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Sample records for biotic interactions drive

  1. Complex biotic interactions drive long-term vegetation dynamics in a subarctic ecosystem

    PubMed Central

    Olofsson, Johan; te Beest, Mariska; Ericson, Lars

    2013-01-01

    Predicting impacts of global warming requires understanding of the extent to which plant biomass and production are controlled by bottom-up and top-down drivers. By annually monitoring community composition in grazed control plots and herbivore-free exclosures at an Arctic location for 15 years, we detected multiple biotic interactions. Regular rodent cycles acted as pulses driving synchronous fluctuations in the biomass of field-layer vegetation; reindeer influenced the biomass of taller shrubs, and the abundance of plant pathogenic fungi increased when densities of their host plants increased in exclosures. Two outbreaks of geometrid moths occurred during the study period, with contrasting effects on the field layer: one in 2004 had marginal effects, while one in 2012 severely reduced biomass in the control plots and eliminated biomass that had accumulated over 15 years in the exclosures. The latter was followed by a dramatic decline of the dominant understory dwarf-shrub Empetrum hermaphroditum, driven by an interaction between moth herbivory on top buds and leaves, and increased disease severity of a pathogenic fungus. We show that the climate has important direct and indirect effects on all these biotic interactions. We conclude that long time series are essential to identify key biotic interactions in ecosystems, since their importance will be influenced by climatic conditions, and that manipulative treatments are needed in order to obtain the mechanistic understanding needed for robust predictions of future ecosystem changes and their feedback effects. PMID:23836791

  2. Flow regime, temperature, and biotic interactions drive differential declines of trout species under climate change

    USGS Publications Warehouse

    Wenger, S.J.; Isaak, D.J.; Luce, C.H.; Neville, H.M.; Fausch, K.D.; Dunham, J.B.; Dauwalter, D.C.; Young, M.K.; Elsner, M.M.; Rieman, B.E.; Hamlet, A.F.; Williams, J.E.

    2011-01-01

    Broad-scale studies of climate change effects on freshwater species have focused mainly on temperature, ignoring critical drivers such as flow regime and biotic interactions. We use downscaled outputs from general circulation models coupled with a hydrologic model to forecast the effects of altered flows and increased temperatures on four interacting species of trout across the interior western United States (1.01 million km2), based on empirical statistical models built from fish surveys at 9,890 sites. Projections under the 2080s A1B emissions scenario forecast a mean 47% decline in total suitable habitat for all trout, a group of fishes of major socioeconomic and ecological significance. We project that native cutthroat trout Oncorhynchus clarkii, already excluded from much of its potential range by nonnative species, will lose a further 58% of habitat due to an increase in temperatures beyond the species' physiological optima and continued negative biotic interactions. Habitat for nonnative brook trout Salvelinus fontinalis and brown trout Salmo trutta is predicted to decline by 77% and 48%, respectively, driven by increases in temperature and winter flood frequency caused by warmer, rainier winters. Habitat for rainbow trout, Oncorhynchus mykiss, is projected to decline the least (35%) because negative temperature effects are partly offset by flow regime shifts that benefit the species. These results illustrate how drivers other than temperature influence species response to climate change. Despite some uncertainty, large declines in trout habitat are likely, but our findings point to opportunities for strategic targeting of mitigation efforts to appropriate stressors and locations.

  3. Flow regime, temperature, and biotic interactions drive differential declines of trout species under climate change

    PubMed Central

    Wenger, Seth J.; Isaak, Daniel J.; Luce, Charles H.; Neville, Helen M.; Fausch, Kurt D.; Dunham, Jason B.; Dauwalter, Daniel C.; Young, Michael K.; Elsner, Marketa M.; Rieman, Bruce E.; Hamlet, Alan F.; Williams, Jack E.

    2011-01-01

    Broad-scale studies of climate change effects on freshwater species have focused mainly on temperature, ignoring critical drivers such as flow regime and biotic interactions. We use downscaled outputs from general circulation models coupled with a hydrologic model to forecast the effects of altered flows and increased temperatures on four interacting species of trout across the interior western United States (1.01 million km2), based on empirical statistical models built from fish surveys at 9,890 sites. Projections under the 2080s A1B emissions scenario forecast a mean 47% decline in total suitable habitat for all trout, a group of fishes of major socioeconomic and ecological significance. We project that native cutthroat trout Oncorhynchus clarkii, already excluded from much of its potential range by nonnative species, will lose a further 58% of habitat due to an increase in temperatures beyond the species’ physiological optima and continued negative biotic interactions. Habitat for nonnative brook trout Salvelinus fontinalis and brown trout Salmo trutta is predicted to decline by 77% and 48%, respectively, driven by increases in temperature and winter flood frequency caused by warmer, rainier winters. Habitat for rainbow trout, Oncorhynchus mykiss, is projected to decline the least (35%) because negative temperature effects are partly offset by flow regime shifts that benefit the species. These results illustrate how drivers other than temperature influence species response to climate change. Despite some uncertainty, large declines in trout habitat are likely, but our findings point to opportunities for strategic targeting of mitigation efforts to appropriate stressors and locations. PMID:21844354

  4. Inferring biotic interactions from proxies.

    PubMed

    Morales-Castilla, Ignacio; Matias, Miguel G; Gravel, Dominique; Araújo, Miguel B

    2015-06-01

    Inferring biotic interactions from functional, phylogenetic and geographical proxies remains one great challenge in ecology. We propose a conceptual framework to infer the backbone of biotic interaction networks within regional species pools. First, interacting groups are identified to order links and remove forbidden interactions between species. Second, additional links are removed by examination of the geographical context in which species co-occur. Third, hypotheses are proposed to establish interaction probabilities between species. We illustrate the framework using published food-webs in terrestrial and marine systems. We conclude that preliminary descriptions of the web of life can be made by careful integration of data with theory. PMID:25922148

  5. Predicting biotic interactions and their variability in a changing environment.

    PubMed

    Kadowaki, Kohmei; Barbera, Claire G; Godsoe, William; Delsuc, Frédéric; Mouquet, Nicolas

    2016-05-01

    Global environmental change is altering the patterns of biodiversity worldwide. Observation and theory suggest that species' distributions and abundances depend on a suite of processes, notably abiotic filtering and biotic interactions, both of which are constrained by species' phylogenetic history. Models predicting species distribution have historically mostly considered abiotic filtering and are only starting to integrate biotic interaction. However, using information on present interactions to forecast the future of biodiversity supposes that biotic interactions will not change when species are confronted with new environments. Using bacterial microcosms, we illustrate how biotic interactions can vary along an environmental gradient and how this variability can depend on the phylogenetic distance between interacting species. PMID:27220858

  6. The role of biotic forces in driving macroevolution: beyond the Red Queen

    PubMed Central

    Voje, Kjetil L.; Holen, Øistein H.; Liow, Lee Hsiang; Stenseth, Nils Chr.

    2015-01-01

    A multitude of hypotheses claim that abiotic factors are the main drivers of macroevolutionary change. By contrast, Van Valen's Red Queen hypothesis is often put forward as the sole representative of the view that biotic forcing is the main evolutionary driver. This imbalance of hypotheses does not reflect our current knowledge: theoretical work demonstrates the plausibility of biotically driven long-term evolution, whereas empirical work suggests a central role for biotic forcing in macroevolution. We call for a more pluralistic view of how biotic forces may drive long-term evolution that is compatible with both phenotypic stasis in the fossil record and with non-constant extinction rates. Promising avenues of research include contrasting predictions from relevant theories within ecology and macroevolution, as well as embracing both abiotic and biotic proxies while modelling long-term evolutionary data. By fitting models describing hypotheses of biotically driven macroevolution to data, we could dissect their predictions and transcend beyond pattern description, possibly narrowing the divide between our current understanding of micro- and macroevolution. PMID:25948685

  7. The role of biotic forces in driving macroevolution: beyond the Red Queen.

    PubMed

    Voje, Kjetil L; Holen, Øistein H; Liow, Lee Hsiang; Stenseth, Nils Chr

    2015-06-01

    A multitude of hypotheses claim that abiotic factors are the main drivers of macroevolutionary change. By contrast, Van Valen's Red Queen hypothesis is often put forward as the sole representative of the view that biotic forcing is the main evolutionary driver. This imbalance of hypotheses does not reflect our current knowledge: theoretical work demonstrates the plausibility of biotically driven long-term evolution, whereas empirical work suggests a central role for biotic forcing in macroevolution. We call for a more pluralistic view of how biotic forces may drive long-term evolution that is compatible with both phenotypic stasis in the fossil record and with non-constant extinction rates. Promising avenues of research include contrasting predictions from relevant theories within ecology and macroevolution, as well as embracing both abiotic and biotic proxies while modelling long-term evolutionary data. By fitting models describing hypotheses of biotically driven macroevolution to data, we could dissect their predictions and transcend beyond pattern description, possibly narrowing the divide between our current understanding of micro- and macroevolution. PMID:25948685

  8. Bacterial cyanogenesis: impact on biotic interactions.

    PubMed

    Zdor, R E

    2015-02-01

    The ability of bacteria to influence organisms that they associate with via metabolite production is one of the hallmarks of microbial interactions. One metabolite of interest is the metabolic poison cyanide. Production of this metabolite is an unique characteristic of certain bacteria that inhabit a wide array of habitats ranging from the human body to the rhizosphere. This review focuses on four targets of cyanogenic bacteria: the human lung, plant pathogens, plants and invertebrates. For a number of cyanogenic bacteria, the contribution of cyanide to the interaction has been rigorously tested using mutants altered in cyanide production. Both deleterious and stimulatory effects of cyanogenic bacteria on other organisms have been documented. In addition, the HCN synthase-encoding gene cluster hcnABC has served as a marker of cyanogenic capability in the soil environment revealing both genetic diversity at this locus and regulatory influences by other organisms. The pervasive nature of cyanogenesis in a number of different ecological contexts encourages exploration of this bacterial ability and its possible optimization for improving human health, crop production and pest control. PMID:25410133

  9. Biotic interactions govern genetic adaptation to toxicants.

    PubMed

    Becker, Jeremias Martin; Liess, Matthias

    2015-05-01

    The genetic recovery of resistant populations released from pesticide exposure is accelerated by the presence of environmental stressors. By contrast, the relevance of environmental stressors for the spread of resistance during pesticide exposure has not been studied. Moreover, the consequences of interactions between different stressors have not been considered. Here we show that stress through intraspecific competition accelerates microevolution, because it enhances fitness differences between adapted and non-adapted individuals. By contrast, stress through interspecific competition or predation reduces intraspecific competition and thereby delays microevolution. This was demonstrated in mosquito populations (Culex quinquefasciatus) that were exposed to the pesticide chlorpyrifos. Non-selective predation through harvesting and interspecific competition with Daphnia magna delayed the selection for individuals carrying the ace-1(R) resistance allele. Under non-toxic conditions, susceptible individuals without ace-1(R) prevailed. Likewise, predation delayed the reverse adaptation of the populations to a non-toxic environment, while the effect of interspecific competition was not significant. Applying a simulation model, we further identified how microevolution is generally determined by the type and degree of competition and predation. We infer that interactions with other species-especially strong in ecosystems with high biodiversity-can delay the development of pesticide resistance. PMID:25833856

  10. Biotic interactions govern genetic adaptation to toxicants

    PubMed Central

    Becker, Jeremias Martin; Liess, Matthias

    2015-01-01

    The genetic recovery of resistant populations released from pesticide exposure is accelerated by the presence of environmental stressors. By contrast, the relevance of environmental stressors for the spread of resistance during pesticide exposure has not been studied. Moreover, the consequences of interactions between different stressors have not been considered. Here we show that stress through intraspecific competition accelerates microevolution, because it enhances fitness differences between adapted and non-adapted individuals. By contrast, stress through interspecific competition or predation reduces intraspecific competition and thereby delays microevolution. This was demonstrated in mosquito populations (Culex quinquefasciatus) that were exposed to the pesticide chlorpyrifos. Non-selective predation through harvesting and interspecific competition with Daphnia magna delayed the selection for individuals carrying the ace-1R resistance allele. Under non-toxic conditions, susceptible individuals without ace-1R prevailed. Likewise, predation delayed the reverse adaptation of the populations to a non-toxic environment, while the effect of interspecific competition was not significant. Applying a simulation model, we further identified how microevolution is generally determined by the type and degree of competition and predation. We infer that interactions with other species—especially strong in ecosystems with high biodiversity—can delay the development of pesticide resistance. PMID:25833856

  11. Chemical ecology: The chemistry of biotic interaction

    SciTech Connect

    Eisner, T.; Meinwald, J.

    1995-12-31

    Chemical signals among organisms form `a vast communicative interplay, fundamental to the fabric of life,` in the words of one expert. Chemical ecology is the discipline that seeks to understand these interactions to use biology in the search for new substances of potential benefit to humankind. This book highlights selected research areas of medicinal and agricultural importance. Leading experts review the chemistry of: (1) insect defense and its applications to pest control; (2) Phyletic dominance--the survival success of insects; (3) Social regulation, with ant societies as a model of multicomponent signaling systems; (4) Eavesdropping, alarm, and deceit--the array of strategies used by insects to find and lure prey; (5) Reproduction--from the gamete attraction to courtship and sexual selection; (6) the chemistry of intracellular immunosuppression. Topics also include the appropriation of dietary factors for defense and communication; the use of chemical signals in the marine environment; the role of the olfactory system in chemical analysis; and the interaction of polydnaviruses, endoparasites, and the immune system of the host.

  12. EDP: A computer program for analysis of biotic interactions

    NASA Astrophysics Data System (ADS)

    Gibson, Michael A.; Bolton, James C.

    1992-07-01

    Analyzing fossils for evidence of biotic interactions such as parasitism, commensalism, and predation can be accomplished using skeletal relationships (e.g. overlapping growth) on individual specimens and statistical information on populations of specimens. The latter approach provides information for use in larger scale paleocommunity analyses. This approach requires a large data set and extensive amounts of information management. The types of information that are needed include data concerning the identity of host and epibiont species, orientation of epibionts on hosts, position of encrustation, growth directions, region of occurrence, and associated fauna. We have written the Epibiont Digitizing Program (EDP) to collect the data necessary to study biotic interactions in the fossil record. The program is operator-interactive at all stages and versatile enough to allow modification depending upon the specific needs of the researcher.

  13. Omic Relief for the Biotically Stressed: Metabolomics of Plant Biotic Interactions.

    PubMed

    Tenenboim, Hezi; Brotman, Yariv

    2016-09-01

    Many aspects of the way plants protect themselves against pathogen attack, or react upon such an attack, are realized by metabolites. The ambitious aim of metabolomics, namely the identification and annotation of the entire cellular metabolome, still poses a considerable challenge due to the high diversity of the metabolites in the cell. Recent advances in analytical methods and data analysis have resulted in improved sensitivity, accuracy, and capacity, allowing the analysis of several hundreds or even thousands of compounds within one sample. Investigators have only recently begun to acknowledge and harness the power of metabolomics to elucidate key questions in the study of plant biotic interactions; we review trends and developments in the field. PMID:27185334

  14. Annual grass invasion in sagebrush steppe: the relative importance of climate, soil properties and biotic interactions.

    PubMed

    Bansal, Sheel; Sheley, Roger L

    2016-06-01

    The invasion by winter-annual grasses (AGs) such as Bromus tectorum into sagebrush steppe throughout the western USA is a classic example of a biological invasion with multiple, interacting climate, soil and biotic factors driving the invasion, although few studies have examined all components together. Across a 6000-km(2) area of the northern Great Basin, we conducted a field assessment of 100 climate, soil, and biotic (functional group abundances, diversity) factors at each of 90 sites that spanned an invasion gradient ranging from 0 to 100 % AG cover. We first determined which biotic and abiotic factors had the strongest correlative relationships with AGs and each resident functional group. We then used regression and structural equation modeling to explore how multiple ecological factors interact to influence AG abundance. Among biotic interactions, we observed negative relationships between AGs and biodiversity, perennial grass cover, resident species richness, biological soil crust cover and shrub density, whereas perennial and annual forb cover, tree cover and soil microbial biomass had no direct linkage to AG. Among abiotic factors, AG cover was strongly related to climate (increasing cover with increasing temperature and aridity), but had weak relationships with soil factors. Our structural equation model showed negative effects of perennial grasses and biodiversity on AG cover while integrating the negative effects of warmer climate and positive influence of belowground processes on resident functional groups. Our findings illustrate the relative importance of biotic interactions and climate on invasive abundance, while soil properties appear to have stronger relationships with resident biota than with invasives. PMID:26920900

  15. Meta-Analysis of Interactions between Arbuscular Mycorrhizal Fungi and Biotic Stressors of Plants

    PubMed Central

    Dai, Yajun; Wang, Xiaohua; Zhu, Liqun; Bian, Xinmin

    2014-01-01

    Naturally, simultaneous interactions occurred among plants, herbivores, and soil biota, that is, arbuscular mycorrhizal fungi (AMF), nematodes, and fungal pathogens. These multiple interactions play fundamental roles in driving process, structure, and functioning of ecosystems. In this study, we conducted a meta-analysis with 144 papers to investigate the interactions between AMF and plant biotic stressors and their effects on plant growth performance. We found that AMF enhanced plant tolerance to herbivores, nematodes, and fungal pathogens. We also found reciprocal inhibition between AMF and nematodes as well as fungal pathogens, but unidirectional inhibition for AMF on herbivores. Negative effects of AMF on biotic stressors of plants depended on herbivore feeding sites and actioning modes of fungal pathogens. More performance was reduced in root-feeding than in shoot-feeding herbivores and in rotting- than in wilt-fungal pathogens. However, no difference was found for AMF negative effects between migratory and sedentary nematodes. In return, nematodes and fungal pathogens generated more reduction of root colonization in Non-Glomeraceae than in Glomeraceae. Our results suggested that AMF positive effects on plants might be indirectly mediated by competitive inhibition with biotic stressors of plants. These positive and negative interactions make potential contributions to maintaining ecosystem stability and functioning. PMID:24558327

  16. Location and foraging as basis for classification of biotic interactions.

    PubMed

    Khabibullin, Viner F

    2016-06-01

    Ecologists face an overwhelming diversity of ecological relationships in natural communities. In this paper, I propose to differentiate various types of the interspecific relations on the basis of two factors: relative localization and foraging activity of interacting partners. I advocate recognition of four types of environments: internal, surface, proximate external and distant external. Then I distinguish four types of synoikia-one partner lives in different degree of proximity to another; and four types of synmensalism: one partner forages in different degree of proximity to another. Intersection of localization-based (four subtypes of synoikia) and foraging-based (four subtypes of synmensalism) rows results in 16 types of interactions. This scheme can serve as a framework that manages diverse biotic interactions in a standardized way. I have made the first step to set up nomenclature standards for terms describing interspecific interactions and hope that this will facilitate research and communication. PMID:27160993

  17. Exercising influence: distinct biotic interactions shape root microbiomes.

    PubMed

    Sloan, Sarah Stuart; Lebeis, Sarah L

    2015-08-01

    Root microbiomes are formed from diverse microbial soil settings with extraordinary consistency, suggesting both defined mechanisms of assembly and specific microbial activity. Recent improvements in sequencing technologies, data analysis techniques, and study design, allow definition of the microbiota within these intimate and important relationships with increasing accuracy. Comparing datasets provides powerful insights into the overlap of plant microbiomes, as well as the impacts of surrounding plants and microbes on root microbiomes and long-term soil conditioning. Here we address how recent studies tease apart the impact of various biotic interactions, including: plant-plant, plant-microbe, and microbe-microbe on root microbiome composition. PMID:26116973

  18. Ecosystem development in roadside grasslands: biotic control, plant–soil interactions and dispersal limitations

    PubMed Central

    García-Palacios, Pablo; Bowker, Matthew A.; Maestre, Fernando T.; Soliveres, Santiago; Valladares, Fernando; Papadopoulos, Jorge; Escudero, Adrián

    2015-01-01

    Roadside grasslands undergoing secondary succession are abundant, and represent ecologically meaningful examples of novel, human-created ecosystems. Interactions between plant and soil communities (hereafter plant–soil interactions) are of major importance in understanding the role of biotic control in ecosystem functioning, but little is known about these links in the context of ecosystem restoration and succession. The assessment of the key biotic communities and interactions driving ecosystem development will help practitioners to better allocate the limited resources devoted to roadside grassland restoration. We surveyed roadside grasslands from three successional stages (0–2, 7–9 and > 20 years) in two Mediterranean regions of Spain. Structural equation modeling was used to evaluate how interactions between plants, biological soil crusts [BSCs], and soil microbial functional diversity [soil microorganisms] affect indicators of ecosystem development and restoration: plant similarity to the reference ecosystem, erosion control and soil C storage and N accumulation. Changes in plant community composition along the successional gradient exerted the strongest influence on these indicators. High BSC cover was associated with high soil stability, and high soil microbial functional diversity from late-successional stages was associated with high soil fertility. Contrary to our expectations, the indirect effects of plants, mediated by either BSCs or soil microorganisms, were very weak in both regions, suggesting a minor role for plant–soil interactions upon ecosystem development indicators over long periods. Our results suggest that natural vegetation dynamics effectively improved ecosystem development within a time frame of 20 years in the grasslands evaluated. They also indicate that this time could be shortened if management actions focus on: 1) maintain well-conserved natural areas close to roadsides to enhance plant compositional changes towards late

  19. Ecosystem development in roadside grasslands: Biotic control, plant-soil interactions, and dispersal limitations

    USGS Publications Warehouse

    Garcia-Palacios, P.; Bowker, M.A.; Maestre, F.T.; Soliveres, S.; Valladares, F.; Papadopoulos, J.; Escudero, A.

    2011-01-01

    Roadside grasslands undergoing secondary succession are abundant, and represent ecologically meaningful examples of novel, human-created ecosystems. Interactions between plant and soil communities (hereafter plant-soil interactions) are of major importance in understanding the role of biotic control in ecosystem functioning, but little is known about these links in the context of ecosystem restoration and succession. The assessment of the key biotic communities and interactions driving ecosystem development will help practitioners to better allocate the limited resources devoted to roadside grassland restoration. We surveyed roadside grasslands from three successional stages (0-2, 7-9, and > 20 years) in two Mediterranean regions of Spain. Structural equation modeling was used to evaluate how interactions between plants, biological soil crusts (BSCs), and soil microbial functional diversity (soil microorganisms) affect indicators of ecosystem development and restoration: plant similarity to the reference ecosystem, erosion control, and soil C storage and N accumulation. Changes in plant community composition along the successional gradient exerted the strongest influence on these indicators. High BSC cover was associated with high soil stability, and high soil microbial functional diversity from late-successional stages was associated with high soil fertility. Contrary to our expectations, the indirect effects of plants, mediated by either BSCs or soil microorganisms, were very weak in both regions, suggesting a minor role for plant-soil interactions upon ecosystem development indicators over long periods. Our results suggest that natural vegetation dynamics effectively improved ecosystem development within a time frame of 20 years in the grasslands evaluated. They also indicate that this time could be shortened if management actions focus on: (1) maintaining wellconserved natural areas close to roadsides to enhance plant compositional changes towards late

  20. Annual grass invasion in sagebrush-steppe: The relative importance of climate, soil properties and biotic interactions

    USGS Publications Warehouse

    Bansal, Sheel; Sheley, Roger L.

    2016-01-01

    The invasion by winter-annual grasses (AGs) such as Bromus tectorum into sagebrush steppe throughout the western USA is a classic example of a biological invasion with multiple, interacting climate, soil and biotic factors driving the invasion, although few studies have examined all components together. Across a 6000-km2 area of the northern Great Basin, we conducted a field assessment of 100 climate, soil, and biotic (functional group abundances, diversity) factors at each of 90 sites that spanned an invasion gradient ranging from 0 to 100 % AG cover. We first determined which biotic and abiotic factors had the strongest correlative relationships with AGs and each resident functional group. We then used regression and structural equation modeling to explore how multiple ecological factors interact to influence AG abundance. Among biotic interactions, we observed negative relationships between AGs and biodiversity, perennial grass cover, resident species richness, biological soil crust cover and shrub density, whereas perennial and annual forb cover, tree cover and soil microbial biomass had no direct linkage to AG. Among abiotic factors, AG cover was strongly related to climate (increasing cover with increasing temperature and aridity), but had weak relationships with soil factors. Our structural equation model showed negative effects of perennial grasses and biodiversity on AG cover while integrating the negative effects of warmer climate and positive influence of belowground processes on resident functional groups. Our findings illustrate the relative importance of biotic interactions and climate on invasive abundance, while soil properties appear to have stronger relationships with resident biota than with invasives.

  1. Biotic interactions mediate soil microbial feedbacks to climate change.

    PubMed

    Crowther, Thomas W; Thomas, Stephen M; Maynard, Daniel S; Baldrian, Petr; Covey, Kristofer; Frey, Serita D; van Diepen, Linda T A; Bradford, Mark A

    2015-06-01

    Decomposition of organic material by soil microbes generates an annual global release of 50-75 Pg carbon to the atmosphere, ∼7.5-9 times that of anthropogenic emissions worldwide. This process is sensitive to global change factors, which can drive carbon cycle-climate feedbacks with the potential to enhance atmospheric warming. Although the effects of interacting global change factors on soil microbial activity have been a widespread ecological focus, the regulatory effects of interspecific interactions are rarely considered in climate feedback studies. We explore the potential of soil animals to mediate microbial responses to warming and nitrogen enrichment within a long-term, field-based global change study. The combination of global change factors alleviated the bottom-up limitations on fungal growth, stimulating enzyme production and decomposition rates in the absence of soil animals. However, increased fungal biomass also stimulated consumption rates by soil invertebrates, restoring microbial process rates to levels observed under ambient conditions. Our results support the contemporary theory that top-down control in soil food webs is apparent only in the absence of bottom-up limitation. As such, when global change factors alleviate the bottom-up limitations on microbial activity, top-down control becomes an increasingly important regulatory force with the capacity to dampen the strength of positive carbon cycle-climate feedbacks. PMID:26038557

  2. Biotic interactions mediate soil microbial feedbacks to climate change

    PubMed Central

    Crowther, Thomas W.; Thomas, Stephen M.; Maynard, Daniel S.; Baldrian, Petr; Covey, Kristofer; Frey, Serita D.; van Diepen, Linda T. A.; Bradford, Mark A.

    2015-01-01

    Decomposition of organic material by soil microbes generates an annual global release of 50–75 Pg carbon to the atmosphere, ∼7.5–9 times that of anthropogenic emissions worldwide. This process is sensitive to global change factors, which can drive carbon cycle–climate feedbacks with the potential to enhance atmospheric warming. Although the effects of interacting global change factors on soil microbial activity have been a widespread ecological focus, the regulatory effects of interspecific interactions are rarely considered in climate feedback studies. We explore the potential of soil animals to mediate microbial responses to warming and nitrogen enrichment within a long-term, field-based global change study. The combination of global change factors alleviated the bottom-up limitations on fungal growth, stimulating enzyme production and decomposition rates in the absence of soil animals. However, increased fungal biomass also stimulated consumption rates by soil invertebrates, restoring microbial process rates to levels observed under ambient conditions. Our results support the contemporary theory that top-down control in soil food webs is apparent only in the absence of bottom-up limitation. As such, when global change factors alleviate the bottom-up limitations on microbial activity, top-down control becomes an increasingly important regulatory force with the capacity to dampen the strength of positive carbon cycle–climate feedbacks. PMID:26038557

  3. How will biotic interactions influence climate change-induced range shifts?

    PubMed

    HilleRisLambers, Janneke; Harsch, Melanie A; Ettinger, Ailene K; Ford, Kevin R; Theobald, Elinore J

    2013-09-01

    Biotic interactions present a challenge in determining whether species distributions will track climate change. Interactions with competitors, consumers, mutualists, and facilitators can strongly influence local species distributions, but few studies assess how and whether these interactions will impede or accelerate climate change-induced range shifts. In this paper, we explore how ecologists might move forward on this question. We first outline the conditions under which biotic interactions can result in range shifts that proceed faster or slower than climate velocity and result in ecological surprises. Next, we use our own work to demonstrate that experimental studies documenting the strength of biotic interactions across large environmental gradients are a critical first step for understanding whether they will influence climate change-induced range shifts. Further progress could be made by integrating results from these studies into modeling frameworks to predict how or generalize when biotic interactions mediate how changing climates influence range shifts. Finally, we argue that many more case studies like those described here are needed to explore the importance of biotic interactions during climate change-induced range shifts. PMID:23876073

  4. Biotic-Abiotic Interactions: Factors that Influence Peptide-Graphene Interactions.

    PubMed

    Kim, Steve S; Kuang, Zhifeng; Ngo, Yen H; Farmer, Barry L; Naik, Rajesh R

    2015-09-16

    Understanding the factors that influence the interaction between biomolecules and abiotic surfaces is of utmost interest in biosensing and biomedical research. Through phage display technology, several peptides have been identified as specific binders to abiotic material surfaces, such as gold, graphene, silver, and so forth. Using graphene-peptide as our model abiotic-biotic pair, we investigate the effect of graphene quality, number of layers, and the underlying support substrate effect on graphene-peptide interactions using both experiments and computation. Our results indicate that graphene quality plays a significant role in graphene-peptide interactions. The graphene-biomolecule interaction appears to show no significant dependency on the number of graphene layers or the underlying support substrate. PMID:26305504

  5. Biotic interactions mediate the expansion of black mangrove (Avicennia germinans) into salt marshes under climate change.

    PubMed

    Guo, Hongyu; Zhang, Yihui; Lan, Zhenjiang; Pennings, Steven C

    2013-09-01

    Many species are expanding their distributions to higher latitudes due to global warming. Understanding the mechanisms underlying these distribution shifts is critical for better understanding the impacts of climate changes. The climate envelope approach is widely used to model and predict species distribution shifts with changing climates. Biotic interactions between species, however, may also influence species distributions, and a better understanding of biotic interactions could improve predictions based solely on climate envelope models. Along the northern Gulf of Mexico coast, USA, subtropical black mangrove (Avicennia germinans) at the northern limit of its distribution grows sympatrically with temperate salt marsh plants in Florida, Louisiana, and Texas. In recent decades, freeze-free winters have led to an expansion of black mangrove into salt marshes. We examined how biotic interactions between black mangrove and salt marsh vegetation along the Texas coast varied across (i) a latitudinal gradient (associated with a winter-temperature gradient); (ii) the elevational gradient within each marsh (which creates different marsh habitats); and (iii) different life history stages of black mangroves (seedlings vs. juvenile trees). Each of these variables affected the strength or nature of biotic interactions between black mangrove and salt marsh vegetation: (i) Salt marsh vegetation facilitated black mangrove seedlings at their high-latitude distribution limit, but inhibited black mangrove seedlings at lower latitudes; (ii) mangroves performed well at intermediate elevations, but grew and survived poorly in high- and low-marsh habitats; and (iii) the effect of salt marsh vegetation on black mangroves switched from negative to neutral as black mangroves grew from seedlings into juvenile trees. These results indicate that the expansion of black mangroves is mediated by complex biotic interactions. A better understanding of the impacts of climate change on ecological

  6. Interactions of biotic and abiotic environmental factors in an ectomycorrhizal symbiosis, and the potential for selection mosaics

    PubMed Central

    Piculell, Bridget J; Hoeksema, Jason D; Thompson, John N

    2008-01-01

    Background Geographic selection mosaics, in which species exert different evolutionary impacts on each other in different environments, may drive diversification in coevolving species. We studied the potential for geographic selection mosaics in plant-mycorrhizal interactions by testing whether the interaction between bishop pine (Pinus muricata D. Don) and one of its common ectomycorrhizal fungi (Rhizopogon occidentalis Zeller and Dodge) varies in outcome, when different combinations of plant and fungal genotypes are tested under a range of different abiotic and biotic conditions. Results We used a 2 × 2 × 2 × 2 factorial experiment to test the main and interactive effects of plant lineage (two maternal seed families), fungal lineage (two spore collections), soil type (lab mix or field soil), and non-mycorrhizal microbes (with or without) on the performance of plants and fungi. Ecological outcomes, as assessed by plant and fungal performance, varied widely across experimental environments, including interactions between plant or fungal lineages and soil environmental factors. Conclusion These results show the potential for selection mosaics in plant-mycorrhizal interactions, and indicate that these interactions are likely to coevolve in different ways in different environments, even when initially the genotypes of the interacting species are the same across all environments. Hence, selection mosaics may be equally as effective as genetic differences among populations in driving divergent coevolution among populations of interacting species. PMID:18507825

  7. Annual grass invasion in sagebrush steppe: the relative importance of climate, soil properties and biotic interactions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Species distributions and abundances are constrained by climate factors (e.g., temperature, precipitation), soil properties (e.g., nutrients), biotic interactions (e.g., competition) and disturbances (e.g., fire). At macroecological scales, species distributions typically follow temperature or preci...

  8. Biotic Interactions Overrule Plant Responses to Climate, Depending on the Species' Biogeography

    PubMed Central

    Welk, Astrid; Welk, Erik; Bruelheide, Helge

    2014-01-01

    This study presents an experimental approach to assess the relative importance of climatic and biotic factors as determinants of species' geographical distributions. We asked to what extent responses of grassland plant species to biotic interactions vary with climate, and to what degree this variation depends on the species' biogeography. Using a gradient from oceanic to continental climate represented by nine common garden transplant sites in Germany, we experimentally tested whether congeneric grassland species of different geographic distribution (oceanic vs. continental plant range type) responded differently to combinations of climate, competition and mollusc herbivory. We found the relative importance of biotic interactions and climate to vary between the different components of plant performance. While survival and plant height increased with precipitation, temperature had no effect on plant performance. Additionally, species with continental plant range type increased their growth in more benign climatic conditions, while those with oceanic range type were largely unable to take a similar advantage of better climatic conditions. Competition generally caused strong reductions of aboveground biomass and growth. In contrast, herbivory had minor effects on survival and growth. Against expectation, these negative effects of competition and herbivory were not mitigated under more stressful continental climate conditions. In conclusion we suggest variation in relative importance of climate and biotic interactions on broader scales, mediated via species-specific sensitivities and factor-specific response patterns. Our results have important implications for species distribution models, as they emphasize the large-scale impact of biotic interactions on plant distribution patterns and the necessity to take plant range types into account. PMID:25356912

  9. Temperature, precipitation and biotic interactions as determinants of tree seedling recruitment across the tree line ecotone.

    PubMed

    Tingstad, Lise; Olsen, Siri Lie; Klanderud, Kari; Vandvik, Vigdis; Ohlson, Mikael

    2015-10-01

    Seedling recruitment is a critical life history stage for trees, and successful recruitment is tightly linked to both abiotic factors and biotic interactions. In order to better understand how tree species' distributions may change in response to anticipated climate change, more knowledge of the effects of complex climate and biotic interactions is needed. We conducted a seed-sowing experiment to investigate how temperature, precipitation and biotic interactions impact recruitment of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) seedlings in southern Norway. Seeds were sown into intact vegetation and experimentally created gaps. To study the combined effects of temperature and precipitation, the experiment was replicated across 12 sites, spanning a natural climate gradient from boreal to alpine and from sub-continental to oceanic. Seedling emergence and survival were assessed 12 and 16 months after sowing, respectively, and above-ground biomass and height were determined at the end of the experiment. Interestingly, very few seedlings were detected in the boreal sites, and the highest number of seedlings emerged and established in the alpine sites, indicating that low temperature did not limit seedling recruitment. Site precipitation had an overall positive effect on seedling recruitment, especially at intermediate precipitation levels. Seedling emergence, establishment and biomass were higher in gap plots compared to intact vegetation at all temperature levels. These results suggest that biotic interactions in the form of competition may be more important than temperature as a limiting factor for tree seedling recruitment in the sub- and low-alpine zone of southern Norway. PMID:26065402

  10. Using Biotic Interaction Networks for Prediction in Biodiversity and Emerging Diseases

    PubMed Central

    Stephens, Christopher R.; Heau, Joaquín Giménez; González, Camila; Ibarra-Cerdeña, Carlos N.; Sánchez-Cordero, Victor; González-Salazar, Constantino

    2009-01-01

    Networks offer a powerful tool for understanding and visualizing inter-species ecological and evolutionary interactions. Previously considered examples, such as trophic networks, are just representations of experimentally observed direct interactions. However, species interactions are so rich and complex it is not feasible to directly observe more than a small fraction. In this paper, using data mining techniques, we show how potential interactions can be inferred from geographic data, rather than by direct observation. An important application area for this methodology is that of emerging diseases, where, often, little is known about inter-species interactions, such as between vectors and reservoirs. Here, we show how using geographic data, biotic interaction networks that model statistical dependencies between species distributions can be used to infer and understand inter-species interactions. Furthermore, we show how such networks can be used to build prediction models. For example, for predicting the most important reservoirs of a disease, or the degree of disease risk associated with a geographical area. We illustrate the general methodology by considering an important emerging disease - Leishmaniasis. This data mining methodology allows for the use of geographic data to construct inferential biotic interaction networks which can then be used to build prediction models with a wide range of applications in ecology, biodiversity and emerging diseases. PMID:19478956

  11. Accounting for dispersal and biotic interactions to disentangle the drivers of species distributions and their abundances

    PubMed Central

    Boulangeat, Isabelle; Gravel, Dominique; Thuiller, Wilfried

    2014-01-01

    Although abiotic factors, together with dispersal and biotic interactions, are often suggested to explain the distribution of species and their abundances, species distribution models usually focus on abiotic factors only. We propose an integrative framework linking ecological theory, empirical data and statistical models to understand the distribution of species and their abundances together with the underlying community assembly dynamics. We illustrate our approach with 21 plant species in the French Alps. We show that a spatially nested modelling framework significantly improves the model’s performance and that the spatial variations of species presence–absence and abundances are predominantly explained by different factors. We also show that incorporating abiotic, dispersal and biotic factors into the same model bring new insights to our understanding of community assembly. This approach, at the crossroads between community ecology and biogeography, is a promising avenue for a better understanding of species co-existence and biodiversity distribution. PMID:22462813

  12. Untangling interactions: do temperature and habitat fragmentation gradients simultaneously impact biotic relationships?

    PubMed Central

    Lakeman-Fraser, Poppy; Ewers, Robert M.

    2014-01-01

    Gaining insight into the impact of anthropogenic change on ecosystems requires investigation into interdependencies between multiple drivers of ecological change and multiple biotic responses. Global environmental change drivers can act simultaneously to impact the abundance and diversity of biota, but few studies have also measured the impact across trophic levels. We firstly investigated whether climate (using temperature differences across a latitudinal gradient as a surrogate) interacts with habitat fragmentation (measured according to fragment area and distance to habitat edges) to impact a New Zealand tri-trophic food chain (plant, herbivore and natural enemy). Secondly, we examined how these interactions might differentially impact both the density and biotic processes of species at each of the three trophic levels. We found evidence to suggest that these drivers act non-additively across trophic levels. The nature of these interactions however varied: location synergistically interacted with fragmentation measures to exacerbate the detrimental effects on consumer density; and antagonistically interacted to ameliorate the impact on plant density and on the interactions between trophic levels (herbivory and parasitoid attack rate). Our findings indicate that the ecological consequences of multiple global change drivers are strongly interactive and vary according to the trophic level studied and whether density or ecological processes are investigated. PMID:24898374

  13. Contrasting the effects of environment, dispersal and biotic interactions to explain the distribution of invasive plants in alpine communities

    PubMed Central

    GALLIEN, Laure; MAZEL, Florent; LAVERGNE, Sébastien; RENAUD, Julien; DOUZET, Rolland; THUILLER, Wilfried

    2015-01-01

    Despite considerable efforts devoted to investigate the community assembly processes driving plant invasions, few general conclusions have been drawn so far. Three main processes, generally acting as successive filters, are thought to be of prime importance. The invader has to disperse (1st filter) into a suitable environment (2nd filter) and succeed in establishing in recipient communities through competitive interactions (3rd filter) using two strategies: competition avoidance by the use of different resources (resource opportunity), or competitive exclusion of native species. Surprisingly, despite the general consensus on the importance of investigating these three processes and their interplay, they are usually studied independently. Here we aim to analyse these three filters together, by including them all: abiotic environment, dispersal and biotic interactions, into models of invasive species distributions. We first propose a suite of indices (based on species functional dissimilarities) supposed to reflect the two competitive strategies (resource opportunity and competition exclusion). Then, we use a set of generalised linear models to explain the distribution of seven herbaceous invaders in natural communities (using a large vegetation database for the French Alps containing 5,000 community-plots). Finally, we measure the relative importance of competitive interaction indices, identify the type of coexistence mechanism involved and how this varies along environmental gradients. Adding competition indices significantly improved model’s performance, but neither resource opportunity nor competitive exclusion were common strategies among the seven species. Overall, we show that combining environmental, dispersal and biotic information to model invasions has excellent potential for improving our understanding of invader success. PMID:26290653

  14. Biotic interactions affect the colonization behavior of aquatic detritivorous macroinvertebrates in a heterogeneous environment

    NASA Astrophysics Data System (ADS)

    Verschut, Thomas A.; Meineri, Eric; Basset, Alberto

    2015-05-01

    It has previously been suggested that macroinvertebrates actively search for suitable patches to colonize. However, it is not well understood how the spatial arrangement of patches can affect colonization rates. In this study, we determined the importance of the environmental factors (distance, connectivity and resource availability) for patch colonization in an experimental system using Gammarus aequicauda (Amphipoda), Lekanesphaera hookeri (Isopoda) and Ecrobia ventrosa (Gastropoda). Furthermore, we also assessed how the relative importance of each of these environmental factors differed in interactions between the three species. The single species experiments showed that distance was the most important factor for G. aequicauda and E. ventrosa. However, while E. ventrosa preferred patches close to the release point, G. aequicauda strongly preferred patches further from the release point. High resource availability was a strong determinant for the patch colonization of G. aequicauda and L. hookeri. Connectivity was only of moderate importance in the study system for L. hookeri and E. ventrosa. The effects of the environmental factors were strongly affected by interspecific interactions in the multispecies experiments. For G. aequicauda, the distance preference was lowered in the presence of E. ventrosa. Moreover, while for L. hookeri the effect of resource availability was ruled out by the species interactions, resource availability gained importance for E. ventrosa in the presence of any of the other species. Our results suggest a strong link between environmental factors and biotic interactions in the colonization of habitat patches and indicate that the effect of biotic interactions is especially important for species sharing similar traits.

  15. Nicotiana tabacum Tsip1-Interacting Ferredoxin 1 Affects Biotic and Abiotic Stress Resistance

    PubMed Central

    Huh, Sung Un; Lee, In-Ju; Ham, Byung-Kook; Paek, Kyung-Hee

    2012-01-01

    Tsip1, a Zn finger protein that was isolated as a direct interactor with tobacco stress-induced 1 (Tsi1), plays an important role in both biotic and abiotic stress signaling. To further understand Tsip1 function, we searched for more Tsip1-interacting proteins by yeast two-hybrid screening using a tobacco cDNA library. Screening identified a new Tsip1-interacting protein, Nicotiana tabacum Tsip1-interacting ferredoxin 1 (NtTfd1), and binding specificity was confirmed both in vitro and in vivo. The four repeats of a cysteine-rich motif (CXXCXGXG) of Tsip1 proved important for binding to NtTfd1. Virus-induced gene silencing of NtTfd1, Tsip1, and NtTfd1/Tsip1 rendered plants more susceptible to salinity stress compared with TRV2 control plants. NtTfd1- and Tsip1-silenced tobacco plants were more susceptible to infection by Cucumber mosaic virus compared with control plants. These results suggest that NtTfd1 might be involved in the regulation of biotic and abiotic stresses in chloroplasts by interaction with Tsip1. PMID:22699755

  16. Energy from Redox Disproportionation of Sugar Carbon Drives Biotic and Abiotic Synthesis

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.

    1997-01-01

    To identify the energy source that drives the biosynthesis of amino acids, lipids, and nucleotides from glucose, we calculated the free energy change due to redox disproportionation of the substrate carbon of: (1) 26-carbon fermentation reactions and (2) the biosynthesis of amino acids and lipids of E. coli from glucose. The free energy (cal/mmol of carbon) of these reactions was plotted as a function of the degree of redox disproportionation of carbon (disproportionative electron transfers (mmol)/mmol of carbon). The zero intercept and proportionality between energy yield and degree of redox disproportionation exhibited by this plot demonstrate that redox disproportionation is the principal energy source of these redox reactions (slope of linear fit = -10.4 cal/mmol of disproportionative electron transfers). The energy and disproportionation values of E. coli amino acid and lipid biosynthesis from glucose lie near this linear curve fit with redox disproportionation accounting for 84% and 96% (and ATP only 6% and 1 %) of the total energy of amino acid and lipid biosynthesis, respectively. These observations establish that redox disproportionation of carbon, and not ATP, is the primary energy source driving amino acid and lipid biosynthesis from glucose. In contrast, we found that nucteotide biosynthesis involves very little redox disproportionation, and consequently depends almost entirely on ATP for energy. The function of sugar redox disproportionation as the major source of free energy for the biosynthesis of amino acids and lipids suggests that sugar disproportionation played a central role in the origin of metabolism, and probably the origin of life.

  17. Energy from Redox Disproportionation of Sugar Carbon Drives Biotic and Abiotic Synthesis

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.

    1997-01-01

    To identify the energy source that drives the biosynthesis of amino acids, lipids, and nucleotides from glucose, we calculated the free energy change due to redox disproportionation of the substrate carbon of: (1) 26-carbon fermentation reactions and (2) the biosynthesis of amino acids and lipids of E. coli from glucose. The free energy (cal/mmol of carbon) of these reactions was plotted as a function of the degree of redox disproportionation of carbon (disproportionative electron transfers (mmol)/mmol of carbon). The zero intercept and proportionality between energy yield and degree of redox disproportionation exhibited by this plot demonstrate that redox disproportionation is the principal energy source of these redox reactions (slope of linear fit = -10.4 cal/mmol of disproportionative electron transfers). The energy and disproportionation values of E. coli amino acid and lipid biosynthesis from glucose lie near this linear curve fit with redox disproportionation accounting for 84% and 96% (and ATP only 6% and 1%) of the total energy of amino acid and lipid biosynthesis, respectively. These observations establish that redox disproportionation of carbon, and not ATP, is the primary energy source driving amino acid and lipid biosynthesis from glucose. In contrast, we found that nucleotide biosynthesis involves very little redox disproportionation, and consequently depends almost entirely on ATP for energy. The function of sugar redox disproportionation as the major source of free energy for the biosynthesis of amino acids and lipids suggests that sugar disproportionation played a central role in the origin of metabolism, and probably the origin of life.

  18. The SnRK1 Energy Sensor in Plant Biotic Interactions.

    PubMed

    Hulsmans, Sander; Rodriguez, Marianela; De Coninck, Barbara; Rolland, Filip

    2016-08-01

    Our understanding of plant biotic interactions has grown significantly in recent years with the identification of the mechanisms involved in innate immunity, hormone signaling, and secondary metabolism. The impact of such interactions on primary metabolism and the role of metabolic signals in the response of the plants, however, remain far less explored. The SnRK1 (SNF1-related kinase 1) kinases act as metabolic sensors, integrating very diverse stress conditions, and are key in maintaining energy homeostasis for growth and survival. Consistently, an important role is emerging for these kinases as regulators of biotic stress responses triggered by viral, bacterial, fungal, and oomycete infections as well as by herbivory. While this identifies SnRK1 as a promising target for directed modification or selection for more quantitative and sustainable resistance, its central function also increases the chances of unwanted side effects on growth and fitness, stressing the need for identification and in-depth characterization of the mechanisms and target processes involved. VIDEO ABSTRACT. PMID:27156455

  19. 'Trophic whales' as biotic buffers: weak interactions stabilize ecosystems against nutrient enrichment.

    PubMed

    Schwarzmüller, Florian; Eisenhauer, Nico; Brose, Ulrich

    2015-05-01

    Human activities may compromise biodiversity if external stressors such as nutrient enrichment endanger overall network stability by inducing unstable dynamics. However, some ecosystems maintain relatively high diversity levels despite experiencing continuing disturbances. This indicates that some intrinsic properties prevent unstable dynamics and resulting extinctions. Identifying these 'ecosystem buffers' is crucial for our understanding of the stability of ecosystems and an important tool for environmental and conservation biologists. In this vein, weak interactions have been suggested as stabilizing elements of complex systems, but their relevance has rarely been tested experimentally. Here, using network and allometric theory, we present a novel concept for a priori identification of species that buffer against externally induced instability of increased population oscillations via weak interactions. We tested our model in a microcosm experiment using a soil food-web motif. Our results show that large-bodied species feeding at the food web's base, so called 'trophic whales', can buffer ecosystems against unstable dynamics induced by nutrient enrichment. Similar to the functionality of chemical or mechanical buffers, they serve as 'biotic buffers' that take up stressor effects and thus protect fragile systems from instability. We discuss trophic whales as common functional building blocks across ecosystems. Considering increasing stressor effects under anthropogenic global change, conservation of these network-intrinsic biotic buffers may help maintain the stability and diversity of natural ecosystems. PMID:25420573

  20. Separating the role of biotic interactions and climate in determining adaptive response of plants to climate change.

    PubMed

    Tomiolo, Sara; Van der Putten, Wim H; Tielbörger, Katja

    2015-05-01

    Altered rainfall regimes will greatly affect the response of plant species to climate change. However, little is known about how direct effects of changing precipitation on plant performance may depend on other abiotic factors and biotic interactions. We used reciprocal transplants between climatically very different sites with simultaneous manipulation of soil, plant population origin, and neighbor conditions to evaluate local adaptation and possible adaptive response of four Eastern Mediterranean annual plant species to climate change. The effect of site on plant performance was negligible, but soil origin had a strong effect on fecundity, most likely due to differential water retaining ability. Competition by neighbors strongly reduced fitness. We separated the effects of the abiotic and biotic soil properties on plant performance by repeating the field experiment in a greenhouse under homogenous environmental conditions and including a soil biota manipulation treatment. As in the field, plant performance differed among soil origins and neighbor treatments. Moreover, we found plant species-specific responses to soil biota that may be best explained by the differential sensitivity to negative and positive soil biota effects. Overall, under the conditions of our experiment with two contrasting sites, biotic interactions had a strong effect on plant fitness that interacted with and eventually overrode climate. Because climate and biotic interactions covary, reciprocal transplants and climate gradient studies should consider soil biotic interactions and abiotic conditions when evaluating climate change effects on plant performance. PMID:26236843

  1. The role of biotic interactions in shaping distributions and realised assemblages of species: implications for species distribution modelling

    PubMed Central

    Wisz, Mary Susanne; Pottier, Julien; Kissling, W Daniel; Pellissier, Loïc; Lenoir, Jonathan; Damgaard, Christian F; Dormann, Carsten F; Forchhammer, Mads C; Grytnes, John-Arvid; Guisan, Antoine; Heikkinen, Risto K; Høye, Toke T; Kühn, Ingolf; Luoto, Miska; Maiorano, Luigi; Nilsson, Marie-Charlotte; Normand, Signe; Öckinger, Erik; Schmidt, Niels M; Termansen, Mette; Timmermann, Allan; Wardle, David A; Aastrup, Peter; Svenning, Jens-Christian

    2013-01-01

    Predicting which species will occur together in the future, and where, remains one of the greatest challenges in ecology, and requires a sound understanding of how the abiotic and biotic environments interact with dispersal processes and history across scales. Biotic interactions and their dynamics influence species' relationships to climate, and this also has important implications for predicting future distributions of species. It is already well accepted that biotic interactions shape species' spatial distributions at local spatial extents, but the role of these interactions beyond local extents (e.g. 10 km2 to global extents) are usually dismissed as unimportant. In this review we consolidate evidence for how biotic interactions shape species distributions beyond local extents and review methods for integrating biotic interactions into species distribution modelling tools. Drawing upon evidence from contemporary and palaeoecological studies of individual species ranges, functional groups, and species richness patterns, we show that biotic interactions have clearly left their mark on species distributions and realised assemblages of species across all spatial extents. We demonstrate this with examples from within and across trophic groups. A range of species distribution modelling tools is available to quantify species environmental relationships and predict species occurrence, such as: (i) integrating pairwise dependencies, (ii) using integrative predictors, and (iii) hybridising species distribution models (SDMs) with dynamic models. These methods have typically only been applied to interacting pairs of species at a single time, require a priori ecological knowledge about which species interact, and due to data paucity must assume that biotic interactions are constant in space and time. To better inform the future development of these models across spatial scales, we call for accelerated collection of spatially and temporally explicit species data. Ideally

  2. Biotic Interactions in Microbial Communities as Modulators of Biogeochemical Processes: Methanotrophy as a Model System

    PubMed Central

    Ho, Adrian; Angel, Roey; Veraart, Annelies J.; Daebeler, Anne; Jia, Zhongjun; Kim, Sang Yoon; Kerckhof, Frederiek-Maarten; Boon, Nico; Bodelier, Paul L. E.

    2016-01-01

    Microbial interaction is an integral component of microbial ecology studies, yet the role, extent, and relevance of microbial interaction in community functioning remains unclear, particularly in the context of global biogeochemical cycles. While many studies have shed light on the physico-chemical cues affecting specific processes, (micro)biotic controls and interactions potentially steering microbial communities leading to altered functioning are less known. Yet, recent accumulating evidence suggests that the concerted actions of a community can be significantly different from the combined effects of individual microorganisms, giving rise to emergent properties. Here, we exemplify the importance of microbial interaction for ecosystem processes by analysis of a reasonably well-understood microbial guild, namely, aerobic methane-oxidizing bacteria (MOB). We reviewed the literature which provided compelling evidence for the relevance of microbial interaction in modulating methane oxidation. Support for microbial associations within methane-fed communities is sought by a re-analysis of literature data derived from stable isotope probing studies of various complex environmental settings. Putative positive interactions between active MOB and other microbes were assessed by a correlation network-based analysis with datasets covering diverse environments where closely interacting members of a consortium can potentially alter the methane oxidation activity. Although, methanotrophy is used as a model system, the fundamentals of our postulations may be applicable to other microbial guilds mediating other biogeochemical processes. PMID:27602021

  3. Biotic Interactions in Microbial Communities as Modulators of Biogeochemical Processes: Methanotrophy as a Model System.

    PubMed

    Ho, Adrian; Angel, Roey; Veraart, Annelies J; Daebeler, Anne; Jia, Zhongjun; Kim, Sang Yoon; Kerckhof, Frederiek-Maarten; Boon, Nico; Bodelier, Paul L E

    2016-01-01

    Microbial interaction is an integral component of microbial ecology studies, yet the role, extent, and relevance of microbial interaction in community functioning remains unclear, particularly in the context of global biogeochemical cycles. While many studies have shed light on the physico-chemical cues affecting specific processes, (micro)biotic controls and interactions potentially steering microbial communities leading to altered functioning are less known. Yet, recent accumulating evidence suggests that the concerted actions of a community can be significantly different from the combined effects of individual microorganisms, giving rise to emergent properties. Here, we exemplify the importance of microbial interaction for ecosystem processes by analysis of a reasonably well-understood microbial guild, namely, aerobic methane-oxidizing bacteria (MOB). We reviewed the literature which provided compelling evidence for the relevance of microbial interaction in modulating methane oxidation. Support for microbial associations within methane-fed communities is sought by a re-analysis of literature data derived from stable isotope probing studies of various complex environmental settings. Putative positive interactions between active MOB and other microbes were assessed by a correlation network-based analysis with datasets covering diverse environments where closely interacting members of a consortium can potentially alter the methane oxidation activity. Although, methanotrophy is used as a model system, the fundamentals of our postulations may be applicable to other microbial guilds mediating other biogeochemical processes. PMID:27602021

  4. Biotic interactions as determinants of ecosystem structure in prairie wetlands: An example using fish

    USGS Publications Warehouse

    Hanson, M.A.; Zimmer, K.D.; Butler, Malcolm G.; Tangen, B.A.; Herwig, B.R.; Euliss, N.H., Jr.

    2005-01-01

    Wetlands are abundant throughout the prairie pothole region (PPR), an area comprising over 700,000 km2 in central North America. Prairie wetland communities are strongly influenced by regional physiography and climate, resulting in extreme spatial and temporal variability relative to other aquatic ecosystems. Given the strong influence of abiotic factors, PPR wetland communities have been viewed traditionally in the context of their responses to chemical and physical features of landscape and climate. Although useful, this physical-chemical paradigm may fail to account for ecosystem variability due to biotic influences, particularly those associated with presence of fish. Spatial and temporal variability in fish populations, in turn, may reflect anthropogenic activities, landscape characteristics, and climate-mediated effects on water levels, surface connectivity, and hydroperiods. We reviewed studies assessing influences of fish on prairie wetlands and examined precipitation patterns and biological data from PPR wetlands in east-central North Dakota and western Minnesota, USA. Our review and analysis indicated that native fish influence many characteristics of permanently flooded prairie wetlands, including water clarity and abundance of phytoplankton, submerged macrophytes, and aquatic invertebrates. We suggest that ecologists and managers will benefit from conceptual paradigms that better meld biotic interactions associated with fish, and perhaps other organisms, with chemical and physical influences on prairie wetland communities. ?? 2005, The Society of Wetland Scientists.

  5. No species is an island: testing the effects of biotic interactions on models of avian niche occupation.

    PubMed

    Morelli, Federico; Tryjanowski, Piotr

    2015-02-01

    Traditionally, the niche of a species is described as a hypothetical 3D space, constituted by well-known biotic interactions (e.g. predation, competition, trophic relationships, resource-consumer interactions, etc.) and various abiotic environmental factors. Species distribution models (SDMs), also called "niche models" and often used to predict wildlife distribution at landscape scale, are typically constructed using abiotic factors with biotic interactions generally been ignored. Here, we compared the goodness of fit of SDMs for red-backed shrike Lanius collurio in farmlands of Western Poland, using both the classical approach (modeled only on environmental variables) and the approach which included also other potentially associated bird species. The potential associations among species were derived from the relevant ecological literature and by a correlation matrix of occurrences. Our findings highlight the importance of including heterospecific interactions in improving our understanding of niche occupation for bird species. We suggest that suite of measures currently used to quantify realized species niches could be improved by also considering the occurrence of certain associated species. Then, an hypothetical "species 1" can use the occurrence of a successfully established individual of "species 2" as indicator or "trace" of the location of available suitable habitat to breed. We hypothesize this kind of biotic interaction as the "heterospecific trace effect" (HTE): an interaction based on the availability and use of "public information" provided by individuals from different species. Finally, we discuss about the incomes of biotic interactions for enhancing the predictive capacities on species distribution models. PMID:25691996

  6. Niche-habitat mechanisms and biotic interactions explain the coexistence and abundance of congeneric sandgrouse species.

    PubMed

    Benítez-López, Ana; Viñuela, Javier; Suárez, Francisco; Hervás, Israel; García, Jesús T

    2014-09-01

    Ascertaining which niche processes allow coexistence between closely related species is of special interest in ecology. We quantified variations in the environmental niches and densities of two congeneric species, the pin-tailed and the black-bellied sandgrouse (Pterocles alchata and Pterocles orientalis) in allopatry and sympatry under similar abiotic, habitat and dispersal contexts to understand their coexistence. Using principal component analysis, we defined environmental gradients (niche dimensions) including abiotic, habitat and anthropogenic variables, and calculated niche breadth, position and overlap of both species in sympatry and allopatry. Additionally, sandgrouse density was modelled as a function of the niche dimensions and the density of the other species. We found evidence that each species occupies distinct environmental niches in sympatry and in allopatry. The black-bellied sandgrouse exploits a broader range of environmental conditions (wider niche breadth) while the pin-tailed sandgrouse reaches high densities where conditions seem to match its optimum. In sympatry, both species shift their niches to intermediate positions, indicating the importance of abiotic factors in setting coexistence areas. Environmental conditions determine regional densities of pin-tailed sandgrouse whereas biotic interactions explain the density of the black-bellied sandgrouse in areas with abiotic conditions similarly conducive for both species. Highly suitable areas for the pin-tailed sandgrouse fall beyond the upper thermal limit of the black-bellied sandgrouse, leading to niche segregation and low densities for the latter. Finally, local niche shift and expansion plus possible heterospecific aggregation allow the pin-tailed sandgrouse to thrive in a priori less favourable environments. This work provides insight into how different mechanisms allow species coexistence and how species densities vary in sympatry compared to allopatry as a result of environmental

  7. Evolution in agriculture: the application of evolutionary approaches to the management of biotic interactions in agro-ecosystems

    PubMed Central

    Thrall, Peter H; Oakeshott, John G; Fitt, Gary; Southerton, Simon; Burdon, Jeremy J; Sheppard, Andy; Russell, Robyn J; Zalucki, Myron; Heino, Mikko; Ford Denison, R

    2011-01-01

    Anthropogenic impacts increasingly drive ecological and evolutionary processes at many spatio-temporal scales, demanding greater capacity to predict and manage their consequences. This is particularly true for agro-ecosystems, which not only comprise a significant proportion of land use, but which also involve conflicting imperatives to expand or intensify production while simultaneously reducing environmental impacts. These imperatives reinforce the likelihood of further major changes in agriculture over the next 30–40 years. Key transformations include genetic technologies as well as changes in land use. The use of evolutionary principles is not new in agriculture (e.g. crop breeding, domestication of animals, management of selection for pest resistance), but given land-use trends and other transformative processes in production landscapes, ecological and evolutionary research in agro-ecosystems must consider such issues in a broader systems context. Here, we focus on biotic interactions involving pests and pathogens as exemplars of situations where integration of agronomic, ecological and evolutionary perspectives has practical value. Although their presence in agro-ecosystems may be new, many traits involved in these associations evolved in natural settings. We advocate the use of predictive frameworks based on evolutionary models as pre-emptive management tools and identify some specific research opportunities to facilitate this. We conclude with a brief discussion of multidisciplinary approaches in applied evolutionary problems. PMID:25567968

  8. The interactive biotic and abiotic processes of DDT transformation under dissimilatory iron-reducing conditions.

    PubMed

    Jin, Xin; Wang, Fang; Gu, Chenggang; Yang, Xinglun; Kengara, Fredrick O; Bian, Yongrong; Song, Yang; Jiang, Xin

    2015-11-01

    The objective of the study was to elucidate the biotic and abiotic processes under dissimilatory iron reducing conditions involved in reductive dechlorination and iron reduction. DDT transformation was investigated in cultures of Shewanella putrefaciens 200 with/without α-FeOOH. A modified first-order kinetics model was developed and described DDT transformation well. Both the α-FeOOH reduction rate and the dechlorination rate of DDT were positively correlated to the biomass. Addition of α-FeOOH enhanced reductive dechlorination of DDT by favoring the cell survival and generating Fe(II) which was absorbed on the surface of bacteria and iron oxide. 92% of the absorbed Fe(II) was Na-acetate (1M) extractable. However, α-FeOOH also played a negative role of competing for electrons as reflected by the dechlorination rate of DDT was inhibited when increasing the α-FeOOH from 1 g L(-1) to 5 g L(-1). DDT was measured to be toxic to S. putrefaciens 200. The metabolites DDD, DDE and DDMU were recalcitrant to S. putrefaciens 200. The results suggested that iron oxide was not the key factor to promote the dissipation of DDX (DDT and the metabolites), whereas the one-electron reduction potential (E1) of certain organochlorines is the main factor and that the E1 higher than the threshold of the reductive driving forces of DIRB probably ensures the occur of reductive dechlorination. PMID:26025430

  9. Climate change and invasion by intracontinental range-expanding exotic plants: the role of biotic interactions

    PubMed Central

    Morriën, Elly; Engelkes, Tim; Macel, Mirka; Meisner, Annelein; Van der Putten, Wim H.

    2010-01-01

    Background and Aims In this Botanical Briefing we describe how the interactions between plants and their biotic environment can change during range-expansion within a continent and how this may influence plant invasiveness. Scope We address how mechanisms explaining intercontinental plant invasions by exotics (such as release from enemies) may also apply to climate-warming-induced range-expanding exotics within the same continent. We focus on above-ground and below-ground interactions of plants, enemies and symbionts, on plant defences, and on nutrient cycling. Conclusions Range-expansion by plants may result in above-ground and below-ground enemy release. This enemy release can be due to the higher dispersal capacity of plants than of natural enemies. Moreover, lower-latitudinal plants can have higher defence levels than plants from temperate regions, making them better defended against herbivory. In a world that contains fewer enemies, exotic plants will experience less selection pressure to maintain high levels of defensive secondary metabolites. Range-expanders potentially affect ecosystem processes, such as nutrient cycling. These features are quite comparable with what is known of intercontinental invasive exotic plants. However, intracontinental range-expanding plants will have ongoing gene-flow between the newly established populations and the populations in the native range. This is a major difference from intercontinental invasive exotic plants, which become more severely disconnected from their source populations. PMID:20354072

  10. Causes of variation in biotic interaction strength and phenotypic selection along an altitudinal gradient.

    PubMed

    Mezquida, Eduardo T; Benkman, Craig W

    2014-06-01

    Understanding the causes of variation in biotic interaction strength and phenotypic selection remains one of the outstanding goals of evolutionary ecology. Here we examine the variation in strength of interactions between two seed predators, common crossbills (Loxia curvirostra) and European red squirrels (Sciurus vulgaris), and mountain pine (Pinus uncinata) at and below tree limit in the Pyrenees, and how this translates into phenotypic selection. Seed predation by crossbills increased whereas seed predation by squirrels decreased with increasing elevation and as the canopy became more open. Overall, seed predation by crossbills averaged about twice that by squirrels, and the intensity of selection exerted by crossbills averaged between 2.6 and 7.5 times greater than by squirrels. The higher levels of seed predation by crossbills than squirrels were related to the relatively open nature of most of the forests, and the higher intensity of selection exerted by crossbills resulted from their higher levels of seed predation. However, most of the differences in selection intensity between crossbills and squirrels were the result of habitat features having a greater effect on the foraging behavior of squirrels than of crossbills, causing selection to be much lower for squirrels than for crossbills. PMID:24593660

  11. Soil biotic interactions and climate change: consequences for carbon cycle feedbacks

    NASA Astrophysics Data System (ADS)

    Bardgett, Richard

    2015-04-01

    There is currently much interest in understanding the biological mechanisms that regulate carbon exchanges between land and atmosphere, and how these exchanges respond to climate change. Climate change impacts on biogeochemical cycles via a variety of mechanisms; but there is now mounting evidence that biotic interactions between plants and diverse soil communities play a major role in determining carbon cycle responses to climate change across a range of spatial and temporal scales. Over seasonal and annual timescales, climate change impacts the growth and physiology of plants and their roots, with knock on effects for the activity of soil biota and carbon transformations; in the longer term, over tens to hundreds of years, climate change can cause shifts in community composition, and species range expansions and contractions, with cascading impacts on belowground communities and carbon cycling in soil. These responses have local and, potentially, global scale implications for carbon cycle feedbacks. In this talk, I will draw on recent research to illustrate this hierarchy of plant-soil feedback responses to climate change, the mechanisms involved, and consequences for the carbon cycle at local and global scales. I will also discuss how such knowledge on plant-soil interactions might be harnessed to inform management strategies for soil carbon sequestration and mitigation of climate change, and identify some major research challenges for the future.

  12. No species is an island: testing the effects of biotic interactions on models of avian niche occupation

    PubMed Central

    Morelli, Federico; Tryjanowski, Piotr

    2015-01-01

    Traditionally, the niche of a species is described as a hypothetical 3D space, constituted by well-known biotic interactions (e.g. predation, competition, trophic relationships, resource–consumer interactions, etc.) and various abiotic environmental factors. Species distribution models (SDMs), also called “niche models” and often used to predict wildlife distribution at landscape scale, are typically constructed using abiotic factors with biotic interactions generally been ignored. Here, we compared the goodness of fit of SDMs for red-backed shrike Lanius collurio in farmlands of Western Poland, using both the classical approach (modeled only on environmental variables) and the approach which included also other potentially associated bird species. The potential associations among species were derived from the relevant ecological literature and by a correlation matrix of occurrences. Our findings highlight the importance of including heterospecific interactions in improving our understanding of niche occupation for bird species. We suggest that suite of measures currently used to quantify realized species niches could be improved by also considering the occurrence of certain associated species. Then, an hypothetical “species 1” can use the occurrence of a successfully established individual of “species 2” as indicator or “trace” of the location of available suitable habitat to breed. We hypothesize this kind of biotic interaction as the “heterospecific trace effect” (HTE): an interaction based on the availability and use of “public information” provided by individuals from different species. Finally, we discuss about the incomes of biotic interactions for enhancing the predictive capacities on species distribution models. PMID:25691996

  13. Plant microRNAs: key regulators of root architecture and biotic interactions.

    PubMed

    Couzigou, Jean-Malo; Combier, Jean-Philippe

    2016-10-01

    Contents 22 I. 22 II. 24 III. 25 IV. 27 V. 29 VI. 10 31 References 32 SUMMARY: Plants have evolved a remarkable faculty of adaptation to deal with various and changing environmental conditions. In this context, the roots have taken over nutritional aspects and the root system architecture can be modulated in response to nutrient availability or biotic interactions with soil microorganisms. This adaptability requires a fine tuning of gene expression. Indeed, root specification and development are highly complex processes requiring gene regulatory networks involved in hormonal regulations and cell identity. Among the different molecular partners governing root development, microRNAs (miRNAs) are key players for the fast regulation of gene expression. miRNAs are small RNAs involved in most developmental processes and are required for the normal growth of organisms, by the negative regulation of key genes, such as transcription factors and hormone receptors. Here, we review the known roles of miRNAs in root specification and development, from the embryonic roots to the establishment of root symbioses, highlighting the major roles of miRNAs in these processes. PMID:27292927

  14. Adding Biotic Interactions into Paleodistribution Models: A Host-Cleptoparasite Complex of Neotropical Orchid Bees

    PubMed Central

    Silva, Daniel Paiva; Varela, Sara; Nemésio, André; De Marco, Paulo

    2015-01-01

    Orchid bees compose an exclusive Neotropical pollinators group, with bright body coloration. Several of those species build their own nests, while others are reported as nest cleptoparasites. Here, the objective was to evaluate whether the inclusion of a strong biotic interaction, such as the presence of a host species, improved the ability of species distribution models (SDMs) to predict the geographic range of the cleptoparasite species. The target species were Aglae caerulea and its host species Eulaema nigrita. Additionally, since A. caerulea is more frequently found in the Amazon rather than the Cerrado areas, a secondary objective was to evaluate whether this species is increasing or decreasing its distribution given South American past and current climatic conditions. SDMs methods (Maxent and Bioclim), in addition with current and past South American climatic conditions, as well as the occurrences for A. caerulea and E. nigrita were used to generate the distribution models. The distribution of A. caerulea was generated with and without the inclusion of the distribution of E. nigrita as a predictor variable. The results indicate A. caerulea was barely affected by past climatic conditions and the populations from the Cerrado savanna could be at least 21,000 years old (the last glacial maximum), as well as the Amazonian ones. On the other hand, in this study, the inclusion of the host-cleptoparasite interaction complex did not statistically improve the quality of the produced models, which means that the geographic range of this cleptoparasite species is mainly constrained by climate and not by the presence of the host species. Nonetheless, this could also be caused by unknown complexes of other Euglossini hosts with A. caerulea, which still are still needed to be described by science. PMID:26069956

  15. Aerobic bacterial catabolism of persistent organic pollutants - potential impact of biotic and abiotic interaction.

    PubMed

    Jeon, Jong-Rok; Murugesan, Kumarasamy; Baldrian, Petr; Schmidt, Stefan; Chang, Yoon-Seok

    2016-04-01

    Several aerobic bacteria possess unique catabolic pathways enabling them to degrade persistent organic pollutants (POPs), including polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs), polybrominated diphenylethers (PBDEs), and polychlorinated biphenyls (PCBs). The catabolic activity of aerobic bacteria employed for removal of POPs in the environment may be modulated by several biotic (i.e. fungi, plants, algae, earthworms, and other bacteria) and abiotic (i.e. zero-valent iron, advanced oxidation, and electricity) agents. This review describes the basic biochemistry of the aerobic bacterial catabolism of selected POPs and discusses how biotic and abiotic agents enhance or inhibit the process. Solutions allowing biotic and abiotic agents to exert physical and chemical assistance to aerobic bacterial catabolism of POPs are also discussed. PMID:26851837

  16. Combined effects of climate and biotic interactions on the elevational range of a phytophagous insect.

    PubMed

    Merrill, Richard M; Gutiérrez, David; Lewis, Owen T; Gutiérrez, Javier; Díez, Sonia B; Wilson, Robert J

    2008-01-01

    1. The ranges of many species have expanded in cool regions but contracted at warm margins in response to recent climate warming, but the mechanisms behind such changes remain unclear. Particular debate concerns the roles of direct climatic limitation vs. the effects of interacting species in explaining the location of low latitude or low elevation range margins. 2. The mountains of the Sierra de Guadarrama (central Spain) include both cool and warm range margins for the black-veined white butterfly, Aporia crataegi, which has disappeared from low elevations since the 1970s without colonizing the highest elevations. 3. We found that the current upper elevation limit to A. crataegi's distribution coincided closely with that of its host plants, but that the species was absent from elevations below 900 m, even where host plants were present. The density of A. crataegi per host plant increased with elevation, but overall abundance of the species declined at high elevations where host plants were rare. 4. The flight period of A. crataegi was later at higher elevations, meaning that butterflies in higher populations flew at hotter times of year; nevertheless, daytime temperatures for the month of peak flight decreased by 6.2 degrees C per 1 km increase in elevation. 5. At higher elevations A. crataegi eggs were laid on the south side of host plants (expected to correspond to hotter microclimates), whereas at lower sites the (cooler) north side of plants was selected. Field transplant experiments showed that egg survival increased with elevation. 6. Climatic limitation is the most likely explanation for the low elevation range margin of A. crataegi, whereas the absence of host plants from high elevations sets the upper limit. This contrasts with the frequent assumption that biotic interactions typically determine warm range margins, and thermal limitation cool margins. 7. Studies that have modelled distribution changes in response to climate change may have underestimated

  17. Species Introductions and Their Cascading Impacts on Biotic Interactions in desert riparian ecosystems.

    PubMed

    Hultine, Kevin R; Bean, Dan W; Dudley, Tom L; Gehring, Catherine A

    2015-10-01

    Desert riparian ecosystems of North America are hotspots of biodiversity that support many sensitive species, and are in a region experiencing some of the highest rates of climatic alteration in North America. Fremont cottonwood, Populus fremontii, is a foundation tree species of this critical habitat, but it is threatened by global warming and regional drying, and by a non-native tree/shrub, Tamarix spp., all of which can disrupt the mutualism between P. fremontii and its beneficial mycorrhizal fungal communities. Specialist herbivorous leaf beetles (Diorhabda spp.) introduced for biocontrol of Tamarix are altering the relationship between this shrub and its environment. Repeated episodic feeding on Tamarix foliage by Diorhabda results in varying rates of dieback and mortality, depending on genetic variation in allocation of resources, growing conditions, and phenological synchrony between herbivore and host plant. In this article, we review the complex interaction between climatic change and species introductions and their combined impacts on P. fremontii and their associated communities. We anticipate that (1) certain genotypes of P. fremontii will respond more favorably to the presence of Tamarix and to climatic change due to varying selection pressures to cope with competition and stress; (2) the ongoing evolution of Diorhabda's life cycle timing will continue to facilitate its expansion in North America, and will over time enhance herbivore impact to Tamarix; (3) defoliation by Diorhabda will reduce the negative impact of Tamarix on P. fremontii associations with mycorrhizal fungi; and (4) spatial variability in climate and climatic change will modify the capacity for Tamarix to survive episodic defoliation by Diorhabda, thereby altering the relationship between Tamarix and P. fremontii, and its associated mycorrhizal fungal communities. Given the complex biotic/abiotic interactions outlined in this review, conservation biologists and riparian ecosystem

  18. Sewage Decomposition in Ambient Water: Influence of Solarradiation and Biotic Interactions on Microorganism Communities and Bacteroidales Real-Time Quantitative PCR Measurements - poster/abstract

    EPA Science Inventory

    AIMS: Sewage and ambient water both consist of a highly complex array of bacteria and eukaryotic microbes. When these communities are mixed, solar radiation and biotic interactions (predation and competition) can influence pathogen decay based on experiments targeting indicator ...

