Volume 62, Issue 5-6

In this work we study two partial differential equations that constitute second- and third-order approximations of water wave equations of the Korteweg - de Vries type. In particular, we first study previous results concerning the derivation of solitary wave solutions of the second-order approximation. We then use a simple assumption and find new solitary wave solutions for both equations.

The present theory is closely related to Dirac’s equation of the electron, but not to his magnetic monopole theory, except for his relation between electric and magnetic charge. The theory is based on the fact, that the massless Dirac equation admits a second electromagnetic coupling, deduced from a pseudo-scalar gauge invariance. The equation thus obtained has the symmetry laws of a massless leptonic, magnetic monopole, able to interact weakly. We give a more precise form of the Dirac relation between electric and magnetic charges and a quantum form of the Poincar´e first integral. In the Weyl representation our equation splits into P-conjugated monopole and antimonopole equations with the correct electromagnetic coupling and opposite chiralities, predicted by P. Curie. Charge-conjugated monopoles are symmetric in space and not in time (contrary to the electric particles), an important fact for the vacuum polarization. Our monopoles are magnetically excited neutrinos, which leads to experimental consequences. These monopoles are assumed to be produced by electromagnetic pulses or arcs, leading to nuclear transmutations and, for beta radioactive elements, a shortening of the life time and the emission of monopoles instead of neutrinos in a magnetic field. A corresponding discussion is given.

We present the wave propagation through stratified double negative stacks to illustrate the scattering characteristics of their structure. The double negative stacks are modeled by using the hypothetical non-dispersive and the frequency dispersive cold plasma media. The stacks are embedded between two double positive media and the incident electric field is assumed a plane electromagnetic wave with any arbitrary polarization. By imposing the boundary conditions, the relations between the fields inside and outside the stacks can be written in a matrix form. Using this transfer matrix, the incident, reflected, and transmitted powers are derived. The variations of the powers for the stratified double negative stacks using the frequency dispersive cold plasma medium have not been investigated yet, in detail. Thus, their characteristics for the perpendicular polarization is computed and presented in numerical results with the emphasis on the plasma frequencies. It is seen from the numerical results that the stratified double negative stacks can be used as electromagnetic filters at some frequency bands.

A structure-descriptor EE, recently proposed by Estrada, is examined. If λ 1 , λ 2 , . . . ,λ n are the eigenvalues of the molecular graph, then . In the case of benzenoid hydrocarbons with n carbon atoms and m carbon-carbon bonds, EE is found to be accurately approximated by means of the formula a 1 n cosh (√2m/n)+a 2 , where a 1 ≈ 1.098 and a 2 = −0.64 are empirically determined fitting constants. Within classes of benzenoid isomers (which all have equal n and m), the Estrada index is linearly proportional to the number of bay regions.

Liquid-state NMR experiments including edited-pulse angles are widely used to distinguish protonated and deuterated carbonyl groups in complex molecules. One of them is maximum quantum correlation NMR spectroscopy (MAXY NMR), which is very suitable to separate CH n groups. The product operator theory is used for the analytical description of these experiments for weakly coupled spin systems. In this study, the MAXY NMR experiment is applied for weakly coupled IS n (I = 1/2; S = 1; n = 1, 2, 3) spin systems using the product operator theory. A theoretical discussion and experimental suggestions for sub-spectral editing of CD n groups are also presented.

A model for the ionic interactions in polyvalent metal halides was originally built for chloroaluminate clusters using an analysis of data on static and dynamic structure of their molecular monomers [for a review see M. P. Tosi, Phys. Chem. Liquids 43, 409 (2005)]. Recently, by continuing the deformation-dipole model calculations, the transferability of the halogen parameters was tested through the calculation of the structure of alkali halides and alkaline-earth halides. In this work we test the usefulness of the deformation-dipole model in the study of ionic materials by examining the transferability of the overlap parameters for the halogen ions across families of halide compounds. Following a comparative discussion of alkali and alkaline-earth halide monomers near equilibrium, results on alkaline-earth halides are given. By using the transferable ionic potential model we also calculate the equilibrium structure of the molecular clusters, as well as the vibrational frequencies of ACl 4 compounds (where A = U, Np, Pu, Am and Th).

The Gibbs energies of formation of the pseudobinary compounds Rb 3 GdCl 6 (s) and RbGd 2 Cl 7 (s) from the constituent metal halides, determined by Knudsen effusion mass spectrometry, were compared with the thermodynamic properties of the solid and liquid phases of the RbCl-GdCl 3 system, obtained by different methods. The compatibility of the results obtained in this work for pseudobinary compounds with literature data was assessed by an optimization procedure using the CALPHAD method. The liquid phase in the RbCl-GdCl 3 system was described by the associate model. The phase diagram, thermodynamic functions of mixing of the system studied, and the Gibbs energies of formation of the pseudobinary compounds: Rb 2 GdCl 5 (s), Rb 3 GdCl6(s), and RbGd 2 Cl 7 (s) resulted from this optimization procedure.

