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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
161

Análise morfológica e molecular de cianobactérias isoladas de efluentes de uma mina de urânio desativada com ênfase em Aphanothece e sua capacidade de biossorção do 226Ra / Morphological and molecular analysis of cyanobacteria isolated from a deactivated uranium mine effuents with emphasis in Aphanothece and its 226Ra biosorption capacity

Karla Nishiyama Marques 31 October 2006 (has links)
As cianobactérias são microrganismos fotossintetizantes oxigênicos com ampla plasticidade metabólica e estrutural, que apresentam potencial biotecnológico para exploração na biossorção de metais pesados e biodegradação de poluentes orgânicos. Devido as suas fortes interações com cátions e ao contínuo suprimento de biomassa barata,as cianobactérias podem ser candidatas promissoras à biossorventes para remoção de metais e radionuclídeos. Dessa maneira, numa tentativa de encontrar uma cianobactéria com esse perfil para remover 226Ra de uma mina de urânio desativada da Unidade de Tratamento de Minérios (UTM) pertencente às Indústrias Nucleares do Brasil (INB), Caldas, MG, doze linhagens de cianobactérias foram isoladas desse ambiente. Essas linhagens foram morfologicamente caracterizadas como Aphanothece sp. CENA75, Rhabdoderma sp. CENA114, Synechococcus cf. lividus CENA79, Aphanocapsa cf. holsatica CENA80, Geitlerinema acutissimum CENA85, Pseudanabaena galeata CENA84, Pseudanabaena sp. CENA81, Leptolyngbya cf. tenerrima CENA76, Leptolyngbya sp. CENA83, Phormidium formosum CENA86, Phormidium violaceum CENA82 e Nostoc sp. CENA87. A análise molecular dos isolados, baseada em seqüências quase completas do gene RNAr 16S (1325 pb), estava de acordo com a análise morfológica, com exceção das linhagens Rhabdoderma sp. CENA114 e Phormidium violaceum CENA82. As seqüências de RNAr 16S dessas duas linhagens mostraram valores baixos de identidades (<92%) com seqüências do GenBank, o que pode representar novas espécies de cianobactérias. Altas percentagens de identidades (>96%) das seqüências do gene de RNAr 16S foram encontradas entre as linhagens restantes e as do GenBank. A árvore filogenética construída usando o método ?Neighbour Joining? mostrou que as linhagens unicelulares das ordens Chroococcales e as filamentosas da Oscillatoriales eram polifiléticas, conforme já relatado. A distribuição e abundância da população de cianobactérias nos efluentes da UTMINB foram investigadas pelo método da contagem de células viáveis (número mais provável, NMP). O NMP mostrou uma população de cianobactérias variando de 4.0 x 100 to ?2.4 x 108 cells?mL-1. Os locais Cava da Mina, com pH médio de 3,88, e o sistema de tratamento da usina, com pH 8,0, mostraram os mais baixos e mais altos valores de NMP, respectivamente. Para identificar os isolados de cianobactérias prejudiciais, um teste imunológico (ELISA) foi realizado para detectar microcistinas, uma hepatotoxina que causa envenenamento em humanos. A produção de microcistinas foi detectada em três isolados, Pseudanabaena galeata CENA84, Pseudanabaena sp. CENA81 e Leptolyngbya cf tenerrima CENA76. Esse resultado é inédito, pois não há relatos dos gêneros Pseudanabaena e Leptolyngbya como produtores de microcistinas. / Cyanobacteria are oxygenic photosynthetic microorganisms with wide metabolic and structural plasticity, which have biotechnological potential for exploration in metals biosorption and organic pollutants biodegradation. Due to its strong interactions with cations and a reliable supply of cheap biomass, cyanobacteria may be a promising biosorbent candidate for removing metals and radionuclides. In this way, in an attempt to find a cyanobacteria with this profile to remove 226Ra from a deactivated uranium mine effluents of the Ores Treatment Unit (UTM) belonging to the Nuclear Industries of Brazil (INB), Caldas, MG, twelve cyanobacterial strains were isolated from this environment. These strains were characterized morphologically as Aphanothece sp. CENA75, Rhabdoderma sp. CENA114, Synechococcus cf. lividus CENA79, Aphanocapsa cf. holsatica CENA80, Geitlerinema acutissimum CENA85, Pseudanabaena galeata CENA84, Pseudanabaena sp. CENA81, Leptolyngbya cf. tenerrima CENA76, Leptolyngbya sp. CENA83, Phormidium formosum CENA86, Phormidium violaceum CENA82 and Nostoc sp. CENA87. The molecular analysis of the isolates, based on the sequences of nearly complete 16S rRNA gene (1325 bp), was in agreement with the morphological analysis, with exception of Rhabdoderma sp. CENA114 and Phormidium violaceum CENA82 strains. The 16S rRNA sequences of these two strains showed low identities scores (<92%) with sequences from GenBank, which may represent novel cyanobacterial species. High percentages of identities (>96%) of 16S rRNA gene sequences were found between the remaining strains and of the GenBank. The phylogenetic tree of 16S rRNA sequences constructed using Neighbour-Joining method showed that unicellular strains of the orders Chroococcales and filamentous Oscillatoriales were polyphyletic, as reported earlier. The distribution and abundance of cyanobacterial population in the effluents of UTMINB were investigated by viable cells counting (most probable number, MPN) method. The MPN showed a cyanobacterial population range from 4.0 x 100 to ?2.4 x 108 cells?mL-1. The locations of the Pit Mine with pH 3.88 and the Plant System Treatment with pH 8.0 showed the lowest and highest MPN values, respectively. To identify harmful cyanobacterial isolates, an immunological test (ELISA) was carried out to detect microcystins, a hepatotoxin which cause human poisoning. Microcystins production was found in three isolates, Pseudanabaena galeata CENA84, Pseudanabaena sp. CENA81 and Leptolyngbya cf. tenerrima CENA76. This is a novel result since there is no report for both genera, Pseudanabaena and Leptolyngbya, as microcystin producers. Based on the obtained results, the Aphanothece CENA75 strain found in all UTM-INB effluents sampled, including in the Pit Mine location, which has an acidic pH (average of 3.88) and high level of uranium (5.68 mg?L-1) and radium, was selected for the 226Ra biosorption assays. The experiments performed in pH 3.5 and 5.0 showed that dried biomass of Aphanothece CENA75 behaves as a weakly acid resin. The ratio (final concentration/initial concentration) of 226Ra adsorption after 135 min in pH 3.5 and 5.0 was 0.86 and 0.82, respectively. These results showed that the dried biomass of Aphanothece CENA75 adsorbed low amount of 226Ra in both studied pH values. However, the increase of the radionuclide retention in pH 5.0 suggests that more adsorption may occur in pH above of this value.
162

