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1
Waldek, Achim Marcus. "Bestimmung der Ionisationsenergie von Actinium und Ultraspurenanalyse von Plutonium mit resonanter Ionisationsmassenspektrometrie (RIMS)". [S.l. : s.n.], 2000. http://ArchiMeD.uni-mainz.de/pub/2001/0071/diss.pdf.
Testo completo
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Niese, Siegfried. "Discovery of actinium and the thorium isotope 230Th". Siegfried Niese, 2017. https://slub.qucosa.de/id/qucosa%3A7825.
Testo completoAbstract (sommario):
In 1902 Friedrich Giesel has discovered after co-precipitation with lanthanum from samples obtained by chemical treatment of uranium minerals a new radioactive element. Because of its emanating properties he named it emanium, which we now know as actinium. In 1899 André-Louis Debierne found a radioactive substance with chemical properties of titanium, and after further investigations in 1900 of thorium. Because of its high activity he explained it as a new element and named it actinium. It mainly consisted of 230Th. In 1904 he explained that his actinium was identical with the emanium found by Giesel. He had taken over the discovery of Giesel and had rejected his own one, because he had been afraid that his discovered substance which he could not separate from thorium would not be accepted as a new chemical element. In 1909 Boltwood looked for the long-lived precursor of radium. He isolated according to the procedure of Debierne the thorium fraction from the pitchblende and after some time he found in it radium but not in emanium produced according the procedure of Giesel. Boltwood named the mother-element of radium ionium, which was first accepted as a new radioactive element and later identified as thorium isotope 230Th. Although Debierne has discovered and later rejected this substance for a long time he was accepted as discoverer of actinium.Entdeckung des Actiniums und des Thoriumisotopes 230Th Im Jahr 1902 entdeckte Friedrich Giesel nach Mitfällung von Lanthan aus Proben der chemischen Behandlung von Uranmineralen ein neues radioaktives Element, das er wegen seiner starken Bildung von Emanation Emanium nannte und mit dem jetzt als Actinium bezeichneten Element identisch ist.1899 fand André-Louis Debierne in Pechblende eine dem Titan chemisch ähnliche radioaktive Substanz, der er 1900 eine größere Ähnlichkeit mit dem Thorium zuschrieb. Wegen seiner hohen Radioaktivität erklärte er sie für ein neues Element und nannte es Actinium. Es bestand hauptsächlich aus 230Th. 1904 erklärte er, dass sein Actinium mit dem von Giesel entdeckten dem Lanthan ähnlichen Emanium identisch sei. Er übernahm Giesels Entdeckung und verwarf seine eigene, weil er fürchtete, dass seine entdeckte Substanz, die er nicht vom Thorium trennen konnte, nicht als neues chemisches Element anerkannt werden würde. Als Bertran Boltwood1909 nach den langlebigen Vorgängerelement von Radium suchte, trennte er nach der Vorschrift von Debierne die Thoriumfraktion aus der Pechblende ab und stellte fest, dass sich daraus mit der Zeit Radium gebildet hatte, wogegen sich aus dem nach der Vorschrift von Giesel abgetrennten Emanium kein Radium gebildet hatte. Boltwod nannte das Vorgängerelement von Radium Ionium, das zuerst als neues radioaktives Element anerkannt und entspäter als Thoriumisotop 230Th identifiziert wurde. Trotzdem Debierne nicht Actinium sondern diese Substanz entdeckt und später verworfen hatte, war er lange Zeit als Entdecker des Actiniums anerkannt.
3
Niese, Siegfried. "Die Entdeckung des Actiniums". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-152864.
Testo completoAbstract (sommario):
Friedrich Giesel entdeckte im Jahre 1902 das Actinium nach Fällung mit Lanthan aus einer Pechblendelösung. Er hatte den Namen Emanium vorgeschlagen, da es stark emanierte. Lange Zeit wurde nur Andre-Louis Debierne als Entdecker des Actiniums akzeptiert, da er 1904 behauptet hatte, dass die von ihm im Jahr 1900 gefundene von ihm Actinium genannte radioaktive Substanz mit den chemischen Eigenschaften des Thoriums, die hauptsächlich das Thoriumisotop 230Th enthielt, mit dem Emanium von Giesel identisch gewesen sei. In dem Beitrag werden die Entdeckungen von Debierne und Giesel und der Weg bis zur Anerkennung von Giesel als Entdecker vorgestelltFriedrich Giesel discovered actinium in 1902 after co precipitation with lanthanum from a solution of pitchblende. He had suggested to name it emanium, because of its emanating properties. But for a long time only Andre-Louis Debierne was accepted as discoverer of actinium, because in 1904 he has explained, that the radioactive substance found by him in 1900, with chemical properties of thorium, named actinium, and mainly consisting of the thorium isotope 230Th, has been identical with the emanium of Giesel. The discoveries of Giesel and Debierne are explained as well as the steps on the way of acceptance of Giesel as discoverer of actinium
4
Geibert, Walter. "Actinium-227 als Tracer für Advektion und Mischung in der Tiefsee = Actinium-227 as a tracer for advection and mixing in the deep-sea /". Bremerhaven : Alfred-Wegener-Institut für Polar- und Meeresforschung, 2001. http://www.awi-bremerhaven.de/GEO/Publ/PhDs/WGeibert.
Testo completo
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Niese, Siegfried. "Die Entdeckung des Actiniums". Gesellschaft Deutscher Chemiker, 2013. https://slub.qucosa.de/id/qucosa%3A4674.
Testo completoAbstract (sommario):
Friedrich Giesel entdeckte im Jahre 1902 das Actinium nach Fällung mit Lanthan aus einer Pechblendelösung. Er hatte den Namen Emanium vorgeschlagen, da es stark emanierte. Lange Zeit wurde nur Andre-Louis Debierne als Entdecker des Actiniums akzeptiert, da er 1904 behauptet hatte, dass die von ihm im Jahr 1900 gefundene von ihm Actinium genannte radioaktive Substanz mit den chemischen Eigenschaften des Thoriums, die hauptsächlich das Thoriumisotop 230Th enthielt, mit dem Emanium von Giesel identisch gewesen sei. In dem Beitrag werden die Entdeckungen von Debierne und Giesel und der Weg bis zur Anerkennung von Giesel als Entdecker vorgestellt.Friedrich Giesel discovered actinium in 1902 after co precipitation with lanthanum from a solution of pitchblende. He had suggested to name it emanium, because of its emanating properties. But for a long time only Andre-Louis Debierne was accepted as discoverer of actinium, because in 1904 he has explained, that the radioactive substance found by him in 1900, with chemical properties of thorium, named actinium, and mainly consisting of the thorium isotope 230Th, has been identical with the emanium of Giesel. The discoveries of Giesel and Debierne are explained as well as the steps on the way of acceptance of Giesel as discoverer of actinium.
6
Bray, Travis Henry Albrecht-Schmitt Thomas E. "Crossroads and terminations in transuranium chemistry". Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SUMMER/Chemistry_and_Biochemistry/Dissertation/Bray_Travis_43.pdf.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Auburn University, 2008.Abstract. Vita. Parts of this dissertation have been published as: Na₂[UO₂(IO₃)₄(H₂O)] (Ch. 2: Bray, T.H.; et al., Inorg. Chem., 2006, 45, 8251-8257.), An(IO₃)₄(An = Np, Pu) and Np(IO₃)₄·nH2O (Ch. 3: Bray, T.H.; et al., Inorg. Chem., 2007, 46, 3663-3668.), Pu(SeO₃)₂ (Ch. 4: Bray, T.H.; et al., J. Solid State Chem., 2008, 181, 493-498.), NpFPO₄ and Cs₂Np₂F₇PO₄ (Ch. 5: Bray, T.H.; et al., J. Solid State Chem., 2007, 180, 70-74.), [C₆H₁₄N₂][(UO₂)₄(HPO₄)₂PO₄)₂(H₂O)]·H₂O (Ch. 6: Bray, T.H.; et al., "Synthesis and Structure of [C6H14N2][(UO2)4(HPO4)2(PO4)2(H2O)]·H₂O: An Expanded Open-Framework Amine-Bearing Uranyl Phosphate," In press: Journal of Solid State Chemistry April 24, 2008.), and Np(CH₃PO₃)(CH₃PO₃H)(NO₃)(H₂O)·H₂O (Ch. 7: Bray, T.H.; et al., Inorg. Chem., 2007, 46, 10959-10961.). Includes bibliographical references.
7
VanSant, Paul Daniel. "Medical Isotope Production of Actinium 225 By Linear Accelerator Photon Irradiation of Radium 226". Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/50984.
Testo completoAbstract (sommario):
There is a present and future need for the medical isotope Actinium-225, currently in short supply worldwide. Only a couple manufacturers produce it in very low quantities. In roughly the past 10 years the medical community has explored the use of Ac-225 and its daughter Bismuth-213 for targeting a number of differing cancers by way of Targeted Alpha Therapy (TAT). This method utilizes the alpha-decay of both Ac-225 (half-life 10 days) and Bi-213 (half-life 46 min) to kill cancerous cells on a localized basis. Maximum energy is delivered to the cancer cells thereby greatly minimizing healthy tissue damage.
This research proposes a production method using a high-energy photon spectrum (generated by a linear accelerator or LINAC) to irradiate a sample of Radium-226 (half-life 1600yrs). The photo-neutron reaction liberates neutrons from Ra-226 atoms leaving behind Radium-225 (half-life 14.7 days). Ra-225 decays naturally through beta emission to Ac-225. Previous research demonstrated it is possible to produce Ac-225 using a LINAC; however, very low yields resulted which questioned the feasibility of this production method. This research proposes a number of LINAC and radium sample modifications that could be greatly increase yield amounts for practical use.
Additionally, photo-neutron cross-section data for Ra-226 was used, which led to improved yield calculations for Ra-225. A MATLAB® model was also created, which enables users to perform quick yield estimates given several key model parameter inputs. Obtaining a sufficient supply of radium material is also of critical importance to this research. Therefore information was gathered regarding availability and inventory of Radium-226. This production method would serve as a way to not only eliminate many hazardous radium sources destined for interim storage, but provide a substantial supply of Ac-225 for future cancer treatment.
Master of Science
8
Melville, Graeme P. "Production of AC-225 for cancer therapy by photon induced transmutation of RA-226". Thesis, View thesis, 2007. http://handle.uws.edu.au:8081/1959.7/18860.
