bluuebunny/crossref_metadata_2025 huggingface dataset:
EXPLORING THE STACKING STATE-SPACE
Authors: LEDEZMA AGAPITO , ALER RICARDO , BORRAJO DANIEL
Published: July 2002

Nowadays, there is no doubt that machine learning techniques can be successfully applied to data mining tasks. Currently, the combination of several classifiers is one of the most active fields within inductive machine learning. Examples of such techniques are boosting, bagging and stacking. From these three techniques, stacking is perhaps the less used one. One of the main reasons for this relates to the difficulty to define and parameterize its components: selecting which combination of base classifiers to use, and which classifier to use as the meta-classifier. One could use for that purpose simple search methods (e.g. hill climbing), or more complex ones (e.g. genetic algorithms). But before search is attempted, it is important to know the properties of the search space itself. In this paper we study exhaustively the space of Stacking systems that can be built by using four base learning systems: C4.5, IB1, Naive Bayes, and PART. We have also used the Multiple Linear Response (MLR) as meta-classifier. The properties of this state-space obtained in this paper will be useful for designing new Stacking-based algorithms and tools.
FRACTAL CHARACTERISTICS OF THE HORIZONTAL MOVEMENT OF WATER IN SOILS
Authors: GUERRINI IVAN A. , SWARTZENDRUBER D.
Published: July 2002

Observed deviations from traditional concepts of soil-water movement are considered in terms of fractals. A connection is made between this movement and a Brownian motion, a random and self-affine type of fractal, to account for the soil-water diffusivity function having auxiliary time dependence for unsaturated soils. The position of a given water content is directly proportional to tn, where t is time, and exponent n for distinctly unsaturated soil is less than the traditional 0.50. As water saturation is approached, n approaches 0.50. Macroscopic fractional Brownian motion is associated with n < 0.50, but shifts to regular Brownian motion for n = 0.50.
ON ACCARDI'S NOTION OF COMPLEMENTARY OBSERVABLES
Authors: CASSINELLI G. , VARADARAJAN V. S.
Published: July 2002

We discuss some examples of complementary observables, in the sense of Accardi. We show that the trace property is not sufficient to determine such a pair of observables.
FEYNMAN'S OPERATIONAL CALCULI FOR NONCOMMUTING OPERATORS: SPECTRAL THEORY
Authors: JEFFERIES B. , JOHNSON G. W.
Published: July 2002

In recent papers the authors presented the key ideas involved in their approach to Feynman's operational calculi for a system of not necessarily commuting bounded linear operators acting on a Banach space. The central objects of the theory are the disentangling algebra, a commutative Banach algebra, and the disentangling map which carries this commutative structure into the noncommutative algebra of operators. Under assumptions concerning the growth of disentangled exponential expressions, the associated functional calculus for the system of operators is a distribution with compact support which we view as the joint spectrum of the operators with respect to the disentangling map. The spectral properties of the disentangling maps are studied in this paper.
Going from Regulation to Supervision: Support for Paradigm Shift from an Efficiency Study of the Merchant Banking Industry In Singapore
Authors: Lim Guan Hua
Published: July 2002

Increasingly we are witnessing a paradigm shift from checklist style regulations of financial institutions to one that emphasizes supervision and the role of the marketplace. Advocates of this new paradigm argue that the size and financial strength of a financial institution does not necessarily equate to excellence and efficiency. This paper offers as evidence from an efficiency study of the merchant banking industry in Singapore that such a paradigm shift is appropriate. The findings of the study indicate that the efficiencies of the merchant banks do not appear to change much over time, profit and cost efficiencies are un-correlated, and that size is not a reliable indicator of efficiency.
TRANSIENT RESPONSE OF VISCOELASTIC MOVING BELTS USING BLOCK-BY-BLOCK METHOD
Authors: ZHANG LIXIN , ZU JEAN W. , ZHONG Z.
Published: July 2002

The linear, viscoelastic, integral constitutive law is employed to model the viscoelastic characteristic of belt materials. By assuming the translating eigenfunctions instead of stationary eigenfunctions to be the spatial solutions, the governing equation is reduced to differential-integral equations in time, which are then solved by the block-by-block method. The transient amplitudes of parametrically excited viscoelastic moving belts with uniform and non-uniform travelling speed are obtained. The effects of viscoelastic parameters and perturbed axial velocity on the system response are also investigated.
A NEW TRIANGULAR ELEMENT BASED ON HIGHER ORDER SHEAR DEFORMATION THEORY FOR FLEXURAL VIBRATION OF COMPOSITE PLATES
Authors: CHAKRABARTI A. , SHEIKH A. H.
Published: July 2002

A triangular element based on Reddy's higher order shear deformation theory is developed for free vibration analysis of composite plates. In the Reddy's plate theory, the transverse shear stress varies in a parabolic manner across the plate thickness and vanishes at the top and bottom surfaces of the plate. Moreover, it does not involve any additional unknowns. Thus the plate theory is quite simple and elegant. Unfortunately, such an attractive plate theory cannot be exploited as expected in finite element analysis, primarily due to the difficulties in satisfying the inter-element continuity requirement. This has inspired us to develop the present element, which has three corner nodes and three mid-side nodes with the same number of degrees of freedom. To demonstrate the performance of the element, numerical examples of isotropic and composite plates under different situations are solved. The results are compared with the analytical solutions and other published results, which show the accuracy and range of applicability of the proposed element in the problem of vibration analysis.
BUCKLING OF STANDING VERTICAL PLATES UNDER BODY FORCES
Authors: WANG C. M. , XIANG Y. , WANG C. Y.
Published: July 2002

