Open Access. Powered by Scholars. Published by Universities.®
- Institution
- Publication Year
- Publication
-
- OES Faculty Publications (17)
- All Graduate Theses and Dissertations, Spring 1920 to Summer 2023 (3)
- Faculty of Science - Papers (Archive) (3)
- Dissertations, Master's Theses and Master's Reports - Open (2)
- IGC Proceedings (1997-2023) (2)
-
- Williams Honors College, Honors Research Projects (2)
- All Faculty Scholarship for the College of the Sciences (1)
- Chemistry & Biochemistry Faculty Publications (1)
- Chemistry and Biochemistry Publications (1)
- Faculty Publications (1)
- Faisal I Hai (1)
- School of Earth, Environmental, and Marine Sciences Faculty Publications and Presentations (1)
- Theses and Dissertations (1)
- UNLV Theses, Dissertations, Professional Papers, and Capstones (1)
- Undergraduate Honors Capstone Projects (1)
- Publication Type
- File Type
Articles 1 - 30 of 38
Full-Text Articles in Life Sciences
Potential Interactions Between Diatoms And Bacteria Are Shaped By Trace Element Gradients In The Southern Ocean, Alexa R. Sterling, Laura Z. Holland, Randelle M. Bundy, Shannon M. Burns, Kristen N. Buck, P. Dreux Chappell, Bethany D. Jenkins
Potential Interactions Between Diatoms And Bacteria Are Shaped By Trace Element Gradients In The Southern Ocean, Alexa R. Sterling, Laura Z. Holland, Randelle M. Bundy, Shannon M. Burns, Kristen N. Buck, P. Dreux Chappell, Bethany D. Jenkins
OES Faculty Publications
The growth of diatoms in the Southern Ocean, especially the region surrounding the West Antarctic Peninsula, is frequently constrained by low dissolved iron and other trace metal concentrations. This challenge may be overcome by mutualisms between diatoms and co-occurring associated bacteria, in which diatoms produce organic carbon as a substrate for bacterial growth, and bacteria produce siderophores, metal-binding ligands that can supply diatoms with metals upon uptake as well as other useful secondary compounds for diatom growth like vitamins. To examine the relationships between diatoms and bacteria in the plankton (diatom) size class (> 3 mu m), we sampled both …
Atmospheric Input And Seasonal Inventory Of Dissolved Iron In The Sargasso Sea: Implications For Iron Dynamics In Surface Waters Of The Subtropical Ocean, Peter N. Sedwick, Bettina M. Sohst, K. N. Buck, S. Caprara, R. J. Johnson, D. C. Ohnemus, L. E. Sofen, A. Tagliabue, B. S. Twining, Tara E. Williams
Atmospheric Input And Seasonal Inventory Of Dissolved Iron In The Sargasso Sea: Implications For Iron Dynamics In Surface Waters Of The Subtropical Ocean, Peter N. Sedwick, Bettina M. Sohst, K. N. Buck, S. Caprara, R. J. Johnson, D. C. Ohnemus, L. E. Sofen, A. Tagliabue, B. S. Twining, Tara E. Williams
OES Faculty Publications
Constraining the role of dust deposition in regulating the concentration of the essential micronutrient iron in surface ocean waters requires knowledge of the flux of seawater-soluble iron in aerosols and the replacement time of dissolved iron (DFe) in the euphotic zone. Here we estimate these quantities using seasonally resolved DFe data from the Bermuda Atlantic Time-series Study region and weekly-scale measurements of iron in aerosols and rain from Bermuda during 2019. In response to seasonal changes in vertical mixing, primary production and dust deposition, surface DFe concentrations vary from ∼0.2 nM in early spring to >1 nM in late summer, …
Application Of Municipal Biosolids To Bahiagrass Pasture: Trace Metals In Harvested Forage, R. M. Muchovej, J. E. Rechcigl
Application Of Municipal Biosolids To Bahiagrass Pasture: Trace Metals In Harvested Forage, R. M. Muchovej, J. E. Rechcigl
IGC Proceedings (1997-2023)
Municipal biosolids (sewage sludge) are the by-products of wastewater treatment plants and their production, worldwide, has steadily increased over the past years. Florida is one of the fastest growing states in the USA. Biosolids are readily and increasingly available throughout the state. Pasture fertilization has been shown to increase biomass and quality of bahiagrass (Paspalum notatum Flugge) dramatically in Florida sandy soils. Nevertheless, with low cattle prices, ranchers are forced to reduce fertilizers inputs. Biosolids contain considerable amounts of nutrients, especially nitrogen (N), phosphorus (P), sulphur (S), calcium (Ca), and micronutrients, and are inexpensive when compared with commercial fertilizers. …
