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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.
91

Mise en émulsion sans tensioactif de résines alkydes et formulation de peintures biosourcées / Free surfactants alkyd resin emulsification and biobased paints formulations

Romand, Alison 21 January 2016 (has links)
Les peintures sont omniprésentes dans nos civilisations modernes et décorent presque tous les supports et ce dans des domaines très variés. L'utilisation massive des peintures pose cependant des problèmes environnementaux et de santé publique, de par la présence de solvants qui, lors du séchage, s'évaporent et émettent des composés organiques volatiles (COV) néfastes pour l'environnement et l'homme. Une démarche européenne et mondiale de réduction d'émission des COV est donc en cours depuis quelques années. De plus, l'engouement croissant pour le développement durable pousse à la transition de produits pétrosourcés vers des produits biosourcés, à coûts et performances similaires. Les résines alkydes en émulsions, développées au début du XXème siècle, constituent une alternative de choix car émettant une quantité limitée de COV et obtenues par polycondensation de matières premières renouvelables. Après un état de l'art sur le contexte des peintures actuelles et la composition d'une peinture alkyde en émulsion, leurs propriétés physiques et chimiques ont été étudiées. Après ce travail de formulation, deux additifs ont été synthétisés afin d'augmenter le taux de biosourcé des peintures alkydes en émulsion : un épaississant et un agent dispersant. De par la présence de surfactants, les formules de peintures alkydes en émulsion sont pour l'heure moins compétitives que les peintures alkydes en phase solvant. En conséquence, la première émulsion alkyde sans tensioactif a été développée et ses performances évaluées en peinture / Paints and coatings occupy a prominent place in the cultural history of mankind. People have always been fascinated by colors and used paints to decorate and beautify themselves and their environment. Nevertheless, these products bring a lot of problems. For instance, some paints still contain organic solvents, which have negative impacts on the environment and human health. Due to environmental legislations and the need to reduce VOCs emission (volatile organic compounds), water-based paints have attracted a lot of interest. Moreover, the raising sustainability awareness is a driving force for the transition from petrobased to biobased products with equivalent costs and performances. In this context, alkyd resin emulsion, introduced in the 1990s, still continue to be the most widely used binder, because they have low VOCs level and are synthesized by polycondensation reactions of renewable raw materials. After reviewing the current state of the art regarding the alkyd paint emulsion, their physical and chemical properties were studied. Two additives, respectively a rheology modifier and a dispersing agent, were also synthesized, in order to increase the biobased content of alkyd paint emulsion Due to the presence of wetting agent, alkyd emulsion paints are still less competitive than solvent-borne alkyd paints. The first surfactant free alkyd emulsion was consequently developed and its film properties characterized in paint formulation
92

Vliv složení modifikátorů tření na trakci v kontaktu kola a kolejnice / Influence of friction modifiers composition on traction in wheel-rail contact

Kvarda, Daniel January 2017 (has links)
Friction modifiers are a new effective way to control adhesion in wheel and rail contact. The aim of this diploma thesis is experimental study of the influence of the constituents of water based friction modifier on adhesion. Measurement of the adhesion behavior for different friction modifier compositions is carried out on a ball–on–disc laboratory device creating point contact. The introductory part of the experiments describes the effect of individual components on adhesion. Subsequently, combinations of different friction modifier compositions are tested. In conclusion, selected compositions are used for wear tests. The results obtained show that the performance of friction modifiers is greatly influenced by evaporation of base medium.
93

Enhanced inhibition of clonogenic survival of human medulloblastoma cells by multimodal treatment with ionizing irradiation, epigenetic modifiers, and differentiation-inducing drugs

