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1
Leeuw, Lerothodi La Pula. "Iras oxygen- and carbon-rich miras close to the galactic plane." Master's thesis, University of Cape Town, 1997. http://hdl.handle.net/11427/18617.
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Observations are presented for 101 I RAS sources that were expected to be Mira Variables and that lie close to the galactic plane: -7.0 3 < b < + 1° and 282.°5 < l < 285.°5. Over 1090 JHKL photometry modules were obtained for the sources. From the photometry the sample was shown to comprise 85 Miras, 12 of which had published periods. New periods were determined for all the Miras. Of the 85 Miras in the sample, 21 had previous published spectra and the rest were tentatively classified as oxygen or carbon-rich Miras using infrared two-colour diagrams. The oxygen and carbon-rich Miras, respectively, have mean periods and K half-amplitudes of 386 days and 0.36 mag and 442 days and 0.46 mag. Statistical tests showed that the probability that the period distribution functions of the oxygen and carbon-rich stars came from the same population was very small: 0.00055. The period as well as the K- Land K- [12μm] colours were shown to be functions of amplitude. For the carbon-rich Miras the [12μm]- [25μm] colour was shown to be correlated with amplitude. Bolometric magnitudes were determined by integrating under a spline curve fitted to the J H K L12, 25μm fluxes of the Miras. Distances to the stars have been calculated using absolute magnitude P- L relations from oxygen-rich and carbon-rich Miras in the LMC, where the LMC distance modulus of 18.57 was adopted. In addition, a search of Miras in the Galactic Bulge using APM-scanned !-plate data are presented. A total of 116 Mira candidates were identified, 43 of which were classified as strong candidates. The presented work will contribute to the study of Galactic structure.
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Jamuna, Sivathasan, and jsivathasan@yahoo com. "Preparation of Clay-dye pigment and its dispersion in polymers." RMIT University. Civil, Environmental and Chemical Engineering, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20090219.160137.
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This thesis is concerned with an experimental study of clay intercalation by organic dye molecule which is crucial for the successful development of a stable clay-dye pigment with combined advantages of organic dye and inorganic clay. Clay-dye pigments were prepared by two different methods. Two different organic dyes were used with unmodified clay and modified clay to study the intercalation. Characteristics of clay-dye pigment have been investigated using X-Ray Diffraction, Thermo-gravimetric Analysis and Transmission Electron Microscopy. In this thesis it is shown that the absorption of cationic dye by unmodified clay in aqueous medium mainly takes place in the interlayer clay surface. More likely the dye molecules with aromatic quaternary ammonium cation intercalate the clay layer and strongly interacts with the clay interlayer oxygen plane, where solvent dye (which is hydrophobic in nature) adsorption by unmodified clay mainly takes place on outer surface of the clay. Dye molecules are weakly interacted with outer surface oxygen plane by hydrogen bonding or Vander Waals forces. Modified clay enabled the solvent dye to intercalate inside the clay interlayer surface with the suitable non-aqueous medium (because of its expanded structure). The modified clay suspension in the selected non-aqueous medium shows only partial desorption of alkyl ammonium molecule from the clay layer with the presence of both cationic dye and solvent dye. Therefore the penetrated dye molecules must have weakly interacted with the interlayer oxygen plane as well as the remaining alkyl ammonium molecule present inside the clay layer. It is believed that the thermal and UV stability of organic dye can only be facilitated by a specific interaction (à-interactions) between aromatic alkyl ammonium cation of organic dye molecule and the interlayer oxygen plane of clay minerals. This interaction possibly enables the high thermal energy or the energy of the UV radiation to transmit immediately into the clay layer. Therefore organic dye molecules are protected from high energy loading and hence thermal and UV stability are improved.
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Björnängen, Therese. "Resistive studies of vortices and fluctuations in single crystal YBa2Cu3O7-." Doctoral thesis, KTH, Physics, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3723.
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High-temperature superconductors have been intensely studiedsince the discovery, almost 20 years ago. Their layeredstructure, extreme type-II behavior, large anisotropy, andstrong fluctuations have led to a large number of new andinteresting problems. In this work the resistive transitionhave been studied in YBa2Cu3O7-δsingle crystals, from the superconductingfluctuations above Tcdown to the vortex matter near the onset of resistivity.Superconducting fluctuations above Tcare suitably studied by measuring themagnetoconductivity Δσ = 1/ρ(B)-1/ρ(0).Such experiments were performed on untwinned, optimally dopedsamples, forI||ab. ForH||c, fluctuations in the CuO-chains was not important, andfluctuations in the CuO2 planes seemed isotropic. The in-planecoherence length anisotropy was determined to be close tounity. ForH||ab, Δσbdepended on the field direction, indicating an effect ofthe chains on the magnetoconductivity in thisconfiguration.
The nature of the vortex phase below Tccan be examined through vortex-correlation measurements.Using a modified pseudo-flux transformer (PFT) geometry forin-plane experiments, the magnetic field could be appliedparallel to both the a, b, and c axis. A strong Lorentz forcewas detected, and observed to be a requirement for the meltingstep feature. The resistive anisotropy close to Tcwas strongly field and temperature dependent, which wasexplained by an almost isotropic fluctuation contribution.
The effect of anisotropy on vortex-liquid correlation infieldsH||ab, was studied byc-axis transport measurements in oxygen-deficientsamples, using a PFT configuration. Increasing disordersuppressed both longitudinal and transverse correlation. Inheavily underdoped samples, vortex correlation was enhanced formagnetic fields exactly aligned with theabplane because of the strong anisotropy. Also, thesolid-to-liquid transition temperature became nearly fieldindependent.
Attempts were also made to connect the fluctuation regime ofthe resistive transition with the vortex region,by accountingfor critical fluctuations close to the transition.
Keywords:high-temperature superconductors, YBa2Cu3O7-δ, untwinned YBCO, oxygen deficiency,superconducting fluctuations, magnetoconductivity, in-planeanisotropy, vortex liquid, vortex solid, vortex correlation
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Santhanam, Venkatesan 1968. "Optimization of the packaging of the Mars oxygen manufacturing plant." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/278162.
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A complete analysis of the various energy losses involved in the Mars oxygen manufacturing plant is performed. The various losses considered are the pressure losses and radiation losses in connections between components, radiative heat losses from and between different components of the plant. These, together with the cost and mass of a library of components are used to construct an objective function to optimize the packaging of the plant. A software package has been created to determine component locations in the package such that this objective function is minimized. The package reads input data from a component database system and performs various iterations to arrive at a configuration having the minimum of the energy losses. The steepest descent method is used for minimizing the nonlinear objective functions describing the energy losses. The minimization of the cost and mass factors are performed by a brute search method. The results of the optimization are presented graphically.
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Nayar, Gautam. "Oxygen transport in animal cell biogreactors with vibrating-plate aerators." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36553.
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Brzezek, Kerstin. "S-nitrosothiols and reactive oxygen species in plant disease resistance and development." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/9653.
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Nitric oxide (NO) as well as reactive oxygen species (ROS) play an important role in defence signalling in plants. After successful recognition of an invading pathogen, an increase in ROS occurs, the ’oxidative burst’; and a ’nitrosative burst’ is also observed. This leads to the induction of defence responses, including the ’hypersensitive response’ (HR), a form of programmed cell death. A balanced production of hydrogen peroxide and NO is crucial for HR induction. In a process called S-nitrosylation, NO can react with cysteine thiols to form S-nitrosothiols, or react with glutathione to form S-nitrosoglutathione (GSNO). The enzyme GNSO reductase (GSNOR) indirectly regulates SNO levels by turning over GNSO. The Arabidopsis thaliana T-DNA insertion mutant atgsnor1-3 shows a complete loss of GNSOR activity and has drastically increased SNO levels, resulting in stunted growth, loss of apical dominance, increased HR, loss of salicylic acid (SA) accumulation and increased susceptibility to avirulent, virulent and non-host pathogens. Two recessive and allelic EMS suppressor mutants in the atgsnor1-3 background were isolated, which showed mostly wild type growth. The mutations were identified by map-based cloning as two different point mutations in At1g20620 or CAT3, one of three catalase genes in Arabidopsis. Catalases break down hydrogen peroxide, with CAT2 being the major catalase in Arabidopsis. All three catalases are structurally very similar, but show temporal and spatial differences in their expression patterns. The suppressor mutants recovered apical dominance, and partially recovered disease resistance to avirulent pathogens, but were still susceptible to virulent pathogens and showed decreased SA levels. The suppressor mutants showed wild type HR in response to different avirulent bacteria. Interestingly, loss-of-function of the other catalase genes as well as loss-of-function of other redox-related genes did not restore apical dominance of atgnsor1-3 plants. This effect seems to be highly specific to CAT3, possibly because of its expression pattern or its expression levels. Further research is needed to fully understand the mechanisms at work here, but these results certainly seem to show a direct connection between redox signalling and S-nitrosylation.
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Benyó, I. (Imre). "Cascade Generalized Predictive Control—Applications in power plant control." Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514280326.
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The Generalized Predictive Controller in transfer function representation is proposed for the cascade control task. The recommended cascade GPC (CGPC) applies one predictor and one cost function that results in several advantageous features:
The disturbance regulations of the inner and the outer loops can be totally decoupled;
The inner disturbance regulation is well damped, the typical overshoot of the traditional cascade control structure is avoided;
The robustness properties of the inner and the outer loops can be designed separately;
The anti-windup properties of the CGPC are exactly as perfect as in the case of the simple SISO GPC. The typical problem of the saturation in the inner loop, resulting in modeling error for the outer loop, is prevented.
The CGPC was applied as the oxygen controller of a pilot fluidized bed boiler. The investigation is based on simulation experiments and on experiments on a pilot scale boiler.
In another simulation experiment, the CGPC was applied as the temperature controller of at a steam superheater stage. The results of the experiments well illustrated the power of the proposed cascade control algorithm.
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Startseva, Tatiana. "Infrared properties of high-temperature superconductors with single and triple copper oxygen planes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0026/NQ51013.pdf.
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Startseva, Tatiana. "Infrared properties of high-temperature superconductors with single and triple copper oxygen planes /." *McMaster only, 1998.
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Scarano, Fabio Rubio. "The effects of ontogeny and environmental oscillations on plant responses to oxygen deprivation." Thesis, University of St Andrews, 1993. http://hdl.handle.net/10023/14344.
