Bifurcation structures and transient chaos in a four-dimensional Chua model

A four-dimensional four-parameter Chua model with cubic nonlinearity is studied applying numerical continuation and numerical solutions methods. Regarding numerical solution methods, its dynamics is characterized on Lyapunov and isoperiodic diagrams and regarding numerical continuation method, the bifurcation curves are obtained. Combining both methods the bifurcation structures of the model were obtained with the possibility to describe the {\it shrimp}-shaped domains and their endoskeletons. We study the effect of a parameter that controls the dimension of the system leading the model to present transient chaos with its corresponding basin of attraction being riddled.Comment: 9 figures, to appear in PL

Meet Me in the Middle: A Scoping Review on Understanding Adolescent Needs in Climate Communication

The greatest effects of climate change are likely to be felt by youth. Young people are disproportionately affected by climate change due to their critical developmental stage and lack of power, and they experience both higher severity and prevalence of mental health issues related to climate change. Strong emotions have long been recognized as potential catalysts for action, or they may lead to paralyzing feelings of being overwhelmed. Climate communication is a critical tool to spark climate concern and encourage action. Activism, in turn, may help youth manage their anxiety about climate change. This scoping review examines emerging evidence on communicating climate change issues with adolescents and identifying key characteristics or factors for success, particularly to facilitate climate action, and provides best practices to support adolescents to communicate their own messages on climate change as a potentially important avenue to engage youth action. The review includes peer-reviewed articles and gray literature focused on contextualizing adolescent development, best practices to work with youth/adolescents, and research on climate change education. The distinct social and neurodevelopmental stage of adolescents should be taken into consideration when communicating with youth on climate change and encouraging activism to harness their strengths and minimize their vulnerabilities. Climate change education should go beyond relaying facts and provide opportunities to support youth agency and action to transform perspectives. This review provides a practical synthesis of current information to foster successful climate communication for and by youth, and highlighting additional areas for further research

Fabricação e caracterização de células solares baseadas em ligas de GaxSe1-x

Orientador: Prof. Dr. Ivo A. HümmelgenTese (doutorado) - Universidade Federal do Paraná, Setor de Ciências Exatas, Curso de Pós-Graduação em Física. Defesa: Curitiba, 18/12/2017Inclui referências : f. 102-110Resumo: A demanda por fontes de energia limpa e eficiente impulsiona a pesquisa por novos materiais e estruturas para aplicações em células solares. Neste sentido, o presente trabalho consistiu em desenvolver diferentes estruturas utilizando filmes finos de selênio (Se) e ligas de seleneto de gálio (GaSe9 e Ga2Se8), produzidas por moagem mecânica, como camada ativa em células solares. Os filmes foram obtidos através de evaporação física dos elementos sob alto vácuo. Filmes de óxidos transparentes como óxido de césio (Cs2O) ou de zinco (ZnO) foram adicionados para aumentar a eficiência de conversão de energia nos dispositivos. Diferentes técnicas de caracterização foram utilizadas para comparar os filmes e as células solares construídas. Para a caracterização das propriedades dos filmes foram realizadas medidas de absorção UV-vis, voltametria cíclica, difração de raios X (XRD) e microscopia eletrônica de varredura (SEM) e de força atômica (AFM). A partir das medidas de absorção UV-vis obteve-se o coeficiente de absorção, enquanto que das medidas de voltametria cíclica foi possível estimar os valores de banda de valência dos filmes. Com isso, diagramas de níveis de energia dos materiais utilizados foram construídos, que facilitam a compreensão do funcionamento dos dispositivos. As imagens de SEM e AFM mostram diferenças na morfologia entre os filmes que impactam na eficiência dos dispositivos. Os filmes de GaSe9 apresentaram uma estrutura cristalina mais compacta em comparação com o Se. Observou-se a partir dos espectros de XRD que os filmes evaporados apresentam uma estrutura amorfa, que é alterada para cristalina após um tratamento térmico. Esta estrutura cristalina influencia no transporte de cargas e melhora as propriedades elétricas das células solares. A caracterização elétrica foi realizada através de medidas elétricas de densidade de corrente - tensão (J - V), capacitância - tensão (C - V), eficiência quântica externa (IPCE) e espectroscopia de impedância dos dispositivos no escuro e sob iluminação AM 1.5G. Através destas medidas parâmetros de eficiência das diferentes estruturas podem ser comparados, mostrando valores maiores para células solares de GaSe9 em uma junção p-n com nanopartículas de ZnO, no qual obteve-se uma eficiência de 2,7%. Através das caracterizações por C - V, informações sobre as junções são obtidas, enquanto a partir das medidas de espectroscopia de impedância foram identificados diferentes comportamentos e processos dinâmicos de geração, transporte e coleta das cargas fotogeradas na camada ativa, indicando as mudanças elétricas que a adição de gálio provoca nos dispositivos, e a influência de diferentes óxidos nas junções. A partir dos resultados obtidos, observa-se que a utilização de ligas de GaxSe1-x e a adição de camadas através de processos simples são alternativas para aumentar a eficiência de células solares de filmes finos de selênio. Palavras-chave: Célula solar. Seleneto de gálio. Moagem mecânica. Junção Schottky. Junção p-n. Espectroscopia de impedância.Abstract: The demand for clean and efficient energy sources drives research into new materials and structures for solar cell applications. In this sense, the present work consists of developing different structures using thin films of selenium (Se) and gallium selenide alloys (GaSe9 and Ga2Se8), made by mechanical alloying, as active layers in solar cells. The films are obtained by physical evaporation of the elements under high vacuum. Transparent oxide films such as cesium oxide (Cs2O) or zinc oxide (ZnO) are added to increase the energy conversion efficiency in the devices. Different characterization techniques were used to compare the films and the constructed solar cells. For the film characterization, UV-vis absorption, cyclic voltammetry, x-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements were performed. From UV-vis absorption measurements, the absorption coefficient was obtained, while from cyclic voltammetry measurements the valence band values of the films were estimated. Thus, energy level diagrams of the materials were built, which facilitate the understanding of the devices behavior. SEM and AFM images show differences in morphology between the films which impact in device efficiency. GaSe9 films presented a more compact crystalline structure compared to Se. It has been observed from the XRD spectra that the evaporated films have an amorphous structure, which changes to crystalline after a heat treatment. This crystalline structure influences the charge transport and improves the electrical properties of solar cells. The electrical characterization was carried out through electrical measurements of current-voltage (J - V), capacitance-voltage (C - V), incident photon-to-current conversion efficiency (IPCE) and impedance spectroscopy of the devices, in the dark and under AM 1.5G illumination. Through these measurements, efficiency parameters of the different structures are compared, showing higher values for GaSe9 solar cells in a p-n junction with ZnO nanoparticles, in which an efficiency of 2.7% was obtained. Through the C - V characterization, information about the junctions is obtained. From impedance spectroscopy measurements different behaviors and dynamic processes of generation, transport and collection of the photogenerated charge carriers in the active layer were identified, indicating electrical changes that the gallium addition causes in the devices, and the influence of different oxides on the junctions. From the obtained results, it is observed that the use of GaxSe1-x alloys and the addition of layers through simple processes are alternatives to increase the efficiency of selenium based thin film solar cells. Keywords: Solar cell. Gallium selenide. Mechanical alloying. Schottky junction. p-n junction. Impedance spectroscopy

