bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics and mechanism of hydrolysis of 3-diazobenzofuran-2-one and its hydrolysis product (3-hydroxybenzofuran-2-one)
Authors: Chiang Y , Kresge A J , Meng Q
Published: July 2002

Rates of acid-catalyzed hydrolysis of 3-diazobenzofuran-2-one, measured in concentrated aqueous perchloric acid and hydrochloric acid solutions, were found to correlate well with the CoxYates Xo excess acidity function, giving kH+ = 1.66 × 104 M1 s1, m = 0.86 and kH+ /kD+ = 2.04. The normal direction (kH/kD > 1) of this isotope effect indicates that hydrolysis occurs by rate-determining protonation of the substrate on its diazo-carbon atom. It was found previously that the next higher homolog of the present substrate, 4-diazoisochroman-3-one, also undergoes hydrolysis by this reaction mechanism but with a rate constant 15 times greater than that for the present substrate; this difference in reactivity can be understood in terms of the various resonance forms that contribute to the structures of these substrates. The product of the present hydrolysis reaction is 3-hydroxybenzofuran-2-one, which itself quickly undergoes subsequent acid-catalyzed hydrolysis to 2-hydroxymandelic acid. The acidity dependence of this subsequent hydrolysis is much shallower than that of the diazo compound precursor, and rates of reaction correlate as well with [H+] as with Xo. This is due in part to incursion of a nonproductive protonation on the hydroxy group of 3-hydroxy benzo furan-2-one that impedes hydrolysis and produces saturation of acid catalysis. Rates of hydrolysis of the hydroxy compound were also measured in dilute HClO4 and NaOH solutions as well as in CH3CO2H, H2PO4, (CH2OH)3CNH3+, and NH4+ buffers, and the rate profile constructed from these data showed the presence of uncatalyzed and hydroxide ion-catalyzed reactions. This hydroxide-ion catalysis became saturated at [NaOH] [Formula: see text] 0.05 M, implying occurrence of yet another nonproductive substrate ionization. Key words: diazo compound hydrolysis, lactone hydrolysis, CoxYates excess acidity, acid catalysis, alcohol protonation.
Environmental photodegradation of pyrimidine fungicides  Kinetics of the visible-light-promoted interactions between riboflavin and 2-amino-4-hydroxy-6-methylpyrimidine
Authors: Haggi E , Bertolotti S , Miskoski S , Amat-Guerri F , García N A
Published: July 2002

To clarify the evolution of pyrimidine fungicides under natural aquatic environmental conditions, the visible-light-promoted degradation of the model fungicide 2-amino-4-hydroxy-6-methylpyrimidine (AHMPD) has been studied in air-equilibrated pH 6 aqueous solutions in the presence of riboflavin (Rf), employing time-resolved and stationary kineticspectroscopic methods. AHMPD, a compound practically inert towards the attack of singlet molecular oxygen (O2(1Δg)), quenches excited singlet and triplet states of Rf with rate constants of 2.7 × 109 M1 s1 and 2.7 × 107 M1 s1, respectively. In the presence of AHMPD, the photodecomposition of Rf, which occurs from the excited triplet state of the pigment, depends on the concentration of the fungicide: at [Formula: see text]4050 mM a limited photochemistry occurs due to the quenching of excited singlet Rf, while at ca. 510 mM triplet Rf is largely photogenerated and subsequently quenched either by oxygen, giving rise to O2(1Δg), or by AHMPD, yielding semireduced Rf through an electron transfer process. Flash photolysis experiments and indirect auxiliary tests confirm the presence of superoxide anion generated by the reaction of Rf anion radical with the dissolved oxygen. The neat result of this intricate scheme of competitive reactions is the photodegradation of both AHMPD and Rf, mainly through a superoxide anion-mediated oxidation, although some contribution of O2(1Δg)-mediated photooxidations cannot be disregarded.Key words: photooxidation, pyrimidine derivatives, riboflavin, singlet molecular oxygen, superoxide anion.
Biocapteurs ampérométriques à cholinestérases pour la détermination des pesticides organophosphorés
Authors: Turdean Graziella , Popescu Ionel Catalin , Oniciu Liviu
Published: July 2002

The purpose of this study is a comparative presentation of the different types of the amperometric biosensors based on cholinesterases for the determination of organophosphorous pesticides using the bibliographical information of the last 20 years. The study contains the presentation of the structure and properties of the cholinesterases, the main reactions implied in the functioning of the amperometric biosensors, their applications and factors influencing the detection or (and) the inhibition process. The detection limit of the mono- or bi-enzymatic amperometric biosensors are relatively higher than those corresponding with the immunobiosensors or with gas and liquid chromatography, which are still considered as the reference methods. As shown, for many other amperometric biosensors, the MichaelisMenten's kinetic treatment used for reactions catalyzed by free enzymes can be extended to describe the response of amperometric biosensors based on immobilized cholinesterases. The positive compromise between advantages and drawbacks, as well as the "soft" experimental conditions, point to the amperometric monoenzymatic bioelectrode, as an attractive analytical tool for the detection of organophosphorous pesticides.Key words: amperometric biosensor, acetylcholinesterase, organophosphorous pesticides, kinetic, inhibition.
Solution and solid-state characterization of a dicopper receptor for large substrates
Authors: Davidson Greg JE , Baer Andrew J , Côté Adrien P , Taylor Nicholas J , Hanan Garry S , Tanaka Yasutaka , Watanabe Masashi
Published: July 2002

