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Environment

Distribution by Scientific Domains
Life Sciences27%
Medical Sciences14%
Humanities and Social Sciences12%
Chemistry8%
Business, Economics, Finance and Accounting7%
Earth and Environmental Science7%
Engineering6%
Information Science and Computing3%
Psychology2%
Polymers and Materials Science2%
Education2%
3 Other Domains10%
Distribution within Life Sciences
Ecology & Organismal Biology14%
Evolution7%
53 Other Subdomains72%

Kinds of Environment

  • abiotic environment
  • academic environment
  • acidic environment
  • acoustic environment
  • adverse environment
  • agricultural environment
  • air environment
  • alkaline environment
  • alpine environment
  • ambient environment
  • and the environment
  • anisotropic environment
  • anoxic environment
  • arid environment
  • artificial environment
  • atmospheric environment
  • atomic environment
  • basic environment
  • biological environment
  • biotic environment
  • bipyramidal environment
  • build environment
  • built environment
  • business environment
  • care environment
  • caregiving environment
  • cell environment
  • cellular environment
  • challenging environment
  • changing environment
  • chemical environment
  • child environment
  • childhood environment
  • chiral environment
  • chloride environment
  • choice environment
  • climatic environment
  • clinical environment
  • clinical learning environment
  • closed environment
  • cluster environment
  • co2 environment
  • coastal environment
  • coastal marine environment
  • cold environment
  • colder environment
  • collaborative virtual environment
  • combustion environment
  • common environment
  • communication environment
  • competitive environment
  • complex environment
  • computational environment
  • computing environment
  • confined environment
  • constant environment
  • contrasting environment
  • control environment
  • controlled environment
  • coordination environment
  • corporate environment
  • corrosive environment
  • critical care environment
  • crystalline environment
  • cultural environment
  • culture environment
  • current environment
  • cytokine environment
  • dense environment
  • depositional environment
  • desert environment
  • design environment
  • deterministic environment
  • development environment
  • different coordination environment
  • different environment
  • different light environment
  • digital environment
  • distinct environment
  • distorted octahedral environment
  • distributed environment
  • disturbed environment
  • diverse environment
  • domestic environment
  • dry environment
  • dynamic environment
  • e-learning environment
  • early environment
  • ecological environment
  • economic environment
    		•
  • education environment
  • educational environment
  • enabling environment
  • enriched environment
  • erp environment
  • estuarine environment
  • experimental environment
  • external environment
  • extracellular environment
  • extreme environment
  • fading environment
  • familiar environment
  • family environment
  • farming environment
  • favourable environment
  • feeding environment
  • field environment
  • financial environment
  • fire environment
  • fire-prone environment
  • floodplain environment
  • fluctuating environment
  • fluvial environment
  • food environment
  • foraging environment
  • forest environment
  • freshwater environment
  • gastrointestinal environment
  • geographical environment
  • geological environment
  • geothermal environment
  • gi environment
  • glacial environment
  • global environment
  • grid environment
  • group environment
  • growth environment
  • harsh environment
  • hatchery environment
  • health and the environment
  • health care environment
  • healthcare environment
  • heterogeneous environment
  • high-altitude environment
  • high-risk environment
  • high-tech environment
  • home environment
  • homogeneous environment
  • hormonal environment
  • hospital environment
  • host environment
  • hostile environment
  • hot environment
  • human environment
  • humid environment
  • hydrodynamic environment
  • hydrophobic environment
  • hydrothermal environment
  • hypersaline environment
  • hypogean environment
  • hypoxic environment
  • ideal environment
  • immediate environment
  • immersive virtual environment
  • incubation environment
  • indoor environment
  • industrial environment
  • inert environment
  • inflammatory environment
  • information environment
  • institutional environment
  • interactive environment
  • internal environment
  • international environment
  • intestinal environment
  • intracellular environment
  • intrauterine environment
  • ionic environment
  • laboratory environment
  • lacustrine environment
  • lake environment
  • large-scale environment
  • learning environment
  • legal environment
  • life environment
  • ligand environment
  • light environment
  • lipid environment
  • liquid environment
  • loading environment
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  • local atomic environment
  • local environment
  • low-oxygen environment
  • macroeconomic environment
  • managed care environment
  • manufacturing environment
  • marine environment
  • market environment
  • marketing environment
  • maternal environment
  • mechanical environment
  • media environment
  • medical environment
  • mediterranean environment
  • membrane environment
  • metabolic environment
  • micellar environment
  • microbial environment
  • modern environment
  • moist environment
  • molecular environment
  • mountain environment
  • multiple environment
  • native environment
  • natural environment
  • neighborhood environment
  • neighbourhood environment
  • network environment
  • new environment
  • nitrogen environment
  • noisy environment
  • non-marine environment
  • normal environment
  • northern environment
  • novel environment
  • nursing practice environment
  • nutrient environment
  • nutritional environment
  • obesogenic environment
  • occupational environment
  • octahedral coordination environment
  • octahedral environment
  • office environment
  • online environment
  • online learning environment
  • operating environment
  • operational environment
  • optimal environment
  • oral environment
  • organisational environment
  • organizational environment
  • osmotic environment
  • other environment
  • outdoor environment
  • oxidizing environment
  • particular environment
  • patchy environment
  • patient environment
  • pelagic environment
  • periglacial environment
  • ph environment
  • physical environment
  • physiological environment
  • plasma environment
  • polar environment
  • policy environment
  • political environment
  • positive work environment
  • postnatal environment
  • practice environment
  • problem-solving environment
  • processing environment
  • production environment
  • programming environment
  • propagation environment
  • protein environment
  • psychosocial work environment
  • quality environment
  • r&d environment
  • random environment
  • reaction environment
  • real environment
  • reality environment
  • rearing environment
  • reducing environment
  • reef environment
  • regional environment
  • regulatory environment
  • research environment
  • resource environment
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  • retail environment
  • rich environment
  • riparian environment
  • riverine environment
  • rural environment
  • safe environment
  • saline environment
  • same environment
  • sample environment
  • school environment
  • seasonal environment
  • secure environment
  • security environment
  • sedimentary environment
  • selective environment
  • semi-arid environment
  • semi-arid mediterranean environment
  • semiarid environment
  • sensory environment
  • service environment
  • several environment
  • shallow marine environment
  • shared environment
  • shelf environment
  • shopping environment
  • similar environment
  • simulation environment
  • single environment
  • social environment
  • software environment
  • soil environment
  • space environment
  • specific environment
  • square-pyramidal environment
  • stable environment
  • stochastic environment
  • strategic environment
  • stream environment
  • stress environment
  • stressed environment
  • stressful environment
  • subsurface environment
  • subtropical environment
  • suitable environment
  • supportive environment
  • surface environment
  • surrounding environment
  • sustainable built environment
  • task environment
  • teaching environment
  • technological environment
  • tectonic environment
  • temperate environment
  • terrestrial environment
  • test environment
  • tetrahedral environment
  • the environment
  • thermal environment
  • three-dimensional environment
  • tissue environment
  • training environment
  • tropical environment
  • tundra environment
  • uncertain environment
  • unfamiliar environment
  • unique environment
  • university environment
  • unpredictable environment
  • unstable environment
  • urban environment
  • variable environment
  • various environment
  • virtual environment
  • virtual learning environment
  • virtual reality environment
  • visual environment
  • vitro environment
  • vivo environment
  • ward environment
  • warm environment
  • water environment
  • wet environment
  • wireless environment
  • work environment
  • workplace environment
  • wound environment
  • xeric environment

