A Revised Age for Upper Scorpius and The Star-Formation History Among the F-Type Members of the Scorpius-Centaurus OB Association

We present an analysis of the ages and star-formation history of the F-type stars in the Upper Scorpius (US), Upper Centaurus-Lupus (UCL) and Lower Centaurus-Crux (LCC) subgroups of Scorpius-Centaurus. We find that 1) our empirical isochrones are consistent with the previously published age-rank of the Sco-Cen subgroups, 2) LCC and UCL appear to reach the main sequence turn-on at spectral types ~F4 and ~F2, respectively. An analysis of the A-type stars shows US reaching the main sequence at about spectral type ~A3. 3) The median ages for the pre-main sequence members of UCL and LCC are 16 Myr and 17 Myr, respectively, in agreement with previous studies, however we find that 4) Upper Sco is much older than previously thought. The luminosities of the F-type stars in US are typically a factor of ~2.5 less luminous than predicted for a 5 Myr old population for four sets of evolutionary tracks. We reexamine the evolutionary state and isochronal ages for the B-, A-, and G-type Upper Sco members, and the evolved M supergiant Antares, and estimate a revised mean age for Upper Sco of 11+/-1+/-2 Myr (statistical, systematic). Using radial velocities and Hipparcos parallaxes we calculate a lower limit on the kinematic expansion age for Upper Sco of >10.5 Myr (99% confidence). However, the data are statistically consistent with no expansion. We reevaluate the inferred masses for the known substellar companions in Upper Sco using the revised age. Specifically, we estimate the mass of 1RXS J1609-2105b to be 14^{+2}_{-3} Mjup, suggesting that it is a brown dwarf rather than a planet. Finally, we find the fraction of F-type stars exhibiting Ha emission and/or a K-band excess consistent with accretion to be 0/17 (<19%; 95% C.L.) in US at ~11 Myr, while UCL has 1/41 (2^{+5}_{-1}%; 68% C.L.) accretors and LCC has 1/50 (2^{+4}_{-1}%; 68% C.L.) accretors at ~16 Myr and ~17 Myr, respectively. [Abridged]Comment: Accepted for publication in ApJ. Formatted with emulateapj, 28 pages, 16 figures, 14 table

Control of star formation by supersonic turbulence

Understanding the formation of stars in galaxies is central to much of modern astrophysics. For several decades it has been thought that stellar birth is primarily controlled by the interplay between gravity and magnetostatic support, modulated by ambipolar diffusion. Recently, however, both observational and numerical work has begun to suggest that support by supersonic turbulence rather than magnetic fields controls star formation. In this review we outline a new theory of star formation relying on the control by turbulence. We demonstrate that although supersonic turbulence can provide global support, it nevertheless produces density enhancements that allow local collapse. Inefficient, isolated star formation is a hallmark of turbulent support, while efficient, clustered star formation occurs in its absence. The consequences of this theory are then explored for both local star formation and galactic scale star formation. (ABSTRACT ABBREVIATED)Comment: Invited review for "Reviews of Modern Physics", 87 pages including 28 figures, in pres

Testing the Mid-Holocene Relative Sea-Level Highstand Hypothesis in North Wales, United Kingdom

Accurate Holocene relative sea-level curves are vital for modelling future sea-level changes, particularly in regions where relative sea-level changes are dominated by isostatically induced vertical land movements. In North Wales, various glacial isostatic adjustment (GIA) models predict a mid-Holocene relative sea-level highstand between 4 and 6 ka, which is unsubstantiated by any geological sea-level data but affects the ability of geophysical models to model accurately past and future sea levels. Here, we use a newly developed foraminifera-based sea-level transfer function to produce a 3300-year-long late-Holocene relative sea-level reconstruction from a salt marsh in the Malltraeth estuary on the south Anglesey coast in North Wales. This is the longest continuous late-Holocene relative sea-level reconstruction in Northwest Europe. We combine this record with two new late-Holocene sea-level index points (SLIPs) obtained from a freshwater marsh at Rhoscolyn, Anglesey, and with previously published regional SLIPs, to produce a relative sea-level record for North Wales that spans from ca. 13,000 BP to the present. This record leaves no room for a mid-Holocene relative sea-level highstand in the region. We conclude that GIA models that include a mid-Holocene sea-level highstand for North Wales need revision before they are used in the modelling of past and future relative sea-level changes around the British Isles

Collagen-Vicryl scaffolds for reconstruction of the diaphragm in a large animal model

Current methods for closure of congenital diaphragmatic hernia using patches are unsatisfactory, and novel collagen-based scaffolds have been developed, and successfully applied in a rat model. However, for translation to the human situation constructs must be evaluated in larger animal models. We developed collagen scaffolds enforced with Vicryl, loaded either with or without the muscle stimulatory growth factor insulin-like growth factor 1 (IGF1). We describe our steps to a surgical method to implant these scaffolds into a diaphragmatic defect in 1.5-3 week old lambs, and evaluate the scaffolds 6 months after implantation. Omentum was attached to the scaffold. At sacrifice, eventration of the implantation site was observed in all animals with a thin layer of tissue separating the abdomen from the thorax. Histologically, no scaffold remnants could be observed. Fatty tissue surrounded by fibrous tissue was seen, resembling encapsulated omentum, with collagen-rich tissue present between this tissue and the original diaphragmatic muscle. Outcomes were not different for scaffolds with or without IGF1. In conclusion, the scaffolds integrated well into the surrounding tissue, but slower degrading materials are needed to prevent eventrations. (c) 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 102B: 756-763, 2014

<b>Moluscos como indicadores paleoambientales en ecosistemas acuáticos del Trópico Americano</b>

Los sedimentos continentales y marinos se utilizan para explorar cambios pasados en el clima y en los ecosistemas. A pesar de que los moluscos son uno de los grupos de invertebrados macroscópicos más comúnmente hallados en los registros sedimentarios, el conocimiento sobre su potencial como paleobiondicadores es fragmentado y generalmente omite el aporte de la información ecológica basándose principalmente en la información isotópica. En el presente estudio, utilizamos restos de moluscos (gasterópodos y bivalvos) así como variables geoquímicas (Ti, TIC/TOC) para inferir las condiciones ambientales durante el Holoceno Tardío (últimos 4 000 años) en tres ecosistemas acuáticos del Trópico Americano. Los sitios de estudio incluyeron el Lago Nahá (Chiapas, México), la laguna costera Río Lagartos (Yucatán, México) y las Islas Belmonte (archipiélago de São Pedro y São Paulo, Brasil) e Ilha do Mel (Paranaguá, Brasil). Se obtuvieron testigos de sedimentos cortos en el Lago Nahá (60 cm; ~500 años) y en la Laguna Río Lagartos (25 cm; ~123 años), mientras que en las islas brasileñas se recuperaron múltiples muestras de depósitos costeros arrecifales. La cronología de los testigos se estableció a través del análisis de 210Pb y 137Cs, mientras que la edad de las muestras de conchas de las islas se determinó mediante radiocarbono (14C). Los moluscos de cada registro se identificaron a nivel de especie y se contabilizaron. De acuerdo con el recambio ecológico de las especies, se observó que los gasterópodos de agua dulce del Lago Nahá respondieron a los cambios en el nivel del agua y el estado trófico del lago, mientras que los moluscos de la laguna costera respondieron a cambios en la salinidad y modificaciones del entorno terrestre. Finalmente, los vermétidos de las islas respondieron a los cambios del nivel del mar.Video presentado en congreso EBRAM-CLAMA 2023</p