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Sample records for anomalous small angle

  1. Anomalous and resonance small angle scattering: Revision

    SciTech Connect

    Epperson, J.E.; Thiyagarajan, P.

    1987-11-01

    Significant changes in the small angle scattered intensity can be induced by making measurements with radiation close to an absorption edge of an appropriate atomic species contained in the sample. These changes can be related quantitatively to the real and imaginary anomalous dispersion terms for the scattering factor (x-rays) or scattering length (neutrons). The physics inherent in these anomalous dispersion terms is first discussed before considering how they enter the relevant scattering theory. Two major areas of anomalous scattering research have emerged; macromolecules in solution and unmixing of metallic alloys. Research in each area is reviewed, illustrating both the feasibility and potential of these techniques. All the experimental results reported to date have been obtained with x-rays. However, it is pointed out that the formalism is the same for the analogue experiment with neutrons, and a number of suitable isotopes exist which exhibit resonance in an accessible range of energy. Potential applications of resonance small angle neutron scatterings are discussed. 54 refs., 8 figs., 1 tab.

  2. Anomalous and resonance small angle scattering

    SciTech Connect

    Epperson, J.E.; Thiyagarajan, P.

    1987-11-01

    Significant changes in the small angle scattered intensity can be induced by making measurements with radiation close to an absorption edge of an appropriate atomic species contained in the sample. These changes can be related quantitatively to the real and imaginary anomalous dispersion terms for the scattering factor (x-rays) or scattering length (neutrons). The physics inherent in these anomalous dispersion terms is first discussed before considering how they enter the relevant scattering theory. Two major areas of anomalous scattering research have emerged; macromolecules in solution and unmixing of metallic alloys. Research in each area is reviewed, illustrating both the feasibility and potential of these techniques. All the experimental results reported to date have been obtained with x-rays. However, it is pointed out that the formalism is the same or the analogue experiment with neutrons, and a number of suitable isotopes exist which exhibit resonance in an accessible range of energy. Potential applications of resonance small-angle neutron scatterings are discussed. 8 figs.

  3. Radiation embrittlement studies using anomalous small-angle x-ray scattering

    SciTech Connect

    Alexander, D. E.; Kestel, B. J.; Seifert, S.; Jemian, P. R.; Odette, G. R.; Klingensmith, D.; Gragg, D.

    1999-12-06

    Anomalous small angle x-ray scattering (ASAXS) was performed on an Fe-O.9 wt.% Cu-1.0 wt.% Mn alloy subjected to annealing or electron irradiation. ASAXS takes advantage of natural variations in the atomic scattering factor which exist at energies very near an element's x-ray absorption edge. By performing systematic SAXS experiments at energies near these absorption edges of the constituent alloy elements it is possible to vary the contrast of scattering centers containing the elements and in doing so quantify scatterer composition. The results of such an analysis for the samples in this work indicate the presence of Cu-rich, Cu{sub 85}Mn{sub 15} precipitates in the alloy. By applying the maximum entropy technique to the scattering data, it was possible to extract size distributions of scattering centers fog the different treatments. The results demonstrate the ability to detect and characterize small (11 {angstrom} radius) scatterers at quite low irradiation damage levels (5x10{sup {minus} 4} displacements per atom).

  4. 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.

  5. 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.

  6. Anomalous grazing incidence small-angle x-ray scattering studies of platinum nanoparticles formed by cluster deposition.

    PubMed

    Lee, Byeongdu; Seifert, Sönke; Riley, Stephen J; Tikhonov, George; Tomczyk, Nancy A; Vajda, Stefan; Winans, Randall E

    2005-08-15

    The size evolution of platinum nanoparticles formed on a SiO2/Si(111) substrate as a function of the level of surface coverage with deposited clusters has been investigated. The anisotropic shapes of sub-nanometer-size nanoparticles are changed to isotropic on the amorphous substrate as their sizes increased. Using anomalous grazing incidence small-angle x-ray scattering (AGISAXS), the scattering from nanoparticles on the surface of a substrate is well separated from that of surface roughness and fluorescence. We show that AGISAXS is a very effective method to subtract the background and can provide unbiased information about particle sizes of less than 1 nm. PMID:16229604

  7. 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.

  8. 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.

  9. The distribution of Sr2+ counterions around polyacrylate chains analyzed by anomalous small-angle X-ray scattering

    NASA Astrophysics Data System (ADS)

    Goerigk, G.; Schweins, R.; Huber, K.; Ballauff, M.

    2004-05-01

    The distribution of Sr counterions around negatively charged sodium polyacrylate chains (NaPA) in aqueous solution was studied by anomalous small-angle X-ray scattering. Different ratios of the concentrations of SrCl2/[NaPA] reveal dramatic changes in the scattering curves. At the lower ratio the scattering curves indicate a coil-like behavior, while at the higher ratio the scattering curves are contracted to smaller q-values, caused by the collapse of the NaPA coil. The form factor of the scattering contribution of the counterions was separated and analyzed. For the scattering curves of the collapsed chains, this analysis agrees with the model of a pearl necklace, consisting of collapsed sphere-like subdomains which are connected by stretched chain segments. An averaged radius of the pearls of 19 nm and a distance between neighbouring pearls close to 60 nm could be established for the collapsed state of the NaPA chains.

  10. In-Situ Anomalous Small-Angle X-ray Scattering Studies of Polymer Electrolyte Membrane Fuel Cell Catalyst Degradation

    NASA Astrophysics Data System (ADS)

    Gilbert, James Andrew

    Polymer electrolyte membrane fuel cells (PEMFCs) are a promising high efficiency energy conversion technology, but their cost effective implementation, especially for automotive power, has been hindered by degradation of the electrochemically-active surface area (ECA) of the Pt nanoparticle electrocatalysts. While numerous studies using ex-situ post-mortem techniques have provided insight into the effect of operating conditions on ECA loss, the governing mechanisms and underlying processes are not fully understood. Toward the goal of elucidating the electrocatalyst degradation mechanisms, we have followed particle size distribution (PSD) growth evolutions of Pt and Pt-alloy nanoparticle catalysts during potential cycling in an aqueous acidic environment (with and without flow of electrolyte) and in a fuel cell environment using in-situ anomalous small-angle X-ray scattering (ASAXS). The results of this thesis show a surface area loss mechanism of Pt nanoparticles supported on carbon to be predominantly controlled by Pt dissolution, the particle size dependence of Pt dissolution, the loss of dissolved Pt into the membrane and electrolyte, and, to a lesser extent, the re-deposition of dissolved Pt onto larger particles. The relative extent of these loss mechanisms are shown to be dependent on the environment, the temperature, and the potential cycling conditions. Correlation of ASAXS-determined particle growth with both calculated and voltammetrically-determined oxide coverages demonstrates that the oxide coverage is playing a key role in the dissolution process and in the corresponding growth of the mean Pt nanoparticle size and loss of ECA. This understanding potentially reduces the complex changes in PSDs and ECA resulting from various voltage profiles to the response to a single variable, oxide coverage. A better understanding of the degradation mechanisms of Pt and Pt-alloy nanoparticle distributions could lead to more stable electrocatalysts while

  11. In situ anomalous small-angle X-ray scattering studies of platinum nanoparticle fuel cell electrocatalyst degradation.

    PubMed

    Gilbert, James A; Kariuki, Nancy N; Subbaraman, Ram; Kropf, A Jeremy; Smith, Matt C; Holby, Edward F; Morgan, Dane; Myers, Deborah J

    2012-09-12

    Polymer electrolyte fuel cells (PEFCs) are a promising high-efficiency energy conversion technology, but their cost-effective implementation, especially for automotive power, has been hindered by degradation of the electrochemically active surface area (ECA) of the Pt nanoparticle electrocatalysts. While numerous studies using ex situ post-mortem techniques have provided insight into the effect of operating conditions on ECA loss, the governing mechanisms and underlying processes are not fully understood. Toward the goal of elucidating the electrocatalyst degradation mechanisms, we have followed Pt nanoparticle growth during potential cycling of the electrocatalyst in an aqueous acidic environment using in situ anomalous small-angle X-ray scattering (ASAXS). ASAXS patterns were analyzed to obtain particle size distributions (PSDs) of the Pt nanoparticle electrocatalysts at periodic intervals during the potential cycling. Oxide coverages reached under the applied potential cycling protocols were both calculated and determined experimentally. Changes in the PSD, mean diameter, and geometric surface area identify the mechanism behind Pt nanoparticle coarsening in an aqueous environment. Over the first 80 potential cycles, the dominant Pt surface area loss mechanism when cycling to 1.0-1.1 V was found to be preferential dissolution or loss of the smallest particles with varying extents of reprecipitation of the dissolved species onto existing particles, resulting in particle growth, depending on potential profile. Correlation of ASAXS-determined particle growth with both calculated and voltammetrically determined oxide coverages demonstrates that the oxide coverage is playing a key role in the dissolution process and in the corresponding growth of the mean Pt nanoparticle size and loss of ECA. This understanding potentially reduces the complex changes in PSD and ECA resulting from various voltage profiles to a response dependent on oxide coverage. PMID:22857132

  12. Anomalous small angle x-ray scattering simulations: proof of concept for distance measurements for nanoparticle-labelled biomacromolecules in solution.

    PubMed

    Pinfield, Valerie J; Scott, David J

    2014-01-01

    Anomalous small angle X-ray scattering can in principle be used to determine distances between metal label species on biological molecules. Previous experimental studies in the past were unable to distinguish the label-label scattering contribution from that of the molecule, because of the use of atomic labels; these labels contribute only a small proportion of the total scattering signal. However, with the development of nanocrystal labels (of 50-100 atoms) there is the possibility for a renewed attempt at applying anomalous small angle X-ray scattering for distance measurement. This is because the contribution to the scattered signal is necessarily considerably stronger than for atomic labels. Here we demonstrate through simulations, the feasibility of the technique to determine the end-to-end distances of labelled nucleic acid molecules as well as other internal distances mimicking a labelled DNA binding protein if the labels are dissimilar metal nanocrystals. Of crucial importance is the ratio of mass of the nanocrystals to that of the labelled macromolecule, as well as the level of statistical errors in the scattering intensity measurements. The mathematics behind the distance determination process is presented, along with a fitting routine than incorporates maximum entropy regularisation. PMID:24759797

  13. Anomalous small angle x-ray scattering study of layered silicate clays containing Ni(II) and Er(III)

    SciTech Connect

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

    1995-12-01

    These studies concern the synthesis of heterogeneous catalysts and the incorporation of heavy metals in trapping media. The Ni(II) containing clays were synthesized at 200{degree}C whereas those containing Er(III) were ion-exchanged natural clays. For the first system, ASAXS data were measured at 5 different energies near the K{alpha} edge of Ni at three different reaction times: unreacted, 4 hrs, and 15 hrs, when the crystallization is essentially complete. The data for the unreacted sample showed no correlations for a lamellar particle, while that reacted for 4 hrs indicated the evolution of lamella, and the crystallized sample (15 hrs) exhibits much larger lamellar correlations. Systematic variations are seen in the data for the 4 hr and 15 hr samples that are due to the anomalous scattering from the ordered Ni atoms in the layered silicates. The erbium study provides the first scattering measurements of heavy metal ion salvation and migration in clays, which has implications for both catalysis and environmental issues. Systematic energy-dependent variations in the signals near the L{sub III} edge of Er are observed for the hydrated sample, but not for the ``dry,`` as-prepared sample.

  14. 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).

  15. Probing the extent of the Sr2+ ion condensation to anionic polyacrylate coils: a quantitative anomalous small-angle x-ray scattering study.

    PubMed

    Goerigk, G; Huber, K; Schweins, R

    2007-10-21

    The shrinking process of anionic sodium polyacrylate (NaPA) chains in aqueous solution induced by Sr2+ counterions was analyzed by anomalous small-angle x-ray scattering. Scattering experiments were performed close to the precipitation threshold of strontium polyacrylate. The pure-resonant scattering contribution, which is related to the structural distribution of the Sr2+ counterions, was used to analyze the extent of Sr2+ condensation onto the polyacrylate coils. A series of four samples with different ratios [Sr2+][NaPA] (between 0.451 and 0.464) has been investigated. From the quantitative analysis of the resonant invariant, the amount of Sr cations localized in the collapsed phase was calculated with concentrations v between 0.94x10(17) and 2.01x10(17) cm(-3) corresponding to an amount of Sr cations in the collapsed phase between 9% and 23% of the total Sr2+ cations in solution. If compared to the concentration of polyacrylate expressed in moles of monomers [NaPA], a degree of site binding of r=[Sr2+][NaPA] between 0.05 and 0.11 was estimated. These values clearly differ from r=0.25, which was established from former light scattering experiments, indicating that the counterion condensation starts before the phase border is reached and increases rather sharply at the border. PMID:17949215

  16. Probing the extent of the Sr2+ ion condensation to anionic polyacrylate coils: A quantitative anomalous small-angle x-ray scattering study

    NASA Astrophysics Data System (ADS)

    Goerigk, G.; Huber, K.; Schweins, R.

    2007-10-01

    The shrinking process of anionic sodium polyacrylate (NaPA) chains in aqueous solution induced by Sr2+ counterions was analyzed by anomalous small-angle x-ray scattering. Scattering experiments were performed close to the precipitation threshold of strontium polyacrylate. The pure-resonant scattering contribution, which is related to the structural distribution of the Sr2+ counterions, was used to analyze the extent of Sr2+ condensation onto the polyacrylate coils. A series of four samples with different ratios [Sr2+]/[NaPA] (between 0.451 and 0.464) has been investigated. From the quantitative analysis of the resonant invariant, the amount of Sr cations localized in the collapsed phase was calculated with concentrations v¯ between 0.94×1017 and 2.01×1017cm-3 corresponding to an amount of Sr cations in the collapsed phase between 9% and 23% of the total Sr2+ cations in solution. If compared to the concentration of polyacrylate expressed in moles of monomers [NaPA], a degree of site binding of r =[Sr2+]/[NaPA] between 0.05 and 0.11 was estimated. These values clearly differ from r =0.25, which was established from former light scattering experiments, indicating that the counterion condensation starts before the phase border is reached and increases rather sharply at the border.

  17. Small Angle Neutron Scattering

    SciTech Connect

    Urban, Volker S

    2012-01-01

    Small Angle Neutron Scattering (SANS) probes structural details at the nanometer scale in a non-destructive way. This article gives an introduction to scientists who have no prior small-angle scattering knowledge, but who seek a technique that allows elucidating structural information in challenging situations that thwart approaches by other methods. SANS is applicable to a wide variety of materials including metals and alloys, ceramics, concrete, glasses, polymers, composites and biological materials. Isotope and magnetic interactions provide unique methods for labeling and contrast variation to highlight specific structural features of interest. In situ studies of a material s responses to temperature, pressure, shear, magnetic and electric fields, etc., are feasible as a result of the high penetrating power of neutrons. SANS provides statistical information on significant structural features averaged over the probed sample volume, and one can use SANS to quantify with high precision the structural details that are observed, for example, in electron microscopy. Neutron scattering is non-destructive; there is no need to cut specimens into thin sections, and neutrons penetrate deeply, providing information on the bulk material, free from surface effects. The basic principles of a SANS experiment are fairly simple, but the measurement, analysis and interpretation of small angle scattering data involves theoretical concepts that are unique to the technique and that are not widely known. This article includes a concise description of the basics, as well as practical know-how that is essential for a successful SANS experiment.

  18. 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

  19. Dietary iron-loaded rat liver haemosiderin and ferritin: in situ measurement of iron core nanoparticle size and cluster structure using anomalous small-angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Bovell, Eliza; Buckley, Craig E.; Chua-anusorn, Wanida; Cookson, David; Kirby, Nigel; Saunders, Martin; St. Pierre, Timothy G.

    2009-03-01

    The morphology, particle size distribution and cluster structure of the hydrated iron(III) oxyhydroxide particles associated with haemosiderin and ferritin in dietary iron-loaded rat liver tissue have been investigated using transmission electron microscopy (TEM) and anomalous small-angle x-ray scattering (ASAXS). Rat liver tissue was removed from a series of female Porton rats which had been fed an iron-rich diet until sacrifice at various ages from 2-24 months. Hepatic iron concentrations ranged from 1 to 65 mg Fe g-1 dry tissue. TEM studies showed both dispersed and clustered iron-containing nanoparticles. The dispersed particles were found to have mean sizes (±standard deviation) of 54 ± 8 Å for the iron-loaded animals and 55 ± 7 Å for the controls. Superposition of particles in TEM images prevented direct measurement of nanoparticulate size in the clusters. The ASAXS data were modelled to provide a quantitative estimate of both the size and spacing of iron oxyhydroxide particles in the bulk samples. The modelling yielded close-packed particles with sizes of 60 to 78 Å which when corrected for anomalous scattering suggests sizes from 54 to 70 Å. Particle size distributions are of particular importance since they determine the surface iron to core iron ratios, which in turn are expected to be related to the molar toxicity of iron deposits in cells.

  20. 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

  1. 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.

  2. 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

  3. The DELPHI small angle tile calorimeter

    SciTech Connect

    Alvsvaag, S.J.; Maeland, O.A.; Klovning, A.

    1995-08-01

    The Small angle TIle Calorimeter (STIC) provides calorimetric coverage in the very forward region for the DELPHI experiment at the CERN LEP collider. A veto system composed of two scintillator layers allows to trigger on single photon events and provides e{minus}{gamma} separation. The authors present here some results of extensive measurements performed on part of the calorimeter and the veto system in the CERN test beams prior to installation and report on the performance achieved during the 1994 LEP run.

  4. 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.

  5. X-Ray Small Angle Scattering

    PubMed Central

    Pape, E. H.

    1974-01-01

    The direct determination of the electron density distributions of multilayered specimens with a small number of unit cells from X-ray small angle scattering experiments via the Q-function method of Hosemann and Bagchi includes the deconvolution of the so-called Qo-function, the generalized Patterson function of one unit cell. In this paper a new and direct deconvolution method on the basis of Fourier series is presented which is suitable for one-dimensional centrosymmetrical (or antisymmetrical) density distributions. A FORTRAN-program has been written which has an execution time of ca. 20 s on an UNIVAC 1106-computer. The procedure has been successfully tested on some convolution functions generated by membrane-type electron density distributions. PMID:4830467

  6. 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

  7. 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.

  8. 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.

  9. Phase sensitive small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Brok, Erik; Majkrzak, Charles F.; Krycka, Kathryn

    It is a well-known problem that information about the scattered wave is lost in scattering experiments because the measured quantity is the modulus squared of the complex wave function. This ''phase problem'' leads to ambiguity in determining the physical properties of the scattering sample. Small angle neutron scattering (SANS) is a useful technique for determining the structure of biomolecules, in particular proteins that cannot be crystallized and studied with x-ray crystallography. However, because the biomolecules are usually suspended in a liquid the observed scattering is an average of all possible orientations, making it difficult to obtain three dimensional structural information. In a proposed method polarized SANS and magnetic nanoparticle references attached to the sample molecules is used to obtain phase sensitive structural information and simultaneously circumvent the problem of orientational averaging (Majkrzak et al. J. Appl. Cryst. 47, 2014) If realized and perfected the technique is very promising for unambiguous determination of the three dimensional structure of biomolecules. We demonstrate the principles of our method and show the first experimental data obtained on a simple test system consisting of core shell magnetic nanoparticles.

  10. 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.

  11. 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.

  12. Small Bowel Obstruction due to Anomalous Congenital Bands in Children

    PubMed Central

    Soysal, Feryal Gun; Ozbey, Huseyin; Keskin, Erbug; Celik, Alaattin; Karadag, Aslı; Salman, Tansu

    2016-01-01

    Introduction. The aim of the study was to evaluate our children who are operated on for anomalous congenital band while increasing the awareness of this rare reason of intestinal obstruction in children which causes a diagnostic challenge. Patients and Methods. We retrospectively reviewed the records of fourteen children treated surgically for intestinal obstructions caused by anomalous congenital bands. Results. The bands were located between the following regions: the ascending colon and the mesentery of the terminal ileum in 4 patients, the jejunum and mesentery of the terminal ileum in 3 patients, the ileum and mesentery of the terminal ileum in 2 patients, the ligament of Treitz and mesentery of the jejunum in one patient, the ligament of Treitz and mesentery of the terminal ileum in one patient, duodenum and duodenum in one patient, the ileum and mesentery of the ileum in one patient, the jejunum and mesentery of the jejunum in one patient, and Meckel's diverticulum and its ileal mesentery in one patient. Band excision was adequate in all of the patients except the two who received resection anastomosis for intestinal necrosis. Conclusion. Although congenital anomalous bands are rare, they should be considered in the differential diagnosis of patients with an intestinal obstruction. PMID:27478432

  13. 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.

  14. Precision Small Angle Bending of Sheet Metals Using Shear Deformation

    NASA Astrophysics Data System (ADS)

    Hirota, Kenji; Mori, Yorifumi

    This paper deals with a new method to bend sheet metals at a small angle precisely, in which a sheet metal is slightly bent by shear deformation at negative punch-die clearance. Deformation behavior and key factors affecting on the bend angle were studied in detail with pure aluminum sheets. It was proved that the bend angle was changed in proportion to both punch penetration and negative punch-die clearance within a certain range. The same was true for high-strength steel and phosphor bronze, which are difficult to bend precisely by conventional methods due to large springback after unloading. By using this relationship as a control law, four kinds of sheet metals were precisely bent within a few degrees. This method was applied to correct the angular errors in U-bend products of high-strength steel and to bend leaf springs of phosphor bronze at an arbitrary small angle.

  15. Small angle scattering signals for (neutron) computerized tomography

    SciTech Connect

    Strobl, M.; Treimer, W.; Hilger, A.

    2004-07-19

    Small angle neutron scattering is a well-established tool for the determination of microscopic structures in various materials. With the ultrasmall angle neutron scattering technique (USANS), structures with sizes of approximately 50 nm to 50 {mu}m can be resolved by a double crystal diffractometer (DCD). USANS signals recorded with a special DCD were used for tomographic purposes investigating the macroscopic structure of a sample with a maximum resolution of 200 {mu}m. Thereby, macroscopic regions within the sample with different ultrasmall angle scattering properties, i.e., with different microscopic structures, could be imaged by the means of tomographic reconstruction from projections (on a macroscopic scale)

  16. 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.

  17. Ergodicity testing for anomalous diffusion: Small sample statistics

    NASA Astrophysics Data System (ADS)

    Janczura, Joanna; Weron, Aleksander

    2015-04-01

    The analysis of trajectories recorded in experiments often requires calculating time averages instead of ensemble averages. According to the Boltzmann hypothesis, they are equivalent only under the assumption of ergodicity. In this paper, we implement tools that allow to study ergodic properties. This analysis is conducted in two classes of anomalous diffusion processes: fractional Brownian motion and subordinated Ornstein-Uhlenbeck process. We show that only first of them is ergodic. We demonstrate this by applying rigorous statistical methods: mean square displacement, confidence intervals, and dynamical functional test. Our methodology is universal and can be implemented for analysis of many experimental data not only if a large sample is available but also when there are only few trajectories recorded.

  18. Ergodicity testing for anomalous diffusion: small sample statistics.

    PubMed

    Janczura, Joanna; Weron, Aleksander

    2015-04-14

    The analysis of trajectories recorded in experiments often requires calculating time averages instead of ensemble averages. According to the Boltzmann hypothesis, they are equivalent only under the assumption of ergodicity. In this paper, we implement tools that allow to study ergodic properties. This analysis is conducted in two classes of anomalous diffusion processes: fractional Brownian motion and subordinated Ornstein-Uhlenbeck process. We show that only first of them is ergodic. We demonstrate this by applying rigorous statistical methods: mean square displacement, confidence intervals, and dynamical functional test. Our methodology is universal and can be implemented for analysis of many experimental data not only if a large sample is available but also when there are only few trajectories recorded. PMID:25877558

  19. 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.

  20. 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.

  1. Gluon transport equations with condensate in the small angle approximation

    NASA Astrophysics Data System (ADS)

    Blaizot, Jean-Paul; Liao, Jinfeng

    2016-05-01

    We derive the set of kinetic equations that control the evolution of gluons in the presence of a condensate. We show that the dominant singularities remain logarithmic when the scattering involves particles in the condensate. This allows us to define a consistent small angle approximation.

  2. 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.

  3. 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.

  4. 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)

  5. 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.

  6. Small-angle neutron scattering from micellar solutions

    NASA Astrophysics Data System (ADS)

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

    2004-07-01

    Micellar solutions are the suspension of the colloidal aggregates of the sur- factant molecules in aqueous solutions. The structure (shape and size) and the interaction of these aggregates, referred to as micelles, depend on the molecular architecture of the surfactant molecule, presence of additives and the solution conditions such as tempera- ture, concentration etc. This paper gives the usefulness of small-angle neutron scattering to the study of micellar solutions with some of our recent results.

  7. SASBDB, a repository for biological small-angle scattering data

    PubMed Central

    Valentini, Erica; Kikhney, Alexey G.; Previtali, Gianpietro; Jeffries, Cy M.; Svergun, Dmitri I.

    2015-01-01

    Small-angle X-ray and neutron scattering (SAXS and SANS) are fundamental tools used to study the global shapes of proteins, nucleic acids, macromolecular complexes and assemblies in solution. Due to recent advances in instrumentation and computational methods, the quantity of experimental scattering data and subsequent publications is increasing dramatically. The need for a global repository allowing investigators to locate and access experimental scattering data and associated models was recently emphasized by the wwPDB small-angle scattering task force (SAStf). The small-angle scattering biological data bank (SASBDB) www.sasbdb.org has been designed in accordance with the plans of the SAStf as part of a future federated system of databases for biological SAXS and SANS. SASBDB is a comprehensive repository of freely accessible and fully searchable SAS experimental data and models that are deposited together with the relevant experimental conditions, sample details and instrument characteristics. At present the quality of deposited experimental data and the accuracy of models are manually curated, with future plans to integrate automated systems as the database expands. PMID:25352555

  8. 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

  9. Finding a covering triangulation whose maximum angle is provably small

    SciTech Connect

    Mitchell, S.A.; Park, J.K.

    1993-03-03

    Given a planar straight-line graph, we find a covering triangulation whose maximum angle is as small as possible. A covering triangulation is a triangulation whose vertex set contains the input vertex set and whose edge set contains the input edge set. Such a triangulation differs from the usual Steiner triangulation in that we may not add a Steiner vertex on any input edge. Covering triangulations provide a convenient method for triangulating multiple regions sharing a common boundary, as each region can be triangulated independently. As it is possible that no finite covering triangulation is optimal in terms of its maximum angle, we propose an approximation algorithm. Our algorithm produces a covering triangulation whose maximum angle {gamma} is probably close to {gamma}{sub opt}, a lower bound on the maximum angle in any covering triangulation of the input graph. Note that we must have {gamma} {le} 3{gamma}{sub opt}, since we always have {gamma}{sub opt} {ge} {pi}/3 and no triangulation can contain an angle of size greater than {pi}. We prove something significantly stronger. We show that {pi} {minus} {gamma} {ge} ({pi} {minus} {gamma}{sub opt})/6, i.e., our {gamma} is not much closer to {pi} than is {gamma}{sub opt}. This result represents the first nontrivial bound on a covering triangulation`s maximum angle. We require a subroutine for the following problem: Given a polygon with holes, find a Steiner triangulation whose maximum angle is bounded away from {pi}. No angle larger than 8{pi}/9 is sufficient for the bound on {gamma} claimed above. The number of Steiner vertices added by our algorithm and its running time are highly dependent on the corresponding bounds for the subroutine. Given an n-vertex planar straight-line graph, we require O(n + S(n)) Steiner vertices and O(n log n + T(n)) time, where S(n) is the number of Steiner vertices added by the subroutine and T(n) is its running time for an O(n)-vertex polygon with holes.

  10. Finding a covering triangulation whose maximum angle is provably small

    SciTech Connect

    Mitchell, S.A.; Park, J.K.

