Pulsed Laval nozzle study of the kinetics of OH with unsaturated hydrocarbons at very low temperatures

The kinetics of reactions of the OH radical with ethene, ethyne (acetylene), propyne (methyl acetylene) and t-butyl-hydroperoxide were studied at temperatures of 69 and 86 K using laser flash-photolysis combined with laser-induced fluorescence spectroscopy. A new pulsed Laval nozzle apparatus is used to provide the low-temperature thermalised environment at a single density of similar to 4 x 10(16) molecule cm(-3) in N-2. The density and temperature within the flow are determined using measurements of impact pressure and rotational populations from laser-induced fluorescence spectroscopy of NO and OH. For ethene, rate coefficients were determined to be k(2) = (3.22 +/- 0.46) x 10(-11) and (2.12 +/- 0.12) x 10(-11) cm(3) molecule(-1) s(-1) at T = 69 and 86 K, respectively, in good agreement with a master-equation calculation utilising an ab initio surface recently calculated for this reaction by Cleary et al. (P. A. Cleary, M. T. Baeza Romero, M. A. Blitz, D. E. Heard, M. J. Pilling, P. W. Seakins and L. Wang, Phys. Chem. Chem. Phys., 2006, 8, 5633-5642) For ethyne, no previous data exist below 210 K and a single measurement at 69 K was only able to provide an approximate upper limit for the rate coefficient of k(3) < 1 x 10(-12) cm(3) molecule(-1) s (-1), consistent with the presence of a small activation barrier of similar to 5 kJ mol (-1) between the reagents and the OH-C2H2 adduct. For propyne, there are no previous measurements below 253 K, and rate coefficients of k(4) = (5.08 +/- 0.65), (5.02 +/- 1.11) and (3.11 +/- 0.09) x 10(-12) cm(3) molecule(-1) s(-1) were obtained at T = 69, 86 and 299 K, indicating a much weaker temperature dependence than for ethene. The rate coefficient k(1) = (7.8 +/- 2.5) x 10(-11) cm(3) molecule(-1) s (-1) was obtained for the reaction of OH with t-butyl-hydroperoxide at T = 86 K. Studies of the reaction of OH with benzene and toluene yielded complex kinetic profiles of OH which did not allow the extraction of rate coefficients. Uncertainties are quoted at the 95% confidence limit and include systematic errors

OH yields from the CH3CO+O-2 reaction using an internal standard

Laser flash photolysis of CH3C(O)OH at 248 nm was used to create equal zero time yields of CH3CO and OH. The absolute OH yield from the CH3CO + O2 (+M) reaction was determined by following the OH temporal profile using the zero time OH concentration as an internal standard. The OH yield from CH3CO + O2 (+M) was observed to decrease with increasing pressure with an extrapolated zero pressure yield close to unity (1.1 ± 0.2, quoted uncertainties correspond to 95% confidence limits). The results are in quantitative agreement with those obtained from 248 nm acetone photolysis in the presence of O2

A black-hole mass measurement from molecular gas kinematics in NGC4526

The masses of the supermassive black-holes found in galaxy bulges are correlated with a multitude of galaxy properties, leading to suggestions that galaxies and black-holes may evolve together. The number of reliably measured black-hole masses is small, and the number of methods for measuring them is limited, holding back attempts to understand this co-evolution. Directly measuring black-hole masses is currently possible with stellar kinematics (in early-type galaxies), ionised-gas kinematics (in some spiral and early-type galaxies) and in rare objects which have central maser emission. Here we report that by modelling the effect of a black-hole on the kinematics of molecular gas it is possible to fit interferometric observations of CO emission and thereby accurately estimate black hole masses. We study the dynamics of the gas in the early-type galaxy NGC4526, and obtain a best fit which requires the presence of a central dark-object of 4.5(+4.2-3.0)x10^8 Msun (3 sigma confidence limit). With next generation mm-interferometers (e.g. ALMA) these observations could be reproduced in galaxies out to 75 megaparsecs in less the 5 hours of observing time. The use of molecular gas as a kinematic tracer should thus allow one to estimate black-hole masses in hundreds of galaxies in the local universe, many more than accessible with current techniques.Comment: To appear in Nature online on 30/01/2013. 3 Pages, 2 Figures (plus two pages of supplementary information

HI Imaging of LGS 3 and an Apparently Interacting High-Velocity Cloud

We present a 93' by 93' map of the area near the Local Group dwarf galaxy LGS 3, centered on an HI cloud 30' away from the galaxy. Previous authors associated this cloud with LGS 3 but relied on observations made with a 36' beam. Our high-resolution (3.4'), wide-field Arecibo observations of the region reveal that the HI cloud is distinct from the galaxy and suggest an interaction between the two. We point out faint emission features in the map that may be gas that has been tidally removed from the HI cloud by LGS 3. We also derive the rotation curve of the cloud and find that it is in solid-body rotation out to a radius of 10', beyond which the rotation velocity begins to decline. Assuming a spherical geometry for the cloud, the implied mass is 2.8 x 10^7 (d/Mpc) M_{Sun}, where d is the distance in Mpc. The observed HI mass is 5.5 x 10^6 (d/Mpc)^2 M_{Sun}, implying that the cloud is dark-matter dominated unless its distance is at least 1.9 Mpc. We propose that the cloud is a high-velocity cloud that is undergoing a tidal interaction with LGS 3 and therefore is located roughly 700 kpc away from the Milky Way. The cloud then contains a total mass of ~2.0 x 10^7 M_{Sun}, 82% of which consists of dark matter.Comment: 5 pages, 2 color figures. Accepted for publication in ApJ Letter

