Ion acceleration in non-relativistic astrophysical shocks

We explore the physics of shock evolution and particle acceleration in non-relativistic collisionless shocks using multidimensional hybrid simulations. We analyze a wide range of physical parameters relevant to the acceleration of cosmic rays (CRs) in astrophysical non-relativistic shock scenarios, such as in supernova remnant (SNR) shocks. We explore the evolution of the shock structure and particle acceleration efficiency as a function of Alfv\'enic Mach number and magnetic field inclination angle $\theta$. We show that there are fundamental differences between high and low Mach number shocks in terms of the electromagnetic turbulence generated in the pre-shock zone and downstream; dominant modes are resonant with the streaming CRs in the low Mach number regime, while both resonant and non-resonant modes are present for high Mach numbers. Energetic power law tails for ions in the downstream plasma can account for up to 15% of the incoming upstream flow energy, distributed over $\sim5$ of the particles in a power law with slope $-2\pm0.2$ in energy. The energy conversion efficiency (for CRs) peaks at $\theta=15^\circ$ to $30^\circ$ and $M_A=6$, and decreases for higher Mach numbers, down to $\sim2$ for $M_A=31$. Accelerated particles are produced by Diffusive Shock Acceleration (DSA) and by Shock Drift Acceleration (SDA) mechanisms, with the SDA contribution to the overall energy gain increasing with magnetic inclination. We also present a direct comparison between hybrid and fully kinetic particle-in-cell results at early times; the agreement between the two models justifies the use of hybrid simulations for longer-term shock evolution. In SNR shocks, particle acceleration will be significant for low Mach number quasi-parallel flows ($M_A < 30$, $\theta< 45$). This finding underscores the need for effective magnetic amplification mechanism in SNR shocks

Contribution for the knowledge of toxoplasmosis in Portugal

Toxoplasma gondii infects over a third of the world's humanity and toxoplasmosis constitutes a life-long threat since humans remain infected throughout life. This PhD dissertation aimed to enrich the knowledge on toxoplasmosis in Portugal and to implement updated approaches regarding T. gondii propagation in the reference laboratory. We started by evaluating the seroprevalence in Portugal by comparing three cross-sectional studies spanning three decades (1979/80, 2001-2002, 2013), with focus on childbearing women. Seroprevalence showed a decreasing trend over time (from 47 % in 1979/80 to 22 % in 2013) and increased with age. The scenario observed for childbearing women indicates that more than 80 % of these are susceptible to primary infection and thus to congenital toxoplasmosis. We also focused on the parasite and genetically characterized 48 strains isolated from biological samples from patients attending to the NIH, for which a retrospective evaluation estimated 1.6 % of new cases of congenital toxoplasmosis in the last 10 years. This study revealed genetic variations in T. gondii and more specifically the existence of a considerable proportion (21 %) of recombinant strains, which are believed to be associated with specific phenotypes. Finally, we evaluated laboratory approaches towards the reduction of sacrificed mice in toxoplasmosis reference laboratories. We observed that the alternate passaging of the parasite in a cell line and in mice constitutes a promising laboratory procedure as, besides the reduction of sacrificed mice in more than 80 %, it enabled T. gondii to retain the virulence potential while keeping a putative stable genome. Globally, this PhD dissertation not only increased the knowledge on toxoplasmosis in Portugal by elucidating the chronological trend of the immune status of the population and the general genetic profile of the T. gondii strains causing human infection, but it also modified the modus operandi of the reference laboratory towards the significant reduction of scarified mice

