Phenomenological viability of orbifold models with three Higgs families

We discuss the phenomenological viability of string multi-Higgs doublet models, namely a scenario of heterotic $Z_3$ orbifolds with two Wilson lines, which naturally predicts three supersymmetric families of matter and Higgs fields. We study the orbifold parameter space, and discuss the compatibility of the predicted Yukawa couplings with current experimental data. We address the implications of tree-level flavour changing neutral processes in constraining the Higgs sector of the model, finding that viable scenarios can be obtained for a reasonably light Higgs spectrum. We also take into account the tree-level contributions to indirect CP violation, showing that the experimental value of $\epsilon_K$ can be accommodated in the present framework.Comment: 31 pages, 12 figures. Comments and references added. Final version to be published in JHE

Abundances of Recently Discovered Planetary Nebulae Towards the Galactic Bulge

In this work we report spectrophotometric observations of a planetary nebula sample towards the galactic bulge. A total of 45 PNe was observed and their physical parameters (electron density and temperature) were derived. Ionic abundances were calculated using a three-level atom model and abundances were derived through ionisation correction factors. Results show low abundance objects at high galactic latitudes, indicating a possible vertical gradient inside the bulge. A few objects with low N/O ratio were found, which could originated from old, low mass progenitors

Globular Clusters: DNA of Early-Type galaxies?

This paper explores if the mean properties of Early-Type Galaxies (ETG) can be reconstructed from "genetic" information stored in their GCs (i.e., in their chemical abundances, spatial distributions and ages). This approach implies that the formation of each globular occurs in very massive stellar environments, as suggested by some models that aim at explaining the presence of multi-populations in these systems. The assumption that the relative number of globular clusters to diffuse stellar mass depends exponentially on chemical abundance, [Z/H], and the presence of two dominant GC sub-populations blue and red, allows the mapping of low metallicity halos and of higher metallicity (and more heterogeneous) bulges. In particular, the masses of the low-metallicity halos seem to scale up with dark matter mass through a constant. We also find a dependence of the globular cluster formation efficiency with the mean projected stellar mass density of the galaxies within their effective radii. The analysis is based on a selected sub-sample of galaxies observed within the ACS Virgo Cluster Survey of the {\it Hubble Space Telescope}. These systems were grouped, according to their absolute magnitudes, in order to define composite fiducial galaxies and look for a quantitative connection with their (also composite) globular clusters systems. The results strengthen the idea that globular clusters are good quantitative tracers of both baryonic and dark matter in ETGs.Comment: 20 pages, 28 figures and 5 table

Pinholes May Mimic Tunneling

Interest in magnetic-tunnel junctions has prompted a re-examination of tunneling measurements through thin insulating films. In any study of metal-insulator-metal trilayers, one tries to eliminate the possibility of pinholes (small areas over which the thickness of the insulator goes to zero so that the upper and lower metals of the trilayer make direct contact). Recently, we have presented experimental evidence that ferromagnet-insulator-normal trilayers that appear from current-voltage plots to be pinhole-free may nonetheless in some cases harbor pinholes. Here, we show how pinholes may arise in a simple but realistic model of film deposition and that purely classical conduction through pinholes may mimic one aspect of tunneling, the exponential decay in current with insulating thickness.Comment: 9 pages, 3 figures, plain TeX; submitted to Journal of Applied Physic

Can aldehyde accumulation rates of red winesundergoing oxidation be predicted inaccelerated conditions? The controverted roleof aldehyde–polyphenol reactivity

BACKGROUND: The accumulation of acetaldehyde and Strecker aldehydes during wine oxidation is detrimental to quality and often determines wine shelf-life. Knowing in advance the specific tendency of a wine to accumulate these compounds would help decision making during winemaking. An accelerated test based on a forced oxidation procedure at 45 °C (5 days) to measure aldehyde accumulation rates (AARs) is proposed and assessed by comparing results with those obtained by oxidation at 25 °C (36 days). Reactivities of aldehydes in those same wines stored in anoxia at both temperatures were also measured. RESULTS: Wine oxygen consumption rates at 25 °C are poorly correlated with those observed at 45 °C. By contrast, AARs of methional and of 2- and 3-methylbutanals measured during wine oxidation at 25 °C are equivalent to those measured at 45 °C. AARs from isobutanal and acetaldehyde are also correlated, while AARs from phenylacetaldehyde are not. Partial least squares models explaining AARs show intriguing differences regarding the apparent limiting role played by wine anthocyanins and other polyphenols in the ability of wines to accumulate aldehydes. Measured differences in aldehyde pattern are similar to those of the other Strecker aldehydes. CONCLUSION: The proposed assay makes it possible to obtain a reasonable estimate of a wine’s tendency to accumulate aldehydes, with the exception phenylacetaldehyde, in 5 days. Neither differences in aldehyde reactivity between wines nor the change in reactivities with temperature support a major role for reactivity in differentially limiting AARs during wine oxidation. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry

Factors that affect the accumulation of strecker aldehydes in standardized wines: the importance of ph in oxidation

