bluuebunny/crossref_metadata_2025 huggingface dataset:
What Can Gauge-Gravity Duality Teach Us About Condensed Matter Physics?
Authors: Sachdev Subir
Published: March 2011

I discuss the impact of gauge-gravity duality on our understanding of two classes of systems: conformal quantum matter and compressible quantum matter.

The first conformal class includes systems, such as the boson Hubbard model in two spatial dimensions, which display quantum critical points described by conformal field theories. Questions associated with nonzero temperature dynamics and transport are difficult to answer using conventional field-theoretic methods. I argue that many of these can be addressed systematically using gauge-gravity duality and discuss the prospects for reliable computation of low-frequency correlations.

Compressible quantum matter is characterized by the smooth dependence of the charge density, associated with a global U(1) symmetry, upon a chemical potential. Familiar examples are solids, superfluids, and Fermi liquids, but there are more exotic possibilities involving deconfined phases of gauge fields in the presence of Fermi surfaces. I survey the compressible systems studied using gauge-gravity duality and discuss their relationship to the condensed matter classification of such states. The gravity methods offer hope of a deeper understanding of exotic and strongly coupled compressible quantum states.
Ice Age Earth Rotation
Authors: Mitrovica Jerry X. , Wahr John
Published: March 2011

Modern predictions of the rotational stability of an ice age Earth reflect a convergence of two classic problems in geophysical analysis—the modeling of the glacial isostatic adjustment (GIA) process and the rotational stability of terrestrial planets. Recent theoretical advances in this area have been motivated not by conventional applications, such as the inference of Earth's deep-mantle viscosity, but rather by efforts to address vexing problems in global climate change research. These advances have demonstrated that traditional calculations of the ongoing motion of the rotation pole relative to the surface geography, or true polar wander (TPW), driven by ice age loading have systematically overestimated this motion by up to a factor of 4 by underestimating by ∼1% the background flattening of Earth's oblate form. The physics of this sensitivity is related to concepts that appear in canonical, mid-twentieth century discussions of Earth rotation, and avoiding the associated inaccuracy resolves numerous perplexing sensitivities evident in previous predictions of ice age TPW. Moreover, these updated predictions provide both an important step in reconciling a recently defined enigma of modern global sea-level rise and a robust framework for analyzing a suite of space-geodetic constraints on Earth's climate system.
Hydrogeology and Mechanics of Subduction Zone Forearcs: Fluid Flow and Pore Pressure
Authors: Saffer Demian M. , Tobin Harold J.
Published: March 2011

At subduction zones, fluid flow, pore pressure, and tectonic processes are tightly interconnected. Excess pore pressure is driven by tectonic loading and fluids released by mineral dehydration, and it has profound effects on fault and earthquake mechanics through its control on effective stress. The egress of these overpressured fluids, which is in part governed by the presence of permeable fault zones, is a primary mechanism of volatile and solute transport to the oceans. Recent field measurements, new constraints gained from laboratory studies, and numerical modeling efforts have led to a greatly improved understanding of these coupled processes. Here, we summarize the current state of knowledge of fluid flow and pore pressure in subduction forearcs, and focus on recent advances that have quantified permeability architecture, fluxes, the nature and timing of transience, and pressure distribution, thus providing new insights into the connections between fluid, metamorphic, mechanical, and fault slip processes.
Optically Stimulated Luminescence Dating of Sediments over the Past 200,000 Years
Authors: Rhodes Edward J.
Published: March 2011

Optical dating of sediment using optically stimulated luminescence has become important for studying Earth surface processes, and this technique continues to develop rapidly. A group of closely linked luminescence methods can be used to estimate the time since grains of quartz and feldspar were last exposed to daylight by detecting their subsequent response to environmental ionizing radiation exposure. The technique is well suited to the dating of deposits as young as one year to several hundred thousand years. Recent technical developments have established a dating protocol with improved precision, a high degree of reliability, and an in-built means to detect incomplete signal removal during deposition. This approach has been extended to age estimation for single grains, opening up a wider range of potential environments and new possibilities for understanding postdepositional grain movement. Ongoing research offers the possibility of significant age range extension and novel applications including low-temperature thermochronology.
A Perspective from Extinct Radionuclides on a Young Stellar Object: The Sun and Its Accretion Disk
Authors: Dauphas Nicolas , Chaussidon Marc
Published: March 2011

