Acoustic estimates of methane gas flux from the seabed in a 6000 km2 region in the Northern Gulf of Mexico

Seeps of free methane gas escaping the seabed can be found throughout the ocean basins. To understand the role of methane gas seeps in the global carbon cycle—including both gas added to the atmosphere and that which is dissolved and potentially oxidized in the ocean volume—it is important to quantify the amount of methane escaping the seabed. Few large-scale mapping projects of natural methane seeps have been undertaken, however, and even among these, quantitative estimates of flux are rare. Here we use acoustic mapping techniques to survey 357 natural methane seeps in a large region (6000 km2) of the northern Gulf of Mexico and outline a general approach for methane seep mapping using a combination of multibeam and split-beam echo sounders. Using additional measurements collected with a remotely operated vehicle (ROV) together with the acoustic mapping results, we estimate the total gas flux within the 6000 km2 region to be between 0.0013 and 0.16 Tg/yr, or between 0.003 and 0.3% of the current estimates for global seabed methane seepage rates

Acoustic and optical observations of methane gas seeps in the Gulf of Mexico

In 2011 and 2012, measurements of acoustic backscatter from natural methane seeps were made in the northern Gulf of Mexico in water depths between 1000-2000 m. The measurementswere made using a calibrated 18 kHz echo sounder with an 11 degree beamwidth in order to estimate the depth-dependent target strength (TS). The TS data indicate a wide variation in the rate of gas seepage from the seafloor. Several of these seeps were revisited with a remotely operated vehicle in order to optically assess the bubble size distribution and to estimate the rate at which gas bubbles were exiting the seafloor. The optical data show bubble sizes between 1-10 mm radius, and similar rates of gas seepage ranging from a few bubbles per second to several tens of bubbles per second. Together, these data help to suggest the requirements for acoustically estimating gas flux from the seafloor over large regions

The effectiveness of online instructional videos in the acquisition and demonstration of cognitive, affective and psychomotor rehabilitation skills

The use of instructional videos to teach clinical skills is an ever growing area of e-learning based upon observational learning that is cited as one of the most basic yet powerful learning strategies. The aim of the current study is to evaluate the effectiveness of online instructional videos for the acquisition and demonstration of cognitive, affective and psychomotor skills among undergraduate students, throughout formative assessments with two different durations of instructional videos. The research suggests that the use of videos to support traditional learning should be encouraged. While a conclusive evidence—base for their usage has not yet been established they are a medium which is likely to benefit a proportion of a cohort, and it is very unlikely that they will be harmful to students' learning

1015-72 Elevated Plasma Homocysteine: An Important Independent Risk Factor for Coronary Artery Disease in the Elderly

BackgroundHigh plasma homocysteine (HCY) concentration is an established risk factor for premature vascular disease which can be reduced using vitamin therapy. The role of increased homocysteine as a coronary risk factor in the elderly, however, remains uncertain.MethodsWe studied 228 patients with angiographically documented coronary disease (≥ 70% stenosis in at least one major epicardial vessel). These included 136 patients less than, and 92 greater than 65 years old. Patients were compared to 223 healthy controls 199 (<65) and 24 (> 65). The presence of traditional risk factors including hypertension, smoking, hypercholesterolemia and diabetes mellitus were noted. Total fasting plasma homocysteine was measured in all subjects. A gender-adjusted threshold for a high homocysteine level was defined as the 80th percentile for healthy controls (corresponding to a level of 11.7 μmol/L in women and 13.6 μmo1/L in men).ResultsAge<65Age>65PatientsControlsPatientsControlsHomocysteine12.2±4.0*11.0±3.414.2±4.6*11.9±3.6High HCY(%)33*2050†25Odds Ratios2.0*NA2.9*NAConfidence Interval1.2–3.2NA1.0–8.3NA*p<am vs controls†p<0.03ConclusionsHomocysteine concentrations are elevated in patients with coronary artery disease older than 65 years in age. A high value confers an independent three-fold risk for coronary disease in this patient group. Accordingly, intervention studies designed to reduce plasma homocysteine levels should not exclude the elderly

