Fracture Mechanisms In The As-Built And Stress-Relieved Laser Powder Bed Fusion Ti6Al4V ELI Alloy

Published ArticleThe influence of a stress-relief treatment on impact and fatigue properties of Ti6Al4V ELI samples manufactured by laser powder bed fusion was analyzed. The heat treatment resulted in removal of residual stresses, coarsening of needles and formation of precipitations between needles. In both, impact and fatigue tests, crack development was correlated to microstructural features. Fracture analysis was carried out by means of optical and electron microscopy to reveal the influence of microstructure on crack development. Ductile fracture was the dominating fracture mode at impact testing. Pore formation and coalescence were the main crack formation mechanisms. The microstructural changes led to a decrease in impact toughness after heat treatment. Presumably, this was a result of the precipitations between needles. Fatigue results showed multiple crack nucleation at the surface in both, as-built and stress-relieved material. The crack propagation rate was slightly higher and the crack was less deflected in the stress-relieved material due to the stress relief and coarsening of the microstructure

Discovery of Extended Main Sequence Turnoffs in Galactic Open Clusters

The color-magnitude diagrams (CMDs) of Galactic open clusters are widely considered to be the prototypes of single stellar populations. By using photometry in ultraviolet and optical bands we discovered that the nearby young cluster NGC 6705 (M11) exhibits an extended main-sequence turnoff (eMSTO) and a broadened main sequence (MS). This is the first evidence of multiple stellar populations in a Galactic open cluster. By using high-resolution Very Large Telescope (VLT) spectra we provide direct evidence that the multiple sequences along the CMD correspond to stellar populations with different rotation rates. Specifically, the blue MS (bMS) is formed of slow-rotating stars, while red-MS (rMS) stars are fast rotators. Moreover, we exploit photometry from Gaia data release 2 (DR2) to show that three Galactic open clusters, namely NGC 2099, NGC 2360, and NGC 2818, exhibit the eMSTO, thus suggesting that it is a common feature among these objects. Our previous work on the Large Magellanic Cloud star cluster NGC 1818 shows that slowly and rapidly rotating stars populate the bMS and rMS observed in its CMD. The similarities between M11 and the young clusters of the Magellanic Clouds (MCs) suggest that rotation is responsible for the appearance of multiple populations in the CMDs of both Milky Way open clusters and MCs young clusters.A.F.M. and L.C. acknowledge support by the Australian Research Council through Discovery Early Career Researcher Award DE160100851 and the Future Fellowship FT160100402. A.P.M. has been supported by the European Research Council through the Starting Grant “GALFOR” (716082) and the FAREMIUR project R164RM93XW “SEMPLICE”. A.S., L.B.N., and F.V. are partially supported by the MINECO (Spanish Ministry of Economy) through grants ESP2017-82674-R and ESP2016- 80079-C2-1-R (MINECO/FEDER, UE), SGR-1131 (Generalitat Catalunya), and MDM-2014-0369 of ICCUB (Unidad de Excelencia “María de Maeztu”)

Rhizosphere Acidification as the Main Trait Characterizing the Differential In Vitro Tolerance to Iron Chlorosis in Interspecific Pyrus Hybrids

Physiological responses of different interspecific Pyrus hybrids and an open pollinated Pyrus communis ‘Williams’ (Pcw) grown under in vitro culture conditions simulating lime induced chlorosis were studied. The hybrids were derived from crosses between the ‘Pyriam’ pear rootstock and four Pyrus species of the Mediterranean region, namely P. amygdaliformis Vill. (Pa), P. amygdaliformis persica Bornme. (Pap), P. communis cordata (Desv.) Hook. (Pcc), and P. elaeagrifolia Pall (Pe), all known for their higher field tolerance to iron-chlorosis than P. communis. Twenty hybrids and one open pollinated Pcw were micropropagated, and plantlets were in vitro characterized for their physiological responses to iron-deficiency conditions. Rooted plantlets were transferred to a culture medium with 2 µM Fe3+ DTPA and 10 or 20 mM NaHCO3. These physiological responses were scored at 1, 3, 7, and 28 days from the start of the in vitro assay. Leaf total chlorophyll content, the capacity of roots to acidify the medium, reduced iron, and exudates of phenolic acids and organic acids were analyzed in each media and time sample. Leaf chlorophyll levels for the clones derived from Pcc were the highest, especially under the highest bicarbonate concentration, followed by those derived from Pap and Pa. The higher chlorophyll content of Pcc clones were related with their higher capacity to acidify the media but not with their iron reduction capacity at the root level. On the other hand, hybrid clones derived from Pe showed a higher Fe3+ reduction ability than clones from all the other species during the whole assay but only when the bicarbonate concentration was lower. The exudation of phenolic acids by the roots was higher in Pcw than in the other species, and this response might explain why the total chlorophyll levels in Pcw clones are similar to those of Pe and Pa ones. These results with Pyrus spp. bring more evidence in support of the idea that iron reduction capacity at the root level is not directly related with a higher tolerance to iron deficiency caused by the high pH of calcareous soils. Instead, the ability to acidify the rhizosphere is the trait of choice for the selection of the pear hybrid clones better adapted to lime induced chlorosis. In addition, the in vitro assay to select the Pyrus clones for tolerance to iron chlorosis could be shortened to one week of culture in 10 mM NaHCO3, measuring the leaf chlorophyll level, acidification of the culture medium, and exudation of phenolic acids as the physiological responses to predict tolerance to lime-induced chlorosisinfo:eu-repo/semantics/publishedVersio

