bluuebunny/crossref_metadata_2025 huggingface dataset:
Demographic structure of three species ofSarcocapnos(Fumariaceae) as a basis for their conservation
Authors: Salinas M Jacoba , Suárez Víctor , Blanca Gabriel
Published: July 2002

The genus Sarcocapnos DC., endemic to the western Mediterranean basin, contains seven species, all of which are rare. Monthly monitoring of the number and flowering status of individuals as well as the appearance of new seedlings in five populations of three species, Sarcocapnos baetica (Boiss. & Reuter) Nyman, Sarcocapnos enneaphylla (L.) DC., and Sarcocapnos pulcherrima Morales & Romero-García, was conducted between July 1997 and June 1998. This monitoring was repeated in May 1999 and 2000. Given the difficulty in establishing the age of individuals, those that did not produce flowers in the study period were considered juveniles, and reproductive individuals that wilted for no apparent external cause were deemed senescent. Sarcocapnos enneaphylla has a short life-span, early sexual maturity, and high seedling production. This combination appears to be highly effective, because the species is widely distributed geographically with many populations. In contrast, S. pulcherrima and S. baetica have longer life-spans, delayed sexual maturity, and lower production of seedlings. The low recruitment rate in these two species is offset by a long life expectancy among reproductive individuals, although this strategy apparently limits their capacity for geographical expansion. The equilibrium growth rate (λ) varied markedly in S. enneaphylla populations (SE-1: λ = 0.570 for 19971998 to 19981999 and λ = 1.226 for 19981999 to 19992000; SE-2: λ = 0.832 for 19971998 to 19981999 and λ = 1.135 for 19981999 to 19992000) while in S. pulcherrima populations, λ was very close to 1 (SP-1: λ = 0.991 for 19971998 to 19981999 and λ = 0.969 for 19981999 to 19992000; SP-2: λ = 1.000 for 19971998 to 19981999 and λ = 1.101 for 19981999 to 19992000). In the S. baetica population, values varied between λ = 0.971 for 19971998 to 19981999 and λ = 1.345 for 19981999 to 19992000. In the three species, an elasticity analysis of matrix projection models revealed that the elements with the greatest effect on population growth were those of reproductive plants remaining within the same reproductive class. In addition, in S. enneaphylla, seedlings had important weight for population growth. The fact that the reproductive stages are the most critical to population growth should be taken into account where protective or conservation action is required.Key words: conservation, demography, endemism, Fumariaceae, Sarcocapnos, western Mediterranean basin.
Iron complexes of the dibenzophospholyl ligand: a synthetic and crystallographic study
Authors: Decken Andreas , Neil Melanie A , Dyker C Adam , Bottomley Frank
Published: July 2002

Iron complexes bearing the dibenzophospholyl (DBP) ligand have been prepared. Reaction of DBP-Li with CpFe(CO)2Br gave [(µ2-DBP)Fe2Cp2(CO)4]Br and reaction of DBP-Li with CpFe(CO)2I gave [(µ2-DBP)Fe2Cp2(CO)4]I. Reaction of bis(1,1'-dibenzophospholyl) and [CpFe(CO)2]2 yielded a mixture of cis- and trans-(µ2-DBP)2Fe2Cp2(CO)2. The mixture was also obtained on heating of [(µ2-DBP)Fe2Cp2(CO)4]X (X = Br, I). The ligands are sigma-bonded through the phosphorus atom in all complexes. The compounds were characterized by 1H, 13C, and 31P NMR and IR spectroscopies, mass spectrometry, micro analysis, and X-ray diffraction.Key words: dibenzophospholyl, iron, heterocycle.
2001 Lemieux Award Lecture Organic chemistry and hemoglobin: Benefits from controlled alteration
Authors: Kluger Ronald
Published: July 2002

Hemoglobin carries oxygen in circulation within red cells but does not function outside the cells because it fails not only to release oxygen but also dissociates into dimers that make up the tetrameric protein. Bifunctional anionic acylating agents that contain a structurally rigid bridge introduce cross-links that stabilize hemoglobin and alter its oxygen affinity so that it could be used to carry oxygen outside cells. Nitric oxide binds to hemoglobin and in circulation this causes undesirable increases in blood pressure. It had been reported that higher weight collections of hemoglobin do not cause vasoconstriction. Reagents with two pairs of reaction sites joined by a rigid link connect and cross-link two hemoglobins. The resulting bis-tetramers lack the cooperativity of the native protein and bind oxygen too tightly to be useful; occupation by oxygen blocks the sites from nitric oxide. Nitric oxide may be delivered from thionitrosyl groups, which occur in hemoglobin in the red cell. Cross-linked hemoglobin can be specifically nitrosylated. These species can then serve as circulating sources of nitric oxide resulting from an internal electron transfer.Key words: proteins, hemoglobin, cross-link, red cells, cooperativity, connecting.
Comparative study of the thermodynamic behaviour of the binary mixtures dimethyl carbonate + (benzene, n-heptane, cyclohexane, or toluene)
Authors: Pardo José M , González-Salgado Diego , Tovar Clara A , Cerdeiriña Claudio A , Carballo Enrique , Romaní Luís
Published: July 2002

Isobaric molar heat capacities at 288.15, 298.15, and 308.15 K and densities and speeds of sound at 288.15, 293.15, 298.15, and 308.15 K were determined for the dimethyl carbonate + benzene system over the whole composition range and at atmospheric pressure. In addition, speeds of sound at the same temperatures for the dimethyl carbonate + n-heptane system are reported. These experimental data were used to obtain molar volumes, isobaric thermal expansivities, isentropic and isothermal compressibilities, and isochoric molar heat capacities. Excess quantities of the above-mentioned properties were calculated using the Benson and Kiyohara criterion. The thermodynamic behaviour of the dimethyl carbonate + (n-heptane, cyclohexane, benzene, or toluene) systems is comparatively analyzed.Key words: binary mixtures, excess properties, dimethyl carbonate, benzene, hydrocarbon.
SYNTHESIZING STATE-BASED OBJECT SYSTEMS FROM LSC SPECIFICATIONS
Authors: HAREL DAVID , KUGLER HILLEL
Published: July 2002

