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35 results on '"Mitchell, C.E."'

1. Historical contingency in parasite community assembly: Community divergence results from early host exposure to symbionts and ecological drift

Author

Joyner, R.L., Mitchell, C.E., and Joyner, B.N.

Abstract

Host individuals are commonly coinfected with multiple parasite species that may interact to shape within-host parasite community structure. In addition to within-host species interactions, parasite communities may also be structured by other processes like dispersal and ecological drift. The timing of dispersal (in particular, the temporal sequence in which parasite species infect a host individual) can alter within-host species interactions, setting the stage for historical contingency by priority effects, but how persistently such effects drive the trajectory of parasite community assembly is unclear, particularly under continued dispersal and ecological drift. We tested the role of species interactions under continued dispersal and ecological drift by simultaneously inoculating individual plants of tall fescue with a factorial combination of three symbionts (two foliar fungal parasites and a mutualistic endophyte), then deploying the plants in the field and tracking parasite communities as they assembled within host individuals. In the field, hosts were exposed to continued dispersal from a common pool of parasites, which should promote convergence in the structure of within-host parasite communities. Yet, analysis of parasite community trajectories found no signal of convergence. Instead, parasite community trajectories generally diverged from each other, and the magnitude of divergence depended on the initial composition of symbionts within each host, indicating historical contingency. Early in assembly, parasite communities also showed evidence of drift, revealing another source of among-host divergence in parasite community structure. Overall, these results show that both historical contingency and ecological drift contributed to divergence in parasite community assembly within hosts. © 2023 Grunberg et al.

Published
2023
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3. Simulations of future particle accelerators: issues and mitigations

Author

Sagan, D., primary, Berz, M., additional, Cook, N.M., additional, Hao, Y., additional, Hoffstaetter, G., additional, Huebl, A., additional, Huang, C.-K., additional, Langston, M.H., additional, Mayes, C.E., additional, Mitchell, C.E., additional, Ng, C.-K., additional, Qiang, J., additional, Ryne, R.D., additional, Scheinker, A., additional, Stern, E., additional, Vay, J.-L., additional, Winklehner, D., additional, and Zhang, H., additional

Published
2021
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5. Nutrient enrichment increases invertebrate herbivory and pathogen damage in grasslands

Author

Ebeling, A., Strauss, A.T., Adler, P., Arnillas, C.A., Barrio, I.C., Biedermann, L.A., Borer, E.T., Bugalho, M.N., Caldeira, M.C., Cadotte, M.W., Daleo, P., Eisenhauer, N., Eskelinen, Anu Maria, Fay, P.A., Firn, J., Graff, P., Hagenah, N., Haider, S., Komatsu, K.J., McCulley, R.L., Mitchell, C.E., Moore, J., Pascual, J., Peri, P.L., Power, S.A., Prober, S.M., Risch, A.C., Roscher, Christiane, Sankaran, M., Seabloom, E.W., Schielzeth, H., Schütz, M., Speziale, K.L., Tedder, M., Virtanen, R., Blumenthal, D.M., Ebeling, A., Strauss, A.T., Adler, P., Arnillas, C.A., Barrio, I.C., Biedermann, L.A., Borer, E.T., Bugalho, M.N., Caldeira, M.C., Cadotte, M.W., Daleo, P., Eisenhauer, N., Eskelinen, Anu Maria, Fay, P.A., Firn, J., Graff, P., Hagenah, N., Haider, S., Komatsu, K.J., McCulley, R.L., Mitchell, C.E., Moore, J., Pascual, J., Peri, P.L., Power, S.A., Prober, S.M., Risch, A.C., Roscher, Christiane, Sankaran, M., Seabloom, E.W., Schielzeth, H., Schütz, M., Speziale, K.L., Tedder, M., Virtanen, R., and Blumenthal, D.M.

