bluuebunny/crossref_metadata_2025 huggingface dataset:
Transporting a portable operating system
Authors: Jalics Paul J. , Heines Thomas S.
Published: July 2002

The “portable” UNIX operating system was transported to an IBM Series/1 minicomputer. The process of transporting is described with emphasis on (1) adapting to the target machine architecture; (2) the selection of the approach taken to transporting; (3) a description of the problems encountered; (4) the degree of portability of the UNIX system; and (5) a summary of the portability lessons learned.
The cube-connected cycles: a versatile network for parallel computation
Authors: Preparata Franco P. , Vuillemin Jean
Published: July 2002

An interconnection pattern of processing elements, the cube-connected cycles (CCC), is introduced which can be used as a general purpose parallel processor. Because its design complies with present technological constraints, the CCC can also be used in the layout of many specialized large scale integrated circuits (VLSI). By combining the principles of parallelism and pipelining, the CCC can emulate the cube-connected machine and the shuffle-exchange network with no significant degradation of performance but with a more compact structure. We describe in detail how to program the CCC for efficiently solving a large class of problems that include Fast Fourier transform, sorting, permutations, and derived algorithms.
System design for usability
Authors: Demers Richard A.
Published: July 2002

The factors underlying system design for usability are examined and the role and responsibilities of a usability committee described. Under the control of a usability committee, a balance between high levels of system function and usability was reached for the IBM System/38. The System/38 command language is presented to illustrate this balance.
Systematic recursion removal
Authors: Auslander M. A. , Strong H. R.
Published: July 2002

The recursion removal algorithm presented by Strong and Walker is amplified and applied to a relatively complex PL/I program. The aim is to demonstrate systematic recursion-removal techniques on something more complex than Knuth's “sturdy toddler” and to obtain measurements of the cost of procedure linkage in PL/I and the savings achievable via procedure integration in the presence of recursion. First, the paper describes the recursion-removal process and the example on which it will be illustrated. Recursion removal is then applied to the two major parts of this example and the final result of the process is displayed. Our performance comparison results are presented, and our conclusions are briefly discussed
Relaxation methods for image reconstruction
Authors: Herman Gabor T. , Lent Arnold , Lutz Peter H.
Published: July 2002

The problem of recovering an image (a function of two variables) from experimentally available integrals of its grayness over thin strips is of great importance in a large number of scientific areas. An important version of the problem in medicine is that of obtaining the exact density distribution within the human body from X-ray projections. One approach that has been taken to solve this problem consists of translating the available information into a system of linear inequalities. The size and the sparsity of the resulting system (typically, 25,000 inequalities with fewer than 1 percent of the coefficients nonzero) makes methods using successive relaxations computationally attractive, as compared to other ways of solving systems of inequalities. In this paper, it is shown that, for a consistent system of linear inequalities, any sequence of relaxation parameters lying strictly between 0 and 2 generates a sequence of vectors which converges to a solution. Under the same assumptions, for a system of linear equations, the relaxation method converges to the minimum norm solution. Previously proposed techniques are shown to be special cases of our procedure with different choices of relaxation parameters. The practical consequences for image reconstruction of the choice of the relaxation parameters are discussed.
Guarded commands, nondeterminacy and formal derivation of programs
Authors: Dijkstra Edsger W.
Published: July 2002

So-called “guarded commands” are introduced as a building block for alternative and repetitive constructs that allow nondeterministic program components for which at least the activity evoked, but possibly even the final state, is not necessarily uniquely determined by the initial state. For the formal derivation of programs expressed in terms of these constructs, a calculus will be be shown.
A method for incrementally compiling languages with nested statement structure
Authors: Earley Jay , Caizergues Paul
Published: July 2002

A method of incremental compilation is presented which applies especially to programming languages in which statements can be nested (such as Algol and PL/I). The method permits editing of the source language using a general purpose text editor, and incremental processing of changes without frequent recompilation of entire routines. The essential points of the method are: (1) the syntax of the language is restricted insofar as which constructs may occur on lines; (2) an internal data structure (called the skeleton) is maintained to represent the statement structure; (3) the recompilation is partially batched in the sense that recompilation of modified lines does not occur until the last of a set of editing commands has been received; and (4) the parsing and compilation are factored into two parts, that done on individual lines and that done globally to handle the relationships between the lines.
A comparison of multivariate normal generators
Authors: Barr Donald R. , Slezak Norman L.
Published: July 2002

Three methods for generating outcomes on multivariate normal random vectors with a specified variance-covariance matrix are presented. A comparison is made to determine which method requires the least computer execution time and memory space when utilizing the IBM 360/67. All methods use as a basis a standard Gaussian random number generator. Results of the comparison indicate that the method based on triangular factorization of the covariance matrix generally requires less memory space and computer time than the other two methods.
Information theory applied to the conversion of decision tables to computer programs
Authors: Ganapathy S. , Rajaraman V.
Published: July 2002

