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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.
151

Subcellular localization of GFP fusions with the seven vacuolar sorting receptors of Arabidopsis thaliana to prevacuolar compartments in transgenic tobacco BY-2 cells.

January 2006 (has links)
Miao Yansong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 78-83). / Abstracts in English and Chinese. / Thesis/Assessment Committee --- p.ii / Statement --- p.iii / 摘要 --- p.vi / Acknowledgements --- p.vii / List of Tables --- p.xi / List of Figures --- p.xii / List of Abbreviations --- p.xiv / Chapter Chapter 1 --- General Introduction --- p.1 / Chapter 1. --- The plant secretory pathway --- p.2 / Chapter 2. --- Two different types of vacuoles in plant cells --- p.2 / Chapter 3. --- Vacuolar sorting receptor (VSR) proteins --- p.3 / Chapter 4. --- BP-80 and prevacuolar compartment --- p.6 / Chapter 5. --- The Arabidopsis VSR proteins --- p.7 / Chapter 6. --- Research objectives --- p.8 / Chapter Chapter 2 --- Development of Transgenic Tobacco BY-2 Cell Lines Expressing GFP-AtVSR Fusions --- p.10 / Chapter 1. --- Introduction --- p.11 / Chapter 2. --- Materials and Methods --- p.12 / Chapter 2.1 --- Structure of Golgi marker and PVC marker --- p.12 / Chapter 2.2 --- Construction of GFP-VSR reporters --- p.14 / Chapter 2.3 --- Agrobacterium electroporation --- p.24 / Chapter 2.4 --- Transformation of tobacco BY-2 cells --- p.24 / Chapter 2.5 --- Screening of transgenic BY-2 cells expressing GFP-VSR fusions --- p.25 / Chapter 2.6 --- Chemicals --- p.27 / Chapter 3. --- Result.s --- p.28 / Chapter 3.1 --- Chimeric GFP reporters as tools to study subcellular localization of Arabidopsis vacuolar sorting receptor proteins in transgenic BY-2 cells --- p.28 / Chapter 3.2 --- Establishment of transgenic tobacco (Nicotiana tabacum) BY-2 cell lines stably expressing seven GFP-AtVSR reporters --- p.29 / Chapter 4. --- Conclusion --- p.38 / Chapter Chapter 3 --- Subcellular Localization of the Seven GFP-AtVSR Fusions to Prevacuolar Compartments in Transgenic Tobacco BY-2 Cells --- p.39 / Chapter 1. --- Introduction --- p.40 / Chapter 2. --- Materials and Methods --- p.41 / Chapter 2.1 --- Confocal immunofluorescence studies --- p.41 / Chapter 2.2 --- Antibodies for immunolabeling --- p.42 / Chapter 2.3 --- Wortmannin and brefeldin A treatment --- p.42 / Chapter 2.4 --- Electron microscopy of resin-embedded cells --- p.43 / Chapter 3. --- Results --- p.44 / Chapter 3.1 --- Vacuolar sorting receptor proteins in plants --- p.44 / Chapter 3.2 --- PVC localization of GFP-AtVSR fusions in transgenic tobacco BY-2 cells --- p.47 / Chapter 3.3 --- The spacer sequences did not affect PVC localization of GFP-AtVSR7 --- p.56 / Chapter 3.4 --- Wortmannin-induced vacuolated PVCs contained VSRs in tobacco BY-2 cells --- p.58 / Chapter 3.5 --- Wortmannin-induced vacuolation of PVCs is a general response in plant cells --- p.62 / Chapter 4. --- Conclusion --- p.65 / Chapter Chapter 4 --- Discussion and Future Perspectives --- p.66 / Chapter 1. --- The hypothesis in this study --- p.67 / Chapter 2. --- GFP and BY-2 cells --- p.67 / Chapter 3. --- A reporter system to study subcellular localization of VSR proteins in transgenic tobacco BY-2 cells --- p.68 / Chapter 4. --- PVC localization of the seven GFP-AtVSR fusions in transgenic BY-2 cells --- p.69 / Chapter 5. --- VSR spacer sequences did not affect PVC localization of GFP-AtVSR fusions in transgenic tobacco BY-2 cells --- p.71 / Chapter 6. --- PVC localization of GFP-PV72 and GFP-AtVSR 1 fusions in transgenic tobacco BY-2 cells --- p.73 / Chapter 7. --- Wortmannin-induced vacuolation of PVC is a general response in plant cells --- p.75 / Chapter 8. --- Future perspectives --- p.75 / References --- p.78
152

