bluuebunny/crossref_metadata_2025 huggingface dataset:
CONTROLLED PROJECTIVE SYNCHRONIZATION IN NONPARTIALLY-LINEAR CHAOTIC SYSTEMS
Authors: XU DAOLIN , LI ZHIGANG
Published: July 2002

Projective synchronization (PS), in which the state vectors synchronize up to a scaling factor, is usually observable only in partially linear systems. We show that PS could, by means of control, be extended to general classes of chaotic systems with nonpartial linearity. Performance of PS may also be manipulated by controlling the scaling factor to any desired value. In numerical experiments, we illustrate the applications to a Rössler system and a Chua's circuit. The feasibility of the control for high dimensional systems is demonstrated in a hyperchaotic system.
DATA FLOW COHERENCE CONSTRAINTS FOR PRUNING THE SEARCH SPACE IN ILP TOOLS
Authors: MURESAN SMARANDA , MURESAN TUDOR , POTOLEA RODICA
Published: July 2002

In this paper we present a new method that uses data-flow coherence constraints in definite logic program generation. We outline three main advantages of these constraints supported by our results: i) drastically pruning the search space (around 90%), ii) reducing the set of positive examples and reducing or even removing the need for the set of negative examples, and iii) allowing the induction of predicates that are difficult or even impossible to generate by other methods. Besides these constraints, the approach takes into consideration the program termination condition for recursive predicates. The paper outlines some theoretical issues and implementation aspects of our system for automatic logic program induction.
VASSILIEV INVARIANTS AND DOUBLE DATING TANGLES
Authors: JEONG MYEONG-JU , PARK CHAN-YOUNG
Published: July 2002

In [1], E. Appleboim introduced the notion of double dating linking class-P invariants of finite type for framed links with a fixed linking matrix P and showed that all Vassiliev link invariants are of finite type for any linking matrix and in [13], R. Trapp provided a necessary condition for a knot invariant to be a Vassiliev invariant by using twist sequences. In this paper we provide a necessary condition for a framed link invariant to be a DD-linking class-P invariant of finite type by considering sequence of links induced from a double dating tangle. As applications we give a generalization of R. Trapp's result to see whether a link invariant is a Vassiliev invariant or not and apply the criterion for all non-zero coefficients of the Jones, HOMFLY, Q-, and Alexander polynomial.
A TEMPERLEY-LIEB BASIS COMING FROM THE BRAID GROUP
Authors: ZINNO MATTHEW G.
Published: July 2002

The Temperley-Lieb algebra An-1, into which the n-strand braid group Bn maps homomorphically, has dimension equal to the Catalan number [Formula: see text]. The elements of the braid group called canonical factors, which come from the band presentation of that group and were used by Birman, Ko, and Lee in their solution to the word problem, form a set whose size is also Cn. In this paper, it is shown that the homomorphic images of the canonical factors form a basis for the vector space underlying the Temperley-Lieb algebra.
THE NUCLEAR BORN–OPPENHEIMER METHOD APPLIED TO NUCLEAR COLLECTIVE MOTION
Authors: ZETTILI NOUREDINE , BOUKAHIL ABDELKRIM
Published: July 2002

We deal with the application of the nuclear Born–Oppenheimer (NBO) method to the study of nuclear collective motion. In particular, we look at the description of nuclear rotations and vibrations. The collective operators are specified within the NBO method only to the extent of identifying the type of collective degrees of freedom we intend to describe; the operators are then determined from the dynamics of the system. To separate the collective degrees of freedom into rotational and vibrational terms, we transform the collective tensor operator from the lab fixed frame of reference to the frame defined by the principal axes of the system; this transformation diagonalizes the tensor operator. We derive a general expression for the NBO mean energy and show that it contains internal, collective and coupling terms. Then, we specify the approximations that need to be made in order to establish a connection between Bohr's collective model and the NBO method. We show that Bohr's collective Hamiltonian can be recovered from the NBO Hamiltonian only after adopting some rather crude approximations. In addition, we try to understand, in light of the NBO approach, why Bohr's collective model gives the wrong inertial parameters. We show that this is due to two major reasons: the ad hoc selection of the collective degrees of freedom within the context of Bohr's collective model and the unwarranted neglect of several important terms from the Hamiltonian.
SOLVING THE INVERSE PROBLEM FOR FUNCTION/IMAGE APPROXIMATION USING ITERATED FUNCTION SYSTEMS II: ALGORITHM AND COMPUTATIONS
Authors: FORTE BRUNO , VRSCAY EDWARD R.
Published: July 2002

In this paper, we provide an algorithm for the construction of IFSM approximations to a target set [Formula: see text], where X ⊂ RD and µ = m(D) (Lebesgue measure). The algorithm minimizes the squared "collage distance" [Formula: see text]. We work with an infinite set of fixed affine IFS maps wi: X → X satisfying a certain density and nonoverlapping condition. As such, only an optimization over the grey level maps ϕi: R+ → R+ is required. If affine maps are assumed, i.e. ϕi = αit + βi, then the algorithm becomes a quadratic programming (QP) problem in the αi and βi. We can also define a "local IFSM" (LIFSM) which considers the actions of contractive maps wi on subsets of X to produce smaller subsets. Again, affine ϕi maps are used, resulting in a QP problem. Some approximations of functions on [0,1] and images in [0, 1]2 are presented.
QUANTITATIVE CLASSIFICATION OF CLOUD MICROPHYSICAL IMAGERY VIA FRACTAL-DIMENSION CALCULATIONS
Authors: LUMB L. IAN , LOW TOM B. , DI LEO ARTHUR
Published: July 2002

