bluuebunny/crossref_metadata_2025 huggingface dataset:
Association between job strain and prevalence of hypertension: a cross sectional analysis in a Japanese working population with a wide range of occupations: the Jichi Medical School cohort study
Authors: Tsutsumi A , Kayaba K , Tsutsumi K , Igarashi M
Published: July 2002

OBJECTIVES

To explore the association between the prevalence of hypertension in a Japanese working population and job strain (a combination of low control over work and high psychological demands), and to estimate this association in different sociodemographic strata.

METHODS

From a multicentre community based cohort study of Japanese people, sex specific cross sectional analyses were performed on 3187 men and 3400 women under 65 years of age, all of whom were actively engaged in various occupations throughout Japan. The baseline period was 1992–4. The association between job characteristics—measured with a Japanese version of the Karasek demand-control questionnaire—and the prevalence of hypertension defined by blood pressure and from clinical diagnoses were examined. Adjustments were made for possible confounders. The analyses were repeated for stratified categories of occupational class, educational attainment, and age group.

RESULTS

In men, the level of job strain (the ratio of psychological job demands to job control) correlated with the prevalence of hypertension. In a multiple logistic regression model, job strain was significantly related to hypertension (odds ratio 1.18; 95% confidence interval 1.05 to 1.32), after adjustment for age, employment (white collarvblue collar), marital status, family history of hypertension, cigarette smoking, alcohol intake, physical activity, and body mass index. The stratified analyses showed significant excess risks in the subordinate groups compared with managers, blue collar workers, less educated workers, and the older age groups. This association was not significant in women. Multiple linear regression analyses, with systolic and diastolic blood pressures as dependent variables, did not show any significant association.

CONCLUSIONS

The findings provided limited proof that job strain is related to hypertension in Japanese working men. Older men in a lower social class may be more vulnerable to the hypertensive effects of job strain.
Interrelations of risk factors and low back pain in scaffolders
Authors: Elders L A M , Burdorf A
Published: July 2002

OBJECTIVES

To assess with a cross sectional study the interrelations between physical, psychosocial, and individual risk factors and different end points of low back pain.

METHODS

In total, 229 scaffolders and 59 supervisors completed a questionnaire about manual handling of materials, awkward back posture, strenuous arm position, perceived exertion, psychosocial load, need for recovery, and general health. Physical load at the worksite was also measured with many frequent observations. Interrelations between risk factors and their relation with four end points of low back pain were investigated.

RESULTS

Interrelations were strong among self reported determinants of physical load but showed an inverted trend for both age and total working experience, which could indicate the presence of a healthy worker effect. Weak relations existed between variables of psychosocial and physical load. The multivariate analyses showed a significant relation between high manual handling of materials, moderate perceived general health, high job demands, and low back pain in the past 12 months. Chronic low back pain was significantly correlated with high perceived exertion and moderate perceived general health. Severe low back pain was significantly correlated with awkward back postures, high need for recovery, and high job demands. Finally, low back pain with perceived disability was significantly related to strenuous shoulder positions and moderate perceived general health. All end points of low back pain were consistently associated with physical load whereas psychosocial aspects showed a more diverse pattern.

CONCLUSIONS

The findings of this study suggest that work related risk factors may vary according to different definitions of low back pain. Distinct patterns of risk factors might enhance different expressions of it. Scaffolders are a group at high risk of developing persistent forms of low back pain.
Pregnancy in systemic lupus erythematosus
Authors: Mok C C , Wong R W S
Published: July 2002

Systemic lupus erythematosus (SLE) is an autoimmune disease that predominantly affects women of reproductive age. Pregnancy and its outcome is a major concern to most SLE patients. Queries regarding the risk of disease flares during pregnancy, chance of fetal loss, and the safety of various drugs are often raised. With the improvement in the understanding of the pathogenesis of SLE and the judicious use of immunosuppressive drugs, better disease control can now be achieved and SLE patients should not be deprived of the opportunity for bearing children. Prepregnancy counselling and close collaboration with other specialists such as the obstetricians and the perinatologists is essential in optimising the maternal and fetal outcome in lupus pregnancies. In this review, important issues regarding the fertility rate, optimal timing of conception, risk of disease flares during lupus pregnancy, pregnancy course, fetal outcome, safety of various drugs used for disease control during pregnancy and lactation, and contraceptive advice are discussed.
Evolution of an inguinal hernia surgery practice
Authors: Mokete M , Earnshaw J J
Published: July 2002

BACKGROUND

Inguinal hernia surgery has undergone numerous advances in the last few years. This study analysed the changes in the practice of one surgeon in a district general hospital over a seven year interval. The effect of changing from Bassini to Lichtenstein repair in 1994 was evaluated.

METHODS

The study involved two parts: first a search of a computerised database of inguinal hernia procedures, and second, postal audits of men who had an inguinal hernia repair in 1993 and 1994 with outpatient follow up for those with a possible recurrence.

RESULTS

A total of 1037 hernias were repaired over the seven years. There was an increase in the proportion of day cases from 18% to 70% and the number of operations performed under local anaesthetic rose from 1% to 45%. The postal audits had response rates of 79% (1993) and 66% (1994). Some 5/98 (5%) recurrent hernias were identified from the 1993 (Bassini) patients compared with 1/67 (1.5%) from the 1994 (Lichtenstein) cohort.

