A theory of transport properties in molten salts

Expressions for diffusion constants in molten salts have been obtained in terms of the inter-ionic pair potentials and the pair distribution functions. Numerical attempts for diffusion constants in molten alkali halides are carried out and results agreed fairly with those obtained by molecular-dynamics simulation and with some experimental data. Based on the coupling of generalized Langevin equation and damped Einstein oscillator equation, ions' velocity autocorrelation functions have also been described and are numerically applied for molten potassium fluoride. The deviation from the Nernst-Einstein relation was also discussed in detail. In Appendixes A x B x C, the short-time expansion of velocity correlation functions in relation to the partial conductivities and the diffusion constants were obtained up to the term of t(4) and these were compared with a model function described by the form of cos(omegat)sech(ttau).     

The action of organic divalent cation on the stability of negative silver iodide sol

Summary The action of organic divalent cations on negative silver iodide sol has been studied. The coagulation values of ethylene-, propylene-and hexamethylene-diammonium chlorides are found considerably less than those of corresponding n-alkylammonium chlorides, which shows the effect of the number of ionized groups. The action of hexamethylene-1,6-bis-trimethylammonium chloride is considered to be due to “adsorption” of the organic ions.

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Zusammenfassung Es wurde die Wirkung von organischen zweiwertigen Kationen auf die Stabilit?t vom negativen Silberjodid-Sol untersucht. Die Flockungswerte von ?thylen-, Propylen-, und Hexamethylen-diammoniumchlorid zeigen sich kleiner als die der entsprechenden n-Alkyl-ammoniumchloride. Es wird angenommen, da? die flockende Wirkung des Hexamethylen-1,6-bis-tri-methylammoniumchlorids auf Adsorption des organischen Ions beruht.

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The author wishes to express his hearty thanks to Prof. B. Tamamushi for his interest in this study and to Dr. K. Meguro and Dr. T. Kondo for their kind supply of sample.     

Preparation of novel silica-cadmium sulfide composite nanoparticles having adjustable void space by size-selective photoetching

The size-selective photoetching technique was used to control the size of a CdS nanoparticle inside a silica shell. With monochromatic light irradiation, the diffuse reflectance spectra of silica-coated CdS nanoparticles were blue-shifted, and the size of the resulting CdS nanoparticles incorporated in the silica shells was adjustable by varying the wavelength of irradiated light. TEM observation revealed that the original CdS nanoparticle seemed to be in close contact with the amorphous silica shell to leave almost no clearance, while the monochromatic light irradiation caused the decrease in the size of CdS particles, resulting in the formation of a void space between the photoetched CdS core particle and the silica shell. The average void spaces available in the shells were calculated to be ca. 1.4 and 2.4 nm with the irradiation at 514 and 458 nm, respectively. These results indicated that the size-selective photoetching technique enables the regulation of void space formed in the core-shell structure by choosing the wavelength of irradiation light.     

Solid-state polymerization of long-chain vinyl compounds. VI. In-source polymerization of octadecyl acrylate by γ-ray irradiation

The in-source polymerization of octadecyl acrylate in the lamellar crystal (hexagonal packing) by γ-ray irradiation has been investigated, as compared with the two-step and one-step postpolymerizations. The viscosity-average molecular weight is very high even in the initial stage and is practically saturated after 3–5 hr, although the conversion increases successively with time. The molecular weight distribution of poly(octadecyl acrylate) obtained by in-source polymerization is very wide (M _w/M _n = 13.1, at 20°C). The results of in-source polymerization of the long-chain vinyl compounds can be interpreted using the cone model for polymerization probability, similar to those of one-step and two-step postpolymerizations.     

The reduced density matrix method for electronic structure calculations and the role of three-index representability conditions

The variational approach for electronic structure based on the two-body reduced density matrix is studied, incorporating two representability conditions beyond the previously used P, Q, and G conditions. The additional conditions (called T1 and T2 here) are implicit in the work of Erdahl [Int. J. Quantum Chem. 13, 697 (1978)] and extend the well-known three-index diagonal conditions also known as the Weinhold-Wilson inequalities. The resulting optimization problem is a semidefinite program, a convex optimization problem for which computational methods have greatly advanced during the past decade. Formulating the reduced density matrix computation using the standard dual formulation of semidefinite programming, as opposed to the primal one, results in substantial computational savings and makes it possible to study larger systems than was done previously. Calculations of the ground state energy and the dipole moment are reported for 47 different systems, in each case using an STO-6G basis set and comparing with Hartree-Fock, singly and doubly substituted configuration interaction, Brueckner doubles (with triples), coupled cluster singles and doubles with perturbational treatment of triples, and full configuration interaction calculations. It is found that the use of the T1 and T2 conditions gives a significant improvement over just the P, Q, and G conditions, and provides in all cases that we have studied more accurate results than the other mentioned approximations.     

