bluuebunny/crossref_metadata_2025 huggingface dataset:
NONCOMMUTATIVITY IN MAXWELL–CHERN–SIMONS-MATTER THEORY SIMULATES PAULI MAGNETIC COUPLING
Authors: GHOSH SUBIR
Published: June 2005

We study interactions between like charges in the noncommutative Maxwell–Chern–Simons electrodynamics minimally coupled to spinors or scalars. We demonstrate that the nonrelativistic potential profiles, for only spatial noncommutativity, are nearly identical to the ones generated by a non-minimal Pauli magnetic coupling, originally introduced by Stern.12 Although the Pauli term has crucial roles in the context of physically relevant objects such as anyons and like-charge bound states (or "Cooper pairs"), its inception12 (see also Ref. 13) was ad hoc and phenomenological in nature. On the other hand, we recover similar results by extending the minimal model to the noncommutative plane, which has developed into an important generalization to ordinary spacetime in recent years. No additional input is needed besides the noncommutativity parameter.

We prove a novel result that for complex scalar matter sector, the bound states (or "Cooper pairs") can be generated only if the Maxwell–Chern–Simons-scalar theory is embedded in noncommutative spacetime. This is all the more interesting since the Chern–Simons term does not directly contribute a noncommutative correction term in the action.
TWO PREDICTIVE SUPERSYMMETRIC S3×Z2 MODELS FOR THE QUARK MASS MATRICES
Authors: LAVOURA LUÍS , MA ERNEST
Published: June 2005

We propose two simple models for the quark mass matrices which may be implemented through an S3×Z2 symmetry in a supersymmetric context. Each model has eight parameters and, therefore, makes two independent predictions for the quark mixing matrix. The first model predicts [Formula: see text] and [Formula: see text]. The second model, in which the forms of the up-type-quark and down-type-quark mass matrices are interchanged relative to the first one, predicts |Vub/Vcb|~0.11 and |Vtd/Vts|~0.33. Both models have sin 2β~0.5.
DIJET EVENT SHAPES AS DIAGNOSTIC TOOLS
Authors: BERGER CAROLA F.
Published: June 2005

Event shapes have long been used to extract information about hadronic final states and the properties of QCD, such as particle spin and the running coupling. Recently, a family of event shapes, the angularities, has been introduced that depends on a continuous parameter. This additional parameter-dependence further extends the versatility of event shapes. It provides a handle on nonperturbative power corrections, on non-global logarithms, and on the flow of color in the final state.
RELATIONAL TOPOLOGY AS THE FOUNDATION FOR QUANTUM GRAVITY
Authors: CRANE LOUIS
Published: June 2005

We propose a new approach to the quantum theory of gravitation, in which the point sets of regions of spacetime are replaced by objects in a category. The objects can be constructed as limits of spin foam models, thus directly connecting to approximations to general relativity which have already been studied, and leading to a mathematically natural interpretation of the meaning of the triangulations in the spin foam models. The physical motivation for our proposal is a connection between ideas about the limited amount of information which can flow from one region to another in General Relativity, an analysis of the problem of the infinities in QFT, and the relational or categorical approach to topology in abstract homotopy theory and algebraic geometry.
FEYNMAN LOOPS AND THREE-DIMENSIONAL QUANTUM GRAVITY
Authors: BARRETT JOHN W.
Published: June 2005

This paper explores the idea that within the framework of three-dimensional quantum gravity one can extend the notion of Feynman diagram to include the coupling of the particles in the diagram with quantum gravity. The paper concentrates on the non-trivial part of the gravitational response, which is to the large momenta propagating around a closed loop. By taking a limiting case one can give a simple geometric description of this gravitational response. This is calculated in detail for the example of a closed Feynman loop in the form of a trefoil knot. The results show that when the magnitude of the momentum passes a certain threshold value, non-trivial gravitational configurations of the knot play an important role.
ANTI-DE SITTER 3-DIMENSIONAL GRAVITY WITH TORSION
Authors: BLAGOJEVIĆ M. , VASILIĆ M.
Published: June 2005

Using the canonical formalism, we study the asymptotic symmetries of the topological 3-dimensional gravity with torsion. In the anti-de Sitter sector, the symmetries are realized by two independent Virasoro algebras with classical central charges. In the simple case of the teleparallel vacuum geometry, the central charges are equal to each other and have the same value as in general relativity, while in the general Riemann-Cartan geometry, they become different.
FUNCTORIAL ASPECTS	OF THE SPACE OF GENERALIZED CONNECTIONS
Authors: VELHINHO J. M.
Published: June 2005

We give a description of the category structure of the space of generalized connections, an extension of the space of connections that plays a central role in loop quantum gravity.
NEW SPIN FOAM MODELS OF QUANTUM GRAVITY
Authors: MIKOVIĆ A.
Published: June 2005

We give a brief and a critical review of the Barret-Crane spin foam models of quantum gravity. Then we describe two new spin foam models which are obtained by direct quantization of General Relativity and do not have some of the drawbacks of the Barret-Crane models. These are the model of spin foam invariants for the embedded spin networks in loop quantum gravity and the spin foam model based on the integration of the tetrads in the path integral for the Palatini action.
WHAT KIND OF NONCOMMUTATIVE GEOMETRY FOR QUANTUM GRAVITY?
Authors: MARTINETTI PIERRE
Published: June 2005

We give a brief account of the description of the standard model in noncommutative geometry as well as the thermal time hypothesis, questioning their relevance for quantum gravity.
HIGH-FREQUENCY FUZZ
Authors: BURIĆ M. , MADORE J.
Published: June 2005

