Organic Molecules in the Galactic Center. Hot Core Chemistry without Hot Cores

We study the origin of large abundances of complex organic molecules in the Galactic center (GC). We carried out a systematic study of the complex organic molecules CH3OH, C2H5OH, (CH3)2O, HCOOCH3, HCOOH, CH3COOH, H2CO, and CS toward 40 GC molecular clouds. Using the LTE approximation, we derived the physical properties of GC molecular clouds and the abundances of the complex molecules.The CH3OH abundance between clouds varies by nearly two orders of magnitude from 2.4x10^{-8} to 1.1x10^{-6}. The abundance of the other complex organic molecules relative to that of CH3OH is basically independent of the CH3OH abundance, with variations of only a factor 4-8. The abundances of complex organic molecules in the GC are compared with those measured in hot cores and hot corinos, in which these complex molecules are also abundant. We find that both the abundance and the abundance ratios of the complex molecules relative to CH3OH in hot cores are similar to those found in the GC clouds. However, hot corinos show different abundance ratios than observed in hot cores and in GC clouds. The rather constant abundance of all the complex molecules relative to CH3OH suggests that all complex molecules are ejected from grain mantles by shocks. Frequent (similar 10^{5}years) shocks with velocities >6km/s are required to explain the high abundances in gas phase of complex organic molecules in the GC molecular clouds. The rather uniform abundance ratios in the GC clouds and in Galactic hot cores indicate a similar average composition of grain mantles in both kinds of regions. The Sickle and the Thermal Radio Arches, affected by UV radiation, show different relative abundances in the complex organic molecules due to the differentially photodissociation of these molecules.Comment: 18 pages, 10 Postscript figures, uses aa.cls, aa.bst, 10pt.rtx, natbib.sty, revsymb.sty revtex4.cls, aps.rtx and aalongtabl.sty. Accepted in A&A 2006. version 2. relocated figures and tables. Language editor suggestions. added reference

El valle medio del Guadalquivir: De Montoro a Alcalá del Río

Consideración de los aspectos más relevantes del tramo medio del río Guadalquivir. Se consideran no sólo los aspectos hidrológicos, sino igualmente aquellos otros que se refieren a los paisajes por los que el gran río de Andalucía va discurriendo. En este orden de cosas, además de identificar claramente el escenario, se consideran los aspectos climáticos, la dinámica y la morfología fluvial (terrazas, meandros, etc…) y ¿cómo no? Los resultados de la intervención antrópica. En este último aspecto tienen tratamiento la relación de las vías de comunicación con el río, la intervención para la regulación de la cuenca, la agricultura irrigada y los efectos del proceso urbanizador

Le centre historique de Cordoue et le premier plan de la ville: Le «Plan des Français», de 1811

Durante la guerra de Independencia, el gobierno de los afrancesados elaboró en 1811 el llamado Plano de los Franceses, el primer plano urbano de Córdoba realizado de manera científica. Por ello, ha resultado ser un documento imprescindible para analizar el pasado y el presente urbano de la ciudad. Con ocasión de su bicentenario, intentamos una lectura contemporánea de la información que en él se contiene, haciendo una valoración de sus autores y de su papel en los procesos de reinvención de una ciudad históricaPendant la Guerre d’Espagne, le gouvernement des occupants réalisa en 1811 le premier plan urbain de la ville basé sur procédés scientifiques, le « Plan des Français », ce qui lui valut devenir un document incontournable pour l’analyse du passé et du présent de la ville. À l’occasion du bicentenaire du plan, nous essayons une lecture contemporaine de son contenu, en faisant une évaluation des auteurs et de son rôle dans les processus de réinvention d’une ville historiqueIn 1811, during the Peninsular War, the Napoleonic government executed the Cordoba first town map made with a scientific procedure, subsequently known as the “Map of the French”, which became an essential document to understand the urban past and present. On the occasion of its bicentenary, we try to make a modern interpretation of its content, as well as an evaluation both of the authorship and the role the map played in the historic city centre reinventio

Interrelación entre ciencia y enseñanza a principios del siglo XX: Juan Carandell Pericay

