Dissertations / Theses on the topic 'Carbon transfer'
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M, Higgins Eleanor. "Proton transfer at carbon." Thesis, Durham University, 2007. http://etheses.dur.ac.uk/2640/.
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This thesis describes the determination of the pKa values of a number of carbon acids in 020 at 25 oc and fixed ionic strength (KCl). Second-order rate constants for the deprotonation of these carbon acids by deuteroxide ion k00 (M-1s- 1), in 0 20 at 25 oc were determined by 1H NMR spectroscopy. These k00 values could be used to calculate values for kHo (M-1s- 1), the second-order rate constant for deprotonation of the carbon acid by hydroxide ion to give the corresponding conjugate base in water. This thesis deals with three different groups of carbon acids: the conjugate acids of N-heterocyclic carbenes, diketopiperazines, and thalidomide and thalidomide analogues. Oiaminocarbenes are of significant interest as ligands in organometallic catalysis and in medicinal chemistry. The syntheses and determination of the pKa values of a series of the azolium ions including 1,3-disubstituted imidazolium ions, 4,5~dihydroimidazolium ions, and 3,4,5-trihydropyrimidinium ions are described. Values for kHo (M-ls- 1), the second order-rate constant for deprotonation at C2 of each azolium ion, were determined as described above. Evidence is presented that the reverse rate constant for carbine protonation by solvent water is limited by solvent reorganization and occurs with a rateconstant of kHoH = kreorg =1011 s- 1. Values for kHo and kHoH permitted the calculation ofreliable carbon acid pKas for ionization of the azolium ions in water. The effects of the N-substituents and ring size of the heterocycle on kHo and pKa values are discussed. The relative hydrolytic stabilities of the azolium ions is also discussed. Oiketopiperazines (DKPs) are an important class of biological compound. The synthesis and determination of the pKa values of bis-0-proline and bis-L-proline diketopiperazine are described. Values for kHo (M- 1s- 1), the second order-rate constant for deprotonation at the a-carbon of the OKP were determined as described above. Evidence is presented that the reverse rate of protonation of the OKP enolates by solvent water is likely to be less than diffusion controlled. Hence, the pKa values were determined by extrapolation from a Bremsted plot of log kHo values against pKa values of other neutral simple carbon acids. The OKP kHo and pKa values are compared with analogous values for acyclic peptide analogues. Thalidomide and analogues such as the chemokine inhibitors, N-(2-0xo-piperidine-3yl)propionamide and N-(2-0xo-azapan-3-yl)propionamide, have been of considerable interest to the pharmaceutical industry for some time. Determination of the rates of hydrolysis and the pKa values for thalidomide and the analogues in 0 20 at 25oC and fixed ionic strength (KCl) are described. The pKa values were determined from a Bronsted plot of log kHo values against pKa of other neutral simple carbon acids in a similar manner to that performed for the diketopiperazines. The rates of hydrolysis and the relative stereo integrity of the species are discussed.
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Moore, D. R. "Carbon transfer in liquid sodium." Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371130.
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Paton, Keith Richard. "Electromagnetic energy transfer into carbon nanotubes." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608860.
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Viel, David William. "Muon transfer from muonic deuterium to carbon." W&M ScholarWorks, 1994. https://scholarworks.wm.edu/etd/1539623853.
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Negative muons were brought to rest in a gas mixture of 30 torr CH$\sb4$ and 570 torr D$\sb2$, using the cyclotron trap at PSI. The muons formed muonic deuterium atoms which diffused through the mixture and transferred their muons to the carbon of the CH$\sb4$ molecules. A planar germanium detector and a silicon detector were used to observe x-rays from the initial muon cascade in the deuterium, and from subsequent cascade in the muonic carbon after transfer. A transfer rate of (4.5 $\pm$ 1.8) $\times$ 10$\sp{10}$/sec was found which agrees well with a previous result measured at 50 bar of (5.1 $\pm$ 1.0) $\times$ 10$\sp{10}$/sec. Transfer was found to occur predominantly to the n = 4 state in $\mu$C. The initial angular momentum state distribution in the $\mu$C was constructed using the cascade program of V. Markushin, and found to be consistent with any combination of two possible initial distributions (I 0.252 (4s) + 0.409 (4f) + 0.339 (4p)) and (II 0.284 (4d)+ 0.377 (4f) + 0.339 (4p)). The transfer theories of Gershtein and that of Holtzwarth and Pfeifer both agree well with the measured transfer rate and initial energy state, but not with the initial angular momentum distributions. The 2S population in $\mu$C was also determined to lie between 5% and 11%, which is higher than the 3% population in direct capture.
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Carney, Kevin. "Supercritical Carbon Dioxide Extraction." DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1755.
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The objective of this thesis is to explore the properties of supercritical carbon dioxide (CO2). In addition, the feasibility of building a small-scale low cost system will be explained. A supercritical fluid is a fluid which exhibits properties between liquid and gas with liquid like densities and viscosities similar to a gas. Since the discovery of supercritical fluids in 1822, the use of supercritical fluids, specifically supercritical CO2, has grown in popularity. The application of supercritical CO2 has continued to grow in industrial applications since the 1970’s. Supercritical CO2’s has many beneficial properties as a “green” solvent. Supercritical CO2 as a solvent is able to be implemented in a wide range of applications from aerospace, microchip manufacturing, food production, biomedical, pharmaceutical, dry-cleaning, and many more.
This thesis project included designing, building and testing a supercritical CO2 extraction apparatus that examines the use of supercritical CO2 as a solvent in the extraction process of decaffeinating coffee. Due to the fact that supercritical CO2 requires high pressure operating conditions, the apparatus design is important not only for function but also for safety. In the description portion of this paper, design considerations related to each component’s function and their specific roles in the overall system are clearly stated. Furthermore, the build process is outlined along with the overall step-by-step operation of the apparatus.
Different methods of data measurements are taken while the system is running, in order to interpret the apparatus’ overall functionality. Through the exploration of this experimental data, the results were compared between different operating parameters. In order to determine the feasibility of the supercritical apparatus, the devise was tested by applying the supercritical CO2 as a solvent for the extraction of caffeine from coffee beans. Analysis of the analytical data recorded from experimental testing confirms that the apparatus produced supercritical CO2. After testing specific operating conditions, it is proven that the supercritical CO2 is able to function as a “green” solvent in this small-scale system. The experimental results from these analytical runs are compared with theoretical maximums in order to determine the efficiency of the devise.
Lastly, the paper presents an overview including lessons learned from the design process and from the information gathered. Data from experimental testing is interpreted and the system design is reevaluated with suggestions for future improvements.
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Gregory, Alison Jane. "Carbon transfer from barley to barley powdery mildew." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359174.
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Beachey, Adam. "Electron transfer in protein-carbon nanotube hybrid structures." Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/111309/.