CONCLUSION

Lichtenstein hernia repair can be performed safely as a day case using local anaesthetic in the majority of patients and appears to have a lower recurrence rate than Bassini repair.
Is there a dissociative process in sleepwalking and night terrors?
Authors: Hartman D , Crisp A H , Sedgwick P , Borrow S
Published: July 2002

The enduring and contentious hypothesis that sleepwalking and night terrors are symptomatic of a protective dissociative mechanism is examined. This is mobilised when intolerable impulses, feelings and memories escape, within sleep, the diminished control of mental defence mechanisms. They then erupt but in a limited motoric or affective form with restricted awareness and subsequent amnesia for the event. It has also been suggested that such processes are more likely when the patient has a history of major psychological trauma. In a group of 22 adult patients, referred to a tertiary sleep disorders service with possible sleepwalking/night terrors, diagnosis was confirmed both clinically and polysomnographically, and only six patients had a history of such trauma. More commonly these described sleepwalking/night terrors are associated with vivid dream-like experiences or behaviour related to flight from attack. Two such cases, suggestive of a dissociative process, are described in more detail.

The results of this study are presented largely on account of the negative findings. Scores on the dissociation questionnaire (DIS-Q) were normal, although generally higher in the small “trauma” subgroup. These were similar to scores characterising individuals with post-traumatic stress disorder. This “trauma” group also scored particularly highly on the anxiety,phobic, and depression scales of the Crown-Crisp experiential index. In contrast the “no trauma” group scored more specifically highly on the anxiety scale, along with major trends to high depressionand hysteria scale scores. Two cases are presented which illustrate exceptional occurrence of later onset of sleepwalking/night terrors with accompanying post-traumatic symptoms during wakefulness. It is concluded that a history of major psychological trauma exists in only a minority of adult patients presenting with sleepwalking/night terror syndrome. In this subgroup trauma appears to dictate the subsequent content of the attacks. However, the symptoms express themselves within the form of the sleepwalking/night terror syndrome rather than as rapid eye movement sleep related nightmares. The main group of subjects with the syndrome and with no history of major psychological trauma show no clinical or DIS-Q evidence of dissociation during wakefulness. The proposition that, within the character structure of this group, the mechanism still operates but exclusively within sleep remains a possibility.
Delayed reactivation of haloperidol induced photosensitive dermatitis by methotrexate
Authors: Thami G P , Kaur S , Kanwar A J
Published: July 2002

A man whose psoriasis was well controlled on methotrexate treatment developed pellagra-like photosensitive dermatitis when he started taking haloperidol. Reactivation of his dermatitis was observed with methotrexate as a recall photosensitivity phenomenon. This false photosensitivity reaction of methotrexate is an important but rarely encountered adverse effect. A possible interaction between methotrexate and haloperidol is emphasised.
Using bioenergetics models to predict stable isotope ratios in fishes
Authors: Harvey Chris J , Hanson Paul C , Essington Timothy E , Brown Paul B , Kitchell James F
Published: July 2002

To describe temporal dynamics of stable isotope ratios in fishes, we developed a bioenergetics-based model that links isotope ratios to growth, as influenced by fish size, temperature, diet, and prey quality. The model includes error terms for isotope ratios, diet proportions, and fractionation. The model accurately predicted temporal δ15N dynamics of lake trout (Salvelinus namaycush) in a diet-switch experiment but was less successful for δ13C, possibly because of variable fractionation. The model was then used in three heuristic applications. In a diet-validation scenario, a model derived from limited knowledge of rainbow smelt (Osmerus mordax) diet reasonably estimated δ13C and δ15N compared with a null model but inaccurately estimated prey consumption. In a scenario where adult lake trout briefly cannibalized stocked lake trout fingerlings, the detectability of a cannibalism-induced δ15N increase depended on predator size, duration of cannibalism, and sample size. In a scenario where seasonal isotopic variability occurred at the base of a food web, variation propagated to higher trophic levels depended on consumer size and diet. Our approach is most valuable when used to examine multiple diet combinations that produce observed stable isotope ratios; one can then identify the most reasonable diets through field tests or other observations.
Anti-invasive activity of bovine lactoferrin towards group A streptococci
Authors: Ajello Maria , Greco Rita , Giansanti Francesco , Massucci Maria Teresa , Antonini Giovanni , Valenti Piera
Published: July 2002

Group A streptococci (GAS) are able to invade cultured epithelial and endothelial cells without evidence of intracellular replication. GAS, like other facultative intracellular bacterial pathogens, evolved such ability to enter and to survive within host cells avoiding the host defences, and bacterial intracellular survival could explain the recurrence of infections. We report here that 1 mg bovine lactoferrin (bLf)/mL significantly hindered the in vitro invasion of cultured epithelial cells by GAS isolated from patients suffering from pharyngitis and completely inhibited the invasiveness of GAS pretreated with subinhibiting concentrations of erythromycin or ampicillin. One milligram of bLf per millilitre was also able to increase the number of epithelial cells undergoing apoptosis following GAS invasion, although the number of intracellular GAS in the presence of bLf decreased by about 10-fold. The ability of bLf to decrease GAS invasion was confirmed by an in vivo trial carried out on 12 children suffering from pharyngitis and already scheduled for tonsillectomy. In tonsil specimens from children treated for 15 days before tonsillectomy with both oral erythromycin (500 mg t.i.d. (three times daily)) and bLf gargles (100 mg t.i.d.), a lower number of intracellular GAS was found in comparison with that retrieved in tonsil specimens from children treated with erythromycin alone (500 mg t.i.d.).Key words: lactoferrin, group A streptococci, invasiveness, anti-invasive activity, apoptosis.
A PROOF OF THE RUELLE OPERATOR THEOREM
Authors: FAN AI HUA
Published: July 2002