Testo completoAbstract (sommario):
Radium needles that were once implanted into tumours as a cancer treatment are now obsolete and constitute a radioactive waste problem, as their half-life is 1600 years. The reduction of radium by photonuclear transmutation by bombarding Ra-226 with high-energy photons from a medical linac has been investigated. The irradiated needles would then be processed to remove the Ac-225, which can then be used for .Targeted Alpha Therapy. (TAT) of cancer. This project has the potential to slowly reduce obsolete radioactive material, and displace future expensive importation of Ac-225 from Russia, Germany (Institute for Transuranium Elements - ITU) and the US in the years ahead. This thesis progresses through a number of stages and begins by providing a background to the usefulness of Ac-225 as an alpha emitter, some of the equipment used in the experimental work such as linear accelerators and detectors, as well as the initialisation of a process whereby a reliable source of high-grade radium is secured, suitable equipment obtained, followed by a series of experiments leading to the production of the desired product, actinium and bismuth.
The second stage of this study involved the formulation of a theoretical model in which the bremsstrahlung photon spectrum at 18 MV linac electron energy is convoluted with the corresponding photonuclear cross sections of Ra- 226. This enabled the total integrated yield of Ra-225 and its daughter product Ac-225 to be obtained. The third stage of this study ties the theoretical and experimental work together by presenting the results of a number of experiments performed on radium sources. These experiments were performed over a period of about three years using a variety of detectors in a hospital setting. These experiments, as presented in this thesis, demonstrate that Ac-225 can be produced in small quantities by a medical linac or in commercial quantities by the use of a high-powered linac or cyclotron, thereby, ensuring a reliable supply of Ra-225 for TAT and also reducing the radium waste product.
9
Moulin, Jeanne. "Comportement des radionucléides des familles de l'uranium dans les eaux superficielles du site de la Crouzille, Limousin : implications géochimiques". Châtenay-Malabry, Ecole centrale de Paris, 2008. http://www.theses.fr/2008ECAP1099.
Testo completoAbstract (sommario):
La compréhension du comportement des radionucléides naturels en milieu continental est importante pour pouvoir mener à bien la réhabilitation d’un site minier uranifère et préserver la qualité de l’eau. L’objectif de cette thèse est à la fois de déterminer la source d’apports de radionucléides dans une réserve d’eau potable et d’améliorer la connaissance du comportement des radionucléides des familles de l’uranium, en particulier de l’actinium. Le site d’étude retenu se situe à proximité d’un site minier réhabilité et permet d’étudier le transport des radionucléides dans les eaux superficielles (ruisseaux) mais aussi leur rétention : influence de la matière organique des tourbières sur les radionucléides et intérêt d’une retenue d’eau. Grâce à des ultrafiltrations tangentielles, la distribution des radionucléides dans les phases particulaire, colloïdale et dissoute est déterminée. Les importants volumes d’eau permettent d’utiliser la spectrométrie gamma comme méthode de mesure. Cette méthode permet de mesurer presque tous les radionucléides naturels en seulement deux comptages. Cependant, la faible activité des radioéléments de la famille du 235U impose l’utilisation de spectromètres gamma à ultra-bas bruit de fond, comme ceux du Laboratoire Souterrain de Modane. Cette étude a tout d’abord permis de montrer que la tourbière des Sagnes ne relargue que pas ou peu de radionucléides dans le ruisseau des Sagnes, comme c’est le cas pour les autres tourbières du monde bien qu’elle soit plus marquée. Dans un deuxième temps, elle a apporté des précisions sur le comportement des radionucléides des familles de l’uranium dans les eaux superficiellesUnderstanding natural radionuclides behaviour in surface water is a required step to achieve uranium mine rehabilitation and preserve water quality. The first objective of this thesis is to determine which are the radionuclides sources in a drinking water reservoir. The second objective is to improve the knowledge about the behaviour of uranium series radionuclides, especially actinium. The investigated site is a brook (Sagnes, Limousin, France) which floods a peat bog contaminated by a former uranium mine and which empties into the Crouzille lake. It allows studying radionuclides transport in surface water and radionuclides retention through organic substance or water reservoir. Radionuclides distribution in particulate, colloidal and dissolved phases is determined thanks to ultrafiltrations. Gamma spectrometry allows measuring almost all natural radionuclides with only two counting stages. However, low activities of 235U serie radionuclides impose the use of very low background well-type Ge detectors, such as those of the Underground Laboratory of Modane (France). Firstly, this study shows that no or few radionuclides are released by the Sagnes peat bog, although its radioactivity is important. Secondly, it provides details on the behaviour of uranium series radionuclides in surface water. More specifically, it provides the first indications of actinium solubility in surface water. Actinium’s behaviour is very close to uranium’s even if it is a little less soluble
10
Levier, Martin. "Développement et utilisation de l'Actinium-227 comme traceur du mélange de l'océan profond". Electronic Thesis or Diss., université Paris-Saclay, 2022. http://www.theses.fr/2022UPASJ006.
Testo completoAbstract (sommario):
Le mélange vertical dans l'océan profond est un processus important pour le fonctionnement de la circulation thermohaline océanique et donc pour le système climatique global. L'actinium-227 (227Ac) est un isotope radioactif naturel produit par désintégration du protactinium-231 (231Pa) dans les sédiments marins profonds. Comme il est soluble, il diffuse dans les eaux de fond. Sa demi-vie courte (22 ans) en fait un traceur spécifique du mélange vertical dans l'océan profond. L'analyse de 227Ac par comptage nucléaire utilisé jusqu'à maintenant nécessite de 50 à plusieurs centaines de litres d'eau et reste malgré tout peu précises. Ceci a limité l'utilisation du 227Ac en océanographie. Au cours de cette thèse, nous avons développé un protocole commun de séparation et d'analyse de 227Ac et 231Pa par MC-ICPMS à partir de 10L d'eau de mer. En plus de ces deux isotopes, ce protocole de séparation produit différentes fractions pouvant permettre d'analyser d'autres traceurs (isotopes du Nd, Ra ou Th) sur un même échantillon d'eau.Ce protocole a été appliqué à des échantillons d'archives prélevés lors de la campagne Bonus GoodHope, dans le secteur Atlantique de l'océan Austral. Le 231Pa a été analysé en parallèle du 227Ac, dont l'analyse est primordiale pour exploiter les données de 227Ac . Ces nouvelles données de 231Pa ont conforté la théorie de sa forte affinité pour l'opale produite par les diatomées et a permis d'affiner le modèle de transport des radionucléides le long des isopycnes remontant au sud de l'ACC. Les résultats obtenus de 227Ac ont permis d'estimer des coefficients de mélange turbulent de 1 cm2/s au-dessus de la dorsale océanique, de 14 cm2/s à cause d'une turbulence accrue près de la marge africaine et de l'ordre de 30 cm2/s dans le gyre de Weddell. Une application de ces valeurs est notamment proposée pour décrire la distribution de la concentration et de la signature isotopique du Nd, à l'aide d'un modèle prenant en compte les processus près de la marge continentaleThe vertical mixing in the deep ocean is an important process for the functioning of thermohaline circulation and also for the global climatic system. L'actinium-227 (227Ac) is a natural radioactive isotope product by the protactinium-231 (231Pa) decay in deep marine sediment. The short half-life of this isotope (22 years) makes it a specific tracer of vertical mixing of deep ocean. 227Ac analysis by nuclear counting used until now required from 50 to several hundred liters of water for a limited accuracy. This limited strongly the use of 227Ac in oceanography until today. During this thesis, we developed a join 231Pa-227Ac purification protocol suitable for 10L seawater sample, to perform analysis by MC-ICPMS. In addition to these two isotopes, this separation protocol provides different fractions that can be used to other tracers (Nd, Ra or Th isotopes) from the same water sample.This protocol was applied to archival samples collected during the Bonus GoodHope cruise, in the Southern Ocean. 231Pa was measured at the same time as 227Ac because its analysis is essential to exploit 227Ac data. These new 231Pa data support the previous hypothesis of a strong affinity toward the opal produced by the diatoms and allow to refine the transport of radionuclides along slopping isopycnal surfaces at the South of the ACC. Results from 227Ac data gave estimates of the vertical eddy diffusion coefficient of 1 cm2/s over the mid-ocean ridge, of 14 cm2/s near the African margin due to an enhanced turbulence and of the order of 30 cm2/s in the Weddell gyre. An application of these values is proposed to describe the concentration and isotopic signature distributions of Nd near the continental margin
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Le, Roy Emilie. "Distribution des radionucléides naturels (226Ra et 227Ac) le long de la section GA01 dans l'Atlantique Nord". Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30226.