Application of the TORO technique of 1H NMR to the structural analysis of cyclic peptide isomers having a slightly distorted symmetry from C2

The extended TORO technique was applied to the structural analysis of endo-D-Tyr-gramicidin S, cyclo(-Val-Orn-Leu-D-Phe-D-Tyr-Pro-Val-Orn-Leu-D-Phe-Pro-), which has a slightly distorted symmetry from C2, by the insertion of D-Tyr and equivalent alpha-proton chemical shifts in the 1H NMR spectrum. All NMR signals of the two dominant isomers of this antibiotic with trans-trans prolines were determined by using the extended TORO technique with TOCSY and ROESY spectra. This technique is generally applicable for distinguishing overlapped signals of alpha- and amide protons from the main chains of peptides.     

Potential neuroleptic agents, N-[(2-pyrrolidinyl)methyl]-2,3-dihydrobenzofuran-7-carboxamide derivatives

A series of 2,3-dihydrobenzofuran-7-carboxamides, presenting a stabilized intramolecular hydrogen bond, was synthesized and evaluated in pharmacological models for antipsychotic activity. Among them, N-[(1-butyl-2-pyrrolidinyl)methyl]-2-methyl-5-sulfamoyl-2, 3-dihydrobenzofuran-7-carboxamide (15) showed an atypical neuroleptic profile similar to that of sulpiride (1) and more lipophilic properties than 1. Compound 15 was 11 times more potent in antagonistic activity on apomorphine-induced hyperactivity in mice (ED50 = 30 mg/kg, p.o.) and stronger in potentiation of methamphetamine lethality in rats than 1, while it was as weak in inhibitory activity of apomorphine-induced stereotype in rats (ED50 greater than 500 mg/kg, p.o.) as 1. On the other hand, N-[(1-ethyl-2-pyrrolidinyl)methyl]-2-methyl-5-methylthio-2, 3-dihydrobenzofuran-7-carboxamide (30) showed a classical neuroleptic profile with a potency comparable to haloperidol in antagonistic activity on apomorphine-induced hyperactivity in mice (ED50 = 0.65 mg/kg, p.o.). The structure-activity relationships were also discussed.     

Helix-sense-selective polymerization of phenyl[bis(2-pyridyl)]methyl methacrylate and chiral recognition ability of the polymer

A novel monomer, phenyl[bis(2-pyridyl)]methyl methacrylate (PB2PyMA), was synthesized. The solvolysis rate of PB2PyMA measured in CDCl₃–CD₃ OD [1/1 (v/v)] by ¹H-NMR spectroscopy at 35°C was much smaller than those of triphenylmethyl methacrylate (TrMA) and diphenyl-2-pyridylmethyl methacrylate (D2PyMA). PB2PyMA was anionically polymerized with the complexes of organolithiums with (?)-sparteine (Sp), (S,S)-(+)-and (R,R)?(-)-2,3-dimethoxy-1,4-bis(dimethylamino)butanes[(+)-and (?) -DDB], and (S)-(+)-1-(2-pyrrolidinylmethyl) pyrrolidine (PMP) in toluene at low temperature. The polymers obtained with Sp and DDB complexes showed low optical activity. PMP complexes, particularly that with N,N′-diphenylethylenediamine monolithium amide, were effective in synthesizing a polymer of high optical rotation ([α]²⁵₃₆₅ ～ +1350°) which was comparable to those of poly(TrMA) and poly(D2PyMA) with one-handed helical structure. The optical rotation of poly(PB2PyMA) in a mixture of CHCl₃ and 2,2,2-trifluoroethanol (9/1, v/v) slowly decreased with time. Optically active poly(PB2PyMA) coated on macroporous silica gel was able to resolve racemic compounds as a chiral stationary phase for high-performance liquid chromatography. © 1993 John Wiley & Sons, Inc.     

The kinetic study of specific adsorption of phosphate species on Pt(111) in acidic solutions

The study of the adsorption/desorption mechanism of phosphate anions at Pt(111) in acidic solution of pH 4.3 and 0.8 was performed by the potential step method in order to reveal the kinetics of anion adsorption. The current-time curve due to phosphate adsorption/desorption showed various decay features, being dependent on the potential region. The rate of current decay depended on pH, being faster in a lower pH solution. Specific adsorption processes were analyzed by the Langmuir and Elovich adsorption equations and also in terms of a two-dimensional nucleation-growth mechanism in different adsorption/desorption regions. In the case of adsorption in 0.3M phosphate buffer solution of pH 4.3, random adsorption without interaction following the Langmuir adsorption, takes place at low coverage, while random adsorption with repulsive force was observed at high coverage. In the desorption process, random desorption with repulsive force takes place at high coverage, and the repulsive force disappears where random adsorption without interaction takes place at medium coverage. When the surface coverage becomes further lower, the desorption mechanism changes dramatically into a two-dimensional nucleation-growth type, suggesting that an ordered adsorbate structure is formed after a rapid discharge process of anion adsorption.     

Determination of trace element in a silicon single crystal

Neutron activation analysis was applied to the determination of trace impurity elements in a silicon ingot. Detection limits of 36 elements were calculated semi — empirically and compared with minimum concentrations detected in a silicon single crystal. The sources of the impurities were estimated from element concentrations detected in polycrystalline silicon and a quartz crucible. Segregation coefficients were determined from the concentration curves in a single crystal and discussed by comparing with reported values.