  19. SEWAGE DECOMPOSITION IN AMBIENT WATER: INFLUENCE OF SOLARRADIATION AND BIOTIC INTERACTIONS ON MICROORGANISM COMMUNITIES AND BACTEROIDALES REAL-TIME QUANTITATIVE PCR MEASUREMENTS - poster

    EPA Science Inventory

    AIMS: Sewage and ambient water both consist of a highly complex array of bacteria and eukaryotic microbes. When these communities are mixed, solar radiation and biotic interactions (predation and competition) can influence pathogen decay based on experiments targeting indicator ...

  20. Process-Based Species Pools Reveal the Hidden Signature of Biotic Interactions Amid the Influence of Temperature Filtering.

    PubMed

    Lessard, Jean-Philippe; Weinstein, Ben G; Borregaard, Michael K; Marske, Katharine A; Martin, Danny R; McGuire, Jimmy A; Parra, Juan L; Rahbek, Carsten; Graham, Catherine H

    2016-01-01

    A persistent challenge in ecology is to tease apart the influence of multiple processes acting simultaneously and interacting in complex ways to shape the structure of species assemblages. We implement a heuristic approach that relies on explicitly defining species pools and permits assessment of the relative influence of the main processes thought to shape assemblage structure: environmental filtering, dispersal limitations, and biotic interactions. We illustrate our approach using data on the assemblage composition and geographic distribution of hummingbirds, a comprehensive phylogeny and morphological traits. The implementation of several process-based species pool definitions in null models suggests that temperature-but not precipitation or dispersal limitation-acts as the main regional filter of assemblage structure. Incorporating this environmental filter directly into the definition of assemblage-specific species pools revealed an otherwise hidden pattern of phylogenetic evenness, indicating that biotic interactions might further influence hummingbird assemblage structure. Such hidden patterns of assemblage structure call for a reexamination of a multitude of phylogenetic- and trait-based studies that did not explicitly consider potentially important processes in their definition of the species pool. Our heuristic approach provides a transparent way to explore patterns and refine interpretations of the underlying causes of assemblage structure. PMID:27277404

  1. ALCOHOL AND DISTRACTION INTERACT TO IMPAIR DRIVING PERFORMANCE

    PubMed Central

    Harrison, Emily L. R.; Fillmore, Mark T.

    2011-01-01

    Background Recognition of the risks associated with alcohol intoxication and driver distraction has led to a wealth of simulated driving research aimed at studying the adverse effects of each of these factors. Research on driving has moved beyond the individual, separate examination of these factors to the examination of potential interactions between alcohol intoxication and driver distraction. In many driving situations, distractions are commonplace and might have little or no disruptive influence on primary driving functions. Yet, such distractions might become disruptive to a driver who is intoxicated. Methods The present study examined the interactive impairing effects of alcohol intoxication and driver distraction on simulated driving performance in 40 young adult drivers using a divided attention task as a distracter activity. The interactive influence of alcohol and distraction was tested by having drivers perform the driving task under four different conditions: 0.65 g/kg alcohol; 0.65 g/kg alcohol + divided attention; placebo; and placebo + divided attention. Results As hypothesized, divided attention had no impairing effect on driving performance in sober drivers. However, under alcohol, divided attention exacerbated the impairing effects of alcohol on driving precision. Conclusions Alcohol and distraction continue to be appropriate targets for research into ways to reduce the rates of driving-related fatalities and injuries. Greater consideration of how alcohol and distraction interact to impair aspects of driving performance can further efforts to create prevention and intervention measures to protect drivers, particularly young adults. PMID:21277119

  2. The Genetics Underlying Natural Variation in the Biotic Interactions of Arabidopsis thaliana: The Challenges of Linking Evolutionary Genetics and Community Ecology.

    PubMed

    Roux, F; Bergelson, J

    2016-01-01

    In the context of global change, predicting the responses of plant communities in an ever-changing biotic environment calls for a multipronged approach at the interface of evolutionary genetics and community ecology. However, our understanding of the genetic basis of natural variation involved in mediating biotic interactions, and associated adaptive dynamics of focal plants in their natural communities, is still in its infancy. Here, we review the genetic and molecular bases of natural variation in the response to biotic interactions (viruses, bacteria, fungi, oomycetes, herbivores, and plants) in the model plant Arabidopsis thaliana as well as the adaptive value of these bases. Among the 60 identified genes are a number that encode nucleotide-binding site leucine-rich repeat (NBS-LRR)-type proteins, consistent with early examples of plant defense genes. However, recent studies have revealed an extensive diversity in the molecular mechanisms of defense. Many types of genetic variants associate with phenotypic variation in biotic interactions, even among the genes of large effect that tend to be identified. In general, we found that (i) balancing selection rather than directional selection explains the observed patterns of genetic diversity within A. thaliana and (ii) the cost/benefit tradeoffs of adaptive alleles can be strongly dependent on both genomic and environmental contexts. Finally, because A. thaliana rarely interacts with only one biotic partner in nature, we highlight the benefit of exploring diffuse biotic interactions rather than tightly associated host-enemy pairs. This challenge would help to improve our understanding of coevolutionary quantitative genetics within the context of realistic community complexity. PMID:27282025

  3. Interactive biotic and abiotic regulators of soil carbon cycling: evidence from controlled climate experiments on peatland and boreal soils.

    PubMed

    Briones, María Jesús I; McNamara, Niall P; Poskitt, Jan; Crow, Susan E; Ostle, Nicholas J

    2014-09-01

    Partially decomposed plant and animal remains have been accumulating in organic soils (i.e. >40% C content) for millennia, making them the largest terrestrial carbon store. There is growing concern that, in a warming world, soil biotic processing will accelerate and release greenhouse gases that further exacerbate climate change. However, the magnitude of this response remains uncertain as the constraints are abiotic, biotic and interactive. Here, we examined the influence of resource quality and biological activity on the temperature sensitivity of soil respiration under different soil moisture regimes. Organic soils were sampled from 13 boreal and peatland ecosystems located in the United Kingdom, Ireland, Spain, Finland and Sweden, representing a natural resource quality range of C, N and P. They were incubated at four temperatures (4, 10, 15 and 20 °C) at either 60% or 100% water holding capacity (WHC). Our results showed that chemical and biological properties play an important role in determining soil respiration responses to temperature and moisture changes. High soil C : P and C : N ratios were symptomatic of slow C turnover and long-term C accumulation. In boreal soils, low bacterial to fungal ratios were related to greater temperature sensitivity of respiration, which was amplified in drier conditions. This contrasted with peatland soils which were dominated by bacterial communities and enchytraeid grazing, resulting in a more rapid C turnover under warmer and wetter conditions. The unexpected acceleration of C mineralization under high moisture contents was possibly linked to the primarily role of fermented organic matter, instead of oxygen, in mediating microbial decomposition. We conclude that to improve C model simulations of soil respiration, a better resolution of the interactions occurring between climate, resource quality and the decomposer community will be required. PMID:24687903

  4. Ecological interactions drive evolutionary loss of traits.

    PubMed

    Ellers, Jacintha; Kiers, E Toby; Currie, Cameron R; McDonald, Bradon R; Visser, Bertanne

    2012-10-01

    Loss of traits can dramatically alter the fate of species. Evidence is rapidly accumulating that the prevalence of trait loss is grossly underestimated. New findings demonstrate that traits can be lost without affecting the external phenotype, provided the lost function is compensated for by species interactions. This is important because trait loss can tighten the ecological relationship between partners, affecting the maintenance of species interactions. Here, we develop a new perspective on so-called `compensated trait loss' and how this type of trait loss may affect the evolutionary dynamics between interacting organisms. We argue that: (1) the frequency of compensated trait loss is currently underestimated because it can go unnoticed as long as ecological interactions are maintained; (2) by analysing known cases of trait loss, specific factors promoting compensated trait loss can be identified and (3) genomic sequencing is a key way forwards in detecting compensated trait loss. We present a comprehensive literature survey showing that compensated trait loss is taxonomically widespread, can involve essential traits, and often occurs as replicated evolutionary events. Despite its hidden nature, compensated trait loss is important in directing evolutionary dynamics of ecological relationships and has the potential to change facultative ecological interactions into obligatory ones. PMID:22747703

  5. Regulation of Copper Homeostasis and Biotic Interactions by MicroRNA 398b in Common Bean

    PubMed Central

    Valdés-López, Oswaldo; Mendoza-Soto, Ana B.; Nova-Franco, Bárbara; Sosa-Valencia, Guadalupe; Reyes, José L.; Hernández, Georgina

    2014-01-01

    MicroRNAs are recognized as important post-transcriptional regulators in plants. Information about the roles of miRNAs in common bean (Phaseolus vulgaris L.), an agronomically important legume, is yet scant. The objective of this work was to functionally characterize the conserved miRNA: miR398b and its target Cu/Zn Superoxide Dismutase 1 (CSD1) in common bean. We experimentally validated a novel miR398 target: the stress up-regulated Nodulin 19 (Nod19). Expression analysis of miR398b and target genes –CSD1 and Nod19- in bean roots, nodules and leaves, indicated their role in copper (Cu) homeostasis. In bean plants under Cu toxicity miR398b was decreased and Nod19 and CSD1, that participates in reactive oxygen species (ROS) detoxification, were up-regulated. The opposite regulation was observed in Cu deficient bean plants; lower levels of CSD1 would allow Cu delivery to essential Cu-containing proteins. Composite common bean plants with transgenic roots over-expressing miR398 showed ca. 20-fold higher mature miR398b and almost negligible target transcript levels as well as increased anthocyanin content and expression of Cu-stress responsive genes, when subjected to Cu deficiency. The down-regulation of miR398b with the consequent up-regulation of its targets was observed in common bean roots during the oxidative burst resulting from short-time exposure to high Cu. A similar response occurred at early stage of bean roots inoculated with Rhizobium tropici, where an increase in ROS was observed. In addition, the miR398b down-regulation and an increase in CSD1 and Nod19 were observed in bean leaves challenged with Sclerotinia scleortiorum fungal pathogen. Transient over-expression of miR398b in Nicotiana benthamiana leaves infected with S. sclerotiorum resulted in enhanced fungal lesions. We conclude that the miR398b-mediated up-regulation of CSD and Nod19 is relevant for common bean plants to cope with oxidative stress generated in abiotic and biotic stresses. PMID

  6. Mechanosensory interactions drive collective behaviour in Drosophila.

    PubMed

    Ramdya, Pavan; Lichocki, Pawel; Cruchet, Steeve; Frisch, Lukas; Tse, Winnie; Floreano, Dario; Benton, Richard

    2015-03-12

    Collective behaviour enhances environmental sensing and decision-making in groups of animals. Experimental and theoretical investigations of schooling fish, flocking birds and human crowds have demonstrated that simple interactions between individuals can explain emergent group dynamics. These findings indicate the existence of neural circuits that support distributed behaviours, but the molecular and cellular identities of relevant sensory pathways are unknown. Here we show that Drosophila melanogaster exhibits collective responses to an aversive odour: individual flies weakly avoid the stimulus, but groups show enhanced escape reactions. Using high-resolution behavioural tracking, computational simulations, genetic perturbations, neural silencing and optogenetic activation we demonstrate that this collective odour avoidance arises from cascades of appendage touch interactions between pairs of flies. Inter-fly touch sensing and collective behaviour require the activity of distal leg mechanosensory sensilla neurons and the mechanosensory channel NOMPC. Remarkably, through these inter-fly encounters, wild-type flies can elicit avoidance behaviour in mutant animals that cannot sense the odour--a basic form of communication. Our data highlight the unexpected importance of social context in the sensory responses of a solitary species and open the door to a neural-circuit-level understanding of collective behaviour in animal groups. PMID:25533959

  7. At the interface: Biotic-abiotic interactions between substrates and a model epithlium

    NASA Astrophysics Data System (ADS)

    Covell, Alan D.

    The need for determining the fundamental mechanisms that define the interaction of biological systems with underlying materials, both natural and synthetic, is important as humanity endeavors to improve the quality of life of individuals through technology. Recently, much work has focused on the role of material properties on the behavior of cells. Most of these studies have concentrated their efforts on fibroblastic cell lines and more recently different kinds of stems cells. While these cells represent an important subset of cells in complex organisms, they do not manifest cell-cell interactions, a feature of epithelial cells, the most abundant cell type. Epithelial cells represent the largest cell type in the body and introduce an intrinsic complexity when researching the interaction of biological systems with materials. Adherens junctions (AJ) play a significant role in many signaling pathways, and therefore there is need to investigate how physical interactions with underlying substrates affect cell-cell interactions, such as the adhesion properties between cells, as well as how cell-substrate interactions influence the morphology and growth of epithelial cells. In this work I seek to determine the effects and identify mechanisms that epithelial cells use to "read" their environment. To do this I examined changes in cell behavior (growth, morphological, adhesion) of a model epithelium on substrates that have similar composition but significant differences in surface organization. In such a manner, I probed the limitations at which the nanoscale differences in substrate topography affect cellular behavior.

  8. Epibiotic mutualists alter coral susceptibility and response to biotic disturbance through cascading trait-mediated indirect interactions

    NASA Astrophysics Data System (ADS)

    Bergsma, G. S.

    2012-06-01

    Biotic disturbances are important drivers of community structure, but interactions among community members can determine trajectories of response and recovery. On coral reefs in French Polynesia, epibiotic amphipods induce the formation of branch-like "fingers" on flat colonies of encrusting Montipora coral. The fingers form as coral encrusts the amphipods' tubes and lead to significant changes in colony morphology. I tested whether the induced morphological changes affect Montipora's susceptibility to predation by pincushion ( Culcita novaeguineae) and crown-of-thorns sea stars ( Acanthaster planci). Montipora with fingers were less likely to be attacked and more likely to survive attack than colonies without fingers. Furthermore, the presence of fingers altered A. planci prey preference. Sea stars preferred Montipora without fingers over other common coral genera, but preferred other genera when Montipora had fingers. Amphipods indirectly affected Montipora's resistance and resilience to predation, and the susceptibility of other coral genera to predation, through induced morphological changes. Such trait-mediated indirect interactions likely play an important role in determining how species respond to periodic sea star outbreaks.

  9. Physiological and molecular implications of plant polyamine metabolism during biotic interactions

    PubMed Central

    Jiménez-Bremont, Juan F.; Marina, María; Guerrero-González, María de la Luz; Rossi, Franco R.; Sánchez-Rangel, Diana; Rodríguez-Kessler, Margarita; Ruiz, Oscar A.; Gárriz, Andrés

    2014-01-01

    During ontogeny, plants interact with a wide variety of microorganisms. The association with mutualistic microbes results in benefits for the plant. By contrast, pathogens may cause a remarkable impairment of plant growth and development. Both types of plant–microbe interactions provoke notable changes in the polyamine (PA) metabolism of the host and/or the microbe, being each interaction a complex and dynamic process. It has been well documented that the levels of free and conjugated PAs undergo profound changes in plant tissues during the interaction with microorganisms. In general, this is correlated with a precise and coordinated regulation of PA biosynthetic and catabolic enzymes. Interestingly, some evidence suggests that the relative importance of these metabolic pathways may depend on the nature of the microorganism, a concept that stems from the fact that these amines mediate the activation of plant defense mechanisms. This effect is mediated mostly through PA oxidation, even though part of the response is activated by non-oxidized PAs. In the last years, a great deal of effort has been devoted to profile plant gene expression following microorganism recognition. In addition, the phenotypes of transgenic and mutant plants in PA metabolism genes have been assessed. In this review, we integrate the current knowledge on this field and analyze the possible roles of these amines during the interaction of plants with microbes. PMID:24672533

  10. Vegetation-Precipitation Interactions Drive Paleoenvironmental Evolution

    NASA Astrophysics Data System (ADS)

    Fraticelli, C. M.; West, B. P.; Bohacs, K. M.; Patterson, P. E.; Heins, W. A.

    2004-12-01

    , increased moisture retention and decreased temperatures ameliorated the climatic extremes of continental interiors, enhancing chemical weathering, retarding sediment fluxes, and increasing the dissolved load of streams. The increased vegetative cover on uplands also stabilized sediment yields and increased the formation of finer-grained sediments in any given paleogeographic setting. The post-Oligocene period spans the evolution of grasslands, tundra and taiga environments, which further expanded the vegetative cover of terrestrial environments. As the nature of vegetation has changed during the Phanerozoic, the nature of the interactions between vegetation, paleoenvironments, and sediment yield has also evolved. These changes dramatically affect what paleoenvironmental conditions are predictable for the past, our understanding of ancient sediment yields, and the relationship between climate and continental depositional systems.

  11. Synergistic interactions of biotic and abiotic environmental stressors on gene expression.

    PubMed

    Altshuler, Ianina; McLeod, Anne M; Colbourne, John K; Yan, Norman D; Cristescu, Melania E

    2015-03-01

    Understanding the response of organisms to multiple stressors is critical for predicting if populations can adapt to rapid environmental change. Natural and anthropogenic stressors often interact, complicating general predictions. In this study, we examined the interactive and cumulative effects of two common environmental stressors, lowered calcium concentration, an anthropogenic stressor, and predator presence, a natural stressor, on the water flea Daphnia pulex. We analyzed expression changes of five genes involved in calcium homeostasis - cuticle proteins (Cutie, Icp2), calbindin (Calb), and calcium pump and channel (Serca and Ip3R) - using real-time quantitative PCR (RT-qPCR) in a full factorial experiment. We observed strong synergistic interactions between low calcium concentration and predator presence. While the Ip3R gene was not affected by the stressors, the other four genes were affected in their transcriptional levels by the combination of the stressors. Transcriptional patterns of genes that code for cuticle proteins (Cutie and Icp2) and a sarcoplasmic calcium pump (Serca) only responded to the combination of stressors, changing their relative expression levels in a synergistic response, while a calcium-binding protein (Calb) responded to low calcium stress and the combination of both stressors. The expression pattern of these genes (Cutie, Icp2, and Serca) were nonlinear, yet they were dose dependent across the calcium gradient. Multiple stressors can have complex, often unexpected effects on ecosystems. This study demonstrates that the dominant interaction for the set of tested genes appears to be synergism. We argue that gene expression patterns can be used to understand and predict the type of interaction expected when organisms are exposed simultaneously to natural and anthropogenic stressors. PMID:26158383

  12. Biotic Interactions in the Rhizosphere: A Diverse Cooperative Enterprise for Plant Productivity1[C

    PubMed Central

    De-la-Peña, Clelia; Loyola-Vargas, Víctor M.

    2014-01-01

    Microbes and plants have evolved biochemical mechanisms to communicate with each other. The molecules responsible for such communication are secreted during beneficial or harmful interactions. Hundreds of these molecules secreted into the rhizosphere have been identified, and their functions are being studied in order to understand the mechanisms of interaction and communication among the different members of the rhizosphere community. The importance of root and microbe secretion to the underground habitat in improving crop productivity is increasingly recognized, with the discovery and characterization of new secreting compounds found in the rhizosphere. Different omic approaches, such as genomics, transcriptomics, proteomics, and metabolomics, have expanded our understanding of the first signals between microbes and plants. In this review, we highlight the more recent discoveries related to molecules secreted into the rhizosphere and how they affect plant productivity, either negatively or positively. In addition, we include a survey of novel approaches to studying the rhizosphere and emerging opportunities to direct future studies. PMID:25118253

  13. Strigolactone Involvement in Root Development, Response to Abiotic Stress, and Interactions with the Biotic Soil Environment

    PubMed Central

    Kapulnik, Yoram; Koltai, Hinanit

    2014-01-01

    Strigolactones, recently discovered as plant hormones, regulate the development of different plant parts. In the root, they regulate root architecture and affect root hair length and density. Their biosynthesis and exudation increase under low phosphate levels, and they are associated with root responses to these conditions. Their signaling pathway in the plant includes protein interactions and ubiquitin-dependent repressor degradation. In the root, they lead to changes in actin architecture and dynamics as well as localization of the PIN-FORMED auxin transporter in the plasma membrane. Strigolactones are also involved with communication in the rhizosphere. They are necessary for germination of parasitic plant seeds, they enhance hyphal branching of arbuscular mycorrhizal fungi of the Glomus and Gigaspora spp., and they promote rhizobial symbiosis. This review focuses on the role played by strigolactones in root development, their response to nutrient deficiency, and their involvement with plant interactions in the rhizosphere. PMID:25037210

  14. Bottom-up and top-down mechanisms indirectly mediate interactions between benthic biotic ecosystem components

    NASA Astrophysics Data System (ADS)

    Van Colen, Carl; Thrush, Simon F.; Parkes, Samantha; Harris, Rachel; Woodin, Sally A.; Wethey, David S.; Pilditch, Conrad A.; Hewitt, Judi E.; Lohrer, Andrew M.; Vincx, Magda

    2015-04-01

    The loss or decline in population size of key species can instigate a cascade of effects that have implications for interacting species, therewith impacting biodiversity and ecosystem functioning. We examined how top-down and bottom-up interactions may mediate knock-on effects of a coastal deposit-feeding clam, Macomona liliana (hereafter Macomona), on sandflat meiobenthos densities. Therefore we manipulated densities of Macomona in combination with predator exclusion and experimental shading that was expected to alter microphytobenthos biomass. We show that Macomona regulated densities of meiobenthic (38-500 μm) nematodes, copepods, polychaetes, turbellarians, and ostracodes during the three months of incubation via indirect mechanisms. Predator pressure on Macomona by eagle rays (Myliobatis tenuicaudatus) was found to have a negative effect on densities of some meiobenthic taxa. Furthermore, experimental shading resulted in the loss of a positive relation between Macomona and microphytobenthos biomass, while concurrently increasing the density of some meiobenthic taxa. We suggest that this observation can be explained by the release from bioturbation interference effects of the cockle Austrovenus stutchburyi that was found to thrive in the presence of Macomona under non-shaded conditions. Our results highlight the importance of interactions between macrofaunal bioturbation, microphyte biomass, sediment stability, and predation pressure for the structuring of benthic communities. This experiment illustrates that manipulative field experiments may be particularly suitable to study such multiple indirect mechanisms that regulate ecosystem diversity and related functioning because such approaches may best capture the complex feedbacks and processes that determine ecosystem dynamics.

  15. Study of toxicity and uptake of nanoparticles towards understanding biotic-abiotic interactions

    NASA Astrophysics Data System (ADS)

    Kosaraju, Karshak

    With the rapid growth in nanotechnology and tremendous applications the engineered nanomaterials (ENs) offer, there is increase in usage of ENs which increases their likelihood of coming in contact with biological systems which include complex beings like humans and other relatively simpler organism like bacteria and other microorganisms. The interaction between the nanomaterials (NMs) and biological systems includes the formation of protein coronas, particle wrapping, intracellular uptake and bio catalytic processes which could have biocompatible or bio adverse outcomes. Understanding these interactions allows the development of predictive relationships between structure and activity that are mainly determined by NM properties such as size, shape, surface chemistry, aggregation, and surface functionality among many others. This understanding will also provide insight towards the design and development of benign nanomaterials. The overarching goal of this dissertation is to understand the influence of the physicochemical characteristics of the NMs and their influence on their uptake and toxicity when they interact with the biological systems (cells and organs). For this purpose, thoroughly characterized NMs will be exposed to a cellular model, A549 cells (alveolar lung epithelial cells), and a mice model (CD-1 mice) through inhalational administration. The effects of NMs on the in vitro and in vivo models will be evaluated by bio- and immuno-chemical methods to understand toxicity, and a combination of analytical spectroscopic and microscopic tools to study uptake. In vivo toxicity assessment will also be performed by using electrocardiogram (ECG) measurements as a tool to study the effects of inhalation of NMs on cardiac response in mice. Through in vivo studies, a novel non-invasive method, Reserve of Refractoriness (RoR), will be introduced as a tool to study cardiotoxicity.

  16. Invasion biology in non-free-living species: interactions between abiotic (climatic) and biotic (host availability) factors in geographical space in crayfish commensals (Ostracoda, Entocytheridae)

    PubMed Central

    Mestre, Alexandre; Aguilar-Alberola, Josep A; Baldry, David; Balkis, Husamettin; Ellis, Adam; Gil-Delgado, Jose A; Grabow, Karsten; Klobučar, Göran; Kouba, Antonín; Maguire, Ivana; Martens, Andreas; Mülayim, Ayşegül; Rueda, Juan; Scharf, Burkhard; Soes, Menno; S Monrós, Juan; Mesquita-Joanes, Francesc

    2013-01-01

    In invasion processes, both abiotic and biotic factors are considered essential, but the latter are usually disregarded when modeling the potential spread of exotic species. In the framework of set theory, interactions between biotic (B), abiotic (A), and movement-related (M) factors in the geographical space can be hypothesized with BAM diagrams and tested using ecological niche models (ENMs) to estimate A and B areas. The main aim of our survey was to evaluate the interactions between abiotic (climatic) and biotic (host availability) factors in geographical space for exotic symbionts (i.e., non-free-living species), using ENM techniques combined with a BAM framework and using exotic Entocytheridae (Ostracoda) found in Europe as model organisms. We carried out an extensive survey to evaluate the distribution of entocytherids hosted by crayfish in Europe by checking 94 European localities and 12 crayfish species. Both exotic entocytherid species found, Ankylocythere sinuosa and Uncinocythere occidentalis, were widely distributed in W Europe living on the exotic crayfish species Procambarus clarkii and Pacifastacus leniusculus, respectively. No entocytherids were observed in the remaining crayfish species. The suitable area for A. sinuosa was mainly restricted by its own limitations to minimum temperatures in W and N Europe and precipitation seasonality in circum-Mediterranean areas. Uncinocythere occidentalis was mostly restricted by host availability in circum-Mediterranean regions due to limitations of P. leniusculus to higher precipitation seasonality and maximum temperatures. The combination of ENMs with set theory allows studying the invasive biology of symbionts and provides clues about biogeographic barriers due to abiotic or biotic factors limiting the expansion of the symbiont in different regions of the invasive range. The relative importance of abiotic and biotic factors on geographical space can then be assessed and applied in conservation plans. This

  17. Abiotic and biotic interactions determine whether increased colonization is beneficial or detrimental to metapopulation management.

    PubMed

    Southwell, Darren M; Rhodes, Jonathan R; McDonald-Madden, Eve; Nicol, Sam; Helmstedt, Kate J; McCarthy, Michael A

    2016-06-01

    Increasing the colonization rate of metapopulations can improve persistence, but can also increase exposure to threats. To make good decisions, managers must understand whether increased colonization is beneficial or detrimental to metapopulation persistence. While a number of studies have examined interactions between metapopulations, colonization, and threats, they have assumed that threat dynamics respond linearly to changes in colonization. Here, we determined when to increase colonization while explicitly accounting for non-linear dependencies between a metapopulation and its threats. We developed patch occupancy metapopulation models for species susceptible to abiotic, generalist, and specialist threats and modeled the total derivative of the equilibrium proportion of patches occupied by each metapopulation with respect to the colonization rate. By using the total derivative, we developed a rule for determining when to increase metapopulation colonization. This rule was applied to a simulated metapopulation where the dynamics of each threat responded to increased colonization following a power function. Before modifying colonization, we show that managers must understand: (1) whether a metapopulation is susceptible to a threat; (2) the type of threat acting on a metapopulation; (3) which component of threat dynamics might depend on colonization, and; (4) the likely response of a threat-dependent variable to changes in colonization. The sensitivity of management decisions to these interactions increases uncertainty in conservation planning decisions. PMID:26948289

  18. Above- and belowground biotic interactions facilitate relocation of plants into cooler environments.

    PubMed

    Spasojevic, Marko J; Harrison, Susan; Day, Howard W; Southard, Randal J

    2014-06-01

    One important but largely unanswered question about floristic responses to climate change is how interactions such as competition, facilitation and plant-soil feedbacks will influence the ability of species to track shifting climates. In a rugged and moisture-limited region that has recently warmed by 2° (Siskiyou Mountains, OR, USA), we planted three species into cooler aspects and elevations than those they currently inhabit, with and without removal of neighbouring plants, and tracked them over 2 years. Two species had higher success in cooler topographic locations, and this success was enhanced by neighbouring plants, which appeared to modulate minimum growing season temperatures. One species' success was also facilitated by the higher soil organic matter found in cooler sites. These results are a novel experimental demonstration of two important factors that may buffer climate change impacts on plants: rugged topography and plant-plant facilitation. PMID:24641109

  19. Environmental conditions and biotic interactions influence ecosystem structure and function in a drying stream

    USGS Publications Warehouse

    Ludlam, J.P.; Magoulick, D.D.

    2010-01-01

    Benthic consumers influence stream ecosystem structure and function, but these interactions depend on environmental context. We experimentally quantified the effects of central stoneroller minnows (Campostoma anomalum (Rafinesque) and Meek's crayfish (Orconectes meeki meeki (Faxon)) on benthic communities using electric exclusion quadrats in Little Mulberry Creek before (June) and during (August) seasonal stream drying. Unglazed ceramic tiles were deployed in June and August to measure periphyton and invertebrate abundance, and leafpack decomposition and primary production were also measured in August. Relationships between stoneroller and crayfish density and the size of consumer effects were evaluated with multiple linear regression models. Average chlorophyll a abundance was greater on exposed than exclusion tiles in August, but not in June. Sediment dry mass, periphyton ash-free dry mass (AFDM), and chironomid densities on tiles did not differ among treatments in either period. Leaf packs decayed faster in exposed than exclusion treatments (kexposed = 0.038 ?? 0.013, kexclusion = 0.007 ?? 0.002), but consumer effects were stronger in some pools than others. Leafpack invertebrate biomass and abundance and tile primary productivity did not differ among treatments. Consumer effects on chlorophyll a were related to crayfish and stoneroller density, and effects on chironomid density were related to stoneroller density. These results contrast with a previous exclusion experiment in Little Mulberry Creek that demonstrated strong consumer effects. The influence of stream drying on consumer effects appears to have been reduced by strong spates, underscoring the importance of conducting multi-year studies to determine the magnitude of variability in ecological interactions. ?? US Government: USGS 2010.

  20. Evolutionary History and Novel Biotic Interactions Determine Plant Responses to Elevated CO2 and Nitrogen Fertilization

    PubMed Central

    Wooliver, Rachel; Senior, John K.; Schweitzer, Jennifer A.; O'Reilly-Wapstra, Julianne M.; Langley, J. Adam; Chapman, Samantha K.; Bailey, Joseph K.

    2014-01-01

    A major frontier in global change research is predicting how multiple agents of global change will alter plant productivity, a critical component of the carbon cycle. Recent research has shown that plant responses to climate change are phylogenetically conserved such that species within some lineages are more productive than those within other lineages in changing environments. However, it remains unclear how phylogenetic patterns in plant responses to changing abiotic conditions may be altered by another agent of global change, the introduction of non-native species. Using a system of 28 native Tasmanian Eucalyptus species belonging to two subgenera, Symphyomyrtus and Eucalyptus, we hypothesized that productivity responses to abiotic agents of global change (elevated CO2 and increased soil N) are unique to lineages, but that novel interactions with a non-native species mediate these responses. We tested this hypothesis by examining productivity of 1) native species monocultures and 2) mixtures of native species with an introduced hardwood plantation species, Eucalyptus nitens, to experimentally manipulated soil N and atmospheric CO2. Consistent with past research, we found that N limits productivity overall, especially in elevated CO2 conditions. However, monocultures of species within the Symphyomyrtus subgenus showed the strongest response to N (gained 127% more total biomass) in elevated CO2 conditions, whereas those within the Eucalyptus subgenus did not respond to N. Root:shoot ratio (an indicator of resource use) was on average greater in species pairs containing Symphyomyrtus species, suggesting that functional traits important for resource uptake are phylogenetically conserved and explaining the phylogenetic pattern in plant response to changing environmental conditions. Yet, native species mixtures with E. nitens exhibited responses to CO2 and N that differed from those of monocultures, supporting our hypothesis and highlighting that both plant

  1. Temperature-mediated biotic interactions influence enemy release of nonnative species in warming environments.

    PubMed

    Fey, Samuel B; Herren, Cristina M

    2014-08-01

    "Enemy release" occurs when invading species suffer from interactions with pathogens, parasites, herbivores, or predators to a lesser degree than native species due to a lack of shared evolutionary history. Here we provide strong support for the hypothesis that variable thermal sensitivities between a consumer and its resources can generate temperature-dependent enemy release using both a mathematical model and a field experiment. We identify three common scenarios where changes in temperature should alter enemy release based on asymmetric responses among enemies and their resources to changes in temperature: (1) the vital rates of a shared enemy are more sensitive to changes in temperature than its resources, (2) the enemy's thermal maximum for consumption is higher than the resources' maxima for growth, and (3) the invading resource has a higher thermal maximum for growth than its native competitor. Mathematical representations indicated that warming is capable of altering enemy release in each of these three scenarios. We also tested our hypothesis using a mesocosm warming experiment in a system that exhibits variable thermal sensitivities between a predator and its native and nonnative prey. We conducted a six-week experiment manipulating the presence of Lepomis sunfish (present, absent) and water temperature (ambient, heated) using the nonnative crustacean zooplankter, Daphnia lumholtzi, whose morphological defenses reduce predation from juvenile sunfish relative to native Daphnia pulex. Our results indicate that D. lumholtzi benefited to a greater extent from the presence of Lepomis predators as temperatures increase. Taken together, our model and experiment indicate that changes in environmental temperature may directly influence the success of nonnative species and may assist with forecasting the community consequences of biological invasions in a warming world. PMID:25230475

  2. Evolutionary history and novel biotic interactions determine plant responses to elevated CO2 and nitrogen fertilization.

    PubMed

    Wooliver, Rachel; Senior, John K; Schweitzer, Jennifer A; O'Reilly-Wapstra, Julianne M; Langley, J Adam; Chapman, Samantha K; Bailey, Joseph K

    2014-01-01

    A major frontier in global change research is predicting how multiple agents of global change will alter plant productivity, a critical component of the carbon cycle. Recent research has shown that plant responses to climate change are phylogenetically conserved such that species within some lineages are more productive than those within other lineages in changing environments. However, it remains unclear how phylogenetic patterns in plant responses to changing abiotic conditions may be altered by another agent of global change, the introduction of non-native species. Using a system of 28 native Tasmanian Eucalyptus species belonging to two subgenera, Symphyomyrtus and Eucalyptus, we hypothesized that productivity responses to abiotic agents of global change (elevated CO2 and increased soil N) are unique to lineages, but that novel interactions with a non-native species mediate these responses. We tested this hypothesis by examining productivity of 1) native species monocultures and 2) mixtures of native species with an introduced hardwood plantation species, Eucalyptus nitens, to experimentally manipulated soil N and atmospheric CO2. Consistent with past research, we found that N limits productivity overall, especially in elevated CO2 conditions. However, monocultures of species within the Symphyomyrtus subgenus showed the strongest response to N (gained 127% more total biomass) in elevated CO2 conditions, whereas those within the Eucalyptus subgenus did not respond to N. Root:shoot ratio (an indicator of resource use) was on average greater in species pairs containing Symphyomyrtus species, suggesting that functional traits important for resource uptake are phylogenetically conserved and explaining the phylogenetic pattern in plant response to changing environmental conditions. Yet, native species mixtures with E. nitens exhibited responses to CO2 and N that differed from those of monocultures, supporting our hypothesis and highlighting that both plant

  3. The net effect of abiotic conditions and biotic interactions in a semi-arid ecosystem NE Spain: implications for the management and restoration.

    NASA Astrophysics Data System (ADS)

    Pueyo, Yolanda; Arroyo, Antonio I.; Saiz, Hugo; Alados, Concepción L.

    2014-05-01

    Degradation in arid and semiarid lands can be irreversible without human intervention, due to a positive plant-soil feedback where the loss of vegetation cover leads to soil degradation, which in turn hampers plant establishment. Human intervention in restoration actions usually involves the amendment of the degraded abiotic conditions, revegetation of bare areas, or both. However, abiotic amelioration is often expensive and too intrusive, and revegetation is not successful in many cases. Biotic interactions between plants, and more specifically facilitation by a "nurse" plant, have been proposed as a new via to take profit of improved abiotic conditions without intervention, and to increase the success rate of revegetation actions. But "nurse" plants can also interfere with others (i.e. by competition for resources or the release of allelopathic compounds), and the net balance between facilitation and interference could depend on plant types involved. We present recent observational and experimental studies performed in the semiarid ecosystems of the Middle Ebro Valley (NE Spain) about the role of abiotic conditions and biotic interactions in the productivity, dynamics and diversity of plant communities under different stress conditions (aridity and grazing). We found that all plant types studied (shrubs and perennial grasses) improved abiotic conditions (soil temperature and water availability for plants) with respect to open areas. However, only some shrubs (mainly Salsola vermiculata) had a positive net balance in the biotic interactions between plants, while other shrubs (Artemisia herba-alba) and perennial grasses (Lygeum spartum) showed interference with other plants. Moreover, the net balance between facilitation and interference among plants in the community shifted from competitive to neutral or from neutral to facilitative with increasing aridity. Grazing status did not strongly change the net biotic interactions between plants. Our results suggest that

  4. Disentangling effects of abiotic factors and biotic interactions on cross-taxon congruence in species turnover patterns of plants, moths and beetles

    PubMed Central

    Duan, Meichun; Liu, Yunhui; Yu, Zhenrong; Baudry, Jacques; Li, Liangtao; Wang, Changliu; Axmacher, Jan C.

    2016-01-01

    High cross-taxon congruence in species diversity patterns is essential for the use of surrogate taxa in biodiversity conservation, but presence and strength of congruence in species turnover patterns, and the relative contributions of abiotic environmental factors and biotic interaction towards this congruence, remain poorly understood. In our study, we used variation partitioning in multiple regressions to quantify cross-taxon congruence in community dissimilarities of vascular plants, geometrid and arciinid moths and carabid beetles, subsequently investigating their respective underpinning by abiotic factors and biotic interactions. Significant cross-taxon congruence observed across all taxon pairs was linked to their similar responses towards elevation change. Changes in the vegetation composition were closely linked to carabid turnover, with vegetation structure and associated microclimatic conditions proposed causes of this link. In contrast, moth assemblages appeared to be dominated by generalist species whose turnover was weakly associated with vegetation changes. Overall, abiotic factors exerted a stronger influence on cross-taxon congruence across our study sites than biotic interactions. The weak congruence in turnover observed particularly between plants and moths highlights the importance of multi-taxon approaches based on groupings of taxa with similar turnovers, rather than the use of single surrogate taxa or environmental proxies, in biodiversity assessments. PMID:27032533

  5. Disentangling effects of abiotic factors and biotic interactions on cross-taxon congruence in species turnover patterns of plants, moths and beetles.

    PubMed

    Duan, Meichun; Liu, Yunhui; Yu, Zhenrong; Baudry, Jacques; Li, Liangtao; Wang, Changliu; Axmacher, Jan C

    2016-01-01

    High cross-taxon congruence in species diversity patterns is essential for the use of surrogate taxa in biodiversity conservation, but presence and strength of congruence in species turnover patterns, and the relative contributions of abiotic environmental factors and biotic interaction towards this congruence, remain poorly understood. In our study, we used variation partitioning in multiple regressions to quantify cross-taxon congruence in community dissimilarities of vascular plants, geometrid and arciinid moths and carabid beetles, subsequently investigating their respective underpinning by abiotic factors and biotic interactions. Significant cross-taxon congruence observed across all taxon pairs was linked to their similar responses towards elevation change. Changes in the vegetation composition were closely linked to carabid turnover, with vegetation structure and associated microclimatic conditions proposed causes of this link. In contrast, moth assemblages appeared to be dominated by generalist species whose turnover was weakly associated with vegetation changes. Overall, abiotic factors exerted a stronger influence on cross-taxon congruence across our study sites than biotic interactions. The weak congruence in turnover observed particularly between plants and moths highlights the importance of multi-taxon approaches based on groupings of taxa with similar turnovers, rather than the use of single surrogate taxa or environmental proxies, in biodiversity assessments. PMID:27032533

  6. Influence of Solar Radiation and Biotic Interactions on Bacterial and Eukaryotic Communities Associated with Sewage Decomposition in Ambient Water - Poster

    EPA Science Inventory

    Sewage and ambient water both consist of a highly complex array of bacteria and eukaryotic microbes. When these communities are mixed, the persistence of sewage-derived pathogens in environmental waters can represent a significant public health concern. Solar radiation and biotic...

  7. Interactions among biotic and abiotic factors affect the reliability of tungsten microneedles puncturing in vitro and in vivo peripheral nerves: A hybrid computational approach.

    PubMed

    Sergi, Pier Nicola; Jensen, Winnie; Yoshida, Ken

    2016-02-01

    Tungsten is an elective material to produce slender and stiff microneedles able to enter soft tissues and minimize puncture wounds. In particular, tungsten microneedles are used to puncture peripheral nerves and insert neural interfaces, bridging the gap between the nervous system and robotic devices (e.g., hand prostheses). Unfortunately, microneedles fail during the puncture process and this failure is not dependent on stiffness or fracture toughness of the constituent material. In addition, the microneedles' performances decrease during in vivo trials with respect to the in vitro ones. This further effect is independent on internal biotic effects, while it seems to be related to external biotic causes. Since the exact synergy of phenomena decreasing the in vivo reliability is still not known, this work explored the connection between in vitro and in vivo behavior of tungsten microneedles through the study of interactions between biotic and abiotic factors. A hybrid computational approach, simultaneously using theoretical relationships and in silico models of nerves, was implemented to model the change of reliability varying the microneedle diameter, and to predict in vivo performances by using in vitro reliability and local differences between in vivo and in vitro mechanical response of nerves. PMID:26652468

  8. Traffic and Driving Simulator Based on Architecture of Interactive Motion.

    PubMed

    Paz, Alexander; Veeramisti, Naveen; Khaddar, Romesh; de la Fuente-Mella, Hanns; Modorcea, Luiza

    2015-01-01

    This study proposes an architecture for an interactive motion-based traffic simulation environment. In order to enhance modeling realism involving actual human beings, the proposed architecture integrates multiple types of simulation, including: (i) motion-based driving simulation, (ii) pedestrian simulation, (iii) motorcycling and bicycling simulation, and (iv) traffic flow simulation. The architecture has been designed to enable the simulation of the entire network; as a result, the actual driver, pedestrian, and bike rider can navigate anywhere in the system. In addition, the background traffic interacts with the actual human beings. This is accomplished by using a hybrid mesomicroscopic traffic flow simulation modeling approach. The mesoscopic traffic flow simulation model loads the results of a user equilibrium traffic assignment solution and propagates the corresponding traffic through the entire system. The microscopic traffic flow simulation model provides background traffic around the vicinities where actual human beings are navigating the system. The two traffic flow simulation models interact continuously to update system conditions based on the interactions between actual humans and the fully simulated entities. Implementation efforts are currently in progress and some preliminary tests of individual components have been conducted. The implementation of the proposed architecture faces significant challenges ranging from multiplatform and multilanguage integration to multievent communication and coordination. PMID:26491711

  9. Traffic and Driving Simulator Based on Architecture of Interactive Motion

    PubMed Central

    Paz, Alexander; Veeramisti, Naveen; Khaddar, Romesh; de la Fuente-Mella, Hanns; Modorcea, Luiza

    2015-01-01

    This study proposes an architecture for an interactive motion-based traffic simulation environment. In order to enhance modeling realism involving actual human beings, the proposed architecture integrates multiple types of simulation, including: (i) motion-based driving simulation, (ii) pedestrian simulation, (iii) motorcycling and bicycling simulation, and (iv) traffic flow simulation. The architecture has been designed to enable the simulation of the entire network; as a result, the actual driver, pedestrian, and bike rider can navigate anywhere in the system. In addition, the background traffic interacts with the actual human beings. This is accomplished by using a hybrid mesomicroscopic traffic flow simulation modeling approach. The mesoscopic traffic flow simulation model loads the results of a user equilibrium traffic assignment solution and propagates the corresponding traffic through the entire system. The microscopic traffic flow simulation model provides background traffic around the vicinities where actual human beings are navigating the system. The two traffic flow simulation models interact continuously to update system conditions based on the interactions between actual humans and the fully simulated entities. Implementation efforts are currently in progress and some preliminary tests of individual components have been conducted. The implementation of the proposed architecture faces significant challenges ranging from multiplatform and multilanguage integration to multievent communication and coordination. PMID:26491711

  10. Interactions of local climatic, biotic and hydrogeochemical processes facilitate phosphorus dynamics along an Everglades forest-marsh gradient

    NASA Astrophysics Data System (ADS)

    Troxler, T. G.; Coronado-Molina, C.; Rondeau, D. N.; Krupa, S.; Newman, S.; Manna, M.; Price, R. M.; Sklar, F. H.

    2013-06-01

    Ecosystem nutrient cycling is often complex because nutrient dynamics within and between systems are mediated by the interaction of biological and geochemical conditions operating at different temporal and spatial scales. Vegetated patches in semiarid and wetland landscapes have been shown to exemplify some of these patterns and processes. We investigated biological and geochemical factors suggested to contribute to phosphorus (P) movement and availability along a forest-marsh gradient in an Everglades tree island. Our study illustrated processes that are consistent with the chemohydrodynamic nutrient (CHNT) hypothesis and the trigger-transfer, pulse-reserve (TTPR) model developed for semiarid systems. Comparison with the TTRP model was constructive as it elaborated several significant patterns and processes of the tree island ecosystem including: (1) concentration of the limiting resource (P) in the source patch [High Head which constitutes the reserve] compared with the resource-poor landscape, (2) soil zone calcite precipitation requiring strong seasonality for evapotranspiration to promote conditions for secondary soil development and calcium phosphate reprecipitation, (3) rewetting of previously dry soils by early wet season precipitation events, and (4) antecedent conditions of the source patch including landscape position that modulated the effect of the precipitation trigger. Thus, our study showed how water availability drives soil water P dynamics and potentially stability of mineral soil P in this tree island ecosystem. In landscapes with extensive water management, these processes can be asynchronous with the seasonality of hydrologic dynamics, tipping the balance between a sink and source of a limiting nutrient.

  11. Interactions of local climatic, biotic and hydrogeochemical processes facilitate phosphorus dynamics along an Everglades forest-marsh gradient

    NASA Astrophysics Data System (ADS)

    Troxler, T. G.; Coronado-Molina, C.; Rondeau, D. N.; Krupa, S.; Newman, S.; Manna, M.; Price, R. M.; Sklar, F. H.

    2014-02-01

    Ecosystem nutrient cycling is often complex because nutrient dynamics within and between systems are mediated by the interaction of biological and geochemical conditions operating at different temporal and spatial scales. Vegetated patches in semiarid and wetland landscapes have been shown to exemplify some of these patterns and processes. We investigated biological and geochemical factors suggested to contribute to phosphorus (P) movement and availability along a forest-marsh gradient in an Everglades tree island. Our study illustrated processes that are consistent with the chemohydrodynamic nutrient (CHNT) hypothesis and the trigger-transfer, pulse-reserve (TTPR) model developed for semiarid systems. Comparison with the TTPR model was constructive as it elaborated several significant patterns and processes of the tree island ecosystem including: (1) concentration of the limiting resource (P) in the source patch (High Head which constitutes the reserve) compared with the resource-poor landscape, (2) soil zone calcite precipitation requiring strong seasonality for evapotranspiration to promote conditions for secondary soil development and calcium phosphate reprecipitation, (3) rewetting of previously dry soils by early wet season precipitation events, and (4) antecedent conditions of the source patch, including landscape position that modulated the effect of the precipitation trigger. Thus, our study showed how water availability drives soil water P dynamics and, potentially, stability of mineral soil P in this tree island ecosystem. In landscapes with extensive water management, these processes can be asynchronous with the seasonality of hydrologic dynamics, tipping the balance between a sink and source of a limiting nutrient.

  12. Limitations to lake trout (Salvelinus namaycush) rehabilitation in the Great Lakes imposed by biotic interactions occurring at early life stages

    USGS Publications Warehouse

    Jones, Michael L.; Eck, Gary W.; Evans, David O.; Fabrizio, Mary C.; Hoff, Michael H.; Hudson, Patrick L.; Janssen, John; Jude, David; O'Gorman, Robert; Savino, Jacqueline F.

    1995-01-01

    We examine evidence that biotic factors, particularly predation, may be limiting early survival of wild lake trout (Salvelinus namaycush) juveniles in many areas of the Great Lakes. The Great Lakes contain numerous potential predators of lake trout eggs and fry, some of which are recent invaders, and most of which were probably absent when lake trout most recently re-invaded the Great Lakes after the last ice age. Simple quantitative models of predation suggest that plausible assumptions about prey densities, predator feeding rates, and duration of exposure of predator to prey can lead to very high estimates of predation mortality, in some instances approaching 100%. Indirect evidence from inter-Great Lake comparisons and inland lake examples also suggest that biotic factors may impede successful lake trout colonization. Our synthesis of the evidence leads to recommendations for research to better define field feeding rates of lake trout egg and fry predators and comparative studies of densities of potential egg and fry predators on lake trout spawning reefs. Management options should be designed to provide useful information as well as achieve short-term goals. From a management standpoint we recommend that: newly constructed lake trout reefs should be placed well away from concentrations of potential predators; offshore spawning reefs should be stocked; salmonine stocking, nutrient abatement, and commercial harvest of alewives should all be considered as options to enhance survival of young lake trout; hatchery lake trout should not be stocked at sites where wild lake trout are showing signs of recovery; and exotic species expansions or introductions must be curtailed to maintain or improve on our recent successes in lake trout rehabilitation.

  13. Hydrothermal plume particles deconstructed: evidence of biotic and abiotic interactions in particle formation at 9N East Pacific Rise

    NASA Astrophysics Data System (ADS)

    Breier, J. A.; Toner, B.; Manganini, S. J.; German, C. R.

    2008-12-01

    We are using non-buoyant hydrothermal plume samples collected at 9° 50' N East Pacific Rise to conduct an unprecedented examination of the fine scale (μm- and nm-range) mineralogical and biogeochemical composition of hydrothermal particulates. Recent findings from studies of sinking particulate, suggest that East Pacific Rise hydrothermal particulates are inorganic/organic aggregates. We confirmed this with suspended particulate samples collected, during a 3-day moored multi-sampler deployment in the non- buoyant hydrothermal plume above Tica vent at 9° 50' N East Pacific Rise in November 2007. A combination of high energy synchrotron x-ray absorption spectroscopy and bulk and trace elemental analysis reveal that the >1 μm suspended particulates consist of inorganic Fe oxide grains in a pervasive organic C matrix with carbon K-edge spectra consistent with proteins, lipids, and polysaccharides. This aggregate structure may preserve reduced Fe phases in the presence of oxygenated seawater and alter our basic assumptions about hydrothermal particle dispersion. Scavenging, by coprecipitation and surface adsorption, of seawater nutrients and trace elements such as P, U, Mo, Cr, V, and As may also be influenced by this particulate composition. These samples were collected with a newly developed Suspended Particulate Rosette multi-sampling system designed to collect geochemical and microbial samples from rising deep-sea hydrothermal plumes to enable investigations of abiotic and biotic plume processes.

  14. Laser-Matter Interactions with a 527 nm Drive

    SciTech Connect

    Glenzer, S; Niemann, C; Witman, P; Wegner, P; Mason, D; Haynam, C; Parham, T; Datte, P

    2007-02-16

    The primary goal of this Exploratory Research is to develop an understanding of laser-matter interactions with 527-nm light (2{omega}) for studies of interest to numerous Laboratory programs including inertial confinement fusion (ICF), material strength, radiation transport, and hydrodynamics. In addition, during the course of this work we will develop the enabling technology and prototype instrumentation to diagnose a high fluence laser beam for energy, power, and near field intensity profile at 2{omega}. Through this Exploratory Research we have established an extensive experimental and modeling data base on laser-matter interaction with 527 nm laser light (2{omega}) in plasma conditions of interest to numerous Laboratory programs. The experiments and the laser-plasma interaction modeling using the code pF3D have shown intensity limits and laser beam conditioning requirements for future 2{omega} laser operations and target physics experiments on the National Ignition Facility (NIF). These findings have set requirements for which present radiation-hydrodynamic simulations indicate the successful generation of relevant pressure regimes in future 2{omega} experiments. To allow these experiments on the NIF, optics and optical mounts were prepared for the 18mm Second Harmonic Generation Crystal (SHG crystal) that would provide the desired high conversion efficiency from 1{omega} to 2{omega}. Supporting experimental activities on NIF included high-energy 1{omega} shots at up to 22kJ/beamline (4MJ full NIF 1{omega} equivalent energy) that demonstrated, in excess, the 1{omega} drive capability of the main laser that is required for 2{omega} operations. Also, a very extensive 3{omega} campaign was completed (see ''The National Ignition Facility Laser Performance Status'' UCRL-JRNL-226553) that demonstrated that not only doubling the laser, but also tripling the laser (a much more difficult and sensitive combination) met our model predictions over a wide range of laser

  15. Biotic interactions and sunlight affect persistence of fecal indicator bacteria and microbial source tracking genetic markers in the upper Mississippi river.

    PubMed

    Korajkic, Asja; McMinn, Brian R; Shanks, Orin C; Sivaganesan, Mano; Fout, G Shay; Ashbolt, Nicholas J

    2014-07-01

    The sanitary quality of recreational waters that may be impacted by sewage is assessed by enumerating fecal indicator bacteria (FIB) (Escherichia coli and enterococci); these organisms are found in the gastrointestinal tracts of humans and many other animals, and hence their presence provides no information about the pollution source. Microbial source tracking (MST) methods can discriminate between different pollution sources, providing critical information to water quality managers, but relatively little is known about factors influencing the decay of FIB and MST genetic markers following release into aquatic environments. An in situ mesocosm was deployed at a temperate recreational beach in the Mississippi River to evaluate the effects of ambient sunlight and biotic interactions (predation, competition, and viral lysis) on the decay of culture-based FIB, as well as molecularly based FIB (Entero1a and GenBac3) and human-associated MST genetic markers (HF183 and HumM2) measured by quantitative real-time PCR (qPCR). In general, culturable FIB decayed the fastest, while molecularly based FIB and human-associated genetic markers decayed more slowly. There was a strong correlation between the decay of molecularly based FIB and that of human-associated genetic markers (r(2), 0.96 to 0.98; P < 0.0001) but not between culturable FIB and any qPCR measurement. Overall, exposure to ambient sunlight may be an important factor in the early-stage decay dynamics but generally was not after continued exposure (i.e., after 120 h), when biotic interactions tended to be the only/major influential determinant of persistence. PMID:24747902

  16. Biotic Interactions and Sunlight Affect Persistence of Fecal Indicator Bacteria and Microbial Source Tracking Genetic Markers in the Upper Mississippi River

    PubMed Central

    McMinn, Brian R.; Shanks, Orin C.; Sivaganesan, Mano; Fout, G. Shay; Ashbolt, Nicholas J.

    2014-01-01

    The sanitary quality of recreational waters that may be impacted by sewage is assessed by enumerating fecal indicator bacteria (FIB) (Escherichia coli and enterococci); these organisms are found in the gastrointestinal tracts of humans and many other animals, and hence their presence provides no information about the pollution source. Microbial source tracking (MST) methods can discriminate between different pollution sources, providing critical information to water quality managers, but relatively little is known about factors influencing the decay of FIB and MST genetic markers following release into aquatic environments. An in situ mesocosm was deployed at a temperate recreational beach in the Mississippi River to evaluate the effects of ambient sunlight and biotic interactions (predation, competition, and viral lysis) on the decay of culture-based FIB, as well as molecularly based FIB (Entero1a and GenBac3) and human-associated MST genetic markers (HF183 and HumM2) measured by quantitative real-time PCR (qPCR). In general, culturable FIB decayed the fastest, while molecularly based FIB and human-associated genetic markers decayed more slowly. There was a strong correlation between the decay of molecularly based FIB and that of human-associated genetic markers (r2, 0.96 to 0.98; P < 0.0001) but not between culturable FIB and any qPCR measurement. Overall, exposure to ambient sunlight may be an important factor in the early-stage decay dynamics but generally was not after continued exposure (i.e., after 120 h), when biotic interactions tended to be the only/major influential determinant of persistence. PMID:24747902

  17. Consumer diversity interacts with prey defenses to drive ecosystem function

    PubMed Central

    Rasher, Douglas B.; Hoey, Andrew S.; Hay, Mark E.

    2013-01-01

    six study reefs. Our findings indicate that the total diet breadth of the herbivore community and the probability of all macroalgae being removed from reefs by herbivores increases with increasing herbivore diversity, but that a few critical species drive this relationship. Therefore, interactions between algal defenses and herbivore tolerances create an essential role for consumer diversity in the functioning and resilience of coral reefs. PMID:23923498

  18. Spatio-temporal variation of biotic factors underpins contemporary range dynamics of congeners.

    PubMed

    Naujokaitis-Lewis, Ilona; Fortin, Marie-Josée

    2016-03-01

    Species' ranges are complex often exhibiting multidirectional shifts over space and time. Despite the strong fingerprint of recent historical climate change on species' distributions, biotic factors such as loss of vegetative habitat and the presence of potential competitors constitute important yet often overlooked drivers of range dynamics. Furthermore, short-term changes in environmental conditions can influence the underlying processes of local extinction and local colonization that drive range shifts, yet are rarely considered at broad scales. We used dynamic state-space occupancy models to test multiple hypotheses of the relative importance of major drivers of range shifts of Golden-winged Warblers (Vermivora chrysoptera) and Blue-winged Warblers (V. cyanoptera) between 1983 and 2012 across North America: warming temperatures; habitat changes; and occurrence of congeneric species, used here as proxy for biotic interactions. Dynamic occupancies for both species were most influenced by spatial relative to temporal variation in temperature and habitat. However, temporal variation in temperature anomalies and biotic interactions remained important. The two biotic factors considered, habitat change and biotic interactions, had the largest relative effect on estimated extinction rates followed by abiotic temperature anomalies. For the Golden-winged Warbler, the predicted presence of the Blue-winged Warbler, a hypothesized competitor, most influenced extinction probabilities, contributing to evidence supporting its role in site-level species replacement. Given the overall importance of biotic factors on range-wide dynamic occupancies, their consideration alongside abiotic factors should not be overlooked. Our results suggest that warming compounds the negative effect of habitat loss emphasizing species' need for habitat to adapt to a changing climate. Notably, even closely related species exhibited individual responses to abiotic and biotic factors considered. PMID

  19. NORTH AMERICAN BIOTIC COMMUNITIES

    EPA Science Inventory

    This digital 1:10,000,000 map (Reichenbacher et al. 1998) of coded polygons depicts the major upland biotic communities of North America using an ecological color scheme that illustrates gradients in available plant moisture, heat, and cold. Biotic communities are regional plant...

  20. Interaction of rock, water, and plants in central Siberia (Russia) dominated by continuous permafrost: biotic versus abiotic fluxes

    NASA Astrophysics Data System (ADS)

    Viers, J.; Pokrovsky, O. S.; Prokushkin, A. S.; Beaulieu, E.; Dupre, B.

    2009-12-01

    -ground biomass in this region. We analyzed large number of soils, larch needles, mosses, dwarf shrubs and waters (from soils and rivers) collected in the various local environments. Plant biomass was regularly collected from May to September 2007. Our efforts focus on weathering processes and elements transport mechanisms between the different chemical reservoirs (soil and litter, plants, atmosphere) using a multidisciplinary approach. The aim of the presentation is : i) to propose a conceptual model of the present-day “biogeochemical” functioning of basaltic watershed located in central Siberia, ii) to evaluate biotic and abiotic element fluxes from the watershed, and iii) to assess the effect of global warming through the local comparison of the north-facing and south-facing environments. The role of plants dominated by larches, dwarf shrubs and mosses will be particularly considered.

  1. INTERACTIONS BETWEEN AGE AND MODERATE ALCOHOL EFFECTS ON SIMULATED DRIVING PERFORMANCE

    PubMed Central

    Sklar, Alfredo L.; Boissoneault, Jeff; Fillmore, Mark T.; Nixon, Sara Jo

    2013-01-01

    Rationale There is a substantial body of literature documenting the deleterious effects of both alcohol consumption and age on driving performance. There is, however, limited work examining the interaction of age and acute alcohol consumption. Objectives The current study was conducted to determine if moderate alcohol doses differentially affect the driving performance of older and younger adults. Methods Healthy older (55 – 70) and younger (25 – 35) adults were tested during a baseline session and again following consumption of one of three beverages (0.0% (placebo), 0.04% or 0.065% target breath alcohol concentration). Measures of driving precision and average speed were recorded. Results Older adults performed more poorly on precision driving measures and drove more slowly than younger adults at baseline. After controlling for baseline performance, interactions between alcohol and age were observed following beverage consumption on two measures of driving precision with older adults exhibiting greater impairment as a result of alcohol consumption. Conclusions These data provide evidence that older adults may be more susceptible to the effects of alcohol on certain measures of driving performance. An investigation of mechanisms accounting for alcohol’s effects on driving in older and younger adults is required. Further evaluation using more complex driving environments is needed to assess the real-world implication of this interaction. PMID:24030469

  2. Impact of spatio-temporal heterogeneities and lateral stirring and mixing on mid-water biotic interactions

    NASA Astrophysics Data System (ADS)

    Martinez, E.; Richards, K. J.

    2010-08-01

    We study the impact of spatial and temporal inhomogeneities in the flux of particles on particle-biology interactions in the mesopelagic zone using a flux-prey-predator model. The mid-water biology is found to affect significantly the carbon flux associated with the sinking particles. Although the annual mean export flux at the bottom of the zone (taken to be at 1000 m depth) is changed at most 25% in the experiments reported here, the timing and amplitude of pulses of the bottom flux are very dependent on the way the flux at the top of the zone (taken to be 100 m depth) is packaged in time and space. The apparent sinking speed, based on the arrival of pulses of the export flux at the bottom of the zone (1000 m), can vary from 5 m day - 1 to 30 m day - 1 . Lateral stirring and mixing also impact the temporal and spatial distributions of the particle flux. A useful metric in determining the impact of stirring and mixing is the "mix-down depth" which combines the effects of the initial patch size, strength of stirring, diffusion and sinking rate. When the mix-down depth is small compared to the depth to which biological interactions are important, then the impact of stirring and mixing is large, producing significant changes to the temporal behavior of the export flux and reducing spatial inhomogeneities. The results have implications for the sampling of the carbon flux associated with sinking particles and the representativeness of point measurements.

  3. Temporal and spatial habitat preferences and biotic interactions between mosquito larvae and antagonistic crustaceans in the field.

    PubMed

    Kroeger, Iris; Liess, Matthias; Duquesne, Sabine

    2014-06-01

    Investigations on natural antagonists of mosquito larvae found that micro-crustaceans (e.g., Cladocera) control mosquito populations under experimental conditions. However, their relevance for mosquito control under field situations remains widely unclear because important information about habitat preferences and time of occurrence of crustaceans and mosquito larvae are still missing. In order to fill this knowledge gap, a field study was undertaken in different wetland areas of Saxony, Germany, in different habitats (i.e., grassland, forest, and reed-covered wetlands). We found negative interactions between larvae of Ae. vexans and predatory Cyclopoida (Crustacean: Copepoda), which both were dominant during the first two weeks of hydroperiod, at ponds located at grassland habitats. Larvae of Cx. pipiens were spatially associated with competing Cladocera, but they colonized ponds more rapidly. Populations of Cladocera established from the third week of hydroperiod and prevented Cx. pipiens colonization thereafter. Ostracoda were highly abundant during the whole hydroperiod, but their presence was restricted to habitats of reed-covered wetland at one geographical area. Mosquito larvae hardly occurred at those ponds. In general, we found that ponds at the reed-covered wetlands provided better conditions for the initial development of crustaceans and hence, mosquito larval colonization was strongly inhibited. Grassland habitat, in contrast, favored early development of mosquito larvae. This study showed that micro-crustaceans are relevant for mosquito management but their impact on mosquito larvae varies between species and depends on environmental conditions. PMID:24820562

  4. Finding the Biotic Fringe

    NASA Astrophysics Data System (ADS)

    Shock, E.

    2014-12-01

    The deepest extent of inhabited rock, known as the biotic fringe, is determined by the interplay of geochemical and biochemical reaction rates. As a consequence it is unlikely that a single parameter, such as temperature, will be generally diagnostic. More probably, shifting combinations of compositional factors, together with temperature and pressure changes, will determine the position and dynamic movements of the biotic fringe. As an example, during serpentinization the biotic fringe may be determined by the depletion of carbon through carbonate precipitation or abiotic organic synthesis at mineral surfaces at temperatures and pressures that are readily inhabited elsewhere. During other weathering, diagenetic and alteration processes, the transition from sterile to populated may be determined by supply rates of reductants, oxidants, nutrients, or their diverse combinations. Where geochemical composition and mineral catalysts permit rapid abiotic organic synthesis and redox equilibration, microbes are unlikely to be able to compete. This is especially true if such conditions inhibit the function of enzymatic catalysts. As abiotic rates slow, opportunities for catalysis emerge as can the biotic fringe where enzymes can function effectively. There are many ways to turn this conceptual model into one that makes quantitative predictions. Rates of many abiotic redox and organic synthesis reactions are amenable to experimental study, and parallel biotic rate experiments yield particularly useful results. Likewise, determining how enzymes are inactivated at the limits of their function will add explicit biochemical constraints. Exploring for the biotic fringe in the subsurface involves using compositional data to evaluate apparent temperatures of equilibration that reveal anomalous approaches to redox equilibrium at conditions where abiotic rates are insufficient. Meanwhile, sampling the inhabitants of the biotic fringe will reveal surprising extents of enzyme behavior.

  5. Interaction Forces Drive the Environmental Transmission of Pathogenic Protozoa

    PubMed Central

    Aubert, Dominique; Puech, Pierre-Henri; Hohweyer, Jeanne; Azas, Nadine; Villena, Isabelle

    2012-01-01

    The protozoan parasites Giardia duodenalis, Cryptosporidium spp., and Toxoplasma gondii are pathogens that are resistant to a number of environmental factors and pose significant risks to public health worldwide. Their environmental transmission is closely governed by the physicochemical properties of their cysts (Giardia) and oocysts (Cryptosporidium and Toxoplasma), allowing their transport, retention, and survival for months in water, soil, vegetables, and mollusks, which are the main reservoirs for human infection. Importantly, the cyst/oocyst wall plays a key role in that regard by exhibiting a complex polymeric coverage that determines the charge and hydrophobic characteristics of parasites' surfaces. Interaction forces between parasites and other environmental particles may be, in a first approximation, evaluated following the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of colloidal stability. However, due to the molecular topography and nano- to microstructure of the cyst/oocyst surface, non-DVLO hydrophobic forces together with additional steric attractive and/or repulsive forces may play a pivotal role in controlling the parasite behavior when the organism is subjected to various external conditions. Here, we review several parameters that enhance or hinder the adhesion of parasites to other particles and surfaces and address the role of fast-emerging techniques for mapping the cyst/oocyst surface, e.g., by measuring its topology and the generated interaction forces at the nano- to microscale. We discuss why characterizing these interactions could be a crucial step for managing the environmental matrices at risk of microbial pollution. PMID:22156429

  6. Biotic transitions in global marine diversity

    NASA Technical Reports Server (NTRS)

    Miller, A. I.

    1998-01-01

    Long-term transitions in the composition of Earth's marine biota during the Phanerozoic have historically been explained in two different ways. One view is that they were mediated through biotic interactions among organisms played out over geologic time. The other is that mass extinctions transcended any such interactions and governed diversity over the long term by resetting the relative diversities of higher taxa. However, a growing body of evidence suggests that macroevolutionary processes effecting biotic transitions during background times were not fundamentally different from those operating during mass extinctions. Physical perturbations at many geographic scales combined to produce the long-term trajectory of Phanerozoic diversity.

  7. Intermolecular interactions of thrombospondins drive their accumulation in extracellular matrix

    PubMed Central

    Kim, Dae Joong; Christofidou, Elena D.; Keene, Douglas R.; Hassan Milde, Marwah; Adams, Josephine C.

    2015-01-01

    Thrombospondins participate in many aspects of tissue organization in adult tissue homeostasis, and their dysregulation contributes to pathological processes such as fibrosis and tumor progression. The incorporation of thrombospondins into extracellular matrix (ECM) as discrete puncta has been documented in various tissue and cell biological contexts, yet the underlying mechanisms remain poorly understood. We find that collagen fibrils are disorganized in multiple tissues of Thbs1−/− mice. In investigating how thrombospondins become retained within ECM and thereby affect ECM organization, we find that accumulation of thrombospondin-1 or thrombospondin-5 puncta within cell-derived ECM is controlled by a novel, conserved, surface-exposed site on the thrombospondin L-type lectin domain. This site acts to recruit thrombospondin molecules into ECM by intermolecular interactions in trans. This mechanism is fibronectin independent, can take place extracellularly, and is demonstrated to be direct in vitro. The trans intermolecular interactions can also be heterotypic—for example, between thrombospondin-1 and thrombospondin-5. These data identify a novel concept of concentration-dependent, intermolecular “matrix trapping” as a conserved mechanism that controls the accumulation and thereby the functionality of thrombospondins in ECM. PMID:25995382

  8. The Role of Cholesterol in Driving IAPP-Membrane Interactions.

    PubMed

    Sciacca, Michele F M; Lolicato, Fabio; Di Mauro, Giacomo; Milardi, Danilo; D'Urso, Luisa; Satriano, Cristina; Ramamoorthy, Ayyalusamy; La Rosa, Carmelo

    2016-07-12

    Our knowledge of the molecular events underlying type 2 diabetes mellitus-a protein conformational disease characterized by the aggregation of islet amyloid polypeptide (IAPP) in pancreatic β cells-is limited. However, amyloid-mediated membrane damage is known to play a key role in IAPP cytotoxicity, and therefore the effects of lipid composition on modulating IAPP-membrane interactions have been the focus of intense research. In particular, membrane cholesterol content varies with aging and consequently with adverse environmental factors such as diet and lifestyle, but its role in the development of the disease is controversial. In this study, we employ a combination of experimental techniques and in silico molecular simulations to shed light on the role of cholesterol in IAPP aggregation and the related membrane disruption. We show that if anionic POPC/POPS vesicles are used as model membranes, cholesterol has a negligible effect on the kinetics of IAPP fibril growth on the surface of the bilayer. In addition, cholesterol inhibits membrane damage by amyloid-induced poration on membranes, but enhances leakage through fiber growth on the membrane surface. Conversely, if 1:2 DOPC/DPPC raft-like model membranes are used, cholesterol accelerates fiber growth. Next, it enhances pore formation and suppresses fiber growth on the membrane surface, leading to leakage. Our results highlight a twofold effect of cholesterol on the amyloidogenicity of IAPP and help explain its debated role in type 2 diabetes mellitus. PMID:27410742

  9. Characterization and interaction of driving factors in karst rocky desertification: a case study from Changshun, China

    NASA Astrophysics Data System (ADS)

    Xu, E. Q.; Zhang, H. Q.

    2014-10-01

    As the most severe ecological issue in Southwest China, karst rocky desertification (KRD) has both threatened and constrained regional sustainable development. Comprehensively understanding the relationship between the evolution of KRD and relevant driving data would provide more information to combat KRD in such complex karst environments. Past studies have been limited in quantifying the relative importance of driving factors influencing fine-scale KRD evolution, and have also lacked insight into their interactive impacts. To address these issues, we have used geographical information system techniques and a geographical detector model to explore the spatial consistency of driving factors and their interactions in relation to the evolution of KRD. Changshun County in China was selected as a representative area for the study. Nine relevant driving factors, including both natural and anthropogenic factors, were studied in regard to their relationships with KRD transformation between 2000 and 2010. Our results demonstrate the relative importance of driving data in influencing the improvement and deterioration of KRD. Lithology, soil type and road influence are identified as the leading factors. Interestingly, to our study at least, there is no significant difference between the impacts of natural and anthropogenic factors. Factors were found to enhance the influence of each other for KRD transformation. In particular, the results show a non-linearly enhanced effect between driving factors, which significantly aggravates KRD. New information found in our study helps to effectively control and restore areas afflicted by KRD.

