Star clusters and the structure of the ISM. Tunnels and wakes in giant extragalactic HII regions

Several structures have been discovered embedded in regions of recent or ongoing star formation, which point to the importance of the interaction between fast moving wind-blowing stars and their environment. Using hydrodynamic simulations, we investigate the passage through the interstellar medium of a supersonic stellar wind source, and show how it can naturally lead to the formation of tubes, channels and swamps of globules as interfaces are crossed. The results are in excellent agreement with observation of 30 Doradus.Comment: 12 pages + 5 figures (GIF format) - Accepted for pub. in Astrophys. J. Letter

The energy spectrum observed by the AGASA experiment and the spatial distribution of the sources of ultra-high energy cosmic rays

Seven and a half years of continuous monitoring of giant air showers triggered by ultra high-energy cosmic rays have been recently summarized by the AGASA collaboration. The resulting energy spectrum indicates clearly that the cosmic ray spectrum extends well beyond the Greisen-Zatsepin-Kuzmin (GZK) cut-off at $\sim 5 \times 10^{19}$ eV. Furthermore, despite the small number statistics involved, some structure in the spectrum may be emerging. Using numerical simulations, it is demonstrated in the present work that these features are consistent with a spatial distribution of sources that follows the distribution of luminous matter in the local Universe. Therefore, from this point of view, there is no need for a second high-energy component of cosmic rays dominating the spectrum beyond the GZK cut-off.Comment: 14 pages, 4 figures, Astrophys. J. Letters (submitted

Improving photon-hadron discrimination based on cosmic ray surface detector data

The search for photons at EeV energies and beyond has considerable astrophysical interest and will remain one of the key challenges for ultra-high energy cosmic ray (UHECR) observatories in the near future. Several upper limits to the photon flux have been established since no photon has been unambiguously observed up to now. An improvement in the reconstruction efficiency of the photon showers and/or better discrimination tools are needed to improve these limits apart from an increase in statistics. Following this direction, we analyze in this work the ability of the surface parameter Sb, originally proposed for hadron discrimination, for photon search. Semi-analytical and numerical studies are performed in order to optimize Sb for the discrimination of photons from a proton background in the energy range from 10^18.5 to 10^19.6 eV. Although not shown explicitly, the same analysis has been performed for Fe nuclei and the corresponding results are discussed when appropriate. The effects of different array geometries and the underestimation of the muon component in the shower simulations are analyzed, as well as the Sb dependence on primary energy and zenith angle.Comment: 9 pages, 19 Figures. Accepted in Astroparticle Physics on May 31th, 201

Impact of electric trucks in GHG inventory – A Uruguayan scenario study

Agencia Nacional de Investigación e Innovación. FSE_1_2019_1_158846. Fondo Sectorial de Energía (Proyecto) – 2019. “Transporte Eléctrico de Carga: Análisis de los desafíos para su introducción en Uruguay”. Duración: octubre 2020 – abril 2022.This paper aims at studying the status of the current fleet of freight vehicles that travel through Uruguay, following international methodologies for calculating GHG gas emissions to determine the current inventory of gases caused by road freight transport. This inventory acts as a starting point to establish three future scenarios where different alternative powertrain technologies are implemented at different rates, such as battery electric vehicles (BEV) and fuel cell electric vehicles (FCEV). The transition from Euro III regulations into Euro V is also considered for these scenarios. Based on these future scenarios, it is possible to project the levels of future emissions that Uruguay will perceive in a time horizon that reaches the year 2050. This study aims to increase the level of information present in the region on the emissions generated in the road freight transport sector, providing new input to the development of future policies on these issues

Cluster Analysis of Extremely High Energy Cosmic Rays in the Northern Sky

The arrival directions of extremely high energy cosmic rays (EHECR) above $4\times10^{19}$ eV, observed by four surface array experiments in the northern hemisphere,are examined for coincidences from similar directions in the sky. The total number of cosmic rays is 92.A significant number of double coincidences (doublet) and triple coincidences (triplet) are observed on the supergalactic plane within the experimental angular resolution. The chance probability of such multiplets from a uniform distribution is less than 1 % if we consider a restricted region within $\pm 10^{\circ}$ of the supergalactic plane. Though there is still a possibility of chance coincidence, the present results on small angle clustering along the supergalactic plane may be important in interpreting EHECR enigma. An independent set of data is required to check our claims.Comment: 9 pages, 6 tables, 8 figures. submitted to Astroparticle Physic

