4,312 research outputs found

    Low energy proton bidirectional anisotropies and their relation to transient interplanetary magnetic structures: ISEE-3 observations

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    It is known that the interplanetary medium in the period approaching solar maximum is characterized by an enhancement in the occurrence of transient solar wind streams and shocks and that such systems are often associated with looplike magnetic structures or clouds. There is observational evidence that bidirectional, field aligned flows of low energy particles could be a signature of such looplike structures, although detailed models for the magnetic field configuration and injection mechanisms do not exist at the current time. Preliminary results of a survey of low energy proton bidirectional anisotropies measured on ISEE-3 in the interplanetary medium between August 1978 and May 1982, together with magnetic field data from the same spacecraft are presented

    2MASS J06164006-6407194: The First Outer Halo L Subdwarf

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    We present the serendipitous discovery of an L subdwarf, 2MASS J06164006-6407194, in a search of the Two Micron All Sky Survey for T dwarfs. Its spectrum exhibits features indicative of both a cool and metal poor atmosphere including a heavily pressured-broadened K I resonant doublet, Cs I and Rb I lines, molecular bands of CaH, TiO, CrH, FeH, and H2O, and enhanced collision induced absorption of H2. We assign 2MASS 0616-6407 a spectral type of sdL5 based on a comparison of its red optical spectrum to that of near solar-metallicity L dwarfs. Its high proper motion (mu =1.405+-0.008 arcsec yr-1), large radial velocity (Vrad = 454+-15 km s-1), estimated uvw velocities (94, -573, 125) km s-1 and Galactic orbit with an apogalacticon at ~29 kpc are indicative of membership in the outer halo making 2MASS 0616-6407 the first ultracool member of this population.Comment: Accepted for publication in Ap

    Mucus entrapment of particles by a suspension-feeding tilapia (Pisces: Cichlidae)

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    A miniature fiberoptic endoscope was used to observe the processes of particle encounter and retention inside the buccopharyngeal cavity of suspension-feeding tilapia. Small particles (38 µm to 1.0 mm in diameter) were trapped in strands and aggregates of mucus, which usually slid posteriorly on the ceratobranchials of arches I­IV towards the esophagus while the fish pumped water through the buccopharyngeal cavity. During stage 1 of periodic reversals of water flow inside the buccopharynx, mucus-bound particles usually lifted off the arch surfaces and travelled a short distance in an anterior or anterodorsal direction. During stage 2 of a reversal, the mucus usually resumed travel in a posterior or posteroventral direction and exited the field of view. Mucus was present less often during feeding on large particles (3­10 mm in diameter) than on small particles, and large particles were rarely observed to be attached to mucus. We discuss the advantages to suspension-feeding fishes of using aerosol filtration by mucus entrapment rather than sieving, and predict that many cichlid and cyprinid suspension feeders that consume bacteria and phytoplankton use mucus for aerosol filtration

    Cut-lengths of perennial ryegrass leaf-blades influences in vitro fermentation by the anaerobic fungus neocallimastix frontalis

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    Anaerobic fungi in the gut of domesticated and wild mammalian herbivores play a key role in the host’s ability to utilize plant biomass. Due to their highly effective ability to enzymatically degrade lignocellulose, anaerobic fungi are biotechnologically interesting. Numerous factors have been shown to affect the ability of anaerobic fungi to break down plant biomass. However, methods to reduce the non-productive lag time in batch cultures and the effect of leaf-blade cut-length and condition on the fungal fermentation are not known. Therefore, experimentation using a novel gas production approach with pre-grown, axenic cultures of Neocallimastix frontalis was performed using both fresh and air-dried perennial ryegrass leaf-blades of different cut-lengths. The methodology adopted removed the lag-phase and demonstrated the digestion of un-autoclaved leaf-blades. Fermentation of leaf-blades of 4.0 cm cut-length produced 18.4% more gas yet retained 11.2% more apparent DM relative to 0.5 cm cut-length leaf-blades. Drying did not affect fermentation by N. frontalis, although an interaction between drying and leaf-blade cut-length was noted. Removal of the lag phase and the use of un-autoclaved substrates are important when considering the biotechnological potential of anaerobic fungi. A hypothesis based upon sporulation at cut surfaces is proposed to describe the experimental results

