bluuebunny/crossref_metadata_2025 huggingface dataset:
OXYGEN AND HYDROGEN ISOTOPES IN THE HYDROLOGIC CYCLE
Authors: Gat J. R.
Published: July 2002

▪ Abstract  Changes of the isotopic composition of water within the water cycle provide a recognizable signature, relating such water to the different phases of the cycle. The isotope fractionations that accompany the evaporation from the ocean and other surface waters and the reverse process of rain formation account for the most notable changes. As a result, meteoric waters are depleted in the heavy isotopic species of H and O relative to ocean waters, whereas waters in evaporative systems such as lakes, plants, and soilwaters are relatively enriched. During the passage through the aquifers, the isotope composition of water is essentially a conservative property at ambient temperatures, but at elevated temperatures, interaction with the rock matrix may perturb the isotope composition. These changes of the isotope composition in atmospheric waters, surface water, soil, and groundwaters, as well as in the biosphere, are applied in the characterization of hydrological system as well as indicators of paleo-climatological conditions in proxy materials in climatic archives, such as ice, lake sediments, or organic materials.
THE EVOLUTION OF THE ALTIPLANO-PUNA PLATEAU OF THE CENTRAL ANDES
Authors: Allmendinger Richard W. , Jordan Teresa E. , Kay Suzanne M. , Isacks Bryan L.
Published: July 2002

▪ Abstract  The enigma of continental plateaus formed in the absence of continental collision is embodied by the Altiplano-Puna, which stretches for 1800 km along the Central Andes and attains a width of 350–400 km. The plateau correlates spatially and temporally with Andean arc magmatism, but it was uplifted primarily because of crustal thickening produced by horizontal shortening of a thermally softened lithosphere. Nonetheless, known shortening at the surface accounts for only 70–80% of the observed crustal thickening, suggesting that magmatic addition and other processes such as lithospheric thinning, upper mantle hydration, or tectonic underplating may contribute significantly to thickening. Uplift in the region of the Altiplano began around 25 Ma, coincident with increased convergence rate and inferred shallowing of subduction; uplift in the Puna commenced 5–10 million years later.
STELLAR NUCLEOSYNTHESIS AND THE ISOTOPIC COMPOSITION OF PRESOLAR GRAINS FROM PRIMITIVE METEORITES
Authors: Zinner Ernst
Published: July 2002

▪ Abstract  Primitive meteorites contain grains of stardust that originated from stellar outflows and supernova ejecta prior to the formation of the Solar System. The study of these grains in the laboratory provide new information on stellar evolution, nucleosynthesis, mixing in supernovae, galactic evolution, and the age of the galaxy. Grains whose isotopically anomalous compositions indicate a stellar origin include diamond, silicon carbide, graphite, corundum, and silicon nitride. Most silicon carbide and corundum come from red giant and asymptotic giant branch stars (low-mass stars at the end of their evolution), and carry the isotopic signatures of H burning in the core and later of H and He burning in thin shells. Diamond carries a supernova isotopic signature in its Xe, and low-density graphite and silicon nitride, as well as a subgroup of silicon carbide, show evidence for a supernova origin in the form of extinct44Ti and large28Si excesses.
EARLY HISTORY OF ARTHROPOD AND VASCULAR PLANT ASSOCIATIONS
Authors: Labandeira Conrad C.
Published: July 2002

▪ Abstract  Although research on modern plant-arthropod associations is one of the cornerstones of biodiversity studies, very little of that interest has percolated down to the fossil record. Much of this neglect is attributable to dismissal of Paleozoic plant-arthropod interactions as being dominated by detritivory, with substantive herbivory not emerging until the Mesozoic. Recent examination of associations from some of the earliest terrestrial communities indicates that herbivory probably extends to the Early Devonian, in the form of spore feeding and piercing-and-sucking. External feeding on pinnule margins and the intimate and intricate association of galling are documented from the Middle and Late Pennsylvanian, respectively. During the Early Permian, the range of external foliage feeding extended to hole feeding and skeletonization and was characterized by the preferential targeting of certain seed plants. At the close of the Paleozoic, surface fluid feeding was established, but there is inconclusive evidence for mutualistic relationships between insect pollinivores and seed plants. These data are gleaned from the largely separate trace-fossil records of gut contents, coprolites, and plant damage and the body-fossil records of plant reproductive and vegetative structures, insect mouthparts, and ovipositors. While these discoveries accentuate the potential for identifying particular associations, the greatest theoretical demand is to establish the spectrum and level of intensity for the emergence of insect herbivory in a range of environments during the Pennsylvanian and Permian.
Dynamics of Volcanic Systems in Iceland: Example of Tectonism and Volcanism at Juxtaposed Hot Spot and Mid-Ocean Ridge Systems
Authors: Gudmundsson Agust
Published: July 2002

