Study by DTA/TG of the formation of calcium aluminate obtained from an aluminium hazardous waste

A Spanish hazardous waste from tertiary aluminium industry was used as a raw material for the synthesis of calcium aluminate. An amorphous precursor was obtained by a hydrothermal method at different values of pH. The transformation of the precursor in a crystalline aluminate was followed by TG/DTA up to 1300 C. At temperatures between 719 and 744 C, the precursors evolve towards the formation of C12A7 which becomes CA at circa 1016 C. Mass spectrometry coupled to thermal analyser allowed the identification of the decomposition productsMEC for financing project CTM2005-01964 and the company Recuperaciones y Reciclajes Roman S.L. (Fuenlabrada, Madrid, Spain) for supplying the waste and Dr. M. I. Martı´n for the FRX analysis and Dr. I. Padilla for the technical assistance. Laura Delgado-Gonzalo is grateful to the CSIC (Spanish National Research Council) for an I3P contractPeer reviewe

Structural and morphological evolution of powders nanostructured ceramics: transitional aluminas

This work aims with the study of the transformation of boehmite into transitional aluminas. Boehmite was obtained by a sol-gel method from an aluminium hazardous waste. The thermal behaviour of boehmite was followed by thermogravimetry and differential thermal analysis to determine the transformation temperatures.  By calcinations of boehmite at temperatures ranging between 250-1000ºC, transitional aluminas (?, ? , ?-Al2O3)  were synthesized and characterized by XRD, TEM and FTIR. All the transitional aluminas exhibit nanometric crystallite size, ranging from 2.5-15nm. ?-Al2O3 was obtained as a nanostructured material at 500ºC with a cell parameter a=7.923Å. ?-phase stars to appear at 850ºC with a crystallite size of 6nm and cell parameters a=5.672Å and c=24.600Å. For ?-Al2O3 the cell parameters, in Å, were a=11.817, b=2.912, c=5.621 and ?=103.8º. The progressive conversion of the transitional phase ?-Al2O3 into the stable polymorph ?-alumina, takes place gradually and a four-phases region is achieved at 1000ºC, where coexist with other transitional phase such as  ?- and ?-Al2O3

Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution

We present deep echelle spectrophotometry of the brightest emission-line knots of the star-forming galaxies He 2-10, Mkn 1271, NGC 3125, NGC 5408, POX 4, SDSS J1253-0312, Tol 1457-262, Tol 1924-416 and the HII region Hubble V in the Local Group dwarf irregular galaxy NGC 6822. The data have been taken with the Very Large Telescope Ultraviolet-Visual Echelle Spectrograph in the 3100-10420 {\AA} range. We determine electron densities and temperatures of the ionized gas from several emission-line intensity ratios for all the objects. We derive the ionic abundances of C$^{2+}$ and/or O$^{2+}$ from faint pure recombination lines (RLs) in several of the objects, permitting to derive their C/H and C/O ratios. We have explored the chemical evolution at low metallicities analysing the C/O vs. O/H, C/O vs. N/O and C/N vs. O/H relations for Galactic and extragalactic HII regions and comparing with results for halo stars and DLAs. We find that HII regions in star-forming dwarf galaxies occupy a different locus in the C/O vs. O/H diagram than those belonging to the inner discs of spiral galaxies, indicating their different chemical evolution histories, and that the bulk of C in the most metal-poor extragalactic HII regions should have the same origin than in halo stars. The comparison between the C/O ratios in HII regions and in stars of the Galactic thick and thin discs seems to give arguments to support the merging scenario for the origin of the Galactic thick disc. Finally, we find an apparent coupling between C and N enrichment at the usual metallicities determined for HII regions and that this coupling breaks in very low-metallicity objects.Comment: 27 pages, 12 figures, Accepted for publication in Monthly Notices of the Royal Astronomical Societ