Live sequence charts (LSCs) have been defined recently as an extension of message sequence charts (MSCs; or their UML variant, sequence charts (MSCs; or their UML variant, sequence diagrams) for rich inter-object specification. One of the main additions is the notion of universal charts and hot, mandatory behavior, which, among other things, enables one to specify forbidden scenarios. LSCs are thus essentially as expressive as statecharts. This paper deals with synthesis, which is the problem of deciding, given an LSC specification, if there exists a satisfying object system and, if so, to synthesize one automatically. The synthesis problem is crucial in the development of complex systems, since sequence diagrams serve as the manifestation of use cases — whether used formally or informally — and if synthesizable they could lead directly to implementation. Synthesis is considerably harder for LSCs than for MSCs, and we tackle it by defining consistency, showing that an entire LSC specification is consistent iff it is satisfiable by a state-based object system, and them synthesizing a satisfying system as a collection of finite state machines or statecharts.
PITCHING TENTS IN SPACE-TIME: MESH GENERATION FOR DISCONTINUOUS GALERKIN METHOD
Authors: ÜNGÖR ALPER , SHEFFER ALLA
Published: July 2002

Space-time discontinuous Galerkin (DG) methods provide a solution for a wide variety of numerical problems such as inviscid Burgers equation and elastodynamic analysis. Recent research shows that it is possible to solve a DG system using an element-by-element procedure if the space-time mesh satisfies a cone constraint. This constraint requires that the dihedral angle of each interior mesh face with respect to the space domain is less than or equal to a specified angle function α(). Whenever there is a face that violates the cone constraint, the elements at the face must be coupled in the solution. In this paper we consider the problem of generating a simplicial space-time mesh where the size of each group of elements that need to be coupled is bounded by a constant number k. We present an algorithm for generating such meshes which is valid for any nD×TIME domain (n is a natural number). The k in the algorithm is based on a node degree in an n-dimensional space domain mesh.
CONFORMAL THEORIES, CURVED PHASE SPACES, RELATIVISTIC WAVELETS AND THE GEOMETRY OF COMPLEX DOMAINS
Authors: COQUEREAUX R. , JADCZYK A.
Published: July 2002

We investigate some aspects of complex geometry in relation with possible applications to quantization, relativistic phase spaces, conformal field theories, general relativity and the music of two and three-dimensional spheres.
ALGEBRAIC FIELD THEORY: RECOLLECTIONS AND THOUGHTS ABOUT THE FUTURE
Authors: KASTLER DANIEL
Published: July 2002

Anecdotal description of Rudolf Haag’s discovery of algebraic field theory. Remarks on field theoretic invariants versus cyclic cohomology, and articulation of algebraic field theory with theories based on non-commutative space-time.
Construction of Kink Sectors for Two-Dimensional Quantum Field Theory Models – An Algebraic Approach
Authors: Schlingemann Dirk
Published: July 2002

Several two-dimensional quantum field theory models have more than one vacuum state. Familiar examples are the Sine-Gordon and the [Formula: see text]-model. It is known that in these models there are also states, called kink states, which interpolate different vacua. A general construction scheme for kink states in the framework of algebraic quantum field theory is developed in a previous paper. However, for the application of this method, the crucial condition is the split property for wedge algebras in the vacuum representations of the considered models. It is believed that the vacuum representations of P(ϕ)2-models fulfill this condition, but a rigorous proof is only known for the massive free scalar field. Therefore, we investigate in a construction of kink states which can directly be applied to a large class of quantum field theory models, by making use of the properties of the dynamics of a P(ϕ)2 and Yukawa2 models.
Stability and Instability of the Wave Equation Solutions in a Pulsating Domain
Authors: Dittrich J. , Duclos P. , Gonzalez N.
Published: July 2002

The behavior of energy is studied for the real scalar field satisfying d'Alembert equation in a finite space interval 0<x<a(t); the endpoint a(t) is assumed to move slower than the light and periodically in most parts of the paper. The boundary conditions are of Dirichlet and Neumann type. We give sufficient conditions for the unlimited growth, the boundedness and the periodicity of the energy E. The case of unbounded energy without infinite limit (0< lim inf t→+∞E(t) < lim sup t→+∞E(t)=+∞) is also possible. For the Neumann boundary condition, E may decay to zero as the time tends to infinity. If a is periodic, the solution is determined by a homeomorphism [Formula: see text] of the circle related to a. The behavior of E depends essentially on the number theoretical characteristics of the rotation number of [Formula: see text].
NEW APPROACH TO THREE-BODY COULOMB PROBLEM WITH NONZERO TOTAL ANGULAR MOMENTUM
Authors: MACHTOUB GHADA H.
Published: July 2002

Our approach aims at a general formalism for the quantum description of the three-body Coulomb systems. We seek the exact solutions of 6D Schrödinger equation. For this, we propose a new algorithm for the case of nonzero total angular momentum, taking into account the overall rotation of the system, which is affected indirectly by the Coriolis coupling. We construct a special set of hyperspherical harmonics, which provide much more flexibility in choosing the best basis for the needs of this particular physical problem. The robustness, efficiency, and accuracy of the adopted algorithm are studied in detail. We apply this method to the computation of the nonrelativistic energy levels of the exotic helium [Formula: see text].
A DESIGN THEORY OF MATERIAL SYSTEMS
Authors: OHTAWARA K. , SHIMOGAWA S. , SHINJO K.
Published: July 2002