    • Terms modified by Environment

  • environment agency
  • environment canada
  • environment chamber
  • environment change
  • environment characteristic
  • environment condition
  • environment conducive
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  • environment consisting
  • environment correlation
  • environment effects
  • environment factor
  • environment interaction
  • environment interplay
  • environment issues
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  • environment lead
  • environment measure
  • environment present
  • environment programme
  • environment relationships
  • environment scale
  • environment similar
    		•
  • environment studies
  • environment suitable
  • environment used
  • environment variable

    • Selected Abstracts

    PLANNING FOR A NATURAL HISTORY MUSEUM IN A UNIVERSITY ENVIRONMENT: A CASE STUDY

    CURATOR THE MUSEUM JOURNAL, Issue 2 2000
    Scott M. Lanyon
    First page of article [source]

    SAVING OUR ENVIRONMENT FROM WASHINGTON: HOW CONGRESS GRABS POWER, SHIRKS RESPONSIBILITY, AND SHORTCHANGES THE PEOPLE by David Schoenbrod

    ECONOMIC AFFAIRS, Issue 2 2006
    Yelena ShagallArticle first published online: 1 JUN 200
    No abstract is available for this article. [source]

    THE REGULATION OF LIFE ASSURERS IN A LOW SOLVENCY ENVIRONMENT: THE UK EXPERIENCE

    ECONOMIC AFFAIRS, Issue 3 2003
    Chris O'Brien
    When adverse financial conditions mean that many life assurers have sharply reduced solvency levels, a number of new issues arise for regulators, including the basic issue of how solvency is measured. There are also issues about life assurers' investments, and their products and how they are priced. Lastly, the regulator (in the UK, the Financial Services Authority) needs to ensure that customers and their advisers have suitable information about the solvency of the firms they are dealing with. [source]

    IS INEQUALITY HARMFUL FOR THE ENVIRONMENT IN A GROWING ECONOMY?

