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1
Olinde, Lindsay. "Sediment Oxygen Demand Kinetics." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/42437.
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Hypolimnetic oxygen diffusers increase sediment oxygen demand (SOD) and, if not accounted for in design, can further exacerbate anoxic conditions. A study using extracted sediment cores, that included both field and laboratory experiments, was performed to investigate SOD kinetics in Carvinâ s Cove Reservoir, a eutrophic water supply reservoir for Roanoke, Virginia. A bubble-plume diffuser is used in Carvinâ s Cove to replenish oxygen consumed while the reservoir is thermally stratified. The applicability of zero-order, first-order, and Monod kinetics to describe transient and steady state SOD was modeled using analytical and numerical techniques. Field and laboratory experiments suggested that first-order kinetics characterize Carvinâ s Cove SOD. SOD calculated from field experiments reflected diffuser flow changes. Laboratory experiments using mini-diffusers to vary dissolved oxygen concentration and turbulence were conducted at 4°C and 20°C. Similar to field observations, the laboratory results followed changes in mini-diffuser flow. Kinetic-temperature relationships were also observed in the laboratory experiments. A definitive conclusion could not be made on the broad applicability of first-order kinetics to Carvinâ s Cove SOD due to variability within field experiments. However, in situ experiments are underway that should assist in the overall understanding of the reservoirâ s SOD kinetics.Master of Science
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Fawkner, Samantha Gieva. "Oxygen uptake kinetics in children." Thesis, University of Exeter, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393144.
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Violette, Steven M. "Oxygen Delignification Kinetics and Selectivity Improvement." Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/VioletteSM2003.pdf.
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Ji, Yun. "Kinetics and Mechanism of Oxygen Delignification." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/JiY2007.pdf.
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Dogan, Ismail. "Mass Transfer And Kinetics In Oxygen Delignification." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605562/index.pdf.
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In this study, the kinetic analysis of oxygen delignification of Turkish southern hardwood Kraft pulp was carried out. Kraft pulp was obtained from Mopak Dalaman pulp and paper mill. The kinetic rate data were collected in a 1 L high pressure batch reactor. The delignification experiments were carried out under a wide range of industrially significant conditions of temperature (90, 100 and 110 oC), alkali charge (1, 3, 5% on oven dry pulp), and oxygen partial pressure (0.5, 3.5, 6.5 bar).
In order to achieve this objective, the study is separated into different stages. In the first stage of the work, the mass transfer effects were examined for different pulp consistencies. It was seen that the inter-fiber mass transfer resistances become negligible at the consistencies below 1%. Therefore, the experiments were performed at 0.5% consistency. In the following stage, the kinetics of oxygen delignification was studied and the governing rate equations were derived. Then, the kinetics of the carbohydrate degradation was analyzed in order to determine the extent of delignification without the reduction in the pulp strength. The delignification and the carbohydrate degredation rate during oxygen delignification increase with increasing in alkali concentration, oxygen partial pressure and temperature. However, the most effective parameters are the alkali concentration and temperature. The dimensionless terms for Kappa number, intrinsic viscosity and reaction time were used in order to generalize the results and to make them independent of the initial Kappa number, the intrinsic viscosity, experimental conditions and pulping conditions prior to oxygen delignification. These dimensionless parameters were fitted to nonlinear equations from which the control of the oxygen delignification towers can be done with a simple equation. The same approach was also used for the reported studies in the literature which allowed the comparison with the results of this study.
In the final stage of the study, the simulation of the oxygen delignification unit preceding the CEHDED bleach plant is performed, in order to see the effect of oxygen delignification on the amount of total wastes coming out from the bleach plant. When an oxygen delignification unit is added to the existing CEHDED bleach plant, the amount of pollutants are decreased by 17.96% with output brightness of 92.95. When the overall process parameter optimization of the CEHDED bleach plant is done with oxygen delignification unit, the total amount of dissolved solids coming out from the six washers are decreased by 25.97% with output brightness of 89.5.
In order to reduce the pollution load and chemical consumption in Mopak Dalaman pulp and paper mill, management has decided to install an oxygen delignification unit to the plant. Therefore, the rate equations obtained from this study can form a basis for the design and optimization of oxygen reactor in the mill.
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Bell, Christopher. "Control and modelling of oxygen uptake kinetics." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ42497.pdf.
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Bauer, Timothy Alan. "Oxygen uptake kinetics in peripheral arterial disease." Diss., Manhattan, Kan. : Kansas State University, 2005. http://hdl.handle.net/2097/125.
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Walker, Forest P. "Kinetics of Arsenopyrite Oxidative Dissolution by Oxygen." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/9881.
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The objective of this study is to use a mixed flow reactor system to determine the dissolution rate and infer potential mechanisms of arsenopyrite (FeAsS) oxidation by dissolved oxygen at 25°C and circumneutral pH. Release rates for iron, arsenic and sulfur are calculated for a variety of initial dissolved oxygen (DO) concentrations. Results indicate that the rate of arsenopyrite oxidation, represented by the rate law r = A(6.76 x 10-11) where the rate, r, is in mol/s and surface area, A, is in m2, is not significantly dependent on DO concentration. Arsenic and sulfur are released in a 1:1 molar ratio while iron is released more slowly due to precipitation of iron oxyhydroxides. Our results suggest that the rate determining step in arsenopyrite oxidation is determined by the attachment of oxygen at the anodic site in the mineral, and not the transfer of electrons from the cathodic site to oxygen, as is suggested for other sulfide minerals such as pyrite.
Previous work on FeAsS oxidation has been limited to low pH conditions with ferric iron as the oxidant. However, not all arsenopyrite weathering occurs exclusively in acidic environments. For example, at an abandoned arsenopyrite mine in Virginia, the pH of ground and surface waters is consistently between 4 and 7. Results of this study provide important insight to arsenic mobilization processes and rates, at field-relevant conditions, consequently aiding in the effort to understand arsenic release and retention in the environment.Master of Science
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Blumoff, Sonja. "Oxygen Uptake Kinetics in Severe Intensity Exercise." Thesis, University of North Texas, 2000. https://digital.library.unt.edu/ark:/67531/metadc2539/.
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The purpose of this study was to describe mathematically the oxygen uptake kinetics during cycle ergometry, and to examine the effect of intensity on the kinetic responses within the severe domain. Sixteen volunteers performed a series of exercise tests at a range of intensities selected to elicit fatigue in ~3 to 10 min. A simple mono-exponential model effectively described the response across all intensities. There was a positive correlation between the response time and the time to fatigue, demonstrating that the maximal oxygen uptake was achieved faster at higher intensities within the severe domain. Models incorporating two components effectively described the responses only in tests lasting 8 min or more. It was concluded that there is a second, slow component in the oxygen uptake response only at the lower intensities within the severe domain.
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Wilkerson, Daryl P. "Oxygen uptake kinetics during supra-maximal intensity exercise." Thesis, Manchester Metropolitan University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424750.
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Claxton, David B. "The measurement of oxygen uptake kinetics in children." Thesis, Sheffield Hallam University, 1999. http://shura.shu.ac.uk/3152/.