Nano-scale systems for the detection and treatment of bacterial infections in burn wounds : modes of action and efficacy

Jamieson, William David January 2014 (has links)
Bacterial infections are and likely always will be a serious and costly complication to treatment in a healthcare environment. However consistent rises in the number of both healthcare associated and antibiotic resistant infections over the last of decades has the potential to turn a serious problem into a catastrophe. Control of infections in hospital wards has improved over the last five years but data from the European Centre for Disease Prevention and Control suggests a stale mate. While the numerical rise in drug resistant organisms has slowed, the severity of drug resistance appears to be on the increase with the prolific emergence of multiple drug resistant isolates. On the front lines of the threat that these organisms represent are some of the most susceptible. In hospitals those who are already sick are more vulnerable, those with co-morbidities, those with surgical or other wounds, the very old and the very young. Children especially show high susceptibility as they are often incapable of communicating clinical complications in the way an adult might. This coupled with higher commonality of specific aetiologies in children such as scalds, open wounds that are prone to infection without proper treatment, creates population in need. Antibiotics are often thought to be part of the problem in drug resistance, indeed to an extent they are. However their real downfall may be improper use. In order to improve treatment outcomes and simultaneously decrease antimicrobial resistance a combination of rapid diagnosis and prophylaxis can be utilised to decrease selection of resistance. As such, this study focuses on the development of a novel vesicle based sensor system for the detection of bacterial infections in burn wounds. Additionally an organometallic antimicrobial system has been developed with the potential for surface attachment. Work with the vesicle based biosensor demonstrates high sensitivity to both Staphylococcus aureus and Pseudomonas aeruginosa. The toxins involved in activation of the sensor have been determined in both cases and an in-depth study into the activity of the staphylococcal agents of lysis (Phenol Soluble Modulins and delta haemolysin), shows a high degree of plasticity and tunability in the sensors function. Work with the zinc based antimicrobial reveals a highly complex system which demonstrates possible functions as a not only an antimicrobial but as a sensor system in its own right.
153