This paper is concerned with the elastic buckling problem of vertical plates under body forces/selfweight. The vertical plate is either clamped or simply supported at its bottom edge while its top edge is free. The two sides of the plate may either be free, simply supported or clamped. For plates with simply supported sides, exact critical buckling solutions are derived using the Levy approach. For other boundary conditions, accurate buckling solutions are obtained for very wide plates to very tall plates using the Ritz method.
STABILITY OF NUMERICAL DISCRETIZATIONS IN MODELLING VIBRATIONAL CHARACTERISTICS OF PIEZOELECTRIC CYLINDRICAL SHELLS
Authors: MELNIK R. V. N. , MELNIK K. N.
Published: July 2002

Many problems in applications of piezoelectric materials are essentially time-dependent, and a conventional treatment of such problems with analytical or semi-analytical techniques based on the analysis of harmonic oscillations become inadequate in those cases where a complete dynamic picture of electromechanical energy transfer is required. For such situations we have developed an efficient explicit numerical methodology allowing us to compute dynamic electromechanical characteristics of piezoelectric structures and devices under various loading conditions. In this paper we demonstrate that the stability conditions for our numerical approximation can be obtained from a discrete conservation law, and can be cast in a form similar to that of the classical CFL condition. However, in our case the velocities of wave propagations, participating in the formulation of the stability conditions, are clearly dependent on the pattern of electromectromechanical coupling. Our discussion in this paper, including computational examples, is centred around finite piezoelectric shells of cylindrical shape.
RECONSTRUCTION OF 3D SPACE STRUCTURE WITH A ROTATIONAL IMAGING SYSTEM
Authors: HILD MICHAEL , NISHIJIMA KAZUYUKI
Published: July 2002

We examine whether the accuracy of 3D space point reconstruction from image pairs can be improved by using rotational imaging. A single camera acquires image pairs at two positions that are separated by a rotation and extracts feature points from both images. Matches of feature point pairs from both images are computed, and then the 3D space coordinates are reconstructed based on the disparity of the matched points. The system carries out optimal rotations to obtain low-error reconstructions, using a specially designed control algorithm. The camera can be rotated 360 degrees around a vertical space axis and approximately 270 degrees around a horizontal space axis. The characteristics of the system are described based on simulations and it is shown, through experiments with a prototype, that this system has low matching error, and can cope with occlusions and periodic image structure. The system is adequate for reconstruction of static scenes.
THE COHOMOLOGY OF STOCHASTIC AND RANDOM DIFFERENTIAL EQUATIONS, AND LOCAL LINEARIZATION OF STOCHASTIC FLOWS
Authors: IMKELLER PETER , LEDERER CHRISTIAN
Published: July 2002

Random dynamical systems can be generated by stochastic differential equations (sde) on the one hand, and by random differential equations (rde), i.e. randomly parametrized ordinary differential equations on the other hand. Due to conflicting concepts in stochastic calculus and ergodic theory, asymptotic problems for systems associated with sde are harder to treat. We show that both objects are basically identical, modulo a stationary coordinate change (cohomology) on the state space. This observation opens completely new opportunities for the treatment of asymptotic problems for systems related to sde: just study them for the conjugate rde, which is often possible by simple path-by-path classical arguments. This is exemplified for the problem of local linearization of random dynamical systems, the classical analogue of which leads to the Hartman–Grobman theorem.
Fast and flexible application-level networking on exokernel systems
Authors: Ganger Gregory R. , Engler Dawson R. , Kaashoek M. Frans , Briceño Hector M. , Hunt Russell , Pinckney Thomas
Published: July 2002

Application-level networking is a promising software organization
for improving performance and functionality for important network
services. The Xok/ExOS exokernel system includes application-level
support for standard network services, while at the same time
allowing application writers to specialize networking services.
This paper describes how Xok/ExOS's kernel mechanisms and library
operating system organization achieve this flexibility, and
retrospectively shares our experiences and lessons learned (both
positive and negative). It also describes how we used this
flexibility to build and specialize three network data services:
the Cheetah HTTP server, the webswamp Web benchmarking tool, and an
application-level TCP forwarder. Overall measurements show large
performance improvements relative to similar services built on
conventional interfaces, in each case reaching the maximum possible
end-to-end performance for the experimental platform. For example,
Cheetah provides factor of 2--4 increases in throughput compared to
highly tuned socket-based implementations and factor of 3--8
increases compared to conventional systems. Webswamp can offer
loads that are two to eight times heavier. The TCP forwarder
provides 50--300% higher throughput while also providing end-to-end
TCP semantics that cannot be achieved with POSIX sockets. With more
detailed measurements and profiling, these overall performance
improvements are also broken down and attributed to the specific
specializations described, providing server writers with insights
into where to focus their optimization efforts.
An algebraic approach to IP traceback
Authors: Dean Drew , Franklin Matt , Stubblefield Adam
Published: July 2002

