36 results on '"Burton, KW"'
Search Results
2. Quantification of stable strontium isotope variability in nature by MC-ICP-MS
- Author
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Nowell, GM, Charlier, BLA, Pearson, DG, and Burton, KW
- Published
- 2016
3. Quantifying the effect of weathering processes on the chemical signal to the oceans
- Author
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Burton, KW, Gannoun, A, Vigier, N, Bayon, G, Reynolds, BC, James, R, and Gislason, SR
- Published
- 2016
4. Molybdenum isotope fractionation accompanying weathering, riverine transport and estuarine mixing
- Author
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Pearce, CR, Burton, KW, Pogge von Strandmann, PAE, James, RH, and Cohen, AS
- Published
- 2016
5. Silicate weathering mechanisms inferred from direct measurements of Hf-176/Hf-177 ratios in river waters
- Author
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Bayon, G, Vigier, N, Burton, KW, Brenot, A, Carignan, J, and Chu, NC
- Published
- 2016
6. Experimental quantification of kinetic Mg-isotope fractionation during magnesite precipitation
- Author
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Pearce, CR, Saldi, GD, Schott, J, Burton, KW, and Oelkers, EH
- Published
- 2016
7. U-series in Icelandic rivers
- Author
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Vigier, N, Burton, KW, Gislason, SR, Rogers, NW, and Hodge, E
- Published
- 2016
8. Miocene Os and Tl isotopes in the Indian Ocean: Implications for Antarctic water export and the residence time of Os
- Author
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Nielsen, SG, Gannoun, A, Burton, KW, Halliday, AN, and Hein, JR
- Published
- 2016
9. Mg-isotopes in terrestrial and extraterrestrial olivines
- Author
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Alard, O, Burton, KW, Bland, PA, and Russell, SS
- Published
- 2016
10. The Miocene ocean Os-187/Os-188 curve: Driven by continental weathering
- Author
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Georg, RB, West, AJ, Gannoun, A, Burton, KW, and Halliday, AN
- Published
- 2016
11. The influence of weathering processes on riverine Mg and Li isotopes in rivers draining basaltic terrain
- Author
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Pogge Von Strandmann, PAE, Burton, KW, James, RH, Van Calsteren, P, and Gislason, SR
- Published
- 2016
12. Osmium isotope constraints on chemical heterogeneities in Indian mid-ocean ridge basalts
- Author
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Burton, KW and Gannoun, A
- Published
- 2016
13. Glacial-interglacial variations in the Sr-87/Sr-86 composition of seawater
- Author
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Mokadem, F, Burton, KW, Parkinson, IJ, Charlier, BLA, and Hathorne, E
- Published
- 2016
14. Unravelling the controls on the molybdenum isotope ratios of river waters
- Author
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Horan, K, Hilton, RG, McCoy-West, AJ, Selby, D, Tipper, ET, Hawley, S, and Burton, KW
- Subjects
13. Climate action ,37 Earth Sciences ,3703 Geochemistry - Abstract
The molybdenum (Mo) isotope ratios (δ98/95Mo) of river waters control the δ98/95Mo values of seawater and impact on the use of Mo isotope ratios as a proxy of past redox conditions. The δ98/95Mo values of river waters vary by more than 2 ‰, yet the relative roles of lithology versus fractionation during weathering remain contested. Here, we combine measurements from river waters (δ98/95Modiss), river bed materials (δ98/95MoBM) and soils from locations with contrasting lithology. The δ98/95Mo values of river bed materials (δ98/95MoBM), set by rock type, vary by ~1 ‰ between rivers in New Zealand, the Mackenzie Basin, and Iceland. However, the difference between dissolved and solid phase Mo isotopes (Δ98/95Modiss-BM) varies from +0.3 ‰ to +1.0 ‰. We estimate Mo removal from solution using the mobile trace element rhenium and find that it correlates with Δ98/95Modiss-BM across the sample set. The adsorption of Mo to Fe-Mn-(oxyhydr) oxides can explain the observed fractionation. Together, the amount of Mo released through dissolution and taken up by (oxyhydr)oxide formation on land may cause changes in the δ98/95Mo values of rivers, driving long term changes in the Mo isotope ratios of seawater.
