bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of the sedative effects of buprenorphine administered with 20 μg/kg detomidine in horses
Authors: Love E. J. , Taylor P. M. , Murrell J. , Whay H. R. , Waterman‐Pearson A. E.
Published: April 2011

The aim of this randomised, observer‐blinded, crossover study was to compare the effects of four treatments, administered intravenously to six horses: saline and saline; 10 µg/kg detomidine and 7.5 µg/kg buprenorphine; 20 µg/kg detomidine and 7.5 µg/kg buprenorphine; and 20 µg/kg detomidine and 10 µg/kg buprenorphine. Sedation was subjectively assessed and recorded on a visual analogue scale. Peak sedation and duration of sedation were investigated using a univariate general linear model with post‐hoc Tukey tests (P<0.05). Increasing the dose of detomidine from 10 to 20 µg/kg increased the degree of sedation when administered with the same dose of buprenorphine (7.5 µg/kg). When administered with 20 µg/kg detomidine, increasing the dose of buprenorphine from 7.5 to 10 µg/kg did not influence the degree of sedation achieved.
VIII.: ON SOME OF THE PARASITIC COPEPODS OF THE BAY OF FUNDY FISH.
Authors: Stock B.A. V.
Published: April 2011

not available
Finite element modelling of pullout testing on a soil nail in a pullout box under different overburden and grouting pressures
Authors: Zhou Wan-Huan , Yin Jian-Hua , Hong Cheng-Yu
Published: April 2011

In this paper, a three-dimensional (3D) finite element (FE) model is developed to simulate the pullout behaviour of a soil nail in a soil-nail pullout box under different overburden and grouting pressures. The FE model simulates all the procedures of a pullout test on a grouted soil nail in a compacted and saturated completely decomposed granite (CDG) soil. The stress–strain behaviour of the CDG soil is described by a modified Drucker–Prager/Cap model, while that of the soil–nail interface is represented by the Coulomb friction model. Triaxial experiment data are used to calibrate the soil parameters in the soil constitutive model. The interface parameters are determined from back-analysis with the laboratory soil-nail pullout data. The soil stress variations surrounding the soil nail during drilling, grouting, saturation, and pullout are all well simulated by the FE modelling and compared with available test data. The comparisons between the modelling and experimental data have shown that the established FE can well simulate the pullout behaviour of a soil nail in a soil mass. Based on this, the verified FE model has the potential to simulate the performance of a soil nail in a field soil slope.
Guidelines for offshore in situ testing and interpretation in deepwater soft clays
Authors: Lunne Tom , Andersen Knut H. , Low Han Eng , Randolph Mark F. , Sjursen Morten
Published: April 2011

Offshore developments for hydrocarbon resources have now progressed to water depths approaching 3000 m, with geotechnical design increasingly focused on soft sediments in the upper 30 m or so of the seabed. Due to the difficulties and high cost in recovering high-quality samples from deepwater sites, there is increasing dependence on in situ testing techniques for determining the geotechnical design parameters. This paper summarizes the findings from a joint industry project, undertaken by the Norwegian Geotechnical Institute and the Centre for Offshore Foundation Systems at The University of Western Australia, on the use of in situ testing for the characterization of deepwater soft soils. The project focused on theoretical and empirical studies for the interpretation of piezocone, T-bar, and ball penetration test data, linking the penetration resistance to shear strengths determined from in situ vane tests and laboratory tests on high-quality samples. Guidelines are summarized for interpreting in situ test data, particularly for estimating intact and remoulded undrained shear strengths from the penetration resistance measured by each type of penetrometer. Suggestions are also given for future development of in situ testing techniques to maximize the potential of in situ testing in characterization of deepwater soft soils.
Movement behaviour of the Little Chief Slide
Authors: Mansour Mohamed F. , Martin C. Derek , Morgenstern Norbert R.
Published: April 2011

The Little Chief Slide has been extremely slow moving at a rate of 4–14 mm/year since the late 1960s. The 800 million m3slide lies about 3 km upstream of Mica Dam in British Columbia. The extremely slow rate was not affected by the Mica Dam reservoir filling in the 1970s. Although the Little Chief Slide is classified as a rock slide, the extremely slow movements take place on seams of soft materials composed mainly of micaceous clay gouge. The characteristics of the movement trends with time were investigated at six zones using in-place inclinometers (IPIs). The trends of the movement with the reservoir level fluctuations and pore pressure changes were investigated to quantify the contribution of steady-state creep to the total in situ movements. The creep behaviour of the clay gouge materials forming the movement zones was also investigated in the laboratory. The laboratory and field creep behaviours were then compared. The movement could be partitioned into steady-state creep and seasonally induced creep movements. This partitioning identified the locations where the seasonal movements are the highest, and, hence, where drainage measures could have the biggest impact.
ON INVARIANTS AND SCALAR CHIRAL CORRELATION FUNCTIONS IN ${\mathcal N} = 1$ SUPERCONFORMAL FIELD THEORIES
Authors: KNUTH HOLGER
Published: April 2011

A general expression for the four-point function with vanishing total R-charge of antichiral and chiral superfields in [Formula: see text] superconformal theories is given. It is obtained by applying the exponential of a simple universal nilpotent differential operator to an arbitrary function of two cross-ratios. To achieve this the nilpotent superconformal invariants according to Park are focused. Several dependencies between these invariants are presented, so that eight nilpotent invariants and 27 monomials of these invariants of degree d > 1 are left being linearly independent. It is analyzed, how terms within the four-point function of general scalar superfields cancel in order to fulfill the chiral restrictions.
A COMPOSITE FERMION APPROACH TO THE ULTRACOLD DILUTE FERMI GAS
Authors: CAZALILLA M. A.
Published: April 2011