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Traditional approaches to exercise testing in children may not provide the most appropriate measures of a child's physiological responses to exercise, partly because they do not reflect children's normal intermittent activity patterns. The measurement of the rate and magnitude of change of oxygen uptake to dynamic exercise, oxygen uptake kinetics (V02 KINETICS provides an alternative approach to exercise testing. A submaximal, intermittent, pseudo-random binary sequence (PRBS) exercise test to measure V02 KINETICS may provide a useful method of measuring the metabolic responses of children to exercise. Traditional methods used in the analysis of V02 KINETICS require the fitting of explicit models in order to characterise the data. These models have not however been validated for use in children. As the responses to the PRBS protocol are analysed in the frequency domain, explicit models and their physiological correlates are not required to characterise the data. Another potential problem in the measurement of V02 KINETICS in children are the small work rate changes that can be employed to stimulate the exercise response whilst constraining the test to the aerobic range. In respiratory gas measurement, breath-by-breath variability (noise) can be large in comparison to the magnitude of the metabolic response and this signal noise can obscure some characteristics of the response. The aim of the study was to develop appropriate measurement techniques to reduce the effects of breath-by-breath variability and to apply the techniques to the measurement of V02 KINETICS in children. The main experimental study compared the V02 KINETICS of children with those of adults. Ten children (3 females) in the age range 8 to 13 and twenty adults (10 females) in the age range 20 to 28 years completed a PRBS test to measure V02 KINETICS and an incremental ramp protocol on a cycle ergometer (Bosch 550 ERG) to establish V02 MAX, T VENT and delta efficiency. Breath-by-breath respiratory gas analysis was undertaken using a respiratory mass spectrometer (MGA1100). Estimates of alveolar gas exchange were made using the algorithm of Beaver et al. (1981) and a post hoc value of an effective lung volume was calculated to minimise the breath-by-breath variability. A cross-correlation technique (CC) was used to filter out the effects of anomalous (nonphysiologic) V02 responses recorded during the PRBS protocol. Subsequent Fourier analysis of the auto-correlation and CC functions provided a description of V02 KINETICS in the frequency domain in terms of amplitude ratio and phase delay over the frequency range of 2.2-8.9mHz. At each of the frequencies assessed amplitude ratio was higher in children (P<0.001) than in either of the adult groups. Phase delay was also significantly shorter in children compared to adults males (P<0.01) and adult females (P<0.001) but this effect was not identifiable at any specific frequency. Maximal oxygen uptake was not significantly different in adult males (42.5 ml"kg "min) and children (44.7 ml-kg'-min') but was lower in adult females (36.9 ml"kg "min) than adult males (P<0.01) and children (P<0.001). Ventilatory threshold (% V02 MAX) was not different between groups. Delta efficiency was significantly lower in children than adult males (P<0.05) and adult females (P<0.01). These results support the contention that there are maturational differences between adults and children in the metabolic processes involved in the utilisation of oxygen during physical activity. It has been argued, theoretically, that in adults the control of V02 KINETICS is driven by ATP demand in the skeletal muscle. As the mitochondria] capacity and the concentration of oxidative enzymes is higher in children than in adults it is likely that the controlling factor(s) for V02 KINETICS in children also relates to some aspect of peripheral metabolism. It is suggested that the PRBS protocol, with appropriate noise reduction techniques, is considered a suitable method for investigating the metabolic responses of children to dynamic exercise.
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Grant, Crystelle Kiyoko. "Influence of cardiac output on oxygen uptake kinetics /." Diss., CLICK HERE for online access, 2010. http://contentdm.lib.byu.edu/ETD/image/etd3341.pdf.
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Grant, Crystelle Kiyoko. "Influence of Cardiac Output on Oxygen Uptake Kinetics." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/1989.
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The purpose of this study was to evaluate increased cardiac output (Q) on oxygen kinetics at exercise intensities above and below the lactate threshold (LT). We hypothesized the increase in Q using head-out water immersion (HOI) while treadmill running would reduce the rate constant of the fast component and reduce the amplitude of the slow component of oxygen kinetics compared with land treadmill running. Subjects (n=10) performed two 6 min exercise bouts at a 15% below and above the LT on a land and underwater treadmill following rest. A single exponential equation [VO2(t) = VO2(b) + A1•(1-e-t/TC1] was used to evaluate VO2. The slow component at the end of exercise was estimated by subtracting (VO2(b) + A1) from the plateau. The mean LT for HOI running 1.80 ± .09 L • min-1 was significantly lower (p < 0.05) than 2.15 ± 1.03 L • min-1 while running on the land. The Q during HOI exercise below and above the LT (16.5 ± 0.6 L • min-1, 18.0 ± 1.2 L • min-1) was significantly higher (p < 0.05) than the Q during exercise below and above the LT on land (11.5 ± 0.8 L • min-1, 13.0 ± 0.7 L • min-1). During HOI exercise below LT time to reach steady-state was delayed (8 ± 2 s). Exercise above LT showed similar phase one time constants for all exercise trials. The amplitude of the slow component was not influenced by HOI. As such, the increase in during HOI exercise did not hastening uptake kinetics.
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Rozier, Robert. "A study of the kinetics of lithium-oxygen reactions." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/14896.
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Baumann, Frank Stephan. "Oxygen reduction kinetics on mixed conducting SOFC model cathodes." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-27056.
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Pringle, Jamie S. M. "The oxygen uptake slow component in human locomotion." Thesis, Manchester Metropolitan University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268988.
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O'Brien, Allison K. "The impact of oxygen on photopolymerization kinetics and polymer structure." Diss., Connect to online resource, 2005. http://wwwlib.umi.com/dissertations/fullcit/3165809.
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Lee, Michael. "Lignin model compound approach to modelling oxygen delignification reaction kinetics." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/36962.
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The oxygen delignification stage is implemented in modern kraft pulp mills to cut the cost of producing bleached bright pulp and reduce emissions from the bleaching process. While several oxygen delignification kinetic models are presented in the literature, most models are derived from and limited to, specific pulp blends. In this work, an oxygen delignification kinetic model was developed based on lignin model compound chemistry found in the literature to create a universal kinetic model applicable to a range of pulp blends. The kinetic model splits the pulp into three reactive lignin groups (fast, slow and non-reacting) each with their own kinetic constants. Along with the starting kappa number, the proposed testing protocol measures kappa number from oxygen delignification experiments at 90°C for three hours (to determine non-reacting lignin fraction) and at 50°C for five minutes (to determine the fast lignin fraction). From the three kappa measurements, the fraction of each lignin group is determined and combined with their respective kinetic constants to create the overall kinetic model. Coupling separately developed mass transfer governing equations for the pulp suspension with the kinetic model, the overall oxygen delignification stage model was developed.
The oxygen delignification model was compared with experiments performed both in the laboratory and in an industrial pulp mill. Laboratory oxygen delignification experiments on four pulp blends (three softwood and one hardwood) showed good agreement between experimental data and simulation values indicating the proposed testing protocol and kinetic constants are able to model the oxygen delignification reaction. In particular, oxygen delignification reaction result at 50°C for five minutes in conjunction with delignification result at 90°C for three hours was able to determine the split between fast, slow, and non-reacting lignin groups. Model simulations using the determined lignin fraction split was able to model experimental data especially well for 90°C experiments that mimics the conditions experienced in an industrial setting. Experiments at a pulp mill showed agreement within one kappa number between measured values and model simulations signifying the applicability of the proposed overall oxygen delignification model to simulate an industrial process.
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Hsu, Chieh-Lung Jay. "Mass transfer and kinetics in oxygen delignification of wood pulp." Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/10965.
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Turner, Anthony Pierce. "Pulmonary oxygen uptake kinetics and exercise intensity : inferences and implications." Thesis, University of Glasgow, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407694.
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Berger, Nicolas J. A. "The effects of training and fitness on oxygen uptake kinetics." Thesis, University of Exeter, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438372.
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Kilding, Andrew E. "Pulmonary oxygen uptake kinetics in middle-and long-distance runners." Thesis, Sheffield Hallam University, 2003. http://shura.shu.ac.uk/20739/.