Ligand 2 contains two metal-binding domains separated by a rigid spacer and assembles into a dicopper receptor with a large central cavity with no evidence of catenation.Key words: copper complex, coordination, X-ray crystallography, molecular recognition.
Acorn production by Kashiwa oak in a coastal forest under fluctuating weather conditions
Authors: Masaka Kazuhiko , Sato Hajime
Published: July 2002

We modeled the annual acorn crops of Kashiwa oak (Quercus dentata Thunb.) in a coastal forest in Hokkaido, northern Japan. Shoots of Kashiwa oak withered away during winter because of sea breeze and cold, and succeeding production of female inflorescences were strongly affected by mortality of buds. Thus, strong sea breeze and cold winters reduced the survival ratio of buds and further resulted in reduction of female flowering. Number of female flowers was related with current acorn crops, however, survival of female flowers after pollination was strongly influenced by warmth in the flowering period. Regression analysis of the annual acorn crop versus weather conditions suggests that acorn crop was decreased by cool conditions in the flowering period. A model equation was constructed to estimate the annual acorn crops by three weather variables: cumulative velocity of sea breeze and mean monthly temperature in winter (DecemberMarch) and maximum monthly temperature in current flowering period (June). This model equation explained 89.2% of observed acorn crops of Kashiwa oak in the coastal forest.
Relationships between anatomical and densitometric characteristics of black spruce and summer temperature at tree line in northern Quebec
Authors: Wang Lily , Payette Serge , Bégin Yves
Published: July 2002

Tracheid cell number, cell diameter, and cell-wall thickness of black spruce (Picea mariana (Mill.) BSP) tree rings at the tree line (northern Quebec, Canada) were measured using image analysis. The densitometric data from the same samples were used to evaluate the features of image analysis. The anatomical data were correlated with summer temperature variables, including: means of pentad temperature (five consecutive days), growing season (May- September), sum of degree-days, and number of frost-free days. Our results suggest that the main cause of the pale appearance of light rings is thinner latewood cell-wall thickness. Some latewood variables are strongly correlated with corresponding indices for ring cell number and diameter, and ring cell wall thickness. Anatomical ring cell number and the sum of cell diameters (ring widths) were correlated to tree-ring width parameters derived from densitometry. Ring cell number and annual sum of cell diameter also showed very similar trends with both chronologies, suggesting that ring-width length may depend on the number of cells within a ring. Ratio diagram of double cell-wall thickness to cell radial diameter showed similar trend to wood density profile. There is a statistically significant correlation between maximum density and the highest annual ratio between cell wall thickness and lumen diameter. Cell-wall thickness was significantly correlated to maximum density, and both were significantly correlated with summer temperature variables. Our results suggest that wood anatomy may be used as a substitute to densitometry for climate reconstruction as densitometric data require expensive equipments. Also the anatomical method allows the recording of intra-annual information for dendroecological purposes.
Trophectoderm development and function: the roles of Na+/K+-ATPase subunit isoforms
Authors: Kidder Gerald M
Published: July 2002

Preimplantation development is a period of cell division, cell shape change, and cell differentiation leading to the formation of an epithelium, the trophectoderm. The trophectoderm is the part of the conceptus that initiates uterine contact and, after transformation to become the trophoblast, uterine invasion. Thus, trophectoderm development during preimplantation stages is a necessary antecedent to the events of implantation. The preimplantation trophectoderm is a transporting epithelium with distinct apical and basolateral membrane domains that facilitate transepithelial Na+and fluid transport for blastocoel formation. That transport is driven by Na+/K+-ATPase localized in basolateral membranes of the trophectoderm. Preimplantation embryos express multiple α and β subunit isoforms of Na+/K+-ATPase, potentially constituting multiple isozymes, but the basolaterally located α1β1isozyme uniquely functions to drive fluid transport. They also express the γ subunit, which is a modulator of Na+/K+-ATPase activity. In the mouse, two splice variants of the γ subunit, γa and γb, are expressed in the trophectoderm. Antisense knockdown of γ subunit accumulation caused a delay of cavitation, implying an important role in trophectoderm function. The preimplantation trophectoderm offers a unique model for understanding the roles of Na+/K+-ATPase subunit isoforms in transepithelial transport.Key words: preimplantation development, trophectoderm, fluid transport, Na+/K+-ATPase, α subunit, β subunit, γ subunit.
Induced morphological defence: evidence from whole-lake manipulation experiments
Authors: Johansson Frank , Wahlström Eva
Published: July 2002

Predator-induced defences are activated by cues associated with predators and confer some degree of resistance to subsequent attacks. Laboratory studies of many taxa have revealed such induced defences, and these data often conform to large-scale surveys of defence levels in habitats with and without predators. However, there have been no studies that make the direct connection between these laboratory studies and field surveys. We conducted a large-scale field manipulation of predators to provide this connection. Previous laboratory experiments on dragonfly (Leucorrhinia dubia) larvae have demonstrated that the presence of fish predators induces the development of elongated abdominal spines that serve to reduce mortality risk. In this study we determine the effect of whole-lake predator manipulation on this induced morphological defence of L. dubia. We monitored the spine lengths of final-instar larvae in two experimental lakes for 7 consecutive years. Fish were present during the first 2 years and then removed for the remaining 5 years. Results demonstrate that the spine lengths of L. dubia larvae decreased significantly in both lakes after the removal of fish. In contrast, there was no corresponding change in the spine lengths of larvae in reference lakes, and we found little change in food supply for larvae. Our results suggest that the plastic response in spine length is strong and attributable to the presence of predators.
Biometry of the branchial plume in the hydrothermal vent tubewormRiftia pachyptila(Vestimentifera; Annelida)
Authors: Andersen Ann C , Jolivet Sylvie , Claudinot Stéphanie , Lallier François H
Published: July 2002

