154 research outputs found
Design Charette of the Don River watershed; final report
No full textOn May the 29th the Consulate General of the Kingdom of the Netherlands in Toronto and Waterfront Toronto hosted the Canada – Netherlands Resilient Cities Summit: ‘Planning and Design in a Changing Climate’. Before and in parallel to this summit, a collaborative student design charrette, including students from Delft University of Technology and the University of Toronto took place. The results of this design charrette were presented as part of the Summit program.UrbanismArchitecture and The Built Environmen
pH-Dependent iron oxide precipitation in a subterranean estuary
No full textAuthor Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Geochemical Exploration 88 (2006): 399-403, doi:10.1016/j.gexplo.2005.08.084.Iron-oxide coated sediment particles in subterranean estuaries can act as a geochemical barrier (“iron curtain”) for various chemical species in groundwater (e.g. phosphate), thus limiting their discharge to coastal waters. Little is known about the factors controlling this Fe-oxide precipitation. Here, we implement a simple reaction network in a 1D reactive transport model (RTM), to investigate the effect of O2 and pH gradients along a flow-line in the subterranean estuary of Waquoit Bay (Cape Cod, Massachusetts) on oxidative precipitation of Fe(II) and subsequent PO4 sorption. Results show that the observed O2 gradient is not the main factor controlling precipitation and that it is the pH gradient at the mixing zone of freshwater (pH 5.5) and seawater (pH 7.9) near the beach face that causes a ~7-fold increase in the rate of oxidative precipitation of Fe(II) at ~15 m. Thus, the pH gradient determines the location and magnitude of the observed iron oxide accumulation and the subsequent removal of PO4 in this subterranean estuary.Financial support was provided by the Netherlands Organisation for Scientific Research (NWO) and WHOI Guest Student Program (grants to C. Spiteri), the Royal Netherlands Academy of Arts and Sciences (KNAW) (fellowship to C.P. Slomp) and US National Science Foundation NSF-OCE0095384 and NSF-OCE0425061 (grants to M.A. Charette)
Marine Chemistry special issue : the renaissance of radium isotopic tracers in marine processes studies
No full textAuthor Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Chemistry 109 (2008): 185-187, doi:10.1016/j.marchem.2008.04.001.M. Charette acknowledges the support of NSF for his
participation in the workshop and in the editing of this special issue (OCE-0425061; ANT-
0443869)
Casein kinase 2 (CK2) is a bona fide member of the yeast SSU processome and links ribosome assembly to cell growth
No full textRibosome assembly is linked to growth. In both normal growth and development, but also in cancer, cells upregulate ribosome assembly in order to meet the protein synthesis needs of growing cells. However, the mechanism underlying the relationship between growth and ribosome assembly is poorly characterized. The Small Subunit Processome (SSUP) is a 6 MDa complex composed of ribosome assembly proteins, and the U3 snoRNA. It is responsible for the assembly and maturation of the small subunit of the ribosome. The CK2 kinase complex has been implicated in the regulation of cell growth and of all three RNA polymerases required for ribosome assembly. CK2 has been suggested to be part of the UtpC subcomplex of the SSUP by genome-wide affinity-purification/mass spec analyses. However, the membership of CK2 in the SSUP has not been validated by the standard criteria: (i) nucleolar localization, the site of ribosome biogenesis; (ii) association by co-IP with known SSUP proteins; and (iii) a ribosome assembly defect upon depletion of the candidate component. Here, we validate the membership of CK2 in the yeast SSUP. By literature curation, we show that the CK2 components are nucleolar. As well, all four CK2 subunits co-IP the SSUP protein Kre33. Lastly, depletion of both CKa1 and CKa2 catalytic subunits yields a synthetic lethal phenotype along with a statistically significant decrease (p-value [less than] 0.0001) in mature 18S and 25S rRNA. We thus propose that CK2 is a master regulator of ribosome assembly and may link growth to ribosome assembly in both development and in cancer.Includes bibliographical references (pages 49-59).Chapter 2 is co-authored with Cluff by Elise Poole (created the GAL1::3xHA tagged strains in the Kre33-9xMYC background) and J. Michael Charette (study design, data analysis, and editing of manuscript)."In partial fulfillment of the requirements for the degree of Master of Science, Evironmental and Life Sciences.
