A study on interstitial heat transfer in consolidated and unconsolidated porous media

The Nusselt number expressions are presented for the interstitial heat transfer coefficients for both consolidated and unconsolidated porous media. A boundary layer consideration is made for unconsolidated porous media to derive a general Nusselt number correlation, which shows its square root dependence of the Reynolds number, and matches fairly well with existing experimental data and correlations. As for low density consolidated porous media, rigorous mathematical arguments based on the volume averaging theory are provided, so as to explain the reason why the Reynolds number exponent of the Nusselt number expression for the case of low density consolidated porous media is much greater than that of unconsolidated porous media. The resulting expressions are compared against available experimental data and empirical correlations, and found to be in good accord with them.     

Formability and properties of self-standing clay film by montmorillonite with different interlayer cations

Influences of exchangeable interlayer cations were investigated on self-standing film formability, film morphology, and properties of the clay films such as flexibility and gas barrier property. Ion-exchanged montmorillonite samples were prepared by a cation exchange from naturally bearing cation, mostly Na⁺, to Li⁺, Mg²⁺, Ca²⁺, Al³⁺, and Fe^{2+, 3+}. Self-standing films were prepared from aqueous colloidal dispersions of these montmorillonite samples with no additives. The montmorillonite samples with monovalent or divalent cation formed flat self-standing films while the Al-montmorillonite sample produced a distorted film. The Fe-montmorillonite sample formed many separated reddish-brown rod-shaped pieces. Clay film microstructures were different with interlayer cations. The films with monovalent interlayer cations were constructed by the stacking of units with delicately waved thin clay sheets in the whole film, but other films show different morphologies between the upper side and lower side; the upper side is laminated with thin sheets; the lower side is laminated with large thick sheets.The self-standing films’ flexibility and gas barrier property differed according to the interlayer cations. These properties were good in cases of samples with monovalent cations. The innumerable short wave and sheet thinness are considered to foster good flexibility and gas barrier properties. The differences in film formability and properties of the films are attributable to different swellability among samples with different interlayer cations. The montmorillonite samples with monovalent cations swell sufficiently by water, but those with polyvalent cations swell poorly. In the latter case, clay crystals aggregate in water, then the aggregate grows into large particles, creating a film with large particles.     

Solvent and pressure effects on quenching by oxygen of 9,10-dimethylanthracene fluorescence in liquid n-alkanes: a study on solvent cage effects

The fluorescence quenching by oxygen of 9,10-dimethylanthracene (DMEA) in liquid ethane and propane at pressures up to 60 MPa and 25 degrees C was investigated. The apparent activation volumes for the quenching rate constant, k(q),DeltaV++(q) , were 5.0 +/- 3.4 and 7.4 +/- 1.0 cm(3)/mol, whereas those for the solvent viscosity, eta,DeltaV++(eta) , were 190 +/- 22 and 42 +/- 1 cm(3)/mol in ethane and propane at 6.0 MPa, respectively. These results were discussed together with those in n-alkanes (C(4)-C(7)) and methylcyclohexane (MCH) that were previously reported, and it was found that DeltaV++(q) increases monotonically but DeltaV++(eta) decreases rapidly with increasing the number of carbon atoms in n-alkanes. The plot of ln k(q) against ln eta showed a leveling-off with decreasing eta. These observations were analyzed satisfactorily by the pressure dependence of the solvent viscosity on k(q) coupled with that of the radial distribution function, g(sigma), at contact with a hard sphere assumption. The apparent bimolecular rate constant, k(bim,0), for the quenching in the solvent cage was evaluated by extrapolating to g(sigma)eta = 0 in the plot of g(sigma)/k(q) against g(sigma)eta, and it was found that k(bim,0) decreased with increasing the radius of the solvent molecule. From the solvent size dependence of k(bim,0), the solvent cage effect was discussed phenomenologically.     