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The effects of ontogeny and environmental oscillations on plant responses to oxygen deprivation were investigated for a wide spectrum of species, ranging from agricultural to forestry crops, and from temperate to tropical plants. The extent to which hypoxia- or anoxia-tolerance were affected by ontogeny and environmental oscillations, was assessed mainly through changes in survival and growth and physiological parameters such as respiratory activity, ethanol production and carbohydrate depletion. Anoxia-tolerance of germinating seeds of chickpea (Cicer arietlnum L.) was found to vary, even within the earlier stages of germination, according to the length of the aerobic imbibition period previous to the anoxic shock. The notable fact was that 6 minutes of seed aerobic imbibition prior to anoxic treatment was sufficient to significantly increase post-anoxic survival after 4 days anoxia, compared to seeds not allowed to previously imbibe aerobically. These survival results were mirrored by the significant increase in the oxygen uptake by the embryos of seeds which were allowed to imbibe aerobically for 2 hours prior to anoxia, compared to the embryos of anaerobically imbibed seeds. Germination stage also affected the response of barley (Hordeum vulgare L.) to washing under anoxia, a treatment used to investigate membrane stability and other factors associated with anoxic injury. Temperature, frequency of washing and nutrients present in the washing solution also affect the post-anoxic responses of barley. Daily washing of seedlings under anoxia was often detrimental to post-anoxic survival. One washing only, at the end of the anoxic period, often enhanced survival. This positive effect seemed to be more linked to protection against plasmamembrane leakage due to calcium ions present in the washing solution than to removal of anaerobically-produced potentially toxic volatiles. Two Brazilian tree species were also studied. The seeds of Parkia pendula (Willd.) Benth. ex. Walp., a species typically present in unflooded areas in the Amazon, were still able to germinate after seven months submergence. P.pendula one-month old seedlings, however, did not survive longer than one month flooding, which can be a considerable disadvantage in the ca. six-month long flooding period of the Amazon floodplains. However, adult trees can still be found, although rarely, in flooded areas. The possible strategies involved in an eventual establishment of P.pendula individuals in flooded areas of the Brazilian Amazon are discussed. A contrast is drawn between the responses to flooding of this species and flood-tolerant Parkia discolor. Enterolobium contortisiliquum (Veil.) Morong, is a tree species which is present in both the dry soils of the cerrados (neotropical savannas) in Central Brazil and in the flood-prone Gallery Forests. This species showed considerable tolerance to flooding and drought, as reflected by the various morphological and metabolic adaptations observed in response to these stresses. The role of the xylopodium, a rigid wood tuber, in such tolerance to flood and drought stresses is discussed. Water-stressed roots of some crop species studied presented higher ethanol levels than control plants. Additionally, these same drought-treated roots showed a considerable amount of shrinkage compared to control roots, as measured by root diameter. It is argued that drought causes root shrinkage, which possibly reduces ability of such roots to capture oxygen and results in hypoxia in the tissues and consequent increase in ethanol production. This hypothesis of drought-induced hypoxia is compared with several recent findings in the literature, and is discussed as a possible factor which allows drought, under specific circumstances, to acclimatise plants to a subsequent flooding. From preliminary experiments with alternation of flooding and drought in Eucalyptus species, it appeared that a previous stress affects a plant's response to a subsequent stress. This effect was not always negative, and in E.regnans a five-week drought allowed a subsequent 3-fold increase in flooding survival. This experiment, however, needs to be repeated in order to confirm these results. A common cause for anaerobic injury seems to be unlikely for the diverse plants studied, and anoxia survival often seemed to be related to a combination of morphological and metabolic adaptations. A critical reflection on the risks of labelling plants as tolerant or sensitive to oxygen deprivation is provided, as well as a discussion on the perspectives of applied research which may further the development of ecophysiological theory.
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Rentel, Maike Christina. "Signal transduction in response to active oxygen species in Arabidopsis thaliana." Thesis, University of Oxford, 2002. http://ora.ox.ac.uk/objects/uuid:5dc0b7f5-5aa9-4633-a8dd-89ca2dcb3982.
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Many environmental stresses result in increased generation of active oxygen species (AOS) in plant cells, leading to the induction of protective mechanisms. In this study, signalling components linking AOS perception to downstream responses were examined, with particular emphasis on H2O2 signalling. All AOS investigated had an early [Ca2+]cyt peak in common, but differed in other aspects of their Ca2+ signatures, indicating that the plant is able to discriminate between different types of AOS. An early event in AOS signal transduction may involve changes in the cellular redox balance as reduction of glutathione levels prior to stress application increased the height of the first [Ca2+]cyt peak. Inhibiting or enhancing the height of the H2O2-triggered Ca2+ signature lead to inhibition or enhancement of GST1 and APX1 induction, respectively, demonstrating that the Ca2+ signature is required for induction of genes encoding antioxidant enzymes. OX1, encoding a putative ser/thr kinase, was shown to be involved in signal transduction in response to H2O2-generating stresses. Transcript levels of OX1 were increased upon treatment with H2O2 and a range of abiotic and biotic stresses as well as ABA, all of which have been shown to result in H2O2 accumulation. Inhibition of stress-induced [Ca2+]cyt elevations inhibited OX1 induction, placing the OX1 kinase downstream of Ca2+ in the signalling chain. OX1 is required for full activation of AtMPKS and AtMPK6 in response to ozone fumigation, indicating that OX1 functions upstream of these MAP kinases. An ox1 null-mutant displayed enhanced susceptibility to infection with a virulent Peronospora parasitica isolate as well as reduced induction of several defence genes. In addition, the ox1 mutant exhibited shorter root hairs and an early flowering phenotype. AOS treatment induced several genes encoding AtERF transcription factors, but did not have an effect on other members of this family. Induction occurred in an ethylene-independent but Ca2+-dependent manner.
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White, Sean D. "Internal pressurisation and convective flow in two species of emergent macrophyte; Typha domingensis and Phragmites australis /." Title page, contents and summary only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phw5877.pdf.
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Wright, William Edward. "Delta-deuterium and delta-oxygen-18 in mixed conifer systems in the United States southwest: The potential of delta-oxygen-18 in Pinus ponderosa tree rings as a natural environmental recorder." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/263512.
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The North American Monsoon provides half of the annual precipitation in Tucson, Arizona. The other half occurs dominantly during the winter and early spring. Late spring is the transitional period to the monsoon and is characterized by high temperatures and low humidity. The reliability of this hyperarid period, the consistency of the timing of monsoon onset, and the recognition that certain high-elevation trees produce annual false latewood bands in response to this transitional period, were critical to the design of this dissertation research. I hypothesized that subannual environmental signals might be fixed in stable oxygen isotopes in cellulose from such trees. Existence of a long-term dataset of deltaD and delta18O from Tucson precipitation provided impetus for the collection of a companion dataset at a high-elevation site in the Santa Catalina Mountains north of Tucson. Trees were sampled near the precipitation collection site. The relations between the stable isotope ratios in the precipitation and in the tree cellulose were identified through extraction of water from bimonthly samples of nearby soil, tree stems and needles. Spatial consistency of the cellulose stable isotope signals was measured using tree samples from seven additional sites across the U.S. desert Southwest. Correlations between Tucson summer precipitation delta18O and both local and extra-regional environmental parameters resulted in the identification of the dominant monsoonal moisture source for the Tucson area. Similar correlations with the cellulose delta18O timeseries from the post-false latewood cellulose, supported the previous interpretations, and suggest long-term reconstructions may be possible. Correlations between the earliest cellulose delta18O division and extra-regional environmental parameters suggest environmental measures may be reconstructable for the cool season. Comparison of the high and low elevation precipitation deltaD and delta18O datasets yielded many baseline measures of precipitation stable-isotope dynamics in the U.S. desert Southwest. Comparison of the high-elevation precipitation stable isotope record with soil and stem water deltaD and delta 18O from nearby confirmed that local trees were using dominantly deeper soil water. I noted correlations between measured needle-water stable isotope values and values calculated using a leaf-water model, but systematic departures suggest an additional unmodeled process may operate in this system.
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Hollinshead, Paul. "Nitrogen fixation (acetylene reduction) in plant rhizospheres with special reference to the effects of oxygen." Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236478.
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Leppäkoski, K. (Kimmo). "Utilisation of non-linear modelling methods in flue-gas oxygen-content control." Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514282418.
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Non-linear methods have been utilised in modelling the processes on a flue-gas oxygen-content control system of a power plant. The ultimate objective is to reduce NOx and CO emissions by enhancing the control system. By investigating the flue-gas emission control strategy, the major factors affecting the flue-gas emissions have been determined. A simulator has been constructed, and it emulates a real process automation system and its physical processes. The process models of the simulator are: a flue-gas oxygen-content model, a secondary air flow model, a primary air flow model and a fuel feeding screw model (a fuel flow). The effort has been focused on two plant models: the flue-gas oxygen-content model and the secondary air flow model. Combustion is a non-linear, timevariant, multi-variable process with a variable delay. The secondary air model is a non-linear, timeinvariant (in principle), multi-variable system. Both phenomenological modelling (mass and energy calculations) and black-box modelling (neural networks) have been utilised in the Wiener/Hammerstein structures. It is possible to use a priori knowledge in model modifying, and therefore the model of flue-gas oxygen-content can be tuned on site. The simulator with precalculated parameters was tested in a full-scale power plant and a pilot-scale circulating fluidised bed boiler. The results in the power plant were remarkable since NOx emissions decreased significantly without increasing CO emissions.
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Scherban, Donna Michele 1954. "LIPOXYGENASE ACTIVITY ASSOCIATED WITH CYANIDE-INSENSITIVE OXYGEN UPTAKE IN MITOCHONDRIAL FRACTIONS FROM SEEDLINGS OF GLYCINE MAX L." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276512.