We give a new proof of the Ruelle operator theorem by using a setup inspired by the G-measure formalism due to Brown-Dooley.
Noncommutative Lattices and the Algebras of Their Continuous Functions
Authors: Ercolessi Elisa , Landi Giovanni , Teotonio-Sobrinho Paulo
Published: July 2002

Recently a new kind of approximation to continuum topological spaces has been introduced, the approximating spaces being partially ordered sets (posets) with a finite or at most a countable number of points. The partial order endows a poset with a nontrivial non-Hausdorff topology. Their ability to reproduce important topological information of the continuum has been the main motivation for their use in quantum physics. Posets are truly noncommutative spaces, or noncommutative lattices, since they can be realized as structure spaces of noncommutative C*-algebras. These noncommutative algebras play the same rôle as the algebra of continuous functions [Formula: see text] on a Hausdorff topological space M and can be thought of as algebras of operator valued functions on posets. In this article, we will review some mathematical results that establish a duality between finite posets and a certain class of C*-algebras. We will see that the algebras in question are all postliminal approximately finite dimensional (AF) algebras.
GLOBAL INHOMOGENEOUS SCHRÖDINGER FLOW
Authors: WANG HONG-YU , WANG YOU-DE
Published: July 2002

In this paper, we consider the global existence of one-dimensional nonautonomous inhomogeneous Schrödinger flow. By exploiting geometric symmetries, we prove that, given a smooth initial map, the Cauchy problem of the one-dimensional nonautonomous inhomogeneous Schrödinger flow from S1 into a complete Kähler manifold with constant holomorphic sectional curvature admits a unique global smooth solution. As a corollary, we establish the global existence for the Cauchy problem of the inhomogeneous Heisenberg spin system.
SIMULTANEOUS GOOD RESOLUTIONS OF DEFORMATIONS OF GORENSTEIN SURFACE SINGULARITIES
Authors: OKUMA TOMOHIRO
Published: July 2002

Let π: X → T be a small deformation of a normal Gorenstein surface singularity X0 over the complex number field [Formula: see text]. We assume that X0 is not log-canonical. Then we prove that if the invariant -Pt · Pt of Xt is constant, then π admits a simultaneous resolution f: M → X such that each ft: Mt → Xt is a smallest resolution among all resolutions of Xt whose exceptional sets are divisors having only normal crossings.
GENERIC KNOTS IN CONTACT 3-MANIFOLDS
Authors: ADACHI JIRO
Published: July 2002

In this paper, the notion of the generic knots in contact 3-manifolds is introduced as an extension of that of the transversal knots. We show that any generic knots in contact 3-manifolds are constructed by perturbations of some Legendrian knots. As for the classification problem, the situation is completely different from the cases of the transversal and Legendrian knots. Two generic knots in a contact 3-manifold are generically isotopic if and only if they have the same number of non-transversal points and belong to the same topological knot class. We treat, in this paper, not only trivial knots in tight contact 3-manifolds but also non-trivial knots and those in overtwisted contact 3-manifolds.
ON SINGULARITIES OF ℳℙ3 (c1, c2)
Authors: ANCONA VINCENZO , OTTAVIANI GIORGIO
Published: July 2002

Let ℳℙ3(c1,c2) be the moduli space of stable rank-2 vector bundles on ℙ3 with Chern classes c1, c2. We prove the following results: (1) Let k, β, γ be three integers such that k > 0, 0 ≤ β < γ, γ ≥ 2, kγ - (k + 1)β > 0; then the moduli space ℳℙ3(0, kγ2 - (k + 1)β2) is singular (the case k = 2, β = 0 was previously proved by M. Maggesi).

(2) Let k, β, γ be three integers, with β and γ odd, such that k > 0, 0 < β < γ, γ ≥ 5, kγ - (k + 1)β + 1 > 0; then the moduli space ℳℙ3(-1,k(γ/2)2 - (k + 1)(β/2)2) + 1/4) is singular.

In particular ℳℙ3(0,5), ℳℙ3(-1,6) are singular.
EFFECT OF CHIRALITY ON THE STABILITY OF CARBON NANOTUBES: MOLECULAR-DYNAMICS SIMULATIONS
Authors: ERKOÇ ŞAKIR , MALCIOĞLU OSMAN BARIŞ
Published: July 2002

The effect of chirality on the structural stability of single-wall carbon nanotubes have been investigated by performing molecular-dynamics computer simulations. Calculations have been realized by using an empirical many-body potential energy function for carbon. It has been found that carbon nanotube in chiral structure is more stable under heat treatment relative to zigzag and armchair models. The diameter of the tubes is slightly enlarged under heat treatment.
GOMPERTZ LAW IN SIMPLE COMPUTER MODEL OF AGING OF BIOLOGICAL POPULATION
Authors: MAKOWIEC DANUTA , STAUFFER DIETRICH , ZIELIŃSKI MARIUSZ
Published: July 2002

It is shown that if the computer model of biological aging proposed by Stauffer is modified such that the late reproduction is privileged, then the Gompertz law of exponential increase of mortality can be retrieved.
WEAKEST SPECIFUNCTIONS FOR BSP
Authors: CHEN YIFENG , SANDERS J. W.
Published: July 2002

This paper introduces a calculus of weakest specification for supporting reuse of established components in deriving a design (in the sense of formal methods). The weakest specifunction generalizes the notions of weakest pre-specification and weakest parallel environment; but instead of calculating the weakest required component of a target specification, it calculates the weakest specification function whose value refines the target when applied to an established component. In particular it overcomes the restriction of those other calculi to taking merely one required component at a time.