Testo completoAbstract (sommario):
L'Atlantique Nord subpolaire, région de formation de masses d'eau profonde, est une région clé pour la circulation thermohaline mondiale et est donc sensible au changement climatique. C'est dans ce contexte que la campagne GEOVIDE a été réalisée entre le Portugal, le Groenland et Terre-Neuve dans le cadre du programme GEOTRACES (GA01 ; 15 mai au 30 juin 2014-R/V Pourquoi Pas ?). Cette campagne ayant traversé différentes caractéristiques topographiques et régions biogéochimiques, a fourni un cadre unique pour l'étude i) du mélange océanique, ii) du transport des masses d'eau et iii) des apports d'éléments chimiques libérés par les sédiments puis déposés sur les marges continentales. Les radionucléides naturels utilisés dans cette thèse comme traceurs sont le radium 226 (226Ra, t1/2 = 1602 y) et l'actinium-227 (227Ac, t1/2 = 21,7 y). En raison de leurs différentes demi-vies, ces radionucléides se comportent différemment dans l'océan et peuvent être utilisés pour étudier ces différents processus. Premièrement, une section détaillée des activités de 226Ra dissous associées aux concentrations de baryum dissous (Ba) est reportée dans cette thèse. Le 226Ra et le Ba ont été largement utilisés comme traceurs des masses d'eau et du mélange océanique, l'étude de leur comportement dans cette région est donc cruciale. L'utilisation du rapport 226Ra/Ba comme chronomètre de la circulation globale est évalué par une analyse multiparamétrique optimale. Les résultats montrent que les distributions de 226Ra et de Ba résultent principalement d'un mélange conservatif, notamment à des profondeurs intermédiaires (c'est-à-dire loin des interfaces océaniques). 226Ra et Ba peuvent donc être considérés comme des traceurs conservatifs du transport des masses d'eau à l'intérieur de l'océan à l'échelle du bassin. Cependant, aux limites de l'océan, 226Ra et Ba ont montré des comportements non-conservatifs dus aux apports sédimentaires, fluviaux et possiblement hydrothermaux. Les particules en suspension qui se forment dans la partie supérieure de la colonne d'eau et qui se déposent sur les fonds marins peuvent également avoir une incidence sur la distribution du 226Ra et du Ba. Deuxièmement, le comportement du 227Ac dans l'Atlantique Nord est étudié. 227Ac est principalement libéré par les sédiments profonds.[...]The Subpolar North Atlantic, being a region of deep water mass formation, is a key region for the global thermohaline circulation and is thus sensitive to climate change. In this context, the GEOVIDE cruise was carried out between Portugal, Greenland and Newfoundland as part of the GEOTRACES program (GA01; May 15 to June 30, 2014-R/V Pourquoi Pas?). This cruise, which crossed different topographic features and biogeochemical regions, provided a unique framework for the study of i) ocean mixing, ii) transport of water masses and iii) inputs of chemical elements released by the sediments deposited onto continental margins. Naturally occurring radionuclides is used as tracers: radium-226 (226Ra, t1/2 = 1602 y) and actinium-227 (227Ac, t1/2 = 21.7 y). Due to their different half-lives, these radionuclides behave differently in the ocean and can be used to study these various processes. First, a detailed section of dissolved 226Ra activities associated with dissolved barium (Ba) concentration is reported. Because 226Ra and Ba have been widely used as tracers of water masses and ocean mixing, their behavior in this crucial region is investigated more thoroughly. The use of the 226Ra/Ba ratio as a chronometer of the global circulation is evaluated using an optimum multiparameter analysis. Results show that 226Ra and Ba distributions mainly result from conservative mixing, notably at intermediate depths (i.e., away from the ocean interfaces). 226Ra and Ba can thus be considered as conservative tracers of water mass transport in the ocean interior at basin scales. However, at the ocean boundaries 226Ra and Ba displayed non-conservative behaviors due to sedimentary, river and possibly hydrothermal inputs. Suspended particles that form in the upper water column which settle to the seafloor may also impact the distributions of 226Ra and Ba. Second, the behavior of 227Ac in the North Atlantic is investigated. 227Ac is primarily released by deep-sea sediments. Due to the low abundance of 227Ac in seawater, the analysis of this radionuclide requires the use of high-sensitivity, low-background instruments and the collection of large volume samples.[...]
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Melville, Graeme P. "Production of AC-225 for cancer therapy by photon induced transmutation of RA-226". View thesis, 2007. http://handle.uws.edu.au:8081/1959.7/18860.
Testo completoAbstract (sommario):
Thesis (Ph.D) -- University of Western Sydney, 2007.A thesis submitted to the University of Western Sydney, College of Health and Science, School of Engineering, in satisfaction of the requirements for the degree of Doctor of Philosophy. Includes bibliography.
13
Baeza, Mario Ivan. "Synthesis and characterization of acetylenic derivatives of the actinide extractant (aryl)-N,N-di-(alkyl)carbamoylmethylphosphine oxide (CMPO)". To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
Testo completo
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Marx, Sebastian [Verfasser], Andreas [Akademischer Betreuer] Türler e Klaus [Akademischer Betreuer] Köhler. "Radium-Aufreinigung zur Herstellung von Actinium-225 am Zyklotron für die Alpha-Immuntherapie / Sebastian Marx. Gutachter: Andreas Türler ; Klaus Köhler. Betreuer: Andreas Türler". München : Universitätsbibliothek der TU München, 2014. http://d-nb.info/1067271414/34.
Testo completo
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Gasparro, Joël. "Études par séparation chromatographique des décroissances α[alpha] de 229Th, 225Ac et 221Fr : application à la structure des états nucléaires de 225Ra, 221Fr et 217At". Nice, 2000. http://www.theses.fr/2000NICE5443.
Testo completoAbstract (sommario):
Ce mémoire concerne l'étude par spectrométrie gamma directe du mode de désexcitation des niveaux du radium 225, du francium 221 de l'astate 217 ainsi que du bismuth 213. Pour réduire l'intensité des raies émises lors de la désexcitation des descendants de chaque noyau étudié, nous avons mis au point des procédés d'élution chromatographique continue des produits de filiation. Ceux-ci ont permis d'obtenir des facteurs de décontamination satisfaisants, ce qui a rendu possible l'attribution de transitions non observées précédemment et entraîné une amélioration des connaissances des méthodes de désexcitation électromagnétique des noyaux étudiés. Dans le cas du thorium 229, 169 raies attribuées à sa désintégration ont été observées, dont 97 pour la première fois. La plupart de ces nouvelles transitions se situe dans une zone d'énergies comprises entre 300 et 600 keV, où aucune raie n'avait été observée lors des études antérieures. Un schéma de niveaux est proposé. (. . . ) La structure de niveaux résultante est interprétée en termes de bandes rotationnelles organisées en doublets de parité (. . . ) découlant d'un modèle de couplage fort impliquant une déformation octupolaire stable. 125 transitions attribuées à la désintégration de l'actinium 225 ont été observées, dont 42 pour la première fois. (. . . ) Enfin, 34 raies consécutives à la désintégration du francium 221 ont été observées, dont 13 non observées auparavant, ainsi que 6 raies attribuées à la désexcitation des niveaux du bismuth 213.
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Bishop, Alexander James. "Actinide surface chemistry". Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54193/.
Testo completoAbstract (sommario):
The surface reactivity of thorium and uranium, and how this links to the 5f electrons, has been investigated under UHV conditions using X-ray photoelectron spectroscopy (XPS), ultra violet photoelectron spectroscopy (UPS), and inverse photoemission spectroscopy (IPES). Water and ammonia adsorption on a polycrystalline thorium surface has been investigated at 100 and 298 K. Water adsorbs and dissociates upon the surface, leading to the formation of oxide and hydroxide species at 298 K, and oxide, hydroxide, and physisorbed water at 100 K. The surfaces after adsorption at both temperatures proved to be unstable when exposed to the low energy electron gun utilised in IPES. Ammonia adsorbs and dissociates upon the surface, leading to the formation of nitride and NH2 species at 298 K, and nitride, NH2, and physisorbed ammonia at 100 K. Upon reaction only the mononitride ThN is formed, the metallic nature of which was confirmed by UPS and IPES. The surface was unstable under the low energy electron gun utilised in IPES, with the ThN species being converted to the non-metallic Th3N4. Water and ammonia adsorption on a polycrystalline uranium surface has also been investigated at 100 and 298 K. Water adsorbs and dissociates upon the surface, leading to the formation of oxide and hydroxide species at 298 K, and oxide, hydroxide, and physisorbed water at 100 K. The rate of reaction of water with uranium is substantially reduced in the presence of residual oxygen on the surface. The small band-gap of semi-conducting UO2 can be observed directly with UPS and IPES. Ammonia adsorbs and dissociates upon the surface, leading to the formation of nitride and NH2 species at 100 and 298 K.
17
Aaliti, Abdellatif. "Réactivité des liaisons sigma actinide-azote et actinide-carbone : applications en synthèse organique". Dijon, 1986. http://www.theses.fr/1986DIJOS015.
Testo completoAbstract (sommario):
Les isonitriles s'insèrent dans une ou deux liaisons sigma u-n des complexes cyclopentadienyles mono- ou bis-alkylaminouranium. La structure carbénoïde des composés d'insertion est établie par spectroscopie. On compare la réactivité de la liaison sigma uranium-méthylène et uranium-méthyle vis à vis des réactions d'insertion et des réactions de substitution par des composés à hydrogène "acide". La réaction d'insertion des composés carbonyles est appliquée à la synthèse chimio- et stéréosélective des alcools secondaires et tertiaires.
18
Al-Farsi, Afkar Nadhim. "Radiological aspects of petroleum exploration and production in the sultanate of Oman". Thesis, Queensland University of Technology, 2008. https://eprints.qut.edu.au/29817/1/Afkar_Al-Farsi_Thesis.pdf.
Testo completoAbstract (sommario):
This thesis is a study of naturally occurring radioactive materials (NORM) activity concentration, gamma dose rate and radon (222Rn) exhalation from the waste streams of large-scale onshore petroleum operations. Types of activities covered included; sludge recovery from separation tanks, sludge farming, NORM storage, scaling in oil tubulars, scaling in gas production and sedimentation in produced water evaporation ponds. Field work was conducted in the arid desert terrain of an operational oil exploration and production region in the Sultanate of Oman.
The main radionuclides found were 226Ra and 210Pb (238U - series), 228Ra and 228Th (232Th - series), and 227Ac (235U - series), along with 40K. All activity concentrations were higher than the ambient soil level and varied over several orders of magnitude. The range of gamma dose rates at a 1 m height above ground for the farm treated sludge had a range of 0.06 0.43 µSv h 1, and an average close to the ambient soil mean of 0.086 ± 0.014 µSv h 1, whereas the untreated sludge gamma dose rates had a range of 0.07 1.78 µSv h 1, and a mean of 0.456 ± 0.303 µSv h 1. The geometric mean of ambient soil 222Rn exhalation rate for area surrounding the sludge was mBq m 2 s 1. Radon exhalation rates reported in oil waste products were all higher than the ambient soil value and varied over three orders of magnitude.
This study resulted in some unique findings including: (i) detection of radiotoxic 227Ac in the oil scales and sludge, (ii) need of a new empirical relation between petroleum sludge activity concentrations and gamma dose rates, and (iii) assessment of exhalation of 222Rn from oil sludge. Additionally the study investigated a method to determine oil scale and sludge age by the use of inherent behaviour of radionuclides as 228Ra:226Ra and 228Th:228Ra activity ratios.
19
Al-Farsi, Afkar Nadhim. "Radiological aspects of petroleum exploration and production in the sultanate of Oman". Queensland University of Technology, 2008. http://eprints.qut.edu.au/29817/.
Testo completoAbstract (sommario):
This thesis is a study of naturally occurring radioactive materials (NORM) activity concentration, gamma dose rate and radon (222Rn) exhalation from the waste streams of large-scale onshore petroleum operations. Types of activities covered included; sludge recovery from separation tanks, sludge farming, NORM storage, scaling in oil tubulars, scaling in gas production and sedimentation in produced water evaporation ponds. Field work was conducted in the arid desert terrain of an operational oil exploration and production region in the Sultanate of Oman.
