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1.
P. R. Holland 《Foundations of Physics》1987,17(4):345-363
The geometrical structures implicit in the de Broglie waves associated with a relativistic charged scalar quantum mechanical particle in an external field are analyzed by employing the ray concept of the causal interpretation. It is shown how an osculating Finslerian metric tensor, a torsion tensor, and a tetrad field define respectively the strain, the dislocation density, and the Burgers vector in the natural state of the wave, which is a non-Riemannian space of distant parallelism. A quantum torque determined by the quantum potential is introduced and the example of a screw dislocated wave is discussed. 相似文献
2.
A one-pot synthesis of unsymmetrical tertiary amines from amides, lactams and urethanes has been developed. The reaction is general for all cases examined with the exception of N-aryl containing examples, which are not accessible by this method. 相似文献
3.
The parent amido complex cis-(PMe(3))(4)Ru(H)(NH(2)) (2) has been prepared via the deprotonation of [cis-(PMe(3))(4)Ru(H)(NH(3))(+)][BPh(4)(-)]. The amido complex is a somewhat weaker base than the DMPE analogue trans-(DMPE)(2)Ru(H)(NH(2)) but is still basic enough to quantitatively deprotonate fluorene and reversibly deprotonate 1,3-cyclohexadiene and toluene. Complex 2 exhibits very labile phosphine ligands, two of which can be replaced by DMPE to yield the mixed complex cis-(PMe(3))(2)(DMPE)Ru(H)(NH(2)). Because of the ligand lability, 2 also undergoes hydrogenolysis and rapid exchange with labeled NH(3). The amide complex reacts with alkyl halides to yield E2 and S(N)2 products, along with ruthenium hydrido halide complexes including the ruthenium fluoride cis-(PMe(3))(4)Ru(H)(F). Ruthenium hydrido ammonia halide ion pair intermediates [cis-(PMe(3))(4)Ru(H)(NH(3))(+)][X(-)] are observed in some deprotonation and E2 reactions, and measurement of the equilibrium constants for NH(3) displacement from these complexes suggests that they benefit from significant hydrogen bonding between X(-) and NH(3) groups. Cumulenes also react with complex 2 to afford the products of insertion into an NH bond. The rates of neither these NH insertion reactions nor the reversible deprotonation reactions show any dependence on the concentration of PMe(3) present, suggesting that these reactions take place directly at the NH(2) group and do not involve precoordination of substrate to the metal center. 相似文献
4.
G. Mountjoy M.A. Holland P. Gunawidjaja G.W. Wallidge D.M. Pickup R.J. Newport M.E. Smith 《Journal of Sol-Gel Science and Technology》2003,26(1-3):161-164
The incorporation of transition-metal oxides into silica can give materials with useful optical, electronic or catalytic properties. For example, ZrO2-SiO2 and HfO2-SiO2 materials are of interest due to their high dielectric constants. Here we present a comparison of extended X-ray absorption fine structure and small-angle X-ray scattering results for acid-catalysed binary (MO2)
x
(SiO2)1 – x
(M = Ti, Zr or Hf) xerogels, with x up to 0.4 and heat treatments up to 750°C. Detailed observations for TiO2-SiO2 and ZrO2-SiO2 xerogels provide a basis for interpretation of new results for HfO2-SiO2 xerogels. At low concentrations metal atoms are homogeneously incorporated into the silica network. Ti adopts coordinations of 4 or 6, and Zr and Hf both adopt higher coordination of 6 or 7 (the larger coordinations being due to ambient moisture). At higher concentrations, phase separation of metal oxide occurs. Such regions become clearly separated from the silica network for TiO2, but remain very finely mixed with silica network for ZrO2 and HfO2. 相似文献
5.
This paper produces several examples of varieties X for whichthe global sections functor (X,): DX-modD(X)-mod is exact,and makes D(X)-mod a quotient category of DX-mod, but is notan equivalence. These varieties are quotients by finite groupactions of D-affine varieties. The torsion of (X,) isalso described, in some cases. Here, Dx-mod denotes the categoryof quasi-coherent DX-modules. 相似文献
6.