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The overall aim of this thesis was to evaluate the importance of pulmonary oxygen uptake (VO[2]) kinetics, in the moderate-domain, in the assessment of endurance-trained runners. Accordingly, there were five objectives: 1) to quantify the reproducibility of measures of VO[2] kinetics; 2) to characterise and compare VO[2] kinetics during the on-and off-transients in middle-distance (MD) and long-distance (LD) runners; 3) to assess the relationship between VO[2] kinetics and maximal VO[2] (VO[2Max]), ventilatory threshold (V[T]) and running economy (RE); 4) to determine the relationship between VO[2] kinetics and running performance and 5) to assess whether VO[2] kinetics is a determinant of running performance. Twelve participants performed two assessments of VO[2] kinetics on separate days to determine the reproducibility. Paired t-tests showed that parameters from test 1 and test 2 did not differ (P > 0.05). Furthermore, narrow 95% limits of agreement (LOA), low measurement and method error suggested that the on- and off-transient time-constants (pion and pioff), mean response times (MRT[on] and MRT[off]) and amplitudes (A[on] and A[off]) were reproducible and could be used for the assessment of runners. Subsequently, VO[2] kinetics were compared in 10 MD and 10 LD runners. There was a tendency for pion (12.5 +/- 2.3 s vs. 14.2 +/- 3.1 s, P = 0.178) and pioff (24.1 +/- 2.3 s vs. 27.1 +/- 3.0 s, P = 0.023) to be shorter in LD than MD runners respectively, despite similar VO[2Max] (MD = 60.0 +/- 4.9 ml-kg[-1]min[-1]; LD = 59.0 +/- 6.3 ml-kg[-1]-min[-1], P = 0.689). Differences in VO[2] kinetics between MD and LD runners were attributed to approaches to training since the volume of training was greater in LD (64.0 +/- 15.7 km-wk[-1]) than MD (47.5 +/- 15.7 km-wk[-1]) runners (P = 0.047). To detail the relationships between VO[2] kinetics and other measures of aerobic function (VO[2max], V[t] and RE), 16 MD and 16 LD runners were assessed. Relationships existed between pion and VO[2max] (r = -0.72, P = 0.002), V[t] (r = -0.66, P = 0.006) and RE (r = -0.59, P = 0.016) in LD runners, but not in MD runners (P >0.05). In addition, pion was related to the volume of training in MD (r = -0.63 , P = 0.009) and LD runners (r = -0.65, P = 0.006).The importance of VO[2] kinetics for 5 km running performance was investigated in 36 endurance trained runners. Runners were categorised as high n=10), low (n=10) and combined [MD + LD (n=36)] performers according to running ability after performing a self-paced 5 km time-trial. Mean (+/-SD) speed for the 5 km time-trial was 5.2 +/-1.0 m-s[-1] (high), 4.5 +/- 0.2 m-s[-1] (low) and 4.9 +/- 0.3 m-s[-1] (combined). Measures of on- and off- transient VO[2] kinetics, VO[2max], V[t] and RE were also determined. Data were explored using bi-variate correlations, ANCOVA and multiple regression techniques. In high and low performers, V0[2] kinetic parameters were not related to running performance. In combined runners, pion, pioff, MRT[on] and MRT[off] were related (r = -0.54, P = 0.001; r = -0.36, P = 0.030; r = -0.50, P = 0.002; r = -0.63, P = 0.003) to running performance. Stepwise multiple regression models were used to identify the primary determinant(s) of 5 km running performance for each group. In high performers, VO[2Max] and RE were included in the model (r = 0.92, R = 0.85, SEE = 0.08 m-s[-1]; SEE% = 1.5). In low performers, VO[2Max] was included in the model (r = 0.76, R[2] = 0.57, SEE = 0.15 m-s[-1], SEE% = 3.3). In combined runners, V0[2Max] RE and MR[off] were included in the model (r = 0.87, R-2 = 0.75, SEE = 0.17 m-s[-1], SEE% = 3.5).Collectively, the results suggest that: 1) VO[2] kinetics can be reproducibly determined using a single visit protocol; 2) measures of VO[2] kinetics are sensitive enough to differentiate MD and LD runners; 3) relationships between VO[2] kinetics and other measures of aerobic function exist in LD runners, but not in MD runners; 4) VO[2] kinetics differ between high and low performers, but do not relate to running performance and 5) VO[2] kinetics discriminate between high and low performers but only contribute minimally to the prediction of running performance in a multiple regression model for combined MD and LD runners.
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Joos, Nathaniel Ian. "Surface oxygen exchange kinetics and oxygen diffusion rates in YSZ single crystals and mixed conducting oxides." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0007/MQ45897.pdf.
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Taylor, Craig A. (Craig Allan). "Kinetic Study of the Reactions of Oxygen Atoms with Nitric Oxide and Silane." Thesis, University of North Texas, 1992. https://digital.library.unt.edu/ark:/67531/metadc935556/.
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The rate constant for the reactions of oxygen atoms with nitric oxide and silane were determined using a discharge flow apparatus. A microwave discharge through O2N2 and Ar was used to produce oxygen atoms. The rate constant for the reaction O + NO + Ar was determined to be (7.0+0.4) x 10^32 cm^6 s^-1 and is in good agreement with previous measurements. Modeling of the O +SiH₄ reaction was performed to determine the correction to the rate constant due to secondary reactions. The rate constant for the reaction O + SiH₄ was determined to be (3.3 +/- 0.3) x 10⁻¹³ cm³ s⁻¹ and is in good agreement with previous measurements. Previous literature, thermochemistry, and spin conservation were used to determine a probable mechanism for the O + SiH₄ reaction.
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Stangl, Alexander. "Oxygen kinetics and charge doping for high critical current YBCO films." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/667212.
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Els superconductors d'alta temperatura, especialment els cuprats en forma de cintes superconductores, tenen el potencial de formar part de la propera revolució tecnològica gràcies a les seves propietats superconductores extraordinàries i inigualables. Els àtoms d'oxigen tenen un paper essencial en aquests superconductors d’alta temperatura, on la superconductivitat es regeix pel dopatge de forats. En aquesta tesi, hem estudiat extensament tots els processos on l'oxigen està implicat, des de la incorporació inicial d'oxigen a l'estructura de l‘YBa2Cu3O7-δ i el mecanisme relacionat a aquesta incorporació, fins a la influència del dopatge d'oxigen en les propietats superconductores. Una comprensió profunda de cada pas concret no només és interessant des del punt de vista acadèmic, sinó que també és necessari en l'optimització i la millora de qualsevol procés de producció comercial. Utilitzant mesures de relaxació de la conductivitat elèctrica in-situ i les mesures de difracció de raigs X in-situ, hem analitzat la cinètica d'intercanvi d'oxigen en capes primes de YBCO. S'ha estudiat una àmplia varietat de mostres i microestructures, obtingudes per diferents mètodes de creixement, amb substitució catiònica, nanocompòsits, variacions de gruix i substrat. Els nostres estudis revelen influències diferents entre la tensió macroscòpica i microscòpica sobre les energies d'activació per a l'intercanvi d'oxigen. En aquest estudi s’ha establert que la plata és un agent catalític excel·lent per a la incorporació d'oxigen, proporcionant una ruta de reacció catalítica alternativa, que permet una cinètica més ràpida d'oxigenació i una menor temperatura d'oxigenació. A més a més, hem identificat amb èxit el pas determinant en la cinètica d'intercanvi d'oxigen en capes primes d‘YBCO recobertes de plata, el qual és la recombinació dels ions d'oxigen amb vacants a la superfície de la capa. L'aprofundiment en les mesures elèctriques in-situ en combinació amb tècniques d'anàlisi ex-situ com ara mesures de XRD, STEM, SEM, resistivitat elèctrica, Hall i magnetització ens ha permès estudiar els efectes dels paràmetres de tractament tèrmic sobre la química de superfície com en la microestructura de les capes primes de YBCO . D'una banda, hem identificat la formació de defecte d'apilament (stacking faults) ja durant els tractaments a baixa temperatura. D'altra banda, hem descobert la desactivació de la cinètica d'intercanvi en superfícies per a capes no recobertes de plata, la qual cosa suposa una cinètica d’incorporació d'oxigen significativament més lenta. Les diferents velocitats de degradció de la superfície depenen del recobriment superficial i apunten cap a una modificació del pas determinant en la cinètica de reacció quan s'afegeix un recobriment de plata en capes primes d'YBCO. No només hem estudiat la incorporació d'oxigen en gran detall, sinó també el seu efecte en l'estat de dopatge del cuprat. S'ha estudiat extensament la influència de la pressió parcial d'oxigen, la temperatura d'oxigenació i el temps d'oxigenació en la densitat de portadors de càrrega i les propietats físiques normals/superconductores. Hem preparat capes primes d'YBCO superdopades per PLD (pulsed laser deposition) i CSD (chemical solution deposition). Hem mostrat que en el cas de PLD es poden acpnseguir densitats de corrent crítiques molt altes, arribant a 90 MA/cm² a 5K i