It is argued that the recently observed Fermi liquids in strongly interacting ultracold Fermi gases are adiabatically connected to a projected Fermi gas. This conclusion is reached by constructing a set of Jastrow wavefunctions, following Tan's observations on the structure of the physical Hilbert space [Annals of Physics 323, 2952 (2008)]. The Jastrow projection merely implements the Bethe–Peierls condition on the BCS and Fermi gas wavefunctions. This procedure provides a simple picture of the emergence of Fermi polarons as composite fermions in the normal state of the highly polarized gas. It is also shown that the projected BCS wavefunction can be written as a condensate of pairs of composite fermions (or Fermi polarons). A Hamiltonian for the composite fermions is derived. Within a mean-field theory, it is shown that the ground state and excitations of this Hamiltonian are those of a non-interacting Fermi gas although they are described by Jastrow–Slater wavefunctions.
ELECTROMAGNETICALLY INDUCED NEGATIVE REFRACTIVE INDEX IN DOPED SEMICONDUCTORS AT OPTICAL FREQUENCIES
Authors: KUSSOW ADIL-GERAI , AKYURTLU ALKIM
Published: April 2011

Based on methods of quantum optics, we discuss the possibility of achieving the negative index of refraction in a semiconductor with donor-like impurities. The quantum states of hydrogen-like donor atom and states of an electron in conduction band constitute a discrete-level atomic medium within the optical range. The coherent coupling of an electric dipole transition with a magnetic dipole transition leads to permeability and permittivity responses and, within some frequency band, ensures the negative refractive index. The magnetic moment between two quasi-atomic states separated by optical frequencies is induced by a low-frequency electromagnetic field. The implementation of this scheme is carried out in tin-doped indium oxide, and the calculations show feasibility of the effect within a broad bandwidth ∼2% with a high figure of merit greater than 10 in the optical regime.
CHAOS SYNCHRONIZATION OF FRACTIONAL ORDER UNIFIED CHAOTIC SYSTEM VIA NONLINEAR CONTROL
Authors: CHEN XIANG RONG , LIU CHONG XIN
Published: April 2011

Based on the stability theory of fractional order systems, an effective but theoretically rigorous nonlinear control method is proposed to synchronize the fractional order chaotic systems. Using this method, chaos synchronization between two identical fractional order unified systems is studied. Simulation results are shown to illustrate the effectiveness of this method.
12-BIT PSEUDO-DIFFERENTIAL CURRENT-SOURCE RESISTOR-STRING HYBRID DAC
Authors: AB-AZIZ M. T. S. , MARZUKI A. , AZIZ Z. A. A.
Published: April 2011

This paper discusses a hybrid Digital-Analog Converter (DAC) architecture which is a combination of a binary-weighted resistor approach for eight bits in the least-significant-bit and thermometer coded approach for four bits in the most-significant-bit. The proposed design combines advantages of the binary-weighted resistor approach and thermometer coded approach. The final design is composed of two 12-bit DACs to achieve a pseudo differential output signal. The converter was designed with a Silterra 0.18 μm 1.8 V/3.3 V CMOS process technology. The post-layout simulation results show that this design achieves 12-bit resolution with INL and DNL of 0.375 LSB and 0.25 LSB, respectively. The power consumption is 6.291 mW when the designed DAC is biased with supply voltage equal to 3 V. The performance is accomplished with a design area of 230 μm × 255 μm.
POWER FACTOR AND DISTORTION MEASURING FOR SMALL LOADS USING USB ACQUISITION MODULE
Authors: DIMITRIJEVIĆ MARKO A. , LITOVSKI VANČO B.
Published: April 2011

Power factor and distortion measuring usually require dedicated and expensive equipments. Computer-based acquisition modules and software provide for a possibility to create simple and nonexpensive methods and instruments for power factor measurement and distortion characterization of small loads and bring all advantages of virtual instrumentation. A new approach to power quality characterization by measuring power factor, distortion, and several other parameters of small electric loads (up to 0.5 kW) will be described in this paper. Besides low price maximum versatility and adaptability are provided without any loss in accuracy.
EXPLICIT ODE REDUCTION OF MEMRISTIVE SYSTEMS
Authors: RIAZA RICARDO
Published: April 2011

The recent discovery of a physical device behaving as a memristor has driven a lot of attention to memristive systems, which are likely to play a relevant role in electronics in the near future, especially at the nanometer scale. The derivation of explicit ODE models for these systems is important because it opens a way for the study of the dynamics of general memristive circuits, including e.g. stability aspects, oscillations, bifurcations or chaotic phenomena. We tackle this problem as a reduction of implicit ODE (differential-algebraic) models, and show how tree-based approaches can be adapted in order to accommodate memristors. Specifically, we prove that the derivation of a tree-based explicit ODE model is feasible for strictly passive memristive systems under broad coupling effects and without a priori current/voltage control assumptions on tree/cotree elements. Our framework applies in particular to topologically degenerate circuits and accommodates a wide class of controlled sources. We also discuss a quasilinear reduction of nonpassive problems, which do not admit an explicit ODE description in the presence of singularities; some related bifurcations are addressed in this context.
DYNAMICAL DISORDER AND SELF-CORRELATION IN THE CHARACTERIZATION OF NONLINEAR SYSTEMS: APPLICATION TO DETERMINISTIC CHAOS
Authors: HERNÁNDEZ JUAN ANTONIO , BENITO ROSA MARÍA , CARLOS LOSADA JUAN
Published: April 2011