    1993-03-03

    Given a planar straight-line graph, we find a covering triangulation whose maximum angle is as small as possible. A covering triangulation is a triangulation whose vertex set contains the input vertex set and whose edge set contains the input edge set. Such a triangulation differs from the usual Steiner triangulation in that we may not add a Steiner vertex on any input edge. Covering triangulations provide a convenient method for triangulating multiple regions sharing a common boundary, as each region can be triangulated independently. As it is possible that no finite covering triangulation is optimal in terms of its maximum angle, we propose an approximation algorithm. Our algorithm produces a covering triangulation whose maximum angle [gamma] is probably close to [gamma][sub opt], a lower bound on the maximum angle in any covering triangulation of the input graph. Note that we must have [gamma] [le] 3[gamma][sub opt], since we always have [gamma][sub opt] [ge] [pi]/3 and no triangulation can contain an angle of size greater than [pi]. We prove something significantly stronger. We show that [pi] [minus] [gamma] [ge] ([pi] [minus] [gamma][sub opt])/6, i.e., our [gamma] is not much closer to [pi] than is [gamma][sub opt]. This result represents the first nontrivial bound on a covering triangulation's maximum angle. We require a subroutine for the following problem: Given a polygon with holes, find a Steiner triangulation whose maximum angle is bounded away from [pi]. No angle larger than 8[pi]/9 is sufficient for the bound on [gamma] claimed above. The number of Steiner vertices added by our algorithm and its running time are highly dependent on the corresponding bounds for the subroutine. Given an n-vertex planar straight-line graph, we require O(n + S(n)) Steiner vertices and O(n log n + T(n)) time, where S(n) is the number of Steiner vertices added by the subroutine and T(n) is its running time for an O(n)-vertex polygon with holes.

  11. 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.

  12. Breaking all the invariants: Anomalous electron radiation belt diffusion by pitch angle scattering in the presence of split magnetic drift shells

    NASA Astrophysics Data System (ADS)

    O'Brien, T. P.

    2014-01-01

    Relativistic electron observations near geostationary orbit routinely show pitch angle distributions peaked away from 90 degrees. These "butterfly" distributions are consistent with magnetic drift shell splitting combined with a radial flux gradient. During magnetic storms, nature adds pitch angle scattering to split drift shells, breaking all three adiabatic invariants of the particle's motion. Therefore, some degree of anomalous radial diffusion is likely, and cross terms between the gyration and drift invariants and between the bounce and drift invariants arise. Using typical assumptions about the pitch angle scattering and the magnetic field topology, we calculate these anomalous diffusion coefficients near geostationary orbit. We show that the anomalous radial diffusion can exceed that due to more traditional drift-resonant wave-particle interactions. We also show that the neglected cross terms, particularly the bounce-drift cross term, can be significant. These results suggest necessary additions to some global electron radiation belt simulations.

  13. Small angle neutron scattering from high impact polystyrene

    SciTech Connect

    Pringle, O.A.

    1981-01-01

    High impact polystyrene (HIPS) is a toughened plastic composed of a polystyrene matrix containing a few percent rubber in the form of dispersed 0.1 to 10 micron diameter rubber particles. Some commercial formulations of HIPS include the addition of a few percent mineral oil, which improves the toughness of the plastic. Little is known about the mechanism by which the mineral oil helps toughen the plastic. It is hypothesized that the oil is distributed only in the rubber particles, but whether this hypothesis is correct was not known prior to this work. The size of the rubber particles in HIPS and their neutron scattering length density contrast with the polystyrene matrix cause HIPS samples to scatter neutrons at small angles. The variation of this small angle neutron scattering (SANS) signal with mineral oil content has been used to determine the location of the oil in HIPS. The SANS spectrometer at the University of Missouri Research Reactor Facility (MURR) was used to study plastic samples similar in composition to commercial HIPS. The MURR SANS spectrometer is used to study the small angle scattering of a vertical beam of 4.75 A neutrons from solid and liquid samples. The scattered neutrons are detected in a 54 x 60 cm/sup 2/ position sensitive detector designed and built at MURR. A series of plastic samples of varying rubber and oil content and different rubber domain sizes and shapes were examined on the MURR SANS spectrometer. Analysis of the scattering patterns showed that the mineral oil is about eight to ten times more likely to be found in the rubber particles than in the polystyrene matrix. This result confirmed the hypothesis that the mineral oil is distributed primarily in the rubber particles.

  14. 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.

  15. Contrast variation in spin-echo small angle neutron scattering

    SciTech Connect

    Chen, Wei-Ren; Herwig, Kenneth W; Li, Xin; Liu, Emily; Liu, Yun; Pynn, Roger; Robertson, J. L.; Shew, Chwen-Yang; Smith, Gregory Scott; Wu, Bin

    2012-01-01

    The principle of using contrast variation spin-echo small angle neutron scattering (SESANS) technique for colloidal structural investigation is discussed. Based on the calculations of several model systems, we find that the contrast variation SESANS technique is not sensitive in detecting the structural characteristics of colloidal suspensions consisting of particles with uniform scattering length density profiles. However, its capability of resolving the structural heterogeneity, at both intra- and inter-colloidal length scales, is clearly demonstrated. The prospect of using this new technique to investigate the structural information that is difficult to be probed by other ways is also explored.

  16. 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.

  17. Analysis of PKR Structure by Small-Angle Scattering

    SciTech Connect

    VanOudenhove, Jennifer; Anderson, Eric; Krueger, Susan; Cole, James L.

    2009-04-27

    Protein kinase R (PKR) is a key component of the interferon antiviral defense pathway. Upon binding double-stranded RNA, PKR undergoes autophosphorylation reactions that activate the kinase. PKR contains an N-terminal double-stranded RNA binding domain, which consists of two tandem double-stranded RNA binding motifs, and a C-terminal kinase domain. We have used small-angle X-ray scattering and small-angle neutron scattering to define the conformation of latent PKR in solution. Guinier analysis indicates a radius of gyration of about 35 {angstrom}. The p(r) distance distribution function exhibits a peak near 30 {angstrom}, with a broad shoulder extending to longer distances. Good fits to the scattering data require models that incorporate multiple compact and extended conformations of the two interdomain linker regions. Thus, PKR belongs to the growing family of proteins that contain intrinsically unstructured regions. We propose that the flexible linkers may allow PKR to productively dimerize upon interaction with RNA activators that have diverse structures.

  18. Longitudinally slotted conical horn antenna with small flare angle

    NASA Astrophysics Data System (ADS)

    Scharten, T.; Nellen, J.; van den Bogaart, F.

    1981-06-01

    The radiation and cross polarization characteristics of a longitudinally slotted, conical horn antenna with small flare angle, excited in the modified TE(11) mode, are investigated. To this end the electromagnetic wave propagation in a longitudinally slotted circular waveguide is studied first, using a wall reactance model. Because of the need to introduce mode-dependent wall reactances in the present structure, conditions for orthogonality are given. Propagation characteristics and field line patterns are presented. It turns out that the modified TE(11) mode in this guide, used as an aperture antenna, produces a main radiation lobe which can be made nearly symmetrical around the axis over a wide frequency range by a proper choice of the slot depth. As a typical example, the maximum cross polarization level in the main lobe is lower than -30 to -45 dB, dependent on slot depth and frequency range. Experiments carried out with a slotted conical horn antenna with small flare angle confirm the theoretical results.

  19. X-ray small angle scattering. A new deconvolution method for evaluating electron density distributions from small angle scattering diagrams.

    PubMed

    Pape, E H

    1974-04-01

    The direct determination of the electron density distributions of multilayered specimens with a small number of unit cells from X-ray small angle scattering experiments via the Q-function method of Hosemann and Bagchi includes the deconvolution of the so-called Q(o)-function, the generalized Patterson function of one unit cell. In this paper a new and direct deconvolution method on the basis of Fourier series is presented which is suitable for one-dimensional centrosymmetrical (or antisymmetrical) density distributions. A FORTRAN-program has been written which has an execution time of ca. 20 s on an UNIVAC 1106-computer. The procedure has been successfully tested on some convolution functions generated by membrane-type electron density distributions. PMID:4830467

  20. Design of a small angle spectrometer: Application to food systems

    NASA Astrophysics Data System (ADS)

    Alexander, Marcela

    This thesis describes the design of a new class of spectrometer developed for the study of light scattering phenomena at very low angles. Its detection system is a state of the art Charged Couple Device (CCD) camera of short data gathering time and very high sensitivity and dynamic range. The Small Angle Light Scattering technique in this work is shown to be a useful tool for determining size distributions of particles whose diameter is larger than approximately 300 nm. For particles smaller than this size, the technique is a sensitive probe of Rayleigh scattering. The advantages presented by the use of a solid state camera enables the study of relatively fast dynamic phenomena such as aggregation. In this particular work, we followed the aggregation of casein micelles caused by the addition of rennet, and the aggregation of β- Lactoglobulin stabilized oil in water emulsions caused by the addition of CaCl2. For this last case, a discrete inversion technique, incorporating the Mie scattering theory, was applied to obtain size distribution histograms of the emulsion droplets as a function of aggregation time.

  1. 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.

  2. 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.

  3. Radiation damage study using small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Rétfalvi, E.; Török, Gy; Rosta, L.

    2000-03-01

    Nuclear radiation provides important changes in the microstructure of metallic components of nuclear power plant and research reactors, influencing their mechanical properties. The investigation of this problem has primary interest for the safety and life-time of such nuclear installations. For the characterization of this kind of nanostructures small angle neutron scattering technique is a very useful tool. We have carried out experiments on samples of irradiated reactor vessel material and welded components of VVER-440-type reactors on the SANS instrument at the Budapest Research Reactor. In our measurements irradiated as well as non-irradiated samples were compared and magnetic field was applied for viewing the magnetic structure effects of the materials. A clear modification of the structure due to irradiation was obtained. Our data were analyzed by the ITP92 code, the inverse Fourier transform program of O. Glatter [1].

  4. 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.

  5. Photometric Study Of 28978 Ixion At Small Phase Angle

    NASA Astrophysics Data System (ADS)

    Rousselot, Philippe; Petit, J.

    2010-10-01

    Discovered in 2001, the Kuiper Belt Object 28978 Ixion belongs to the dynamical class of Plutinos. Because of its brightness (R magnitude about 19.5) it has been extensively studied, its diameter and albedo being estimated by Spitzer to be about 570 km and 15% (Stansberry et al., 2008). Absorption feature of cristalline water ice has been detected (Merlin et al., 2010) and negative linear polarisation has been measured (Boehnhardt et al., 2004). So far no lightcurve nor phase curve at very small phase angle has been published, the only information being that the lightcurve amplitude was inferior to 0.15 magnitude (Ortiz et al., 2003). We present new photometric observations obtained with the 3.5-m telescope NTT at the European Southern Observatory with broad band filters (B, V, R and I). These observations permit to derive a rotation period of 15.9+/-0.5 hr (if a single-peaked lightcurve is assumed) with a peak to peak amplitude of 0.06+/-0.03 magnitude. The phase curve does not reveal any bright opposition surge even for very small phase angle (α=0.02 deg). When our data are combined with the one of Boehnhardt et al. (up to α=1.34 deg) a linear fit provides a slope of 0.201+/-0.014 mag/deg. References : Boehnhardt H., Bagnulo S., Muinonen K. et al., 2004, A&A 415, L21-L25 Merlin F., Barucci M.A., de Bergh C. et al., 2010, Icarus 208, 945-954 Ortiz J.L., Gutiérrez P.J., Casanova V., Sota A., 2003, A&A 407, 1149-1155 Stansberry J., Grundy W., Brown M. et al., 2008, The Solar System Beyond Neptune, Univ. of Arizona Press, pp161-179

  6. 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.

  7. The vectorial small angle modification of the spherical harmonics method for an arbitrary angle of irradiance of a slab

    NASA Astrophysics Data System (ADS)

    Budak, V. P.; Korkin, S. V.

    2006-11-01

    We offer the generalization of the vectorial small angle modification of the spherical harmonics method (VMSH) for an arbitrary angle and polarization sate of irradiance of a slab. Non diagonal elements of an aerosol scattering matrix were admitted. The smooth addition part for the VMSH is given. Thus we obtain a complete and accelerated solution of the vectorial radiative transfer equation.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. 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

  16. Branch Content in Hybrid Materials using Small-Angle Scattering

    NASA Astrophysics Data System (ADS)

    Beaucage, Greg

    2005-03-01

    Inorganic/organic hybrid materials often display ramified mass- fractal structures characterized by primary particle size, aggregate size, and mass-fractal dimension. Physical properties, such as mechanical and dynamic mechanical properties and electrical conductivity (in carbon composites for instance), can not be predicted using only these structural features since such properties are intimately tied to the degree and type of branching as shown by Witten [1]. Witten suggested the use of the minimum dimension, or the related connectivity dimension, to calculate mechanical response in these hybrid systems. A viable technique to quantify the minimum dimension and connectivity dimension in hybrid materials has, until recently, been absent from the literature. This presentation will discuss the use of small-angle x-ray and neutron scattering to describe branch content in hybrid materials [2] and will outline an approach to use the minimum dimension and connectivity dimension to predict static and dynamic mechanical properties for hybrid materials based on structure [1, 3]. 1. Witten TA, Rubinstein M, Colby RH Reinforcement of Rubber by Fractal Aggregates J Phys II 3 (3): 367-383 (1993). 2. Beaucage G Determination of branch fraction and minimum dimension of mass-fractal aggregates Phys Rev E 70 (3): art. no. 031401 Part 1 (2004). 3. Kohls DJ, Beaucage G Rational design of reinforced rubber Curr Opin Solid St M 6 (3): 183-194 (2002).

  17. 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

  18. 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.

  19. 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.

  20. Three Biomedical Beamlines at NSLS-II for Macromolecular Crystallography and Small-Angle Scattering

    NASA Astrophysics Data System (ADS)

    Schneider, D. K.; Berman, L. E.; Chubar, O.; Hendrickson, W. A.; Hulbert, S. L.; Lucas, M.; Sweet, R. M.; Yang, L.

    2013-03-01

    We report on the status of the development of three beamlines for the National Synchrotron Light Source-II (NSLS-II), two for macromolecular crystallography (MX), and one for wide- and small-angle x-ray scattering (SAXS). Funded by the National Institutes of Health, this suite of Advanced Beamlines for Biological Investigations with X-rays (ABBIX) is scheduled to begin operation by 2015. The two MX beamlines share a sector with identical canted in-vacuum undulators (IVU21). The microfocusing FMX beamline on the inboard branch employs a two-stage horizontal source demagnification scheme, will cover an energy range of 5 - 23 keV, and at 12.7 keV will focus a flux of up to 1013 ph/s into a spot of 1 μm width. The companion AMX beamline on the short outboard branch of the sector is tunable in the range of 5 - 18 keV and has a native focus of 4 μm (h) × 2 μm (v). This robust beamline will be highly automated, have high throughput capabilities, and with larger beams and low divergence will be well suited for structure determinations on large complexes. The high brightness SAXS beamline, LIX, will provide multiple dynamic and static experimental systems to support scientific programs in solution scattering, membrane structure determination, and tissue imaging. It will occupy a different sector, equipped with a single in-vacuum undulator (IVU23). It can produce beams as small as 1 μm across, and with a broad energy range of 2.1 - 18 keV it will support anomalous SAXS.

  1. 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

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

    PubMed

    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

  3. Long cavity and low repetition rate passively mode-locked fiber laser with high-energy right angle trapezoid shaped soliton in anomalous dispersion regime

    NASA Astrophysics Data System (ADS)

    Luo, Wenfeng; Lv, Shuyuan; Zhao, Xiaoxia; Qiao, Dun

    2015-05-01

    A long cavity passively mode locked fiber laser in the anomalous dispersion regime is reported. Nonlinear polarization rotation technique is employed to achieve the mode locking in our experiments. The output pulse from the fiber laser has the Gaussian profile spectrum and right angle trapezoid shape. Stable mode locking is achieved without using any dispersion-compensation components. The single pulse with an energy of 652 nJ and a repetition rate of 836 kHz at the pump power of approximately 500 mW is obtained and the duration of the output pulse increases linearly with the pump power. Different from the conventional low-energy soliton pulse, experimental results demonstrate that the passively mode locked fiber laser operating in the anomalous regime can also realize high energy pulse.

  4. Time-resolved small-angle x-ray-scattering study of ordering kinetics in diblock styrene-butadiene

    NASA Astrophysics Data System (ADS)

    Singh, M. A.; Harkless, C. R.; Nagler, S. E.; Shannon, R. F., Jr.; Ghosh, S. S.

    1993-04-01

    A detailed study of the kinetics of phase transformations of the diblock copolymer, styrene-butadiene, is reported. The technique of in situ time-resolved small-angle x-ray scattering with the use of synchrotron radiation has been used to study the first-order phase transitions of microphase separation and microdomain ordering. These transitions occur following a rapid, thermal quench from the homogeneous, disordered state to temperatures below the transition point. The isothermal ordering process is discussed in the context of classical theories of nucleation and growth. Anomalous temporal oscillations in the ordered-volume fraction are observed following quenches to temperatures just below the ordering transition. These results are reported and qualitatively discussed.

  5. Time-resolved small-angle x-ray-scattering study of ordering kinetics in diblock styrene-butadiene

    SciTech Connect

    Singh, M.A. ); Harkless, C.R. ); Nagler, S.E. ); Shannon, R.F. Jr.; Ghosh, S.S. )

    1993-04-01

    A detailed study of the kinetics of phase transformations of the diblock copolymer, styrene-butadiene, is reported. The technique of [ital in] [ital situ] time-resolved small-angle x-ray scattering with the use of synchrotron radiation has been used to study the first-order phase transitions of microphase separation and microdomain ordering. These transitions occur following a rapid, thermal quench from the homogeneous, disordered state to temperatures below the transition point. The isothermal ordering process is discussed in the context of classical theories of nucleation and growth. Anomalous temporal oscillations in the ordered-volume fraction are observed following quenches to temperatures just below the ordering transition. These results are reported and qualitatively discussed.

  6. 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.

  7. Measurement of small angle based on a (1 0 0) silicon wafer and heterodyne interferometer

    NASA Astrophysics Data System (ADS)

    Hsieh, Meng-Chang; Lin, Jiun-You; Chen, Yu-Fong; Chang, Chia-Ou

    2016-06-01

    In this paper, a new optical material application and a heterodyne interferometer are proposed for measuring small angles. In the proposed interferometer, the optical material is a (1 0 0) silicon wafer applied to compose a new architecture of small angle sensor. The small angle measurement used the phase difference which is dependent on the incident angle at the silicon wafer surface to deduce the angular variation. The proposed architecture is simple and uses the common path method to compare test and reference signals; thus, small angles can be easily and accurately measured by estimating the phase difference. The experimental results demonstrate the feasibility of this method. The angular resolution and sensitivity levels superior to 7 × 10-5° (1.3 × 10-6 rad) and 150 (deg/deg), respectively, were attainable in a dynamic range of 0.45°.

  8. 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

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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.

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

    NASA Astrophysics Data System (ADS)

    Dragolici, Cristian A.

    2014-11-01

    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.

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. Conceptual Design of the Small Angle Scattering Beamline at the Australian Synchrotron

    NASA Astrophysics Data System (ADS)

    Kirby, N.; Boldeman, J. W.; Gentle, I.; Cookson, D.

    2007-01-01

    A high performance small angle and wide angle x-ray scattering (SAXS/WAXS) beamline is one of the initial suite of beamlines to be built at the 3 GeV Australian Synchrotron. This beamline will be ready for use in 2008, for structural analysis across a wide range of research applications over length scales of ˜ 1 to greater than 5000 Å. The instrument is intended for advanced analysis capabilities only possible using synchrotron radiation, such as time, space and energy resolved analysis, and for weak scattering systems. Photon energies will be readily variable between 5.2 and 20 keV.

  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 PAGESBeta

    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. 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.

  8. 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

  9. 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)

  10. Effective phase function of light scattered at small angles by polydisperse particulate media

    NASA Astrophysics Data System (ADS)

    Turcu, I.

    2008-06-01

    Particles with typical dimensions higher than the light wavelength and relative refraction indexes close to one, scatter light mainly in the forward direction where the scattered light intensity has a narrow peak. For particulate media accomplishing these requirements the light scattered at small angles in a far-field detecting set-up can be described analytically by an effective phase function (EPF) even in the multiple scattering regime. The EPF model which was built for monodispersed systems has been extended to polydispersed media. The main ingredients consist in the replacement of the single particle phase function and of the optical thickness with their corresponding averaged values. Using a Gamma particle size distribution (PSD) as a testing model, the effect of polydispersity was systematically investigated. The increase of the average radius or/and of the PSD standard deviation leads to the decrease of the angular spreading of the small angle scattered light.

  11. 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

  12. 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)

  13. 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

  14. Ay Measurement in p→p-Elastic Scattering at Small Angles

    NASA Astrophysics Data System (ADS)

    Macharashvili, G.

    2016-02-01

    The proton analysing power in p→p elastic scattering has been measured at small angles at COSY-ANKE at 796MeV and five other beam energies between 1.6 and 2.4GeV using a polarized proton beam. The asymmetries obtained by detecting the fast proton in the ANKE forward detector or the slow recoil proton in a silicon tracking telescope are completely consistent. The sources of the systematic uncertainties and the time stability issue were considered. The ANKE data at the higher energies lie well above the predictions of the most recent partial wave solution at small angles. An updated phase shift analysis that uses the ANKE results together with the World data leads to a better description of these new measurements.

  15. Solution properties of a CO{sub 2}-soluble fluoropolymer via small angle neutron scattering

    SciTech Connect

    McClain, J.B.; Combes, J.R.; Romack, T.J.; Canelas, D.A.; Betts, D.E.; Samulski, E.T.; DeSimone, J.M.; Londono, D.; Wignall, G.D.

    1996-01-31

    In this communication, we report the first characterization of solutions of a high molecular weight polymer in supercritical CO{sub 2} by small-angle neutron scattering (SANS). It is shown that small-angle neutron scattering gives key molecular parameters of an amorphous fluoropolymer in supercritical CO{sub 2}, i.e., the molecular weight, radius of gyration, and second virial coefficient, and thereby gives insights into a polymer chain`s behavior in this unique solvent. The positive sign of the second virial coefficients indicate that this medium is a good solvent - there is no evidence of a collapsed chain conformation. In fact, we conclude from the SANS data that, in CO{sub 2}, the poly(FOA) chain dimensions are expanded relative to those characteristic of its melt. 29 refs., 2 figs., 1 tab.

  16. Elastic properties of polymer-doped dilute lamellar phases: A small-angle neutron scattering study

    NASA Astrophysics Data System (ADS)

    Ficheux, M.-F.; Bellocq, A.-M.; Nallet, F.

    2001-03-01

    We investigate experimentally, using small-angle neutron scattering the elastic properties of polymer-doped dilute lamellar phases. In our system the polymer is water-soluble but nevertheless partially adsorbs onto the negatively charged surfactant bilayers. The effective polymer-mediated interaction between bilayers is less repulsive than the weakly screened electrostatic interaction that prevails at zero polymer content. It even becomes attractive in some regions of the phase diagram. Small-angle neutron scattering allows us to measure directly the Caillé exponent η characterizing the bilayer fluctuations in lamellar (smectic A) phases, and thus indirectly estimate the compression modulus bar{B} as a measure of the strength of the bilayer-bilayer interactions. The compression modulus appears to be vanishing at a point located on the lamellar-lamellar phase separation boundary, a candidate critical point.

  17. 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

  18. Small-angle scattering of laser radiation by stable micron particles in twice-distilled water

    SciTech Connect

    Bunkin, N F; Suyazov, N V; Tsipenyuk, D Yu

    2005-02-28

    Small-angle scattering of laser radiation in purified (twice-distilled) water is studied experimentally. The scattering indicatrix shows that such water contains scattering micron impurities. The parameters of the size distribution of these impurities are estimated from the experimental data. The results obtained in the paper confirm the earlier proposed hypothesis about the presence of stable microbubbles of gas, bubstons, dissolved in pure liquids. (scattering of laser radiation)

  19. 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.

  20. 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.

  1. Reversible membrane reorganizations during photosynthesis in vivo: revealed by small-angle neutron scattering.

    PubMed

    Nagy, Gergely; Posselt, Dorthe; Kovács, László; Holm, Jens K; Szabó, Milán; Ughy, Bettina; Rosta, László; Peters, Judith; Timmins, Peter; Garab, Gyozo

    2011-06-01

    In the present study, we determined characteristic repeat distances of the photosynthetic membranes in living cyanobacterial and eukaryotic algal cells, and in intact thylakoid membranes isolated from higher plants with time-resolved small-angle neutron scattering. This non-invasive technique reveals light-induced reversible reorganizations in the seconds-to-minutes time scale, which appear to be associated with functional changes in vivo. PMID:21473741

  2. 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.

  3. 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.

  4. 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.

  5. X-ray small angle scattering of the human transferrin protein aggregates. A fractal study.

    PubMed Central

    Castellano, A C; Barteri, M; Bianconi, A; Borghi, E; Cassiano, L; Castagnola, M; Della Longa, S

    1993-01-01

    X-ray small angle scattering experiments, using a pin hole SAXS camera with Synchrotron radiation source, have been performed to study the conformational changes of lyophilized samples of Apo-, Mono-, and Diferric- human transferrin. We report the experimental evidence that the analysis of the scattered intensity through the fractal theory may give information on the particle size and its variation upon iron binding. PMID:8457675

  6. 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.

  7. 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

  8. 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.

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

    PubMed

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

    2016-05-21

    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. PMID:27082147

  10. A hierarchical algorithm for fast Debye summation with applications to small angle scattering.

    PubMed

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

    2012-09-30

    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 article 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. Effective Long-Range Attraction between Protein Molecules in Solutions Studied by Small Angle Neutron Scattering

    SciTech Connect

    Liu Yun; Chen, W.-R.; Chen, S.-H.; Fratini, Emiliano; Baglioni, Piero

    2005-09-09

    Small angle neutron scattering intensity distributions taken from cytochrome C and lysozyme protein solutions show a rising intensity at a very small wave vector Q, which can be interpreted in terms of the presence of a weak long-range attraction between protein molecules. This interaction has a range several times that of the diameter of the protein molecule, much greater than the range of the screened electrostatic repulsion. We show evidence that this long-range attraction is closely related to the type of anion present and ion concentration in the solution.

  12. 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...

  13. Small-angle (e-, Na) scattering in the 6-25-eV range

    NASA Astrophysics Data System (ADS)

    Jaduszliwer, B.; Weiss, P.; Tino, A.; Bederson, B.

    1984-09-01

    We have investigated elastic and inelastic scattering of electrons by sodium atoms at intermediate energies (6-25 eV) by the atomic-recoil technique, using a new atomic-beams apparatus. The effects of the apparatus geometry, atomic velocity, and electron energy distributions on the analysis of the experimental results have been examined in detail, and their effects on small-angle scattering have been incorporated into the present work. We present absolute measurements of the elastic (e-, Na) differential cross section at 10 eV for electron polar angles ranging between 12° and 22°. These measurements are in good agreement with the normalized results of S. K. Srivastava and L. Vuskovic

    [J. Phys. B 13, 2633 (1980)]
    and in reasonable agreement with the two-state close-coupling calculation of
    M. R. Issa (Ph.D. theis, University of Durham, 1977)
    . We also present absolute measurements of an integral over small angles of the 32P impact-excitation differential cross section, together with a precise prescription for comparison with theory. We found that the distortedwave-polarized-orbital calculation of J. V. Kennedy, V. P. Myerscough, and M. R. C. McDowell
    [J. Phys. B 10 3759 (1977)]
    gives results which are too high in the forward direction, while those of Issa are somewhat low.

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

    PubMed

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

    2015-11-19

    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

  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. 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.

  18. Note: Grazing incidence small and wide angle x-ray scattering combined with imaging ellipsometry

    SciTech Connect

    Koerstgens, V.; Meier, R.; Ruderer, M. A.; Guo, S.; Chiang, H.-Y.; Mueller-Buschbaum, P.; Perlich, J.; Roth, S. V.; Gehrke, R.

    2012-07-15

    The combination of grazing incidence small angle x-ray scattering (GISAXS) and grazing incidence wide angle x-ray scattering (GIWAXS) with optical imaging ellipsometry is presented as an upgrade of the available measurement techniques at the wiggler beamline BW4 of the Hamburger Synchrotronstrahlungslabor. The instrument is introduced with the description of the alignment procedure to assure the measurement of imaging ellipsometry and GISAXS/GIWAXS on the same sample spot. To demonstrate the possibilities of the new instrument examples of morphological investigation on films made of poly(3-hexylthiophene) and [6,6]-phenyl-C{sub 61} butyric acid methyl ester as well as textured poly(9,9-dioctylfluorene-alt-benzo-thia-diazole) are shown.

  19. 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.

