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  • 1
    Electronic Resource
    Electronic Resource
    A Neutron Scattering Study of Poly(ethylene glycol) in Electrolyte Solutions (1995)
    s.l. : American Chemical Society
    Macromolecules 28 (1995), S. 7730-7736 
    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/ma00127a020
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  • 2
    Electronic Resource
    Electronic Resource
    Neutron-scattering studies of chromatin subunits under a variety of contrast conditions (1978)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 11 (1978), S. 483-484 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Neutron-scattering studies of chromatin core particles in solutions containing various mixtures of D2O/H2O and small molecules (glycerol) show that the water closely associated (or bound) with the particles is largely in the outer DNA-rich regions. This confirms the fact that the particles contain a core composed of the hydrophobic regions of histone proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889878013655
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  • 3
    Electronic Resource
    Electronic Resource
    The small-angle approximation of X-ray and neutron scatter from rigid rods of non-uniform cross section of finite length (1985)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 18 (1985), S. 452-460 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The theory of small-angle neutron or X-ray scattering from a solution consisting of rods that are uncorrelated in position and orientation and its use in determining the mass per unit length and cross-sectional radius of gyration is extended to rods of finite length and non-uniform cross-sectional structure. The case of a rod made up of identical motifs spaced in a regularly repeating axial structure is considered first. Analysis of the small-angle scatter by a modified Guinier plot gives the mean mass per unit length of the motifs. The apparent squared cross-sectional radius of gyration is the weight average. These results are then generalized to the case where variable randomly distributed structural elements are present including variable spacing between the motifs making up the rod. In this way expressions are obtained that describe the scatter from rods with structural contributions from random thermal fluctuations, bound ligands and intrinsic structural heterogeneity. It is shown that, in general, systematic errors are introduced in the analysis of rods of finite length having variable structural components. However, if all the motifs have the same mass, and if the variance in their spacing is small, such errors are not important provided that the rods are of sufficient length.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889885010706
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  • 4
    Electronic Resource
    Electronic Resource
    Resolution of time-of-flight small-angle neutron diffractometers (1987)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 20 (1987), S. 273-279 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A simple method of calculating the resolution of small-angle neutron data from diffractometers which use time-of-flight techniques has been derived in terms of the variances of the time and spatial channels of the measurement. The method is used to calculate the resolution in scattering-vector space of scattering intensity from a simulated isotropic scatterer on the small-angle neutron diffractometer at the Intense Pulsed Neutron Source at Argonne National Laboratory. The effects of the various instrumental geometries, time-of-flight measurement strategies and data reduction methods that can be chosen by the experimenter are considered. It is found that the best resolution is obtained with weighted constant Δt/t time-of-flight data acquisition schemes, with the detector placed in the beam in such a way that the highest possible angular range is accessed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889887086679
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  • 5
    Electronic Resource
    Electronic Resource
    A small-angle neutron scattering study of the effects of dilution on particle morphology in mixtures of glycocholate and lecithin (1988)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 21 (1988), S. 858-863 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Small-angle neutron scattering measurements have been made to determine the morphology of particles formed in mixed dispersions of lecithin and the bile salt, glycocholate, at a phospholipid to bile salt molar ratio of 0.56 at different total lipid concentrations. At higher lipid concentrations interparticle correlation effects are present, making analysis of the structure difficult. At lower concentrations, however, such effects are not important, and it is seen that the particle morphology is highly dependent on total lipid concentration. As the system is diluted the particles grow in size by elongation along a single axis. The eventual result of this is the formation of long rods with an apparent cross-sectional radius of 27.2(3) Å. On further dilution the rods coalesce to form large sheet-like structures or vesicles. At still lower concentrations the vesicles decrease in size and become more spherical and/or less polydisperse. The initial growth of the particles by the formation of rods is a new observation for this system and is contrary to the predictions of the currently held mechanism for dilution-driven particle growth in these systems. The vesicle formation at low lipid concentrations has been inferred from the results of other work, but the SANS results given here provide the best and most direct evidence for their existence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S002188988800531X
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  • 6
    Electronic Resource
    Electronic Resource