auto-camp, que correspon a un terç de la densitat de corrent crítica fonamental de desaparellament. El dopatge s’ha analitzat mitjançant l'ús de mesures de resistivitat en funció temperatura, mesures d’efecte Hall i mobilitat, així com raigs-X i mesures de temperatura crítica. Mitjançant l'ús d'un model de dues bandes per al transport elèctric d'electrons i forats, hem obtingut una densitat de càrrega independent de la temperatura. Hem demostrat una correlació lineal entre la densitat de portadors de càrrega i la densitat de corrents crítica en l'estat superdopat, evidenciant així el potencial d'aquests estudis per a la millora de les propietats superconductores de les capes d'YBCO.High temperature superconductors, especially cuprates, in the form of coated conductors have the potential to be part of the next technological revolution due to unchallenged, extraordinary superconducting properties. Oxygen plays an essential role in these cuprate high-temperature superconductors, where superconductivity is governed by hole doping. In this thesis we have intensively studied all oxygen involved processes, from the initial incorporation of oxygen into the YBa2Cu3O7-δ structure and related mechanism, up to the influence of oxygen doping on the superconducting properties. A deep understanding of each particular step is not only interesting from an academic point of view, but also necessary in the optimisation and improvement for any commercial production line. Using in situ electrical conductivity relaxation and in situ X-ray diffraction measurements we have analysed oxygen exchange kinetics in YBCO thin films. A broad variety of samples and microstructures, obtained by different growth methods, cation substitution, nanocomposites, variations in thickness and substrate, have been studied. Our studies reveal different influences of macroscopic and microscopic strain on activation energies for oxygen exchange. In this work silver was found to be an excellent catalytic agent for oxygen incorporation, by providing a catalytic alternative reaction path, which enabled faster oxygenation kinetics and lower oxygenation temperatures. Further, we have successfully identified the rate determining step (RDS) of oxygen exchange kinetics in silver coated YBCO thin films, which we have found to be the recombination of oxygen ions with surface vacancies. The thorough use of electrical in situ measurements in combination with ex situ analysis techniques as XRD, STEM, SEM, electrical resistivity, Hall and magnetisation measurements enabled us to study the effects of thermal treatment parameters on the surface chemistry and bulk microstructure of YBCO thin films. On one hand, we have identified the formation of stacking faults already during low temperature annealings . On the other hand, a deactivation of surface exchange kinetics was found for non-silver coated films, resulting in significantly slower oxygen incorporation with increasing annealing time. Surface coating dependent degeneration rates point towards a modification of the RDS upon silver coating of YBCO thin films. We have not only studied the incorporation of oxygen in great detail, but also its effect on the doping state of the cuprate material. The influence of oxygen partial pressure, oxygenation temperature and oxygenation time on the charge carrier density and normal/superconducting physical properties was intensively studied. We have prepared highly overdoped YBCO thin films grown by PLD with record-high critical current densities reaching 90 MA/cm² at 5 K and self-field, reaching a third of the depairing current density. The doping state was analysed by the use of temperature dependent resistivity, Hall and mobility measurements, as well as XRD and critical temperature measurements. By using a two band model for the electrical transport of electrons and holes, we have obtained a temperature independent charge carrier density. We have demonstrated a linear correlation between the charge carrier density and the critical current densities in the overdoped state, thus evidencing the powerfulness of these studies for the enhancement of superconducting properties of YBCO thin films.
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Jarvis, David R. "Multifrequent work rate forcings in the assessment of oxygen uptake kinetics." Thesis, Sheffield Hallam University, 1999. http://shura.shu.ac.uk/19870/.
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During dynamic exercise, the response of the cardiorespiratory system is structured to maintain homeostasis at the cellular level. The rate at which homeostasis is established is largely dependent on the system's structural and physiological integrity. Evidence suggests that any impairment in the functioning of the system might be reflected in a determination of oxygen uptake (VO[2]) kinetics. The kinetics of VO[2] have been quantified in response to step, impulse, ramp and sinusoidal changes in work rate (WR). An alternative approach uses a technique in which the WR is perturbed according to a pseudorandom binary signal. Pseudorandom binary sequence (PRBS) WR forcings have the advantage of being able to provide a determination of vo2 kinetics from a single test session of ~30 min duration. The assessment of VO[2]kinetics using PRBS WR forcings demands that the controlling process behaves in a linear manner. To minimise the contribution of non-linear influences, changes in work intensity must be constrained to the sub-lactate threshold domain. When examining clinical, untrained or young subjects, the necessary reduction in the upper work limit of a PRBS forcing can effect a fall in the distribution of power across the bandwidth of the sequence. If the distribution of power should fall below a critical level, then it can become difficult to elicit discernible responses from the forcing. To resolve this problem, this thesis investigated the potential for developing a multifrequent WR forcing altered to enhance identification of the underlying VO[2] response. The multifrequent WR forcing developed for use in this thesis took the form of a binary sequence. Binary transitions were determined according to a specially constructed multifrequent signal. Signal construction involved redistributing the available signal power to specific harmonics in a chosen range of frequencies. To validate estimates of VO[2] kinetics derived from the multifrequent binary sequence (MFBS) WR forcing, comparisons were made with the data obtained from an established PRBS forcing. When comparing physiological data, it is necessary to consider the amount of variability between trials. Therefore, prior to assessing the agreement between data obtained from the MFBS and PRBS methods, this thesis sought to establish the degree of variability in estimates of VO[2] kinetics derived from PRBS exercise tests. The results presented in this thesis show estimates of the mean response time (MRT) of VO[2] derived from the MFBS method to be 46.8 (4.2) s (mean (standard deviation) seconds), compared with 45.2 (5.0) s for the PRBS method. This suggests that the two methods yield comparable determinations of VO[2] kinetics. Supporting evidence is provided by the limits of agreement. These indicate that the maximum difference likely to occur between the MRT obtained from the two methods (-6.5 to +9.6 s) is less than that expected due to variability in the MRT derived from PRBS forcings (-11.6 to +8.0 s). However, the limits also reveal the poor repeatability of VO[2] response data obtained from the PRBS used in the thesis. Consequently, the use of this data to assess the validity of t the MRT derived from MFBS forcings is not recommended. In addition to poor repeatability, the possibility exists that assessments of VO[2] kinetics derived from MFBS WR forcings will also depend on the distribution of power across the harmonic content of the sequence. Therefore, whilst MFBS WR forcings may be suited to the assessment of VO[2] kinetics in subjects with a reduced tolerance to exercise, there remain doubts concerning both the validity of the response data and applicability of the method. Until these issues have been resolved, care would need to be taken when using estimates of VO[2] kinetics derived from MFBS WR forcings to determine the functional state of the cardiorespiratory system.
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Ahmed, Shamsuddin. "Kinetics of the reaction of oxygen with carbon and of the explosive reaction of carbon monoxide and oxygen." Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/4811.
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Moy, Andrew Peter. "Mean blood velocity and oxygen uptake kinetics in older and younger men." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ58065.pdf.
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Jeans, Christopher. "Studies of the reduction kinetics of P680+ in oxygen evolving Photosystem II." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369087.
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Baker, Jonathan. "The interaction between the oxygen uptake kinetics and the power-duration relationship." Thesis, Aberystwyth University, 2011. http://hdl.handle.net/2160/09701472-16dc-4156-b66b-53fda7cca581.