    Use of Guided Wave Inspections to Monitor the Integrity of Nuclear Power Station Boilers

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    This paper describes a ground-breaking application of guided wave testing for the nuclear power industry. Hartlepool and Heysham 1 power stations in the UK contain boilers of a unique ‘pod’ design in which the spiral boiler tubes are supported from above by a central vertical ‘spine’, which is a tubular component approximately 520mm in diameter and 21m long with complex changes in cross-section and attachments along its length. There are 32 boilers in the two stations. The gas which has passed through the reactor core flows down over the boiler tubes, heating the water inside. Only the top 2m of each spine is accessible above the top of the boiler pod. Plant Integrity Ltd was engaged by to inspect these ‘spine’ supports in 2003 using its Teletest guided wave system at statutory outages, which occur on a 3-year interval for each reactor. The Teletest tool was positioned in the only accessible place, just below the inlet header which protrudes approximately 2m from the top of the boiler. A procedure was developed to enable the full 21m length of the spine inside the boiler pod itself to be examined. During one of the regular Teletest inspections, at Heysham 1 power station in September 2013, a significant change in response was detected from the central part of one of the boiler spines. As a result, two of the eight boilers at Heysham 1 Reactor 1 were shut down pending further investigations. The indication was confirmed to be a structurally significant crack in the spine concerned. The crack detected was at the exact position and of the approximate extent reported by Teletest, which had detected the flaw from some 10m away. All four reactors at Hartlepool and Heysham 1 power stations were shut down in the latter part of 2014 while a new safety case for return to service of the remaining boilers was made. There is currently no viable alternative to guided wave inspection for monitoring the integrity of these boiler spines and a significant programme of work has been carried out to demonstrate the performance of Teletest for detection of flaws in these components under a variety of circumstances in order to support the safety case for operation. This has involved theoretical modelling, review of information contained in historical inspection data, practical tests on a full scale mock-up component, development of high temperature Teletest tooling to allow in- service tests and production of automated Teletest data collection equipment to allow real time in-service monitoring of the spines. TWI’s and Plant Integrity’s support enabled all four reactors to be returned to service before the end of 2014

    Alternative job search strategies in remote rural and peri-urban labour markets: the role of social networks

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    This paper examines the importance of informal methods (especially social networking) to the job search strategies used by unemployed people. It compares three areas: a small rural town; a larger, more sparsely populated, remote rural area; and a centrally-located, peri-urban labour market. The analysis is based first on survey research undertaken with 490 job seekers across the study areas. Emerging issues were then followed up during a series of twelve focus groups. The survey research showed that job seekers in the rural study areas were significantly more likely to use social networks to look for work. However, those who had experienced repeated or long-term periods out of work, the unskilled and young people were significantly less likely to use such networks. Focus groups confirmed the perceived importance of social networking to the job search process in rural areas, in contrast to the more marginal role such methods appear to play in peri-urban settings. For many rural job seekers, formal job search activities conducted through Jobcentres were seen as largely symbolic, lacking the practical value of social networking. These results suggest that service providers seeking to assist unemployed people in rural areas need to address the problems faced by many disadvantaged job seekers who are currently caught between their lack of social network relations and the absence of local public employment service facilities in more remote communities

    Association between exposure to environmental tobacco smoke and biomarkers of oxidative stress among patients hospitalised with acute myocardial infarction

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    Objective To determine whether exposure to environmental tobacco smoke was associated with oxidative stress among patients hospitalised for acute myocardial infarction.<p></p> Design An existing cohort study of 1,261 patients hospitalised for acute myocardial infarction.<p></p> Setting Nine acute hospitals in Scotland.<p></p> Participants Sixty never smokers who had been exposed to environmental tobacco smoke (admission serum cotinine ≥3.0 ng/mL) were compared with 60 never smokers who had not (admission serum cotinine ≤0.1 ng/mL).<p></p> Intervention None.<p></p> Main outcome measures Three biomarkers of oxidative stress (protein carbonyl, malondialdehyde (MDA) and oxidised low-density lipoprotein (ox-LDL)) were measured on admission blood samples and adjusted for potential confounders.<p></p> Results After adjusting for baseline differences in age, sex and socioeconomic status, exposure to environmental tobacco smoke was associated with serum concentrations of both protein carbonyl (beta coefficient 7.96, 95% CI 0.76, 15.17, p = 0.031) and MDA (beta coefficient 10.57, 95% CI 4.32, 16.81, p = 0.001) but not ox-LDL (beta coefficient 2.14, 95% CI −8.94, 13.21, p = 0.703).<p></p> Conclusions Exposure to environmental tobacco smoke was associated with increased oxidative stress. Further studies are requires to explore the role of oxidative stress in the association between environmental tobacco smoke and myocardial infarction.<p></p&gt