The problem of obtaining the material systems with more enhanced material constants characterizing physical property is considered within the framework of Suh's theory of design. The design problem is to find the mapping between the functional requirements (FR) and the design parameters (DP). The material parameters (the design parameters) for the material design are unable to move freely. Thus, our strategy is to substantially decrease the number of design parameters and to learn which directions to move the design parameters in order to efficiently enhance the material constants. To accomplish, we study the mathematical properties of the relationship, called design function, between the FRs and the DPs to find the decomposition property. The decomposition has several effective properties. We apply our method to a special case where the third-order nonlinear optical susceptibility is enhanced. We also discuss some methods for moving the material parameters as well as the scope of problems where the concept of decomposition seems to be effective.
PROBLEMS WITH DATA PARALLELISM
Authors: PHILLIPS C. , PERROTT R.
Published: July 2002

The gradual evolution of language features and approaches used for the programming of distributed memory machines underwent substantial advances in the 1990s. One of the most promising and widely praised approaches was based on data parallelism and resulted in High Performance Fortran. This paper reports on an experiment using that approach based on a commercial distributed memory machine, available compilers and simple test programs. The results are disappointing and not encouraging. The variety of components involved and the lack of detailed knowledge available for the compilers compound the difficulties of obtaining results and doing comparisons. The results show great variation and question the premise that communication is the decisive factor in performance determination. The results are also a contribution towards the difficult tasks of predicating performance on a distributed memory computer.
A NOVEL APPROACH TO NONCOMMUTATIVITY IN PLANAR QUANTUM MECHANICS
Authors: BANERJEE RABIN
Published: July 2002

Noncommutative algebra in planar quantum mechanics is shown to follow from 't Hooft's recent analysis on dissipation and quantization. The noncommutativity in the coordinates or in the momenta of a charged particle in a magnetic field with an oscillator potential is shown as dual description of the same phenomenon. Finally, noncommutativity in a fluid dynamical model, analogous to the lowest Landau level problem, is discussed.
ON THE RELAXATION OF SUPERSTRING AXIONS
Authors: POLLOCK M. D.
Published: July 2002

The theoretical existence of oscillating boson stars consisting of a real scalar field, stable to radial perturbations, has been proven by Seidel and Suen. For the QCD axion of the heterotic superstring theory, this implies a mini-star of mass [Formula: see text], where λ≡ fa′/fa is the ratio of the decay constants of the second and model-independent axions, which, for a suitable value in the range 1≲λ≲10, can explain the astronomical microlensing observations towards the Galactic centre and the Large and Small Magellanic Clouds. Here, we apply the non-linear relaxation theory developed by Tkachev to show that the condition τ f <τ r <τ0 for the formation of such an object, where τ f , τ r and τ0 are the free-fall and relaxation times and the age of the Universe, respectively, leads to the condition [Formula: see text], where [Formula: see text] is the strong-interaction coupling parameter and C is a dimensionless constant defined below. From this, we argue, considering the approximations involved, that the star does condense.
LAGRANGIAN Sp(3) BRST SYMMETRY FOR IRREDUCIBLE GAUGE THEORIES
Authors: BIZDADEA C. , SALIU S. O.
Published: July 2002

The Lagrangian Sp(3) BRST symmetry for irreducible gauge theories is constructed in the framework of homological perturbation theory. The canonical generator of this extended symmetry is shown to exist. A gauge-fixing procedure specific to the standard antibracket–antifield formalism, that leads to an effective action, which is invariant under all the three differentials of the Sp(3) algebra, is given.
LABORATORY LIMITS ON THEORIES WITH STERILE NEUTRINOS IN THE BULK
Authors: IOANNISIAN ARA , PILAFTSIS APOSTOLOS
Published: July 2002

We discuss the phenomenological consequences of theories which describe sterile neutrinos in large extra dimensions, in the so-called bulk. We briefly outline how the cumulative non-decoupling effect due to the tower of Kaluza-Klein singlet neutrinos may equivalently be described by a higher-dimensional effective theory with original order-unity Yukawa couplings. Based on this cumulative phenomenon, we obtain strong constraints on the fundamental quantum gravity scale and/or on the higher-dimensional Yukawa couplings.
BRANE-BULK NEUTRINO OSCILLATIONS
Authors: LUKAS ANDRÉ , RAMOND PIERRE , ROMANINO ANDREA , ROSS GRAHAM G.
Published: July 2002

A plausible explanation for the existence of additional light sterile neutrinos is that they correspond to modulini, fermionic partners of moduli, which propagate in new large dimensions. We discuss the phenomenological implications of such states and show that solar neutrino oscillation is well described by small angle MSW oscillation to the tower of Kaluza Klein States associated with the Modulini. We also consider how all oscillation phenomena can be explained in a model including bulk neutrino states.
APPLICATION OF DISCRETE LIGHT-CONE QUANTIZATION TO YUKAWA THEORY IN FOUR DIMENSIONS
Authors: HILLER J. R.
Published: July 2002

The numerical technique of discrete light-cone quantization (DLCQ) is applied to a single-fermion truncation of Yukawa theory in four dimensions. The truncated theory is regulated by three Pauli-Villars bosons, which are introduced directly in the DLCQ Fock-state basis. A special form of the Lanczos diagonalization algorithm is used to handle the indefinite metric. Renormalization is done nonperturbatively.
FIBRE BUNDLE FORMULATION OF NONRELATIVISTIC QUANTUM MECHANICS IV: MIXED STATES AND EVOLUTION TRANSPORT'S CURVATURE
Authors: ILIEV BOZHIDAR Z.
Published: July 2002

We propose a new systematic fibre bundle formulation of nonrelativistic quantum mechanics. The new form of the theory is equivalent to the usual one and is in harmony with the modern trends in theoretical physics and potentially admits new generalizations in different directions. In it the Hilbert space of a quantum system (from conventional quantum mechanics) is replaced with an appropriate Hilbert bundle of states and a pure state of the system is described by a lifting of paths or section along paths in this bundle. The evolution of a pure state is determined through the bundle (analog of the) Schrödinger equation. Now the dynamical variables and density operators are described via liftings of paths or morphisms along paths in suitable bundles. The mentioned quantities are connected by a number of relations derived in this work.