As a simple example of the "blurring" influence of noncommutative geometry, a noncommutative version of a high-frequency perturbation of a background metric is calculated. The relation between the principal null vectors of the wave and those of the induced symplectic structure is in this case particularly clear.
NON-COMMUTATIVE GAUGE THEORY ON FUZZY ℂP2
Authors: STEINACKER HAROLD
Published: June 2005

Gauge theory on fuzzy ℂP2 can be defined as a multi-matrix model, which consistently combines a UV cutoff with the classical symmetries of ℂP2. The degrees of freedom are 8 hermitian matrices of finite size, 4 of which are tangential gauge fields and 4 are auxiliary variables. The model depends on a noncommutativity parameter [Formula: see text], and reduces to the usual U(n) Yang-Mills action on the 4-dimensional classical ℂP2 in the limit N→∞. The quantization of the model is defined in terms of a path integral, which is manifestly finite.
NONCOMMUTATIVE SCALAR FIELD MINIMALLY COUPLED TO GRAVITY
Authors: BERTOLAMI ORFEU
Published: June 2005

A model for noncommutative scalar fields coupled to gravity based on the generalization of the Moyal product is proposed. Solutions compatible with homogeneous and isotropic flat Robertson-Walker spaces to first non-trivial order in the perturbation of the star-product are presented. It is shown that in the context of a typical chaotic inflationary scenario, at least in the slow-roll regime, noncommutativity yields no observable effect.
DEFORMATION QUANTIZATION AND WIGNER FUNCTIONS
Authors: COSTA DIAS N. , PRATA J. N.
Published: June 2005

We review the Weyl-Wigner formulation of quantum mechanics in phase space. We discuss the concept of Narcowich-Wigner spectrum and use it to state necessary and sufficient conditions for a phase space function to be a Wigner distribution. Based on this formalism we analize the modifications introduced by the presence of boundaries. Finally, we discuss the concept of environment-induced decoherence in the context of the Weyl-Wigner approach.
ON κ IN THE ⋆ PRODUCT
Authors: KOIKAWA TAKAO
Published: June 2005

We discuss the role of the parameter κ appearing in the definition of the ⋆ product. It is known that the ⋆ product is used in the Moyal quantization. The soliton equations are also formulated by using the ⋆ product. We investigate how the parameter κ plays the role in the different fields of physics, the Moyal quantization and the soliton equations.
PARASUPERSYMMETRIC QUANTUM MECHANICS OF ORDER THREE AND A GENERALIZED WITTEN INDEX
Authors: STOŠIĆ MARKO , PICKEN ROGER
Published: June 2005

In this paper we generalize the Rubakov-Spiridonov parasupersymmetry algebra to the order three case. We also generalize the notion of the Witten index, and we provide a class of models satisfying our parasupersymmetry algebra. Finally, we show that there is a correspondence between the Hamiltonian and the index in our class of models.
THE MASSES OF WR TRIPLET HIGGS, AND Z′ BOSONS IN THE LEFT–RIGHT SYMMETRIC MODEL
Authors: SAHOO S. , MAHARANA L. , ACHARYA S. , ROUL A.
Published: June 2005

In the Left–Right Symmetric Model, [Formula: see text] and [Formula: see text] mass differences are considered, taking the effect of the triplet Higgs, WR and Z′ bosons in the effective Hamiltonian in Vacuum Insertion Method and in Heavy Quark Effective Theory. It is observed that the masses MR, MH, and MZ′ are well within the experimental search in the forthcoming accelerators.
DOUBLET GROUPS, EXTENDED LIE ALGEBRAS, AND WELL DEFINED GAUGE THEORIES FOR THE TWO-FORM FIELD
Authors: CANTCHEFF MARCELO BOTTA
Published: June 2005

We propose a symmetry law for a doublet of different form fields, which resembles gauge transformations for matter fields. This may be done for general Lie groups, resulting in an extension of Lie algebras and group manifolds. It is also shown that nonassociative algebras naturally appear in this formalism, which are briefly discussed.

Afterwards, a general connection which includes a two-form field is settled-down, solving the problem of setting a gauge theory for the Kalb–Ramond field for generical groups.

Topological Chern–Simons theories can also be defined in four dimensions, and this approach clarifies their relation to the so-called B ∧ F theories. We also revise some standard aspects of Kalb–Ramond theories in view of these new perspectives.

Since this gauge connection is built upon a pair of fields consisting of a one-form and a two-form, one may define Yang–Mills theories as usually and, remarkably, also minimal coupling with bosonic matter, where the Kalb–Ramond field appears naturally as mediator; so, a new associated conserved charge can be defined. For the Abelian case, we explicitly construct the minimal interaction between B-field and matter following a "gauge principle" and find a novel conserved tensor current. This is our most significative result from the physical viewpoint.