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We have developed a method of site-specific attachment of proteins to pristine carbon nanotube (CNT) sidewalls using genetically encoded unnatural amino acids with functional moieties. Here, we incorporated an azido phenylalanine (AzPhe) group at different positions in the protein to assess the importance of different protein-CN configurations. This site-directed mutation of the protein structure has provided routes for direct covalent attachment to the sidewall of the CNT, as well as providing a functional group for modification with another molecule such as pyrene for non-covalent CNT attachment. We have employed a variety of techniques to study these nanoscale systems in order to gain an insight into the binding mechanism, the protein-CNT interaction dynamics and their electronic properties. Using atomic force microscopy (AFM), we found that the proteins bind regular patterns dictated by the position of the phenyl azide. By integrating CNTs into electrical transistor-like devices, we have performed electrical measurements across the CNTs to monitor the attachment of various proteins to the CNT sidewalls. Using these protein-CNT systems, we have also been able to study the interaction between proteins and CNTs using Raman spectroscopy and total internal reflection fluorescence microscopy (TIRFM). Here we present evidence of covalent attachment of proteins to CNTs using Raman spectroscopy to study the changes in vibrational modes present in the CNTs. TIRFM has provided evidence of post cross-linking activity of proteins on CNTs using super-folder green fluorescent protein (sfGFP) as a marker. By analysing the protein's fluorescent properties, we have produced evidence suggesting the importance of the orientation of the protein with respect to the CNT, which in turn determines the distance between the CNT interface and the active site of the protein. The approach developed here provides a versatile and convenient generic approach to interfacing proteins, in defined orientations, to CNTs that holds promise for exploitation in bioelectronics tools and biomolecular sensors.
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Abu, Hajer Ahmad. "Enhancing an Air to Liquid Mass Transfer Unit." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1573875898139361.
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Delport, Géraud. "Non-convalent functionalization of carbon nanotubes : From the organization of surfactants to the self-assembly ofporphyrins." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLN075/document.
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Ce manuscrit présente une étude expérimentale sur le processus de recouvrement de nanotubes de carbone mono parois en suspension micellaire par des molécules de colorants organiques. En raison des propriétés électroniques exceptionnelles et de la structure chimique carbonée de ces nanotubes, une modification de leur environnement physico-chimique a une grande influence sur leurs propriétés optoélectroniques. Les conséquences de cette fonctionnalisation de surface sont étudiées par des techniques de spectroscopie optique. Le procédé de fonctionnalisation non covalente de nanotubes par des molécules de porphyrines en milieu micellaire est détaillé selon trois axes de recherches complémentaires. Dans un premier temps, les aspects cinétiques de ce processus réactionnels seront discutés. En particulier, le rôle de l'organisation de l'environnement micellaire est mis en évidence. Cela permet de comprendre et de contrôler la durée de la réaction. Une étude thermodynamique de l'interaction nanotube/porphyrines sera ensuite détaillée. Le comportement associatif des porphyrines au cours de leur interaction avec le nanotube sera démontré. Dans un troisième chapitre, les caractéristiques spectrales de la porphyrine lorsqu'elle est adsorbée sur la surface de carbone seront discutées. Un modèle de couplage dipôle- dipôle est développé pour comprendre ces effets. Ce modèle permet de mettre en évidenceThis manuscript presents an experimental study on the process of coverage of single-wall carbon nanotubes by organic dyes molecules. Due to the exceptional electronic properties and the monolayer carbon structures of such nanotubes, a modification of their physico-chemical environment has a great influence on their optoelectronic properties. The consequences of this surface functionalization are studied by means of optical spectroscopy. The process of non covalent functionalization of surfactant suspended nanotubes by porphyrin molecules is separated in three complementary studies. The first one details the kinetic aspects of this reaction process. In particular, the role of the organization of the surfactant environment will be highlighted. This allows to understand and control the reaction timescale. On the second hand, a comprehensive thermodynamic study of the nanotube/porphyrins interaction is performed. The associative behavior of the porphyrin during the interaction with the nanotube is evidenced. Then, the spectral characteristics of the porphyrin when it is adsorbed on a carbon surface is discussed. A dipole-dipole coupling model is developed to understand such effects. This model allows to highlight the geometry followed by the molecules when they are organized on the carbon template (nanotube or graphene)
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Fedorenko, O. O., and J. K. Warchoł. "Structural and mass transfer characteristics of carbon-fiber materials." Thesis, Київський національний університет технологій та дизайну, 2017. https://er.knutd.edu.ua/handle/123456789/6750.
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Pierce, Matthew Ryan. "Microvascular Heat Transfer Analysis in Carbon Fiber Composite Materials." University of Dayton / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1280944914.
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Parlapalli, Rohit. "Effect of twist on load transfer and tensile strength in carbon nanotube bundles." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1382372894.
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Hu, Tao. "Non-covalent functionalization of carbon nanostructures : a DFT study." Thesis, Toulouse, INSA, 2013. http://www.theses.fr/2013ISAT0011/document.
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Le dopage non covalent de nanostructures carbonées par transfert de charge depuis/vers des molécules donneuses ou acceptrices (EDA) ou bien par des molécules d’acide sulfurique H2SO4, est considéré comme potentiellement intéressant pour de nombreuses applications. Parmi celles-ci on peut citer: capteur chimique, transistor à effet de champ, et d’autre l'électronique. Cependant, d'un point de vue théorique, on en sait peu au sujet de ces processus de transfert de charge par électrons ou par trous.Dans un premier temps, nous nous sommes intéressés à l’interaction entre des molécules d’acide sulfurique et des nanostructures modèles, car elles sont capables de doper des nanotubes, de s’intercaler dans le graphite et même d’aligner les tubes dans une phase nématique, ce qui pourrait mener à la création de matériaux composites à forte valeur ajoutée.Bien que certaines études théoriques DFT ont été menées récemment, leurs résultats restent source de confusion. Par exemple, même s’il est rapporté un transfert de charge entre une molécule de H2SO4 et un plan de graphène, tous nos efforts pour reproduire ces calculs ont été infructueux. Nous proposons dans ce travail de thèse, un mécanisme de réaction qui expliquent la "protonation" des parois du tube, tel que proposé dans la littérature. Enfin nous proposons un scénario possible pour une meilleure compréhension de la structuration à grande échelle des molécules d'acide autour de points d'ancrage, telles que des défauts, de la structure carbonéeNon-covalent doping of carbon nanostructures by charge transfer from/to donor/acceptor molecules (EDA) or by H2SO4 molecules, be it with holes or electrons, is usually thought as potentially interesting for many applications of carbon based nano-devices. However, from a theoretical point of view, little is known about such “charge transfer” processes.Employing first-principles method based on Density Functional Theory (DFT), we have studied in details, and proposed a model to rationalize, the interaction between a prototypical donor molecule the tetrathiafulvalene (TTF), a standard acceptor organic molecule, tetracyanoethylene (TCNE) and carbon nanostructures: graphene layer and SWNTs with various chiral indices. Main results concern structural and thermodynamic aspects including dispersion forces effects, and evidently electronic structure modifications of the nanostructures. Various adsorption modes and concentration effects have been investigated. At very low coverage values, we have reported a charge transfer between graphene and TCNE or TTF. Moreover, we have shown that the charge transfer can be enhanced by increasing the concentration of those two EDA molecules, as it has been demonstrated experimentally. Those results are beneficial for comprehending the nonchemical doping mechanism in graphene structure by means of charge transfers. Considering the interaction between these prototypical molecules and carbon nanotubes, we have found that charge transfers tend to decrease while the curvature of nanotube is increasing. Besides, a strong influence of the metallic/semi-conductor character of the SWNTs can be observed and be explained by the change of polarisability of the curved carboneous substrates. Additionally, we have studied the adsorption properties of sulfuric acid molecules, in its non-hydrated form, on carboneous nanostructures. Against the common believe, no charge transfer is observed in the H2SO4@graphene or H2SO4@CNTs cases, even at very high concentrations. Instead, in order to elucidate the origin of p-doping observed experimentally, we have proposed that molecule is responsible of the reversible doping. Besides we have shown that a proton transfer could cause the experimental phenomenon of crystallization of H2SO4 molecules on SWNT’s surface. Finally in such process, defects like vacancy are of first importance, since they could provide anchorage points for hydrogen atoms. The results of the present work will certainly help to understand the charge transfer and doping mechanism of carbon nanostructures by means of non-covalent functionalization, which is a promising method for their future applications
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Faithfull, Carolyn. "Productivity and carbon transfer in pelagic food webs in response to carbon, nutrients and light." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-43467.