Using ideas from information theory, this paper develops a heuristic algorithm that converts a limited entry decision table to a tree structured computer program with near minimum average processing time. The method is applicable to any limited entry decision table and does not require that actions have single rules or that the cost of testing conditions be equal. It is thus more general than the previously published heuristic algorithms. Compared to the optimal algorithm of Reinwald and Soland, this algorithm is easy to code and takes a much smaller translation time; it is thus felt that it is more useful in practice. The algorithm is well suited for manual conversion of decision tables to flowcharts.
A statechart-based model for hypermedia applications
Authors: de Oliveira Maria Cristina Ferreira , Turine Marcelo Augusto Santos , Masiero Paulo Cesar
Published: July 2002

This paper presents a formal definition for HMBS (Hypermedia Model Based on Statecharts). HMBS uses the structure and execution semantics of statecharts to specify both the structural organization and the browsing semantics of hypermedia applications. Statecharts are an extension of finite-state machines and the model is thus a generalization of hypergraph-based hypertext models. Some of the most important features of HMBS are its ability to model hierarchy and synchronization of information; provision of mechanisms for specifying access structures, navigational contexts, access control, multiple tailored versions,and hierarchical views. Analysis of the underlying statechart machine allows verification of page reachability, valid paths, and other properties, thus providing mechanisms to support authors in the development of structured applications.
An empirical study of regression test selection techniques
Authors: Graves Todd L. , Harrold Mary Jean , Kim Jung-Min , Porter Adam , Rothermel Gregg
Published: July 2002

Regression testing is the process of validating modified software to detect whether new errors have been introduced into previously tested code and to provide confidence that modifications are correct. Since regression testing is an expensive process, researchers have proposed regression test selection techniques as a way to reduce some of this expense. These techniques attempt to reduce costs by selecting and running only a subset of the test cases in a program's existing test suite. Although there have been some analytical and empirical evaluations of individual techniques, to our knowledge only one comparative study, focusing on one aspect of two of these techniques, has been reported in the literature. We conducted an experiment to examine the relative costs and benefits of several regression test selection techniques. The experiment examined five techniques for reusing test cases, focusing on their relative ablilities to reduce regression testing effort and uncover faults in modified programs. Our results highlight several differences between the techiques, and expose essential trade-offs that should be considered when choosing a technique for practical application.
Three-dimensional object recognition
Authors: Besl Paul J. , Jain Ramesh C.
Published: July 2002

A general-purpose computer vision system must be capable of recognizing three-dimensional (3-D) objects. This paper proposes a precise definition of the 3-D object recognition problem, discusses basic concepts associated with this problem, and reviews the relevant literature. Because range images (or depth maps) are often used as sensor input instead of intensity images, techniques for obtaining, processing, and characterizing range data are also surveyed.
An experimental evaluation of the impact of data display format on recall performance
Authors: Schmell Richard W. , Umanath Narayan S.
Published: July 2002

Recall, while an important topic in the study of learning and memory, has received relatively little attention as a dependent variable in studies that investigate alternative formats for presenting information. This paper describes two experiments, performed back to back, that examined the relationship between data display format and recall performance across different task categories. The results of Experiment 1 were reaffirmed by Experiment 2 and collectively suggest that a graphical presentation enhances recall when the task possesses a spatial orientation while the recall of specific facts is indifferent to data display format.
Computer systems and the design of organizational interaction
Authors: Flores Fernando , Graves Michael , Hartfield Brad , Winograd Terry
Published: July 2002

The goal of this paper is to relate theory to invention and application in the design of systems for organizational communication and management. We propose and illustrate a theory of design, technology, and action that we believe has been missing in the mainstream of work on office systems. At the center of our thinking is a theory of language as social action, which differs from the generally taken-for-granted understandings of what goes on in an organization. This approach has been presented elsewhere, and our aim here is to examine its practical implications and assess its effectiveness in the design of The Coordinator, a workgroup productivity system that is in widespread commercial use on personal computers.
Abstraction-based software development
Authors: Berzins Valdis , Gray Michael , Naumann David
Published: July 2002

A five-year experience with abstraction-based software-development techniques in the university environment indicates that the investment required to support the paradigm in practice is returned in terms of greater ability to control complexity in large projects—provided there exists a set of software tools sufficient to support the approach.
Intersection of convex objects in two and three dimensions
Authors: Chazelle B. , Dobkin D. P.
Published: July 2002

One of the basic geometric operations involves determining whether a pair of convex objects intersect. This problem is well understood in a model of computation in which the objects are given as input and their intersection is returned as output. For many applications, however, it may be assumed that the objects already exist within the computer and that the only output desired is a single piece of data giving a common point if the objects intersect or reporting no intersection if they are disjoint. For this problem, none of the previous lower bounds are valid and algorithms are proposed requiring sublinear time for their solution in two and three dimensions.
Marx and Anthropology
Authors: Roseberry William
Published: July 2002