Patties, Ina, Kortmann, Rolf-Dieter, Menzel, Franziska, Glasow, Annegret January 2016 (has links)
Background: Medulloblastoma (MB) is the most common pediatric brain tumor. Current treatment regimes consisting of primary surgery followed by radio- and chemotherapy, achieve 5-year overall survival rates of only about 60 %. Therapy-induced endocrine and neurocognitive deficits are common late adverse effects. Thus, improved antitumor strategies are urgently needed. In this study, we combined irradiation (IR) together with epigenetic modifiers and differentiation inducers in a multimodal approach to enhance the efficiency of tumor therapy in MB and also assessed possible late adverse effects on neurogenesis. Methods: In three human MB cell lines (DAOY, MEB-Med8a, D283-Med) short-time survival (trypan blue exclusion assay), apoptosis, autophagy, cell cycle distribution, formation of gH2AX foci, and long-term reproductive survival (clonogenic assay) were analyzed after treatment with 5-aza-2′-deoxycytidine (5-azadC), valproic acid (VPA), suberanilohydroxamic acid (SAHA), abacavir (ABC), all-trans retinoic acid (ATRA) and resveratrol (RES) alone or combined with 5-aza-dC and/or IR. Effects of combinatorial treatments on neurogenesis were evaluated in cultured murine hippocampal slices from transgenic nestin-CFPnuc C57BL/J6 mice. Life imaging of nestin-positive neural stem cells was conducted at distinct time points for up to 28 days after treatment start. Results: All tested drugs showed a radiosynergistic action on overall clonogenic survival at least in two-outof-three MB cell lines. This effect was pronounced in multimodal treatments combining IR, 5-aza-dC and a second drug. Hereby, ABC and RES induced the strongest reduction of clongenic survival in all three MB cell lines and led to the induction of apoptosis (RES, ABC) and/or autophagy (ABC). Additionally, 5-aza-dC, RES, and ABC increased the S phase cell fraction and induced the formation of gH2AX foci at least in oneout-of-three cell lines. Thereby, the multimodal treatment with 5-aza-dC, IR, and RES or ABC did not change the number of normal neural progenitor cells in murine slice cultures. Conclusions: In conclusion, the radiosensitizing capacities of epigenetic and differentiation-inducing drugs presented here suggest that their adjuvant administration might improve MB therapy. Thereby, the combination of 5-aza-dC/IR with ABC and RES seemed to be the most promising to enhance tumor control without affecting the normal neural precursor cells.
94

From the midst of darkness to a nugget of hope : Post-nominal of-phrases in translation

Mickelsson Sparv, Susanne January 2020 (has links)
The aim of this thesis is to analyze how post-nominal of-phrases are translated from English to Swedish in a non-fiction text about the musician Dave Grohl and his band Foo Fighters. The analysis is both quantitative and qualitative. The of-phrases are categorized according to Keizer’s (2007) categories, and the results show that most of-phrases are translated to prepositional phrases, although it differs which prepositions are used, depending on the type of ofphrase. For of-phrases of the possession-type, i is the most common preposition, and for compound-like of-phrases, av is the most common preposition. Of-phrases of possession-type are also frequently translated into genitive constructions, especially if the possessor is animate or syntactically light. Other structural changes also occur in the translation, although no pattern was found for this strategy in the analysis.
95

Application of Optical Detection Methods for Top-of-Rail (TOR) Lubricity Evaluation on a Moving Platform for Revenue Service Track

