Young stars in Epsilon Cha and their disks: disk evolution in sparse associations

(abridge) The nearby young stellar association Epsilon Cha association has an estimated age of 3-5 Myr, making it an ideal laboratory to study the disk dissipation process and provide empirical constraints on the timescale of planet formation. We combine the available literature data with our Spitzer IRS spectroscopy and VLT/VISIR imaging data. The very low mass stars USNO-B120144.7 and 2MASS J12005517 show globally depleted spectral energy distributions pointing at strong dust settling. 2MASS J12014343 may have a disk with a very specific inclination where the central star is effectively screened by the cold outer parts of a flared disk but the 10 micron radiation of the warm inner disk can still reach us. We find the disks in sparse stellar associations are dissipated more slowly than those in denser (cluster) environments. We detect C_{2}H_{2} rovibrational band around 13.7 micron on the IRS spectrum of USNO-B120144.7. We find strong signatures of grain growth and crystallization in all Epsilon Cha members with 10 micron features detected in their IRS spectra. We combine the dust properties derived in the Epsilon Cha sample with those found using identical or similar methods in the MBM 12, Coronet cluster, Eta Cha associations, and in the cores to disks (c2d) legacy program. We find that disks around low-mass young stars show a negative radial gradient in the mass-averaged grain size and mass fraction of crystalline silicates. A positive correlation exists between the mass-averaged grain sizes of amorphous silicates and the accretion rates if the latter is above ~10^{-9} Msun/yr, possibly indicating that those disks are sufficiently turbulent to prevent grains of several microns in size to sink into the disk interior.Comment: 17 pages, 18 figures, 6 tables, language revised; accepted to A&

Concept for a Time-of-Flight Small Angle Neutron Scattering Instrument at the European Spallation Source

A new Small Angle Neutron Scattering instrument is proposed for the European Spallation Source. The pulsed source requires a time-of-flight analysis of the gathered neutrons at the detector. The optimal instrument length is found to be rather large, which allows for a polarizer and a versatile collimation. The polarizer allows for studying magnetic samples and incoherent background subtraction. The wide collimation will host VSANS and SESANS options that increase the resolution of the instrument towards um and tens of um, respectively. Two 1m2 area detectors will cover a large solid angle simultaneously. The expected gains for this new instrument will lie in the range between 20 and 36, depending on the assessment criteria, when compared to up-to-date reactor based instruments. This will open new perspectives for fast kinetics, weakly scattering samples, and multi-dimensional contrast variation studies.Comment: 18 pages, 10 figure

Global Opportunities to Increase Agricultural Independence Through Phosphorus Recycling

Food production hinges largely upon access to phosphorus (P) fertilizer. Most fertilizer P used in the global agricultural system comes from mining of nonrenewable phosphate rock deposits located within few countries. However, P contained in livestock manure or urban wastes represents a recyclable source of P. To inform development of P recycling technologies and policies, we examined subnational, national, and global spatial patterns for two intersections of land use affording high P recycling potential: (a) manure‐rich cultivated areas and (b) populous cultivated areas. In turn, we examined overlap between P recycling potential and nation‐level P fertilizer import dependency. Populous cultivated areas were less abundant globally than manure‐rich cultivated areas, reflecting greater segregation between crops and people compared to crops and livestock, especially in the Americas. Based on a global hexagonal grid (290‐km2 grid cell area), disproportionately large shares of subnational “hot spots” for P recycling potential occurred in India, China, Southeast Asia, Europe, and parts of Africa. Outside of China, most of the remaining manure‐rich or populous cultivated areas occurred within nations that had relatively high imports of P fertilizer (net P import:consumption ratios ≥0.4) or substantial increases in fertilizer demand between the 2000s (2002–2006) and 2010s (2010–2014). Manure‐rich cultivated grid cells (those above the 75th percentiles for both manure and cropland extent) represented 12% of the global grid after excluding cropless cells. Annually, the global sum of animal manure P was at least 5 times that contained in human excreta, and among cultivated cells the ratio was frequently higher (median = 8.9). The abundance of potential P recycling hot spots within nations that have depended on fertilizer imports or experienced rising fertilizer demand could prove useful for developing local P sources and maintaining agricultural independence

