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  • 1
    Electronic Resource
    Electronic Resource
    Hydrogen Bonding in Calcium Orthophosphates (1962)
    [s.l.] : Nature Publishing Group
    Nature 195 (1962), S. 1090-1091 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In dicalcium 6is(dihydrogen phosphate) mono-hydrate3, Ca(H2PO4)2.H2O, we find that the distances between oxygens in phosphate groups which we believe to be hydrogen-bonded cover the range from 2-48 0-03 A to 2-87 0-05 A with infra-red peaks at 2,320, 2,430, 2,670, 2,920, 3,160, and 3,450 cm-1. In ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/1951090a0
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  • 2
    Electronic Resource
    Electronic Resource
    A refinement of the crystal structure of potassium imidodisulphate (1963)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 16 (1963), S. 877-883 
    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/S0365110X63002371
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  • 3
    Electronic Resource
    Electronic Resource
    Conformation and packing differences between two anomeric xylofuranosyl uracil nucleosides: Crystal structure of α-C14N2O7H18 monohydrate (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 123-128 
    Details
    ISSN: 1572-8854
    Keywords: Nucleoside ; hydrated nucleoside ; anomeric differences ; pyrimidine ; uracil ; xylofuranosyl ring ; isopropylidene rings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 5-Acetyl-1-(3,5-O-isopropylidene-α-D-xylofuranosyl) uracil monohydrate (α-AXU·H2O) crystallizes in an orthorhombic cell of dimensionsa=7.286(6),b 14.281(10),c=15.852(11) Å. Its structure has been determined by direct methods from single-crystal CuK α X-ray data and refined to a conventionalR factor of 0.055 over 1708 unique reflections. The furanose ring has conformation C2'endo-C3'endo (rather than the uncommon C3'endo-C4'exo as in β-AXU) and the glycosidic torsion angle is −31° (17° in β-AXU). The oxygen of the water molecule in α-AXU·H2O accepts a hydrogen bond (O 10...O 5=2.70 Å) from the sugar hydroxyl O5 and the hydrogens form hydrogen bonds to a uracil carbonyl (O 10...O 2=2.78 Å) and an isopropylidene oxygen atom (O 10...O 7=2.90 Å).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665987
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  • 4
    Electronic Resource
    Electronic Resource
    The cyanocarbonyl group: synthesis and crystal structure of an imidazole carbonyl cyanide, C12N5OH17 (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 561-564 
    Details
    ISSN: 1572-8854
    Keywords: Acylcyanide ; cyanocarbonyl ; imidazole ; carbonyl cyanide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 1-t-Butyl-5-N-(dimethylaminomethylene)aminoimidazole-4-carbonyl cyanide (BUNDAMIC) is the first acyl cyanide to be synthesized from an imidazole-4-carboxylic acid, diethylphosphorocyanidate, and triethylamine and its structure determined by x-ray crystallography. It crystallizes with four molecules in the monoclinic space group C2/m with a = 17.824(2), b = 6.784(2), c = 11.039(2) Å, and β = 96.17(1)°; R = 0.036 over 1086 unique x-ray reflections. The cyanocarbonyl group is nearly linear, C-C≡ N angle 174.4(3)°, with dimensions C≡ N, 1.137(3); C-C 1.493(3); and C=O≡ N 1.224(3) Å. The imidazole ring, in the mirror plane, has a lengthened C4 = C5 bond of 1.421(3) A, and there is a short ring-closing approach, H⋯ O6 =2.07 Å, between the methyleneamino hydrogen and the carbonyl oxygen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023200307429
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  • 5
    Electronic Resource
    Electronic Resource
    Differential cholinergic regulation in Alzheimer's patients compared to controls following chronic blockade with scopolamine: a SPECT study (1995)
    Springer
    Psychopharmacology 121 (1995), S. 231-241 
    Details
    ISSN: 1432-2072
    Keywords: Scopolamine ; Alzheimer's disease ; SPECT ; I-QNB ; HMPAO ; cholinergic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of low-dose chronic scopolamine on measures of cerebral perfusion and muscarinic receptors were tested in eight Alzheimer's disease (AD) subjects and eight elderly controls. Single photon emission computed tomography (SPECT) scans using technetium-labelled hexamethypropylene amine oxide (99mTc-HMPAO) to measure cerebral perfusion before and after chronic scopolamine revealed a significant 12% increase in the normal controls (P〈0.01) while the AD subjects showed no significant change. In contrast, the controls showed decreased muscarinic binding as evidenced by123I-quinuclidinyl-4-iodobenzilate (123I-QNB) labelling after chronic drug (−10%,P〈0.01) whereas the AD subjects showed increased123I-QNB labelling (+8%,P〈0.05). The difference between AD and control subjects was even more marked when the ratio of I-QNB to HMPAO uptake was compared, pointing to a double dissociation in the SPECT results. These data cannot be explained by group differences in cerebral perfusion alone and suggest a differential sensitivity between AD and elderly controls to chronic cholinergic blockade.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245634