The present fourth part of this series is devoted mainly to the fibre bundle description of mixed quantum states. We show that to the conventional density operator there corresponds a unique density lifting of paths for which the corresponding equations of motion are derived. It is also investigated the bundle description of mixed quantum states in the different pictures of motion. We calculate the curvature of the evolution transport and prove that it is curvature free iff the values of the Hamiltonian operator at different moments commute.
SUPERSYMMETRY: A CONSEQUENCE OF SMOOTHNESS?
Authors: NIELSEN H. B. , PALLUA S. , PRESTER P.
Published: July 2002

The consequences of certain simple assumptions like smoothness of ground state properties and vanishing of the vacuum energy (at least perturbatively) are explored. It would be interesting from the point of view of building realistic theories to obtain these properties without supersymmetry. Here we show, however, at least in some quantum mechanical models, that these simple assumptions lead to supersymmetric theories.
HIGH-ORDER COUPLED CLUSTER RESULTS FOR QUANTUM ANTIFERROMAGNETS AND THEIR PHASE TRANSITIONS
Authors: BISHOP R. F. , FARNELL D. J. J.
Published: July 2002

The normal coupled cluster method is implemented to high orders in a systematic approximation scheme, and is shown to give accurate ground- and excited-state properties of anisotropic Heisenberg antiferromagnets and their quantum phase transitions at zero temperature.
BULK AND EDGE EXCITATIONS IN A ν=1 QUANTUM HALL FERROMAGNET
Authors: RAY RASHMI
Published: July 2002

In this article, we shall focus on the collective dynamics of the fermions in a ν=1 quantum Hall droplet. Specifically, we propose to look at the quantum Hall ferromagnet. In this system, the electron spins are ordered in the ground state due to the exchange part of the Coulomb interaction and the Pauli exclusion principle. The low energy excitations are ferromagnetic magnons. To provide a means for describing these magnons, we shall discuss a method of introducing collective coordinates in the Hilbert space of many-fermion systems. These collective coordinates are bosonic in nature. They map a part of the fermionic Hilbert space into a bosonic Hilbert space. Using this technique, we shall interpret the magnons as bosonic collective excitations in the Hilbert space of the many-electron Hall system. By considering a Hall droplet of finite extent, we shall also obtain the effective Lagrangian governing the spin collective excitations at the edge of the sample.
EFFECT OF IONIC RADIUS OF THE A SITE ON EPR LINE IN PARAMAGNETIC AND FERROMAGNETIC PHASE OF La0.7-xRxCa0.3MnO3
Authors: RAO G. NARSINGA , BABU Y. , SASTRY M. D. , BABU D. SURESH
Published: July 2002

The effects of partial substitution of La by a smaller Lanthanide element (R) in La 0.7-x R x Ca 0.3 MnO 3 ( R = Ce , Pr, Nd Sm, Gd, Dy with x = 0 and 0.1) ceramic pellets on the electron paramagnetic resonance has been investigated. The line width increased with decrease in ionic radius of the A site  in paramagnetic phase, which is explained on the basis of tolerance factor. The observed increase in g-value and line width with increase in  in ferromagnetic phase explained qualitatively by Mn-O-Mn bond angle distortion and Mn-O orbital overlap which in turn is governed by the size of the substitution ion.
OXIDATION OF Mg(0001) STUDIED BY LEED AND ESDIAD
Authors: GOONEWARDENE A. U. , KURTZ R. L. , STOCKBAUER R. L.
Published: July 2002

The oxidation of Mg(0001) was studied using LEED (Low Energy Electron Diffraction) and ESDIAD (Electron Stimulated Desorption Ion Angular Distributions) with supplemental information from STM (Scanning Tunneling Microscopy). In agreement with previous work, two kinds of oxide were observed: a sub-oxide consisting of subsurface oxygen and ionic MgO. From 0 to 8 L (Langmuir=1×10-6 Torr Sec) oxygen exposure, the 1×1 LEED pattern obtained for clean Mg(0001) becomes diffuse and almost disappears, indicating that the initial stages of oxidation lead to a disordering of the surface. At higher oxygen exposure (~12 L) a diffuse 1×1 returns, showing that this new growth is in registry with the Mg substrate. The ESD O + ion yield, which is initially near zero for substrate oxygen, increases dramatically at this point, indicating that the oxide is now on the surface. The desorbing O + forms a normal emission pattern in the ESDIAD experiment at still higher oxygen exposures.
TIME-RESOLVED SPECTROSCOPY OF KI UNDER ONE-PHOTON EXCITATION BY AN ArF EXCIMER LASER
Authors: ICHIMURA NOBUKO , KONDO HISAO , HASHIMOTO SATOSHI
Published: July 2002

We investigated the absorption spectra of KI under excitation by an ArF excimer laser at 11 K. The laser light excited the sample through a one-photon process. Stable F centres were formed with excitation at a power level above ~ 2 mJ/cm2. From the time-resolved absorption spectrum, it is evident that the F centres are generated within 50 ns after the time of initiation of the laser pulse. The width of the F band at 50 ns was broader than that of the stationary F band at 11 K, suggesting the temperature increase of the crystal. We discuss the relaxation process in KI under dense electronic excitation.
EXCITON LOCALIZATION IN (Cd,Zn)O EPILAYERS AND (Cd,Zn)O/(Mg,Zn)O MULTI-QUANTUM WELLS ON LATTICE-MATCHED SUBSTRATES
Authors: MAKINO T. , TUAN N. T. , CHIA C. H. , SEGAWA Y. , KAWASAKI M. , OHTOMO A. , TAMURA K. , KOINUMA H.
Published: July 2002

