Dissertations / Theses on the topic 'Metal selenide'
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1
Kamada, Rui. "Copper(indium,gallium)selenide film formation from selenization of mixed metal/metal-selenide precursors." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 226 p, 2009. http://proquest.umi.com/pqdweb?did=1654501631&sid=4&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Boscher, Nicolas D. "Atmospheric pressure chemical vapour deposition of transition metal selenide thin films." Thesis, University College London (University of London), 2006. http://discovery.ucl.ac.uk/1444549/.
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This thesis investigates the formation of thin films of metal selenides via atmospheric pressure chemical vapour deposition (APCVD). The films and powders produced were characterised by SEM, EDAX/WDX, XPS, XRD, Raman, SQUID, reflectance and absorbance measurements. The APCVD reaction of TiCl4, V(NMe2)4 and NbCl5 with fBu2Se were respectively found to be a convenient route to stable and crystalline titanium, vanadium and niobium diselenide films. The use of VCI4 and VOCI3 showed that they were both found unsuitable for producing VSe2 from the APCVD reaction with 'Bu2Se. Molybdenum and tungsten diselenide films were respectively synthesised using M0CI5 and WC16 with Et2Se. The WSe2 films produced were highly hydrophobic with contact angles for water droplets in the range of 135 - 145 . Furthermore these surfaces were highly adherent for water droplets that did not roll or slide even at a tilt angle of 90 . The deposition of tin monoselenide and tin diselenide films was achieved by the reaction of SnCU with Et2Se. The deposition temperature, flow rates and position on the substrate determined whether mixed SnSe - SnSe2, pure SnSe or pure SnSe2 thin films could be obtained. The characterisation of the films and powders formed from the APCVD or gas phase reaction of Cr02Cl2 and Et2Se confirmed the formation of an unknown solid solution of Cr2Se3_xOx. Cr2Se3-xOx adopts the hexagonal Cr2C>3 structure for a stoichiometry between Cr2C>3 and Cr2Seo.202.g, and the rhombohedral Cr2Se3 structure for a stoichiometry varying from Cr2Seo.302.7 to Cr2Se2.15O0.85- Magnetic studies showed that all the Cr2Se3.xOx compounds formed with the rhombohedral Cr2Se3 structure had an antiferromagnetic ordering with a Neel temperature lower than the expected one for Cr2Se3.
3
Kim, Changsu. "Optical, laser spectroscopic, and electrical characterization of transition metal doped ZnSe and ZnS nano- and microcrystals." Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2009r/kim.pdf.
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Thesis (Ph. D.)--University of Alabama at Birmingham, 2009.Title from PDF title page (viewed Feb. 3, 2010). Additional advisors: Renato Camata, Derrick Dean, Chris M. Lawson, Andrei Stanishevsky, Sergey Vyazovkin. Includes bibliographical references (p. 133-140).
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Gatuna, Ngigi wa. "Intrinsic vacancy chalcogenides as dilute magnetic semiconductors : theoretical investigation of transition-metal doped gallium selenide /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/10595.
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Luo, Ming. "Transition-metal ions in II-VI semiconductors ZnSe and ZnTe /." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4630.
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Thesis (Ph. D.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains xiv, 141 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 135-141).
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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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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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Beer, Michael P. "A study of volatile precursors for the growth of cadmium sulphide and cadmium selenide by Metal Organic Vapour Deposition." Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303986.
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Ashraf, Shakeel. "Evolution of IR Absorber for Integration in an IR Sensitive CO2 Detector." Thesis, Mittuniversitetet, Institutionen för informationsteknologi och medier, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-14088.
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The maximum sensitivity of a thermal IR sensor can be available either by means of the sensor material, having its own absorbing properties, or by the deposition of an additional absorber structure on the detector surface. In this thesis, the theory of two absorption structures is discussed. The first is called the interferometric absorber structure. The second structure under investigation uses a lead selenide layer for the IR absorption. In the interferometric structure, a new epoxy material SU8-2002 was used as a dielectric medium. This material has a very low thermal conductivity of 0.3 W/mK, which makes it suitable for thermal detectors. The interferometric structure is based on three layers, a 40–60 Å thick Ti layer, a SU8–2002 layer with a thickness of 2000 Å thick and a 2000Å Al layer. Using standard cleanroom processing an interferometric structure was fabricated. Transfer matrix theory was used in order to simulate the interferometric structure and the lead selenide was fabricated by means of an argon-plasma sputtering process. Both fabricated samples were characterized through Fourier transfer infrared (FTIR) spectroscopy together with a specular reflectance accessory. The thicknesses of the added layers were measured using Atomic force microscopy (AFM) for both the interferometric and lead selenide structure. It was determined that by changing the reflective index value of the SU8-2002 from the reported value of 1.575 to about 2.40 that this provided a better agreement with the experimental results. The absorption results for the interferometric structure were determined to be approximately 82–98% for the wavelength region of 2-20µm at 30 degree. The PbSe absorption spectra showed 30%–50% absorption for the wavelength region 2.5 – 6.67μm.
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Kling, Willig Fabian. "Selenium Recovery in Precious Metal Technology." Thesis, Umeå universitet, Kemiska institutionen, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-86735.
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Walton, Richard I. "The characterisation and structure of amorphous and poorly crystalline transition-metal chalcogenides." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388467.
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Morris, R. E. "Synthesis and characterization of metal phosphites and selenites." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314881.
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Chiu, Winnie Wai Hang. "Metal complexes with sulfur and selenium donor ligands /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202009%20CHIU.
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d'Arbeloff-Wilson, Sarah. "Reactions of the phosphaalkyne, PCBu't with metal sulphides, selenides and tellurides." Thesis, University of Sussex, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324201.
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Vergnaud, Céline. "Optimisation de la croissance de MoSe2 - WSe2 par épitaxie de Van der Waals pour la valleytronique." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALY038.
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Cette thèse a pour objet l’optimisation de la croissance par épitaxie par jets moléculaires dans le régime de van der Waals de couches semi-conductrices bidimensionnelles (2D) de diséléniures de métaux de transition (MoSe2, WSe2) pour les études magnéto-optiques et électriques. Cette optimisation passe par l’amélioration de la qualité cristallographique des couches sur de grandes surfaces en ajustant les paramètres de croissances (température et flux). En particulier, la maîtrise de l’état de surface du substrat est déterminante sur les mécanismes de croissance de ces couches. L’élaboration de ces matériaux de basse dimensionnalité a nécessité l’utilisation de techniques de caractérisation avancées (Diffraction de rayons X en incidence rasante, Microscopie électronique en transmission en mode haute résolution, ect). Dans cette thèse, nous nous sommes concentrés sur deux substrats particuliers : l’oxyde de silicium et le mica. Ils présentent tous les deux la particularité d’être isolants et inertes d’un point de vue électronique, ce qui est indispensable pour sonder les propriétés optiques et électriques intrinsèques des couches 2D. Finalement, nous avons développé les dopages électrique (dopage p) pour la microélectronique et magnétique (dopage Mn) pour la valleytroniqueThe purpose of this thesis is to optimize growth by molecular beam epitaxy in the van der Waals regime of two-dimensional (2D) semiconductor layers of transition metal diselenides (MoSe2, WSe2) for magneto-optical and electric studies. This optimization involves improving the crystallographic quality of the layers over large areas by adjusting the growth parameters (temperature and flux). In particular, the control of the surface state of the substrate is decisive on the growth mechanisms of these layers. The development of these low-dimensional materials required the use of advanced characterization techniques (Grazing incidence X-ray diffraction, High Resolved Transmission Electronic Microscopy, ect). In this thesis, we focused on two specific substrates : silicon oxide and mica. They both have the particularity of being insulating and inert from an electronic point of view, which is essential to probe the optical and electrical intrinsic properties of 2D layers. Finally, we developed electrical doping (p doping) for microelectronics and magnetic (Mn doping) for valleytronics
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Al-Attar, A. F. "Selenium and trace metals as pollutants." Thesis, University of Bristol, 1987. http://hdl.handle.net/1983/1858b91b-362e-422f-b91c-84aa44e23e90.
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Weber, Frank. "Präparative Studien in den Mehrstoffsystemen Selten-Erd-Metall - Selen bzw. - Tellur und Sauerstoff." [S.l.] : Universität Stuttgart , Fakultät Chemie, 1999. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB8287476.
