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Wu, Xiawa. "Properties of thin film cadmium sulfide used in cadmium telluride/cadmium sulfide solar cell". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 79 p, 2009. http://proquest.umi.com/pqdweb?did=1654493821&sid=1&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Weston, Steven John. "The optical spectroscopy of novel cadmium telluride/cadmium manganese telluride heterostructures". Thesis, University of Hull, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321049.
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Sheridan, Liam A. "Alternative cadmium source precursors for the growth of cadmium sulphide and cadmium selenide by metal-organic chemical vapour deposition". Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339511.
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Jinadasa, K. B. P. Neelantha. "Cadmium effects on vegetables : production, physiology and biochemistry /". View thesis View thesis, 1998. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030520.085431/index.html.
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Lange, Anke. "Glutathione response to cadmium in fish cells in vitro and in vivo : relation to metallothionein, cadmium accumulation and cadmium cytotoxicity /". Leipzig ; Halle : UFZ, 2002. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=015383336&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Blanks, Roger Graham. "Cadmium : a human carcinogen". Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309678.
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Churchouse, Stephen John. "Electrocrystallisation studies on cadmium". Thesis, University of Newcastle Upon Tyne, 1985. http://hdl.handle.net/10443/809.
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An investigation into the electrocrystallisation deposition of cadmium has been carried out. The work presented here was followed with the aim of increasing the understanding of cadmium electrodeposition processes, with relevance to general metal deposition. In particular the cadmium deposition behaviour that leads to dendritic growth has been studied. This is particularly relevant in the nickel/cadmium battery industry, where cadmium dendritic growth is a frequently attributed cause for cell failure. The investigative approach has been from both the theoretical and direct experimental sides. The main experimental techniques involved, a. c. impedance, electron microscopy, rotating disc and potentiostatic studies. The usage of a. c. impedance to study double layer capacity changes, proved to be a very accurate method of detecting dendritic growth (through surface area changes). From a more theoretical angle, extensive use has been made of computer simulation, in order to follow the initial stages of deposition of hexagonal close-packed atoms. Experiments involving cadmium dissolved as the species Cd(OH)42 , in 10.00M KOH (saturation limit 0.00035M), have revealed that only grainy cadmium is deposited at timescales of <20 Hours (-400mV overpotential). Continued deposition in 10.00M KOH + 0.00028M Cd(II) at -300mV overpotential, has revealed dendrites of length 30μm can be grown after 6 days. This deposition behaviour remains largely unaffected by changes in surface roughness, electrode pretreatment and the presence of oxygen. However, cadmium deposition behaviour is highly dependent on the presence of small quantities of cadmium salts in suspension. As little as 1x 10-6M of Cd(OH)2 in suspension will dramatically lower the time required for dendrite deposition (25μm dendrites can be grown within 6 hours). This finding is of importance to the battery industry, since the negative plate in the nickel cadmium cell, consists of powdered Cd(OH)2 contained within a nickel-plated steel support. In the absence of suspension, cadmium dendritic growth was found to follow along conventional lines, such that the growth time required for a particular dendrite is given by; At = ln[h/ho ]prb MDCQ Observed dendritic growth times quite closely fitted the calculated values. Studies involving deposition from acidic cadmium sulphate (0.001 - 0.1M) solutions, revealed a similar agreement with the calculated dendritic growth times. However, these times are considerably lower than for the alkaline solutions, primarily due to the concentration increase in Cd(II). In 0.1M CdSO4 + 0.5M H2SO4 the growth time for a 25fLm dendrite is reduced to -60 s. Applying an adapted "Monte Carlo' method, computer simulation of multilayer electrodeposition onto perfect hexagonal close-packed surfaces has been simulated. it is shown that under diffusion-independent conditions the shape of the computer-generated current/time curve is dependent on the size of the lattice used and the trueness" of the random site selection. When diffusion is allowed to become important in the simulation, the deposit shows a dramatic change in morphology, with some clear parallels to observed deposits of cadmium. It is shown that even in the absence of surface defects and impurities, grainy microcrystallites can be simulated under the linear diffusion conditions. This implies that, contrary to the established belief, surface abnormalities are not necessary precursors for dendritic growth.
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McEntee, J. D. "Microbial responses to cadmium". Thesis, Liverpool John Moores University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370177.
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Dakers, Mark A. R. "Toward selectivity for cadmium". Thesis, University of Newcastle Upon Tyne, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244985.
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Palmer, Stephen. "Cadmium biosorption by bacteria". Thesis, University of Bath, 1988. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233027.
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Hanson, Miranda Leah. "Prenatal cadmium exposure dysregulates sonic hedgehog and Wnt/beta-catenin signaling in the thymus resulting in immunomodulatory effects". Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10625.
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Thesis (Ph. D.)--West Virginia University, 2009.Title from document title page. Document formatted into pages; contains vii, 250 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.
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Nguyen, Nu Hoai Vi School of Chemical Engineering & Industrial Chemistry UNSW. "Photocatalytic reduction of cadmium and selenium ions and the deposition of cadmium selenide". Awarded by:University of New South Wales. School of Chemical Engineering and Industrial Chemistry, 2005. http://handle.unsw.edu.au/1959.4/20849.
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Titanium dioxide (TiO2) photocatalysis, which can oxidise or reduce organic and inorganic pollutants, is a developing technology for water and wastewater treatment. The current work investigates the photocatalytic reduction of cadmium and selenium species as the presence of these elements in water are of environmental concern. Although TiO2 has been widely used for the photocatalytic process, its light absorption is limited to the UV region of the solar spectrum. Hence, the current project also explores the possibility to deposit cadmium selenide (CdSe) onto TiO2 to extend the photoresponse to the visible region. This study demonstrated that cadmium (Cd(II)) could be reduced to its metallic form by photocatalysis. The choice of hole scavengers and reaction pH are of importance in determining whether the photocatalytic reduction reaction will occur. It is also essential that both Cd(II) and organic additives are adsorbed on the surface of TiO2. A mechanism for cadmium photoreduction in the presence of formate as the hole scavenger was proposed. The current investigation elucidated the mechanism for the photoreduction of selenite (Se(IV)). Selenite was found to be photoreduced to its elemental form (Se(0)) as films, by direct photoreduction of Se(IV), and as discrete particles, by the reaction between Se(IV) and selenide (Se(2-)) ions. The Se(2-) ions are believed to have been generated from the 6 electron photoreduction of Se(IV) and/or the further photoreduction of the Se(0) deposits. Photocatalytic reduction reactions of Se(IV) and selenate (Se(VI)) using different commercial TiO2 materials was also studied. The current work also successfully deposited CdSe by photocatalysis using Se-TiO2 obtained from the photoreduction of Se(IV) and Se(VI). The mechanism for CdSe deposition was clarified and attributed to the reaction of Cd(II) present in the system and the Se(2-) released from the reduction of Se(0) upon further illumination. The Se??TiO2 photocatalysts obtained from the photoreduction of different selenium precursors (Se(IV) and Se(VI)) resulted in the dominance of different morphologies of the CdSe particles. This suggests a new approach to manipulate the properties of CdSe during its formation, and hence control over electrical and optical properties of this semiconductor.
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Stewart, Nicholas Michael. "A study of the diffusion of cadmium, copper and gallium in cadmium telluride". Thesis, Coventry University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279426.
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López, Fernández de Villaverde Estíbaliz. "Mechanisms behind Cadmium-Induced Teratogenicity". Doctoral thesis, Uppsala University, Toxicology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6223.
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Heavy metals polluting our environment cause concern for developing organisms. Among them, cadmium with extremely slow elimination from the body, causes lower birth weight in humans but has not been classify as a human teratogen. Studies in different laboratory animals have shown that cadmium indeed is a potent teratogen. Exposure to cadmium during early mouse embryonic stages (e.g. day 7-8 post-coitus) interferes with the closure of the anterior neural pore producing exencephalic embryos. The underlying mechanisms are not understood, but the heavy accumulation of cadmium in extra- and intraembryonic endoderm and chorioallantoic placenta, however not in the neuroepithelium, suggests that the effects on neural tube closure is due to indirect mechanisms. In this thesis, the disruption in the mouse embryo at the time of neural tube closure of the hierarchies of some signalling pathways and gene regulatory networks that control embryonic development has been studied after cadmium exposure. Cadmium was shown to cause DNA damage as measured by Comet assay, and to activate genes and proteins in the apoptotic pathways (p53, p21, Bcl-2, Bax, and caspase-3), increasing the number of apoptotic cells mostly in areas of physiological cell death, especially in the neuroepithelium. Many of these effects could be reversed by zinc pre-treatment, known to counteract the teratogenic effect of cadmium. Cadmium was also shown to affect Zn-transport and –regulatory proteins in the embryo, but perhaps more importantly in yolk sac placenta, and in the decidua (ZnT-1, MT-I, and ZIP-4). Using gene arrays, cadmium was found to considerably affect gene expression of rather few genes, such as those of metallothioneins and stress-related proteins, supporting in principle an extraembryonic site of action of cadmium. In addition, a number of genes expressed in the anterior visceral endoderm (Hesx1, HNF3β, Cerl, Otx2 and Sox2) where cadmium accumulates, and known to signal to the anterior neuroepithelium, was affected by cadmium. This finding may suggest a new principle for chemical teratogenesis.
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Klose, Ralf. "Arsen und Cadmium in Winterweizen". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-87989.