Desenvolvimento de um método quântico/clássico híbrido para o estudo dos processos de transferência de carga e energia em estruturas moleculares

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Física, Florianópolis, 2014.Desenvolvimento de um método teórico/computacional capaz de descrever processos de transferência de carga e energia em sistemas moleculares. O método, denominado QMMM/DinEMol, descreve as dinâmicas eletrônica e nuclear de formas diferentes: a dinâmica eletrônica de todo o sistema é calculada através de um formalismo quântico baseado na teoria estendida de Hückel (TEH) onde são adicionadas interações não consideradas originalmente pela TEH, mas que estão presentes em sistemas moleculares fotoexcitados, enquanto que a dinâmica nuclear é calculada através de mecânica molecular. O método QMMM/DinEMol permite calcular a dinâmica do sistema de duas maneiras, denominadas dinâmicas sequencial e paralela. Na dinâmica sequencial primeiramente é calculada a mecânica molecular considerando a estrutura eletrônica no estado fundamental e em seguida, utilizando as trajetórias nucleares calculadas previamente, é calculada a dinâmica eletrônica. Já na dinâmica paralela, ambas dinâmicas nuclear e eletrônica são calculadas simultaneamente, considerando a distribuição eletrônica do sistema durante a mecânica molecular. Desta forma, é considerado o acoplamento entre os graus de liberdade eletrônicos e nucleares. O método QMMM/DinEMol foi utilizado para investigar o processo de transferência de carga eletrônica em um sistema formado por um semicondutor de TiO2 sensibilizado por corantes do tipo doador-ponte-aceitador (D-p-A), onde foi estudado, principalmente, a relevância do movimento nuclear e da interação coulombiana durante o processo de injeção de carga no semicondutor e também, o efeito de solvatação no sistema. Além disto, foi investigado a relevância do acoplamento entre os graus de liberdades nucleares e eletrônicos em sistemas moleculares fotoexcitados.Abstract : We developed of a theoretical/computational method to describe processes of charge and energy transfers in molecular systems. The method, called QMMM/DinEMol, describes the electronic and nuclear dynamics of different modes: The electronic dynamics of the entire system is calculated using a quantum formalism, which is based in the extended Hückel theory (EHT) where is added interactions not originally considered by EHT, but which are presents in photoexcited molecular systems, whereas the nuclear dynamics is calculated by molecular mechanics. The QMMM/DinEMol method allows to calculate the dynamics of the system in two forms, called sequential and parallel dynamics. In the sequential dynamics, the molecular mechanics is calculated considering the electronic structure in the ground state and posteriorly, using the nuclear trajectories previously obtained, the electronic dynamics is calculated. Already in the parallel dynamics, boththe electronic and nuclear dynamics are calculated simultaneously considering the electronic distribution of the system during the molecular mechanic. Thus, it is considered the coupling between the nuclei and electronics degrees of freedom.The QMMM/DinEMol method was used to investigate the process of electronic transfer in a system formed by a TiO2 semiconductor sensitized by dyes of the type donor-bridge-acceptor (D-p-A), where it was studied mainly the significance of the nuclear motion and the Coulomb interaction during the process of charge injection in the semiconductor and also the effect of solvation on the system. Furthermore, we investigated the relevance of the coupling between the nuclei and electronics degrees of freedom in photoexcited molecular systems