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Some of the major problems we face today are human induced changes to the nitrogen (N), phosphorus (P) and carbon (C) cycles. Predicted increases in rainfall and temperature due to climate change, may also increase dissolved organic matter (DOM) inflows to freshwater ecosystems in the boreal zone. N, P, C and light, are essential resources that most often limit phytoplankton (PPr) and bacterial production (BP) in the pelagic zone of lakes. PPr and BP not only constitute the total basal C resource for the pelagic aquatic food web, but also influence ecosystem function and biogeochemical cycles. In this thesis I studied how N, P, C and light affect the relative and absolute rates of PPr and BP, along a wide latitudinal and trophic gradient using published data, and in two in situ mesocosm experiments in a clear water oligotrophic lake. In the experiments I manipulated bottom-up drivers of production and top-down predation to examine how these factors interact to affect pelagic food web structure and function. The most important predictors of PPr globally (Paper I) were latitude, TN, and lake shape. Latitude alone explained the most variation in areal (50%) and volumetric (40%) PPr. In terms of nutrients PPr was primarily N-limited and BP was P-limited. Therefore bacteria and phytoplankton were not directly competing for nutrients. BP:PPr was mostly driven by PPr, therefore light, N, temperature and other factors affecting PPr controlled this ratio. PPr was positively correlated with temperature, but not BP, consequently, higher temperatures may reduce BP:PPr and hence the amount of energy mobilised through the microbial food web on a global scale. In papers II and III interaction effects were found between C-additions and top-down predation by young-of-the-year (YOY) perch. Selective predation by fish on copepods influenced the fate of labile C-addition, as rotifer biomass increased with C-addition, but only when fish were absent. Interaction effects between these top-down and bottom-up drivers were evident in middle of the food web, which is seldom examined in this type of study. Although the energy pathway from bacteria to higher consumers is generally longer than from phytoplankton to higher trophic levels, increased BP still stimulated the biomass of rotifers, calanoid copepods and YOY fish. However, this appeared to be mediated by intermediate bacterial grazers such as flagellates and ciliates. Light was an important driver of crustacean zooplankton biomass (paper IV), but the light:nutrient hypothesis was inadequate to predict the mechanisms behind the decrease in zooplankton biomass at low light. Instead, it appeared that reduced edibility of the phytoplankton community under low light conditions and reduced BP most strongly affected zooplankton biomass. Thus, the LNH may not apply in oligotrophic lakes where PPr is primarily N-limited, Daphnia is rare or absent and mixotrophic phytoplankton are abundant. N, P, C and light manipulations have very different effects on different parts of the pelagic food web. They influence the relative rates of PPr and BP, affect phytoplankton community composition, alter the biomass of higher trophic levels and change pathways of energy transfer through the pelagic food web. This thesis adds valuable information as to how major changes in these resources will affect food web structure and function under different environmental conditions and future climate scenarios.Lake ecosystem response to environmental change
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Lansangan, Roberto M. "Gravitationally induced mass transfer of carbon dioxide in hydrocarbon liquids /." Access abstract and link to full text, 1986. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/8703999.
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Cross, Robert. "Processing of vertically aligned carbon nanotubes for heat transfer applications." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/31828.
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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Graham, Samuel; Committee Member: Das, Suman; Committee Member: Joshi, Yogendra. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Bowling, Robert John. "Effects of microstructure on heterogeneous electron transfer at carbon electrodes /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487671108306195.
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DuVall, Stacy Hunt. "Electron transfer kinetics of catechols on modified glassy carbon electrodes /." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488199501404497.
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Liao, Shengming. "Heat transfer of supercritical carbon dioxide in MINI/MICRO tubes /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?MECH%202002%20LIAO.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 145-150). Also available in electronic version. Access restricted to campus users.
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Miller, Jacob. "Modelling the Effect of Catalysis on Membrane Contactor Mass Transfer Coefficients for Carbon Dioxide Absorption Systems." University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1627662756315225.
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Noon, Michael S. "Mass transfer of near critical carbon dioxide in poly(methyl methacrylate)." Connect to resource, 2007. http://hdl.handle.net/1811/25012.
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Thesis (Honors)--Ohio State University, 2007.Title from first page of PDF file. Document formatted into pages: contains vii, 28 p.; also includes graphics. Includes bibliographical references (p. 26-28). Available online via Ohio State University's Knowledge Bank.
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Keller, Klaus 1966. "Chemical enhancement of carbon dioxide transfer across the air-sea interface." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/35997.
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Vijaya, Kumar Supradeep. "Measurement of Carbon Dioxide Mass Transfer Rate for Three Membrane Morphologies." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1399388795.
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Chen, Peihong. "Effects of surface chemistry on electron transfer kinetics at carbon electrodes /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487935573773327.
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Coularis, Cindy. "Dynamique et transfert du carbone dans le bassin versant de la Loire : Traçage par les isotopes du carbone." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS132.
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Cette thèse présente une étude du cycle du carbone dans la Loire et ses principaux affluents dans le but (1) de décrire, en s’appuyant sur la composition isotopique (14C et 13C), les sources, la nature et l’âge du Carbone Inorganique et Organique Dissous (CID, COD) et du Carbone Organique Particulaire (COP) prélevés lors de quatre missions en 2013-2014 et (2) d’utiliser le carbone 14 anthropique, présent dans les rejets liquides des 5 Centres Nucléaires de Production d’Electricité (CNPE) en service sur le bassin, comme traceur de transfert de carbone entre les différentes phases.Les archéologues ont mis en évidence que les âges radiocarbone déterminés sur des échantillons d’os ou de matériels non-humains (poteries, céramiques, sédiments…) ne sont pas à l’équilibre avec l’atmosphère de l’époque et nécessitent une correction. Ce biais provient de l’âge de l’eau ingérée ou utilisée et plus précisément de l’âge du CID appelé âge réservoir. Dans la Loire et ses affluents, le CID est principalement issu de l’érosion et de la dissolution du substrat géologique. Les concentrations en CID sont plus élevées en terrain sédimentaire carbonaté localisé en Loire moyenne. Les âges réservoirs étant directement corrélés à la teneur en CID, ils présentent une grande variabilité spatiale (de 135 à 2251 années 14C) du fait de la traversée de zones géologiques plus ou moins carbonatées par la Loire et ses affluents.Par ailleurs, ce CID est principalement consommé lors des processus photosynthétiques pour produire le COP algal. Ce COP algal est l’une des deux composantes de la matière organique (MO) particulaire avec le COP détritique. Les concentrations en COP suivent un cycle temporel très marqué avec des teneurs plus élevées au printemps. Le marquage du carbone algal dépend de la signature isotopique