The branchial plume of the hydrothermal vent tubeworm Riftia pachyptila is the main organ by which this mouth- and gut-less tubeworm directly exchanges metabolites with its environment. We estimated the total branchial surface area per unit wet mass, termed the specific branchial surface area (SBSA), from planimetric measurements. Changes in the SBSA during the growth of the worm were inferred from 16 individuals ranging from 1 to 112 g wet mass. Riftia pachyptila has a mean SBSA of 22 cm2·g1, the second highest among all aquatic animals, representing 9 times the surface area of the rest of the body. Three significantly different classes of SBSA could be distinguished, corresponding to small, medium-sized, and large individuals. The SBSA values for small and medium-sized R. pachyptila are twice that for large individuals. Negative growth allometry between the length of the branchial plume and that of the trunk may be correlated with this variation in SBSA, the plume growing faster than the trunk in the small and medium-sized groups. In large individuals the trunk length exceeds the plume length, inducing an increase in body mass that lowers the SBSA. However, a lower SBSA does not imply reduced metabolite diffusion through the plume of large tubeworms, since their longer free filaments bear more developed pinnules, which are probably the preferred pathway of metabolite diffusion, owing to a minimal transepithelial distance of 2 µm.
LOAD BALANCING IN HOME-BASED SOFTWARE DSMS
Authors: SHI WEISONG , TANG ZHIMIN
Published: July 2002

Load balancing is a critical issue for achieving good performance in parallel and distributed systems. However, this issue is neglected in the research area of software DSMs in the past decade. Based on the observation that scientific applications can be classified into two categories: iterative and non-iterative, we propose two dynamic scheduling schemes for these two cases respectively in this paper. For iterative scientific applications, a dynamic task migration technique is proposed which characterizes itself with integrating computation migration and data migration together. An affinity-based self scheduling (ABS) is proposed for non-iterative scientific applications, which take both the static and dynamic processor affinity into consideration when scheduling. The target experiment platform is a state-of-the-art home-based DSM system named JIAJIA. Performance evaluation results show that the novel task migration scheme improves the performance ranging from 36% to 50% compared with a static task allocation scheme in a metacomputing environment, and performs better than traditional task (computation-only) migration approach about 12.5% for MAT, and 37.5% for SOR and EM3D. Higher resource utilization is achieved via the new task migration scheme too. In comparison with other loop scheduling schemes, the ABS achieves the best performance among all scheduling schemes in a metacomputing environment because of the reduction of synchronization overhead and the great improvement of waiting time resulting from load imbalance.
ON THE COTANGENT SHEAF OF QUOT-SCHEMES
Authors: LEHN MANFRED
Published: July 2002

It is the purpose of this short note to give a global description of the cotangent sheaf of Grothendieck's Quot-scheme in terms of a relative Ext-sheaf of the universal subsheaf and the universal quotient sheaf. As an application one gets a description of the cotangent sheaf of the moduli space of stable sheaves in terms of a relative Ext-sheaf involving only a universal family in case such a family exists.
CONSTRUCTION OF HARMONIC MAPS BETWEEN SPHERES BY JOINING THREE EIGENMAPS
Authors: GASTEL ANDREAS
Published: July 2002

Given three harmonic eigenmaps between spheres, we discuss the possibility of representing the homotopy class of their join by a harmonic map. This is done by minimizing energy in a suitable class of equivariant W1,2 mappings, followed by a discussion of the regularity of the minimizer. Sufficient conditions for its smoothness are proved, which imply existence of a (smooth) harmonic representative. As an application we have several new examples of nontrivial harmonic maps between spheres, including harmonic maps representing all elements of π10(S10), π11(S11), and π17(S17).
STABILITY OF HARMONIC MORPHISMS TO A SURFACE
Authors: MONTALDO STEFANO
Published: July 2002

Using the fact that harmonic morphisms to a surface have minimal fibres, links between the volume-stability of the fibres and the energy-stability of the map are found of manifolds without boundary. A stability result for harmonic morphisms from a manifold with boundary to a Riemann surface is also established.
M CENTER DIFFUSION, EXCITONS AND ADSORPTIVITY OF ATOMIC H AND He ON LiH (001) SURFACE: ab initio STUDY
Authors: SHALABI A. S. , EID KH. M. , KAMEL M. A. , FATHI Z. M.
Published: July 2002

An attempt has been made to examine the energetic properties of M center diffusion, excitons near M 2+, M +, M, M - and M 2- centers and adsorptivity of atomic H and He over defect free and defect containing surfaces of LiH using an ab initio embedded cluster method at the Hatrtree–Fock approximation and Moller–Plesset second order perturbation correction. The results confirm the following, (1) the calculated barriers to diffusion of M center in its lowest triplet excited state is always greater than those in its singlet ground state; (2) the triplet M center is not produced directly by optical processes, but, indirectly by thermal diffusion; (3) the exclusive dependence of exciton bands and the nonexclusive dependence of band gaps on the defect charge; (4) surface relaxation is not more important than bulk relaxation; (5) the M center changes the nature of H adsorption from physical adsorption to chemical adsorption; (6) bulk or surface M 2- changes the nature of LiH from an insulator to a semiconductor; (7) as M center is introduced, the HOMO and LUMO levels of the substrate shift to higher energies and band gaps become narrower. This change in the electronic structure makes charge transfer between adsorbate and substrate levels and spin pairing with atomic H more facile.
DISTINGUISHING BETWEEN CHAOTIC AND STOCHASTIC SYSTEMS IN FINANCIAL TIME SERIES
Authors: MENNA MASSIMILIANO , ROTUNDO GIULIA , TIROZZI BRUNELLO
Published: July 2002