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Ling, Jie Albrecht-Schmitt Thomas E. "Hydrothermal syntheses, structures, and properties of new iodate and selenite compounds of transition metals, lanthanides, and actinides." Auburn, Ala, 2007. http://repo.lib.auburn.edu/2007%20Fall%20Dissertations/LING_JIE_49.pdf.
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Lachaîne, Martin. "Monte Carlo optimization of a metal/amorphous-selenium portal imager." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ37138.pdf.
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Greenfield, Joshua Thomas. "Synthesis and Characterization of Low-Dimensional Iron Selenides and Transition Metal Formate-Chlorides." Thesis, University of California, Davis, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10682102.
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Several solvothermal synthetic methods have been developed to produce novel low-dimensional magnetic materials and determine their structure-properties relationships. Two main classes of compounds were investigated, including iron selenides and transition metal formate-chlorides.
Chapter 2 details the development of the first solution-based synthetic route to superconducting iron (II) selenide. Samples were found to retain superconducting properties only when air and water were rigorously excluded from the synthesis.
Chapter 3 presents the synthesis, structure, and magnetic properties of two new mixed-valence compounds with infinite ∞1(FeSe 2) tetrahedral chains separated by Fe-amine complexes. The use of different Fe-amine complexes allows for tuning of the magnetic properties without changing the general structural motif.
Chapters 4 and 5 report the first members of the transition metal chloride-formate family of compounds, which contain linear zig-zag chains of octahedrally coordinated metal atoms linked by μ2-Cl and syn-syn formate bridges. These compounds order antiferromagnetically and exhibit metamagnetic transitions.
Chapter 6 describes a related set of transition metal formate-chloride compounds that are comprised of helical chains of edge-sharing M2+ -centered octahedra. These compounds undergo 3D ferrimagnetic ordering at low temperature, and are rare examples of homospin topological ferrimagnets.
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Thiagarajan, Suraj Joottu. "Thermoelectric properties of rare-earth lead selenide alloys and lead chalcogenide nanocomposites." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1196263620.
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Garland, Jacqueline M. "Studies in phosphorus-selenium chemistry." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/3688.
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Phosphorus-Selenium chemistry has seen a surge in development over the last five to ten years thanks to the optimisation of the synthesis of 2,4-diphenyl-1,3,2,4-diselenadiphosphetane-2,4-diselenide, Woollins' Reagent. This selenium analogue of the well known Lawesson's Reagent has proved itself to be a valuable asset to modern inorganic chemistry, providing a route to novel heterocycles, as well as acting as a selenation reagent with a wide range of functional groups. A series of new ammonium phenylphosphonamidodiselenoate ligands were synthesised via the reaction of Woollins' Reagent with a range of amines. The products were obtained in high yields and could be used as ligands for the synthesis of novel metal complexes. The reaction of diisopropylamine N-isopropyl-P-phenylphosphonamidodiselenoate with nickel(II) acetate produces a dimeric structure, whilst the reaction with copper(II) acetate yields a beautiful cluster of the form Cu₆Se₃L₆. The phenylphosphonamidodiselenoate ligands were further reacted with a range of cis-Pt(PR₃)₂Cl₂ complexes to form a library of 20 novel compounds, which were studied by ³¹P{¹H}, ⁷⁷Se{¹H} and ¹⁹⁵Pt{¹H} NMR spectroscopy. The X-ray crystal structure of one of these compounds was obtained, which confirmed the atom connectivity and spatial arrangement of the complexes and the geometry around the platinum centre. During investigations into the above-mentioned platinum complexes, it was postulated that an increase in steric bulk of the phosphine ligands would aid crystallisation of the products. As such, trimesityl-, dimesitylphenyl- and mesityldiphenyl phosphine were synthesised and reacted with elemental sulfur and selenium and hydrogen peroxide, as well as Pt(cod)Cl₂ and K₂[PtCl₄], yielding nine new structures, all of which were characterised by X-ray crystallography, ³¹P{¹H}, ¹³C{¹H} and ¹H NMR spectroscopy. Finally Woollins' Reagent was reacted directly with a selection of metal complexes, yielding some new insights into its reactivity with inorganic moieties, which has been relatively sparsely reported until now.
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Chan, Alan Chin Luen. "Fabrication and measurements on metal-semiconductor diodes." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63966.
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Sadler, Mark. "Main group selenium chemistry and a series of hydrophobic bispidone-transition metal complexes." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515118.
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This thesis encompasses two distinct areas of chemistry. The first part involves the synthesis and characterisation of phenylselenium(II) halides and pseudohalides and their further reactions with tertiary phosphines. The molecular structures of phenylselenium(II) chloride and thiocyanide are reported along with a large series of reactions involving phenylselenium(lI) chloride with tertiary phosphines. In addition to an extensive study of the products in solution using multinuclear NMR, suitable crystals were characterised using X-ray crystallography, yielding three novel crystal structures, two of which feature the rare [PhSeCI2] anion. The effect of doubling the starting quantity of phenylselenium(ll) chloride was noted to have the effect of encouraging more compounds containing the [R3PSePh] cation. The second part of the work incorporates the synthesis and characterisation of a series of hydrophobic bispidone - transition metal complexes. This study was the first example of bispidone ligands substituted with long alkyl chains and three novel crystal structures are reported. Their molecular configuration shows that each adopts the expected back-to-back double chair backbone as observed in similar studies by other chemists. Furthermore, the molecular structures of four piperidone precursor molecules were obtained, the first examples of piperidones substituted with hydrophobic alkyl chains. Their structures reveal that these molecules tautomerise in the solid state due to the formation of an intramolecular six-membered ring stabilised by hydrogen bonding.
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Su, Sheng-Han [Verfasser]. "Investigations into Rare-Earth Metal(III) Oxoselenates(IV) and Ultra-Thin Layered Selenides / Sheng-Han Su." München : Verlag Dr. Hut, 2018. http://d-nb.info/1164293583/34.
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Lima, Leonardo Warzea [UNESP]. "Selenium and sulfur: mitigation in plant stresses." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/138897.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
As plantas não possuem mecanismos de defesa específicos para combater a diversidade de estresses abióticos e poluentes do ambiente, e sua sobrevivência depende da flexibilidade e adaptação dos seus próprios mecanismos de defesa naturais. Além disso, a manutenção da homeostase celular depende de vários mecanismos interligados e complexos, enquanto o sistema de defesa celular não segue um padrão específico de ação e pode ainda variar devido a vários fatores tais como a espécie do vegetal, o tempo de exposição ao estresse, o estágio de desenvolvimento da planta e também nos diferentes órgãos e tecidos analisados. Com base nessas considerações, esta dissertação teve como objetivo destacar e investigar o papel do Enxofre (S) e do Selênio (Se) contra diferentes estresses nas plantas, através das respostas enzimáticas, não enzimáticas e também outros mecanismos de defesa relacionados. No primeiro capítulo, o autor caracteriza os mecanismos bioquímicos gerais da defesa celular antioxidante, especificamente a formação das espécies reativas de oxigênio (EROs) e suas singularidades químicas e o estresse oxidativo induzido, o sistema de defesa antioxidante enzimático, especificamente as enzimas Superóxido Dismutase (SOD) e a Catalase (CAT), os mecanismos não-enzimáticas contra o estresse, incluindo o ciclo Aascorbato-Glutationa, a GSH (glutationa reduzida), as fitoquelatinas e também a formação de prolina. O estado nutricional da planta durante o estresse é crucial a fim de manter uma resposta de defesa adequada. Em vista disso, o capítulo dois apresenta uma revisão sobre a participação de Enxofre (S) na defesa contra o estresse. Este nutriente tem um papel importante em processos fundamentais, tais como o transporte de elétrons, estrutura, regulação, produção de oxigênio fotossintético, resistência a estresses abióticos e bióticos e no metabolismo secundário. Além disso, alguns elementos químicos são considerados benéficos para as plantas, no qual o Selênio (Se) é o mais relevante. No capítulo três, o autor descreve o papel do Se na amenização do estresse induzido pela contaminação por metais pesados, suas poderosas características antioxidantes, a melhoria da atividade de enzimas antioxidantes e também dos mecanismos globais de defesa. O capítulo quatro consiste em um projeto científico conduzido pelo autor. O objetivo deste estudo foi investigar se o Selênio, sob a forma de selenito (Na2SeO3), é capaz de evitar a absorção, translocação e concentração de cádmio (CdCl2), em diferentes tecidos no tomate, indicando os possíveis mecanismos para amenizar o estresse, bem como também analisar o estado geral dos frutos através das análises nutricionais, peso seco, pigmentos e concentração de Prolina livre. Os resultados demonstram que efeito atenuante do Se em tomateiro submetido ao Cd poderia estar relacionado com a restrição da absorção e translocação de Cd2+, aumentando a concentração de micronutrientes nos frutos e, finalmente, aumentando a concentração de prolina livre nos frutos.