15. Carbon dioxide emissions by rock organic carbon oxidation and the net geochemical carbon budget of the Mackenzie River Basin
- Author
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Horan, K, Hilton, RG, Dellinger, M, Tipper, E, Galy, V, Calmels, D, Selby, D, Gaillardet, J, Ottley, CJ, Parsons, DR, and Burton, KW
- Subjects
erosion and weathering ,13. Climate action ,carbon cycle ,petrogenic organic carbon ,rhenium ,Mackenzie River - Abstract
© 2019 American Journal of Science. All rights reserved. The exposure of organic carbon in rocks to oxidative weathering can release carbon dioxide (CO2) to the atmosphere and consume atmospheric oxygen. Alongside volcanism, metamorphism, and the weathering of carbonate minerals by sulfuric acid, this is a major source of atmospheric CO2 over million year timescales. The balance between CO2 release and CO2 drawdown by silicate weathering and organic carbon burial sets the net geochemical carbon budget during weathering and erosion. However, the rates of rock-derived organic carbon (petrogenic organic carbon, OCpetro) oxidation remain poorly constrained. Here, we use rhenium as a proxy to trace and quantify CO2 release by OCpetro oxidation in the Mackenzie River Basin, Canada, where the other carbon fluxes have been well constrained previously. River water and sediment samples were collected between 2009 and 2013 at gauging stations along the Mackenzie River and its main tributaries (Liard, Peel and Arctic Red). To assess rhenium inputs from silicate, sulfide and OCpetro mineral phases we normalize dissolved rhenium concentrations, [Re]diss, to sodium and sulfate ion concentrations. This approach suggests that >85 percent of Re]diss is derived from OC tro in the main river channels. [Re]diss and water discharge measurements are used to quantify dissolved Re yields. River sediments provide a measure of the Re to OC tro ratio of materials undergoing weathering in the basin, and agree well with published rock samples. Dissolved Re yields are combined with river sediment [Re]/[OCpetro] ratios to estimate the CO2 emissions by OCpetro weathering. These are 0.45+019/-0.11 metric tonnes of carbon, tC km2 yr-1 for the Mackenzie River at Tsiigehtchic (3.8+1.5/0.9 × 104 moles km-2 yr-1), and 0.94+0.41/-0.26 tC km-2yr-1, 0.78+0.35/-0.21tC km-2 yr-1 and 1.01+0.42./-0.25tC km-2 yr-1 for the Peel, Arctic Red and Liard catchments, respectively. When considered alongside published silicate and carbonate weathering rates and the sedimentary burial of biospheric organic carbon, these data suggest that the upper part of the Mackenzie River Basin presently acts as an atmospheric CO2 sink of ∼1 tC km-2 yr-1 (∼8 × 104 moles km-2 yr-1) as a result of the carbon transfers by weathering and erosion. During the Last Glacial Maximum, it is possible that the net geochemical carbon balance may have been very different: potential increases in CO2 emissions from oxidative weathering of OCpetro and carbonate minerals, coupled with reduced biospheric carbon burial, may have tipped the balance to a net source of CO2
16. Strontium stable isotope behaviour accompanying melting and magmatism in the earth - moon system
- Author
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Sutcliffe, NC, Burton, KW, Halliday, AN, and Porcelli, D
- Subjects
Geochemistry - Abstract
This thesis concerns the application of a new technique for measuring the stable isotopes of Sr, specifically pertaining to mass dependent fractionation in high temperature processes on the Earth and Moon. Processes such as mantle melting and differentiation on Earth and the formation of the Lunar Magma Ocean are investigated by the application of a double-spike TIMS method to terrestrial and lunar material to obtain high-precision 87Sr/86Sr, 88Sr/86Sr and 84Sr/86Sr data. Measurements of mantle-derived mafic material provide insights into the 88Sr/86Sr composition of the silicate mantle. Ocean Island Basalts possess restricted δ88Sr compositions, whilst Mid-Ocean Ridge Basalts from the Pacific, Atlantic and Indian ridges reveal variations in δ88Sr, the majority of which is seen within the FAMOUS section of the Mid-Atlantic Ridge. These variations are attributed partly due to the effects of plagioclase crystallisation and partly due to mantle source heterogeneity. Analyses of mineral separates from three different igneous systems provide an understanding of δ88Sr fractionation at a mineral-scale. The possibility of δ88Sr fractionation as a result of magmatic differentiation has also been assessed, and found to occur between the basalt and rhyolitic end-members of the Icelandic Hekla suite. Variations in the 87Sr/86Sr ratios of these rocks are also found, and considered most likely to be due to contamination. Analyses of lunar rocks indicate that the highland suite appears to be relatively uniform in δ88Sr, whilst significant fractionation to light δ88Sr compositions occurs in the mare basalts. Such variations are thought to be associated with the crystallisation of plagioclase during the differentiation of the lunar magma ocean. Lastly, precise 87Rb/86Sr and 87Sr/86Sr data yield a model age for the Moon of 4.523 ± 0.019 Ga.
- Published
- 2016
17. Retrospective analysis of canine fecal flotation and coproantigen immunoassay hookworm positive results in Greyhounds and other dog breeds.
