Open cluster Dolidze 25: Stellar parameters and the metallicity in the Galactic Anticentre

The young open cluster Dolidze 25, in the direction of the Galactic Anticentre, has been attributed a very low metallicity, with typical abundances between $-0.5$ and $-0.7$ dex below solar. We intend to derive accurate cluster parameters and accurate stellar abundances for some of its members. We have obtained a large sample of intermediate- and high-resolution spectra for stars in and around Dolidze 25. We used the FASTWIND code to generate stellar atmosphere models to fit the observed spectra. We derive stellar parameters for a large number of OB stars in the area, and abundances of oxygen and silicon for a number of stars with spectral types around B0. We measure low abundances in stars of Dolidze 25. For the three stars with spectral types around B0, we find $0.3$ dex (Si) and $0.5$ dex (O) below the values typical in the solar neighbourhood. These values, even though not as low as those given previously, confirm Dolidze 25 and the surrounding H II region Sh2-284 as the most metal-poor star-forming environment known in the Milky Way. We derive a distance $4.5\pm0.3\:$kpc to the cluster ($r_{\textrm{G}}\approx12.3\:$kpc). The cluster cannot be older than $\sim3\:$Myr, and likely is not much younger. One star in its immediate vicinity, sharing the same distance, has Si and O abundances at most $0.15\:$dex below solar. The low abundances measured in Dolidze 25 are compatible with currently accepted values for the slope of the Galactic metallicity gradient, if we take into account that variations of at least $\pm0.15\:$dex are observed at a given radius. The area traditionally identified as Dolidze 25 is only a small part of a much larger star-forming region that comprises the whole dust shell associated with Sh2-284 and very likely several other smaller H II regions in its vicinity.Comment: Accepted for publication in Astronomy \& Astrophysics. 16 pages, 12 figure

Estudio técnico-financiero sobre la construcción de un parque eólico marino flotante en el litoral español

RESUMEN El objetivo del trabajo es analizar, desde un punto de vista financiero, las diversas soluciones técnicas para un emplazamiento “tipo” en aguas profundas en el litoral español. Se examinará exhaustivamente los elementos que intervienen en el diseño, construcción, instalación, operación, mantenimiento y desmantelamiento de dicha infraestructura, optando por aquellas soluciones que se estimen óptimas tanto técnica como económicamente. Además se analizarán todos aquellos aspectos referentes a los buques necesarios para dar el soporte logístico al parque. Para ello se plantearán diversos escenarios, considerando buques de nueva construcción, transformación de buques y buques fletados bajo las distintas modalidades de flete, estudiando el impacto que representan las distintas opciones en la totalidad de los costes y de esta forma poder definir la viabilidad del parque. ABSTRACT The goal of this paper is to analyze, from a financial point of view, several technique solutions for a deep water standard location in Spanish littoral. All the elements concerning to design, build, installation, operation, maintenance and dismantle of the offshore wind mill farm will be examinated deeply, focusing on those optimum solutions as technically as financially way. Besides we will take into account those aspects refer to different vessels in order to offer the offshore logistic support. Several scenarios will be raised, considering new vessel, conversion vessel and charter vessel, studying their impacts in all costs and enabling to define the offshore wind mill farm viabilit

Ballistic performance of aramid composite combat helmet for protection against small projectiles

This paper focuses on the ballistic performance of aramid composite combat helmet commonly worn by military and security corps, against small projectiles threat. We propose a numerical finite element model for aramid composite protections, considering a multi-layer architecture, able to predict its ballistic behaviour and damage extension. The aim is determining the minimum number of layers required for a correct protection against a given ballistic thread. The constitutive aramid behaviour has been calibrated by means of experimental tests with FSP (Fragment Simulate Projectiles) projectiles and steel spheres on aramid flat plates. Once calibrated, a predictive numerical model of the helmet against different small projectiles and impacted localisations was developed and compared with experimental tests performed in the real head protection. The results calculated for the absorbed impact energy by the helmet and the induced damage due to small projectiles at different impact location, are in good agreement with experimental results and postmortem helmet analysis, validating the proposed numerical model. The numerical model is thus validated for the design of optimized head protections based on aramid compositeThe authors acknowledge the Ministry of Economy and Competitiveness of Spain and the European Regional Development Fund, (FEDER) program under the Project RTC-2015-3887-8 and the Project DPI2017-88166-R for the financial support of the work

