bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Symmetric Formulation of Maxwell's Equations
Authors: Múnera Héctor A. , Guzmán Octavio 
Published: October 2003

The electromagnetic field formed by the pair (E, B) obeying Maxwell's equations (MEs) is reformulated as another pair (P, N) obeying a symmetric set of four equations tautologically equivalent to MEs. The symmetric set is formed by a pair of induction and a pair of source equations, each pair with exactly the same structure. In contrast to (E, B), charge and current densities contribute equally to both P and N. The equation of continuity is not an independent condition, but it is automatically fulfilled by any four-tuple (P, N, J, ρ) solving the symmetric MEs. The symmetric equations in terms of potentials may be explicitly solved for a variety of constraint conditions, thus leading to different classes of solutions. Each class represents a family of problems defined by the constraints. One such family is the conventional class of solutions of MEs. Some unexpected results regarding the conventional solutions of MEs in terms of potentials are: (a) it is a particular case, (b) it may contain magnetic scalar potentials, and (c) there is no Coulomb gauge, thus removing the magnetic transversality constraint. It is not known whether the other classes of solutions correspond to physical problems.
Quanta Without Quantization
Authors: Wheeler James T. 
Published: October 2003

The dimensional properties of fields in classical general relativity lead to a tangent tower structure which gives rise directly to quantum mechanical and quantum field theory structures without quantization. We derive all the fundamental elements of quantum mechanics from the tangent tower structure, including fundamental commutation relations, a Hilbert space of pure and mixed states, measurable expectation values, Schrödinger time evolution, "collapse" of a state and the probability interpretation. The most central elements of string theory also follow, including an operator valued mode expansion like that in string theory as well as the Virasoro algebra with central charges.
Evaluation of Periods via Fibrations in Seiberg–Witten Theories and in Type-II String
Authors: Suzuki Hisao 
Published: October 2003

We show how the periods can be evaluated in Seiberg–Witten theories and in K3-fibered Calabi–Yau manifolds by using fibrations of the theories. In the Seiberg–Witten theories, it is shown that the dual pair of fields can be constructed from the classical fields in a simple form. As for Calabi–Yau manifolds which are fibrations of K3 surface, we obtain the solutions of the Picard–Fuchs equations from the periods of K3 surface. By utilizing the expression of periods for two-parameter models of type-II string, we derive the solutions of the Picard–Fuchs equations around the points of enhanced gauge symmetry and show a simple connection to the SU(2) Seiberg–Witten theory.
Interplay of Magnetic Field and Disorder: Magnetic Subbands and Bound States
Authors: Valente Loredana , Ramaglia Vincenzo Marigliano 
Published: October 2003

The effect of an impurity on the spectrum of a Bloch electron in a uniform magnetic field is studied. Rational values of the magnetic flux parameter, defined as the ratio between the magnetic flux through a unit cell and the flux quantum, have been considered, corresponding to a subband spectrum for the electron energy. The impurity levels are determined through an extension of the Koster–Slater method, using the magnetic Wannier functions, a generalization of the usual Wannier functions in the presence of a magnetic field.
The Anomalous Diffusion of the Self-Interacting Passive Scalar in the Turbulent Environment
Authors: Antonov N. , Hnatich M. , Horváth D. , Nalimov M. 
Published: October 2003

Two variants of the statistical model of diffusing self-interacting passive scalar θ(x, t) driven by the incompressible Navier–Stokes turbulence were studied by means of the field-theoretical renormalization group technique and ∊-expansion scheme, where ∊ denotes the parameter of the forcing spectrum. Dual ∫ ddxdt[θ(x, t)]2 and triple ∫ ddxdt[θ(x, t)]3 interaction terms of the action represent two different mechanisms of the self-interaction matching two alternative values of the critical dimension: d c =4 and d c =6. The major part of the calculations was carried out in the one loop order, nevertheless, the inclusion of the specific two loop contributions represents the important step of the analysis of some renormalization group functions. In the basic model variant the effective action is renormalizable for the supercritical dimensions d > d c . This theory exhibits the presence of the asymptotical regime, which is stable for the inertial-conductive range of wave numbers. It was also shown that stability of this regime remains preserved for a variety of the parametric paths connecting domain ∊>0, d>d c with ∊<2, d=3. In the second model variant, the effective action is constructed to be renormalizable at dimensions d≥d c and to justify the realizability of the continuation from ∊>0, d>d c to ∊< 2, d=3. This variant of the model was analyzed using "double expansion" method with the expansion parameters (d-d c )/2 and ∊. The negative correction ζ(ζ≃0.039 for d=3) to the universal Richardson exponent 4/3 is the physical consequence stemming from the calculations.
Electron Diffraction Study of α-AlMnSi Crystals Along Non-Crystallographic Zone Axes
Authors: Song G. L. , Bursill L. A. 
Published: October 2003