Relatório final de Estágio Pedagógico realizado na Escola Secundária de Caneças

Convido o leitor a fazer uma viagem pelo que considerei uma época de sonho (Estágio Pedagógico) e todos os procedimentos que envolveram a minha intervenção aquando do exercício da profissão de docente. É ao longo da vida que o professor constrói e se identifica com a profissão (Resende et al., 2014). Este processo começa a desenvolver-se na socialização antecipatória, onde o professor molda as suas ideias sobre o ato de ensinar, prosseguindo-se a formação inicial (Resende et al., 2014; Gomes et al., 2014) e estende-se por todo o período subsequente de indução profissional e por toda a vida profissional (Onofre, 1996). A formação de professores poderá ser compreendida como um processo contínuo e sistemático de aprendizagem, onde é suposto subsistir um aperfeiçoamento de atitudes, saberes e saberes-fazer numa perspetiva reflexiva sobre valores que caracterizam o exercício das funções inerentes à profissão (Onofre, 1996). Nóvoa (2017) refere que o suporte exercido pelos professores mais experientes nos formandos é crucial para uma formação profissional de professores, Onofre (1996) também destaca o peso da Supervisão Pedagógica. A Supervisão é uma estratégia de formação que implica uma relação entre um professor com experiência e um professor com menos, ou mesmo, sem experiência (Onofre, 1996).That way, I invite the reader to join me through what I considered a dream season (Pedagogical Internship), and all the procedures related to my intervention as a professional schoolteacher. It is throughout his life that the teacher builds and identifies with his profession (Resende et al., 2014). This process begins developing itself before the initial training, being in the anticipatory socialization that the teacher shapes his ideas about the act of teaching, the process follows through the initial training (Resende et al., 2014; Gomes et al., 2014), extends along all the following period of professional induction and finally throughout the professor’s professional life (Onofre, 1996). The teachers training can be defined as a continuous and systematic learning process, where perfecting attitudes, knowledge and know-how should rein, while also having a reflective perspective about the values that characterize the profession (Onofre, 1996). Nóvoa (2017) refers that the experienced teachers support to the trainee is crucial for his professional training, Onofre (1996) also highlights the weight of the Pedagogical Supervision. Supervision is considered a training strategy that requires a relationship between an experienced teacher and a less experienced one, or even completely inexperienced (Onofre, 1996)

A importância da formação musical no contexto do ensino especializado da música

Resumo O presente relatório incide sobre a unidade curricular de Prática de Ensino Supervisionada, do ciclo de estudos conducentes ao grau de mestre em Ensino da Música - Formação Musical e Música de Conjunto. O relatório divide-se em duas partes. Na primeira apresenta-se a descrição e reflexão crítica do estágio de natureza profissional, resultante do trabalho desenvolvido nas disciplinas de Formação Musical e Classe de Conjunto na Escola de Artes do Norte Alentejano em Portalegre e no polo de Sousel, respetivamente, durante o ano letivo de 2013/2014. Apresenta-se a caracterização do meio, das escolas e das turmas e, também, planificações e reflexões das respetivas aulas, por disciplina, para ilustração da prática de ensino supervisionada desenvolvida. A segunda parte do relatório apresenta um estudo de investigação que se centra na análise da importância da disciplina de Formação Musical no contexto do Ensino Artístico Especializado da Música. Este estudo emergiu do contexto da prática, pela perceção, por um lado, do desfasamento entre os desatualizados programas da disciplina e a realidade atual desta, no âmbito da aprendizagem do instrumento nos cursos básicos, por outro, pelo facto de o ensino da música é ser procurado por muitos alunos, para quem o objetivo não é o de se tornarem profissionais na área da música mas apenas o de adquirirem alguma formação básica. Com vista a evidenciar a importância que é atribuída à Formação Musical no contexto do Ensino Especializado da Música, estabeleceram-se, como objetivos do estudo, identificar o papel da formação musical no Ensino Especializado de Música; identificar as razões que levam as crianças e seus encarregados de educação a optar pelo ensino Especializado da Música; identificar, junto dos docentes de várias comunidades educativas, as problemáticas e as necessidades mais prementes para o sucesso da disciplina; analisar o grau de satisfação dos discentes no âmbito da Formação Musical; estabelecer um paralelo entre a forma como se ensina e a forma como se aprende. Consideramos que a Formação Musical deve contribuir para que os alunos tenham a oportunidade de contactar, de conhecer e de adquirir uma visão universal da música, que lhes permita ter consciência da diversidade cultural. Contudo, existem vários problemas envolvidos que têm de ser ultrapassados. Nos programas da disciplina de Formação Musical, os diferentes géneros musicais não estão explicitamente assinalados, pelo que dependem da valorização que lhes é atribuída por cada um dos professores. Assim, os professores são os agentes do sistema de ensino cuja ação é determinante na escolha do repertório estando esta ação condicionada pela formação que tiveram.Abstract : This report focuses on the course of Supervised Teaching Practice, the course that leads to the degree of Master in Music Education - Music Ensemble and Music Training. The report is divided into two parts. The first shows the description and critical reflection of the professional internship resulting from work in the disciplines of Music Theory and set of class at the North Alentejo Art School in Portalegre and campus of Sousel, respectively, during the school year 2013/2014. This study represents the characterization of the classes of the middle schools and also lesson plans and reflections of the respective classes for each discipline, and illustrates the supervised teaching practice developed. The second part of the report presents a research study that focuses on the analysis of the importance of Musical Training course in the context of specialized artistic education for Music. This study emerged from the practical context, the perception on the one hand, and the gap between the out-dated programs of discipline and the current reality of it within the learning of instrument in basic courses, on the other hand, the fact is that the music education is sought by many students, for whom the goal is not to become professionals in music but only to acquire some basic training. In order to highlight the importance that is attributed to the Musical Training in the context of Specialized Music School, were established the following the study aims: to identify the role of music education in Specialist Music Education; identify the reasons why children and their parents are choosing the Specialized Music education; identify, among teachers of various educational communities, the issues and the most pressing needs for the success of the discipline; analyse the degree of satisfaction of students within the Musical Training; establish a parallel between the way we teach and how we learn. We believe that the Musical Education should help students to have the opportunity to meet, to know and to acquire a universal vision of music, enabling them to be aware of cultural diversity. However, there are various problems involved that must be overcome. Programs of the Musical Training course, different genres are not explicitly marked, so it depends on the value attributed to them by each of the teachers. Thus, teachers are the agents of the education system whose action is decisive in the choice of list, being this action conditioned by the training they had

