bluuebunny/crossref_metadata_2025 huggingface dataset:
SYMBOLIC COMPUTATION AND WEIERSTRASS ELLIPTIC FUNCTION SOLUTIONS OF THE DAVEY–STEWARTSON (DS) SYSTEM
Authors: YAN ZHENYA
Published: March 2004

In this paper, with the symbolic computation, the doubly-periodic solutions of the Davey–Stewartson (DS) system, which describes the modulational instability of uniform train of weakly nonlinear water waves in the two-dimensional space, are investigated in terms of the Weierstrass elliptic function ℘(ξ; g2, g3). In particular, we also give new solitary wave solutions of this system.
AUTOMATIC GENERATION OF VACUUM AMPLITUDE MANY-BODY PERTURBATION SERIES
Authors: STEVENSON P. D.
Published: March 2004

An algorithm and a computer program in Fortran 95 are presented which enumerate the Hugenholtz diagram representation of the many-body perturbation series for the ground state energy with a two-body interaction. The output is in a form suitable for post-processing such as automatic code generation. The result of a particular application, generation of LATEX code to draw the diagrams, is shown.
CLOSED NEWTON–COTES TRIGONOMETRICALLY-FITTED FORMULAE FOR LONG-TIME INTEGRATION
Authors: SIMOS T. E.
Published: March 2004

The connection between closed Newton–Cotes, trigonometrically-fitted differential methods and symplectic integrators is investigated in this paper. It is known from the literature that several one-step symplectic integrators have been obtained based on symplectic geometry. However, the investigation of multistep symplectic integrators is very poor. Zhu et al.2 presented the well known open Newton–Cotes differential methods as multilayer symplectic integrators. Chiou and Wu2 also investigated the construction of multistep symplectic integrators based on the open Newton–Cotes integration methods. In this paper we investigate the closed Newton–Cotes formulae and we write them as symplectic multilayer structures. After this we construct trigonometrically-fitted symplectic methods which are based on the closed Newton–Cotes formulae. We apply the symplectic schemes in order to solve Hamilton's equations of motion which are linear in position and momentum. We observe that the Hamiltonian energy of the system remains almost constant as integration procceeds.
EXTENSIONS IN REVERSIBLE ONE-DIMENSIONAL CELLULAR AUTOMATA ARE EQUIVALENT WITH THE FULL SHIFT
Authors: MORA JUAN CARLOS SECK TUOH , HERNÁANDEZ MANUEL GONZÁLEZ , MARTÍNEZ GENARO JUÁREZ , VERGARA SERGIO V. CHAPA
Published: March 2004

Cellular automata are discrete dynamical systems based on simple local interactions among its components, but sometimes they are able to yield quite a complex global behavior. A special kind of cellular automaton is the one where the global behavior is invertible, this type of cellular automaton is called reversible. In this paper we expose the graph representation provided by de Bruijn diagrams of reversible one-dimensional cellular automata and we define the distinct types of paths between self-loops in such diagrams. With this, we establish the way in which a reversible one-dimensional cellular automaton generates sequences composed by subsequences produced by the undefined repetition of a single state. Using this graph presentation, we define Welch diagrams which will be useful for proving that all the extensions of the ancestors in reversible one-dimensional cellular automata are equivalent to the full shift. In this way an important result of this paper is that we understand and classify the behavior of a reversible automaton analyzing the extensions of the ancestors of a given sequence by means of symbolic dynamics tools. A final example illustrates the results exposed in the paper.
PERSISTENCE MEASURES FOR 2D SOAP FROTH
Authors: FENG Y. , RUSKIN H. J. , ZHU B.
Published: March 2004

Soap froths as typical disordered cellular structures, exhibiting spatial and temporal evolution, have been studied through their distributions and topological properties. Recently, persistence measures, which permit representation of the froth as a two-phase system, have been introduced to study froth dynamics at different length scales. Several aspects of the dynamics may be considered and cluster persistence has been observed through froth experiment. Using a direct simulation method, we have investigated persistent properties in 2D froth both by monitoring the persistence of survivor cells, a topologically independent measure, and in terms of cluster persistence. It appears that the area fraction behavior for both survivor and cluster persistence is similar for Voronoi froth and uniform froth (with defects). Survivor and cluster persistent fractions are also similar for a uniform froth, particularly when geometries are constrained, but differences observed for the Voronoi case appear to be attributable to the strong topological dependency inherent in cluster persistence. Survivor persistence, on the other hand, depends on the number rather than size and position of remaining bubbles and does not exhibit the characteristic decay to zero.
DIFFUSION-LIMITED AGGREGATION IN LAMINAR FLOWS
Authors: MERKS R. M. H. , HOEKSTRA A. G. , KAANDORP J. A. , SLOOT P. M. A.
Published: March 2004

In the diffusion-limited aggregation (DLA) model, pioneered by Witten and Sander (Phys. Rev. Lett.47, 1400 (1981)), diffusing particles irreversibly attach to a growing cluster which is initiated with a single solid seed. This process generates clusters with a branched morphology. Advection–diffusion-limited aggregation (ADLA) is a straightforward extension to this model, where the transport of the aggregating particles not only depends on diffusion, but also on a fluid flow. The authors studying two-dimensional and three-dimensional ADLA in laminar flows reported that clusters grow preferentially against the flow direction. The internal structure of the clusters was mostly reported to remain unaffected, except by Kaandorp et al. (Phys. Rev. Lett.77, 2328 (1996)) who found compact clusters "as the flow becomes more important". In the present paper we present three-dimensional simulations of ADLA. We did not find significant effects of low Reynolds-number advection on the cluster structure. The contradicting results by Kaandorp et al. (1996) were recovered only when the relaxation into equilibrium of the advection–diffusion field was too slow, in combination with the synchronous addition of multiple particles.
AVERAGE DISTANCE IN GROWING TREES
Authors: MALARZ K. , CZAPLICKI J. , KAWECKA-MAGIERA B. , KUŁAKOWSKI K.
Published: March 2004