Ionic liquids represent a unique class of solvents that offer unprecedented versatility and tunability. Nature has developed a wide variety of materials based upon both proteins and polysaccharides. Many of these materials have unique properties that are a function not only of the material identity but are also largely dictated by processing conditions. Recent work has shown the potential of ionic liquids as solvents for the dissolution and processing of biopolymers. In this research we have expanded upon the limited data available to date using several biopolymers including: silk, chitin, collagen and elastin.

A series of new hydrophobic and protic alkylammonium ionic liquids with bis(trifluoromethylsulfonyl) imide or bis(perfluoroethylsulfonyl)imide as conjugated anions was synthesized in a one-pot reaction with a high yield. In essence our synthesis method involves the combination of neutralization and metathesis reactions. Some of these hydrophobic and protic ionic liquids were liquids at room temperature and therefore investigated as new extraction media for separation of Sr 2+ and Cs + from aqueous solutions. An excellent extraction efficiency was found for some of these ionic liquids using dicyclohexano-18-crown-6 and calix[4]arene-bis(tert-octylbenzo-crown-6) as extractants. The observed enhancement in the extraction efficiency can be attributed to the greater hydrophilicity of the cations of the protic ionic liquids. The application of the protic ionic liquids as new solvent systems for solvent extraction opens up a new avenue in searching for simple and efficient ionic liquids for tailored separation processes.

Previous work, mainly from this research group, is re-visited on electrochemical reduction of solid metal oxides, in the form of compacted powder, in molten CaCl 2 , aiming at further understanding of the roles of cationic and elemental calcium. The discussion focuses on six aspects: 1.) debate on two mechanisms proposed in the literature, i. e. electro-metallothermic reduction and electro-reduction (or electro-deoxidation), for the electrolytic removal of oxygen from solid metals or metal oxides in molten CaCl 2 ; 2.) novel metallic cavity working electrodes for electrochemical investigations of compacted metal oxide powders in high temperature molten salts assisted by a quartz sealed Ag/AgCl reference electrode (650 ºC- 950 ºC); 3.) influence of elemental calcium on the background current observed during electrolysis of solid metal oxides in molten CaCl 2 ; 4.) electrochemical insertion/ inclusion of cationic calcium into solid metal oxides; 5.) typical features of cyclic voltammetry and chronoamperometry (potentiostatic electrolysis) of metal oxide powders in molten CaCl 2 ; and 6.) some kinetic considerations on the electrolytic removal of oxygen.

The densities of binary mixtures of LiF with CsCl, KBr, RbBr, CsBr, KI, RbI and CsI have been investigated at 1093 - 1253 K. For the system LiF with KBr the dependence of the density on the temperature was measured up to the critical point, where the system became single-phased, and the critical behaviour was evaluated. The critical exponent of the order parameter, which was found from the density measurements, is close to 0.5.

The interfacial tension (IFT) between aluminium and cryolite melts containing different salt additions (AlF 3 , NaF,Na 2 SO 4 ) has been measured during electrolysis by the capillary depression method. The technique is based on the measurement of the capillary depression occurring when a capillary, which is moved vertically down through the molten salt layer, passes through the metal/salt interface. The depression is measured by simultaneous video recording of the immersion height of the alumina capillary. The interfacial tension is strongly dependent on the n(NaF)/n(AlF 3 ) ratio. The addition of Na 2 SO 4 decreases the IFT of the aluminium/electrolyte interface. We also found the different influence of the conditions of electrolysis on the IFT in systems with and without Na 2 SO 4 . In systems without Na 2 SO 4 the IFT decreases with increasing current density, and in systems with Na 2 SO 4 it increases.

PbO-Ga 2 O 3 -P 2 O 5 glasses containing different amounts of Cr 2 O 3 , ranging from 0 to 1.0 mol%, were prepared. The dielectric properties (viz., constant ε’, loss tanδ , ac conductivity σac over a wide range of frequencies and temperatures, dielectric breakdown strength) have been studied as a function of the concentration of chromium ions. An anomaly has been observed in the dielectric properties of these glasses, when the concentration of Cr 2 O 3 is about 0.4 mol%. This anomaly has been explained in the light of different oxidation states of chromium ions with the aid of data of differential thermal analysis and optical absorption spectra of these glasses.

A theoretical approach to the dissociation and low-energy electronic excitation of polyatomic organic molecules with donor and acceptor substructures is suggested. The donor hydrocarbon molecular substructures can serve as antennas for low-energy infrared (IR)-photon absorption, which coherently induce collective vibrational excitations (excimols). Due to dipole-dipole interactions, the accumulated energy can transit to the molecular acceptors: dipole-type trap-bonds or molecular parts with π-electron orbits. The analytical expressions for the probability functions of molecular fragmentation and electronic excitation induced by IR-multiphoton absorption are derived. The vibrational energy accumulation and redistribution in the molecules of diphenylalkanes irradiated by infrared photons are considered from the presented point of view.