Examining Ecological Succession Of Diatoms In California Current System Cyclonic Mesoscale Eddies, Zuzanna M. Abdala, Sophie Clayton, Sveinn V. Einarsson, Kimberly Powell, Claire P. Till, Tyler H. Coale, P. Dreux Chappell
Examining Ecological Succession Of Diatoms In California Current System Cyclonic Mesoscale Eddies, Zuzanna M. Abdala, Sophie Clayton, Sveinn V. Einarsson, Kimberly Powell, Claire P. Till, Tyler H. Coale, P. Dreux Chappell
OES Faculty Publications
The California Current System is a diatom-dominated region characterized by seasonal coastal upwelling and additional elevated mesoscale activity. Cyclonic mesoscale eddies in the region trap productive coastal waters with their planktonic communities and transport them offshore with limited interaction with surrounding waters, effectively acting as natural mesocosms, where phytoplankton populations undergo ecological succession as eddies age. This study examines diatom community composition within two mesoscale cyclonic eddies that formed in the same region of the California Current System 2 months apart and in the California Current waters surrounding them. The diatom communities were analyzed in the context of shifting environmental …
A Multi-Modal Approach To Measuring Particulate Iron Speciation In Buoyant Hydrothermal Plumes, Brandy D. Stewart, Jeffry V. Sorensen, Kathleen Wendt, Jason B. Sylvan, Christopher R. German, Karthik Anantharaman, Gregory J. Dick, John A. Breier, Brandy M. Toner
A Multi-Modal Approach To Measuring Particulate Iron Speciation In Buoyant Hydrothermal Plumes, Brandy D. Stewart, Jeffry V. Sorensen, Kathleen Wendt, Jason B. Sylvan, Christopher R. German, Karthik Anantharaman, Gregory J. Dick, John A. Breier, Brandy M. Toner
School of Earth, Environmental, and Marine Sciences Faculty Publications and Presentations
Processes active within buoyant hydrothermal plumes are expected to modulate the flux of elements, such as Fe, to the deep ocean; however, they are yet to be described in a comprehensive manner through observations or models. In this study, we compare observed particulate Fe (pFe) speciation with thermodynamic (equilibrium) reaction path modeling for three vent fields in the Eastern Lau Spreading Center (ELSC). At each site, particles were collected from the buoyant rising portion of hydrothermal plumes using in situ filtration with a Remotely Operated Vehicle. Filter bound particles were analyzed by synchrotron micro-probe X-ray fluorescence mapping (XRF), X-ray diffraction …
Comparing Capabilities Of Shewanella Oneidensis Mr-1 And The Microbial Community Of Iron Caves To Reduce Fe(Iii), Aaron Douglas Pham
Comparing Capabilities Of Shewanella Oneidensis Mr-1 And The Microbial Community Of Iron Caves To Reduce Fe(Iii), Aaron Douglas Pham
Williams Honors College, Honors Research Projects
Caves are generally formed by the erosion and/or dissolution of rock and its subsequent removal by water. Iron ore caves (IOCs) form despite being hosted by relatively insoluble and weathering-resistant rock. Due to the discovery of a microbial community behind the walls of these caves, it was hypothesized that these bacteria could be responsible for speleogenesis. Iron ore exists in an oxidized (Fe(III)) state, but reduced (Fe(II)) form is soluble. It was further reasoned that the bacteria might be able to reduce Fe(III) through direct metabolic activity, which uses iron as an electron acceptor. Here we show that cave microorganisms …
Changes Of Mineral Nutriments In Leaves Of Two Tall Fescue Cultivars By Foliar Application Of Iron And Zinc Under Heat Stress, Sheng Xu, Xingyuan He, Wei Chen, Jianlong Li
Changes Of Mineral Nutriments In Leaves Of Two Tall Fescue Cultivars By Foliar Application Of Iron And Zinc Under Heat Stress, Sheng Xu, Xingyuan He, Wei Chen, Jianlong Li
IGC Proceedings (1997-2023)
No abstract provided.
