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1
Hatzios, Stavroula K. (Stavroula-Artemis K. ). „Human alkaloid biosynthesis : chemical inducers of Parkinson's disease?“ Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/36162.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2005.Includes bibliographical references (leaves 26-29).
The occurrence of certain alkaloids in the human brain appears to be associated with the onset of Parkinson's disease (PD). Recently, a human protein bearing homology to an alkaloid synthase in plants was identified. This protein, termed BSCv, may catalyze alkaloid formation in humans. If such activity is confirmed, regulation of BSCv through the use of small molecule inhibitors could provide novel drug therapies for PD patients. This paper describes the first heterologous expression and purification of this transmembrane protein and examines its biological function through a series of enzyme assays. The assays used to evaluate enzyme activity were modeled after the Pictet-Spengler condensation catalyzed by the plant enzyme. Substrates were selected based on their potential to form alkaloids previously identified in central nervous system tissue. Product formation was monitored via high-performance liquid chromatography. Preliminary data suggest that BSCv does not function as an alkaloid synthase. However, further studies are needed to ascertain such conclusions. Alternative detergents should be evaluated to assess their influence on enzyme activity. The use of an expanded substrate pool may also provide insight into protein function since substrate specificity may have restricted product formation in the performed assays. Finally, incubation of BSCv with rat brain extract, which contains another species homologue of the protein, could provide insight into its natural substrates. If these studies are unsuccessful, consideration should be given to the possibility that BSCv may function as a receptor. Once the mechanistic and structural properties of the plant enzyme are elucidated, it may be possible to take a more direct approach to the characterization of its human homologue.
by Stavroula K. Hatzios.
S.B.
2
Ogunleye, Olatokumbo Olajumi Luca. „Chemical Inducers of Dimerization for Profiling Protein Kinases“. Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/579019.
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Chemical inducers of dimerization (CID) represent an important tool that has been implemented in numerous biological applications namely protein functions, protein stability, signal transduction, gene transcription, etc. Most generally CIDs are defined as bivalent molecules capable of inducing proximity between two targeted proteins. This proximity can in turn promote or disfavor a certain biological activity. Cell permeable small molecules in particular represent a very effective method to induce precise temporal and spatial control over a specific biological target. Our lab has devoted much effort in studying and elucidating the activity and functions of protein kinases, which represent a very attractive therapeutic target for the treatment of cancer and many other disorders. Towards this goal we have developed a general CID enabled three-hybrid split-luciferase methodology for the investigation of kinase-inhibitor interactions in vitro. We demonstrate that by modulating the kinase-ligand affinity of the CID we are able to successfully profile many structurally non-related protein kinases. We also investigate the use of weaker affinity kinase ligands to allow competitive displacement of CID by the selected inhibitor. In addition we report the design, synthesis and applications of novel CID's for the profiling of kinase inhibitors in mammalian cells and we demonstrate the feasibility of the assay to be used as a new platform for the discovery of cell permeable kinase inhibitors. Finally, we report a new ligand-gated split-kinase that can be selectively activated by photocleavable inducers of dimerization. We further prove how the activity of split-proteins can be deactivated with temporal control with use of non DNA damaging UV radiation.
3
Sarkar, Tanushree. „Studies on resistance of trichosanthes dioica and their induction with chemical inducers against fungal pathogen“. Thesis, University of North Bengal, 2021. http://ir.nbu.ac.in/handle/123456789/4760.
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Petrie, Christopher David. „Effectiveness of Chemical Inducers on Settling and Settlement of Scleractinian Coral Larvae on Various Substrates“. NSUWorks, 2000. http://nsuworks.nova.edu/occ_stuetd/310.
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Sessile marine invertebrates often exhibit non-random distributions both horizontally and vertically. The larvae of scleractinian corals settle and metamorphose in response to numerous environmental stimuli including substrate composition and the presence of chemical signals, such as extracts of certain red crustose coralline algae. In this study, seven different substrates common to past research efforts were infused with an extract from the red crustose coralline alga, Hydrolithon boergesenii, and placed on the bottom of the ocean, as were similar plates containing no extract. Substrate plates were deployed during the months following the August 1999 coral-spawning event on a reef near Fort Lauderdale, Florida.
Larvae settled on plates placed on the shoreward side of the reef 2.12 times as often as plates placed on the seaward side of the reef. This difference was significant whether the plates contained algal extracts (p=0.004 by two-way ANOVA) or did not contain algal extracts (P = 0.003 by Two-way ANOVA). Reef location also influenced settling independent of plate composition. Peak settlement was observed on unglazed ceramic tiles on the shoreward side of the reef, while the lowest settlement was observed on glass plates on the shoreward side of the reef. Two-way ANOVA with replication showed significant differences in plate material (P = 0.031), presence or absence of algal extract (P = 0.002), and in the interaction of these variables (P = 0.009). Larvae settled on plates containing the algal extracts 2.60 times as often as plates without algal extract.
Multiple analysis of variance (MANOVA) for the interaction of all variables indicated significant interactions for extract presence (P = 0.002), reef zone location (P = 0.036), and plate material (P = .031). The interactions between algal extract presence and reef zone were also significant (P = 0.009), as were the interactions between plate material and algal extract presence (P = 0.009). Simultaneous MANOVA for all variables was not significant (P = 0.071), probably due to large variation in settling plate composition, variation in the concentration and activity of the algal extracts applied to the plates, as well as variation in the microhabitat across the reef.
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Robinson, Michael W. „Synthesis and Evaluation of Inducers of Methuotic Cell Death and Preliminary Identification of Their Cellular Targets in Glioblastoma Cells“. University of Toledo Health Science Campus / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=mco1372430209.
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Ruz, Estévez Lídia. „Improvement of strategies for the management of fire blight (Erwinia amylovora). Evaluation and optimization of physical and chemical control methods, and use of decision support systems“. Doctoral thesis, Universitat de Girona, 2003. http://hdl.handle.net/10803/7923.
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El foc bacterià és una malaltia que afecta a plantes de la família de la rosàcies, causada pel bacteri Erwinia amylovora. El seu rang d'hostes inclou arbres fruiters, com la perera, la pomera o el codonyer, i plantes ornamentals de gran interès comercial i econòmic. Actualment, la malaltia s'ha dispersat i es troba àmpliament distribuïda en totes les zones de clima temperat del món. A Espanya, on la malaltia no és endèmica, el foc bacterià es va detectar per primer cop al 1995 al nord del país (Euskadi) i posteriorment, han aparegut varis focus en altres localitzacions, que han estat convenientment eradicats. El control del foc bacterià, és molt poc efectiu en plantes afectades per la malaltia, de manera que es basa en mesures encaminades a evitar la dispersió del patogen, i la introducció de la malaltia en regions no endèmiques. En aquest treball, la termoteràpia ha estat avaluada com a mètode d'eradicació d'E. amylovora de material vegetal de propagació asimptomàtic. S'ha demostrat que la termoteràpia és un mètode viable d'eradicar E. amylovora de material de propagació. Gairebé totes les espècies i varietats de rosàcies mantingudes en condicions d'humitat sobrevivien 7 hores a 45 ºC i més de 3 hores a 50 ºC, mentre que més d'1 hora d'exposició a 50 ºC amb calor seca produïa danys en el material vegetal i reduïa la brotació. Tractaments de 60 min a 45 ºC o 30 min a 50 ºC van ser suficients per reduir la població epífita d'E. amylovora a nivells no detectables (5 x 102 ufc g-1 p.f.) en branques de perera.
Els derivats dels fosfonats i el benzotiadiazol són efectius en el control del foc bacterià en perera i pomera, tant en condicions de laboratori, com d'hivernacle i camp. Els inductors de defensa de les plantes redueixen els nivells de malaltia fins al 40-60%. Els intervals de temps mínims per aconseguir el millor control de la malaltia van ser 5 dies pel fosetil-Al, i 7 dies per l'etefon i el benzotiadiazol, i les dosis òptimes pel fosetil-Al i el benzotiadiazol van ser 3.72 g HPO32- L-1 i 150 mg i.a. L-1, respectivament. Es millora l'eficàcia del fosetil-Al i del benzotiadiazol en el control del foc bacterià, quan es combinen amb els antibiòtics a la meitat de la dosi d'aquests últims. Tot i que l'estratègia de barrejar productes és més pràctica i fàcil de dur a terme a camp, que l'estratègia de combinar productes, el millor nivell de control de la malaltia s'aconsegueix amb l'estratègia de combinar productes.
Es va analitzar a nivell histològic i ultrastructural l'efecte del benzotiadiazol i dels fosfonats en la interacció Erwinia amylovora-perera. Ni el benzotiadiazol, ni el fosetil-Al, ni l'etefon van induir canvis estructurals en els teixits de perera 7 dies després de la seva aplicació. No obstant, després de la inoculació d'E. amylovora es va observar en plantes tractades amb fosetil-Al i etefon una desorganització estructural cel·lular, mentre que en les plantes tractades amb benzotiadiazol aquestes alteracions tissulars van ser retardades.