We report on optical properties of epitaxial (Cd,Zn)O layers and multi-quantum wells grown by laser molecular-beam epitaxy on lattice-matched ScAlMgO 4 substrates. Exciton-phonon coupling strength in (Cd,Zn)O layers estimated by temperature dependence of the excitonic energy was similar to that deduced in ZnO . Time-resolved photoluminescence studies were performed on the multi-quantum wells, which are almost perfectly lattice-matched (0.034%). Radiative recombination of excitons exhibits a spectral distribution of times. We found that the radiative lifetime increases linearly with temperature, showing a two-dimensional feature of excitons in quantum wells.
MULTISTABLE NATURES AND PHOTO-INDUCED CHARGE-SEPARATION IN HOLE-DOPED STATES OF STRONGLY COUPLED ELECTRON-PHONON SYSTEMS
Authors: Hitoshi NITTA , Masato SUZUKI , Takeshi IIDA
Published: July 2002

We investigate the effects of hole doping in the charge-density wave (CDW) state that has the strong electron-phonon (e-p) coupling, using the two-dimensional molecular crystal model. In calculations, we use the mean-filed theory for the interelectronic interactions and the adiabatic approximation for phonons. On the basis of this theory, we calculate e-p states of doped ground states for various values of the doping concentration of holes. From the calculated results, it is found that a multistable nature appears in the doped e-p states just before the CDW-metal phase transition. In order to see the effects of the photoexcitation in the hole-doped states, we also investigate the exciton states taking into account the electron-hole correlation. Results calculated here indicate that the separation of electron and hole occurs in the photoexcited states as a consequence of the energy relaxation of excitons.
STUDY OF A NON-INTERACTING BOSON GAS
Authors: CORGINI M. , SANKOVICH D. P.
Published: July 2002

For a non-interacting many particle Bose system whose energy operator is diagonal in the number of occupation operators [Formula: see text] upper bounds on the thermal averages [Formula: see text] are obtained. These bounds lead to the proof of Bose–Einstein condensation for finite values of the inverse temperature β and for chemical potential μ=0. Finally for μ<0, in the case of a generalization of the studied model system, the property of Local Gaussian Domination for the grand canonical partition function is proved.
ALGEBRAIC GEOMETRY AND HOFSTADTER TYPE MODEL
Authors: LIN SHAO-SHIUNG , ROAN SHI-SHYR
Published: July 2002

In this report, we study the algebraic geometry aspect of Hofstadter type models through the algebraic Bethe equation. In the diagonalization problem of certain Hofstadter type Hamiltonians, the Bethe equation is constructed by using the Baxter vectors on a high genus spectral curve. When the spectral variables lie on rational curves, we obtain the complete and explicit solutions of the polynomial Bethe equation; the relation with the Bethe ansatz of polynomial roots is discussed. Certain algebraic geometry properties of Bethe equation on the high genus algebraic curves are discussed in cooperation with the consideration of the physical model.
OPTICAL AND ELECTRICAL PROPERTIES OF VANADIUM NITRIDE THIN FILMS
Authors: KRISHNA M. GHANASHYAM , BHATTACHARYA A. K.
Published: July 2002

Vanadium nitride thin films have been deposited on to quartz substrates by dc magnetron sputtering at two different total pressures and a series of nitrogen partial pressures. The spectral transmittance of these films, in the region 350 to 1500 nm, is strongly dependent on the nitrogen partial pressure during sputtering and relatively insensitive to total pressure. The films became more transparent as the nitrogen partial pressure was decreased at a constant total pressure. The optical constants, refractive index and extinction coefficient, exhibited a similar dependence on the nitrogen partial pressure. The sheet resistivity of the films decreased with increasing nitrogen partial pressure. The values of resistivity indicate that the films are semiconducting rather than metalic.
Flux-Flow and Fluctuations in the Microwave Resistivity of YBa2Cu3O7-δ
Authors: Silva E. , Neri D. , Marcon R. , Fastampa R. , Giura M. , Sarti S. , Sparvieri N.
Published: July 2002

We present measurements of the microwave resistivity at 48 GHz in YBa 2 Cu 3 O 7-δ film, as a function of the temperature and the magnetic field. The magneto-dissipation from 60 K up to a few kelvins below Tc finds a quantitative description in terms of free flux flow. Approaching Tc, the data are not consistent with a dissipative mechanism based solely on flux dynamic. Fluxon viscosity is measured as a function of the temperature, and the in-plane coherence length is estimated. The analysis of the zero-field transition at 48 GHz in terms of anisotropic renormalized fluctuations yields identical estimate.
Design and Optimization of HTC DC Squids for Magnetometric Applications
Authors: Testa G. , Monaco A. , Camerlingo C. , Russo M. , Sarnelli E.
Published: July 2002

In order to optimize the magnetic field sensitivity [Formula: see text] we have followed two different approaches. In the former we have analyzed the influence of the quality of YBCO films on the superconducting properties and noise characteristics of bicrystal grain boundary junctions and dc-SQUIDs. For this purpose we have studied and compared three different YBCO deposition processes. In the latter we have reported the different criteria for the design of SQUID magnetometers usable for applicalions in shielded and unshielded environment.
ER Properties of a Suspension of Polymer Graft Carbon Black Particles
Authors: Konishi Masayoshi , Nagashima Teruhisa , Asako Yoshinobu
Published: July 2002