SEDIMENTARY RESPONSES TO GROWTH FAULT SLIP AND CLAY SHRINK AND SWELL INDUCED ELEVATION VARIATIONS: EAST MATAGORDA PENINSULA, TEXAS

Ji, Wei 01 January 2017 (has links)
East Matagorda Peninsula in southwestern Texas is characterized geologically by active, regional-scale and near-surface growth faulting. Decimeter scale (up to 0.42 m) vertical displacement was recorded at the study site over a period of four years, not believed to be associated with growth faulting. This research tested the hypotheses that fault slip rates were correlated with sediment accumulation rates, and that the observed vertical displacement was produced by shrink-and-swell clays in near surface sediments. To quantify sediment accumulation rates, a suite of radionuclides (7Be, 137Cs, and 210Pb) were used. To understand the effects of shrink-and-swell clays, analyses including particle size distribution, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were completed. Additionally, the free swell index test (FSI) was used to record the swelling potential of the sediment. Strong correlation (R2 = 0.99) indicates coupling between mean fault slip rates and mean sediment accumulation rates. Near surface sediment clay size fraction percentages ranged from 0.96 - 6.26% containing more than 90% smectite. Based on FSI results, maximum volume change in the top six cm was determined to be 208%. The presence and behavior of shrink-and-swell clay minerals in the region is an important contributor to the vertical displacement observed.
163