Plants do not have specific defense mechanisms to counteract the diverse range of abiotic stresses and pollutants into the environment, and its survival depends on the flexibility and adaptability of its own natural defense mechanisms. Furthermore, the maintenance of cellular homeostasis depends on several interlinked and complex mechanisms, while the cellular defense system does not follow a specific pattern of action and may differ due to various factors such as plant species, exposure time to the stress, plant developmental stage, different organs and tissues analyzed. In the light of these considerations, this dissertation aimed to highlight and investigate the role of Sulfur and Selenium against different plant stresses, through the enzymatic and non-enzymatic plant responses and other related defense mechanisms. In the first chapter the author characterize the general biochemical mechanisms of the antioxidant cell defense, specifically the reactive oxygen species (EROs) formation and its chemical singularities and the induced oxidative stress, the enzymatic antioxidant defense system, specifically the superoxide dismutase (SOD) and Catalase (CAT) enzymes, the non-enzymatic mechanisms against the stress, including the Ascorbate-Glutathione cycle, the GSH (reduced glutathione), the phytochelatins and also proline formation. The plant nutritional status during the stress is crucial in order to maintain a proper defense response. In view of this, the chapter two is a published review about the participation of Sulfur (S) on the stress defense. This nutrient has a role in fundamental processes such as electron transport, structure, regulation and it is also associated with photosynthetic oxygen production, abiotic and biotic stress resistance and secondary metabolism. Moreover, few chemical elements are considered benefic to plants, while Selenium (Se) is the most relevant. In the chapter three the author describes the role of Se to detoxify the stress induced by heavy metal contamination, its powerful antioxidant characteristics and the improvement of the antioxidant enzymes activity and overall defense mechanisms. The chapter four consists of a scientific project conducted by the author. The aim of this study was to investigate whether Selenium, under the form of selenite (Na2SeO3), may avoid the uptake, translocation and concentration of Cadmium (CdCl2), in different tomato tissues, indicating possible mechanisms to counteract the stress, as well as to analyze the fruits overall status through the nutritional analyses, dry weight, pigments and proline concentration. The results demonstrate that alleviating effect of Se in tomato under Cd contamination could be related to restriction of Cd2+ uptake and translocation, enhancing micronutrient concentration in fruits and, finally, enhancing fruit proline concentration.
CAPES: 445978/2014-7
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Peschke, Simon [Verfasser], and Dirk [Akademischer Betreuer] Johrendt. "Synthesis and characterization of rare-earth oxide transition-metal arsenides and selenides / Simon Peschke ; Betreuer: Dirk Johrendt." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2017. http://d-nb.info/1130587436/34.
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Jolley, Dianne F., and n/a. "The accumulation and storage of selenium in Anadara Trapezia." University of Canberra. Applied Science, 1999. http://erl.canberra.edu.au./public/adt-AUC20060802.172608.
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This study examines the occurrence, distribution and storage of selenium in seagrass
communities of Lake Macquarie, which is a heavily industrialised area of NSW, where
notably high trace metal concentrations have been reported previously. Initially a suite
of organisms was collected from a seagrass bed (Zostera capricornia) in the southeastern
section of the lake to investigate the bioaccumulation and biomagnification of
selenium. All organisms contained selenium, with sediment-dwelling organisms
containing the highest Se concentrations. No consistent pattern of significant Se-metal
correlations with Cu, Zn and Cd was found. Biomagnification of Se was evident, as
concentrations increased from sediments and water to flora (algae and seagrass) to
bivalves to Crustacea. However, this trend was not continued to the higher trophic
groups of invertebrate predators and teleost fish.
The bivalve Anadara trapezia was further studied. Intrinsic and extrinsic factors
affecting the accumulation of Se were examined. Gender and mass were assessed in a
single day study, followed by a temporal investigation of the effect of gender,
reproductive cycle, temperature and salinity on Se accumulation. Gender had no effect
on the accumulation of Se in A. trapezia. Se was present in all tissues (adductor,
blood, foot, gills, intestine and mantle) and not immobilised or stored in a specific
tissue, indicating that it plays a structural role in the tissues of A. trapezia. Se burden
increased relative to size (shell length and dry mass) suggesting that Se is metabolically
controlled within the organism. Se concentrations were found to fluctuate temporally
because of: food availability in response to water temperatures; the reproductive cycle;
and associated metabolic activities responding to temperature changes and food
availability.
Subcellular selenium associations in A. trapezia were examined to assist in the
understanding of the fate of Se in marine tissues. Most of the Se was associated with
proteins, suggesting that Se has a metabolic role in this marine organism. Proteins
are intrinsically associated with the lipid bilayer of the cell membranes. A number of
proteins (94, 85, 43, 36.5, 30, 23.4, 17.4 and 15 kDa) were separated by SDS PAGE
from ethanol fractions. Determination of the Se concentration within individual
proteins was not possible because the ratio of Se to protein was too low for further
analysis.
These findings indicated that Se plays a metabolic role in the tissues of the marine
organism A. trapezia. The biochemical regulatory mechanism responsible for
maintaining Se concentrations within the tissues is currently unknown.
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Safoula, Gabriel. "Caracterisation des couches minces polycristallines de selenium dope par un halogene (cl, i) et etude des interfaces metal-selenium (m = cr, bi, te)." Nantes, 1988. http://www.theses.fr/1988NANT2018.
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L'effet du dopage a ete analyse par diffraction rx, microscopie electronique a balayage, spectrometrie de masse des ions secondaires, diffusion raman, emission photoelectronique rx, emission electronique auger. On effectue des mesures de conductivite electrique, d'effet hall et de pouvoir thermoelectrique en fonction de la temperature, de la concentration initiale en halogene et du vieillissement. On en deduit que, seule une fraction d'halogene, non uniformement reparti, a un role electriquement actif
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Layer, Teresa. "Synthesis and characterisation of novel phosphorus and selenium substituted carbonyl clusters of ruthenium and osmium." Thesis, University of Cambridge, 1993. https://www.repository.cam.ac.uk/handle/1810/272563.
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Norris, Pauline Rose Hack. "Arsenic and Selenium Distribution in Coal-Fired Plant Samples." TopSCHOLAR®, 2009. http://digitalcommons.wku.edu/theses/52.
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Arsenic and selenium distributions in coal-fired plant samples are studied. This research includes arsenic and selenium concentrations in samples of coal, fly ash, bottom ash, economizer ash, Flue Gas Desulfurization (FGD) slurry and flue gas taken from four power plants with the goal being to examine the distribution of these metals in these materials and calculate a materials balance for the system. All samples were analyzed using ICP-ES.
This research shows that 60-80% of the arsenic in coal-fired plant samples will be associated with the fly ash. Approximately 35-55% of the selenium will be associated with the fly ash and approximately 30-40% will be associated with the FGD slurry materials. The amount of arsenic and selenium present in the flue gases escaping the stack is very little, 6-7% or less.
Hopefully, research in this area will be helpful when setting emissions limits, identifying and disposing of hazardous wastes and improving air pollution control devices for maximum metal removal.
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Wessels, Charlotte Elize. "Reduction of selenium by Pseudomonas Stutzeri NT-l; Growth reduction and kinetics." Diss., University of Pretoria, 2017. http://hdl.handle.net/2263/62802.
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Bioremediation of seleniferous water is gaining more momentum, especially when it comes to bacterial reduction of the selenium oxyanions. More and more bacterial strains that are able to reduce selenium are being isolated. These bacteria need to be studied further to determine whether they are suited for industrial application. In this study, the reduction of Se(VI) to Se(0) by Pseudomonas stutzeri NT-I was examined using batch experiments with the bacteria suspended in MSM. For the determination of the optimum conditions for the growth of the bacteria, the linearized rate during the exponential phase for different conditions were compared. A pH of 7, temperature of 37 ⁰C, salinity of 20 g.L-1 NaCl and initial concentration of 5 mM selenate were found to be the best at promoting growth. To determine the optimum conditions for the reduction of selenium, the amount of Se(0) recovered from the plug after 16 hours of incubation was measured. A pH of 8, temperature of 37 ⁰C and salinity of 5 g.L-1 resulted in the most Se(0) recovered. The kinetics of the reduction of Se(VI) to Se(0) was found to follow the adapted Monod equation. An increase in the initial Se(VI) concentration positively affected the reduction rate indicating that substrate saturation had not yet been reached. One kmax could be fitted to each of the two reactions but not one Ks. It was found that Ks decreased with increasing initial selenate concentration. Visually it can be deduced that inhibition starts playing a role in the reduction of selenate at a concentration of 4 mM. Pseudomonas stutzeri NT-I is an exemplary selenium reducing agent and deserves more attention, not only for industrial application but also in the research world, for further understanding of the complex mechanism behind metal reduction in bacteria.Dissertation (MEng)--University of Pretoria, 2017.
