The Kinematic and Chemical Properties of a Potential Core-Forming Clump: Perseus B1-E

We present 13CO and C18O (1-0), (2-1), and (3-2) maps towards the core-forming Perseus B1-E clump using observations from the James Clerk Maxwell Telescope (JCMT), Submillimeter Telescope (SMT) of the Arizona Radio Observatory, and IRAM 30 m telescope. We find that the 13CO and C18O line emission both have very complex velocity structures, indicative of multiple velocity components within the ambient gas. The (1-0) transitions reveal a radial velocity gradient across B1-E of 1 km/s/pc that increases from north-west to south-east, whereas the majority of the Perseus cloud has a radial velocity gradient increasing from south-west to north-east. In contrast, we see no evidence of a velocity gradient associated with the denser Herschel-identified substructures in B1-E. Additionally, the denser substructures have much lower systemic motions than the ambient clump material, which indicates that they are likely decoupled from the large-scale gas. Nevertheless, these substructures themselves have broad line widths (0.4 km/s) similar to that of the C18O gas in the clump, which suggests they inherited their kinematic properties from the larger-scale, moderately dense gas. Finally, we find evidence of C18O depletion only toward one substructure, B1-E2, which is also the only object with narrow (transonic) line widths. We suggest that as prestellar cores form, their chemical and kinematic properties are linked in evolution, such that these objects must first dissipate their turbulence before they deplete in CO.Comment: Accepted by ApJ, 34 pages, 12 figure

Aldebaran's angular diameter: how well do we know it?

The bright, well-known K5 giant Aldebaran, alpha Tau, is probably the star with the largest number of direct angular diameter determinations, achieved over a long time by several authors using various techniques. In spite of this wealth of data, or perhaps as a direct result of it, there is not a very good agreement on a single angular diameter value. This is particularly unsettling if one considers that Aldebaran is also used as a primary calibrator for some angular resolution methods, notably for optical and infrared long baseline interferometry. Directly connected to Aldebaran's angular diameter and its uncertainties is its effective temperature, which also has been used for several empirical calibrations. Among the proposed explanations for the elusiveness of an accurate determination of the angular diameter of Aldebaran are the possibility of temporal variations as well as a possible dependence of the angular diameter on the wavelength. We present here a few, very accurate new determinations obtained by means of lunar occultations and long baseline interferometry. We derive an average value of 19.96+-0.03 milliarcseconds for the uniform disk diameter. The corresponding limb-darkened value is 20.58+-0.03 milliarcseconds, or 44.2+-0.9 R(sun). We discuss this result, in connection with previous determinations and with possible problems that may affect such measurements.Comment: 8 pages, 4 figures, accepted for publication in A&

Twitter journal clubs and continuing professional development: An analysis of a #MedRadJClub tweet chat

Introduction Online Twitter journal clubs are a recent and popular innovation with the potential to increase research awareness and inform practice. The medical radiation sciences' MedRadJournalClub (MJRC) is a Twitter-based event that attracts a global group of participants at the monthly chats. An analysis of a recent MedRadJournalClub discussion evaluated the perceived benefits and limitations of medical radiation practitioners participating in an online journal club. Methods The February 2017 chat used for analysis was based on the Journal of Medical Imaging and Radiation Sciences article by Currie et al. “Twitter Journal Club in Medical Radiation Science” that examines the educational theory behind learning and evidencing professional development through MRJC and social media. The data consisted of chat tweets which were collated using the Twitter advanced search function using the #medradjclub. An initial reviewed was performed to exclude irrelevant content. A second review was then undertaken to categorize the main theme of the tweet. The data were then subjected to thematic analysis which yielded seven different categories. Results The main benefits included global access due to the online nature of MRJC that has facilitated networking and collaboration. Open access to recently published research was another key benefit. The character limitation of a tweet was the most common constraint, and the dynamic nature of the twitter conversation requires multi-tasking that may be difficult. Conclusion Our analysis indicated that participants use MedRadJournalClub as a source of continuing professional development with some evidence that this is directly informing clinical and educational practice

