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203 results on '"Oakes, Ken D."'

25. Temporal resolution of solid-phase microextraction: measurement of real-time concentrations within a dynamic system

Author

Zhang, Xu, Oakes, Ken D., Luong, Di, Wen, John Z., Metcalfe, Chris D., Pawliszyn, Janusz, and Servos, Mark R.

Subjects
Extraction (Chemistry) -- Technology application, Technology application, Chemistry
Abstract

To address the challenge of measuring real-time analyte concentrations within dynamic systems, the temporal resolution of the solid-phase microextraction (SPME) approach has been investigated. A mass-uptake model for SPME within a dynamic system was developed and validated, with experimental factors affecting the temporal resolution (sampling time, agitation, SPME fiber dimensions, sample concentration and change rate, and instrument sensitivity) characterized. Calibration methods for time-resolved sampling in a dynamic system were compared. To demonstrate the efficacy of time-resolved SPME, this approach was successfully applied to investigate the binding kinetics between plasma proteins and pharmaceuticals, which verified a decrease in free pharmaceutical concentrations over time in the presence of bovine serum albumin. The current study provides the theoretical and logistical framework for applying SPME to the real-time measurement of dynamic systems, facilitating future SPME applications such as in vivo metabolomic studies. 10.1021/ac102186u

Published
2010

26. Development of the space-resolved solid-phase microextraction technique and its application to biological matrices

Author

Zhang, Xu, Cai, Jibao, Oakes, Ken D., Breton, Francois, Servos, Mark R., and Pawliszyn, Janusz

Subjects
Extraction (Chemistry) -- Methods, Chemistry, Analytic -- Methods, Chemistry
Abstract

To facilitate rapid in situ analyte monitoring within heterogeneous samples, a space-resolved solid phase microextraction (SR-SPME) technique was developed that utilized miniaturized segmented fibers. Initially, a multi-layered agarose gel was used to determine the effects of diffusion-based mass transfer and fiber dimension on the space-resolving capability of SPME. For diazepam within agarose gel, the SR-SPME limit of detection was 2.5 ng/ mL, with a linear dynamic range up to 500 ng/mL The efficacy of the SR-SPME technique was further evaluated within diverse biological matrices (onion bulb, fish muscle, and adipose tissues) containing stratified pharmaceutical analytes. Empirically, the results agreed well with established techniques such as microdialysis and liquid extraction, but SR-SPME was simpler to implement, displayed higher spatial resolution, and was more cost-effective than traditional approaches. Additionally, the segmented design of the SPME fibers and stepwise desorption protocols offer potential advantages within high throughput applications.

Published
2009

30. Surface interaction of doxorubicin with anatase determines its photodegradation mechanism: insights into removal of waterborne pharmaceuticals by TiO2 nanoparticles

Author

Curry, Dennis E., primary, Andrea, Kori A., additional, Carrier, Andrew J., additional, Nganou, Collins, additional, Scheller, Hope, additional, Yang, Dongchang, additional, Youden, Brian, additional, Zhang, Youwei, additional, Nicholson, Amanda, additional, Cui, Shufen, additional, Oakes, Ken D., additional, MacQuarrie, Stephanie L., additional, Lu, Mingsheng, additional, and Zhang, Xu, additional

Published
2018
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32. Cross‐ecosystem effects of a large terrestrial herbivore on stream ecosystem functioning.

Author

MacSween, Jessica, Leroux, Shawn J., and Oakes, Ken D.