- Author
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Burton KW, Hegarty E, and Couto CG
- Subjects
- Animals, Dogs, Retrospective Studies, Hookworm Infections veterinary, Hookworm Infections parasitology, Hookworm Infections diagnosis, Immunoassay veterinary, Immunoassay methods, Ancylostomiasis veterinary, Ancylostomiasis diagnosis, Ancylostomiasis parasitology, Antigens, Helminth analysis, Antigens, Helminth immunology, Female, Male, Dog Diseases parasitology, Dog Diseases diagnosis, Feces parasitology, Ancylostoma isolation & purification
- Abstract
Recent studies demonstrated that Greyhounds are commonly infected with Ancylostoma caninum and these infections have been shown to be resistant to anthelmintics. This study evaluated samples submitted to a commercial reference laboratory (IDEXX Laboratories) for canine fecal flotation zinc sulfate centrifugation and coproantigen immunoassay between January 1, 2019, and July 30, 2023 for evidence that Greyhounds were more often positive for Ancylostoma spp. (hookworms) compared to other breeds. The purpose of the study was to determine if Greyhounds were more likely to be hookworm-positive compared to other breeds, if Greyhounds on preventives with efficacy against hookworm infections are more likely to test positive than other breeds, if their infections take longer to resolve, to estimate how long this takes and to assess whether the proportion of hookworm positive tests for all breeds is increasing over time. Records of 25,440,055 fecal results were obtained representing 17,671,724 unique dogs. Of these, 49,795 (∼0.3%) were Greyhounds. The overall odds ratio (OR) of 15.3 (p < 0.001) suggests that Greyhounds are at significantly higher risk than other breeds for hookworm positive float findings, and the OR of 14.3 (p < 0.001) suggests significantly higher risk for hookworm antigen positive results. The median time to negative testing event from the Turnbull distribution estimate was in the interval of 1-2 days for other breeds and 71-72 days for Greyhounds. These results provide evidence that anthelmintic resistant A. caninum strains may be having population-level impacts on the frequency and duration of infections in Greyhounds. The findings have broader health implications beyond Greyhounds as MADR A. caninum strains could spread to other breeds and even pet owners., Competing Interests: Declaration of competing interest The study was funded by IDEXX Laboratories, Inc. Westbrook, ME, USA., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)
- Published
- 2024
- Full Text
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18. Spatial and risk factor analyses of vector-borne pathogens among shelter dogs in the Eastern United States.
- Author
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Hazelrig CM, Gettings JR, Cleveland CA, Varela-Stokes A, Majewska AA, Hubbard K, Burton KW, and Yabsley MJ
- Subjects
- Dogs, Humans, Animals, United States epidemiology, Seroepidemiologic Studies, Antibodies, Bacterial, Antibodies, Helminth, Ehrlichia, Anaplasma, Risk Assessment, Lyme Disease epidemiology, Lyme Disease veterinary, Anaplasmosis epidemiology, Ehrlichiosis epidemiology, Ehrlichiosis veterinary, Dirofilariasis epidemiology, Coinfection epidemiology, Coinfection veterinary, Dog Diseases epidemiology, Dirofilaria immitis
- Abstract
Background: Vector-borne infections pose significant health risks to humans, domestic animals, and wildlife. Domestic dogs (Canis lupus familiaris) in the United States may be infected with and serve as sentinel hosts for several zoonotic vector-borne pathogens. In this study, we analyzed the geographical distribution, risk factors, and co-infections associated with infection with Ehrlichia spp., Anaplasma spp., Borrelia burgdorferi, and Dirofilaria immitis in shelter dogs in the Eastern United States., Methods: From 2016 to 2020, blood samples from 3750 shelter dogs from 19 states were examined with IDEXX SNAP
® 4Dx® Plus tests to determine the seroprevalence of infection with tick-borne pathogens and infection with D. immitis. We assessed the impact of factors including age, sex, intact status, breed group, and location on infection using logistic regression., Results: The overall seroprevalence of D. immitis was 11.2% (n = 419/3750), the seroprevalence of Anaplasma spp. was 2.4% (n = 90/3750), the seroprevalence of Ehrlichia spp. was 8.0% (n = 299/3750), and the seroprevalence of B. burgdorferi was 8.9% (n = 332/3750). Regional variation in seroprevalence was noted: D. immitis (17.4%, n = 355/2036) and Ehrlichia spp. (10.7%, n = 217/2036) were highest in the Southeast while seroprevalence for B. burgdorferi (19.3%, n = 143/740) and Anaplasma spp. (5.7%, n = 42/740) were highest in the Northeast. Overall, 4.8% (n = 179/3750) of dogs had co-infections, the most common of which were D. immitis/Ehrlichia spp. (1.6%, n = 59/3750), B. burgdorferi/Anaplasma spp. (1.5%, n = 55/3750), and B. burgdorferi/Ehrlichia spp. (1.2%, n = 46/3750). Risk factors significantly influenced infection across the evaluated pathogens were location and breed group. All evaluated risk factors were significant for the seroprevalence of D. immitis antigens., Conclusions: Our results demonstrate a regionally variable risk of infection with vector-borne pathogens in shelter dogs throughout the Eastern United States, likely due to varying distributions of vectors. However, as many vectors are undergoing range expansions or other changes in distribution associated with climate and landscape change, continued vector-borne pathogen surveillance is important for maintaining reliable risk assessment., (© 2023. The Author(s).)- Published
- 2023
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19. Decoupling of inorganic and organic carbon during slab mantle devolatilisation.