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Soybean seeds are known to contain high levels of lipoxygenase activity, especially during early stages of germination. Crude mitochondrial fractions from germinating soybeans also have been shown to exhibit high rates of cyanide-insensitive oxygen uptake. These results show the effects of successive discontinuous PercollR density gradients on mitochondrial fractions from 2 day old soybean seeds as judged by polarographic studies and Ouchterlony double diffusion. Axis mitochondria exhibited totally cyanide-sensitive oxygen uptake after two gradients and cotyledon mitochondria exhibited from none to 11% cyanide-insensitive oxygen uptake after three gradients. Mitochondrial fractions which were assayed for lipoxygenase with double diffusion exhibited positive results with fractions that showed cyanide-insensitive oxygen uptake and negative results with cyanide-sensitive mitochondria. These results suggest that lipoxygenase can loosely associate with the mitochondrial membrane and that gradient centrifugation can purify mitochondria free of both lipoxygenase and cyanide-insensitive oxygen uptake.
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Dewhirst, Rebecca Alice. "Formation and subsequent metabolism of ascorbate oxidation products in vitro and in plant cells." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/20384.
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Vitamin C (ascorbate and dehydroascorbic acid) is vital for plants and found throughout the plant cell including in the apoplast. The structure of ascorbate was determined eighty years ago; however, many of its degradation pathways remain unclear. Numerous degradation products of ascorbate have been reported to occur in the apoplast but many still remained unidentified. Ascorbate is well known as an antioxidant, and acts to quench reactive oxygen species (ROS), such as hydrogen peroxide and ozone in the plant apoplast. The immediate oxidation product of ascorbate is dehydroascorbic acid (DHA), which may be quickly hydrolysed to diketogulonic acid (DKG). The further reactions of radiolabelled and non-radiolabelled DHA and DKG with various ROS have been investigated. Differences were observed in the products formed from the various ROS, allowing a unique fingerprint of oxidation products to be described for each ROS. Equally, different compounds were produced depending on the starting substrate; for example cyclic oxalyl threonate was only observed in the reactions of DHA and not DKG. A major oxidation product of DHA is OxT. A novel enzyme activity involving the transfer of the oxalyl group from OxT to an acceptor substrate such as a sugar has been detected. This enzyme activity could have potential cell wall modification roles, in the formation of oxalate cross-linkages between cell wall components. This would provide a novel role for ascorbate derivatives in cell growth. Vitamin C is also a vital component of the human diet, and most dietary ascorbate comes from plants such as salads. The degradation of ascorbate during post-harvest processing and storage of salad leaves has been investigated. Spinach leaves were found to be particularly prone to losing ascorbate during the industrial washing process. The use of radiolabelled ascorbate has allowed the determination that the major degradation product formed from ascorbate during spinach washing was oxalate.
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Hendry, Garth S. "Dependence of substrate-water binding on protein and inorganic cofactors of photosystem II /." View thesis entry in Australian Digital Theses Program, 2002. http://thesis.anu.edu.au/public/adt-ANU20041124.140348/index.html.
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Yoshida, Hiroshi. "Fungal response to plant sugars: nutrition, metabolic state changes, and differentiation switching." Kyoto University, 2019. http://hdl.handle.net/2433/242714.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第21837号
農博第2350号
新制||農||1069(附属図書館)
学位論文||H31||N5209(農学部図書室)
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 田中 千尋, 教授 本田 与一, 准教授 刑部 正博
学位規則第4条第1項該当
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Argyn, Aidar. "Material And Heat Balance Calculations Of Eti-bakir Plant By Computer." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12609734/index.pdf.
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In this study the data taken from Outokumpu type Flash smelter of Eti-Bakir Plant (Samsun, Turkey) was used to write a computer program in Visual Basic with interface to Excel. Flash smelting is the pyrometallurgical process for smelting metal sulfide concentrates, used in Eti-Bakir plant. In this plant, copper flash smelting consists of blowing fine, dried copper sulfide concentrate mixtures, silica flux, lignite with air into the furnace and natural gas as main fuel. The molten matte is the principal product of the furnace and slag contains 0.5-2% Cu. It is sent to a slag treatment (flotation) process for Cu recovery. This flash furnace off-gas contains from 8-12 volume % SO2 which is fixed as H2SO4. Written program was used to optimize the consumption of oxygen enriched air, fuel and lignite in this Flash Smelter by making material and heat balance of the plant.
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Hodzic, Elvisa. "Total organic carbon (TOC) and chemical oxygen demand (COD) - Monitoring of organic pollutants in wastewater." Thesis, Uppsala universitet, Institutionen för medicinsk biokemi och mikrobiologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-160105.
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Total organic carbon (TOC) and chemical oxygen demand (COD) are two methods used for measuring organic pollutants in wastewater. Both methods are widely used but the COD method results in production of hazardous wastes, including mercury.The purpose of this study was to validate the method TOC that will replace COD and find a factor to convert TOC to COD. In this study 26 samples were analyzed from four sewage treatment plant in the municipality of Enköping.The results show that the COD method could be replaced by the TOC method.The factor for COD/TOC was between 3.1 - 3.3. Both methods will be used in parallel until 2013 when it will be forbidden to use the COD analysis.
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Nair, Arthur William. "Investigation of the Effects of Sequential Anaerobic, Anoxic and Aerobic Zones on Dissolved Oxygen Transfer Parameters in a biological Nutrient Removal Pilot Plant." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/46264.
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Bench and pilot scale determinations of the volumetric oxygen transfer coefficient, KLa, were performed on an improved A²/O biological nutrient removal (BNR) pilot plant. Effluent from a full scale primary clarifier, used as pilot plant influent, was found to have an alpha (ratio of process to clean water KLa) of 0.71 as determined in a 21 liter bench scale reactor and an alpha of 0.332 as determined in a 0.45 m³ aeration basin of the 2.4 m³ pilot plant. Alpha of a 1:1 mixture of primary clarifier effluent with pilot plant return activated sludge was determined to be 0.94 at bench scale and 0.71 at pilot scale. An assay of alphas through the initial non aerated treatment zones of the pilot plant using the bench scale reactor indicated that alphas peaked in the effluent of the first anaerobic zone (alpha equal to 1.01) and were lower in the second anaerobic zone and first anoxic zone. An assay of alphas in the three pilot plant series sideline aeration basins indicated that alpha was maximum in the first aeration basin (alpha equal to 0.905) and were lower in the second and third aeration basins (0.716 and 0.661 respectively). A consistent increase in average surface tension was noted from the first to second to third aeration basins, however the differences were not statistically significant. A comparison of pilot plant alphas determined in the first aeration basin following anaerobic nominal hydraulic retention times of 0.0, 0.21, 0.43, and 0.64 hours yielded alpha values of 0.71, 0.94, 0.64, and 0.74 respectively. Like the assay using the bench scale reactor, the alpha values at pilot scale peaked following treatment in only one anaerobic zone (nominal HRT of 0.21 hours). The study concludes that short exposures in an initial anaerobic reactor as required for biological phosphorus removal may benefit oxygen transfer efficiency through increased alphas, however the benefits of long periods of anaerobic reaction time (over 0.43 hours) are uncertain.Master of Science
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Mühlenbock, Per. "Genetic and Molecular Mechanisms Controlling Reactive Oxygen Species and Hormonal Signalling of Cell Death in Response to Environmental Stresses in Arabidopsis thaliana." Doctoral thesis, Stockholms universitet, Botaniska institutionen, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-1358.
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In the present work the regulation of environmentally induced cell death and signaling of systemic acquired acclimation (SAA) in Arabidopsis thaliana is characterized. We used the lesion simulating disease1 (lsd1) mutant as a model system that is deregulated in light acclimation and programmed cell death (PCD). In this system we identify that redox status controlling SAA and cell death is controlled by the genes LSD1, EDS1, EIN2 and PAD4 which regulate cellular homeostasis of salicylic acid (SA), ethylene (ET), auxin (IAA) and reactive oxygen species (ROS). Furthermore we propose that the roles of LSD1 in light acclimation and in biotic stress are functionally linked. The influence of SA on plant growth, short-term acclimation to high light (HL), and on the redox homeostasis of Arabidopsis leaves was also assessed. SA impaired acclimation of wild-type plants to prolonged conditions of excess excitation energy (EEE). This indicates an essential role of SA in acclimation and regulation of cellular redox homeostasis. We also show that cell death in response to EEE is controlled by specific redox changes of photosynthetic electron transport carriers that normally regulate EEE acclimation. These redox changes cause production of ET that signals through the EIN2 gene and regulon. In the lsd1 mutant, we found that propagation of cell death depends on the plant defence regulators EDS1 and PAD4 operating upstream of ET production. We conclude that the balanced activities of LSD1, EDS1, PAD4 and EIN2 regulate chloroplast dependent acclimatory and defence responses. Furthermore, we show that Arabidopsis hypocotyls form lysigenous aerenchyma in response to hypoxia and that this process involves H2O2 and ET signalling. We found that formation of lysigenous aerenchyma depends on LSD1, EDS1 and PAD4. Conclusively we show that LSD1, EDS1 and PAD4, in their functions as major plant redox and hormone regulators provide a basis for fundamental plant survival in natural contitions.
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Smith, Samson William. "Effects of Reactive Oxygen Species on Life History Traits of Caenorhabditis elegans." PDXScholar, 2012. https://pdxscholar.library.pdx.edu/open_access_etds/712.
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Evolutionary life history theory predicts that tradeoffs among fitness-related phenotypes will occur as a result of resource limitations and/or physiological constraints. Such tradeoffs are defined as the cost(s) incurred on one component of fitness (e.g., reproduction) by the increased expression of another fitness-related trait (e.g., longevity). Only recently have researchers begun to investigate the mechanistic bases of life history tradeoffs. A recent proposal is that reactive oxygen species (ROS) have a central role in shaping life history traits and tradeoffs. Research on disparate animal taxa has highlighted strong correlations between oxidative stress resistance and fitness-related life history traits, for example. Here, I use the model organism Caenorhabditis elegans to test several hypotheses concerning the effects of ROS on life history traits and the manifestation of life history tradeoffs. Additionally, I use heat stress and an alternate food source to explore the responses of life history traits to other forms of physiological stress. Relative fitness and other traits related to reproduction were found to be affected in mostly negative ways by increasing oxidative insult. Lifespan was surprisingly unaffected by oxidative stress, but was modified by temperature. In vivo ROS levels as measured by fluorescent microscopy reveal a tradeoff between antioxidant production and reproduction in this species.
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Searle, Stephanie Yoke-Ying. "The temperature dependence of plant alternative oxidase and its impact on respiration rates in nature." Thesis, University of Canterbury. School of Biological Sciences, 2010. http://hdl.handle.net/10092/5930.