Volcanic systems are swarms of tectonic fractures and basalt volcanoes formed as a result of plate-pull (as the plates are pulled apart) associated with the mid-ocean ridges and the magma dynamics of the Iceland Mantle Plume. Most systems are 40–150 km long, 5–20 km wide, and develop a central volcano. They supply magma to all eruptions in Iceland. Data obtained in the last few years have greatly improved our knowledge of their volcanotectonic environment; as a result, the geometry of the plume is better constrained, and the crust, previously considered thin (∼10 km), is now modeled as thick (∼20–40 km). Depending on the location of the volcanic systems, their activity either decreases or increases faulting in the two main seismic zones. From this, we can infer that emplacement of the feeder-dike to the largest historical eruption in Iceland (that of Laki in 1783) increased shear stress in the South Iceland Seismic Zone and almost certainly triggered the largest (M∼7.1 in 1784) historical earthquake in Iceland. [ Addendum posted 20 April, 2010 ]
Understanding Oblique Impacts from Experiments, Observations, and Modeling
Authors: Pierazzo E. , Melosh H. J.
Published: July 2002

Natural impacts in which the projectile strikes the target vertically are virtually nonexistent. Nevertheless, our inherent drive to simplify nature often causes us to suppose most impacts are nearly vertical. Recent theoretical, observational, and experimental work is improving this situation, but even with the current wealth of studies on impact cratering, the effect of impact angle on the final crater is not well understood. Although craters’ rims may appear circular down to low impact angles, the distribution of ejecta around the crater is more sensitive to the angle of impact and currently serves as the best guide to obliquity of impacts. Experimental studies established that crater dimensions depend only on the vertical component of the impact velocity. The shock wave generated by the impact weakens with decreasing impact angle. As a result, melting and vaporization depend on impact angle; however, these processes do not seem to depend on the vertical component of the velocity alone. Finally, obliquity influences the fate of the projectile: in particular, the amount and velocity of ricochet are a strong function of impact angle.
Ground Penetrating Radar for Environmental Applications
Authors: Knight Rosemary
Published: July 2002

▪ Abstract  Ground penetrating radar (GPR) is a near-surface geophysical technique that can provide high resolution images of the dielectric properties of the top few tens of meters of the earth. In applications in contaminant hydrology, radar data can be used to detect the presence of liquid organic contaminants, many of which have dielectric properties distinctly different from those of the other solid and fluid components in the subsurface. The resolution (approximately meter-scale) of the radar imaging method is such that it can also be used in the development of hydrogeologic models of the subsurface, required to predict the fate and transport of contaminants. GPR images are interpreted to obtain models of the large-scale architecture of the subsurface and to assist in estimating hydrogeologic properties such as water content, porosity, and permeability. Its noninvasive capabilities make GPR an attractive alternative to the traditional methods used for subsurface characterization.
GENE TREES, SPECIES TREES, AND SYSTEMATICS: A Cladistic Perspective
Authors: Brower A. V. Z. , DeSalle R. , Vogler A.
Published: July 2002

▪ Abstract  The proliferation of molecular data in systematics has opened a Pandora's box of alternate approaches to inferring hierarchical patterns of relationship among taxa. In this review, we examine practical and theoretical reasons for employing some methods and avoiding others. We offer a philosophical overview of the relationship between systematics patterns and evolutionary processes, and we discuss the differential emphasis given to each of these areas by opposing methodological camps. We review the sources and types of incongruence between data partitions from different sources and recommend a specific procedure for contending with incongruence. We then focus on inference of relationships among closely related taxa, with particular emphasis on mtDNA as a source of characters, its advantages and potential pitfalls. We conclude with a review of several widely cited empirical studies and suggest that the gene tree–species tree problem may be less severe than its prevalence in the literature would suggest.
EXTINCTION BY HYBRIDIZATION AND INTROGRESSION
Authors: Rhymer Judith M. , Simberloff Daniel
Published: July 2002

▪ Abstract  Nonindigenous species can bring about a form of extinction of native flora and fauna by hybridization and introgression either through purposeful introduction by humans or through habitat modification, bringing previously isolated species into contact. These phenomena can be especially problematic for rare species coming into contact with more abundant ones. Increased use of molecular techniques focuses attention on the extent of this underappreciated problem that is not always apparent from morphological observations alone. Some degree of gene flow is a normal, evolutionarily constructive process, and all constellations of genes and genotypes cannot be preserved. However, hybridization with or without introgression may, nevertheless, threaten a rare species' existence.
Echinoderm Larvae and Phylogeny
Authors: Smith Andrew B.
Published: July 2002

New robust phylogenies for echinoderms, based on congruent patterns derived from multiple data sets, provide a sound foundation for plotting the evolution of life-history strategies and comparing rates and patterns of larval and adult morphological change. This approach demonstrates that larval morphology has been evolving independently of adult morphology, that larval morphology displays more homoplasy than adult morphology, and that early developmental patterns are remarkably flexible. Larval morphology on its own can mislead phylogenetic analysis, not because of lateral gene transfer among distantly related taxa, but because of massive convergence in the form of nonfeeding larvae brought about by the loss of complex structures and the strong functional constraints on feeding larvae. The degree to which larval tissue is resorbed at metamorphosis is believed to be important in determining adult body plan. Although the correspondence is not precise, it does provide a model for understanding skeletal homologies among the classes.
The Ecology of Interfaces: Riparian Zones
Authors: Naiman Robert J. , Décamps Henri
Published: July 2002

