41 research outputs found
CSO and CARMA Observations of L1157. II. Chemical Complexity in the Shocked Outflow
L1157, a molecular dark cloud with an embedded Class 0 protostar possessing a
bipolar outflow, is an excellent source for studying shock chemistry, including
grain-surface chemistry prior to shocks, and post-shock, gas-phase processing.
The L1157-B1 and B2 positions experienced shocks at an estimated ~2000 and 4000
years ago, respectively. Prior to these shock events, temperatures were too low
for most complex organic molecules to undergo thermal desorption. Thus, the
shocks should have liberated these molecules from the ice grain-surfaces en
masse, evidenced by prior observations of SiO and multiple grain mantle species
commonly associated with shocks. Grain species, such as OCS, CH3OH, and HNCO,
all peak at different positions relative to species that are preferably formed
in higher velocity shocks or repeatedly-shocked material, such as SiO and HCN.
Here, we present high spatial resolution (~3") maps of CH3OH, HNCO, HCN, and
HCO+ in the southern portion of the outflow containing B1 and B2, as observed
with CARMA. The HNCO maps are the first interferometric observations of this
species in L1157. The maps show distinct differences in the chemistry within
the various shocked regions in L1157B. This is further supported through
constraints of the molecular abundances using the non-LTE code RADEX (Van der
Tak et al. 2007). We find the east/west chemical differentiation in C2 may be
explained by the contrast of the shock's interaction with either cold, pristine
material or warm, previously-shocked gas, as seen in enhanced HCN abundances.
In addition, the enhancement of the HNCO abundance toward the the older shock,
B2, suggests the importance of high-temperature O-chemistry in shocked regions.Comment: Accepted for publication in the Astrophysical Journa
A Search for Light Hydrides in the Envelopes of Evolved Stars
We report a search for the diatomic hydrides SiH, PH, and FeH along the line
of sight toward the chemically rich circumstellar envelopes of IRC+10216 and VY
Canis Majoris. These molecules are thought to form in high temperature regions
near the photospheres of these stars, and may then further react via gas-phase
and dust-grain interactions leading to more complex species, but have yet to be
constrained by observation. We used the GREAT spectrometer on SOFIA to search
for rotational emission lines of these molecules in four spectral windows
ranging from 600 GHz to 1500 GHz. Though none of the targeted species were
detected in our search, we report their upper limit abundances in each source
and discuss how they influence the current understanding of hydride chemistry
in dense circumstellar media. We attribute the non-detections of these hydrides
to their compact source sizes, high barriers of formation, and proclivity to
react with other molecules in the winds.Comment: Accepted for publication in ApJ. 14 pages, 4 figures, 3 table
CSO and CARMA Observations of L1157. II. Chemical Complexity in the Shocked Outflow
L1157, a molecular dark cloud with an embedded Class 0 protostar possessing a bipolar outflow, is an excellent source for studying shock chemistry, including grain-surface chemistry prior to shocks, and post-shock, gas-phase processing. The L1157-B1 and B2 positions experienced shocks at an estimated ~2000 and 4000 years ago, respectively. Prior to these shock events, temperatures were too low for most complex organic molecules to undergo thermal desorption. Thus, the shocks should have liberated these molecules from the ice grain-surfaces en masse, evidenced by prior observations of SiO and multiple grain mantle species commonly associated with shocks. Grain species, such as OCS, CH_3OH, and HNCO, all peak at different positions relative to species that are preferably formed in higher-velocity shocks or repeatedly shocked material, such as SiO and HCN. Here, we present high spatial resolution (~3") maps of CH_3OH, HNCO, HCN, and HCO^+ in the southern portion of the outflow containing B1 and B2, as observed with Combined Array for Research in Millimeter-Wave Astronomy. The HNCO maps are the first interferometric observations of this species in L1157. The maps show distinct differences in the chemistry within the various shocked regions in L1157B. This is further supported through constraints of the molecular abundances using the non-LTE code radex. We find that the east/west chemical differentiation in C2 may be explained by the contrast of the shock's interaction with either cold, pristine material or warm, previously shocked gas, as seen in enhanced HCN abundances. In addition, the enhancement of the HNCO abundance toward the the older shock, B2, suggests the importance of high-temperature O-chemistry in shocked regions
LSST: from Science Drivers to Reference Design and Anticipated Data Products
(Abridged) We describe here the most ambitious survey currently planned in
the optical, the Large Synoptic Survey Telescope (LSST). A vast array of
science will be enabled by a single wide-deep-fast sky survey, and LSST will
have unique survey capability in the faint time domain. The LSST design is
driven by four main science themes: probing dark energy and dark matter, taking
an inventory of the Solar System, exploring the transient optical sky, and
mapping the Milky Way. LSST will be a wide-field ground-based system sited at
Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m
effective) primary mirror, a 9.6 deg field of view, and a 3.2 Gigapixel
camera. The standard observing sequence will consist of pairs of 15-second
exposures in a given field, with two such visits in each pointing in a given
night. With these repeats, the LSST system is capable of imaging about 10,000
square degrees of sky in a single filter in three nights. The typical 5
point-source depth in a single visit in will be (AB). The
