On the Stability of Compactified D=11 Supermembranes

We prove D=11 supermembrane theories wrapping around in an irreducible way over $S^{1} \times S^{1}\times M^{9}$ on the target manifold, have a hamiltonian with strict minima and without infinite dimensional valleys at the minima for the bosonic sector. The minima occur at monopole connections of an associated U(1) bundle over topologically non trivial Riemann surfaces of arbitrary genus. Explicit expressions for the minimal connections in terms of membrane maps are presented. The minimal maps and corresponding connections satisfy the BPS condition with half SUSY.Comment: 15 pages, latex. Added comments in conclusions and more reference

Tracing shocks and photodissociation in the Galactic center region

We present a systematic study of the HNCO, C18O, 13CS, and C34S emission towards 13 selected molecular clouds in the Galactic center region. The molecular emission in these positions are used as templates of the different physical and chemical processes claimed to be dominant in the circumnuclear molecular gas of galaxies. The relative abundance of HNCO shows a variation of more than a factor of 20 amo ng the observed sources. The HNCO/13CS abundance ratio is highly contrasted (up to a factor of 30) between the shielded molecular clouds mostly affected by shocks, where HNCO is released to gas-phase from grain mantles, and those pervaded by an intense UV radiation field, where HNCO is photo-dissociated and CS production favored via ion reactions. We propose the relative HNCO to CS abundance ratio as a highly contrasted diagnostic tool to distinguish between the influence of shocks and/or the radiation field in the nuclear regions of galaxies and their relation to the evolutionary state of their nuclear star formation bursts.Comment: 25 pages, 5 figures, Accepted for publication in Ap

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

PPl 15: The First Brown Dwarf Spectroscopic Binary

PPl 15 is the first object to have been confirmed as a brown dwarf by the lithium test (in 1995), though its inferred mass was very close to the substellar limit. It is a member of the Pleiades open cluster. Its position in a cluster color-magnitude diagram suggested that it might be binary, and preliminary indications that it is a double-lined spectroscopic binary were reported by us in 1997. Here we report on the results of a consecutive week of Keck HIRES observations of this system, which yield its orbit. It has a period of about 5.8 days, and an eccentricity of 0.4+/-0.05. The rotation of the stars is slow for this class of objects. Because the system luminosity is divided between 2 objects with a mass ratio of 0.85, this renders each of them an incontrovertible brown dwarf, with masses between 60-70 jupiters. We show that component B is a little redder than A by studying their wavelength-dependent line ratios, and that this variation is compatible with the mass ratio. We confirm that the system has lithium, but cannot support the original conclusion that it is depleted (which would be surprising, given the new masses). This is a system of very close objects which, if they had combined, would have produced a low mass star. We discuss the implications of this discovery for the theories of binary formation and formation of very low mass objects.Comment: Latex, 18 pages, 4 figures, submitted to Astron.

Diferenciación de carnes de jabalí europeo (Sus scrofa scrofa) y cerdo doméstico (Sus scrofa domestica) mediante el análisis por PCR de la región mitocondrial D-loop y el gen nuclear MC1R

En este trabajo se describe la diferenciación de carnes procedentes de jabalí europeo (Sus scrofa scrofa) y cerdo doméstico (Sus scrofa domestica) mediante el análisis por PCR de la región mitocondrial D-loop y del gen nuclear que codifica para el receptor 1 de la melanocortina (MC1R). La discriminación por PCR-RFLP de jabalí y cerdo en la región D loop no fue posible. Sin embargo, la técnica de PCR-RFLP desarrollada en el gen MC1R determinó perfiles de bandas característicos que permitieron la diferenciación de jabalí y cerdo mediante el empleo de las endonucleasas BspHI y BstUI.This work describes the differentiation of European wild boar (Sus scrofa scrofa) and domestic swine (Sus scrofa domestica) meats by PCR targeting sequences from the mitochondrial displacement loop (D-loop) region and the nuclear melanocortin receptor 1 (MC1R) gene. Detailed analysis of every D-loop sequence obtained indicated that PCR RFLP differentiation between wild and domestic Sus scrofa meats was not possible. Nevertheless, the PCR-RFLP technique developed targeting the MC1R gene generated characteristic PCR–RFLP profiles that allowed discrimination among meats from wild and domestic swine specimens using BspHI and BstUI endonucleases

Polymerase chain reaction detection of rabbit DNA in food and animal feed

[EN] A polymerase chain reaction (PCR) based on oligonucleotide primers targeting the mitochondrial 12S rRNA gene was developed for the specific identification of rabbit DNA (Oryctolagus cuniculus) in food and feedstuffs. The specificity of the primers was verified by PCR analysis of DNA from 32 non-target species including mammals, birds, fish, and plant species. Analysis of experimental mixtures demonstrated the presence of rabbit-derived materials in the range of 0.1-100%. Prolonged heat treatment (up to 133ºC for 20 min at 300 kPa) applied to rabbit muscle/oats binary mixtures did not affect the performance of the method, which could therefore be said to be very useful for the accurate identification of rabbit materials in products submitted to denaturing technologies when other methods are not suitable.This study was supported by Grant Nº. AGL 2007-60077 from the Spanish Ministerio de Educación y Ciencia and the Programa de Vigilancia Sanitaria S-0505/AGR/000265 of the Comunidad de Madrid (Spain). Irene Martín is the recipient of a fellowship from the Universidad Complutense de Madrid (Spain). Violeta Fajardo and María Rojas are recipients of fellowships from the Ministerio de Educación y Ciencia (Spain).Martín, I.; García, T.; Fajardo, V.; Rojas, M.; Pegels, N.; Hernández, P.; González, I.... (2009). Polymerase chain reaction detection of rabbit DNA in food and animal feed. World Rabbit Science. 17(1):27-34. doi:10.4995/wrs.2009.667273417