  20. Structure and morphology of charged graphene platelets in solution by small-angle neutron scattering.

    PubMed

    Milner, Emily M; Skipper, Neal T; Howard, Christopher A; Shaffer, Milo S P; Buckley, David J; Rahnejat, K Adam; Cullen, Patrick L; Heenan, Richard K; Lindner, Peter; Schweins, Ralf

    2012-05-23

    Solutions of negatively charged graphene (graphenide) platelets were produced by intercalation of nanographite with liquid potassium-ammonia followed by dissolution in tetrahydrofuran. The structure and morphology of these solutions were then investigated by small-angle neutron scattering. We found that >95 vol % of the solute is present as single-layer graphene sheets. These charged sheets are flat over a length scale of >150 Å in solution and are strongly solvated by a shell of solvent molecules. Atomic force microscopy on drop-coated thin films corroborated the presence of monolayer graphene sheets. Our dissolution method thus offers a significant increase in the monodispersity achievable in graphene solutions. PMID:22574888

  1. Small angle neutron scattering data of polymer electrolyte membranes partially swollen in water

    PubMed Central

    Zhao, Yue; Yoshida, Miru; Oshima, Tatsuya; Koizumi, Satoshi; Rikukawa, Masahiro; Szekely, Noemi; Radulescu, Aurel; Richter, Dieter

    2016-01-01

    In this article, we show the small-angle neutron scattering (SANS) data obtained from the polymer electrolyte membranes (PEMs) equilibrated at a given relative humidity. We apply Hard-Sphere (HS) structure model with Percus–Yervick interference interactions to analyze the dataset. The molecular structure of these PEMs and the morphologies of the fully water-swollen membranes have been elucidated by Zhao et al. “Elucidation of the morphology of the hydrocarbon multi-block copolymer electrolyte membranes for proton exchange fuel cells” [1]. PMID:27054164

  2. Amorphous soft-magnetic ribbons studied by ultra-small-angle polarized neutron scattering

    NASA Astrophysics Data System (ADS)

    Badurek, G.; Jericha, E.; Grössinger, R.; Sato-Turtelli, R.

    2010-02-01

    When we investigated the magnetic structure of a variety of soft-magnetic amorphous ribbons by means of ultra-small-angle neutron scattering (USANSPOL) we were confronted with one particularly interesting Fe65.7Co18Si0.8B15.5 ribbon, provided by VAC Hanau. Due to a special thermal treatment during production a field- and stress-induced transverse domain texture was expected. Although the USANSPOL technique encountered its resolution limits during the investigation of this specific sample ribbon, such a texture could indeed be verified.

  3. 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.

  4. An overview of resid characterization by mass spectrometry and small angle scattering techniques.

    SciTech Connect

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

    1999-07-14

    The purpose of this presentation is to discuss what is known about the molecular structures found in petroleum resid from mass spectrometry and small angle neutron and X-ray scattering methods. The question about molecular size distributions and the occurrence of aggregation in the asphaltene fraction will be examined. Our understanding of this problem has evolved with the application of new analytical methods. Also, correlations with results from other approaches will be discussed. In addition, the issue of the nature of the heteroatom-containing molecules will be examined and the challenges that remain in this area.

  5. 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.

  6. 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.

  7. 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

  8. Small-angle X-ray scattering probe of intermolecular interaction in red blood cells

    NASA Astrophysics Data System (ADS)

    Liu, Guan-Fen; Wang, We-Jia; Xu, Jia-Hua; Dong, Yu-Hui

    2015-03-01

    With high concentrations of hemoglobin (Hb) in red blood cells, self-interactions among these molecules could increase the propensities of their polymerization and aggregation. In the present work, high concentration Hb in solution and red blood cells were analyzed by small-angle X-ray scattering. Calculation of the effective structure factor indicates that the interaction of Hb molecules is the same when they are crowded together in both the cell and physiological saline. The Hb molecules stay individual without the formation of aggregates and clusters in cells. Supported by National Basic Research Program of China (2009CB918600) and National Natural Science Foundation of China (10979005)

  9. Measurement of protein size in concentrated solutions by small angle X-ray scattering.

    PubMed

    Liu, Jun; Li, Zhihong; Wei, Yanru; Wang, Wenjia; Wang, Bing; Liang, Hongli; Gao, Yuxi

    2016-08-01

    By simulations on the distance distribution function (DDF) derived from small angle X-ray scattering (SAXS) theoretical data of a dense monodisperse system, we found a quantitative mathematical correlation between the apparent size of a spherically symmetric (or nearly spherically symmetric) homogenous particle and the concentration of the solution. SAXS experiments on protein solutions of human hemoglobin and horse myoglobin validated the correlation. This gives a new method to determine, from the SAXS DDF, the size of spherically symmetric (or nearly spherically symmetric) particles of a dense monodisperse system, specifically for protein solutions with interference effects. PMID:27241796

  10. Small angle neutron scattering data of polymer electrolyte membranes partially swollen in water.

    PubMed

    Zhao, Yue; Yoshida, Miru; Oshima, Tatsuya; Koizumi, Satoshi; Rikukawa, Masahiro; Szekely, Noemi; Radulescu, Aurel; Richter, Dieter

    2016-06-01

    In this article, we show the small-angle neutron scattering (SANS) data obtained from the polymer electrolyte membranes (PEMs) equilibrated at a given relative humidity. We apply Hard-Sphere (HS) structure model with Percus-Yervick interference interactions to analyze the dataset. The molecular structure of these PEMs and the morphologies of the fully water-swollen membranes have been elucidated by Zhao et al. "Elucidation of the morphology of the hydrocarbon multi-block copolymer electrolyte membranes for proton exchange fuel cells" [1]. PMID:27054164

  11. 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. PMID:9611762

  12. 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.

  13. Small-angle X-ray scattering analysis of stearic acid modified lipase.

    PubMed

    Maruyama, T; Nakajima, M; Ichikawa, S; Sano, Y; Nabetani, H; Furusaki, S; Seki, M

    2001-04-01

    Stearic acid modified lipase (from Rhizopus japonicus) exhibited remarkable interesterification activity in n-hexane, but crude native lipase did not. The structure of the fatty acid modified lipase had not been analyzed until now. We analyzed the modified lipase by small-angle X-ray scattering (SAXS) measurements in order to clarify the structure. SAXS measurements showed that the modified lipase consisted of a lipid lamellar structure and implied that the lipase was incorporated into the lamellar structure of stearic acid. The long spacings in the lamellar structures of the modified lipase and stearic acid were measured. PMID:11388447

  14. 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.

  15. A small angle neutron scattering study of mica based glass-ceramics with applications in dentistry

    NASA Astrophysics Data System (ADS)

    Kilcoyne, S. H.; Bentley, P. M.; Al-Jawad, M.; Bubb, N. L.; Al-Shammary, H. A. O.; Wood, D. J.

    2004-07-01

    We are currently developing machinable and load-bearing mica-based glass-ceramics for use in restorative dental surgery. In this paper we present the results of an ambient temperature small angle neutron scattering (SANS) study of several such ceramics with chemical compositions chosen to optimise machinability and strength. The SANS spectra are all dominated by scattering from the crystalline-amorphous phase interface and exhibit Q-4 dependence (Porod scattering) indicating that, on a 100Å scale, the surface of the crystals is smooth.

  16. Ion track annealing in quartz investigated by small angle X-ray scattering

    NASA Astrophysics Data System (ADS)

    Schauries, D.; Afra, B.; Rodriguez, M. D.; Trautmann, C.; Hawley, A.; Kluth, P.

    2015-12-01

    We report on the reduction of cross-section and length of amorphous ion tracks embedded within crystalline quartz during thermal annealing. The ion tracks were created via Au ion irradiation with an energy of 2.2 GeV. The use of synchrotron-based small angle X-ray scattering (SAXS) allowed characterization of the latent tracks, without the need for chemical etching. Temperatures between 900 and 1000 °C were required to see a notable change in track size. The shrinkage in cross-section and length was found to be comparable for tracks aligned perpendicular and parallel to the c-axis.

  17. Depth profiling of polymer films with grazing-incidence small-angle X-ray scattering

    PubMed Central

    Singh, Marsha A.; Groves, Michael N.

    2009-01-01

    A model-free method of reconstructing depth-specific lateral scattering from incident-angle-resolved grazing-incidence small-angle X-ray scattering (GISAXS) data is proposed. The information on the material which is available through variation of the X-ray penetration depth with incident angle is accessed through reference to the reflected branch of the GISAXS process. Reconstruction of the scattering from lateral density fluctuations is achieved by solving the resulting Fredholm integral equation with minimal a priori information about the experimental system. Results from simulated data generated for hypothetical multilayer polymer systems with constant absorption coefficient are used to verify that the method can be applied to cases with large X-ray penetration depths, as typically seen with polymer materials. Experimental tests on a spin-coated thick film of a blend of diblock copolymers demonstrate that the approach is capable of reconstruction of the scattering from a multilayer structure with the identification of lateral scattering profiles as a function of sample depth. PMID:19349663

  18. The performance of the small-angle diffractometer, SAND at IPNS.

    SciTech Connect

    Thiyagarajan, P.

    1998-07-17

    The time-of-flight small-angle diffractometer SAND has been serving the scientific user community since 1996. One notable feature of SAND is its capability to measure the scattered intensity in a wide Q (4{pi}sin{theta}/{lambda}, where 2{theta} is the scattering angle and {lambda} is the wavelength of the neutrons) range of 0.0035 to 0.5 {angstrom}{sup {minus}1} in a single measurement. The optical alignment system makes it easy to set up the instrument and the sample. The cryogenically cooled MgO filter reduces the fast neutrons over two orders of magnitude, while still transmitting over 70% of the cold neutrons. A drum chopper running at 15 Hz suppresses the delayed neutron background. SAND has a variety of ancillary equipment to control the sample environment. In this paper we describe the features of the SAND instrument, compare its data on a few standard samples with those measured at well established centers in the world, and display two scientific examples which take advantage of measuring data in a wide Q-range in a single measurement. With a new set of tight collimators the Q{sub min} can be lowered to 0.002 {angstrom}{sup {minus}1} and the presently installed high-angle bank of detectors will extend the Q{sub max} to 2 {angstrom}{sup {minus}1}.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. Drift-pots for small angle elastic scattering at the fermilab collider

    NASA Astrophysics Data System (ADS)

    Amos, N.; Baker, W.; Bertani, M.; Block, M.; DeSalvo, R.; Dimitryiannis, D.; Donati, A.; Eartly, D.; Ellsworth, R.; Giacomelli, G.; Goodman, J.; Lennox, A.; Maleyran, R.; Manarin, A.; Mondardini, M.; Orear, J.; Pruss, S.; Rubinstein, R.; Shukla, S.; Yodh, G.; York, T.; Zucchelli, S.

    1986-12-01

    In order to measure the small angle p- overlinep scattering at the Fermilab Tevatron collider we developed very small drift chambers integrated with thin-wall roman pots. We named them drift-pots. The drift-pots are active 100 μm from the vacuum of the beam with an expected resolution of 60 μm in the drift direction and 250 μm in charge division. They are radiation resistant detectors intrinsically insensitive to the beam pickup pulses and their multiple hit readout capability will allow us to push them into the beam halo where p- overlinep Coulomb elastic scattering dominates. For our application, we belive the drift-pots, are superior to state of the art silicon detectors.

  4. Riboswitch Conformations Revealed by Small-Angle X-Ray Scattering

    PubMed Central

    Lipfert, Jan; Herschlag, Daniel; Doniach, Sebastian

    2015-01-01

    Summary Riboswitches are functional RNA molecules that control gene expression through conformational changes in response to small-molecule ligand binding. In addition, riboswitch 3D structure, like that of other RNA molecules, is dependent on cation–RNA interactions as the RNA backbone is highly negatively charged. Here, we show how small-angle X-ray scattering (SAXS) can be used to probe RNA conformations as a function of ligand and ion concentration. In a recent study of a glycine-binding tandem aptamer from Vibrio cholerae, we have used SAXS data and thermodynamic modeling to investigate how Mg2+-dependent folding and glycine binding are energetically coupled. In addition, we have employed ab initio shape reconstruction algorithms to obtain low-resolution models of the riboswitch structure from SAXS data under different solution conditions. PMID:19381558

  5. Three dimensional reconstruction of nanoislands from grazing-incidence small-angle X-ray scattering

    NASA Astrophysics Data System (ADS)

    Yefanov, O. M.; Vartanyants, I. A.

    2009-02-01

    The combination of grazing-incidence small-angle x-ray scattering (GISAXS) with tomographic methods and phase retrieval is proposed for the reconstruction of the three-dimensional (3D) electron density of nanometer sized objects. In this approach GISAXS data from a small object are collected successively at different azimuthal angular positions. This 3D intensity distribution in reciprocal space is used for the phase retrieval and reconstruction of the 3D electron density. The power of our approach is demonstrated in a series of calculations performed in the frame of kinematical and distorted-wave Born approximation (DWBA) theories for the case of GISAXS scattering on a 200 nm island in the form of truncated pyramid.

  6. 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.

  7. 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.

  8. 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.

  9. Pressure Denaturation of Staphylococcal Nuclease Studied by Neutron Small-Angle Scattering and Molecular Simulation

    PubMed Central

    Paliwal, Amit; Asthagiri, Dilipkumar; Bossev, Dobrin P.; Paulaitis, Michael E.

    2004-01-01

    We studied the pressure-induced folding/unfolding transition of staphylococcal nuclease (SN) over a pressure range of ∼1–3 kilobars at 25°C by small-angle neutron scattering and molecular dynamics simulations. We find that applying pressure leads to a twofold increase in the radius of gyration derived from the small-angle neutron scattering spectra, and P(r), the pair distance distribution function, broadens and shows a transition from a unimodal to a bimodal distribution as the protein unfolds. The results indicate that the globular structure of SN is retained across the folding/unfolding transition although this structure is less compact and elongated relative to the native structure. Pressure-induced unfolding is initiated in the molecular dynamics simulations by inserting water molecules into the protein interior and applying pressure. The P(r) calculated from these simulations likewise broadens and shows a similar unimodal-to-bimodal transition with increasing pressure. The simulations also reveal that the bimodal P(r) for the pressure-unfolded state arises as the protein expands and forms two subdomains that effectively diffuse apart during initial stages of unfolding. Hydrophobic contact maps derived from the simulations show that water insertions into the protein interior and the application of pressure together destabilize hydrophobic contacts between these two subdomains. The findings support a mechanism for the pressure-induced unfolding of SN in which water penetration into the hydrophobic core plays a central role. PMID:15347583

  10. 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

  11. 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.

  12. 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.

  13. 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. PMID:25725857

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

    NASA Astrophysics Data System (ADS)

    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.

  15. 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.

  16. Small-angle Neutron Scattering Measurements of Liquid Helium Mixtures Confined in MCM-41

    NASA Astrophysics Data System (ADS)

    Kaiser, Helmut; Prisk, Timothy; Sokol, Paul; Steward, Ian; Pantalei, Claudia

    2011-03-01

    Small-angle neutron scattering (SANS) was used to study the isotopic distribution of liquid helium mixtures confined in MCM- 41, a silica glass with a 2D hexagonal net of monodisperse cylindrical pores, as a function of filling and He 3 concentration. The ordered pore array of MCM-41 gives rise to Bragg reflections with intensities determined by both how the liquid fills the pores and how the isotopes are distributed within the pores. The modulation in peak intensity can be modeled by writing down a form factors for cylindrical objects with varying scattering length density. Comparison will be made with small-angle X-ray (SAXS) scattering measurements performed with synchrotron light on liquid helium mixtures confined in aerogel. This work was supported by award 70NANB5H1163 from NIST, U.S. DOC. This Research at Oak Ridge National Laboratory's High Flux Isotope was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U. S. Department of Energy.

  17. 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.

  18. Small-Angle Scattering and Neutron Contrast Variation for Studying Bio-Molecular Complexes

    NASA Astrophysics Data System (ADS)

    Whitten, Andrew E.; Trewhella, Jill

    Structural molecular biology over the past several decades has progressed from studies of the individual proteins, subunits, and domains that accomplish specific biochemistry to seeking to understand the dynamic bio-molecular complexes and assemblies that are responsible for biological function. This progress has led to an expansion of the structural analysis “tool box” to include methods that complement the mainstay techniques of the field: X-ray crystallography, nuclear magnetic resonance (NMR), and cryo-electron microscopy. Small-angle scattering of X-rays or neutrons is one such complementary technique that provides information on the size and shape of scattering particles in solution. This low-resolution structural information can be a powerful complement to high-resolution structural data, especially for the study of bio-molecular interactions with ligands or each other. Further, exploitation of the different neutron-scattering properties of the stable isotopes of hydrogen (1H and 2H) can be used to enrich the information available from the small-angle scattering data, especially for bio-molecular complexes.

  19. Using Small-Angle Scattering Techniques to Understand Mechanical Properties of Biopolymer-Based Biomaterials

    PubMed Central

    Hyland, Laura L.; Taraban, Marc B.

    2013-01-01

    The design and engineering of innovative biopolymer-based biomaterials for a variety of biomedical applications should be based on the understanding of the relationship between their nanoscale structure and mechanical properties. Down the road, such understanding could be fundamental to tune the properties of engineered tissues, extracellular matrices for cell delivery and proliferation/differentiation, etc. In this tutorial review, we attempt to show in what way biomaterial structural data can help to understand the bulk material properties. We begin with some background on common types of biopolymers used in biomaterials research, discuss some typical mechanical testing techniques and then review how others in the field of biomaterials have utilized small-angle scattering for material characterization. Detailed examples are then used to show the full range of possible characterization techniques available for biopolymer-based biomaterials. Future developments in the area of material characterization by small-angle scattering will undoubtedly facilitate the use of structural data to control the kinetics of assembly and final properties of prospective biomaterials. PMID:24273590

  20. 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

  1. 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

  2. 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.

  3. Small-angle optical deflection from collinear configuration for sensitive detection in microfluidic systems.

    PubMed

    Yang, Li; Li, Xiangtang; Li, Jing; Yuan, Hongyan; Zhao, Shulin; Xiao, Dan

    2012-07-01

    This paper describes a novel detection system based on small-angle optical deflection from the collinear configuration of a microfluidic chip. In this system, the incident light beam was focused on the microchannel through the edge of a lens, resulting in a small deflection angle that deviated 20° from the collinear configuration. The emitted fluorescence was collected through the center of the same lens and delivered to a photomultiplier tube in the vertical direction; the reflection light of the chip plate was kept away from the detector. In contrast to traditional confocal and nonconfocal laser-induced fluorescence detection systems, background levels resulting from scattered excitation light, reflection and refraction from the microchip was significantly eliminated. Significant enhancement of the signal-to-noise ratio was obtained by shaping a laser beam that combined an attenuator with a spectral filter to optimize laser power and the dimensions of the laser beam. FITC and FITC-labeled amino acid were used as model analytes to demonstrate the performance sensitivity, separation efficiency, and reproducibility of this detection system by using a hybrid polydimethylsiloxane/glass microfluidic device. The limit of detection of FITC was estimated to be 2 pM (0.55 zmol) (S/N = 3). Furthermore, the single cell analysis for the determination of intracellular glutathione in a single 3T3 mouse fibroblast cell was demonstrated. The results suggest that the proposed optical arrangements will be promising for development of sensitive, low-cost microfluidic systems. PMID:22806465

  4. Diffraction limit of the theory of multiple small-angle neutron scattering by a dense system of scatterers

    NASA Astrophysics Data System (ADS)

    Dzheparov, F. S.; Lvov, D. V.

    2016-02-01

    Multiple small-angle neutron scattering by a high-density system of inhomogeneities has been considered. A combined approach to the analysis of multiple small-angle neutron scattering has been proposed on the basis of the synthesis of the Zernike-Prince and Moliére formulas. This approach has been compared to the existing multiple small-angle neutron scattering theory based on the eikonal approximation. This comparison has shown that the results in the diffraction limit coincide, whereas differences exist in the refraction limit because the latter theory includes correlations between successive scattering events. It has been shown analytically that the existence of correlations in the spatial position of scatterers results in an increase in the number of unscattered neutrons. Thus, the narrowing of spectra of multiple small-angle neutron scattering observed experimentally and in numerical simulation has been explained.

  5. MAGNETIC RECONNECTION IN THE SOLAR WIND AT CURRENT SHEETS ASSOCIATED WITH EXTREMELY SMALL FIELD SHEAR ANGLES

    SciTech Connect

    Gosling, J. T.; Phan, T. D.

    2013-02-01

    Using Wind 3 s plasma and magnetic field data, we have identified nine reconnection exhausts within a solar wind disturbance on 1998 October 18-20 driven by a moderately fast interplanetary coronal mass ejection (ICME). Three of the exhausts within the ICME were associated with current sheets having local field shear angles, {theta}, ranging from 4 Degree-Sign to 9 Degree-Sign , the smallest reported values of {theta} yet associated with reconnection exhausts in a space plasma. They were observed in plasma characterized by extremely low (0.02-0.04) plasma {beta}, and very high (281-383 km s{sup -1}) Alfven speed, V{sub A}. Low {beta} allows reconnection to occur at small {theta} and high V{sub A} leads to exhaust jets that are fast enough relative to the surrounding solar wind to be readily identified. Very small-{theta} current sheets are common in the solar wind at 1 AU, but typically are not associated with particularly low plasma {beta} or high V{sub A}. On the other hand, small-{theta} current sheets should be common in the lower solar corona, a plasma regime of extremely low {beta} and extremely high V{sub A}. Our observations lend credence to models that predict that reconnection at small-{theta} current sheets is primarily responsible for coronal heating.

  6. 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

  7. 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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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.

  9. 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

  10. 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

  11. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    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.

  13. 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.

  14. 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.

  15. 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

  16. 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

  17. Glassy Carbon as an Absolute Intensity Calibration Standard for Small-Angle Scattering

    NASA Astrophysics Data System (ADS)

    Zhang, Fan; Ilavsky, Jan; Long, Gabrielle G.; Quintana, John P. G.; Allen, Andrew J.; Jemian, Pete R.

    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.

  18. Morphological and structural characterization of PHBV/organoclay nanocomposites by small angle X-ray scattering.

    PubMed

    Carli, Larissa N; Bianchi, Otávio; Machado, Giovanna; Crespo, Janaina S; Mauler, Raquel S

    2013-03-01

    In this work, the morphological and structural behaviors of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) nanocomposites were investigated using small angle X-ray scattering (SAXS), wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). The nanocomposites with 1, 3 and 5 wt.% of organically modified montmorillonite Cloisite® 30B (OMMT) were prepared by melt processing in a twin screw extruder using two different processing conditions (low and high shear intensity). The lamellar long period of the polymer was lower for the nanocomposites, with high polydispersity values. However, the crystalline thickness increased with the clay content and was independent of the processing conditions. This behavior resulted in a high linear crystallinity of the nanocomposites with 3 and 5 wt.% OMMT. The disruption factor (β) was in agreement with the WAXD and TEM findings, indicating a good dispersion of the nanoparticles in the PHBV matrix with 3 wt.% of OMMT during the high shear intensity of melt processing. PMID:25427508

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. Nucleon-nucleon scattering at small angles, measured at ANKE-COSY

    NASA Astrophysics Data System (ADS)

    Bagdasarian, Z.

    2016-03-01

    The most accepted approach to describe nucleon-nucleon (NN) interaction is the partial wave analysis (PWA), which translates various experimental observables to the common language of the partial waves. The reliable analysis relies not only on the quality experimental data, but also on the measurements of scattering observables over preferably the full angular range. Small angle scattering has been measured for six beam energies between 0.8 and 2.4 GeV using polarized proton beam incident on both proton and deuteron unpolarized targets at COSY-ANKE. This proceeding will report on the published and preliminary results for both pp and pn scattering from this and other recent experiments at ANKE. This study aims to provide the valuable observables to the SAID group in order to improve the phenomenological understanding of the nucleon-nucleon interaction.

  6. 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

  7. Kinetics of structural reorganizations in multilamellar photosynthetic membranes monitored by small-angle neutron scattering.

    PubMed

    Nagy, Gergely; Kovács, László; Ünnep, Renáta; Zsiros, Ottó; Almásy, László; Rosta, László; Timmins, Peter; Peters, Judith; Posselt, Dorthe; Garab, Győző

    2013-07-01

    We demonstrate the power of time-resolved small-angle neutron scattering experiments for the investigation of the structure and structural reorganizations of multilamellar photosynthetic membranes. In addition to briefly summarizing our results on thylakoid membranes isolated from higher plants and in unicellular organisms, we discuss the advantages and technical and methodological limitations of time-resolved SANS. We present a detailed and more systematical investigation of the kinetics of light-induced structural reorganizations in isolated spinach thylakoid membranes, which show how changes in the repeat distance and in the long-range order of the multilamellar membranes can be followed with a time resolution of seconds. We also present data from comparative measurements performed on thylakoid membranes isolated from tobacco. PMID:23839900

  8. 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.

  9. 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.

  10. A new 40 m small angle neutron scattering instrument at HANARO, Korea

    NASA Astrophysics Data System (ADS)

    Han, Young-Soo; Choi, Sung-Min; Kim, Tae-Hwan; Lee, Chang-Hee; Cho, Sang-Jin; Seong, Baek-Seok

    2013-09-01

    A new 40 m Small Angle Neutron Scattering (SANS) instrument was constructed, and has been opened to outside users since November 2010 at HANARO, Korea. The instrument is equipped with state-of-the-art components, and the performance of the instrument is comparable to that of advanced SANS instruments. The flux at the sample position is measured as 2.9×107/cm2 s with a wavelength of 5 Å and a collimation length of 1.7 m. The Q-range of the instrument covers from 0.0007 to 1.1 Å-1 when the lens option is applied. In this paper, the design and characteristics of the 40 m SANS instrument are described, and data showing their performance are presented.

  11. Aggregates structure analysis of petroleum asphaltenes with small-angle neutron scattering.

    SciTech Connect

    Tanaka, R.; Hunt, J. E.; Winans, R. E.; Thiyagarajan, P.; Sato, S.; Takanohashi, T.; Idemitsu Kosan Co.; National Institute of Advanced Industrial Science and Technology

    2003-01-01

    The objective of this study is to examine changes in the structures of petroleum asphaltene aggregates in situ with small-angle neutron scattering (SANS). Asphaltenes were isolated from three different crude oils: Maya, Khafji, and Iranian Light. An aliquot of the 5 wt % asphaltene solution in deuterated Decalin, 1-methylnaphthalene, or quinoline was loaded in a special stainless steel cell for SANS measurements. SANS data measured at various temperatures from 25 to 350 {sup o}C showed various topological features different with asphaltene or solvent species. A fractal network was formed only with asphaltene of Maya in Decalin, and it remained even at 350 {sup o}C. In all of the solvents, asphaltenes aggregate in the form of a prolate ellipsoid with a high aspect ratio at 25 {sup o}C and got smaller with increasing temperature. That became a compact sphere with the size of around 25 {angstrom} in radius at 350 {sup o}C.

  12. Thirty meters small angle neutron scattering instrument at China advanced research reactor

    NASA Astrophysics Data System (ADS)

    Zhang, Hongxia; Cheng, He; Yuan, Guangcui; Han, Charles C.; Zhang, Li; Li, Tianfu; Wang, Hongli; Liu, Yun Tao; Chen, Dongfeng

    2014-01-01

    A high resolution 30 m small angle neutron scattering (SANS) instrument has been constructed by the Institute of Chemistry, Chinese Academy of Sciences (ICCAS), and installed at China Advanced Research Reactor (CARR). It is equipped with a mechanical velocity selector, pinhole (including multi-pinhole) collimation system, sample chamber, and high resolution two dimensional 3He position sensitive neutron detector. The flexible variations of incident neutron wavelength, source to sample distance, sample to detector distance and the presence of neutron focusing lenses enable a wide Q range from 0.001 Å-1 to 0.5 Å-1 in reciprocal space and to optimize the resolution required. The instrument is the first SANS instrument in China, and can be widely used for the structure characterization of various materials, as well as kinetic and dynamic observation during external stimulation. The design and characteristics of the instrument are presented in the manuscript.

  13. 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.