    ECONOMICS & POLITICS, Issue 1 2007
    HUBERT KEMPF
    In this paper, we investigate the relationship between inequality and the environment in a growing economy from a political-economy perspective. We consider an endogenous growth economy, where growth generates pollution and a deterioration of the environment. Public expenditures may either be devoted to supporting growth or abating pollution. The decision over the public programs is made in a direct democracy, with simple majority rule. We prove that the median voter is decisive and show that inequality is harmful for the environment: the poorer the median voter relative to the average individual, the less she will tax and devote resources to the environment, preferring to support growth. [source]

    A COMPARATIVE METHOD FOR STUDYING ADAPTATION TO A RANDOMLY EVOLVING ENVIRONMENT

    EVOLUTION, Issue 8 2008
    Thomas F. Hansen
    Most phylogenetic comparative methods used for testing adaptive hypotheses make evolutionary assumptions that are not compatible with evolution toward an optimal state. As a consequence they do not correct for maladaptation. The "evolutionary regression" that is returned is more shallow than the optimal relationship between the trait and environment. We show how both evolutionary and optimal regressions, as well as phylogenetic inertia, can be estimated jointly by a comparative method built around an Ornstein,Uhlenbeck model of adaptive evolution. The method considers a single trait adapting to an optimum that is influenced by one or more continuous, randomly changing predictor variables. [source]

    CONCORDANCE OF THE CIRCADIAN CLOCK WITH THE ENVIRONMENT IS NECESSARY TO MAXIMIZE FITNESS IN NATURAL POPULATIONS

    EVOLUTION, Issue 4 2008
    Kevin J. Emerson
    The ubiquity of endogenous, circadian (daily) clocks among eukaryotes has long been held as evidence that they serve an adaptive function, usually cited as the ability to properly time biological events in concordance with the daily cycling of the environment. Herein we test directly whether fitness is a function of the matching of the period of an organism's circadian clock with that of its environment. We find that fitness, measured as the per capita expectation of future offspring, a composite measure of fitness incorporating both survivorship and reproduction, is maximized in environments that are integral multiples of the period of the organism's circadian clock. Hence, we show that organisms require temporal concordance between their internal circadian clocks and their external environment to maximize fitness and thus the long-held assumption is true that, having evolved in a 24-h world, circadian clocks are adaptive. [source]

    THE EFFECTS OF GENOTYPE, AGE, AND SOCIAL ENVIRONMENT ON MALE ORNAMENTATION, MATING BEHAVIOR, AND ATTRACTIVENESS

    EVOLUTION, Issue 11 2005
    Lisa K. Miller
    Abstract The traits thought to advertise genetic quality are often highly susceptible to environmental variation and prone to change with age. These factors may either undermine or reinforce the potential for advertisement traits to signal quality depending on the magnitude of age-dependent expression, environmental variation, and genotype-age and genotype-environment interaction. Measurements of the magnitude of these effects are thus a necessary step toward assessing the implications of age dependence and environmental variability for the evolution of signals of quality. We conducted a longitudinal study of male guppies (Poecilia reticulata) from 22 full-sibling families. Each fish was assigned at maturity to one of three treatments in order to manipulate his allocation of resources to reproduction: a control in which the male was kept alone, a courtship-only treatment in which he could see and court a female across a clear partition, and a mating treatment in which he interacted freely with a female. We measured each male's size, ornamental color patterns, courtship, attractiveness to females, and mating success at three ages. Size was influenced by treatment and age-treatment interactions, indicating that courtship and mating may impose costs on growth. Tail size and color patterns were influenced by age but not by treatment, suggesting fixed age-dependent trajectories in these advertisement traits. By contrast, display rate and attempted sneak copulation rate differed among treatments but not among ages, suggesting greater plasticity of these behavioral traits. As a result of the different patterns of variation in ornamentation and behavior, male attractiveness and mating success responded to male age, treatment, and the interaction between age and treatment. Neither age nor treatment obscured the presence of genetic variation, and the genetic relationship between male ornamentation and attractiveness remained the same among treatments. Our findings suggest that neither age-dependent variation nor environmentally induced variation in reproductive effort is likely to undermine the reliability of male signaling. [source]

    INCREASED RATES OF MOLECULAR EVOLUTION IN AN EQUATORIAL PLANT CLADE: AN EFFECT OF ENVIRONMENT OR PHYLOGENETIC NONINDEPENDENCE?

    EVOLUTION, Issue 1 2005
    Jeremy M. Brown
    Abstract A recent study of environmental effects on rates of molecular evolution in the plant subgenus Mearnsia shows that species occurring in more equatorial latitudes have higher rates of substitution in rDNa sequences as compared to their more southerly congeners (Wright et al. 2003). However, we believe that the statistical approach employed by Wright et al. (2003) insufficiently accounts for the phylogenetic nonindependence of the species examined, given that all six equatorial species of Mearnsia form a clade. To distinguish between the effect of latitude and that of phylogenetic nonindependence, we have employed a variety of comparative approaches that use independent contrasts to test for an effect of environment across this entire subgenus. We find very little evidence for an effect of latitude on rate of molecular evolution using these approaches and believe that the shared evolutionary history of the clade is a plausible explanation of the apparent rate difference between equatorial and subequatorial Mearnsia species. [source]

    INTEGRATED LANDSCAPE ANALYSES OF CHANGE OF MIOMBO WOODLAND IN TANZANIA AND ITS IMPLICATION FOR ENVIRONMENT AND HUMAN LIVELIHOOD

    GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 1 2009
    LENNART STRÖMQUIST
    ABSTRACT. Landscapes bear witness to past and present natural and societal processes influencing the environment and human livelihoods. By analysing landscape change at different spatial scales over time the effects on the environment and human livelihoods of various external and internal driving forces of change can be studied. This paper presents such an analysis of miombo woodland surrounding the Mkata plains in central Tanzania. The rich natural landscape diversity of the study area in combination with its historical and political development makes it an ideal observation ground for this kind of study. The paper focuses on long-term physical and biological changes, mainly based on satellite information but also on field studies and a review of documents and literature. The miombo woodlands are highly dynamic semi-arid ecosystems found on a number of nutrient-poor soil groups. Most of the woodlands are related to an old, low-relief geomorphology of erosion surfaces with relatively deep and leached soils, or to a lesser extent also on escarpments and steep Inselberg slopes with poor soils. Each period in the past has cast its footprints on the landscape development and its potential for a sustainable future use. On a regional level there has been a continual decrease in forest area over time. Expansion of agriculture around planned villages, implemented during the 1970s, in some cases equals the loss of forest area (Mikumi-Ulaya), whilst in other areas (Kitulangalo), the pre-independence loss of woodland was small; the agricultural area was almost the same during the period 1975,1999, despite the fact that forests have been lost at an almost constant rate over the same period. Illegal logging and charcoal production are likely causes because of the proximity to the main highway running through the area. Contrasting to the general regional pattern are the conditions in a traditional village (Ihombwe), with low immigration of people and a maintained knowledge of the resource potential of the forest with regards to edible plants and animals. In this area the local community has control of the forest resources in a Forest Reserve, within which the woody vegetation has increased in spite of an expansion of agriculture on other types of village land. The mapping procedure has shown that factors such as access to transport and lack of local control have caused greater deforestation of certain areas than during the colonial period. Planned villages have furthermore continued to expand over forest areas well after their implementation, rapidly increasing the landscape fragmentation. One possible way to maintain landscape and biodiversity values is by the sustainable use of traditional resources, based on local knowledge of their management as illustrated by the little change observed in the traditionally used area. [source]

    ROCK-SURFACE TEMPERATURES OF BASALT IN THE DRAKENSBERG ALPINE ENVIRONMENT, LESOTHO

    GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 3 2007
    STEFAN GRAB
    ABSTRACT. Rock temperature data are presented for a variety of topographic localities at a high Drakensberg site. The objective is to investigate the spatiotemporal variations of surface rock temperatures in high Drakensberg basalt. The temperature results are then used to discuss possible implications for thermal stress fatigue and frost-induced weathering. TinytalkÔ data loggers and probes were used for rock-surface temperature recording. Long-term measurements were recorded over 12 months from May 2002 to April 2003, at a 1-hour logging interval and rock depth of 1 cm for a highaltitude (3300 m a.s.l.) interfluve and fracture site. Whilst the north-facing rock surface experiences negligible hours below ,3°C, the south-facing rock surface and interfluve sites are subjected to considerable periods below ,3°C, which falls within the ,frost cracking window'. It is concluded that the substantial contrasts of recorded rock thermal parameters over small spatial scales between various topographic settings, highlight that site-specific measurements across the broader scale are required for an adequate evaluation of regional weathering and its associated landform development. [source]

    ENVIRONMENT: Great Green Wall

    AFRICA RESEARCH BULLETIN: ECONOMIC, FINANCIAL AND TECHNICAL SERIES, Issue 6 2010
    Article first published online: 3 AUG 2010
    No abstract is available for this article. [source]