Abstract

Plant damage by invertebrate herbivores and pathogens influences the dynamics of grassland ecosystems, but anthropogenic changes in nitrogen and phosphorus availability can modify these relationships.Using a globally-distributed experiment, we describe leaf damage on 153 plant taxa from twenty-seven grasslands worldwide, under ambient conditions and with experimentally elevated nitrogen and phosphorus.Invertebrate damage significantly increased with nitrogen addition, especially in grasses and non-leguminous forbs. Pathogen damage increased with nitrogen in grasses and legumes but not forbs. Effects of phosphorus were generally weaker. Damage was higher in grasslands with more precipitation, but climatic conditions did not change effects of nutrients on leaf damage. On average, invertebrate damage was relatively higher on legumes and pathogen damage was relatively higher on grasses. Community-weighted mean damage reflected these functional group patterns, with no effects of N on community-weighted pathogen damage (due to opposing responses of grasses and forbs) but stronger effects of N on community-weighted invertebrate damage (due to consistent responses of grasses and forbs).Synthesis: As human-induced inputs of nitrogen and phosphorus continue to increase, understanding their impacts on invertebrate and pathogen damage becomes increasingly important. Our results demonstrate that eutrophication frequently increases plant damage and that damage increases with precipitation across a wide array of grasslands. Invertebrate and pathogen damage in grasslands is likely to increase in the future, with potential consequences for plant, invertebrate and pathogen communities, as well as the transfer of energy and nutrients across trophic levels.

Published
2021

6. Mitigation of space charge effects using electron column at IOTA ring

Author

Park, C.S., Freemire, B., Stern, E., and Mitchell, C.E.

Subjects
Physics::Accelerator Physics, Accelerators and Storage Rings
Abstract

We investigate a novel method to mitigate space charge effects of high intensity proton beams propagating in circular accelerators by means of trapping and controlling electrons generated from beam-induced residual gas ionization. This compensation method uses Coulomb repulsion force between a proton beam and electrons to mitigate self-space charge effects of the beam if it passes through a plasma column. The transverse electron-proton (e-p) instability in the plasma column is well controlled by the longitudinal magnetic field of a solenoid magnet and the bias voltages on electrodes. In this report, we will show simulation results how to control distributions of electrons and ions as well as that of the proton beam inside the column., CERN Yellow Reports: Conference Proceedings, Vol. 9 (2020): Proceedings of the ICFA mini-Workshop on Mitigation of Coherent Beam Instabilities in Particle Accelerators, Zermatt, Switzerland, 23–27 September 2019

Published
2020

7. Development of the tracer gas method for large bore natural gas engines--Part II: measurement of scavenging parameters

Author

Olsen, D.B., Hutcherson, G.C., Willson, B.D., and Mitchell, C.E.

Subjects
Gas-turbines -- Research, Two-stroke cycle engines -- Research, Engineering and manufacturing industries, Science and technology
Abstract

In this work the tracer gas method using nitrous oxide as the tracer gas is implemented on a stationary two-stroke cycle, four-cylinder, fuel-injected large-bore natural gas engine. The engine is manufactured by Cooper-Bessemer, model number GMV-4TF. It is representative of the large bore natural gas stationary engine fleet currently in use by the natural gas industry for natural gas compression and power generation. Trapping efficiency measurements are carried out with the tracer gas method at various engine operating conditions, and used to evaluate the scavenging efficiency and trapped A/F ratio. Scavenging efficiency directly affects engine power and trapped A/F ratio has a dramatic impact on pollutant emissions. Engine operating conditions are altered through variations in boost pressure, speed, back pressure, and intake port restriction.

Published
2002

8. Development of the tracer gas method for large bore natural gas engines--Part I: method validation

Author

Olsen, D.B., Hutcherson, G.C., Willson, B.D., and Mitchell, C.E.

