Chromospheric Inversions of a Micro-flaring Region

We use spectropolarimetric observations of the Ca II 8542~\AA\ line, taken from the Swedish 1-m Solar Telescope (SST), in an attempt to recover dynamic activity in a micro-flaring region near a sunspot via inversions. These inversions show localized mean temperature enhancements of $\sim$1000~K in the chromosphere and upper photosphere, along with co-spatial bi-directional Doppler shifting of 5 - 10 km s$^{-1}$. This heating also extends along a nearby chromospheric fibril, co-spatial to 10 - 15 km s$^{-1}$ down-flows. Strong magnetic flux cancellation is also apparent in one of the footpoints, concentrated in the chromosphere. This event more closely resembles that of an Ellerman Bomb (EB), though placed slightly higher in the atmosphere than is typically observed.Comment: 9 pages, 9 figures, accepted in ApJ. Movies are stored here: https://star.pst.qub.ac.uk/webdav/public/areid/Microflare

Opposite polarity field with convective downflow and its relation to magnetic spines in a sunspot penumbra

We discuss NICOLE inversions of Fe I 630.15 nm and 630.25 nm Stokes spectra from a sunspot penumbra recorded with the CRISP imaging spectropolarimeter on the Swedish 1-m Solar Telescope at a spatial resolution close to 0.15". We report on narrow radially extended lanes of opposite polarity field, located at the boundaries between areas of relatively horizontal magnetic field (the intra-spines) and much more vertical field (the spines). These lanes harbor convective downflows of about 1 km/s. The locations of these downflows close to the spines agree with predictions from the convective gap model (the "gappy penumbra") proposed six years ago, and more recent 3D MHD simulations. We also confirm the existence of strong convective flows throughout the entire penumbra, showing the expected correlation between temperature and vertical velocity, and having vertical RMS velocities of about 1.2 km/s.Comment: Accepted for publication in A&A (06-March-2013). Minor corrections made in this version

A farinha do mesocarpo dp babaçu (Orbignya phalerata) como componente de uma mistura protéica em dieta semi-purificada e seus reflexos sobre a colesterolemia e a trigliceridemia em ratos.

Suplemento 1. Edição dos resumos do XV Congresso Latinoamericano de Nutricion e XVI Jornadas de la Sociedad Chilena de Nutrición, Santiago do Chile, 2009

A perturbative approach to the polaron shift of excitons in transition metal dichalcogeniedes

In this Letter, we study the effect of phonons on the position of the 1s excitonic resonance of the fundamental absorption transition line in two-dimensional transition metal dichalcogenides. We apply our theory to WS2, a two-dimensional material where the shift in the absorption peak position has been measured as a function of temperature. The theory is composed of two ingredients only: (i) the effect of longitudinal optical phonons on the absorption peak position, which we describe with second-order perturbation theory, and (ii) the effect of phonons on the value of the single-particle energy gap, which we describe with the Huang Rhys model. Our results show excellent agreement with the experimentally measured shift of the absorption peak with the temperature.- N.M.R.P. acknowledges support by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020. J.C.G.H. acknowledges the Center of Physics for a grant funded by the UIDB/04650/2020 strategic project. N.M.R.P. acknowledges support from the European Commission through the project Graphene-Driven Revolutions in ICT and Beyond (Ref. No. 881603, CORE 3), COMPETE 2020, PORTUGAL 2020, FEDER, and the FCT through Projects No. POCI-01-0145FEDER-028114 and No. PTDC/NAN-OPT/29265/2017