Synthesis And Characterization Of Synthetic Urban Melt Glass, Rebecca Kristien Lowe
Synthesis And Characterization Of Synthetic Urban Melt Glass, Rebecca Kristien Lowe
UNLV Theses, Dissertations, Professional Papers, and Capstones
Melt glass formed from the explosion of a nuclear device is a unique post-detonation material that can aid in the ensuing forensics investigation. Trapped in the melt glass are chemical and isotopic signatures that can provide diagnostic and source information about the weapon by comparison with documentation of previous detonations. A nuclear terrorist attack would likely take place in an urban environment and as such, the melt glass formed would consist of a complex matrix including urban materials like cement and glass, activation products from the large neutron flux that will be seen, and fission products from the detonation. The …
Determination Of Iron-Reducing Bacterial Activities In Lake Sediments., Alexandra Kahn
Determination Of Iron-Reducing Bacterial Activities In Lake Sediments., Alexandra Kahn
Williams Honors College, Honors Research Projects
Algal blooms are growing rampantly in lacustrine systems due to an increase of phosphorus, a nutrient for algae. Phosphorus is being released into the environment causing overpopulation and eutrophication which damages the ecosystem. The availability of phosphorus is affected by the solubility of iron which is regulated through iron reducing and iron oxidizing bacteria. Phosphorus adheres to insoluble Fe(III), which prohibits algae from utilizing it, while phosphorus does not attach to soluble Fe(II) and therefore it remains available to algae. The purpose of this study was to determine how bacteria influence iron solubility and what are the ideal environmental conditions …
Covalently Functionalized Sawdust For The Remediation Of Phosphate From Agricultural Wastewater, Daniel Meister, David Ure, Angela Awada, Jean-Claude Barrette, Joel Gagnon, Bluent Mutus, John F. Trant
Covalently Functionalized Sawdust For The Remediation Of Phosphate From Agricultural Wastewater, Daniel Meister, David Ure, Angela Awada, Jean-Claude Barrette, Joel Gagnon, Bluent Mutus, John F. Trant
Chemistry and Biochemistry Publications
Phosphate remediation from wastewater is rapidly becoming an ever more attractive process due to a combination of both the economic pressure of increasing phosphate scarcity and the environmental damage caused by untreated agricultural runoff. Ideally, remediated phosphate will be recoverable and would be able to be reused as fertilizer. Many different resins have been investigated, but due to the scale of the challenge, any feasible solution will involve the use of very inexpensive waste products as the solid support. Sawdust, functionalized with iron-binding ligands, is such a potential resin. Sawdust alone binds 0.3 g/kg of phosphate which is insufficient. Iron …
Patterns Of Diatom Diversity Correlate With Dissolved Trace Metal Concentrations And Longitudinal Position In The Notheast Pacific Coastal Offshore Transition Zone, P. Dreux Chappell, E. Virginia Armbrust, Katherine A. Barbeau, Randelle M. Bundy, Jagruti Vedamati, Bethany D. Jenkins
Patterns Of Diatom Diversity Correlate With Dissolved Trace Metal Concentrations And Longitudinal Position In The Notheast Pacific Coastal Offshore Transition Zone, P. Dreux Chappell, E. Virginia Armbrust, Katherine A. Barbeau, Randelle M. Bundy, Jagruti Vedamati, Bethany D. Jenkins
OES Faculty Publications
Diatoms are important primary producers in the northeast Pacific Ocean, with their productivity closely linked to pulses of trace elements in the western high nitrate, low chlorophyll (HNLC) region of the oceanographic time series transect 'Line P.' Recently, the coastal-HNLC transition zone of the Line P transect was identified as a hotspot of phytoplankton productivity, potentially controlled by a combination of trace element and macronutrient concentrations. Here we describe diatom community composition in the eastern Line P transect, including the coastal- HNLC transition zone, with a method using high-throughput sequencing of diatom 18S gene amplicons. We identified significant correlations between …