The theory of specifunctions is applied to a new weakest-design calculus in the context of BSP. The calculus is based on the par-seq specifunction which involves two required components: it places one established component in parallel with one required component and the result in sequence with another required component to meet a given specification. A calculus is provided for the par-seq specifunction and it is applied to the derivation of a distributed BSP algorithm for greatest common divisor.
KÄHLER POLARIZATION AND WICK QUANTIZATION OF HAMILTONIAN SYSTEMS SUBJECT TO SECOND-CLASS CONSTRAINTS
Authors: LYAKHOVICH S. L. , SHARAPOV A. A.
Published: July 2002

The necessary and sufficient conditions are established for the second-class constraint surface to be (an almost) Kähler manifold. The deformation quantization for such systems is mentioned resulting in the Wick-type symbols for the respective Dirac brackets.
LAGRANGIAN Sp(3) BRST SYMMETRY FOR YANG–MILLS THEORY
Authors: BIZDADEA C. , SALIU S. O.
Published: July 2002

The Sp (3) BRST symmetry for Yang–Mills theory is derived in the framework of the antibracket–antifield formalism.
A COHOMOLOGICAL INTERPRETATION OF THE MIGDAL–MAKEENKO EQUATIONS
Authors: AGARWAL A. , RAJEEV S. G.
Published: July 2002

The equations of motion of quantum Yang–Mills theory (in the planar "large-N" limit), when formulated in loop-space are shown to have an anomalous term, which makes them analogous to the equations of motion of WZW models. The anomaly is the Jacobian of the change of variables from the usual ones, i.e. the connection one-form A, to the holonomy U. An infinite-dimensional Lie algebra related to this change of variables (the Lie algebra of loop substitutions) is developed, and the anomaly is interpreted as an element of the first cohomology of this Lie algebra. The Migdal–Makeenko equations are shown to be the condition for the invariance of the Yang–Mills generating functional Z under the action of the generators of this Lie algebra. Connections of this formalism to the collective field approach of Jevicki and Sakita are also discussed.
DYSON-SCHWINGER EQUATIONS – ASPECTS OF THE PION
Authors: HECHT M. B. , ROBERTS C. D. , SCHMIDT S. M.
Published: July 2002

The contemporary use of Dyson-Schwinger equations in hadronic physics is exemplified via applications to the calculation of pseudoscalar meson masses, and inclusive deep inelastic scattering with a determination of the pion's valence-quark distribution function.
ELECTRON–PHONON SCATTERING AND ELECTRONIC TRANSPORT IN LAYERED STRUCTURES
Authors: AUSLOOS M. , DURCZEWSKI K.
Published: July 2002

The two-dimensional degenerate electron gas with electron–phonon scattering is analyzed. The normal-phase temperature dependence of the electrical resistivity and the thermo-electrical power are calculated, based on the electron–phonon scattering and other usual ones. Results are compared to those of earlier studies on three-dimensional phonon-limited scattering. Comparison is qualitatively made for several layered materials of interest (MOS, heterostructures, etc.). It occurs that the theory does not seem to apply to YBCO-like Tc superconductors which have a too low Fermi energy with respect to the Debye temperature.
ULTRAFAST CARRIER DYNAMICS IN ZnO EPITAXIAL THIN FILMS STUDIED BY OPTICAL KERR GATE LUMINESCENCE SPECTROSCOPY
Authors: TAKEDA JUN , KURITA SUSUMU , CHEN YEFAN , YAO TAKAFUMI
Published: July 2002

Time-resolved luminescence spectra of ZnO epitaxial thin films have been measured by the optical Kerr gate luminescence spectroscopy under resonant excitation of the excitonic state. At moderate excitation density, a luminescence band (P band) which is attributed to an exciton-exciton collision process was observed. With increasing the excitation density, the P band disappears while a new luminescence band (EHP band) due to radiative recombination of electrons with holes in an electron-hole plasma appears. The EHP band has a rise time of ~1 ps, and shifts to lower energy with time and then finally shifts to higher energy. The rise time of the EHP band shows a transition time from a high density excitonic state to an unbound electron-hole system due to the screening of Coulomb interaction. The red shift of the EHP band comes from the reduced band-gap effect, while the blue shift to the EHP band is mainly attributed to recovery of the renormalized band-gap, which occurs with decreasing the carrier density due to the radiative recombination of electrons with holes.
THEORY OF EXCITATION ENERGY TRANSFER IN THE INTERMEDIATE COUPLING CASE AND ITS APPLICATION TO THE PHOTOSYNTHETIC ANTENNA SYSTEMS
Authors: KIMURA AKIHIRO , KAKITANI TOSHIAKI , YAMATO TAKAHISA
Published: July 2002

We developed the theory of excitation energy transfer (EET) in the intermediate coupling case using the decoupling procedure. We succeeded in treating the theory analytically by assuming that the two-time correlation function is represented as an exponential function. We examined the validity of its approximation. We calculated the time dependent probability na(t) of the EET, in which the acceptor molecule is in the excited state by making alternative calculation of the cumulant expansion method. Applying this calculation by this method to the photosynthetic antenna systems and comparing its result with the analytical formula, we found that these results coincide well with each other in the due time region of the approximation.
VERY LOW THRESHOLD ELECTRON FIELD EMISSION FROM AMORPHOUS CARBON FILMS WITH HYDROGEN DILUTION
Authors: XU JUN , HUANG XIAOHUI , LI WEI , WANG LI , CHEN KUNJI , XU JIANBIN , WILSON I. H.
Published: July 2002