Mast, Timothy Edward 17 April 2020 (has links)
This research serves to evaluate the ability of optical detection techniques to ascertain the lubricity of revenue service track from a moving platform for railroad applications. A literature review is presented that covers the rail vehicle dynamics that drive the need of Top-of-Rail lubrication and directly affect the manner in which the Top-of-Rail Friction Modifiers (TORFM) and flange grease both spread down rail and eventually wear away. This literature review also highlights previous research in the field of rail lubrication and the benefits that rail lubricants, specifically TORFM, provide for the railroads. Finally, the literature review covers the governing optical principals inherent to the synchronous spot radiometer that has been developed for use in the research as a gloss ratio instrument and also addresses the drawbacks and challenges inherent to applying this type of instrument in the railroad industry. The research then overviews previous rail lubricity sensors developed by the Railway Technologies Laboratory (RTL) at Virginia Tech and the lessons learned from their application. The preceding field testing conducting with a modified second generation rail lubricity sensor and a rail push car is briefly summarized with emphasis on the drawbacks and issues that were used to develop the third generation sensor used for this research. The development of the third generation sensor is covered, including the issues that it attempts to solve from its predecessor and the governing optical principals that govern the operation of the sensor. The laboratory evaluations conducting to commission the sensor are also covered in preparation for deploying the new third generation sensor in medium speed, medium distance revenue service testing. This includes a shakedown run on a siding in Riverside, VA prior to conducting mainline in-service testing. Finally, this research thesis covers the in-service testing on revenue track conducted with the new third generation rail lubricity sensor and the accompanying remote-controlled (RC) rail cart. The two components, when combined, create a Lubricity Assessment System which is capable of being operated at speeds upwards of 10 mph remotely from a follow hy-rail truck. The data collected from this field test is analyzed for the lubricity assessments that are able to be drawn from this initial phase of field service testing. The conclusions from this testing affirm the ability of optical methods to determine and evaluate Top-of-Rail (TOR) lubricity from a moving platform. Specifically, the new sensor is able to identify several local phenomena that demonstrate the high potential for errant evaluation of rail lubricity evaluation from spot check based methods that are solved by evaluating the track in a continuous, moving fashion. Based on the continuous moving data collected for this test, several new signal traits such as the spatial frequency (wavenumber) associated with the passing freight cart wheels in the lubricity signal and the phantom applicator effect of transient lubricity conditions at the entrances and exits of curves can be detected and investigated. The success of this research indicates the continued evaluation of lubricity signals from a moving platform is warranted and suggests the potential for introducing one of these systems to various track metrology cars deployed throughout the United States railroads. / Master of Science / The United States railroads have been employing rail lubricants to the rails since the beginning of the industry and have recently, in the past 20 years, introduced another type of lubricant: Top-of-Rail Friction Modifiers (TORFM). TORFM creates a third body layer between the train wheels and the Top-of-Rail surface to minimize asset wear of both the wheel and rail and to increase the train efficiency. As the United States railroads embrace Precision Scheduled Railroading (PSR), increased train efficiency can allow the railroads to run longer trains with fewer locomotives. This increases the efficiency and capability of the rail network and also decreases the fuel burned and the amount of rail and wheel wear. TORFM has been proven to be effective and is widely adopted, but the railroads are still in need of tools to determine the presence and absence of these thin and often nearly invisible layers of lubricant on the rail surface. This research uses lasers as tool to quantify the level of lubrication of the rail surface. The presence of rail lubricants, such as TORFM, on the rail surface change the amount of light that is reflected and scattered off the shiny steel surface. These changes are often small but can be captured by photodetectors housed in the instrument. By plotting the detected sensor values, trends in the lubricity signal can be tracked and evaluated to determine the presence or absence of rail lubricants and assess the overall quality of lubrication on the rail at specific locations down track. The research in this thesis takes existing methods that were used for single spot inspections and adapts them to a moving platform. The moving platform is able to continuously scan the Top-of-Rail surface as the instrument moves along and generates continuous moving evaluations of rail lubricity. This can be especially important when the lubricity is not uniform and allows for trends in the data to be analyzed to provide more consistent and precise evaluations of the lubricity trends down rail. Optical tools like this sensor, which are by nature non-contact sensors, can easily be adapted to existing track measurement railcars and deployed system wide. This solves a strong need for railroad engineers: to be able to identify the presence of rail lubricants and evaluate the effectiveness of their lubrication practices.
96

SUMO-1 conjugation blocks beta-amyloid-induced astrocyte reactivity.

Hoppe, J.B., Rattray, Marcus, Tu, H., Salbego, C.G., Cimarosti, H. 06 1900 (has links)
No / Astrocyte reactivity is implicated in the neuronal loss underlying Alzheimer's disease. Curcumin has been shown to reduce astrocyte reactivity, though the exact pathways underlying these effects are incompletely understood. Here we investigated the role of the small ubiquitin-like modifier (SUMO) conjugation in mediating this effect of curcumin. In beta-amyloid (Aβ)-treated astrocytes, morphological changes and increased glial fibrillary acidic protein (GFAP) confirmed reactivity, which was accompanied by c-jun N-terminal kinase activation. Moreover, the levels of SUMO-1 conjugated proteins, as well as the conjugating enzyme, Ubc9, were decreased, with concomitant treatment with curcumin preventing these effects. Increasing SUMOylation in astrocytes, by over-expression of constitutively active SUMO-1, but not its inactive mutant, abrogated Aβ-induced increase in GFAP, suggesting astrocytes require SUMO-1 conjugation to remain non-reactive.
97