In last years several mathematical methods were successfully used for financial time series modeling. The main problem is to check whether irregularities of data are generated by a stochastic process or they are due to some deterministic chaos and to the presence of low-dimensional strange attractor. We focus on a test based on the correlation dimension. In particular we examine the time series of the daily closure prices of the Italian car industry "FIAT" shares.
Effectiveness of Acupuncture and Moxibustion Treatment for Lymphedema Following Intrapelvic Lymph Node Dissection: A Preliminary Report
Authors: Kanakura Yoichi , Niwa Kuniaki , Kometani Kunio , Nakazawa Kazumi , Yamaguchi Yoko , Ishikawa Hiroshi , Watanabe Asaka , Tokunaga Yasumoto
Published: July 2002

Although it is difficult in Western medicine to eliminate edema occurring in the lower extremities after intrapelvic lymph node dissection for malignant gynecologic tumors, we successfully treated or prevented this postoperative complication with moxibustion and acupuncture, initiated after the occurrence of lymphedema in 12 patients and as soon as possible after surgery in 12 others. An increase in deep body temperature with acupuncture or moxibustion was found to be essential for successful treatment.
RUNNING COUPLING CONSTANTS OF FERMIONS WITH MASSES IN QUANTUM ELECTRODYNAMICS AND QUANTUM CHROMODYNAMICS
Authors: NI GUANG-JIONG , YANG GUO-HONG , FU RONG-TANG , WANG HAIBIN
Published: July 2002

Based on a simple but effective regularization-renormalization method (RRM), the running coupling constants (RCC) of fermions with masses in quantum electrodynamics (QED) and quantum chromodynamics (QCD) are calculated by renormalization group equation (RGE). Starting at Q=0 (Q being the momentum transfer), the RCC in QED increases with the increase of Q whereas the RCCs for different flavors of quarks with masses in QCD are different and they increase with the decrease of Q to reach a maximum at low Q for each flavor of quark and then decreases to zero at Q→0. Thus a constraint on the mass of light quarks, the hadronization energy scale of quark–antiquark pairs are derived.
THE STRAIN QUANTUM CRITICAL POINT FOR SUPERSTRIPES IN THE PHASE DIAGRAM OF ALL CUPRATE PEROVSKITES
Authors: BIANCONI A. , SAINI N. L. , AGRESTINI S. , CASTRO D. DI , BIANCONI G.
Published: July 2002

The metallic phase in doped cuprate perovskites is determined by both the hope doping δ and the micro-strain ε of the planar Cu-O bond length. The micro-strain ε in the CuO 2 plane has been measured by Cu K-edge EXAFS and x-ray diffraction using synchrotron radiation. The critical micro-strain ε c for the onset of local lattice distortions (LLD) and stripe formation has been determined. The strain quantum critical point (QCP) is found at (ε c ,δ c ). The superconducting critical temperature is measured as a function of two variables T c (ε,δ) and it reaches its maximum at the strain QCP. The superconducting phase occurs in the region of critical fluctuations around this QCP. The critical fluctuations near the strain QCP drives the self-organization of the metallic plane forming a particular superlattice of quantum stripes called "superstripes" that favors the amplification of the superconducting critical temperature.
PHASE DIAGRAM OF STRIPE ORDER IN THE EXTENDED HUBBARD MODEL
Authors: KATO MASARU
Published: July 2002

The extended Hubbard model with the nearest-neighbor Coulomb interaction on the square lattice is studied within the mean-field approximation. The stable states for 8×8 sites lattice with the periodic boundary condition and the electron filling n=0.875, as well as for 10×10 lattice and n=0.80, are obtained. For 8×8 lattice where quarter-filled straight stripe is expected because of the long-range Coulomb interaction, the cross stripe phases become stable.
ON POSSIBLE FORMALISM OF ANISOTROPIC FERMI LIQUID AND BCS–TYPE SUPERCONDUCTIVITY
Authors: GONCZAREK R. , GŁADYSIEWICZ M. , MULAK M.
Published: July 2002

We prove that an arbitrary crystal with anisotropic lattice and partially filled conduction band, for which one-electron energy spectrum is known, can be considered, after some curvilinear transformation of the reciprocal lattice as the Fermi liquid of the Landau–type quasiparticles in the isotropic system. However, the additional scalar field modifying the size of quantum-mechanical states in the reciprocal space has to be included. It is shown that the established formalism can be employed for two- and three-dimensional systems. As an example one-band Hubbard model has been investigated in details. The new precise formulas for the postulated scalar field and the density of states are derived. Additionally, assuming the microscopic mechanism which leads to the pairing interaction in a crystal, the anisotropic Fermi liquid formalism is extended to superconducting system according to the BCS theory principles. The obtained results enable us to explain and understand the great success of the BCS theory.
THEORY OF SINUSOIDAL MODULATION OF THE RESONANT NEUTRON SCATTERING IN HIGH TEMPERATURE SUPERCONDUCTORS
Authors: LI TAO
Published: July 2002

A model with interlayer pairing is proposed to explain the sinusoidal modulation of the resonant neutron scattering in high temperature superconductors. It is found that the interlayer pairing has s-wave symmetry in the CuO 2 plane and has comparable magnitude with the d-wave intralayer pairing. It is also found that the interlayer pairing mainly affects momentum close to the hot spots on the Fermi surface while its effect on the gap nodes is negligible. It is pointed out that these characteristics of the interlayer pairing can be understood in a model in which the superconducting pairing originates from the exchange of the antiferromagnetic spin fluctuation.
FERROMAGNETIC AND MOTT TRANSITIONS MODULATED BY VARYING FRACTAL DIMENSIONS IN FRACTAL–SHAPED NANOSTRUCTURES
Authors: UGAJIN R. , HIRATA S. , MORI Y.
Published: July 2002