The potential use of radioiodinated fatty acids as myocardial imaging agents

Chung, Connie Joan January 1979 (has links)
The potential use of four radioiodinated fatty acids as myocardial imaging agents were evaluated. Preliminary distribution studies revealed that the terminal labeled fatty acids demonstrated higher myocardial uptake. Thus, 10-Iodocapric acid (10-iododecanoic) and 12-Iodolauric acid were subjected to further investigation. Comprehensive tissue distribution studies involving both radioiodinated fatty acids in mice indicated that the highest accumulation of the total injected activity occurred in the muscle and the blood. Other organs investigated included the heart, liver, lung, kidneys, spleen, stomach, intestines, bone and adrenals. The heart exhibited the highest concentration of the radioiodinated fatty acids for the relative accumulation of activity per unit weight. Erom the tissue distribution studies, the optimum scanning time was found to be immediately following injection of the radiopharmaceutical. Toxicity studies were performed in mice after intravenous administration of 10-Bromocapric acid and 12-Bromolauric acid. The LD₅₀ of Sodium Bromolaurate in 10% Human Serum Albumin was found to be 210 mg/kg (194 mg/kg - 228 mg/kg). The stability problem encountered with 10-Bromocapric acid necessitated the use of a different solvent system. The LD₅₀ obtained after intravenous injection was found to be 86.1 mg/kg (83.0 mg/kg - 89.3 mg/kg). However, this observed toxicity may not necessarily reflect the toxicity of the Bromocapric acid solely. Whole body excretion studies were performed in mice and revealed a triexponential excretion curve. For 10-Iodocapric acid, the effective half-lives were .90 hours (36.7%), 3.91 hours (61.6%) and 74.9 hours (14.5%). For 12-Iodolauric acid, the effective half-lives were 1.67 hours (46.6%), 7.68 hours (38.4%), and 71.6 hours (17.8%). For both 10-Iodocapric acid and 12-Iodolauric acid, the first as well as the second component of the excretion curve presumably represented a decrease in the whole body activity due mainly to urinary excretion. The third component appeared to represent activity which was tightly bound and slowly released. The third component presumably represented elimination by fecal excretion. The excretion of the injected activity was primarily in the urine, although some activity was recovered in the feces. For 10-Iodocapric acid, 82.4% of the injected activity had been recovered in the urine within the first 24 hours and 8.88% had been recovered in the feces. For 12-Iodolauric acid, 78.9% of the injected dose was recovered in the urine at 24 hours and 9.4% in the feces. From the urine results, the effective half-life of the radio-iodinated fatty acids in the kidneys was found to be 4.8 hours. Myocardial scans were done on rabbits using ¹³¹I-capric acid, ¹³¹I-lauric acid, NaI-131 (6% Human Serum Albumin), and Thallium-201 at specified time intervals after injection. Iodine-123, a radionuclide possessing more favorable imaging properties, was not readily available due to production problems at the time of scanning. The mean absorbed dose to the whole body, the liver, the kidneys, the muscle, and the heart were computed based on the results from the distribution and excretion studies. The dosimetry calculations were done using Iodine-123 as the radionuclide. For ¹³¹I-capric acid, the radiation doses were calculated as 34.76 mrads/2 mCi for the whole body, 136.3 mrads/2 mCi for the kidneys, 86.6 mrads/2 mCi for the liver, 38.5 mrads/2 mCi for the muscle, and 25.89 mrads/2 mCi for the heart. For ¹³¹I-lauric acid, the radiation doses were 41.73 mrads/2 mCi for the whole body, 199.8 mrads/2 mCi for the kidneys, 185.9 mrads/2 mCi for the liver, 52.07 mrads/2 mCi for the muscle, and 46.39 mrads/2 mCi for the heart. / Pharmaceutical Sciences, Faculty of / Unknown
164

The role of imaging with iodine-131-meta-iodobenzylguanidine in the diagnosis and localisation of suspected phaeochromocytoma