Subjects
Gas-turbines -- Research, Two-stroke cycle engines -- Research, Engineering and manufacturing industries, Science and technology
Abstract

The tracer gas method is investigated as a means to study scavenging in fuel-injected large-bore two-stroke cycle engines. The investigation is performed on a Cooper-Bessemer GMV-4TF natural gas engine, with a 36-cm bore and a 36-cm stroke. Two important parameters are evaluated from the tracer gas measurements, which are scavenging efficiency and trapped A/F ratio. Measurements with the tracer gas method are compared with in-cylinder sampling techniques to evaluate the accuracy of the method. Two different tracers are evaluated, monomethylamine and nitrous oxide. Monomethylamine is investigated because of its common use historically as a tracer gas. Nitrous oxide is a new tracer gas that overcomes many of the difficulties experienced with monomethylamine. The tracer gas method with nitrous oxide is determined to be accurate for evaluating scavenging efficiency and trapped A/F ratio in comparison to the in-cylinder sampling techniques implemented.

Published
2002

9. Plastic potential: how the phenotypes and adaptations of pathogens are influenced by microbial interactions within plants

Author

Mitchell, C.E., Carbone, I., Jones, C.D., and O'Keeffe, K.R.

Subjects
fungi, food and beverages
Abstract

Predicting the effects of plant-associated microbes on emergence, spread, and evolution of plant pathogens demands an understanding of how pathogens respond to these microbes at two levels of biological organization: that of an individual pathogen and that of a pathogen population across multiple individual plants. We first examine the plastic responses of individual plant pathogens to microbes within a shared host, as seen through changes in pathogen growth and multiplication. We then explore the limited understanding of how within-plant microbial interactions affect pathogen populations and discuss the need to incorporate population-level observations with population genomic techniques. Finally, we suggest that integrating across levels will further our understanding of the ecological and evolutionary impacts of within-plant microbial interactions on pathogens.

Published
2017
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10. Comment on 'Worldwide evidence of a unimodal relationship between productivity and plant species richness'

Author

Tredennick, A.T., Adler, P.B., Grace, J.B., Harpole, W.S., Borer, E.T., Seabloom, E.W., Anderson, T.M., Bakker, J.D., Biederman, L.A., Brown, C.S., Buckley, Y.M., Chu, C., Collins, S.L., Crawley, M.J., Fay, P.A., Firn, J., Gruner, D.S., Hagenah, N., Hautier, Y., Hector, A., Hillebrand, H., Kirkman, K., Knops, J.M.H., Laungani, R., Lind, E.M., MacDougall, A.S., McCulley, R.L., Mitchell, C.E., Moore, J.L., Morgan, J.W., Orrock, J.L., Peri, P.L., Prober, S.M., Risch, A.C., Schutz, M., Speziale, K.L., Standish, R.J., Sullivan, L.L., Wardle, G.M., Williams, R.J., Yang, L.H., Tredennick, A.T., Adler, P.B., Grace, J.B., Harpole, W.S., Borer, E.T., Seabloom, E.W., Anderson, T.M., Bakker, J.D., Biederman, L.A., Brown, C.S., Buckley, Y.M., Chu, C., Collins, S.L., Crawley, M.J., Fay, P.A., Firn, J., Gruner, D.S., Hagenah, N., Hautier, Y., Hector, A., Hillebrand, H., Kirkman, K., Knops, J.M.H., Laungani, R., Lind, E.M., MacDougall, A.S., McCulley, R.L., Mitchell, C.E., Moore, J.L., Morgan, J.W., Orrock, J.L., Peri, P.L., Prober, S.M., Risch, A.C., Schutz, M., Speziale, K.L., Standish, R.J., Sullivan, L.L., Wardle, G.M., Williams, R.J., and Yang, L.H.

Abstract

Fraser et al. (Reports, 17 July 2015, p. 302) report a unimodal relationship between productivity and species richness at regional and global scales, which they contrast with the results of Adler et al. (Reports, 23 September 2011, p. 1750). However, both data sets, when analyzed correctly, show clearly and consistently that productivity is a poor predictor of local species richness.