    Multi-model simulations of the impact of international shipping on Atmospheric Chemistry and Climate in 2000 and 2030

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    The global impact of shipping on atmospheric chemistry and radiative forcing, as well as the associated uncertainties, have been quantified using an ensemble of ten state-of-the-art atmospheric chemistry models and a predefined set of emission data. The analysis is performed for present-day conditions ( year 2000) and for two future ship emission scenarios. In one scenario ship emissions stabilize at 2000 levels; in the other ship emissions increase with a constant annual growth rate of 2.2% up to 2030 ( termed the "Constant Growth Scenario" (CGS)). Most other anthropogenic emissions follow the IPCC ( Intergovernmental Panel on Climate Change) SRES ( Special Report on Emission Scenarios) A2 scenario, while biomass burning and natural emissions remain at year 2000 levels. An intercomparison of the model results with observations over the Northern Hemisphere (25 degrees - 60 degrees N) oceanic regions in the lower troposphere showed that the models are capable to reproduce ozone (O-3) and nitrogen oxides (NOx= NO+ NO2) reasonably well, whereas sulphur dioxide (SO2) in the marine boundary layer is significantly underestimated. The most pronounced changes in annual mean tropospheric NO2 and sulphate columns are simulated over the Baltic and North Seas. Other significant changes occur over the North Atlantic, the Gulf of Mexico and along the main shipping lane from Europe to Asia, across the Red and Arabian Seas. Maximum contributions from shipping to annual mean near-surface O-3 are found over the North Atlantic ( 5 - 6 ppbv in 2000; up to 8 ppbv in 2030). Ship contributions to tropospheric O3 columns over the North Atlantic and Indian Oceans reach 1 DU in 2000 and up to 1.8 DU in 2030. Tropospheric O-3 forcings due to shipping are 9.8 +/- 2.0 mW/m(2) in 2000 and 13.6 +/- 2.3 mW/m(2) in 2030. Whilst increasing O-3, ship NOx simultaneously enhances hydroxyl radicals over the remote ocean, reducing the global methane lifetime by 0.13 yr in 2000, and by up to 0.17 yr in 2030, introducing a negative radiative forcing. The models show future increases in NOx and O-3 burden which scale almost linearly with increases in NOx emission totals. Increasing emissions from shipping would significantly counteract the benefits derived from reducing SO2 emissions from all other anthropogenic sources under the A2 scenario over the continents, for example in Europe. Globally, shipping contributes 3% to increases in O-3 burden between 2000 and 2030, and 4.5% to increases in sulphate under A2/CGS. However, if future ground based emissions follow a more stringent scenario, the relative importance of ship emissions will increase. Inter-model differences in the simulated O-3 contributions from ships are significantly smaller than estimated uncertainties stemming from the ship emission inventory, mainly the ship emission totals, the distribution of the emissions over the globe, and the neglect of ship plume dispersion

    A multi-model study of the hemispheric transport and deposition of oxidised nitrogen.

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    Fifteen chemistry-transport models are used to quantify, for the first time, the export of oxidised nitrogen (NOy) to and from four regions (Europe, North America, South Asia, and East Asia), and to estimate the uncertainty in the results. Between 12 and 24% of the NOx emitted is exported from each region annually. The strongest impact of each source region on a foreign region is: Europe on East Asia, North America on Europe, South Asia on East Asia, and East Asia on North America. Europe exports the most NOy, and East Asia the least. East Asia receives the most NOy from the other regions. Between 8 and 15% of NOx emitted in each region is transported over distances larger than 1000 km, with 3–10% ultimately deposited over the foreign regions
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