was found to be quite similar to that of the water confined in hydrophilic MCM-41-S-15 suggesting an intrinsic property of water, which does not sensitively depend on the confinement surface.« less

  2. The dynamic duo: Combining NMR and small angle scattering in structural biology

    PubMed Central

    Hennig, Janosch; Sattler, Michael

    2014-01-01

    Structural biology provides essential information for elucidating molecular mechanisms that underlie biological function. Advances in hardware, sample preparation, experimental methods, and computational approaches now enable structural analysis of protein complexes with increasing complexity that more closely represent biologically entities in the cellular environment. Integrated multidisciplinary approaches are required to overcome limitations of individual methods and take advantage of complementary aspects provided by different structural biology techniques. Although X-ray crystallography remains the method of choice for structural analysis of large complexes, crystallization of flexible systems is often difficult and does typically not provide insights into conformational dynamics present in solution. Nuclear magnetic resonance spectroscopy (NMR) is well-suited to study dynamics at picosecond to second time scales, and to map binding interfaces even of large systems at residue resolution but suffers from poor sensitivity with increasing molecular weight. Small angle scattering (SAS) methods provide low resolution information in solution and can characterize dynamics and conformational equilibria complementary to crystallography and NMR. The combination of NMR, crystallography, and SAS is, thus, very useful for analysis of the structure and conformational dynamics of (large) protein complexes in solution. In high molecular weight systems, where NMR data are often sparse, SAS provides additional structural information and can differentiate between NMR-derived models. Scattering data can also validate the solution conformation of a crystal structure and indicate the presence of conformational equilibria. Here, we review current state-of-the-art approaches for combining NMR, crystallography, and SAS data to characterize protein complexes in solution. PMID:24687405

  3. Solution Properties of 1,3-Cyclohexadiene Polymers by Small Angle Neutron and Light Scattering

    SciTech Connect

    Yun, Seok I; Melnichenko, Yuri B; Wignall, George D; Hong, Kunlun; Mays, Jimmy; Britt, Phillip F; Terao, Ken; Nakamura, Yo

    2006-01-01

    1,3-Cyclohexdiene polymers (PCHD) and their derivatives are of interest due to the six-member rings in the main chain, which are expected to impart higher mechanical strength and better thermal and chemical stability, as compared to common vinyl polymers. For example, hydrogenated PCHD has the highest glass transition temperature (T{sub g} {approx} 231 C) of all hydrocarbon polymers, and it also shows good heat, weather, impact, abrasion, and chemical resistance as well as low water absorption. In addition, PCHD has unique photochemical properties, such as excellent transparency, due to the isolated double bonds in the main chain. Also, block copolymers containing PCHD show unusual phase separation behavior. For example, a styrene/1,3-CHD block copolymer (PS-b-PCHD) with 50 vol % CHD (1,4/1,2 {approx} 95/5) exhibits a core-shell or hollow cylinder morphology, while a typical styrene/acyclic diene (isoprene or butadiene) block copolymer with similar composition exhibits a lamellar structure. Such phase behavior and many other properties strongly depend on the conformation of the polymer in solution or bulk. However, almost no data have been reported on the conformation of PCHD, probably because of the lack of well-defined and well-characterized samples. Here we report solution properties of PCHD in tetrahydrofuran (THF) and chloroform by multiangle laser light scattering, viscometry, and small-angle neutron scattering (SANS).

  4. Six-dimensional real and reciprocal space small-angle X-ray scattering tomography.

    PubMed

    Schaff, Florian; Bech, Martin; Zaslansky, Paul; Jud, Christoph; Liebi, Marianne; Guizar-Sicairos, Manuel; Pfeiffer, Franz

    2015-11-19

    When used in combination with raster scanning, small-angle X-ray scattering (SAXS) has proven to be a valuable imaging technique of the nanoscale, for example of bone, teeth and brain matter. Although two-dimensional projection imaging has been used to characterize various materials successfully, its three-dimensional extension, SAXS computed tomography, poses substantial challenges, which have yet to be overcome. Previous work using SAXS computed tomography was unable to preserve oriented SAXS signals during reconstruction. Here we present a solution to this problem and obtain a complete SAXS computed tomography, which preserves oriented scattering information. By introducing virtual tomography axes, we take advantage of the two-dimensional SAXS information recorded on an area detector and use it to reconstruct the full three-dimensional scattering distribution in reciprocal space for each voxel of the three-dimensional object in real space. The presented method could be of interest for a combined six-dimensional real and reciprocal space characterization of mesoscopic materials with hierarchically structured features with length scales ranging from a few nanometres to a few millimetres--for example, biomaterials such as bone or teeth, or functional materials such as fuel-cell or battery components.

  5. Small angle neutron scattering (SANS) study of γ' precipitates in single crystals of AM1 superalloy

    NASA Astrophysics Data System (ADS)

    Bellet, D.; Bastie, P.; Royer, A.; Lajzerowicz, J.; Legrand, J. F.; Bonnet, R.

    1992-06-01

    The morphology of γ' precipitates of AM1 single crystal superalloys has been studied by small neutron scattering (SANS), and electron microscopy. Due to the single crystal nature of the samples, the SANS patterns are anisotropic and exhibit a fourfold symmetry corresponding both to the shape and to the spatial arrangement of the precipitates in a (001) plane. Measurements for other sample orientations have allowed us to improve the analysis of the shape of the precipitates. After creep deformation along the < 001 > axis, a twofold symmetry corresponding to the “rafting” of the γ' precipitates is observed in the (010) plane. The main effect of heat treatments at 1 050 °C, commonly used for industrial applications, is the coarsening of the precipitates. From the displacement of the correlation peaks towards smaller angles, we deduce an average centre-to-centre spacing between the precipitates which increases with the annealing time from 0.3 μm to 0.6 μm according to the Lifshitz, Slyosov, Wagner behaviour. The results are compared to electron microscopy measurements, performed on the same samples.

  6. A Small-Angle Scattering Study of the Bulk Structure of a Symmetric Diblock Copolymer System

    NASA Astrophysics Data System (ADS)

    Papadakis, Christine M.; Almdal, Kristoffer; Mortensen, Kell; Posselt, Dorthe

    1997-12-01

    The bulk structure of a homologous series of symmetric polystyrene-polybutadiene (SB) diblock copolymers is investigated using small-angle X-ray and neutron scattering (SANS). The study focuses on the lamellar thickness, the lamellar correlation length and the concentration profile as a function of the chain length and the preparation method applied. The characteristic length, D, scales with the chain length, N, in the whole range studied, but with a clear change in scaling exponent near χ N = 29, in accordance with theoretical predictions of a crossover from an Intermediate-Segregation Regime (ISR) to the Strong-Segregation Limit (SSL). In the ISR (χ N simeq 5-29), D is found to scale like D propto N^{0.83} and in the SSL (χ N > 29) like D propto N^{0.61} . The temperature dependence of the SANS spectra is studied for a low molar mass sample in an interval around the order-disorder transition temperature (TODT). The peak position is found to vary more strongly with temperature than expected for Gaussian chains. Only a weak discontinuity of the peak position at TODT is observed. In summary, the phase behavior of symmetric SB diblock copolymers in the bulk spans three regimes: the Gaussian regime in the region χ N < 5, the ISR for 5 < χ N < 29 and the SSL for χ N > 29.

  7. Investigation of Monodisperse Dendrimeric Polysaccharide Nanoparticle Dispersions Using Small Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Atkinson, John; Nickels, Jonathan; Papp-Szabo, Erzsi; Katsaras, John; Dutcher, John

    2015-03-01

    Phytoglycogen is a highly branched polysaccharide that is very similar to the energy storage molecule glycogen. We have isolated monodisperse phytoglycogen nanoparticles from corn and these particles are attractive for applications in the cosmetic, food and beverage, and biomedical industries. Many of these promising applications are due to the special interaction between the nanoparticles and water, which results in: (1) high solubility; (2) low viscosity and high stability in aqueous dispersions; and (3) a remarkable capacity to sequester and retain water. Our rheology measurements indicate that the nanoparticles behave like hard spheres in water, with the viscosity diverging for concentrations >25% (w/w). Because of this, aqueous suspensions of phytoglycogen provide an ideal platform for detailed testing of theories of colloidal glasses and jamming. To further explore the interaction of the phytoglycogen particles and water, we have performed small angle neutron scattering (SANS) measurements on the Extended Q-Range SANS (EQ-SANS) diffractometer at the Spallation Neutron Source at Oak Ridge National Laboratory. Measurements performed on phytoglycogen dispersions in mixtures of hydrogenated and deuterated water have allowed us to determine the particle size and average particle spacing as a function of the phytoglycogen concentration in the limits of dilute and concentrated dispersions.

  8. Small Angle Neutron Scattering (SANS) Studies on the Structural Evolution of Pyromellitamide Self-assembled Gels

    SciTech Connect

    Scott, Jamieson; Tong, Katie; William, Hamilton; He, Lilin; James, Michael; Thordarson, Pall; Boukhalfa, Sofiane

    2014-10-31

    The kinetics of aggregation of two pyromellitamide gelators; tetrabutyl- (C4) and tetrahexylpyromellitamide (C6), in deuterated cyclohexane has been investigated by small angle neutron scattering (SANS) for up to six days. The purpose of this study was to improve our understanding of how self-assembled gels are formed. Short-term (< 3 hour) time scales revealed multiple phases with the data for the tetrabutylpyromellitamide C4 indicating one dimensional stacking and aggregation corresponding to a multi-fiber braided cluster arrangement that is about 35 Å in diameter. The corresponding tetrahexylpyromellitamide C6 data suggests that the C6 also forms one-dimensional stacks but that these aggregate to a thicker multi-fiber braided cluster that have a diameter of 61.8 Å. Over a longer period of time, the radius, persistence length and contour length all continue to increase in 6 days after cooling. This data suggests that structural changes in self-assembled gels occur over a period exceeding several days and that fairly subtle changes in the structure (e.g. tail-length) can influence the packing of molecules in self-assembled gels on the single-to-few fiber bundle stage.

  9. Quantification of microstructural features in HMX using small angle neutron scattering techniques

    SciTech Connect

    Mang, J.T.; Skidmore, C.B.; Hjelm, R.P.; Howe, P.M.

    1998-12-01

    Microstructural features in raw powders of High Explosives have been qualitatively observed by many researchers, using polarized light and scanning electron microscopy. Here, the authors present a method for non-destructive quantification of volume fraction and structure of intragranular cracks and crystallization voids in a bulk sample (100--300 mg). By employing Small Angle Neutron Scattering (SANS) in conjunction with the method of contrast variation, they can effectively highlight different structural features of a complex system. The technique of contrast variation relies on immersing the sample in a uniform fluid of known neutron scattering length density. By selectively varying the scattering length density of the immersion fluid, scattering contributions from internal and external structures can be separated. This approach is analogous to varying the index of refraction for immersion oil relative to a sample in polarized light microscopy. SANS experiments on HMX were conducted using loose powders (261 and 10 micron mean particle diameters) and pellets made by uniaxial consolidation (without binder) to 7 and 10 volume percent porosity respectively. Detailed modeling of the SANS data indicate significant alteration of the intragranular void/crack/pore structure, with pressing, of the HMX powders.

  10. Six-dimensional real and reciprocal space small-angle X-ray scattering tomography

    NASA Astrophysics Data System (ADS)

    Schaff, Florian; Bech, Martin; Zaslansky, Paul; Jud, Christoph; Liebi, Marianne; Guizar-Sicairos, Manuel; Pfeiffer, Franz

    2015-11-01

    When used in combination with raster scanning, small-angle X-ray scattering (SAXS) has proven to be a valuable imaging technique of the nanoscale, for example of bone, teeth and brain matter. Although two-dimensional projection imaging has been used to characterize various materials successfully, its three-dimensional extension, SAXS computed tomography, poses substantial challenges, which have yet to be overcome. Previous work using SAXS computed tomography was unable to preserve oriented SAXS signals during reconstruction. Here we present a solution to this problem and obtain a complete SAXS computed tomography, which preserves oriented scattering information. By introducing virtual tomography axes, we take advantage of the two-dimensional SAXS information recorded on an area detector and use it to reconstruct the full three-dimensional scattering distribution in reciprocal space for each voxel of the three-dimensional object in real space. The presented method could be of interest for a combined six-dimensional real and reciprocal space characterization of mesoscopic materials with hierarchically structured features with length scales ranging from a few nanometres to a few millimetres—for example, biomaterials such as bone or teeth, or functional materials such as fuel-cell or battery components.

  11. Microstructure of 3D-Printed Polymer Composites Investigated by Small-Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Kang, Tae Hui; Compton, Brett G.; Heller, William T.; Urban, Voker S.; Duty, Chad E.; Do, Changwoo

    Polymer composites printed from the large scale printer at Manufacturing Demonstration Facility at Oak Ridge National Laboratory have been investigated by small-angle neutron scattering (SANS). For the Acrylonitrile Butadiene Styrene (ABS)/Carbon Fiber (CF) composites, the microstructure of polymer domains and the alignment of CF have been characterized across the layer from the printed piece. CF shows strong anisotropic alignment along the printing direction due to the flow of polymer melt at the nozzle. Order parameter of the anisotropy which ranges from -0.11 to -0.06 exhibits strong correlation with the position within the layer: stronger alignment near the layer interface. It is also confirmed that the existence of CF reduces the polymer domain correlation length significantly and reinforces the mechanical strength of the polymer composites. For the Epoxy/nano-clay platelet composites, the effect of processing condition, nozzle size, and the addition of the another filler, Silicon Carbide (SC), have been investigated by SANS. Nano-clay platelet shows strong anisotropic alignment along the printing direction as well. Order parameter of the anisotropy varies according to nozzle size and presence of the SC, and difference disappears at high Q region. Scientific User Facilities Division and Materials Sciences and Energy Division, Office of Basic Energy Sciences, U.S. Department of Energy.

  12. Small-Angle Neutron Scattering study of the NIST mAb reference material

    NASA Astrophysics Data System (ADS)

    Castellanos, Maria Monica; Liu, Yun; Krueger, Susan; Curtis, Joseph

    Monoclonal antibodies (mAbs) are of great interest to the biopharmaceutical industry because they can be engineered to target specific antigens. Due to their importance, the biomanufacturing initiative at NIST is developing an IgG1 mAb reference material `NIST mAb', which can be used by industry, academia, and regulatory authorities. As part of this collaborative effort, we aim at characterizing the reference material using neutron scattering techniques. We have studied the small-angle scattering profile of the NIST mAb in a histidine buffer at 0 and 150 mM NaCl. Using Monte Carlo simulations, we generate an ensemble of structures and calculate their theoretical scattering profile, which can be directly compared with experimental data. Moreover, we analyze the structure factor to understand the effect of solution conditions on the protein-protein interactions. Finally, we have measured the solution scattering of the NIST mAb, while simultaneously performing freeze/thaw cycles, in order to investigate if the solution structure was affected upon freezing. The results from neutron scattering not only support the development of the reference material, but also provide insights on its stability and guide efforts for its development under different formulations.

  13. Automated acquisition and analysis of small angle X-ray scattering data

    NASA Astrophysics Data System (ADS)

    Franke, Daniel; Kikhney, Alexey G.; Svergun, Dmitri I.

    2012-10-01

    Small Angle X-ray Scattering (SAXS) is a powerful tool in the study of biological macromolecules providing information about the shape, conformation, assembly and folding states in solution. Recent advances in robotic fluid handling make it possible to perform automated high throughput experiments including fast screening of solution conditions, measurement of structural responses to ligand binding, changes in temperature or chemical modifications. Here, an approach to full automation of SAXS data acquisition and data analysis is presented, which advances automated experiments to the level of a routine tool suitable for large scale structural studies. The approach links automated sample loading, primary data reduction and further processing, facilitating queuing of multiple samples for subsequent measurement and analysis and providing means of remote experiment control. The system was implemented and comprehensively tested in user operation at the BioSAXS beamlines X33 and P12 of EMBL at the DORIS and PETRA storage rings of DESY, Hamburg, respectively, but is also easily applicable to other SAXS stations due to its modular design.

  14. Determining the melt miscibility of commercial polyolefin blends by Small-Angle Light Scattering

    NASA Astrophysics Data System (ADS)

    Peng, Ping

    2005-03-01

    The melt miscibility of high-density polyethylene (HDPE) (Mw = 52 kg/mol, PDI = 2.9) and linear low-density polyethylenes (LLDPEs) based on homogeneous ethylene-1-butene copolymers (EB0187: 18.7 mol% butene branches, Mw = 58.1 kg/mol and EB0059: 5.9 mol% butene branches, Mw = 70 kg/mol) is determined by Small-Angle Light Scattering (SALS) under parallel-polarized optical alignment. Blends with branching density differences (δy) ranging from 5.9 to 18.7 mol% were studied. For the HDPE/EB0187 blend, (δy = 18.7%), cooling and isothermal measurements (2 h) in the melt can be used to determine the miscibility and the phase boundary. When this blend is rapidly cooled room temperature, the resulting SALS patterns show that the size of phase separated domain (˜ 1 μm) is much smaller than the average spherulite size (68 μm). These results consist with our microscopic observations and the transmitted light measured simultaneously with the VV scattering in the melt. From the compositions studied, we can conclude that this blend exhibits UCST behavior. For blends with lower δy, isothermal measurements provide a sensitive means for determining the melt miscibility. Based on the above observations, we can conclude that SALS can be used to determine the melt miscibility of polyolefin blends.

  15. Estimation and modeling of coal pore accessibility using small angle neutron scattering

    SciTech Connect

    Zhang, Rui; Liu, Shimin; Bahadur, Jitendra; Elsworth, Derek; Melnichenko, Yuri; He, Lilin; Wang, Yi

    2015-09-04

    Gas diffusion in coal is controlled by nano-structure of the pores. The interconnectivity of pores not only determines the dynamics of gas transport in the coal matrix but also influences the mechanical strength. In this study, small angle neutron scattering (SANS) was employed to quantify pore accessibility for two coal samples, one of sub-bituminous rank and the other of anthracite rank. Moreover, a theoretical pore accessibility model was proposed based on scattering intensities under both vacuum and zero average contrast (ZAC) conditions. Our results show that scattering intensity decreases with increasing gas pressure using deuterated methane (CD4) at low Q values for both coals. Pores smaller than 40 nm in radius are less accessible for anthracite than sub-bituminous coal. On the contrary, when the pore radius is larger than 40 nm, the pore accessibility of anthracite becomes larger than that of sub-bituminous coal. Only 20% of pores are accessible to CD4 for anthracite and 37% for sub-bituminous coal, where the pore radius is 16 nm. For these two coals, pore accessibility and pore radius follows a power-law relationship.

  16. Estimation and modeling of coal pore accessibility using small angle neutron scattering

    DOE PAGES

    Zhang, Rui; Liu, Shimin; Bahadur, Jitendra; Elsworth, Derek; Melnichenko, Yuri; He, Lilin; Wang, Yi

    2015-09-04

    Gas diffusion in coal is controlled by nano-structure of the pores. The interconnectivity of pores not only determines the dynamics of gas transport in the coal matrix but also influences the mechanical strength. In this study, small angle neutron scattering (SANS) was employed to quantify pore accessibility for two coal samples, one of sub-bituminous rank and the other of anthracite rank. Moreover, a theoretical pore accessibility model was proposed based on scattering intensities under both vacuum and zero average contrast (ZAC) conditions. Our results show that scattering intensity decreases with increasing gas pressure using deuterated methane (CD4) at low Qmore » values for both coals. Pores smaller than 40 nm in radius are less accessible for anthracite than sub-bituminous coal. On the contrary, when the pore radius is larger than 40 nm, the pore accessibility of anthracite becomes larger than that of sub-bituminous coal. Only 20% of pores are accessible to CD4 for anthracite and 37% for sub-bituminous coal, where the pore radius is 16 nm. For these two coals, pore accessibility and pore radius follows a power-law relationship.« less

  17. Small-angle scattering studies of the pore spaces of shaly rocks

    NASA Astrophysics Data System (ADS)

    Hall, Peter L.; Mildner, David F. R.; Borst, Roger L.

    1986-02-01

    Small-angle neutron and X ray scattering (SANS and SAXS) measurements have been performed on shaly rocks from a variety of oil field locations. Thin core sections cut parallel to their bedding planes give circularly symmetric scattering patterns. On the basis of the model of Debye et al., the data indicate characteristic pore dimensions of 9-15 nm. Sections cut normal to the bedding planes exhibit elliptically symmetric scattering indicative of pores flattened in the direction of sedimentary compaction. Fourier inversion of the symmetric SANS data in all cases yields a broad distribution of pore diameters having peaks typically in the range 4-6 nm. These distributions are in reasonable agreement with distributions derived from nitrogen adsorption isotherms, although often in disagreement with nitrogen desorption or mercury porosimetry data. At higher scattering vectors, in the Porod region, differences between the SAXS and SANS data are observed which are explained in terms of the rather different sensitives of the two techniques to empty and filled pores. The data indicate that a significant component of the total porosity is due to pores of less than 2 nm in diameter, in which water is retained under ambient conditions. In several cases, pore dimensions measured by SANS increase after extraction of bitumens by methylene chloride solution, suggesting an intimate microscopic association of hydrocarbon and fine mineral grains.

  18. In situ microfluidic dialysis for biological small-angle X-ray scattering

    PubMed Central

    Skou, Magda; Skou, Søren; Jensen, Thomas G.; Vestergaard, Bente; Gillilan, Richard E.

    2014-01-01

    Owing to the demand for low sample consumption and automated sample changing capabilities at synchrotron small-angle X-ray (solution) scattering (SAXS) beamlines, X-ray microfluidics is receiving continuously increasing attention. Here, a remote-controlled microfluidic device is presented for simultaneous SAXS and ultraviolet absorption measurements during protein dialysis, integrated directly on a SAXS beamline. Microfluidic dialysis can be used for monitoring structural changes in response to buffer exchange or, as demonstrated, protein concentration. By collecting X-ray data during the concentration procedure, the risk of inducing protein aggregation due to excessive concentration and storage is eliminated, resulting in reduced sample consumption and improved data quality. The proof of concept demonstrates the effect of halted or continuous flow in the microfluidic device. No sample aggregation was induced by the concentration process at the levels achieved in these experiments. Simulations of fluid dynamics and transport properties within the device strongly suggest that aggregates, and possibly even higher-order oligomers, are preferentially retained by the device, resulting in incidental sample purification. Hence, this versatile microfluidic device enables investigation of experimentally induced structural changes under dynamically controllable sample conditions. PMID:25242913

  19. Percolating bulk-heterostructures from neutron reflectometry and small angle scattering data

    NASA Astrophysics Data System (ADS)

    Olds, Daniel; Duxbury, Phillip

    2013-03-01

    We present a novel algorithm for efficiently calculating the simulated small angle scattering data of any discretized morphological model of arbitrary scale and resolution, referred to as the distribution function method (DFM). Unlike standard SAS fitting methods, the DFM algorithm allows for the calculation of form factors and structure factors from complex nanoscale morphologies commonly encountered in many modern polymeric and nanoparticle based systems, which have no exact analytical corollary. The computational efficiency of the DFM algorithm suggests it's use in morphological model refinement. We will present a number of simple examples to demonstrate the accuracy and limits of the algorithm, followed by an example of incorporation of the DFM algorithm into reverse Monte Carlo structural refinement of bulk-heterojunction two-phase morphologies, such as those commonly found in organic photovoltaic devices. We will show that morphological features introduced via direct incorporation of experimental neutron reflectometry and SANS data to the models has a direct effect on the results of device simulations. The authors thank CORE-CM at Michigan State University for it's funding of this research.

  20. Fractal Structures on Fe3O4 Ferrofluid: A Small-Angle Neutron Scattering Study

    NASA Astrophysics Data System (ADS)

    Giri Rachman Putra, Edy; Seong, Baek Seok; Shin, Eunjoo; Ikram, Abarrul; Ani, Sistin Ari; Darminto

    2010-10-01

    A small-angle neutron scattering (SANS) which is a powerful technique to reveal the large scale structures was applied to investigate the fractal structures of water-based Fe3O4ferrofluid, magnetic fluid. The natural magnetite Fe3O4 from iron sand of several rivers in East Java Province of Indonesia was extracted and purified using magnetic separator. Four different ferrofluid concentrations, i.e. 0.5, 1.0, 2.0 and 3.0 Molar (M) were synthesized through a co-precipitation method and then dispersed in tetramethyl ammonium hydroxide (TMAH) as surfactant. The fractal aggregates in ferrofluid samples were observed from their SANS scattering distributions confirming the correlations to their concentrations. The mass fractal dimension changed from about 3 to 2 as ferrofluid concentration increased showing a deviation slope at intermediate scattering vector q range. The size of primary magnetic particle as a building block was determined by fitting the scattering profiles with a log-normal sphere model calculation. The mean average size of those magnetic particles is about 60 - 100 Å in diameter with a particle size distribution σ = 0.5.

  1. Characterization of lysozyme adsorption in cellulosic chromatographic materials using small-angle neutron scattering.

    PubMed

    Koshari, Stijn H S; Wagner, Norman J; Lenhoff, Abraham M

    2015-06-19

    Measurements of the nanoscale structure of chromatographic adsorbents and the associated distribution of sorbed protein within the media can facilitate improvements in such media. We demonstrate a new technique for this purpose using small-angle neutron scattering (SANS) to characterize the nano- to microscale structure of the chromatographic media and sorbed protein under conditions relevant for preparative chromatographic separations. The adsorption of lysozyme on cellulosic S HyperCel™ (Pall Corporation), a strong cation exchanger, was investigated by SANS. The scattering spectrum is reduced to three contributions arising from (1) the chromatographic medium, (2) discrete protein molecules, and (3) the distribution of sorbed protein within the medium. These contributions are quantified for a range of protein loadings. The total concentration of protein in the chromatographic media can be quantified from the SANS spectrum and the protein is observed to retain its tertiary structure upon adsorption, within the resolution of the method. Further analysis of the SANS spectra shows that protein adsorption is uniform in the media. These measurement techniques provide new and valuable nanoscale information about protein sorption in chromatographic media.

  2. Electron-nucleus scattering at small angles in the field of a pulsed laser wave

    NASA Astrophysics Data System (ADS)

    Lebed', A. A.

    2016-04-01

    We study scattering of an electron by a screened potential of a nucleus in the field of a pulsed laser wave at small scattering angles. The interaction of an electron with the field of a nucleus is considered in the first Born approximation. An external field of a pulsed laser is accounted accurately as a quasimonochromatic wave. Analytical expressions are obtained for the transition amplitude and the cross section of the considered process. Scattering kinematics is defined at the minimal value of a transferred momentum. In this case the cross section contains a peak near the preferred scattering direction. It is shown that the maximum value of the cross section is determined by both the initial-electron energy and the energy of an external-field photon. Thus, the cross section of electron-nucleus scattering in a pulsed laser field can exceed in two orders of magnitude the cross section in absence of an external field in the case of ultrarelativistic energies and external field of a free-electron laser with keV-order photon energy.

  3. Small-angle neutron scattering reveals a pH-dependent conformational change in cellobiohydrolase I

    SciTech Connect

    Pingali, Sai Venkatesh; O'Neill, Hugh Michael; McGaughey, Joseph; Urban, Volker S; Myles, Dean A A; Petridis, Loukas; Smith, Jeremy C; Evans, Barbara R; Heller, William T

    2011-01-01

    Cellobiohydrolase I (Cel7A) of the fungus Trichoderma reesei (now classified as an anamorph of Hypocrea jecorina) hydrolyzes crystalline cellulose to soluble sugars, making it of key interest for producing fermentable sugars from biomass for biofuel production. The activity of the enzyme is pH-dependent, with its highest activity occurring at pH 4-5. To probe the response of the solution structure of Cel7A to changes in pH, we measured small angle neutron scattering of it in a series of solutions having pH values of 7.0, 6.0, 5.3, and 4.2. As the pH decreases from 7.0 to 5.3, the enzyme structure remains well defined, possessing a spatial differentiation between the cellulose binding domain and the catalytic core that only changes subtly. At pH 4.2, the solution conformation of the enzyme changes to a structure that is intermediate between a properly folded enzyme and a denatured, unfolded state, yet the secondary structure of the enzyme is essentially unaltered. The results indicate that at the pH of optimal activity, the catalytic core of the enzyme adopts a structure in which the compact packing typical of a fully folded polypeptide chain is disrupted and suggest that the increased range of structures afforded by this disordered state plays an important role in the increased activity of Cel7A through conformational selection.

  4. Small-angle neutron scattering correlation functions of bulk magnetic materials

    PubMed Central

    Mettus, Denis; Michels, Andreas

    2015-01-01

    On the basis of the continuum theory of micromagnetics, the correlation function of the spin-misalignment small-angle neutron scattering cross section of bulk ferromagnets (e.g. elemental polycrystalline ferromagnets, soft and hard magnetic nanocomposites, nanoporous ferromagnets, or magnetic steels) is computed. For such materials, the spin disorder which is related to spatial variations in the saturation magnetization and magnetic anisotropy field results in strong spin-misalignment scattering dΣM/dΩ along the forward direction. When the applied magnetic field is perpendicular to the incoming neutron beam, the characteristics of dΣM/dΩ (e.g. the angular anisotropy on a two-dimensional detector or the asymptotic power-law exponent) are determined by the ratio of magnetic anisotropy field strength H p to the jump ΔM in the saturation magnetization at internal interfaces. Here, the corresponding one- and two-dimensional real-space correlations are analyzed as a function of applied magnetic field, the ratio H p/ΔM, the single-particle form factor and the particle volume fraction. Finally, the theoretical results for the correlation function are compared with experimental data on nanocrystalline cobalt and nickel. PMID:26500464

  5. Characterization of fullerenes and fullerene derivatives by small-angle neutron scattering and transmission measurements

    SciTech Connect

    Melnichenko, Y.B.; Wignall, G.D.; Affholter, K.A.

    1997-01-01

    Small-angle neutron scattering (SANS) has been shown to be an appropriate technique for the structural characterization of fullerenes (1) in solvents with strong SANS contrast (e.g. CS{sub 2}) and we have extended initial studies of C{sub 60} (1) to include C{sub 70} and C{sub 84} moieties. Deuterated solvents (e.g. toluene-d{sub 8}) have a high scattering length density (SLD), which is close to that of C{sub 60}, so there is virtually no SANS contrast with the solvent. Hence, these particles are practically {open_quotes}invisible{close_quotes} in such media, though the negative scattering length of hydrogen means that SLD of H{sup 1}-containing materials is much lower, so they have strong contrast with toluene-d{sub 8}. Thus, SANS makes it possible to study the size and shapes of modified buckyballs and this paper describes the first results on cyclohexane-substituted fullerenes.

  6. Small-angle light scattering by airborne particulates: Environnement S.A. continuous particulate monitor

    NASA Astrophysics Data System (ADS)

    Renard, Jean-Baptiste; Thaury, Claire; Mineau, Jean-Luc; Gaubicher, Bertrand

    2010-08-01

    Airborne particulate matter may have an effect on human health. It is therefore necessary to determine and control in real time the evolution of the concentration and mass of particulates in the ambient air. These parameters can be obtained using optical methods. We propose here a new instrument, 'CPM' (continuous particulate monitor), for the measurement of light scattered by ambient particulates at small angles. This geometry allows simultaneous and separate detections of PM10, PM2.5 and PM1 fractions of airborne particulate matter, with no influence of their chemical nature and without using theoretical calculations. The ambient air is collected through a standard sampling head (PM10 inlet according to EN 12341, PM2.5 inlet according to EN 14907; or PM1, TSP inlets, standard US EPA inlets). The analysis of the first measurements demonstrates that this new instrument can detect, for each of the seven defined size ranges, real-time variations of particulate content in the ambient air. The measured concentrations (expressed in number per liter) can be converted into total mass concentrations (expressed in micrograms per cubic meter) of all fractions of airborne particulate matters sampled by the system. Periodic comparison with a beta-attenuation mass monitor (MP101M Beta Gauge Analyzer from Environnement S.A. company) allows the calculation of a calibration factor as a function of the mean particulate density that is used for this conversion. It is then possible to provide real-time relative variations of aerosol mass concentration.

  7. Dynamic Conformations of Nucleosome Arrays in Solution from Small-Angle X-ray Scattering

    NASA Astrophysics Data System (ADS)

    Howell, Steven C.

