New theorems for bianisotropic media

The general volume equivalence theorem for bianisotropic scatterers is presented, where the equivalent electric and magnetic currents are determined by a pair of coupled vector integral equations. Moreover, using the general volume equivalence theorem and conventional image principle, image theory is developed for a bianisotropic body over an infinite perfect electric or magnetic conducting ground plane.     

High-frequency oscillations,generated in the resistive state of a superconducting film

Summary The effect of non-Josephson generation (high-frequency oscillations of voltage) in the resistive state of the superconducting film is studied theoretically in the presence of a constant magnetic field. The density of the generation current in the magnetic field is calculated. The consideration is based on the earlier developed model, in which the above effect is due to the bremsstrahlung radiation from the particles with the energy ε>Δ which are injected from the quasi-normal layer of the phase slip centre to the superconducting bank. The quasi-particles pick up the energy in the process of the multiple Andreev scattering at theN-S boundaries, and the bremsstrahlung radiation is only possible if ε-Δ is of the order of the perturbation energy of the off-diagonal potential at theN-S boundary (~ΔΓ ^3/2, where γ is the depairing factor of the super-conductor).     

Thermally stimulated depolarization currents of films obtained from supernatant layer of mixed solutions of stereoregular polymethyl methacrylates

Summary Thermally stimulated depolarization currents were investigated for films obtained from supernatant layer of mixed solutions ofi- ands-PMMA ini/s weight ratio of 1/1 and 1/2. The results showed that the degree of stereocomplex formation is not uniform: the mixed solutions contain the insoluble and the soluble stereocomplex aggregates and in some case the residual (free)i-PMMA. The stereocomplex is formed ini/s weight ratio of 1/2.     

Transient Currents of Carbon Monoxide and Methanol Adsorption on Platinum Electrodes and Determination of Composition of Chemisorption Layers

Transients of currents during the adsorption of CO on polycrystalline (pc) Pt in solutions of H₂SO₄ and H₂SO₄ + HCl are measured at a constant potential. The obtained values are compared with relevant reference data for Pt electrodes. Possible reasons for the established differences are discussed. Transient currents for the methanol adsorption on pcPt and Pt/Pt are compared. A method for correct determination of the composition of a chemisorption layer, which forms during dissociative adsorption of simple organic compounds of the type of RH _m , is considered. Experimental data on the methanol adsorption suggest that adsorption products on pcPt are chiefly species of CO. On Pt/Pt, at low potentials, in addition to CO one should assume the adsorption of species of HCO in perceptible amounts.     

Theory for a general system of increments for the properties of polycyclic hydrocarbons

A general non-empirical system of increments for the calculation of molecular properties of polycyclic, conjugated hydrocarbons is proposed. It is based on identifying the conjugation circuits in all Kekulé structures and assuming an increment from each circuit comparable to the magnitude of the property in the associated annulene. These increments are calculated by a simple free-electron theory with a Kuhn-type harmonic potential. No adjustable parameters are used to fit the property being calculated. The relation between this method and a very simplistic VB formalism is considered. The reason why the non-empirical parametrization of such crudely approximated formalism may lead to rather improved results is discussed in some detail. This novel system of increments is tested for two properties, resonance energy and magnetic ring-currents. The results obtained by this method correlate well with those of standard techniques. This system of increments for estimating local properties of molecules gave particularly gratifying results when used to predict ring-current intensities. It is hoped that this method, being equally applicable to other properties, will prove to be a valuable instrument for the rapid estimation of a wide range of properties of polycyclic, conjugated hydrocarbons. A preliminary account of this work was presented at the International Symposium on Aromaticity held at Dubrovnik, Croatia, Yugoslavia, September 3–5, 1979     

DC dielectric study of polyethylene/CaCO3 composites

The dielectric properties of composite samples prepared by polymerizing ethylene on the surface of filler are compared to those of mechanical mixtures consisting of CaCO₃ and ultra high molecular weight polyethylene. After presenting the normalized master curves of AC dispersion and loss measured at different relative humidities, the field strength dependence of the 50 Hz AC and DC responses were studied. With one exception, the effect is small. Thermally stimulated polarization (TSP) and depolarization (TSD) curves are presented; the peak appearing on the TSP curves of the samples stored under ambient conditions is interpreted as a result of water desorption. The high temperature DC conductivity and the depolarization current density are higher in the composites and mechanical mixtures than in the matrix. The dielectric properties of the wet filler particles were calculated from the measured composite and matrix data using various mixture formulae. The results can be understood and interpreted if the dielectric properties of adsorbed water are described by the cluster theory of dielectric relaxation.     

