Computing Optimal Distances to Pareto Sets of Multi-Objective Optimization Problems in Asymmetric Normed Lattices

[EN] Given a finite dimensional asymmetric normed lattice, we provide explicit formulae for the optimization of the associated (non-Hausdorff) asymmetric distance among a subset and a point. Our analysis has its roots and finds its applications in the current development of effective algorithms for multi-objective optimization programs. We are interested in providing the fundamental theoretical results for the associated convex analysis, fixing in this way the framework for this new optimization tool. The fact that the associated topology is not Hausdorff forces us to define a new setting and to use a new point of view for this analysis. Existence and uniqueness theorems for this optimization are shown. Our main result is the translation of the original abstract optimal distance problem to a clear optimization scheme. Actually, this justifies the algorithms and shows new aspects of the numerical and computational methods that have been already used in visualization of multi-objective optimization problems.This work was supported by the Ministerio de Economia y Competitividad (Spain) under grants DPI2015-71443-R and MTM2016-77054-C2-1-P.Blasco, X.; Reynoso-Meza, G.; Sánchez Pérez, EA.; Sánchez Pérez, JV. (2019). Computing Optimal Distances to Pareto Sets of Multi-Objective Optimization Problems in Asymmetric Normed Lattices. Acta Applicandae Mathematicae. 159(1):75-93. https://doi.org/10.1007/s10440-018-0184-z7593159

Submillimeter H2O masers in water-fountain nebulae

We report the first detection of submillimeter water maser emission toward water-fountain nebulae, which are post-AGB stars that exhibit high-velocity water masers. Using APEX we found emission in the ortho-H2O (10_29-9_36) transition at 321.226 GHz toward three sources: IRAS 15445-5449, IRAS 18043-2116 and IRAS 18286-0959. Similarly to the 22 GHz masers, the submillimeter water masers are expanding with a velocity larger than that of the OH masers, suggesting that these masers also originate in fast bipolar outflows. In IRAS 18043-2116 and IRAS 18286-0959, which figure among the sources with the fastest water masers, the velocity range of the 321 GHz masers coincides with that of the 22 GHz masers, indicating that they likely coexist. Towards IRAS 15445-5449 the submillimeter masers appear in a different velocity range, indicating that they are tracing different regions. The intensity of the submillimeter masers is comparable to that of the 22 GHz masers, implying that the kinetic temperature of the region where the masers originate should be Tk > 1000 K. We propose that the passage of two shocks through the same gas can create the conditions necessary to explain the presence of strong high-velocity 321 GHz masers coexisting with the 22 GHz masers in the same region.Comment: 4 pages, 1 figure. Accepted for publication in A&A Letter

The role of stellar radial motions in shaping galaxy surface brightness profiles

Aims. The physics driving features such as breaks observed in galaxy surface brightness (SB) profiles remains contentious. Here, we assess the importance of stellar radial motions in shaping their characteristics. Methods. We use the simulated Milky Way-mass cosmological discs from the Ramses Disc Environment Study (RaDES) to characterise the radial redistribution of stars in galaxies displaying type-I (pure exponentials), II (downbending), and III (upbending) SB profiles. We compare radial profiles of the mass fractions and the velocity dispersions of different sub-populations of stars according to their birth and current location. Results. Radial redistribution of stars is important in all galaxies regardless of their light profiles. Type-II breaks seem to be a consequence of the combined effects of outward-moving and accreted stars. The former produce shallower inner profiles (lack of stars in the inner disc) and accumulate material around the break radius and beyond, strengthening the break; the latter can weaken or even convert the break into a pure exponential. Further accretion from satellites can concentrate material in the outermost parts, leading to type-III breaks that can coexist with type-II breaks, but situated further out. Type-III galaxies would be the result of an important radial redistribution of material throughout the entire disc, as well as a concentration of accreted material in the outskirts. In addition, type-III galaxies display the most efficient radial redistribution and the largest number of accreted stars, followed by type-I and II systems, suggesting that type-I galaxies may be an intermediate case between types-II and III. In general, the velocity dispersion profiles of all galaxies tend to flatten or even increase around the locations where the breaks are found. The age and metallicity profiles are also affected, exhibiting different inner gradients depending on their SB profile, being steeper in the case of type-II systems (as found observationally). The steep type-II profiles might be inherent to their formation rather than acquired via radial redistribution

Self-organization of ultrasound in viscous fluids

We report the theoretical and experimental demonstration of pattern formation in acoustics. The system is an acoustic resonator containing a viscous fluid. When the system is driven by an external periodic force, the ultrasonic field inside the cavity experiences different pattern-forming instabilities leading to the emergence of periodic structures. The system is also shown to possess bistable regimes, in which localized states of the ultrasonic field develop. The thermal nonlinearity in the viscous fluid, together with the far-from-equilibrium conditions, are is the responsible of the observed effects

Wide-targeted gene expression infers tissue-specific molecular signatures of lipid metabolism in fed and fasted fish

European sea bass (Dicentrarchus labrax) is one of the most important species for Mediterranean aquaculture. It is therefore crucial to establish appropriate feeding management regimens and to gain better knowledge of nutritional requirements for this species, exploring not only new feed ingredients and feeding strategies, but also understanding the molecular mechanisms that regulate the metabolism of nutrients. Accordingly, transcriptomic analysis represents a useful nutrigenomic discovery tool for identifying the molecular basis of biological responses to nutrition as well as nutritional biomarkers in fish. This study evaluated how the transcriptional activity of genes controlling lipid metabolism in European sea bass were modulated in a tissue-specific manner in response to fasting and refeeding. Such approach focused on a panel of 29 genes in which desaturases, elongases, triacylglycerol lipases, fatty acid-binding proteins, β-oxidation and oxidative phosphorylation enzymes, phospholipid-related enzymes, and transcription factors that regulate lipid homeostasis were represented. Fasting activated the lipolytic machinery in adipose tissue, liver and muscle of European sea bass, whereas markers of lipogenesis were downregulated in liver and adipose tissue. Genes involved in phospholipid and oxidative metabolism were differentially regulated in liver and skeletal muscle of fasted European sea bass. However, 12 days of refeeding were sufficient, for the most part, to reverse the expression of key genes. Overall, our data clearly showed a tissue-specific regulation of lipid-related genes according to the different metabolic capabilities of each tissue, being the brain the most refractory organ to changes in nutrient and energy availability and liver the most responsive tissue.This research was partly funded by AQUAEXCEL EU 7 FP Project (Grant Agreement 262336): Trans National Access Grant to S.R. for accessing to IATS-CSIC facilities. This work has been partly funded under the EU seventh Framework Program by the ARRAINA Project N288925: Advanced Research Initiatives for Nutrition & Aquaculture.Peer Reviewe