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Untersucht wurde der Arsen- und Cadmiumtransfer vom Boden in die Pflanze. Die Boden- und Kornproben entstammten den Dauertestflächen aller Bodenregionen in Sachsen. Um die Pflanzenverfügbarkeit der beiden Elemente zu untersuchen, wurden sieben verschiedene Extraktionsmethoden verglichen. Der Aufschluss mit Königswasser oder Calcium-Ammonium-Lactat (CAL) zeigt dabei die höchsten Konzentrationen im Extrakt. Die Einhaltung des aktuellen Cadmium-Höchstgehalts für Brotweizen ist bis zu einem Cadmium-Gehalt des Bodens (Königswasser) von 1,0 mg/kg mit einer Wahrscheinlichkeit von 80 % gegeben. Auf der Grundlage der CAL-Extraktion beträgt dieser Schwellenwert 0,4 mg/kg. Die erwartete Absenkung des zulässigen Höchstgehalts auf 0,10 mg/kg Korn verschiebt die Schwellenwerte auf 0,40 mg CdKW/kg bzw. 0,22 mg CdCAL/kg.
Die Untersuchungen im Freiland bestätigen die sortenspezifische Aufnahme von Cadmium aus Gefäßversuchen. Für die Transferuntersuchungen wird eine mehrfache Beprobung eines Schlages empfohlen, wobei jeweils von einem ca. 4 m² großen Teilstück eine Bodenmischprobe und eine Mischprobe des zugehörigen pflanzlichen Materials entnommen werden sollte.
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Young, Aidan Gerard, i n/a. "Chemistry at cadmium sulfide surfaces". University of Otago. Department of Chemistry, 2008. http://adt.otago.ac.nz./public/adt-NZDU20080806.164202.
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Probing the surface chemistry of thiol ligand binding to cadmium chalcogenide nanoparticles is important to clarify factors involved in quantum dot stability and surface functionalisation. This research is a spectroscopic investigation aimed at gaining a better understanding of the interaction/bonding of various ligands to CdS, with respect to the use of CdS in biological imaging. The findings of this research are important to the more general field of cadmium chalcogenide materials as biological imaging agents.
Deposited CdS nanoparticle films were used in this work as model quantum dot surfaces for ligand adsorption studies. The adsorption of the monothiol-containing ligands, mercaptoacetic acid, mercaptopropionic acid, and mercaptoethanol, to CdS thin films were studied in situ using attenuated total reflectance infrared spectroscopy. The absence of an S-H stretch absorption for the adsorbed species showed that adsorption occurred via the deprotonated thiol group.
The adsorption of the dithiol-containing ligands α-lipoic acid, dihydrolipoic acid, and dithiothreitol to CdS nanoparticle films was investigated. The adsorption of dihydrolipoic acid and dithiothreitol was found to occur via both thiol functional groups and an additional interaction between the carboxylate group and the CdS surface. The adsorption of α-lipoic acid to CdS in the presence of light proceeded with photo-oxidation of the CdS surface and reductive cleavage of the disulfide bond of α-lipoic acid to produce some adsorbed dihydrolipoic acid and thiosulfate. The adsorption of α-lipoic acid to CdS in the absence of visible light showed no photo-oxidation, and suggested adsorption occurred via retention of the disulfide bond.
The kinetics of adsorption and desorption of oxalic acid on deposited anatase TiO₂ films were studied to investigate the feasibility of extracting molecular information from attenuated total reflectance infrared spectroscopic kinetic data of ligand processes on deposited particle films. Oxalic acid adsorbed on anatase TiO₂ is a well-studied example and is reported to result in three different surface species. The profile of the desorption data indicated contributions from three different components. Different component contributions were unable to be obtained from the adsorption data which is attributed to adsorption occurring much faster than desorption and thus being relatively insensitive to the presence of different adsorbed species.
The kinetics of adsorption and desorption of mercaptoacetic acid on CdS were investigated. The desorption data profile indicated the presence of two adsorbed species with different affinities for the CdS surface, the exact chemical nature of which can only be speculated upon given the absence of distinguishing IR spectral features.
Ligand exchange reactions at the surface of oleate and trioctylphosphine oxide-capped CdS quantum dot films were investigated. Adsorbed oleate was coordinated to the CdS in a chelating bidentate manner through the carboxylate functional group, while adsorbed trioctylphosphine oxide was coordinated though the P=O functional group. Ligand exchange reactions on the oleate and trioctylphosphine-capped CdS films were studied, and exchange with monothiol-containing ligands was observed only at solution pH where the exchanging ligand was uncharged.
Avidin-biotin bioconjugation reactions were carried out on CdS films, which involved the sequential adsorption of mercaptoacetic acid, the protein avidin, and the subsequent binding of the ligand biotin. The spectral data suggested that avidin underwent a conformational change upon adsorption to the CdS surface. This conformation appeared to be perturbed again upon binding of biotin, and it is speculated that the conformation partially reverted back to the native solution conformation.
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Hamidian, Amir Hossein, i n/a. "Cadmium in the marine environment". University of Otago. Department of Chemistry, 2008. http://adt.otago.ac.nz./public/adt-NZDU20090728.100026.
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Cadmium in the ocean has a nutrient-like cycling pattern: with biological uptake at the surface, subsequent sinking in particulate form and then regeneration as dissolved species in deeper waters. Many measurements have been made over time of the ratio of the concentrations of dissolved Cd to those of PO₄ (Cd/PO₄) in the world ocean and this has become one of the best relationships documented between a trace metal and a nutrient. Combined with the measurements of the Cd/Ca ratio in foraminifera, the Cd/PO₄ ratio has been used to reconstruct the oceanographic circulation patterns that existed during past glacial periods and hence provides information on past climate changes.
In the present study Cd/PO₄ ratios of the Southern Indian Ocean in surface and deep waters were investigated. The slopes of the relationships between Cd and PO₄ concentrations in waters of this region are high compared to the global correlations, and lie between those reported for other parts of the Southern Ocean and the Pacific Ocean. In surface waters of the Southern Indian Ocean, Cd/PO₄ ratios decrease from regions exhibiting high nutrient-low chlorophyll (HNLC) characteristic in the south to oligotrophic waters further north. It is also found that particulate Cd plays an important role in regulating the high Cd/PO₄ ratios reported in waters south of the Polar Front.
Very low Cd/PO₄ ratios were measured in waters associated with the Subtropical Front southeast of New Zealand compared to other Southern Ocean and global oceanic waters. Seasonal variations in the Cd/PO₄ ratios measured for these waters strongly suggest they are associated with a significant biological uptake of dissolved Cd particularly during the phytoplankton growth season in summer.
Dissolved Fe concentrations in the Southern Indian Ocean and seasonal variations of Fe in waters off the Otago Coast (southeast of New Zealand) suggest that Fe may stimulate phytoplankton growth and this might result in lower Cd/PO₄ ratios in surface waters through enhanced Cd uptake relative to PO₄ by the phytoplankton. However there is no distinct relationship between dissolved Fe concentrations and the dissolved Cd/PO₄ ratios measured in these surface waters. This finding is in disagreement with the recent 2006 hypothesis put forward by J.T. Cullen, which proposed that waters exhibiting low dissolved Cd/PO₄ ratios were associated with the HNLC regions. From a consideration of the potential Zn concentrations calculated from Si concentration measurements reported for these waters, it would appear that Zn may play a more important role than Fe in regulating Cd/PO₄ ratios in these waters.
Measurements of dissolved and total Cd concentrations relative to those of PO₄ were also undertaken in the Otago Harbour and immediate surrounding coastal waters. These exhibited higher Cd concentrations and higher Cd/PO₄ ratios than open ocean waters further off the Otago Coast. The particulate Cd concentrations showed a negative correlation with Cd concentrations measured in cockle species (Austrovenus stuchburyi) collected in the harbour, suggesting that particulate Cd is not the source of Cd measured in the tissue of this species.
The concentrations of Cd and other trace metals were also measured in samples of green mussel (Perna canaliculus), ribbed mussel (Aulacomya atra maoriana) and oyster (Saccostrea cucullata) collected from Otago Harbour and possible correlations explored between these concentrations and other parameters such as the shellfish condition indices and environmental gradients in the harbour.
In summary, measurements of dissolved and particulate Cd concentrations in the water column can provide unique information on a number of processes occurring in the global marine environment.
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López, Fernández de Villaverde Estíbaliz. "Mechanisms behind cadmium-induced teratogenicity /". Uppsala : Acta Universitatis Upsaliensis: Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6223.
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Åkesson, Agneta. "Cadmium exposure and iron status /". Stockholm, 2000. http://diss.kib.ki.se/2000/91-628-4290-0/.
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Awan, G. R. "Cadmium telluride for solar cells". Thesis, Durham University, 1987. http://etheses.dur.ac.uk/6852/.
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Cadmium telluride is an attractive material for solar cell applications because of its near optimum bandgap and high absorption coefficient. This thesis presents the results of a study into the use of CdTe for solar cells. Three types of cell have been investigated, namely; CdS/CdTe devices fabricated by the vacuum evaporation of CdS onto either: (a) single crystal p-CdTe substrates or (b) p-CdTe thin films, and (c) p-Cu(_2)Te/n-CdTe devices made by a chemiplating process onto single crystal n-CdTe. The effects of substrate polishing and preparation on the performance of CdS/CdTe bulk crystal cells have been Investigated together with the problems of doping and contacting to p-type CdTe. These studies have shown that the best results are obtained with devices that have been prepared on pad polished, phosphorus doped substrates using carbon contacts (efficiency = 7.2%). The influence of deposition conditions on the electrical and structural properties of thin CdS and CdTe layers, and their effect on CdS/CdTe device efficiency were also studied, and optimum growth conditions established. In the third group of CU(_2)Te/CdTe solar cells a number of structural and electrical aspects such as the phase of Cu(_2)Te, and the Influence of dopants, substrate resistivity and preparation and ageing on cell efficiency have been examined. As secondary objectives, an investigation Into the epitaxial growth of CdS on CdTe, and the characterisation of as-grown and doped CdTe have been carried out. It has been shown that epitaxy is possible on the {111} and {221} faces of CdTe. The characterisation of CdTe has revealed the presence of dominant levels at energies above the valence band of 0.50 eV in the as-grown crystals; 0.53, 0.71 and 0.84 eV in Te-annealed single crystals; and 0.35 eV in Cu doped CdTe thin films.
