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You searched for subject:(Composition function relationships). Showing records 1 – 2 of 2 total matches.

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University of Illinois – Urbana-Champaign

1. Cohen, Dora Boyd. Microbial community assembly and hydrologic variability as controls on potential denitrification rates in restored freshwater wetlands.

Degree: PhD, Ecol, Evol, Conservation Biol, 2018, University of Illinois – Urbana-Champaign

Denitrification is a microbial process in wetlands that transforms nitrate pollutants into nitrogen gas under anaerobic conditions. Restored wetlands do not always reach equivalent denitrification rates as those they were intended to replace, and this is sometimes linked to differences in microbial composition. Further, increased drought and variability in flood regimes represents an additional threat because the stress of fluctuation between extreme dry or saturated conditions could alter the microbial community itself and the ability of remaining microbial taxa to transform nitrate via denitrification. One of the goals of this dissertation was to identify either microbial or hydrologic factors that could limit the ability of restored wetland communities to reach high potential denitrification rates. Based on a survey of 30 restored and 15 reference wetlands, restored wetlands surprisingly reached equivalent rates as observed from reference sites. This survey was conducted twice: Once during a drought in 2012, and again in 2013 following unusually intense floods. Similar results were found both years, but average rates were an order of magnitude greater in 2013 than in 2012. These potential denitrification assays were performed under identical saturated anaerobic conditions in the lab each year, so the differences observed must be due to inherent differences in the active microbial community. The magnitude increase in rates between the two years could be explained by soil variables such as pH and moisture, as well as to the abundance of nirS-harboring denitrifiers in the community. Soil moisture and oxygen availability strongly influence microbial community composition, so regions of a single floodplain wetland may contain vastly different communities depending on the hydrology. Another goal of this dissertation was to determine if past hydrologic variability filters microbial taxa such that these communities exhibit high resistance or resilience and high functional stability in the face of altered hydrology. I established an experiment where I manipulated the hydrology of soil collected from upland, lowland and the transition region of a single wetland. The transition region contained a unique composition compared to the upland and lowland regions, and composition remained relatively stable compared to the other regions, indicating either high resistance or resilience. This community also exhibited stable potential rates compared to the other regions. Since denitrification can also be influenced by soil factors, such as pH and texture, which differ among wetlands and even differ among regions of the same wetland, my final study included an experimental design that removed any differences between soil types. Sterilized soil mesocosms were inoculated by live wetland soil collected from wetlands that exhibited different historical flood regimes: Flashy floods, long extended floods, and high variability from year to year. These wetlands exhibited distinct microbial composition initially. Following inoculation of… Advisors/Committee Members: Kent, Angela D. (advisor), Kent, Angela D. (Committee Chair), Matthews, Jeffrey W. (committee member), Yannarell, Anthony C. (committee member), Zilles, Julie L. (committee member).

Subjects/Keywords: microbial ecology; denitrification; wetland restoration; composition-function relationships; drought

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Cohen, D. B. (2018). Microbial community assembly and hydrologic variability as controls on potential denitrification rates in restored freshwater wetlands. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/101669

Chicago Manual of Style (16th Edition):

Cohen, Dora Boyd. “Microbial community assembly and hydrologic variability as controls on potential denitrification rates in restored freshwater wetlands.” 2018. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed October 28, 2020. http://hdl.handle.net/2142/101669.

MLA Handbook (7th Edition):

Cohen, Dora Boyd. “Microbial community assembly and hydrologic variability as controls on potential denitrification rates in restored freshwater wetlands.” 2018. Web. 28 Oct 2020.

Vancouver:

Cohen DB. Microbial community assembly and hydrologic variability as controls on potential denitrification rates in restored freshwater wetlands. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2018. [cited 2020 Oct 28]. Available from: http://hdl.handle.net/2142/101669.

Council of Science Editors:

Cohen DB. Microbial community assembly and hydrologic variability as controls on potential denitrification rates in restored freshwater wetlands. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2018. Available from: http://hdl.handle.net/2142/101669


Georgia Tech

2. Palmer, Ashley Wells. Investigations of the Composition-Function Relationships in Normal, Degraded, and Engineered Articular Cartilage Using Epic-Microcomputed Tomography.