The ferromagnetic transition in a fractal-shaped structure is analyzed using standard Monte Carlo simulations of discrete spin models. Mott transition of half-filled electrons in a fractal-shaped structure is investigated using Green's functions for a single-band Hubbard model. Our fractal-shaped structure is generated using the dielectric-breakdown model in a three-dimensional lattice, enabling the fractal dimensions to be reduced from three to two. The critical temperature of the ferromagnetic transition and the critical strength of the electron–electron interaction in the Mott transition are dependent on the fractal dimensions, thus the critical values of these phase transitions can be modulated by varying fractal dimensions.
Preparation and excitonic properties of high quality organic-inorganic nanocomposite CdSe nanocrystals
Authors: Hashizume Kenichi , Suzuki Hitoshi , Vacha Martin , Tani Toshiro
Published: July 2002

TOPO (trioctyl phosphine oxide) capped-CdSe nanocrystals were prepared chemically by injecting organometallic reagents into a hot coordinating solvent over a range of optical absorption peaks of 482 ~580 nm . For limited size range of nanocrystals, we have succeeded to synthesize high quality nanocrystals which show fairly sharp excitonic spectral features, by controlling the particle size with the concentration of precursors. Overcoating of ZnS following the synthesis of CdSe nanocrystals have lead to a large enhancement of the fluorescence intensity (quantumefficiency).
LOCAL MORPHOLOGY AND SUB-WAVELENGTH REGION SPECTROSCOPY OF MOLECULAR J-AGGREGATES: ONSET OF EXCITON-POLARITON STATES IN INDIVIDUAL AGGREGATE FIBERS
Authors: VACHA MARTIN , TAKEI SHOJI , HASHIZUME KEN-ICHI , TANI TOSHIRO
Published: July 2002

We present results on reflection microscopy and local spectroscopy of J-aggregates of pseudoisocyanine dyes in a thin film polymer matrix. Local reflectance spectra reveal a wide distribution of optical properties within different locations of one sample. The spectral lineshapes and absolute reflectivities are suggested to originate from varying strength of exciton-photon interaction. Polarization dependence measurements of local reflectivities at different wavelengths provide orientations of the excitonic transition dipole moments with respect to the orientation of the aggregate fibers.
SEQUENCE DESIGN AND FOLDING DYNAMICS OF LATTICE PROTEIN-LIKE MODELS
Authors: QIN MENG , WANG JUN , LI TANPING , WANG WEI
Published: July 2002

A sequence design method based on maximizing the thermodynamic occupying probability of the target structure is investigated. Some model-protein sequences are designed using the occupying-probability-maximized procedure on a 3×3×3 lattice. The thermodynamic and dynamic features of these sequences show their great improvement comparing with those of the sequences designed by an energy-minimized method. A better foldability is achieved for the occupying-probability-maximized sequences. These results suggest that the native occupying probability rather than the energy would be a better judgment for protein-like models.
SPECTROSCOPIC FEATURES DUE TO Ni-RELATED DEFECTS IN HPHT SYNTHETIC DIAMONDS
Authors: YELISSEYEV A. , NADOLINNY V. , FEIGELSON B. , BABICH YU
Published: July 2002

Investigation of visible light excited photoluminescence (PL) in HPHT synthetic diamonds, grown in the Ni-containing melt, revealed a variety of new systems. The PL excitation spectra were recorded for the most intense systems and position of zero-phonon lines and energies of participating phonons were determined. Analysis of PL versus annealing temperature T and ESR data allowed one to establish a sequence of nickel defect transformations as T increases. Only PL systems related to complicated nickel-nitrogen complexes with number of nitrogen atoms n ≥ 2 were found in natural diamonds.
SILICON NITRIDE THIN FILMS PACKAGING FOR FLEXIBLE ORGANIC LIGHT EMITTING DEVICES
Authors: FENG TAO , WANG XI , ZHANG FU MIN , ZOU SHI CHANG , HUANG WEI DONG , WANG XU HONG , LUO LE , XU LI QIANG , STUBHAN FRANK , LEE SHUIT TONG
Published: July 2002

We present a simple thin film encapsulation technique for organic light emitting devices (OLEDS), for use in flexible flat panel displays (FPDs). We systematically studied the moisture-resistant properties of silicon nitride thin films prepared by plasma-enhanced chemical vapor deposition (PECVD) and found that silicon nitride thin films have a low water vapor permeation (WVP) rate even deposited at low substrate temperature (20°C). Then OLEDs prototypes were successfully packaged by depositing silicon nitride thin films on them. Based on the analysis of the degradation of the OLEDs, we found the lifetime of the encapsulated devices was increased by more than two orders of magnitude over that of the unencapsulated ones. Our results demonstrated the feasibility of thin film packaging for OLEDs and the possibility to realize the flexible FPDs.
CHARGE-SPIN FREEZING AND FINITE SIZE SCALING IN YBa2Cu3O6+x
Authors: SANNA S. , MANCA P. , DE RENZI R. , ALLODI G.
Published: July 2002

