732 research outputs found
Multiscale Modeling of Curing and Crack Propagation in Fiber-Reinforced Thermosets
Aufgrund ihres Leichtbaupotenzials bei relativ geringen Kosten gewinnen glasfaserverstärkte Polymere in industriellen Anwendungen zunehmend an Bedeutung. Sie verbinden die hohe Festigkeit von Glasfasern mit der Beständigkeit von z.B. duroplastischen Harzen. Bei der Verarbeitung von faserverstärkten Duroplasten kommt es zu einer chemischen Reaktion des Harzes. Die chemische Reaktion geht mit einer chemischen Schrumpfung einher. In Verbindung mit der thermischen Ausdehnung kann das Material bereits beim Herstellungsprozess beschädigt werden. Auch wenn das Komposit nicht vollständig versagt, kann es zu Mikrorissbildung kommen. Diese Schäden können die Blastbarkeit des Bauteils und damit seine Lebensdauer beeinträchtigen. Faserverstärkte Duroplaste enthalten Strukturen auf verschiedenen Längenskalen, die das Verhalten des Gesamtbauteils beeinflussen und daher für eine genaue Vorhersage der Rissbildung berücksichtigt werden müssen. Das Verständnis der Mechanismen der Rissbildung auf den verschiedenen Längenskalaen ist daher von großem Interesse. Auf der Grundlage von Molekulardynamiksimulationen wird ein Harzsystem zusammen mit einer Faseroberfläche und einer Schlichte auf der Nanoskala betrachtet und ein systematisches Verfahren für die Entwicklung eines ausgehärteten Systems vorgestellt. Eine zweistufige Reaktion, eine Polyurethanreaktion und eine radikale Polymerisation, wird auf der Grundlage eines etablierten Ansatzes modelliert. Anhand des fertig ausgehärteten Systems werden Auswertungen über gemittelte Größen und entlang der Normalenrichtung der Faseroberfläche durchgeführt, was eine räumliche Analyse der Faser-Schlichtharz-Grenzfläche erlaubt. Auf der Mikrolängenskala werden die einzelnen Fasern räumlich aufgelöst. Mit Hilfe der Kontinuumsmechanik und der Phasenfeldmethode wird das Versagen während des Aushärtungsprozesses auf dieser Längenskala untersucht. In der Materialwissenschaft wird die Phasenfeldmethode häufig zur Modellierung der Rissausbreitung verwendet. Sie ist in der Lage, das komplexe Bruchverhalten zu beschreiben und zeigt eine gute Übereinstimmung mit analytischen Lösungen. Dennoch sind die meisten Modelle auf homogene Systeme beschränkt, und nur wenige Ansätze für heterogene Systeme existieren. Es werden bestehende Modelle diskutiert und ein neues Modell für heterogene Systeme abgeleitet, das auf einem etablierten Phasenfeldansatz zur Rissausbreitung basiert. Das neue Modell mit mehreren Rissordnungsparametern ist in der Lage, quantitatives Risswachstum vorherzusagen, wo die etablierten Modelle eine analytische Lösung nicht reproduzieren können. Darüber hinaus wird ein verbessertes Homogenisierungsschema, das auf der mechanischen Sprungbedingung basiert, auf das neuartige Modell angewandt, was zu einer Verbesserung der Rissvorhersage selbst bei unterschiedlichen Steifigkeiten und Risswiderständen der betrachteten Materialien führt. Zudem wird zur Erzeugung digitaler Mikrostrukturen, die für Aushärtungssimulationen im Mikrobereich verwendet werden, ein Generator für gekrümmte Faserstrukturen eingeführt. Anschließend wird die Verteilung mechanischer und thermischer Größen für verschiedene Abstraktionsebenen der realen Mikrostruktur sowie für verschiedene Faservolumenanteile verglichen. Schließlich wird das neue Rissausbreitungsmodell mit dem Aushärtungsmodell kombiniert, was die Vorhersage der Mikrorissbildung während des Aushärtungsprozesses von glasfaserverstärktem UPPH-Harz ermöglicht
Illuminating palaeolithic art using virtual reality: A new method for integrating dynamic firelight into interpretations of art production and use
Approaches to Palaeolithic art have increasingly shifted beyond the traditional focus on engraved or depicted forms in isolation, to appreciating the sensorial experience of art making as integral to shaping the form of depictions and the meaning imbued within them. This kind of research appreciates an array of factors pertinent to how the art may have been understood or experienced by people during the Palaeolithic, including placement, lighting, accessibility, sound, and tactility. This paper contributes to this “sensory turn” in Palaeolithic art research, arguing that the roving light cast by the naked flame of fires, torches or lamps is an important dimension in understanding artistic experiences. However, capturing these effects, whether during analysis, as part of interpretation, or presentation, can be challenging. A new method is presented in virtual reality (VR) modelling – applied to Palaeolithic art contexts for the first time - as a safe and non-destructive means of simulating dynamic light sources to facilitate analysis, interpretation, and presentation of Palaeolithic art under actualistic lighting conditions. VR was applied to two Magdalenian case studies: parietal art from Las Monedas (Spain) and portable stone plaquettes from Montastruc (France). VR models were produced using Unity software and digital models of the art captured via whitelight (Montastruc) and photogrammetric (Las Monedas) scans. The results demonstrate that this novel application of VR facilitates the testing of hypotheses related to the sensorial and experiential dimensions of Palaeolithic art, allowing discussions of these elements to be elevated beyond theoretical ideas
