bluuebunny/crossref_metadata_2025 huggingface dataset:
Acid-Base Properties of Substituted Naphthoic Acids in Nonaqueous Media
Authors: Pařík Patrik , Ludwig Miroslav
Published: July 2002

Thirteen substituted 1-naphthoic acids have been prepared and their dissociation constants, along with those of twenty-five substituted 2-naphthoic acids, have been measured potentiometrically in methanol, N,N-dimethylformamide, pyridine, and acetonitrile. The pKHA values obtained have been treated by linear regression using four sets of substituent constants. The experimental data have also been interpreted by statistical methods using latent variables. The first latent variable calculated by these methods can be used as a new set of substituent constants for describing substituent effects in naphthalene skeleton.
Thermodynamic Study of Na2Cr2O7(aq) at 25 °C
Authors: Christov Christomir , Velikova Snejana , Ivanova Kalina , Tanev Stefan
Published: July 2002

The isopiestic method was used to determine osmotic coefficients of binary Na2Cr2O7(aq) solutions of concentrations 0.6777-3.8792 mol kg-1 at 25 °C. The concentration of a saturated binary solution Na2Cr2O7(aq) at 25 °C was determined. The Pitzer ion-interaction model has been used for thermodynamic analysis of the results obtained. Optimum values of the binary parameters of interionic interaction have been calculated and important thermodynamic characteristics of Na2Cr2O7·2 H2O determined.
A Novel Heterooctametallic Metallacarborane Tetramer
Authors: Parker Keith G. , Russell J. Monte , Sabat Michal , Grimes Russell N.
Published: July 2002

The synthesis and X-ray crystal structure determination of [(2,3-Et2C2B4H4)Co(2,3-Et2C2B3H3-5-Bu)Ru]4 (3) are reported. Complex 3 was obtained serendipitously in low yield from a reaction of [(η4-C8H12)Ru(MeCN)4][PF6]2 with the (Et2C2B4H4)Co(Et2C2B3H3Bu)2- anion in THF solution at room temperature. The molecular geometry of 3, isolated as a yellow-orange crystalline solid, is without precedent in boron cluster chemistry and consists of an array of four (Et2C2B4H4)Co(Et2C2B3H3Bu)Ru units linked via intercluster Ru-B covalent bonds. Each cluster moiety contains a double-decker (C2B4)Co(C2B3) sandwich with an exo-polyhedral ruthenium atom occupying a "wedging" position in which it is bound to the C2B3 and the C2B4 ligands as well as to a neighboring sandwich unit.
Novel Addition and [3+2] Cycloaddition Reactions of Stannyl- and Silyl-ortho-carboranes to Carbonyl Compounds
Authors: Nakamura Hiroyuki , Yamamoto Yoshinori
Published: July 2002

Stannyl- and silyl-ortho-carboranes serve as an ortho-carborane carbanion equivalents in the addition reaction to aldehydes. The reaction of (tributylstannyl)-ortho-carborane 2 with aldehydes 4 in the presence of palladium(0) catalysts gave the corresponding (ortho-carboranyl) carbinols 5 in good to high yields. The reaction of (trimethylsilyl)-ortho-carborane 3 with aldehydes 4 in the presence of tetrabutylammonium fluoride (TBAF) gave the corresponding (ortho-carboranyl) carbinols 5 in high yields. Furthermore, (trimethylsilyl)-ortho-carborane 3 underwent a facile [3+2] annulation reaction with various α,β-unsaturated enals and enones in the presence of tetrabutylammonium fluoride, giving the corresponding five-membered carboracyclic products 14 in good to high yields.
Topological Correspondence Between Crystal Structure of 2,4,6-Trimethylbenzene-1,3,5-tris(methanaminium) 2,4,6-Trimethylbenzene-1,3,5-triacetate and Cesium Chloride
Authors: Podlaha Jaroslav , Císařová Ivana , Alexander Daniel , Holý Petr , Kraus Tomáš , Závada Jiří
Published: July 2002

Solid-state self-assembly of 2,4,6-trimethylbenzene-1,3,5-tris(methanaminium) 2,4,6-trimethylbenzene-1,3,5-triacetate is mediated by hydrogen bonding. It gives rise to three-dimensional network of hydrogen bonds in which each trication is coordinated with eight trianions and vice versa. The resulting crystal structure topologically corresponds to the simple inorganic cesium chloride type.
Sweet’s syndrome in association with Crohn’s disease
Authors: Vaz A , Kramer K , Kalish R A
Published: July 2002

A case of Sweet’s syndrome in association with Crohn’s disease in a young woman is reported. Sweet’s syndrome is a rare extraintestinal manifestation of Crohn’s disease and ulcerative colitis.
Misinterpretation of the chest x ray as a factor in the delayed diagnosis of lung cancer
Authors: Turkington P M , Kennan N , Greenstone M A
Published: July 2002

All patients in 1997 with a histologically proved diagnosis of lung cancer in Castle Hill Hospital in whom a full set of case notes and x rays could be retrieved were studied. All previous chest x rays were reviewed by a consultant chest physician and a radiologist, who were blinded to the eventual site of the lesion and the point at which a suspicious abnormality first appeared. Case notes were inspected to clarify the cause of any error. Fifty eight patients were eligible, 28 of whom had previous chest x rays. Of these 14 were found to be abnormal. A significant difference (p=0.007) in time from diagnosis to death was found between those with a missed abnormality, median (interquartile range, IQR) 105 (55–219) days and those with no previous abnormality, median (IQR) 260 (137–512) days. In the 14 in whom the diagnosis was missed the median (IQR) delay from first abnormal chest x ray to the eventual diagnostic x ray was 101 (48–339) days. A significant difference (p=0.001) was also found between the median (IQR) time from first abnormal chest x ray to start of treatment between those with missed abnormalities, 155 (115–376) days, and those with no previous abnormality on chest x ray, 51 (44–77) days. The most common reason (47%) for the diagnosis to be missed was failure of the radiologist reporting the x ray to recognise the abnormality.

