787 research outputs found

    Census of HII regions in NGC 6754 derived with MUSE: Constraints on the metal mixing scale

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    We present a study of the HII regions in the galaxy NGC 6754 from a two pointing mosaic comprising 197,637 individual spectra, using Integral Field Spectrocopy (IFS) recently acquired with the MUSE instrument during its Science Verification program. The data cover the entire galaxy out to ~2 effective radii (re ), sampling its morphological structures with unprecedented spatial resolution for a wide-field IFU. A complete census of the H ii regions limited by the atmospheric seeing conditions was derived, comprising 396 individual ionized sources. This is one of the largest and most complete catalogue of H ii regions with spectroscopic information in a single galaxy. We use this catalogue to derive the radial abundance gradient in this SBb galaxy, finding a negative gradient with a slope consistent with the characteristic value for disk galaxies recently reported. The large number of H ii regions allow us to estimate the typical mixing scale-length (rmix ~0.4 re ), which sets strong constraints on the proposed mechanisms for metal mixing in disk galaxies, like radial movements associated with bars and spiral arms, when comparing with simulations. We found evidence for an azimuthal variation of the oxygen abundance, that may be related with the radial migration. These results illustrate the unique capabilities of MUSE for the study of the enrichment mechanisms in Local Universe galaxies.Comment: 13 pages, 7 Figurs, accepted for publishing in A&

    Potenciación de la respuesta inmune humoral sistémica en ratas lactantes por el ácido linoleico conjugado (CLA)

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    Cis-9, trans-11 (c9, t11) and trans-10, cis-12 (t10, c12) are the predominating molecules in the positional and geometrical isomers mixture termed CLA. Although CLA has shown positive effects on human health and seems to be associated with immunomodulatory activities, its effect in the developing immune system has not been studied. Thus, the present study was designed to establish the effect of CLA supplementation during gestation and/or lactation on humoral immune response, i.e. by analysing sera Ig levels during the suckling period. Wistar rats were allocated to four groups (A, B, C and W) on day 7 of pregnancy. From day 7 and throughout the study period group C and W gestating mothers were fed standard pellet chow. Group A and B dams were fed 10 g CLA (80% cis-9, trans-11, 20% trans-10, cis-12; Lipid Nutrition B. V. Wormerveer, The Netherlands)/kg pellet chow during gestation. Moreover, group A mothers were also fed the CLA-supplemented chow until the litters were 21 d old, the end of suckling period. Group B and C litters received the CLA mixture of isomers by daily oral administration while their respective dams were fed standard pellet chow during lactation. In all cases litters were equalised to ten rats per lactating mother. Pups from each experimental group were killed at the end of the second week of life (day 14) and at the end of the suckling period (day 21), and blood samples were collected. Serum IgA, IgG and IgM levels were quantified by the ELISA sandwich technique. ANOVA and post hoc comparisons (LSD test) were performed. Differences were considered to be significant at P<0.05. Animals receiving CLA passively from their mothers (group A) during gestation and the suckling period exhibited the highest concentrations of IgG and IgM at 14 d old (P<0.05; see Table). At the end of suckling period the serum IgG concentration in this group was also increased, up to three times more than in the other groups (P<0.05). Those animals supplemented with CLA only during suckling period (group C) showed no difference in relation to those receiving no supplement. Thus, these results demonstrate that CLA supplementation during gestation and lactation promotes systemic humoral immune response

    Stability of the Horizontal Curvature of the LHC Cryodipoles During Cold Tests

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    The LHC will be composed of 1232 horizontally curved, 15 meter long, superconducting dipole magnets cooled at 1.9 K. They are supported within their vacuum vessel by three Glass Fiber Reinforced Epoxy (GFRE) support posts. Each cryodipole is individually cold tested at CERN before its installation and interconnection in the LHC 27 km circumference tunnel. As the magnet geometry under cryogenic operation is extremely important for the LHC machine aperture, a new method has been developed at CERN in order to monitor the magnet curvature change between warm and cold states. It enabled us to conclude that there is no permanent horizontal curvature change of the LHC dipole magnet between warm and cold states, although a systematic horizontal transient deformation during cool-down was detected. This deformation generates loads in the dipole supporting system; further investigation permitted us to infer this behavior to the asymmetric thermal contraction of the rigid magnet thermal shield during cool-down. Controlling the helium flow rate in the thermal shield of the cryomagnet enabled us to reduce the maximal deformation by a factor of approximately two, thus increasing significantly the mechanical safety margin of the supporting system during the CERN cold tests