Meteorites, which are remnants of solar system formation, provide a direct glimpse into the dynamics and evolution of a young stellar object (YSO), namely our Sun. Much of our knowledge about the astrophysical context of the birth of the Sun, the chronology of planetary growth from micrometer-sized dust to terrestrial planets, and the activity of the young Sun comes from the study of extinct radionuclides such as 26Al (t1/2=0.717 Myr). Here we review how the signatures of extinct radionuclides (short-lived isotopes that were present when the solar system formed and that have now decayed below detection level) in planetary materials influence the current paradigm of solar system formation. Particular attention is given to tying meteorite measurements to remote astronomical observations of YSOs and modeling efforts. Some extinct radionuclides were inherited from the long-term chemical evolution of the Galaxy, others were injected into the solar system by a nearby supernova, and some were produced by particle irradiation from the T-Tauri Sun. The chronology inferred from extinct radionuclides reveals that dust agglomeration to form centimeter-sized particles in the inner part of the disk was very rapid (<50 kyr), planetesimal formation started early and spanned several million years, planetary embryos (possibly like Mars) were formed in a few million years, and terrestrial planets (like Earth) completed their growths several tens of million years after the birth of the Sun.
The Paleocene-Eocene Thermal Maximum: A Perturbation of Carbon Cycle, Climate, and Biosphere with Implications for the Future
Authors: McInerney Francesca A. , Wing Scott L.
Published: March 2011

During the Paleocene-Eocene Thermal Maximum (PETM), ∼56 Mya, thousands of petagrams of carbon were released into the ocean-atmosphere system with attendant changes in the carbon cycle, climate, ocean chemistry, and marine and continental ecosystems. The period of carbon release is thought to have lasted <20 ka, the duration of the whole event was ∼200 ka, and the global temperature increase was 5–8°C. Terrestrial and marine organisms experienced large shifts in geographic ranges, rapid evolution, and changes in trophic ecology, but few groups suffered major extinctions with the exception of benthic foraminifera. The PETM provides valuable insights into the carbon cycle, climate system, and biotic responses to environmental change that are relevant to long-term future global changes.
Building and Destroying Continental Mantle
Authors: Lee Cin-Ty A. , Luffi Peter , Chin Emily J.
Published: March 2011

Continents, especially their Archean cores, are underlain by thick thermal boundary layers that have been largely isolated from the convecting mantle over billion-year timescales, far exceeding the life span of oceanic thermal boundary layers. This longevity is promoted by the fact that continents are underlain by highly melt-depleted peridotites, which result in a chemically distinct boundary layer that is intrinsically buoyant and strong (owing to dehydration). This chemical boundary layer counteracts the destabilizing effect of the cold thermal state of continents. The compositions of cratonic peridotites require formation at shallower depths than they currently reside, suggesting that the building blocks of continents formed in oceanic or arc environments and became “continental” after significant thickening or underthrusting. Continents are difficult to destroy, but refertilization and rehydration of continental mantle by the passage of melts can nullify the unique stabilizing composition of continents.
Learning to Read the Chemistry of Regolith to Understand the Critical Zone
Authors: Brantley Susan L. , Lebedeva Marina
Published: March 2011

The base of the Critical Zone includes the mantle of altered soil and rock—regolith—that changes in response to chemical, physical, and biological processes occurring at Earth's surface. These processes are recorded in the chemistry of the regolith, and this long-term record can often be deciphered. For example, on eroding ridgetops where flows are generally downward for water and upward for earth material, element concentrations vary with depth to constitute depletion, addition, depletion-enrichment, and biogenic profiles. Models can be used to explore the records of mineral dissolution, atmospheric input, coupled dissolution-precipitation, and biolifting documented in these profiles. These models enable interpretation of the effects of time, climate, rates of erosion, and human and other biotic impacts on the profile patterns. By testing quantitative models against the long-term record of information in regolith, we will learn to project changes arising from human and natural perturbations of the Critical Zone.
Plate Tectonics, the Wilson Cycle, and Mantle Plumes: Geodynamics from the Top
Authors: Burke Kevin
Published: March 2011

By 1968, J. Tuzo Wilson had identified three basic elements of geodynamics: plate tectonics, mantle plumes of deep origin, and the Wilson Cycle of ocean opening and closing, which provides evidence of plate tectonic behavior in times before quantifiable plate rotations. My pre-1968 experience disposed me to try to play a part in testing these ideas. Most recently, with colleagues, I have been able to show that deep-seated plumes of the past ∼5.5 × 108 years have risen only from narrow plume generation zones (PGZs) at the core-mantle boundary (CMB) mostly on the edges of two Large Low Shear wave Velocity Provinces (LLSVPs) that have been stable, antipodal, and equatorial in their present positions for hundreds of millions of years and perhaps much longer. A need now is to develop an understanding of Earth that embodies plate tectonics, deeply subducted slabs, and stable LLSVPs with plumes that rise from PGZs on the CMB.
Paleoecologic Megatrends in Marine Metazoa
Authors: Bush Andrew M. , Bambach Richard K.
Published: March 2011