Chemical Engineering
MEng
Unrestricted
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Waddell, Paul G. "Metal-chalcogen-nitrogen ring complexes and crystallographic studies." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/987.
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A series of Pt(S₂N₂)(P(OR)[subscript n]R′[subscript(3-n)])₂ complexes were prepared and analysed using ³¹P NMR and IR spectroscopy, elemental analysis and X-ray crystallography. Similarly, a series of Pt(SeSN₂)(P(OR)[subscript n]R′[subscript(3-n)])₂ complexes were also prepared and analysed. The ¹J[subscript(Pt-P)] coupling constants and Pt-P bond lengths for these complexes are influenced by the oxygen content of their phosphorus ligands. The ³¹P NMR spectra for a series of [Pt(S3N)(P(OR)[subscript n]R′[subscript(3-n)])₂][BF₄] complexes are also reported. Planar [S₂N₂H]⁻ complexes were prepared and the X-ray crystal structure of [Pd(S₂N₂H)(bipy)][Cl] is reported. The X-ray structures of MX₂(P(OR)[subscript n]R′[subscript(3-n)])₂ are reported and compared with the previously reported analogues. The magnitude of the ¹J[subscript(Pt-P)] varies linearly with the Pt-P bond length (l[subscript(Pt-P)] = 2.421 – J/24255) for the 12 platinum-containing complexes. This correlation is compared to that of a larger series of complexes. A series of M(ndsdsd₂ (ndsdsd = bis[(nitrilo(diphenyl)-λ⁶-sulfanyl)](diphenyl)-λ⁶-sulfanediimide (Ph₂S(=N-(Ph₂)S≡N)₂)) complexes were prepared and characterised using elemental analysis and multinuclear NMR and IR spectroscopy where appropriate. The X-ray crystal structures of five examples are reported.
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Jain, Rohan. "Biogenic nanoparticles of elemental selenium : synthesis, characterization and relevance in wastewater treatment." Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1178/document.
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Les nanoparticules exposent beaucoup de propriétés uniques en comparaison de la possession de matériels (matières) en gros (vrac) à leur haute surface au ratio de volume. Des nanoparticules de sélénium élémentaires exposent aussi les nouvelles propriétés qui sont exploitées dans la formation de cellules solaires, des redresseurs de semi-conducteur et le déplacement (déménagement) de mercure et le cuivre. Cependant, la synthèse chimique de nanoparticules de sélénium élémentaires est coûteuse, exige des équipements spécialisés et utilise des produits chimiques toxiques. D'autre part, la production biologique de nanoparticules de sélénium élémentaires (BioSeNPs) peut être un remplacement(remplaçant) vert pour les chimiquement produits. BioSeNPs sont produit par la réduction microbienne de sélénite et selenate. La source du sélénium oxyanions peut être le wastewaters, où la réduction microbienne est employée comme une technologie de remédiation pour le déplacement (déménagement) de sélénium (...)Nanoparticles exhibit many unique properties as compared to the bulk materials owning to their high surface to volume ratio. Elemental selenium nanoparticles also exhibit novel properties that are exploited in formation of solar cells, semiconductor rectifiers and removal of mercury and copper. However, the chemical synthesis of elemental selenium nanoparticles is costly, requires specialized equipments and uses toxic chemicals. On the other hand, biological production of elemental selenium nanoparticles (BioSeNPs) can be a green replacement for the chemically produced ones.BioSeNPs are produced by microbial reduction of selenite and selenate. The source of the selenium oxyanions can be the wastewaters, where microbial reduction is employed as a remediation technology for the removal of selenium. The formed BioSeNPs are colloidal poly-disperse particles with negative surface charge and are present in the effluent of the microbial reactor. However, the properties of these BioSeNPs are not very well understood. This knowledge would help us to produce better quality selenium nanomaterials, exploit produced BioSeNPs in the wastewater treatment and control the fate of these BioSeNPs in the microbial reactors. The characterization of BioSeNPs revealed the presence of the extracellular polymeric substances (EPS) on the surface of BioSeNPs. The EPS was identified to control the surface charge and to some extent the shape of the BioSeNPs. It was also found that the microbial reduction at 55 and 65 °C can lead to the formation of selenium nanowires as compared to nanospheres when the reduction takes place at 30 °C. These selenium nanowires are present in trigonal crystalline structure and are colloidal suspension, unlike the chemically formed trigonal selenium nanorods. This colloidal nature is due to negative ζ-potential values owning to the presence of EPS on the surface of biogenic selenium nanowires. Since proteins are a major component present in the EPS, the presence of various proteins on the surface of BioSeNPs was determined. The interaction of the various amino acids with the BioSeNPs was also evaluated.The interaction of heavy metals and BioSeNPs was studied with a view of developing a technology where BioSeNPs present in the effluent of an upflow anaerobic sludge blanket (UASB) reactor are mixed with heavy metals containing wastewater leading to removal of both BioSeNPs and heavy metals. It was found that Cu, Cd and Zn can be effectively adsorbed onto BioSeNPs. Cu was 4.7 times preferentially adsorbed onto BioSeNPs. The interaction of BioSeNPs with the heavy metals led to less negative ζ-potential of BioSeNPs loaded with heavy metals and thus better settling of BioSeNPs was achieved. The presence of BioSeNPs in the effluent of the microbial reactor treating selenium oxyanions containing wastewaters is undesirable due to higher total selenium concentrations. Thus, the attempts to capture of these BioSeNPs in the biomass/bioreactors were made. The activated sludge reactor system was investigated to aerobically reduce selenite to BioSeNPs and trap them in the activated sludge flocs. Around 80% of the fed selenium was trapped in the biomass. Sequential extraction revealed that the trapped selenium is BioSeNPs. The trapping of BioSeNPs in the sludge improved the settleability and hydrophilicity of the activated sludge flocs. When the UASB reactor were operated under mesophilic and thermophilic conditions, the total selenium concentration in the effluent under thermophilic conditions were lower than that of observed in mesophilic conditions suggesting better trapping of BioSeNPs.Keywords: Selenium, bioreduction, BioSeNPs, EPS, ζ-potential, heavy metals, activated sludge, UASB reactors, thermophilic
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Tong, Yongfeng. "Self-Assembly of Organic Molecules on Reactive Metal Substrates." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS522/document.
