Predictive haemodynamics in a one-dimensional human carotid artery bifurcation. Part II: application to graft design

A Bayesian surrogate modelling technique is proposed that may be able to predict an optimal bypass graft configuration for patients suffering with stenosis in the internal carotid artery (ICA). At the outset, this statistical technique is considered as a means for identifying key geometric parameters influencing haemodynamics in the human carotid bifurcation. This methodology uses a design of experiments (DoE) technique to generate candidate geometries for flow analysis. A pulsatile one dimensional Navier-Stokes solver incorporating fluid-wall interactions for a Newtonian fluid which predicts pressure and flow in the carotid bifurcation (comprising a stenosed segment in the internal carotid artery) is used for the numerical simulations. Two metrics, pressure variation factor (PVF) and maximum pressure (pm) are employed to directly compare the global and local effects, respectively, of variations in the geometry. The values of PVF and pm are then used to construct two Bayesian surrogate models. These models are statistically analysed to visualise how each geometric parameter influences PVF and pm. Percentage of stenosis is found to influence these pressure based metrics more than any other geometric parameter. Later, we identify bypass grafts with optimal geometric and material properties which have low values of PVF on five test cases with 70%, 75%, 80%, 85% and 90% stenosis in the ICA, respectively

Heat engines and heat pumps in a hydrostatic atmosphere: How surface pressure and temperature constrain wind power output and circulation cell size

The kinetic energy budget of the atmosphere's meridional circulation cells is analytically assessed. In the upper atmosphere kinetic energy generation grows with increasing surface temperature difference \$\Delta T_s\$ between the cold and warm ends of a circulation cell; in the lower atmosphere it declines. A requirement that kinetic energy generation is positive in the lower atmosphere limits the poleward cell extension \$L\$ of Hadley cells via a relationship between \$\Delta T_s\$ and surface pressure difference \$\Delta p_s\$: an upper limit exists when \$\Delta p_s\$ does not grow with increasing \$\Delta T_s\$. This pattern is demonstrated here using monthly data from MERRA re-analysis. Kinetic energy generation along air streamlines in the boundary layer does not exceed \$40\$~J~mol\$^{-1}\$; it declines with growing \$L\$ and reaches zero for the largest observed \$L\$ at 2~km height. The limited meridional cell size necessitates the appearance of heat pumps -- circulation cells with negative work output where the low-level air moves towards colder areas. These cells consume the positive work output of the heat engines -- cells where the low-level air moves towards the warmer areas -- and can in theory drive the global efficiency of atmospheric circulation down to zero. Relative contributions of \$\Delta p_s\$ and \$\Delta T_s\$ to kinetic energy generation are evaluated: \$\Delta T_s\$ dominates in the upper atmosphere, while \$\Delta p_s\$ dominates in the lower. Analysis and empirical evidence indicate that the net kinetic power output on Earth is dominated by surface pressure gradients, with minor net kinetic energy generation in the upper atmosphere. The role of condensation in generating surface pressure gradients is discussed.Comment: 26 pages, 9 figures, 2 tables; re-organized presentation, more discussion and a new figure (Fig. 4) added; in Fig. 3 the previously invisible dots (observations) can now be see

Regional economic benefits of air services versus the environmental cost of emissions

This study examines the relationship between the economic benefit of specific air services and the perceived cost of the carbon dioxide emissions from the aircraft operating the services. Initially a review is made of the basic evidence of climate change and air transport's contribution to it. This is to help put the conclusions of the study into the relevant context. As well as determining air transport's contribution to global warming, the study also considers the current and likely future taxation of air travel from the UK and the importance of air services to the World and specifically to the UK. These assessments are in macro terms. In order to obtain the necessary data to determine the relationship between the perceived cost of the CO~ produced and the economic value of the air services, research has been carried out at two UK airports - London City Airport, predominantly used by business travellers and Newquay, Cornwall Airport predominantly used by leisure travellers. Passengers were interviewed to obtain data relating to the benefit of their travel. The data was extrapolated for a full year and compared with the amount of CO~ produced by the aircraft operating the air services from and to the two airports in the same year. Forecasts of the cost of the cost of CO-, were used leading- to a ratio of economic benefit to CO-, cost. The results suggest a significantly greater economic value and this, plus the qualitative assessment of the value of air transport, provide evidence to question plans for increased taxation of air transport. The study then uses a further survey to assess this conclusion in the context of global warming. Consideration is given to air transport's catalytic role as an enabler for business development leading to conclusions that economic damage would result from increased taxation. This proves the research hypothesis

