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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 97 (1993), S. 4514-4522 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: In all organisms the multi-subunit enzyme DNA-dependent RNA polymerase catalyses the first basic step in gene expression, the transcription of DNA into RNA. The neutron small-angle scattering effects were studied in the Guinier region by applying the contrast-matching technique. Isotopic labelling was realised by culturing fully deuterated E. coli cells in a heavy-water medium containing deuterated substrates. One or two completely deuterated components (subunits) of polymerase holoenzyme (composition formula α2ββ′σ, molecular weight 497000) were recombined with the remaining natural (`hydrogenated') subunits for these neutron measurements. Measurements are presented of radii of gyration R, overall shapes, and pair distances d, of three components (subunits α2β,β′) in RNA polymerase of E. coli. The subunits β′, β and α2 are obviously rather elongated in situ and exhibit (as scattering-equivalent prolate ellipsoids) axial ratios of about 7:1 up to 9:1. The intersubunit centre of gravity distances were analysed to be 7.3 ± 0.8 nm for β−β′, 8.2 ± 1.2 nm for α2−β′ and 7.0 ± 1.7 nm for α2−β.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 18 (1985), S. 61-64 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Following the procedure suggested by May, Ibel & Haas [J. Appl. Cryst. (1982), 15, 15–19] for the correlation of transmission data with the level of neutrons scattered incoherently into the full solid angle 4π measurements have been made of the transmission and incoherent scattering intensities of aqueous buffers of different H2O/D2O ratios at temperatures between 280 and 343 K. That it is possible to extend the proposed calibration procedure to absorbing-ions-containing buffers is also shown.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 18 (1985), S. 65-70 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Small-angle neutron scattering experiments have been performed with aqueous dispersions of binary lipid mixtures. One component was protonated, the other was partly deuterated. By varying the mole fraction of the deuterated species the mean scattering-length density of the lipid lamellas and hence the contrast between liposomes and the solvent was changed. It is shown that this inverse contrast variation has the advantage of (i) a simpler data analysis, (ii) an increased resolution of homogeneous and heterogenous lipid distributions and (iii) a considerably increased sensitivity for the evaluation of phase diagrams in segregated lipid mixtures. Phase boundaries can now be determined to an accuracy of better than 1 mol%.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 7 (1974), S. 96-116 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The use of neutrons in small-angle scattering has opened a wide field of applications for investigations in magnetism, polymeric science, for certain problems in biology, and in metallurgy. In the first part, this review deals with the experimental aspects of neutron small-angle scattering. In particular, the compensation of the relatively small luminosity of neutron sources as compared to X-ray tubes will be discussed in detail. This is mainly achieved by large beam cross sections, leading to correspondingly long instruments, and by an optimization of the intensity with respect to the different contributions to the resolution width of the scattering vector κ(κ = 2π&thgr;/λ, &thgr; = scattering angle, λ = wavelength). Instruments which have been developed along these lines are described, especially the 40 m instrument in Jülich and the 80 m instrument at the high-flux reactor in Grenoble. The Grenoble instrument covers a range of scattering vectors between 1 Å−1 and 3.10−4Å−1; the maximum possible resolution is about 10−4 Å−1. Typical applications are reviewed and discussed, namely those dealing with (i) density and compositional fluctuations in solids (alloys, defect clusters, dislocations, grains), (ii) magnetic inhomogeneities in solids (alloys, magnetic domains), (iii) flux-line lattices in type-II superconductors (form factors, imperfections and morphology), (iv) polymers in the solid state, and (v) biological substances.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 7 (1974), S. 230-232 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The correlation of magnetic moments has been investigated by neutron small-angle scattering in superconducting and normal Ce1−xTbxRu2. Samples with 20% Tb are superconducting below 2.6°K. In these samples ferromagnetic short-range order is found below 10°K. In spite of a maximum in the static susceptibility at 5°K no transition to long-range order is observed. In the whole temperature range between 1.5 and 10°K the experimental data can be fitted by an Ornstein–Zernike correlation function. At 1–5°K the correlation length is about 15 Å. No significant change is observed at the superconductive transition temperature. Samples with 40% Tb are not superconducting. The static susceptibility shows a maximum at 13°K. Above this temperature again ferromagnetic short-range order of the Ornstein–Zernike type is found. Below 13°K the intensity of scattered neutrons drops faster with scattering angle indicating long-range order.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 11 (1978), S. 484-486 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Chromatin fibres containing histone H1 as well as the DNA and histones H2A, H2B, H3 and H4 show the same off-meridional diffraction maxima at ̃10 nm as reported by Carpenter, Baldwin, Bradbury & Ibel [Nucleic Acids Res.(1976), 3, 1739–1746] for chromatin fibres depleted of histone HI. It is shown that the intensity of the maximum (as a function of solvent scattering-length density and deuteration of histones and DNA) can be quantitatively explained in terms of a globular protein component to the chromatin subunits in a matrix of hydrated DNA. The off-meridional diffraction maximum suggests that the chromatin is in the form of a flat helix and clearly the relative amounts of protein and hydrated DNA vary along the length of the chromatin fibre.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 9 (1976), S. 296-309 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The neutron small-angle scattering system at the high-flux reactor in Grenoble consists of three major parts: the supply of cold neutrons via bent neutron guides; the small-angle camera D11; and the data handling facilities. The camera D11 has an overall length of 80 m. The effective length of the camera is variable. The full length of the collimator before the fixed sample position can be reduced by movable neutron guides; the secondary flight path of 40 m full length contains detector sites in various positions. Thus, a large range of momentum transfers can be used with the same relative resolution. Scattering angles between 5 × 10−4 and 0.5 rad and neutron wavelengths from 0.2 to 2.0 nm are available. A large-area position-sensitive detector is used which allows simultaneous recording of intensities scattered at different angles; it is a multiwire proportional chamber. 3808 elements of 1 cm2 are arranged in a two-dimensional matrix.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 15-19 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The forward scattering of cold neutrons in small-angle scattering experiments on macromolecules dissolved in mixtures of light and heavy water is predominantly determined by the large incoherent cross section of the hydrogen atoms leading to an isotropic background level. The probability per unit solid angle for forward scattering by samples rich in H2O is approximately equal to the fraction of the primary beam which has not been transmitted through the sample, divided by the full solid angle 4π. When using the camera D11 at the high flux reactor in Grenoble [Ibel (1976). J. Appl. Cryst. 9, 296–309] this simple relation is fulfilled within ±5% by a 1 mm thick sample of H2O at 281.8 K using neutrons of 1.0 nm wavelength. In D2O, the coherent cross section is of the same order as the incoherent one, and about one half of all those neutrons which had been removed from the primary beam are scattered into large angles. Our experimental results and the derived graphs allow us to determine the effective forward scattering per unit solid angle for any volume fraction of D2O in H2O/D2O mixtures around room temperature by a simple and accurate transmission experiment in conjunction with the measurement of the scattering of one single sample of H2O of 1 mm thickness, for neutrons of wavelengths from 0.45 to 1.0 nm.
    Type of Medium: Electronic Resource
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