- Author
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Bouilhol P, Debret B, Inglis EC, Warembourg M, Grocolas T, Rigaudier T, Villeneuve J, and Burton KW
- Abstract
Serpentinites are an important sink for both inorganic and organic carbon, and their behavior during subduction is thought to play a fundamental role in the global cycling of carbon. Here we show that fluid-derived veins are preserved within the Zermatt-Saas ultra-high pressure serpentinites providing key evidence for carbonate mobility during serpentinite devolatilisation. We show through the O, C, and Sr isotope analyses of vein minerals and the host serpentinites that about 90% of the meta-serpentinite inorganic carbon is remobilized during slab devolatilisation. In contrast, graphite-like carbonaceous compounds remain trapped within the host rock as inclusions within metamorphic olivine while the bulk elemental and isotope composition of organic carbon remains relatively unchanged during the subduction process. This shows a decoupling behavior of carbon during serpentinite dehydration in subduction zones. This process will therefore facilitate the transfer of inorganic carbon to the mantle wedge and the preferential slab sequestration of organic carbon en route to the deep mantle., (© 2022. The Author(s).)
- Published
- 2022
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20. Fossil records of early solar irradiation and cosmolocation of the CAI factory: A reappraisal.
- Author
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Bekaert DV, Auro M, Shollenberger QR, Liu MC, Marschall H, Burton KW, Jacobsen B, Brennecka GA, MacPherson GJ, von Mutius R, Sarafian A, and Nielsen SG
- Abstract
Calcium-aluminum–rich inclusions (CAIs) in meteorites carry crucial information about the environmental conditions of the nascent Solar System prior to planet formation. Based on models of
50 V–10 Be co-production by in-situ irradiation, CAIs are considered to have formed within ~0.1 AU from the proto-Sun. Here, we present vanadium (V) and strontium (Sr) isotopic co-variations in fine- and coarse-grained CAIs and demonstrate that kinetic isotope effects during partial condensation and evaporation best explain V isotope anomalies previously attributed to solar particle irradiation. We also report initial excesses of10 Be and argue that CV CAIs possess essentially a homogeneous level of10 Be, inherited during their formation. Based on numerical modeling of50 V–10 Be co-production by irradiation, we show that CAI formation during protoplanetary disk build-up likely occurred at greater heliocentric distances than previously considered, up to planet-forming regions (~1AU), where solar particle fluxes were sufficiently low to avoid substantial in-situ irradiation of CAIs.- Published
- 2021
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21. Comparative evaluation of field samples using 2 in-clinic assays for heartworm antigen detection in dogs.
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Burton KW, Liu J, Drexel JP, Pulaski C, Heartsill S, and Dupuy C
- Subjects
- Animals, Antigens, Helminth immunology, Dirofilaria immitis immunology, Dirofilariasis parasitology, Dog Diseases parasitology, Dogs, Sensitivity and Specificity, Antigens, Helminth analysis, Dirofilaria immitis isolation & purification, Dirofilariasis diagnosis, Dog Diseases diagnosis, Parasitology methods
- Abstract
Dirofilaria immitis (heartworm) antigen testing is routinely performed in veterinary practices to detect canine heartworm infections. The purpose of this study was to evaluate the performance of two in-clinic assays to detect heartworm antigen on field samples from practices in heartworm endemic regions. Veterinary staff in 3 practices located in the Southern United States performed a side by side comparison of the SNAP® 4Dx® Plus Test (IDEXX) and the VETSCAN FLEX4® Test (Zoetis) on samples from canine patients presented for vector-borne disease screening. Assays were performed according to the manufacturer's instructions. The remaining plasma sample was submitted for confirmatory testing using the PetChek® Heartworm Test (IDEXX) including immune complex dissociation (ICD) by heat treatment. A total of 232 samples were evaluated by the two in-clinic assays and PetChek Test. SNAP 4Dx Plus was significantly more sensitive for the detection of heartworm antigen in this study; sensitivity was 97.4 % for the SNAP 4Dx Plus test and 76.9 % for VETSCAN FLEX4 test (p < 0.01). The specificity of both tests was 99.5 %. This study reveals significant difference in detecting canine heartworm antigen in field samples., (Copyright © 2020 Elsevier B.V. All rights reserved.)
- Published
- 2020
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22. Rapid CO 2 mineralisation into calcite at the CarbFix storage site quantified using calcium isotopes.