    DEPOSITIONAL ENVIRONMENT AND DIAGENESIS OF THE EOCENE JDEIR FORMATION, GABES-TRIPOLI BASIN, WESTERN OFFSHORE, LIBYA

    JOURNAL OF PETROLEUM GEOLOGY, Issue 4 2000
    J. M. Anketell
    The late Ypresian (early Eocene) Jdeir Formation was deposited in the Mesozoic-Cenozoic Gabes-Tripoli Basin, offshore Libya. The basin developed on the northern passive margin of the African Plate and was relatively unstable being affected by syn-sedimentary tectonic movements. Deposition was coeval with a relative rise of sea-level and the subsequent highstand. A lower, thinly-developed nummulitic bank facies with restricted distribution records the transgressive event and is succeeded by more micritic sediments that record the time of maximum flooding. The succeeding sea-level highstand is represented by a thick, and widely developed, progradational-aggradational nummulitic sequence that displays lateral changes across WE-ESE trending facies belts. Three major lithofacies are recognized in the Jdeir Formation: Nummulites packstone-grainstone, Alveolina-Orbitoliteswackestone-packtone, andFragmental-Discocyclina-Assilina wackestone-packstone, depositedin bank, back-bank, and fore-bank environments, respectively. The formation passes to the NNE into the pelagic lithofacies of the Hallab Formation; landward, to the south, it passes into shoreline evaporitic facies of the Taljah Formation. The lithofacies were structurally controlled by contemporaneous and/or syndepositional tectonic movements, with nummulitic facies tending to develop on uplifted areas. Petrographic and petrophysical studies indicate that porosity in the Jdeir Formation is controlled by depositional environment, tectonic setting and diagenesis. The combined effects of salt tectonics, a major unconformity at the top of the formation and meteoric diagenesis have produced excellent-quality reservoir facies at the Bouri oilfield and in other areas. Porosity is highest in the nummulitic bank facies and lowest in the Alveolina-Orbitolites micrite facies. Good to excellent reservoir quality occurs in the upper part of the nummulitic packstone-grainstone facies, especially where these sediments overlie structurally high areas. High rates of dissolution found at the crests of domes and anticlines suggest that early diagenetic processes and features are, in part, structurally controlled. Future exploration success will depend on investigation of similar structures within the Gabes-Tripoli Basin. Both porosity initiation and preservation are related to early depositional and diagenetic processes. The wide time-gap between hydrocarbon generation and reservoir formation points to the role of the seal in porosity preservation and rules out the assumption that early emplacement of oil had preserved the porosity. [source]

    RENEWING PEOPLE AND PLACES: INSTITUTIONAL INVESTMENT POLICIES THAT ENHANCE SOCIAL CAPITAL AND IMPROVE THE BUILT ENVIRONMENT OF DISTRESSED COMMUNITIES

    JOURNAL OF URBAN AFFAIRS, Issue 5 2006
    REX L. LAMORE
    ABSTRACT:,The challenges confronting distressed communities in the United States are complex and multifaceted. Communities large and small have been significantly affected by a myriad of social, environmental, and economic forces, including a continuing decline in manufacturing employment, uncontrolled sprawl, and the transition to a global economy. The traditional choice between a "place-based" theory of redevelopment strategy versus a "people-focused" theory no longer seems feasible or appropriate. This article outlines sustainable development as an alternative strategy that combines a place-based development strategy, a human development focus, and an environmentally mindful approach. It posits that there exists a direct positive relationship between the creation of social capital, the redevelopment of the built environment utilizing sustainable development practices, and community-based organizations in distressed communities. Furthermore, the authors suggest that through community investment,a socially responsible investment strategy,institutions of higher education can facilitate the rebuilding of communities by providing financial capital while gaining a moderate yet secure financial return as well as a substantial social return. [source]

    FOREIGN INVESTMENT POLICIES AND ENVIRONMENT

    NATURAL RESOURCE MODELING, Issue 2 2005
    HAMID BELADI
    ABSTRACT. We consider a North-South model of capital mobility in which foreign investment adversely impacts the environment in South. By focusing on the strategic aspects of environmental policies, among other things, we compare different policy regimes, i.e., different combinations of tax and quota. More specifically, we investigate the (non)equivalence of these policy regimes. [source]

    CONSTANT EFFORT AND CONSTANT QUOTAFISHING POLICIES WITH CUT-OFFS IN A RANDOM ENVIRONMENT

    NATURAL RESOURCE MODELING, Issue 2 2001
    CARLOS A. BRAUMANN
    ABSTRACT. Consider a population subjected to constant effort or constant quota fishing with a generaldensity-dependence population growth function (because that function is poorly known). Consider environmental random fluctuations that either affect an intrinsic growth parameter or birth/death rates, thus resulting in two stochastic differential equations models. From previous results of ours, we obtain conditions for non-extinction and for existence of a population size stationary density. Constant quota (which always leads to extinction in random environments) and constant effort policies are studied; they are hard to implement for extreme population sizes. Introducing cut-offs circumvents these drawbacks. In a deterministic environment, for a wide range of values, cutting-off does not affect the steady-state yield. This is not so in a random environment and we will give expressions showing how steady-state average yield and population size distribution vary as functions of cut-off choices. We illustrate these general results with function plots for the particular case of logistic growth. [source]

    TOWARDS A MORE FACILITATING PEER ENVIRONMENT,

    THE INTERNATIONAL JOURNAL OF PSYCHOANALYSIS, Issue 4 2001
    David Tuckett
    First page of article [source]

    THE POTENTIAL OF CARBONIZED GRAIN TO PRESERVE BIOGENIC 87SR/86SR SIGNATURES WITHIN THE BURIAL ENVIRONMENT*

    ARCHAEOMETRY, Issue 2 2009
    A. HEIER
    Carbonized grains survive for millennia in many archaeological contexts. Their stable structure raises the possibility that they preserve biogenic strontium isotope signatures. This hypothesis was investigated using short-term, laboratory experiments with modern grain immersed in Chalk solution. HCl leaching removed > 95% of secondary alteration from charred grain, and isotope ratios close to the starting value were recovered. This could not be achieved with uncharred grains. HCl leaching of archaeological carbonized grains produced comparable levels of decontamination. Although preliminary, these results suggest that strontium isotope analysis of archaeological carbonized grains from calcareous burial contexts could be used to investigate ancient trade and agriculture. [source]