En estos momentos (primer tercio del siglo XXI), etapa en que de una forma tan tajante se están modificando muchos de los que fueran axiomas pedagógicos en todas las disciplinas, partiendo de los contenidos mismos que se enseñan y continuando con las formas mismas de enseñar, se plantea la conveniencia de una mirada hacia atrás para intentar recordar cómo eran y se hacían las cosas a principios del s. XX. Y para ello se plantea el análisis de la trayectoria –científica y pedagógica- de un catedrático de Bachillerato, D. Juan Carandell Pericay, en el que se aúnan de modo inseparable la pasión por el conocimiento científico, el afán ferviente de enseñarlo y, además, de enseñarlo correctamente

Abundant Z-cyanomethanimine in the interstellar medium: paving the way to the synthesis of adenine

We report the first detection in the interstellar medium of the Z-isomer of cyanomethanimine (HNCHCN), an HCN dimer proposed as precursor of adenine. We identified six transitions of Z-cyanomethanimine, along with five transitions of E-cyanomethanimine, using IRAM 30m observations towards the Galactic Center quiescent molecular cloud G+0.693. The Z-isomer has a column density of (2.0$\pm$0.6)$\times$10$^{14}$ cm$^{-2}$ and an abundance of 1.5$\times$10$^{-9}$. The relative abundance ratio between the isomers is [Z/E]$\sim$6. This value cannot be explained by the two chemical formation routes previously proposed (gas-phase and grain surface), which predicts abundances ratios between 0.9 and 1.5. The observed [Z/E] ratio is in good agreement with thermodynamic equilibrium at the gas kinetic temperature (130$-$210 K). Since isomerization is not possible in the ISM, the two species may be formed at high temperature. New chemical models, including surface chemistry on dust grains and gas-phase reactions, should be explored to explain our findings. Whatever the formation mechanism, the high abundance of Z-HNCHCN shows that precursors of adenine are efficiently formed in the ISM.Comment: Accepted in Monthly Notices of the Royal Astronomical Society Letter

Complex organic molecules in the Galactic Centre: the N-bearing family

We present an unbiased spectral line survey toward the Galactic Centre (GC) quiescent giant molecular cloud (QGMC), G+0.693 using the GBT and IRAM 30$\,$ telescopes. Our study highlights an extremely rich organic inventory of abundant amounts of nitrogen (N)-bearing species in a source without signatures of star formation. We report the detection of 17 N-bearing species in this source, of which 8 are complex organic molecules (COMs). A comparison of the derived abundances relative to H$_2$ is made across various galactic and extragalactic environments. We conclude that the unique chemistry in this source is likely to be dominated by low-velocity shocks with X-rays/cosmic rays also playing an important role in the chemistry. Like previous findings obtained for O-bearing molecules, our results for N-bearing species suggest a more efficient hydrogenation of these species on dust grains in G+0.693 than in hot cores in the Galactic disk, as a consequence of the low dust temperatures coupled with energetic processing by X-ray/cosmic ray radiation in the GC.Comment: 24 pages, 23 figures, 7 tables, accepted for publication in MNRA

3 mm spectral line survey of two lines of sight toward two typical cloud complexes in the Galactic Center

We present the results of two Mopra 3-mm spectral line surveys of the Lines of Sight (LOS) toward the Galactic Center (GC) molecular complexes Sgr B2 (LOS+0.693) and Sgr A (LOS-0.11). The spectra covered the frequency ranges of ~77-93 GHz and ~105-113 GHz. We have detected 38 molecular species and 25 isotopologues. The isotopic ratios derived from column density ratios are consistent with the canonical values, indicating that chemical isotopic fractionation and/or selective photodissociation can be considered negligible (<10%) for the GC physical conditions. The derived abundance and rotational temperatures are very similar for both LOSs, indicating very similar chemical and excitation conditions for the molecular gas in the GC. The excitation conditions are also very similar to those found for the nucleus of the starburst galaxy NGC 253. We report for the first time the detection of HCO and HOC+ emission in LOS+0.693. Our comparison of the abundance ratios between CS, HCO, HOC+ and HCO+ found in the two LOSs with those in typical Galactic photodissociation regions (PDRs) and starbursts galaxies does not show any clear trend to distinguish between UV and X-ray induced chemistries. We propose that the CS/HOC+ ratio could be used as a tracer of the PDR components in the molecular clouds in the nuclei of galaxies