The use of fractal-dimension calculations, for quantitative classification of various objects, is well established in many areas of the physical and life sciences. Such fractal-dimension calculations are useful in that they furnish some measure of geometrical complexity that is not available through "traditional" approaches. In the present context, we focus attention on the application of such calculations to cloud microphysical data. In particular, we consider data from in-situ, two-dimensional particle imagery. Whereas previous efforts have typically characterized the imaged hydrometeoric fields by dimensional and statistical measures, distinguishing between the various hydrometeoric types should also be possible with fractal dimension based analyses. Although typical data sets may include thousands of individual images, each of these single images is typically quite small in size, and has intensity values that span only a few levels. Thus the need for computationally efficient algorithms, that can process these individual images, presents interesting challenges for fractal-dimension calculations. Here we report on our preliminary findings regarding the capacity and information dimension of various synthetic images.
FRACTAL TRAFFIC FLOWS IN HIGH-SPEED COMMUNICATIONS NETWORKS
Authors: ERRAMILLI ASHOK , WILLINGER WALTER , PRUTHI PARAG
Published: July 2002

Traditional queueing models for traffic flows in communications networks are based on Markovian assumptions. However, recent studies within Bellcore of large sets of real-time network traffic measurements have revealed that traffic in computer and emerging high-speed networks has features that are more accurately and more efficiently described in terms of fractal models, rather than traditional Markovian models. This paper briefly reviews these measurement studies, and motivates the application of fractals to describe and analyze traffic flows in modern communications networks.
CROSSOVER FROM WHITE NOISE TO LONG RANGE CORRELATED NOISE IN DNA SEQUENCES AND WRITINGS
Authors: DIETLER GIOVANNI , ZHANG YI-CHENG
Published: July 2002

Human writings and DNA chains are considered here as n-dimensional random walkers, where n is the number of different symbols appearing in the sequences. Long range scaling behavior appears only for length scales greater than a crossover length ξ and the scaling exponents are non-universal, but comparable to the one found previously. These two languages have similar behavior, but with different crossover lengths and can be considered as a collection of segments of length ξ consisting of randomly arranged symbols, which show non-trivial long range correlations.
AMERICAN OPTIONS WITH REGIME SWITCHING
Authors: BUFFINGTON JOHN , ELLIOTT ROBERT J.
Published: July 2002

A Black-Scholes market is considered in which the underlying economy, as modeled by the parameters and volatility of the processes, switches between a finite number of states. The switching is modeled by a hidden Markov chain. European options are priced and a Black-Scholes equation obtained. The approximate valuation of American options due to Barone-Adesi and Whaley is extended to this setting.
A CORRELATED STOCHASTIC VOLATILITY MODEL MEASURING LEVERAGE AND OTHER STYLIZED FACTS
Authors: MASOLIVER JAUME , PERELLÓ JOSEP
Published: July 2002

We analyze a stochastic volatility market model in which volatility is correlated with return and is represented by an Ornstein-Uhlenbeck process. In the framework of this model we exactly calculate the leverage effect and other stylized facts, such as mean reversion, leptokurtosis and negative skewness. We also obtain a close analytical expression for the characteristic function and study the heavy tails of the probability distribution.
CORRECTING DISTORTION OF IMAGE BY IMAGE REGISTRATION WITH THE IMPLICIT FUNCTION THEOREM
Authors: TAMAKI TORU , YAMAMURA TSUYOSHI , OHNISHI NOBORU
Published: July 2002

We propose a method for correcting image distortion due to camera lenses by calibrating intrinsic camera parameters. The proposed method is based on image registration and doesn't require point-to-point correspondence. Parameters of three successive transformations — view change, radial distortion and illumination change — are estimated using the Gauss–Newton method. Estimating all 19 unknowns simultaneously, we introduce the implicit function theorem for calculating the Jacobian. To avoid local minima, we first estimate parameters for view change and employ coarse-to-fine minimization. Experimental results using real images demonstrate the robustness and the usefulness of the proposed method.
DICHOTOMY SPECTRUM OF NONAUTONOMOUS LINEAR STOCHASTIC DIFFERENTIAL EQUATIONS
Authors: CONG NGUYEN DINH , SIEGMUND STEFAN
Published: July 2002

We investigate a concept of dichotomy spectrum for nonautonomous linear stochastic differential equations, which is defined with sample-wise exponential dichotomy of the two-parameter flow generated by the equation. We use random norm and cohomology to capture the nature of the stochastic nonuniformity. The main result is our spectral theorem stating that the dichotomy spectrum consists of compact random intervals with corresponding spectral manifolds, which are Oseledets spaces if the equation generates a random dynamical system. The dichotomy spectrum is nonrandom and equals the Lyapunov spectrum if the stochastic differential equation is Lyapunov regular.
Managing with web-based IT in mind
Authors: Kock Ned
Published: July 2002

A framework that ties together relevant management ideas that help organizations strategically and operationally align themselves with new Web-based IT.
Global perceptions of journals publishing e-commerce research
Authors: Bharati Pratyush , Tarasewich Peter
Published: July 2002