We present a new solution to the problem of determining the path a packet traversed over the Internet (called the traceback problem) during a denial-of-service attack. This article reframes the traceback problem as a polynomial reconstruction problem and uses algebraic techniques from coding theory and learning theory to provide robust methods of transmission and reconstruction.
A fine-grained access control system for XML documents
Authors: Damiani Ernesto , De Capitani di Vimercati Sabrina , Paraboschi Stefano , Samarati Pierangela
Published: July 2002

Web-based applications greatly increase information availability and ease of access, which is optimal for public information. The distribution and sharing of information via the Web that must be accessed in a selective way, such as electronic commerce transactions, require the definition and enforcement of security controls, ensuring that information will be accessible only to authorized entities. Different approaches have been proposed that address the problem of protecting information in a Web system. However, these approaches typically operate at the file-system level, independently of the data that have to be protected from unauthorized accesses. Part of this problem is due to the limitations of HTML, historically used to design Web documents. The extensible markup language (XML), a markup language promoted by the World Wide Web Consortium (W3C), is de facto the standard language for the exchange of information on the Internet and represents an important opportunity to provide fine-grained access control. We present an access control model to protect information distributed on the Web that, by exploiting XML's own capabilities, allows the definition and enforcement of access restrictions directly on the structure and content of the documents. We present a language for the specification of access restrictions, which uses standard notations and concepts, together with a description of a system architecture for access control enforcement based on existing technology. The result is a flexible and powerful security system offering a simple integration with current solutions.
Controlled publication of digital scientific data
Authors: Helly John J. , Elvins T. Todd , Sutton Don , Martinez David , Miller Scott E. , Pickett Steward , Ellison Aaron M.
Published: July 2002

How to balance free and open access to scientific data with privileged access to new results by authors while protecting them from being scooped by competing interpretations of their own data.
Personalized multimedia information access
Authors: Light Marc , Maybury Mark T.
Published: July 2002

Ask questions, get personalized answers.
Peer-to-peer data trading to preserve information
Authors: Cooper Brian F. , Garcia-Molina Hector
Published: July 2002

Data archiving systems rely on replication to preserve information. This paper discusses how a network of autonomous archiving sites can trade data to achieve the most reliable replication. A series of binary trades among sites produces a peer-to-peer archiving network. Two trading algorithms are examined, one based on trading collections (even if they are different sizes) and another based on trading equal sized blocks of space (which can then store collections). The concept of
deeds
is introduced; deeds track the blocks of space owned by one site at another. Policies for tuning these algorithms to provide the highest reliability, for example by changing the order in which sites are contacted and offered trades, are discussed. Finally, simulation results are presented that reveal which policies are best. The experiments indicate that a digital archive can achieve the best reliability by trading blocks of space (deeds), and that following certain policies will allow that site to maximize its reliability.
The evolution of Coda
Authors: Satyanarayanan M.
Published: July 2002

Failure-resilient, scalable, and secure read-write access to shared information by mobile and static users over wireless and wired networks is a fundamental computing challenge. In this article, we describe how the Coda file system has evolved to meet this challenge through the development of mechanisms for server replication, disconnected operation, adaptive use of weak connectivity, isolation-only transactions, translucent caching, and opportunistic exploitation of hardware surrogates. For each mechanism, the article explains how usage experience with it led to the insights for another mechanism. It also shows how Coda has been influenced by the work of other researchers and by industry. The article closes with a discussion of the technical and nontechnical lessons that can be learned from the evolution of the system.
Let caches decay
Authors: Hu Zhigang , Kaxiras Stefanos , Martonosi Margaret
Published: July 2002

Power dissipation is increasingly important in CPUs ranging from those intended for mobile use, all the way up to high-performance processors for highend servers. Although the bulk of the power dissipated is dynamic switching power, leakage power is also beginning to be a concern. Chipmakers expect that in future chip generations, leakage's proportion of total chip power will increase significantly. This article examines methods for reducing leakage power within the cache memories of the CPU. Because caches comprise much of a CPU chip's area and transistor counts, they are reasonable targets for attacking leakage. We discuss policies and implementations for reducing cache leakage by invalidating and "turning off" cache lines when they hold data not likely to be reused. In particular, our approach is targeted at the generational nature of cache line usage. That is, cache lines typically have a flurry of frequent use when first brought into the cache, and then have a period of "dead time" before they are evicted. By devising effective, low-power ways of deducing dead time, our results show that in many cases we can reduce L1 cache leakage energy by 4x in SPEC2000 applications without having an impact on performance. Because our decay-based techniques have notions of competitive online algorithms at their roots, their energy usage can be theoretically bounded at within a factor of two of the optimal oracle-based policy. We also examine adaptive decay-based policies that make energy-minimizing policy choices on a per-application basis by choosing appropriate decay intervals individually for each cache line. Our proposed adaptive policies effectively reduce L1 cache leakage energy by 5x for the SPEC2000 with only negligible degradations in performance.
The state of the art in locally distributed Web-server systems
Authors: Cardellini Valeria , Casalicchio Emiliano , Colajanni Michele , Yu Philip S.
Published: July 2002