    Chromatin conformation and dynamics remains unsolved despite the critical role of the chromatin in fundamental genetic functions such as transcription, replication, and repair. At the molecular level, chromatin can be viewed as a linear array of nucleosomes, each consisting of 147 base pairs (bp) of double-stranded DNA (dsDNA) wrapped around a protein core and connected by 10 to 90 bp of linker dsDNA. Using small-angle X-ray scattering (SAXS), we investigated how the conformations of model nucleosome arrays in solution are modulated by ionic condition as well as the effect of linker histone proteins. To facilitate ensemble modeling of these SAXS measurements, we developed a simulation method that treats coarse-grained DNA as a Markov chain, then explores possible DNA conformations using Metropolis Monte Carlo (MC) sampling. This algorithm extends the functionality of SASSIE, a program used to model intrinsically disordered biological molecules, adding to the previous methods for simulating protein, carbohydrates, and single-stranded DNA. Our SAXS measurements of various nucleosome arrays together with the MC generated models provide valuable solution structure information identifying specific differences from the structure of crystallized arrays.

  8. Alzheimer's disease imaging biomarkers using small-angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Choi, Mina; Alam, Nadia; Dahal, Eshan; Ghammraoui, Bahaa; Badano, Aldo

    2016-03-01

    There is a need for novel imaging techniques for the earlier detection of Alzheimer's disease (AD). Two hallmarks of AD are amyloid beta (Aβ) plaques and tau tangles that are formed in the brain. Well-characterized x-ray cross sections of Aβ and tau proteins in a variety of structural states could potentially be used as AD biomarkers for small-angle x-ray scattering (SAXS) imaging without the need for injectable probes or contrast agents. First, however, the protein structures must be controlled and measured to determine accurate biomarkers for SAXS imaging. Here we report SAXS measurements of Aβ42 and tau352 in a 50% dimethyl sulfoxide (DMSO) solution in which these proteins are believed to remain monomeric because of the stabilizing interaction of DMSO solution. Our SAXS analysis showed the aggregation of both proteins. In particular, we found that the aggregation of Aβ42 slowly progresses with time in comparison to tau352 that aggregates at a faster rate and reaches a steady-state. Furthermore, the measured signals were compared to the theoretical SAXS profiles of Aβ42 monomer, Aβ42 fibril, and tau352 that were computed from their respective protein data bank structures. We have begun the work to systematically control the structural states of these proteins in vitro using various solvent conditions. Our future work is to utilize the distinct SAXS profiles of various structural states of Aβ and tau to build a library of signals of interest for SAXS imaging in brain tissue.

  9. New Insights into Pore Characteristics and Hydrocarbon Generation of Shale Using Small-Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Ding, M.; Hartl, M.; Wang, Y.; Hjelm, R.

    2014-12-01

    Pore size, distribution, connectivity, and shape as well as hydrocarbon saturation and composition reflect the history of hydrocarbon maturation and migration. However, characterization of the underlying factors and processes controlling hydrocarbons behavior in tight rocks is extremely limited, especially lacking of direct experimental observations. We have studied the pore characteristics of marine and lacustrine shale from the Erdos basin, China during laboratory pyrolysis using small-angle neutron scattering (SANS). Our SANS results show that scattering intensity of smaller pores (< 20 nm)/larger Q values of shale samples increase systematically as temperature increase during pyrolysis from 250 oC to 600oC (Fig.1a). These results in combination with hydrocarbon fractions measurements during the same process (Fig. 1b) provide a quantitative relation between pore characteristics and hydrocarbons generation. Our results indicate that hydrocarbon expulsion primarily causes the observed changes in smaller pores. They also demonstrate that due to its sensitivity to hydrogen, SANS locates all pores whether the pore is filled or not with hydrocarbons. Thus, SANS is particularly suited for probing hydrocarbon behavior in tight shale reservoirs and the factors that impact their pore dynamics for the petroleum industry.

  10. Quasielastic small-angle neutron scattering from heavy water solutions of cyclodextrins.

    PubMed

    Kusmin, André; Lechner, Ruep E; Saenger, Wolfram

    2011-01-14

    We present a model for quasielastic neutron scattering (QENS) by an aqueous solution of compact and inflexible molecules. This model accounts for time-dependent spatial pair correlations between the atoms of the same as well as of distinct molecules and includes all coherent and incoherent neutron scattering contributions. The extension of the static theory of the excluded volume effect [A. K. Soper, J. Phys.: Condens. Matter 9, 2399 (1997)] to the time-dependent (dynamic) case allows us to obtain simplified model expressions for QENS spectra in the low Q region in the uniform fluid approximation. The resulting expressions describe the quasielastic small-angle neutron scattering (QESANS) spectra of D(2)O solutions of native and methylated cyclodextrins well, yielding in particular translational and rotational diffusion coefficients of these compounds in aqueous solution. Finally, we discuss the full potential of the QESANS analysis (that is, beyond the uniform fluid approximation), in particular, the information on solute-solvent interactions (e.g., hydration shell properties) that such an analysis can provide, in principle.

  11. How Random are Intrinsically Disordered Proteins? A Small Angle Scattering Perspective

    PubMed Central

    Receveur-Bréchot, Véronique; Durand, Dominique

    2012-01-01

    While the crucial role of intrinsically disordered proteins (IDPs) in the cell cycle is now recognized, deciphering their molecular mode of action at the structural level still remains highly challenging and requires a combination of many biophysical approaches. Among them, small angle X-ray scattering (SAXS) has been extremely successful in the last decade and has become an indispensable technique for addressing many of the fundamental questions regarding the activities of IDPs. After introducing some experimental issues specific to IDPs and in relation to the latest technical developments, this article presents the interest of the theory of polymer physics to evaluate the flexibility of fully disordered proteins. The different strategies to obtain 3-dimensional models of IDPs, free in solution and associated in a complex, are then reviewed. Indeed, recent computational advances have made it possible to readily extract maximum information from the scattering curve with a special emphasis on highly flexible systems, such as multidomain proteins and IDPs. Furthermore, integrated computational approaches now enable the generation of ensembles of conformers to translate the unique flexible characteristics of IDPs by taking into consideration the constraints of more and more various complementary experiment. In particular, a combination of SAXS with high-resolution techniques, such as x-ray crystallography and NMR, allows us to provide reliable models and to gain unique structural insights about the protein over multiple structural scales. The latest neutron scattering experiments also promise new advances in the study of the conformational changes of macromolecules involving more complex systems. PMID:22044150

  12. Discovering New Features of Protein Complexes Structures by Small-Angle X-Ray Scattering

    NASA Astrophysics Data System (ADS)

    Oliveira, C. L. P.; Vorup-Jensen, T.; Andersen, C. B. F.; Andersen, G. R.; Pedersen, J. S.

    In spite of the recent advances in the X-Ray crystallography and nuclear magnetic resonance techniques, the determination of the quaternary structure of large protein complexes is still a challenge in molecular biology and biological sciences. In this respect, small-angle X-ray scattering (SAXS) is a key technique, enabling the determination of the possible structural conformation of complexes in an almost native state. Despite of this book being devoted to scattering techniques by synchrotron radiation, in this chapter we present two examples of application of laboratory-based SAXS to protein solution. The fundaments of the technique are obviously the same and have been deeply described in Chap. 2. In this chapter, we will introduce the application of SAXS to protein solution. Special emphasis is done on data reduction and absolute units calibration. As an example to illustrate the power of this technique, two new data sets for two protein complexes will be presented. This will show how high-quality SAXS data combined with advanced model strategies enables the determination of the quaternary structure of protein complexes.

  13. Small Angle Neutron Scattering (SANS) Studies on the Structural Evolution of Pyromellitamide Self-assembled Gels

    DOE PAGES

    Scott, Jamieson; Tong, Katie; William, Hamilton; He, Lilin; James, Michael; Thordarson, Pall; Boukhalfa, Sofiane

    2014-10-31

    The kinetics of aggregation of two pyromellitamide gelators; tetrabutyl- (C4) and tetrahexylpyromellitamide (C6), in deuterated cyclohexane has been investigated by small angle neutron scattering (SANS) for up to six days. The purpose of this study was to improve our understanding of how self-assembled gels are formed. Short-term (< 3 hour) time scales revealed multiple phases with the data for the tetrabutylpyromellitamide C4 indicating one dimensional stacking and aggregation corresponding to a multi-fiber braided cluster arrangement that is about 35 Å in diameter. The corresponding tetrahexylpyromellitamide C6 data suggests that the C6 also forms one-dimensional stacks but that these aggregate tomore » a thicker multi-fiber braided cluster that have a diameter of 61.8 Å. Over a longer period of time, the radius, persistence length and contour length all continue to increase in 6 days after cooling. This data suggests that structural changes in self-assembled gels occur over a period exceeding several days and that fairly subtle changes in the structure (e.g. tail-length) can influence the packing of molecules in self-assembled gels on the single-to-few fiber bundle stage.« less

  14. Small-angle neutron scattering studies of chlorophyll micelles: Models for bacterial antenna chlorophyll

    PubMed Central

    Worcester, D. L.; Michalski, T. J.; Katz, J. J.

    1986-01-01

    Micelles of hydrated chlorophyll a (P740), bacteriochlorophyll a (P865), bacteriochlorophyll c (P750), and pheophytin a prepared in organic media have been studied by small-angle neutron scattering to determine their shape, size, and mass per unit length. All of the micelles are hollow cylinders of well-defined size. The P740 and P750 cylinders are essentially monolayers of macrocycles crosslinked by water, probably in an arrangement similar to that of crystals of chlorophyll derivatives. The P865 micelle is more nearly a bilayer of macrocycles. We show that the curvature necessary to form cylinders probably results from intrinsic curvature of the five-coordinated chlorophyll macrocycle. Studies of P740 micelle formation and the disaggregating effects of another nucleophile (pyridine) are described. As the P750 micelles are nearly identical in size and optical spectra to the rod-shaped structures observed in chlorosomes, and the P865 micelles have optical properties very similar to the in vivo properties of the long-wavelength antenna of purple photosynthetic bacteria, we propose that features of the hydrated cylindrical micelles of these chlorophylls provide good models for antenna chlorophyll in photosynthetic bacteria. Images PMID:16593703

  15. Optical phase curves of exoplanets at small and large phase angles

    NASA Astrophysics Data System (ADS)

    García Muñoz, Antonio

    2016-10-01

    Phase curves and secondary eclipses provide key information on exoplanet atmospheres. Indeed, recent work on close-in giant planets observed by Kepler has shown that it is possible to constrain various reflecting, dynamical and thermal properties of their atmospheres from the analysis of the planets' phase curves. This presentation discusses new diagnostic possibilities for the characterization of exoplanet atmospheres with optical phase curves. These possibilities benefit from the fact that at optical wavelengths the signal from the planet is either partly or mostly determined by scattering of starlight within its atmosphere, which entails that the structure of the planet's phase curve mimics to some extent the optical properties of the atmospheric medium. In particular, we will show how cloud properties such as the particle size or the atmospheric scale height might be constrained through observations at small (i.e. near transit) and large (i.e. near occultation) phase angles. We will emphasize how the interpretation of optical phase curves differs from the interpretation of phase curves obtained at longer wavelengths. The conclusions are relevant to the study of Kepler planets, but also to the investigation of phase curves to be delivered by upcoming space missions such as CHEOPS, JWST, PLATO and TESS.

  16. Small-Angle Neutron Scattering and Fluorescence Studies of Mixed Surfactants with Dodecyl Tails.

    PubMed

    Griffiths; Whatton; Abbott; Kwan; Pitt; Howe; King; Heenan

    1999-07-01

    The mixed micelles formed in solutions of the anionic surfactant sodium dodecylsulfate (SDS) and the nonionic surfactant dodecylmalono-bis-N-methylglucamide (DBNMG) were studied by surface tension, fluorescence, and small-angle neutron scattering. Measurements of the critical micelle concentration (CMC) by surface tension and fluorescence show that these two surfactants mix nonideally. The experimental values of the CMCs for surfactant mixtures for all compositions are less than the ideal prediction proposed by Clint (J. Chem. Soc. 71, 1327 (1975)). Regular solution theory (for example, Penfold et al., Langmuir 11, 2498 (1995)) can be used to calculate the composition of the micelle at the CMC. The micellar composition thus calculated differs significantly from that at higher total surfactant concentrations, the latter being much closer to the stoichiometric composition. The polarity of the micellar environment, as perceived by a solubilized fluorescence probe, is identical for both the single-component and the mixed micelles. The scattering data show that the mixed micelles are comparable in size to the pure nonionic micelle and slightly larger than the anionic micelle. Parallel studies with deuterated SDS showed no evidence of segregation or local ordering within the mixed micelle. The effective charge on the mixed micelle is determined by the amount of ionic surfactant within the micelle. Addition of 0.1 M NaCl to these systems has no effect on the CMC, micelle ellipticity, and aggregation number-a behavior very different from that observed for simple SDS solutions. Copyright 1999 Academic Press.

  17. Structure of Nanoporous Biocarbon for Hydrogen Storage as Determined by Small Angle X-Ray Scattering

    NASA Astrophysics Data System (ADS)

    Wood, Mikael; Burress, J.; Pobst, J.; Carter, S.; Pfeifer, P.; Wexler, C.; Shah, P.; Suppes, G.

    2008-03-01

    As a member of the Alliance for Collaborative Research in Alternative Fuel Technology (ALL-CRAFT) our research group studies the properties of nanoporous biocarbon, produced from waste corn cob, with the goal of achieving the Department of Energy's gravimetric and volumetric standards for both hydrogen and methane gas storage. Small Angle X-Ray Scattering (SAXS) is a valuable tool in our investigation of the geometry of the pore space in our carbon samples. In this talk, we will compare the experimental SAXS data with theoretical results for various pore geometries to determine which pore models are consistent with experiment. Using data from nitrogen adsorption isotherms, along with SAXS, yields significant structural information about the pore space. This analysis should allow us to fully optimize our production process and to achieve the DOE's target storage capacities. This work supported by: 1. National Science Foundation (PFI-0438469) 2. U.S. Department of Education (P200A040038) 3. U.S. Department of Energy (DE-AC02-06CH11357) 4. University of Missouri (RB-06-040) 5. U.S. Department of Defense (N00164-07-P-1306) 6. U.S. Department of Energy (DE-FG02-07ER46411)

  18. Accurate assessment of mass, models and resolution by small-angle scattering

    PubMed Central

    Rambo, Robert P.; Tainer, John A.

    2013-01-01

    Modern small angle scattering (SAS) experiments with X-rays or neutrons provide a comprehensive, resolution-limited observation of the thermodynamic state. However, methods for evaluating mass and validating SAS based models and resolution have been inadequate. Here, we define the volume-of-correlation, Vc: a SAS invariant derived from the scattered intensities that is specific to the structural state of the particle, yet independent of concentration and the requirements of a compact, folded particle. We show Vc defines a ratio, Qr, that determines the molecular mass of proteins or RNA ranging from 10 to 1,000 kDa. Furthermore, we propose a statistically robust method for assessing model-data agreements (X2free) akin to cross-validation. Our approach prevents over-fitting of the SAS data and can be used with a newly defined metric, Rsas, for quantitative evaluation of resolution. Together, these metrics (Vc, Qr, X2free, and Rsas) provide analytical tools for unbiased and accurate macromolecular structural characterizations in solution. PMID:23619693

  19. Preserving the excitation profile of small flip angle RF pulses in the presence of rapid transverse relaxation.

    PubMed

    Shen, Jun

    2012-11-01

    Degradation of excitation profile of selective RF pulses by rapid transverse relaxation has been a long-standing concern. In this report we demonstrate that transverse relaxation can be incorporated into small flip angle RF pulse design based on the linear response theory. Small flip angle pulses that were designed without considering transverse relaxation effects can be transformed for a predefined pulse duration/T(2) ratio. The transformed pulses, within the realm of the linear response theory, produce the same transverse frequency response as if there were no relaxation.

  20. Size And Shape of Detergent Micelles Determined By Small-Angle X-Ray Scattering

    SciTech Connect

    Lipfert, Jan; Columbus, Linda; Chu, Vincent B.; Lesley, Scott A.; Doniach, Sebastian; /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept. /SLAC, SSRL /Pasteur Inst., Paris /Scripps Res. Inst. /Novartis Res. Found.

    2009-04-29

    We present a systematic analysis of the aggregation number and shape of micelles formed by nine detergents commonly used in the study of membrane proteins. Small-angle X-ray scattering measurements are reported for glucosides with 8 and 9 alkyl carbons (OG/NG), maltosides and phosphocholines with 10 and 12 alkyl carbons (DM/DDM and FC-10/FC-12), 1,2-dihexanoyl-sn-glycero-phosphocholine (DHPC), 1-palmitoyl-2-hydroxy-sn-glycero-3-[phospho-rac-(1-glycerol)] (LPPG), and 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate (CHAPS). The SAXS intensities are well described by two-component ellipsoid models, with a dense outer shell corresponding to the detergent head groups and a less electron dense hydrophobic core. These models provide an intermediate resolution view of micelle size and shape. In addition, we show that Guinier analysis of the forward scattering intensity can be used to obtain an independent and model-free measurement of the micelle aggregation number and radius of gyration. This approach has the advantage of being easily generalizable to protein-detergent complexes, where simple geometric models are inapplicable. Furthermore, we have discovered that the position of the second maximum in the scattering intensity provides a direct measurement of the characteristic head group-head group spacing across the micelle core. Our results for the micellar aggregation numbers and dimensions agree favorably with literature values as far as they are available. We de novo determine the shape of FC-10, FC-12, DM, LPPG, and CHAPS micelles and the aggregation numbers of FC-10 and OG to be ca. 50 and 250, respectively. Combined, these data provide a comprehensive view of the determinants of micelle formation and serve as a starting point to correlate detergent properties with detergent-protein interactions.

  1. Structure and properties of aqueous methylcellulose gels by small-angle neutron scattering.

    PubMed

    Chatterjee, Tirtha; Nakatani, Alan I; Adden, Roland; Brackhagen, Meinolf; Redwine, David; Shen, Hongwei; Li, Yongfu; Wilson, Tricia; Sammler, Robert L

    2012-10-01

    Cold, semidilute, aqueous solutions of methylcellulose (MC) are known to undergo thermoreversible gelation when warmed. This study focuses on two MC materials with much different gelation performance (gel temperature and hot gel modulus) even though they have similar metrics of their coarse-grained chemical structure (degree-of-methylether substitution and molecular weight distribution). Small-angle neutron scattering (SANS) experiments were conducted to probe the structure of the aqueous MC materials at pre- and postgel temperatures. One material (MC1, higher gel temperature) exhibited a single almost temperature-insensitive gel characteristic length scale (ζ(c) = 1090 ± 50 Å) at postgelation temperatures. This length scale is thought to be the gel blob size between network junctions. It also coincides with the length scale between entanglement sites measured with rheology studies at pregel temperatures. The other material (MC2, lower gel temperature) exhibited two distinct length scales at all temperatures. The larger length scale decreased as temperature increased. Its value (ζ(c1) = 1046 ± 19 Å) at the lowest pregel temperature was indistinguishable from that measured for MC1, and reached a limiting value (ζ(c1) = 450 ± 19 Å) at high temperature. The smaller length scale (ζ(c2) = 120 to 240 Å) increased slightly as temperature increased, but remained on the order of the chain persistence length (130 Å) measured at pregel temperatures. The smaller blob size (ζ(c1)) of MC2 suggests a higher bond energy or a stiffer connectivity between network junctions. Moreover, the number density of these blobs, at the same reduced temperature with respect to the gel temperature, is orders of magnitude higher for the MC2 gels. Presumably, the smaller gel length scale and higher number density lead to higher hot gel modulus for the low gel temperature material.

  2. Strategies for Choosing Descent Flight-Path Angles for Small Jets

    NASA Technical Reports Server (NTRS)

    Wu, Minghong Gilbert; Green, Steven M.

    2012-01-01

    Three candidate strategies for choosing the descent flight path angle (FPA) for small jets are proposed, analyzed, and compared for fuel efficiency under arrival metering conditions. The strategies vary in operational complexity from a universally fixed FPA, or FPA function that varies with descent speed for improved fuel efficiency, to the minimum-fuel FPA computed for each flight based on winds, route, and speed profile. Methodologies for selecting the parameter for the first two strategies are described. The differences in fuel burn are analyzed over a year s worth of arrival traffic and atmospheric conditions recorded for the Dallas/Fort Worth (DFW) Airport during 2011. The results show that the universally fixed FPA strategy (same FPA for all flights, all year) burns on average 26 lbs more fuel per flight as compared to the minimum-fuel solution. This FPA is adapted to the arrival gate (direction of entry to the terminal) and various timespans (season, month and day) to improve fuel efficiency. Compared to a typical FPA of approximately 3 degrees the adapted FPAs vary significantly, up to 1.3 from one arrival gate to another or up to 1.4 from one day to another. Adapting the universally fixed FPA strategy to the arrival gate or to each day reduces the extra fuel burn relative to the minimum-fuel solution by 27% and 34%, respectively. The adaptations to gate and time combined shows up to 57% reduction of the extra fuel burn. The second strategy, an FPA function, contributes a 17% reduction in the 26 lbs of extra fuel burn over the universally fixed FPA strategy. Compared to the corresponding adaptations of the universally fixed FPA, adaptations of the FPA function reduce the extra fuel burn anywhere from 15-23% depending on the extent of adaptation. The combined effect of the FPA function strategy with both directional and temporal adaptation recovers 67% of the extra fuel relative to the minimum-fuel solution.

  3. Signal, noise, and resolution in correlated fluctuations from snapshot small-angle x-ray scattering

    SciTech Connect

    Kirian, Richard A.; Schmidt, Kevin E.; Wang Xiaoyu; Doak, R. Bruce; Spence, John C. H.

    2011-07-15

    It has been suggested that the three-dimensional structure of one particle may be reconstructed using the scattering from many identical, randomly oriented copies ab initio, without modeling or a priori information. This may be possible if these particles are frozen in either space or time, so that the conventional two-dimensional small-angle x-ray scattering (SAXS) distribution contains fluctuations and is no longer isotropic. We consider the magnitude of the correlated fluctuation SAXS (CFSAXS) signal for typical x-ray free-electron laser (XFEL) beam conditions and compare this against the errors derived with the inclusion of Poisson photon counting statistics. The resulting signal-to-noise ratio (SNR) is found to rapidly approach a limit independent of the number of particles contributing to each diffraction pattern, so that the addition of more particles to a ''single-particle-per-shot'' experiment may be of little value, apart from reducing solvent background. When the scattering power is significantly less than one photon per particle per Shannon pixel, the SNR grows in proportion to incident flux. We provide simulations for protein molecules in support of these analytical results, and discuss the effects of solvent background scatter. We consider the SNR dependence on resolution and particle size, and discuss the application of the method to glasses and liquids, and the implications of more powerful XFELs, smaller focused beams, and higher pulse repetition rates for this approach. We find that an accurate CFSAXS measurement may be acquired to subnanometer resolution for protein molecules if a 9-keV beam containing 10{sup 13} photons is focused to a {approx}100-nm spot diameter, provided that the effects of solvent background can be reduced sufficiently.

  4. Metastable ripple phase of fully hydrated dipalmitoylphosphatidylcholine as studied by small angle x-ray scattering

    PubMed Central

    Yao, Haruhiko; Matuoka, Sinzi; Tenchov, Boris; Hatta, Ichiro

    1991-01-01

    Fully hydrated dipalmitoylphosphatidylcholine (DPPC) undergoes liquid crystalline to metastable Pβ, phase transition in cooling. A small angle x-ray scattering study has been performed for obtaining further evidence about the structure of this phase. From a high-resolution observation of x-ray diffraction profiles, a distinct multipeak pattern has become obvious. Among them the (01) reflection in the secondary ripple structure is identified clearly. There are peaks assigned straightforwardly to (10) and (20) reflections in the primary ripple structure and peaks assigned to (10) and (20) reflections in the secondary ripple structure. Therefore the multipeak pattern is due to superposition of the reflections cause by the primary and secondary ripple structures. The lattice parameters are estimated as follows: for the primary ripple structure a = 7.09 nm, b = 13.64 nm, and γ = 95°, and for the secondary ripple structure a = 8.2 nm, b = 26.6 nm, and γ = 90°. The lattice parameters thus obtained for the secondary ripple structure are not conclusive, however. The hydrocarbon chains in the primary ripple structure have been reported as being tilted against the bilayer plane and, on the other hand, the hydrocarbon chains in the secondary ripple structure are likely to be perpendicular to the bilayer plane. This fact seems to be related to a sequential mechanism of phase transitions. On heating from the Lβ, phase where the hydrocarbon chains are tilted the primary ripple structure having tilted hydrocarbon chains takes place and on cooling from the Lα phase where the hydrocarbon chains are not tilted the secondary ripple structure with untilted chains tends to be stabilized. It appears that the truly metastable ripple phase is expressed by the second ripple structure although in the course of the actual cooling transition both the secondary and primary ripple structures form and coexist. PMID:19431787

  5. Characterization of Sol-gel Encapsulated Proteins using Small-angle Neutron Scattering

    SciTech Connect

    Luo, Guangming; Zhang, Qiu; Del Castillo, Alexis Rae; Urban, Volker S; O'Neill, Hugh Michael

    2009-01-01

    Entrapment of biomolecules in silica-derived sol-gels has grown into a vibrant area of research since it was originally demonstrated. However, accessing the consequences of entrapment on biomolecules and the gel structure remains a major challenge in characterizing these biohybrid materials. We present the first demonstration that it is possible with small-angle neutron scattering (SANS) to study the conformation of dilute proteins that are entrapped in transparent and dense sol-gels. Using deuterium-labeled green fluorescent protein (GFP) and SANS with contrast variation, we demonstrate that the scattering signatures of the sol-gel and the protein can be separated. Analysis of the scattering curves of the sol-gels using a mass-fractal model shows that the size of the colloidal silica particles and the fractal dimensions of the gels were similar in the absence and presence of protein, demonstrating that GFP did not influence the reaction pathway for the formation of the gel. The major structural difference in the gels was that the pore size was increased 2-fold in the presence of the protein. At the contrast match point for silica, the scattering signal from GFP inside the gel became distinguishable over a wide q range. Simulated scattering curves representing a monomer, end-to-end dimer, and parallel dimer of the protein were calculated and compared to the experimental data. Our results show that the most likely structure of GFP is that of an end-to-end dimer. This approach can be readily applied and holds great potential for the structural characterization of complex biohybrid and other materials.

  6. Recent improvements in small angle x-ray diffraction for the study of muscle physiology

    NASA Astrophysics Data System (ADS)

    Reconditi, Massimo

    2006-10-01

    The molecular mechanism of muscle contraction is one of the most important unresolved problems in biology and biophysics. Notwithstanding the great advances of recent years, it is not yet known in detail how the molecular motor in muscle, the class II myosin, converts the free energy of ATP hydrolysis into work by interacting with its track, the actin filament; neither is it understood how the high efficiency in energy conversion depends on the cooperative action of myosin motors working in parallel along the actin filament. Research in muscle contraction involves the combination of mechanical, biochemical and structural methods in studies that span from tissue to single molecule. Therefore, more than for any other research field, progress in the comprehension of muscle contraction at the molecular level is related to, and in turn contributes to, the advancement of methods in biophysics. This review will focus on the progress achieved by time-resolved small angle x-ray scattering (SAXS) from muscle, an approach made possible by the highly ordered arrangement of both the contractile proteins myosin and actin in the ca 2 µm long structural unit, the sarcomere, that repeats along the whole length of the muscle cell. Among time-resolved structural techniques, SAXS has proved to be the most powerful method of investigation, as it allows the molecular motor to be studied in situ, in intact single muscle cells, where it is possible to combine the structural study with fast mechanical methods that synchronize the action of the molecular motors. The latest development of this technique allows Angstrom-scale measurements of the axial movement of the motors that pull the actin filament towards the centre of the sarcomere, by exploiting the x-ray interference between the two arrays of myosin motors in the two halves of the sarcomere.

  7. Structural characterization of the human cerebral myelin sheath by small angle x-ray scattering.

    PubMed

    De Felici, M; Felici, R; Ferrero, C; Tartari, A; Gambaccini, M; Finet, S

    2008-10-21

    Myelin is a multi-lamellar membrane surrounding neuronal axons and increasing their conduction velocity. When investigated by small-angle x-ray scattering (SAXS), the lamellar quasi-periodical arrangement of the myelin sheath gives rise to distinct peaks, which allow the determination of its molecular organization and the dimensions of its substructures. In this study we report on the myelin sheath structural determination carried out on a set of human brain tissue samples coming from surgical biopsies of two patients: a man around 60 and a woman nearly 90 years old. The samples were extracted either from white or grey cerebral matter and did not undergo any manipulation or chemical-physical treatment, which could possibly have altered their structure, except dipping them into a formalin solution for their conservation. Analysis of the scattered intensity from white matter of intact human cerebral tissue allowed the evaluation not only of the myelin sheath periodicity but also of its electronic charge density profile. In particular, the thicknesses of the cytoplasm and extracellular regions were established, as well as those of the hydrophilic polar heads and hydrophobic tails of the lipid bilayer. SAXS patterns were measured at several locations on each sample in order to establish the statistical variations of the structural parameters within a single sample and among different samples. This work demonstrates that a detailed structural analysis of the myelin sheath can also be carried out in randomly oriented samples of intact human white matter, which is of importance for studying the aetiology and evolution of the central nervous system pathologies inducing myelin degeneration. PMID:18812651

  8. Structural characterization of the human cerebral myelin sheath by small angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    DeFelici, M.; Felici, R.; Ferrero, C.; Tartari, A.; Gambaccini, M.; Finet, S.

    2008-10-01

    Myelin is a multi-lamellar membrane surrounding neuronal axons and increasing their conduction velocity. When investigated by small-angle x-ray scattering (SAXS), the lamellar quasi-periodical arrangement of the myelin sheath gives rise to distinct peaks, which allow the determination of its molecular organization and the dimensions of its substructures. In this study we report on the myelin sheath structural determination carried out on a set of human brain tissue samples coming from surgical biopsies of two patients: a man around 60 and a woman nearly 90 years old. The samples were extracted either from white or grey cerebral matter and did not undergo any manipulation or chemical-physical treatment, which could possibly have altered their structure, except dipping them into a formalin solution for their conservation. Analysis of the scattered intensity from white matter of intact human cerebral tissue allowed the evaluation not only of the myelin sheath periodicity but also of its electronic charge density profile. In particular, the thicknesses of the cytoplasm and extracellular regions were established, as well as those of the hydrophilic polar heads and hydrophobic tails of the lipid bilayer. SAXS patterns were measured at several locations on each sample in order to establish the statistical variations of the structural parameters within a single sample and among different samples. This work demonstrates that a detailed structural analysis of the myelin sheath can also be carried out in randomly oriented samples of intact human white matter, which is of importance for studying the aetiology and evolution of the central nervous system pathologies inducing myelin degeneration.

  9. Small-Angle X-ray Study of the Three-Dimensional Collagen/Mineral Superstructure in Intramuscular Fish Bone

    SciTech Connect

    Zhou,H.; Burger, C.; Sics, I.; Hsiao, B.; Chu, B.; Graham, L.; Glimcher, M.

    2007-01-01

    Synchrotron small-angle X-ray scattering (SAXS) was conducted on native intramuscular shad/herring bone samples. Two-dimensional SAXS patterns were quantitatively analyzed with special consideration for preferred orientation effects, leading to new insights into the three-dimensional superstructure of mineralized collagen fibrils in shad/herring bone.

  10. Studies of protein structure in solution and protein folding using synchrotron small-angle x-ray scattering

    SciTech Connect

    Chen, Lingling

    1996-04-01

    Synchrotron small angle x-ray scattering (SAXS) has been applied to the structural study of several biological systems, including the nitrogenase complex, the heat shock cognate protein (hsc70), and lysozyme folding. The structural information revealed from the SAXS experiments is complementary to information obtained by other physical and biochemical methods, and adds to our knowledge and understanding of these systems.