Researchers rate publications by perception, quality, and how these factors determine where they would prefer their own e-commerce work be published.
Cloning parallel simulations
Authors: Hybinette Maria , Fujimoto Richard M.
Published: July 2002

We present a cloning mechanism that enables the evaluation of multiple simulated futures. Performance of the mechanism is analyzed and evaluated experimentally on a shared memory multiprocessor. A running parallel discrete event simulation is dynamically cloned at
decision points
to explore different execution paths concurrently. In this way, what-if and alternative scenario analysis can be performed in applications such as gaming or tactical and strategic battle management. A construct called
virtual logical processes
avoids repeating common computations among clones and improves efficiency. The advantages of cloning are preserved regardless of the number of clones (or execution paths). Our performance results with a commercial air traffic control simulation demonstrate that cloning can significantly reduce the time required to compute multiple alternate futures.
Extreme collaboration
Authors: Mark Gloria
Published: July 2002

For engineers comfortable with the noise and distraction of working closely together, a technology "war room" at the Jet Propulsion Laboratory is the perfect environment for speeding delivery of space mission design proposals.
Toward open, secure, widely distributed services
Authors: Bacon Jean , Moody Ken
Published: July 2002

The OASIS open architecture controls the interoperation of independent services in distributed environments, including the constant monitoring of security conditions, as illustrated by a U.K. application in health-record management.
Numerical bifurcation analysis of delay differential equations using DDE-BIFTOOL
Authors: Engelborghs K. , Luzyanina T. , Roose D.
Published: July 2002

We describe DDE-BIFTOOL, a Matlab package for numerical bifurcation analysis of systems of delay differential equations with several fixed, discrete delays. The package implements continuation of steady state solutions and periodic solutions and their stability analysis. It also computes and continues steady state fold and Hopf bifurcations and, from the latter, it can switch to the emanating branch of periodic solutions. We describe the numerical methods upon which the package is based and illustrate its usage and capabilities through analysing three examples: two models of coupled neurons with delayed feedback and a model of two oscillators coupled with delay.
Renovating the collected algorithms from ACM
Authors: Hopkins Tim
Published: July 2002

Since 1960 the Association for Computing Machinery has published a series of refereed algorithm implementations known as the Collected Algorithms of the ACM (CALGO). Most of those published since 1975 are mathematical algorithms, and many of them remain useful today. In this paper we describe measures that have been taken to bring some 300 of these latter codes to an up-to-date and consistent state.
Managing electronic interchange of business documents
Authors: Banerjee Snehamay , Kumar Ram L.
Published: July 2002

Establishing a framework for controlled growth of electronic document interchange, based on a diverse set of technological, organizational, and interorganizational factors.
NEW INSIGHTS INTO THE REGULATION AND FUNCTIONAL SIGNIFICANCE OF LYSINE METABOLISM IN PLANTS
Authors: Galili Gad
Published: July 2002

▪ Abstract  Lysine is one of the most limiting essential amino acids in vegetative foods consumed by humans and livestock. In addition to serving as a building block of proteins, lysine is also a precursor for glutamate, an important signaling amino acid that regulates plant growth and responses to the environment. Recent genetic, molecular, and biochemical evidence suggests that lysine synthesis and catabolism are regulated by novel concerted mechanisms. These include intracellular compartmentalization of enzymes and metabolites, complex transcriptional and posttranscriptional controls of genes encoding enzymes in lysine metabolism during plant growth and development, as well as interactions between different metabolic fluxes. The recent advances in our understanding of the regulation of lysine metabolism in plants may also prove valuable for future production of high-lysine crops.
PHYTOCHELATINS AND METALLOTHIONEINS: Roles in Heavy Metal Detoxification and Homeostasis
Authors: Cobbett Christopher , Goldsbrough Peter
Published: July 2002

▪ Abstract  Among the heavy metal-binding ligands in plant cells the phytochelatins (PCs) and metallothioneins (MTs) are the best characterized. PCs and MTs are different classes of cysteine-rich, heavy metal-binding protein molecules. PCs are enzymatically synthesized peptides, whereas MTs are gene-encoded polypeptides. Recently, genes encoding the enzyme PC synthase have been identified in plants and other species while the completion of the Arabidopsis genome sequence has allowed the identification of the entire suite of MT genes in a higher plant. Recent advances in understanding the regulation of PC biosynthesis and MT gene expression and the possible roles of PCs and MTs in heavy metal detoxification and homeostasis are reviewed.
THE LIPOXYGENASE PATHWAY
Authors: Feussner Ivo , Wasternack Claus
Published: July 2002

▪ Abstract  Lipid peroxidation is common to all biological systems, both appearing in developmentally and environmentally regulated processes of plants. The hydroperoxy polyunsaturated fatty acids, synthesized by the action of various highly specialized forms of lipoxygenases, are substrates of at least seven different enzyme families. Signaling compounds such as jasmonates, antimicrobial and antifungal compounds such as leaf aldehydes or divinyl ethers, and a plant-specific blend of volatiles including leaf alcohols are among the numerous products. Cloning of many lipoxygenases and other key enzymes within the lipoxygenase pathway, as well as analyses by reverse genetic and metabolic profiling, revealed new reactions and the first hints of enzyme mechanisms, multiple functions, and regulation. These aspects are reviewed with respect to activation of this pathway as an initial step in the interaction of plants with pathogens, insects, or abiotic stress and at distinct stages of development.
THECOMPLEXFATE OFα-KETOACIDS
Authors: Mooney Brian P. , Miernyk Jan A. , Randall Douglas D.
Published: July 2002