Two kinds of evolving trees are considered here: the exponential trees, where subsequent nodes are linked to old nodes without any preference, and the Barabási–Albert scale-free networks, where the probability of linking to a node is proportional to the number of its pre-existing links. In both cases, new nodes are linked to m=1 nodes. The average node–node distance d is calculated numerically in evolving trees as dependent on the number of nodes N. The results for N not less than a thousand are averaged over a thousand of growing trees. The results on the mean node–node distance d for large N can be approximated by d=2 ln (N)+c1 for the exponential trees, and d= ln (N)+c2 for the scale-free trees, where ci are constant. We also derive iterative equations for d and its dispersion for the exponential trees. The simulation and the analytical approach give the same results.
LOCAL COMPLEXITY OF PROTEIN SEQUENCES
Authors: XIAO SAIFENG , HUANG YANZHAO , XIAO YI
Published: March 2004

Protein sequences are typical complex systems and the knowledge of their local features is very important to predict their secondary structures and biological function. In the present paper a compositional complexity is used to measure the local features of the protein sequences. We found that the transition segments between the regular secondary structures (α-helices and β-strands) and irregular secondary structures (loops and turns) usually have higher complexity than the neighboring segments. This result may be useful to identify the locations of irregular secondary structures which usually are active sites.
STRUCTURAL AND ELECTRONIC PROPERTIES OF AlP DOPED HÜCKEL TYPE CYCLACENE WITH FOUR BENZENOID RINGS
Authors: ERKOÇ ŞAKİR , MALCIOĞLU OSMAN BARIŞ
Published: March 2004

Cyclacene of the Hückel type having four benzenoid rings have been subjected to centric perturbations along both peripheral circuits such that Al and P atoms are alternatingly located. The present structure of perturbed cyclacene let two types of isomeric compounds to arise such that in one case the peri-positions and fusion-points occupied by Al and P atoms, respectively and in the other case reversal of occupation of locations occur. For these structures, AM1-RHF type semi-empirical calculations have been carried out and the systems are analyzed from various energetic points of view.
VARIABLE-COEFFICIENT FORCED BURGERS SYSTEM IN NONLINEAR FLUID MECHANICS AND ITS POSSIBLY OBSERVABLE EFFECTS
Authors: GAO YI-TIAN , XU XIAO-GE , TIAN BO
Published: March 2004

The forced Burgers equation works as a testing ground for a real turbulence, and as the qualitative model for a wide variety of problems including charge density waves, vortex lines in superconductors, disordered solids and epitaxial growth, etc. Its variable-coefficient generalizations call for better modeling of the physical situations. In this paper, we investigate a variable-coefficient generalization of the forced Burgers equation, and obtain several sets of exact soliton-like and other exact analytic solutions, via the extension of a generalized hyperbolic-function method with computerized symbolic computation. We also discuss the Wu method. We find some possibly observable effects, which might be discovered with the relevant experiments.
PHASE TRANSITIONS, MEMORY AND FRUSTRATION IN A SZNAJD-LIKE MODEL WITH SYNCHRONOUS UPDATING
Authors: SABATELLI LORENZO , RICHMOND PETER
Published: March 2004

We introduce a consensus model inspired by the Sznajd Model. The updating is synchronous and memory plays a decisive role in making possible the reaching of total consensus. We study the transition between the state with no-consensus to the state with total consensus.
MONTE CARLO SIMULATIONS OF THE ISING AND THE SZNAJD MODEL ON GROWING BARABÁSI–ALBERT NETWORKS
Authors: BONNEKOH JOHANNES
Published: March 2004

The Ising model on growing Barabási–Albert networks shows the same ferromagnetic behavior as on static Barabási–Albert networks. Sznajd models on growing Barabási–Albert networks show an hysteresis-like behavior. A nearly full consensus builds up and the winning opinion depends on history. On slow growing Barabási–Albert networks a full consensus builds up. At five opinions in the Sznajd model with limited persuasion on growing Barabási–Albert networks, all odd opinions win and all even opinions loose supporters.
A PREDATOR–PREY MODEL BASED ON THE FULLY PARALLEL CELLULAR AUTOMATA
Authors: HE MINGFENG , RUAN HONGBO , YU CHANGLIANG
Published: March 2004

We presented a predator–prey lattice model containing moveable wolves and sheep, which are characterized by Penna double bit strings. Sexual reproduction and child-care strategies are considered. To implement this model in an efficient way, we build a fully parallel Cellular Automata based on a new definition of the neighborhood. We show the roles played by the initial densities of the populations, the mutation rate and the linear size of the lattice in the evolution of this model.
REDUCTION OF SPURIOUS VELOCITY IN FINITE DIFFERENCE LATTICE BOLTZMANN MODELS FOR LIQUID–VAPOR SYSTEMS
Authors: CRISTEA ARTUR , SOFONEA VICTOR
Published: March 2004