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Lawal, Akeem Olalekan. "Molecular mechanisms of cadmium toxic". Thesis, University of Strathclyde, 2009. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25780.
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Cadmium is a heavy metal which has been associated with a number of pathological diseases. However, despite the known toxicity of this metal, there is inconclusive evidence about its mechanism(s) of action in the cells. The present study was therefore undertaken with the aim of defining the role of oxidative stress, intracellular Ca²⁺ alteration via phospholipase C- Inositol-1,4,5-triphosphate (PLC-IP3) and mitochondrial-cytochrome c dependent pathways in the etiology of cadmium-induced toxicity in three human cell lines: HepG2 (human hepatoma), 1321N1 (human astrocytoma) and HEK 293 (human embryonic kidney) cell lines after 24hrs exposure to 5, 10 and 50 μM cadmium chloride (CdCl₂). The role of the Nrf2-Keap1-ARE pathway in the adaptive response of these cell lines to Cd exposure was examined, and the possible mechanism(s) involved in the protective response of garlic extracts to CdCl₂ were also investigated. Finally, this work examined changes in the proteomic profile of the three human cell lines after Cd exposure in order to develop suitable biomarkers for Cd toxicity. In summary, this study shows that the oxidative stress induced by Cd occurs by different mechanisms depending on cell type and that Ca²⁺ alteration may play an important role in Cd-induced toxicity in HEK 293 cells, while the mitochondrial-cytochrome c dependent pathway is important in Cd toxicity in all three cell lines. Also, the study shows that Nrf2-Keap1-ARE mediated adaptive response to Cd may be activated by PKCδ and that Cd generally alters the metabolism of exposed cells.
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Ng, Jasmine Christina. "Toxicity of cadmium in hepatocytes". Thesis, University of Surrey, 1986. http://epubs.surrey.ac.uk/844145/.
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Freshly isolated hepatocytes from fed and starved rats were used as a model in the investigation of the mechanisms by which cadmium chloride exerts its toxic effects at the cellular level. Exposure to cadmium chloride resulted in a slight decrease in viability, more pronounced in hepatocytes from starved rats. Morphological changes preceded the increase in membrane permeability. Hepatocytes exhibited a rapid initial uptake of cadmium chloride, followed by a second slower phase. The accumulation of more metal in hepatocytes from starved rats may contribute to their enhanced susceptibility to cadmium chloride. Adverse metabolic effects of cadmium chloride included an increase in the lactate:pyruvate ratio in hepatocytes from fed rats, with a concomitant decrease in the 3-hydroxybutyrate:acetoacetate ratio in hepatocytes from fed and starved rats. Incubation with cadmium chloride resulted in increased glycogenolysis and glycolysis. Decreased rates of gluconeogenesis from lactate and pyruvate reflected the decreased uptake of gluconeogenic precursors. Studies of intracellular lactate concentrations could not resolve whether the decrease in gluconeogenesis was due to an inhibition of lactate transport into the hepatocyte or due to a decrease in its metabolism. Cadmium chloride caused a slight decrease in the basal and pyruvate-stimulated rates of cellular respiration, a marked dose-related decrease with lactate, and no significant effects with succinate. Carbonyl- cyanide-m-chlorophenylhydrazone was less effective in stimulating respiration in hepatocytes incubated with cadmium chloride, this effect being more pronounced with lactate and pyruvate than with succinate. Cadmium chloride had little effect on the uncoupled rates of FADH2 oxidation with succinate suggesting that electron transport from succinate dehydrogenase to cytochrome a/a3 was not impaired. The results from these studies suggest a primary effect of cadmium chloride on mitochondrial function and cellular energy production, resulting in secondary metabolic changes in an attempt to overcome the declining levels of ATP within the cell.
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Silva, Mariana Scicia Gabriel da [UNESP]. "Adsorção de cádmio e chumbo em solução aquosa por lama vermelha natural e com diferentes ativações". Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/132704.
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000854252.pdf: 2290541 bytes, checksum: 870be8be16d3cd0d6879c3a2083d04e6 (MD5)Alguns elementos são considerados tóxicos, mesmo em baixas concentrações, causando diversos problemas de saúde pública. Dentre os metais tóxicos, o cádmio e chumbo possuem destaque, pois são amplamente utilizados em atividades industriais, podendo provocar contaminação do solo e de águas superficiais e subterrâneas. Diversas alternativas vêm sendo estudadas para a remoção destes metais. A indústria de aluminio gera um subproduto conhecido como lama vermelha, formado em larga escala necessitando de extensa área para sua disposição . Estudos vêm sendo feitos com o objetivo de reduzir a quantidade gerada de rejeitos por meio de tecnologias que possibilitem sua reutilização. Uma alternativa é o uso da lama vermelha como adsorvedor para tratamento de áreas contaminadas e efluentes líquidos, que quando ativada por tratamento térmico e químico tem apresentado aumento das propriedades de adsorção. Assim, na primeira etapa deste trabalho amostras de lama vermelha foram ativadas por tratamento térmico e químico, caracterizadas, obtidas as isotermas de adsorção, utilizando-se os modelos de Langmuir e Freundlich. Posteriormente, foram analisadas a influência de diferentes valores do pH e da temperatura na adsorção e obtidos o tempo de equilíbrio e cinética da reação da adsorção, permitindo quantificar o potencial de adsorção de cádmio e chumbo. A lama vermelha é um material argiloso, com mesosporos e cxom elevado teor alcalino, além de alta condutividade elétrica. Na maior parte dos casos estudados neste trabalho, as amostras foram melhores descritas pelo modelo de Freundlich, sendo que a alma vermelha ativada termicamente a 400ºC apresentou a melhor capacidade de adsorção, 0,96 m/mol/g de Cd2+ e 2,93 mmol/g de Pb2+. Em todos os casos, a maior eficiência de adsorção ocorreu em pH próximo a 7, o tempo de equilíbrio foi próximo a 420 minutos, a cinética da reação obedeceu melhor ao modelo de pseudo...
Some elements are considered toxic, even in low concentrations, causing many public health problems. Among the toxic metals cadmium and lead have highlighted, as they are widely used in industrial activities, can cause contamination of soil and surface water and groundwater. Several alternatives are being studied for the removal of these metals. The aluminum industry generates a by-product known as red mud, formed large-scale requiring large area for your disposal. Studies have been made in order to reduce the amount of waste generated through technologies that will enables their reuse. An alternative is the use of red mud as adsorbent for treating contaminated liquids and waste areas, which when activated by heat and chemical treatment have shown increased adsorption properties. Thus, in the first step of this work red mud samples were activated by heat and chemical treatment, characterized the adsorption isotherms obtained using the Langmuir model and Freundlich. Subsequently, we analyzed the effect of different values of pH and temperature in the adsorption and obtained time balance and adsorption kinetics of the reaction, allowing to quantify the adsorption potential of cadmium and lead. The red mud is a clay material with mesoporous and high alkaline content, and high electrical conductivity. In most cases studied, the samples were best described by the Freundlich model, and the red mud thermally activated 400ºC showed the best adsortpion capacity 0.96 mmol/g Cd2+ and 2.93 mmol/g Pb2+. In all cases, the greater adsorption efficiency occurred at pH around 7, the equilibration time was close to 420 minutes, the reaction kinetics followed best to the pseudo second order model and endothermic reaction occurred
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Silva, Mariana Scicia Gabriel da. "Adsorção de cádmio e chumbo em solução aquosa por lama vermelha natural e com diferentes ativações /". Bauru, 2015. http://hdl.handle.net/11449/132704.
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Orientador: Fabiano Tomazini da ConceiçãoBanca: Rodrigo Braga Moruzzi
Banca: Amauri Antonio Menegário
Resumo: Alguns elementos são considerados tóxicos, mesmo em baixas concentrações, causando diversos problemas de saúde pública. Dentre os metais tóxicos, o cádmio e chumbo possuem destaque, pois são amplamente utilizados em atividades industriais, podendo provocar contaminação do solo e de águas superficiais e subterrâneas. Diversas alternativas vêm sendo estudadas para a remoção destes metais. A indústria de aluminio gera um subproduto conhecido como lama vermelha, formado em larga escala necessitando de extensa área para sua disposição . Estudos vêm sendo feitos com o objetivo de reduzir a quantidade gerada de rejeitos por meio de tecnologias que possibilitem sua reutilização. Uma alternativa é o uso da lama vermelha como adsorvedor para tratamento de áreas contaminadas e efluentes líquidos, que quando ativada por tratamento térmico e químico tem apresentado aumento das propriedades de adsorção. Assim, na primeira etapa deste trabalho amostras de lama vermelha foram ativadas por tratamento térmico e químico, caracterizadas, obtidas as isotermas de adsorção, utilizando-se os modelos de Langmuir e Freundlich. Posteriormente, foram analisadas a influência de diferentes valores do pH e da temperatura na adsorção e obtidos o tempo de equilíbrio e cinética da reação da adsorção, permitindo quantificar o potencial de adsorção de cádmio e chumbo. A lama vermelha é um material argiloso, com mesosporos e cxom elevado teor alcalino, além de alta condutividade elétrica. Na maior parte dos casos estudados neste trabalho, as amostras foram melhores descritas pelo modelo de Freundlich, sendo que a alma vermelha ativada termicamente a 400ºC apresentou a melhor capacidade de adsorção, 0,96 m/mol/g de Cd2+ e 2,93 mmol/g de Pb2+. Em todos os casos, a maior eficiência de adsorção ocorreu em pH próximo a 7, o tempo de equilíbrio foi próximo a 420 minutos, a cinética da reação obedeceu melhor ao modelo de pseudo...