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Dans cette thèse, la formation de monocouches auto-assemblées de différentes molécules de chalcogénure et de molécules p-conjuguées planaire et leurs caractéristiques structurelles et électroniques ont été systématiquement étudiées principalement par spectroscopie photoélectronique à rayons X effectuée utilisant la lumière synchrotron, microscopie à effet tunnel à balayage et diffraction d'électrons à faible énergie. Une étude de la formation de structures hybrides organiques-inorganiques auto-assemblées a été réalisée par assemblage couche par couche d'un dithiol sur ZnO (0001) avec dépôt de métal intermédiaire. De plus en complément de l'étude des molécules comportant un atome de chalcogènure, les caractéristiques d'adsorption du sélénium et du soufre ont été étudiées. La spectroscopie XPS à haute résolution et la spectroscopie de structure fine d’absorption au seuil d’excitation (NEXAFS) ont permis d'étudier les caractéristiques des monocouches auto-assemblées du sélénure de benzène et du sélénophène sur Cu (100) et dihexyldiselénure sur Ni (111) et Pd (111) et ont montré en particulier l’existence de processus de rupture de liaison Se-C ainsi que l’existence de différents sites d'adsorption de molécules. Ces conclusions ont été soutenues par l'étude de l'adsorption atomique du sélénium, qui montre également l'existence de différents sites d'adsorption pour le Se atomique avec différents environnements chimiques. Ces conclusions sont principalement basées sur une étude XPS haute résolution des spectres caractéristiques Se3d, Se3p, du spectre de bande de valence et de l'imagerie LEED. La formation de monocouche de 5,5-bis (mercaptéthyl) -2,20-bipyridine (BPD) avec terminaison SH libre sur ZnO(0001) a été démontrée, permettant le greffage ultérieur d'Ag et Ni et de l’ assemblage d’une autre couche de BPD sur cette couche de métal-dithiol. Les changements dans les propriétés électroniques ont été déterminés à partir des spectres de la bande de valence. La molécule π-conjuguée, NTCDA, a été déposée sur différentes surfaces métalliques et sa morphologie structurelle et ses propriétés chimiques par rapport à la surface métallique ont été étudiées. Les molécules NTCDA affichent une structure « couchée » avec deux domaines différents sur Ag (110) et Cu (100) mais trois domaines sur la surface de Cu (111). Par rapport à celui sur la surface inerte de Au, une forte interaction entre les molécules et les substrats de Cu, Ag existe et joue un rôle important dans la détermination de l'orientation et de l'état de liaison des films organiquesIn this thesis, the formation of self-assembled monolayers of different chalcogenide molecules and planer π-conjugated molecules and their electronic and structural characteristics were systematically studied mainly by synchrotron based X-ray photoelectron spectroscopy, scanning tunneling microscopy and low energy electron diffraction. A study of formation of hybrid organic-inorganic self assembled structure was performed by layer by layer assembly of a dithiol on ZnO(0001) with intermediate metal deposition. Additionally as a complement to the study of chalcogen head group molecules the adsorption characteristics of selenium and sulfur were investigated. The high resolution XPS and near edge absorption fine structure spectroscopy allowed to investigate the characteristics of self-assembled monolayers of benzene selenide and selenophene on Cu (100), and dihexyldiselenide on Ni(111) and Pd(111) and showed in particular the existence of Se-C bond breaking processes and existence of different adsorption sites of molecules. These conclusions were supported by the study of atomic selenium adsorption, which also shows existence different adsorption sites for the atomic Se with different chemical environments. These conclusions are mainly based on high resolution XPS study of characteristic Se3d, Se3p spectra, valance band spectrum and LEED imaging. The formation of a 5,5- bis (mercaptomethyl)-2,20- bipyridine (BPD) with SH termination on ZnO(0001) was demonstrated allowing subsequent grafting of Ag and Ni and further assembly of BPD on this metal-dithiol layer. The changes in electronic properties were determined from valence band spectra. The large π-conjugated molecule, NTCDA, was deposited on different metal surfaces and its structure morphology and chemical properties with respect to the metal surface was investigated. The NTCDA molecules displays a lying down structure with two different domains on Ag (110) and Cu(100) but three domain on Cu(111) surface. Compared with the one on the inert Au surface, a strong interface interaction between the molecules and Cu, Ag substrates plays an important role in determining the orientation and bonding state of the organic films
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Bello, Yusuf O. "Tellurium and selenium precipitation from copper sulphate solutions." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/95895.
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Thesis (MEng) -- Stellenbosch University, 2014.ENGLISH ABSTRACT: The copper sulphate leach solutions produced during the final pressure leach stages in base metal refinery processes contain low concentrations of other precious metals (OPMs, namely Rh, Ru and Ir ) and impurities in addition to the base metals (BMs) of interest. Se and Te impurities, in particular, must be removed from the leach solution before it is fed to copper electrowinning because these species have adverse effects on electrowinning efficiency. Currently, these elements are being precipitated from the leach solution with sulphurous acid. Se precipitation is satisfactory but Te removal still proves challenging. Previous studies have shown that tellurium can either be precipitated as cuprous telluride from copper sulphate solutions by reduction with sulphurous acid alone, or by the addition of SO2 as a precipitating agent and metallic copper as an additional precipitating agent. The objective of this study was to evaluate the effects of different process variables on Te and Se recovery in order to propose operating conditions at which increased tellurium precipitation can be achieved with minimal co-precipitation of base metals of interest (notably Cu and Ni). This would also aid in the development of a better understanding of tellurium and selenium precipitation mechanisms in CuSO4-H2SO4 medium.
AFRIKKANSE OPSOMMING: Die kopersulfaat logingsoplossing wat gedurende die finale druklogingstadia in basis metaal raffinaderye produseer word bevat, behalwe vir die basis metale van belang, ook lae konsentrasies ander edelmetale (AEM, naamlik Rh, Ru, en Ir) sowel as onsuiwerhede. Se en Te onsuiwerhede, in die besonder, moet vanuit die logingsoplossing verwyder word voordat die oplossing na die koper elektrowinning gevoer word omdat hierdie spesies negatiewe effekte op die elektrowinning effektiwiteit het. Hierdie elemente word tans met swaweligsuur vanuit die logingsoplossing gepresipiteer. Se presipitasie is voldoende, maar die Te verwydering bly steeds problematies. Vorige studies het getoon dat tellurium as kuprotelluried vanuit kopersulfaat oplossings presipiteer kan word deur middel van reduksie met swaweligsuur alleen, of met die byvoeging van SO2 as presipiteermiddel en metallieke koper as addisionele presipiteermiddel. Die doelwit van hierdie studie was om die effekte van verskillende prosesveranderlikes op Te en Se presipitasie te ondersoek ten einde bedryfstoestande voor te stel wat verbeterde tellurium presipitasie toelaat met minimale kopresipitasie van basis metale van belang (hoofsaaklik Cu en Ni). Dit sal ook bydra tot die ontwikkeling van ʼn beter begrip van die tellurium en selenium presipitasie meganisme in ʼn CuSO4-H2SO4 medium.
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Mei, Jenny J. "The relationship between dietary and supplemental selenium, magnesium, zinc, and copper intake and depression score in older adults." Thesis, California State University, Long Beach, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10105270.
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The importance of investigating relationships between depression and mineral intake is necessary due to concerns over the mental health and nutrition status of the growing older adult population in America. Due to lack of research in this area, the development of nutrition therapies for depressed older adults with special consideration for minerals is hindered. This study explored whether mean depression scores significantly differed between quartile intake groups of selenium, magnesium, zinc, and copper in a nationally representative sample of older adults (n = 901) from the 2011-2012 National Health and Nutrition Examination Survey (NHANES). For all four minerals, those within the highest quartile of intake had significantly lower depression scores than those within the lowest quartile. Nutrition and mental health care professionals should be aware of a possible association between mineral intake and depression and emphasize healthy eating patterns and nutrient-dense diets to maintain optimal mental and physical functioning.
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DeNicola, Cafferky Katie. "ASSESSMENT OF METAL CONCENTRATIONS AND SPECIES IN BIOLOGICALLY RELEVANT SAMPLES WITH INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRIC TECHNIQUES." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1155754956.
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Milner, Harry. "The use of O-(diphenylphosphinyl)hydroxylamines and nitrogen-selenium ylides in transition-metal-free aminations of sp2 carbon centres." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/25510.
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Due to their abundance in both natural products and synthetic pharmaceuticals, and their diverse and interesting biological properties, nitrogen containing compounds are of great importance to organic chemists. As such, synthetic methodology for the incorporation of nitrogen into organic compounds via the construction of C-N bonds is highly sought after. The research described in this thesis concerns the development of three methodologies for the synthesis of small nitrogen containing compounds via the amination of carbon sp2 centres: 1) Synthesis of N-Boc-aziridines Building upon recent reported methodology utilising O-(diphenylphosphinyl) hydroxylamine (DppONH2) as a nitrogen source for NH-aziridinations, studies were undertaken into the use of N-Boc-O-(diphenylphosphinyl) hydroxylamine (DppONHBoc) in the synthesis of N- Boc-aziridines. Described herein are studies into the use of DppONHBoc as a nucleophilic nitrogen transfer agent (NNTA) for the aziridination of enones and vinyl sulfones under mildly basic conditions. 2) Amination of aromatic C-H centres The use of a N-methyl morpholine (NMM)-derived aminimine as an aminating agent in the vicarious nucleophilic amination (VNA) of electron-deficient (hetero)arenes is also reported. Initial studies which used iodide hydrazinium salts as aminimines precursors in the amination of a range of electron-deficient substrates are described. An alternative reaction system utilising the in situ formation of NMM/DppONH2 hydrazinium salts, in-place of preformed hydrazinium salts, in the vicarious nucleophilic amination reaction was then developed. 3) Synthesis of enantioenriched allylic amines Finally, the NCS-meditated amination/[2,3]-sigmatropic rearrangement of enantioenriched allylic selenides, utilising a range of amino acid derived and aryl amine nucleophiles, is used to access a wide range of novel vinyl glycine derived unnatural peptides and peptidomimetic products.