The main radionuclides found were 226Ra and 210Pb (238U - series), 228Ra and 228Th (232Th - series), and 227Ac (235U - series), along with 40K. All activity concentrations were higher than the ambient soil level and varied over several orders of magnitude. The range of gamma dose rates at a 1 m height above ground for the farm treated sludge had a range of 0.06 0.43 µSv h 1, and an average close to the ambient soil mean of 0.086 ± 0.014 µSv h 1, whereas the untreated sludge gamma dose rates had a range of 0.07 1.78 µSv h 1, and a mean of 0.456 ± 0.303 µSv h 1. The geometric mean of ambient soil 222Rn exhalation rate for area surrounding the sludge was mBq m 2 s 1. Radon exhalation rates reported in oil waste products were all higher than the ambient soil value and varied over three orders of magnitude.
This study resulted in some unique findings including: (i) detection of radiotoxic 227Ac in the oil scales and sludge, (ii) need of a new empirical relation between petroleum sludge activity concentrations and gamma dose rates, and (iii) assessment of exhalation of 222Rn from oil sludge. Additionally the study investigated a method to determine oil scale and sludge age by the use of inherent behaviour of radionuclides as 228Ra:226Ra and 228Th:228Ra activity ratios.
20
El-Lawindy, A. M. Y. "Spectroscopic studies in actinide nuclei". Thesis, University of Liverpool, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372684.
Testo completo
21
Flanders, David John. "Structural studies of actinide compounds". Thesis, University of Warwick, 1985. http://wrap.warwick.ac.uk/108758/.
Testo completoAbstract (sommario):
The work described in this thesis was an investigation into the coordination chemistry of uranium(VI) and neptunium(VI). Structural determinations of comparable uranium and neptunium compounds were used to examine the actinide contraction between uranium and neptunium, the changes in metal-ligand bond length on substituting nitrogen for oxygen as the donor atom and to establish the mode of coordination of certain ligands around the actinyl(VI) ion. These areas have been explored through the determination of the crystal structures of the following compounds:- a) The 2,2'-dipyridyl complexes [CO2(NO3),C10H8N2], [NpO2(N [UOa(CH3COO)2Cl0H8N2] and [NpO2a(CH3COO)2C10H8N2]. b) The 1,10-phenanthroline complex [C02(NC3)2C12H8N2]. c) The pentan-2,4-dionate complexes [CO2(CH3COCHCOCH3)aC5H5N], [NpOa(CH3COCHCOCH3)2C 5HsN], [UO2(CH3COCHCOCH3)a.HaO] and [U0aCH3C0CHC0CH3)2H2C[UO2CH3COCHCOCH3(NO3)2 [(CH3)3C5H3N]* d) The 4,4'-dipyridyl compound [(UO2(NO3)2OH2] [C10H10N2]2* In addition the structure determination of the compound bis(nitrato)dioxo tetrakis(glycinato)uranium(VI) showed that the glycine ligands are coordinated via the oxygen atoms with two bidentate and two monodentate glycines. Other structures which have been determined are the mixed oxidation state neptunium alkali metal salt [CsTNp( v,Oa(Np( w|Oa)aClia], the organoneptunium(IV) compound [(CsHs)CI3Np(OPPh3)a] and the photo-oxidation product [L'OjfCCIjCOOICMOPPhj),] There is also an uncompleted structure of a 1,10-phenanthroline complex with uranyl(VI)acetate which is described as far as possible.
22
Wåhlin, Pernilla. "Theoretical Actinide Chemistry – Methods and Models". Doctoral thesis, Stockholms universitet, Fysikum, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-54848.
Testo completoAbstract (sommario):
The chemistry of actinides in aqueous solution is important, and it is essential to build adequate conceptual models and develop methods applicable for actinide systems. The complex electronic structure makes benchmarking necessary. In the thesis a prototype reaction of the water exchange reaction for uranyl(VI), for both ground and luminescent states, described with a six-water model, was used to study the applicability of density functional methods on actinides and different solvation models. An excellent agreement between the wave function methods CCSD(T) and MP2 was obtained in the ground state, implying that near-minimal CASPT2 can be used with confidence for the reaction in the luminescent state of uranyl(VI), while density functionals are not suited to describe energetics for this type of reaction. There was an ambiguity concerning the position of the waters in the second hydration sphere. This issue was resolved by investigating a larger model, and prop- erly used the six-water model was found to adequately describe the water exchange reaction. The effect of solvation was investigated by comparing the results from conductor-like polarizable continuum models using two cavity models. Scattered numbers made it difficult to determine which solvation model to use. The final conclusion was that the water exchange reaction in the luminescent state of uranyl(VI) should be addressed with near-minimal CASPT2 and a solvation model without explicit cavities for hydrogens. Finally it was shown that no new chemistry appears in the luminescent state for this reaction. The thesis includes a methodological investigation of a multi-reference density functional method based on a range separation of the two-electron interaction. The method depends on a universal parameter, which has been determined for lighter elements. It is shown here that the same parameter could be used for actinides, a prerequisite for further development of the method. The results are in that sense promising.
23
Dickson, Catherine Louise. "Immobilisation of actinide simulants in cement". Thesis, University of Aberdeen, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300954.
Testo completoAbstract (sommario):
The current UK strategy for radioactive waste management is to permanently store the waste in an underground repository. Final disposal of the radwaste may then be preceded by chemical conditioning and physical encapsulation. The objective of this work was to determine the extent of actinide immobilisation in cement. Since actinides are hazardous and costly to study directly, a chemical analogue approach to studying actinide immobilisation was adopted. Th(IV), Ce(III, IV) and Eu(III) were chosen as actinide simulants and their suitability assessed by a critical review of the literature. Ca(OH)2 and C-S-H dominate the observed chemical properties of the aqueous phase in cement. As they are of such importance, it was these cement components which were used to investigate the reaction of the simulant elements with cement. The phases found to be predicted were ThO2, ThSiO4, Eu(OH)3, Ca2Eu8(SiO4)6O2, CeO2, CeSiO4 and Ca2(SiO4)6O2. CeSiO4 and Ca2Ce8(SiO4)O2 are newly reported phases, produced by hydrothermal synthesis. Rietveld refinement confirmed CeSiO4 to have the zircon structure, with space group 141/amd and cell parameters a = 6.9564(3) A, c = 6.1953 (4) A. Ca2Ce8(SiO4)6O2 exhibits the apatite structure, with space group P63/m and cell parameters a = 9.4343(3) a, c = 6.8885(4) A. Preliminary solubility studies were carried out on all of the solubility-limiting phases. Phase impurity, poor crystallinity and incongruent solubility of phases hindered the generation of solubility product data. Nevertheless, these phases have naturally occurring analogues which are known to be environmentally stable and have low solubilities. On the basis of the experimental results obtained, it may be concluded that cement has the potential to be a very effective immobilisation matrix for actinide elements. Recommendations for future experiments using active elements are discussed.
24
Visosky, Mark Michael. "Actinide minimization using pressurized water reactors". Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/41276.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2006.Includes bibliographical references (p. 227-232).
Transuranic actinides dominate the long-term radiotoxity in spent LWR fuel. In an open fuel cycle, they impose a long-term burden on geologic repositories. Transmuting these materials in reactor systems is one way to ease the long-term burden on the repository. Examining the maximum possible burning of trans-uranic elements in Combined Non-Fertile and U02 (CONFU) PWR assemblies is evaluated. These assemblies are composed of a mix of standard U02 fuel pins and pins made of recycled trans-uranics (TRU) in an inert matrix, and are designed to fit in current or future PWRs. Applying appropriate limits on the neutronic and thermal safety parameters, a CONFU-Burndown (CONFU-B) assembly design is shown to attain net TRU destruction in each fuel batch through at least 9 recycles. This represents a time span of nearly 100 years of in-core residence and out-of-core storage time. In this way, when the TRU is multi-recycled, only fission products and separation/reprocessing losses are sent to the repository, and the initial inventory of TRU is reduced over time. Thus, LWRs are able to eventually operate in a fuel cycle system with an inventory of transuranic actinides much lower than that accumulated to date. Three recycling strategies are considered, all using a 4.5-year in core irradiation, followed by cooling and reprocessing. The three strategies involve a short-term cooling (6-year) after discharge, a longer-term cooling (16.5-year) after discharge, or a strategy called Remix. The Remix strategy involves partitioning the Pu/Np after 6-year cooling for immediate recycle, and partitioning the Am/Cm for an additional 10.5-year cooling before remixing it into the next CONFU-B batch. At equilibrium, the CONFU-B can burn approximately 1.5 kg to 10.0 kg of TRU per TWhe depending on the recycle strategy used.
(cont.) This represents a net burning rate of 2-8% of the TRU loaded per assembly, in addition to burning an amount equivalent to the TRU produced in the U02 pins. However, the highly heterogeneous nature of these assemblies can result in fairly high intra-assembly pin power peaking. By design, an IMF pin in the assembly carries the highest power to maximize the TRU destruction. For the initial TRU loading, the highest power peaking in an IMF pin is 1.183. This is compensated by having cooler pins in the immediate vicinity. Even so, the pin peaking distribution in the assembly can result in reduced thermal margins. The assembly mentioned above has an MDNBR of 1.43, instead of 1.62 for the all-U02 assembly, based on a core-wide radial peak-to-average assembly power peaking of 1.50. Use of neutron poisons and tailored enrichment schemes reduces the neutronic reactivity of fresh assemblies, while improving MDNBR to 1.51. In addition, RELAP was used to evaluate the fuel behavior under large break LOCA conditions. CONFU-B performance under these conditions was comparable to the standard all-UO2 assembly. Several options for spent fuel recycling in LWRs are compared economically, and all are found to be more costly than making fresh U02 fuel from mined ore. However, the CONFU-B strategy is less costly on a mills/kWhe basis than other thermal recycling strategies that recycle the full TRU vector. Given OECD estimates for the unit costs of each fuel type, and assuming 10% carrying charge factor, this cost is 12.3 mills/kWhe for the CONFU-B recycle, compared to 25.7 mills/kWhe for MOX-UE and 4.9 mills/kWhe for all UO2.
(cont.) Note that these FCCs assume the disposal fee collected during power generation of a previous cycle can be invested while the fuel is cooling and provide a credit to the cycle that uses the fuel after reprocessing. The fuel handling challenges of multirecycling TRU in CONFU-B assemblies are compared to other multi-recycling strategies. If we assume that the spent fuel from, the seventh recycle in each strategy is no longer recyclable and must be sent to the repository in its entirety. the CONFU-B strategy still places much less total burden on the repository than the once-through cycle, and even less burden than the current MOX cycle. Finally, a methodology for calculating the time integrated proliferation risk of a fuel cycle is introduced. An innovation of this methodology is the discounting of future risks to calculate an overall present value risk of a given cycle. Under this methodology, the CONFU-B presents lower risks than other multi-recycling strategies in the first 100 years. For a 10% rate of discount of risk, the CONFU-B risks are comparable to the once-through cycle. The longer term risk favors recycling due to the limited accumnulation of repository risk.
by Mark M. Visosky.