The origin of the spurious interface velocity in finite difference lattice Boltzmann models for liquid–vapor systems is related to the first order upwind scheme used to compute the space derivatives in the evolution equations. A correction force term is introduced to eliminate the spurious velocity. The correction term helps to recover sharp interfaces and sets the phase diagram close to the one derived using the Maxwell construction.
CALCULATING TWO- AND THREE-BODY DECAYS WITH FeynArts AND FormCalc
Authors: KLASEN MICHAEL
Published: March 2004

The Feynman diagram generator FeynArts and the computer algebra program FormCalc allow for an automatic computation of 2→2 and 2→3 scattering processes in High Energy Physics. We have extended this package by four new kinematical routines and adapted one existing routine in order to accomodate also two- and three-body decays of massive particles. This makes it possible to compute automatically two- and three-body particle decay widths and decay energy distributions as well as resonant particle production within the Standard Model and the Minimal Supersymmetric Standard Model at the tree- and loop-level. The use of the program is illustrated with three standard examples: [Formula: see text], [Formula: see text], and [Formula: see text].
LIFE-SPAN OF FAMILIES IN FOSSIL DATA FORMS q-EXPONENTIAL DISTRIBUTION
Authors: SHIMADA TAKASHI , YUKAWA SATOSHI , ITO NOBUYASU
Published: March 2004

The distribution of life span of families known as "skewed profile" is shown to be well-fitted by q-exponential function. It implies the mortality of the families has age-dependent form of ∝1/(1-αt). This feature is also reproduced by the so-called "size-free" model which was proposed by the present authors.
NUMERICAL CALCULATION OF ELECTRON ENERGY STATES FOR NANOSCOPIC InAs/GaAs QUANTUM RINGS
Authors: LI YIMING
Published: March 2004

In this paper we study the electron energy states for nanoscopic semiconductor quantum rings. The effective one-band Hamiltonian approximation and the Ben Daniel–Duke boundary conditions are simultaneously considered in our three-dimensional (3D) model. The rectangular and ellipsoidal torus-shaped rings have been investigated with the 3D model. The proposed model is numerically solved with nonlinear iterative method. This computational method calculates the solution without any fitting parameters and is robust for all simulation cases. For InAs/GaAs quantum rings, it is found that (1) there is a significant energy difference between the 2D and 3D models; (2) the electron energy state depends strongly on the ring shape and size; and (3) the dependency of the energy state on an external magnetic field is different from conventional 1D/2D periodical result. We find the electron energy state nonperiodically oscillates versus the applied magnetic field which is in agreement with the experimental observation.
INTERPLAY BETWEEN THE ALGEBRAIC STRUCTURE OF A GROUP AND ARITHMETIC PROPERTIES OF ITS SPECTRUM
Authors: BANAKH TARAS
Published: March 2004

We investigate the interplay between the algebraic structure of a group G and arithmetic properties of its spectrum σ(G) which consists of the eigenvalues of all the inner automorphisms of G. A complex number λ is called an eigenvalue of a group automorphism A:G→G if φ◦A|H=λ·φ for some non-trivial homomorphism [Formula: see text] defined on an A-invariant subgroup H⊂G.

It is shown that many properties of a group G (such as the presence of a finitely generated subgroup of infinite rank, nilpotence, periodicity, polycyclicity, etc.) are coded in its spectrum. In this paper the spectra are applied to the investigation of the so-called reversive properties of groups. The paper ends with a list of related open problems.
FREE GROUPS OF QUATERNIONS
Authors: D'ALESSANDRO FLAVIO
Published: March 2004

This paper deals with the study of the free noncommutative group in the multiplicative group of the skewfield of the real Hamilton quaternions. The main results proved in this paper allows us to obtain the following interesting corollary: let G be a subgroup of rational quaternions. Then G is either solvable or contains the free noncommutative group.
SPECIAL LAGRANGIAN CYCLES AND HERMITIAN YANG–MILLS CONNECTIONS
Authors: CHEN JINGYI
Published: March 2004

We consider the adiabatic limit of a sequence of Hermitian Yang–Mills connections on a SU(r)-bundle over a semi-flat smooth special Lagrangian torus fibration π:M→B. The restriction of these connections to the fiber tori can be viewed as a family of SU(r)-connections on the fiber tori which are parameterized by B. We show that there is a gauge equivalent subsequence such that the restriction of each connection to the fiber tori converges in the Hausdorff topology, away from some closed subset of B of codimension at least two, to a limit which defines a r-sheeted special Lagrangian cycle in the dual special Lagrangian torus fibration.
GEOMETRIC-OPTICS FOR NONLINEAR CONCENTRATING WAVES IN FOCUSING AND NON-FOCUSING TWO GEOMETRIES
Authors: IBRAHIM SLIM
Published: March 2004

With the methods used in [1] and [4], we prove that in the absence of focus, nonlinear geometrical optics of the critical wave equation with variable coefficients, is reduced to linear geometrical optics combined with wave operators for the critical wave equation with coefficients fixed on concentrating points. On the odd-dimensional spheres, we prove that passing through a focus is generated by a modified scattering operator.
GLOBAL REGULARITY FOR A SINGULAR EQUATION AND LOCAL H1 MINIMIZERS OF A NONDIFFERENTIABLE FUNCTIONAL
Authors: DÁVILA JUAN
Published: March 2004