Degree: PhD, Mechanical Engineering, 2007, Georgia Tech

Articular cartilage provides a low-friction surface during normal joint motion and distributes forces to the underlying bone. The extracellular matrix (ECM) composition of healthy cartilage has previously been shown to be an excellent predictor of its mechanical properties. Changes in ECM composition and loss of mechanical function are known to occur with degenerative conditions such as osteoarthritis. Identifying differences in the composition-function relationships of cartilage under different anabolic, catabolic, and homeostatic conditions may thus be a useful approach for identifying factors (e.g. ECM content, distribution, and structure) which are critical to mechanical function. In addition, diagnostic tools capable of monitoring changes in the cartilage ECM may increase our understanding of the effects of ECM changes on composition-functions relationships. The goals of this work were to investigate composition-function relationships in healthy, degraded, and engineered cartilage and to develop a microcomputed tomography-based approach to analyze changes in matrix composition and morphology in articular cartilage. In healthy explants, compressive and shear properties were dependent on both sGAG and collagen content. In contrast, the compressive properties of IL-1stimulated cartilage were dependent on sGAG but not collagen content. To assess changes in sGAG content, EPIC-microcomputed tomography, a 3D contrast-enhanced microcomputed tomography technique was developed. EPIC-microcomputed tomography attenuation was found to be an excellent predictor of sGAG content in IL-1-stimulated cartilage explants and engineered cartilage. In addition, analytical approaches were developed to use EPIC-microcomputed tomography for the in situ analysis of cartilage morphology. EPIC-microcomputed tomography was also used to analyze spatial differences in sGAG accumulation in bilayer engineered cartilage for comparison with the local strain profile. This work underscores the significance of ECM composition and structure in regulating cartilage mechanical properties and validates the use of EPIC-microcomputed tomography as a diagnostic for monitoring sGAG content and potentially for assessing mechanical function in models of degeneration and regeneration. Advisors/Committee Members: Dr. Marc E. Levenston (Committee Chair), Dr. Ravi V. Bellamkonda (Committee Member), Dr. Raymond P. Vito (Committee Member), Dr. Robert E. Guldberg (Committee Member), Dr. Robert L. Sah (Committee Member).

Subjects/Keywords: Articular cartilage; Microcomputed tomography; Cartilage mechanics; Composition-function relationships; Extracellular matrix Mechanical properties; Articular cartilage Mechanical properties; Tomography

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Palmer, A. W. (2007). Investigations of the Composition-Function Relationships in Normal, Degraded, and Engineered Articular Cartilage Using Epic-Microcomputed Tomography. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/14572

Chicago Manual of Style (16th Edition):

Palmer, Ashley Wells. “Investigations of the Composition-Function Relationships in Normal, Degraded, and Engineered Articular Cartilage Using Epic-Microcomputed Tomography.” 2007. Doctoral Dissertation, Georgia Tech. Accessed October 28, 2020. http://hdl.handle.net/1853/14572.

MLA Handbook (7th Edition):

Palmer, Ashley Wells. “Investigations of the Composition-Function Relationships in Normal, Degraded, and Engineered Articular Cartilage Using Epic-Microcomputed Tomography.” 2007. Web. 28 Oct 2020.

Vancouver:

Palmer AW. Investigations of the Composition-Function Relationships in Normal, Degraded, and Engineered Articular Cartilage Using Epic-Microcomputed Tomography. [Internet] [Doctoral dissertation]. Georgia Tech; 2007. [cited 2020 Oct 28]. Available from: http://hdl.handle.net/1853/14572.

Council of Science Editors:

Palmer AW. Investigations of the Composition-Function Relationships in Normal, Degraded, and Engineered Articular Cartilage Using Epic-Microcomputed Tomography. [Doctoral Dissertation]. Georgia Tech; 2007. Available from: http://hdl.handle.net/1853/14572

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