Hydrogenated amorphous carbon films were fabricated with and without hydrogen dilution in a small d.c bias-assisted plasma chemical vapor deposition system. It was found that the hydrogen dilution can reduce the sp 2/ sp 3 ratio in carbon films which results in blue shift of room temperature photoluminescence spectrum. The field emission characteristics were investigated by using parallel plates test configuration. A very low threshold electric field (~0.5 V/μm) was achieved from thin amorphous carbon film prepared with hydrogen dilution. The improvement to field emission property in the present carbon films was tentatively attributed to the field enhancement effect due to the electronic structure inhomogeneity of the carbon films and the reduction of the surface emission barrier due to the hydrogen termination.
DIMERS AND SPANNING TREES: SOME RECENT RESULTS
Authors: WU F. Y.
Published: July 2002

This paper reviews some recent progress on dimer and spanning tree enumerations. We use the Kasteleyn formulation to enumerate close-packed dimers on a simple-quartic net embedded on non-orientable surfaces, and obtain solutions in the form of double products. For spanning trees the enumeration is carried out by evaluating the eigenvalues of the Laplacian matrix associated with the lattice, a procedure which holds in any spatial dimension. In two dimensions a bijection due to Temperley relates spanning tree and dimer configurations on two related lattices. We use this bijection to enumerate dimers on a net with a vacancy on the boundary. It is found that the occurrence of a vacancy induces a [Formula: see text] correction to the enumeration, where N is the linear size of the lattice, and changes the central charge from c = 1 to -2.
FEMTOSECOND LASER-INDUCED DAMAGE OF DIELECTRICS
Authors: LENZNER M.
Published: July 2002

Optical damage in non-metals (dielectrics) may severely affect the performance of high-power laser systems as well as the efficiency of optical systems based on nonlinear processes and has therefore been subject to extensive research for some 30 years. The current knowledge of laser-induced optical damage in these materials is reviewed. Emphasis is placed on the recent extension of available experimental data into the femtosecond range. Recent results are presented achieved with a sub-10 fs laser system which explores the limits of time resolution as well as the limit of intensities that a solid can sustain without irreversible damage. It is concluded that sub-10fs laser pulses open up the way to reversible nonperturbative nonlinear optics at intensities greater than 1014 W/cm 2 (slightly below damage threshold) and to nanometer-precision laser ablation (slightly above threshold) in dielectric materials.
ON TOPOLOGICAL DEFECT FORMATION IN THE PROCESS OF SYMMETRY BREAKING PHASE TRANSITIONS
Authors: ALFINITO ELEONORA , ROMEI ORESTE , VITIELLO GIUSEPPE
Published: July 2002

By resorting to some results in quantum field theories with spontaneous breakdown of symmetry, we show that an explanation based on microscopic dynamics can be given for the fact that topological defect formation is observed during the process of non-equilibrium phase transitions characterized by a non-zero order parameter. We show that the Nambu–Goldstone particle acquires an effective non-zero mass due to boundary (finite volume) effects and this is related to the size of the defect. We also relate such volume effects with temperature effects.
Molecular-Dynamics Simulations of Granular Axial Segregation in a Rotating Cylinder
Authors: Shoichi Sakamoto
Published: July 2002

In order to investigate segregation of granular binary-mixtures in a horizontally rotating cylinder, three-dimensional molecular dynamics simulations are carried out. Two kinds of particles, which have different diameters and/or different roughness of surfaces, are segregated into three bands. It is found that particles receive averaged force cohesively at the boundaries of segregated bands. The present analysis shows that segregated narrow bands are formed by diffusion process and that the cohesive forces operating at the boundaries stabilize them.
The Electron Localization Problem Via a Local Functional Integral Approach
Authors: Botelho L. C. , da Silva E. P. , Lyra M. L. , Cavalcanti S. B.
Published: July 2002

We employ a path integral representation for the three-dimensional Schrödinger equation describing the motion of a quantum particle in a static random potential. Within a semi-classical approximation (pure phase wave function) and a one-loop order path integral evaluation, we obtain three-dimensional electron localization in the presence of static disorder and zero temperature.
INTEGRABLE BOUNDARY CONDITIONS FOR THE q-DEFORMED EXTENDED HUBBARD MODEL
Authors: GE XIANG-YU
Published: July 2002

Integrable open-boundary condition for the q-deformed Essler–Korepin–Schoutens extended Hubbard model of strongly correlated electrons are studied in the framework of the boundary quantum inverse scattering method. Diagonal boundary K-matrices are found and nine classes of integrable boundary terms are determined.
COMPUTING THE FUNDAMENTAL GROUP IN DIGITAL SPACES
Authors: MALGOUYRES RÉMY
Published: July 2002

As its analogue in the continuous framework, the digital fundamental group represents major information on the topology of discrete objects. However, the fundamental group is abstract information and cannot directly be encoded in a computer by only using its definition. A classical mathematical way to encode a discrete group is to find a presentation of this group. In this paper, we construct a presentation for the fundamental group of an arbitrary graph, and a finite presentation (hence encodable in the memory of a computer) of any subset of ℤ3. This presentation can be computed by an efficient algorithm.
SALIENT POINTS OF Q-CONVEX SETS
Authors: DAURAT ALAIN
Published: July 2002