  14. Small-angle neutron scattering of nanocrystalline gadolinium and holmium with random paramagnetic susceptibility.

    PubMed

    Döbrich, Frank; Bick, Jens-Peter; Birringer, Rainer; Wolff, Matthias; Kohlbrecher, Joachim; Michels, Andreas

    2015-02-01

    A neutron study of nanocrystalline terbium (Balaji G et al 2008 Phys. Rev. Lett. 100 227202) has shown that the randomly oriented anisotropy of the paramagnetic susceptibility tensor may lead to strongly correlated nanoscale spin disorder in the paramagnetic state which can be probed very effectively by magnetic small-angle neutron scattering (SANS). In principle, this scenario is also applicable to other rare-earth metals and the size of the effect is expected to scale with the strength of the anisotropy in the paramagnetic state. Here, we report SANS results (in the paramagnetic state) on nanocrystalline inert-gas condensed samples of Gd and Ho, which represent the cases of low and high anisotropy, respectively. PMID:25563439

  15. Small-angle neutron scattering of nanocrystalline gadolinium and holmium with random paramagnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Döbrich, Frank; Bick, Jens-Peter; Birringer, Rainer; Wolff, Matthias; Kohlbrecher, Joachim; Michels, Andreas

    2015-02-01

    A neutron study of nanocrystalline terbium (Balaji G et al 2008 Phys. Rev. Lett. 100 227202) has shown that the randomly oriented anisotropy of the paramagnetic susceptibility tensor may lead to strongly correlated nanoscale spin disorder in the paramagnetic state which can be probed very effectively by magnetic small-angle neutron scattering (SANS). In principle, this scenario is also applicable to other rare-earth metals and the size of the effect is expected to scale with the strength of the anisotropy in the paramagnetic state. Here, we report SANS results (in the paramagnetic state) on nanocrystalline inert-gas condensed samples of Gd and Ho, which represent the cases of low and high anisotropy, respectively.

  16. Small Angle X-ray and Neutron Scattering in the Study of Polymers and Supramolecular Systems

    NASA Astrophysics Data System (ADS)

    Zeng, X. B.; Liu, F.; Xie, F.; Ungar, G.; Tschierske, C.; MacDonald, J. E.

    2008-03-01

    Some recent work carried out in our research group on complex structures found in polymers and supramolecular systems, using Small Angle X-ray and Neutron Scattering (SAXS and SANS) methods, are reviewed. These include, Combined SAXS and SANS study of superlattice structures in pure and mixed model polymers; Real-time SANS study of transient phases during polymer crystallization; Columnar phases with polygonal cross-sections in T-shaped polyphilic compounds;Complex 3-d phases formed by packing spherical objects (e.g. micelles self-assembled from tree-like molecules), including the recently discovered liquid quasi-crystals which possess 12-fold rotational symmetry. Examples of powder, fibre or surface oriented, and single-domain diffractions will be given. Reconstruction of electron density maps as well as computer modelling are also applied to help solving various complex structures.

  17. Quantification of Complex Topologies in Macromolecular and Nanoscale Structures using Small-Angle Scattering

    NASA Astrophysics Data System (ADS)

    Pradhan, Siddharth; Ramachandran, Ramanth; Rai, Durgesh; Beaucage, Gregory

    2012-02-01

    Polymers are characterized by molecular weight distribution, tacticity, block copolymer content and branch content and chain topology. The branch structure and particularly the topology of branched chains has remained a difficult characterization problem. Recently we have developed a scaling model that can be coupled with small-angle scattering to measure the average branch length, number of branches and branch-on-branch structure in macromolecules of complex topology. This method has been extended to understand the structure of two dimensional structures and crumpling in these macromolecular systems. We have explored a wide range of materials in this regard. This poster will give an overview of the current uses for the scaling model for macromolecular topology. References pertaining to this poster can be found at http://www.eng.uc.edu/˜gbeaucag/BranchingPapers.html.

  18. 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.

  19. 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.

  20. Small angle x ray scattering studies of aggregation in supercritical fluid solutions

    NASA Astrophysics Data System (ADS)

    Fulton, J. L.; Pfund, D. M.

    1994-10-01

    Small-angle x ray scattering (SAXS) can be used to derive structural information on molecular aggregates having sizes from 2 to 200 nm. Not only is the technique useful for probing fluid structure in pure and simple binary supercritical fluid systems, but the technique is also well suited to investigate a range of much more complex multi-molecular aggregates that form when surfactants are added to supercritical fluids. The authors describe the experimental apparatus that was constructed for these studies and the experimental approach used to collect the scattering data. They present scattering results for pure fluids and for fluids containing various types of microemulsion phases, including reverse micelle and normal micelle phases. These results demonstrate that SAXS is a powerful technique for probing various types of molecular aggregation in supercritical fluid solutions.

  1. Small angle neutron scattering study on the structural variation of lysozyme in bioprotectants

    NASA Astrophysics Data System (ADS)

    Koda, Shota; Takayama, Haruki; Shibata, Tomohiko; Mori, Tatsuya; Kojima, Seiji; Park, In-Sung; Shin, Tae-Gyu

    2015-05-01

    The thermal denaturation and subsequent structural variation of lysozyme in various bioprotectant candidate solutions such as trehalose and choline acetate have been investigated by using small angle neutron scattering and differential scanning calorimetry. The gyration radius shows little change with the addition of additives in a native state at room temperature. On heating the lysozyme solution, a remarkable increase in the gyration radius is observed at temperatures above the denaturation temperature without any bioprotectants. Such an increase is suppressed by the additives owing to the intermolecular interactions between the lysozyme molecules and the bioprotectants of trehalose and choline acetate. The fractal dimension of lysozyme varies slightly with the addition of the bioprotectant solutions, and shows a remarkable drop in the vicinity of the denaturation temperature for all the solutions.

  2. Accurate determination of relative metatarsal protrusion with a small intermetatarsal angle: a novel simplified method.

    PubMed

    Osher, Lawrence; Blazer, Marie Mantini; Buck, Stacie; Biernacki, Tomasz

    2014-01-01

    Several published studies have explained in detail how to measure relative metatarsal protrusion on the plain film anteroposterior pedal radiograph. These studies have demonstrated the utility of relative metatarsal protrusion measurement in that it correlates with distal forefoot deformity or pathologic features. The method currently preferred by practitioners in podiatric medicine and surgery often presents one with the daunting challenge of obtaining an accurate measurement when the intermetatarsal 1-2 angle is small. The present study illustrates a novel mathematical solution to this problem that is simple to master, relatively quick to perform, and yields accurate results. Our method was tested and proven by 4 trained observers with varying degrees of clinical skill who independently measured the same 10 radiographs. PMID:24933656

  3. Small-angle neutron scattering studies on nonionic surfactant: Effect of sugars

    NASA Astrophysics Data System (ADS)

    Shivaji Sharma, K.; Joshi, J. V.; Aswal, V. K.; Goyal, P. S.; Rakshit, A. K.

    2004-08-01

    Micellar solution of nonionic surfactant n-dodecyloligo ethyleneoxide surfactant, decaoxyethylene monododecyl ether [CH3(CH2)11(OCH2CH2) 10OH], C12E10 in D2O solution have been analysed by small-angle neutron scattering (SANS) at different temperatures (30, 45 and 60oC) both in the presence and absence of sugars. The structural parameters like micelle shape and size, aggregation number and micellar density have been determined. It is found that the micellar structure significantly depends on the temperature and concentration of sugars. The micelles are found to be prolate ellipsoids at 30oC and the axial ratio of the micelle increases with the increase in temperature. The presence of lower concentration of sugar reduces the size of micelles and it grows at higher concentration of sugar. The structure of micelles is almost independent of the different types of sugars used.

  4. π-conjugation and conformation in a semiconducting polymer: small angle x-ray scattering study

    NASA Astrophysics Data System (ADS)

    Choudhury, Paramita Kar; Bagchi, Debjani; Menon, Reghu

    2009-05-01

    Small angle x-ray scattering (SAXS) in a poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) solution has shown the important role of π-electron conjugation in controlling the chain conformation and assembly. By increasing the extent of conjugation from 30 to 100%, the persistence length (lp) increases from 20 to 66 Å. Moreover, a pronounced second peak in the pair distribution function has been observed in a fully conjugated chain, at larger length scales. This feature indicates that the chain segments tend to self-assemble as the conjugation along the chain increases. Xylene enhances the rigidity of the PPV backbone to yield extended structures, while tetrahydrofuran solvates the side groups to form compact coils in which the lp is much shorter.

  5. Structured water in polyelectrolyte dendrimers: Understanding small angle neutron scattering results through atomistic simulation

    SciTech Connect

    Chen, Wei-Ren; Do, Changwoo; Hong, Kunlun; Liu, Emily; Liu, Yun; Porcar, L.; Smith, Gregory Scott; Wu, Bin; Egami, T; Smith, Sean C

    2012-01-01

    Based on atomistic molecular dynamics (MD) simulations, the small angle neutron scattering (SANS) intensity behavior of a single generation-4 (G4) polyelectrolyte polyamidoamine (PAMAM) starburst dendrimer is investigated at different levels of molecular protonation. The SANS form factor, P(Q), and Debye autocorrelation function, (r), are calculated from the equilibrium MD trajectory based on a mathematical approach proposed in this work which provides a link between the neutron scattering experiment and MD computation. The simulations enable scattering calculations of not only the hydrocarbons, but also the contribution to the scattering length density fluctuations caused by structured, confined water within the dendrimer. Based on our computational results, we question the validity of using radius of gyration RG for microstructure characterization of a polyelectrolyte dendrimer from the scattering perspective.

  6. Magnetic Field and Pressure Dependence of Small Angle Neutron Scattering in MnSi

    SciTech Connect

    Pfleiderer, C.; Reznik, D.; Pintschovius, L.; Haug, J.

    2007-10-12

    We report small angle neutron scattering of spontaneous and magnetic field aligned components of the helical spin polarization in MnSi for temperatures T down to 0.35 K, at pressures p up to 21 kbar, and magnetic field B up to 0.7 T. The parameter range of our study spans the first order transition between helical order and partial magnetic order at p{sub c}=14.6 kbar, which coincides with the onset of an extended regime of non-Fermi liquid resistivity. Our study suggests that MnSi above p{sub c} is not dominated by the remnants of the first order transition at p{sub c}, but that an unidentified mechanism favors stabilization of a new ground state other than helical order.

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

    SciTech Connect

    Stebbins, A. ); Veeraraghavan, S. )

    1995-02-15

    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 [ital 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.

  8. 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

  9. 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

  10. Brain tumor imaging using small-angle x-ray scattering tomography

    NASA Astrophysics Data System (ADS)

    Jensen, Torben H.; Bech, Martin; Bunk, Oliver; Thomsen, Maria; Menzel, Andreas; Bouchet, Audrey; Le Duc, Géraldine; Feidenhans'l, Robert; Pfeiffer, Franz

    2011-03-01

    We demonstrate high-resolution small-angle x-ray scattering computed tomography (SAXS-CT) of soft matter and soft tissue samples. Complete SAXS patterns over extended ranges of momentum transfer are reconstructed spatially resolved from volumes inside an extended sample. Several SAXS standard samples are used to quantitatively validate the method and demonstrate its performance. Further results on biomedical tissue samples (rat brains) are presented that demonstrate the advantages of the method compared to existing biomedical x-ray imaging approaches. Functional areas of the brains as well as tumor morphology are imaged. By providing insights into the structural organization at the nano-level, SAXS-CT complements and extends results obtainable with standard methods such as x-ray absorption tomography and histology.

  11. 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.}

  12. 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.

  13. 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.

  14. Small angle neutron scattering as fingerprinting of ancient potteries from Sicily (Southern Italy)

    SciTech Connect

    Barone, G.; Mazzoleni, P.; Crupi, V.; Majolino, D.; Venuti, V.; Teixeira, J.

    2009-09-01

    Small angle neutron scattering measurements have been carried out in order to investigate, in microdestructive way, the mesoscopic structure of a variety of potteries of relevance to cultural heritage coming from different Sicilian (Southern Italy) archeological sites belonging to the 'Strait of Messina' area and dated back to 7th-3rd century B.C. Data have been compared with the mesoscopic parameters extracted for two series of clayey sediments typical of the Strait of Messina area and fired under controlled conditions. The observed agreement between the features of reference and archeological samples allowed us to estimate the maximum firing temperature of the latter. Information on the pore sizes was obtained by the use of the concept of fractal surface, and compared with porosimetry results.

  15. Response properties of gerbil otolith afferents to small angle pitch and roll tilts

    NASA Technical Reports Server (NTRS)

    Dickman, J. D.; Angelaki, D. E.; Correia, M. J.

    1991-01-01

    The responses from isolated single otolith afferent fibers were obtained to small angle sinusoidal pitch and roll tilts in anesthetized gerbils. The stimulus directions that produced the maximum (response vector) and minimum response sensitivities were determined for each otolith afferent, with response vectors for the units being spread throughout the horizontal plane, similar to those reported for other species. A breadth of tuning measure was derived, with narrowly tuned neurons responding maximally to stimulation in one direction and minimally along an orthogonal ('null') direction. Most (approximately 80%) otolith afferents are narrowly tuned, however, some fibers were broadly tuned responding significantly to stimulations in any direction in the horizontal plane. The number of broadly tuned otolith afferents (approximately 20%) differs significantly from the more substantial number of broadly tuned vestibular nuclei neurons (88%) recently reported in rats.

  16. Characterization of hyperuniformity in colloidal suspensions through small angle static light scattering

    NASA Astrophysics Data System (ADS)

    Bretz, Coline; Still, Tim; Bartolo, Denis; Baudry, Jean; Yodh, Arjun; Dreyfus, Remi

    Hyperuniform materials have attracted increasing interest over the past decade due to their potential exciting photonic properties. Our work aims at exploring novel ways of assembling hyperuniform materials from colloidal suspensions. Three-dimensional systems of micrometer-sized colloids are considered and characterized by studying their structure factor using static small angle light scattering (SLS). A SLS set-up has been constructed for this purpose. Using an index-matched suspension of colloidal particles, we are able to record the structure factors of suspensions of micrometer-sized colloids in a three-dimensional cell. We will show how our apparatus allows us to follow the spatial organization of the colloids and characterize their hyperuniformity.

  17. 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.

  18. Probing ballistic microdrop coalescence by stroboscopic small-angle X-ray scattering

    NASA Astrophysics Data System (ADS)

    Graceffa, R.; Burghammer, M.; Davies, R. J.; Riekel, C.

    2012-12-01

    The coalescence of ballistic microdrops has been explored by stroboscopic synchrotron radiation microbeam small-angle X-ray scattering (μSAXS). About 80 μm diameter microdrops generated by a drop-on-demand inkjet system travelled at ˜1.7 m/s through a ˜1 μm X-ray beam. Microdrops of cytochrome C and acetate buffer solutions were merged in order to study the pH driven conformational change. μSAXS patterns were accumulated on a pixel detector, which was activated for a few μsec during the transit time of each microdrop through the microbeam. Local probing of the merging microdrops reveals the internal protein solution flow.

  19. 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.

  20. New developments in the ATSAS program package for small-angle scattering data analysis

    PubMed Central

    Petoukhov, Maxim V.; Franke, Daniel; Shkumatov, Alexander V.; Tria, Giancarlo; Kikhney, Alexey G.; Gajda, Michal; Gorba, Christian; Mertens, Haydyn D. T.; Konarev, Petr V.; Svergun, Dmitri I.

    2012-01-01

    New developments in the program package ATSAS (version 2.4) for the processing and analysis of isotropic small-angle X-ray and neutron scattering data are described. They include (i) multiplatform data manipulation and display tools, (ii) programs for automated data processing and calculation of overall parameters, (iii) improved usage of high- and low-resolution models from other structural methods, (iv) new algorithms to build three-dimensional models from weakly interacting oligomeric systems and complexes, and (v) enhanced tools to analyse data from mixtures and flexible systems. The new ATSAS release includes installers for current major platforms (Windows, Linux and Mac OSX) and provides improved indexed user documentation. The web-related developments, including a user discussion forum and a widened online access to run ATSAS programs, are also presented. PMID:25484842

  1. 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.

  2. 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.

  3. Kinetic analysis of spinodal decomposition process in Fe-Cr alloys by small angle neutron scattering

    SciTech Connect

    Ujihara, T.; Osamura, K.

    2000-04-19

    The rate of spinodal decomposition depends on the spatial composition distribution. In order to estimate the time dependence of its rate experimentally, the structure change was investigated in Fe-30 at.% Cr and Fe-50 at.% Cr alloys aged at 748, 773, 798, and 823 K via small angle neutron scattering and a kinetic analysis of experimental data was carried out by using the Langer-Bar-on-Miller (LBM) theory. Their theory contains a rate term of a physical meaning similar to the diffusion coefficient. As a result, it becomes clear that the rate term corresponding to the diffusion coefficient decreases as decomposition advances and this fact can be explained by the modified LBM theory considering the composition-dependent mobility.

  4. Small-angle polarized neutron studies of perpendicular magnetic recording media

    NASA Astrophysics Data System (ADS)

    Lister, S. J.; Wismayer, M. P.; Venkataramana, V.; de Vries, M. A.; Ray, S. J.; Lee, S. L.; Thomson, T.; Kohlbrecher, J.; Do, H.; Ikeda, Y.; Takano, K.; Dewhurst, C.

    2009-09-01

    Polarized small-angle neutron scattering has been used to measure the local magnetic structure of writable thin-film perpendicular media with a granular CoCrPt-SiOx recording layer. By exploiting the cross terms between the nuclear and magnetic scattering, we are able to probe simultaneously both the grain structure and the subgranular magnetic structure of the recording layer, which has a thickness of only 15 nm and which is embedded within a full perpendicular media structure including soft underlayer. Two models are used to analyze the data, one analytical and the other a numerical approach based on transmission electron microscopy measurements of the grains. Both models show that the recording layer consists of ferromagnetically ordered core regions that are smaller in extent than the corresponding grains and allow a direct, quantitative comparison of these two length scales.

  5. Small angle X-ray scattering studies of aggregation in supercritical fluid solutions

    SciTech Connect

    Fulton, J.L.; Pfund, D.M.

    1994-10-01

    Small-angle X-ray scattering (SAXS) can be used to derive structural information on molecular aggregates having sizes from 2 to 200 nm. Not only is the technique useful for probing fluid structure in pure and simple binary supercritical fluid systems, but the technique is also well suited to investigate a range of much more complex multi-molecular aggregates that form when surfactants are added to supercritical fluids. The authors describe the experimental apparatus that was constructed for these studies and the experimental approach used to collect the scattering data. They present scattering results for pure fluids and for fluids containing various types of microemulsion phases, including reverse micelle and normal micelle phases. These results demonstrate that SAXS is a powerful technique for probing various types of molecular aggregation in supercritical fluid solutions.

  6. 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.

  7. Micromagnetic modeling and small-angle neutron scattering characterization of magnetic nanocomposites

    NASA Astrophysics Data System (ADS)

    Erokhin, Sergey; Berkov, Dmitry; Gorn, Nataliya; Michels, Andreas

    2012-01-01

    A new methodology for micromagnetic simulations of magnetic nanocomposites is presented. The methodology is especially suitable for simulations of two-phase composites consisting of magnetically hard inclusions in a soft magnetic matrix phase. The proposed technique allows us to avoid unnecessary discretization of the “hard” inclusions (these are normally in a single-domain state) but enables arbitrary fine discretization of the “soft” phase. The method is applied to the determination of the equilibrium magnetization state of an iron-based nanocomposite from the Nanoperm (FeZrBCu) family of alloys and to the calculation of the corresponding small-angle neutron scattering (SANS) cross-section. The results of our simulations exhibit a remarkable agreement with nontrivial “clover-leaf” SANS cross-sections observed experimentally.

  8. Time-resolved studies of dynamic biomolecules using small angle X-ray scattering.

    PubMed

    Kirby, Nigel M; Cowieson, Nathan P

    2014-10-01

    Small angle X-ray scattering (SAXS) of biomacromolecules in solution has become a prominent technique in structural biology. Whilst the majority of current use is for static measurements, the field is also advancing for measurements where the sample at the beam position changes with time, using high throughput systems, chromatography, high speed mixing and pump-probe techniques in particular. Time resolved work is greatly aided by increasingly sophisticated software for acquiring and analysing data, together with developments in X-ray sources, beamline optics and detectors. The exploitation of spatial coherence is under development, with X-ray free electron lasers aiming to provide major advances in single molecule structure reconstruction and time resolution. Here we provide an overview of current developments advancing time resolved solution SAXS. PMID:25108308

  9. 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.

  10. Quantitative Analysis of Cementite Spheroidization in Pearlite by Small-Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Su, Yuhua; Morooka, Satoshi; Ohnuma, Masato; Suzuki, Junichi; Tomota, Yo

    2015-04-01

    Small-angle neutron scattering (SANS) was used to investigate the spheroidization of cementite in pearlite upon annealing. Globally averaged information on the shape and size of cementite particles was collected by using the SANS profile analysis of 0.8 mass pct C pearlitic steel (0.8C) samples annealed at 973 K (700 °C) for 3.6 to 86.4 ks. The change in the total area of the ferrite-cementite interface or aspect ratio determined by ex situ SANS exhibits excellent correspondence with scanning electron microscopy observations. Then, in situ SANS data were collected during isothermal annealing of the 0.8C steel and the commercially available 0.45C carbon steel (JIS-S45C). The shape change of the cementite plate was monitored, and the spheroidization rate of the 0.8C steel was found to be faster than that of the 0.45C steel.

  11. 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.

  12. Small-angle neutron scattering study of micropore collapse in amorphous solid water.

    PubMed

    Mitterdorfer, Christian; Bauer, Marion; Youngs, Tristan G A; Bowron, Daniel T; Hill, Catherine R; Fraser, Helen J; Finney, John L; Loerting, Thomas

    2014-08-14

    Vapor-deposited amorphous solid water (ASW) is the most abundant solid molecular material in space, where it plays a direct role in both the formation of more complex chemical species and the aggregation of icy materials in the earliest stages of planet formation. Nevertheless, some of its low temperature physics such as the collapse of the micropore network upon heating are still far from being understood. Here we characterize the nature of the micropores and their collapse using neutron scattering of gram-quantities of D2O-ASW of internal surface areas up to 230 ± 10 m(2) g(-1) prepared at 77 K. The model-free interpretation of the small-angle scattering data suggests micropores, which remain stable up to 120-140 K and then experience a sudden collapse. The exact onset temperature to pore collapse depends on the type of flow conditions employed in the preparation of ASW and, thus, the specific surface area of the initial deposit, whereas the onset of crystallization to cubic ice is unaffected by the flow conditions. Analysis of the small-angle neutron scattering signal using the Guinier-Porod model suggests that a sudden transition from three-dimensional cylindrical pores with 15 Å radius of gyration to two-dimensional lamellae is the mechanism underlying the pore collapse. The rather high temperature of about 120-140 K of micropore collapse and the 3D-to-2D type of the transition unraveled in this study have implications for our understanding of the processing and evolution of ices in various astrophysical environments. PMID:24963740

  13. 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.

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

    DOE PAGESBeta

    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

  15. 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.

  16. 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

  17. 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.

  18. Insight into asphaltene nanoaggregate structure inferred by small angle neutron and X-ray scattering.

    PubMed

    Eyssautier, Joëlle; Levitz, Pierre; Espinat, Didier; Jestin, Jacques; Gummel, Jérémie; Grillo, Isabelle; Barré, Loïc

    2011-06-01

    Complementary neutron and X-ray small angle scattering results give prominent information on the asphaltene nanostructure. Precise SANS and SAXS measurements on a large q-scale were performed on the same dilute asphaltene-toluene solution, and absolute intensity scaling was carried out. Direct comparison of neutron and X-ray spectra enables description of a fractal organization made from the aggregation of small entities of 16 kDa, exhibiting an internal fine structure. Neutron contrast variation experiments enhance the description of this nanoaggregate in terms of core-shell disk organization, giving insight into core and shell dimensions and chemical compositions. The nanoaggregates are best described by a disk of total radius 32 Å with 30% polydispersity and a height of 6.7 Å. Composition and density calculations show that the core is a dense and aromatic structure, contrary to the shell, which is highly aliphatic. These results show a good agreement with the general view of the Yen model (Yen, T. F.; et al. Anal. Chem.1961, 33, 1587-1594) and as for the modified Yen model (Mullins, O. C. Energy Fuels2010, 24, 2179-2207), provide characteristic dimensions of the asphaltene nanoaggregate in good solvent. PMID:21553910

  19. 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

  20. Structure Parameters of Synaptic Vesicles Quantified by Small-Angle X-Ray Scattering

    PubMed Central

    Castorph, Simon; Riedel, Dietmar; Arleth, Lise; Sztucki, Michael; Jahn, Reinhard; Holt, Matthew; Salditt, Tim

    2010-01-01

    Synaptic vesicles (SVs) are small, membrane-bound organelles that are found in the synaptic terminal of neurons, and which are crucial in neurotransmission. After a rise in internal [Ca2+] during neuronal stimulation, SVs fuse with the plasma membrane releasing their neurotransmitter content, which then signals neighboring neurons. SVs are subsequently recycled and refilled with neurotransmitter for further rounds of release. Recently, tremendous progress has been made in elucidating the molecular composition of SVs, as well as putative protein-protein interactions. However, what is lacking is an empirical description of SV structure at the supramolecular level—which is necessary to enable us to fully understand the processes of membrane fusion, retrieval, and recycling. Using small-angle x-ray scattering, we have directly investigated the size and structure of purified SVs. From this information, we deduced detailed size and density parameters for the protein layers responsible for SV function, as well as information about the lipid bilayer. To achieve a convincing model fit, a laterally anisotropic structure for the protein shell is needed, as a rotationally symmetric density profile does not explain the data. Not only does our model confirm many of the preexisting ideas concerning SV structure, but also for the first time, to our knowledge, it indicates structural refinements, such as the presence of protein microdomains. PMID:20371319

  1. 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.

  2. Modeling RNA topological structures using small angle X-ray scattering.

    PubMed

    Bhandari, Yuba R; Jiang, Wei; Stahlberg, Eric A; Stagno, Jason R; Wang, Yun-Xing

    2016-07-01

    Detailed understanding of the structure and function relationship of RNA requires knowledge about RNA three-dimensional (3D) topological folding. However, there are very few unique RNA entries in structure databases. This is due to challenges in determining 3D structures of RNA using conventional methods, such as X-ray crystallography and NMR spectroscopy, despite significant advances in both of these technologies. Computational methods have come a long way in accurately predicting the 3D structures of small (<50nt) RNAs to within a few angstroms compared to their native folds. However, lack of an apparent correlation between an RNA primary sequence and its 3D fold ultimately limits the success of purely computational approaches. In this context, small angle X-ray scattering (SAXS) serves as a valuable tool by providing global shape information of RNA. In this article, we review the progress in determining RNA 3D topological structures, including a new method that combines secondary structural information and SAXS data to sample conformations generated through hierarchical moves of commonly observed RNA motifs. PMID:27090001

  3. 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.

  4. 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.

  5. 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.

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

    PubMed Central

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

    2015-01-01

    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. PMID:25615859

  7. Shear stabilization of critical fluctuations in bulk polymer blends studied by small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Nakatani, Alan I.; Kim, Hongdoo; Takahashi, Yoshiaki; Matsushita, Yushu; Takano, Atsushi; Bauer, Barry J.; Han, Charles C.

    1990-07-01

    The small angle neutron scattering (SANS) technique has been used to study the concentration fluctuations of binary polymer mixtures under shear. Two different polymer systems, deuterated polystyrene/poly(vinylmethylether) and deuterated polystyrene/polybutadiene, have been studied as a function of temperature and shear rate. Due to the small wavelength of the incident neutron radiation compared with light, the shear dependence of concentration fluctuations in the one-phase region and in the strong shear limit has been obtained from the q dependence of the scattering structure factor for the first time. From a detailed analysis of the scattering structure factor S(q) a crossover value of the wave number qs has been obtained as a function of temperature and shear rate. This crossover wave number represents the inverse of the lowest fluctuation mode which is not affected by shear. The temperature, viscosity, and shear rate dependence of this experimentally determined qs agree well with a simple rotatory diffusion model and also the dynamic mode-mode coupling analysis of Kawasaki and Ferrell. The apparent spinodal temperature as a function of shear rate is shown to be consistent with the prediction of Onuki.

  8. 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

  9. 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.

  10. An Assessment of Critical Dimension Small Angle X-ray Scattering Metrology for Advanced Semiconductor Manufacturing

    NASA Astrophysics Data System (ADS)

    Settens, Charles M.