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Pogge von Strandmann PAE, Burton KW, Snæbjörnsdóttir SO, Sigfússon B, Aradóttir ES, Gunnarsson I, Alfredsson HA, Mesfin KG, Oelkers EH, and Gislason SR
- Abstract
The engineered removal of atmospheric CO
2 is now considered a key component of mitigating climate warming below 1.5 °C. Mineral carbonation is a potential negative emissions technique that, in the case of Iceland's CarbFix experiment, precipitates dissolved CO2 as carbonate minerals in basaltic groundwater settings. Here we use calcium (Ca) isotopes in both pre- and post-CO2 injection waters to quantify the amount of carbonate precipitated, and hence CO2 stored. Ca isotope ratios rapidly increase with the pH and calcite saturation state, indicating calcite precipitation. Calculations suggest that up to 93% of dissolved Ca is removed into calcite during certain phases of injection. In total, our results suggest that 165 ± 8.3 t CO2 were precipitated into calcite, an overall carbon storage efficiency of 72 ± 5%. The success of this approach opens the potential for quantification of similar mineral carbonation efforts where drawdown rates cannot be estimated by other means.- Published
- 2019
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23. Mountain glaciation drives rapid oxidation of rock-bound organic carbon.
- Author
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Horan K, Hilton RG, Selby D, Ottley CJ, Gröcke DR, Hicks M, and Burton KW
- Abstract
Over millions of years, the oxidation of organic carbon contained within sedimentary rocks is one of the main sources of carbon dioxide to the atmosphere, yet the controls on this emission remain poorly constrained. We use rhenium to track the oxidation of rock-bound organic carbon in the mountain watersheds of New Zealand, where high rates of physical erosion expose rocks to chemical weathering. Oxidative weathering fluxes are two to three times higher in watersheds dominated by valley glaciers and exposed to frost shattering processes, compared to those with less glacial cover; a feature that we also observe in mountain watersheds globally. Consequently, we show that mountain glaciation can result in an atmospheric carbon dioxide source during weathering and erosion, as fresh minerals are exposed for weathering in an environment with high oxygen availability. This provides a counter mechanism against global cooling over geological time scales.
- Published
- 2017
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24. Persistence of deeply sourced iron in the Pacific Ocean.
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Horner TJ, Williams HM, Hein JR, Saito MA, Burton KW, Halliday AN, and Nielsen SG
- Abstract
Biological carbon fixation is limited by the supply of Fe in vast regions of the global ocean. Dissolved Fe in seawater is primarily sourced from continental mineral dust, submarine hydrothermalism, and sediment dissolution along continental margins. However, the relative contributions of these three sources to the Fe budget of the open ocean remains contentious. By exploiting the Fe stable isotopic fingerprints of these sources, it is possible to trace distinct Fe pools through marine environments, and through time using sedimentary records. We present a reconstruction of deep-sea Fe isotopic compositions from a Pacific Fe-Mn crust spanning the past 76 My. We find that there have been large and systematic changes in the Fe isotopic composition of seawater over the Cenozoic that reflect the influence of several, distinct Fe sources to the central Pacific Ocean. Given that deeply sourced Fe from hydrothermalism and marginal sediment dissolution exhibit the largest Fe isotopic variations in modern oceanic settings, the record requires that these deep Fe sources have exerted a major control over the Fe inventory of the Pacific for the past 76 My. The persistence of deeply sourced Fe in the Pacific Ocean illustrates that multiple sources contribute to the total Fe budget of the ocean and highlights the importance of oceanic circulation in determining if deeply sourced Fe is ever ventilated at the surface.
- Published
- 2015
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25. Heartworm 'lack of effectiveness' claims in the Mississippi delta: computerized analysis of owner compliance--2004-2011.
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Atkins CE, Murray MJ, Olavessen LJ, Burton KW, Marshall JW, and Brooks CC
- Subjects
- Animals, Dirofilaria immitis, Dogs, Electronic Data Processing, Retrospective Studies, Southeastern United States, Tennessee, Treatment Outcome, Dirofilariasis prevention & control, Dog Diseases prevention & control, Filaricides administration & dosage, Medication Adherence statistics & numerical data
- Abstract
A retrospective medical record review was conducted to identify factors from veterinary clinic medical records that may have contributed to suspected ineffectiveness of a heartworm preventive product. Patient records of 271 dogs, comprising 301 instances of positive heartworm antigen test results while the dogs were receiving heartworm preventive were evaluated. Nineteen veterinary practices in 17 counties and parishes in Arkansas, Louisiana, Mississippi, and Tennessee participated in the study. Records were selected by the veterinary clinics as representative of cases of suspected lack of effectiveness for a heartworm preventive, and for which an owner satisfaction claim had been filed with the manufacturer. Medical record data were entered into a software program, and a graphic representation was created to facilitate analysis of whether pet owners had purchased sufficient heartworm preventive for the dog to be compliant during the period when infection with Dirofilaria immitis could have led to the positive heartworm antigen test result for that patient ("window of infection"). In 243 (80.7%) cases, there was insufficient heartworm preventive purchased, leading to a gap in protection during the "window of infection". In only five cases (1.7%) there were no purchase lapses or extenuating circumstances (underdosing of medication, multiple purchase gaps outside the established window of infection, or dogs have been diagnosed with heartworm infection more than once during the period studied). Half the cases were from multiple-dog households, and in many of these households, sharing of product between pets was acknowledged. In another 28% of the cases from multiple-dog households, more product was purchased than was needed for one dog, suggesting that the product was being shared between more than one pet. In most cases, there was at least one reason that a dog did not receive sufficient heartworm preventive product, placing the dog at risk of developing an infection with mature heartworms. Several actions were identified that veterinary clinics can take to improve heartworm disease prevention in their patients., (Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.)