We newly developed ER particles with sub-micron size. The particle was polymer graft carbon black (GCB1) composed of carbon black particles and a polymer. The average particle size of GCB1 was found to be 81 nm. An ER suspension (ER1) was obtained by mixing GCB1 (30 wt%) with silicone oil (70 wt%). The ER1 showed excellent dispersion stability. Further, GCB1 particles did not settle under centrifuging at 9000G. The zero-field viscosity was 80 mPa·s at 25°C. The kinetic friction coefficient of ER1 was 0.15, while that of the silicone oil used was 0.23. When the electric field of 3 kV/mm (AC 1000 Hz) at the temperature of 25°C and the shear rate of 700 s -1 was applied to ER1, the shear stress of 116Pa was induced. The induced shear stress did not change for a long period of time period. In the temperature range between 25 and 150°C the induced shear stress and the current density were almost constant at any electric field. When 3 kV/mm (AC 50Hz) at 25°C and 700s-1 was applied to ER1, the shear stress of 88Pa was induced but the deviation of the induced shear stress from the average value was pluses and minuses 3 Pa.
Dynamics of Dipole Chains in a Ferrofluid Emulsion
Authors: Hagenbüchle Martin , Liu Jing
Published: July 2002

Structure formation and chain dynamics in a dilute, monodisperse ferrofluid emulsion under the influence of an external magnetic field have been studied using dynamic light scattering. Chain formation is found to be a diffusion-limited process that is well described by the Smoluchowski theory of irreversible aggregation. The characteristic time on which chain formation occurs depends strongly on volume fraction and on magnetic field strength. Rescaling the time leads to a universal behavior. Internal chain dynamics i.e.chain fluctuations are revealed by measurements of the apparent short-time diffusion coefficient as a function of the scattering angle. They show a strong dependence on the strength of the applied magnetic field.
Dynamic Analysis of a Ferromagnetic Colloidal System
Authors: Morimoto Hisao , Maekawa Toru
Published: July 2002

We studied cluster structures formed in two- and three-dimensional magnetic fluid systems numerically. We developed a Brownian dynamics calculation method in which both the translational and rotational motions of ferromagnetic particles were taken into account. The cluster formations are analysed from the point of view of second order phase transition and the dependence of the cluster size on the temperature and magnetic field is investigated. The fractal dimensions were, respectively, 1.3 and 1.6 for the two- and three-dimensional systems in the absence of a magnetic field. On the other hand, the fractal dimension was very close to 1.0 for both two- and three-dimensional systems when the system was subjected to a magnetic field. The cluster-cluster aggregations are also investigated and the validity of the dynamic scaling law is examined. It has been found that the fractal dimensions obtained by the dynamic analysis coincide with those obtained by the analysis of the cluster structures. The critical exponents were 0.7 and 0.8 in the absence of a magnetic field and in a magnetic field, respectively, in the case of the two-dimensional system, and 1.2 and 0.8 in the case of the three-dimensional system for λ=12 where λ is the ratio of magnetic dipole energy to thermal energy.
Control Characteristics of ER Devices
Authors: Choi Seung-Bok
Published: July 2002

The successful development of a new generation of technology incorporating an electro-rheological (ER) fluid requires three principal ingredients; advanced ER fluid, reliable mechanical mechanism and efficacious control scheme. This paper discusses the third one. After describing general, but stringent requirements for semiactive or active control systems featuring the ER fluid, feedback control characteristics of some specific ER devices are presented; a frequency-dependent feedback control of mode shape in a smart flexible structure containing the ER fluid, an optimal control of vibration in a semi-active suspension installed with ER shock absorbers, and a neural network control of position in a hydraulic ER valve-cylinder system.
NONLINEAR DOMAIN GROWTH OF TEMPERED INCOMMENSURATE AND RELATED SYSTEMS
Authors: PARK YUNG
Published: July 2002

This paper is no longer available. Please contact "ijmpb@wspc.com"
GINZBURG-LANDAU THEORY OF MIXED WAVE SUPERCONDUCTORS
Authors: WANG Z. D. , LI Q. , WANG Q. H.
Published: July 2002

We address vortex state and dynamics of mixed wave superconductors in the framework of Ginzburg-Landau theory. We find that the s- and d-wave components of a single vortex in the d+is-state exhibit two-fold symmetry and the intrinsic Hall effect displays a different angle dependence from that of d-wave state. For dx2-y2+idxy-wave superconductors, a Ginzburg-Landau theory is developed from a microscopic theory with a strong coupling term being included. In the absence of a magnetic field, the theory predicts a pure dx2-y2 state at T>T* and a second order phase transition at T* to a time-reversal-symmetry-breaking dx2-y2+idxy state, with T* being very small. In a magnetic field, the strong coupling effect could lead to that a dx2-y2+idxy state is always established, albeit with decreasing dxy amplitude with increasing temperature.
OPTIMIZATION OF HEAT TREATMENTS OF AFRICAN GREEN SAPPHIRES
Authors: WINOTAI P. , SAISENG S. , SUDYOADSUK T.
Published: July 2002

Under suitable heating conditions designed for a particular sapphire it is possible to change the color in order to increase its value. It was found that heating African green sapphires in an oxygen atmosphere could improve their quality and thus increase their prices. The color of green sapphires is due to the presence of trace amounts of Fe 3+, Ni 3+, Fe 2+ and Ti 4+ ions. It is known that Fe 3+ yields pale yellow and Ni 3+ a golden color while the charge transfer mechanism between Fe 2+ and Ti 4+ gives sapphire its blue color. It is obvious that the green color is due to a high ratio of Fe 2+ to Ti 4+. By using an X-ray diffractometer, the maximum decrease of the c/a ratio of the hexagonal structure is found to occur after heat treatment at 1200°C. These results are also confirmed by the shift of emission spectra toward shorter wavelengths. Furthermore, the number of Fe 2+ ions converted to Fe 3+ was detected by electron spin resonance spectrometry and found to increase with temperature. The sapphire with trace Ti 4+ ions, appeared slightly bluish green after heating at 1500°C. The optimal temperature is therefore at 1300°C, where we can achieve yellowish green sapphires instead.
A STUDY OF 2D ISING FERROMAGNETS WITH DIPOLE INTERACTIONS
Authors: IFTI M. , LI Q. , SOUKOULIS C. M. , VELGAKIS M. J.
Published: July 2002

