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Dissertations / Theses on the topic 'Dimethylsulfone'
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1
Borodina, Elena. "Bacterial metabolism of dimethylsulfone." Thesis, King's College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251998.
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Матрунчик, Ольга Леонідівна, Альона Геннадіївна Тульська, Світлана Германівна Дерібо, and Сергій Анатолійович Лещенко. "Анодні процеси в електрохімічному синтезі метансульфонової кислоти." Thesis, Дослідно-видавничий центр Наукового товариства ім. Т. Г. Шевченка, 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/45473.
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Synthesis of methanesulfonic acid occurs during the course of an anode reaction – oxidation of dimethyl sulfoxide (DMSO). The application of the electrochemical method of oxidation DMSO allows you to control the process. The control parameters are: the potential of the anode, the catalytic activity of the anode material, the temperature of the electrolyte, promoters and inhibitors in the electrolyte. Voltamperic dependences of methanesulfonic acid from dilute solutions of DMSO with background with sulphate acid were contemplated. The emergence of a half-wave at cyclic voltammetric dependences and the dependence of its limiting current density on the concentration of DMSO indicates the occurrence of adsorption processes. We can talk about the process of oxidation of DMSO to methanesulfonic acid through the intermediate stage of the formation of dimethylsulphone. The possibility of electrochemical synthesis of methanesulfonic acid in a diaphragm electrolyzer with the ratio of the anode current density to the cathode 20:1 is shown.
3
Boden, Rich. "Metabolism of dimethylsulfide in the bacteria." Thesis, University of Warwick, 2009. http://wrap.warwick.ac.uk/2741/.
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Dimethylsulfide (DMS) is a volatile organosulfur compound which has been implicated as playing key roles in climate control and in the biogeochemical cycling of sulfur. Metabolism of DMS by Bacteria has been previously identified as an important sink of DMS in soils and in the marine environment; however, relatively little is known about the physiology or biochemistry of Bacteria that metabolism DMS. The key enzyme of DMS oxidation in Hyphomicrobium spp. – DMS monooxygenase - has been purified and characterised from H. sulfonivorans. It has been shown to be a two-componant monooxygenase, related to bacterial luciferase, comprising two subunits – an FMNH2-dependent DMS monooxygenase (DmoA) and an NADHdependent FMN oxidoreductase (DmoB). For DMS, DMS monooxygenase from H. sulfonivorans has a Vmax of 1250 nmol DMS oxidised min-1 (mg protein)-1 and a kM of 16.5μM, corresponding to a kCAT of 5.2s-1. DMS oxidation in terms of acting as a sole-carbon source and as a supplementary energy source has been demonstrated in methylotrophic and heterotrophic bacteria. Chemolithoheterotrophic growth in which DMS carbon is assimilated to biomass whilst DMS sulfur is oxidised to tetrathionate with a net energy gain has been demonstrated in “M. thiooxidans”. Both “internal” and “external” chemolithoheterotrophy has been observed in “M. thiooxidans”, with endogenous and exogenous thiosulfate being oxidised to tetrathionate with a net energy gain. As far as can be found from the literature, this is the first recorded production of a polythionate from an organosulfur compound, as such, representing a potential new step in the biogeochemical sulfur cycle. Stable-isotope probing with [13C2]-DMS has been performed for the first time and has confirmed Methylophaga spp. as dominant DMS-oxidising Bacteria in the marine environment. The oxidation of marine thiosulfate to tetrathionate has been demonstrating during a phytoplankton bloom, indicating that chemolithoheterotrophic Bacteria are active during the bloom. Preliminary analyses have been carried out on the genome sequence of “Methylophaga thiooxidans” and the genes encoding the major enzymes of formaldehyde assimilation via the KDPG aldolase variant RuMP pathway have been identified. Genes encoding key enzymes involved in the dissimilation of methanol and methylated amines have been indentified, in addition to those involved in nitrogen uptake from ammonia, nitrate, nitrite and urea. Chemoorganoheterotrophic growth, coupling the oxidation of DMS to DMSO with ATP formation, has been demonstrated in Sagittula stellata E-37T, though the enzyme(s) responsible for this oxidation remain unclear.
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Heine, Christian Klaus. "NMR von rotatorischer und translatorischer Dynamik." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=96484916X.
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Bergeijk, Stefanie Anne van. "Production of dimethylsulfoniopropionate and dimethylsulfide in intertidal sediment ecosystems." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2000. http://dare.uva.nl/document/83755.
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Shema, Richard A. "Correlation of satellite-detected aerosol characteristics and oceanic dimethylsulfide (DMS)." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/22994.
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Eisman, Greg A. "Cloud reflectance characteristics in the presence of variable dimethylsulfide (DMS) sources." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26915.