Since their appearance in the Neoproterozoic, marine metazoan ecosystems have increased in ecological diversity, complexity, energy use, motility, predation, infaunality, and biological disturbance. A common theme is an increase in organismal control over internal physiology and the external environment. Often, these changes have been examined in the context of discrete events (e.g., the Cambrian Explosion, Mesozoic Marine Revolution), but they may represent linked, ongoing megatrends. This review examines changes in ecological composition in the context of changes in taxonomic composition, as represented by a more detailed version of Sepkoski's evolutionary fauna analysis. Ecological change occurred during major radiations and extinctions, as well as between them. Due to its ecological selectivity, the Permian-Triassic extinction had particularly significant ecological effects on the biota. Recoveries from mass extinctions may be important episodes of ecological change. Further research could help elucidate the fundamental causes of long-term ecological change, including any role played by the environment.
Rates and Mechanisms of Mineral Carbonation in Peridotite: Natural Processes and Recipes for Enhanced, in situ CO2 Capture and Storage
Authors: Kelemen Peter B. , Matter Juerg , Streit Elisabeth E. , Rudge John F. , Curry William B. , Blusztajn Jerzy
Published: March 2011

Near-surface reaction of CO2-bearing fluids with silicate minerals in peridotite and basalt forms solid carbonate minerals. Such processes form abundant veins and travertine deposits, particularly in association with tectonically exposed mantle peridotite. This is important in the global carbon cycle, in weathering, and in understanding physical-chemical interaction during retrograde metamorphism. Enhancing the rate of such reactions is a proposed method for geologic CO2 storage, and perhaps for direct capture of CO2 from near-surface fluids. We review, synthesize, and extend inferences from a variety of sources. We include data from studies on natural peridotite carbonation processes, carbonation kinetics, feedback between permeability and volume change via reaction-driven cracking, and proposed methods for enhancing the rate of natural mineral carbonation via in situ processes (“at the outcrop”) rather than ex situ processes (“at the smokestack”).
Ecological Lessons from Free-Air CO2 Enrichment (FACE) Experiments
Authors: Norby Richard J. , Zak Donald R.
Published: March 2011

Free-air CO2 enrichment (FACE) experiments have provided novel insights into the ecological mechanisms controlling the cycling and storage of carbon in terrestrial ecosystems and contribute to our ability to project how ecosystems respond to increasing CO2 in the Earth's atmosphere. Important lessons emerge by evaluating a set of hypotheses that initially guided the design and longevity of forested FACE experiments. Net primary productivity is increased by elevated CO2, but the response can diminish over time. Carbon accumulation is driven by the distribution of carbon among plant and soil components with differing turnover rates and by interactions between the carbon and nitrogen cycles. Plant community structure may change, but elevated CO2 has only minor effects on microbial community structure. FACE results provide a strong foundation for next-generation experiments in unexplored ecosystems and inform coupled climate-biogeochemical models of the ecological mechanisms controlling ecosystem response to the rising atmospheric CO2 concentration.
Evolution in the Genus Homo
Authors: Wood Bernard , Baker Jennifer
Published: March 2011

We review the fossil and genetic evidence that relate to evolution in the genus Homo. We focus on the origin of Homo and on the evidence for taxonomic diversity at the beginning of the evolutionary history of Homo and in the last 200,000 years. We set out the arguments for recognizing a second early Homo taxon, Homo rudolfensis, and the arguments for and against including Homo habilis sensu stricto and Homo rudolfensis within Homo. We end by reviewing recent genomic evolution within Homo. The challenge of the upcoming decades is to meld innovations in molecular genetic methods and technology with evidence from the fossil record to generate hypotheses about the developmental bases of the phenotypic and behavioral developments we see within the genus Homo.
Integrated Land-Sea Conservation Planning: The Missing Links
Authors: Álvarez-Romero Jorge G. , Pressey Robert L. , Ban Natalie C. , Vance-Borland Ken , Willer Chuck , Klein Carissa Joy , Gaines Steven D.
Published: March 2011

Spatial management, including setting aside conservation areas, is central to curbing the global decline of biodiversity, but many threats originate from beyond the boundaries of conservation areas. This is a particular problem in marine systems, which are influenced by many activities on land. In addition, connections between land and sea support many species and ecological processes valued for conservation. Integrated land and sea conservation planning is therefore of utmost importance. We review the literature describing connections between land and sea and how they have been incorporated into conservation planning. Land-sea connections include land-sea processes, the natural flows occurring between realms; cross-system threats, which originate in one realm and affect another; and socioeconomic interactions associated with management decisions to maintain or restore land-sea processes and to prevent or mitigate cross-system threats. We highlight the need to explicitly incorporate land-sea connections in conservation planning and suggest ways of doing this through the use of a novel operational framework for integrated land-sea planning. On the basis of expert surveys and a literature review, we also identify those aspects of conservation planning for which improved integration between land and sea is most needed.
Biogeography of the Indo-Australian Archipelago
Authors: Lohman David J. , de Bruyn Mark , Page Timothy , von Rintelen Kristina , Hall Robert , Ng Peter K.L. , Shih Hsi-Te , Carvalho Gary R. , von Rintelen Thomas
Published: March 2011