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The physiological function of the plant enzyme alternative oxidase has long been a topic of debate. The cyanide-resistant alternative oxidase (AOX), along with the cytochrome c oxidase (COX), catalyzes the reduction of oxygen to water in the electron transport chain of mitochondrial respiration. Although respiration via the alternative pathway (AP) results in approximately one third of the ATP production as respiration via the cytochrome pathway (CP), the AP is utilized by all plants and some fungi and animals. This “energy wasteful” pathway has been proposed to reduce oxidative stress in plant cells under a variety of stressful conditions. Virtually all previous work on the AP has been performed on laboratory-grown plants in controlled environment conditions; thus, there is little knowledge of how the AP responds to unstable conditions and multiple environmental stresses in the field. This thesis presents new methodology for studying AP respiration and the AOX protein in field-grown plants, and investigates how the AP responds to natural changes in environmental conditions in the field in several plant species grown in diverse ecosystem types. The experimental work presented here also investigates how AP activity is related to changes in total rates of respiration, and questions whether abundance of the AOX protein determines electron partitioning to the AP.
AP partitioning (or relative changes in AP partitioning) varied over seasonal timescales in each of the experimental studies. Chapter 3 reports on two species of Chionochloa, a native New Zealand tussock grass growing along an altitudinal gradient. In Chapter 4, seasonal variation was studied in two tree types: Populus x canadensis, a deciduous angiosperm, and Pinus radiata, an evergreen gymnosperm. Quercus rubra trees were studied along an urban-rural gradient originating in New York City in Chapter 5. In a highly exposed and variable environment, relative changes in AP partitioning in two species of Chionochloa were correlated with the previous day’s integrated light. In Quercus rubra, the AP was instead related to temperature changes: relative AP partitioning increased in response to seasonally low temperature in trees grown at colder, more rural field sites, while at the warmer, urban sites, it increased in response to high summer temperatures. Each of these environmental conditions that were related to increases in the AP (high light, low temperatures, and heat) are potentially stressful to plants. Thus, it is possible that the increases in AP respiration observed in these studies served to oxidize excess reducing equivalents generated through stressful conditions. In Chapter 4, although AP partitioning in Populus x canadensis and Pinus radiata varied seasonally, these changes were not directly related to environmental parameters. However, AP partitioning in Populus x canadensis was clearly shown to be dependent on measurement temperature.
In each of the studies presented here, changes in the AP were not related to abundance of the AOX protein. AOX protein abundance showed consistent seasonal patterns in the two deciduous angiosperms, Populus sp. and Quercus sp, and was correlated with seasonal changes in temperature in Chionochloa spp. However, the lack of correlation between protein abundance and AP partitioning indicates that the AP is subject to post-translational control and likely varies more rapidly than protein levels. In each of Chapters 3 – 5, there was no clear impact of changes in AP partitioning on rates of total respiration. As the AP produces less ATP than the CP, I hypothesized that increases in AP activity would lead to higher respiration rates in order to meet a plant’s energy demands. However, in Populus x canadensis and Quercus rubra, respiration rates remained stable during sharp increases in AP partitioning, indicating that, at least under certain conditions, increases in AP activity are accompanied by a decrease in the CP.
In some of the first research studying AP partitioning in field-grown plants, this thesis illuminates possible mechanisms, functions, and implications of the AP. Over a range of plant taxa and environmental settings, this work shows that the AP does respond to stressful conditions in the wild, but that this does not result in increased respiration. Lastly, the methods presented here to study AP activity and AOX proteins in the field enable future studies to further probe the specific responses of AOX to natural stresses.
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Williams, Jon A. "Enabling Validation of a CubeSat Compatible Wind Sensor." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78711.
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The Ram Energy Distribution Detector (REDD) is a new CubeSat-compatible space science instrument that measures neutral wind characteristics in the upper atmosphere. Neutral gas interactions with plasma in the ionosphere/thermosphere are responsible for spacecraft drag, radio frequency disturbances such as scintillation, and other geophysical phenomena. REDD is designed to collect in-situ measurements within this region of the atmosphere where in-flight data collection using spacecraft has proven particularly challenging due to both the atmospheric density and the dominating presence of highly reactive atomic oxygen (AO). NASA Marshall Space Flight Center has a unique AO Facility (AOF) capable of simulating the conditions the sensor will encounter on orbit by creating a supersonic neutral beam of AO. Collimating the beam requires an intense magnetic field that creates significant interference for sensitive electronic devices. REDD is undergoing the final stages of validation testing in the AOF. In this presentation, we describe the LabVIEW-automated system design, the measured geometry and magnitude of the field and the specially designed mount and passive shielding that are utilized to mitigate the effects of the magnetic interference.Master of Science
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Chillakuru, Dheeraj R. "Towards locating and quantifying respiration in the soil and in the plant using a novel 18-oxygen labelling technique." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/15228.
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Respiration is typically measured by monitoring either carbon dioxide release or oxygen consumption. An alternative approach, used here, is to monitor the product of oxygen consumption, namely water. Although the metabolic water produced will, like carbon dioxide, ultimately diffuse away from mitochondria or be carried off by other processes, it will do so at a much slower rate and may therefore be captured at or near the site of respiration. In this way, the amount and within limits the location of the label provided can be known. Plant species and tissues under investigation were vacuum infiltrated with ¹⁸O₂ (99.97%) and kept devoid of light for a 30 minute period to prevent photosynthesis and allow sufficient time for the label to be incorporated. Labelled metabolic water was
easily detected and recovered against a large background of normal tissue water, in
Medicago sativa L. sprouts. We investigated four other species, representing different
functional groups: a C3 plant {Helianthus giganteus L.), a CAM plant (Crassula ovata
(Miller) Druce), a desert plant {Disocactus flagelliformis (L.) Barthlott), and a tree
(Populus trichocarpa Torr & Gray). The δ¹⁸O values of tissue water ranged from +7.93%o
to +216%o. Higher values were associated with tissues with high respiration rates per unit water content. In some experiments, labelling was followed by immersing the tissues in unlabelled water to monitor exchange (i.e. leakage) over periods of 5 to 60 minutes. Exchange of labelled water was more rapid during the first 5 minutes (X = 63.4% complete over all species, tissues and treatments) than over the 5-10 min interval,
suggesting the existence of two pools of water available for exchange; namely apoplastic and symplastic water. Attempts to modify aquaporin activity failed to influence
exchange. A model system was constructed to test whether high rates of exchange could
also be expected in a soil environment, using Helianthus. In conclusion, the movement of metabolic water across cellular membranes was very rapid, severely limiting the utility of ¹⁸O labelling for pin-pointing sites of respiratory activity.
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Teske, Johanna Kavanagh. "Connecting the Dots: Investigating Planet Formation and Composition Through Observations of Carbon and Oxygen Species in Stars, Disks, and Planets." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/318831.
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What physical processes and sources of material contribute to exoplanet compositions? Specifically, what roles do the protoplanetary disk composition and structure, and host star abundances play in the different stages of planet formation? In this thesis, beginning with a brief literature review in Chapter 2, I trace oxygen and carbon species through these stages to inform how, when, and where planets form. In Chapter 3 I describe a study of the molecular emission from the warm inner disks of T Tauri stars, where terrestrial planets likely form. I report moderate correlations between HCN emission strength and both stellar accretion rate (measured from UV or optical excess emission associated with accretion) and X-ray luminosity. These correlations point towards accretion related processes being an important source of disk atmosphere heating, and suggests that efficient H₂O formation and/or UV dissociation of N₂ (both also associated with higher stellar accretion rates) may aid in the production of HCN. Studies following mine have further connected the abundance of HCN versus H₂O to the growth and migration of planetesimals in the disk, which helps control the formation of both giant and terrestrial planets. I shift to an already-formed exoplanet in Chapter 4, where I present optical photometry of the best-observed transiting super-Earth GJ 1214b with the goal of constraining the short-wavelength slope of its transmission spectrum. Most previous observations suggested a flat spectrum from the near-IR to the optical, corresponding to a low-scale-height, high-molecular-weight atmosphere. My observations are in general agreement with these findings, keeping the "door open" for a H₂O-rich atmosphere for GJ 1214b, which other published g-band observations appeared to contradict. Chapters 5-7 of my thesis focus on measuring stellar abundances, particularly C/O ratios, in transiting (mostly) hot Jupiter exoplanet host stars from high resolution optical spectroscopy. Host star abundances may indicate the precursor materials present in the disk and available for incorporation into planets. In hot Jupiters, the C/O ratio affects the partitioning of C in the major observable molecules, making C and O diagnostic of temperature structure and composition. I also demonstrate that extra caution is necessary in deriving carbon and oxygen abundances, especially for cool and metal-rich stars. Though exoplanetary C/O ratios are still uncertain, the more precise abundance analysis possible right now for their host stars can help constrain their formation environments and current compositions. I summarize my graduate school research in Chapter 8, and discuss the next steps I will take in my postdoctoral career.
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Flora, Christopher S. "The Silicon-Mediated Alleviation of Copper Toxicity in Nicotiana tabacum." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1537286692916071.
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Erans, Moreno Mari´a. "Enhanced sorbents for the calcium looping cycle and effects of high oxygen concentrations in the calciner." Thesis, Cranfield University, 2017. http://dspace.lib.cranfield.ac.uk/handle/1826/12914.