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Lucas, Donald David 1969. "Mechanistic, sensitivity, and uncertainty studies of the atmospheric oxidation of dimethylsulfide." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29759.
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Thesis (Ph. D. in Atmospheric Chemistry)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2003.Includes bibliographical references (p. 238-249).
The global-scale emissions and reactivity of dimethylsulfide (CH3SCH3, DMS) make it an integral component in the atmospheric sulfur cycle. DMS is rapidly oxidized in the atmosphere by a complex gas-phase mechanism involving many species and reactions. The resulting oxidized sulfur-bearing products are hygroscopic and interact with aerosols through condensation and secondary aerosol formation. Predictions of the impacts of DMS chemistry on aerosols and climate are inhibited by the poorly understood DMS oxidation mechanism. This thesis diagnoses the gas-phase connections between DMS and its oxidation products by simulating comprehensive DMS chemistry (approximately 50 reactions and 30 species) using three atmospheric models of varying size and complexity. A diurnally-varying box model of the DMS cycle in the remote marine boundary layer is used to identify important DMS-related parameters and propagate parameter uncertainties to the sulfur-containing species. This analysis shows that the concentrations of DMS and sulfur dioxide (SO2) are sensitive to relatively few parameters. Moreover, the concentrations of DMS and SO2 are found to have factor of 2 uncertainties caused primarily (more than 60% of the variance) by uncertainties in DMS emissions and heterogeneous removal, respectively. In contrast, the concentrations of other products, such as sulfuric acid (H2SO4) and methanesulfonic acid (CH3SO3H, MSA), are found to be sensitive to many parameters and have larger uncertainties (factors of 2 to 7) resulting from multiple uncertain chemical and non-photochemical processes. The DMS oxidation mechanism is quantitatively assessed using a one-dimensional column model constrained by high-frequency aircraft measurements from the
(cont.) First Aerosol Characterization Experiment (ACE-1). From this analysis, the baseline mechanism predicts DMS and SO2 concentrations in statistical agreement with the observations, yet it underestimates MSA concentrations by a factor of 10⁴ to 10⁵. These differences for MSA are statistically very significant and indicative of missing gas-phase reactions in the DMS mechanism. To reconcile these differences, five hypothetical MSA production paths are individually tested which greatly improve the model predictions to within a factor of 2 to 3 of the observations. Overall, the best improvement occurs when MSA is produced from the oxidation of methanesulfinic acid (CH3S(O)OH). Furthermore, the boundary layer model predictions of H2SO4 show improve ment after an SO2-independent sulfuric acid production channel is added to the mechanism. The DMS cycle is simulated in a global three-dimensional chemical transport model using, for the first time, comprehensive DMS oxidation chemistry. Four model cases are considered, which include two new comprehensive mechanisms and two parameterized schemes of 4 to 5 reactions taken from previous global sulfur models. The mole fractions of DMS, SO2, H2SO4, and MSA are compared between these four cases and with observations from the ACE-1 and PEM-Tropics A campaigns. Among the four cases, the calculated mole fractions of DMS and SO2 are largely invariant, while those for H2SO4 and MSA exhibit order-of-magnitude differences ...
by Donald David Lucas.
Ph.D.in Atmospheric Chemistry
9
Ledyard, Kathleen Mei. "Marine microbial production of dimethylsulfide from dissolved dimethylsulfoniopropionate by Kathleen Mei Ledyard." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/54359.
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Carnat, Gauthier. "Towards an understanding of the physical and biological controls on the cycling of dimethylsulfide (DMS) in Arctic and Antarctic sea ice." International Glaciological Society, 2013. http://hdl.handle.net/1993/23732.
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Little is known about the factors driving the cycle of the climate-active gas dimethylsulfide (DMS) and of its precursor the metabolite dimethylsulfoniopropionate (DMSP) in sea ice. To date, studies have focused on biotic factors, linking high DMSP concentrations to the high biomass of sympagic communities, and to physiological adaptations to the low temperatures and high salinities of the brine habitat. This thesis presents an approach integrating biotic and abiotic factors, investigating the influence of ice growth processes and brine dynamics on the DMS cycle. First, brine dynamics from growth to melt are explored based on ice temperature and salinity profiles measured in the Arctic. A strong but brief desalination phase is identified in spring. Using calculated proxies of permeability (brine volume fraction) and of the intensity of brine convection (Rayleigh number), this phase is shown to correspond to full-depth gravity drainage initiated by restored connectivity of brines on warming. Full-depth gravity drainage is crucial for the vertical transfer of DMS-compounds at the ice-ocean interface. This physical background is then used to investigate the spatio-temporal variability of DMS in Arctic sea ice during a year-round survey in Amundsen Gulf. The influence of processes such as scavenging and brine convection on the DMS cycle is shown, and the first combined measurement of DMS, DMSP, and dimethylsulfoxide (DMSO), a compound acting as source/sink for DMS through photo-chemical and bacterial processes, is presented. DMSO is shown to dominate the dimethylated sulfur pool in surface ice when the snow cover is low. Based on correlations with irradiance, it is suggested that this DMSO originates from photo-chemical oxidation of DMS trapped in impermeable ice. Finally, the spatio-temporal variability of DMS in Antarctic sea ice is investigated during another year-round survey in McMurdo Sound. Platelet crystals growth under the influence of ice-shelf waters are shown to favor the incorporation of strong DMSP producers, to increase the environmental stress on cells, and to favor the accumulation of DMS,P by reducing permeability. The increase of permeability on warming is shown to trigger strong release of DMS in the ocean and a vertical redistribution of DMSP in the ice cover.