This framework is also generalized in such a way that any p-rank tensor may be formulated as a gauge field.
FLUID DYNAMICS OF NSR STRINGS
Authors: POLYAKOV DIMITRI
Published: June 2005

We show that the renormalization group flows of the massless superstring modes in the presence of fluctuating D-branes satisfy the equations of fluid dynamics. In particular, we show that the D-brane's U(1) field is related to the velocity function in the Navier–Stokes equation while the dilaton plays the role of the passive scalar advected by the turbulent liquid. This leads us to suggest a possible isomorphism between the off-shell superstring theory in the presence of fluctuating D-branes and the fluid mechanical degrees of freedom.
UNIFIED ALGEBRAIC TREATMENT OF RESONANCE
Authors: ALHAIDARI A. D.
Published: June 2005

Energy resonance in scattering is usually investigated either directly in the complex energy plane (E-plane) or indirectly in the complex angular momentum plane (ℓ-plane). Another formulation complementing these two approaches was introduced recently. It is an indirect algebraic method that studies resonances in a complex charge plane (Z-plane). This latter approach will be generalized to provide a unified algebraic treatment of resonances in the complex E-, ℓ-, and Z-planes. The complex scaling (rotation) method will be used in the development of this approach. The resolvent operators (Green's functions) are formally defined in these three spaces. Bound states spectrum and resonance energies in the E-plane are mapped onto a discrete set of poles of the respective resolvent operator on the real line of the ℓ- and Z-planes. These poles move along trajectories as the energy is varied. A finite L2 basis is used in the numerical implementation of this approach. Stability of poles and trajectories against variation in all computational parameters is demonstrated. Resonance energies for a given potential are calculated and compared with those obtained by other studies.
THE SUPERFIELD QUANTISATION OF A SUPERPARTICLE ACTION WITH AN EXTENDED LINE ELEMENT
Authors: FITZGERALD P. L.
Published: June 2005

A massive superparticle action based on the generalised line element in N = 1 global superspace is quantised canonically. A previous method of quantising this action, based on a Fock space analysis, showed that states existed in three supersymmetric multiplets, each of a different mass. The quantisation procedure presented uses the single first class constraint as an operator condition on a general N = 1 superwavefunction. The constraint produces coupled equations of motion for the component wavefunctions. Transformations of the component wavefunctions are derived that decouple the equations of motion and partition the resulting wavefunctions into three separate supermultiplets. Unlike previous quantisations of superparticle actions in N = 1 global superspace, the spinor wavefunctions satisfy the Dirac equation and the vector wavefunctions satisfy the Proca equation.

The off-shell closure of the commutators of the supersymmetry transformations, that include mass parameters, are derived by the introduction of auxiliary wavefunctions.

To avoid the ghosts arising in a previous Fock space quantisation an alternative conjugation is used in the definition of the current, based on a Krein space approach.
A NEW GENERAL APPROXIMATION SCHEME IN QUANTUM THEORY: APPLICATION TO THE ANHARMONIC AND THE DOUBLE WELL OSCILLATORS
Authors: MAHAPATRA B. P. , SANTI N. , PRADHAN N. B.
Published: June 2005

A self-consistent, nonperturbative approximation scheme is proposed which is potentially applicable to arbitrary interacting quantum systems. For the case of self-interaction, the scheme consists in approximating the original interaction HI(ϕ) by a suitable "potential" V(ϕ) which satisfies the following two basic requirements, (i) exact solvability (ES): the "effective" Hamiltonian H0 generated by V(ϕ) is exactly solvable i.e., the spectrum of states |n〉 and the eigenvalues En are known and (ii) equality of quantum averages (EQA): 〈n|HI(ϕ)|n〉 = 〈n|V(ϕ)|n〉 for arbitrary n. The leading order (LO) results for |n〉 and En are thus readily obtained and are found to be accurate to within a few percent of the "exact" results. These LO-results are systematically improvable by the construction of an improved perturbation theory (IPT) with the choice of H0 as the unperturbed Hamiltonian and the modified interaction, λH′(ϕ)≡λ(HI(ϕ) - V(ϕ)), as the perturbation where λ is the coupling strength. The condition of convergence of the IPT for arbitrary λ is satisfied due to the EQA requirement which ensures that 〈n|λH′(ϕ)|n〉 = 0for arbitrary λ and n. This is in contrast to the divergence (which occurs even for infinitesimal λ!) in the naive perturbation theory where the original interaction λHI(ϕ) is chosen as the perturbation. We apply the method to the different cases of the anharmonic and the double well potentials, e.g. quartic-, sextic- and octic-anharmonic oscillators and quartic-, sextic-double well oscillators. Uniformly accurate results for the energy levels over the full allowed range of λ and n are obtained. The results compare well with the exact results predicted by supersymmetry for the case of the sextic anharmonic potential and the double well partner potential. Further improvement in the accuracy of the results by the use of IPT, is demonstrated. We also discuss the vacuum structure and stability of the resulting theory in the above approximation scheme.
HIGGS BOSON SEARCHES AT HADRON COLLIDERS
Authors: BÜSCHER VOLKER , JAKOBS KARL
Published: June 2005

The investigation of the dynamics responsible for electroweak symmetry breaking is one of the prime tasks of experiments at present and future colliders. Experiments at the Tevatron [Formula: see text] Collider and at the CERN Large Hadron Collider (LHC) must be able to discover a Standard Model Higgs boson over the full mass range as well as Higgs bosons in extended models. In this review, the discovery potential for the Standard Model Higgs boson and for Higgs bosons in the Minimal Supersymmetric extension is summarized. Emphasis is put on those studies which have been performed recently within the experimental collaborations using a realistic simulation of the detector performance. This includes a discussion of the search for Higgs bosons using the vector boson fusion mode at the LHC, a discussion of the measurement of Higgs boson parameters as well as a detailed review of the MSSM sector for different benchmark scenarios. The Tevatron part of the review also contains a discussion of first physics results from data taken in the ongoing Run II.
THE ELECTRORHEOLOGICAL FLUIDS WITH HIGH SHEAR STRESS
Authors: LU KUNQUAN , SHEN RONG , WANG XUEZHAO , SUN GANG , WEN WEIJIA
Published: June 2005