Abstract: Some elements are considered toxic, even in low concentrations, causing many public health problems. Among the toxic metals cadmium and lead have highlighted, as they are widely used in industrial activities, can cause contamination of soil and surface water and groundwater. Several alternatives are being studied for the removal of these metals. The aluminum industry generates a by-product known as red mud, formed large-scale requiring large area for your disposal. Studies have been made in order to reduce the amount of waste generated through technologies that will enables their reuse. An alternative is the use of red mud as adsorbent for treating contaminated liquids and waste areas, which when activated by heat and chemical treatment have shown increased adsorption properties. Thus, in the first step of this work red mud samples were activated by heat and chemical treatment, characterized the adsorption isotherms obtained using the Langmuir model and Freundlich. Subsequently, we analyzed the effect of different values of pH and temperature in the adsorption and obtained time balance and adsorption kinetics of the reaction, allowing to quantify the adsorption potential of cadmium and lead. The red mud is a clay material with mesoporous and high alkaline content, and high electrical conductivity. In most cases studied, the samples were best described by the Freundlich model, and the red mud thermally activated 400ºC showed the best adsortpion capacity 0.96 mmol/g Cd2+ and 2.93 mmol/g Pb2+. In all cases, the greater adsorption efficiency occurred at pH around 7, the equilibration time was close to 420 minutes, the reaction kinetics followed best to the pseudo second order model and endothermic reaction occurred
Mestre
25
Zorrig, Walid. "Recherche des déterminants contrôlant l’accumulation du cadmium chez la laitue "Lactuca sativa"". Thesis, Montpellier, SupAgro, 2011. http://www.theses.fr/2011NSAM0001/document.
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Les activités humaines agricoles, urbaines et industrielles, sans cesse croissantes, sont à l'origine d'une contamination de notre environnement par les métaux lourds. Alors que de nombreuses molécules organiques peuvent être dégradées, les métaux lourds ne le peuvent pas et leur concentration augmente régulièrement dans les sols et les eaux. Ceci expose les plantes à des concentrations croissantes de métaux lourds. L'accumulation de métaux lourds dans les plantes présente un risque toxique pour l'Homme, car les plantes cultivées sont le point d'entrée dans la chaîne alimentaire. Par comparaison aux autres espèces, la laitue «Lactuca sativa» a tendance à présenter des teneurs élevées en cadmium, un métal lourd très toxique dont la concentration croît régulièrement dans les sols cultivés pour des raisons environnementales. En termes de sécurité alimentaire, il est donc important de produire des variétés accumulant des teneurs en cadmium réduites, et la laitue est un bon modèle pour débuter ce type d'approche. L'objectif de notre thèse était de caractériser aux niveaux physiologique, génétique, et moléculaire, les déterminants majeurs contrôlant l'accumulation du cadmium chez la laitue. Notre objectif a été décliné en différentes opérations. Tout d'abord une analyse de diversité nous a permis de décrire la capacité d'accumulation de cadmium de 18 génotypes de laitue et de sélectionner des génotypes présentant des performances extrêmes vis-à-vis du cadmium. Ainsi, des génotypes présentant des performances extrêmes du point de vue de la tolérance au cadmium, de l'accumulation de cadmium et de la capacité de translocation du cadmium des racines vers les parties aériennes ont été sélectionnés. Dans une deuxième étape, nos variétés extrêmes pour les caractères d'accumulation de cadmium et de translocation de cadmium des racines vers la partie aérienne ont été utilisées pour développer une approche physiologique. L'objectif de cette approche était de montrer l'origine de leur variabilité afin de comprendre les déterminants physiologiques contrôlant l'accumulation du cadmium chez la laitue. Dans le cadre de cette approche, des expériences d'efflux faites en utilisant du cadmium radioactif (109Cd) ont montré que la variété la moins accumulatrice de cadmium se caractérise par un efflux de cadmium marqué plus important par comparaison aux autres variétés. Cette variété possède vraisemblablement un mécanisme d'efflux plus efficace par comparaison aux autres variétés qui pourraient être le déterminant majeur permettant d'obtenir une plus faible accumulation de cadmium chez cette variété. Notre étude a permis de montrer une forte corrélation positive entre teneur en cadmium et teneur en zinc. Ce qui a permis d'émettre l'hypothèse d'un transport très associé entre le cadmium et le zincCadmium is an extremely toxic pollutant causing a great number of diseases. It is a widespread metal which concentration rises in cultivated soils, thus exposing food or feed crops to it and ultimately causing potential major sanitary problems as a consequence of its entry in the food chain. Among the vegetable species used for food, lettuce shows one of the highest capacities of accumulating cadmium. Our objectives are to characterize mechanisms controlling cadmium accumulation in this species and identify the corresponding genetic determinants, ultimately aiming at breeding lettuce for cadmium under-accumulation.A phenotypical analysis of cadmium accumulation was carried out on 18 lettuce genotypes representing the genetic diversity of the species, revealing a great variability of response, both with respect to cadmium accumulation and cadmium translocation from roots to shoot. The lettuce genotypes displayed independent variations for both traits, and also between these traits and cadmium tolerance. In contrast, a very strong positive correlation linked cadmium and zinc accumulation. Increasing calcium and iron concentration in the culture medium had a protective effect against cadmium accumulation, however this characteristic did not discriminate the lettuce genotypes presenting extreme cadmium accumulation phenotypes. Interestingly, experiments measuring 109Cd influx in roots, 109Cd efflux from roots and 109Cd translocation from roots to shoots revealed that the genotype displaying the least cadmium accumulation could be discriminated from the genotype displaying the highest one by its markedly increased ability to efflux cadmium from the roots to the culture medium. Progeny analysis from crosses between the genotypes displaying extreme performances for cadmium accumulation, cadmium translocation from roots to shoots and cadmium tolerance revealed that none of these traits was supported by a single genetic determinism. QTL mapping is under development. Surprisingly, the genetic analysis demonstrated that the ability to limit cadmium accumulation (and thus probably to increase cadmium efflux from the roots) was recessive.In conclusion, phenotypic analysis of cadmium accumulation in a large set of lettuce genotypes revealed that a major determinant limiting cadmium accumulation in these species is the ability to efflux cadmium from the root to the culture medium
26
Roy, Santanu. "Spectroscopic study of defects in cadmium selenide quantum dots (QDS) and cadmium selenide nanorods (NRS)". Diss., Kansas State University, 2013. http://hdl.handle.net/2097/16118.
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Doctor of PhilosophyDepartment of Chemistry
Viktor Chikan
Ever depleting sources of fossil fuel has triggered more research in the field of alternate sources of energy. Over the past few years, CdSe nanoparticles have emerged as a material with a great potential for optoelectronic applications because of its easy exciton generation and charge separation. Electronic properties of CdSe nanoparticles are highly dependent on their size, shape and electronic environment. The main focus of this research is to explore the effect of different electronic environments on various spectroscopic properties of CdSe nanoparticles and link this to solar cell performance. To attain that goal, CdSe quantum dots (QDs) and nanorods (NRs) have been synthesized and either doped with metal dopants or embedded in polymer matrices. Electronic properties of these nanocomposites have been studied using several spectroscopic techniques such as absorption, photoluminescence, time-resolved photoluminescence, confocal microscopy and wide field microscopy. Indium and tin are the two metal dopants that have been used in the past to study the effect of doping on conductivity of CdSe QDs. Based on the photoluminescence quenching experiments, photoluminescence of both indium and tin doped samples suggest that they behave as n-type semiconductors. A comparison between theoretical and experimental data suggests that energy levels of indium doped and tin doped QDs are 280 meV and 100 meV lower than that of the lowest level of conduction band respectively. CdSe nanorods embedded in two different polymer matrices have been investigated using wide field fluorescence microscopy and confocal microscopy. The data reveals significant enhancement in bandedge luminescence of NRs in the vicinity of a conjugated polymer such as P3HT. Photoactive charge transfer from polymers to the surface traps of NRs may account for the observed behavior. Further study shows anti-correlation between bandedge and trap state emission of CdSe NRs. A recombination model has been proposed to explain the results. The origin of traps is also investigated and plausible explanations are drawn from the acquired data.
27
Ergunt, Hasan Yasin. "Bulk Growth And Characterization Of Cadmium Zinc Telluride Crystals For Mercury Cadmium Telluride Infrared Detector Applications". Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614738/index.pdf.
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HgCdTe (MCT) infrared (IR) photodetectors have been used for various military and civilian applications including thermal imaging, medical imaging, and astronomy. These detectors are commonly fabricated on MCT layers grown on a foreign substrate epitaxially using delicate growth techniques such as Molecular Beam Epitaxy (MBE). The crystal quality of epitaxial layers grown on a substrate critically depends on the quality of the substrate. One of the stringent requirements in choosing the substrate material is the lattice match between grown layer and the underlying substrate. With perfectly matching lattice structure, CdZnTe has been the major substrate material for the MCT growth. The production of defect free single crystal CdZnTe bulk crystal has then attracted great attention among the research and industrial community of MCT based photodetectors. This thesis focuses on the growth and characterization of Cd1-xZnxTe crystals with the main objective of obtaining high-quality, CZT bulk crystal with large crystal sizes. To be compatible with the subsequent MCT growth, we aimed to obtain Cd0.96Zn0.04Te crystals with (211) crystal surface orientation. CdZnTe bulk crystal growths were performed in three-zone vertical Bridgman furnace by a high temperature melt process called &ldquoModified Bridgman Technique&rdquo
. Difficulties in both growth and characterization are presented and discussed in this report. Characterization of the grown CdZnTe crystal was performed to determine the crystallographic orientation, crystal quality, Zn distribution, IR transmission, resistivity, polarity, etch pit density, and surface properties. For this purpose, electron microscopy with analytical diagnostic tools like EDS and EBSD, XRD, optical transmission spectroscopy, and electrical measurement systems have been employed. We demonstrated the successful growth of single crystal CZT crystals using our simple Bridgman furnace. Physical properties of the grown crystal were very promising and encouraging for future applications. Crystal pieces having sizes larger than 5 x 5 mm2 with uniform Zn distribution and (211) surface orientation were obtained. IR transmission of nearly 60% which is as good as that of the commercial substrates was achieved. The electrical resistivity was much better (higher) than generally accepted values. However, the XRD results indicated the presence of defects and/or micro grains in the bulk crystal. These structures seemed to have prevented obtaining good FWHM values, which are the measure of crystal quality, in the XRD analysis.