It is not unusual to find previous significant radiological abnormalities in patients in whom a diagnosis of lung cancer is later made. This leads to a diagnostic delay which has a significant effect on time to initiation of treatment and palliation of symptoms, although not necessarily to eventual outcome.
Osteoporosis prophylaxis during corticosteroid treatment: failure to prescribe
Authors: Hart S R , Green B
Published: July 2002

Aims

To investigate prescribing patterns to prevent steroid induced osteoporosis. To compare prophylactic prescribing with National Osteoporosis Society (NOS) guidelines.

Method

All patients (n=92) taking oral corticosteroids admitted to general medical wards at a district general hospital were prospectively investigated over a nine month period.

Results

Variations from recommended management were revealed. Altogether 64.7% of all inpatients who qualified for prophylaxis for steroid induced osteoporosis were not provided with any suitable agent. It was also found that 21.6% of those who qualified for treatment received a bisphosphonate, the only treatment currently licensed for preventing steroid induced osteoporosis. Of those prescribed prophylactic treatment, a bisphosphonate was selected for 39.3%, hormone replacement therapy was given to 25.0%, and 35.7% received treatment that is not recommended in NOS guidelines.

Conclusion

This study revealed substantial variations from NOS guidelines. It is suggested that osteoporosis prophylaxis during steroid treatment is promoted by local hospital guidelines, hospital and community pharmacists, audit, and general practitioners.
Repetitive DNAs of wild emmer wheat (Triticum dicoccoides) and their relation to S-genome species: molecular cytogenetic analysis
Authors: Raskina Olga , Belyayev Alexander , Nevo Eviatar
Published: July 2002

We have analyzed the chromosomal GISH molecular banding patterns of three populations of the wild allopolyploid wheat Triticum dicoccoides in an attempt to unravel the evolutionary relationships between highly repetitive DNA fractions of T. dicoccoides and proposed diploid progenitors of the B genome. Aegilops speltoides showed almost complete affinity of its repetitive DNA to C-heterochromatin of T. dicoccoides, whereas other S-genome species demonstrated relatedness only to distal heterochromatin. This substantiates the priority of Ae. speltoides as the most similar to the wheat B-genome donor in comparison with other Sitopsis species. Using molecular banding technique with DNA of different Aegilops species as a probe permits tracing of the origin of each heterochromatin cluster. Molecular banding analysis reveals polymorphism between three wild emmer wheat populations. Comparison of molecular banding patterns with chromosomal distribution of the Ty1-copia retrotransposons, which constitute a large share of T. dicoccoides genome, makes it possible to propose that the activity of transposable elements may lie in the background of observed intraspecific polymorphism.Key words: Aegilops, evolution, heterochromatin, Ty1-copia retrotransposons, Triticum.
Experimental basis for the effective length factors of steel solid round cross-braced diagonals in CSA Standard S37-01
Authors: Ding Yongcong , Jaboo Kalid S , Sun Yean , Madugula Murty K.S
Published: July 2002

The effective length factors for steel solid round diagonals in all-welded communication towers are investigated in this paper to provide experimental basis for the relevant clauses in CSA Standard S37-01. The results of a total of 31 all-welded lattice tower specimens with three types of cross-braced diagonals are presented. The failure loads for these members were determined from the maximum axial strains measured during the tests. The effective length factors were then back-calculated from the experimental failure loads using the compressive resistance formulas. The test results showed that even the significantly lower effective length factors specified in CSA S37-01, compared to CSA S37-94, are still conservative.Key words: all-welded towers, communication towers, cross-bracing, effective length factors, solid round steel diagonals.
Application of genetic algorithms to construction scheduling with or without resource constraints
Authors: Toklu Y Cengiz
Published: July 2002

The difficulties encountered in scheduling construction projects with resource constraints are highlighted by means of a simplified bridge construction problem. A genetic algorithm applicable to projects with or without resource constraints is described. In this application, chromosomes are formed by genes consisting of the start days of the activities. This choice necessitated introducing two mathematical operators (datum operator and left compression operator) and emphasizing one genetic operator (fine mutation operator). A generalized evaluation of the fitness function is conducted. The algorithm is applied to the example problem. The results and the effects of some of the parameters are discussed.Key words: scheduling, genetic algorithms, construction management, computer application.
Electron-spin conservation and methyl-substitution effects on bonds in closed- and open-shell systems  A G3 ab initio study of small boron-containing molecules and radicals
Authors: Poon Clement , Mayer Paul M
Published: July 2002

High level ab initio molecular orbital theory calculations have been used to study the geometries and thermochemistry of molecules and free radicals substituted by BH2, BHCH3, and B(CH3)2. The heats of formation and RR'BX bond strengths (RR' = H, H; H, CH3; CH3, CH3 and X = CH3, NH2, OH, F, SiH3, PH2, SH, and Cl) together with those for the open-shell systems RR'BY· (RR' = H, H; H, CH3; CH3, CH3 and Y = CH2, NH, O, SiH2, PH, and S) have been calculated at the G3 level of theory. The trends observed for the homolytic bond strengths in the closed-shell systems are those expected from electronegativity arguments, i.e., as the difference in electronegativity between the two atoms in the BX bond increases, the bond strength increases. Methyl substitution on B in the closed- and open-shell species increases the ionic contribution to the bond thereby decreasing the bond strength. The lowest possible homolytic dissociation energy for the free radicals RR'BY· is lower than those of their closed-shell counterparts, yet the BY· bonds are shorter. This is due to the demands of spin conservation in the dissociation of the radicals favouring the formation of higher energy products.Key words: ab initio calculations, bond dissociation energy, organoboron compounds, thermochemistry.
A theoretical study of the mechanism of 1,2-migrations in methoxysiloxycarbene
Authors: Loncke Paul G , Gadosy Timothy A , Peslherbe Gilles H
Published: July 2002