A series of high performance ER fluids newly manufactured in our laboratory are presented. The yield stress of those ER fluids can reach several tens of kPa, 100 kPa and even 200 kPa, respectively. For understanding the high shear stress effect a model is proposed base on the electric field induced molecular bounding effect. The main effective factors in fabricating the high performance ER are discussed.
LARGE ENHANCEMENT IN ELECTRORHEOLOGICAL ACTIVITY OF MESOPOROUS CERIUM-DOPED TIO2 FROM HIGH SURFACE AREA AND ROBUST PORE WALLS
Authors: YIN JIANBO , ZHAO XIAOPENG
Published: June 2005

Considering the importance of large interfacial or surface polarization to strong electrorheological (ER) effect, we developed a high surface area mesoporous doped TiO 2 ER material by using block-copolymer. By comparing the ER experiments between samples with mesopore and without mesopore, we demonstrate a very large enhancement in ER activity of mesoporous ER material and its yield stress is 100 times that of the pure TiO 2 ER material and 5-8 times that of single doped TiO 2 without mesoporous structure. We give a preliminary discussion about the improvement in ER activity based on previous dielectric analysis.
MAGNETORHEOLOGICAL ELASTOMERS BASED ON POLYURETHANE/SI-RUBBER HYBRID
Authors: Hu Y. , Wang Y. L. , Gong X. Q. , Gong X. L. , Zhang X. Z. , Jiang W. Q. , Zhang P. Q. , Chen Z. Y.
Published: June 2005

A kind of magnetorheological elastomers based on polyurethane (PU)/silicone rubber ( Si -rubber) hybrid is fabricated without applying magnetic fields. The MR effect is improved by optimizing preparation conditions, in particular by adjusting PU/Si -rubber ratio, and improving compatibility between PU and Si -rubber. The influences of the preparation condition and the relationship between the microstructure and MR effect of this kind of magnetorheological elastomers are discussed in detail. The results show that this kind of MR elastomers has better MR effect than that of MR elastomers based on pure Si -rubber or PU matrix with same testing conditions. SEM analysis indicates that the former forms a peculiar interpenetrating microstructure in the presence of PU in the matrix. The maximum increase in shear modulus of this kind of MR elastomers can be up to 0.5MPa when exposed to a magnetic field of about 0.2T.
RHEOLOGICAL PROPERTIES OF ER-FLUIDS IN TERM OF MULTIPARTICLE PHYSICAL MODEL AND MONTE-CARLO COMPUTER SIMULATION
Authors: Yanovsky Yu. G. , Zgaevskii V. E. , Teplukhin A. V. , Karnet Yu. N.
Published: June 2005

An electrorheological fluids (ERF) are the suspensions consisting of dielectric rigid particles in the viscous (or viscoelastic) media. Based on the three-dimensional well-ordered multi-particle model (the crystal model) we describe rheological properties of ERF. We use the model of cubic body-centered lattice. We also assume that the electric field is orthogonal to the velocity of shear of fluid's layers. The displacement gradients are assumed to be different (from small to finite values). For small deformations in the framework of the approach proposed and under assumptions made it was stated that the ERF can be treated as a viscoelastic body and it is consequently described on the basis of the linear theory of viscoelasticity. We obtain a complex dynamic shear modulus as a function of the electric field strength, volume fraction of filler, electric properties of components of ERF and viscosity of the fluid phase. For finite deformation the relation between stresses and shear rate gradients has also been made. The relation does not keeps whatever phenomenological or arbitrary parameters and takes into account contribution an electrostatic interaction painted by external field dipoles. From other side a bunch of computational experiments by Monte-Carlo approximation to model both the structure and the peculiarities of ERF were made. We use a procedure by Metropolis for canonic NVT ensemble and parallel computational technologies. The structural characteristics, density, energetic parameter and others for system under consideration have been estimated. In order to verify a theoretical predictions we compare both approaches and some experimental data.
EFFECT OF PARTICLE ROTATION ON THE ELECTRORHEOLOGICAL (ER) EFFECTS IN SOME ER SUSPENSIONS
Authors: NEGITA K. , MISONO Y. , SHINAGAWA J. , INAMASU Y.
Published: June 2005

The electrorheological (ER) and dielectric properties were measured simultaneously on carbon and BaTiO 3 suspensions to investigate the relationships between the ER effect and the dielectric permittivities at high electric field strength. In the carbon suspension, frequency dependence of the ER effect and the 1st order dielectric permittivity shows a relaxation type of spectra, while in the 3rd order dielectric permittivity a resonance type of spectrum due to shear-induced particle rotation is observed. On the other hand, in BaTiO 3 suspension, a resonance type of spectrum is observed in each spectrum of the ER effect, 1st order and 3rd order dielectric permittivities. These resonance spectra are also attributed to the shear-induced particle rotation. From a theoretical analysis, it is indicated that the magnitude of the relaxation time of the interfacial polarization is responsible for the difference in the type of the spectra. It is also suggested that the shear-induced particle rotation would be a general property of the ER suspension since the resonance peak in the 3rd order dielectric permittivity, which is caused by the particle rotation, is observed in most of ER suspensions.
OPTIMIZATION OF MAGNETORHEOLOGICAL FLUID VALVES
Authors: KUZHIR P. , BOSSIS G. , BASHTOVOI V.
Published: June 2005