- Published
- 2014
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26. Late accretion on the earliest planetesimals revealed by the highly siderophile elements.
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Dale CW, Burton KW, Greenwood RC, Gannoun A, Wade J, Wood BJ, and Pearson DG
- Abstract
Late accretion of primitive chondritic material to Earth, the Moon, and Mars, after core formation had ceased, can account for the absolute and relative abundances of highly siderophile elements (HSEs) in their silicate mantles. Here we show that smaller planetesimals also possess elevated HSE abundances in chondritic proportions. This demonstrates that late addition of chondritic material was a common feature of all differentiated planets and planetesimals, irrespective of when they accreted; occurring ≤5 to ≥150 million years after the formation of the solar system. Parent-body size played a role in producing variations in absolute HSE abundances among these bodies; however, the oxidation state of the body exerted the major control by influencing the extent to which late-accreted material was mixed into the silicate mantle rather than removed to the core.
- Published
- 2012
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27. Habitual emotion regulation and the facial grimace.
- Author
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Burton KW
- Subjects
- Adolescent, Adult, Arousal physiology, Female, Humans, Internal-External Control, Male, Middle Aged, Personality Inventory statistics & numerical data, Psychometrics, Young Adult, Electromyography, Emotions physiology, Facial Expression, Facial Muscles physiology, Habits, Individuality
- Abstract
Summary.-Images of pleasant scenes usually produce increased activity over the zygomaticus major muscie, as measured by electromyography (EMG), while less activity is elicited by unpleasant images. However, increases in zygomaticus major EMG activity while viewing unpleasant images have occasionally been reported in the literature on affective facial expression (i.e., "grimacing"). To examine the possibility that individual differences in emotion regulation might be responsible for this inconsistently observed phenomenon, the habitual emotion regulation tendencies of 63 participants (32 women) were assessed and categorized according to their regulatory tendencies. Participants viewed emotionally salient images while zygomaticus major EMG activity was recorded. Participants also provided self-report ratings of their experienced emotional valence and arousal while viewing the pictures. Despite demonstrating intact affective ratings, the "grimacing" pattern of zygomaticus major activity was observed in those who were less likely to use the cognitive reappraisal strategy to regulate their emotions.
- Published
- 2011
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28. Emotional experience and facial expression in Alzheimer's disease.
- Author
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Burton KW and Kaszniak AW
- Subjects
- Aged, Analysis of Variance, Case-Control Studies, Electromyography methods, Female, Humans, Male, Mental Status Schedule statistics & numerical data, Neuropsychological Tests statistics & numerical data, Pattern Recognition, Visual physiology, Alzheimer Disease physiopathology, Emotions physiology, Facial Expression, Recognition, Psychology physiology
- Abstract
Emotional experiences and facial muscle activity of individuals with Alzheimer's Disease (AD) (n = 13) and healthy elderly control subjects (n = 21) were measured while viewing emotion-eliciting images. Alzheimer's disease and control groups rated their emotional experiences similarly and in the expected directions on dimensions of valence and arousal. Change in corrugator activity while viewing images, compared to baseline, was comparable across groups and was greatest while viewing negative images. Change in zygomatic activity, however, was significantly different between AD and control groups, with AD subjects demonstrating an inverted pattern of activity compared to controls. These findings are discussed as possible consequences of frontal cortical system involvement accompanying the disease process.
- Published
- 2006
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29. Cloning in America: the Genetics and Public Policy Center surveys the nation.
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Burton KW
- Subjects
- Animals, Data Collection, Embryo, Mammalian cytology, Government Regulation, Humans, Nuclear Transfer Techniques, Reproductive Techniques, Assisted legislation & jurisprudence, Research Embryo Creation ethics, Research Embryo Creation legislation & jurisprudence, Stem Cells, United States, Cloning, Organism ethics, Cloning, Organism legislation & jurisprudence, Cloning, Organism methods, Public Opinion
- Abstract
The Genetics and Public Policy Center, a part of the Phoebe R. Berman Bioethics Institute at Johns Hopkins University, compiled the survey information found in the following article for a 2005 publication entitled "Cloning: A Public Policy Report." This article is a summation of the Genetics and Public Policy Center's findings on the public opinion of cloning, stem cell research, and the legal environment which regulates these fields. The original report can be found in it entirety at www.dnapolicy.org. The author of this article is a freelance writer who compiled the report on behalf of The Genetics and Public Policy Center.