The overall increase in traffic on the World Wide Web is augmenting user-perceived response times from popular Web sites, especially in conjunction with special events. System platforms that do not replicate information content cannot provide the needed scalability to handle large traffic volumes and to match rapid and dramatic changes in the number of clients. The need to improve the performance of Web-based services has produced a variety of novel content delivery architectures. This article will focus on Web system architectures that consist of multiple server nodes distributed on a local area, with one or more mechanisms to spread client requests among the nodes. After years of continual proposals of new system solutions, routing mechanisms, and policies (the first dated back to 1994 when the NCSA Web site had to face the first million of requests per day), many problems concerning multiple server architectures for Web sites have been solved. Other issues remain to be addressed, especially at the network application layer, but the main techniques and methodologies for building scalable Web content delivery architectures placed in a single location are settled now. This article classifies and describes main mechanisms to split the traffic load among the server nodes, discussing both the alternative architectures and the load sharing policies. To this purpose, it focuses on architectures, internal routing mechanisms, and dispatching request algorithms for designing and implementing scalable Web-server systems under the control of one content provider. It identifies also some of the open research issues associated with the use of distributed systems for highly accessed Web sites.
Timely
financial reporting at corporate web sites?
Authors: Ettredge Michael , Richardson Vernon J. , Scholz Susan
Published: July 2002

Considering the competitive advantage of having current financial information available online, it's curious how few institutions actually succeed in this regard.
An extension of the divide-and-conquer method for a class of symmetric block-tridiagonal eigenproblems
Authors: Gansterer Wilfried N. , Ward Robert C. , Muller Richard P.
Published: July 2002

A divide-and-conquer method for computing eigenvalues and eigenvectors of a block-tridiagonal matrix with rank-one off-diagonal blocks is presented. The implications of unbalanced merging operations due to unequal block sizes are analyzed and illustrated with numerical examples. It is shown that an unfavorable order for merging blocks in the synthesis phase of the algorithm may lead to a significant increase of the arithmetic complexity. A strategy to determine a good merging order that is at least close to optimal in all cases is given. The method has been implemented and applied to test problems from a quantum chemistry application.
Algorithm 816:r2d2lri
Authors: Robinson Ian , Hill Michael
Published: July 2002

r2d2lriis a non-adaptive algorithm implemented in C++ for performing automatic cubature over a wide variety of finite and non-finite two-dimensional domains. The core integrator uses a sixth-order Sidi transformation applied to a sequence of embedded lattice rules in such a fashion as to incur virtually no computational overhead. Even for integrals over non-finite domains, for which several non-finite to finite transformations may be attempted, the algorithm remains very fast. Performance data are presented which demonstrate both the effectiveness and efficiency ofr2d2lri, taking into account the number of function evaluations needed and the execution speed.
A call for the home media network
Authors: Bell Gordon , Gemmell Jim
Published: July 2002

"The best way to predict the future is to invent it."---Alan Kay "…or at least posit a vision for others to build."---The authors
Smart card evolution
Authors: Shelfer Katherine M. , Procaccino J. Drew
Published: July 2002

Smart cards and their related technologies are an emerging component of electronic commerce worldwide. In some countries, they are revolutionizing aspects of commerce, healthcare, and recreation.
ABSCISSION, DEHISCENCE, ANDOTHERCELLSEPARATIONPROCESSES
Authors: Roberts Jeremy A. , Elliott Katherine A. , Gonzalez-Carranza Zinnia H.
Published: July 2002

▪ Abstract  Cell separation is a critical process that takes place throughout the life cycle of a plant. It enables roots to emerge from germinating seeds, cotyledons, and leaves to expand, anthers to dehisce, fruit to ripen, and organs to be shed. The focus of this review is to examine how processes such as abscission and dehiscence are regulated and the ways new research strategies are helping us to understand the mechanisms involved in bringing about a reduction in cell-to-cell adhesion. The opportunities for using this information to manipulate cell separation for the benefit of agriculture and horticulture are evaluated.
Mechanisms of Fast Protein Folding
Authors: Myers Jeffrey K. , Oas Terrence G.
Published: July 2002

▪ Abstract  An explosion of in vitro experimental data on the folding of proteins has revealed many examples of folding in the millisecond or faster timescale, often occurring in the absence of stable intermediate states. We review experimental methods for measuring fast protein folding kinetics, and then discuss various analytical models used to interpret these data. Finally, we classify general mechanisms that have been proposed to explain fast protein folding into two catagories, heterogeneous and homogeneous, reflecting the nature of the transition state. One heterogeneous mechanism, the diffusion-collision mechanism, can be used to interpret experimental data for a number of proteins.
ATP-Dependent Nucleosome Remodeling
Authors: Becker Peter B. , Hörz Wolfram
Published: July 2002

▪ Abstract  It has been a long-standing challenge to decipher the principles that enable cells to both organize their genomes into compact chromatin and ensure that the genetic information remains accessible to regulatory factors and enzymes within the confines of the nucleus. The discovery of nucleosome remodeling activities that utilize the energy of ATP to render nucleosomal DNA accessible has been a great leap forward. In vitro, these enzymes weaken the tight wrapping of DNA around the histone octamers, thereby facilitating the sliding of histone octamers to neighboring DNA segments, their displacement to unlinked DNA, and the accumulation of patches of accessible DNA on the surface of nucleosomes. It is presumed that the collective action of these enzymes endows chromatin with dynamic properties that govern all nuclear functions dealing with chromatin as a substrate. The diverse set of ATPases that qualify as the molecular motors of the nucleosome remodeling process have a common history and are part of a superfamily. The physiological context of their remodeling action builds on the association with a wide range of other proteins to form distinct complexes for nucleosome remodeling. This review summarizes the recent progress in our understanding of the mechanisms underlying the nucleosome remodeling reaction, the targeting of remodeling machines to selected sites in chromatin, and their integration into complex regulatory schemes.
Physics and Applications of Microfluidics in Biology
Authors: Beebe David J. , Mensing Glennys A. , Walker Glenn M.
Published: July 2002