Deflection of ultra high energy cosmic rays by the galactic magnetic field: from the sources to the detector

We report the results of 3D simulations of the trajectories of ultra-high energy protons and Fe nuclei (with energies $E = 4 \times 10^{19}$ and $2.5 \times 10^{20} eV$) propagating through the galactic magnetic field from the sources to the detector. A uniform distribution of anti-particles is backtracked from the detector, at the Earth, to the halo of the Galaxy. We assume an axisymmetric, large scale spiral magnetic field permeating both the disc and the halo. A normal field component to the galactic plane ($B_z$) is also included in part of the simulations. We find that the presence of a large scale galactic magnetic field does not generally affect the arrival directions of the protons, although the inclusion of a $B_z$ component may cause significant deflection of the lower energy protons ($E = 4 \times 10^{19}$ eV). Error boxes larger than or equal to $\sim 5^{\circ}$ are most expected in this case. On the other hand, in the case of heavy nuclei, the arrival direction of the particles is strongly dependent on the coordinates of the particle source. The deflection may be high enough ($> 20^{\circ}$) as to make extremely difficult any identification of the sources unless the real magnetic field configuration is accurately determined. Moreover, not every incoming particle direction is allowed between a given source and the detector. This generates sky patches which are virtually unobservable from the Earth. In the particular case of the UHE events of Yakutsk, Fly's Eye, and Akeno, they come from locations for which the deflection caused by the assumed magnetic field is not significant.Comment: LaTeX + 2 postscript figures - Color versions of both figures (highly recommended) available via anonymous ftp at ftp://capc07.ast.cam.ac.uk/pub/uhecr_gmf as fig*.g

Analyzing the alignment between the Green Lean and Circular strategies: Towards a Circular Lean approach

Green Lean tools are aligned with the Circular Economy strategy as they aim at reducing waste, however, they miss the creation of value through waste. Therefore, this paper investigates whether the current implementation of the Green Lean strategy promotes the introduction of the Circular philosophy to achieve sustainable management production processes. It analyses how the resources were managed by implementing the different strategies and tools presented in Green Lean case studies under the lens of Circular Economy, and highlights future research paths on the Circular Lean integration. An analysis of the implementation of Green Lean case studies, selected through a Systematic Literature Review, from the manufacturing sector is conducted.The majority of Green Lean implementations were aimed at minimizing waste, which is aligned with the narrowing strategy of Circular Economy and only a few cases studies aimed at closing the production cycles. Even though the main results indicate that being eco-efficient is a good starting point to move towards sustainability, from a Circular Economy point of view, this approach could remain limited. Therefore, the current contribution of Green Lean to the implementation of circular practices is limited. It can be concluded that introducing the circular philosophy in the Green Lean methodology can be achieved through redirecting Green Lean from waste reduction towards a value creation focus. The originality of this paper is that it provides a critical review of the literature on the topic of Green Lean integration and Circular Economy

Carbon molecular sieve membranes for selective CO2 separation at elevated temperatures and pressures

The use of Carbon Molecular Sieve Membranes (CMSM) for selective CO2 separation from post-combustion CO2-rich streams from steel plant was experimentally evaluated and reported in this paper. Efficient CMSMs were developed for such application and their promising potentials in operating at elevated temperatures and pressures were experimentally demonstrated. The best performance in terms of flux as well as perm-selectivity, above the Robeson upper bound, was obtained using a CMSM developed with ethylenediamine in the dip-coating stage of the fabrication. In fact, adding ethylenediamine was proven to be particularly important in narrowing down the pore size distribution to ultra-micropore and establishing effective CO2 adsorption site over the membrane surface and the pores wall. It was shown that using a tailored CMSM with a precursor synthesized by co-polymerization of ethylenediamine with Novolac can improve the CO2/N2 ideal perm-selectivity from 33 to 97 at operational conditions of 200 °C and 20 bar.The project has received funding through the NWO P16-10 project