du CID utilisé lors de la synthèse chlorophyllienne. Les âges réservoirs déterminés dans le COP varient alors entre 124 et 1597 années 14C avec une variation spatio-temporelle identique à celle observée dans le CID. La proportion de carbone algal, variant entre 2 et 100%, dépend de la rivière et des conditions climatiques et hydrologiques sans qu’il soit possible d’énoncer une règle générale. La composante détritique du COP possède un marquage proche du COP et du COP algal impliquant que ce carbone détritique n’est pas d’origine géologique et donc qu’il n’est pas réfractaire.La décomposition de cette MO particulaire est une source de COD au même titre que l’activité métabolique des organismes (lyse et exsudation) et l’apport de vieille MO par la rivière, le lessivage des sols ou les nappes souterraines. Les concentrations en COD suivent donc les mêmes cycles saisonniers que le COP. Cependant, les teneurs sont plus élevées que celles du COP et augmentent peu le long des rivières (±1mg/L). Il peut être âgé si le COP et/ou la MO exportée sont anciens. Ainsi, les âges réservoirs dans le COD sont compris entre 101 et 2494 années 14C en avril 2013 avec des âges plus vieux en zone agricole.L’utilisation du radiocarbone anthropique a permis, outre la visualisation des transferts entre les différentes phases, de confirmer l’émission de 14C enrichi (ou actif) sous la forme CID par les CNPE et infirmer celle d’une composante 14C anthropique actif dans le COP et le COD. Cependant, l’activité 14C du CID ne représente pas l’activité totale du rejet en raison des échanges eau-atmosphère induisant un flux sortant de 14C. Le COP marqué enregistre l’activité initiale du rejet liquide en utilisant le CID émis par les CNPE. Le COP étant isolé de l’atmosphère, l’activité mesurée dans le COP est proche de son activité d’origine dans le rejet.L’acquisition de toutes ces données et la compréhension des processus de transferts entre CID, COP et COD permettra d’améliorer le modèle de prédiction existant et à terme, d’anticiper le comportement de ce radionucléide dans le milieu récepteur de son émission à son arrivée dans l’estuaire puis dans l’Océan AtlantiqueThis thesis focuses on carbon cycle in the Loire River and its major tributaries. It aims to (1) use isotopic composition (14C and 13C) to describe the sources, the nature and the age of the Dissolved Inorganic and Organic Carbon (DIC, DOC) and of the Particular Organic Carbon (POC) sampled during four campaigns in 2013 and 2014; and (2) to use anthropogenic 14C found in the liquid releases of the 5 Nuclear Power Plants (NPP) operating in the basin as a tool to track carbon transfer between the different phases.Archaeologists demonstrated that 14C ages of samples coming from bones or non-human material (potteries, ceramics, sediments,…) are not in balanced with the atmosphere of the time they were created and thus need to be corrected. This bias stems from the age of water (as beverage or raw material), and more precisely the DIC age, also known as reservoir age. In the Loire River and its tributaries, DIC mainly comes from erosion and dissolution of the geological substratum. DIC concentrations are higher in the carbonated areas located in the middle Loire. As the reservoir ages are directly related to the DIC content, their values present a wide spatial variability (from 135 to 2251 yr 14C BP) because the Loire River and its tributaries cross areas with variable content of carbonates among their geological formations.Also, DIC is mainly absorbed during photosynthetic processes that produce algal POC. Algal POC and detrital POC form the particulate organic matter (OM). POC concentrations follow a temporal cycle with higher values during Spring time. Algal carbon marking depends on the DIC isotopic signature used by the chlorophyll synthesis. Reservoir ages calculated from POC values range from 306 to 1597 14C years, with the same spatial and temporal variation as the DIC. Algal carbon ratio, ranging from 2 to 100%, depends on the river, and climatic and hydrologic conditions. However, no systematic pattern can be found. The detrital fraction of POC has an activity close to the activity of POC and algal POC involving that the component is not of geological origin and thus, it is not refractory.The decomposition of this particular OM, the metabolic activity of organisms (lysis and exudation) and the input of old OM from the river, the soil or the groundwater are all sources for DOC production. Thus, DOC concentrations follow the same seasonal pattern as the POC. However, DOC contents are higher than the POC ones, and increase a bit from upstream to downstream (±1mg/L). It can be aged if POC and/or exported OM are old. Thus reservoir ages in the DOC range from 101 to 2494 14C years in April 2013, with older ages in agricultural areas.Not only did the use of anthropogenic 14C made it possible to visualize transfers between different phases, but also it confirmed the emission of enriched 14CDIC and unconfirmed the emission of 14CPOC and 14CDOC by the NPP. However, the 14CDIC activity does not represent the complete activity of the release because of water-atmosphere exchange involving 14C outflow. The marked POC records the initial NPP liquid release activity using the DIC from the NPP. The POC being isolated from the atmosphere, the POC measured activity is close to the originate activity in the release.All these data combined to the understanding of the transfers processes between DIC, POC and DOC will make it possible to improve the existing prediction model and, eventually, to anticipate the behavior of this radionuclide in the river from its emission to its arrival in the estuary and then in the Atlantic Ocean
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Johnson, Alan M. "Relaxation of Vibrationally Excited Trifluorobenzene and Tetrafluorobenzene by Collisions with Carbon Dioxide." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/2177.
Full textAbstract:
An investigation into the relaxation of highly vibrationally excited trifluorobenzene and tetrafluorobenzene following collisions with carbon dioxide was performed using diode laser transient absorption spectroscopy. A 248 nm excimer laser prepared the vibrationally hot (E'~41,000 cm-1) fluorobenzene molecules. Large amounts of translational and rotational energy are transferred through collisions between the hot donor molecule and CO2. Rate constants and collisional probabilities were calculated by probing the high J states (J=58~80) of CO2 in the vibrational ground state, 0000, with measurements taken 1 µsec, ¼ the mean gas collision time, following each excimer laser pulse. The energy transfer probability distribution function, P(E,E'), was calculated for each molecule using the state-resolved probabilities and the energy gain of the bath. The study found a relationship between the fraction of strong collisions and the donor's dipole moment. Additionally, these findings support an application of Fermi's Golden rule to collisional energy transfer by linking the shape of P(E,E') to the shape of the donor's density of states as a function of ΔE.
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Hassan, Mohamed Abdel-Rahman Mohamed. "Flow boiling of pure and oil contaminated carbon dioxide as refrigerant : with focus on heat transfer and pressure drop /." Online version, 2004. http://bibpurl.oclc.org/web/31435.
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Vishwanath, Indushri Vikas. "Development of a Catalytic System for Air-to-Liquid Mass Transfer Mechanism." Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1479135783395588.
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Essenhigh, Katherine Anne. "Energy transfer and chemistry of carbon monoxide in vibrational mode non-equilibrium." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1124292824.
Full textAbstract:
Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xiv, 172 p.; also includes graphics (some col.). Includes bibliographical references (p. 167-172). Available online via OhioLINK's ETD Center
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Kendrick, Adrian Hugh. "Pulmonary transfer factor for carbon monoxide in exercise and its clinical applications." Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239917.
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Muchmore, Suzi. "Knowledge transfer : a qualitative investigation of the UK low carbon innovation system." Thesis, Loughborough University, 2018. https://dspace.lboro.ac.uk/2134/35118.