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The aim of the present thesis was to experimentally test hypotheses originally forwarded by Burnley and Jones (2007): that the kinetics interact with an individual’s capacity for substrate-level phosphorylation and maximal oxygen uptake to determine the power-duration relationship. Experiments were designed to manipulate the kinetics, the “anaerobic capacity,” and/or the maximal oxygen uptake, and determine the effect of these manipulations on the power-duration relationship. Prior high-intensity exercise was used to investigate the classic priming effect during subsequent high-intensity exercise. Both heavy- and severe-intensity exercise ‘primed’ the kinetics (i.e., increased primary amplitude, reduced the slow component trajectory and amplitude). Following 10 min recovery, prior heavy-intensity exercise increased exercise tolerance as a result of an increase in W (C: 16.0 4.8 vs. PHE: 18.7 4.8 kJ; 95% CI, 0.3, 5.2 kJ). In contrast, following the same recovery period, no difference was seen in performance or the power-duration relationship after prior severe-intensity exercise. It was considered that the accumulation of H+ ions (thereby reducing pH) during high-intensity exercise may be implicated in the fatigue process. Sodium bicarbonate ingestion was used to increase the buffering capacity of the blood. This intervention had no effect on the kinetics or , but increased CO2 production, , and blood [lactate] at exhaustion. Despite these results, no overall difference was seen in exercise tolerance between conditions; however, CP was reduced (Pl: 303 ± 48 vs. Na: 296 ± 53 W; 95% CI, 0,14 W) and W increased (Pl: 19.5 ± 8.6 vs. Na: 22.4 ± 9.2 kJ; 95% CI, -5.2, -0.7 kJ), following alkalosis. The final two studies were designed to reduce muscle O2 availability by lowering the O2 carrying capacity of the blood (Blood donation), or through a reduction in perfusion pressure (Supine exercise). Each of these interventions has similar effects on the kinetics: a reduction in the primary amplitude (and a longer time constant; supine only); no change in the slow component trajectory; and a reduction in its amplitude and . Blood donation reduced exercise tolerance, and supine exercise was performed at the same relative intensity, so no difference was seen in time to exhaustion. Each of these interventions reduced CP for blood donation and supine exercise (C: 259 ± 54; vs. BD: 246 ± 42 W; 95% CI: 2, 26W) and (UP: 275 ± 36 vs. SUP: 216 ± 13 W; 95% CI, 40, 78 W), while W was unchanged following each intervention. The experiments conducted in the current programme of research demonstrate that manipulating the kinetics, , or the parameters of the power-duration relationship have predictable effects on exercise tolerance. Hence, these data support the notion that the interaction between the kinetics, the maximal oxygen uptake, and substrate-level phosphorylation determines exercise tolerance and therefore shapes the power-duration relationship.
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Dascombe, Benjamin James, and b. dascombe@cqu edu au. "Pulmonary Oxygen Uptake and Muscle Oxygenation Responses to Exercise in Well-Trained Young and Middle-Aged Cyclists." Central Queensland University. Department of Health and Human Performance, 2007. http://library-resources.cqu.edu.au./thesis/adt-QCQU/public/adt-QCQU20070719.105750.
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This thesis details four consecutive research investigations which were designed to examine the effect of age on the pulmonary oxygen uptake (VO2)and muscle oxygenation (mOxy) responses to exercise in well-trained cyclists. (Abridged)
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DiMenna, Fred J. "The influence of muscle fibre recruitment on VO2 kinetics." Thesis, University of Exeter, 2010. http://hdl.handle.net/10036/106719.
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When O2 uptake at the lung is used to characterise the oxidative metabolic response to increased contractile activity ( O2 kinetics) in exercising muscle, the O2 profile reflects the combined influence of all involved muscle fibres. Consequently, during high-intensity exercise that mandates activation of fibres with considerable metabolic diversity (e.g., both principal fibre types), response characteristics specific to discrete segments of the recruited pool cannot be determined. The purpose of this thesis was to identify fibre-type-specific effects of conditions that might impact O2 delivery and/or motor unit recruitment patterns on O2 kinetics by using two models that increase fibre recruitment homogeneity during exercise transitions. In four experiments, subjects initiated high-intensity exercise from a moderate baseline (i.e., performed ‘work-to-work’ transitions; M→H) to target higher-order fibres, and in two experiments, subjects cycled at extremely slow and fast pedal rates to skew recruitment toward slow- and fast-twitch fibres, respectively. At mid-range contraction frequency, O2 kinetics (as indicated by the primary time constant, τp) was slower for M→H compared to unloaded-to-high-intensity transitions (U→H) (e.g., 42 v. 33 s; Ch 4) and this slowing was ~50% greater for M→H in a supine body position (decreased oxygenation; Ch 6). Slower kinetics was also present for U→H cycling at fast compared to slow pedal rates (τp, 48 v. 31 s; Ch 8). Conversely, M→H slowing relative to U→H was absent at extreme cadences (36 v. 31 s and 53 v. 48 s for slow and fast, respectively; Ch 7). After ‘priming’ (increased oxygenation), τp was reduced for U→H after fast-cadence priming only (Ch 8) and for M→H in the supine position (Ch 6), but unaffected for upright cycle and prone knee-extension M→H, for which priming reduced the O2 slow component and delayed-onset fibre activation (as indicated by iEMG; Chs 4 and 5). These results provide evidence in exercising humans that high-order fibres possess innately slow O2 kinetics and are acutely susceptible to interventions that might alter O2 delivery to muscle.
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Skiba, Philip Friere. "The kinetics of the work capacity above critical power." Thesis, University of Exeter, 2014. http://hdl.handle.net/10871/15727.
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The critical power (CP) model includes two constants: the CP and the W′ [P = W′ / t) + CP]. The W′ is the finite work capacity available above CP. Power output above CP results in depletion of the W′; complete depletion of the W′ results in exhaustion. It is possible to model the charge and discharge of the W′ during intermittent exercise using a novel integrating model (the W′BAL model), and to generate a function describing a curvilinear relationship between time constants of reconstitution of the W′ in terms of the difference between recovery power and CP (DCP) (r2 = 0.77). The depletion of the W′ as predicted by the W′BAL model during intermittent exercise is linearly related to the rise in V ̇O_2 above exercise baseline (r2 = 0.82 – 0.96). During intermittent exercise, the W′BAL model is generally robust with respect to the length of work and recovery interval, yielding a mean under-prediction of the W′BAL of only -1.6 ±1.1 kJ. The amount of W′ remaining after a period of intermittent exercise correlates with the difference between the subject’s V ̇O_2 at that time (V ̇O_2START) and V ̇O_2PEAK (DVO2) (r = 0.79, p < 0.01). Moreover, the W′BAL model also performs well in the field, permitting accurate estimation of the point at which an athlete becomes exhausted during hard training or competition (mean W′BAL at exhaustion = 0.5 ± 1.3 kJ (95% CI = 0 – 0.9 kJ). The W′BAL model meets the mathematical criteria of an excellent diagnostic test for exhaustion (area under ROC curve = 0.91). 31P magnetic resonance spectroscopy during single leg extensor exercise revealed a correlation between the recovery of the W′BAL model and recovery of creatine phosphate ([PCr]) after a bout of exhaustive single leg extensor exercise (r = 0.99, p < 0.01). The W′BAL model also accurately predicted recovery of the W′ in this setting (r = 0.97, p < 0.05). However, a complete understanding of the relationship between the depletion and recovery of [PCr] and the depletion and recovery of the W′ remains elusive. Muscle carnosine content is curvilinearly related to the rate of W′BAL recovery, with higher muscle carnosine associated with faster recovery, with implications for muscle buffering capacity and calcium handling. The W′BAL model may be recast in the form of a differential equation, permitting definition of the time constant of recovery of the W′BAL in terms of the subject’s known W′ and the DCP. This permits the scaling of the model to different muscle groups or exercise modalities. Moreover, modifications to this mathematical form may help explain some of the variability noted in the model in earlier studies, suggesting novel avenues of research. However, the present formulation of the W′BAL model is mathematically robust and represents an important addition to the scientific armamentarium, which may aid the understanding the physiology of human performance.