    Simultaneous migration of planar transistors to FinFET architectures, the introduction of a plurality of materials to ensure suitable electrical characteristics, and the establishment of reliable multiple patterning lithography schemes to pattern sub-10 nm feature sizes imposes formidable challenges to current in-line dimensional metrologies. Because the shape of a FinFET channel cross-section immediately influences the electrical characteristics, the evaluation of 3D device structures requires measurement of parameters beyond traditional critical dimension (CD), including their sidewall angles, top corner rounding and footing, roughness, recesses and undercuts at single nanometer dimensions; thus, metrologies require sub-nm and approaching atomic level measurement uncertainty. Synchrotron critical dimension small angle X-ray scattering (CD-SAXS) has unique capabilities to non-destructively monitor the cross-section shape of surface structures with single nanometer uncertainty and can perform overlay metrology to sub-nm uncertainty. In this dissertation, we perform a systematic experimental investigation using CD-SAXS metrology on a hierarchy of semiconductor 3D device architectures including, high-aspect-ratio contact holes, H 2 annealed Si fins, and a series of grating type samples at multiple points along a FinFET fabrication process increasing in structural intricacy and ending with fully fabricated FinFET. Comparative studies between CD-SAXS metrology and other relevant semiconductor dimensional metrologies, particularly CD-SEM, CD-AFM and TEM are used to determine physical limits of CD-SAXS approach for advanced semiconductor samples. CD-SAXS experimental tradeoffs, advice for model-dependent analysis and thoughts on the compatibility with a semiconductor manufacturing environment are discussed.

  11. 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.

  12. 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

  13. Small angle multiple scattering of fast ions, physics, stochastic theory and numerical calculations

    NASA Astrophysics Data System (ADS)

    Amsel, G.; Battistig, G.; L'Hoir, A.

    2003-02-01

    We present the physical principles underlying small angle multiple scattering of ions (MS) along with a renewed and comprehensive analytical approach to MS, based on probability theory, more precisely on stochastic processes. New theoretical results are derived, bearing in particular on the combination of angular and lateral spread. The scattering of ions by the screened target nuclei is governed by cross sections decreasing slowly with angle: large deflections may occur with probabilities high enough to render the basic characteristics of MS radically different from energy loss processes. These large deflections induce behaviour that may at first appear paradoxical. The width of the angular distributions presents a power law type dependence on thickness t of matter crossed, far from the familiar t1/2 behaviour: it varies as t1/ ν, where the exponent ν increases from ≈0.4 for small t, but does not exceed ≈1.8 for large t. Mathematical concepts such as Lévy flights and fractals are briefly discussed for a deeper insight into the nature of MS. The paper is intended to be self-contained, starting from first principles to present the basic elements of the physical and theoretical concepts required to describe MS processes. Projected angular distributions and the corresponding probability densities of the lateral spread of the trajectories with respect to the initial axis are calculated theoretically and numerically for a large range of thicknesses, as well as the statistical dependence between angular and lateral spread and the linear combination of their effects. The cases of both mono- and multielemental media, as well as that of thick targets are examined and the validity of the theory for projectiles heavier than the atoms of the medium and for ions with very high energies is discussed. Typical applications of MS theory are described, with particular emphasis on depth profiling of elements or isotopes in ion beam analysis. A large number of numerical data

  14. 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.

  15. 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

  16. Nano-scale morphology of melanosomes revealed by small-angle X-ray scattering.

    PubMed

    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

  17. 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

  18. Polarized Resonant Critical Dimension Small Angle X-Ray Scattering for the Characterization of Polymer Patterns

    NASA Astrophysics Data System (ADS)

    Liman, Christopher; Sunday, Daniel; Ro, Hyun Wook; Richter, Lee; Hannon, Adam; Kline, R. Joseph

    Critical dimension small angle X-ray scattering (CDSAXS) is a recently developed technique that enables the characterization of the three-dimensional shape of periodic patterns, such as directed self-assembled (DSA) block copolymer (BCP) lamellae thin films. Information about the polymer patterns is extracted by fitting simulated scattering patterns to the experimental ones using an inverse iterative algorithm. Conducting CDSAXS at resonant energies near the carbon or nitrogen edge can enhance the strength of the scattering, but also causes the scattering to be influenced by any anisotropic orientation of the polymer chains. In this work, to assess the degree to which the scattering may be influenced by orientation, we simulate polarized resonant CDSAXS patterns for BCP lamellae with varying degrees of orientation, as well as orientation as a function of location within the lamellae, for different polarizations of the incident X-rays. Also, to assess the influence of a higher degree of orientation, we use capillary force lithography to pattern nanogratings of two semiconducting homopolymers which are known to orient strongly. We characterize these nanogratings, which have similar length scales to DSA BCP lamellae, with polarized resonant CDSAXS and spectroscopic ellipsometry. Finally, we fit simulated CDSAXS and ellipsometric data to the experimental data to obtain information about the shape and the orientation of the nanogratings.

  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. Docking and small angle X-ray scattering studies of purine nucleoside phosphorylase.

    PubMed

    Filgueira de Azevedo, Walter; dos Santos, Giovanni César; dos Santos, Denis Marangoni; Olivieri, Johnny Rizzieri; Canduri, Fernanda; Silva, Rafael Guimarães; Basso, Luiz Augusto; Renard, Gaby; da Fonseca, Isabel Osório; Mendes, Maria Anita; Palma, Mário Sérgio; Santos, Diógenes Santiago

    2003-10-01

    Docking simulations have been used to assess protein complexes with some success. Small angle X-ray scattering (SAXS) is a well-established technique to investigate protein spatial configuration. This work describes the integration of geometric docking with SAXS to investigate the quaternary structure of recombinant human purine nucleoside phosphorylase (PNP). This enzyme catalyzes the reversible phosphorolysis of N-ribosidic bonds of purine nucleosides and deoxynucleosides. A genetic deficiency due to mutations in the gene encoding for PNP causes gradual decrease in T-cell immunity. Inappropriate activation of T-cells has been implicated in several clinically relevant human conditions such as transplant rejection, rheumatoid arthritis, lupus, and T-cell lymphomas. PNP is therefore a target for inhibitor development aiming at T-cell immune response modulation and has been submitted to extensive structure-based drug design. The present analysis confirms the trimeric structure observed in the crystal. The potential application of the present procedure to other systems is discussed. PMID:13679062

  1. Heat-induced structural transitions of alpha-crystallin studied by small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Krivandin, A. V.; Kuklin, A. I.; Muranov, K. O.; Murugova, T. N.; Kozlov, S. S.; Genkina, N. K.

    2012-03-01

    Alpha-crystallin from the bovine eye lens was studied by small-angle neutron scattering (SANS) in 90% D2O buffer solution at 20, 50, 60, 65, 75, 85 and 95°C. The temperature points for this study were specified on the basis of differential scanning calorimetric analysis of alpha-crystallin solutions which has shown two endothermic transitions with midpoints at 64.5 and 86°C. The SANS study revealed no significant alpha-crystallin quaternary structure alterations at 50°C as compared with 20°C. At 60-65°C the SANS data confirmed substantial alpha-crystallin quaternary structure rearrangements which resulted in the formation of alpha-crystallin oligomers with a similar shape but approximately twofold increased molecular weight as compared to the native state at 20°C. At higher temperatures (75, 85 and 95°C) the SANS patterns were very similar and were consistent with the scattering by rod-like particles with a cross-section radius of gyration ~55 This transformation of alpha-crystallin to the rod-like particles was evidently irreversible as these particles remained in solution after cooling to 20°C. Ab initio shape models of the native and high-temperature alpha-crystallin were retrieved with DAMMIN and DAMAVER software. Schematic model of alpha-crystallin heat-induced quaternary structure transitions was considered.

  2. 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.

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

    DOE PAGESBeta

    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

  4. 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.

  5. 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.

  6. 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).

  7. 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).

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    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 (αp) 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 αp 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.

  9. Application of small angle X-ray scattering synchrotron technology for measuring ovine meat quality.

    PubMed

    Hoban, J M; Hopkins, D L; Kirby, N; Collins, D; Dunshea, F R; Kerr, M G; Bailes, K; Cottrell, J J; Holman, B W B; Brown, W; Ponnampalam, E N

    2016-07-01

    A small angle X-ray scattering (SAXS) synchrotron was used to evaluate 100 ovine m. longissimus lumborum, representing lamb (n=50) and sheep (n=50). The diffraction of X-rays gives information on muscle myofibril structure and fat content. The linear relationships between SAXS measures with measures such as, shear force, intramuscular fat content (IMF) and collagen content/solubility, were investigated. A relationship was found between the d-spacing of the actin/myosin fibril spacing (SAX1 and SAX2) and the cross sectional area of the rhombohedral unit cell (Cell area) and shear force after 1 and 5day ageing. There was a positive relationship between IMF and a SAXS Fat area measure. There was a muscle site effect on SAX1, SAX2 and Cell area, with the cranial site having a larger distance between myofibrils. The potential of SAXS as a powerful research tool to determine not only the structural components of ovine tenderness, but also the fat content related to IMF is evident. PMID:26971308

  10. 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.

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

    DOE PAGESBeta

    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

  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. Charging and uncharging a neutral polymer in solution: a small-angle neutron scattering investigation.

    PubMed

    Fajalia, Ankitkumar I; Tsianou, Marina

    2014-09-11

    Aqueous formulations containing polymers and surfactants find several applications in pharmaceutics, coatings, inks, and home products. The association between polymers and surfactants contributes greatly to the function of these complex fluids, however, the effects of polar organic solvents, ubiquitous in formulations, remain mostly unexplored. We have analyzed small angle neutron scattering (SANS) data to determine the conformation of a "model" nonionic polymer, poly(ethylene oxide) (PEO), in aqueous solutions as affected by the presence of an ionic surfactant, sodium dodecyl sulfate (SDS), and subsequent addition of short-chain alcohol (ethanol or 2-propanol). PEO chains (MW = 90,000) are Gaussian in dilute aqueous solutions, but become polyelectrolyte-like upon the addition of 30 mM SDS, with about 6 SDS micelles bound to each PEO chain. Micelles associated with polymer are similar in structure and interactions to micelles that form in aqueous solutions in the absence of polymer. Addition of alcohol alters both the polymer and micelle structure and interactions, leads to detachment of micelles from the polymer, and the PEO chains regain their Gaussian conformation. 2-Propanol is more effective than ethanol in influencing the polymer conformation and the properties of SDS micelles in aqueous solutions, either in the presence or in the absence of PEO. This study contributes fundamental insights on polymer and surfactant organization in solution, as well as new, quantitative information on systems that are widely used in practice. PMID:25014246

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. Deciphering conformational transitions of proteins by small angle X-ray scattering and normal mode analysis.

    PubMed

    Panjkovich, Alejandro; Svergun, Dmitri I

    2016-02-17

    Structural flexibility and conformational rearrangements are often related to important functions of biological macromolecules, but the experimental characterization of such transitions with high-resolution techniques is challenging. At a lower resolution, small angle X-ray scattering (SAXS) can be used to obtain information on biomolecular shapes and transitions in solution. Here, we present SREFLEX, a hybrid modeling approach that uses normal mode analysis (NMA) to explore the conformational space of high-resolution models and refine the structure guided by the agreement with the experimental SAXS data. The method starts from a given conformation of the protein (which does not agree with the SAXS data). The structure is partitioned into pseudo-domains either using structural classification databases or automatically from the protein dynamics as predicted by the NMA. The algorithm proceeds hierarchically employing NMA to first probe large rearrangements and progresses into smaller and more localized movements. At the large rearrangements stage the pseudo-domains stay as rigid bodies allowing one to avoid structural disruptions inherent to the earlier NMA-based algorithms. To validate the approach, we compiled a representative benchmark set of 88 conformational states known experimentally at high resolution. The performance of the algorithm is demonstrated in the simulated data on the benchmark set and also in a number of experimental examples. SREFLEX is included into the ATSAS program package freely available to the academic users, both for download and in the on-line mode. PMID:26611321

  19. 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

  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 PAGESBeta

    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. 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.

  3. Structure of a Unimolecular Dendritic Reverse Micelle in Dense CO2 Via Small Angle Scattering

    NASA Astrophysics Data System (ADS)

    Lin, J. S.

    1997-03-01

    Dilute solutions in dense CO2 (5Kpsi and 25 degC) of a unimolecular reverse micelle were studied via small angle x ray scattering (SAXS). The unimolecular micelle was based on a fourth generation poly(propylene imine) dendrimer, functionalized with perfluoropolyether acid fluoride chains. A value of 26 added chains per dendrimer was obtained from other characterization techniques, and this number of chains was fixed in the fitting of the SAXS data to an f-arm star model. The molecular weight ( 33.5K g mol-1) agreed well with estimates from other techniques. The observed negative second virial coefficient, A2 = -1.2 x 10-4 cm^3 g-2 mol, correlates with prior observations, as does the observed radius of gyration, Rg = 32ÅSponsors: Div. of Mat. Sci., Basic Energy Sc., USDOE, contract DE-AC05-96OR22464, Oak Ridge Nat. Lab., managed by Lockheed Martin Energy Research Corp.; The Royal Commission for the Exhibition of 1851; National Science Foundation; Consortium for the Sythesis and Processing of Polymeric Materials in Carbon Dioxide.

  4. Small-angle x-ray scattering to discern microstructure of semicrystalline polyanhydrides for drug delivery.

    SciTech Connect

    Kipper, M. J.; Seifert, S.; Thiyagarajan, P.; Narasimhan, B.; Iowa State Univ.

    2005-01-01

    Polyanhydride copolymers based on 1,6-bis(p-carboxyphenoxy)hexane (CPH) and sebacic acid (SA) are bioerodible, semicrystalline polymers that have been used for drug delivery. In addition to their semicrystallinity, these materials also exhibit microphase separation in the amorphous phase. This complex phase behavior, combined with the disparity in the erosion rates of the two different chemical moieties, leads to a complex erosion kinetics that can be used to tailor drug release kinetics. Thus, accurate design of drug delivery devices requires a detailed description of the microphase separation. Here, we employ in situ synchrotron small-angle X-ray scattering (SAXS) to explore the microstructure of these materials. First, we examine the crystallization kinetics of the homopolymers and CPH-SA copolymers. Next, we perform experiments on poly(CPH)/poly(SA) homopolymer blends in the miscible melt in order to discern the segment-segment interaction parameter, {chi}{sub CPH-SA}. This parameter predicts the enthalpy of mixing poly(CPH) and poly(SA) at the monomer level and can be used to predict the phase behavior of the blend. It also offers insights into the thermodynamics that drive the microphase separation in the copolymers. The homopolymer phase diagram has an upper-critical solution temperature and compares well with cloud point data obtained from optical microscopy and predictions of the interaction parameter from molecular simulation.

  5. The small angle x-ray scattering of globular proteins in solution during heat denaturation

    NASA Astrophysics Data System (ADS)

    Banuelos, Jose; Urquidi, Jacob

    2008-10-01

    The ability of proteins to change their conformation in response to changes in their environment has consequences in biological processes like metabolism, chemical regulation in cells, and is believed to play a role in the onset of several neurodegenerative diseases. Factors such as a change in temperature, pressure, and the introduction of ions into the aqueous environment of a protein can give rise to the folding/unfolding of a protein. As a protein unfolds, the ratio of nonpolar to polar groups exposed to water changes, affecting a protein's thermodynamic properties. Using small angle x-ray scattering (SAXS), we are currently studying the intermediate protein conformations that arise during the folding/unfolding process as a function of temperature for five globular proteins. Trends in the observed intermediate structures of these globular proteins, along with correlations with data on protein thermodynamics may help elucidate shared characteristics between all proteins in the folding/unfolding process. Experimental design considerations will be discussed and preliminary results for some of these systems will be presented.

  6. 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

  7. 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.

  8. 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.

  9. Prospect for characterizing interacting soft colloidal structures using spin-echo small angle neutron scattering

    SciTech Connect

    Chen, Wei-Ren; Herwig, Kenneth W; Li, Xin; Liu, Emily; Liu, Yun; Pynn, Roger; Robertson, J. L.; Shew, Chwen-Yang; Smith, Gregory Scott

    2011-01-01

    Spin-echo small angle neutron scattering (SESANS) presents a new experimental tool for structural investigation. Regarding the material study using neutron scattering it is of particular novel: Due to the action of spin echo encoding, SESANS registers the spatial correlations function in real space, which is distinct from the measurables of conventional elastic neutron scattering techniques. To make viable the use of SESANS in structural characterization, particularly for the interacting colloidal suspensions, we have conducted a theoretical study focusing on understanding the essential features of the SESANS correlation functions obtained from different model systems consisting of particles with uniform density profile (J. Chem. Phys. 132, 174509 (2010)). Within the same framework, we continue to explore the prospect of using SESANS to investigate the structural characteristics of colloid systems consisting of particle with non-uniform intra-particle mass distribution. As an example, a Gaussian model of interacting soft colloids is put forward in our mean-field calculations to investigate the manifestation of structural softness in SESANS measurement. The exploration shows a characteristically different SESANS correlation function for interacting soft colloids, in comparison to that of the referential uniform hard sphere system, due to the Abel transform imbedded in the mathematical formalism bridging the SESANS spectra and the spatial autocorrelation.

  10. 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.

  11. Colloidal crystallite suspensions studied by high pressure small angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Schroer, M. A.; Westermeier, F.; Lehmkühler, F.; Conrad, H.; Schavkan, A.; Zozulya, A. V.; Fischer, B.; Roseker, W.; Sprung, M.; Gutt, C.; Grübel, G.

    2016-02-01

    We report on high pressure small angle x-ray scattering on suspensions of colloidal crystallites in water. The crystallites made out of charge-stabilized poly-acrylate particles exhibit a complex pressure dependence which is based on the specific pressure properties of the suspending medium water. The dominant effect is a compression of the crystallites caused by the compression of the water. In addition, we find indications that also the electrostatic properties of the system, i.e. the particle charge and the dissociation of ions, might play a role for the pressure dependence of the samples. The data further suggest that crystallites in a metastable state induced by shear-induced melting can relax to a similar structural state upon the application of pressure and dilution with water. X-ray cross correlation analysis of the two-dimensional scattering patterns indicates a pressure-dependent increase of the orientational order of the crystallites correlated with growth of these in the suspension. This study underlines the potential of pressure as a very relevant parameter to understand colloidal crystallite systems in aqueous suspension.

  12. 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

  13. 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.

  14. Small Angle Neutron Scattering of Mixtures of Linear and Network Polyelectrolyes with an Oppositely Charged Surfactant

    NASA Astrophysics Data System (ADS)

    Lee, Wonjoo; Kofinas, Peter; Briber, Robert M.

    2007-03-01

    In general, it has been found solutions containing a (linear) polyelectrolyte and an oppositely charged surfactant exhibit a complex range of phase behavior. We have performed small angle neutron scattering (SANS) on dilute and semi-dilute solutions of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) with sodium dodecylsulfate (SDS). And, a structured hydrogel was formed by crosslinking a semi-dilute PDMAEMA solution containing SDS. SANS intensity of a dilute PDMAEMA solution shows that this polymer in D2O has only a few charges. In a dilute PDMAEMA solution with SDS, it was confirmed by SANS that spherical micelle-like structures associated along the polymer chain in a bead-and-necklace structure consistent with what has been observed in the (uncharged) poly(ethylene oxide)/SDS system. As the PDMAEMA concentration increased, a change of a peak position and a scattering shape was observed due to the interaction of the SDS with PDMAEMA. Furthermore, it is shown that the interaction between PDMAEMA and micelles is strong enough to maintain the nanoscale structure formed along the polymer chain, even after crosslinking, leading to a structured hydrogel.

  15. 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.

  16. Elastic deformations in hexagonal phases studied by small-angle X-ray diffraction and simulations.

    PubMed

    Perutková, Šárka; Daniel, Matej; Rappolt, Michael; Pabst, Georg; Dolinar, Gregor; Kralj-Iglič, Veronika; Iglič, Aleš

    2011-02-28

    In this study we present experimental and theoretical results which concern the deviations from circularity of the pivotal plane in the inverse hexagonal phases (H(II)) of phospholipid self-assemblies. Due to packing constraints, the cross-section of the polar/apolar interface deviates from a circle, which we studied in minute detail by analysing small-angle X-ray diffraction data of dioleoyl-phosphatidylethanolamine (DOPE) and stearoyl-oleoyl-phosphatidylethanolamine (SOPE), respectively. On this structural basis, Monte Carlo (MC) simulated annealing variations of the free energy were carried out, both on the formation of the H(II)-phase and on the particular shape of the cross-section in the H(II)-phase. The equilibrium of the H(II)-phase pivotal plane contour and the corresponding values of the mean intrinsic curvature, H(m), and the hydrocarbon chain stiffness, τ, were determined from MC calculations. The results of these calculations were tested by solving the corresponding system of non-linear differential equations derived using variational calculus. Here our main aim is to predict the range of possible values of H(m) and τ. Comparing the measured structural data with predictions from MC calculations including lipid anisotropy, and accounting for the elastic deformations of the pivotal plane allowed us to determine a relationship between the bending deformation and stretching of hydrocarbon chains. PMID:21063616

  17. 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. PMID:26581292

  18. Simultaneous small- and wide-angle scattering at high X-ray energies.

    PubMed

    Daniels, J E; Pontoni, D; Hoo, Rui Ping; Honkimäki, V

    2010-07-01

    Combined small- and wide-angle X-ray scattering (SAXS/WAXS) is a powerful technique for the study of materials at length scales ranging from atomic/molecular sizes (a few angstroms) to the mesoscopic regime ( approximately 1 nm to approximately 1 microm). A set-up to apply this technique at high X-ray energies (E > 50 keV) has been developed. Hard X-rays permit the execution of at least three classes of investigations that are significantly more difficult to perform at standard X-ray energies (8-20 keV): (i) in situ strain analysis revealing anisotropic strain behaviour both at the atomic (WAXS) as well as at the mesoscopic (SAXS) length scales, (ii) acquisition of WAXS patterns to very large q (>20 A(-1)) thus allowing atomic pair distribution function analysis (SAXS/PDF) of micro- and nano-structured materials, and (iii) utilization of complex sample environments involving thick X-ray windows and/or samples that can be penetrated only by high-energy X-rays. Using the reported set-up a time resolution of approximately two seconds was demonstrated. It is planned to further improve this time resolution in the near future. PMID:20567079

  19. 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.

  20. In-situ small-angle neutron scattering from a block copolymer solution under shear

    SciTech Connect

    Balsara, N.P.; Kesani, P.K.; Jonnalagadda, S.V. . Dept. of Chemical Engineering); Hammouda, B. ); Straty, G.C. )

    1994-04-25

    Small-angle neutron scattering profiles from a concentrated (65 wt%) polystyrene-polyisoprene block copolymer solution in dioctyl phthalate under shear were obtained both above and below the quiescent order--disorder transition (ODT). The ordered solution has a lamellar structure under quiescent conditions. The shear-induced structure was inferred from scattering measurements in two planes: the v-vx[del]v plane and the [del]v-vx[del]v plane (v is the fluid velocity direction and [del]v is the velocity gradient direction). Below the quiescent ODT, oscillatory shear produces lamellae that are aligned along the shearing surface, while steady shear results in a reorientation of the lamellae normals from the v-vx[del]v plane to the [del]v-vx[del]v plane. Above the quiescent ODT, steady shear induces order above a critical shear rate. The resulting scattering anisotropy obtained at different temperatures obeys a universal scaling law, and the critical shear rate increases exponentially with temperature.

  1. Investigation of the interaction of dimethyl sulfoxide with lipid membranes by small-angle neutron scattering

    SciTech Connect

    Gorshkova, J. E. Gordeliy, V. I.

    2007-05-15

    The influence of dimethyl sulfoxide (CH{sub 3}){sub 2}SO (DMSO) on the structure of membranes of 1,2-dimiristoyl-sn-glycero-3-phosphatidylcholine (DMPC) in an excess of a water-DMSO solvent is investigated over a wide range of DMSO molar concentrations 0.0 {<=} X{sub DMSO} {<=} 1.0 at temperatures T = 12.5 and 55 deg. C. The dependences of the repeat distance d of multilamellar membranes and the thickness d{sub b} of single vesicles on the molar concentration X{sub DMSO} in the L{sub {beta}}{sub '} gel and L{sub {alpha}} liquid-crystalline phases are determined by small-angle neutron scattering. The intermembrane distance d{sub s} is determined from the repeat distance d and the membrane thickness d{sub b}. It is shown that an increase in the molar concentration X{sub DMSO} leads to a considerable decrease in the intermembrane distance and that, at X{sub DMSO} = 0.4, the neighboring membranes are virtually in steric contact with each other. The use of the deuterated phospholipid (DMSO-D6) and the contrast variation method makes it possible, for the first time, to determine the number of DMSO molecules strongly bound to the membrane.

  2. 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.

  3. Measuring material microstructure under flow using 1-2 plane flow-small angle neutron scattering.

    PubMed

    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

  4. 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

  5. BCL::SAXS: GPU Accelerated Debye Method for computation of Small Angle X Ray Scattering Profiles

    PubMed Central

    Putnam, Daniel K.; Weiner, Brian E.; Woetzel, Nils; Lowe, Edward W.; Meiler, Jens

    2016-01-01

    Small angle X-ray scattering (SAXS) is an experimental technique used for structural characterization of macromolecules in solution. Here, we introduce BCL::SAXS – an algorithm designed to replicate SAXS profiles from rigid protein models at different levels of detail. We first show our derivation of BCL::SAXS and compare our results with the experimental scattering profile of Hen Egg White Lysozyme. Using this protein we show how to generate SAXS profiles representing: 1) complete models, 2) models with approximated side chain coordinates, and 3) models with approximated side chain and loop region coordinates. We evaluated the ability of SAXS profiles to identify a correct protein topology from a non-redundant benchmark set of proteins. We find that complete SAXS profiles can be used to identify the correct protein by receiver operating characteristic (ROC) analysis with an area under the curve (AUC) > 99%. We show how our approximation of loop coordinates between secondary structure elements improves protein recognition by SAXS for protein models without loop regions and side chains. Agreement with SAXS data is a necessary but not sufficient condition for structure determination. We conclude that experimental SAXS data can be used as a filter to exclude protein models with large structural differences from the native. PMID:26018949

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

    PubMed

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

    2015-09-01

    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 (αp) 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 αp 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. PMID:26342380

  7. 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

  8. 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

  9. Small angle neutron scattering study of the gemini nonionic surfactant in heavy water solutions

    NASA Astrophysics Data System (ADS)

    Rajewska, A.

    2012-03-01

    The nonionic gemini surfactant α α'-[2,4,7,9-tetramethyl-5-decyne-4,7diyl]bis[ω hydroxyl-polyoxyethylene] (S-10) was investigated in heavy water solutions only for concentrations: 2.3%, 2.5%,3%, 3.4%, 4% and 5% at temperature 25°C with small angle neutron scattering (SANS) method. All of surfactants solutions were prepared using D2O (99.9% deuterated, Prikladnaia Chimia, St. Petersburg, Russia) as a solvent. The nonionic gemini surfactant S-10 was obtained from Air Products & Chemicals, Inc., and used without further purification. All SANS measurements were performed on V-4 SANS spectrometer at BENSC, Berlin (Germany). Neutrons were used in wavelength range of 0.02 - 4 nm-1. For the measurements quartz cells of were used during experiment. Up to 14 such cells were placed in a holder. Results from experiment was calculated and evaluated with PCG 2.0 program from Graz University (Austria). In the investigated solutions two axis ellipsoidal micelles was observed.

  10. 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.

  11. Small angle x-ray scattering study of the porosity in coals

    NASA Astrophysics Data System (ADS)

    Schmidt, P. W.; Kalliat, M.; Kwak, C. Y.

    1981-02-01

    Small-angle scattering curves have bee obtained for some Pennsylvania State University PSOC coal samples and for several other coals. The x-ray scattering data provide information about the porosity in the coals and suggest that there are three classes of pores, which have average dimensions of the order of 1000 A˚, 30 A˚, and less than 5 A˚, corresponding to the macropores, transition pores and micropores discussed by Dubinin. The principal factor determining the form of the scattering curves has been found to be the rank of the coal. In coals of all ranks, the specific surface associated with the macropores is about 1 to 10 m2/gm. The micropores are most highly developed in high-rank coals. Comparison of the x-ray and adsorption results suggests that x-ray scattering and nitrogen adsorption detect only the specific surface of the macropores and transition pores, while carbon dioxide adsorption measures the total porosity from the micropores. Scattering data have also been recorded for a series of coals which had been tested for their suitability for conversion to liquid fuels. All the coals which were well-suited for producing liquid fuels were found to have a well-developed transition pore structure, while coals which were not especially good for coal liquefaction processes had almost no transition pores.

  12. Modeling and small-angle neutron scattering spectra of chromatin supernucleosomal structures at genome scale

    NASA Astrophysics Data System (ADS)

    Ilatovskiy, Andrey V.; Lebedev, Dmitry V.; Filatov, Michael V.; Grigoriev, Mikhail; Petukhov, Michael G.; Isaev-Ivanov, Vladimir V.