We prove optimal Hölder estimates up to the boundary for the maximal solution of a singular elliptic equation. The techniques used in this argument are applied to show that in some situations the maximal solution is a local minimizer of the corresponding functional in the topology of H1.
VERTEX OPERATOR REPRESENTATIONS OF QUANTUM TORI AT ROOTS OF UNITY
Authors: BILLIG Y. , ZHAO K.
Published: March 2004

As Lie algebra, we add the center c1 (and the outer derivation d1) to the quantum torus [Formula: see text] to give the extended torus Lie algebra [Formula: see text] (and [Formula: see text] respectively). Before the present paper, only some level 1 vertex operator representations for some [Formula: see text] (and [Formula: see text]) were constructed. In this paper, we first give vertex operator representations for [Formula: see text] where I is an arbitrary index set. By embedding some [Formula: see text] into [Formula: see text], we obtain a series of higher level vertex operator representations for [Formula: see text] and [Formula: see text]. Most of these vertex operator representations yield irreducible highest weight modules over these [Formula: see text]. Also their character formulas follow directly.
VERTEX ALGEBRAS AND VERTEX POISSON ALGEBRAS
Authors: LI HAISHENG
Published: March 2004

This paper studies certain relations among vertex algebras, vertex Lie algebras and vertex Poisson algebras. In this paper, the notions of vertex Lie algebra (conformal algebra) and vertex Poisson algebra are revisited and certain general construction theorems of vertex Poisson algebras are given. A notion of filtered vertex algebra is formulated in terms of a notion of good filtration and it is proved that the associated graded vector space of a filtered vertex algebra is naturally a vertex Poisson algebra. For any vertex algebra V, a general construction and a classification of good filtrations are given. To each ℕ-graded vertex algebra V=∐n∈ℕV(n) with [Formula: see text], a canonical (good) filtration is associated and certain results about generating subspaces of certain types of V are also obtained. Furthermore, a notion of formal deformation of a vertex (Poisson) algebra is formulated and a formal deformation of vertex Poisson algebras associated with vertex Lie algebras is constructed.
CRITICAL POINTS OF MASTER FUNCTIONS AND FLAG VARIETIES
Authors: MUKHIN E. , VARCHENKO A.
Published: March 2004

We consider critical points of master functions associated with integral dominant weights of Kac–Moody algebras and introduce a generating procedure constructing new critical points starting from a given one. The set of all critical points constructed from a given one is called a population. We formulate a conjecture that a population is isomorphic to the flag variety of the Langlands dual Kac–Moody algebra and prove the conjecture for algebras slN+1, so2N+1, and sp2N.

We show that populations associated with a collection of integral dominant slN+1-weights are in one to one correspondence with intersection points of suitable Schubert cycles in a Grassmannian variety.
A REDUCED STABILITY CONDITION FOR NONLINEAR RELAXATION TO CONSERVATION LAWS
Authors: BOUCHUT FRANÇOIS
Published: March 2004

We consider multidimensional hyperbolic systems of conservation laws with relaxation, together with their associated limit systems. A strong stability condition for such asymptotics has been introduced by Chen, Levermore and Liu, namely the existence of an entropy extension. We propose here a new stability condition, the reduced stability condition, which is weaker than the previous one, but still has the property to imply the subcharacteristic or interlacing conditions, and the dissipativity of the leading term in the Chapman–Enskog expansion. This reduced stability condition has the advantage of involving only the submanifold of equilibria, or maxwellians, so that it is much easier to check than the entropy extension condition. Our condition generalizes the one introduced by the author in the case of kinetic, i.e. diagonal semilinear relaxation. We provide an adapted stability analysis in the context of approximate Riemann solvers obtained via relaxation systems.
GLOBAL WELL-POSEDNESS OF THE BENJAMIN–ONO EQUATION IN H1(R)
Authors: TAO TERENCE
Published: March 2004

We show that the Benjamin–Ono equation is globally well-posed in Hs(R) for s≥1. This is despite the presence of the derivative in the nonlinearity, which causes the solution map to not be uniformly continuous in Hsfor any s [18]. The main new ingredient is to perform a global gauge transformation which almost entirely eliminates this derivative.
GLOBAL EXISTENCE OF SHOCK FRONT SOLUTIONS TO THE AXIALLY SYMMETRIC PISTON PROBLEM FOR COMPRESSIBLE FLUIDS
Authors: CHEN SHUXING , WANG ZEJUN , ZHANG YONGQIAN
Published: March 2004

In this paper, we study the axially symmetric piston problem for compressible fluids when the velocity of the piston is a perturbation of a constant. Under the assumptions that both the velocity of the piston and the density of the gas outside the piston are small, we prove the global existence of a shock front solution by using a modified Glimm scheme.
RICCI DEFECTS OF MICROLOCALIZED EINSTEIN METRICS
Authors: KLAINERMAN SERGIU , RODNIANSKI IGOR
Published: March 2004

This is the third and last in our series of papers concerning rough solutions of the Einstein vacuum equations expressed relative to wave coordinates. In this paper we prove an important result, concerning Ricci defects of microlocalized solutions, stated and used in the proof of the crucial Asymptotics Theorem in [1]. The result is of independent interest in situations when one has to smooth out the given spacetime metric in order to achieve good causality properties.
FRONT TRACKING FOR SCALAR BALANCE EQUATIONS
Authors: KARLSEN K. H. , RISEBRO N. H. , TOWERS J. D.
Published: March 2004