S'han avaluat dos models (Maryblyt, Cougarblight) en un camp a Espanya afectat per la malaltia, per determinar la precisió de les prediccions. Es van utilitzar dos models per elaborar el mapa de risc, el BRS-Powell combinat i el BIS95 modificat. Els resultats van mostrar dos zones amb elevat i baix risc de la malaltia. Maryblyt i Cougarblight són dos models de fàcil ús, tot i que la seva implementació en programes de maneig de la malaltia requereix que siguin avaluats i validats per un període de temps més llarg i en àrees on la malaltia hi estigui present.
Fire blight, caused by the bacterium Erwinia amylovora, is a serious disease of rosaceous plants that affects fruit trees such as pear, apple or quince, and ornamental plants with great commercial and economic interest. The disease is spread and well distributed in all temperate regions of the world. In Spain, where the disease is non endemic, fire blight was first detected in 1995 in the North of the country (Euskadi) and later, several new outbreaks have appeared in other locations that have been properly eradicated. Control of fire blight is very slightly effective in affected plants and is based on measures to avoid the spread of pathogen, and the introduction of disease in non-endemic regions.
In this work, thermotherapy has been evaluated as a method for eradication of E. amylovora from symptomless propagating plant material. It has been demonstrated that heat is a viable method for eradicating E. amylovora from the propagation material of the pear. Almost all rosaceous species and cultivars maintained under moist conditions survived 7 hours at 45 ºC and up to 3 hours at 50 ºC, while more than 1 hour of exposure at 50 ºC under dry heat injured plants and reduced shooting. However, 60 min at 45 ºC or 30 min at 50 ºC were enough to reduce epiphytic E. amylovora population on pear budwoods to non-detectable level (5 x 102 cfu g-1 f.w.).
Phosphonate derivatives and benzothiadiazole were effective in fire blight control in pear and apple, under laboratory, greenhouse and field conditions. Plant defense inducers reduced disease levels to 40-60%. The minimal time intervals to achieve the best control of disease were 5 days for fosetyl-Al, and 7 days for ethephon and benzothiadiazole, and the optimal doses of fosetyl-Al and benzothiadiazole were 3.72 g HPO32- L-1 and 150 mg a.i. L-1, respectively. The efficacy of fosetyl-Al and benzothiadiazole in fire blight control was improved when consecutively sprayed (combined strategy) with a half-reduced dose of antibiotics. Although the mixed strategy is more practical and easier to apply in the orchard than the combined one, the best level of fire blight control was achieved with the combined strategy.
The effect of benzothiadiazole and phosphonates in Erwinia amylovora-pear interaction was analyzed at histological and ultrastructural level. Neither benzothiadiazole, nor fosetyl-Al, nor ethephon induced structural changes in pear leaf tissues 7 days after their application. However, after E. amylovora inoculation structural cell disorganization was observed in fosetyl-Al and ethephon-sprayed plants, while in benzothiadiazole-sprayed plants these tissue alterations were delayed.
Two predictive models (Maryblyt and Cougarblight) were evaluated in an orchard naturally affected by fire blight in Spain, to determine the accuracy of the predictions. The combined BRS-Powell model and the modified BIS95 model were also evaluated. Results showed two clearly differentiated geographical areas with high and low fire blight risk. Maryblyt and Cougarblight are easy models to use, but their implementation in disease management programs must be evaluated and validated for more seasons and in areas where the disease is present.
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Casa, Maria V. „Accumulation of Emerging Chemicals in Southern Hemisphere Humpback Whales (Megaptera novaeangliae) and Species-specific Chemical Effect Assessment“. Thesis, Griffith University, 2022. http://hdl.handle.net/10072/411890.
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Millions of hazardous chemicals are synthesized each year. Their release often represents a risk for the environment and biota. As part of a broader effort to investigate the accumulation and effect of emerging chemicals of concern in the Antarctic sea-ice ecosystem, this thesis focuses upon exposure and effect assessment in southern hemisphere (SH) humpback whales (Megaptera novaeangliae). Cetaceans traditionally represent ideal targets for exposure assessment to Persistent Organic Pollutants (POPs), that is chemicals identified as persistent, bioaccumulative, toxic and capable of long-range environmental transport. Their extended life span and high proportion of body fat render cetaceans susceptible to accumulation of elevated burdens. Southern hemisphere humpback whales feed almost exclusively on Antarctic krill (Euphasia superba) and thus represent second order consumers of the Antarctic sea-ice ecosystem. Exposure assessment consisted of targeted analysis of short-chain chlorinated paraffins (SCCPs) included under the Stockholm Convention (SC) in 2017, and brominated structures listed in 2009 as well as novel, naturally occurring brominated structures, already detected at lower trophic levels of the Antarctic sea-ice ecosystem. SCCPs were targeted in stranded specimens and were detected in 77.7 % of samples, representing the first detection of SCCPs in any mysticetes or any Antarctic foraging marine mammal.Blubber samples from free-swimming and stranded specimens were dedicated to the analysis of the modern category of POPs, polybromodiphenilethers (PBDEs), and a naturally occurring brominated compound, 2,4,6-tribromoanysole (TBA), the chemical structure of which closely resembles PBDEs, flagging the possibility of similar toxic action. Humpback whale PBDEs profiles were dominated by tetra- and penta- congeners, supporting a single previous study on PBDE accumulation in Southern hemisphere humpback whales feeding in the Antarctic Peninsula region. Further, the detection of decaBDE adds support for the local emissions or particle bound transport to Antarctica. PBDE congeners were detected in all samples analysed, whilst TBA was 88 detected in 80% of samples. Upon establishing accumulation of three novel chemical groups in the Antarctic sea-ice ecosystem, species-specific effect assessment was performed through cytotoxicity assessment implementing the newly established immortalized humpback whale fibroblast cell line (HuWaTERT). Two endpoints were targeted, namely membrane integrity and metabolic activity following 24h exposure to an SCCP cocktail, BDE-47, BDE-99, TBA. Each assay also incorporated the assay reference chemical, p,p’-DDE. The four chemicals did not show a dose-dependent response comparable to the one produced by the reference chemical. Whilst p,p’-DDE induced a decrease of both metabolic activity and membrane integrity, the cell response to BDE-99 indicated a positive, or potentially hermetic relationship with regards to the metabolic activity, warranting further investigation of underlying mechanisms.The final thesis chapter explores the unique potential of HuWaTERT for the generation of induced pluripotent stem cells (iPSCs). The main objective of this work was to generate a source of a number of different cell lines from the iPSCs, that could be applied for a more tailored approach to in-vitro chemical effect evaluation to fill the gap currently existing in the field of cetacean toxicology. The re-generation trial involved the use of the Sendai virus, which induces the de-differentiation mechanism in HuWaTERT to become iPSCs without integrating into the cell genome. After successfully generating a number of iPC colonies, the cells ultimately did not thrive, likely due to a fungal infection. Overall, this thesis combines both chemical exposure and effect assessment of novel chemical groups, for unique insight into chemical accumulation and impact in the Antarctic sea-ice ecosystem. The work provides new information regarding the range of chemicals that Antarctic consumers are exposed to, a reflection of hemispheric chemical usage and local input, and also contributes invaluable species-specific in vitro toxicity assessment data, which represents a critical research gap for cetacean chemical impact assessment.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
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Cross, David Henry. „Laser induced chemical vapour deposition of aluminium“. Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/815.
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9
Preece, N. E. „Studies on chemical-induced autoxidation in vivo“. Thesis, University of Surrey, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376361.
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Yellowhair, Monica. „The Chemical-Induced Genotoxicity of Depleted Uranium“. Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202509.