Genetic basis and timing of a major mating system shift in Capsella

Bachmann, J.A., Tedder, Andrew, Laenen, B., Fracassetti, M., Désamoré, A., Lafon-Placette, C., Steige, K.A., Callot, C., Marande, W., Neuffer, B., Bergès, H., Köhler, C., Castric, V., Slotte, T. 13 September 2019 (has links)
Yes / A crucial step in the transition from outcrossing to self-fertilization is the loss of genetic self-incompatibility (SI). In the Brassicaceae, SI involves the interaction of female and male speci-ficity components, encoded by the genesSRKandSCRat the self-incompatibility locus (S-lo-cus). Theory predicts thatS-linked mutations, and especially dominant mutations inSCR, arelikely to contribute to loss of SI. However, few studies have investigated the contribution ofdominant mutations to loss of SI in wild plant species. Here, we investigate the genetic basis of loss of SI in the self-fertilizing crucifer speciesCapsella orientalis, by combining genetic mapping, long-read sequencing of completeS-hap-lotypes, gene expression analyses and controlled crosses. We show that loss of SI inC. orientalisoccurred<2.6 Mya and maps as a dominant trait totheS-locus. We identify a fixed frameshift deletion in the male specificity geneSCRand con-firm loss of male SI specificity. We further identify anS-linked small RNA that is predicted tocause dominance of self-compatibility. Our results agree with predictions on the contribution of dominantS-linked mutations toloss of SI, and thus provide new insights into the molecular basis of mating system transitions. / Work at Uppsala Genome Center is funded by 550 RFI / VR and Science for Life Laboratory, Sweden. The SNP&SEQ Platform is supported by 551 the Swedish Research Council and the Knut and Alice Wallenberg Foundation. V.C. 552 acknowledges support by a grant from the European Research Council (NOVEL project, 553 grant #648321). The authors thank the French Ministère de l’Enseignement Supérieur et de la 554 Recherche, the Hauts de France Region and the European Funds for Regional Economical 555 Development for their financial support to this project. This work was supported by a grant 556 from the Swedish Research Council (grant #D0432001) and by a grant from the Science for 557 Life Laboratory, Swedish Biodiversity Program to T.S. The Swedish Biodiversity Program is 558 supported by the Knut and Alice Wallenberg Foundation.
98

Low-concentrating, stationary solar thermal collectors for process heat generation

Hess, Stefan January 2014 (has links)
The annual gain of stationary solar thermal collectors can be increased by non-focusing reflectors. Such concentrators make use of diffuse irradiance. A collector’s incidence angle modifier for diffuse (diffuse-IAM) accounts for this utilization. The diffuse irra-diance varies over the collector hemisphere, which dynamically influences the diffuse-IAM. This is not considered by state-of-the-art collector models. They simply calculate with one constant IAM value for isotropic diffuse irradiance from sky and ground. This work is based on the development of a stationary, double-covered process heat flat-plate collector with a one-sided, segmented booster reflector (RefleC). This reflector approximates one branch of a compound parabolic concentrator (CPC). Optical meas-urement results of the collector components as well as raytracing results of different variants are given. The thermal and optical characterization of test samples up to 190 °C in an outdoor laboratory as well as the validation of the raytracing are discussed. A collector simulation model with varying diffuse-IAM is described. Therein, ground reflected and sky diffuse irradiance are treated separately. Sky diffuse is weighted with an anisotropic IAM, which is re-calculated in every time step. This is realized by gener-ating an anisotropic sky radiance distribution with the model of Brunger and Hooper, and by weighting the irradiance from distinct sky elements with their raytraced beam-IAM values. According to the simulations, the RefleC booster increases the annual out-put of the double-covered flat-plate in Würzburg, Germany, by 87 % at a constant inlet temperature of 120 °C and by 20 % at 40 °C. Variations of the sky diffuse-IAM of up to 25 % during one day are found. A constant, isotropic diffuse-IAM would have under-valued the gains from the booster by 40 % at 40 °C and by 20 % at 120 °C. The results indicate that the gain of all non-focusing solar collectors is undervalued when constant, isotropic diffuse-IAMs calculated from raytracing or steady-state test data are used. Process heat generation with RefleC is demonstrated in a monitored pilot plant at work-ing temperatures of up to 130 °C. The measured annual system utilization ratio is 35 %. Comparing the gains at all inlet temperatures above 80 °C, the booster increases the an-nual output of the double-covered flat-plates by 78 %. Taking all inlet temperatures, the total annual gains of RefleC are 39 % above that of the flat-plates without reflectors. A qualitative comparison of the new simulation model results to the laboratory results and monitoring data shows good agreement. It is shown that the accuracy of existing collector models can be increased with low effort by calculating separate isotropic IAMs for diffuse sky and ground reflected irradiance. The highest relevance of this work is seen for stationary collectors with very distinctive radiation acceptance.
99

Evaluating the biological relevance of disease consensus modules : An in silico study of IBD pathology using a bioinformatics approach