Energy absorption analysis of aramid composite during blunt projectile impact

In this work, a numerical model for aramid composites is experimentally validated in terms of permanent deformation, energy absorption and damage mechanisms for ballistic applications. Novel experimental and numerical results of non-perforating ballistic impacts with blunt projectiles are presented. The resistance forces and absorption energy by the specimen are measured for different impact velocities. A post-mortem analysis of the failure mechanisms is performed using computed tomography and a profilometer device. The numerical model is used to analyse the influence of impactor mass and impact velocity below the ballistic limit.The authors acknowledge the Ministry of Economy and Competitiveness of Spain and FEDER program under the Project DPI2017-88166-R for the financial support of the work. Prof. A. Rusinek acknowledges the financial support from the program UC3M-Santander Chair of Excellence in additive manufacturing

GU Monocerotis: A high-mass eclipsing overcontact binary in the young open cluster Dolidze 25

Context. The eclipsing binary GU Mon is located in the star-forming cluster Dolidze 25, which has the lowest metallicity measured in a Milky Way young cluster. Aims. GU Mon has been identified as a short-period eclipsing binary with two early B-type components. We set out to derive its orbital and stellar parameters. Methods. We present a comprehensive analysis, including B and V light curves and 11 high-resolution spectra, to verify the orbital period and determine parameters. We used the stellar atmosphere code FASTWIND to obtain stellar parameters and create templates for cross-correlation. We obtained a model to fit the light and radial-velocity curves using the Wilson-Devinney code iteratively and simultaneously. Results. The two components of GU Mon are identical stars of spectral type B1 V with the same mass and temperature. The light curves are typical of an EW-type binary. The spectroscopic and photometric analyses agree on a period of 0.896640 ± 0.000007 d. We determine a mass of 9.0 ± 0.6 M⊙ for each component and for temperatures of 28 000 ± 2000 K. Both values are consistent with the spectral type. The two stars are overfilling their respective Roche lobes, sharing a common envelope and, therefore the orbit is synchronised and circularised. Conclusions. The GU Mon system has a fill-out factor above 0.8, containing two dwarf B-type stars on the main sequence. The two stars are in a very advanced stage of interaction, with their extreme physical similarity likely due to the common envelope. The expected evolution of such a system very probably leads to a merger while still on the main sequence.This research is partially supported by the Spanish Ministerio de Economía y Competitividad under grants AYA2012-39364-C02-01/02 and AYA2015-68012-C2-1/2, and the European Union

Evolución humana en Europa: registro y debates

Tres son los principales debates en los estudios de evolución humana en Europa: primer poblamiento de nuestro continente, patrón evolutivo durante el Pleistoceno medio, origen del Hombre moderno y su relación con los neandertales. Hasta la fecha, no existe consenso en admitir la presencia humana en Europa antes del episodio isotópico 13, pero el reciente hallazgo de fósiles humanos e industria lítica en ni veles del Pleistoceno inferior del yacimiento Gran Dolina (S ierra de Atapuerca), permite zanjar definitivamente la cuestión. En el Pleistoceno medio tiene lugar, en nuestro conti nente, un proceso de evolución local que desemboca en los neandertales. Este proceso está especialmente bien documentado en el yac imiento de la Sima de los Huesos de la Sierra de Atapuerca, que ha proporcionado la mayor parte del registro fósil mundial de homínidos para la tolalidad del Pleistoceno medio. En el Pleistoceno superior, las poblaciones neandertales fueron reemplazadas en Europa por la humanidad moderna, sin que haya continuidad evolutiva. Por último, se analizan en este trabajo las posibles relaciones filogenéticas entre las diferentes poblaciones humanas del Pleistoceno medio y superior

