bluuebunny/crossref_metadata_2025 huggingface dataset:
Type Ia Supernova Explosion Models
Authors: Hillebrandt Wolfgang , Niemeyer Jens C.
Published: July 2002

▪ Abstract  Because calibrated light curves of type Ia supernovae have become a major tool to determine the local expansion rate of the universe and also its geometrical structure, considerable attention has been given to models of these events over the past couple of years. There are good reasons to believe that perhaps most type Ia supernovae are the explosions of white dwarfs that have approached the Chandrasekhar mass, [Formula: see text], and are disrupted by thermonuclear fusion of carbon and oxygen. However, the mechanism whereby such accreting carbon-oxygen white dwarfs explode continues to be uncertain. Recent progress in modeling type Ia supernovae as well as several of the still open questions are addressed in this review. Although the main emphasis is on studies of the explosion mechanism itself and on the related physical processes, including the physics of turbulent nuclear combustion in degenerate stars, we also discuss observational constraints.
Gamma-Ray Burst Afterglows
Authors: Paradijs Jan van , Kouveliotou Chryssa , Wijers Ralph A. M. J.
Published: July 2002

▪ Abstract  The discovery of counterparts in X-ray and optical to radio wavelengths has revolutionized the study of γ-ray bursts, until recently the most enigmatic of astrophysical phenomena. We now know that γ-ray bursts are the biggest explosions in nature, caused by the ejection of ultrarelativistic matter from a powerful energy source and its subsequent collision with its environment. We have just begun to uncover a connection between supernovae and γ-ray bursts, and are finally constraining the properties of the ultimate source of γ-ray burst energy. We review here the observations that have led to this breakthrough in the field; we describe the basic theory of the fireball model and discuss the theoretical understanding that has been gained from interpreting the new wealth of data on γ-ray bursts.
The Hubble Deep Fields
Authors: Ferguson Henry C. , Dickinson Mark , Williams Robert
Published: July 2002

▪ Abstract  The Hubble space telescope observations of the northern Hubble deep field, and more recently its counterpart in the south, provide detections and photometry for stars and field galaxies to the faintest levels currently achievable, reaching magnitudes V ∼ 30. Since 1995, the northern Hubble deep field has been the focus of deep surveys at nearly all wavelengths. These observations have revealed many properties of high redshift galaxies and have contributed to important data on the stellar mass function in the Galactic halo.
BACTERIAL CELL DIVISION AND THE Z RING
Authors: Lutkenhaus Joe , Addinall S. G.
Published: July 2002

Bacterial cell division occurs through the formation of an FtsZ ring (Z ring) at the site of division. The ring is composed of the tubulin-like FtsZ protein that has GTPase activity and the ability to polymerize in vitro. The Z ring is thought to function in vivo as a cytoskeletal element that is analogous to the contractile ring in many eukaryotic cells. Evidence suggests that the Z ring is utilized by all prokaryotic organisms for division and may also be used by some eukaryotic organelles. This review summarizes our present knowledge about the formation, function, and evolution of the Z ring in prokaryotic cell division.
Import of Peroxisomal Matrix and Membrane Proteins
Authors: Subramani S. , Koller Antonius , Snyder William B.
Published: July 2002

▪ Abstract  This review summarizes the progress made in our understanding of peroxisome biogenesis in the last few years, during which the functional roles of many of the 23 peroxins (proteins involved in peroxisomal protein import and peroxisome biogenesis) have become clearer. Previous reviews in the field have focussed on the metabolic functions of peroxisomes ( 1 , 2 ), aspects of import/biogenesis ( 3 , 4 , 5 , 6 , 7 ), the role of peroxins in human disease ( 2 , 8 ), and involvement of the endoplasmic reticulum in peroxisome membrane biogenesis ( 9 , 10 , 11 ) as well as the degradation of this organelle ( 5 , 12 ). This review refers to some of the earlier work for the sake of introduction and continuity but deals primarily with the more recent progress. The principal areas of progress are the identification of new peroxins, definition of protein-protein interactions among peroxins leading to the recognition of complexes involved in peroxisomal protein import, insight into the biogenesis of peroxisomal membrane proteins, and, of most importance, the elucidation of the role of many conserved peroxins in human disease. Given the rapid progress in the field, this review also highlights some of the unanswered questions that remain to be tackled.
Regulation of Chromosome Replication
Authors: Kelly Thomas J. , Brown Grant W.
Published: July 2002

▪ Abstract  The initiation of DNA replication in eukaryotic cells is tightly controlled to ensure that the genome is faithfully duplicated once each cell cycle. Genetic and biochemical studies in several model systems indicate that initiation is mediated by a common set of proteins, present in all eukaryotic species, and that the activities of these proteins are regulated during the cell cycle by specific protein kinases. Here we review the properties of the initiation proteins, their interactions with each other, and with origins of DNA replication. We also describe recent advances in understanding how the regulatory protein kinases control the progress of the initiation reaction. Finally, we describe the checkpoint mechanisms that function to preserve the integrity of the genome when the normal course of genome duplication is perturbed by factors that damage the DNA or inhibit DNA synthesis.
Robotics for Surgery
Authors: Howe Robert D. , Matsuoka Yoky
Published: July 2002

