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  • 1
    Electronic Resource
    Electronic Resource
    Small-Angle X-ray and Neutron Scattering from Bulk and Oriented Triblock Copolymer Gels (1995)
    s.l. : American Chemical Society
    Macromolecules 28 (1995), S. 2054-2062 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00110a045
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  • 2
    Electronic Resource
    Electronic Resource
    Scaling in the aggregation behaviour of zinc-free insulin studied by small-angle neutron scattering (1994)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 1447-1455 
    Details
    ISSN: 0392-6737
    Keywords: Disperse systems ; Molecular biophysics ; Physical chemistry of solutions of biological macromolecules ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The aggregation behaviour of zinc-free insulin has been studied by small-angle neutron scattering as a function of protein concentration,pH, and ionic strength of the solution. The distance distribution functions for the 12 samples have been obtained by indirect Fourier transformation. The weight-averaged molecular mass and thez-averaged radius of gyration were determined. Both quantities vary systematically with the experimental conditions. They increase with decreasingpH and with increasing ionic strength. The radius of gyration scales as a power law of the weight-average mass with the exponent 0.44. A similar scaling is found for a set of oligomers structures based on the crystal structure of zinc-free insulin. The mass distribution between the oligomers was determined by a model based on these oligomers. The results from this model and the Fourier transformations have been compared to an equilibrium model recently introduced by Kadimaet al. The model takes into account the variation of the effective charge of the monomer withpH and ionic strength. The neutron scattering results agree well with the predictions of the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02462029
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  • 3
    Electronic Resource
    Electronic Resource
    Small-angle neutron scattering behavior of Fe91Zr9 glass under magnetic field : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5146-5148 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Zero-field and in-field small-angle neutron scattering measurements over a wide Q range are presented for the Fe91Zr9 metallic glass in the 10–290 K range. Two transitions observed at 210 K and around 60 K are related to Tc and reentrant transition temperature, respectively. The spectra (0.003 A(ring)−1〈Q〈0.5 A(ring)−1) reveal the existence of an important contribution at the lowest Q values and at least two humps in the entire curves. The application of the magnetic field results in an anisotropic signal, and a global decrease of intensity. The magnetic field drastically reduces I(Q) in the region for Q〈0.04 A(ring)−1, but not so strongly at larger Q values (even at H=4 T), becoming more evident a remaining hump. Its origin can so far be uniquely explained by the models dealing with the existence of clusters embedded in a ferromagnetic matrix. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361918
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic ordering in pyrochlore Ho2Mn2O7 : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6173-6175 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic susceptibility of Ho2Mn2O7 with a spontaneous rise below about 40 K and a paramagnetic Curie temperature of +39 K suggests a ferromagnetic ordering. Indeed neutron diffraction profiles show strongly enhanced Bragg peaks with a temperature dependence which indicates an apparent Tc≈35 K. Nonetheless, the magnetic diffraction pattern is not consistent with a collinear ferro or ferrimagnetic ordering of the Ho3+ and Mn4+ sublattices. Furthermore, specific heat and small angle neutron scattering (SANS) show features which are also incompatible with conventional long-range order. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362063
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  • 5
    Electronic Resource
    Electronic Resource
    Neutron diffraction from the vortex lattice in the heavy fermion superconductor UPt3 (invited) (abstract) : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6788-6788 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The heavy fermion superconductor UPt3 is thought to have a d-wave pairing ground state. The principal experimental evidence for this consists of the anisotropy of the power-law behavior observed in transverse ultrasound and μ+ SR measurements. The observation of a complex phase diagram in the superconducting state in ultrasound, torsional oscillator, and specific heat measurements may be a further indication of an unconventional pairing state. Theoretical investigations suggest the possibility of vortex lattices that are unconventional in their symmetry, their quantization, or the structure of their composite vortex cores. Transitions between such exotic vortex lattices are in principle allowed and could explain the observed features at H≈0.6 Hc2 (for H(parallel)cˆ) and H≈0.3Hc2 (for H⊥cˆ). Neutron diffraction is an ideal bulk probe of the microscopic properties of the vortex lattice. We have studied the vortex lattice with H⊥cˆ and T≈50 mK in the field range 0.75〈H〈10 kG. The structure of the vortex lattice and the quantization of the vortices, in addition to the London penetration depth, λL, the coherence length, ξ, and the effective mass anisotropy are all well determined by our measurements. The lattice is oblique hexagonal with conventional quantization. Its anisotropy can be explained by considering a combination of Fermi surface and gap anisotropy. However, the lattice does not appear to change near the transition between superconducting phases identified by other techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358129