Is the perceived impact of disciplinary procedures on medical doctors’ professional practice associated with working in an open culture and feeling supported?:A questionnaire among medical doctors in the Netherlands who have been disciplined

Introduction Disciplinary procedures can have a negative impact on the professional functioning of medical doctors. In this questionnaire study, doctors’ experience with open culture and support during a disciplinary procedure is studied to determine whether open culture and support are associated with perceived changes in the professional practice of doctors. Methods All doctors who received a warning or a reprimand from the Dutch Medical Disciplinary Board between July 2012 and August 2016 were invited to fill in a 60-item questionnaire concerning open culture, perceived support during the disciplinary procedure and the impact of the procedure on professional functioning as reported by doctors themselves. The response rate was 43% (n=294). Results A majority of doctors perceive their work environment as a safe environment in which to talk about and report incidents (71.2% agreed). Respondents felt supported by a lawyer or legal representative and colleagues (92.8% and 89.2%, respectively). The disciplinary procedure had effects on professional practice. Legal support and support from a professional confidant and a professional association were associated with fewer perceived changes to professional practice. Conclusion Our study shows that doctors who had been disciplined perceive their working environment as open. Doctors felt supported by lawyers and/or legal representatives and colleagues. Legal support was associated with less of a perceived impact on doctors’ professional practice

Kinship in Aegean Prehistory? Ancient DNA in Human Bones from Mainland Greece and Crete

Attempts were made to detect ancient DNA (aDNA) in samples of 89 human skeletons from Neolithic and Bronze Age sites in Greece and Crete. Ancient DNA was absent in specimens from Nea Nicomedia, Lerna, Kato Zakro: Karaviádena, and Mycenae Grave Circle A. For each of three skeletons sampled from Antron Grave Circle B, polymerase chain reactions (PCRs) gave products for nuclear but not mitochondrial DNA, but the yield of DNA was low and inconsistent, with replicate PCRs failing to give reproducible results. At Kouphovouno evidence for mitochondrial and/or nuclear aDNA was obtained from eight of the 20 skeletons that were examined, while at Mycenae Grave Circle B evidence for mitochondrial aDNA was obtained for four of the 22 skeletons that were studied, and in two cases confirmed the evidence of close kinship that had already been suggested by facial reconstruction: this in turn raises interesting questions of social relationships and the role of high-status women in MBA/LBA society. We conclude that, although aDNA might be present in some Eastern Mediterranean skeletons from later centuries of the Bronze Age, it is not commonly found in material from this period and is likely to be absent from older material.Στη μελέτη αυτή έγιναν προσπάθειες να αναγνωριστεί αρχαίο DNA (aDNA) σε δείγματα ογδόντα εννέα ανθρώπινων σκελετών προερχομένων από θέσεις της Νεολιθικής περιόδου και της Εποχής του Χαλκού στην Ελλάδα και την Κρήτη. Αρχαίο DNA δεν εντοπίστηκε σε δείγματα από τη Νέα Νικομήδεια, τη Λέρνα, την Κάτω Ζάκρο (Καραβιάδενα) και τον Ταφικό Κύκλο Α των Μυκηνών. Για κάθε έναν από τους τρεις σκελετούς, οι οποίοι εξετάστηκαν από τον Ταφικό Κύκλο Β της Αντρώνας, οι αλυσιδωτές αντιδράσεις πολυμεράσης (PCRs) απέφεραν αποτελέσματα για πυρηνικό αλλά όχι μιτοχονδριακό DNA. Η παραγωγή DNA ήταν χαμηλή και αντιφατική, με τα αντίγραφα πολυμεράσης να αποτυγχάνουν να αποφέρουν αναπαραγώγιμα αποτελέσματα. Στο Κουφόβουνο οκτώ από τους είκοσι σκελετούς, που εξετάστηκαν, έδωσαν στοιχεία για μιτοχονδρνακό ή/και πυρηνικό DNA, ενώ στον Ταφικό Κύκλο Β των Μυκηνών ενδείξεις για μιτοχονδριακό DNA έδωσαν τέσσερεις από τους είκοσι δύο σκελετούς, που μελετήθηκαν. Σε δύο περιπτώσεις επιβεβαιώθηκε η ένδειξη στενής συγγένειας, κάτι το οποίο είχε ήδη προταθεί με την αποκατάσταση των προσώπων: το γεγονός αυτό εγείρει ενδιαφέροντα ερωτήματα σχετικά με τις κοινωνικές σχέσεις και το ρόλο γυναικών υψηλής κοινωνικής στάθμης στην κοινωνία της Μέσης και της Ύστερης Εποχής του Χαλκού. Συμπεραίνουμε ότι, αν και μπορεί να αναγνωριστεί DNA σε ορισμένους σκελετούς της Ανατολικής Μεσογείου των τελευταίων αιώνων της Εποχής του Χαλκού, δεν εντοπίζεται συχνά σε υλικό αυτής της εποχής και ενδεχομένως απουσιάζει από παλαιότερο υλνκό.</jats:p