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Uranium has been mined for many years and used for fuel for nuclear reactors and materials for atomic weapons, ammunition, and armor. While the radioactivity associated with uranium mining has been linked to the development of lung and kidney cancers, and leukemia, little is known about the direct chemical genotoxicity of uranium. The overall hypothesis of the current research is that uranium can produce DNA damage by chemical genotoxicity mechanisms. Three specific aims were tested. In Aim 1, specific DNA lesions caused by direct interaction of uranium and DNA were investigated. Chinese Hamster Ovary cells (CHO) with mutations in various DNA repair pathways were exposed to 0 – 300 μM of soluble depleted uranium (DU) as uranyl acetate (UA) for 0 – 48 hr. Results indicate that UA readily enters CHO cells, with the highest concentration localizing in the nucleus. Clonogenics assay shows that UA is cytotoxic in each cell line with the greatest cytotoxicity in the base excision repair deficient EM9 cells and the nuclear excision repair deficient UV5 cells compared to the non-homologous end joining deficient V3.3 cells and the parental AA8 cells after 48 hr. This indicates that UA is forming DNA adducts that may be producing single strand breaks through hydrolysis rather than double strand breaks in CHO cells. Fast Micromethod® results indicate an increased amount of single strand breaks in the EM9 cells after 48 hr UA exposure compared to the V3.3 and AA8 cells. In Aim 2, the role of oxidative stress in producing DNA lesions was determined. Cellular oxidative stress has been implicated in the genotoxicity of many heavy metals as a mechanism of induced DNA damage. To investigate this possible mechanism, human bronchial epithelial cells (16HBE14o⁻) were exposed to 30 ppb (0.13 μM U) UA for 2 – 24 hr. UA did not significantly induce oxidative stress compared to untreated cells at 3 – 4 hr time points. These results suggest that cellular oxidative stress is not a major pathway of DU genotoxicity at low concentrations. In Aim 3, DNA damage response to uranium-induced DNA damage was investigated. It has been widely reported that metals can be genotoxic by inhibiting DNA repair. Cultured cells were co-exposed to 0.13 μM UA in the presence of 0 – 25 μM of etoposide for 0 – 48 hr. Results indicate that UA inhibited double strand break repair. Coexposures of etoposide and UA synergistically induced cytotoxicity compared to individual treatments and untreated cells. Co-exposed UA and etoposide treated 16HBE14o⁻ cells exhibited a decrease in phosphorylation of DNA repair proteins compared to etoposide treatments. Untreated and UA-treated 16HBE14o⁻ cells did not induce phosphorylation of DNA repair proteins. These results suggest that DU inhibits double strand break DNA repair at low concentrations in the presence of a known DNA double-strand damaging agent, etoposide. The inhibition of DNA repair by DU at environmentally relevant concentrations suggests a novel means by which uranium may exert its genotoxic effects. Results found at low dose exposures are not consistent with alterations seen with radioactivity, suggesting that the effects of uranium at low doses are due to its chemical genotoxic effects. Understanding how uranium reacts with DNA is important to better understand how this suspected carcinogen induces cancer and to help to elucidate mechanisms that produce cancers in people exposed to uranium.
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Wigenstam, Elisabeth. „Pathogenesis and treatment of chemical-induced lung injury“. Doctoral thesis, Umeå universitet, Institutionen för folkhälsa och klinisk medicin, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-52738.
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Inhalation of chemical substances can cause irritation to airways and in high doses acute airway injury. When mice are exposed to the alkylating nitrogen mustard analogue melphalan they develop an acute airway inflammation with a rapid influx of neutrophils to the lungs. The acute phase is followed by long-term respiratory complications characterized by bronchitis, lung fibrosis, and airway hyperreactivity. In this thesis, a mouse model for chemical airway inflammation was established and the effects on the lungs in a time span from 6 hours up to 3 months were investigated in order to study both acute effects and possible chronic injury. We find that treatment with corticosteroids, e.g. dexamethasone, effectively blocks the inflammatory reaction in several ways: Neutrophil influx to the lungs is diminished, the expression of the proinflammatory cytokines interleukin (IL) -6 and IL-1b is decreased and edema formation as well as development of lung fibrosis is mitigated. In acute airway inflammation we show that the antioxidant vitamin E can be used as a possible complement to corticosteroids but not as a replacement since it causes insufficient downregulation of the inflammatory response. We show the importance of the T lymphocytes as they play a prominent role in the pathogenesis of long-term lung injuries caused by melphalan. Especially the minor gd T cell subset is of major importance orchestrating a number of responses including the acute cytokine and neutrophil response and late-phase lung fibrosis. In order to find the critical time for dexamethasone treatment, mice were exposed to melphalan, treated with dexamethasone at specific time points and lung physiology and airway reactivity was measured in anaesthetized, tracheostomized mice using a small animal ventilator. From these results we conclude that an early treatment, i.e. within one hour after exposure, with dexamethasone is needed to prevent chronic lung injury. This thesis was undertaken with the main goal to better understand the pathogenesis of melphalan-induced airway inflammation. We believe that our findings have shed new light in this area of research and hope that this increased knowledge may be of future clinical use.
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Delacour, Quentin. „Light-induced protein degradation : a chemical biology approach“. Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066347/document.
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La régulation de la protéolyse est un outil efficace pour le contrôle de la fonction d'une protéine dans des cellules. Nous présentons dans ce travail une stratégie générique permettant d'activer la protéolyse de façon conditionnelle par la lumière, améliorant ainsi la résolution spatio-temporelle. Notre approche repose sur un système de dégradation inductible par l'auxine (AID), mis au point en transposant des composants de la voie de dégradation contrôlée par l'auxine existant chez les plantes dans des cellules de mammifères. Nous présentons une version optimisée du système AID qui a permis de diminuer de façon significative la stabilité de protéines cibles en présence d'auxine. Nous avons en parallèle développé un déclencheur de dégradation photo-activable sous la forme d'une auxine cagée. Une illumination courte et locale permet la libération efficace de l'auxine dans les cellules et induit la dégradation de protéine d'intérêt avec un bon contrôle spatiotemporel. Cette méthode générique a été utilisée dans des contextes nucléaires et cytoplasmiquesThe regulation of proteolysis is an efficient way to control protein function in cells. Here, we present a general strategy enabling to increase the spatiotemporal resolution of conditional proteolysis by using light activation as trigger. Our approach relies on the auxin-inducible degradation (AID) system obtained by transposing components of the plant auxin-dependent degradation pathway in mammalian cells. We developed an optimized version of the AID which enables to significantly destabilize target proteins in presence of auxin. Parallely, we developed a photoactivatable auxin that acts as a photoactivatable inducer of degradation. Upon local and short light illumination, auxin is released in cells and triggers the degradation of a protein of interest with spatiotemporal control. This generic method was implemented in nuclear and cytoplasmic contexts
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Wright, Andrew David. „Chemical ionization and collision induced dissociation mass spectrometry“. Thesis, University of Warwick, 1989. http://wrap.warwick.ac.uk/39043/.
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The work contained in this thesis covers two aspects of mass spectrometry, namely chemical ionization (CI) and collision induced dissociation (CIO). Chapter 2 deals with an investigation into the CI mass spectra of tetraisopropyl methylenebisphosphonate recorded using mixtures of argon and dimethylamine as the reagent gas. Comparison of the mixed gas spectra with those obtained using the individual gases revealed additional fragmentation in the case of the mixed gases. The conclusion drawn from the study is that the dilution of dimethylarnine with argon causes the formation of additional protonating species of lower proton affinity than dimethylamine which can undergo more exothermic proton transfer reactions with the sample. Chapter 3 reports a comprehensive study of the chemical ionization mass spectra of urethanes. Four main classes of fragment ions are found in the spectra and the mechanisms for their formation are postulated. Evidence for these mechanisms is obtained from parallel studies of methyl carbamates and from a CIO study. A study of the effects of the collision gas on the CIO mass spectra of leucine-enkephalin is presented in chapter 4. The collision gases used were helium, argon, krypton and carbon tetrafluoride The monatomic gases used cause more fragmentation of the peptide ion as the mass of the collision gas is increased. Conversely, when a poly atomic species is used, the CIO spectra resemble those acquired using a much less heavy target gas. Two possible explanations are proposed. Either the additional internal energy which would be expected to be transferred to the incident ion is absorbed by vibrational modes of the target molecule, or that the amount of energy transferred during the collision is dependent on the particular atoms of the colliding species rather than their overall masses. The final chapter of this thesis is a report of the development of new linked-scan equations for the detection of fragment ions resulting from CID in the first field-free region of a forward geometry mass spectrometer. These scan laws and terms relating to the size of the translational energy losses are incorporated into the calibration software for use with a commercial mass spectrometer.
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Kiss, Istvan Zoltan. „Advection and diffusion induced transport in chemical systems“. Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400945.
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Economides, Aristodemos G. „Chemical changes induced by fermentation with saccharomyces species“. Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292728.
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Vashchuk, Alina, Sviatoslav Motrunich und Maksym Iurzhenko. „Thermally induced chemical welding of epoxy-based films“. Thesis, National Aviation University, 2021. https://er.nau.edu.ua/handle/NAU/50610.
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1. Vakulenko I.O. Influence of chemical compounds on the forming of welding arc /
I.O. Vakulenko, S.O. Plitchenko, D.M. Makarevich // Science and transport progress. – 2014. -
№5. – Р. 92-100Chemical welding is a relatively new welding approach resulting from chemical reactions that occur at the interface opens the way towards assembly epoxybased materials without adhesives or molds
Хімічне зварювання є відносно новим підходом до зварювання, який базується на хімічних реакціях, які перебігають на межі розділу фаз, і відкриває можливість монтажу епоксидних матеріалів без клеїв та форм.
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Reding, Derek James. „Shock induced chemical reactions in energetic structural materials“. Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28174.
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Thesis (M. S.)--Aerospace Engineering, Georgia Institute of Technology, 2009.Committee Chair: Hanagud, Sathya; Committee Member: Kardomateas, George; Committee Member: McDowell, David; Committee Member: Ruzzene, Massimo; Committee Member: Thadhani, Naresh.
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Grantier, David Raymond. „Chemically induced raman scattering“. Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/30321.