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  • 6
    Electronic Resource
    Electronic Resource
    Crystallization of experimental bioactive glass compositions (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 32 (1996), S. 119-124 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Crystallization kinetics studies for six experimental glass formulations in the system Na2O-CaO-SiO2-P2O5 synthesized by wet chemistry were conducted by means of differential thermal analysis. These glasses had CaO/P2O5 and SiO2/(CaO + Na2O) ratios ranging from 8.74-3.38 and 0.92-3.03, respectively. Samples of each glass (n = 30 were heated from 23 to 1250°C under N2 atmosphere at heating rates ranging from 10 to 50°C/min. Glass-ceramics were obtained after heat treating the initial glasses at temperatures determined from their DTA exotherms. The activation energy of crystallization for each glass composition was calculated from an expression-relating log-heating rate and the reciprocal of the exothermic peak temperature. The compositions of the six glasses were significantly different (p = 0.05). The activation energy of crystallization (Q) values ranged from 196 to 782 kJ/mole. A correlation was obtained between Q and CaO/P2O5 and between Q and the Young's modulus (p 〈 0.001). Two of the six glasses exhibited bulk crystallization. X-ray diffraction studies showed that four of the six glasses exhibited different proportions of crystalline phases following heat treatment. These phases were wollastonite (CaSiO3), Na2CaSi3O9, combeite [Na4Ca3SI6O16(OH)2], and some unidentifiable phases. Two of the six bioceramic materials had a mixture of unknown crystalline phases. © 1996 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Crystalline modifications of cellulose. Part V. A crystallographic study of ordered molecular arrangements (1960)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 42 (1960), S. 173-188 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: With the arrangements of molecular chains postulated in Part III as a basis, crystal structures for the ordered regions of ramie and regenerated celluloses have been set up. Comparison of the (hkl) x-ray intensities calculated for cellulose I structures with the measurements reported in Part IV reveals serious discrepancies on the first layer-line. From extensive calculations over a range of structures, it appears that no conventionally ordered structure built from a P21 unit cell of approximate dimensions 8.2 × 10.3 × 7.9 A., β = 84°, can be expected to yield as weak (h1l) planes as are observed. An element of randomness in the polarity of the chains would diminish the discrete intensities on the higher layers relative to the (h0l) reflections and so be more in accord with experiment. For cellulose II, attention was concentrated on antiparallel chain structures with the r shift near 0.29. Although the overall agreement was better than for cellulose I, such structures did not account for the very weak low-order (h1l) reflections observed. The disparity was not reduced by types of disordering acceptable on stereochemical and spectroscopic grounds. The major part of the disagreement is tentatively attributed to regarding the observed coherent scattering as emanating from fully ordered unit cells of the accepted dimensions and symmetry, and to neglecting contributions from oriented amorphous regions.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1960.1204213920
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  • 8
    Electronic Resource
    Electronic Resource
    Proton magnetic resonance absorption in dry nylons 66 and 610 (1962)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 59 (1962), S. 271-281 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A comparison of the temperature dependence of the nuclear resonance line-width and second moment for dried chip and rod samples of nylon 66 and 610, as measured by several authors, reveals discrepancies within the range 80 to 400°K. Room temperature measurements with a Pound-Watkins spectrometer suggest that neither linewidth nor second moment varies greatly with radiofrequency field, although saturation may occur at low temperatures. It is concluded that the nuclear resonance differences reflect sample differences, at least for the higher temperatures. Evidence is considered for the decomposition of the continuous nuclear resonance changes in polyamides into more discrete “transitions;” in nylon 66, there are nuclear resonance effects near 120, 200, 330, and 370°K.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1962.1205916805
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