Solar type II radio bursts associated with CME expansions as shown by EUV waves

We investigate the physical conditions of the sources of two metric Type-II bursts associated with CME expansions with the aim of verifying the relationship between the shocks and the CMEs, comparing the heights of the radio sources and the heights of the EUV waves associated with the CMEs. The heights of the EUV waves associated with the events were determined in relation to the wave fronts. The heights of the shocks were estimated by applying two different density models to the frequencies of the Type-II emissions and compared with the heights of the EUV waves. For the 13 June 2010 event, with band-splitting, the shock speed was estimated from the frequency drifts of the upper and lower branches of the harmonic lane, taking into account the H/F frequency ratio fH/fF = 2. Exponential fits on the intensity maxima of the branches revealed to be more consistent with the morphology of the spectrum of this event. For the 6 June 2012 event, with no band-splitting and with a clear fundamental lane on the spectrum, the shock speed was estimated directly from the frequency drift of the fundamental emission, determined by linear fit on the intensity maxima of the lane. For each event, the most appropriate density model was adopted to estimate the physical parameters of the radio source. The 13 June 2010 event presented a shock speed of 664-719 km/s, consistent with the average speed of the EUV wave fronts of 609 km/s. The 6 June 2012 event was related to a shock of speed of 211-461 km/s, also consistent with the average speed of the EUV wave fronts of 418 km/s. For both events, the heights of the EUV wave revealed to be compatible with the heights of the radio source, assuming a radial propagation of the shock.Comment: Accepted for publication in Astronomy and Astrophysic

Experimental Demonstration of a Structured Material with Extreme Effective Parameters at Microwaves

Following our recent theoretical studies [M. G. Silveirinha, C. A. Fernandes, Phys. Rev. B, 78, 033108, 2008], it is experimentally verified that an array of crossed metallic wires may behave as a nonresonant material with extremely large index of refraction at microwaves, and may enable the realization of ultra-subwavelength waveguides.Comment: accepted for publication in Applied Physics Letters (in press). Applied Physics Letters (in press) (2008

Regeneração de plantas de alho in vitro após o cultivo de ápices caulinares.

Foram avaliados o potencial de regeneração de genótipos de alho (Gigante de Lavínia, San Valentim, Ito, Caçador, Chinês real, Cattura, Jorans, Gravata, Peruano, Roxo Caxiense, Amarante, Gigante do núcleo, Bergamota, Hozan, RAL 41, RE5118.1 e Ribeiro) após a termoterapi e o cultivo de ápices caulinares, procedimentos que compõem a limpeza clonal do alho

Stellar population gradients in Seyfert 2 galaxies. Northern sample

We use high signal-to-noise ratio long-slit spectra in the 3600-4700A range of the twenty brightest northern Seyfert 2 galaxies to study the variation of the stellar population properties as a function of distance from the nucleus. In order to characterize the stellar population and other continuum sources (e.g. featureless continuum FC) we have measured equivalent widths Ws of six absorption features, four continuum colours and their radial variations, and performed spectral population synthesis as a function of distance from the nucleus. About half the sample has CaIIK and G-band W values smaller at the nucleus than at 1 kpc from it, due to a younger population and/or FC. The stellar population synthesis shows that, while at the nucleus, 75% of the galaxies present contribution > 20% of ages younger or equal than 100Myr and/or of a FC, this proportion decreases to 45% at 3 kpc. In particular, 55% of the galaxies have contribution > 10% of the 3 Myr/FC component (a degenerate component in which one cannot separate what is due to a FC or to a 3 Myr stellar population) at the nucleus, but only 25% of them have this contribution at 3 kpc. As reference, the stellar population of 10 non-Seyfert galaxies, spanning the Hubble types of the Seyfert (from S0 to Sc) was also studied. A comparison between the stellar population of the Seyferts and that of the non-Seyferts shows systematic differences: the contribution of ages younger than 1 Gyr is in most cases larger in the Seyfert galaxies than in non-Seyferts, not only at the nucleus but up to 1 kpc from it.Comment: 23 pages, 18 figures, MNRAS in pres

