Area Littlewood-Paley functions associated with Hermite and Laguerre operators

In this paper we study Lp-boundedness properties for area Littlewood-Paley functions associated with heat semigroups for Hermite and Laguerre operator

Connection between type B (or C) and F factorizations and construction of algebras

In a recent paper (Del Sol Mesa A and Quesne C 2000 J. Phys. A: Math. Gen. 33 4059), we started a systematic study of the connections among different factorization types, suggested by Infeld and Hull, and of their consequences for the construction of algebras. We devised a general procedure for constructing satellite algebras for all the Hamiltonians admitting a type E factorization by using the relationship between type A and E factorizations. Here we complete our analysis by showing that for Hamiltonians admitting a type F factorization, a similar method, starting from either type B or type C ones, leads to other types of algebras. We therefore conclude that the existence of satellite algebras is a characteristic property of type E factorizable Hamiltonians. Our results are illustrated with the detailed discussion of the Coulomb problem.Comment: minor changes, 1 additional reference, final form to be published in JP

Materiales para la hidrobiología de Navarra: 2. Dípteros quironómidos (Diptera, Chironomidae)

Se han identificado 37 especies de dípteros quironómidos de Navarra. De cada una de las especies se presentan las sinonimias más significativas, una pequeña descripción con iconografía original, el material que se ha colectado, algunos datos sobre la biología y la distribución geográfica

Polarization Properties of Extragalactic Radio Sources and Their Contribution to Microwave Polarization Fluctuations

We investigate the statistical properties of the polarized emission of extragalactic radio sources and estimate their contribution to the power spectrum of polarization fluctuations in the microwave region. The basic ingredients of our analysis are the NVSS polarization data, the multifrequency study of polarization properties of the B3-VLA sample (Mack et al. 2002) which has allowed us to quantify Faraday depolarization effects, and the 15 GHz survey by Taylor et al. (2001), which has provided strong constraints on the high-frequency spectral indices of sources. The polarization degree of both steep- and flat-spectrum at 1.4 GHz is found to be anti-correlated with the flux density. The median polarization degree at 1.4 GHz of both steep- and flat-spectrum sources brighter than $S(1.4 \hbox{GHz})=80$mJy is $\simeq 2.2$. The data by Mack et al. (2002) indicate a substantial mean Faraday depolarization at 1.4 GHz for steep spectrum sources, while the depolarization is undetermined for most flat/inverted-spectrum sources. Exploiting this complex of information we have estimated the power spectrum of polarization fluctuations due to extragalactic radio sources at microwave frequencies. We confirm that extragalactic sources are expected to be the main contaminant of Cosmic Microwave Background (CMB) polarization maps on small angular scales. At frequencies $< 30$GHz the amplitude of their power spectrum is expected to be comparable to that of the $E$-mode of the CMB. At higher frequencies, however, the CMB dominates.Comment: 10 pages, A&A in pres

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

Avances en la obtención de tableros de fibras a partir de mezclas de residuales lignocelulósicos de bagazo

El pretratamiento del bagazo resulta fundamental en el fraccionamiento de la biomasa en sus componentes principales: celulosa, hemicelulosa y lignina, en la reducción de la cristalinidad de la celulosa y en el aumento del área superficial accesible. El trabajo tiene como objetivo la obtención preliminar de tableros de fibras a partir de la utilización de mezclas de bagazo con residuales lignocelulósicos obtenidos en las etapas de pretratamiento del bagazo (hidrólisis ácida y enzimática). Se realiza un diseño de experimento de mezclas, enrejado simplex de Scheffe utilizando una prensa de calentamiento. Se caracterizan los residuales celulósicos utilizando la técnica analítica Pulsy se evalúa la resistencia a la flexión de los tableros de fibras obtenidos. Los resultados favorecen a la utilización de mezclas de bagazo y sólido de la hidrólisis enzimática para la obtención de los tableros. Como conclusión, se propone continuar con el estudio de mezclas con adición de aglutinante y/o resina de manera que favorezcan las propiedades mecánicas de los tableros.