▪ Abstract  Robotic technology is enhancing surgery through improved precision, stability, and dexterity. In image-guided procedures, robots use magnetic resonance and computed tomography image data to guide instruments to the treatment site. This requires new algorithms and user interfaces for planning procedures; it also requires sensors for registering the patient’s anatomy with the preoperative image data. Minimally invasive procedures use remotely controlled robots that allow the surgeon to work inside the patient’s body without making large incisions. Specialized mechanical designs and sensing technologies are needed to maximize dexterity under these access constraints. Robots have applications in many surgical specialties. In neurosurgery, image-guided robots can biopsy brain lesions with minimal damage to adjacent tissue. In orthopedic surgery, robots are routinely used to shape the femur to precisely fit prosthetic hip joint replacements. Robotic systems are also under development for closed-chest heart bypass, for microsurgical procedures in ophthalmology, and for surgical training and simulation. Although results from initial clinical experience is positive, issues of clinician acceptance, high capital costs, performance validation, and safety remain to be addressed.
New Currents in Electrical Stimulation of Excitable Tissues
Authors: Basser Peter J. , Roth Bradley J.
Published: July 2002

▪ Abstract  Electric fields can stimulate excitable tissue by a number of mechanisms. A uniform long, straight peripheral axon is activated by the gradient of the electric field that is oriented parallel to the fiber axis. Cortical neurons in the brain are excited when the electric field, which is applied along the axon-dendrite axis, reaches a particular threshold value. Cardiac tissue is thought to be depolarized in a uniform electric field by the curved trajectories of its fiber tracts. The bidomain model provides a coherent conceptual framework for analyzing and understanding these apparently disparate phenomena. Concepts such as the activating function and virtual anode and cathode, as well as anode and cathode break and make stimulation, are presented to help explain these excitation events in a unified manner. This modeling approach can also be used to describe the response of excitable tissues to electric fields that arise from charge redistribution (electrical stimulation) and from time-varying magnetic fields (magnetic stimulation) in a self-consistent manner. It has also proved useful to predict the behavior of excitable tissues, to test hypotheses about possible excitation mechanisms, to design novel electrophysiological experiments, and to interpret their findings.
THE LYSOSOMAL CYSTEINE PROTEASES
Authors: McGrath Mary E.
Published: July 2002

▪ Abstract  A significant number of exciting papain-like cysteine protease structures have been determined by crystallographic methods over the last several years. This trove of data allows for an analysis of the structural features that empower these molecules as they efficiently carry out their specialized tasks. Although the structure of the paradigm for the family, papain, has been known for twenty years, recent efforts have reaped several structures of specialized mammalian enzymes. This review first covers the commonalities of architecture and purpose of the papain-like cysteine proteases. From that broad platform, each of the lysosomal enzymes for which there is an X-ray structure (or structures) is then examined to gain an understanding of what structural features are used to customize specificity and activity. Structure-based design of inhibitors to control pathological cysteine protease activity will also be addressed.
Structural Symmetry and Protein Function
Authors: Goodsell David S. , Olson Arthur J.
Published: July 2002

▪ Abstract  The majority of soluble and membrane-bound proteins in modern cells are symmetrical oligomeric complexes with two or more subunits. The evolutionary selection of symmetrical oligomeric complexes is driven by functional, genetic, and physicochemical needs. Large proteins are selected for specific morphological functions, such as formation of rings, containers, and filaments, and for cooperative functions, such as allosteric regulation and multivalent binding. Large proteins are also more stable against denaturation and have a reduced surface area exposed to solvent when compared with many individual, smaller proteins. Large proteins are constructed as oligomers for reasons of error control in synthesis, coding efficiency, and regulation of assembly. Symmetrical oligomers are favored because of stability and finite control of assembly. Several functions limit symmetry, such as interaction with DNA or membranes, and directional motion. Symmetry is broken or modified in many forms: quasisymmetry, in which identical subunits adopt similar but different conformations; pleomorphism, in which identical subunits form different complexes; pseudosymmetry, in which different molecules form approximately symmetrical complexes; and symmetry mismatch, in which oligomers of different symmetries interact along their respective symmetry axes. Asymmetry is also observed at several levels. Nearly all complexes show local asymmetry at the level of side chain conformation. Several complexes have reciprocating mechanisms in which the complex is asymmetric, but, over time, all subunits cycle through the same set of conformations. Global asymmetry is only rarely observed. Evolution of oligomeric complexes may favor the formation of dimers over complexes with higher cyclic symmetry, through a mechanism of prepositioned pairs of interacting residues. However, examples have been found for all of the crystallographic point groups, demonstrating that functional need can drive the evolution of any symmetry.
Electrokinetically Controlled Microfluidic Analysis Systems
Authors: Bousse Luc , Cohen Claudia , Nikiforov Theo , Chow Andrea , Kopf-Sill Anne R. , Dubrow Robert , Parce J. Wallace
Published: July 2002