▪ Abstract  Fluid flow at the microscale exhibits unique phenomena that can be leveraged to fabricate devices and components capable of performing functions useful for biological studies. The physics of importance to microfluidics are reviewed. Common methods of fabricating microfluidic devices and systems are described. Components, including valves, mixers, and pumps, capable of controlling fluid flow by utilizing the physics of the microscale are presented. Techniques for sensing flow characteristics are described and examples of devices and systems that perform bioanalysis are presented. The focus of this review is microscale phenomena and the use of the physics of the scale to create devices and systems that provide functionality useful to the life sciences.
Density Functional Studies of Multiferroic Magnetoelectrics
Authors: Hill Nicola A.
Published: July 2002

▪ Abstract  Multiferroic magnetoelectrics are materials that are both ferromagnetic and ferroelectric in the same phase. As a result, they have a spontaneous magnetization that can be switched by an applied magnetic field and a spontaneous polarization that can be switched by an applied electric field. In this paper we show that density functional theory has been invaluable both in explaining the properties of known magnetically ordered ferroelectric materials, and in predicting the occurrence of new ones. Density functional calculations have shown that, in general, the transition metal d electrons essential for magnetism reduce the tendency for off-center ferroelectric distortion. Consequently, an additional electronic or structural driving force must be present for ferromagnetism and ferroelectricity to occur simultaneously.
Statistical Description of Microstructures
Authors: Torquato S.
Published: July 2002

▪ Abstract  We review progress made in quantitatively ascertaining the various statistical correlation functions that are fundamental to determining the material properties of specific classes of disordered materials. Topics covered include the definitions of the correlation functions, a unified theoretical means of representing and computing the different statistical descriptors, structural characterization from two-dimensional and three-dimensional images of materials, scalar order metrics and particle packings, and reconstruction techniques.
Atomistic Aspects of Crack Propagation in Brittle Materials: Multimillion Atom Molecular Dynamics Simulations
Authors: Rountree Cindy L. , Kalia Rajiv K. , Lidorikis Elefterios , Nakano Aiichiro , Van Brutzel Laurent , Vashishta Priya
Published: July 2002

▪ Abstract  Atomistic aspects of dynamic fracture in a variety of brittle crystalline, amorphous, nanophase, and nanocomposite materials are reviewed. Molecular dynamics (MD) simulations, ranging from a million to 1.5 billion atoms, are performed on massively parallel computers using highly efficient multiresolution algorithms. These simulations shed new light on (a) branching, deflection, and arrest of cracks; (b) growth of nanoscale pores ahead of the crack and how pores coalesce with the crack to cause fracture; and (c) the influence of these mechanisms on the morphology of fracture surfaces. Recent advances in novel multiscale simulation schemes combining quantum mechanical, molecular dynamics, and finite-element approaches and the use of these hybrid approaches in the study of crack propagation are also discussed.
Auditory System Development: Primary Auditory Neurons and Their Targets
Authors: Rubel Edwin W. , Fritzsch Bernd
Published: July 2002

▪ Abstract  The neurons of the cochlear ganglion transmit acoustic information between the inner ear and the brain. These placodally derived neurons must produce a topographically precise pattern of connections in both the inner ear and the brain. In this review, we consider the current state of knowledge concerning the development of these neurons, their peripheral and central connections, and their influences on peripheral and central target cells. Relatively little is known about the cellular and molecular regulation of migration or the establishment of precise topographic connection to the hair cells or cochlear nucleus (CN) neurons. Studies of mice with neurotrophin deletions are beginning to yield increasing understanding of variations in ganglion cell survival and resulting innervation patterns, however. Finally, existing evidence suggests that while ganglion cells have little influence on the differentiation of their hair cell targets, quite the opposite is true in the brain. Ganglion cell innervation and synaptic activity are essential for normal development of neurons in the cochlear nucleus.
A Decade of Molecular Studies of Fragile X Syndrome
Authors: O'Donnell William T. , Warren Stephen T.
Published: July 2002

▪ Abstract  Fragile X syndrome is one of the most common forms of inherited mental retardation. In most cases the disease is caused by the methylation-induced transcriptional silencing of the fragile X mental retardation 1 (FMR1) gene that occurs as a result of the expansion of a CGG repeat in the gene's 5′UTR and leads to the loss of protein product fragile X mental retardation protein (FMRP). FMRP is an RNA binding protein that associates with translating polyribosomes as part of a large messenger ribonucleoprotein (mRNP) and modulates the translation of its RNA ligands. Pathological studies from the brains of patients and from Fmr1 knockout mice show abnormal dendritic spines implicating FMRP in synapse formation and function. Evidence from both in vitro and in vivo neuronal studies indicates that FMRP is located at the synapse and the loss of FMRP alters synaptic plasticity. As synaptic plasticity has been implicated in learning and memory, analysis of synapse abnormalities in patients and Fmr1 knockout mice should prove useful in studying the pathogenesis of fragile X syndrome and understanding learning and cognition in general.

