Frequency and temperature dependence of actuating performance of Bi1/2Na1/2TiO3-BaTiO3 based relaxor/ferroelectric composites

Recently, composites of relaxors (matrix) and either ferroelectric or nonergodic relaxor (seed) were proposed as a solution to resolving one of the main drawbacks of incipient piezoceramics, namely the requirement for high driving electric fields. In this study, we investigate the temperature and frequency dependence of the actuating performance of Bi1/2Na1/2TiO3-BaTiO3-based composites. Apart from the reduction of driving field, the composite architecture offers an extra degree of freedom for tailoring the temperature stability for different operational conditions for actuators. High strain values appear to be sensitive especially to driving frequency. This is originated by the time-dependent process of the coalescence of polar nanoregions. In effect, proximity of driving field and poling field leads to high strain sensitivity. Hence, the driving electric field needs to be adjusted in order to meet the desired frequency specifications for given applications.open0

Age-, experience- and avoidance learning-related synaptic plasticity in leaf-cutting ants

Dissertação de mestrado em Biologia Celular e Molecular apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra.A proteína mixed-lineage kinase 3 (MLK3) é uma cinase de serina/treonina vastamente expressa que está envolvida em diferentes funções fisiológicas como proliferação, apoptose, sobrevivência e migração celular. Ao responder a mitogénios e estímulos de stress regula a sinalização das MAPK através da activação das vias da ERK, JNK e p38. O seu domínio cinase é crucial para fosforilar e consequentemente activar moléculas alvo. Contudo, a activação da MLK3 nem sempre é requerida para a modulação de algumas funções por ela induzidas. A MLK3 pode ainda funcionar como proteína scaffold, ligando diferentes vias de sinalização. Mutações na MLK3 foram descritas, pela primeira vez, em 2010 pelo nosso grupo. Nesse mesmo trabalho, foi demonstrado que mutações missense na MLK3 possuíam potencial transformante e tumorigénico. Duas dessas mutações (P252H e R799C) mostraram um comportamento invasivo. Tendo em conta estas informações nós estabelecemos linhas celulares (HEK293) que expressam de uma forma estável estas mutações para assim identificar os efeitos celulares a elas associados e avaliar quais os alvos moleculares dependentes desses dois mutantes da MLK3. Verificámos que a mutação no domínio cinase da MLK3 (P252H) confere propriedades diferentes quando comparada com a mutação localizada no domínio rico em prolina. A mutação P252H parece induzir uma maior migração celular, enquanto a mutação R799C parece interferir com a diferenciação celular. Além disso, nós verificámos que ambas as mutações regulam a via do WNT de maneira distinta, seja através da activação da via canónica ou da não canónica. Em resumo, o trabalho descrito nesta tese mostra que duas das mutações na MLK3, previamente descritas, interferem com vias de sinalização cruciais do desenvolvimento colorectal e neste sentido contribuem para a tumorigénese colorectal.Mixed-lineage kinase 3 (MLK3) is a serine/threonine kinase widely expressed and involved in different physiological functions, such as proliferation, apoptosis, cell survival and cell migration. Responding to mitogens and stress stimuli it regulates MAPK signalling through activation of ERK, JNK, p38 pathways. Its kinase domain is crucial to phosphorylate and thus activate downstream targets. However, MLK3 activation is not always required to MLK3-induced modulation of some cellular functions. MLK3 may indeed function as a scaffold protein, linking different signalling pathways. MLK3 mutations were reported, for the first time, in 2010 by our group. Missense MLK3 mutations were found to be able to harbour transforming and tumourigenic potential. Two of the mutations (P252H and R799C) were found to show an invasive behaviour. Taking this data into account we generated HEK293 stable cell lines harbouring these mutations in order to identify associated cellular effects and evaluate which molecular targets were dependent of these two MLK3 mutants. We found that a mutation in MLK3 kinase domain (P252H) confers different properties when compared to a one localized in the proline-rich domain. P252H mutation seems to induce increased cell migration, while R799C seems to interfere with cell differentiation. Furthermore, we verified that both mutations regulate the WNT pathway in distinct manner, either through the activation of the canonical or non-canonical pathway. In summary, we showed that two of the MLK3 mutations previously described interfere with crucial pathways of colorectal development and in this way contribute to colorectal tumourigenesis