Ph.D.
25
Tassell, M. J. "Computational investigations of molecular actinide chemistry". Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1386659/.
Testo completoAbstract (sommario):
This thesis is a computational study of the first members of the actinide series, thorium, protactinium, uranium, neptunium, plutonium, americium and curium. There are two general themes that occur throughout this thesis; the first is the electronic structures of the aforementioned actinides, and in particular what is the role of the 5f and 6d orbitals in the electronic structure of some early actinide complexes. The second is how covalent are the interactions between the early actinides and lighter members of the periodic table, in particular carbon, halogens and the chalcogens. The principal quantity that has been probed to assess this covalency is the electron density. Chapter 2 makes use of both time dependent density functional theory (TDDFT) and multiconfigurational self-consistent field theory (CASPT2) to assess the experimentally determined Cl K edge spectra of [AnCl6]2-; An = Th, Pa, U, Np and Pu. Particular attention is applied to the [NpCl6]2- and [PuCl6]2- spectra as an anomalous transition splitting pattern is seen. Quantum theory of atoms in molecules (QTAIM) theory has been used to probe the actinide cyclopentadienyl bond in chapter 3 and the actinide halogen bond in chapter 4. Unlike more traditional Mulliken and orbital analysis QTAIM is based on the topology of the electron density and is therefore an observable quantity. The actinide halide bond is then also probed with bond orders derived from QTAIM. The [M{N(EPPh2}2]3 ;(M = La, Ce, Eu, U, Pu, Am, Cm; E = S, Se) molecules studied in chapter 5 have been purposely synthesized so as to assess the degree of covalency between An(III) and La(III) chalcogen bonds. Natural population analysis and QTAIM is used to study these complexes.
26
Brulé, Cédric. "Vieillissement musculaire : impact de la protéolyse intracellulaire calcium-dépendante". Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13899/document.
Testo completoAbstract (sommario):
La sarcopénie ou perte involontaire progressive de la masse musculaire chez le sujet âgé s’accompagne de l’altération de nombreux phénomènes physiologiques comparables à ceux observés chez les myopathes. Le processus de régénération musculaire est très ralenti, les activités protéolytiques intracellulaires sont modifiées et de nombreuses fonctions cellulaires sont perturbées en raison d’un stress oxydatif incontrôlé. L’intervention des calpaïnes, protéases neutres calcium-dépendantes, dans les processus associés au développement, à la régénération et à l’intégrité du tissu musculaire est incontestable. Les calpaïnes apparaissent, en effet, comme des acteurs clefs des voies de transductions liées à la myogenèse, la prolifération et la survie cellulaire. Toutefois aucune étude permettant d’établir la relation vieillissement du tissu musculaire- activité calpaïne n’a été entreprise à ce jour. Le projet a donc pour but principal d’inventorier les signaux pro-sarcopéniques interagissant avec les calpaïnes et d’établir leurs relations avec la fonctionnalité des cellules satellites, le stress oxydant et l’apoptose. Nous avons mis en évidence une augmentation de l’expression/activité des calpaïnes durant le vieillissement musculaire chez le rat et identifié des partenaires des calpaïnes impliqués dans des fonctions physiologiques altérées durant la sarcopénie: homéostasie calcique, activité contractile, production d’ATP, régénération musculaire. Nous avons également montré que l’induction d’un stress oxydant entraîne l’activation des calpaïnes au cours de la prolifération des cellules satellites de façon corrélée à une augmentation de l’apoptose. D’une manière intéressante, un traitement préventif par un antioxydant naturel d’écorce de pin (Oligopin®) est capable de prévenir à la fois l’apoptose et l’activation des calpaïnes. L’ensemble de ces résultats suggère que le stress oxydant associé au vieillissement induirait des mécanismes calpaïno-dépendants responsables de l’altération de processus essentiels à la fonction musculaireAging is associated with a progressive and involuntary loss of muscle mass also known as sarcopenia. This condition represents a major public health concern. Although sarcopenia is well documented, the molecular mechanisms of this condition still remain unclear. The calcium-dependent proteolytic system is composed of calcium dependent cystein-proteases named calpains. Calpains are involved in a large number of physiological processes such as muscle growth and differentiation, and pathological conditions such as muscular dystrophies. The aim of this study was to determine the involvement of the proteolytic system in the phenotype associated with sarcopenia by identify the key proteins (substrates or regulators) interacting with calpains during muscle aging and identify pro-sarcopenic signals after oxidative stress induction in satellite cells. Muscle aging was correlated with the up-regulation of calpain activity. Ryanodine receptor 1, ATP synthase subunit alpha and alpha actinin 3 appear as key partners of calpains during muscle aging. Such interactions suggest an implication of calpains in many processes altered during aging including cytoskeletal disorganisation, regulation of calcium homeostasis and mitochondrial dysfunction. Furthermore, oxidative stress induction led to an increase in the activity of calpains correlated to an increase in apoptosis of proliferating satellite cells. In a very interesting way, a preventive treatment with a commercial antioxidant (Oligopin®) prevented these effects. All these data suggest that oxidative stress coupled observed during muscle aging could lead to calpaïno-dependent mechanisms responsible for apoptosis and muscle dysorganisation
27
Farkas, Ildiko. "Coordination Chemistry of Actinide and Lanthanide Ions". Doctoral thesis, KTH, Chemistry, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3236.
Testo completo
28
Farkas, Ildikó. "Coordination chemistry of actinide and lanthanide ions /". Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3236.
Testo completo
29
Harvey, E. J. "Actinide immobilisation in zirconate and titanate ceramics". Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603819.
Testo completoAbstract (sommario):
Pyrochlores (A=2B2O7, Fd3m) have been proposed as candidate phases for the immobilisation of actinides from high level nuclear waste. They may form part of a multi-barrier approach to final waste disposition in an underground repository. Titanate and zirconate pyrochlores are particularly interesting; titanates show high chemical durability, whilst some zirconate pyrochlores display very high resistance to structural damage by radiation. To fully evaluate the likely performance of a pyrochlore-based waste-form, a comprehensive understanding of its structure and behaviour must be developed. Related phases, which might exsolve, must also be characterised, to test whether their presence will have a deleterious effect. Various zirconate and titanate oxides including (La1-xNdx)2Zr2O7, Nd2(Zr1-xTix)2O7, La2(Zr1-xTix)2O7 and (Y1-xLax)2Ti2O7 were synthesized and characterised by X-ray and neutron powder diffraction, electron microscopy and electron probe micro-analysis. Rare earth elements acted as non-radioactive analogues for actinide behaviour. The extent of solid solubility and factors governing exsolution were explored. The conductivity of Nd2(Zr1-xTix)2O7 ceramics was measured using impedance spectroscopy. Pyrochlores find application in a wide variety of technologies, including those which exploit the electrical properties of the pyrochlore structure. The effect of Ti substitution in Nd2Zr2O7 was studied and compared to the conductivity of monoclinic Nd2Ti2O7. The correlation between ionic mobility and critical radiation dose is discussed. Leaching from (Gd1.4Ce0.2La0.1Sm0.1Eu0.1)(Zr0.9Ti0.9Sc0.1In0.1)O7 was investigated. This composition facilitated comparison of numerous elemental dissolution rates from a single sample. Experimental conditions mimicked those likely in a repository at 1000m depth. Alteration of the solid was characterised by light and electron microscopy. The dissolved concentrations of leached elements were determined by inductively coupled plasma-mass spectrometry. Various synthetic routes were considered, to maximise the sample density.
30
McCubbin, David. "Influence of seawater components upon actinide behaviour". Thesis, University of East Anglia, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359304.
Testo completo
31
Kervazo, Sophie. "Computational actinide chemistry : structure, bonding and thermodynamics". Thesis, Lille 1, 2018. http://www.theses.fr/2018LIL1R042/document.
Testo completoAbstract (sommario):
La question générale traitée dans cette thèse est de déterminer si, à l’heure actuelle, nous disposons d’outils théoriques efficaces pour décrire la structure, la liaison et les propriétés thermodynamiques de système comprenant un actinide. Cette large question va être abordée à l’aide de trois études différentes. Les deux premières sont directement liées à l’industrie plastique et à la sureté nucléaire. La dernière, plus fondamentale concerne une analyse comparative d’une approche théorique nouvellement développée sur des systèmes comprenant des éléments f. Tout d’abord, les cations alkyles contenant un actinide (Th, U) ou un métal de transition (Zr) coordonné à un arène se sont révélés efficaces pour la catalyse de la synthèse du polyéthylène. Étonnamment, les activités catalytiques des cations alkyles dépendent du solvant. Pour comprendre cela et confirmer la tendance qu’ont ces complexes à se lier à l’arène, une étude en DFT dans un contexte relativiste combinée à une caractérisation de liaison avec la méthode ETS-NOCV fut faite. La deuxième étude vise à étoffer les bases de données thermodynamiques qui servent à explorer numériquement les scénarios d’accidents. Notre étude in silico porte sur la détermination des enthalpies de formation des deux espèces pour lesquelles des incertitudes expérimentales subsistent (PuO3 ou PuO2(OH)2 …), en utilisant une méthode quantique multiconfigurationnelle et relativiste. La dernière partie de la théorie se concentre sur l’estimation de la précision de la fonctionnelle B2-PLYP pour les éléments f, qui s'avère assez précise en comparaison aux données expérimentales et à la méthode de référence CCSD(T)The main question of this thesis is: do we have today the tools to efficiently describe the structure, the bonding and the thermodynamics of actinide systems? This broad question is answered thanks to three studies. The first two are directly applied to the plastic industry and the nuclear plant safety. The last one, more fundamental, concerns the benchmarking of newly developed theoretical approach on f-element systems.First, actinides and transition metal arene-coordinated alkyl cations have been recently proven to be efficient catalysts for ethylene polymerizations. Interestingly, thorium, uranium and zirconium alkyl cations’ catalytic activity depends on the solvent. To understand these behaviors and to confirm the tendency of these complexes to engage in unusual-arene coordination, relativistic DFT calculations combined with a characterization of the interaction thanks to the ETS-NOCV method are used. Second, in accident scenario along the reprocessing of spent nuclear fuel, plutonium can be released in various volatile forms (PuO2, PuO3 or PuO2(OH)2, …). The exploration of these scenarios by the use of simulations requires, among the various parameters, the knowledge of the thermodynamic properties of the possibly formed elements. Our in-silico study focusses on the determination of the enthalpies of formation of the former two species for which experimental uncertainties remain, using multi-configurational relativistic wavefunction method. The last part of the thesis focusses on the benchmark of the B2-PLYP functional for f-element systems, which turns out quite accurate with respect to the experimental data and the gold-standard CCSD(T) method
32
Noyes, Karen Lynn 1977. "Synthesis and evaluation of actinide imprinted resins". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/30012.