In this paper we analyze efficiency of a magnetorheological (MR) fluid valve consisting of a flow channel placed inside a solenoid. The scope of the optimization is to find a proper geometry and dimensions of the flow channel in order to achieve the highest possible inlet pressure ΔP(H) at a given field strength H. We analyze two types of flow channels: spiral channels with different helix angles and packed beds of spherical and cylindrical particles with different aspect ratios, both nonmagnetic and paramagnetic. For the prediction of the valve discharge characteristics in the presence of the magnetic field of an arbitrary orientation, we have used our recent physical models for MR fluid flows through capillaries and porous media. We show that among spiral channels the most efficient is the one having the minimal helix angle, i.e. the densest winding of the spiral. At H=20 kA/m this channel provides the inlet pressure 9 times the pressure in the absence of the field. Comparing the porous beds, we conclude that those made of superparamagnetic material are always more effective than nonmagnetic beds. The shape of the bed particles has also been found to affect the inlet pressure by affecting porosity and tortuosity of the beds. The most effective bed consists of packed cylinders made of magnetically soft steel and having the length-to-diameter ratio of either 0.5 or 5. At H=20 kA/m these beds give the pressure near 40 times the pressure at zero field and thus show a higher effectiveness compared to spiral channels.
MECHANICAL PROPERTIES OF ELECTRORHEOLOGICAL FLUIDS
Authors: TIAN Y. , ZHU K. Q. , MENG Y. G. , WEN S. Z.
Published: June 2005

Electrorheological (ER) fluids are usually described by the continuous theory, Newtonian model and Bingham model. But during recent years, experiments showed that the mechanical properties of ER fluids were much complex than the traditional definitions. Many-body effect, modeling mechanical properties of ER fluids from particle chains or columns, and other problems are thought to be some key issues in ER effect and for ER mechanism.
MAGNETOELASTICS AND THEIR PROPERTIES
Authors: NIKITIN L. V. , SAMUS A. N.
Published: June 2005

The effect of a uniform magnetic field on the elastic and viscous properties of new magnetocontrolled materials (magnetoelastics) was studied. It was found that the application of a magnetic field leads to a considerable rise both in Young's modulus and in the viscosity of these materials. We investigated the samples prepared both in the absence of magnetic field and in the magnetic field applied during magnetoelastic curing.
Frequency Dependence of Electrorheological (ER) Effect and Its Relationship to Dielectric and Electrical Properties in Ba1-xSrxTiO3 Suspensions
Authors: Misono Yasuhito , Furukawa Shoichi , Yosinaga Hitomi , Sugiyama Junko , Negita Keishi
Published: June 2005

Varying the electric field strength (E), the ER effect, the dielectric permittivity, and the electrical conductivity were simultaneously measured on the Ba 0.75 Sr 0.25 TiO 3 suspension. It was found that at high E the ER effect increased with the frequency (f), while at low E it once decreased and then increased with increase in f. At high E, the dielectric permittivity at low frequencies was much larger than that at high frequencies, indicating that an electrode polarization was formed as a result of accumulations of ions, which were dissociated from the liquid at high E, near the electrodes. This electrode polarization was further confirmed in the time dependence of the electrical conductivity after the electric field was switched on. From these results it is suggested that the E-dependent frequency dependence of the ER effect may be due to the electrode polarization, which causes larger shielding of the applied electric field at lower f while smaller shielding at higher f.
RATE-DEPENDENT ELASTO-SLIDE MODEL FOR SINGLE AND DUAL FREQUENCY MR LAG DAMPER BEHAVIOR
Authors: HU WEI , WERELEY NORMAN M.
Published: June 2005

In order to capture MR lag damper behavior accurately in the context of helicopter rotor dynamic analyses, a physically motivated rate-dependent elasto-slide model was developed based on the Bingham plastic model. This time-domain model uses a rate-dependent slide and a parallel viscous damper to simulate the yield behavior of the MR fluid and uses a stiff spring in series with the slide to represent the preyield stiffness. A method of determination of the model parameters was introduced using MR damper single frequency hysteresis data. The fidelity of the model was justified by the good correlation between modeling results and experimental steady-state data over a wide amplitude and moderate frequency range. Significantly, the rate-dependent elasto-slide model is applicable in predicting response under single and dual frequency loading conditions encountered by an MR lag damper.
SOFTWARE RELIABILITY ANALYSIS INCORPORATING SECOND-ORDER ARCHITECTURAL STATISTICS
Authors: GOKHALE SWAPNA S.
Published: June 2005

Architecture-based techniques for reliability assessment of software applications have received increased attention in the past few years due to the advent of component-based software development paradigm. Most of the prior research efforts in architecture-based analysis use the composite solution approach to solve the architecture-based models in order to estimate application reliability. Though the composite solution approach produces an accurate estimate of application reliability, it suffers from several drawbacks. The most notable drawback of the composite solution approach is that it does not allow an analysis of the sensitivity of the application reliability to the reliabilities of the components comprising the application and the application structure. The hierarchical solution approach on the other hand, has the potential of overcoming the drawbacks of the composite approach. However, in the present form, the hierarchical solution approach produces an estimate of application reliability which is only an approximation of the estimate produced by the composite approach since it does not take into consideration the second-order architectural statistics. Also, although the hierarchical solution approach can be used for sensitivity analysis, mathematical techniques to perform such analysis are lacking. Development of an accurate hierarchical solution approach to estimate application reliability based on its architecture is the focus of this paper. Using the approach described in this paper, an analytical application reliability function which incorporates second-order architectural statistics can be obtained. Sensitivity analysis techniques and expressions to determine the mean time to failure of the application are developed based on this analytical reliability function. We illustrate the reliability prediction, sensitivity analysis, and mean time to failure computation techniques presented in this paper using two case studies.
Hypothermia enhances phosphorylation of IκB kinase and prolongs nuclear localization of NF-κB in lipopolysaccharide-activated macrophages
Authors: Fairchild Karen D. , Singh Ishwar S. , Carter Heather C. , Hester Lisa , Hasday Jeffrey D.
Published: June 2005