  11. Structural behaviour of mixed cationic surfactant micelles: a small-angle neutron scattering study.

    PubMed

    Bergström, L Magnus; Garamus, Vasil M

    2012-09-01

    Self-assembly in mixtures of two single-chain cationic surfactants, with different tail lengths (CTAB and DTAB) as well as of a single-chain (DTAB) and a double-chain (DDAB) cationic surfactant, with identical tail lengths, have been investigated with small-angle neutron scattering (SANS) and rationalised in terms of bending elasticity properties. The growth behaviour of micelles with respect to surfactant composition appears completely different in the two surfactant mixtures. DTAB form small oblate spheroidal micelles in presence of [NaBr]=0.1 M that transform into prolate spheroidal mixed CTAB/DTAB micelles upon adding moderate amounts of CTAB, so as to give a mole fraction y=0.20 in solution. Most unexpectedly, upon further addition of CTAB the mixed CTAB/DTAB micelles grow with an almost equal rate in both length and width directions to form tablets. In contrast to this behaviour, mixed DDAB/DTAB micelles grow virtually exclusively in the length direction, in presence of [NaBr]=0.1 M, to form elongated ellipsoidal (tablet-shaped) and subsequently long wormlike micelles as the fraction of DDAB in the micelles increases. Mixed DDAB/DTAB micelles grow to become as long as 2000Å before an abrupt transition to large bilayer structures occurs. This means that the micelles are much longer at the micelle-to-bilayer transition as compared to the same mixture in absence of added salt. It is found that the point of transition from micelles to bilayers is significantly shifted towards higher fractions of aggregated DTAB as an appreciable amount of salt is added to DDAB/DTAB mixtures, indicating a considerable reduction of the spontaneous curvature with an increasing [NaBr]. By means of deducing the various bending elasticity constants from our experimental results, according to a novel approach by ours, we are able to conclude that the different growth behaviours appear as a consequence of a considerably lower bending rigidity, as well as higher saddle-splay constant

  12. Small-angle light scattering from polymer-dispersed liquid-crystal films

    SciTech Connect

    Loiko, V. A. Maschke, U.; Zyryanov, V. Ya.; Konkolovich, A. V.; Misckevich, A. A.

    2008-10-15

    A method is developed for modeling and computing the angular distribution of light scattered forward from a single-layer polymer-dispersed liquid-crystal (PDLC) film. The method is based on effective-medium approximation, anomalous diffraction approximation, and far-field single-scattering approximation. The angular distribution of forward-scattered light is analyzed for PDLC films with droplet size larger than the optical wavelength. The method can be used to study field-and temperature-induced phase transitions in LC droplets with cylindrical symmetry by measuring polarized scattered light intensity.

  13. Application of advanced shearing techniques to the calibration of autocollimators with small angle generators and investigation of error sources.

    PubMed

    Yandayan, T; Geckeler, R D; Aksulu, M; Akgoz, S A; Ozgur, B

    2016-05-01

    The application of advanced error-separating shearing techniques to the precise calibration of autocollimators with Small Angle Generators (SAGs) was carried out for the first time. The experimental realization was achieved using the High Precision Small Angle Generator (HPSAG) of TUBITAK UME under classical dimensional metrology laboratory environmental conditions. The standard uncertainty value of 5 mas (24.2 nrad) reached by classical calibration method was improved to the level of 1.38 mas (6.7 nrad). Shearing techniques, which offer a unique opportunity to separate the errors of devices without recourse to any external standard, were first adapted by Physikalisch-Technische Bundesanstalt (PTB) to the calibration of autocollimators with angle encoders. It has been demonstrated experimentally in a clean room environment using the primary angle standard of PTB (WMT 220). The application of the technique to a different type of angle measurement system extends the range of the shearing technique further and reveals other advantages. For example, the angular scales of the SAGs are based on linear measurement systems (e.g., capacitive nanosensors for the HPSAG). Therefore, SAGs show different systematic errors when compared to angle encoders. In addition to the error-separation of HPSAG and the autocollimator, detailed investigations on error sources were carried out. Apart from determination of the systematic errors of the capacitive sensor used in the HPSAG, it was also demonstrated that the shearing method enables the unique opportunity to characterize other error sources such as errors due to temperature drift in long term measurements. This proves that the shearing technique is a very powerful method for investigating angle measuring systems, for their improvement, and for specifying precautions to be taken during the measurements.

  14. Origin of recombination activity at small angle grain boundaries in multicrystalline silicon using multi-seed casting growth method

    NASA Astrophysics Data System (ADS)

    Kojima, Takuto; Tachibana, Tomihisa; Ohshita, Yoshio; Prakash, Ronit R.; Sekiguchi, Takashi; Yamaguchi, Masafumi

    2015-08-01

    The effect of misorientation on the recombination activity of tilt small angle grain boundaries was studied by temperature-dependent electron beam induced current (EBIC) analyses of artificially induced grain boundaries in multicrystal grown by casting from multiple seeds. For small misorientation, there is no significant difference in the recombination of grain boundaries at the middle of a grown ingot, whereas moderate contamination on grain boundaries caused changes in the EBIC contrast, especially at room temperature. The EBIC contrast of moderately contaminated grain boundaries at room temperature has a peak at a misorientation of ∼3°, and for misorientation θ > 6°, the recombinative nature diminishes with increasing misorientation. The results indicate differences in the gettering ability of small angle grain boundaries.

  15. Ultra small angle x-ray scattering in complex mixtures of triacylglycerols

    NASA Astrophysics Data System (ADS)

    Peyronel, Fernanda; Quinn, Bonnie; Marangoni, Alejandro G.; Pink, David A.

    2014-11-01

    Ultra-small angle x-ray scattering (USAXS) has been used to elucidate, in situ, the aggregation structure of unsheared model edible oils. Each system comprised one or two solid lipids and a combination of liquid lipids. The 3D nano- to micro-structures of each system were characterized. The length scale investigated, using the Bonse-Hart camera at beamline ID-15D at the Advanced Photon Source, ANL, ranged from 300 Å-10 µm. Using the Unified Fit model, level-1 analysis showed that the scatterers were 2D objects with either a smooth, a rough, or a diffuse surface. These 2D objects had an average radius of gyration Rg1 between 200-1500 Å. Level-2 analysis displayed a slope between -1 and -2. Use of the Guinier-Porod model gave s ≈ 1 thus showing that it was cylinders (TAGwoods) aggregating with fractal dimension 1 ≤ D2 ≤ 2. D2 = 1 is consistent with 1D structures formed from TAGwoods, while D2 = 2 implies that the TAGwoods had formed structures characteristic of diffusion or reaction limited cluster-cluster aggregation (DLCA/RLCA). These aggregates exhibited radii of gyration, Rg2, between 2500 and 6500 Å. Level-3 analyses showed diffuse surfaces, for most of the systems. These interpretations are in accord with theoretical models which studied crystalline nano-platelets (CNPs) coated with nano-scale layers arising from phase separation at the CNP surfaces. These layers could be due to either liquid-liquid phase separation with the CNPs coated, uniformly or non-uniformly, by a diffuse layer of TAGs, or solid-liquid phase separation with the CNPs coated by a rough layer of crystallites. A fundamental understanding of the self-organizing structures arising in these systems helps advance the characterization of fat crystal networks from nanometres to micrometres. This research can be used to design novel fat structures that use healthier fats via nano- and meso-scale structural engineering.

  16. Initial characterization of mudstone nanoporosity with small angle neutron scattering using caprocks from carbon sequestration sites.

    SciTech Connect

    McCray, John; Navarre-Sitchler, Alexis; Mouzakis, Katherine; Heath, Jason E.; Dewers, Thomas A.; Rother, Gernot

    2010-11-01

    Geological carbon sequestration relies on the principle that CO{sub 2} injected deep into the subsurface is unable to leak to the atmosphere. Structural trapping by a relatively impermeable caprock (often mudstone such as a shale) is the main trapping mechanism that is currently relied on for the first hundreds of years. Many of the pores of the caprock are of micrometer to nanometer scale. However, the distribution, geometry and volume of porosity at these scales are poorly characterized. Differences in pore shape and size can cause variation in capillary properties and fluid transport resulting in fluid pathways with different capillary entry pressures in the same sample. Prediction of pore network properties for distinct geologic environments would result in significant advancement in our ability to model subsurface fluid flow. Specifically, prediction of fluid flow through caprocks of geologic CO{sub 2} sequestration reservoirs is a critical step in evaluating the risk of leakage to overlying aquifers. The micro- and nanoporosity was analyzed in four mudstones using small angle neutron scattering (SANS). These mudstones are caprocks of formations that are currently under study or being used for carbon sequestration projects and include the Marine Tuscaloosa Group, the Lower Tuscaloosa Group, the upper and lower shale members of the Kirtland Formation, and the Pennsylvanian Gothic shale. Total organic carbon varies from <0.3% to 4% by weight. Expandable clay contents range from 10% to {approx}40% in the Gothic shale and Kirtland Formation, respectively. Neutrons effectively scatter from interfaces between materials with differing scattering length density (i.e. minerals and pores). The intensity of scattered neutrons, I(Q), where Q is the scattering vector, gives information about the volume of pores and their arrangement in the sample. The slope of the scattering data when plotted as log I(Q) vs. log Q provides information about the fractality or geometry of

  17. Anomalous dimensions of conformal baryons

    NASA Astrophysics Data System (ADS)

    Pica, Claudio; Sannino, Francesco

    2016-10-01

    We determine the anomalous dimensions of baryon operators for the three-color theory as functions of the number of massless flavors within the conformal window to the maximum known order in perturbation theory. We show that the anomalous dimension of the baryon is controllably small, within the δ expansion, for a wide range of number of flavors. We also find that this is always smaller than the anomalous dimension of the fermion mass operator. These findings challenge the partial compositeness paradigm.

  18. Small-Angle and Ultrasmall-Angle Neutron Scattering (SANS/USANS) Study of New Albany Shale: A Treatise on Microporosity

    SciTech Connect

    Bahadur, Jitendra; Radlinski, Andrzej P.; Melnichenko, Yuri B.; Mastalerz, Maria; Schimmelmann, Arndt

    2014-12-17

    We applied small-angle neutron scattering (SANS) and ultrasmall-angle neutron scattering (USANS) techniques to study the microstructure of several New Albany shales of different maturity. It has been established that the total porosity decreases with maturity and increases somewhat for post-mature samples. A new method of SANS data analysis was developed, which allows the extraction of information about the size range and number density of micropores from the relatively flat scattering intensity observed in the limit of the large scattering vector Q. Macropores and significant number of mesopores are surface fractals, and their structure can be described in terms of the polydisperse spheres (PDSP) model. The model-independent Porod invariant method was employed to estimate total porosity, and the results were compared with the PDSP model results. It has been demonstrated that independent evaluation of incoherent background is crucial for accurate interpretation of the scattering data in the limit of large Q-values. Moreover, pore volumes estimated by the N2 and CO2 adsorption, as well as via the mercury intrusion technique, have been compared with those measured by SANS/USANS, and possible reasons for the observed discrepancies are discussed.

  19. Small-Angle and Ultrasmall-Angle Neutron Scattering (SANS/USANS) Study of New Albany Shale: A Treatise on Microporosity

    DOE PAGES

    Bahadur, Jitendra; Radlinski, Andrzej P.; Melnichenko, Yuri B.; Mastalerz, Maria; Schimmelmann, Arndt

    2014-12-17

    We applied small-angle neutron scattering (SANS) and ultrasmall-angle neutron scattering (USANS) techniques to study the microstructure of several New Albany shales of different maturity. It has been established that the total porosity decreases with maturity and increases somewhat for post-mature samples. A new method of SANS data analysis was developed, which allows the extraction of information about the size range and number density of micropores from the relatively flat scattering intensity observed in the limit of the large scattering vector Q. Macropores and significant number of mesopores are surface fractals, and their structure can be described in terms of themore » polydisperse spheres (PDSP) model. The model-independent Porod invariant method was employed to estimate total porosity, and the results were compared with the PDSP model results. It has been demonstrated that independent evaluation of incoherent background is crucial for accurate interpretation of the scattering data in the limit of large Q-values. Moreover, pore volumes estimated by the N2 and CO2 adsorption, as well as via the mercury intrusion technique, have been compared with those measured by SANS/USANS, and possible reasons for the observed discrepancies are discussed.« less

  20. Small-angle and wide-angle X-ray scattering study on the bilayer structure of synthetic and bovine heart cardiolipins

    NASA Astrophysics Data System (ADS)

    Takahashi, Hiroshi; Hayakawa, Tomohiro; Ito, Kazuki; Takata, Masaki; Kobayashi, Toshihide

    2010-10-01

    Cardiolipin (CL) is a membrane phospholipid containing four fatty acid chains. CL plays an important role in energy transformation in mitochondria. The disorder of CL biosynthesis is involved in a genetic disease, Barth syndrome. Alteration of fatty acid composition of CLs has been found in Barth syndrome patients, i.e., the decrease of unsaturated fatty acid chains. In this study, we investigated how the degree of saturation alters the structure of CL bilayers by using X-ray scattering. Bovine heart CL and two synthetic CLs were compared. Fatty acid compositions of these three CLs have different saturation. Small-angle X-ray scattering data showed that the decrease of the number of double bonds in the unsaturated fatty acid chains causes to thicken the CL bilayers. In addition, wide-angle X-ray scattering data suggested that the decrease reduces the degree of disorder of the hydrophobic region in a liquid crystalline phase. These results may be related to the dysfunction of mitochondria in Barth syndrome.

  1. The new small-angle neutron scattering instrument SANS-1 at MLZ-characterization and first results

    NASA Astrophysics Data System (ADS)

    Mühlbauer, S.; Heinemann, A.; Wilhelm, A.; Karge, L.; Ostermann, A.; Defendi, I.; Schreyer, A.; Petry, W.; Gilles, R.

    2016-10-01

    A thorough characterization of the key features of the new small-angle neutron scattering instrument SANS-1 at MLZ, a joint project of Technische Universität München and Helmholtz Zentrum Geesthacht, is presented. Measurements of the neutron beam profile, divergency and flux are given for various positions along the instrument including the sample position, and agree well with Monte Carlo simulations of SANS-1 using the program McStas. Secondly, the polarization option of SANS-1 is characterized for a broad wavelength band. A key feature of SANS-1 is the large accessible Q-range facilitated by the sideways movement of the detector. Particular attention is hence paid to the effects that arise due to large scattering angles on the detector where a standard cos3 solid angle correction is no longer applicable. Finally the performance of the instrument is characterized by a set of standard samples.

  2. Small blaze angle gratings with various surface treatments for use in the extreme ultraviolet

    NASA Technical Reports Server (NTRS)

    Miller, Anne; Jelinsky, Patrick; Bowyer, Stuart; Welsh, Barry Y.

    1989-01-01

    Three replica gratings made from a single master, including two epoxy-overcoated gratings with different thicknesses of gold and one grating replicated directly in gold, were studied by measuring and comparing the performances of the gratings in EUV light at grazing incidence angles. The results show that, in situations which require a very low grazing angle, high-quality, mechanically ruled straight groove gratings provide good efficiency and uniform blaze independent of coating thickness up to 1000 A. However, the technique of direct replication in the surface material seems to result in substantially more light scattering and does not seem to have other obvious advantages.

  3. Development of a large-angle pinhole gamma camera with depth-of-interaction capability for small animal imaging

    NASA Astrophysics Data System (ADS)

    Baek, C.-H.; An, S. J.; Kim, H.-I.; Choi, Y.; Chung, Y. H.

    2012-01-01

    A large-angle gamma camera was developed for imaging small animal models used in medical and biological research. The simulation study shows that a large field of view (FOV) system provides higher sensitivity with respect to a typical pinhole gamma cameras by reducing the distance between the pinhole and the object. However, this gamma camera suffers from the degradation of the spatial resolution at the periphery region due to parallax error by obliquely incident photons. We propose a new method to measure the depth of interaction (DOI) using three layers of monolithic scintillators to reduce the parallax error. The detector module consists of three layers of monolithic CsI(Tl) crystals with dimensions of 50.0 × 50.0 × 2.0 mm3, a Hamamatsu H8500 PSPMT and a large-angle pinhole collimator with an acceptance angle of 120°. The 3-dimensional event positions were determined by the maximum-likelihood position-estimation (MLPE) algorithm and the pre-generated look up table (LUT). The spatial resolution (FWHM) of a Co-57 point-like source was measured at different source position with the conventional method (Anger logic) and with DOI information. We proved that high sensitivity can be achieved without degradation of spatial resolution using a large-angle pinhole gamma camera: this system can be used as a small animal imaging tool.

  4. Recording of anomalous shear energy in the teleseismic P-wave coda at Long Valley Caldera, California, on a small aperture array

    SciTech Connect

    Zucca, J.J.; Zandt, G. ); Steck, L.K.; Prothero, W.A. . Dept. of Geology)

    1990-03-01

    Anomalous energy in the coda of teleseismic P-waves at Long Valley caldera has been suggested to be a P to S converted arrival, perhaps with the conversion occurring at the boundaries of magma bodies beneath the caldera. We have collected new data with a small-aperture, three-component array located in the northwestern quadrant of the caldera with the purpose of testing this hypothesis. An examination of three teleseismic events using array and particle motion techniques shows that converted P- to S-waves comprise a significant fraction of the early arriving anomalous energy. In volcanic areas such as Long Valley, the scattered energy could originate at a high velocity contrast feature such as magma body interface. In addition, later arriving energy was detected with slow phase velocity and is tentatively identified as body wave to surface wave scattering. Our interpretation is illustrated with waveforms of two earthquakes from the Kuril Islands and one in northern Peru. Our results show that a small-aperture, three-component array can be used to perform detailed analysis of the coda. 12 refs., 8 figs., 1 tab.

  5. Molecular dynamics simulation analysis of small-angle neutron scattering by a solution of stearic acid in benzene

    NASA Astrophysics Data System (ADS)

    Eremin, R. A.; Kholmurodov, Kh. T.; Petrenko, V. I.; Rosta, L.; Avdeev, M. V.

    2014-01-01

    Data of small-angle neutron scattering by a diluted solution of stearic acid in deuterated benzene have been analyzed using the results of molecular dynamics simulation. The molecular dynamics simulation approach has been used to calculate the time-averaged distribution of the neutron scattering length density at the interface between the acid molecule and the solvent. It has been shown that the organization of the solvent at the interface with the acid molecule leads to a modulation of the neutron scattering length density and makes a significant contribution to the scattering. This contribution should be taken into account when interpreting the experimental small-angle neutron scattering curves for both the considered system and its analogues.

  6. Grazing-incidence small-angle X-ray scattering: application to the study of quantum dot lattices

    SciTech Connect

    Buljan, Maja Radić, Nikola; Bernstorff, Sigrid; Dražić, Goran; Bogdanović-Radović, Iva; Holý, Václav

    2012-01-01

    The modelling of grazing-incidence small-angle X-ray scattering (GISAXS) from three-dimensional quantum dot lattices is described. The ordering of quantum dots in three-dimensional quantum dot lattices is investigated by grazing-incidence small-angle X-ray scattering (GISAXS). Theoretical models describing GISAXS intensity distributions for three general classes of lattices of quantum dots are proposed. The classes differ in the type of disorder of the positions of the quantum dots. The models enable full structure determination, including lattice type, lattice parameters, the type and degree of disorder in the quantum dot positions and the distributions of the quantum dot sizes. Applications of the developed models are demonstrated using experimentally measured data from several types of quantum dot lattices formed by a self-assembly process.

  7. Small-Angle X-ray Scattering Study of Intramuscular Fish Bone: Collagen Fibril Superstructure Determined from Equidistant Meridional Reflections

    SciTech Connect

    Burger,C.; Zhou, H.; Sics, I.; Hsiao, B.; Chu, B.; Graham, L.; Glimcher, M.

    2008-01-01

    New insights into the bone collagen fibril superstructure have been obtained by novel small-angle X-ray scattering analysis. The analysis was carried out on the small-angle equidistant meridional reflections resulting from the periodic structure of collagen fibrils in their axial direction. Conventional two-dimensional analysis is difficult because of the large discrepancy of longitudinal and lateral length scales for individual fibrils, as well as their preferred orientation. The new approach represents an unapproximated analysis of the equidistant meridional reflections, which takes the exact separation of preferred orientation and fibril size effects into account. The analytical results (e.g. axial period, fibril diameter etc.) agree well with the parameters obtained from transmission electron microscopy.

  8. SU8 3D prisms with ultra small inclined angle for low-insertion-loss fiber/waveguide interconnection.

    PubMed

    Nguyen, Minh-Hang; Chang, Chia-Jung; Lee, Ming-Chang; Tseng, Fan-Gang

    2011-09-26

    This paper presents a simple method for fabricating SU8 three dimensional (3D) prisms with very small inclined-angles for optical-fiber/planar-waveguide interconnection with low insertion-loss by combining self-filling, molding and nano-lithography processes on plane surface. The prisms possess ultra low 3D inclined angle of 0.6° and a small surface roughness of 3.5 nm. It is demonstrated that the transmission efficiency of SOI waveguides improved about 4.6 times at the presence of SU8 prisms with a coupling loss of 11 dB per taper and radiation loss of 2.4 dB per taper.

  9. Small-Angle Neutron Scattering Studies of a-Si:H and a-Si:D

    SciTech Connect

    Williamson, D. L.; Marr, D. W. M.; Nelson, B. P.; Iwaniczko, E.; Yang, J.; Yan, B.; Guha, S.

    2000-01-01

    The heterogeneity of hydrogen and deuterium on the nanometer scale has been probed by samll-angle neutron scattering (SANS) from a-Si:H and a-Si:D films. Films were depsoited by two techniques, plasma-enhanced chemical vapor deposition (PECVD) and hot-wire chemical vapor deposition (HWCVD) using conditions that yield high quality films and devices.

  10. Zeeman Electromagnetically Induced Transparency with crossed pump and probe beams: Small angle dependence

    NASA Astrophysics Data System (ADS)

    Campbell, Kaleb; Madkhaly, Samaya; de Medeiros, Dillon; Bali, Samir; Macklin Quantum Information Sciences Collaboration

    2016-05-01

    Progress toward undergraduate oriented experiments on image storage in room-temperature atomic vapor using Electromagnetically Induced Transparency is described. Using a scanning longitudinal magnetic field technique we diagnose and suppress stray magnetic fields and polarization impurity. We consider the pump-probe angular dependence of the EIT signal but at much smaller angles of less than a milliradian.

  11. Relationship Between the Atomic Pair Distribution Function and Small-Angle Scattering: Implications for Modeling of Nanoparticles

    SciTech Connect

    Billinge, S.; Farrowa, C.L.

    2009-05-01

    The relationship between the equations used in the atomic pair distribution function (PDF) method and those commonly used in small-angle-scattering (SAS) analyses is explicitly shown. The origin of the sloping baseline, -4{pi}r{rho}{sub 0}, in PDFs of bulk materials is identified as originating from the SAS intensity that is neglected in PDF measurements. The nonlinear baseline in nanoparticles has the same origin, and contains information about the shape and size of the nanoparticles.

  12. Measurement of energy spectra of small-angle scattering and distribution of optical microinhomogeneities in laser ceramics

    SciTech Connect

    Tverdokhleb, P E; Shepetkin, Yu A; Steinberg, I Sh; Belikov, A Yu; Vatnik, S M; Vedin, I A; Kurbatov, P F

    2014-06-30

    The energy spectra of small-angle light scattering from the samples of Nd:YAG ceramics and the spatial distributions of optical microinhomogeneities in them are measured. The spatial profiles of microinhomogeneities are found using the collinear heterodyne microprobe technique. Based on the obtained data, the comparison of noise and lasing characteristics of foreign and domestic samples of laser ceramics is carried out. (extreme light fields and their applications)

  13. Monte-Carlo simulation of an ultra small-angle neutron scattering instrument based on Soller slits

    SciTech Connect

    Rieker, T.; Hubbard, P.

    1997-09-01

    Monte Carlo simulations are used to investigate an ultra small-angle neutron scattering instrument for use at a pulsed source based on a Soller slit collimator and analyzer. The simulations show that for a q{sub min} of {approximately}le-4 {angstrom}{sup -1} (15 {angstrom} neutrons) a few tenths of a percent of the incident flux is transmitted through both collimators at q=0.

  14. Small angle X-ray scattering and transmission electron microscopy study of the Lactobacillus brevis S-layer protein

    NASA Astrophysics Data System (ADS)

    Jääskeläinen, Pentti; Engelhardt, Peter; Hynönen, Ulla; Torkkeli, Mika; Palva, Airi; Serimaa, Ritva

    2010-10-01

    The structure of self-assembly domain containing recombinant truncation mutants of Lactobacillus brevis surface layer protein SlpA in aqueous solution was studied using small-angle X-ray scattering and transmission electron microscopy. The proteins were found out to interact with each other forming stable globular oligomers of about 10 monomers. The maximum diameter of the oligomers varied between 75 Å and 435 Å.

  15. The method of characteristics for the determination of supersonic flow over bodies of revolution at small angles of attack

    NASA Technical Reports Server (NTRS)

    Ferri, Antonio

    1951-01-01

    The method of characteristics has been applied for the determination of the supersonic-flow properties around bodies of revolution at a small angle of attack. The system developed considers the effect of the variation of entropy due to the curved shock and determines a flow that exactly satisfies the boundary conditions in the limits of the simplifications assumed. Two practical methods for numerical calculations are given. (author)

  16. Jointed magnetic skyrmion lattices at a small-angle grain boundary directly visualized by advanced electron microscopy

    PubMed Central

    Matsumoto, Takao; So, Yeong-Gi; Kohno, Yuji; Sawada, Hidetaka; Ishikawa, Ryo; Ikuhara, Yuichi; Shibata, Naoya

    2016-01-01

    The interactions between magnetic skyrmions and structural defects, such as edges, dislocations, and grain boundaries (GBs), which are all considered as topological defects, will be important issues when magnetic skyrmions are utilized for future memory device applications. To investigate such interactions, simultaneous visualization of magnetic skyrmions and structural defects at high spatial resolution, which is not feasible by conventional techniques, is essential. Here, taking advantages of aberration-corrected differential phase-contrast scanning transmission electron microscopy, we investigate the interaction of magnetic skyrmions with a small-angle GB in a thin film of FeGe1−xSix. We found that the magnetic skyrmions and the small-angle GB can coexist each other, but a domain boundary (DB) was formed in the skyrmion lattice along the small-angle GB. At the core of the DB, unexpectedly deformed magnetic skrymions, which appear to be created by joining two portions of magnetic skyrmions in the adjacent lattices, were formed to effectively compensate misorientations between the two adjacent magnetic skyrmion lattices. These observations strongly suggest the flexible nature of individual magnetic skyrmions, and also the significance of defect engineering for future device applications. PMID:27775056

  17. From nuclei to micro-structure in colloidal crystallization: Investigating intermediate length scales by small angle laser light scattering

    NASA Astrophysics Data System (ADS)

    Beyer, Richard; Franke, Markus; Schöpe, Hans Joachim; Bartsch, Eckhard; Palberg, Thomas

    2015-08-01

    Hard sphere suspensions are well recognized model systems of statistical physics and soft condensed matter. We here investigate the temporal evolution of the immediate environment of nucleating and growing crystals and/or their global scale distribution using time resolved Small Angle Light Scattering (SALS). Simultaneously performed Bragg scattering measurements provide an accurate temporal gauging of the sequence of events. We apply this approach to studies of re-crystallization in several different shear molten hard sphere and attractive hard sphere samples with the focus being on the diversity of observable signal shapes and their change in time. We demonstrate that depending on the preparation conditions different processes occur on length scales larger than the structural scale, which significantly influence both the crystallization kinetics and the final micro-structure. By careful analysis of the SALS signal evolution and by comparing different suggestions for small angle signal shapes to our data, we can for most cases identify the processes leading to the observed signals. These include form factor scattering from crystals surrounded by depletion zones and structure factor scattering from late stage inter-crystallite ordering. The large variety of different small angle signals thus in principle contains valuable information complementary to that gained from Bragg scattering or microscopy. Our comparison, however, also shows that further refinement and adaptation of the theoretical expressions to the sample specific boundary conditions is desired for a quantitative kinetic analysis of micro-structural evolution.

  18. Investigation of the structure of unilamellar dimyristoylphosphatidylcholine vesicles in aqueous sucrose solutions by small-angle neutron and X-ray scattering

    SciTech Connect

    Kiselev, M. A. Zemlyanaya, E. V.; Zhabitskaya, E. I.; Aksenov, V. L.

    2015-01-15

    The structure of a polydispersed population of unilamellar dimyristoylphosphatidylcholine (DMPC) vesicles in sucrose solutions has been investigated by small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS). Calculations within the model of separated form factors (SFF) show that the structure of the vesicle system depends strongly on the sucrose concentration.

  19. Operation of a U-shaped thermosiphon at small angles of inclination

    SciTech Connect

    Krivonos, V.A.

    1988-01-01

    The combined effects of the volume of heat transfer fluid and the angles of inclination of the branches of a thermosyphon on its internal thermal resistance are determined in a parametric analysis for the optimization of the configuration and fluid charge and the thermal efficiency of the thermosyphon. The dependence of the operating temperature gradient on the power input is investigated and the power input optimized on the basis of the results.

  20. Effect of shadowing on electromagnetic scattering from rough ocean wavelike surfaces at small grazing angles

    SciTech Connect

    West, J.C.

    1997-03-01

    A hybrid moment-method/geometrical-theory-of-diffraction technique (MM/GTD) has been implemented to numerically calculate the electromagnetic scattering from one-dimensionally rough surfaces at extreme illumination angles (down to 0{degree} grazing). The hybrid approach allows the extension of the modeled scattering surface to infinity, avoiding the artificial edge diffraction that prevents use of the standard moment method at the smallest grazing angles. Numerical calculation of the backscattering from slightly rough large-scale surfaces approximating ocean wave features shows that roughness in strongly shadowed regions can contribute significantly to the total backscatter at vertical polarization. This is observed when the shadowing obstacle is several wavelengths high, and the magnitude of the shadow-region contribution does not depend on the radius-of-curvature of the shadowing feature. Strongly shadowed roughness does not significantly contribute to the backscatter at horizontal polarization, although weakly shadowed roughness near the incidence shadow boundary does. The calculations indicate that a shadowing-corrected two-scale model may be able to predict the distributed-surface portion of the sea-surface scattering from the ocean surface at grazing angles down to about 15{degree}, but at lower grazing the shadowing and large-scale curvature of the surface prevent the establishment of a Bragg resonance and invalidate the model.

  1. Light scattering by red blood cells in ektacytometry: Fraunhofer versus anomalous diffraction.

    PubMed

    Streekstra, G J; Hoekstra, A G; Nijhof, E J; Heethaar, R M

    1993-05-01

    In the present literature on ektacytometry, small angle light scattering by ellipsoidal red blood cells is commonly approximated by Fraunhofer diffraction. Calculations on a sphere with the size and relative refractive index of a red cell, however, show that Fraunhofer diffraction deviates significantly from exact Mie theory. Anomalous diffraction is found to be a much better approximation. The anomalous diffraction theory is used to calculate the intensity distribution of the light scattered by an ellipsoidally deformed red blood cell. The derived expression shows that the ellipticity of isointensity curves in forward scattered light are equal to the ellipticity of the red blood cell. The theoretical expression is fitted to the intensity patterns measured with an ektacytometer. For the small observation angles used in ektacytometry, the experimental results confirm the validity of the anomalous diffraction approach.

  2. Mineral crystal alignment in mineralized fracture callus determined by 3D small-angle X-ray scattering

    NASA Astrophysics Data System (ADS)

    Liu, Yifei; Manjubala, Inderchand; Roschger, Paul; Schell, Hanna; Duda, Georg N.; Fratzl, Peter

    2010-10-01

    Callus tissue formed during bone fracture healing is a mixture of different tissue types as revealed by histological analysis. But the structural characteristics of mineral crystals within the healing callus are not well known. Since two-dimensional (2D) scanning small-angle X-ray scattering (sSAXS) patterns showed that the size and orientation of callus crystals vary both spatially and temporally [1] and 2D electron microscopic analysis implies an anisotropic property of the callus morphology, the mineral crystals within the callus are also expected to vary in size and orientation in 3D. Three-dimensional small-angle X-ray scattering (3D SAXS), which combines 2D SAXS patterns collected at different angles of sample tilting, has been previously applied to investigate bone minerals in horse radius [2] and oim/oim mouse femur/tibia [3]. We implement a similar 3D SAXS method but with a different way of data analysis to gather information on the mineral alignment in fracture callus. With the proposed accurate yet fast assessment of 3D SAXS information, it was shown that the plate shaped mineral particles in the healing callus were aligned in groups with their predominant orientations occurring as a fiber texture.