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Rahman, Mahfuzar. „Nonmalignant health effects of arsenic exposure /“. Linköping : Univ, 1999. http://www.bibl.liu.se/liupubl/disp/disp99/Med612s.htm.
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Tiang, Jen. „Shear-induced crystallization of nucleated polymers“. Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=92255.
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Crystallization that occurs during or after a strong shear is important in polymer processing due to its strong effect on product properties and production rate. This study addresses several major gaps in our knowledge of this phenomenon by investigating shear-induced crystallization of nucleated isotactic polypropylenes by simultaneous measurement of light intensity and rheology using a sliding plate rheometer at high, uniform shear rates. An optical fiber probe was devised for the light intensity measurement. For the conditions studied, both measurements were found equally able to detect nascent crystalline structures, but light intensity is more suitable for monitoring changes during the early stages, whereas rheology is more useful for tracking the late kinetics. The relative influence of a melt-insensitive nucleating agent, molecular weight, shear rate, and strain were studied under isothermal, low-supercooling conditions following brief shearing. In contrast to that in quiescent crystallization, the nucleation pathway of nucleated polymers after strong shear was found to be governed not by the nucleating agent but by the molecular weight. The primary effect of shear was confirmed to be in inducing nucleation and is much weaker in changing growth kinetics. Shear and nucleating agent both shorten the induction time, but the effects were found not to be additive. With increasing shear rate or strain, crystallization was found to first accelerate as a result of the increase in the number of point-like nuclei, then saturate due to either slip or consumption of high-molecular weight components for the creation of nuclei, and finally accelerate again at the onset of the transition from spherulitic to highly oriented morphology. Both a critical shear rate and a critical strain are necessary to initiate this morphological transition. The product of shear rate and strain was found useful for describing the acceleration in crystallization associated with the increaseLa cristallisation sous ou après un cisaillement fort est importante dans les procédés de mise en forme des polymères dus à ses effets significatifs sur les propriétés du produit et sur le taux de production. Cette étude traite de plusieurs importantes lacunes dans notre connaissance de ce phénomène en étudiant la cristallisation induite par cisaillement des polypropylènes isotactiques contenant un agent nucléant par une mesure simultanée de l'intensité lumineuse et de la rhéologie en utilisant un rhéomètre à plaques parallèles à des taux de cisaillement élevés et homogènes. Une sonde à fibres optiques a été conçue pour mesurer l'intensité lumineuse. Pour les conditions étudiées, ces deux mesures se sont avérées être aussi bien en mesure de détecter des structures cristallines naissantes, mais l'intensité lumineuse est mieux adaptée pour surveiller les changements au cours des premiers stades de la cristallisation, considérant que la rhéologie est plus utile pour en suivre les derniers stades. L'influence relative d'un agent nucléant ne réagissant pas à la fusion, le poids moléculaire, le taux et la déformation du cisaillement ont été étudiés en conditions isothermes avec faible surfusion après un cisaillement bref. Si on la compare à une cristallisation en condition statique, la voie de la germination des polymères nucléés suite à un fort cisaillement est apparue être régie non pas par l'agent nucléant, mais par le poids moléculaire. Le principal effet du cisaillement a été confirmé être présent durant la germination induite et est beaucoup plus faible en changeant la cinétique de croissance. Le cisaillement et l'agent nucléant ont à la fois réduit le temps d'induction, mais les effets se sont révélés ne pas être cumulatifs. Avec l'augmentation du taux de cisaillement ou de la déformation, la cristallisation s'est avérée tout d'abord accélérée comme une conséquence de l'augmentation du
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Hopkins, John. „The laser induced chemical vapour deposition of gallium arsenide“. Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/1501.
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Randle, Laura Elizabeth. „Pharmacological and physiological protective mechanisms in chemical-induced hepatotoxicity“. Thesis, University of Liverpool, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420287.
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Walsh, Rachel J. „Chemical and biochemical aspects of drug-induced liver injury“. Thesis, University of Liverpool, 2010. http://livrepository.liverpool.ac.uk/1487/.
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Adverse drug reactions (ADRs) are a major obstacle for the development of new medicines. They are also a leading cause of patient morbidity and mortality. Although ADRs affect many different organs and bodily systems, drug induced liver injury has lead to the withdrawal of several drugs at the post licensing stage, and is a key cause of drug attrition. Many of the drugs that cause liver injury are thought to do so through metabolism to a reactive metabolite, exposure to which can cause modification of cellular proteins, leading to loss of function, and can result in a loss of cellular homoeostasis. It is therefore important to understand the chemistry and the downstream biochemical events associated with bioactivation. Information on the chemistry of metabolism coupled with mechanistic biomarkers reflective of certain pathways of hepatic injury would enable both researchers and physicians to predict and diagnose DILI, leading to the improvement of safe drug design. This thesis focuses firstly on the use of in vitro models and mass spectrometry to provide integrated data on the metabolism and toxicity of xenobiotics, using thiophene containing molecules as a paradigm. The thiophene ring has the potential to be bioactivated via S-oxidation and epoxidation pathways, and several thiophene containing drugs have been associated with drug induced liver injury. The investigations described intended firstly to elucidate the chemistry of methapyrilene bioactivation using mass spectrometry and hydrogen-deuterium exchange. The following two chapters aimed to establish a link between bioactivation and toxicity of thiophenes and to evaluate two in vitro models as tool for predicting DILI. The final experimental chapter aims to investigate the potential of ophthalmic acid (OA) to act as a serum biomarker reflective of depletion of hepatic levels of the protective tripeptide, glutathione (GSH). Disturbance of GSH levels through quenching of reactive metabolites can lead to disturbance of its anabolism and catabolism pathways. Indeed, serum OA levels, a GSH analog, have been shown to rise following hepatic GSH depletion. This work utilises GSH adduct formation as a marker of bioactivation of thiophenes in several different in vitro models. Rat liver microsomal incubations were analysed using hydrogen deuterium exchange and LC-MS to define the reactive metabolite of methapyrilene as an S-oxide of the thiophene ring. Freshly isolated rat hepatocytes or single P450 expressing THLE cell cultures were exposed to either methapyrilene, tienilic acid, ticlopidine or 2-phenylthiophene and subsequent LC-MS analysis confirmed GSH adduct formation for all compounds in the isolated rat hepatocyte model, but only for 2-phenylthiophene in the THLE cell model. Cytotoxicity was also investigated in both models, and all compounds were found to cause a greater degree of toxicity in the isolated rat hepatocyte molecule than in the THLE model. By exposing rodents to depletors of hepatic GSH, such as acetaminophen and diethylmaleate, and monitoring the resultant serum OA levels, it has been determined that OA is not a reliable mechanistic marker of hepatic GSH depletion. Kinetic studies of OA in rat serum have revealed that OA is subject to a similar metabolic and elimination pathway as GSH. The overall scope of this work reveals the usefulness of LC-MS/MS to determine S-oxide and epoxide adducts in in vitro studies. The freshly isolated rat hepatocyte model was a useful tool for providing integrated metabolic and toxicological data of thiophene containing molecules and has the potential to be expanded to include data on covalent binding and levels of DILI biomarkers. The single CYP expressing THLE cell model was not as useful in this case, but has been used in other studies to explore the role of discrete P450 enzymes in toxicity and metabolism. Whilst it is unfortunate that serum OA did not reflect hepatic OA in such a way that it could be easily exploited as a biomarker, this does help us to understand that the plethora of potential biomarkers uncovered by proteomic, metabolomic and transcriptomic studies need to be investigated in depth in order to understand their applications across different species and systems.
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Leijonmarck, Simon. „Electrically Induced Debonding of Adhesives“. Licentiate thesis, KTH, Tillämpad elektrokemi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-27742.