  10. Characterization and interaction of driving factors in karst rocky desertification: a case study from Changshun, China

    NASA Astrophysics Data System (ADS)

    Xu, E. Q.; Zhang, H. Q.

    2014-12-01

    As the most severe ecological issue in southwest China, karst rocky desertification (KRD) has both threatened and constrained regional sustainable development. Comprehensively understanding the relationship between the evolution of KRD and relevant driving data would provide more information to combat KRD in such complex karst environments. Past studies have been limited in quantifying the relative importance of driving factors influencing fine-scale KRD evolution, and have also lacked insight into their interactive impacts. To address these issues, we have used geographical information system techniques and a geographical detector model to explore the spatial consistency of driving factors and their interactions in relation to the evolution of KRD. Changshun County in China was selected as a representative area for the study. Nine relevant driving factors, including both natural and anthropogenic factors, were studied in regard to their relationships with KRD transformation between 2000 and 2010. Our results demonstrate the relative importance of driving data in influencing the improvement and deterioration of KRD. Lithology, soil type and road influence are identified as the leading factors. Interestingly, to our study at least, there is no significant difference between the impacts of natural and anthropogenic factors influencing KRD improvement, and even natural factors have a higher impact on KRD deterioration. Factors were found to enhance the influence of each other for KRD transformation. In particular, the results show a non-linearly enhanced effect between driving factors, which significantly aggravates KRD. New information found in our study helps to effectively control and restore areas afflicted by KRD.

  11. Differences in Anticipated Interaction Drive Own Group Biases in Face Memory

    PubMed Central

    Wilson, John Paul; See, Pirita E.; Bernstein, Michael J.; Hugenberg, Kurt; Chartier, Christopher

    2014-01-01

    According to much research, the Own Group Bias (OGB) in face memory occurs as a consequence of social categorization – ingroup members are more likely than outgroup members to be encoded as individuals and remembered well. The current work is an examination of the role of anticipated future interaction in the OGB. We conducted two studies showing that anticipated interaction influences group-based face memory. In Study 1, we provided correlational evidence that beliefs about the amount and importance of future interaction one will have with racial outgroup members is associated with the OGB, such that people expecting more interaction with outgroup members show a reduced OGB. In Study 2, we manipulated expectations about future interactions with lab-created groups and observed that high levels of anticipated future interaction with the outgroup eliminated the OGB. Thus, social group categorization drives face memory biases to the extent that group membership affords the expectation of interpersonal interaction. PMID:24599294

  12. Synergistic Parasite-Pathogen Interactions Mediated by Host Immunity Can Drive the Collapse of Honeybee Colonies

    PubMed Central

    Nazzi, Francesco; Brown, Sam P.; Annoscia, Desiderato; Del Piccolo, Fabio; Di Prisco, Gennaro; Varricchio, Paola; Della Vedova, Giorgio; Cattonaro, Federica; Caprio, Emilio; Pennacchio, Francesco

    2012-01-01

    The health of the honeybee and, indirectly, global crop production are threatened by several biotic and abiotic factors, which play a poorly defined role in the induction of widespread colony losses. Recent descriptive studies suggest that colony losses are often related to the interaction between pathogens and other stress factors, including parasites. Through an integrated analysis of the population and molecular changes associated with the collapse of honeybee colonies infested by the parasitic mite Varroa destructor, we show that this parasite can de-stabilise the within-host dynamics of Deformed wing virus (DWV), transforming a cryptic and vertically transmitted virus into a rapidly replicating killer, which attains lethal levels late in the season. The de-stabilisation of DWV infection is associated with an immunosuppression syndrome, characterized by a strong down-regulation of the transcription factor NF-κB. The centrality of NF-κB in host responses to a range of environmental challenges suggests that this transcription factor can act as a common currency underlying colony collapse that may be triggered by different causes. Our results offer an integrated account for the multifactorial origin of honeybee losses and a new framework for assessing, and possibly mitigating, the impact of environmental challenges on honeybee health. PMID:22719246

  13. Metaphors to Drive By: Exploring New Ways to Guide Human-Robot Interaction

    SciTech Connect

    David J. Bruemmer; David I. Gertman; Curtis W. Nielsen

    2007-08-01

    Autonomous behaviors created by the research and development community are not being extensively utilized within energy, defense, security, or industrial contexts. This paper provides evidence that the interaction methods used alongside these behaviors may not provide a mental model that can be easily adopted or used by operators. Although autonomy has the potential to reduce overall workload, the use of robot behaviors often increased the complexity of the underlying interaction metaphor. This paper reports our development of new metaphors that support increased robot complexity without passing the complexity of the interaction onto the operator. Furthermore, we illustrate how recognition of problems in human-robot interactions can drive the creation of new metaphors for design and how human factors lessons in usability, human performance, and our social contract with technology have the potential for enormous payoff in terms of establishing effective, user-friendly robot systems when appropriate metaphors are used.

  14. Mutualistic Interactions Drive Ecological Niche Convergence in a Diverse Butterfly Community

    PubMed Central

    Elias, Marianne; Gompert, Zachariah; Jiggins, Chris; Willmott, Keith

    2008-01-01

    Ecological communities are structured in part by evolutionary interactions among their members. A number of recent studies incorporating phylogenetics into community ecology have upheld the paradigm that competition drives ecological divergence among species of the same guild. However, the role of other interspecific interactions, in particular positive interactions such as mutualism, remains poorly explored. We characterized the ecological niche and inferred phylogenetic relationships among members of a diverse community of neotropical Müllerian mimetic butterflies. Müllerian mimicry is one of the best studied examples of mutualism, in which unpalatable species converge in wing pattern locally to advertize their toxicity to predators. We provide evidence that mutualistic interactions can drive convergence along multiple ecological axes, outweighing both phylogeny and competition in shaping community structure. Our findings imply that ecological communities are adaptively assembled to a much greater degree than commonly suspected. In addition, our results show that phenotype and ecology are strongly linked and support the idea that mimicry can cause ecological speciation through multiple cascading effects on species' biology. PMID:19055316

  15. Highly Accurate Structure-Based Prediction of HIV-1 Coreceptor Usage Suggests Intermolecular Interactions Driving Tropism

    PubMed Central

    Kieslich, Chris A.; Tamamis, Phanourios; Guzman, Yannis A.; Onel, Melis; Floudas, Christodoulos A.

    2016-01-01

    HIV-1 entry into host cells is mediated by interactions between the V3-loop of viral glycoprotein gp120 and chemokine receptor CCR5 or CXCR4, collectively known as HIV-1 coreceptors. Accurate genotypic prediction of coreceptor usage is of significant clinical interest and determination of the factors driving tropism has been the focus of extensive study. We have developed a method based on nonlinear support vector machines to elucidate the interacting residue pairs driving coreceptor usage and provide highly accurate coreceptor usage predictions. Our models utilize centroid-centroid interaction energies from computationally derived structures of the V3-loop:coreceptor complexes as primary features, while additional features based on established rules regarding V3-loop sequences are also investigated. We tested our method on 2455 V3-loop sequences of various lengths and subtypes, and produce a median area under the receiver operator curve of 0.977 based on 500 runs of 10-fold cross validation. Our study is the first to elucidate a small set of specific interacting residue pairs between the V3-loop and coreceptors capable of predicting coreceptor usage with high accuracy across major HIV-1 subtypes. The developed method has been implemented as a web tool named CRUSH, CoReceptor USage prediction for HIV-1, which is available at http://ares.tamu.edu/CRUSH/. PMID:26859389

  16. Transcription rate and transcript length drive formation of chromosomal interaction domain boundaries.

    PubMed

    Le, Tung Bk; Laub, Michael T

    2016-07-15

    Chromosomes in all organisms are highly organized and divided into multiple chromosomal interaction domains, or topological domains. Regions of active, high transcription help establish and maintain domain boundaries, but precisely how this occurs remains unclear. Here, using fluorescence microscopy and chromosome conformation capture in conjunction with deep sequencing (Hi-C), we show that in Caulobacter crescentus, both transcription rate and transcript length, independent of concurrent translation, drive the formation of domain boundaries. We find that long, highly expressed genes do not form topological boundaries simply through the inhibition of supercoil diffusion. Instead, our results support a model in which long, active regions of transcription drive local decompaction of the chromosome, with these more open regions of the chromosome forming spatial gaps in vivo that diminish contacts between DNA in neighboring domains. These insights into the molecular forces responsible for domain formation in Caulobacter likely generalize to other bacteria and possibly eukaryotes. PMID:27288403

  17. Laser-Plasma Interactions in Drive Campaign targets on the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Hinkel, D. E.; Callahan, D. A.; Moody, J. D.; Amendt, P. A.; Lasinski, B. F.; MacGowan, B. J.; Meeker, D.; Michel, P. A.; Ralph, J.; Rosen, M. D.; Ross, J. S.; Schneider, M. B.; Storm, E.; Strozzi, D. J.; Williams, E. A.

    2016-03-01

    The Drive campaign [D A Callahan et al., this conference] on the National Ignition Facility (NIF) laser [E. I. Moses, R. N. Boyd, B. A. Remington, C. J. Keane, R. Al-Ayat, Phys. Plasmas 16, 041006 (2009)] has the focused goal of understanding and optimizing the hohlraum for ignition. Both the temperature and symmetry of the radiation drive depend on laser and hohlraum characteristics. The drive temperature depends on the coupling of laser energy to the hohlraum, and the symmetry of the drive depends on beam-to-beam interactions that result in energy transfer [P. A. Michel, S. H. Glenzer, L. Divol, et al, Phys. Plasmas 17, 056305 (2010).] within the hohlraum. To this end, hohlraums are being fielded where shape (rugby vs. cylindrical hohlraums), gas fill composition (neopentane at room temperature vs. cryogenic helium), and gas fill density (increase of ∼ 150%) are independently changed. Cylindrical hohlraums with higher gas fill density show improved inner beam propagation, as should rugby hohlraums, because of the larger radius over the capsule (7 mm vs. 5.75 mm in a cylindrical hohlraum). Energy coupling improves in room temperature neopentane targets, as well as in hohlraums at higher gas fill density. In addition cross-beam energy transfer is being addressed directly by using targets that mock up one end of a hohlraum, but allow observation of the laser beam uniformity after energy transfer. Ideas such as splitting quads into “doublets” by re-pointing the right and left half of quads are also being pursued. LPI results of the Drive campaign will be summarized, and analyses of future directions presented.

  18. Pili-mediated Interactions between Neisseria Gonorrhoeae Bacteria are the Driving Mechanism of Microcolony Merging

    NASA Astrophysics Data System (ADS)

    Poenisch, Wolfram; Weber, Christoph; Alzurqa, Khaled; Nasrollahi, Hadi; Biais, Nicolas; Zaburdaev, Vasily; Collective Dynamics of Cells Team; Mechano-Micro-Biology Lab Team

    2015-03-01

    During the early infection with Neisseria gonorrhoeae the bacteria form microcolonies consisting of a few hundreds to a few thousands of cells. The formation of colonies is mediated by type IV pili, thin and long filaments that are also involved in the motion of single cells over a substrate. A related process causes attractive cell-cell-interactions. While the motion of single cells has been extensively studied during the past years, the physical principles driving the growth of these colonies are poorly understood. One key mechanism of colony growth is coalescence of smaller colonies. Therefore we experimentally examine the process of merging of two Neisseria gonorrhoeae colonies. We develop a theoretical microscopic model of single cells interacting solely by their pili. The experimental data and the results obtained from our model are in excellent quantitative agreement. We observe a fast initial approach of the two merging colonies within a few minutes, that is followed by a slow relaxation of the colony shape with a characteristic time of several hours. These findings suggest that pili-mediated interactions are the primary driving mechanism of the microcolony merging process.

  19. Interactive effects of xenobiotic, abiotic and biotic stressors on Daphnia pulex--results from a multiple stressor experiment with a fractional multifactorial design.

    PubMed

    Scherer, Christian; Seeland, Anne; Oehlmann, Jörg; Müller, Ruth

    2013-08-15

    Pollutant effects on aquatic key species are confounded by multiple abiotic and biotic stressors. To better discriminate and understand the intrinsic and environmental correlates of changing aquatic ecosystems, we untangle in present study how the effects of a low-dosed fungicide on daphnids (via different exposure routes) becomes modified by increasing temperature and the presence of a predator. Using a fractional multifactorial test design, the individual growth, reproduction and population growth rate of Daphnia pulex were investigated under exposure to the fungicide pyrimethanil at an environmental relevant concentration--either directly (via the water phase), indirectly (via food), dually (via water and food) or for multiple generations (fungicide treated source population)--at three temperatures and in presence/absence of the predator kairomones of Chaoborus flavicans. Our results clearly illustrate that multiple stress factors can modify the response of an aquatic key species to pollutants. The environmentally relevant exposure of the contaminant via food or the medium is of same importance. Nevertheless, temperature and the presence of a predator are the dominant factors controlling the reproduction of D. pulex. We conclude that sublethal pyrimethanil pollution can disturb the zooplankton community at suboptimal temperature conditions, but the effects will become masked by low temperatures or if chaoborid larvae are present. PMID:23727598

  20. How to integrate geology, biology, and modern wireless technologies to assess biotic-abiotic interactions on coastal dune systems: a new multidisciplinary approach

    NASA Astrophysics Data System (ADS)

    Sarti, Giovanni; Bertoni, Duccio; Bini, Monica; Ciccarelli, Daniela; Ribolini, Adriano; Ruocco, Matteo; Pozzebon, Alessandro; Alquini, Fernanda; Giaccari, Riccardo; Tordella, Stefano

    2014-05-01

    Coastal dune systems are arguably one of the most dynamic environments because their evolution is controlled by many factors, both natural and human-related. Hence, they are often exposed to processes leading to erosion, which in turn determine serious naturalistic and economic losses. Most recent studies carried out on different dune fields worldwide emphasized the notion that a better definition of this environment needs an approach that systematically involves several disciplines, striving to merge every data collected from any individual analyses. Therefore, a new multidisciplinary method to study coastal dune systems has been conceived in order to integrate geology, biology, and modern wireless technologies. The aim of the work is threefold: i) to check the reliability of this new approach; ii) to provide a dataset as complete as ever about the factors affecting the evolution of coastal dunes; and iii) to evaluate the influence of any biotic and abiotic factors on plant communities. The experimentation site is located along the Pisa coast within the Migliarino - S. Rossore - Massaciuccoli Regional Park, a protected area where human influence is low (Tuscany, Italy). A rectangle of 100 x 200 m containing 50 grids of 20 x 20 m was established along the coastal dune systems from the coastline to the pinewood at the landward end of the backdune area. Sampling from each grid determined grain-size analysis carried out on surface sediment samples such as geologic aspects; topographic surveys performed by means of DGPS-RTK instruments; geophysical surveys conducted with a GPR equipment, which will be matched with core drilling activities; digital image analysis of high definition pictures taken by means of a remote controlled aircraft drone flying over the study area; biological data obtained by percent cover of each vascular plant species recorded in the sampling unit. Along with geologic and biologic methodologies, this research implemented the use of informatics

  1. FOXP2 drives neuronal differentiation by interacting with retinoic acid signaling pathways

    PubMed Central

    Devanna, Paolo; Middelbeek, Jeroen; Vernes, Sonja C.

    2014-01-01

    FOXP2 was the first gene shown to cause a Mendelian form of speech and language disorder. Although developmentally expressed in many organs, loss of a single copy of FOXP2 leads to a phenotype that is largely restricted to orofacial impairment during articulation and linguistic processing deficits. Why perturbed FOXP2 function affects specific aspects of the developing brain remains elusive. We investigated the role of FOXP2 in neuronal differentiation and found that FOXP2 drives molecular changes consistent with neuronal differentiation in a human model system. We identified a network of FOXP2 regulated genes related to retinoic acid signaling and neuronal differentiation. FOXP2 also produced phenotypic changes associated with neuronal differentiation including increased neurite outgrowth and reduced migration. Crucially, cells expressing FOXP2 displayed increased sensitivity to retinoic acid exposure. This suggests a mechanism by which FOXP2 may be able to increase the cellular differentiation response to environmental retinoic acid cues for specific subsets of neurons in the brain. These data demonstrate that FOXP2 promotes neuronal differentiation by interacting with the retinoic acid signaling pathway and regulates key processes required for normal circuit formation such as neuronal migration and neurite outgrowth. In this way, FOXP2, which is found only in specific subpopulations of neurons in the brain, may drive precise neuronal differentiation patterns and/or control localization and connectivity of these FOXP2 positive cells. PMID:25309332

  2. Early life stress interactions with the epigenome: potential mechanisms driving vulnerability towards psychiatric illness

    PubMed Central

    Olive, Michael Foster

    2014-01-01

    Throughout the 20th century a body of literature concerning the long lasting effects of early environment was produced. Adverse experiences in early life, or early life stress (ELS), is associated with a higher risk for developing various psychiatric illnesses. The mechanisms driving the complex interplay between ELS and adult phenotype has baffled many investigators for decades. Over the last decade, the new field of neuroepigenetics has emerged as one possible mechanism by which ELS can have far reaching effects on adult phenotype, behavior, and risk for psychiatric illness. Here we review two commonly investigated epigenetic mechanisms, histone modifications and DNA methylation, and the emerging field of neuroepigenetics as they relate to ELS. We discuss the current animal literature demonstrating ELS induced epigenetic modulation of gene expression that results in altered adult phenotypes. We also briefly discuss other areas in which neuroepigenetics has emerged as a potential mechanism underlying environmental and genetic interactions. PMID:25003947

  3. Functional Plant Types Drive Plant Interactions in a Mediterranean Mountain Range.

    PubMed

    Macek, Petr; Prieto, Iván; Macková, Jana; Pistón, Nuria; Pugnaire, Francisco I

    2016-01-01

    Shrubs have positive (facilitation) and negative (competition) effects on understory plants, the net interaction effect being modulated by abiotic conditions. Overall shrubs influence to great extent the structure of plant communities where they have significant presence. Interactions in a plant community are quite diverse but little is known about their variability and effects at community level. Here we checked the effects of co-occurring shrub species from different functional types on a focal understory species, determining mechanisms driving interaction outcome, and tested whether effects measured on the focal species were a proxy for effects measured at the community level. Growth, physiological, and reproductive traits of Euphorbia nicaeensis, our focal species, were recorded on individuals growing in association with four dominant shrub species and in adjacent open areas. We also recorded community composition and environmental conditions in each microhabitat. Shrubs provided environmental conditions for plant growth, which contrasted with open areas, including moister soil, greater N content, higher air temperatures, and lower radiation. Shrub-associated individuals showed lower reproductive effort and greater allocation to growth, while most physiological traits remained unaffected. Euphorbia individuals were bigger and had more leaf N under N-fixing than under non-fixing species. Soil moisture was also higher under N-fixing shrubs; therefore soil conditions in the understory may counter reduced light conditions. There was a significant effect of species identity and functional types in the outcome of plant interactions with consistent effects at individual and community levels. The contrasting allocation strategies to reproduction and growth in Euphorbia plants, either associated or not with shrubs, showed high phenotypic plasticity and evidence its ability to cope with contrasting environmental conditions. PMID:27242863

  4. A Colloidal Description of Intermolecular Interactions Driving Fibril-Fibril Aggregation of a Model Amphiphilic Peptide.

    PubMed

    Owczarz, Marta; Motta, Anna C; Morbidelli, Massimo; Arosio, Paolo

    2015-07-14

    We apply a kinetic analysis platform to study the intermolecular interactions underlying the colloidal stability of dispersions of charged amyloid fibrils consisting of a model amphiphilic peptide (RADA 16-I). In contrast to the aggregation mechanisms observed in the large majority of proteins and peptides, where several elementary reactions involving both monomers and fibrils are present simultaneously, the system selected in this work allows the specific investigation of the fibril-fibril aggregation process. We examine the intermolecular interactions driving the aggregation reaction at pH 2.0 by changing the buffer composition in terms of salt concentration, type of ion as well as type and concentration of organic solvent. The aggregation kinetics are followed by dynamic light scattering, and the experimental data are simulated by Smoluchowski population balance equations, which allow to estimate the energy barrier between two colliding fibrils in terms of the Fuchs stability ratio (W). When normalized on a dimensionless time weighted on the Fuchs stability ratio, the aggregation profiles under a broad range of conditions collapse on a single master curve, indicating that the buffer composition modifies the aggregation kinetics without affecting the aggregation mechanism. Our results show that the aggregation process does not occur under diffusion-limited conditions. Rather, the reaction rate is limited by the presence of an activation energy barrier that is largely dominated by electrostatic repulsive interactions. Such interactions could be reduced by increasing the concentration of salt, which induces charge screening, or the concentration of organic solvent, which affects the dielectric constant. It is remarkable that the dependence of the activation energy on the ionic strength can be described quantitatively in terms of charge screening effects in the frame of the DLVO theory, although specific anion and cation effects are also observed. While anion

  5. Functional Plant Types Drive Plant Interactions in a Mediterranean Mountain Range

    PubMed Central

    Macek, Petr; Prieto, Iván; Macková, Jana; Pistón, Nuria; Pugnaire, Francisco I.

    2016-01-01

    Shrubs have positive (facilitation) and negative (competition) effects on understory plants, the net interaction effect being modulated by abiotic conditions. Overall shrubs influence to great extent the structure of plant communities where they have significant presence. Interactions in a plant community are quite diverse but little is known about their variability and effects at community level. Here we checked the effects of co-occurring shrub species from different functional types on a focal understory species, determining mechanisms driving interaction outcome, and tested whether effects measured on the focal species were a proxy for effects measured at the community level. Growth, physiological, and reproductive traits of Euphorbia nicaeensis, our focal species, were recorded on individuals growing in association with four dominant shrub species and in adjacent open areas. We also recorded community composition and environmental conditions in each microhabitat. Shrubs provided environmental conditions for plant growth, which contrasted with open areas, including moister soil, greater N content, higher air temperatures, and lower radiation. Shrub-associated individuals showed lower reproductive effort and greater allocation to growth, while most physiological traits remained unaffected. Euphorbia individuals were bigger and had more leaf N under N-fixing than under non-fixing species. Soil moisture was also higher under N-fixing shrubs; therefore soil conditions in the understory may counter reduced light conditions. There was a significant effect of species identity and functional types in the outcome of plant interactions with consistent effects at individual and community levels. The contrasting allocation strategies to reproduction and growth in Euphorbia plants, either associated or not with shrubs, showed high phenotypic plasticity and evidence its ability to cope with contrasting environmental conditions. PMID:27242863

  6. Driving select architectures of nanoparticles: the role of the van der Waals interactions

    NASA Astrophysics Data System (ADS)

    Almora-Barrios, Neyvis; López, Nuria; Theoretical Heterogeneous Catalysis Team

    2014-03-01

    The simulations with dispersion corrections provide a detailed atomistic model for understand of structure-function relations in the study of materials. Two scenarios that require this level of theoretical approximation are the study of the different architectures of Au nanoparticles and the stability, activity and selectivity properties of c-Pd nanocatalysts. We have investigated a model based on DFT-D2 surface energy calculations to identify key of the leading interactions that drive the formation of Au nanorods. The complexity of the procedure can be analyzed in detail and the information provided by the calculations paves the way to a better compression of synthetic-structure relationships. In the field of catalytic activity, we have simulated surfactant on Pd surface and our results contribute to a better understanding of activity of the catalyst, modeling for the first time the structure of this novel family of material. The resulting insights significantly advance the state-of-the-art to improve our knowledge of the roles and effects of electrostatic and van der Waals interactions, opening a complete new perspective in the control of new architectures to design of the nanoparticles. The authors thank the ERC-2010-StG-258406 Bio2chem-d project, MINECO (CTQ2012-33826) and BSC-RES for supporting this work.

  7. Wave-Particle Interactions As a Driving Mechanism for the Solar Wind

    NASA Technical Reports Server (NTRS)

    Wagner, William J.

    2004-01-01

    Our research has been focusing on a highly experimentally relevant issue: intermittency of the fluctuating fields in outflowing plasmas. We have contributed to both the theoretical and experimental research of the topic. In particular, we have developed a theoretical model and data analyzing programs to examine the issue of intermittency in space plasma outflows, including the solar wind. As fluctuating electric fields in the solar wind are likely to provide a heating and acceleration mechanism for the ions, our studies of the intermittency in turbulence in space plasma outflows help us toward achieving the goal of comparing major physical mechanisms that contribute to the driving of the fast solar wind. Our new theoretical model extends the utilities of our global hybrid model, which has allowed us to follow the kinetic evolution of the particle distributions along an inhomogeneous field line while the particles are subjected to various physical mechanisms. The physical effects that were considered in the global hybrid model included wave-particle interactions, an ambipolar electric field that was consistent with the particle distributions themselves, and Coulomb collisions. With an earlier version of the global hybrid model, we examined the overall impact on the solar wind flow due to the combination of these physical effects. In particular, we studied the combined effects of two major mechanisms that had been proposed as the drivers of the fast solar wind: (1) velocity filtration effect due to suprathermal electrons; (2) ion cyclotron resonance. Since the approval of this research grant, we have updated the model such that the effects due to these two driving mechanisms can be examined separately, thereby allowing us to compare their contributions to the acceleration of the solar wind. In the next section, we shall demonstrate that the velocity filtration effect is rather insignificant in comparison with that due to ion cyclotron resonance.

  8. Plasma Interactions with High Voltage Solar Arrays for a Direct Drive Hall Effect Thruster System

    NASA Technical Reports Server (NTRS)

    Schneider, T.; Horvater, M. A.; Vaughn, J.; Carruth, M. R.; Jongeward, G. A.; Mikellides, I. G.

    2003-01-01

    The Environmental Effects Group of NASA s Marshall Space Flight Center (MSFC) is conducting research into the effects of plasma interaction with high voltage solar arrays. These high voltage solar arrays are being developed for a direct drive Hall Effect Thruster propulsion system. A direct drive system configuration will reduce power system mass by eliminating a conventional power-processing unit. The Environmental Effects Group has configured two large vacuum chambers to test different high-voltage array concepts in a plasma environment. Three types of solar arrays have so far been tested, an International Space Station (ISS) planar array, a Tecstar planar array, and a Tecstar solar concentrator array. The plasma environment was generated using a hollow cathode plasma source, which yielded densities between 10(exp 6) - 10(exp 7) per cubic centimeter and electron temperatures of 0.5-1 eV. Each array was positioned in this plasma and biased in the -500 to + 500 volt range. The current collection was monitored continuously. In addition, the characteristics of arcing, snap over, and other features, were recorded. Analysis of the array performance indicates a time dependence associated with the current collection as well as a tendency for "conditioning" over a large number of runs. Mitigation strategies, to reduce parasitic current collection, as well as arcing, include changing cover-glass geometry and layout as well as shielding the solar cell edges. High voltage performance data for each of the solar array types tested will be presented. In addition, data will be provided to indicate the effectiveness of the mitigation techniques.

  9. Dynamic stability and slider-lubricant interactions in hard disk drives

    NASA Astrophysics Data System (ADS)

    Ambekar, Rohit Pradeep

    2007-12-01

    Hard disk drives (HDD) have played a significant role in the current information age and have become the backbone of storage. The soaring demand for mass data storage drives the necessity for increasing capacity of the drives and hence the areal density on the disks as well as the reliability of the HDD. To achieve greater areal density in hard disk drives, the flying height of the airbearing slider continually decreases. Different proximity forces and interactions influence the air bearing slider resulting in fly height modulation and instability. This poses several challenges to increasing the areal density (current goal is 2Tb/in.2) as well as making the head-disk interface (HDI) more reliable. Identifying and characterizing these forces or interactions has become important for achieving a stable fly height at proximity and realizing the goals of areal density and reliability. Several proximity forces or interactions influencing the slider are identified through the study of touchdown-takeoff hysteresis. Slider-lubricant interaction which causes meniscus force between the slider and disk as well as airbearing surface contamination seems to be the most important factor affecting stability and reliability at proximity. In addition, intermolecular forces and disk topography are identified as important factors. Disk-to-slider lubricant transfer leads to lubricant pickup on the slider and also causes depletion of lubricant on the disk, affecting stability and reliability of the HDI. Experimental and numerical investigation as well as a parametric study of the process of lubricant transfer has been done using a half-delubed disk. In the first part of this parametric study, dependence on the disk lubricant thickness, lubricant type and slider ABS design has been investigated. It is concluded that the lubricant transfer can occur without slider-disk contact and there can be more than one timescale associated with the transfer. Further, the transfer increases non

  10. Goal Representations and Motivational Drive in Schizophrenia: The Role of Prefrontal–Striatal Interactions

    PubMed Central

    Barch, Deanna M.; Dowd, Erin C.

    2010-01-01

    The past several years have seen a resurgence of interest in understanding the psychological and neural bases of what are often referred to as “negative symptoms” in schizophrenia. These aspects of schizophrenia include constructs such as asociality, avolition (a reduction in the motivation to initiate or persist in goal-directed behavior), and anhedonia (a reduction in the ability to experience pleasure). We believe that these dimensions of impairment in individuals with schizophrenia reflect difficulties using internal representations of emotional experiences, previous rewards, and motivational goals to drive current and future behavior in a way that would allow them to obtain desired outcomes, a deficit that has major clinical significance in terms of functional capacity. In this article, we review the major components of the systems that link experienced and anticipated rewards with motivated behavior that could potentially be impaired in schizophrenia. We conclude that the existing evidence suggests relatively intact hedonics in schizophrenia, but impairments in some aspects of reinforcement learning, reward prediction, and prediction error processing, consistent with an impairment in “wanting.” As of yet, there is only indirect evidence of impairment in anterior cingulate and orbital frontal function that may support value and effort computations. However, there are intriguing hints that individuals with schizophrenia may not be able to use reward information to modulate cognitive control and dorsolateral prefrontal cortex function, suggesting a potentially important role for cortical–striatal interactions in mediating impairment in motivated and goal-directed behavior in schizophrenia. PMID:20566491

  11. Electrostatic Interactions Drive Membrane Association of the Human Immunodeficiency Virus Type 1 Gag MA Domain▿

    PubMed Central

    Dalton, Amanda K.; Ako-Adjei, Danso; Murray, Paul S.; Murray, Diana; Vogt, Volker M.

    2007-01-01

    The assembly of most retroviruses occurs at the plasma membrane. Membrane association is directed by MA, the N-terminal domain of the Gag structural protein. For human immunodeficiency virus type 1 (HIV-1), this association is mediated in part by a myristate fatty acid modification. Conflicting evidence has been presented on the relative importance of myristoylation, of ionic interactions between protein and membrane, and of Gag multimerization in membrane association in vivo. We addressed these questions biochemically by determining the affinity of purified myristoylated HIV-1 MA for liposomes of defined composition, both for monomeric and for dimeric forms of the protein. Myristoylation increases the barely detectable intrinsic affinity of the apo-protein for liposomes by only 10-fold, and the resulting affinity is still weak, similar to that of the naturally nonmyristoylated MA of Rous sarcoma virus. Membrane binding of HIV-1 MA is absolutely dependent on the presence of negatively charged lipid and is abrogated at high ionic strength. Forced dimerization of MA increases its membrane affinity by several orders of magnitude. When green fluorescent protein fusions of monomeric or dimeric MA are expressed in cells, the dimeric but not the monomeric protein becomes strongly membrane associated. Computational modeling supports these results and suggests a molecular mechanism for the modest effect of myristoylation on binding, wherein the membrane provides a hydrophobic environment for the myristate that is energetically similar to that provided by the protein. Overall, the results imply that the driving force for membrane association stems largely from ionic interactions between multimerized Gag and negatively charged phospholipids. PMID:17392361

  12. Cooperative Electrostatic Interactions Drive Functional Evolution in the Alkaline Phosphatase Superfamily

    PubMed Central

    2015-01-01

    It is becoming widely accepted that catalytic promiscuity, i.e., the ability of a single enzyme to catalyze the turnover of multiple, chemically distinct substrates, plays a key role in the evolution of new enzyme functions. In this context, the members of the alkaline phosphatase superfamily have been extensively studied as model systems in order to understand the phenomenon of enzyme multifunctionality. In the present work, we model the selectivity of two multiply promiscuous members of this superfamily, namely the phosphonate monoester hydrolases from Burkholderia caryophylli and Rhizobium leguminosarum. We have performed extensive simulations of the enzymatic reaction of both wild-type enzymes and several experimentally characterized mutants. Our computational models are in agreement with key experimental observables, such as the observed activities of the wild-type enzymes, qualitative interpretations of experimental pH-rate profiles, and activity trends among several active site mutants. In all cases the substrates of interest bind to the enzyme in similar conformations, with largely unperturbed transition states from their corresponding analogues in aqueous solution. Examination of transition-state geometries and the contribution of individual residues to the calculated activation barriers suggest that the broad promiscuity of these enzymes arises from cooperative electrostatic interactions in the active site, allowing each enzyme to adapt to the electrostatic needs of different substrates. By comparing the structural and electrostatic features of several alkaline phosphatases, we suggest that this phenomenon is a generalized feature driving selectivity and promiscuity within this superfamily and can be in turn used for artificial enzyme design. PMID:26091851

  13. Minimize Adverse Motor and Adjustable Speed Drive Interactions - Motor Tip Sheet #15

    SciTech Connect

    2008-07-01

    Electronic adjustable speed drives (ASDs) are an extremely efficient and valuable asset to motor systems. They allow precise process control and provide energy savings within systems that do not need to continuously operate at full output.

  14. Genomics of Biotic Interactions in the Triticeae

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plant diseases pose threats to agriculture in all corners of the world. In highly productive systems, the genetic uniformity required for mechanized production renders crops vulnerable to severe losses. The advent of Triticeae microarrays built upon community-wide sequencing efforts is empowering ...

  15. Running with the Red Queen: the role of biotic conflicts in evolution

    PubMed Central

    Brockhurst, Michael A.; Chapman, Tracey; King, Kayla C.; Mank, Judith E.; Paterson, Steve; Hurst, Gregory D. D.

    2014-01-01

    What are the causes of natural selection? Over 40 years ago, Van Valen proposed the Red Queen hypothesis, which emphasized the primacy of biotic conflict over abiotic forces in driving selection. Species must continually evolve to survive in the face of their evolving enemies, yet on average their fitness remains unchanged. We define three modes of Red Queen coevolution to unify both fluctuating and directional selection within the Red Queen framework. Empirical evidence from natural interspecific antagonisms provides support for each of these modes of coevolution and suggests that they often operate simultaneously. We argue that understanding the evolutionary forces associated with interspecific interactions requires incorporation of a community framework, in which new interactions occur frequently. During their early phases, these newly established interactions are likely to drive fast evolution of both parties. We further argue that a more complete synthesis of Red Queen forces requires incorporation of the evolutionary conflicts within species that arise from sexual reproduction. Reciprocally, taking the Red Queen's perspective advances our understanding of the evolution of these intraspecific conflicts. PMID:25355473

  16. Biotic homogenization and differentiation of soil faunal communities in the production forest landscape: taxonomic and functional perspectives.

    PubMed

    Mori, Akira S; Ota, Aino T; Fujii, Saori; Seino, Tatsuyuki; Kabeya, Daisuke; Okamoto, Toru; Ito, Masamichi T; Kaneko, Nobuhiro; Hasegawa, Motohiro

    2015-02-01

    Biotic homogenization has been reported worldwide. Although simplification of communities across space is often significant at larger scales, it could also occur at the local scale by changing biotic interactions. This study aimed to elucidate local community processes driving biotic homogenization of soil faunal communities, and the possibility of biotic re-differentiation. We recorded species of oribatid mites in litter and soil layers along a gradient of forest conversion from monoculture larch plantation to primary forests in central Japan. We collected data for functional traits of the recorded species to quantify functional diversity. Then we quantified their taxonomic/functional turnover. Litter diversity was reduced in the larch-dominated stands, leading to habitat homogenization. Consequently, litter communities were biologically homogenized and differentiated in the plantations and in the natural forest, respectively. Turnover of functional traits for litter communities was lower and higher than expected by chance in the plantations and in the natural stand, respectively. This result suggests that the dominant assembly process shifts from limiting similarity to habitat filtering along the forest restoration gradient. However, support for such niche-based explanations was not observed for communities in the soil layer. In the monocultures, functional diversity expected from a given regional species pool significantly decreased for litter communities but not for those in the soil layer. Such discrepancy between communities in different layers suggests that communities more exposed to anthropogenic stresses are more vulnerable to the loss of their functional roles. Our study explains possible community processes behind the observed patterns of biological organization, which can be potentially useful in guiding approaches for restoring biodiversity. PMID:25322821

  17. Uranium isotopes fingerprint biotic reduction

    SciTech Connect

    Stylo, Malgorzata; Neubert, Nadja; Wang, Yuheng; Monga, Nikhil; Romaniello, Stephen J.; Weyer, Stefan; Bernier-Latmani, Rizlan

    2015-04-20

    Knowledge of paleo-redox conditions in the Earth’s history provides a window into events that shaped the evolution of life on our planet. The role of microbial activity in paleo-redox processes remains unexplored due to the inability to discriminate biotic from abiotic redox transformations in the rock record. The ability to deconvolute these two processes would provide a means to identify environmental niches in which microbial activity was prevalent at a specific time in paleo-history and to correlate specific biogeochemical events with the corresponding microbial metabolism. Here, we demonstrate that the isotopic signature associated with microbial reduction of hexavalent uranium (U), i.e., the accumulation of the heavy isotope in the U(IV) phase, is readily distinguishable from that generated by abiotic uranium reduction in laboratory experiments. Thus, isotope signatures preserved in the geologic record through the reductive precipitation of uranium may provide the sought-after tool to probe for biotic processes. Because uranium is a common element in the Earth’s crust and a wide variety of metabolic groups of microorganisms catalyze the biological reduction of U(VI), this tool is applicable to a multiplicity of geological epochs and terrestrial environments. The findings of this study indicate that biological activity contributed to the formation of many authigenic U deposits, including sandstone U deposits of various ages, as well as modern, Cretaceous, and Archean black shales. In addition, engineered bioremediation activities also exhibit a biotic signature, suggesting that, although multiple pathways may be involved in the reduction, direct enzymatic reduction contributes substantially to the immobilization of uranium.

  18. Uranium isotopes fingerprint biotic reduction

    DOE PAGESBeta

    Stylo, Malgorzata; Neubert, Nadja; Wang, Yuheng; Monga, Nikhil; Romaniello, Stephen J.; Weyer, Stefan; Bernier-Latmani, Rizlan

    2015-04-20

    Knowledge of paleo-redox conditions in the Earth’s history provides a window into events that shaped the evolution of life on our planet. The role of microbial activity in paleo-redox processes remains unexplored due to the inability to discriminate biotic from abiotic redox transformations in the rock record. The ability to deconvolute these two processes would provide a means to identify environmental niches in which microbial activity was prevalent at a specific time in paleo-history and to correlate specific biogeochemical events with the corresponding microbial metabolism. Here, we demonstrate that the isotopic signature associated with microbial reduction of hexavalent uranium (U),more » i.e., the accumulation of the heavy isotope in the U(IV) phase, is readily distinguishable from that generated by abiotic uranium reduction in laboratory experiments. Thus, isotope signatures preserved in the geologic record through the reductive precipitation of uranium may provide the sought-after tool to probe for biotic processes. Because uranium is a common element in the Earth’s crust and a wide variety of metabolic groups of microorganisms catalyze the biological reduction of U(VI), this tool is applicable to a multiplicity of geological epochs and terrestrial environments. The findings of this study indicate that biological activity contributed to the formation of many authigenic U deposits, including sandstone U deposits of various ages, as well as modern, Cretaceous, and Archean black shales. In addition, engineered bioremediation activities also exhibit a biotic signature, suggesting that, although multiple pathways may be involved in the reduction, direct enzymatic reduction contributes substantially to the immobilization of uranium.« less

  19. Uranium isotopes fingerprint biotic reduction.

    PubMed

    Stylo, Malgorzata; Neubert, Nadja; Wang, Yuheng; Monga, Nikhil; Romaniello, Stephen J; Weyer, Stefan; Bernier-Latmani, Rizlan

    2015-05-01

    Knowledge of paleo-redox conditions in the Earth's history provides a window into events that shaped the evolution of life on our planet. The role of microbial activity in paleo-redox processes remains unexplored due to the inability to discriminate biotic from abiotic redox transformations in the rock record. The ability to deconvolute these two processes would provide a means to identify environmental niches in which microbial activity was prevalent at a specific time in paleo-history and to correlate specific biogeochemical events with the corresponding microbial metabolism. Here, we demonstrate that the isotopic signature associated with microbial reduction of hexavalent uranium (U), i.e., the accumulation of the heavy isotope in the U(IV) phase, is readily distinguishable from that generated by abiotic uranium reduction in laboratory experiments. Thus, isotope signatures preserved in the geologic record through the reductive precipitation of uranium may provide the sought-after tool to probe for biotic processes. Because uranium is a common element in the Earth's crust and a wide variety of metabolic groups of microorganisms catalyze the biological reduction of U(VI), this tool is applicable to a multiplicity of geological epochs and terrestrial environments. The findings of this study indicate that biological activity contributed to the formation of many authigenic U deposits, including sandstone U deposits of various ages, as well as modern, Cretaceous, and Archean black shales. Additionally, engineered bioremediation activities also exhibit a biotic signature, suggesting that, although multiple pathways may be involved in the reduction, direct enzymatic reduction contributes substantially to the immobilization of uranium. PMID:25902522

  20. Uranium isotopes fingerprint biotic reduction

    PubMed Central

    Stylo, Malgorzata; Neubert, Nadja; Wang, Yuheng; Monga, Nikhil; Romaniello, Stephen J.; Weyer, Stefan; Bernier-Latmani, Rizlan

    2015-01-01

    Knowledge of paleo-redox conditions in the Earth’s history provides a window into events that shaped the evolution of life on our planet. The role of microbial activity in paleo-redox processes remains unexplored due to the inability to discriminate biotic from abiotic redox transformations in the rock record. The ability to deconvolute these two processes would provide a means to identify environmental niches in which microbial activity was prevalent at a specific time in paleo-history and to correlate specific biogeochemical events with the corresponding microbial metabolism. Here, we demonstrate that the isotopic signature associated with microbial reduction of hexavalent uranium (U), i.e., the accumulation of the heavy isotope in the U(IV) phase, is readily distinguishable from that generated by abiotic uranium reduction in laboratory experiments. Thus, isotope signatures preserved in the geologic record through the reductive precipitation of uranium may provide the sought-after tool to probe for biotic processes. Because uranium is a common element in the Earth’s crust and a wide variety of metabolic groups of microorganisms catalyze the biological reduction of U(VI), this tool is applicable to a multiplicity of geological epochs and terrestrial environments. The findings of this study indicate that biological activity contributed to the formation of many authigenic U deposits, including sandstone U deposits of various ages, as well as modern, Cretaceous, and Archean black shales. Additionally, engineered bioremediation activities also exhibit a biotic signature, suggesting that, although multiple pathways may be involved in the reduction, direct enzymatic reduction contributes substantially to the immobilization of uranium. PMID:25902522

  1. Landscape simplification filters species traits and drives biotic homogenization.

    PubMed

    Gámez-Virués, Sagrario; Perović, David J; Gossner, Martin M; Börschig, Carmen; Blüthgen, Nico; de Jong, Heike; Simons, Nadja K; Klein, Alexandra-Maria; Krauss, Jochen; Maier, Gwen; Scherber, Christoph; Steckel, Juliane; Rothenwöhrer, Christoph; Steffan-Dewenter, Ingolf; Weiner, Christiane N; Weisser, Wolfgang; Werner, Michael; Tscharntke, Teja; Westphal, Catrin

    2015-01-01

    Biodiversity loss can affect the viability of ecosystems by decreasing the ability of communities to respond to environmental change and disturbances. Agricultural intensification is a major driver of biodiversity loss and has multiple components operating at different spatial scales: from in-field management intensity to landscape-scale simplification. Here we show that landscape-level effects dominate functional community composition and can even buffer the effects of in-field management intensification on functional homogenization, and that animal communities in real-world managed landscapes show a unified response (across orders and guilds) to both landscape-scale simplification and in-field intensification. Adults and larvae with specialized feeding habits, species with shorter activity periods and relatively small body sizes are selected against in simplified landscapes with intense in-field management. Our results demonstrate that the diversity of land cover types at the landscape scale is critical for maintaining communities, which are functionally diverse, even in landscapes where in-field management intensity is high. PMID:26485325

  2. Landscape simplification filters species traits and drives biotic homogenization

    PubMed Central

    Gámez-Virués, Sagrario; Perović, David J.; Gossner, Martin M.; Börschig, Carmen; Blüthgen, Nico; de Jong, Heike; Simons, Nadja K.; Klein, Alexandra-Maria; Krauss, Jochen; Maier, Gwen; Scherber, Christoph; Steckel, Juliane; Rothenwöhrer, Christoph; Steffan-Dewenter, Ingolf; Weiner, Christiane N.; Weisser, Wolfgang; Werner, Michael; Tscharntke, Teja; Westphal, Catrin

    2015-01-01

    Biodiversity loss can affect the viability of ecosystems by decreasing the ability of communities to respond to environmental change and disturbances. Agricultural intensification is a major driver of biodiversity loss and has multiple components operating at different spatial scales: from in-field management intensity to landscape-scale simplification. Here we show that landscape-level effects dominate functional community composition and can even buffer the effects of in-field management intensification on functional homogenization, and that animal communities in real-world managed landscapes show a unified response (across orders and guilds) to both landscape-scale simplification and in-field intensification. Adults and larvae with specialized feeding habits, species with shorter activity periods and relatively small body sizes are selected against in simplified landscapes with intense in-field management. Our results demonstrate that the diversity of land cover types at the landscape scale is critical for maintaining communities, which are functionally diverse, even in landscapes where in-field management intensity is high. PMID:26485325

  3. Laser-plasma interaction in direct-drive inertial confinement fusion

    NASA Astrophysics Data System (ADS)

    Myatt, J. F.; Shaw, J.; Goncharov, V. N.; Zhang, J.; Maximov, A. V.; Short, R. W.; Follett, R. K.; Seka, W.; Edgell, D. H.; Froula, D. H.

    2016-05-01

    Hot electrons generated by the two-plasmon-decay instability in direct-drive targets are a preheat concern. A mitigation strategy that employs a layered ablator [V. N. Goncharov et al., Phys. Plasmas 21, 056315 (2014)] has been investigated both numerically and experimentally. The numerical simulations described here predict reduced hot-electron production compared with similar targets using either a solid CH or Be ablator. These findings are shown to be consistent with experimental observations

  4. The impact of laser plasma interactions on three-dimensional drive symmetry in inertial confinement fusion implosions

    SciTech Connect

    Peterson, J. L. Michel, P.; Thomas, C. A.; Town, R. P. J.

    2014-07-15

    Achieving symmetric hohlraum radiation drive is an important aspect of indirectly driven inertial confinement fusion experiments. However, when experimentally delivered laser powers deviate from ideal conditions, the resultant radiation field can become asymmetric. Two situations in which this may arise are random uncorrelated fluctuations, in as-delivered laser power and laser beams that do not participate in the implosion (either intentionally or unintentionally). Furthermore, laser plasma interactions in the hohlraum obfuscate the connection between laser powers and radiation drive. To study the effect of these situations on drive symmetry, we develop a simplified model for crossed-beam energy transfer, laser backscatter, and plasma absorption that can be used in conjunction with view factor calculations to expediently translate laser powers into three-dimensional capsule flux symmetries. We find that crossed-beam energy transfer can alter both the statistical properties of uncorrelated laser fluctuations and the impact of missing laser beams on radiation symmetry. A method is proposed to mitigate the effects of missing laser beams.

  5. Emission switching in carbon dots coated CdTe quantum dots driving by pH dependent hetero-interactions

    SciTech Connect

    Dai, Xiao; Wang, Hao; Yi, Qinghua; Wang, Yun; Cong, Shan; Zhao, Jie; Sun, Yinghui; Zou, Guifu E-mail: jiexiong@uestc.edu.cn; Qian, Zhicheng; Huang, Jianwen; Xiong, Jie E-mail: jiexiong@uestc.edu.cn; Luo, Hongmei

    2015-11-16

    Due to the different emission mechanism between fluorescent carbon dots and semiconductor quantum dots (QDs), it is of interest to explore the potential emission in hetero-structured carbon dots/semiconducting QDs. Herein, we design carbon dots coated CdTe QDs (CDQDs) and investigate their inherent emission. We demonstrate switchable emission for the hetero-interactions of the CDQDs. Optical analyses indicate electron transfer between the carbon dots and the CdTe QDs. A heterojunction electron process is proposed as the driving mechanism based on N atom protonation of the carbon dots. This work advances our understanding of the interaction mechanism of the heterostructured CDQDs and benefits the future development of optoelectronic nanodevices with new functionalities.

  6. Characterising the interaction of individual-wheel drives with traction by linear parameter-varying model: a method for analysing the role of traction in torsional vibrations in wheel drives and active damping

    NASA Astrophysics Data System (ADS)

    Zhun Yeap, Khang; Müller, Steffen

    2016-02-01

    A model-based approach for characterising the interaction of individual-wheel drives with traction is contributed in this article. The primary aim is to investigate the influence of traction on torsional vibration behaviour in the drive train. The essence of this approach lies in reformulating the nonlinear traction behaviour into its differential form, which enables an analytical description of this interaction in its linear parameter-varying model equivalence. Analytical statements on the vibration behaviour for different driving scenarios are inferred from this model and validated with measurement samples from a high-performance electric road vehicle. Subsequent influences of traction on the performance of active damping of torsional vibrations are derived from this model.

  7. Interacting environmental mosaics drive geographic variation in mussel performance and predation vulnerability.

    PubMed

    Kroeker, Kristy J; Sanford, Eric; Rose, Jeremy M; Blanchette, Carol A; Chan, Francis; Chavez, Francisco P; Gaylord, Brian; Helmuth, Brian; Hill, Tessa M; Hofmann, Gretchen E; McManus, Margaret A; Menge, Bruce A; Nielsen, Karina J; Raimondi, Peter T; Russell, Ann D; Washburn, Libe

    2016-07-01

    Although theory suggests geographic variation in species' performance is determined by multiple niche parameters, little consideration has been given to the spatial structure of interacting stressors that may shape local and regional vulnerability to global change. Here, we use spatially explicit mosaics of carbonate chemistry, food availability and temperature spanning 1280 km of coastline to test whether persistent, overlapping environmental mosaics mediate the growth and predation vulnerability of a critical foundation species, the mussel Mytilus californianus. We find growth was highest and predation vulnerability was lowest in dynamic environments with frequent exposure to low pH seawater and consistent food. In contrast, growth was lowest and predation vulnerability highest when exposure to low pH seawater was decoupled from high food availability, or in exceptionally warm locations. These results illustrate how interactions among multiple drivers can cause unexpected, yet persistent geographic mosaics of species performance, interactions and vulnerability to environmental change. PMID:27151381

  8. The Assessment Interaction Plan--A Tool for Driving Performance Improvement through Analysis to Application

    ERIC Educational Resources Information Center

    Christensen, Brett; Barr, Jason

    2009-01-01

    The assessment interaction plan (AIP) is a performance support tool developed by members of the Canadian Defence Academy's Directorate of Learning Innovation. This article provides a brief overview of the performance gap that led to the creation of the AIP, its function within the overall courseware design process, a description of its components,…

  9. Viruses at Solid-Water Interfaces: A Systematic Assessment of Interactions Driving Adsorption.

    PubMed

    Armanious, Antonius; Aeppli, Meret; Jacak, Ronald; Refardt, Dominik; Sigstam, Thérèse; Kohn, Tamar; Sander, Michael

    2016-01-19

    Adsorption to solid-water interfaces is a major process governing the fate of waterborne viruses in natural and engineered systems. The relative contributions of different interaction forces to adsorption and their dependence on the physicochemical properties of the viruses remain, however, only poorly understood. Herein, we systematically studied the adsorption of four bacteriophages (MS2, fr, GA, and Qβ) to five model surfaces with varying surface chemistries and to three dissolved organic matter adlayers, as a function of solution pH and ionic strength, using quartz crystal microbalance with dissipation monitoring. The viruses were selected to have similar sizes and shapes but different surface charges, polarities, and topographies, as identified by modeling the distributions of amino acids in the virus capsids. Virus-sorbent interactions were governed by long-ranged electrostatics and favorable contributions from the hydrophobic effect, and shorter-ranged van der Waals interactions were of secondary importance. Steric effects depended on the topographic irregularities on both the virus and sorbent surfaces. Differences in the adsorption characteristics of the tested viruses were successfully linked to differences in their capsid surface properties. Besides identifying the major interaction forces, this work highlights the potential of computable virus surface charge and polarity descriptors to predict virus adsorption to solid-water interfaces. PMID:26636722

  10. Herbivory drives large-scale spatial variation in reef fish trophic interactions

    PubMed Central

    Longo, Guilherme O; Ferreira, Carlos Eduardo L; Floeter, Sergio R

    2014-01-01

    Trophic interactions play a critical role in the structure and function of ecosystems. Given the widespread loss of biodiversity due to anthropogenic activities, understanding how trophic interactions respond to natural gradients (e.g., abiotic conditions, species richness) through large-scale comparisons can provide a broader understanding of their importance in changing ecosystems and support informed conservation actions. We explored large-scale variation in reef fish trophic interactions, encompassing tropical and subtropical reefs with different abiotic conditions and trophic structure of reef fish community. Reef fish feeding pressure on the benthos was determined combining bite rates on the substrate and the individual biomass per unit of time and area, using video recordings in three sites between latitudes 17°S and 27°S on the Brazilian Coast. Total feeding pressure decreased 10-fold and the composition of functional groups and species shifted from the northern to the southernmost sites. Both patterns were driven by the decline in the feeding pressure of roving herbivores, particularly scrapers, while the feeding pressure of invertebrate feeders and omnivores remained similar. The differential contribution to the feeding pressure across trophic categories, with roving herbivores being more important in the northernmost and southeastern reefs, determined changes in the intensity and composition of fish feeding pressure on the benthos among sites. It also determined the distribution of trophic interactions across different trophic categories, altering the evenness of interactions. Feeding pressure was more evenly distributed at the southernmost than in the southeastern and northernmost sites, where it was dominated by few herbivores. Species and functional groups that performed higher feeding pressure than predicted by their biomass were identified as critical for their potential to remove benthic biomass. Fishing pressure unlikely drove the large

  11. Interactions Within Susceptible Hosts Drive Establishment of Genetically Distinct Variants of an Insect-Borne Pathogen.

    PubMed

    Blaisdell, G K; Zhang, S; Bratburd, J R; Daane, K M; Cooper, M L; Almeida, R P P

    2015-08-01

    Coinfections are common, leading to pathogen interactions during transmission and establishment in a host. However, few studies have tested the relative strengths of pathogen interactions in vectors and hosts that determine the outcome of infection. We tested interactions between two genetically distinct variants of the mealybug-transmitted Grapevine leafroll-associated virus 3. The transmission efficiency of each variant in single variant inoculations by two vector species was determined. The effects of vector species, a coinfected source, and simultaneous inoculation from multiple hosts to one host on variant establishment were examined. Within-vector interactions could have a role in transmission from hosts containing mixed infections, but not when vectors were moved from separate singly infected source plants to a single recipient plant. The invasive Planococcus ficus (Signoret) was a more efficient vector than Pseudococcus viburni (Signoret). Transmission efficiency of the two variants did not differ in single variant inoculations. Overall infections were the same whether from singly or coinfected source plants. In mixed inoculations, establishment of one variant was reduced. Mixed inoculations from two singly infected source plants resulted in fewer mixed infections than expected by chance. Therefore, the observed outcome was determined subsequent to host inoculation rather than in the vector. The outcome may be due to resource competition between pathogens. Alternatively apparent competition may be responsible; the pathogens' differential ability to overcome host defenses and colonize the host may determine the final outcome of new infections. Detailed knowledge of interactions between pathogens during transmission and establishment could improve understanding and management of disease spread. PMID:26470292

  12. Herbivory drives large-scale spatial variation in reef fish trophic interactions.

    PubMed

    Longo, Guilherme O; Ferreira, Carlos Eduardo L; Floeter, Sergio R

    2014-12-01

    Trophic interactions play a critical role in the structure and function of ecosystems. Given the widespread loss of biodiversity due to anthropogenic activities, understanding how trophic interactions respond to natural gradients (e.g., abiotic conditions, species richness) through large-scale comparisons can provide a broader understanding of their importance in changing ecosystems and support informed conservation actions. We explored large-scale variation in reef fish trophic interactions, encompassing tropical and subtropical reefs with different abiotic conditions and trophic structure of reef fish community. Reef fish feeding pressure on the benthos was determined combining bite rates on the substrate and the individual biomass per unit of time and area, using video recordings in three sites between latitudes 17°S and 27°S on the Brazilian Coast. Total feeding pressure decreased 10-fold and the composition of functional groups and species shifted from the northern to the southernmost sites. Both patterns were driven by the decline in the feeding pressure of roving herbivores, particularly scrapers, while the feeding pressure of invertebrate feeders and omnivores remained similar. The differential contribution to the feeding pressure across trophic categories, with roving herbivores being more important in the northernmost and southeastern reefs, determined changes in the intensity and composition of fish feeding pressure on the benthos among sites. It also determined the distribution of trophic interactions across different trophic categories, altering the evenness of interactions. Feeding pressure was more evenly distributed at the southernmost than in the southeastern and northernmost sites, where it was dominated by few herbivores. Species and functional groups that performed higher feeding pressure than predicted by their biomass were identified as critical for their potential to remove benthic biomass. Fishing pressure unlikely drove the large

  13. Dynamic interaction of separate INS/GPS Kalman filters (Filter-driving - Filter dynamics)

    NASA Astrophysics Data System (ADS)

    Cunningham, Joseph R.; Lewantowicz, Zdzislaw H.

    This paper examines the basic behavior of the inertial navigation system (INS) errors under high-dynamic conditions, such as combat maneuvering of a fighter aircraft. Examination of the INS linearized error dynamics eigenvalue migrations during various dynamic maneuvers reveals significantly stronger instability than the classical vertical channel instability. The Global Positioning System (GPS) offers high accuracy navigation performance benefits with global coverage, but is has limitations during the dynamic maneuvering of fighter aircraft. The optimal integration of the GPS with an INS promises synergistic system performance benefits not realizable with either system individually. A candidate maneuver is selected for which a covariance analysis is performed to demonstrate the performance characteristics of an optimally integrated INS/GPS system. Significant insight into the potential instability of a particular INS/GPS integration scheme is presented. The characteristic and unstable behavior of the INS error dynamics eigenfunctions provides the basis for the 'filter-driving-filter' performance analysis. Several phenomena were observed which should aid future efforts attempting to characterize the performance of various INS/GPS integration methods.

  14. Interactions of Multiple Atmospheric Circulation Drive the Drought in Tarim River Basin

    PubMed Central

    Wu, Yong-Ping; Feng, Guo-Lin; Li, Bai-Lian

    2016-01-01

    Global warming is likely to cause overall drying of land surfaces and aridity increasing leading to expansion of dry climate zones. There is an increased risk of extremely arid environment and large deserts developed progressively in the central Asia. However, the key factors causing the drying in mid-Asia remain inconclusive. Here, we analyzed the relationship among precipitation, water vapor transportation in Tarim River Basin (TRB) and Multiple Atmospheric Circulation (MAC) to explore the mechanism of MAC driving the drying in TRB, through comparing MAC between abundant and scarce precipitation years. We found that Westerly Circulation (WC) and Asian Summer Monsoon (ASM) are likely to promote the precipitation respectively. Whereas, they not only have their own influence but also restrict each other and facilitate the forming of peculiar water vapor transport channel for TRB, which is probably to restrain the precipitation and its distribution pattern and accelerate the drying in this region. Our results enrich the findings on mechanisms of wet places becoming wetter while dry areas getting drier under the global warming. PMID:27198665

  15. Interactions of Multiple Atmospheric Circulation Drive the Drought in Tarim River Basin

    NASA Astrophysics Data System (ADS)

    Wu, Yong-Ping; Feng, Guo-Lin; Li, Bai-Lian

    2016-05-01

    Global warming is likely to cause overall drying of land surfaces and aridity increasing leading to expansion of dry climate zones. There is an increased risk of extremely arid environment and large deserts developed progressively in the central Asia. However, the key factors causing the drying in mid-Asia remain inconclusive. Here, we analyzed the relationship among precipitation, water vapor transportation in Tarim River Basin (TRB) and Multiple Atmospheric Circulation (MAC) to explore the mechanism of MAC driving the drying in TRB, through comparing MAC between abundant and scarce precipitation years. We found that Westerly Circulation (WC) and Asian Summer Monsoon (ASM) are likely to promote the precipitation respectively. Whereas, they not only have their own influence but also restrict each other and facilitate the forming of peculiar water vapor transport channel for TRB, which is probably to restrain the precipitation and its distribution pattern and accelerate the drying in this region. Our results enrich the findings on mechanisms of wet places becoming wetter while dry areas getting drier under the global warming.

  16. Interactions of Multiple Atmospheric Circulation Drive the Drought in Tarim River Basin.

    PubMed

    Wu, Yong-Ping; Feng, Guo-Lin; Li, Bai-Lian

    2016-01-01

    Global warming is likely to cause overall drying of land surfaces and aridity increasing leading to expansion of dry climate zones. There is an increased risk of extremely arid environment and large deserts developed progressively in the central Asia. However, the key factors causing the drying in mid-Asia remain inconclusive. Here, we analyzed the relationship among precipitation, water vapor transportation in Tarim River Basin (TRB) and Multiple Atmospheric Circulation (MAC) to explore the mechanism of MAC driving the drying in TRB, through comparing MAC between abundant and scarce precipitation years. We found that Westerly Circulation (WC) and Asian Summer Monsoon (ASM) are likely to promote the precipitation respectively. Whereas, they not only have their own influence but also restrict each other and facilitate the forming of peculiar water vapor transport channel for TRB, which is probably to restrain the precipitation and its distribution pattern and accelerate the drying in this region. Our results enrich the findings on mechanisms of wet places becoming wetter while dry areas getting drier under the global warming. PMID:27198665

  17. Design and Implementation of High Interaction Client Honeypot for Drive-by-Download Attacks

    NASA Astrophysics Data System (ADS)

    Akiyama, Mitsuaki; Iwamura, Makoto; Kawakoya, Yuhei; Aoki, Kazufumi; Itoh, Mitsutaka

    Nowadays, the number of web-browser targeted attacks that lead users to adversaries' web sites and exploit web browser vulnerabilities is increasing, and a clarification of their methods and countermeasures is urgently needed. In this paper, we introduce the design and implementation of a new client honeypot for drive-by-download attacks that has the capacity to detect and investigate a variety of malicious web sites. On the basis of the problems of existing client honeypots, we enumerate the requirements of a client honeypot: 1) detection accuracy and variety, 2) collection variety, 3) performance efficiency, and 4) safety and stability. We improve our system with regard to these requirements. The key features of our developed system are stepwise detection focusing on exploit phases, multiple crawler processing, tracking of malware distribution networks, and malware infection prevention. Our evaluation of our developed system in a laboratory experiment and field experiment indicated that its detection variety and crawling performance are higher than those of existing client honeypots. In addition, our system is able to collect information for countermeasures and is secure and stable for continuous operation. We conclude that our system can investigate malicious web sites comprehensively and support countermeasures.

  18. Competitive Interactions upon Secondary Contact Drive Elevational Divergence in Tropical Birds.

    PubMed

    Freeman, Benjamin G

    2015-10-01

    Tropical mountains harbor exceptionally high biodiversity, which is in part due to the marked elevational stratification of tropical biotas. However, the factors that influence the evolution of elevational distributions remain uncertain. I used a database of sister species of tropical montane birds from 41 families and three regions-the Neotropics, the Himalayas, and New Guinea-to test whether patterns of elevational divergence were consistent with (1) a stochastic process, (2) ecological sorting of elevational divergence that occurred in allopatry, or (3) elevational divergence driven by competitive interactions upon secondary contact. The stochastic and ecological sorting hypotheses predict that increased elevational divergence in sympatric sister species is explained by their greater evolutionary age, whereas the competitive interactions hypothesis predicts that elevational divergence is explained by geographical overlap. I found that genetic distances were unrelated to elevational divergence and that allopatric sister species occupied similar elevational distributions regardless of genetic distance in each region. Instead, sympatry was the only significant predictor of elevational divergence; regardless of evolutionary age, sympatric sister species had greater elevational divergence than allopatric sister species in each region, as predicted by the competitive interactions hypothesis. Importantly, this pattern occurred in all three geographic regions, which suggests that competition-driven elevational divergence upon secondary contact is a general process of community assembly in tropical montane avifaunas. PMID:26655571

  19. Conspecific and Heterospecific Plant Densities at Small-Scale Can Drive Plant-Pollinator Interactions

    PubMed Central

    Janovský, Zdeněk; Mikát, Michael; Hadrava, Jiří; Horčičková, Eva; Kmecová, Kateřina; Požárová, Doubravka; Smyčka, Jan; Herben, Tomáš

    2013-01-01

    Generalist pollinators are important in many habitats, but little research has been done on small-scale spatial variation in interactions between them and the plants that they visit. Here, using a spatially explicit approach, we examined whether multiple species of flowering plants occurring within a single meadow showed spatial structure in their generalist pollinator assemblages. We report the results for eight plant species for which at least 200 individual visits were recorded. We found that for all of these species, the proportions of their general pollinator assemblages accounted for by particular functional groups showed spatial heterogeneity at the scale of tens of metres. This heterogeneity was connected either with no or only subtle changes of vegetation and flowering species composition. In five of these species, differences in conspecific plant density influenced the pollinator communities (with greater dominance of main pollinators at low-conspecific plant densities). The density of heterospecific plant individuals influenced the pollinator spectrum in one case. Our results indicate that the picture of plant-pollinator interactions provided by averaging data within large plots may be misleading and that within-site spatial heterogeneity should be accounted for in terms of sampling effort allocation and analysis. Moreover, spatially structured plant-pollinator interactions may have important ecological and evolutionary consequences, especially for plant population biology. PMID:24204818

  20. RAC1 activation drives pathologic interactions between the epidermis and immune cells.

    PubMed

    Winge, Mårten C G; Ohyama, Bungo; Dey, Clara N; Boxer, Lisa M; Li, Wei; Ehsani-Chimeh, Nazanin; Truong, Allison K; Wu, Diane; Armstrong, April W; Makino, Teruhiko; Davidson, Matthew; Starcevic, Daniela; Kislat, Andreas; Nguyen, Ngon T; Hashimoto, Takashi; Homey, Bernard; Khavari, Paul A; Bradley, Maria; Waterman, Elizabeth A; Marinkovich, M Peter

    2016-07-01

    Interactions between the epidermis and the immune system govern epidermal tissue homeostasis. These epidermis-immune interactions are altered in the inflammatory disease psoriasis; however, the pathways that underlie this aberrant immune response are not well understood. Here, we determined that Ras-related C3 botulinum toxin substrate 1 (RAC1) is a key mediator of epidermal dysfunction. RAC1 activation was consistently elevated in psoriatic epidermis and primary psoriatic human keratinocytes (PHKCs) exposed to psoriasis-related stimuli, but not in skin from patients with basal or squamous cell carcinoma. Expression of a constitutively active form of RAC1 (RACV12) in mice resulted in the development of lesions similar to those of human psoriasis that required the presence of an intact immune system. RAC1V12-expressing mice and human psoriatic skin showed similar RAC1-dependent signaling as well as transcriptional overlap of differentially expressed epidermal and immune pathways. Coculture of PHKCs with immunocytes resulted in the upregulation of RAC1-dependent proinflammatory cytokines, an effect that was reproduced by overexpressing RAC1 in normal human keratinocytes. In keratinocytes, modulating RAC1 activity altered differentiation, proliferation, and inflammatory pathways, including STAT3, NFκB, and zinc finger protein 750 (ZNF750). Finally, RAC1 inhibition in xenografts composed of human PHKCs and immunocytes abolished psoriasiform hyperplasia and inflammation in vivo. These studies implicate RAC1 as a potential therapeutic target for psoriasis and as a key orchestrator of pathologic epidermis-immune interactions. PMID:27294528

  1. Relative importance of driving force and electrostatic interactions in the reduction of multihaem cytochromes by small molecules.

    PubMed

    Quintas, Pedro O; Cepeda, Andreia P; Borges, Nuno; Catarino, Teresa; Turner, David L

    2013-06-01

    Multihaem cytochromes are essential to the energetics of organisms capable of bioremediation and energy production. The haems in several of these cytochromes have been discriminated thermodynamically and their individual rates of reduction by small electron donors were characterized. The kinetic characterization of individual haems used the Marcus theory of electron transfer and assumed that the rates of reduction of each haem by sodium dithionite depend only on the driving force, while electrostatic interactions were neglected. To determine the relative importance of these factors in controlling the rates, we studied the effect of ionic strength on the redox potential and the rate of reduction by dithionite of native Methylophilus methylotrophus cytochrome c″ and three mutants at different pH values. We found that the main factor determining the rate is the driving force and that Marcus theory describes this satisfactorily. This validates the method of the simultaneous fitting of kinetic and thermodynamic data in multihaem cytochromes and opens the way for further investigation into the mechanisms of these proteins. PMID:23428398

  2. Electrostatic Contributions Drive the Interaction Between Staphylococcus aureus Protein Efb-C and its Complement Target C3d

    SciTech Connect

    Haspel, N.; Ricklin, D.; Geisbrecht, B.V.; Kavraki, L.E.; Lambris, J.D.

    2008-11-13

    The C3-inhibitory domain of Staphylococcus aureus extracellular fibrinogen-binding protein (Efb-C) defines a novel three-helix bundle motif that regulates complement activation. Previous crystallographic studies of Efb-C bound to its cognate subdomain of human C3 (C3d) identified Arg-131 and Asn-138 of Efb-C as key residues for its activity. In order to characterize more completely the physical and chemical driving forces behind this important interaction, we employed in this study a combination of structural, biophysical, and computational methods to analyze the interaction of C3d with Efb-C and the single-point mutants R131A and N138A. Our results show that while these mutations do not drastically affect the structure of the Efb-C/C3d recognition complex, they have significant adverse effects on both the thermodynamic and kinetic profiles of the resulting complexes. We also characterized other key interactions along the Efb-C/C3d binding interface and found an intricate network of salt bridges and hydrogen bonds that anchor Efb-C to C3d, resulting in its potent complement inhibitory properties.

  3. Electrostatic contributions drive the interaction between Staphylococcus aureus protein Efb-C and its complement target C3d

    PubMed Central

    Haspel, Nurit; Ricklin, Daniel; Geisbrecht, Brian V.; Kavraki, Lydia E.; Lambris, John D.

    2008-01-01

    The C3–inhibitory domain of Staphylococcus aureus extracellular fibrinogen-binding protein (Efb-C) defines a novel three-helix bundle motif that regulates complement activation. Previous crystallographic studies of Efb-C bound to its cognate subdomain of human C3 (C3d) identified Arg-131 and Asn-138 of Efb-C as key residues for its activity. In order to characterize more completely the physical and chemical driving forces behind this important interaction, we employed in this study a combination of structural, biophysical, and computational methods to analyze the interaction of C3d with Efb-C and the single-point mutants R131A and N138A. Our results show that while these mutations do not drastically affect the structure of the Efb-C/C3d recognition complex, they have significant adverse effects on both the thermodynamic and kinetic profiles of the resulting complexes. We also characterized other key interactions along the Efb-C/C3d binding interface and found an intricate network of salt bridges and hydrogen bonds that anchor Efb-C to C3d, resulting in its potent complement inhibitory properties. PMID:18687868

  4. CCL2 Mediates Neuron-Macrophage Interactions to Drive Proregenerative Macrophage Activation Following Preconditioning Injury.

    PubMed

    Kwon, Min Jung; Shin, Hae Young; Cui, Yuexian; Kim, Hyosil; Thi, Anh Hong Le; Choi, Jun Young; Kim, Eun Young; Hwang, Dong Hoon; Kim, Byung Gon

    2015-12-01

    CNS neurons in adult mammals do not spontaneously regenerate axons after spinal cord injury. Preconditioning peripheral nerve injury allows the dorsal root ganglia (DRG) sensory axons to regenerate beyond the injury site by promoting expression of regeneration-associated genes. We have previously shown that peripheral nerve injury increases the number of macrophages in the DRGs and that the activated macrophages are critical to the enhancement of intrinsic regeneration capacity. The present study identifies a novel chemokine signal mediated by CCL2 that links regenerating neurons with proregenerative macrophage activation. Neutralization of CCL2 abolished the neurite outgrowth activity of conditioned medium obtained from neuron-macrophage cocultures treated with cAMP. The neuron-macrophage interactions that produced outgrowth-promoting conditioned medium required CCL2 in neurons and CCR2/CCR4 in macrophages. The conditioning effects were abolished in CCL2-deficient mice at 3 and 7 d after sciatic nerve injury, but CCL2 was dispensable for the initial growth response and upregulation of GAP-43 at the 1 d time point. Intraganglionic injection of CCL2 mimicked conditioning injury by mobilizing M2-like macrophages. Finally, overexpression of CCL2 in DRGs promoted sensory axon regeneration in a rat spinal cord injury model without harmful side effects. Our data suggest that CCL2-mediated neuron-macrophage interaction plays a critical role for amplification and maintenance of enhanced regenerative capacity by preconditioning peripheral nerve injury. Manipulation of chemokine signaling mediating neuron-macrophage interactions may represent a novel therapeutic approach to promote axon regeneration after CNS injury. PMID:26631474

  5. Understanding the dynamic interactions driving Zambian health centre performance: a case-based health systems analysis

    PubMed Central

    Topp, Stephanie M; Chipukuma, Julien M; Hanefeld, Johanna

    2015-01-01

    Background Despite being central to achieving improved population health outcomes, primary health centres in low- and middle-income settings continue to underperform. Little research exists to adequately explain how and why this is the case. This study aimed to test the relevance and usefulness of an adapted conceptual framework for improving our understanding of the mechanisms and causal pathways influencing primary health centre performance. Methods A theory-driven, case-study approach was adopted. Four Zambian health centres were purposefully selected with case data including health-care worker interviews (n = 60); patient interviews (n = 180); direct observation of facility operations (2 weeks/centre) and key informant interviews (n = 14). Data were analysed to understand how the performance of each site was influenced by the dynamic interactions between system ‘hardware’ and ‘software’ acting on mechanisms of accountability. Findings Structural constraints including limited resources created challenging service environments in which work overload and stockouts were common. Health workers’ frustration with such conditions interacted with dissatisfaction with salary levels eroding service values and acting as a catalyst for different forms of absenteeism. Such behaviours exacerbated patient–provider ratios and increased the frequency of clinical and administrative shortcuts. Weak health information systems and lack of performance data undermined providers’ answerability to their employer and clients, and a lack of effective sanctions undermined supervisors’ ability to hold providers accountable for these transgressions. Weak answerability and enforceability contributed to a culture of impunity that masked and condoned weak service performance in all four sites. Conclusions Health centre performance is influenced by mechanisms of accountability, which are in turn shaped by dynamic interactions between system hardware and system software. Our

  6. Driving Force Analysis in an Infinite Anisotropic Plate with Multiple Crack Interactions

    NASA Technical Reports Server (NTRS)

    Binienda, Wieslaw K.; Arnold, Steven M.