    [Commentary] GENETICALLY INFORMATIVE STUDIES OF ,ENVIRONMENT'

    ADDICTION, Issue 3 2009
    MICHAEL T. LYNSKEY
    No abstract is available for this article. [source]

    PLANNING IN REACTIVE ENVIRONMENTS

    COMPUTATIONAL INTELLIGENCE, Issue 4 2007
    A. Milani
    The diffusion of domotic and ambient intelligence systems have introduced a new vision in which autonomous deliberative agents operate in environments where reactive responses of devices can be cooperatively exploited to fulfill the agent's goals. In this article a model for automated planning in reactive environments, based on numerical planning, is introduced. A planner system, based on mixed integer linear programming techniques, which implements the model, is also presented. The planner is able to reason about the dynamic features of the environment and to produce solution plans, which take into account reactive devices and their causal relations with agent's goals by exploitation and avoidance techniques, to reach a given goal state. The introduction of reactive domains in planning poses some issues concerning reasoning patterns which are briefly depicted. Experiments of planning in reactive domains are also discussed. [source]

    TAIL SHEDDING IN ISLAND LIZARDS [LACERTIDAE, REPTILIA]: DECLINE OF ANTIPREDATOR DEFENSES IN RELAXED PREDATION ENVIRONMENTS

    EVOLUTION, Issue 5 2009
    Panayiotis Pafilis
    The ability of an animal to shed its tail is a widespread antipredator strategy among lizards. The degree of expression of this defense is expected to be shaped by prevailing environmental conditions including local predation pressure. We test these hypotheses by comparing several aspects of caudal autotomy in 15 Mediterranean lizard taxa existing across a swath of mainland and island localities that differ in the number and identity of predator species present. Autotomic ease varied substantially among the study populations, in a pattern that is best explained by the presence of vipers. Neither insularity nor the presence of other types of predators explain the observed autotomy rates. Final concentration of accumulated tail muscle lactate and duration of movement of a shed tail, two traits that were previously thought to relate to predation pressure, are in general not shaped by either predator diversity or insularity. Under conditions of relaxed predation selection, an uncoupling of different aspects of caudal autotomy exists, with some elements (ease of autotomy) declining faster than others (duration of movement, lactate concentration). We compared rates of shed tails in the field against rates of laboratory autotomies conducted under standardized conditions and found very high correlation values (r > 0.96). This suggests that field autotomy rates, rather than being a metric of predatory attacks, merely reflect the innate predisposition of a taxon to shed its tail. [source]

    SELECTION IN HETEROGENEOUS ENVIRONMENTS MAINTAINS THE GENE ARRANGEMENT POLYMORPHISM OF DROSOPHILA PSEUDOOBSCURA

    EVOLUTION, Issue 12 2008
    Stephen W. Schaeffer
    Chromosomal rearrangements may play an important role in how populations adapt to a local environment. The gene arrangement polymorphism on the third chromosome of Drosophila pseudoobscura is a model system to help determine the role that inversions play in the evolution of this species. The gene arrangements are the likely target of strong selection because they form classical clines across diverse geographic habitats, they cycle in frequency over seasons, and they form stable equilibria in population cages. A numerical approach was developed to estimate the fitness sets for 15 gene arrangement karyotypes in six niches based on a model of selection,migration balance. Gene arrangement frequencies in the six different niches were able to reach a stable meta-population equilibrium that matched the observed gene arrangement frequencies when recursions used the estimated fitnesses with a variety of initial inversion frequencies. These analyses show that a complex pattern of selection is operating in the six niches to maintain the D. pseudoobscura gene arrangement polymorphism. Models of local adaptation predict that the new inversion mutations were able to invade populations because they held combinations of two to 13 local adaptation loci together. [source]

    COEVOLUTION DRIVES TEMPORAL CHANGES IN FITNESS AND DIVERSITY ACROSS ENVIRONMENTS IN A BACTERIA,BACTERIOPHAGE INTERACTION

    EVOLUTION, Issue 8 2008
    Samantha E. Forde
    Coevolutionary interactions are thought to play a crucial role in diversification of hosts and parasitoids. Furthermore, resource availability has been shown to be a fundamental driver of species diversity. Yet, we still do not have a clear understanding of how resource availability mediates the diversity generated by coevolution between hosts and parasitoids over time. We used experiments with bacteria and bacteriophage to test how resources affect variation in the competitive ability of resistant hosts and temporal patterns of diversity in the host and parasitoid as a result of antagonistic coevolution. Bacteria and bacteriophage coevolved for over 150 bacterial generations under high and low-resource conditions. We measured relative competitive ability of the resistant hosts and phenotypic diversity of hosts and parasitoids after the initial invasion of resistant mutants and again at the end of the experiment. Variation in relative competitive ability of the hosts was both time- and environment-dependent. The diversity of resistant hosts, and the abundance of host-range mutants attacking these phenotypes, differed among environments and changed over time, but the direction of these changes differed between the host and parasitoid. Our results demonstrate that patterns of fitness and diversity resulting from coevolutionary interactions can be highly dynamic. [source]