  3. Small angle scattering polarization biopsy: a comparative analysis of various skin diseases

    NASA Astrophysics Data System (ADS)

    Zimnyakov, D. A.; Alonova, M. V.; Yermolenko, S. B.; Ivashko, P. V.; Reshetnikova, E. M.; Galkina, E. M.; Utz, S. R.

    2013-12-01

    An approach to differentiation of the morphological features of normal and pathological human epidermis on the base of statistical analysis of the local polarization states of laser light forward scattered by in-vitro tissue samples is discussed. The eccentricity and the azimuth angle of local polarization ellipses retrieved for various positions of the focused laser beam on the tissue surface, and the coefficient of collimated transmittance are considered as the diagnostic parameters for differentiation. The experimental data obtained with the psoriasis, discoid lupus erythematosus, alopecia, lichen planus, scabies, demodex, and normal skin samples are presented.

  4. Imaging method based on attenuation, refraction and ultra-small-angle-scattering of x-rays

    DOEpatents

    Wernick, Miles N.; Chapman, Leroy Dean; Oltulu, Oral; Zhong, Zhong

    2005-09-20

    A method for detecting an image of an object by measuring the intensity at a plurality of positions of a transmitted beam of x-ray radiation emitted from the object as a function of angle within the transmitted beam. The intensity measurements of the transmitted beam are obtained by a crystal analyzer positioned at a plurality of angular positions. The plurality of intensity measurements are used to determine the angular intensity spectrum of the transmitted beam. One or more parameters, such as an attenuation property, a refraction property and a scatter property, can be obtained from the angular intensity spectrum and used to display an image of the object.

  5. Metastatic Extrapulmonary Small Cell Carcinoma to the Cerebellopontine Angle: A Case Report and Review of the Literature

    PubMed Central

    Theodros, Debebe; Goodwin, C. Rory; Crane, Genevieve M.; Liauw, Jason; Kleinberg, Lawrence

    2015-01-01

    Extrapulmonary small cell carcinomas (EPSCC) are rare malignancies with poor patient prognoses. We present the case of a 63-year-old male who underwent surgical resection of a poorly differentiated small cell carcinoma, likely from a small intestinal primary tumor that metastasized to the cerebellopontine angle (CPA). A 63-year-old male presented with mild left facial paralysis, hearing loss, and balance instability. MRI revealed a 15 mm mass in the left CPA involving the internal auditory canal consistent with a vestibular schwannoma. Preoperative MRI eight weeks later demonstrated marked enlargement to 35 mm. The patient underwent a suboccipital craniectomy and the mass was grossly different visually and in consistency from a standard vestibular schwannoma. The final pathology revealed a poorly differentiated small cell carcinoma. Postoperative PET scan identified avid uptake in the small intestine suggestive of either a small intestinal primary tumor or additional metastatic disease. The patient underwent whole brain radiation therapy and chemotherapy and at last follow-up demonstrated improvement in his symptoms. Surgical resection and radiotherapy are potential treatment options to improve survival in patients diagnosed with NET brain metastases. We present the first documented case of skull base metastasis of a poorly differentiated small cell carcinoma involving the CPA. PMID:25810937

  6. The interaction of small molecules with phospholipid membranes studied by 1H NOESY NMR under magic-angle spinning.

    PubMed

    Scheidt, Holger A; Huster, Daniel

    2008-01-01

    The interaction of small molecules with lipid membranes and the exact knowledge of their binding site and bilayer distribution is of great pharmacological importance and represents an active field of current biophysical research. Over the last decade, a highly resolved 1H solid-state NMR method has been developed that allows measuring localization and distribution of small molecules in membranes. The classical solution 1H NMR NOESY technique is applied to lipid membrane samples under magic-angle spinning (MAS) and NOESY cross-relaxation rates are determined quantitatively. These rates are proportional to the contact probability between molecular segments and therefore an ideal tool to study intermolecular interactions in membranes. Here, we review recent 1H MAS NOESY applications that were carried out to study lateral lipid organization in mixed membranes and the interaction of membranes with water, ethanol, small aromatic compounds, peptides, fluorescence labels, and lipophilic nucleosides.

  7. Interaction between Metal Impurities and Small-Angle Grain Boundaries on Recombination Properties in Multicrystalline Silicon for Solar Cells

    NASA Astrophysics Data System (ADS)

    Sameshima, Takashi; Miyazaki, Naoto; Tsuchiya, Yuki; Hashiguchi, Hiroki; Tachibana, Tomihisa; Kojima, Takuto; Ohshita, Yoshio; Arafune, Koji; Ogura, Atsushi

    2012-04-01

    Recombination properties at small-angle grain boundaries (SA-GBs) in multicrystalline silicon were evaluated. After Fe contamination, the electron-beam-induced current (EBIC) contrast at most SA-GBs became stronger, especially at >1.5°. After Al gettering, EBIC contrast of most <1.5° SA-GBs became as weak as before contamination. Then, some EBIC contrast of >1.5° SA-GBs showed comparable contrast before gettering. In addition, there were SA-GBs which have different recombination properties even with the same misorientation angle. Between these SA-GBs, there were differences in the rotation axis, boundary direction, and existence of defects. The associativity of metals might be affected by the existence of defects caused by these differences.

  8. Modulated heterodyne light scattering set-up for measuring long relaxation time at small and wide angle

    SciTech Connect

    Leone, Nancy; Villari, Valentina; Micali, Norberto

    2012-08-15

    We present a simple, compact, and versatile experimental setup working in the heterodyne detection mode with modulation of the reference beam. The system is implemented with a collection optics based on a unimodal optical fiber coupler. This choice allows the heterodyne to be used in a wide range of scattering angles, even for very small ones, without losing the optical beating. The apparatus can be successfully used to study translational diffusive dynamics of dispersed particles at scattering angles smaller than 5 Degree-Sign and it is suitable for exploring slow relaxation processes in sub-Hertz frequency domain, for example, in glass-forming systems. It is also possible to measure the electrophoretic mobility by applying an electric field into a charged particles solution.

  9. Characterizing the Morphologies of Mechanically Manipulated Multiwall Carbon Nanotube Films by Small-Angle X-ray Scattering

    SciTech Connect

    Wang,B.; Bennett, R.; Verploegen, E.; Hart, A.; Cohen, R.

    2007-01-01

    We used small-angle X-ray scattering (SAXS) to quantitatively characterize the morphological characteristics of pristine and mechanically manipulated multiwall carbon nanotube (MWCNT) films. We determined that CNT diameters measured near the edges of a film were smaller compared to those measured in the interior. Uniaxially compressed MWCNT films exhibited a buckling deformation that was observable both in scanning electron microscopy (SEM) and SAXS. CNT films were also converted into cellular foams of CNTs through capillarity-induced densification. By examining spatially- and time-resolved SAXS data for the cellular foams, we identified low angle features in the scattering curves that correspond to the average spacing between CNTs, demonstrating that SAXS is a useful method for monitoring the packing density of CNTs in a film. For all of the morphologies that were examined (aligned, disordered, compressed, and densified), SAXS data showed good correspondence with SEM images.

  10. Development of a One-Dimensional Small-Angle Neutron Scattering Instrument at the University of Illinois TRIGA Reactor Laboratory

    NASA Astrophysics Data System (ADS)

    Monti, D. A.; Guillermo, N. R.; Hulin, M. J.; Heuser, B. J.; Toreja, A.; Moschetti, T. L.

    1996-03-01

    A small-angle neutron scattering instrument with slit-smeared geometry (1-D SANS) has been constructed at the University of Illinois 1.5 MWatt TRIGA reactor. This facility falls under the general heading of "low-flux research reactors" which typically are not used for neutron scattering research. Low-flux reactors can support neutron scattering research under certain conditions, however. 1-D SANS using elastically-bent crystal optics is one such example [Popovici, et al. (1995). J. Phys. Chem. Solids 56, 1425-1431]. Our instrument uses a pyrolytic graphite pre-monochromator and two elastically-bent Si wafers, all in a (+,+,-) configuration. Instrumental performance including low-angle resolution, on-sample intensity, resolution variability, and cross-section measurement capability will be presented.

  11. Performance of the micro-PIC gaseous area detector in small-angle X-ray scattering experiments.

    PubMed

    Hattori, Kaori; Tsuchiya, Ken'ichi; Ito, Kazuki; Okada, Yoko; Fujii, Kotaro; Kubo, Hidetoshi; Miuchi, Kentaro; Takata, Masaki; Tanimori, Toru; Uekusa, Hidehiro

    2009-03-01

    The application of a two-dimensional photon-counting detector based on a micro-pixel gas chamber (micro-PIC) to high-resolution small-angle X-ray scattering (SAXS), and its performance, are reported. The micro-PIC is a micro-pattern gaseous detector fabricated by printed circuit board technology. This article describes the performance of the micro-PIC in SAXS experiments at SPring-8. A dynamic range of >10(5) was obtained for X-ray scattering from a polystyrene sphere solution. A maximum counting rate of up to 5 MHz was observed with good linearity and without saturation. For a diffraction pattern of collagen, weak peaks were observed in the high-angle region in one accumulation of photons.

  12. Energy-dispersive small-angle X-ray scattering with cone collimation using X-ray capillary optics

    NASA Astrophysics Data System (ADS)

    Li, Fangzuo; Liu, Zhiguo; Sun, Tianxi

    2016-09-01

    Energy-dispersive small-angle X-ray scattering (ED-SAXS) with an innovative design of cone collimation based on an ellipsoidal single-bounce capillary (ESBC) and a polycapillary parallel X-ray lens (PPXRL) had been explored. Using this new cone collimation system, scattering angle 2θ has a theoretical minimum angle related to the mean half-opening angle of the hollow cone beam of 1.42 mrad, and with the usable X-ray energy ranging from 4 to 30 keV, the resulting observable scattering vector q is down to a minimum value of about 0.003 Å-1 (or a Bragg spacing of about 2100 Å). However, the absorption of lower energies by X-ray capillary optics, sample transmission, and detector response function limits the application range to lower energy. Cone collimation ED-SAXS experiments carried out on pure water, Lupolen, and in situ temperature-dependent measurement of diacetylenic acid/melamine micelle solid were presented at three different scattering angles 2θ of 0.18°, 0.70° and 1.18° to illustrate the new opportunities offered by this technique as well as its limitations. Also, a comparison has been made by replacing the PPXRL with a pinhole, and the result shows that cone collimation ED-SAXS based on ESBC with PPXRL was helpful in improving the signal-to-noise ratio (i.e., reducing the parasitic background scattering) than ESBC with a pinhole. The cone collimation instrument based on X-ray capillary optics could be considered as a promising tool to perform SAXS experiments, especially cone collimation ED-SAXS has potential application for the in situ temperature-dependent studying on the kinetics of phase transitions.

  13. Noise-like femtosecond pulse in passively mode-locked Tm-doped NALM-based oscillator with small net anomalous dispersion

    NASA Astrophysics Data System (ADS)

    Liu, Shuo; Yan, Feng-Ping; Zhang, Lu-Na; Han, Wen-Guo; Bai, Zhuo-Ya; Zhou, Hong

    2016-01-01

    A passively mode-locked thulium-doped fiber laser (TDFL) based on a nonlinear amplifying loop mirror (NALM) is presented. By adjusting the polarization controllers, stable noise-like (NL) mode-locked femtosecond pulse operation is obtained at the 2 μm band. In the experimental period of 200 min, the output power fluctuation is less than 0.06 dB and the 3 dB spectral bandwidth variation is less than 0.02 nm, indicating that the pulsed TDFL possesses good long-term stability. To the best of our knowledge, this is the first 2 μm band NALM-based TDFL with small net anomalous dispersion for a NL femtosecond pulse. At the maximum pump power of 3.52 W, the emitting laser has a NL pulse width of 460 fs, the repetition rate of 9.1 MHz, and the NL pulse energy of 32.72 nJ.

  14. Anomalous Diffusion Near Resonances

    SciTech Connect

    Sen, Tanaji; /Fermilab

    2010-05-01

    Synchro-betatron resonances can lead to emittance growth and the loss of luminosity. We consider the detailed dynamics of a bunch near such a low order resonance driven by crossing angles at the collision points. We characterize the nature of diffusion and find that it is anomalous and sub-diffusive. This affects both the shape of the beam distribution and the time scales for growth. Predictions of a simplified anomalous diffusion model are compared with direct simulations. Transport of particles near resonances is still not a well understood phenomenon. Often, without justification, phase space motion is assumed to be a normal diffusion process although at least one case of anomalous diffusion in beam dynamics has been reported [1]. Here we will focus on the motion near synchro-betatron resonances which can be excited by several means, including beams crossing at an angle at the collision points as in the LHC. We will consider low order resonances which couple the horizontal and longitudinal planes, both for simplicity and to observe large effects over short time scales. While the tunes we consider are not practical for a collider, nonetheless the transport mechanisms we uncover are also likely to operate at higher order resonances.

  15. Small angle scattering study of the structure and organization of RNA and protein in Brome Mosaic Virus (BMV)

    NASA Astrophysics Data System (ADS)

    Das, Narayan C.; Warren, Garfield T.; Cheng, Si; Kao, C. Cheng; Ni, Peng; Dragnea, Bogdan; Sokol, Paul E.

    2012-02-01

    Brome mosaic virus (BMV) is a small icosahedral of the alpha virus-like superfamily of RNA with a segmented positive-strand RNA genome and a mean diameter ˜ 268å that offers high levels of RNA synthesis and virus production in plants. BMV also tightly regulates the packaging of its four RNAs (RNA1 through RNA4) into three separate particles; RNA1 and RNA2 are encapsidated separately while one copy each of RNA3 and RNA4 are normally packaged together. Small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) were applied to study the size, shape and protein-RNA organization of BMV. D2O/H2O mixture was used to enhance contrast in SANS measurement. The radial distribution of BMV from the Fourier transform of scattering spectrum gives a clear indication of RNA packing, and distribution and their structure in the BMV. The result reveals that the virus is about 266 å in diameter and is composed of RNA inside the virion coated with a protein shell.

  16. Small-Tip-Angle Spokes Pulse Design Using Interleaved Greedy and Local Optimization Methods

    PubMed Central

    Grissom, William A.; Khalighi, Mohammad-Mehdi; Sacolick, Laura I.; Rutt, Brian K.; Vogel, Mika W.

    2013-01-01

    Current spokes pulse design methods can be grouped into methods based either on sparse approximation or on iterative local (gradient descent-based) optimization of the transverse-plane spatial frequency locations visited by the spokes. These two classes of methods have complementary strengths and weaknesses: sparse approximation-based methods perform an efficient search over a large swath of candidate spatial frequency locations but most are incompatible with off-resonance compensation, multifrequency designs, and target phase relaxation, while local methods can accommodate off-resonance and target phase relaxation but are sensitive to initialization and suboptimal local cost function minima. This article introduces a method that interleaves local iterations, which optimize the radiofrequency pulses, target phase patterns, and spatial frequency locations, with a greedy method to choose new locations. Simulations and experiments at 3 and 7 T show that the method consistently produces single- and multifrequency spokes pulses with lower flip angle inhomogeneity compared to current methods. PMID:22392822

  17. New neutron small-angle diffraction instrument at the Brookhaven High Flux Beam Reactor

    SciTech Connect

    Schneider, D.K.; Schoenborn, B.P.

    1982-01-01

    The new instrument utilizes cold neutrons emerging from a series of straight neutron guides. A multilayered monochromator is used in combination with a short collimator to obtain a monochromatized beam with a wavelength between 4 and 10 A and a wavelength spread of about 10%. The flux at 5 A exceeds 10/sup 6/ ns/sup -1/ cm/sup -2/ in a typical beam of 6-mm diameter at the sample. The spectrometer itself incorporates provisions for computer-controlled positioning of samples and a two-dimensional detector. At a sample-detector distance between 50 and 200 cm the detector can be centered at scattering angles of up to 45/sup 0/. The beam-defining components, the monochromator, the collimator, and various slits, are easily accessible and exchangeable for alternative devices. These features make the instrument modular and give it flexibility approaching that of standard x-ray equipment.

  18. Measurement of the absolute differential cross section of proton–proton elastic scattering at small angles

    DOE PAGES

    Mchedlishvili, D.; Chiladze, D.; Dymov, S.; Bagdasarian, Z.; Barsov, S.; Gebel, R.; Gou, B.; Hartmann, M.; Kacharava, A.; Keshelashvili, I.; et al

    2016-02-03

    The differential cross section for proton-proton elastic scattering has been measured at a beam kinetic energy of 1.0 GeV and in 200 MeV steps from 1.6 to 2.8 GeV for centre-of-mass angles in the range from 12°-16° to 25°-30°, depending on the energy. A precision in the overall normalisation of typically 3% was achieved by studying the energy losses of the circulating beam of the COSY storage ring as it passed repeatedly through the windowless hydrogen target of the ANKE magnetic spectrometer. It is shown that the data have a significant impact upon the results of a partial wave analysis.more » Furthermore, after extrapolating the differential cross sections to the forward direction, the results are broadly compatible with the predictions of forward dispersion relations.« less

  19. Angled Cool-Tip Electrode for Radiofrequency Ablation of Small Superficial Subcapsular Tumors in the Liver: A Feasibility Study

    PubMed Central

    Kim, Il Jung; Lee, Shin Jae; Shin, Min Woo; Shin, Won Sun; Chung, Yong Eun; Kim, Gyoung Min; Kim, Man Deuk; Won, Jong Yun; Lee, Do Yun; Choi, Jin Sub; Han, Kwang-Hyub

    2016-01-01

    Objective To evaluate the feasibility of angled cool-tip electrode for radiofrequency ablation of small superficial subcapsular liver tumors abutting abdominal wall, in order to traverse normal liver parenchyma, and thereby, obtain favorable configuration of ablation margin. Materials and Methods In this study, we retrospectively analyzed 15 small superficial subcapsular liver tumors abutting abdominal wall in 15 patients, treated with radiofrequency ablation from March 2013 to June 2015 using a cool-tip electrode manually modified to create 25–35° angle at the junction between exposed and insulated segments. The tumors were hepatocellular carcinoma (n = 13) and metastases (n = 2: cholangiocellular carcinoma and rectosigmoid cancer), with maximum diameter of 10–26 mm (mean, 15.68 ± 5.29 mm). Under ultrasonographic guidance, the electrode tip was advanced to the depth of the tumors' epicenter about 1 cm from the margin. The tip was re-directed to penetrate the tumor for radiofrequency ablation. Minimal ablation margin was measured at immediate post-treatment CT. Radiological images and medical records were evaluated for success rate, length of minimal ablation margin and complications. Results Technical success rate of obtaining complete necrosis of the tumors was 100%, with no procedure-related complication. Minimal ablation margin ranged from 3–12 mm (mean, 7.07 ± 2.23 mm). CT/MRI follow-up at 21–1022 days (mean, 519.47 ± 304.51 days) revealed no local recurrence, but distant recurrence in 9 patients. Conclusion Using an angled cool-tip electrode for radiofrequency ablation of small superficial subcapsular tumors abutting abdominal wall may be a feasible technique for obtaining adequate ablation margin and lower complication rate. PMID:27587963

  20. On the structure of concentrated detonation nanodiamond hydrosols with a positive ζ potential: Analysis of small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Avdeev, Mikhail V.; Tomchuk, Oleksandr V.; Ivankov, Oleksandr I.; Alexenskii, Alexander E.; Dideikin, Artur T.; Vul, Alexander Ya.

    2016-08-01

    Small-angle neutron scattering (SANS) was applied for the structure characterization of detonation nanodiamond (DND) aqueous suspensions with a positive ζ potential. The contrast variation technique (based on mixtures of light and heavy water) was used to study the structure of DND particles and their clusters in solutions. The results were compared with the data of the previous similar experiments for DND suspensions with a negative ζ potential. The experimental range of the neutron scattering contrast in the system was extended to maximally possible by starting with the initial concentrated suspensions separately prepared in light and heavy water.

  1. Synchrotron radiation small- and wide- angle scattering study of dispergation of Equoral, a novel drug delivery system with cyclosporine A.

    PubMed

    Uhríková, D; Andrýsek, T; Funari, S S; Balgavý, P

    2004-08-01

    Equoral oral solution is a novel drug delivery system for cyclosporine consisting mainly of non-ionic surfactants, polyglycerol esters and polyoxyethylated fatty acids aggregates, and gives microdispersions in the aqueous enviroment. To simulate dispergation, Equoral was mixed with varying amounts of water. Changes in the structure of the prepared aggregates were studied using synchrotron x-ray small- and wide-angle scattering. A lamellar phase is the most probable structure, arising spontaneously after dispergation of Equoral in the region of 30-70 wt% H2O.

  2. Small-angle neutron scattering study of recombinant yeast-derived human hepatitis B virus surface antigen vaccine particle

    NASA Astrophysics Data System (ADS)

    Sato, M.; Ito, Y.; Kameyama, K.; Imai, M.; Ishikawa, N.; Takagi, T.

    1995-02-01

    The overall and internal structure of recombinant yeast-derived human hepatitis B virus surface antigen vaccine particles was investigated by small-angle neutron scattering using the contrast variation method. The vaccine is a nearly spherical particle, and its contrast-matching point was determined to be at about 24% D 2O content, indicating that a large part of the vaccine particle is occupied by lipids and carbohydrates from the yeast. The Stuhrmann plot suggests that the surface antigens exist predominantly in the peripheral region of the particle, which is favorable to the induction of anti-virus antibodies.

  3. Single-crystal CVD diamonds as small-angle X-ray scattering windows for high-pressure research

    PubMed Central

    Wang, Suntao; Meng, Yu-fei; Ando, Nozomi; Tate, Mark; Krasnicki, Szczesny; Yan, Chih-shiue; Liang, Qi; Lai, Joseph; Mao, Ho-kwang; Gruner, Sol M.; Hemley, Russell J.

    2012-01-01

    Small-angle X-ray scattering (SAXS) was performed on single-crystal chemical vapor deposition (CVD) diamonds with low nitrogen concentrations, which were fabricated by microwave plasma-assisted chemical vapor deposition at high growth rates. High optical quality undoped 500 µm-thick single-crystal CVD diamonds grown without intentional nitrogen addition proved to be excellent as windows on SAXS cells, yielding parasitic scattering no more intense than a 7.5 µm-thick Kapton film. A single-crystal CVD diamond window was successfully used in a high-pressure SAXS cell. PMID:22675230

  4. Structure of spontaneously formed solid-electrolyte interphase on lithiated graphite determined using small-angle neutron scattering

    DOE PAGES

    Sacci, Robert L.; Banuelos, Jose Leobardo; Veith, Gabriel M.; Littrell, Ken C.; Cheng, Yongqiang Q.; Wildgruber, Christoph U.; Jones, Lacy L.; Ramirez-Cuesta, Anibal J.; Rother, Gernot; Dudney, Nancy J.

    2015-03-25

    We report the first small-angle neutron scattering of a chemically formed solid-electrolyte interphase from LixC6 reacting with ethylene carbonate/dimethyl carbon solvent. This provides a different and perhaps simpler view of SEI formation than the usual electrochemically-driven reaction. We show that an organic layer coats the graphite particles filling in micro-pores and is polymeric in nature being 1-3 nm thick. We used inelastic neutron scattering to probe the chemistry, and we found that the SEI showed similar inelastic scattering to polyethylene oxide.

  5. Structure of the magnetite-oleic acid-decalin magnetic fluid from small-angle neutron scattering data

    NASA Astrophysics Data System (ADS)

    Nagornyi, A. V.; Petrenko, V. I.; Bulavin, L. A.; Avdeev, M. V.; Almásy, L.; Rosta, L.; Aksenov, V. L.

    2014-01-01

    Structural parameters of the magnetite-oleic acid-decalin magnetic fluid at various excesses of oleic acid (up to 25 vol %) have been determined using small-angle neutron scattering. Based on the comparison of the behavior of oleic acid in the magnetic fluid and in the pure solvent (decalin), it has been concluded that the interaction between the molecules of free (unadsorbed) surfactant changes in the presence of magnetic nanoparticles. However, the system remains stable and does not form aggregates of magnetic particles or free oleic acid. These results are compared with the previously presented data for similar benzene-based magnetic fluids.

  6. Small-angle neutron scattering studies of the template-mediated crystallization of ZSM-5 type zeolite

    SciTech Connect

    Iton, L.E.; Brun, T.O.; Epperson, J.E. . Materials Science and Technology Div.); Trouw, F. . Intense Pulsed Neutron Source Program); White, J.W.; Henderson, S.J. )

    1988-03-01

    Small-angle neutron scattering is a useful new approach to the study of zeolite crystallization from aluminosilicate gels and the action of template molecules. It has been applied to gels for synthesis of zeolite ZSM-5 using tetrapropylammonium ions as templates where the scattering length densities of the gel particles and their texture were determined using contrast variation methods. Gels formulated from soluble silicate incorporate template molecules promptly into an amorphous embryonic'' structure and crystallization ensues via a solid hydrogel transformation mechanism. Gels formulated from colloidal silica show different scattering behavior, and a liquid phase transport mechanism is inferred. 8 refs., 4 figs., 2 tabs.

  7. Limiting cases of the small-angle scattering approximation solutions for the propagation of laser beams in anisotropic scattering media

    NASA Technical Reports Server (NTRS)

    Box, M. A.; Deepak, A.

    1981-01-01

    The propagation of photons in a medium with strongly anisotropic scattering is a problem with a considerable history. Like the propagation of electrons in metal foils, it may be solved in the small-angle scattering approximation by the use of Fourier-transform techniques. In certain limiting cases, one may even obtain analytic expressions. This paper presents some of these results in a model-independent form and also illustrates them by the use of four different phase-function models. Sample calculations are provided for comparison purposes

  8. Quaternary structure of alpha-crustacyanin from lobster as seen by small-angle X-ray scattering.

    PubMed

    Dellisanti, Cosma D; Spinelli, Silvia; Cambillau, Christian; Findlay, John B C; Zagalsky, Peter F; Finet, Stéphanie; Receveur-Bréchot, Véronique

    2003-06-01

    The structure of alpha-crustacyanin, the blue carotenoprotein of lobster (Homarus gammarus) carapace, has been investigated for the first time using small-angle X-ray scattering. In this paper, we have determined the dimensions of this protein composed of eight heterodimeric subunits of beta-crustacyanin. Analysis of the scattering spectra and estimation of the shape of alpha-crustacyanin show that the protein fits into a cylinder with an axial length of 238 A and a radius of 47.5 A, in which the eight beta-crustacyanin molecules are probably arranged in a helical manner. PMID:12782314

  9. Determination of some structural and dispersion characteristics of Perftoran emulsions by the small-angle X-ray scattering

    NASA Astrophysics Data System (ADS)

    Aul'chenko, V. M.; Vazina, A. A.; Galimov, P. V.; Korneev, V. N.; Maevskii, E. I.; Matyushin, A. M.; Tuzikov, F. V.; Tuzikova, N. A.

    2005-05-01

    By the method of small-angle X-ray scattering, it is shown that preparation Perftoran—the blood substitute with the function of carrying oxygen—contains a huge amount of spherical micellar particles in an abundance, essentially of smaller sizes, than a particle of an emulsion of perfluorochemicals. The distribution function of the form and the size of micellar particles of preparation Perftoran is determined. The assumption, that a number of clinical properties of a preparation is caused by these particles is put forward.

  10. Structural transitions of CTAB micelles in the presence of n-octylamine: A small angle neutron scattering study

    SciTech Connect

    Prasad, C.D.; Singh, H.N. ); Goyal, P.S.; Rao, K.S. )

    1993-02-01

    Small angle neutron scattering (SANS) was used to characterize the micelles of cetyltrimethylammonium bromide (CTAB) in D[sub 2]O solutions, with or without added n-octylamine. SANS data have been analyzed using various models. Micellar parameters, such as mean aggregation numbers, micelle dimensions, and fractional charge on the micelles, are reported from the analysis of SANS spectra for the CTAB/n-octylamine system as a function of octylamine concentration and temperature. Results are interpreted in terms of micellar sphere-to-rod transition prompted by amine concentration in CTAB micellar solution. The size of the micelle decreases as the temperature increases.

  11. Second-order Wagner theory for two-dimensional water-entry problems at small deadrise angles

    NASA Astrophysics Data System (ADS)

    Oliver, J. M.

    The theory of Wagner from 1932 for the normal symmetric impact of a two-dimensional body of small deadrise angle on a half-space of ideal and incompressible liquid is extended to derive the second-order corrections for the locations of the higher-pressure jet-root regions and for the upward force on the impactor using a systematic matched-asymptotic analysis. The second-order predictions for the upward force on an entering wedge and parabola are compared with numerical and experimental data, respectively, and it is concluded that a significant improvement in the predictive capability of Wagner's theory is afforded by proceeding to second order.

  12. Investigation of coercivity mechanism in hot deformed Nd-Fe-B permanent magnets by small-angle neutron scattering

    SciTech Connect

    Yano, M. Manabe, A.; Shoji, T.; Kato, A.; Ono, K.; Harada, M.; Kohlbrecher, J.

    2014-05-07

    The magnetic reversal behaviors of single domain sized Nd-Fe-B permanent magnets, with and without isolation between the Nd{sub 2}Fe{sub 14}B grains, was clarified using small-angle neutron scattering (SANS). The SANS patterns obtained arose from changes in the magnetic domains and were analyzed using the Teubner–Stray model, a phenomenological correlation length model, to quantify the periodicity and morphology of the magnetic domains. The results indicated that the magnetic reversal evolved with the magnetic domains that had similar sized grains. The grain isolation enabled us to realize the reversals of single domains.

  13. A Study of Cross-linked Regions of Poly(Vinyl Alcohol) Gels by Small-Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Lawrence, Mathias B.; Desa, J. A. E.; Aswal, V. K.

    2011-07-01

    A poly(vinyl alcohol)-borax cross-linked hydrogel has been studied by Small Angle Neutron Scattering as a function of borax concentration in the wave-vector transfer (Q) range of 0.017 Å-1 to 0.36 Å-1. It is found that as the concentration of borax increases, so does the intensity of scattering in this range. Beyond a borax concentration of 2 mg/ml, the increase in cross-linked PVA chains leads to cross-linked units larger than 150 Å as evidenced by a reduction in intensity in the lower Q region.

  14. Measurement of yarn twist based on backward light scattering and small-angle far-field diffraction

    NASA Astrophysics Data System (ADS)

    Pei, Z. G.; Tao, X. M.

    2015-12-01

    This paper presents a non-destructive, non-contact method for measuring the twist of a yarn based on light scattering and diffraction. The surface twist angle is measured by determining the direction of the line with the highest intensity on the backward light scattering pattern which is perpendicular to the surface fibers, which is verified by both theoretical analysis based on Beckmann’s scattering model and experiments. The yarn diameter is measured with good accuracy by using the small-angle far-field diffraction pattern of the yarn body. Yarn twist is then derived from the measured surface twist angle and yarn diameter. Further studies reveal that the measured yarn twists by the proposed method are comparable to those measured based on microscopic images of the yarn. This method requires no high-magnification optics and is able to pick up short-term variations of twist with less labor intensity, indicating its potential application in the on-line measuring of yarn twist and its distribution.

  15. Small-Angle Neutron Scattering Investigation of Growth Modifiers on Hydrate Crystal Surfaces

    NASA Astrophysics Data System (ADS)

    Sun, Thomas; Hutter, Jeffrey L.; Lin, M.; King, H. E., Jr.

    1998-03-01

    Hydrates are crystals consisting of small molecules enclathrated within an ice-like water cage. Suppression of their growth is important in the oil industry. The presence of small quantities of specific polymers during hydrate crystallization can induce a transition from an octahedral to planar growth habit. This symmetry breaking is surprising because of the suppression of two 111 planes relative to the other six crystallographically equivalent faces. To better understand the surface effects leading to this behavior, we have studied the surface adsorption of these growth-modifing polymers onto the hydrate crytals using SANS. The total hydrate surface area, as measured by Porod scattering, increases in the presence of the growth modifier, but, no significant increase in polymer concentration on the crystal surfaces is found. Implications for possible growth mechanisms will be discussed.