▪ Abstract  Plant cells are unique in that they contain four species of α-ketoacid dehydrogenase complex: plastidial pyruvate dehydrogenase, mitochondrial pyruvate dehydrogenase, α-ketoglutarate (2-oxoglutarate) dehydrogenase, and branched-chain α-ketoacid dehydrogenase. All complexes include multiple copies of three components: an α-ketoacid dehydrogenase/decarboxylase, a dihydrolipoyl acyltransferase, and a dihydrolipoyl dehydrogenase. The mitochondrial pyruvate dehydrogenase complex additionally includes intrinsic regulatory protein-kinase and -phosphatase enzymes. The acyltransferases form the intricate geometric core structures of the complexes. Substrate channeling plus active-site coupling combine to greatly enhance the catalytic efficiency of these complexes. These α-ketoacid dehydrogenase complexes occupy key positions in intermediary metabolism, and a basic understanding of their properties is critical to genetic and metabolic engineering. The current status of knowledge of the biochemical, regulatory, structural, genomic, and evolutionary aspects of these fascinating multienzyme complexes are reviewed.
The La Protein
Authors: Wolin Sandra L. , Cedervall Tommy
Published: July 2002

▪ Abstract  Ubiquitous in eukaryotic cells, the La protein associates with the 3′ termini of many newly synthesized small RNAs. RNAs bound by the La protein include all nascent transcripts made by RNA polymerase III as well as certain small RNAs synthesized by other RNA polymerases. Recent genetic and biochemical analyses have revealed that binding by the La protein protects the 3′ ends of these RNAs from exonucleases. This La-mediated stabilization is required for the normal pathway of pre-tRNA maturation, facilitates assembly of small RNAs into functional RNA-protein complexes, and contributes to nuclear retention of certain small RNAs. Studies of mutant La proteins have given some insights into how the La protein specifically recognizes its RNA targets. However, many questions remain regarding the molecular mechanisms by which La protein binding influences multiple steps in small RNA biogenesis. This review focuses on the roles of the La protein in small RNA biogenesis and also discusses data that implicate the La protein in the translation of specific mRNAs.
Order Out of Chaos: Assembly of Ligand Binding Sites in Heparan Sulfate
Authors: Esko Jeffrey D. , Selleck Scott B.
Published: July 2002

▪ Abstract  Virtually every cell type in metazoan organisms produces heparan sulfate. These complex polysaccharides provide docking sites for numerous protein ligands and receptors involved in diverse biological processes, including growth control, signal transduction, cell adhesion, hemostasis, and lipid metabolism. The binding sites consist of relatively small tracts of variably sulfated glucosamine and uronic acid residues in specific arrangements. Their formation occurs in a tissue-specific fashion, generated by the action of a large family of enzymes involved in nucleotide sugar metabolism, polymer formation (glycosyltransferases), and chain processing (sulfotransferases and an epimerase). New insights into the specificity and organization of the biosynthetic apparatus have emerged from genetic studies of cultured cells, nematodes, fruit flies, zebrafish, rodents, and humans. This review covers recent developments in the field and provides a resource for investigators interested in the incredible diversity and specificity of this process.
RNA Editing by Adenosine Deaminases That Act on RNA
Authors: Bass Brenda L.
Published: July 2002

▪ Abstract  ADARs are RNA editing enzymes that target double-stranded regions of nuclear-encoded RNA and viral RNA. These enzymes are particularly abundant in the nervous system, where they diversify the information encoded in the genome, for example, by altering codons in mRNAs. The functions of ADARs in known substrates suggest that the enzymes serve to fine-tune and optimize many biological pathways, in ways that we are only starting to imagine. ADARs are also interesting in regard to the remarkable double-stranded structures of their substrates and how enzyme specificity is achieved with little regard to sequence. This review summarizes ongoing investigations of the enzyme family and their substrates, focusing on biological function as well as biochemical mechanism.
Roles for Learning Sciences and Learning Technologies in Biomedical Engineering Education: A Review of Recent Advances
Authors: Harris Thomas R. , Bransford John D. , Brophy Sean P.
Published: July 2002

▪ Abstract  Education in biomedical engineering offers a number of challenges to all constituents of the educational process—faculty, students, and employers of graduates. Although biomedical engineering educational systems have been under development for 40 years, interest in and the pace of development of these programs has accelerated in recent years. New advances in the learning sciences have provided a framework for the reexamination of instructional paradigms in biomedical engineering. This work shows that learning environments should be learner centered, knowledge centered, assessment centered, and community centered. In addition, learning technologies offer the potential to achieve this environment with efficiency. Biomedical engineering educators are in a position to design and implement new learning systems that can take advantage of advances in learning science, learning technology, and reform in engineering education.
On the Metrics and Euler-Lagrange Equations of Computational Anatomy
Authors: Miller Michael I. , Trouvé Alain , Younes Laurent
Published: July 2002