▪ Abstract  Electrokinetic forces are emerging as a powerful means to drive microfluidic systems with flow channel cross-sectional dimensions in the tens of micrometers and flow rates in the nanoliter per second range. These systems provide many advantages such as improved analysis speed, improved reproducibility, greatly reduced reagent consumption, and the ability to perform multiple operations in an integrated fashion. Planar microfabrication methods are used to make these analysis chips in materials such as glass or polymers. Many applications of this technology have been demonstrated, such as DNA separations, enzyme assays, immunoassays, and PCR amplification integrated with microfluidic assays. Further development of this technology is expected to yield higher levels of functionality of sample throughput on a single microfluidic analysis chip.
Ab Initio Protein Structure Prediction: Progress and Prospects
Authors: Bonneau Richard , Baker David
Published: July 2002

▪ Abstract  Considerable recent progress has been made in the field of ab initio protein structure prediction, as witnessed by the third Critical Assessment of Structure Prediction (CASP3). In spite of this progress, much work remains, for the field has yet to produce consistently reliable ab initio structure prediction protocols. In this work, we review the features of current ab initio protocols in an attempt to highlight the foundations of recent progress in the field and suggest promising directions for future work.
MITOCHONDRIAL DYNAMICS IN YEAST
Authors: Hermann Greg J. , Shaw Janet M.
Published: July 2002

▪ Abstract  Proteins that control mitochondrial dynamics in yeast are being identified at a rapid pace. These proteins include cytoskeletal elements that regulate organelle distribution and inheritance and several outer membrane proteins that are required to maintain the branched, mitochondrial reticulum. Interestingly, three of the high molecular weight GTPases encoded by the yeast genome are required for mitochondrial integrity and are potential regulators of mitochondrial branching, distribution, and membrane fusion. The recent finding that mtDNA mixing is restricted in the mitochondrial matrix has stimulated the hunt for the molecular machinery that anchors mitochondrial nucleoids in the organelle. Considering that many aspects of mitochondrial structure and behavior are strikingly similar in different cell types, the functional analyses of these yeast proteins should provide general insights into the mechanisms governing mitochondrial dynamics in all eukaryotes.
Mid-Ocean Ridge Hydrothermal Fluxes and the Chemical Composition of the Ocean
Authors: Elderfield H. , Schultz A.
Published: July 2002

▪ Abstract  Geophysical estimates of mid-ocean ridge axial heat fluxes (2–4 × 1012 W) and of the total hydrothermal flux (9 ± 2 × 1012 W) are well established. Problems arise in calculation of water fluxes because of uncertainties in (a) values of off-axis fluxes and (b) the partition of axial heat flow between high-temperature black smoker and lower-temperature diffuse flow. Of the various geochemical methods of estimating fluxes, 3 He/heat data are extremely variable, the Mg method is sensitive to flank fluxes, Sr isotopes agree with geophysical estimates only if flank fluxes are important, Li isotopes data are consistent with geophysical values, and Ge/Si ratios give low fluxes, which may reflect low-temperature processes not yet fully quantified. Estimates of hydrothermal heat and water fluxes derived from these approaches are presented as are hydrothermal chemical fluxes at the ridge axis, off axis, and as affected by hydrothermal plumes.
THE QUALITY OF THE FOSSIL RECORD: Populations, Species, and Communities
Authors: Kidwell Susan M. , Flessa Karl W.
Published: July 2002

▪ Abstract  Paleontologists have always been concerned about the documentary quality of the fossil record, and this has also become an important issue for biologists, who increasingly look to accumulations of bones, shells, and plant material as possible ways to extend the time-frame of observation on species and community behaviors. Quantitative data on the postmortem behavior of organic remains in modern environments are providing new insights into death and fossil assemblages as sources of biological information. Important findings include: 1. With the exception of a few circumstances, usually recognizable by independent criteria, transport out of the original life habitat affects few individuals. 2. Most species with preservable hardparts are in fact represented in the local death assemblage, commonly in correct rank importance. Molluscs are the most durable of modern aquatic groups studied so far, and they show highest fidelity to the original community. 3. Time-averaging of remains from successive generations and communities often prevents the detection of short-term (seasons, years) variability but provides an excellent record of the natural range of community composition and structure over longer periods. Thus, although a complex array of processes and circumstances influences preservation, death assemblages of resistant skeletal elements are for many major groups good to excellent records of community composition, morphological variation, and environmental and geographic distribution of species, and such assemblages can record temporal dynamics at ecologically and evolutionarily meaningful scales.
CHEMICALLY REACTIVE FLUID FLOW DURING METAMORPHISM
Authors: Ferry John M. , Gerdes Martha L.
Published: July 2002