    1995-01-01

    The methodology and a rigorous solution formulation are presented for stress intensity factors (SIF's, k) and total strain energy release rates (SERR, G(sub T)) of a multicracked plate, that has fully interacting cracks and is subjected to a far-field arbitrary stress state. The fundamental perturbation problem is derived, and the steps needed to formulate the system of singular integral equations whose solution gives rise to the evaluation of the SIF's are identified. Parametric studies are conducted for two, three, and four crack problems. The sensitivity and characteristics of the model is demonstrated.

  7. Nucleotide-induced asymmetry within ATPase activator ring drives σ54-RNAP interaction and ATP hydrolysis

    SciTech Connect

    Sysoeva, Tatyana A.; Chowdhury, Saikat; Guo, Liang; Nixon, B. Tracy

    2013-12-10

    It is largely unknown how the typical homomeric ring geometry of ATPases associated with various cellular activities enables them to perform mechanical work. Small-angle solution X-ray scattering, crystallography, and electron microscopy (EM) reconstructions revealed that partial ATP occupancy caused the heptameric closed ring of the bacterial enhancer-binding protein (bEBP) NtrC1 to rearrange into a hexameric split ring of striking asymmetry. The highly conserved and functionally crucial GAFTGA loops responsible for interacting with σ54–RNA polymerase formed a spiral staircase. We propose that splitting of the ensemble directs ATP hydrolysis within the oligomer, and the ring's asymmetry guides interaction between ATPase and the complex of σ54 and promoter DNA. Similarity between the structure of the transcriptional activator NtrC1 and those of distantly related helicases Rho and E1 reveals a general mechanism in homomeric ATPases whereby complex allostery within the ring geometry forms asymmetric functional states that allow these biological motors to exert directional forces on their target macromolecules.

  8. Impact of risk attitudes and perception on game theoretic driving interactions and safety.

    PubMed

    Arbis, David; Dixit, Vinayak V; Rashidi, Taha Hossein

    2016-09-01

    This study employs game theory to investigate behavioural norms of interaction between drivers at a signalised intersection. The choice framework incorporates drivers' risk perception as well as their risk attitudes. A laboratory experiment is conducted to study the impact of risk attitudes and perception in crossing behaviour at a signalised intersection. The laboratory experiment uses methods from experimental economics to induce incentives and study revealed behaviour. Conflicting drivers are considered to have symmetric disincentives for crashing, to represent a no-fault car insurance environment. The study is novel as it uses experimental data collection methods to investigate perceived risk. Further, it directly integrates perceived risk of crashing with other active drivers into the modelling structure. A theoretical model of intersection crossing behaviour is also developed in this paper. This study shows that right-of-way entitlements assigned without authoritative penalties to at-fault drivers may still improve perceptions of safety. Further, risk aversion amongst drivers attributes to manoeuvring strategies at or below Nash mixed strategy equilibrium. These findings offer a theoretical explanation for interactive manoeuvres that lead to crashes, as opposed to purely statistical methods which provide correlation but not necessarily explanation. PMID:27289391

  9. Electrostatic Interactions between Elongated Monomers Drive Filamentation of Drosophila Shrub, a Metazoan ESCRT-III Protein.

    PubMed

    McMillan, Brian J; Tibbe, Christine; Jeon, Hyesung; Drabek, Andrew A; Klein, Thomas; Blacklow, Stephen C

    2016-08-01

    The endosomal sorting complex required for transport (ESCRT) is a conserved protein complex that facilitates budding and fission of membranes. It executes a key step in many cellular events, including cytokinesis and multi-vesicular body formation. The ESCRT-III protein Shrub in flies, or its homologs in yeast (Snf7) or humans (CHMP4B), is a critical polymerizing component of ESCRT-III needed to effect membrane fission. We report the structural basis for polymerization of Shrub and define a minimal region required for filament formation. The X-ray structure of the Shrub core shows that individual monomers in the lattice interact in a staggered arrangement using complementary electrostatic surfaces. Mutations that disrupt interface salt bridges interfere with Shrub polymerization and function. Despite substantial sequence divergence and differences in packing interactions, the arrangement of Shrub subunits in the polymer resembles that of Snf7 and other family homologs, suggesting that this intermolecular packing mechanism is shared among ESCRT-III proteins. PMID:27452459

  10. a Study of Head-Disk Interaction Detection in the Hard-Disk Drives

    NASA Astrophysics Data System (ADS)

    Segu, Dawit Zenebe; Khan, Polina V.; Hwang, Pyung

    2015-09-01

    The reliability and performance of precision mechanical components that experience sliding under contact depend heavily on the friction and wear characteristics at the sliding interface. In order to improve the reliability of the sliding interface, there is a need to predict, measure and monitor any physical interactions at the head-disk interface (HDI). In the present work, the basic tribological characteristics of HDI were analyzed. The HDI during start-stop and constant speed operation using acoustic emission (AE) were studied. The Fast Fourier Transform (FFT) analysis of the AE signal was used to understand the interaction between the AE signal and the state of contact. In addition, we developed laser textured (LT) disk and the contact start-stop (CSS) tests were performed to investigate the effect of dimples on the stiction performance of the HDI. Furthermore, numerical analysis between the slider and disk surface pressure were performed using the boundary coordinate system and divergence formulation for the nonlinear Reynold's equation solution.

  11. Biotic replacement and mass extinction of the Ediacara biota

    PubMed Central

    Darroch, Simon A. F.; Sperling, Erik A.; Boag, Thomas H.; Racicot, Rachel A.; Mason, Sara J.; Morgan, Alex S.; Tweedt, Sarah; Myrow, Paul; Johnston, David T.; Erwin, Douglas H.; Laflamme, Marc

    2015-01-01

    The latest Neoproterozoic extinction of the Ediacara biota has been variously attributed to catastrophic removal by perturbations to global geochemical cycles, ‘biotic replacement’ by Cambrian-type ecosystem engineers, and a taphonomic artefact. We perform the first critical test of the ‘biotic replacement’ hypothesis using combined palaeoecological and geochemical data collected from the youngest Ediacaran strata in southern Namibia. We find that, even after accounting for a variety of potential sampling and taphonomic biases, the Ediacaran assemblage preserved at Farm Swartpunt has significantly lower genus richness than older assemblages. Geochemical and sedimentological analyses confirm an oxygenated and non-restricted palaeoenvironment for fossil-bearing sediments, thus suggesting that oxygen stress and/or hypersalinity are unlikely to be responsible for the low diversity of communities preserved at Swartpunt. These combined analyses suggest depauperate communities characterized the latest Ediacaran and provide the first quantitative support for the biotic replacement model for the end of the Ediacara biota. Although more sites (especially those recording different palaeoenvironments) are undoubtedly needed, this study provides the first quantitative palaeoecological evidence to suggest that evolutionary innovation, ecosystem engineering and biological interactions may have ultimately caused the first mass extinction of complex life. PMID:26336166

  12. Interactions driving the collapse of islet amyloid polypeptide: Implications for amyloid aggregation

    NASA Astrophysics Data System (ADS)

    Cope, Stephanie M.

    Human islet amyloid polypeptide (hIAPP), also known as amylin, is a 37-residue intrinsically disordered hormone involved in glucose regulation and gastric emptying. The aggregation of hIAPP into amyloid fibrils is believed to play a causal role in type 2 diabetes. To date, not much is known about the monomeric state of hIAPP or how it undergoes an irreversible transformation from disordered peptide to insoluble aggregate. IAPP contains a highly conserved disulfide bond that restricts hIAPP(1-8) into a short ring-like structure: N_loop. Removal or chemical reduction of N_loop not only prevents cell response upon binding to the CGRP receptor, but also alters the mass per length distribution of hIAPP fibers and the kinetics of fibril formation. The mechanism by which N_loop affects hIAPP aggregation is not yet understood, but is important for rationalizing kinetics and developing potential inhibitors. By measuring end-to-end contact formation rates, Vaiana et al. showed that N_loop induces collapsed states in IAPP monomers, implying attractive interactions between N_loop and other regions of the disordered polypeptide chain . We show that in addition to being involved in intra-protein interactions, the N_loop is involved in inter-protein interactions, which lead to the formation of extremely long and stable beta-turn fibers. These non-amyloid fibers are present in the 10 muM concentration range, under the same solution conditions in which hIAPP forms amyloid fibers. We discuss the effect of peptide cyclization on both intra- and inter-protein interactions, and its possible implications for aggregation. Our findings indicate a potential role of N_loop-N_loop interactions in hIAPP aggregation, which has not previously been explored. Though our findings suggest that N_loop plays an important role in the pathway of amyloid formation, other naturally occurring IAPP variants that contain this structural feature are incapable of forming amyloids. For example, hIAPP readily

  13. Host-Parasite Interactions from the Inside: Plant Reproductive Ontogeny Drives Specialization in Parasitic Insects

    PubMed Central

    Boivin, Thomas; Gidoin, Cindy; von Aderkas, Patrick; Safrana, Jonathan; Candau, Jean-Noël; Chalon, Alain; Sondo, Marion; El Maâtaoui, Mohamed

    2015-01-01

    Host plant interactions are likely key drivers of evolutionary processes involved in the diversification of phytophagous insects. Granivory has received substantial attention for its crucial role in shaping the interaction between plants and their seed parasites, but fine-scale mechanisms explaining the role of host plant reproductive biology on specialization of seed parasites remain poorly described. In a comparative approach using plant histological techniques, we tested the hypotheses that different seed parasite species synchronize their life cycles to specific stages in seed development, and that the stage they target depends on major differences in seed development programs. In a pinaceous system, seed storage products are initiated before ovule fertilization and the wasps target the ovule’s nucellus during megagametogenesis, a stage at which larvae may benefit from the by-products derived from both secreting cells and dying nucellar cells. In a cupressaceous system, oviposition activity peaks later, during embryogenesis, and the wasps target the ovule’s megagametophyte where larvae may benefit from cell disintegration during embryogenesis. Our cytohistological approach shows for the first time how, despite divergent oviposition targets, different parasite species share a common strategy that consists of first competing for nutrients with developing plant structures, and then consuming these developed structures to complete their development. Our results support the prediction that seed developmental program is an axis for specialization in seed parasites, and that it could be an important parameter in models of their ecological and taxonomic divergence. This study provides the basis for further investigating the possibility of the link between plant ontogeny and pre-dispersal seed parasitism. PMID:26441311

  14. The interactions of compressive stress and weathering in driving rock fracture.

    NASA Astrophysics Data System (ADS)

    de Vilder, Saskia; Brain, Matthew; Rosser, Nick; Vann Jones, Emma

    2016-04-01

    under stress but was subjected to the same weathering cycles. Monitoring of colour, surface texture, surface hardness and axial displacement was undertaken during the experiments, which lasted for 90 days. The samples were then removed and UCS values were obtained at the end of each test. These UCS results were compared with a baseline data-set of UCS tests (n = 10) to determine how strength had changed, if at all, in the samples due to weathering. Initial results show that samples which were preloaded prior to the tests showed the greatest difference in strength when compared with their corresponding control samples. This suggests that weathering processes are more effective in driving fracture in locations where stress concentrations have created a population of pre-existing microcracks. These microcracks can subsequently be exploited by weathering processes to further weaken the rock. Areas of higher stress in a rock slope may, therefore, form zones of enhanced weathering and greater rock weakening, which may preferentially fail prior to other areas of the rock slope. In turn, the decimetre- to metre-scale topography of the rock slope, an often overlooked component, can play a role in dictating the occurrence of failure on a rock slope.

  15. Electrostatic interactions drive the nonsteric directional block of OmpF channel by La3+.

    PubMed

    Queralt-Martín, María; Verdiá-Báguena, Carmina; Aguilella, Vicente M; Alcaraz, Antonio

    2013-12-10

    Ion channels regulate the transport of molecules and the electric signal transduction in living cells by means of complex and even highly sophisticated mechanisms. We focus here on the crucial role that polyvalent ions, well-known modulators of many biological nanosystems, play in ion channel function. In particular, we show that trace amounts of lanthanum are able to block the bacterial porin OmpF, a large biological pore of Escherichia coli wide enough to exchange antibiotics and other larger molecules. The underlying mechanism has a strong directional character: it is sensitive to the sign of the applied voltage and to the side of the blocker addition. We explore these channel features by combining planar lipid bilayer electrophysiology at the single channel level, site-directed mutagenesis, and inductively coupled plasma mass spectrometry (ICP-MS). In contrast to other well-described channel blockers, which seem to occlude the narrower part of the pore, we envisage a nonsteric mechanism based on electrostatic interactions. PMID:24256306

  16. Interaction of Vaccination and Reduction of Antibiotic Use Drives Unexpected Increase of Pneumococcal Meningitis

    PubMed Central

    de Cellès, Matthieu Domenech; Pons-Salort, Margarita; Varon, Emmanuelle; Vibet, Marie-Anne; Ligier, Caroline; Letort, Véronique; Opatowski, Lulla; Guillemot, Didier

    2015-01-01

    Antibiotic-use policies may affect pneumococcal conjugate-vaccine effectiveness. The reported increase of pneumococcal meningitis from 2001 to 2009 in France, where a national campaign to reduce antibiotic use was implemented in parallel to the introduction of the 7-valent conjugate vaccine, provides unique data to assess these effects. We constructed a mechanistic pneumococcal transmission model and used likelihood to assess the ability of competing hypotheses to explain that increase. We find that a model integrating a fitness cost of penicillin resistance successfully explains the overall and age-stratified pattern of serotype replacement. By simulating counterfactual scenarios of public health interventions in France, we propose that this fitness cost caused a gradual and pernicious interaction between the two interventions by increasing the spread of nonvaccine, penicillin-susceptible strains. More generally, our results indicate that reductions of antibiotic use may counteract the benefits of conjugate vaccines introduced into countries with low vaccine-serotype coverages and high-resistance frequencies. Our findings highlight the key role of antibiotic use in vaccine-induced serotype replacement and suggest the need for more integrated approaches to control pneumococcal infections. PMID:26063589

  17. Interaction complexity matters: disentangling services and disservices of ant communities driving yield in tropical agroecosystems

    PubMed Central

    Wielgoss, Arno; Tscharntke, Teja; Rumede, Alfianus; Fiala, Brigitte; Seidel, Hannes; Shahabuddin, Saleh; Clough, Yann

    2014-01-01

    Owing to complex direct and indirect effects, impacts of higher trophic levels on plants is poorly understood. In tropical agroecosystems, ants interact with crop mutualists and antagonists, but little is known about how this integrates into the final ecosystem service, crop yield. We combined ant exclusion and introduction of invasive and native-dominant species in cacao agroecosystems to test whether (i) ant exclusion reduces yield, (ii) dominant species maximize certain intermediate ecosystem services (e.g. control of specific pests) rather than yield, which depends on several, cascading intermediate services and (iii) even, species-rich ant communities result in highest yields. Ants provided services, including reduced leaf herbivory and fruit pest damage and indirect pollination facilitation, but also disservices, such as increased mealybug density, phytopathogen dissemination and indirect pest damage enhancement. Yields were highest with unmanipulated, species-rich, even communities, whereas ant exclusion decreased yield by 27%. Introduction of an invasive-dominant ant decreased species density and evenness and resulted in 34% lower yields, whereas introduction of a non-invasive-dominant species resulted in similar species density and yields as in the unmanipulated control. Species traits and ant community structure affect services and disservices for agriculture in surprisingly complex ways, with species-rich and even communities promoting highest yield. PMID:24307667

  18. Interspecific interactions and learning variability jointly drive geographic differences in mate preferences.

    PubMed

    Verzijden, Machteld N; Svensson, Erik I

    2016-08-01

    Co-occurrence of closely related species can cause behavioral interference in mating and increase hybridization risk. Theoretically, this could lead to the evolution of more species-specific mate preferences and sexual signaling traits. Alternatively, females can learn to reject heterospecific males, to avoid male sexual interference from closely related species. Such learned mate discrimination could also affect conspecific mate preferences if females generalize from between species differences to prefer more species-specific mating signals. Female damselflies of the banded demoiselle (Calopteryx splendens) learn to reject heterospecific males of the beautiful demoiselle (C. virgo) through direct premating interactions. These two species co-occur in a geographic mosaic of sympatric and microallopatric populations. Whereas C. virgo males have fully melanized wings, male C. splendens wings are partly melanized. We show that C. splendens females in sympatry with C. virgo prefer smaller male wing patches in conspecific males after learning to reject heterospecific males. In contrast, allopatric C. splendens females with experimentally induced experience with C. virgo males did not discriminate against larger male wing patches. Wing patch size might indicate conspecific male quality in allopatry. Co-occurrence with C. virgo therefore causes females to prefer conspecific male traits that are more species specific, contributing to population divergence and geographic variation in female mate preferences. PMID:27302691

  19. Mechanisms driving change: altered species interactions and ecosystem function through global warming.

    PubMed

    Traill, Lochran W; Lim, Matthew L M; Sodhi, Navjot S; Bradshaw, Corey J A

    2010-09-01

    1. We review the mechanisms behind ecosystem functions, the processes that facilitate energy transfer along food webs, and the major processes that allow the cycling of carbon, oxygen and nitrogen, and use case studies to show how these have already been, and will continue to be, altered by global warming. 2. Increased temperatures will affect the interactions between heterotrophs and autotrophs (e.g. pollination and seed dispersal), and between heterotrophs (e.g. predators-prey, parasites/pathogens-hosts), with generally negative ramifications for important ecosystem services (functions that provide direct benefit to human society such as pollination) and potential for heightened species co-extinction rates. 3. Mitigation of likely impacts of warming will require, in particular, the maintenance of species diversity as insurance for the provision of basic ecosystem services. Key to this will be long-term monitoring and focused research that seek to maintain ecosystem resilience in the face of global warming. 4. We provide guidelines for pursuing research that quantifies the nexus between ecosystem function and global warming. These include documentation of key functional species groups within systems, and understanding the principal outcomes arising from direct and indirect effects of a rapidly warming environment. Localized and targeted research and monitoring, complemented with laboratory work, will determine outcomes for resilience and guide adaptive conservation responses and long-term planning. PMID:20487086

  20. Coevolutionary aesthetics in human and biotic artworlds.

    PubMed

    Prum, Richard O

    2013-01-01

    This work proposes a coevolutionary theory of aesthetics that encompasses both biotic and human arts. Anthropocentric perspectives in aesthetics prevent the recognition of the ontological complexity of the aesthetics of nature, and the aesthetic agency of many non-human organisms. The process of evaluative coevolution is shared by all biotic advertisements. I propose that art consists of a form of communication that coevolves with its own evaluation. Art and art history are population phenomena. I expand Arthur Danto's Artworld concept to any aesthetic population of producers and evaluators. Current concepts of art cannot exclusively circumscribe the human arts from many forms of non-human biotic art. Without assuming an arbitrarily anthropocentric perspective, any concept of art will need to engage with biodiversity, and either recognize many instances of biotic advertisements as art, or exclude some instances of human art. Coevolutionary aesthetic theory provides a heuristic account of aesthetic change in both human and biotic artworlds, including the coevolutionary origin of aesthetic properties and aesthetic value within artworlds. Restructuring aesthetics, art criticism, and art history without human beings at the organizing centers of these disciplines stimulate new progress in our understanding of art, and the unique human contributions to aesthetics and aesthetic diversity. PMID:23970809

  1. RNA polymerase III drives alternative splicing of the potassium channel–interacting protein contributing to brain complexity and neurodegeneration

    PubMed Central

    Massone, Sara; Vassallo, Irene; Castelnuovo, Manuele; Fiorino, Gloria; Gatta, Elena; Robello, Mauro; Borghi, Roberta; Tabaton, Massimo; Russo, Claudio; Dieci, Giorgio; Cancedda, Ranieri

    2011-01-01

    Alternative splicing generates protein isoforms that are conditionally or differentially expressed in specific tissues. The discovery of factors that control alternative splicing might clarify the molecular basis of biological and pathological processes. We found that IL1-α−dependent up-regulation of 38A, a small ribonucleic acid (RNA) polymerase III–transcribed RNA, drives the synthesis of an alternatively spliced form of the potassium channel–interacting protein (KCNIP4). The alternative KCNIP4 isoform cannot interact with the γ-secretase complex, resulting in modification of γ-secretase activity, amyloid precursor protein processing, and increased secretion of β-amyloid enriched in the more toxic Aβ x-42 species. Notably, synthesis of the variant KCNIP4 isoform is also detrimental to brain physiology, as it results in the concomitant blockade of the fast kinetics of potassium channels. This alternative splicing shift is observed at high frequency in tissue samples from Alzheimer’s disease patients, suggesting that RNA polymerase III cogenes may be upstream determinants of alternative splicing that significantly contribute to homeostasis and pathogenesis in the brain. PMID:21624954

  2. Unexpected Interaction with Dispersed Crude Oil Droplets Drives Severe Toxicity in Atlantic Haddock Embryos

    PubMed Central

    Sørhus, Elin; Edvardsen, Rolf B.; Karlsen, Ørjan; Nordtug, Trond; van der Meeren, Terje; Thorsen, Anders; Harman, Christopher; Jentoft, Sissel; Meier, Sonnich

    2015-01-01

    The toxicity resulting from exposure to oil droplets in marine fish embryos and larvae is still subject for debate. The most detailed studies have investigated the effects of water-dissolved components of crude oil in water accommodated fractions (WAFs) that lack bulk oil droplets. Although exposure to dissolved petroleum compounds alone is sufficient to cause the characteristic developmental toxicity of crude oil, few studies have addressed whether physical interaction with oil micro-droplets are a relevant exposure pathway for open water marine speices. Here we used controlled delivery of mechanically dispersed crude oil to expose pelagic embryos and larvae of a marine teleost, the Atlantic haddock (Melanogrammus aeglefinus). Haddock embryos were exposed continuously to two different concentrations of dispersed crude oil, high and low, or in pulses. By 24 hours of exposure, micro-droplets of oil were observed adhering and accumulating on the chorion, accompanied by highly elevated levels of cyp1a, a biomarker for exposure to aromatic hydrocarbons. Embryos from all treatment groups showed abnormalities representative of crude oil cardiotoxicity at hatch (5 days of exposure), such as pericardial and yolk sac edema. Compared to other species, the frequency and severity of toxic effects was higher than expected for the waterborne PAH concentrations (e.g., 100% of larvae had edema at the low treatment). These findings suggest an enhanced tissue uptake of PAHs and/or other petroleum compounds from attached oil droplets. These studies highlight a novel property of haddock embryos that leads to greater than expected impact from dispersed crude oil. Given the very limited number of marine species tested in similar exposures, the likelihood of other species with similar properties could be high. This unanticipated result therefore has implications for assessing the ecological impacts of oil spills and the use of methods for dispersing oil in the open sea. PMID:25923774

  3. Unexpected interaction with dispersed crude oil droplets drives severe toxicity in Atlantic haddock embryos.

    PubMed

    Sørhus, Elin; Edvardsen, Rolf B; Karlsen, Ørjan; Nordtug, Trond; van der Meeren, Terje; Thorsen, Anders; Harman, Christopher; Jentoft, Sissel; Meier, Sonnich

    2015-01-01

    The toxicity resulting from exposure to oil droplets in marine fish embryos and larvae is still subject for debate. The most detailed studies have investigated the effects of water-dissolved components of crude oil in water accommodated fractions (WAFs) that lack bulk oil droplets. Although exposure to dissolved petroleum compounds alone is sufficient to cause the characteristic developmental toxicity of crude oil, few studies have addressed whether physical interaction with oil micro-droplets are a relevant exposure pathway for open water marine speices. Here we used controlled delivery of mechanically dispersed crude oil to expose pelagic embryos and larvae of a marine teleost, the Atlantic haddock (Melanogrammus aeglefinus). Haddock embryos were exposed continuously to two different concentrations of dispersed crude oil, high and low, or in pulses. By 24 hours of exposure, micro-droplets of oil were observed adhering and accumulating on the chorion, accompanied by highly elevated levels of cyp1a, a biomarker for exposure to aromatic hydrocarbons. Embryos from all treatment groups showed abnormalities representative of crude oil cardiotoxicity at hatch (5 days of exposure), such as pericardial and yolk sac edema. Compared to other species, the frequency and severity of toxic effects was higher than expected for the waterborne PAH concentrations (e.g., 100% of larvae had edema at the low treatment). These findings suggest an enhanced tissue uptake of PAHs and/or other petroleum compounds from attached oil droplets. These studies highlight a novel property of haddock embryos that leads to greater than expected impact from dispersed crude oil. Given the very limited number of marine species tested in similar exposures, the likelihood of other species with similar properties could be high. This unanticipated result therefore has implications for assessing the ecological impacts of oil spills and the use of methods for dispersing oil in the open sea. PMID:25923774

  4. Climate and local geomorphic interactions drive patterns of riparian forest decline along a Mediterranean Basin river

    NASA Astrophysics Data System (ADS)

    Stella, John C.; Riddle, Jess; Piégay, Hervé; Gagnage, Matthieu; Trémélo, Marie-Laure

    2013-11-01

    discharge, and this will increase both chronic and acute water shortage for riparian trees. This study shows that drought-prone riparian forests are vulnerable to hydrogeomorphological changes, but the severity of impacts is conditioned by interactions between drivers at different scales, including regional climate variability, reach-based geomorphic alteration, and local lithological controls.

  5. Interactions of Grazing History, Cattle Removal and Time since Rain Drive Divergent Short-Term Responses by Desert Biota

    PubMed Central

    Frank, Anke S. K.; Dickman, Chris R.; Wardle, Glenda M.; Greenville, Aaron C.

    2013-01-01

    Arid grasslands are used worldwide for grazing by domestic livestock, generating debate about how this pastoral enterprise may influence native desert biota. One approach to resolving this question is to experimentally reduce livestock numbers and measure the effects. However, a key challenge in doing this is that historical grazing impacts are likely to be cumulative and may therefore confound comparisons of the short-term responses of desert biota to changes in stocking levels. Arid areas are also subject to infrequent flooding rainfalls that drive productivity and dramatically alter abundances of flora and fauna. We took advantage of an opportunity to study the recent effects of a property-scale cattle removal on two properties with similarly varied grazing histories in central Australia. Following the removal of cattle in 2006 and before and after a significant rainfall event at the beginning of 2007, we sampled vegetation and small vertebrates on eight occasions until October 2008. Our results revealed significant interactions of time of survey with both grazing history and grazing removal for vascular plants, small mammals and reptiles. The mammals exhibited a three-way interaction of time, grazing history and grazing removal, thus highlighting the importance of careful sampling designs and timing for future monitoring. The strongest response to the cessation of grazing after two years was depressed reproductive output of plants in areas where cattle continued to graze. Our results confirm that neither vegetation nor small vertebrates necessarily respond immediately to the removal of livestock, but that rainfall events and cumulative grazing history are key determinants of floral and faunal performance in grassland landscapes with low and variable rainfall. We suggest that improved assessments could be made of the health of arid grazing environments if long-term monitoring were implemented to track the complex interactions that influence how native biota

  6. Temporal dynamics of biotic and abiotic drivers of litter decomposition.

    PubMed

    García-Palacios, Pablo; Shaw, E Ashley; Wall, Diana H; Hättenschwiler, Stephan

    2016-05-01

    Climate, litter quality and decomposers drive litter decomposition. However, little is known about whether their relative contribution changes at different decomposition stages. To fill this gap, we evaluated the relative importance of leaf litter polyphenols, decomposer communities and soil moisture for litter C and N loss at different stages throughout the decomposition process. Although both microbial and nematode communities regulated litter C and N loss in the early decomposition stages, soil moisture and legacy effects of initial differences in litter quality played a major role in the late stages of the process. Our results provide strong evidence for substantial shifts in how biotic and abiotic factors control litter C and N dynamics during decomposition. Taking into account such temporal dynamics will increase the predictive power of decomposition models that are currently limited by a single-pool approach applying control variables uniformly to the entire decay process. PMID:26947573

  7. Abiotic vs. biotic influences on habitat selection of coexisting species: Climate change impacts?

    USGS Publications Warehouse

    Martin, T.E.

    2001-01-01

    Species are commonly segregated along gradients of microclimate and vegetation. I explore the question of whether segregation is the result of microhabitat partitioning (biotic effects) or choice of differing microclimates (abiotic effects). I explored this question for four ground-nesting bird species that are segregated along a microclimate and vegetation gradient in Arizona. Birds shifted position of their nests on the microhabitat and microclimate gradient in response to changing precipitation over nine years. Similarly, annual bird abundance varied with precipitation across 12 yr. Those shifts in abundance and nesting microhabitat with changing precipitation demonstrate the importance of abiotic influences on bird distributions and habitat choice. However, nest-site shifts and microhabitat use also appear to be influenced by interactions among coexisting species. Moreover, shifts in habitat use by all species caused nest predation (i.e., biotic) costs that increased with increasing distance along the microclimate gradient. These results indicate that abiotic and biotic costs can strongly interact to influence microhabitat choice and abundances of coexisting species. Global climate change impacts have been considered largely in terms of simple distributional shifts, but these results indicate that shifts can also increase biotic costs when species move into habitat types for which they are poorly adapted or that create new biotic interactions.

  8. The effects of social interactions with in-vehicle agents on a driver's anger level, driving performance, situation awareness, and perceived workload.

    PubMed

    Jeon, Myounghoon; Walker, Bruce N; Gable, Thomas M

    2015-09-01

    Research has suggested that interaction with an in-vehicle software agent can improve a driver's psychological state and increase road safety. The present study explored the possibility of using an in-vehicle software agent to mitigate effects of driver anger on driving behavior. After either anger or neutral mood induction, 60 undergraduates drove in a simulator with two types of agent intervention. Results showed that both speech-based agents not only enhance driver situation awareness and driving performance, but also reduce their anger level and perceived workload. Regression models show that a driver's anger influences driving performance measures, mediated by situation awareness. The practical implications include design guidelines for the design of social interaction with in-vehicle software agents. PMID:25959334

  9. Conserved sequence-specific lincRNA-steroid receptor interactions drive transcriptional repression and direct cell fate

    PubMed Central

    Hudson, William H.; Pickard, Mark R.; de Vera, Ian Mitchelle S.; Kuiper, Emily G.; Mourtada-Maarabouni, Mirna; Conn, Graeme L.; Kojetin, Douglas J.; Williams, Gwyn T.; Ortlund, Eric A.

    2014-01-01

    The majority of the eukaryotic genome is transcribed, generating a significant number of long intergenic non-coding RNAs (lincRNAs). While lincRNAs represent the most poorly understood product of transcription, recent work has shown lincRNAs fulfill important cellular functions. In addition to low sequence conservation, poor understanding of structural mechanisms driving lincRNA biology hinders systematic prediction of their function. Here, we report the molecular requirements for the recognition of steroid receptors (SRs) by the lincRNA Gas5, which regulates steroid-mediated transcriptional regulation, growth arrest, and apoptosis. We identify the functional Gas5-SR interface and generate point mutations that ablate the SR-Gas5 lincRNA interaction, altering Gas5-driven apoptosis in cancer cell lines. Further, we find that the Gas5 SR-recognition sequence is conserved among haplorhines, with its evolutionary origin as a splice acceptor site. This study demonstrates that lincRNAs can recognize protein targets in a conserved, sequence-specific manner in order to affect critical cell functions. PMID:25377354

  10. Conserved sequence-specific lincRNA-steroid receptor interactions drive transcriptional repression and direct cell fate

    SciTech Connect

    Hudson, William H.; Pickard, Mark R.; de Vera, Ian Mitchelle S.; Kuiper, Emily G.; Mourtada-Maarabouni, Mirna; Conn, Graeme L.; Kojetin, Douglas J.; Williams, Gwyn T.; Ortlund, Eric A.

    2014-12-23

    The majority of the eukaryotic genome is transcribed, generating a significant number of long intergenic noncoding RNAs (lincRNAs). Although lincRNAs represent the most poorly understood product of transcription, recent work has shown lincRNAs fulfill important cellular functions. In addition to low sequence conservation, poor understanding of structural mechanisms driving lincRNA biology hinders systematic prediction of their function. Here we report the molecular requirements for the recognition of steroid receptors (SRs) by the lincRNA growth arrest-specific 5 (Gas5), which regulates steroid-mediated transcriptional regulation, growth arrest and apoptosis. We identify the functional Gas5-SR interface and generate point mutations that ablate the SR-Gas5 lincRNA interaction, altering Gas5-driven apoptosis in cancer cell lines. Further, we find that the Gas5 SR-recognition sequence is conserved among haplorhines, with its evolutionary origin as a splice acceptor site. This study demonstrates that lincRNAs can recognize protein targets in a conserved, sequence-specific manner in order to affect critical cell functions.

  11. Biotic effects of impacts and volcanism

    NASA Astrophysics Data System (ADS)

    Keller, Gerta

    2003-10-01

    The biotic effects of late Maastrichtian mantle plume volcanism on Ninetyeast Ridge and Deccan volcanism mirror those of the Cretaceous-Tertiary (KT) mass extinction and impact event. Planktonic foraminifera responded to high stress conditions with the same impoverished and small-sized species assemblages dominated by the disaster/opportunists Guembelitria cretacea, which characterize the KT mass extinction worldwide. Similar high stress late Maastrichtian assemblages have recently been documented from Madagascar, Israel and Egypt. Biotic effects of volcanism cannot be differentiated from those of impacts, though every period of intense volcanism is associated with high stress assemblages, this is not the case with every impact. The most catastrophic biotic effects occurred at the KT boundary (65.0 Ma) when intense Deccan volcanism coincided with a major impact and caused the mass extinction of all tropical and subtropical species. The Chicxulub impact, which now appears to have predated the KT boundary by about 300 kyr, coincided with intense Deccan volcanism that resulted in high biotic stress and greenhouse warming, but no major extinctions. The unequivocal connection between intense volcanism and high stress assemblages during the late Maastrichtian to early Danian, and the evidence of multiple impacts, necessitates revision of current impact and mass extinction theories.

  12. Subtropical Biotic Fringing Reefs as Ecological Laboratories.

    ERIC Educational Resources Information Center

    Hunt, Jeffrey W.

    1980-01-01

    Describes a 16-week course in marine biology involving a class-coordinated investigation of a subtropical biotic fringing reef of Hawaii. Describes in detail the development of preliminary hypotheses regarding general cause-effect relationships on the reef, and the exploration of specific areas, such as chemical or physical factors. (CS)

  13. Design, engineering and utility of biotic games.

    PubMed

    Riedel-Kruse, Ingmar H; Chung, Alice M; Dura, Burak; Hamilton, Andrea L; Lee, Byung C

    2011-01-01

    Games are a significant and defining part of human culture, and their utility beyond pure entertainment has been demonstrated with so-called 'serious games'. Biotechnology--despite its recent advancements--has had no impact on gaming yet. Here we propose the concept of 'biotic games', i.e., games that operate on biological processes. Utilizing a variety of biological processes we designed and tested a collection of games: 'Enlightenment', 'Ciliaball', 'PAC-mecium', 'Microbash', 'Biotic Pinball', 'POND PONG', 'PolymerRace', and 'The Prisoner's Smellemma'. We found that biotic games exhibit unique features compared to existing game modalities, such as utilizing biological noise, providing a real-life experience rather than virtual reality, and integrating the chemical senses into play. Analogous to video games, biotic games could have significant conceptual and cost-reducing effects on biotechnology and eventually healthcare; enable volunteers to participate in crowd-sourcing to support medical research; and educate society at large to support personal medical decisions and the public discourse on bio-related issues. PMID:21085736

  14. Probing into the Supramolecular Driving Force of an Amphiphilic β-Cyclodextrin Dimer in Various Solvents: Host-Guest Recognition or Hydrophilic-Hydrophobic Interaction?

    PubMed

    Bai, Yang; Fan, Xiao-dong; Yao, Hao; Yang, Zhen; Liu, Ting-ting; Zhang, Hai-tao; Zhang, Wan-bin; Tian, Wei

    2015-09-01

    Tuning of the morphology and size of supramolecular self-assemblies is of theoretical and practical significance. To date, supramolecular driving forces in different solvents remain unclear. In this study, we first synthesized an amphiphilic β-cyclodextrin (β-CD) dimer that consists of one hydrophobic ibuprofen (Ibu) and two hydrophilic β-CD moieties (i.e., Ibu-CD2). Ibu-CD2 possesses double supramolecular driving forces, namely, the host-guest recognition and hydrophilic-hydrophobic interaction. The host-guest interaction of Ibu-CD2 induced the formation of branched supramolecular polymers (SPs) in pure water, whereas the hydrophilic-hydrophobic interaction generated spherical or irregular micelles in water/organic mixtures. The SP size increased with the increase in Ibu-CD2 concentration in pure water. By contrast, the size of micelles decreased with the increase in volume ratio of water in mixtures. PMID:26301920

  15. Pivoting from Arabidopsis to wheat to understand how agricultural plants integrate responses to biotic stress

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Here we argue for a research initiative on gene-for-gene (g-f-g) interactions between wheat and its parasites. One aim is to begin a conversation between the disparate communities of plant pathology and entomology. Another is to understand how responses to biotic stress are integrated in an import...

  16. Ecological and evolutionary consequences of biotic homogenization.

    PubMed

    Olden, Julian D; Leroy Poff, N; Douglas, Marlis R; Douglas, Michael E; Fausch, Kurt D

    2004-01-01

    Biotic homogenization, the gradual replacement of native biotas by locally expanding non-natives, is a global process that diminishes floral and faunal distinctions among regions. Although patterns of homogenization have been well studied, their specific ecological and evolutionary consequences remain unexplored. We argue that our current perspective on biotic homogenization should be expanded beyond a simple recognition of species diversity loss, towards a synthesis of higher order effects. Here, we explore three distinct forms of homogenization (genetic, taxonomic and functional), and discuss their immediate and future impacts on ecological and evolutionary processes. Our goal is to initiate future research that investigates the broader conservation implications of homogenization and to promote a proactive style of adaptive management that engages the human component of the anthropogenic blender that is currently mixing the biota on Earth. PMID:16701221

  17. The importance of biotic entrainment for base flow fluvial sediment transport

    NASA Astrophysics Data System (ADS)

    Rice, Stephen P.; Johnson, Matthew F.; Mathers, Kate; Reeds, Jake; Extence, Chris

    2016-05-01

    Sediment transport is regarded as an abiotic process driven by geophysical energy, but zoogeomorphological activity indicates that biological energy can also fuel sediment movements. It is therefore prudent to measure the contribution that biota make to sediment transport, but comparisons of abiotic and biotic sediment fluxes are rare. For a stream in the UK, the contribution of crayfish bioturbation to suspended sediment flux was compared with the amount of sediment moved by hydraulic forcing. During base flow periods, biotic fluxes can be isolated because nocturnal crayfish activity drives diel turbidity cycles, such that nighttime increases above daytime lows are attributable to sediment suspension by crayfish. On average, crayfish bioturbation contributed at least 32% (474 kg) to monthly base flow suspended sediment loads; this biotic surcharge added between 5.1 and 16.1 t (0.21 to 0.66 t km-2 yr-1) to the annual sediment yield. As anticipated, most sediment was moved by hydraulic forcing during floods and the biotic contribution from baseflow periods represented between 0.46 and 1.46% of the annual load. Crayfish activity is nonetheless an important impact during baseflow periods and the measured annual contribution may be a conservative estimate because of unusually prolonged flooding during the measurement period. In addition to direct sediment entrainment by bioturbation, crayfish burrowing supplies sediment to the channel for mobilization during floods so that the total biotic effect of crayfish is potentially greater than documented in this study. These results suggest that in rivers, during base flow periods, bioturbation can entrain significant quantities of fine sediment into suspension with implications for the aquatic ecosystem and base flow sediment fluxes. Energy from life rather than from elevation can make significant contributions to sediment fluxes.

  18. Modeling biotic habitat high risk areas

    USGS Publications Warehouse

    Despain, D.G.; Beier, P.; Tate, C.; Durtsche, B.M.; Stephens, T.

    2000-01-01

    Fire, especially stand replacing fire, poses a threat to many threatened and endangered species as well as their habitat. On the other hand, fire is important in maintaining a variety of successional stages that can be important for approach risk assessment to assist in prioritizing areas for allocation of fire mitigation funds. One example looks at assessing risk to the species and biotic communities of concern followed by the Colorado Natural Heritage Program. One looks at the risk to Mexican spottled owls. Another looks at the risk to cutthroat trout, and a fourth considers the general effects of fire and elk.

  19. The relative contribution of climatic, edaphic, and biotic drivers to risk of tree mortality from drought

    NASA Astrophysics Data System (ADS)

    March, R. G.; Moore, G. W.; Edgar, C. B.; Lawing, A. M.; Washington-Allen, R. A.

    2015-12-01

    In recorded history, the 2011 Texas Drought was comparable in severity only to a drought that occurred 300 years ago. By mid-September, 88% of the state experienced 'exceptional' conditions, with the rest experiencing 'extreme' or 'severe' drought. By recent estimates, the 2011 Texas Drought killed 6.2% of all the state's trees, at a rate nearly 9 times greater than average. The vast spatial scale and relatively uniform intensity of this drought has provided an opportunity to examine the comparative interactions among forest types, terrain, and edaphic factors across major climate gradients which in 2011 were subjected to extreme drought conditions that ultimately caused massive tree mortality. We used maximum entropy modeling (Maxent) to rank environmental landscape factors with the potential to drive drought-related tree mortality and test the assumption that the relative importance of these factors are scale-dependent. Occurrence data of dead trees were collected during the summer of 2012 from 599 field plots distributed across Texas with 30% used for model evaluation. Bioclimatic variables, ecoregions, soils characteristics, and topographic variables were modeled with drought-killed tree occurrence. Their relative contribution to the model was seen as their relative importance in driving mortality. To test determinants at a more local scale, we examined Landsat 7 scenes in East and West Texas with moderate-resolution data for the same variables above with the exception of climate. All models were significantly better than random in binomial tests of omission and receiver operating characteristic analyses. The modeled spatial distribution of probability of occurrence showed high probability of mortality in the east-central oak woodlands and the mixed pine-hardwood forest region in northeast Texas. Both regional and local models were dominated by biotic factors (ecoregion and forest type, respectively). Forest density and precipitation of driest month also

  20. Abiotic mediation of a mutualism drives herbivore abundance.

    PubMed

    Mooney, Emily H; Phillips, Joseph S; Tillberg, Chadwick V; Sandrow, Cheryl; Nelson, Annika S; Mooney, Kailen A

    2016-01-01

    Species abundance is typically determined by the abiotic environment, but the extent to which such effects occur through the mediation of biotic interactions, including mutualisms, is unknown. We explored how light environment (open meadow vs. shaded understory) mediates the abundance and ant tending of the aphid Aphis helianthi feeding on the herb Ligusticum porteri. Yearly surveys consistently found aphids to be more than 17-fold more abundant on open meadow plants than on shaded understory plants. Manipulations demonstrated that this abundance pattern was not due to the direct effects of light environment on aphid performance, or indirectly through host plant quality or the effects of predators. Instead, open meadows had higher ant abundance and per capita rates of aphid tending and, accordingly, ants increased aphid population growth in meadow but not understory environments. The abiotic environment thus drives the abundance of this herbivore exclusively through the mediation of a protection mutualism. PMID:26563752

  1. iDriving (Intelligent Driving)

    Energy Science and Technology Software Center (ESTSC)

    2012-09-17

    iDriving identifies the driving style factors that have a major impact on fuel economy. An optimization framework is used with the aim of optimizing a driving style with respect to these driving factors. A set of polynomial metamodels is constructed to reflect the responses produced in fuel economy by changing the driving factors. The optimization framework is used to develop a real-time feedback system, including visual instructions, to enable drivers to alter their driving stylesmore » in responses to actual driving conditions to improve fuel efficiency.« less

  2. iDriving (Intelligent Driving)

    SciTech Connect

    Malikopoulos, Andreas

    2012-09-17

    iDriving identifies the driving style factors that have a major impact on fuel economy. An optimization framework is used with the aim of optimizing a driving style with respect to these driving factors. A set of polynomial metamodels is constructed to reflect the responses produced in fuel economy by changing the driving factors. The optimization framework is used to develop a real-time feedback system, including visual instructions, to enable drivers to alter their driving styles in responses to actual driving conditions to improve fuel efficiency.

  3. Multi-atom entanglement engineering and phase-covariant quantum cloning with a single resonant interaction assisted by external driving

    NASA Astrophysics Data System (ADS)

    Zhang, Xian-Peng; Shen, Li-Tuo; Yang, Zhen-Biao

    2014-12-01

    We propose a scheme to realize multi-atom entanglement and phase-covariant quantum cloning in a short-time manner possessing the advantage of its robustness with respect to parameter fluctuations. The process is achieved by externally driving the atoms to resonantly couple to the cavity mode. Compared to other strategies, such as the adiabatic or virtual-photon techniques, it provides a method which allows the relatively fast coherent manipulation.

  4. Biotic homogenization can decrease landscape-scale forest multifunctionality.

    PubMed

    van der Plas, Fons; Manning, Pete; Soliveres, Santiago; Allan, Eric; Scherer-Lorenzen, Michael; Verheyen, Kris; Wirth, Christian; Zavala, Miguel A; Ampoorter, Evy; Baeten, Lander; Barbaro, Luc; Bauhus, Jürgen; Benavides, Raquel; Benneter, Adam; Bonal, Damien; Bouriaud, Olivier; Bruelheide, Helge; Bussotti, Filippo; Carnol, Monique; Castagneyrol, Bastien; Charbonnier, Yohan; Coomes, David Anthony; Coppi, Andrea; Bastias, Cristina C; Dawud, Seid Muhie; De Wandeler, Hans; Domisch, Timo; Finér, Leena; Gessler, Arthur; Granier, André; Grossiord, Charlotte; Guyot, Virginie; Hättenschwiler, Stephan; Jactel, Hervé; Jaroszewicz, Bogdan; Joly, François-Xavier; Jucker, Tommaso; Koricheva, Julia; Milligan, Harriet; Mueller, Sandra; Muys, Bart; Nguyen, Diem; Pollastrini, Martina; Ratcliffe, Sophia; Raulund-Rasmussen, Karsten; Selvi, Federico; Stenlid, Jan; Valladares, Fernando; Vesterdal, Lars; Zielínski, Dawid; Fischer, Markus

    2016-03-29

    Many experiments have shown that local biodiversity loss impairs the ability of ecosystems to maintain multiple ecosystem functions at high levels (multifunctionality). In contrast, the role of biodiversity in driving ecosystem multifunctionality at landscape scales remains unresolved. We used a comprehensive pan-European dataset, including 16 ecosystem functions measured in 209 forest plots across six European countries, and performed simulations to investigate how local plot-scale richness of tree species (α-diversity) and their turnover between plots (β-diversity) are related to landscape-scale multifunctionality. After accounting for variation in environmental conditions, we found that relationships between α-diversity and landscape-scale multifunctionality varied from positive to negative depending on the multifunctionality metric used. In contrast, when significant, relationships between β-diversity and landscape-scale multifunctionality were always positive, because a high spatial turnover in species composition was closely related to a high spatial turnover in functions that were supported at high levels. Our findings have major implications for forest management and indicate that biotic homogenization can have previously unrecognized and negative consequences for large-scale ecosystem multifunctionality. PMID:26979952

  5. Impaired Driving

    MedlinePlus

    ... Risk Factors BAC Effects Prevention Additional Resources How big is the problem? In 2014, 9,967 people ... Driving: A Threat to Everyone (October 2011) Additional Data Drunk Driving State Data and Maps Motor Vehicle ...

  6. Drugged Driving

    MedlinePlus

    ... Infographics » Drugged Driving Drugged Driving Email Facebook Twitter Text Description of Infographic Top Right Figure : In 2009, ... crash than those who don't smoke. Bottom Text: Develop Social Strategies Offer to be a designated ...

  7. Rapid biotic homogenization of marine fish assemblages.

    PubMed

    Magurran, Anne E; Dornelas, Maria; Moyes, Faye; Gotelli, Nicholas J; McGill, Brian

    2015-01-01

    The role human activities play in reshaping biodiversity is increasingly apparent in terrestrial ecosystems. However, the responses of entire marine assemblages are not well-understood, in part, because few monitoring programs incorporate both spatial and temporal replication. Here, we analyse an exceptionally comprehensive 29-year time series of North Atlantic groundfish assemblages monitored over 5° latitude to the west of Scotland. These fish assemblages show no systematic change in species richness through time, but steady change in species composition, leading to an increase in spatial homogenization: the species identity of colder northern localities increasingly resembles that of warmer southern localities. This biotic homogenization mirrors the spatial pattern of unevenly rising ocean temperatures over the same time period suggesting that climate change is primarily responsible for the spatial homogenization we observe. In this and other ecosystems, apparent constancy in species richness may mask major changes in species composition driven by anthropogenic change. PMID:26400102

  8. Integrated stratigraphy of the Carnian biotic crises

    NASA Astrophysics Data System (ADS)

    Kuerschner, Wolfram; Krystyn, Leopold

    2016-04-01

    The Carnian is characterized by a series of events that are expressed as significant facies changes and biotic turnovers, known as the Reingraben turnover, the Carnian pluvial event/episode/phase, the Carnian crisis... European Carnian marine deposits are characterized by the occurrence of extensive siliciclastic units that interrupt the predominantly marine carbonate successions while continental basins are characterized by the occurrence of fluvial channels that interrupt widespread sabkha deposits. These facies changes have been generally attributed to a humid episode in an otherwise predominantly dry climate. However, the exact stratigraphic age of these events and their correlation within and between the marine and terrestrial basins are not well established. In fact, major facies changes and associated sedimentary breaks hamper the development of a solid stratigraphic framework for the Carnian events. In this presentation we will summarize the current knowledge on the stratigraphy of the Carnian events and present new data from ongoing investigations in the Dinaric Alps, Bosnia-Herzegovina.

  9. Field chronobiology of a molluscan bivalve: how the moon and sun cycles interact to drive oyster activity rhythms.

    PubMed

    Tran, Damien; Nadau, Arnaud; Durrieu, Gilles; Ciret, Pierre; Parisot, Jean-Paul; Massabuau, Jean-Charles

    2011-05-01

    The present study reports new insights into the complexity of environmental drivers in aquatic animals. The focus of this study was to determine the main forces that drive mollusc bivalve behavior in situ. To answer this question, the authors continuously studied the valve movements of permanently immersed oysters, Crassostrea gigas, during a 1-year-long in situ study. Valve behavior was monitored with a specially build valvometer, which allows continuously recording of up to 16 bivalves at high frequency (10 Hz). The results highlight a strong relationship between the rhythms of valve behavior and the complex association of the sun-earth-moon orbital positions. Permanently immersed C. gigas follows a robust and strong behavior primarily driven by the tidal cycle. The intensity of this tidal driving force is modulated by the neap-spring tides (i.e., synodic moon cycle), which themselves depend of the earth-moon distance (i.e., anomalistic moon cycle). Light is a significant driver of the oysters' biological rhythm, although its power is limited by the tides, which remain the predominant driver. More globally, depending where in the world the bivalves reside, the results suggest their biological rhythms should vary according to the relative importance of the solar cycle and different lunar cycles associated with tide generation. These results highlight the high plasticity of these oysters to adapt to their changing environment. PMID:21539422

  10. Engineering non-linear resonator mode interactions in circuit QED by continuous driving: Manipulation of a photonic quantum memory

    NASA Astrophysics Data System (ADS)

    Reagor, Matthew; Pfaff, Wolfgang; Heeres, Reinier; Ofek, Nissim; Chou, Kevin; Blumoff, Jacob; Leghtas, Zaki; Touzard, Steven; Sliwa, Katrina; Holland, Eric; Albert, Victor V.; Frunzio, Luigi; Devoret, Michel H.; Jiang, Liang; Schoelkopf, Robert J.

    2015-03-01

    Recent advances in circuit QED have shown great potential for using microwave resonators as quantum memories. In particular, it is possible to encode the state of a quantum bit in non-classical photonic states inside a high-Q linear resonator. An outstanding challenge is to perform controlled operations on such a photonic state. We demonstrate experimentally how a continuous drive on a transmon qubit coupled to a high-Q storage resonator can be used to induce non-linear dynamics of the resonator. Tailoring the drive properties allows us to cancel or enhance non-linearities in the system such that we can manipulate the state stored in the cavity. This approach can be used to either counteract undesirable evolution due to the bare Hamiltonian of the system or, ultimately, to perform logical operations on the state encoded in the cavity field. Our method provides a promising pathway towards performing universal control for quantum states stored in high-coherence resonators in the circuit QED platform.

  11. BIOTIC: A Novel Method for Variable Rate Irrigation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The BIOTIC irrigation protocol was developed as an irrigation scheduling protocol that utilizes a biologically based temperature optimum to detect plant water deficits. BIOTIC provides full irrigation that is comparable to other methods under a variety of crops and environments. The utilization of...

  12. Mycobacterium ulcerans dynamics in aquatic ecosystems are driven by a complex interplay of abiotic and biotic factors

    PubMed Central

    Garchitorena, Andrés; Guégan, Jean-François; Léger, Lucas; Eyangoh, Sara; Marsollier, Laurent; Roche, Benjamin

    2015-01-01

    Host–parasite interactions are often embedded within complex host communities and can be influenced by a variety of environmental factors, such as seasonal variations in climate or abiotic conditions in water and soil, which confounds our understanding of the main drivers of many multi-host pathogens. Here, we take advantage of a combination of large environmental data sets on Mycobacterium ulcerans (MU), an environmentally persistent microorganism associated to freshwater ecosystems and present in a large variety of aquatic hosts, to characterize abiotic and biotic factors driving the dynamics of this pathogen in two regions of Cameroon. We find that MU dynamics are largely driven by seasonal climatic factors and certain physico-chemical conditions in stagnant and slow-flowing ecosystems, with an important role of pH as limiting factor. Furthermore, water conditions can modify the effect of abundance and diversity of aquatic organisms on MU dynamics, which suggests a different contribution of two MU transmission routes for aquatic hosts (trophic vs environmental transmission) depending on local abiotic factors. DOI: http://dx.doi.org/10.7554/eLife.07616.001 PMID:26216042

  13. Per capita interactions and stress tolerance drive stress-induced changes in biodiversity effects on ecosystem functions.

    PubMed

    Baert, Jan M; Janssen, Colin R; Sabbe, Koen; De Laender, Frederik

    2016-01-01

    Environmental stress changes the relationship between biodiversity and ecosystem functions, but the underlying mechanisms are poorly understood. Because species interactions shape biodiversity-ecosystem functioning relationships, changes in per capita interactions under stress (as predicted by the stress gradient hypothesis) can be an important driver of stress-induced changes in these relationships. To test this hypothesis, we measure productivity in microalgae communities along a diversity and herbicide gradient. On the basis of additive partitioning and a mechanistic community model, we demonstrate that changes in per capita interactions do not explain effects of herbicide stress on the biodiversity-productivity relationship. Instead, assuming that the per capita interactions remain unaffected by stress, causing species densities to only change through differences in stress tolerance, suffices to predict the stress-induced changes in the biodiversity-productivity relationship and community composition. We discuss how our findings set the stage for developing theory on how environmental stress changes biodiversity effects on ecosystem functions. PMID:27534986

  14. Per capita interactions and stress tolerance drive stress-induced changes in biodiversity effects on ecosystem functions

    PubMed Central

    Baert, Jan M.; Janssen, Colin R.; Sabbe, Koen; De Laender, Frederik

    2016-01-01

    Environmental stress changes the relationship between biodiversity and ecosystem functions, but the underlying mechanisms are poorly understood. Because species interactions shape biodiversity–ecosystem functioning relationships, changes in per capita interactions under stress (as predicted by the stress gradient hypothesis) can be an important driver of stress-induced changes in these relationships. To test this hypothesis, we measure productivity in microalgae communities along a diversity and herbicide gradient. On the basis of additive partitioning and a mechanistic community model, we demonstrate that changes in per capita interactions do not explain effects of herbicide stress on the biodiversity–productivity relationship. Instead, assuming that the per capita interactions remain unaffected by stress, causing species densities to only change through differences in stress tolerance, suffices to predict the stress-induced changes in the biodiversity–productivity relationship and community composition. We discuss how our findings set the stage for developing theory on how environmental stress changes biodiversity effects on ecosystem functions. PMID:27534986

  15. Inter-annual variability of carbon fluxes in temperate forest ecosystems: effects of biotic and abiotic factors

    NASA Astrophysics Data System (ADS)

    Chen, M.; Keenan, T. F.; Hufkens, K.; Munger, J. W.; Bohrer, G.; Brzostek, E. R.; Richardson, A. D.

    2014-12-01

    Carbon dynamics in terrestrial ecosystems are influenced by both abiotic and biotic factors. Abiotic factors, such as variation in meteorological conditions, directly drive biophysical and biogeochemical processes; biotic factors, referring to the inherent properties of the ecosystem components, reflect the internal regulating effects including temporal dynamics and memory. The magnitude of the effect of abiotic and biotic factors on forest ecosystem carbon exchange has been suggested to vary at different time scales. In this study, we design and conduct a model-data fusion experiment to investigate the role and relative importance of the biotic and abiotic factors for inter-annual variability of the net ecosystem CO2 exchange (NEE) of temperate deciduous forest ecosystems in the Northeastern US. A process-based model (FöBAAR) is parameterized at four eddy-covariance sites using all available flux and biometric measurements. We conducted a "transplant" modeling experiment, that is, cross- site and parameter simulations with different combinations of site meteorology and parameters. Using wavelet analysis and variance partitioning techniques, analysis of model predictions identifies both spatial variant and spatially invariant parameters. Variability of NEE was primarily modulated by gross primary productivity (GPP), with relative contributions varying from hourly to yearly time scales. The inter-annual variability of GPP and NEE is more regulated by meteorological forcing, but spatial variability in certain model parameters (biotic response) has more substantial effects on the inter-annual variability of ecosystem respiration (Reco) through the effects on carbon pools. Both the biotic and abiotic factors play significant roles in modulating the spatial and temporal variability in terrestrial carbon cycling in the region. Together, our study quantifies the relative importance of both, and calls for better understanding of them to better predict regional CO2

  16. Pile Driving

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Machine-oriented structural engineering firm TERA, Inc. is engaged in a project to evaluate the reliability of offshore pile driving prediction methods to eventually predict the best pile driving technique for each new offshore oil platform. Phase I Pile driving records of 48 offshore platforms including such information as blow counts, soil composition and pertinent construction details were digitized. In Phase II, pile driving records were statistically compared with current methods of prediction. Result was development of modular software, the CRIPS80 Software Design Analyzer System, that companies can use to evaluate other prediction procedures or other data bases.

  17. Vision and Driving

    PubMed Central

    Owsley, Cynthia; McGwin, Gerald

    2010-01-01

    Driving is the primary means of personal travel in many countries and is relies heavily on vision for its successful execution. Research over the past few decades has addressed the role of vision in driver safety (motor vehicle collision involvement) and in driver performance (both on-road and using interactive simulators in the laboratory). Here we critically review what is currently known about the role of various aspects of visual function in driving. We also discuss translational research issues on vision screening for licensure and re-licensure and rehabilitation of visually impaired persons who want to drive. PMID:20580907

  18. Biotic controls on solute distribution and transport in headwater catchments

    NASA Astrophysics Data System (ADS)

    Herndon, E. M.; Dere, A. L.; Sullivan, P. L.; Norris, D.; Reynolds, B.; Brantley, S. L.

    2015-01-01

    Solute concentrations in stream water vary with discharge in patterns that record complex feedbacks between hydrologic and biogeochemical processes. In a comparison of headwater catchments underlain by shale in Pennsylvania, USA (Shale Hills) and Wales, UK (Plynlimon), dissimilar concentration-discharge behaviors are best explained by contrasting landscape distributions of soil solution chemistry - especially dissolved organic carbon (DOC) - that have been established by patterns of vegetation. Specifically, elements that are concentrated in organic-rich soils due to biotic cycling (Mn, Ca, K) or that form strong complexes with DOC (Fe, Al) are spatially heterogeneous in pore waters because organic matter is heterogeneously distributed across the catchments. These solutes exhibit non-chemostatic "bioactive" behavior in the streams, and solute concentrations either decrease (Shale Hills) or increase (Plynlimon) with increasing discharge. In contrast, solutes that are concentrated in soil minerals and form only weak complexes with DOC (Na, Mg, Si) are spatially homogeneous in pore waters across each catchment. These solutes are chemostatic in that their stream concentrations vary little with stream discharge, likely because these solutes are released quickly from exchange sites in the soils during rainfall events. Differences in the hydrologic connectivity of organic-rich soils to the stream drive differences in concentration behavior between catchments. As such, in catchments where soil organic matter (SOM) is dominantly in lowlands (e.g., Shale Hills), bioactive elements are released to the stream early during rainfall events, whereas in catchments where SOM is dominantly in uplands (e.g., Plynlimon), bioactive elements are released later during rainfall events. The distribution of vegetation and SOM across the landscape is thus a key component for predictive models of solute transport in headwater catchments.

  19. Emergence of Strong Exchange Interaction in the Actinide Series: The Driving Force for Magnetic Stabilization of Curium

    SciTech Connect

    Moore, K; der Laan, G v; Haire, D; Wall, M; Schwartz, A; Soderlind, P

    2007-01-04

    Using electron energy-loss spectroscopy in a transmission electron microscope, many-electron atomic spectral calculations and density functional theory, we examine the electronic and magnetic structure of Cm metal. We show that angular momentum coupling in the 5f states plays a decisive role in the formation of the magnetic moment. The 5f states of Cm in intermediate coupling are strongly shifted towards the LS coupling limit due to exchange interaction, unlike most actinide elements where the effective spin-orbit interaction prevails. It is this LS-inclined intermediate coupling that is the key to producing the large spin polarization which in turn dictates the newly found crystal structure of Cm under pressure.

  20. Nodes with high centrality in protein interaction networks are responsible for driving signaling pathways in diabetic nephropathy

    PubMed Central

    Abedi, Maryam

    2015-01-01

    In spite of huge efforts, chronic diseases remain an unresolved problem in medicine. Systems biology could assist to develop more efficient therapies through providing quantitative holistic sights to these complex disorders. In this study, we have re-analyzed a microarray dataset to identify critical signaling pathways related to diabetic nephropathy. GSE1009 dataset was downloaded from Gene Expression Omnibus database and the gene expression profile of glomeruli from diabetic nephropathy patients and those from healthy individuals were compared. The protein-protein interaction network for differentially expressed genes was constructed and enriched. In addition, topology of the network was analyzed to identify the genes with high centrality parameters and then pathway enrichment analysis was performed. We found 49 genes to be variably expressed between the two groups. The network of these genes had few interactions so it was enriched and a network with 137 nodes was constructed. Based on different parameters, 34 nodes were considered to have high centrality in this network. Pathway enrichment analysis with these central genes identified 62 inter-connected signaling pathways related to diabetic nephropathy. Interestingly, the central nodes were more informative for pathway enrichment analysis compared to all network nodes and also 49 differentially expressed genes. In conclusion, we here show that central nodes in protein interaction networks tend to be present in pathways that co-occur in a biological state. Also, this study suggests a computational method for inferring underlying mechanisms of complex disorders from raw high-throughput data. PMID:26557424

  1. Few Residues within an Extensive Binding Interface Drive Receptor Interaction and Determine the Specificity of Arrestin Proteins*

    PubMed Central

    Vishnivetskiy, Sergey A.; Gimenez, Luis E.; Francis, Derek J.; Hanson, Susan M.; Hubbell, Wayne L.; Klug, Candice S.; Gurevich, Vsevolod V.

    2011-01-01

    Arrestins bind active phosphorylated forms of G protein-coupled receptors, terminating G protein activation, orchestrating receptor trafficking, and redirecting signaling to alternative pathways. Visual arrestin-1 preferentially binds rhodopsin, whereas the two non-visual arrestins interact with hundreds of G protein-coupled receptor subtypes. Here we show that an extensive surface on the concave side of both arrestin-2 domains is involved in receptor binding. We also identified a small number of residues on the receptor binding surface of the N- and C-domains that largely determine the receptor specificity of arrestins. We show that alanine substitution of these residues blocks the binding of arrestin-1 to rhodopsin in vitro and of arrestin-2 and -3 to β2-adrenergic, M2 muscarinic cholinergic, and D2 dopamine receptors in intact cells, suggesting that these elements critically contribute to the energy of the interaction. Thus, in contrast to arrestin-1, where direct phosphate binding is crucial, the interaction of non-visual arrestins with their cognate receptors depends to a lesser extent on phosphate binding and more on the binding to non-phosphorylated receptor elements. PMID:21471193

  2. The interactions between temperature and activity levels in driving metabolic rate: theory, with empirical validation from contrasting ectotherms.

    PubMed

    Halsey, L G; Matthews, P G D; Rezende, E L; Chauvaud, L; Robson, A A

    2015-04-01

    The rate of change in resting metabolic rate (RMR) as a result of a temperature increase of 10 °C is termed the temperature coefficient (Q10), which is often used to predict how an organism's total MR will change with temperature. However, this method neglects a potentially key component of MR; changes in activity level (and thus activity MR; AMR) with temperature may significantly alter the relationship between MR and temperature. The present study seeks to describe how thermal effects on total MR estimated from RMR-temperature measurements can be misleading when the contribution of activity to total MR is neglected. A simple conceptual framework illustrates that since the relationship between activity levels and temperature can be different to the relationship between RMR and temperature, a consistent relationship between RMR and total MR cannot be assumed. Thus the thermal effect on total MR can be considerably different to the thermal effect on RMR. Simultaneously measured MR and activity from three ectotherm species with differing behavioural and physiological ecologies were used to empirically examine how changes in temperature drive changes in RMR, activity level, AMR and the Q10 of MR. These species exhibited varied activity- and MR-temperature relationships, underlining the difficulty in predicting thermal influences on activity levels and total MR. These data support a model showing that thermal effects on total MR will deviate from predictions based solely on RMR; this deviation will depend upon the difference in Q10 between AMR and RMR, and the relative contribution of AMR to total MR. To develop mechanistic, predictive models for species' metabolic responses to temperature changes, empirical information about the relationships between activity levels, MR and temperature, such as reported here, is required. This will supersede predictions based on RMR alone. PMID:25575673

  3. Caspase-9b Interacts Directly with cIAP1 to Drive Agonist-Independent Activation of NF-κB and Lung Tumorigenesis.

    PubMed

    Vu, Ngoc T; Park, Margaret A; Shultz, Michael D; Bulut, Gamze B; Ladd, Amy C; Chalfant, Charles E

    2016-05-15

    Alternate RNA processing of caspase-9 generates the splice variants caspase 9a (C9a) and caspase 9b (C9b). C9b lacks a domain present in C9a, revealing a tumorigenic function that drives the phenotype of non-small cell lung cancer (NSCLC) cells. In this study, we elucidated the mechanistic underpinnings of the malignant character of this splice isoform. In NSCLC cells, C9b expression correlated with activation of the canonical arm of the NF-κB pathway, a major pathway linked to the NSCLC tumorigenesis. Mechanistic investigations revealed that C9b activates this pathway via direct interaction with cellular inhibitor of apoptosis 1 (cIAP1) and subsequent induction of the E3 ligase activity of this IAP family member. The C9b:cIAP1 interaction occurred via the BIR3 domain of cIAP1 and the IAP-binding motif of C9b, but did not require proteolytic cleavage of C9b. This protein:protein interaction was essential for C9b to promote viability and malignant growth of NSCLC cells in vitro and in vivo, broadly translating to diverse NSCLC oncogenotypes. Overall, our findings identified a novel point for therapeutic invention in NSCLC that may be tractable to small-molecule inhibitors, as a new point to broadly address this widespread deadly disease. Cancer Res; 76(10); 2977-89. ©2016 AACR. PMID:27197231

  4. Shifting grassland plant community structure drives positive interactive effects of warming and diversity on aboveground net primary productivity.

    PubMed

    Cowles, Jane M; Wragg, Peter D; Wright, Alexandra J; Powers, Jennifer S; Tilman, David

    2016-02-01

    Ecosystems worldwide are increasingly impacted by multiple drivers of environmental change, including climate warming and loss of biodiversity. We show, using a long-term factorial experiment, that plant diversity loss alters the effects of warming on productivity. Aboveground primary productivity was increased by both high plant diversity and warming, and, in concert, warming (≈1.5 °C average above and belowground warming over the growing season) and diversity caused a greater than additive increase in aboveground productivity. The aboveground warming effects increased over time, particularly at higher levels of diversity, perhaps because of warming-induced increases in legume and C4 bunch grass abundances, and facilitative feedbacks of these species on productivity. Moreover, higher plant diversity was associated with the amelioration of warming-induced environmental conditions. This led to cooler temperatures, decreased vapor pressure deficit, and increased surface soil moisture in higher diversity communities. Root biomass (0-30 cm) was likewise consistently greater at higher plant diversity and was greater with warming in monocultures and at intermediate diversity, but at high diversity warming had no detectable effect. This may be because warming increased the abundance of legumes, which have lower root : shoot ratios than the other types of plants. In addition, legumes increase soil nitrogen (N) supply, which could make N less limiting to other species and potentially decrease their investment in roots. The negative warming × diversity interaction on root mass led to an overall negative interactive effect of these two global change factors on the sum of above and belowground biomass, and thus likely on total plant carbon stores. In total, plant diversity increased the effect of warming on aboveground net productivity and moderated the effect on root mass. These divergent effects suggest that warming and changes in plant diversity are likely to have both

  5. Driving the need to feed: Insight into the collaborative interaction between ghrelin and endocannabinoid systems in modulating brain reward systems.

    PubMed

    Edwards, Alexander; Abizaid, Alfonso

    2016-07-01

    Independent stimulation of either the ghrelin or endocannabinoid system promotes food intake and increases adiposity. Given the similar distribution of their receptors in feeding associated brain regions and organs involved in metabolism, it is not surprising that evidence of their interaction and its importance in modulating energy balance has emerged. This review documents the relationship between ghrelin and endocannabinoid systems within the periphery and hypothalamus (HYP) before presenting evidence suggesting that these two systems likewise work collaboratively within the ventral tegmental area (VTA) to modulate non-homeostatic feeding. Mechanisms, consistent with current evidence and local infrastructure within the VTA, will be proposed. PMID:27136126

  6. Enzyme-ligand interactions that drive active site rearrangements in the Helicobacter pylori 5´-methylthioadenosine/S-adenosylhomocysteine nucleosidase

    SciTech Connect

    Ronning, Donald R; Iacopelli, Natalie M; Mishra, Vidhi

    2012-03-15

    The bacterial enzyme 5'-methylthioadenosine/S-adenosylhomocysteine nucleosidase (MTAN) plays a central role in three essential metabolic pathways in bacteria: methionine salvage, purine salvage, and polyamine biosynthesis. Recently, its role in the pathway that leads to the production of autoinducer II, an important component in quorum-sensing, has garnered much interest. Because of this variety of roles, MTAN is an attractive target for developing new classes of inhibitors that influence bacterial virulence and biofilm formation. To gain insight toward the development of new classes of MTAN inhibitors, the interactions between the Helicobacter pylori-encoded MTAN and its substrates and substrate analogs were probed using X-ray crystallography. The structures of MTAN, an MTAN-Formycin A complex, and an adenine bound form were solved by molecular replacement and refined to 1.7, 1.8, and 1.6 Å, respectively. The ribose-binding site in the MTAN and MTAN-adenine cocrystal structures contain a tris[hydroxymethyl]aminomethane molecule that stabilizes the closed form of the enzyme and displaces a nucleophilic water molecule necessary for catalysis. This research gives insight to the interactions between MTAN and bound ligands that promote closing of the enzyme active site and highlights the potential for designing new classes of MTAN inhibitors using a link/grow or ligand assembly development strategy based on the described H. pylori MTAN crystal structures.

  7. Olivine Weathering: Abiotic Versus Biotic Processes as Possible Biosignatures

    NASA Technical Reports Server (NTRS)

    Longazo, T. G.; Wentworth, S. J.; McKay, D. S.; Southam, G.; Clemett, S. J.

    2001-01-01

    A preliminary study to determine how abiotic versus biotic processes affect the weathering of olivine crystals. Perhaps the differences between these weathering processes could be used as biosignatures. Additional information is contained in the original extended abstract.

  8. Multi-trophic interactions driving the transmission cycle of Borrelia afzelii between Ixodes ricinus and rodents: a review.