▪ Abstract  This paper reviews literature, current concepts and approaches in computational anatomy (CA). The model of CA is a Grenander deformable template, an orbit generated from a template under groups of diffeomorphisms. The metric space of all anatomical images is constructed from the geodesic connecting one anatomical structure to another in the orbit. The variational problems specifying these metrics are reviewed along with their associated Euler-Lagrange equations. The Euler equations of motion derived by Arnold for the geodesics in the group of divergence-free volume-preserving diffeomorphisms of incompressible fluids are generalized for the larger group of diffeomorphisms used in CA with nonconstant Jacobians. Metrics that accommodate photometric variation are described extending the anatomical model to incorporate the construction of neoplasm. Metrics on landmarked shapes are reviewed as well as Joshi's diffeomorphism metrics, Bookstein's thin-plate spline approximate-metrics, and Kendall's affine invariant metrics. We conclude by showing recent experimental results from the Toga & Thompson group in growth, the Van Essen group in macaque and human cortex mapping, and the Csernansky group in hippocampus mapping for neuropsychiatric studies in aging and schizophrenia.
Paramagnetic Resonance of Biological Metal Centers
Authors: Ubbink M. , Worrall J. A. R. , Canters G. W. , Groenen E. J. J. , Huber M.
Published: July 2002

▪ Abstract  The review deals with recent advances in magnetic resonance spectroscopy (hf EPR and NMR) of paramagnetic metal centers in biological macromolecules. In the first half of our chapter, we present an overview of recent technical developments in the NMR of paramagnetic bio-macromolecules. These are illustrated by a variety of examples deriving mainly from the spectroscopy of metalloproteins and their complexes. The second half focuses on recent developments in high-frequency EPR spectroscopy and the application of the technique to copper, iron, and manganese proteins. Special attention is given to the work on single crystals of copper proteins.
Subnanoscale Studies of Segregation at Grain Boundaries: Simulations and Experiments
Authors: Seidman David N.
Published: July 2002

▪ Abstract  Lattice statics (0 K) and Monte Carlo (Metropolis algorithm) simulation are utilized to determine equilibrium and metastable structures of 21 [110] symmetric tilt boundaries between 0° and 180° at 800 K, employing a Ni embedded-atom method potential; attention is paid to the effects of the macroscopic and microscopic degrees of freedom (DOFs) on grain boundary (GB) structure. Segregation of Pd is studied at all GB structures at 800 K, employing Monte Carlo and overlapping distributions Monte Carlo simulation, which yield the Gibbsian interfacial excess of Pd (ΓPd) as a function of tilt angle for both stable and metastable structures, thereby demonstrating that ΓPdis an anisotropic function of a GB's five macroscopic DOFs. In addition, atom-probe experiments on GBs on an Fe-3 at.% Si alloy, whose five macroscopic DOFs are measured by transmission electron microscopy, directly yield ΓSiand thereby demonstrate experimentally that this quantity is an anisotropic function of these DOFs.
Large-Scale Sources of Neural Stem Cells
Authors: Gottlieb David I.
Published: July 2002

▪ Abstract  Large-scale sources of neural stem cells are crucial for both basic research and novel approaches toward treating neurological disorders. Three sources that produce neural cells closely resembling their normal counterparts are now available: oncogene immortalized stem cells, neurospheres, and embryonic stem cell (ES)-derived neural cells. Cells including multiple subtypes of CNS and PNS neurons, as well as oligodendrocytes, Schwann cells, and astrocytes, are modeled by these large-scale sources. Although most cell lines were originally from rodents, their human counterparts are being discovered and characterized.
Multiple Sclerosis: Deeper Understanding of Its Pathogenesis Reveals New Targets for Therapy
Authors: Steinman Lawrence , Martin Roland , Bernard Claude , Conlon Paul , Oksenberg Jorge R.
Published: July 2002

▪ Abstract  Recent technological breakthroughs allowing for large-scale analysis of gene transcripts and large-scale monitoring of the immune response with protein chips are revealing new participants in the pathogenesis of multiple sclerosis. Some of these participants may be useful targets for therapy.
VACUUM ULTRAVIOLET SPECTROSCOPY AND CHEMISTRY BY PHOTOIONIZATION AND PHOTOELECTRON METHODS
Authors: Ng Cheuk-Yiu
Published: July 2002

▪ Abstract  The recent developments of vacuum ultraviolet (VUV) laser and third generation synchrotron radiation sources, together with the introduction of pulsed field ionization (PFI) schemes for photoion-photoelectron detection, have had a profound impact on the field of VUV spectroscopy and chemistry. Owing to the mediation of near-resonant autoionizing states, rovibronic states of ions with negligible Franck-Condon factors for direct photoionization can be examined by VUV-PFI measurements with rotational resolutions. The VUV-PFI spectra thus obtained have provided definitive ionization energies (IEs) for many small molecules. The recent synchrotron-based PFI-photoelectron-photoion coincidence experiments have demonstrated that dissociative photoionization thresholds for a range of molecules can be determined to the same precision as in PFI-photoelectron measurements. Combining appropriate dissociation thresholds and IEs measured in PFI studies, thermochemical data for many neutrals and cations can be determined with unprecedented precision. The further development of two-color excitation-ionization schemes promises to expand the scope of spectroscopic and chemical applications using the photoionization-photoelectron method.
THE MOLECULAR HAMILTONIAN
Authors: Meyer Henning
Published: July 2002