▪ Abstract  Stable isotopic, mineralogical, and chemical alteration in metamorphic terranes is evidence for reactive fluid flow during metamorphism. In many cases, the amount and spatial distribution of the alteration can be quantitatively interpreted using transport theory in terms of fundamental properties of metamorphic flow systems such as time-integrated flux, flow direction, and Peclet number. Many estimates of time-integrated flux in the upper and middle crust are surprisingly large, 105–106 cm3 fluid/cm2 rock; estimates for the lower crust are much smaller. Rather than pervasive and uniform, reactive fluid flow in all metamorphic environments is channelized on scales of <1–104 m. Channelization results from heterogeneous permeability structures controlled by features such as lithologic layering, contacts, folds, fractures, and faults. Consequently flow may be in the direction of either decreasing or increasing temperature or isothermal. Site-specific thermal-hydrologic models of metamorphic terranes that explicitly consider chemical reactions and dynamic permeability structures will help resolve outstanding questions with regard to the driving forces and duration of flow, metamorphic permeability distributions, and how deformation controls fluid flow.
THE PLATE TECTONIC APPROXIMATION: Plate Nonrigidity, Diffuse Plate Boundaries, and Global Plate Reconstructions
Authors: Gordon Richard G.
Published: July 2002

▪ Abstract  The central assumption of plate tectonics, that plate interiors are rigid, remains a useful but uncertain approximation. Strain rates of stable plate interiors are bounded between 10−12–10−11 year−1 and ∼4 × 10−10 year−1. The narrowness of all plate boundaries, the other main assumption of plate tectonics as originally conceived, is contradicted by many observations, both in the continents and in the oceans. Some diffuse plate boundaries in both continents and oceans exceed dimensions of 1000 km on a side. Diffuse plate boundaries cover ∼15% of Earth's surface. The maximum speed of relative plate motion across any one diffuse plate boundary ranges from ∼2 to ∼15 mm/year, which is faster than some upper bounds on intraplate motion across stable plate interiors (≤2 mm year−1). Strain rates in diffuse plate boundaries can be as high as ∼10−8 year−1, ∼25 times higher than the upper bound on strain rates of stable plate interiors, but ∼600 times lower than the lowest strain rates across typical narrow plate boundaries. The poles of rotation of the plates flanking a diffuse oceanic plate boundary tend to be located in the diffuse boundary, which is a consequence of the strong coupling across the boundary.
SEAFLOOR TECTONIC FABRIC FROM SATELLITE ALTIMETRY
Authors: Smith Walter H. F.
Published: July 2002

▪ Abstract  Ocean floor structures with horizontal scales of 10 to a few hundred kilometers and vertical scales of 100 m or more generate sea surface gravity anomalies observable with satellite altimetry. Prior to 1990, altimeter data resolved only tectonic lineaments, some seamounts, and some aspects of mid-ocean ridge structure. New altimeter data available since mid-1995 resolve 10-km–scale structures over nearly all the world's oceans. These data are the basis of new global bathymetric maps and have been interpreted as exhibiting complexities in the sea floor spreading process including ridge jumps, propagating rifts, and variations in magma supply. This chapter reviews the satellite altimetry technique and its resolution of tectonic structures, gives examples of intriguing tectonic phenomena, and shows that structures as small as abyssal hills are partially resolved. A new result obtained here is that the amplitude of the fine-scale (10–80 km) roughness of old ocean floor is spreading-rate dependent in the same way that it is at mid-ocean ridges, suggesting that fine-scale tectonic fabric is generated nearly exclusively by ridge-axis processes.
Tectonic Evolution of the Japanese Island Arc System
Authors: Taira Asahiko
Published: July 2002

▪ Abstract  Growth of the Japanese arc system, which has mainly taken place along the continental margin of Asia since the Permian, is the result of subduction of the ancient Pacific ocean floor. Backarc basin formation in the Tertiary shaped the present-day arc configuration. The neotectonic regime, which is characterized by strong east-west compression, has been triggered by the eastward motion of the Amur plate in the Quaternary. The tectonic evolution of the Japanese arc system includes formation of rock assemblages common in most orogenic belts. Because the origin and present-day tectonics of these assemblages are better defined in the case of the Japanese arc system, study of the system provides useful insight into orogenesis and continental crust evolution.
EVOLUTIONARY SIGNIFICANCE OF LOCAL GENETIC DIFFERENTIATION IN PLANTS
Authors: Linhart Yan B. , Grant Michael C.
Published: July 2002

▪ Abstract  The study of natural plant populations has provided some of the strongest and most convincing cases of the operation of natural selection currently known, partly because of amenability to reciprocal transplant experiments, common garden work, and long-term in situ manipulation. Genetic differentiation among plant populations over small scales (a few cm to a few hundred cm) has been documented and is reviewed here, in herbaceous annuals and perennials, woody perennials, aquatics, terrestrials, narrow endemics, and widely distributed species. Character differentiation has been documented for most important features of plant structure and function. Examples are known for seed characters, leaf traits, phenology, physiological and biochemical activities, heavy metal tolerance, herbicide resistance, parasite resistance, competitive ability, organellar characters, breeding systems, and life history. Among the forces that have shaped these patterns of differentiation are toxic soils, fertilizers, mowing and grazing, soil moisture, temperature, light intensity, pollinating vectors, parasitism, gene flow, and natural dynamics. The breadth and depth of the evidence reviewed here strongly support the idea that natural selection is the principal force shaping genetic architecture in natural plant populations; that view needs to be more widely appreciated than it is at present.
Insect Mouthparts: Ascertaining the Paleobiology of Insect Feeding Strategies
Authors: Labandeira Conrad C.
Published: July 2002

One of the most intensively examined and abundantly documented structures in the animal world is insect mouthparts. Major structural types of extant insect mouthparts are extensive, consisting of diverse variations in element structure within each of the five mouthpart regions—labrum, hypopharynx, mandibles, maxillae, and labium. Numerous instances of multielement fusion both within and among mouthpart regions result in feeding organs capable of ingesting in diverse ways foods that are solid, particulate, and liquid in form. Mouthpart types have a retrievable and interpretable fossil history in well-preserved insect deposits. In addition, the trace-fossil record of insect-mediated plant damage, gut contents, coprolites, and insect-relevant floral features provides complementary data documenting the evolution of feeding strategies during the past 400 million years.