Published
2016

11. Plant species’ origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands

Author

Seabloom, E.W., Borer, E.T., Buckley, Y.M., Cleland, E.E., Davies, K.F., Firn, J., Harpole, William Stanley, Hautier, Y., Lind, E.M., MacDougall, A.S., Orrock, J.L., Prober, S.M., Adler, P.B., Anderson, T.M., Bakker, J.D., Biederman, L.A., Blumenthal, D.M., Brown, C.S., Brudvig, L.A., Cadotte, M., Chu, C., Cottingham, K.L., Crawley, M.J., Damschen, E.I., Dantonio, C.M., DeCrappeo, N.M., Du, G., Fay, P.A., Frater, P., Gruner, D.S., Hagenah, N., Hector, A., Hillebrand, H., Hofmockel, K.S., Humphries, H.C., Jin, V.L., Kay, A., Kirkman, K.P., Klein, J.A., Knops, J.M.H., La Pierre, K.J., Ladwig, L., Lambrinos, J.G., Li, Q., Li, W., Marushia, R., McCulley, R.L., Melbourne, B.A., Mitchell, C.E., Moore, J.L., Morgan, J., Mortensen, B., O'Halloran, L.R., Pyke, D.A., Risch, A.C., Sankaran, M., Schuetz, M., Simonsen, A., Smith, M.D., Stevens, C.J., Sullivan, L., Wolkovich, E., Wragg, P.D., Wright, J., Yang, L., Seabloom, E.W., Borer, E.T., Buckley, Y.M., Cleland, E.E., Davies, K.F., Firn, J., Harpole, William Stanley, Hautier, Y., Lind, E.M., MacDougall, A.S., Orrock, J.L., Prober, S.M., Adler, P.B., Anderson, T.M., Bakker, J.D., Biederman, L.A., Blumenthal, D.M., Brown, C.S., Brudvig, L.A., Cadotte, M., Chu, C., Cottingham, K.L., Crawley, M.J., Damschen, E.I., Dantonio, C.M., DeCrappeo, N.M., Du, G., Fay, P.A., Frater, P., Gruner, D.S., Hagenah, N., Hector, A., Hillebrand, H., Hofmockel, K.S., Humphries, H.C., Jin, V.L., Kay, A., Kirkman, K.P., Klein, J.A., Knops, J.M.H., La Pierre, K.J., Ladwig, L., Lambrinos, J.G., Li, Q., Li, W., Marushia, R., McCulley, R.L., Melbourne, B.A., Mitchell, C.E., Moore, J.L., Morgan, J., Mortensen, B., O'Halloran, L.R., Pyke, D.A., Risch, A.C., Sankaran, M., Schuetz, M., Simonsen, A., Smith, M.D., Stevens, C.J., Sullivan, L., Wolkovich, E., Wragg, P.D., Wright, J., and Yang, L.

Abstract

Exotic species dominate many communities; however the functional significance of species’ biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of native and exotic plant species at 64 grasslands in 13 countries, and at a subset of the sites we experimentally tested native and exotic species responses to two fundamental drivers of invasion, mineral nutrient supplies and vertebrate herbivory. Exotic species are six times more likely to dominate communities than native species. Furthermore, while experimental nutrient addition increases the cover and richness of exotic species, nutrients decrease native diversity and cover. Native and exotic species also differ in their response to vertebrate consumer exclusion. These results suggest that species origin has functional significance, and that eutrophication will lead to increased exotic dominance in grasslands.