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Increasing CO2 emissions from the energy and industrial sectors are a worldwide concern due to the effects that these emissions have on the global climate. Carbon capture and storage has been identified as one of a portfolio of technologies that would mitigate the effects of global warming in the upcoming decades. Calcium looping is a second generation carbon capture technology aimed at reducing the CO2 emissions from the power and industrial sectors. This thesis assesses the improvement of the calcium looping cycle for CO2 capture through enhanced sorbent production and testing at lab-, bench- and pilot-scale, and a new operational mode with high oxygen concentrations in the calciner through experimental campaigns in Cranfield’s 25 kWth pilot unit. Novel biomass-templated sorbents were produced using the pelletisation technique and tested at different conditions in a thermogravimetric analyser (TGA) and a bench-scale plant comprising a bubbling fluidised bed (BFB) reactor. Moreover, the effects of sorbent poisoning by SO2, and the influence of steam were studied in order to explore the effects of real flue gas on this type of material. In addition to the chemical performance, the mechanical strength, i.e. resistance to fragmentation of these materials was tested. In additon, two different kinds of enhanced materials were produced and tested at pilot-scale. Namely, calcium aluminate pellets and HBr-doped limestone were used in experimental campaigns in Cranfield’s 25 kWth pilot plant comprising a CFB carbonator and a BFB calciner. The suitability of these materials for Ca looping was assessed and operation challenges were identified in order to provide a basis for synthetic sorbent testing at a larger scale. Lastly, a new operational mode was tested, which is aimed at reducing the heat provided to the calciner through high oxygen concentration combustion of a hydrocarbon (in this case natural gas) in the calciner. This approach reduces or even eliminates the recirculated CO2 stream in the calciner. In consequence, this results in a lower capital (reduced size of the calciner) and operational cost (less oxygen and less fuel use). Several pilot plant campaigns were performed using limestone as solid sorbent in order to prove this concept, which was successfully verified for concentrations of up to 100% vol oxygen in the inlet to the calciner.
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Zidenga, Tawanda. "Cyanide Metabolism, Postharvest Physiological Deterioration and Abiotic Stress Tolerance in Cassava (Manihot esculenta Crantz)." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1299018818.
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Bercoff, Alexandra. "Investigation of the treatment process at Kungsberget's wastewater treatment plant under periods of irregular and low loads." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-210159.
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At Kungsberget ski-resort in Gävleborg county all wastewater produced at the facility is treated on-site. The treatment takes place at their own wastewater treatment plant in a so-called Sequence Batch Reactor (SBR), which has been in operation for about a year before this study. Kungsberget AB is currently in charge of the facility but their goal is to hand responsibility over to Sandviken Energy AB. In order for this handover to occur Kungsberget has to produce three approved treatment results. This means that the concentrations of BOD7 needs to lie under 0.3 mg/l and total phosphorous under 10 mg/l in the effluent water for three consecutive samples. The results show momentaneous values. These limits are stated in the permit Kungsberget received from the Environmental Protection Division. Kungsberget has had problems with high and fluctuating phosphorous concentrations and therefore the transfer has not yet taken place. In this project several parameters have been analysed in order to obtain an overview of prevailing influent and effluent concentrations. Some of the parameters that have been analysed are; phosphorous, nitrogen, BOD7, suspended solids and pH. A lot of time and effort has been put into elucidating operational routines at the wastewater treatment plant (WWTP) and gaining knowledge from available literature regarding different parameters’ effect on treatment results. Kungsberget has had problems adapting operating routines and reaching stable treatment results as the load is highly effected of seasonal fluctuation. This has not been taken into account earlier and the WWTP has been operated in the same manner all year around. Suggestions to how operating routines can be modified in to better meeting the needs have been produced and alternative treatment methods have been presented in the report. Two of the suggestions include biological phosphorous removal and adding carrier media to increase bacteria growth. An aerobic solids retention time has been calculated in order to evaluate whether nitrifying bacteria have enough time for grow and maintain a stable population. The calculation was carried out by measuring suspended solids and aeration time and the result was a solids retention time of approximately 6 days.
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Messenger, David James. "Impact of UV light on the plant cell wall, methane emissions and ROS production." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/4347.
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This study presents the first attempt to combine the fields of ultraviolet (UV) photobiology, plant cell wall biochemistry, aerobic methane production and reactive oxygen species (ROS) mechanisms to investigate the effect of UV radiation on vegetation foliage. Following reports of a 17% increase in decomposition rates in oak (Quercus robur) due to increased UV, which were later ascribed to changes in cell wall carbohydrate extractability, this study investigated the effects of decreased UV levels on ash (Fraxinus excelsior), a fast-growing deciduous tree species. A field experiment was set up in Surrey, UK, with ash seedlings growing under polytunnels made of plastics chosen for the selective transmission of either all UV wavelengths, UV-A only, or no UV. In a subsequent field decomposition experiment on end-of-season leaves, a significant increase of 10% in decomposition rate was found after one year due to removal of UV-B. However, no significant changes in cell wall composition were found, and a sequential extraction of carbohydrate with different extractants suggested no effects of the UV treatments on cell wall structure. Meanwhile, the first observations of aerobic production of methane from vegetation were reported. Pectin, a key cell wall polysaccharide, was identified as a putative source of methane, but no mechanism was suggested for this production. This study therefore tested the effect of UV irradiation on methane emissions from pectin. A linear response of methane emissions against UV irradiation was found. UV-irradiation of de-esterified pectin produced no methane, demonstrating esters (probably methyl esters) to be the source of the observed methane. Addition of ROS-scavengers significantly decreased emissions from pectin, while addition of ROS without UV produced large quantities of methane. Therefore, this study proposes that UV light is generating ROS which are then attacking methyl esters to create methane. The study also demonstrates that this mechanism has the potential to generate several types of methyl halides. These findings may have implications for the global methane budget. In an attempt to demonstrate ROS generation in vivo by UV irradiation, radio-labelling techniques were developed to detect the presence of oxo groups, a product of carbohydrate attack by ROS. Using NaB3H4, the polysaccharides of ash leaflets from the field experiment were radio-labelled, but did not show any significant decrease in oxo groups due to UV treatments. However, UV-irradiation of lettuce leaves showed a significant increase in radio-labelling, suggesting increased UV irradiation caused an increase in the production of ROS. The study shows that the use of this radio-labelling technique has the potential to detect changes in ROS production due to changes in UV levels and could be used to demonstrate a link between ROS levels and methane emissions.
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Chang, Christine Chi-Chen. "Mechanisms and genes controlling the signalling network for biotic and abiotic stress defences in Arabidopsis thaliana (L.) Heyhn : Functional cross-talk between photo-produced reactive oxygen species, photosynthesis and plant disease defence responses." Doctoral thesis, Stockholm : Department of Botany, Stockholm University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-418.
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Miradji, Faoulat. "Quantum modelling of Ruthenium chemistry in the field of nuclear power plant safety." Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10192/document.
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Lors d’un Accident Grave (AG) survenant à un réacteur nucléaire à eau pressurisée, sous atmosphère fortement oxydante, des relâchements importants de ruthénium, depuis le combustible dégradé, sont attendus du fait de la formation d’oxydes gazeux. Les composés de Ru représentent un risque sanitaire lié aux isotopes 103Ru et 106Ru, radio-contaminants à court et moyen terme. En outre l’oxyde RuO4, volatil à température ambiante, est susceptible d’être relâché à l’environnement via les fuites de l’enceinte de confinement. L’évaluation de ce rejet à l’environnement présente des incertitudes importantes, liées entre autres aux données thermochimiques des composés de ruthénium gazeux avec des disparités entre les valeurs de la littérature pour les oxydes. Concernant les oxyhydroxydes, les données sont très parcellaires et celles disponibles sont sujettes à caution. Une première étape de ces travaux de thèse a consisté au développement d’une méthodologie de calcul pour obtenir les données thermochimiques des oxydes de ruthénium gazeux en fonction de la température, via des outils de chimie quantique, avec la fonctionnelle TPSSh-5%HF pour l’optimisation de géométrie, suivi de la méthode CCSD(T) pour le calcul des énergies électroniques. Cette méthodologie fut ensuite étendue aux oxyhydroxydes. Des calculs de spéciation chimique ont été effectués afin de prédire les espèces gazeuses les plus stables lors d’un AG. A l’aide des propriétés thermochimiques des espèces d’intérêts et des méthodologies développées, une étude cinétique a été conduite afin de déterminer les chemins réactionnels conduisant à la formation d’oxydes de Ru, espèces gazeuses les plus stables en conditions AGDuring a severe accident (SA) occurring to a pressurized water reactor (PWR), fission products (FPs) are released from the nuclear fuel and may reach the nuclear containment building. Among the FPs, ruthenium (Ru) is of particular interest due to its ability to form volatile oxide compounds in highly oxidizing conditions combined with its high radiotoxicity (103Ru and 106Ru isotopes) at middle term after the accident. Uncertainties concerning evaluation releases of Ru are important and some R&D efforts are led to get a better understanding of ruthenium chemistry in such conditions. The thermodynamic database on ruthenium species used to estimate these releases shows some discrepancies for most ruthenium oxides and for other species such as oxyhydroxides, data are scarce and not reliable, calling for quantum chemical calculations. The most suitable approach corresponds to TPSSh-5%HF for geometry optimization, followed by CCSD(T) for the calculation of the total electronic energies. The energetics are combined with statistical physics to obtain the thermochemical properties of ruthenium oxides and ruthenium oxyhydroxide species as the latter may play an important role on the transport of ruthenium in the primary circuit due to high steam content. The revised thermodynamic database is then used to predict which species are most stable in representative severe accident conditions. Next, kinetic calculations are also performed to obtain pathways of formations for ruthenium trioxide and tetraoxide gaseous compounds, which are the most stable Ru volatile species in steam/air atmospheres
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Hadjur, Christophe. "Etude du potentiel photochimiothérapeutique de l'hypéricine." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10041.
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Le travail presente dans ce memoire s'inscrit dans le cadre d'une recherche qui se situe a l'interface de la photochimie et de la photobiologie. Les differentes etudes qui le constituent, mettent en evidence le potentiel photochimiotherapeutique de l'hypericine. Dans la premiere partie la technique du piegeage de spin, couplee a la resonance paramagnetique electronique, a permis de caracteriser la photosensibilisation de l'oxygene singulet et de l'anion superoxyde par l'hypericine dans un modele in vitro. Le protocole mis au point sur l'hypericine a ete utilise pour l'etude photochimique d'autres sensibilisateurs. D'autre part des methodes indirectes de detection ont permis de quantifier la formation de ces especes. Il a ete suggere qu'un processus de transfert d'electron pouvait avoir lieu entre l'hypericine et l'oxygene singulet, conduisant au radical superoxyde. Toutefois des etudes complementaires devront etre realisees afin de verifier cette hypothese. Dans la seconde partie, nous nous sommes interesses aux proprietes phototoxiques de l'hypericine. Le fibroblaste humain diploide sain a ete choisi du fait de sa bonne reproductibilite cellulaire dans le but de demontrer, par l'utilisation de piegeurs et d'antioxydants, que l'hypericine exerce une action photocytotoxique via une reaction de type ii et de type i. Enfin nous avons etudie les consequences des reactions photodynamiques de l'hypericine sur les systemes antioxydants enzymatiques et endogenes de melanocytes pigmentes et achromiques malins. Ces experiences ont montre que (i) l'hypericine peut etre un agent phototherapeutique efficace dans le traitement du melanome (ii) il existe une relation entre la quantite de melanine et la sensibilite des melanocytes humains malins a la phototoxicite de l'hypericine
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Forget, Amélie. "Caractérisations électro- et spectroélectrochimique d'électrodes d'ITO planes et nanostructurées modifiées par des sondes organophosphorées." Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCC235.