From a cluster analysis of insect mouthparts, I recognize 34 fundamental mouthpart classes among extant insects and their geochronological evolution by a five-phase pattern. This pattern is characterized, early in the Devonian, by coarse partitioning of food by mandibulate and piercing-and-sucking mouthpart classes, followed by a rapid rise in herbivore mouthpart types for fluid- and solid-feeding during the Late Carboniferous and Early Permian. Mouthpart innovation during the Late Triassic to Early Jurassic added mouthpart classes for fluid and aquatic particle-feeding. This ecomorphological expansion of mouthpart design was associated with the radiation of holometabolous insects, especially Diptera. The final phase of mouthpart class expansion occurred during the Late Jurassic and Early Cretaceous, with addition of surface-fluid-feeding mouthpart classes that subsequently became important during the ecological expansion of angiosperms. Conclusions about the evolution of mouthpart design are based on the mapping of phenetic mouthpart classes onto (ideally) cladistic phylogenies of lineages bearing those same mouthpart classes. The plotting of phenetic and associated ecological attributes onto baseline phylogenies is one of the most important uses of cladistic data.
Allometry for Sexual Size Dimorphism: Pattern and Process in the Coevolution of Body Size in Males and Females
Authors: Fairbairn D. J.
Published: July 2002

Sexual size dimorphism (SSD) is common in both plants and animals, and current evidence suggests that it reflects the adaptation of males and females to their different reproductive roles. When species are compared within a clade, SSD is frequently found to vary with body size. This allometry is detected as β ≠ 1, where β is the slope of a model II regression of log(male size) on log(female size). Most frequently, β exceeds 1, indicating that SSD increases with size where males are the larger sex, but decreases with size where females are larger, a trend formalized as “Rensch's rule.” Exceptions are uncommon and associated with female-biased SSD. These trends are derived from a sample of 40 independent clades of terrestrial animals, primarily vertebrates. Their extension to plants and aquatic animals awaits quantitative assessments of allometry for SSD within these groups. Many functional hypotheses have been proposed to explain the evolution of allometry for SSD, most featuring sexual selection on males or reproductive selection on females. Of these, the hypothesis that allometry evolves because of correlational selection between the sexes appears most promising as a general model but remains untested.
PHYLOGENY OF VASCULAR PLANTS
Authors: Doyle James A.
Published: July 2002

▪ Abstract  Morphological and molecular analyses resolve many aspects of vascular plant phylogeny, though others remain uncertain. Vascular plants are nested within bryophytes; lycopsids and zosterophylls are one branch of crown-group vascular plants, and euphyllophytes (Psilophyton, sphenopsids, ferns, seed plants) are the other. In Filicales, Osmundaceae are basal; water ferns and Polypodiaceae sensu lato are both monophyletic. Seed plants are nested within progymnosperms, and coniferophytes are nested within platyspermic seed ferns. Morphology indicates that angiosperms and Gnetales are related, but detailed scenarios depend on uncertain relationships of fossils; molecular data are inconsistent but indicate that both groups are monophyletic. Amborella, Nymphaeales, Austrobaileya, and Illiciales appear basal in angiosperms. Groups with tricolpate pollen form a clade (eudicots), with ranunculids and lower hamamelids basal. Most eudicots belong to the rosid and asterid lines, with higher hamamelids in the rosid line and dilleniids scattered in both. Alismids, Arales, and Acorus are basal in monocots; palms are linked with Commelinidae.
Impacts of Airborne Pollutants on Soil Fauna
Authors: Rusek Josef , Marshall Valin G.
Published: July 2002

▪ Abstract  The impacts of airborne pollutants have been studied in only a few groups of soil animals, notably protozoans, nematodes, potworms, earthworms, mites, and collembolans. Pollutants in the form of acid depositions, which contain SO42−, NOx, H+, heavy metals, and some organic compounds, are not homogeneously distributed on the landscape. Deposition patterns depend mainly on landscape configuration and plant cover. Airborne pollutants affect soil animals both directly and indirectly. Direct toxic effects are associated with uptake of free acidic water from the environment by some soil animals and with consumption of polluted food by others. Indirect effects are mediated primarily through disappearance or reduction of the food resources (microflora and microfauna) of soil animals, changes in organic matter content, and modification of microclimate. In the field, changes in competition among species are probably important factors that influence the soil animal community structure as well as the reactions of individual species to soil acidification or liming. The overall effect is a depauperation of soil with an attendant reduction in the rate of organic matter decomposition. We have provided five hypotheses, using soil fauna as indicators, to allow for quick evaluation of environmental changes caused by airborne pollutants.
INTERNATIONAL TECHNOLOGY TRANSFER FOR CLIMATE CHANGE MITIGATION AND THE CASES OF RUSSIA AND CHINA
Authors: Martinot Eric , Sinton Jonathan E. , Haddad and Brent M.
Published: July 2002