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Electrically induced adhesive debonding is a process where an adhesive can be debonded at command with help of an applied voltage. To make this process function, the adhesive is bonded between two metal substrates. In this study an epoxy adhesive is adhered between two aluminium foils forming a laminate structure. The adhesive is made ionically conductive by an addition of an ionic liquid before the curing. This arrangement forms an electrochemical cell, where the metal substrates act as the electrodes while the ionically conductive adhesive acts as the electrolyte. When a voltage is applied over the laminate, a current passes due to electrochemical reactions at the electrode interfaces and ionic transport in the adhesive. This type of material can potentially be used in a wide range of applications. This includes making adhesive joints in automotives to both reduce the total weight but also to simplify the disassembly after end-of-life, enabling an inexpensive recycling process. Another potenital use for debondable adhesives is within consumer packaging. Here it could be possible to pack and transport goods using less packaging material as well as making the handling easier. The aim of this study was to increase the understanding about the processes leading to debonding. This knowledge is important in the development of new types of debonding adhesives. In this study, the commercial laminate Sinuate® was used as a model system. The experiments were focused on the electrochemical behavior and were performed mainly using galvanostatic polarization and electrochemical impedance spectroscopy. Information about the chemistry of debonding was collected with techniques such as scanning electron microscopy (SEM), mass spectrometry (MS) and Raman spectroscopy. The debonding did always take place at the anodic interface, separating the adhesive and the anode aluminium foil. It was found that the total cell resistance increased drastically during polarization, and that essentially all of this increase originated within the anodic half of the laminate. Examining the resistance behavior with EIS, it was found that the increase in total resistance was reversible. The anodic electrochemical reaction during polarization was determined to consist mainly of an oxidation of aluminium, while the major reaction at the cathodic interface was reduction of water into hydrogen. The debonding process, which took place at the anodic interface, could be related to reaction products formed in the polarization process. These products grew out from the anodic aluminium surface into the adhesive. A debonding mechanism is proposed where these products induce an increase in the adhesive volume, causing stresses at the interface which ultimately result in debonding.Elektriskt framkallad delaminering är en process som gör att en limfog kan fås att släppa på kommando med hjälp av en pålagd elektrisk spänning. För att processen ska fungera måste limmet vara bundet till två metallytor. I den här studien används ett epoxylim, bundet mellan två folier av aluminium, vilket bildar en laminatstruktur. Limmet gjordes jonledande genom en tillsats av en jonvätska innan härdningen. Detta laminat bildar en elektrokemisk cell, där metallytorna agerar som elektroder och limmet som elektrolyt. När en elektrisk spänning läggs över laminatet, uppstår en elektrisk ström till följd av elektrokemiska reaktioner vid elektrodytorna och jontransport i limmet. Dessa material skulle kunna användas inom ett brett spektrum av användningsområden. Exempel på detta är användandet av limmade fogar i fordon, vilket skulle både minska fordonens vikt och underlätta demonteringen efter livscykelns slut. En förenklad demontering skulle resultera i en billig återvinningsprocess. Andra exempel på användningsområden för elektriskt släppbara limmer är konsumentförpackningar. Inom detta område skulle varor kunna packas med mindre mängd förpackningsmaterial och hanteringen under transport och uppackning skulle kunna förenklas. Målet med det här arbetet var att öka förståelsen kring processerna som leder till delaminering. Dessa kunskaper är viktiga för utvecklande av nya sorter av elektriskt släppande limmer. Det kommersiella laminatet Sinuate® användes som ett modellsystem. Experimenten fokuserades kring elektrokemin och utfördes främst med galvanostatisk polarisering och elektrokemisk impedansspektroskopi (EIS). Information om släpprocessens kemi inhämtades med tekniker som svepelektronmikroskopi (SEM), masspektrometri (MS) och Raman-spektroskopi. Det upptäcktes att delamineringen alltid skedde i det anodiska gränsskiktet, på så sätt att aluminiumfolien och limytan separerades. Polarisationsprocessen ledde till en drastisk ökning av den totala cellresistansen och större delen av denna härrörde sig från den anodiska delen av laminatet. Denna ökning i resistans fanns vara reversibel genom att använda EIS. Den elektrokemiska reaktionen vid anoden bestod till största delen av en oxidation av aluminium, medan den katodiska reaktionen bestod av en reduktion av vatten till vätgas. Processerna som ledde till släpp i det anodiska gränsskitet kunde härledas till SEM-resultaten, där reaktionsprodukter observerades. Dessa produkter växte ut från aluminiumytan och in i limmet. En släppmekanism föreslås, där de bildade produkterna orsakar en volymsökning i limmet, vilket leder till spänningar i gränsskiktet som i sin tur gör att limmet släpper.
QC 20101222
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Vilariño-Güell, Carles. „Analysis of germline mutations induced by chemicals“. Thesis, University of Leicester, 2002. http://hdl.handle.net/2381/9415.
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The high abundance of chemical pollutants in the environment represents a genetic risk to humans. The development of reliable and sensitive tests for the analysis of the genetic effects of exposure to chemical mutagens is required. Previous work has shown that expanded simple tandem repeat (ESTR) loci provide a sensitive system for monitoring radiation-induced mutation in the mouse germline. Here, the results of the first systematic study on germline mutation induction at mouse ESTR loci by chemical mutagens are presented. Mutation rates at two ESTR loci were studied in the germline of male mice exposed to two monofunctional alkylating agents, ethyl-nitrosourea (ENU) and isopropyl methanesulfonate (iPMS), as well as to the topoisomerase-II inhibitor, etoposide (ET). Pre-meiotic exposure to alkylating agents resulted in a highly significant increase in ESTR mutation rate, but did not alter post-meiotically exposed cells. Pre-meiotic mutation induction by ENU and iPMS was linear within the interval of doses from 12.5 mg/kg to 25 mg/kg and reached a plateau at higher concentrations. Paternal exposure to etoposide resulted in ESTR mutation induction at meiotic stages but did not affect post- or pre-meiotic cells. The pattern of ESTR mutation induction after pre-meiotic and meiotic exposure to chemical mutagens was similar to that previously obtained by various traditional approaches for monitoring germline mutation in mice. Using microarrays, the analysis of the pattern of changes in gene expression in the testis of male mice exposed to ENU was studied. This analysis revealed that exposure to this chemical mutagen does not result in detectable changes in gene expression. The results of this study show that ESTR loci provide a new and efficient biomonitoring system for assessing the genetic effects of chemical mutagens, capable of detecting increases in mutation rates at very low doses and in small sample sizes.
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Tearle, William Mark. „Chemically induced discotic liquid crystals“. Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296362.
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Yu, Betty (Betty Pei Yuan) 1974. „Elucidation of chemically-induced transdermal transport processes“. Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8494.
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Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2002.Includes bibliographical references.
In this thesis, chemically-induced transdermal transport enhancement has been examined as one of the many techniques currently used to increase the skin permeability to a broader range of pharmaceutically relevant drugs. By taking advantage of the current developments in instrumentation technology, the mechanisms underlying the well-known chemical enhancer action of oleic acid have been examined using novel applications of Two-Photon Microscopy (TPM). For the first time, TPM was used to visualize and quantify the oleic acid-induced three-dimensional spatial distributions of rhodamine B hexyl ester (RBHE), a model hydrophobic fluorescent probe, and of sulforhodamine B (SRB), a model hydrophilic fluorescent probe, based on a sampling of 4 to 6 different skin sites per skin sample. The fluorescent probe intensity profiles, that capture the fluorescent probe concentrations as a function of skin depth, were further evaluated using fundamental transport equations to quantify the oleic acid-induced changes in the vehicle to skin partition coefficient, the concentration gradient, the skin diffusion coefficient, and the skin barrier diffusion length. The application of the quantification methodology revealed that oleic acid-induced increases in the probe vehicle to skin partitioning was the primary effect for both the hydrophobic and the hydrophilic model fluorescent probes. The validity of the transport property enhancement values calculated based on the sample sizes examined (4-6 skin sites), was then addressed, in light of the inherent heterogeneity of the skin morphology.
(cont.) The increased sampling efficiency provided by High-Speed Two-Photon Microscopy (HTPM) enables the imaging of clinically more relevant skin areas over shorter times. Using HTPM, the fluorescent probe spatial distributions in 400 consecutive skin sites, comprising a total skin area of 2mm by 2mm, were quantified for the control (no oleic acid exposure) and the enhancer (oleic acid exposure) cases of RBHE and SRB. Following the application of a randomized skin site sampling subroutine, the optimum number of skin sites needed to accurately represent the globally-induced changes in transdermal transport properties was determined. For the hydrophobic probe, a limited sampling of 4-6 skin sites was found to be sufficient, whereas for the hydrophilic probe, 12-24 skin sites was recommended. Furthermore, the oleic acid-induced variations in the wide-area spatial distributions of two transdermal transport parameters- the probe surface intensity and the probe intensity gradient- were evaluated to determine the rate-limiting steps in transdermal transport for each fluorescent probe examined. Lateral diffusion through the lipid multilamellae, for the hydrophobic fluorescent probe, and probe partitioning from the vehicle into the skin, for the hydrophilic fluorescent probe, were determined to be the rate-limiting steps in transdermal transport. In the final application of TPM presented in this thesis, the oleic acid-induced changes in the fluorescent probe spatial distributions with respect to the skin structural features were examined, for the first time, utilizing dual-channel HTPM, where the skin autofluorescence intensity and the probe intensity spatial distributions are simultaneously visualized...
by Betty Yu.
Sc.D.
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Schumacher-Novak, Gregory Donald. „RFID tags / planar inductors as chemical sensor platforms in liquid sensing applications“. [Milwaukee, Wis.] : e-Publications@Marquette, 2009. http://epublications.marquette.edu/theses_open/5.
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Moore, Peter Nathaniel 1974. „A fundamental investigation of surface-induced skin irritation“. Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8532.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2002.Includes bibliographical references.