We propose and prove convergence of a front tracking method for scalar conservation laws with source term. The method is based on writing the single conservation law as a 2×2 quasilinear system without a source term, and employ the solution of the Riemann problem for this system in the front tracking procedure. In this way the source term is processed in the Riemann solver, and one avoids using operator splitting. Since we want to treat the resonant regime, classical arguments for bounding the total variation of numerical solutions do not apply here. Instead compactness of a sequence of front tracking solutions is achieved using a variant of the singular mapping technique invented by Temple [69]. The front tracking method has no CFL-condition associated with it, and it does not discriminate between stiff and non-stiff source terms. This makes it an attractive approach for stiff problems, as is demonstrated in numerical examples. In addition, the numerical examples show that the front tracking method is able to preserve steady-state solutions (or achieving them in the long time limit) with good accuracy.
ADVANCED HYPERBOLIC DIVERGENCE CLEANING SCHEME FOR SHALLOW WATER MAGNETOHYDRODYNAMICS
Authors: LEE YONG-JOONG , MUNZ CLAUS-DIETER
Published: March 2004

An advanced hyperbolic divergence cleaning scheme based on "generalized Lagrange multiplier" (GLM) for the equations of "shallow water magnetohydrodynamics" (SMHD) is presented. This scheme is based on the two-step method which is comprised of the standard finite-volume updating step for the nonlinear genuine SMHD system and the divergence cleaning step for the linear GLM-based Maxwell subsystem. The divergence cleaning step can be applied several times per each computational time step, in order to accelerate the transports of the divergence error out of the computational domain. The presented two-step method is compared with the standard GLM method based on operator splitting. It is shown that the standard operator-splitting based method has the shock dissipation problem, particularly when the multiple subcycles of the divergence cleaning step is performed per each time step. On the contrary, the introduction of the multiple subcycles for the new GLM–Maxwell subsystem does not suffer from the dissipation of the shocks, and produces better shock resolution. The presented method can be further applied to the full magnetohydrodynamics equations.
MIXED EQUATIONS AND TRANSONIC FLOW
Authors: MORAWETZ CATHLEEN SYNGE
Published: March 2004

This paper reviews the present situation with existence and uniqueness theorems for mixed equations and their application to the problems of transonic flow. Some new problems are introduced and discussed. After a very brief discussion of time-dependent flows (Sec. 1) the steady state and its history is described in Sec. 2. In Secs. 3 and 4, early work on mixed equations and their connection to 2D flow are described and Sec. 5 brings up the problem of shocks, the construction of good airfoils and the relevant boundary value problems. In Sec. 6 we look at what two linear perturbation problems could tell us about the flow. In Sec. 7 we describe other examples of fluid problems giving rise to similar problems. Section 8 is devoted to the uniqueness by a conservation law and Secs. 9–11 to the existence proofs by Friedrichs' multipliers. In Sec. 12 a proof is given of the existence of a steady flow corresponding to some of the previous examples but the equations have been modified to a higher order system with a small parameter which when set to zero yields the equations of transonic flow. It remains to show that this formal limit really holds. Much has been left out especially modern computational results and the text reflects the particular interests of the author.
Statistical and Substantive Inferences in Public Health: Issues in the Application of Multilevel Models
Authors: Bingenheimer Jeffrey B. , Raudenbush Stephen W.
Published: March 2004

Multilevel statistical models have become increasingly popular among public health researchers over the past decade. Yet the enthusiasm with which these models are being adopted may obscure rather than solve some problems of statistical and substantive inference. We discuss the three most common applications of multilevel models in public health: (a) cluster-randomized trials, (b) observational studies of the multilevel etiology of health and disease, and (c) assessments of health care provider performance. In each area of investigation, we describe how multilevel models are being applied, comment on the validity of the statistical and substantive inferences being drawn, and suggest ways in which the strengths of multilevel models might be more fully exploited. We conclude with a call for more careful thinking about multilevel causal inference.
The Role of Culture in Health Communication
Authors: Kreuter Matthew W. , McClure Stephanie M.
Published: March 2004

This paper examines the role of culture as a factor in enhancing the effectiveness of health communication. We describe culture and how it may be applied in audience segmentation and introduce a model of health communication planning—McGuire's communication/persuasion model—as a framework for considering the ways in which culture may influence health communication effectiveness. For three components of the model (source, message, and channel factors), the paper reviews how each affects communication and persuasion, and how each may be affected by culture. We conclude with recommendations for future research on culture and health communication.
Genetic Testing in the Workplace: Ethical, Legal, and Social Implications
Authors: Brandt-Rauf Paul W. , Brandt-Rauf Sherry I.
Published: March 2004

With the completion of the Human Genome Project, it is likely that genetic testing for susceptibility to a wide range of diseases will increase in society. One venue for such increased testing is likely to be the workplace as employers attempt to protect workers from unhealthy gene-environment interactions, improve productivity, and control escalating health care costs. Past and recent examples of genetic testing in the workplace raise serious concerns that such testing could pose a significant threat to workers' privacy, autonomy, and dignity. Thus, defining the ethically, legally, and socially appropriate and inappropriate uses of genetic testing in the workplace presents a major challenge for occupational health professionals in the years ahead.
Housing and Public Health
Authors: Shaw Mary
Published: March 2004