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Kröber, Eileen. "Environmental genomics and proteomics of plant-associated microbial dimethylsulfide degradation in a coastal salt marsh." Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/81391/.
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The methylated sulfur compound dimethylsulfide (DMS) plays a major role in the biogeochemical sulfur cycle and atmospheric chemistry. Bacteria are a main sink for DMS in the global sulfur cycle and can utilise DMS as a sole carbon and energy source. This study investigated the diversity and activity of bacteria capable of DMS degradation and associated with the salt marsh plant Spartina anglica known to be a producer of the DMS precursor dimethylsulfoniopropionate (DMSP). Initially, it was shown that S. anglica is rich in DMSP throughout the entire seasonal cycle in the Stiffkey salt marsh providing a likely hotspot for DMSP- and DMS-degrading bacteria. DMS uptake experiments demonstrated that DMS degradation takes place in the phyllosphere and rhizosphere of S. anglica and denaturing gradient gel electrophoresis (DGGE) and high-throughput amplicon sequencing of the 16S rRNA revealed the dominance of bacteria related to α - and γ- Proteobacteria, as well as Flavobacteria in the phyllosphere of S. anglica, whereas the rhizosphere was mainly colonised by members of the classes γ-, δ-, α-, and ε-Proteobacteria and Bacteroidia. The diversity of DMS-degrading bacteria associated with S. anglica was first assessed by enrichment culture. DGGE analysis and high-throughput sequencing diversity of DMS enriched samples using the 16S rRNA gene as a marker suggested the dominance of Piscirickettsiaceae, Methylophaga and Methylophaga-like bacteria in DMS-enrichments of phyllosphere and rhizosphere samples of S. anglica. A functional gene marker analyses was carried out using the gene encoding methanethiol oxidase (mtoX), a key enzyme in DMS degradation and the gene encoding a DMSP lyase (dddP) to determine the diversity of bacteria degrading DMS and DMSP, respectively, in the phyllosphere and rhizosphere of S. anglica. The analysis for mtoX showed a great diversity of this gene in phyllosphere and rhizosphere of S. anglica and that major clades of mtoX clustered together with Sedimenticola, Methylohalobius, Methylophaga and other mtoX clones previously detected in surface sediments of the same salt marsh. The results for the functional marker gene analysis for the dddP gene suggested the dominance of Ruegeria-like species and Roseobacter-like bacteria but also of unidentified Ddd+ bacteria in the phyllosphere and rhizosphere of S. anglica. In order to identify the active DMS degraders in the phyllosphere and rhizosphere of S. anglica stable-isotope probing (SIP) combined with DGGE and highthroughput sequencing of the 16S rRNA gene was carried out. The SIP experiments revealed the dominance of Piscirickettsiaceae, Methylophaga and Methylophaga-like microorganisms in the rhizosphere of S. anglica. However, the DMS-degrading microbial community in the phyllosphere seemed more diverse than in the rhizosphere and microorganisms like Halothiobacillus, Xanthomonadaceae, Rhodanobacter but also Piscirickettsiaceae seemed to be involved. A comparative proteomic and transcriptomic experiment of Methylophaga thiooxydans, a microorganism found in phyllosphere and rhizosphere of S. anglica, revealed the general pathways involved in methanol but especially DMS degradation. During DMS cycling the protein and the protein-encoding gene for the methanethiol oxidase (MtoX/mtoX) was highly expressed. A metaproteogenomic experiment provided an insight into the taxonomy and functional diversity of the microbial community associated with the Spartina anglica phyllosphere. Analysis of the metagenome provided evidence that the microbial community associated with S. anglica is dominated by γ-Proteobacteria such as Halomonadales, Alteromonadales, Oceanospirillales, and Thiotrichales and the alphaproteobacterial order Rhodobacterales and showed therefore a major difference to the bacterial community composition in the phyllosphere of for instance A. thaliana, clover, soybean and rice. The detection of DMSP lyase encoding genes and genes encoding proteins for DMS degradation confirmed the genetic potential for the observed DMSP and DMS degradation activity previously measured in the phyllosphere of S. anglica. The metaproteomic experiment allowed a first insight into the proteins expressed in the phyllosphere of S. anglica which also suggested that mainly γ-Proteobacteria and α-Proteobacteria are dominant populations occurring in this habitat. New insights were gained into the activity and diversity of DMS-degrading microbial communities associated with a salt marsh plant that represents a significant component of salt marsh plant communities world wide. Not only was the taxonomic and functional diversity of DMS-degrading microorganisms associated with S. anglica greater then previously realised, the observation of considerable potential of above-ground plant-associated DMS degradation in the phyllosphere demonstrates a previously unrealised sink in the DMS cycle in coastal ecosystems, which is clearly more complex than previously appreciated.
