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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 398 (1999), S. 681-684 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Ice exhibits many solid-state transformations under pressure, and also displays a variety of metastable phases. Most of the high-pressure phases of ice can be recovered at ambient pressure provided that they are first cooled below about 100 K. These ice polymorphs might exist on the ...
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Neutron powder diffraction can provide important structural information on hydrogenous compounds which are gases at ambient temperature. For high pressure studies, however, this technique has been seriously limited by the fact that it was impossible (a) to load such gases in large volume devices and (b) to compress them to elevated pressures above some 1 GPa. In this letter we show that, using a previously described pressure cell, a wide range of gaseous samples may be loaded and compressed to ∼10 GPa with standard tungsten carbide anvils. We illustrate the effectiveness of the technique with neutron powder diffraction data recently collected on deuterated ammonia ND3 phase IV, where accurate structural data were obtained after a few hours collection time. © 1995 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1735-1737 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Full structural studies of condensed media under high pressure by neutron powder diffraction have been limited in practice to 2–3 GPa for several decades. This range is in general too small to allow a precise determination of the pressure dependence of atomic coordinates. As a consequence, almost no direct measurements exist, for example, of the pressure dependence of the bond lengths in H2 and the planetary ices. In this letter, a technique is presented which makes it possible to pressurize samples of 35 mm3 volume up to 30 GPa and to collect neutron diffraction patterns in a few hours by time-of-flight techniques. This method provides data which can be treated by Rietveld profile refinement methods, as demonstrated on a sample of D2O ice VII at 26 GPa. This represents a tenfold increase of the pressure range over which refinable neutron diffraction data can be obtained and should have a number of applications in such fields as fundamental physicochemistry, and geo- and planetary sciences. © 1995 American Institute of Physics.
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  • 4
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  The structures of deuterated pyrochroite, Mn(OD)2 and β−Cο(OD)2 have been refined using the Rietveld method and neutron powder diffraction data collected in an opposed-anvil high pressure (Paris-Edinburgh) cell from room pressure to 9 GPa. The equation of state for Mn(OD)2 was determined (K=41(3) GPa for fixed K′=4.7) and found to be consistent with previous studies of the isostructural brucite, Mg(OD)2. The compressibility of β−Cο(OD)2 on the other hand is apparently anomalous. The c-axis initially decreases at 3 times the rate of decrease of the a-axis; the ratio decreases to about 1.5 at an estimated 6 GPa before increasing again beyond this pressure. There is no obvious corresponding anomaly in the details of the atomic structure. In both materials there is an increase in the D-site disorder with pressure. A split-site model for the D-positions best fits the data at pressures above 8 GPa. There is no statistically significant increase in the O-D interatomic distance at increased pressure while the hydrogen bonding interaction D...O appears to increase as this distance decreases and the O-D...O angle increases. The intramolecular O-D bond valences, determined indirectly from the intermolecular D...O distances, decrease steadily for both materials as pressure is increased.
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  • 5
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Research carried out at Loughborough during the last five years on the impedance of Leclanché, alkaline Zn-MnO2, alkaline Zn-HgO, Li-CuO, Li-SO2, Li-SOCl2 primary cells is briefly reviewed. The use of alternating current methods for the estimation of the state of charge of the cells is discussed. A search was made for properties of the impedance of each cell system which change in a marked and reliable manner when a prescribed amount of charge is withdrawn from the cell. It is concluded that simple tests based upon an assessment of these properties are adequate for the estimation of the state of charge of some of the systems studied. However, other systems are not so ‘well-behaved’. The impedance of each cell changed significantly during discharge and, although making measurements of these changes would enable the state of charge to be estimated, the test techniques required would not necessarily be simple. Using the results obtained on the impedance of the cells, test sets have been constructed which provide a digital presentation of the open-circuit voltage and the state of charge of Leclanché cells (Ever Ready type SP11), mercury cells (Mallory, type RM502R) and lithium cells (Mallory, type L032S and SAFT, type LC01). The electronic techniques employed in these test sets are described in outline with reference in block-schematic diagrams. A proposal is made for the construction of a general-purpose tester for primary cells which would incorporate microprocessors and provide an indication of state of charge based upon data relating to impedance, temperature and discharge history. The tester might also be made self-calibrating for field use.
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