Intramolecular rearrangements of methoxysiloxycarbene (CH3OCOSiH3) have been investigated by means of ab initio molecular orbital theory and hybrid density functional theory calculations. Particular attention was paid to 1,2-silyl migration from oxygen to the carbene carbon, and to the analogous 1,2-methyl migration for comparison. A combination of frontier molecular orbital (FMO) theory, natural bond orbital (NBO) analysis, and the theory of atoms in molecules (AIM) were used to shed light on the mechanistic details of these rearrangements. The present analyses clearly indicate that 1,2-silyl migration involves nucleophilic attack by the carbene lone pair at silicon, whereas 1,2-methyl migration seems to involve an anion-like shift of the methyl group from oxygen to the "vacant" carbene p-orbital. Finally, based on the computed relative Gibbs free energy barriers, it is apparent that 1,2-silyl migration is much more favorable than 1,2-methyl migration, in keeping with experimental observations.Key words: carbenes, oxycarbenes, intramolecular rearrangements, 1,2-migrations, quantum chemistry, theory of atoms in molecules, natural bond orbital analysis
Nitrogen storage and availability during stand development in a New Zealand Nothofagus forest
Authors: Clinton P W , Allen R B , Davis M R
Published: July 2002

Stemwood production, N pools, and N availability were determined in even-aged (10, 25, 120, and >150-year-old) stands of a monospecific mountain beech (Nothofagus solandri var. cliffortioides (Hook. f.) Poole) forest in New Zealand recovering from catastrophic canopy disturbance brought about by windthrow. Nitrogen was redistributed among stemwood biomass, coarse woody debris (CWD), the forest floor, and mineral soil following disturbance. The quantity of N in stemwood biomass increased from less than 1 kg/ha in seedling stands (10 years old) to ca. 500 kg/ha in pole stands (120 years old), but decreased in mature stands (>150 years old). In contrast, the quantity of N stored in CWD declined rapidly with stand development. Although the mass of N stored in the forest floor was greatest in the pole stands and least in the mature stands, N availability in the forest floor did not vary greatly with stand development. The mass of N in the mineral soil (0100 mm depth) was also similar for all stands. Foliar N concentrations, net N mineralization, and mineralizable N in the mineral soil (0100 mm depth) showed similar patterns with stage of stand development, and indicated that N availability was greater in sapling (25 years old) and mature stands than in seedling and pole stands. We conclude that declining productivity in older stands is associated more with reductions in cation availability, especially calcium, than N availability.
CATEGORICAL MODEL CONSTRUCTION FOR PROVING SYNTACTIC PROPERTIES
Authors: SAKURAI TAKAFUMI
Published: July 2002

It is observed that the proof of strong normalizability of typed terms of typed λ-calculus looks like the process of the model construction. The observation is clarified by the works of Hyland and Ong [8], Altenkirch [2], Stefanova and Geuvers [15], and so on. The model of Hyland and Ong is based on PL-category [14] and the model of Altenkirch or Stefanova and Geuvers is a non-categorical model that is specially designed for this purpose. In this paper, we will construct yet another categorical model for the second order λ-calculus — a non-extensional PL-category. To demonstrate the significance of the non-extensional model, we will give a model in which we can carry out the proof of the uniqueness of the β-normal form. The non-extensionality comes from the use of semi-adjoint for interpretation of abstraction and application (uncurry).
HUYGENS' PRINCIPLE AND SEPARATION OF VARIABLES
Authors: BEREST YURI , WINTERNITZ PAVEL
Published: July 2002

We demonstrate a close relation between the algebraic structure of the (local) group of conformal transformations on a smooth Lorentzian manifold [Formula: see text] and the existence of nontrivial hierarchies of wave-type hyperbolic operators satisfying Huygens' principle on [Formula: see text]. The mechanism of such a relation is provided through a local separation of variables for linear second order partial differential operators with a metric principal symbol. The case of flat (Minkowski) spaces is studied in detail. As a result, some new nontrivial classes of Huygens operators are constructed. Their relation to the classical Hadamard conjecture and its modifications is discussed.
SYMMETRIES IN THEORY OF LOCAL OBSERVABLES AND THE CHOICE OF THE NET OF LOCAL ALGEBRAS
Authors: ARAKI HUZIHIRO
Published: July 2002

For a given net of algebras of local observables, satisfying standard assumptions, we propose the problem of classifying a net of subalgebras which provides the same physical consequences (possibly via Doplicher-Haag-Roberts sector theory) such as particle spectrum and scattering theory.

The notion of symmetry of the net of local algebras are introduced and its geometrical aspects are analyzed, with the conclusion that the net reproduces the geometry of supporting regions to some extent.

The internal symmetries provides a possible net of subalgebras, as is discussed by Doplicher, Haag and Roberts. We discuss other possibilities by generating subalgebras from a local observable.