Nickel Exposure Reduces Enterobactin Production In Escherichia Coli, Clorissa L. Washington-Hughes, Geoffrey T. Ford, Alsten D. Jones, Kimberly Mcrae, Franklin Wayne Outten
Nickel Exposure Reduces Enterobactin Production In Escherichia Coli, Clorissa L. Washington-Hughes, Geoffrey T. Ford, Alsten D. Jones, Kimberly Mcrae, Franklin Wayne Outten
Faculty Publications
Escherichia coli is a well- studied bacterium that can be found in many niches, such as industrial wastewater, where the concentration of nickel can rise to low- millimolar levels. Recent studies show that nickel exposure can repress pyochelin or induce pyo-verdine siderophore production in Pseudomonas aueroginosa. Understanding the mo-lecular cross- talk between siderophore production, metal homeostasis, and metal toxicity in microorganisms is critical for designing bioremediation strategies for metal- contaminated sites. Here, we show that high- nickel exposure prolongs lag phase duration as a result of low- intracellular iron levels in E. coli. Although E. coli cells respond to low- …
Phytoplankton Plastid Proteomics: Cracking Open Diatoms To Understand Plastid Biochemistry Under Iron Limitation, Skyler J. Nunn, Phoebe Dreux Chappell, Kristofer Gomes, Anasthasia Bonderenko, Bethany D. Jenkins, Brook L. Nunn
Phytoplankton Plastid Proteomics: Cracking Open Diatoms To Understand Plastid Biochemistry Under Iron Limitation, Skyler J. Nunn, Phoebe Dreux Chappell, Kristofer Gomes, Anasthasia Bonderenko, Bethany D. Jenkins, Brook L. Nunn
OES Faculty Publications
Diatoms, such as Thalassiosira pseudonana, are important oceanic primary producers, as they sequester carbon dioxide (CO₂) out of the atmosphere, die, and precipitate to the ocean floor. In many areas of the world’s oceans, phytoplankton, such as diatoms, are limited in growth by the availability of iron (Fe). Fe is an essential nutrient for phytoplankton, as it is central in the electron transport chain component of photosynthesis. Through this study, we examined if Fe-limitation makes a significant difference in the proteins expressed within the chloroplast, the power source for diatoms. Here, we utilized a new plastid isolation technique specific …
Studies On Hydroxyl Radical Formation And Correlated Photoflocculation Process Using Degraded Wood Leachate As A Cdom Source, Luni Sun, Kenneth Mopper
Studies On Hydroxyl Radical Formation And Correlated Photoflocculation Process Using Degraded Wood Leachate As A Cdom Source, Luni Sun, Kenneth Mopper
Chemistry & Biochemistry Faculty Publications
In this study, we examined hydroxyl radical (•OH) formation with respect to photoreactivity of colored dissolved organic matter (CDOM), the Fenton reaction, and photoflocculation using leachate from decaying wood. The relationship between •OH photoproduction rate and leachate optical properties (UV-visible absorption and fluorescence excitation-emission matrices (EEMS)) was studied during irradiation using a UV solar simulator. The results showed that the •OH photochemical formation rate is strongly related to humic-like fluorescence as characterized by parallel factor analysis (PARAFAC), and that these fluorescence components are more photolabile than most of the other CDOM components. Fourier transform infrared spectroscopy (FT-IR) indicated the photodegradation …
Restoration Of Headwater And Coastal Fens In The Lake Superior Basin Of Upper Michigan, James A. Bess
Restoration Of Headwater And Coastal Fens In The Lake Superior Basin Of Upper Michigan, James A. Bess
Dissertations, Master's Theses and Master's Reports - Open
