Electromagnetic topology: Characterization of internal electromagnetic coupling

The main principles are presented of a method dealing with the resolution of electromagnetic internal problems: Electromagnetic Topology. A very interesting way is to generalize the multiconductor transmission line network theory to the basic equation of the Electromagnetic Topology: the BLT equation. This generalization is illustrated by the treatment of an aperture as a four port junction. Analytical and experimental derivations of the scattering parameters are presented. These concepts are used to study the electromagnetic coupling in a scale model of an aircraft, and can be seen as a convenient means to test internal electromagnetic interference

Angiogenesis in the Gonadal Capillary Network of the Chick Embryo

Seventy-one chick embryos of both sexes at the 35 Hamburger and Hamilton (H-H) developmental stage were processed for scanning electron microscopy of vascular corrosion casts and of critical point dried specimens, as well as transmission electron- and light microscopy, in order to study the angiogenic structures. The gonadal subepithelial capillary network was located at the level of the tunica albuginea under the covering epithelium. The casts showed a densely-meshed capillary network and numerous sprouting (nodular protrusions or capillary sprouts) and non-sprouting (enlarged vessels and angiogenic holes) angiogenic structures that were randomly distributed and mixed. Four types of angio-genic holes were encountered in the casts: primary (diameter \u3c 2.5 μm), secondary (diameter \u3e 2.5 μm), tertiary (variable diameter and circular narrowings on one side), and open angiogenic holes. We suggest that the different morphologies reflect evolution of these holes. Furthermore, the open angiogenic hole would probably either form nodular protrusions at its open ends, which tend to join with other nodular protrusions and neighboring capillaries and form new vessels; or there would be fusion with two or more neighboring open holes. Correlative critical point dried sections showed fenestrations in the capillary walls and transcapillary pillars that corresponded to the angiogenic holes found in the casts. Ultrathin sections of the vessels presented typical characteristics of growing endothelium: large nuclei with loosely textured chromatin, abundant cytoplasm rich in cell organelles and intraluminal endothelial processes

A WFC3/HST view of the three stellar populations in the Globular Cluster NGC6752

Multi-band Hubble Space Telescope photometry reveals that the main sequence, sub-giant, and the red giant branch of the globular cluster NGC6752 splits into three main components in close analogy with the three distinct segments along its horizontal branch stars. These triple sequences are consistent with three stellar groups: a stellar population with a chemical composition similar to field halo stars (population a), a population (c) with enhanced sodium and nitrogen, depleted carbon and oxygen and enhanced helium abundance (Delta Y ~0.03), and a population (b) with an intermediate (between population a and c) chemical composition and slightly helium enhanced (Delta Y ~0.01). These components contain ~25% (population a), ~45% (population b), and ~30% (population c) of the stars. No radial gradient for the relative numbers of the three populations has been identified out to about 2.5 half mass radii.Comment: 42 pages, 24 figures, accepted for publication in Ap

Vascular Architecture of the Lactating and Non-Lactating Teat of the Bitch: A Scanning Electron- and Light Microscope Study

Tissues from fourteen mammary glands of eight bitches were prepared for scanning electron microscopy of vascular corrosion casts and for histology to study the vasculature of the lactating and non-lactating teats. The densely-meshed mammary dermal capillary network formed ridges and troughs. The teat ducts were vascularized by a relatively densely-meshed capillary network which drained into veins longitudinally oriented to the ducts. Between eight and fifteen teat duct openings were seen on the tip of the teat, that were sometimes divided by a septum. The inner vascularization of the teat showed that the main papillary arteries divided into undulating secondary papillary arteries which presented numerous semi-constrictions and loops. Their structure may help during erection of the teat. Arteriovenous anastomoses found at different points may participate in blood flow maintenance during suckling, heat regulation and teat erection. Veins freely anastomosed and ran longitudinally to the axis of the teat. They exhibited numerous bicuspid valves. In non-lactating teats, vessels showed the same main architecture and characteristics mentioned above, although these were considerably less marked. The structure of the vascular elements in the teat of the bitch could favor blood flow during suckling and suggest that vessels adapt to the physiological situation

Hallazgo de una nueva columna miliaria perteneciente a la Via Augusta

By means of this article we let you know about the discovery of a new milliary column which belonged to the Roman Via Augusta. It has been found in the environs of La Torrecilla industrial area close to Córdoba. Its chronology based upon epigraphic analysis allow us to date it in the early years of Nero mandate.Mediante este artículo damos a conocer una nueva columna miliaria correspondiente a la Via Augusta y hallada en las inmediaciones del Polígono Industrial de La Torrecilla. Su cronología, basada en el análisis epigráfico, nos permite adjudicarla al emperador Nerón, en los primeros años de su mandato

