Microscopic theory of intrinsic shear and bulk viscosities

A microscopic theory of intrinsic shear and bulk viscosities of solutions is given for a model of particles that interact with hard-sphere cores and weak longrange attraction. The approximation considered (the velocity chaos assumption of the Enskog theory) can be expected to yield quantitatively useful values for viscosities of the model solute-solvent system when the solute particles are not much larger than the solvent particles. Under solute-solvent mixing conditions of constant pressure and temperature we find that the intrinsic viscosities of a hard-sphere solute in a hard-sphere solvent can be positive or negative, depending upon size and mass ratios; for solute and solvent particles whose mass ratio equals their volume ratio, the intrinsic shear and bulk viscosities are always positive for solute particles larger than solvent particles: in the opposite case, the intrinsic shear viscosity is always negative while the intrinsic bulk viscosity is for the most part negative, becoming positive again when the solute particle is sufficiently small. For solute particles smaller than solvent particles, this result is sensitive to change in mass ratio. The addition of solvent-solvent attraction is found to lower the intrinsic viscosities substantially; the addition of solute-solvent attraction raises it. Detailed quantitative analysis of these effects is given.     

Kinetics and mechanisms of the oxidation of sulfur dioxide over titanium dioxide and nickel oxide

The reactions between SO₂ and O₂ were carried out in the presence of TiO₂ and NiO under various partial pressures of SO₂ and O₂ at temperatures from 240 to 330°C. TiO₂ and NiO were pretreated by applying an annealing effect from which the catalysts would have the different activity. The rates are the highest for TiO₂ pretreated at high temperature in the region of 400 to 600deg;C in vacuum, 1.21 × 10^?4 mmHg. In contrast, the rates are the lowest for NiO pretreated at high temperaturefrom 350 to 550°C. The data have been correlated with 1.4 and first-order kinetics for TiO₂ and NiO, respectively. A reaction mechanism to explain the data was suggested. The quantities of anionic vacancies in TiO₂ surfaces and of positive holes in NiO appeared to be paramount in determining the type of kinetics.     

90,91Zr photoproton spectra and the core-excitation model

Photoproton energy spectra have been measured for the ^90,91Zr(γ,P)^89,90Y reactions at an E_γ endpoint energy of 30 MeV, and for the ^90,91Zr,(e, e'p)^89,90Y reactions at a number of different electron beam energies around E_e = 21 MeV. Isotopically enriched target foils of metallic ⁹⁰Zr(97.65%) and ⁹¹Zr(89.2%) were used, and the proton spectra measured at 90°. Prominent proton groups are observed in the ⁹¹Zr spectra, particularly around E_p ≈ 11 MeV, which closely resemble groups produced in the ⁹⁰Zr photoreactions. Moreover, the correlating non-ground state proton groups are being produced in transitions leaving the corresponding ⁸⁹Y, ⁹⁰Y residual nuclei in excited levels which also correlate in energy. These photoproton groups from ⁹⁰Zr have previously been identified as representing T_> strength. A qualitative explanation is proposed in terms of the core-excitation model, in which the structure in the ⁹¹Zr proton spectrum is described as representing dipole $\text{T}{}_{\mathrm{>}}\text{(T =}\text{13}\text{2}\text{)}$ strength formed by coupling the 2d$\text{5}\text{2}$ neutron to dipole T_> (T = 6) excitations of a ⁹⁰Zr core.     

Iron Mössbauer spectra of lava from Jeju island and its similarities to Moon basalts

We report the result of measurements of the⁵⁷Fe Mössbauer spectrum for powder samples of lava taken from four widely separated sites on Jeju island. The spectra consist of well defined quadrupole doublets having a 2+ charge state and indicate the presence of olivine, clinopyroxene, and ilmenite. In addition we find a six line magnetically split hyperfine pattern characteristic of impure hematite, with considerable line broadening and reduced internal field. The observed spectra have a remarkable similarity to those found for moon basalts. A recently popularized “collision ejection” model for the moon formation would be consistent with our observations. The data is a particularly simple and direct illustration of the well-known fact that the iron silicates and ilmenite found on the moon are very similar in composition and relative abundance to that found on earth.     