- Published
- 2005
30. In situ Os isotopes in abyssal peridotites bridge the isotopic gap between MORBs and their source mantle.
- Author
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Alard O, Luguet A, Pearson NJ, Griffin WL, Lorand JP, Gannoun A, Burton KW, and O'Reilly SY
- Abstract
Abyssal peridotites are assumed to represent the mantle residue of mid-ocean-ridge basalts (MORBs). However, the osmium isotopic compositions of abyssal peridotites and MORB do not appear to be in equilibrium, raising questions about the cogenetic relationship between those two reservoirs. However, the cause of this isotopic mismatch is mainly due to a drastic filtering of the data based on the possibility of osmium contamination by sea water. Here we present a detailed study of magmatic sulphides (the main carrier of osmium) in abyssal peridotites and show that the 187Os/188Os ratio of these sulphides is of primary mantle origin and can reach radiogenic values suggesting equilibrium with MORB. Thus, the effect of sea water on the osmium systematics of abyssal peridotites has been overestimated and consequently there is no true osmium isotopic gap between MORBs and abyssal peridotites.
- Published
- 2005
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31. Osmium isotope heterogeneity in the constituent phases of mid-ocean ridge basalts.
- Author
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Gannoun A, Burton KW, Thomas LE, Parkinson IJ, Van Calsteren P, and Schiano P
- Abstract
Radiogenic isotope variations in mid-ocean ridge basalts (MORB) are commonly attributed to compositional variations in Earth's upper mantle. For the rheniumosmium isotope system, constituent MORB phases are shown to possess exceptionally high Re/Os (parent/daughter) ratios, consequently radiogenic 187Os is produced from the decay of 187Re over short periods of time. Thus, in the absence of precise age constraints, Os isotope variations cannot be unambiguously attributed to their source, although Re-Os isotope data for constituent minerals can yield crystallization ages, details of equilibration, and initial Os isotope values that relate directly to the mantle source.
- Published
- 2004
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32. Extended release peptide delivery systems through the use of PLGA microsphere combinations.
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Burton KW, Shameem M, Thanoo BC, and DeLuca PP
- Subjects
- Animals, Chromatography, High Pressure Liquid, Drug Carriers, Injections, Leuprolide pharmacokinetics, Leuprolide pharmacology, Microspheres, Polylactic Acid-Polyglycolic Acid Copolymer, Rats, Rats, Sprague-Dawley, Testosterone blood, Biocompatible Materials, Lactic Acid, Leuprolide administration & dosage, Polyglycolic Acid, Polymers
- Abstract
The purpose of this study was to evaluate the utility of combining polymer matrices to overcome extended lag periods or unacceptably short durations of action intrinsic in the individual polymer systems. Leuprolide, an LHRH superagonist, was incorporated into a variety of poly(lactide-co-glycolide) (PLGA) matrices using a solvent extraction/evaporation method. The in vitro release of Leuprolide from these matrices was evaluated at pH 7.0 and 37 degrees C in phosphate buffer. The formulations were administered to an animal model at 3 or 9 mg kg(-1) doses and serum testosterone levels were followed using a RIA method. A two-part system was made by combining microspheres made from a 75:25 acid terminated PLGA and microspheres made from a 75:25 ester terminated PLGA. This combination elicited chemical castration from 10-100 days. A three-part combination composed of an ester terminated 75:25 PLGA formulation, an ester terminated 50:50 PLGA formulation and an acid terminated 50:50 PLGA formulation also provided a composite profile with an onset of 10 days and a duration of approximately 100 days. Additionally, a single polymer system composed of a high molecular weight ester terminated 75:25 PLGA was employed to produce release over the desired 90-day release period. This study demonstrates that microsphere combinations can potentially provide effective therapies over extended intervals when combined at the proper ratio.
- Published
- 2000
- Full Text
- View/download PDF
33. Hafnium isotope stratigraphy of ferromanganese crusts
- Author
-
Lee DC, Halliday AN, Hein JR, Burton KW, Christensen JN, and Gunther D
- Abstract
A Cenozoic record of hafnium isotopic compositions of central Pacific deep water has been obtained from two ferromanganese crusts. The crusts are separated by more than 3000 kilometers but display similar secular variations. Significant fluctuations in hafnium isotopic composition occurred in the Eocene and Oligocene, possibly related to direct advection from the Indian and Atlantic oceans. Hafnium isotopic compositions have remained approximately uniform for the past 20 million years, probably reflecting increased isolation of the central Pacific. The mechanisms responsible for the increase in (87)Sr/(86)Sr in seawater through the Cenozoic apparently had no effect on central Pacific deep-water hafnium.