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Walsh, Timothy Simon. "Oxygen kinetics and energy expenditure in fulminant hepatic failure and during liver transplantation." Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/27613.
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The purpose of this thesis was to examine aspects of oxygen transport and uptake in patients with acute chronic liver disease with specific reference to the management of fulminant hepatic failure (FHF) and the intraoperative management of patients undergoing liver transplantation. A prospective randomised controlled study was carried out in patients with FHF with two major objectives: first to compare the reverse Fick method of calculating oxygen consumption (VO2) with a gas exchange method. Second, to evaluate the effect of the drug N-acetylcysteine in patients with FHF which previous work suggested may improve DO2, VO2, and tissue oxygen extraction in this condition. These studies showed that the reverse Fick method is inaccurate in patients with FHF because of propagation of measurement errors. Mathematical coupling could explain the apparent dependence of VO2 on DO2 when the Fick method was used to calculate VO2. The factors which increase the likelihood of mathematical coupling in oxygen kinetics studies were considered. With the gas exchange method of measuring VO2 no clinically significant relationship was found between DO2 and VO2 during N-acetylcysteine infusion, and no improvement in oxygen extraction by tissues was found. Variable effects on cardiovascular parameters were found, but overall no differences from the control group were demonstrated. No relationship was found between plasma N-acetylcysteine concentrations and clinical response. Energy expenditure and the acute phase response was investigated in patients with FHF. Energy expenditure was increased by approximately 20-25% in FHF in comparison with spontaneously breathing healthy volunteers and physically anhepatic patients with chronic liver disease studied during liver transplantation. Plasma TNFα, IL-6, and C-reactive protein were measured. These were significantly elevated in comparison with healthy controls in keeping with a significant acute phase response. Studies were carried out in patients undergoing liver transplantation using indirect calorimetry. Significant changes in metabolic rate, oxygen transport, and acid-base balance were demonstrated following graft reperfusion and the factors which influence these changes were discussed.
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Wang, Yongqiang. "Oxygen kinetics in the laccase-catalyzed removal of cresols and phenol from water." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ62299.pdf.
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Paggiosi, Margaret Anne. "Oxygen uptake kinetics in the frequency domain as a test for cardiorespiratory fitness." Thesis, Sheffield Hallam University, 1998. http://shura.shu.ac.uk/20158/.
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Oxygen uptake kinetics describe the characteristics of the rate of change of VO[2] in response to the onset of exercise or a change in work rate. There is a lack of knowledge concerning the use of VO[2] kinetics in the frequency domain as a test for cardiorespiratory fitness. The PRBS exercise test has been developed to study the dynamic responses of the cardiorespiratory system to random changes in submaximal work rate. This exercise test technique provides a multi-frequent assessment of VO[2] kinetics that can be expressed in terms of amplitude (ml-min[-1]W[-1]) or phase shift (degrees) over a frequency range of 0.0022 to 0.0089 Hz. The VO[2] kinetics of young women were investigated using this submaximal test during which the work rate was alternated between two levels. The upper work rate level was chosen to be below the ventilatory threshold. In the first experiment, the variability of replicate tests was investigated in a cohort of eight moderately active women (age = 22.6 +/- 0.8 years). Although there were wide limits of agreement between the two tests there was no significant difference between test 1 and test 2.In a second experiment to test the discriminant ability, oxygen uptake kinetics were compared to VO[2peak] in twenty-eight sedentary or moderately active young women (age = 22.9 +/-3.1 years). The PRBS exercise test technique was able to discriminate between a group of subjects with lower VO[2peak] (VO[2peak] = 32.3 +/- 3.3 ml-kg-1min-1) and a group of subjects with higher VO[2peak] (VO[2peak] = 41.1 +/- 3.2 ml-kg-1min-1). Differences in VO[2] kinetics occurred at frequencies of 0.0022 Hz for amplitude, and at frequencies of 0.0022 Hz to 0.0067 Hz for phase shift. Significant relationships were found to exist between VO[2peak] and VO[2] kinetics at frequencies of 0.0022Hz, 0.0044 Hz and 0.0067 Hz. The following model explained the highest proportion of the variation between VO[2peak] and VO[2] kinetics (r = - 0.72, P0.001): VO[2peak] (in ml-kg[-1]min[-1]) = 0.503(phase shift at 0.0067 Hz) (in degrees) + 72.24In a third experiment to test the sensitivity to detect change, both VO[2] kinetics and VO[2peak] were measured before, during and after an eight week endurance-type training programme completed by fifteen young women (age = 21.6 +/- 1.9 years). Thirteen young women (age = 24.3 +/-3.5 years) acted as a non-training control group. Faster VO[2] kinetics were measured at a frequency of 0.0044 Hz for amplitude and at frequencies of 0.0022Hz to 0.0067 Hz for phase shift following the training programme. Increases in VO[2peak] also occurred as a result of the exercise regimen. No changes in either VO[2] kinetics or VO[2peak] were observed in the non-training group. This study showed that the PRBS exercise test technique was sensitive to short-term endurance-type training adaptations. In conclusion, the parameters measured during the PRBS exercise test provide valuable information that can not be gained from a standard assessment of VO[2] kinetics in the time domain. It is proposed that this exercise test technique has potential as a means of assessing cardiorespiratory fitness within the area of sports science and within the clinical environment.
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Bowman, Sherrie S. "Atomic and Molecular Oxygen Kinetics Involved in Low Temperature Repetitively Pulsed Nonequilibrium Plasmas." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1370365358.
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Forlines, Robert Alan. "Laser Initiated Chain Reactions: The Kinetics of the Chlorine/Cyclohexane/Oxygen Chain System." Wright State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=wright1182792546.
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Dynkin, Alexey. "Effects of strontium doping on oxygen reduction kinetics in thin-film LSCF cathodes." Thesis, Boston University, 2013. https://hdl.handle.net/2144/12092.
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Thesis (M.S.)--Boston UniversityDense films of the mixed ionic-electronic conductor lanthanum strontium cobalt fenite (La1-xSrxCo0.2Fe0.8O3-δ) with x= 0.4, 0.3 and 0.2 (thereafter refened to as LSCF-6428, LSCF-7328 and LSCF-8228) were deposited in fixed patterns on yttria-stabilized zirconia (YSZ) substrates on top of a gadolinium-doped ceria (GDC) barrier layer by pulsed laser deposition (PLD) at the Pacific Northwest National Laboratory (PNNL) in Richland, WA. A counter electrode of porous 50-50 wt %/48.3-51.7 vol.% LCMIYSZ was screen-printed on the opposite side of the substrates. Electrochemical impedance spectroscopy (EIS) data were gathered for each of the compositions in air, but at varying temperatures (600, 700 and 800 °C). The total electrode polarization resistance, Rpob was plotted as a function of composition and temperature. Results show that, for all temperatures, the total polarization resistance drops considerably when the Sr composition is reduced from 0.4 to 0.3, and then increases slightly as the Sr composition is further reduced from 0.3 to 0.2 The relatively high polarization resistance for LSCF-6428 may be explained by recent evidence found by other members of our research group of surface strontium migration in LSCF-6428 films, which results in the formation of phases that could potentially affect electrochemical performance.
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McNulty, Craig R. "The complex reality of VO2 kinetics to steady state: Reassessment of the models used to quantify and interpret VO2 kinetics, steady state, and time to steady state." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/108025/2/Craig_McNulty_Thesis.pdf.
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This thesis developed new methods of modelling oxygen uptake in exercising humans during cycling exercise sessions to steady-state. The results will contribute to the redefinition of conventional methods of data acquisition, processing, and modelling across exercise physiology, sports science, and respiratory disease research and application. The thesis identified misconceptions within current methods of data handling, and proposed innovative methods for improved data modelling.