The Q-convexity is a kind of convexity in the discrete plane. This notion has practically the same properties as the usual convexity: an intersection of two Q-convex sets is Q-convex, and the salient points can be defined like the extremal points. Moreover a Q-convex set is characterized by its salient point. The salient points can be generalized to any finite subset of ℤ2.
ON THE CONTROL OF HIGH DIMENSIONAL CHAOTIC DYNAMICAL SYSTEMS USING NONLINEAR APPROXIMATIONS
Authors: HILL D. L.
Published: July 2002

The effectiveness of a particular technique of using nonlinear approximations to control chaotic dynamical systems in the case when the systems are of dimension higher than two is investigated.
CONTROL OF THE DIFFERENTIALLY FLAT LORENZ SYSTEM
Authors: JOO JIN MAN , PARK JIN BAE
Published: July 2002

This paper presents an approach for the control of the Lorenz system. We first show that the controlled Lorenz system is differentially flat and then compute the flat output of the Lorenz system. A two degree of freedom design approach is proposed such that the generation of full state feasible trajectory incorporates with the design of a tracking controller via the flat output. The stabilization of an equilibrium state and the tracking of a feasible state trajectory are illustrated.
TRANSITION TO HIGH-DIMENSIONAL CHAOS THROUGH QUASIPERIODIC MOTION
Authors: PAZÓ DIEGO , SÁNCHEZ ESTEBAN , MATÍAS MANUEL A.
Published: July 2002

In this contribution we report on a transition to high-dimensional chaos through three-frequency quasiperiodic behavior. The resulting chaotic attractor has a one positive and two null Lyapunov exponents. The transition occurs at the point at which two symmetry related three-dimensional tori merge in a crisis-like bifurcation. The route can be summarized as: 2D torus → 3D torus → high-dimensional chaotic attractor.
CONTROLLING CHAOS IN A STATE-DEPENDENT NONLINEAR SYSTEM
Authors: KOUSAKA TAKUJI , UETA TETSUSHI , KAWAKAMI HIROSHI
Published: July 2002

In this paper, we propose a general method for controlling chaos in a nonlinear dynamical system containing a state-dependent switch. The pole assignment for the corresponding discrete system derived from such a nonsmooth system via Poincaré mapping works effectively. As an illustrative example, we consider controlling the chaos in the Rayleigh-type oscillator with a state-dependent switch, which is changed by the hysteresis comparator. The unstable one- and two-periodic orbits in the chaotic attractor are stabilized in both numerical and experimental simulations.
BIFURCATION AND CHAOS OF SYNCHRONIZED STATES IN OSCILLATORS WITH HARD CHARACTERISTICS AND STATE COUPLING
Authors: KITAJIMA H. , KAWAKAMI H.
Published: July 2002

We investigate the phase transition between solutions with distinct symmetrical property observed in a system of coupled three-oscillators with hard characteristics and state coupling. By a symmetry-breaking bifurcation, a symmetrical in-phase solution bifurcates into synchronized modes with a partially in-phase solution and an almost in-phase solution. Moreover, by using the definition of symmetrical and asymmetrical three-phase solutions, we confirmed the existence of a stable symmetrical three-phase quasi-periodic solution and an asymmetrical three-phase chaotic solution in the coupled system.
CONTROLLING CHAOS USING NONLINEAR APPROXIMATIONS FOR A PENDULUM WITH FEEDFORWARD AND FEEDBACK CONTROL
Authors: YAGASAKI KAZUYUKI , YAMASHITA SHINTARO
Published: July 2002

The OGY method is one of the most powerful techniques for controlling chaotic dynamical systems, but often requires very long time for stabilization of the targets. Recently, it was shown that the problem can be improved by using nonlinear approximations for the chaotic dynamical systems and the stable manifolds of the targets. We consider a pendulum with feedforward and feedback control and apply the improved method to the associated Poincaré map. The derivatives of the Poincaré map, which are necessary for application of the method, are computed by solving certain differential equations. Numerical examples are given and the effectiveness of the control method is demonstrated.
QUALITATIVE ANALYSIS OF A NEURAL NETWORK MODEL WITH MULTIPLE TIME DELAYS
Authors: CAMPBELL SUE ANN , RUAN SHIGUI , WEI JUNJIE
Published: July 2002

We consider a simplified neural network model for a ring of four neurons where each neuron receives two time delayed inputs: One from itself and another from the previous neuron. Local stability analysis of the positive equilibrium leads to a characteristic equation containing products of four transcendental functions. By analyzing the equivalent system of four scalar transcendental equations, we obtain sufficient conditions for the linear stability of the positive equilibrium. Furthermore, we show that a Hopf bifurcation can occur when the positive equilibrium loses stability.
New presentations of surface braid groups
Authors: González-Meneses Juan
Published: July 2002

In this paper we give new presentations of the braid groups and the pure braid groups of a closed surface. We also give an algorithm to solve the word problem in these groups, using the given presentations.
The quantum ${\mathfrak g}_2$ invariant and relations of multiple zeta values
Authors: Ihara Kentaro , Takamuki Takashi
Published: July 2002

In this paper we obtain a family of relations among the multiple zeta values by calculating the quantum [Formula: see text]-invariant of a framed oriented link, where Γ1,0 is the 7-dimensional irreducible representation of the exceptional simple Lie algebra [Formula: see text] over [Formula: see text].
ON A CALCULUS FOR 2-KNOTS AND SURFACES IN 4-SPACE
Authors: SWENTON FRANK J.
Published: July 2002