A new methodology to characterize nonlinear systems is described. It is based on the measurement over the time series of two quantities: the "Dynamical order" and the "Self-correlation". The averaged "Scalar" and "Perpendicular" products are introduced to measure these quantities. While this approach can be applied to general nonlinear systems, the aim of this work is to focus on the characterization and modeling of chaotic systems. In order to illustrate the method, applications to a two-dimensional chaotic system and the modeling of real telephony traffic series are presented. Three important aspects are discussed: the use of the averaged "Scalar" product as supplement of the "Lyapunov exponent", the use of the averaged "Perpendicular" product as a refinement of the "Mutual information" and the reduction of m-dimensional systems to the study of only one dimension. This new conceptual framework introduces a perspective to characterize real and theoretical processes with a unifying method, irrespective of the system classification.
EXPERIMENTAL OBSERVATION OF A CHAOS-TO-CHAOS TRANSITION IN LASER DROPLET GENERATION
Authors: KRESE BLAŽ , PERC MATJAŽ , GOVEKAR EDVARD
Published: April 2011

We examine the dynamics of laser droplet generation that is dependent on the detachment pulse power. In the absence of the detachment pulse, undulating pendant droplets are formed at the end of a properly fed metal wire due to the impact of the primary laser pulse that induces melting. Eventually, these droplets detach, i.e. overcome the surface tension, because of their increasing mass. We show that this spontaneous dripping is deterministically chaotic by using a positive largest Lyapunov exponent and a negative divergence. In the presence of the detachment pulse, however, the generation of droplets is fastened depending on the pulse power. At high powers, the spontaneity of dripping is completely overshadowed by the impact of the detachment pulse. Still, amplitude chaos can be detected, which similarly as the spontaneous dripping, is characterized by a positive largest Lyapunov exponent and a negative divergence, thus indicating that the observed dynamics is deterministically chaotic with an attractor as solution in the phase space. In the intermediate regime, i.e. for low and medium detachment pulse powers, the two chaotic states compete for supremacy, yielding an intermittent period-doubling to amplitude chaos transition, which we characterize by means of recurrence plots and their properties. Altogether, the transition from spontaneous to triggered laser droplet generation is characterized by a chaos-to-chaos transition with an intermediate dynamically nonstationary phase in-between. Since metal droplets can be used in various industrial applications, we hope that the accurate determination of the dynamical properties underlying their formation will facilitate their use and guide future attempts at mathematical modeling.
FEED FORWARD RESIDUE HARMONIC BALANCE METHOD FOR A QUADRATIC NONLINEAR OSCILLATOR
Authors: LEUNG AYT , GUO ZHONGJIN
Published: April 2011

The harmonic balance method truncates the Fourier series in a finite number of terms. In this paper we show that the truncated residues may be important to determine the stability of the approximated solution and that the truncated residues in the stability analysis can fully be considered without increasing the number of equations in the original solution. Therefore, the high order superharmonic and subharmonic responses and the cascade of bifurcations to irregular attractor can be accurately approximated by just the first few terms of the Fourier series so that analytical prediction is possible. A harmonically driven oscillator with quadratic nonlinearity is taken as examples. The explicitly analytical solutions are obtained for the steady state solutions and for the high order superharmonic approximation. The stabilities of the solutions are determined by the Floquet theory. It is shown that the predicted stability of the solution can be qualitatively different with and without the consideration of the feed forward residues. The second-, fourth- and eighth-order subharmonic analytical bifurcation solutions are calculated to obtain the cascades of bifurcations to irregular attractor. The improved analytical harmonic approximations are compared with other results and with numerical solutions. It is proved that a two superharmonic expansion with appropriate subharmonic is sufficient for determining the characteristics of the solutions of a harmonically driven oscillator with quadratic nonlinearity.
PHASE OSCILLATORS WITH SINUSOIDAL COUPLING INTERPRETED IN TERMS OF PROJECTIVE GEOMETRY
Authors: STEWART IAN
Published: April 2011

Marvel et al. [2009] studied sinusoidally coupled phase oscillators, generalizing coupled Josephson junctions. They obtained an explicit reduction of the dynamics to a parametrised family of ODEs on the three-dimensional Möbius group. This differs from the usual reduction on to the orbit space of a symmetry group. We apply the viewpoint of complex projective geometry to obtain an alternative proof that trajectories lie on orbits of the Möbius group, and derive a different explicit form for the reduced ODE. The main innovation is the use of homogeneous coordinates, which linearize the action of the Möbius group and lead to a simple coordinate system in which to write the reduced ODE. We also discuss a Lie-theoretic interpretation.
HIGH-ORDER BISECTION METHOD FOR COMPUTING INVARIANT MANIFOLDS OF TWO-DIMENSIONAL MAPS
Authors: GOODMAN ROY H. , WRÓBEL JACEK K.
Published: April 2011