On estimating tropical forest carbon dynamics in Papua New Guinea

One of the few initiatives to address ongoing global warming that did not completely stall at the UNFCCC climate change negotiations was the reduction emissions from deforestation and forest degradation (REDD). REDD has a focus on the forests of the tropics. Unfortunately forest mensuration in most tropical countries has been inadequate to accurately determine forest carbon stocks, much less the effects of land use and changes in land use on them (Houghton et al. 2009; Bryan et al. 2010a). Whilst tropical logging is known to be widespread, the exact areas of tropical forest subject to logging have not been accurately mapped (Asner et al. 2009) or mapped with sufficient regularity to provide adequate data on the areas subject to this activity. Biomass losses due to logging have usually been derived from limited plot data, or derived via various models from estimates of regional biomass and timber extraction volumes (Houghton et al. 2009) and thus encapsulate considerable uncertainty. For these reasons the carbon impact of tropical logging remains an open question, and one that needs to be closed before any international institutional arrangement considers promoting forms of timber extraction as a tool for controlling carbon emissions. Here, we examine the current state of forest carbon research in Papua New Guinea (PNG) to illustrate the problems that can arise by developing forest management policy prematurely from incomplete forest research

Thromboxane and neutrophil changes following intermittent claudication suggest ischaemia-reperfusion injury

Objectives:It has been postulated that ischaemia-reperfusion occurs in intermittent claudication resulting in neutrophil activation and release of soluble mediators, increasing systemic vascular permeability and enhancing atherogenesis.Methods:We measured neutrophil deformability, plasma thromboxane levels, and urinary microalbumin excretion in 30 male claudicants, and 10 age- and sex-matched controls, before and after exercise to maximum walking distance. Blood was taken from an antecubital vein.ResultsThere was an increase in urinary microalbumin excretion after exercise in claudicants. Statistically significant increases in the median and 90th percentile transit times (markers of neutrophil deformability) for isolated neutrophils from blood drawn 5 min after exercise in the claudicants were observed with no change in control subjects. Plasma thromboxane concentrations in claudicants increased within 10 min post-exercise. Plasma concentrations in controls were significantly lower throughout the study period. In the claudicant group, a positive correlation between the percentage change in the median transit time for neutrophils, and the percentage change in plasma thromboxane at 60 min post-exercise was found.Conclusions:The results lend further support to the concept of ischaemia-reperfusion events in patients with intermittent claudication, leading to a systemic increase in vascular permeability as a result of endothelial injury or dysfunction (a crucial step in atherogenesis), associated with thromboxane production and neutrophil activation. We suggest that the above changes may contribute to the increased mortality seen in such patients

Measurement of cardiorespiratory fitness in children from two commonly used field tests after accounting for body fatness and maturity

Body fat and maturation both influence cardiorespiratory fitness, however few studies have taken these variables into account when using field tests to predict children's fitness levels. The purpose of this study was to determine the relationship between two field tests of cardiorespiratory fitness (20 m Maximal Multistage Shuttle Run [20-MST], 550 m distance run [550-m]) and direct measurement of VO2max after adjustment for body fatness and maturity levels. Fifty-three participants (25 boys, 28 girls, age 10.6 ± 1.2 y, mean ± SD) had their body fat levels estimated using bioelectrical impedance (16.6% ± 6.0% and 20.0% ± 5.8% for boys and girls, respectively). Participants performed in random order, the 20-MST and 550-m run followed by a progressive treadmill test to exhaustion during which gas exchange measures were taken. Pearson correlation coefficient analysis revealed that the participants' performance in the 20-MST and 550-m run were highly correlated to VO2 max obtained during the treadmill test to exhaustion (r = 0.70 and 0.59 for 20-MST and 550-m run, respectively). Adjusting for body fatness and maturity levels in a multivariate regression analysis increased the associations between the field tests and VO2max (r = 0.73 for 20-MST and 0.65 for 550-m). We may conclude that both the 20-MST and the 550-m distance run are valid field tests of cardiorespiratory fitness in New Zealand 8-13 year old children and incorporating body fatness and maturity levels explains an additional 5-7% of the variance. © Editorial Committee of Journal of Human Kinetics