Riparian zones possess an unusually diverse array of species and environmental processes. The ecological diversity is related to variable flood regimes, geographically unique channel processes, altitudinal climate shifts, and upland influences on the fluvial corridor. The resulting dynamic environment supports a variety of life-history strategies, biogeochemical cycles and rates, and organisms adapted to disturbance regimes over broad spatial and temporal scales. Innovations in riparian zone management have been effective in ameliorating many ecological issues related to land use and environmental quality. Riparian zones play essential roles in water and landscape planning, in restoration of aquatic systems, and in catalyzing institutional and societal cooperation for these efforts.
FUNGAL ENDOPHYTES: A Continuum of Interactions with Host Plants
Authors: Saikkonen K. , Faeth S. H. , Helander M. , Sullivan T. J.
Published: July 2002

▪ Abstract  Endophytic fungi living asymptomatically within plant tissues have been found in virtually all plant species. Endophytes are considered plant mutualists: They receive nutrition and protection from the host plant while the host plant may benefit from enhanced competitive abilities and increased resistance to herbivores, pathogens, and various abiotic stresses. Limited evidence also indicates that endophytes may influence population dynamics, plant community diversity, and ecosystem function. However, most of the empirical evidence for this mutualism and its ecological consequences has been based on a few agronomic grass endophytes. More recent studies suggest that endophyte-host plant interactions are variable and range from antagonistic to mutualistic. A more comprehensive view of the ecology and evolution of endophytes and host plants is needed. This article discusses how life history traits—such as fungal reproduction and pattern of infections and genotypic variation and ecological factors—influence the direction and strength of the endophyte-host plant interaction.
THE FUNCTIONAL SIGNIFICANCE OF THE HYPORHEIC ZONE IN STREAMS AND RIVERS
Authors: Boulton Andrew J. , Findlay Stuart , Marmonier Pierre , Stanley Emily H. , Valett H. Maurice
Published: July 2002

▪ Abstract  The hyporheic zone is an active ecotone between the surface stream and groundwater. Exchanges of water, nutrients, and organic matter occur in response to variations in discharge and bed topography and porosity. Upwelling subsurface water supplies stream organisms with nutrients while downwelling stream water provides dissolved oxygen and organic matter to microbes and invertebrates in the hyporheic zone. Dynamic gradients exist at all scales and vary temporally. At the microscale, gradients in redox potential control chemical and microbially mediated nutrient transformations occurring on particle surfaces. At the stream-reach scale, hydrological exchange and water residence time are reflected in gradients in hyporheic faunal composition, uptake of dissolved organic carbon, and nitrification. The hyporheic corridor concept describes gradients at the catchment scale, extending to alluvial aquifers kilometers from the main channel. Across all scales, the functional significance of the hyporheic zone relates to its activity and connection with the surface stream.
Inbreeding Depression in Conservation Biology
Authors: Hedrick Philip W. , Kalinowski Steven T.
Published: July 2002

▪ Abstract  Inbreeding depression is of major concern in the management and conservation of endangered species. Inbreeding appears universally to reduce fitness, but its magnitude and specific effects are highly variable because they depend on the genetic constitution of the species or populations and on how these genotypes interact with the environment. Recent natural experiments are consistent with greater inbreeding depression in more stressful environments. In small populations of randomly mating individuals, such as are characteristic of many endangered species, all individuals may suffer from inbreeding depression because of the cumulative effects of genetic drift that decrease the fitness of all individuals in the population. In three recent cases, introductions into populations with low fitness appeared to restore fitness to levels similar to those before the effects of genetic drift. Inbreeding depression may potentially be reduced, or purged, by breeding related individuals. However, the Speke's gazelle example, often cited as a demonstration of reduction of inbreeding depression, appears to be the result of a temporal change in fitness in inbred individuals and not a reduction in inbreeding depression.

     Down, July 17, 1870

 My Dear Lubbock,

 …In England and many parts of Europe the marriages of cousins are objected to from their supposed injurious consequences: but this belief rests on no direct evidence. It is therefore manifestly desirable that the belief should be either proved false, or should be confirmed, so that in this latter case the marriages of cousins might be discouraged…

  It is moreover, much to be wished that the truth of the often repeated assertion that consanguineous marriages lead to deafness and dumbness, blindness, &c, should be ascertained: and all such assertions could be easily tested by the returns from a single census.