Testo completoAbstract (sommario):
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2003.Includes bibliographical references (p. 143-146).
Organic resins have previously shown good results with application to actinide separations. Large portions of recent research have been dedicated to the synthesis and evaluation of resins with phenolic-type functional groups. Other recent chemical research with lighter metals has developed a technique known as ion imprinting which can provide greater selectivity for the target metal ion. Initial work with ion imprinting and phenolic-type resins has shown these two areas to be largely incompatible. Identifying the ion imprinting technique as potentially the more valuable of the two, further work was undertaken with resins that incorporate a carboxylic acid-type functionality. These new resins are synthesized via a radical polymerization method, which proved to be very compatible with both actinides and the ion imprinting procedure. Polymer-based resins were synthesized without a metal template as well as ion imprinted, or templated, with U(VI), Th(IV), Np(V), and a resin for use with Am(III). Each of these resins were individually characterized and evaluated for use with their respective target metals. Characterization provides a means of comparing theoretical binding capacities of various resins, which the evaluations define the binding characteristics of interest (capacity, selectivity, kinetics, etc.). Based on the initial results for the selectivity of the U(VI) and Th(IV) ions, a new type of resin was developed in an effort to further increase the selectivity of the resin for the target metal ion. This new resin, known as a "capped" resin, seeks to remove the binding capability of any potential binding sites not involved in the ion imprinting process.
(cont.) Results show that the ion imprinting technique can be successfully applied in the synthesis of resins for actinide separations with good success. The resins created through this process also show an affinity for their target metals over both competing ions as well as ions of similar ionic charge and radii. The removal of so-called random binding sites is also possible, with the addition of a few synthetic steps.
by Karen Lynn Noyes.
Sc.D.
33
Pheiffer, Fazlin. "Investigating the antimicrobial potential of Thalassomonas actiniarum". University of Western Cape, 2020. http://hdl.handle.net/11394/7995.
Testo completoAbstract (sommario):
Philosophiae Doctor - PhDThe World Health Organisation predicts that by the year 2050, 10 million people could die annually as a result of infections caused by multidrug resistant bacteria. Individuals with compromised immune systems, caused by underlying disease such as HIV, MTB and COVID-19, are at a greater risk. Antibacterial resistance is a global concern that demands the discovery of novel drugs. Natural products, used since ancient times to treat diseases, are the most successful source of new drug candidates with bioactivities including antibiotic, antifungal, anticancer, antiviral, immunosuppressive, anti-inflammatory and biofilm inhibition. Marine bioprospecting has contributed significantly to the discovery of novel bioactive NPs with unique structures and biological activities, superior to that of compounds from terrestrial origin. Marine invertebrate symbionts are particularly promising sources of marine NPs as the competition between microorganisms associated with invertebrates for space and nutrients is the driving force behind the production of antibiotics, which also constitute pharmaceutically relevant natural products.
34
Lavelle, Kevin B. "Evaluation of Environmental Concentratorsfor Trace Actinide Measurements". University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479816761576791.
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Kay, Rajiv Robert. "Actinide partition in humic colloidal ternary systems". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/actinide-partition-in-humic-colloidal-ternary-systems(c21f9744-46fb-477f-9ebc-af87d3e6fca0).html.
Testo completoAbstract (sommario):
The partition of radionuclides between solid and solution phase has been studied in humic/quartz sand ternary systems. Data have been recorded under ambient (air) and inert (O2 and CO2 free) atmospheres. For Eu (III) and Th (IV), the systems show simple ternary behaviour, with sorption decreasing (and mobility increasing) in the presence of humic, whilst for U (VI), the behaviour is more complex, with the humic enhancing sorption and reducing mobility. There is also evidence that the sorbed humic has an enhanced affinity for the uranyl, which is probably due to fractionation of the humic. Further, the behaviour of plutonium has also been studied in these systems. Pu (IV) showed the simple ternary characteristics, which had been observed for Eu (III) and Th (IV). Pu (V) and Pu (VI) systems exhibited more complex behaviour, with low concentrations of humic actually enhancing sorption, probably due to ternary complex formation. A simple mathematical model has been developed to predict the behaviour of both metal ion and humic acid. The model performs well in predicting the partition of the humic and that of the metal ions in the systems that show simpler ternary behaviour.
36
Wells, Jordann Ashley Logan Slovenne Denis. "Bimetallic actinide complexes for small molecule activation". Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31167.
Testo completoAbstract (sommario):
The work described in this thesis concerns the synthesis of actinide complexes and their reactivity towards small unsaturated molecules. Complexes bearing tetraphenoxide, borohydride and boroxide ligands have been evaluated. Additionally, work towards the synthesis of heterobimetallic uranium transition metal complexes and their applications in catalysis is discussed. Chapter one reviews important organoactinide complexes reported in the literature which effect chemical transformations on small unsaturated substrates. Actinide complexes supported by aryloxide or borohydride ligands are reviewed, along with actinide complexes in which metal p-arene interactions are present. Chapter two reports the synthesis and characterisation of a set of tetraphenol ligands, in addition to a number of attempted synthetic routes to tetraphenol ligands with alternate substitution. The chemistry of those tetradentate aryloxide ligands is introduced with bimetallic uranium(IV) and thorium(IV) complexes using different An(IV) and U(III) precursors. Chapter three reports the synthesis and characterisation of monometallic uranium and thorium complexes using a tetraphenol ligand. The varying chemistry between the two similar An(IV) ions, where the uranium complexes exist as a mixture of oligomers and the thorium complexes remain as well defined mononuclear complexes, is discussed within. A range of base adducts of mononuclear actinide complexes are reported, including a thorium trimethylsilylazide complex, a rare example of a metal organoazide. Chapter four describes the synthesis of homoleptic boroxide and heteroleptic borohydride complexes of uranium(III). The reactivities of these complexes with small unsaturated molecules are assessed, including the reaction of a low coordinate uranium(III) boroxide complex towards CO2 to provide a dinuclear uranium carbonate bridged complex. Chapter five introduces work towards heterobimetallic uranium transition metal complexes carried out in the Arnold group. The application of these complexes towards ring opening polymerisation chemistry is discussed in addition to investigations into the incorporation of transition metals into uranium(IV) complexes. Chapter Six presents the detailed experimental methods used to carry out this research.
37
Graham, Margaret C. "An investigation of actinide interactions with humic substances". Thesis, University of Glasgow, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360263.
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Nicoll, Steven. "Simulation studies of transition metal and actinide oxides". Thesis, University College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308937.
Testo completo
39
Sizer, Calvin Gregory. "Minor actinide waste disposal in deep geological boreholes". Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/41595.
Testo completoAbstract (sommario):
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2006.Includes bibliographical references (leaves 63-65).
The purpose of this investigation was to evaluate a waste canister design suitable for the disposal of vitrified minor actinide waste in deep geological boreholes using conventional oil/gas/geothermal drilling technology. The nature of minor actinide waste was considered, paying particular attention to nuclides whose decay energy and half lives were of relative significance to the minor actinide waste as a whole. Thermal Analysis was performed based on a reference borehole design, by Ian C. Hoag. The strategy of the thermal analysis is aimed at finding peak temperatures within the configuration, paying particular attention to the heat transfer under deep geological conditions in the air gap between the canister and the borehole. A first order economic analysis was made to compare the designed canister emplacement costs to that of intact spent fuel. The results of this analysis show that three minor actinide nuclides dominate heat generation after ten years cooling: Cm-244, Am-241, and Am-243 account for 97.5% of minor actinide decay heat. These three nuclides plus Np-237 account for 99% of the minor actinide mass. The thermal analysis was based on an irretrievable canister design, consisting of a 5 meter long synroc waste form, with minor actinides loaded to 1% wt, an outer radius of 15.8 cm and inner annular radius of 8.5 cm. Filling the annulus with a vitrified technetium and iodine waste form was found to be feasible using a multi-stage emplacement process. This process would only be required for three of the fifty boreholes because technetium and iodine have low heat generations after 10 years cooling. The suggested borehole waste form has a maximum centerline temperature of 349C. The costs of drilling boreholes to meet the demand of 100,000MT of PWR waste are estimated to be 3.5% of the current nuclear waste fund, or about $9.6/kg of original spent fuel.
by Calvin Gregory Sizer.
S.B.
40
Ingram, K. I. M. "Computational studies of molecular actinide and lanthanide complexes". Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1444746/.
Testo completoAbstract (sommario):
This thesis reports computational DFT studies of three families of complexes (see below). Before presenting the results from these studies, the first chapter introduces the lanthanides and actinides and investigates their similarities and differences through a discussion of selected compounds of each of the series of metals. The second chapter introduces the electronic structure methods that were used in this research and mentions some of the relevant computational utilities. Chapter 3 discusses DFT studies of mixed water/hydroxide uranyl systems, U02(H20)a-:r- OH)x (2-x)+ for x = 0 -> 5 with a = 5, and some a = 3, 4. The reasons for the observed lengthening, and resultant weakening, of U-Oy/ as x increases are investigated. These studies show that this lengthening appears to be predominantly due to a reduction in ionic character stemming from charge build up on the U centre, and not from hydroxide / Oyi competition for U 6d, as has been previously suggested. Time-Dependent DFT is used in chapter 4 to simulate the electronic spectra of U02(NCN)2 and U02(NPN)2 in order to investigate why these complexes are coloured red rather than the normally observed green/yellow of uranyl systems. This chapter involves some preliminary benchmarking calculations on three other uranyl complexes, U02Cl2(TBP)2 , UC>2Cl2(THF)2 , U02(NC>3)2(TBP)2 , as there is as yet no literature suggesting suitable exchange potentials and/or basis sets for TD-DFT calculations on actinides. The conclusion was reached that the unusual colour of the nitrogen donor complexes is due to a small HOMO-LUMO gap resulting from the relatively low energy nitrogen based ligand MOs compared with usual uranyl ligands such as O and CI. Chapter 5 systematically investigates M(N(EPR.2)2)3 , M = Ln (Ln = La, Ce, Pr, Pm, Eu), An (An = U, Np, Pu, Am, Cm) E = O, S, Se, Te R = H to investigate the ligands' suitability for extraction of An(III) from Ln(III), and also to test the suitability of La and U as models for Eu and Am/Cm respectively. The results lead me to conclude that chalcogen donor ligands are extremely promising for successful separation of Cm from Am and Eu, but good separation factors of Am from Eu seem unlikely. Furthermore I conclude that La and U are not suitable models for Eu and Am/Cm as the 2+ capability of Eu seems present in with S, Se, Te U shows considerable covalency in M-E with the heavier chalcogens and there is no evidence of covalency in any Am-E or Cm-E.