    Supramolecular coordination chemistry of aromatic polyoxalamide ligands: A metallosupramolecular approach toward functional magnetic materials

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    The impressive potential of the metallosupramolecular approach in designing new functional magnetic materials constitutes a great scientific challenge for the chemical research community that requires an interdisciplinary collaboration. New fundamental concepts and future applications in nanoscience and nanotechnology will emerge from the study of magnetism as a supramolecular function in metallosupramolecular chemistry. Our recent work on the rich supramolecular coordination chemistry of a novel family of aromatic polyoxalamide (APOXA) ligands with first-row transition metal ions has allowed us to move one step further in the rational design of metallosupramolecular assemblies of increasing structural and magnetic complexity. Thus, we have taken advantage of the new developments of metallosupramolecular chemistry and, in particular, the molecular-programmed self-assembly methods that exploit the coordination preferences of paramagnetic metal ions and suitable designed polytopic ligands. The resulting self-assembled di- and trinuclear metallacyclic complexes with APOXA ligands, either metallacyclophanes or metallacryptands, are indeed ideal model systems for the study of the electron exchange mechanism between paramagnetic metal centers through extended π-conjugated aromatic bridges. So, the influence of different factors such as the topology and conformation of the bridging ligand or the electronic configuration and magnetic anisotropy of the metal ion have been investigated in a systematic way. These oligonuclear metallacyclic complexes can be important in the development of a new class of molecular magnetic devices, such as molecular magnetic wires (MMWs) and switches (MMSs), which are major goals in the field of molecular electronics and spintronics. On the other hand, because of their metal binding capacity through the outer carbonyl-oxygen atoms of the oxamato groups, they can further be used as ligands, referred to as metal–organic ligands (MOLs), toward either coordinatively unsaturated metal complexes or fully solvated metal ions. This well-known “complex-as-ligand” approach affords a wide variety of high-nuclearity metal–organic clusters (MOCs) and high-dimensionality metal–organic polymers (MOPs). The judicious choice of the oligonuclear MOL, ranging from mono- to di- and trinuclear species, has allowed us to control the overall structure and magnetic properties of the final oxamato-bridged multidimensional (nD, n = 0–3) MOCs and MOPs. The intercrossing between short- (nanoscopic) and long-range (macroscopic) magnetic behavior has been investigated in this unique family of oxamato-bridged metallosupramolecular magnetic materials expanding the examples of low-dimensional, single-molecule (SMMs) and single-chain (SCMs) magnets and high-dimensional, open-framework magnets (OFMs), which are brand-new targets in the field of molecular magnetism and materials science

    Neutron capture measurements with high efficiency detectors and the Pulse Height Weighting Technique

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    Neutron capture cross section measurements in time-of-flight facilities are usually performed by detecting the prompt Îł-rays emitted in the capture reactions. One of the difficulties to be addressed in these measurements is that the emitted Îł-rays may change with the neutron energy, and therefore also the detection efficiency. To deal with this situation, many measurements use the so called Total Energy Detection (TED) technique, usually in combination with the Pulse Height Weighting Technique (PHWT). With it, it is sought that the detection efficiency depends only on the total energy of the Îł-ray cascade, which does not vary much with the neutron energy. This technique was developed in the 1960s and has been used in many neutron capture experiments to date. One of the requirements of the technique is that Îł-ray detectors have a low efficiency. This has meant that the PHWT has been used with experimental setups with low detection efficiencies. However, this condition does not have to be fulfilled by the experimental system as a whole. The main goal of this work is to show that it is possible to measure with a high efficiency detection system that uses the PHWT, and how to analyze the measured data.This work was supported in part by the I+D+i grant PGC2018- 096717-B-C21 funded by MCIN/AEI/10.13039/501100011033 and by the European Commission H2020 Framework Programme project SANDA (Grant agreement ID: 847552)
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