This essay explores the continuing relevance of Marx's work in anthropological theory by examining three dimensions of his thought, concentrating on a central text in each: historical materialism (The German Ideology), the analysis of capitalism (Volume 1 of Capital), and political analysis (The Eighteenth Brumaire). Each of these dimensions is related to present-day discussions in anthropological and social theory, but the emphasis remains on an interpretation of Marx's work.
REGULATION OF LIGHT HARVESTING IN GREEN PLANTS
Authors: Horton P. , Ruban A. V. , Walters R. G.
Published: July 2002

▪ Abstract  When plants are exposed to light intensities in excess of those that can be utilized in photosynthetic electron transport, nonphotochemical dissipation of excitation energy is induced as a mechanism for photoprotection of photosystem II. The features of this process are reviewed, particularly with respect to the molecular mechanisms involved. It is shown how the dynamic properties of the proteins and pigments of the chlorophyll a/b light-harvesting complexes of photosystem II first enable the level of excitation energy to be sensed via the thylakoid proton gradient and subsequently allow excess energy to be dissipated as heat by formation of a nonphotochemical quencher. The nature of this quencher is discussed, together with a consideration of how the variation in capacity for energy dissipation depends on specific features of the composition of the light-harvesting system. Finally, the prospects for future progress in understanding the regulation of light harvesting are assessed.
ELABORATION OF BODY PLAN AND PHASE CHANGE DURING DEVELOPMENT OF ACETABULARIA: How Is the Complex Architecture of a Giant Unicell Built?
Authors: Mandoli Dina F.
Published: July 2002

▪ Abstract  While uninucleate and unicellular, Acetabularia acetabulum establishes and maintains functionally and morphologically distinct body regions and executes phase changes like those in vascular plants. Centimeters tall at maturity, this species has allowed unusual experimental approaches. Amputations revealed fates of nucleate and enucleate portions from both wild type and mutants. Historically, graft chimeras between nucleate and enucleate portions suggested that morphological instructions were supplied by the nucleus but resided in the cytoplasm and could be expressed interspecifically. Recently, graft chimeras enabled rescue of mutants arrested in vegetative phase. Since the 1930s, when Acetabularia provided the first evidence for the existence of mRNAs, a dogma has arisen that it uses long-lived mRNAs to effect morphogenesis. While the evidence favors translational control, the postulated mRNAs have not been identified, and the mechanism of morphogenesis remains unknown. Amenable to biochemistry, physiology, and both classical and molecular genetics, Acetabularia may contribute yet new insights into plant development and morphogenesis.
CEREAL CHROMOSOME STRUCTURE, EVOLUTION, AND PAIRING
Authors: Moore Graham
Published: July 2002

▪ Abstract  The determination of the order of genes along cereal chromosomes indicates that the cereals can be described as a single genetic system. Such a framework provides an opportunity to combine data generated from the studies on different cereals, enables chromosome evolution to be traced, and sheds light on key structures involved in cereal chromosome pairing. Centromeric and telomeric regions have been highlighted as important in these processes.
OLD AND INTERMEDIATE-AGE STELLAR POPULATIONS IN THE MAGELLANIC CLOUDS
Authors: Olszewski Edward W. , Suntzeff Nicholas B. , Mateo Mario
Published: July 2002

▪ Abstract  The Magellanic Clouds have galactocentric distances of 50 and 63 kiloparsecs, making it possible to probe the older populations of clusters and stars in some detail. Although it is clear that both galaxies contain an old population, it is not yet certain whether this population is coeval with the date of formation of the oldest globulars in the Milky Way. The kinematics of this old population in the Large Magellanic Cloud (LMC) are surprising; no component of this old population is currently measured to be part of a hot halo supported by velocity dispersion. Spectroscopy of field stars is beginning to show the existence of a small population of stars with abundances [Fe/H] less than −1.4. These stars will help to unravel the star-formation history when the next generation of telescopes are commissioned. Asymptotic giant branch stars, long-period variables, planetary nebulae, and horizontal-branch clump stars can be used to trace the extent and kinematics of the intermediate-age population. Deep color-magnitude diagrams can be used to derive the relative proportions of stars older than 1 Gyr. The age distribution of populous clusters and the age-metallicity relation are used to compare the evolution of the two Magellanic Clouds to each other. The issue of where the LMC's metals originated is explored, as is the question of what triggers star formation in the Clouds.
HIGH-VELOCITY CLOUDS
Authors: Wakker B. P. , van Woerden H.
Published: July 2002

▪ Abstract  High-velocity clouds (HVCs) consist of neutral hydrogen (HI) at velocities incompatible with a simple model of differential galactic rotation; in practice one uses [Formula: see text] vLSR[Formula: see text] [Formula: see text]90 km/s to define HVCs. This review describes the main features of the sky and velocity distributions, as well as the available information on cloud properties, small-scale structure, velocity structure, and observations other than in 21-cm emission. We show that HVCs contain heavy elements and that the more prominent ones are more than 2 kpc from the Galactic plane. We evaluate the hypotheses proposed for their origin and reject those that account for only one or a few HVCs. At least three different hypotheses are needed: one for the Magellanic Stream and possibly related clouds, one for the Outer Arm Extension, and one (or more) for the other HVCs. We discuss the evidence for the accretion and the fountain model but cannot rule out either one.
IMPLICATIONS OF ATOMIC-RESOLUTION STRUCTURES FOR CELL ADHESION
Authors: Leahy Daniel J.
Published: July 2002