28
Wilkins, Janine Catherine. "Cadmium tolerance in Holcus lanatus L. : studies of stability and differential cadmium uptake in two ecotypes". Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297644.
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Diederich, Geoffrey M. "Synthesis of Zinc Telluride/Cadmium Selenide/Cadmium Sulfide Quantum Dot Heterostructures for use in Biological Applications". Bowling Green State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1342542873.
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Esch, Victor Clark. "Optical properties of cadmium sulfide and cadmium telluride microcrystallites in glass and an optical associative memory". Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/184966.
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The linear and nonlinear properties of CdTe and CdS microcrystallites, or 'quantum dots', grown in glass were investigated. The CdTe quantum dots investigated, the first ever grown, demonstrated the most confinement peaks observed for quantum dots of this kind. The linear absorption for CdTe was modeled. The growth of the microcrystallites in glass was optimized using quantum confined behavior as the criteria. The temperature dependent red shift of the band gap, and the phonon broadening of the 1s-1s transition feature were measured. The fluorescence spectra for CdS and CdTe were taken and found to be different in some respects. The quantum confined Franz-Keldysh effect was modeled and measured for CdTe. Very good agreement with theory was found. The effect of trap state electric fields was considered. The Franz-Keldysh effect for bulk-like microcrystallites was observed. The results for CdS quantum dots were not similar to that of CdTe. The differential absorption for CdS and CdTe was measured with nanosecond time scale optical excitation. Typical differential signals were observed, and long lifetimes were measured. Microsecond time scale excitation was used for CdTe and exceptionally long lifetimes were seen. Differential signals were found to correlate to fluorescence lifetimes. The differential signals were attributed to trap state electric fields (coulombic interaction) with at least two lifetime components. Photodarkening was considered in the context of this trap state scheme.
31
Strady, Emilie. "Mécanismes biogéochimiques de la contamination des huîtres Crassostrea gigas en Cadmium en baie de Marennes Oléron". Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14060/document.
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La baie de Marennes Oléron, premier site ostréicole français, est influencée par la pollution polymétallique historique de l’estuaire de la Gironde avec des concentrations en cadmium dans les huîtres proches de la limite de consommation européenne (RNO 2006; 5 μg.g-1 ps, ECNo.466/2001). Ces travaux de recherche pluridisciplinaires ont pour objectif de caractériser le comportement des ETM en zone côtière et les mécanismes de contamination en ETM des huîtres, spécifiquement en Cd, dans la baie de Marennes Oléron. Pour cela, sept missions océanographiques en période contrastée ont permis de caractériser la spéciation des ETM à l’embouchure des estuaires de la Charente et de la Gironde ainsi qu’au Pertuis de Maumusson.Une étude spatio-temporelle complémentaire des sédiments de surface de la baie de Marennes Oléron a montré un enrichissement des sédiments de surface en Cd dans la zone sud baie,confirmant la connexion des eaux girondines et l’apport en Cd particulaire à la baie par le Pertuis de Maumusson. Cette zone sud a ainsi été choisie pour mener une transplantation d’huîtres pendant trois mois. L’hydrodynamique régionale, observée par imagerie satellite, a présenté unrôle important dans la distribution et la variation temporelle des concentrations en Cd dissous et particulaires minérales de la baie. La bioaccumulation en Cd des différents organes d’huîtres cultivées sur table a été plus importante que celle des huîtres cultivées directement sur le sol,suggérant le faible rôle de la diffusion de Cd par la remise en suspension des sédiments de surface et du microphytobenthos sur la bioaccumulation. De plus, le temps d’immersion étant relativement proche entre les deux conditions, nous suggérons que la voie trophique via le plankton pélagique participe à la contamination des huîtres en plus de la voie directe. Cette contribution de la voie trophique a été confirmée lors d’expérimentations en conditions contrôlées en laboratoire par le développement d’une méthode de traçage simultané des voies de contamination directe et trophique par ajouts d’isotopes stables de Cd, conduites pour des concentrations 10 fois supérieures à l’environnement et des concentrations réalistes observées en baie de Marennes Oléron (40 ng.l-1 et ~0.7 mg.kg-1)The Marennes-Oléron Bay, hosting the largest oyster production in France, is influenced by thehistoric polymetallic pollution of the Gironde Estuary, with cadmium levels in oysters close tothe consumption limit level (5 μg.g-1 dw, EC No.466/2001). The aim of this pluridisciplinarywork was to characterize the behaviour of trace metals in the coastal zone and the mechanisms ofCd contamination in oysters in the Marennes Oléron Bay. Seven oceanographic cruises wereconducted during contrasting season to characterize trace metals behaviour and speciation in theGironde and Charente estuaries and the coastal zone. Then, a spatial and temporal study of tracemetals in the surface sediments of the Marennes-Oléron Bay showed punctual Cd-enrichedsediments in the southern part, reflecting the connexion with the Gironde waters and theparticulate Cd inputs via the Maumusson inlet. Thus, this area was chosen to study Cdbioaccumulation in oysters over a three months transplantation. The regional hydrodynamic,observed by satellite images, played an important role on Cd speciation and the temporalvariability of dissolved and particulate Cd concentrations. Cadmium bioaccumulation in organsof oysters reared on tables at 60 cm height was more important than in oysters reared near thesediment, suggesting the absence of Cd released during tidal suspension from sediment andmicrophytobenthos. Furthermore, as the immersion time was closed between the two rearingconditions, we suggested Cd bioaccumulation via the direct pathway and also via trophicpathway of contamination by pelagic plankton ingestion. This trophic pathway of Cdcontamination was validated during laboratory experiments using a simultaneous tracing of Cddirect and trophic pathways in oysters by stable isotope spikes at concencentrations 10-foldhigher than the Gironde Estuary and at realistic concentrations observed in the Marennes-OléronBay
32
Cardilli, Emanuele. "Aluminium-based coatings for cadmium replacement". Thesis, Cranfield University, 2008. http://dspace.lib.cranfield.ac.uk/handle/1826/3208.
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Cadmium electroplating is widely used in the aerospace industry for the corrosion protection of high strength steels. Cadmium is also used as compatible coating to reduce the galvanic corrosion generated in the assembly of components manufactured with different materials. However, environmental and safety concerns over the high toxicity of cadmium has led to the investigation of suitable replacements. Aluminium coatings are promising coatings for the replacement of electroplated cadmium. Previous studies have shown that the use of SermeTel 984, a commercial aluminium sprayed coating, is beneficial in eliminating the hydrogen direct embrittlement without increasing the risk of re-embrittlement. However, the coating has shown to be prone to passivation in the mild corrosive environment. The addition of active zinc and magnesium particles are thought to avoid the passivation of the aluminium. A range of modified SermeTel 984 coatings, containing 0.5%, 3%, 10% and 50% of zinc, and SermeTel 984 modified with the addition of 30% and 50% of Mg/Al alloy particles in weight have been evaluated as possible alternatives. Chromium free SermeTel 984 and a SermeTel 984 modified with aluminium alloy 7075 particles together with IVD aluminium coatings have also been included in the project. The sacrificial protection of the new coatings has been evaluated together with the associated risk of hydrogen re-embrittlement and compared with the electroplated cadmium. Zinc modified SermeTel 984, containing 1% of zinc and 5% of zinc electroplated aluminium, IVD aluminium and electroplated Zn-Ni coatings have been studied as alternative coatings to cadmium as compatible coatings. Slow strain rate testing has been performed to study the effect of hydrogen on the re- embrittlement of steel substrate as a result of the corrosion of the aluminium-based coatings in 3.5% NaCl. Linear polarisation testing in 3.5% NaCl has been used to evaluate the self-corrosion rates of the coatings; galvanic coupling measurements have been used in the case of steel substrate to evaluate the sacrificial properties or, in the case of bronze/aluminium assembly, to evaluate the compatibility properties of the coatings. Polarisation behaviour tests have been used to study the anodic or cathodic control of the corrosion mechanisms. Total corrosion, calculated as the addition of self-corrosion and galvanic corrosion, has been calculated to evaluate the duration of the coating in service compared to electroplated cadmium.
33
Lindén, Anna. "Biomonitoring of cadmium in pig production /". Uppsala : Dept. of Pharmacology and Toxicology, Swedish Univ. of Agricultural Sciences ([Institutionen för farmakologioch toxikologi], Sveriges lantbruksuniv.), 2002. http://projkat.slu.se/SafariDokument/222.htm.
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Cox, Michael Jason. "Zinc, cadmium and mercury 1,1-dithiolates /". Title page, abstract and contents only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phc8775.pdf.
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Bauer, Cletus P. "Electron irradiation n type cadmium telluride". Thesis, Monterey, California. Naval Postgraduate School, 1985. http://hdl.handle.net/10945/21306.
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Archer, Neil Andrew. "Mercury diffusion in cadmium mercury telluride". Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262522.
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Cowling, Lucinda. "Epigenetic dysregulation in cadmium urothelial carcinogenesis". Thesis, University of York, 2015. http://etheses.whiterose.ac.uk/13052/.
