A numerical analysis of the relation between CTOD and fatigue crack growth

El cálculo de la vida a fatiga durante la etapa de propagación de la grieta se suele realizar relacionando da/dN con ΔK. Sin embargo, la influencia que en estos análisis tiene el parámetro ΔK debe recaer en algún otro parámetro no lineal cercano al frente de la grieta, ya que estos son los que realmente controlan la velocidad de crecimiento de la grieta. El principal objetivo del presente artículo es intentar mejorar la comprensión del crecimiento de grieta en fatiga empleando el desplazamiento de apertura de la punta de la grieta (CTOD). Este parámetro no ha sido muy empleado en el problema del cierre de grieta y su propagación en fatiga, teniendo un gran potencial. Por este motivo, se ha realizado un análisis numérico para un amplio rango de cargas de amplitud constante en dos aleaciones de aluminio (6016-T4 y 6082-T6). Cuando no se considera el contacto entre los flancos de la grieta se puede observar una relación bien definida entre el valor máximo de CTOD y ΔK, lo cual indica que no existe influencia de la relación de cargas y valida la mecánica de la fractura elástica lineal. Se ha encontrado una relación lineal entre los valores de CTOD y ΔK al considerar una doble escala logarítmica. Los valores de CTOD cuando se considera el contacto se superpone a los resultados sin contacto, únicamente cuando se emplea el ΔK efectivo, lo cual valida el concepto del cierre de grieta. Se ha encontrado una relación lineal entre da/dN y CTOD cuando se considera una doble escala logarítmica para la aleación de aluminio 6082-T6.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Binary Neutron Star Merger Remnants as Sources of Cosmic Rays Below the "Ankle"

We investigate non-thermal electron and nuclei energy losses within the binary neutron star merger remnant produced by the event GW170817. The lack of a cooling feature within the detected synchrotron emission from the source is used to constrain the magnetic field at the mG level, assuming that this emission is electron synchrotron in origin, and that the accelerated spectrum in the electrons follows the form $dN/dE_e \propto E_e^{-2}$. The level of subsequent gamma-ray emission from the source is demonstrated to provide a further constraint on the source magnetic field strength. We also put forward alternative strong ($\sim$G) magnetic field scenarios able to support this emission. For such stronger fields, the photo-disintegration of non-thermal nuclei within the source is considered, and a bottleneck period of $\sim$5-30 days is found when this process peaks. We find that this class of source is in principle able to support the population of cosmic rays detected at Earth below the "ankle".Comment: Accepted for publication in Astropart. Phy

Considerations on the role of federalism in managing ethnic plurality in multinational states in conflict prevention

The existence of several ethnic, religious and/or linguistic groups whose rights are not acknowledged or are continuously violated leads to tension with unpredictable consequences. If, in some cases, those groups use peaceful means to ensure that their specificities are acknowledged but, in other cases, there is frequent use of force to attain the same goals. This type of conflict occurred in the western Balkans in the 1990s or still take place in regions such as the Caucasus, the Democratic Republic of Congo, Nigeria or Myanmar in which the ethnic element, together with the religious issue, are the main causes. Though it is true that several solutions have been presented to respond to the tensions inherent to ethnic diversity of multinational States, it is also true that the several theoretical practical models have not always met the objectives and, above all, resolved situations of peace, which are often of negative peace. From minority rights to federalism, we may identify principles whose importance and adequacy to contexts may be defined as formal peace. Nevertheless, it remains important to include and frame those elements within specific cases, considering that each case is different and adapting these principles to a specific situation does not prevent them from being inadequate to a situation apparently similar. It is therefore crucial that considerations are raised on the role a political and administrative organization model such as federalism may play, partly as a complement to the law of minorities as a tool to manage ethnic diversity in States that may be defined as multinational, as well as to prevent ethnic conflicts