     Believe me,

     Yours very sincerely,

     Charles Darwin
Temporal Variation in Fitness Components and Population Dynamics of Large Herbivores
Authors: Gaillard J.-M. , Festa-Bianchet M. , Yoccoz N. G. , Loison A. , Toïgo C.
Published: July 2002

▪ Abstract  In large-herbivore populations, environmental variation and density dependence co-occur and have similar effects on various fitness components. Our review aims to quantify the temporal variability of fitness components and examine how that variability affects changes in population growth rates. Regardless of the source of variation, adult female survival shows little year-to-year variation [coefficient of variation (CV <10%)], fecundity of prime-aged females and yearling survival rates show moderate year-to-year variation (CV <20%), and juvenile survival and fecundity of young females show strong variation (CV >30%). Old females show senescence in both survival and reproduction. These patterns of variation are independent of differences in body mass, taxonomic group, and ecological conditions. Differences in levels of maternal care may fine-tune the temporal variation of early survival. The immature stage, despite a low relative impact on population growth rate compared with the adult stage, may be the critical component of population dynamics of large herbivores. Observed differences in temporal variation may be more important than estimated relative sensitivity or elasticity in determining the relative demographic impact of various fitness components.
Dispersal in Freshwater Invertebrates
Authors: Bilton David T. , Freeland Joanna R. , Okamura Beth
Published: July 2002

▪ Abstract  Movement between discrete habitat patches can present significant challenges to organisms. Freshwater invertebrates achieve dispersal using a variety of mechanisms that can be broadly categorized as active or passive, and which have important consequences for processes of colonization, gene flow, and evolutionary divergence. Apart from flight in adult freshwater insects, active dispersal appears relatively uncommon. Passive dispersal may occur through transport by animal vectors or wind, often involving a specific desiccation-resistant stage in the life cycle. Dispersal in freshwater taxa is difficult to study directly, and rare but biologically significant dispersal events may remain undetected. Increased use of molecular markers has provided considerable insight into the frequency of dispersal in freshwater invertebrates, particularly for groups such as crustaceans and bryozoans that disperse passively through the transport of desiccation-resistant propagules. The establishment of propagule banks in sediment promotes dispersal in time and may be particularly important for passive dispersers by allowing temporal escape from unfavorable conditions. Patterns that apply to dispersal in freshwater invertebrates can be readily extended to other freshwater taxa, since common challenges arise from the colonization of isolated aquatic systems.
The Role of Disturbance in the Ecology and Conservation of Birds
Authors: Brawn Jeffrey D. , Robinson Scott K. , Thompson III Frank R.
Published: July 2002

▪ Abstract  Natural ecological disturbance creates habitats that are used by diverse groups of birds. In North America, these habitats or ecosystems include grasslands or prairies, shrublands, savannas, early successional forests, and floodplains. Whereas the extent of all natural habitats has diminished significantly owing to outright loss from agriculture and development, the suppression of disturbance by agents such as fire and flooding has led to further losses. Accordingly, the abundances of many bird species adapted to disturbance-mediated habitats have declined as well. In North America, these declines have been more severe and common than those of species associated with less frequently disturbed habitats such as mature or closed-canopy forests. Field studies consistently reveal the direct role of disturbance and successional processes in structuring avian habitats and communities. Conservation strategies involving the management of disturbance through some combination of flooding, application of fire, or the expression of wildfire, and use of certain types of silviculture have the potential to diversify avian habitats at the local, landscape, and regional scale. Many aspects of the disturbance ecology of birds require further research. Important questions involve associations between the intensity and frequency of disturbance and the viability of bird populations, the scale of disturbance with respect to the spatial structure of populations, and the role of natural vs. anthropogenic disturbance. The effects of disturbance and ensuing successional processes on birds are potentially long-term, and comprehensive monitoring is essential.
Ecology, Conservation, and Public Policy
Authors: Ludwig Donald , Mangel Marc , Haddad Brent
Published: July 2002

▪ Abstract  A new sense of urgency about environmental problems has changed the relationship between ecology, other disciplines, and public policy. Issues of uncertainty and scientific inference now influence public debate and public policy. Considerations that formerly may have appeared to be mere technicalities now may have decisive influence. It is time to re-examine our methods to ensure that they are adequate for these new requirements. When science is used in support of policy-making, it cannot be separated from issues of values and equity. In such a context, the role of specialists diminishes, because nobody can be an expert in all the aspects of complicated environmental, social, ethical, and economic issues. The disciplinary boundaries that have served science so well in the past are not very helpful in coping with the complex problems that face us today, and ecology now finds itself in intense interaction with a host of other disciplines. The next generation of ecologists must be prepared to interact with such disciplines as history, religion, philosophy, geography, economics, and political science. The requisite training must involve not only words, but core skills in these disciplines. A sense of urgency has affected not only ecology but other disciplines that influence environmental problems: they are undergoing a similar transformation of their outlook and objectives.
CARBON DIOXIDE RECOVERY AND DISPOSAL FROM LARGE ENERGY SYSTEMS
Authors: Herzog H. J. , Drake E. M.
Published: July 2002