▪ Abstract  The molecular Hamiltonian represents one of the most basic concepts in spectroscopy and molecular reaction dynamics. Its derivation is notoriously difficult owing to the use of a rotating reference frame which, in turn, is necessary to define the concept of vibration and rotation. In this article, we review the construction of the molecular Hamiltonian in normal mode and in internal coordinates. For normal mode coordinates, the Watson Hamiltonian including its modification for linear molecules is derived using an approach based on classical mechanics and the Podolsky transformation. The method is subsequently used to derive the molecular Hamiltonian in terms of Jacobi and valence coordinates. Results are presented for the triatomic system and for the extension toward N-atom systems with N ≥ 3.
CONNECTING LOCAL STRUCTURE TO INTERFACE FORMATION: A Molecular Scale van der Waals Theory of Nonuniform Liquids
Authors: Weeks John D.
Published: July 2002

▪ Abstract  This article reviews a new and general theory of nonuniform fluids that naturally incorporates molecular scale information into the classical van der Waals theory of slowly varying interfaces. The method optimally combines two standard approximations, molecular (mean) field theory to describe interface formation and linear response (or Gaussian fluctuation) theory to describe local structure. Accurate results have been found in many different applications in nonuniform simple fluids and these ideas may have important implications for the theory of hydrophobic interactions in water.
From Factors to Actors: Computational Sociology and Agent-Based Modeling
Authors: Macy Michael W. , Willer Robert
Published: July 2002

▪ Abstract  Sociologists often model social processes as interactions among variables. We review an alternative approach that models social life as interactions among adaptive agents who influence one another in response to the influence they receive. These agent-based models (ABMs) show how simple and predictable local interactions can generate familiar but enigmatic global patterns, such as the diffusion of information, emergence of norms, coordination of conventions, or participation in collective action. Emergent social patterns can also appear unexpectedly and then just as dramatically transform or disappear, as happens in revolutions, market crashes, fads, and feeding frenzies. ABMs provide theoretical leverage where the global patterns of interest are more than the aggregation of individual attributes, but at the same time, the emergent pattern cannot be understood without a bottom up dynamical model of the microfoundations at the relational level. We begin with a brief historical sketch of the shift from “factors” to “actors” in computational sociology that shows how agent-based modeling differs fundamentally from earlier sociological uses of computer simulation. We then review recent contributions focused on the emergence of social structure and social order out of local interaction. Although sociology has lagged behind other social sciences in appreciating this new methodology, a distinctive sociological contribution is evident in the papers we review. First, theoretical interest focuses on dynamic social networks that shape and are shaped by agent interaction. Second, ABMs are used to perform virtual experiments that test macrosociological theories by manipulating structural factors like network topology, social stratification, or spatial mobility. We conclude our review with a series of recommendations for realizing the rich sociological potential of this approach.
Vascular Endothelial Growth Factor Induces Shc Association With Vascular Endothelial Cadherin
Authors: Zanetti Adriana , Lampugnani Maria Grazia , Balconi Giovanna , Breviario Ferruccio , Corada Monica , Lanfrancone Luisa , Dejana Elisabetta
Published: July 2002

Vascular endothelial (VE)-cadherin is endothelium specific, mediates homophilic adhesion, and is clustered at intercellular junctions. VE-cadherin is required for normal development of the vasculature in the embryo and for angiogenesis in the adult. Here, we report that VE-cadherin is associated with VE growth factor (VEGF) receptor-2 (VEGFR-2) on the exposure of endothelial cells to VEGF. The binding parallels receptor phosphorylation on tyrosine residues, which is maximal at 5 minutes and then declines within 30 minutes. Tyrosine phosphorylation of VE-cadherin was maximal at 30 minutes after the addition of the growth factor. At this time point, the protein could be coimmunoprecipitated with the adaptor protein Shc. Pull-down experiments with different Shc domains and mutants of the VE-cadherin cytoplasmic tail have shown that Shc binds to the carboxy-terminal domain of the VE-cadherin tail through its Src homology 2 domain (SH2). We found that Shc phosphorylation lasts longer in endothelial cells carrying a targeted null mutation in the
VE-cadherin
gene than in VE-cadherin–positive cells. These data suggest that VE-cadherin expression exerts a negative effect on Shc phosphorylation by VEGFR-2. We speculate that VE-cadherin binding to Shc promotes its dephosphorylation through associated phosphatases.
Inhibitory Effect on Arterial Injury-Induced Neointimal Formation by Adoptive B-Cell Transfer in Rag-1 Knockout Mice
Authors: Dimayuga Paul , Cercek Bojan , Oguchi Sumito , Fredrikson Gunilla Nordin , Yano Juliana , Shah Prediman K. , Jovinge Stefan , Nilsson Jan
Published: July 2002

We investigated the effect of B-cell reconstitution in immune-deficient Rag-1 knockout (KO) mice subjected to arterial injury. After 21 days, injury induced a 4- to 5-fold increase in neointimal formation in Rag-1 KO mice fed normal chow compared with wild-type (WT) mice (0.020±0.0160 [n=8] versus 0.0049±0.0022 [n=8] mm2, respectively;P<0.05) and in western-type diet–fed Rag-1 KO mice compared with WT mice (0.0312±0.0174 [n=7] versus 0.0050±0.0028 [n=6] mm2, respectively;P<0.05). To investigate the role of B cells in response to injury, Rag-1 KO mice were reconstituted with B cells derived from the spleens of WT mice, with donors and recipients on the same diet. Reconstitution of Rag-1 KO mice with B cells from WT mice (both fed normal chow) reduced neointimal formation compared with the effect in unreconstituted Rag-1 KO mice (0.0076±0.0039 [n=9] versus 0.020±0.0160 [n=8] mm2, respectively;P<0.05). Reconstitution of Rag-1 KO mice with B cells from WT mice (both fed a western diet) reduced neointimal formation compared the effect in Rag-1 KO mice (0.0087±0.0037 [n=8] versus 0.0312±0.0174 [n=7] mm2, respectively;P<0.05). Injured carotid arteries from reconstituted Rag-1 KO mice had detectable IgM and IgG, indicating viable transfer of B cells. The results suggest that B cells modulate the response to arterial injury.
Role of ADP Receptor P2Y12in Platelet Adhesion and Thrombus Formation in Flowing Blood
Authors: Remijn Jasper A. , Wu Ya-Ping , Jeninga Ellen H. , IJsseldijk Martin J.W. , van Willigen Gijsbert , de Groot Philip G. , Sixma Jan J. , Nurden Alan T. , Nurden Paquita
Published: July 2002

