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  • 2020-2022  (3)
  • 1995-1999  (4)
  • 1940-1944  (1)
  • 1
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Nucleoside ; hydrated nucleoside ; anomeric differences ; pyrimidine ; uracil ; xylofuranosyl ring ; isopropylidene rings
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01665987
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Acylcyanide ; cyanocarbonyl ; imidazole ; carbonyl cyanide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1023200307429
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: 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.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
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    Unbekannt
    The Shearwater Field, Blocks 22/30b and 22/30e, UK North Sea (2020)
    Geological Society of London
    Details
    Publikationsdatum: 2020-01-01
    Beschreibung: The Shearwater Field is a high-pressure–high-temperature (HPHT) gas condensate field located 180 km east of Aberdeen in UKCS Blocks 22/30b and 22/30e within the East Central Graben. Shell UK Limited operates the field on behalf of co-venturers Esso Exploration and Production UK Limited and Arco British Limited, via a fixed steel jacket production platform and bridge-linked wellhead jacket in a water depth of 295 ft.Sandstones of the Upper Jurassic Fulmar Formation constitute the primary reservoir upon which the initial field development was sanctioned; however, additional production has been achieved from intra-Heather Formation sandstones, as well as from the Middle Jurassic Pentland Formation. Following first gas in 2000, a series of well failures occurred such that by 2008 production from the main field Fulmar reservoir had ceased. This resulted in a shut-in period for the main field from 2010 before a platform well slot recovery and redevelopment drilling campaign reinstated production from the Fulmar reservoir in 2015. In addition to replacement wells, the redevelopment drilling also included the design and execution of additional wells targeting undeveloped reservoirs and near-field exploration targets, based on the lessons learned during the initial development campaign, resulting in concurrent production from all discovered reservoirs via six active production wells by 2018.
    Print ISSN: 0435-4052
    Digitale ISSN: 2041-4722
    Thema: Geologie und Paläontologie
    Publiziert von Geological Society of London
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    facet.materialart.
    Unbekannt
    The Effect of Melt Pond Geometry on the Distribution of Solar Energy Under First‐Year Sea Ice (2020)
    American Geophysical Union
    Details
    Publikationsdatum: 2020-02-17
    Print ISSN: 0094-8276
    Digitale ISSN: 1944-8007
    Thema: Geologie und Paläontologie , Physik
    Publiziert von American Geophysical Union
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    facet.materialart.
    Unbekannt
    The Constituents of Wheat and Wheat Products (1944)
    Springer Nature
    Details
    Publikationsdatum: 1944-09-01
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Springer Nature
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    facet.materialart.
    Unbekannt
    Economic Growth and Sustainability: A New Challenge (1996)
    Wiley
    Details
    Publikationsdatum: 1996-02-01
    Print ISSN: 1051-0761
    Digitale ISSN: 1939-5582
    Thema: Biologie
    Publiziert von Wiley im Namen von Ecological Society of America.
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
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    Unbekannt
    Magmatic channelisation by reactive and shear-driven instabilities at mid-ocean ridges: a combined analysis (2021)
    Oxford University Press
    Details
    Publikationsdatum: 2021-03-26
    Beschreibung: Summary It is generally accepted that melt extraction from the mantle at mid-ocean ridges is concentrated in narrow regions of elevated melt fraction called channels. Two feedback mechanisms have been proposed to explain why these channels grow by linear instability: shear flow of partially molten mantle and reactive flow of the ascending magma. These two mechanisms have been studied extensively, in isolation from each other, through theory and laboratory experiments as well as field and geophysical observations. Here, we develop a consistent theory that accounts for both proposed mechanisms and allows us to weigh their relative contributions. We show that interaction of the two feedback mechanisms is insignificant and that the total linear growth rate of channels is well-approximated by summing their independent growth rates. Furthermore, we explain how their competition is governed by the orientation of channels with respect to gravity and mantle shear. By itself, analysis of the reaction-infiltration instability predicts the formation of tube-shaped channels. We show that with the addition of even a small amount of extension in the horizontal, the combined instability favours tabular channels, consistent with the observed morphology of dunite bodies in ophiolites. We apply the new theory to mid-ocean ridges by calculating the accumulated growth and rotation of channels along streamlines of the solid flow. We show that reactive flow is the dominant instability mechanism deep beneath the ridge axis, where the most unstable orientation of high-porosity channels is sub-vertical. Channels are then rotated by the solid flow away from the vertical. The contribution of the shear-driven instability is confined to the margins of the melting region. Within the limitations of our study, the shear-driven feedback does not appear to be responsible for significant melt focusing or for the shallowly dipping seismic anisotropy that has been obtained by seismic inversions.
    Print ISSN: 0956-540X
    Digitale ISSN: 1365-246X
    Thema: Geologie und Paläontologie
    Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.
    Standort Signatur Erwartet Verfügbarkeit
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