▪ Abstract  Increases in greenhouse gas emissions and concerns about potential global climate change are stimulating worldwide interest in the feasibility of capture, disposal, and utilization of CO2 from large energy systems. Technology to capture CO2 from power plant flue gas, while energy intensive and expensive, is commercially available. Capture from advanced combustion systems offers a further opportunity to significantly reduce cost and energy requirements of CO2 capture compared to that from today's pulverized coal power plants. No viable disposal options exist today for large quantities of captured CO2. Ocean disposal of CO2 and geological storage, especially in depleted oil and gas wells, are leading candidates. Although some niche utilization may occur, utilization seems unlikely to become a major sequestration option. Since CO2 capture and sequestration is a relatively expensive mitigation option, it can be regarded as an insurance policy. However, since CO2 mitigation options are few in number, continued research to reduce the costs of CO2 capture and to develop feasible sequestration options is important.
MANAGING MILITARY URANIUM AND PLUTONIUM IN THE UNITED STATES AND THE FORMER SOVIET UNION
Authors: Bunn and Matthew , Holdren John P.
Published: July 2002

▪ Abstract  Effective approaches to the management of plutonium and highly enriched uranium (HEU)—the essential ingredients of nuclear weapons—are fundamental to controlling nuclear proliferation and providing the basis for deep, transparent, and irreversible reductions in nuclear weapons stockpiles. The collapse of the Soviet Union and the ongoing dismantlement of tens of thousands of nuclear weapons are creating unprecedented stresses on the systems for managing these materials, as well as unprecedented opportunities for cooperation to improve these systems. In this article, we summarize the technical background to this situation, and the current and prospective security challenges posed by military stockpiles of these materials in the United States and Russia. We then review the programs in place to address these challenges, the progress of these programs to date, and the work remaining to be done, in five areas: (a) preventing theft and smuggling of nuclear warheads and fissile materials; (b) building a regime of monitored reductions in nuclear warhead and fissile material stockpiles; (c) ending further production of excess fissile materials; (d ) reducing stockpiles of excess fissile materials; and (e) avoiding economic collapse in the nuclear cities where substantial fractions of these materials and their guardians reside.
Rewards and Penalties of Monitoring the Earth
Authors: Keeling Charles D.
Published: July 2002

When I began my professional career, the pursuit of science was in a transition from a pursuit by individuals motivated by personal curiosity to a worldwide enterprise with powerful strategic and materialistic purposes. The studies of the Earth's environment that I have engaged in for over forty years, and describe in this essay, could not have been realized by the old kind of science. Associated with the new kind of science, however, was a loss of ease to pursue, unfettered, one's personal approaches to scientific discovery. Human society, embracing science for its tangible benefits, inevitably has grown dependent on scientific discoveries. It now seeks direct deliverable results, often on a timetable, as compensation for public sponsorship. Perhaps my experience in studying the Earth, initially with few restrictions and later with increasingly sophisticated interaction with government sponsors and various planning committees, will provide a perspective on this great transition from science being primarily an intellectual pastime of private persons to its present status as a major contributor to the quality of human life and the prosperity of nations.
PROSPECTS FORBUILDINGA HYDROGENENERGYINFRASTRUCTURE
Authors: Ogden Joan M.
Published: July 2002

▪ Abstract  About two-thirds of primary energy today is used directly as transportation and heating fuels. Any discussion of energy-related issues, such as air pollution, global climate change, and energy supply security, raises the issue of future use of alternative fuels. Hydrogen offers large potential benefits in terms of reduced emissions of pollutants and greenhouse gases and diversified primary energy supply. Like electricity, hydrogen is a premium-quality energy carrier, which can be used with high efficiency and zero emissions. Hydrogen can be made from a variety of feedstocks, including natural gas, coal, biomass, wastes, solar sources, wind, or nuclear sources. Hydrogen vehicles, heating, and power systems have been technically demonstrated. Key hydrogen end-use technologies such as fuel cells are making rapid progress toward commercialization. If hydrogen were made from renewable or decarbonized fossil sources, it would be possible to have a large-scale energy system with essentially no emissions of pollutants or greenhouse gases. Despite these potential benefits, the development of a large-scale hydrogen energy infrastructure is often seen as an insurmountable technical and economic barrier. Here we review the current status of technologies for hydrogen production, storage, transmission, and distribution; describe likely areas for technological progress; and discuss the implications for developing hydrogen as an energy carrier.
GLOBAL ELECTRIC POWER REFORM, PRIVATIZATION, AND LIBERALIZATION OF THE ELECTRIC POWER INDUSTRY IN DEVELOPING COUNTRIES
Authors: Bacon R. W. , Besant-Jones J.
Published: July 2002

▪ Abstract  This paper reviews the progress of the movement to privatize and liberalize the power sector in developing countries. It reviews the forces driving the movement and then describes the steps that should be taken to achieve success. Data on actual steps taken and preliminary information on the impact of reform are presented. Finally, lessons from this past experience are highlighted.
Indirect Sperm Transfer in Arthropods: Behavioral and Evolutionary Trends
Authors: Proctor H. C.
Published: July 2002