Perimeter Effects on Ring Currents in Polycyclic Aromatic Hydrocarbons: Circumcoronene and Two Hexabenzocoronenes

Current‐density maps are calculated at an ab initio level for the three symmetrical polycyclic aromatic hydrocarbons, circumcoronene [ 1 (D_6h)], hexabenzo[bc,ef,hi,kl,no,qr]coronene [ 2 a (D_6h) and 2 b (D_3d)], and hexabenzo[a,d,g,j,m,p]coronene [ 3 a (D_6h), 3 b (D₆) and 3 c (D_3d)], all of which can be formally derived by annelation of benzene rings to a coronene core. Whilst 1 is planar, 2 has a non‐planar minimum that is effectively isoenergetic with its planar form, and 3 has a well defined non‐planar structure. The shape of the molecular boundary rather than the planarity of the molecule plays the critical rôle in the character of the predicted currents. Formal deletion of outer hexagons from circumcoronene ( 1 ) in two different ways produces either hexabenzocoronene 2 with a prediction of disjoint local benzenoid diatropic currents linked by a global perimeter, or 3 with a giant diatropic perimeter current enclosing a weak paramagnetic circulation on the central hexagon. The current density map of 1 is effectively a superposition of those of 2 and 3 . Its strong diatropic perimeter current subsumes the six weaker diatropic benzenoid circulations evident in 2 , and bifurcates in the six outer benzenoid rings that form the corners of the giant hexagon; its benzene “hub” sustains a diatropic current, as would be expected from the partial cancellation of the strong diatropic hub current of 2 by the weaker paratropic hub current of 3 . The relationship between the three molecules is rationalised by considering orbital contributions to their current density maps.     

The diverse effect of antiplasticizer in the molecular dynamics of an organic dye-doped polymer observed at different motional lengthscales

Complementary thermal analysis techniques were used to study blending-induced perturbations in polymer dynamics pertaining to different motional lengthscales. The antiplasticizing role of common neutral and apolar fluorescent perylimides on the cooperative relaxation dynamics of poly(methyl methacrylate) (PMMA) chain segments is evidenced by a clear rise of both the glass transition (T_g) and liquid-liquid transition (T_LL) temperatures. Simultaneously, the dielectric strength, Δε_β, of the signal ascribed to restricted rotational movements of lateral groups, shows a substantial reduction. Most aspects of the observed behavior bear analogies with recent experimental observations in nanoconfined PMMAs (e.g., PMMA with homogeneously dispersed SiO₂ nanospheres, in-situ polymerized in silica nanopores or in the form of supported ultrathin films), suggesting that a common mechanism is operational. In our mixtures, confinement effects, such as a modification in the macroconformation of the polymer, and changes in the orientation and packing of the polymer random coil, provide a plausible explanation of the observed changes regardless of the motional lengthscale concerned. Consonant with this scenario are reports of advanced optical properties for perylimide + PMMA blends, ascribed to the high rigidity of the matrix together with weak intercomponent interactions.     

DERIVATION OF THE LEHNERT FIELD EQUATIONS FROM GAUGE THEORY IN VACUUM: SPACE CHARGE AND CURRENT

It is shown that the Lehnert field equations in vacuum, with concomitant space charge and current, can be derived straightforwardly from standard gauge theory applied in vacuum, using the concept of covariant derivative and Feynman's universal influence. The Lehnert and Proca field equations are shown to be inter-related through the well-known de Broglie theorem, in which the photon mass can be interpreted as finite. These ideas go some way towards addressing the inconsistency inherent in Maxwell's famous displacement current, which has no concomitant vacuum space charge.     

Numerical modelling of residual flow and salinity in the Río de la Plata

The Río de la Plata discharges into the Atlantic Ocean. The particular characteristics of the study area, the variable width and shallowness of the river, the high fluvial discharges and the dynamic processes involving interactions between river discharges, tidal currents and wind, generate complex velocity and salinity fields. We applied the hydrodynamic model RMA-10 to examine the effects of various forcing (tides, flow discharge and winds) on residual currents and salinity fields in the Río de la Plata, focusing on the outer zone of the river. The RMA-10 code, developed by Ian King, is a multiparameter finite element model representing estuarine flow in three dimensions. In this study the model has been applied in a depth-averaged-baroclinic mode and a series of observed data is used for model calibration and verification. The model result shows that it is able to simulate velocity and the salinity fields with a reasonable accuracy. The analysis of residual currents in the river, when forced by freshwater discharge and astronomical tide, shows that the flow discharge takes place mainly over the shallower areas of the river and that the saline water is advected up-river through the deeper channels. The numerical simulations show that the winds from the South-West and North-East quadrants have a great influence over the salinity and velocity fields.