Fluorescent carbon dots as sensitizers for nanostructured solar cells

Marinovic, Adam January 2016 (has links)
Fluorescent carbon dots are a new class of carbon nanomaterials that have emerged recently, and have created a lot of interest as a potential competitor to classical semiconductor quantum dots. Carbon dots possess low toxicity, biocompatibility, easy and low-cost synthesis, and good optical properties. They show huge potential as novel and versatile nanomaterials for a wide range of applications such as bioimaging, drug delivery, chemical sensing, photocatalysis, and as sensitizers for photovoltaic solar cells. The main motivation for this research was the need to produce non-toxic, low-cost nanomaterials with good optical and electrical properties for the use in the fabrication of sustainable, inexpensive nanostructured solar cells with good efficiency. The main aims and objectives of this PhD research were: to synthesize fluorescent carbon dots from biomass-derived precursors by using the hydrothermal synthesis method, to understand and explain structural and optical properties of the as-synthesized carbon dots, and to use the carbon dots as sensitizers for nanostructured solar cells. Carbon dots (CDs) were synthesized using hydrothermal synthesis method from polysaccharides (chitosan and chitin), monosaccharide (D-glucose), amino acids (L-arginine and L-cysteine), and from real food waste in the form of lobster shells. Carbon dots were thoroughly characterized to obtain the information about their structural and optical properties. The as-synthesized carbon dots showed polydispersity and quasi-spherical morphology, with particle sizes ranging from 5-17 nm. Carbon dots showed predominantly amorphous nature, and the functional groups from the starting precursors were successfully incorporated into the as-synthesized carbon dots. Diluted solutions of carbon dots were transparent under daylight and showed blue-green photoluminescence emission under UV excitation. All carbon dots showed excitation-dependent photoluminescence emission which was more pronounced for excitation wavelengths larger than 320 nm. Chitosan CDs, L-cysteine CDs and lobster CDs also showed excitation-independent emission for excitation wavelength in the range of 200 - 320 nm. The highest fluorescence quantum yield of (43.3 ± 2.1) % was calculated for L-arginine CDs. It was concluded that the origin of light emission in carbon dots must be governed by the interplay between the absorption due to the carbon cores and the surface functional groups. Considering the application of the as-synthesized carbon dots, two types of solar cells were fabricated. Carbon dots were used as sensitizers for ZnO-nanorod-based and for TiO2-based nanostructured solar cells. Three types of carbon dots (chitosan CDs, chitin CDs and D-glucose CDs) were used as sensitizers for ZnO-nanorod-based solar cells. ZnO nanorods were successfully coated with carbon dots, and the chitosan-CDs-sensitized solar cells showed the efficiency of 0.061 %. When using layer-by-layer coating method, solar cells with combination of chitosan- and chitin-CDs as sensitizers showed the efficiency of 0.077 %. All six types of carbon dots (chitosan CDs, chitin CDs, D-glucose CDs, L-arginine CDs, L-cysteine CDs, and lobster CDs) were used as sensitizers for TiO2-based nanostructured solar cells. TiO2-based solar cells sensitized with carbon dots showed much higher efficiency compared to the ZnO-nanorod-based solar cells. L-arginine-CDs sensitized TiO2-based solar cells showed the highest efficiency of (0.362 ± 0.007) %, which was the best efficiency of all fabricated solar cells. By surveying a range of biomass-derived carbon dots, and demonstrating a clear link between functionalisation and solar cell performance, this PhD research project provides a guide to direct future development of low-cost, biomass-derived sensitizers for nanostructured solar cells.
154

Immunofluorescent study of IgM in the canine small intestine

Willard, Michael D January 2011 (has links)
Typescript. / Digitized by Kansas Correctional Industries
155

Development of Fluorescent Probes for Imaging Synaptic Activity at Individual Presynaptic Terminals

Merchant, Paolomi January 2014 (has links)
This thesis describes the design, synthesis and development of fluorescent probes to monitor synaptic transmission at individual presynaptic terminals in the mouse brain. Two distinct approaches to accomplish this are discussed. The first approach seeks to monitor synaptic activity by using pH-sensitive endocytic membrane probes to label active presynaptic terminals. The second approach seeks to monitor synaptic activity by loading small fluorescent molecules into presynaptic vesicles and studying their evoked release upon stimulation. The first chapter of this thesis describes currently available techniques that are used to study synaptic transmission in the brain. The use of electrochemical techniques is discussed and the use of fluorescent reporters is introduced as a means to image single synapses with high resolution. Chapter II of this thesis describes the rational design of pH-sensitive membrane probes for labeling recycling vesicles. The synthesis, photophysical properties and biological characterization of these probes are described. Although these probes proved to be too lipophilic to work well in the brain tissue and neuronal culture, their use on the cell surface is demonstrated. Furthermore, the structure activity relationship established by this library of probes can be used to direct the future development of pH-sensing endocytic dyes. Chapter III and IV of this thesis describe the development of new generations of Fluorescent False Neurotransmitters (FFNs) for imaging vesicular content release from individual presynaptic terminals in the brain. Chapter III introduces a novel imaging agent, FFN200, for monitoring and quantifying dopamine release from individual synaptic terminals in the mouse brain. Chapter IV describes the exploration and screening of small fluorescent molecules in the mouse brain for the purpose of developing FFNs at synaptic terminals other than dopamine. FFN7122 is introduced as the first FFN to be developed for terminals outside of dopamine. FFN7122 is shown to be a marker for glutamatergic terminals in the hippocampus, dorsal striatum, and motor cortex of the mouse brain. The evoked release of this probe from presynaptic vesicles is demonstrated and two hypotheses for its uptake mechanism are proposed.
156

Localização e dinâmica de sondas fluorescentes em modelos de membranas: estudos por dinâmica molecular e anisotropia de fluorescência resolvida no tempo / Location and dynamics of fluorescent probes in model membranes: study by Molecular Dynamics and Time-resolved Fluorescence Anisotropy.