We describe an efficient and accurate numerical method for computing smooth approximations to invariant manifolds of planar maps, based on geometric modeling ideas from Computer Aided Geometric Design (CAGD). The unstable manifold of a hyperbolic fixed point is modeled by a piecewise Bézier interpolant (a Catmull–Rom spline) and properties of such curves are used to define a rule for adaptively adding points to ensure that the approximation resolves the manifold to within a specified tolerance. Numerical tests on a variety of example mappings demonstrate that the new method produces a manifold of a given accuracy with far fewer calls to the map, compared with previous methods. A brief introduction to the relevant ideas from CAGD is provided.
HUYGENS' ODD SYMPATHY EXPERIMENT REVISITED
Authors: CZOLCZYNSKI K. , PERLIKOWSKI P. , STEFANSKI A. , KAPITANIAK T.
Published: April 2011

We repeat Huygens' experiment using real pendulum clocks in the same way as it was done originally, i.e. we hang two clocks on the same beam and observe the behavior of the pendulums. The clocks in the experiment have been selected in such a way so as to be as identical as possible. It has been observed that when the beam is allowed to move horizontally, the clocks can synchronize both in-phase and anti-phase. We perform computer simulations of the clocks' behavior to answer the question how the nonidentity of the clocks influences the synchronization process. We show that even the clocks with significantly different periods of oscillations can synchronize, but their periods are modified by the beam motion so they are no more accurate.
TORUS KNOTS EMBODYING CURVATURE AND TORSION IN AN OTHERWISE FEATURELESS CONTINUUM
Authors: AVRIN J. S.
Published: April 2011

The subject is a localized disturbance in the form of a torus knot of an otherwise featureless continuum. The knot's topologically quantized, self-sustaining nature emerges in an elementary, straightforward way on the basis of a simple geometric model, one that constrains the differential geometric basis it otherwise shares with General Relativity (GR). Two approaches are employed to generate the knot's solitonic nature, one emphasizing basic differential geometry and the other based on a Lagrangian. The relationship to GR is also examined, especially in terms of the formulation of an energy density for the Lagrangian. The emergent knot formalism is used to derive estimates of some measurable quantities for a certain elementary particle model documented in previous publications. Also emerging is the compatibility of the torus knot formalism and, by extension, that of the cited particle model, with general relativity as well as with the Dirac theoretic notion of antiparticles.
BLENX MODELS OF α-SYNUCLEIN AND PARKIN KINETICS IN NEUROPATHOLOGY OF PARKINSON'S DISEASE
Authors: LECCA PAOLA
Published: April 2011

In this paper two stochastic kinetic models of a faulty ubiquitin–proteasome are presented. In the first model, mutant variants of the α-synuclein, induced by environmental stress factors, inhibit the ubiquitin–proteasome pathway that is in charge to start the degradation of misfolded proteins. In the second model mutant variants of parkin proteins are not able to transfer the ubiquitin molecules on the faulty proteins, so that they are not targeted and recognized as toxic products. The models are specified in BlenX and simulated with Beta Workbench (Beta WB) simulator. BlenX is a new programming language that has been recently designed by the CoSBi team of researchers to describe components and interactions among components of a biochemical system. It implements a process calculus in which the communication and synchronization between computational processes abstract the biochemical interaction and reactions between molecules, proteins and functional complexes. The aim of this study is twofold: (i) to move the current focus on the structural studies of the components of the protein ubiquitination and degradation to the dynamics of such components in a typical systems biology perspective; (ii) to provide first stochastic models in a new language suitable to systemic approach to the modelling of biochemical kinetics. This tool makes it possible for biologists and medical researchers a high-level modeling of molecular mechanisms underlying the pathogenesis of the disease. Consequently, the suitable abstraction provided by the language makes possible the elucidation of important and still elusive aspects of the involved biochemical interactions. The agreement of the simulations of our models with the available qualitative experimental observations and previous theoretical studies supports the confidence in the model validity.
SURVIVAL ANALYSIS OF A STOCHASTIC COOPERATION SYSTEM IN A POLLUTED ENVIRONMENT
Authors: LIU MENG , WANG KE
Published: April 2011

Stochastic cooperation model of two species with generalized dose-response function in a polluted environment is studied. Sufficient criteria for extinction, non-persistence in the mean, weak persistence in the mean, strong persistence in the mean and stochastic persistence are established. The threshold between weak persistence in the mean and extinction for each species is obtained. Certain long-run-average limits of the solutions are represented by two constants in some cases. The results also reveal that both the stochastic noises and the dose-response function play important roles in determining the persistence or extinction of the species.
A TUBERCULOSIS (TB) MODEL WITH UNDETECTED COMPARTMENT: AN APPLICATION TO CHINA
Authors: LI XUE-ZHI , BHATTACHARYA SOUVIK , YANG JUN-YUAN , MARTCHEVA MAIA
Published: April 2011

This article introduces a novel model that studies the major factors jeopardizing tuberculosis (TB) control programme in China. A previously developed two-strain TB model is augmented with a class of individuals not registered under the TB control programme. The paper investigates the basic reproduction number and proves the global stability of the disease-free equilibrium. The presence of three endemic equilibria is established in the model. With the help of numerical simulations, a comparative study has been performed to test the validity of the model presented here to the real data available from the Ministry of Health of the People's Republic of China. Sensitivity and elasticity analysis give the key parameters that would govern successful TB control in China.
EFFECT OF MAGNETIC FIELD ON PERISTALTIC TRANSPORT OF COUPLE STRESS FLUIDS THROUGH A POROUS MEDIUM
Authors: PANDEY S. K. , CHAUBE M. K.
Published: April 2011