The extraordinary species richness and endemism of the Indo-Australian Archipelago (IAA) exists in one of the most geologically dynamic regions of the planet. The provenance of its biota has been debated, particularly in the area known as Wallacea. Application of molecular genetic approaches and a better understanding of the region's complex geology have stimulated much recent biogeographic work in the IAA. We review molecular phylogenetic and phylogeographic studies in light of current geological evidence. Present distribution patterns of species have been shaped largely by pre-Pleistocene dispersal and vicariance events, whereas more recent changes in the connectivity of islands within the Archipelago have influenced the partitioning of intraspecific variation. Many genetic studies have uncovered cryptic species with restricted distributions. We discuss the conservation significance of the region and highlight the need for cross-taxon comparative studies using newly developed analytical approaches well suited to the challenges of historical inference in this region.
The Biogeography of Marine Invertebrate Life Histories
Authors: Marshall Dustin J. , Krug Patrick J. , Kupriyanova Elena K. , Byrne Maria , Emlet Richard B.
Published: March 2011

Biologists have long sought to identify and explain patterns in the diverse array of marine life histories. The most famous speculation about such patterns is Gunnar Thorson's suggestion that species producing planktonic larvae are rarer at higher latitudes (Thorson's rule). Although some elements of Thorson's rule have proven incorrect, other elements remain untested. With a wealth of new life-history data, statistical approaches, and remote-sensing technology, new insights into marine reproduction can be generated. We gathered life-history data for more than 1,000 marine invertebrates and examined patterns in the prevalence of different life histories. Systematic patterns in marine life histories exist at a range of scales, some of which support Thorson, whereas others suggest previously unrecognized relationships between the marine environment and the life histories of marine invertebrates. Overall, marine life histories covary strongly with temperature and local ocean productivity, and different regions should be managed accordingly.
Effects of Host Diversity on Infectious Disease
Authors: Ostfeld Richard S. , Keesing Felicia
Published: March 2011

The dynamics of infectious diseases can be affected by genetic diversity within host populations, species diversity within host communities, and diversity among communities. In principle, diversity can either increase or decrease pathogen transmission and disease risk. Theoretical models and laboratory experiments have demonstrated that a dilution effect (decreased disease risk with increasing diversity) can occur under a wide range of conditions. Field studies of plants, aquatic invertebrates, amphibians, birds, and mammals demonstrate that the phenomenon indeed does occur in many natural systems. A dilution effect is expected when (a) hosts differ in quality for pathogens or vectors; (b) higher quality hosts tend to occur in species-poor communities, whereas lower quality hosts tend to occur in more diverse communities; and (c) lower quality hosts regulate abundance of high-quality hosts or of vectors, or reduce encounter rates between these hosts and pathogens or vectors. Although these conditions characterize many disease systems, our ability to predict when and where the dilution effect occurs remains poor. The life-history traits that cause some hosts to be widespread and resilient might be correlated with those that promote infection and transmission by some pathogens, supporting the notion that the dilution effect might be widespread among disease systems. Criticisms of the dilution effect have focused on whether species richness or species composition (both being metrics of biodiversity) drives disease risk. It is well established, however, that changes in species composition correlate with changes in species richness, and this correlation could explain why the dilution effect appears to be a general phenomenon.
Microbially Mediated Plant Functional Traits
Authors: Friesen Maren L. , Porter Stephanie S. , Stark Scott C. , von Wettberg Eric J. , Sachs Joel L. , Martinez-Romero Esperanza
Published: March 2011

Plants are rife with bacteria and fungi that colonize roots and shoots both externally and internally. By providing novel nutritional and defense pathways and influencing plant biochemical pathways, microbes can fundamentally alter plant phenotypes. Here we review the widespread nature of microbially mediated plant functional traits. We highlight that there is likely fitness conflict between hosts and symbionts and that fitness outcomes can depend on partner genotypes and ecological factors. Microbes may influence ecosystems through their effects on the functional trait values and population dynamics of their plant hosts. These effects may feed back on symbiont evolution by altering transmission rates of symbionts and scale up to ecosystem processes and services. We end by proposing new avenues of research in this emerging field.
New Insights into Pelagic Migrations: Implications for Ecology and Conservation
Authors: Costa Daniel P. , Breed Greg A. , Robinson Patrick W.
Published: March 2011