Cartographic and geohistoric resources for the inventory of temporary wetlands and mediterranean desections

El presente artículo recopila y examina, desde una vertiente metodológica y geográfica, las fuentes o recursos cartográficos que se han analizado y utilizado para la realización del in-ventario de humedales temporales en el Medio Guadalquivir, y en el seno de nuestro proyecto de investigación. Estudiaremos fundamentalmente las fuentes cartográficas disponibles para el área citada, aunque en gran medida puedan ser extrapolables a la mayor parte de España. Se lleva a cabo una exposición de las líneas de trabajo y de los autores más representativos para el inventario de humedales temporales o desecados, mediante la investigación de la historia de los Archivos, de las Bibliotecas, de los Museos y de los Centros de Documentación convencionales y digitales actuales. En un segundo momento se aborda una propuesta metodológica para la investigación de esta faceta particular, acompañada por un nutrido apéndice en el que se recopilan las fuentes más significativas que venimos utilizando en nuestra investigación.This paper compiles and examines, from a methodological and geographical perspective, the sources or cartographic resources that have been analyzed and used for the realization of the inventory of temporary wetlands in the Middle Guadalquivir, and within our research project. We will study fundamentally the cartographic sources available for the mentioned area, although to a large extent they can be extrapolated to the greater part of Spain. An exposition of the lines of work and of the most representative authors for the inventory of temporary or dried wetlands is carried out, through the investigation of the History of Archives, of Libraries, of Museums and of Conventional Documentation Centers And digital technologies. In a second moment, a methodological proposal for the investigation of this particular facet is approached, accompanied by several appendices in which are collected the most significant sources that we have been using in our investigatio

Fabrication of zinc oxide and nanostructured porous silicon composite micropatterns on silicon

The luminescent properties of zinc oxide (ZnO) and nanostructured porous silicon (PSi) make these materials very appealing for photoemission applications. The current study reports on the fabrication of a composite of ZnO and nanostructured porous silicon micropatterns (ZnO + PSi micropatterns) onto heavily-doped silicon surfaces. The proposed composite micropattern is devoted to the future development of light-emitting diodes. The fabrication of the ZnO + PSi micropatterns was carried out in a two–step process. (1) A regular hexagonal micropattern of a photoresist/ZnO stack was fabricated by UV lithography on crystalline silicon substrates. (2) Before being lifted off the photoresist, nanostructured PSi micropatterns were fabricated by electrochemically etching the exposed areas of the silicon substrate. Subsequently, wet etching of the photoresist was carried out for the final development of the composite ZnO and PSi micropatterns. Further, thin films of ZnO and nanostructured PSi layers were characterized. In particular, their photoluminescent properties were analyzed, as well as their morphology and composition. The experimental PL results show that the ZnO layers have emission broadbands centered at (2.63 eV, blue), while the PSi layers show a band centered at (1.71 eV, red). Further, the emission peaks from the PSi layers can be tuned by changing their fabrication conditions. It was observed that the properties of the ZnO thin films are not influenced by either the surface morphology of PSi or by its PL emissions. Therefore, the PL properties of the composite ZnO + PSi micropatterns are equivalent to those featuring the addition of PSi layers and ZnO thin films. Accordingly, broadband optical emissions are expected to arise from a combination between the ZnO layer (blue band) and PSi (red band). Furthermore, the electrical losses associated with the PSi areas can be greatly reduced since ZnO is in contact with the Si surface. As a result, the proposed composite micropatterns might be attractive for many solid-state lighting applications, such as light-emitting diodesThis research was partially funded by Universidad Autónoma de Madrid, FPI-UAM grant (2019) and by the Egyptian Ministry of Higher Education, Missions Section under Egyptian Joint Supervision Grant, call 015/01