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Innovation programmes require organisations to transfer both technology and knowledge to the diverse actors who operate within innovation eco-systems. The changing relationship between science and society has witnessed the growth of public private partnerships (PPP) to create new knowledge, while also triggering the emergence of a new role for universities as catalysts for innovation. This brings many challenges, stemming from the inherent nature of knowledge and the complex interactions involved with inter-disciplinary knowledge transfer. Concurrently, these public-funded programmes come under increasing scrutiny to demonstrate greater societal and economic impact as a return on research investment. Knowledge generated within the UK low carbon energy innovation system has the potential to facilitate the achievement of national emission targets. However, while knowledge may be successfully created, there is no guarantee that it will be disseminated and utilised in a way that contributes to the achievement of knowledge-related objectives. Current literature concentrates on the micro level inhibitors and enablers of knowledge transfer; however, a gap in empirical work which investigates system level knowledge interactions is evident. Research and practical application in this field has historically centred on technology transfer whilst under-emphasising the crucial role of knowledge within this complex, socio-technical innovation system. The overall aim of this qualitative study is to achieve a better understanding of the influences of knowledge transfer across a defined innovation system. This is achieved through the perceptions of participants via two case studies; one in a PPP and one in a University. Semi-structured interviews were conducted with twenty-eight participants, along with document analysis and participant observation at workshops, to investigate the participant perceptions. A three tier (macro-, meso- and micro-level) data analysis approach was adopted to reflect the systems level interactions. The study found that knowledge transfer is often perceived as the dissemination of information via explicit forms of knowledge, which may or may not be used by stakeholders to achieve innovation objectives. The main barriers to stakeholders utilising knowledge included: accessibility to knowledge; fit-for-purpose knowledge; stakeholder motivation/ability to use the knowledge; and viewing knowledge as an object. While there is an emerging impact agenda in academia, cultural and normative influences direct researchers towards traditional academic outputs (e.g. publications). Knowledge utilisation by stakeholders was found to be maximised through relational, stakeholder driven models, which view knowledge as a process. Knowledge utilisation was context specific, and, due to complex system influences, was never guaranteed to occur. Although planning for knowledge utilisation was undertaken at both the PPP and the University, implementing and measuring results was found to be difficult due to dynamic system influences such as understanding stakeholder motivations, resourcing constraints and complexity in the desired project outcomes. This makes adaptability and responsiveness important qualities for knowledge producers, while also necessitating specific skill sets. Based on this work, a set of principles were developed which should guide more effective utilisation of knowledge and promote more impactful research outcomes.
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Khaliji, Oskouei Mohammadhasan. "Thermodynamic and heat transfer analysis of an activated carbon-R723 adsorption system." Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/95081/.
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The main challenge of adsorption systems today is to improve the performance of the thermal generator in order to make adsorption systems economically viable. The key novelty of this doctoral thesis is its evaluation of the potential use of a new refrigerant, R723, in an adsorption system using activated carbon as adsorbent. Granular activated carbon is a well-known and effective adsorbent in adsorption systems. The R723 refrigerant was introduced into the market in early 2004; this new refrigerant is an azeotropic mixture of 40% ammonia and 60% dimethyl ether by mass. The new refrigerant is compatible with copper alloy (Cu-Ni 90/10), in comparison with ammonia, which is only compatible with stainless steel. The high thermal conductivity of Cu-Ni 90/10 causes an improvement in heat exchange in the thermal generator. This work investigates the effect of granular activated carbon packed bed density on gas permeability. A correlation was found between granular activated carbon packing density and refrigerant pressure drop over the thermal generator. The porosity of granular activated carbon in terms of adsorbing the R723 was determined. The porosity was evaluated using the gas mixture adsorption theory and using the porosity experimental data for granular activated carbon / ammonia and granular activated carbon / dimethyl ether pairs. The performance of the adsorption system for different applications was determined with the activated carbon / R723 pair. The effects of concentration of R723 and granular activated carbon packing density on the thermal parameters of activated carbon packing, including the thermal conductivity and heat transfer coefficients of the contact wall/packed carbon, were studied simultaneously. A correlation was established showing the connection between the thermal parameters of the packed bed, and the concentration of R723 and the density of the granular activated carbon packed bed. Finally, this thesis demonstrates modelling procedures for a tubular generator with the granular activated carbon (208-C) / R723 pair, with regard to different applications such as air conditioning, ice making and a heat pump. The model under consideration included the ideal desorption effect without heat and mass recovery, while imposing the ideal temperature jump into the boundary of the tubular generator. During the modelling, information such as driving temperature (Tg), coefficient of performance (COP), and specific cooling and heating powers (SCP & SHP), was collected. The collected information was used to established a correlation in order to estimate the optimum driving temperature, COP, SHP and SCP, based on different governing parameters, such as granular activated carbon packing density, outside diameter (OD) and the length of the thermal generator. This information is useful in choosing the correct typical standard tube size of the thermal generator with the granular activated carbon (208-C) / R723 pair for specific applications, based on optimum governing parameters, such as the range of heat source availability and the power requirement. The other key point which was examined was the effect of tubular generator body material on COP and SCP (SHP) for different applications. The model used stainless steel and Cu-Ni 90/10 with standard wall thickness.
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Betts, Makayla N. (Makayla Nicole). "Gene transfer history of carbon fixation proteins constrains marine cyanobacteria divergence times." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/118026.
Full textAbstract:
Thesis: S.M. in Geophysics, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2018.Cataloged from PDF version of thesis. "June 2018."
Includes bibliographical references (pages 18-24).
Carboxysomes provide an avenue for narrowing the timing of evolutionary events in groups of cyanobacteria that are ecologically dominant in modem marine environments - groups that may have an integral role in oxygenating the Earth's atmosphere. Here I show that using concatenated phylogenies of carbon fixation proteins better informs the horizontal gene transfer event that brought carboxysomes from purple sulfur bacteria into marine cyanobacteria and that this gene history aids in constraining the evolutionary timing of carbon fixation. Genes encoding the proteins for the a-carboxysomal shell as well as RuBisCO and carbonic anhydrase are co-located on the genomes of various cyanobacteria in the Prochlorococcus and Synechococcus groups. Previous studies have shown that these genes were likely horizontally transferred together from Chromatiales (purple sulfur bacteria), a group of phototrophic Gammaproteobacteria. While many of these genes are highly conserved and thus yield poorly resolved phylogenies, their concatenation clarifies a shared evolutionary history. This work integrates gene transfer with molecular clock calibration methods to determine divergence times. Accordingly, I evaluate the relationship between atmospheric evolution and the ecology of important groups of phototrophs.
by Makayla N. Betts.
S.M. in Geophysics
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Rivero, Pacho Ángeles María. "Thermodynamic and heat transfer analysis of a carbon-ammonia adsorption heat pump." Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/66341/.
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The modelling, design, construction and experimental testing of a carbon-ammonia adsorption heat pump is presented. The main objective of the research was to computer simulate and test a 4-beds thermal wave adsorption cycle and to improve the heat transfer rate in an existing shell and tube generator. The existing generators were shell and tube type and were made of nickel brazed stainless steel but their heat transfer performance was poor. New heat exchangers with same design but larger in size were manufactured. The sorbent material, active carbon, was tested in order to characterise its thermal properties and a new generator filling technique was developed and presented. Computational modelling was carried out to evaluate the performance of the 4-beds thermal wave adsorption cycle. The proposed system was an air source heat pump that could deliver an output heating power of 7 kW and a seasonal heating COP of 1.47. The adsorption generators were tested in a 4-bed thermal wave air-source heat pump system and achieved heating output powers between 4.5 to 5.20 kW if taking into account the system heat losses (4.30 to 4.90 kW without heat losses) and heating COP’s of between 1.26 and 1.31 if taking into account the system heat losses (1.13 to 1.18 kW without heat losses). These values were significantly lower than the predicted performance of the simulation. The main cause of this discrepancy was the water distributors located at the end of the generators that distorted during the testing stage and blocked the tubes of the generators.
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Dahlgren, Kristin. "Food web structures and carbon transfer efficiencies in a brackish water ecosystem." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-38014.