Adams, B K 24 August 2017 (has links)
No description available.
165

Metody stanovení radiologických dopadů v potravních řetězcích / Methods for the determination of radiological impact of the food chains

Tesař, Jakub January 2011 (has links)
The diploma work presents comprehensive overview of methods of determination of radiological impact on food chains. It describes the determination of radionuclides in groceries in common radiation situation and in unusual radiation situation. Practical part of the work presents two model radiation events. These are radiation event in the territory of Czech Republic and radiation event in the territory of other country and its impact on Czech Republic. In the end both model situations are compared.
166

Optimalizace podmínek stanovení sorpčních vlastností dnových sedimentů / Optimization of conditions for determination of bottom sediment sorption characteristics

Ramešová, Lucie January 2014 (has links)
Univerzita Karlova v Praze Lucie Ramešová Přírodovědecká fakulta Květen 2014 Ústav pro životní prostředí a VÚV T.G.M. v.v.i. OPTIMIZATION OF CONDITIONS FOR DETERMINATION OF BOTTOM SEDIMENT SORPTION CHARACTERISTICS ABSTRACT An option of this study was to optimize conditions of distribution coefficients determination in the water-sediment system. The study results will be applied in the task A research on influence of Temelín Nuclear Power Plant accident on the Vltava and Labe water environment contamination to the border profile Labe - Hřensko. After finding optimal conditions for sorption experiments, these will be applied on the experiments using real sediment samples and corresponding surface water extracted from different localities of Vltava River, Labe River respectively. A goal of the whole project is to contribute to creation of a crisis scenario of potential accident of Temelin Nuclear Power Plant and its impact on Vltava and Labe water environments. Above all, the aim is to answer the question which processes would take place in dams and basins during the contamination by fission and activation products, whether and which products would be preferably adsorbed and would consequently settle down and which would supposedly be transported to the lower parts of the watershed. The practical part of the...
167