Regucalcin regulation by extracellular calcium in prostate cells

Prostate cancer is one of the most diagnosed diseases in men at the present time. It is well known that changes in calcium (Ca2+) homeostasis are derived from modifications in Ca2+ regulating elements. Regucalcin (RGN) is a Ca2+-binding protein which plays an important role in maintenance of intracellular Ca2+ homeostasis and regulation of apoptosis and proliferation. RGN is underexpressed in prostate cancer cells, suggesting that a loss of RGN expression may be associated with tumor development. In vivo studies have also shown that Ca2+ administration acts as a regulator of RGN expression in liver and kidney tissues. However, no studies on the characterization of RGN regulation by extracelular Ca2+ in prostate cells have been conducted. To attain this goal, prostate cells were stimulated with different doses of CaCl2 during several periods of time. To assess RGN mRNA and protein expression, Real Time PCR and Western Blot were carried out, respectively. Moreover, the cell viability in response to treatments was evaluated through MTS assays. Our results show that nonneoplastic PNT1A cells present higher levels of RGN when compared to neoplastic LNCaP or PC3 cells. We also verified that RGN expression in PNT1A cells is up-regulated by extracellular Ca2+ at 1,5h after stimuli, but its expression decreases after 3h of stimulation. We also showed that high doses of extracellular Ca2+ induce different effects on cell proliferation between PNT1A and LNCaP cells. This study led us to conclude that RGN appears to be regulated by extracellular Ca2+ levels in prostate cells and that an elevation of extracellular Ca2+ promotes high rates of cell proliferation in LNCaP cells, possibly due to the down-regulation in RGN expression in cancer cells.O cancro da próstata é de umas das doenças mais diagnosticadas em homens de países Ocidentais. É sabido que as alterações na homeostase do cálcio (Ca2+) derivam de modificações ao nível dos elementos reguladores do Ca2+ . A regucalcina (RGN) é uma proteína de ligação ao Ca2+ que desempenha um papel importante ao nível da manutenção da homeostase do Ca2+ intracelular, tal como na regulação da apoptose e da proliferação. A RGN é sub-expressa em células do cancro da próstata, sugerindo que a perda de expressão da RGN poderá estar associada com o desenvolvimento tumoral. Estudos in vivo mostram que a administração de Ca2+ actua como um regulador da expressão de RGN em fígado e de rim de rato. No entanto, ainda nenhum estudo acerca da caracterização da regulação da RGN pelo Ca2+ extracelular foi conduzido em células de próstata. Para atingir este objectivo, células da próstata foram estimuladas com diferentes doses de CaCl2 durante vários períodos de tempo. Para avaliar a expressão do mRNA e da proteína, estudos de Real Time PCR e de Western Blot foram efectuados, respectivamente. A viabilidade celular em resposta aos diferentes tratamentos foi avaliada através de ensaios de MTS. Os nossos resultados mostram que células não neoplásicas PNT1A apresentam níveis elevados de RGN quando comparados com células neoplásicas LNCaP e PC3. Também verificamos que a expressão de RGN em células PNT1A é regulada positivamente pelo Ca2+ extracelular às 1,5h de estímulo, sendo que a sua expressão começa a diminuir após as 3h. Mostramos ainda que elevadas doses de Ca2+ extracelular induzem diferentes efeitos ao nível da proliferação entre as células PNT1A e LNCaP. Este estudo levou-nos a concluir que a RGN aparenta ser regulada através do Ca2+ extracelular em células da próstata e que uma elevação nos níveis de Ca2+ extracelular poderá promover elevadas taxas de proliferação em células LNCaP, possivelmente devido a sub-expressão de RGN verificada em células tumorais

Implementation of an information retrieval system within a central knowledge management system

Páginas numeradas: I-XIII, 14-126Estágio realizado na Wipro Portugal SA e orientado pelo Eng.º Hugo NetoTese de mestrado integrado. Engenharia Informática e Computação. Faculdade de Engenharia. Universidade do Porto. 201