▪ Abstract  The environmental agenda for mitigating climate change through international transfers of technology is linked with a diverse literature, reviewed here within a framework that combines technological, agent/agenda, and market/transaction perspectives. Literature that bears on international technology transfer for climate change mitigation is similar in many w ays for Russia and China: opportunities for energy efficiency and renewable energy, economic reform and restructuring, the difficulties enterprises face in responding to market conditions, international assistance policies, international joint ventures, market intermediation, and capacity building for market development. In both countries, capacity building means enhancing market-oriented capabilities in addition to technological capabilities. For Russia, institutional development is critical, such as new commercial legal codes and housing-sector changes beyond privatization. For China, technology policies and modernization programs significantly influence technology transfers.
RECYCLING METALS FOR THE ENVIRONMENT
Authors: Wernick Iddo K. , Themelis Nickolas J.
Published: July 2002

▪ Abstract  Society uses metals derived from primary and secondary sources. Secondary sources include all metals that have entered the economy but no longer serve their initial purpose. The environmental benefits of increasing reliance on secondary metal production include conserving energy, landscapes, and natural resources, and reducing toxic and nontoxic waste streams. A variety of technologies are used to recover and process metals from waste streams and their use for metal production influences the amount of secondary metal that reenters the system. Environmental regulation also affects secondary metal production through laws that control emissions and govern the classification and treatment of metal-loaded wastes. Industry must develop better technology to isolate and recover maximum value from metals in waste streams, and governments must institute policies that remove barriers to their economically and environmentally sound recovery. Only through a concerted effort can society recover a maximum amount of metal from the industrial/social system to benefit the environment.
Fire and Insects in Northern and Boreal Forest Ecosystems of North America
Authors: McCullough Deborah G. , Werner Richard A. , Neumann David
Published: July 2002

▪ Abstract  Fire and insects are natural disturbance agents in many forest ecosystems, often interacting to affect succession, nutrient cycling, and forest species composition. We review literature pertaining to effects of fire-insect interactions on ecological succession, use of prescribed fire for insect pest control, and effects of fire on insect diversity from northern and boreal forests in North America. Fire suppression policies implemented in the early 1900s have resulted in profound changes in forest species composition and structure. Associated with these changes was an increased vulnerability of forest stands to damage during outbreaks of defoliating insects. Information about the roles that both fire and insects play in many northern forests is needed to increase our understanding of the ecology of these systems and to develop sound management policies.
A NEW VIEW OF NONLINEAR WATER WAVES: The Hilbert Spectrum
Authors: Huang Norden E. , Shen Zheng , Long Steven R.
Published: July 2002

▪ Abstract  We survey the newly developed Hilbert spectral analysis method and its applications to Stokes waves, nonlinear wave evolution processes, the spectral form of the random wave field, and turbulence. Our emphasis is on the inadequacy of presently available methods in nonlinear and nonstationary data analysis. Hilbert spectral analysis is here proposed as an alternative. This new method provides not only a more precise definition of particular events in time-frequency space than wavelet analysis, but also more physically meaningful interpretations of the underlying dynamic processes.
Liquid Jet Instability and Atomization in a Coaxial Gas Stream
Authors: Lasheras J. C. , Hopfinger E. J.
Published: July 2002

▪ Abstract  An overview of the near and far-field breakup and atomization of a liquid jet by a high speed annular gas jet is presented. The various regimes of liquid jet breakup are discussed in the parameter space of the liquid Reynolds number, the aerodynamic Weber number, and the ratio of the momentum fluxes between the gas and the liquid streams. Recent measurements of the gas-liquid interfacial instabilities are reviewed and used to analyze the underlying physical mechanisms involved in the primary breakup of the liquid jet. This process is shown to consist of the periodic stripping of liquid sheets, or ligaments, which subsequently break up into smaller lumps or drops. Models to predict the liquid shedding frequency, as well as the global parameters of the spray such as the liquid core length and spray spreading angle are discussed and compared with the experiments. The role of the secondary liquid breakup on the far-field atomization of the liquid jet is also considered, and an attempt is made to apply the classical turbulent breakup concepts to explain qualitatively the measurement of the far-field droplet size distribution and its dependence on the liquid to gas mass and momentum flux ratios. Models for the droplet breakup frequency in the far-field region of the jet, and for the daughter-size probability density function, which account for the effect of the liquid loading on the local turbulent dissipation rate in the gas, are discussed in the context of the statistical description of the spray in the far field. The striking effect of the addition of swirl in the gas stream is also examined.
Flows in Stenotic Vessels
Authors: Berger S. A. , Jou L-D.
Published: July 2002