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Cette thèse présente la mise au point d'un protocole de fonctionnalisation des surfaces d'oxyde d'indium dopé à l'étain (ITO) planes et tridimensionnelles par des sondes redox organophosphorées (ferrocène et cofacteur enzymatique). Ce protocole de fonctionnalisation sous conditions douces a permis de caractériser et étudier la stabilité de monocouches en milieu aqueux par différentes techniques spectroscopiques. Ce protocole a été étendu à des surfaces d'ITO poreuses nanostructurées. Les avantages de ces surfaces tridimensionnelles d'ITO sont (i) une grande surface conductrice, permettant l'adsorption d'une large quantité de molécules redox, et (ii) une bonne transparence optique permettant leur caractérisation simultanée par électrochimie et spectroscopie d'absorption UV-visible. L'utilisation de ces électrodes mésoporeuse permet alors des études spectroélectrochimiques en temps réel. Cette technique résolue en temps peut être puissante pour la détermination d'intermédiaire réactionnel et a permis de mettre en avant un comportement atypique d'un capteur chimique de métaux lourd dont sa structure est basée sur un dérivé de diaminoanthraquinoneThis thesis concerns the development of a functionalization process of planar and tridimensional indium tin oxide surfaces by organophosphorus (ferrocene and enzymatic cofactor). The functionalization process under mild conditions allowed to characterize and study their stability in aqueous medium thanks to different spectroscopic methods. This protocol has been extrapolated to nanostructured and mesoporous ITO surfaces. This tridimensional surfaces present advantages that are (i) a high conductive surface permitting the adsorption of a huge quantity of redox molecules and (ii) a good optical transparency for their simultaneous analyses by electrochemistry and UV-vis spectroscopy. The use of these mesoporous electrodes permits real time spectroelectrochemistry studies. This method can be powerful for detection of intermediates and permitted to highlight an unusual behavior of a heavy metal chemical sensor based on a diaminoanthraquinone derivative
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Mateo, Alfonso. "Roles of LESIONS SIMULATING DISEASE1 and Salicylic Acid in Acclimation of Plants to Environmental Cues : Redox Homeostasis and physiological processes underlying plants responses to biotic and abiotic challenges." Doctoral thesis, Stockholm University, Department of Botany, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-698.
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In the natural environment plants are confronted to a multitude of biotic and abiotic stress factors that must be perceived, transduced, integrated and signaled in order to achieve a successful acclimation that will secure survival and reproduction. Plants have to deal with excess excitation energy (EEE) when the amount of absorbed light energy is exceeding that needed for photosynthetic CO2 assimilation. EEE results in ROS formation and can be enhanced in low light intensities by changes in other environmental factors.
The lesions simulating disease resistance (lsd1) mutant of Arabidopsis spontaneously initiates spreading lesions paralleled by ROS production in long day photoperiod and after application of salicylic acid (SA) and SA-analogues that trigger systemic acquired resistance (SAR). Moreover, the mutant fails to limit the boundaries of hypersensitive cell death (HR) after avirulent pathogen infection giving rise to the runaway cell death (rcd) phenotype. This ROS-dependent phenotype pointed towards a putative involvement of the ROS produced during photosynthesis in the initiation and spreading of the lesions.
We report here that the rcd has a ROS-concentration dependent phenotype and that the light-triggered rcd is depending on the redox-state of the PQ pool in the chloroplast. Moreover, the lower stomatal conductance and catalase activity in the mutant suggested LSD1 was required for optimal gas exchange and ROS scavenging during EEE. Through this regulation, LSD1 can influence the effectiveness of photorespiration in dissipating EEE. Moreover, low and high SA levels are strictly correlated to lower and higher foliar H2O2 content, respectively. This implies an essential role of SA in regulating the redox homeostasis of the cell and suggests that SA could trigger rcd in lsd1 by inducing H2O2 production.
LSD1 has been postulated to be a negative regulator of cell death acting as a ROS rheostat. Above a certain threshold, the pro-death pathway would operate leading to PCD. Our data suggest that LSD1 may be subjected to a turnover, enhanced in an oxidizing milieu and slowed down in a reducing environment that could reflect this ROS rheostat property. Finally, the two protein disulphide isomerase boxes (CGHC) present in the protein and the down regulation of the NADPH thioredoxin reductase (NTR) in the mutant connect the rcd to a putative impairment in the reduction of the cytosolic thioredoxin system. We propose that LSD1 suppresses the cell death processes through its control of the oxidation-reduction state of the TRX pool. An integrated model considers the role of LSD1 in both light acclimatory processes and in restricting pathogen-induced cell death.
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Partin, Camille Ann. "On the evolution of atmosphere-ocean oxygenation and plate tectonic processes as recorded in Paleoproterozoic sedimentary basins." Elsevier, 2013. http://hdl.handle.net/1993/22727.
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Important geochemical and tectonic events in the Paleoproterozoic Era lay the foundation for the status and operation of the modern Earth, including the initial rise of atmospheric oxygen paving the path for animal evolution, and the emergence of modern plate tectonic processes leading to the amalgamation of the Canadian Shield (Laurentia). Rudimentary geological and geochronological documentation of Paleoproterozoic sedimentary basins is the foundation from which we can ask larger questions about geochemical changes or plate tectonic events on the evolving Earth, since those questions are largely answered by analyzing the sedimentary record. This thesis outlines the stratigraphy, detrital zircon U-Pb geochronology, elemental and isotopic geochemistry, and basin evolution of the Paleoproterozoic Penrhyn and Piling basins on the Rae craton in Arctic Canada, which record important tectonic and geochemical events on both a regional and global scale.
The concentration of the redox-sensitive trace element, U, in seawater has not been constant throughout geologic time and is linked to changes in oceanic and atmospheric oxygen content. Secular variations in the record of U contents of shales and iron formations indicate that the redox state of the atmosphere-ocean system after the Great Oxidation Event (GOE) was more dynamic than previously thought. Trends towards lower oxygen content recorded after ~2.05 Ga in the middle Proterozoic suggest that oxygen level decreased. This is contrary to traditional models assuming unidirectional atmospheric oxygen rise throughout the Proterozoic. The data demonstrate the earliest signal of oxidative U cycling, manifested in 2.47 - 2.43 Ga iron formations, and show that oxygenation was a protracted process initiated shortly after the end of the Archean.
It has been proposed that a global and long-lived magmatic and tectonic shutdown event from ~2.45 to 2.22 Ga played a causal role in the GOE, since it overlaps the time interval in which atmospheric oxygen initially rose on Earth. Coupled U-Pb, Hf, and O isotope data on magmatic and detrital zircon determine that plate tectonic processes continued to operate during this interval. It is argued instead that plate tectonic processes are necessary to promote conditions favorable for atmospheric oxygen to rise.
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Ghazian, Tafrishi Babak. "Study of Argon Shrouding in Ingot Casting, with Focus on Improving the Operation at Scana Björneborg Steel Plant." Thesis, KTH, Materialvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-160530.
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This thesis has been carried out as a development project at Scana Steel Björneborg with the purpose to study the influential parameters in argon shrouded ingot casting during the manufacturing of low-alloy steels. In the first stage, a literature study was conducted in order to investigate the theoretical background of the procedure and the importance of protecting the melt during ingot casting. Next, a computer model of the shield was designed using COMSOL Multiphysics® with regard to the process conditions at Scana Steel Björneborg. The effect of various parameters on the process was examined through simulations of the argon gas flow pattern, heat transfer between the gas and the melt stream, and the chemical species transport in the gas around the melt stream. Based on the simulation results, two different shapes of shield were proposed for the argon shrouding operation. A set of implementation tests was executed in order to check the installation and usage conditions of the two new shields. After deciding the proper shape of the shield, a full-scale ingot-casting test was performed with the selected shield to investigate the protection behavior. Moreover, the impact of the new casting-protection shield on the nitrogen and oxygen contents of steel was examined through sampling and analyzing the steel before and after casting. It was found that the use of the new shield during the uphill ingot casting is an effective way to reduce the final nitrogen and oxygen contents of the casted ingot. Therefore, the new design of the shield can be used as a developed substitute for the protection of the melt stream in the ingot casting operation.
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Melo, Onécimo Ubiratã Medina. "Determinantes fisiológicos e biomecânicos do desempenho de corrida no plano inclinado em corredores recreacionais." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/163725.