Extreme Differences in Forest Degradation in Borneo: Comparing Practices in Sarawak, Sabah, and Brunei

The Malaysian states of Sabah and Sarawak are global hotspots of forest loss and degradation due to timber and oil palm industries; however, the rates and patterns of change have remained poorly measured by conventional field or satellite approaches. Using 30 m resolution optical imagery acquired since 1990, forest cover and logging roads were mapped throughout Malaysian Borneo and Brunei using the Carnegie Landsat Analysis System. We uncovered ∼364,000 km of roads constructed through the forests of this region. We estimated that in 2009 there were at most 45,400 km(2) of intact forest ecosystems in Malaysian Borneo and Brunei. Critically, we found that nearly 80% of the land surface of Sabah and Sarawak was impacted by previously undocumented, high-impact logging or clearing operations from 1990 to 2009. This contrasted strongly with neighbouring Brunei, where 54% of the land area remained covered by unlogged forest. Overall, only 8% and 3% of land area in Sabah and Sarawak, respectively, was covered by intact forests under designated protected areas. Our assessment shows that very few forest ecosystems remain intact in Sabah or Sarawak, but that Brunei, by largely excluding industrial logging from its borders, has been comparatively successful in protecting its forests.CLASlite is made possible by the Gordon and Betty Moore Foundation, the John D. and Catherine T. MacArthur Foundation, and the Grantham Foundation for the Protection of the Environment. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Diagnosis of the Three-Dimensional Circulation Associated with Mesoscale Motion in the California Current

A high-resolution upper-ocean survey of a cyclonic jet meander and an adjacent cyclonic eddy in the California Current region near 38°N, 126°W was conducted as part of the summer of 1993 Eastern Boundary Currents program. Temperature and salinity were measured from a SeaSoar vehicle, and velocity was measured by shipboard acoustic Doppler current profiler (ADCP). SeaSoar data show a density front at a depth of 70–100 m with strong cyclonic curvature. The geostrophic velocity fields, referenced to the ADCP data at 200 m, show a strong surface-intensified jet (maximum speed of 0.9 m s⁻¹) that follows the density front along a cyclonic meander. Relative vorticities within the jet are large, ranging from −0.8ƒ to +1.2ƒ, where ƒ is the local Coriolis parameter. The SeaSoar density and ADCP velocity data are used to diagnose the vertical velocity via the Q-vector form of the quasigeostrophic omega equation. The diagnosed vertical velocity field shows a maximum speed of 40–45 m d⁻¹. The lateral distribution of vertical velocity is characterized by two length scales: a large (~75 km) pattern where there is downwelling upstream and upwelling downstream of the cyclonic bend, and smaller patches arrayed along the jet core with diameters of 20–30 km. Geostrophic streamline analysis of vertical velocity indicates that water parcels make net vertical excursions of 20–30 m over 2–3 days, resulting in net vertical velocities of 7–15 m d⁻¹. Water parcels moving along geostrophic streamlines experience maximum vertical velocities in the regions of maximum alongstream change in relative vorticity, an indication of potential vorticity conservation

Synthesis of a mitochondria-targeted spin trap using a novel Parham-type cyclization

A new cyclic nitrone spin trap, [4-(3′,3′-dibutyl-2′-oxy-3′H-isoindol-5′-yloxy)butyl]triphenylphosphonium bromide (MitoSpin), bearing a lipophilic cation has been prepared by a route that involves a novel Parham-type lithiation–cyclization of an isocyanate to give the isoindolinone core. MitoSpin accumulates in a membrane potential dependent way in energized mitochondria and its oxidation could potentially be used in the study of oxidative stress resulting from reactive oxygen species generated in mitochondria