Semi-empirical analysis of Sloan Digital Sky Survey galaxies: II. The bimodality of the galaxy population revisited

We revisit the bimodal distribution of the galaxy population commonly seen in the local universe. Here we address the bimodality observed in galaxy properties in terms of spectral synthesis products, such as mean stellar ages and stellar masses, derived from the application of this powerful method to a volume-limited sample, with magnitude limit cutoff M_r = -20.5, containing about 50 thousand luminous galaxies from the SDSS Data Release 2. In addition, galaxies are classified according to their emission line properties in three distinct spectral classes: star-forming galaxies, with young stellar populations; passive galaxies, dominated by old stellar populations; and, hosts of active nuclei, which comprise a mix of young and old stellar populations. We show that the extremes of the distribution of some galaxy properties, essentially galaxy colours, 4000 A break index, and mean stellar ages, are associated to star-forming galaxies at one side, and passive galaxies at another. We find that the mean light-weighted stellar age of galaxies is the direct responsible for the bimodality seen in the galaxy population. The stellar mass, in this view, has an additional role since most of the star-forming galaxies present in the local universe are low-mass galaxies. Our results also give support to the existence of a 'downsizing' in galaxy formation, where massive galaxies seen nowadays have stellar populations formed at early times.Comment: 18 pages, 19 figures, accepted for publication in MNRA

Bibliometric analysis of 50 years of IEEE Industrial Electronics Society publications

Tertiary education increasingly relies on publications. Arguably, Ph.D.\@ work is also increasingly produced within larger teams or with more extensive collaborations. As way to obtain an objective measure of this trend, this manuscript examines authorship trends in IEEE Industrial Electronics Society (IEEE-IES) publications for the 50-year period from 1963 to 2012. We emphasize the trends related to the number of authors and pages per publication. In order to identify several bibliometric indicators, we have analyzed 34,409 entries from IEEE-Xplore digital library for IEEE-IES publications. We provide results for two different sets of publications. Firstly, we present evidence that the number of authors and the number of pages of articles in the IEEE Transactions in Industrial Electronics (TIE) for the 50-year period are increasing per decade an average of +0.42 authors and +0.87 pages, respectively. Secondly, we provide evidence that the number of authors per article in 14 publication venues for the 25-year period from 1988 to 2012 are increasing per decade an average of +0.375 authors.This work was partially supported by FCT - Fundação para a Ciência e Tecnologia in the framework of the Project Scope UID/CEC/00319/2013, and project UID/EEA/00066/2013

A day in the life of a germ cell - on gametogenesis and pluripotency

In this thesis, several critical time-points of human germ cell development are addressed.In Chapter 2, we adopted a culture system combining features of human embryonicstem cells (hESCs) derivation, by supplementation with Activin A, and extended blastocyst culture in vitro to examine lineage segregation in human blastocyst outgrowths. In Chapter 3, migratory and early post-migratory hPGCs were extensively characterized in a rare 4.5 week-old human embryo. In Chapter 4 an extensive characterization of the expression pattern and subcellularcompartmentalization of the PIWIL protein family during human embryonic development and spermatogenesis was performed.Several studies suggest that at some point during the transition from naïve to primed, pluripotency competency for PGC induction is acquired in culture, in parallel with what happens in vivo. In Chapter 5, requirement of BMP-SMAD signalling to keep pluripotency in naïve and ground state culture conditions was analysed.LUMC / Geneeskund

Hydrological and erosion response at micro-plot to -catchment scale following forest wildfire, north-central Portugal

Wildfires can have important impacts on hydrological and soil erosion processes, due to the destruction of vegetation cover and changes to soil properties. According to Shakesby and Doerr (2006), these wildfire effects are: i) much better known at small spatial scales (especially erosion plots) than at the scale of catchments; ii) much better studied with respect to overland flow and streamflow (and, then, especially peak discharges) than to soil erosion. Following up on a precursor project studying runoff generation and the associated soil losses from micro-plot to slope-scale in Portuguese eucalypt forests, the EROSFIRE-II project addresses the connectivity of these processes across hillslopes as well as within the channel network. This is done in the Colmeal study area in central Portugal, where the outlet of an entirely burnt catchment of roughly 10 ha was instrumented with a gauging station continuously recording water level and tubidity, and five slopes were each equipped with 4 runoff plots of < 0,5 m2 (“micro-plot”) and 4 slope-scale plots as well as 1 slope-scale sediment fence. Starting one month after the August 2008 wildfire, the plots were monitored at 1- to 2-weekly intervals, depending on the occurrence of rainfall. The gauging station became operational at the end of November 2008, since the in-situ construction of an H-flume required several weeks. A preliminary analysis of the data collected till the end of 2008, focusing on two slopes with contrasting slope lengths as well as the gauging station: revealed clear differences in runoff and erosion between: (i) the micro-plot and slope-scale plots on the same hillslope; (ii) the two slopes; (iii) an initial dry period and a subsequent much wetter period; (iv) the slopes and the catchment-scale, also depending on the sampling period. These results suggest that the different processes govern the hydrological and erosion response at different spatial scales as well as for different periods, with soil water repellency playing a role during the initial post-fire period. The current presentation will review these preliminary results based on the data collected during the first year after the wildfire

Congruences on monoids of order-preserving or order-reversing transformations on a finite chain

Glasgow Mathematical Journal, nº 47 (2005), pg. 413-424This paper is mainly dedicated to describing the congruences on certain monoids of transformations on a finite chain Xn with n elements. Namely, we consider the monoids ODn and PODn of all full, respectively partial, transformations on Xn that preserve or reverse the order, as well as the submonoid POn of PODn of all its order-preserving elements. The inverse monoid PODIn of all injective elements of PODn is also considered. We show that in POn any congruence is a Rees congruence, but this may not happen in the monoids ODn, PODIn and PODn. However in all these cases the congruences form a chain.This work was developed within the activities of Centro de ´Algebra da Universidade de Lisboa, supported by FCT and FEDER, within project POCTI ”Fundamental and Applied Algebra