59 research outputs found

    Analysis of thermoelectric properties in arsenic-based structures using DFT

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    Thermoelectric materials are useful tools for energy conversion that are becoming increasingly ubiquitous in the modern world thanks to their reliability, their autonomy and their compact nature. Their primary limitation is usually their relatively low efficiency, which struggles to be competitive with other energy conversion systems. This thesis focuses on the computational analysis of semiconductors with complex Fermi surfaces in order to identify properties that may be beneficial to thermoelectric function. In doing so, it attempts to refine a methodology built on first principles cal- culations so as to realistically evaluate the characteristics of highly anisotropic crystals, in a field where this approach has traditionally been applied to isotropic materials. Despite the goal specified of thermoelectricity, the properties studied included elec- trical transport properties that may be of interest in multiple other fields of material research. As such, a priority throughout this body of work is to test the strengths, versatility and limitations of a new methodology while applying it on computationally challenging materials. These are the different phases of As2Te3 and As2S3, along with doped and alloyed variants. These materials have, as of the time of writing, been subject to relatively little computational research despite key similarities to well-known thermoelectrics. As a result, a variety of key behaviours have been identified in correlation to ther- moelectric function, and promising figure of merit values have been predicted for As2Te3. While less promising overall, As2S3 has also shown that it can offer some interesting thermoelectric characteristics if specifically selected for, while revealing some of the computational and theoretical limitations of our models. Our method was effective for materials that are very computationally challenging and physically anisotropic, and involved steps that for the most part were quite systematic. This suggests that it may be possible to incorporate its use into a high-throughput evaluation of computationally cheaper materials for thermoelectric optimization

    Exposition Camilo Egas

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    d'Harcourt Marguerite. Exposition Camilo Egas. In: Journal de la Société des Américanistes. Tome 18, 1926. p. 361

    L'opinion catholique allemande et la victoire de Hitler

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    Datos tomados do textoSeparata de: Études (jan. 1931

    Transgenerational transmission of epigenetic traits in traumatization

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    Being the victim of traumatizing events has consequences that can lead to wellknown mental disorders, such as depression. However, newest studies show that these events do not only affect the victims’ behavior, but also the expression levels of specific genes in their blood and in their brain. Latest research discovered little pieces of RNA in the cells that were long thought to be genetic junk. Nevertheless, these so-called miRNAs can regulate the expression of multiple genes, thus modulating metabolism and cell functioning. The aim of this study was to see if childhood traumatization led to a set of differentially expressed miRNA profiles in the peripheral blood. For this, we used subjects from the SHIP trend cohort, who had previously answered various questionnaires, among them the Childhood Trauma Questionnaire and the Patients Health Questionnaire-9 and analyzed the miRNAs in their blood to find out whether there was an association between the score and the dysregulation of certain miRNAs. Furthermore, we selected 5 different independent variables: PHQ-trend, CTQ score, as well as its subscales Abuse and Neglect, and Major Depressive Disorder lifetime prevalence. The analyses showed a set of up- or downregulated miRNAs in the blood. In a second step, we tried to replicate our results comparing them to results in the literature. Some of the significantly dysregulated miRNAs had previously been described as key players in the pathogenesis of MDD, a few even displaying similar results to ours. The next step was to see if the significant miRNAs had common target genes and if these had been described in the literature as having an influence on MDD, showing positive results. One last step was to see if there were also common biological pathways that were modulated by the differentially expressed miRNA. This analysis did not show promising results since there were almost no brain pathways among the results. For future studies, it will be necessary to validate our results using a clinical sample, such as GANI_MED, where the prevalence of childhood traumatization, as well as MDD, is much higher. By doing this, new possibilities of trauma treatment through modulation of epigenetic pathways could arise. If childhood traumatization leads to a set of dysregulated miRNAs that can end in a positive diagnosis of MDD in adulthood, what effects could have a targeted miRNA therapy on the pathogenesis of these psychiatric disorders?Traumatische Erlebnisse können bei ihren Opfern zu belegten psychiatrischen Störungen fĂŒhren. Aktuelle Studien zeigen zudem, dass die Auswirkung von Traumata sich nicht nur im Verhalten der Betroffenen zeigt, sie beeinflusst sogar die AktivitĂ€t spezifischer Gene in Blut und Gehirn. Demnach besitzen miRNAs, RNABruchstĂŒcke die lange als genetischer Abfall eingeordnet wurden, die FĂ€higkeit, Gene zu beeinflussen, und somit den Metabolismus und Zellfunktionen zu regulieren. Diese Arbeit eruiert, ob Kindheitstraumata die Expression von miRNAs im Blut der Opfer verĂ€ndern. Im Rahmen der SHIP Trend Studie beantworteten Probanden unter anderem die standardisierten Fragebögen ‚PHQ 9‘, ‚CTQ‘, und ‚Munich Composite International Diagnostic Interview‘. Eine Blutanalyse vergleicht die Ergebnisse der Fragebögen mit der Expression bestimmter miRNAs bei den Probanden und zeigt eine Reihe hoch- und herabregulierter miRNAs auf. Manche der in unserer Studie als dysreguliert erwiesenen miRNAs wurden in der Literatur bereits im Zusammenhang mit Depression dokumentiert, teils mit vergleichbaren Ergebnissen zu unseren. Als nĂ€chstes prĂŒften wir, ob signifikante miRNAs unseres Experiments gemeinsame Gene modulieren und ob diese Gene in der Literatur als Akteure in der Entstehung und Erhaltung von Depression verstanden werden. Abschließende Untersuchungen sollten zeigen, ob die miRNAs auch gemeinsame biologische Signalwege regulieren. Obgleich sie tatsĂ€chlich an gemeinsamen Signalwegen beteiligt sind, zeigte sich kaum Einfluss auf Gehirnmetabolismus oder -aktivitĂ€t. Unsere Ergebnisse bedĂŒrfen der Validierung in weiteren Experimenten. Wir sehen die Möglichkeit der Wiederholung mit einer klinischen Stichprobe, zum Beispiel im Rahmen der GANI_MED Studie, wo die PrĂ€valenz von Kindheitstraumata, aber auch von Depression höher sind. Dieser Ansatz eröffnet neue Möglichkeiten der Therapierbarkeit psychiatrischer Folgeerkrankungen ĂŒber die Regulierung epigenetischer Mechanismen. Wenn Kindheitstraumata die Expression von miRNAs im Blut der Opfer so verĂ€ndern, dass im Erwachsenenalter folglich eine Depression diagnostiziert wird, welche Auswirkungen hĂ€tte eine gezielte, frĂŒhzeitige Therapie mittels miRNA-Modulation auf die EindĂ€mmung dieser psychiatrischen Erkrankungen
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