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Chan, Wing-wai Stephen, and 陳永偉. "The comparison of recovery kinetics of oxygen consumption and heart rate between children and adults: a practicalsuggestion on maximizing the usage of recovery kinetics in clinicalsetting." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31257367.
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Hertz, Joshua L. (Joshua Lee). "Microfabrication methods to improve the kinetics of the yttria stabilized zirconia -- platinum -- oxygen electrode." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37354.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 183-194).
Solid oxide fuel cells are a potential electrical power source that is silent, efficient, modular, and capable of operating on a wide variety of fuels. Unfortunately, current technologies are severely limited in that they provide sufficient power output only at very high temperatures (>800°C). One reason for this is because the electrodes have very poor (and poorly understood) kinetics. The work described in this dissertation involves the microfabrication of model systems with triple phase boundary lengths that varied over an order of magnitude to systematically quantify and ultimately improve the kinetics of platinum electrodes on the surface of yttria stabilized zirconia electrolytes. Platinum electrodes with well controlled geometry were sputtered onto the surface of bulk YSZ and onto sputtered YSZ thin films. An unexpected result was found whereby YSZ films of composition Y0.09Zr0.91O2-x had an ionic conductivity remarkably enhanced by a factor of 20-30. This is attributed to the films exhibiting nanometric grain sizes and thereby stabilizing the cubic morphology at considerably lower yttrium levels than is normally needed. This metastable cubic phase is suspected of having reduced defect ordering.
(cont.) Grain boundary resistance, which in YSZ is normally due to impurities that segregate and block ionic transfer, was found to also be significantly reduced in YSZ films. The films had a specific grain boundary conductivity enhanced by a factor of 30-100 compared to the bulk polycrystalline sample. This was believed to be due to the very low impurity content of the film grain boundaries. Concerning the electrode polarization resistance, it was found that the electrodes placed on bulk standards and films deposited at high temperatures were on par with the best electrode conductance values from the literature. However, when the electrolyte surface was a film deposited at reduced temperature, the resistance decreased further by a factor of 300-500. The cause of this was revealed to be silicon contamination on the surfaces of the poorer-performing electrolytes. Triple phase boundary length-specific resistances as low as 3.7·104 O·cm at 378°C and 4.0·107 O·cm at 215°C were measured; these appear to be the lowest ever recorded. The measurements are possibly the first electrochemical characterization of nearly silicon-free YSZ surfaces. This study emphasizes the key role of chemical purity at the electrode-electrolyte interface.
(cont.) Photolithography alone is unlikely to give technologically useful triple phase boundary lengths. In an attempt to achieve the triple phase boundary lengths needed for a practical device, reactive co-sputtering was used to produce composite Pt-YSZ thin films with a bi-continuous network morphology and grain sizes on the order of 30 nm. Such intimate mixing of the electronic and ionic conducting phases created an effective mixed ionic-electronic conductor with the entire surface of the film electrochemically active to the electrode reaction. The best processing conditions resulted in electrodes with an area specific polarization resistance less than 500 O·cm2 at 400°C and, by extrapolation, 10 O·cm2 at 511°C and 1 O·cm2 at 608°C. These films may enable operation of a micro-solid oxide fuel cell at intermediate temperatures (400-500°C), and perhaps even lower temperatures with further microstructural optimization.
by Joshua L. Hertz.
Ph.D.
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Jester-Weinstein, Jack (Jack L. ). "Progress in an oxygen-carrier reaction kinetics experiment for rotary-bed chemical looping combustion." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/83722.
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Thesis (S.B.)--Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (page 44).
The design process for an experimental platform measuring reaction kinetics in a chemical looping combustion (CLC) process is documented and justified. To enable an experiment designed to characterize the reaction kinetics of the reduction/oxidation cycle in a rotary channeled oxygen carrier, a platform was designed to deliver controlled conditions of temperature and gas flow around a central disc of oxygen-carrier material and determine the rates of oxidation and reduction using real-time gas analysis (RTGA). In order to deliver precise and accurate results, it was necessary to identify and either minimize or compensate for interfering factors such as gas turbulence, temperature fluctuation, and flow equipment response time delays. This paper serves as a progress report on the experimental reactor; the overall design process is discussed, including equipment selection, reactor design, electronics and control hardware setup, and software interface design, and the current state of the reactor is discussed, including an assessment of the current capabilities and drawbacks of the system, future work, and potential methods for improvement.
by Jack Jester-Weinstein.
S.B.
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De, Jager Debbie. "Streptomyces coelicolor biofilm growth kinetics and oxygen mass transfer within a membrane gradostat bioreactor." Thesis, Cape Peninsula University of Technology, 2009. http://hdl.handle.net/20.500.11838/892.
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Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2009The main purpose of this study was to quantify the growth and oxygen mass transfer kinetic parameters of the filamentous bacterium Streptomyces coelicolor, immobilised on the external surface of a ceramic membrane in a continuously operated pressurised Membrane Gradostat Bioreactor (MGR). One of the most important and critical parameters required when studying biofilms, are the growth kinetics, as they can be utilised to model both the mass transfer and biological reactions occurring within the biofilm. Single fibre MGR's (SFMGR) were operated using a pneumatic system to supply humidified pressurised air to the extra capillary space (ECS) and pressurised growth medium to the lumen of the ceramic membrane. Two growth media; a complex growth medium, ISP2, and a defined growth medium, were tested and supplied to the lumen of the ceramic membrane in the dead-end mode
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Li, Hao. "Kinetics and Mechanisms of the Oxidation Processes for Unsaturated-Hydrocarbon-Modified Scavengers." University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1279218555.
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Li, Qian. "Electrochemical reduction of oxygen." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:2f37a1ae-dab0-4581-a8fd-e01ce59246c4.
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The main aim of the work reported is the design of proof-of-concept of at point-of-use hydrogen peroxide electrogeneration from air. The experimental work discussed within this thesis explores five major areas: the kinetics of electrocatalysis, ion-pairing, change of solvent media, the electrode surface modication by a redox mediator, and the electrochemical reduction of oxygen within enhanced mass transport systems. The electrocatalytic rates and mass transport of two oxygen reduction redox meditors, viz. anthraquinone and methyl viologen, are studied in aqueous solutions. The investigation is facilitated through the use of a boron-doped diamond electrode, allowing the catalytic response to be clearly delineated from that of the direct oxygen reduction process. The use of simulation software is highlighted in combination with experimental voltammograms to extract kinetic data. Specifically, the voltammetric features, such as the `reverse' peak and the `split waves', are given particular attention. Consequently, it is possible to deconvolute the electrocatalytic reaction mechanisms. The reactivity of the viologen radical cation is comparable to the semiquinone radical anion in aqueous solution ((4.8~6)x10^9 M^-1 s^-1), but over a far wider pH range (pH 2.5 - pH 8.5). The change of local proton concentration, and sequential electron transfers play key roles here. Moreover, the reduced reactivity of semiquinone is observed upon formation of ion-pairs with tetrabutylammonium cations in alkaline solutions. The electro-reduction of oxygen and its mediated pathways are also investigated in non-aqueous media; in particular the thermodynamics, the kinetics, and mass transport involved in these processes. Through a variable temperature study in electrolytic acetonitrile solution, the oxygen dissolution is quantitatively shown to be an endothermic process. Moreover, the diffusion coeficients and concentration of oxygen upon change of acetonitrile mole fraction is also explored in water-acetonitrile mixtures. The rates of bimolecular reactions are extracted from simulation programs, involving semiquinone in anhydrous acetonitrile and viologen radical cation in ethanol, and show a 3 - 4 orders of magnitude reduction compared to that in aqueous solution. Although the solubility of oxygen is ca. 6 - 8 times larger in non-aqueous solvents, the much reduced homogeneous rates limit the electrogeneration of hydrogen peroxide in pure organic media. Novel surface modification methodologies for graphitic surfaces with covalently attached anthraquinonyl groups are studied and characterised. The anthraquinonyl-modified carbon surfaces show much reduced overpotentials required for oxygen reduction. In the final chapter, utilising the new surface modification methodology and novel designs, two gravity-feed flow cells for electrochemical reduction of oxygen in aqueous solutions are proposed and characterised, one based upon the tubular electrode geometry. The other exhibits much enhanced current conversion by using a porous reticulated vitreous carbon electrode. The latter may provide a prototype hydrodynamic system to produce dilute hydrogen peroxide solution at point-of-use.