Summary The keto-enol tautomerism of the 2- and 3-isomers of thianaphthenoyltrifluoroacetone has been studied and the results explained by considering the relative negativities of the 2- and 3-position of thianaphthene. The results of the comparison of the keto-enol tautomerism of 3-thianaphthenoyltrifluoroacetone to that of 2-thenoyltrifluoroacetone in 80% benzene-20% ethanol may explain in part the greater sensitivity of the former in trace metal analysis.
Zusammenfassung Die Keto-Enol-Tautomerie der 2- und 3-Isomeren des Thianaphthenoyltrifluoracetons wurde untersucht und mit der relativen Negativität der 2- und 3-Stellung des Thianaphtens zu erklären versucht. Der Vergleich der Keto-Enol-Tautomerie von II mit der des 2-Thenoyltrifluoracetons in BenzolÄthanol (80+20) könnte eine Erklärung für die größere Sensitivität von II bei der Spurenmetallanalyse bieten.相似文献
7.
Mass spectra of some naturally occurring stictane triterpenoids and their trimethylsilyl derivatives
The mass spectra of ten di- and tri-oxygenated stictane triterpenoids and their trimethylsilyl derivatives have been studied in detail. Gas chromatography mass spectrometry of the TMS derivatives on OV-17 and OV-101 columns provided useful separations and identifications of mixtures of stictanes triterpenoids in lichen extracts. The major fragmentations involve ring C, but specific cleavages in rings A, B and E are also observed which allow the substitution pattern of the skeleton to be readily determined. The formation of an intense [M – C5H11?]+ ion for 22α-OTMS stictanes appears specific to their ring E configuration. 相似文献
8.
Summary A solvent extraction method for the spectrophotometric determination of gold is described. The effects due to pH, time, reagent concentration and diverse ions have been evaluated. Sensitivity was increased by the use of 4-cm cells, Beer's law was obeyed and the molar absorptivity at 477 nm was 2.34×104.
Spektrophotometrische Bestimmung von Goldspuren mit 2-Pyridyl-2-thienyl-Z-ketoxim
Zusammenfassung Eine Extraktionsmethode zur spektrophotometrischen Goldbestimmung wurde beschrieben. Der Einfluß von pH, Zeit, Reagenskonzentration und verschiedenen Fremdionen wurde ermittelt. Die Empfindlichkeit wurde mittels 4-cm-Küvetten erhöht. Das Beersche Gesetz wird befolgt, die molare Extinktion bei 477 nm beträgt 2,34×104.相似文献
9.
Recent advances in micellar electrokinetic chromatography 总被引:2,自引:0,他引:2
This review contains nearly 200 reference citations, and covers advances in electrokinetic capillary chromatography based on micelles, including stabilized micelle complexes, polymeric and mixed micelles from 2003-2004. Detection strategies, analyte determinations, and applications in micellar electrokinetic capillary chromatography (MEKC) are discussed. Information regarding methods of analyte concentration, analyte specific analyses, and nonstandard micelles has been summarized in tabular form to provide a means of rapid access to information pertinent to the reader. 相似文献
10.
Poly(vinyl alcohol) single crystal platelets having a stepheight of approximately 100 A. were obtained by isothermal crystallization from dilute triethylene glycol solution. Material crystallized at temperature Tc redissolved in the same solvent at a higher temperature Ts. A plot of Tc versus Ts gave a straight line of slope 0.47. Extrapolation of this line to Tc = Ts gave (Tm)∞, which may be regarded as the dissolution temperature of the crystal of infinite stepheight. (Tm)∞ for this sample in triethylene glycol was 220°C. The crystalline nature of the platelets was established by electron and x-ray diffraction techniques. A total of three Bragg d spacings having the values of 3.9, 4.4, and 4.6 A. (±0.05 A.) were measured. These spacings were indexed as the (200), (101), and (101 ) reflections, respectively, of the monoclinic unit cell of Bunn. The x-ray diffractogram exhibits sharp intensities of the (101 ) and (101) reflections. The crystallinity calculated from the density of the poly(vinyl alcohol) precipitated from dilute solutions in triethylene glycol was 42%. Although the overall degree of crystalline perfection of this poly(vinyl alcohol) is low, the linear relationship between Ts and Tc and the formation of definite shaped single crystals when crystallized from dilute solution suggest that poly(vinyl alcohol) crystallizes in the same manner as other semicrystalline polymers. 相似文献