Flare parameters inferred from a 3D loop model database

We developed a data base of pre-calculated flare images and spectra exploring a set of parameters which describe the physical characteristics of coronal loops and accelerated electron distribution. Due to the large number of parameters involved in describing the geometry and the flaring atmosphere in the model used, we built a large data base of models (∼250 000) to facilitate the flare analysis. The geometry and characteristics of non-thermal electrons are defined on a discrete grid with spatial resolution greater than 4 arcsec. The data base was constructed based on general properties of known solar flares and convolved with instrumental resolution to replicate the observations from the Nobeyama radio polarimeter spectra and Nobeyama radioheliograph (NoRH) brightness maps. Observed spectra and brightness distribution maps are easily compared with the modelled spectra and images in the data base, indicating a possible range of solutions. The parameter search efficiency in this finite data base is discussed. 8 out of 10 parameters analysed for 1000 simulated flare searches were recovered with a relative error of less than 20 per cent on average. In addition, from the analysis of the observed correlation between NoRH flare sizes and intensities at 17 GHz, some statistical properties were derived. From these statistics, the energy spectral index was found to be δ ∼ 3, with non-thermal electron densities showing a peak distribution ⪅107 cm−3, and Bphotosphere ⪆ 2000 G. Some bias for larger loops with heights as great as ∼2.6 × 109 cm, and looptop events were noted. An excellent match of the spectrum and the brightness distribution at 17 and 34 GHz of the 2002 May 31 flare is presented as well

Minimal anomaly-free chiral fermion sets and gauge coupling unification

We look for minimal chiral sets of fermions beyond the standard model that are anomaly free and, simultaneously, vectorlike particles with respect to colour SU(3) and electromagnetic U(1). We then study whether the addition of such particles to the standard model particle content allows for the unification of gauge couplings at a high energy scale, above $5.0 \times 10^{15}$ GeV so as to be safely consistent with proton decay bounds. The possibility to have unification at the string scale is also considered. Inspired in grand unified theories, we also search for minimal chiral fermion sets that belong to SU(5) multiplets. Restricting to representations up to dimension 50, we show that some of these sets can lead to gauge unification at the GUT and/or string scales.Comment: 13 pages, 5 figures, 8 tables; Comments and references added, final version to appear in Phys. Rev.

Reconstruction of Quark Mass Matrices with Weak Basis Texture Zeroes from Experimental Input

All quark mass matrices with texture zeroes obtained through weak basis transformations are confronted with the experimental data. The reconstruction of the quark mass matrices M_u and M_d at the electroweak scale is performed in a weak basis where the matrices are Hermitian and have a maximum of three vanishing elements. The same procedure is also accomplished for the Yukawa coupling matrices at the grand unification scale in the context of the Standard Model and its minimal supersymmetric extension as well as of the two Higgs doublet model. The analysis of all viable power structures on the quark Yukawa coupling matrices that could naturally appear from a Froggatt-Nielsen mechanism is also presented.Comment: RevTeX4, 3 tables, 21 pages; misprints corrected and one reference adde

Repeatability and Reproducibility of Peripapillary Choroidal Thickness Using a Medical Image-Processing Software

Although choroid has been shown to have a vital role in the pathophysiology of many ocular diseases, its role in the pathogenesis of several other conditions remains uncertain. The authors propose a novel methodology to establish a more accurate Peripapillary Choroidal Thickness (PPCT), using an image-processing software. This study sought to evaluate the reproducibility and repeatability of PPCT evaluation with ImageJ software in healthy volunteers. Forty-eight eyes of 24 volunteers were subjected to PPCT area determination, after imaging acquisition and recording with Spectral-domain Optical Coherence Tomography (SD-OCT) Heidelberg Spectralis®, during two different sessions, by two blinded assessors. The age of the subjects was 29.2 ± 4.5 years (mean ± SD). The Coefï¬cient of Repeatability (CR) average measurements of PPCT area was 17.06 mm2 and 9.48 mm2 correspondingly, for the ï¬rst and second examiners. Intra-class Correlation Coefï¬cient (ICC) was 0.994 (95% CI 0.989 to 0.997) and 0.998 (95% CI 0.997 to 0.999). Inter-observer Concordance Correlation Coefï¬cient (CCC) was 0.998 (95% CI 0.996 to 0.999) for both examiners. Intra-observer CCC ranged from 0.997 (95% CI 0.996 to 0.999) to 0.998 (95% CI 0.997 to 0.999), correspondingly, for the first and second examiners. The PPCT quantification by means of the proposed methodology showed good inter- and intra-observer agreement for both operators, indicating feasibility and good reproducibility of the proposed methodology. This approach might be used in different clinical settings and potentially contributes to elucidation of the choroid role in ocular pathology

Expression of Sympathetic Nervous System Genes in Lamprey Suggests Their Recruitment for Specification of a New Vertebrate Feature

The sea lamprey is a basal, jawless vertebrate that possesses many neural crest derivatives, but lacks jaws and sympathetic ganglia. This raises the possibility that the factors involved in sympathetic neuron differentiation were either a gnathostome innovation or already present in lamprey, but serving different purposes. To distinguish between these possibilities, we isolated lamprey homologues of transcription factors associated with peripheral ganglion formation and examined their deployment in lamprey embryos. We further performed DiI labeling of the neural tube combined with neuronal markers to test if neural crest-derived cells migrate to and differentiate in sites colonized by sympathetic ganglia in jawed vertebrates. Consistent with previous anatomical data in adults, our results in lamprey embryos reveal that neural crest cells fail to migrate ventrally to form sympathetic ganglia, though they do form dorsal root ganglia adjacent to the neural tube. Interestingly, however, paralogs of the battery of transcription factors that mediate sympathetic neuron differentiation (dHand, Ascl1 and Phox2b) are present in the lamprey genome and expressed in various sites in the embryo, but fail to overlap in any ganglionic structures. This raises the intriguing possibility that they may have been recruited during gnathostome evolution to a new function in a neural crest derivative

Association of radio polar cap brightening with bright patches and coronal holes

Radio-bright regions near the solar poles are frequently observed in Nobeyama Radioheliograph (NoRH) maps at 17 GHz, and often in association with coronal holes. However, the origin of these polar brightening has not been established yet. We propose that small magnetic loops are the source of these bright patches, and present modeling results that reproduce the main observational characteristics of the polar brightening within coronal holes at 17 GHz. The simulations were carried out by calculating the radio emission of the small loops, with several temperature and density profiles, within a 2D coronal hole atmospheric model. If located at high latitudes, the size of the simulated bright patches are much smaller than the beam size and they present the instrument beam size when observed. The larger bright patches can be generated by a great number of small magnetic loops unresolved by the NoRH beam. Loop models that reproduce bright patches contain denser and hotter plasma near the upper chromosphere and lower corona. On the other hand, loops with increased plasma density and temperature only in the corona do not contribute to the emission at 17 GHz. This could explain the absence of a one-to-one association between the 17 GHz bright patches and those observed in extreme ultraviolet. Moreover, the emission arising from small magnetic loops located close to the limb may merge with the usual limb brightening profile, increasing its brightness temperature and width.Comment: 8 pages, 6 figures, 1 table. Accepted for publication in The Astrophysical Journa

EP20.01: Twin pregnancy birth in a new non-tertiary hospital

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