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Carroll, Brett Ian. "Microbial and Geochemical aspects of Selenium cycling in an Estuarine system: Lake Macquarie N.S.W." University of Sydney, Chemical Engineering, 1999. http://hdl.handle.net/2123/378.
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ABSTRACT This work examined the role of micro-organisms in the biogeochemical cycling of selenium within the benthic ecosystem of Lake Macquarie, a coastal lake in New South Wales with a history of anthropogenic heavy metal contamination. Certain micro-organisms possess the ability to oxidise or reduce selenium (Fleming and Alexander, 1973; Doran and Alexander, 1977), and microbial volatilisation of selenium from contaminated sediments and soils utilising naturally-occurring microflora has been shown in overseas research (Thompson-Eagle and Frankenberger, 1992) to be a potentially effective remediation strategy. In examining the impact of micro-organisms upon the oxidation state of selenium in Lake Macquarie sediments, this work also investigated and characterised selenium (and heavy metal) concentrations, speciation and geochemical phase associations (an indicator of potential bioavailability) in the sediments. Seven distinct bacterial species indigenous to Lake Macquarie were identified in this work with the ability to reduce selenium as selenite to elemental selenium, and selenium as selenate to organic forms of selenium, including volatile methylated selenium compounds. Metabolic parameters calculated for these organisms compared favourably with those reported in the literature by other researchers. Mixed populations of sediment micro-organisms were also isolated and studied in this work for their selenite and selenate reduction abilities. Total reduction of added selenite at levels up to 100 mg/L was recorded for a number of the organisms studied in this work. A maximum specific uptake rate for selenite of 3040 mgSe(IV).(gcells)-1.(h)-1 for one isolate (Shewanella putrefaciens) was determined, exceeding rates reported in the literature by other authors. Use of the indigenous micro-organisms from Lake Macquarie for the bioremediation of selenium containing waste streams was also examined in this work and selenium reduction in an immobilised cell reactor was demonstrated with such organisms. Concentrations, speciation, sediment core profiles and geochemical phase associations for selenium were determined for sediment samples collected at a variety of sites throughout Lake Macquarie and from Wyee Creek, a selenium-impacted fluvial input to the lake. The maximum concentration of selenium obtained in this work for the lake proper was 4.04 mg/kg, considerably lower than values reported over a decade ago (Batley, 1987) but consistent with reported reductions of selenium input into the lake from the lead-zinc smelter. Selective extraction methodology (Tessier et al. and BCR methods) studied geochemical phase association of selenium in Lake Macquarie sediments and found up to 44% of selenium was in bioavailable forms. Of interest and environmental concern was levels of selenium found in sediments of Wyee Creek, which previously received overflows from the ash dam associated with the Vales Point Power Station. Sediment selenium levels of up to 300 mg/kg were determined for this creek. These were an order of magnitude or more greater than those recorded for the lake itself and are of concern as to the potential impact on benthic organisms and those animals, including humans, who consume them. While this work can only provide a 'snapshot' of conditions within Lake Macquarie at the time of the sampling events recorded herein, it does make several important contributions to the understanding of selenium biogeochemistry in Lake Macquarie. These include: presentation of the hypothesis that selenium levels in surficial sediments being deposited in the north of the lake have decreased in recent years as a result of selenium reduction measures undertaken by the lead-zinc smelter; determination that up to 44% of selenium in surficial sediments from the lake is associated with sediment phases in which selenium has the potential to become remobilized and hence possibly bioavailable; and documentation of selenium concentrations in Wyee Creek, identifying the area as having selenium concentrations an order of magnitude or more greater than the lake itself. Concerning the role played by microorganisms in the biogeochemical cycling of selenium in Lake Macquarie, this work has: identified individual isolated and mixed cultures of bacteria that can reduce selenium as selenite to lower oxidation states; identified individual isolated and mixed cultures of bacteria that can reduce selenium as selenate to lower oxidation states; identified volatile methylated selenium compounds in the headspace gases of microorganisms reducing selenate; determined Minimum Inhibitory Concentrations for selenate and selenite for organisms isolated from Lake Macquarie; identified casein hydrolysate as a preferred carbon source for selenium reducing microorganisms from Lake Macquarie; and demonstrated that bioremediation of selenium contaminated waste streams using indigenous organisms from Lake Macquarie is feasible on the laboratory scale. Further research areas suggested by this work include: additional investigations of elevated selenium levels in Wyee Creek sediments; determination of the role of microbes in in-situ selenium reduction; and optimisation of selenium biotreatment/bioremediation of selenium-containing waste streams and sediments. In summary, this work, in rejecting the null hypothesis that the oxidation states of selenium in sediments from Lake Macquarie, NSW, are independent of microbial activity and accepting the alternate hypothesis that these oxidation states are not independent of microbial activity, contributes to the understanding of the role of microorganisms in the biogeochemical cycling of selenium, having applicability to both the specific ecosystem of Lake Macquarie, NSW, and also to selenium cycling in the environment in general. In addition, this work has identified selenium contamination in Wyee Creek, one of the fluvial inputs to Lake Macquarie, which was previously been undocumented in the literature and which may pose significant potential risk to humans and the ecosystem due to sediment selenium levels one or more orders of magnitude higher than those recorded in the lake itself. Finally, this work has also identified a number of microorganisms indigenous to Lake Macquarie with the ability to reduce selenium from toxic, mobile forms to less toxic, immobile or volatile forms, and these organisms have been shown to have the potential for use in treatment of selenium contaminated waste streams and also in the bioremediation of selenium-contaminated sediments.
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Moffo, Nathan. "Differential Analysis of Unique Genes Expressed in Stenotrophomonas maltophilia Strain OR02 in Response to Selenite." Youngstown State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ysu15663177454459.
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Kruger, John Scott. "Synthesis and characterization of several novel aluminum and gallium phosphates templated by cobalt complexes." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/30553.
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Kirby, Jason K., and n/a. "Trace metal and metalloid accumulation, distribution, and, speciation in Lake Macquarie, N.S.W., Australia." University of Canberra. Resource, Environmental & Heritage Sciences, 2005. http://erl.canberra.edu.au./public/adt-AUC20051129.124508.
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THESIS ORGANISATION
This thesis is organised into nine chapters that include seven international and
national publications (six accepted and one submitted for publication). The initial
overview chapter outlines the justification and direction for this thesis. With the
exception of chapter 8 (accepted for publication on the 1st May 2005); all chapters are
exact duplicates of published articles in international and national refereed journals
(chapters 2 to 7). The initial chapters (2 and 3) presents research findings using a
marine fish species, mullet (Mugil cephalus), to measure trace metal bioavailability in
Lake Macquarie, NSW Australia. While subsequent chapters (4 to 8) are presenting
research under taken to improve the understanding of arsenic cycling in marine and
estuarine environments. The final chapter (chapter 9) is a synopsis of the major
findings presented in this thesis. Due to the publication nature of this thesis, an
unavoidable degree of replication exists within chapters (publications).
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Yathavakilla, Santha Venkata. "Speciation of Selenium, Mercury and Arsenic in Food by Inductively Coupled Plasma Mass Spectrometry." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1179516979.
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Zhang, Julie Zhiling. "The Toxicity Assessment of Heavy Metals and Their Species in Rice." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1249602453.
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Staicu, Lucian. "Production of colloidal biogenic elemental selenium and removal by different coagulation-flocculation approaches." Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1180/document.