project is in the construction phase and will begin regular survey operations
by 2022. The survey area will be contained within 30,000 deg with
, and will be imaged multiple times in six bands, ,
covering the wavelength range 320--1050 nm. About 90\% of the observing time
will be devoted to a deep-wide-fast survey mode which will uniformly observe a
18,000 deg region about 800 times (summed over all six bands) during the
anticipated 10 years of operations, and yield a coadded map to . The
remaining 10\% of the observing time will be allocated to projects such as a
Very Deep and Fast time domain survey. The goal is to make LSST data products,
including a relational database of about 32 trillion observations of 40 billion
objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures
available from https://www.lsst.org/overvie
The Habitable Exoplanet Observatory (HabEx) Mission Concept Study Final Report
The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars in order to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx is a space telescope with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities allow for a broad suite of compelling science that cuts across the entire NASA astrophysics portfolio. HabEx has three primary science goals: (1) Seek out nearby worlds and explore their habitability; (2) Map out nearby planetary systems and understand the diversity of the worlds they contain; (3) Enable new explorations of astrophysical systems from our own solar system to external galaxies by extending our reach in the UV through near-IR. This Great Observatory science will be selected through a competed GO program, and will account for about 50% of the HabEx primary mission. The preferred HabEx architecture is a 4m, monolithic, off-axis telescope that is diffraction-limited at 0.4 microns and is in an L2 orbit. HabEx employs two starlight suppression systems: a coronagraph and a starshade, each with their own dedicated instrument
The Habitable Exoplanet Observatory (HabEx) Mission Concept Study Final Report
The Habitable Exoplanet Observatory, or HabEx, has been designed to be the
Great Observatory of the 2030s. For the first time in human history,
technologies have matured sufficiently to enable an affordable space-based
telescope mission capable of discovering and characterizing Earthlike planets
orbiting nearby bright sunlike stars in order to search for signs of
habitability and biosignatures. Such a mission can also be equipped with
instrumentation that will enable broad and exciting general astrophysics and
planetary science not possible from current or planned facilities. HabEx is a
space telescope with unique imaging and multi-object spectroscopic capabilities
at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities
allow for a broad suite of compelling science that cuts across the entire NASA
astrophysics portfolio. HabEx has three primary science goals: (1) Seek out
nearby worlds and explore their habitability; (2) Map out nearby planetary
systems and understand the diversity of the worlds they contain; (3) Enable new
explorations of astrophysical systems from our own solar system to external
galaxies by extending our reach in the UV through near-IR. This Great
Observatory science will be selected through a competed GO program, and will
account for about 50% of the HabEx primary mission. The preferred HabEx
architecture is a 4m, monolithic, off-axis telescope that is
diffraction-limited at 0.4 microns and is in an L2 orbit. HabEx employs two
starlight suppression systems: a coronagraph and a starshade, each with their
own dedicated instrument.Comment: Full report: 498 pages. Executive Summary: 14 pages. More information
about HabEx can be found here: https://www.jpl.nasa.gov/habex
Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries
Abstract
Background
Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres.
Methods
This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries.
Results
In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia.
Conclusion
This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries
Ecosystem modelling in the Northwestern Mediterranean Sea: Structure and functioning of a complex system
International audienceEcopath mass-balanced models are widely-used tools to address various challenges in the understanding and protection of ecosystems. To track the continuing improvements in data and the evolving environment (climate change, anthropic pressure), new models are regularly being developed. In this study, we built a Gulf of Lion Ecopath model, focused on the continental shelf, featuring enhanced representation of benthic invertebrates and a realistic assessment of catches, and which takes into account the significant changes observed after 2008–2009 in the trophic structure of this ecosystem as well as related changes in fisheries activities. The model is composed of 68 functional groups, including 6 primary producers, discards and detritus, 27 invertebrate groups, 31 fish groups, dolphins and seabirds. New datasets were taken into account for biomasses, as well as for diets. P/B and Q/B parameters were calculated to include the most recent and geographically closest data. Model results highlight a food web diagram, ranging over 5 trophic levels and placing Prionace glauca, Squalus acanthias and dolphins as top predators. The mixed trophic impact analysis showed that the groups with the highest accumulated negative impacts are, in decreasing order, benthic trawls, nets and carnivorous echinoderms. The groups with the highest accumulated positive impacts are, in decreasing order, detritus, microphytoplankton and nanoplankton. The flux analysis shows that a major part of the flows occurs at trophic level 2 with 35.1% of the model total throughput and 43.8% of the total biomass. The catches have a mean trophic level of 3.47, higher than in previous studies, reflecting the changes in the fisheries activities