Strecker aldehydes (SA) can be formed in wine from the degradation of Strecker and, to a lesser degree, via the oxidation of higher alcohols. The objective of this article is to assess the magnitude of the differences introduced by wine compositional factors other than amino acids and Fe, in the accumulation of SA during oxidation. Eight red, two rosé and two white wines were oxidized. The accumulation of SA was analyzed. Whites and rosés presented negative accumulations for isobutyraldehyde, and in general, these wines accumulated smaller concentrations of the other SA than red wines. Only methional and phenylacetaldehyde were accumulated in all of the wines during oxidation. 2-methylbutanal and 3-methylbutanal were accumulated in 9 out of the 12 wines, whereas isobutyraldehyde was accumulated only in 5 out of the 12. 2-methylbutanal was, on average, the least accumulated aldehyde. Methional was the aldehyde formed most homogenously. Most of the observed differences can be attributed to three factors: the pH, oxidation time and native levels of Strecker aldehydes. The influence of pH was particularly intense in the cases of phenylacetaldehyde and methional. An independent test using synthetic wines with Strecker amino acids and 4-methylcatechol with different pHs (4.2, 3.5 and 2.8) was carried out in order to verify the higher pH value, the greater accumulation in SA after oxidation process. The results strongly suggest the important role played by pH in the accumulation of SA in wine oxidatio

The populations of planetary nebulae in the direction of the Galactic bulge

We have observed 44 planetary nebulae (PNe) in the direction of the Galactic bulge, and merged our data with published ones. We have distinguished, in the merged sample of 164 PNe, those PNe most likely to prtain physically to the Galactic bulge and those most likely to belong to the Galactic disk. We have determined the chemical composition of all the 164 objects in a coherent way. We looked for stellar emission features and discovered 14 new [WR] stars and 15 new weak emission line central stars. The analyzed data led us to the following conclusions: (1) The spectral type distribution of [WR] stars is very different in the bulge and in the disk of the Galaxy. However, the observed distributions are strongly dependent on selection effects. (2) The proportion of [WR] PNe is significantly larger in the bulge than in the disk. (3) The oxygen abundances in [WR] stars do no appear to be significantly affected by nucleosynthesis and mixing in the progenitors. (4) The O/H gradient of the Galactic disk PNe population flattens in the most internal parts of the Galaxy. (5) The median oxygen abundance in the bulge PN population is larger by 0.2 dex than in the disk population seen in the direction of the bulge. (6) Bulge PNe with smaller O/H tend to have smaller radial velocities. (7) The oxygen abundance distribution of bulge PNe is similar in shape to that of the metallicity distribution of bulge giants, but significantly narrower. (8) The location of SB 32 (PN G 349.7-09.1) in the (V_lsr, l_II) diagram and its low oxygen abundance argues that it probably belongs to the halo population.Comment: 14 pages, 16 figures. Accepted for publication in A&

Synthesis and Functionalization of Monodisperse Near-ultraviolet and Visible Excitable Multifunctional Eu3+, Bi3+:REVO4 Nanophosphors for Bioimaging and Biosensing Applications

Near-ultraviolet and visible excitable Eu- and Bi-doped NPs based on rare earth vanadates (REVO4, RE = Y, Gd) have been synthesized by a facile route from appropriate RE precursors, europium and bismuth nitrate, and sodium orthovanadate, by homogeneous precipitation in an ethylene glycol/water mixture at 120 °C. The NPs can be functionalized either by a one-pot synthesis with polyacrylic acid (PAA) or by a Layer-by-Layer approach with poly(allylamine hydrochloride) (PAH) and PAA. In the first case, the particle size can also be tuned by adjusting the amount of PAA. The Eu- Bi-doped REVO4 based nanophosphors show the typical red luminescence of Eu(III), which can be excited through an energy transfer process from the vanadate anions, resulting in a much higher luminescence intensity in comparison to the direct excitation of the europium cations. The incorporation of Bi into the REVO4 structure shifts the original absorption band of the vanadate anions towards longer wavelengths, giving rise to nanophosphors with an excitation maximum at 342 nm, which can also be excited in the visible range. The suitability of such nanophosphors for bioimaging and biosensing applications, as well as their colloidal stability in different buffer media of biological interest, their cytotoxicity, their degradability at low pH, and their uptake by HeLa cells have been evaluated. Their suitability for bioimaging and biosensing applications is also demonstrated.European Union 267226Ministerio de Economía y Competitividad MAT2014-54852-

Chemical evolution of the galactic bulge: single and double infall models

Recent work has produced a wealth of data concerning the chemical evolution of the galactic bulge, both for stars and nebulae. Present theoretical models generally adopt a limited range of such constraints, frequently using a single chemical element (usually iron), which is not enough to describe it unambiguously. In this work, we take into account constraints involving as many chemical elements as possible, basically obtained from bulge nebulae and stars. Our main goal is to show that different scenarios can describe, at least partially, the abundance distribution and several distance-independent correlationss for these objects. Three classes of models were developed. The first is a one-zone, single-infall model, the second is a one-zone, double-infall model and the third is a multizone, double infall model. We show that a one-zone model with a single infall episode is able to reproduce some of the observational data, but the best results are achieved using a multizone, double infall model.Comment: 15 pages, 7 figures, accepted for publication in Baltic Astronomy, Latex, uses baltlat5.sty, epsfig.st