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Apesar da incerteza a respeito dos efeitos de alguns marcadores fisiológicos e biomecânicos durante a corrida em plano inclinado (CPI), em comparação com a corrida em plano horizontal (CPH), variáveis fisiológicas tais como o consumo máximo de Oxigênio (VO2máx), a frequência cardíaca (FC) e a concentração de lactato sanguíneo apresentam maiores valores durante a CPI (aclive) em comparação com a CPH, implicando em uma maior carga mecânica nos músculos de membros inferiores. O presente estudo investigou o comportamento de variáveis fisiológicas e biomecânicas preditoras do desempenho da corrida de longa-distância realizada nos planos horizontal (0%) e inclinado (7%). Vinte corredores do sexo masculino (idade: 26,3 ± 6,7anos; massa corporal: 74,1 ± 9,2kg; estatura: 175 ± 0,05m; gordura corporal: 8,0 ± 2,8%) foram submetidos a dois testes incrementais e dois testes de Economia de Corrida a 10 km.h-1, todos em esteira rolante a 0% e 7% de inclinação, para a determinação do VO2máx, da velocidade máxima (pico) de corrida (vVO2máx), dos limiares ventilatórios (LVs), da FC submáxima, do consumo submáximo de oxigênio (ECO) e da magnitude de variáveis espaço-temporais da técnica de corrida, precedidos de um teste de força máxima (em leg press) e duas provas simuladas de 5.000 m em pista (0 %) e em plano inclinado (7%). Foi feita análise descritiva e aplicados os testes de Normalidade, Correlação Produto Momento de Pearson e Regressão Linear Múltipla, todos com α de 0,05. Verificaram-se fortes relações das variáveis fisiológicas vVO2máx (- 85,55%), 1o LV (- 7,42%), 2o LV (- 0,06%) e FC de ECO (6,92%) com o desempenho para a CPH, sendo o coeficiente de determinação do modelo de 80 %. Para a situação de CPI as variáveis fisiológicas 2o LV (16,70%), vVO2máx (72,30%) e FC de ECO (11,00%) foram as que apresentaram maiores relações com o desempenho, sendo o coeficiente de determinação do modelo correspondente a 69%. Para ambas as situações, as variáveis fisiológicas apresentaram maiores associações com o desempenho em comparação com as variáveis biomecânicas adotadas no presente estudo. Dessa maneira, conclui-se que o desempenho de corridas de longa-distância (i. e., 5.000 m), realizadas em plano horizontal e/ou inclinado, pode ser melhor predito considerando-se o comportamento de variáveis fisiológicas tais como a vVO2máx.Despite the uncertainty about the effects of some physiological and biomechanical markers during the slope running (SR) compared with running in the horizontal plane (PR), physiological variables such as maximal oxygen uptake (VO2max), heart rate (HR) and blood lactate concentration have higher values for the SR (slope) compared to the PR, resulting in a greater mechanical load on the muscles of the lower limbs. The present study investigated the behavior of physiological and biomechanical performance predictors of long-distance race held in horizontal (0%) and inclined (7%) planes. Twenty male runners (age: 26.0 ± 6.7 years; body mass: 74.1 ± 0.0 kg; height: 175 ± 0.05 m, body fat: 8.0 ± 2.8%) performed two incremental maximal tests and two running economy tests at 10 km h-1, all on a treadmill at 0% and 7% gradient, for determining the VO2max, maximum speed (peak) race (vVO2max), ventilatory threshold (VTs), submaximal heart rate (HR), submaximal oxygen consumption (ECO), and spatiotemporal variables of running technique, preceded by a maximum force test (leg press) and two tests simulated 5,000 m on the track (0%) and slope (7%). We carried out descriptive analysis and applied the Normality tests, Correlation Product Moment of Pearson and Multiple Linear Regression, all with 0.05 α. There were strong relationships of physiological variables vVO2max (- 85.55%), 1 (LV - 7.42%), 2 (LV - 0.06%) and HR of ECO (6.92%) with the performance for PR and the coefficient of determination of 80% model. For the SR situation physiological variables second TV (16.70%), vVO2max (72.30%) and HR of ECO (11.00%) showed the highest ratios with the performance, and the determination of the corresponding model coefficient to 69%. For both situations, physiological variables showed stronger associations with the performance compared to the biomechanical variables used in this study. Thus, it is concluded that the performance of long-distance running (i. e., 5.000 m) held in horizontal and / or inclined plane, may be better predicted by considering the behavior of physiological variables such as vVO2max.
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Bryan, Donita Lynn. "Influence of planting depth on landscape establishment of container-grown trees." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3179.
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Pourrut, Bertrand Pinelli Eric. "Implication du stress oxydatif dans la toxicité du plomb sur une plante modèle, Vicia faba." Toulouse : INP Toulouse, 2008. http://ethesis.inp-toulouse.fr/archive/00000709.
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Pourrut, Bertrand. "Implication du stress oxydatif dans la toxicité du plomb sur une plante modèle, Vicia faba." Phd thesis, Toulouse, INPT, 2008. http://oatao.univ-toulouse.fr/7760/1/pourrut.pdf.
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Le plomb est un des métaux les plus utilisés par l'Homme mais c'est aussi l'un des plus toxiques. Dans les écosystèmes, la teneur en plomb d'origine anthropique n'a cessé d'augmenter depuis plusieurs siècles. Dans plusieurs régions en France, le plomb pose actuellement des problèmes importants en matière de contamination de l'environnement. Les plantes, du fait de leur immobilité, sont particulièrement exposées. De nombreuses études ont déjà évalué la toxicité de ce métal sur les végétaux, mais la très grande majorité a utilisé des concentrations en plomb très largement supérieures à celles pouvant se retrouver dans des sites pollués. Le but de ces travaux a été d'évaluer sur une espèce sentinelle, Vicia faba, la toxicité de doses de plomb réalistes. Nous avons montré que le plomb pénétrait rapidement dans le système racinaire et générait, après seulement quelques heures, un important stress oxydatif à l'origine d'une peroxydation lipidique et de l'induction d'effets génotoxiques dans les cellules racinaires : cassures au niveau de l'ADN et induction d'aberrations chromosomiques. Nous avons pu mettre en évidence que la source de ce stress oxydatif était directement liée à l'activation de NADPH oxydases racinaires via une calmoduline kinase. L'utilisation d'inhibiteurs de cette enzyme et d'antioxydants a permis de montrer que la production d'espèces réactives de l'oxygène, initiée par la NADPH oxydase, était impliquée dans la toxicité du plomb et plus particulièrement dans sa génotoxicité.
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Cances, Julien. "NOx formation and reduction by a coal, a lignite, an anthracite and a petroleum coke in conditions of cement plant calciner." Phd thesis, Toulouse, INPT, 2006. http://oatao.univ-toulouse.fr/7554/1/cances.pdf.
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The cement industry is a high energy consumer. This energy is mostly provided by the combustion of pulverized carbonaceous solid fuels. Up to 60 % of this fuel income may be injected into the calciner. However, the combustion of solid fuels produces pollutants, particularly NOx. Several reduction technology were developed. The most promising one, in term of cost and efficiency, is the reburning. It consists in a secondary fuel injection, creating a fuel rich zone favorable to NOx reduction. The fuel injection in cement plant calciners may be compared to this technique. The solids interact with NOx at different levels : through gas phase reactions with volatile matters released during the pyrolysis, and through solid-gas heterogeneous reactions : i.e. char oxidation that produces N-species and NO reduction at the char surface. A coupled experimental and modeling protocol was developed to determine the relative contribution of these different phenomena. The used fuels are of four distinct types, commonly used in cement plants: a lignite, a coal, an anthracite and a petcoke. Thus, the elementary heterogeneous reactions – devolatilisation, char oxidation and NO reduction by char – were characterized by specific experiments and modelings. One observes a large disparity between the four fuels in terms of kinetic parameters and quantity of volatile matters released. Finally, the experiments and modelings representative of the reactions occurring simultaneously during reburning in calciner conditions were performed. It appears that the effect of NO reduction in the gas phase is of the same order of magnitude that the effect of reduction by char after a particle residence time of 2 s. The NO reduction by char increases continuously with the temperature, whereas the gas phase reduction presents singularities in function of the temperature for the high volatile fuels: The NO reduction is lower at 900C than at 800 and 1000C, in case of lignite and coal. A detailed chemical analysis of these singularities was carried out and enabled to determine the main reaction paths occurring during NOx formation and reduction in the gas phase.
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Magnusson, Hans. "From recovery boiler to integration of a textile fiber plant : Combination of mass balance analysis and chemical engineering." Licentiate thesis, Karlstads universitet, Institutionen för ingenjörs- och kemivetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-37266.
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Modern chemical technology is an efficient tool for solving problems, particularly within the complex environment of the pulp and paper industry, and the combination of experimental studies, mill data and mass balance calculations are of fundamental importance to the development of the industry. In this study various examples are presented, whereby chemical technology is of fundamental importance. It is well documented that under normal conditions the molten salt mixture from the kraft recovery boiler flows down into the dissolving tank without problems. However, in the case of alternatives to the kraft recovery boiler, knowledge of more precise data of the molten salts is required for the design calculations. In this study the viscosity for the case of sodium carbonate and 30 mole% sulphide has been measured and is of the magnitude 2 – 3 cP at temperatures relevant for a recovery boiler, i.e. similar to water at room temperature. The presence of non-process elements (NPE) in a typical pulp mill has been investigated. The main input is with regards to the wood, and anticipated problems include; deposits in evaporators, high dead-load in liquor streams, plugging of the upper part of the recovery boiler and decreasing efficiency in the causticization department. Efficient green liquor clarification is of the greatest importance as an efficient kidney for many NPE. Mill data and calculations show that the magnesium added in the oxygen delignification does not form a closed loop. Integration of a prehydrolysis kraft pulp mill producing dissolving pulp with a plant producing viscose textile fiber could be highly beneficial. The prehydrolysis liquor will contain both sugars and acetic acid. It is however not possible to fully replace the sulphuric acid of the viscose spinning bath with acetic acid of own production. The sulphuric chemicals from the viscose plant can be partly taken care of in the kraft recovery area as well as the viscose plant which can be supplied with alkali and sulphuric acid. Zinc-containing effluents from the viscose plant can be treated with green liquor to precipitate zinc sulphide.Modern chemical technology is an extremely efficient tool for solving problems particularly in a complicated environment such as the pulp and paper industry. Here, examples are studied during which chemical technology is of fundamental importance. At normal conditions the molten salt mixture from the kraft recovery boiler flows down into the dissolving tank without hindrance. However, for certain kraft recovery boiler alternatives, knowledge of more precise data of the molten salts is required. The viscosity for the case of sodium carbonate and 30 mole% sulphide has been measured and is of the magnitude 2 – 3 cP at relevant temperatures. The main input of non-process elements (NPE) is down to the wood, and known problems include deposits in evaporators and decreasing efficiency in the causticization department. Green liquor clarification is an efficient kidney for many NPE. Magnesium added in the oxygen delignification does not form a closed loop. Integration of a prehydrolysis kraft pulp mill producing dissolving pulp with a plant producing viscose textile fiber could be of significant interest, as the handling of both alkali and sulphuric compounds can be integrated. Problems will however arise as the capacity of the pulping line and the chemical recovery has to be adjusted.
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Hu, Ying. "The roles of glutaredoxin GRXS17 in improving chilling tolerance in tomato and drought tolerance in rice via different mechanisms." Diss., Kansas State University, 2015. http://hdl.handle.net/2097/20512.