ADP plays a central role in regulating platelet function. It induces platelet aggregation via the activation of 2 major ADP receptors, P2Y1and P2Y12. We have investigated the role of P2Y12in platelet adhesion and thrombus formation under physiological flow by using blood from a patient with a defect in the gene encoding P2Y12. Anticoagulated blood from the patient and from healthy volunteers was perfused over collagen-coated coverslips. The patient’s thrombi were smaller and consisted of spread platelets overlying platelets that were not spread, whereas control thrombi were large and densely packed. Identical platelet surface coverage, aggregate size, and morphology were found when a P2Y12antagonist,N6-(2-methylthioethyl)-2-(3,3,3-trifluoropropylthio)-β,γ-dichloromethylene ATP (also known as AR-C69931 MX), was added to control blood. The addition of a P2Y1antagonist (adenosine-3′,5′-diphospate) to control blood resulted in small, but normally structured, thrombi. Thus, the ADP-P2Y12interaction is essential for normal thrombus buildup on collagen. The patient’s blood also showed reduced platelet adhesion on fibrinogen, which was not due to changes in morphology. Comparable results were found by using control blood with AR-C69931 MX and also with adenosine-3′,5′-diphospate. This suggested that P2Y12and P2Y1were both involved in platelet adhesion on immobilized fibrinogen, thereby revealing it as ADP dependent. This was confirmed by complete inhibition on the addition of creatine phosphate/creatine phosphokinase.
Regulation of Functions of Vascular Wall Cells by Tissue Factor Pathway Inhibitor
Authors: Kato Hisao
Published: July 2002

Tissue factor pathway inhibitor (TFPI) is a Kunitz-type protease inhibitor that inhibits the initial reactions of blood coagulation. A major pool of TFPI is the form associated with the surface of endothelial cells, which is speculated to play an important role in regulating the functions of vascular wall cells. TFPI consists of 3 tandem Kunitz inhibitor domains, the first and second of which inhibit the tissue factor–factor VIIa complex and factor Xa, respectively. Recent findings indicate that TFPI has another function, ie, the modulation of cell proliferation. This function is based on the interaction of the C-terminal region of TFPI with these cells. In addition to endothelial cells, it has been shown that many other vascular wall cells can synthesize TFPI, eg, mesangial cells, smooth muscle cells, monocytes, fibroblasts, and cardiomyocytes. TFPI is associated with these cells mainly through heparan sulfate proteoglycans on their surface. However, recent findings suggest that there are several other candidates for TFPI-binding proteins on these cells. On the other hand, studies on plasma levels of TFPI in patients with various diseases suggest that TFPI may be a marker of endothelial cell dysfunction. An increasing number of reports suggest that recombinant TFPI may attenuate thrombosis and prevent restenosis. Clinical trials are needed to explore these possibilities. Recent reports also indicate that the application of recombinant TFPI or TFPI gene transfer prevents restenosis in addition to thrombosis after arterial injury in the animal model; corroboration of these reports awaits clinical investigation.
Intensive Lipid Lowering by Statin Therapy Does Not Improve Vasoreactivity in Patients With Type 2 Diabetes
Authors: van Etten Ronald W. , de Koning Eelco J.P. , Honing Marina L. , Stroes Erik S. , Gaillard Carlo A. , Rabelink Ton J.
Published: July 2002

Cardiovascular disease is the most important cause of morbidity and mortality in patients with type 2 diabetes. Endothelial dysfunction predicts cardiovascular outcome. Type 2 diabetes is characterized by endothelial dysfunction, which may be caused by dyslipidemia. Statin therapy restores endothelial function in hyperlipidemic patients. Therefore, we hypothesize a beneficial effect of atorvastatin on NO-dependent vasodilation in patients with type 2 diabetes and mild dyslipidemia (low density lipoproteins >4.0 mmol/L and/or triglycerides >1.8 mmol/L). We evaluated the effect of intensive lipid lowering (4 weeks of 80 mg atorvastatin once daily) on vasoreactivity in 23 patients with type 2 diabetes by using venous occlusion plethysmography. Twenty-one control subjects were matched for age, sex, body mass index, blood pressure, and smoking habits. The ratio of blood flows in the infused (measurement [M]) and noninfused (control [C]) arm was calculated for each recording (M/C ratio), and M/C% indicates the percentage change from the baseline M/C ratio. Serotonin-induced NO-dependent vasodilation was significantly blunted (52±30 versus 102±66 M/C%,
P
<0.005), and nitroprusside-induced endothelium-independent vasodilation was modestly reduced (275±146 versus 391±203 M/C%,
P
<0.05) in patients with type 2 diabetes compared with control subjects. Despite significant reduction of total cholesterol, low density lipoproteins, and triglycerides (5.8±1.0 to 3.2±0.6 [
P
<0.0001], 4.1±1.1 to 1.8±0.7 [
P
<0.0001], and 2.2±1.3 to 1.4±0.5 [
P
<0.05] mmol/L, respectively), no effect on NO-dependent (59±44 M/C%) and endothelium-independent (292±202 M/C%) vasodilation was demonstrated. These data suggest that intensive lipid lowering by atorvastatin has no effect on NO availability in forearm resistance arteries in type 2 diabetic patients. Other factors, such as hyperglycemia, may be a more important contributing factor regarding impaired vasoreactivity in this patient group.
Sol Sherry Lecture in Thrombosis
Authors: Prescott Stephen M. , McIntyre Thomas M. , Zimmerman Guy A. , Stafforini Diana M.
Published: July 2002

