Classical Radiation Reaction in Particle-In-Cell Simulations

Under the presence of ultra high intensity lasers or other intense electromagnetic fields the motion of particles in the ultrarelativistic regime can be severely affected by radiation reaction. The standard particle-in-cell (PIC) algorithms do not include radiation reaction effects. Even though this is a well known mechanism, there is not yet a definite algorithm nor a standard technique to include radiation reaction in PIC codes. We have compared several models for the calculation of the radiation reaction force, with the goal of implementing an algorithm for classical radiation reaction in the Osiris framework, a state-of-the-art PIC code. The results of the different models are compared with standard analytical results, and the relevance/advantages of each model are discussed. Numerical issues relevant to PIC codes such as resolution requirements, application of radiation reaction to macro particles and computational cost are also addressed. The Landau and Lifshitz reduced model is chosen for implementation.Comment: 12 pages, 8 figure

Full-scale ab initio 3D PIC simulations of an all-optical radiation reaction configuration at 1021W/cm210^{21}\mathrm{W/cm^2}

Using full-scale 3D particle-in-cell simulations we show that the radiation reaction dominated regime can be reached in an all optical configuration through the collision of a $\sim$1 GeV laser wakefield accelerated (LWFA) electron bunch with a counter propagating laser pulse. In this configuration radiation reaction significantly reduces the energy of the particle bunch, thus providing clear experimental signatures for the process with currently available lasers. We also show that the transition between classical and quantum radiation reaction could be investigated in the same configuration with laser intensities of $10^{24}\mathrm{W/cm^2}$

Particle Merging Algorithm for PIC Codes

Particle-in-cell merging algorithms aim to resample dynamically the six-dimensional phase space occupied by particles without distorting substantially the physical description of the system. Whereas various approaches have been proposed in previous works, none of them seemed to be able to conserve fully charge, momentum, energy and their associated distributions. We describe here an alternative algorithm based on the coalescence of N massive or massless particles, considered to be close enough in phase space, into two new macro-particles. The local conservation of charge, momentum and energy are ensured by the resolution of a system of scalar equations. Various simulation comparisons have been carried out with and without the merging algorithm, from classical plasma physics problems to extreme scenarios where quantum electrodynamics is taken into account, showing in addition to the conservation of local quantities, the good reproducibility of the particle distributions. In case where the number of particles ought to increase exponentially in the simulation box, the dynamical merging permits a considerable speedup, and significant memory savings that otherwise would make the simulations impossible to perform

Characterization of bacPPK34 a bacteriocin produced by Pediococcus pentosaceus strain K34 isolated from “Alheira”

Different lactic acid bacteria were isolated during different stages in the production of “Alheiras”, a traditionally fermented sausage produced in the north of Portugal, between 2005 and 2007, in a total of 484 isolates. One of 484 isolates (K34) produced a bacteriocin, designated as bacPPK34, and was identified as a strain of Pediococcus pentosaceus by 16S rRNA sequencing. The highest bacteriocin production was noted at late log/early stationary phase after 15e18 h of growth in MRS broth at 37 ºC (3200 AU/ml) against Enterococcus faecalis ATCC 29212 and 12800 AU/ml against Listeria monocytogenes (L1, L2, L3). bacPPK34 was between 2.5 kDa and 6.2 kDa in size, as determined by tricine-SDS-PAGE. Complete inactivation or significant reduction in antimicrobial activity was observed after treatment of cell-free supernatants with proteinase K, pepsin and trypsin. No change in activity was recorded when treated with catalase. The bacteriocin was resistant to treatments with lipase and detergents Triton X-100, Tween 20, SDS, NaCl, urea and EDTA. Furthermore, the bacteriocin remained active after 2 h at pH 2e12 and temperature treatments at 60, 80, 100 ºC, 1 month of storage at º20 and 4 ºC and 20 min at 121 ºC. Addition of bacPPK34 to a mid-log culture of L. monocytogenes and E. faecalis ATCC 29212 inhibited growth. The bacteriocin did not adhere to the surface of the producer cells.info:eu-repo/semantics/acceptedVersio

Absolute quantification of the host-to-parasite DNA ratio in Theileria parva-infected lymphocyte cell lines