Heterocycles from ketenimines XI. Oxindoles

The reaction of ketenimines with heterocyclic N-oxides yields N-substituted oxindoles. Hydrolysis of these adducts or acid work-up of the original reaction mixtures leads directly to oxindoles in which the nitrogen atom is unsubstituted.     

Theoretical Study of the Electronic States of the Rb(2) Molecule

We have calculated the electronic states of Rb(2) by multireference configuration interactions using the averaged relativistic effective small-core potential and the core-polarization potential. The potential energy curves for a large number of states dissociating into from 5s+5s up to 7s+5s asymptotic limits are calculated and the spectroscopic constants are reported. The spin-orbit effects for the states dissociating into 5p+5s and 4d+5s are calculated using the effective spin-orbit potential. The results are compared with available experimental data and other theoretical works. Copyright 2001 Academic Press.     

Sodium dodecyl sulfate-capillary gel electrophoresis of polyethylene glycolylated interferon alpha

Sodium dodecyl sulfate-capillary gel electrophoresis (SDS-CGE) using a hydrophilic replaceable polymer network matrix was applied to characterize the polyethylene glycol(PEG)ylated interferon alpha (PEG-IFN). The SDS-CGE method resulted in a clearer resolution in both the PEG-IFN species and the native IFN species. The distribution profile of PEGylation determined by SDS-CGE was consistent with that obtained by SDS-polyacrylamide gel electrophoresis (PAGE) with Coomassie blue or barium iodide staining. The result was also compared using matrix-assisted laser desorption/ionization-time of flight-mass spectrometry. SDS-CGE was also useful for monitoring the PEGylation reaction to optimize the reaction conditions, such as reaction molar ratio. This study shows the potential of SDS-CGE as a new method for characterizing the PEGylated proteins with advantages of speed, minimal sample consumption and high resolution.     

An excimer-based, binuclear, on-off switchable calix[4]crown chemosensor

A new fluorescent chemosensor with two different types of cation binding sites on the lower rims of a 1,3-alternate calix[4]arene (1) is synthesized. Two pyrene moieties linked to a cation recognition unit composed of two amide groups form a strong excimer in solution. For 1, the excimer fluorescence is quenched by Pb2+, but revived by addition of K+ to the Pb2+ ligand complex. Thus, metal ion exchange produces an on-off switchable, fluorescent chemosensor. Computational results show that the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbitals (LUMO) of the two pyrene moieties interact under UV irradiation of 1 and its K+ complex, while such HOMO-LUMO interactions are absent in the Pb2+ complex.     

Conservation laws for a class of third order evolutionary differential systems

Conservation laws of third order quasi-linear scalar evolution equations are studied via exterior differential system and characteristic cohomology. We find a subspace of 2-forms in the infinite prolongation space in which every conservation law has a unique representative. Analysis of the structure of this subspace based upon the symbol of the differential equation leads to a universal integrability condition for an evolution equation to admit any higher order (weight) conservation laws. As an example, we give a complete classification of a class of evolution equations which admit conservation laws of the first three consecutive weights , , . The differential system describing the flow of a curve in the plane by the derivative of its curvature with respect to the arc length is also shown to exhibit the KdV property, i.e., an infinite sequence of conservation laws of distinct weights.

     

Thermal conductivity of geometrically frustrated, ferroelectric YMnO3: extraordinary spin-phonon interactions

The thermal conductivity of the magnetically frustrated, ferroelectric YMnO3 exhibits an isotropic suppression in the cooperative paramagnetic state, followed by a sudden increase upon magnetic ordering. This unprecedented behavior without an associated static structural distortion probably originates from the strong dynamic coupling between acoustic phonons and low-energy spin fluctuations in geometrically frustrated magnets. The replacement of magnetic Ho for Y at the ferroelectrically active site results in an even larger effect, suggestive of the strong influence of multiferroicity.