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of size distribution from small-angle scattering data for systems with effective hard-sphere interactions (1994)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 27 (1994), S. 595-608 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Methods for the free-form determination of size distributions for systems with hard-sphere interactions are described. An approximation, called the local monodisperse approximation, is introduced. Model calculations show that this approximation gives relatively small errors even at relatively high polydispersities and large volume fractions. The size distributions are determined by least-squares methods with smoothness and non-negativity constraints. The local monodisperse approximation leads to normal equations that are linear in the amplitude of the size distribution. This is used when solving the least-squares problem: only the two effective parameters describing the interference effects are treated as nonlinear parameters in an external optimization routine. The parameters describing the size distribution are determined by a linear least-squares method. The size distribution is also determined using the nonlinear equations from the calculation of the scattering intensity in the Percus–Yevick approximation. For this, a nonlinear least-squares routine with a smoothness constraint and a non-negativity constraint is used. Both approaches are tested by analysis of simulated examples calculated by the analytical expressions in the Percus–Yevick approximation. Finally, the methods are applied to two sets of experimental data from silica particles and from δ′ precipitates in an Al–Li alloy. For the simulated examples, good agreement is found with the input distributions. For the experimental examples, the results agree with the expected and known properties of the samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889893013810
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  • 7
    Electronic Resource
    Electronic Resource
    Instrumental Smearing Effects in Radially Symmetric Small-Angle Neutron Scattering by Numerical and Analytical Methods (1995)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 28 (1995), S. 105-114 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A numerical calculation method for determining the resolution functions for radially symmetric collimation and scattering is described. In the present approach, the total number of integrations is reduced to four by use of the radial symmetry of the geometry. Furthermore, the beam-stop shadowing effect is included exactly. A typical calculation can be completed in minutes on current personal computers. An interactive computer program allows the user to enter the experimental parameters such as aperture size and wavelength spread, allowing smearing calculations to be handled routinely as a `black box' operation. The exact smearing treatment is compared both to an improved technique involving Gaussian resolution functions where corrections for the beam stop are included and to results from Monte Carlo simulations. In most experiments, the use of a Gaussian distribution to approximate the resolution is preferred on account of its ease of calculation. But in a few cases, such as Porod scattering, the present more extensive numerical calculation or inclusion of the developed beam-stop-shadowing correction factors into a Gaussian scheme are needed for an adequate prediction of the smearing effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889894010095
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  • 8
    Electronic Resource
    Electronic Resource
    Cross-Section Structure of Cylindrical and Polymer-Like Micelles from Small-Angle Scattering Data. I. Test of Analysis Methods (1996)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 29 (1996), S. 646-661 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The application of the indirect Fourier transformation method and the square-root deconvolution procedure of Glatter [Glatter (1977). J. Appl. Cryst. 10, 415–421; Glatter (1981). J. Appl. Cryst. 14, 101–108] for a determination of the cross-section structure of cylindrical and polymer-like micelles is investigated. The data analysis methods assume: (i) the rod-like structures are infinitely long and straight; (ii) the particles have cylindrical symmetry; (iii) the particles are monodisperse in the cross-section size and have no fluctuations in the cross-section structure. The influence of the violations of these assumptions on the applicability of the methods and the limitations have been investigated by analyzing series of simulated scattering data. In addition, the influence of finite range of scattering vectors for the data and the presence of diffuse correlations along the rod-like particles have been determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889896006589
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  • 9
    Electronic Resource
    Electronic Resource
    Analytical treatment of the resolution function for small-angle scattering (1990)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 23 (1990), S. 321-333 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Analytical expression for the resolution function for small-angle scattering in pinhole geometry are derived. The contributions to the resolution function due to wavelength spread, finite collimation and detector resolution are determined separately using Gaussian functions to approximate the contributions. A general resolution function is derived which is the result of the combined effect of the three contributions. An azimuthal-integrated resolution function, which can be applied to scattering from a material with a circular symmetric scattering cross section, is calculated. This resolution function contains in addition a contribution from the averaging procedure itself. The analytical results are compared with the results of computer simulations. The comparison shows that Gaussian functions give a good description of the resolution function and that the widths agree with those calculated by the analytical expressions. The resolution function is applied in the analysis of two experimental examples: neutron scattering from latex particles [Wignall, Christen & Ramakrishnan (1988). J. Appl. Cryst. 21, 438–451] and neutron scattering from lamellar structures of bilayer lipid membranes (Mortensen, Pfeiffer, Sackmann & Knoll, unpublished). The analytical expressions for the resolution function allow a least-squares analysis to be performed and excellent agreement between experimental and theoretical scattering patterns are obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889890003946
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  • 10
    Electronic Resource
    Electronic Resource
    Analysis of neutron and X-ray reflectivity data. I. Theory (1994)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 27 (1994), S. 29-35 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Different methods and approximations for calculating reflectivity curves from scattering-length density profiles are carefully discussed and compared. Dynamical theory and the approximations leading to single-scattering dynamical theory, kinematical theory with an optical path-length correction and kinematical theory with refraction corrections are described. The differences are illustrated by calculations for model profiles for which dynamical effects are important.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889893006260
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