Generalized dynamic reduction in finite element dynamic optimization

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76662/1/AIAA-8826-211.pd

Characterization and Quantification of Livestock Odorants using Sorbent Tube Sampling and Thermal Desorption coupled with Multidimensional Gas Chromatography–Mass Spectrometry–Olfactometry (TD-MDGC-MS-O)

Characterization and quantification of livestock odorants is one of the most challenging analytical tasks because odor-causing gases are very reactive, polar and often present at very low concentrations in a complex matrix of less important or irrelevant gases. The objectives of this research is to develop a novel analytical method for characterization of the livestock odorants including their odor character, odor intensity, and hedonic tone and further quantitative analysis of the key odorants responsible for livestock odor emissions. Sorbent tubes packed with Tenax TA were employed for sampling. The automated one-step thermal desorption coupled with multidimensional gas chromatography-mass spectrometry-olfactometry system was developed for simultaneous chemical and odor analysis. Fifteen odorants identified from different livestock species operations are quantified. In addition, odor character, odor intensity and hedonic tone associated with each of the target compounds are also analyzed. The method developed in this research is being used on a multistate, multispecies project focused on quantifying odor and chemical analysis of odor

Inverse perturbation method for structural redesign with frequency and mode shape constraints

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76581/1/AIAA-8777-705.pd

Doing gender locally: The importance of ‘place’ in understanding marginalised masculinities and young men’s transitions to ‘safe’ and successful futures

Observable anxieties have been developing about the position of boys and young men in contemporary society in recent years. This is expressed as a crisis of masculinity, in which place is often implicitly implicated, but is rarely considered for its role in the shaping of young men’s practices, trajectories and aspirations. Drawing on research conducted with young people who accessed a range of social care support services, this article argues that transition means different things for young men in different locales and that local definitions of masculinity are required to better understand young men’s lives and the opportunities available to them. The authors argue that home life, street life, individual neighbourhoods, regions and nations all shaped the young men’s identities and the practices they (and the staff working with them) drew on in order to create successful futures and ‘safe’ forms of masculinity. It is suggested that this place-based approach has the potential to re-shape the ‘crisis’ discourse surrounding masculinity and the anxieties associated with young men

Physical activity and incidence of atrial fibrillation: A systematic review and meta-analysis

Whether physical activity increases or decreases the risk of atrial fibrillation (AF) remains controversial. We conducted a systematic review and meta-analysis to evaluate the relationship between AF and extent of physical activity. We searched Medline and EMBASE in June 2014 for studies that reported on the associated risk of AF according to history of physical activity. Pooled risk ratios for AF were calculated using inverse variance random effects model, and heterogeneity assessed using I2. Subgroup analysis was performed according to the nature of the physical activity, and the quality of the studies. We identified 19 relevant studies with a total of over half a million participants (n = 511,503). The pooled analysis showed no association between intensive physical activity and AF (RR 1.00 95% CI 0.82–1.22, I2 = 73%, 8 studies, 152,925 participants) with no difference considering low and moderate to high risk of bias studies. Pooled analysis of studies reporting on increasing amount of time spent on physical activities did not show a significant association with AF (RR 0.95 95% CI 0.72–1.26, I2 = 84%, 4 studies, 112,784 participants). Studies of athletes or participants with a history of sports activity which were of poor methodology quality showed a borderline significant association with AF (pooled RR 1.98 95% CI 1.00–3.94, I2 = 59%, 6 studies, 1973 participants). In conclusion, we found no significant increase in AF with a higher level of physical activity. These findings support clinical guidelines encouraging patients to exercise as there is no evidence for harm associated with increased physical activity

Europe’s Care Regimes and the Role of Migrant Care Workers Within Them

This paper is an examination of the recent restructuring and subsequent convergence of European long-term care models. This paper also aims to highlight the increased role of migrant care workers and the need for great social and governmental recognition for all care providers. The provision of long term care is complex, divided between state, market and family providers; the state alone could not and does not act as the sole provider of care (Banks 1998). The extent to which different sectors are relied upon is largely dependent on the ideology of the country's welfare state (Timonen and Doyle 2007)