Results and problems for the simple case of a neutral massive scalar free Held are summarized.
LOCALLY SMOOTH OPERATORS AND THE LIMITING ABSORPTION PRINCIPLE FOR N-BODY HAMILTONIANS
Authors: DE MONVEL-BERTHIER ANNE BOUTET , GEORGESCU VLADIMIR , MANTOIU MARIUS
Published: July 2002

We develop a variant of the (abstract) Mourre theory under very weak assumptions of regularity on the hamiltonian H with respect to the conjugate operator A. We find large classes of H-smooth operators and prove the limiting absorption principle in a class of (abstract) Besov spaces. As an example we extend the results of Agmon and Hörmander from the two-body to the N-body case.
Sparse Schrödinger Operators
Authors: Guille-Biel Claire
Published: July 2002

We study spectral properties of a family [Formula: see text], indexed by a non-negative integer p, of one-dimensional discrete operators associated to an ergodic dynamical system (T,X,ℬ,μ) and defined for u in ℓ2(ℤ) and n in ℤ by [Formula: see text], where Vx(n)=f(Tnx) and f is a real-valued measurable bounded map on X. In some particular cases, we prove that the nature of the spectrum does not change with p. Applications include some classes of random and quasi-periodic substitutional potentials.
Attractor for Dissipative Zakharov Equations in an Unbounded Domain
Authors: Li Yong-Sheng , Guo Bo-Ling
Published: July 2002

In this paper the authors consider the Cauchy problem of dissipative Zakharov equations in R and prove the existence of the maximal attractor.
Brownian Survival in a Clusterized Trapping Medium
Authors: Albeverio Sergio , Bogachev Leonid V.
Published: July 2002

The survival problem for a Brownian particle moving among random traps is considered in the case where the traps are correlated in a particular fashion being gathered in clusters. It is assumed that the clusters are statistically identical and independent of each other and are distributed in space according to a Poisson law. Mathematically, such a trapping medium is described via a Poisson cluster point process. We prove that the particle survival probability is increased at all times as compared to the case of noncorrelated (Poissonian) traps, which implies the slowdown of the trapping process. It is shown that this effect may be interpreted as the manifestation of the trap "attraction", thus supporting assertions on the qualitative influence of the trap "interaction" on the trapping rate claimed earlier in the physical literature. The long-time survival asymptotics (of Donsker–Varadhan type) is also derived. By way of appendix, FKG inequalities for certain functionals are proven and the limiting distribution for a Poisson cluster process, under clusters' scaling, is determined.
THE DOMINO EFFECT FOR MARKETS
Authors: SCHULZE CHRISTIAN
Published: July 2002

A generalization of the Cont–Bouchaud market model to three markets agrees with the correlations between New York, Tokyo, and Frankfurt as observed by Vandewalle et al.
CONSISTENT QUANTIZATION OF NONCOMMUTATIVE D-BRANE IN NON-CONSTANT B FIELD BACKGROUND
Authors: LEE JEN-CHI
Published: July 2002

We perform the consistent quantization of open string D-brane in non-constant NS–NS closed string B field background by directly imposing the worldsheet conformal symmetry. In addition to the previous noncommutative D-brane coordinates quantization with constant noncommutative parameter θ, we obtain a set of constraints on the B field which can be interpreted as a quantum consistent deformation of a curved noncommutative D-brane.
SELF-CONSISTENT RENORMALIZATION GROUP EQUATION
Authors: LIAO SEN-BEN
Published: July 2002

We propose a self-consistent renormalization group prescription for the scalar field theory. The formalism coincides with the local potential approximation in the sharp cutoff limit but differ with a smooth cutoff. The dependence of the critical exponent ν on the smoothness parameter and the field of expansion is explored. We employ an optimization scheme based on the minimum sensitivity principle to ensure the most rapid convergence of ν with the polynomial truncation level.
ON WILSONIAN FLOWS IN GAUGE THEORIES
Authors: PAWLOWSKI JAN M.
Published: July 2002

An Exact Renormalisation Group (ERG) approach to non-Abelian gauge theories is discussed. We focus on the derivation of universal beta-functions and the choice of the initial effective action, the latter being a key input in the approach. To that end we establish the map between Gell-Mann–Low scaling of the full theory and the scaling in an ERG approach. Then this map is used to derive the 2-loop β-function within a simple straightforward calculation. The implications for the choice of the initial effective action are discussed.
QUANTUM EQUIVALENCE OF SOME INTERACTING (2 + 1)-DIMENSIONAL FIELD THEORY
Authors: FLECK MARTIN
Published: July 2002

The embedding procedure of Batalin, Fradkin and Tyutin, which allows us to convert a second-class system into a first-class one, is employed to convert second-class interacting models. Two cases are considered. The first one, is the self-dual model minimally coupled to a Dirac fermion field. The other, the self-dual model minimally coupled to a charged scalar field. In both cases, they are found equivalent interacting Maxwell–Chern–Simons type field theories. These equivalences are pushed beyond the formal level, by analyzing some tree level probability amplitudes associated to them.
THE SEARCH FOR GRAVITATIONAL WAVES WITH LIGO: STATUS AND PLANS
Authors: SHAWHAN PETER S.
Published: July 2002

The Laser Interferometer Gravitational-Wave Observatory (LIGO) project has been designed to detect gravitional waves directly using large interferometers at two widely separated sites. Construction of the observatory facilities is now complete, and commissioning of the interferometers is well underway. Following a series of engineering runs, science running is scheduled to begin in 2002. A parallel effort is underway to develop improved detector to achieve dramatically greater sensitivity in the future.
TESTING FRONT-END ELECTRONICS FOR THE CDF SILICON TRACKER UPGRADE
Authors: VOLOBOUEV IGOR
Published: July 2002