If an appreciable portion of the total variance (in IQ) is due to sex linked genes, it is of more importance that a boy should have a clever mother than a clever father.

     Hogben 1932 (quoted in Lehrke 1974 )
REACTIVE COLLISIONS OF HYPERTHERMAL ENERGY MOLECULAR IONS WITH SOLID SURFACES
Authors: Jacobs Dennis C.
Published: July 2002

▪ Abstract  Recent experimental advances have uncovered many of the diverse reaction pathways following an energetic collision between a molecular ion and a solid surface. Hyperthermal translational energies (5–500 eV) are sufficient to activate a number of chemical transformations in the near-surface region, including charge transfer, dissociation, abstraction, and deposition. State-of-the-art scattering studies probe the consumption and disposal of energy and the effects of approach geometry and surface electronic structure on the operative reaction mechanisms. These fundamental investigations provide insight relevant to the fabrication of microelectronics devices, the interaction of space vehicles with the earth's atmosphere, and the development of analytical techniques in mass spectrometry.
Violence in Social Life
Authors: Jackman Mary R.
Published: July 2002

▪ Abstract  Two features have marked the sociological analysis of violence: (a) disparate clusters of research on various forms of violence that have been the object of urgent social concern, and relatedly, (b) an overwhelming focus on forms of violence that are socially deviant and motivated by willful malice. The resulting literature is balkanized and disjointed, and yet narrowly focused. The systematic understanding of violence as a broad genus of social behavior has suffered accordingly. I examine the issues that have clouded the analysis of violence: the importance of physical injuries vs. psychological, social, and material injuries; the weight placed on physical vs. verbal and written actions; the role of force vs. victim complicity in the infliction of injuries; and the emphasis on interpersonal vs. corporate agents and victims. That discussion highlights the widely varying forms of violence in social life, including many instances that are neither driven by malicious intent nor socially repudiated. I consider the diverse motives that drive violent actions and the variant social acceptance or repudiation that they meet. I propose a generic definition of violence, freed of ad hoc restrictions, that encompasses the full population of violent social actions. This directs us to more systematic questions about violence in social life.
Electrochemistry of Poly(1,5‐diaminoanthraquinone) and Its Application in Electrochemical Capacitor Materials
Authors: Naoi Katsuhiko , Suematsu Shunzo , Manago Ari
Published: July 2002

A poly(1,5‐diaminoanthraquinone) [poly(DAAQ)], which is a conducting polymer condensed with 1,4‐benzoquinone, was studied electrochemically and was proposed as a new category of electrochemical capacitor material. In common nonaqueous media, the poly(DAAQ) showed two sets of reproducible redox couples for repeated cycles. The potential window of the material was in the range from ca. −1.5 to +1.0 V (vs. Ag/AgCl). In situ UV‐visible spectroscopy suggested that the redox couple observed around −1.5 V is responsible for the quinone group and that around +1.0 V is due to the π‐conjugated system. The poly(DAAQ) showed high conductivity

(
0.3
–
2.0
 

Ω

−
1

 

cm

−
1

)

over a wide range of potential (−2.0 to 0.8 V), which suggests extension of the π‐conjugated system. It is proposed here that one can construct an electrochemical capacitor device by utilizing poly(DAAQ) as both positive and negative electrodes. We constructed the poly(DAAQ)/poly(DAAQ) electrochemical capacitor for test purposes. The poly(DAAQ)/poly(DAAQ) electrochemical capacitor exhibited high specific energy

(
25
–
46
 

Wh kg

−
1

)

and high specific power

(
10
,
200
–
30
,
500
W

kg

−
1

)

at discharge rates from 30 to 90 C. © 2000 The Electrochemical Society. All rights reserved.
Quantification of mRNA for Endothelial NO Synthase in Mouse Blood Vessels by Real-Time Polymerase Chain Reaction
Authors: Chu Yi , Heistad Donald D. , Knudtson Kevin L. , Lamping Kathryn G. , Faraci Frank M.
Published: July 2002

The mouse is useful in studies of vascular biology because of its well-defined genetics and because the mouse genome can be manipulated. However, because only small amounts of mRNA can be extracted from blood vessels, the quantification of gene expression in individual mice is difficult. Endothelial NO synthase (eNOS) plays a major role in the regulation of vascular tone and growth. In addition, there appear to be sex differences in the production of NO under basal conditions in mouse aortas. The goals of this study were to develop a real-time polymerase chain reaction (PCR) method to quantify eNOS mRNA in blood vessels from mice and to examine eNOS mRNA levels in vessels from male and female mice. Blood vessels were isolated from C57BL/6 mice. Total RNA from individual mice was isolated and reverse-transcribed. The number of molecules of eNOS mRNA (after reverse transcription) was determined against cDNA standards, with 18S rRNA used as a control for RNA input and reverse-transcription efficiency. When expressed as copy numbers per nanogram of total RNA or as the ratio of eNOS to 18S rRNA, eNOS mRNA was lower in the aortas of female mice than in those of male mice at 7 to 9 months of age. In contrast, no difference in eNOS mRNA was found in the aortas of 2-month-old mice. In addition, eNOS mRNA levels were similar in the carotid, cerebral, and coronary arteries. These findings provide the first quantitative measurements of eNOS mRNA by using real-time PCR in the vessels of mice and suggest age- and sex-related differences in the basal levels of eNOS mRNA in mice. In addition, the eNOS region that was used for real-time PCR was amplified and sequenced for monkeys and other species. With modifications, this region may be used to design real-time PCR for eNOS in other species.
Opposite Effects of Plasma From Human Apolipoprotein A-II Transgenic Mice on Cholesterol Efflux From J774 Macrophages and Fu5AH Hepatoma Cells
Authors: Fournier Natalie , Cogny Anne , Atger Véronique , Pastier Danièle , Goudouneche Dominique , Nicoletti Antonino , Moatti Nicole , Chambaz Jean , Paul Jean-Louis , Kalopissis Athina-Despina
Published: July 2002

