A recollimation shock 80 mas from the core in the jet of the radio galaxy 3C120: Observational evidence and modeling

We present Very Long Baseline Array observations of the radio galaxy 3C120 at 5, 8, 12, and 15 GHz designed to study a peculiar stationary jet feature (hereafter C80) located ~80 mas from the core, which was previously shown to display a brightness temperature ~600 times lager than expected at such distances. The high sensitivity of the images -- obtained between December 2009 and June 2010 -- has revealed that C80 corresponds to the eastern flux density peak of an arc of emission (hereafter A80), downstream of which extends a large (~20 mas in size) bubble-like structure that resembles an inverted bow shock. The linearly polarized emission closely follows that of the total intensity in A80, with the electric vector position angle distributed nearly perpendicular to the arc-shaped structure. Despite the stationary nature of C80/A80, superluminal components with speeds up to ~3 c have been detected downstream from its position, resembling the behavior observed in the HST-1 emission complex in M87. The total and polarized emission of the C80/A80 structure, its lack of motion, and brightness temperature excess are best reproduced by a model based on synchrotron emission from a conical shock with cone opening angle \eta=10 degrees, jet viewing angle \theta=16 degrees, a completely tangled upstream magnetic field, and upstream Lorentz factor \gamma=8.4. The good agreement between our observations and numerical modeling leads us to conclude that the peculiar feature associated with C80/A80 corresponds to a conical recollimation shock in the jet of 3C120 located at a de-projected distance of ~190 pc downstream from the nucleus.Comment: Accepted for publication in Ap

NS 1987A in SN 1987A

The possible detection of a compact object in the remnant of SN 1987A presents an unprecedented opportunity to follow its early evolution. The suspected detection stems from an excess of infrared emission from a dust blob near the compact object's predicted position. The infrared excess could be due to the decay of isotopes like 44Ti, accretion luminosity from a neutron star or black hole, magnetospheric emission or a wind originating from the spindown of a pulsar, or thermal emission from an embedded, cooling neutron star (NS 1987A). It is shown that the last possibility is the most plausible as the other explanations are disfavored by other observations and/or require fine-tuning of parameters. Not only are there indications the dust blob overlaps the predicted location of a kicked compact remnant, but its excess luminosity also matches the expected thermal power of a 30 year old neutron star. Furthermore, models of cooling neutron stars within the Minimal Cooling paradigm readily fit both NS 1987A and Cas A, the next-youngest known neutron star. If correct, a long heat transport timescale in the crust and a large effective stellar temperature are favored, implying relatively limited crustal n-1S0 superfluidity and an envelope with a thick layer of light elements, respectively. If the locations don't overlap, then pulsar spindown or accretion might be more likely, but the pulsar's period and magnetic field or the accretion rate must be rather finely tuned. In this case, NS 1987A may have enhanced cooling and/or a heavy-element envelope.Comment: 21 pages, 6 figures, to be published in Ap

Coulomb's law corrections from a gauge-kinetic mixing

We study the static quantum potential for a gauge theory which includes the mixing between the familiar photon $U(1)_{QED}$ and a second massive gauge field living in the so-called hidden-sector $U(1)_h$. Our discussion is carried out using the gauge-invariant but path-dependent variables formalism, which is alternative to the Wilson loop approach. Our results show that the static potential is a Yukawa correction to the usual static Coulomb potential. Interestingly, when this calculation is done inside a superconducting box, the Coulombic piece disappears leading to a screening phase.Comment: 4 page

The Power Spectrum in de Sitter Inflation, Revisited

We find that the amplitude of quantum fluctuations of the invariant de Sitter vacuum coincides exactly with that of the vacuum of a comoving observer for a massless scalar (inflaton) field. We propose redefining the actual physical power spectrum as the difference between the amplitudes of the above vacua. An inertial particle detector continues to observe the Gibbons-Hawking temperature. However, although the resulting power spectrum is still scale-free, its amplitude can be drastically reduced since now, instead of the Hubble's scale at the inflationary period, it is determined by the square of the mass of the inflaton fluctuation field.Comment: 4 page

Capacitance Measurements for Subcell Characterization in Multijunction Solar Cells.

On this paper we present an alternative way to analyze de electronic properties of each subcell from the complete device. By illuminating the cell with light sources which energy is near one of the subcell bandgaps, it is possible to “erase” the presence of such subcell on the CV curve. The main advantages of this technique are that it is not destructive, it can be measured on the complete cell so can be easily implemented as a diagnostic technique for controlling electronic deviations

Design optimization of welded steel plate girders configured as a hybrid structure