The upgraded silicon tracker for the Collider Detector at Fermilab has 722,432 strips. These strips are instrumented with SVX3D ASICs fabricated in the Honeywell 0.8 μm radiation hard CMOS process. We describe test setup and procedures used to screen production chips and to ensure reliability of the silicon system front-end electronics.
TWO–LOOP EULER-HEISENBERG LAGRANGIANS AND BOREL ANALYSIS
Authors: DUNNE GERALD V. , SCHUBERT CHRISTIAN
Published: July 2002

We present a simple closed formula for the two-loop scalar QED Euler-Heisenberg Lagrangian in a Euclidean self-dual field. The use of Borel techniques for the construction of Euler-Heisenberg Lagrangians is shortly discussed.
SPATIAL ROTATION AND TIME-EVOLUTION OPERATOR OF TWO-LEVEL SYSTEMS
Authors: LI CHUN-FANG , ZHAO XIAN-GENG
Published: July 2002

All the six kinds of rotation approach with the same form to the evolution problem of arbitrarily time-dependent two-level system are investigated in this paper. A time-dependent two-level system can be viewed as a spin-1/2 system in a time-varying magnetic field. It is shown that for each kind of rotation approach, we can always find a rotating frame in which the direction of the effective magnetic field is fixed. This property reduces the problem of finding the time-evolution operator to the solution of a second-order differential equation. Applications are made to the J C model in quantum optics and the L and au–Zener model in resonance physics.
ELECTRON STRINGS IN OXIDES
Authors: KUSMARTSEV FEODOR V
Published: July 2002

We found that insulating and conducting electron strings may arise in oxide materials with not very wide bands, like HTSC, due to electron-phonon and electron-electron interactions including antiferromagnetic correlations. We estimate the string length and the number of particles self-trapped into a single string taking into account the typical parameters of cuprates, like La2CuO4. The conducting strings typically may have a small doping (n<0.3) and are created mostly due to the long-range electron-phonon interaction associated with ionic bonding of Oxides.
INTERFACIAL SUPER-ROUGHENING BY LINEAR GROWTH EQUATIONS
Authors: PANG NING-NING , TZENG WEN-JER
Published: July 2002

We give an extensive analytical study of a class of linear growth equations in 1+1 dimensions which describe certain interfacial super-roughening processes. With our calculation, we give a first rigorous analytical affirmation on the applicability of the anomalous dynamic scaling ansatz, which has been proposed to describe the dynamics of super-rough interfaces in finite systems. In addition, we explicitly evaluate not only the leading order but also all the sub-leading orders which dominate over the ordinary dynamic scaling term. Finally, we briefly discuss the influence of the macroscopic background formation on the interfacial anomalous roughening in super-rough growth processes.
EFFECT OF SURFACE ROUGHNESS ON THE ADHESIVE AND TRIBOLOGICAL CHARACTERISTICS OF DLC COATING PREPARED ON Co-Cr-Mo ALLOY
Authors: Sheeja D. , Tay B. K. , Lam H. M. , Ng S. K.
Published: July 2002

The Co-Cr-Mo alloy is extensively used for tribological applications, including orthopaedic components in total joint replacements. High quality diamond-like carbon (DLC) coatings on metal/alloy substrates are of great interest as they are able to protect them from severe wear and thus prolong the life span of the component. Since the roughness of the metal/alloy varies depending on the applications, a study has been carried out to investigate the effect of substrate surface roughness on the microstructure, sliding life, wear-resistance, coefficient of friction, adhension and hardness of DLC coatings prepared on Co-Cr-Mo alloy substrates under the same deposition condition.

The microstructure of the films studied using Raman spectroscopy suggests that the film prepared on a smoother surface contains slightly higher fraction of sp 3 bonded carbon atoms. The characterization using a pin-on-disk tribometer reveals that, the film prepared on the roughest sample (Ra ~ 0.06 μm) exhibits a very short life span of about 20 cycles compared to the film that is prepared on a relatively smoother surface (Ra ~ 0.02 μm), which exhibits a life span of about 340,000 cycles. In order to investigate the origin of this improved property of the DLC film on the smoother surface, adhesive strength and hardness of the films were studied by using a micro-scratch tester and a Nano-indenter, respectively. The results suggest that the film prepared on the smoother surface exhibits better adhesion (higher critical load) and relatively higher hardness.
Effects of Chance of Collision Among Particles on Electro-Rheological Response
Authors: Tanaka K. , Nakamura K. , Takada K. , Iwaki F. , Kubono A. , Akiyama R. , Kuramoto N.
Published: July 2002

The electro-rheological (ER) responses of suspensions with cation exchange resin particles and polyaniline particles were measured under different experimental conditions such as the strength of applied electric field, the viscosity of continuous phase, the shear rate, and the volume fraction of particles. The ER response became faster as the strength of applied electric field, the shear rate, and the volume fraction of particles increased while it became slower as the viscosity of continuous phase increased. These results were discussed in terms of the electrical and hydrodynamic interactions, as well as the chance of collision among particles.
Preparation and Property of Model Homogeneous ER Fluids Having Urethane Groups
Authors: Minagawa Keiji , Okamura Hirokazu , Masuda Seizo , Tanaka Masami , Gohko Naoto , Masubuchi Yuichi , Takimoto Jun-Ichi , Koyama Kiyohito , Uemura Takashi
Published: July 2002

Urethane modified polyether liquids composed of hard and soft segments exhibit either positive or negative ER effect depending on the structure. Here some model compounds of the urethane polymers were synthesized, and the influence of chemical structure, e.g. displacement of hard and soft segments and existence of branches, on the ER effect was studied. It was found that negative ER effect is enhanced by introducing a branched structure in the polyether main-chain or a hard segment at center of the linear polyether.
Dynamics of a Radial Electrorheological Clutch
Authors: Whittle M. , Atkin R. J. , Bullough W. A.
Published: July 2002