Overexpression of human apolipoprotein A-II (hapo A-II) in transgenic mice (hAIItg mice) induced marked hypertriglyceridemia and low levels of plasma high density lipoprotein (HDL) with a high hapo A-II content. We sought to determine whether cholesterol efflux to plasma and HDL from these mice would be affected. In the Fu5AH cell system, plasma from hAIItg mice induced a markedly lower cholesterol efflux than did control plasma, in accordance with the dependence of efflux on HDL concentration. Moreover, HDLs from hAIItg mice were less effective acceptors than were control HDLs. In the J774 macrophage cell system, pretreatment with cAMP, which upregulates ATP binding cassette transporter 1, induced a marked increase in the efflux to hAIItg plasma as well as to purified hapo A-I and hapo A-II, whereas it had no effect on cholesterol efflux to control plasma. A strong positive correlation was established between percent cAMP stimulation of efflux and plasma hapo A-II concentration. The cAMP stimulation of efflux to hAIItg mouse plasma may be linked to the presence of pre-β migrating HDL containing hapo A-II. Thus, despite lower HDL and apolipoprotein A-I contents, the increased ability of plasma from hAIItg mice to extract cholesterol from macrophage-like cells may have an antiatherogenic influence.
Delayed and Exaggerated Postprandial Complement Component 3 Response in Familial Combined Hyperlipidemia
Authors: Meijssen S. , van Dijk H. , Verseyden C. , Erkelens D.W. , Cabezas M. Castro
Published: July 2002

Very low density lipoprotein overproduction is the major metabolic characteristic in familial combined hyperlipidemia (FCHL). Peripheral handling of free fatty acids (FFAs) in vitro may be impaired in FCHL by decreased action of acylation-stimulating protein (ASP), which is identical to the immunologically inactive complement component 3a (C3adesArg). Because decreased FFA uptake by impaired complement component 3 (C3) response (as the precursor for ASP) may result in enhanced FFA flux to the liver in FCHL, we have evaluated postprandial C3 changes in vivo in FCHL patients. Accordingly, 10 untreated FCHL patients and 10 matched control subjects underwent an oral fat loading test. Fasting plasma C3 and ASP levels were higher in FCHL patients (1.33±0.09 g/L and 70.53±4.37 mmol/L, respectively) than in control subjects (0.91±0.03 g/L and 43.21±8.96 mmol/L, respectively;P=0.01 andP<0.05). In control subjects, C3 concentrations increased significantly after 4 hours (to 1.03±0.04 g/L). In FCHL, plasma C3 was unchanged after 4 hours. The earliest postprandial C3 rise in FCHL patients occurred after 8 hours (1.64±0.12 g/L). The maximal apolipoprotein B-48 concentration was reached after 6 hours in FCHL patients and control subjects. Postprandial FFA and hydroxybutyric acid (as a marker of hepatic FFA oxidation) were significantly higher in FCHL patients than in control subjects, and the early postprandial C3 rise was negatively correlated with the postprandial FFA and hydroxybutyric acid concentrations. The present data suggest an impaired postprandial plasma C3 response in FCHL patients, most likely as a result of a delayed response by C3, as the precursor for the biologically active ASP, acting on FFA metabolism. Therefore, an impaired postprandial C3 response may be associated with impaired peripheral postprandial FFA uptake and, consequently, lead to increased hepatic FFA flux and very low density lipoprotein overproduction.
Haplotype-Specific Effects on Endothelial NO Synthase Promoter Efficiency
Authors: Wang Jian , Dudley Donald , Wang Xing Li
Published: July 2002

The T–786C promoter and 27-bp repeat intron 4 polymorphisms in the endothelial NO synthase (eNOS) gene have been inconsistently associated with various eNOS-related phenotypic changes. We explored molecular mechanisms underlying the inconsistency. We constructed pGL3 luciferase reporter vectors by inserting an eNOS promoter fragment containing either T or C nucleotide at −786 bp at the 5′ end of the luciferase coding region and eNOS intron 4 containing either 5× or 4×27-bp repeats at the 3′ end of the luciferase gene. The transcription efficiency in the T promoter was lower than in the C promoter (15.7±1.0% vs 83.3±5.8%,
P
<0.01 when 5×27-bp was an enhancer and 37.6±4.7% vs 58.9±7.5%,
P
<0.01 when 4×27bp was an enhancer). Although cigarette smoking extracts treatment increased the transcription efficiency significantly in the T promoter (1.7-fold,
P
<0.01), it reduced the C promoter efficiency (by 10% to 15%). A mobility shift assay revealed positive binding of the 27-bp repeat fragment with endothelial cell nuclear protein extracts. Our study demonstrates a
cis
-acting role of the 27-bp repeats in eNOS promoter function and a haplotype-specific expression pattern determined by DNA variants at −786 bp and intron 4 of the eNOS gene that is also modifiable by cigarette smoking.
Inhibition of Vascular Smooth Muscle Cell Proliferation, Migration, and Survival by the Tumor Suppressor Protein PTEN
Authors: Huang Jianhua , Kontos Christopher D.
Published: July 2002