▪ Abstract  Molecules involved in cell adhesion processes are often both structurally and functionally modular, with subdomains that are members of large protein families. Recently, high-resolution structures have been determined for representative members of many of these families including fragments of integrins, cadherins, fibronectin-like domains, and immunoglobulin-like domains. These structures have enhanced our understanding of cell adhesion processes at several levels. In almost all cases, ligand-binding sites have been visualized and provide insight into how these molecules mediate biologically important interactions. Metal-binding sites have been identified and characterized, allowing assessment of the role of bound ions in cell adhesion processes. Many of these structures serve as templates for modeling homologous domains in other proteins or, when the structure of a fragment consisting of more than one domain is determined, the structure of multidomain arrays of homologous domains. Knowledge of atomic structure also allows rational design of drugs that either mimic or target specific binding sites. In many cases, high-resolution structures have revealed unexpected relationships that pose questions about the evolutionary origin of specific domains. This review briefly describes several recently determined structures of cell adhesion molecules, summarizes some of the main results of each structure, and highlights common features of different systems.
Streamflow Necessary for Environmental Maintenance
Authors: Whiting Peter J.
Published: July 2002

▪ Abstract  In the last decades, insights from the fields of ecology, geomorphology, and hydrology have been applied to the question of the streamflows necessary for environmental maintenance. For instance, determining the streamflow needed for spawning by salmon or trout requires ascertaining how much water, for how long, and at what time it will be needed? And what flows are necessary for the sustenance of streamside vegetation? Answers to these and similar questions have been sought to minimize environmental degradation in the development or relicensing of water projects, in restoring riverine ecosystems, and in balancing multiple uses for limited water resources. In this contribution, the varieties of environmental maintenance flows applied to rivers are described, as are their fundamental principles. These environmental maintenance flows include flows to maintain aesthetics and recreation, streambed sediment size and its mobility, the channel, its features and continuity, and the floodplain, its wetness regime, and riparian vegetation.
INCIDENCE AND CONSEQUENCES OF INHERITED ENVIRONMENTAL EFFECTS
Authors: Rossiter MaryCarol
Published: July 2002

▪ Abstract  Inherited environmental effects are those components of the phenotype that are derived from either parent, apart from nuclear genes. Inherited environmental effects arise as the product of parental genes and the parental environment, or their interation, and can include contributions that reflect the abiotic, nutritional, and other ecological features of a parental environment. Separating the impact of inherited environmental effects from inherited genetic effects on offspring phenotype variation has been and continues to be a challenge. This complexity is represented in the presentation of a qualitative model that distinguishes the possible paths of nongenetic cross-generational transmission. This model serves as the framework for considering the nature, in published works, of what was actually measured. Empirical evidence of inherited environmental effects arising from these pathways is documented for a diversity of plant and animal taxa. From these results one can conclude that the impact of inherited environmental effects on offspring can be positive or negative depending on the nature of the contribution and the ecological context in which the offspring exists. Finally, there is a description of theoretical and experimental efforts to understand the consequences of parental effects relative to their impact on population dynamics, the expression of adaptive phenotype plasticity, and character evolution.
THE DISTRIBUTED UTILITY:A New Electric Utility Planning and Pricing Paradigm
Authors: Feinstein Charles D. , Orans Ren , Chapel Stephen W.
Published: July 2002

▪ Abstract  The distributed utility concept provides an alternate approach to guide electric utility expansion. The fundamental idea within the distributed utility concept is that particular local load increases can be satisfied at least cost by avoiding or delaying the more traditional investments in central generation capacity, bulk transmission expansion, and local transmission and distribution upgrades. Instead of these investments, the distributed utility concept suggests that investments in local generation, local storage, and local demand-side management technologies can be designed to satisfy increasing local demand at lower total cost. Critical to installation of distributed assets is knowledge of a utility system's area- and time-specific costs. This review introduces the distributed utility concept, describes an application of ATS costs to investment planning, discusses the various motivations for further study of the concept, and reviews relevant literature. Future research directions are discussed.
THE ROLE OF MOISTURE TRANSPORT BETWEEN GROUND AND ATMOSPHERE IN GLOBAL CHANGE
Authors: Rind D. , Rosenzweig C. , Stieglitz M.
Published: July 2002