Modeling Star counts in the Monoceros stream and the Galactic anti-centre

There is a continued debate as to the form of the outer disc of the Milky Way galaxy, which has important implications for its formation. Stars are known to exist at a galacto-centric distance of at least 20 kpc. However, there is much debate as to whether these stars can be explained as being part of the disc or whether another extra galactic structure, the so called Monoceros ring/stream, is required. To examine the outer disc of the Galaxy toward the anti-centre to determine whether the star counts can be explained by the thin and thick discs alone. Using Sloan star counts and extracting the late F and early G dwarfs it is possible to directly determine the density of stars out to a galacto-centric distance of about 25 kpc. These are then compared with a simple flared disc model. A flared disc model is shown to reproduce the counts along the line of sights examined, if the thick disc does not have a sharp cut off. The flare starts at a Galacto-centric radius of 16 kpc and has a scale length of 4.5+/-1.5 kpc. Whilst the interpretation of the counts in terms of a ring/stream cannot be definitely discounted, it does not appear to be necessary, at least along the lines of sight examined towards the anti centre.Comment: 11 pages, 4 figures, accepted to be published in A&

Improved prediction of the optical properties in pi-conjugated polymers: the case of benzochalcogenodiazole-based copolymers with different heteroatom substitution

Donor−acceptor (D−A) approach to conjugated polymer design has become a widely used method for preparing conjugated polymers with narrow band gaps.1 One outstanding D−A polymer is poly(cyclopentadithiophene)benzothiadiazole, PCPDTBT (P1 in Figure 1), for which power conversion efficiencies in solar cells of 4.5-5.5% are reported.2 In this work, we use resonance Raman (RR) and density functional theory (DFT) calculations to investigate the tuning of the electronic and structural properties of cyclopentadithiophene-benzochalcogenodiazole D−A polymers, wherein a single atom in the benzochalcogenodiazole unit is varied from sulfur to selenium to tellurium (Fig. 1).3 Sophisticated DFT calculations have been carried out using long-range corrected functionals, considering both tuned and default range-separation parameters, aiming at predicting their optical and charge transport properties. In addition, the nature of the electronic excitation is described by analyzing the enhancement pattern in the RR spectra using Raman excitation wavelengths coincident with the various transitions in the copolymers.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Google Scholar Metrics evolution: an analysis according to languages