The charge and spin freezing phenomena in high T c YBa 2 Cu 3 O 6+x superconductor is investigated in the low doping region (0<x<0.4) by the zero-field muon spin relaxation (ZF-μSR) technique. For x>0.2, the observed spin freezing is correlated to the charge freezing of the holes in the Cu(2)O2 planes. The data may be fitted to a model of size-dependent reduction of the staggered magnetization implied in a stripe scenario. The hole concentration dependence of these freezing phenomena is mapped onto the phase diagram of YBa 2 Cu 3 O 6+x.
PHONON ANOMALY IN RAMAN ACTIVE PHONONS OF CUPRATES IN NORMAL STATE
Authors: PANDA B. N. , ROUT G. C.
Published: July 2002

We present here a microscopic theory to explain phonon anomaly in Raman active phonons of the cuprates R 2-x M x CuO 4 in normal state. We used electronic Hamiltonion of Fulde in presence of antiferromagnetism. We incorporated phonon interaction to the hybridisation between the conduction electrons of the system and the f-electrons. The spectral density is calculated by the Green fuction technique of Zubarev type at zero wave vector and low temperature limit. Temperature dependence of Raman active phonon frequencies are studied numerically to discern phonon anomalies by varying model parameters like position of f-level (∊f), the effective electron–phonon coupling strength (g), the staggered magnetic field (h) and the hybridisation parameter (V). The phonon anomalies are explained on the basis of softening, hardening and temperature dependence of different Raman modes.
Interplay Between as Grown Defects and Heavy Ion Induced Defects in YBCO Films
Authors: Crescio E. , Gerbaldo R. , Ghigo G. , Gozzelino L. , Camerlingo C. , Monaco A. , Nappi C. , Cuttone G. , Rovelli A.
Published: July 2002

The dominating pinning mechanism in YBa 2 Cu 3 O 7-x thin film has been investigated by means of resistivity and ac susceptibility measurements and by structural characterizations. The aim of the work is to determine optimal pinning conditions in order to prevent the field-induced drop of the critical current density. The Clem and Sanchez model is used to extract critical current values from the susceptibility data. In this framework, the role of columnar-like defects is extensively studied. The formation of columnar pins was promoted by a suitable modification in the preparation process. In addition, columnar tracks of different density were induced by Au-ion irradiation. Analysis of the critical current dependence on the magnetic field reveals that linearly-correlated defects are effective in improving the vortex lattice stability in "matching regions" of field and temperature.
THE STUDY ON THE SPIN GAP PHENOMENON IN OXYGEN DEFICIENT YBa2Cu3O6+δ AND Ca-DOPED Y1-xCaxBa2Cu3O6+δ SUPERCONDUCTORS
Authors: SHEN L. J. , LAM C. C. , JIN X. , LAM H. S. , LI S. H.
Published: July 2002

The understanding of the spin gap phenomenon in the normal state of the high temperature superconductors can provide the mechanism of the high temperature superconductivity. A specific function of thermal excitation for quasiparticles was introduced based on the experimental relationship between resistivity and temperature. This specific function describes the deviation in resistivity from the T-linear relationship w.r.t. the normal state of the high temperature superconductors. With this function, the spin gap is naturally introduced. Our experimental results indicate that the spin gap behavior is closely related not only to the oxygen deficiency but also to the structural change in the a–b plane. Furthermore, we found that the crossover from anomalous metallic state to spin gap state takes place within a temperature range T S <T<T*, which depends on the oxygen content and the Ca-doping level. Pressure effects on the spin gap phenomenon in bulk samples of oxygen-deficient YBa 2 Cu 3 O 6+δ and Ca-doped Y 1-x Ca x Ba 2 Cu 3 O 6+δ were also investigated. Under high hydrostatic pressure the spin gap behavior is also severely influenced by the contraction of the a–b plane due to the pressure.
TOPOLOGICAL ASPECTS OF HIGH-Tc SUPERCONDUCTIVITY, FRACTIONAL QUANTUM HALL EFFECT AND BERRY PHASE
Authors: BASU B. , PAL D. , BANDYOPADHYAY P.
Published: July 2002

We have analysed here the equivalence of RVB states with ν=1/2 FQH states in terms of the Berry Phase which is associated with the chiral anomaly in 3+1 dimensions. It is observed that the three-dimensional spinons and holons are chracterised by the non-Abelian Berry phase and these reduce to 1/2 fractional statistics when the motion is confined to the equatorial planes. The topological mechanism of superconductivity is analogous to the topological aspects of fractional quantum Hall effect with ν=1/2.
CHARGE CARRIER MASS IN HIGH Tc SUPERCONDUCTORS
Authors: ZOLI MARCO
Published: July 2002

The theory of polarons has experienced a surge of activity in the last years partly due to the possible role of polaronic quasiparticles in high Tc superconductors. This numerical study of the Holstein model shows that the polaronic effective masses become essentially dimension independent and of order ≃10–50 times the electron mass at sufficiently strong intermolecular coupling forces. Such values (which are much lower than those obtained by traditional small polaron theory) would erase one the serious objections against a (bi)polaronic picture for high Tc superconductors.
GROWTH KINETICS OF A NONEQUILIBRIUM ISING MODEL
Authors: SOUKOULIS C. M. , TRINGIDES M. C. , VELGAKIS M. J.
Published: July 2002

The growth kinetics of a system with spin-exchange dynamics has been investigated by means of computer simulations. These systems are used to simulate diffusive processes and kinetic phenomena far away from equilibrium. As a measure of growth we have studied the mean square displacement  of tagged particles. It is found that t1-n follows a sublinear time dependence, which is explained in terms of the changes of the distribution of atoms between sites within the ordered region and sites of the domain boundaries. The time-dependence of the diffusion coefficient has been derived. The analogies to the relaxation in disordered systems, such as in a:Si–H and in O/W(110), is discussed.
VORTEX POTENTIAL BARRIERS IN THE GRANULAR SUPERCONDUCTORS
Authors: BELEVTSOV LEONID V.
Published: July 2002