▪ Abstract  Projections of the effect of climate change on future water availability are examined by reviewing the formulations used to calculate moisture transport between the ground and the atmosphere. General circulation models and climate change impact models have substantially different formulations for evapotranspiration, so their projections of future water availability often disagree, even though they use the same temperature and precipitation forecasts. General circulation models forecast little change in tropical and subtropical water availability, while impact models show severe water and agricultural shortages. A comparison of observations and modeling techniques shows that the parameterizations in general circulation models likely lead to an underestimate of the impacts of global warming on soil moisture and vegetation. Such errors would crucially affect the temperature and precipitation forecasts used in impact models. Some impact model evaporation formulations are probably more appropriate than those in general circulation models, but important questions remain. More observations are needed, especially in the vicinity of forests, to determine appropriate parameterizations.
SCIENCE AND NONSCIENCE CONCERNING HUMAN-CAUSED CLIMATE WARMING
Authors: Mahlman J. D.
Published: July 2002

▪ Abstract  The human-caused global warming problem is now the focus of intense international attention in many sectors of society. As we learn more about the science of the problem, the sense of controversy about the state of the science has actually increased, sharply so over the past decade. This essay highlights the fundamental aspects of the science underlying global warming. The vital roles of climate models and of climate data in sharpening scientific understanding are featured. Finally, the roles of controversy in the science and the sociology of this problem are addressed, and new insights are offered on the inevitability of future major conflicts and controversies as society begins to deal with the need to either reduce the use of fossil fuels considerably or adapt to substantial changes in Earth's climate.
ADAPTATIONS IN SCALE INSECTS
Authors: Gullan Penny J. , Kosztarab Michael
Published: July 2002

▪ Abstract  Many unusual features of scale insects (Hemiptera: Coccoidea) can be explained as historical legacy. Developmental specializations in ancestral coccoids resulted in a neotenous adult female and a drastic metamorphosis of the male. Subsequent evolution led to numerous, often convergently derived, adaptations to parasitic life on higher plants. The sedentary lifestyle of female scale insects has favored the evolution of appendage reduction or loss, gross changes in body shape, and protective wax secretions, tests, and other scale covers. Morphological peculiarities of adult males relate to flight or to mating with concealed females. Scale insects have diverse egg-protecting methods, a range of chromosome behaviors (including several methods of sex determination), marked sexual dimorphism [even sometimes in first-instar nymphs (crawlers)], and more rarely sexual dichronism. Crawlers have evolved as the main agents of dispersal. The biotic interactions of scale insects include diverse endosymbioses with microorganisms, sometimes morphological and behavioral adaptations for obligate association with ants, and often highly specific host-plant associations that may lead to demic adaptation or the evolution of complex galls.
PROTEASES AND THEIR TARGETS IN ESCHERICHIA COLI
Authors: Gottesman Susan
Published: July 2002

▪ Abstract  Proteolysis in Escherichia coli serves to rid the cell of abnormal and misfolded proteins and to limit the time and amounts of availability of critical regulatory proteins. Most intracellular proteolysis is initiated by energy-dependent proteases, including Lon, ClpXP, and HflB; HflB is the only essential E. coli protease. The ATPase domains of these proteases mediate substrate recognition. Recognition elements in target are not well defined, but are probably not specific amino acid sequences. Naturally unstable protein substrates include the regulatory sigma factors for heat shock and stationary phase gene expression, σ32 and RpoS. Other cellular proteins serve as environmental sensors that modulate the availability of the unstable proteins to the proteases, resulting in rapid changes in sigma factor levels and therefore in gene transcription. Many of the specific proteases found in E. coli are well-conserved in both prokaryotes and eukaryotes, and serve critical functions in developmental systems.
EPITOPE TAGGING
Authors: Jarvik Jonathan W. , Telmer Cheryl A.
Published: July 2002

▪ Abstract  Epitope tagging is a recombinant DNA method by which a protein encoded by a cloned gene is made immunoreactive to a known antibody. This review discusses the major advantages and limitations of epitope tagging and describes a number of recent applications. Major areas of application include monitoring protein expression, localizing proteins at the cellular and subcellular levels, and protein purification, as well as the analysis of protein topology, dynamics and interactions. Recently the method has also found use in transgenic and gene therapy studies and in the emerging fields of functional genomics and proteomics.
IMMUNOPHARMACOLOGY OF RAPAMYCIN
Authors: Abraham Robert T. , Wiederrecht Gregory J.
Published: July 2002

▪ Abstract  The potent immunosuppressive drugs FK506 and rapamycin interfere with signal transduction pathways required for T cell activation and growth. The distinct inhibitory effects of these drugs on the T cell activation program are mediated through the formation of pharmacologically active complexes with members of a family of intracellular receptors termed the FK506 binding proteins (FKBPs). The FKBP12 · FK506 complex specifically binds to and inhibits calcineurin, a signaling protein required for transcriptional activation of the interleukin (IL)-2 gene in response to T cell antigen receptor engagement. The FKBP12 · rapamycin complex interacts with a recently defined target protein termed the mammalian target of rapamycin (mTOR). Accumulating data suggest that mTOR functions in a previously unrecognized signal transduction pathway required for the progression of IL-2-stimulated T cells from G1into the S phase of the cell cycle. Here we review the immunopharmacology of rapamycin, with particular emphasis on the characterization of mTOR.
Prospects for Vaccine Protection Against HIV-1 Infection and AIDS
Authors: Letvin Norman L. , Barouch Dan H. , Montefiori David C.
Published: July 2002