Hypothermia (HT) has been associated with both beneficial and detrimental consequences in various pathophysiological states. While HT is generally thought to have anti-inflammatory and cytoprotective effects, we have previously shown that moderate in vitro HT prolongs TNF-α production by LPS-stimulated mononuclear phagocytes, in part by prolonging TNF-α gene transcription and activation of the pleiotropic transcription factor NF-κB. In this study, we have further characterized the effect of moderate (32°C) and marked (28°C) HT in human monocytic THP-1 cells by showing that even short (2 h) exposure to HT followed by a return to normothermic conditions for 22 h resulted in augmented and prolonged production of TNF-α. Production of heat shock protein 72 and activation of heat shock factor 1 are not affected by HT in these studies, suggesting that the effect is not part of a generalized stress response. Using immunoblotting, we have shown that HT augments phosphorylation of IKK-β and IKK-α (up to an 8-fold increase at 28°C and a 3.6-fold increase at 32°C vs. 37°C). Furthermore, nuclear accumulation of NF-κB p65 was significantly prolonged in hypothermic cells (1.4- and 2.5-fold more nuclear p65 at 2 and 4 h at 28 vs. 37°C). Reexpression of IκB-α, which contributes to the termination of NF-κB-dependent transcription, was delayed several hours in HT-exposed cells. Thus we have shown that clinically relevant HT alters both cytosolic and nuclear events responsible for NF-κB activation and deactivation. Enhanced NF-κB activation may contribute to the immunomodulatory effects of HT in various clinical settings.
Age-related apoptotic responses to stretch-induced hypertrophy in quail slow-tonic skeletal muscle
Authors: Siu Parco M. , Alway Stephen E.
Published: June 2005

In the present study, we examined the responses of apoptosis and apoptotic regulatory factors to muscle hypertrophy induced by stretch overload in quail slow-tonic muscles. The wings from one side of young and aged Japanese quails were loaded by attaching a tube weight corresponding to 12% of the bird's body weight for 7 or 21 days. Muscle from the contralateral side served as the intraanimal control. Relative to the intraanimal contralateral control side, the muscle wet weight increased by 96% in young birds, whereas the muscle weight gain in aged birds was not significant after 7 days of loading. After 21 days of loading, muscle weight significantly increased by 179% and 102% in young and aged birds, respectively. Heat shock protein (HSP)72 and HSP27 protein contents in the loaded sides were higher than on the control sides exclusively in young birds after 7 days of loading. Compared with the contralateral control muscle, the extent of apoptotic DNA fragmentation and the total cytosolic apoptosis-inducing factor protein content were reduced in all loaded muscles except for the 7-day-loaded muscles from the aged birds. Bax protein content was diminished in the loaded muscle relative to the control side from all groups, whereas Bcl-2 protein content was reduced in the young and aged muscles after 21 days of loading. The total cytosolic cytochrome c protein content was decreased and the X chromosome-linked inhibitor of apoptosis protein content was elevated in 7- and 21-day-loaded muscles relative to the intraanimal control muscle from young birds. Furthermore, after 7 days of loading the muscles of aged birds, H2O2 content and the total cytosolic protein content of second mitochondrial activator of caspases/direct inhibitor of apoptosis-binding protein with low isoelectric point were elevated compared with the intraanimal control side. These data suggest that stretch overload-induced muscle hypertrophy is associated with changes in apoptosis in slow-tonic skeletal muscle. Moreover, discrepant apoptotic responses to muscle overload in young and aged muscles may account in part for the age-related decline in the capability for muscle hypertrophy.
Differential effects of NF-κB and p38 MAPK inhibitors and combinations thereof on TNF-α- and IL-1β-induced proinflammatory status of endothelial cells in vitro
Authors: Kułdo Joanna M. , Westra Johanna , Ásgeirsdóttir Sigridur A. , Kok Robbert J. , Oosterhuis Koen , Rots Marianne G. , Schouten Jan P. , Limburg Pieter C. , Molema Grietje
Published: June 2005