Under construction: infrastructure and modern fiction
In this dissertation, I argue that infrastructural development, with its technological promises but widening geographic disparities and social and environmental consequences, informs both the narrative content and aesthetic forms of modernist and contemporary Anglophone fiction. Despite its prevalent material forms—roads, rails, pipes, and wires—infrastructure poses particular formal and narrative problems, often receding into the background as mere setting. To address how literary fiction theorizes the experience of infrastructure requires reading “infrastructurally”: that is, paying attention to the seemingly mundane interactions between characters and their built environments. The writers central to this project—James Joyce, William Faulkner, Karen Tei Yamashita, and Mohsin Hamid—take up the representational challenges posed by infrastructure by bringing transit networks, sanitation systems, and electrical grids and the histories of their development and use into the foreground. These writers call attention to the political dimensions of built environments, revealing the ways infrastructures produce, reinforce, and perpetuate racial and socioeconomic fault lines. They also attempt to formalize the material relations of power inscribed by and within infrastructure; the novel itself becomes an imaginary counterpart to the technologies of infrastructure, a form that shapes and constrains what types of social action and affiliation are possible
Mapeamento dos processos de movimentos de massa gravitacionais e erosivos na porção leste da Ilha da Trindade, Brasil
Orientadora: Profa. Dra. Maria Cristina de SouzaCoorientadores: Prof. Dr. Lázaro Valentin Zuquette, Prof. Dr. Rodolfo José AnguloTese (doutorado) - Universidade Federal do Paraná, Setor de Ciências da Terra, Programa de Pós-Graduação em Geologia. Defesa : Curitiba, 29/03/2023Inclui referênciasResumo: A Ilha da Trindade é um território brasileiro remoto e de difícil acesso, localizado no Atlântico Sul, a cerca de 1.140 km do setor sudeste da margem continental brasileira. O acesso à ilha é restrito a militares e pesquisadores, sendo realizado por navios da Marinha do Brasil. A Ilha da Trindade desempenha um papel estratégico no contexto das questões oceanopolíticas e é uma região de grande importância para a Amazônia Azul, justificando a presença de ocupação e operações de soberania no local. Com uma área emersa de 12 km2, apresenta um relevo escarpado dominado por rochas vulcânicas alcalinas, como derrames de lava, corpos fonolíticos remanescentes e depósitos piroclásticos. A evolução da paisagem na ilha é influenciada pela geodinâmica destrutiva, resultando na formação de depósitos quaternários que cobrem grande parte do terreno. Nesse contexto, a ocupação atual na Ilha da Trindade está sujeita a processos geológicos exógenos, como erosão e movimentos de massa gravitacionais. No entanto, a avaliação do risco desses processos na ilha é desafiadora devido à heterogeneidade geológica, ao isolamento geográfico de difícil acesso e à falta de dados temporais e mapeamentos detalhados. O objetivo principal desta tese foi realizar um mapeamento geológico-geotécnico para compartimentar a área de estudo, concentrando-se nas condições propícias para ocorrência de movimentos de massa gravitacionais e processos erosivos. A área de estudo abrange as bacias hidrográficas localizadas na região leste da ilha, onde há ocupação permanente, edifícios e infraestrutura. Para atingir o objetivo proposto, foram conduzidas extensas campanhas de campo entre 2018 e 2022, utilizando técnicas de campo e geoprocessamento, visando o mapeamento e inventário dos processos erosivos e de movimentos gravitacionais. Realizaram-se descrições detalhadas do substrato rochoso, dos materiais inconsolidados e das feições resultantes dos processos exógenos, utilizando critérios geológico-geotécnicos. Para a caracterização do terreno, incluindo a geomorfologia, hidrografia e a obtenção de dados temporais da evolução das feições, foram empregadas geotecnologias, como a utilização de aeronaves remotamente pilotadas (RPA) e o sistema global