The Arctic Radium Isotope Observing Network (ARION): tracking climate-driven changes in Arctic Ocean chemistry
No full text© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kipp, L., University, R., & Charette, M. The Arctic Radium Isotope Observing Network (ARION): tracking climate-driven changes in Arctic Ocean chemistry. Oceanography, 35(2), (2022): 13, https://doi.org/10.5670/oceanog.2022.105.The transport of elements from terrestrial sources to the open ocean is particularly important in the Arctic, where continental shelves comprise half the ocean area (Jakobsson, 2002) and over 10% of the world’s river water is discharged (McClelland et al., 2012). Climate change is further increasing land-ocean exchange by thawing permafrost, increasing river discharge, and enhancing coastal erosion (Günther et al., 2013; Moon et al., 2021)
Flow and nutrient dynamics in a subterranean estuary (Waquoit Bay, MA, USA) : field data and reactive transport modeling
No full textAuthor Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 72 (2008): 3398-3412, doi:10.1016/j.gca.2008.04.027.A two-dimensional (2D) reactive transport model is used to investigate the controls on
nutrient (NO3-, NH4+, PO4) dynamics in a coastal aquifer. The model couples density
dependent flow to a reaction network which includes oxic degradation of organic
matter, denitrification, iron oxide reduction, nitrification, Fe2+ oxidation and sorption of PO4 onto iron oxides. Porewater measurements from a well transect at Waquoit
Bay, MA, USA indicate the presence of a reducing plume with high Fe2+, NH4+, DOC
(dissolved organic carbon) and PO4 concentrations overlying a more oxidizing NO3--rich plume. These two plumes travel nearly conservatively until they start to overlap in the intertidal coastal sediments prior to discharge into the bay. In this zone, the aeration of the surface beach sediments drives nitrification and allows the
precipitation of iron oxide, which leads to the removal of PO4 through sorption. Model
simulations suggest that removal of NO3-
through denitrification is inhibited by the
limited overlap between the two freshwater plumes, as well as by the refractory nature
of terrestrial DOC. Submarine groundwater discharge is a significant source of NO3-
to the bay.This research was funded by the Netherlands Organisation for Scientific Research
(NWO) and WHOI Guest Student Program (C. Spiteri), the Royal Netherlands
Academy of Arts and Sciences (KNAW) and the Netherlands Organization for
Scientific Research (NWO VIDI-grant) (C.P. Slomp), the US National Science
Foundation NSF-OCE0095384 and NSF-OCE0425061 (M.A. Charette) and the
Georgia Sea Grant of the National Sea Grant College Program of the U.S. Department
of Commerce’s National Oceanic and Atmospheric Administration under NOAA
Grant #NA04OAR4170033 (C. Meile)
My major discovery online guide: a retention based advising tool promoting access and awareness of resources supporting UAA prospective and current rural and Alaska Native students' journey to select a major
No full textMaster's Project (M.A.) University of Alaska Fairbanks, 201
Investigation of PGC-1α function in zebrafish
No full textAnimal life must carefully balance energetic resources with physiological demands to promote growth and ensure survival. Energy serves as a valuable resource to cope with ever-changing environmental demands and requires complex regulatory networks to ensure efficient energy utilization. In mammals, PGC-1α (Peroxisome Proliferator Activated Receptor Co-Activator 1 α) is a master regulator of metabolism coordinating many essential metabolic processes. However, the importance of PGC-1α is currently unknown amongst lower vertebrates, despite controversy suggesting divergent roles for PGC-1α in teleost species. Here, I describe the creation of a mutant zebrafish line dedicated to uncovering the role of PGC-1α in zebrafish. In chapter 2, I disrupted an evolutionary conserved region upstream of the PGC-1α promoter, simultaneously increasing PGC-1α expression in skeletal muscle 4-fold and decreasing PGC-1α expression in cardiac muscle 4-fold. This mutation increased O2 consumption in white muscle fibres and doubled the resting metabolism in juvenile zebrafish demonstrating that PGC-1α retains its role as a metabolic regulator in fish. In chapter 3, I hypothesized that PGC-1α mutant zebrafish experience impaired growth due to having a decreased metabolic efficiency. Mutant zebrafish larvae displayed decreased heart rate alongside increased yolk fatty acid (FA) content, indicating decreased FA metabolism during early development. Surprisingly, mutant adult zebrafish had increased FA metabolism, resisted growth when presented with a high-fat diet and decreased Dihomo-Gamma-Linoleic-Acid in skeletal muscle, a FA that prevents mitochondrial leakage. In summary, this mutation greatly impedes the metabolic function of zebrafish and provides a promising model for the continued study of PGC-1α in lower vertebrate muscles.Includes bibliographical references (pages 86-106).Chapter 2, entitled "An evolutionary conserved regulatory sequence dictates PGC-1α exoression in Zebrafish striated muscles" is co-authored with Kurchaba by Michael Charette (study design and methodology) and Christophe LeMoine (study design, data curation, methodology, analysis, and writing). Chapter 3, entitled "Altered PGC-1α expression in Zebrafish limits growth irrespective of nutrient consumption" is co-authored with Kurchaba by Ellie Duncan (methodology and data analysis) and Christophe LeMoine (study design, data curation, methodology, analysis, and writing)"In partial fulfillment of the requirements for the degree of Master of Science, Evironmental and Life Sciences.