The rapid and devastating spread of the AIDS epidemic in the developing world as well as the difficulties associated with delivering antiretroviral drugs in affected countries underscore the urgent need for the development of a safe and effective AIDS vaccine. In this review, we discuss recent advances in our understanding of the cellular and humoral immune responses to human immunodeficiency virus type 1 (HIV-1) infection. We then describe vaccine strategies that have been explored and discuss the evidence suggesting that cellular immune responses elicited by novel vaccine modalities may attenuate clinical disease caused by HIV-1.
Layered Magnetic Manganites
Authors: Kimura T. , Tokura Y.
Published: July 2002

▪ Abstract  We review the recent progress in the study of layered magnetic manganites La2−2xSr1+2xMn2O7, which have many unique features of charge transport and magnetism inherent to the quasi-two-dimensional electronic structure. The system shows a wide variety of magnetic-field-induced phenomena due to the layered crystal and magnetic structure, such as the highly anisotropic ferromagnetic metallic ground state, the colossal magnetoresistance (CMR) effect, and the tunneling-type magnetoresistance (TMR). The charge transport properties, as well as the magnetic ones, strongly depend on the carrier-doping level and the applied pressure, which reflects the variation of the orbital-dependent occupancy of itinerant eg-like electrons. Although the layered manganite is one of a new class of CMR materials, the study of this system may also reveal some of the key issues for understanding the CMR effect in mixed-valent manganese oxide.
TRANSJUGULAR INTRAHEPATIC PORTOSYSTEMIC SHUNTS
Authors: Skeens J. , Semba C. , Dake M.
Published: July 2002

▪ Abstract  Management of bleeding esophageal varices due to portal hypertension has traditionally relied on endoscopic sclerotherapy and operative intervention with placement of a portosystemic shunt. Although percutaneous decompression of portal hypertension was investigated 25 years ago, it was not clinically feasible until recently. With the advent of intravascular stents, the technique of creating a transjugular intrahepatic portosystemic shunt (TIPS) can now be effectively applied to treat the complications of portal hypertension, including variceal hemorrhage and refractory ascites. Since its introduction in 1989, TIPS has enjoyed widespread clinical application. The initial results with this procedure are encouraging and suggest that it is an effective means of reducing the frequency of variceal hemorrhage in patients with portal hypertension. The long-term patency rate and frequency of complications, however, have not been clearly defined. Similarly, the role of TIPS in the treatment of refractory ascites, Budd-Chiari syndrome, and hepatorenal syndrome remains unclear because sufficient data do not yet exist to support its general use in these settings.
ROLE OF ENDOTHELIUM IN THROMBOSIS AND HEMOSTASIS
Authors: Wu, M.D K. K. , Thiagarajan, M.D P.
Published: July 2002

▪ Abstract  Vascular endothelium is strategically located at the interface between tissue and blood. It is pivotal for protecting against vascular injury and maintaining blood fluidity. Normal endothelium releases prostacyclin and nitric oxide, potent inhibitors of platelet and monocyte activation and vasodilators. Their syntheses are governed by isoforms of enzymes. Normal endothelial surface expresses ecto-adenosine diphosphatase, which degrades adenosine diphosphate and inhibits platelet aggregation; thrombomodulin, which serves as a binding site for thrombin to activate protein C; and heparin-like molecules, which serve as a cofactor for antithrombin III. Normal endothelium secretes tissue plasminogen activator, which activates the fibrinolysis system. Endothelium produces and secretes von Willebrand factor, which mediates platelet adhesion and shear-stress-induced aggregation. Injury to endothelium is accompanied by loss of protective molecules and expression of adhesive molecules, procoagulant activities, and mitogenic factors, leading to development of thrombosis, smooth muscle cell migration, and proliferation and atherosclerosis.
Global Epidemiology of Influenza: Past and Present
Authors: Cox N. J. , Subbarao K.
Published: July 2002

▪ Abstract  Pandemics are the most dramatic presentation of influenza. Three have occurred in the twentieth century: the 1918 H1N1 pandemic, the 1957 H2N2 pandemic, and the 1968 H3N2 pandemic. The tools of molecular epidemiology have been applied in an attempt to determine the origin of pandemic viruses and to understand what made them such successful pathogens. An excellent example of this avenue of research is the recent phylogenetic analysis of genes of the virus that caused the devastating 1918 pandemic. This analysis has been used to identify evolutionarily related influenza virus genes as a clue to the source of the pandemic of 1918. Molecular methods have been used to investigate the avian H5N1 and H9N2 influenza viruses that recently infected humans in Hong Kong. Antigenic, genetic, and epidemiologic analyses have also furthered our understanding of interpandemic influenza. Although many questions remain, advances of the past two decades have demonstrated that several widely held concepts concerning the global epidemiology of influenza were false.
GENETICS OF THE ROTAVIRUSES
Authors: Ramig Robert F.
Published: July 2002