Surfactants frequently come in contact with the skin in the form of personal care products, where they are used to improve the wetting and oil solubilizing qualities of the products. Surfactants are also known to induce skin irritation by damaging the barrier properties of the stratum corneum, the outer layer of the skin, and denaturing proteins in the epidermis and the dermis. The goal of this thesis has been to understand the relationship between the physicochemical properties of surfactant solutions and their skin irritation potential. In vitro tests were developed to measure: (1) the effect of surfactants on the barrier properties of the skin, (2) the concentration of surfactant in the skin, and (3) surfactant-induced protein denaturation, all of which can be related to skin irritation. The physicochemical properties of the surfactant solution, specifically, the concentration of the surfactant monomers (unmicellized surfactant), the composition of the surfactant monomers, and the size and shape of the surfactant micelles, were related to the results of these tests. An in vitro skin irritation test was developed that measures the electrical conductivity of pig skin to quantify the reduction in the barrier properties of the skin, or the skin damage, induced by surfactant solutions. Skin conductivity was found to be directly related to the transdermal water permeability, directly relating the skin conductivity to in vitro skin irritation. Skin conductivity was used to measure the in vitro skin irritation potential of mixtures of the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic surfactant dodecyl hexa(ethylene oxide) (C12E6), and a relationship was observed between the surfactant monomer concentration and
(cont.) the skin conductivity. The in vitro skin irritation test correctly ranked the in vivo irritation potential of three mild commercial soap bars-Dove, Lever 200, and Ivory. In order to understand the relationship between the micelle concentration and the surfactant-induced damage to the skin, a method was developed to measure the penetration of 14C-radiolabeled SDS surfactant into pig skin. It was found that both monomeric and micellar SDS are able to penetrate into the skin, and that the contribution of the micellar SDS to the concentration of SDS in the skin is comparable to the contribution of the monomeric SDS. SDS penetration into the skin was also measured in the presence of poly(ethylene oxide) (PEO), which forms PEO-bound SDS micelles, and C12E6, which forms SDS/C12E6 mixed micelles. In mixtures of PEO-bound and free SDS micelles, the PEO-bound SDS micelles were found not to penetrate into the skin while the free SDS micelles were found to penetrate. Mixing SDS with C12E6 led to a reduction in the penetration of SDS into the skin by reducing the SDS monomer concentration, as well as by reducing, or preventing altogether, the penetration of micellar SDS. The hydrodynamic radii of the free SDS micelles (21 A), the PEO-bound SDS micelles (25 A), and the SDS-C12E6 mixed micelles (24-30 A) were measured using dynamic light scattering. Based on these results, a new model of surfactant penetration into the skin was proposed, in which the penetration of micellar surfactant into the skin is limited by the size of the micelles...
by Peter Nathaniel Moore.
Ph.D.
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Aunins, John Grant. „Induced flocculation of animal cells in suspension culture“. Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14330.
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Gibert, Gutiérrez Marta. „Self-assembled strain-induced oxide nanostructures grown by chemical solutions“. Doctoral thesis, Universitat Autònoma de Barcelona, 2009. http://hdl.handle.net/10803/3416.
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En aquest treball hem investigat una metodologia d'aproximació baix-cap dalt i baix cost per la generació de nanoestructures oxides interficials autoassemblades preparades mitjançant la deposició de soluciones químiques. La innovació del treball rau en l'aplicació dels processos d'autoassemblatge i autoorganització en materials òxids, i en l'ús de solucions químiques pel creixement d'illes interficials. Estudis sistemàtics basats en la modificació de les condicions de creixement mostren la capacitat i versatilitat de la metodologia usada per ajustar la morfologia, mida, densitat i distribució de les nanoilles interficials. Concretament, hem estudiat el creixement de nanoestructures de les fases òxides BaZrO3, CeO2, Ce0.9Gd0.1O2-y (CGO) y La2O3, resultant el l'obtenció de plantilles amb nanoilles amb estretes distribucions de mida i notable tendència a ordenar-se espontàniament sobre substrats monocristal·lins de SrTiO3 i LaAlO3 (LAO). Hem determinat un rang de paràmetres (concentració de la solució precursora, temperatura, etc.) que estableixen un conjunt de condicions inicials per la generació de nanoilles interficials d'altres fases òxides.
S'ha analitzat detalladament el sistema d'estructures dissemblants CGO/LAO (fluorita/perovskita) com a model per estudiar la formació i creixement de nanoilles induïdes per tensions elàstiques. La capacitat de seleccionar l'orientació cristal·logràfica de la nanoilles de CGO a partir del control de les condicions de creixement ens ha permès seleccionar l'anisotropia de tensions i d'energies de superfície de les nanoilles, resultant en la formació d'illes de CGO amb trets morfològics i cinètics molt distints. Tensions isotròpiques comporten la formació d'illes isomòrfiques de base quadrada, uniformes i estables. Aquests nanopunts creixen epitaxialment (001)CGO[110]||(001)LAO[100], tenen un diàmetre mig de ~45 nm, alçada ~7 nm i densitat 60 punts/μm2 i s'autoorganitzen en files al llarg dels esglaons del substrat. En canvi, tensions anisotròpiques indueixen la formació de nanoestructures rectangulars (nanofils) d'acord amb la relació epitaxial (011)CGO[100]||(001)LAO[100]. L'eix llarg dels nanofils pot arribar a mesurar 2 μm de longitud en menys de 30 minuts de tractament tèrmic a 1000oC en Ar-H2 mentre que l'eix curt roman <50 nm, fet que resulta en illes amb elevat índexs d'aspecte lateral (eix llarg/eix curt ~ 40). Els nanofils s'alineen al llarg dels eixos fàcils del substrat, i contínuament s'uneixen formant laberints de fils ortogonals que ràpidament es reconstrueixen en fils més llargs. L'existència d'atracció atractiva sembla ser la responsable la cinètica ultraràpida d'aquestes nanoilles tensades anisotròpicament. La dinàmica ultraràpida d'aquest sistema és una eina molt valuosa per estudiar l'evolució de nanoilles interficials; concretament, s'han identificat diferents mecanismes de coarsening actuant simultàniament (maduració Ostwald, coalescència dinàmica, coalescència estàtica, etc.).
Simulacions basades en models termodinàmics ens han permès confirmar la morfologia i dimensió d'equilibri de cada tipus d'illa de CGO d'acord amb el seu estat de tensió elàstic i energies de superfícies. La combinació dels anàlisis experimentals amb els estudis termodinàmics ha permès establir una llista de les condicions necessàries per la formació de nanofils interficials extremadament llargs. Aquestes estratègies no es limiten a materials òxids i de fet poden ser usades per generació de nanoilles anisotròpiques en una gran varietat de sistemes, provant així la generalitat del treball fet.
Finalment, es mostra una aplicació pràctica de les plantilles nanoestructurades òxides per induir centres artificials d'ancoratge de vòrtexs en capes primes de YBa2Cu3O7 (YBCO) també preparades mitjançant solucions químiques. Anàlisis metodològics basats en mesures angulars elèctriques de transport han evidenciat una important millora de la contribució anisotròpica-forta de la densitat de corrent crític per H||c en les capes primes de YBCO nanoestructurades respecte les mostres estàndard, indicant que la nanoestructuració interficial és una estratègia possible i prometedora per millorar la actuació de les capes primes de YBCO. També s'han realitzat anàlisis de les propietats superconductores en funció del gruix de YBCO.
In this work we have investigated a bottom-up high throughput methodology to generate interfacial self-assembled oxide nanostructures through the deposition of chemical solutions. The innovation of this work is two-fold, since we have studied the application of self-assembling and self-organizing processes to oxide materials and because the study of the formation of interfacial islands from solutions.
Systematic studies based on the modification of growth conditions show the capabilities and versatility of the methodology used to tune the shape, size, density and distribution of the resulting oxide interfacial nanoislands. Specifically, we have studied the growth of nanostructures of the oxides phases BaZrO3, CeO2, Ce0.9Gd0.1O2-y (CGO) y La2O3, leading to the generation of templates with interfacial nanoislands with narrow distribution of sizes and notable tendency to form ordered arrays on top of the single-crystal substrates SrTiO3 y LaAlO3 (LAO). We have determined a range of parameters (precursor solution concentration, temperature, etc.) which establish a set of initial conditions for the generation of interfacial nanoislands of other oxide phases.
The system of dissimilar structures CGO/LAO (fluorite/perovskite) is analyzed in great detail as a model to study the formation and growth of strain-induced nanoislands. The capacity to select the crystallographic orientation of CGO nanoislands through tuning of growth conditions enables us to control the anisotropy of strains and surface energies of the nanoislands, leading to the formation of CGO nanostructures with highly different morphological and kinetic characteristics. Square-based isomorphic nanoislands, uniform and stable, form under isotropic strains. These nanodots grow epitaxially accordingly to (001)CGO[110]||(001)LAO[100], and have mean lateral size ~45 nm and ~7 nm height, and density of ~60 dots/μm2. They order into rows along lattice steps of the substrate, resulting into highly self-organized templates. Instead, highly elongated rectangular nanostructures (nanowires) grow induced by anisotropic strains and anisotropic surface energies in the epitaxial relation (011)CGO[100]||(001)LAO[100]. The long axis of these wires can reach lengths of 2 μm in less than 30 minutes of heat treatment at 1000oC in Ar-H2 whereas short axes remain <50 nm, resulting in high lateral aspect ratios (long axis/short axis ~ 40). Wires are aligned along substrate soft axes and continuously join into intricate clusters of orthogonal wires which rapidly reconstruct into larger wires. The attractive interaction between wires seems to be the driving force of the ultrafast kinetics of these islands biaxially anisotropic strained. This ultrarapid dynamics is a powerful tool to study the evolution of interfacial nanoislands; particularly, several coarsening mechanisms simultaneously acting have been identified (Ostwald ripening, dynamic coalescence, static coalescence, etc.).