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Doctor of PhilosophyHorticulture, Forestry, and Recreation Resources
Sunghun Park
Abiotic stresses, including chilling and drought stresses, are considered to be major limiting factors for growth and yield of agricultural and horticultural crops. One of the inevitable consequences of abiotic stresses is the accumulation of reactive oxygen species (ROS) in plants. ROS can either act as an alarm signal to induce the defense pathway when kept at a low level or cause oxidative damage to various cellular components when increased to a phytotoxic level. Glutaredoxins (GRXs) are members of ROS scavenging system that can maintain the cell redox homeostasis by using the reducing power of glutathione. In this research, we characterized the roles of GRXs in protecting tomato (Solanum lycopersicum) from chilling stresses and rice (Oryza sativa L.) from drought stresses. Our results indicated that ectopic expression of an Arabidopsis gene AtGRXS17 in tomato could enhance the chilling tolerance by increasing antioxidant enzyme activities and reducing H₂O₂ accumulation to ameliorate oxidative damage to cell membranes and photosystems. Furthermore, AtGRXS17-expressing tomato plants had increased accumulation of soluble sugars to protect plant cells from dehydration stress. In rice, silenced expression of a rice glutaredoxin gene OsGRXS17 was used as a reverse-genetic approach to elucidate the roles of OsGRXS17 in drought stress tolerance. Our results showed that silenced expression of OsGRXS17 conferred improved tolerance to drought stress in rice. ABA-mediated stomatal closure is an important protection mechanism that plants adapt to a drought stress conditions, and H2O2 acts as secondary messenger in ABA signaling to induce the stomatal closure. Silenced expression of OsGRXS17 gave rise to H₂O₂ accumulation in the guard cells and promoted ABA-mediated stomatal closure, resulting in reduced water loss, higher relative water content, and consequently enhanced drought tolerance in rice. This research provides a new perspective on the functions of GRXs in chilling and drought stress tolerance of tomato and rice, and an important genetic engineering approach to improve chilling and drought stress tolerance for other crop species.
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Lachaud, Stéphane. "Décharge pointe-plan dans les mélanges gazeux correspondant aux effluents industriels. : Etude électrique et physico-chimique, application à la destruction du dioxyde d'azote." Pau, 2002. http://www.theses.fr/2002PAUU3023.
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Ce travail est une étude de la décharge couronne positive à pression atmosphérique appliquée aux effluents de type industriels (air, eau, CO2 et NO2). L'étude électrique pour ces mélanges montre que l'eau et le CO2 facilitent l'apparition d'un régime d'impulsions et peuvent abaisser la tension inter-électrodes à courant fixe. Une interprétation tenant compte de l'électronégativité de l'eau et du CO2 ainsi que du phénomène de "clusterisation" est proposée. L'hydrodynamique de la décharge est observée et comparée à des résultats de simulations numériques. Son action de brassage gazeux est mise en évidence. Une analyse de vieillissement de la cathode a été réalisée par X. P. S. Et a montré l'apparition de phénomènes d'oxydation surfacique en cours de décharge en milieu humide. Des mesures par spectroscopie d'absorption U. V. Montrent que la meilleure destruction de NO2 est obtenue en atmosphère humide et s'accompagne de la création d'une phase liquide d'acide nitriqueThis work is a study of the atmospheric pressure positive corona discharge applied to industrial effluents (air, water, CO2 and NO2). For these mixtures, electrical study shows that water vapour and CO2 facilitate appearance of pulses regime and may reduce the inter-electrodes voltage for a fixed current. Water and CO2 electronegativity and clusterisation phenomenon are taken into account in order to offer an interpretation. Hydrodynamical aspect of discharge is observed and compared with numerical simulation results. Its mixing action makes evident. Analysis of cathode alteration by X. P. S. Was realised and shows appearance of a surfacic oxidation during discharge in wet ambience. Measurements were made by U. V. Absorption spectroscopy. It seems that the best NO2 abatement is obtained in wet atmosphere and joined with creation of a nitric acid liquid phase
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Maligne, David. "Diagnostics optiques capables de localiser la formation de NO dans les moteurs diesel : fluorescence par plan laser sur deux raies atomiques chimiluminescence de l’oxyde de bore." Rouen, 2007. https://tel.archives-ouvertes.fr/tel-00223973.
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La réduction à la source des émissions d’oxyde d’azote est un objectif important pour les constructeurs de moteurs automobiles. Dans ces moteurs la principale voie de formation de NO (mécanisme de Zeldovich) est gouvernée par la réaction initiatrice N2+O->NO+N dont le taux croit fortement avec la température. La formation de NO est donc générée par la présence conjointe d’oxygène atomique et d’une température élevée dont le diagnostic requiert des images instantanées. Deux techniques optiques capables d’être appliquées dans un moteur ont été étudiées au laboratoire. Une thermométrie basée sur la fluorescence de deux raies atomiques successivement excitées a été développée en mode d’imagerie. L’étude a été menée sur des flammes laminaires méthane-air ensemencées en indium. Après étalonnage dans une flamme de référence, les températures obtenues dans une flamme de diffusion sont en accord satisfaisant avec celles d’un thermocouple et elles sont encore accessibles dans les zones polluées par les suies. La lumière verte émise quand une flamme est ensemencée avec un sel de bore vient de la relaxation radiative du dioxyde de bore qui est chimiquement créé sur son état excité par la réaction BO+O®BO2*. Comme le taux de cette réaction croît lui aussi fortement avec la température, la chimiluminescence de BO2 réalise une simulation expérimentale in situ de la vitesse de formation de NO. Les études spectroscopiques montrent un bon accord avec les prévisions du code ChemKin sauf dans les flammes riches. Dans les flammes de diffusion les images de chimiluminescence et les modèles montrent que le seuil de production du NO thermique se situe vers 1800KThe reduction of the Nox emissions in engines is of critical interest for the automotive industry. The main formation pathway of NO at high temperatures is the Zeldovich mechanism which rate of the limiting initiation step N2+O->NO+N is strongly increasing with temperature. The formation of thermal NO comes then from the local conjunction of high temperature and high concentration of atomic oxygen. In the present work, two optical diagnostics are studied to map the temperature and NO formation rate. A thermometry technique based on Two-line Atomic Fluorescence of seeded indium atoms in a two-dimensional planar imaging mode was performed. The two transitions were not excited successively. The reference temperature measurement is obtained in a premixed flame. The TLAF temperature measurement show good agreements with thermocouple measurements in soot-free flame regions and in soot-ing regions where thermocouple is unsuitable. A flame seeded by boron salts shows the green chemiluminescence of boron dioxide, chemically created on its excited state according to the reaction BO+O->BO2*, which depends on the concentration of atomic oxygen and on the temperature in a similar way as the formation of nitric oxides does. In premixed flames, the spectroscopic studies show reasonable agreement between BO2* chemiluminescence and calculated formation rate of thermal NO from the PREMIX code of CHEMKIN, despite some reserve for fuel rich premixed flames. In diffusion flames for two dimensional imaging mode, both BO2* emissions location and computed thermal NO profile take place in high temperature regions (T>1800K)
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Siebritz, Alex. "Isolation and characterization of stem endophytic bacteria from weed plants for enhancing Vanadium tolerance in Brassica napus." University of the Western Cape, 2019. http://hdl.handle.net/11394/7226.
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Masters of ScienceBacterial endophytes are able to improve the growth of their hosts through a number of different mechanisms such as nutrient uptake regulation, plant hormone production and regulation, siderophore production and phosphate solubilisation. They have also been shown to be able to provide protection to plants against various abiotic stressors, through various means such as oxidative stress protection. The purpose of this study was therefore to isolate endophytic bacteria from the stems of different weeds, to characterize their ability to use some of the most important growth promoting mechanisms including the ability to produce IAA, siderophores and ACC deaminase, what effect they had on the nutrient uptake in their hosts and to determine to what extent they could promote growth in the roots, stems and leaves of Brassica napus plants. In addition to this the endophytes were tested to see to what extent they could protect Brassica napus from the negative effects of vanadium stress and how this affected the plant physiologically in terms of morphology, overall biomass, the plants nutrient profile, lipid peroxidation and levels of cell death. The effect of vanadium stress on the oxidative state of Brassica napus was also monitored by determining the levels of stress induced reactive oxygen species (ROS) and the corresponding antioxidants that are responsible for regulating these reactive oxygen species. Six different endophytes (P1, P2, P3, P4, P5, P6) were isolated from different weed samples. Each endophyte was found to be able to significantly improve germination and growth in their host plant. Each isolate was able to improve the uptake of certain macronutrients and micronutrients in their respective hosts, while all of the isolates were shown to be capable of producing siderophores and ACC deaminase. One isolate had high levels of IAA production, with the remaining isolates producing small amounts of IAA. All isolates were also unable to solubilize phosphate. The five best performing endophytes (P1, P2, P3, P5, P6) in the preliminary growth trials were used in the follow up vanadium stressed growth trials, with endophyte P4 being left out of the remaining experiments. All of the endophytes showed improvements in growth promotion in comparison to the control, with endophyte treated plants showing both increased growth and biomass in both the non-stressed and vanadium stressed treatments of the vanadium stressed growth trial; however, the leaves of the vanadium stressed plants were significantly smaller than their non-stressed counterparts. When looking at the oxidative state it was found that vanadium stress caused a significant increase in the development of O2 -, H2O2 and •OH in the control and in addition to this it was shown that treatment with endophytes was able to cause a significant decrease in the levels of stress induced H2O2 and •OH in all of the treatments and O2 - for plants treated with endophyte P5. The noted change in the oxidative state of endophyte treated plants was attributed to an increase in the antioxidant activity of these plants, as it was found that endophyte treated plants showed a combination of increased activity for Superoxide dismutase, catalase and ascorbate peroxidase. This study has shown that endophytic bacteria from plant stems can be used to improve crop growth and yield, while simultaneously producing more nutrient dense crops from the same amount of land. It has also determined that endophytes P1, P2, P3, P5 and P6 are able to successfully provide protection to crop plants from the harmful effects of exposure to vanadium stress. This has great potential for improving food security locally and around the world, by allowing those who cannot gain access to large amounts of food to take in more nutrients from the same amount of food. Furthermore, it also presents the opportunity to use endophyte treatments to grow crops on land that has been previously contaminated with certain heavy metals.
2023-12-01