This paper analyses peristaltic flow of a couple stress fluid in a channel through a porous medium in the presence of an external magnetic field. The flow is induced by sinusoidal traveling waves along the walls of the channel. The nonlinear convective acceleration terms are duly considered and a perturbation technique is used to solve the problem for the case of small amplitude ratio. The effects of couple-stress parameter, magnetic parameter and permeability parameter on mean velocity on the channel walls, mean axial velocity and critical reflux condition are discussed in detail. Computational results show that the mean velocity at the boundary decreases with increasing couple stress parameter and permeability parameter while it increases with magnetic parameter. It is also revealed that mean axial velocity decreases with increasing couple stress parameter and magnetic parameter while it increases with permeability parameter.
CHASING R0: UNDERSTANDING THE EFFECTS OF POPULATION DYNAMICS ON THE BASIC REPRODUCTION NUMBER
Authors: JOHNSON TINA V. , MIKLER ARMIN R.
Published: April 2011

Preparation for pandemic events depends heavily on understanding specific disease characteristics and predicting the dynamics of a particular outbreak. The basic reproduction number, R0, is an established epidemiologic statistic that provides an indication of secondary infections in the early stages of an outbreak. Assigning a specific value of R0 to a given disease may be misleading. While an estimate of R0 can be calculated after an outbreak has occurred, it is questionable that the same disease will manifest itself in a similar manner under different geographical and/or demographic circumstances. R0 values for a given disease are often represented as a single number or a narrow range of numbers. The experiments discussed in this paper support evidence that a change in population-dependent parameters may affect the value of R0, even though the disease parameters stay constant. When the contact rate, subpopulation interaction, or neighborhood size is adjusted, R0 values fluctuate accordingly. This suggests that the value of R0 is too complex to be attributed to a specific disease with no consideration of other factors that influence the course of disease spread.
ON A PREY–PREDATOR–PATHOGEN MODEL WITH PREY PREFERENCE: A THEORETICAL STUDY
Authors: MUKHOPADHYAY B. , BHATTACHARYYA R.
Published: April 2011

In the present paper, we study a prey–predator–pathogen model where the prey population suffer from an SI epidemic. The predator is assumed to exercise preferential predation. The prey preference mechanism ranges from predation only on the susceptible or only on the infective to proportional predation on both the prey types. The formulation maintains the native Holling type-II functional response in one hand and invokes prey switching on the other. We first describe stability and persistence results for the model without preference, which highlights the significance of some system parameters namely, predator mortality rate and predation pressure on the susceptible in shaping the system dynamics. Then we investigate the model with the preference mechanism, which shows the importance of the preference parameter (α) in controlling the stability and existence criteria of component populations. Our study reveals the existence of preference parameter ranges that (i) guarantees stable species coexistence (ii) exhibits rich dynamics in the form of oscillatory phenomena, point attractors and limit cycle attractors and (iii) causes possible extinction of the predators together with the susceptible prey. The ecological meaning of the corresponding ranges is also elaborated.
THE PRICE OF NASH EQUILIBRIA IN MULTICAST TRANSMISSION GAMES
Authors: BILÒ VITTORIO
Published: April 2011

We consider the problem of sharing the cost of multicast transmissions in non-cooperative undirected networks where a set of receivers R wants to be connected to a common source s. The set of choices available to each receiver r ∈ R is represented by the set of all (s, r)-paths in the network. Given the choices performed by all the receivers, a public known cost sharing method determines the cost share to be charged to each of them. Receivers are selfish agents aiming to obtain the transmission at the minimum cost share and their interactions create a non-cooperative game. Devising cost sharing methods yielding games whose price of anarchy (price of stability), defined as the worst-case (best-case) ratio between the cost of a Nash equilibrium and that of an optimal solution, is not too high is thus of fundamental importance in non-cooperative network design. Moreover, since cost sharing games naturally arise in socio-economical contests, it is convenient for a cost sharing method to meet some constraining properties. In this paper, we first define several such properties and analyze their impact on the prices of anarchy and stability. We also reconsider all the methods known so far by classifying them according to which properties they satisfy and giving the first non-trivial lower bounds on their price of stability. Finally, we propose a new method, namely the free-riders method, which admits a polynomial time algorithm for computing a pure Nash equilibrium whose cost is at most twice the optimal one. Some of the ideas characterizing our approach have been independently proposed in Ref. 10.
AN INDICATOR FUNCTION LIMIT THEOREM IN DYNAMICAL SYSTEMS
Authors: DURIEU OLIVIER , VOLNÝ DALIBOR
Published: April 2011

We give a constructive proof of the following result: in all aperiodic dynamical system, for all sequences (an)n∈ℕ ⊂ ℝ+ such that an ↗ ∞ and [Formula: see text] as n → ∞, there exists a set [Formula: see text] having the property that the sequence of the distributions of [Formula: see text] is dense in the space of all probability measures on ℝ. This extends a result of O. Durieu and D. Volný, Ergod. Th. Dynam. Syst. to the non-ergodic case.
INVOLUTIONS AND FREE PAIRS OF BASS CYCLIC UNITS IN INTEGRAL GROUP RINGS
Authors: GONÇALVES J. Z. , PASSMAN D. S.
Published: April 2011