Endothelial cells actively participate in inflammatory events by regulating leukocyte recruitment via the expression of inflammatory genes such as E-selectin, VCAM-1, ICAM-1, IL-6, IL-8, and cyclooxygenase (COX)-2. In this study we showed by real-time RT-PCR that activation of human umbilical vein endothelial cells (HUVEC) by TNF-α and IL-1β differentially affected the expression of these inflammatory genes. Combined treatment with TNF-α and IL-1β resulted in nonadditive, additive, and even synergistic induction of expression of VCAM-1, IL-8, and IL-6, respectively. Overexpression of dominant-negative inhibitor κB protein blocking NF-κB signaling confirmed a major role of this pathway in controlling both TNF-α- and IL-1β-induced expression of most of the genes studied. Although dexamethasone exerted limited effects at 1 μM, the thioredoxin inhibitor MOL-294, which regulates the redox state of NF-κB, mainly inhibited adhesion molecule expression. Its most pronounced effect was seen on VCAM-1 mRNA levels, especially in IL-1β-activated endothelium. One micromolar RWJ-67657, an inhibitor of p38 MAPK activity, diminished TNF-α- and IL-1β-induced expression of IL-6, IL-8, and E-selectin but had little effect on VCAM-1 and ICAM-1. Combined treatment of HUVEC with MOL-294 and RWJ-67657 resulted in significant blocking of the expression of E-selectin, IL-6, IL-8, and COX-2. The inhibitory effects were much stronger than those observed with single drug treatment. Application of combinations of drugs that affect multiple targets in activated endothelial cells may therefore be considered as a potential new therapeutic strategy to inhibit inflammatory disease activity.
Respiratory muscle responses elicited by dorsal periaqueductal gray stimulation in rats
Authors: Zhang Weirong , Hayward Linda F. , Davenport Paul W.
Published: June 2005

The periaqueductal gray matter is an essential neural substrate for central integration of defense behavior and accompanied autonomic responses. The dorsal half of the periaqueductal gray matter (dPAG) is also involved in mediating emotional responses of anxiety and fear, psychological states that often are associated with changes in ventilation. However, information regarding respiratory modulation elicited from this structure is limited. The present study was undertaken to investigate the relationship between stimulus frequency and magnitude on ventilatory pattern and respiratory muscle activity in urethane-anesthetized, spontaneously breathing rats. Electrical stimulation in the dPAG-recruited abdominal muscle activity increased ventilation and increased respiratory frequency by significantly shortening both inspiratory time and expiratory time. Ventilation increased within the first breath after the onset of stimulation, and the respiratory response increased with increasing stimulus frequency and magnitude. dPAG stimulation also increased baseline EMG activity in the diaphragm and recruited baseline external abdominal oblique EMG activity, normally quiescent during eupneic breathing. Significant changes in cardiorespiratory function were only evoked by stimulus intensities >10 μA and when stimulus frequencies were >10 Hz. Respiratory activity of both the diaphragm and abdominal muscles remained elevated for a minimum of 60 s after cessation of stimulation. These results demonstrate that there is a short-latency respiratory response elicited from the dPAG stimulation, which includes both inspiratory and expiratory muscles. The changes in respiratory timing suggest rapid onset and sustained poststimulus dPAG modulation of the brain stem respiratory network that includes expiratory muscle recruitment.
Cathodal current-induced vasodilation to single application and the amplified response to repeated application in humans rely on aspirin-sensitive mechanisms
Authors: Tartas M. , Bouyé P. , Koïtka A. , Jaquinandi V. , Tan L. , Saumet J. L. , Abraham P.
Published: June 2005

Assumed to rely on an axon reflex, the current-induced vasodilation (CIV) interferes with the microvascular response to iontophoretic drug delivery. Mechanisms resulting in CIV are likely different at the anode and at the cathode. While studies have been conducted to understand anodal CIV, little information is available on cathodal CIV. The present study investigates CIV observed following 0.1-mA cathodal applications on forearms of healthy volunteers and the possible mechanisms involved. Results are expressed in percentage of the cutaneous heat-induced maximal vascular conductance [%MVC (means ± SE)]. 1) The amplitude of CIV was proportional to the duration of cathodal currents for periods of <1 min: r = 0.99. 2) Two current applications of 10 s, with 10-min interstimulation interval, induced a higher peak value of CIV (79.1 ± 8.6% MVC) than the one obtained with all-at-once 20-s current application (39.5 ± 4.3% MVC, P < 0.05). This amplified vascular response due to segmental application was observed for all tested interstimulation intervals (up to 40 min). 3) Two hours and 3 days following pretreatment with 1-g oral aspirin, the CIV observed following cathodal application, as well as the difference of cathodal CIV amplitude between all-at-once and segmented applications, were reduced. These findings suggest a role of prostaglandins, not only released from endothelial or smooth muscle cells, as direct vasodilator and/or as a sensitizer. Thus aspirin pretreatment could be used to decrease CIV resulting from all-at-once and repeated cathodal application and facilitate the study of the specific vascular effect induced by the drug delivered.
Fetal acidosis and hypotension during repeated umbilical cord occlusions are associated with enhanced chemoreflex responses in near-term fetal sheep
Authors: Bennet Laura , Westgate Jenny A. , Liu Yung-Chi (“Jack”) , Wassink Guido , Gunn Alistair J.
Published: June 2005

This study examined the hypothesis that repeated episodes of brief but severe hypoxia would not attenuate the chemoreflex-mediated rapid initial fall in fetal heart rate (FHR) and, further, that greater hypoxic stress, as shown by hypotension and metabolic acidosis, would be associated with an enhanced chemoreflex response. Chronically instrumented, near-term fetal sheep received 1 min total umbilical cord occlusion either every 5 min for 4 h (1:5 group; n = 8) or every 2.5 min (1:2.5 group; n = 8) until mean arterial blood pressure fell to <20 mmHg on two successive occlusions. Umbilical cord occlusion caused variable decelerations, with sustained hypertension in the 1:5 group and little change in acid-base status (pH 7.34 ± 0.03 after 4 h). In contrast, the 1:2.5 group showed progressive hypotension and metabolic acidemia (pH 6.92 ± 0.04 after the last occlusion). The 1:2.5 group showed a significant increase in the rate of initial fall in FHR during the occlusion series, which was greater than the 1:5 group in the last 30 min of the occlusion series (9.4 ± 1.4 vs. 3.5 ± 0.3 beats·min−1·s−1; P < 0.01), with a greater fall in FHR (71.9 ± 6.5 vs. 47.0 ± 8.7 beats/min; P < 0.05). In summary, this study demonstrated that repetitive laborlike cord occlusions, which led to severe fetal compromise, were associated with an increase in the slope and magnitude of the initial FHR deceleration. These findings support the concept of the chemoreflex as a central, robust component of fetal adaptation to severe hypoxia.
Effect of nasal continuous or intermittent positive airway pressure on nonnutritive swallowing in the newborn lamb
Authors: Samson Nathalie , St-Hilaire Marie , Nsegbe Elise , Reix Philippe , Moreau-Bussière François , Praud Jean-Paul
Published: June 2005