This review considers the broad area of housing and public health, one of the traditional and core areas of public health research and intervention. The review takes into account the range of factors, acting at different levels, directly and indirectly, through which housing affects health. In public health terms, housing affects health in a myriad of relatively minor ways, in total forming one of the key social determinants of health. The paper closes by considering how the improvement of housing and neighborhoods has been a core activity of public health and a central component in tackling poverty. Investment in housing can be more than an investment in bricks and mortar: It can also form a foundation for the future health and well-being of the population. Addressing poor-quality housing and detrimental neighborhoods, in the broadest sense, is thus a task that should be grasped with vigor and determination by all those involved in public health.
Emission Trading and Public Health
Authors: Farrell Alexander E. , Lave Lester B.
Published: March 2004

Emission trading policies are increasingly important in environmental protection, especially in controlling air pollution in the United States. Their popularity results in part from the limitations and frustrations of centralized command and control regulation. Well-designed emission trading programs can achieve the same or better environmental and health outcomes as command and control regulations but provide regulated industries with greater flexibility. This lowers costs and improves the process of negotiating environmental policy. We present key concepts and important applications of emission trading, focusing on health impacts. These programs generally are well-designed, speeding emission abatement; improving health outcomes; and reducing compliance costs. Flaws have stopped a few poorly designed emission trading programs. A key issue in evaluating emission trading is our inability to know what the environmental outcome would have been under another approach.
Modeling Infection Transmission
Authors: Koopman Jim
Published: March 2004

Understanding what determines patterns of infection spread in populations is important for controlling infection transmission. The science that advances this understanding uses mathematical and computer models that vary from deterministic models of continuous populations to models of dynamically evolving contact networks between individuals. These provide insight, serve as scientific theories, help design studies, and help analyze data. The key to their use lies in assessing the robustness of inferences made using them to violation of their simplifying assumptions. This involves changing model forms from deterministic to stochastic and from compartmental to network, as well as adding realistic detail and changing parameter values. Currently inferences about infection transmission are often made using stratified rate or risk comparisons, logistic regression models, or proportionate hazards models that assume an absence of transmission. Robustness assessment will show many of these inferences to be wrong. A community of epidemiologist modelers is needed for effective robustness assessment.
The Public Health Workforce
Authors: Tilson Hugh , Gebbie Kristine M.
Published: March 2004

The development of a fully-competent public health workforce as a key component of the nation's public health infrastructure has become the focus of increasing attention. The subject is included in one, and is the major topic of a second, report from the Institute of Medicine published late in 2002. Workforce issues have stimulated the convening of the majority of public health–related associations in a range of collaborations on the subjects of defining, enumerating, credentialing, educating, and studying the workforce. The authors review the major questions confronting the field and introduce key components of current thinking about approaches to improvement.
Trends in the Health of the Elderly
Authors: Crimmins Eileen M.
Published: March 2004

Health among the older population as measured by most dimensions has improved during the last two decades. Mortality has continued to decline, and disability and functioning loss are less common now than in the past. However, the prevalence of most diseases has increased in the older population as people survive longer with disease, and the reduction in incidence does not counter the effect of increased survival. On the other hand, having a disease appears to be less disabling than in the past.
Harm Reduction Approaches to Reducing Tobacco-Related Mortality
Authors: Hatsukami Dorothy K. , Henningfield Jack E. , Kotlyar Michael
Published: March 2004

Tobacco harm reduction approaches are gaining increased attention. Much of this attention is due to a growing concern that significant populations of smokers either do not want to quit or believe they are unable to quit smoking, and to a concern over tobacco-industry attempts to produce tobacco products that claim to result in less toxin exposure. Decreasing tobacco toxin exposure as a method for reducing mortality and morbidity may be a reasonable tobacco control strategy. However, the impact of this strategy must be explored both on individual and population levels. A significant amount of independent research is needed to inform policy decisions. Regulatory authority over potential reduced exposure products is also essential.
What Do We Do with Missing Data? Some Options for Analysis of Incomplete Data
Authors: Raghunathan Trivellore E.
Published: March 2004

Missing data are a pervasive problem in many public health investigations. The standard approach is to restrict the analysis to subjects with complete data on the variables involved in the analysis. Estimates from such analysis can be biased, especially if the subjects who are included in the analysis are systematically different from those who were excluded in terms of one or more key variables. Severity of bias in the estimates is illustrated through a simulation study in a logistic regression setting. This article reviews three approaches for analyzing incomplete data. The first approach involves weighting subjects who are included in the analysis to compensate for those who were excluded because of missing values. The second approach is based on multiple imputation where missing values are replaced by two or more plausible values. The final approach is based on constructing the likelihood based on the incomplete observed data. The same logistic regression example is used to illustrate the basic concepts and methodology. Some software packages for analyzing incomplete data are described.
Gelified Co-continuous Polymer Blend System as Polymer Electrolyte for Li Batteries
Authors: Passerini S. , Lisi M. , Momma T. , Ito H. , Shimizu T. , Osaka T.
Published: March 2004