de navegação por satélite (GNSS) em tempo real (RTK). Além disso, foram realizados ensaios de campo em parcela experimental e instalou-se um pluviógrafo digital (com resolução de 0,33 mm/s) para analisar a relação entre as chuvas e os processos superficiais. A área de estudo apresenta uma variação altimétrica de 425 metros, com declividades que variam de 0% a 75%. Isso resulta em um relevo fortemente ondulado, que abrange 34% da área total. As bacias hidrográficas possuem drenagens predominantemente efêmeras com sistemas de até a 4ª ordem. Também foram observados conjuntos de drenagens efêmeras e ramificadas relacionados à dinâmica dos leques aluviais. A área de estudo foi dividida em 23 unidades de terreno, incluindo zona costeira com infraestrutura, rios efêmeros e perenes, encostas com erosão linear, erosão interna, erosão intersulcos, formação de leques aluviais, encostas cobertas por depósitos de avalanche, quedas e tombamentos, encostas íngremes com rochas expostas, e estruturas vulcânicas como necks e domos. O substrato rochoso predominante é constituído por fonolitos e depósitos piroclásticos do Complexo Trindade, correspondendo a aproximadamente 40% da área, enquanto olivina-nefelinitos e depósitos piroclásticos da Formação Morro Vermelho compõem cerca de 60%. Os depósitos quaternários recobrem cerca de 44% da área, sendo que aproximadamente 56% da superfície é composta por rochas expostas. Foi constatado que a topografia da área de estudo está passando por uma intensa fase destrutiva, relacionada ao processo de erosão diferencial deflagrada principalmente pelo escoamento superficial de águas das chuvas, alta declividade do terreno e baixa densidade de vegetação. As chuvas episódicas, como ciclones e tempestades, têm um papel crucial nos processos destrutivos da ilha, deflagrando processos erosivos acelerados, movimentos de massa gravitacionais e danos ambientais. Sua ocorrência deve ser monitorada ao analisar a degradação e evolução da região. Neste contexto, a ocupação e o patrimônio da Ilha da Trindade estão sujeitos a processos geológicos que representam perigos significativos de danos e perda de vidas. Os movimentos de massa gravitacionais acelerados pelos processos erosivos hídricos, particularmente desencadeados pelas chuvas episódicas, emergem como a maior ameaça. Além disso, a evolução da paisagem na ilha é uma combinação de processos naturais e da influência humana, com impactos expressivos desde a colonização inicial. Portanto, a Ilha da Trindade se enquadra em um contexto de processos quase-naturais. O trabalho pioneiro e de extrema importância realizado nesta tese destaca a necessidade de medidas de mitigação e proteção adequadas para garantir a segurança das áreas habitadas na Ilha da Trindade, devido aos perigos significativos representados pelos processos geológicos, como os movimentos de massa gravitacionais acelerados pelos processos erosivos hídricos, especialmente desencadeados pelas chuvas episódicas.Abstract: Trindade Island is an inhabited Brazilian territory. It is a remote and isolated island in the South Atlantic Ocean, approximately 1,140 km southeast of the Brazilian coast. Trindade Island plays a strategic role in the context of ocean political issues. It is a region of great importance to the Blue Amazon and justifies the presence of occupation and sovereignty operations on the island. The island presents a 12 km2 emergent area with rugged terrain formed by alkaline volcanic rocks, such as lava flows, remaining phonolitic structures, and pyroclastic deposits. Also, destructive geodynamics influences the evolution of the landscape. These processes lead to the Quaternary deposits formation that encompass a significant portion of the land. In this context, the Trindade Island occupation has been exposed to exogenous geological processes, such as erosion and gravitational mass movement. However, assessing the risk of these processes on the island is challenging due to geological heterogeneity, difficult-to-access isolation, and the lack of temporal data and detailed mapping. This research aimed to conduct comprehensive geological-geotechnical mapping to target areas prone to gravitational mass movements and erosive processes. The study area encompasses the watersheds from the eastern region of the island, where there are permanent settlements, buildings, and infrastructure. Extensive field campaigns were conducted from 2018 to 2022, utilizing field techniques and geoprocessing methods. The primary focus was to map and document erosive processes and gravitational movements. We conducted detailed descriptions utilizing geological-geotechnical criteria to analyze the bedrock, unconsolidated materials, and features resulting from exogenous processes. We employed technologies