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The urothelium, the epithelial lining of the bladder, is exposed to urinary-excreted carcinogens from environmental, occupational and dietary sources. These carcinogens include heavy metals such as cadmium. As cadmium is a weak mutagen, this suggests that genetic mechanisms are not responsible for cadmium-induced carcinogenesis. Non-genotoxic carcinogenesis is relatively poorly understood, however recent advances show that epigenetic dysregulation of gene expression may play an important role. The aim of my research was to investigate epigenetic dysregulation as the candidate mechanism underlying cadmium carcinogenesis of human urothelial cells. Normal human urothelial (NHU) cells were cultured as finite cell lines following isolation from surgical specimens. When established in vitro, NHU cells have a highly proliferative phenotype and can be induced to differentiate using two published methods: either through PPARγ-mediated differentiation or serum-mediated differentiation. Exposure of NHU cells to cadmium inhibited expression of the tumour suppressor genes, p16, APC and RASSF1A. As dysplasia is axiomatic of carcinoma in situ, the precursor to muscle invasive urothelial carcinoma, the potential of NHU cells to differentiate in the presence of cadmium was investigated. Following exposure to cadmium, there was a failure to upregulate archetypical differentiation-associated genes, including uroplakin 1A and 2, and cytokeratins 13 and 20. Trichostatin A, a histone deacetylase inhibitor was able to reverse some of these changes. Mass spectrometry and immunoblotting were utilised to investigate post-translational histone modification changes caused by cadmium exposure. Data showed that there was a change in histone modification marks present in NHU cell cultures exposed to cadmium that failed to upregulate differentiation markers. An increase in repressive histone marks such as methylation at H3K9 was found alongside a decrease in active marks such as acetylation at H3K18 and H3K23. This study presents evidence that cadmium exposure changes the epigenome of NHU cells and leads to compromised urothelial differentiation and downregulation of tumour suppressor genes.
38
HOUPERT, PASCALE. "Toxicocinetique du cadmium chez la brebis". Paris 7, 1996. http://www.theses.fr/1996PA077220.
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L'objectif de notre travail est d'etudier la toxicocinetique du cadmium chez la brebis. Un modele tricompartimental a permis d'analyser le devenir du cadmium chez la brebis tarie et en lactation apres administrations uniques ou repetees de chlorure de cadmium par voies intraveineuse et orale. Nous avons de solides arguments en faveur de la linearite du modele. Chez les brebis taries, la biodisponibilite orale du cadmium a ete tres faible (0,12-0,50%), la distribution dans l'organisme large (vss=17-35 l/kg) et les capacites d'epuration faibles (c1=0,12-0,24 l/kg/j). Chez les brebis en lactation, les temps moyens de residence n'ont pas ete augmentes (mrt-1100,013 l/kg/j) parce que la distribution du cadmium dans l'organisme a ete plus large (vss=48,810,3 l/kg/j). Lors de nos experimentations, une brebis tarie a absorbe plus de cadmium que les autres brebis (f=5%) et l'a elimine plus rapidement (mrt=78j). Le cadmium, absorbe en plus grande quantite, a pu induire des lesions tubulaires renales qui ont pu accelerer son elimination. La clairance mammaire du cadmium a ete faible et a varie dans le temps. Sur l'ensemble de la lactation, elle a represente 2 a 5% de la clairance totale. Les reins puis le foie ont presente les concentrations les plus elevees en cadmium. Le lendemain et 81 j apres la derniere administration orale de cadmium, 0,09% de la dose totale etait presente dans les reins ; dans le foie ces pourcentages etaient 0,19 et 0,10%. Les reins semblaient retenir le cadmium plus durablement que le foie. L'administration simultanee de plomb a augmente les concentrations en cadmium dans le sang, le lait et les organes. Ce modele pourrait etre utilise pour tester des methodes susceptibles de diminuer la biodisponibilite du cadmium
39
Mackay, Elaine A. "Polymorphism of cadmium-induced mussel metallothioneins". Thesis, University of Aberdeen, 1990. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU024434.
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Metallothioneins are ubiquitous sulphur-rich heavy metal binding proteins whose biosynthesis is induced in response to a variety of agents, including heavy metals. A number of isoforms of metallothionein are known to be induced by heavy metals in the common mussel Mytilus edulis, and recently interest has centred on the nature of these proteins and their possible utility as pollution indicator agents. Cadmium-induced metallotheioneins were isolated from mussels by procedures which included gel permeation and anion-exchange chromatography. They were shown to comprise two molecular mass classes of 10 and 20KDa. The 10kDa class was resolved by anion-exchange into four components designated 10-I, 10-II, 1--III and 10-IV. The 20kDa class was similarly resolved into three components designated 20-I, 20-II and 20-III. The amino acid sequences of each of the components in both of the classes were determined. This involved digestion with a variety of proteinases and separation of the resulting peptides. The abundance of crysteines in these mussel metallotheioneins necessitated their derivatisation with methyl-p-nitrobenzenesulphonate to generate the S-methyl derivative of cysteine which has been found to be suitable for peptide mapping by HPLC and sequence analysis by automated methods. The components of the 20kDa class were shown to possess linked peptides consisting of 71 amino acids, which were distinct from the 72 amino acid peptides of the 10kDa class. It is suggested that the two monomers in the 20kDa proteins are linked via S-Cd-S bonding, i.e. a bridging cadmium ion. The various components within both classes exhibited homology, particularly with regard to the location of the cysteine residues, to metallothioneins from other species, including mammals. On the basis of this homology these proteins were classified as class I metallothioneins.
40
Xue, Zichen. "Cadmium isotope variations in the oceans". Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/10547.
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A number of previous studies have identified considerable mass dependent variations in the Cd isotope compositions of both terrestrial and extraterrestrial samples. On Earth, stable isotope effects for Cd are particularly prominent in the oceans, and the largest natural terrestrial Cd isotope fractionations of about 4‰ have been reported for Cd-depleted surface seawater. These effects have generally been attributed to reflect isotope fractionation of Cd that occurs during biological uptake and utilization of dissolved seawater Cd. This finding confirms studies, which identified Cd as an essential marine micronutrient. This was first inferred from the phosphate-like distribution of the metal in the oceans and more recently demonstrated by work, which confirmed that Cd can act as catalytic metal ion in carbonic anhydrase, an enzyme which plays a central role in inorganic carbon acquisition of phytoplankton in the oceans. The marine Cd isotope fractionations are thus of interest, as they can be used to study the cycling of the micronutrient Cd as well as its impact on ocean productivity and the global carbon cycle. As part of this PhD project, I have developed a new procedure for Cd isotope analyses of seawater, which is suitable for samples as large as 20 L and Cd concentrations as low as 1 pmol/L. The procedure involves use of a 111Cd-113Cd double spike, co-precipitation of Cd from seawater with Al(OH)3 Cd purification by column chromatography, and subsequent isotope analysis by MC-ICP-MS (multiple collector inductively coupled plasma mass spectrometry). The methodology can routinely provide є114=110Cd data with a precision of about ± 0:5є (2sd) when at least 20-30 ng of natural Cd are available for analysis. However, even seawater samples with Cd contents of only 1-3 ng can be analysed with a reproducibility of about ±3 to ± 5є. The new methodology was applied to investigate Cd isotope variations in about 150 seawater samples from the North Atlantic Ocean, the Southern Ocean HNLC (high nutrient low chlorophyll) region, and the Peruvian oxygen minimum zone in the Eastern Pacific Ocean. The samples exhibited variable but highly systematic Cd isotope variations that were comprehensively interpreted in the context of previously published oceanographic and biogeochemical data.
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Jain, Swati. "Photoluminescence study of cadmium zinc telluride". Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=1876.
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Thesis (M.S.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains x, 84 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 79-83).
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Milham, Paul J. "The behaviour of cadmium in soil". Thesis, View thesis, 2008. http://handle.uws.edu.au:8081/1959.7/39519.
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Long-term low-level ingestion of cadmium (Cd) causes human health problems, and in Australia, vegetables supply ~40% of the Cd in the typical diet. Plants take up Cd from the soil; however, the uptake is poorly predicted by simple soil tests, such as the total concentration of Cd (Cdt). Therefore, a greater understanding of Cd behaviour in soils is needed to improve the prediction of Cd uptake by plants and open a new path to minimise the risks for human health. The objectives of the research in this thesis were to: identify key soil properties affecting Cd behaviour, identify/develop selective methods to measure them, and to formulate a conceptual model of Cd partitioning. These objectives were based on the hypothesis that empirical modelling informed by a better understanding of Cd chemistry would accurately describe Cd partitioning in soil. To test the hypothesis, the key properties were measured on soils from the peri-urban fringe of Greater Sydney (n = 41) and a series of models of increasing complexity were fitted to the data. A model with three explanatory variables— log10 Cdt, pH and log10 ECEC (effective cation exchange capacity)—explained
94.6% of variation in log10 CdCa (the concentration of Cd in solution in a suspension of soil in 10 mM CaCl2), which strongly supported the hypothesis. The study also indicated that the explanatory variables, Cdt, pH and ECEC, may describe Cd behaviour in many soils, and that for these general models, partition coefficients, such as log10 (Cdt/CdCa), are unsuitable dependent variables. The preceding model used Cdt as an explanatory variable, notwithstanding that labile Cd (CdE) was mechanistically preferable. However, CdE can only be measured using isotopic techniques: a requirement that has constrained the evaluation of CdE as an index of Cd behaviour and bioavailability. Therefore, a simple proxy measure of CdE was investigated. The literature indicated that solutions of chloride salts might selectively extract CdE, and Cd extracted into 1 M NH4Cl (CdNH4Cl) was compared with CdE measured by stable isotope dilution ICPMS. For 23 soils from the partitioning study, 1 M NH4Cl failed to completely extract CdE, unless the pH was less than 5. The cause(s) of this effect will be investigated with the aim of developing a universally applicable measure of CdE that does not require isotopic measurements. All models of Cd uptake by plants rely on soil properties measured on homogenised samples, although the distribution and bioavailability of Cd vary spatially in the field. Were such variability to increase at the micro-scale, its effects could erode the accuracy with which models could predict Cd behaviour and uptake. Consequently, I tested whether the distribution of Cd could be mapped by using synchrotron micro-x-ray fluorescence spectroscopy (micro- XRFS): the most sensitive method of observation. The soils examined contained 0.3–6.4 mg Cd/kg, i.e. were typical agricultural soils, and one was spiked to ~100 mg Cd/kg. Micro-XRFS mapped the Cd in the spiked soil, and in one particle in the other soils. For typical agricultural soils, the sensitivity realised in this study would have been sufficient to characterise the average Cd binding site, but fell at least 10-fold below that needed to map the Cd distribution in them. The research satisfied the objectives, advanced knowledge of Cd behaviour in soils, and provided new research leads. These leads include the possibility of developing general models of Cd partitioning in soils, derivatives of which may predict Cd uptake by plants. The accuracy of these models may be strengthened by the use of CdE as an explanatory variable, but may be weakened by the effects of in situ variation in the distribution of Cd. The benefits to human health of agricultural practices that decrease dietary Cd justify continuation of research to develop models that accurately predict Cd uptake by plants.