Let ℤG be the integral group ring of the finite nonabelian group G over the ring of integers ℤ, and let * be an involution of ℤG that extends one of G. If x and y are elements of G, we investigate when pairs of the form (uk, m(x), uk, m(x*)) or (uk, m(x), uk, m(y)), formed respectively by Bass cyclic and *-symmetric Bass cyclic units, generate a free noncyclic subgroup of the unit group of ℤG.
STAR-INVERTIBILITY AND t-FINITE CHARACTER IN INTEGRAL DOMAINS
Authors: FINOCCHIARO CARMELO ANTONIO , PICOZZA GIAMPAOLO , TARTARONE FRANCESCA
Published: April 2011

Let A be an integral domain. We study new conditions on families of integral ideals of A in order to get that A is of t-finite character (i.e. each nonzero element of A is contained in finitely many t-maximal ideals). We also investigate problems connected with the local invertibility of ideals.
ON MINIMAL WEAKLY s-SUPPLEMENTED SUBGROUPS OF FINITE GROUPS
Authors: LI YANGMING , LI BAOJUN
Published: April 2011

Suppose G is a finite group and H is subgroup of G. H is said to be s-permutable in G if HGp = GpH for any Sylow p-subgroup Gp of G; H is called weakly s-supplemented subgroup of G if there is a subgroup T of G such that G = HT and H ∩ T ≤ HsG, where HsG is the subgroup of H generated by all those subgroups of H which are s-permutable in G. We investigate the influence of minimal weakly s-supplemented subgroups on the structure of finite groups and generalize some recent results. Furthermore, we give a positive answer in the minimal subgroup case for Skiba's Open Questions in [On weakly s-permutable subgroups of finite groups, J. Algebra315 (2007) 192–209].
SEMIDIRECT PRODUCTS AND FUNCTIONAL EQUATIONS FOR QUANTUM MULTIPLICATION
Authors: NATHANSON MELVYN B.
Published: April 2011

The quantum integer [n]q is the polynomial 1 + q + q2 + ⋯ + qn-1, and the sequence of polynomials [Formula: see text] is a solution of the functional equation fmn(q) = fm(q)fn(qm). In this paper, semidirect products of semigroups are used to produce families of functional equations that generalize the functional equation for quantum multiplication.
EXPLORATION OF FINITE-DIMENSIONAL KAC ALGEBRAS AND LATTICES OF INTERMEDIATE SUBFACTORS OF IRREDUCIBLE INCLUSIONS
Authors: DAVID MARIE-CLAUDE , THIÉRY NICOLAS M.
Published: April 2011

We study the four infinite families KA(n), KB(n), KD(n), and KQ(n) of finite-dimensional Hopf (in fact Kac) algebras constructed, respectively, by A. Masuoka and L. Vainerman: isomorphisms, automorphism groups, self-duality, lattices of coideal sub-algebras. We reduce the study to KD(n) by proving that the others are isomorphic to KD(n), its dual, or an index 2 subalgebra of KD(2n). We derive many examples of lattices of intermediate subfactors of the inclusions of depth 2 associated to those Kac algebras, as well as the corresponding principal graphs, which is the original motivation. Along the way, we extend some general results on the Galois correspondence for depth 2 inclusions, and develop some tools and algorithms for the study of twisted group algebras and their lattices of coideal subalgebras. This research was driven by heavy computer exploration, whose tools and methodology we describe.
INFINITE DESCENDING CHAINS OF COCOMPACT LATTICES IN KAC–MOODY GROUPS
Authors: CARBONE LISA , COBBS LEIGH
Published: April 2011

Let A be a symmetrizable affine or hyperbolic generalized Cartan matrix. Let G be a locally compact Kac–Moody group associated to A over a finite field 𝔽q. We suppose that G has type ∞, that is, the Weyl group W of G is a free product of ℤ/2ℤ's. This includes all locally compact Kac–Moody groups of rank 2 and three possible locally compact rank 3 Kac–Moody groups of noncompact hyperbolic type. For every prime power q, we give a sufficient condition for the rank 2 Kac–Moody group G to contain a cocompact lattice [Formula: see text] with quotient a simplex, and we show that this condition is satisfied when q = 2s. If further Mqand [Formula: see text] are abelian, we give a method for constructing an infinite descending chain of cocompact lattices … Γ3≤ Γ2≤ Γ1≤ Γ. This allows us to characterize each of the quotient graphs of groups Γi\\X, the presentations of the Γiand their covolumes, where X is the Tits building of G, a homogeneous tree. Our approach is to extend coverings of edge-indexed graphs to covering morphisms of graphs of groups with abelian groupings. This method is not specific to cocompact lattices in Kac–Moody groups and may be used to produce chains of subgroups acting on trees in a general setting. It follows that the lattices constructed in the rank 2 Kac–Moody group have the Haagerup property. When q = 2 and rank (G) = 3 we show that G contains a cocompact lattice Γ′1that acts discretely and cocompactly on a simplicial tree [Formula: see text]. The tree [Formula: see text] is naturally embedded in the Tits building X of G, a rank 3 hyperbolic building. Moreover Γ′1≤ Λ′ for a non-discrete subgroup Λ′ ≤ G whose quotient Λ′ \ X is equal to G\X. Using the action of Γ′1on [Formula: see text] we construct an infinite descending chain of cocompact lattices …Γ′3≤ Γ′2≤ Γ′1in G. We also determine the quotient graphs of groups [Formula: see text], the presentations of the Γ′iand their covolumes.
ON G-TYPE DOMAINS
Authors: KARAMZADEH O. A. S. , MOSLEMI B.
Published: April 2011