Theileria parva is a tick-transmitted intracellular apicomplexan pathogen of cattle in sub-Saharan Africa that causes East Coast fever (ECF). ECF is an acute fatal disease that kills over one million cattle annually, imposing a tremendous burden on African small-holder cattle farmers. The pathology and level of T. parva infections in its wildlife host, African buffalo (Syncerus caffer), and in cattle are distinct. We have developed an absolute quantification method based on quantitative PCR (qPCR) in which recombinant plasmids containing single copy genes specific to the parasite (apical membrane antigen 1 gene, ama1) or the host (hypoxanthine phosphoribosyltransferase 1, hprt1) are used as the quantification reference standards. Our study shows that T. parva and bovine cells are present in similar numbers in T. parva-infected lymphocyte cell lines and that consequently, due to its much smaller genome size, T. parva DNA comprises between 0.9% and 3% of the total DNA samples extracted from these lines. This absolute quantification assay of parasite and host genome copy number in a sample provides a simple and reliable method of assessing T. parva load in infected bovine lymphocytes, and is accurate over a wide range of host-to-parasite DNA ratios. Knowledge of the proportion of target DNA in a sample, as enabled by this method, is essential for efficient high-throughput genome sequencing applications for a variety of intracellular pathogens. This assay will also be very useful in future studies of interactions of distinct host-T. parva stocks and to fully characterize the dynamics of ECF infection in the field

Contributos para o desenvolvimento da literacia: a aprendizagem da leitura e da escrita ao longo do 1º ciclo do ensino básico

Este projecto tem por objectivo principal estudar as relações entre a implementação de um programa de promoção de competências de leitura e a aquisição da leitura e da escrita ao longo do primeiro ciclo. O programa foi desenvolvido no ano lectivo 2000/01 junto de um grupo de crianças com 5 anos de idade, envolvendo jardins de infância e famílias. As crianças foram avaliadas no final do ensino pré-escolar e durante o 1º ano de escolaridade. As análises então efectuadas enfatizaram a relação entre a participação da família no programa e o desenvolvimento de competências linguísticas, de descodificação da leitura e codificação da escrita. Durante o ano 2003/04 foram avaliadas cerca de 60 crianças frequentando o 3º ano de escolaridade. Este grupo de crianças incluía aquelas crianças que tinham frequentado o programa atrás citado. Privilegiou-se, nesta fase, a análise dos processos envolvidos na compreensão de textos lidos. Esta comunicação pretende descrever o trabalho efectuado ao longo deste ano lectivo enfatizando os resultados sobre as possíveis relações entre os processos agora avaliados e a participação no programa implementado no final do ensino pré-escolar

Terras e Territórios Indígenas: dilemas, avanços e dificuldades na demarcação e garantia dos direitos dos povos indígenas no Basil atual

Resumo: este artigo traz uma refl exão a respeito do que são as terras indígenas, em contraposição aos territórios indígenas. Traz também informações sobre como uma terra indígena é reconhecida como tal e quais as etapas para a homologação fi nal de uma terra. Compara-se a demarcação de áreas nos governos Collor, Fernando Henrique e Luiz Inacio da Silva, assim como se busca entender a violência contra os índios, concluindo-se que, em neste último período houve um aumento da violência contra índios e, ao mesmo tempo, uma diminuição do reconhecimento de novas terras. Palavras-chave: Terra indígena. Território indígena. Política indigenista

Effect of mining residues treated with an electrodialytic technology on cement-based mortars

UIDB/04085/2020 PD/BD/135170/2017Mining residues have been accumulated for centuries due to excavation and mining processes, causing environmental degradation worldwide. Their application in cementitious products is a feasible alternative to waste disposal. Electrodialytic technologies can promote a safer reuse of mining residues in the construction sector, coupling economic advantages due to the possible removal of toxic elements and the recovery of critical raw materials. The application of treated mining residues in construction products, namely their effects on physico-mechanical properties, in comparison to raw residues and cement uses needs to be addressed. This work presents a study of cement-based mortars with the incorporation of mining residues treated with an electrodialytic process in comparison to raw mining residues. The replacement percentages studied were 0, 10, 25 and 50 % of the binder in volume. Tests were conducted to evaluate fresh and hardened properties of mortars considering physical, microstructural and mechanical performances. Results show the viability of applying mining residues after the electrodialytic treatment as mortars materials in rendering, plastering, joint repointing, bedding masonry or screed requirements, with improved thermal conductivity and eco-efficiency.proofpublishe