    2011-11-01

    Eukaryotic genome is a highly compacted nucleoprotein complex organized in a hierarchical structure based on nucleosomes. Detailed organization of this structure remains unknown. In the present work we developed algorithms for geometry modeling of the supernucleosomal chromatin structure and for computing distance distribution functions and small-angle neutron scattering (SANS) spectra of the genome-scale (˜106 nucleosomes) chromatin structure at residue resolution. Our physical nucleosome model was based on the mononucleosome crystal structure. A nucleosome was assumed to be rigid within a local coordinate system. Interface parameters between nucleosomes can be set for each nucleosome independently. Pair distance distributions were computed with Monte Carlo simulation. SANS spectra were calculated with Fourier transformation of weighted distance distribution; the concentration of heavy water in solvent and probability of H/D exchange were taken into account. Two main modes of supernucleosomal structure generation were used. In a free generation mode all interface parameters were chosen randomly, whereas nucleosome self-intersections were not allowed. The second generation mode (generation in volume) enabled spherical or cubical wall restrictions. It was shown that calculated SANS spectra for a number of our models were in general agreement with available experimental data.

  13. 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.

  14. 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.

  15. 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.

  16. Diamond-shaped small-angle scattering and the deformation of fibrous textures

    NASA Astrophysics Data System (ADS)

    Wang, Wenjie; Sanjeeva Murthy, N.

    2009-03-01

    Small-angle x-ray scattering from materials with fibrous texture are typically characterized by intense diamond-shaped equatorial streaks. Single family of elongated voids aligned along the fiber axis modeled as ellipsoids with a certain orientation distribution yield a fan-like 2D pattern. The diamond-shaped patterns from fibers, such as polyesters, polyamide 6 and polyacrylonitrile, could not be explained with such single class of misoriented voids. Analysis of the orientation distribution and the isointensity contours suggest that there are at least two distinct entities that contribute to this equatorial scattering. Voids with larger cross section (˜ 20 nm dia.), which are likely to be in the interfibrillar regions, give rise to low-q contours with smaller eccentricities and respond poorly to deformation. Entities with smaller cross section (˜ 5 nm dia.), which are likely to be in the intrafibrillar regions, give rise to high-q contours with larger eccentricities and respond to deformation in the same way as crystalline domains. The scattering from these objects appear as two distinct families of elliptical contours with different eccentricities, and the observed diamond-shaped scattering results from the superposition of these two sets of contours.

  17. Small angle neutron scattering for the structural study of intrinsically disordered proteins in solution: a practical guide.

    PubMed

    Gabel, Frank

    2012-01-01

    Small angle neutron scattering (SANS) allows studying bio-macromolecular structures and interactions in solution. It is particularly well-suited to study structural properties of intrinsically disordered proteins (IDPs) over a wide range of length-scales ranging from global aspects (radii of gyration and molecular weight) down to short-distance properties (e.g., cross-sectional analysis). In this book chapter, we provide a practical guide on how to carry out SANS experiments on IDPs and discuss the complementary aspects and strengths of SANS with respect to small angle X-ray scattering (SAXS). PMID:22821521

  18. On-axis microbeam wide- and small-angle scattering experiments of a sectioned poly(p-phenylene terephthalamide) fiber

    NASA Astrophysics Data System (ADS)

    Davies, Richard J.; Koenig, Christian; Burghammer, Manfred; Riekel, Christian

    2008-03-01

    Poly(p-phenylene terephthalamide) fiber sections of ˜15μm length were prepared by a laser microdissection system. On-axis mesh scans by combined small- and wide-angle x-ray scattering using a micron-sized synchrotron radiation beam confirms a radial texture of crystalline domains with orientational order differing for skin, central core and intermediate layers. A skin-core variation in small-angle scattering demonstrates the evolution of fiber structure due to the heat-treatment process.

  19. (abstract) Observation by Clementine of a Hugh Opposition Surge on the Moon at Very Small Solar Phase Angles

    NASA Technical Reports Server (NTRS)

    Buratti, B. J.; Wang, M. C.

    1994-01-01

    The Clementine mission enabled the first quantative observations of the Moon at very small solar phase angles. It is well established from Earth-based observations that the Moon exhibits a non-linear increase in brightness as its face becomes fully illuminated to a terrestrial observer. Because the models of the opposition effect are sensitive indicators of surfical compaction state and particle size, observations at small solar phase angles are important to obtain. A recent model for optical coherent backscatter seeks to explain a narrow opposition spike at very small phase angles (< 1 degree) seen on several icy satellites , including Europa, Icarus 90, and Oberon . Over 90 images of the Moon's surface at phase angles less than 0.5(deg) (the minimum phase angle observable from Earth due to the Moon's angular size) were obtained by the Clementine spacecraft. Our analysis of these images shows the moon exhibits a surge in brightness of approximately 20% below 0.25(deg), comparable to the values observed on icy satellites. No color dependence was detected in the lunar phase curve below 2 degrees.

  20. Nanostructure in block copolymer solutions: Rheology and small-angle neutron scattering

    SciTech Connect

    Habas, Jean-Pierre; Pavie, Emmanuel; Perreur, Christelle; Lapp, Alain; Peyrelasse, Jean

    2004-12-01

    Triblock copolymers composed of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) present an amphiphilic character in aqueous solutions. Since PPO is less hydrophilic than PEO and since their solubilities decrease when the temperature increases, the copolymers self-assemble spontaneously, forming micelles at moderate temperatures. For higher temperatures or concentrations, the copolymers or the micelles are ordered because of repulsive interactions and form lyotropic liquid crystalline phases. These are phases of very great viscosity with the aspect of gels, and transitions between different crystalline phases can occur at fixed concentration during an increase of temperature. We studied solutions of three different copolymers. The first two have a star structure. They are both composed of four branches (EO){sub x}(PO){sub y} fixed on an ethylene diamine, but differ by the values of x and y. Their commercial name is Tetronic 908 (x=114, y=21) and Tetronic 704 (x=16, y=18). The third copolymer (EO){sub 37}(PO){sub 56}(EO){sub 37} is linear and is known under the name of Pluronic P105. The measurements of the shear complex elastic modulus according to the temperature is used to determine the temperatures of the different transitions. Then, small-angle neutron scattering on samples under flow and true crystallographic arguments make it possible to identify the nature of the crystalline phases. For the systems studied, we show that the branched copolymers form only one type of liquid crystalline phase, which is bcc for the T908 and lamellar for the T704. For the linear copolymer, it is possible to identify three transitions: micellar solution to hexagonal phase, hexagonal phase to body-centered cubic phase, and finally body-centered cubic phase to lamellar phase.

  1. Characterization of polymer adsorption onto drug nanoparticles using depletion measurements and small-angle neutron scattering.

    PubMed

    Goodwin, Daniel J; Sepassi, Shadi; King, Stephen M; Holland, Simon J; Martini, Luigi G; Lawrence, M Jayne

    2013-11-01

    Production of polymer and/or surfactant-coated crystalline nanoparticles of water-insoluble drugs (nanosuspensions) using wet bead milling is an important formulation approach to improve the bioavailability of said compounds. Despite the fact that there are a number of nanosuspensions on the market, there is still a deficiency in the characterization of these nanoparticles where further understanding may lead to the rational selection of polymer/surfactant. To this end small-angle neutron scattering (SANS) measurements were performed on drug nanoparticles milled in the presence of a range of polymers of varying molecular weight. Isotopic substitution of the aqueous solvent to match the scattering length density of the drug nanoparticles (i.e., the technique of contrast matching) meant that neutron scattering resulted only from the adsorbed polymer layer. The layer thickness and amount of hydroxypropylcellulose adsorbed on nabumetone nanoparticles derived from fitting the SANS data to both model-independent and model dependent volume fraction profiles were insensitive to polymer molecular weight over the range Mv = 47-112 kg/mol, indicating that the adsorbed layer is relatively flat but with tails extending up to approximately 23 nm. The constancy of the absorbed amount is in agreement with the adsorption isotherm determined by measuring polymer depletion from solution in the presence of the nanoparticles. Insensitivity to polymer molecular weight was similarly determined using SANS measurements of nabumetone or halofantrine nanoparticles stabilized with hydroxypropylmethylcellulose or poly(vinylpyrrolidone). Additionally SANS studies revealed the amount adsorbed, and the thickness of the polymer layer was dependent on both the nature of the polymer and drug particle surface. The insensitivity of the adsorbed polymer layer to polymer molecular weight has important implications for the production of nanoparticles, suggesting that lower molecular weight polymers

  2. 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.

  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. 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.

  5. Tensile Properties and Small-Angle Neutron Scattering Investigation of Stereoblock Elastomeric Polypropylene

    SciTech Connect

    Pople, John A

    2002-08-06

    Elastomeric polypropylene (ePP) produced from unbridged 2-arylindene metallocene catalysts was studied by uniaxial tensile and small-angle neutron scattering (SANS) techniques. The ePP can be separated into three fractions by successive boiling-solvent fractionation method to yield: a low-tacticity fraction soluble in ether (ES), an intermediate-tacticity fraction soluble in heptane (HS), and a high-tacticity fraction insoluble in heptane (HI). Tensile properties of ePP were compared to its solvent fractions, and the role of each solvent fraction residing within ePP was investigated by blending 5 weight % deuterated fraction with ePP. The tensile properties of each fraction vary considerably, exhibiting properties from a weak gum elastomer for ES, to a semi-crystalline thermoplastic for HI. The intermediate-tacticity HS fraction exhibits elastic properties similar to the parent elastomer (ePP). In the melt at 160 C, SANS shows that all deuterated fractions are homogeneously mixed with ePP in a one-phase system. At 25 C upon a slow cooling from the melt, the low-tacticity fraction is preferentially segregated in the amorphous domains induced by different crystallization temperatures and kinetics of the deuterated ES and high-tacticity components. The high-tacticity component within ePP (dHI-ePP) retains its plastic properties in the blend. Despite its low crystallinity ({le} 2%), the low-tacticity fraction can co-crystallize with the crystalline matrix. The dES-ePP shows little or no relaxation when held under strain and recovers readily upon the release of stress.

  6. 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.

  7. Polymer conformations of gas-hydrate kinetic inhibitors: A small-angle neutron scattering study

    NASA Astrophysics Data System (ADS)

    King, H. E.; Hutter, Jeffrey L.; Lin, Min Y.; Sun, Thomas

    2000-02-01

    We have used small-angle neutron scattering to characterize the polymer conformations of four nonionic water soluble polymers: poly(ethylene oxide), poly(N-vinyl-2-pyrollidone), poly(N-vinyl-2-caprolactam), and an N-methyl, N-vinylacetamide/N-vinyl-2-caprolactam copolymer. The last three of these are able to kinetically suppress hydrate crystallization, and their inhibitor activity ranges from moderate to very effective. This attribute is of significant commercial importance to the oil and gas industry, but the mechanism of the activity is unknown. The dilute-solution polymer conformation in a hydrate-forming tetrahydrofuran/water fluid shows little difference among the four polymers: the majority of the scattering is that expected for a polymer in a good solvent. Each solution also exhibits some additional low-q scattering which we attribute to aggregates. In the presence of a hydrate-crystal/liquid slurry, the three inhibitor polymers significantly change their conformation. Utilizing results from our previous contrast variation study, we show that this arises from polymer adsorbed to the hydrate-crystal surface. Furthermore, we find a strong correlation between the scattering intensity at low q values and the effectiveness of the inhibitor polymer. We suggest this is an indication that as surface adsorption increases, the inhibitor's blocking of growth sites increases. Also measured for one of the kinetic-inhibitor polymers was the dilute-solution polymer conformation in a hydrate-forming propane/water fluid (hydrate crystal free). This system shows additional low-q scattering, possibly indicating a polymer-propane interaction prior to crystal formation. This may affect hydrate nucleation behavior and offer a second mechanism for kinetic hydrate inhibition.

  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. Monitoring thylakoid ultrastructural changes in vivo using small-angle neutron scattering.

    PubMed

    Unnep, Renáta; Nagy, Gergely; Markó, Márton; Garab, Győző

    2014-08-01

    The light reactions of oxygenic photosynthesis take place in the thylakoid membranes, flattened vesicles, which contain the two photosystems and also embed the cytochrome b6f complex and the ATP synthase. In general, the thylakoid membranes are assembled into multilamellar membrane systems, which warrant an optimal light capturing efficiency. In nature, they show astounding variations, primarily due to large variations in their protein composition, which is controlled by multilevel regulatory mechanisms during long-term acclimation and short-term adaptation processes and also influenced by biotic or abiotic stresses - indicating a substantial degree of flexibility in the membrane ultrastructure. The better understanding of the dynamic features of this membrane system requires the use of non-invasive techniques, such as small angle neutron scattering (SANS), which is capable of providing accurate, statistically and spatially averaged information on the repeat distances of periodically organized thylakoid membranes under physiologically relevant conditions with time resolutions of seconds and minutes. In this review, after a short section on the basic properties of neutrons, we outline the fundamental principles of SANS measurements, its strengths and weaknesses in comparison to complementary structure investigation techniques. Then we overview recent results on isolated plant thylakoid membranes, and on living cyanobacterial and algal cells as well as on whole leaves. Special attention is paid to light-induced reversible ultrastructural changes in vivo, which, in cyanobacterial and diatom cells, were uncovered with the aid of SANS measurements; we also discuss the role of membrane reorganizations in light adaptation and photoprotection mechanisms. PMID:24629664

  10. 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

  11. 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.

  12. 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.

  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. PMID:27250375

  14. Small-angle neutron scattering data on C{sub 60} clusters in weakly polar solutions of fullerenes

    SciTech Connect

    Tropin, T. V. Avdeev, M. V.; Aksenov, V. L.

    2007-05-15

    Solutions of fullerence C{sub 60} in carbon disulfide CS{sub 2} have been investigated by small-angle neutron scattering. Combination of solubility, contrast, and incoherent scattering make it possible to measure and analyze the relatively small scattering cross section of this system. Along with single fullerene molecules, a small amount of large fullerene clusters (more than 100 A in size) is found in these solutions. The formation of these clusters depends on the procedure of solution preparation. The size distribution functions of clusters are compared with the results of the phenomenological cluster model of fullerene solubility.

  15. Trajectory Control for Vehicles Entering the Earth's Atmosphere at Small Flight Path Angles

    NASA Technical Reports Server (NTRS)

    Eggleston, John M.

    1959-01-01

    Methods of controlling the trajectories of high-drag-low-lift vehicles entering the earth's atmosphere at angles of attack near 90 deg and at initial entry angles up to 3 deg are studied. The trajectories are calculated for vehicles whose angle of attack can be held constant at some specified value or can be perfectly controlled as a function of some measured quantity along the trajectory. The results might be applied in the design of automatic control systems or in the design of instruments which will give the human pilot sufficient information to control his trajectory properly during an atmospheric entry. Trajectory data are compared on the basis of the deceleration, range, angle of attack, and, in some cases, the rate of descent. The aerodynamic heat-transfer rate and skin temperature of a vehicle with a simple heat-sink type of structure are calculated for trajectories made with several types of control functions. For the range of entry angles considered, it is found that the angle of attack can be controlled to restrict the deceleration down to an arbitrarily chosen level of 3g. All the control functions tried are successful in reducing the maximum deceleration to the desired level. However, in order to avoid a tendency for the deceleration to reach an initial peak decrease, and then reach a second peak, some anticipation is required in the control function so that the change in angle of attack will lead the change in deceleration. When the angle of attack is controlled in the aforementioned manner, the maximum rate of aerodynamic heat transfer to the skin is reduced, the maximum skin temperature of the vehicle is virtually unaffected, and the total heat absorbed is slightly increased. The increase in total heat can be minimized, however, by maintaining the maximum desired deceleration for as much of the trajectory as possible. From an initial angle of attack of 90 deg, the angle-of-attack requirements necessary to maintain constant values of deceleration (1g

  16. 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.

  17. 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

  18. Small-Angle and Ultrasmall-Angle Neutron Scattering (SANS/USANS) Study of New Albany Shale: A Treatise on Microporosity

    DOE PAGESBeta

    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

  19. 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.

  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. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Shear Induced Alignment of Multi-Walled Carbon Nanotube Dispersions via Small Angle X-Ray Scattering

    NASA Astrophysics Data System (ADS)

    Pujari, Saswati; Burghardt, Wesley R.; Rahatekar, Sameer S.; Windle, Alan H.; Koziol, Krzysztof K.

    2008-07-01

    We report small-angle x-ray scattering studies of shear-induced alignment of multi-walled carbon nanotube (MWCNT) dispersions. Uncured epoxy was used as a viscous, Newtonian suspending medium, and samples were prepared from `aligned' MWCNTs using methods previously reported (Rahatekar et al. J Rheol 40:599, 2006); here we emphasize measurements on rather dilute dispersions. Flow-induced alignment was studied in both the flow-gradient (1-2) plane, and the flow-vorticity (1-3) plane using, respectively, annular cone and plate and rotating disk x-ray shear cells. Small-angle x-ray scattering patterns were rendered anisotropic under application of shear flow. Measurements in the 1-2 plane indicate that the average MWCNT orientation direction is intermediate between the flow and gradient directions. Transient measurements of structure evolution enabled by high flux synchrotron radiation allowed study of time-dependent behavior following flow reversal and flow cessation.

  7. 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.

  8. 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.

  9. Analysis coherent signal processing methods in synthetic aperture radar on small-scale viewing angles under voluntary movement aircraft

    NASA Astrophysics Data System (ADS)

    Anikin, Sergey N.; Vishentsev, Mihail V.; Stukalova, Anna S.

    2007-02-01

    In the article realize analysis the coherent processing method which uses to form synthetic aperture antenna on a board of aircraft. The factors, which send for distortion radar image on small-scale viewing angle during high-intensity maneuvering velocity shown for considering method of synthesizing aperture antenna. A synthetic aperture antenna software model was designing and analyzing. Some results of research of the coherent processing methods for receiving earth's imagery are shown.

  10. 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.

  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. Quantitative Analysis of the Orientation of Mineral in Bone from Small-Angle X-Ray Scattering Patterns

    NASA Astrophysics Data System (ADS)

    Matsushima, Norio; Akiyama, Morio; Terayama, Yoshio

    1982-01-01

    The small-angle X-ray scattering data from a rabbit femur is quantitatively evaluated with respect to the mineral distribution in bone. The results show the existence of a needle-like mineral with a length of at least 300 A and a preferred orientation of the needle axes parallel to the long axis of the bone. The angular distribution of the needle axes gives a value of 30° for the mean inclination.

  13. 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)

  14. 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)

  15. An unusual case of non-small cell lung cancer presenting with renal angle pain and hematuria.

    PubMed

    Peedell, Clive; Dykes, Rachel

    2007-07-01

    A 53-year-old woman was referred urgently to the urology department with a history of worsening right renal angle pain and associated hematuria. Further investigations revealed the presence of a primary non-small cell lung cancer (NSCLC) invading the posterior chest wall with an associated vaginal metastasis. To our knowledge, this is only the second case report in the literature of a vaginal metastasis from NSCLC. PMID:17607127

  16. Porosity of silica Stöber particles determined by spin-echo small angle neutron scattering.

    PubMed

    Parnell, S R; Washington, A L; Parnell, A J; Walsh, A; Dalgliesh, R M; Li, F; Hamilton, W A; Prevost, S; Fairclough, J P A; Pynn, R

    2016-05-25

    Stöber silica particles are used in a diverse range of applications. Despite their widespread industrial and scientific uses, information on the internal structure of the particles is non-trivial to obtain and is not often reported. In this work we have used spin-echo small angle neutron scattering (SESANS) in conjunction with ultra small angle X-ray scattering (USAXS) and pycnometry to study an aqueous dispersion of Stöber particles. Our results are in agreement with models which propose that Stöber particles have a porous core, with a significant fraction of the pores inaccessible to solvent. For samples prepared from the same master sample in a range of H2O : D2O ratio solutions we were able to model the SESANS results for the solution series assuming monodisperse, smooth surfaced spheres of radius 83 nm with an internal open pore volume fraction of 32% and a closed pore fraction of 10%. Our results are consistent with USAXS measurements. The protocol developed and discussed here shows that the SESANS technique is a powerful way to investigate particles much larger than those studied using conventional small angle scattering methods. PMID:27021920

  17. 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.

  18. 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.

  19. Kinetic asymmetry of subunit exchange of homooligomeric protein as revealed by deuteration-assisted small-angle neutron scattering.

    PubMed

    Sugiyama, Masaaki; Kurimoto, Eiji; Yagi, Hirokazu; Mori, Kazuhiro; Fukunaga, Toshiharu; Hirai, Mitsuhiro; Zaccai, Giuseppe; Kato, Koichi

    2011-10-19

    We developed a novel, to our knowledge, technique for real-time monitoring of subunit exchange in homooligomeric proteins, using deuteration-assisted small-angle neutron scattering (SANS), and applied it to the tetradecamer of the proteasome α7 subunit. Isotopically normal and deuterated tetradecamers exhibited identical SANS profiles in 81% D(2)O solution. After mixing these solutions, the isotope sensitive SANS intensity in the low-q region gradually decreased, indicating subunit exchange, whereas the small-angle x-ray scattering profile remained unchanged confirming the structural integrity of the tetradecamer particles during the exchange. Kinetic analysis of zero-angle scattering intensity indicated that 1), only two of the 14 subunits were exchanged in each tetradecamer and 2), the exchange process involves at least two steps. This study underscores the usefulness of deuteration-assisted SANS, which can provide quantitative information not only on the molecular sizes and shapes of homooligomeric proteins, but also on their kinetic properties. PMID:22004758

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. Equilibrium properties of the fluxoid lattice in single-crystal niobium. II. Small-angle neutron-diffraction measurements

    SciTech Connect

    Christen, D.K.; Kerchner, H.R.; Sekula, S.T.; Thorel, P.

    1980-01-01

    A small-angle neutron-diffraction technique has been used to measure several properties of the flux-line lattice (FLL) in a single-crystal sphere of pure niobium. For applied fields parallel to several crystallographic directions in the (100) and (110) planes, the low-field mixed state and intermediate mixed state were investigated. From these results, the orientation dependence of the low-field critical parameters H/sub c/1 and B/sub 0/ are deduced. The consistency of these results is verified by comparison with direct measurements of the equilibrium misalignment angle between the applied-field direction and the fluxoid axes. In addition, results are reported which extend the available information concerning correlations between the FLL and crystal lattice (CL) symmetry properties.

  5. Concept for a time-of-flight Small Angle Neutron Scattering instrument at the European Spallation Source

    NASA Astrophysics Data System (ADS)

    Jaksch, S.; Martin-Rodriguez, D.; Ostermann, A.; Jestin, J.; Duarte Pinto, S.; Bouwman, W. G.; Uher, J.; Engels, R.; Frielinghaus, H.

    2014-10-01

    A new Small Angle Neutron Scattering instrument is proposed for the European Spallation Source. The pulsed source requires a time-of-flight analysis of the gathered neutrons at the detector. The optimal instrument length is found to be rather large, which allows for a polarizer and a versatile collimation. The polarizer allows for studying magnetic samples and incoherent background subtraction. The wide collimation will host VSANS and SESANS options that increase the resolution of the instrument towards μm and tens of μm, respectively. Two 1 m2 area detectors will cover a large solid angle simultaneously. The expected gains for this new instrument will lie in the range between 20 and 36, depending on the assessment criteria, when compared to up-to-date reactor based instruments. This will open new perspectives for fast kinetics, weakly scattering samples, and multi-dimensional contrast variation studies.

  6. Quantitative analysis of nanoripple and nanoparticle patterns by grazing incidence small-angle x-ray scattering 3D mapping

    NASA Astrophysics Data System (ADS)

    Babonneau, D.; Camelio, S.; Vandenhecke, E.; Rousselet, S.; Garel, M.; Pailloux, F.; Boesecke, P.

    2012-06-01

    3D reciprocal space mapping in the grazing incidence small-angle x-ray scattering geometry was used to obtain accurate morphological characteristics of nanoripple patterns prepared by broad beam-ion sputtering of Al2O3 and Si3N4 amorphous thin films as well as 2D arrays of Ag nanoparticles obtained by glancing angle deposition on Al2O3 nanorippled buffer layers. Experiments and theoretical simulations based on the distorted-wave Born approximation make it possible to determine the average 3D shape of the ripples and nanoparticles together with crucial information on their in-plane organization. In the case of nanoparticle arrays, the approach was also used to quantify the growth conformity of an additional capping layer, which proceeds by replication of the buried ripple pattern.

  7. 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.

  8. 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.

  9. SANS (small-angle neutron scattering) evaluation of the RPA (random phase approximation) theory for binary homopolymer mixtures

    SciTech Connect

    Bates, F.S.; Koehler, W.C.; Wignall, G.D.; Fetters, L.J.

    1986-12-01

    A well characterized binary mixture of normal (protonated) and perdeuterated monodisperse 1,2 polybutenes has been studied by small-angle neutron scattering (SANS). For scattering wavevectors q greater than the inverse radius-of-gyration R/sub g//sup -1/, the SANS intensity is quantitatively predicted by the random phase approximation (RPA) theory of deGennes over all measured values of the segment-segment interaction parameter Chi. In the region (Chi s-Chi)Chi s/sup -1/ > 0.5 the interaction parameter determined using the RPA theory for q > R/sub g//sup -1/ is greater than that calculated from the zero-angle intensity based on an Ornstein-Zernike plot, where Chi s represents the limit of single phase stability. These findings indicate a correlation between the critical fluctuation length xi and R/sub g/ which is not accounted for by the RPA theory.

  10. Probing helium nano-bubble formation in tungsten with grazing incidence small angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Thompson, M.; Kluth, P.; Doerner, R. P.; Kirby, N.; Corr, C.

    2015-04-01

    Helium nano-bubble formation in plasma facing materials has emerged as a major concern for the next-step fusion experiment ITER, where helium plasmas will be used during the tokamak's start-up phase. Here, we demonstrate that grazing incidence small-angle x-ray scattering is a powerful technique for the analysis of helium nano-bubble formation in tungsten. We measured helium bubbles with sizes between 1.5-2.5 nm in tungsten exposed to helium plasma at 700 °C, where a smaller number of larger bubbles were also observed. Depth distributions can be estimated by taking successive measurements across a range of x-ray incidence angles. Compared with traditional approaches in the field, such as transmission electron microscopy, this technique provides information across a much larger volume with high statistical precision, whilst also being non-destructive.

  11. Measurement of the absolute differential cross section of proton-proton elastic scattering at small angles

    NASA Astrophysics Data System (ADS)

    Mchedlishvili, D.; Chiladze, D.; Dymov, S.; Bagdasarian, Z.; Barsov, S.; Gebel, R.; Gou, B.; Hartmann, M.; Kacharava, A.; Keshelashvili, I.; Khoukaz, A.; Kulessa, P.; Kulikov, A.; Lehrach, A.; Lomidze, N.; Lorentz, B.; Maier, R.; Macharashvili, G.; Merzliakov, S.; Mikirtychyants, S.; Nioradze, M.; Ohm, H.; Prasuhn, D.; Rathmann, F.; Serdyuk, V.; Schroer, D.; Shmakova, V.; Stassen, R.; Stein, H. J.; Stockhorst, H.; Strakovsky, I. I.; Ströher, H.; Tabidze, M.; Täschner, A.; Trusov, S.; Tsirkov, D.; Uzikov, Yu.; Valdau, Yu.; Wilkin, C.; Workman, R. L.; Wüstner, P.

    2016-04-01

    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. After extrapolating the differential cross sections to the forward direction, the results are broadly compatible with the predictions of forward dispersion relations.

  12. Measurement of the absolute differential cross section of proton–proton elastic scattering at small angles

    DOE PAGESBeta

    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

  13. Time of flight grazing incidence small angle neutron scattering. A novel scattering technique for the investigation of nanostructured polymer films

    NASA Astrophysics Data System (ADS)

    Müller-Buschbaum, P.; Metwalli, E.; Moulin, J.-F.; Kudryashov, V.; Haese-Seiller, M.; Kampmann, R.

