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  • 1
    Electronic Resource
    Electronic Resource
    The determination of crystal size and disorder from X-ray diffraction photographs of polymer fibres. 1. The accuracy of determination of Fourier coefficients of the intensity profile of a reflection (1989)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 22 (1989), S. 363-371 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Methods which determine the number and disorder of lattice planes in a crystal from the Fourier cosine coefficients of the intensity profile of an X-ray reflection use only the low harmonics and require that the coefficients be normalized so that the zero harmonic is unity. Experimentally, the profiles can only be recorded over a smaller range of scattering angle than required by the theory, and it is necessary to subtract background, which is likely to be estimated with considerable error, before determining the coefficients. It is shown that with polymer fibres this causes serious errors in the normalization, and in the values of those low harmonics used in the size and disorder determination, and prevents reliable values being obtained. Methods which avoid normalization and use only high harmonics are needed. It is shown that disorder may be obtained in such a way, but not size, for which low-order normalized coefficients are essential. A method of extrapolation is described and tested which enables the accurate high harmonics to be used to improve the estimates of the low ones. Whilst this will yield more reliable values of crystal size than are obtainable from existing methods, the accuracy depends entirely on the validity of the extrapolation, which cannot be tested in many cases of interest.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889889004085
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The structure of bis(1,2-dihydro-4-phenyl-4H-[1,4]oxazino[4,3-α]benzimidazole)dinitratonickel(II) acetonitrile solvate, [Ni(C16H14N2O)2(NO3)2].CH3CN (1985)
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 41 (1985), S. 372-374 
    Details
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S010827018500395X
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Small-angle-X-ray scattering by crystalline polymer fibres 1. Experimental method and investigation of the linear paracrystalline model (1987)
    Springer
    Colloid & polymer science 265 (1987), S. 383-393 
    Details
    ISSN: 1435-1536
    Keywords: Small-angleX-ray ; linearparacrystal ; poly(butylene terephthalate) ; orientedpolymerfibre
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Hosemann's formula for X-ray scattering by a linear paracrystal is investigated using the distribution of intensity parallel to the fibre axis of oriented poly(butylene terephthalate). The formula was put into a form suitable for numerical analysis, and a stepping refinement procedure used to adjust the paracrystalline parameters so that the discrepancy between the calculated and measured intensity was minimised. The measured intensity had been corrected for the spread of scattering transverse to the fibre axis before making this comparison. The pin-hole collimation system was designed so that resolution was limited only by the linear position-sensitive detector, and was good enough not to distort the recorded scattering distribution. Although parasitic scatter could not be measured to the same accuracy, it was so small that negligible error was introduced when it was subtracted. “Top-hat”, Gaussian and Reinhold distribution functions for the lengths of the two phases all fitted well in the region of the main peak although detailed analysis suggested significant disagreement on the low-angle side. Only the asymmetric Reinhold function fitted around the third-order peak and beyond. The range of parameter values giving a good fit for this distribution were determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01412216
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  • 4
    Electronic Resource
    Electronic Resource
    Linear solvation energy relationships. A comparison of molar volume and intrinsic molecular volume as measures of the cavity term in reversed phase liquid chromatography (1986)
    Springer
    Chromatographia 21 (1986), S. 473-477 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase capacity factors ; Cavity term ; Molar volumes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase liquid chromatographic capacity factors are well correlated by an equation of the form: $$logk' = (logk')_0 + mV/100 + s\pi ^* + b\beta + a\alpha $$ wheremV/100 measures the cavity term and π*, β, and α are the solvatochromic parameters that measure solute dipolarity/polarizability, hydrogen bond acceptor basicity, and hydrogen bond donor acidity respectively. Liquid molar volume (molecular weight divided by liquid density at 20°C) $$\bar V$$ , and computer-calculated intrinsic (van der Waals) molecular volume, $$\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{V} _I $$ , are compared as measures of the cavity term in a number of correlations. $$\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{V} _I $$ leads to more precise correlations as well as to a “cleaner” dissection of the multiple solute/solvent interactions. The opposing exoergic effect of solvent donor/solute acceptor hydrogen bonding, and endoergic cavity term are the main factors influencing HPLC capacity factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02341273
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  • 5
    Electronic Resource
    Electronic Resource
    Some observations regarding different retention properties of HPLC stationary phases (1988)
    Springer
    Chromatographia 25 (1988), S. 373-381 
    Details
    ISSN: 1612-1112
    Keywords: Reversed-phase liquid chromatography ; Solvatochromic linear solvation energy relationships ; Parameter robustness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention of 32 monocyclic aromatic compounds and 14 polynuclear aromatic hydrocarbons (PAHs) has been studied on four different bonded phases in each of two mobile phases. An additional data set of 21 monocyclic aromatics judiciously chosen for their well-established solvatochromic parameters, 12 PAHs and 12 polychlorinated biphenyls (containing up to 10 chlorines), were studied on a single column. The results indicate that despite the accuracy of the solvatochromic linear solvation energy method for predicting and correlating the octanol/water partition coefficients and water solubilities of these environmentally important materials, the methodology is limited to only certain types of bonded phases. As a corollary to this observation, we caution others that the common practice of estimating log Kow (Kow=octanol-water partition coefficient) based on measurement of the reversed-phase capacity factors should be limited to specific types of columns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02324777
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    Paper (German National Licenses)
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