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Tallant, Thomas Clinton. "The Methylthiol:coenzyme M methyltransferase from methanosarcina barkeri; an enzyme of bethanogenesis from dimethylsulfide and methylmercaptopropionate /." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488203857250408.
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Nemcek, Nina. "Membrane inlet mass spectrometry (M(MS) : a novel approach to the oceanic measurement of dimethylsulfide." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/32146.
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A novel technique, membrane inlet mass spectrometry (MIMS), was used to measure
dimethylsulfide gas (DMS) and algal dimethylsulfoniopropionate (DMSPp) concentrations in
two different marine ecosystems of the NE Pacific. In oceanic waters along Line P, DMS levels
had been observed to be unusually high, yet particulate DMSP levels had not been extensively
measured. DMSPp concentrations during 3 consecutive spring cruises ranged from 0.2-63.2 nM
(mean 21.5 nM , s.d. 15.0 nM ) in the upper 50 m of the water column, and varied significantly
with depth, across stations and between study years. DMSPp generally decreased with depth and
distance from the coast. DMSPp concentrations at most stations in 2003 were 2 to 3-fold higher
than in subsequent years, and were significantly correlated to the biomass of dinoflagellates
(r2 = 0.46) across the survey region. Although phytoplankton biomass (chlorophyll a) also
declined in 2004-2005, DMSPp:chl ratios did as well, indicating a physiological or taxonomic
change in the phytoplankton community.
Surface DMS concentrations were measured underway along with pCO₂, O₂/Ar,
temperature, salinity and chlorophyll a in productive, coastal waters off British Columbia. All
parameters exhibited large ranges, (pCO₂, 200-747 ppm; DMS, Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Zaveri, Rahul A. "Development and Evaluation of a Comprehensive Tropospheric Chemistry Model for Regional and Global Applications." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30673.
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Accurate simulations of the global radiative impact of anthropogenic
emissions must employ a tropospheric chemistry model that predicts
realistic distributions of aerosols of all types. The need for a such
a comprehensive yet computationally efficient tropospheric chemistry
model is addressed in this research via systematic development of the
various sub-models/mechanisms representing the gas-, aerosol-, and
cloud-phase chemistries.
The gas-phase model encompasses three tropospheric chemical regimes -
background and urban, continental rural, and remote marine.
The background and urban gas-phase mechanism is based on the paradigm
of the Carbon Bond approach, modified for global-scale applications.
The rural gas-phase chemistry includes highly condensed isoprene and
a-pinene reactions. The isoprene photooxidation scheme is adapted for
the present model from an available mechanism in the literature, while
an a-pinene photooxidation mechanism, capable of predicting secondary
organic aerosol formation, is developed for the first time from the
available kinetic and product formation data. The remote marine gas-
phase chemistry includes a highly condensed dimethylsulfide (DMS)
photooxidation mechanism, based on a comprehensive scheme available
in the literature. The proposed DMS mechanism can successfully explain
the observed latitudinal variation in the ratios of methanesulfonic
acid to non-sea-salt sulfate concentrations.
A highly efficient dynamic aerosol growth model is developed for
condensing inorganic gases. Algorithms are presented for calculating
equilibrium surface concentrations over dry and wet multicomponent
aerosols containing sulfate, nitrate, chloride, ammonium, and sodium.
This alternative model is capable of predictions as accurate for
completely dissolved aerosols, and more accurate for completely dry
aerosols than some of the similar models available in the literature.
For cloud processes, gas to liquid mass-transfer limitations to
aqueous-phase reactions within cloud droplets are examined for all
absorbing species by using the two-film model coupled with a
comprehensive gas and aqueous-phase reaction mechanisms. Results
indicate appreciable limitations only for the OH, HO2, and NO3
radicals. Subsequently, an accurate highly condensed aqueous-phase
mechanism is derived for global-scale applications.Ph. D.