Piezoresponse force microscopy investigations of Aurivillius phase thin films

The sol-gel synthesis and characterization of n≥3n≥3 Aurivillius phase thin filmsdeposited on Pt/Ti/SiO2–SiPt/Ti/SiO2–Si substrates is described. The number of perovskite layers, nn, was increased by inserting BiFeO3BiFeO3 into three layered Aurivillius phase Bi4Ti3O12Bi4Ti3O12 to form compounds such as Bi5FeTi3O15Bi5FeTi3O15 (n=4)(n=4). 30% of the Fe3+Fe3+ ions in Bi5FeTi3O15Bi5FeTi3O15 were substituted with Mn3+Mn3+ ions to form the structureBi5Ti3Fe0.7Mn0.3O15Bi5Ti3Fe0.7Mn0.3O15. The electromechanical responses of the materials were investigated using piezoresponse force microscopy and the results are discussed in relation to the crystallinity of the films as measured by x-ray diffraction

Room temperature electromechanical and magnetic investigations of ferroelectric Aurivillius phase Bi5Ti3(FexMn1−x)O15 (x = 1 and 0.7) chemical solution deposited thin films

Aurivillius phase thin films of Bi5Ti3(FexMn1−x)O15 with x = 1 (Bi5Ti3FeO15) and 0.7 (Bi5Ti3Fe0.7Mn0.3O15) on SiO2-Si(100) and Pt/Ti/SiO2-Si substrates were fabricated by chemical solution deposition. The method was optimized in order to suppress formation of pyrochlore phase Bi2Ti2O7 and improve crystallinity. The structuralproperties of the films were examined by x-ray diffraction, scanning electron microscopy, and atomic force microscopy. Optimum crystallinity and pyrochlore phase suppression was achieved by the addition of 15 to 25 mol. % excess bismuth to the sols. Based on this study, 17.5 mol. % excess bismuth was used in the preparation of Bi2Ti2O7-free films of Bi5Ti3FeO15 on SrTiO3(100) and NdGaO3(001) substrates, confirming the suppression of pyrochlore phase using this excess of bismuth. Thirty percent of the Fe3+ ions in Bi5Ti3FeO15 was substituted with Mn3+ ions to form Bi2Ti2O7-free thin films of Bi5Ti3Fe0.7Mn0.3O15 on Pt/Ti/SiO2-Si, SiO2-Si(100), SrTiO3(100), and NdGaO3(001) substrates. Bi5Ti3FeO15 and Bi5Ti3Fe0.7Mn0.3O15thin films on Pt/Ti/SiO2-Si and SiO2-Si(100) substrates were achieved with a higher degree of a-axis orientation compared with the films on SrTiO3(100) and NdGaO3(001) substrates. Room temperature electromechanical and magnetic properties of the thin films were investigated in order to assess the potential of these materials for piezoelectric,ferroelectric, and multiferroic applications. Vertical piezoresponse force microscopy measurements of the films demonstrate that Bi5Ti3FeO15 and Bi5Ti3Fe0.7Mn0.3O15thin films are piezoelectric at room temperature. Room temperature switching spectroscopy-piezoresponse force microscopy measurements in the presence and absence of an applied bias demonstrate local ferroelectric switching behaviour (180°) in the films. Superconducting quantum interference device magnetometry measurements do not show any room temperature ferromagnetic hysteresis down to an upper detection limit of 2.53 × 10−3 emu; and it is concluded, therefore, that such films are not mutiferroic at room temperature. Piezoresponse force microscopy lithography images of Bi5Ti3Fe0.7Mn0.3O15thin films are presented