[EN] This paper implements structural design optimization to improve the economic indexes of welded steel plate girders. The optimization problem is formulated in a way that allows the use of hybrid configurations, i.e., different types of steel in the flanges and web. Besides the cross-sectional dimensions, eleven steel grades are included as optimization variables. In addition to weight and material cost, the manufacturing cost is formulated as an optimization objective, which includes seven other activities, such as welding or painting. The geometrically double symmetric I-girder design subjected to a uniform transverse load is carried out through the Eurocode 3 rules. Nine case studies are implemented by varying the girder span and load values. The results show significant differences depending on the optimization objective, especially between weight and cost optimization. On the other hand, optimization-assisted design provides solutions up to 50% more economical than traditional design methods. Hybrid-optimized configurations can also improve these indexes by about 10% compared to their homogeneous counterpart, demonstrating the applicability of this novel practice. Certain concepts highlighting mechanical properties are proposed to compare the optimal solutions for each case study. These concepts can serve as design recommendations for future projects that include this structural element. Finally, based on the research gaps and the promising results obtained, future lines of research on this topic are established.This work was supported by the grant PID2020-117056RB-I00, which was funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe". Grant PRE2021-097197 funded by CIN/AEI/10.13039/501100011033 and by FSE+.Negrín-Díaz, IA.; Kripka, M.; Yepes, V. (2023). Design optimization of welded steel plate girders configured as a hybrid structure. Journal of Constructional Steel Research. 211:1-14. https://doi.org/10.1016/j.jcsr.2023.10813111421

Metamodel-assisted meta-heuristic design optimization of reinforced concrete frame structures considering soil-structure interaction

[EN] It is well known that conventional heuristic optimization is the most common approach to deal with structural optimization problems. However, metamodel-assisted optimization has become a valuable strategy for decreasing computational consumption. This paper applies conventional heuristic and Kriging-based meta-heuristic optimization to minimize the CO2 emissions of spatial reinforced concrete frame structures, considering an aspect usually ignored during modeling, such as the soil-structure interaction (SSI). Due to the particularities of the formulated problem, there are better strategies than simple Kriging-based optimization to solve it. Thus, a meta-heuristic strategy is proposed using a Kriging-based two-phase methodology and a local search algorithm. Three different models of structures are used in the study. Results show that including the SSI leads to different design results than those obtained using classical supports. The foundations, usually ignored in this type of research, also prove significant within the structural assembly. Additionally, using an appropriate coefficient of penalization, the meta-heuristic approach can find (on average) results up to 98.24% accuracy for cohesive soils and 98.10% for frictional ones compared with the results of the heuristic optimization, achieving computational savings of about 90%. Therefore, considering aspects such as the SSI, the proposed metamodeling strategy allows for dealing with high-complexity structural optimization problems.This work was supported by the grant PID2020-117056RB-I00, which was funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe". Grant PRE2021-097197 funded by MCIN/AEI/10.13039/501100011033 and by FSE+.Negrín-Díaz, IA.; Kripka, M.; Yepes, V. (2023). Metamodel-assisted meta-heuristic design optimization of reinforced concrete frame structures considering soil-structure interaction. Engineering Structures. 293:1-17. https://doi.org/10.1016/j.engstruct.2023.11665711729

Multi-criteria optimization for sustainability-based design of reinforced concrete frame buildings

[EN] This paper implements the multi-criteria design optimization of three-dimensional reinforced concrete frame building structures, considering aspects such as the realistic design of the elements, including foundations within the structural assembly, or considering the soil-structure interaction. The criteria for a more comprehensive sustainable approach are related to environmental, constructive, and durability aspects. The environmental factor is measured through CO2 emissions, considering its capture due to concrete carbonation. The use of multi-objective strategies is evident in solving the multi-criteria problem. Still, it is also proposed to formulate this problem with a single function containing all the criteria to solve it as a single-objective optimization problem. Strategies are also offered to perform multi-objective optimization based on Kriging metamodels. Several alternatives for multi-criteria decision-making are explored. The results show that multi-objective metamodel-based optimization is a good strategy for solving this problem. Alternatively, the results of the single-objective optimization of the multi-criteria problem are very satisfactory. The solutions obtained are analyzed according to the type of optimization and the decision-making criteria. Optimized solutions significantly improve the sustainability indexes compared to traditional design. Multi-criteria optimization contributes significantly to achieving these indexes. Therefore, the proposed methodology allows for the sustainable design of any reinforced concrete frame structure. It highlights the importance of integrating more encompassing formulations and advanced optimization techniques into traditional design procedures to adopt cleaner production practices in the construction sector. Finally, several promising lines of research are presented.This work was supported by the grant PID2020-117056RB-I00, funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe". Grant PRE2021-097197 funded by MCIN/AEI/10.13039/501100011033 and by FSE + and Grant CNPq- 306578/2020-4 funded by the Brazilian National Council for Scientific and Technological Development.Negrín-Díaz, IA.; Kripka, M.; Yepes, V. (2023). Multi-criteria optimization for sustainability-based design of reinforced concrete frame buildings. Journal of Cleaner Production. 425. https://doi.org/10.1016/j.jclepro.2023.13911542

Physical-chemical factors that regulate spermatic motility in fish: basic and applied aspects. A review

El objetivo de esta revisión es analizar los factores que regulan o alteran la motilidad espermática en peces “de fecundación externa” antes y después del contacto con el agua para dar a conocer herramientas que optimicen las metodologías utilizadas en piscicultura y así mejorar la capacidad fecundante de los espermatozoides.In most teleost fish with external fertilization, the spermatozoids are immobile in the seminal fluid and they are activated only after making contact with an aqueous medium. The time of flagellar movement is short in most species. Furthermore, the factors that trigger this process are different for each one. However, almost for all species, factors such as osmolarity, temperature, pH and ionic composition have a key role in activating or modulating the flagellar activity. The present review examines the factors involved in the activation of sperm and its regulation in fish with external fertilization. Additionally, an analysis is conducted regarding the management of commercially farmed fish semen, with emphasis on salmonid species