1,531 research outputs found

    Traditional small waterbodies as key landscape elements for farmland bird conservation in Mediterranean semiarid agroecosystems

    Get PDF
    © 2022. Elsevier Ltd. This document is made available under the CC-BY 4.0 license http://creativecommons.org/licenses/by /4.0/ This document is the accepted version of a published work that appeared in final form in Global Ecology and Conservatio

    Composición química del aceite esencial de hojas de Hedyosmum translucidum Cuatrec., Chloranthaceae (Granizo)

    Get PDF
    En el presente trabajo se realizó el análisis de la composición del aceite esencial de hojas de “Granizo”, Hedyosmum translucidum Cuatrec., Chloranthaceae, con certificado de identificación del Herbario PSO, recolectado en el corregimiento de Santa Bárbara, Pasto, Colombia. Este género es reportado con un índice de valor de importancia eco sistémico. El aceite esencial se obtuvo mediante hidrodestilación asistida por microondas, con un rendimiento de 1,2 %. Los componentes presentes en el aceite esencial se identificaron mediante cromatografía de gases acoplada a espectroscopia de masas GC-MS. Los componentes mayoritarios fueron: α- eudesmol (11,4%), germacreno D (8,9%), trans-β-cariofileno (7,8%), elemol (5,8%) y óxido de cariofileno (5,3%). Estos compuestos se clasifican como sesquiterpenos. La proporción de los componentes mayoritarios del aceite esencial de H. translucidum presenta diferencias con las reportadas para otras especies del género Hedyosmum en Bolivia, Venezuela y Brasil. Este trabajo constituye un conocimiento inicial para definirse como una especie promisoria

    Asymmetric organocatalytic Strecker-type reactions of aliphatic N,N-dialkylhydrazones

    Get PDF
    The enantioselective organocatalytic Strecker-type reaction of aliphatic N,N-dialkylhydrazones is presented. Using trimethylsilyl cyanide (TMSCN) as the cyanide source, the reaction can be efficiently catalyzed by a tert-leucine-derived bifunctional thiourea to afford the corresponding hydrazino nitriles in good to excellent yields (50-96%) and moderate to good enantioselectivities, up to 86% ee. Further transformations of the nitrile functionality allow access to useful protected hydrazino acids and imidazolidinones. Interestingly, some of the hydrazino nitriles and their derivatives could be recrystallized in high recovery, yielding essentially pure enantiomers.Ministerio de Ciencia e Innovación CTQ2010-15297, CTQ2010-14974Junta de Andalucía 2008/FQM-3833, 2009/FQM-453

    Uracil grafted imine-based covalent organic framework for nucleobase recognition

    Full text link
    An imine-based covalent organic framework (COF) decorated in its cavities with uracil groups has shown selective recognition towards adenine in water. These results show how the confinement of the base-pair inside the COF's pores allows a remarkable selective recognition in aqueous mediaThis work was financially supported by MINECO (MAT2016-77608-C3-1-P and 2-P, SAF2017-87305-R). IMDEA Nanociencia acknowledges support from the ‘Severo Ochoa’ Programme for Centres of Excellence in R&D (MINECO, Grant SEV-2016-0686). Funding from the European Research Council (ERC-StG 279548) and MINECO (CTQ2014-27729-P and CTQ2017-84727-P) is gratefully acknowledged (DGR

    The one-loop elastic coefficients for the Helfrich membrane in higher dimensions

    Full text link
    Using a covariant geometric approach we obtain the effective bending couplings for a 2-dimensional rigid membrane embedded into a (2+D)(2+D)-dimensional Euclidean space. The Hamiltonian for the membrane has three terms: The first one is quadratic in its mean extrinsic curvature. The second one is proportional to its Gaussian curvature, and the last one is proportional to its area. The results we obtain are in agreement with those finding that thermal fluctuations soften the 2-dimensional membrane embedded into a 3-dimensional Euclidean space.Comment: 9 page

    Chemical abundance gradients from open clusters in the Milky Way disk: results from the APOGEE survey

    Get PDF
    Metallicity gradients provide strong constraints for understanding the chemical evolution of the Galaxy. We report on radial abundance gradients of Fe, Ni, Ca, Si, and Mg obtained from a sample of 304 red-giant members of 29 disk open clusters, mostly concentrated at galactocentric distances between ~8 - 15 kpc, but including two open clusters in the outer disk. The observations are from the APOGEE survey. The chemical abundances were derived automatically by the ASPCAP pipeline and these are part of the SDSS III Data Release 12. The gradients, obtained from least squares fits to the data, are relatively flat, with slopes ranging from -0.026 to -0.033 dex/kpc for the alpha-elements [O/H], [Ca/H], [Si/H] and [Mg/H] and -0.035 dex/kpc and -0.040 dex/kpc for [Fe/H] and [Ni/H], respectively. Our results are not at odds with the possibility that metallicity ([Fe/H]) gradients are steeper in the inner disk (R_GC ~7 - 12 kpc) and flatter towards the outer disk. The open cluster sample studied spans a significant range in age. When breaking the sample into age bins, there is some indication that the younger open cluster population in our sample (log age < 8.7) has a flatter metallicity gradient when compared with the gradients obtained from older open clusters.Comment: 4 pages, 3 figures, To appear in Astronomische Nachrichten, special issue "Reconstruction the Milky Way's History: Spectroscopic surveys, Asteroseismology and Chemo-dynamical models", Guest Editors C. Chiappini, J. Montalb\'an, and M. Steffen, AN 2016 (in press)

    Comment on Rojas-Bracho and Colleagues (2019): Unsubstantiated Claims Can Lead to Tragic Conservation Outcomes

    Get PDF
    The vaquita’s decline is a tragic story indeed. However, the lack of action to prevent the extinction of this species is not due to unsubstantiated claims and scientific uncertainty
    corecore