to characterize the terrain, such as remotely piloted aircraft (RPA) and real-time kinematic (RTK) global navigation satellite systems (GNSS). These techniques involved assessing geomorphology and hydrography and gathering temporal data on the evolution of terrain features. We conducted field tests in an experimental plot and installed a digital pluviograph (with a resolution of 0.33 mm/s) to analyze the relationship between rainfall and surface processes. The study area exhibits an altimetric variation of 425 meters, with slopes ranging from 0% to 75%. This results in a highly undulating relief, covering 34% of the total area. The watersheds feature predominantly ephemeral streams with systems up to the 4th order. We observed sets of ephemeral and branching streams related to the dynamics of alluvial fans. We divided the study area into 23 land units, including the coastal zone with infrastructure, ephemeral and perennial rivers, linear erosion slopes, internal erosion, gully erosion, alluvial fan formation, slopes covered by avalanche deposits, cliffs, and toppled rocks, steep slopes with exposed rocks, and volcanic structures such as necks and domes. The dominant bedrock substrate is composed of phonolites and pyroclastic deposits from the Trindade Complex, which account for approximately 40% of the area, while olivine-nephelinites and pyroclastic deposits from the Morro Vermelho Formation make up around 60%. Quaternary deposits cover about 44% of the terrain, with exposed rocks comprising approximately 56% of the surface. We observed that the topography of the study area is undergoing an intense phase of destruction, primarily associated with differential erosion processes triggered by surface runoff from rainfall, high terrain slopes, and low vegetation density. Episodic rainfall events, such as cyclones and storms, play a crucial role in the destructive processes on the island, triggering accelerated erosive processes, gravitational mass movements, and environmental damage. Monitoring their occurrence is essential when assessing the degradation and evolution of the region. In this context, the occupation and heritage of Trindade Island are subject to geological processes that pose significant hazards to life and property. Accelerated gravitational mass movements, driven by water-induced erosive processes triggered by episodic rainfall events, emerge as the greatest threat. Additionally, the island's landscape evolution encompasses natural processes and human influence, with significant impacts dating back to its initial colonization. Thus, Trindade Island exists within a context of quasi-natural processes. The pioneering and crucial research carried out in this thesis emphasizes the need for appropriate mitigation and protection measures to ensure the safety of inhabited areas on Trindade Island, given the significant hazards posed by geological processes such as accelerated gravitational mass movements driven by water-induced erosive processes triggered by episodic rainfall events
Assessing the therapeutic potential of mitochondrial uncoupler BAM15
Our health rests on the condition of our mitochondria. One class of drugs shown to improve mitochondrial function by targeting bioenergetics are mitochondrial uncouplers. These drugs decrease the efficiency of adenosine triphosphate (ATP) production and concurrently decrease the production of reactive oxygen species (ROS). Therefore, mitochondrial uncoupling may have efficacy in treating conditions of nutrient excess such as obesity and metabolic disease, as well as conditions associated with oxidative damage such as ageing.
The objective of this thesis was to assess the therapeutic potential of small molecule mitochondrial uncoupler BAM15. BAM15 was found to increase energy expenditure in a dose dependent manner, without evidence of toxicity or hyperthermia. BAM15 was subsequently tested in C57BL/6J mouse models of obesity, non-alcoholic fatty liver disease (NASH) and healthy ageing. In a western diet-induced model of obesity BAM15 was found to prevent and reverse fat accumulation and insulin resistance without altering food intake or decreasing lean body mass. Beneficial effects were observed on liver fat accumulation, inflammation, and oxidative damage. Hyperinsulinemic-euglycemic clamp studies showed that BAM15 improved insulin sensitivity in multiple tissue types. In a biopsy-confirmed Amylin diet-induced model of non-alcoholic steatohepatitis (NASH), BAM15 led to improvements in liver enzymes, steatosis, and inflammation. Finally, BAM15 was found to prevent age-related fat gain, without loss of lean mass. It was also protective against age-related loss of insulin sensitivity and loss of circadian fluctuation in respiratory exchange ratio (RER).