Preza, Sérgio Leandro Espindola 27 August 2013 (has links)
As moléculas AHBA (2-Amino-N-hexadecil-benzamida) e DPH (1,6-Difenil-1,3,5- hexatrieno) são sondas fluorescentes com características particulares, comumente utilizadas para monitorar diferentes regiões das bicamadas lipídicas, no entanto, pouco se sabe sobre a mobilidade e dinâmica destas sondas em membranas e quais os principais fatores que influenciam as suas interações com solventes polares e apolares. Esta tese teve por objetivo estudar essas sondas em diferentes ambientes, para ampliar o entendimento de suas estruturas, mobilidade e dinâmicas rotacionais em diferentes solventes e em bicamadas lipídicas. Utilizou-se a técnica de Dinâmica Molecular (DM) para obter as trajetórias das sondas em caixas com diferentes proporções de água e 1,4-dioxano e também nas membranas de POPC (1-palmitoil-2-oleoil-sn-glicerol-3-fosfocolina) e DMPC (1,2-dimiristoil-sn-glicerol-3-fosfocolina). Com as trajetórias geradas, foram analisadas a estrutura, a solvatação e a dinâmica rotacional das sondas em misturas de solventes e membranas modelo. Para as DM em solventes, os resultados indicaram um comportamento atípico das duas moléculas, com a diminuição da interação com a água a medida que diminuía-se a proporção de 1,4-dioxano na caixa. Em membranas, a localização e mobilidade da sonda AHBA apresentaram comportamento semelhante em POPC e DMPC, com os tempos obtidos a partir da curva de autocorrelação rotacional do seu dipolo comparáveis aos medidos pelo experimento de anisotropia de fluorescência resolvida no tempo. Já para o DPH, os resultados em POPC indicaram que a sonda alinha-se paralelamente à superfície da membrana e apresenta muito mais liberdade para se movimentar quando comparada às aos resultados de DM em DMPC, onde a sonda se alinhou paralelamente às caudas dos fosfolipídios e teve uma restrição bem maior para seus movimentos. Os tempos de correlação rotacional do seu dipolo em POPC apresentaram boa concordância com os obtidos experimentalmente. Em contrapartida, os resultados em DMPC mostraram que é preciso mais tempo de DM para comparação entre a correlação rotacional teórica e a experimental, por ser um sistema mais compactado. De qualquer forma, os resultados indicam que a DM é uma técnica promissora para modelagem da dinâmica rotacional de moléculas em membranas. / AHBA (2-Amino-N-hexadecyl benzamide) and DPH (1,6-diphenyl-1,3,5-hexatriene) molecules are fluorescent probes with particular characteristics commonly used to monitor different regions of the lipid bilayers, however, little is known about the mobility and dynamics of these probes in membranes and the main factors that influence their interactions with polar and non-polar solvents. This thesis aimed to study these probes in different environments, to extend the understanding of their structures, mobility and rotational dynamics in different solvents and in lipid bilayers. It was used the Molecular Dynamic (MD) technique to obtain the trajectories of the probes in boxes with different proportions of water and 1,4-dioxane, and also in membranes of POPC (1-palmitoyl-2- oleoy l-sn-glycerol-3 -phosphocholine) and DMPC (1,2-dimyristoyl-sn-glycerol-3-phosphocholine). With the trajectories generated, the structure, solvation and rotational dynamics of the probes were analyzed in solvent mixtures and model membranes. For simulations in solvents, the results indicate an atypical behavior of the two molecules with the decrease of the interaction with water, when decreased the proportion of 1,4-dioxane in the box. In membranes, the location and mobility of AHBA showed similar behavior for on DMPC and POPC, with the decay times obtained from the dipole rotational autocorrelation curve comparable to experimental time-resolved fluorescence anisotropy data. For the DPH in POPC, the results indicated that the probe is aligned parallel to the membrane surface and is much more free to move when compared to simulations in DMPC, where the probe is aligned parallel to the tails of the phospholipids, and had a greater restriction for their movement. The rotational correlation times of their dipole in POPC showed good agreement with those obtained experimentally. On the other hand, the results in DMPC, showed that it needs more time of simulation for comparison between the theoretical and experimental rotational correlation, because it a more compressed system. In any way, the results indicate that MD is a promising technique for modeling the rotational dynamics of molecules in membranes.
157