Time dependent solutions to the equations of motion for flow in an enclosed radial electro-rheological clutch are developed and discussed in relation to the speed of operation. The method follows a procedure previously developed for cylindrical clutch geometry but in this case analytical solutions are obtained. The fluid is treated as a homogeneous continuum obeying the Bingham plastic constitutive equation incorporating a yield stress and viscous component. The results show that the acceleration expected from a consideration of yield stress and inertia is not always achieved. The viscous component places fluid dynamic restriction on the maximum acceleration of the output rotor. However, this limit is only approached if the output load inertia is very low. The results have a bearing on the choice of fluid for high speed operation.
ANISOTROPIC FERMI SURFACES AND KOHN–LUTTINGER SUPERCONDUCTIVITY IN TWO DIMENSIONS
Authors: GONZÁLEZ J. , GUINEA F. , VOZMEDIANO M. A. H.
Published: July 2002

The instabilities induced on a two-dimensional system of correlated electrons by the anisotropies of its Fermi line are analyzed on general grounds. Simple scaling arguments allow to predict the opening of a superconducting gap with a well-defined symmetry prescribed by the geometry of the Fermi line. The same arguments predict a critical dimension of 3/2 for the transition of the two-dimensional system to non-Fermi liquid behavior. The methods are applied to the t–t′ Hubbard model in a wide range of dopings.
SPECTRAL PROPERTIES OF THE GENERALISED SPIN-FERMION MODELS
Authors: KUZEMSKY A. L.
Published: July 2002

In order to account for competition and interplay of localized and itinerant magnetic behaviour in correlated many body systems with complex spectra the various types of spin-fermion models have been considered in the context of the Irreducible Green's Functions (IGF) approach. Examples are generalised d–f model and Kondo–Heisenberg model. The calculations of the quasiparticle excitation spectra with damping for these models has been performed in the framework of the equation-of-motion method for two-time temperature Green's Functions within a non-perturbative approach. A unified scheme for the construction of Generalised Mean Fields (elastic scattering corrections) and self-energy (inelastic scattering) in terms of the Dyson equation has been generalised in order to include the presence of the two interacting subsystems of localised spins and itinerant electrons. A general procedure is given to obtain the quasiparticle damping in a self-consistent way. This approach gives the complete and compact description of quasiparticles and show the flexibility and richness of the generalised spin-fermion model concept.
FT RAMAN AND FTIR SPECTRA OF FOUR DISELENITES PbSe2O5, CdSe2O5, MnSe2O5 and Cr2(Se2O5)3
Authors: GOPINATH A. BINDU , DEVANARAYANAN S.
Published: July 2002

The vibrational spectra of Lead diselenite, Cadmium diselenite, Manganese diselenite and chromium diselenite have been recorded and analysed on the basis of vibrations due to [Formula: see text] ion. The observed spectra clearly indicate the presence of diselenite group in all these compounds. The spectral analysis confirms the orthorhombic nature of MnSe 2 O 5 as suggested by Koskenlinna et al. A large number of vibrational bands in the symmetric stretching region of PhSe 2 O 5 is due to the existence of different Se-O bond lengths. From the spectra it can be seen that the anion is highly distorted angularly in chromium compound. This high distortion in all modes confirms the presence of three crystallographically distinct diselenite groups in chromium compound.
63,65Cu NQR Study of Ba-site Occupation in Y1-xPrxBa2Cu3O7-δ
Authors: ABDELRAZEK M. M. , REYES A. P. , KUHNS P. L. , MOULTON W. G.
Published: July 2002

We report measurements of 63,65 Cu nuclear quadrupole resonance (NQR) at ambient temperatures to indirectly probe Ba-site occupation of Pr atoms in doped Y 1-x Pr x Ba 2 Cu 3 O 7-δ (0≤x≤1.0). Preliminary results show anomalous peaks in the spectra attributed to the O(5) atoms as would be expected in the presence of a Pr atom on the adjacent Ba-O plane.
MORPHOLOGICAL STABILITY OF A NANOWIRE DURING GROWTH PROCESS
Authors: CHEN X. L. , LI J. Y. , LAN Y. C. , CAO Y. G.
Published: July 2002

In this letter, we analyze the morphological stability of a nanowire during the vapor–solid (VS) side growth process at the same time as it grows along its axial direction by the vapor–liquid–solid (VLS) mechanism. The longitudinal perturbations due to the fluctuations of the growth conditions are introduced to describe the morphological variance of a nanowire along its fibre direction. It is shown that the side growth can induce the morphological instability for a nanowire with side perturbations if the perturbation's wavelengths are larger than a nanowire's perimeter.
GROWTH AND CHARACTERIZATION OF GaAsp-n JUNCTIONS OBTAINED BY THE CSVT TECHNIQUE USING ATOMIC HYDROGEN
Authors: SILVA-ANDRADE F. , ILINSKII A. , CHÁVEZ F. , PRUTSKIJ T. , TENORIO F. , BRAVO-GARCÍA Y. , PEÑA-SIERRA R.
Published: July 2002