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Two differently structured food webs can be distinguished in the pelagic habitat of aquatic systems; the classical one (autotrophic) with phytoplankton as a base and the microbial food web (heterotrophic) with bacteria as a base. Energy (produced at the basal trophic level) reaches higher trophic levels, i.e. zooplankton, directly in the classical food web in contrast to the microbial food web where it passes through additional trophic levels before reaching zooplankton. Energy is lost between each trophic level and therefore less energy should reach higher trophic levels in the microbial food web than in the classical food web. However, factors such as edibility of prey, temperature and properties of the predator, might also influence the food web structures and functions. In this thesis I studied which factors are important for an efficient carbon transfer and how a potential climate change might alter the food web efficiency in pelagic and pelagic-benthic food webs in the Baltic Sea. Furthermore, one of the most dominant zooplankton in the northern Baltic Sea, Limnocalanus macrurus, was studied in order to establish the seasonal pattern of lipid reserves in relation to food consumption. My studies showed that the carbon transfer efficiency during summer was not directly connected to the basal production, but factors such as the ratio between heterotrophs and autotrophs, the relationship between cladocerans and calanoid copepods and the size and community structure of both phytoplankton and zooplankton were important for the carbon transfer efficiency. In a climate change perspective, the temperature as well as the relative importance of the microbial food web is likely to increase. A temperature increase may have a positive effect on the pelagic food web efficiency, whereas increasing heterotrophy will have a negative effect on the pelagic and pelagic-benthic food web efficiency, reduce the fatty acid content of zooplankton and reduce the individual weight of both zooplankton and the benthic amphipod Monoporeia affinis. During the seasonal study on the calanoid copepod L. macrurus, I found that this species is mainly a carnivore, feeding on mesozooplankton during most of the year but switches to feeding on phytoplankton when these are abundant. Furthermore, when food is scarce, it utilizes lipids that are built up during the course of the year. From these studies I can draw some major conclusions; there are many factors that influence how efficient carbon is transferred in the food web and different factors are probably of various importance in different areas. In order to determine the carbon transfer efficiency, the various strategies exerted by different organism groups have to be considered, as for example that some zooplankton utilize lipid reserves instead of feeding all year around. Also, in a climate change perspective, the pelagic-benthic food web efficiency will decrease, as will the quality of zooplankton and M. affinis, possibly having implications for higher trophic levels such as fish.
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Cramer, Theodore A. "Membrane gas transfer of methane and carbon dioxide in submerged coal deposits." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1400969221&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Karabelchtchikova, Olga. "Fundamentals of Mass Transfer in Gas Carburizing." Digital WPI, 2007. https://digitalcommons.wpi.edu/etd-dissertations/424.
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"Gas carburizing is an important heat treatment process used for steel surface hardening of automotive and aerospace components. The quality of the carburized parts is determined by the hardness and the case depth required for a particular application. Despite its worldwide application, the current carburizing process performance faces some challenges in process control and variability. Case depth variability if often encountered in the carburized parts and may present problems with i) manufacturing quality rejections when tight tolerances are imposed or ii) insufficient mechanical properties and increased failure rate in service. The industrial approach to these problems often involves trial and error methods and empirical analysis, both of which are expensive, time consuming and, most importantly, rarely yield optimal solutions. The objective for this work was to develop a fundamental understanding of the mass transfer during gas carburizing process and to develop a strategy for the process control and optimization. The research methodology was based on both experimental work and theoretical developments, and included modeling the thermodynamics of the carburizing atmosphere with various enriching gasses, kinetics of mass transfer at the gas-steel interface and carbon diffusion in steel. The models accurately predict: 1) the atmosphere gas composition during the enriching stage of carburizing, 2) the kinetics of carbon transfer at the gas-steel surfaces, and 3) the carbon diffusion coefficient in steel for various process conditions and steel alloying. The above models and investigations were further combined to accurately predict the surface carbon concentration and the carbon concentration profile in the steel during the heat treatment process. Finally, these models were used to develop a methodology for the process optimization to minimize case depth variation, carburizing cycle time and total cycle cost. Application of this optimization technique provides a tradeoff between minimizing the case depth variation and total cycle cost and results in significant energy reduction by shortening cycle time and thereby enhancing carburizing furnace capacity."
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Pathak, Sayali V. "Enhanced Heat Transfer in Composite Materials." Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1368105955.
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Sakata, Mazuki. "Phase-transfer Catalyzed Asymmetric Synthesis of All-carbon Quaternary Centers and Tetrasubstituted Allenes." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/175139.
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Maligaspe, Eranda. "Carbon nanostructured based donor-acceptor conjugates for light-induced energy and electron transfer." Diss., Wichita State University, 2010. http://hdl.handle.net/10057/3636.
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The research presented in this dissertation deals with the syntheses, characterization, electrochemical, computational and photophysical studies of carbon nanostructures such fullerenes, single-wall carbon nanotubes (SWCNT) and highly colored pigment containing donor-acceptor supramolecular assembles. Using these fascinating chromophores, we have designed and synthesized donor-acceptor systems to mimic natural photosynthesis. Photosynthesis involves two major steps, absorption and transportation of light energy to the reaction center, and photoinduced electron transfer (PET) to generate charge separated entities by using the electronic excitation energy.
We have designed elegant photosynthetic architectures using fullerene as carbon nanostructure based material for mimicry of antenna, mimicry of reaction center and mimicry of 'combined antenna-reaction center' functionalities in the natural photosynthetic system. Semiconducting single-wall carbon nanotube (SWNT)-based supramolecular nanoarchitectures are constructed using photosensitizing donor and acceptor molecules which reveal efficient photoinduced charge separation. The kinetic and thermodynamic data suggests feasibility of these nanohybrids for the construction of photovoltaic cell and other devices. Interestingly, the photoelectrochemical behavior of the nanohybrids indicates that by choosing nanotubes of appropriate diameter, it is possible to improve the light-harvesting conversion efficiency.Thesis (Ph.D.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Chemistry
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Boudoire, Guillaume. "Architecture et dynamique des systèmes magmatiques associés aux volcans basaltiques : exemple du Piton de la Fournaise." Thesis, La Réunion, 2017. http://www.theses.fr/2017LARE0022/document.
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Contraindre l'architecture et la dynamique des systèmes magmatiques est d’une importance capitale dans la compréhension des phénomènes volcaniques. Les principaux objectifs de cette thèse sont (1) de contraindre l'architecture du système magmatique du Piton de la Fournaise dans son ensemble, et (2) d'étudier l’évolution des magmas et les transferts associés en son sein. En couplant l'étude pétro-géochimique des magmas et du dégazage de CO2 à travers le sol, nous développons une approche intégrée, focalisée sur le flanc ouest de l'édifice. Cette zone témoigne d'une activité éruptive récente très peu étudiée, traçant potentiellement des processus magmatiques profonds. Nos résultats permettent de valider l'hypothèse du caractère décentré de la plomberie magmatique profonde du Piton de la Fournaise sous le flanc ouest de l'édifice. Nous démontrons que les magmas stockés dans la partie profonde de la plomberie magmatique préservent une certaine variabilité géochimique, principalement liée à de légères hétérogénéités de source et à des processus polybariques de cristallisation et d'assimilation. Nous montrons également que les flux de CO2 à travers le sol du flanc ouest de l'édifice enregistrent le dégazage précoce des magmas au sein du manteau lithosphérique. Nous soulignons ici que les variations temporelles des flux de CO2 à travers le sol peuvent être utilisées pour détecter les recharges du système magmatique central via des transferts magmatiques profonds.Nos résultats ouvrent des perspectives prometteuses quant à la surveillance des processus magmatiques profonds sous les édifices volcaniques, même en conditions tropicalesConstraining the architecture and dynamics of magma systems is fundamental in volcanology. The main objectives of this study are to (1) constrain the architecture of the whole plumbing system of Piton de la Fournaise, and (2) study magma evolution and transfers from the deepest roots of the plumbing system. Coupling magma petrogeochemistry and diffusive soil degassing, we develop an integrated approach, focused on the western flank of the volcano. This zone shows evidences of a recent eruptive activity, poorly documented, but potentially related to deep magma processes. Our results allow to confirm the offset of the deep part of the Piton de la Fournaise plumbing system beneath the western flank of the volcano. We demonstrate that magma stored in the deepest roots of the plumbing system display a geochemical variability, mainly related to minor mantle source heterogeneities and to polybaric crystallization and assimilation processes. We show that soil CO2 fluxes on the western flank of the volcano record early magma degassing in the lithospheric mantle. We highlight that temporal variations of soil CO2 flux may be used to detect magma replenishement of the central magmatic system by deep magma transfers, hardly detectable by the geophysical network.Our results opens exciting prospects to improve the monitoring of deep magma processes below volcanoes, even in tropical conditions
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Yang, Yue. "Thermal Conductivity of Carbon Fibre Fabrics and Multi-Scale Composites with Heat Transfer Simulations for RFI Manufacturing." Thesis, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/30252.