The inflammatory response is characterized by a multistep molecular interaction between “signaling” cells, such as endothelial cells, and “responding” cells, such as neutrophils and monocytes. In the first step, selectins produced by signaling cells mediate the tethering of responding cells at sites of inflammation. Subsequently, an additional mediator expressed by signaling cells activates the tethered responding cells. Under pathological conditions, the same mechanism is invoked in inappropriate ways: (1) by prolonged presentation of selectins on the cell surface and (2) by the unregulated production of oxidized phospholipids that mimic the normal secondary signaling molecule, platelet-activating factor (PAF). The enzyme PAF acetylhydrolase (PAF-AH) inactivates PAF and oxidized phospholipids and constitutes an “off” switch that suppresses inflammation. Inhibition of normal PAF-AH function or inactivating mutations of the PAF-AH gene can lead to increased susceptibility to inflammatory disease. These studies have relevance to atherosclerosis and thrombosis, because inflammation is a central feature of both.
Genetic Influences on Aortic Root Size in American Indians
Authors: Bella Jonathan N. , MacCluer Jean W. , Roman Mary J. , Almasy Laura , North Kari E. , Welty Thomas K. , Lee Elisa T. , Fabsitz Richard R. , Howard Barbara V. , Devereux Richard B.
Published: July 2002

Aortic root dilatation is a major pathophysiological mechanism for aortic regurgitation and predisposes the aortic root to dissection or rupture. However, only a small proportion of the variance of aortic root size can be explained by its known clinical and demographic correlates. The present study was undertaken to determine the heritability of echocardiographically derived aortic root diameter in the American Indian participants in the second Strong Heart Study examination. Echocardiograms were analyzed in 1373 SHS participants who had ≥1 family member in the cohort. Heritability calculations were performed by using variance component analysis as implemented in SOLAR, a computer analysis program. In a polygenic model, the variables entered and identified as covariates of larger aortic root diameter were older age, male sex, and center (
P
<0.001), which accounted for 35% of the overall variability of aortic root diameter. After simultaneous adjustment was made for these significant covariates, the proportion of phenotypic variance due to additive genetic contribution or residual heritability (
h

2

) was 0.51 (SE=0.08,
P
<0.001). Additionally, simultaneous adjustment for height, weight, and systolic and diastolic BPs yielded slightly lower residual
h

2

of aortic root diameter (
h

2

=0.44, SE=0.08,
P
<0.001), which accounted for 26% of the overall variance of aortic root size. Because center effects were identified as significant covariates in the analyses,
h

2

analyses were performed separately in Arizona, Oklahoma, and North/South Dakota centers, which confirmed that a significant proportion of the phenotypic variance of aortic root diameter is due to additive genetic contribution. Heredity explains a substantial proportion of the variability of aortic root size that is not accounted for by age, sex, body size, and blood pressure. Echocardiographic screening of family members with aortic root dilatation may identify other individuals predisposed to aortic dissection or rupture.
Spontaneous Ischemic Events in the Brain and Heart Adapt the Hearts of Severely Atherosclerotic Mice to Ischemia
Authors: Tokuno Shinichi , Hinokiyama Kazuhiro , Tokuno Kumi , Löwbeer Christian , Hansson Lars-Olof , Valen Guro
Published: July 2002

To investigate if spontaneous ischemic events in mice with severe multi-organ atherosclerosis could adapt to ischemia, apolipoprotein E/LDL receptor knockout mice were fed an atherogenic diet for 7 to 9 months. Signs of spontaneous ischemia occurred. One to two days later, hearts were excised, Langendorff-perfused with induced global ischemia, and compared with mice without signs of disease. In vivo heart or brain infarctions were verified by heart histology and/or increased serum levels of cardiac troponin T and S100B. Hearts of mice with spontaneous ischemic events had improved function and reduced Langendorff-induced infarctions. To investigate the remote preconditioning effect of brain ischemia, bilateral ligation of the internal carotid arteries was performed in C57BL6 mice. Twenty-four hours later, their isolated hearts were protected against induced global ischemia. A possible role of inducible NO synthase (iNOS) was studied in iNOS knock out mice, who were not preconditioned by induced brain ischemia. Cardiac iNOS was unchanged 24 hours after preconditioning, suggesting that NO is a trigger rather than a mediator of protection. These findings suggest that spontaneous ischemic events in the brain and heart adapt the heart to ischemia. This can be mimicked by induced brain ischemia, with iNOS as a key factor of protection.