Highly pelagic large marine vertebrates have evolved the capability of moving across large expanses of the marine environment; some species routinely move across entire ocean basins. Our understanding of these movements has been enhanced by new technologies that now allow us to follow their movements over great distances and long time periods in great detail. This technology provides not only detailed information on the movements of a wide variety of marine species, but also detailed characteristics of the habitats they use and clues to their navigation abilities. Advances in electronic tracking technologies have been coupled with rapid development of statistical and analytical techniques. With these developments, conservation of highly migratory species has been aided by providing new information on where uncommon or endangered species go, what behaviors they perform and why, which habitats are critical, and where they range, as well as, in many cases, better estimates of their population size and the interconnectedness of subpopulations. Together these tools are providing critical insights into the ecology of highly pelagic marine vertebrates that are key for their conservation and management.
Phylogenetic Insights on Evolutionary Novelties in Lizards and Snakes: Sex, Birth, Bodies, Niches, and Venom
Authors: Sites Jack W. , Reeder Tod W. , Wiens John J.
Published: March 2011

Squamate reptiles (lizards and snakes) are a diverse clade in which there appear to have been multiple origins of many remarkable traits, including (a) parthenogenetic reproduction, (b) viviparity, (c) snake-like, limb-reduced body form, (d) herbivory, and (e) venom. These repeated transitions make squamates an outstanding/excellent system for addressing many fundamental questions in evolutionary biology. For example, they are the only vertebrate group with true parthenogenesis (with at least 40 separate origins), they have more origins of viviparity than any other group of vertebrates, and they have undergone dramatic changes in body form (lizard-like to snake-like) dozens of times. New molecular phylogenies for squamates have overturned many traditional hypotheses and taxonomies based on morphology and are now revealing exciting new insights into the evolution of many of these traits at both higher and lower taxonomic levels. In this review, we summarize many of these new insights and outline important areas for future research.
Physiological Correlates of Geographic Range in Animals
Authors: Bozinovic Francisco , Calosi Piero , Spicer John I.
Published: March 2011

We evaluate the extent to which physiological tolerances and capacities can be considered as factors that impact the geographic range of animals. We also discuss the importance of understanding how environmental variability interacts with physiological function, concluding with a consideration of how our understanding of physiology in a macroecological context may contribute to our ability to predict the effects of climate change. The extent to which advances have occurred in predicting geographic range through constructing and testing hypotheses involving tolerances, physiological capacities, and plasticity (namely pervasive plasticity, climatic variability, and the Brattstrom hypothesis) is evaluated. Finally, we attempt to integrate our understanding of the interaction between physiology and distribution within current global warming scenarios. We suggest that it may be necessary to evaluate patterns of physiological diversity as a function of different ecological regions oriented to produce mechanistic explanations regarding the likely new (or lack of) physiological responses of animals to altered climatic conditions along geographic ranges.
Toward an Era of Restoration in Ecology: Successes, Failures, and Opportunities Ahead
Authors: Suding Katharine N.
Published: March 2011

As an inevitable consequence of increased environmental degradation and anticipated future environmental change, societal demand for ecosystem restoration is rapidly increasing. Here, I evaluate successes and failures in restoration, how science is informing these efforts, and ways to better address decision-making and policy needs. Despite the multitude of restoration projects and wide agreement that evaluation is a key to future progress, comprehensive evaluations are rare. Based on the limited available information, restoration outcomes vary widely. Cases of complete recovery are frequently characterized by the persistence of species and abiotic processes that permit natural regeneration. Incomplete recovery is often attributed to a mixture of local and landscape constraints, including shifts in species distributions and legacies of past land use. Lastly, strong species feedbacks and regional shifts in species pools and climate can result in little to no recovery. More forward-looking paradigms, such as enhancing ecosystem services and increasing resilience to future change, are exciting new directions that need more assessment. Increased evidence-based evaluation and cross-disciplinary knowledge transfer will better inform a wide range of critical restoration issues such as how to prioritize sites and interventions, include uncertainty in decision making, incorporate temporal and spatial dependencies, and standardize outcome assessments. As environmental policy increasingly embraces restoration, the opportunities have never been greater.
The Patterns and Causes of Variation in Plant Nucleotide Substitution Rates
Authors: Gaut Brandon , Yang Liang , Takuno Shohei , Eguiarte Luis E.
Published: March 2011

Early studies of protein evolution established that evolutionary rates vary among sites, genes, and lineages. Here, we review rate variation within each of these three components, with an emphasis on plant nuclear genes. Evolutionary rates vary among nucleotide sites as a consequence of selection and mutational biases. Mutation varies among sites as a function of the base, its neighboring bases, and its proximity to insertion-deletion polymorphisms. Nonsynonymous rate variation among genes correlates most strongly with gene expression, perhaps owing to selection for translational robustness. Among lineages, perennial plants evolve more slowly than annuals, but the mechanism driving this effect remains unclear. There are also interactions among these three main components; we discuss the patterns of interaction and their significance for understanding the evolutionary forces that shape nucleotide substitution rates in plants. Finally, we highlight gaps in our knowledge and future opportunities to answer fundamental questions in plant molecular evolution.
Rent Seeking and Corruption in Financial Markets
Authors: Khwaja Asim Ijaz , Mian Atif
Published: March 2011