  16. Hypersonic phononic stopbands at small angles of wave incidence in porous silicon multilayers

    NASA Astrophysics Data System (ADS)

    Aliev, Gazi N.; Goller, Bernhard

    2015-08-01

    We report theoretical simulation and experimental observation of the mode conversion effect in a hypersonic distributed Bragg reflector of porous silicon. Acoustic transmission of longitudinal waves through the multilayered structure has been measured in the frequency range 0-3 GHz. It is found that the measured transmittance at the gap frequencies is always higher than that theoretically predicted for normal incidence. We attribute this to non-perpendicular wave propagation that was not deliberately sought, which subsequently increases the center gap transmittance due to the mode conversion effect. Oblique incidence with angles of about 1° results in truncated gap depth in acoustic transmission spectra from about  -80 dB, and deeper, to about  -40 dB and shallower. The spectra were simulated by employing the stiffness matrix method. Porosity-dependent acoustic viscous damping was included in the calculations. A way to optimize reflectors in the frequency range, where the forbidden gaps for longitudinal and shear waves overlap, is discussed.

  17. Freeform lens design for providing LED small angle illumination in underwater application

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaohui; Chen, Chen

    2015-08-01

    With high light efficiency and long aging life, LED solid-state light source has attracted much attention in underwater application, such as optical communication and imaging. But, the large divergence angle of LED illumination has been a big challenge in practical underwater application, such as the light attenuation in water and then the decreased signal-to-noise ratio. Source-target map is a vital method in illumination optics design, and the focus is to solve numerically differential equations and then construct the freeform surface. To achieve high accuracy freeform surface, an improved method is suggested and optimized through much more advanced and accuracy Runge-Kutta method, which is different from the original design one through Euler method. The designed lens is simulated by ray trace software TracePro, and the simulation results show that the uniformity of 0.8 and the efficacy of 0.6 is obtained. While as, the method is proven to be effective, and also the accuracy of the smooth freeform surface is strengthened. One designed illumination lens is fabricated by computer numeric control (CNC) machine to demonstrate the design experimentally.

  18. Resolving Individual Components in Protein-RNA Complexes Using Small-Angle X-ray Scattering Experiments.

    PubMed

    Rambo, Robert P

    2015-01-01

    Small-angle X-ray scattering (SAXS) of protein-RNA complexes has developed into an efficient and economical approach for determining low-resolution shapes of particles in solution. Here, we demonstrate a mutliphase volumetric modeling approach capable of resolving individual components within a low-resolution shape. Through three case studies, we describe the SAXS data collecting strategies, premodeling analysis, and computational methods required for deconstructing complexes into their respective components. This chapter presents an approach using the programs ScÅtter and MONSA and custom scripts for averaging and aligning of multiple independent modeling runs. The method can image small (7kDa) masses within the context of complex and is capable of visualizing ligand-induced conformational changes. Nevertheless, computational algorithms are not without error, and we describe specific considerations during SAXS data reduction and modeling to mitigate possible false positives.

  19. Small-angle X-ray scattering: a bridge between RNA secondary structures and three-dimensional topological structures

    SciTech Connect

    Fang, Xianyang; Stagno, Jason R.; Bhandari, Yuba R.; Zuo, Xiaobing; Wang, Yun-Xing

    2015-02-01

    Whereas the structures of small to medium-sized well folded RNA molecules often can be determined by either X-ray crystallography or NMR spectroscopy, obtaining structural information for large RNAs using experimental, computational, or combined approaches remains a major interest and challenge. RNA is very sensitive to small-angle X-ray scattering (SAXS) due to high electron density along phosphate-sugar backbones, whose scattering contribution dominates SAXS intensity. For this reason, SAXS is particularly useful in obtaining global RNA structural information that outlines backbone topologies and, therefore, molecular envelopes. Such information is extremely valuable in bridging the gap between the secondary structures and three-dimensional topological structures of RNAmolecules, particularly those that have proven difficult to study using other structuredetermination methods. Here we review published results of RNA topological structures derived from SAXS data or in combination with other experimental data, as well as details on RNA sample preparation for SAXS experiments.

  20. Accounting for Observed Small Angle X-ray Scattering Profile in the Protein-Protein Docking Server ClusPro

    PubMed Central

    Xia, Bing; Mamonov, Artem; Leysen, Seppe; Allen, Karen N; Strelkov, Sergei V.; Paschalidis, Ioannis Ch.; Vajda, Sandor; Kozakov, Dima

    2015-01-01

    The protein-protein docking server ClusPro is used by thousands of laboratories, and models built by the server have been reported in over 300 publications. Although the structures generated by the docking include near-native ones for many proteins, selecting the best model is difficult due to the uncertainty in scoring. Small Angle X-ray Scattering (SAXS) is an experimental technique for obtaining low resolution structural information in solution. While not sufficient on its own to uniquely predict complex structures, accounting for SAXS data improves the ranking of models and facilitates the identification of the most accurate structure. Although SAXS profiles are currently available only for a small number of complexes, due to its simplicity the method is becoming increasingly popular. Since combining SAXS experiments will provide a viable strategy for fairly high-throughput determination of protein complex structures, the option of using SAXS restraints is added to the ClusPro server. PMID:26095982

  1. Critical dimension small angle X-ray scattering measurements of FinFET and 3D memory structures

    NASA Astrophysics Data System (ADS)

    Settens, Charles; Bunday, Benjamin; Thiel, Brad; Kline, R. Joseph; Sunday, Daniel; Wang, Chengqing; Wu, Wen-li; Matyi, Richard

    2013-04-01

    We have demonstrated that transmission critical dimension small angle X-ray scattering (CD-SAXS) provides high accuracy and precision CD measurements on advanced 3D microelectronic architectures. The competitive advantage of CD-SAXS over current 3D metrology methods such as optical scatterometry is that CD-SAXS is able to decouple and fit cross-section parameters without any significant parameter cross-correlations. As the industry aggressively scales beyond the 22 nm node, CD-SAXS can be used to quantitatively measure nanoscale deviations in the average crosssections of FinFETs and high-aspect ratio (HAR) memory devices. Fitting the average cross-section of 18:1 isolated HAR contact holes with an effective trapezoid model yielded an average pitch of 796.9 +/- 0.4 nm, top diameter of 70.3 +/- 0.9 nm, height of 1088 +/- 4 nm, and sidewall angle below 0.1°. Simulations of dense 40:1 HAR contact holes and FinFET fin-gate crossbar structures have been analyzed using CD-SAXS to inquire the theoretical precision of the technique to measure important process parameters such as fin CD, height, and sidewall angle; BOX etch recess, thickness of hafnium oxide and titanium nitride layers; gate CD, height, and sidewall angle; and hafnium oxide and titanium nitride etch recess. The simulations of HAR and FinFET structures mimic the characteristics of experimental data collected at a synchrotron x-ray source. Using the CD-SAXS simulator, we estimate the measurement capabilities for smaller similar structures expected at future nodes to predict the applicability of this technique to fulfill important CD metrology needs.

  2. Method to study sample object size limit of small-angle x-ray scattering computed tomography

    NASA Astrophysics Data System (ADS)

    Choi, Mina; Ghammraoui, Bahaa; Badal, Andreu; Badano, Aldo

    2016-03-01

    Small-angle x-ray scattering (SAXS) imaging is an emerging medical tool that can be used for in vivo detailed tissue characterization and has the potential to provide added contrast to conventional x-ray projection and CT imaging. We used a publicly available MC-GPU code to simulate x-ray trajectories in a SAXS-CT geometry for a target material embedded in a water background material with varying sample sizes (1, 3, 5, and 10 mm). Our target materials were water solution of gold nanoparticle (GNP) spheres with a radius of 6 nm and a water solution with dissolved serum albumin (BSA) proteins due to their well-characterized scatter profiles at small angles and highly scattering properties. The background material was water. Our objective is to study how the reconstructed scatter profile degrades at larger target imaging depths and increasing sample sizes. We have found that scatter profiles of the GNP in water can still be reconstructed at depths up to 5 mm embedded at the center of a 10 mm sample. Scatter profiles of BSA in water were also reconstructed at depths up to 5 mm in a 10 mm sample but with noticeable signal degradation as compared to the GNP sample. This work presents a method to study the sample size limits for future SAXS-CT imaging systems.

  3. Asymmetric grazing incidence small angle x-ray scattering and anisotropic domain wall motion in obliquely grown nanocrystalline Co films.

    PubMed

    Quirós, C; Peverini, L; Díaz, J; Alija, A; Blanco, C; Vélez, M; Robach, O; Ziegler, E; Alameda, J M

    2014-08-22

    Strong asymmetries have been observed in grazing incidence small angle x-ray scattering (GISAXS) in situ patterns obtained from 30 nm-thick nanocrystalline Co films prepared by oblique sputtering (15°-75° off-sample normal). These asymmetries have been qualitatively simulated by a simple model consisting of an ensemble of 8 nm-wide inclined Co nanocolumns. It is found that narrow inclined features appear in the diffuse background resembling those characteristic of faceted systems, which can be used to obtain straightforward non-destructive estimations of buried nanocolumnar grains inclination, even for oblique angles below 45°, when the stronger and broader asymmetric features of the pattern are not yet fully formed. Furthermore, using magneto-optical microscopy, a marked change in the magnetic domain's nucleation and growth process has been observed in the sample prepared at 75°, with the stronger GISAXS asymmetries. Easy axis magnetization reversal starts by a random and homogeneous nucleation of small (∼μm) elongated domains aligned with the nanocolumn's long axis and proceeds through the preferred propagation of head-to-head domain walls (DWs) along the applied field direction. This peculiar magnetic behavior indicates that the strongly anisotropic nanostructuring created by the oblique growth process is equivalent, from a magnetic point of view, to an array of self-assembled buried nanowires. These results show how GISAXS and magneto-optical microscopy can be combined as a powerful tool for correlating the morphology and magnetism of thin nanostructured systems.

  4. A Combined Small-Angle X-ray and Neutron Scattering Study of the Structure of Purified Soluble Gastrointestinal Mucins

    PubMed Central

    Georgiades, Pantelis; di Cola, Emanuela; Heenan, Richard K; Pudney, Paul D A; Thornton, David J; Waigh, Thomas A

    2014-01-01

    The structures of purified soluble porcine gastric (Muc5ac) and duodenal (Muc2) mucin solutions at neutral and acidic pH were examined using small-angle X-ray scattering and small-angle neutron scattering experiments. We provide evidence for the morphology of the network above the semidilute overlap concentration and above the entanglement concentration. Furthermore, we investigated the gelation of both types of mucin solutions in response to a reduction in pH, where we observed the formation of large-scale heterogeneities within the polymer solutions, typical of microphase-separated gels. The concentration dependence of the inhomogeneity length scale (Ξ) and the amplitude of the excess scattering intensity [Iex(0)] are consistent with previously studied gelled synthetic polymeric systems. The persistence lengths of the chains were found to be similar for both Muc5ac and Muc2 from Kratky plots of the neutron data (8 ± 2 nm). © 2014 Wiley Periodicals, Inc. Biopolymers 101: 1154–1164, 2014. PMID:25041765

  5. X-ray crystal structure and small-angle X-ray scattering of sheep liver sorbitol dehydrogenase

    SciTech Connect

    Yennawar, Hemant; Møller, Magda; Gillilan, Richard; Yennawar, Neela

    2011-05-01

    The X-ray crystal structure and a small-angle X-ray scattering solution structure of sheep liver sorbitol dehydrogenase have been determined. The details of the interactions that enable the tetramer scaffold to be the functional biological unit have been analyzed. The X-ray crystal structure of sheep liver sorbitol dehydrogenase (slSDH) has been determined using the crystal structure of human sorbitol dehydrogenase (hSDH) as a molecular-replacement model. slSDH crystallized in space group I222 with one monomer in the asymmetric unit. A conserved tetramer that superposes well with that seen in hSDH (despite belonging to a different space group) and obeying the 222 crystal symmetry is seen in slSDH. An acetate molecule is bound in the active site, coordinating to the active-site zinc through a water molecule. Glycerol, a substrate of slSDH, also occupies the substrate-binding pocket together with the acetate designed by nature to fit large polyol substrates. The substrate-binding pocket is seen to be in close proximity to the tetramer interface, which explains the need for the structural integrity of the tetramer for enzyme activity. Small-angle X-ray scattering was also used to identify the quaternary structure of the tetramer of slSDH in solution.

  6. Design of Ultra Small Angle Neutron Scattering (KIST-USANS) at HANARO Cold Neutron Guide, CG4B

    NASA Astrophysics Data System (ADS)

    Kim, Man-Ho

    2013-03-01

    The ultra small angle neutron scattering instrument can measure the lower limit of scattering vector to near Q ~ 2.0x10-5 Å-1 while the upper limit can reach to an intermediate scattering vector Q ~ 10-2 Å-1 of a typical small angle neutron scattering (SANS) depending on the contrast of sample. USANS is useful when measuring objects that are micron to submicron in size while SANS is useful when measuring objects that are micron to nano in size. When both USANS and SANS were used together, we could measure sizes from micron to nano scale, which is useful when studying the hierarchical structures in the wide scale of Q and total cross-section, d Σ/d Ω(Q). Recently, KIST has developed the USANS (so called KIST-USANS) at HANARO cold neutron guide hall of KAERI. We will present the instrument design, performance, future plan, and some examples of measurements that cover approximately 11 orders of magnitude in the d Σ/d Ω(Q) and 4 orders in the Q. This work was partially supported by the KIST (2v02632) and the National Research Foundation of Korea(NRF) grant funded by the Korea government(MEST) (No. 2012M2B2A4030220)

  7. A posteriori determination of the useful data range for small-angle scattering experiments on dilute monodisperse systems.

    PubMed

    Konarev, Petr V; Svergun, Dmitri I

    2015-05-01

    Small-angle X-ray and neutron scattering (SAXS and SANS) experiments on solutions provide rapidly decaying scattering curves, often with a poor signal-to-noise ratio, especially at higher angles. On modern instruments, the noise is partially compensated for by oversampling, thanks to the fact that the angular increment in the data is small compared with that needed to describe adequately the local behaviour and features of the scattering curve. Given a (noisy) experimental data set, an important question arises as to which part of the data still contains useful information and should be taken into account for the interpretation and model building. Here, it is demonstrated that, for monodisperse systems, the useful experimental data range is defined by the number of meaningful Shannon channels that can be determined from the data set. An algorithm to determine this number and thus the data range is developed, and it is tested on a number of simulated data sets with various noise levels and with different degrees of oversampling, corresponding to typical SAXS/SANS experiments. The method is implemented in a computer program and examples of its application to analyse the experimental data recorded under various conditions are presented. The program can be employed to discard experimental data containing no useful information in automated pipelines, in modelling procedures, and for data deposition or publication. The software is freely accessible to academic users. PMID:25995844

  8. ORNL_SAS: Versatile software for calculation of small-angle x-ray and neutron scattering intensity profiles from arbitrary structures

    SciTech Connect

    Heller, William T; Tjioe, Elina

    2007-01-01

    ORNL{_}SAS is software for calculating solution small-angle scattering intensity profiles from any structure provided in the Protein Data Bank format and can also compare the results with experimental data.

  9. Anomalous Arms

    NASA Technical Reports Server (NTRS)

    2007-01-01

    In this composite image of spiral galaxy M106 (NGC 4258), optical data from the Digitized Sky Survey is shown as yellow, radio data from the Very Large Array appears as purple, X-ray data from Chandra is coded blue, and infrared data from the Spitzer Space Telescope appears red. Two anomalous arms, which aren't visible at optical wavelengths, appear as purple and blue emission.

  10. The quaternary structure of the ribosome from E. coli. A neutron small-angle scattering study

    NASA Astrophysics Data System (ADS)

    Nowotny, V.; Nowotny, P.; Voß, H.; Nierhaus, K. H.; May, R. P.

    1989-01-01

    Ribosomes synthesize proteins in living cells. The E. coli ribosome is composed of a small (30S) and a large subunit (50S). They consist of different proteins (21 or 34, respectively) and of ribosomal RNAs (16S or 23S and 5S). The inter-protein distances within the ribosomal subunits can be measured from scattering experiments with selectively labeled protein pairs from which the quaternary distribution of the proteins is reconstructed. We have developed the strategy of the “glassy ribosome”: the rRNAs and the proteins are deuterated such that they reach the same scattering density and are “invisible” in a corresponding buffer solution. A preliminary quaternary map of the 50S subunit which is the result of our new method for the extraction of the distances from the scattering data as well as shape parameters of proteins in situ will be presented.

  11. Nonlocal Anomalous Hall Effect

    NASA Astrophysics Data System (ADS)

    Zhang, Steven S.-L.; Vignale, Giovanni

    2016-04-01

    The anomalous Hall (AH) effect is deemed to be a unique transport property of ferromagnetic metals, caused by the concerted action of spin polarization and spin-orbit coupling. Nevertheless, recent experiments have shown that the effect also occurs in a nonmagnetic metal (Pt) in contact with a magnetic insulator [yttrium iron garnet (YIG)], even when precautions are taken to ensure that there is no induced magnetization in the metal. We propose a theory of this effect based on the combined action of spin-dependent scattering from the magnetic interface and the spin-Hall effect in the bulk of the metal. At variance with previous theories, we predict the effect to be of first order in the spin-orbit coupling, just as the conventional anomalous Hall effect—the only difference being the spatial separation of the spin-orbit interaction and the magnetization. For this reason we name this effect the nonlocal anomalous Hall effect and predict that its sign will be determined by the sign of the spin-Hall angle in the metal. The AH conductivity that we calculate from our theory is in order of magnitude agreement with the measured values in Pt /YIG structures.

  12. Nonlocal Anomalous Hall Effect.

    PubMed

    Zhang, Steven S-L; Vignale, Giovanni

    2016-04-01

    The anomalous Hall (AH) effect is deemed to be a unique transport property of ferromagnetic metals, caused by the concerted action of spin polarization and spin-orbit coupling. Nevertheless, recent experiments have shown that the effect also occurs in a nonmagnetic metal (Pt) in contact with a magnetic insulator [yttrium iron garnet (YIG)], even when precautions are taken to ensure that there is no induced magnetization in the metal. We propose a theory of this effect based on the combined action of spin-dependent scattering from the magnetic interface and the spin-Hall effect in the bulk of the metal. At variance with previous theories, we predict the effect to be of first order in the spin-orbit coupling, just as the conventional anomalous Hall effect-the only difference being the spatial separation of the spin-orbit interaction and the magnetization. For this reason we name this effect the nonlocal anomalous Hall effect and predict that its sign will be determined by the sign of the spin-Hall angle in the metal. The AH conductivity that we calculate from our theory is in order of magnitude agreement with the measured values in Pt/YIG structures.

  13. An in situ study using anomalous wide angle X-ray scattering and X-ray absorption spectroscopy of the binary metal oxide catalytic system SnO2-ZnAI2O4 supported on alumina

    NASA Astrophysics Data System (ADS)

    Revel, R.; Bazin, D.; Bouchet-Fabre, B.; Seigneurin, A.; Kihn, Y.

    2002-07-01

    A fine structural description of the local order around zinc and tin atoms of a binary metal oxide catalyst, namely SnO2-ZnAl2O4/AI2O3 which can be used as a DeNOx catalyst, is achieved through XAS (X-ray absorption Spectroscopy) and AWAXS (Anomalous wide angle X-ray scattering). The analysis of the data was supported by ab initio calculations based on the multiple scattering processes for the XAS spectroscopy and ab initio calculations based on the Debye equation in the case of anomalous scattering. We found that the tetrahedral sites occupied by the zinc atoms are not completely filled and that part of the zinc atoms are engaged in a SnO2 like structure. Also, it seems that most of the tin atoms are engaged in tin dioxide clusters. For the set of in situ XAS experiments done at the K Zn edge and K Sn edge, no significant modification of the interatomic distances around each of the two metals versus the reactive gases are measured. Taking into account the previous results obtained on the monoxide metal supported catalyst ZnAl2O4/Al2O3, we can assume thus that only a dramatic lack of occupancy on the metal site favours an incursion of light atoms in the network. This structural property can explain in return the expansion of the crystallographic cell as well as a significant increased of the Debye-Waller factor associated to zinc-zinc pairs. Une description détaillée de l'ordre local autour du zinc et de l'étain est effectuée sur un catalyseur SnO2-ZnAl2O4/AI2O3 par deux techniques spécifiques au rayonnement synchrotron, la spectroscopie d'absorption X et la diffraction anomale. Une attention particulière est portée sur l'analyse des données. En ce qui concerne la spectroscopie d'absorption X, celle-ci s'effectue par le biais de logiciels prenant en compte les processus de diffusion multiple du photoélectron. La simulation numérique des différentielles obtenues par soustraction des diagrammes de diffraction s'effectue à partir de l'équation de Debye en

  14. Anomalous scattering of light on Triton

    NASA Technical Reports Server (NTRS)

    Helfenstein, Paul; Lee, Pascal; Mccarthy, Derek; Veverka, Joseph

    1991-01-01

    Researchers report here the discovery of an isolated region of anomalously forward scattering materials on the surface of Triton. The researchers' best-fit Hapke parameters indicate that regolith particles in the anomalous scattering region are not only less backward scattering, but also slightly lower in single scattering albedo than average materials on Triton's surface. While it might be possible to account for such differences in terms of differences in particle size and transparency, it is also possible that the anomalous region is compositionally distinct from other terrains. It is noteworthy that, for the anomalous region, there exists a distinctively strong spatial correlation between the photometric ratios at different phase angles, and that, relative to other terrains, the anomalous region reddens at a different rate with increasing phase angle.

  15. The stability of high internal phase emulsions at low surfactant concentration studied by small angle neutron scattering.

    PubMed

    Reynolds, Philip A; McGillivray, Duncan J; Mata, Jitendra P; Yaron, Peter N; White, John W

    2010-09-15

    The changes in structure of high internal phase emulsions at low concentrations and at elevated temperature are reported for comparison with the same emulsions under conditions well away from instability. Small angle neutron scattering measurements on aqueous ammonium nitrate droplets dispersed in hexadecane and stabilized by very small quantities of a polyisobutylene-based surfactant (PIBSA) as well as related inverse micellar solutions in hexadecane, have been made as a function of temperature and surfactant concentration. Experimental conditions here favour larger and more deformable droplets than in previous studies. Besides the expected micelles and adsorbed surfactant, planar bilayers of micron lateral extent between touching droplets cover 20% of the droplet surface. Another difference from previous experiments is that the oil phase in the emulsions, and corresponding inverse micellar solutions are different in micellar radii and composition. The differences, and changes with surfactant concentration and temperature, are attributed to fractionation of the polydisperse PIBSA in the emulsions, but not the inverse micellar solutions. At low PIBSA concentration and high temperature the SANS shows emulsion decomposing into separate oil and aqueous phases. This occurs when the micelle concentration reaches a very small but measurable value. The inverse micelles may suppress by steric action long wavelength unstable capillary waves in the bilayers. Depletion repulsion forces here have a minor role in the emulsion stabilization.

  16. Imaging the nanostructure of bone and dentin through small- and wide-angle X-ray scattering.

    PubMed

    Pabisch, Silvia; Wagermaier, Wolfgang; Zander, Thomas; Li, Chenghao; Fratzl, Peter

    2013-01-01

    X-ray scattering is a powerful nondestructive experimental method that is well suited to study biomineralized tissues such as bone. Small-angle X-ray scattering (SAXS) gives information about the size, shape, and predominant orientation of the nanometer-sized mineral particles in the bone. Wide-angle X-ray diffraction (WAXD) allows the characterization of structural parameters, describing size and orientation of the hydroxyapatite crystals. Furthermore, scanning an area with nano- or micrometer-sized X-ray beams allows one to extend this local information to map large bone or dentin sections. Therefore, this method contributes to obtaining information on several length scales simultaneously. Combining results from scanning SAXS and WAXD with those from other position-sensitive methods such as backscattered electron imaging or X-ray fluorescence spectroscopy of the same bone sections allows the exploration of complex biological processes. The method is described and illustrated by a few examples, including the mapping of a complete tooth and the effect of osteoporosis treatment on the bone mineral.

  17. Structural changes in C–S–H gel during dissolution: Small-angle neutron scattering and Si-NMR characterization

    SciTech Connect

    Trapote-Barreira, Ana; Porcar, Lionel; Cama, Jordi; Soler, Josep M.; Allen, Andrew J.

    2015-06-15

    Flow-through experiments were conducted to study the calcium–silicate–hydrate (C–S–H) gel dissolution kinetics. During C–S–H gel dissolution the initial aqueous Ca/Si ratio decreases to reach the stoichiometric value of the Ca/Si ratio of a tobermorite-like phase (Ca/Si = 0.83). As the Ca/Si ratio decreases, the solid C–S–H dissolution rate increases from (4.5 × 10{sup −} {sup 14} to 6.7 × 10{sup −} {sup 12}) mol m{sup −} {sup 2} s{sup −} {sup 1}. The changes in the microstructure of the dissolving C–S–H gel were characterized by small-angle neutron scattering (SANS) and {sup 29}Si magic-angle-spinning nuclear magnetic resonance ({sup 29}Si-MAS NMR). The SANS data were fitted using a fractal model. The SANS specific surface area tends to increase with time and the obtained fit parameters reflect the changes in the nanostructure of the dissolving solid C–S–H within the gel. The {sup 29}Si MAS NMR analyses show that with dissolution the solid C–S–H structure tends to a more ordered tobermorite structure, in agreement with the Ca/Si ratio evolution.

  18. ``Ordered'' structure in dilute solutions of biopolymers as studied by small-angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Matsuoka, Hideki; Ise, Norio; Okubo, Tsuneo; Kunugi, Shigeru; Tomiyama, Hiroshi; Yoshikawa, Yukihiro

    1985-07-01

    Dilute aqueous solutions of bovine serum albumin, lysozyme, chondroitin sulfate, and tRNA were measured by small-angle x-ray scattering. The scattering curves showed a single, broad peak as was observed for synthetic polyelectrolytes, indicating the presence of an ordered distribution of charged solutes. The intermolecular distance evaluated from the peak position (2Dexpt) increased with decreasing polymer concentration and with increasing salt concentration. Except for chondroitin sulfate, 2Dexpt values were nearly equal to the interparticle distance (2D0) calculated based on the assumption of a uniform distribution. The observed relationship between 2Dexpt and 2D0 was in agreement with the proposal that intermacroion attraction is weak for low-charge density particles under discussion. This attraction and repulsive interparticle interaction create a ``secondary'' minimum in the potential curve enabling ordering to take place. For tRNA, the scattering peak became lower with rising temperature. The fact that only a single, broad peak could be observed was rationalized by invoking the concept of distortions of ordering particles such as the paracrystallinity, and the thermal motion and the crystalline size effect. The correlation hole theory based on repulsive interaction is critically discussed, particularly in light of the experimental fact that the peak position of albumin shifts toward wider angles with increasing number of charges.

  19. Quantitative angle-resolved small-spot reflectance measurements on plasmonic perfect absorbers: impedance matching and disorder effects.

    PubMed

    Tittl, Andreas; Harats, Moshe G; Walter, Ramon; Yin, Xinghui; Schäferling, Martin; Liu, Na; Rapaport, Ronen; Giessen, Harald

    2014-10-28

    Plasmonic devices with absorbance close to unity have emerged as essential building blocks for a multitude of technological applications ranging from trace gas detection to infrared imaging. A crucial requirement for such elements is the angle independence of the absorptive performance. In this work, we develop theoretically and verify experimentally a quantitative model for the angular behavior of plasmonic perfect absorber structures based on an optical impedance matching picture. To achieve this, we utilize a simple and elegant k-space measurement technique to record quantitative angle-resolved reflectance measurements on various perfect absorber structures. Particularly, this method allows quantitative reflectance measurements on samples where only small areas have been nanostructured, for example, by electron-beam lithography. Combining these results with extensive numerical modeling, we find that matching of both the real and imaginary parts of the optical impedance is crucial to obtain perfect absorption over a large angular range. Furthermore, we successfully apply our model to the angular dispersion of perfect absorber geometries with disordered plasmonic elements as a favorable alternative to current array-based designs. PMID:25251075

  20. Beam splitting target reflector based compensation for angular drift of laser beam in laser autocollimation of measuring small angle deviations

    NASA Astrophysics Data System (ADS)

    Zhu, Fan; Tan, Jiubin; Cui, Jiwen

    2013-06-01

    Beam splitting target reflector based compensation for the angular drift of laser beam in laser autocollimation is proposed in this article to improve the measurement accuracy and stability of small angle deviations. A beam splitting target reflector is used to replace the plane mirror in laser autocollimation to generate a reference beam when returning the measurement beam. The reference beam and measurement beam have the same angular drift, but have different sensitivities to the rotation angle of the reflector due to the unique characteristics of the reflector. Thus, the angular drift of laser beam in laser autocollimation can be compensated in real time by using the drift of reference beam. Experimental results indicate that an output stability of 0.085 arc sec in 2 h can be achieved after compensation. And a measurement accuracy of ±0.032 arc sec can be obtained over the range of ±1190 arc sec with an effective resolution of 0.006 arc sec. It is confirmed that the compensation method for the angular drift of laser beam is necessary for improving the measurement accuracy and stability in laser autocollimation.

  1. Theoretical studies on particle shape classification based on simultaneous small forward angle light scattering and aerodynamic sizing

    NASA Astrophysics Data System (ADS)

    Jin-Bi, Zhang; Lei, Ding; Ying-Ping, Wang; Li, Zhang; Jin-Lei, Wu; Hai-Yang, Zheng; Li, Fang

    2016-03-01

    Particle shape contributes to understanding the physical and chemical processes of the atmosphere and better ascertaining the origins and chemical compositions of the particles. The particle shape can be classified by the aspect ratio, which can be estimated through the asymmetry factor measured with angularly resolved light scattering. An experimental method of obtaining the asymmetry factor based on simultaneous small forward angle light scattering and aerodynamic size measurements is described briefly. The near forward scattering intensity signals of three detectors in the azimuthal angles at 120° offset are calculated using the methods of T-matrix and discrete dipole approximation. Prolate spheroid particles with different aspect ratios are used as the shape models with the assumption that the symmetry axis is parallel to the flow axis and perpendicular to the incident light. The relations between the asymmetry factor and the optical size and aerodynamic size at various equivalent sizes, refractive indices, and mass densities are discussed in this paper. The numerically calculated results indicate that an elongated particle may be classified at diameter larger than 1.0 μm, and may not be distinguished from a sphere at diameter less than 0.5 μm. It is estimated that the lowest detected aspect ratio is around 1.5:1 in consideration of the experimental errors. Project supported by the National Natural Science Foundation of China (Grant No. 41275132).

  2. Rod Packing in Chiral Nematic Cellulose Nanocrystal Dispersions Studied by Small-Angle X-ray Scattering and Laser Diffraction.

    PubMed

    Schütz, Christina; Agthe, Michael; Fall, Andreas B; Gordeyeva, Korneliya; Guccini, Valentina; Salajková, Michaela; Plivelic, Tomás S; Lagerwall, Jan P F; Salazar-Alvarez, German; Bergström, Lennart

    2015-06-16

    The packing of cellulose nanocrystals (CNC) in the anisotropic chiral nematic phase has been investigated over a wide concentration range by small-angle X-ray scattering (SAXS) and laser diffraction. The average separation distance between the CNCs and the average pitch of the chiral nematic phase have been determined over the entire isotropic-anisotropic biphasic region. The average separation distances range from 51 nm, at the onset of the anisotropic phase formation, to 25 nm above 6 vol % (fully liquid crystalline phase) whereas the average pitch varies from ≈15 μm down to ≈2 μm as ϕ increases from 2.5 up to 6.5 vol %. Using the cholesteric order, we determine that the twist angle between neighboring CNCs increases from about 1° up to 4° as ϕ increases from 2.5 up to 6.5 vol %. The dependence of the twisting on the volume fraction was related to the increase in the magnitude of the repulsive interactions between the charged rods as the average separation distance decreases.

  3. Beam splitting target reflector based compensation for angular drift of laser beam in laser autocollimation of measuring small angle deviations

    SciTech Connect

    Zhu Fan; Tan Jiubin; Cui Jiwen

    2013-06-15

    Beam splitting target reflector based compensation for the angular drift of laser beam in laser autocollimation is proposed in this article to improve the measurement accuracy and stability of small angle deviations. A beam splitting target reflector is used to replace the plane mirror in laser autocollimation to generate a reference beam when returning the measurement beam. The reference beam and measurement beam have the same angular drift, but have different sensitivities to the rotation angle of the reflector due to the unique characteristics of the reflector. Thus, the angular drift of laser beam in laser autocollimation can be compensated in real time by using the drift of reference beam. Experimental results indicate that an output stability of 0.085 arc sec in 2 h can be achieved after compensation. And a measurement accuracy of {+-}0.032 arc sec can be obtained over the range of {+-}1190 arc sec with an effective resolution of 0.006 arc sec. It is confirmed that the compensation method for the angular drift of laser beam is necessary for improving the measurement accuracy and stability in laser autocollimation.