Simulations based on thermodynamic models have enabled to confirm the equilibrium shape and size of each sort of CGO island in relation to its misfit strain and surface energies. The combined analyses of the experimental results and thermodynamic studies have allowed us to establish a list of the requirements for the formation of extremely long interfacial nanowires. These strategies are not limited to oxides and can be extended to the generation of anisotropic nanoislands in a large variety of systems, proving the generality of the work done.
Finally, we have showed a practical application of oxide nanostructured templates to induce artificial vortex pinning centres in YBa2Cu3O7 (YBCO) thin films also prepared from chemical solutions. Methodological analyses based on electrical transport angular measurements have evidenced a strong improvement of the anisotropic-strong contribution to the critical current density for H||c in interfacial nanostructured YBCO thin films as compared to standard ones, proving that interfacial nanostructuration is a possible and promising strategy to improve the performance of YBCO thin films. Analyses of the superconducting properties as function of YBCO thickness have also been carried out.
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Murray, Ashley Rebecca. „Oxidative stress in skin induced by chemical and physical agents“. Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4558.
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Thesis (Ph. D.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains xii, 203 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.
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Nave, Andy [Verfasser]. „Physico-chemical investigation of plasma induced deposition processes / Andy Nave“. Greifswald : Universitätsbibliothek Greifswald, 2017. http://d-nb.info/1141405997/34.
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Chatwin, Heather M. „Molecular genetic analysis of chemical-induced sporulation of Myxococcus xanthus“. Thesis, University of Warwick, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387398.
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Taraboletti, Alexandra Anna. „Chemical and Metabolomic Analyses of Cuprizone-Induced Demyelination and Remyelination“. University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1498535047689141.
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Varma, Pritam S. „Solvent induced NMR chemical shifts that arise from molecular encounters“. Thesis, Aston University, 1987. http://publications.aston.ac.uk/9729/.
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Recently Homer and Percival have postulated that intermolecular van der Waals dispersion forces can be characterized by three mechanisms. The first arises via the mean square reaction field < R1; 2> due to the transient dipole of a particular solute molecule that is considered situated in a cavity surrounded by solvent molecules; this was characterized by an extended Onsager approach. The second stems from the extra cavity mean square reaction field < R2; 2> of the near neighbour solvent molecules. The third originates from square field electric fields E2BI due to a newly characterized effect in which solute atoms are `buffeted' by the peripheral atoms of adjacent solvent molecules. The present work concerns more detailed studies of the buffeting screening, which is governed by sterically controlled parameter (2T - T)2, where and are geometric structural parameters. The original approach is used to characterise the buffeting shifts induced by large solvent molecules and the approach is found to be inadequate. Consequently, improved methods of calculating and are reported. Using the improved approach it is shown that buffeting is dependent on the nature of the solvent as well as the nature of the solute molecule. Detailed investigation of the buffeting component of the van der Waals chemical shifts of selected solutes in a range of solvents containing either H or Cl as peripheral atoms have enabled the determination of a theoretical acceptable value for the classical screening coefficient B for protons. 1H and 13C resonance studies of tetraethylmethane and 1H, 13C and 29Si resonance studies of TMS have been used to support the original contention that three (< R1; 2> , < R2; 2> and E2BI) components of intermolecular van der Waals dispersion fields are required to characterise vdW chemical shifts.
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Chen, Yong-Jun. „Autonomous Motion Induced by Marangoni-Driven Spreading Under Chemical Nonequilibricity“. 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/120639.
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Ismail, Wan Iryani Wan. „Molecular Basis of insulin resistance induced by antiretroviral drugs“. Doctoral thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/4398.
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BANDODKAR, RUSHIK G. „ADSORPTION INDUCED SOLID PHASE TRANSITION OF MIL-53(Al)“. Cleveland State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=csu1566984113575368.
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Rotchell, Jeanette M. „Chemically-induced genetic damage in fish“. Thesis, Glasgow Caledonian University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318550.
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Goy, Michel. „Gamma Radiation-Induced Synthesis of Cerium Oxide Mesocrystals“. Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-260137.
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Nanoparticles of cerium dioxide was synthesized by gamma irradiation of aqueous solutions containing CeCl3 and CeBr3. ICP-OES was used to determine the precipitation yield. X-ray powder diffraction and transmission electron microscope were used to characterize the products. The crystal structurewas found by Fourier transform of high resolution electron microscope images,selected area electron diffraction, electron pair distribution function and X-ray powder diffraction. The morphology was examined from high resolution electron microscope images. The chemical composition was examined by electron energy loss spectra. Nanoparticles of 3-4 nm were found to agglomerate and fuse into cubic mesocrystals of 20-40 nm. Changing precursor did not influence the final product. An attempt to change the morphology by increasing the ionic strength with sodium perchlorate was made. At higher ionic strength, the morphology was more random and the yield increased. The size distribution also broadened. Future research can evaluate the catalytic activity of the samples, test other ions to increase the ionic strength to see if it is the ionic strength or the counterion that influences the growth, and do more analysis on the samples prepared.Nanopartiklar av ceriumdioxid syntetiserades genom gammabestrålning av vatten innehållande CeCl3 och CeBr3. ICP-OES användes för att bestämma utfällningsutbytet. Röntgenkristallografi och transmissionselektronmikroskop användes för att karaktärisera produkterna. Kristallstrukturen hittades genom Fouriertransformering av elektronikmikroskopbilder med hög upplösning, selected area electron diffraction, elektronparfördelningsfunktion och röntgenkristallografi. Morfologi undersöktes från högupplösta elektronmikroskopbilder. Kemisk sammansättning undersöktes med elektronenergiförlustspektra. 3-4 nm stora nanopartiklar agglomerade i kubiska mesokristaller på 20-40 nm. De olika startmaterialen påverkade inte slutprodukten. Ett försök att ändra morfologin genom att öka jonstyrkan med natriumperklorat gjordes. Vid högre jonstyrka ändrades mesokristallernas morfologi till mer slumpmässig och utbytet ökade. Storleksfördelningen blev bredare. Framtida forskning kan utvärdera den katalytiska aktiviteten hos proverna, testa andra joner för att utröna om det är den förhöjda jonstyrkan eller valet av jon som påverkar tillväxten av partiklar, och göra flera analyser av de beredda proverna.
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Oh, Junsuk. „Computational simulation and morphological analysis of polymerization-induced phase separation“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0031/MQ64240.pdf.
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Abdallah, Mohammad Raji AlGhazi. „Role of polymer entanglements in polyethylene oxide induced fines flocculation“. Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38140.
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On a papermaking machine, fines and colloids are retained in a paper sheet. The most important particle interactions are among particles having a high weight fraction and a short characteristic interaction time. Most of these interactions follow Langmuir kinetics, in which the flocculation efficiency is one of the important parameters. To enhance retention, many retention aids are available, one of which is neutral polyethylene oxide (PEO) used in combination of a phenolic cofactor (CF).In this work, a new model was derived in which all possible interactions were considered and assumed to follow Langmuir kinetics. Since fines are the main component in the headbox of mechanical grade furnishes, fines homo- and heteroflocculation with a PEO/CF retention aid were investigated in a circulating flow loop, and found to follow Langmuir kinetics. The small amount of fines deposited on the fibers was attributed to the large detachment rate in turbulent shear. The apparent difference in the deposition time and the half time of flocculation was attributed to difference in efficiency. Fines homoflocculation showed that fines are flocculated (without a retention aid) to various extents depending on shear, and that aggregates of flocs will form when a retention aid is added.
The PEO/CF flocculation efficiency was found to be a function of various parameters, i.e., aging of PEO solution, stirring intensity and time of stirring during dissolution, concentration at storage, shearing and dilution prior to injection. Optimum conditions were found for most parameters, and a critical shear intensity was determined. This PEO behavior was attributed to the extent of entanglements of PEO coils, which can be characterized prior to its addition to the flocculation vessel by a newly developed method. In this method, the pressure drop of a PEO solution passing through a capillary constriction was measured and correlated with its flocculation efficiency. Using the derived correlation, the flocculation efficiency can be estimated, and the relevant parameters can be controlled. Moreover, the salt effect on a PEO/CF system in a pulp was investigated. Salt was found to react with a CF causing a decrease in the flocculation efficiency. The effect of this reaction can be eliminated if PEO is added directly after CF addition.