Full textAbstract:
Composites are increasingly used in aerospace applications where performance is the
foremost priority of industry. Research on carbon nanotube (CNT)-reinforced polymers
conducted in the past decade showed promising results for the improvement of mechanical,
thermal and electrical properties of composites. This thesis was undertaken in the context of
a larger project, the main goal of which is to develop a complete solution for the
manufacturing of carbon fibre-epoxy composites using CNT-reinforced epoxies, referred to
as multi-scale composites. This thesis focuses on the thermal aspect of this project under
three topics: 1) thermal conductivity of dry carbon fibre fabrics for understanding heat
diffusion in composites and similar fabric materials 2) thermal conductivity of CNTreinforced
polymers and composites for determining the effect of parameters including CNT
addition, and 3) modelling of heat transfer during composite manufacturing for ensuring that
their temperature distribution remains controlled.
In-plane k rip and through-thickness k rtt thermal conductivity data were measured for
two dry carbon fibre fabrics as a function of fibre volume fraction Vf . Results showed that
k rip varies linearly with Vf whilst k rtt varies in an exponential recovery trend with Vf . An
existing analytical model was used successfully for predicting k rip and simulations developed
for predicting k rtt values demonstrated that k rtt depends on the evolution of heat conduction
paths in the through-thickness direction as a result of improvements in the fibre contact
network.
A procedure was developed for manufacturing composites using the RFI process.
Thirty-two composites and multi-scale composite plates were manufactured and
characterised for investigating the effects of eleven material and manufacturing parameters
on fibre volume fraction, porosity, k rip and k rtt . Results showed that the effect of using
multi-walled CNT-reinforced epoxy on thermal conductivity of composites is negligible at
0.3% CNT loading. However, this reduced the porosity of the composites significantly.
Results also showed that using fabrics with higher surface densities led to a slight increase in
k cip .
A heat transfer model coupled with cure kinetics was developed for predicting
temperature profiles of the laminate during RFI manufacturing. The model was validated
experimentally and eleven simulation cases were run for investigating the effects of five
material and manufacturing parameters on temperature profiles in the laminate. Results
showed that the epoxy resins used in this project combined with the cure cycle recommended
by the manufacturer are well-suited for manufacturing laminates with a typical thickness of
approximately 5 mm as well as thick laminates of 15 mm to 20 mm.
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Kerr, Brittany. "Strengthening Potential of Single-Walled Carbon Nanotubes in Phenolic Resin Composites." Master's thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2219.
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Strengthening potential of single-walled carbon nanotubes (SWCNTs) in a phenolic resin composite was evaluated by characterization of purified and phenyl sulfonated SWCNTs, investigation of the load transfer capability of the purified SWCNTs, and characterization of the composites. Purified and phenyl sulfonated SWCNTs, as well as their composites, were examined by Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy equipped with energy dispersive spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and ultra violet-visible spectrometry. Fabrication of the SWCNT/phenolic resin composite was performed by first dispersing the SWCNTs in ethylene glycol and then homogenizing the mixture with phenolic resin. The ethylene glycol was then evaporated from the mixture and the SWCNT/phenolic resin composite was cured at 200°C for 1 hour. The dispersion of SWCNTs in the phenolic resin was reduced with higher SWCNT concentrations. Load was transferred from the phenolic resin to the purified SWCNTs. This demonstrated the potential to strengthen phenolic resin composite with SWCNT reinforcement. The load transfer efficiency in total tension (0.8%) decreased with an increase in SWCNT concentration, while in total compression (-0.8%), the load transfer efficiency remained constant. At very low strain (± 0.2%), the load transfer efficiency remained constant regardless of SWCNT concentration in both tension and compression. Characterization of the phenyl sulfonated SWCNTs indicated that calcium was introduced as a contaminant that interfered with functionalization of the SWCNTs. The use of contaminated phenyl sulfonated SWCNTs resulted in macroscopic inhomogeneity within the composite.M.S.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science & Engr MSMSE
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Wasem, Klein Felipe. "Photoactive polymer – carbon nanotubes hybrid nanostructures." Thesis, Strasbourg, 2021. http://www.theses.fr/2021STRAE004.
Full textAbstract:
L’objectif de cette thèse est la préparation de matériaux hybrides polymères conjugués (P3HT et un copolymère dérivé) - nanotubes de carbone, ainsi que leur caractérisation par des méthodes spectroscopiques et par microscopie électronique. Des nanohybrides non-covalents sont obtenus par la sonication des deux composants dans le THF. L’interaction entre ces composants entraîne l’enroulement du polymère autour des nanotubes ainsi que la formation d'agrégats de polymère sur leur surface. L’effet de différents paramètres, tels que la masse molaire du polymère, ont été étudiés. Des nanohybrides covalents sont obtenus en utilisant un copolymère portant une aniline au bout de la chaîne alkyle. Les spectroscopies optique et Raman suggèrent un faible taux de fonctionnalisation ainsi qu’une conformation plus désordonnée des chaînes de polymères par rapport aux nanohybrides non-covalents. Des études préliminaires montrent que le copolymère peut fonctionnaliser aussi des dispositifs à base de nanotubes de carbone. Le bas taux de fonctionnalisation ne permet pas de conclure sur la modification des propriétés électroniques, mais les défauts induits permettent l’observation d’un photocourantThe objective of this thesis is the preparation of conjugated polymers (P3HT and a derivated copolymer) – carbon nanotubes hybrid materials and their characterization through different spectroscopies and transmission electron microscopy. Non-covalent nanohybrids can be obtained by sonicating both components together in THF. The interaction between both components leads to the wrapping of the polymer around the carbon nanotubes as well as the formation of polymer aggregates on the surface of the nanotubes. The effect of different parameters such as the polymer chain length are described. Covalent nanohybrids can be obtained using a specially designed copolymer bearing an aniline at the end of its side chain. Optical and Raman spectroscopies indicate a low level of functionalization, and suggest that the polymer chains are in a more disordered state compared to non-covalent nanohybrids. Preliminary studies show that the obtained copolymer can be used for functionalizing carbon nanotube based devices. Modification of electrical properties of the devices were small and compatible with the low functionalization degree, but the induced defects allow observation of a photocurrent
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Richard, Lannig. "Impact du dioxyde de carbone sur la levure Saccharomyces cerevisiae : caractérisation du transfert liquide/gaz et implications sur les métabolismes énergétiques." Thesis, Toulouse, INSA, 2014. http://www.theses.fr/2014ISAT0041/document.