▪ Abstract  Genetic analyses have contributed significantly to our understanding of the biology of the rotaviruses. The distinguishing feature of the virus is a genome consisting of 11 segments of double-stranded RNA. The segmented nature of the genome allows reassortment of genome segments during mixed infections, which is the major distinguishing feature of rotavirus genetics. Reassortment has been a powerful tool for mapping viral mutations and other determinants of biological phenotypes to specific genome segments. However, more detailed genetic analysis of rotaviruses is currently limited by the inability to perform reverse genetics. Development of a reverse genetic system will facilitate analysis of the molecular mechanisms involved in various genetic, biochemical, and biological phenomena of the virus.
Bacterial Fatty Acid Biosynthesis: Targets for Antibacterial Drug Discovery
Authors: Campbell John W. , Cronan John E.
Published: July 2002

▪ Abstract  The increase in drug-resistant pathogenic bacteria has created an urgent demand for new antibiotics. Among the more attractive targets for the development of new antibacterial compounds are the enzymes of fatty acid biosynthesis. Although a number of potent inhibitors of microbial fatty acid biosynthesis have been discovered, few of these are clinically useful drugs. Several of these fatty acid biosynthesis inhibitors have potential as lead compounds in the development of new antibacterials. This review encompasses the known inhibitors and prospective targets for new antibacterials.
NEUROTROPHINS AND SYNAPTIC PLASTICITY
Authors: McAllister A. Kimberley , Katz Lawrence C. , Lo Donald C.
Published: July 2002

▪ Abstract  Despite considerable evidence that neuronal activity influences the organization and function of circuits in the developing and adult brain, the molecular signals that translate activity into structural and functional changes in connections remain largely obscure. This review discusses the evidence implicating neurotrophins as molecular mediators of synaptic and morphological plasticity. Neurotrophins are attractive candidates for these roles because they and their receptors are expressed in areas of the brain that undergo plasticity, activity can regulate their levels and secretion, and they regulate both synaptic transmission and neuronal growth. Although numerous experiments show demonstrable effects of neurotrophins on synaptic plasticity, the rules and mechanisms by which they exert their effects remain intriguingly elusive.
CENTRAL NERVOUS SYSTEM NEURONAL MIGRATION
Authors: Hatten Mary E.
Published: July 2002

▪ Abstract  Widespread cell migrations are the hallmark of vertebrate brain development. In the early embryo, morphogenetic movements of precursor cells establish the rhombomeres of the hindbrain, the external germinal layer of the cerebellum, and the regional boundaries of the forebrain. In midgestation, after primary neurogenesis in compact ventricular zones has commenced, individual postmitotic cells undergo directed migrations along the glial fiber system. Radial migrations establish the neuronal layers. Three molecules have been shown to function in glial guided migration—astrotactin, glial growth factor, and erbB. In the postnatal period, a wave of secondary neurogenesis produces huge numbers of interneurons destined for the cerebellar cortex, the hippocampal formation, and the olfactory bulb. Molecular analysis of the genes that mark stages of secondary neurogenesis show similar expression patterns of a number of genes. Thus these three regions may have genetic pathways in common. Finally, we consider emerging studies on neurological mutant mice, such as reeler, and human brain malformations. Positional cloning and identification of mutated genes has led to new insights on laminar patterning in brain.
Neuronal Coding of Prediction Errors
Authors: Schultz Wolfram , Dickinson Anthony
Published: July 2002

Associative learning enables animals to anticipate the occurrence of important outcomes. Learning occurs when the actual outcome differs from the predicted outcome, resulting in a prediction error. Neurons in several brain structures appear to code prediction errors in relation to rewards, punishments, external stimuli, and behavioral reactions. In one form, dopamine neurons, norepinephrine neurons, and nucleus basalis neurons broadcast prediction errors as global reinforcement or teaching signals to large postsynaptic structures. In other cases, error signals are coded by selected neurons in the cerebellum, superior colliculus, frontal eye fields, parietal cortex, striatum, and visual system, where they influence specific subgroups of neurons. Prediction errors can be used in postsynaptic structures for the immediate selection of behavior or for synaptic changes underlying behavioral learning. The coding of prediction errors may represent a basic mode of brain function that may also contribute to the processing of sensory information and the short-term control of behavior.
TRANSGENIC ANIMALS AS NEW APPROACHES IN PHARMACOLOGICAL STUDIES
Authors: Wei Li-Na
Published: July 2002