41
Stuber, Wanda. "Direct monitoring of speciation for minor actinide separations". Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:afbc10e6-9c8e-477d-90ab-c939776b625d.
Testo completoAbstract (sommario):
One of the major challenges in the development of future generations of nuclear reprocessing procedures is the separation of the minor actinides from the chemically similar trivalent lanthanide ions. In this thesis, the potential of two purely N-donor ligands for minor actinide separations is evaluated and behaviour in aqueous and extraction conditions investigated. Of two chosen ligands, 12N4Py4 and 9N3Py3, only the larger 12N4Py4 was found to be able to complex lanthanide ions; however, both bind readily to divalent calcium ions. In comparison to earlier published properties of Ln(III)- 12N4Py4 complexes, the cerium complex was found to show differences based on greater d-orbital mixing. Conjugated acid dissociation constants and metal binding constants were determined using newly developed fitting functions in several conditions and found to be comparable to those of other extractants. As the investigation was performed in aqueous conditions, side reactions such as hydroxide formation and precipitation had to be considered and included into fitting procedures. Studies on U(IV) and Am(III) were conducted, but due to unfavourable conditions complexation by 12N4Py4 could not be verified beyond reasonable doubt. Extraction of ligand species and metal complexes was studied in various conditions and in the presence of various anions. Beside the main target cations, Ln(III) and An(III), 12N4Py4 is also capable of complexing and extracting protonated ligand species and Na+ with considerably higher partition coefficients than those observed for species with higher charge. Low solubilities of potassium, sodium and protonated species involving 12N4Py4 in presence of lipophilic anions such as pertechnetate, perrhenate and triiodide lead to precipitation. Formation of solids is of considerable concern in minor actinide separations, but could also offer novel pathways for iodine trapping.
42
McGregor, Alistair. "Studies on the cytoskeletal protein α-actinin". Thesis, University of Leicester, 1992. http://hdl.handle.net/2381/35108.
Testo completoAbstract (sommario):
The interaction between the cytoskeletal proteins α-actinin and vinculin is considered to be fundamental to the link between actin microfilaments and the cytoplasmic face of integral membrane proteins that support cell adhesion. Evidence is provided here for an interaction between α-actinin and vinculin. Electron microscopy of negatively stained samples was used to directly visualise α-actinin/vinculin complexes. The micrographs showed that an α-actinin dimer could bind two vinculin molecules, one at each end of the α-actinin rod. Low speed equilibrium centrifugation demonstrated that the two proteins interacted with a Kd of approximately 1.6X10-5M. An interaction between α-actinin and vinculin was also demonstrated using a 125I-vinculin overlay technique. Appropriate concentrations of unlabelled vinculin or α-actinin inhibited the binding of 125I-vinculin to α-actinin electroblotted onto nitrocellulose. The vinculin binding site of α-actinin has been localised to a 37 amino acid sequence (residues 713 to 749). Thermolysin generated fragments of α-actinin and glutathione-S-transferase linked α-actinin fusion proteins were used to define the binding site. Their ability to bind vinculin was assayed using 125I-vinculin overlays, by their ability to compete in 125I-vinculin overlays, and in a solid phase binding assay. Determination of the three dimensional structure of α-actinin may prove useful in elucidating a number of α-actinin/protein interactions. As yet, intact α-actinin has not been crystallised. The actin binding domain of α-actinin (residues 1 to 268) was expressed in E. coli. A purification protocol that produces milligram quantities for crystallisation studies was devised. No crystals have as yet been produced. The repeats of α-actinin (residues 240 to 749) were expressed. However, a satisfactory purification protocol could not be devised. The possible homology between the actin binding domains of α-actinin and filamin was investigated. An immunological approach, in conjunction with peptide mapping, was used to identify the actin binding domain of filamin for N-terminal sequencing.
43
Berg, Isak. "Analysis of α-actinin in Phytophthora infestans". Thesis, Umeå universitet, Kemiska institutionen, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-150537.
Testo completo
44
Teixeira, Marcelo Costa. "Infrerências moleculares sobre Passiflora Actinia Hook.(Passifloreaceae)". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/131690.
Testo completoAbstract (sommario):
Passiflora actinia Hook. (Passifloraceae) é uma liana típica da Floresta Atlântica, que cresce geralmente no interior ou eventualmente na borda de florestas até seus ramos atingirem a parte mais alta e exposta à luz do dossel. A espécie possui uma ampla distribuição, desde a encosta Atlântica até a borda oriental do Planalto Brasileiro, não avançando muito em direção a oeste. A Floresta Atlântica está entre os biomas mais ricos em biodiversidade do mundo, especialmente em termos de endemismos. Devido a grande utilização de seus recursos e ao desmatamento para cultivo agrícola, pastoril e ocupação imobiliária, a fragmentação da floresta aumenta constantemente, trazendo consigo os efeitos prejudiciais à biodiversidade. Estudos filogenéticos e filogeográficos envolvendo P. actinia determinaram seu posicionamento próximo de P. elegans Mast. e demonstraram uma estruturação da variabilidade genética no sentido norte-sul da distribuição. Com o intuito de avaliar os padrões de variabilidade genética de populações de P. actinia ao longo de sua distribuição geográfica, através da análise de marcadores moleculares nucleares e plastidiais e determinar os efeitos climáticos sobre a distribuição desta diversidade, nós aplicamos métodos filogeográficos e de modelagem climática para o passado, presente e futuro. Os tempos de diversidade encontrados para P. actinia datam do Pleistoceno e os resultados indicam uma forte influência das mudanças climáticas deste período na estruturação da diversidade genética desta espécie. Os resultados de modelagem climática indicaram a manutenção de áreas adequadas para a espécie em localidades de maior altitude e sua redução em áreas de baixa altitude, especialmente para cenários com maiores concentrações de carbono. O risco maior para a manutenção desta espécie é a destruição de seu habitat por desflorestamento. Sendo assim, a espécie P. actinia pode ser considerada um excelente parâmetro para descrever os acontecimentos históricos que levaram à formação da Floresta Atlântica e um indicador das transformações futuras. Seu monitoramento poderá auxiliar no controle da ação antrópica sobre a Floresta Atlântica e na preservação da biodiversidade nesta região considerada como hotspot de diversidade.Passiflora actinia Hook. (Passifloraceae) is a vine species typical from the Atlantic Forest. Usually, it grows inside or on the edge of forests where the branches reach the highest part and exposed to light in the canopy. The species has a wide distribution from the Atlantic slope to the eastern edge of the Brazilian Plateau, not much moving toward the west. The Atlantic Forest is among the richest in biodiversity biomes in the world, especially in terms of endemism. Due to the great use of its resources and deforestation for agricultural farming, pastoral, and property occupation, forest fragmentation constantly increases, bringing the effects harmful to biodiversity. Phylogenetic and phylogeographic studies involving P. actinia determined its position close to P. elegans Mast. and demonstrated a genetic structuring the variability in the north-south distribution sense. In order to assess the genetic variability patterns of P. actinia, we analyzed populations throughout its geographical distribution based on nuclear and plastid molecular markers employing phylogeographic methods and climate modelling analyses to past, present, and future implementing an ensemble forecasting framework. The diversification age in P. actinia was compatible to Pleistocene period indicating strong influence of climate changes over genetic diversity distribution to this species. Our results predicted the persistence of suitable regions to P. actinia located in highlands and forecast a reduction in lowlands, especially for the scenario with higher greenhouse gas concentration. Most preserving efforts must be focused over localities carrying unique genetic units and distributed areas with more climatic instability. Habitat loss due to deforestation in Atlantic Forest constitutes the major risk to this species maintenance that comprises only few populations and low diversity indices. Thus, P. actinia can be considered an excellent parameter describing historical events that led to the formation of Atlantic Forest and an indicator of future changes. Monitoring this species may be helpful to control anthropic effect on the Atlantic Forest and to preserve the biodiversity in this region considered as a hotspot of diversity.
45
Le, Gurun Gwenaelle. "The application of colloidal photocatalysis in actinide photoredox chemistry". Thesis, University of Central Lancashire, 2003. http://clok.uclan.ac.uk/20090/.
Testo completoAbstract (sommario):
Colloidal semiconductor particles may act as efficient photocatalysts for a range of environmentally usellil reactions such as pollution abatement and nitrogen fixation. The primary step in these reactions is the absorption of ultra-band gap energy photons by the particles, which generates electron-hole (eB,htB) pairs within the semiconductor lattice. The valence band holes/conduction band electrons may react with oxidisable/reducible species in solution or particle lattice sites. Photocatalytic treatment of metal ion species by such particles has a number of important commercial applications in precious metal recovery and in the removal of heavy elements from effluent streams. The selective manipulation of actinide metal oxidation states plays an important role in the purification/separation of target metal ions from process/waste streams during nuclear reprocessing. Thus, the technological objective of this project is to explore the use of photocatalysis in metal ion redox chemistry leading to an assessment of its potential for application within nuclear reprocessing. Consequent to this, the scientific objective of this project is to identi& factors contributive to efficient photocatalytic metal ion valence control. Nuclear reprocessing streams typically have pFls of 1 or less. Thus, the photocatalyst employed must be both stable toward acid dissolution at low p1-I and be possessed of charge carrier thermodynamics which may be exploited in actinide metal valence control experiments. Equilibrium thermodynamic calculations have indicated that Sn0 2 flilfils both conditions, and atomic spectrometric studies of acid photodissolution of Sn02 have confirmed material stability under illuminated conditions. The Ce4 VCe3 system is widely used as a non-radioactive, thermodynamic analogue of the Pu4 fPu3 system. Thus, valence control experiments have concentrated on studying the light-on transient behaviour of the Ce 4 VCe3 couple using experimental techniques such as photopotentiometry and UV-Visible spectrophotometry, the former being wholly developed within these laboratories. From these experiments, the effect of particle thermodynamics on reaction yield has been identified and the rate determining step in the valence control process elucidated. The roles played by static and dynamic quenching reactions of the photogenerated holes and electrons respectively have also been determined. A model has been developed that allows for the reliable assessment/prediction of whether efficient valence control is occurring in any one candidate system.