Carbon and oxygen in HII regions of the Magellanic Clouds: abundance discrepancy and chemical evolution

We present C and O abundances in the Magellanic Clouds derived from deep spectra of HII regions. The data have been taken with the Ultraviolet-Visual Echelle Spectrograph at the 8.2-m VLT. The sample comprises 5 HII regions in the Large Magellanic Cloud (LMC) and 4 in the Small Magellanic Cloud (SMC). We measure pure recombination lines (RLs) of CII and OII in all the objects, permitting to derive the abundance discrepancy factors (ADFs) for O^2+, as well as their O/H, C/H and C/O ratios. We compare the ADFs with those of other HII regions in different galaxies. The results suggest a possible metallicity dependence of the ADF for the low-metallicity objects, but more uncertain for high-metallicity objects. We compare nebular and B-type stellar abundances and we find that the stellar abundances agree better with the nebular ones derived from collisionally excited lines (CELs). Comparing these results with other galaxies we observe that stellar abundances seem to agree better with the nebular ones derived from CELs in low-metallicity environments and from RLs in high-metallicity environments. The C/H, O/H and C/O ratios show almost flat radial gradients, in contrast with the spiral galaxies where such gradients are negative. We explore the chemical evolution analysing C/O vs. O/H and comparing with the results of HII regions in other galaxies. The LMC seems to show a similar chemical evolution to the external zones of small spiral galaxies and the SMC behaves as a typical star-forming dwarf galaxy.Comment: Accepted for publication in MNRAS, 17 pages, 11 figures, 8 table

A possibly inflated planet around the bright, young star DS Tuc A

The origin of the observed diversity of planetary system architectures is one of the main topic of the exoplanetary research. The detection of a statistically significant sample of planets around young stars allows us to study the early stages of planet formation and evolution, but only a handful of them is known so far. In this regard, a considerable contribution is expected from the NASA TESS satellite, which is now performing a survey of $\sim 85 \%$ of the sky to search for short-period transiting planets In its first month of operations, TESS found a planet candidate with an orbital period of 8.14 days around a member of the Tuc-Hor young association ($\sim$ 40 Myr), the G6V main component of the binary system DS\,Tuc. If confirmed, it would be the first transiting planet around a young star suitable for radial velocity and/or atmospheric characterization. We aim to validate the planetary nature of this companion and to measure its orbital and physical parameters. We obtain accurate planet parameters by coupling an independent reprocessing of the TESS light curve with improved stellar parameters and the dilution caused by the binary companion; we analyse high precision archival radial velocities to impose an upper limit of about 0.1 M$_{\rm Jup}$ on the planet mass; we finally rule out the presence of external companions beyond 40 au with adaptive optics images. We confirm the presence of a young, giant (${\rm R} = 0.50$ R$_{\rm Jup}$) planet having a not negligible possibility to be inflated (theoretical mass $\lesssim 20$ M$_{\oplus}$) around DS\,Tuc~A. We discuss the feasibility of mass determination, Rossiter-McLaughlin analysis and atmosphere characterization, allowed by the brightness of the star.Comment: 12 pages, 11 figures. Accepted for publication in A&

Estudio faunístico del macizo de Quinto Real. I. Acaros Oribátidos (Acari, Oribatei)

Se han estudiado 3.995 ejemplares de ácaros oribátidos (Acari, Òribatei) de 65 muestras pertenecientes a dos hayedos de Quinto Real (Pirineos Occidentales), correspondientes a 69 especies de 43 géneros. Diez especies son nuevas para la Fauna de España Damaeus verticillipes (Nicolet) , Cepheus tuberoulosus Strenzke, Liaoarus tremella (Linneo), Cara bodes femoralis (Nicolet) , Carabodes retioulatus Berlese, Oppia translamellata~ (Willmann) , Oribella paolii Oudemans, Phauloppia luoorum (Linneo) , Bdwardzetes edwardsii (Nicolet) y Ophidiotrichus aonexus borussica (Sellnick) . Se dan las características climatológicas, geológicas, edafológicas y florísticas del biotopo