We describe recent advances in the study of rent seeking and corruption in financial markets. We outline three areas of inquiry: (a) conceptualizing rent seeking, (b) identifying rent-provision channels and their general equilibrium impact, and (c) designing feasible remedial mechanisms. We provide suggestions for making further progress in these areas and review a variety of approaches taken in the recent literature.
Bargaining with Optimism
Authors: Yildiz Muhamet
Published: March 2011

Excessive optimism is a prominent explanation for bargaining delays. Recent results demonstrate that optimism plays a subtle role in bargaining, and its careful analysis may shed valuable insights into negotiation behavior. This article reviews some of these results, focusing on the following findings. First, when there is a nearby deadline, optimistic players delay the agreement to the last period before the deadline, replicating a broad empirical regularity known as the deadline effect. Second, there cannot be a substantial delay under persistent optimism; i.e., excessive optimism alone cannot explain delays. Third, when optimistic players are expected to learn during the negotiation, they delay the agreement in order to persuade their opponents. The delays in these results can be quite costly, Pareto inefficient, and common knowledge at the beginning of the game.
Choosing Treatment Policies Under Ambiguity
Authors: Manski Charles F.
Published: March 2011

Economists studying choice with partial knowledge typically assume that the decision maker places a subjective distribution on unknown quantities and maximizes expected utility. Someone lacking a subjective distribution faces a problem of choice under ambiguity. This article reviews recent research on policy choice under ambiguity, when the task is to choose treatments for a population. Ambiguity arises when a planner has partial knowledge of treatment response and does not feel able to place a subjective distribution on the unknowns. I first discuss dominance and alternative criteria for choice among undominated policies. I then illustrate with the choice of a vaccination policy by a planner who has partial knowledge of the effect of vaccination on illness. I next study a class of problems in which a planner may want to cope with ambiguity by diversification, assigning observationally identical persons to different treatments. Lastly, I consider a setting in which a planner should not diversify treatment.
Empirical Models of Consumer Behavior
Authors: Nevo Aviv
Published: March 2011

Models of consumer behavior play a key role in modern empirical industrial organization. In this review, I survey some of the models used in this literature. In particular, I discuss two commonly used demand systems: multistage budgeting approaches and discrete choice models. I motivate their use and highlight some key modeling assumptions. I next briefly discuss key issues of estimation and conclude by summarizing some extensions.
Practical Methods for Estimation of Dynamic Discrete Choice Models
Authors: Arcidiacono Peter , Ellickson Paul B.
Published: March 2011

Many discrete decisions are made with an eye toward how they will affect future outcomes. Formulating and estimating the underlying models that generate these decisions is difficult. Conditional choice probability (CCP) estimators often provide simpler ways to estimate dynamic discrete choice problems. Recent work shows how to frame dynamic discrete choice problems in a way that is conducive to CCP estimation and demonstrates that CCP estimators can be adapted to handle rich patterns of unobserved state variables.
Frictional Matching Models
Authors: Smith Lones
Published: March 2011

This article reviews the developments in frictional matching models from 1990 to 2010, exploring how search frictions skew the matches that occur. This research succeeded by exploiting new tools from monotone methods under uncertainty. Seeing how this journey plays out is instructive in itself for economic theory. The article also describes in detail the different attacks on the existence of equilibrium required for these search and matching models.
Gender and Competition
Authors: Niederle Muriel , Vesterlund Lise
Published: March 2011

Laboratory studies have documented that women often respond less favorably to competition than men. Conditional on performance, men are often more eager to compete, and the performance of men tends to respond more positively to an increase in competition. This means that few women enter and win competitions. We review studies that examine the robustness of these differences as well the factors that may give rise to them. Both laboratory and field studies largely confirm these initial findings, showing that gender differences in competitiveness tend to result from differences in overconfidence and in attitudes toward competition. Gender differences in risk aversion, however, seem to play a smaller and less robust role. We conclude by asking what could and should be done to encourage qualified males and females to compete.
Confronting Prior Convictions: On Issues of Prior Sensitivity and Likelihood Robustness in Bayesian Analysis
Authors: Lopes Hedibert F. , Tobias Justin L.
Published: March 2011

In this review we explore issues of the sensitivity of Bayes estimates to the prior and form of the likelihood. With respect to the prior, we argue that non-Bayesian analyses also incorporate prior information, illustrate that the Bayes posterior mean and the frequentist maximum likelihood estimator are often asymptotically equivalent, review a simple computational strategy for analyzing sensitivity to the prior in practice, and finally document the potentially important role of the prior in Bayesian model comparison. With respect to issues of likelihood robustness, we review a variety of computational strategies for significantly expanding the maintained sampling model, including the use of finite Gaussian mixture models and models based on Dirichlet process priors.
Nonlinear Panel Data Analysis
Authors: Arellano Manuel , Bonhomme Stéphane
Published: March 2011