    THE FITNESS EFFECT OF MUTATIONS ACROSS ENVIRONMENTS: A SURVEY IN LIGHT OF FITNESS LANDSCAPE MODELS

    EVOLUTION, Issue 12 2006
    Guillaume Martin
    Abstract The fitness effects of mutations on a given genotype are rarely constant across environments to which this genotype is more or less adapted, that is, between more or less stressful conditions. This can have important implications, especially on the evolution of ecological specialization. Stress is thought to increase the variance of mutations' fitness effects, their average, or the number of expressed mutations. Although empirical evidence is available for these three mechanisms, their relative magnitude is poorly understood. In this paper, we propose a simple approach to discriminate between these mechanisms, using a survey of empirical measures of mutation effects in contrasted environments. This survey, across various species and environments, shows that stress mainly increases the variance of mutations effects on fitness, with a much more limited impact on their average effect or on the number of expressed mutations. This pattern is consistent with a simple model in which fitness is a Gaussian function of phenotypes around an environmentally determined optimum. These results suggest that a simple, mathematically tractable landscape model may not be quantitatively as unrealistic as previously suggested. They also suggest that mutation parameter estimates may be strongly biased when measured in stressful environments. [source]

    THE EVOLUTION OF ENVIRONMENTAL AND GENETIC SEX DETERMINATION IN FLUCTUATING ENVIRONMENTS

    EVOLUTION, Issue 12 2003
    Tom J. M. Van Dooren
    Abstract Twenty years ago, Bulmer and Bull suggested that disruptive selection, produced by environmental fluctuations, can result in an evolutionary transition from environmental sex determination (ESD) to genetic sex determination (GSD). We investigated the feasibility of such a process, using mutation-limited adaptive dynamics and individual-based computer simulations. Our model describes the evolution of a reaction norm for sex determination in a metapopulation setting with partial migration and variation in an environmental variable both within and between local patches. The reaction norm represents the probability of becoming a female as a function of environmental state and was modeled as a sigmoid function with two parameters, one giving the location (i.e., the value of the environmental variable for which an individual has equal chance of becoming either sex) and the other giving the slope of the reaction norm for that environment. The slope can be interpreted as being set by the level of developmental noise in morph determination, with less noise giving a steeper slope and a more switchlike reaction norm. We found convergence stable reaction norms with intermediate to large amounts of developmental noise for conditions characterized by low migration rates, small differential competitive advantages between the sexes over environments, and little variation between individual environments within patches compared to variation between patches. We also considered reaction norms with the slope parameter constrained to a high value, corresponding to little developmental noise. For these we found evolutionary branching in the location parameter and a transition from ESD toward GSD, analogous to the original analysis by Bulmer and Bull. Further evolutionary change, including dominance evolution, produced a polymorphism acting as a GSD system with heterogamety. Our results point to the role of developmental noise in the evolution of sex determination. [source]

    SEDIMENTARY FLUXES AND BUDGETS IN CHANGING COLD ENVIRONMENTS: THE GLOBAL IAG/AIG SEDIMENT BUDGETS IN COLD ENVIRONMENTS (SEDIBUD) PROGRAMME

    GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 2 2010
    ACHIM A. BEYLICH
    No abstract is available for this article. [source]

    PHYSIOLOGICAL CHARACTERIZATION OF A SYNECHOCOCCUS SP. (CYANOPHYCEAE) STRAIN PCC 7942 IRON-DEPENDENT BIOREPORTER FOR FRESHWATER ENVIRONMENTS,

    JOURNAL OF PHYCOLOGY, Issue 1 2003
    David Porta
    The complex chemical speciation of Fe in aquatic systems and the uncertainties associated with biological assimilation of Fe species make it difficult to assess the bioavailability of Fe to phytoplankton in relation to total dissolved Fe concentrations in natural waters. We developed a cyanobacterial Fe-responsive bioreporter constructed in Synechococcus sp. strain PCC 7942 by fusing the Fe-responsive isiAB promoter to Vibrio harveyi luxAB reporter genes. A comprehensive physiological characterization of the bioreporter has been made in defined Fraquil medium at free ferric ion concentrations ranging from pFe 21.6 to pFe 19.5. Whereas growth and physiological parameters are largely constrained over this range of Fe bioavailability, the bioreporter elicits a luminescent signal that varies in response to Fe deficiency. A dose-response characterization of bioreporter luminescence made over this range of Fe3+ bioavailability demonstrates a sigmoidal response with a dynamic linear range extending between pFe 21.1 and pFe 20.6. The applicability of using this Fe bioreporter to assess Fe availability in the natural environment has been tested using water samples from Lake Huron (Laurentian Great Lakes). Parallel assessment of dissolved Fe and bioreporter response from these samples reinforces the idea that measures of dissolved Fe should not be considered alone when assessing Fe availability to phytoplankton communities. [source]