The grain-boundary effects the potential barriers for Abrikosov vortex penetration into polycrystalline superconductors are investigated using a model in which the vortex, the grain and the grain boundaries are treated on equal basis. It is shown that the Bean–Livingston surface barrier have some substantial features near the grain boundaries for weak coupling between the grains. The potential barriers for magnetic vortex penetration into a grain from Josephson junction is an order to value of the pinning one in these superconducting materials.
THE HOT CARRIER TEMPERATURE IN THE ANALYSIS OF THE FREE TO ACCEPTOR PHOTOLUMINESCENCE TRANSITION
Authors: Fonthal G. , de los Rios M. , Quintero J. , Piraquive N. , Ariza-Calderón H.
Published: July 2002

We analyzed the free to acceptor (e-A) photoluminescence transition on a GaAs:Ge sample using the hot carrier temperature and the Kane's DOS. This latter temperature was calculated by the spectra largest energy tail. While the lattice temperature was put in the e-A Eagles' shape equation, the fitting was poor but if the modified line was put into the equation, the fitting was better. So, the ionization impurity energy, the band gap, the Fermi level and the band tail can be measured with a better precision than the measurements traditionally made with this method, Additional information about phonons participant can be obtained. In conclusion, the hot carrier temperature and the density of states due to the impurity concentration should be used in the e-A transition photoluminescence analysis.
ON STRONG AND WEAK CHAOTIC PARTIAL SYNCHRONIZATION
Authors: MAISTRENKO Yu. , POPOVYCH O. , HASLER M.
Published: July 2002

We study coupled nonlinear dynamical systems with chaotic behavior in the case when two or more (but not all) state variables synchronize, i.e. converge to each other asymptotically in time. It is shown that for symmetrical systems, such partial chaotic synchronization is usually only weak, whereas with nonsymmetrical coupling it can be strong in large parameter ranges. These facts are illustrated with systems of three coupled one-dimensional maps, for which a rich variety of different "partial chaotic synchronizing" phenomena takes place.
TEMPORAL EVOLUTION OF NONLINEAR DYNAMICS IN VENTRICULAR ARRHYTHMIA
Authors: SMALL MICHAEL , YU DEJIN , HARRISON ROBERT G. , CLAYTON RICHARD , EFTESTØL TRYGVE , SUNDE KJETIL , STEEN PETTER ANDREAS
Published: July 2002

Ventricular fibrillation (VF) is a rapidly lethal cardiac arrhythmia and one of the leading causes of sudden death in many industrialized nations. VF appears at random, but is produced by a spatially extended excitable system. We generated VF-like "pseudo-ECG" signals from a numerical caricature of cardiac tissue of 100 × 100 × 50 elements. The VF-like "pseudo-ECG" signals represent the propagation and break-up of an excitation scroll wave under FitzHugh–Nagumo dynamics.

We use surrogate data and correlation dimension techniques to show that the dynamics observed in these computational simulations is consistent with the evolution of spontaneous VF in humans. Furthermore, we apply a novel adaptation of the traditional first return map technique to show that scroll wave break-up may be represented by a characteristic structural transition in the first return plot. The patterns and features identified by the first return mapping technique are found to be independent of the observation function and location. These methods offer insight into the evolution of VF and hint at potential new methods for diagnosis and analysis of this rapidly lethal condition.
TRANSITION TO SPATIOTEMPORALLY IRREGULAR STATES IN A SINGLE-MIRROR FEEDBACK SYSTEM
Authors: AUMANN A. , ACKEMANN T. , WESTHOFF E. GROßE , LANGE W.
Published: July 2002

In an optical pattern forming system (sodium vapor with feedback from a single plane mirror) different scenarios for the destabilization of stationary patterns in favor of states that are irregular in space and in time are studied experimentally and numerically. Secondary bifurcations from hexagons to squares occur via a time dependent state whose origin is traced back to noise-driven hexagon–square competition in a region of bistability between the two states. Squares can display a transition to another state with irregular — probably intrinsic — time dependence in which a whole band of wave vectors is excited. In real space pentagons are a prominent feature.
ON ADAPTING TEST FUNCTION METHODS FOR FAST DETECTION OF FOLD BIFURCATIONS IN POWER SYSTEMS
Authors: HUSSEIN ANWAR , CHEN KE , WAN HAIBIN
Published: July 2002

Test function methods are well known techniques to monitor a continuation method to determine if a fold (saddle-point) bifurcation point has been reached. Two such test functions due to [Abbott, 1978] and [Seydel, 1979] are considered here in a unified framework and their connection to the tangent vector index method from power system community is shown. The challenge in power systems applications is to adapt a test function method to produce a performance index that approximates the fold parameter λ* without the need of following the solution path to the fold point (x*, λ*). We demonstrate that the tangent vector index method, due to its connection with the mathematically justifiable test function methods, can lead to a useful performance index.
GEOMETRY AND ORDER OF CHAOS
Authors: AWREJCEWICZ J. , LAMARQUE C.-H. , BROUGHAN K. A.
Published: July 2002

In the beginning a brief introduction to a symmetry increasing as well as to quantified geometrical structures of chaotic attractors have been given. Then, the research is focused on the Chossat–Golubitsky map. A saddle-node bifurcation on the boundary of the umbrella shape set of saddles, crises of two peculiar structures of saddles and an extremely high order of infinitely many flip and regular saddle orbits have been reported. The geometrical properties of hyperchaos and its relation to the Kakeya–Besicovitch and the Apollonian packing have been illustrated and discussed. A fractal organization of the successive periodic saddles and fractal normal forms have been described.
HIGHER-ORDER AVERAGING FOR PERIODICALLY FORCED WEAKLY NONLINEAR SYSTEMS
Authors: YAGASAKI K. , ICHIKAWA T.
Published: July 2002