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Kettle, Anthony J. "Extrapolations of the flux of dimethylsulfide, carbon monoxide, carbonyl sulfide, and carbon disulfide from the oceans." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0012/NQ59143.pdf.
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Robinson, Fiona. "Dimethylsulfate (DMS) protection footprinting of the interaction of cruciform DNA with a human cruciform binding protein (CBP)." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30736.
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Cruciforms are an alternative secondary structure which may be adopted by DNA containing inverted repeats, under conditions of adequate torsional strain. Inverted repeats are distributed, in a non-random fashion, throughout the genomes of prokaryotes and eucaryotes. Mounting evidence suggests that they are involved in the initiation of DNA replication. A structure-specific cruciform DNA binding protein (CBP) has previously been enriched from HeLa cells, and demonstrated to be a member of the 14-3-3 family of proteins. This thesis reports the dimethylsulfate (DMS) protection footprinting of this protein on a stable cruciform, with the goal of testing a model proposed for this interaction. The footprint obtained was not clear or reproducible enough to allow this verification, however, it does support previously identified regions of binding on the cruciform DNA. Possible explanations for the nature of the footprint obtained, and suggestions which may allow the achievement of verification of the model, are discussed.
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Robinson, Fiona. "Dimethylsulfate (DMS) protection footprinting of the interaction of cruciform DNA with a human cruciform binding protein (CBP)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0030/MQ64441.pdf.
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Polsinelli, Gregory Anthony. "Bacterial generation of the anti-greenhouse gas dimethylsulfide kinetic, spectroscopic, and computational studies of the DMSO reductase system /." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1198876055.
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Bopp, Laurent. "Changements climatiques et biogéochimie marine : modélisation du Dernier Maximum Glaciaire et de l'Ere Industrielle." Paris 6, 2001. http://www.theses.fr/2001PA066397.
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Levine, Naomi Marcil. "Understanding the ocean carbon and sulfur cycles in the context of a variable ocean : a study of anthropogenic carbon storage and dimethylsulfide production in the Atlantic Ocean." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/57553.
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Thesis (Ph.D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references.
Anthropogenic activity is rapidly changing the global climate through the emission of carbon dioxide. Ocean carbon and sulfur cycles have the potential to impact global climate directly and through feedback loops. Numerical modeling, field and laboratory studies are used to improve our mechanistic understanding of the impact of natural variability on carbon and sulfur cycling. Variability in ocean physics, specifically changes in vertical mixing, is shown to significantly impact both cycles. The impact of interannual variability on the detection and attribution of anthropogenic carbon (Canthro) and the storage of Canthro in the Atlantic Ocean is analyzed using a three-dimensional global ocean model. Several regions are identified where empirical methods used to estimating Canthro are not able to correct for natural variability in the ocean carbon system. This variability is also shown to bias estimates of long term trends made from hydrographic observations. In addition, the storage of Canthro in North Atlantic mode waters is shown to be strongly influenced by water mass transformation during wintertime mixing events. The primary mechanisms responsible for seasonal variability in dimethylsulfoniopropionate (DMSP) degradation and dimethylsulfide (DMS) production in the oligotrophic North Atlantic are investigated using potential enzyme activity and gene expression and abundance data. Vertical mixing and UV radiative stress appear to be the dominant mechanisms behind seasonal variability in DMS production in the Sargasso Sea. This thesis demonstrates the importance of and dynamics of bacterial communities responsible for DMSP degradation and DMS production in oligotrophic surface waters. These findings suggest that modifications to current numerical models of the upper ocean sulfur cycle may be needed. Specifically, current static parameterizations of bacterial DMSP cycling should be replaced with a dynamic bacterial component including DMSP degradation and DMS production.
by Naomi Marcil Levine.
Ph.D.
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Speeckaert, Gaelle. "Variabilité des concentrations cellulaires phytoplanctoniques de diméthylsulfoniopropionate (DMSP) et de diméthylsulfoxyde (DMSO) en Baie Sud de la Mer du Nord." Doctoral thesis, Universite Libre de Bruxelles, 2018. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/278748.