The JCMT Gould Belt survey: Dense core clusters in Orion B

The James Clerk Maxwell Telescope Gould Belt Legacy Survey obtained SCUBA-2 observations of dense cores within three sub-regions of OrionB: LDN1622, NGC2023/2024, and NGC2068/2071, all of which contain clusters of cores. We present an analysis of the clustering properties of these cores, including the two-point correlation function and Cartwright’s Q parameter. We identify individual clusters of dense cores across all three regions using a minimal spanning tree technique, and find that in each cluster, the most massive cores tend to be centrally located. We also apply the independent M–Σ technique and find a strong correlation between core mass and the local surface density of cores. These two lines of evidence jointly suggest that some amount of mass segregation in clusters has happened already at the dense core stage

New system for measuring cosmogenic Ne in terrestrial and extra-terrestrial rocks

Cosmogenic Ne isotopes are used for constraining the timing and rate of cosmological and Earth surface processes. We combined an automated gas extraction (laser) and purification system with a Thermo Fisher ARGUS VI mass spectrometer for high through-put, high precision Ne isotope analysis. For extra-terrestrial material with high cosmogenic Ne concentrations, we used multi-collection on Faraday detectors. Multiple measurements (n = 26) of 1.67 × 10−8 cm3 air-derived 20Ne yielded an uncertainty of 0.32%, and 21Ne/20Ne = 0.17% and 22Ne/20Ne = 0.09%. We reproduced the isotope composition of cosmogenic Ne in the Bruderheim chondrite and Imilac pallasite in a sub-ten mg sample. For lower Ne amounts that are typical of terrestrial samples, an electron multiplier detector was used in peak jumping mode. Repeated analysis of 3.2 × 10−11 cm3 STP 20Ne from air reproduced 21Ne/20Ne and 22Ne/20Ne with 1.1% and 0.58%, respectively, and 20Ne intensity with 1.7% (n = 103) over a 4-month period. Multiple (n = 8) analysis of cosmogenic Ne in CREU-1 quartz yielded 3.25 ± 0.24 × 108 atoms/g (2 s), which overlaps with the global mean value. The repeatability is comparable to the best data reported in the international experiments performed so far on samples that are 2–5× smaller. The ability to make precise Ne isotope determinations in terrestrial and extra-terrestrial samples that are significantly smaller than previously analysed suggests that the new system holds great promise for studies with limited material

The JCMT Gould Belt Survey: a quantitative comparison between SCUBA-2 data reduction methods

Performing ground-based submillimetre observations is a difficult task as the measurements are subject to absorption and emission from water vapour in the Earth's atmosphere and time variation in weather and instrument stability. Removing these features and other artefacts from the data is a vital process which affects the characteristics of the recovered astronomical structure we seek to study. In this paper, we explore two data reduction methods for data taken with the Submillimetre Common-User Bolometer Array-2 (SCUBA-2) at the James Clerk Maxwell Telescope (JCMT). The JCMT Legacy Reduction 1 (JCMT LR1) and The Gould Belt Legacy Survey Legacy Release 1 (GBS LR1) reduction both use the same software (starlink) but differ in their choice of data reduction parameters. We find that the JCMT LR1 reduction is suitable for determining whether or not compact emission is present in a given region and the GBS LR1 reduction is tuned in a robust way to uncover more extended emission, which better serves more in-depth physical analyses of star-forming regions. Using the GBS LR1 method, we find that compact sources are recovered well, even at a peak brightness of only three times the noise, whereas the reconstruction of larger objects requires much care when drawing boundaries around the expected astronomical signal in the data reduction process. Incorrect boundaries can lead to false structure identification or it can cause structure to be missed. In the JCMT LR1 reduction, the extent of the true structure of objects larger than a point source is never fully recovered

Altered vascular smooth muscle function in the ApoE knockout mouse during the progression of atherosclerosis