A massive nebula around the Luminous Blue Variable star RMC143 revealed by ALMA

The luminous blue variable (LBV) RMC143 is located in the outskirts of the 30~Doradus complex, a region rich with interstellar material and hot luminous stars. We report the $3\sigma$ sub-millimetre detection of its circumstellar nebula with ALMA. The observed morphology in the sub-millimetre is different than previously observed with HST and ATCA in the optical and centimetre wavelength regimes. The spectral energy distribution (SED) of RMC143 suggests that two emission mechanisms contribute to the sub-mm emission: optically thin bremsstrahlung and dust. Both the extinction map and the SED are consistent with a dusty massive nebula with a dust mass of $0.055\pm0.018~M_{\odot}$ (assuming $\kappa_{850}=1.7\rm\,cm^{2}\,g^{-1}$). To date, RMC143 has the most dusty LBV nebula observed in the Magellanic Clouds. We have also re-examined the LBV classification of RMC143 based on VLT/X-shooter spectra obtained in 2015/16 and a review of the publication record. The radiative transfer code CMFGEN is used to derive its fundamental stellar parameters. We find an effective temperature of $\sim 8500$~K, luminosity of log$(L/L_{\odot}) = 5.32$, and a relatively high mass-loss rate of $1.0 \times 10^{-5}~M_{\odot}$~yr$^{-1}$. The luminosity is much lower than previously thought, which implies that the current stellar mass of $\sim8~M_{\odot}$ is comparable to its nebular mass of $\sim 5.5~M_{\odot}$ (from an assumed gas-to-dust ratio of 100), suggesting that the star has lost a large fraction of its initial mass in past LBV eruptions or binary interactions. While the star may have been hotter in the past, it is currently not hot enough to ionize its circumstellar nebula. We propose that the nebula is ionized externally by the hot stars in the 30~Doradus star-forming region.Comment: Paper accepted by A&A on 09/05/2019 and in proof stage. Second comments by referee are included in this versio

Tailoring of unipolar strain in lead-free piezoelectrics using the ceramic/ceramic composite approach

The electric-field-induced strain response mechanism in a polycrystalline ceramic/ceramic composite of relaxor and ferroelectric materials has been studied using in situ high-energy x-ray diffraction. The addition of ferroelectric phase material in the relaxor matrix has produced a system where a small volume fraction behaves independently of the bulk under an applied electric field. Inter- and intra-grain models of the strain mechanism in the composite material consistent with the diffraction data have been proposed. The results show that such ceramic/ceramic composite microstructure has the potential for tailoring properties of future piezoelectric materials over a wider range than is possible in uniform compositions.open1

La profesionalización de los graduados universitarios en turismo en Misiones. Análisis de competencias, desempeño y propuestas de mejora. 16H371

La actividad turística se encuentra en una etapa de crecimiento constante en la Argentina como así también en la provincia de Misiones. Sin embargo, se conoce muy poco sobre la profesionalización de los graduados universitarios en este sector de la economía, tanto en la actividad privada en los rubros hotelería (categoría 4* y 5*), empresas de viaje y turismo receptivas de la ciudad de Posadas y Puerto Iguazú como en el sector público, sus dificultades, desafíos y necesidades de capacitación y entrenamiento. En esta investigación se estudiará mediante encuestas la evolución laboral y mejora del desempeño profesional de los graduados Guías y Licenciados en turismo de la provincia de Misiones. Se realizarán entrevistas a empresarios y referentes institucionales, para analizar la influencia en el desempeño laboral y profesional y por último se diseñarán indicadores para medir competencias que nos permitirá delinear un índice de profesionalización turística en Misiones. Los resultados a los que se quiere llegar se relacionan con conocer el nivel y percepción del profesionalismo en turismo e identificar las necesidades respecto a la formación en competencias necesarias a implementar para poder de esta forma desarrollar propuestas para lograr la profesionalización turística en la Provincia

Plant Polyphenols and Oxidative Metabolites of the Herbal Alkenylbenzene Methyleugenol Suppress Histone Deacetylase Activity in Human Colon Carcinoma Cells

Evidence has been provided that diet and environmental factors directly influence epigenetic mechanisms associated with cancer development in humans. The inhibition of histone deacetylase (HDAC) activity and the disruption of the HDAC complex have been recognized as a potent strategy for cancer therapy and chemoprevention. In the present study, we investigated whether selected plant constituents affect HDAC activity or HDAC1 protein status in the human colon carcinoma cell line HT29. The polyphenols (−)-epigallocatechin-3-gallate (EGCG) and genistein (GEN) as well as two oxidative methyleugenol (ME) metabolites were shown to inhibit HDAC activity in intact HT29 cells. Concomitantly, a significant decrease of the HDAC1 protein level was observed after incubation with EGCG and GEN, whereas the investigated ME metabolites did not affect HDAC1 protein status. In conclusion, dietary compounds were found to possess promising HDAC-inhibitory properties, contributing to epigenetic alterations in colon tumor cells, which should be taken into account in further risk/benefit assessments of polyphenols and alkenylbenzenes