    2009-02-01

    Grazing incidence small angle neutron scattering (GISANS) overcomes the limitations of conventional small angle scattering with respect to extremely small sample volumes in the thin film geometry. In time of flight (TOF) mode neutrons with a broad range of wavelengths are used simultaneously and recorded as a function of their respective times of flight. The combination of both, TOF-GISANS, enables the simultaneous performance of several GISANS measurements, which differ in wavelength. As a consequence, within one measurement a full set of GISANS pattern related to different scattering vectors, different scattering depths and resolutions result. This allows the detection of nanostructures with a chemical sensitivity. The possibilities of TOF-GISANS are demonstrated by the simple example of polymer nano-dots located on top of a silicon surface. As probed with atomic force microscopy (AFM) the nano-dots exhibit a large characteristic nearest neighbour distance of 545 nm and a surface coverage of 28%. From the analysis of the wavelength dependent data in combination with AFM the mass density of the polymer nano-dots is determined to be equal to the bulk value. A comparison to common single wavelength GISANS experiments is shown.

  14. 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.

  15. 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

  16. Flux-lines lattice order and critical current studied by time-of-flight small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Pautrat, Alain; Brulet, Annie; Simon, Charles; Mathieu, Patrice

    2012-05-01

    Small-angle neutron scattering is a historical technique to study the flux-lines lattice (FLL) in a superconductor. Structural characteristics of the FLL can be revealed, providing fundamental information for the physics of a vortex lattice. However, the spatial resolution is limited and all of the correlation lengths of order are difficult to extract with precision. We show here that a time-of-flight technique reveals the Bragg peak of the FLL, and also its translational order with a better resolution. We discuss the implication of these results for pinning mechanisms in a niobium sample.

  17. 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.

  18. Calculation of the cluster size distribution functions and small-angle neutron scattering data for C60/N-methylpyrrolidone

    NASA Astrophysics Data System (ADS)

    Tropin, T. V.; Jargalan, N.; Avdeev, M. V.; Kyzyma, O. A.; Sangaa, D.; Aksenov, V. L.

    2014-01-01

    The aggregate growth in a C60/N-methylpyrrolidone (NMP) solution has been considered in the framework of the approach developed earlier for describing the cluster growth kinetics in fullerene polar solutions. The final cluster size distribution functions in model solutions have been estimated for two fullerene aggregation models including the influence of complex formation on the cluster growth using extrapolations of the characteristics of the cluster state and distribution parameters. Based on the obtained results, the model curves of small-angle neutron scattering have been calculated for a C60/NMP solution at various values of the model parameters.

  19. 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.

  20. Structure of spontaneously formed solid-electrolyte interphase on lithiated graphite determined using small-angle neutron scattering

    DOE PAGESBeta

    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.

  1. 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.

  2. Analysis of small-angle X-ray scattering data in the presence of significant instrumental smearing

    PubMed Central

    Bergenholtz, Johan; Ulama, Jeanette; Zackrisson Oskolkova, Malin

    2016-01-01

    A laboratory-scale small-angle X-ray scattering instrument with pinhole collimation has been used to assess smearing effects due to instrumental resolution. A new, numerically efficient method to smear ideal model intensities is developed and presented. It allows for directly using measured profiles of isotropic but otherwise arbitrary beams in smearing calculations. Samples of low-polydispersity polymer spheres have been used to show that scattering data can in this way be quantitatively modeled even when there is substantial distortion due to instrumental resolution. PMID:26937235

  3. 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.

  4. 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.

  5. 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.

  6. [Prediction of Protein Conformational Mobility and Evaluation of Its Reliability Using Small-Angle X-ray Scattering].

    PubMed

    Knyazev, S N; Kalyakin, V Y; Deryabin, I N; Fedorov, B A; Smirnov, A V; Stepanov, E O; Porozov, Yu B

    2015-01-01

    The "coarse-grained" model of protein conformational mobility is presented. We compared the trajectories of conformational motions predicted for five proteins using this model with the motion obtained by the method of the "nearest neighbor", based on small-angle X-ray scattering data. It is shown that for all studied proteins the sequence of conformations calculated on the basis of "coarse-grained" model and on the basis of the "nearest neighbor", coincides well, although there are exceptions. Some separate consideration should be given to each protein to discern the causes of these exceptions. PMID:26841499

  7. Transforming a spatially coherent light beam into a diffused beam of small diffusion angle using suitable surface scattering

    NASA Astrophysics Data System (ADS)

    Dashtdar, M.; Tavassoly, M. T.

    2013-11-01

    Imposing a phase random distribution in an interval larger than 2π on a spatially coherent light beam transforms the beam into a diffuse one. However, if the required random phase distribution is imposed by a rough transparent plate immersed in a transparent liquid or covered by another transparent material of refractive index close to that of the plate, the diffused light is confined in a small cone around the light incident angle. This renders to fabricate diffusers with high transmission efficiency that has applications in computer displays, bar code scanners, and image forming systems including conventional optical microscopes.

  8. Analysis of biostructural changes, dynamics, and interactions - Small-angle X-ray scattering to the rescue.

    PubMed

    Vestergaard, Bente

    2016-07-15

    Solution small angle X-ray scattering from biological macromolecules (BioSAXS) plays an increasingly important role in biostructural research. The analysis of complex protein mixtures, dynamic equilibriums, intrinsic disorder and evolving structural processes is facilitated by SAXS data, either in stand-alone applications, or with SAXS taking a prominent role in hybrid biostructural analysis. This is not the least due to the significant advances in both hardware and software that have taken place in particular at the large-scale facilities. Here, recent developments and the future potential of BioSAXS are reviewed, exemplified by numerous examples of elegant applications to challenging systems. PMID:26945933

  9. 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

  10. Size-dependent reversal of grains in perpendicular magnetic recording media measured by small-angle polarized neutron scattering

    NASA Astrophysics Data System (ADS)

    Lister, S. J.; Thomson, T.; Kohlbrecher, J.; Takano, K.; Venkataramana, V.; Ray, S. J.; Wismayer, M. P.; de Vries, M. A.; Do, H.; Ikeda, Y.; Lee, S. L.

    2010-09-01

    Polarized small-angle neutron scattering has been used to measure the magnetic structure of a CoCrPt-SiOx thin-film data storage layer, contained within a writable perpendicular recording media, at granular (<10 nm) length scales. The magnetic contribution to the scattering is measured as the magnetization is reversed by an external field, providing unique spatial information on the switching process. A simple model of noninteracting nanomagnetic grains provides a good description of the data and an analysis of the grain-size dependent reversal provides strong evidence for an increase in magnetic anisotropy with grain diameter.

  11. Measuring helium bubble diameter distributions in tungsten with grazing incidence small angle x-ray scattering (GISAXS)

    NASA Astrophysics Data System (ADS)

    Thompson, M.; Kluth, P.; Doerner, R. P.; Kirby, N.; Riley, D.; Corr, C. S.

    2016-02-01

    Grazing incidence small angle x-ray scattering was performed on tungsten samples exposed to helium plasma in the MAGPIE and Pisces-A linear plasma devices to measure the size distributions of resulting helium nano-bubbles. Nano-bubbles were fitted assuming spheroidal particles and an exponential diameter distribution. These particles had mean diameters between 0.36 and 0.62 nm. Pisces-A exposed samples showed more complex patterns, which may suggest the formation of faceted nano-bubbles or nano-scale surface structures.

  12. Asymptotic approach in the limit of small contact angles to sessile vapor bubble growth in a superheated environment

    NASA Astrophysics Data System (ADS)

    Rednikov, Alexey; Hollander, Nicolas; Hernando Revilla, Marta; Colinet, Pierre

    2014-11-01

    A model of nucleate pool boiling is considered, and more concretely the growth dynamics of a single spherical-cap vapor bubble on a flat superheated substrate in a large volume of an equally superheated liquid. An asymptotic scheme is developed valid in the limit of small contact angles. These are basically supposed to be the evaporation-induced ones and hence finite even in the case of a perfectly wetting liquid implied here. The consideration generally involves four regions: i) microregion, where the contact line singularities are resolved and the evaporation-induced contact angles are established, ii) Cox-Voinov region, iii) foot of the bubble, and iv) macroregion. It is only in the latter region, which remarkably appears to leading order in the form of the exterior of a sphere touching a planar surface in one point (hence a fixed geometry even for variable contact angles), that the full Navier-Stokes and heat equations are to be (numerically) resolved. ESA & BELSPO PRODEX, F.R.S.-FNRS.

  13. 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.

  14. Miniature Wide-Angle Lens for Small-Pixel Electronic Camera

    NASA Technical Reports Server (NTRS)

    Mouroulils, Pantazis; Blazejewski, Edward

    2009-01-01

    A proposed wideangle lens is shown that would be especially well suited for an electronic camera in which the focal plane is occupied by an image sensor that has small pixels. The design of the lens is intended to satisfy requirements for compactness, high image quality, and reasonably low cost, while addressing issues peculiar to the operation of small-pixel image sensors. Hence, this design is expected to enable the development of a new generation of compact, high-performance electronic cameras. The lens example shown has a 60 degree field of view and a relative aperture (f-number) of 3.2. The main issues affecting the design are also shown.

  15. A small angle neutron scattering (SANS) experiment using very cold neutrons (VCN)

    NASA Astrophysics Data System (ADS)

    Bleuel, M.; Carpenter, J. M.; Micklich, B. J.; Geltenbort, P.; Mishima, K.; Shimizu, H. M.; Iwashita, Y.; Hirota, K.; Hino, M.; Kennedy, S. J.; Lal, J.

    2009-09-01

    This paper describes the results of SANS measurements of small samples using the very cold neutron (VCN) beam of the PF2 instrument at the Institut Laue Langevin (ILL), France. In addition to a classical SANS pinhole collimation, the experiment used a polarizing supermirror as a monochromator and a magnetic sextupole lens to focus the neutron beam in order to gain intensity and avoid any material in the neutron beam besides the sample.

  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. Reexamination of data analysis for -2 spectral index at small θVB angle

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Tu, Chuanyi; He, Jiansen; Marsch, Eckart; Wang, Linghua

    2016-03-01

    The power spectrum of magnetic field in the solar wind turbulence was reported to be anisotropic with respect to the angle (θV B) between local mean magnetic field (B0) and sampling direction. When the local B0 is nearly parallel (perpendicular) to the sampling direction, the spectral index was found to be close to -2 (-5/3). This result was widely considered as observational evidence for the critical balance theory. However, it was also found that after intermittent structures were removed, the spectral index in the parallel direction turned out to be about -1.6, and the anisotropy disappeared. Here, we present a method to guarantee a nearly constant θV B in each local time window that is mainly influenced by the mother function of the Morlet wavelet. Then we reexamine the anisotropy of the spectral index of the magnetic field, by using the observations from WIND spacecraft in the fast solar wind. Our result shows that the -2 spectral index at the parallel angular bin θV B < 6◦ disappears, and the spectral indices become close to -1.5 at all the θV B bins. Accordingly, we conclude that the -2 index is caused by the large variation of the local B0, which supports the explanation of the spectral anisotropy as being caused by the intermittency.

  18. 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.

  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. Structure of Carbon Nanotube Porins in Lipid Bilayers: An in Situ Small-Angle X-ray Scattering (SAXS) Study.

    PubMed

    Tran, Ich C; Tunuguntla, Ramya H; Kim, Kyunghoon; Lee, Jonathan R I; Willey, Trevor M; Weiss, Thomas M; Noy, Aleksandr; van Buuren, Tony

    2016-07-13

    Carbon nanotube porins (CNTPs), small segments of carbon nanotubes capable of forming defined pores in lipid membranes, are important future components for bionanoelectronic devices as they could provide a robust analog of biological membrane channels. In order to control the incorporation of these CNT channels into lipid bilayers, it is important to understand the structure of the CNTPs before and after insertion into the lipid bilayer as well as the impact of such insertion on the bilayer structure. Here we employed a noninvasive in situ probe, small-angle X-ray scattering, to study the integration of CNT porins into dioleoylphosphatidylcholine bilayers. Our results show that CNTPs in solution are stabilized by a monolayer of lipid molecules wrapped around their outer surface. We also demonstrate that insertion of CNTPs into the lipid bilayer results in decreased bilayer thickness with the magnitude of this effect increasing with the concentration of CNTPs. PMID:27322135

  1. Adsorption of sodium dodecylsulfate on single-walled carbon nanotubes characterised using small-angle neutron scattering.

    PubMed

    Kastrisianaki-Guyton, E S; Chen, L; Rogers, S E; Cosgrove, T; van Duijneveldt, J S

    2016-06-15

    Aqueous dispersions of single-walled carbon nanotubes are often made using sodium dodecylsulfate (SDS), which adsorbs to the nanotube surface to stabilise them. Despite SDS being commonly used with single-walled carbon nanotubes, there is no consensus on the structure of the adsorbed layer. Small-angle neutron and X-ray scattering results reported here show that the data can be fitted to a relatively simple core-shell cylinder model, consistent with a polydisperse nanotube core of radius 10Å, surrounded by an adsorbed surfactant layer of thickness 18Å and volume fraction of 0.5. This is consistent with small nanotube bundles surrounded by an adsorbed layer of extended SDS molecules. PMID:27015390

  2. 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.

  3. High-pressure instrument for small- and wide-angle x-ray scattering. II. Time-resolved experiments

    NASA Astrophysics Data System (ADS)

    Steinhart, M.; Kriechbaum, M.; Pressl, K.; Amenitsch, H.; Laggner, P.; Bernstorff, S.

    1999-02-01

    An instrument to facilitate small- and wide-angle x-ray scattering measurements of samples under elevated hydrostatic pressures or exposed to pressure jumps is described. Pressure from atmospheric up to 0.35 GPa is produced by a motor-driven, piston-type generator and transferred through a network containing pressurizing liquid to a sample cell. The cell, with the optical path length of 1.6 mm, has two Beryllium windows with a total transmission of 0.4 (for x rays of λ=0.154 nm) and low background scattering. Scattering can be observed at angles up to 30°. Samples can be solid or liquid with a minimal volume less than 30 μl and the irradiated volume up to 3 μl. Separation of the samples from the pressurizing medium is accomplished by Teflon pistons. The high-pressure network has two sections separated by a pneumatic valve. The inner section is connected permanently to the cell and the outer one to the pressure generator. For pressure jumps, the outer section is brought to a different pressure level than the inner one and the jumps are accomplished by opening fast the connection between both sections. At the same time a trigger signal is sent to the data acquisition electronics. All functions of the instrument are PC controlled. To illustrate the performance characteristics of the instrument, time-resolved small-angle x-ray scattering measurements of phase transitions in liquid crystalline phospholipid, dioleoylphosphatidylethanolamine are shown. Pressure-jump experiments with 5 ms time resolution as well as temperature scans at a constant elevated pressure are presented.

  4. Rheo-small-angle neutron scattering at the National Institute of Standards and Technology Center for Neutron Research

    NASA Astrophysics Data System (ADS)

    Porcar, L.; Pozzo, D.; Langenbucher, G.; Moyer, J.; Butler, P. D.

    2011-08-01

    We describe the design and operation of a modified commercial rheometer to simultaneously perform rheological measurements and structural studies by small angle neutron scattering (SANS). The apparatus uses a Couette geometry shear cell allowing two of the three scattering planes to be observed by performing experiments in either the radial or tangential geometries. The device enables small angle neutron scattering patterns to be obtained simultaneously with a wide variety of rheological measurements such as stress/strain flow curves, oscillatory deformations, and creep, recovery and relaxation tests, from -20 °C to 150 °C, for samples with viscosities varying by several orders of magnitude. We give a brief report of recent experiments performed on a dispersion of acicular nanoparticles and biopolymer network under stress demonstrating the utility of such measurements. This device has been developed at the National Institute of Standards and Technology's Center for Neutron Research (NCNR) and made available to the complex fluids community as part of the standard sample environment equipment.

  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. A posteriori determination of the useful data range for small-angle scattering experiments on dilute monodisperse systems

    PubMed Central

    Konarev, Petr V.; Svergun, Dmitri I.

    2015-01-01

    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

  7. Extensive small-angle X-ray scattering studies of blood coagulation factor VIIa reveal interdomain flexibility.

    PubMed

    Mosbaek, Charlotte Rode; Nolan, David; Persson, Egon; Svergun, Dmitri I; Bukrinsky, Jens Thostrup; Vestergaard, Bente

    2010-11-16

    Blood coagulation factor VIIa (FVIIa) is used in the treatment of replacement therapy resistant hemophilia patients, and FVIIa is normally activated upon complex formation with tissue factor (TF), potentially in context with structural rearrangements. The solution behavior of uncomplexed FVIIa is important for understanding the mechanism of activation and for the stability and activity of the pharmaceutical product. However, crystal structures of FVIIa in complex with TF and of truncated free FVIIa reveal different overall conformations while previous small-angle scattering studies suggest FVIIa always to be fully extended in solution. Here, small-angle X-ray scattering analysis of multiple forms of FVIIa and TF under several experimental conditions elaborate extensively on the understanding of the solution behavior of FVIIa. We reveal significant FVIIa domain flexibility in solution, whereas TF has a well-defined conformation. Unspecific formation of dimers of FVIIa is also observed and varies with experimental conditions. In particular, active site-inhibited FVIIa displays a distinct solution behavior different from that of uninhibited FVIIa, which may reflect structural rearrangements causing resistance to activation, thereby emphasizing the connection between the distribution of different conformations of FVII and the mechanism of activation. PMID:20873866

  8. A neutron detector to monitor the intensity of transmitted neutrons for small-angle neutron scattering instruments

    NASA Astrophysics Data System (ADS)

    De Lurgio, Patrick M.; Klann, Raymond T.; Fink, Charles L.; McGregor, Douglas S.; Thiyagarajan, Pappannan; Naday, Istvan

    2003-06-01

    A semiconductor-based neutron detector was developed at Argonne National Laboratory (ANL) for use as a neutron beam monitor for small-angle neutron scattering instruments. The detector is constructed using a coating of 10B on a gallium-arsenide semiconductor detector and is mounted directly within a cylindrical (2.2 cm dia. and 4.4 cm long) enriched 10B 4C beam stop in the time-of-flight Small Angle Neutron Diffractometer (SAND) instrument at the Intense Pulsed Neutron Source (IPNS) facility at ANL. The neutron beam viewed by the SAND is from a pulsed spallation source moderated by a solid methane moderator that produces useful neutrons in the wavelength range of 0.5-14 Å. The SAND instrument uses all detected neutrons in the above wavelength range sorted by time-of-flight into 68 constant Δ T/ T=0.05 channels. This new detector continuously monitors the transmitted neutron beam through the sample during scattering measurements and takes data concurrently with the other detectors in the instrument. The 10B coating on the GaAs detector allows the detection of the cold neutron spectrum with reasonable efficiency. This paper describes the details of the detector fabrication, the beam stop monitor design, and includes a discussion of results from preliminary tests using the detector during several run cycles at the IPNS.

  9. 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. PMID:25074483

  10. 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.

  11. Study of the effect of ultrasonic agitation on the defects size in electro-deposited chromium layer by small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Choi, Y.; Hahn, Y. S.; Seong, B. S.; Kim, M.

    2006-11-01

    Ultrasonic agitation during electro-plating results in increasing deposition rate and neutral salt fog spray test (NSFST) life. Small-angle neutron scattering (SANS) showed that improvement of NSFST life is related to homogeneous size distribution of the defects.

  12. 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.

  13. The investigation of Fe-Mn-based alloys with shape memory effect by small-angle scattering of polarized neutrons

    NASA Astrophysics Data System (ADS)

    Kopitsa, G. P.; Runov, V. V.; Grigoriev, S. V.; Bliznuk, V. V.; Gavriljuk, V. G.; Glavatska, N. I.

    2003-07-01

    The small-angle polarized neutron scattering (SAPNS) technique has been used to study a nuclear and magnetic homogeneity in the distribution of both substituent (Si, Cr, Ni) and interstitial (C, N) alloying elements on the mesoscopic range in Fe-Mn-based alloys with shape memory effect (SME). The four groups of alloys with various basic compositions: FeMn 18 (wt%), FeMn 20Si 6, FeMn 20Cr 9N 0.2 and FeMn 17Cr 9Ni 4Si 6 were investigated. It was found that the small-angle scattering of neutrons and depolarization on these alloys are very small altogether. The scattering did not exceed 1.5% from the incident beam and depolarization ∼2% for all samples. It means that these alloys are well nuclear and magnetically homogeneous on the scale of 10-1000 Å. However, the difference in the homogeneity depending on the compositions still takes place. Thus, the adding of Si in FeMn 18 and FeMn 20Cr 9N 0.2 alloys improves the homogeneity pronouncedly. At once, the effect of the doping by C or N atoms on the homogeneity in FeMn 20Si 6 and FeMn 17Cr 9Ni 4Si 6 alloys is multivalued and depend on the presence of substitutional atoms (Ni and Cr). The capability of SAPNS as a method for the study of mesoscopic homogeneity in materials with SME and testing of the quality of their preparation is discussed.

  14. 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.

  15. Small angle neutron scattering studies of critical phenomena in a three-component microemulsion

    SciTech Connect

    Seto, H.; Komura, S.; Wignall, G.D.; Triolo, R.; Chillura-Martino, D.

    1996-12-31

    Critical density fluctuations of a ``water-in-oil`` microemulsion consisting of water, benzene, and BHDC (benzyldimethyl-n-hexadecyl ammonium chloride) were observed near the phase boundary by SANS. Observed profiles were well described by product of a form factor of spherical droplets and a structure factor, consisting of a term describing the inter-droplet correlations and also an Ornstein- Zernike component describing the droplet density fluctuations. Allowance was also made fro droplet polydispersity,though the width of the distribution turned out to be very small (1-2%). Observed temperature dependence of osmotic compressibility was fitted using the crossover function proposed by Belyakov et al., and the Ginzburg numbers were obtained on the order of 10{sup -2}. This indicates that long range interdroplet forces are not significant in this system, which displays upper critical solution temperature behavior. In contrast, previous studies of systems displaying lower critical solution temperature behavior (e.g., water, n-decane, and dioctyl sulfosuccinate sodium salt) indicate that long range interactions appear to dominate the phase separation behavior.

  16. 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).

  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. 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

  19. 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.

  20. Metastable states of a flux-line lattice studied by transport and small-angle neutron scattering

    SciTech Connect

    Pautrat, A.; Scola, J.; Simon, Ch.; Brulet, A.; Bhattacharya, S.

    2005-02-01

    Flux-line lattice (FLL) states have been studied using transport measurements and small-angle neutron scattering in low-T{sub c} materials. In Pb-In, the bulk dislocations in the FLL do not influence the transport properties. In Fe-doped NbSe{sub 2}, transport properties can differ after a field cooling (FC) or a zero field cooling (ZFC) procedure, as previously reported. The ZFC FLL is found ordered with narrow Bragg peaks and is linked to a linear V(I) curve and to a superficial critical current. The FC FLL pattern exhibits two Bragg peaks and the corresponding V(I) curve shows an S-shape. This can be explained by the coexistence of two ordered FLLs slightly tilted from the applied field direction by different superficial currents. These currents are wiped out when the transport current is increased.

  1. Metastable states of a flux-line lattice studied by transport and small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Pautrat, A.; Scola, J.; Simon, Ch.; Mathieu, P.; Brûlet, A.; Goupil, C.; Higgins, M. J.; Bhattacharya, S.

    2005-02-01

    Flux-line lattice (FLL) states have been studied using transport measurements and small-angle neutron scattering in low- Tc materials. In Pb-In , the bulk dislocations in the FLL do not influence the transport properties. In Fe -doped NbSe2 , transport properties can differ after a field cooling (FC) or a zero field cooling (ZFC) procedure, as previously reported. The ZFC FLL is found ordered with narrow Bragg peaks and is linked to a linear V(I) curve and to a superficial critical current. The FC FLL pattern exhibits two Bragg peaks and the corresponding V(I) curve shows an S -shape. This can be explained by the coexistence of two ordered FLLs slightly tilted from the applied field direction by different superficial currents. These currents are wiped out when the transport current is increased.

  2. Influence of monovalent ions on density fluctuations in hydrothermal aqueous solutions by small angle X-ray scattering

    NASA Astrophysics Data System (ADS)

    Da Silva-Cadoux, Cécile; Hazemann, Jean-Louis; Testemale, Denis; Proux, Olivier; Rochas, Cyrille

    2012-01-01

    Synchrotron small angle X-ray scattering measurements on water and alkaline bromine aqueous solutions (XBr, with X = Li, Rb, or Cs) were carried out from ambient to supercritical conditions. The temperature was increased from 300 to 750 K along several isobars between 24 and 35 MPa. The correlation length and the structure factor were extracted from the data following the Ornstein-Zernike formalism. We obtained experimental evidence of the shift of the critical point and isochore and their dependence on the ions concentration (0.33 mol/kg and 1.0 mol/kg). We also observed that the size of the density fluctuations and the structure factor increase with the presence of the ions and that this effect is positively correlated with the atomic number of the cation. These behaviors were compared with ZnBr2 and NaCl systems from the literature.

  3. 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.

  4. Measurement of latent tracks in amorphous SiO 2 using small angle X-ray scattering

    NASA Astrophysics Data System (ADS)

    Kluth, P.; Schnohr, C. S.; Sprouster, D. J.; Byrne, A. P.; Cookson, D. J.; Ridgway, M. C.

    2008-06-01

    In this paper we present preliminary yet promising results on the measurement of latent ion tracks in amorphous, 2 μm thick SiO2 layers using small angle X-ray scattering (SAXS). The tracks were generated by ion irradiation with 89 MeV Au ions to fluences between 3 × 1010 and 3 × 1012 ions/cm2. Transmission SAXS measurements show distinct scattering from the irradiated SiO2 as compared to the unirradiated material. Analysis of the SAXS spectra using a cylindrical model suggests a core-shell like density distribution in the ion tracks with a lower density core and a higher density shell as compared to unirradiated material. The total track radius of ∼48 Å is in very good agreement with previous experiments and calculations based on an inelastic thermal spike model.

  5. Microstructural investigations of materials for low temperature co-fired ceramic (LTCC) based fuel cell using small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Mohamed, A. A.; Ahmad, M. H.; Ibrahim, A.; Azman, A.; Alias, R.; Ambak, Z.; Shapee, S.; Putra, E. G.; Patriati, A.; Sharom, M. A.; Yazid, H.; Mamat, M. R.; Karim, J. A.; Idris, F. M.; Yazid, K.; Zin, M. R.

    2013-06-01

    The concept and the realization fuel cell based on LTCC technology require the investigations of fired LTCC microstructures. The majority of the works involved using small angle neutron scattering studies on the microstructural of LTCC ceramic tape and development of neutron tomography for future tool to visualize channels inside the fired tape. Most SANS characterization were carried out at Smarter SANS instrument at BATAN, Indonesia. Standard sample for resolving tens of micron of object size were measured using simple neutron tomography setup utilizing monochromatic SANS beam at Malaysian Nuclear Agency. The initial microstructural findings indicates that organic additives shape the final microstructural of LTCC after firing with the glassy material possibly fill the space left by the burned organic additives. The tomography results showed that 40 micron size object can be differentiated. The conductor deposited on LTCC is preliminary investigated which will later be used as support for catalyst.

  6. A practical guide to small angle X-ray scattering (SAXS) of flexible and intrinsically disordered proteins.

    PubMed

    Kikhney, Alexey G; Svergun, Dmitri I

    2015-09-14

    Small-angle X-ray scattering (SAXS) is a biophysical method to study the overall shape and structural transitions of biological macromolecules in solution. SAXS provides low resolution information on the shape, conformation and assembly state of proteins, nucleic acids and various macromolecular complexes. The technique also offers powerful means for the quantitative analysis of flexible systems, including intrinsically disordered proteins (IDPs). Here, the basic principles of SAXS are presented, and profits and pitfalls of the characterization of multidomain flexible proteins and IDPs using SAXS are discussed from the practical point of view. Examples of the synergistic use of SAXS with high resolution methods like X-ray crystallography and nuclear magnetic resonance (NMR), as well as other experimental and in silico techniques to characterize completely, or partially unstructured proteins, are presented. PMID:26320411

  7. 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

  8. Use of Ultra Small Angle X-Ray Scattering to Measure Grain Size of Styrene-Butadiene Block Copolymers

    NASA Astrophysics Data System (ADS)

    Cohen, Robert E.; Myers, Randall T.; Bellare, Anuj

    1998-03-01

    Simultaneous determination of the lamellar morphological length scale and the grain size of several commercial heterogeneous styrene - butadiene block copolymers was accomplished through the use of ultra small angle x-ray scattering measurements. NIST's X23A3 ultra SAXS beamline at the Brookhaven National Laboratory provided a range of scattering vector q from 0.0004 to 0.1 ÅThe grain dimension was determined by analysis of both the Bragg peaks and the Porod region coupled with the invarient assosciated with the scattering intensities at very low values of q. Grain size was controlled in a given block copolymer by the choice of evaporation solvent and temperature as well as annealing time and temperature. Conventional 2-dimensional SAXS and transmission electron microscopy corroborated the ultra SAXS analysis.