Radium isotopes as tracers of iron sources fueling a Southern Ocean phytoplankton bloom
No full textElevated levels of productivity in the wake of Southern Ocean island systems are common despite the fact that they are encircled by high-nutrient low-chlorophyll (HNLC) waters. In the Crozet Plateau region, it has been hypothesized that iron from island runoff or sediments of the plateau could be fueling the austral summer phytoplankton bloom. Here, we use radium isotopes to quantify the rates of surface-ocean iron supply fueling the bloom in the Crozet Plateau region. A 1-D eddy-diffusion-mixing model applied to a 228Ra profile (t1/2=5.75 years) at a station north of the islands suggests fast vertical mixing in the upper 300 m (Kz=11–100 cm2 s?1) with slower mixing between 300 and 1000 m (Kz=1.5 cm2 s?1). This estimate is discussed in the context of Kz derived from the CTD/LADCP data. In combination with the dissolved Fe profile at this location, we estimated a vertical flux of between 5.6 and 31 nmol Fe m?2 d?1. The cross-plateau gradients in the short-lived radium isotopes, 224Ra (t1/2=3.66 d) and 223Ra (t1/2=11.4 d), yielded horizontal eddy diffusivities (Kh) of 39 and 6.6 m2 s?1, respectively. If we assume that the islands (surface runoff) alone were supplying dissolved Fe to the bloom region, then the flux estimates range from 2.3 to 14 nmol Fe m?2 d?1. If the plateau sediments are considered a source of Fe, and conveyed to the bloom region through deep winter mixing combined with horizontal transport, then this flux may be as high as 64–390 nmol Fe m?2 d?1. Combined, these Fe sources are sufficient to initiate and maintain the annual phytoplankton bloom
Density Functional Theory Study of the Mechanism and Origins of Stereoselectivity in the Asymmetric Simmons-Smith Cyclopropanation with Charette Chiral Dioxaborolane Ligand
No full textAsymmetric Simmons-Smith reaction using Charette chiral dioxaborolane ligand is a widely applied method for the construction of enantiomerically enriched cyclopropanes. The detailed mechanism and the origins of stereoselectivity of this important reaction were investigated using density functional theory (DFT) calculations. Our computational studies suggest that, in the traditional Simmons-Smith reaction conditions, the monomeric iodomethylzinc allyloxide generated in situ from the allylic alcohol and the zinc reagent has a strong tendency to form a dimer or a tetramer. The tetramer can easily undergo an intramolecular cyclopropanation to give the racemic cyclopropane product. However, when a stoichiometric amount of Charette chiral dioxaborolane ligand is employed, monomeric iodomethylzinc allyloxide is converted into an energetically more stable four-coordinated chiral zinc/ligand complex. The chiral complex has the zinc bonded to the CH(2)I group and coordinated by three oxygen atoms (one from the allylic alcohol and the other two oxygen atoms from the carbonyl oxygen and the ether oxygen in, the dioxaborolane ligand), and it can undergo the cyclopropanation reaction easily. Three key factors influencing the enantioselectivity have been identified through examining the cyclopropanation transition states: (1) the torsional strain along the forming C-C bond, (2) the 1,3-allylic strain caused by the chain conformation, and (3) the ring strain generated in the transition states. In addition, the origin of the high anti diastereoselectivity for the substituent on the zinc reagent and the hydroxymethyl group of the allylic alcohol has been rationalized through analyzing the steric repulsion and the ring strain in the cyclopropanation transition states
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