  4. From Non-equilibrium to Equilibrium: Micellar Kinetics seen by Time-resolved Small-angle Scattering

    NASA Astrophysics Data System (ADS)

    Lund, Reidar

    The kinetic pathways of self-assembled nanostructures are not fully understood. Time-resolved small-angle X-ray/neutron scattering (TR-SAXS/SANS) is powerful technique1 that allows kinetics processes such as nucleation processes2,3 and morphological transitions4,5 to be followed with structural resolution over time scales starting from milliseconds. Neutrons offer the additional advantage of facile contrast variation through H/D substitution schemes, which also allow equilibrium processes such as molecular exchange and diffusion to be studied1 , 6 , 7. Here we will highlight the current capabilities of TR-SAS and show results on the kinetics of polymeric micelles. We will address how the understanding of kinetic pathways can be used control the nanostructure.

  5. In situ probing calcium carbonate formation by combining fast controlled precipitation method and small-angle X-ray scattering.

    PubMed

    Chao, Yanjia; Horner, Olivier; Vallée, Philippe; Meneau, Florian; Alos-Ramos, Olga; Hui, Franck; Turmine, Mireille; Perrot, Hubert; Lédion, Jean

    2014-04-01

    The initial stage of calcium carbonate nucleation and growth, found usually in "natural" precipitation conditions, is still not well understood. The calcium carbonate formation for moderate supersaturation level could be achieved by an original method called the fast controlled precipitation (FCP) method. FCP was coupled with SAXS (small-angle X-ray scattering) measurements to get insight into the nucleation and growth mechanisms of calcium carbonate particles in Ca(HCO3)2 aqueous solutions. Two size distributions of particles were observed. The particle size evolutions of these two distributions were obtained by analyzing the SAXS data. A nice agreement was obtained between the total volume fractions of CaCO3 obtained by SAXS analysis and by pH-resistivity curve modeling (from FCP tests).

  6. Structural investigations of E. Coli dihydrolipoamide dehydrogenase in solution: Small-angle X-ray scattering and molecular docking

    NASA Astrophysics Data System (ADS)

    Dadinova, L. A.; Rodina, E. V.; Vorobyeva, N. N.; Kurilova, S. A.; Nazarova, T. I.; Shtykova, E. V.

    2016-05-01

    Dihydrolipoamide dehydrogenase from Escherichia coli (LpD) is a bacterial enzyme that is involved in the central metabolism and shared in common between the pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase complexes. In the crystal structure, E. coli LpD is known to exist as a dimer. The present work is focused on analyzing the solution structure of LpD by small-angle X-ray scattering, molecular docking, and analytical ultracentrifugation. It was shown that in solution LpD exists as an equilibrium mixture of a dimer and a tetramer. The presence of oligomeric forms is determined by the multifunctionality of LpD in the cell, in particular, the required stoichiometry in the complexes.

  7. Saturation magnetostriction dependence on torsion in amorphous wire as measured by modified small angle magnetization rotation method

    NASA Astrophysics Data System (ADS)

    Chubykalo, O. A.; González, J.; Aragoneses, P.; Blanco, J. M.; Domínguez, L.; González, J. M.

    1997-05-01

    The small angle magnetization rotation (SAMR) method has been applied to the measurement of the torsional dependence of the saturation magnetostriction in a low-magnetostrictive amorphous Co-rich wire. The behaviour of the electric signal picked up from the sense coil has been investigated using experimental and numerical methods. The torsion introduces the first harmonic into the signal but the general formula for the measurement of the saturation magnetostriction remains valid. The conditions for the application of the method are discussed. The measurements of the saturation magnetostriction in the presence of an applied torsion have been carried out for as-quenched and annealed samples using different intensities of the annealing current. The magnetostriction coefficient, λs, depends linearly on the applied stress σ: λs = λs(0) + Aσ. The experimental dependence of the parameters λs(0) and A on the applied torsion and for different thermal treatments of the samples are also presented.

  8. A small-angle X-ray scattering study of alpha-synuclein from human red blood cells

    PubMed Central

    Araki, Katsuya; Yagi, Naoto; Nakatani, Rie; Sekiguchi, Hiroshi; So, Masatomo; Yagi, Hisashi; Ohta, Noboru; Nagai, Yoshitaka; Goto, Yuji; Mochizuki, Hideki

    2016-01-01

    α-synuclein (α-syn) is the main component of Lewy bodies, which are neuropathological hallmarks of patients with Parkinson’s disease. As it has been controversial whether human α-syn from erythrocytes exists as a tetramer under physiological conditions, we tried solving this issue by the small-angle X-ray solution scattering method. Under two different conditions (high ionic strength with a Tris buffer and low ionic strength with an ammonium acetate buffer), no evidence was found for the presence of tetramer. When comparing erythrocyte and recombinant α-syn molecules, we found no significant difference of the molecular weight and the secondary structure although the buffer conditions strongly affect the radius of gyration of the protein. The results indicate that, even though a stable tetramer may not be formed, conformation of α-syn depends much on its environment, which may be the reason for its tendency to aggregate in cells. PMID:27469540

  9. Early nucleation events in the polymerization of actin, probed by time-resolved small-angle x-ray scattering

    PubMed Central

    Oda, Toshiro; Aihara, Tomoki; Wakabayashi, Katsuzo

    2016-01-01

    Nucleators generating new F-actin filaments play important roles in cell activities. Detailed information concerning the events involved in nucleation of actin alone in vitro is fundamental to understanding these processes, but such information has been hard to come by. We addressed the early process of salt-induced polymerization of actin using the time-resolved synchrotron small-angle X-ray scattering (SAXS). Actin molecules in low salt solution maintain a monomeric state by an electrostatic repulsive force between molecules. On mixing with salts, the repulsive force was rapidly screened, causing an immediate formation of many of non-polymerizable dimers. SAXS kinetic analysis revealed that tetramerization gives the highest energetic barrier to further polymerization, and the major nucleation is the formation of helical tetramers. Filaments start to grow rapidly with the formation of pentamers. These findings suggest an acceleration mechanism of actin assembly by a variety of nucleators in cells. PMID:27775032

  10. X-ray magnetic circular dichroism and small angle neutron scattering study of thiol capped gold nanoparticles.

    SciTech Connect

    de la Venta, J.; Bouzas, V.; Pucci, A.; Laguna-Marco, M. A.; Haskel, D.; Pinel, E. F.; te Velthuis, S. G. E.; Hoffmann, A.; Lal, J.; Bleuel, M.; Ruggeri, G.; de Julian, C.; Garcia, M. A.; Univ. Complutense de Madrid; Inst. de Magnetismo Aplicado UCM; Univ. Pisa; Univ. di Padova

    2009-11-01

    X-ray magnetic circular dichroism (XMCD) and Small Angle Neutron Scattering (SANS) measurements were performed on thiol capped Au nanoparticles (NPs) embedded into polyethylene. An XMCD signal of 0.8 {center_dot} 10{sup -4} was found at the Au L{sub 3} edge of thiol capped Au NPs embedded in a polyethylene matrix for which Superconducting Quantum Interference Device (SQUID) magnetometry yielded a saturation magnetization, M{sub s}, of 0.06 emu/g{sub Au}. SANS measurements showed that the 3.2 nm average-diameter nanoparticles are 28% polydispersed, but no detectable SANS magnetic signal was found with the resolution and sensitivity accessible with the neutron experiment. A comparison with previous experiments carried out on Au NPs and multilayers, yield to different values between XMCD signals and magnetization measured by SQUID magnetometer. We discuss the origin of those differences.

  11. Beyond simple small-angle X-ray scattering: developments in online complementary techniques and sample environments

    PubMed Central

    Bras, Wim; Koizumi, Satoshi; Terrill, Nicholas J

    2014-01-01

    Small- and wide-angle X-ray scattering (SAXS, WAXS) are standard tools in materials research. The simultaneous measurement of SAXS and WAXS data in time-resolved studies has gained popularity due to the complementary information obtained. Furthermore, the combination of these data with non X-ray based techniques, via either simultaneous or independent measurements, has advanced understanding of the driving forces that lead to the structures and morphologies of materials, which in turn give rise to their properties. The simultaneous measurement of different data regimes and types, using either X-rays or neutrons, and the desire to control parameters that initiate and control structural changes have led to greater demands on sample environments. Examples of developments in technique combinations and sample environment design are discussed, together with a brief speculation about promising future developments. PMID:25485128

  12. A combined small- and wide-angle x-ray scattering detector for measurements on reactive systems

    NASA Astrophysics Data System (ADS)

    Vallenhag, Linda; Canton, Sophie E.; Sondhauss, Peter; Haase, Dörthe; Ossler, Frederik

    2011-08-01

    A detector with high dynamic range designed for combined small- and wide-angle x-ray scattering experiments has been developed. It allows measurements on single events and reactive systems, such as particle formation in flames and evaporation of levitating drops. The detector consists of 26 channels covering a region from 0.5° to 60° and it provides continuous monitoring of the sampled signal without readout dead time. The time resolution for fast single events is about 40 μs and for substances undergoing slower dynamics, the time resolution is set to 0.1 or 1 s with hours of continuous sampling. The detector has been used to measure soot particle formation in a flame, burning magnesium and evaporation of a toluene drop in a levitator. The results show that the detector can be used for many different applications with good outcomes and large potential.

  13. In situ Electrochemical Small-Angle Neutron Scattering (eSANS) for Quantitative Structure and Redox Properties of Nanoparticles.

    PubMed

    Prabhu, Vivek M; Reipa, Vytas

    2012-03-01

    The rapid growth in nanomaterial applications have revealed limitations in available physicochemical characterization methods. An in situ electrochemical small-angle neutron scattering (eSANS) methodology was devised that enables direct measurements of nanomaterial dispersion structure while undergoing reduction-oxidation (redox) reactions at the vitreous carbon electrode. Furthermore, these porous electrodes are amenable to contrast-variant neutron scattering strategies to measure nanoparticle structure and polymer conformation in multicomponent systems. The eSANS method was tested for feasibility by characterizing ZnO nanoparticles in 50 mmol/L NaCl deuterium oxide solution undergoing bulk electrolysis at negative potentials. Irreversible nanoparticle structural changes are observed during the potential cycle. The complete reduction of Zn(2+) to Zn(0) nanoparticles is unlikely, but a peak in the characteristic correlation length occurs during the redox bias with reduced average characteristic size.

  14. Dipolar structures in magnetite ferrofluids studied with small-angle neutron scattering with and without applied magnetic field.

    PubMed

    Klokkenburg, M; Erné, B H; Wiedenmann, A; Petukhov, A V; Philipse, A P

    2007-05-01

    Field-induced structure formation in a ferrofluid with well-defined magnetite nanoparticles with a permanent magnetic dipole moment was studied with small-angle neutron scattering (SANS) as a function of the magnetic interactions. The interactions were tuned by adjusting the size of the well-defined, single-magnetic-domain magnetite (Fe3O4) particles and by applying an external magnetic field. For decreasing particle dipole moments, the data show a progressive distortion of the hexagonal symmetry, resulting from the formation of magnetic sheets. The SANS data show qualitative agreement with recent cryogenic transmission electron microscopy results obtained in 2D [Klokkenburg, Phys. Rev. Lett. 97, 185702 (2006)] on the same ferrofluids. PMID:17677066

  15. The study of the structural properties of very low viscosity sodium alginate by small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Badita, C. R.; Aranghel, D.; Radulescu, A.; Anitas, E. M.

    2016-03-01

    Sodium alginate is a linear polymer extract from brown algae and it is used in the biomedical, food, cosmetics and pharmaceutical industries as solution property modifiers and gelling agents. But despite the extensive studies of the alginate gelation process, still some fundamental questions remain unresolved. The fractal behavior of very low viscosity sodium alginate solutions and their influence on the critical gelation of alginate induced by Ca2+ ions were investigated using Small-Angle Neutron Scattering (SANS) measurements. SANS data are interpreted using both standard linear plots and the Beaucage model. The scattering intensity is dependent by alginate concentration and Ca2+ concentration. From a critical concentration of 1.0 % w/w our polymer swelled forming spherical structures with rough surfaces. Also the addition of the salt induces the collapse and the appearance of the aggregation and clusters formation.

  16. A small-angle X-ray scattering study of alpha-synuclein from human red blood cells.

    PubMed

    Araki, Katsuya; Yagi, Naoto; Nakatani, Rie; Sekiguchi, Hiroshi; So, Masatomo; Yagi, Hisashi; Ohta, Noboru; Nagai, Yoshitaka; Goto, Yuji; Mochizuki, Hideki

    2016-01-01

    α-synuclein (α-syn) is the main component of Lewy bodies, which are neuropathological hallmarks of patients with Parkinson's disease. As it has been controversial whether human α-syn from erythrocytes exists as a tetramer under physiological conditions, we tried solving this issue by the small-angle X-ray solution scattering method. Under two different conditions (high ionic strength with a Tris buffer and low ionic strength with an ammonium acetate buffer), no evidence was found for the presence of tetramer. When comparing erythrocyte and recombinant α-syn molecules, we found no significant difference of the molecular weight and the secondary structure although the buffer conditions strongly affect the radius of gyration of the protein. The results indicate that, even though a stable tetramer may not be formed, conformation of α-syn depends much on its environment, which may be the reason for its tendency to aggregate in cells. PMID:27469540

  17. Grazing incidence small angle X-ray scattering study of silver nanoparticles in ion-exchanged glasses

    NASA Astrophysics Data System (ADS)

    Cheng, Weidong; Wu, Zhaojun; Gu, Xiaohua; Xing, Xueqing; Mo, Guang; Wu, Zhonghua

    2015-05-01

    The size and distribution of silver nanoparticles in ion-exchanged silicate glass induced by thermal treatments in air at different temperatures were investigated by means of grazing incidence small angle X-ray scattering technique, X-ray diffraction and optical absorption spectra. Silver-sodium ion exchange of soda-lime silicate glasses was done at 350 °C for 240 min, then the samples were treated by thermal annealing in air at different temperatures 400, 500 and 550 °C, respectively, for 1 h. After the annealing treatment above 400 °C for 1 h, smaller Ag nanoparticles occurred, together with bigger ones. Both dissolution of smaller Ag nanoparticles and diffusion of larger ones are discussed in these stages of annealing in this contribution.

  18. A combined small- and wide-angle x-ray scattering detector for measurements on reactive systems.

    PubMed

    Vallenhag, Linda; Canton, Sophie E; Sondhauss, Peter; Haase, Dörthe; Ossler, Frederik

    2011-08-01

    A detector with high dynamic range designed for combined small- and wide-angle x-ray scattering experiments has been developed. It allows measurements on single events and reactive systems, such as particle formation in flames and evaporation of levitating drops. The detector consists of 26 channels covering a region from 0.5° to 60° and it provides continuous monitoring of the sampled signal without readout dead time. The time resolution for fast single events is about 40 μs and for substances undergoing slower dynamics, the time resolution is set to 0.1 or 1 s with hours of continuous sampling. The detector has been used to measure soot particle formation in a flame, burning magnesium and evaporation of a toluene drop in a levitator. The results show that the detector can be used for many different applications with good outcomes and large potential.

  19. Dipolar structures in magnetite ferrofluids studied with small-angle neutron scattering with and without applied magnetic field

    SciTech Connect

    Klokkenburg, M.; Erne, B. H.; Petukhov, A. V.; Philipse, A. P.; Wiedenmann, A.

    2007-05-15

    Field-induced structure formation in a ferrofluid with well-defined magnetite nanoparticles with a permanent magnetic dipole moment was studied with small-angle neutron scattering (SANS) as a function of the magnetic interactions. The interactions were tuned by adjusting the size of the well-defined, single-magnetic-domain magnetite (Fe{sub 3}O{sub 4}) particles and by applying an external magnetic field. For decreasing particle dipole moments, the data show a progressive distortion of the hexagonal symmetry, resulting from the formation of magnetic sheets. The SANS data show qualitative agreement with recent cryogenic transmission electron microscopy results obtained in 2D [Klokkenburg et al., Phys. Rev. Lett. 97, 185702 (2006)] on the same ferrofluids.

  20. Distribution of Sulfur in Carbon/Sulfur Nanocomposites Analyzed by Small-Angle X-ray Scattering.

    PubMed

    Petzold, Albrecht; Juhl, Anika; Scholz, Jonas; Ufer, Boris; Goerigk, Günter; Fröba, Michael; Ballauff, Matthias; Mascotto, Simone

    2016-03-22

    The analysis of sulfur distribution in porous carbon/sulfur nanocomposites using small-angle X-ray scattering (SAXS) is presented. Ordered porous CMK-8 carbon was used as the host matrix and gradually filled with sulfur (20-50 wt %) via melt impregnation. Owing to the almost complete match between the electron densities of carbon and sulfur, the porous nanocomposites present in essence a two-phase system and the filling of the host material can be precisely followed by this method. The absolute scattering intensities normalized per unit of mass were corrected accounting for the scattering contribution of the turbostratic microstructure of carbon and amorphous sulfur. The analysis using the Porod parameter and the chord-length distribution (CLD) approach determined the specific surface areas and filling mechanism of the nanocomposite materials, respectively. Thus, SAXS provides comprehensive characterization of the sulfur distribution in porous carbon and valuable information for a deeper understanding of cathode materials of lithium-sulfur batteries.

  1. Morphology of crystalline–amorphous olefin block copolymers in solution characterized by small-angle neutron scattering and microscopy

    PubMed Central

    Radulescu, Aurel; Goerigk, Günter; Fetters, Lewis; Richter, Dieter

    2015-01-01

    The single-chain properties and self-assembly behavior in dilute solution of olefin block copolymers obtained by chain-shuttling technology and consisting of alternating crystallizable and amorphous ethylene/1-octene blocks were investigated by pinhole and focusing small-angle neutron scattering techniques, optical microscopy in bright-field and crossed-polarizer modes, and differential scanning calorimetry. The complex hydrocarbon soluble (precipitant free) macro-aggregates formed with decreasing temperature are characterized by spherulitic textures. The spherulites yield, on one hand, a morphology that depends on the chain structure properties and, on the other hand, multiple structural levels with a hierarchical organization that ranges from 10 Å up to tens of micrometres. This morphology displays peculiarities dictated by the polydisperse character of these materials. PMID:26664344

  2. Beyond simple small-angle X-ray scattering: developments in online complementary techniques and sample environments.

    PubMed

    Bras, Wim; Koizumi, Satoshi; Terrill, Nicholas J

    2014-11-01

    Small- and wide-angle X-ray scattering (SAXS, WAXS) are standard tools in materials research. The simultaneous measurement of SAXS and WAXS data in time-resolved studies has gained popularity due to the complementary information obtained. Furthermore, the combination of these data with non X-ray based techniques, via either simultaneous or independent measurements, has advanced understanding of the driving forces that lead to the structures and morphologies of materials, which in turn give rise to their properties. The simultaneous measurement of different data regimes and types, using either X-rays or neutrons, and the desire to control parameters that initiate and control structural changes have led to greater demands on sample environments. Examples of developments in technique combinations and sample environment design are discussed, together with a brief speculation about promising future developments.

  3. [The author's principles for treating small angle scoliosis in view of current concepts about scoliosis etiology and pathogenesis].

    PubMed

    Malawski, S

    1994-01-01

    Hypothetical assumption, based on phylogenetic, anatomical and epidemiological studies as well as on clinical findings led the author to the conclusion, that regardless of an etiologic factor and the duration of its action the chief determinant for preserving the curve is the contracture of the short muscles and ligaments of the spine backed by scoliosis action of the long spinal muscles. Taking this into consideration the author has developed a method for small angle scolioses treatment by means of gravitational counteraction and removal of mainly ligamentous contracture of the spine. That can be accomplished by flexion-rotation exercises supplemented by "segmental gymnastics". The principles are validated by 30 years of clinical experience and advantageous results. PMID:7555343

  4. Small-angle X-ray scattering study on pectin-chitosan mixed solutions and thermoreversible gels.

    PubMed

    Ventura, Irit; Bianco-Peled, Havazelet

    2015-06-01

    Hot solutions containing pectin and chitosan with pectin weight fraction of 0.75, in acidic pH, demonstrate gelation occurring upon cooling to room temperature. This study explores the origin of this gelation using small angle X-ray scattering (SAXS) as the main experimental tool. Modeling SAXS patterns revealed rigid rod conformation in chitosan solutions, whereas pectin formed a self-avoiding chain. In addition, nanometric aggregates were detected in pectin solutions. Pectin and chitosan in mixed solutions adopted a similar semiflexible conformation. The only sample that created a visually stable gel displayed a different pattern, characteristic to polymers gels. Manipulating the composition by adding urea and salts highlighted the important role of hydrogen bonding, which governs the gelation mechanism. Nevertheless, electrostatic interactions were also found to take part in the gelation. To the best of our knowledge, this is the first comprehensive and systematic SAXS study on these pectin-chitosan mixtures.

  5. Characterization of oligomerization of a peptide from the ebola virus glycoprotein by small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Egorov, V. V.; Gorshkov, A. N.; Murugova, T. N.; Vasin, A. V.; Lebedev, D. V.; Isaev-Ivanov, V. V.; Kiselev, O. I.

    2016-01-01

    Transmission electron microscopy (TEM) and small-angle neutron scattering (SANS) studies showed that model peptides QNALVCGLRQ (G33) and QNALVCGLRG (G31) corresponding to region 551-560 of the GP protein of the Sudan Ebola virus are prone to oligomerization in solution. Both peptides can form amyloid-like fibrills. The G33 peptide forms fibrils within one day of incubation, whereas the fibrillogenesis of the G31 peptide is observed only after incubation for several months. The possible role of the observed processes in the pathogenesis and the possibility of applying a combination of the TEM and SANS techniques to search for new compounds that are able to influence the protein oligomerization are discussed.

  6. Guinier peak analysis for visual and automated inspection of small-angle X-ray scattering data

    PubMed Central

    Putnam, Christopher D.

    2016-01-01

    The Guinier region in small-angle X-ray scattering (SAXS) defines the radius of gyration, R g, and the forward scattering intensity, I(0). In Guinier peak analysis (GPA), the plot of qI(q) versus q 2 transforms the Guinier region into a characteristic peak for visual and automated inspection of data. Deviations of the peak position from the theoretical position in dimensionless GPA plots can suggest parameter errors, problematic low-resolution data, some kinds of intermolecular interactions or elongated scatters. To facilitate automated analysis by GPA, the elongation ratio (ER), which is the ratio of the areas in the pair-distribution function P(r) after and before the P(r) maximum, was characterized; symmetric samples have ER values around 1, and samples with ER values greater than 5 tend to be outliers in GPA analysis. Use of GPA+ER can be a helpful addition to SAXS data analysis pipelines. PMID:27738411

  7. Exploring the melting of a semirigid-chain polymer with temperature-resolved small-angle X-ray scattering.

    PubMed

    Ivanov, D A; Hocquet, S; Dosiére, M; Koch, M H J

    2004-04-01

    The thermal behavior of semirigid semicrystalline polymers differs significantly from that of flexible-chain polymers. The origin of the differences is believed to lie in the higher energy expenditure associated with the formation of adjacent re-entry folds at the crystalline surface in the case of semirigid chains. The effect of constraints imposed by the interlamellar amorphous regions on the neighboring crystals was studied with temperature-resolved synchrotron radiation small-angle X-ray scattering (SAXS). The analysis of SAXS patterns with a generalized paracrystalline lamellar stack model indicates that melting of a semirigid-chain polymer is not a random process but that the crystals grown in the smallest amorphous gaps melt first. This suggests that the hitherto largely neglected geometrical confinement effects may play an important role in determining the thermodynamic stability of semirigid-chain polymer crystals.

  8. Spin waves in full-polarized state of Dzyaloshinskii-Moriya helimagnets: Small-angle neutron scattering study

    NASA Astrophysics Data System (ADS)

    Grigoriev, S. V.; Sukhanov, A. S.; Altynbaev, E. V.; Siegfried, S.-A.; Heinemann, A.; Kizhe, P.; Maleyev, S. V.

    2015-12-01

    We develop the technique to study the spin-wave dynamics of the full-polarized state of the Dzyaloshinskii-Moriya helimagnets by polarized small-angle neutron scattering. We have experimentally proven that the spin-waves dispersion in this state has the anisotropic form. We show that the neutron scattering image displays a circle with a certain radius which is centered at the momentum transfer corresponding to the helix wave vector in helimagnetic phase ks, which is oriented along the applied magnetic field H . The radius of this circle is directly related to the spin-wave stiffness of this system. This scattering depends on the neutron polarization showing the one-handed nature of the spin waves in Dzyaloshinskii-Moriya helimagnets in the full-polarized phase. We show that the spin-wave stiffness A for MnSi helimagnet decreased twice as the temperature increases from zero to the critical temperature Tc.

  9. Comparison of the Behavior of Polymers in Supercritical Fluids and Organic Solvents Via Small Angle Neutron Scattering

    SciTech Connect

    Melnichenko, Y.B.; Kiran, E.; Heath, K.D.; Salaniwal, S.; Cochran, H.D.; Stamm, M.; Van Hook, W.A.; Wignall, G.D.

    1999-05-17

    Small-angle neutron scattering has been used to study the effect of temperature and pressure on the phase behavior of semidilute solutions of polymers dissolved in organic and supercritical solvents. Above the theta temperature (To), these systems exhibit a ''good solvent'' domain, where the molecules expand beyond the unperturbed dimensions in both organic solvents and in COZ. However, this transition can be made to occur at a critical ''theta pressure'' (PO) in CO2 and this represents a new concept in the physics of polymer-solvent systems. For T < To, and P < Po, the system enters the ''poor solvent'' domain where diverging concentration fluctuations prevent the chains from collapsing and allow them to maintain their unperturbed dimensions.

  10. Magnetic vortex lattice in HgBa2CuO4+δ observed by small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Egetenmeyer, N.; Gavilano, J. L.; Barišić, N.; Greven, M.

    2011-02-01

    We report the direct observation of the magnetic vortex lattice in the model high-temperature superconductor HgBa2CuO4+δ. Using small-angle neutron scattering on high-quality crystals, we observe two equal domains of undistorted triangular vortex lattices well aligned with the tetragonal crystallographic axes. The signal decreases rapidly with increasing magnetic field and vanishes above 0.4 T, which we attribute to a crossover from a three-dimensional to a two-dimensional vortex system, similar to previous results for the more anisotropic compound Bi2.15Sr1.95CaCu2O8+δ. Our result indicates that a triangular vortex lattice (with or without distortion) at low magnetic fields is a generic property of cuprates with critical temperatures above 80 K.

  11. Effect of surfactant excess on the stability of low-polarity ferrofluids probed by small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Petrenko, V. I.; Avdeev, M. V.; Bulavin, L. A.; Almasy, L.; Grigoryeva, N. A.; Aksenov, V. L.

    2016-01-01

    The structures of ferrofluids (FFs) based on nonpolar solvent decahydronaphthalene, stabilized by saturated monocarboxylic acids with hydrocarbon chains of different lengths, C16 (palmitic acid) and ?12 (lauric acid), with an excess of acid molecules, have been studied by small-angle neutron scattering. It is found that the addition of acid to an initially stable system with optimal composition leads to more significant structural changes (related to aggregation) than those observed previously for this class of FFs. A comparison of the influence of monocarboxylic acids on the stability of nonpolar FFs suggests that the enhancement of aggregation is much more pronounced in the case of palmitic acid excess. This fact confirms the conclusion of previous studies, according to which an increase in the hydrocarbon chain length in a saturated acid reduces the efficiency of the corresponding FF stabilization.

  12. Conformational landscape of cytochrome c folding studied by microsecond-resolved small-angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Akiyama, Shuji; Takahashi, Satoshi; Kimura, Tetsunari; Ishimori, Koichiro; Morishima, Isao; Nishikawa, Yukihiro; Fujisawa, Tetsuro

    2002-02-01

    To investigate protein folding dynamics in terms of compactness, we developed a continuous-flow mixing device to make small-angle x-ray scattering measurements with the time resolution of 160 μs and characterized the radius of gyration (Rg) of two folding intermediates of cytochrome c (cyt c). The early intermediate possesses 20 Å of Rg, which is smaller by 4 Å than that of the acid-unfolded state. The Rg of the later intermediate is ≈18 Å, which is close to that of the molten globule state. Considering the α-helix content (fH) of the intermediates, we clarified the folding pathway of cyt c on the conformational landscape defined by Rg and fH. Cyt c folding proceeds with a collapse around a specific region of the protein followed by a cooperative acquisition of secondary structures and compactness.

  13. Recent Development of a 36 meter Small-Angle Neutron Scattering BATAN Spectrometer (SMARTer) in Serpong Indonesia

    NASA Astrophysics Data System (ADS)

    Giri Rachman Putra, Edy; Bharoto; Seong, Baek Seok

    2010-10-01

    The 36 meter small-angle neutron scattering (SANS) spectrometer BATAN (SMARTer) in Serpong, Indonesia has been revitalised for several years. The work on replacing, upgrading and improving the control system and the experimental method were conducted in order to setup the spectrometer back in operation. Two main personal computers, one for handling and controlling the mechanical system and another one for acquiring neutron data were employed at the spectrometer. The standard and established SANS data reduction and analysis programs, such as GRASP and NIST Igor have been implemented to subtract the raw scattered neutron data with the backgrounds and then analyse the corrected data. The scattering data of ferrofluids samples, Fe3O4 and MnZnFe2O4 have been obtained using SANS spectrometers in BATAN Serpong, Indonesia and HANARO-KAERI, Republic of Korea for inter-laboratory comparison and investigation of proposed research interest. The results were comparable from both scattering data analysis.

  14. Small-angle neutron scattering reveals the assembly mode and oligomeric architecture of TET, a large, dodecameric aminopeptidase

    SciTech Connect

    Appolaire, Alexandre; Girard, Eric; Colombo, Matteo; Durá, M. Asunción; Moulin, Martine; Härtlein, Michael; Franzetti, Bruno; Gabel, Frank

    2014-11-01

    The present work illustrates that small-angle neutron scattering, deuteration and contrast variation, combined with in vitro particle reconstruction, constitutes a very efficient approach to determine subunit architectures in large, symmetric protein complexes. In the case of the 468 kDa heterododecameric TET peptidase machine, it was demonstrated that the assembly of the 12 subunits is a highly controlled process and represents a way to optimize the catalytic efficiency of the enzyme. The specific self-association of proteins into oligomeric complexes is a common phenomenon in biological systems to optimize and regulate their function. However, de novo structure determination of these important complexes is often very challenging for atomic-resolution techniques. Furthermore, in the case of homo-oligomeric complexes, or complexes with very similar building blocks, the respective positions of subunits and their assembly pathways are difficult to determine using many structural biology techniques. Here, an elegant and powerful approach based on small-angle neutron scattering is applied, in combination with deuterium labelling and contrast variation, to elucidate the oligomeric organization of the quaternary structure and the assembly pathways of 468 kDa, hetero-oligomeric and symmetric Pyrococcus horikoshii TET2–TET3 aminopeptidase complexes. The results reveal that the topology of the PhTET2 and PhTET3 dimeric building blocks within the complexes is not casual but rather suggests that their quaternary arrangement optimizes the catalytic efficiency towards peptide substrates. This approach bears important potential for the determination of quaternary structures and assembly pathways of large oligomeric and symmetric complexes in biological systems.

  15. Monitoring intermediate filament assembly by small-angle x-ray scattering reveals the molecular architecture of assembly intermediates

    PubMed Central

    Sokolova, Anna V.; Kreplak, Laurent; Wedig, Tatjana; Mücke, Norbert; Svergun, Dmitri I.; Herrmann, Harald; Aebi, Ueli; Strelkov, Sergei V.