In 2009, research projects were initiated at Michigan Technological University to develop restoration techniques for headwater fens and coastal wetlands in the southern Lake Superior Basin in Michigan’s Upper Peninsula. The primary focus of these was to quantify the efficacy of using locally collected seeds as a technique for wetland restoration. Two primary sites were selected, the Sleeper Lake Fen complex in Luce County and the Portage Waterway-Keweenaw Bay region of Lake Superior in Baraga and Houghton Counties. At the Sleeper Lake site, a combination of heavy machinery, seeding and mulch application was used to restore a 1.6 km ditch …
Iron Supply And Demand In Antarctic Shelf Ecosystem, D. J. Mcgillicuddy Jr., Peter N. Sedwick, Michael S. Dinniman, K. R. Arrigo, T. S. Bibby, B. J. W. Greenan, Eileen E. Hofmann, John M. Klinck, W. O. Smith Jr., S. L. Mack, C. M. Marsay, B. M. Sohst, G. L. Van Dijken
Iron Supply And Demand In Antarctic Shelf Ecosystem, D. J. Mcgillicuddy Jr., Peter N. Sedwick, Michael S. Dinniman, K. R. Arrigo, T. S. Bibby, B. J. W. Greenan, Eileen E. Hofmann, John M. Klinck, W. O. Smith Jr., S. L. Mack, C. M. Marsay, B. M. Sohst, G. L. Van Dijken
OES Faculty Publications
The Ross Sea sustains a rich ecosystem and is the most productive sector of the Southern Ocean. Most of this production occurs within a polynya during the November-February period, when the availability of dissolved iron (dFe) is thought to exert the major control on phytoplankton growth. Here we combine new data on the distribution of dFe, high-resolution model simulations of ice melt and regional circulation, and satellite-based estimates of primary production to quantify iron supply and demand over the Ross Sea continental shelf. Our analysis suggests that the largest sources of dFe to the euphotic zone are wintertime mixing and …
Ionic Liquid Extraction Unveils Previously Occluded Humicbound Iron In Peat Porewater, Timothy J. Veverica
Ionic Liquid Extraction Unveils Previously Occluded Humicbound Iron In Peat Porewater, Timothy J. Veverica
Dissertations, Master's Theses and Master's Reports - Open
Extracellular iron reduction has been suggested as a candidate metabolic pathway that may explain a large proportion of carbon respiration in temperate peatlands. However, the o-phenanthroline colorimetric method commonly employed to quantitate iron and partition between redox species is known to be unreliable in the presence of humic and fulvic acids, both of which represent a considerable proportion of peatland dissolved organic matter. We propose ionic liquid extraction as a more accurate iron quantitation and redox speciation method in humic-rich peat porewater. We evaluated both o-phenanthroline and ionic liquid extraction in four distinct peatland systems spanning a gradient of physico-chemical …
Distributions Of Particulate Heme B In The Atlantic And Southern Oceans- Implications For Electron Transport In Phytoplankton, Martha Gledhill, Eric P. Achterberg, David J. Honey, Maria C. Nielsdottir, Micha J.A. Rijkenberg
Distributions Of Particulate Heme B In The Atlantic And Southern Oceans- Implications For Electron Transport In Phytoplankton, Martha Gledhill, Eric P. Achterberg, David J. Honey, Maria C. Nielsdottir, Micha J.A. Rijkenberg
OES Faculty Publications
Concentrations of heme b, the iron-containing component of b-type hemoproteins, ranged from b concentrations were enhanced in the photic zone and decreased with depth. Heme b concentrations correlated positively with chlorophyll a (chl a) in the TNA (r=0.41, pb did not correlate with chl a in the IB or SS. In the IB and SS, stations with high-chlorophyll and low-nutrient (Fe and/or Si) concentrations exhibited low heme bconcentrations relative to particulate organic carbon (< 0.1 μmolmol-1, and high chl a:heme b ratios (> 500). High chl a:heme b ratios resulted from relative decreases in …
Diatom Proteomics Reveals Unique Acclimation Strategies To Mitigate Fe Limitation, Brook L. Nunn, Jessica F. Faux, Anna A. Hippman, Maria T. Maldonado, H. Rodger Harvey, David R. Goodlett, Philip W. Boyd, Robert F. Strzepek
Diatom Proteomics Reveals Unique Acclimation Strategies To Mitigate Fe Limitation, Brook L. Nunn, Jessica F. Faux, Anna A. Hippman, Maria T. Maldonado, H. Rodger Harvey, David R. Goodlett, Philip W. Boyd, Robert F. Strzepek