The final publication is available at Springer via http://dx.doi.org/10.1007/s11192-013-1164-8In November 2012 the Google Scholar Metrics (GSM) journal rankings were updated, making it possible to compare bibliometric indicators in the ten languages indexed—and their stability—with the April 2012 version. The h-index and h-5 median of 1,000 journals were analysed, comparing their averages, maximum and minimum values and the correlation coefficient within rankings. The bibliometric figures grew significantly. In just seven and a half months the h-index of the journals increased by 15 % and the median h-index by 17 %. This growth was observed for all the bibliometric indicators analysed and for practically every journal. However, we found significant differences in growth rates depending on the language in which the journal is published. Moreover, the journal rankings seem to be stable between April and November, reinforcing the credibility of the data held by Google Scholar and the reliability of the GSM journal rankings, despite the uncontrolled growth of Google Scholar. Based on the findings of this study we suggest, firstly, that Google should upgrade its rankings at least semi-annually and, secondly, that the results should be displayed in each ranking proportionally to the number of journals indexed by language.Orduña Malea, E.; Delgado López-Cózar, E. (2014). Google Scholar Metrics evolution: an analysis according to languages. Scientometrics. 98(3):2353-2367. doi:10.1007/s11192-013-1164-8S23532367983Aguillo, & Isidro, F. (2012). Is Google Scholar useful for bibliometrics? A webometric analysis. Scientometrics, 91(2), 343–351.Brewington, B. E., & Cybenko, G. (2000). How dynamic is the Web? Computer Networks, 33(1–6), 257–276.Chen, X. (2010). Google Scholar’s dramatic coverage improvement five years after debut. Serials Review, 36(4), 221–226.Cho, Y. & Garcia-Molina, H. (2000). The evolution of the web and implications for an incremental crawler. Proceedings of the 26th International Conference on very large data bases, 200–209.Costas, R., & Bordons, M. (2007). The h-index: advantages, limitations and its relation with other bibliometric indicators at the micro level. Journal of Informetrics, 1(3), 193–203.de Winter, J. C. F., Zadpoor, A. A., & Dodou, D. (2013). The expansion of Google Scholar versus Web of Science: a longitudinal study. Scientometrics. doi: 10.1007/s11192-013-1089-2 .Delgado López-Cózar, E., & Cabezas-Clavijo, A. (2012). Google Scholar Metrics: an unreliable tool for assessing scientific journals. El profesional de la información, 21(4), 419–427.Delgado López-Cózar, E., & Cabezas-Clavijo, A. (2013). Ranking journals: could Google Scholar metrics be an alternative to journal citation reports and Scimago journal ranks. Learned publishing, 26(2), 101–114.Fetterly, D., Manasse, M., Najork, M. & Wiener, J. (2003). A large scale study of the evolution of web pages. Proceedings of the Twelfth International Conference on World Wide Web, 669–678.Harzing, A.-W. (2013). A preliminary test of Google Scholar as a source for citation data: a longitudinal study of Nobel prize winners. Scientometrics, 94(3), 1057–1075.Jacsó, P. (2012). Google Scholar Metrics for Publications—The software and content feature of a new open access bibliometric service. Online Information Review, 36(4), 604–619.Koehler, W. (2002). Web page change and persistence-4-year longitudinal web study. Journal of the American Society for Information Science and Technology, 53(2), 162–171.Koehler, W (2004). A longitudinal study of Web pages continued a consideration of document persistence. Information Research, 9(2). http://informationr.net/ir/9-2/paper174.html . Accessed 1 Sep 2013.Kousha, K., & Thelwall, M. (2007). Google Scholar Citations and Google Web/URL citations: a multidiscipline exploratory analysis. Journal of the American Society for Information Science and Technology, 58(7), 1055–1065.Leydesdorff, L. (2012). World shares of publications of the USA, EU-27, and China compared and predicted using the new Web of Science interface versus Scopus. El profesional de la información, 21(1), 43–49.Neuhaus, C., Neuhaus, E., Asher, A., & Wrede, C. (2006). The depth and breadth of Google Scholar: An empirical study. Libraries and the Academy, 6(2), 127–141.Orduña-Malea, E., Serrano-Cobos, J., & Lloret-Romero, N. (2009). Las universidades públicas españolas en Google Scholar: presencia y evolución de su publicación académica web. El profesional de la información, 18(5), 493–500.Orduña-Malea, E., Serrano-Cobos, J., Ontalba-Ruipérez, J.-A., & Lloret-Romero, N. (2010). Presencia y visibilidad web de las universidades públicas españolas. Revista española de documentación científica, 33(2), 246–278.Ortega, J. L., Aguillo, I. F., & Prieto, J. A. (2006). Longitudinal study of contents and elements in the scientific Web environment. Journal of Information Science, 32(4), 344–351.Payne, N., & Thelwall, M. (2007). A longitudinal study of academic webs: growth and stabilization. Scientometrics, 71(3), 523–539

Effect of Defoliation Frequency and Planting Density on Yield and Nutritive Value of \u3ci\u3eCoursetia ferruginea\u3c/i\u3e (HBK) Lavin

The aim of the present study was to asses the influence of the frequency of defoliation and density of sowing on yield and nutritive value of Coursetia ferruginea. Three defoliation frequencies (6, 8 and 10 weeks) and three densities of planting (1 x 1 m, 1 x 1.5 m and 1 x 2 m) were evaluated. A randomized block design, in a split plot arrangement and four repetitions, was used. Frequency of defoliation has a strong significant (P\u3c 0.01) effect on dry matter (DM) yield (13.6, 18.1 and 27.8 g DM/plant for 6, 8 and 10-week defoliation frequencies), plant height (63.5, 76.6 and 101.2 cm) and plant survival (71, 74 and 86%). Nutritive value was significantly (P\u3c 0.05) affected by the frequency of defoliation. Mineral content was reduced as the defoliation interval increased. Density of planting did not affect (P\u3e 0.05) any of the variables. It is concluded that, C. ferruginea is a forage shrub with potential to improve animal feed quality, but it does not stand frequent defoliation