Comprehensive two-dimensional capillary supercritical fluid chromatography in stop-flow mode with synchronized pressure programming

A comprehensive two-dimensional capillary supercritical fluid chromatography method was developed. The interface consisted of a ten-port valve, a capillary trap and two fused silica restrictors. The primary column was operated in stop-flow mode: the flow in the primary column was stopped during the separation of the second dimension. The pressure of the system was controlled with a single pump. The pressure program was synchronized with the sampling: the pressure was only ramped up during the sampling time, when the primary column effluent was transferred from the first dimension to the trap, and was maintained constant during the second-dimension separation. All of the operations were automated using in-house software. The separation characteristics of the present system can be readily regulated by changing the size of the restrictors and/or the programmed pressure rate. The use of synchronized pressure programming allowed the sampling duration and/or the second-dimension separation time (and therefore, the total analysis time) to be changed without affecting the separation pattern. Widely different selectivities were attained depending on the combination of the three columns with different polarities (such as the nonpolar DB-1, the medium-polarity DB-17 and the polar DB-WAX columns) used. The present system afforded improved separation and identification capabilities for analytes in complex mixtures.     

New members of a family of layered bismuth compounds

Two new compounds, Bi₃Ti₂O₈F and PbBi₃Ti₃O₁₁F, were prepared and identified by X-ray diffraction analysis. These compounds are members of the family called layered bismuth compounds. Thermal properties of the new compounds were also studied. Besides the preparation and identification of these new compounds, a new method for preparing already known members, Bi₂NbO₅F and Bi₂TiO₄F₂, was reported. Moreover, the possibility of the existence of other new members belonging to the family was discussed.     

Is multiple production in proton-proton collisions similar to that ine + e − annihilation?

A model is constructed to simulate recent experimental finding that distributions of hadrons produced in proton-proton collisions are similar to those ine ⁺ e ^? annihilation if the leading proton effects are subtracted properly in the former process. It is found that the predicted multiplicity distribution in proton-proton collisions is too narrow compared to experimental data. As an alternative, we propose a simple quark model that produces correctly the observed multiplicity distribution including the approximate KNO scaling in proton-proton collisions.     

Steady laminar flow of a power-law fluid in a curved pipe of circular cross-section with varying curvature

The steady laminar flow of power-law fluid through pipes of circular cross-section, whose center-line curvature varies locally, is analyzed theoretically. The flows, in three kinds of pipes whose center-lines are specified by

as examples of once, twice, and periodically-curved pipes, respectively, are discussed in comparison with Newtonian flow. The analysis is valid for any other two-dimensionally curved pipes, when the center-line curvature is small.     

Alkylation of toluene with methanol over a zeolite disc synthesized through solid state reactions

Outstandingpara-xylene selectivity in the alkylation of toluene with methanol was observed for a new, disc-shaped ZSM-5 zeolite catalyst synthesized by solid state reactions.     

Reaction between ethanol and silicon–hydrogen of poly(p-vinylphenyldimethylsilane)

A kinetic approach to the polymer reaction, with KOH as catalyst, between ethanol and poly(p-vinylphenyldimethylsilane) containing silicon–hydrogen as a functional group on the side chain was carried out. The rate equation was obtained by measuring the initial rate of the model reaction as v = k[KOH] [SiH] [EtOH] in benzene and v = k[KOH] [SiH] in methyl ethyl ketone. It was observed that the rate of reaction was affected by the polarity of the solvents. In the polymer reaction the rate constant decreased markedly with increasing ethanol concentration. A change of viscosity of the polymer in various solvents was observed to have a good correlation with the decrease in reaction rate in corresponding solvents. In mixed solvents, consisting of both good and poor solvents for the polymers, the reaction rate depended upon two factors, the entanglement of the polymer chain and the polarity of the solvents. The equivalent globular model of the polymer chain is suggested for study of the polymer reaction. A schematic local-distribution curve of the reaction species is proposed.     

Regioselective hydroxylation of the xylyl linker in a diiron(III) complex having a carboxylate-rich ligand with H2O2

Reaction of a diiron(III) complex having a xylta4- ligand (N,N,N',N'-m-xylylenediamine tetraacetate) with H2O2 resulted in regioselective hydroxylation of the m-xylyl linker. The reaction mimics the self-hydroxylation of a phenylalanine side chain found for ribonucleotide reductase (R2-W48F/D84E).