▪ Abstract  Arachnids, myriapods, and wingless hexapods exhibit a fascinating diversity of sperm transfer behaviors. Modes of sperm transfer can be categorized by the degree of contact between male and female during transfer, with direct transfer (copulation) involving the greatest contact, paired-indirect transfer an intermediate degree, and dissociated transfer the least. Internal fertilization, spermatophores, and copulation are sometimes assumed to have evolved after invasion of land, but all have evolved many times in the marine habitat. Behaviors associated with indirect sperm transfer include those having close parallels with direct transfer (provision of nuptial gifts) as well as unique phenomena (spermatophore trampling by rival males). The morphology and physiology of indirectly transferred spermatophores have been shaped by environmental factors (e.g. humidity) as well as biological ones (e.g. clutch size of females), and they may provide useful phylogenetic characters. Unanswered questions about indirect transfer include the following: Are females of dissociated species able to choose their partners? What determines size and number of spermatophores? Do speciation rates differ between taxa with direct versus indirect transfer?
HIGHER-ORDER PREDATORS AND THE REGULATION OF INSECT HERBIVORE POPULATIONS
Authors: Rosenheim Jay A.
Published: July 2002

▪ Abstract  Empirical research has not supported the prediction that populations of terrestrial herbivorous arthropods are regulated solely by their natural enemies. Instead, both natural enemies (top-down effects) and resources (bottom-up effects) may play important regulatory roles. This review evaluates the hypothesis that higher-order predators may constrain the top-down control of herbivore populations. Natural enemies of herbivorous arthropods generally are not top predators within terrestrial food webs. Insect pathogens and entomopathogenic nematodes inhabiting the soil may be attacked by diverse micro- and mesofauna. Predatory and parasitic insects are attacked by their own suite of predators, parasitoids, and pathogens. The view of natural enemy ecology that has emerged from laboratory studies, where natural enemies are often isolated from all elements of the biotic community except for their hosts or prey, may be an unreliable guide to field dynamics.

Experimental work suggests that interactions of biological control agents with their own natural enemies can disrupt the effective control of herbivore populations. Disruption has been observed experimentally in interactions of bacteria with bacteriophages, nematodes with nematophagous fungi, parasitoids with predators, parasitoids with hyperparasitoids, and predators with other predators. Higher-order predators have been little studied; manipulative field experiments will be especially valuable in furthering our understanding of their roles in arthropod communities.
ASSESSMENT OF THE APPLICATION OF BACULOVIRUSES FOR CONTROL OF LEPIDOPTERA
Authors: Moscardi Flávio
Published: July 2002

▪ Abstract  Baculoviruses, among other insect viruses, are regarded as safe and selective bioinsecticides, restricted to invertebrates. They have been used worldwide against many insect pests, mainly Lepidoptera. Their application as microbial pesticides, however, has not met their potential to control pests in crops, forests, and pastures, with the exception of the nuclear polyhedrosis virus of the soybean caterpillar (Anticarsia gemmatalis), which is used on approximately 1 million ha annually in Brazil. Problems that have limited expansion of baculovirus use include narrow host range, slow killing speed, technical and economical difficulties for in vitro commercial production, timing of application based on frequent host population monitoring, variability of field efficacy due to climatic conditions, and farmers' attitudes toward pest control, which have been based on application of fast-killing chemical insecticides. Farmer education regarding use of biological insecticides and their characteristics is considered one of the major actions necessary for increased use of baculoviruses. Strategies to counteract some of the limitations of baculoviruses, especially their slow killing activity, have been investigated and are promising. These include the use of chemical or biological substances added to virus formulations and genetic engineering of the viruses themselves to express insect toxins or hormones. Such strategies can enhance viral activity and increase speed of kill as well as reduce larval feeding activity. The use of baculoviruses against Lepidoptera is reviewed, with the utilization of the nuclear polyhedrosis virus of A. gemmatalis in Brazil serving as a case-study.
THE INSECT VOLTAGE-GATED SODIUM CHANNEL AS TARGET OF INSECTICIDES
Authors: Zlotkin Eliahu
Published: July 2002

▪ Abstract  Examination of the function, chemistry, and pharmacology of the voltage-gated insect sodium channel (ISC) reveals that the ISC closely resembles its vertebrate counterpart in electrophysiology and ion conductance, primary structure and allocation of all functional domains, and its pharmacological diversity and flexibility exhibited by the occurrence of different allosterically coupled receptor-binding sites for various neurotoxicants.

The toxicants include several groups of insecticides, namely DDT and its analogues, pyrethroids, N-alkylamides, and dihydropyrazoles, which affect channel gating and ion permeability.

Despite their similarity, the insect and vertebrate channels are pharmacologically distinguishable, as revealed by the responsiveness of the heterologously expressed Drosophila para clone to channel modifiers and blockers and the occurrence of the insect-selective sodium channel neurotoxins derived from arachnid venoms presently used for the design of recombinant baculovirus-mediated selective bioinsecticides.

The pharmacological specificity of the ISC may lead to the design of insect-selective toxicants, and its pharmacological flexibility may direct the use of ISC insecticides for resistance management. Insecticide resistance [such as knockdown resistance (KDR)] is acquired by natural selection and operated by increased metabolism, channel mutagenesis, or both.