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Lepikhin, Nikita. "Fast energy relaxation in the afterglow of a nanosecond capillary discharge in nitrogen/oxygen mixtures." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX087/document.
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L'objectif principal du présent travail était d'étudier, comment la cinétique du plasma change dans les conditions de dépôt d'énergie spécifique élevé dans des champs électriques réduits élevé. La décharge capillaire nanoseconde a été utilisée comme outil expérimental. Les mesures sont effectuées dans l'azote pur et dans les mélanges azote/oxygène. Les paramètres électriques de la décharge sont mesurés: la tension appliquée, le dépôt d'énergie, le champ électrique et le courant électrique. Les spectres de l'émission optique de la décharge sont obtenus. La densité électronique dans les impulsions de décharge est mesurée. La décroissance du plasma est étudiée par les mesures de la densité électronique dans la post‐luminescence de la décharge. Les processus contrôlant la décroissance du plasma sont déterminés. La dépopulation de molécules excitées sur l'exemple de l'azote moléculaire N2(C) est étudié dans des mélanges azote/oxygène. Les processus responsables de la dépopulation des espèces excitées lors de la post‐luminescence de la décharge de nanoseconde à les conditions de dépôt d'énergie spécifique élevé dans des champs électriques réduits élevé sont examinés. La distribution radiale des espèces excitées à différentes compositions de gaz sont étudiée et comparées. L'étude expérimentale et numérique des processus responsables du chauffage rapide du gaz dans l'azote pur et dans les mélanges azote/oxygène dans la post‐luminescence de la décharge capillaire à la nanoseconde sont effectuées. Les particularités du chauffage rapide du gaz aux conditions de la décharge de nanoseconde à de dépôt d'énergie spécifique élevé dans des champs électriques réduits élevé sont étudués. La modification du schéma cinétique actuellement utilisé est proposéeThe main aim of the present work was to investigate, how the plasma kinetics changes at the conditions of high specific energy deposition at high reduced electric fields. The nanosecond capillary discharge was used as an experimental tool. The measurements are performed for pure nitrogen and nitrogen/oxygen mixtures. Electric parameters of the discharge are measured: the applied voltage, the energy deposition, the electric field, and the electric current. The spectra of the optical emission of the discharge are obtained. The electron density in the discharge pulses is measured. The plasma decay is studied by the measurements of the electron density in the afterglow of the discharge as well. The processes controlling the plasma decay are determined. Depopulation of excited molecules on the example of N2(C) state of molecular nitrogen is studied in nitrogen/oxygen mixtures. The processes responsible for depopulation of excited species in the afterglow of the nanosecond discharge at high specific deposited energy at high reduced electric field are discussed. The radial distributions of the excited species at different gas compositions are investigated and compared. The experimental and numerical studies of the processes responsible for fast gas heating in pure nitrogen and in nitrogen/oxygen mixtures in the afterglow of nanosecond capillary discharge are performed. The peculiarities of the fast gas heating at conditions of the nanosecond discharge at high specific deposited energy at high reduced electric field are discussed. The modification of the kinetic scheme currently in use is proposed
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McNarry, Melitta Anne. "The influence of training status on the physiological responses to exercise of young girls." Thesis, University of Exeter, 2010. http://hdl.handle.net/10036/3043.
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Exercise training represents a potent stimulus to the parameters of aerobic and anaerobic fitness in adults; whether the same is true in young girls is unclear. For some parameters, such as peak oxygen uptake, the influence of training status remains controversial whilst for other parameters, such as oxygen uptake kinetics, the influence of training status remains simply uninvestigated in young girls. Despite this lack of empirical evidence, it has been suggested for some time now that children may lack trainability and that this may be related to the presence of a maturational threshold below which significant adaptations to training cannot occur. This suggestion requires investigation, not least because the findings of some studies which appear to support this contention may in reality be a reflection of the use of an inappropriate test modality for the investigation of training status influences. The purpose of this thesis was therefore to determine the physiological trainability of girls at different stages of maturation and to investigate the interaction between training status, maturity and exercise modality. To achieve this purpose a series of 5 studies was completed, in which trained and untrained girls completed ramp incremental exercise, constant-work-rate exercise and Wingate exercise on two exercise modalities, one upper (arm crank) and one lower body (cycle). During these tests, cardiovascular, respiratory, metabolic and mechanical power parameters were assessed. In response to ramp incremental exercise, trained girls were shown to have a higher peak O2, SV and at all stages of maturity, along with an altered SV and fractional muscle oxygen extraction pattern, irrespective of exercise modality. The importance of exercise modality was evident during heavy intensity constant-work-rate exercise in pre-pubertal girls, where training status was only associated with significant influences on O2 kinetics (faster phase II time constant in trained girls) during upper body ergometry. In contrast, pubertal trained girls had faster O2 kinetics during both exercise modalities, an influence which may suggest both central and peripheral adaptations to the delivery and utilisation of oxygen. Exercise modality was also revealed to be an important factor in the demonstration of training status influences during a 30 s Wingate test, with trained girls at all stages of maturity exhibiting higher mechanical power indices during upper body ergometry only. An influence of training status was also evident in the lower fatigue index found in the trained girls at all stages of maturity during both modalities, but no influence was found in the oxidative contribution to the Wingate test. None of these studies revealed an influence of maturity status in determining the magnitude of training status effects. Overall, the 5 studies encompassed within this thesis demonstrate that children are trainable and that this is not moderated by maturity.
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Hickson, Kevin Michael. "A study of several reactions relevant to atmospheric ozone chemistry." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343854.
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Koep, Erik Kenneth. "A Quantitative Determination of Electrode Kinetics using Micropatterned Electrodes." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10524.
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Interfacial polarization resistances limit the performance of many thin film solid-state devices, especially at low temperatures. To improve performance, a fundamental understanding of the electrode kinetics that govern interfacial reaction rates must be developed. The goal of this work is to determine site-specific reaction mechanisms and the relative significance of various reactions in order to quantify optimum structural parameters within the cathode microstructure. Key parameters include the length of triple phase boundary (TPB), the quantity of exposed electrolyte/electrode surface, and the ratio of electrolyte to electrode material. These parameters, when studied in a specific system, can be incorporated into broader models, which will encompass the specific conductivity of each component to develop an optimized three-dimensional network.
The emphasis of this work is the systematic control and manipulation of potential cathodic reaction sites in order to develop an understanding of the relative importance of specific reaction sites. Since the physical dimensions of reaction sites are relatively small, an approach has been developed that utilizes micro-fabrication (similar to that used in integrated-circuit fabrication) to produce small and highly controlled microstructures.
Investigations were made into the nature and reactivity of Triple Phase Boundaries (hereafter TPB) through the use of patterned platinum electrodes since only the TPBs are active in these electrodes. After the processing details of micro-fabrication were established for the platinum electrodes, patterned Mixed-Ionic/Electronic Conducting (MIEC) electrodes were fabricated and studied using impedance spectroscopy to determine the contributions from the MIEC surface versus the TPB. Systematically changing the geometry of the MIEC electrodes (thickness and line width) allowed for the determination of the effect of ambipolar transport within the MIEC on the activity of MIEC surfaces versus the TPB. This information is critical to rational design of functionally graded electrodes (with optimal particle size, shape, porosity and conductivity). In addition to experimental studies, representative patterned electrode samples were made available for collaborative studies with surface scientists at other institutions to provide additional techniques (such as Raman Spectroscopy) on the carefully designed and controlled cathode surfaces.