To study the effect of side chain and ring substitutions on the solid state geometry of amides of the general formulae C 6 H 5 NH-CO-CX 3 and 2,4,6-X 3 C 6 H 2 NH-CO-CH 3−y X y (X = CH 3 or Cl and y = 0,1,2, 3), crystal structures of N-(phenyl)-2,2,2-trimethyl-acetamide, C 6 - H 5 NH-CO-C(CH 3 ) 3 (PTMA); N-(2,4,6-trimethylphenyl)-2,2,2-trimethyl-acetamide, 2,4,6-(CH 3 ) 3 - C 6 H 2 NH-CO-C(CH 3 ) 3 (TMPTMA) and N-(2,4,6-trimethylphenyl)-2,2,2-trichloro-acetamide, 2,4, 6-(CH 3 ) 3 C 6 H 2 NH-CO-CCl 3 (TMPTCA) have been determined. The data are analyzed along with those of N-(phenyl)-acetamide, C 6 H 5 NH-CO-CH 3 ; N-(phenyl)-2,2,2-trichloro-acetamide, C 6 - H 5 NH-CO-CCl 3 ; N-(2,4,6-trimethylphenyl)-acetamide, 2,4,6-(CH 3 ) 3 C 6 H 2 NH-CO-CH 3 ; N-(2,4,6- trimethylphenyl)-2-chloro-acetamide, 2,4,6-(CH 3 ) 3 C 6 H 2 NH-CO-CH 2 Cl; N-(2,4,6-trimethylphenyl)- 2,2-dichloro-acetamide, 2,4,6-(CH 3 ) 3 C 6 H 2 NH-CO-CHCl 2 ; N-(2,4,6-trimethylphenyl)-2-methyl- acetamide, 2,4,6-(CH 3 ) 3 C 6 H 2 NH-CO-CH 2 CH 3 ; N-(2,4,6-trimethylphenyl)-2,2-dimethyl-acetamide, 2,4,6-(CH 3 ) 3 C 6 H 2 NH-CO-CH(CH 3 ) 2 ; N-(2,4,6-trichlorophenyl)-acetamide, 2,4,6-Cl 3 C 6 H 2 - NH-CO-CH 3 ; N-(2,4,6-trichlorophenyl)-2-chloro-acetamide, 2,4,6-Cl 3 C 6 H 2 NH-CO-CH 2 Cl; N-(2, 4,6-trichlorophenyl)-2,2-dichloro-acetamide, 2,4,6-Cl 3 C 6 H 2 NH-CO-CHCl 2 and N-(2,4,6-trichlorophenyl)- 2,2,2-trichloro-acetamide, 2,4,6-Cl 3 C 6 H 2 NH-CO-CCl 3 . The crystallographic system, space group, formula units and lattice constants in Å are: PTMA: orthorhombic, Pca2 1 , Z = 4, a = 9.969(3), b = 10.642(3), c = 10.172(3); TMPTMA: tetragonal, P4 1 2 1 2, Z = 8, a = 12.708(3), b = 12.708(3), c = 17.354(4); TMPTCA: monoclinic, P2 1 /n, Z = 8, a = 12.255(4), b = 17.904(6), c = 12.619(4), β = 95.23(2)◦. PTMA and TMPTMA have 1 molecule each in their asymmetric units, but TMPTMA shows disorder. TMPTCA has 2 molecules in its asymmetric unit. The comparison of the bond parameters reveals that there are significant changes in the structural parameters with ring and side chain substitutions.

The defect structure and the anisotropic g factors of a tetragonal Ni 3+ center in PbTiO 3 are theoretically investigated from improved perturbation formulas of the g factors for a 3d 7 ion with low spin S = 1/2 in tetragonally elongated octahedra, established in this work. Based on the studies, the distance between the impurity Ni 3+ and the center of the oxygen octahedron is found to be about 0.14 Å, which is smaller than that ( ≈ 0 . 3 Å) for the host Ti 4+ site due to the inward shift ( ≈ 0 . 16 Å ) towards the center of the oxygen octahedron. The theoretical g factors based on the above defect structure agree well with the observed values.

The electron paramagnetic resonance parameters g ‖ and g ⊥ of Dy 3+ , and the hyperfine structure parameters A ‖ and A ⊥ of 161 Dy 3+ and 163 Dy 3+ in a La 2 Mg 3 (NO 3 ) 12 · 24H 2 O crystal are calculated by the perturbation formulas of the EPR parameters for a 4f 9 ion in trigonal symmetry. In these formulas, the J-mixing among the 6 HJ (J = 15/2, 13/2 and 11/2) states via crystal-field interactions, the mixtures of the states with the same J-value via spin-orbit coupling interaction and the interactions between the lowest Kramers doublet Γ γ and the same irreducible representations in the other 20 Kramers doublets ΓX via the crystal-field and orbital angular momentum (or hyperfine structure) are all considered. The crystal-field parameters for the studied Dy 3+ center are obtained with the superposition model. The calculated results are in good agreement with the observed values.