- Published
- 1999
- Full Text
- View/download PDF
34. A comparison of the skeletal effects of intermittent and continuous administration of calcitonin in ovariectomized rats.
- Author
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Li M, Shen Y, Burton KW, DeLuca PP, Mehta RC, Baumann BD, and Wronski TJ
- Subjects
- Analysis of Variance, Animals, Bone Density physiology, Bone Development physiology, Bone Diseases, Metabolic drug therapy, Bone Diseases, Metabolic physiopathology, Calcitonin administration & dosage, Calcitonin pharmacology, Calcium blood, Disease Models, Animal, Female, Humans, Infusion Pumps, Implantable, Injections, Subcutaneous, Osteoclasts cytology, Osteoclasts drug effects, Osteoporosis, Postmenopausal physiopathology, Ovariectomy, Random Allocation, Rats, Rats, Sprague-Dawley, Tibia drug effects, Tibia metabolism, Tibia physiology, Bone Density drug effects, Bone Development drug effects, Calcitonin therapeutic use, Osteoporosis, Postmenopausal drug therapy
- Abstract
The study was designed to compare the skeletal effects of intermittent and continuous administration of calcitonin (CT) in ovariectomized (OVX) rats. Female rats were sham operated or OVX at 3 months of age and treated for 6 weeks with vehicle or salmon CT. Sham-operated control rats were injected subcutaneously with vehicle on alternate days. One group of OVX rats was treated with vehicle intermittently by subcutaneous injection or continuously via Alzet osmotic minipumps. The remaining OVX rats were treated with CT by either subcutaneous injections (16 U/kg) on alternate days or by continuous infusion via minipumps at a daily dose of 8 U/kg. OVX rats treated with CT continuously were mildly hypocalcemic compared with all other groups. The proximal tibial metaphyses of vehicle-treated OVX rats were osteopenic with a cancellous bone volume at only 28% of the vehicle-treated control level. This bone loss was associated with increased indices of bone turnover such as osteoclast surface, osteoblast surface, and bone formation rate. Cancellous bone volume in OVX rats treated with CT either intermittently or continuously was significantly higher than that of vehicle-treated OVX rats, but lower than that of vehicle-treated control rats. Treatment of OVX rats with intermittent or continuous CT significantly decreased all indices of bone turnover compared with vehicle-treated OVX rats. However, osteoclast and osteoblast surfaces of OVX rats treated with CT continuously were still significantly higher than those of vehicle-treated control rats. These results indicate that intermittent and continuous administration of CT had similar skeletal effects in OVX rats. Both treatment regimens depressed bone turnover and partially prevented cancellous bone loss in the estrogen-deplete skeleton.
- Published
- 1996
- Full Text
- View/download PDF
35. Skeletal effects of calcitonin in ovariectomized rats.
- Author
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Wronski TJ, Yen CF, Burton KW, Mehta RC, Newman PS, Soltis EE, and DeLuca PP
- Subjects
- Animals, Body Weight drug effects, Bone Development drug effects, Calcium blood, Female, Ovariectomy, Pharmaceutical Vehicles, Rats, Rats, Inbred Strains, Tibia drug effects, Bone and Bones drug effects, Calcitonin pharmacology
- Abstract
Although calcitonin (CT) has been shown to be effective for the prevention of bone loss in early postmenopausal women, the skeletal effects of the hormone specifically during the early stages of estrogen deficiency have not been characterized histomorphometrically to date. The current study involves use of the ovariectomized (OVX) rat as an animal model for early postmenopausal bone loss to perform such a histomorphometric analysis. One group of OVX rats was injected sc with salmon CT on alternate days for a 6-week period. Additional groups of OVX and sham-operated control rats were treated with vehicle alone. In comparison to control rats, the proximal tibia of vehicle-treated OVX rats were characterized by a 3-fold decrease in cancellous bone volume and significant increases in osteoblast surface (+200%), osteoclast surface (+143%), mineralizing surface (+111%), mineral apposition rate (+36%), bone formation rate (+181%), and longitudinal bone growth (+38%). In contrast, treatment of OVX rats with CT normalized tibial cancellous bone volume and significantly decreased all of the above cellular- and fluorochrome-based indices of bone turnover to near control levels. The results indicate that CT treatment depresses bone turnover and prevents the development of osteopenia in OVX rats. These findings are consistent with the bone protective effect of CT in early postmenopausal women and further support the OVX rat as an animal model for the preclinical evaluation of prophylactic treatments for postmenopausal bone loss.
- Published
- 1991
- Full Text
- View/download PDF
36. A spraying reagent for anions.
- Author
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POLLARD FH, NICKLESS G, and BURTON KW
- Subjects
- Anions, Chromatography, Coloring Agents, Fluorescent Dyes, Indicators and Reagents, Silver Nitrate
- Published
- 1962
- Full Text
- View/download PDF
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