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Le sélénium (Se) est un élément chalcogène avec un domaine de concentration étroit entre essentialité et toxicité. La toxicité est principalement liée à la spéciation chimique du Se qui évolue en fonction des conditions redox du milieu. Les formes oxyanioniques de Se, le sélénite (Se [IV], SeO32-) et le séléniate (Se [VI], SeO42-), sont solubles dans l'eau, biodisponibles et toxiques. En revanche, le sélénium élémentaire, Se(0), est insoluble et moins toxique. Néanmoins, les nanoparticules du Se(0) sont potentiellement dangereuses pour certains groupes des mollusques (comme les bivalves) et aussi pour les poissons. En outre, lorsque le Se(0) est rejeté dans les écosystèmes aquatiques, sa ré-oxydation jusqu'au sélénite et séléniate peut se produire. Le sélénium élémentaire d'origine biogénique Se(0) a été produit par la réduction de SeO42- dans des conditions anaérobies en utilisant un inoculum microbien mixte (boues granulaires) et par la réduction de SeO32- dans des conditions aérobies en utilisant une culture bactérienne pure (une nouvelle souche de Pseudomonas moraviensis identifiée et caractérisée pour la première fois dans cette thèse). Les deux types de Se(0) ont montré une forte stabilité colloïdale dans l'écart de pH variant de 2 à 12. La stabilité colloïdale est due à la charge négative (-15 mV à -30 mV) de la couche de biopolymère qui entoure Se(0) et à la taille nanométrique des particules de Se(0). La taille des particules de Se(0) produite par la boue anaérobie granulaire se situait entre 50 et 300 nm, avec une taille moyenne de 166 nm. A l'inverse, les nanoparticules de Se(0) produites par Pseudomonas moraviensis stanleyae sont caractérisées par un diamètre plus faible (~ 100 nm).Compte tenu des risques pour l'environnement engendrés par le relargage du Se(0) biogénique, des mesures appropriées doivent être mises en œuvre pour la séparation solide-liquide en utilisant une technologie efficace. Le potentiel de séparation solide-liquide de Se(0) généré a été évaluée par centrifugation, filtration, coagulation-floculation et électrocoagulation. Alors que toutes les approches présentent des rendements de séparation de Se(0) variables, l'électrocoagulation en utilisant des électrodes sacrificielles de fer a montré l'efficacité d'élimination le plus élevée (97%)Selenium (Se) is a chalcogen element with a narrow window between essentiality and toxicity. The toxicity is mainly related to the chemical speciation that Se undergoes under changing redox conditions. Se oxyanions, namely selenite (Se[IV], SeO32-) and selenate (Se[VI], SeO42-), are water-soluble, bioavailable and toxic. In contrast, elemental selenium, Se(0), is solid and less toxic. Nevertheless, Se(0) nanoparticles are potentially harmful as particulate Se(0) has been reported to be bioavailable to filter feeding mollusks (e.g. bivalves) and fish. Furthermore, Se(0) is prone to re-oxidation to toxic SeO32- and SeO42- when discharged into aquatic ecosystems. Biogenic Se(0) under investigation was produced by the reduction of Na2SeO4 under anaerobic conditions using a mixed bacterial inoculum (anaerobic granular sludge) and through the reduction of Na2SeO3 under aerobic conditions using a pure microbial culture (Pseudomonas moraviensis stanleyae, a novel strain identified and characterized for the first time herein). Both types of Se(0) showed strong colloidal stability within the 2-12 pH range. The colloidal stability is caused by the negatively charged (-15 mV to -30 mV) biopolymer layer covering biogenic Se(0) particles and by their nanometer size. The particle size of Se(0) produced by anaerobic granular sludge ranged between 50 and 300 nm, with an average size of 166 nm. Conversely, the Se(0) particles produced by Pseudomonas moraviensis stanleyae are characterized by a lower diameter (~ 100 nm).The solid-liquid separation potential of Se(0) was assessed by centrifugation, filtration, coagulation-flocculation and electrocoagulation. While all approaches can bring about Se(0) removal from suspension with various degrees of success, electrocoagulation using iron sacrificial electrodes showed the highest removal efficiency (97%). Because biogenic Se(0) is harmful to the environment, appropriate measures must be implemented for the solid-liquid separation using an efficient technology
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Mohammadi, Farid. "A Meta-Analysis on Solar Cell Technologies." Thesis, Mittuniversitetet, Avdelningen för elektronikkonstruktion, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-32584.
Full textAbstract:
The objective of this study is analysing the characteristics of five different solar cell technologies regarding their efficiency, fill factor, cost and environmental impacts and comparing their improvement records over years considering their efficiency. The five solar cell technologies of interest are amorphous silicon, monocrystalline silicon, polycrystalline silicon, cupper indium gallium selenide thin film and cadmium telluride thin film. The structure and manufacturing process of each of cell technologies were discussed. The study was conducted by the aid of available scientific reports regarding the electrical characteristics of different solar cell technologies. The extracted information regarding efficiency rate and fill factor was analysed using graphs and significant findings are discussed. The five technologies are also compared regarding their cost and ease of fabrication and their impacts on environment and recycling challenges. The result of this study is suggesting the most promising technology that may be the optimal option for further investment and research.
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SENCE, MARTINE. "Etude des proprietes optiques du seleniure de cadmium sous hautes intensites d'excitation lumineuse." Université Louis Pasteur (Strasbourg) (1971-2008), 1989. http://www.theses.fr/1989STR13021.
Full textAbstract:
Etude des caracteristiques du plasma electron-trou. Interpretation des courbes de gain optique obtenues par deux modeles theoriques. Etude des proprietes des biexcitons par melange degenere a quatre ondes et determination de leur energie de liaison (2 mev)
49
Taylor, Anne Marie, and n/a. "Biomarkers of Cadmium, Lead and Selenium Toxicity in the Marine Bivalve Molluscs Tellina deltoidalis and Anadara trapezia: Linking Exposure, Dose and Response." University of Canberra. Environmental Science, 2009. http://erl.canberra.edu.au./public/adt-AUC20091214.104734.
Full textAbstract:
The relationships between metal exposure, dose and response were investigated in two
sediment dwelling marine bivalves: a deposit feeder Tellina deltoidalis and a filter feeder
Anadara trapezia. The bivalves were exposed in the laboratory to individual metal spiked
sediments: Cadmium 10 and 50 Ag/g; lead 100 and 300 Ag/g; selenium 5 and 20 Ag/g dry
mass, T. deltoidalis for 28 days A. trapezia for 56 days. A. trapezia was also exposed in the
laboratory for 56 days to sediments from three sites along a metal contamination gradient of
cadmium, lead, selenium, zinc and copper from Lake Macquarie, NSW. Metal total tissue
dose was measured in whole tissue of T. deltoidalis over 28 days and in gill, hepatopancreas
and haemolymph tissues in A. trapezia over 56 days. Subcellular metal distribution,
biologically active metal (BAM) versus biologically detoxified metal (BDM) was measured
in whole tissues of T. deltoidalis at day 28 and in gill and hepatopancreas tissues of
A. trapezia at day 56. Biomarkers of response measured in spiked sediment exposed, at day
28 T. deltoidalis and day 56 A. trapezia were: total antioxidant capacity (TAOC); glutathione
peroxidase enzyme activity (GPx); total glutathione concentration (GSH+2GSSG); reduced to
oxidised glutathione ratio (GSH:GSSG); lipid peroxidation (TBARS); lysosomal membrane
stability and micronuclei frequency. Response indices measured in A. trapezia exposed to
Lake Macquarie sediments were: TAOC, TBARS, lysosomal membrane stability,
micronucleus frequency and condition index. Native A. trapezia and sediments were also
collected from Lake Macquarie and measured for sediment and tissue metal concentrations,
TAOC, TBARS, lysosomal membrane stability and condition index to allow comparison
between chronically exposed and previously unexposed organisms.
T. deltoidalis and A. trapezia accumulated metal over time in all sediment metal exposures
with most reaching equilibrium tissue metal concentrations by the end of the exposure period.
T. deltoidalis generally reached equilibrium with the exposure concentration for cadmium and
lead but had significantly higher selenium tissue concentrations than the sediment metal at the
5 Ag/g exposure. A. trapezia tissue lead was below the sediment concentration for all
exposures including in the native organisms. A high proportion of accumulated lead and
copper in A. trapezia was in the haemolymph, probably associated with haemoglobin which
has a high affinity for these metals`. A. trapezia cadmium tissue concentrations were higher
than the sediment metal in the 10 Ag/g spiked sediment exposure and between half and one
eighth the sediment concentrations in other treatments, including in native organisms.
A. trapezia including the native organisms exposed to selenium sediment concentrations at or
below 5 Ag/g in the Lake Macquarie mixed metal sediments accumulated significantly higher
than ambient selenium tissue concentrations while those exposed to 5 and 20 Ag/g selenium
spiked sediments had lower than ambient selenium tissue concentrations. The majority of
accumulated cadmium, selenium and zinc was associated with the gill/mantle tissues.
A. trapezia hepatopancreas contributed significant selenium concentrations in the later part of
the exposure period indicating and increased contribution from dietary derived selenium.
Native A. trapezia had significantly lower tissue concentrations of selenium, copper and zinc,
higher cadmium and approximately equal lead compared to organisms exposed to similar
sediment metal concentrations in the laboratory.