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The eutrophication of the Southern Bight of the North Sea has been benefitting to the prymnesiophyte Phaeocystis globosa (P. globosa). This species is a known high dimethylsulfoniopropionate (DMSP) producer whose bloom accounts for 95% of spring phytoplankton biomass. An increase in DMS(P) and its oxidation product dimethylsulfoxide (DMSO) cellular contents have been frequently observed in cellular stress conditions. To test this, we have first analysed the natural distribution of DMS(P,O) cellular contents in the North Sea. Secondly, we have measured DMS(P,O) cellular contents in monospecific cultures of several key species of the North Sea and their responses to salinity variations. Our main working hypothesis is that DMSP acts as an osmoregulator and/or as an antioxidant, depending on the species. The DMS(P,O) annual cycle in the Southern Bight of the North Sea revealed a seasonality linked to the spring phytoplankton communities succession: (1) colonial diatoms (reappearing in autumn), (2) Chaetoceros spp. (3) P. globosa, (4) large-size summer diatoms (mainly Guinardia spp.), and (5) dinoflagellates. Spatial gradients of DMS(P) were related to those of phytoplankton biomass, itself related to the inputs of nutrients from the Scheldt estuary. It also discharges suspended matter in which DMSO may have been produced by anaerobic oxidation of DMS. Laboratory measurements confirmed a large variability in DMSP cellular contents between the six studied diatoms (Nitzschia closterium, Skeletonema costatum, Thalassiosira rotula, Chaetoceros socialis, Chaetoceros debilis, and Guinardia delicatula), low producers in comparison with P. globosa and even more with Heterocapsa triquetra (Dinoflagellate). In particular, communities 2 and 4 have lower DMSP cellular contents than community 1 (N. closterium, S. costatum and T. rotula). Senescence induces a decrease in DMSP/DMSO suggesting an oxidative stress caused by nutrients and/or light limitation in DMSP producers. In S. costatum, DMSP seems to play an osmoregulatory role and is oxidised into DMSO in hyposaline conditions. In P. globosa and H. triquetra, an oxidative stress appears in hypo- and hypersaline conditions diverging from their salinity optimum.Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Cosme, Emmanuel. "Cycle du soufre des moyennes et hautes latitudes Sud dans un modèle de circulation générale atmosphérique." Phd thesis, Université Joseph Fourier (Grenoble), 2002. http://tel.archives-ouvertes.fr/tel-00705168.
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L'objectif de ce travail est de contribuer à la compréhension du cycle atmosphérique du soufre en Antarctique par l'utilisation d'un Modèle de Circulation Générale Atmosphérique (MCGA). Les versions "Antarctique" et "soufre" du MCGA LMD-ZT ("Laboratoire de Météorologie Dynamique- Zoom Traceurs") ont été fusionnées pour l'étude à haute résolution Antarctique du cycle du soufre dans les moyennes et hautes latitudes Sud. Une méthode de forçage "latéral" de la circulation atmosphérique antarctique par des analyses du Centre Européen de Prévision Météorologique à Moyen Terme (CEPMMT) a été spécifiquement développée et appliquée. Le modèle a d'abord été évalué. Il représente correctement le cycle saisonnier des espéces soufrées aux sites d'observation en Antarctique. Plusieurs défauts ont cependant été identifiés , discutés, et certains ont été étudiés par des expériences numériques spécifiques. Ceci nous a permis, dans la suite de ce travail, de décrire de manière critique le cycle du soufre en Antarctique à partir des résultats du modèle. Le modèle a été utilisé pour trois applications. La première a été une mise en oeuvre directe du modèle, tel qu'il a été évalué, dans le but d'estimer les distributions spatiales, le cycle saisonnier dans les régions centrales, et le bilan annuel des espèces soufrées en Antarctique. La deuxième se présente sous forme d'études de sensibilité à la formulation des émissions de sulfure de diméthyle (DMS) océanique, que la phase d'évaluation a révélé comme déterminante pour la modélisation du cycle du soufre. Pour la troisième, l'adjoint du modèle de transport (qui, en première approximation, permet de remonter le temps), complété par l'adjoint du module chimique spécifiquement développé pour ce travail, a été mis en oeuvre pour une recherche quantitative de l'origine géographlque et de l'âge des espèces soufrées en Antarctique.
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Hayashida, Hakase. "Modelling sea-ice and oceanic dimethylsulfide production and emissions in the Arctic." Thesis, 2018. https://dspace.library.uvic.ca//handle/1828/10486.