    2006-01-01

    Intermediate filaments (IFs), along with microtubules, microfilaments, and associated cross-bridging proteins, constitute the cytoskeleton of metazoan cells. While crystallographic data on the dimer representing the elementary IF “building block” have recently become available, little structural detail is known about both the mature IF architecture and its assembly pathway. Here, we have applied solution small-angle x-ray scattering to investigate the in vitro assembly of a 53-kDa human IF protein vimentin at pH 8.4 by systematically varying the ionic strength conditions, and complemented these experiments by electron microscopy and analytical ultracentrifugation. While a vimentin solution in 5 mM Tris·HCl (pH 8.4) contains predominantly tetramers, addition of 20 mM NaCl induces further lateral assembly evidenced by the shift of the sedimentation coeficient and yields a distinct octameric intermediate. Four octamers eventually associate into unit-length filaments (ULFs) that anneal longitudinally. Based on the small-angle x-ray scattering experiments supplemented by crystallographic data and additional structural constraints, 3D molecular models of the vimentin tetramer, octamer, and ULF were constructed. Within each of the three oligomers, the adjacent dimers are aligned exclusively in an approximately half-staggered antiparallel A11 mode with a distance of 3.2–3.4 nm between their axes. The ULF appears to be a dynamic and a relatively loosely packed structure with a roughly even mass distribution over its cross-section. PMID:17050693

  16. Study of thermally and chemically unfolded conformations of a small β-protein by means of small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Russo, D.; Durand, D.; Desmadril, M.; Calmettes, P.

    2000-03-01

    Small-angle neutron scattering experiments shows that the unfolded conformation of neocarzinostatin heated at 78°C is different from that obtained with 5 M guanidinium chloride at 12°C. The values of the second virial coefficient of the protein solutions indicates that the interactions between the polypeptide chain and the solvent are different for the thermally and the chemically unfolded states. In the first case the protein conformation is like that of an ideal chain whereas it is similar to an excluded volume chain in the second one. The corresponding values of the contour length, the statistical length, and the apparent radius of the chain cross-section are given.

  17. Small-Angle X-ray Scattering Demonstrates Similar Nanostructure in Cortical Bone from Young Adult Animals of Different Species.

    PubMed

    Kaspersen, Jørn Døvling; Turunen, Mikael Juhani; Mathavan, Neashan; Lages, Sebastian; Pedersen, Jan Skov; Olsson, Ulf; Isaksson, Hanna

    2016-07-01

    Despite the vast amount of studies focusing on bone nanostructure that have been performed for several decades, doubts regarding the detailed structure of the constituting hydroxyapatite crystal still exist. Different experimental techniques report somewhat different sizes and locations, possibly due to different requirements for the sample preparation. In this study, small- and wide-angle X-ray scattering is used to investigate the nanostructure of femur samples from young adult ovine, bovine, porcine, and murine cortical bone, including three different orthogonal directions relative to the long axis of the bone. The radially averaged scattering from all samples reveals a remarkable similarity in the entire q range, which indicates that the nanostructure is essentially the same in all species. Small differences in the data from different directions confirm that the crystals are elongated in the [001] direction and that this direction is parallel to the long axis of the bone. A model consisting of thin plates is successfully employed to describe the scattering and extract the plate thicknesses, which are found to be in the range of 20-40 Å for most samples but 40-60 Å for the cow samples. It is demonstrated that the mineral plates have a large degree of polydispersity in plate thickness. Additionally, and equally importantly, the scattering data and the model are critically evaluated in terms of model uncertainties and overall information content.

  18. Fast, quantitative, and nondestructive evaluation of hydrided LWR fuel cladding by small angle incoherent neutron scattering of hydrogen

    NASA Astrophysics Data System (ADS)

    Yan, Y.; Qian, S.; Littrell, K.; Parish, C. M.; Plummer, L. K.

    2015-05-01

    A nondestructive neutron scattering method to precisely measure the uptake of hydrogen and the distribution of hydride precipitates in light water reactor (LWR) fuel cladding was developed. Zircaloy-4 cladding used in commercial LWRs was used to produce hydrided specimens. The hydriding apparatus consists of a closed stainless-steel vessel that contains Zr alloy specimens and hydrogen gas. Following hydrogen charging, the hydrogen content of the hydrided specimens was measured using the vacuum hot extraction method, by which the samples with desired hydrogen concentrations were selected for the neutron study. Optical microscopy shows that our hydriding procedure results in uniform distribution of circumferential hydrides across the wall thickness. Small angle neutron incoherent scattering was performed in the High Flux Isotope Reactor at Oak Ridge National Laboratory. Our study demonstrates that the hydrogen in commercial Zircaloy-4 cladding can be measured very accurately in minutes by this nondestructive method over a wide range of hydrogen concentrations from a very small amount (≈20 ppm) to over 1000 ppm. The hydrogen distribution in a tube sample was obtained by scaling the neutron scattering rate with a factor determined by a calibration process using standard, destructive direct chemical analysis methods on the specimens. This scale factor can be used in future tests with unknown hydrogen concentrations, thus providing a nondestructive method for determining absolute hydrogen concentrations.

  19. Small-Angle Neutron Scattering and Neutron Spin Echo Characterization of Monoclonal Antibody Self-Associations at High Concentrations

    NASA Astrophysics Data System (ADS)

    Yearley, Eric; Zarraga, Isidro (Dan); Godfrin, Paul (Doug); Perevozchikova, Tatiana; Wagner, Norman; Liu, Yun

    2013-03-01

    Concentrated therapeutic protein formulations offer numerous delivery and stability challenges. In particular, it has been found that several therapeutic proteins exhibit a large increase in viscosity as a function of concentration that may be dependent on the protein-protein interactions. Small-Angle Neutron Scattering (SANS) and Neutron Spin Echo (NSE) investigations have been performed to probe the protein-protein interactions and diffusive properties of highly concentrated MAbs. The SANS data demonstrate that the inter-particle interactions for a highly viscous MAb at high concentrations (MAb1) are highly attractive, anisotropic and change significantly with concentration while the viscosity and interactions do not differ considerably for MAb2. The NSE results furthermore indicate that MAb1 and MAb2 have strong concentration dependencies of dynamics at high Q that are correlated to the translational motion of the proteins. Finally, it has also been revealed that the individual MAb1 proteins form small clusters at high concentrations in contrast to the MAb2 proteins, which are well-dispersed. It is proposed that the formation of these clusters is the primary cause of the dramatic increase in viscosity of MAb1 in crowded or concentrated environments.

  20. Methods for analysis of size-exclusion chromatography–small-angle X-ray scattering and reconstruction of protein scattering

    PubMed Central

    Malaby, Andrew W.; Chakravarthy, Srinivas; Irving, Thomas C.; Kathuria, Sagar V.; Bilsel, Osman; Lambright, David G.

    2015-01-01

    Size-exclusion chromatography in line with small-angle X-ray scattering (SEC–SAXS) has emerged as an important method for investigation of heterogeneous and self-associating systems, but presents specific challenges for data processing including buffer subtraction and analysis of overlapping peaks. This paper presents novel methods based on singular value decomposition (SVD) and Guinier-optimized linear combination (LC) to facilitate analysis of SEC–SAXS data sets and high-quality reconstruction of protein scattering directly from peak regions. It is shown that Guinier-optimized buffer subtraction can reduce common subtraction artifacts and that Guinier-optimized linear combination of significant SVD basis components improves signal-to-noise and allows reconstruction of protein scattering, even in the absence of matching buffer regions. In test cases with conventional SAXS data sets for cytochrome c and SEC–SAXS data sets for the small GTPase Arf6 and the Arf GTPase exchange factors Grp1 and cytohesin-1, SVD–LC consistently provided higher quality reconstruction of protein scattering than either direct or Guinier-optimized buffer subtraction. These methods have been implemented in the context of a Python-extensible Mac OS X application known as Data Evaluation and Likelihood Analysis (DELA), which provides convenient tools for data-set selection, beam intensity normalization, SVD, and other relevant processing and analytical procedures, as well as automated Python scripts for common SAXS analyses and Guinier-optimized reconstruction of protein scattering. PMID:26306089

  1. Small-Angle X-ray Scattering Demonstrates Similar Nanostructure in Cortical Bone from Young Adult Animals of Different Species.

    PubMed

    Kaspersen, Jørn Døvling; Turunen, Mikael Juhani; Mathavan, Neashan; Lages, Sebastian; Pedersen, Jan Skov; Olsson, Ulf; Isaksson, Hanna

    2016-07-01

    Despite the vast amount of studies focusing on bone nanostructure that have been performed for several decades, doubts regarding the detailed structure of the constituting hydroxyapatite crystal still exist. Different experimental techniques report somewhat different sizes and locations, possibly due to different requirements for the sample preparation. In this study, small- and wide-angle X-ray scattering is used to investigate the nanostructure of femur samples from young adult ovine, bovine, porcine, and murine cortical bone, including three different orthogonal directions relative to the long axis of the bone. The radially averaged scattering from all samples reveals a remarkable similarity in the entire q range, which indicates that the nanostructure is essentially the same in all species. Small differences in the data from different directions confirm that the crystals are elongated in the [001] direction and that this direction is parallel to the long axis of the bone. A model consisting of thin plates is successfully employed to describe the scattering and extract the plate thicknesses, which are found to be in the range of 20-40 Å for most samples but 40-60 Å for the cow samples. It is demonstrated that the mineral plates have a large degree of polydispersity in plate thickness. Additionally, and equally importantly, the scattering data and the model are critically evaluated in terms of model uncertainties and overall information content. PMID:26914607

  2. Fast, quantitative, and nondestructive evaluation of hydrided LWR fuel cladding by small angle incoherent neutron scattering of hydrogen

    SciTech Connect

    Yan, Y.; Qian, S.; Littrell, K.; Parish, C. M.; Plummer, L. K.

    2015-02-13

    A non-destructive neutron scattering method to precisely measure the uptake of hydrogen and the distribution of hydride precipitates in light water reactor (LWR) fuel cladding was developed. Zircaloy-4 cladding used in commercial LWRs was used to produce hydrided specimens. The hydriding apparatus consists of a closed stainless steel vessel that contains Zr alloy specimens and hydrogen gas. Following hydrogen charging, the hydrogen content of the hydrided specimens was measured using the vacuum hot extraction method, by which the samples with desired hydrogen concentration were selected for the neutron study. Optical microscopy shows that our hydriding procedure results in uniform distribution of circumferential hydrides across the wall. Small angle neutron incoherent scattering was performed in the High Flux Isotope Reactor at Oak Ridge National Laboratory. This study demonstrates that the hydrogen in commercial Zircaloy-4 cladding can be measured very accurately in minutes by this nondestructive method over a wide range of hydrogen concentrations from a very small amount ( 20 ppm) to over 1000 ppm. The hydrogen distribution in a tube sample was obtained by scaling the neutron scattering rate with a factor determined by a calibration process using standard, destructive direct chemical analysis methods on the specimens. This scale factor will be used in future tests with unknown hydrogen concentrations, thus providing a nondestructive method for absolute hydrogen concentration determination.

  3. Fast, quantitative, and nondestructive evaluation of hydrided LWR fuel cladding by small angle incoherent neutron scattering of hydrogen

    DOE PAGES

    Yan, Y.; Qian, S.; Littrell, K.; Parish, C. M.; Plummer, L. K.

    2015-02-13

    A non-destructive neutron scattering method to precisely measure the uptake of hydrogen and the distribution of hydride precipitates in light water reactor (LWR) fuel cladding was developed. Zircaloy-4 cladding used in commercial LWRs was used to produce hydrided specimens. The hydriding apparatus consists of a closed stainless steel vessel that contains Zr alloy specimens and hydrogen gas. Following hydrogen charging, the hydrogen content of the hydrided specimens was measured using the vacuum hot extraction method, by which the samples with desired hydrogen concentration were selected for the neutron study. Optical microscopy shows that our hydriding procedure results in uniform distributionmore » of circumferential hydrides across the wall. Small angle neutron incoherent scattering was performed in the High Flux Isotope Reactor at Oak Ridge National Laboratory. This study demonstrates that the hydrogen in commercial Zircaloy-4 cladding can be measured very accurately in minutes by this nondestructive method over a wide range of hydrogen concentrations from a very small amount ( 20 ppm) to over 1000 ppm. The hydrogen distribution in a tube sample was obtained by scaling the neutron scattering rate with a factor determined by a calibration process using standard, destructive direct chemical analysis methods on the specimens. This scale factor will be used in future tests with unknown hydrogen concentrations, thus providing a nondestructive method for absolute hydrogen concentration determination.« less

  4. Measurement of carbon condensates using small-angle x-ray scattering during detonation of the high explosive hexanitrostilbene

    DOE PAGES

    Bagge-Hansen, M.; Lauderbach, L.; Hodgin, R.; Bastea, S.; Fried, L.; Jones, A.; van Buuren, T.; Hansen, D.; Benterou, J.; May, C.; et al

    2015-06-24

    In this study, the dynamics of carbon condensation in detonating high explosives remains controversial. Detonation model validation requires data for processes occurring at nanometer length scales on time scales ranging from nanoseconds to microseconds. A new detonation end station has been commissioned to acquire and provide time-resolved small-angle x-ray scattering (SAXS) from detonating explosives. Hexanitrostilbene (HNS) was selected as the first to investigate due to its ease of initiation using exploding foils and flyers, vacuum compatibility, high thermal stability, and stoichiometric carbon abundance that produces high carbon condensate yields. The SAXS data during detonation, collected with 300 ns time resolution,more » provide unprecedented signal fidelity over a broad q-range. This fidelity permits the first analysis of both the Guinier and Porod/power-law regions of the scattering profile during detonation, which contains information about the size and morphology of the resultant carbon condensate nanoparticles. To bolster confidence in these data, the scattering angle and intensity were additionally cross-referenced with a separate, highly calibrated SAXS beamline. The data show that HNS produces carbon particles with a radius of gyration of 2.7 nm in less than 400 ns after the detonation front has passed, and this size and morphology are constant over the next several microseconds. These data directly contradict previous pioneering work on RDX/TNT mixtures and TATB, where observations indicate significant particle growth (50% or more) continues over several microseconds. The power-law slope is about -3, which is consistent with a complex disordered, irregular, or folded sp2 sub-arrangement within a relatively monodisperse structure possessing radius of gyration of 2.7 nm after the detonation of HNS.« less

  5. Measurement of carbon condensation using small-angle x-ray scattering during detonation of the high explosive hexanitrostilbene

    SciTech Connect

    Bagge-Hansen, M.; Lauderbach, L. M.; Hodgin, R.; Bastea, S.; Fried, L.; Jones, A.; van Buuren, T.; Hansen, D.; Benterou, J.; May, C.; Graber, T.; Jensen, B. J.; Ilavsky, J.; Willey, T. M.

    2015-06-24

    The dynamics of carboncondensation in detonating high explosives remains controversial. Detonation model validation requires data for processes occurring at nanometer length scales on time scales ranging from nanoseconds to microseconds. A new detonation endstation has been commissioned to acquire and provide time-resolved small-angle x-ray scattering (SAXS) from detonating explosives. Hexanitrostilbene (HNS) was selected as the first to investigate due to its ease of initiation using exploding foils and flyers, vacuum compatibility, high thermal stability, and stoichiometric carbon abundance that produces high carbon condensate yields. The SAXS data during detonation, collected with 300 ns time resolution, provide unprecedented signal fidelity over a broad q-range. This fidelity permits the first analysis of both the Guinier and Porod/power-law regions of the scattering profile during detonation, which contains information about the size and morphology of the resultant carbon condensate nanoparticles. To bolster confidence in these data, the scattering angle and intensity were additionally cross-referenced with a separate, highly calibrated SAXS beamline. The data show that HNS produces carbon particles with a radius of gyration of 2.7 nm in less than 400 ns after the detonation front has passed, and this size and morphology are constant over the next several microseconds. These data directly contradict previous pioneering work on RDX/TNT mixtures and TATB, where observations indicate significant particle growth (50% or more) continues over several microseconds. As a result, the power-law slope is about –3, which is consistent with a complex disordered, irregular, or folded sp2 sub-arrangement within a relatively monodisperse structure possessing radius of gyration of 2.7 nm after the detonation of HNS.

  6. Studying nanostructure gradients in injection-molded polypropylene/montmorillonite composites by microbeam small-angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Stribeck, Norbert; Schneider, Konrad; Zeinolebadi, Ahmad; Li, Xuke; Sanporean, Catalina-Gabriela; Vuluga, Zina; Iancu, Stela; Duldner, Monica; Santoro, Gonzalo; Roth, Stephan V.

    2014-02-01

    The core-shell structure in oriented cylindrical rods of polypropylene (PP) and nanoclay composites (NCs) from PP and montmorillonite (MMT) is studied by microbeam small-angle x-ray scattering (SAXS). The structure of neat PP is almost homogeneous across the rod showing regular semicrystalline stacks. In the NCs the discrete SAXS of arranged crystalline PP domains is limited to a skin zone of 300 μm thickness. Even there only frozen-in primary lamellae are detected. The core of the NCs is dominated by diffuse scattering from crystalline domains placed at random. The SAXS of the MMT flakes exhibits a complex skin-core gradient. Both the direction of the symmetry axis and the apparent perfection of flake-orientation are varying. Thus there is no local fiber symmetry, and the structure gradient cannot be reconstructed from a scan across the full rod. To overcome the problem the rods are machined. Scans across the residual webs are performed. For the first time webs have been carved out in two principal directions. Comparison of the corresponding two sets of SAXS patterns demonstrates the complexity of the MMT orientation. Close to the surface (< 1 mm) the flakes cling to the wall. The variation of the orientation distribution widths indicates the presence of both MMT flakes and grains. The grains have not been oriented in the flowing melt. An empirical equation is presented which describes the variation from skin to core of one component of the inclination angle of flake-shaped phyllosilicate filler particles.

  7. Measurement of carbon condensates using small-angle x-ray scattering during detonation of the high explosive hexanitrostilbene

    SciTech Connect

    Bagge-Hansen, M.; Lauderbach, L.; Hodgin, R.; Bastea, S.; Fried, L.; Jones, A.; van Buuren, T.; Hansen, D.; Benterou, J.; May, C.; Graber, T.; Jensen, B. J.; Ilavsky, J.; Willey, T. M.

    2015-06-24

    In this study, the dynamics of carbon condensation in detonating high explosives remains controversial. Detonation model validation requires data for processes occurring at nanometer length scales on time scales ranging from nanoseconds to microseconds. A new detonation end station has been commissioned to acquire and provide time-resolved small-angle x-ray scattering (SAXS) from detonating explosives. Hexanitrostilbene (HNS) was selected as the first to investigate due to its ease of initiation using exploding foils and flyers, vacuum compatibility, high thermal stability, and stoichiometric carbon abundance that produces high carbon condensate yields. The SAXS data during detonation, collected with 300 ns time resolution, provide unprecedented signal fidelity over a broad q-range. This fidelity permits the first analysis of both the Guinier and Porod/power-law regions of the scattering profile during detonation, which contains information about the size and morphology of the resultant carbon condensate nanoparticles. To bolster confidence in these data, the scattering angle and intensity were additionally cross-referenced with a separate, highly calibrated SAXS beamline. The data show that HNS produces carbon particles with a radius of gyration of 2.7 nm in less than 400 ns after the detonation front has passed, and this size and morphology are constant over the next several microseconds. These data directly contradict previous pioneering work on RDX/TNT mixtures and TATB, where observations indicate significant particle growth (50% or more) continues over several microseconds. The power-law slope is about -3, which is consistent with a complex disordered, irregular, or folded sp2 sub-arrangement within a relatively monodisperse structure possessing radius of gyration of 2.7 nm after the detonation of HNS.

  8. Measurement of carbon condensates using small-angle x-ray scattering during detonation of the high explosive hexanitrostilbene

    SciTech Connect

    Bagge-Hansen, M.; Lauderbach, L.; Hodgin, R.; Bastea, S.; Fried, L.; Jones, A.; Buuren, T. van; Hansen, D.; Benterou, J.; May, C.; Willey, T. M.; Graber, T.; Jensen, B. J.; Ilavsky, J.

    2015-06-28

    The dynamics of carbon condensation in detonating high explosives remains controversial. Detonation model validation requires data for processes occurring at nanometer length scales on time scales ranging from nanoseconds to microseconds. A new detonation endstation has been commissioned to acquire and provide time-resolved small-angle x-ray scattering (SAXS) from detonating explosives. Hexanitrostilbene (HNS) was selected as the first to investigate due to its ease of initiation using exploding foils and flyers, vacuum compatibility, high thermal stability, and stoichiometric carbon abundance that produces high carbon condensate yields. The SAXS data during detonation, collected with 300 ns time resolution, provide unprecedented signal fidelity over a broad q-range. This fidelity permits the first analysis of both the Guinier and Porod/power-law regions of the scattering profile during detonation, which contains information about the size and morphology of the resultant carbon condensate nanoparticles. To bolster confidence in these data, the scattering angle and intensity were additionally cross-referenced with a separate, highly calibrated SAXS beamline. The data show that HNS produces carbon particles with a radius of gyration of 2.7 nm in less than 400 ns after the detonation front has passed, and this size and morphology are constant over the next several microseconds. These data directly contradict previous pioneering work on RDX/TNT mixtures and TATB, where observations indicate significant particle growth (50% or more) continues over several microseconds. The power-law slope is about −3, which is consistent with a complex disordered, irregular, or folded sp{sup 2} sub-arrangement within a relatively monodisperse structure possessing radius of gyration of 2.7 nm after the detonation of HNS.

  9. Measurement of carbon condensates using small-angle x-ray scattering during detonation of the high explosive hexanitrostilbene

    NASA Astrophysics Data System (ADS)

    Bagge-Hansen, M.; Lauderbach, L.; Hodgin, R.; Bastea, S.; Fried, L.; Jones, A.; van Buuren, T.; Hansen, D.; Benterou, J.; May, C.; Graber, T.; Jensen, B. J.; Ilavsky, J.; Willey, T. M.

    2015-06-01

    The dynamics of carbon condensation in detonating high explosives remains controversial. Detonation model validation requires data for processes occurring at nanometer length scales on time scales ranging from nanoseconds to microseconds. A new detonation endstation has been commissioned to acquire and provide time-resolved small-angle x-ray scattering (SAXS) from detonating explosives. Hexanitrostilbene (HNS) was selected as the first to investigate due to its ease of initiation using exploding foils and flyers, vacuum compatibility, high thermal stability, and stoichiometric carbon abundance that produces high carbon condensate yields. The SAXS data during detonation, collected with 300 ns time resolution, provide unprecedented signal fidelity over a broad q-range. This fidelity permits the first analysis of both the Guinier and Porod/power-law regions of the scattering profile during detonation, which contains information about the size and morphology of the resultant carbon condensate nanoparticles. To bolster confidence in these data, the scattering angle and intensity were additionally cross-referenced with a separate, highly calibrated SAXS beamline. The data show that HNS produces carbon particles with a radius of gyration of 2.7 nm in less than 400 ns after the detonation front has passed, and this size and morphology are constant over the next several microseconds. These data directly contradict previous pioneering work on RDX/TNT mixtures and TATB, where observations indicate significant particle growth (50% or more) continues over several microseconds. The power-law slope is about -3, which is consistent with a complex disordered, irregular, or folded sp2 sub-arrangement within a relatively monodisperse structure possessing radius of gyration of 2.7 nm after the detonation of HNS.

  10. Anomalous magnetoresistance in magnetized topological insulator cylinders

    NASA Astrophysics Data System (ADS)

    Siu, Zhuo Bin; Jalil, Mansoor B. A.

    2015-05-01

    The close coupling between the spin and momentum degrees of freedom in topological insulators (TIs) presents the opportunity for the control of one to manipulate the other. The momentum can, for example, be confined on a curved surface and the spin influenced by applying a magnetic field. In this work, we study the surface states of a cylindrical TI magnetized in the x direction perpendicular to the cylindrical axis lying along the z direction. We show that a large magnetization leads to an upwards bending of the energy bands at small |kz| . The bending leads to an anomalous magnetoresistance where the transmission between two cylinders magnetized in opposite directions is higher than when the cylinders are magnetized at intermediate angles with respect to each other.

  11. Anomalous magnetoresistance in magnetized topological insulator cylinders

    SciTech Connect

    Siu, Zhuo Bin; Jalil, Mansoor B. A.

    2015-05-07

    The close coupling between the spin and momentum degrees of freedom in topological insulators (TIs) presents the opportunity for the control of one to manipulate the other. The momentum can, for example, be confined on a curved surface and the spin influenced by applying a magnetic field. In this work, we study the surface states of a cylindrical TI magnetized in the x direction perpendicular to the cylindrical axis lying along the z direction. We show that a large magnetization leads to an upwards bending of the energy bands at small |k{sub z}|. The bending leads to an anomalous magnetoresistance where the transmission between two cylinders magnetized in opposite directions is higher than when the cylinders are magnetized at intermediate angles with respect to each other.

  12. The microstructure and morphology of carbon black: a study using small angle neutron scattering and contrast variation

    SciTech Connect

    Hjelm, R.P. Jr. ); Wampler, W.A. ); Seeger, P.A. ); Gerspacher, M. )

    1994-12-01

    This is a study of the form and structure of particles and particle aggregates of an experimental high surface area carbon black (HSA) using small-angle neutron scattering and the method of contrast variation. Contrast variation was effected by studying suspensions of the carbon black in cyclohexane containing different fractions of deutero-cyclohexane. We find that the approximately 29 nm diameter HSA particles are arranged as small, linear aggregates with average aggregation number between 4 and 6. The structure averaged over the particle population is best represented by a prolate ellipsoid of revolution with semi axes 14.5 and 76.4 nm. The surface of the aggregates appears smooth over length scales larger than 1 nm, which places an upper limit on the surface roughness observed by other methods. The internal structure of the aggregates is described by a shell-core model, with the shell density being consistent with a graphitic structure and the core being of lower density, more like amorphous carbon. Some fraction of the core volume (0.1 to 0.2) is taken up by voids that are not accessible to the solvent. An estimate of the shell thickness gives 1 to 2 nm along the ellipsoid minor axis and 6 to 10 nm along the major axis. The particles of the aggregate appear to be fused so that the less dense amorphous core is continuous through the inner parts of the aggregate. The information that can be obtained on the internal structure using contrast variation is limited by heterogeneity in the chemical composition of carbon black aggregates.

  13. EXPRESSION, PURIFICATION, AND SMALL ANGLE X-RAY SCATTERING OF DNA REPLICATION AND REPAIR PROTEINS FROM THE HYPERTHERMOPHILE SULFOLOBUS SOLFATARICUS

    SciTech Connect

    Patterson, S.M.; Hatherill, J.R.; Hammel, M.; Hura, G.L.; Tainer, J.A.; Yannone, S.M.

    2008-01-01

    Vital molecular processes such as DNA replication, transcription, translation, and maintenance occur through transient protein interactions. Elucidating the mechanisms by which these protein complexes and interactions function could lead to treatments for diseases related to DNA damage and cell division control. In the recent decades since its introduction as a third domain, Archaea have shown to be simpler models for complicated eukaryotic processes such as DNA replication, repair, transcription, and translation. Sulfolobus solfataricus is one such model organism. A hyperthermophile with an optimal growth temperature of 80°C, Sulfolobus protein-protein complexes and transient protein interactions should be more stable at moderate temperatures, providing a means to isolate and study their structure and function. Here we provide the initial steps towards characterizing three DNA-related Sulfolobus proteins with small angle X-ray scattering (SAXS): Sso0257, a cell division control and origin recognition complex homolog, Sso0768, the small subunit of the replication factor C, and Sso3167, a Mut-T like protein. SAXS analysis was performed at multiple concentrations for both short and long exposure times. The Sso0257 sample was determined to be either a mixture of monomeric and dimeric states or a population of dynamic monomers in various conformational states in solution, consistent with a fl exible winged helix domain. Sso0768 was found to be a complex mixture of multimeric states in solution. Finally, molecular envelope reconstruction from SAXS data for Sso3167 revealed a novel structural component which may function as a disordered to ordered region in the presence of its substrates and/or protein partners.

  14. SMALL-ANGLE NEUTRON SCATTERING CHARACTERIZATION OF THE STRUCTURE OF NANOPOROUS CARBONS FOR ENERGY-RELATED APPLICATIONS

    SciTech Connect

    He, Lilin; Mavila Chathoth, Suresh; Melnichenko, Yuri B; Presser, Volker; Mcdonough, John; Gogotsi, Yury G.

    2011-01-01

    We used small-angle neutron scattering (SANS) and neutron contrast variation to study the structure of four nanoporouscarbons prepared by thermo-chemical etching of titanium carbide TiC in chlorine at 300, 400, 600, and 800 C with pore diameters ranging between -4 and -11 {angstrom}. SANS patterns were obtained from dry samples and samples saturated with deuterium oxide (D{sub 2}O) in order to delineate origin of the power law scattering in the low Q domain as well as to evaluate pore accessibility for D{sub 2}O molecules. SANS cross section of all samples was fitted to Debye-Anderson-Brumberger (DAB), DAB-Kirste-Porod models as well as to the Guinier and modified Guinier formulae for cylindrical objects, which allowed for evaluating the radii of gyration as well as the radii and lengths of the pores under cylindrical shape approximation. SANS data from D{sub 2}O-saturated samples indicate that strong upturn in the low Q limit usually observed in the scattering patterns from microporous carbon powders is due to the scattering from outer surface of the powder particles. Micropores are only partially filled with D{sub 2}O molecules due to geometrical constraints and or partial hydrophobicity of the carbon matrix. Structural parameters of the dry carbons obtained using SANS are compared with the results of the gas sorption measurements and the values agree for carbide-derived carbons (CDCs) obtained at high chlorination temperatures (>600 C). For lower chlorination temperatures, pore radii obtained from gas sorption overestimate the actual pore size as calculated from SANS for two reasons: inaccessible small pores are present and the model-dependent fitting based on density functional theory models assumes non-spherical pores, whereas SANS clearly indicates that the pore shape in microporous CDC obtained at low chlorination temperatures is nearly spherical.

  15. Effects of biological molecules on calcium mineral formation associated with wastewater desalination as assessed using small-angle neutron scattering.

    PubMed

    Pipich, Vitaliy; Dahdal, Yara; Rapaport, Hanna; Kasher, Roni; Oren, Yoram; Schwahn, Dietmar

    2013-06-25

    Calcium phosphate scale formation on reverse osmosis (RO) membranes is one of the main limitations on cost-effective desalination of domestic wastewater worldwide. It has been shown that organic agents affect mineralization. In this study, we explored mineralization in the presence of two biofilm-relevant organic compounds, the proteins bovine serum albumin (BSA) and lysozyme, in a simulated secondary effluent (SSE) solution using small-angle neutron scattering (SANS), and applied the results to analyses of mineral precipitation in RO desalination of secondary effluents of wastewater. The two proteins are prominent members of bacterial extracellular polymeric substances (EPSs), forming biofilms that are frequently associated with RO-membrane fouling during wastewater desalination. Laboratory experiments showed that both proteins in SSE solution are involved in complex mineralization processes. Only small portions of both protein fractions are involved in mineralization processes, whereas most of the protein fractions remain as monomers in solution. Contrast variation showed that composite particles of mineral and protein are formed instantaneously to a radius of gyration of about 300 Å, coexisting with particles of about μm size. After about one day, these large particles start to grow again at the expense of the 300 Å particles. The volume fraction of the 300 Å particles is of the order of 2 × 10(-4), which is too large to represent calcium phosphate such as hydroxyapatite as the only mineral present. Considering the data of mineral volume fraction obtained here as well as the solubility product of possible mineral polymorphs in the SSE solution, we suggest the formation of protein-mineral particles of hydroxyapatite and calcium carbonate during scale formation.

  16. Interactions between block copolymers and single-walled carbon nanotubes in aqueous solutions: a small-angle neutron scattering study.