The structure of crystalline α-AlMnSi is examined by electron diffraction. Six distinct zone axes are examined, including both normal crystallographic and non-crystallographic zone axes, allowing the space group symmetry of α-AlMnSi to be studied. A method for indexing the non-crystallographic zone axis diffraction patterns, which involve reflections from several nearby crystallographic zone axes, is described and applied to electron diffraction patterns of the quasi-5-fold, 3-fold and 2-fold axes of the icosahedral building units of cubic α-AlMnSi. These are compared with electron diffraction patterns from the corresponding 5-fold, 3-fold and 2-fold axes of the quasicrystalline phase i-AlMnSi, from which we may make some conclusions concerning the occupancies of the icosahedral units in i-AlMnSi. Electron diffraction patterns characteristic of [Formula: see text] were obtained for thicker specimens. However, for thin specimens, as used for HRTEM imaging, the electron diffraction patterns were characteristic of [Formula: see text] space group symmetry. This unusual behaviour arises because the structural basis for the [Formula: see text] to [Formula: see text] phase transition is a weak effect, involving changes in occupancy of the icosahedral structural elements located at the corners (double-MacKay icosahedra) and body-centers (MacKay icosahedra) of the cubic unit cell. The effects of changing the occupancies of the outer shells of the MI and DMI structural units on the diffraction intensities of the weak reflections were examined. Thus, calculation of the dynamical diffraction amplitudes shows that in fact the weak reflections characteristic of [Formula: see text] only develop sufficient intensity if two conditions are satisfied: namely (1) the crystal thickness exceeds approx. 50 nm and (2) if a significant proportion of [Formula: see text] occupancies are included in the structural model. By fitting the observed thickness variation of the diffraction intensities we propose a new set of occupancies for α-AlMnSi, which is consistent with the electron, X-ray and neutron diffraction data.
Elastic Constants and Pair Potentials for Nematogenic Lattice Models
Authors: Romano S. 
Published: October 2003

Director configurations in nematic Liquid Crystals can be determined by minimizing their elastic free-energy density, on the basis of elastic constants and of specific boundary conditions; in some published cases, this has been obtained by numerical procedures where the elastic free-energy density plays the same role as the overall potential energy in a standard Monte Carlo simulation. The "potentials" used in these papers are short-ranged but, in general, not pairwise additive, unless the three elastic constants are set to a common value, thus reducing the potential to the well-known Lebwohl–Lasher lattice model.On the other hand, one can construct, possibly in different ways, a lattice model with pairwise additive interactions, approximately reproducing the elastic free-energy density, where parameters defining the pair potential are expressed as linear combinations of elastic constants; a nematogenic pair interaction of this kind, originally proposed by Gruhn and Hess (T. Gruhn and S. Hess, Z. Naturforsch.A51, 1 (1996)), has been investigated here by Monte Carlo simulation with periodic boundary conditions, i.e. aimed at the resulting bulk behavior.
An Investigation of the Electron Transfer and Repulsive Coulomb Interactions in the One-, Two-, Three-Dimensional Isotropic Hubbard Models II: Extension to a Wannier and Higher Angular Momentum Basis
Authors: Dixon J. M. , Tuszyński J. A. 
Published: October 2003

In the previous paper we have investigated the isotropic Hubbard model, with S-orbits on each site, for one-, two- and three-dimensional isotropic lattices. The method involved the determination of the one-electron energies and eigenfunctions of the transfer interaction, the latter being utilised to form determinantal eigenfunctions for the many-electron system as a whole. In this paper we have examined the consequences of using an atomic basis by introducing Wannier functions and studied physical consequences of this more exact approach. To reduce the transformed two-body interaction to manageable form we have used the rotational properties of individual atomic orbitals incorporating them via irreducible tensorial methods. We find that, although additional components due to Wannier "tails" are small they may modify the nearest neighbor transfer terms significantly and also introduce next-nearest and next-next nearest neighbor transfer interactions. We have also investigated the effect of using atomic orbitals with a higher angular momentum on each site. Both p-orbitals and d-orbitals have been studied and the broad conclusion is that the corresponding Hubbard model reduces to a series of S-like orbital models, one for each component, m, of the degenerate set on each site. The transfer interaction in each case becomes, in general, m dependent, each m component being effectively decoupled from others.
Density Fluctuation and Hydrogen-Bonded Clusters in Supercritical Water. A Molecular Dynamics Analysis Using a Polarizable Potential Model
Authors: Yoshii Noriyuki , Miura Shinichi , Okazaki Susumu 
Published: October 2003