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Recent field observations suggest that the radiative forcing of aerosol and clouds in the Arctic may be seasonally regulated by the oceanic emissions of the climatically-important biogenic trace gas dimethylsulfide (DMS). However, the validity of the proposed argument is challenged by the limited spatio-temporal coverage of these earlier studies in this difficult-to-access region. In particular, little is known about the pan-Arctic distribution of the oceanic DMS emissions, its temporal variability, and the impacts of sea-ice biogeochemistry on these emissions. In this dissertation, I investigated these unexplored subjects through numerical modelling. Using a one-dimensional (1-D) column modelling framework, I developed a coupled sea ice-ocean biogeochemical model and assessed the impacts of bottom-ice algae ecosystems on the underlying pelagic ecosystems and the associated production and emissions of DMS. The model was calibrated by time-series measurements of snow and melt-pond depth, ice thickness, bottom-ice and under-ice concentrations of chlorophyll-a and dimethylsulfoniopropionate (DMSP), and under-ice irradiance obtained on the first-year landfast sea ice in Resolute Passage during May-June of 2010. Many of the model parameters for the DMSP and DMS production and removal processes were derived from recent field measurements in the Arctic, which is advantageous over the previous Arctic-focused DMS model studies as their model parameters were based on the measurements in extra-polar regions. The impacts of sea-ice biogeochemistry on the DMS production in the underlying water column and its potential emissions into the overlying atmosphere were quantified through sensitivity experiments. To extend the study domain to the pan-Arctic, I implemented the sea-ice ecosystem and the coupled sea ice-pelagic DMS cycling components of the 1-D column model into a three-dimensional (3-D) regional modelling framework. A multi-decadal model simulation was performed over the period 1969-2015 using realistic atmospheric forcing and lateral boundary conditions. The results of the simulation were evaluated by direct comparisons with available data products and reported values based on field and satellite measurements and other model simulations. The decline of Arctic sea ice was successfully simulated by the model. The magnitude of the pan-Arctic sea-ice and pelagic annual primary production and their general spatial patterns were comparable to other model studies. The mean seasonal cycle and the spatial distribution of the model-based surface seawater DMS climatology within the pan-Arctic showed some similarities with in situ measurement- and satellite-based climatologies. However, at the same time, the comparison of the DMS climatologies was challenged by the bias in the measurement-based climatology, emphasizing the need to update this data product, which was created almost a decade ago, by incorporating data acquired during the recent field campaigns. The analysis of the modelled fluxes of DMS at the ice-sea and sea-air interfaces revealed different responses to the accelerated decline of sea ice over the recent decades (1996-2015). There was no trend in the pan-Arctic ice-to-sea DMS flux due to the counteracting effect of vertical thinning and horizontal shrinking of sea ice that drove ice algal production. In contrast, the pan-Arctic sea-to-air DMS flux showed a consistent increase (about 40 % over the last two decades) driven by the reduction of sea ice cover that promoted outgassing and biological productivity. This finding suggests that the climate warming in the Arctic causes an increase in DMS emissions, and encourages further exploration of the biological climate regulation in the Arctic.Graduate
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陳鈺芳. "Surface Characterization and Platelet Adhesion Studies of Plasma Polymerized of Trimethylphosphite, Triisopropylphosphite and Dimethylsulfate thin films." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/59456364910175502884.
Full textAbstract:
碩士國立成功大學
化學工程研究所
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Plasma surface modification has been shown to modify the surface properties without altering the physical properties of teh substrates. Meanwhile, sev eral studies have indicated the blood interactions with the artificial surfaces were altered with the addition of phosphorus - containing functionalities on the surface. Henceforth, plasma surface modification using trimethylphosphite. Henceforth, plasma surface modification using trimethylphosphite ((CH3O)3P) or triisopropylphosphite ((CH3)2CHO)3P) as the monomer source were investigated with an aim to improve the blood compatbility of the substrate, cover glass. Various surface characterization techniques, such as ATR - FTIR, ESCA, SEM and contact angle measurement, were carried out to evaluate the surface properties of the films formed under different processing conditions (e. g. plasma pressure, RF power, treatmetn time duration, monomer mass flow rate etc.). ATR - FTR and ESCA results indicated phosphorus - containing functionalities, such as phosphate or phosphite, were formed at all plasma polymers studied. In addition, ESCA and SEM results have shown a smooth, continuous plasma polymerized thin film was formed at 400 mtorr, 20 watts and 20 minutes treatment conditions for trimethylphosphite, and at 250 mtorr, 20 watts and 10 minutes for triisopropylphosphite. Films formed at lower pressure, lower power, shorter treatment duration were discontinuous. The smooth plasma polymerized thin films were damaged while the RF power or treatment time was further increased than the optimum film formation condition. Contact angle measurement indicated the contact angle values of these thin films at the optimum film formation conditions were 6.3° and 8.5° for the plasma polymerized trimethylphosphite and plasma polymerized trissopropylphosphite, respectively. In vitro platelet adhesion studies showed less platelet adhesion, less platelet aggregation and less platelet activation on the thin films created at the optimum film formation conditions than on the cover glass control and others formed at different plasma processing conditions. Furthermore, plasma copolymerization of trissopropylphosphite and dimethylsulfate ( (CH3O)2SO2), suing cover glass as the substrate, was studied in order to incorporate both phosphorous - containgin and sulfur - contaning functionalities onto the thin film surface. An optimum film formation condition was found at 310 mtorr, 20 watts and 10 minutes plasma treatment duration while the mass flow rate of trisopropylphosphite was fixed at the rate which made the process pressure reading 250 mtorr initially. Contact angle value of this thin film is only 4.7°, which is more hydrophilic than the plasma polymerized triisopropylphosphite thin film. In yitro platelet adhesion studies have shown this plasma copolymerized thin film is more platelet compatible than either plasma polymerized triisopropylphosphite or trimethylphosphite thin films.