Nonlinear panel data models arise naturally in economic applications, yet their analysis is challenging. Here we provide a progress report on some recent advances in the area. We start by reviewing the properties of random-effects likelihood approaches. We emphasize a link with Bayesian computation and Markov chain Monte Carlo, which provides a convenient approach to estimation and inference. The relaxation of parametric assumptions on the distribution of individual effects raises serious identification problems. In discrete choice models, common parameters and average marginal effects are generally set identified. The availability of continuous outcomes, however, provides opportunities for point identification. We end by reviewing recent progress on non-fixed-T approaches. In panel applications in which the time dimension is not negligible relative to the size of the cross section, it makes sense to view the estimation problem as a time-series finite-sample bias. Several perspectives to bias reduction are now available. We review their properties, with a special emphasis on random-effects methods.
Life-Cycle Assessment of Electric Power Systems
Authors: Masanet Eric , Chang Yuan , Gopal Anand R. , Larsen Peter , Morrow William R. , Sathre Roger , Shehabi Arman , Zhai Pei
Published: March 2011

The application of life-cycle assessment (LCA) to electric power (EP) technologies is a vibrant research pursuit that is likely to continue as the world seeks ways to meet growing electricity demand with reduced environmental and human health impacts. Although LCA is an evolving methodology with a number of barriers and challenges to its effective use, LCA studies to date have improved our understanding of the life-cycle energy, greenhouse gas emissions, air pollutant emissions, and water-use implications of EP technologies. With continued progress, LCA offers promise for assessing and comparing EP technologies in an analytically thorough and environmentally holistic manner for more robust deployment decisions. This article summarizes (a) current challenges in applying LCA to EP technologies, (b) LCA results to date on various impacts of EP technologies, and (c) opportunities for improving LCAs of EP technologies.
Transportation and the Environment
Authors: Banister David , Anderton Karen , Bonilla David , Givoni Moshe , Schwanen Tim
Published: March 2011

The growth of CO2-intensive transport, mobility and the impact of transport on the environment are reviewed. The recent global exponential growth in transport is unsustainable and must end unless the transport sector can decarbonize. The paper examines solutions for low-carbon transport systems; the behavioral options; possible demand reduction; the role of innovative technologies; and the means by which international agreements on pricing, standards, and regulations can be effectively used. Transport brings enormous benefits to society, and it has been instrumental in the globalization of the world economy, with substantial capital investments in its material infrastructure. Transport governance also needs rethinking to understand the major challenges, to implement major policy changes, and to address the problems of fragmented decision making. Holistic approaches, using ideas from transition management and niche development, are proposed as a framework within which both technological innovation and new patterns of travel and trade can be brought about.
Energy Poverty
Authors: Guruswamy Lakshman
Published: March 2011

The energy poor (EP) encompass between 1.25 billion and 3 billion people who do not have access to beneficial energy for their cooking, illumination, or mechanical needs. Their lives are disfigured by ill health, poverty, lack of education, and underdevelopment. The universally accepted norm of sustainable development (SD) demands that the rest of the world, spearheaded by the rich nations, address the plight of the EP. In a welcome response, the United Nations (UN) has recently embraced the need for universal access to electricity and declared 2012 the “International Year of Sustainable Energy for All” with a focus on providing electricity. Although access to electricity must remain the ultimate objective, the daunting additional costs of electricity, and the time taken to do so—realistically 30 years—will shunt the EP into limbo unless interim measures are also taken. Beneficial energy based on appropriate sustainable energy technologies (ASETs) can provide such intermediate energy. ASETs bridge the gap between capital-intensive electricity and the traditional subsistence technologies of the EP. ASETs demand serious consideration.
Tourism and Environment
Authors: Buckley Ralf
Published: March 2011

Tourism is a large, diffuse global industry. Environmental aspects are little studied, with ∼1,500 publications in total. Impacts range from global contributions to climate change and ocean pollution to localized effects on endangered plant and animal species in protected areas. Environmental management is limited more by lack of adoption than by lack of technology. Government regulation is more effective than industry-based ecocertification. In developing nations, tourism can contribute to conservation by providing political and financial support for public protected area agencies and for conservation on private and communally owned lands. This is important in building resilience to climate change. In developed nations, such effects are outweighed by the impacts of recreational use and by political pressures from tourism property developers. These interactions deserve research in both natural and social sciences. Research priorities include more sophisticated recreation ecology as well as legal and social frameworks for conservation tourism.
Aerosol Impacts on Climate and Biogeochemistry
Authors: Mahowald Natalie , Ward Daniel S. , Kloster Silvia , Flanner Mark G. , Heald Colette L. , Heavens Nicholas G. , Hess Peter G. , Lamarque Jean-Francois , Chuang Patrick Y.
Published: March 2011