Objectives: Relaxation of vascular smooth muscle (VSM) requires re-uptake of cytosolic Ca2+ into the sarcoplasmic reticulum (SR) via the Sarco/Endoplasmic Reticulum Ca2+ ATPase (SERCA), or extrusion via the Plasma Membrane Ca2+ ATPase (PMCA) or sodium Ca2+ exchanger (NCX). Peroxynitrite, a reactive species formed in vascular inflammatory diseases, upregulates SERCA activity to induce relaxation but, chronically, can contribute to atherogenesis and altered vascular function by escalating endoplasmic reticulum stress. Our objectives were to determine if peroxynitrite-induced relaxation and Ca2+ handling processes within vascular smooth muscle cells were altered as atherosclerosis develops.<p></p> Methods: Aortae from control and ApoE−/− mice were studied histologically, functionally and for protein expression levels of SERCA and PMCA. Ca2+ responses were assessed in dissociated aortic smooth muscle cells in the presence and absence of extracellular Ca2+.<p></p> Results: Relaxation to peroxynitrite was concentration-dependent and endothelium-independent. The abilities of the SERCA blocker thapsigargin and the PMCA inhibitor carboxyeosin to block this relaxation were altered during fat feeding and plaque progression. SERCA levels were progressively reduced, while PMCA expression was upregulated. In ApoE−/− VSM cells, increases in cytosolic Ca2+ [Ca2+]c in response to SERCA blockade were reduced, while SERCA-independent Ca2+ clearance was faster compared to control.<p></p> Conclusion: As atherosclerosis develops in the ApoE−/− mouse, expression and function of Ca2+ handling proteins are altered. Up-regulation of Ca2+ removal via PMCA may offer a potential compensatory mechanism to help normalise the dysfunctional relaxation observed during disease progression

Impact of the earthworm Lumbricus terrestris (L.) on As, Cu, Pb and Zn mobility and speciation in contaminated soils

To assess the risks that contaminated soils pose to the environment properly a greater understanding of how soil biota influence the mobility of metal(loid)s in soils is required. Lumbricus terrestris L. were incubated in three soils contaminated with As, Cu, Pb and Zn. The concentration and speciation of metal(loid)s in pore waters and the mobility and partitioning in casts were compared with earthworm-free soil. Generally the concentrations of water extractable metal(loid)s in earthworm casts were greater than in earthworm-free soil. The impact of the earthworms on concentration and speciation in pore waters was soil and metal specific and could be explained either by earthworm induced changes in soil pH or soluble organic carbon. The mobilisation of metal(loid)s in the environment by earthworm activity may allow for leaching or uptake into biota

The structure of molecular gas associated with NGC2264: wide-field 12CO and H2 imaging

We present wide-field, high-resolution imaging observations in 12CO 3-2 and H2 1-0 S(1) towards a ~1 square degree region of NGC2264. We identify 46 H2 emission objects, of which 35 are new discoveries. We characterize several cores as protostellar, reducing the previously observed ratio of prestellar/protostellar cores in the NGC2264 clusters. The length of H2 jets increases the previously reported spatial extent of the clusters. In each cluster, <0.5% of cloud material has been perturbed by outflow activity. A principal component analysis of the 12CO data suggests that turbulence is driven on scales >2.6 pc, which is larger than the extent of the outflows. We obtain an exponent alpha=0.74 for the size-linewidth relation, possibly due to the high surface density of NGC2264. In this very active, mixed-mass star forming region, our observations suggest that protostellar outflow activity is not injecting energy and momentum on a large enough scale to be the dominant source of turbulence.Comment: MNRAS accepte

Warm dusty discs: Exploring the A star 24um debris population

(Abridged) Studies of debris discs have shown that most systems are analogous to the EKB. In this study we aim to determine how many IRAS 25um excesses towards A stars are real, and investigate where the dust lies. We observe with TIMMI2, VISIR, Michelle and TReCS a sample of A and B-type main sequence stars reported as having mid-IR excess. We constrain the location of the debris through combined modelling of the emission spectrum and a modelling technique designed to constrain the radial extent of emission in mid-IR imaging. We independently confirm the presence of warm dust around 3 of the candidates: HD3003, HD80950 and eta Tel. For the binary HD3003 a stability analysis indicates the dust is either circumstellar and lying at ~4 AU with the binary orbiting at >14AU, or the dust lies in an unstable location; there is some evidence for temporal evolution of its excess emission on a ~20 year timescale. For 7 of the targets we present quantitative limits on the location of dust around the star. We demonstrate that the disc around HD71155 must have spatially distinct components at 2 and 60AU. We model the limits of current instrumentation and show that most of the known A star debris discs which could be readily resolved at 18um on 8m instruments have been resolved. Limits from unresolved imaging can help distinguish between competing models of the disc emission, but resolved imaging is key to the determination of the disc location. Modelling of the detection limits for extended emission can be useful for targeting future observational campaigns. MIRI on the JWST will be able to resolve most of the known A star debris disc population. METIS on the E-ELT will provide the opportunity to explore the hot disc population more thoroughly by detecting extended emission where calibration accuracy limits disc detection through photometry, reaching levels below 1 zodi for stars at <10pc.Comment: Accepted for publication in Astronomy and Astrophysic