The 2008 outburst of EX Lup - silicate crystals in motion

EX Lup is the prototype of the EXor class of eruptive young stars. These objects show optical outbursts which are thought to be related to runaway accretion onto the star. In a previous study we observed in-situ crystal formation in the disk of EX Lup during its latest outburst in 2008, making the object an ideal laboratory to investigate circumstellar crystal formation and transport. This outburst was monitored by a campaign of ground-based and Spitzer Space Telescope observations. Here we modeled the spectral energy distribution of EX Lup in the outburst from optical to millimeter wavelengths with a 2D radiative transfer code. Our results showed that the shape of the SED at optical wavelengths was more consistent with a single temperature blackbody than a temperature distribution. We also found that this single temperature component emitted 80-100 % of the total accretion luminosity. We concluded that a thermal instability, the most widely accepted model of EXor outbursts, was likely not the triggering mechanism of the 2008 outburst of EX Lup. Our mid-infrared Spitzer spectra revealed that the strength of all crystalline bands between 8 and 30 um increased right after the end of the outburst. Six months later, however, the crystallinity in the 10 um silicate feature complex decreased. Our modeling of the mid-infrared spectral evolution of EXLup showed that, although vertical mixing should be stronger during the outburst than in the quiescent phase, fast radial transport of crystals (e.g., by stellar/disk wind) was required to reproduce the observed mid-infrared spectra.Comment: Accepted for publication in ApJ, 37 pages, 11 figures, 2 table

Medium-separation binaries do not affect the first steps of planet formation

The first steps of planet formation are marked by the growth and crystallization of sub-micrometer-sized dust grains accompanied by dust settling toward the disk midplane. In this paper we explore whether the first steps of planet formation are affected by the presence of medium-separation stellar companions. We selected two large samples of disks around single and binary T Tauri stars in Taurus that are thought to have only a modest age spread of a few Myr. The companions of our binary sample are at projected separations between 10 and 450 AU with masses down to about 0.1 solar masses. We used the strength and shape of the 10 micron silicate emission feature as a proxy for grain growth and for crystallization respectively. The degree of dust settling was evaluated from the ratio of fluxes at two different mid-infrared wavelengths. We find no statistically significant difference between the distribution of 10 micron silicate emission features from single and binary systems. In addition, the distribution of disk flaring is indistinguishable between the single and binary system samples. These results show that the first steps of planet formation are not affected by the presence of a companion at tens of AU.Comment: To appear in the Astrophysical Journa