OES Faculty Publications
Phytoplankton growth rates are limited by the supply of iron (Fe) in approximately one third of the open ocean, with major implications for carbon dioxide sequestration and carbon (C) biogeochemistry. To date, understanding how alteration of Fe supply changes phytoplankton physiology has focused on traditional metrics such as growth rate, elemental composition, and biophysical measurements such as photosynthetic competence (Fv/Fm). Researchers have subsequently employed transcriptomics to probe relationships between changes in Fe supply and phytoplankton physiology. Recently, studies have investigated longer-term (i.e. following acclimation) responses of phytoplankton to various Fe conditions. In the present study, the coastal diatom, Thalassiosira pseudonana, …
Approaches To Development Of A User-Friendly Community Based Arsenic/Iron Removal Unit In Bangladesh, Khondoker Mahabub Hassan, Farooque Ahmed, Faisal Hai, Saleh Faraj Magram
Approaches To Development Of A User-Friendly Community Based Arsenic/Iron Removal Unit In Bangladesh, Khondoker Mahabub Hassan, Farooque Ahmed, Faisal Hai, Saleh Faraj Magram
Faisal I Hai
The present stydy focuses on the strategies to modify the design of a community based Arsenic - Iron Removal Unit (AIRU) based on the field performance of the AIRU and the feedback from the users. The ultimate aim was to offer a user-friendly and sustainable system. Appropriate modifications in the design of the developed unit reduced the propensities of water head-loss and media clogging, thereby yielding sustained flow rate. Introduction of a simple cleaning procerdure (98% flow-recovery with three successive backwashing sequences) successfully reduced the frequency of requirement of labor-intensive replacement of the whole filter media. Raw water with arsenic …
Inorganic Arsenic And Iron(Ii) Distributions In Sediment Porewaters Investigated By A Combined Dgt - Colourimetric Det Technique, William Bennett, Peter R. Teasdale, David T. Welsh, Jarad Panther, Ryan R. Stewart, Helen L. Price, Dianne F. Jolley
Inorganic Arsenic And Iron(Ii) Distributions In Sediment Porewaters Investigated By A Combined Dgt - Colourimetric Det Technique, William Bennett, Peter R. Teasdale, David T. Welsh, Jarad Panther, Ryan R. Stewart, Helen L. Price, Dianne F. Jolley
Faculty of Science - Papers (Archive)
No abstract provided.
Optimization Of Colorimetric Det Technique For The In Situ, Two-Dimensional Measurement Of Iron(Ii) Distributions In Sediment Porewaters, William W. Bennett, Peter R. Teasdale, David T. Welsh, Jarad G. Panther, Dianne F. Jolley
Optimization Of Colorimetric Det Technique For The In Situ, Two-Dimensional Measurement Of Iron(Ii) Distributions In Sediment Porewaters, William W. Bennett, Peter R. Teasdale, David T. Welsh, Jarad G. Panther, Dianne F. Jolley
Faculty of Science - Papers (Archive)
No abstract provided.
Controls On Dissolved Cobalt In Surface Waters Of The Sargasso Sea: Comparisons With Iron And Aluminum, R. U. Shelley, Peter N. Sedwick, T. S. Bibby, P. Cabedo-Sanz, T. M. Church, R. J. Johnson, A. I. Macey, C. M. Marsay, E. R. Sholkovitz, S. J. Ussher, P. J. Worsfold, M. C. Lohan
Controls On Dissolved Cobalt In Surface Waters Of The Sargasso Sea: Comparisons With Iron And Aluminum, R. U. Shelley, Peter N. Sedwick, T. S. Bibby, P. Cabedo-Sanz, T. M. Church, R. J. Johnson, A. I. Macey, C. M. Marsay, E. R. Sholkovitz, S. J. Ussher, P. J. Worsfold, M. C. Lohan
OES Faculty Publications
Dissolved cobalt (dCo), iron (dFe) and aluminum (dAl) were determined in water column samples along a meridional transect (∼31°N to 24°N) south of Bermuda in June 2008. A general north-to-south increase in surface concentrations of dFe (0.3-1.6 nM) and dAl (14-42 nM) was observed, suggesting that aerosol deposition is a significant source of dFe and dAl, whereas no clear trend was observed. for near-surface dCo concentrations. Shipboard aerosol samples indicate fractional solubility values of 8-100% for aerosol Co, which are significantly higher than corresponding estimates of the solubility of aerosol Fe (0.44-45%). Hydrographic observations and analysis of time series rain …