    Small-angle neutron scattering at pulsed spallation sources (1991)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 24 (1991), S. 467-478 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The importance of small-angle neutron scattering (SANS) in biological, chemical, physical and engineering research mandates that all intense neutron sources be equipped with SANS instruments. Four existing instruments at pulsed sources are described and the general differences between pulsed-source and reactor-based instrument designs are discussed. The basic geometries are identical, but dynamic range is generally achieved by using a broad band of wavelengths (with time-of-flight analysis) rather than by moving the detector. This allows optimization for maximum beam intensity at a given beam size over the full dynamic range with fixed collimation. Data-acquisition requirements at a pulsed source are more severe, requiring large fast histograming memories. Data reduction is also more complex, as all wavelength-dependent and angle-dependent backgrounds and nonlinearities must be accounted for before data can be transformed to intensity versus momentum transfer (Q). A comparison is shown between the Los Alamos pulsed instrument and DII (Institut Laue–Langevin) and examples from the four major topics of the conference are shown. The general conclusion is that reactor-based instruments remain superior at very low Q or if only a narrow range of Q is required, but that the current generation of pulsed-source instruments is competitive at moderate Q and may be faster when a wide range of Q is required.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889891004764
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  • 7
    Electronic Resource
    Electronic Resource
    The resolution of TOF low-Q diffractometers: instrumental, data acquisition and reduction factors (1988)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 21 (1988), S. 618-628 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The resolution of scattering vector, Q, in small-angle neutron scattering (SANS) measurements derives from uncertainties in scattered neutron wavelength and direction. The manner in which these are manifest on broad-band time-of-flight (TOF) spectrometers at pulsed sources is different from that for instruments using monochromated sources. In TOF instruments the uncertainties arise from the TOF measurement as well as the directional uncertainties due to collimation, finite sample and detector-element size that are present in any small-angle scattering instrument. Further, data from a TOF instrument must be mapped into Q space, and the strategy used to accomplish this affects the final resolution of the measurement. Thus for TOF-SANS instruments the question of resolution is more complicated than for instruments on monochromated sources. There is considerable flexibility in TOF data acquisition and Q mapping that can be utilized to optimize for intensity and Q resolution requirements of a particular measurement. In this work, present understanding of the effects of instrument geometry, TOF data acquisition and Q mapping strategies on the precision of the measurement is outlined. The goal is to establish guidelines on the best manner in which a particular measurement can be set up. Toward this end some new aspects are presented of optimal Q-mapping procedures, the effect of inelastic scattering on the measurement, and the calculation of instrument resolution functions. Some of these ideas are tested by comparison of simulations with measurement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889888005229
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  • 8
    Electronic Resource
    Electronic Resource
    Small-Angle Neutron Scattering Studies of Vesicle Stability (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 461-470 
    Details
    ISSN: 1572-9567
    Keywords: small-angle neutron scattering ; stability ; vesicles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Small-angle neutron scattering (SANS) was used to investigate the structure of mixed colloids of egg yolk phosphatidylcholine (EYPC) with the bile salt, cholylglycine (CG), in D2O as a function of pressure (P) and temperature (T). At atmospheric pressure, the system forms an isotropic phase of mixed, single-bilayer vesicles (SLVs). Increasing the external hydrostatic pressure brought about significant changes in particle morphology. At T=25°C, application of a pressure of 3.5 MPa resulted in collapse of the SLVs. A further increase in P, up to 51.8 MPa, resulted in a transition from a phase of ordered (stacked), collapsed vesicles to one of stacked, ribbon-like particles. A similar collapse of the vesicles was observed at a higher temperature (T=37°C) with increasing P, but at this temperature, no ribbon phase was found at the highest pressure explored.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022517511951
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  • 9
    Electronic Resource
    Electronic Resource
    The solution structure of liquid-crystal polymers with small liquid-crystal thermoset maleimides and nadimides (1995)
    Springer
    International journal of thermophysics 16 (1995), S. 309-317 
    Details
    ISSN: 1572-9567
    Keywords: composites ; liquid crystals ; neutron scattering ; solution structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The solution structure of the deuterated liquid-crystal polyamide polymer (LCP) poly(p-phenylene-2-nitroterephtludamide), alone and mixed with small, rodlike, amide, liquid-crystal molecules (LCT) inN-methyl-2-pyrroliditione (NMP), is studied using small-angle neutron scattering. Measurements were made as a function of LCP concentration using different LCTs mixed at 20 and 40 wt % relative to LCP. Our motivation for studying this system comes from a need to connect SOIm6Om structure with film morphology in processing these materials for high-performance molecular composites. Our analysis shows that the LCP in NMP forms large domain-like structures. The presence of LCT breaks LIP the LCP domains into smaller structures. some of which are filamentous LCP-LCT aggregates. This result suggests that the simple entropic description of the solution behavior of mixtures of long and short rods is no adequate in describing systems of this type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01441896
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  • 10
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    Phase Behavior of Diblock Copolymers between Styrene andn-Alkyl Methacrylates (1998)
    American Chemical Society
    Details
    Publication Date: 1998-12-01
    Print ISSN: 0024-9297
    Electronic ISSN: 1520-5835
    Topics: Chemistry and Pharmacology , Physics
    Published by American Chemical Society
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