    PubMed

    van Duijvendijk, Gilian; Sprong, Hein; Takken, Willem

    2015-01-01

    The tick Ixodes ricinus is the main vector of the spirochaete Borrelia burgdorferi sensu lato, the causal agent of Lyme borreliosis, in the western Palearctic. Rodents are the reservoir host of B. afzelii, which can be transmitted to I. ricinus larvae during a blood meal. The infected engorged larvae moult into infected nymphs, which can transmit the spirochaetes to rodents and humans. Interestingly, even though only about 1% of the larvae develop into a borreliae-infected nymph, the enzootic borreliae lifecycle can persist. The development from larva to infected nymph is a key aspect in this lifecycle, influencing the density of infected nymphs and thereby Lyme borreliosis risk. The density of infected nymphs varies temporally and geographically and is influenced by multi-trophic (tick-host-borreliae) interactions. For example, blood feeding success of ticks and spirochaete transmission success differ between rodent species and host-finding success appears to be affected by a B. afzelii infection in both the rodent and the tick. In this paper, we review the major interactions between I. ricinus, rodents and B. afzelii that influence this development, with the aim to elucidate the critical factors that determine the epidemiological risk of Lyme borreliosis. The effects of the tick, rodent and B. afzelii on larval host finding, larval blood feeding, spirochaete transmission from rodent to larva and development from larva to nymph are discussed. Nymphal host finding, nymphal blood feeding and spirochaete transmission from nymph to rodent are the final steps to complete the enzootic B. afzelii lifecycle and are included in the review. It is concluded that rodent density, rodent infection prevalence, and tick burden are the major factors affecting the development from larva to infected nymph and that these interact with each other. We suggest that the B. afzelii lifecycle is dependent on the aggregation of ticks among rodents, which is manipulated by the pathogen

  9. Soil fertility and disturbance interact to drive contrasting responses of co-occurring native and nonnative species.

    PubMed

    Peltzer, Duane A; Kurokawa, Hiroko; Wardle, David A

    2016-02-01

    Some plant functional groups such as nonnative invasive and nitrogen (N)-fixing plants are widely thought to have consistent, coordinated differences in their functional traits relative to other groups such as native and non -N-fixing plants. Recent evidence suggests that these trait differences between groups can be context dependent, varying with environmental factors such as resource availability and disturbance. However, many previous comparisons among plant groups differing in invasion status have not standardized growth form between groups or have compared species that do not co-occur, which could result in invasion status per se being confounded with other factors. We determined growth and leaf functional trait responses of 20 co-occurring woody species, that is, five species within each of four functional groups (native N-fixers, native non -N-fixers, nonnative [invasive] N-fixers and nonnative [invasive] non-N-fixers), to factorial combinations of soil fertility and defoliation treatments in a mesocosm experiment to test each of two hypotheses. First, we hypothesized that nonnative invasive and N-fixing species will have functional traits associated with rapid resource acquisition whereas natives and non -N-fixing species will have traits linked to resource conservation. Second, we hypothesized that plant growth and leaf traits of nonnative and N-fixing species will be more strongly influenced by environmental factors (i.e., soil fertility and disturbance) than will natives and non-N-fixers. Plant growth, foliar nutrients, and leaf structural traits varied among plant functional groups in a manner consistent with our first hypothesis. Support for our second hypothesis was mixed; origin (native vs. nonnative) and soil fertility rarely interacted to determine plant growth or variation in leaf traits whereas interactions involving N-fixing ability and soil fertility were common. Further, there were no consistent interactive effects between plant groupings and

  10. Interactions of aromatic heterocycles with water: the driving force from free-jet rotational spectroscopy and model electrostatic calculations.

    PubMed

    Maris, Assimo; Melandri, Sonia; Miazzi, Marta; Zerbetto, Francesco

    2008-06-23

    The interaction of isolated aromatic nitrogen atoms with water is explored within free jets by using rotational spectroscopy. To the existing data on diazines, we add the case of the 1:1 complex of 1,3,5-triazine and water (where water donates a proton to one of the nitrogen heterocyclic atoms to form a planar adduct). An electrostatic model based on distributed multipoles accurately reproduces the structures of the four azine-water complexes and allows us to understand the forces that stabilize these structures. The applied intermolecular potential allows us to estimate the changes in the thermodynamic functions of the complexes-compared to the separated constituents-and evaluate the temperature at which the complexes are stable under standard conditions. PMID:18470857

  11. Distracted Driving

    MedlinePlus

    ... combines all three types of distraction. 3 How big is the problem? Deaths In 2013, 3,154 ... European countries. More A CDC study analyzed 2011 data on distracted driving, including talking on a cell ...

  12. Distracted driving

    MedlinePlus

    ... stay safe with a cell phone in the car. ... for Disease Control and Prevention Injury Prevention & Control. Motor Vehicle Safety. www.cdc.gov/motorvehiclesafety/distracted_driving . Accessed May ...

  13. Driving Safely

    MedlinePlus

    ... drivers’ flexibility and coordination, and reduced driving errors. S l Hand grip strengthening to help you hold on to the steering wheel l Shoulder and upper arm flexibility exercises to make ...

  14. Actin Interacting Protein1 and Actin Depolymerizing Factor Drive Rapid Actin Dynamics in Physcomitrella patens[W

    PubMed Central

    Augustine, Robert C.; Pattavina, Kelli A.; Tüzel, Erkan; Vidali, Luis; Bezanilla, Magdalena

    2011-01-01

    The remodeling of actin networks is required for a variety of cellular processes in eukaryotes. In plants, several actin binding proteins have been implicated in remodeling cortical actin filaments (F-actin). However, the extent to which these proteins support F-actin dynamics in planta has not been tested. Using reverse genetics, complementation analyses, and cell biological approaches, we assessed the in vivo function of two actin turnover proteins: actin interacting protein1 (AIP1) and actin depolymerizing factor (ADF). We report that AIP1 is a single-copy gene in the moss Physcomitrella patens. AIP1 knockout plants are viable but have reduced expansion of tip-growing cells. AIP1 is diffusely cytosolic and functions in a common genetic pathway with ADF to promote tip growth. Specifically, ADF can partially compensate for loss of AIP1, and AIP1 requires ADF for function. Consistent with a role in actin remodeling, AIP1 knockout lines accumulate F-actin bundles, have fewer dynamic ends, and have reduced severing frequency. Importantly, we demonstrate that AIP1 promotes and ADF is essential for cortical F-actin dynamics. PMID:22003077

  15. Cascading life-history interactions: alternative density-dependent pathways drive recruitment dynamics in a freshwater fish.

    PubMed

    Vandenbos, Rena E; Tonn, William M; Boss, Shelly M

    2006-07-01

    Although density-dependent mechanisms in early life-history are important regulators of recruitment in many taxa, consequences of such mechanisms on other life-history stages are poorly understood. To examine interacting and cascading effects of mechanisms acting on different life-history stages, we stocked experimental ponds with fathead minnow (Pimephales promelas) at two different densities. We quantified growth and survival of the stocked fish, the eggs they produced, and the resulting offspring during their first season of life. Per-capita production and survival of eggs were inversely related to density of stocked fish; significant egg cannibalism by stocked minnows resulted in initial young-of-the-year (YOY) densities that were inversely related to adult densities. Subsequent growth and survival of YOY were then inversely related to these initial YOY densities, and survival of YOY was selective for larger fish. Because of these compensatory processes in the egg and YOY stages, treatments did not differ in YOY abundance and mean size at the end of the growing season. Because of differences in the intensity of size-selective mortality, however, variation in end-of season sizes of YOY was strongly (and inversely) related to densities of stocked fish. When mortality was severe in the egg stage (high densities of stocked fish), final YOY size distributions were more variable than when the dominant mortality was size-selective in the YOY stage (low stocked fish densities). These differences in size variation could have subsequent recruitment consequences, as overwinter survival is typically selective for YOY fish larger than a critical threshold size. Density-dependent effects on a given life stage are not independent, but will be influenced by earlier stages; alternative recruitment pathways can result when processes at earlier stages differ in magnitude or selectivity. Appreciation of these cascading effects should enhance our overall understanding of the

  16. Function of ABA in Stomatal Defense against Biotic and Drought Stresses

    PubMed Central

    Lim, Chae Woo; Baek, Woonhee; Jung, Jangho; Kim, Jung-Hyun; Lee, Sung Chul

    2015-01-01

    The plant hormone abscisic acid (ABA) regulates many key processes involved in plant development and adaptation to biotic and abiotic stresses. Under stress conditions, plants synthesize ABA in various organs and initiate defense mechanisms, such as the regulation of stomatal aperture and expression of defense-related genes conferring resistance to environmental stresses. The regulation of stomatal opening and closure is important to pathogen defense and control of transpirational water loss. Recent studies using a combination of approaches, including genetics, physiology, and molecular biology, have contributed considerably to our understanding of ABA signal transduction. A number of proteins associated with ABA signaling and responses—especially ABA receptors—have been identified. ABA signal transduction initiates signal perception by ABA receptors and transfer via downstream proteins, including protein kinases and phosphatases. In the present review, we focus on the function of ABA in stomatal defense against biotic and abiotic stresses, through analysis of each ABA signal component and the relationships of these components in the complex network of interactions. In particular, two ABA signal pathway models in response to biotic and abiotic stress were proposed, from stress signaling to stomatal closure, involving the pyrabactin resistance (PYR)/PYR-like (PYL) or regulatory component of ABA receptor (RCAR) family proteins, 2C-type protein phosphatases, and SnRK2-type protein kinases. PMID:26154766

  17. Function of ABA in Stomatal Defense against Biotic and Drought Stresses.

    PubMed

    Lim, Chae Woo; Baek, Woonhee; Jung, Jangho; Kim, Jung-Hyun; Lee, Sung Chul

    2015-01-01

    The plant hormone abscisic acid (ABA) regulates many key processes involved in plant development and adaptation to biotic and abiotic stresses. Under stress conditions, plants synthesize ABA in various organs and initiate defense mechanisms, such as the regulation of stomatal aperture and expression of defense-related genes conferring resistance to environmental stresses. The regulation of stomatal opening and closure is important to pathogen defense and control of transpirational water loss. Recent studies using a combination of approaches, including genetics, physiology, and molecular biology, have contributed considerably to our understanding of ABA signal transduction. A number of proteins associated with ABA signaling and responses--especially ABA receptors--have been identified. ABA signal transduction initiates signal perception by ABA receptors and transfer via downstream proteins, including protein kinases and phosphatases. In the present review, we focus on the function of ABA in stomatal defense against biotic and abiotic stresses, through analysis of each ABA signal component and the relationships of these components in the complex network of interactions. In particular, two ABA signal pathway models in response to biotic and abiotic stress were proposed, from stress signaling to stomatal closure, involving the pyrabactin resistance (PYR)/PYR-like (PYL) or regulatory component of ABA receptor (RCAR) family proteins, 2C-type protein phosphatases, and SnRK2-type protein kinases. PMID:26154766

  18. Pivoting from Arabidopsis to wheat to understand how agricultural plants integrate responses to biotic stress.

    PubMed

    Harris, M O; Friesen, T L; Xu, S S; Chen, M S; Giron, D; Stuart, J J

    2015-02-01

    In this review, we argue for a research initiative on wheat's responses to biotic stress. One goal is to begin a conversation between the disparate communities of plant pathology and entomology. Another is to understand how responses to a variety of agents of biotic stress are integrated in an important crop. We propose gene-for-gene interactions as the focus of the research initiative. On the parasite's side is an Avirulence (Avr) gene that encodes one of the many effector proteins the parasite applies to the plant to assist with colonization. On the plant's side is a Resistance (R) gene that mediates a surveillance system that detects the Avr protein directly or indirectly and triggers effector-triggered plant immunity. Even though arthropods are responsible for a significant proportion of plant biotic stress, they have not been integrated into important models of plant immunity that come from plant pathology. A roadblock has been the absence of molecular evidence for arthropod Avr effectors. Thirty years after this evidence was discovered in a plant pathogen, there is now evidence for arthropods with the cloning of the Hessian fly's vH13 Avr gene. After reviewing the two models of plant immunity, we discuss how arthropods could be incorporated. We end by showing features that make wheat an interesting system for plant immunity, including 479 resistance genes known from agriculture that target viruses, bacteria, fungi, nematodes, insects, and mites. It is not likely that humans will be subsisting on Arabidopsis in the year 2050. It is time to start understanding how agricultural plants integrate responses to biotic stress. PMID:25504642

  19. Relative Importance of Biotic and Abiotic Soil Components to Plant Growth and Insect Herbivore Population Dynamics

    PubMed Central

    Vandegehuchte, Martijn L.; de la Peña, Eduardo; Bonte, Dries

    2010-01-01

    Background Plants are affected by several aspects of the soil, which have the potential to exert cascading effects on the performance of herbivorous insects. The effects of biotic and abiotic soil characteristics have however mostly been investigated in isolation, leaving their relative importance largely unexplored. Such is the case for the dune grass Ammophila, whose decline under decreasing sand accretion is argued to be caused by either biotic or abiotic soil properties. Methodology/Principal Findings By manipulating dune soils from three different regions, we decoupled the contributions of region, the abiotic and biotic soil component to the variation in characteristics of Ammophila arenaria seedlings and Schizaphis rufula aphid populations. Root mass fraction and total dry biomass of plants were affected by soil biota, although the latter effect was not consistent across regions. None of the measured plant properties were significantly affected by the abiotic soil component. Aphid population characteristics all differed between regions, irrespective of whether soil biota were present or absent. Hence these effects were due to differences in abiotic soil properties between regions. Although several chemical properties of the soil mixtures were measured, none of these were consistent with results for plant or aphid traits. Conclusions/Significance Plants were affected more strongly by soil biota than by abiotic soil properties, whereas the opposite was true for aphids. Our results thus demonstrate that the relative importance of the abiotic and biotic component of soils can differ for plants and their herbivores. The fact that not all effects of soil properties could be detected across regions moreover emphasizes the need for spatial replication in order to make sound conclusions about the generality of aboveground-belowground interactions. PMID:20886078

  20. Large-scale mass transfers related to pressure solution creep-faulting interactions in mudstones: Driving processes and impact of lithification degree

    NASA Astrophysics Data System (ADS)

    Richard, J.

    2014-02-01

    Where normal faulting is associated with PSC (Pressure Solution Creep), it generates evolutions in petrophysical properties of mudstones like chalk: decrease in reservoir qualities and transport properties in the deformed zones adjacent to the fault plane and increase (or no change) in reservoir qualities and transport properties in the outermost deformed zones. These modifications result from large-scale mass transfers linked to a transport of solutes through the pore space over distances of several grains within decimeter or larger zones (open systems at the grain scale). In the lithified mudstones, these large-scale mass transfers consist in a mass redistribution from the outermost deformed zones (mass and volume loss) to the deformed zones adjacent to the fault planes (mass gain). In the weakly lithified mudstones, the mass redistribution occurs in an opposite direction. A deeper understanding of these large-scale mass redistributions is essential because the PSC-faulting interactions and the associated petrophysical modifications can be a key topic in several geological applications (oil and gas migration and entrapment in mudstone reservoirs, anthropogenic waste storage, carbon dioxyde geosequestration). The results of two studies about mass transfers and volume changes induced by natural fault systems in “white chalk” allowed to point out that two driving processes control the large-scale mass transfers during PSC-faulting interactions: the advective mass transport related to pore fluid flows and the large-scale diffusive mass transport linked to chemical potential gradients. The present contribution also highlights that the lithification degree of the host material plays a key role in the large-scale mass transfers related to PSC-faulting interactions by controlling (1) the spatial distribution of voids induced by the deformation, (2) the particle displacement on the fault plane and in the adjacent zones and (3) the petrophysical properties of the host

  1. Coupled biotic-abiotic oxidation of organic matter by biogenic MnO_{2}

    NASA Astrophysics Data System (ADS)

    Gonzalez, Julia; Peña, Jasquelin

    2016-04-01

    Some reactive soil minerals are strongly implicated in stabilising organic matter. However, others can play an active role in the oxidation of organic molecules. In natural systems, layer-type manganese oxide minerals (MnO2) typically occur as biomineral assemblages consisting of mineral particles and microbial biomass. Both the mineral and biological fractions of the assemblage can be powerful oxidants of organic C. The biological compartment relies on a set of enzymes to drive oxidative transformations of reduced C-substrates, whereas MnO2 minerals are strong, less specific abiotic oxidants that are assumed to rely on interfacial interactions between C-substrates and the mineral surface. This project aims to understand the coupling between microbial C mineralization and abiotic C oxidation mediated by MnO2 in bacterial-MnO2 assemblages. Specifically, under conditions of high C turnover, microbial respiration can significantly alter local pH, dissolved oxygen and pool of available reductants, which may modify rates and mechanism of C oxidation by biotic and abiotic components. We first investigated changes in the solution chemistry of Pseudomonas putida suspensions exposed to varying concentrations of glucose, chosen to represent readily bioavailable substrates in soils. Glucose concentrations tested ranged between 0 and 5.5mM and changes in pH, dissolved oxygen and dissolved organic and inorganic carbon were tracked over 48h. We then combined literature review and wet-chemical experiments to compile the pH dependence of rates of organic substrate oxidation by MnO2, including glucose. Our results demonstrate a strong pH dependence for these abiotic reactions. In assemblages of P. putida - MnO2, kinetic limitations for abiotic C oxidation by MnO2 are overcome by changes in biogeochemical conditions that result from bacterial C metabolism. When extrapolated to a soil solution confronted to an input of fresh dissolved organic matter, bacterial C metabolism of the

  2. The abiotic and biotic drivers of rapid diversification in Andean bellflowers (Campanulaceae).

    PubMed

    Lagomarsino, Laura P; Condamine, Fabien L; Antonelli, Alexandre; Mulch, Andreas; Davis, Charles C

    2016-06-01

    The tropical Andes of South America, the world's richest biodiversity hotspot, are home to many rapid radiations. While geological, climatic, and ecological processes collectively explain such radiations, their relative contributions are seldom examined within a single clade. We explore the contribution of these factors by applying a series of diversification models that incorporate mountain building, climate change, and trait evolution to the first dated phylogeny of Andean bellflowers (Campanulaceae: Lobelioideae). Our framework is novel for its direct incorporation of geological data on Andean uplift into a macroevolutionary model. We show that speciation and extinction are differentially influenced by abiotic factors: speciation rates rose concurrently with Andean elevation, while extinction rates decreased during global cooling. Pollination syndrome and fruit type, both biotic traits known to facilitate mutualisms, played an additional role in driving diversification. These abiotic and biotic factors resulted in one of the fastest radiations reported to date: the centropogonids, whose 550 species arose in the last 5 million yr. Our study represents a significant advance in our understanding of plant evolution in Andean cloud forests. It further highlights the power of combining phylogenetic and Earth science models to explore the interplay of geology, climate, and ecology in generating the world's biodiversity. PMID:26990796

  3. Biotic Nitrogen Enrichment Regulates Calcium Sources to Forests

    NASA Astrophysics Data System (ADS)

    Pett-Ridge, J. C.; Perakis, S. S.; Hynicka, J. D.

    2015-12-01

    Calcium is an essential nutrient in forest ecosystems that is susceptible to leaching loss and depletion. Calcium depletion can affect plant and animal productivity, soil acid buffering capacity, and fluxes of carbon and water. Excess nitrogen supply and associated soil acidification are often implicated in short-term calcium loss from soils, but the long-term role of nitrogen enrichment on calcium sources and resupply is unknown. Here we use strontium isotopes (87Sr/86Sr) as a proxy for calcium to investigate how soil nitrogen enrichment from biological nitrogen fixation interacts with bedrock calcium to regulate both short-term available supplies and the long-term sources of calcium in montane conifer forests. Our study examines 22 sites in western Oregon, spanning a 20-fold range of bedrock calcium on sedimentary and basaltic lithologies. In contrast to previous studies emphasizing abiotic control of weathering as a determinant of long-term ecosystem calcium dynamics and sources (via bedrock fertility, climate, or topographic/tectonic controls) we find instead that that biotic nitrogen enrichment of soil can strongly regulate calcium sources and supplies in forest ecosystems. For forests on calcium-rich basaltic bedrock, increasing nitrogen enrichment causes calcium sources to shift from rock-weathering to atmospheric dominance, with minimal influence from other major soil forming factors, despite regionally high rates of tectonic uplift and erosion that can rejuvenate weathering supply of soil minerals. For forests on calcium-poor sedimentary bedrock, we find that atmospheric inputs dominate regardless of degree of nitrogen enrichment. Short-term measures of soil and ecosystem calcium fertility are decoupled from calcium source sustainability, with fundamental implications for understanding nitrogen impacts, both in natural ecosystems and in the context of global change. Our finding that long-term nitrogen enrichment increases forest reliance on atmospheric

  4. Biotic versus geomorphic control of landscape soil carbon accumulation

    NASA Astrophysics Data System (ADS)

    Van Hemelryck, Hendrik; Govers, Gerard; Van Oost, Kristof

    2013-04-01

    Soil organic matter (SOM) is the largest terrestrial pool of carbon. In order to assess the impact of increasing human-induced land use changes and future climate on this huge reservoir, it is important to understand the complex process of carbon cycling at different temporal and spatial scales. A key challenge in this effort is the correct representation in global assessments and models of those processes that vary strongly over small scales and are strongly affected by the spatial distribution of carbon stocks (both horizontally and vertically) within the landscape. Many studies have shown that spatial variation of SOC storage at the landscape scale is related to topography as a result of either the redistribution of soil or spatial variation in biological C fluxes (input and decomposition). The objective of this study, is to assess the relative importance of biotic versus geomorphic controls in determining SOC patterns and their potential interactions. Therefore the relationships between topography on the one hand and SOC and carbon isotopes on the other hand, were quantified along an erosional gradient. For this purpose, a grassland area and two agricultural fields with a different management regime (conventional tillage, reduced tillage) were selected. All field sites have a similar topography but are characterized by different rates of soil redistribution, related to management regime. Our results show clearly that for temperate climate regions without moisture/nutrient deficit, soil redistribution is the main driver for spatial variations in SOC, dwarfing any biological effects. From the results, the impact of soil redistribution on carbon dynamics by the continued maintenance of a disequilibrium between carbon in-and output at different landscape positions is reconstructed and we discuss the implications for C sequestration processes.

  5. Forces Driving Chaperone Action.

    PubMed

    Koldewey, Philipp; Stull, Frederick; Horowitz, Scott; Martin, Raoul; Bardwell, James C A

    2016-07-14

    It is still unclear what molecular forces drive chaperone-mediated protein folding. Here, we obtain a detailed mechanistic understanding of the forces that dictate the four key steps of chaperone-client interaction: initial binding, complex stabilization, folding, and release. Contrary to the common belief that chaperones recognize unfolding intermediates by their hydrophobic nature, we discover that the model chaperone Spy uses long-range electrostatic interactions to rapidly bind to its unfolded client protein Im7. Short-range hydrophobic interactions follow, which serve to stabilize the complex. Hydrophobic collapse of the client protein then drives its folding. By burying hydrophobic residues in its core, the client's affinity to Spy decreases, which causes client release. By allowing the client to fold itself, Spy circumvents the need for client-specific folding instructions. This mechanism might help explain how chaperones can facilitate the folding of various unrelated proteins. PMID:27293188

  6. Daphnia response to biotic stress is modified by PCBs.

    PubMed

    Bernatowicz, Piotr; Pijanowska, Joanna

    2011-05-01

    The aim of this study was to examine the influence of xenobiotics (PCBs) on the responses of Daphnia to biotic factors such as the presence of a predator (fish kairomone) or filamentous cyanobacteria. Both behaviour (depth selection) and life history (body size at first reproduction and fecundity) were affected by these stressors. Though there was no direct effect of PCBs, their influence resulted in disruption of the "natural" reaction to the presence of fish or cyanobacteria, leading to inadequate responses of Daphnia to these biotic threats. Examined clones of Daphnia showed significant diversity in their reaction to these stress factors, which was greater than that between Daphnia clones exposed to different environmental conditions. PCB pollution may change the frequency of Daphnia clones in favour of those whose responses to biotic stress are similar in both the absence and presence of these toxic chemicals. PMID:21095006

  7. Effect of Temperature on the Biotic Potential of Honeybee Microsporidia▿

    PubMed Central

    Martín-Hernández, Raquel; Meana, Aránzazu; García-Palencia, Pilar; Marín, Pilar; Botías, Cristina; Garrido-Bailón, Encarna; Barrios, Laura; Higes, Mariano

    2009-01-01

    The biological cycle of Nosema spp. in honeybees depends on temperature. When expressed as total spore counts per day after infection, the biotic potentials of Nosema apis and N. ceranae at 33°C were similar, but a higher proportion of immature stages of N. ceranae than of N. apis were seen. At 25 and 37°C, the biotic potential of N. ceranae was higher than that of N. apis. The better adaptation of N. ceranae to complete its endogenous cycle at different temperatures clearly supports the observation of the different epidemiological patterns. PMID:19233948

  8. BIOTIC FACTORS IN AMPHIBIAN POPULATION DECLINES

    EPA Science Inventory

    Amphibians evolved in, and continue to exist in, habitats that are replete with many other organisms. Some of these organisms serve as prey for amphibians and others interact with amphibians as predators, competitors, pathogens, or symbionts. Still other organisms in their enviro...

  9. Elucidating biotic factors that influence assembly of fungal endophyte communities

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Most plants harbor a diverse assemblage of non-mycorrhizal fungal endophytes. These fungi can directly influence the host plant, and can instigate trophic cascades that affect surrounding communities of herbivores, plants, and animals. Despite this, biotic mechanisms that influence assembly of funga...

  10. River Quality Investigations, Part 1: Some Diversity and Biotic Indices.

    ERIC Educational Resources Information Center

    Hewitt, G.

    1991-01-01

    The following indices for assessing river water quality are described: Shannon-Weiner Diversity Index, Sorenson Quotient of Similarity, Czekanowski's Index of Similarity, Trent Biotic Index, Chandler Score, and Biological Monitoring Working Party Score. Their advantages and disadvantages are outlined. (Author)

  11. Weighing Abiotic and Biotic Influences on Weed Seed Predation Rates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Weed seed predation is an important ecosystem service supporting weed management in low-external-input agroecosystems. Current knowledge of weed seed predation focuses on biotic mechanisms, with less understood about the relative impact of abiotic variables. In order to quantify relative contributio...

  12. Weighing Abiotic and Biotic Influences on Weed Seed Predation Rates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Weed seed predation is an important ecosystem service supporting weed management in low-external-input agroecosystems. Current knowledge of weed seed predation in arable systems focuses on biotic mechanisms, with less understood about the relative impact of abiotic variables on this process. In orde...

  13. Biotic Communities. [Project ECOLogy ELE Pak, Amoe-Thorson Pak].

    ERIC Educational Resources Information Center

    Amoe, Ruth; Thorson, Michael

    This is one of a series of units for environmental education developed by the Highline Public Schools. This unit provides a number of activities to introduce students to ways of studying biotic communities, help them become good observers, and provide them with opportunities to use their skills. The materials include suggested activities, and…

  14. The floodplain large-wood cycle hypothesis: A mechanism for the physical and biotic structuring of temperate forested alluvial valleys in the North Pacific coastal ecoregion

    NASA Astrophysics Data System (ADS)

    Collins, Brian D.; Montgomery, David R.; Fetherston, Kevin L.; Abbe, Tim B.

    2012-02-01

    A 'floodplain large-wood cycle' is hypothesized as a mechanism for generating landforms and influencing river dynamics in ways that structure and maintain riparian and aquatic ecosystems of forested alluvial river valleys of the Pacific coastal temperate rainforest of North America. In the cycle, pieces of wood large enough to resist fluvial transport and remain in river channels initiate and stabilize wood jams, which in turn create alluvial patches and protect them from erosion. These stable patches provide sites for trees to mature over hundreds of years in river valleys where the average cycle of floodplain turnover is much briefer, thus providing a future source of large wood and reinforcing the cycle. Different tree species can function in the floodplain large-wood cycle in different ecological regions, in different river valleys within regions, and within individual river valleys in which forest composition changes through time. The cycle promotes a physically complex, biodiverse, and self-reinforcing state. Conversely, loss of large trees from the system drives landforms and ecosystems toward an alternate stable state of diminished biogeomorphic complexity. Reestablishing large trees is thus necessary to restore such rivers. Although interactions and mechanisms may differ between biomes and in larger or smaller rivers, available evidence suggests that large riparian trees may have similarly fundamental roles in the physical and biotic structuring of river valleys elsewhere in the temperate zone.

  15. Interactions between seasonality and oceanic forcing drive the phytoplankton variability in the tropical-temperate transition zone (~ 30°S) of Eastern Australia

    NASA Astrophysics Data System (ADS)

    Armbrecht, Linda H.; Schaeffer, Amandine; Roughan, Moninya; Armand, Leanne K.

    2015-04-01

    The East Australian Current (EAC) has been shown to be warming rapidly, which is expected to cause latitudinal shifts in phytoplankton abundance, distribution and composition along the east Australian coast. Yet a lack of phytoplankton information exists northward of 34°S. Here, we provide the first detailed taxonomic time-series survey (monthly sampling for about one annual cycle, 2011-2012) in the east Australian tropical-temperate transition zone (~ 30°S, upstream of the EAC separation point at ~ 31-32°S). All phytoplankton (categorised depending on their association with specific water-types) show a seasonal signal with abundance maxima (minima) during summer (winter). This seasonal signal is most pronounced in the seasonal/bloom category and least expressed by deep-water taxa, which prefer cold, saline and dense bottom water independent of the season. Different extents of EAC encroachment onto the continental shelf drive the cross-shelf phytoplankton composition and distribution, such that a weak EAC is associated with phytoplankton community being organised along 'depth' and 'distance from the coast' gradients with high phytoplankton abundances inshore. A strong EAC favours the occurrence of warm-water taxa offshore and an increase in diatom abundance on the mid-shelf (53% shelf width). We conclude that the phytoplankton community in the tropical-temperate transition zone of Eastern Australia is driven by an interaction of intrinsic seasonal cycles and primarily EAC-driven oceanic forcing. Our findings benefit studies located in Western Boundary Current systems worldwide, in which warming and strengthening of these currents are predicted to severely impact phytoplankton dynamics.

  16. Does prescribed burning result in biotic homogenization of coastal heathlands?

    PubMed

    Velle, Liv Guri; Nilsen, Liv Sigrid; Norderhaug, Ann; Vandvik, Vigdis

    2014-05-01

    Biotic homogenization due to replacement of native biodiversity by widespread generalist species has been demonstrated in a number of ecosystems and taxonomic groups worldwide, causing growing conservation concern. Human disturbance is a key driver of biotic homogenization, suggesting potential conservation challenges in seminatural ecosystems, where anthropogenic disturbances such as grazing and burning are necessary for maintaining ecological dynamics and functioning. We test whether prescribed burning results in biotic homogenization in the coastal heathlands of north-western Europe, a seminatural landscape where extensive grazing and burning has constituted the traditional land-use practice over the past 6000 years. We compare the beta-diversity before and after fire at three ecological scales: within local vegetation patches, between wet and dry heathland patches within landscapes, and along a 470 km bioclimatic gradient. Within local patches, we found no evidence of homogenization after fire; species richness increased, and the species that entered the burnt Calluna stands were not widespread specialists but native grasses and herbs characteristic of the heathland system. At the landscapes scale, we saw a weak homogenization as wet and dry heathland patches become more compositionally similar after fire. This was because of a decrease in habitat-specific species unique to either wet or dry habitats and postfire colonization by a set of heathland specialists that established in both habitat types. Along the bioclimatic gradient, species that increased after fire generally had more specific environmental requirements and narrower geographical distributions than the prefire flora, resulting in a biotic 'heterogenisation' after fire. Our study demonstrates that human disturbance does not necessarily cause biotic homogenization, but that continuation of traditional land-use practices can instead be crucial for the maintenance of the diversity and ecological

  17. Toward a mechanistic understanding and prediction of biotic homogenization.

    PubMed

    Olden, Julian D; Poff, N LeRoy

    2003-10-01

    The widespread replacement of native species with cosmopolitan, nonnative species is homogenizing the global fauna and flora. While the empirical study of biotic homogenization is substantial and growing, theoretical aspects have yet to be explored. Consequently, the breadth of possible ecological mechanisms that can shape current and future patterns and rates of homogenization remain largely unknown. Here, we develop a conceptual model that describes 14 potential scenarios by which species invasions and/or extinctions can lead to various trajectories of biotic homogenization (increased community similarity) or differentiation (decreased community similarity); we then use a simulation approach to explore the model's predictions. We found changes in community similarity to vary with the type and number of nonnative and native species, the historical degree of similarity among the communities, and, to a lesser degree, the richness of the recipient communities. Homogenization is greatest when similar species invade communities, causing either no extinction or differential extinction of native species. The model predictions are consistent with current empirical data for fish, bird, and plant communities and therefore may represent the dominant mechanisms of contemporary homogenization. We present a unifying model illustrating how the balance between invading and extinct species dictates the outcome of biotic homogenization. We conclude by discussing a number of critical but largely unrecognized issues that bear on the empirical study of biotic homogenization, including the importance of spatial scale, temporal scale, and data resolution. We argue that the study of biotic homogenization needs to be placed in a more mechanistic and predictive framework in order for studies to provide adequate guidance in conservation efforts to maintain regional distinctness of the global biota. PMID:14582007

  18. Biotic resistance to invasion along an estuarine gradient

    PubMed Central

    Hovel, Kevin A.

    2010-01-01

    Biotic resistance is the ability of native communities to repel the establishment of invasive species. Predation by native species may confer biotic resistance to communities, but the environmental context under which this form of biotic resistance occurs is not well understood. We evaluated several factors that influence the distribution of invasive Asian mussels (Musculista senhousia) in Mission Bay, a southern California estuary containing an extensive eelgrass (Zostera marina) habitat. Asian mussels exhibit a distinct spatial pattern of invasion, with extremely high densities towards the back of Mission Bay (up to 4,000 m−2) in contrast with near-complete absence at sites towards the front of the bay. We established that recruits arrived at sites where adult mussels were absent and found that dense eelgrass does not appear to preclude Asian mussel growth and survival. Mussel survival and growth were high in predator-exclusion plots throughout the bay, but mussel survival was low in the front of the bay when plots were open to predators. Additional experiments revealed that consumption by spiny lobsters (Panulirus interruptus) and a gastropod (Pteropurpura festiva) likely are the primary factors responsible for resistance to Asian mussel invasion. However, biotic resistance was dependent on location within the estuary (for both species) and also on the availability of a hard substratum (for P. festiva). Our findings indicate that biotic resistance in the form of predation may be conferred by higher order predators, but that the strength of resistance may strongly vary across estuarine gradients and depend on the nature of the locally available habitat. Electronic supplementary material The online version of this article (doi:10.1007/s00442-010-1700-7) contains supplementary material, which is available to authorized users. PMID:20602118

  19. A direct-gradient multivariate index of biotic condition

    USGS Publications Warehouse

    Miranda, Leandro E.; Aycock, J.N.; Killgore, K. J.

    2012-01-01

    Multimetric indexes constructed by summing metric scores have been criticized despite many of their merits. A leading criticism is the potential for investigator bias involved in metric selection and scoring. Often there is a large number of competing metrics equally well correlated with environmental stressors, requiring a judgment call by the investigator to select the most suitable metrics to include in the index and how to score them. Data-driven procedures for multimetric index formulation published during the last decade have reduced this limitation, yet apprehension remains. Multivariate approaches that select metrics with statistical algorithms may reduce the level of investigator bias and alleviate a weakness of multimetric indexes. We investigated the suitability of a direct-gradient multivariate procedure to derive an index of biotic condition for fish assemblages in oxbow lakes in the Lower Mississippi Alluvial Valley. Although this multivariate procedure also requires that the investigator identify a set of suitable metrics potentially associated with a set of environmental stressors, it is different from multimetric procedures because it limits investigator judgment in selecting a subset of biotic metrics to include in the index and because it produces metric weights suitable for computation of index scores. The procedure, applied to a sample of 35 competing biotic metrics measured at 50 oxbow lakes distributed over a wide geographical region in the Lower Mississippi Alluvial Valley, selected 11 metrics that adequately indexed the biotic condition of five test lakes. Because the multivariate index includes only metrics that explain the maximum variability in the stressor variables rather than a balanced set of metrics chosen to reflect various fish assemblage attributes, it is fundamentally different from multimetric indexes of biotic integrity with advantages and disadvantages. As such, it provides an alternative to multimetric procedures.

  20. Biogeomorphology of a Mojave Desert landscape - Configurations and feedbacks of abiotic and biotic land surfaces during landform evolution

    NASA Astrophysics Data System (ADS)

    Pietrasiak, Nicole; Drenovsky, Rebecca E.; Santiago, Louis S.; Graham, Robert C.

    2014-02-01

    Terrestrial ecosystems can be more holistically understood by investigating the morphology of landscape mosaics, the assemblage of their ecological communities, and the linkages and feedbacks between the mosaics and communities. The overarching objectives of this study were to: (1) study the abiotic and biotic configurations of landform units as mosaics within a Mojave Desert chronosequence; and (2) elucidate their potential feedbacks, interactions, and dynamics during landform evolution. Seven landform units distributed over three geomorphic ages were identified, including: young bars and swales; intermediate-aged flattened bars, flattened swales, and bioturbation units; and old desert pavements and shrub zones. These landform units were characterized according to abiotic and biotic land surface properties. Landform units were statistically distinct and predictable based on a specific suite of abiotic and biotic properties. Vascular plant functional group and biological soil crust community diversity varied with geomorphology, with greatest diversity associated with bars and shrub zones and lowest diversity associated with desert pavements. Biological soil crust communities were controlled by geomorphic age, surface rock size, and protruding rocks with young bar units having the highest abundance and diversity. Perennial forbs were observed in old shrub zones with small rocks and few protruding rocks. A high clast density and a finer-sized clast distribution were found particularly in desert pavements and flattened swales, and generally inhibited biological soil crust and plant cover. Evolutionary trajectories for landforms of a lower piedmont landscape can be dominated by either abiotic and biotic landform processes. These two trajectories are distinctly different and are associated with their own unique linkages, feedbacks, and dynamics of abiotic and biotic land surface properties, producing a highly diverse desert landscape.

  1. Seed Dispersers, Seed Predators, and Browsers Act Synergistically as Biotic Filters in a Mosaic Landscape

    PubMed Central

    Zamora, Regino; Matías, Luis

    2014-01-01

    In this study, we analize the functional influence of animals on the plants they interact with in a mediterranean mountain. We hypothesise that seed dispersers, seed predators, and browsers can act as biotic filters for plant communities. We analyse the combined effects of mutualistic (seed dispersal) and antagonistic (seed predation, herbivory) animal interactions in a mosaic landscape of Mediterranean mountains, basing our results on observational and experimental field. Most of the dispersed seeds came from tree species, whereas the population of saplings was composed predominantly of zoochorous shrub species. Seed predators preferentially consumed seeds from tree species, whereas seeds from the dominant fleshy-fruited shrubs had a higher probability of escaping these predators. The same pattern was repeated among the different landscape units by browsers, since they browsed selectively and far more intensely on tree-species saplings than on the surrounding shrubs. In synthesis, our work identifies the major biotic processes that appear to be favoring a community dominated by shrubs versus trees because seed dispersers, predators, and herbivores together favored shrub dispersal and establishment versus trees. PMID:25233342

  2. Seed dispersers, seed predators, and browsers act synergistically as biotic filters in a mosaic landscape.

    PubMed

    Zamora, Regino; Matías, Luis

    2014-01-01

    In this study, we analize the functional influence of animals on the plants they interact with in a mediterranean mountain. We hypothesise that seed dispersers, seed predators, and browsers can act as biotic filters for plant communities. We analyse the combined effects of mutualistic (seed dispersal) and antagonistic (seed predation, herbivory) animal interactions in a mosaic landscape of Mediterranean mountains, basing our results on observational and experimental field. Most of the dispersed seeds came from tree species, whereas the population of saplings was composed predominantly of zoochorous shrub species. Seed predators preferentially consumed seeds from tree species, whereas seeds from the dominant fleshy-fruited shrubs had a higher probability of escaping these predators. The same pattern was repeated among the different landscape units by browsers, since they browsed selectively and far more intensely on tree-species saplings than on the surrounding shrubs. In synthesis, our work identifies the major biotic processes that appear to be favoring a community dominated by shrubs versus trees because seed dispersers, predators, and herbivores together favored shrub dispersal and establishment versus trees. PMID:25233342

  3. A biotic video game smart phone kit for formal and informal biophysics education

    NASA Astrophysics Data System (ADS)

    Kim, Honesty; Lee, Seung Ah; Riedel-Kruse, Ingmar

    2015-03-01

    Novel ways for formal and informal biophysics education are important. We present a low-cost biotic game design kit that incorporates microbial organisms into an interactive gaming experience: A 3D-printable microscope containing four LEDs controlled by a joystick enable human players to provide directional light stimuli to the motile single-celled organism Euglena gracilis. These cellular behaviors are displayed on the integrated smart phone. Real time cell-tracking couples these cells into interactive biotic video game play, i.e., the human player steers Euglena to play soccer with virtual balls and goals. The player's learning curve in mastering this fun game is intrinsically coupled to develop a deeper knowledge about Euglena's cell morphology and the biophysics of its phototactic behavior. This kit is dual educational - via construction and via play - and it provides an engaging theme for a formal biophysics devices class as well as to be presented in informal outreach activities; its low cost and open soft- and hardware should enable wide adoption.

  4. Enhancing crop resilience to combined abiotic and biotic stress through the dissection of physiological and molecular crosstalk

    PubMed Central

    Kissoudis, Christos; van de Wiel, Clemens; Visser, Richard G. F.; van der Linden, Gerard

    2014-01-01

    Plants growing in their natural habitats are often challenged simultaneously by multiple stress factors, both abiotic and biotic. Research has so far been limited to responses to individual stresses, and understanding of adaptation to combinatorial stress is limited, but indicative of non-additive interactions. Omics data analysis and functional characterization of individual genes has revealed a convergence of signaling pathways for abiotic and biotic stress adaptation. Taking into account that most data originate from imposition of individual stress factors, this review summarizes these findings in a physiological context, following the pathogenesis timeline and highlighting potential differential interactions occurring between abiotic and biotic stress signaling across the different cellular compartments and at the whole plant level. Potential effects of abiotic stress on resistance components such as extracellular receptor proteins, R-genes and systemic acquired resistance will be elaborated, as well as crosstalk at the levels of hormone, reactive oxygen species, and redox signaling. Breeding targets and strategies are proposed focusing on either manipulation and deployment of individual common regulators such as transcription factors or pyramiding of non- (negatively) interacting components such as R-genes with abiotic stress resistance genes. We propose that dissection of broad spectrum stress tolerance conferred by priming chemicals may provide an insight on stress cross regulation and additional candidate genes for improving crop performance under combined stress. Validation of the proposed strategies in lab and field experiments is a first step toward the goal of achieving tolerance to combinatorial stress in crops. PMID:24904607

  5. Biotic Processes Regulating the Carbon Balance of Desert Ecosystems

    SciTech Connect

    R. S. Nowak; J. Arnone; L. Fenstermaker; and S. D. Smith

    2005-07-26

    This project provided the funding to operate and maintain the Nevada Desert FACE Facility. This support funds the CO{sub 2}, system repairs and maintenance, basic physical and biological site information, and personnel that are essential for the experiment to continue. They have continued to assess the effects of elevated CO{sub 2} on three key processes: (1) leaf- to plant-level responses of desert vegetation to elevated atmospheric CO{sub 2}; (2) ecosystem-level responses; and (3) integration of plant and ecosystem processes to understand carbon balance of deserts. The focus is the seminal interactions among atmospheric CO{sub 2}, water, and nitrogen that drive desert responses to elevated CO{sub 2} and explicitly address processes that occur across scales (biological, spatial, and temporal).

  6. Biotic and abiotic controls of argentine ant invasion success at local and landscape scales

    USGS Publications Warehouse

    Menke, S.B.; Fisher, R.N.; Jetz, W.; Holway, D.A.

    2007-01-01

    Although the ecological success of introduced species hinges on biotic interactions and physical conditions, few experimental studies - especially on animals - have simultaneously investigated the relative importance of both types of factors. The lack of such research may stem from the common assumption that native and introduced species exhibit similar environmental tolerances. Here we combine experimental and spatial modeling approaches (1) to determine the relative importance of biotic and abiotic controls of Argentine ant (Linepithema humile) invasion success, (2) to examine how the importance of these factors changes with spatial scale in southern California (USA), and (3) to assess how Argentine ants differ from native ants in their environmental tolerances. A factorial field experiment that combined native ant removal with irrigation revealed that Argentine ants failed to invade any dry plots (even those lacking native ants) but readily invaded all moist plots. Native ants slowed the spread of Argentine ants into irrigated plots but did not prevent invasion. In areas without Argentine ants, native ant species showed variable responses to irrigation. At the landscape scale, Argentine ant occurrence was positively correlated with minimum winter temperature (but not precipitation), whereas native ant diversity increased with precipitation and was negatively correlated with minimum winter temperature. These results are of interest for several reasons. First, they demonstrate that fine-scale differences in the physical environment can eclipse biotic resistance from native competitors in determining community susceptibility to invasion. Second, our results illustrate surprising complexities with respect to how the abiotic factors limiting invasion can change with spatial scale, and third, how native and invasive species can differ in their responses to the physical environment. Idiosyncratic and scale-dependent processes complicate attempts to forecast where

  7. The nature of cumulative impacts on biotic diversity of wetland vertebrates

    NASA Astrophysics Data System (ADS)

    Harris, Larry D.

    1988-09-01

    There is no longer any doubt that cumulative impacts have important effects on wetland vertebrates. Interactions of species diversity and community structure produce a complex pattern in which environmental impacts can play a highly significant role. Various examples show how wetlands maintain the biotic diversity within and among vertebrate populations, and some of the ways that environmental perturbations can interact to reduce this diversity. The trophic and habitat pyramids are useful organizing concepts. Habitat fragmentation can have severe effects at all levels, reducing the usable range of the larger habitat generalists while threatening the genetic integrity of small, isolated populations. The complexity of trophic interactions, and the propensity, or necessity, of vertebrates to switch from one food source to another—something we know little about—makes using food chain support as a variable for predicting environmental impacts very questionable. Historical instances illustrate the effects of the accumulation of impacts on vertebrates. At present it is nearly impossible to predict the result of three or more different kinds of perturbations, although long-range effects can be observed. One case in point is waterfowl; while their ingestion of lead shot, harvesting by hunters during migration, and loss of habitat have caused waterfowl populations to decline, the proportional responsibility of these factors has not been determined. Further examples show multiplicative effects of similar actions, effects with long time lags, diffuse processes in the landscape that may have concentrated effects on a component subsystem, and a variety of other interactions of increasing complexity. Not only is more information needed at all levels; impacts must be assessed on a landscape or regional scale to produce informed management decisions. I conclude that a system of replicate wetland reserves that are allowed to interact naturally with the surrounding landscape will

  8. Dementia and driving

    MedlinePlus

    ... not drive at times of the day when traffic is heaviest. Do not drive when the weather is bad. Do not drive long distances. Drive only on roads the person is used to. Caregivers should try to lessen ...

  9. Calcium Sensors as Key Hubs in Plant Responses to Biotic and Abiotic Stresses

    PubMed Central

    Ranty, Benoît; Aldon, Didier; Cotelle, Valérie; Galaud, Jean-Philippe; Thuleau, Patrice; Mazars, Christian

    2016-01-01

    The Ca2+ ion is recognized as a crucial second messenger in signaling pathways coupling the perception of environmental stimuli to plant adaptive responses. Indeed, one of the earliest events following the perception of environmental changes (temperature, salt stress, drought, pathogen, or herbivore attack) is intracellular variation of free calcium concentrations. These calcium variations differ in their spatio-temporal characteristics (subcellular location, amplitude, kinetics) with the nature and strength of the stimulus and, for this reason, they are considered as signatures encrypting information from the initial stimulus. This information is believed to drive a specific response by decoding via calcium-binding proteins. Based on recent examples, we illustrate how individual calcium sensors from the calcium-dependent protein kinase and calmodulin-like protein families can integrate inputs from various environmental changes. Focusing on members of these two families, shown to be involved in plant responses to both abiotic and biotic stimuli, we discuss their role as key hubs and we put forward hypotheses explaining how they can drive the signaling pathways toward the appropriate plant responses. PMID:27014336

  10. Abiotic/biotic coupling in the rhizosphere: a reactive transport modeling analysis

    USGS Publications Warehouse

    Lawrence, Corey R.; Steefel, Carl; Maher, Kate

    2014-01-01

    A new generation of models is needed to adequately simulate patterns of soil biogeochemical cycling in response changing global environmental drivers. For example, predicting the influence of climate change on soil organic matter storage and stability requires models capable of addressing complex biotic/abiotic interactions of rhizosphere and weathering processes. Reactive transport modeling provides a powerful framework simulating these interactions and the resulting influence on soil physical and chemical characteristics. Incorporation of organic reactions in an existing reactive transport model framework has yielded novel insights into soil weathering and development but much more work is required to adequately capture root and microbial dynamics in the rhizosphere. This endeavor provides many advantages over traditional soil biogeochemical models but also many challenges.

  11. Spectroscopic Studies of Pre-Biotic Carbon Chemistry

    NASA Technical Reports Server (NTRS)

    Blake, Geoffrey A.

    2003-01-01

    As described in the original proposal and in our progress reports, research in the Blake group supported by the Exobiology program seeks to understand the pre-biotic chemistry of carbon along with that of other first- and second-row elements from the earliest stages of star formation through the development of planetary systems. The major tool used is spectroscopy, and the program has observational, laboratory, and theoretical components. The observational and theoretical programs are concerned primarily with a quantitative assessment of the chemical budgets of the biogenic elements in the circumstellar environment of forming stars and planetary systems, while the laboratory work is focused on the complex species that characterize the pre-biotic chemistry of carbon. We outline below our results over the past year acquired, in part, with Exobiology support.

  12. Pattern and process of biotic homogenization in the New Pangaea.

    PubMed

    Baiser, Benjamin; Olden, Julian D; Record, Sydne; Lockwood, Julie L; McKinney, Michael L

    2012-12-01

    Human activities have reorganized the earth's biota resulting in spatially disparate locales becoming more or less similar in species composition over time through the processes of biotic homogenization and biotic differentiation, respectively. Despite mounting evidence suggesting that this process may be widespread in both aquatic and terrestrial systems, past studies have predominantly focused on single taxonomic groups at a single spatial scale. Furthermore, change in pairwise similarity is itself dependent on two distinct processes, spatial turnover in species composition and changes in gradients of species richness. Most past research has failed to disentangle the effect of these two mechanisms on homogenization patterns. Here, we use recent statistical advances and collate a global database of homogenization studies (20 studies, 50 datasets) to provide the first global investigation of the homogenization process across major faunal and floral groups and elucidate the relative role of changes in species richness and turnover. We found evidence of homogenization (change in similarity ranging from -0.02 to 0.09) across nearly all taxonomic groups, spatial extent and grain sizes. Partitioning of change in pairwise similarity shows that overall change in community similarity is driven by changes in species richness. Our results show that biotic homogenization is truly a global phenomenon and put into question many of the ecological mechanisms invoked in previous studies to explain patterns of homogenization. PMID:23055062

  13. Biotic resistance limits the invasiveness of the western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), in Florida.

    PubMed

    Funderburk, Joe; Frantz, Galen; Mellinger, Charles; Tyler-Julian, Kara; Srivastava, Mrittunjai

    2016-04-01

    The spread of the western flower thrips, Frankliniella occidentalis (Pergande), has resulted in the world-wide destabilization of established integrated pest management programs for many crops. It is hypothesized that frequent exposure to insecticides in intensive agriculture selected for resistant populations, which allowed invasive populations in the eastern USA to overcome biotic resistance from the native community of species. Research conducted in Florida to understand the role of biotic factors in limiting the abundance of the western flower thrips is reviewed. Orius spp. (Hemiptera: Anthocoridae) are effective predators that suppress populations of thrips on crop and non-crop hosts in southern and northern Florida. Orius are more effective predators of the western flower thrips than the native flower thrips, F. tritici (Fitch) and F. bispinosa (Morgan). The native species are competitors of the western flower thrips. Excessive fertilization and the use of broad-spectrum insecticides in crop fields further enhances populations of the western flower thrips. Interactions with native species clearly limit the abundance of western flower thrips in Florida, but populations are abundant in fertilized crop fields where application of insecticides excludes predators and competitor species. PMID:26149353

  14. Conciliation biology: the eco-evolutionary management of permanently invaded biotic systems

    PubMed Central

    Carroll, Scott P

    2011-01-01

    Biotic invaders and similar anthropogenic novelties such as domesticates, transgenics, and cancers can alter ecology and evolution in environmental, agricultural, natural resource, public health, and medical systems. The resulting biological changes may either hinder or serve management objectives. For example, biological control and eradication programs are often defeated by unanticipated resistance evolution and by irreversibility of invader impacts. Moreover, eradication may be ill-advised when nonnatives introduce beneficial functions. Thus, contexts that appear to call for eradication may instead demand managed coexistence of natives with nonnatives, and yet applied biologists have not generally considered the need to manage the eco-evolutionary dynamics that commonly result from interactions of natives with nonnatives. Here, I advocate a conciliatory approach to managing systems where novel organisms cannot or should not be eradicated. Conciliatory strategies incorporate benefits of nonnatives to address many practical needs including slowing rates of resistance evolution, promoting evolution of indigenous biological control, cultivating replacement services and novel functions, and managing native–nonnative coevolution. Evolutionary links across disciplines foster cohesion essential for managing the broad impacts of novel biotic systems. Rather than signaling defeat, conciliation biology thus utilizes the predictive power of evolutionary theory to offer diverse and flexible pathways to more sustainable outcomes. PMID:25567967

  15. Modeling of acute cadmium toxicity in solution to barley root elongation using biotic ligand model theory.

    PubMed

    Wang, Xuedong; Wu, Mingyan; Ma, Jingxing; Chen, Xiaolin; Hua, Luo

    2016-04-01

    Protons (H(+)) as well as different major and trace elements may inhibit cadmium (Cd) uptake in aquatic organisms and thus alleviate Cd toxicity. However, little is known about such interactions in soil organisms. In this study, the independent effects of the cations calcium (Ca(2+)), magnesium (Mg(2+)), potassium (K(+)), H(+) and zinc (Zn(2+)) on Cd toxicity were investigated with 5-day long barley root elongation tests in nutrient solutions. The tested concentrations of selected cations and trace metal ions were based on the ranges that occur naturally in soil pore water. The toxicity of Cd decreased with increasing activity of Ca(2+), Mg(2+), H(+) and Zn(2+), but not K(+). Accordingly, conditional binding constants were obtained for the binding of Cd(2+), Ca(2+), Mg(2+), H(+), and Zn(2+) with the binding ligand: logKCdBL 5.19, logKCaBL 2.87, logKMgBL 2.98, logKHBL 5.13 and logKZnBL 5.42, respectively. Furthermore, it was calculated that on average 29% of the biotic ligand sites needed to be occupied by Cd to induce a 50% decrease in root elongation. Using the estimated constants, a biotic ligand model was successfully developed to predict the Cd toxicity to barley root elongation as a function of solution characteristics. The feasibility and accuracy of its application for predicting Cd toxicity in soils were discussed. PMID:27090701

  16. Biotic games and cloud experimentation as novel media for biophysics education

    NASA Astrophysics Data System (ADS)

    Riedel-Kruse, Ingmar; Blikstein, Paulo

    2014-03-01

    First-hand, open-ended experimentation is key for effective formal and informal biophysics education. We developed, tested and assessed multiple new platforms that enable students and children to directly interact with and learn about microscopic biophysical processes: (1) Biotic games that enable local and online play using galvano- and photo-tactic stimulation of micro-swimmers, illustrating concepts such as biased random walks, Low Reynolds number hydrodynamics, and Brownian motion; (2) an undergraduate course where students learn optics, electronics, micro-fluidics, real time image analysis, and instrument control by building biotic games; and (3) a graduate class on the biophysics of multi-cellular systems that contains a cloud experimentation lab enabling students to execute open-ended chemotaxis experiments on slimemolds online, analyze their data, and build biophysical models. Our work aims to generate the equivalent excitement and educational impact for biophysics as robotics and video games have had for mechatronics and computer science, respectively. We also discuss how scaled-up cloud experimentation systems can support MOOCs with true lab components and life-science research in general.

  17. In Search for Factors that Drive Hantavirus Epidemics

    PubMed Central

    Heyman, Paul; Thoma, Bryan R.; Marié, Jean-Lou; Cochez, Christel; Essbauer, Sandra Simone

    2012-01-01

    In Europe, hantaviruses (Bunyaviridae) are small mammal-associated zoonotic and emerging pathogens that can cause hemorrhagic fever with renal syndrome (HFRS). Puumala virus, the main etiological agent carried by the bank vole Myodes glareolus is responsible for a mild form of HFRS while Dobrava virus induces less frequent but more severe cases of HFRS. Since 2000 in Europe, more than 3000 cases of HFRS have been recorded, in average, each year, which is nearly double compared to the previous decade. In addition to this upside long-term trend, significant oscillations occur. Epidemic years appear, usually every 2–4 years, with an increased incidence, generally in localized hot spots. Moreover, the virus has been identified in new areas in the recent years. A great number of surveys have been carried out in order to assess the prevalence of the infection in the reservoir host and to identify links with different biotic and abiotic factors. The factors that drive the infections are related to the density and diversity of bank vole populations, prevalence of infection in the reservoir host, viral excretion in the environment, survival of the virus outside its host, and human behavior, which affect the main transmission virus route through inhalation of infected rodent excreta. At the scale of a rodent population, the prevalence of the infection increases with the age of the individuals but also other parameters, such as sex and genetic variability, interfere. The contamination of the environment may be correlated to the number of newly infected rodents, which heavily excrete the virus. The interactions between these different parameters add to the complexity of the situation and explain the absence of reliable tools to predict epidemics. In this review, the factors that drive the epidemics of hantaviruses in Middle Europe are discussed through a panorama of the epidemiological situation in Belgium, France, and Germany. PMID:22934002

  18. Identifying biotic integrity and water chemistry relations in nonwadeable rivers of Wisconsin: Toward the development of nutrient criteria

    USGS Publications Warehouse

    Weigel, B.M.; Robertson, D.M.

    2007-01-01

    variation to interactions among the categories. In contrast, partial RDA attributed much of the explained variation to the nutrient (25%) and other water chemistry (38%) categories for the fish model. Our analyses suggest that it would be beneficial to develop criteria based upon a suite of biotic and nutrient variables simultaneously to deem waters as not meeting their designated uses. ?? 2007 Springer Science+Business Media, LLC.

  19. Identifying Biotic Integrity and Water Chemistry Relations in Nonwadeable Rivers of Wisconsin: Toward the Development of Nutrient Criteria

    NASA Astrophysics Data System (ADS)

    Weigel, Brian M.; Robertson, Dale M.

    2007-10-01

    explained variation to interactions among the categories. In contrast, partial RDA attributed much of the explained variation to the nutrient (25%) and other water chemistry (38%) categories for the fish model. Our analyses suggest that it would be beneficial to develop criteria based upon a suite of biotic and nutrient variables simultaneously to deem waters as not meeting their designated uses.

  20. Identifying biotic integrity and water chemistry relations in nonwadeable rivers of Wisconsin: toward the development of nutrient criteria.

    PubMed

    Weigel, Brian M; Robertson, Dale M

    2007-10-01

    , assigning 89% of the explained variation to interactions among the categories. In contrast, partial RDA attributed much of the explained variation to the nutrient (25%) and other water chemistry (38%) categories for the fish model. Our analyses suggest that it would be beneficial to develop criteria based upon a suite of biotic and nutrient variables simultaneously to deem waters as not meeting their designated uses. PMID:17638041

  1. Abiotic Versus Biotic Weathering Of Olivine As Possible Biosignatures

    NASA Technical Reports Server (NTRS)

    Longazo, Teresa G.; Wentworth, Susan J.; Clemett, Simon J.; Southam, Gordon; McKay, David S.

    2001-01-01

    We are investigating the weathering of silicate minerals by both purely inorganic, and biologically mediated processes using field-emission scanning electron microscopy (FESEM) and energy dispersive x-ray spectroscopy (EDS). By resolving surface textures and chemical compositions of weathered surfaces at the sub-micron scale we hope to be able to distinguish abiotic from biotic weathering processes and so establish a new biosignature applicable to the study of astromaterials including but not limited to the Martian meteorites. Sterilized olivine grains (San Carlos, Arizona) no more than 1-2 mm in their longest dimension were optically assayed to be uniform in color and free of inclusions were selected as weathering subjects. Prior to all experiments surface morphologies and Fe/Mg ratios were determined for each grain using FE-SEM and EDS. Experiments were divided into two categories abiotic and biotic and were compared with "naturally" weathered samples. For the preliminary experiments, two trials (open and closed to the ambient laboratory environment) were performed under abiotic conditions, and three trials under biotic conditions (control, day 1 and day 2). The open system abiotic trials used sterile grains heated at 98 C and 200 C for both 24 and 48 hours in 1L double distilled de-ionized water. The closed system abiotic trials were conducted under the same conditions but in a sealed two layer steel/Teflon "bomb" apparatus. The biotic trials used sterile grains mounted in a flow-through device attached to a wellhead on the Columbia River aquifer. Several discolored, altered, grains were selected to document "natural" weathering surface textures for comparison with the experimental samples. Preliminary results indicate there are qualitative differences in weathered surface textures among all the designed experiments. The olivine grains in abiotic trials displayed etching, pitting, denticulate margins, dissolution and clay formation. The scale of the features

  2. Spatial variability of biotic and abiotic tree establishment constraints across a treeline ecotone in the Alaska Range

    USGS Publications Warehouse

    Stueve, K.M.; Isaacs, R.E.; Tyrrell, L.E.; Densmore, R.V.

    2011-01-01

    Throughout interior Alaska (USA), a gradual warming trend in mean monthly temperatures occurred over the last few decades (;2-48C). The accompanying increases in woody vegetation at many alpine treeline (hereafter treeline) locations provided an opportunity to examine how biotic and abiotic local site conditions interact to control tree establishment patterns during warming. We devised a landscape ecological approach to investigate these relationships at an undisturbed treeline in the Alaska Range. We identified treeline changes between 1953 (aerial photography) and 2005 (satellite imagery) in a geographic information system (GIS) and linked them with corresponding local site conditions derived from digital terrain data, ancillary climate data, and distance to 1953 trees. Logistic regressions enabled us to rank the importance of local site conditions in controlling tree establishment. We discovered a spatial transition in the importance of tree establishment controls. The biotic variable (proximity to 1953 trees) was the most important tree establishment predictor below the upper tree limit, providing evidence of response lags with the abiotic setting and suggesting that tree establishment is rarely in equilibrium with the physical environment or responding directly to warming. Elevation and winter sun exposure were important predictors of tree establishment at the upper tree limit, but proximity to trees persisted as an important tertiary predictor, indicating that tree establishment may achieve equilibrium with the physical environment. However, even here, influences from the biotic variable may obscure unequivocal correlations with the abiotic setting (including temperature). Future treeline expansion will likely be patchy and challenging to predict without considering the spatial variability of influences from biotic and abiotic local site conditions. ?? 2011 by the Ecological Society of America.

  3. The WRKY transcription factors in the diploid woodland strawberry Fragaria vesca: Identification and expression analysis under biotic and abiotic stresses.

    PubMed

    Wei, Wei; Hu, Yang; Han, Yong-Tao; Zhang, Kai; Zhao, Feng-Li; Feng, Jia-Yue

    2016-08-01

    WRKY proteins comprise a large family of transcription factors that play important roles in response to biotic and abiotic stresses and in plant growth and development. To date, little is known about the WRKY gene family in strawberry. In this study, we identified 62 WRKY genes (FvWRKYs) in the wild diploid woodland strawberry (Fragaria vesca, 2n = 2x = 14) accession Heilongjiang-3. According to the phylogenetic analysis and structural features, these identified strawberry FvWRKY genes were classified into three main groups. In addition, eight FvWRKY-GFP fusion proteins showed distinct subcellular localizations in Arabidopsis mesophyll protoplasts. Furthermore, we examined the expression of the 62 FvWRKY genes in 'Heilongjiang-3' under various conditions, including biotic stress (Podosphaera aphanis), abiotic stresses (drought, salt, cold, and heat), and hormone treatments (abscisic acid, ethephon, methyl jasmonate, and salicylic acid). The expression levels of 33 FvWRKY genes were upregulated, while 12 FvWRKY genes were downregulated during powdery mildew infection. FvWRKY genes responded to drought and salt treatment to a greater extent than to temperature stress. Expression profiles derived from quantitative real-time PCR suggested that 11 FvWRKY genes responded dramatically to various stimuli at the transcriptional level, indicating versatile roles in responses to biotic and abiotic stresses. Interaction networks revealed that the crucial pathways controlled by WRKY proteins may be involved in the differential response to biotic stress. Taken together, the present work may provide the basis for future studies of the genetic modification of WRKY genes for pathogen resistance and stress tolerance in strawberry. PMID:27105420

  4. Mismatch in microbial food webs: predators but not prey perform better in their local biotic and abiotic conditions.

    PubMed

    Parain, Elodie C; Gravel, Dominique; Rohr, Rudolf P; Bersier, Louis-Félix; Gray, Sarah M

    2016-07-01

    Understanding how trophic levels respond to changes in abiotic and biotic conditions is key for predicting how food webs will react to environmental perturbations. Different trophic levels may respond disproportionately to change, with lower levels more likely to react faster, as they typically consist of smaller-bodied species with higher reproductive rates. This response could cause a mismatch between trophic levels, in which predators and prey will respond differently to changing abiotic or biotic conditions. This mismatch between trophic levels could result in altered top-down and bottom-up control and changes in interaction strength. To determine the possibility of a mismatch, we conducted a reciprocal-transplant experiment involving Sarracenia purpurea food webs consisting of bacterial communities as prey and a subset of six morphologically similar protozoans as predators. We used a factorial design with four temperatures, four bacteria and protozoan biogeographic origins, replicated four times. This design allowed us to determine how predator and prey dynamics were altered by abiotic (temperature) conditions and biotic (predators paired with prey from either their local or non-local biogeographic origin) conditions. We found that prey reached higher densities in warmer temperature regardless of their temperature of origin. Conversely, predators achieved higher densities in the temperature condition and with the prey from their origin. These results confirm that predators perform better in abiotic and biotic conditions of their origin while their prey do not. This mismatch between trophic levels may be especially significant under climate change, potentially disrupting ecosystem functioning by disproportionately affecting top-down and bottom-up control. PMID:27547320

  5. Seasonal Variability in Airborne Biotic Contaminants in Swine Confinement Buildings

    PubMed Central

    Kumari, Priyanka; Choi, Hong L.

    2014-01-01

    Little is known about the seasonal dynamics of biotic contaminants in swine confinement buildings (SCBs). The biotic contaminants of seven SCBs were monitored during one visit in the winter and one during the summer. Paired-end Illumina sequencing of the 16S rRNA gene, V3 region, was used to examine seasonal shifts in bacterial community composition and diversity. The abundances of 16S rRNA genes and six tetracycline resistance genes (tetB, tetH, tetZ, tetO, tetQ, and tetW) were also quantified using real-time PCR. Bacterial abundances, community composition and diversity all showed strong seasonal patterns defined by winter peaks in abundance and diversity. Microclimatic variables of SCBs, particularly air speed, PM2.5 and total suspended particles (TSP) were found significantly correlated to abundances, community composition, and diversity of bacterial bioaerosols. Seasonal fluctuations were also observed for four tetracycline resistance genes, tetH, tetO, tetQ, and tetW. The frequency of occurrences of these resistance genes were significantly higher in samples collected during winter and was also significantly correlated with air speed, PM2.5 and TSP. Overall, our results indicate that biotic contaminants in SCBs exhibit seasonal trends, and these could be associated with the microclimatic variables of SCBs. The correlations established in the current study could be helpful in establishing better management strategies to minimize the potential health impacts on both livestock and humans working in this environment. PMID:25393011

  6. A Model of Continental Growth and Mantle Degassing Comparing Biotic and Abiotic Worlds

    NASA Astrophysics Data System (ADS)

    Höning, D.; Hansen-Goos, H.; Spohn, T.

    2012-12-01

    While examples for interaction of the biosphere with the atmosphere can be easily cited (e.g., production and consumption of O2), interaction between the biosphere and the solid planet and its interior is much less established. It has been argued (e.g., Rosing et al. 2006; Sleep et al, 2012) that the formation of continents could be a consequence of bioactivity harvesting solar energy through photosynthesis to help build the continents and that the mantle should carry a chemical biosignature. We present an interaction model that includes mantle convection, mantle water vapor degassing at mid-oceanic ridges and regassing through subduction zones, continental crust formation and erosion and water storage and transport in a porous oceanic crust that includes hydrous mineral phases. The mantle viscosity in this model depends on the water concentration in the mantle. We use boundary layer theory of mantle convection to parameterize the mantle convection flow rate and assume that the plate speed equals the mantle flow rate. The biosphere enters the calculation through the assumption that the continental erosion rate is enhanced by a factor of several through bioactivity and through an assumed reduction of the kinetic barrier to diagenetic and metamorphic reactions (e.g., Kim et al. 2004) in the sedimentary basins in subduction zones that would lead to increased water storage capacities. We further include a stochastic model of continent-to-continent interactions that limits the effective total length of subduction zones. We use present day parameters of the Earth and explore a phase plane spanned by the percentage of surface coverage of the Earth by continents and the total water content of the mantle. We vary the ratio of the erosion rate in a postulated abiotic Earth to the present Earth, as well as the activation barrier to diagenetic and metamorphic reactions that affect the water storage capacity of the subducting crust. We find stable and unstable fixed points in

  7. Model Comparison for Abiotic versus Biotic Pollen Dispersal.

    PubMed

    Foster, Erich L; Chan, David M; Dyer, Rodney J

    2016-10-01

    An agent-based model with a correlated random walk is used to explore pollination within a forest. For abiotic dispersal, say via the wind, we use a purely random walk where there is no correlation between consecutive steps and for biotic dispersal, say via insect, we use a moderate or highly correlated random walk. In particular, we examine the differences in a number of biological measurement between a purely random walk and a correlated random walk in terms of gene dispersal in low and high plant densities. PMID:27550704

  8. Biotic and abiotic carbon to sulfur bond cleavage

    SciTech Connect

    Frost, J.W.

    1991-01-01

    Cleavage of aliphatic organosulfonate carbon to sulfur (C-S) bonds, a critical link in the global biogeochemical sulfur cycle, has been identified in Escherichia coli K-12. Enormous quantities of inorganic sulfate are continuously converted (Scheme I) into methanesulfonic acid 1 and acylated 3-(6-sulfo-{alpha}-D-quinovopyranosyl)-L-glycerol 2. Biocatalytic desulfurization (Scheme I) of 1 and 2, which share the structural feature of an aliphatic carbon bonded to a sulfonic acid sulfur, completes the cycle, Discovery of this desulfurization in E. coli provides an invaluable paradigm for study of a biotic process which, via the biogeochemical cycle, significantly influences the atmospheric concentration of sulfur-containing molecules.

  9. Predator-guided sampling reveals biotic structure in the bathypelagic.

    PubMed

    Benoit-Bird, Kelly J; Southall, Brandon L; Moline, Mark A

    2016-02-24

    We targeted a habitat used differentially by deep-diving, air-breathing predators to empirically sample their prey's distributions off southern California. Fine-scale measurements of the spatial variability of potential prey animals from the surface to 1,200 m were obtained using conventional fisheries echosounders aboard a surface ship and uniquely integrated into a deep-diving autonomous vehicle. Significant spatial variability in the size, composition, total biomass, and spatial organization of biota was evident over all spatial scales examined and was consistent with the general distribution patterns of foraging Cuvier's beaked whales (Ziphius cavirostris) observed in separate studies. Striking differences found in prey characteristics between regions at depth, however, did not reflect differences observed in surface layers. These differences in deep pelagic structure horizontally and relative to surface structure, absent clear physical differences, change our long-held views of this habitat as uniform. The revelation that animals deep in the water column are so spatially heterogeneous at scales from 10 m to 50 km critically affects our understanding of the processes driving predator-prey interactions, energy transfer, biogeochemical cycling, and other ecological processes in the deep sea, and the connections between the productive surface mixed layer and the deep-water column. PMID:26888030

  10. Response of plant tundra communities to changes in abiotic and biotic environments: Importance of the temporal dimension

    NASA Astrophysics Data System (ADS)

    Saccone, P.; Virtanen, R.

    2015-12-01

    Understanding of ecosystem response to changing environment have been improved by the convergence of observational and experimental approaches that allow disentangling mechanisms involved and large scale subsequent patterns. However, such approaches often face context-dependence of underlying processes, and a major challenge of community ecology is to deepen our understanding of this context-dependency for reliable upscaling. Here we used the results from several transplant experiments of heath communities in the Northern Fennoscandian during the last two decades to investigate the relative importance of abiotic and biotic drivers and the plant functional response. The plant community composition of blocks of heath vegetation from diverse origins transplanted in contrasted abiotic and biotic conditions was monitored from 6 to 23 years depending on the design. Considering both abiotic severity and biotic environment, the transplantation along altitudinal gradient constituted major habitat perturbation, in particular for communities from the mountain tundra vulnerable to strong functional shift. In addition, the joint effects of multiple drivers associated to grazing pressure and abiotic micro heterogeneity resulted in divergent community in the long-term. However, the different factors operated on different temporal scales. The vegetation depending on their origin and functional type also showed contrasted patterns from immediate and transient response to strong biological inertia. Our results reveal the potential for alternative response of plant communities depending on the interplay between the multiple drivers and the functional attributes of the vegetation. This interplay should drive plant communities toward divergent alternative states, but our ability to extrapolate longer-term trajectories from partial dynamics is challenged by the temporal differences in drivers pressure and plant response. The responses to manipulation appear as successional processes and

  11. Zebra mussel effects on benthic invertebrates: physical or biotic?

    USGS Publications Warehouse

    Botts, P. Silver; Patterson, Benjamin A.; Schloesser, Don W.