CD133-Targeted Radionuclide Therapy and Molecular Imaging

Wyszatko, Kevin January 2024 (has links)
To address the unmet clinical need to eradicate treatment-resistant CD133+ cancer stems within tumors, a CSC-targeted radionuclide therapy (TRT) and companion diagnostic imaging probes were developed utilizing CD133-targeting antibodies and antibody fragments. In Chapter 1, background research providing context for the work in this Thesis is presented. In Chapter 2, a CD133-targeting antibody, RW03IgG, underwent radiolabeling with lutetium-177 to synthesize [177Lu]Lu-DOTA-RW03IgG for CD133-TRT. The CD133-TRT was evaluated for pharmacokinetics and treatment of a CD133 expressing human colorectal tumor bearing mouse model. Biodistribution studies on [177Lu]Lu-DOTA-RW03IgG demonstrated notable uptake in the colorectal tumors and off-target organ uptake consistent with previously reported antibody-based TRTs. Confirmation that tumor uptake was mediated by antibody-antigen binding was verified through co-injection with an excess dose of unlabeled RW03IgG. A dose-escalation therapy trial using [177Lu]Lu-DOTA-RW03IgG for treatment of the colorectal cancer mouse model revealed a dose-dependent reduction in tumor growth rate at well-tolerated doses. The decrease in tumor growth rate observed due to [177Lu]Lu-DOTA-RW03IgG treatment, along with an improvement in overall mouse survival, demonstrate the therapeutic efficacy of CD133-TRT. Additionally, histopathological and immunohistochemical (IHC) analyses indicated low off-target organ toxicity and significant anti-tumor effects. These findings suggested the potential for enhanced overall survival benefits through multiple doses. However, results on multiple-dosed CD133-TRT on the tumor growth rate and overall mouse survival were inconclusive. In Chapter 3, an orthotopic patient-derived glioblastoma (GBM) mouse model was developed that replicates anatomical pharmacokinetic challenges and CSC populations observed in patient tumors. Stereotactic engraftment of the patient GBM cells was optimized to reproducibly deliver tumor cells to the thalamus and growth was monitored using bioluminescence imaging. Ex vivo analysis confirmed various key characteristics of patient GBM, including CD133 expression, hypercellularity, and invasiveness. Biodistribution studies on [177Lu]Lu-DOTA-RW03IgG using the PDX GBM mouse model indicate antibody-antigen driven tumor uptake, determined through co-injection an excess dose of unlabeled RW03IgG. Ex vivo autoradiography supported the biodistribution results and showed elevated uptake of [177Lu]Lu-DOTA-RW03IgG in tumor relative to non-tumor bearing brain tissue. Chapters 4 and 5 centered on the development and evaluation of companion diagnostic CD133-targeted immunoPET probes. Chapter 4 specifically explored probes derived from the full antibody, RW03IgG. The probes were synthesized by conjugating RW03IgG with DFO-NCS to produce DFO-RW03IgG at different chelator-to-antibody ratios. The various DFO-RW03IgG conjugates were then radiolabeled with zirconium-89 to obtain [89Zr]-DFO-RW03IgG. Biodistribution studies and PET imaging revealed promising tumor uptake of [89Zr]-DFO-RW03IgG, and it was observed that higher chelator-to-antibody ratios led to increased accumulation in off-target organs. Chapter 5 investigated a probe derived from an scFv-Fc fragment of RW03, [89Zr]-DFO-RW03scFv-Fc. Biodistribution studies and PET images of colorectal tumor-bearing mice administered [89Zr]-DFO-RW03scFv-Fc showed favorable tumor uptake and low off-target organ accumulation. In Chapter 6, a probe for CD133-Photoacoustic Imaging (PAI) was synthesized through conjugation of RW03IgG with IR-783, an organic dye recognized for its favorable photoacoustic properties. Challenges were encountered in isolating the product, (IR-783)-RW03IgG, at high degrees of labeling (DOL) due to product aggregation. In vitro binding assays indicated that (IR-783)-RW03IgG (DOL = 1) maintained a comparable binding affinity to native RW03IgG. In vivo, colorectal tumors in mice administered (IR-783)-RW03IgG (DOL = 1) did not exhibit significant contrast from the background tissue, and the tumor PA signal did not differ significantly compared to tumors in mice administered an IR-783 labeled isotype IgG. The results suggest that a higher concentration of dye is needed within colorectal tumors for effective tumor visualization than what was provided by IR-783-RW03IgG. Chapter 7 investigated the use of Imaging Mass Cytometry (IMC) to simultaneously visualize [177Lu]Lu-DOTA-RW03IgG and multiple tumor biomarkers in tissue specimens collected from colorectal tumor xenograft mice treated with CD133-TRT. IMC showed undetectable concentrations of hafnium-177 (the decay product of lutetium-177) in tumors treated with CD133-TRT. However, lutetium-176 and lutetium-175, sourced from the carrier-added [177Lu]LuCl3 used in the synthesis of [177Lu]Lu-DOTA-RW03IgG, were present at levels sufficient for IMC visualization. The distribution of lutetium-176, representing [177Lu]Lu-DOTA-RW03IgG, within tumors, was imaged concomitantly with CD133, DNA damage markers, and several additional biomarkers that describe elements of the tumor microenvironment. These collective results endorse IMC as a useful tool to assess the distribution of TRT within tumors and uncover changes to the microenvironment in response to treatment. / Thesis / Doctor of Philosophy (PhD) / Targeted radionuclide therapy (TRT) and molecular imaging strategies were developed to aid in the elimination of the rare and particularly resilient Cancer Stem Cell (CSC) population in tumors. A fully human monoclonal antibody and antibody fragments targeting CD133, a molecular biomarker for CSCs, provided the means to deliver radioactive isotopes for therapy and imaging to CD133+ cells in tumors. The therapeutic efficacy of CD133-TRT for treatment of a colorectal cell line-derived xenograft mouse model was promising, and the treatment showed uptake in orthotopic patient derived glioblastoma tumors engrafted in mice. ImmunoPET probes targeting CD133 were optimized and successfully delineated CD133 expressing tumors from background tissue, warranting further evaluation using patient-representative cancer models. A non-invasive CD133-targeting Photoacoustic Imaging (PAI) probe was synthesized through conjugation of the CD133-targeting antibody to an organic dye, IR-783, although further probe optimization is required to provide tumor contrast. Tumor specimens from mice treated with CD133-TRT were assessed by Imaging Mass Cytometry (IMC), which revealed detectable concentrations of carrier isotopes from the therapy in the tumors, implicating the discovery of a powerful new tool for multiplexed single-cell level resolution imaging for cellular-scale analysis of targeted radionuclide therapy. The CSC-therapy and select molecular imaging probes generated in this Thesis warrant further evaluation using patient-representative mouse models of cancer.
168