▪ Abstract  Transgenic animals are becoming useful tools for pharmacological studies. The use of transgenic technology raises two types of questions, “How are transgenic animals made?” and “What types of pharmacological questions can be answered using transgenic technologies?” Answers to these questions are discussed in this review. The production of animals with specific genetic alteration can be achieved by two strategies. The first involves the simple addition of DNA sequences to the chromosomes. The second strategy is to select particular genetic loci for site-specific changes. There are two well-established procedures for simple introduction of DNA into an animal genome, pronuclear DNA injection and transduction using a retrovirus. In contrast, methods for targeting specific DNA sequences to definite sites in the chromosomes are evolving rapidly. Some of these procedures can be used in combination to make a different variety of gene alterations in animals. Pharmacological studies where transgenic technology has been extensively used are discussed, including studies in the cardiovascular system, the nervous system, the endocrine system, cancer, and toxicology.
PROTEIN TARGETS OF XENOBIOTIC REACTIVE INTERMEDIATES
Authors: Pumford and Neil R. , Halmes N. Christine
Published: July 2002

▪ Abstract  Many xenobiotics are metabolically activated to electrophilic intermediates that form covalent adducts with proteins; the mechanism of toxicity is either intrinsic or idiosyncratic in nature. Many intrinsic toxins covalently modify cellular proteins and somehow initiate a sequence of events that leads to toxicity. Major protein adducts of several intrinsic toxins have been identified and demonstrate significant decreases in enzymatic activity. The reactivity of intermediates and subcellular localization of major targets may be important in the toxicity. Idiosyncratic toxicities are mediated through either a metabolic or immune-mediated mechanism. Xenobiotics that cause hypersensitivity/autoimmunity appear to have a limited number of protein targets, which are localized within the subcellular fraction where the electrophile is produced, are highly substituted, and are accessible to the immune system. Metabolic idiosyncratic toxins appear to have limited targets and are localized within a specific subcellular fraction. Identification of protein targets has given us insights into mechanisms of xenobiotic toxicity.
Role of Osteopontin in Cellular Signaling and Toxicant Injury
Authors: Denhardt David T , Giachelli Cecilia M , Rittling Susan R
Published: July 2002

Osteopontin (OPN) is a glycosylated phosphoprotein found in all body fluids and in the proteinaceous matrix of mineralized tissues. It can function both as a cell attachment protein and as a cytokine, delivering signals to cells via a number of receptors including several integrins and CD44. Expression of OPN is enhanced by a variety of toxicants, especially those that activate protein kinase C. In its capacity as a signaling molecule, OPN can modify gene expression and promote the migration of monocytes/macrophages up an OPN gradient. It has both inflammatory and anti-inflammatory actions. Some experiments suggest that it may inhibit apoptosis, possibly contributing to the survival of cells in response to toxicant injury. Elevated OPN expression often correlates with malignancy and has been shown to enhance the tumorigenic and/or metastatic phenotype of the cancer cell. Recent studies have revealed that OPN plays critical roles in bone remodeling and cell-mediated immunity.
FUNDAMENTAL STUDIES OF HALOGEN REACTIONS WITH III-V SEMICONDUCTOR SURFACES
Authors: Simpson William C. , Yarmoff Jory A.
Published: July 2002

▪ Abstract  It is technologically important to understand how halogens react with semiconductor surfaces because halogen compounds are commonly used to etch semiconductor wafers in the microelectronics industry. Halogens are also model adsorbates for studying chemisorption on covalently bonded materials, such as semiconductors, owing to the simple nature of the bonds that they form. The growing use of III-V materials in the manufacture of optoelectronic devices has prompted investigations of the reactions of molecular halogens (XeF2, Cl2, Br2, and I2) with III-V semiconductor surfaces (GaAs, GaSb, InP, InAs, and InSb). This review examines the more fundamental of these investigations, which involve model systems in ultra-high vacuum, focusing on the chemistry of the halogen surface reactions and the physical and electronic structure of the reacted surfaces.
ULTRAFAST SOLVATION DYNAMICS EXPLORED BY FEMTOSECOND PHOTON ECHO SPECTROSCOPIES
Authors: de Boeij Wim P. , Pshenichnikov Maxim S. , Wiersma Douwe A.
Published: July 2002

▪ Abstract  Chemical reaction and optical dynamics in the liquid phase are strongly affected by specific solute-solvent interactions. The dynamical part of this coupling leads to energy fluctuations. The associated energy gap dynamics can be probed by using various nonlinear optical spectroscopies. We discuss various forms of photon echo—time-integrated, time-gated, and heterodyne-detected photon echo—as well as Fourier transform spectral interferometry. It is shown that for solutions of the dye molecule DTTCI, a system-bath correlation function can be acquired that provides a quantitative description of all (non)linear spectroscopic experiments. The deduced correlation function is projected onto the multimode Brownian oscillator model, which allows for a physical interpretation of the multiple-time correlation function and a determination of the spectral density relevant to the solvation process. The following applications of photon echo to condensed phase dynamics are discussed: enhanced vibrational mode suppression, Liouville pathways interference, and dynamical Stokes shift. Recent results of echo-peak shift experiments on the hydrated electron are also presented. The review concludes that photon echo should be useful as a novel tool to explore transition state dynamics.