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  • 1
    Electronic Resource
    Electronic Resource
    A new method of obtaining phase angles of structure factors of non-centrosymmetric structure by the use of anomalous dispersion (1967)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 23 (1967), S. 898-901 
    Details
    ISSN: 0001-5520
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0365110X67004001
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  • 2
    Electronic Resource
    Electronic Resource
    Entschmierung von fehlerbehafteten Röntgen-Kleinwinkel-Streukurven (1971)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 27 (1971), S. 11-18 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The experimentally determined small-angle X-ray scattering curve is approximated by a Fourier series. For smoothing the scattering curve a limit for the correlation range of the difference of the electron density from the average is presupposed. The smoothing, the correction of the slit width error by deconvolution and the differentiation for the correction of slit height error are carried out with the Fourier coefficients. The smeared scattering curve is reconstructed by Fourier synthesis. The method makes it possible to correct scattering curves with random and no-random errors working with digital computers in on-line or off-line technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739471000032
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  • 3
    Electronic Resource
    Electronic Resource
    On the calculation of a slit-smeared small-angle X-ray scattering function for coated spheres (1974)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 7 (1974), S. 445-446 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A formula is presented for calculating `infinite-slit' smeared small-angle X-ray scattering curves for concentrically coated spheres of uniform electron densities ρ1 and ρ2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889874010119
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  • 4
    Electronic Resource
    Electronic Resource
    The database BIOSCAT: a tool for structure research by scattering and hydrodynamic methods (1992)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 25 (1992), S. 803-806 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The crystal structures of a large number of proteins and nucleic acids are known and the corresponding sets of coordinates are stored in the Brookhaven Protein Data Bank. For structure investigations of biological macromolecules in solution, scattering and hydrodynamical methods are powerful biophysical tools when starting the data interpretation on the basis of the crystal structure of the molecules. The database BIOSCAT covers the main structural parameters estimable by X-ray scattering, translation and rotation diffusion methods and the X-ray scattering intensities and low- and high-resolution real-space electron distance distribution functions of 70 biological macromolecules and of oligonucleotides in standard conformation. The parameters and the scattered intensities are calculated from the atomic coordinates using the improved cube method and the real-space functions are estimated via a termination-error-reduced Fourier sine transformation. The database access is organized by the program PASSDB, which can generally be used for `readable' databases. A simple query language allows enquiries into the database without knowledge of a programming language. The program CONVSQL converts the database into normalized relations that can be handled by structured query languages (SQLs).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889892006733
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  • 5
    Electronic Resource
    Electronic Resource
    A study of high-resolution X-ray scattering data evaluation by the maximum-entropy method (1994)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 27 (1994), S. 257-270 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The ability of the maximum-entropy method (in the program MAXENT) to estimate the distance-distribution function from high-resolution X-ray scattering data is studied. It is demonstrated that a key element for the successful application of MAXENT is the use of a good prior estimate for the distance-distribution function. For simulated as well as experimental data, the effects of different priors, noise levels, smearing and measuring intervals are investigated. For practical applications of MAXENT, various methods for the calculation of priors are treated and a principle for the subsequent choice between the priors is suggested. It is demonstrated that, when the construction of the prior is given sufficient consideration, MAXENT provides a very useful method for estimating the distance distribution from the scattering data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889893008398
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison and optimization of smoothing procedures for small-angle X-ray scattering curves. Polynomial fitting and modified frequency filtering (1979)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 12 (1979), S. 267-274 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The filter theory allows one to compare the efficiencies of smoothing procedures widely used in the field of small-angle X-ray scattering. This method is demonstrated for polynomial fitting and modified frequency filtering. Optimized and objective smoothing parameters are determined for both procedures through the knowledge of variance reduction factors, transfer functions of the filters, the largest value of the spatial frequencies of the scattering curve and the distortions caused by the smoothing procedures. The comparison of the efficiency of polynomial fitting and frequency filtering clearly shows the superiority of the latter; therefore, this method has to be preferred.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889879012450
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  • 7
    Electronic Resource
    Electronic Resource
    Determination of the largest particle dimension by direct Fourier cosine transformation of experimental small-angle X-ray scattering data (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 280-283 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The largest dimension, L, of a scattering particle is an essential structure parameter of the sample and is necessary both for designing and carrying out experiments and also for analysis of the scattering data. It is shown that L, which is identical to the upper-limit frequency of the scattering curve, can always be evaluated from a Fourier cosine transformation of scattering data which are not corrected for collimation effects, regardless of the shape of the primary beam.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S002188988001206X
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  • 8
    Electronic Resource
    Electronic Resource
    The model resolution function – a technique for estimating the quality of approximation of particles by models in small-angle X-ray or neutron scattering (1985)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 18 (1985), S. 241-247 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Although the quality of a structure model obtained from small-angle X-ray or neutron scattering curves for polymers can be determined qualitatively by comparing the isotropic scattering curve calculated for the model with the experimental scattering data for a solution of polymer molecules, other methods are needed for a more precise evaluation. A model resolution function has been defined to permit quantitative comparisons. With this function, the quality of the approximation can be assessed, and the structure resolution can be determined. An overinterpretation of scattering curves by use of complex but uniform-density models can thus be avoided. Furthermore, the value of the Porod volume calculated from the scattering data has been found to depend strongly on the interval in which the scattering data are recorded or selected for evaluation. The calculations with the atomic model curves showed that it is impossible to compute physically meaningful values of the hydration of the molecules from the Porod volume and the dry volume by use of extrapolated scattering curves with an insufficient resolution. The theory of the model resolution function and the interpretation of the Porod volume have been verified and tested with experimental scattering curves from solutions of RNA molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889885010214
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  • 9
    Electronic Resource
    Electronic Resource
    Multimodal Particle-Size Distribution or Fractal Surface of Acrylic Acid Copolymer Nanoparticles: A Small-Angle X-ray Scattering Study using Direct Fourier and Indirect Maximum-Entropy Methods (1995)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 28 (1995), S. 774-781 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Acrylic acid copolymers are potential carriers for drug delivery. The surface, surface rugosity and the absolute dimension of the particles are parameters that determine the binding of drugs or detergents, diffusion phenomena at the surface and the distribution of the carrier within the human body. The particle-size distribution and surface rugosity of the particles have been investigated by small-angle X-ray scattering and dynamic light scattering. Direct Fourier transform as well as a new strategy for the indirect maximum-entropy method MAXENT are used for data evaluation. Scattering equivalence of a pure multimodal distribution of hard spheres (five populations) and a mixed multimodal-surface-fractal model (four populations) was found. Model calculations and dynamic light-scattering experiments gave evidence of the multimodal particle-size distribution combined with the fractal surface of the carrier. The main moiety consists of particles 90 nm in diameter which are surface fractals in the 10 nm region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889895007230
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  • 10
    Electronic Resource
    Electronic Resource
    Glass-capillary collimator for distance compensation and partial monochromatization at rotating-anode X-ray generators (1995)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 28 (1995), S. 853-855 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Access to the beam ports of rotating-anode X-ray generators is often obstructed by direct-coupled or belt-driven target drives. The construction of an easily adjustable stable glass-capillary collimator is described, which renders possible the unrestricted use of beam ports of these generators. Transmitted intensity and monochromaticity of the primary beam are sufficient for precession photographs of proteins after additional 20 μm Ni filtering as demonstrated by a precession photograph of hen egg lysozyme. The straight capillary collimator is now a routinely usable low-cost device for each X-ray laboratory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889895009708
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