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21.
The rheological properties of dense silica in water suspensions (approx. 50% solids by volume) containing additions of metal oxides were examined. Metal oxides used were ferric, zinc and stannic. To prevent settling, testing was performed in a rheometer which was modified to provide for continual stirring of the materials. Relatively small oxide additions had the effect of thickening the mixtures and making them non-Newtonian. Different rate-limiting steps for flow were identified depending on the particular mixture, testing temperature and shear strain rate. Flow could be described using empirical equations which are identical to those often used to describe plastic flow in solid crystalline materials. 相似文献
22.
23.
Richard E. Smalley Lennard Wharton Donald H. Levy Dean W. Chandler 《Journal of Molecular Spectroscopy》1977,66(3):375-388
The fluorescence excitation spectrum of the transition in s-tetrazine has been observed and measured. The sample was cooled to a rotational temperature of <1 K by expansion in a supersonic free jet. In this way the rotational structure arising from asymmetry split low J lines could be observed. The rotational A and B axes of the 2H112C214N4 isotope were observed to interchange upon electronic excitation and a theory describing the effect of this interchange upon the optical selection rules has been developed. Analysis of the resolved rotational structure suggests that the geometry change upon electronic excitation is smaller than that deduced from previous analysis of the room temperature optical spectrum. 相似文献
24.
Enrico Mincione Anthony J. Pearson Paolo Bovicelli Malcolm Chandler Geoffrey C. Heywood 《Tetrahedron letters》1981,22(30):2929-2932
New Methodology is described for the synthesis 6-ketosteroids, of potential value for the synthesis of β-ecdysone, tricarbonyl (4-methoxy-1-methylcyclohexadienyl) iron hexafluorophosphate . 相似文献
25.
26.
McLeod MC Kitchens CL Roberts CB 《Langmuir : the ACS journal of surfaces and colloids》2005,21(6):2414-2418
Deposition of nanoparticles into uniform, wide-area thin films using CO(2) as an antisolvent is presented. Ligand-stabilized silver particles are controllably precipitated from organic solvents by pressurizing and expanding the solution with carbon dioxide. Subsequent addition of carbon dioxide as a dense supercritical fluid provides for removal of the organic solvent while avoiding the surface tensions common to evaporating solvents that are detrimental to nanoscale assemblies and structures. This brand new CO(2)-expanded liquid particle deposition technique allows for the targeted deposition of particles and results in more uniform and lower defect metal nanoparticle thin films than are provided by conventional solvent evaporation techniques. 相似文献
27.
Lewis SP Henderson LD Chandler BD Parvez M Piers WE Collins S 《Journal of the American Chemical Society》2005,127(1):46-47
Lewis acidic, chelating diborane 1 forms stable oxonium acids 2 in the presence of excess MeOH or water. Diborane 1 is shown to be an effective co-initiator for the suspension polymerization of isobutene in aqueous media at sufficiently low temperatures. Poly(isobutene) or butyl rubber is obtained at moderate to high conversion and with Mw < 200 K and PDI approximately 2 under these conditions. 相似文献
28.
Several improvements are made to available computer programs for calculating formation constants from pH data. The most important features are wide portability of program among computers, ability to optimize any parameter in the model equations and to fix any parameters (including stepwise formation constants) to a constant, and options to allow for variations in thermodynamic activity of ions and to fit pH after fitting the volume of added reagent. The latter feature was used with synthetic data to explore the effects of random errors in either reagent volume or pH or both. Whereas fits to reagent volume will usually be more accurate for systems with pKa values near 7, this is not the case for systems with pKa values which differ by > 2.0 from 7. 相似文献
29.
We study the permutation action of a finite symplectic group of characteristic 2 on the set of subspaces of its standard module which are either totally isotropic or else complementary to totally isotropic subspaces with respect to the alternating form. A general formula is obtained for the 2-rank of the incidence matrix for the inclusion of one-dimensional subspaces in the distinguished subspaces of a fixed dimension. 相似文献
30.
Rochau GA Bailey JE Maron Y Chandler GA Dunham GS Fisher DV Fisher VI Lemke RW Macfarlane JJ Peterson KJ Schroen DG Slutz SA Stambulchik E 《Physical review letters》2008,100(12):125004
The Z-pinch dynamic hohlraum is an x-ray source for high energy-density physics studies that is heated by a radiating shock to radiation temperatures >200 eV. The time-dependent 300-400 eV electron temperature and 15-35 mg/cc density of this shock have been measured for the first time using space-resolved Si tracer spectroscopy. The shock x-ray emission is inferred from these measurements to exceed 50 TW, delivering >180 kJ to the hohlraum. 相似文献