    THE TYCHOPELAGIC DIATOM, PARALIA SULCATA, AS PALEOINDICATOR SPECIES IN COASTAL MARINE ENVIRONMENTS

    JOURNAL OF PHYCOLOGY, Issue 2000
    M.R. McQuoid
    Paralia sulcata is a diatom commonly found in both the plankton and benthos of coastal environments. This species is heavily silicified and, thus preserves well in sedimentary records making it a potentially useful paleoindicator species. However, its tychopelagic nature and its association with a wide range of environmental conditions have made detailed paleoecological interpretations complicated. High-resolution sediment records from coastal fjords in both Canada and Sweden show variations in the abundance and morphology of P. sulcata that provide evidence of changes in benthic habitat distribution and surface water properties in the fjords on timescales of decades to centuries. These studies suggest that P. sulcata can be an important paleoindicator species when interpretations are made in the context of its complex ecology. [source]

    CARBONATE DEPOSITIONAL ENVIRONMENTS, SEQUENCE STRATIGRAPHY AND EXCEPTIONAL SKELETAL PRESERVATION IN THE MUCH WENLOCK LIMESTONE FORMATION (SILURIAN) OF DUDLEY, ENGLAND

    PALAEONTOLOGY, Issue 1 2007
    DAVID C. RAY
    Abstract:, The Much Wenlock Limestone Formation of the Dudley inliers, West Midlands, contains one of the world's richest and most exquisitely preserved Silurian marine biotas. However, for most museum specimens, little is known of their exact provenance and mode of preservation. Detailed comparisons between outcrops and museum collections allow the identification of five faunal-lithological associations and numerous horizons of exceptional skeletal preservation. The associations are interpreted as a series of transient carbonate mid-platform environments extending from below storm wave-base to above fair-weather wave-base. Erosive surfaces, condensed sections, flooding surfaces and the stacking patterns of genetically related bed-sets (parasequences) have allowed the formation to be interpreted as a single third-order sequence stratigraphic cycle of sea-level change. The articulated preservation of taxa such as pelmatozoan echinoderms and trilobites can be attributed to either rapid burial by obrution deposits close to fair-weather wave-base or smothering by storm sequestered muds in slightly deeper-water settings. Such intervals of exceptional preservation are commonly associated with flooding surfaces, presumably reflecting reduced likelihood of reworking once rapid burial had taken place. [source]

    CHANGES IN THE METAL CONTENT OF HUMAN HAIR DURING DIAGENESIS FROM 500 YEARS, EXPOSURE TO GLACIAL AND AQUEOUS ENVIRONMENTS

    ARCHAEOMETRY, Issue 3 2010
    I. M. KEMPSON
    Scanning electron microscopy, inductively coupled plasma mass spectroscopy and time-of-flight secondary ion mass spectrometry have been used to examine the extent and possible mechanisms by which the metal content of human hair is altered by exposure to aqueous environments. The results, using both modern hair and samples from 500-year-old hair associated with glacier-entombed remains, show that the metal content has been altered sufficiently so that the interpretation of the metal signature in terms of diet or disease is problematic. While endogenous information is difficult to glean from these data, interesting observations have been made of possible early stages of mineral authigenic deposition. The chemistry of the outer hair surface was found to be consistent with deposition of Fe and Al silicates, as well as other mineral phases. The ancient hair was analysed at the root region and included a comparison of the internal versus external composition to assist in identifying the diagenetic processes. [source]

    Measuring the plasma environment at Mercury: The fast imaging plasma spectrometer

    METEORITICS & PLANETARY SCIENCE, Issue 9 2002
    P. L. KOEHN
    Three primary populations of ions exist at Mercury: solar wind, magnetospheric, and pickup ions. These pickup ions are generated through the ionization of Mercury's exosphere or are sputtered particles from the Mercury surface. A comprehensive mission to Mercury, such as MESSENGER (MErcury: Surface, Space ENvironment, GEochemistry, Ranging), should include a sensor that is able to determine the dynamical properties and composition of all these plasma components. An instrument to measure the composition of these ion populations and their three-dimensional velocity distribution functions must be lightweight, fast, and have a very large field of view. The fast imaging plasma spectrometer (FIPS) is an imaging mass spectrometer, part of NASA's MESSENGER mission, the first Mercury orbiter. This versatile instrument has a very small footprint, and has a mass that is ,1 order of magnitude less than other comparable systems. It maintains a nearly full-hemisphere field of view, suitable for either spinning or three-axis-stabilized platforms. The major piece of innovation to enable this sensor is a new deflection system geometry that enables a large instantaneous (,1.5,) field of view. This novel electrostatic analyzer system is then combined with a position sensitive time-of-flight system. We discuss the design and prototype tests of the FIPS deflection system and show how this system is expected to address one key problem in Mercury science, that of the nature of the radar-bright regions at the Hermean poles. [source]