A two-dimensional Ising model with competing short range ferromagnetic and long range dipolar interactions is used to study the transition properties and phase diagram in ultrathin magnetic films. Monte Carlo simulations in systems with exchange and dipolar interactions reveal a ground state of striped phases with varying width. By raising the temperature, the domain walls are smeared out by fluctuations, leading to a random domain mesoscopic phase with no long-range order, and finally the domains are melted to the high-temperature disordered phase. Local magnetic field distributions and specific heat calculations reproduced transition points consistent with the previous phase diagram of the model. The resemblance to the phase diagram in ultrathin magnetic films, such as in Fe/Cu(100), is discussed.
SUBSTRATE CHARACTERISTICS OF Ba2HoNbO6 FOR THE FABRICATION OF LaBaCaCu3O7-δ SUPERCONDUCTING FILMS
Authors: LANDÍNEZ TÉLLEZ D. A. , ALBINO AGUIAR J. , YADAVA Y. P. , CHAVIRA E. , ROA-ROJAS J.
Published: July 2002

We have synthesized and studied the characteristics of Ba 2 HoNbO 6 (BHNO) substrates for the fabrication of LaBaCaCu 3 O 7-δ (LBCCO) superconducting films. BHNO has an A 2 BB'O 6 complex cubic perovskite structure with lattice constant a = 8, 439 Å. Energy-dispersive X-ray (EDX) analysis shows that BHNO is free from impurity traces and scanning electron micrographs reveal that it has uniform surface morphology and particle size distribution. Based on the doubling of the ABO 3 cubic perovskite unit cell, (1/2)a = 4, 220 Å, BHNO has fairly good lattice matching (lattice mismatch ~ 9%) with LBCCO superconductors. X-ray diffractometry, back-scattered scanning electron microscopy and magnetic measurements effectuated on BHNO/LBCCO composites show that BHNO is chemically and physically compatible and it could be used as a potential substrate material for the growth of LBCCO superconducting films.
TWO-MODE PHASE-STATE REPRESENTATIONS IN QUANTUM OPTICS
Authors: FAN HONG-YI , LIANG XIAN-TING , SUN ZHI-HU
Published: July 2002

A phase state presentation |ξ= reiθ> for a two-mode light field is constructed in the context of quantum optics. This phase space formalism is directly connected to phase-related operators. The generalized quasi-probability distribution function Q(ξ) and measurable phase probability distribution function P(θ) are constructed and are useful to obtain information about phase properties of light fields.
HALL CONDUCTIVITY FLUCTUATIONS IN EPITAXIAL YBa2Cu3O7-δ THIN FILMS
Authors: ROA-ROJAS J. , PRIETO P. , PUREUR P.
Published: July 2002

We present systematic measurements of the longitudinal and Hall resistivities in YBa2Cu3O7-δ epitaxial thin films. Above the critical temperature, T c , the longitudinal resistivity, ρxx(T), increases linearly with temperature, whereas the Hall resistivity, ρxy(T), varies inversely proportional to T. Consequently, the cotangent of the Hall angle shows quadratic temperature dependence. The fluctuation contributions to both the longitudinal and Hall conductivities in the normal phase are studied. In the case of the longitudinal conductivity, 2D and 3D Gaussian regimes are observed. In addition, a genuine 3D-XY critical regime is discerned closely above T c in experiments performed at low applied fields. The value of the corresponding critical exponent, λ C =0.33, indicates that the dynamic universality class for the superconducting transition in the analyzed system is given by the Model E of Hohenberg and Halperin. The analysis of the Hall conductivity fluctuations above T c reveals the occurrence of 2D and 3D Gaussian regimes which are consistent with those identified in the longitudinal conductivity results. Below T c the Hall resistivity shows a sign reversal before attaining the zero resistance state.
A VARIATIONAL APPROACH IN THE DISSIPATIVE CUBIC-QUINTIC NONLINEAR SCHRÖDINGER EQUATION
Authors: FREITAS DAGOBERTO S. , DE OLIVEIRA JAIRO R.
Published: July 2002

The properties of pulse propagation in a nonlinear fiber including a linear damped term added in the nonlinear Schrödinger equation with cubic and quintic terms is analyzed analytically. We apply the variational modified approach based on the Lagrangian that describes the dynamic of a system and, with a suitable trial function, we obtain a solution which is as accurate as a pertubative solution found by inverse scattering transformation in earlier works. As a result, we show that the quintic term can retain the pulse propagation more stably and in a greater time in optical fiber.
THE OPTICAL AND EPR SPECTRA OF THE HYDROGEN ANNEALED KTiOPO4 CRYSTALS
Authors: NAZAROVA V. A. , EFIMOV V. N. , LARUHIN M. A.
Published: July 2002

In this work, the results of the hydrogen treatment and following that, the annealing in air of flux-grown KTiOPO 4 (KTP) crystals are represented. We have tried to correlate our optical and EPR results. The main conclusion is that the Ti 3+ A, B, C, D centers are not associated with optical absorption in the visible light region.
SYLLABLE-BASED CHINESE TEXT/SPOKEN DOCUMENT RETRIEVAL USING TEXT/SPEECH QUERIES
Authors: BAI BO-REN , CHEN BERLIN , WANG HSIN-MIN
Published: July 2002