In this work, the co-continuous polymer blend was synthesized for use as the electrolyte in lithium batteries. Such electrolytes were characterized by a co-continuous morphology consisting of two three-dimensionally interpenetrated polymer networks simply formed by hot-mixing two nonmiscible polymers. A preliminary electrochemical characterization of the gelified co-continuous polymer blend as electrolyte for lithium batteries is also reported. © 2004 The Electrochemical Society. All rights reserved.
Overexpression or ablation of JNK in skeletal muscle has no effect on glycogen synthase activity
Authors: Fujii Nobuharu , Boppart Marni D. , Dufresne Scott D. , Crowley Patricia F. , Jozsi Alison C. , Sakamoto Kei , Yu Haiyan , Aschenbach Williams G. , Kim Shokei , Miyazaki Hitoshi , Rui Liangyou , White Morris F. , Hirshman Michael F. , Goodyear Laurie J.
Published: March 2004

c-Jun NH2-terminal kinase (JNK) is highly expressed in skeletal muscle and is robustly activated in response to muscle contraction. Little is known about the biological functions of JNK signaling in terminally differentiated muscle cells, although this protein has been proposed to regulate insulin-stimulated glycogen synthase activity in mouse skeletal muscle. To determine whether JNK signaling regulates contraction-stimulated glycogen synthase activation, we applied an electroporation technique to induce JNK overexpression (O/E) in mouse skeletal muscle. Ten days after electroporation, in situ muscle contraction increased JNK activity 2.6-fold in control muscles and 15-fold in the JNK O/E muscles. Despite the enormous activation of JNK activity in JNK O/E muscles, contraction resulted in similar increases in glycogen synthase activity in control and JNK O/E muscles. Consistent with these findings, basal and contraction-induced glycogen synthase activity was normal in muscles of both JNK1- and JNK2-deficient mice. JNK overexpression in muscle resulted in significant alterations in the basal phosphorylation state of several signaling proteins, such as extracellular signal-regulated kinase 1/2, p90 S6 kinase, glycogen synthase kinase 3, protein kinase B/Akt, and p70 S6 kinase, in the absence of changes in the expression of these proteins. These data suggest that JNK signaling regulates the phosphorylation state of several kinases in skeletal muscle. JNK activation is unlikely to be the major mechanism by which contractile activity increases glycogen synthase activity in skeletal muscle.
Expression of the 56-kDa B2 subunit isoform of the vacuolar H+-ATPase in proton-secreting cells of the kidney and epididymis
Authors: Păunescu Teodor G. , Silva Nicolas Da , Marshansky Vladimir , McKee Mary , Breton Sylvie , Brown Dennis
Published: March 2004

B1 and B2 are two highly homologous isoforms of the vacuolar H+-ATPase (V-ATPase) 56-kDa B subunit. We investigated whether the B2 subunit is expressed alongside B1 in proton-secreting cells of the rodent kidney collecting duct (intercalated cells, IC) and epididymis (clear cells) by using antibodies against distinct COOH-terminal peptides from the two B isoforms. B2 was detected not only in the kidney proximal tubule, thick ascending limb, distal convoluted tubule, and connecting segment but also in A- and B-type IC of collecting ducts (CD) in both rat and mouse. B2 had a predominant cytoplasmic localization in most IC but was clearly located in a tighter apical band together with the V-ATPase 31-kDa E subunit in some A-IC, especially in the medulla. Apical membrane staining was confirmed by immunogold electron microscopy. B2 was very weakly expressed on the basolateral membranes of B-IC in control kidney CD, but some connecting segment B-IC had more distinct basolateral staining. In response to chronic carbonic anhydrase inhibition by acetazolamide, many A-IC showed a strong apical membrane localization of B2, where it colocalized with E and B1. In rat and mouse epididymis, B2 isoform expression was detected in clear cells, where it was concentrated in subapical vesicles. Unlike B1, B2 did not colocalize with the E subunit in the apical microvilli. These findings indicate that in addition to its role in the acidification of intracellular organelles, the B2 isoform could also contribute to transepithelial proton secretion and the maintenance of acid-base homeostasis.
Obscurin regulates the organization of myosin into A bands
Authors: Kontrogianni-Konstantopoulos Aikaterini , Catino Dawn H. , Strong John C. , Randall William R. , Bloch Robert J.
Published: March 2004

Obscurin is a giant sarcomeric protein composed of adhesion modules and signaling domains. It surrounds myofibrils at the level of the Z disk and the M line. To study the role of obscurin during myofibrillogenesis, we used adenovirus-mediated gene delivery to overexpress part of its COOH terminus in primary cultures of postnatal day 1 (P1) skeletal myotubes. Examination of the subcellular distribution of a number of sarcomeric proteins revealed that the organization of myosin into A bands was dramatically reduced. Myosin assembled into A bands normally in mock- or control-infected P1 myotubes. Overexpression of the COOH terminus of obscurin did not affect the organization of other sarcomeric markers, including actin, α-actinin, titin, and myomesin. Assembly of myomesin into nascent M lines in treated myotubes suggests that these structures can form independently of A bands. Immunoblot analysis indicated that there was a small (∼20%) but consistent decrease in the amount of myosin expressed in cells infected with the COOH terminus of obscurin. Coimmunoprecipitation experiments in which we used adult skeletal muscle homogenates demonstrated that obscurin exists in a complex with myosin. Thus our findings suggest that the COOH-terminal region of obscurin interacts with sarcomeric myosin and may play a critical role in its ability to assemble into A bands in striated muscle.
Rapid desensitization of G protein-gated inwardly rectifying K+ currents is determined by G protein cycle
Authors: Leaney Joanne L. , Benians Amy , Brown Sean , Nobles Muriel , Kelly David , Tinker Andrew
Published: March 2004