Phosphatidylinositol (PI) 3-kinase signaling regulates numerous cellular processes, including proliferation, migration, and survival, which are required for neointimal hyperplasia and restenosis. The effectors of PI 3-kinase are activated by the phospholipid products of PI 3-kinase. In this report, we investigated the hypothesis that overexpression of the tumor suppressor protein PTEN, an inositol phosphatase specific for the products of PI 3-kinase, would inhibit the vascular smooth muscle cell (VSMC) responses necessary for neointimal hyperplasia and restenosis. Effects of PTEN were assessed in primary rabbit VSMCs after overexpression with a recombinant adenovirus and compared with uninfected or control virus-infected cells. PTEN was expressed endogenously in VSMCs, and PTEN overexpression inhibited PDGF-induced phosphorylation of p70
s6k
, Akt, and glycogen synthase kinase-3-α and -β but not ERK1 or -2. Overexpression of PTEN significantly inhibited both basal and PDGF-mediated VSMC proliferation and migration, the latter possibly due in part to downregulation of focal adhesion kinase. Moreover, PTEN overexpression induced cleavage of caspase-3 and significantly increased apoptosis compared with control cells. Taken together, these results demonstrate that PTEN overexpression potently inhibits the VSMC responses required for neointimal hyperplasia and restenosis. Adenovirus-expressed PTEN may therefore provide a useful tool for the local treatment of these and other vascular proliferative disorders.
Ethnicity Affects Vasodilation, but Not Endothelial Tissue Plasminogen Activator Release, in Response to Bradykinin
Authors: Rosenbaum David A. , Pretorius Mias , Gainer James V. , Byrne Daniel , Murphey Laine J. , Painter Corrie A. , Vaughan Douglas E. , Brown Nancy J.
Published: July 2002

Previous studies indicate that the vasodilator response to bradykinin (BK) and other endothelium-dependent and -independent agonists is decreased in black Americans compared with white Americans. The purpose of the present study was to determine the effect of ethnicity on fibrinolytic function in humans. Graded doses of BK (100, 200, and 400 ng/min), acetylcholine (15, 30, and 60 μg/min; N=20), or methacholine (3.2, 6.4, 12.8 μg/min; N=20), and sodium nitroprusside (0.8, 1.6, and 3.2 μg/min) were infused via brachial artery in 19 white and 21 black age-matched normotensive subjects. Forearm blood flow (FBF) was measured by plethysmography, and venous and arterial samples were collected for tissue plasminogen activator (tPA) antigen. Compared with whites (increase in FBF from 3.7±0.5 to 23.9±2.5 mL · min
−1
· 100 mL
−1
), blacks (increase in FBF from 2.8±0.3 to 15.2±1.9 mL · 100 mL
−1
· min
−1
) exhibited a blunted FBF response to BK (
P
=0.035). Responses to sodium nitroprusside and methacholine or acetylcholine were similarly decreased. In contrast, there was no effect of ethnicity on net tPA antigen release in response to BK (increase from −0.2±0.4 to 67.3±15.2 ng · min
−1
· 100 mL
−1
in blacks; from 0.04±0.9 to 65.9±13.6 ng · min
−1
· 100 mL
−1
in whites). Thus, ethnicity significantly influenced the relationship between the flow and tPA release responses to BK (
P
=0.037). These data suggest that the BK-dependent alterations in vascular fibrinolytic function are preserved in black Americans compared with white Americans.
Normal Production Rate of Apolipoprotein B in LDL Receptor–Deficient Mice
Authors: Millar John S. , Maugeais Cyrille , Fuki Ilia V. , Rader Daniel J.
Published: July 2002

The low density lipoprotein (LDL) receptor is well known for its role in mediating the removal of apolipoprotein B (apoB)-containing lipoproteins from plasma. Results from in vitro studies in primary mouse hepatocytes suggest that the LDL receptor may also have a role in the regulation of very low density lipoprotein (VLDL) production. We conducted in vivo experiments using
LDLR
−/−,
LDLR
+/−, and wild-type mice (
LDLR
indicates LDL receptor gene) in which the production rate of VLDL was measured after the injection of [
35
S]methionine and the lipase inhibitor Triton WR1339. Despite the fact that
LDLR
−/− mice had a 3.7-fold higher total cholesterol level and a 2.1-fold higher triglyceride level than those of the wild-type mice, there was no difference in the production rate of VLDL triglyceride or VLDL apoB between these groups of animals. Experiments were also conducted in
apobec1
−/− mice, which make only apoB-100, the form of apoB that binds to the LDL receptor. Interestingly, the
apobec1
−/− mice had a significantly higher production rate of apoB than did the wild-type mice. However, despite significant differences in total cholesterol and triglyceride levels, there was no difference in the production rate of total or VLDL triglyceride or VLDL apoB between
LDLR
−/− and
LDLR
+/− mice on an
apobec1
−/− background. These results indicate that the LDL receptor has no effect on the production rate of VLDL triglyceride or apoB in vivo in mice.