Abstract
A series of molecular dynamics calculations of supercritical (SC) water along an isotherm at 600 K have been performed using a polarizable potential model. A relatively large system composed of 1000 molecules was adopted to reproduce long-ranged density fluctuations in SC water. The oxygen–oxygen partial static structure factor has been calculated for various densities. The strong intensity of the static structure factor in the small wave number region has successfully been reproduced for the fluid near the critical point. The density fluctuation was investigated using a concept of “cluster,” which was defined by a set of molecules connected by “bonds.” In this paper, two kinds of bonds were adopted. One is a bond defined simply using the oxygen–oxygen distance (D-bond) and the other is a hydrogen bond (H-bond). Size distribution of both the D- and H-bond clusters was described well by Fisher’s droplet model. These clusters have bulky structures compared with closely packed low temperature clusters, and can be regarded as “fractal." The larger the D- and H-bond clusters, the longer the relaxation times. Together with the size distribution of the clusters, this may give a molecular picture of critical slowing down.
Solvolysis of Styryliodonium Salt: Products, Rates, and Mechanisms
Authors: Okuyama Tadashi , Ishida Yoshimi , Ochiai Masahito 
Published: October 2003

Abstract
The solvolysis of phenyl[(E)-styryl]iodonium tetrafluoroborate in various solvents was examined at 50—70 °C by means of product and kinetic studies with the normal and labeled substrates. The reactions involved are α-elimination and substitutions with configurational retention and inversion. In methanol and ethanol, the main reaction is α-elimination, along with about 5% of substitution with the ratio of inversion/retention from 4/6 to 3/7. As the basicity of the solvent decreases, the reaction rate and the fraction of α-elimination decrease, and at the same time the ratio of inversion/retention of substitution also decreases. In 2,2,2-trifluoroethanol, only the substitution with retention was observed. Labeling experiments showed that complete isotope scrambling occurred between the olefinic hydrogens of the retained product while the deuterium remained at the original position of the inverted product. The substitution mechanism is concluded to involve parallel pathways: an SN1-type with a vinylenebenzenium ion intermediate leading to retention and a vinylic SN2-type with a direct attack by the nucleophilic solvent leading to inversion.
NMR Study of the Transformation of Perfluorinated Surfactant Solutions
Authors: Iijima Hiroshi , Koyama Seiji , Fujio Katsuhiko , Uzu Yuhei 
Published: October 2003

Abstract
The formation of micelles and aggregates in D2O solutions of the homologous series of surfactant cesium perfluoroalkanoates CnF2n+1COO−Cs+ (n = 5, 7, 9) and the other salts (Na+, NH4+, and Rb+) of perfluorooctanoic acids were studied at 30 and 50 °C by using some NMR techniques. The critical micelle concentrations (cmc) were determined by 19F chemical shift measurements. The studies of Cs salts have shown that the effect of each CF2 group on micelle formation is roughly equivalent to that of 1.5 CH2 groups. Except for the n = 5 system at 50 °C, second breaks other than cmc at higher concentration were observed for α-CF2 groups of all Cs salts, which suggest the transformation into a larger micelle, most likely ellipsoidal. In the case of ω-CF3 groups these second breaks were not observed. Support for the 19F results was furnished by 133Cs chemical shift studies. The perfluorooctanoate surfactants with the Cs+ as a counter ion showed the behavior that was different from the other salts of the same chain length. This could be explained in terms of electrostatic and hydrophobic interactions between the counter ions and the micelles. Additionally, the molecular motions in monomer and micellar states are discussed by means of the 19F relaxation times of the fluorine nuclei in the micelles.
Structural Genealogy of BEDT-TTF-Based Organic Conductors II. Inclined Molecules: θ, α, and κ Phases
Authors: Mori Takehiko , Mori Hatsumi , Tanaka Shoji 
Published: October 2003