    PubMed

    Granite, Meirav; Radulescu, Aurel; Pyckhout-Hintzen, Wim; Cohen, Yachin

    2011-01-18

    The amphiphilic copolymers of the Pluronic family are known to be excellent dispersants for single-walled carbon nanotubes (SWCNT) in water, especially F108 and F127, which have rather long end-blocks of poly(ethylene oxide) (PEO). In this study, the structure of the CNT/polymer hybrid formed in water is evaluated by measurements of small-angle neutron scattering (SANS) with contrast variation, as supported by cryo-transmission electron microscopy (cryo-TEM) imaging. The homogeneous, stable, inklike dispersions exhibited very small isolated bundles of carbon nanotubes in cryo-TEM images. SANS experiments were conducted at different D(2)O/H(2)O content of the dispersing solvent. The data for both systems showed surprisingly minimal intensity values at 70% D(2)O solvent composition, which is much higher than the expected value of 17% D(2)O that is based on the scattering length density (SLD) of PEO. At this near match point, the data exhibited a q(-1) power law relation of intensity to the scattering vector (q), indicating rodlike entities. Two models are evaluated, as extensions to Pederson's block copolymer micelles models. One is loosely adsorbed polymer chains on a rodlike CNT bundle. In the other, the hydrophobic block is considered to form a continuous hydrated shell on the CNT surface, whereas the hydrophilic blocks emanate into the solvent. Both models were found to fit the experimental data reasonably well. The model fit required special considerations of the tight association of water molecules around PEO chains and slight isotopic selectivity.

  17. Tertiary and quaternary structural differences between two genetic variants of bovine casein by small-angle X-ray scattering

    SciTech Connect

    Pessen, H.; Kumosinski, T.F.; Farrell, H.M. Jr.; Brumberger, H. )

    1991-01-01

    The casein complexes of bovine milk consist of four major protein fractions, alpha s1, alpha s2, beta, and kappa. Colloidal particles of casein (termed micelles) contain inorganic calcium and phosphate; they are very roughly spherical with an average radius of 650 A. Removal of Ca2+ leads to the formation of smaller protein aggregates with an average radius of 94 A. Two genetic variants, A and B, of the predominant fraction, alpha s1-casein, result in milks with markedly different physical properties, such as solubility and heat stability. To investigate the molecular basis for these differences, small-angle X-ray scattering was performed on the respective colloidal micelles and submicelles. Scattering curves for submicelles of both variants showed multiple Gaussian character; data for the B variant were previously interpreted in terms of two concentric regions of different electron density, i.e., a compact core and a relatively loose shell. For the submicelle of A, there was a third Gaussian, reflecting a negative contribution due to interparticle interference. Molecular parameters for submicelles of both A and B are in agreement with hydrodynamic data in the literature. Data for the micelles, for which scattering yields cross-sectional information, were fitted by a sum of three Gaussians for both variants; for these, the corresponding two lower radii of gyration represent the two concentric regions of the submicelles, while the third reflects the average packing of submicelles within the micellar cross section. Most of the molecular parameters obtained showed small but consistent differences between A and B, but for submicelles within the micelle several differences were particularly notable: A has a greater molecular weight for the compact region of the constituent submicelle (82,000 vs 60,000) and a much greater submicellar packing number.

  18. LORES: Low resolution shape program for the calculation of small angle scattering profiles for biological macromolecules in solution

    NASA Astrophysics Data System (ADS)

    Zhou, J.; Deyhim, A.; Krueger, S.; Gregurick, S. K.

    2005-08-01

    A program for determining the low resolution shape of biological macromolecules, based on the optimization of a small angle neutron scattering profile to experimental data, is presented. This program, termed LORES, relies on a Monte Carlo optimization procedure and will allow for multiple scattering length densities of complex structures. It is therefore more versatile than utilizing a form factor approach to produce low resolution structural models. LORES is easy to compile and use, and allows for structural modeling of biological samples in real time. To illustrate the effectiveness and versatility of the program, we present four specific biological examples, Apoferritin (shell model), Ribonuclease S (ellipsoidal model), a 10-mer dsDNA (duplex helix) and a construct of a 10-mer DNA/PNA duplex helix (heterogeneous structure). These examples are taken from protein and nucleic acid SANS studies, of both large and small scale structures. We find, in general, that our program will accurately reproduce the geometric shape of a given macromolecule, when compared with the known crystallographic structures. We also present results to illustrate the lower limit of the experimental resolution which the LORES program is capable of modeling. Program summaryTitle of program:LORES Catalogue identifier: ADVC Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADVC Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer:SGI Origin200, SGI Octane, SGI Linux, Intel Pentium PC Operating systems:UNIX64 6.5 and LINUX 2.4.7 Programming language used:C Memory required to execute with typical data:8 MB No. of lines in distributed program, including test data, etc.:2270 No. of bytes in distributed program, including test data, etc.:13 302 Distribution format:tar.gz External subprograms used:The entire code must be linked with the MATH library

  19. Structural Evolution of Polylactide Molecular Bottlebrushes: Kinetics Study by Size Exclusion Chromatography, Small Angle Neutron Scattering and Simulations

    SciTech Connect

    Pickel, Deanna L; Kilbey, II, S Michael; Uhrig, David; Hong, Kunlun; Carrillo, Jan-Michael Y; Sumpter, Bobby G; Ahn, Suk-Kyun; Han, Youngkyu; Kim, Dr. Tae-Hwan; Smith, Gregory Scott; Do, Changwoo

    2014-01-01

    Structural evolution from poly(lactide) (PLA) macromonomer to resultant PLA molecular bottlebrush during ring opening metathesis polymerization (ROMP) was investigated for the first time by combining size exclusion chromatography (SEC), small-angle neutron scattering (SANS) and coarse-grained molecular dynamics (CG-MD) simulations. Multiple aliquots were collected at various reaction times during ROMP, and subsequently analyzed by SEC and SANS. The two complementary techniques enable the understanding of systematic changes in conversion, molecular weight and dispersity as well as structural details of PLA molecular bottlebrushes. CG-MD simulation not only predicts the experimental observations, but it also provides further insight into the analysis and interpretation of data obtained in SEC and SANS experiments. We find that PLA molecular bottlebrushes undergo three conformational transitions with increasing conversion (i.e., increasing the backbone length): (1) from an elongated to a globular shape due to longer side chain at lower conversion, (2) from a globular to an elongated shape at intermediate conversion caused by excluded volume of PLA side chain, and (3) the saturation of contour length at higher conversion due to chain transfer reactions.

  20. Temperature Assisted in-Situ Small Angle X-ray Scattering Analysis of Ph-POSS/PC Polymer Nanocomposite

    PubMed Central

    Yadav, Ramdayal; Naebe, Minoo; Wang, Xungai; Kandasubramanian, Balasubramanian

    2016-01-01

    Inorganic/organic nanofillers have been extensively exploited to impart thermal stability to polymer nanocomposite via various strategies that can endure structural changes when exposed a wide range of thermal environment during their application. In this abstraction, we have utilized temperature assisted in-situ small angle X-ray scattering (SAXS) to examine the structural orientation distribution of inorganic/organic nanofiller octa phenyl substituted polyhedral oligomeric silsesquioxane (Ph-POSS) in Polycarbonate (PC) matrix from ambient temperature to 180 °C. A constant interval of 30 °C with the heating rate of 3 °C/min was utilized to guise the temperature below and above the glass transition temperature of PC followed by thermal gravimetric, HRTEM, FESEM and hydrophobic analysis at ambient temperature. The HRTEM images of Ph-POSS nano unit demonstrated hyperrectangular structure, while FESEM image of the developed nano composite rendered separated phase containing flocculated and overlapped stacking of POSS units in the PC matrix. The phase separation in polymer nanocomposite was further substantiated by thermodynamic interaction parameter (χ) and mixing energy (Emix) gleaned via Accelrys Materials studio. The SAXS spectra has demonstrated duplex peak at higher scattering vector region, postulated as a primary and secondary segregated POSS domain and followed by abundance of secondary peak with temperature augmentation. PMID:27436152

  1. Collagen fibril alignment and deformation during tensile strain of leather: a small-angle X-ray scattering study.

    PubMed

    Basil-Jones, Melissa M; Edmonds, Richard L; Norris, Gillian E; Haverkamp, Richard G

    2012-02-01

    The distribution and effect of applied strain on the collagen fibrils that make up leather may have an important bearing on the ultimate strength and other physical properties of the material. While sections of ovine and bovine leather were being subjected to tensile strain up to rupture, synchrotron-based small-angle X-ray scattering (SAXS) spectra were recorded edge-on to the leather at points from the corium to the grain. Measurements of both fibril orientation and collagen d spacing showed that, initially, the fibers reorient under strain, becoming more aligned. As the strain increases (5-10% strain), further fibril reorientation diminishes until, at 37% strain, the d spacing increases by up to 0.56%, indicating that significant tensile forces are being transmitted to individual fibrils. These changes, however, are not uniform through the cross-section of leather and differ between leathers of different strengths. The stresses are taken up more evenly through the leather cross-section in stronger leathers in comparison to weaker leathers, where stresses tended to be concentrated during strain. These observations contribute to our understanding of the internal strains and structural changes that take place in leather under stress.

  2. Research on some issues of the method of photoelectric autocollimation for two-dimensional small angle measurement

    NASA Astrophysics Data System (ADS)

    Tan, Qimeng; Yan, Bixi; Lu, Naiguang

    2008-12-01

    Four issues of the method of photoelectric autocollimation for two-dimensional small angle measurement such as adjustment of calibration system, elimination of the effect on the measurement result induced by the installing position of the CCD camera relative to the autocollimator, processing methods of experimental data and repeatability of the system are studied in the paper. The calibration system which is composed of a precision motorized stage, a dual-frequency laser interferometer and a photoelectric autocollimator, is regulated to accomplish two separate calibrations around Z-axis and X-axis in the measuring coordinates system which is established by considering horizontal, vertical line of the crosshair and optical axis as X-axis, Z-axis and Y-axis respectively. Experimental results show that the formula method which can reduce the random error and remove the system error effectively with the average error of zero and the standard deviation 0.59". Compared with traditional optical autocollimator, the improvement of the photoelectric autocollimation method can be used to achieve rapid and automatic positional detection and error compensation of CNC rotary shaft.

  3. Facilitating model reconstruction for single-particle scattering using small-angle X-ray scattering methods1

    PubMed Central

    Ma, Shufen; Liu, Haiguang

    2016-01-01

    X-ray free-electron lasers generate intense femtosecond X-ray pulses, so that high-resolution structure determination becomes feasible from noncrystalline samples, such as single particles or single molecules. At the moment, the orientation of sample particles cannot be precisely controlled, and consequently the unknown orientation needs to be recovered using computational algorithms. This delays the model reconstruction until all the scattering patterns have been re-oriented, which often entails a long elapse of time and until the completion of the experiment. The scattering patterns from single particles or multiple particles can be summed to form a virtual powder diffraction pattern, and the low-resolution region, corresponding to the small-angle X-ray scattering (SAXS) regime, can be analysed using existing SAXS methods. This work presents a pipeline that converts single-particle data sets into SAXS data, from which real-time model reconstruction is achieved using the model retrieval approach implemented in the software package SASTBX [Liu, Hexemer & Zwart (2012). J. Appl. Cryst.45, 587–593]. To illustrate the applications, two case studies are presented with real experimental data sets collected at the Linac Coherent Light Source. PMID:27047310

  4. Dissecting diffusive and advective motion in colloidal sedimentation by multi-speckle Ultra-Small-Angle XPCS

    NASA Astrophysics Data System (ADS)

    Möller, Johannes; Narayanan, Theyencheri

    In colloidal suspensions internal or external fields can induce directed motions of particles in addition to Brownian diffusion. Here, gradients in temperature or chemical potential, shear flow as well as gravity can act as an external field. Examples for internal motions can be found in synthetic self-propelling particles and microorganisms, generally coined as active matter. We present multi-speckle X-ray photon correlation spectroscopy measurements in the Ultra-Small-Angle scattering range which probes an expanded length scale comparable to DLS and optical microscopy. To demonstrate the advanced capabilities, we show measurements probing the motions within a settling suspension of sub-micron sized silica particles. A global fitting procedure has been applied to separate the diffusive and advective contributions to the particle dynamics. With this, macroscopic parameters such as the sedimentation velocity can be probed on a microscopic level in highly opaque and concentrated systems, which are in general difficult to access for optical investigations. This procedure may prove its value for investigating various kinds of non-equilibrium systems.

  5. Determination by Small-angle X-ray Scattering of Pore Size Distribution in Nanoporous Track-etched Polycarbonate Membranes

    NASA Astrophysics Data System (ADS)

    Jonas, A. M.; Legras, R.; Ferain, E.

    1998-03-01

    Nanoporous track-etched membranes with narrow pore size distributions and average pore size diameters tunable from 100 to 1000 Åare produced by the chemical etching of latent tracks in polymer films after irradiation by a beam of accelerated heavy ions. Nanoporous membranes are used for highly demanding filtration purposes, or as templates to obtain metallic or polymeric nanowires (L. Piraux et al., Nucl. Instr. Meth. Phys. Res. 1997, B131, 357). Such applications call for developments in nanopore size characterization techniques. In this respect, we report on the characterization by small-angle X-ray scattering (SAXS) of nanopore size distribution (nPSD) in polycarbonate track-etched membranes. The obtention of nPSD requires inverting an ill-conditioned inhomogeneous equation. We present different numerical routes to overcome the amplification of experimental errors in the resulting solutions, including a regularization technique allowing to obtain the nPSD without a priori knowledge of its shape. The effect of deviations from cylindrical pore shape on the resulting distributions are analyzed. Finally, SAXS results are compared to results obtained by electron microscopy and conductometry.

  6. Small-angle neutron scattering reveals the assembly mode and oligomeric architecture of TET, a large, dodecameric aminopeptidase.

    PubMed

    Appolaire, Alexandre; Girard, Eric; Colombo, Matteo; Durá, M Asunción; Moulin, Martine; Härtlein, Michael; Franzetti, Bruno; Gabel, Frank

    2014-11-01

    The specific self-association of proteins into oligomeric complexes is a common phenomenon in biological systems to optimize and regulate their function. However, de novo structure determination of these important complexes is often very challenging for atomic-resolution techniques. Furthermore, in the case of homo-oligomeric complexes, or complexes with very similar building blocks, the respective positions of subunits and their assembly pathways are difficult to determine using many structural biology techniques. Here, an elegant and powerful approach based on small-angle neutron scattering is applied, in combination with deuterium labelling and contrast variation, to elucidate the oligomeric organization of the quaternary structure and the assembly pathways of 468 kDa, hetero-oligomeric and symmetric Pyrococcus horikoshii TET2-TET3 aminopeptidase complexes. The results reveal that the topology of the PhTET2 and PhTET3 dimeric building blocks within the complexes is not casual but rather suggests that their quaternary arrangement optimizes the catalytic efficiency towards peptide substrates. This approach bears important potential for the determination of quaternary structures and assembly pathways of large oligomeric and symmetric complexes in biological systems.

  7. Idiosyncratically tuned switching behavior of riboswitch aptamer domains revealed by comparative small-angle X-ray scattering analysis

    SciTech Connect

    Baird, Nathan J.; Ferré-D'Amaré, Adrian R.

    2010-05-25

    Riboswitches are structured mRNA elements that regulate gene expression upon binding specific cellular metabolites. It is thought that the highly conserved metabolite-binding domains of riboswitches undergo conformational change upon binding their cognate ligands. To investigate the generality of such a mechanism, we employed small-angle X-ray scattering (SAXS). We probed the nature of the global metabolite-induced response of the metabolite-binding domains of four different riboswitches that bind, respectively, thiamine pyrophosphate (TPP), flavin mononucleotide (FMN), lysine, and S-adenosyl methionine (SAM). We find that each RNA is unique in its global structural response to metabolite. Whereas some RNAs exhibit distinct free and bound conformations, others are globally insensitive to the presence of metabolite. Thus, a global conformational change of the metabolite-binding domain is not a requirement for riboswitch function. It is possible that the range of behaviors observed by SAXS, rather than being a biophysical idiosyncrasy, reflects adaptation of riboswitches to the regulatory requirements of their individual genomic context.

  8. Conformational Changes in Sindbis Virus Induced by Decreased pH Are Revealed by Small-Angle Neutron Scattering

    PubMed Central

    He, Lilin; Piper, Amanda; Meilleur, Flora; Hernandez, Raquel; Heller, William T.

    2012-01-01

    Alphaviruses, such as Sindbis virus, undergo dramatic changes in three-dimensional structure upon exposure to low pH, and such exposure can establish conditions allowing fusion of the virus membrane with a cell plasma membrane upon return to neutral pH. While exposure to low pH is not required for entry of Sindbis virus into vertebrate or invertebrate cells, the conformational changes occurring at low pH may mimic those occurring upon virus-receptor interaction. Here, we employed small-angle neutron scattering with contrast variation to probe how the structure of a mammalian-grown Sindbis virus responds to moderately acidic pH. Several changes took place throughout the virion structure when the pH decreased from 7.2 to 6.4. Specifically, the RNA in the virion core underwent a conformational change. Additionally, the protein was redistributed. A significant amount of protein moved from the layer containing the lipid bilayer to the exterior of the virion. The results improve our understanding of the pH-driven alteration of Sindbis virus structure. PMID:22156534

  9. Mass-fractal growth in niobia/silsesquioxane mixtures: a small-angle X-ray scattering study

    PubMed Central

    Besselink, Rogier; ten Elshof, Johan E.

    2014-01-01

    The nucleation and growth of niobium pentaethoxide (NPE)-derived clusters in ethanol, through acid-catalyzed hydrolysis/condensation in the presence and absence of the silsesquioxane 1,2-bis(triethoxysilyl)ethane (BTESE), was monitored at 298–333 K by small-angle X-ray scattering. The data were analyzed with a newly derived model for polydisperse mass-fractal-like structures. At 298–313 K in the absence of BTESE the data indicated the development of relatively monodisperse NPE-derived structures with self-preserving polydispersity during growth. The growth exponent was consistent with irreversible diffusion-limited cluster agglomeration. At 333 K the growth exponent was characteristic for fast-gelling reaction-limited cluster agglomeration. The reaction yielded substantially higher degrees of polydispersity. In the presence of BTESE the growth exponents were substantially smaller. The smaller growth exponent in this case is not consistent with irreversible Smoluchowski-type agglomeration. Instead, reversible Lifshitz–Slyozov-type agglomeration seems to be more consistent with the experimental data. PMID:25294980

  10. A Method for Helical RNA Global Structure Determination in Solution Using Small Angle X-ray Scattering and NMR Measurements

    PubMed Central

    Wang, Jinbu; Zuo, Xiaobing; Yu, Ping; Xu, Huan; Starich, Mary R.; Tiede, David M.; Shapiro, Bruce A.; Schwieters, Charles D.; Wang, Yun-Xing

    2009-01-01

    We report a “top-down” method that uses mainly duplexes' global orientations and overall molecular dimension and shape restraints, which were extracted from experimental NMR and small angle X-ray scattering (SAXS) data respectively, to determine global architectures of RNA molecules consisting of mostly A-form like duplexes. The method is implemented in the G2G (from Global measurement to Global Structure) toolkit of programs. We demonstrate the efficiency and accuracy of the method by determining the global structure of a 71-nucleotide RNA using experimental data. The backbone root-mean-square-deviation (RMSD) of the ensemble of the calculated global structures relative to the X-ray crystal structure using the experimental data is 3.0 ± 0.3 Å, and the RMSD is only 2.5 ± 0.2 Å for the three duplexes that were orientation-restrained during the calculation. The global structure simplifies interpretation of multi-dimensional nuclear Overhauser spectra for high resolution structure determination. The potential general application of the method for RNA structure determination is discussed. PMID:19666030

  11. Pauli Limiting and Multi-Band Superconductivity in KFe2As2 Studied by Small-Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Eskildsen, M. R.; Kuhn, S. J.; Kawano-Furukawa, H.; Ono, M.; Forgan, E. M.; Jellyman, E.; Riyat, R.; Lee, C. H.; Kihou, K.; Hardy, F.; Wolf, Th.; Meingast, C.; Gavilano, J. L.

    We have studied the intrinsic anisotropy of the superconducting state in KFe2As2, using used small-angle neutron scattering to image the vortex lattice (VL) as the applied magnetic field is rotated towards the FeAs planes. The anisotropy is found to be strongly field dependent, indicating multi-band superconductivity. Furthermore, the high field anisotropy significantly exceeds that of the upper critical field, providing further support for Pauli limiting in KFe2As2 for field applied along the basal plane. Finally, we are able determine the contribution to the field modulation in the mixed state due to Pauli Paramagnetic Effects by measuring both the non-spin flip and spin flip VL scattered intensity. This represents the first instance where all the effects listed above have been obtained simultaneously and in a comprehensive manner by a single experimental technique. This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Award DE-FG02-10ER46783.

  12. Conformational changes in Sindbis virus induced by decreased pH revealed by small-angle neutron scattering

    SciTech Connect

    Hernandez, Raquel; He, Lilin; Piper, Amanda; Meilleur, Flora; Brown, Dennis; Heller, William T

    2012-01-01

    Alphaviruses, such as Sindbis virus, undergo dramatic changes in three-dimensional structure upon exposure to low pH, and such exposure can establish conditions allowing fusion of the virus membrane with a cell plasma membrane upon return to neutral pH. While exposure to low pH is not required for entry of Sindbis virus into vertebrate or invertebrate cells, the conformational changes occurring at low pH may mimic those occurring upon virus-receptor interaction. Here, we employed small-angle neutron scattering with contrast variation to probe how the structure of a mammalian-grown Sindbis virus responds to moderately acidic pH. Several changes took place throughout the virion structure when the pH decreased from 7.2 to 6.4. Specifically, the RNA in the virion core underwent a conformational change. Additionally, the protein was redistributed. A significant amount of protein moved from the layer containing the lipid bilayer to the exterior of the virion. The results improve our understanding of the pH-driven alteration of Sindbis virus structure.

  13. Understanding inelastically scattered neutrons from water on a time-of-flight small-angle neutron scattering (SANS) instrument

    NASA Astrophysics Data System (ADS)

    Do, Changwoo; Heller, William T.; Stanley, Christopher; Gallmeier, Franz X.; Doucet, Mathieu; Smith, Gregory S.

    2014-02-01

    It is generally assumed by most of the small-angle neutron scattering (SANS) user community that a neutron's energy is unchanged during SANS measurements. Here, the scattering from water, specifically light water, was measured on the EQ-SANS instrument, a time-of-flight (TOF) SANS instrument located at the Spallation Neutron Source of Oak Ridge National Laboratory. A significant inelastic process was observed in the TOF spectra of neutrons scattered from water. Analysis of the TOF spectra from the sample showed that the scattered neutrons have energies consistent with room-temperature thermal energies (~20 meV) regardless of the incident neutron's energy. With the aid of Monte Carlo particle transport simulations, we conclude that the thermalization process within the sample results in faster neutrons that arrive at the detector earlier than expected based on the incident neutron energies. This thermalization process impacts the measured SANS intensities in a manner that will ultimately be sample- and temperature-dependent, necessitating careful processing of the raw data into the SANS cross-section.

  14. Micro-focused Small Angle Neutron Scattering and Imaging for Science and Engineering Using RTP--A Preliminary Study

    SciTech Connect

    Mohamed, Abdul Aziz; Al Rashid Megat Ahmad, Megat Harun; Md Idris, Faridah; Azman, Azraf; Jamro, Rafhayudi; Ibrahim, Mohd Rizal Mamat; Rahman, Anwar Abdul

    2010-01-05

    Malaysian Nuclear Agency's (Nuclear Malaysia) Small Angle Neutron Scattering (SANS) facility--(MYSANS)--is utilizing low flux of thermal neutron at the agency's 1 MW TRIGA reactor. As the design nature of the 8 m SANS facility can allow object resolution in the range between 5 and 80 nm to be obtained. It can be used to study alloys, ceramics and polymers in certain area of problems that relate to samples containing strong scatterers or contrast. The current SANS system at Malaysian Nuclear Agency is only capable to measure Q in limited range with a PSD (128x128) fixed at 4 m from the sample. The existing reactor hall that incorporate this MYSANS facility has a layout that prohibits the rebuilding of MYSANS therefore the position between the wavelength selector (HOPG) and sample and the PSD cannot be increased for wider Q range. The flux of the neutron at current sample holder is very low which around 10{sup 3} n/cm{sup 2}/sec. Thus it is important to rebuild the MYSANS to maximize the utilization of neutron. Over the years, the facility has undergone maintenance and some changes have been made. Modification on secondary shutter and control has been carried out to improve the safety level of the instrument. A compact micro-focus SANS method can suit this objective together with an improve cryostat system. This paper will explain some design concept and approaches in achieving higher flux and the modification needs to establish the micro-focused SANS.

  15. Magnetic scattering in the simultaneous measurement of small-angle neutron scattering and Bragg edge transmission from steel1

    PubMed Central

    Oba, Yojiro; Morooka, Satoshi; Ohishi, Kazuki; Sato, Nobuhiro; Inoue, Rintaro; Adachi, Nozomu; Suzuki, Jun-ichi; Tsuchiyama, Toshihiro; Gilbert, Elliot Paul; Sugiyama, Masaaki

    2016-01-01

    Pulsed neutron sources enable the simultaneous measurement of small-angle neutron scattering (SANS) and Bragg edge transmission. This simultaneous measurement is useful for microstructural characterization in steel. Since most steels are ferromagnetic, magnetic scattering contributions should be considered in both SANS and Bragg edge transmission analyses. An expression for the magnetic scattering contribution to Bragg edge transmission analysis has been derived. The analysis using this expression was applied to Cu steel. The ferrite crystallite size estimated from this Bragg edge transmission analysis with the magnetic scattering contribution was larger than that estimated using conventional expressions. This result indicates that magnetic scattering has to be taken into account for quantitative Bragg edge transmission analysis. In the SANS analysis, the ratio of magnetic to nuclear scattering contributions revealed that the precipitates consist of body-centered cubic Cu0.7Fe0.3 and pure Cu, which probably has 9R structure including elastic strain and vacancies. These results show that effective use of the magnetic scattering contribution allows detailed analyses of steel microstructure. PMID:27738416

  16. Small angle X-ray scattering studies of CTNNBL1 dimerization and CTNNBL1/CDC5L complex

    PubMed Central

    Ahn, Jae-Woo; Sik Jin, Kyeong; Francis Son, Hyeoncheol; Ho Chang, Jeong; Kim, Kyung-Jin

    2015-01-01

    The hPrp19/CDC5L complex is a non-snRNP spliceosome complex that plays a key role in the spliceosome activation during pre-mRNA splicing, and CTNNBL1 and CDC5L are essential components of the complex. In this study, to investigate the oligomeric state of CTNNBL1 in solution, we performed small angle X-ray scattering experiments in various concentrations of NaCl. We observed that CTNNBL1 existed as a dimer in physiological NaCl concentrations. Site-directed mutagenesis experiment of CTNNBL1 confirmed that N-terminal capping region and the first four ARM repeats are important for dimerization of the protein. We also found that the positively-charged NLS3-containing region (residues 197–235) of CDC5L bound to the negatively-charged patch of CTNNBL1 and that the CTNNBL1/CDC5L complex formed a heterotetramer consisting of one CTNNBL1 dimer and one CDC5L dimer. Moreover, reconstruction of 3D models of CTNNBL1/CDC5L complexes containing CTNNBL1 and three different truncated forms of CDC5L showed that the CDC5L141–196 region and the CDC5L236–377 region were positioned at the top of the N-terminal capping region and at the bottom of ARM VII of CTNNBL1, respectively. PMID:26381213

  17. Temperature Assisted in-Situ Small Angle X-ray Scattering Analysis of Ph-POSS/PC Polymer Nanocomposite

    NASA Astrophysics Data System (ADS)

    Yadav, Ramdayal; Naebe, Minoo; Wang, Xungai; Kandasubramanian, Balasubramanian

    2016-07-01

    Inorganic/organic nanofillers have been extensively exploited to impart thermal stability to polymer nanocomposite via various strategies that can endure structural changes when exposed a wide range of thermal environment during their application. In this abstraction, we have utilized temperature assisted in-situ small angle X-ray scattering (SAXS) to examine the structural orientation distribution of inorganic/organic nanofiller octa phenyl substituted polyhedral oligomeric silsesquioxane (Ph-POSS) in Polycarbonate (PC) matrix from ambient temperature to 180 °C. A constant interval of 30 °C with the heating rate of 3 °C/min was utilized to guise the temperature below and above the glass transition temperature of PC followed by thermal gravimetric, HRTEM, FESEM and hydrophobic analysis at ambient temperature. The HRTEM images of Ph-POSS nano unit demonstrated hyperrectangular structure, while FESEM image of the developed nano composite rendered separated phase containing flocculated and overlapped stacking of POSS units in the PC matrix. The phase separation in polymer nanocomposite was further substantiated by thermodynamic interaction parameter (χ) and mixing energy (Emix) gleaned via Accelrys Materials studio. The SAXS spectra has demonstrated duplex peak at higher scattering vector region, postulated as a primary and secondary segregated POSS domain and followed by abundance of secondary peak with temperature augmentation.

  18. Probing Anisotropic Structure Changes in Proteins with Picosecond Time-Resolved Small Angle X-ray Scattering

    PubMed Central

    Cho, Hyun Sun; Schotte, Friedrich; Dashdorj, Naranbaatar; Kyndt, John; Anfinrud, Philip A.

    2014-01-01

    We have exploited the principle of photoselection and the method of time-resolved Small Angle X-ray Scattering (SAXS) to investigate protein size and shape changes following photoactivation of photoactive yellow protein (PYP) in solution with ~150 ps time resolution. This study partially overcomes the orientational average intrinsic to solution scattering methods, and provides structural information at a higher level of detail. Photoactivation of the p-coumaric acid (pCA) chromophore in PYP produces a highly-contorted, short-lived, red shifted intermediate (pR0), and triggers prompt, protein compaction of approximately 0.3% along the direction defined by the electronic transition dipole moment of the chromophore. Contraction along this dimension is accompanied by expansion along the orthogonal directions, with the net protein volume change being approximately -0.25%. More than half the strain arising from formation of pR0 is relieved by the pR0 to pR1 structure transition (1.8 ± 0.2 ns), with the persistent strain presumably contributing to the driving force needed to generate the spectroscopically blue-shifted pB signaling state. The results reported here are consistent with the near-atomic resolution structural dynamics reported in a recent time-resolved Laue crystallography study of PYP crystals, and suggest that the early-time structural dynamics in the crystalline state carry over to proteins in solution. PMID:24125473

  19. Investigation of a catalyst ink dispersion using both ultra-small-angle X-ray scattering and cryogenic TEM.

    PubMed

    Xu, Fan; Zhang, HangYu; Ilavsky, Jan; Stanciu, Lia; Ho, Derek; Justice, Matthew J; Petrache, Horia I; Xie, Jian

    2010-12-21

    The dispersion of Nafion ionomer particles and Pt/C catalyst aggregates in liquid media was studied using both ultra-small-angle X-ray scattering (USAXS) and cryogenic TEM. A systematic approach was taken to study first the dispersion of each component (i.e., ionomer particles and Pt/C aggregates), then the combination of the components, and last the catalyst ink. Multiple-level curve fitting was used to extract the particle size, size distribution, and geometry of the Pt/C aggregates and the Nafion particles in liquid media from the scattering data. The results suggest that the particle size, size distribution, and geometry are not uniform throughout the systems but rather vary significantly. It was found that the interaction of each component (i.e., the Nafion ionomer particles and the Pt/C aggregates) occurs in the dispersion. Cryogenic TEM was used to observe the size and geometry of the particles in liquid directly and to validate the scattering results. The TEM results showed excellent agreement.

  20. Insitu multilevel structural characterization of semicrystalline polymer blends:New insights from small-angle light scattering

    NASA Astrophysics Data System (ADS)

    Lin, Youyu; Akpalu, Yvonne

    2002-03-01

    We demonstrate that the simultaneous measurement of transmitted light and small-angle light scattering (SALS) under H_V(cross-polarized) optical alignments during melting can be used to measure thermodynamic and structural variables necessary for describing the multiphase behavior of crystal-amorphous blends. HV SALS can be used to determine melting temperatures of crystalline components, the melt phase separation temperature of the polymer blend, the volume fraction of superstructures, the volume crystallinity within the superstructures and parameters that describe the distribution of the crystalline-rich and amorphous-rich domains. In addition we are able to evaluate the orientation of crystalline volume elements within the superstructures. The simultaneous measurement of transmitted intensity provides a reliable estimate of the total scattering arising from density and orientation fluctuations and the size of the crystalline and amorphous phases. For solution cast poly(ɛ-caprolactone)/poly(D,L-lactic acid) blends, our multivariable measurements during melting provide the necessary parameters to generate a crystal-liquid and liquid-liquid phase diagram. We discuss new insights into the segregation of non-crystallizable components revealed by the simultaneous measurement of transmitted light and SALS on model semicrystalline LCST and UCST polymer blends.