Evaluation of Combat Helmet Behavior under Blunt Impact

This article belongs to the Special Issue Armour and Protection SystemsNew threats are a challenge for the design and manufacture of modern combat helmets. These helmets must satisfy a wide range of impact velocities from ballistic impacts to blunt impacts. In this paper, we analyze European Regulation ECE R22.05 using a standard surrogate head and a human head model to evaluate combat helmet performance. Two critical parameters on traumatic brain analysis are studied for different impact locations, i.e., peak linear acceleration value and head injury criterion (HIC). The results obtained are compared with different injury criteria to determine the severity level of damage induced. Furthermore, based on different impact scenarios, analyses of the influence of impact velocity and the geometry impact surface are performed. The results show that the risks associated with a blunt impact can lead to a mild traumatic brain injury at high impact velocities and some impact locations, despite satisfying the different criteria established by the ECE R22.05 standard. The results reveal that the use of a human head for the estimation of brain injuries differs slightly from the results obtained using a surrogate head. Therefore, the current combat helmet configuration must be improved for blunt impacts. Further standards should take this into account and, consequently, combat helmet manufacturers on their design process.This work has been carried out within the framework of the research project DPI2017-88166-R of the FEDER program financed by the Ministerio de Economía, Industria y Competitividad and the Spanish Ministry of Education, Culture and Sports for the professor's mobility program José Castillejo's 2018 grant (CAS18/00292)

Impact response of advance combat helmet pad systems

Combat helmets are designed to protect against ballistic threats and fragments of explosive devices. There are numerous types of helmet comfort foams available. However, pad systems have not been evaluated in combat helmets to understand to what extent they mitigate head accelerations. In this work, different pad systems are studied to analyze the ballistic performance of combat helmets using a Hybrid III dummy equipped with longitudinal accelerometers at the head and a neck simulator. The tests are conducted with 9 mm Full Metal Jacket (FMJ) projectiles according to the performance requirements III-A of the NIJ 0106.01 standard. This experimental methodology allows the evaluation of brain and neck injuries. The thicker bicomponent polyurethane foams and the honeycomb configuration provided the best results in terms of mitigating brain damage due to accelerations applying different criteria (PLA, WSTC, HIC). However, it was concluded that there is no cervical injury or cranial fracture risk for any of the cases studied.The authors acknowledge the Ministry of Economy and Competitiveness of Spain and the FEDER program under Projects DPI2017-88166-R and PID2020-118946RB-I00 for the financial support of the work. M. Rodriguez-Millan acknowledges the Spanish Ministry of Universities, the National Program for the Promotion of Talent, and its Employability in Research and Development and Innovation (R&D&I), National Mobility Subprogram of the National Plan for Scientific and Technical Research and Innovation 2021–2023, for the professor’s mobility program (PRX21/00329). It has to thank the funding for APC: Universidad Carlos III de Madrid (Read and Publish Agreement CRUECSIC 2023).Publicad

Interlayer-Confined Cu(II) Complex as an Efficient and Long-Lasting Catalyst for Oxidation of H2S on Montmorillonite

Removal of highly toxic H2S for pollution control and operational safety is a pressing need. For this purpose, a montmorillonite intercalated with Cu(II)-phenanthroline complex [Cu[(Phen)(H2O)2]2+ (Mt-CuPhen) was prepared to capture gaseous H2S under mild conditions. This hybrid material was simple to obtain and demonstrated an outstanding ability to entrap H2S at room temperature, retaining high efficiency for a very long time (up to 36.8 g of S/100 g Mt-CuPhen after 3 months of exposure). Sorbent and H2S uptake were investigated by elemental analysis, X-ray powder diffraction measurements, diffuse reflectance (DR) UV–Vis and infrared spectroscopy, thermal analysis and evolved gas mass spectrometry, scanning electron microscopy equipped with energy-dispersive X-ray spectrometer, and X-ray absorption spectroscopy. The H2S capture was studied over time and a mechanism of action was proposed. The entrapping involves a catalytic mechanism in which [Cu[(Phen)(H2O)2]2+ acts as catalyst for H2S oxidation to S0 by atmospheric oxygen. The low cost and the long-lasting performance for H2S removal render Mt-CuPhen an extremely appealing trap for H2S removal and a promising material for many technological applications

Mechanism of voltage sensing in Ca2+- and voltage-activated K + (BK) channels

In neurosecretion, allosteric communication between voltage sensors and C