The spatial and age distribution of stellar populations in DDO 190

The spatial distribution of stellar populations, the star formation history, and other properties of the dIrr galaxy DDO 190 have been analyzed using color--magnitude diagrams (CMDs) of about 3900 resolved stars and the Ha fluxes of HII regions. From the mean color index of the red giant branch, a mean metallicity [Fe/H]=-2.0 is obtained. The I magnitude of the TRGB has been used to estimate the distance. DDO 190 is 2.9+/-0.2 Mpc from the Milky Way, 2.1 Mpc from the M 94 group (CnV-I), 2.4 Mpc from the M 81 group and 2.9 Mpc from the barycenter of the Local Group, all indicating that it is an isolated, field galaxy. The surface-brightness distribution of the galaxy is well fitted by ellipses of ellipticity e=1-a/b=0.1 and P.A.=82deg. The radial star density distribution follows an exponential law of scale length a=43."4, corresponding to 611 pc. The Holmberg semi-major axis to mu_B=26.5 is estimated to be r^B_(26.5)=3.'0. Stellar populations of different ages in DDO 190 show strong spatial decoupling, the oldest population appearing much more extended than the youngest. Stars younger than 0.1 Gyr occupy only the central 40'' (0.55 kpc); stars younger than a few (~4) Gyr extend out to ~80'' (125 kpc), and for larger galactocentric distances only older stars seem to be present. This behavior is found in all the dIrr galaxies for which spatially extended studies have been performed and could be related with the kinematical history of the galaxy.Comment: To be published in the AJ. 29 pages, 13 figure

The Star Formation History of the Local Group dwarf galaxy Leo I

We present a quantitative analysis of the star formation history (SFH) of the Local Group dSph galaxy Leo I, from the information in its HST [(V-I),I] color-magnitude diagram (CMD). The method we use is based in comparing, via synthetic CMDs, the expected distribution of stars in the CMD for different evolutionary scenarios, with the observed distribution. We consider the SFH to be composed by the SFR(t), the Z(t), the IMF, and a function $\beta(f,q)$, controlling the fraction $f$ and mass ratio distribution $q$ of binary stars. The comparison between the observed CMD and the model CMDs is done through chi-square minimization of the differences in the number of stars in a set of regions of the CMD. Our solution for the SFH of Leo I defines a minimum of chi-square in a well defined position of the parameter space, and the derived SFR(t) is robust, in the sense that its main characteristics are unchanged for different combinations of the remaining parameters. However, only a narrow range of assumptions for Z(t), IMF and $\beta(f,q)$ result in a good agreement between the data and the models, namely: Z=0.0004, a Kroupa et al. (1993) IMF or slightly steeper, and a relatively large fraction of binary stars. Most star formation activity (70% to 80%) occurred between 7 and 1 Gyr ago. At 1 Gyr ago, it abruptly dropped to a negligible value, but seems to have been active until at least ~ 300 Myr ago. Our results don't unambiguously answer the question of whether Leo I began forming stars around 15 Gyr ago, but it appears that the amount of this star formation, if existing at all, would be small.Comment: 25 pages + 14 figures. Accepted by The Astronomical Journa

The Chemical Enrichment History of the Large Magellanic Cloud

Ca II triplet spectroscopy has been used to derive stellar metallicities for individual stars in four LMC fields situated at galactocentric distances of 3\arcdeg, 5\arcdeg, 6\arcdeg\@ and 8\arcdeg\@ to the north of the Bar. Observed metallicity distributions show a well defined peak, with a tail toward low metallicities. The mean metallicity remains constant until 6\arcdeg\@ ([Fe/H]$\sim$-0.5 dex), while for the outermost field, at 8\arcdeg, the mean metallicity is substantially lower than in the rest of the disk ([Fe/H]$\sim$-0.8 dex). The combination of spectroscopy with deep CCD photometry has allowed us to break the RGB age--metallicity degeneracy and compute the ages for the objects observed spectroscopically. The obtained age--metallicity relationships for our four fields are statistically indistinguishable. We conclude that the lower mean metallicity in the outermost field is a consequence of it having a lower fraction of intermediate-age stars, which are more metal-rich than the older stars. The disk age--metallicity relationship is similar to that for clusters. However, the lack of objects with ages between 3 and 10 Gyr is not observed in the field population. Finally, we used data from the literature to derive consistently the age--metallicity relationship of the bar. Simple chemical evolution models have been used to reproduce the observed age--metallicity relationships with the purpose of investigating which mechanism has participated in the evolution of the disk and bar. We find that while the disk age--metallicity relationship is well reproduced by close-box models or models with a small degree of outflow, that of the bar is only reproduced by models with combination of infall and outflow.Comment: 45 pages, 10 figures, accepted for publication in Astronomical Journa

The Recent Star Formation History of NGC 5102

We present Hubble Space Telescope photometry of young stars in NGC 5102, a nearby gas-rich post-starburst S0 galaxy with a bright young stellar nucleus. We use the IAC-pop/MinnIAC algorithm to derive the recent star formation history in three fields in the bulge and disk of NGC 5102. In the disk fields, the recent star formation rate has declined monotonically and is now barely detectable, but a starburst is still in progress in the bulge and has added about 2 percent to the mass of the bulge over the last 200 Myr. Other studies of star formation in NGC 5102 indicate that about 20 percent of its stellar mass was added over the past Gyr. If this is correct, then much of the stellar mass of the bulge may have formed over this period. It seems likely that this star formation was fueled by the accretion of a gas-rich system with HI mass of about 2 x 10^9 Msol which has now been almost completely converted into stars. The large mass of recently formed stars and the blue colours of the bulge suggest that the current starburst, which is now fading, may have made a significant contribution to build the bulge of NGC 5102.Comment: 36 pages, 16 figures, accepted in A