This thesis has validated the therapeutic potential of BAM15 and laid the foundation for continued research into how targeting mitochondrial bioenergetics can improve health
Disinformation and Fact-Checking in Contemporary Society
Funded by the European Media and Information Fund and research project PID2022-142755OB-I00
In-vivo corneal confocal microscopy in chemotherapy-induced peripheral neuropathy
Chemotherapy-induced peripheral neuropathy (CIPN) is a debilitating condition affecting up to 80% of treated patients with severe impact on their quality of life. While some patients experience improvement in signs and symptoms after dose reduction or cessation of treatment, many develop chronic neuropathy which can last for years leading to high economic and disease burden. Assessment of CIPN currently relies on crude severity grading by clinicians, subjective patient questionnaires and nerve conduction studies limited to large nerve fibre assessment. Unfortunately, there is still an absence of reliable and efficient methods which can provide sensitive endpoint measures particularly with small nerve fibre assessments. While ocular surface neural changes have been well established as potential diagnostic and prognostic markers in other aetiologies of peripheral neuropathy particularly diabetes, there have been limited studies in CIPN. Hence, the overall aim of this thesis was to investigate whether neural changes on the ocular surface occurred with neurotoxic chemotherapy along with CIPN development.
This was explored across several studies primarily with in-vivo corneal confocal microscopy (CCM). The first series, comprised of five cross-sectional studies, assessed patients who have already completed neurotoxic chemotherapy treatment for cancer and may have persistent CIPN. Neurotoxic chemotherapeutic drugs including taxanes or platinum compounds were the focus as these were the most commonly associated with CIPN. Chapter 2 analysed the reproducibility of corneal nerve image selection and analysis outcomes from the central cornea and inferior whorl region, a distinct landmark of the sub-basal nerve plexus. Analysis of both regions produced reliable and reproducible findings, although the inferior whorl region had slightly higher variability compared to the central cornea. This study also demonstrated that complex inferior whorl patterns, more commonly found in patients with CIPN compared to healthy individuals, may reduce reproducibility of image selection and analysis. Chapter 3 assessed whether corneal nerve damage occurred in patients who have already completed treatment with neurotoxic chemotherapy prior to assessment. This study established that there was corneal nerve reduction particularly in patients treated with paclitaxel who still had peripheral neuropathy post-treatment cessation, and this reduction was associated with worse fine hand dexterity. Chapter 4 then investigated whether the loss of nerves described in the previous study contributed to ocular surface discomfort associated with dry eye disease, which is a widespread and overlooked condition severely impacting quality of life analogous to CIPN. In this study, paclitaxel-treated patients with CIPN who had more severe corneal nerve fibre reduction, also had higher risk of suffering from ocular surface discomfort and worse visual function compared to patients without neuropathy and healthy controls. The study highlighted the need for eye care clinicians and medical oncologists to be aware of such ocular surface symptoms even in those who have completed neurotoxic chemotherapy treatment. Chapter 5 investigated corneal dendritic cells which are antigen-presenting cells and potent initiators of inflammatory responses residing in the sub-basal corneal nerve plexus. This study was conducted as these immune cells can also be observed with CCM, and neuroinflammation and immune cell infiltration have been implicated in the pathophysiology of CIPN. The findings indicated that there was an elevated presence of immature dendritic cell density in oxaliplatin-treated patients well after treatment cessation, but not in paclitaxel-treated patients. Chapter 6 evaluated the concentration of substance P, a sensory neuropeptide primarily expressed by small nerve fibres in the cornea and essential for maintenance of ocular surface health, in the tears. While the previous study demonstrated elevated dendritic cell density in oxaliplatin-treated patients, this study showed reduced substance P concentration in paclitaxel-treated patients instead. These two studies further emphasise potential differences in pathophysiological mechanisms underlying CIPN associated with these two drugs.
Chapter 7 involved a longitudinal study which observed ocular surface and peripheral neuropathic changes during the treatment period, and monitoring patients up to twelve months post-treatment cessation. The study found a progressive loss in corneal nerve parameters with increasing cumulative dose from baseline to end of treatment particularly with taxane treatment, while other ocular surface measures including corneal dendritic cells and tear film substance P levels did not have significant changes. The findings indicated a potential mixed pattern of small and large nerve fibre involvement with taxane treatment, while oxaliplatin affects predominantly large nerve fibres. Corneal nerve fibre length measured during the treatment period was also lower in patients who continued to have persistent CIPN after treatment cessation compared to patients who did not, indicating the potential for early detection of corneal nerve fibre loss as an indicator of CIPN progression.
Future studies investigating corneal nerve changes at multiple timepoints in larger studies involving taxane-treated patients may provide greater insight into the diagnostic and predictive utility of CCM in CIPN. Improvements in CCM instrumentation and methodology may also contribute to better assessment of the state of the sub-basal corneal nerve plexus. The discussion section further explores these issues in relation to the clinical applicability or scalability of CCM and potential solutions to improve imaging capabilities in the future
2008 GREAT Day Program
SUNY Geneseo’s Second Annual GREAT Day.https://knightscholar.geneseo.edu/program-2007/1002/thumbnail.jp
- …