Eliminating Error in the Chemical Abundance Scale for Extragalactic HII Regions

In an attempt to remove the systematic errors which have plagued the calibration of the HII region abundance sequence, we have theoretically modeled the extragalactic HII region sequence. We then used the theoretical spectra so generated in a double blind experiment to recover the chemical abundances using both the classical electron temperature + ionization correction factor technique, and the technique which depends on the use of strong emission lines (SELs) in the nebular spectrum to estimate the abundance of oxygen. We find a number of systematic trends, and we provide correction formulae which should remove systematic errors in the electron temperature + ionization correction factor technique. We also provide a critical evaluation of the various semi-empirical SEL techniques. Finally, we offer a scheme which should help to eliminate systematic errors in the SEL-derived chemical abundance scale for extragalactic HII regions.Comment: 24 pages, 9 Tables, 13 figures, accepted for publication in MNRAS. Updated considering minor changes during the final edition process and some few missing reference

The spatially resolved star formation history of CALIFA galaxies: Cosmic time scales

This paper presents the mass assembly time scales of nearby galaxies observed by CALIFA at the 3.5m telescope in Calar Alto. We apply the fossil record method of the stellar populations to the complete sample of the 3rd CALIFA data release, with a total of 661 galaxies, covering stellar masses from 10$^{8.4}$ to 10$^{12}$ M$_{\odot}$ and a wide range of Hubble types. We apply spectral synthesis techniques to the datacubes and process the results to produce the mass growth time scales and mass weighted ages, from which we obtain temporal and spatially resolved information in seven bins of galaxy morphology and six bins of stellar mass (M$_{\star}$) and stellar mass surface density ($\Sigma_{\star}$). We use three different tracers of the spatially resolved star formation history (mass assembly curves, ratio of half mass to half light radii, and mass-weighted age gradients) to test if galaxies grow inside-out, and its dependence with galaxy stellar mass, $\Sigma_{\star}$, and morphology. Our main results are as follows: (a) The innermost regions of galaxies assemble their mass at an earlier time than regions located in the outer parts; this happens at any given M$_{\star}$, $\Sigma_{\star}$, or Hubble type, including the lowest mass systems. (b) Galaxies present a significant diversity in their characteristic formation epochs for lower-mass systems. This diversity shows a strong dependence of the mass assembly time scales on $\Sigma_{\star}$ and Hubble type in the lower-mass range (10$^{8.4}$ to 10$^{10.4}$), but a very mild dependence in higher-mass bins. (c) All galaxies show negative $\langle$log age$\rangle_{M}$ gradients in the inner 1 HLR. The profile flattens with increasing values of $\Sigma_{\star}$. There is no significant dependence on M$_{\star}$ within a particular $\Sigma_{\star}$ bin, except for the lowest bin, where the gradients becomes steeper.Comment: 15 pages, 13 figures, 3 tables, accepted for publication in Astronomy & Astrophysics. *Abridged abstract

Integral field spectroscopy of selected areas of the Bright Bar and Orion-S cloud in the Orion Nebula

We present integral field spectroscopy of two selected zones in the Orion Nebula obtained with the Potsdam Multi-Aperture Spectrophotometer (PMAS), covering the optical spectral range from 3500 to 7200 A and with a spatial resolution of 1". The observed zones are located on the prominent Bright Bar and on the brightest area at the northeast of the Orion South cloud, both containing remarkable ionization fronts. We obtain maps of emission line fluxes and ratios, electron density and temperatures, and chemical abundances. We study the ionization structure and morphology of both fields, which ionization fronts show different inclination angles with respect to the plane of the sky. We find that the maps of electron density, O+/H+ and O/H ratios show a rather similar structure. We interpret this as produced by the strong dependence on density of the [OII] lines used to derive the O+ abundance, and that our nominal values of electron density-derived from the [SII] line ratio-may be slightly higher than the appropriate value for the O+ zone. We measure the faint recombination lines of OII in the field at the northeast of the Orion South cloud allowing us to explore the so-called abundance discrepancy problem. We find a rather constant abundance discrepancy across the field and a mean value similar to that determined in other areas of the Orion Nebula, indicating that the particular physical conditions of this ionization front do not contribute to this discrepancy.Comment: 15 pages, 10 figures. Accepted for publication in MNRA