The resistance issue can be dealt with in several ways. One is by simultaneous application of low doses of synergistic, allosterically coupled mixtures (thus delaying or preventing the onset of resistance). An alternative is to replace an insecticide to which resistance was acquired by channel mutation with a different ISC toxicant to which increased susceptibility was conferred by the same mutation. Such a possibility was exemplified by a significant increase in susceptibility to N-alkylamides, as well as an insect-selective neurotoxin revealed by KDR insects. Third, both of these methods can be combined. Thus owing to its pharmacological uniqueness, the ISC may serve as a high-priority target for future selective and resistance-manageable insecticides.
INFLUENCE OF THE LARVAL HOST PLANT ON REPRODUCTIVE STRATEGIES OF CERAMBYCID BEETLES
Authors: Hanks L. M.
Published: July 2002

▪ Abstract  This investigation into the natural history and behavior of 81 species of cerambycid beetles suggests that reproductive behavior is correlated with the condition of the larval host: Adults of species whose larvae attack living trees tend to show behavioral differences from those that attack dying or dead hosts. Behavioral differences among species that are associated with larval host condition include: (a) choice of adult food source and whether adults feed at all; (b) mechanisms of mate location and the role of long-range pheromones; (c) vagility and dispersal behaviors of adults; (d) location of the mating site; and (e) duration of copulation.
Regulation of Diapause
Authors: Denlinger David L.
Published: July 2002

▪ Abstract  Environmental and hormonal regulators of diapause have been reasonably well defined, but our understanding of the molecular regulation of diapause remains in its infancy. Though many genes are shut down during diapause, others are specifically expressed at this time. Classes of diapause-upregulated genes can be distinguished based on their expression patterns: Some are upregulated throughout diapause, and others are expressed only in early diapause, late diapause, or intermittently throughout diapause. The termination of diapause is accompanied by a rapid decline in expression of the diapause-upregulated genes and, conversely, an elevation in expression of many genes that were downregulated during diapause. A comparison of insect diapause with other forms of dormancy in plants and animals suggests that upregulation of a subset of heat shock protein genes may be one feature common to different types of dormancies.
TURBULENCE IN ASTROPHYSICS: Stars
Authors: Canuto V. M. , Christensen-Dalsgaard J.
Published: July 2002

▪ Abstract  Turbulence is ubiquitous in astrophysics, ranging from cosmology, interstellar medium to stars, supernovae, accretion disks, etc. Large scales and small viscosities combine to form large Reynolds numbers. Because it is not possible in a single article to review all the above scenarios, we limit ourselves to stars, in which thermal instabilities give rise to turbulent convection as the dominant heat transport mechanism. (Accretion disks, where shear instabilities dominate the outward transport of angular momentum, will be the subject of a second article, planned for Volume 31.) Because of the lack of a satisfactory theory, turbulence constitutes a bottleneck that prevents astrophysical models from being fully predictive. Because continued use of phenomenological turbulence expressions would make astrophysical models perennially unpredictive, a way must be found to make astrophysical models as prognostic as possible. In addition to the difficulties brought about by turbulence, astrophysical settings introduce “malicious conditions,” of which the most refractory to a satisfactory quantification are compressibility (caused by the large density excursions that characterize convective zones in stars) and rotation. Basic understanding of how they affect turbulence in general is still rather sketchy. Reasons for the choice of stars and accretion disks as prototype examples are the following: The underlying instabilities are very basic; laboratory and direct numerical simulations data help constrain theoretical models; and new observational data, especially from helioseismology, help discriminate among different models with unprecedented accuracy.
Hydrodynamics of Fishlike Swimming
Authors: Triantafyllou M. S. , Triantafyllou G. S. , Yue D. K. P.
Published: July 2002

▪ Abstract  Interest in novel forms of marine propulsion and maneuvering has sparked a number of studies on unsteadily operating propulsors. We review recent experimental and theoretical work identifying the principal mechanism for producing propulsive and transient forces in oscillating flexible bodies and fins in water, the formation and control of large-scale vortices. Connection with studies on live fish is made, explaining the observed outstanding fish agility.
MILTON VAN DYKE, THE MAN AND HIS WORK
Authors: Schwartz Leonard W.
Published: July 2002

I was moved and honored when the Editors of the Annual Review of Fluid Mechanics asked me to write a biography of Professor Van Dyke. I did my Ph.D. with Milton in the Department of Aeronautics and Astronautics at Stanford during the late 1960s and early 1970s. Since the first time that I met him almost 35 years ago, I have admired and respected him as a scientist but also have enjoyed his kindness, modesty, and wit. A few years ago, several of Milton’s students organized a birthday celebration for him. His wife, Sylvia, wrote a biography of him as part of the informal proceedings volume. In writing this article, I have drawn liberally from that biography as well as from other written and oral recollections of Milton.