    1996-01-01

    In soft sediments, Dreissena spp. create firm substrate in the form of aggregates of living mussels (druses) that roll free on the sediments. Druses provide physical structure which increases habitat heterogeneity, and the mussels increase benthic organic matter through the production of pseudofeces and feces. Descriptive and experimental studies were used to determine: 1) whether the density of benthic invertebrates in soft sediments increased in the presence of druses, and 2) whether the invertebrate assemblage responded to the physical structure provided by a druse or to some biotic effect associated with the presence of living mussels. In core samples collected biweekly during summer in Presque Isle Bay, Erie, Pennsylvania, amphipods, chironomids, oligochaetes, turbellarians, and hydrozoans were significantly more abundant in sand with druses than in bare sand. When mesh bags containing either a living druse, non-living druse, or no druse were incubated in the bay for 33 d, we found that chironomids were significantly more abundant in treatments with living druses than with non-living druses, and in treatments with non-living druses than with no druse; turbellarians, amphipods, and hydrozoans were significantly more abundant in treatments with living or non-living druses than with no druse; oligochaetes showed no significant differences among treatments. This study demonstrates that most taxa of benthic invertebrates in soft substrate respond specifically to the physical structure associated with aggregates of mussel shells, but further study is needed to examine chironomid responses to some biotic effect dependent on the presence of living mussels.

  12. Biotic and abiotic carbon to sulfur bond cleavage. Final report

    SciTech Connect

    Frost, J.W.

    1994-05-01

    The microbial desulfurization of organosulfur compounds occurs by unprecedented and largely unexplored biochemical processes. A study of such biotic desulfurizations can be expected to give rise to new and useful chemistry and enzymology. The potential value of understanding and harnessing these processes is seen in relation to the need for methods for the removal of organically bound sulfur from coal and the degradation of organic sulfur-containing pollutants. This research effort has been directed towards an examination of desulfurization ability in well characterized microorganisms, the isolation of bacteria with desulfurization ability from natural sources, the characterization and mechanistic evaluation of the observed biocatalytic processes, the development of biomimetic synthetic organic chemistry based on biotic desulfurization mechanisms and the design and preparation of improved coal model compounds for use in microbial selection processes. A systematic approach to studying biodesulfurizations was undertaken in which organosulfur compounds have been broken down into classes based on the oxidation state of the sulfur atom and the structure of the rest of the organic material. Microbes have been evaluated in terms of ability to degrade organosulfur compounds with sulfur in its sulfonic acid oxidation state. These compounds are likely intermediates in coal desulfurization and are present in the environment as persistent pollutants in the form of detergents. It is known that oxygen bonded to sulfur lowers the carbon-sulfur bond energy, providing a thermodynamic basis for starting with this class of compounds.

  13. Biotic stress: a significant contributor to organic aerosol in Europe?

    NASA Astrophysics Data System (ADS)

    Bergström, R.; Hallquist, M.; Simpson, D.; Wildt, J.; Mentel, T. F.

    2014-12-01

    We have investigated the potential impact on organic aerosol formation from biotic stress-induced emissions (SIE) of organic molecules from forests in Europe (north of lat. 45° N). Emission estimates for sesquiterpenes (SQT), methyl salicylate (MeSA) and unsaturated C17 compounds, due to different stressors, are based on experiments in the Jülich Plant Atmosphere Chamber (JPAC), combined with estimates of the fraction of stressed trees in Europe based on reported observed tree damage. SIE were introduced in the EMEP MSC-W chemical transport model and secondary organic aerosol (SOA) yields from the SIE were taken from the JPAC experiments. Based on estimates of current levels of infestation and the JPAC aerosol yields, the model results suggest that the contribution to SOA in large parts of Europe may be substantial. It is possible that SIE contributes as much, or more, to organic aerosol than the constitutive biogenic VOC emissions, at least during some periods. Based on the assumptions in this study, SIE-SOA are estimated to constitute between 50 and 70 % of the total biogenic SOA (BSOA) in a current-situation scenario where the biotic stress in northern and central European forests causes large SIE of MeSA and SQT. An alternative current-situation scenario with lower SIE, consisting solely of SQT, leads to lower SIE-SOA, between 20 and 40 % of the total BSOA. Hypothetical future scenarios with increased SIE, due to higher degrees of biotic stress, show that SOA formation due to SIE can become even larger. Unsaturated C17 BVOC (biogenic volatile organic compounds) emitted by spruce infested by the forest-honey generating bark louse, Cinara pilicornis, have a high SOA-forming potential. A model scenario investigating the effect of a regional, episodic infestation of Cinara pilicornis in Baden-Württemberg, corresponding to a year with high production of forest honey, shows that these types of events could lead to very large organic aerosol formation in the

  14. Considerations in forecasting the demand for carbon sequestration and biotic storage technologies

    SciTech Connect

    Trexler, M.C.

    1997-12-31

    The Intergovernmental Panel on Climate Change (IPCC) has identified forestry and other land-use based mitigation measures as possible sources and sinks of greenhouse gases. An overview of sequestration and biotic storage is presented, and the potential impacts of the use of carbon sequestration as a mitigation technology are briefly noted. Carbon sequestration is also compare to other mitigation technologies. Biotic mitigation technologies are concluded to be a legitimate and potentially important part of greenhouse gas mitigation due to their relatively low costs, ancillary benefits, and climate impact. However, not all biotic mitigation techniques perfectly match the idealized definition of a mitigation measure, and policies are becoming increasingly biased against biotic technologies.

  15. At limits of life: multidisciplinary insights reveal environmental constraints on biotic diversity in continental Antarctica.

    PubMed

    Magalhães, Catarina; Stevens, Mark I; Cary, S Craig; Ball, Becky A; Storey, Bryan C; Wall, Diana H; Türk, Roman; Ruprecht, Ulrike

    2012-01-01

    Multitrophic communities that maintain the functionality of the extreme Antarctic terrestrial ecosystems, while the simplest of any natural community, are still challenging our knowledge about the limits to life on earth. In this study, we describe and interpret the linkage between the diversity of different trophic level communities to the geological morphology and soil geochemistry in the remote Transantarctic Mountains (Darwin Mountains, 80°S). We examined the distribution and diversity of biota (bacteria, cyanobacteria, lichens, algae, invertebrates) with respect to elevation, age of glacial drift sheets, and soil physicochemistry. Results showed an abiotic spatial gradient with respect to the diversity of the organisms across different trophic levels. More complex communities, in terms of trophic level diversity, were related to the weakly developed younger drifts (Hatherton and Britannia) with higher soil C/N ratio and lower total soluble salts content (thus lower conductivity). Our results indicate that an increase of ion concentration from younger to older drift regions drives a succession of complex to more simple communities, in terms of number of trophic levels and diversity within each group of organisms analysed. This study revealed that integrating diversity across multi-trophic levels of biotic communities with abiotic spatial heterogeneity and geological history is fundamental to understand environmental constraints influencing biological distribution in Antarctic soil ecosystems. PMID:23028563

  16. Extended Driving Impairs Nocturnal Driving Performances

    PubMed Central

    Sagaspe, Patricia; Taillard, Jacques; Åkerstedt, Torbjorn; Bayon, Virginie; Espié, Stéphane; Chaumet, Guillaume; Bioulac, Bernard; Philip, Pierre

    2008-01-01

    Though fatigue and sleepiness at the wheel are well-known risk factors for traffic accidents, many drivers combine extended driving and sleep deprivation. Fatigue-related accidents occur mainly at night but there is no experimental data available to determine if the duration of prior driving affects driving performance at night. Participants drove in 3 nocturnal driving sessions (3–5am, 1–5am and 9pm–5am) on open highway. Fourteen young healthy men (mean age [±SD] = 23.4 [±1.7] years) participated Inappropriate line crossings (ILC) in the last hour of driving of each session, sleep variables, self-perceived fatigue and sleepiness were measured. Compared to the short (3–5am) driving session, the incidence rate ratio of inappropriate line crossings increased by 2.6 (95% CI, 1.1 to 6.0; P<.05) for the intermediate (1–5am) driving session and by 4.0 (CI, 1.7 to 9.4; P<.001) for the long (9pm–5am) driving session. Compared to the reference session (9–10pm), the incidence rate ratio of inappropriate line crossings were 6.0 (95% CI, 2.3 to 15.5; P<.001), 15.4 (CI, 4.6 to 51.5; P<.001) and 24.3 (CI, 7.4 to 79.5; P<.001), respectively, for the three different durations of driving. Self-rated fatigue and sleepiness scores were both positively correlated to driving impairment in the intermediate and long duration sessions (P<.05) and increased significantly during the nocturnal driving sessions compared to the reference session (P<.01). At night, extended driving impairs driving performances and therefore should be limited. PMID:18941525

  17. Dissolved and labile concentrations of Cd, Cu, Pb, and Zn in the South Fork Coeur d'Alene River, Idaho: Comparisons among chemical equilibrium models and implications for biotic ligand models

    USGS Publications Warehouse

    Balistrieri, L.S.; Blank, R.G.

    2008-01-01

    In order to evaluate thermodynamic speciation calculations inherent in biotic ligand models, the speciation of dissolved Cd, Cu, Pb, and Zn in aquatic systems influenced by historical mining activities is examined using equilibrium computer models and the diffusive gradients in thin films (DGT) technique. Several metal/organic-matter complexation models, including WHAM VI, NICA-Donnan, and Stockholm Humic model (SHM), are used in combination with inorganic speciation models to calculate the thermodynamic speciation of dissolved metals and concentrations of metal associated with biotic ligands (e.g., fish gills). Maximum dynamic metal concentrations, determined from total dissolved metal concentrations and thermodynamic speciation calculations, are compared with labile metal concentrations measured by DGT to assess which metal/organic-matter complexation model best describes metal speciation and, thereby, biotic ligand speciation, in the studied systems. Results indicate that the choice of model that defines metal/organic-matter interactions does not affect calculated concentrations of Cd and Zn associated with biotic ligands for geochemical conditions in the study area, whereas concentrations of Cu and Pb associated with biotic ligands depend on whether the speciation calculations use WHAM VI, NICA-Donnan, or SHM. Agreement between labile metal concentrations and dynamic metal concentrations occurs when WHAM VI is used to calculate Cu speciation and SHM is used to calculate Pb speciation. Additional work in systems that contain wide ranges in concentrations of multiple metals should incorporate analytical speciation methods, such as DGT, to constrain the speciation component of biotic ligand models. ?? 2008 Elsevier Ltd.

  18. Electrical drive for automobile

    SciTech Connect

    Fobbs, H.

    1980-09-16

    Electrical apparatus for driving an automobile is described that is comprised of a dc motor operationally connected to the rear axle through a drive shaft with the motor energized from storage batteries and recharged from alternators coupled to the drive shaft adjacent a clutch at the rear end of the automobile through an auxiliary drive shaft.

  19. Coaxial Redundant Drives

    NASA Technical Reports Server (NTRS)

    Brissette, R.

    1983-01-01

    Harmonic drives allow redundancy and high out put torque in small package. If main drive fails, standby drive takes over and produces torque along same axis as main drive. Uses include power units in robot for internal pipeline inspection, manipulators in deep submersible probes or other applications in which redundancy protects against costly failures.

  20. Bacterial-fungal interactions enhance power generation in microbial fuel cells and drive dye decolourisation by an ex situ and in situ electro-Fenton process.

    PubMed

    Fernández de Dios, María Ángeles; del Campo, Araceli González; Fernández, Francisco Jesús; Rodrigo, Manuel; Pazos, Marta; Sanromán, María Ángeles

    2013-11-01

    In this work, the potential for sustainable energy production from wastes has been exploited using a combination fungus-bacterium in microbial fuel cell (MFC) and electro-Fenton technology. The fungus Trametes versicolor was grown with Shewanella oneidensis so that the bacterium would use the networks of the fungus to transport the electrons to the anode. This system generated stable electricity that was enhanced when the electro-Fenton reactions occurred in the cathode chamber. This configuration reached a stable voltage of approximately 1000 mV. Thus, the dual benefits of the in situ-designed MFC electro-Fenton, the simultaneous dye decolourisation and the electricity generation, were demonstrated. Moreover, the generated power was effectively used to drive an ex situ electro-Fenton process in batch and continuous mode. This newly developed MFC fungus-bacterium with an in situ electro-Fenton system can ensure a high power output and a continuous degradation of organic pollutants. PMID:24035817

  1. Structural Variants in the Soybean Genome Localize to Clusters of Biotic Stress-Response Genes1[W][OA

    PubMed Central

    McHale, Leah K.; Haun, William J.; Xu, Wayne W.; Bhaskar, Pudota B.; Anderson, Justin E.; Hyten, David L.; Gerhardt, Daniel J.; Jeddeloh, Jeffrey A.; Stupar, Robert M.

    2012-01-01

    Genome-wide structural and gene content variations are hypothesized to drive important phenotypic variation within a species. Structural and gene content variations were assessed among four soybean (Glycine max) genotypes using array hybridization and targeted resequencing. Many chromosomes exhibited relatively low rates of structural variation (SV) among genotypes. However, several regions exhibited both copy number and presence-absence variation, the most prominent found on chromosomes 3, 6, 7, 16, and 18. Interestingly, the regions most enriched for SV were specifically localized to gene-rich regions that harbor clustered multigene families. The most abundant classes of gene families associated with these regions were the nucleotide-binding and receptor-like protein classes, both of which are important for plant biotic defense. The colocalization of SV with plant defense response signal transduction pathways provides insight into the mechanisms of soybean resistance gene evolution and may inform the development of new approaches to resistance gene cloning. PMID:22696021

  2. Solar array drive system

    NASA Technical Reports Server (NTRS)

    Berkopec, F. D.; Sturman, J. C.; Stanhouse, R. W.

    1976-01-01

    A solar array drive system consisting of a solar array drive mechanism and the corresponding solar array drive electronics is being developed. The principal feature of the solar array drive mechanism is its bidirectional capability which enables its use in mechanical redundancy. The solar array drive system is of a widely applicable design. This configuration will be tested to determine its acceptability for generic mission sets. Foremost of the testing to be performed is the testing for extended duration.

  3. Biotic ligand modeling approach: Synthesis of the effect of major cations on the toxicity of metals to soil and aquatic organisms.

    PubMed

    Ardestani, Masoud M; van Straalen, Nico M; van Gestel, Cornelis A M

    2015-10-01

    The biotic ligand model (BLM) approach is used to assess metal toxicity, taking into account the competition of other cations with the free metal ions for binding to the biotic ligand sites of aquatic and soil organisms. The bioavailable fraction of metals, represented by the free metal ion, is a better measure than the total concentration for assessing their potential risk to the environment. Because BLMs are relating toxicity to the fraction of biotic ligands occupied by the metal, they can be useful for investigating factors affecting metal bioaccumulation and toxicity. In the present review, the effects of major cations on the toxicity of metals to soil and aquatic organisms were comprehensively studied by performing a meta-analysis of BLM literature data. Interactions at the binding sites were shown to be species- and metal-specific. The main factors affecting the relationships between toxicity and conditional binding constants for metal binding at the biotic ligand appeared to be Ca(2+) , Mg(2+) , and protons. Other important characteristics of the exposure medium, such as levels of dissolved organic carbon and concentrations of other cations, should also be considered to obtain a proper assessment of metal toxicity to soil and aquatic organisms. PMID:25953362

  4. The interplay between habitat structure and chemical contaminants on biotic responses of benthic organisms

    PubMed Central

    Matias, Miguel G.; Coleman, Ross A.

    2016-01-01

    Habitat structure influences the diversity and distribution of organisms, potentially affecting their response to disturbances by either affecting their ‘susceptibility’ or through the provision of resources that can mitigate impacts of disturbances. Chemical disturbances due to contamination are associated with decreases in diversity and functioning of systems and are also likely to increase due to coastal urbanisation. Understanding how habitat structure interacts with contaminants is essential to predict and therefore manage such effects, minimising their consequences to marine systems. Here, we manipulated two structurally different habitats and exposed them to different types of contaminants. The effects of contamination and habitat structure interacted, affecting species richness. More complex experimental habitats were colonized by a greater diversity of organisms than the less complex habitats. These differences disappeared, however, when habitats were exposed to contaminants, suggesting that contaminants can override effects of habitats structure at small spatial scales. These results provide insight into the complex ways that habitat structure and contamination interact and the need to incorporate evidence of biotic responses from individual disturbances to multiple stressors. Such effects need to be taken into account when designing and planning management and conservation strategies to natural systems. PMID:27168991

  5. Characterization of Citrus sinensis type 1 mitochondrial alternative oxidase and expression analysis in biotic stress.

    PubMed

    Daurelio, Lucas Damián; Checa, Susana Karina; Barrio, Jorgelina Morán; Ottado, Jorgelina; Orellano, Elena Graciela

    2010-02-01

    The higher plant mitochondrial electron transport chain contains an alternative pathway that ends with the AOX (alternative oxidase). The AOX proteins are encoded by a small gene family composed of two discrete gene subfamilies. Aox1 is present in both monocot and eudicot plants, whereas Aox2 is only present in eudicot plants. We isolated a genomic clone from Citrus sinensis containing the Aox1a gene. The orange Aox1a consists of four exons interrupted by three introns and its promoter harbours diverse putative stress-specific regulatory motifs including pathogen response elements. The role of the Aox1a gene was evaluated during the compatible interaction between C. sinensis and Xanthomonas axonopodis pv. citri and no induction of the Aox1a at the transcriptional level was observed. On the other hand, Aox1a was studied in orange plants during non-host interactions with Pseudomonas syringae pv. tomato and Xanthomonas campestris pv. vesicatoria, which result in hypersensitive response. Both phytopathogens produced a strong induction of Aox1a, reaching a maximum at 8 h post-infiltration. Exogenous application of salicylic acid produced a slight increase in the steady-state level of Aox1a, whereas the application of fungi elicitors showed the highest induction. These results suggest that AOX1a plays a role during biotic stress in non-host plant pathogen interaction. PMID:19257856

  6. The interplay between habitat structure and chemical contaminants on biotic responses of benthic organisms.

    PubMed

    Mayer-Pinto, Mariana; Matias, Miguel G; Coleman, Ross A

    2016-01-01

    Habitat structure influences the diversity and distribution of organisms, potentially affecting their response to disturbances by either affecting their 'susceptibility' or through the provision of resources that can mitigate impacts of disturbances. Chemical disturbances due to contamination are associated with decreases in diversity and functioning of systems and are also likely to increase due to coastal urbanisation. Understanding how habitat structure interacts with contaminants is essential to predict and therefore manage such effects, minimising their consequences to marine systems. Here, we manipulated two structurally different habitats and exposed them to different types of contaminants. The effects of contamination and habitat structure interacted, affecting species richness. More complex experimental habitats were colonized by a greater diversity of organisms than the less complex habitats. These differences disappeared, however, when habitats were exposed to contaminants, suggesting that contaminants can override effects of habitats structure at small spatial scales. These results provide insight into the complex ways that habitat structure and contamination interact and the need to incorporate evidence of biotic responses from individual disturbances to multiple stressors. Such effects need to be taken into account when designing and planning management and conservation strategies to natural systems. PMID:27168991

  7. An Economic Valuation of Biotic Pollination Services in Georgia.

    PubMed

    Barfield, Ashley S; Bergstrom, John C; Ferreira, Susana; Covich, Alan P; Delaplane, Keith S

    2015-04-01

    As agriculture faces documented decline in bees and other insect pollinators, empirical assessments of potential economic losses are critical for contextualizing the impacts of this decline and for prioritizing research needs. For the state of Georgia, we show that the annual economic value of biotic pollinators is substantial--US$367 million, equivalent to 13 percent of the total production value of crops studied and 3 percent of the total production value of Georgia's agricultural sector. Our unique Geographic Information Systems analysis reveals an irregular pattern of vulnerability. While the Georgia counties displaying the highest economic values of pollination are clustered in southern Georgia, those with the highest dependency on pollinators in terms of their contribution to crop production value are more dispersed throughout the state. PMID:26470149

  8. [Simplification of biotic ligand model and evaluation of predicted results].

    PubMed

    Wang, Wan-Bin; Chen, Sha; Wu, Min; Su, De-Li; Zhao, Jing

    2014-01-01

    The prediction accuracy of LC50 on four species (Fathead minnow, D. magna, D. pulex, Rainbow trout) was 0. 075, 0. 52, 0.96 and 0.29 respectively as determined by their onserved values of LC50 in surface water. Predicted results indicated that the correlation between forecast error and LA50 was exponential. The accuracy of Fathead minnow and Rainbow trout became 0.59 and 0.42 after adjusting LA50. The correlation between hardness and LA50 showed that the prediction effectiveness of BLM was poor in soft water. In addition, four important parameters (DOC, pH values, the concentration of HCO3-, temperature) were selected to build the multiple linear relationship with LC50 by applying 500 groups of random uniform water quality parameter in BLM. Biotic ligand model was effectively simplified. PMID:24720219

  9. The biotic crisis and the future of evolution.

    PubMed

    Myers, N; Knoll, A H

    2001-05-01

    The biotic crisis overtaking our planet is likely to precipitate a major extinction of species. That much is well known. Not so well known but probably more significant in the long term is that the crisis will surely disrupt and deplete certain basic processes of evolution, with consequences likely to persist for millions of years. Distinctive features of future evolution could include a homogenization of biotas, a proliferation of opportunistic species, a pest-and-weed ecology, an outburst of speciation among taxa that prosper in human-dominated ecosystems, a decline of biodisparity, an end to the speciation of large vertebrates, the depletion of "evolutionary powerhouses" in the tropics, and unpredictable emergent novelties. Despite this likelihood, we have only a rudimentary understanding of how we are altering the evolutionary future. As a result of our ignorance, conservation policies fail to reflect long-term evolutionary aspects of biodiversity loss. PMID:11344283

  10. Spectroscopic Studies of Pre-Biotic Carbon Chemistry

    NASA Technical Reports Server (NTRS)

    Blake, Geoffrey A.

    2002-01-01

    As described in the original proposal and in our progress reports, research in the Blake group supported by the Exobiology program seeks to understand the pre-biotic chemistry of carbon along with that of other first- and second-row elements from the earliest stages of star formation through the development of planetary systems. The major tool used is spectroscopy, and the program has observational, laboratory, and theoretical components. The observational and theoretical programs are concerned primarily with a quantitative assessment of the chemical budgets of the biogenic elements in star-forming molecular cloud cores, while the laboratory work is focused on the complex species that characterize the prebiotic chemistry of carbon. We outline below our results over the past two years acquired, in part, with Exobiology support.

  11. [Philosophy of the mutual biotic system of man-environment].

    PubMed

    Mertz, D P

    2009-06-01

    With regard to environmental changes, outstanding importance is meanwhile to be attached to the cultural side of human evolution. The evolution both of mankind and of its environment are mutually dependent as processes of change and together they form a complete biotic system. First disorders of balance concerning the close relationship network between mankind and environment eventually developed following man's change from the biosphere to the "noosphere" created by him. In the course of the "neolithic revolution" mankind, while becoming more and more settled, began to become increasingly estranged from its ecological surroundings. Environmental problems caused by man led to climatic changes already about 8,000 years ago. So far they have caused an extraordinary climatic stability following the Ice Age. "Environmental art" i. e. an improved evolution - is required to escape an imminent "collapse" caused by pollution. Nowadays mankind is on the way to being the almost exclusive carrier of future evolution of this planet. PMID:19544720

  12. Early Triassic Marine Biotic Recovery: The Predators' Perspective

    PubMed Central

    Scheyer, Torsten M.; Romano, Carlo; Jenks, Jim; Bucher, Hugo

    2014-01-01

    Examining the geological past of our planet allows us to study periods of severe climatic and biological crises and recoveries, biotic and abiotic ecosystem fluctuations, and faunal and floral turnovers through time. Furthermore, the recovery dynamics of large predators provide a key for evaluation of the pattern and tempo of ecosystem recovery because predators are interpreted to react most sensitively to environmental turbulences. The end-Permian mass extinction was the most severe crisis experienced by life on Earth, and the common paradigm persists that the biotic recovery from the extinction event was unusually slow and occurred in a step-wise manner, lasting up to eight to nine million years well into the early Middle Triassic (Anisian) in the oceans, and even longer in the terrestrial realm. Here we survey the global distribution and size spectra of Early Triassic and Anisian marine predatory vertebrates (fishes, amphibians and reptiles) to elucidate the height of trophic pyramids in the aftermath of the end-Permian event. The survey of body size was done by compiling maximum standard lengths for the bony fishes and some cartilaginous fishes, and total size (estimates) for the tetrapods. The distribution and size spectra of the latter are difficult to assess because of preservation artifacts and are thus mostly discussed qualitatively. The data nevertheless demonstrate that no significant size increase of predators is observable from the Early Triassic to the Anisian, as would be expected from the prolonged and stepwise trophic recovery model. The data further indicate that marine ecosystems characterized by multiple trophic levels existed from the earliest Early Triassic onwards. However, a major change in the taxonomic composition of predatory guilds occurred less than two million years after the end-Permian extinction event, in which a transition from fish/amphibian to fish/reptile-dominated higher trophic levels within ecosystems became apparent. PMID

  13. Desertification, salinization, and biotic homogenization in a dryland river ecosystem

    USGS Publications Warehouse

    Miyazono, S.; Patino, Reynaldo; Taylor, C.M.

    2015-01-01

    This study determined long-term changes in fish assemblages, river discharge, salinity, and local precipitation, and examined hydrological drivers of biotic homogenization in a dryland river ecosystem, the Trans-Pecos region of the Rio Grande/Rio Bravo del Norte (USA/Mexico). Historical (1977-1989) and current (2010-2011) fish assemblages were analyzed by rarefaction analysis (species richness), nonmetric multidimensional scaling (composition/variability), multiresponse permutation procedures (composition), and paired t-test (variability). Trends in hydrological conditions (1970s-2010s) were examined by Kendall tau and quantile regression, and associations between streamfiow and specific conductance (salinity) by generalized linear models. Since the 1970s, species richness and variability of fish assemblages decreased in the Rio Grande below the confluence with the Rio Conchos (Mexico), a major tributary, but not above it. There was increased representation of lower-flow/higher-salinity tolerant species, thus making fish communities below the confluence taxonomically and functionally more homogeneous to those above it. Unlike findings elsewhere, this biotic homogenization was due primarily to changes in the relative abundances of native species. While Rio Conchos discharge was > 2-fold higher than Rio Grande discharge above their confluence, Rio Conchos discharge decreased during the study period causing Rio Grande discharge below the confluence to also decrease. Rio Conchos salinity is lower than Rio Grande salinity above their confluence and, as Rio Conchos discharge decreased, it caused Rio Grande salinity below the confluence to increase (reduced dilution). Trends in discharge did not correspond to trends in precipitation except at extreme-high (90th quantile) levels. In conclusion, decreasing discharge from the Rio Conchos has led to decreasing flow and increasing salinity in the Rio Grande below the confluence. This spatially uneven desertification and

  14. Desertification, salinization, and biotic homogenization in a dryland river ecosystem.

    PubMed

    Miyazono, Seiji; Patiño, Reynaldo; Taylor, Christopher M

    2015-04-01

    This study determined long-term changes in fish assemblages, river discharge, salinity, and local precipitation, and examined hydrological drivers of biotic homogenization in a dryland river ecosystem, the Trans-Pecos region of the Rio Grande/Rio Bravo del Norte (USA/Mexico). Historical (1977-1989) and current (2010-2011) fish assemblages were analyzed by rarefaction analysis (species richness), nonmetric multidimensional scaling (composition/variability), multiresponse permutation procedures (composition), and paired t-test (variability). Trends in hydrological conditions (1970s-2010s) were examined by Kendall tau and quantile regression, and associations between streamflow and specific conductance (salinity) by generalized linear models. Since the 1970s, species richness and variability of fish assemblages decreased in the Rio Grande below the confluence with the Rio Conchos (Mexico), a major tributary, but not above it. There was increased representation of lower-flow/higher-salinity tolerant species, thus making fish communities below the confluence taxonomically and functionally more homogeneous to those above it. Unlike findings elsewhere, this biotic homogenization was due primarily to changes in the relative abundances of native species. While Rio Conchos discharge was>2-fold higher than Rio Grande discharge above their confluence, Rio Conchos discharge decreased during the study period causing Rio Grande discharge below the confluence to also decrease. Rio Conchos salinity is lower than Rio Grande salinity above their confluence and, as Rio Conchos discharge decreased, it caused Rio Grande salinity below the confluence to increase (reduced dilution). Trends in discharge did not correspond to trends in precipitation except at extreme-high (90th quantile) levels. In conclusion, decreasing discharge from the Rio Conchos has led to decreasing flow and increasing salinity in the Rio Grande below the confluence. This spatially uneven desertification and

  15. Oxidation of Black Carbon by Biotic and Abiotic Processes

    SciTech Connect

    Cheng, Chih-hsin; Lehmann, Johannes C.; Thies, Janice E.; Burton, Sarah D.; Engelhard, Mark H.

    2006-11-01

    The objectives of this study were to quantify the relative importance of either biotic or abiotic oxidation of biomass-derived black carbon (BC) and to characterize the surface properties and charge characteristics of oxidized particulate BC. We incubated BC and BC-soil mixtures at two different temperatures (30 C and 70 C) with and without microbial inoculation, nutrient additions, or manure amendments for four months. Abiotic processes were more important for oxidation of BC than biotic processes during this short-term incubation, as inoculation with microorganisms did not change any of the measured parameters. Black C incubated at both 30 C and 70 C without microbial activity showed dramatic decreases in pH (in water) from 5.4 to 5.2 and 3.4, as well as increases in cation exchange capacity (CEC at pH 7) by 53% and 538% and in oxygen (O) contents by 4% and 38%, respectively. Boehm titration and Fourier transform infrared (FTIR) spectroscopy suggested that the formation of carboxylic functional groups was the reason for the enhanced CEC during oxidation. The analyses of BC surface properties by X-ray photoelectron spectroscopy (XPS) indicated that the oxidation of BC particles initiated on the surface. Incubation at 30 C only enhanced oxidation on particle surfaces, while oxidation during incubation at 70 C penetrated into the interior of particles. Such short-term oxidation of BC has great significance for the stability of BC in soils as well as for its effects on soil fertility and biogeochemistry.

  16. Biotic homogenization of three insect groups due to urbanization.

    PubMed

    Knop, Eva

    2016-01-01

    Cities are growing rapidly, thereby expected to cause a large-scale global biotic homogenization. Evidence for the homogenization hypothesis is mostly derived from plants and birds, whereas arthropods have so far been neglected. Here, I tested the homogenization hypothesis with three insect indicator groups, namely true bugs, leafhoppers, and beetles. In particular, I was interested whether insect species community composition differs between urban and rural areas, whether they are more similar between cities than between rural areas, and whether the found pattern is explained by true species turnover, species diversity gradients and geographic distance, by non-native or specialist species, respectively. I analyzed insect species communities sampled on birch trees in a total of six Swiss cities and six rural areas nearby. In all indicator groups, urban and rural community composition was significantly dissimilar due to native species turnover. Further, for bug and leafhopper communities, I found evidence for large-scale homogenization due to urbanization, which was driven by reduced species turnover of specialist species in cities. Species turnover of beetle communities was similar between cities and rural areas. Interestingly, when specialist species of beetles were excluded from the analyses, cities were more dissimilar than rural areas, suggesting biotic differentiation of beetle communities in cities. Non-native species did not affect species turnover of the insect groups. However, given non-native arthropod species are increasing rapidly, their homogenizing effect might be detected more often in future. Overall, the results show that urbanization has a negative large-scale impact on the diversity specialist species of the investigated insect groups. Specific measures in cities targeted at increasing the persistence of specialist species typical for the respective biogeographic region could help to stop the loss of biodiversity. PMID:26367396

  17. Discovering Biotic Minerals at Martian Subsurface/Surface

    NASA Astrophysics Data System (ADS)

    Coll, P.; Stalport, F.; Cabane, M.; Navarro-Gonzalez, R.; Person, A.; Raulin, F.

    2004-11-01

    Many observations of Mars confirm the presence of liquid water running out freely on its surface and a dense atmosphere (20-30bars) made up primarily of CO2 in the first million years after formation. Such conditions were met for Earth, allowing the development of Life. Consequently a form of Martian Life could also have appeared. But Mars thereafter did not follow the same evolution as Earth: the only water traces currently observed are in solid or gas forms and the main atmosphere disappeared (6hPa). What happened to CO2 on Mars? The presence, at beginning, of liquid water undoubtedly allowed as on Earth the formation of inorganic and maybe organic carbonates, supposing that a form of carboneous Life appeared over Mars as on Earth. The absence of tectonics and volcanicity on Mars would not have counterbalanced the loss of atmospheric CO2. This description of past Life on Mars requires to lay out of databases of terrestrial-biomineral characteristics used as Martian-analogues. Within this framework, we studied the thermal behevior of carbonate samples (calcite, aragonite...) of biotic and abiotic origin in order to highlight specificities of materials of biological origin. We used samples collected allover the world (present and fossil carbonates of shells, corals, stromatolites, microbialites, samples from extreme environments...). Materials have been analysed by TDA-TG to determine and compare profiles of mass loss in CO2 according to temperature. Measurements by X-ray diffraction and by Pyr-GC-MS have been carried out, isotopic ratios of O and C complete these characterizations. These results are of primary importance to propose an original method of in situ detection of a biotic activity over Mars (for example in the frame of the SAM suite of instruments proposed on MSL09) and for laboratory analysis in case of Martian Sample Return. This work has been supported by CNES grants since 2002.

  18. Identifying the interacting roles of stressors in driving the global loss of canopy-forming to mat-forming algae in marine ecosystems.

    PubMed

    Strain, Elisabeth M A; Thomson, Russell J; Micheli, Fiorenza; Mancuso, Francesco P; Airoldi, Laura

    2014-11-01

    Identifying the type and strength of interactions between local anthropogenic and other stressors can help to set achievable management targets for degraded marine ecosystems and support their resilience by identifying local actions. We undertook a meta-analysis, using data from 118 studies to test the hypothesis that ongoing global declines in the dominant habitat along temperate rocky coastlines, forests of canopy-forming algae and/or their replacement by mat-forming algae are driven by the nonadditive interactions between local anthropogenic stressors that can be addressed through management actions (fishing, heavy metal pollution, nutrient enrichment and high sediment loads) and other stressors (presence of competitors or grazers, removal of canopy algae, limiting or excessive light, low or high salinity, increasing temperature, high wave exposure and high UV or CO2 ), not as easily amenable to management actions. In general, the cumulative effects of local anthropogenic and other stressors had negative effects on the growth and survival of canopy-forming algae. Conversely, the growth or survival of mat-forming algae was either unaffected or significantly enhanced by the same pairs of stressors. Contrary to our predictions, the majority of interactions between stressors were additive. There were however synergistic interactions between nutrient enrichment and heavy metals, the presence of competitors, low light and increasing temperature, leading to amplified negative effects on canopy-forming algae. There were also synergistic interactions between nutrient enrichment and increasing CO2 and temperature leading to amplified positive effects on mat-forming algae. Our review of the current literature shows that management of nutrient levels, rather than fishing, heavy metal pollution or high sediment loads, would provide the greatest opportunity for preventing the shift from canopy to mat-forming algae, particularly in enclosed bays or estuaries because of the

  19. The Biotic Indexing of Water Quality and Its Application to Field Work in Schools and Colleges.

    ERIC Educational Resources Information Center

    Dale, C. R.

    1980-01-01

    Discussed is the biotic indexing of water quality and its application to A-level field work with reference to the Trent Biotic Index and Chandler Score system. These indices are related to the classification of water quality used by the Department of the Environment. Interpretations and limitations of the indices are discussed. (Author/DS)

  20. A Report on the Methods to Associate Variations in Aquatic Biotic Condition to Variations in Stressors

    EPA Science Inventory

    In this report we present examples of methods that we have used to explore associations between aquatic biotic condition and stressors in two different aquatic systems: estuaries and lakes. We review metrics and indices of biotic condition in lakes and estuaries; discuss some ph...

  1. Feedbacks between biotic and abiotic influences on travertine deposition, Fossil Creek, Arizona.

    NASA Astrophysics Data System (ADS)

    Fuller, B. M.; Sklar, L. S.; Compson, Z. G.; Adams, K. J.; Marks, J. C.

    2008-12-01

    The linkages between fluvial geomorphology and aquatic ecosystems are commonly modeled as a linear causal chain in which geomorphic processes create the physical template for ecological dynamics. In a variety of settings, however, biotic processes may strongly influence channel morphodynamics, creating the potential for numerous feedbacks. For example, because travertine is often composed of wood and algae cemented together by physically-driven calcite precipitation, travertine-dominated streams provide an opportunity to examine how topography evolves in a system where biology exerts strong controls on geomorphic processes. Decommissioning of a hydro-electric project on Fossil Creek, Arizona, after a century of flow diversion, has restored a steady base-flow of CaCO3-rich spring water, and triggered rapid re- growth of channel-spanning travertine dams. These structures create a step-pool morphology that provides a diverse set of aquatic and riparian habitats. Biotic processes in turn can catalyze travertine deposition and vertical growth of travertine dams, potentially accelerating the recovery of a once-threatened ecosystem. Here we report results of an ongoing study of the complex set of feedbacks between biotic and abiotic processes that control the rate of travertine growth and channel morphodynamics. To document vertical growth of travertine, we imbedded 1cm diameter magnets into nascent travertine dams and calculate growth rates from changes over time in the magnetic field intensity. So far we have installed 310 magnets along a 12 km stretch of Fossil Creek and calculated 539 individual growth rates over time periods ranging from 1 to 14 months. At each magnet, we record the flow depth, apparent travertine surface composition and numerous attributes of the local hydraulics and dam-pool morphology. To characterize conditions favorable for algal growth we measure sunlight availability by taking photos of riparian canopy looking directly up with a fisheye lens

  2. Associations between Ectomycorrhizal Fungi and Bacterial Needle Endophytes in Pinus radiata: Implications for Biotic Selection of Microbial Communities.

    PubMed

    Rúa, Megan A; Wilson, Emily C; Steele, Sarah; Munters, Arielle R; Hoeksema, Jason D; Frank, Anna C

    2016-01-01

    Studies of the ecological and evolutionary relationships between plants and their associated microbes have long been focused on single microbes, or single microbial guilds, but in reality, plants associate with a diverse array of microbes from a varied set of guilds. As such, multitrophic interactions among plant-associated microbes from multiple guilds represent an area of developing research, and can reveal how complex microbial communities are structured around plants. Interactions between coniferous plants and their associated microbes provide a good model system for such studies, as conifers host a suite of microorganisms including mutualistic ectomycorrhizal (ECM) fungi and foliar bacterial endophytes. To investigate the potential role ECM fungi play in structuring foliar bacterial endophyte communities, we sampled three isolated, native populations of Monterey pine (Pinus radiata), and used constrained analysis of principal coordinates to relate the community matrices of the ECM fungi and bacterial endophytes. Our results suggest that ECM fungi may be important factors for explaining variation in bacterial endophyte communities but this effect is influenced by population and environmental characteristics, emphasizing the potential importance of other factors - biotic or abiotic - in determining the composition of bacterial communities. We also classified ECM fungi into categories based on known fungal traits associated with substrate exploration and nutrient mobilization strategies since variation in these traits allows the fungi to acquire nutrients across a wide range of abiotic conditions and may influence the outcome of multi-species interactions. Across populations and environmental factors, none of the traits associated with fungal foraging strategy types significantly structured bacterial assemblages, suggesting these ECM fungal traits are not important for understanding endophyte-ECM interactions. Overall, our results suggest that both biotic species

  3. Associations between Ectomycorrhizal Fungi and Bacterial Needle Endophytes in Pinus radiata: Implications for Biotic Selection of Microbial Communities

    PubMed Central

    Rúa, Megan A.; Wilson, Emily C.; Steele, Sarah; Munters, Arielle R.; Hoeksema, Jason D.; Frank, Anna C.

    2016-01-01

    Studies of the ecological and evolutionary relationships between plants and their associated microbes have long been focused on single microbes, or single microbial guilds, but in reality, plants associate with a diverse array of microbes from a varied set of guilds. As such, multitrophic interactions among plant-associated microbes from multiple guilds represent an area of developing research, and can reveal how complex microbial communities are structured around plants. Interactions between coniferous plants and their associated microbes provide a good model system for such studies, as conifers host a suite of microorganisms including mutualistic ectomycorrhizal (ECM) fungi and foliar bacterial endophytes. To investigate the potential role ECM fungi play in structuring foliar bacterial endophyte communities, we sampled three isolated, native populations of Monterey pine (Pinus radiata), and used constrained analysis of principal coordinates to relate the community matrices of the ECM fungi and bacterial endophytes. Our results suggest that ECM fungi may be important factors for explaining variation in bacterial endophyte communities but this effect is influenced by population and environmental characteristics, emphasizing the potential importance of other factors — biotic or abiotic — in determining the composition of bacterial communities. We also classified ECM fungi into categories based on known fungal traits associated with substrate exploration and nutrient mobilization strategies since variation in these traits allows the fungi to acquire nutrients across a wide range of abiotic conditions and may influence the outcome of multi-species interactions. Across populations and environmental factors, none of the traits associated with fungal foraging strategy types significantly structured bacterial assemblages, suggesting these ECM fungal traits are not important for understanding endophyte-ECM interactions. Overall, our results suggest that both biotic

  4. Synergistic interactions of blood-borne immune cells, fibroblasts and extracellular matrix drive repair in an in vitro peri-implant wound healing model

    PubMed Central

    Burkhardt, Melanie A; Waser, Jasmin; Milleret, Vincent; Gerber, Isabel; Emmert, Maximilian Y; Foolen, Jasper; Hoerstrup, Simon P; Schlottig, Falko; Vogel, Viola

    2016-01-01

    Low correlations of cell culture data with clinical outcomes pose major medical challenges with costly consequences. While the majority of biomaterials are tested using in vitro cell monocultures, the importance of synergistic interactions between different cell types on paracrine signalling has recently been highlighted. In this proof-of-concept study, we asked whether the first contact of surfaces with whole human blood could steer the tissue healing response. This hypothesis was tested using alkali-treatment of rough titanium (Ti) surfaces since they have clinically been shown to improve early implant integration and stability, yet blood-free in vitro cell cultures poorly correlated with in vivo tissue healing. We show that alkali-treatment, compared to native Ti surfaces, increased blood clot thickness, including platelet adhesion. Strikingly, blood clots with entrapped blood cells in synergistic interactions with fibroblasts, but not fibroblasts alone, upregulated the secretion of major factors associated with fast healing. This includes matrix metalloproteinases (MMPs) to break down extracellular matrix and the growth factor VEGF, known for its angiogenic potential. Consequently, in vitro test platforms, which consider whole blood-implant interactions, might be superior in predicting wound healing in response to biomaterial properties. PMID:26883175

  5. Synergistic interactions of blood-borne immune cells, fibroblasts and extracellular matrix drive repair in an in vitro peri-implant wound healing model

    NASA Astrophysics Data System (ADS)

    Burkhardt, Melanie A.; Waser, Jasmin; Milleret, Vincent; Gerber, Isabel; Emmert, Maximilian Y.; Foolen, Jasper; Hoerstrup, Simon P.; Schlottig, Falko; Vogel, Viola

    2016-02-01

    Low correlations of cell culture data with clinical outcomes pose major medical challenges with costly consequences. While the majority of biomaterials are tested using in vitro cell monocultures, the importance of synergistic interactions between different cell types on paracrine signalling has recently been highlighted. In this proof-of-concept study, we asked whether the first contact of surfaces with whole human blood could steer the tissue healing response. This hypothesis was tested using alkali-treatment of rough titanium (Ti) surfaces since they have clinically been shown to improve early implant integration and stability, yet blood-free in vitro cell cultures poorly correlated with in vivo tissue healing. We show that alkali-treatment, compared to native Ti surfaces, increased blood clot thickness, including platelet adhesion. Strikingly, blood clots with entrapped blood cells in synergistic interactions with fibroblasts, but not fibroblasts alone, upregulated the secretion of major factors associated with fast healing. This includes matrix metalloproteinases (MMPs) to break down extracellular matrix and the growth factor VEGF, known for its angiogenic potential. Consequently, in vitro test platforms, which consider whole blood-implant interactions, might be superior in predicting wound healing in response to biomaterial properties.

  6. A novel GSK3-regulated APC:Axin interaction regulates Wnt signaling by driving a catalytic cycle of efficient βcatenin destruction

    PubMed Central

    Pronobis, Mira I; Rusan, Nasser M; Peifer, Mark

    2015-01-01

    APC, a key negative regulator of Wnt signaling in development and oncogenesis, acts in the destruction complex with the scaffold Axin and the kinases GSK3 and CK1 to target βcatenin for destruction. Despite 20 years of research, APC's mechanistic function remains mysterious. We used FRAP, super-resolution microscopy, functional tests in mammalian cells and flies, and other approaches to define APC's mechanistic role in the active destruction complex when Wnt signaling is off. Our data suggest APC plays two roles: (1) APC promotes efficient Axin multimerization through one known and one novel APC:Axin interaction site, and (2) GSK3 acts through APC motifs R2 and B to regulate APC:Axin interactions, promoting high-throughput of βcatenin to destruction. We propose a new dynamic model of how the destruction complex regulates Wnt signaling and how this goes wrong in cancer, providing insights into how this multiprotein signaling complex is assembled and functions via multivalent interactions. DOI: http://dx.doi.org/10.7554/eLife.08022.001 PMID:26393419

  7. A novel GSK3-regulated APC:Axin interaction regulates Wnt signaling by driving a catalytic cycle of efficient βcatenin destruction.

    PubMed

    Pronobis, Mira I; Rusan, Nasser M; Peifer, Mark

    2015-01-01

    APC, a key negative regulator of Wnt signaling in development and oncogenesis, acts in the destruction complex with the scaffold Axin and the kinases GSK3 and CK1 to target βcatenin for destruction. Despite 20 years of research, APC's mechanistic function remains mysterious. We used FRAP, super-resolution microscopy, functional tests in mammalian cells and flies, and other approaches to define APC's mechanistic role in the active destruction complex when Wnt signaling is off. Our data suggest APC plays two roles: (1) APC promotes efficient Axin multimerization through one known and one novel APC:Axin interaction site, and (2) GSK3 acts through APC motifs R2 and B to regulate APC:Axin interactions, promoting high-throughput of βcatenin to destruction. We propose a new dynamic model of how the destruction complex regulates Wnt signaling and how this goes wrong in cancer, providing insights into how this multiprotein signaling complex is assembled and functions via multivalent interactions. PMID:26393419

  8. [Useful assessment for identifying unsafe driving].

    PubMed

    Gonthier, Régis; Fabrigoule, Colette; Domont, Alain

    2005-03-01

    Ability to drive safely is the resultant of interactions between the individual (the driver), the vector (the car) and the environment (the state of the road). For some aged drivers, an important decline of visual, musculosquelettic and cognitive performances, may affect the ability to drive and increase the rate of crashes per vehicle-kilometer-driven, and the morbidity and mortality related to crash. Therefore, each holder of a driving licence should be medically suited to control his driving ability. In case of transitory or lasting driving incapacity, drivers must, of their own initiative, stop driving according to the Highway code and the contractual obligations appearing in their vehicle insurance contract. A medical examination for aptitude to driving requires a standardized, reliable, reproducible procedure based on consensual assessment tools to avoid arbitrary decisions for driving cessation. We propose a multidisciplinary approach to detect important decline of visuospatial and motor skills, paroxystic drops of attention and vigilance, and decreased cognitive capacity to anticipate and adapt driving at every moment. This assessment is based on a semi-directed interview and simple diagnostic tests. According to the present French law, only twelve medical conditions or functional deficits are inconsistent with the retain of the driving licence for a light vehicle. PMID:15814324

  9. Driving and neurodegenerative diseases.

    PubMed

    Uc, Ergun Y; Rizzo, Matthew

    2008-09-01

    The proportion of elderly people in the general population is rising, resulting in greater numbers of drivers with neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. These neurodegenerative disorders impair cognition, visual perception, and motor function, leading to reduced driver fitness and greater crash risk. Yet neither medical diagnosis nor age alone is reliable enough to predict driver safety or crashes or to revoke the driving privileges of these individuals. Driving research utilizes tools such as questionnaires about driving habits and history, driving simulators, standardized road tests utilizing instrumented vehicles, and state driving records. Research challenges include outlining the evolution of driving safety, understanding the mechanisms of driving impairment, and developing a reliable and efficient standardized test battery for prediction of driver safety in neurodegenerative disorders. This information will enable healthcare providers to advise their patients with neurodegenerative disorders with more certainty, affect policy, and help develop rehabilitative measures for driving. PMID:18713573

  10. Gear bearing drive

    NASA Technical Reports Server (NTRS)

    Weinberg, Brian (Inventor); Mavroidis, Constantinos (Inventor); Vranish, John M. (Inventor)

    2011-01-01

    A gear bearing drive provides a compact mechanism that operates as an actuator providing torque and as a joint providing support. The drive includes a gear arrangement integrating an external rotor DC motor within a sun gear. Locking surfaces maintain the components of the drive in alignment and provide support for axial loads and moments. The gear bearing drive has a variety of applications, including as a joint in robotic arms and prosthetic limbs.

  11. Magnetic drive coupling

    NASA Technical Reports Server (NTRS)

    Carter, Edward L. (Inventor)

    1987-01-01

    The driving and driven members of a magnetic drive are separated by en enlarged gap to provide clearance for a conduit or other member. Flux pins in the gap maintain the torque transmitting capability of the drive. The spacing between two of the flux pins is increased to provide space for the conduit.

  12. Magnetic drive coupling

    NASA Technical Reports Server (NTRS)

    Carter, Edward L. (Inventor)

    1989-01-01

    The driving (30) and driven (32) members of a magnetic drive (20) are separated by an enlarged gap (35) to provide clearance for a conduit (23) or other member. Flux pins (40) in the gap (35) maintain the torque transmitting capability of the drive (20). The spacing between two of the flux pins is increased to provide space for the conduit (23).

  13. Sequential Dependencies in Driving

    ERIC Educational Resources Information Center

    Doshi, Anup; Tran, Cuong; Wilder, Matthew H.; Mozer, Michael C.; Trivedi, Mohan M.

    2012-01-01

    The effect of recent experience on current behavior has been studied extensively in simple laboratory tasks. We explore the nature of sequential effects in the more naturalistic setting of automobile driving. Driving is a safety-critical task in which delayed response times may have severe consequences. Using a realistic driving simulator, we find…

  14. Grieving while Driving

    ERIC Educational Resources Information Center

    Rosenblatt, Paul C.

    2004-01-01

    Secondary analysis of data from 84 people in 2 interview studies shows that some bereaved people grieve actively while driving. The grief can be intense, even years after a death. Grief while driving may erupt spontaneously or be set off by a wide range of reminders. Some bereaved people seem to save their grieving for times when they drive,…

  15. Carbon isotopic fractionation of CFCs during abiotic and biotic degradation.

    PubMed

    Archbold, Marie E; Elliot, Trevor; Kalin, Robert M

    2012-02-01

    Carbon stable isotope ((13)C) fractionation in chlorofluorocarbon (CFC) compounds arising from abiotic (chemical) degradation using zero-valent iron (ZVI) and biotic (landfill gas attenuation) processes is investigated. Batch tests (at 25 °C) for CFC-113 and CFC-11 using ZVI show quantitative degradation of CFC-113 to HCFC-123a and CFC-1113 following pseudo-first-order kinetics corresponding to a half-life (τ(1/2)) of 20.5 h, and a ZVI surface-area normalized rate constant (k(SA)) of -(9.8 ± 0.5) × 10(-5) L m(-2) h(-1). CFC-11 degraded to trace HCFC-21 and HCFC-31 following pseudo-first-order kinetics corresponding to τ(1/2) = 17.3 h and k(SA) = -(1.2 ± 0.5) × 10(-4) L m(-2) h(-1). Significant kinetic isotope effects of ε(‰) = -5.0 ± 0.3 (CFC-113) and -17.8 ± 4.8 (CFC-11) were observed. Compound-specific carbon isotope analyses also have been used here to characterize source signatures of CFC gases (HCFC-22, CFC-12, HFC-134a, HCFC-142b, CFC-114, CFC-11, CFC-113) for urban (UAA), rural/remote (RAA), and landfill (LAA) ambient air samples, as well as in situ surface flux chamber (FLUX; NO FLUX) and landfill gas (LFG) samples at the Dargan Road site, Northern Ireland. The latter values reflect biotic degradation and isotopic fractionation in LFG production, and local atmospheric impact of landfill emissions through the cover. Isotopic fractionations of Δ(13)C ∼ -13‰ (HCFC-22), Δ(13)C ∼ -35‰ (CFC-12) and Δ(13)C ∼ -15‰ (CFC-11) were observed for LFG in comparison to characteristic solvent source signatures, with the magnitude of the isotopic effect for CFC-11 apparently similar to the kinetic isotope effect for (abiotic) ZVI degradation. PMID:22191586

  16. Evidence for biotic controls on topography and soil production

    NASA Astrophysics Data System (ADS)

    Roering, Joshua J.; Marshall, Jill; Booth, Adam M.; Mort, Michele; Jin, Qusheng

    2010-09-01

    The complex interplay of biological, physical, and chemical processes in pedogenesis and hillslope evolution limits our ability to predict and interpret landscape dynamics. Here, we synthesize a suite of observations from the steep, forested Oregon Coast Range to analyze the role of trees in topographic modification and bedrock-to-soil conversion. Using topographic data derived from airborne lidar, we demonstrate that the topographic signature of forest-driven soil and bedrock disturbance is pervasive. For length scales greater than 7.5 m, the land surface is defined by ridge-valley landforms, whereas smaller scales are dominated by pit-mound features generated by the turnover of large coniferous trees. From field surveys, the volume of bedrock incorporated in overturned rootwads increases rapidly with diameter for large conifers, reflecting the highly nonlinear increase in root biomass with tree diameter. Because trees younger than 60 years detach negligible bedrock, short timber harvest intervals may limit the extent to which root systems penetrate bedrock and facilitate bedrock fracturing and biogeochemical weathering. Using ground-penetrating radar, we show that the rootwads of large trees root achieve substantial penetration (1-3 m) into shallow bedrock. The radar transects also reveal that variations in soil thickness have characteristic length scales of 1 to 5 m, consistent with the scale of large rootwads, indicating that both the landscape surface and soil-bedrock interface exhibit a biogenic imprint. In our study area, the residence time of bedrock within dense rooting zones directly below large trees is similar to the time required for trees to occupy the entire forest floor through multiple cycles of forest succession, suggesting that biological modification of shallow bedrock is ubiquitous. Given increases in erosion rate, the ability of roots to initiate soil production may decline as bedrock exhumation through the biotic zone is rapid relative to the

  17. Conserved functional domains and a novel tertiary interaction near the pseudoknot drive translational activity of hepatitis C virus and hepatitis C virus-like internal ribosome entry sites

    PubMed Central

    Easton, Laura E.; Locker, Nicolas; Lukavsky, Peter J.

    2009-01-01

    The translational activity of the hepatitis C virus (HCV) internal ribosome entry site (IRES) and other HCV-like IRES RNAs depends on structured RNA elements in domains II and III, which serve to recruit the ribosomal 40S subunit, eukaryotic initiation factor (eIF) 3 and the ternary eIF2/Met-tRNAiMet/GTP complex and subsequently domain II assists subunit joining. Porcine teschovirus-1 talfan (PTV-1) is a member of the Picornaviridae family, with a predicted HCV-like secondary structure, but only stem-loops IIId and IIIe in the 40S-binding domain display significant sequence conservation with the HCV IRES. Here, we use chemical probing to show that interaction sites with the 40S subunit and eIF3 are conserved between HCV and HCV-like IRESs. In addition, we reveal the functional role of a strictly conserved co-variation between a purine–purine mismatch near the pseudoknot (A–A/G) and the loop sequence of domain IIIe (GAU/CA). These nucleotides are involved in a tertiary interaction, which serves to stabilize the pseudoknot structure and correlates with translational efficiency in both the PTV-1 and HCV IRES. Our data demonstrate conservation of functional domains in HCV and HCV-like IRESs including a more complex structure surrounding the pseudoknot than previously assumed. PMID:19596815

  18. Multiple interactions drive adaptor-mediated recruitment of the ubiquitin ligase rsp5 to membrane proteins in vivo and in vitro.

    PubMed

    Sullivan, James A; Lewis, Michael J; Nikko, Elina; Pelham, Hugh R B

    2007-07-01

    Recognition of membrane proteins by the Nedd4/Rsp5 ubiquitin ligase family is a critical step in their targeting to the multivesicular body pathway. Some substrates contain "PY" motifs (PPxY), which bind to WW domains in the ligase. Others lack PY motifs and instead rely on adaptors that recruit the ligase to them. To investigate the mechanism of adaptor-mediated ubiquitination, we have characterized the interactions between the adaptor Bsd2, the ubiquitin ligase Rsp5, and the membrane proteins Cps1, Tre1, and Smf1 from Saccharomyces cerevisiae. We have reconstituted adaptor-mediated modification of Cps1 and Tre1 in vitro, and we show that two PY motifs in Bsd2 and two WW domains (WW2 and WW3) in Rsp5 are crucial for this. The binding of a weak noncanonical DMAPSY motif in Bsd2 to WW3 is an absolute requirement for Bsd2 adaptor function. We show that sorting of the manganese transporter Smf1, which requires both Bsd2 and Tre1, depends upon two PY motifs in Bsd2 and one motif in Tre1 but only two WW domains in Rsp5. We suggest that sequential assembly of first a Bsd2/Rsp5 complex, then a Tre1/Bsd2/Rsp5 complex followed by a rearrangement of PY-WW interactions is required for the ubiquitination of Smf1. PMID:17429078

  19. The Evolutionary Ecology of Biotic Association in a Megadiverse Bivalve Superfamily: Sponsorship Required for Permanent Residency in Sediment

    PubMed Central

    Li, Jingchun; Ó Foighil, Diarmaid; Middelfart, Peter

    2012-01-01

    Background Marine lineage diversification is shaped by the interaction of biotic and abiotic factors but our understanding of their relative roles is underdeveloped. The megadiverse bivalve superfamily Galeommatoidea represents a promising study system to address this issue. It is composed of small-bodied clams that are either free-living or have commensal associations with invertebrate hosts. To test if the evolution of this lifestyle dichotomy is correlated with specific ecologies, we have performed a statistical analysis on the lifestyle and habitat preference of 121 species based on 90 source documents. Methodology/Principal Findings Galeommatoidea has significant diversity in the two primary benthic habitats: hard- and soft-bottoms. Hard-bottom dwellers are overwhelmingly free-living, typically hidden within crevices of rocks/coral heads/encrusting epifauna. In contrast, species in soft-bottom habitats are almost exclusively infaunal commensals. These infaunal biotic associations may involve direct attachment to a host, or clustering around its tube/burrow, but all commensals locate within the oxygenated sediment envelope produced by the host’s bioturbation. Conclusions/Significance The formation of commensal associations by galeommatoidean clams is robustly correlated with an abiotic environmental setting: living in sediments (). Sediment-dwelling bivalves are exposed to intense predation pressure that drops markedly with depth of burial. Commensal galeommatoideans routinely attain depth refuges many times their body lengths, independent of siphonal investment, by virtue of their host’s burrowing and bioturbation. In effect, they use their much larger hosts as giant auto-irrigating siphon substitutes. The evolution of biotic associations with infaunal bioturbating hosts may have been a prerequisite for the diversification of Galeommatoidea in sediments and has likely been a key factor in the success of this exceptionally diverse bivalve superfamily. PMID

  20. Stronger biotic resistance in tropics relative to temperate zone: effects of predation on marine invasion dynamics.

    PubMed

    Freestone, Amy L; Rutz, Gregory M; Torchin, Mark E

    2013-06-01

    Latitudinal patterns of nonnative species richness suggest fewer successful invasions in the tropics, relative to temperate regions. One main hypothesis for this pattern is that biotic resistance to invasion is stronger in the tropics than at higher latitudes. Biotic resistance can limit the distribution and abundance of nonnative species and, in extreme cases, can prevent establishment. We provide the first experimental test of this hypothesis, comparing the strength of biotic resistance in a tropical and a temperate marine ecosystem. Predation is one mechanism of biotic resistance, and since predation can be stronger at lower latitudes, we predicted that predation will serve to increase biotic resistance more in the tropics than at higher latitude. We conducted predator-exclusion experiments on marine epifaunal communities, a heavily invaded system, focusing on nonnative tunicates as a model fauna. The effect of predation on species richness of nonnative tunicates was more than three times greater at sites in tropical Panama than in temperate Connecticut, consistent with the prediction of stronger biotic resistance in the tropics. In Connecticut, predation reduced the abundance of one nonnative tunicate but did not affect the abundances of any other nonnative tunicate species, and no species were excluded from communities. In contrast, predation resulted in striking reductions in abundance and often exclusion of nonnative tunicates from experimental communities in Panama. If proved to be general, latitudinal differences in the biotic resistance of communities to nonnative species establishment may help explain emerging patterns of global invasions. PMID:23923500

  1. Electric versus hydraulic drives

    SciTech Connect

    Not Available

    1983-01-01

    This volume records the proceedings of a conference organised by the Engineering Manufacturing Industries Division of the Institution of Mechanical Engineers. Topics considered include high performance position control - a review of the current state of developments; hydrostatic drives - present and future; electric drives - present and future trends; electrical and hydraulic drives for heavy industrial robots; the development of an electro-mechanical tilt system for the advanced passenger train; industrial hydraulic ring mains - effective or efficient. the comparison of performance of servo feed-drive systems; overhead crane drives; the future of d.c. servodrives; the choice of actuator for military systems; linear electro-hydraulic actuators; and actuation for industrial robots.

  2. MUC1 drives epithelial-mesenchymal transition in renal carcinoma through Wnt/β-catenin pathway and interaction with SNAIL promoter.

    PubMed

    Gnemmi, Viviane; Bouillez, Audrey; Gaudelot, Kelly; Hémon, Brigitte; Ringot, Bélinda; Pottier, Nicolas; Glowacki, François; Villers, Arnauld; Vindrieux, David; Cauffiez, Christelle; Van Seuningen, Isabelle; Bernard, David; Leroy, Xavier; Aubert, Sébastien; Perrais, Michaël

    2014-05-01

    MUC1 is overexpressed in human carcinomas. The transcription factor SNAIL can activate epithelial-mesenchymal transition (EMT) in cancer cells. In this study, in renal carcinoma, we demonstrate that (i) MUC1 and SNAIL were overexpressed in human sarcomatoid carcinomas, (ii) SNAIL increased indirectly MUC1 expression, (iii) MUC1 overexpression induced EMT, (iv) MUC1 C-terminal domain (MUC1-C) and β-catenin increased SNAIL transcriptional activity by interaction with its promoter and (v) blocking MUC1-C nuclear localization decreased Wnt/β-catenin signaling pathway activation and SNAIL expression. Altogether, our findings demonstrate that MUC1 is an actor in EMT and appears as a new therapeutic target. PMID:24384091

  3. Non-Bonded Interactions Drive the Sub-Picosecond Bilin Photoisomerization in the P(fr) State of Phytochrome Cph1.

    PubMed

    Yang, Yang; Heyne, Karsten; Mathies, Richard A; Dasgupta, Jyotishman

    2016-02-01

    Phytochromes are protein-based photoreceptors harboring a bilin-based photoswitch in the active site. The timescale of photosignaling via C15 =C16 E-to-Z photoisomerization has been ambiguous in the far-red-absorbing Pfr state. Here we present a unified view of the structural events in phytochrome Cph1 post excitation with femtosecond precision, obtained via stimulated Raman and polarization-resolved transient IR spectroscopy. We demonstrate that photoproduct formation occurs within 700 fs, determined by a two-step partitioning process initiated by a planarization on the electronic excited state with a 300 fs time scale. The ultrafast isomerization timescale for Pfr -to-Pr conversion highlights the active role of the nonbonding methyl-methyl clash initiating the reaction in the excited state. We envision that our results will motivate the synthesis of new artificial photoswitches with precisely tuned non-bonded interactions for ultrafast response. PMID:26630441

  4. Lessons from the past: Biotic recoveries from mass extinctions

    PubMed Central

    Erwin, Douglas H.

    2001-01-01

    Although mass extinctions probably account for the disappearance of less than 5% of all extinct species, the evolutionary opportunities they have created have had a disproportionate effect on the history of life. Theoretical considerations and simulations have suggested that the empty niches created by a mass extinction should refill rapidly after extinction ameliorates. Under logistic models, this biotic rebound should be exponential, slowing as the environmental carrying capacity is approached. Empirical studies reveal a more complex dynamic, including positive feedback and an exponential growth phase during recoveries. Far from a model of refilling ecospace, mass extinctions appear to cause a collapse of ecospace, which must be rebuilt during recovery. Other generalities include the absence of a clear correlation between the magnitude of extinction and the pace of recovery or the resulting ecological and evolutionary disruption the presence of a survival interval, with few originations, immediately after an extinction and preceding the recovery phase, and the presence of many lineages that persist through an extinction event only to disappear during the subsequent recovery. Several recoveries include numerous missing lineages, groups that are found before the extinction, then latter in the recovery, but are missing during the initial survival–recovery phase. The limited biogeographic studies of recoveries suggest considerable variability between regions. PMID:11344285

  5. Understanding Organics in Meteorites and the Pre-Biotic Environment

    NASA Technical Reports Server (NTRS)

    Zare, Richard N.

    2003-01-01

    (1) Refinement of the analytic capabilities of our experiment via characterization of molecule-specific response and the effects upon analysis of the type of sample under investigation; (2) Measurement of polycyclic aromatic hydrocarbons (PAHs) with high sensitivity and spatial resolution within extraterrestrial samples; (3) Investigation of the interstellar reactions of PAHs via the analysis of species formed in systems modeling dust grains and ices; (4) Investigations into the potential role of PAHs in prebiotic and early biotic chemistry via photoreactions of PAHs under simulated prebiotic Earth conditions. To meet these objectives, we use microprobe laser-desorption, laser-ionization mass spectrometry (MuL(exp 2)MS), which is a sensitive, selective, and spatially resolved technique for detection of aromatic compounds. Appendix A presents a description of the MuL(exp 2)MS technique. The initial grant proposal was for a three-year funding period, while the award was given for a one-year interim period. Because of this change in time period, emphasis was shifted from the first research goal, which was more development-oriented, in order to focus more on the other analysis-oriented goals. The progress made on each of the four research areas is given below.

  6. H2-rich fluids from serpentinization: geochemical and biotic implications.

    PubMed

    Sleep, N H; Meibom, A; Fridriksson, Th; Coleman, R G; Bird, D K

    2004-08-31

    Metamorphic hydration and oxidation of ultramafic rocks produces serpentinites, composed of serpentine group minerals and varying amounts of brucite, magnetite, and/or FeNi alloys. These minerals buffer metamorphic fluids to extremely reducing conditions that are capable of producing hydrogen gas. Awaruite, FeNi3, forms early in this process when the serpentinite minerals are Fe-rich. Olivine with the current mantle Fe/Mg ratio was oxidized during serpentinization after the Moon-forming impact. This process formed some of the ferric iron in the Earth's mantle. For the rest of Earth's history, serpentinites covered only a small fraction of the Earth's surface but were an important prebiotic and biotic environment. Extant methanogens react H2 with CO2 to form methane. This is a likely habitable environment on large silicate planets. The catalytic properties of FeNi3 allow complex organic compounds to form within serpentinite and, when mixed with atmospherically produced complex organic matter and waters that circulated through basalts, constitutes an attractive prebiotic substrate. Conversely, inorganic catalysis of methane by FeNi3 competes with nascent and extant life. PMID:15326313

  7. Paleosol formation during the Early Triassic Biotic Crisis in Norway

    NASA Astrophysics Data System (ADS)

    Knies, Jochen; Müller, Axel; Zwingmann, Horst; Fredin, Ola; Brönner, Marco; Viola, Giulio

    2016-04-01

    Fractured and kaolinite weathered basement rocks have been discovered in various wells off the Norwegian coast and inferences on timing, source to sink relationships, and environmental implications have been widely discussed. The reason for the kaolitinization has often been related to intensive chemical weathering during late Triassic to early Jurassic times. Chronological control has primarily been inferred from the overlying late Jurassic/early Cretaceous marine transgression and poorly constrained K-Ar datings from weathered basement onshore as well as climate conditions favourable for kaolinite formation. In this study, we present evidence that the deeply weathered basement off the mid-Norwegian coast represent a complete paleosol profile. Quartz geochemical fingerprinting indicate that transgressional marine inorganic sediments of late Jurassic age are derived from the paleosols. Whole-rock XRD analysis suggests characteristic mineral alteration zones topped with a kaolinite-Fe-oxyhyroxide zones composed of >80% kaolinite. Potassium feldspar is practically absent in the uppermost kaolinitic zones. Mass-balance changes show significant depletion-enrichment trends. Applying potassium/argon (K/Ar) geochronology on authigenic illite clay that grew in-situ at the time of paleosol formation reveals a early Triassic age (~250 Ma). The age corroborates with the Early Triassic biotic crisis and suggest a causal relationship between intense chemical weathering, high atmospheric CO2 concentration, extreme ocean warming, increased riverine flux of nutrients and widespread anoxia/euxinia on adjacent epicontinental seas.

  8. Reductive transformation of carbamazepine by abiotic and biotic processes.

    PubMed

    König, Anne; Weidauer, Cindy; Seiwert, Bettina; Reemtsma, Thorsten; Unger, Tina; Jekel, Martin

    2016-09-15

    The antiepileptic drug carbamazepine (CBZ) is ubiquitously present in the anthropogenic water cycle and is therefore of concern regarding the potable water supply. Despite of its persistent behavior in the aquatic environment, a redox dependent removal at bank filtration sites with anaerobic aquifer passage was reported repeatedly but not elucidated in detail yet. The reductive transformation of CBZ was studied, using abiotic systems (catalytic hydrogenation, electrochemistry) as well as biologically active systems (column systems, batch degradation tests). In catalytic hydrogenation CBZ is gradually hydrogenated and nine transformation products (TPs) were detected by liquid chromatography high-resolution mass spectrometry. 10,11-Dihydro-CBZ ((2H)-CBZ) was the major stable product in these abiotic, surface catalyzed reduction processes and turned out to be not a precursor of the more hydrogenated TPs. In the biotic reduction processes the formation of (2H)-CBZ alone could not explain the observed CBZ decline. There, also traces of (6H)-CBZ and (8H)-CBZ were formed by microbes under anaerobic conditions and four phase-II metabolites of reduced CBZ could be detected and tentatively identified. Thus, the spectrum of reduction products of CBZ is more diverse than previously thought. In environmental samples CBZ removal along an anaerobic soil passage was confirmed and (2H)-CBZ was determined at one of the sites. PMID:27267475

  9. Lessons from the past: biotic recoveries from mass extinctions.

    PubMed

    Erwin, D H

    2001-05-01

    Although mass extinctions probably account for the disappearance of less than 5% of all extinct species, the evolutionary opportunities they have created have had a disproportionate effect on the history of life. Theoretical considerations and simulations have suggested that the empty niches created by a mass extinction should refill rapidly after extinction ameliorates. Under logistic models, this biotic rebound should be exponential, slowing as the environmental carrying capacity is approached. Empirical studies reveal a more complex dynamic, including positive feedback and an exponential growth phase during recoveries. Far from a model of refilling ecospace, mass extinctions appear to cause a collapse of ecospace, which must be rebuilt during recovery. Other generalities include the absence of a clear correlation between the magnitude of extinction and the pace of recovery or the resulting ecological and evolutionary disruption the presence of a survival interval, with few originations, immediately after an extinction and preceding the recovery phase, and the presence of many lineages that persist through an extinction event only to disappear during the subsequent recovery. Several recoveries include numerous missing lineages, groups that are found before the extinction, then latter in the recovery, but are missing during the initial survival-recovery phase. The limited biogeographic studies of recoveries suggest considerable variability between regions. PMID:11344285

  10. Biotic and abiotic mercury methylation and demethylation in sediments

    SciTech Connect

    Zhang, L.; Planas, D. )

    1994-05-01

    Inorganic mercury (Hg(II)) methylation and methylmercury (MeHg) demethylation may occur in the water column, sediment-water interface and subsurficial sediment of aquatic ecosystems. These transformations involve mainly microbial mechanisms, although abiotic methylation may play a more important role in the water compartment. The relative importance of biotic versus abiotic mechanisms of methylation has not been determined however, and abiotic demethylation remains unknown. Little quantitative information is available on the role of bacterial activity in mercury transformations. It has been reported that at least 16 genera of aerobic and anaerobic microorganisms are able to methylate HG(II), and that a greater number are able to demethylate MeHg. Nevertheless, not all populations of these species are capable of methyl- and demethyl-transformations. The actual concentration of MeHg in the aquatic environment is regulated by the relative production and decomposition rates. This, in turn, depends on the availability of Hg(II), MeHg, and bacteria as well as on the physico-chemical properties of the sample. The objective of this study was to compare mercury methylation and demethylation rates in sediment samples with and without active bacterial populations. We therefore performed experiments to follow bacterial evolution during the course of Hg(II) methylation and MeHg demethylation in sediment slurries containing both sterile and non-sterile sediments.

  11. H2-rich fluids from serpentinization: Geochemical and biotic implications

    PubMed Central

    Sleep, N. H.; Meibom, A.; Fridriksson, Th.; Coleman, R. G.; Bird, D. K.

    2004-01-01

    Metamorphic hydration and oxidation of ultramafic rocks produces serpentinites, composed of serpentine group minerals and varying amounts of brucite, magnetite, and/or FeNi alloys. These minerals buffer metamorphic fluids to extremely reducing conditions that are capable of producing hydrogen gas. Awaruite, FeNi3, forms early in this process when the serpentinite minerals are Fe-rich. Olivine with the current mantle Fe/Mg ratio was oxidized during serpentinization after the Moon-forming impact. This process formed some of the ferric iron in the Earth's mantle. For the rest of Earth's history, serpentinites covered only a small fraction of the Earth's surface but were an important prebiotic and biotic environment. Extant methanogens react H2 with CO2 to form methane. This is a likely habitable environment on large silicate planets. The catalytic properties of FeNi3 allow complex organic compounds to form within serpentinite and, when mixed with atmospherically produced complex organic matter and waters that circulated through basalts, constitutes an attractive prebiotic substrate. Conversely, inorganic catalysis of methane by FeNi3 competes with nascent and extant life. PMID:15326313

  12. Drill drive mechanism

    DOEpatents

    Dressel, Michael O.