Activation of G protein-gated inwardly rectifying K+ (GIRK) channels, found in the brain, heart, and endocrine tissue, leads to membrane hyperpolarization that generates neuronal inhibitory postsynaptic potentials, slows the heart rate, and inhibits hormone release. During stimulation of Gi/o-coupled receptors and subsequent channel activation, it has been observed that the current desensitizes. In this study we examined mechanisms underlying fast desensitization of cloned heteromeric neuronal Kir3.1+3.2A and atrial Kir3.1+3.4 channels and also homomeric Kir3.0 currents in response to stimulation of several Gi/o G protein-coupled receptors (GPCRs) expressed in HEK-293 cells (adenosine A1, adrenergic α2A, dopamine D2S, M4 muscarinic, and GABAB1b/2 receptors). We found that all agonist-induced currents displayed a similar degree of desensitization except the adenosine A1 receptor, which exhibits an additional desensitizing component. Using the nonhydrolyzable GTP analog guanosine 5′- O-(3-thiotriphosphate) (GTPγS), we found that this is due to a receptor-dependent, G protein-independent process. Using Ca2+ imaging we showed that desensitization is unlikely to be accounted for solely by phospholipase C activation and phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis. We examined the contribution of the G protein cycle and found the following. First, agonist concentration is strongly correlated with degree of desensitization. Second, competitive inhibition of GDP/GTP exchange by using nonhydrolyzable guanosine 5′- O-(2-thiodiphosphate) (GDPβS) has two effects, a slowing of channel activation and an attenuation of the fast desensitization phenomenon. Finally, using specific Gα subunits we showed that ternary complexes with fast activation rates display more prominent desensitization than those with slower activation kinetics. Together our data suggest that fast desensitization of GIRK currents is accounted for by the fundamental properties of the G protein cycle.
Increased tolerance to oxygen and glucose deprivation in astrocytes from Na+/H+ exchanger isoform 1 null mice
Authors: Kintner Douglas B. , Su Gui , Lenart Brett , Ballard Andy J. , Meyer Jamie W. , Ng Leong L. , Shull Gary E. , Sun Dandan
Published: March 2004

The ubiquitously expressed Na+/H+ exchanger isoform 1 (NHE1) functions as a major intracellular pH (pHi) regulatory mechanism in many cell types, and in some tissues its activity may contribute to ischemic injury. In the present study, cortical astrocyte cultures from wild-type (NHE1+/+) and NHE1-deficient (NHE1−/−) mice were used to investigate the role of NHE1 in pHi recovery and ischemic injury in astrocytes. In the absence of HCO3−, the mean resting pHi levels were 6.86 ± 0.03 in NHE1+/+ astrocytes and 6.53 ± 0.04 in NHE1−/− astrocytes. Removal of extracellular Na+ or blocking of NHE1 activity by the potent NHE1 inhibitor HOE-642 significantly reduced the resting level of pHi in NHE1+/+ astrocytes. NHE1+/+ astrocytes exhibited a rapid pHi recovery (0.33 ± 0.08 pH unit/min) after NH4Cl prepulse acid load. The pHi recovery in NHE1+/+ astrocytes was reversibly inhibited by HOE-642 or removal of extracellular Na+. In NHE1−/− astrocytes, the pHi recovery after acidification was impaired and not affected by either Na+-free conditions or HOE-642. Furthermore, 2 h of oxygen and glucose deprivation (OGD) led to an ∼80% increase in pHi recovery rate in NHE1+/+ astrocytes. OGD induced a 5-fold rise in intracellular [Na+] and 26% swelling in NHE1+/+ astrocytes. HOE-642 or genetic ablation of NHE1 significantly reduced the Na+ rise and swelling after OGD. These results suggest that NHE1 is the major pHi regulatory mechanism in cortical astrocytes and that ablation of NHE1 in astrocytes attenuates ischemia-induced disruption of ionic regulation and swelling.
Taurine kinetics assessed using [1,2-13C2]taurine in healthy adult humans
Authors: Rakotoambinina Benjamin , Marks Lisa , Badran Abdul Monem , Igliki Frank , Thuillier François , Crenn Pascal , Messing Bernard , Darmaun Dominique
Published: March 2004

To assess the dynamics of taurine metabolism in vivo, two sets of studies were carried out in healthy volunteers. First, pilot studies were carried in a single human subject to determine the time course of plasma and whole blood isotope enrichment over the course of an 8-h, unprimed continuous infusion of [1,2-13C2]taurine. Second, five healthy adult males received two tracer infusions on separate days and in randomized order: 1) a 6-h continuous infusion of [1,2-13C2]taurine (3.1 ± 0.2 μmol·kg−1·h−1) and 2) a bolus injection of [13C2]taurine (3.0 ± 0.1 μmol/kg). Isotope enrichments in plasma and whole blood taurine were determined by gas chromatography-mass spectrometry. The pilot experiments allowed us to establish that steady-state isotope enrichment was reached in plasma and whole blood by the 5th h of tracer infusion. The plateau enrichment reached in whole blood was lower than that obtained in plasma taurine ( P < 0.02). In the second set of studies, the appearance rate (Ra) of plasma taurine, determined from continuous infusion studies was 31.8 ± 3.1 μmol·kg−1·h−1. After a bolus injection of tracer, the enrichment decay over the subsequent 2 h was best fitted by a two-exponential curve. Taurine Ra was ≈85% higher when determined using the bolus injection technique compared with continuous infusion of tracer. We conclude that 1) taurine Ra into plasma is very low in healthy postabsorptive humans, and, due to taurine compartmentation between the extra- and intracellular milieus, may represent only interorgan taurine transfer and merely a small fraction of whole body taurine turnover; and 2) the bolus injection technique may overestimate taurine appearance into plasma. Further studies are warranted to determine whether alterations in bile taurine dynamics affect taurine Ra.