Tightly Correlated HI and FUV Emission in the Outskirts of M83

We compare sensitive HI data from The HI Nearby Galaxy Survey (THINGS) and deep far UV (FUV) data from GALEX in the outer disk of M83. The FUV and HI maps show a stunning spatial correlation out to almost 4 optical radii (r25), roughly the extent of our maps. This underscores that HI traces the gas reservoir for outer disk star formation and it implies that massive (at least low level) star formation proceeds almost everywhere HI is observed. Whereas the average FUV intensity decreases steadily with increasing radius before leveling off at ~1.7 r25, the decline in HI surface density is more subtle. Low HI columns (<2 M_solar/pc^2) contribute most of the mass in the outer disk, which is not the case within r25. The time for star formation to consume the available HI, inferred from the ratio of HI to FUV intensity, rises with increasing radius before leveling off at ~100 Gyr, i.e., many Hubble times, near ~1.7 r25. Assuming the relatively short H2 depletion times observed in the inner parts of galaxies hold in outer disks, the conversion of HI into bound, molecular clouds seems to limit star formation in outer galaxy disks. The long consumption times suggest that most of the extended HI observed in M83 will not be consumed by in situ star formation. However, even these low star formation rates are enough to expect moderate chemical enrichment in a closed outer disk.Comment: Accepted for Publication in ApJ

Health challenges in refugee reception: dateline Europe 2016

The arrival of more than one million migrants, many of them refugees, has proved a major test for the European Union. Although international relief and monitoring agencies have been critical of makeshift camps in Calais and Eidomeni where infectious disease and overcrowding present major health risks, few have examined the nature of the official reception system and its impact on health delivery. Drawing upon research findings from an Economic and Social Research Council (ESRC) funded project, this article considers the physical and mental health of asylum-seekers in transit and analyses how the closure of borders has engendered health risks for populations in recognised reception centres in Sicily and in Greece. Data gathered by means of a survey administered in Greece (300) and in Sicily (400), and complemented by in-depth interviews with migrants (45) and key informants (50) including representatives of government offices, humanitarian and relief agencies, NGOs and activist organisations, are presented to offer an analysis of the reception systems in the two frontline states. We note that medical provision varies significantly from one centre to another and that centre managers play a critical role in the transmission of vital information. A key finding is that, given such disparity, the criteria used by the UNHCR to grade health services reception do not address the substantive issue that prevent refugees from accessing health services, even when provided on site. Health provision is not as recorded in UNHCR reporting but rather there are critical gaps between provision, awareness, and access for refugees in reception systems in Sicily and in Greece. This article concludes that there is a great need for more information campaigns to direct refugees to essential services

Experimental Modeling of Eddy Current Inspection Capabilities

An experimental modeling technique based on the use of liquid mercury samples containing artificial discontinuities has been examined to establish the applicability of this approach to the assessment of eddy current inspection capabilities. Results show that the mercury modeling concept provides an accurate, rapid and inexpensive approach to the calibration and characterization of eddy current inspection techniques. Data are presented which clearly show the impact of defect size, type and location on the eddy current response developed with a surface riding “pancake” probe. The potential of mercury modeling to enhance the understanding of eddy current inspection techniques and also to guide the development of rational analytical modeling is discussed

Counting the Population in Need of International Protection Globally

Statistical data and evidence-based claims are increasingly central to our everyday lives. Critically examining ‘Big Data’, this book charts the recent explosion in sources of data, including those precipitated by global developments and technological change. It sets out changes and controversies related to data harvesting and construction, dissemination and data analytics by a range of private, governmental and social organisations in multiple settings. Analysing the power of data to shape political debate, the presentation of ideas to us by the media, and issues surrounding data ownership and access, the authors suggest how data can be used to uncover injustices and to advance social progress

Unusually Luminous Giant Molecular Clouds in the Outer Disk of M33

We use high spatial resolution (~7pc) CARMA observations to derive detailed properties for 8 giant molecular clouds (GMCs) at a galactocentric radius corresponding to approximately two CO scale lengths, or ~0.5 optical radii (r25), in the Local Group spiral galaxy M33. At this radius, molecular gas fraction, dust-to-gas ratio and metallicity are much lower than in the inner part of M33 or in a typical spiral galaxy. This allows us to probe the impact of environment on GMC properties by comparing our measurements to previous data from the inner disk of M33, the Milky Way and other nearby galaxies. The outer disk clouds roughly fall on the size-linewidth relation defined by extragalactic GMCs, but are slightly displaced from the luminosity-virial mass relation in the sense of having high CO luminosity compared to the inferred virial mass. This implies a different CO-to-H2 conversion factor, which is on average a factor of two lower than the inner disk and the extragalactic average. We attribute this to significantly higher measured brightness temperatures of the outer disk clouds compared to the ancillary sample of GMCs, which is likely an effect of enhanced radiation levels due to massive star formation in the vicinity of our target field. Apart from brightness temperature, the properties we determine for the outer disk GMCs in M33 do not differ significantly from those of our comparison sample. In particular, the combined sample of inner and outer disk M33 clouds covers roughly the same range in size, linewidth, virial mass and CO luminosity than the sample of Milky Way GMCs. When compared to the inner disk clouds in M33, however, we find even the brightest outer disk clouds to be smaller than most of their inner disk counterparts. This may be due to incomplete sampling or a potentially steeper cloud mass function at larger radii.Comment: Accepted for Publication in ApJ; 7 pages, 4 figure