I also discuss some of Milton’s technical work. The emphasis and perspective on these works is my own, including, of course, any possible misinterpretations. Prior to becoming a full-time graduate student at Stanford, I had worked in the Re-entry Aerodynamics Group at Lockheed Missiles and Space Company in Sunnyvale, California. Thus, I was quite familiar with several of Milton’s papers on supersonic and hypersonic flow. Some of this work and follow-up work by other NACA and NASA scientists was used by us virtually on a daily basis. In addition to Milton’s technical mathematics and fluid mechanics and his personal history, I highlight his extensive “public service” work. These largely unsung contributions bring many benefits to the worldwide fluid mechanics community. Perhaps most obviously, Milton co-founded the Annual Review of Fluid Mechanics more than 30 years ago. He has been the principal guide of this most important repository of our professional knowledge ever since.
HUMAN TYPE 1 DIABETES AND THE INSULIN GENE: Principles of Mapping Polygenes
Authors: Bennett S. T. , Todd J. A.
Published: July 2002

▪ Abstract  We review the strategy used to identify a susceptibility locus (IDDM2) for type 1 (insulin dependent) diabetes mellitus. As type 1 diabetes is becoming the paradigm for dissecting multifactorial disease genetics, the approach described provides important general guidelines for positional cloning of human disease polygenes. Main topics include: (a) historical conspectus of the mapping and identification of IDDM2—a critical survey of the work leading up to the conclusion that IDDM2 most likely corresponds to allelic variation at the insulin gene minisatellite (VNTR) locus; (b) the nature of allelic (length and sequence) variation at the VNTR locus; (c) gene interactions and disease pathogenesis; (d) mechanism of action of the INS VNTR in type 1 diabetes—insulin gene expression, parent-of-origin effects (genomic imprinting); and (e) summary and future prospects—alleles of the insulin VNTR that are protective for type 1 diabetes appear to encode susceptibility to type 2 diabetes.
VIRAL TRANSACTIVATING PROTEINS
Authors: Flint Jane , Shenk Thomas
Published: July 2002

▪ Abstract  Many viruses utilize the cellular transcription apparatus to express their genomes, and they encode transcriptional regulatory proteins that modulate the process. Here we review the current understanding of three viral regulatory proteins. The adenovirus E1A protein acts within the nucleus to regulate transcription through its ability to bind to other proteins. The herpes simplex type 1 virus VP16 protein acts within the nucleus to control transcription by binding to DNA in conjunction with cellular proteins. The human T-cell leukemia virus Tax protein influences transcription through interactions with cellular proteins in the nucleus as well as the cytoplasm.
TARGETING AND ASSEMBLY OF PERIPLASMIC AND OUTER-MEMBRANE PROTEINS IN ESCHERICHIA COLI
Authors: Danese Paul N. , Silhavy Thomas J.
Published: July 2002

▪ Abstract  Escherichia coli must actively transport many of its proteins to extracytoplasmic compartments such as the periplasm and outer membrane. To perform this duty, E. coli employs a collection of Sec (secretion) proteins that catalyze the translocation of various polypeptides through the inner membrane. After translocation across the inner membrane, periplasmic and outer-membrane proteins are folded and targeted to their appropriate destinations. Here we review our knowledge of protein translocation across the inner membrane. We also discuss the various signal transduction systems that monitor extracytoplasmic protein folding and targeting, and we consider how these signal transduction systems may ultimately control these processes.
Fas Ligand-Induced Apoptosis
Authors: Nagata Shigekazu
Published: July 2002

▪ Abstract  The immune response is regulated not only by cell proliferation and differentiation, but also by programmed cell death, or apoptosis. In response to various stimuli, death factors bind to their respective receptors and activate the apoptotic death program in target cells. A cascade of specific proteases termed caspases mediates the apoptotic process. The activated caspases cleave various cellular components, a process that leads to morphological changes of the cells and nuclei, as well as to degradation of the chromosomal DNA. Loss-of-function mutations in the signaling molecules involved in apoptosis cause hyper-proliferation of cells in mouse and human. In contrast, exaggeration of this death cascade causes the destruction of various tissues.
Toward an Integrated Genetic Epidemiology of Parasitic Protozoa and Other pathogens
Authors: Tibayrenc M
Published: July 2002

▪ Abstract  Due to the increase of human migrations, the appearance of emerging and reemerging endemies, growing antibiotic resistance, and climatic changes, infectious diseases most probably constitute the major challenge for medicine in the next century. The advent of molecular methods of pathogen characterization has considerably improved our knowledge of the epidemiology of these diseases. However, the use of concepts of evolutionary genetics for interpreting “molecular epidemiology” data remains limited, although the application of such methods would broaden considerably the scope of this field of research, and allow epidemiologic and taxonomic approaches to be ascertained on a much firmer basis. In turn, pathogens, hosts, and vectors provide fascinating models for basic research. The artificial character of the border between “basic” and “applied” research is especially apparent with regard to the “integrated genetic epidemiology of infectious diseases” concept. The goal of this chapter is to evaluate the respective impact, on the transmission and pathogenicity of infectious diseases, of the host's, the pathogen's, and the vector's (for vector-borne diseases) genetic diversity, and the interactions between these three parameters (coevolution phenomena).