In light of the rapid growth of Chinese information resources on the Internet, this study investigates a novel approach that deals with the problem of Chinese text and spoken document retrieval using both text and speech queries. By properly utilizing the monosyllabic structure of the Chinese language, the proposed approach estimates the statistical similarity between the text/speech queries and the text/spoken documents at the phonetic level using the syllable-based statistical information. The investigation successfully implemented a prototype system with an interface supporting some user-friendly functions and the initial test results demonstrate the feasibility of the proposed approach.
CHAOTIC AND QUASIPERIODIC MOTIONS OF THREE PLANAR CHARGED PARTICLES
Authors: CHANG SHU-MING , LIN WEN-WEI , LIN TAI-CHIA
Published: July 2002

We study two dynamical systems for the motion of three planar charged particles with charges nj ∈ {±1}, j = 1, 2, 3. Both dynamical systems are parametric with a parameter α ∈ [0, 1] and have the same nonlinear terms. As α = 0, 1, the dynamical systems have no chaos. However, one dynamical system may create chaos as α varies from zero to one. This may provide an example to show that the homotopy deformation of dynamical systems cannot preserve the long-time dynamics even though the dynamical systems have the same nonlinear terms.
SPATIOTEMPORAL CHAOS, LOCALIZED STRUCTURES AND SYNCHRONIZATION IN THE VECTOR COMPLEX GINZBURG–LANDAU EQUATION
Authors: HERNÁNDEZ-GARCÍA EMILIO , HOYUELOS MIGUEL , COLET PERE , MIGUEL MAXI SAN , MONTAGNE RAÚL
Published: July 2002

We study the spatiotemporal dynamics, in one and two spatial dimensions, of two complex fields which are the two components of a vector field satisfying a vector form of the complex Ginzburg–Landau equation. We find synchronization and generalized synchronization of the spatiotemporally chaotic dynamics. The two kinds of synchronization can coexist simultaneously in different regions of the space, and they are mediated by localized structures. A quantitative characterization of the degree of synchronization is given in terms of mutual information measures.
BISTABLE PHASE SYNCHRONIZATION AND CHAOS IN A SYSTEM OF COUPLED VAN DER POL–DUFFING PSCILLATORS
Authors: KOZLOV A. K. , SUSHCHIK M. M. , MOLKOV Ya. I. , KUZNETSOV A. S.
Published: July 2002

Analysis of numerical solutions for a system of two van der Pol–Duffing oscillators with nonlinear coupling showed that there exist chaotic switchings (occurring at irregular time intervals) between two oscillatory regimes differing by nearly time-constant phase shifts between the coupled subsystems. The analysis includes the investigation of bifurcations of the periodic motions corresponding to synchronization of two subsystems, finding stability regions of synchronization regimes and scenarios of the transitions to chaos.
MULTIPLICATIVE INVARIANT POLYNOMIALS OF PLANE CURVES
Authors: AICARDI F.
Published: July 2002

This note answer a question of V. F. R. Jones, whether there exist topological invariant polynomials of plane curves that, instead of additive as the Arnold invariants, are multiplicative with respect to the connected sum of two curves.
GEOMETRY AND STATISTICS OF COSMIC MICROWAVE POLARIZATION
Authors: DOLGOV A. D. , DOROSHKEVICH A. G. , NOVIKOV D. I. , NOVIKOV I. D.
Published: July 2002

Geometrical and statistical properties of polarization of CMB are analyzed. Singular points of the vector field which describes CMB polarization are found and classified. Statistical distribution of the singularities is studied. A possible signature of tensor perturbations in CMB polarization is discussed. For a further analysis of CMB statistics, Minkowski functionals are used, which present a technically simple method to search for deviations from a Gaussian distribution.
STRING DILATON FLUID COSMOLOGY
Authors: CAPOZZIELLO S. , LAMBIASE G. , CAPALDO R.
Published: July 2002

We investigate (n+1)-dimensional string–dilaton cosmology with effective dilaton potential in presence of perfect-fluid matter. We get exact solutions parametrized by the constant γ of the state equation p=(γ-1)ρ, the spatial dimension number n, the bulk of matter, and the spatial curvature constant k. Several interesting cosmological behaviours are selected. Finally we discuss the recovering of ordinary Einstein gravity starting from string dominated regime and a sort of asymptotic freedom due to string effective coupling.
EFFECT OF RANDOM FRACTALS ON THE DIELECTRIC RELAXATION OF A HETEROGENEOUS MEDIUM
Authors: PARK YUNG
Published: July 2002

This paper is no longer available. Please contact "fractals@wspc.com"
A STUDY OF THE DIFFUSION OF Pb ON THE Au(111) SURFACE BY STM AND EAM-MD SIMULATIONS
Authors: ROBINSON M. C. , SLAVIN A. J. , DE'BELL K.
Published: July 2002

Surface reconstructions often result in novel growth morphologies, and are therefore of potential technological interest. The Au(111) surface will reconstruct into the [Formula: see text] "herringbone" structure. Low coverages (up to 0.3 monolayers) have been studied with scanning tunneling microscopy (STM) at room temperature, to determine the impact of the reconstruction on diffusion and thin film growth. The same system has been studied using embedded-atom model molecular dynamics (EAM-MD). These simulations, in addition to providing morphological information, permit qualitative comparison of diffusion phenomena. Experimental results indicate that initial sites for Pb adsorption are located at the herringbone kinks. For higher coverages, Pb prefers hcp and fcc stacking regions, avoiding the herringbone ridges. The reconstruction is removed for some coverage between 0.05 and 0.2 monolayers. STM and EAM results will be compared.