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61.
Vibrational spectra of the hydrated carbonate minerals ikaite,monohydrocalcite, lansfordite and nesquehonite 总被引:2,自引:0,他引:2
Coleyshaw EE Crump G Griffith WP 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(10):2231-2239
The Raman (200-4000 cm(-1)) and infrared (600-4000 cm(-1)) spectra of four rare carbonate hydrate minerals are reported. These are naturally occurring and synthetic ikaite CaCO3.6H2O, and nesquehonite MgCO3.3H2O; natural monohydrocalcite CaCO3.H2O, and synthetic lansfordite MgCO3.5H2O. The spectra of synthetic ikaite partially substituted with 2H2O and also with 13C were measured, as were those of synthetic deuteriated nesquehonite. Spectra of ikaite and lansfordite, both of which decompose at room temperatures, were measured below 0 degrees C. Assignments of fundamental modes are proposed. 相似文献
62.
Phillip Griffith 《Compositio Mathematica》1998,110(3):251-262
For an extension R A of commutative Noetherian rings the behavior of the associated morphism of topological spaces Spec A Spec R is often measured by its behavior on each of its fibers. Specifically, one studies the 'splitting' (or 'branching') and the 'ramification' that occurs in each fiber. In the classical constructions of faithfully flat analytic extensions (e.g., completion or Henselization) of excellent local rings the splitting and ramification properties are fairly well understood; see EGA IV [6, 18.10], Nagata [13, Sect. 37] or Raynaud [15, Ch. IX]. The strongest results are usually achieved for fibers over a 'normal point' of Spec R, that is, over p Spec R such that R/p is a normal domain [e.g., the property of a normal prime p in a local ring to be 'unibranched', i.e., the Henselization of R/p is a (normal) domain]. 相似文献
63.
Mino R. Caira Vivienne J. Griffith Luigi R. Nassimbeni Bosch van Oudtshoorn 《Journal of inclusion phenomena and macrocyclic chemistry》1994,17(2):187-201
An inclusion complex with the formula (-cyclodextrin) (sulfathiazole) 8.3 H2O has been crystallized and characterized by physicochemical methods including single crystal X-ray analysis. The complex crystallizes in the monoclinic system, space group P21, witha=15.264(4),b= 16.500(6),c=15.559(5) Å,=117.29(3)o andZ=2. The structure was solved using published co-ordinates for-cyclodextrin in an isomorphous complex. Refinement by block-diagonal leastsquares yieldedR=0.061 for 4706 unique observed reflections. Inclusion of sulfathiazole produces a slight ellipticity in the host conformation, but the guest adopts a conformation similar to that observed in its polymorphs. The guest is held in the macrocyclic cavity predominantly by hydrophobic forces, with the phenyl ring near the host primary hydroxyl side and the thiazole ring near the secondary hydroxyl side. The complex packs in layers parallel to theac-plane. Layers are linked by hydrogen bonding to water molecules which are located outside the cyclodextrin cavity. An extensive network of hydrogen bonds mediated chiefly by water molecules stabilizes the crystal structure. 相似文献
64.
Summary Addition reactions of [MNCl4]– (M = Os or Ru) with ligands L or L to give [MNCl4 · L]– or [(MNCl4)2L]2– (L = pyridine, pyridine-N-oxide,iso-quinoline or DMSO; L = hexamethylenetetramine, pyrazine or dioxan) are described. With NCO–, [OsNCl5]– gives [OsN(NCO)5]2– but NCS– gives a thionitrosyl complex, [Os(NS)(NCS)5]2–. Reactions of OsNCl3(AsPh3)2 with pyridine, 1,10-phenanthroline and tertiary phosphites and phosphinites have been studied, as have reactions of triphenylphosphine with OsOCl4 andtrans- [MO2Cl4]2– (M = Os or Ru). The nitrido-iodo complexes [OsNI4]– and OsNI3, (SbPh3)2 are also reported. 相似文献
65.
P. G. Coleman T. C. Griffith G. R. Heyland T. L. Killeen 《Applied Physics A: Materials Science & Processing》1974,3(4):271-273
A conventional positron lifetime system is described which gives data of high statistical accuracy and is especially suitable for gases at low density. Several factors contribute to the significant improvement in performance. The fraction of positrons annihilating in the gas is greatly enhanced by backscattering, and the small dimensions of the pressure vessel coupled with large plastic scintillators yields about 1200 coincidence events per second. Simple electronics are used with no side channel gating, and very clean spectra are obtained with overall resolution better than 1.5 nsec. The true start and stop pulses are counted, which enables the data to be treated by the authors' signal restoration method. The results of measurements in Ar?CO mixtures and data for H2 and D2 are presented and discussed. 相似文献
66.
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68.
The role of lipid spin labels in membrane biophysics 总被引:1,自引:0,他引:1
69.
In a conducting system consisting of a short fine wire carrying a current between two larges masses of the same metal, the maximum temperature attained depends only upon the properties of the material and the applied potential difference, provided the heat lost from the surface of the wire is negligible compared with that conducted. Measurement of the maximum temperature as a function of the potential difference allows the ratio of the thermal conductivityλ to the electrical conductivityχ, and hence the Lorenz numberλ/χ T whereT is the absolute temperature, to be determined over a wide range of temperature. Experiments with platinum in various gases at atmospheric pressure and also at low gas pressures to test the effect of heat losses due to the surrounding gas are described. Under the conditions of the experiments, these losses are very small except in the case of hydrogen, the results agreeing among themselves and with those previously published. Values of the Lorenz number for palladium from 1000 to 1550? C are given. 相似文献
70.