Published
2015

13. Plant diversity predicts beta but not alpha diversity of soil microbes across grasslands worldwide

Author

Prober, S.M., Leff, J.W., Bates, S.T., Borer, E.T., Firn, J., Harpole, William Stanley, Lind, E.M., Seabloom, E.W., Adler, P.B., Bakker, J.D., Cleland, E.E., DeCrappeo, N.M., DeLorenze, E., Hagenah, N., Hautier, Y., Hofmockel, K.S., Kirkman, K.P., Knops, J.M.H., LaPierre, K.J., MacDougall, A.S., McCulley, R.L., Mitchell, C.E., Risch, A.C., Schuetz, M., Stevens, C.J., Williams, R.J., Fierer, N., Prober, S.M., Leff, J.W., Bates, S.T., Borer, E.T., Firn, J., Harpole, William Stanley, Lind, E.M., Seabloom, E.W., Adler, P.B., Bakker, J.D., Cleland, E.E., DeCrappeo, N.M., DeLorenze, E., Hagenah, N., Hautier, Y., Hofmockel, K.S., Kirkman, K.P., Knops, J.M.H., LaPierre, K.J., MacDougall, A.S., McCulley, R.L., Mitchell, C.E., Risch, A.C., Schuetz, M., Stevens, C.J., Williams, R.J., and Fierer, N.

Abstract

Aboveground–belowground interactions exert critical controls on the composition and function of terrestrial ecosystems, yet the fundamental relationships between plant diversity and soil microbial diversity remain elusive. Theory predicts predominantly positive associations but tests within single sites have shown variable relationships, and associations between plant and microbial diversity across broad spatial scales remain largely unexplored. We compared the diversity of plant, bacterial, archaeal and fungal communities in one hundred and forty-five 1 m2 plots across 25 temperate grassland sites from four continents. Across sites, the plant alpha diversity patterns were poorly related to those observed for any soil microbial group. However, plant beta diversity (compositional dissimilarity between sites) was significantly correlated with the beta diversity of bacterial and fungal communities, even after controlling for environmental factors. Thus, across a global range of temperate grasslands, plant diversity can predict patterns in the composition of soil microbial communities, but not patterns in alpha diversity.

Published
2014

15. Response to Comments on “Productivity Is a Poor Predictor of Plant Species Richness”

Author

Grace, J.B., Adler, P.B., Seabloom, E., Borer, E.T., Hillebrand, H., Hautier, Y., Hector, A., Harpole, W.S., O’Halloran, L.R., Anderson, T.M., Bakker, J.D., Brown, C.S., Buckley, Y., Collins, S.L., Cottingham, K.L., Crawley, M.J., Damschen, E.I., Davies, K.F., DeCrappeo, N.M., Fay, P.A., Firn, J., Gruner, D., Hagenah, N., Jin, V.L., Kirkham, K.P., Knops, J., La Pierre, K.J., Lambrinos, J., Li, W., Melbourne, B.A., Mitchell, C.E., Moore, J., Morgan, J., Orrock, J., Prober, S., Stevens, Carly, Wragg, P., Yang, L.H., Grace, J.B., Adler, P.B., Seabloom, E., Borer, E.T., Hillebrand, H., Hautier, Y., Hector, A., Harpole, W.S., O’Halloran, L.R., Anderson, T.M., Bakker, J.D., Brown, C.S., Buckley, Y., Collins, S.L., Cottingham, K.L., Crawley, M.J., Damschen, E.I., Davies, K.F., DeCrappeo, N.M., Fay, P.A., Firn, J., Gruner, D., Hagenah, N., Jin, V.L., Kirkham, K.P., Knops, J., La Pierre, K.J., Lambrinos, J., Li, W., Melbourne, B.A., Mitchell, C.E., Moore, J., Morgan, J., Orrock, J., Prober, S., Stevens, Carly, Wragg, P., and Yang, L.H.

Abstract

Pan et al. claim that our results actually support a strong linear positive relationship between productivity and richness, whereas Fridley et al. contend that the data support a strong humped relationship. These responses illustrate how preoccupation with bivariate patterns distracts from a deeper understanding of the multivariate mechanisms that control these important ecosystem properties.