Abstract
Overlap integrals between HOMO’s of two non-parallel BEDT-TTF (bis(ethylenedithio)tetrathiafulvalene) molecules have been calculated. As the dihedral angle between the molecular planes decreases from 180° (parallel) to 90° (perpendicular), the overlap integral increases and attains a maximum around 90°. This accounts for the “universal phase diagram” of the θ-phase; θ-salts vary from an insulator to a metal with decreasing the dihedral angle. The ratio of the lattice constants in the conducting plane, c/a, changes in proportion to the dihedral angle. Thus c/a can be used instead of the dihedral angle. A similar universal phase diagram is applicable to analogous phases like α and α″, and also to the corresponding phases of other donors. The properties of κ-phase salts are similarly scaled by c/a. As c/a increases, the intradimer overlap integral decreases owing to the increase of the intradimer spacing, and correlated insulator, superconductor, and simple-metal phases appear in succession. When c/a increases further, another insulating phase emerges due to the decrease of the interdimer overlaps. Chemical pressure in both θ- and κ-phases reduces c/a, and stabilizes the insulating state. Hydrostatic physical pressure gives the same influence in the θ-phase, but enhances the interdimer interaction in the κ-phase to result in the opposite effect. A diagram is proposed to illustrate which structures of β, β″, θ, and κ are favored by BEDT-TTF and other donors.
Ab Initio Molecular Orbital Study of Reaction of Pentafluoroethyl Radical with Hydroxyl and Hydrogen Radicals
Authors: Fukaya Haruhiko , Ono Taizo , Abe Takashi 
Published: October 2003

Abstract
Ab initio molecular orbital theory calculations have been done on the reactions of the pentafluoroethyl radical with the hydroxyl and the hydrogen radicals to estimate its fire suppression efficiency. It was found that pentafluoroethyl radical was more effective than trifluoromethyl radical: i.e. the former was easier to regenerate and more difficult to decompose than the latter. The differences between the zero-point energies calculated by the HF and the MP2 method are also described.
Theoretical Studies of Decomposition Reactions of Dioxetane, Dioxetanone, and Related Species. CT Induced Luminescence Mechanism Revisited
Authors: Takano Yu , Tsunesada Tsunaki , Isobe Hiroshi , Yoshioka Yasunori , Yamaguchi Kizashi , Saito Isao 
Published: October 2003

Abstract
The electronic structures and relative stabilities of homopolar biradicals (BR) and CT BR with significant one-electron transfer (ET) BR characters were investigated by ab initio MO calculations. The previously presented inter- and intra-molecular CT models were extended in order to elucidate possible mechanisms for decomposition reactions of dioxetane, dioxetanone, and related species. The computational results indicate that endothermic O–O cleavages, followed by charge-transfers, are operative for the chemiluminescence reactions of these peroxides with several anionic species, in contradiction to the chemically initiated electron-exchange luminescence (CIEEL) mechanism, where complete one-electron transfer (ET) is required for the formation of excited carbonyl fragments. The ionization potentials of monoanions of phenol, indole and luciferins were calculated semiempirically in order to estimate the CT excitation energies from these species to the O–O antibonding orbital. The CT excitation energies are used to distinguish between the CT induced luminescence (CTIL) mechanism and the CIEEL mechanism for chemiluminescence reactions. Orbital-interaction models are also presented to explain of the so-called odd/even selection rule for the efficiency of chemiluminescence reactions. The implications of these results are discussed in relation to recent experimental results, together with biological chemiluminescence reactions of luciferins and related species.
Response Properties of a Platinum Electrode Coated with an Oxo(phthalocyaninato)vanadium(IV) Conjugate Polymer to Various Anions in Nonaqueous Solutions
Authors: Nakamura Toshio , Ueda Takahiro , Yanagisawa Tatsushi , Watanabe Hirofumi 
Published: October 2003

Abstract
The potentiometric response behavior of an electrode consisting of a non-plasticized polyacrylamide polymer (PAA) coupled to oxo(phthalocyaninato)vanadium(IV) ([VO(pc)]) was examined for various anions in such nonaqueous solvents as acetonitrile (AN), propylene carbonate (PC), dimethylacetamide (DMA), and N-methylpyrrolidinone (NMP). The electrode shows a selective Nernstian or a near-Nernstian response to F− and CN− in AN, PC, DMA, and NMP. It shows a non-Nernstian response to I−, NO2−, and CF3SO3−, but a very poor response to Cl−, Br−, SCN−, BPh4−, PF6−, and ClO4−. Complex formation reactions of [VO(pc)]s with F− and CN− are suggested based on the UV/vis spectra, and may occur due to ligand exchange reactions of F− and CN− with AN or water molecule(s) coordinated to [VO(pc)]s. The PAA–[VO(pc)] electrode has been confirmed as being available for use in determining the solubility product constant of sodium fluoride in AN.
Transesterification by (Hydroxo)nickel(II) Complex in the Presence of External Alcohol
Authors: Ito Masami , Sakai Ken , Tsubomura Taro , Takita Yu-saku 
Published: October 2003