    1979-01-01

    A drill drive mechanism is especially adapted to provide both rotational drive and axial feed for a drill of substantial diameter such as may be used for drilling holes for roof bolts in mine shafts. The drill shaft is made with a helical pattern of scroll-like projections on its surface for removal of cuttings. The drill drive mechanism includes a plurality of sprockets carrying two chains of drive links which are arranged to interlock around the drill shaft with each drive link having depressions which mate with the scroll-like projections. As the chain links move upwardly or downwardly the surfaces of the depressions in the links mate with the scroll projections to move the shaft axially. Tangs on the drive links mate with notch surfaces between scroll projections to provide a means for rotating the shaft. Projections on the drive links mate together at the center to hold the drive links tightly around the drill shaft. The entire chain drive mechanism is rotated around the drill shaft axis by means of a hydraulic motor and gear drive to cause rotation of the drill shaft. This gear drive also connects with a differential gearset which is interconnected with a second gear. A second motor is connected to the spider shaft of the differential gearset to produce differential movement (speeds) at the output gears of the differential gearset. This differential in speed is utilized to drive said second gear at a speed different from the speed of said gear drive, this speed differential being utilized to drive said sprockets for axial movement of said drill shaft.

  13. The nucleotide exchange factor MGE exerts a key function in the ATP-dependent cycle of mt-Hsp70-Tim44 interaction driving mitochondrial protein import.

    PubMed Central

    Schneider, H C; Westermann, B; Neupert, W; Brunner, M

    1996-01-01

    Import of preproteins into the mitochondrial matrix is driven by the ATP-dependent interaction of mt-Hsp70 with the peripheral inner membrane import protein Tim44 and the preprotein in transit. We show that Mge1p, a co-chaperone of mt-Hsp70, plays a key role in the ATP-dependent import reaction cycle in yeast. Our data suggest a cycle in which the mt-Hsp70-Tim44 complex forms with ATP: Mge1p promotes assembly of the complex in the presence of ATP. Hydrolysis of ATP by mt-Hsp70 occurs in complex with Tim44. Mge1p is then required for the dissociation of the ADP form of mt-Hsp70 from Tim44 after release of inorganic phosphate but before release of ADP. ATP hydrolysis and complex dissociation are accompanied by tight binding of mt-Hsp70 to the preprotein in transit. Subsequently, the release of mt-Hsp70 from the polypeptide chain is triggered by Mge1p which promotes release of ADP from mt-Hsp70. Rebinding of ATP to mt-Hsp70 completes the reaction cycle. Images PMID:8918457

  14. Additive and interaction effects at three amino acid positions in HLA-DQ and HLA-DR molecules drive type 1 diabetes risk

    PubMed Central

    Hu, Xinli; Deutsch, Aaron J; Lenz, Tobias L; Onengut-Gumuscu, Suna; Han, Buhm; Chen, Wei-Min; Howson, Joanna M M; Todd, John A; de Bakker, Paul I W; Rich, Stephen S; Raychaudhuri, Soumya

    2016-01-01

    Variation in the human leukocyte antigen (HLA) genes accounts for one-half of the genetic risk in type 1 diabetes (T1D). Amino acid changes in the HLA-DR and HLA-DQ molecules mediate most of the risk, but extensive linkage disequilibrium complicates the localization of independent effects. Using 18,832 case-control samples, we localized the signal to 3 amino acid positions in HLA-DQ and HLA-DR. HLA-DQβ1 position 57 (previously known; P = 1 × 10−1,355) by itself explained 15.2% of the total phenotypic variance. Independent effects at HLA-DRβ1 positions 13 (P = 1 × 10−721) and 71 (P = 1 × 10−95) increased the proportion of variance explained to 26.9%. The three positions together explained 90% of the phenotypic variance in the HLA-DRB1–HLA-DQA1–HLA-DQB1 locus. Additionally, we observed significant interactions for 11 of 21 pairs of common HLA-DRB1–HLA-DQA1–HLA-DQB1 haplotypes (P = 1.6 × 10−64). HLA-DRβ1 positions 13 and 71 implicate the P4 pocket in the antigen-binding groove, thus pointing to another critical protein structure for T1D risk, in addition to the HLA-DQ P9 pocket. PMID:26168013

  15. Interactions between Adipocytes and Breast Cancer Cells Stimulate Cytokine Production and Drive Src/Sox2/miR-302b-Mediated Malignant Progression.

    PubMed

    Picon-Ruiz, Manuel; Pan, Chendong; Drews-Elger, Katherine; Jang, Kibeom; Besser, Alexandra H; Zhao, Dekuang; Morata-Tarifa, Cynthia; Kim, Minsoon; Ince, Tan A; Azzam, Diana J; Wander, Seth A; Wang, Bin; Ergonul, Burcu; Datar, Ram H; Cote, Richard J; Howard, Guy A; El-Ashry, Dorraya; Torné-Poyatos, Pablo; Marchal, Juan A; Slingerland, Joyce M

    2016-01-15

    Consequences of the obesity epidemic on cancer morbidity and mortality are not fully appreciated. Obesity is a risk factor for many cancers, but the mechanisms by which it contributes to cancer development and patient outcome have yet to be fully elucidated. Here, we examined the effects of coculturing human-derived adipocytes with established and primary breast cancer cells on tumorigenic potential. We found that the interaction between adipocytes and cancer cells increased the secretion of proinflammatory cytokines. Prolonged culture of cancer cells with adipocytes or cytokines increased the proportion of mammosphere-forming cells and of cells expressing stem-like markers in vitro. Furthermore, contact with immature adipocytes increased the abundance of cancer cells with tumor-forming and metastatic potential in vivo. Mechanistic investigations demonstrated that cancer cells cultured with immature adipocytes or cytokines activated Src, thus promoting Sox2, c-Myc, and Nanog upregulation. Moreover, Sox2-dependent induction of miR-302b further stimulated cMYC and SOX2 expression and potentiated the cytokine-induced cancer stem cell-like properties. Finally, we found that Src inhibitors decreased cytokine production after coculture, indicating that Src is not only activated by adipocyte or cytokine exposures, but is also required to sustain cytokine induction. These data support a model in which cancer cell invasion into local fat would establish feed-forward loops to activate Src, maintain proinflammatory cytokine production, and increase tumor-initiating cell abundance and metastatic progression. Collectively, our findings reveal new insights underlying increased breast cancer mortality in obese individuals and provide a novel preclinical rationale to test the efficacy of Src inhibitors for breast cancer treatment. PMID:26744520

  16. The modality of cell-particle interactions drives the toxicity of nanosized CuO and TiO₂ in human alveolar epithelial cells.

    PubMed

    Moschini, Elisa; Gualtieri, Maurizio; Colombo, Miriam; Fascio, Umberto; Camatini, Marina; Mantecca, Paride

    2013-10-24

    Metal oxide NPs are abundantly produced in nanotech industries and are emitted in several combustion processes, suggesting the need to characterize their toxic impact on the human respiratory system. The acute toxicity and the morphological changes induced by copper oxide and titanium dioxide NPs (nCuO and nTiO₂) on the human alveolar cell line A549 are here investigated. Cell viability and oxidative stress have been studied in parallel with NP internalization and cell ultrastructural modifications. TiO₂ NPs were abundantly internalized by cells through the endocytic pathway, even they did not induce cell death and ultrastructural lesions. Only after 24h cells were affected by an abundant NP internalization presenting a consequent altered morphology. High cytotoxicity, oxidative stress and severe ultrastructural damages were produced by nCuO, since cell membrane and mitochondria resulted to be heavily affected, even at early exposure time. nCuO-induced toxicity has been interpreted as a consequence of both NPs reactivity and copper ions dissolution in lysosomal compartments, even the free NPs, scattered throughout all the cell compartments, might contribute to the toxicity. The antioxidant N-acetylcysteine was effective in recovering nCuO exposed cells viability and Bafilomycin A1 inhibited copper ions release in phagolysosomes and significantly rescued cells, suggesting a relevant cytotoxic mechanism relative to oxidative damages and authophagic cell death, together with NP internalization and dissolution. Our results support the previous data reporting CuO NPs are highly cytotoxic and genotoxic, and associate their toxic effects with their cell penetration and interaction with various compartments. In conclusion, the so-called "Trojan horse" mechanism and autophagy, are involved in nCuO-induced cell death, even a further research is needed to explain the events occurring at early exposure time. PMID:23906720

  17. Habitability for Complex Life and the Development and Self-Limitations of the Biotic Enhancement of Weathering

    NASA Astrophysics Data System (ADS)

    Schwartzman, D. W.; Volk, T.

    2014-12-01

    We submit that the tightly coupled coevolution of biota and climate is a critical driver of the self-organization of the biosphere over geologic time. The long-term carbon biogeochemical cycle includes a major influence of biology relevant to climatic, namely the biotic enhancement of weathering (BEW). According to a meta-analysis of field and experimental evidence, the likely magnitude of the present BEW is roughly two orders of magnitude, the culmination of its progressive increase over geologic time. Within the context of modeling this long-term cycle, this value can be used to estimate the likely abiotic temperature history of the Earth's surface, assuming plausible initial temperatures, and histories of volcanic outgassing and continental crust growth. The result of this modeling is that the Earth would have been habitable for thermophilic life (growing above 50 deg C) for the past 4.4 billion years, but not for low-temperature life, including plants and animals. Hence biospheric cooling due to biotic actions allowed the emergence of complex life. Much larger increases in BEW are self-limiting, since the atmospheric CO2 level would plunge below the lower limit potentially for photosynthesis, thereby driving a decline in the biological productivity and global BEW, related to reduced plant and soil activities, with the system being kept at this threshold or going back to higher CO2 levels, with scenarios dependent on volcanic outgassing and solar inputs. We will present astrobiological implications of this modeling. References: Schwartzman D (1999, 2002) Life, Temperature, and the Earth: The Self Organizing Biosphere. Columbia Univ. Press; Schwartzman, D. (2013) Keynote: The Geobiology of Weathering: The 13th Hypothesis. Goldschmidt Conference. (Schwartzman D. and Brantley S. (2013) Mineral. Mag. 77(5): 2170); Volk T (1998) Gaia's Body: Toward a Physiology of Earth. Copernicus.

  18. Magnetostrictive roller drive motor

    NASA Astrophysics Data System (ADS)

    Vranish, John M.

    1992-01-01

    A magnetostrictive drive motor is disclosed which has a rotary drive shaft in the form of a drum which is encircled by a plurality of substantially equally spaced roller members in the form of two sets of cones which are in contact with the respective cam surfaces on the inside surface of an outer drive ring. The drive ring is attached to sets of opposing pairs of magnetostrictive rods. Each rod in a pair is mutually positioned end to end within respective energizing coils. When one of the coils in an opposing pair is energized, the energized rod expands while the other rod is caused to contract, causing the drive ring to rock, i.e., rotate slightly in either the clockwise or counterclockwise direction, depending upon which rod in a pair is energized. As the drive ring is activated in repetitive cycles in either direction, one set of drive cones attempts to roll up their respective cam surface but are pinned between the drive shaft drum and the drive ring. As the frictional force preventing sliding builds up, the cones become locked, setting up reaction forces including a tangential component which is imparted to the drive shaft drum to provide a source of motor torque. Simultaneously the other set of cones are disengaged from the drive shaft drum. Upon deactivation of the magnetostrictive rod coils, the force on the drive cones is released, causing the system to return to an initial rest position. By repetitively cycling the energization of the magnetostrictive rods, the drive shaft drum indexes in microradian rotational steps.

  19. Effects of biotic and abiotic factors on phenotypic partitioning of wing morphology and development in Sclerodermus pupariae (Hymenoptera: Bethylidae).

    PubMed

    Wang, Xiaoyi; Wei, Ke; Yang, Zhongqi; Jennings, David E; Duan, Jian J

    2016-01-01

    Wing phenotype polymorphism is commonly observed in insects, yet little is known about the influence of environmental cues on the development or expression of the alternative phenotypes. Here, we report how both biotic and abiotic factors affect the wing morph differentiation of a bethylid parasitoid Sclerodermus pupariae. The percentage of winged female parasitoid progeny increased exponentially with temperature between 20 °C to 30 °C. Low intensity light and short-day photoperiod conditions also significantly induced the development of winged morphs. Interestingly, wingless maternal parasitoids produced more winged progeny. Furthermore, the degree of wing dimorphism was significantly influenced by the interactions between light intensity and maternal wing morphs. The percentage of winged female progeny was not significantly influenced by foundress densities, but increased significantly with parasitoid brood sizes. However, the percentage of male progeny increased significantly with the densities of maternal parasitoids. Our findings highlight the phenotypic partitioning of wing morphology and development in the parasitoid S. pupariae under varied environmental cues, and reveal the most favourable conditions for the production of winged females in this bethylid wasp. It is thus possible to increase winged female parasitoid production for the purposes of biological control by manipulation of biotic and abiotic conditions. PMID:27194095

  20. Model-based Analysis of Mixed Uranium(VI) Reduction by Biotic and Abiotic Pathways During in Situ Bioremediation

    SciTech Connect

    Zhao, Jiao; Scheibe, Timothy D.; Mahadevan, Radhakrishnan

    2013-10-24

    Uranium bioremediation has emerged as a potential strategy of cleanup of radionuclear contamination worldwide. An integrated geochemical & microbial community model is a promising approach to predict and provide insights into the bioremediation of a complicated natural subsurface. In this study, an integrated column-scale model of uranium bioremediation was developed, taking into account long-term interactions between biotic and abiotic processes. It is also combined with a comprehensive thermodynamic analysis to track the fate and cycling of biogenic species. As compared with other bioremediation models, the model increases the resolution of the connection of microbial community to geochemistry and establishes direct quantitative correlation between overall community evolution and geochemical variation, thereby accurately predicting the community dynamics under different sedimentary conditions. The thermodynamic analysis examined a recently identified homogeneous reduction of U(VI) by Fe(II) under dynamic sedimentary conditions across time and space. It shows that the biogenic Fe(II) from Geobacter metabolism can be removed rapidly by the biogenic sulphide from sulfate reducer metabolism, hence constituting one of the reasons that make the abiotic U(VI) reduction thermodynamically infeasible in the subsurface. Further analysis indicates that much higher influent concentrations of both Fe(II) and U(VI) than normal are required to for abiotic U(VI) reduction to be thermodynamically feasible, suggesting that the abiotic reduction cannot be an alternative to the biotic reduction in the remediation of uranium contaminated groundwater.

  1. Green Light to Plant Responses to Pathogens: The Role of Chloroplast Light-Dependent Signaling in Biotic Stress.

    PubMed

    Delprato, María Laura; Krapp, Adriana R; Carrillo, Néstor

    2015-01-01

    Light has a key impact on the outcome of biotic stress responses in plants by providing most of the energy and many signals for the deployment of defensive barriers. Within this context, chloroplasts are not only the major source of energy in the light; they also host biosynthetic pathways for the production of stress hormones and secondary metabolites, as well as reactive oxygen species and other signals which modulate nuclear gene expression and plant resistance to pathogens. Environmental, and in particular, light-dependent regulation of immune responses may allow plants to anticipate and react more effectively to pathogen threats. As more information is gathered, increasingly complex models are developed to explain how light and reactive oxygen species signaling could interact with endogenous defense pathways to elicit efficient protective responses against invading microorganisms. The emerging picture places chloroplasts in a key position of an intricate regulatory network which involves several other cellular compartments. This article reviews current knowledge on the extent and the main features of chloroplast contribution to plant defensive strategies against biotic stress. PMID:25989185

  2. Effects of biotic and abiotic factors on phenotypic partitioning of wing morphology and development in Sclerodermus pupariae (Hymenoptera: Bethylidae)

    PubMed Central

    Wang, Xiaoyi; Wei, Ke; Yang, Zhongqi; Jennings, David E.; Duan, Jian J.

    2016-01-01

    Wing phenotype polymorphism is commonly observed in insects, yet little is known about the influence of environmental cues on the development or expression of the alternative phenotypes. Here, we report how both biotic and abiotic factors affect the wing morph differentiation of a bethylid parasitoid Sclerodermus pupariae. The percentage of winged female parasitoid progeny increased exponentially with temperature between 20 °C to 30 °C. Low intensity light and short-day photoperiod conditions also significantly induced the development of winged morphs. Interestingly, wingless maternal parasitoids produced more winged progeny. Furthermore, the degree of wing dimorphism was significantly influenced by the interactions between light intensity and maternal wing morphs. The percentage of winged female progeny was not significantly influenced by foundress densities, but increased significantly with parasitoid brood sizes. However, the percentage of male progeny increased significantly with the densities of maternal parasitoids. Our findings highlight the phenotypic partitioning of wing morphology and development in the parasitoid S. pupariae under varied environmental cues, and reveal the most favourable conditions for the production of winged females in this bethylid wasp. It is thus possible to increase winged female parasitoid production for the purposes of biological control by manipulation of biotic and abiotic conditions. PMID:27194095

  3. From the Cover: Environmental and biotic controls on the evolutionary history of insect body size

    NASA Astrophysics Data System (ADS)

    Clapham, Matthew E.; Karr, Jered A.

    2012-07-01

    Giant insects, with wingspans as large as 70 cm, ruled the Carboniferous and Permian skies. Gigantism has been linked to hyperoxic conditions because oxygen concentration is a key physiological control on body size, particularly in groups like flying insects that have high metabolic oxygen demands. Here we show, using a dataset of more than 10,500 fossil insect wing lengths, that size tracked atmospheric oxygen concentrations only for the first 150 Myr of insect evolution. The data are best explained by a model relating maximum size to atmospheric environmental oxygen concentration (pO2) until the end of the Jurassic, and then at constant sizes, independent of oxygen fluctuations, during the Cretaceous and, at a smaller size, the Cenozoic. Maximum insect size decreased even as atmospheric pO2 rose in the Early Cretaceous following the evolution and radiation of early birds, particularly as birds acquired adaptations that allowed more agile flight. A further decrease in maximum size during the Cenozoic may relate to the evolution of bats, the Cretaceous mass extinction, or further specialization of flying birds. The decoupling of insect size and atmospheric pO2 coincident with the radiation of birds suggests that biotic interactions, such as predation and competition, superseded oxygen as the most important constraint on maximum body size of the largest insects.

  4. The timing and pattern of biotic recovery following the end-Permian mass extinction

    NASA Astrophysics Data System (ADS)

    Chen, Zhong-Qiang; Benton, Michael J.

    2012-06-01

    The aftermath of the great end-Permian period mass extinction 252 Myr ago shows how life can recover from the loss of >90% species globally. The crisis was triggered by a number of physical environmental shocks (global warming, acid rain, ocean acidification and ocean anoxia), and some of these were repeated over the next 5-6 Myr. Ammonoids and some other groups diversified rapidly, within 1-3 Myr, but extinctions continued through the Early Triassic period. Triassic ecosystems were rebuilt stepwise from low to high trophic levels through the Early to Middle Triassic, and a stable, complex ecosystem did not re-emerge until the beginning of the Middle Triassic, 8-9 Myr after the crisis. A positive aspect of the recovery was the emergence of entirely new groups, such as marine reptiles and decapod crustaceans, as well as new tetrapods on land, including -- eventually -- dinosaurs. The stepwise recovery of life in the Triassic could have been delayed either by biotic drivers (complex multispecies interactions) or physical perturbations, or a combination of both. This is an example of the wider debate about the relative roles of intrinsic and extrinsic drivers of large-scale evolution.

  5. Environmental and biotic controls on the evolutionary history of insect body size.

    PubMed

    Clapham, Matthew E; Karr, Jered A

    2012-07-01

    Giant insects, with wingspans as large as 70 cm, ruled the Carboniferous and Permian skies. Gigantism has been linked to hyperoxic conditions because oxygen concentration is a key physiological control on body size, particularly in groups like flying insects that have high metabolic oxygen demands. Here we show, using a dataset of more than 10,500 fossil insect wing lengths, that size tracked atmospheric oxygen concentrations only for the first 150 Myr of insect evolution. The data are best explained by a model relating maximum size to atmospheric environmental oxygen concentration (pO(2)) until the end of the Jurassic, and then at constant sizes, independent of oxygen fluctuations, during the Cretaceous and, at a smaller size, the Cenozoic. Maximum insect size decreased even as atmospheric pO(2) rose in the Early Cretaceous following the evolution and radiation of early birds, particularly as birds acquired adaptations that allowed more agile flight. A further decrease in maximum size during the Cenozoic may relate to the evolution of bats, the Cretaceous mass extinction, or further specialization of flying birds. The decoupling of insect size and atmospheric pO(2) coincident with the radiation of birds suggests that biotic interactions, such as predation and competition, superseded oxygen as the most important constraint on maximum body size of the largest insects. PMID:22665762

  6. Abiotic and biotic factors that influence the bioavailability of gold nanoparticles to aquatic macrophytes.

    PubMed

    Glenn, J Brad; Klaine, Stephen J

    2013-09-17

    This research identified and characterized factors that influenced nanomaterial bioavailability to three aquatic plants: Azolla caroliniana Willd, Egeria densa Planch., and Myriophyllum simulans Orch. Plants were exposed to 4-, 18-, and 30-nm gold nanoparticles. Uptake was influenced by nanoparticle size, the presence of roots on the plant, and dissolved organic carbon in the media. Statistical analysis of the data also revealed that particle uptake was influenced by a 4-way (plant species, plant roots, particle size, and dissolved organic carbon) interaction suggesting nanoparticle bioavailability was a complex result of multiple parameters. Size and species dependent absorption was observed that was dependent on the presence of roots and nanoparticle size. The presence of dissolved organic carbon was found to associate with 4- and 18-nm gold nanoparticles in suspension and form a nanoparticle/organic matter complex that resulted in (1) minimized particle aggregation and (2) a decrease of nanoparticle absorption by the aquatic plants. The same effect was not observed with the 30-nm nanoparticle treatment. These results indicate that multiple factors, both biotic and abiotic, must be taken into account when predicting bioavailability of nanomaterials to aquatic plants. PMID:23947987

  7. Chemical controls on abiotic and biotic release of geogenic arsenic from Pleistocene aquifer sediments to groundwater.

    PubMed

    Gillispie, Elizabeth C; Andujar, Erika; Polizzotto, Matthew L

    2016-08-10

    Over 150 million people in South and Southeast Asia consume unsafe drinking water from arsenic-rich Holocene aquifers. Although use of As-free water from Pleistocene aquifers is a potential mitigation strategy, such aquifers are vulnerable to geogenic As pollution, placing millions more people at potential risk. The goal of this research was to define chemical controls on abiotic and biotic release of geogenic As to groundwater. Batch incubations of sediments with natural chemical variability from a Pleistocene aquifer in Cambodia were conducted to evaluate how interactions among arsenic, manganese and iron oxides, and dissolved and sedimentary organic carbon influenced As mobilization from sediments. The addition of labile dissolved organic carbon produced the highest concentrations of dissolved As after >7 months, as compared to sediment samples incubated with sodium azide or without added carbon, and the extent of As release was positively correlated with the percent of initial extractable Mn released from the sediments. The mode of As release was impacted by the source of DOC supplied to the sediments, with biological processes responsible for 81% to 85% of the total As release following incubations with lactate and acetate but only up to 43% to 61% of the total As release following incubations with humic and fulvic acids. Overall, cycling of key redox-active elements and organic-carbon reactivity govern the potential for geogenic As release to groundwater, and results here may be used to formulate better predictions of the arsenic pollution potential of aquifers in South and Southeast Asia. PMID:27463026

  8. Biotic nitrogen fixation in the bryosphere is inhibited more by drought than warming.

    PubMed

    Whiteley, Jonathan A; Gonzalez, Andrew

    2016-08-01

    The boreal forest is of particular interest to climate change research due to its large circumpolar distribution and accumulated soil carbon pool. Carbon uptake in this ecosystem is nitrogen (N)-limited, therefore factors affecting carbon or nitrogen dynamics in the boreal forest can have consequences for global climate. We used a 2-year field experiment to investigate the response of biotic nitrogen fixation by cyanobacteria associated with boreal forest bryophytes, in a factorial experiment combining simulated climate change with habitat fragmentation treatments. We simulated climate change conditions using open-top greenhouse chambers in the field, which increased mean and maximum temperatures, and created a precipitation gradient from ambient levels in the center to extreme drought conditions at the periphery of the chamber. The dry patches near the chamber walls exhibited almost no N-fixation, despite having similar densities of cyanobacteria (predominantly Stigonema sp.) as other patches. Rates of N-fixation were best explained by a model containing moisture, fragmentation, cyanobacteria density and time; warming was not a significant variable affecting N-fixation. There was no significant interaction between warming and fragmentation. These results suggest that cyanobacteria responded physiologically to drought by reducing N-fixation activity long before any changes in density. Ecosystem processes, such as N-fixation, can respond in the short term to environmental change much more rapidly than changes in the underlying community structure. Such rapid physiological responses may occur faster than demographic insurance effects of biodiversity. PMID:27098528

  9. Abiotic, biotic, and evolutionary control of the distribution of C and N isotopes in food webs.

    PubMed

    Laiolo, Paola; Illera, Juan Carlos; Meléndez, Leandro; Segura, Amalia; Obeso, José Ramón

    2015-02-01

    Ecosystem functioning depends on nutrient cycles and their responses to abiotic and biotic determinants, with the influence of evolutionary legacies being generally overlooked in ecosystem ecology. Along a broad elevation gradient characterized by shifting climatic and grazing environments, we addressed clines of plant N and C∶N content and of δ(13)C and δ(15)N in producers (herbs) and in primary (grasshoppers) and secondary (birds) consumers, both within and between species in phylogenetically controlled scenarios. We found parallel and significant intra- and interspecific trends of isotopic variation with elevation in the three groups. In primary producers, nutrient and isotope distributions had a detectable phylogenetic signal that constrained their variation along the environmental gradient. The influence of the environment could not be ascribed to any single factor, and both grazing and climate had an effect on leaf stoichiometry and, thus, on the resources available to consumers. Trends in consumers matched those in plants but often became nonsignificant after controlling for isotopic values of their direct resources, revealing direct bottom-up control and little phylogenetic dependence. By integrating ecosystem and mechanistic perspectives, we found that nutrient dynamics in food webs are governed at the base by the complex interaction between local determinants and evolutionary factors. PMID:25616137

  10. Biotic interchange between the Indian subcontinent and mainland Asia through time

    PubMed Central

    Klaus, Sebastian; Morley, Robert J.; Plath, Martin; Zhang, Ya-Ping; Li, Jia-Tang

    2016-01-01

    Biotic interchange after the connection of previously independently evolving floras and faunas is thought to be one of the key factors that shaped global biodiversity as we see it today. However, it was not known how biotic interchange develops over longer time periods of several million years following the secondary contact of different biotas. Here we present a novel method to investigate the temporal dynamics of biotic interchange based on a phylogeographical meta-analysis by calculating the maximal number of observed dispersal events per million years given the temporal uncertainty of the underlying time-calibrated phylogenies. We show that biotic influx from mainland Asia onto the Indian subcontinent after Eocene continental collision was not a uniform process, but was subject to periods of acceleration, stagnancy and decrease. We discuss potential palaeoenvironmental causes for this fluctuation. PMID:27373955

  11. Biotic interchange between the Indian subcontinent and mainland Asia through time.

    PubMed

    Klaus, Sebastian; Morley, Robert J; Plath, Martin; Zhang, Ya-Ping; Li, Jia-Tang

    2016-01-01

    Biotic interchange after the connection of previously independently evolving floras and faunas is thought to be one of the key factors that shaped global biodiversity as we see it today. However, it was not known how biotic interchange develops over longer time periods of several million years following the secondary contact of different biotas. Here we present a novel method to investigate the temporal dynamics of biotic interchange based on a phylogeographical meta-analysis by calculating the maximal number of observed dispersal events per million years given the temporal uncertainty of the underlying time-calibrated phylogenies. We show that biotic influx from mainland Asia onto the Indian subcontinent after Eocene continental collision was not a uniform process, but was subject to periods of acceleration, stagnancy and decrease. We discuss potential palaeoenvironmental causes for this fluctuation. PMID:27373955

  12. BOOTSTRAPPING AND MONTE CARLO METHODS OF POWER ANALYSIS USED TO ESTABLISH CONDITION CATEGORIES FOR BIOTIC INDICES

    EPA Science Inventory

    Biotic indices have been used ot assess biological condition by dividing index scores into condition categories. Historically the number of categories has been based on professional judgement. Alternatively, statistical methods such as power analysis can be used to determine the ...

  13. THE INFLUENCE OF SUBURBAN LAND USE ON HABITAT AND BIOTIC INTEGRITY OF COASTAL RHODE ISLAND STREAMS

    EPA Science Inventory

    Watershed land use in suburban areas can affect stream biota through degradation of instream habitat, water quality, and riparian vegetation. By monitoring stream biotic communities in various geographic regions, we can better understand and conserve our watershed ecosystems. The...

  14. What is really driving cell-surface interactions? Layer-by-layer assembled films may help to answer questions concerning cell attachment and response to biomaterials.

    PubMed

    Sergeeva, Yulia N; Huang, Tongtong; Felix, Olivier; Jung, Laura; Tropel, Philippe; Viville, Stephane; Decher, Gero

    2016-06-01

    Layer-by-layer (LbL) assembled multicomponent films offer the opportunity to control and to fine-tune cell attachment and behavior on solid surfaces [Layer-by-Layer Films for Biomedical Applications, edited by Picart et al. (Wiley, Weinheim, 2014) and El-Khouri et al., "Multifunctional layer-by-layer architectures for biological applications," in Functional Polymeric Ultrathin Films, edited by Advincula and Knoll (Wiley, Weinheim, 2011), Vol. 1]. At the same time, these films allow for quite detailed physicochemical characterization of static and dynamic surface properties that are typically not available in classic cell culture. In this report, the authors investigate cell adhesion and cytocompatibility of compositionally and morphologically similar thin films composed of oppositely charged synthetic or natural polyelectrolytes in which different physical parameters such as surface charge or water content are varied through chemical composition and deposition conditions. Human adult dermal fibroblasts were chosen as a model because of the need for chemically defined matrix in the field of primary cell amplification. The growth and the stability of the multilayer films in the incubation media were studied dissipation-enhanced quartz crystal micobalance (QCM-D) and ellipsometry. The QCM-D signals observed during the film deposition were analyzed qualitatively to estimate the viscoelastic properties of the films. The authors used contact angle measurements with water to study the contribution of the chemical functionalities to wetting behavior of the films. Most importantly, they also studied the interaction of the films with serum components. Our results underline that cell adhesion is a highly complex process which is not only governed by the functionality of a surface but also by its morphology, its affinity for serum components, and also by changes of surface properties brought about by adsorbing molecules. Of the many LbL-films tested, poly(4-styrenesulfonate

  15. Development and validation of an aquatic Fine Sediment Biotic Index.

    PubMed

    Relyea, Christina D; Minshall, G Wayne; Danehy, Robert J

    2012-01-01

    The Fine Sediment Biotic Index (FSBI) is a regional, stressor-specific biomonitoring index to assess fine sediment (<2 mm) impacts on macroinvertebrate communities in northwestern US streams. We examined previously collected data of benthic macroinvertebrate assemblages and substrate particle sizes for 1,139 streams spanning 16 western US Level III Ecoregions to determine macroinvertebrate sensitivity (mostly at species level) to fine sediment. We developed FSBI for four ecoregion groupings that include nine of the ecoregions. The grouping were: the Coast (Coast Range ecoregion) (136 streams), Northern Mountains (Cascades, N. Rockies, ID Batholith ecoregions) (428 streams), Rockies (Middle Rockies, Southern Rockies ecoregions) (199 streams), and Basin and Plains (Columbia Plateau, Snake River Basin, Northern Basin and Range ecoregions) (262 streams). We excluded rare taxa and taxa identified at coarse taxonomic levels, including Chironomidae. This reduced the 685 taxa from all data sets to 206. Of these 93 exhibited some sensitivity to fine sediment which we classified into four categories: extremely, very, moderately, and slightly sensitive; containing 11, 22, 30, and 30 taxa, respectively. Categories were weighted and a FSBI score calculated by summing the sensitive taxa found in a stream. There were no orders or families that were solely sensitive or resistant to fine sediment. Although, among the three orders commonly regarded as indicators of high water quality, the Plecoptera (5), Trichoptera (3), and Ephemeroptera (2) contained all but one of the species or species groups classified as extremely sensitive. Index validation with an independent data set of 255 streams found FSBI scores to accurately predict both high and low levels of measured fine sediment. PMID:22086207

  16. Distinguishing Biotic from Abiotic Phosphate Oxygen Isotopic Signatures

    NASA Astrophysics Data System (ADS)

    Blake, R.; Moyer, C.; Colman, A.; Liang, Y.; Dogru, D.

    2006-05-01

    On earth, phosphate has a strong biological oxygen isotope signature due to its concentration and intense cycling by living organisms as an essential nutrient. Phosphate does not undergo oxygen isotope exchange with water at low temperature without enzymatic catalysis, making the oxygen isotope ratio (18O/16O) of phosphate, δ18OP, an attractive biosignature in the search for early and extraterrestrial life. Recent laboratory and field studies have demonstrated that the δ18OP value of dissolved inorganic phosphate (PO4) records specific microbial activity and enzymatic reaction pathways in both laboratory cultures and natural waters/sediments (Blake et al., 2005; Colman et al 2005; Liang and Blake, 2005). Phosphate oxygen isotope biosignatures may be distinguished from abiotic signatures by: (1) evaluating the degree of temperature-dependent PO4-water oxygen isotope exchange in aqueous systems and deviation from equilibrium; and (2) evolution from an abiotic P reservoir signature towards a biotic P reservoir signature. Important abiotic processes potentially affecting phosphate δ18OP values include dissolution/precipitation, adsorption/desorption, recrystallization of PO4 mineral phases, diagenesis and metamorphism. For most of these processes, the recording, retention and alteration of δ18OP biosignatures have not been evaluated. Deep-sea hydrothermal vent fields are an ideal system in which to study the preservation and alteration of δ18OP biosignatures, as well as potential look-alikes produced by heat-promoted PO4 -water oxygen isotope exchange. Results from recent studies of δ18OP biosignatures in hydrothermal deposits near 9 and 21 degrees N. EPR and at Loihi seamount will be presented.

  17. Development and Validation of an Aquatic Fine Sediment Biotic Index

    NASA Astrophysics Data System (ADS)

    Relyea, Christina D.; Minshall, G. Wayne; Danehy, Robert J.

    2012-01-01

    The Fine Sediment Biotic Index (FSBI) is a regional, stressor-specific biomonitoring index to assess fine sediment (<2 mm) impacts on macroinvertebrate communities in northwestern US streams. We examined previously collected data of benthic macroinvertebrate assemblages and substrate particle sizes for 1,139 streams spanning 16 western US Level III Ecoregions to determine macroinvertebrate sensitivity (mostly at species level) to fine sediment. We developed FSBI for four ecoregion groupings that include nine of the ecoregions. The grouping were: the Coast (Coast Range ecoregion) (136 streams), Northern Mountains (Cascades, N. Rockies, ID Batholith ecoregions) (428 streams), Rockies (Middle Rockies, Southern Rockies ecoregions) (199 streams), and Basin and Plains (Columbia Plateau, Snake River Basin, Northern Basin and Range ecoregions) (262 streams). We excluded rare taxa and taxa identified at coarse taxonomic levels, including Chironomidae. This reduced the 685 taxa from all data sets to 206. Of these 93 exhibited some sensitivity to fine sediment which we classified into four categories: extremely, very, moderately, and slightly sensitive; containing 11, 22, 30, and 30 taxa, respectively. Categories were weighted and a FSBI score calculated by summing the sensitive taxa found in a stream. There were no orders or families that were solely sensitive or resistant to fine sediment. Although, among the three orders commonly regarded as indicators of high water quality, the Plecoptera (5), Trichoptera (3), and Ephemeroptera (2) contained all but one of the species or species groups classified as extremely sensitive. Index validation with an independent data set of 255 streams found FSBI scores to accurately predict both high and low levels of measured fine sediment.

  18. Superluminal warp drive

    NASA Astrophysics Data System (ADS)

    González-Díaz, Pedro F.

    2007-09-01

    In this Letter we consider a warp drive spacetime resulting from that suggested by Alcubierre when the spaceship can only travel faster than light. Restricting to the two dimensions that retains most of the physics, we derive the thermodynamic properties of the warp drive and show that the temperature of the spaceship rises up as its apparent velocity increases. We also find that the warp drive spacetime can be exhibited in a manifestly cosmological form.

  19. Diabetes and driving.

    PubMed

    Inkster, B; Frier, B M

    2013-09-01

    The principal safety concern for driving for people treated with insulin or insulin secretagogues is hypoglycaemia, which impairs driving performance. Other complications, such as those causing visual impairment and peripheral neuropathy, are also relevant to medical fitness to drive. Case control studies have suggested that drivers with diabetes pose a modestly increased but acceptable and measurable risk of motor vehicle accidents compared to non-diabetic drivers, but many studies are limited and of poor quality. Factors which have been shown to increase driving risk include previous episodes of severe hypoglycaemia, previous hypoglycaemia while driving, strict glycaemic control (lower HbA1c) and absence of blood glucose monitoring before driving. Impaired awareness of hypoglycaemia may be counteracted by frequent blood glucose testing. The European Union Third directive on driving (2006) has necessitated changes in statutory regulations for driving licences for people with diabetes in all European States, including the UK. Stricter criteria have been introduced for Group 1 vehicle licences while those for Group 2 licences have been relaxed. Insulin-treated drivers can now apply to drive Group 2 vehicles, but in the UK must meet very strict criteria and be assessed by an independent specialist to be issued with a 1-year licence. PMID:23350766

  20. Biotic carbon feedbacks in a materially closed soil-vegetation-atmosphere system

    NASA Astrophysics Data System (ADS)

    Milcu, Alexandru; Lukac, Martin; Subke, Jens-Arne; Manning, Pete; Heinemeyer, Andreas; Wildman, Dennis; Anderson, Robert; Ineson, Phil

    2012-04-01

    The magnitude and direction of the coupled feedbacks between the biotic and abiotic components of the terrestrial carbon cycle is a major source of uncertainty in coupled climate-carbon-cycle models. Materially closed, energetically open biological systems continuously and simultaneously allow the two-way feedback loop between the biotic and abiotic components to take place, but so far have not been used to their full potential in ecological research, owing to the challenge of achieving sustainable model systems. We show that using materially closed soil-vegetation-atmosphere systems with pro rata carbon amounts for the main terrestrial carbon pools enables the establishment of conditions that balance plant carbon assimilation, and autotrophic and heterotrophic respiration fluxes over periods suitable to investigate short-term biotic carbon feedbacks. Using this approach, we tested an alternative way of assessing the impact of increased CO2 and temperature on biotic carbon feedbacks. The results show that without nutrient and water limitations, the short-term biotic responses could potentially buffer a temperature increase of 2.3°C without significant positive feedbacks to atmospheric CO2. We argue that such closed-system research represents an important test-bed platform for model validation and parameterization of plant and soil biotic responses to environmental changes.

  1. DETECTING INTERACTIONS BETWEEN ELLIPTIO WACCAMAWENSIS AND LEPTODEA OCHRACEA: THE INFLUENCE OF EXPERIMENTAL SCALE.

    EPA Science Inventory

    Manipulative field experiments are used in ecology to study biotic interactions in populations and communities. In benthic suspension-feeding organisms, these interactions can occur over multiple spatial scales, but this has rarely received experimental attention. A field experim...

  2. Commercial Truck Driver Health and Safety: Exploring Distracted Driving Performance and Self-Reported Driving Skill.

    PubMed

    Stavrinos, Despina; Heaton, Karen; Welburn, Sharon C; McManus, Benjamin; Griffin, Russell; Fine, Philip R

    2016-08-01

    Reducing distracters detrimental to commercial truck driving is a critical component of improving the safety performance of commercial drivers, and makes the highways safer for all drivers. This study used a driving simulator to examine effects of cell phone, texting, and email distractions as well as self-reported driver optimism bias on the driving performance of commercial truck drivers. Results revealed that more visually demanding tasks were related to poorer driving performance. However, the cell phone task resulted in less off-the-road eye glances. Drivers reporting being "very skilled" displayed poorer driving performance than those reporting being "skilled." Onboard communication devices provide a practical, yet visually and manually demanding, solution for connecting drivers and dispatchers. Trucking company policies should minimize interaction between dispatchers and drivers when the truck is in motion. Training facilities should integrate driving simulators into the instruction of commercial drivers, targeting over-confident drivers. PMID:26809775

  3. Neural substrates of driving behaviour

    PubMed Central

    Spiers, Hugo J.; Maguire, Eleanor A.

    2007-01-01

    Driving a vehicle is an indispensable daily behaviour for many people, yet we know little about how it is supported by the brain. Given that driving in the real world involves the engagement of many cognitive systems that rapidly change to meet varying environmental demands, identifying its neural basis presents substantial problems. By employing a unique combination of functional magnetic resonance imaging (fMRI), an accurate interactive virtual simulation of a bustling central London (UK) and a retrospective verbal report protocol, we surmounted these difficulties. We identified different events that characterise the driving process on a second by second basis and the brain regions that underlie them. Prepared actions such as starting, turning, reversing and stopping were associated with a common network comprised of premotor, parietal and cerebellar regions. Each prepared action also recruited additional brain areas. We also observed unexpected hazardous events such as swerving and avoiding collisions that were associated with activation of lateral occipital and parietal regions, insula, as well as a more posterior region in the medial premotor cortex than prepared actions. By contrast, planning future actions and monitoring fellow road users were associated with activity in superior parietal, lateral occipital cortices and the cerebellum. The anterior pre-SMA was also recruited during action planning. The right lateral prefrontal cortex was specifically engaged during the processing of road traffic rules. By systematically characterising the brain dynamics underlying naturalistic driving behaviour in a real city, our findings may have implications for how driving competence is considered in the context of neurological damage. PMID:17412611

  4. Reading Text While Driving

    PubMed Central

    Horrey, William J.; Hoffman, Joshua D.

    2015-01-01

    Objective In this study, we investigated how drivers adapt secondary-task initiation and time-sharing behavior when faced with fluctuating driving demands. Background Reading text while driving is particularly detrimental; however, in real-world driving, drivers actively decide when to perform the task. Method In a test track experiment, participants were free to decide when to read messages while driving along a straight road consisting of an area with increased driving demands (demand zone) followed by an area with low demands. A message was made available shortly before the vehicle entered the demand zone. We manipulated the type of driving demands (baseline, narrow lane, pace clock, combined), message format (no message, paragraph, parsed), and the distance from the demand zone when the message was available (near, far). Results In all conditions, drivers started reading messages (drivers’ first glance to the display) before entering or before leaving the demand zone but tended to wait longer when faced with increased driving demands. While reading messages, drivers looked more or less off road, depending on types of driving demands. Conclusions For task initiation, drivers avoid transitions from low to high demands; however, they are not discouraged when driving demands are already elevated. Drivers adjust time-sharing behavior according to driving demands while performing secondary tasks. Nonetheless, such adjustment may be less effective when total demands are high. Application This study helps us to understand a driver’s role as an active controller in the context of distracted driving and provides insights for developing distraction interventions. PMID:25850162

  5. Subsoil Soil Organic Matter Complexation and Stabilization: Assessment of Abiotic and Biotic Controls

    NASA Astrophysics Data System (ADS)

    Rosier, C. L.; Kan, J.; Aufdenkampe, A. K.; Yoo, K.

    2011-12-01

    Approximately 1200-2000 petagrams (Pg-1015 g) of carbon are stored in the Earth's soil as soil organic matter (SOM), representing two times the amount of carbon stored in the Earth's vegetation and atmosphere combined. SOM significantly influences several essential ecosystem services including nutrient cycling, mitigation of soil erosion, and storage of atmospheric CO2. The majority of studies investigating SOM complexation and stabilization potential mainly occur within the A soil horizon completely ignoring deeper soil horizons. Studies aimed at investigating specific abiotic and biotic interactions that facilitate the complexation and stabilization potential of SOM to C-limited subsoil horizons are needed in order to develop an accurate soil carbon budget. The purpose of this study was to determine the degree to which the presence or absence of iron oxide in combination with increasing degrees of biological processing (micro-macrofauna) would complex and stabilize SOM. We conducted a series of laboratory soil incubation experiments using carbon amended B horizon soils with low and high iron oxide concentrations with increasing levels of biological processing. The experimental design of our study allowed us to track the possible fate of soil carbon: (i) CO2 mineralization (modified Li-COR), (ii) particulate organic matter (density fractionization), mineral surface complexed carbon (N2 adsorption BET method) and (iii) organism biomass. Results from our study clearly demonstrate that the greater the degree of macro-scale biological processing (i.e. mixing) in conjunction with the presence of iron oxide significantly increased the complexation and stabilization potential of SOM. Our results further suggest that organic matter interaction with mineral surfaces and entombment within stable soil aggregates were the primary mechanisms controlling SOM storage. This study reveals the importance of biological SOM burial and mixing with C-limited subsoil horizons as a

  6. Coupled Abiotic-Biotic Degradation of Bisphenol A

    NASA Astrophysics Data System (ADS)

    Im, J.; Prevatte, C.; Campagna, S. R.; Loeffler, F.

    2014-12-01

    Bisphenol A (BPA) is a ubiquitous environmental contaminant with weak estrogenic activity. BPA is readily biodegradable with oxygen available, but is recalcitrant to microbial degradation under anoxic conditions. However, BPA is susceptible to abiotic transformation under anoxic conditions. To better understand the fate of BPA in anoxic environments, the kinetics of BPA transformation by manganese oxide (d-MnO2) were investigated. BPA was rapidly transformed by MnO2 with a pseudo-first-order rate constant of 0.413 min-1. NMR and LC-MS analyses identified 4-hydroxycumyl alcohol (HCA) as a major intermediate. Up to 64% of the initial amount of BPA was recovered as HCA within 5 min, but the conversion efficiency decreased with time, suggesting that HCA was further degraded by MnO2. Further experiments confirmed that HCA was also susceptible to transformation by MnO2, albeit at 5-fold lower rates than BPA transformation. Mass balance approaches suggested that HCA was the major BPA transformation intermediate, but other compounds may also be formed. The abiotic transformation of BPA by MnO2 was affected by pH, and 10-fold higher transformation rates were observed at pH 4.5 than at pH 10. Compared to BPA, HCA has a lower octanol-water partitioning coefficient (Log Kow) of 0.76 vs 2.76 for BPA and a higher aqueous solubility of 2.65 g L-1 vs 0.31 g L-1 for BPA, suggesting higher mobility of HCA in the environment. Microcosms established with freshwater sediment materials collected from four geographically distinct locations and amended with HCA demonstrated rapid HCA biodegradation under oxic, but not under anoxic conditions. These findings suggest that BPA is not inert under anoxic conditions and abiotic reactions with MnO2 generate HCA, which has increased mobility and is susceptible to aerobic degradation. Therefore, coupled abiotic-biotic processes can affect the fate and longevity of BPA in terrestrial environments.

  7. Piezoelectric drive circuit

    DOEpatents

    Treu, C.A. Jr.

    1999-08-31

    A piezoelectric motor drive circuit is provided which utilizes the piezoelectric elements as oscillators and a Meacham half-bridge approach to develop feedback from the motor ground circuit to produce a signal to drive amplifiers to power the motor. The circuit automatically compensates for shifts in harmonic frequency of the piezoelectric elements due to pressure and temperature changes. 7 figs.

  8. Piezoelectric drive circuit

    DOEpatents

    Treu, Jr., Charles A.

    1999-08-31

    A piezoelectric motor drive circuit is provided which utilizes the piezoelectric elements as oscillators and a Meacham half-bridge approach to develop feedback from the motor ground circuit to produce a signal to drive amplifiers to power the motor. The circuit automatically compensates for shifts in harmonic frequency of the piezoelectric elements due to pressure and temperature changes.

  9. Dual drive actuators

    NASA Technical Reports Server (NTRS)

    Packard, D. T.

    1982-01-01

    A new class of electromechanical actuators is described. These dual drive actuators were developed for the NASA-JPL Galileo Spacecraft. The dual drive actuators are fully redundant and therefore have high inherent reliability. They can be used for a variety of tasks, and they can be fabricated quickly and economically.

  10. Contributions of Abiotic and Biotic Processes to the Aerobic Removal of Phenolic Endocrine-Disrupting Chemicals in a Simulated Estuarine Aquatic Environment.

    PubMed

    Yang, Lihua; Cheng, Qiao; Tam, Nora Fy; Lin, Li; Su, Weiqi; Luan, Tiangang

    2016-04-19

    The contributions of abiotic and biotic processes in an estuarine aquatic environment to the removal of four phenolic endocrine-disrupting chemicals (EDCs) were evaluated through simulated batch reactors containing water-only or water-sediment collected from an estuary in South China. More than 90% of the free forms of all four spiked EDCs were removed from these reactors at the end of 28 days under aerobic conditions, with the half-life of 17α-ethynylestradiol (EE2) longer than those of propylparaben (PP), nonylphenol (NP) and 17β-estradiol (E2). The interaction with dissolved oxygen contributed to NP removal and was enhanced by aeration. The PP and E2 removal was positively influenced by adsorption on suspended particles initially, whereas abiotic transformation by estuarine-dissolved matter contributed to their complete removal. Biotic processes, including degradation by active aquatic microorganisms, had significant effects on the removal of EE2. Sedimentary inorganic and organic matter posed a positive effect only when EE2 biodegradation was inhibited. Estrone (E1), the oxidizing product of E2, was detected, proving that E2 was removed by the naturally occurring oxidizers in the estuarine water matrixes. These results revealed that the estuarine aquatic environment was effective in removing free EDCs, and the contributions of abiotic and biotic processes to their removal were compound specific. PMID:26984110

  11. Design of traction drives

    NASA Technical Reports Server (NTRS)

    Loewenthal, S. H.; Zaretsky, E. V.

    1985-01-01

    Traction drives are among the simplest of all speed-changing mechanisms. Because of their simplicity and their ability to smoothly and continuously adjust speed, they are excellent choices for many drive system applications. They have been used in industrial service for more than 100 years. Today's traction drives have power capacities which rival the best gear and belt drives due to modern traction fluids and highly fatigue-resistant bearing steels. This report summarizes methods to analyze and size traction drives. Lubrication principles, contact kinematics, stress, fatigue life, and performance prediction methods are presented. The effects of the lubricant's traction characteristics on life and power loss are discussed. An example problem is given which illustrates the effects of spin on power loss. Loading mechanism design and the design of nonlubricated friction wheels and rings are also treated.

  12. Abiotic Versus Biotic Pathogens: Replicative Growth in Host Tissues Key to Discriminating Between Biotoxic Injury and Active Pathogenesis

    NASA Technical Reports Server (NTRS)

    Schuerger, Andrew C.; Ming, Douglas W.; Golden, D. C.

    2012-01-01

    Life can be defined as a self-sustaining chemical system capable of undergoing Darwinian evolution; a self-bounded, self-replicating, and self-perpetuating entity [1]. This definition should hold for terrestrial as well as extraterrestrial life-forms. Although, it is reasonable to expect that a Mars life-form would be more adaptable to Mars-like conditions than to Earth-like environments, it remains possible that negative ecological or host interactions might occur if Mars microbiota were to be inadvertently released into the terrestrial environment. A biogenic infectious agent can be defined as a self-sustaining chemical system capable of undergoing Darwinian evolution and derives its sustenance from a living cell or from the by-products of cell death. Disease can be de-fined as the detrimental alteration of one or more ordered metabolic processes in a living host caused by the continued irritation of a primary causal factor or factors; disease is a dynamic process [2]. In contrast, an injury is due to an instantaneous event; injury is not a dynamic process [2]. A causal agent of disease is defined as a pathogen, and can be either abiotic or biotic in nature. Diseases incited by biotic pathogens are the exceptions, not the norms, in terrestrial host-microbe interactions. Disease induction in a plant host can be conceptually characterized using the Disease Triangle (Fig. 1) in which disease occurs only when all host, pathogen, and environ-mental factors that contribute to the development of disease are within conducive ranges for a necessary minimum period of time. For example, plant infection and disease caused by the wheat leaf rust fungus, Puccinia recondita, occur only if virulent spores adhere to genetically susceptible host tissues for at least 4-6 hours under favorable conditions of temperature and moisture [3]. As long as one or more conditions required for disease initiation are not available, disease symptoms will not develop.

  13. The effects of biotic and abiotic factors on the spatial heterogeneity of alpine grassland vegetation at a small scale on the Qinghai-Tibet Plateau (QTP), China.

    PubMed

    Wen, Lu; Dong, Shi Kui; Li, Yuan Yuan; Sherman, Ruth; Shi, Jian Jun; Liu, De Mei; Wang, Yan Long; Ma, Yu Shou; Zhu, Lei

    2013-10-01

    Understanding the complex effects of biotic and abiotic factors on the composition of vegetation is very important for developing and implementing strategies for promoting sustainable grassland development. The vegetation-disturbance-environment relationship was examined in degraded alpine grasslands in the headwater areas of three rivers on the Qinghai-Tibet Plateau in this study. The investigated hypotheses were that (1) the heterogeneity of the vegetation of the alpine grassland is due to a combination of biotic and abiotic factors and that (2) at a small scale, biotic factors are more important for the distribution of alpine vegetation. On this basis, four transects were set along altitudinal gradients from 3,770 to 3,890 m on a sunny slope, and four parallel transects were set along altitudinal gradients on a shady slope in alpine grasslands in Guoluo Prefecture of Qinghai Province, China. It was found that biological disturbances were the major forces driving the spatial heterogeneity of the alpine grassland vegetation and abiotic factors were of secondary importance. Heavy grazing and intensive rat activity resulted in increases in unpalatable and poisonous weeds and decreased fine forages in the form of sedges, forbs, and grasses in the vegetation composition. Habitat degradation associated with biological disturbances significantly affected the spatial variation of the alpine grassland vegetation, i.e., more pioneer plants of poisonous or unpalatable weed species, such as Ligularia virgaurea and Euphorbia fischeriana, were found in bare patches. Environmental/abiotic factors were less important than biological disturbances in affecting the spatial distribution of the alpine grassland vegetation at a small scale. It was concluded that rat control and light grazing should be applied first in implementing restoration strategies. The primary vegetation in lightly grazed and less rat-damaged sites should be regarded as a reference for devising vegetation

  14. Redundant motor drive system

    NASA Technical Reports Server (NTRS)

    Calvert, J. A. (Inventor)

    1980-01-01

    A drive system characterized by a base supporting a pair of pillars arranged in spaced parallelism, a shaft extended between and supported by the pillars for rotation about the longitudinal axis thereof, a worm gear affixed to the shaft and supported in coaxial relation therewith is described. A bearing housing of a sleeve like configuration is concentrically related to the shaft and is supported thereby for free rotation. A first and a second quiescent drive train, alternatively activatable, is provided for imparting rotation into said bearing housing. Each of the drive trains is characterized by a selectively energizable motor connected to a spur gear.

  15. The Test Drive

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image taken at NASA's Jet Propulsion Laboratory shows engineers rehearsing the sol 133 (June 8, 2004) drive into 'Endurance' crater by NASA's Mars Exploration Rover Opportunity. Engineers and scientists have recreated the martian surface and slope the rover will encounter using a combination of bare and thinly sand-coated rocks, simulated martian 'blueberries' and a platform tilted at a 25-degree angle. The results of this test convinced engineers that the rover was capable of driving up and down a straight slope before it attempted the actual drive on Mars.

  16. Quantitative patterns between plant volatile emissions induced by biotic stresses and the degree of damage

    PubMed Central

    Niinemets, Ülo; Kännaste, Astrid; Copolovici, Lucian

    2013-01-01

    Plants have to cope with a plethora of biotic stresses such as herbivory and pathogen attacks throughout their life cycle. The biotic stresses typically trigger rapid emissions of volatile products of lipoxygenase (LOX) pathway (LOX products: various C6 aldehydes, alcohols, and derivatives, also called green leaf volatiles) associated with oxidative burst. Further a variety of defense pathways is activated, leading to induction of synthesis and emission of a complex blend of volatiles, often including methyl salicylate, indole, mono-, homo-, and sesquiterpenes. The airborne volatiles are involved in systemic responses leading to elicitation of emissions from non-damaged plant parts. For several abiotic stresses, it has been demonstrated that volatile emissions are quantitatively related to the stress dose. The biotic impacts under natural conditions vary in severity from mild to severe, but it is unclear whether volatile emissions also scale with the severity of biotic stresses in a dose-dependent manner. Furthermore, biotic impacts are typically recurrent, but it is poorly understood how direct stress-triggered and systemic emission responses are silenced during periods intervening sequential stress events. Here we review the information on induced emissions elicited in response to biotic attacks, and argue that biotic stress severity vs. emission rate relationships should follow principally the same dose–response relationships as previously demonstrated for different abiotic stresses. Analysis of several case studies investigating the elicitation of emissions in response to chewing herbivores, aphids, rust fungi, powdery mildew, and Botrytis, suggests that induced emissions do respond to stress severity in dose-dependent manner. Bi-phasic emission kinetics of several induced volatiles have been demonstrated in these experiments, suggesting that next to immediate stress-triggered emissions, biotic stress elicited emissions typically have a secondary induction

  17. An evaluation of biotic ligand models predicting acute copper toxicity to Daphnia magna in wastewater effluent.

    PubMed

    Constantino, Carlos; Scrimshaw, Mark; Comber, Sean; Churchley, John

    2011-04-01

    The toxicity of Cu to Daphnia magna was investigated in a series of 48-h immobilization assays in effluents from four wastewater treatment works. The assay results were compared with median effective concentration (EC50) forecasts produced by the HydroQual biotic ligand model (BLM), the refined D. magna BLM, and a modified BLM that was constructed by integrating the refined D. magna biotic ligand characterization with the Windermere humic aqueous model (WHAM) VI geochemical speciation model, which also accommodated additional effluent characteristics as model inputs. The results demonstrated that all the BLMs were capable of predicting toxicity by within a factor of two, and that the modified BLM produced the most accurate toxicity forecasts. The refined D. magna BLM offered the most robust assessment of toxicity in that it was not reliant on the inclusion of effluent characteristics or optimization of the dissolved organic carbon active fraction to produce forecasts that were accurate by within a factor of two. The results also suggested that the biotic ligand stability constant for Na may be a poor approximation of the mechanisms governing the influence of Na where concentrations exceed the range within which the biotic ligand stability constant value had been determined. These findings support the use of BLMs for the establishment of site-specific water quality standards in waters that contain a substantial amount of wastewater effluent, but reinforces the need for regulators to scrutinize the composition of models, their thermodynamic and biotic ligand parameters, and the limitations of those parameters. PMID:21184526

  18. Dementia and driving

    MedlinePlus

    ... getting more dangerous include: Getting lost on familiar roads Reacting more slowly in traffic Driving too slowly ... attention to traffic signs Taking chances on the road Drifting into other lanes Getting more agitated in ...

  19. Control rod drive

    SciTech Connect

    Hawke, Basil C.

    1986-01-01

    A control rod drive uses gravitational forces to insert one or more control rods upwardly into a reactor core from beneath the reactor core under emergency conditions. The preferred control rod drive includes a vertically movable weight and a mechanism operatively associating the weight with the control rod so that downward movement of the weight is translated into upward movement of the control rod. The preferred control rod drive further includes an electric motor for driving the control rods under normal conditions, an electrically actuated clutch which automatically disengages the motor during a power failure and a decelerator for bringing the control rod to a controlled stop when it is inserted under emergency conditions into a reactor core.

  20. Drive program documentation

    NASA Technical Reports Server (NTRS)

    Graham, S.

    1979-01-01

    The program description and user's guide for the Downlist Requirement Integrated Verification and Evaluation (DRIVE) program is provided. The program is used to compare existing telemetry downlist files with updated downlist requirements.

  1. Safe driving for teens

    MedlinePlus

    ... drivers. Do not use cell phones for talking, texting, or email when you are driving. Mobile phones ... pull off of the road before answering or texting. Other tips include: Avoid putting on makeup while ...

  2. Direct drive wind turbine

    DOEpatents

    Bywaters, Garrett Lee; Danforth, William; Bevington, Christopher; Stowell, Jesse; Costin, Daniel

    2006-09-19

    A wind turbine is provided that minimizes the size of the drive train and nacelle while maintaining the power electronics and transformer at the top of the tower. The turbine includes a direct drive generator having an integrated disk brake positioned radially inside the stator while minimizing the potential for contamination. The turbine further includes a means for mounting a transformer below the nacelle within the tower.

  3. Direct drive wind turbine

    DOEpatents

    Bywaters, Garrett; Danforth, William; Bevington, Christopher; Jesse, Stowell; Costin, Daniel

    2007-02-27

    A wind turbine is provided that minimizes the size of the drive train and nacelle while maintaining the power electronics and transformer at the top of the tower. The turbine includes a direct drive generator having an integrated disk brake positioned radially inside the stator while minimizing the potential for contamination. The turbine further includes a means for mounting a transformer below the nacelle within the tower.

  4. Direct drive wind turbine

    DOEpatents

    Bywaters, Garrett; Danforth, William; Bevington, Christopher; Stowell, Jesse; Costin, Daniel

    2006-07-11

    A wind turbine is provided that minimizes the size of the drive train and nacelle while maintaining the power electronics and transformer at the top of the tower. The turbine includes a direct drive generator having an integrated disk brake positioned radially inside the stator while minimizing the potential for contamination. The turbine further includes a means for mounting a transformer below the nacelle within the tower.

  5. Direct drive wind turbine

    DOEpatents

    Bywaters, Garrett; Danforth, William; Bevington, Christopher; Jesse, Stowell; Costin, Daniel

    2006-10-10

    A wind turbine is provided that minimizes the size of the drive train and nacelle while maintaining the power electronics and transformer at the top of the tower. The turbine includes a direct drive generator having an integrated disk brake positioned radially inside the stator while minimizing the potential for contamination. The turbine further includes a means for mounting a transformer below the nacelle within the tower.

  6. CONTROL ROD DRIVE

    DOEpatents

    Chapellier, R.A.

    1960-05-24

    BS>A drive mechanism was invented for the control rod of a nuclear reactor. Power is provided by an electric motor and an outside source of fluid pressure is utilized in conjunction with the fluid pressure within the reactor to balance the loadings on the motor. The force exerted on the drive mechanism in the direction of scramming the rod is derived from the reactor fluid pressure so that failure of the outside pressure source will cause prompt scramming of the rod.

  7. Common drive unit

    NASA Technical Reports Server (NTRS)

    Ellis, R. C.; Fink, R. A.; Moore, E. A.

    1987-01-01

    The Common Drive Unit (CDU) is a high reliability rotary actuator with many versatile applications in mechanism designs. The CDU incorporates a set of redundant motor-brake assemblies driving a single output shaft through differential. Tachometers provide speed information in the AC version. Operation of both motors, as compared to the operation of one motor, will yield the same output torque with twice the output speed.

  8. Self-driving carsickness.

    PubMed

    Diels, Cyriel; Bos, Jelte E

    2016-03-01

    This paper discusses the predicted increase in the occurrence and severity of motion sickness in self-driving cars. Self-driving cars have the potential to lead to significant benefits. From the driver's perspective, the direct benefits of this technology are considered increased comfort and productivity. However, we here show that the envisaged scenarios all lead to an increased risk of motion sickness. As such, the benefits this technology is assumed to bring may not be capitalised on, in particular by those already susceptible to motion sickness. This can negatively affect user acceptance and uptake and, in turn, limit the potential socioeconomic benefits that this emerging technology may provide. Following a discussion on the causes of motion sickness in the context of self-driving cars, we present guidelines to steer the design and development of automated vehicle technologies. The aim is to limit or avoid the impact of motion sickness and ultimately promote the uptake of self-driving cars. Attention is also given to less well known consequences of motion sickness, in particular negative aftereffects such as postural instability, and detrimental effects on task performance and how this may impact the use and design of self-driving cars. We conclude that basic perceptual mechanisms need to be considered in the design process whereby self-driving cars cannot simply be thought of as living rooms, offices, or entertainment venues on wheels. PMID:26446454

  9. Parkinson disease and driving

    PubMed Central

    Classen, Sherrilene; Uc, Ergun Y.

    2012-01-01

    ABSTRACT The growing literature on driving in Parkinson disease (PD) has shown that driving is impaired in PD compared to healthy comparison drivers. PD is a complex neurodegenerative disorder leading to motor, cognitive, and visual impairments, all of which can affect fitness to drive. In this review, we examined studies of driving performance (on-road tests and simulators) in PD for outcome measures and their predictors. We searched through various databases and found 25 (of 99) primary studies, all published in English. Using the American Academy of Neurology criteria, a study class of evidence was assigned (I–IV, I indicating the highest level of evidence) and recommendations were made (Level A: predictive or not; B: probably predictive or not; C: possibly predictive or not; U: no recommendations). From available Class II and III studies, we identified various cognitive, visual, and motor measures that met different levels of evidence (usually Level B or C) with respect to predicting on-road and simulated driving performance. Class I studies reporting Level A recommendations for definitive predictors of driving performance in drivers with PD are needed by policy makers and clinicians to develop evidence-based guidelines. PMID:23150533

  10. Hydraulic drive system prevents backlash

    NASA Technical Reports Server (NTRS)

    Acord, J. D.

    1965-01-01

    Hydraulic drive system uses a second drive motor operating at reduced torque. This exerts a relative braking action which eliminates the normal gear train backlash that is intolerable when driving certain heavy loads.

  11. Family Influences and Unconscious Drives.

    ERIC Educational Resources Information Center

    English, Fanita

    2001-01-01

    Drives for survival, expression, and quiescence influence early human development and continue to influence career development throughout life. Turmoil may arise when a drive conflicts with others or is suppressed by other drives. (SK)

  12. The abundance of biotic exoplanets and life on planets of Red Dwarf stars

    NASA Astrophysics Data System (ADS)

    Wandel, Amri; Gale, Joseph

    2016-07-01

    The Kepler mission has shown that Earthlike planets orbiting within the Habitable Zones of their host stars are common. We derive an expression for the abundance of life bearing (biotic) extra-solar-system planets (exoplanets) in terms of the (yet unknown) probability for the evolution of biotic life. This "biotic probability" may be estimated by future missions and observations, e.g. spectral analyses of the atmospheres of exoplanets, looking for biomarkers. We show that a biotic probability in the range 0.001-1 implies that a biotic planet may be expected within ~10-100 light years from Earth. Of particular interest in the search for exolife are planets orbiting Red Dwarf (RD) stars, the most frequent stellar type. Previous researches suggested that conditions on planets near RDs would be inimical to life, e.g. the Habitable Zone of RDs is small, so their habitable planets would be close enough to be tidally locked. Recent calculations show that this and other properties of RDs, presumed hostile for the evolution of life, are less severe than originally estimated. We conclude that RD planets could be hospitable for the evolution of life as we know it, not less so than planets of solar-type stars. This result, together with the large number of RDs and their Kepler planet-statistics, makes finding life on RD planets ~10-1000 times more likely than on planets of solar-type stars. Our nearest biotic RD-planet is likely to be 2-10 times closer than the nearest solar-type one.

  13. Mechanisms and Dynamics of Abiotic and Biotic Interactions at Environmental Interfaces

    SciTech Connect

    Roso, Kevin M.

    2006-06-01

    The Stanford EMSI (SEMSI) was established in 2004 through joint funding by the National Science Foundation and the OBER-ERSD. It encompasses a number of universities and national laboratories. The PNNL component of the SEMSI is funded by ERSD and is the focus of this report. This component has the objective of providing theory support to the SEMSI by bringing computational capabilities and expertise to bear on important electron transfer problems at mineral/water and mineral/microbe interfaces. PNNL staff member Dr. Kevin Rosso, who is also ''matrixed'' into the Environmental Molecular Sciences Laboratory (EMSL) at PNNL, is a co-PI on the SEMSI project and the PNNL lead. The EMSL computational facilities being applied to the SEMSI project include the 11.8 teraflop massively-parallel supercomputer. Science goals of this EMSL/SEMSI partnership include advancing our understanding of: (1) The kinetics of U(VI) and Cr(VI) reduction by aqueous and solid-phase Fe(II), (2) The structure of mineral surfaces in equilibrium with solution, and (3) Mechanisms of bacterial electron transfer to iron oxide surfaces via outer-membrane cytochromes.

  14. Remote Environmental Monitoring of Hydrologic/ Biotic Interaction in a Mountain Environment

    NASA Astrophysics Data System (ADS)

    Hartsough, P. C.; Malazian, A.; Tuli, A.; Kamai, T.; Kizito, F.; Bales, R.; Broad, A.; Hopmans, J.

    2008-12-01

    Wireless sensor networks offer several advantages in monitoring of dynamic environmental variables in remote landscapes and offer a promising approach to realize the full potential of environmental monitoring. Wireless sensors also offer the advantage of real time data collection and sensor/network management and reduced long-term costs. Better understanding of surface water budgets in remote landscapes warrants close monitoring of moisture and temperature variability in near surfaces soils. This work describes field data demonstrating the functionality of four different wireless networks, at two field sites, both part of the Southern Sierra Critical Zone Observatory (CZO). Equipment used varied from traditional point to point radio communication to a wireless mote based, distributed network. Sensors measuring water potential, volumetric water content, and soil temperature were deployed at a variety of sites including, a remote alpine meadow, along a topographic gradient with a dense tree canopy and within the root structure of an individual tree. The sensors were reactive to moisture and temperature variations and the wireless systems met the goal of providing informative data on dynamic responses of soil moisture to precipitation, snow melt and changes in vegetative demand. The systems were dependable, with low power consumption and were robust enough to withstand harsh winter conditions at a high elevation site. The study highlights measurement accuracy, power consumption, and data transmission limitations of the three systems. We demonstrate that deployment, implementation and long-term field monitoring in remote and challenging environments is possible with a variety of wireless systems.

  15. Genomics of Secondary Metabolism in Populus: Interactions with Biotic and Abiotic Environments

    SciTech Connect

    Chen, F.; Liu, C.; Tschaplinski, T. J.; Zhao, N.

    2009-09-01

    Populus trees face constant challenges from the environment during their life cycle. To ensure their survival and reproduction, Populus trees deploy various types of defenses, one of which is the production of a myriad of secondary metabolites. Compounds derived from the shikimate-phenylpropanoid pathway are the most abundant class of secondary metabolites synthesized in Populus. Among other major classes of secondary metabolites in Populus are terpenoids and fatty acid-derivatives. Some of the secondary metabolites made by Populus trees have been functionally characterized. Some others have been associated with certain biological/ecological processes, such as defense against insects and microbial pathogens or acclimation or adaptation to abiotic stresses. Functions of many Populus secondary metabolites remain unclear. The advent of various novel genomic tools will enable us to explore in greater detail the complexity of secondary metabolism in Populus. Detailed data mining of the Populus genome sequence can unveil candidate genes of secondary metabolism. Metabolomic analysis will continue to identify new metabolites synthesized in Populus. Integrated genomics that combines various 'omics' tools will prove to be the most powerful approach in revealing the molecular and biochemical basis underlying the biosynthesis of secondary metabolites in Populus. Characterization of the biological/ecological functions of secondary metabolites as well as their biosynthesis will provide knowledge and tools for genetically engineering the production of seconday metabolites that can lead to the generation of novel, improved Populus varieties.

  16. A review of abiotic and biotic interactions in pelagic communities: Processes relevant to L Lake

    SciTech Connect

    Bowers, J.A.

    1988-01-01

    The purpose of this report is to provide a state-of-the-art review of structural and functional processes in pelagic communities and extrapolate these empirical and theoretical results to L Lake, the once-through cooling reservoir at the Savannah River Plant. Man-made reservoirs differ from natural lakes in their origins, hydrodynamics, sedimentation patterns, and general eutrophication histories. Phosphorus and nitrogen limitation of phytoplankton productivity controls the rate of eutrophication, while also determining algal community structure. Here the Lean and Monod models of nutrient fluxing and uptake kinetics provide useful constructs for predictive purposes. Much of the reduced carbon synthesized by primary production is shunted through the microbial loop where heterotrophic flagellates and protozoans pass this carbon on to the macrozooplankton. This recently discovered pathway is common to eutrophic reservoirs where blue-green species dominate phytoplankton assemblages. Through selective grazing and tactile oriented predation, the crustacean zooplankton partially regulates the relative abundance of algae and microzooplankton species. 194 refs., 10 figs.

  17. The Great American Biotic Interchange: Dispersals, Tectonics, Climate, Sea Level and Holding Pens

    PubMed Central

    2010-01-01

    The biotic and geologic dynamics of the Great American Biotic Interchange are reviewed and revised. Information on the Marine Isotope Stage chronology, sea level changes as well as Pliocene and Pleistocene vegetation changes in Central and northern South America add to a discussion of the role of climate in facilitating trans-isthmian exchanges. Trans-isthmian land mammal exchanges during the Pleistocene glacial intervals appear to have been promoted by the development of diverse non-tropical ecologies. Electronic supplementary material The online version of this article (doi:10.1007/s10914-010-9144-8) contains supplementary material, which is available to authorized users. PMID:21125025

  18. Why are biotic iron pools uniform across high- and low-iron pelagic ecosystems?

    NASA Astrophysics Data System (ADS)

    Boyd, P. W.; Strzepek, R. F.; Ellwood, M. J.; Hutchins, D. A.; Nodder, S. D.; Twining, B. S.; Wilhelm, S. W.