The eclipsing, double-lined, Of supergiant binary Cyg OB2-B17

Massive, eclipsing, double-lined, spectroscopic binaries are not common but are necessary to understand the evolution of massive stars as they are the only direct way to determine stellar masses. They are also the progenitors of energetic phenomena such as X-ray binaries and gamma-ray bursts. We present a photometric and spectroscopic analysis of the candidate binary system Cyg OB2-B17 to show that it is indeed a massive evolved binary. We utilise V band and white-light photometry to obtain a light curve and period of the system, and spectra at different resolutions to calculate preliminary orbital parameters and spectral classes for the components. Our results suggest that B17 is an eclipsing, double-lined, spectroscopic binary with a period of 4.0217+/-0.0004 days, with two massive evolved components with preliminary classifications of O7 and O9 supergiants. The radial velocity and light curves are consistent with a massive binary containing components with similar luminosities, and in turn with the preliminary spectral types and age of the association.Comment: 10 pages, 10 figures (1 degraded), accepted for publication in Astronomy and Astrophysic

VLT multi-object spectroscopy of 33 eclipsing binaries in the Small Magellanic Cloud. New distance and depth of the SMC, and a record-breaking apsidal motion

Aim: Our purpose is to provide reliable stellar parameters for a significant sample of eclipsing binaries, which are representative of a whole dwarf and metal-poor galaxy. We also aim at providing a new estimate of the mean distance to the SMC and of its depth along the line of sight for the observed field of view. Method: We use radial velocity curves obtained with the ESO FLAMES facility at the VLT and light curves from the OGLE-II photometric survey. The radial velocities were obtained by least-squares fits of the observed spectra to synthetic ones, excluding the hydrogen Balmer lines. Results: Our sample contains 23 detached, 9 semi-detached and 1 overcontact systems. Most detached systems have properties consistent with stellar evolution calculations from single-star models at the standard SMC metallicity Z = 0.004, though they tend to be slightly overluminous. The few exceptions are probably due to third light contribution or insufficient signal-to-noise ratio. The mass ratios are consistent with a flat distribution, both for detached and semi-detached/contact binaries. A mass-luminosity relation valid from ~4 to ~18 Msol is derived. The uncertainties are in the +-2 to +-11% range for the masses, in the +-2 to +-5% range for the radii and in the +-1 to +-6% range for the effective temperatures. The average distance modulus is 19.11+-0.03 (66.4+-0.9 kpc). The moduli derived from the V and from the I data are consistent within 0.01 mag. The 2-sigma depth of the SMC is, for our field, of 0.25 mag or 7.6 kpc under the assumption of a gaussian distribution of stars along the line of sight. Three systems show significant apsidal motion, one of them with an apsidal period of 7.6 years, the shortest known to date for a detached system with main sequence stars.Comment: 61 pages, 41 figures; accepted for publication in Astronomy & Astrophysic

Gestió, conservació i destrucció de documents: guies tècniques de l'Institut Català de la Salut

Gestió de documents; Destrucció de documents; Confidencialitat de dades clíniquesGestión de documentos; Destrucción de documentos; Confidencialidad de datos clínicosDocument management; Destruction of documents; Confidentiality of clinical dataAquesta guia pretén introduir un nou concepte, encara no gaire desenvolupat a la nostra institució, que consisteix a conciliar el dret a la confidencialitat i alhora la col·laboració en el desenvolupament sostenible de la societat, tot preservant en la mesura que sigui possible el medi ambient.Esta guía pretende introducir un nuevo concepto, todavía no muy desarrollado en nuestra institución, que consiste en conciliar el derecho a la confidencialidad y a la vez la colaboración en el desarrollo sostenible de la sociedad, preservando en la medida de lo posible el medio ambiente.This guide aims to introduce a new concept, not yet very developed in our institution, which consists of reconciling the right to confidentiality and at the same time collaboration in the sustainable development of society, preserving the environment as much as possible

The Gaia spectrophotometric standard stars survey. I. Preliminary results

We describe two ground based observing campaigns aimed at building a grid of approximately 200 spectrophotometric standard stars (SPSS), with an internal ~1% precision and tied to Vega within ~3%, for the absolute flux calibration of data gathered by Gaia, the ESA astrometric mission. The criteria for the selection and a list of candidates are presented, together with a description of the survey strategy and the adopted data analysis methods. We also discuss a short list of notable rejected SPSS candidates and difficult cases, based on identification problems, literature discordant data, visual companions, and variability. In fact, all candidates are also monitored for constancy (within \pm5 mmag, approximately). In particular, we report on a CALSPEC standard, 1740346, that we found to be a delta Scuti variable during our short-term monitoring (1-2 h) campaign.Comment: 16 pages, 4 tables, 9 figures, accepted for publication by MNRAS on 20 July 201

A chemical survey of exoplanets with ARIEL

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10–100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio

Degradation of YRA1 Pre-mRNA in the Cytoplasm Requires Translational Repression, Multiple Modular Intronic Elements, Edc3p, and Mex67p

The yeast YRA1 pre-mRNA contains multiple intronic elements that regulate transcript decay and translatability via the Edc3p decapping activator and the Mex67p/Mtr2p export receptor