In this paper, we introduce and study the notion of G-type domains (a domain R is G-type if its quotient field is countably generated R-algebra). We extend some of the basic properties of G-domains to G-type domains. It's observed that a prime ideal of R[x1, x2,…,xn,…] is G-type if and only if its contractions in R, R[x1, x2,…,xn] for all n ≥ 1 are G-type. Using this concept we give a natural proof of the well-known Hilbert Nullstellensatz in infinite countable-dimensional spaces. Characterizations of Noetherian G-type domains, Noetherian G-type domains with the countable prime avoidance property are given. As a consequence, we observe that in complete Noetherian semi-local rings, G-type ideals and G-ideals are the same. Rings with countable Noetherian dimension which are direct sum of G-type domains are fully determined. Finally, we characterize Noetherian rings in which G-type ideals are maximal.
A CONSTRUCTION OF QUASI-GORENSTEIN RINGS
Authors: BAGHERI AMIR , SALIMI MARYAM , TAVASOLI ELHAM , YASSEMI SIAMAK
Published: April 2011

Let R be a commutative Noetherian ring and let I be an ideal of R. In this paper, we study the amalgamated duplication ring R ⋈ I which is introduced by D'Anna and Fontana. It is shown that if R satisfies Serre's condition (Sn) and I𝔭 is a maximal Cohen–Macaulay R𝔭-module for every 𝔭 ∈ Spec (R), then R ⋈ I satisfies Serre's condition (Sn). Moreover if R ⋈ I satisfies Serre's condition (Sn), then so does R. This gives a generalization of the same result for Cohen–Macaulay rings in [D'Anna, A construction of Gorenstein rings, J. Algebra306 (2006) 507–519]. In addition it is shown that if R is a local ring and Ann R(I) = 0, then R ⋈ I is quasi-Gorenstein if and only if [Formula: see text] satisfies Serre's condition (S2) and I is a canonical ideal of R. This result improves the result of D'Anna which is corrected by Shapiro and states that if R is a Cohen–Macaulay local ring, then R ⋈ I is Gorenstein if and only if the canonical ideal of R exists and is isomorphic to I, provided Ann R(I) = 0.
TWO SPACES OF MINIMAL PRIMES
Authors: BHATTACHARJEE PAPIYA
Published: April 2011

This paper studies algebraic frames L and the set Min (L) of minimal prime elements of L. We will endow the set Min (L) with two well-known topologies, known as the Hull-kernel (or Zariski) topology and the inverse topology, and discuss several properties of these two spaces. It will be shown that Min (L) endowed with the Hull-kernel topology is a zero-dimensional, Hausdorff space; whereas, Min (L) endowed with the inverse topology is a T1, compact space. The main goal will be to find conditions on L for the spaces Min (L) and Min (L)-1 to have various topological properties; for example, compact, locally compact, Hausdorff, zero-dimensional, and extremally disconnected. We will also discuss when the two topological spaces are Boolean and Stone spaces.
A SURVEY ON GEODESIC COMPLETENESS OF NONDEGENERATE SUBMANIFOLDS IN SEMI-RIEMANNIAN GEOMETRY
Authors: ERKEKOGLU FAZİLET
Published: April 2011

In this survey, we study the geodesic completeness of nondegenerate submanifolds in semi-Riemannian geometry. We also include the study of the geodesic completeness of nondegenerate submanifolds in semi-Euclidean spaces by extending the study of Beem and Ehrlich [4] to semi-Euclidean spaces.
TWISTED TOPOLOGICAL STRUCTURES RELATED TO M-BRANES
Authors: SATI HISHAM
Published: April 2011

Studying the M-branes leads us naturally to new structures that we call Membrane-, Membranec, StringK(ℤ,3)and FivebraneK(ℤ,4)structures, which we show can also have twisted counterparts. We study some of their basic properties, highlight analogies with structures associated with lower levels of the Whitehead tower of the orthogonal group, and demonstrate the relations to M-branes.
ON EULER'S THEOREM IN SEMI-EUCLIDEAN SPACES $\mathbb{E}_{v}^{n+1}$
Authors: ÇÖKEN A. CEYLAN
Published: April 2011

In this paper, we study Euler's theorem for semi-Euclidean hypersurfaces in the semi-Euclidean spaces [Formula: see text]. We obtain an analog of the well-known Euler's theorem for semi-Euclidean hypersurfaces in the semi-Euclidean spaces [Formula: see text]. Then we give corollaries of Euler's theorem concerning conjugate and asymptotic directions. After that, we express Euler's theorem and its corollaries for hypersurfaces in the Euclidean space 𝔼m in the case n = m - 1, v = 0. In addition, we give the well-known Euler's theorem and its corollaries for surfaces in the case n = 2, v = 0, for Lorentz surfaces in the case n = 2, v = 1 and for hypersurfaces in Lorentz spaces in the case n = m - 1, v = 1.
TOPOLOGICAL AND GEOMETRICAL PROPRIETIES OF BRANE-WORLDS
Authors: MONTE EDMUNDO M.
Published: April 2011