Sodium iodide symporter based strategy for treatment of thyroid and non-thyroid malignancy

Shen, Daniel Hueng-Yuan 19 March 2003 (has links)
No description available.
169

Factors controlling the sorption of Cs, Ni and U in soil : A statistical analysis with experimental sorption data of caesium, nickel and uranium in soils from the Laxemar area / Faktorer som styr sorptionen av Cs, Ni och U i mark : En statistisk analys med experimentella sorptionsdata för caesium, nickel och uran i jordar från

Johansson, Emilia January 2020 (has links)
In the fall of 2006, soils from three small valleys in the Laxemar/Oskarshamn area were sampled. A total of eight composite samples were characterized for a number of soil parameters that are important for geochemical sorption and were later also used in batch sorption experiments. Solid/liquid partition coefficients (Kd values) were then determined for seven radionuclides in each of the eight samples. To contribute to the interpretation of the sorption results together with the soil characterizations, this study aims to describe the sorption behavior of the radionuclides caesium, nickel and uranium and also discern which parameters that could provide a basis for estimating the strength of sorption of radionuclides in general. The methodology included quantitative methodologies such as compilation of chemical equilibrium diagrams by the software Hydra/Medusa and correlation analyses using the statistical software SPSS statistics. Based on the speciation diagrams of each radionuclide and identified important linear and non-linear relationships of the Kd values with a number of soil parameters, the following soil- and soil solution properties were found to have controlled the sorption of Cs, Ni and U, respectively, in the Laxemar soils. Cs: the specific surface area of the soil coupled to the clay content. Ni: the cation exchange capacity, alkaline solution pH, soil organic matter and dissolved organic matter. U: the cation exchange capacity, soil organic matter, dissolved organic matter, dissolved carbonate and alkaline solution pH. The soil that showed the strongest sorption varied between the nuclides, which can be related to the individual sorption behavior of caesium, nickel and uranium, as well as the different physicochemical properties of the soils. The parameters that should be prioritized in characterizations of soil samples are identified to be: solution pH, the cation exchange capacity, the specific surface area of the soil, soil organic matter and soil texture (clay content). / För att kunna fatta beslut relaterade till hypotetisk framtida kontaminering från slutförvar av radioaktivt avfall är det direkt avgörande att förstå mobiliteten av radioaktiva element i miljön. Sorption är en av de viktigaste kemiska mekanismerna som kan minska spridningen av radionuklider i vatten/jord/bergssystem, där nukliderna fördelar sig mellan vätskefasen och ytor på fasta partiklar i dessa system. Fördelningskoefficienter (Kd värden) används generellt som ett kvantitativt mått på sorptionen, där ett högt Kd värde innebär att en större andel av ämnet i fråga är bundet till den fasta fasen. Under hösten 2006 togs jordprover från tre dalgångar i Laxemar/Oskarshamn. Totalt åtta jordprover karakteriserades för ett antal jordparametrar som är viktiga för geokemisk sorption och användes senare i batchförsök tillsammans med ett naturligt grundvatten. Fördelningskoefficienter (Kd värden) bestämdes för sju radionuklider (Cs, Eu, I, Ni, Np, Sr and U) för vart och ett av de åtta jordproverna. För att bidra till tolkningen av sorptionsresultaten tillsammans med jordprovernas egenskaper syftar denna studie till att beskriva sorptionsbeteendet hos radionukliderna caesium, nickel och uran samt urskilja vilka parametrar som kan fungera som grund för att uppskatta sorptionsstyrkan av radionuklider i allmänhet. För att uppnå detta syfte så har studien följande mål. Identifiera de jord- och marklösningsegenskaper som kontrollerar sorptionen av Cs, Ni respektive U i de åtta Laxemar proverna. Bestämma vilket Laxemar-jordprov som starkast sorberar de tre radionukliderna. Identifiera de jordparametrar som bör prioriteras vid jordkarakteriseringar, baserat på deras sorptionsinflytande, för att kunna uppskatta Kd värden endast med begränsad information om ett jordsystem. Metoden innefattade kvantitativa metoder såsom sammanställning av kemiska jämviktsdiagram med programvaran Hydra/Medusa och korrelationsanalyser med hjälp av statistikprogramvaran SPSS statistics. De kemiska jämviktsdiagrammen bidrog till att beskriva specieringen av respektive nuklid som en funktion av pH och korrelationsanalyserna bidrog till att identifiera linjära samband mellan par av variabler, tex mellan Kd och jordparametrar. Baserat på specieringsdiagrammen för varje radionuklid och identifierade viktiga linjära och icke-linjära förhållanden mellan Kd-värdena och ett antal jordparametrar har följande egenskaper hos jordarna och marklösningen visat sig huvudsakligen kontrollera sorptionen av Cs, Ni respektive U i de åtta Laxemar jordarna: För caesium gäller jordens specifika ytarea kopplad till lerinnehållet, medan för nickel är det katjonbytarkapaciteten, organiskt material, alkaliska pH-värden samt löst organiskt material. Sorptionen av uran befanns kontrolleras av katjonbytarkapaciteten, organiskt material, löst organiskt material, alkaliska pH-värden samt lösta karbonater. Den jord som visade starkast sorption varierar mellan de tre nukliderna, vilket kan relateras till nuklidernas individuella sorptionsbeteende i jord samt jordarnas olika fysikaliska och kemiska egenskaper. Parametrarna som bör prioriteras vid karaktärisering av jordprov identifierades vara: pH, katjonbytarkapaciteten, jordens specifika ytarea, mängden organiskt material samt jordtexturen (lerinnehåll).
170