  9. Grazing-incidence small-angle X-ray scattering from alkaline phosphatase immobilized in atmospheric plasmapolymer coatings

    NASA Astrophysics Data System (ADS)

    Ortore, M. G.; Sinibaldi, R.; Heyse, P.; Paulussen, S.; Bernstorff, S.; Sels, B.; Mariani, P.; Rustichelli, F.; Spinozzi, F.

    2008-06-01

    Grazing-incidence small-angle X-ray scattering (GISAXS) has been used to study proteins embedded in thin polymer films obtained by a new cold, atmospheric-pressure plasma technique. In order to test the efficiency of the technology, four samples of alkaline phosphatase incorporated in organic polymer coatings in different plasma conditions have been investigated. Data have been analysed in the framework of the distorted-wave Born approximation (DWBA), by using a new method for the simultaneous fitting of the two-dimensional diffuse scattering from each sample. As a result, protein film concentration and aggregation state as well as a set of parameters describing the polymer coatings have been obtained.

  10. Grazing-incidence small-angle X-ray scattering: application to the study of quantum dot lattices

    PubMed Central

    Buljan, Maja; Radić, Nikola; Bernstorff, Sigrid; Dražić, Goran; Bogdanović-Radović, Iva; Holý, Václav

    2012-01-01

    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. PMID:22186289

  11. Exploring the structure of biological macromolecules in solution using Quokka, the small angle neutron scattering instrument, at ANSTO

    NASA Astrophysics Data System (ADS)

    Wood, Kathleen; Jeffries, Cy M.; Knott, Robert B.; Sokolova, Anna; Jacques, David A.; Duff, Anthony P.

    2015-10-01

    Small angle neutron scattering (SANS) is widely used to extract structural parameters, shape and other types of information from a vast array of materials. The technique is applied to biological macromolecules and their complexes in solution to reveal information often not accessible by other techniques. SANS measurements on biomolecules present some particular challenges however, one of which is suitable instrumentation. This review details SANS experiments performed on two well-characterised globular proteins (lysozyme and glucose isomerase) using Quokka, the recently commissioned SANS instrument at the Australian Nuclear Science and Technology Organisation (ANSTO). The instrument configuration as well as data collection and reduction strategies for biological investigations are discussed and act as a general reference for structural biologists who use the instrument. Both model independent analysis of the two proteins and ab initio modelling illustrate that Quokka-SANS data can be used to successfully model the overall shapes of proteins in solution, providing a benchmark for users.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. Modular structure of the full-length DNA gyrase B subunit revealed by small-angle X-ray scattering.

    PubMed

    Costenaro, Lionel; Grossmann, J Günter; Ebel, Christine; Maxwell, Anthony

    2007-03-01

    DNA gyrase, the only topoisomerase able to introduce negative supercoils into DNA, is essential for bacterial transcription and replication; absent from humans, it is a successful target for antibacterials. From biophysical experiments in solution, we report a structural model at approximately 12-15 A resolution of the full-length B subunit (GyrB). Analytical ultracentrifugation shows that GyrB is mainly a nonglobular monomer. Ab initio modeling of small-angle X-ray scattering data for GyrB consistently yields a "tadpole"-like envelope. It allows us to propose an organization of GyrB into three domains-ATPase, Toprim, and Tail-based on their crystallographic and modeled structures. Our study reveals the modular organization of GyrB and points out its potential flexibility, needed during the gyrase catalytic cycle. It provides important insights into the supercoiling mechanism by gyrase and suggests new lines of research. PMID:17355868

  17. [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

  18. 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

  19. Intermediate states of globular proteins during temperature-induced folding and unfolding studied using small angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Banuelos, Jose; Urquidi, Jacob

    2009-03-01

    The ability of proteins to change their conformation in response to changes in their environment has consequences in biological processes like metabolism, chemical regulation in cells, and is believed to play a role in the onset of several neurodegenerative diseases. Factors such as concentration, degree of crowding from other entities, and solvent medium affect how a protein folds. As a protein unfolds, the ratio of nonpolar to polar groups exposed to water changes, affecting a protein's thermodynamic properties. Using small angle x-ray scattering (SAXS), we are currently studying the intermediate protein conformations that arise during the folding/unfolding process as a function of temperature for a series of globular proteins. The temporal stability of these ensembles is also under investigation. Trends in the scattering profiles, along with correlations with protein thermodynamics, may help elucidate shared characteristics between all proteins in their folding behavior.

  20. The new `BerSANS-PC' software for reduction and treatment of small angle neutron scattering data

    NASA Astrophysics Data System (ADS)

    Keiderling, U.

    Measurements on small angle neutron scattering (SANS) instruments are typically characterized by a large number of samples, short measurement times for the individual samples, and a frequent change of visiting scientist groups. Besides this, recent advances in instrumentation have led to more frequent measurements of kinetic sequences and a growing interest in analyzing two-dimensional scattering data, these requiring special software tools that enable the users to extract physically relevant information from the scattering data with a minimum of effort. The new `BerSANS-PC' data-processing software has been developed at the Hahn-Meitner-Institut (HMI) in Berlin, Germany, to meet these requirements and to support an efficiently working guest-user service. Comprising some basic functions of the `BerSANS' program available at the HMI and other institutes in the past, BerSANS-PC is a completely new development for network-independent use on local PCs with a full-feature graphical interface.

  1. 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.

  2. 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.

  3. Orientation and Relaxation of Polymer-clay Solutions Studied by Rheology and Small-angle Neutron Scattering

    SciTech Connect

    Malwitz, M. M.; Butler, Paul D; Porcar, L.; Angelette, D. P.; Schmidt, G.

    2004-01-01

    The influence of shear on viscoelastic solutions of poly(ethylene oxide) (PEO) and clay [montmorillonite, i.e., Cloisite NA+ (CNA)] was investigated with rheology and small-angle neutron scattering (SANS). The steady-state viscosity and SANS were used to measure the shear-induced orientation and relaxation of the polymer and clay platelets. Anisotropic scattering patterns developed at much lower shear rates than in pure clay solutions. The scattering anisotropy saturated at low shear rates, and the CNA clay platelets aligned with the flow, with the surface normal parallel to the gradient direction. The cessation of shear led to partial and slow randomization of the CNA platelets, whereas extremely fast relaxation was observed for laponite (LRD) platelets. These PEO-CNA networklike solutions were compared with previously reported PEO-LRD networks, and the differences and similarities, with respect to the shear orientation, relaxation, and polymer-clay interactions, were examined.

  4. 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.

  5. Characterization of protein flexibility using small-angle x-ray scattering and amplified collective motion simulations.

    PubMed

    Wen, Bin; Peng, Junhui; Zuo, Xiaobing; Gong, Qingguo; Zhang, Zhiyong

    2014-08-19

    Large-scale flexibility within a multidomain protein often plays an important role in its biological function. Despite its inherent low resolution, small-angle x-ray scattering (SAXS) is well suited to investigate protein flexibility and determine, with the help of computational modeling, what kinds of protein conformations would coexist in solution. In this article, we develop a tool that combines SAXS data with a previously developed sampling technique called amplified collective motions (ACM) to elucidate structures of highly dynamic multidomain proteins in solution. We demonstrate the use of this tool in two proteins, bacteriophage T4 lysozyme and tandem WW domains of the formin-binding protein 21. The ACM simulations can sample the conformational space of proteins much more extensively than standard molecular dynamics (MD) simulations. Therefore, conformations generated by ACM are significantly better at reproducing the SAXS data than are those from MD simulations. PMID:25140431

  6. Small Angle Neutron Scattering with Hydrogenated Amorphous Cu50 Ti50 and Ni-Ti-Si Alloys

    NASA Astrophysics Data System (ADS)

    Lamparter, P.; Boucher, B.

    1993-11-01

    The metallic glasses Cu50Ti50, Ni30Ti60Si10, Ni32Ti52Si16 , Ni16Ti68Si16 and Ti84Si16 were produced by melt spinning. The alloys in the blank state as well as after loading with hydrogen or deuterium were investigated by small angle neutron (SANS) and X-ray (SAXS) scattering. The scattering of the different amorphous alloys exhibited common features. SANS follows a power-law with exponent of the scattering vector between -3 and -4. The melt-spun glasses contain extended structural inhomogeneities which are associated rather with the local composition than with the local density. SAXS measurements did not show effects above the background level. Loading the alloys with hydrogen or deuterium causes strong effects in the SANS behaviour. From the results it is concluded that the amorphous alloys contain inner surfaces where the hydrogen atoms segregate.

  7. 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. PMID:25485128

  8. 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.

  9. New opportunities provided by modernized small-angle neutron scattering two-detector system instrument (YuMO)

    NASA Astrophysics Data System (ADS)

    Kuklin, A. I.; Soloviov, D. V.; Rogachev, A. V.; Utrobin, P. K.; Kovalev, Yu S.; Balasoiu, M.; Ivankov, O. I.; Sirotin, A. P.; Murugova, T. N.; Petukhova, T. B.; Gorshkova, Yu E.; Erhan, R. V.; Kutuzov, S. A.; Soloviev, A. G.; Gordeliy, V. I.

    2011-04-01

    Main features of the modernized small-angle neutron scattering spectrometer (YuMO) at IBR-2M pulsed reactor are described. New installations for sample environment of the spectrometer are highlighted. The modernized SANS instrument (YuMO) is equipped with a new type of position sensitive detector as well as two detector system which provide a unique dynamic range (Qmax/Qmin ratio is about 90). Sample environment is extended with a magnetic system (magnetic field about 2.5 Tesla), automated high pressure setup which allows simultaneous SANS and volumetric high pressure studies and light illumination system. In particular, these developments led to considerable improvements of resolution of the instrument (about 1%) and opened the possibility to study anisotropic materials and perform efficient high pressure studies.

  10. Characterization of Protein Flexibility Using Small-Angle X-Ray Scattering and Amplified Collective Motion Simulations

    PubMed Central

    Wen, Bin; Peng, Junhui; Zuo, Xiaobing; Gong, Qingguo; Zhang, Zhiyong

    2014-01-01

    Large-scale flexibility within a multidomain protein often plays an important role in its biological function. Despite its inherent low resolution, small-angle x-ray scattering (SAXS) is well suited to investigate protein flexibility and determine, with the help of computational modeling, what kinds of protein conformations would coexist in solution. In this article, we develop a tool that combines SAXS data with a previously developed sampling technique called amplified collective motions (ACM) to elucidate structures of highly dynamic multidomain proteins in solution. We demonstrate the use of this tool in two proteins, bacteriophage T4 lysozyme and tandem WW domains of the formin-binding protein 21. The ACM simulations can sample the conformational space of proteins much more extensively than standard molecular dynamics (MD) simulations. Therefore, conformations generated by ACM are significantly better at reproducing the SAXS data than are those from MD simulations. PMID:25140431

  11. Theoretical studies on the structure of interacting colloidal suspensions by spin-echo small angle neutron scattering.

    PubMed

    Li, Xin; Shew, Chwen-Yang; Liu, Yun; Pynn, Roger; Liu, Emily; Herwig, Kenneth W; Smith, Gregory S; Robertson, J Lee; Chen, Wei-Ren

    2010-05-01

    The application of the spin-echo small angle neutron scattering (SESANS) technique for structural characterization of interacting colloidal suspensions is considered in this work. The framework to calculate the theoretical SESANS correlation function is briefly laid out. A general discussion regarding the features of the SESANS correlation functions obtained from different model systems is presented. In comparison with conventional elastic scattering tools operating at the same length scale, our mean-field calculations, based on a monodisperse spherical colloidal system, show that the real-space measurement provided by SESANS presents a powerful probe for studying the intercolloid potential. The reason of this sensitivity is discussed from the standpoint of way, in which how the spatial correlations are manifested in different neutron scattering implementations. This study leads to a better understanding regarding the distinction between SANS and SESANS. PMID:20459176

  12. 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.

  13. Pressure-induced structural phase transition of dense droplet microemulsions studied by small-angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Seto, Hideki; Nagao, Michihiro; Kawabata, Youhei; Takeda, Takayoshi

    2001-11-01

    A small-angle x-ray scattering (SAXS) study of dense water-in-oil droplet microemulsions composed of water, decane, and AOT [sodium bis(2-ethylhexyl) sulfosuccinate] was performed in order to clarify phase behavior with applied pressure and the corresponding structural phase transitions. SAXS spectra were collected for pressures between ambient pressure (0.1 MPa) and 80 MPa and droplet volume fraction, φ, from 0.40 to 0.70. With increasing φ, the mean radius of droplets decreased slightly and polydispersity increased. With increasing pressure, the droplet structure transformed to a two-phase system with coexistence of lamellar and droplet structures, independent of the droplet volume fraction. These results suggest that, with increasing pressure, the increasing inter-droplet attractive force controls the pressure variation of the structure.

  14. 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.

  15. 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.

  16. Cavitation on deterministically nanostructured surfaces in contact with an aqueous phase: a small-angle neutron scattering study.

    PubMed

    Melnichenko, Yuri B; Lavrik, N V; Popov, E; Bahadur, J; He, L; Kravchenko, I I; Smith, G; Pipich, V; Szekely, N K

    2014-08-26

    The structure of deterministically nanopatterned surfaces created using a combination of electron beam lithography and reactive ion etching was evaluated using small-angle neutron scattering (SANS). Samples exhibit 2D neutron scattering patterns that confirm the presence of ordered nanoscale cavities consistent with the targeted morphologies as well as with SEM data analysis. Comparison of SANS intensities obtained from samples in air and in contact with an aqueous phase (pure deuterium oxide, D2O, or a contrast matched mixture of D2O + H2O) reveals formation of stable gaseous nanobubbles trapped inside the cavities. The relative volume of nanobubbles depends strongly on the hydrophobicity of the cavity walls. In the case of hydrophobic surfaces, nanobubbles occupy up to 87% of the total cavity volume. The results demonstrate the high degree of sensitivity of SANS measurements for detecting and characterizing nano- and mesoscale bubbles with the volume fraction as low as ∼10(-6). PMID:25084807

  17. 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

  18. 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.

  19. The ultrastructure and flexibility of thylakoid membranes in leaves and isolated chloroplasts as revealed by small-angle neutron scattering.

    PubMed

    Unnep, R; Zsiros, O; Solymosi, K; Kovács, L; Lambrev, P H; Tóth, T; Schweins, R; Posselt, D; Székely, N K; Rosta, L; Nagy, G; Garab, G

    2014-09-01

    We studied the periodicity of the multilamellar membrane system of granal chloroplasts in different isolated plant thylakoid membranes, using different suspension media, as well as on different detached leaves and isolated protoplasts-using small-angle neutron scattering. Freshly isolated thylakoid membranes suspended in isotonic or hypertonic media, containing sorbitol supplemented with cations, displayed Bragg peaks typically between 0.019 and 0.023Å(-1), corresponding to spatially and statistically averaged repeat distance values of about 275-330 Å⁻¹. Similar data obtained earlier led us in previous work to propose an origin from the periodicity of stroma thylakoid membranes. However, detached leaves, of eleven different species, infiltrated with or soaked in D2O in dim laboratory light or transpired with D2O prior to measurements, exhibited considerably smaller repeat distances, typically between 210 and 230 Å⁻¹, ruling out a stromal membrane origin. Similar values were obtained on isolated tobacco and spinach protoplasts. When NaCl was used as osmoticum, the Bragg peaks of isolated thylakoid membranes almost coincided with those in the same batch of leaves and the repeat distances were very close to the electron microscopically determined values in the grana. Although neutron scattering and electron microscopy yield somewhat different values, which is not fully understood, we can conclude that small-angle neutron scattering is a suitable technique to study the periodic organization of granal thylakoid membranes in intact leaves under physiological conditions and with a time resolution of minutes or shorter. We also show here, for the first time on leaves, that the periodicity of thylakoid membranes in situ responds dynamically to moderately strong illumination. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy. PMID:24508217

  20. 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

  1. Report of the wwPDB Small-Angle Scattering Task Force: data requirements for biomolecular modeling and the PDB.

    PubMed

    Trewhella, Jill; Hendrickson, Wayne A; Kleywegt, Gerard J; Sali, Andrej; Sato, Mamoru; Schwede, Torsten; Svergun, Dmitri I; Tainer, John A; Westbrook, John; Berman, Helen M

    2013-06-01

    This report presents the conclusions of the July 12-13, 2012 meeting of the Small-Angle Scattering Task Force of the worldwide Protein Data Bank (wwPDB; Berman et al., 2003) at Rutgers University in New Brunswick, New Jersey. The task force includes experts in small-angle scattering (SAS), crystallography, data archiving, and molecular modeling who met to consider questions regarding the contributions of SAS to modern structural biology. Recognizing there is a rapidly growing community of structural biology researchers acquiring and interpreting SAS data in terms of increasingly sophisticated molecular models, the task force recommends that (1) a global repository is needed that holds standard format X-ray and neutron SAS data that is searchable and freely accessible for download; (2) a standard dictionary is required for definitions of terms for data collection and for managing the SAS data repository; (3) options should be provided for including in the repository SAS-derived shape and atomistic models based on rigid-body refinement against SAS data along with specific information regarding the uniqueness and uncertainty of the model, and the protocol used to obtain it; (4) criteria need to be agreed upon for assessment of the quality of deposited SAS data and the accuracy of SAS-derived models, and the extent to which a given model fits the SAS data; (5) with the increasing diversity of structural biology data and models being generated, archiving options for models derived from diverse data will be required; and (6) thought leaders from the various structural biology disciplines should jointly define what to archive in the PDB and what complementary archives might be needed, taking into account both scientific needs and funding. PMID:23747111

  2. 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.

  3. Conformation of human IgG subclasses in solution. Small-angle X-ray scattering and hydrodynamic studies.

    PubMed

    Kilár, F; Simon, I; Lakatos, S; Vonderviszt, F; Medgyesi, G A; Závodszky, P

    1985-02-15

    The structure of six human myeloma proteins: IgG1(Bal), IgG2(Klu), IgG3(Bak), IgG3(Het), IgG4(Kov) and IgG4(Pol), was studied in solution using small-angle X-ray scattering and hydrodynamic methods. For IgG1(Bal) and IgG3(Het) the experimental data, including radius of gyration (Rg degree), radii of gyration of the cross-section (Rq1, Rq2), intrinsic viscosity [eta], sedimentation coefficient (S degree 20,w) and molecular mass, were interpreted in terms of structural models based on the Fab and Fc conformations, observed in crystal, by varying the relative positions of the Fab and Fc parts, i.e. their relative angles and distances. The values Rg degree = (6.00 +/- 0.05) nm, S degree 20,w = (6.81 +/- 0.10) S and [eta] = 0.0062 +/- 0.0005 cm3/mg obtained for IgG1(Bal) are compatible with a planar model in which the angle between the Fab arms is about 120 degrees. For IgG3(Het) the following data were obtained: Rg degree = (4.90 +/- 0.05) nm, S degree 20,w = (6.32 +/- 0.01) S and [eta] = (0.0065 +/- 0.0005) cm3/mg. The apparent contradiction between the higher molecular mass and lower Rg degree and S degree 20,w values for IgG3(Het) in comparison to IgG1(Bal) can be resolved by proposing a 'non-planar' (tetrahedral) molecular shape, in which the long hinge peptide is in a folded conformation and the two Fab and Fc parts are in a closely packed arrangement. In this model the angle between the two Fab arms is about 90 degrees, in the average position. The X-ray scattering and hydrodynamic behaviour of the IgG2 and IgG4 types of antibodies appeared to be similar to IgG1(Bal). The parameters of the two IgG3 proteins are similar while they are different to the others. PMID:3971974

  4. 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.

  5. Peptide-induced Asymmetric Distribution of Charged Lipids in a Vesicle Bilayer Revealed by Small-Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Heller, William; Qian, Shuo

    2012-02-01

    Cellular membranes are complex mixtures of lipids, proteins and other small molecules that provide functional, dynamic barriers between the cell and its environment, as well as between environments within the cell. The lipid composition of the membrane is highly specific and controlled in terms of both content and lipid localization. Here, small-angle neutron scattering and selective deuterium labeling were used to probe the impact of the membrane-active peptides melittin and alamethicin on the structure of lipid bilayers composed of a mixture of the lipids dimyristoyl phosphatidylglycerol (DMPG) and chain-perdeuterated dimyristoyl phosphatidylcholine (DMPC). We found that both peptides enriched the outer leaflet of the bilayer with the negatively charged DMPG, creating an asymmetric distribution of lipids. The level of enrichment is peptide concentration-dependent and is stronger for melittin than alamethicin. The enrichment between the inner and outer bilayer leaflets occurs at very low peptide concentrations, and increases with peptide concentration, including when the peptide adopts a membrane-spanning, pore-forming state.

  6. Comparative analysis of the structure of sterically stabilized ferrofluids on polar carriers by small-angle neutron scattering.

    PubMed

    Avdeev, M V; Aksenov, V L; Balasoiu, M; Garamus, V M; Schreyer, A; Török, Gy; Rosta, L; Bica, D; Vékás, L

    2006-03-01

    Results of experiments on small-angle neutron scattering from ferrofluids on polar carriers (pentanol, water, methyl-ethyl-ketone), with double-layer sterical stabilization of magnetic nanoparticles, are reported. Several types of spatial structural organization are observed. The structure of highly stable pentanol-based samples is similar to that of stable ferrofluids based on organic non-polar carriers (e.g., benzene) with mono-layer covered magnetic nanoparticles. At the same time, the effect of the interparticle interaction on the scattering is stronger in polar ferrofluids because of the structural difference in the surfactant shell. The structure of the studied methyl-ethyl-ketone- and water-based ferrofluids essentially different from the previous case. The formation of large (>100 nm in size) elongated or fractal aggregates, respectively, is detected even in the absence of external magnetic field, which corresponds to weaker stability of these types of ferrofluids. The structure of the fractal aggregates in water-based ferrofluids does not depend on the particle concentration, but it is sensitive to temperature. A temperature increase results in a decrease in their fractal dimension reflecting destruction of the aggregates. In addition, in water-based ferrofluids these aggregates consist of small (radius approximately 10 nm) and temperature-stable primary aggregates. PMID:16102775

  7. Fast, quantitative, and nondestructive evaluation of hydrided LWR fuel cladding by small angle incoherent neutron scattering of hydrogen

    DOE PAGESBeta

    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

  8. 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.

  9. Theoretical studies on the structure of interacting colloidal suspensions by spin-echo small angle neutron scattering

    SciTech Connect

    Chen, Wei-Ren; Herwig, Kenneth W; Liu, Yun; Smith, Gregory Scott; Shew, Chwen-Yang; Pynn, Roger; Robertson, J. L.; Liu, Emily; Li, Xin

    2010-01-01

    Theoretical calculations based on integral equation theory have been carried out to elucidate the real-space correlation function obtained from the novel Spin-Echo Small Angle Neutron Scattering (SESANS) technique. Several potential models are investigated to mimic various interacting colloidal particles. A general discussion regarding the profiles of the real-space SESANS correlation functions corresponding to different model systems is presented. In the conventional elastic scattering tools, the spectral signature to differentiate attractive and repulsive molecular forces is found at small angels, which may impose technical difficulties to exact such information. Whereas, in SESANS, the characteristic feature occurs at the lengthscale near particle size, and is quite sensitive to interaction potentials and their strength. Besides the model monodisperse spherical colloidal systems, our calculation is extended to study the binary hard sphere mixture in which the attractive depletion forces between larger particles, induced by smaller particles, is reflected in the characteristic feature of the SESANS correlation function. Our model studies show that the real-space measurement SESANS presents a powerful probe in discerning intercolloid potential.

  10. 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

  11. Effect of crystal shape on neutron rocking curves of perfect single crystals designed for ultra-small-angle scattering experiments

    NASA Astrophysics Data System (ADS)

    Freund, A. K.; Rehm, C.

    2014-07-01

    The present study has been conducted in the framework of the channel-cut crystal design for the Kookaburra ultra-small-angle neutron scattering (USANS) instrument to be installed at the OPAL reactor of ANSTO. This facility is based on the classical Bonse-Hart method that uses two multiple-reflection crystal systems. The dynamical theory of diffraction by perfect crystals distinguishes two cases: the Darwin case applying to infinitely thick crystals and the Ewald solution for very small absorption taking into account the reflection from the rear face of a plane-parallel crystal reflecting in Bragg geometry. The former is preferable because it yields narrower rocking curves. To prevent the neutrons to "see" the rear face, grooves were machined into the backside of perfect Si test crystals for single reflection and filled with neutron absorbing material. These samples were examined at the S18 instrument of the Institut Laue-Langevin. Unexpectedly the crystals with empty slots showed an increase of the rocking curve width. When filling the slots with an absorber the widths decreased, but without reaching that of the Darwin curve. Understanding the results and achieving a successful crystal design call for the development of a theory that permits to describe neutron diffraction from crystals with a structured back face.

  12. Measurement of illite particle thickness using a direct Fourier transform of small-angle X-ray scattering data

    USGS Publications Warehouse

    Shang, C.; Rice, J.A.; Eberl, D.D.; Lin, S.-J.

    2003-01-01

    It has been suggested that interstratified illite-smectite (I-S) minerals are composed of aggregates of fundamental particles. Many attempts have been made to measure the thickness of such fundamental particles, but each of the methods used suffers from its own limitations and uncertainties. Small-angle X-ray scattering (SAXS) can be used to measure the thickness of particles that scatter X-rays coherently. We used SAXS to study suspensions of Na-rectorite and other illites with varying proportions of smectite. The scattering intensity (I) was recorded as a function of the scattering vector, q = (4 ??/??) sin(??/2), where ?? is the X-ray wavelength and ?? is the scattering angle. The experimental data were treated with a direct Fourier transform to obtain the pair distance distribution function (PDDF) that was then used to determine the thickness of illite particles. The Guinier and Porod extrapolation were used to obtain the scattering intensity beyond the experimental q, and the effects of such extrapolations on the PDDF were examined. The thickness of independent rectorite particles (used as a reference mineral) is 18.3 A??. The SAXS results are compared with those obtained by X-ray diffraction peak broadening methods. It was found that the power-law exponent (??) obtained by fitting the data in the region of q = 0.1 -0.6 nm-1 to the power law (I = Ioq-??) is a linear function of illite particle thickness. Therefore, illite particle thickness could be predicted by the linear relationship as long as the thickness is within the limit where ?? <4.0.

  13. 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.

  14. 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.

  15. Measurement of carbon condensates using small-angle x-ray scattering during detonation of the high explosive hexanitrostilbene

    DOE PAGESBeta

    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

  16. 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.

  17. 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.

  18. 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.

  19. Size Determination of a Liposomal Drug by Small-Angle X-ray Scattering Using Continuous Contrast Variation.

    PubMed

    Garcia-Diez, Raul; Gollwitzer, Christian; Krumrey, Michael; Varga, Zoltan

    2016-01-26

    The continuously growing complexity of nanodrugs urges for complementary characterization techniques which can elude the current limitations. In this paper, the applicability of continuous contrast variation in small-angle X-ray scattering (SAXS) for the accurate size determination of a complex nanocarrier is demonstrated on the example of PEGylated liposomal doxorubicin (Caelyx). The mean size and average electron density of Caelyx was determined by SAXS using a gradient of aqueous iodixanol (Optiprep), an iso-osmolar suspending medium. The study is focused on the isoscattering point position and the analysis of the Guinier region of the scattering curves recorded at different solvent densities. An average diameter of (69 ± 5) nm and electron density of (346.2 ± 1.2) nm(-3) were determined for the liposomal formulation of doxorubicin. The response of the liposomal nanocarrier to increasing solvent osmolality and the structure of the liposome-encapsulated doxorubicin after the osmotic shrinkage of the liposome are evaluated with sucrose contrast variation in SAXS and wide-angle X-ray scattering (WAXS). In the case of using sucrose as contrast agent, a clear osmolality threshold at 670 mOsm kg(-1) was observed, above which the liposomal drug carriers start to shrink, though preserving the intraliposomal doxorubicin structure. The average size obtained by this technique is smaller than the value measured by dynamic light scattering (DLS), though this difference is expected due to the hydrodynamic size of the PEG moieties attached to the liposomal surface, which are not probed with solvent contrast variation in SAXS. The advantages and drawbacks of the proposed technique are discussed in comparison to DLS, the most frequently used sizing method in nanomedicine. PMID:26673729

  20. 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.