Ströbaek, Joel January 2019 (has links)
Inflammatory bowel disease encompasses a variety of heterogeneous chronic inflammatory diseases that affect the gastrointestinal tract, where Crohn’s disease and ulcerative colitis are the principal examples. The etiology of these, and many other complex human diseases, remain largely unknown and therefore pose relevant targets for novel research strategies. One such strategy is the in silico application of network theory derived methods to data sourced from publicly available repositories of e.g. gene expression data. Specifically, methods generating graphs of interconnected elements enriched by differentially expressed genes—disease modules—were inferred with data available through the Gene Expression Omnibus. Based on a previous method, the current project aimed to evaluate disease modules, combined from stand-alone inferential methods, in disease consensus modules: representing pathophenotypical motifs for the diseases of interest. The modules found to be significantly enriched by genome-wide association study inferred single-nucleotide polymorphisms, as validated using the Pathway Scoring Algorithm, were subsequently subjects for further analysis using Kyoto Encyclopedia of Genes and Genomes-pathway enrichment, and literature searches. The results of this study adheres to previous findings relating to the employed method, but lack any novelty pertaining the diseases of interest. However, the results substantiate the preceding methods’ conclusion by including parameters that increase statistical validity. In addition, the study contributed to peripheral results concerning both the methodology of consensus module methods, and the elucidation of inflammatory bowel disease etiology and disease subtype differentiation, that pose interesting subjects for future investigation.
100

Determinação de chumbo em açúcar por espectrometria de absorção atômica em forno de grafite tratado com tugstênio e ródio / Determination of lead in sugar by graphite furnace atomic absorption spectrometry (GFAAS) treated with tungsten-rhodium

Souza, Paulino Florêncio de 18 January 2005 (has links)
Um método de baixo custo é proposto para determinação direta de chumbo em açúcar por espectrometria de absorção atômica com forno de grafite e correção de fundo com fonte de deutério, empregando modificação química permanente com 250µg W + 200µg Rh e co-injeção de 5µg Rh. Os experimentos foram realizados com plataforma integrada ou ao no tubo de grafite com aquecimento longitudinal. Para avaliação da modificação química permanente, foram feitos experimentos na ausência de modificação e na presença de modificação química convencional com Pd+Mg. No decorrer do trabalho observou-se ser imprescindível a co-injeção de Rh para a estabilização térmica de chumbo na presença de açúcar. A amostra (8 g) é dissolvida em 100 ml de solução aquosa 0,2% v/v HNO3, e uma alíquota de 10 l é injetada com 5µl de solução de Rh na plataforma do tubo de grafite modelo Universal da Varian tratada com W e Rh. A massa característica (mo) e o limite de detecção do método foram 11 pg Pb e 5 ng g-1 respectivamente, e a vida útil do tubo de grafite foi de 860 queimas. O método apresentou boa reprodutibilidade com coeficiente de variação inferior a 2,5 % (n=3). As características analíticas foram comparadas com os métodos recomendados na literatura. A exatidão do método proposto para determinação direta de chumbo em açúcar foi avaliada pela comparação com método convencional utilizando Pd+Mg e nenhuma diferença estatística foi observada aplicando-se o teste t de Student ao nível de 95% de probabilidade, em amostras que receberam adição de chumbo / A simple method for the direct determination of lead in sugar by graphite furnace atomic absorption spectrometry (GFAAS) with platform treated with 250µg W + 200µg Rh and deuterium background correction is proposed. Samples (8 g) were dissolved in 100 ml of an aqueous solution containing 0,2% v/v HNO3 and 10µl aliquots were co-injected with 5µg Rh into the integrated platform modified with W-Rh of the Universal Varian longitudinal heated graphite atomizer. The characteristic mass (mo) and the method detection limit were 11 pg Pb and 5,0 ng g-1 Pb, respectively, and the tube life time was 860 firings. The relative standard deviation of measurements (n=3) was lower than 2,5 %. For the evaluation of the permanent chemical modifier, parallel experiments were carried in the presence of diluted nitric acid and with the conventional Pd+Mg chemical modifier. Experiments were made either with manual inserted graphite plataforms or integrated plataforms into longitudinal graphite tubes. Comparison of the proposed method with a method based on Pd+Mg chemical modifier showed no statistical differences by applying a t-test at 95% confidence level, for sugar sample solution spiked with lead

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