Through the characterization of a spherically symmetric space-time as a local brane-world immersed into six-dimensional pseudo-Euclidean spaces, with different signatures of the bulk, we investigate the existence of a topological difference in the immersed brane-world. In particular the Schwarzschild's brane-world and its Kruskal (or Frønsdal) brane-world extension are examined from point of view of the immersion formalism. We prove that there is a change of signature of the bulk when we consider a local isometric immersion and different topologies of a brane-world in that bulk.
BUILDING COSMOLOGICAL MODELS VIA NONCOMMUTATIVE GEOMETRY
Authors: MARCOLLI MATILDE
Published: April 2011

This is an overview of new and ongoing research developments aimed at constructing cosmological models based on noncommutative geometry, via the spectral action functional, thought of as a modified gravity action, which includes the coupling with matter when computed on an almost commutative geometry. This survey is mostly based on recent results obtained in collaboration with Elena Pierpaoli and Kevin Teh. We describe various aspects of cosmological models of the very early universe, developed by the author and Pierpaoli, based on the asymptotic expansion of the spectral action functional and on renormalization group analysis of the associated particle physics model (an extension of the standard model with right-handed neutrinos and Majorana mass terms previously developed in collaboration with Chamseddine and Connes). We also describe nonperturbative results, more recently obtained by Pierpaoli, Teh, and the author, which extend to the more modern universe, which show that, for different candidate cosmic topologies, the form of the slow-roll inflation potentials obtained from the nonperturbative calculation of the spectral action are strongly coupled to the underlying geometry and topology. We discuss some ongoing directions of research and open questions in this new field of "noncommutative cosmology". The paper is based on the talk given by the author at the conference "Geometry and Quantum Field Theory" at the MPI, in honor of Alan Carey.
WHEN INTRA-FIRM AND INTER-FIRM COLLABORATIONS CO-OCCUR: COMPARING THEIR IMPACT ACROSS NEW SERVICES VERSUS NEW PRODUCT INNOVATIONS
Authors: Schleimer Stephanie C. , Shulman Arthur D.
Published: April 2011

There is evidence that intra-firm collaboration and inter-firm collaboration are important for new service development (NSD) and new product development (NPD) success. However, evidence of the contributions of each to innovative outcomes is inconsistent. This inconsistency is associated with the tendency of studies to examine the impact of intra-firm collaboration or inter-firm collaborations exclusively. However, most firms involved in NSD or NPD engage simultaneously in intra-firm and inter-firm collaborations. Using a multi-dimensional conception of collaboration we advance a deeper understanding of the relative contributions of these attributes in intra-firm versus inter-firm collaborative environments during NSD versus NPD. Analyses of survey data from 134 innovations confirm that collaboration clearly matters for both NSD and NPD success, but its impact differs depending on (a) whether a new product or service was developed, (b) on the collaborative environment (intra-firm or inter-firm), and (c) on the collaborative attributes examined. Implications for advancing innovation theory and practice are provided.
MANAGING QUALITY AND NETWORK EFFECTS IN THE HIGH-TECH MARKET: THE CASE OF RESEARCH AND DEVELOPMENT TOOLS IN LIFE SCIENCE INDUSTRY
Authors: HU YANSONG , McLOUGHLIN DAMIEN
Published: April 2011

We seek to extend current theory on research and development (R&D) tools and create new insights by adopting a multi-disciplinary approach and drawing from literatures on quality and network effects in the high-tech market. More specifically, we use a unified framework on quality and network effects, and examine two forms of quality effects (third party quality reviews and company-advertised quality) and two types of network effects (network externalities effect and social network effect) in driving the popularity and success of R&D tools. By tracking two categories of R&D tools in the life science industry for a decade, our research provides a sharper understanding of R&D tools and therefore can help R&D tool producers to accelerate the market acceptance of their new tools, which should promote faster innovation and ultimately benefit the whole R&D community.
A MULTISCALE APPROACH TO FAILURE ASSESSMENT IN DEPLOYMENT FOR CARDIOVASCULAR STENTS
Authors: HAREWOOD F. , GROGAN J. , McHUGH P.
Published: April 2011

Cardiovascular stents are tiny scaffolds that are used in the treatment of heart disease. The recent development of drug-eluting stents has lead to stent implantation in arterial regions that would previously have been considered too complex. Deployment in these tortuous and branched regions results in an increased deformation of the stent. It is thus important to assess whether there is an increased likelihood of stent failure in deployment in such regions. A multiscale approach, incorporating the results of microscale modeling of failure in individual stent struts and macroscale modeling of stent deployment in realistic arterial geometries is considered in this work. Such an approach allows for a more accurate assessment of failure than is obtainable through the macroscale modeling of deployment in idealized arterial geometries alone, as is presented in previous studies. Results give an insight into failure risks for different stent implantation scenarios: stent failure is unlikely in deployment in tortuous vessels, however there may be risks associated with certain bifurcational stenting techniques.
On P vs. NP and geometric complexity theory
Authors: Mulmuley Ketan D.
Published: April 2011

This article gives an overview of the geometric complexity theory (GCT) approach towards the P vs. NP and related problems focusing on its main complexity theoretic results. These are: (1) two concrete lower bounds, which are currently the best known lower bounds in the context of the P vs. NC and permanent vs. determinant problems, (2) the Flip Theorem, which formalizes the self-referential paradox in the P vs. NP problem, and (3) the Decomposition Theorem, which decomposes the arithmetic P vs. NP and permanent vs. determinant problems into subproblems without self-referential difficulty, consisting of positivity hypotheses in algebraic geometry and representation theory and easier hardness hypotheses.