We consider periodically forced, weakly nonlinear systems and perform higher-order averaging analyses. Especially, we describe an algorithm for computing the higher-order averaging terms by the Lie transforms. The necessary computations can be implemented on a developed package of the computer algebra system, Mathematica. We also give three examples for two Duffing-type oscillators with the primary or ultra-subharmonic resonance and a two-degree-of-freedom system with internal and external resonances, to demonstrate our results.
EXPERIMENTAL STUDY OF IMPULSIVE SYNCHRONIZATION OF CHAOTIC AND HYPERCHAOTIC CIRCUITS
Authors: ITOH MAKOTO , YANG TAO , CHUA LEON O.
Published: July 2002

In this paper, experimental results on impulsive synchronization of two kinds of chaotic circuits; namely, Chua's oscillator and a hyperchaotic circuit, are presented. To impulsively synchronize two Chua's oscillators, synchronization impulses sampled from one state variable of the driving circuit are transmitted to the driven circuit. To impulsively synchronize two hyperchaotic circuits, synchronizing impulses sampled from two signals of the driving circuit are sent to the driven circuit. Our experimental results show that the accuracy of impulsive synchronization depends on both the period and the width of the impulse. The ratio between the impulse width and impulse period for "almost-identical" synchronization increases as the impulse period increases. The robustness of impulsive synchronization to additive noise is also experimentally studied. For sufficiently short impulse periods, no significant differences are observed between impulsive and continuous synchronizations. The performance of chaotic spread spectrum communication systems based on impulsive synchronization is also studied experimentally.
COFINITENESS OF THE SET OF PERIODS FOR TOTALLY TRANSITIVE TREE MAPS
Authors: ALSEDÀ LL. , DEL RÍO M. A. , RODRÍGUEZ J. A.
Published: July 2002

The aim of this paper is to show that the cofiniteness of the set of periods characterizes the totally transitive maps among transitive tree maps.
SELF-EXPLANATORY COMPONENTS: A NEW PROGRAMMING PARADIGM
Authors: MIRENKOV NIKOLAY , VAZHENIN ALEXANDER , YOSHIOKA RENTARO , EBIHARA TSUKASA , HIROTOMI TETSUYA , MIRENKOVA TATIANA
Published: July 2002

A new multimedia programming paradigm is presented. It is based on a system of micro- and macro-icons (composite pictures) representing self-explanatory software components in a "film" format. A film is a series of color stills supported, if necessary, by text and sound. Each still is to represent a view of objects or processes. Each film is to represent a multiple view (an extended set of dynamic and/or static features) of objects or processes. A self-explanatory film means that the associated stills are organized and presented in such a way that the semantic richness of a computational scheme is clearly brought out. Icons and films are acquired in a net-accessible database. The user should not study them in advance. The film management system provides simple access to database items and modes to manipulate films. In this paper we explain where the database items are taken from and how the self-explanatory features of items are reached. We also describe how these items can be used for multimedia representation of methods and data and for programming users' algorithmic ideas. In addition, some technical details related to the film management system, rendering engines used for displaying various features of the software components, and the icon language are presented. Special attention is paid to how computational formulas can be attached to a film.
ON THE FREIHEITSSATZ IN CERTAIN ONE-RELATOR FREE PRODUCTS I
Authors: SHWARTZ ROBERT
Published: July 2002

We study one relator free products in which one of the factors is a cyclic group and the relator has free-product length 4. We find conditions for such presentations to have a Freiheitssatz and classify all non-aspherical presentations under certain conditions.
PROFINITE SEMIGROUPS, VARIETIES, EXPANSIONS AND THE STRUCTURE OF RELATIVELY FREE PROFINITE SEMIGROUPS
Authors: RHODES JOHN , STEINBERG BENJAMIN
Published: July 2002

Building on the now generally accepted thesis that profinite semigroups are important to the study of finite semigroups, this paper proposes to apply various of the techniques, already used in studying algebraic semigroups, to profinite semigroups. The goal in mind is to understand free profinite semigroups on a finite set. To do this we define profinite varieties. We then introduce expansions of profinite semigroups, giving examples of several classes of such expansions. These expansions will then be useful in studying various structural properties of relatively free profinite semigroups, since these semigroups will be fixed points of certain expansions. This study also requires a look at profinite categories, semigroupoids, and Cayley graphs, all of which we handle in turn.

We also study the structure of the minimal ideal of relatively free profinite semigroups showing, in particular, that the minimal ideal of the free profinite semigroup on a finite set with more than two generators is not a relatively free profinite completely simple semigroup, as well as some generalizations to related pseudovarieties.
MODEL SELECTION VIA META-LEARNING: A COMPARATIVE STUDY
Authors: ALEXANDROS KALOUSIS , MELANIE HILARIO
Published: July 2002

The selection of an appropriate inducer is crucial for performing effective classification. In previous work we presented a system called NOEMON which relied on a mapping between dataset characteristics and inducer performance to propose inducers for specific datasets. Instance-based learning was used to create that mapping. Here we explore the use of decision trees inducers as the inducers on the meta-learning level. We believe that they posses a set of properties that match the properties of the meta-learning problem that we are trying to solve. The results show that the performance of the system is indeed improved with the use of the decision tree learners.