In this paper, we use knots with bands ("kwb") to define a calculus for smoothly embedded surfaces in 4-space. This approach has its roots in the classical method of moving pictures of hyperplane slices, and thus shares its simplicity and naturality. Unlike moving pictures, however, kwb are combinatorial knotlike objects in 3-space (which can, in turn, be represented by planar diagrams), and a set of three simple combinatorial moves is sufficient to connect the kwb representing isotopic surfaces. Thus we obtain a one-to-one correspondence between isotopy classes of embedded surfaces and certain kwb modulo these moves, answering a question first posed in 1994 by Katsuyuki Yoshikawa.
CLASSICALITY OF PRIMORDIAL FLUCTUATIONS AND PRIMORDIAL BLACK HOLES
Authors: POLARSKI D.
Published: July 2002

The production of Primordial Black Holes (PBH) from inflationary perturbations provides a physical process where the effective classicality of the fluctuations does not hold for certain scales. For adiabatic perturbations produced during inflation, this range of scales corresponds to PBH with masses M≪1015 g. For PBH with masses M ~ M H (te), the horizon mass at the end of inflation, the generation process during the preheating stage could be classical as well, in contrast to the formation of PBH on these scales by adiabatic inflationary perturbations. For the nonevaporated PBH, the generation process is essentially classical.
SUPERQUINTESSENCE
Authors: FARAONI VALERIO
Published: July 2002

There is marginal evidence that the quintessential form of matter responsible for the acceleration of the universe observed today has ratio between pressure and energy density w < -1. Such a regime, called superacceleration, cannot be achieved with conventional scalar field models. The simplest nonexotic model achieving superacceleration is that of a scalar field nonminimally coupled to the Ricci curvature. This model is studied for general potentials and an exact superaccelerating solution is presented. In quintessential inflation, the model can have blue gravitational wave spectra, improving the prospects for the detection of cosmological gravitational waves.
REPLY TO REMARKS ON A DECRUMPLING MODEL OF THE UNIVERSE
Authors: MOHAZZAB MASOUD , LIMA J. A. S.
Published: July 2002

Decrumpling model of the Universe is a new sort of cosmological scenario based on the assumption that the basic building blocks of the spacetime are fractally structured.1–6 In the original papers, the spatial dimension of the Universe was considered as a continuous time dependent variable.1,2 As the universe expands, its spatial dimension decreases continuously, thereby generating what has been named a decrumpling Universe. Recently, this model has been overlooked and the quantum cosmological aspects, as well as, a possible test theory have also been discussed.5,6
MEASUREMENT OF RECOIL RANGES IN THE 12C+165Ho SYSTEM BELOW 7 MeV/NUCLEON
Authors: GUPTA SUNITA , SINGH B. P. , KUMAR SHARMA MANOJ , PRASAD R. , MUSTHAFA M. M. , BHARDWAJ H. D.
Published: July 2002

With a view to study complete (CF) and incomplete fusion (ICF) of 12 C with 165 Ho below 7 MeV/nucleon, the recoil range distribution of various evaporation residues formed in the interaction of 12 C with 165 Ho have been measured. In the case of (C, xn)(x = 3,4,5) channels recoil range distributions show only one peak. Two distinct peaks, one having a lower mean value for range and another having a higher mean range (nearly the same as that for (C, xn) channel) are observed in some cases. The two peaks in the recoil range distributions may be assigned, respectively, to the incomplete and completely fused systems.
SIMULATION OF KINETIC OSCILLATIONS IN CATALYTIC REACTIONS ACCOMPANIED BY OXIDE FORMATION
Authors: ZHDANOV V. P.
Published: July 2002

One of the generic mechanisms of oscillations in heterogeneous catalytic reactions with participation of oxygen is based on slow oxidation and reduction of the metal surface. We present Monte Carlo simulations of spatiotemporal patterns corresponding to this mechanism. As an example, we analyze the 2A+B2 → 2AB reaction mimicking CO (or H 2) oxidation on Pt. Calculations taking into account the nonideality of the kinetics of oxidation and reduction of the substrate are executed with a qualitatively realistic ratio of the rates of elementary steps. The results obtained indicate that the reaction scheme under consideration possesses the ability of spatial self-organization even if cooperative effects in nucleation, growth and decay of oxide islands are neglected. In this case, however, the islands are small and rather disordered. With the cooperative effects, the size of islands becomes larger but not dramatically. A very strong tendency to form oxide islands is found to suppress oscillations.
SPIN-POLARIZED VACUUM TUNNELING: CORRELATION OF ELECTRONIC AND MAGNETIC PROPERTIES ON THE NANOMETER SCALE
Authors: GETZLAFF M. , BODE M. , WIESENDANGER R.
Published: July 2002

The realization of spin-polarized vacuum tunneling is demonstrated for the Gd(0001) surface, which is ideally suited since it exhibits a surface state that is exchange-split into two parts with opposite spin polarization. Both appear as distinct features in the tunneling spectra. The use of ferromagnetic probe tips leads to magnetic-field-dependent asymmetries in the differential tunneling conductivity at bias voltages which correspond to the energies of the spin components. By mapping the asymmetry parameter we can image the magnetic domain structure of the sample. The spin polarization of the differential tunneling conductivity is found to be in excellent agreement with (inverse) photoemission data.
STRUCTURE AND DYNAMICS OF Al TRIMER ON Al(111) SURFACE
Authors: CHANG C. M. , WEI C. M.
Published: July 2002