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Milham, Paul J. "The behaviour of cadmium in soil". View thesis, 2008. http://handle.uws.edu.au:8081/1959.7/39519.
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Thesis (Ph.D.) -- University of Western Sydney, 2008.A thesis submitted to the University of Western Sydney, College of Health and Science, Centre for Plant and Food Science, in fulfilment of the requirements for the degree of Doctor of Philosophy. Includes bibliographical references.
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Promnim, Phatthanawan. "Potential use of pineapple (Ananas comosus L.) and cadmium tolerant bacteria to reduce cadmium toxicity in soil". Thesis, University of Newcastle Upon Tyne, 2012. http://hdl.handle.net/10443/1687.
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Cadmium (Cd) is a toxic metal that occurs in the environment naturally and as a pollutant from industrial and agricultural sources. The Cd concentration of agricultural soils in Thailand has increased during the last few decades as a consequence of mining activities. This toxic metal is allocated to edible plant parts and moves into the food chain via rice grains in some provinces in the Northern part of Thailand. Pineapple (Ananas comosus L.) is the most widely cultivated tropical fruit in Thailand and possesses the photosynthetic specialisation of crassulacean acid metabolism (CAM). Since CAM plants are generally tolerant to abiotic stress, it was hypothesised that pineapple would be relatively tolerant to Cd and could potentially be grown as a crop in Cd-contaminated soils. The present study determined the effect of Cd on photosynthetic performance, growth and Cd accumulation in different parts of pineapple. Pineapple plants grown in Cd-contaminated soil did not show any visual symptoms of toxicity and whilst light use efficiency (Fv/Fm) and rates of net dark CO2 uptake were reduced by Cd treatment, biomass reductions were only 14% of control at the highest concentration of Cd (150 mg Cd kg-1). Levels of Cd accumulated by pineapple increased as the Cd concentration in soil increased. Pineapple plants took up Cd from the soil, resulting in lower Cd concentrations in the rhizosphere soil compared with the bulk soil. The soil-extractable Cd decreased over time which may have been due to the uptake of Cd by plant and to remaining metal ions becoming more tightly bound with organic materials or root exudates. Calculated as Cd μg per g dry weight, roots accumulated higher amount of Cd than shoots. Short-term and long-term exposure to Cd resulted in a reduction in the numbers and diversity of soil microbes as indicated using plate count and DGGE techniques. The pineapple rhizosphere exhibited increased numbers of bacteria and fungi and a distinct and more diverse bacterial population when compared to bulk soil. Cd pollution of soil reduced both microbial numbers and bacterial diversity of all soil samples. Certain bacteria in the phyla Nitrospirae, Verrucomicrobia, Acidobacteria and Chloroflexi were only present in Cd-contaminated soil. Cd-resistant bacteria were isolated from the rhizosphere of pineapple grown in Cd-contaminated soil and were subsequently used as inoculants in an effort to improve plant growth and reduce Cd toxicity. Nine isolates of Cd-resistant bacteria were isolated from the rhizosphere soil of pineapple. Two bacterial strains, Bacillus firmus and Arthrobacter humicola were identified as having the potential to alleviate Cd toxicity in soil since both isolates were found to accumulate Cd at 17.21 and 19.83 mg Cd per g biomass at an initial Cd level of 50 mg Cd l-1. Application of B. firmus and A. humicola near the root zone of pineapple grown in Cd-contaminated soil resulted in an increased uptake of nutrients compared with non-inoculated plants. In addition, soil inoculation resulted in higher rates of dark CO2 uptake, reduced Cd accumulation and increased biomass of pineapple plants grown in Cd-contaminated soil as compared with non-inoculated plants. Overall it would appear that pineapple could be grown commercially in Cd contaminated soils as it is relatively Cd resistant and it would also reduce total and extractable Cd soil levels over time. Bacterial inoculation of soil could be used to improve pineapple growth but the financial viability of this would need to be determined.
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Boupha, Prasongsidh C. "The effect of cadmium on food allergy /". Richmond, N.S.W. : Hawkesbury Agricultural College, 1994. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030820.163219/index.html.
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Viala, Yoann. "Elaboration d'un modèle de prédiction de la phytodisponibilité du cadmium dans les sols agricoles : application à la contamination cadmiée du blé dur". Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0091/document.
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Le cadmium (Cd) est un élément trace présent dans les sols agricoles qui contamine la chaîne alimentaire en étant prélevé par les plantes et accumulé dans les produits végétaux consommés. La biodisponibilité du Cd est un concept au cœur de l’évaluation des risques de transfert excessif du Cd du sol vers les plantes. Les plantes prélevant essentiellement l’ion Cd2+ dans la solution de sol, la biodisponibilité est fonction de deux principaux processus, la spéciation du Cd en solution (les différentes formes chimiques prises par le Cd en solution) et le partitionnement du Cd2+ entre la phase solide et la solution. L’objectif principal de ce travail a été d’élaborer des modèles simples à visée opérationnelle prédictifs de la concentration en Cd2+ dans la solution de sols agricoles, en modélisant soit la spéciation du Cd en solution de sol, soit le partitionnement phase solide-solution du Cd2+, celui-ci permettant de renseigner en outre la capacité de la phase à réapprovisionner la solution de sol lors de l’absorption racinaire. Nous avons également recherché des modèles pour la prédiction des teneurs en Cd2+ retrouvées dans les grains de blé dur. Nous avons développé deux approches de modélisation. La première, statistique, permet de produire des modèles simples à visée opérationnelle. La seconde, géochimique, permet de comprendre les mécanismes dominants et donc de juger de la cohérence de modèles statistiques simples pour représenter des processus physico-chimiques complexes. Ces deux approches ont montré de manière cohérente que pour les sols agricoles faiblement contaminés, le Cd qui s’échange entre la phase solide et la solution est vraisemblablement sorbé faiblement et peut-être estimé par le Cd extrait par NH4NO3 1 M minoré par une fraction fixée à des oxydes de manganèse. Les modélisations ont également montré l’importance du pH et de la teneur en Ca en solution comme variables contrôlant la solubilité de Cd2+, probablement en raison de leur rôle à régir la disponibilité des sites de sorption et de complexation vis-à-vis du Cd. Le modèle statistique le plus performant pour prédire la teneur en Cd dans le grain de blé dur reprend également ces variables, suggérant ainsi que les modèles statistiques simples de prédiction de la spéciation en solution et de partitionnement sol-solution du Cd sont des modèles pertinents pour estimer la biodisponibilité et qu’ils peuvent permettre de classer des sols en fonction des risques de transfert du Cd du sol vers une culture. Par rapport à l’évolution du contexte réglementaire, le modèle statistique prédictif de la teneur en Cd dans le grain a montré par validation croisée qu’il pourrait discerner de façon assez fiable (88 %) des différences de 0.05 mg Cd.kg-1 de grain et que sa fiabilité serait moindre (65 %) pour des différences de 0.025 mg Cd.kg-1Cadmium (Cd) is a trace element found in agricultural soils which can contaminate the food chain by being taken up by plants and accumulated in consumed plant products. The bioavailability of Cd is a concept at the centre of the risk assessment of Cd transfer from soil to plants. Plants, taking up essentially the free form of Cd (Cd2+) in the soil solution, bioavailability is a function of two main processes, the Cd speciation in solution (the different chemical forms taken by the Cd in solution) and the partitioning of Cd2+ between the solid phase and the solution. The main objective of this work was to develop simple predictive operational models of Cd2+ concentrations in agricultural soil solution, by modelling either Cd speciation in soil solution or Cd2+ solid-solution partitioning, the latter to further inform the ability of the phase to replenish the soil solution during root absorption. We also looked for models for the prediction of Cd2+ levels found in durum wheat grains. We have developed two modelling approaches. The first, statistical, allows to produce simple models for operational purposes. The second, geochemical, allows to understand the dominant mechanisms and thus to judge the coherence of simple statistical models to represent complex physicochemical processes. These two approaches have consistently shown that for poorly contaminated agricultural soils, the exchanged Cd between the solid phase and the solution is likely to be weakly sorbed and can be estimated by the Cd extracted by 1M NH4NO3 minus a fraction attached to amorphous manganese oxides. Modelling also showed the importance of pH and Ca content in solution as variables controlling the solubility of Cd2+, probably because of their role in controlling the sorption site availability and Cd complexation. The best-performing statistical model for predicting Cd content in durum wheat also picks up these variables, suggesting that simple statistical models for speciation in solution and soil-solution partitioning of Cd are relevant models to estimate bioavailability and that they can be used to classify soils according to the risks of the transfer of soil Cd to a crop. Compared to the evolution of the regulatory context, the statistical model predictive of the Cd content in the grain shown by cross validation that it could discern relatively reliably (88%) the differences of 0.05 mg Cd.kg-1 of grain and that its reliability would be less (65%) for differences of 0.025 mg Cd.kg-1
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Bonaventura, Paola. "Changement de l’homéostasie du Zinc et du Cadmium par l’inflammation chronique et nouvelles options thérapeutiques pour le traitement de l’arthrite". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1081/document.