    2015-07-01

    Dissolved iron supply is pivotal in setting global phytoplankton productivity and pelagic ecosystem structure. However, most studies of the role of iron have focussed on carbon biogeochemistry within pelagic ecosystems, with less effort to quantify the iron biogeochemical cycle. Here we compare mixed-layer biotic iron inventories from a low-iron (~0.06 nmol L-1) subantarctic (FeCycle study) and a seasonally high-iron (~0.6 nmol L-1) subtropical (FeCycle II study) site. Both studies were quasi-Lagrangian, and had multi-day occupation, common sampling protocols, and indirect estimates of biotic iron (from a limited range of available published biovolume/carbon/iron quotas). Biotic iron pools were comparable (~100 ± 30 pmol L-1) for low- and high-iron waters, despite a tenfold difference in dissolved iron concentrations. Consistency in biotic iron inventories (~80 ± 24 pmol L-1, largely estimated using a limited range of available quotas) was also conspicuous for three Southern Ocean polar sites. Insights into the extent to which uniformity in biotic iron inventories was driven by the need to apply common iron quotas obtained from laboratory cultures were provided from FeCycle II. The observed twofold to threefold range of iron quotas during the evolution of FeCycle II subtropical bloom was much less than reported from laboratory monocultures. Furthermore, the iron recycling efficiency varied by fourfold during FeCycle II, increasing as stocks of new iron were depleted, suggesting that quotas and iron recycling efficiencies together set biotic iron pools. Hence, site-specific differences in iron recycling efficiencies (which provide 20-50% and 90% of total iron supply in high- and low-iron waters, respectively) help offset the differences in new iron inputs between low- and high-iron sites. Future parameterization of iron in biogeochemical models must focus on the drivers of biotic iron inventories, including the differing iron requirements of the resident biota

  19. NATURE OF CUMULATIVE IMPACTS ON BIOTIC DIVERSITY OF WETLAND VERTEBRATES

    EPA Science Inventory

    There is no longer any doubt that cumulative impacts have important effects on wetland vertebrates. he interactions of species diversity and community structure produce a complex pattern in which environmental impacts can play a highly significant role. ariety of examples shows h...

  20. Mental workload and driving

    PubMed Central

    Paxion, Julie; Galy, Edith; Berthelon, Catherine

    2014-01-01

    The aim of this review is to identify the most representative measures of subjective and objective mental workload in driving, and to understand how the subjective and objective levels of mental workload influence the performance as a function of situation complexity and driving experience, i.e., to verify whether the increase of situation complexity and the lack of experience increase the subjective and physiological levels of mental workload and lead to driving performance impairments. This review will be useful to both researchers designing an experimental study of mental workload and to designers of drivers’ training content. In the first part, we will broach the theoretical approach with two factors of mental workload and performance, i.e., situation complexity and driving experience. Indeed, a low complex situation (e.g., highways), or conversely a high complex situation (e.g., town) can provoke an overload. Additionally, performing the driving tasks implies producing a high effort for novice drivers who have not totally automated the driving activity. In the second part, we will focus on subjective measures of mental workload. A comparison of questionnaires usually used in driving will allow identifying the most appropriate ones as a function of different criteria. Moreover, we will review the empirical studies to verify if the subjective level of mental workload is high in simple and very complex situations, especially for novice drivers compared to the experienced ones. In the third part, we will focus on physiological measures. A comparison of physiological indicators will be realized in order to identify the most correlated to mental workload. An empirical review will also take the effect of situation complexity and experience on these physiological indicators into consideration. Finally, a more nuanced comparison between subjective and physiological measures will be established from the impact on situation complexity and experience. PMID:25520678

  1. Quantifying Variability in Four U.S. Streams Using a Long-Term Dataset: Patterns in Biotic Endpoints

    NASA Astrophysics Data System (ADS)

    Flinders, Camille A.; McLaughlin, Douglas B.; Ragsdale, Renee L.

    2015-08-01

    Effective water resources assessment and management requires quantitative information on the variability of ambient and biological conditions in aquatic communities. Although it is understood that natural systems are variable, robust estimates of long-term variation in community-based structure and function metrics are rare in U.S. waters. We used a multi-year, seasonally sampled dataset from multiple sites ( n = 5-6) in four streams (Codorus Creek, PA; Leaf River, MS; McKenzie and Willamette Rivers, OR) to examine spatial and temporal variation in periphyton chlorophyll a, and fish and macroinvertebrate metrics commonly used in bioassessment programs. Within-site variation of macroinvertebrate metrics and benthic chlorophyll a concentration showed coefficient of variation ranging from 16 to 136 %. Scale-specific variability patterns (stream-wide, season, site, and site-season patterns) in standardized biotic endpoints showed that within-site variability patterns extended across sites with variability greatest in chlorophyll a and lowest in Hilsenhoff's Biotic Index. Across streams, variance components models showed that variance attributed to the interaction of space and time and sample variance accounted for the majority of variation in macroinvertebrate metrics and chlorophyll a, while most variation in fish metrics was attributed to sample variance. Clear temporal patterns in measured endpoints were rare and not specific to any one stream or assemblage, while apparent shifts in metric variability related to point source discharges were seen only in McKenzie River macroinvertebrate metrics in the fall. Results from this study demonstrate the need to consider and understand spatial, seasonal, and longer term variability in the development of bioassessment programs and subsequent decisions.

  2. Expression of an Engineered Heterologous Antimicrobial Peptide in Potato Alters Plant Development and Mitigates Normal Abiotic and Biotic Responses

    PubMed Central

    Goyal, Ravinder K.; Hancock, Robert E. W.; Mattoo, Autar K.; Misra, Santosh

    2013-01-01

    Antimicrobial cationic peptides (AMPs) are ubiquitous small proteins used by living cells to defend against a wide spectrum of pathogens. Their amphipathic property helps their interaction with negatively charged cellular membrane of the pathogen causing cell lysis and death. AMPs also modulate signaling pathway(s) and cellular processes in animal models; however, little is known of cellular processes other than the pathogen-lysis phenomenon modulated by AMPs in plants. An engineered heterologous AMP, msrA3, expressed in potato was previously shown to cause resistance of the transgenic plants against selected fungal and bacterial pathogens. These lines together with the wild type were studied for growth habits, and for inducible defense responses during challenge with biotic (necrotroph Fusarium solani) and abiotic stressors (dark-induced senescence, wounding and temperature stress). msrA3-expression not only conferred protection against F. solani but also delayed development of floral buds and prolonged vegetative phase. Analysis of select gene transcript profiles showed that the transgenic potato plants were suppressed in the hypersensitive (HR) and reactive oxygen species (ROS) responses to both biotic and abiotic stressors. Also, the transgenic leaves accumulated lesser amounts of the defense hormone jasmonic acid upon wounding with only a slight change in salicylic acid as compared to the wild type. Thus, normal host defense responses to the pathogen and abiotic stressors were mitigated by msrA3 expression suggesting MSRA3 regulates a common step(s) of these response pathways. The stemming of the pathogen growth and mitigating stress response pathways likely contributes to resource reallocation for higher tuber yield. PMID:24147012

  3. As Old as the Hills: Montane Scorpions in Southwestern North America Reveal Ancient Associations between Biotic Diversification and Landscape History

    PubMed Central

    Bryson, Robert W.; Riddle, Brett R.; Graham, Matthew R.; Smith, Brian Tilston; Prendini, Lorenzo

    2013-01-01

    Background The age of lineages has become a fundamental datum in studies exploring the interaction between geological transformation and biotic diversification. However, phylogeographical studies are often biased towards lineages that are younger than the geological features of the landscapes they inhabit. A temporally deeper historical biogeography framework may be required to address episodes of biotic diversification associated with geologically older landscape changes. Signatures of such associations may be retained in the genomes of ecologically specialized (stenotopic) taxa with limited vagility. In the study presented here, genetic data from montane scorpions in the Vaejovis vorhiesi group, restricted to humid rocky habitats in mountains across southwestern North America, were used to explore the relationship between scorpion diversification and regional geological history. Results Strong phylogeographical signal was evident within the vorhiesi group, with 27 geographically cohesive lineages inferred from a mitochondrial phylogeny. A time-calibrated multilocus species tree revealed a pattern of Miocene and Pliocene (the Neogene period) lineage diversification. An estimated 21 out of 26 cladogenetic events probably occurred prior to the onset of the Pleistocene, 2.6 million years ago. The best-fit density-dependent model suggested diversification rate in the vorhiesi group gradually decreased through time. Conclusions Scorpions of the vorhiesi group have had a long history in the highlands of southwestern North America. Diversification among these stenotopic scorpions appears to have occurred almost entirely within the Neogene period, and is temporally consistent with the dynamic geological history of the Basin and Range, and Colorado Plateau physiographical provinces. The persistence of separate lineages at small spatial scales suggests that a combination of ecological stenotopy and limited vagility may make these scorpions particularly valuable indicators

  4. Identification of Genes Involved in the Response of Arabidopsis to Simultaneous Biotic and Abiotic Stresses1[C][W][OPEN

    PubMed Central

    Atkinson, Nicky J.; Lilley, Catherine J.; Urwin, Peter E.

    2013-01-01

    In field conditions, plants may experience numerous environmental stresses at any one time. Research suggests that the plant response to multiple stresses is different from that for individual stresses, producing nonadditive effects. In particular, the molecular signaling pathways controlling biotic and abiotic stress responses may interact and antagonize one another. The transcriptome response of Arabidopsis (Arabidopsis thaliana) to concurrent water deficit (abiotic stress) and infection with the plant-parasitic nematode Heterodera schachtii (biotic stress) was analyzed by microarray. A unique program of gene expression was activated in response to a combination of water deficit and nematode stress, with 50 specifically multiple-stress-regulated genes. Candidate genes with potential roles in controlling the response to multiple stresses were selected and functionally characterized. RAPID ALKALINIZATION FACTOR-LIKE8 (AtRALFL8) was induced in roots by joint stresses but conferred susceptibility to drought stress and nematode infection when overexpressed. Constitutively expressing plants had stunted root systems and extended root hairs. Plants may produce signal peptides such as AtRALFL8 to induce cell wall remodeling in response to multiple stresses. The methionine homeostasis gene METHIONINE GAMMA LYASE (AtMGL) was up-regulated by dual stress in leaves, conferring resistance to nematodes when overexpressed. It may regulate methionine metabolism under conditions of multiple stresses. AZELAIC ACID INDUCED1 (AZI1), involved in defense priming in systemic plant immunity, was down-regulated in leaves by joint stress and conferred drought susceptibility when overexpressed, potentially as part of abscisic acid-induced repression of pathogen response genes. The results highlight the complex nature of multiple stress responses and confirm the importance of studying plant stress factors in combination. PMID:23800991

  5. Stable carbon isotope analysis to distinguish biotic and abiotic degradation of 1,1,1-trichloroethane in groundwater sediments.

    PubMed

    Broholm, Mette M; Hunkeler, Daniel; Tuxen, Nina; Jeannottat, Simon; Scheutz, Charlotte

    2014-08-01

    The fate and treatability of 1,1,1-TCA by natural and enhanced reductive dechlorination was studied in laboratory microcosms. The study shows that compound-specific isotope analysis (CSIA) identified an alternative 1,1,1-TCA degradation pathway that cannot be explained by assuming biotic reductive dechlorination. In all biotic microcosms 1,1,1-TCA was degraded with no apparent increase in the biotic degradation product 1,1-DCA. 1,1,1-TCA degradation was documented by a clear enrichment in (13)C in all biotic microcosms, but not in the abiotic control, which suggests biotic or biotically mediated degradation. Biotic degradation by reductive dechlorination of 1,1-DCA to CA only occurred in bioaugmented microcosms and in donor stimulated microcosms with low initial 1,1,1-TCA or after significant decrease in 1,1,1-TCA concentration (after∼day 200). Hence, the primary degradation pathway for 1,1,1-TCA does not appear to be reductive dechlorination via 1,1-DCA. In the biotic microcosms, the degradation of 1,1,1-TCA occurred under iron and sulfate reducing conditions. Biotic reduction of iron and sulfate likely resulted in formation of FeS, which can abiotically degrade 1,1,1-TCA. Hence, abiotic degradation of 1,1,1-TCA mediated by biotic FeS formation constitute an explanation for the observed 1,1,1-TCA degradation. This is supported by a high 1,1,1-TCA (13)C enrichment factor consistent with abiotic degradation in biotic microcosms. 1,1-DCA carbon isotope field data suggest that this abiotic degradation of 1,1,1-TCA is a relevant process also at the field site. PMID:24559936

  6. Biotic survival in the cryobiosphere on geological scale: implication for astro/terrestrial biogeoscience

    NASA Astrophysics Data System (ADS)

    Gilichinsky, D.

    2003-04-01

    In current opinion the most fundamental aspect of any environment, the temperature regime, acts as a regulator of all of the physical-chemical reactions and forms the basis of all biological processes. Now hard data indicate the biotic survival over geological periods from subzero temperatures (down to -27oC in permafrost and to -50oC in ice) to positive one in amber and halite. All these very different environments have, nevertheless, common features: complete isolation, stability and waterproof. In such unique physical-chemical complexes, the dehydration of macromolecules and the reorganization of membrane components apparently lead to a considerable decrease or stop of metabolic activity independently of temperature. This allowed the prolonged survival of ancient microbial lineage that realize unknown possibilities of physiological and biochemical adaptation incomparably longer than any other known habitat. The ability of microorganisms to survive on geological scale within the broad limits of natural systems forces us to redefine the spatial and temporal limits of the terrestrial and extraterrestrial biospheres and suggested that universal mechanisms of such adaptation might operate for millions of years. Among new scientific directions formed on this base, the most general is the fundamental question: how long the life might be preserved and what mechanisms could ensure survival? Because the length of lifetime cannot be reproduced, this highlights the natural storages that make possible the observation of the results of biotic survival on geological scale. Of special interest is the interaction of knowledge to understanding of the limits of the deep cold biosphere as a depository of ancient active biosignatures (biogases, biominerals, pigments, lipids, enzymes, proteins, RNA/DNA fragments) and viable cells. The last are the only known a huge mass of organisms that have retained viability over geological periods and upon thawing, renew physiological activity

  7. Driving Anger and Driving Behavior in Adults with ADHD

    ERIC Educational Resources Information Center

    Richards, Tracy L.; Deffenbacher, Jerry L.; Rosen, Lee A.; Barkley, Russell A.; Rodricks, Trisha

    2006-01-01

    Objective: This study assesses whether anger in the context of driving is associated with the negative driving outcomes experienced by individuals with ADHD. Method: ADHD adults (n = 56) complete measures of driving anger, driving anger expression, angry thoughts behind the wheel, and aggressive, risky, and crash-related behavior. Results are…

  8. Driving anger in Malaysia.

    PubMed

    Sullman, Mark J M; Stephens, Amanda N; Yong, Michelle

    2014-10-01

    The present study examined the types of situations that cause Malaysian drivers to become angry. The 33-item version of the driver anger scale (Deffenbacher et al., 1994) was used to investigate driver anger amongst a sample of 339 drivers. Confirmatory factor analysis showed that the fit of the original six-factor model (discourtesy, traffic obstructions, hostile gestures, slow driving, illegal driving and police presence), after removing one item and allowing three error pairs to covary, was satisfactory. Female drivers reported more anger, than males, caused by traffic obstruction and hostile gestures. Age was also negatively related to five (discourtesy, traffic obstructions, hostile gestures, slow driving and police presence) of the six factors and also to the total DAS score. Furthermore, although they were not directly related to crash involvement, several of the six forms of driving anger were significantly related to the crash-related conditions of: near misses, loss of concentration, having lost control of a vehicle and being ticketed. Overall the pattern of findings made in the present research were broadly similar to those from Western countries, indicating that the DAS is a valid measure of driving anger even among non-European based cultures. PMID:24863369

  9. [Drug use and driving].

    PubMed

    Lemaire-Hurtel, Anne-Sophie; Goullé, Jean-Pierre; Alvarez, Jean-Claude; Mura, Patrick; Verstraete, Alain G

    2015-10-01

    Some drugs are known to impair driving because they can change the vision or hearing, and/or disrupt the intellectual or motor abilities: impaired vigilance, sedation, disinhibition effect, the coordination of movement disorders and the balance. The doctor during prescribing and the pharmacist during deliverance of drug treatment should inform their patients of the potential risks of drugs on driving or operating machinery. The driver has direct responsibility, who hired him and him alone, to follow the medical advice received. The pictograms on the outer packaging of medicinal products intended to classify substances according to their risk driving: The driver can whether to observe simple precautions (level one "be prudent"), or follow the advice of a health professional (level two "be very careful"), or if it is totally not drive (level three "danger caution: do not drive"). This classification only evaluates the intrinsic danger of drugs but not the individual variability. Medicines should be taken into account also the conditions for which the medication is prescribed. It is important to inform the patient on several points. PMID:25956300

  10. Belowground neighbor perception in Arabidopsis thaliana studied by transcriptome analysis: roots of Hieracium pilosella cause biotic stress.

    PubMed

    Schmid, Christoph; Bauer, Sibylle; Müller, Benedikt; Bartelheimer, Maik

    2013-01-01

    Root-root interactions are much more sophisticated than previously thought, yet the mechanisms of belowground neighbor perception remain largely obscure. Genome-wide transcriptome analyses allow detailed insight into plant reactions to environmental cues. A root interaction trial was set up to explore both morphological and whole genome transcriptional responses in roots of Arabidopsis thaliana in the presence or absence of an inferior competitor, Hieracium pilosella. Neighbor perception was indicated by Arabidopsis roots predominantly growing away from the neighbor (segregation), while solitary plants placed more roots toward the middle of the pot. Total biomass remained unaffected. Database comparisons in transcriptome analysis revealed considerable similarity between Arabidopsis root reactions to neighbors and reactions to pathogens. Detailed analyses of the functional category "biotic stress" using MapMan tools found the sub-category "pathogenesis-related proteins" highly significantly induced. A comparison to a study on intraspecific competition brought forward a core of genes consistently involved in reactions to neighbor roots. We conclude that beyond resource depletion roots perceive neighboring roots or their associated microorganisms by a relatively uniform mechanism that involves the strong induction of pathogenesis-related proteins. In an ecological context the findings reveal that belowground neighbor detection may occur independently of resource depletion, allowing for a time advantage for the root to prepare for potential interactions. PMID:23967000

  11. Ceramic vane drive joint

    DOEpatents

    Smale, Charles H.

    1981-01-01

    A variable geometry gas turbine has an array of ceramic composition vanes positioned by an actuating ring coupled through a plurality of circumferentially spaced turbine vane levers to the outer end of a metallic vane drive shaft at each of the ceramic vanes. Each of the ceramic vanes has an end slot of bow tie configuration including flared end segments and a center slot therebetween. Each of the vane drive shafts has a cross head with ends thereof spaced with respect to the sides of the end slot to define clearance for free expansion of the cross head with respect to the vane and the cross head being configured to uniformly distribute drive loads across bearing surfaces of the vane slot.

  12. U.S. DRIVE

    SciTech Connect

    2012-03-16

    U.S. DRIVE, which stands for United States Driving Research and Innovation for Vehicle efficiency and Energy sustainability, is an expanded government-industry partnership among the U.S. Department of Energy; USCAR, representing Chrysler Group LLC, Ford Motor Company and General Motors; Tesla Motors; five energy companies – BP America, Chevron Corporation, ConocoPhillips, ExxonMobil Corporation, and Shell Oil Products US; two utilities – Southern California Edison and Michigan-based DTE Energy; and the Electric Power Research Institute (EPRI). The U.S. DRIVE mission is to accelerate the development of pre-competitive and innovative technologies to enable a full range of affordable and clean advanced light-duty vehicles, as well as related energy infrastructure.

  13. Climatic and biotic extreme events moderate long-term responses of above- and belowground sub-Arctic heathland communities to climate change.

    PubMed

    Bokhorst, Stef; Phoenix, Gareth K; Berg, Matty P; Callaghan, Terry V; Kirby-Lambert, Christopher; Bjerke, Jarle W

    2015-11-01

    Climate change impacts are not uniform across the Arctic region because interacting factors causes large variations in local ecosystem change. Extreme climatic events and population cycles of herbivores occur simultaneously against a background of gradual climate warming trends and can redirect ecosystem change along routes that are difficult to predict. Here, we present the results from sub-Arctic heath vegetation and its belowground micro-arthropod community in response to the two main drivers of vegetation damage in this region: extreme winter warming events and subsequent outbreaks of the defoliating autumnal moth caterpillar (Epirrita autumnata). Evergreen dwarf shrub biomass decreased (30%) following extreme winter warming events and again by moth caterpillar grazing. Deciduous shrubs that were previously exposed to an extreme winter warming event were not affected by the moth caterpillar grazing, while those that were not exposed to warming events (control plots) showed reduced (23%) biomass from grazing. Cryptogam cover increased irrespective of grazing or winter warming events. Micro-arthropods declined (46%) following winter warming but did not respond to changes in plant community. Extreme winter warming and caterpillar grazing suppressed the CO2 fluxes of the ecosystem. Evergreen dwarf shrubs are disadvantaged in a future sub-Arctic with more stochastic climatic and biotic events. Given that summer warming may further benefit deciduous over evergreen shrubs, event and trend climate change may both act against evergreen shrubs and the ecosystem functions they provide. This is of particular concern given that Arctic heath vegetation is typically dominated by evergreen shrubs. Other components of the vegetation showed variable responses to abiotic and biotic events, and their interaction indicates that sub-Arctic vegetation response to multiple pressures is not easy to predict from single-factor responses. Therefore, while biotic and climatic events may

  14. Are pine plantations valid tools for restoring Mediterranean forests? An assessment along abiotic and biotic gradients.

    PubMed

    Gómez-Aparicio, Lorena; Zavala, Miguel A; Bonet, Francisco J; Zamora, Regino

    2009-12-01

    The ecological impacts of forest plantations are a focus of intense debate, from studies that consider plantations as "biological deserts" to studies showing positive effects on plant diversity and dynamics. This lack of consensus might be influenced by the scarcity of studies that examine how the ecological characteristics of plantations vary along abiotic and biotic gradients. Here we conducted a large-scale assessment of plant regeneration and diversity in plantations of southern Spain. Tree seedling and sapling density, plant species richness, and Shannon's (H') diversity index were analyzed in 442 pine plantation plots covering a wide gradient of climatic conditions, stand density, and distance to natural forests that act as seed sources. Pronounced variation in regeneration and diversity was found in plantation understories along the gradients explored. Low- to mid-altitude plantations showed a diverse and abundant seedling bank dominated by Quercus ilex, whereas high-altitude plantations showed a virtually monospecific seeding bank of Pinus sylvestris. Regeneration was null in plantations with stand densities exceeding 1500 pines/ha. Moderate plantation densities (500-1000 pines/ha) promoted recruitment in comparison to low or null canopy cover, suggesting the existence of facilitative interactions. Quercus ilex recruitment diminished exponentially with distance to the nearest Q. ilex forest. Richness and H' index values showed a hump-shaped distribution along the altitudinal and radiation gradients and decreased monotonically along the stand density gradient. From a management perspective, different strategies will be necessary depending on where a plantation lies along the gradients explored. Active management will be required in high-density plantations with arrested succession and low diversity. Thinning could redirect plantations toward more natural densities where facilitation predominates. Passive management might be recommended for low- to moderate

  15. LCLS Injector Drive Laser

    SciTech Connect

    Dowell, D.H.; Castro, J.; Emma, P.; Frisch, J.; Gilevich, A.; Hays, G.; Hering, P.; Limborg-Deprey, C.; Loos, H.; Miahnahri, A.; White, W.; /SLAC

    2007-11-02

    Requirements for the LCLS injector drive laser present significant challenges to the design of the system. While progress has been demonstrated in spatial shape, temporal shape, UV generation and rep-rate, a laser that meets all of the LCLS specifications simultaneously has yet to be demonstrated. These challenges are compounded by the stability and reliability requirements. The drive laser and transport system has been installed and tested. We will report on the current operational state of the laser and plans for future improvements.

  16. Optotech 5984 Drive Overview

    NASA Astrophysics Data System (ADS)

    Lee, Tzuo-Chang; Chen, Di

    1987-01-01

    We present in this paper an overview of Optotech's 5984 Optical Disk Drive. Key features such as the modulation code, the disk format, defect mapping scheme and the optical head and servo subsystem will be singled out for discussion. Description of Optotech's 5984 disk drive The Optotech 5984 optical disk drive is a write-once-read-mostly (WORM) rotating optical memory with 200 Megabyte capacity on each side of the disk. It has a 5 1/4 inch form factor that will fit into any personal computer full-height slot. The drive specification highlights are given in Table 1. A perspective view of the drive mechanical assembly is shown in Figure 1. The spindle that rotates the disk has a runout of less than 10 um. The rotational speed at 1200 revolutions per minute (rpm) is held to an accuracy of 10-3. The total angular tolerance from perfect perpendicular alignment between the rotating disk and the incident optical beam axis is held to less than 17 milliradians. The coarse seek is accomplished through a stepping motor driving the optical head with 1.3 milliseconds per step or 32 tracks per step. The analog channels including read/write, the phase lock loop and the servo loops for focus and track control are contained on one surface mount pc board while the digital circuitry that interfaces with the drive and the controller is on a separate pc board. A microprocessor 8039 is used to control the handshake and the sequence of R/W commands. A separate power board is used to provide power to the spindle and the stepping motors. In the following we will discuss some of the salient features in the drive and leave the details to three accompanying Optotech papers. These salient features are derived from a design that is driven by three major considerations. One is precise control of the one micron diameter laser spot to any desired location on the disk. The second consideration is effective management of media defects. Given the state of the art of the Te-based disk technology with

  17. CONTROL ROD DRIVE

    DOEpatents

    Chapellier, R.A.; Rogers, I.

    1961-06-27

    Accurate and controlled drive for the control rod is from an electric motor. A hydraulic arrangement is provided to balance a piston against which a control rod is urged by the application of fluid pressure. The electric motor drive of the control rod for normal operation is made through the aforementioned piston. In the event scramming is required, the fluid pressure urging the control rod against the piston is relieved and an opposite fluid pressure is applied. The lack of mechanical connection between the electric motor and control rod facilitates the scramming operation.

  18. USE OF PERIPHYTON ASSEMBLAGE DATA AS AN INDEX OF BIOTIC INTEGRITY

    EPA Science Inventory

    Periphyton assemblages data collected from 233 stream site-visits (49 in 1993, 56 in 1994, and 128 in 1995) throughout the Mid-Appalachian region were used to develop a periphyton index of biotic integrity (PIBI} based on 1) algal genera richness; 2)the relative abundances of dia...

  19. White-tailed deer are a biotic filter during community assembly, reducing species and phylogenetic diversity

    PubMed Central

    Begley-Miller, Danielle R.; Hipp, Andrew L.; Brown, Bethany H.; Hahn, Marlene; Rooney, Thomas P.

    2014-01-01

    Community assembly entails a filtering process, where species found in a local community are those that can pass through environmental (abiotic) and biotic filters and successfully compete. Previous research has demonstrated the ability of white-tailed deer (Odocoileus virginianus) to reduce species diversity and favour browse-tolerant plant communities. In this study, we expand on our previous work by investigating deer as a possible biotic filter altering local plant community assembly. We used replicated 23-year-old deer exclosures to experimentally assess the effects of deer on species diversity (H′), richness (SR), phylogenetic community structure and phylogenetic diversity in paired browsed (control) and unbrowsed (exclosed) plots. Additionally, we developed a deer-browsing susceptibility index (DBSI) to assess the vulnerability of local species to deer. Deer browsing caused a 12 % reduction in H′ and 17 % reduction in SR, consistent with previous studies. Furthermore, browsing reduced phylogenetic diversity by 63 %, causing significant phylogenetic clustering. Overall, graminoids were the least vulnerable to deer browsing based on DBSI calculations. These findings demonstrate that deer are a significant driver of plant community assembly due to their role as a selective browser, or more generally, as a biotic filter. This study highlights the importance of knowledge about the plant tree of life in assessing the effects of biotic filters on plant communities. Application of such knowledge has considerable potential to advance our understanding of plant community assembly. PMID:24916059

  20. Abiotic and biotic controls of soil moisture spatiotemporal variability and the occurrence of hysteresis

    NASA Astrophysics Data System (ADS)

    Fatichi, Simone; Katul, Gabriel G.; Ivanov, Valeriy Y.; Pappas, Christoforos; Paschalis, Athanasios; Consolo, Ada; Kim, Jongho; Burlando, Paolo

    2015-05-01

    An expression that separates biotic and abiotic controls on the temporal dynamics of the soil moisture spatial coefficient of variation Cv(θ) was explored via numerical simulations using a mechanistic ecohydrological model, Tethys-Chloris. Continuous soil moisture spatiotemporal dynamics at an exemplary hillslope domain were computed for six case studies characterized by different climate and vegetation cover and for three configurations of soil properties. It was shown that abiotic controls largely exceed their biotic counterparts in wet climates. Biotic controls on Cv(θ) were found to be more pronounced in Mediterranean climates. The relation between Cv(θ) and spatial mean soil moisture θ¯ was found to be unique in wet locations, regardless of the soil properties. For the case of homogeneous soil texture, hysteretic cycles between Cv(θ) and θ¯ were observed in all Mediterranean climate locations considered here and to a lesser extent in a deciduous temperate forest. Heterogeneity in soil properties increased Cv(θ) to values commensurate with field observations and weakened signatures of hysteresis at all of the studied locations. This finding highlights the role of site-specific heterogeneities in hiding or even eliminating the signature of climatic and biotic controls on Cv(θ), thereby offering a new perspective on causes of confounding results reported across field experiments.

  1. DEVELOPMENT OF A FISH INDEX OF BIOTIC INTEGRITY FOR ASSESSING WADEABLE STREAMS IN WEST VIRGINIA

    EPA Science Inventory

    We used Environmental Monitoring Assessment Program (EMAP) data from the Mid-Atlantic Highlands Assessment (MAHA) to develop an Index of Biotic Integrity (IBI) for West Virginia (WV). Standard techniques were used to evaluate a candidate pool of 58 fish assemblage metrics. Resp...

  2. Experimental test of biotic resistance to an invasive herbivore provided by potential plant mutualists

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding the influence of resident species on the success of invaders is a core objective in the study and management of biological invasions. We asked whether facultative, food-for-protection mutualism between resident, nectar-feeding ants and extra floral nectar-bearing plants confers biotic...

  3. Biotic soil crusts in relation to topography, cheatgrass, and fire in the Columbia Basin, Washington

    USGS Publications Warehouse

    Ponzetti, Jeanne; McCune, B.; Pyke, David A.

    2007-01-01

    We studied lichen and bryophyte soil crust communities in a large public grazing allotment within a sagebrush steppe ecosystem in which the biotic soil crusts are largely intact. The allotment had been rested from grazing for 12 years, but experienced an extensive series of wildfires. In the 350, 4 ?? 0.5 m plots, stratified by topographic position, we found 60 species or species groups that can be distinguished in the field with a hand lens, averaging 11.5 species groups per plot. Lichen and bryophyte soil crust communities differed among topographic positions. Draws were the most disturbed, apparently from water erosion in a narrow channel and mass wasting from the steepened sides. Presumably because of this disturbance, draws had the lowest average species richness of all the topographic strata we examined. Biotic crust species richness and cover were inversely related to cover of the invasive annual, cheatgrass (Bromus tectorum), and positively related to cover of native bunchgrasses. Integrity of the biotic crust was more strongly related to cheatgrass than to fire. In general, we observed good recovery of crusts following fire, but only in those areas dominated by perennial bunchgrasses. We interpret the resilience of the biotic crust, in this case, to the low abundance of cheatgrass, low amounts of soil disturbance and high moss cover. These fires have not resulted in an explosion of the cheatgrass population, perhaps because of the historically low levels of livestock grazing.

  4. Electrode impedance analysis of chronic tungsten microwire neural implants: understanding abiotic vs. biotic contributions.

    PubMed

    Sankar, Viswanath; Patrick, Erin; Dieme, Robert; Sanchez, Justin C; Prasad, Abhishek; Nishida, Toshikazu

    2014-01-01

    Changes in biotic and abiotic factors can be reflected in the complex impedance spectrum of the microelectrodes chronically implanted into the neural tissue. The recording surface of the tungsten electrode in vivo undergoes abiotic changes due to recording site corrosion and insulation delamination as well as biotic changes due to tissue encapsulation as a result of the foreign body immune response. We reported earlier that large changes in electrode impedance measured at 1 kHz were correlated with poor electrode functional performance, quantified through electrophysiological recordings during the chronic lifetime of the electrode. There is a need to identity the factors that contribute to the chronic impedance variation. In this work, we use numerical simulation and regression to equivalent circuit models to evaluate both the abiotic and biotic contributions to the impedance response over chronic implant duration. COMSOL® simulation of abiotic electrode morphology changes provide a possible explanation for the decrease in the electrode impedance at long implant duration while biotic changes play an important role in the large increase in impedance observed initially. PMID:24847248

  5. PREDICTING SEDIMENT METAL TOXICITY USING A SEDIMENT BIOTIC LIGAND MODEL: METHODOLOGY AND INITIAL APPLICATION

    EPA Science Inventory

    An extension of the simultaneously extracted metals/acid-volatile sulfide (SEM/AVS) procedure is presented that predicts the acute and chronic sediment metals effects concentrations. A biotic ligand model (BLM) and a pore water–sediment partitioning model are used to predict the ...

  6. Biotic and abiotic drivers of phenotypic plasticity of wing dimorphism in Sclerodermus pupariae

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wing phenotype polymorphism is commonly observed in insects, yet little is known about the influence of environmental cues on the development or expression of the alternative phenotypes. Here, we examined the effects of biotic and abiotic factors including temperature, photoperiod, light intensity,...

  7. Biotic regulation of CO2 uptake-climate responses: links to vegetation proproperties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Identifying the plant traits and patterns of trait distribution in communities that are responsible for biotic regulation of CO2 uptake-climate responses remains a priority for modelling terrestrial C dynamics. We used remotely-sensed estimates of GPP from plots planted to different combinations of...

  8. Development of a wireless computer vision instrument to detect biotic stress in wheat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of soil water deficits, crop water stress, and biotic stress from disease or insect pressure is important for optimal irrigation scheduling and water management. While spectral reflectance and thermometry provide a means to quantify crop stress remotely, measurements can be cumbersome, exp...

  9. Using biotechnology and genomics to improve biotic and abiotic stress in apple

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Genomic sequencing, molecular biology, and transformation technologies are providing valuable tools to better understand the complexity of how plants develop, function, and respond to biotic and abiotic stress. These approaches should complement but not replace a solid understanding of whole plant ...

  10. REGIONAL APPLICATIONS OF AN INDEX OF BIOTIC INTEGRITY FOR USE IN WATER RESOURCE MANAGEMENT

    EPA Science Inventory

    The index of biotic integrity (IBI) integrates 12 measures of stream fish assemblages for assessing water resource quality. Initially developed and tested in the Midwest, the IBI recently was adapted for use in western Oregon, northeastern Colorado, New England, the Appalachians ...

  11. Electrode impedance analysis of chronic tungsten microwire neural implants: understanding abiotic vs. biotic contributions

    PubMed Central

    Sankar, Viswanath; Patrick, Erin; Dieme, Robert; Sanchez, Justin C.; Prasad, Abhishek; Nishida, Toshikazu

    2014-01-01

    Changes in biotic and abiotic factors can be reflected in the complex impedance spectrum of the microelectrodes chronically implanted into the neural tissue. The recording surface of the tungsten electrode in vivo undergoes abiotic changes due to recording site corrosion and insulation delamination as well as biotic changes due to tissue encapsulation as a result of the foreign body immune response. We reported earlier that large changes in electrode impedance measured at 1 kHz were correlated with poor electrode functional performance, quantified through electrophysiological recordings during the chronic lifetime of the electrode. There is a need to identity the factors that contribute to the chronic impedance variation. In this work, we use numerical simulation and regression to equivalent circuit models to evaluate both the abiotic and biotic contributions to the impedance response over chronic implant duration. COMSOL® simulation of abiotic electrode morphology changes provide a possible explanation for the decrease in the electrode impedance at long implant duration while biotic changes play an important role in the large increase in impedance observed initially. PMID:24847248

  12. SENSITIVITY OF INDICES OF BIOTIC INTEGRITY TO SIMULATED FISH ASSEMBLAGE CHANGES

    EPA Science Inventory

    Multi-metric indices of biotic integrity (IBI) are commonly used to assess condition of stream fish assemblages, but their ability to monitor trends within streams over time is largely unknown. We assessed the trend detection ability of two IBI formulations (one with traditional ...

  13. Comprehensive Analysis Suggests Overlapping Expression of Rice ONAC Transcription Factors in Abiotic and Biotic Stress Responses

    PubMed Central

    Sun, Lijun; Huang, Lei; Hong, Yongbo; Zhang, Huijuan; Song, Fengming; Li, Dayong

    2015-01-01

    NAC (NAM/ATAF/CUC) transcription factors comprise a large plant-specific gene family that contains more than 149 members in rice. Extensive studies have revealed that NAC transcription factors not only play important roles in plant growth and development, but also have functions in regulation of responses to biotic and abiotic stresses. However, biological functions for most of the members in the NAC family remain unknown. In this study, microarray data analyses revealed that a total of 63 ONAC genes exhibited overlapping expression patterns in rice under various abiotic (salt, drought, and cold) and biotic (infection by fungal, bacterial, viral pathogens, and parasitic plants) stresses. Thirty-eight ONAC genes exhibited overlapping expression in response to any two abiotic stresses, among which 16 of 30 selected ONAC genes were upregulated in response to exogenous ABA. Sixty-five ONAC genes showed overlapping expression patterns in response to any two biotic stresses. Results from the present study suggested that members of the ONAC genes with overlapping expression pattern may have pleiotropic biological functions in regulation of defense response against different abiotic and biotic stresses, which provide clues for further functional analysis of the ONAC genes in stress tolerance and pathogen resistance. PMID:25690040

  14. DEVELOPMENT AND EVALUATION OF A FISH ASSEMBLAGE INDEX OF BIOTIC INTEGRITY FOR NORTHWESTERN GREAT PLAINS STREAMS

    EPA Science Inventory

    Quantitative indicators of biological integrity are needed for streams in the Great Plains of North America, but it was not known if the Index of Biotic Integrity (IBI) approach would be effective in this semi-arid region. Great Plains streams have a depauperate and tolerant i...

  15. SENSITIVITY OF INDICES OF BIOTIC INTEGRITY TO SIMULATED FISH ASSEMBLAGE CHANGES - 2

    EPA Science Inventory

    Multi-metric indices of biotic integrity (IBI) are commonly used to compare fish communities among streams, but their ability to monitor trends within streams is largely unknown. We assessed the IBI trend detection ability using simulations which progressively degraded the fish a...

  16. Nutrient Concentrations and Their Relations to the Biotic Integrity of Nonwadeable Rivers in Wisconsin

    USGS Publications Warehouse

    Robertson, Dale M.; Weigel, Brian M.; Graczyk, David J.

    2008-01-01

    Excessive nutrient [phosphorus (P) and nitrogen (N)] input from point and nonpoint sources is frequently associated with degraded water quality in streams and rivers. Point-source discharges of nutrients are fairly constant and are controlled by the U.S. Environmental Protection Agency's (USEPA) National Pollutant Discharge Elimination System. To reduce inputs from nonpoint sources, agricultural performance standards and regulations for croplands and livestock operations are being proposed by various States. In addition, the USEPA is establishing regionally based nutrient criteria that can be refined by each State to determine whether actions are needed to improve water quality. More confidence in the environmental benefits of the proposed performance standards and nutrient criteria would be possible with improved understanding of the biotic responses to a range of nutrient concentrations in different environmental settings. To achieve this general goal, the U.S. Geological Survey and the Wisconsin Department of Natural Resources collected data from 282 streams and rivers throughout Wisconsin during 2001 through 2003 to: (1) describe how nutrient concentrations and biotic-community structure differ throughout the State, (2) determine which environmental characteristics are most strongly related to the distribution of nutrient concentrations and biotic-community structure, (3) determine reference conditions for water quality and biotic indices for streams and rivers in the State, (4) determine how the biotic communities in streams and rivers in different areas of the State respond to differences in nutrient concentrations, (5) determine the best regionalization scheme to describe the patterns in reference conditions and the corresponding responses in water quality and the biotic communities (primarily for smaller streams), and (6) develop algorithms to estimate nutrient concentrations in streams and rivers from a combination of biotic indices. The ultimate goal of

  17. Metabolomics of cereals under biotic stress: current knowledge and techniques

    PubMed Central

    Balmer, Dirk; Flors, Victor; Glauser, Gaetan; Mauch-Mani, Brigitte

    2013-01-01

    Prone to attacks by pathogens and pests, plants employ intricate chemical defense mechanisms consisting of metabolic adaptations. However, many plant attackers are manipulating the host metabolism to counteract defense responses and to induce favorable nutritional conditions. Advances in analytical chemistry have allowed the generation of extensive metabolic profiles during plant-pathogen and pest interactions. Thereby, metabolic processes were found to be highly specific for given tissues, species, and plant-pathogen/pest interactions. The clusters of identified compounds not only serve as base in the quest of novel defense compounds, but also as markers for the characterization of the plants' defensive state. The latter is especially useful in agronomic applications where meaningful markers are essential for crop protection. Cereals such as maize make use of their metabolic arsenal during both local and systemic defense responses, and the chemical response is highly adapted to specific attackers. Here, we summarize highlights and recent findings of metabolic patterns of cereals under pathogen and pest attack. PMID:23630531

  18. CSI: Hard Drive

    ERIC Educational Resources Information Center

    Sturgeon, Julie

    2008-01-01

    Acting on information from students who reported seeing a classmate looking at inappropriate material on a school computer, school officials used forensics software to plunge the depths of the PC's hard drive, searching for evidence of improper activity. Images were found in a deleted Internet Explorer cache as well as deleted file space.…

  19. DrivePy

    Energy Science and Technology Software Center (ESTSC)

    2014-08-30

    DrivePy is physics-based drivetrain model that sizes drivetrain components based on aerodynamic and operational loads for use in a systems engineering model. It also calculates costs based on empirical data collected by NREL's National Wind Technology Center.

  20. No Pass, No Drive?

    ERIC Educational Resources Information Center

    Zirkel, Perry A.

    2001-01-01

    Discusses basis for Kentucky appellate court decision that state's no-pass, no-drive statute did not violate due-process and equal-protection clauses of the Kentucky and federal constitutions, but did violate the federal Family Education Rights and Privacy Act, but nevertheless did not invalidate the statute. Explains why the decision is…

  1. Teachers with Drive

    ERIC Educational Resources Information Center

    Coggins, Celine; Diffenbaugh, P. K.

    2013-01-01

    For students in U.S. classrooms today, the odds of being assigned to an inexperienced teacher are higher than they have ever been because so many teachers, some in the top 20 percent of effectiveness are leaving the classroom in their first five years. Coggins and Diffenbaugh turn to Daniel Pink's work on drive to determine how to motivate…

  2. [Epilepsy and driving].

    PubMed

    Adam, Claude

    2015-10-01

    Epilepsy contributes little to road traffic accidents (0.25% of accidents) compared, for instance, to alcohol abuse (at least 30 times higher). Current factors, such as age and sex, or other chronic medical conditions also increase the risk of road traffic accidents but do not carry driving restrictions. So, the European Commission fairly established rules permitting individuals having experienced one or more epileptic seizures to drive if their road accident risk is low. Road accident risk related to epileptic seizures in various clinical situations is evaluated by the driving license commission, mainly with the aid of criteria based on seizure-free periods. A person who has had an epileptic seizure should notify the authorities. He should be advised by treating physician not to drive before. In case of an authorisation, any new relevant event should be notified to the authorities in the course of legal follow-up. Improvements of the current regulations by European data registries are under way. PMID:26482490

  3. COMMENT: No warp drive

    NASA Astrophysics Data System (ADS)

    Coule, D. H.

    1998-08-01

    The warp drive spacetime of Alcubierre is impossible to set up without first being able to distribute matter at tachyonic speed, put roughly, you need one to make one! However, over small distances, where the energy conditions possibly can be violated, one can envision opening the light-cones to increase the apparent speed of light.

  4. Drive-Through Training

    ERIC Educational Resources Information Center

    Carter, Margie

    2010-01-01

    In this article, the author discusses how the early childhood field's approach to staff training reflects the drive-through, fast-food culture. Year after year directors send their teachers to workshops to get some quick refresher techniques. The author suggests that rather than focusing professional development on topics, focus on observing…

  5. Driving skills after whiplash.

    PubMed

    Gimse, R; Bjørgen, I A; Straume, A

    1997-09-01

    Previous studies have shown that some persons with longlasting problems after whiplash have changed eye movements. These changes have been related to disturbance of the posture control system. The question raised in the present study is whether such disturbances can influence daily life functions connected with balance, position and external movements, such as car driving. A group of 23 persons with disturbed eye movements due to whiplash injury, was tested in a driving simulator, together with a closely matched control group. The results revealed significant differences between the two groups with respect to response times to the traffic signs presented, identification of type of sign, as well as steering precision while the subjects' attention was directed to the process of identifying the signs. Alternative explanations such as driving experience, pain, medication or malingering are at least partly controlled for, but cannot completely be ruled out. A distorted posture control system leading to disturbance of eye movements seems to be the most likely primary causative factor, but these disturbances are most certainly complexly determined. Reduced attention capacity is considered to be a mediating secondary factor. Registration of eye movements may be a useful diagnostic tool to evaluate driving skill after whiplash. PMID:9309948

  6. Driving While Intoxicated.

    ERIC Educational Resources Information Center

    Brick, John

    Alcohol intoxication increases the risk of highway accidents, the relative risk of crash probability increasing as a function of blood alcohol content (BAC). Because alcohol use is more prevalent than use of other drugs, more is known about the relationship between alcohol use and driving. Most states presume a BAC of .10% to be evidence of drunk…

  7. Identification of Arabidopsis Candidate Genes in Response to Biotic and Abiotic Stresses Using Comparative Microarrays

    PubMed Central

    Sham, Arjun; Moustafa, Khaled; Al-Ameri, Salma; Al-Azzawi, Ahmed; Iratni, Rabah; AbuQamar, Synan

    2015-01-01

    Plants have evolved with intricate mechanisms to cope with multiple environmental stresses. To adapt with biotic and abiotic stresses, plant responses involve changes at the cellular and molecular levels. The current study was designed to investigate the effects of combinations of different environmental stresses on the transcriptome level of Arabidopsis genome using public microarray databases. We investigated the role of cyclopentenones in mediating plant responses to environmental stress through TGA (TGACG motif-binding factor) transcription factor, independently from jasmonic acid. Candidate genes were identified by comparing plants inoculated with Botrytis cinerea or treated with heat, salt or osmotic stress with non-inoculated or non-treated tissues. About 2.5% heat-, 19% salinity- and 41% osmotic stress-induced genes were commonly upregulated by B. cinerea-treatment; and 7.6%, 19% and 48% of genes were commonly downregulated by B. cinerea-treatment, respectively. Our results indicate that plant responses to biotic and abiotic stresses are mediated by several common regulatory genes. Comparisons between transcriptome data from Arabidopsis stressed-plants support our hypothesis that some molecular and biological processes involved in biotic and abiotic stress response are conserved. Thirteen of the common regulated genes to abiotic and biotic stresses were studied in detail to determine their role in plant resistance to B. cinerea. Moreover, a T-DNA insertion mutant of the Responsive to Dehydration gene (rd20), encoding for a member of the caleosin (lipid surface protein) family, showed an enhanced sensitivity to B. cinerea infection and drought. Overall, the overlapping of plant responses to abiotic and biotic stresses, coupled with the sensitivity of the rd20 mutant, may provide new interesting programs for increased plant resistance to multiple environmental stresses, and ultimately increases its chances to survive. Future research directions towards a

  8. Identification of Arabidopsis candidate genes in response to biotic and abiotic stresses using comparative microarrays.

    PubMed

    Sham, Arjun; Moustafa, Khaled; Al-Ameri, Salma; Al-Azzawi, Ahmed; Iratni, Rabah; AbuQamar, Synan

    2015-01-01

    Plants have evolved with intricate mechanisms to cope with multiple environmental stresses. To adapt with biotic and abiotic stresses, plant responses involve changes at the cellular and molecular levels. The current study was designed to investigate the effects of combinations of different environmental stresses on the transcriptome level of Arabidopsis genome using public microarray databases. We investigated the role of cyclopentenones in mediating plant responses to environmental stress through TGA (TGACG motif-binding factor) transcription factor, independently from jasmonic acid. Candidate genes were identified by comparing plants inoculated with Botrytis cinerea or treated with heat, salt or osmotic stress with non-inoculated or non-treated tissues. About 2.5% heat-, 19% salinity- and 41% osmotic stress-induced genes were commonly upregulated by B. cinerea-treatment; and 7.6%, 19% and 48% of genes were commonly downregulated by B. cinerea-treatment, respectively. Our results indicate that plant responses to biotic and abiotic stresses are mediated by several common regulatory genes. Comparisons between transcriptome data from Arabidopsis stressed-plants support our hypothesis that some molecular and biological processes involved in biotic and abiotic stress response are conserved. Thirteen of the common regulated genes to abiotic and biotic stresses were studied in detail to determine their role in plant resistance to B. cinerea. Moreover, a T-DNA insertion mutant of the Responsive to Dehydration gene (rd20), encoding for a member of the caleosin (lipid surface protein) family, showed an enhanced sensitivity to B. cinerea infection and drought. Overall, the overlapping of plant responses to abiotic and biotic stresses, coupled with the sensitivity of the rd20 mutant, may provide new interesting programs for increased plant resistance to multiple environmental stresses, and ultimately increases its chances to survive. Future research directions towards a

  9. Influence of Environmental Factors on Biotic Responses to Nutrient Enrichment in Agricultural Streams1

    PubMed Central

    Maret, Terry R; Konrad, Christopher P; Tranmer, Andrew W

    2010-01-01

    The influence of environmental factors on biotic responses to nutrients was examined in three diverse agricultural regions of the United States. Seventy wadeable sites were selected along an agricultural land use gradient while minimizing natural variation within each region. Nutrients, habitat, algae, macroinvertebrates, and macrophyte cover were sampled during a single summer low-flow period in 2006 or 2007. Continuous stream stage and water temperature were collected at each site for 30 days prior to sampling. Wide ranges of concentrations were found for total nitrogen (TN) (0.07-9.61 mg/l) and total phosphorus (TP) (<0.004-0.361 mg/l), but biotic responses including periphytic and sestonic chlorophyll a (RCHL and SCHL, respectively), and percent of stream bed with aquatic macrophyte (AQM) growth were not strongly related to concentrations of TN or TP. Pearson’s coefficient of determination (R2) for nutrients and biotic measures across all sites ranged from 0.08 to 0.32 and generally were not higher within each region. The biotic measures (RCHL, SCHL, and AQM) were combined in an index to evaluate eutrophic status across sites that could have different biotic responses to nutrient enrichment. Stepwise multiple regression identified TN, percent canopy, median riffle depth, and daily percent change in stage as significant factors for the eutrophic index (R2 = 0.50, p < 0.001). A TN threshold of 0.48 mg/l was identified where eutrophic index scores became less responsive to increasing TN concentrations, for all sites. Multiple plant growth indicators should be used when evaluating eutrophication, especially when streams contain an abundance of macrophytes. PMID:22457568

  10. Current drive by helicon waves

    SciTech Connect

    Paul, Manash Kumar; Bora, Dhiraj

    2009-01-01

    Helicity in the dynamo field components of helicon wave is examined during the novel study of wave induced helicity current drive. Strong poloidal asymmetry in the wave magnetic field components is observed during helicon discharges formed in a toroidal vacuum chamber of small aspect ratio. High frequency regime is chosen to increase the phase velocity of helicon waves which in turn minimizes the resonant wave-particle interactions and enhances the contribution of the nonresonant current drive mechanisms. Owing to the strong poloidal asymmetry in the wave magnetic field structures, plasma current is driven mostly by the dynamo-electric-field, which arise due to the wave helicity injection by helicon waves. Small, yet finite contribution from the suppressed wave-particle resonance cannot be ruled out in the operational regime examined. A brief discussion on the parametric dependence of plasma current along with numerical estimations of nonresonant components is presented. A close agreement between the numerical estimation and measured plasma current magnitude is obtained during the present investigation.

  11. Transcriptome dynamics of Arabidopsis during sequential biotic and abiotic stresses.

    PubMed

    Coolen, Silvia; Proietti, Silvia; Hickman, Richard; Davila Olivas, Nelson H; Huang, Ping-Ping; Van Verk, Marcel C; Van Pelt, Johan A; Wittenberg, Alexander H J; De Vos, Martin; Prins, Marcel; Van Loon, Joop J A; Aarts, Mark G M; Dicke, Marcel; Pieterse, Corné M J; Van Wees, Saskia C M

    2016-05-01

    In nature, plants have to cope with a wide range of stress conditions that often occur simultaneously or in sequence. To investigate how plants cope with multi-stress conditions, we analyzed the dynamics of whole-transcriptome profiles of Arabidopsis thaliana exposed to six sequential double stresses inflicted by combinations of: (i) infection by the necrotrophic fungus Botrytis cinerea, (ii) herbivory by chewing larvae of Pieris rapae, and (iii) drought stress. Each of these stresses induced specific expression profiles over time, in which one-third of all differentially expressed genes was shared by at least two single stresses. Of these, 394 genes were differentially expressed during all three stress conditions, albeit often in opposite directions. When two stresses were applied in sequence, plants displayed transcriptome profiles that were very similar to the second stress, irrespective of the nature of the first stress. Nevertheless, significant first-stress signatures could be identified in the sequential stress profiles. Bioinformatic analysis of the dynamics of co-expressed gene clusters highlighted specific clusters and biological processes of which the timing of activation or repression was altered by a prior stress. The first-stress signatures in second stress transcriptional profiles were remarkably often related to responses to phytohormones, strengthening the notion that hormones are global modulators of interactions between different types of stress. Because prior stresses can affect the level of tolerance against a subsequent stress (e.g. prior herbivory strongly affected resistance to B. cinerea), the first-stress signatures can provide important leads for the identification of molecular players that are decisive in the interactions between stress response pathways. PMID:26991768

  12. An Exploratory Investigation: Are Driving Simulators Appropriate to Teach Pre-Driving Skills to Young Adults with Intellectual Disabilities?

    ERIC Educational Resources Information Center

    Brooks, Johnell O.; Mossey, Mary E.; Tyler, Peg; Collins, James C.

    2014-01-01

    Research examining driver training for young adults with intellectual disabilities has been limited since the 1970s. The current pilot and exploratory study investigated teaching pre-driving skills (i.e. lane keeping and speed maintenance) to young adults with intellectual disabilities using an interactive driving simulator to provide dynamic and…

  13. Mud, Macrofauna and Microbes: An ode to benthic organism-abiotic interactions at varying scales

    EPA Science Inventory

    Benthic environments are dynamic habitats, subject to variable sources and rates of sediment delivery, reworking from the abiotic and biotic processes, and complex biogeochemistry. These activities do not occur in a vacuum, and interact synergistically to influence food webs, bi...

  14. How severe is the modern biotic crisis?—A comparison of global change and biotic crisis between Permian-Triassic transition and modern times

    NASA Astrophysics Data System (ADS)

    Yin, Hongfu; He, Weihong; Xie, Shucheng

    2011-03-01

    A comparison of the modern condition with the Permian-Triassic Boundary (PTB) times was made to estimate how severe the modern biotic crisis is. About the global changes, the two periods are correlative in carbon dioxide concentration and carbon isotope negative excursion, UV strengthening, temperature increase, ocean acidification, and weathering enhancement. The following tendencies of biotic crises are also correlative: acceleration of extinction rates accompanied by parabolic curve of extinction with a turning interval representing the critical crisis; decline of the three main ecosystems: reefs, tropical rain forests and marine phytoplankton. It is also interesting to note that certain leading organism in both periods undergo accelerated evolution during the crisis. The comparison shows that the modern crisis is about at the turning point from decline to decimation. The extinction curve is now parabolic, and the extinction rate has been accelerated, but the decimation is not yet in real. This is also justified by the modern situation of the three main ecosystems. Modern biotic decline may worsen into decimation and mass extinction but may also get better and recover to ordinary evolution. Since human activities are the main cause of the deterioration of environments and organisms, mankind should be responsible and able to strive for the recovery of the crisis. For the future of mankind, Homo sapiens may become extinct, i.e., disappear without leaving descendants, or evolve into a new and more advanced species, i.e., disappear but leave descendants. For a better future, mankind should be conscious of the facing danger and act as a whole to save biodiversity and harmonize with the environments.

  15. The transcriptional network of WRKY53 in cereals links oxidative responses to biotic and abiotic stress inputs.

    PubMed

    Van Eck, Leon; Davidson, Rebecca M; Wu, Shuchi; Zhao, Bingyu Y; Botha, Anna-Maria; Leach, Jan E; Lapitan, Nora L V

    2014-06-01

    The transcription factor WRKY53 is expressed during biotic and abiotic stress responses in cereals, but little is currently known about its regulation, structure and downstream targets. We sequenced the wheat ortholog TaWRKY53 and its promoter region, which revealed extensive similarity in gene architecture and cis-acting regulatory elements to the rice ortholog OsWRKY53, including the presence of stress-responsive abscisic acid-responsive elements (ABRE) motifs and GCC-boxes. Four proteins interacted with the WRKY53 promoter in yeast one-hybrid assays, suggesting that this gene can receive inputs from diverse stress-related pathways such as calcium signalling and senescence, and environmental cues such as drought and ultraviolet radiation. The Ser/Thr receptor kinase ORK10/LRK10 and the apoplastic peroxidase POC1 are two downstream targets for regulation by the WRKY53 transcription factor, predicted based on the presence of W-box motifs in their promoters and coregulation with WRKY53, and verified by electrophoretic mobility shift assay (EMSA). Both ORK10/LRK10 and POC1 are upregulated during cereal responses to pathogens and aphids and important components of the oxidative burst during the hypersensitive response. Taken with our yeast two-hybrid assay which identified a strong protein-protein interaction between microsomal glutathione S-transferase 3 and WRKY53, this implies that the WRKY53 transcriptional network regulates oxidative responses to a wide array of stresses. PMID:24777609

  16. Nutrient concentrations and their relations to the biotic integrity of wadeable streams in Wisconsin

    USGS Publications Warehouse

    Robertson, Dale M.; Graczyk, David J.; Garrison, Paul J.; Wang, Lizhu; LaLiberte, Gina; Bannerman, Roger

    2006-01-01

    Excessive nutrient (phosphorus and nitrogen) loss from watersheds is frequently associated with degraded water quality in streams. To reduce this loss, agricultural performance standards and regulations for croplands and livestock operations are being proposed by various States. In addition, the U.S. Environmental Protection Agency is establishing regionally based nutrient criteria that can be refined by each State to determine whether actions are needed to improve a stream's water quality. More confidence in the environmental benefits of the proposed performance standards and nutrient criteria will be possible with a better understanding of the biotic responses to a range of nutrient concentrations in different environmental settings. The U.S. Geological Survey and the Wisconsin Department of Natural Resources collected data from 240 wadeable streams throughout Wisconsin to: 1) describe how nutrient concentrations and biotic-community structure vary throughout the State; 2) determine which environmental characteristics are most strongly related to the distribution of nutrient concentrations; 3) determine reference water-quality and biotic conditions for different areas of the State; 4) determine how the biotic community of streams in different areas of the State respond to changes in nutrient concentrations; 5) determine the best regionalization scheme to describe the patterns in reference conditions and the responses in water quality and the biotic community; and 6) develop new indices to estimate nutrient concentrations in streams from a combination of biotic indices. The ultimate goal of this study is to provide the information needed to guide the development of regionally based nutrient criteria for Wisconsin streams. For total nitrogen (N) and suspended chlorophyll (SCHL) concentrations and water clarity, regional variability in reference conditions and in the responses in water quality to changes in land use are best described by subdividing wadeable streams

  17. The Status of the Warp Drive

    NASA Astrophysics Data System (ADS)

    Long, K. F.

    The prospects for a realistic engineered warp drive are currently within the realms of scientific speculation. The pioneering paper by Alcubierre has started a new field of research and in a period of a little over a decade has seen some encouraging developments. This has led to a better definition of the problem using the mathematical tools of general relativity and quantum field theory. Many publications now exist which have identified many technical problems and explored realisable solutions. Some of these ideas may one day make warp drive a genuine contender for breaking the interstellar distance barrier - the biggest obstacle towards the potential interaction of interstellar civilizations. This paper will review the current status of the warp drive since the seminal paper and discuss the tremendous theoretical advances that have been made. The problem definition will be considered in the context of the NASA Horizon mission methodology.

  18. Cytokinin cross-talking during biotic and abiotic stress responses

    PubMed Central

    O’Brien, José A.; Benková, Eva

    2013-01-01

    As sessile organisms, plants have to be able to adapt to a continuously changing environment. Plants that perceive some of these changes as stress signals activate signaling pathways to modulate their development and to enable them to survive. The complex responses to environmental cues are to a large extent mediated by plant hormones that together orchestrate the final plant response. The phytohormone cytokinin is involved in many plant developmental processes. Recently, it has been established that cytokinin plays an important role in stress responses, but does not act alone. Indeed, the hormonal control of plant development and stress adaptation is the outcome of a complex network of multiple synergistic and antagonistic interactions between various hormones. Here, we review the recent findings on the cytokinin function as part of this hormonal network. We focus on the importance of the crosstalk between cytokinin and other hormones, such as abscisic acid, jasmonate, salicylic acid, ethylene, and auxin in the modulation of plant development and stress adaptation. Finally, the impact of the current research in the biotechnological industry will be discussed. PMID:24312105

  19. [Driving ability with multiple sclerosis].

    PubMed

    Küst, J; Dettmers, C

    2014-07-01

    Driving is an important issue for young patients, especially for those whose walking capacity is impaired. Driving might support the patient's social and vocational participation. The question as to whether a patient with multiple sclerosis (MS) is restricted in the ability to drive a car depends on neurological and neuropsychological deficits, self-awareness, insight into deficits and ability to compensate for loss of function. Because of the enormous variability of symptoms in MS the question is highly individualized. A practical driving test under supervision of a driving instructor (possibly accompanied by a neuropsychologist) might be helpful in providing both patient and relatives adequate feedback on driving abilities. PMID:24906536

  20. Drive-by-Downloads

    SciTech Connect

    Narvaez, Julia; Endicott-Popovsky, Barbara E.; Seifert, Christian; Aval, Chiraag U.; Frincke, Deborah A.

    2010-02-01

    Abstract: Drive-by-downloads are malware that push, and then execute, malicious code on a client system without the user's consent. The purpose of this paper is to introduce a discussion of the usefulness of antivirus software for detecting the installation of such malware, providing groundwork for future studies. Client honeypots collected drive-by malware which was then evaluated using common antivirus products. Initial analysis showed that most of such antivirus products identified less than 70% of these highly polymorphic malware programs. Also, it was observed that the antivirus products tested, even when successfully detecting this malware, often failed to classify it, leading to the conclusion that further work could involve not only developing new behavioral detection technologies, but also empirical studies that improve general understanding of these threats. Toward that end, one example of malicious code was analyzed behaviorally to provide insight into next steps for the future direction of this research.

  1. Magnetostrictive direct drive motors

    NASA Technical Reports Server (NTRS)

    Naik, Dipak; Dehoff, P. H.

    1990-01-01

    Developing magnetostrictive direct drive research motors to power robot joints is discussed. These type motors are expected to produce extraordinary torque density, to be able to perform microradian incremental steps and to be self-braking and safe with the power off. Several types of motor designs have been attempted using magnetostrictive materials. One of the candidate approaches (the magnetostrictive roller drive) is described. The method in which the design will function is described as is the reason why this approach is inherently superior to the other approaches. Following this, the design will be modelled and its expected performance predicted. This particular candidate design is currently undergoing detailed engineering with prototype construction and testing scheduled for mid 1991.

  2. Variable speed drive

    NASA Technical Reports Server (NTRS)

    Obler, H. D. (Inventor)

    1983-01-01

    A variable speed drive wherein a first embodiment is comprised of a pivotally mounted prime mover coupled to a rotary fluid output device, such as a fan or pump, through a variable and fixed pulley drive arrangement is described. The pivotal position of the prime mover and accordingly the pitch diameter of variable pulley means is controlled in accordance with fluid motor means coupled to the prime mover. This is actuated in response to a fluid feedback control signal derived from a sensed output of the rotary fluid output device. The pivotal motion of the prime mover imparts an arcuate motion to the variable pulley means which effects a speed variation of the rotary fluid output device in accordance with the variation of the pitch diameter ratio of opposing variable and fixed pulley means.

  3. Sex chromosome drive.

    PubMed

    Helleu, Quentin; Gérard, Pierre R; Montchamp-Moreau, Catherine

    2015-02-01

    Sex chromosome drivers are selfish elements that subvert Mendel's first law of segregation and therefore are overrepresented among the products of meiosis. The sex-biased progeny produced then fuels an extended genetic conflict between the driver and the rest of the genome. Many examples of sex chromosome drive are known, but the occurrence of this phenomenon is probably largely underestimated because of the difficulty to detect it. Remarkably, nearly all sex chromosome drivers are found in two clades, Rodentia and Diptera. Although very little is known about the molecular and cellular mechanisms of drive, epigenetic processes such as chromatin regulation could be involved in many instances. Yet, its evolutionary consequences are far-reaching, from the evolution of mating systems and sex determination to the emergence of new species. PMID:25524548

  4. Advanced Motor Drives Studies

    NASA Technical Reports Server (NTRS)

    Ehsani, M.; Tchamdjou, A.

    1997-01-01

    This report presents an evaluation of advanced motor drive systems as a replacement for the hydrazine fueled APU units. The replacement technology must meet several requirements which are particular to the space applications and the Orbiter in general. Some of these requirements are high efficiency, small size, high power density. In the first part of the study several motors are compared, based on their characteristics and in light of the Orbiter requirements. The best candidate, the brushless DC is chosen because of its particularly good performance with regards to efficiency. Several power electronics drive technologies including the conventional three-phase hard switched and several soft-switched inverters are then presented. In the last part of the study, a soft-switched inverter is analyzed and compared to its conventional hard-switched counterpart. Optimal efficiency is a basic requirement for space applications and the soft-switched technology represents an unavoidable trend for the future.

  5. Biotic and Climatic Velocity Identify Contrasting Areas of Vulnerability to Climate Change

    PubMed Central

    Carroll, Carlos; Lawler, Joshua J.; Roberts, David R.; Hamann, Andreas

    2015-01-01

    Metrics that synthesize the complex effects of climate change are essential tools for mapping future threats to biodiversity and predicting which species are likely to adapt in place to new climatic conditions, disperse and establish in areas with newly suitable climate, or face the prospect of extirpation. The most commonly used of such metrics is the velocity of climate change, which estimates the speed at which species must migrate over the earth’s surface to maintain constant climatic conditions. However, “analog-based” velocities, which represent the actual distance to where analogous climates will be found in the future, may provide contrasting results to the more common form of velocity based on local climate gradients. Additionally, whereas climatic velocity reflects the exposure of organisms to climate change, resultant biotic effects are dependent on the sensitivity of individual species as reflected in part by their climatic niche width. This has motivated development of biotic velocity, a metric which uses data on projected species range shifts to estimate the velocity at which species must move to track their climatic niche. We calculated climatic and biotic velocity for the Western Hemisphere for 1961–2100, and applied the results to example ecological and conservation planning questions, to demonstrate the potential of such analog-based metrics to provide information on broad-scale patterns of exposure and sensitivity. Geographic patterns of biotic velocity for 2954 species of birds, mammals, and amphibians differed from climatic velocity in north temperate and boreal regions. However, both biotic and climatic velocities were greatest at low latitudes, implying that threats to equatorial species arise from both the future magnitude of climatic velocities and the narrow climatic tolerances of species in these regions, which currently experience low seasonal and interannual climatic variability. Biotic and climatic velocity, by approximating

  6. Gear Drive Testing

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Philadelphia Gear Corporation used two COSMIC computer programs; one dealing with shrink fit analysis and the other with rotor dynamics problems in computerized design and test work. The programs were used to verify existing in-house programs to insure design accuracy by checking its company-developed computer methods against procedures developed by other organizations. Its specialty is in custom units for unique applications, such as Coast Guard ice breaking ships, steel mill drives, coal crusher, sewage treatment equipment and electricity.

  7. Driving on the Descartes

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Astronaut John W. Young, Apollo 16 mission commander, drives the 'Rover', Lunar Roving Vehicle (LRV) to its final parking place near the end of the third extravehicular activity (EVA-3) at the Descartes landing site. Astronaut Charles M. Duke Jr., Lunar Module pilot, took this photograph looking southward. The flank of Stone Mountain can be seen on the horizon at left. The shadow of the Lunar Module 'Orion' is visible in the foreground.

  8. Variable reluctance drive system

    SciTech Connect

    Lipo, T.A.; Liang, F.

    1995-10-17

    A variable reluctance drive system including a motor and corresponding converter for improved current commutation is described. The motor incorporates a salient pole rotor and a salient pole stator having one or more full pitch windings which operate by mutual inductance to transfer the current from the active short pitch winding following phase alignment. This increases output torque and/or speed and permits a number of simple and economical converter circuits. 17 figs.

  9. Predators, energetics and fitness drive neonatal reproductive failure in red squirrels.

    PubMed

    Studd, Emily K; Boutin, Stan; McAdam, Andrew G; Krebs, Charles J; Humphries, Murray M

    2015-01-01

    Neonatal reproductive failure should occur when energetic costs of parental investment outweigh fitness benefits. However, little is known about the drivers of neonatal reproductive failure in free-ranging species experiencing continuous natural variation in predator abundance and in the energetic and fitness costs and benefits associated with parental investment. Long-term comprehensive studies are required to better understand how biotic, abiotic and life-history conditions interact to drive occurrences of reproductive failure in the wild. Using 24 years (1987-2011) of reproductive data from a northern boreal population of North American red squirrels in south-western Yukon, we examined the effects of predator abundance, energetics (resource availability, ambient temperature and litter size) and fitness benefits (probability of overwinter juvenile survival and maternal age) on occurrences of neonatal reproductive failure (494/2670 reproductive attempts; 18·5%). Neonatal reproductive failure was driven by a combination of predator abundance, and the energetic and fitness costs and benefits of parental investment. The abundance of mustelids and maternal age was positively related to the occurrence of neonatal reproductive failure. High energy costs associated with a combination of low resource availability and cold ambient temperatures or large litters, corresponded to increased occurrences of neonatal reproductive failure. However, the strength of these relationships was influenced by variation in juvenile overwinter survival (i.e. fitness benefits). We provide evidence that predation pressure is an important driver of neonatal reproductive failure. In addition, we found a trade-off occurs between resource-dependent energetic and fitness costs and benefits of raising the current litter to independence. PMID:25132293

  10. [Automobile driving capacity in dementia].

    PubMed

    Seeger, Rolf

    2015-04-01

    Dementia influences at an early stage the driving aptitude of motor vehicle steering persons. Every year in Switzerland, around 16'000 driving permit holders suffer newly from dementia; therefore the driving aptitude is questioned, especially because of possibly limited executive functions. Individuals with early-stage dementia often may show a dangerous driving stile. However, a mild dementia does not a priori exclude the driving aptitude, and less than half of these drivers can continue driving for another 1 - 3 years. In contrast, there is no further driving aptitude in presence of moderate dementia. In the assessment of driving aptitude, the underlying cause of dementia is always taken into account. Cognitive short tests such as the Mini-Mental Status Exam, Clock Drawing Test and Trail-Making Test are not suitable to make reliable statements about the aptitude to drive, but these tests are very important for the initial diagnosis of dementia in primary care practice and can lead the way for further examination concerning driving aptitude. The legally prescribed regular check-up for motorists aged over 70 years in Switzerland provides an ideal opportunity for early detection of incipient dementia. The practical procedure for the assessment of aptitude to drive in the primary care practice is presented. The physician-guided on-road driving test represents a meaningful, practical and relatively cost-effective tool for the evaluation of driving aptitude in cases of doubt. PMID:25791047

  11. Energy Considerations of Hypothetical Space Drives

    NASA Technical Reports Server (NTRS)

    Millis, Marc G.

    2007-01-01

    The energy requirements of hypothetical, propellant-less space drives are compared to rockets. This serves to provide introductory estimates for potential benefits and to suggest analytical approaches for further study. A "space drive" is defined as an idealized form of propulsion that converts stored potential energy directly into kinetic energy using only the interactions between the spacecraft and its surrounding space. For Earth-to-orbit, the space drive uses 3.7 times less energy. For deep space travel, energy is proportional to the square of delta-v, whereas rocket energy scales exponentially. This has the effect of rendering a space drive 150-orders-of-magnitude better than a 17,000-s Specific Impulse rocket for sending a modest 5000 kg probe to traverse 5 ly in 50 years. Indefinite levitation, which is impossible for a rocket, could conceivably require 62 MJ/kg for a space drive. Assumption sensitivities and further analysis options are offered to guide further inquires.

  12. Space Drive Physics: Introduction and Next Steps

    NASA Astrophysics Data System (ADS)

    Millis, M. G.

    Research toward the visionary goal of propellantless ``space drives'' is introduced, covering key physics issues and a listing of roughly 2-dozen approaches. The targeted advantage of a space drive is to circumvent the propellant constraints of rockets and the maneuvering limits of light sails by using the interactions between the spacecraft and its surrounding space for propulsion. At present, the scientific foundations from which to engineer a space drive have not been discovered and, objectively, might be impossible. Although no propulsion breakthroughs appear imminent, the subject has matured to where the relevant questions have been broached and are beginning to be answered. The critical make-break issues include; conservation of momentum, uncertain sources of reaction mass, and the net-external thrusting requirement. Note: space drives are not necessarily faster- than-light devices. Speed limits are a separate, unanswered issue. Relevant unsolved physics includes; the sources and mechanisms of inertial frames, coupling of gravitation and electromagnetism, and the nature of the quantum vacuum. The propulsion approaches span mostly stages 1 through 3 of the scientific method (defining the problem, collecting data, and articulating hypotheses), while some have matured to stage 4 (testing hypotheses). Nonviable approaches include `stiction drives,' `gyroscopic antigravity,' and `lifters.' No attempt is made to gauge the prospects of the remaining approaches. Instead, a list of next-step research questions is derived from the examination of these goals, unknowns, and concepts.

  13. Who's Driving Home?: Assessing Adolescent Drinking and Driving.

    ERIC Educational Resources Information Center

    Swisher, John D.; Bibeau, Daniel

    1987-01-01

    Data from 13,998 students revealed that high percentages of students drank often and that many of these students reported being drunk often. While most students indicated they would prefer not