Aerosols are suspensions of solid and/or liquid particles in the atmosphere and modify atmospheric radiative fluxes and chemistry. Aerosols move mass from one part of the earth system to other parts of the earth system, thereby modifying biogeochemistry and the snow surface albedo. This paper reviews our understanding of the impacts of aerosols on climate through direct radiative changes, aerosol-cloud interactions (indirect effects), atmospheric chemistry, snow albedo, and land and ocean biogeochemistry. Aerosols play an important role in the preindustrial (natural) climate system and have been perturbed substantially over the anthropocene, often directly by human activity. The most important impacts of aerosols, in terms of climate forcing, are from the direct and indirect effects, with large uncertainties. Similarly large impacts of aerosols on land and ocean biogeochemistry have been estimated, but these have larger uncertainties.
Agency, Capacity, and Resilience to Environmental Change: Lessons from Human Development, Well-Being, and Disasters
Authors: Brown Katrina , Westaway Elizabeth
Published: March 2011

Human agency is considered a key factor in determining how individuals and society respond to environmental change. This article synthesizes knowledge on agency, capacity, and resilience across human development, well-being, and disasters literature to provide insights to support more integrated and human-centered approaches to understanding environmental change. It draws out the key areas of agreement across these diverse fields and identifies the main points of contestation and uncertainty. This highlights the need to consider subjective and relational factors in addition to objective measures of capacity and to view these as reflexive and dynamic, as well as differentiated socially and temporally. These findings can help distinguish between coping, adaptation, and transformation as responses to environmental and other stressors.
Global Forest Transition: Prospects for an End to Deforestation
Authors: Meyfroidt Patrick , Lambin Eric F.
Published: March 2011

Although global rates of tropical deforestation remain alarmingly high, they have decreased over the period 2000–2010, and a handful of tropical developing countries have recently been through a forest transition—a shift from net deforestation to net reforestation. This review synthesizes existing knowledge on the occurrence, causes, and ecological impacts of forest transitions and examines the prospects and policy options for a global forest transition. The ecological quality of forest transitions depends on multiple factors, including the importance of natural forest regeneration versus plantations. Given an increased competition for productive land between different land uses, a global forest transition will require major technological and policy innovations to supply wood and agricultural products. In the globalization era, national strategies aimed at forest protection and sustainable use of forest resources may have unintended effects abroad owing to a displacement of land use across countries. Decisions by consumers combined with certification schemes and moratoriums have an increasing influence on the fate of forests.
Literature and Environment
Authors: Buell Lawrence , Heise Ursula K. , Thornber Karen
Published: March 2011

Since prehistory, literature and the arts have been drawn to portrayals of physical environments and human-environment interactions. The modern environmentalist movement as it emerged first in the late-nineteenth century and, in its more recent incarnation, in the 1960s, gave rise to a rich array of fictional and nonfictional writings concerned with humans' changing relationship to the natural world. Only since the early 1990s, however, has the long-standing interest of literature studies in these matters generated the initiative most commonly known as “ecocriticism,” an eclectic and loosely coordinated movement whose contributions thus far have been most visible within its home discipline of literature but whose interests and alliances extend across various art forms and media. In such areas as the study of narrative and image, ecocriticism converges with its sister disciplines in the humanities: environmental anthropology, environmental history, and environmental philosophy. In the first two sections, we begin with a brief overview of the nature, significance, and evolution of literature-environment studies. We then summarize in more detail six specific centers of interest: (a) the imagination of place and place-attachment, (b) the enlistment and critique of models of scientific inquiry in the study of literature and the arts, (c) the examination of the significance of gender difference and environmental representation, (d) the cross-pollination of ecocritical and postcolonial scholarship as ecocriticism has extended its horizons beyond its original focus on Anglo-American imagination, (e) ecocriticism's evolving interest in indigenous art and thought, and (f) ecocri-ticism's no less keen and complex attentiveness to artistic representation and the ethics of relations between humans and animals.
Consumption-Based Asset Pricing Models
Authors: Mehra Rajnish
Published: March 2011

A major research initiative in finance focuses on the determinants of the cross-sectional and time series properties of asset returns. With that objective in mind, asset pricing models have been developed, starting with the capital asset pricing models of Sharpe (1964), Lintner (1965), and Mossin (1966). Consumption-based asset pricing models use marginal rates of substitution to determine the relative prices of the date, event-contingent, composite consumption good. This model class is characterized by a stochastic discount factor process that puts restrictions on the joint process of asset returns and per capita consumption. This review takes a critical look at this class of models and their inability to rationalize the statistics that have characterized US financial markets over the past century. The intuition behind the discrepancy between model prediction and empirical data is explained. Finally, the research efforts to enhance the model's ability to replicate the empirical data are summarized.