Use of fluorescent imaging to monitor drug responses in mouse models of tumourigenesis

Balderstone, Lucy Anne January 2014 (has links)
As our understanding of the complexities of cancer biology has increased, the ability to exploit unique features of tumour cells with molecularly targeted therapies has become a reality. However, despite unprecedented volumes of new molecules in clinical trials, the number of highly effective drugs approved by the regulatory authorities remains disappointingly low. Moreover, oncology drug development is plagued by high levels of attrition in late phase clinical development. Failure due to poor efficacy and toxicity issues are not believed to be a result of the development of molecules with inadequate pharmaceutical properties, but rather due to a lack of understanding of their full mechanism of action. All of this points to imprecise analysis of the drugs during the preclinical phase, highlighting the need for better preclinical drug development tools. Animal models provide a key preclinical tool, and as a therapeutic area, oncology is characterised by models which are not predictive of the true human pathology. Overexpression of the human epidermal growth factor receptor two (HER2) oncogene, and inactivation of the phosphatase and tensin (PTEN) tumour suppressor, are two important events in human breast cancer. A novel conditional mouse model driven by overexpression of HER2 coupled with / without the loss of PTEN has been characterised to interrogate the importance of these two cellular perturbations. Multifocal tumours arose in mice from both lines, while luminal tumour characteristics were shown to be reduced and basal characteristics increased with a reduction in PTEN expression. Disruption of PTEN rapidly accelerated tumour onset (from 138 to 82 days) and tumour growth (with the time from tumour onset to maximum tumour size reduced from 38 to 21 days), significantly reducing overall survival (from 165 to 102 days). The ability of tumour cells to colonize the lungs was not significantly affected by the loss of PTEN. Tumours arising in both mice genotypes were utilized to generate cell lines. These failed to provide an in vitro representation of the tumours, and found little utility in drug efficacy studies with HER family targeted agents, a situation which could be improved by the use of different culture methods. Since suppression of apoptosis is a hallmark of human cancer, and a desired endpoint of many anticancer therapies is the induction of cell death, the generation of cell lines inherently capable of sensing caspase-mediated apoptotic cell death would be a valuable drug development tool. Given that fluorescence imaging is also emerging as a potentially powerful modality for preclinical drug development, a novel fluorescent in house apoptosis reporter construct was generated (pCasFSwitch). Initial validation of pCasFSwitch by transient transfection into murine mammary carcinoma cells proved difficult due to transfection associated toxicity, yet proof-of-principle was indicated. Transfer of pCasFSwitch into a retroviral backbone vector enabled the generation of stably transfected squamous carcinoma cells more suitable for further analysis. Incubation of lysates from these cells with recombinant enzymes revealed the construct could be cleaved by caspase-3, but not by other members of the cysteine protease family. Furthermore, assessment of apoptosis levels in the cells upon staurosporine treatment proved the utility of the construct to quantify cell death, and was validated against data generated with a commercial competitor, NucView. Further comparison of the specificity of the imaging agents using caspase inhibitors was limited by the functionality of currently available inhibitors, but did reveal that in common with NucView, construct quantified levels of apoptosis were affected by inhibition. This thesis details the development of two preclinical drug development tools. A novel mouse model enables biological interrogation of two key events in human breast carcinogenesis. Since PTEN loss is associated with resistance to HER2 targeted therapies, it is ideally suited for efficacy testing to overcome such resistance. The in house fluorescent apoptosis imaging agent allows a temporal read-out of drug effects in live single cells. While the use of intravital imaging of stable cell lines implanted under imaging windows would allow in vivo validation of in vitro data. Taken together, such facilitation of thorough evaluation of therapies at the preclinical stage, will reduce the adverse effects felt by the pharmaceutical industry of failure late in the drug development pipeline.
158