The Heat Capacity And Thermodynamic Properties Of The Iron Oxides And Their Relation To The Mineral Core Of The Iron Storage Protein Ferritin, Claine Lindsey Morton Snow
The Heat Capacity And Thermodynamic Properties Of The Iron Oxides And Their Relation To The Mineral Core Of The Iron Storage Protein Ferritin, Claine Lindsey Morton Snow
Theses and Dissertations
The iron oxides are a group of materials with geological, biological, and technological importance. A thermodynamic understanding of these materials is important because it provides information about their relative stabilities, chemical reactivity, and transformations. This study provides the heat capacity of a nanocrystalline magnetite (Fe3O4) sample, bulk hematite (α-Fe2O3), nanocrystalline hematite, akaganéite (β-FeOOH), and lepidocrocite (γ-FeOOH) at temperatures as low as 0.5 K. These measurements were fit to theoretical functions at temperatures lower than 15 K, and the respective thermophysical properties of these materials are discussed. Also the molar entropies of bulk hematite and hydrous nanocrystalline hematite as well as …
Hydroxyl Radical Is Produced Via The Fenton Reaction In Submitochondrial Particles Under Oxidative Stress: Implications For Diseases Associated With Iron Accumulation, Carin Thomas, Melissa M. Mackey, Amy A. Diaz, David P. Cox
Hydroxyl Radical Is Produced Via The Fenton Reaction In Submitochondrial Particles Under Oxidative Stress: Implications For Diseases Associated With Iron Accumulation, Carin Thomas, Melissa M. Mackey, Amy A. Diaz, David P. Cox
All Faculty Scholarship for the College of the Sciences
Mitochondrial dysfunction and reactive oxygen species (ROS) are often implicated in diseases involving oxidative stress and elevated iron. As mitochondria produce ATP by oxidative phosphorylation, ROS by-products are generated from the electron transport chain. Although superoxide and hydrogen peroxide have been thoroughly investigated, little evidence documents hydroxyl radical (HO•) production in mitochondria. In order to determine whether HO• is generated under oxidative stress conditions by a Fenton-type mechanism, bovine heart submitochondrial particles were examined for HO• in the presence and absence of iron ligands, antioxidant enzymes and HO• scavengers. HO• was measured as 2,3- and 2,5-dihydroxybenzoic acid (DHBA), using HPLC …
Cross-Basin Comparison Of Phosphorus Stress And Nitrogen Fixation In Trichodesmium, Annette M. Hynes, P. Dreux Chappell, Sonya T. Dyhrman, Scott C. Doney, Eric A. Webb
Cross-Basin Comparison Of Phosphorus Stress And Nitrogen Fixation In Trichodesmium, Annette M. Hynes, P. Dreux Chappell, Sonya T. Dyhrman, Scott C. Doney, Eric A. Webb
OES Faculty Publications
We investigated the phosphorus (P) status and N2 fixation rates of Trichodesmium populations from the North Pacific, western South Pacific, and western North Atlantic. Colonies of Trichodesmium were collected and analyzed for endogenous alkaline phosphatase (AP) activity using enzyme-labeled fluorescence ( ELF) and for nitrogenase activity using acetylene reduction. AP hydrolyzes dissolved inorganic phosphate (DIP) from dissolved organic phosphorus and is active in Trichodesmium colonies experiencing P stress. Across multiple stations in the subtropical North and South Pacific, there was low to moderate ELF labeling in Trichodesmium, although labeling was present in other taxa. In contrast, Trichodesmium ELF …
Influence Of Irradiance And Iron On The Growth Of Colonial Phaeocystic Antarctica: Implications For Seasonal Bloom Dynamics In The Ross Sea, Antarctica, Nathan S. Garcia, Peter N. Sedwick, Giacomo R. Ditullio
Influence Of Irradiance And Iron On The Growth Of Colonial Phaeocystic Antarctica: Implications For Seasonal Bloom Dynamics In The Ross Sea, Antarctica, Nathan S. Garcia, Peter N. Sedwick, Giacomo R. Ditullio