Published
2012

16. Productivity is a poor predictor of plant species richness

Author

Adler, P.B., Seabloom, E., Borer, E.T., Hillebrand, H., Hautier, Y., Hector, A., Harpole, W.S., O'Halloran, L.R., Grace, J.B., Anderson, T.M., Bakker, J.D., Biederman, L.A., Brown, C.S., Buckley, Y., Calabrese, L., Chu, C.J., Cleland, E.E., Collins, S.L., Cottingham, K.L., Crawley, Michael J., Damschen, E.I., Davies, K.F., DeCrappeo, N.M., Fay, P.A., Firn, J., Frater, P., E.I., Gasarch, Gruner, D., Hagenah, N., HilleRisLambers, J., Humphryes, H., Jin, V.L., Kay, A., Kirkham, K.P., Klein, J.A., Knops, J., La Pierre, K.J., Lambrinos, J., Li, W., MacDougall, A.S., McCulley, R., Melbourne, B.A., Mitchell, C.E., Moore, J., Morgan, J., Mortenson, B., Orrock, J., Prober, S., Pyke, D.A., Risch, A., Schuetz, M., Smith, M.D., Stevens, Carly, Sullivan, L. L., Wang, G., Wragg, P., Wright, J, Yang, J.H., Adler, P.B., Seabloom, E., Borer, E.T., Hillebrand, H., Hautier, Y., Hector, A., Harpole, W.S., O'Halloran, L.R., Grace, J.B., Anderson, T.M., Bakker, J.D., Biederman, L.A., Brown, C.S., Buckley, Y., Calabrese, L., Chu, C.J., Cleland, E.E., Collins, S.L., Cottingham, K.L., Crawley, Michael J., Damschen, E.I., Davies, K.F., DeCrappeo, N.M., Fay, P.A., Firn, J., Frater, P., E.I., Gasarch, Gruner, D., Hagenah, N., HilleRisLambers, J., Humphryes, H., Jin, V.L., Kay, A., Kirkham, K.P., Klein, J.A., Knops, J., La Pierre, K.J., Lambrinos, J., Li, W., MacDougall, A.S., McCulley, R., Melbourne, B.A., Mitchell, C.E., Moore, J., Morgan, J., Mortenson, B., Orrock, J., Prober, S., Pyke, D.A., Risch, A., Schuetz, M., Smith, M.D., Stevens, Carly, Sullivan, L. L., Wang, G., Wragg, P., Wright, J, and Yang, J.H.

Abstract

For more than 30 years, the relationship between net primary productivity and species richness has generated intense debate in ecology about the processes regulating local diversity. The original view, which is still widely accepted, holds that the relationship is hump-shaped, with richness first rising and then declining with increasing productivity. Although recent meta-analyses questioned the generality of hump-shaped patterns, these syntheses have been criticized for failing to account for methodological differences among studies. We addressed such concerns by conducting standardized sampling in 48 herbaceous-dominated plant communities on five continents. We found no clear relationship between productivity and fine-scale (meters−2) richness within sites, within regions, or across the globe. Ecologists should focus on fresh, mechanistic approaches to understanding the multivariate links between productivity and richness.

Published
2011

18. A final report on the GSSP candidate of the Hirnantian Stage

Author

Chen, Xu, Jia-yu, Rong, Juan-xuan, Fan, Ren-bin, Zhan, Mitchell, C.E., Harper, D.A.T., Melchin, M.J., Xiao-feng, Wang, Chen, Xu, Jia-yu, Rong, Juan-xuan, Fan, Ren-bin, Zhan, Mitchell, C.E., Harper, D.A.T., Melchin, M.J., and Xiao-feng, Wang

Published
2004

31. Identification of DNA damage as a result of exposure of rats of diesel engine exhaust.

Author

Wong, D., Mitchell, C.E., Wolff, R.K., Mauderly, J.L., and Jeffrey, A.M.

Abstract

Owing to the concern regarding genotoxic agents which may be present in diesel engine emissions we have studied the effect, with respect to DNA damage, of the exposure of F344 rats to such emissions for ∼ 31 months at levels of parttiulate material of 7.1 mg/m. Rats were killed and the DNA extracted from the right lung lobe and coded prior to analysis for DNA adducts by theP-postlabeling technique. Although a gradation of adduct intensity was found from high levels to none being detectable, distinction could be made between exposed and unexposed groups based upon the intensity of DNA adducts present. [ABSTRACT FROM PUBLISHER]

Published
1986

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