The present study was aimed at investigating the effects of nasal continuous positive airway pressure (nCPAP; 6 cmH2O) or intermittent positive pressure ventilation (nIPPV; 10/4 cmH2O) on nonnutritive swallowing (NNS) and on the coordination between NNS and phases of the respiratory cycle, while taking into account the potential effects of states of alertness. Twelve full-term lambs were chronically instrumented at 48 h after birth for polysomnographic recordings, including NNS, diaphragm electromyographic activity, respiratory movements, pulse oximetry, and states of alertness. Studies in control conditions, with nCPAP and nIPPV, were performed in random order in nonsedated lambs at 4, 5, and 6 days of life. Results demonstrate that nCPAP significantly decreased overall NNS frequency, more specifically isolated NNS during quiet sleep and bursts of NNS in active sleep. In comparison, the effects of nIPPV on NNS frequency were more variable, with an inhibition of NNS only in wakefulness and an increase in isolated NNS frequency in active sleep. In addition, neither nCPAP nor nIPPV disrupted the coordination between NNS and phases of the respiratory cycle. In conclusion, nCPAP inhibits NNS occurrence in newborn lambs. Clinical relevance of this novel finding is related to the importance of NNS for clearing the upper airways from secretions and gastric content frequently regurgitated in the neonatal period.
Exercise-induced oxidative stress leads hemolysis in sedentary but not trained humans
Authors: Şentürk Ümit Kemal , Gündüz Filiz , Kuru Oktay , Koçer Günnur , Özkaya Yaşar Gül , Yeşilkaya Akin , Bor-Küçükatay Melek , Üyüklü Murat , Yalçin Özlem , Başkurt Oğuz K.
Published: June 2005

Intravascular hemolysis is one of the most emphasized mechanisms for destruction of erythrocytes during and after physical activity. Exercise-induced oxidative stress has been proposed among the different factors for explaining exercise-induced hemolysis. The validity of oxidative stress following exhaustive cycling exercise on erythrocyte damage was investigated in sedentary and trained subjects before and after antioxidant vitamin treatment (A, C, and E) for 2 mo. Exercise induced a significant increase in thiobarbituric acid-reactive substance and protein carbonyl content levels in sedentary subjects and resulted in an increase of osmotic fragility and decrease in deformability of erythrocytes, accompanied by signs for intravascular hemolysis (increase in plasma hemoglobin concentration and decrease in haptoglobulin levels). Administration of antioxidant vitamins for 2 mo prevented exercise-induced oxidative stress (thiobarbituric acid-reactive substance, protein carbonyl content) and deleterious effects of exhaustive exercise on erythrocytes in sedentary subjects. Trained subjects' erythrocyte responses to exercise were different from those of sedentary subjects before antioxidant vitamin treatment. Osmotic fragility and deformability of erythrocytes, plasma hemoglobin concentration, and haptoglobulin levels were not changed after exercise, although the increased oxidative stress was observed in trained subjects. After antioxidant vitamin treatment, functional and structural parameters of erythrocytes were not altered in the trained group, but exercise-induced oxidative stress was prevented. Increased percentage of young erythrocyte populations was determined in trained subjects by density separation of erythrocytes. These findings suggest that the exercise-induced oxidative stress may contribute to exercise-induced hemolysis in sedentary humans.
Voluntary Control of Human Jaw Stiffness
Authors: Shiller Douglas M. , Houle Guillaume , Ostry David J.
Published: June 2005

Recent studies of human arm movement have suggested that the control of stiffness may be important both for maintaining stability and for achieving differences in movement accuracy. In the present study, we have examined the voluntary control of postural stiffness in 3D in the human jaw. The goal is to address the possible role of stiffness control in both stabilizing the jaw and in achieving the differential precision requirements of speech sounds. We previously showed that patterns of kinematic variability in speech are systematically related to the stiffness of the jaw. If the nervous system uses stiffness control as a means to regulate kinematic variation in speech, it should also be possible to show that subjects can voluntarily modify jaw stiffness. Using a robotic device, a series of force pulses was applied to the jaw to elicit changes in stiffness to resist displacement. Three orthogonal directions and three magnitudes of forces were tested. In all conditions, subjects increased the magnitude of jaw stiffness to resist the effects of the applied forces. Apart from the horizontal direction, greater increases in stiffness were observed when larger forces were applied. Moreover, subjects differentially increased jaw stiffness along a vertical axis to counteract disturbances in this direction. The observed changes in the magnitude of stiffness in different directions suggest an ability to control the pattern of stiffness of the jaw. The results are interpreted as evidence that jaw stiffness can be adjusted voluntarily, and thus may play a role in stabilizing the jaw and in controlling movement variation in the orofacial system.