The uses of atomic hydrogen to obtain semiconductor materials has increased significantly during the last decade. First, the passivating effects of energy levels, borders of grain, and interfaces were observed. Then we observed and took advantage of the capacity that atomic hydrogen has to form elementary volatile compounds to subsequently carry out an "in situ" etch. Since 1994 [1], our research group has taken advantage of this last modality to recover volatile compounds, making an inverse chemical reaction and obtaining epitaxial growths by means of the close space vapor transport technique (CSVT). The results, obtained by low temperature photoluminiscence and Hall effect measurements, show that it is possible to obtain GaAs films with p-type conductivity [2]. The optic and electric characteristics were suitable in order to manufactures semiconductor devices. For the realization of the p-n junction diodes, we used n-type GaAs (tellurium doped); we grew p-type GaAs films (zinc doped) and we showed that it is possible to obtain light emitting diodes whose emmision is on the edge. Our work showed the I-V characteristic curves at room temperature and continuous regime. The saturation current under forward bias was obtained on the order of 10-11 Amp. Photographs are shown of the radiation patterns in the near field of the p-n junctions; some regions with nonhomogeneous light are related to the presence of regions with different electric properties.
MAGNETIC FIELD AND TEMPERATURE DEPENDENCE OF THERMALLY ACTIVATED DISSIPATION IN EPITAXIAL THIN FILMS OF YBa2 (Cu1-xZnx)3O7-d
Authors: ILONCA G. , POP A. V. , JURCUT T. , MOCOCEAN E. , BEIUSEANU C. , LUNG C. , STIUFIUC G. , STIUFIUC R. , YE M. , DELTOUR R.
Published: July 2002

The scaling behavior of the effective activation energy of high-quality epitaxial c-oriented YBa 2( Cu 1-x Zn x)3 O 7-d thin films has been studied as a function of temperature and magnetic field. For all samples, the effective activation energy scales as U(T, μ0H) = U0(1 - T/T c )mHn with exponent m = 1.6 ± 0.02 - 1.3 ± 0.02 and the field scaling 1/μ0H and - ln μ0H for thick films and ultrathin films, respectively. The results are discussed taking account of the influence of the Zn substitution on the flux pinning in epitaxial YBa 2( Cu 1-x Zn x)3 O 7-d thin films.
ORDER PARAMETER FROM (p-ETHOXYBENZYLIDENE-)-p-n-BUTYLANILINE CHANNELED SPECTRA
Authors: SOCACIU MARGARETA , URSACHE MARCELA , PETRESCU EMIL , IACOBESCU GABRIELA
Published: July 2002

The dispersion of refractive indices and birefringence of EBBA were determined at different temperatures and the band contributions to these dependencies were computed. An improved Talbot–Rayleigh experimental setup was used and, in order to increase the accuracy and minimize the computation time, a new data processing method was proposed. The temperature dependence of the order parameter and of the correction factor g, originating from the anisotropy of the local field, were computed.
APPLICATIONS OF ION BEAM ANALYSIS TO THE ELEMENTAL AND ISOTOPIC CHARACTERISATION OF ADVANCED MATERIALS
Authors: VICKRIDGE I. C.
Published: July 2002

The accelerator laboratory of the Groupe de Physique des Solides, Paris, has pioneered a number of IBA techniques and applications over the last few decades. In particular, in the 1960's and 1970's, Nuclear Reaction analysis (NRA) including nuclear resonance depth profiling, isotopic tracing combined with NRA, and channelling techniques were developed under the leadership of G. Amsel. In this paper I will present a selection of recent applications from this laboratory of NRA, isotopic tracing with stable isotopes, and ion channelling, intended to illustrate the present status of these techniques in condensed matter physics and materials science, and to act as a backdrop for a discussion of future directions for development of Ion Beam Analysis in condensed matter physics and advanced materials research.
CLASSICAL ABSORPTION IN SMALL METAL PARTICLES AND THIN FILMS
Authors: SEROTA R. A. , GOODMAN B.
Published: July 2002

We study the electric dipole absorption in small metal particles and thin films in a longitudinal electric field. In diffusive approximation, we give both the phenomenological and microscopic derivations with the account for Thomas–Fermi screening and Drude relaxation.
A FUZZY DISSIMILARITY FUNCTION FOR REGION BASED SEGMENTATION OF COLOR IMAGES
Authors: MAKROGIANNIS S. , ECONOMOU G. , FOTOPOULOS S.
Published: July 2002

In this paper a novel Fuzzy Rule Based Dissimilarity Function is presented, to determine the hierarchical merging sequence in a region based segmentation scheme. The proposed technique, based on distinct region features and fuzzy logic principles, is designed to cope with the problems inherent in the segmentation task that the traditional merging cost functions cannot overcome. It combines the global (color) and local (spatial) information of the image to compare two adjacent regions in the rgb space. The validity of the approach has been subjectively and objectively verified for several types of color images such as head and shoulders, natural and texture images.
A CONTEXT-BASED APPROACH FOR COLOR IMAGE RETRIEVAL
Authors: SHIH JAU-LING , CHEN LING-HWEI
Published: July 2002

In this paper, a color image retrieval method based on the primitives of images will be proposed. First, the context of each pixel in an image will be defined. Then, the contexts in the image are clustered into several classes based on the algorithm of fast noniterative clustering. The mean of the context in the same class is considered as a primitive of the image. The primitives are used as feature vectors. Since the numbers of primitives between images are different, a specially designed similarity measure is then proposed to do color image retrieval. To better adapt to the preferences of users, a relevance feedback algorithm is provided to automatically determine the weight of each primitive according to the user's response. To demonstrate the effectiveness of the proposed system, several test databases from Corel are used to compare the performances of the proposed system with other methods. The experimental results show that the proposed system is superior to others.
DELAYED FEEDBACK CONTROL WITH STATE PREDICTOR FOR CONTINUOUS-TIME CHAOTIC SYSTEMS
Authors: NAKAJIMA HIROYUKI
Published: July 2002