Molecular mechanisms of neuronal homoeostasis in vivo

Seo, Sang soo January 2016 (has links)
Homeostatic plasticity is important in neurobiology for stabilising neuronal networks in the face of Hebbian forms of synaptic plasticity that are thought to mediate memory storage. Impairment of homeostatic plasticity has also been implicated in neurological diseases such as Rett syndrome and fragile X syndrome. Homeostatic plasticity can be achieved through scaling of the strength of synaptic connections between neurones or by changes in intrinsic excitability. While homeostatic plasticity has been studied mainly using in vitro preparations, it is for the most part not known whether changes of neural activity in vivo induce homeostatic changes. The molecular pathway responsible for homeostatic plasticity still remains unclear. In this thesis, I have used stereotaxic surgery to over express Kir2.1, an inwardly rectifying potassium channel, in vivo in the brains of adult mice. I show that the expression of Kir2.1 through adeno-associated virus (AAV) does not cause any adverse effects in the dentate gyrus nor the CA1 of the mouse hippocampus. I go on to use slice patch clamp methods to measure the change in electrical properties of granule cells in the dentate gyrus and pyramidal cells in CA1 caused by expression of Kir2.1. I show that the excitability of neurones expressing Kir2.1 was reduced compared to control neurones. By 2 weeks after virus injection the neurones showed homeostatic plasticity in response to Kir2.1 over expression. Interestingly, the mechanism of adaptation was different in different types of cells; dentate gyrus granule cells adapted through change in their intrinsic excitability, whereas CA1 pyramidal cells adapted by modifying the strength of their synaptic inputs. To establish whether induction of homeostatic plasticity is associated with changes in gene expression I used fluorescent activated cell sorting (FACs) to isolate pure population of neurones infected with viruses. I then sequenced RNA extracted from neurones expressing Kir2.1 and control neurones. Analysis of the RNAseq data revealed molecular candidates involved in homeostatic plasticity. In summary, I show that Kir2.1 over expression causes change in excitability and subsequent homeostatic plasticity in vivo. The mechanism of adaptation differs between cell types. RNAseq results identify novel candidates for future investigation.
159

Síntese de seleno- e teluro-cumarinas para estudos de emissão e supressão de fluorescência e aplicações analíticas e/ou biológicas / Synthesis of selenium- and tellurium-coumarins for fluorescence emission and supression studies and analytical and/or biological applications