30S Beam Development and the 30S Waiting Point in Type I X-Ray Bursts

Kahl, David Miles 09 1900 (has links)
Nuclear physics tells us a lot about astrophysics, particularly the energy generation in stars. The present work is a thesis in experimental nuclear physics, reporting the results of 30S radioactive beam development for a future experiment directly measuring data to extrapolate the 30S(α,p) stellar reaction rate in Type I X-ray bursts, a phenomena where nuclear explosions occur repeatedly on the surface of accreting neutron stars. On the astrophysics side, the work details basic stellar physics and stellar reaction formalism in Chapter 1, the behaviour of compact stars in Chapter 2, and a full literature review of Type I X-ray bursts in Chapter 3. Nuclear experiments are non-trivial, and the results reported here were not accomplished by the author alone. Stable-beam experiments are technically challenging and involved, but for the case at hand, the halflife of 30S is a mere 1.178 seconds, and in order to measure reaction cross-sections, we must make a beam of the radionuclide 30S in situ and use these rare nuclei immediately in our measurement. Particle accelerator technology and radioactive ion production are treated in Chapter 4, and the experimental facility and nuclear measurement techniques are discussed in some detail in Chapter 5. In order to perform a successful future experiment which allows us to calculate the stellar 30S(α, p) reaction rate, calculations indicate we require a 30S beam of ~ 10^5 particles per second at ~ 32 MeV. Based on our recent beam development experiments in 2006 and 2008, it is believed that such a beam may be fabricated in 2009 according to the results presented in Chapters 6 and 7. We plan to measure the 4He(30S,p) cross-section at astrophysical energies in 2009, and some remarks on the planned (α,p) technique are also elucidated in Chapters 5, 6 and 7. / Thesis / Master of Science (MSc)

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