We propose an application of state predictor to delayed feedback control (DFC) for continuous-time dynamical systems. First, we define the DFC for continuous-time systems clearly. Next, on the basis of this definition, we propose a DFC method with state-predictor to stabilize unstable equilibrium points in autonomous systems and derive a sufficient condition for stabilization. Then we extend this method to stabilizing unstable periodic orbits and also derive a sufficient condition for stabilization. Finally, we briefly discuss the relation between the conditions for stabilization of our methods and those of the dynamic DFC and the prediction-based feedback control for discrete-time systems.
PARTIAL MEASURE SYNCHRONIZATION IN HAMILTONIAN SYSTEMS
Authors: WANG XINGANG , LI HAIHONG , HU KAI , HU GANG
Published: July 2002

Partial synchronization in Hamiltonian systems is investigated based on the concept of measure-synchronization. The classical φ4 model is used for the investigation. A macroscopic observable of long-term average of particle energy is computed to describe transitions between desynchronization, different partial synchronization, and complete synchronization structures. It is found that, prior to the entire synchronization of all oscillators, partial measure-synchronization for some clusters of oscillators is stable within certain regions. Moreover, transition from quasiperiodicity to chaos is observed to be associated with the measure-synchronization as the coupling strength is increased.
AN ALTERNATIVE APPROACH TO POINCARÉ SECTIONING IN WEAKLY NONLINEAR SYSTEMS
Authors: TODD M. D. , VOHRA S. T.
Published: July 2002

A large array of dynamical systems can be broadly classified as weakly nonlinear, where a common feature is the presence of dual time-scale dynamics. Often it is desirable to isolate the dynamics at one time scale (typically the slower time scale), and this paper presents a generic phase-sensitive detection method that successfully isolates the slow-time dynamics, stripping off the less-relevant and often dominant fast-time dynamics. We shall also show for the first time, under certain phase considerations, the equivalence of the present method and the traditional Poincaré section of the original full response. The method is first presented in theory and then applied to data from a numerical simulation of the forced spherical pendulum followed by data from a similar spherical pendulum experiment. The method is successful provided certain conditions apply for phase stationarity.
A NEW PHYSICAL EFFECT MODELED BY AN IKEDA MAP DEPENDING ON A MONOTONICALLY TIME-VARYING PARAMETER
Authors: ARGYRIS JOHN , CIUBOTARIU CORNELIU
Published: July 2002

In this paper we study the dynamics of a charged particle in a constant external magnetic field and the field due to a polarized electromagnetic wave. We observe a new phenomenon, the chaotic gun effect, which appears in the case of a sufficiently large amplitude of the wave. We show that the longitudinal component of the momentum undergoes oscillations with a chaotic modulation of the amplitude which increases suddenly to a value which remains constant between two consecutive phase Larmor circles. The novel effect may be modeled by a time-regressive system associated with an Ikeda map depending on a monotonically time-varying parameter.
IRREDUCIBLE COMPONENTS IN AN ALGEBRAIC VARIETY OF REPRESENTATIONS OF A CLASS OF ONE RELATOR GROUPS
Authors: LIRIANO SAL
Published: July 2002

Given a finitely generated group H, the set Hom(H, SL2C) inherits the structure of an algebraic variety R(H) called the representation variety of H. This algebraic variety is an invariant of H. Let [Formula: see text] where p, t are integers greater than one. In this paper, a formula is produced yielding the number of four dimensional irreducible components of the affine algebraic variety R(Gpt).
FINITENESS PROPERTIES OF LOCALLY FINITE ABELIAN VARIETIES
Authors: KEARNES KEITH A. , WILLARD ROSS
Published: July 2002

We show that any locally finite abelian variety is generated by a finite algebra. We solve a problem posed by D. Hobby and R. McKenzie by exhibiting a nonfinitely based finite abelian algebra.
THE INTEGRATION OF EXTENSION THEORY TO DESIGN A NEW FUZZY INFERENCE MODEL
Authors: HUANG YO-PING , CHEN HUNG-JIN , OUYANG CHI-PENG
Published: July 2002

A novel extension-based fuzzy model is proposed in this paper. The newly established extension theory is integrated into the conventional fuzzy system to enhance the reasoning capability. In parameter identification process, adjusting a membership function to satisfy one pattern may deteriorate the others performance and result in a lengthy turning process. This incompatible issue is alleviated by the extension theory. We will investigate how to define the extended relational functions and how to refine the roughly designed model to meet the system requirement. During the refining process, both the fired and the neighborhood of the fired membership functions are adjusted simultaneously. Simulation results from single-input-single-output and double-input-single-output models verified that better results than the conventional methods have been obtained.
IDENTIFYING OVERLAPPED OBJECTS FOR VIDEO INDEXING AND MODELING IN MULTIMEDIA DATABASE SYSTEMS
Authors: CHEN SHU-CHING , SHYU MEI-LING , ZHANG CHENGCUI , KASHYAP R. L.
Published: July 2002

The identification of the overlapped objects is a great challenge in object tracking and video data indexing. For this purpose, a backtrack-chain-updation split algorithm is proposed to assist an unsupervised video segmentation method called the "simultaneous partition and class parameter estimation" (SPCPE) algorithm to identify the overlapped objects in the video sequence. The backtrack-chain-updation split algorithm can identify the split segment (object) and use the information in the current frame to update the previous frames in a backtrack-chain manner. The split algorithm provides more accurate temporal and spatial information of the semantic objects so that the semantic objects can be indexed and modeled by multimedia input strings and the multimedia augmented transition network (MATN) model. The MATN model is based on the ATN model that has been used in artificial intelligence (AI) areas for natural language understanding systems, and its inputs are modeled by the multimedia input strings. In this paper, we will show that the SPCPE algorithm together with the backtrack-chain-updation split algorithm can significantly enhance the efficiency of spatio-temporal video indexing by improving the accuracy of multimedia database queries related to semantic objects.