▪ Abstract  The relationship between flow in the arteries, particularly the wall shear stresses, and the sites where atherosclerosis develops has motivated much of the research on arterial flow in recent decades. It is now well accepted that it is sites where shear stresses are low, or change rapidly in time or space, that are most vulnerable. These conditions are likely to prevail at places where the vessel is curved; bifurcates; has a junction, a side branch, or other sudden change in flow geometry; and when the flow is unsteady. These flows, often but not always involving flow separation or secondary motions, are also the most difficult ones in fluid mechanics to analyze or compute. In this article we review the modeling studies and experiments on steady and unsteady, two-and three-dimensional flows in arteries, and in arterial geometries most relevant in the context of atherosclerosis. These include studies of normal vessels—to identify, on the basis of the fluid mechanics, lesion foci—and stenotic vessels, to model and measure flow in vessels after the lesions have evolved into plaques sufficiently large to significantly modify the flow. We also discuss recent work that elucidates many of the pathways by which mechanical forces, primarily the wall shear stresses, are transduced to effect changes in the arterial wall at the cellular, subcellular, and genetic level.
Vapor Explosions
Authors: Berthoud Georges
Published: July 2002

▪ Abstract  A vapor explosion results from the rapid and intense heat transfer that may follow contact between a hot liquid and a cold, more volatile one. Because it can happen during severe-accident sequences of a nuclear power plan, that is, when a large part of the core is molten, vapor explosions have been widely studied. The different sequences of a vapor explosion are presented, including premixing, triggering, propagation, and expansion. Typical experimental results are also analyzed to understand the involved physics. Then the different physics involved in the sequences are addressed, as well as the present experimental program.
AERODYNAMICS OF HIGH-SPEED TRAINS
Authors: Schetz Joseph A
Published: July 2002

▪ Abstract  This review highlights the differences between the aerodynamics of high-speed trains and other types of transportation vehicles. The emphasis is on modern, high-speed trains, including magnetic levitation (Maglev) trains. Some of the key differences are derived from the fact that trains operate near the ground or a track, have much greater length-to-diameter ratios than other vehicles, pass close to each other and to trackside structures, are more subject to crosswinds, and operate in tunnels with entry and exit events. The coverage includes experimental techniques and results and analytical and numerical methods, concentrating on the most recent information available.
PROTEIN-SPLICING INTEIN: Genetic Mobility, Origin, and Evolution
Authors: Liu Xiang-Qin
Published: July 2002

▪ Abstract  Intein is the protein equivalent of intron and has been discovered in increasing numbers of organisms and host proteins. A self-splicing intein catalyzes its own removal from the host protein through a posttranslational process of protein splicing. A mobile intein displays a site-specific endonuclease activity that confers genetic mobility to the intein through intein homing. Recent findings of intein structure and the mechanism of protein splicing illuminated how inteins work and yielded clues regarding intein's origin, spread, and evolution. Inteins can evolve into new structures and new functions, such as split inteins that do trans-splicing. The structural basis of intein function needs to be identified for a full understanding of the origin and evolution of this marvelous genetic element.
Does Nonneutral Evolution Shape Observed Patterns of DNA Variation in Animal Mitochondrial Genomes?
Authors: Gerber Anne S. , Loggins Ronald , Kumar Sudhir , Dowling Thomas E.
Published: July 2002

▪ Abstract  Early studies of animal mitochondrial DNA (mtDNA) assumed that nucleotide sequence variation was neutral. Recent analyses of sequences from a variety of taxa have brought the validity of this assumption into question. Here we review analytical methods used to test for neutrality and evidence for nonneutral evolution of animal mtDNA. Evaluations of mitochondrial haplotypes in different nuclear backgrounds identified differences in performance, typically favoring coevolved mitochondrial and nuclear genomes. Experimental manipulations also indicated that certain haplotypes have an advantage over others; however, biotic and historical effects and cyto-nuclear interactions make it difficult to assess the relative importance of nonneutral factors. Statistical analyses of sequences have been used to argue for nonneutrality of mtDNA; however, rejection of neutral patterns in the published literature is common but not predominant. Patterns of replacement and synonymous substitutions within and between species identified a trend toward an excess of replacement mutations within species. This pattern has been viewed as support for the existence of mildly deleterious mutations within species; however, other alternative explanations that can produce similar patterns cannot be eliminated.
The Human Major Histocompatibility Complex: Lessons from the DNA Sequence
Authors: Beck Stephan , Trowsdale John
Published: July 2002

The entire 3.6-MbpDNA sequence of a human major histocompatibility complex derived from a composite of DNA clones from different haplotypes, was completed in 1999, primarily through the work of four main groups. At that time, it was the longest contiguous human DNA sequence to have been determined. The sequence is of extremely high quality and accuracy. In this review, we discuss how the DNA sequence has facilitated our understanding of the biology and genetics of the major histocompatibility complex. We suggest some ways in which the sequence may be exploited in the future to explore the relationship between the extraordinary polymorphism of the region and its association with both autoimmune and infectious diseases.
Gene Therapy: Promises and Problems
Authors: Pfeifer Alexander , Verma Inder M.
Published: July 2002