Cavalcante, Victor Fernandes 17 July 2017 (has links)
Nos últimos anos, o desenvolvimento e a aplicação de sondas contendo átomos de calcogênio, expandiu significativamente, devido principalmente à reatividade dos elementos dessa família que são facilmente oxidados aos seus correspondentes calcogenóxidos e calcogenonas, permitindo diversas aplicações, especialmente em sistemas biológicos. A inserção de átomos pesados como os calcogênios, ao núcleo fluorofórico, leva à supressão de fluorescência, processo conhecido por \"efeito do átomo pesado\" também atribuída por Transferência Eletrônica Fotoinduzida (Photoinduced Electron Transfer). A oxidação do calcogênio ao correspondente calcogenóxido ou calcogenona inibe esse processo reestabelecendo a fluorescência. Todavia, moléculas com núcleo fluorofórico contendo, principalmente, os átomos de selênio e telúrio tem suas propriedades fotofísicas pouco investigadas, se comparado com moléculas contendo o átomo de enxofre. Neste trabalho foi tratado do desenvolvimento de metodologias de preparação de sondas contendo os átomos de selênio (II) e telúrio (II), mais especificamente, através da funcionalização da 7-hidróxi-4-metil-cumarina. Foram preparadas 6 calcogeno-cumarinas inéditas em rendimentos que variaram de 27% a 69%. Esses compostos apresentaram comportamento fluorescente condizente com o que havia sido idealizado: suas propriedades fotofísicas foram determinadas em acetonitrila, a 298 K, observando-se máximos de absorção em 290 nm e em 320 nm e máximo de emissão de fluorescência em 380 nm. Demais propriedades fotofísicas como rendimento quântico e tempo de vida do estado excitado também foram obtidas. Também foram realizados estudos com os compostos sintetizados frente a espécies oxidantes endógenas (ClO- e H2O2) permitindo inicializar estudos em sistemas celulares, observando-se que as cumarinas contendo o átomo de telúrio (II) demonstraram resultados promissores para seu uso como sondas fluorescentes. / In the last years, the development and application of chalcogen-containing dyes has expanded significantly, mainly due to the chalcogen elements reactivity that are are easily oxidized to their correspondent chalcogenides and chalcogenones, allowing several applications, especially in biological systems. The insertion of heavy atoms such as chalcogens to the fluorophoric core of the molecule leads to a fluorescence suppression, process known as \"heavy atom effect\", also attributed as Photoinduced Electron Transfer (PeT). The chalcogen oxidation to its correspondent chalcogenoxide or chalcogenone inhibts this process reestablishing the fluorescence of the molecule. However, fluorophoric molecules containing selenium and tellurium are not very investigated towards its photophysical properties if compared to their sulfur analogues. It is discussed in this this work, the development of methodologies for the preparation of probes containing selenium (II) and tellurium (II), more specifically, through the functionalization of the 7-methyl-4-hydroxi-coumarin. Six novel chalcogen-coumarins were prepared presenting yields varying from 27% to 69%. These compounds presented consistent fluorescent behavior for what it was predicted: their photophysical properties were determined observing absorption maxima at 290 nm and 320 nm and fluorescence maxima at 380 nm. Other photophysical properties such as quantum yields and excited state lifetime were also obtained. Studies with the synthetized compounds related to their behavior against endogenous oxidant species (ClO- and H2O2) were also conducted, allowing initial studies in cell systems, which demonstrated that the tellurium (II) derived coumarins presented promising results as fluorescent probes
160

The Design, Construction, and Thermal Diffusivity Measurements of the Fluorescent Scanning Thermal Microscope (FSTM)

Hayden, Samuel Hunter 01 December 2018 (has links)
Over the life of nuclear fuel, inhomogeneous structures develop, negatively impacting thermal properties. New fuels are under development, but require more accurate knowledge of how the properties change to model performance and determine safe operational conditions. Measurement systems capable of small–scale, pointwise thermal property measurements and low cost are necessary to measure these properties and integrate into hot cells where electronics are likely to fail during fuel investigation. This project develops a cheaper, smaller, and easily replaceable Fluorescent Scanning Thermal Microscope (FSTM) using the blue laser and focusing circuitry from an Xbox HD-DVD player. The FSTM also incorporates novel fluorescent thermometry methods to determine thermal diffusivity. The FSTM requires minimal sample preparation, does not require access to both sides of the sample, and components can be easily swapped out if damaged, as is likely in irradiated hot cells. Using the optical head from the Xbox for sensing temperature changes, an infrared laser diode provides periodic heating to the sample, and the blue laser induces fluorescence in Rhodamine B deposited on the sample's surface. Thermal properties are fit to modulated temperature models from the literature based on the phase delay response at different modulated heating frequencies. With the FSTM method, the thermal diffusivity of a 10 cent euro coin was found to be 21±5 mm2/s. This value is compared to Laser Flash Analysis and a Thermal Conductivity Microscope (which used thermoreflectance a method), which found the thermal diffusivity to be 30.4±0.1 mm2/s and 19±3 mm2/s, respectively. The hardware and instrumentation performed as expected, but the property measurements show that the device is not yet optimized to provide accurate measurements with current heat transfer models. Future work is discussed to investigate the accuracy and necessary modeling adjustments, as well as refinements to the instrumentation.

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