Trimer is the smallest cluster that can have a one-dimensional or a two-dimensional structure on fcc (111) surface. Using first-principles density-functional-theory calculations, the structural and dynamical properties of Al trimer on Al(111) surface have been studied in detail. Al trimer on Al(111) surface has four close-packed (compact) triangular configurations, two linear configurations, and some other noncompact triangular configurations. The close-packed triangular trimers are more stable than the noncompact triangular trimers as well as the linear trimers. For the dynamics of Al trimer on Al(111) surface, the diffusion processes are much more complicated than the adatom and dimer diffusions. There are three different kinds of diffusion mechanisms: concerted translations and rotation of compact triangular trimers (the energy barrier, Ed=0.24 eV); back and forth transformation between compact triangular trimers and linear trimers (Ed=0.21 eV); and translation of linear trimers (Ed= 0.28 eV). Among these different mechanisms with similar height of diffusion barriers, the concerted translations of the compact triangular trimers have the longest displacement of the center of mass in each step. Therefore, we expect that the long-range diffusion of Al trimer on Al(111) surface is dominated by the concerted motion process of the compact triangular trimers.
TENSOR LEED ANALYSES FOR THREE CHEMISORBED STRUCTURES FORMED BY IODINE ON A Pt(111) SURFACE
Authors: SAIDY M. , MITCHELL K. A. R. , FURMAN S. A. , LABAYEN M. , HARRINGTON D. A.
Published: July 2002

Three distinct ordered iodine structures on a Pt(111) surface have been studied with LEED crystallography in the coverage range 0.33–0.44 monolayers. These surfaces have translational symmetries of the [Formula: see text], [Formula: see text] and (3×3) types, and they all involve overlayer adsorption on the basically unreconstructed metal structures. The [Formula: see text] surface phase is indicated to have essentially all I atoms adsorbed at the regular threefold sites of the fcc type (i.e. 3f sites), with no significant involvement by the corresponding sites of the hcp type (i.e. 3h sites). The [Formula: see text] structure has one I on an atop Pt site, and one each at 3f and 3h sites per unit mesh, while the (3×3) surface has one I on an atop site and three on bridge sites per unit mesh. The I corrugation is about 0.5 Å for the [Formula: see text] structure, but is reduced to around 0.1 Å at the (3×3) surface. The surface I–Pt bond lengths from these analyses show a general tendency to follow trends expected with the varying I coordination numbers. A preliminary discussion is given for uncertainties associated with some relaxations indicated in the metallic structures.
IMITATION IN FINANCIAL MARKETS
Authors: BHAMRA HARJOAT SINGH
Published: July 2002

It is believed that trading agents often imitate the behaviour of those around them. In its excessive form this imitation can help lead to large increases or decreases in asset-prices over a small time, often described as bubbles and crashes. In this paper we examine a model in which rational agents repeatedly trade one asset whose price is influenced by supply and demand together with a stochastic noise term. Each agent is able to observe and remember the actions of her nearest neighbours. Furthermore the agents receive private information about the asset-price. We find that profit-maximization implies that agents should to some extent imitate the behaviour of the people around them allowing the use of the Ising Spin Model to investigate agent-agent interactions.
A TAYLOR FORMULA TO PRICE AND HEDGE EUROPEAN CONTINGENT CLAIMS
Authors: MANCINO MARIA ELVIRA
Published: July 2002

We present the no-arbitrage price and the hedging strategy of an European contingent claim through a representation formula which is an extension of the Clark-Ocone formula. Our formula can be interpreted as a second order Taylor formula of the no arbitrage price of a contingent claim. The zero order term is given by the mean of the contingent claim payoff, the first order term by the stochastic integral of the mean of its Malliavin derivative and the second order term by the stochastic integral of the conditional expectation of the second Malliavin derivative. A Taylor series expansion is also provided together with a bound to the approximation error obtained by neglecting the second order term in the Taylor formula.
A NOTE ON THE NONLINEAR SCHRÖDINGER EQUATION IN WEAK LpSPACES
Authors: CAZENAVE THIERRY , VEGA LUIS , VILELA MARI CRUZ
Published: July 2002

We study the global Cauchy problem for the equation iut+Δu+λ|u|αu=0 in ℝN. Using generalized Strichartz' inequalities we show that, under some restrictions on α, if the initial value is sufficiently small in some weak Lpspace then there exists a global solution. This result provides a common framework to the "classical" Hssolutions and to the self-similar solutions, thereby extending previous results by Planchon.
DESIGN OF MEMS-BASED STABILIZATION FOR BUCKLING CONSTRAINED STRUCTURES
Authors: SMITH BRAM W. , CHASE J. GEOFFREY
Published: July 2002

Linear buckling of plates and columns is a critical design parameter in many engineering systems. Active stabilization of buckling constrained structures promises positive tradeoffs in terms of mass and performance. An optimal design method for actively stabilizing structural instability, while guaranteeing the performance and stability of the closed loop system, is presented. This method accounts for major design criteria such as active critical load, and sensor and actuator placement. Practical tradeoffs and limitations of this approach are presented for delineating the design space and evaluating potential design applications. These methods are shown to describe the feasible region and tradeoffs for active buckling control to highlight those application areas where active stabilization has greatest promise for expanding design spaces and creating novel structural systems.