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Ware, Margaret Faye 1969. „Growth factor-induced cell migration : a quantitative and mechanistic analysis“. Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50357.
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Harms, Brian David 1976. „Quantitative cue-signal-response analysis of EGF-induced cell migration“. Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28658.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2004.Page 172 blank.
Includes bibliographical references.
(cont.) curve is explained mechanistically by the results of the first study. In a final study, we investigated the phenomenological structure of CHO-EGFR cell paths using turn angle distribution and time series analyses. Increased local cell speed correlated with increased likelihood of local directional persistence, a result independent of biochemical modulation of overall cell motility. Time-based directional autocorrelations were observed that indicate an unusual non-Markov behavior in CHO migration. Overall, these studies demonstrate how biophysical analysis is an effective tool for gaining insight into the quantitative regulation of motility by intracellular signaling.
The physiological importance of cell motility has resulted in intense efforts dedicated towards deconstructing its molecular control mechanisms. Most research employs qualitative approaches, yet quantitative understanding of how altering the function of genes or proteins changes migration responses is critical for engineering therapies targeting pathological cell motility. In this work, we deconstruct hierarchical quantitative relationships between biochemical, biophysical, and phenomenological descriptions of cell motility. Specifically, this thesis establishes quantitative correlations between the activation of key intracellular signaling proteins by extracellular motility cues and the effects of these signals on both the biophysical processes comprising motility and parameters describing the overall paths of translocating cells. Our model system consisted of Chinese Hamster Ovary (CHO) cells transfected with the epidermal growth factor (EGF) receptor. In initial experiments employing EGF and fibronectin (Fn) as extracellular cues, we found that adhesion-mediated stabilization of lamellipodial protrusions governed the magnitude of directional persistence in cell paths. To connect this biophysical control of persistence to intracellular signaling, a second study examined the role of extracellular signal-related kinase (ERK) and phosphatidylinositol 3-kinase (PI3K) signaling in EGF-induced migration. Both molecules controlled directional persistence biphasically, with maximal persistence at intermediate signal strength. Studies of lamellipodial protrusion, in concert with experiments using soluble anti-adhesion peptides to modulate persistence, indicated that the ERK, but not the PI3K, biphasic
by Brian David Harms.
Ph.D.
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Fang, Jia. „Experimental Evidence of Fracture-Induced Formation of Ordered Strip Structures“. University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1322683924.
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Roth, Olivia. „Physical and Chemical Aspects of Radiation Induced Oxidative Dissolution of UO2“. Licentiate thesis, KTH, Kemi, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-622.
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Denna licensiatavhandling behandlar oxidativ upplösning av UO2. Upplösning av UO2 studeras huvudsakligen då UO2-matrisen hos använt kärnbränsle förväntas fungera som en barriär mot frigörande av radionuklider i ett framtida djupförvar. Lösligheten av U(IV) är mycket låg under i djupförvaret rådande förhållanden emedan U(VI) har betydligt högre löslighet. Oxidation av UO2-matrisen kommer därför att påverka dess löslighet och därmed dess funktion som barriär. I denna avhandling studeras den relativa effektiviteten av en- och två-elektronoxidanter för upplösning av UO2. Vid låga oxidantkoncentrationer är utbytet för upplösningen för en-elektronoxidanter signifikant lägre än för två-elektronoxidanter. För en-elektronoxidanter ökar dock utbytet med ökande oxidanthalt, vilket kan förklaras av den ökade sannolikheten för två konsekutiva en-elektronoxidationer av samma reaktionssite och den ökade möjligheten till disproportionering. Radikaler och molekylära radiolysprodukters relativa inverkan på oxidativ upplösning av UO2 studeras också i denna avhandling genom mätning av mängden upplöst U(VI) i γ-bestrålade system som dominerades av olika oxidanter. Dessa studier visade att upplösningshastigheten av UO2 kan uppskattas från oxidantkoncentrationer framtagna genom simuleringar av radiolys i motsvarande homogena system och hastighetskonstanterna för ytreaktionerna. Simuleringarna visar att de molekylära oxidanterna kommer vara de viktigaste oxidanterna i alla system i denna studie vid långa bestrålningstider (>10 timmar). Vid liknande simuleringar av α-bestrålade system fanns att vid förhållanden relevanta för ett djupförvar för använt kärnbränsle, är det endast de molekylära oxidanterna (i huvudsak H2O2) som är av betydelse för upplösningen av bränslematrisen. Då använt kärnbränsle innehåller en mängd radionuklider som utsätter UO2-matrisen för kontinuerlig bestrålning, är det av vikt att undersöka hur bestrålning påverkar reaktiviteten av UO2. Bestrålningseffekten på reaktionen mellan UO2 och MnO4- studerades. Dessa försök visade att bestrålning av UO2 vid doser >40 kGy leder till att reaktiviteten ökar upp till 1.3 gånger reaktiviteten av obestrålad UO2. Den ökade reaktiviteten kvarstår efter bestrålningen och effekten kan därför möjligen tillskrivas permanenta förändringar i materialet. Vid uppskattning av reaktiviteten hos använt kärnbränsle måste hänsyn tas till denna effekt då bränslet redan efter ett par dagar i reaktor blivit utsatt för doser >40 kGy. Det har tidigare föreslagits att hastigheten för en heterogen västka/fast-fas reaktion är beroende av partikelstorleken hos det fasta materialet, vilket har studerats för UO2-partiklar i denna avhandling. Experimentellt bestämda kinetiska parametrar jämförs med de föreslagna ekvationerna för fyra storleksfraktioner av UO2-pulver och en UO2-pellet. Studien visade partikelstorleksberoendet av andra ordningens hastighetskonstant och aktiveringsenergin för oxidation av UO2 med MnO4- beskrivs relativt väl av de föreslagna ekvationerna.The general subject of this thesis is oxidative dissolution of UO2. The dissolution of UO2 is mainly investigated because of the importance of the UO2 matrix of spent nuclear fuel as a barrier against radionuclide release in a future deep repository. U(IV) is extremely insoluble under the reducing conditions prevalent in a deep repository, whereas U(VI) is more soluble. Hence, oxidation of the UO2-matrix will affect its solubility and thereby its function as a barrier. In this thesis the relative efficiency of one- and two electron oxidants in dissolving UO2 is studied. The oxidative dissolution yield of UO2 was found to differ between one- and two-electron oxidants. At low oxidant concentrations the dissolution yields for one-electron oxidants are significantly lower than for two-electron oxidants. However, the dissolution yield for one-electron oxidants increases with increasing oxidant concentration, which could be rationalized by the increased probability for two consecutive one-electron oxidations at the same site and the increased possibility for disproportionation. Furthermore, the relative impact of radical and molecular radiolysis products on oxidative dissolution of UO2 is investigated. Experiments were performed where the amount of dissolved U(VI) was measured in γ-irradiated systems dominated by different oxidants. We have found that the UO2 dissolution rate in systems exposed to γ-irradiation can be estimated from oxidant concentrations derived from simulations of radiolysis in the corresponding homogeneous systems and rate constants for the surface reactions. These simulations show that for all systems studied in this work, the molecular oxidants will be the most important oxidants for long irradiation times (>10 hours). Similar simulations of α-irradiated systems show that in systems relevant for a deep repository for spent nuclear fuel, only the molecular oxidants (mainly H2O2) are of importance for the dissolution of the fuel matrix. The effect on UO2 reactivity by irradiation of the material is of importance when predicting the spent fuel dissolution rate since the fuel, due to its content of radionuclides, is exposed to continuous self-irradiation. The effect of irradiation on the reaction between solid UO2 and MnO4- in aqueous solutions was studied. It was found that irradiation of UO2 at doses >40 kGy increases the reactivity of the material up to ~1.3 times the reactivity of unirradiated UO2. The increased reactivity remains after the irradiation and can possibly be attributed to permanent changes in the material. This issue must be taken into account when predicting the reactivity of spent nuclear fuel since the fuel is exposed to doses >40 kGy after only a few days in the reactor. It has earlier been suggested that the rate of a heterogeneous liquid-solid reaction depends on the size of the solid particles. This was investigated for UO2 particles in this thesis. Experimental kinetic parameters are compared to the previously proposed equations for UO2 powder of four size fractions and a UO2 pellet. We have found that the particle size dependence of the second order rate constant and activation energy for oxidation of UO2 by MnO4- is described quite well by the proposed equations.
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Mora, Alejandro. „Discrete model for pattern formation in laser induced jet chemical etching“. Berlin Logos-Verl, 2006. http://deposit.ddb.de/cgi-bin/dokserv?id=2788032&prov=M&dok_var=1&dok_ext=htm.
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Roth, Olivia. „Physical and chemical aspects of radiation induced oxidative issolution of UO₂ /“. Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-622.
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Lovatt, Cerys Ann. „The role of glutathione S-transferase Pi in chemical-induced toxicity“. Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412639.
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