Particle hydrodynamics with tessellation techniques

Lagrangian smoothed particle hydrodynamics (SPH) is a well-established approach to model fluids in astrophysical problems, thanks to its geometric flexibility and ability to automatically adjust the spatial resolution to the clumping of matter. However, a number of recent studies have emphasized inaccuracies of SPH in the treatment of fluid instabilities. The origin of these numerical problems can be traced back to spurious surface effects across contact discontinuities, and to SPH's inherent prevention of mixing at the particle level. We here investigate a new fluid particle model where the density estimate is carried out with the help of an auxiliary mesh constructed as the Voronoi tessellation of the simulation particles instead of an adaptive smoothing kernel. This Voronoi-based approach improves the ability of the scheme to represent sharp contact discontinuities. We show that this eliminates spurious surface tension effects present in SPH and that play a role in suppressing certain fluid instabilities. We find that the new `Voronoi Particle Hydrodynamics' described here produces comparable results than SPH in shocks, and better ones in turbulent regimes of pure hydrodynamical simulations. We also discuss formulations of the artificial viscosity needed in this scheme and how judiciously chosen correction forces can be derived in order to maintain a high degree of particle order and hence a regular Voronoi mesh. This is especially helpful in simulating self-gravitating fluids with existing gravity solvers used for N-body simulations.Comment: 26 pages, 24 figures, currentversion is accepted by MNRA

Gasoline: An adaptable implementation of TreeSPH

The key algorithms and features of the Gasoline code for parallel hydrodynamics with self-gravity are described. Gasoline is an extension of the efficient Pkdgrav parallel N-body code using smoothed particle hydrodynamics. Accuracy measurements, performance analysis and tests of the code are presented. Recent successful Gasoline applications are summarized. These cover a diverse set of areas in astrophysics including galaxy clusters, galaxy formation and gas-giant planets. Future directions for gasdynamical simulations in astrophysics and code development strategies for tackling cutting edge problems are discussed.Comment: 30 pages, 11 figures, submitted to New Astronomy. Movies and high resolution images are available at http://imp.mcmaster.ca/image

Second chances: Investigating athletes’ experiences of talent transfer

Talent transfer initiatives seek to transfer talented, mature individuals from one sport to another. Unfortunately talent transfer initiatives seem to lack an evidence-based direction and a rigorous exploration of the mechanisms underpinning the approach. The purpose of this exploratory study was to identify the factors which successfully transferring athletes cite as facilitative of talent transfer. In contrast to the anthropometric and performance variables that underpin current talent transfer initiatives, participants identified a range of psychobehavioral and environmental factors as key to successful transfer. We argue that further research into the mechanisms of talent transfer is needed in order to provide a strong evidence base for the methodologies employed in these initiatives

Developing a methodology for integration of Whole Life Costs into BIM processes to assist design decision making

A growing body of evidence suggests that the most common barrier to achieving design intent is the absence of comprehensive information during design development, leading to poor decision-making which impacts on actual building performance, and thus Whole Life Cost (WLC). Building Information Modeling (BIM) has the potential to facilitate a more comprehensive and accurate design approach from the early stages. A detailed model can allow designers and clients to understand the wider impacts of design changes, and to track this information through construction stages. However, dependencies between design decisions and WLC have yet to be understood. This paper is based on a project that focuses on the Private Rental Sector (PRS), which is the fastest growing new sector in the UK housing market. The study adopts a mixed method approach for the development and validation of a structured standardised process for timely WLC estimation through BIM. As a result, the main problems in WLC BIM management are identified, and coordinated into a reverse-engineered systematic process that uses the Integrated DEFinition (IDEF) 3 structured diagramming modeling technique. The research outputs aim to enhance BIM lifecycle management through a smart decision-making approach that is integral to the natural design development process

Cosmological neutrinos

The current status of neutrino cosmology is reviewed, from the question of neutrino decoupling and the presence of sterile neutrinos to the effects of neutrinos on the cosmic microwave background and large scale structure. Particular emphasis is put on cosmological neutrino mass measurements.Comment: 21 pages, 4 figures, review for NJP focus issue on neutrino

Red clover (Trifolium pratense L.) draft genome provides a platform for trait improvement

Red clover (Trifolium pratense L.) is a globally significant forage legume in pastoral livestock farming systems. It is an attractive component of grassland farming, because of its high yield and protein content, nutritional value and ability to fix atmospheric nitrogen. Enhancing its role further in sustainable agriculture requires genetic improvement of persistency, disease resistance, and tolerance to grazing. To help address these challenges, we have assembled a chromosome-scale reference genome for red clover. We observed large blocks of conserved synteny with Medicago truncatula and estimated that the two species diverged ~23 million years ago. Among the 40,868 annotated genes, we identified gene clusters involved in biochemical pathways of importance for forage quality and livestock nutrition. Genotyping by sequencing of a synthetic population of 86 genotypes show that the number of markers required for genomics-based breeding approaches is tractable, making red clover a suitable candidate for association studies and genomic selection