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Kettle, A. James. "Extrapolations of the flux of dimethylsulfide, carbon monoxide, carbonyl sulfide, and carbon disulfide from the oceans /." 2000. http://wwwlib.umi.com/cr/yorku/fullcit?pNQ59143.
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Thesis (Ph. D.)--York University, 2000. Graduate Programme in Chemistry.Typescript. Includes bibliographical references (leaves 370-416). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ59143
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Tesdal, Jan-Erik. "The spatial and temporal distribution of oceanic dimethylsulfide and its effects on atmospheric composition and aerosol forcing." Thesis, 2014. http://hdl.handle.net/1828/5676.
Full textAbstract:
The ocean emission and subsequent oxidation of dimethylsulfide (DMS) provides a source of sulfate in the atmosphere, potentially affecting the amount of solar radiation reaching the Earth's surface through both direct and indirect radiative effects of sulfate aerosols. DMS in the ocean can be quite variable with season and location, which in turn leads to high spatial and temporal variability of ocean DMS emissions. This study tested currently available observational and empirically-based climatologies of DMS concentration in the surface ocean. The exploration of the existing parameterizations mainly reveals the limitations of estimating DMS with an empirical model based on variables such as chlorophyll and mixed layer depth. The different algorithms show significant differences in spatial pattern, and none correlate strongly with observations. There is considerable uncertainty both in terms of the spatiotemporal distribution in DMS concentration and flux, as well as in the global total DMS flux. The present research investigates the influence of DMS on sulfate aerosols and radiative fluxes given different DMS climatologies in the fourth generation of the Canadian Global Atmospheric Climate Model (CanAM4.1). In general, the response in the radiative flux seems to follow the variation in the global mean flux of DMS linearly. Differences in the spatial and temporal structure of oceanic DMS have only a secondary effect on the radiative changes. The overall response of the atmosphere to the presence or absence of structure of DMS in space and time is distinctly smaller compared to the possible uncertainty of this response associated with the magnitude of the annually averaged global flux.Graduate
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0725
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jetesdal@uvic.ca
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Moreira, Cláudia Sofia Pombo da Fonseca. "Contribution to the chemoreception capacity of juvenile Loggerhead sea turtles (Caretta caretta, L.)." Master's thesis, 2010. http://hdl.handle.net/10400.13/393.
Full textAbstract:
Loggerhead sea turtle juveniles (Caretta caretta), pelagic stage, are found in waters of Madeira archipelago. Pelagic turtles are in the main growth phase of their life cycle and consequently higher energy needs. However, knowledge about the ecology of pelagic loggerhead sea turtles is still quite rudimentary, mainly about the mechanisms that lead them to find food in the vast ocean.
Studies with other pelagic species, such as procellariiform birds, revealed that the olfactory system play an important role for the detection of feeding areas, through the detection of concentration peaks of DMS (dimethylsulfide), a scent compound that naturally exists in the marine environment and it is related to areas of high productivity. Based on the assumption that loggerhead sea turtles use a similar mechanism, behavioural experiments were conducted in order to analyze the chemoreception capacity to DMS (airborne chemoreception - theoretically responsible for the long distance detection of areas with food patches; and aquatic chemoreception - theoretically responsible for the short distance detection of preys). The first step was to observe if pelagic loggerheads demonstrate sensitivity to DMS and the second was to verify if they really use the DMS, in natural conditions, as an airborne cue to find areas where food patches might be available.
Four juveniles of loggerhead sea turtles were tested in captivity and three wild turtles in the open ocean. The results of airborne chemoreception experiments in captivity revealed that one turtle clearly demonstrated sensitivity to DMS and the sea experiments confirmed this result. However, the experiments were not conclusive on the question whether the pelagic turtles actually use the DMS as an airborne cue to detect long distance food patches. In aquatic chemoreception experiments was not observed sensitivity to DMS by the three sea turtles tested. In the classical conditioning experiment, where DMS and food were given nearly at the same time revealed that after a certain period of time, the sea turtle tested did not associated the DMS stimulus with a possible food reward.
The main cause of mortality of loggerhead sea turtles in Madeira waters is due to the accidental capture (bycatch) by deep pelagic longlines fishery which the target species is the black-scabbard (Aphanopus carbo) fish. Chub mackerel (Scomber japonicus) is one of the baits used in this fishery. Aquatic chemoreception experiments were conducted in order to evaluate the attractiveness of the chub mackerel for sea turtles. For the three sea turtles tested, the results showed that in 90% of the cases the sea turtles were extremely attracted by the underwater smell of this fish.Centro de Ciências e Tecnologia da Madeira