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La polyarthrite rhumatoïde (PR) est une maladie inflammatoire chronique caractérisée par des atteintes articulaires. Les synoviocytes, cellules qui tapissent la membrane synoviale, deviennent réfractaires à l‘apoptose et, en produisant la cytokine inflammatoire Interleukin 6 (IL-6), participent à la chronicité de l‘inflammation qui est à l‘origine de la perte osseuse dans la PR.Le zinc (Zn) et le cadmium (Cd) partagent leurs propriétés physico-chimiques et leurs mécanismes de transport cellulaire. Le Zn régule des fonctions du système immunitaire, contrairement au Cd avec des propriétés sur le système immunitaire peu décrites dans la littérature.Notre travail vise à identifier les mécanismes impliqués dans la modification de l‘homéostasie des métaux dans les synoviocytes par l‘inflammation et les conséquences de cette altération.L‘inflammation induit l‘accumulation des métaux dans les synoviocytes en augmentant l‘expression de l‘importeur ZIP-8. En revanche, l‘expression de l‘exporteur ZnT1 et des metallothionéines (MTs, régulateurs de l‘homéostasie des métaux) est dépendante de la présence des métaux. L‘affinité Cd-MTs permet une accumulation irréversible du Cd dans les cellules qui réduit leur prolifération et la production d‘IL-6.Les effets antiprolifératif et anti-inflammatoire du Cd ont été testés dans le modèle d‘arthrite chez le rat où une seule injection intra-articulaire de Cd à faible dose prévient la perte osseuse et réduit les scores cliniques d‘arthrite. Cela pourrait représenter une nouvelle approche thérapeutique pour le traitement de la PR et d'autres pathologies caractérisées par une hyperplasie et une inflammation localiséesRheumatoid arthritis (RA) is a chronic inflammatory disease. Synoviocytes, cells forming the inner layer the synovium, become refractory to apoptosis and participate in the chronicity of inflammation through the production of IL-6. The perpetuation of inflammation causes an important induction of bone loss in joints.Zinc (Zn) and Cadmium (Cd) share many physico-chemical properties and cell transport mechanism. Zn is known as a regulator of the normal function of the immune system, while Cd properties on the immune system are not well defined.Our aim was to provide information on the metal homeostasis mechanisms in synoviocytes during chronic inflammation and on the consequences of metal homeostasis changes. After studying the differential effect of Zn and Cd at the cellular level, we could provide an innovative tool to control synoviocyte contribution to rheumatoid arthritis, which was tested on an in vivo model of arthritis.Results show that IL-17/TNF-a combination drives the accumulation of metals inside synoviocytes through the enhancing of ZIP-8 importer expression and regardless of the concentration of metals in the culture medium. In contrast, the expression of the metal exporter ZnT1 and of the homeostasis regulators metallothioneins (MTs) was primarily dependent on metal levels.Addition of Zn stimulated the inflammatory response, while addition of Cd can reduce both viability and inflammation.The anti-proliferative and anti-inflammatory properties of Cd were used in the rat model of arthritis as intra-articular treatment to reduce local inflammation and joint destruction and it may represent a new local therapeutic approach for RA treatment
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Gardarin, Aurélie. "Cadmium, ATPase-P , Levure : Du transport à la toxicité". Université Joseph Fourier (Grenoble), 2007. http://www.theses.fr/2007GRE10283.
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Mes travaux ont consisté en l'étude fonctionnelle de l'A TPase-CdL+, CadA de Listeria monocytogenes e't en compréhension des mécanismes de toxicité et de réponse vis-à-vis du cadmium chez Saccharomyces cerevisiae. 'originalité de ce travail repose sur l'utilisation d'un phénotype de sensibilité au cadmium associé à l'expression de CadA chez S. Cerevisiae. Ce phénotype s'est révélé être un système de criblage pertinent pour l'identification des acides aminés essentiels au fonctionnement de CadA et un système d'étude de la toxicité du cadmium chez la levure. L'ATPase-P CadA transporte les ions Cd2+ d'un côté à l'autre d'une membrane en utilisant l'hydrolyse de l'ATPomme source d'énergie. La mutagenèse dirigée des acides aminés membranaires de CadA a permis de mettre en évidence que 2 ions Cd2+ seraient transportés par A TP hydrolysé et que les sites de transport du métal impliquent les cystéines et la proline du motif CPC (TM6), un aspartate (TM8), un glutamate (TM4) et une méthionine (TM3). L'expression de CadA rend la levure S. Cerevisiae hypersensible au cadmium. Une souche sauvage croît en présence de lOOIlM de cadmium alors que la souche exprimant CadA est incapable de croître en présence de IIlM de cadmium. Ce phénotype a permis de montrer que l'entrée du cadmium se fait par un transporteur de manganèse et que la sensibilité au cadmium résulte d'une accumulation de cadmium dans le réticulum endoplasmique (RE), accumulation réalisée par CadA. Dans le RE, le cadmium altère le processus de repliement, ce à quoi la levure répond en déclenchant la réponse UPR. Cette réponse, aussi observée chez une levure normale fait du RE une cible majeure de la toxicité du cadmiumTwo projects has been developed during my PhD. One consisting in the functional study of CadA, the Cd2+ -A TPase from Listeria monocytogenes, the other one was focused on the toxicity of cadmium and the associated response of the yeast Saccharomyces cerevisiae. This two studies used a a phenotype of sensitivity to cadmium induced by CadA expression in yeast. This phenotype was used as a screening tool to identify essential amino acids of Cd transport byCadA and to study cadmium toxicity and the corresponding yeast cellular response. CadA actively transports Cd using A TP hydrolysis as energy source. Directed mutagenesis of the membranous amino-acids revealed that Cd transport pathway implied four transmembrane segments (Tm) and more precisely the cysteine C354, C356 and pro line P355 of the CPC motif located in Tm6, aspartate D692 in Tm8, glutamate EI64 in Tm4 and methionine Ml49 in Tm5. From our studies, 2 Cd ions would be translocated for each hydrolysis A TP. Expression of CadA in the yeast Saccharomyces cerevisiae induces an hypersensitivity to Cd. A wild type cell can grow up to IOOIlM cadmium whereas CadA expressing yeast cannot grow with IIlM cadmium in the culture medium. This cadmium sensitivity was due to the localisation of CadA in the endoplasmic reticulum membrane. Transport of cadmium in this compartment poduces an accumulation of misfolded proteins that induces the Unfolded Protein Response (UPR). As UPR also occurs in a wild type yeast exposed to low Cd concentration, one can point out endoplasmic reticulum as a extremely sensitive cellular compartment. UPR also appears as an early response to Cd as it happens far before any visible signs oftoxicity
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Rousselet-Russo, Estelle. "Réponses cellulaires vis-à vis de l’exposition au cadmium chez les animaux". Grenoble 1, 2007. http://www.theses.fr/2007GRE10196.
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Les conséquences de l'exposition au cadmium sont l'inactivation de diverses bio-molécules et son interférence avec les homéostasies de métaux essentiels comme le zinc. Une lignée cellulaire fortement résistante au zinc (HZR), dérivée de la lignée épithéliale HeLa est résistante au Cd. Des sollicitations accrues du réticulum endoplasmique affectent la résistance des cellules HZR. Une adaptation catabolique concernant la tyrosine, en rapport avec la production de mélanine, a aussi été notée suite aux analyses protéomiques. La résistance des cellules HZR vis-à-vis du Cd est due à la limitation de Cd intracellulaire. Cela ne se produit pas par augmentation de l'efflux de toxique, mais par inhibition de l'influx dont la voie d'entrée semble inédite. Pour son identification, une analyse globale du transcriptome des cellules HZR a indiqué la modification de multiples voies de signalisation. Le Cd peut engendrer une anémie par perturbation de l'homéostasie du fer. Au niveau cellulaire, elle est assurée au niveau traductionnel par le système IRP (Iron Regulatory Proteins)!IRE (Iron Responsive Element). Des souris intoxiquées au Cd par voie orale, n'ont pas montré d'anémie et l'activité tissulaire des IRP est restée insensible bien que le Cd se soit accumulé dans ces organes. Dans les cellules HeLa, le Cd diminue la stabilité d'IRPI au contraire des cellules HZR. Les réponses suite à un stress Cd dépendent des conditions cellulaires, en accord avec la prépondérance et la diversité des voies de signalisation sensibles au stress extracellulaire révélées pour les cellules HZRMost consequences of cadmium exposure arise from the interaction with a range of bio-molecules and by interference with homeostasis of other metals. Zinc is the biologically metal that most closely resembles Cd. A High Resistant Zinc (HZR) cellline derived from HeLa cells was found to be resistant to Cd toxicity. The induction of endoplasmic reticulum stress decreases resistance of HZR cells to Cd exposure. Also tyrosine catabolism, may be as a way of producing melanin, is involved in adaptation to high zinc concentrations, as witnessed by proteomic analysis. The Cd resistance of HZR cells is due to the limitation of intracellular cadmium. The over-expression of major efflux pumps was not responsible for expelling Cd from HZR cells. Instead, Cd uptake was limited by a not already known Cd transporters characterized in other cell types. A genome-wide analysis of the HZR transcripts underlines a series of signalisation pathways in which the number of cellular components that are sensitive is too large to identify individual molecules directly responsible for handling zinc or Cd. Ln mammals, Cd intoxication could lead to anemia. At the cellular level, iron homeostasis is regulated at the translational level by the IRE (Iron Responsive Element)! IRP (Iron Regulatory Proteins) system. Mice, orally treated with Cd, show neither anemia nor changes in tissue IRP activities, although significant accumulation of Cd in these organs. Ln HeLa cells Cd decreases the IRPI stability, contrary to the HZR cells. The cellular responses to Cd depend on the cellular conditions, most probably by the interplay among the signalling cascades evidenced in the HZR transcriptomic studies
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Cooke, Sharon A. "Alternative chalcogen sources for the growth of cadmium sulfide and cadmium selenide by metal organic chemical vapour deposition". Thesis, University of Reading, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284186.
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