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L’objectif de ce travail est l’étude de l’impact du dioxyde de carbone (CO2) sur la physiologie et le métabolisme de la levure Saccharomyces cerevisiae, en particulier son impact sur le catabolisme oxydatif du glucose et son rôle dans le déclenchement de la transition respiro-fermentaire. Le CO2 est au coeur des interactions entre phénomènes biologiques et phénomènes physiques de transfert existant au sein d’un réacteur biologique. La compréhension de son impact sur la physiologie de la levure nécessite la connaissance de sa concentration en phase liquide et donc la maitrise des phénomènes de transfert interphasiques.Le transfert liquide / gaz du CO2 en fermenteur a été étudié par une approche couplant modélisation et expérimentation avec un effort particulier sur l’analyse intégrée des phénomènes biologiques et de transfert. En comparaison avec les hypothèses de transfert généralement admises une sursaturation du moût en CO2 dissous dans le moût a été observée lors de cultures de S.cerevisiae et attribuée à l‘existence d’une distribution asymétrique de tailles de bulles de la phase dispersée. Il a été démontré que le transfert liquide / gaz du CO2 lors d’une culture microbienne intensive ne peut être décrit par analogie avec le transfert gaz / liquide de l’oxygène et que la connaissance de la concentration en CO2 dissous ne peut être réalisée que par sa mesure directe.L’impact du CO2 sur le métabolisme oxydatif de la levure a été investigué par le suivi de la réponse dynamique de la réponse à différents incréments mesurés de la concentration en CO2 dissous en culture continue. Cette réponse est constituée d’une réponse transitoire et intense et d’une réponse à long-terme plus modérée Elle se caractérise par l’impact du CO2 sur l’énergétique cellulaire en augmentant la génération et la dissipation d’énergie ce qui est traduit à court-terme par une augmentation transitoire de +24 à +37 % des vitesses spécifiques de respiration lors d’échelons de la concentration en CO2 dissous de +2.96 et +5.29 mM et à long-terme par une diminution de 18% YATP de % lorsque la concentration en CO2 dissous augmente de 1.6 mM à 17 mM. L’effet du CO2 sur la transition respiro-fermentaire a été étudié en culture de type accélérostat en présence d’une concentration élevée en CO2 dissous. Dans ces conditions, la bascule vers le métabolisme réductif est obtenue pour un taux de croissance (0.122 h-1) et des vitesses spécifiques de respiration (5.2 mmoleO2.gX-1.h-1) inférieurs aux valeurs obtenues avec un accélérostat sans apport exogène de CO2 (0.256h-1 et 8.65 mmoleO2.gX-1.h-1) respectivement. Cette modification du métabolisme n’a pu être corrélée directement à un déficit de potentiel énergétique oxydatif et semble probablement liée à une perte de flexibilité d’adaptation à la dynamique de variation de l’environnementThe aim of this work was to evaluate the impact of carbon dioxide (CO2) on the physiology of the yeast Saccharomyces cerevisiae, more precisely on the oxidative metabolism and on the onset of alcoholic fermentation. CO2 is involved in the interactions between transfer phenomena and biological phenomena in fermenters. The knowledge of the dissolved CO2 concentration and then of the CO2 liquid / gas mass transfer phenomena is required to assess the impact of this compound on the yeast physiology.Investigation of CO2 liquid / gas in biological reactors has been carried out using simulations and experiments taking into consideration both biological and transfer phenomena. CO2 supersaturation was observed in an intensive fed-batch culture of S.cerevisiae and may be caused by an asymmetric bubble size distribution of the gas phase. We demonstrated that CO2 liquid / gas transfer cannot be described based on O2 gas / liquid transfer and that CO2 concentration must be estimated through direct measurement.The impact of CO2 on the oxidative metabolism of S.cerevisiae was investigated using chemostat cultures submitted to different step-increases of the dissolved CO2 concentrations with direct measurement of the dissolved CO2 concentration. The yeast culture showed a transient response with an increase of the specific respiration rates ranging from with a +24 to +37 % during + 2.96 mM and+5.29 mM dissolved CO2 step-increases. This transient response was followed by a long-term response characterized by a decrease of the YATP value with increasing dissolved CO2 concentrations (down to -18% when the CO2 concentration increased from 1.6 mM to 17 mM).The impact of CO2 on the onset of the Crabtree effect in S.cerevisiae was investigated using the accelerostat technique with and without CO2 enrichment. The onset of alcoholic fermentation occurred at a much lower specific growth rate (0.122 h-1) and specific oxygen consumption rate (5.2 mmoleO2.gX-1.h-1) in CO2 enriched conditions than without CO2 enrichment (0.256h-1 and 8.65 mmoleO2.gX-1.h-1 respectively). These modifications may be linked with a decreased cellular adaptability to changing environment
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Sethi, Sunny. "Carbon Nanotube Based Functional Superhydrophobic Coatings." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1271346171.
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Maag, Gilles. "Monte Carlo radiative heat transfer analysis of a CH₄ flow laden with carbon particles." Zürich : ETH, Eidgenössische Technische Hochschule Zürich, Institute of Energy Technology, 2006. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=283.
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Ajja, Rameshwar. "Numerical heat transfer analysis of carbon-based foams for use in thermal protection system." FIU Digital Commons, 2006. http://digitalcommons.fiu.edu/etd/1179.
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The applicability of carbon-based foams as an insulating or active cooling material in thermal protection systems (TPSs) of space vehicles is considered using a computer modeling.
This study focuses on numerical investigation of the performance of carbon foams for use in TPSs of space vehicles. Two kinds of carbon foams are considered in this study. For active cooling, the carbon foam that has a thermal conductivity of 100 W/m-k is used and for the insulation, the carbon foam having a thermal conductivity of 0.225 W/m-k is used. A 3D geometry is employed to simulate coolant flow and heat transfer through carbon foam model. Gambit has been used to model the 3D geometry and the numerical simulation is carried out in FLUENT.
Numerical results from this thesis suggests that the use of CFOAM and HTC carbon foams in TPS's may effectively protect the aluminum structure of the space shuttle during reentry of the space vehicle.
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Cenci, Steven Michael. "Acoustic agitation of dense carbon dioxide/water mixtures : emulsification, mass transfer, and reaction engineering." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5381/.
Full textAbstract:
Acoustic agitation of a carbon dioxide/water mixture in a 1 dm3 cylindrical, high-pressure reactor led to the simultaneous formation of carbon dioxide/water (C/W) and water/carbon dioxide (W/C) emulsions, with the dispersed phase occupying up to 10% of the volume. These emulsions were stable for several minutes. Inclusion of 1% of the non-ionic surfactant Tween 80 led to the generation of C/W emulsions which were stable for over 1 hour after ceasing sonication, in which all of the carbon dioxide present in the system comprised the dispersed phase. The mixing capacity of pulsed ultrasound was assessed by studying the mass transfer of benzaldehyde across the carbon dioxide/water interface, leading to determination of the system mixing time. A model for mass transfer with a fast chemical reaction, namely the hydrolysis of benzoyl chloride, was used to separate the mass transfer and kinetic effects, and to identify those reactions that would most significantly benefit from ultrasound-induced emulsification. For the first time, the Barbier synthesis was shown to occur in a carbon dioxide/water mixture as solvent, leading to moderate to high yields. Moreover, it was possible to recover the homoallylic alcohol product directly from the carbon dioxide phase in which it was preferentially partitioned.
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Sternitzke, Kent D. "Laser activation of heterogeneous electron-transfer processes at carbon electrodes : effect on analytical applications /." The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487683756123637.
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