Obscuring Active Galactic Nuclei with Nuclear Starburst Disks

We assess the potential of nuclear starburst disks to obscure the Seyfert-like AGN that dominate the hard X-ray background at z~1. Over 1200 starburst disk models, based on the theory developed by Thompson et al., are calculated for five input parameters: the black hole mass, the radial size of the starburst disk, the dust-to-gas ratio, the efficiency of angular momentum transport in the disk, and the gas fraction at the outer disk radius. We find that a large dust-to-gas ratio, a relatively small starburst disk, a significant gas mass fraction, and efficient angular momentum transport are all important to produce a starburst disk that can potentially obscure an AGN. The typical maximum star-formation rate in the disks is ~10 solar masses per year. Assuming no mass-loss due to outflows, the starburst disks feed gas onto the black hole at rates sufficient to produce hard X-ray luminosities of 10^{43}-10^{44} erg s^{-1}. The starburst disks themselves should be detectable at mid-infrared and radio wavelengths; at z=0.8, the predicted fluxes are ~1 mJy at 24microns and ~10-30 microJy at 1.4GHz. Thus, we predict a large fraction of radio/X-ray matches in future deep radio surveys. The starburst disks should be easily distinguished from AGN in future 100microns surveys by Herschel with expected fluxes of ~5 mJy. Any AGN-obscuring starbursts will be associated with hot dust, independent of AGN heating, resulting in observable signatures for separating galactic and nuclear star-formation. Finally, because of the competition between gas and star-formation, nuclear starbursts will be associated with lower-luminosity AGN. Thus, this phenomenon is a natural explanation for the observed decrease in the fraction of obscured AGN with luminosity.Comment: 13 pages, 12 figures, 3 in color; accepted by Ap

The Ratio of Ortho- to Para-H2 in Photodissociation Regions

We discuss the ratio of ortho- to para-H2 in photodissociation regions (PDRs). We draw attention to an apparent confusion in the literature between the ortho-to-para ratio of molecules in FUV-pumped vibrationally excited states, and the H2 ortho-to-para abundance ratio. These ratios are not the same because the process of FUV-pumping of fluorescent H2 emission in PDRs occurs via optically thick absorption lines. Thus, gas with an equilibrium ratio of ortho- to para-H2 equal to 3 will yield FUV-pumped vibrationally excited ortho-to-para ratios smaller than 3, because the ortho-H2 pumping rates are preferentially reduced by optical depth effects. Indeed, if the ortho and para pumping lines are on the ``square root'' part of the curve-of-growth, then the expected ratio of ortho and para vibrational line strengths is the square root of 3, ~ 1.7, close to the typically observed value. Thus, contrary to what has sometimes been stated in the literature, most previous measurements of the ratio of ortho- to para-H2 in vibrationally excited states are entirely consistent with a total ortho-to-para ratio of 3, the equilibrium value for temperatures greater than 200 K. We present an analysis and several detailed models which illustrate the relationship between the total ratios of ortho- to para-H2 and the vibrationally excited ortho-to-para ratios in PDRs. Recent Infrared Space Observatory (ISO) measurements of pure rotational and vibrational H2 emissions from the PDR in the star-forming region S140 provide strong observational support for our conclusions.Comment: 23 pages (including 5 figures), LaTeX, uses aaspp4.sty, accepted for publication in Ap

Iterative receiver combining IB-DFE with MRC for massive MIMO schemes

Once we are moving to the 5G system it is imperative to reduce the complexity of massive MIMO (Multiple-Input, Multiple Output) receivers. This paper considers the uplink transmission using massive MIMO combined with SC-FDE (Single-Carrier with Frequency-Domain Equalization). We propose an iterative frequency-domain receiver merging IB-DFE (Iterative Block Decision-Feedback Equalizer) with MRC (Maximal Ratio Combining). We propose a novel approach to reduce the complexity of the receiver by avoiding matrix inversions while maintaining a level of performance very close to the Matched Filter Bound (MFB), which makes it an excellent option for 5G systems.info:eu-repo/semantics/acceptedVersio