Excitons in phosphorene: A semi-analytical perturbative approach

In this paper we develop a semi-analytical perturbation-theory approach to the calculation of the energy levels (binding energies) and wave functions of excitons in phosphorene. Our method gives the exciton wave function in both real and reciprocal spaces with the same ease. This latter aspect is important for the calculation of the nonlinear optical properties of phosphorene. We find that our results are in agreement with calculations based both on the Bethe-Salpeter equation and on Monte Carlo simulations, which are computationally much more demanding. Our approach thus introduces a simple, viable, and accurate method to address the problem of excitons in anisotropic two-dimensional materials.N.M.R.P. acknowledges support from the European Commission through the project "Graphene-Driven Revolutions in ICT and Beyond" (Reference No. 785219) and the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Financing UID/FIS/04650/2019. In addition, N.M.R.P. acknowledges COMPETE2020, PORTUGAL2020, FEDER, and the FCT through Projects No. PTDC/FIS-NAN/3668/2013, No. POCI-01-0145-FEDER-028114, No. POCI-01-0145FEDER-029265, No. PTDC/NAN-OPT/29265/2017, and No. POCI-01-0145-FEDER-02888. The authors acknowledge P. A. Goncalves and R. Ribeiro for a critical reading of the manuscript

Diluted Random Fields in Mixed Cyanide Crystals

A percolation argument and a dilute compressible random field Ising model are used to present a simple model for mixed cyanide crystals. The model reproduces quantitatively several features of the phase diagrams altough some crude approximations are made. In particular critical thresholds x_c at which ferroelastic first order transitions disappear, are calculated. Moreover, transitions are found to remain first order down to x_c for all mixtures except for bromine, for which the transition becomes continuous. All the results are in full agreement with experimental data.Comment: 8 pages, late

Galaxy formation in the Planck cosmology - II. Star-formation histories and post-processing magnitude reconstruction

We adapt the L-Galaxies semi-analytic model to follow the star-formation histories (SFH) of galaxies -- by which we mean a record of the formation time and metallicities of the stars that are present in each galaxy at a given time. We use these to construct stellar spectra in post-processing, which offers large efficiency savings and allows user-defined spectral bands and dust models to be applied to data stored in the Millennium data repository. We contrast model SFHs from the Millennium Simulation with observed ones from the VESPA algorithm as applied to the SDSS-7 catalogue. The overall agreement is good, with both simulated and SDSS galaxies showing a steeper SFH with increased stellar mass. The SFHs of blue and red galaxies, however, show poor agreement between data and simulations, which may indicate that the termination of star formation is too abrupt in the models. The mean star-formation rate (SFR) of model galaxies is well-defined and is accurately modelled by a double power law at all redshifts: SFR proportional to $1/(x^{-1.39}+x^{1.33})$, where $x=(t_a-t)/3.0\,$Gyr, $t$ is the age of the stars and $t_a$ is the loopback time to the onset of galaxy formation; above a redshift of unity, this is well approximated by a gamma function: SFR proportional to $x^{1.5}e^{-x}$, where $x=(t_a-t)/2.0\,$Gyr. Individual galaxies, however, show a wide dispersion about this mean. When split by mass, the SFR peaks earlier for high-mass galaxies than for lower-mass ones, and we interpret this downsizing as a mass-dependence in the evolution of the quenched fraction: the SFHs of star-forming galaxies show only a weak mass dependence.Comment: Accepted version of the paper, to appear in MNRAS. Compared to the original version, contains more detail on the post-processing of magnitudes, including a table of rms magnitude errors. SFHs available on Millennium database http://gavo.mpa-garching.mpg.de/MyMillennium

Determination of phytoextraction potential of plant speciesfor toxic elements in soils of abandoned sulphide-mining areas

This study has determined contamination levels in soils and plants from the Sa˜o Domingos mining area, Portugal, by k0-INAA. Total concentrations of As, Sb, Cr, Hg, Cu, Zn and Fe in soils were very high, exceeding the maximum limits in Portuguese legislation. Concentrations of toxic elements like As, Sb and Zn were highest in roots of Erica andevalensis, Juncus acutus, Agrostis castellana and Nicotiana glauca. Additionally, As, Br, Cr, Fe, Sb and Zn in all organs of most plants were above toxicity levels. Those species that accumulated relatively high concentrations of toxic elements in roots (and tops) may be cultivated for phytostabilisation of similar areas