T. deltoidalis detoxified around 50 % of accumulated cadmium and 70 % of lead while
A. trapezia detoxified around 70 % of accumulated cadmium and 60 % of lead. Much of
T. deltoidalis BDM cadmium was converted to metal rich granules (MRG), while A. trapezia
had most in the metallothionein like proteins (MTLP) fraction. The conversion of lead to
MRG was 75 % of the total BDM in T. deltoidalis while A. trapezia had an even distribution
between MRG and MTLP. The majority of recovered selenium in both species was
associated with the nuclei+cellular debris fraction, probably as protein bound selenium
associated with plasma and selenium bound directly to cell walls. Selenium exposed
organisms had increased BDM selenium burdens which were associated with both MRG and
MTLP fractions, indicating selenium detoxification. The majority of BAM cadmium, lead
and selenium was associated with the mitochondrial fraction in both species with increases in
cadmium burden in this organelle of T. deltoidalis up to 7200 fold; lead 154 fold; and
selenium 7 fold and in A. trapezia up to 84 fold cadmium, 50 fold lead and selenium 7 fold in
exposed organisms compared to controls. The subcellular distribution of all three metals in
T. deltoidalis and A. trapezia indicates active metal detoxification processes which at these
exposure concentrations were unable to prevent significant metal burdens from accumulating
in sensitive organelles.
A contamination gradient of zinc, lead, copper, cadmium and selenium was established in
Lake Macquarie sediments which emanated from the same source. A. trapezia accumulated
all metals in each sediment exposure. Accumulation and tissue distribution patterns of
cadmium, lead and selenium were similar to those of the single metal spiked sediment
exposures. Cadmium and lead BAM burdens increased at all exposures while selenium, zinc
and copper did not.
T. deltoidalis and A. trapezia in the spiked sediment metal exposures generally had reduced
GPx activity. This resulted in an increase in total glutathione concentrations which the
reduced GSH:GSSG ratios indicated was due to a build up of oxidised glutathione.
T. deltoidalis and A. trapezia had reduced TAOC in all laboratory sediment metal exposures
which corresponded with increased TBARS concentrations, lysosomal destabilisation and
micronucleus frequency. A. trapezia exposed to Lake Macquarie metal contaminated
sediments also had a reduction in physiological condition, indicated by the reduced condition
index, after 56 days at the higher metal exposures.
Clear exposure - dose - response relationships have been demonstrated for T. deltoidalis and
A. trapezia exposed to single cadmium, lead and selenium spiked sediments and for
A. trapezia exposed to Lake Macquarie mixed metal contaminated sediments. Detoxification
of all metals was evident in both T. deltoidalis and A. trapezia but detoxification capacity was
exceeded for cadmium, lead and selenium leading to significant accumulation of these metals
in sensitive organelles. The significant relationships, in the laboratory exposed T. deltoidalis
and A. trapezia, between TAOC reduction with increased TBARS, lysosomal destabilisation
and micronuclei frequency and between increased TBARS with lysosomal destabilisation and
micronuclei frequency indicates that increased tissue metal dose and BAM burdens caused
significant impairment of the antioxidant reduction capacity which resulted in a cascade of
effects from lipid peroxidation to cellular perturbation and genotoxic damage. The reduction
in physiological condition in the organisms with the highest tissue metal doses suggests the
response goes beyond subcellular perturbations to whole organism and potentially population
effects.
Chronically metal exposed native Lake Macquarie A. trapezia did not show a clear metal
exposure - dose - response relationship. Accumulation of the essential elements zinc, copper
and selenium appeared to be regulated while cadmium and lead were not. TAOC was
significantly reduced and TBARS significantly increased compared to reference organisms
but lysosomal stability and condition were not significantly affected.
The suite of interrelated biomarkers used offers a weight of evidence approach for
demonstrating adverse effects of metal tissue accumulation in T. deltoidalis and A. trapezia
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Moreno, Achurra Ana Karina. "Revisión meta-analítica del efecto de selenio orgánico sobre la retención a nivel muscular y la actividad de glutatión peroxidasa en peces." Tesis, Universidad de Chile, 2012. http://www.repositorio.uchile.cl/handle/2250/112230.
Full textAbstract:
Memoria para optar al Título Profesional de
Ingeniera AgrónomaEl selenio es un mineral traza esencial en la nutrición animal, y posee funciones importantes relacionadas con el sistema antioxidante del organismo. Actualmente los mercados se encuentran dirigidos a una producción más limpia y que implique menores costos para su obtención. Es por esto que surge la idea de suplementar las dietas de peces con selenio orgánico, ya que aumenta su absorción y retención, conllevando con ello un aumento en la biodisponibilidad del mineral. Para evaluar esto, se realizó un meta-análisis, el cual permitió contrastar los resultados obtenidos por siete autores en relación a la suplementación de selenio orgánico en la alimentación de peces y su efecto en la retención de este mismo a nivel muscular y la actividad de la enzima glutatión peroxidasa a nivel plasmático y hepático. Los resultados obtenidos de los estudios fueron llevados a una métrica común mediante el cálculo del índice del tamaño del efecto. A partir de él, se obtuvo la estimación del efecto global (d·), con valores de 2,279, 1,085 y 1,884 para las variables, retención de selenio a nivel muscular, actividad de la enzima glutatión peroxidasa a nivel plasmático y actividad de la enzima glutatión peroxidasa a nivel hepático respectivamente, siendo este efecto alto en cada una de las variables. La homogeneidad calculada entre los estudios presentó valores de p-value iguales a 9,96·10-9, 8,9·10-1 y 7,88·10-3 para cada una de las variables respectivamente, presentando para cada variable heterogeneidad entre los resultados analizados. En tanto, la comparación realizada entre las fuentes de selenio (selenito de sodio y selenometionina), indicó que con un p-value 9,955·10-9 y 7,88·10-3 para retención a nivel muscular y actividad a nivel hepático respectivamente, existe diferencia significativa entre las fuentes, por lo que la selenometionina aumentaría la retención a nivel muscular y la actividad de la enzima a nivel hepático, mientras que con un p-value de 8,6·10-1 no se presenta diferencia entre las fuentes para actividad enzimática a nivel plasmático. Los estudios con mayor influencia en el cálculo del efecto global para cada una de las variables fueron los de Lorentzen et al. (1994) y Wang et al. (2004) para la variable retención a nivel muscular, Lorentzen et al. (1994) y Liu et al. (2010) para actividad enzimática a nivel plasmático y los estudios de Zhou et al. (2009) y Raider et al. (2010) para actividad enzimática a nivel hepático. Estos estudios son además, los que presentaron el mayor cambio en magnitud en la estimación del efecto global al removerlos del meta-análisis y graficar el efecto provocado por su ausencia en el análisis de sensibilidad.
Selenium is a trace mineral which is essential in animal nutrition and has important functions related to the antioxidant system of the organism. At present fish farming markets are oriented towards a cleaner production involving lower costs. Based on this, supplementing fish diets with organic selenium arose as a feasible idea since this mineral increases its absorption and retention, which leads to an increase in the bioavailability of the mineral. To evaluate this possibility, a meta-analysis was carried out to contrast the results obtained by seven authors in relation to supplementing fish feed with organic selenium and its effect on the retention of this mineral at the muscle level and on the activity of the glutathione peroxidase enzyme at plasma and hepatic levels. The results obtained from the above studies were transformed to a common metric by means of the effect size estimation. Based on it, an estimate of the global effect (d·) was obtained with values of 2.279, 1.085, and 1.884 for the variables selenium retention at muscle level, activity of the glutathione peroxidase enzyme at plasma level and activity of the glutathione peroxidase enzyme at hepatic level, respectively, this effect being high in each of the variables. Homogeneity calculated among the studies showed p-values of 9.96·10-9, 8.9·10-1 and 7.88·10-3 for each of the variables, respectively, thus presenting heterogeneity among the results analyzed for each variable. Meanwhile, the comparison among the sources of selenium, sodium selenite and selenomethionine indicated that with p-values of 9.955·10-9 and 7.88·10-3 for retention at muscle level and activity at hepatic level, respectively, there is a significant difference among the sources. Consequently, selenomethionine would increase retention at muscle level and the enzymatic activity at hepatic level, while with a p-value of 8.6·10-1 no difference exists among the sources for the enzymatic activity at plasma level. The studies with greater influence on the estimation of the global effect for each of the variables were those by Lorentzen et al. (1994) and Wang et al. (2004) for the variable retention at muscle level, those by Lorentzen et al. (1994) and Liu et al. (2010) for the enzymatic activity at plasma level, and those by Zhou et al. (2009) and Raider et al. (2010) for the enzymatic activity at hepatic level.