Gene therapy can be broadly defined as the transfer of genetic material to cure a disease or at least to improve the clinical status of a patient. One of the basic concepts of gene therapy is to transform viruses into genetic shuttles, which will deliver the gene of interest into the target cells. Based on the nature of the viral genome, these gene therapy vectors can be divided into RNA and DNA viral vectors. The majority of RNA virus-based vectors have been derived from simple retroviruses like murine leukemia virus. A major shortcoming of these vectors is that they are not able to transduce nondividing cells. This problem may be overcome by the use of novel retroviral vectors derived from lentiviruses, such as human immunodeficiency virus (HIV). The most commonly used DNA virus vectors are based on adenoviruses and adeno-associated viruses. Although the available vector systems are able to deliver genes in vivo into cells, the ideal delivery vehicle has not been found. Thus, the present viral vectors should be used only with great caution in human beings and further progress in vector development is necessary.
Privacy and Confidentiality of Genetic Information: What Rules for the New Science?
Authors: Anderlik Mary R. , Rothstein Mark A.
Published: July 2002

This review covers the ethical, legal, and policy issues associated with the generation and dissemination of genetic information. First, conceptual issues, such as the definition of terms and the description of two modes of analysis, are addressed. Research findings on public attitudes toward privacy and genetics and other factors relevant to policy making are also reviewed. Second, the example of genetic research is used to highlight the importance of attention to the intrinsic harms associated with violations of genetic privacy. Subtopics include national databases and biobanks, gene brokers, and pharmacogenomics. Third, the example of insurer access to genetic information is used to highlight the importance of attention to discrimination and other instrumental harms associated with failures of regulation. Fourth, a summary of the preceding sections leads into an outline of a program for realizing the benefits of the new science in a manner that affirms rather than erodes privacy and other important values.
NITRIC OXIDE AND MACROPHAGE FUNCTION
Authors: MacMicking John , Xie Qiao-wen , Nathan Carl
Published: July 2002

▪ Abstract  At the interface between the innate and adaptive immune systems lies the high-output isoform of nitric oxide synthase (NOS2 or iNOS). This remarkable molecular machine requires at least 17 binding reactions to assemble a functional dimer. Sustained catalysis results from the ability of NOS2 to attach calmodulin without dependence on elevated Ca2+. Expression of NOS2 in macrophages is controlled by cytokines and microbial products, primarily by transcriptional induction. NOS2 has been documented in macrophages from human, horse, cow, goat, sheep, rat, mouse, and chicken. Human NOS2 is most readily observed in monocytes or macrophages from patients with infectious or inflammatory diseases. Sustained production of NO endows macrophages with cytostatic or cytotoxic activity against viruses, bacteria, fungi, protozoa, helminths, and tumor cells. The antimicrobial and cytotoxic actions of NO are enhanced by other macrophage products such as acid, glutathione, cysteine, hydrogen peroxide, or superoxide. Although the high-output NO pathway probably evolved to protect the host from infection, suppressive effects on lymphocyte proliferation and damage to other normal host cells confer upon NOS2 the same protective/destructive duality inherent in every other major component of the immune response.
DNA VACCINES
Authors: Donnelly John J. , Ulmer Jeffrey B. , Shiver John W. , Liu Margaret A.
Published: July 2002

▪ Abstract  Observations in the early 1990s that plasmid DNA could directly transfect animal cells in vivo sparked exploration of the use of DNA plasmids to induce immune responses by direct injection into animals of DNA encoding antigenic proteins. This method, termed DNA immunization, now has been used to elicit protective antibody and cell-mediated immune responses in a wide variety of preclinical animal models for viral, bacterial, and parasitic diseases. DNA vaccination is particularly useful for the induction of cytotoxic T cells. This review summarizes current knowledge on the vectors, immune responses, immunological mechanisms, safety considerations, and potential for further application of this novel method of immunization.
XENOGENEIC TRANSPLANTATION
Authors: Auchincloss Hugh , Sachs David H.
Published: July 2002

▪ Abstract  This review summarizes the clinical history and rationale for xenotransplantation; recent progress in understanding the physiologic, immunologic, and infectious obstacles to the procedure's success; and some of the strategies being pursued to overcome these obstacles. The problems of xenotransplantation are complex, and a combination of approaches is required. The earliest and most striking immunologic obstacle, that of hyperacute rejection, appears to be the closest to being solved. This phenomenon depends on the binding of natural antibody to the vascular endothelium, fixation of complement by that antibody, and finally, activation of the endothelium and initiation of coagulation. Therefore, these three pathways have been targeted as sites for intervention in the process. The mechanisms responsible for the next immunologic barrier, that of delayed xenograft/acute vascular rejection, remain to be fully elucidated. They probably also involve multiple pathways, including antibody and/or immune cell binding and endothelial cell activation. The final immunologic barrier, that of the cellular immune response, involves mechanisms that are similar to those involved in allograft rejection. However, the strength of the cellular immune response to xenografts is so great that it is unlikely to be controlled by the types of nonspecific immunosuppression used routinely to prevent allograft rejection. For this reason, it may be essential to induce specific immunologic unresponsiveness to at least some of the most antigenic xenogeneic molecules.