Magnetic and density spikes in cosmic ray shock precursors

In shock precursors populated by accelerated cosmic rays (CR), the CR return current instability is believed to significantly enhance the pre-shock perturbations of magnetic field. We have obtained fully-nonlinear exact ideal MHD solutions supported by the CR return current. The solutions occur as localized spikes of circularly polarized Alfven envelopes (solitons, or breathers). As the conventional (undriven) solitons, the obtained magnetic spikes propagate at a speed $C$ proportional to their amplitude, $C=C_{A}B_{{\rm max}}/\sqrt{2}B_{0}$. The sufficiently strong solitons run thus ahead of the main shock and stand in the precursor, being supported by the return current. This property of the nonlinear solutions is strikingly different from the linear theory that predicts non-propagating (that is, convected downstream) circularly polarized waves. The nonlinear solutions may come either in isolated pulses (solitons) or in soliton-trains (cnoidal waves). The morphological similarity of such quasi-periodic soliton chains with recently observed X-ray stripes in Tycho supernova remnant (SNR) is briefly discussed. The magnetic field amplification determined by the suggested saturation process is obtained as a function of decreasing SNR blast wave velocity during its evolution from the ejecta-dominated to the Sedov-Taylor stage.Comment: 21 pages, 4 figure

Could Cosmic Rays Affect Instabilities in the Transition Layer of Nonrelativistic Collisionless Shocks?

There is an observational correlation between astrophysical shocks and non-thermal particle distributions extending to high energies. As a first step toward investigating the possible feedback of these particles on the shock at the microscopic level, we perform particle-in-cell (PIC) simulations of a simplified environment consisting of uniform, interpenetrating plasmas, both with and without an additional population of cosmic rays. We vary the relative density of the counterstreaming plasmas, the strength of a homogeneous parallel magnetic field, and the energy density in cosmic rays. We compare the early development of the unstable spectrum for selected configurations without cosmic rays to the growth rates predicted from linear theory, for assurance that the system is well represented by the PIC technique. Within the parameter space explored, we do not detect an unambiguous signature of any cosmic-ray-induced effects on the microscopic instabilities that govern the formation of a shock. We demonstrate that an overly coarse distribution of energetic particles can artificially alter the statistical noise that produces the perturbative seeds of instabilities, and that such effects can be mitigated by increasing the density of computational particles.Comment: 22 pages, 5 figures, published in Ap

Sep acceleration in CME driven shocks using a hybrid code

WOS:000341172100009 (Nº de Acesso Web of Science)We perform hybrid simulations of a super-Alfvénic quasi-parallel shock, driven by a coronal mass ejection (CME), propagating in the outer coronal/solar wind at distances of between 3 to 6 solar radii. The hybrid treatment of the problem enables the study of the shock propagation on the ion timescale, preserving ion kinetics and allowing for a self-consistent treatment of the shock propagation and particle acceleration. The CME plasma drags the embedded magnetic field lines stretching from the sun, and propagates out into interplanetary space at a greater velocity than the in situ solar wind, driving the shock, and producing very energetic particles. Our results show that electromagnetic Alfvén waves are generated at the shock front. The waves propagate upstream of the shock and are produced by the counter-streaming ions of the solar wind plasma being reflected at the shock. A significant fraction of the particles are accelerated in two distinct phases: first, particles drift from the shock and are accelerated in the upstream region, and second, particles arriving at the shock get trapped and are accelerated at the shock front. A fraction of the particles diffused back to the shock, which is consistent with the Fermi acceleration mechanism