46
Thompson, Gary S. "Studies of some actinide ions with polyhydroxy carboxylic acids". Thesis, University of Reading, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385733.
Testo completo
47
Rogers, Brendan James. "Arrangement and structure of α-actinins in striated muscle". Thesis, University of Leeds, 2018. http://etheses.whiterose.ac.uk/22905/.
Testo completoAbstract (sommario):
The smallest contractile unit within striated muscle cells are called sarcomeres. The boundary regions between sarcomeres are called Z-discs, which contain over 30 different proteins, organised within a narrow ~100 nm wide structure. Standard fluorescence microscopy approaches do not reveal the arrangement of Z-disc proteins, as the width of the Z-disc is below the resolution limit (~250 nm). The arrangement of the actin filaments and the cross-linking proteins α-actinin in the Z-discs are well characterised by electron microscopy (EM) studies, however other Z-disc proteins are not. With the development of super-resolution fluorescence microscopy techniques, it is now possible to obtain Z-disc protein localisation information. Here, dSTORM (direct Stochastic Optical Reconstruction Microscopy) was used, to investigate the arrangement of α-actinins in Z-discs of cardiomyocytes, and then the arrangement of the N-terminal ends of the giant protein titin in the Z-discs. Affimers were generated to bind α-actinin 2 and the N-terminal titin domains (Z1/Z2), to use as binders in dSTORM. Affimers are small (~12 kDa) non-antibody binding proteins, about 1/10th the size of antibodies, that can be selected to bind to a specific protein. The localisation data of dSTORM using the Affimer binders showed the same regular arrangement of α-actinins observed in EM studies. The use of dSTORM with Affimers also suggests the titin Z1/Z2 domains do not only localise at the edges of the Z-discs but arranged throughout the Z-disc with regular spacing (~25 nm) in the transverse plane of the Z-discs. Also, three mutations located in the actin binding domain of α-actinin 2 associated to hypertrophic cardiomyocytes (G111V, A119T and M228T) were characterised by in vitro co-sedimentation assays with actin. The mutants G111V and A119T did not show a significant difference in binding affinity to actin compared to the wild-type. The co-sedimentation assays did however suggest the mutation M228T significantly increases the binding affinity of α-actinin 2.
48
Du, Toit Erasmus Johannes. "Cluster model analysis of exotic decay in actinide nuclei". Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/95812.
Testo completoAbstract (sommario):
Thesis (MSc)--Stellenbosch University, 2014.ENGLISH ABSTRACT: The binary cluster model is used to investigate the properties of exotic structures and decays in various nuclei. A simple method is described to choose the possible clusters forming within the nucleus, by assuming the nucleus consists of a mixture of up to four different core-cluster pairs. A phenomenological potential is then used, with optimized parameters, to describe the even-even 222-232Th nuclei within the binary cluster model, by calculating exotic decay half-lives, reduced electromagnetic transition probabilities, and energy spectra. After finding that all experimentally observed heavy ion emissions are predicted with the model and calculated structure observables are reproduced within good agreement of the experimentally measured values, the model was extended to include the even-even 230-234U, 236-240Pu and 222-224Ra nuclei. We found that almost all experimentally observed heavy ion emissions are predicted within the model with reasonable accuracy in the calculated halflives, and found good agreement in the other calculated structure observables.
AFRIKAANSE OPSOMMING: Die binêre bondel model is gebruik om die eienskappe van eksotiese strukture en verval in verskeie nukliedes te ondersoek. ’n Eenvoudige metode is gebruik om die moontlike bondels wat binne die nuklied vorm te kies, deur die aanname te maak dat die nuklied uit ’n mengsel van tot vier verskillende kern-bondel pare bestaan. ’n Fenomenologiese potensiaal is dan gebruik, met optimale parameters, om die ewe-ewe 222-232Th nukliedes met die binêre bondel model te beskryf, deur eksotiese verval halfleeftye, verminderde elektromagnetiese oorgangswaarskynlikhede, en energie spektra te bereken. Nadat daar gevind is dat alle vrygestelde swaar ione wat eksperimenteel waargeneem is deur die model voorspel word, en berekende struktuur waarneembares tot goeie ooreenstemming met die eksperimentele waardes produseer is, is die model uitgebrei om die ewe-ewe 230-234U, 236-240Pu en 222-224Ra nukliedes in te sluit. Daar is gevind dat byna alle vrygestelde swaar ione wat eksperimenteel waargeneem is deur die model voorspel word met redelike akkuraathied in die berekening van hul halfleeftye, asook dat daar goeie ooreenstemming tussen die berekende en eksperimentele waardes van ander struktuur waarneembares was.
49
Vinogradoff, Susan I. "An investigation of soil actinide-humic interactions using electrophoresis". Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/14611.
Testo completoAbstract (sommario):
This study focused on the associations of U and Pu with humic substances and the implications for migration in deciduous broadleaf and coniferous forest soils. Humic substances were isolated from soil samples by (i) solvent extraction (0.045 M Tris-borate and 0.1 N NaOH) and (ii) novel gel electrophoretic extraction (pH 8.5; 0.045 M Tris-borate as running buffer). Gel electrophoresis was also used to extract humic substances from soil that had been 'pre-equilibrated' with a solution containing 236U or 242Pu (pH 4.2). The relative concentrations of humic substances in the solvent and electrophoretic extracts were obtained by UV-visible spectrophotometry (A254 nm) whilst the 238U concentrations in the extracts were determined by inductively coupled plasma-mass spectrometry (ICP-MS). In addition, the molecular size and functional group content of the humic molecules in selected fractions of the gel electrophoretic extracts were investigated using gel filtration chromatography and FTIR spectroscopy, respectively. The methodology developed in this study enabled identification of several operationally defined soil actinide pools: (i) labile (< 0.2 mm, at pH 4.2), (ii) hydrophilic-mobile (< 0.15 mm, negatively-charged at pH 8.5) and (iii) immobile (> 0.15 mm and/or uncharged at pH 8.5). The adopted procedures avoid the extremes of pH used in the traditional methods of extraction (pH 13) and fractionation (pH < 2) which may alter humic substances. It was found that the 238U content of the hydrophilic-mobile pool (i.e. the gel electrophoretic extract) accounted for 14-41 % and 15-34 % of the total 238U in the deciduous broadleaf and coniferous forest soils, respectively. In general, these values were grater than those obtained by 0.045 M Tris-borate solvent extraction but less than those obtained using 0.1 N NaOH as the solvent. A further advantage of the new methodology was that the distribution of 238U within the humic extract could be investigated.
50
Toral, Rizo Victor Hugo 1977. "Estudo clinicopatologico e imunoistoquimico de prurigo actinico de labio". [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/288363.
Testo completoAbstract (sommario):
Orientador: Oslei Paes de AlmeidaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: O prurigo actínico (PA) é uma fotodermatose familiar específica que afeta principalmente os mestiços, fruto da miscigenação entre índios e europeus, que habitam vários países da América do Norte, Central e do Sul. Pode manifestar-se em qualquer idade, no entanto a doença inicia-se freqüentemente na infância, entre os seis e oito anos de idade. É mais freqüente em mulheres, e atinge principalmente pessoas que vivem em regiões acima de mil metros de altitude. O PA afeta principalmente áreas da pele expostas ao sol. Clinicamente se apresenta de forma polimórfica. O objetivo deste estudo foi analisar as características clínicas, histopatológicas e a expressão de marcadores imunoistoquímicos de 43 casos de PA de lábio. Dezesseis casos envolviam pacientes do gênero masculino e 27 casos (62,80%) do gênero feminino, com idade média de 28,6 anos. Todos os casos envolviam o lábio inferior e outras áreas da face e do corpo, e 17 casos (39,54%) somente apresentavam manifestação em lábio inferior. As principais alterações clínicas eram: crosta, pápulas eritematosas, hiperpigmentação, descamação, placas, úlceras e edema. Microscopicamente observou-se no epitélio superficial principalmente hiperqueratose, ulceração, vacuolização das células da camada basal e exocitose. No conjuntivo subjacente observou-se quadro inflamatório crônico, em muitos casos predominando a presença de folículos linfóides em diversos graus de organização. Nenhum dos casos apresento elastose solar. Os marcadores imunoistoquímicos mostraram que os folículos linfóides apresentavam organização semelhante ao normal. Syndecan-1 marcou as células da camada espinhosa de forma homogênea, mas estava ausente nas células basais e suprabasais. D2-40 com marcação positiva e forte nas células dendríticas do centro folicular e camada basal do epitélio superficial. Mastócitos, eosinófilos e macrófagos estavam distribuídos entre as células linfoplasmocitárias.
Abstract: Actinic prurigo (AP) is a specific familial photodermatosis that affects mainly mestizos, who live in many parts of North, Central and South America. AP can be clinically evident at any age, but it starts in infancy, between 6 and 8 years of age. It is more frequent in women. AP affects mainly persons living in regions above one thousand meters sea level. The disease affects mainly sun exposed skin, andclinically it is polymorphic. The objective of this study was to evaluate the clinical, histological and immunohistochemistry characteristics of 43 cases of AP of the lower lip. Sixteen cases were in males and 24 females (62.8%), with mean age of 28.6%. All cases involved the lower lip and other skin sites, but in 17 cases the lesions occurred only in the lower lip (39.54%). Hyperpigmentation, descamation, plaques, ulcers and edema were the main clinical alterations in our series. Microscopically on the superficial epithelial it was found mainly hyperqueratosis, ulceration, vacuolization of the basal and supra basal layer cells and exocytosis. In the subjacent connective tissue predominated a chronic inflammatory process, in many cases rich in lymphoid follicles in various degrees of organization. In none of the cases it was observed elastosis in the connective tissue. Immunohistochemistry markers confirmed that the follicles showed an organization similar to normal follicles. Syndecan-1 was expressed homogenously in the spinous layers of the superficial epithelium, but it was negative in the basal and suprabasal layers. D2-40 was positive in the dendritic cells of the follicular centers and basal cells of the superficial epithelium. Mast cell, eosinophils, and macrophages were found among the plasmatic cells.
Mestrado
Patologia
Mestre em Estomatopatologia