Abstract
The nickel(II) complexes, [(tpa)NiII(μ-OH)2NiII(tpa)](ClO4)2 (tpa = tris(2-pyridylmethyl)amine) (2), [NiII(CH3CN)(tpa)(H2O)](ClO4)2 (3) have been prepared and fully characterized. X-Ray crystallography of complex 2 and its methanol adduct, [(tpa)NiII(μ-OH)2NiII(tpa)](ClO4)2·2MeOH ((2)·2MeOH) revealed a molecular structure containing two Ni centers bridged by two OH ligands. The Ni–O distances in 2·2MeOH are longer than those in 2. The MeCN ligand in complex 3 is replaced by EtCN to give [NiII(EtCN)(tpa)(H2O)](ClO4)2 (4), which was characterized by X-ray crystallography. The kinetic study of p-NPA (p-nitrophenyl acetate, 0.1, 0.5, 1 mM) hydrolysis by complex 2 (20, 10, 6 mM) was performed in the presence of ethanol (100 mM) in MeCN solution (1 M = 1 mol dm−3). By following the 400 nm absorption derived from p-nitrophenolate ion, we obtained the second-order kinetics; first-order in [2] and first-order in [p-NPA]. Additon of ethanol resulted in enhancement of the second-order rate constant (from 1.6 × 10−3 M−1 s−1 to 1.6 × 10−2 M−1 s−1 at 25 °C) as well as formation of a transesterified product, ethyl acetate. The second-order rate constant of the reaction in the presence of added ethanol (0.016 M−1 s−1) at 25 °C is much larger than that of the reaction without ethanol (0.0016 M−1 s−1). Also observed was a transesterified product, ethyl acetate, from the reaction of 2 with p-NPA in the presence of ethanol. The pKa value of the ligated water molecule in 3 was estimated to be 10.7 by kinetic measurements in 40% MeCN aqueous solution at 25 °C, I = 0.3.
Determination of Ultratrace Beryllium in Natural Water by Electrothermal Atomic Absorption Spectrometry after Preconcentration with One-Drop Solvent
Authors: Shimizu Tokuo , Ohya Keiji , Kawaguchi Hiroshi , Shijo Yoshio 
Published: October 2003

Abstract
An effective method for the determination of beryllium at sub ng dm−3 levels in natural water is described. Beryllium is extracted with acetylacetone into chloroform. The organic phase is transferred to a Teflon® beaker containing a micro volume of dimethyl sulfoxide (DMSO, a high boiling-point solvent); chloroform is then removed by evaporation in a water bath (ca. 35 °C). Beryllium is concentrated in the residual DMSO and determined by electrothermal atomic absorption spectrometry. The sensitivity and stability of beryllium atomic absorption were enhanced in the presence of palladium as a matrix modifier. The detection limit (3σ) for beryllium was 0.050 ng dm−3, based on a 400-fold preconcentration using 40 cm3 of the sample water; the relative standard deviation was 1.8% (2.0 ng dm−3, n = 8). The concentration of dissolved beryllium in natural water was found to be 0.25—0.63 ng dm−3 by the proposed method.
Electron Transfer between N-Substituted Phenothiazines and the 1-Oxopiperidinium Ion in the Presence of β-Cyclodextrin
Authors: Zheng Xiao-Qi , Ruan Xiu-Qin , Wang Wei , Zhang Hai-Ming , Guo Qing-Xiang , Liu You-Cheng 
Published: October 2003

Abstract
The electron-transfer reactions between N-substituted phenothiazines and 4-acetoxy-2,2,6,6-tetramethyl-1-oxopiperidinium hexachloroantimonate (ATPO) in the presence of β-cyclodextrin (β-CD) in an aqueous solution have been studied. N-phenylphenothiazine (PPT) and N-phenethylphenothiazine (PEPT), included by β-CD, can transfer an electron to the β-CD·ATPO complex. However, no electron-transfer reaction between the β-CD·N-benzylphenothiazine (β-CD·BPT) complex and the β-CD·ATPO complex was observed under the same conditions. It has been suggested that the electron-transfer reactions were controlled by the conformations of the N-substituted phenothiazines in the cavity of β-CD.
Microwave-Assisted Rate-Enhanced Method for the Synthesis of 2,2-Dimethyl-2H-chromenes
Authors: Subburaj Kandasamy , Trivedi Girish K 
Published: October 2003

Abstract
Herein we describe a simple and facile method for the synthesis of chromenes by base catalyzed condensation of phenols with 3-methyl-2-butenal under microwave irradiation.