Subjects
ECOSYSTEMS, HERBIVORES, RIVERS, TAIGAS, CAPE Breton Highlands National Park (N.S.)
Abstract

Large terrestrial consumers have direct and indirect effects on forest ecosystem function, but few studies have investigated the impacts of terrestrial consumers on freshwater ecosystems. In the Cape Breton Highlands of Nova Scotia, browsing by hyper‐abundant moose following a spruce budworm outbreak has transformed boreal forest into grasslands. We conducted a field study to investigate the potential for cross‐ecosystem effects of hyper‐abundant moose following budworm outbreak on small boreal stream ecosystem structure and function. With our field study, we tested the prediction that watersheds with higher levels of moose‐mediated grasslands in their sub‐basin would have higher stream temperatures, total nitrogen, electrical conductivity, periphyton biomass and macroinvertebrate abundances. While our data supported several of our predictions pertaining to moose impacts on the abiotic variables (i.e. temperature range, total nitrogen, electrical conductivity) we found evidence of variable moose impacts on the benthic community. Specifically, we observed lower relative abundance of predatory invertebrates in streams with high moose impacts compared to streams with low moose impacts in their watersheds but no evidence of moose impacts on the relative abundance of shredders, filterers, gatherers, and grazers. This empirical study fills a key gap in our understanding of spatial ecosystem ecology by providing insight into the effects of large terrestrial consumers across ecosystem boundaries with potential implications for landscape‐scale management of hyper‐abundant ungulates. Given the broad availability and improvement in remote sensing technology, the novel integration of remote sensing and field studies employed here may provide a roadmap for future studies of meta‐ecosystem dynamics. [ABSTRACT FROM AUTHOR]

Published
2019
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33. Chemisorption Mechanism of DNA on Mg/Fe Layered Double Hydroxide Nanoparticles: Insights into Engineering Effective SiRNA Delivery Systems

Author

Lu, Mingsheng, primary, Shan, Zhi, additional, Andrea, Kori, additional, MacDonald, Bruce, additional, Beale, Stefanie, additional, Curry, Dennis E., additional, Wang, Li, additional, Wang, Shujun, additional, Oakes, Ken D., additional, Bennett, Craig, additional, Wu, Wenhui, additional, and Zhang, Xu, additional

Published
2016
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36. Adsorption of doxorubicin on citrate-capped gold nanoparticles: insights into engineering potent chemotherapeutic delivery systems

Author

Curry, Dennis, primary, Cameron, Amanda, additional, MacDonald, Bruce, additional, Nganou, Collins, additional, Scheller, Hope, additional, Marsh, James, additional, Beale, Stefanie, additional, Lu, Mingsheng, additional, Shan, Zhi, additional, Kaliaperumal, Rajendran, additional, Xu, Heping, additional, Servos, Mark, additional, Bennett, Craig, additional, MacQuarrie, Stephanie, additional, Oakes, Ken D., additional, Mkandawire, Martin, additional, and Zhang, Xu, additional

Published
2015
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41. Surface interaction of doxorubicin with anatase determines its photodegradation mechanism: insights into removal of waterborne pharmaceuticals by TiO2nanoparticlesElectronic supplementary information (ESI) available: Detailed experimental methods and supporting data. See DOI: 10.1039/c7en01171g

Author

Curry, Dennis E., Andrea, Kori A., Carrier, Andrew J., Nganou, Collins, Scheller, Hope, Yang, Dongchang, Youden, Brian, Zhang, Youwei, Nicholson, Amanda, Cui, Shufen, Oakes, Ken D., MacQuarrie, Stephanie L., Lu, Mingsheng, and Zhang, Xu

Abstract

Titanium dioxide (TiO2) nanomaterials are extensively used in environmental and energy research. However, their utility is governed by surface interactions with surrounding environments and molecules. A deep understanding of these interactions is critical for the development of advanced TiO2applications. Herein, we systematically investigate the adsorption of doxorubicin (DOX), a highly toxic chemotherapeutic and model antibiotic pharmaceutical, onto anatase TiO2nanoparticles and correlate the photodegradation mechanism of DOX with its surface adsorption. Compared to the photodegradation of non-adsorbed species in solution by mobile hydroxyl radicals, the adsorption-dependent surface oxidation by UV-induced holes on TiO2is more efficient. This study underscores the importance of controlling surface adsorption within photodegradation applications viapH alteration, which would be highly relevant for photo-oxidative remediation of environmental organic pollutants with amine or carbonyl functionalities that chemisorb on titania surfaces.

Published
2018
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