OES Faculty Publications
Laboratory culture experiments were used to investigate the growth rate of colonial Phaeocystis anarctica as a function of irradiance and dissolved iron concentration. The experiments were conducted with a P. antarctica strain isolated from the southern Ross Sea, Antarctica, and made use of natural, low-iron (P. antarctica attained an average maximum cell-specific growth rate of 0.37 d-1at an irradiance of 68 μE m-2s-1, above which growth rates decreased to 0.27 d-1 at an irradiance of 314 μE m-2s-1. The dependence of growth rate on ambient dissolved iron concentration was …
Approaches To Development Of A User-Friendly Community Based Arsenic/Iron Removal Unit In Bangladesh, Khondoker Mahabub Hassan, Farooque Ahmed, Faisal Ibney Hai, Saleh Faraj Magram
Approaches To Development Of A User-Friendly Community Based Arsenic/Iron Removal Unit In Bangladesh, Khondoker Mahabub Hassan, Farooque Ahmed, Faisal Ibney Hai, Saleh Faraj Magram
Faculty of Science - Papers (Archive)
The present stydy focuses on the strategies to modify the design of a community based Arsenic - Iron Removal Unit (AIRU) based on the field performance of the AIRU and the feedback from the users. The ultimate aim was to offer a user-friendly and sustainable system. Appropriate modifications in the design of the developed unit reduced the propensities of water head-loss and media clogging, thereby yielding sustained flow rate. Introduction of a simple cleaning procerdure (98% flow-recovery with three successive backwashing sequences) successfully reduced the frequency of requirement of labor-intensive replacement of the whole filter media. Raw water with arsenic …
Interactions Between Changing Pco2, N2 Fixation, And Fe Limitation In The Marine Unicellular Cyanobacterium Crocosphaera, Fei-Xue Fu, Margaret R. Mulholland, Nathan S. Garcia, Aaron Beck, Mark E. Warner, Sergio A. Sañudo, David A. Hutchins
Interactions Between Changing Pco2, N2 Fixation, And Fe Limitation In The Marine Unicellular Cyanobacterium Crocosphaera, Fei-Xue Fu, Margaret R. Mulholland, Nathan S. Garcia, Aaron Beck, Mark E. Warner, Sergio A. Sañudo, David A. Hutchins
OES Faculty Publications
We examined the physiological responses of steady-state iron (Fe)-replete and Fe-limited cultures of the biogeochemically critical marine unicellular diazotrophic cyanobacterium Crocosphaera at glacial (19 Pa; 190 ppm), current (39 Pa; 380 ppm), and projected year 2100 (76 Pa; 750 ppm) CO2 levels. Rates of N2 and CO2 fixation and growth increased in step with increasing partial pressure of CO2 (pCO2), but only under Fe- replete conditions. N2) and carbon fixation rates at 75 Pa CO2 were 1.4-1.8-fold and 1.2-2.0-fold higher, respectively, relative to those at present day and glacial pCO2 …
Iron In The Sargasso Sea (Bermuda Atlantic Time-Series Study Region) During Summer: Eolian Imprint, Spatiotemporal Variability, And Ecological Implications, Peter N. Sedwick, T. M. Church, A. R. Bowie, C. M. Marsay, S. J. Ussher, K. M. Achilles, P. J. Lethaby, R. J. Johnson, M. M. Sarin, D. J. Mcgillicuddy
Iron In The Sargasso Sea (Bermuda Atlantic Time-Series Study Region) During Summer: Eolian Imprint, Spatiotemporal Variability, And Ecological Implications, Peter N. Sedwick, T. M. Church, A. R. Bowie, C. M. Marsay, S. J. Ussher, K. M. Achilles, P. J. Lethaby, R. J. Johnson, M. M. Sarin, D. J. Mcgillicuddy
OES Faculty Publications
We report iron measurements for water column and aerosol samples collected in the Sargasso Sea during July-August 2003 (summer 2003) and April-May 2004 (spring 2004). Our data reveal a large seasonal change in the dissolved iron (dFe) concentration of surface waters in the Bermuda Atlantic Time-series Study region, from ∼1-2nM in summer 2003, when aerosol iron concentrations were high (mean 10 nmol/m-3), to ∼0.1-0.2nM in spring 2004, when aerosol iron concentrations were low (mean 0.64 nmol/m-3). During summer 2003, we observed an increase of ∼0.6nM in surface water dFe concentrations over 13 days, presumably due to …