Rotating Electromagnetic Waves in Toroid-Shaped Regions

Electromagnetic waves, solving the full set of Maxwell equations in vacuum, are numerically computed. These waves occupy a fixed bounded region of the three dimensional space, topologically equivalent to a toroid. Thus, their fluid dynamics analogs are vortex rings. An analysis of the shape of the sections of the rings, depending on the angular speed of rotation and the major diameter, is carried out. Successively, spherical electromagnetic vortex rings of Hill's type are taken into consideration. For some interesting peculiar configurations, explicit numerical solutions are exhibited.Comment: 27 pages, 40 figure

Plasma creatine kinase indicates major amputation or limb preservation in acute lower limb ischemia

ObjectiveAcutely ischemic limbs are often of uncertain viability. To assist operative management, this study determined prospectively which indicators on admission were the best predictors of major amputation and, conversely, limb preservation.MethodsData were collected on admission. Presenting complaint, history, clinical assessment, and blood test results, including creatine kinase (CK), were recorded. Surgical procedures were noted—in particular, the presence or absence of major amputation by death or discharge. The setting was a tertiary vascular referral center in a university teaching hospital. Subjects included all patients referred as emergency cases to the vascular unit over an 18-month period who were admitted for inpatient management with acute lower limb ischemia. The main outcome measure was major amputation.ResultsA total of 97 patients with acute ischemia were studied prospectively (51 men and 46 women). Twenty-one patients (21.6%) underwent major amputation. Previous vascular surgery (P = .012), mottling (P = .001), sensory loss (P = .003), motor loss (P = .001), muscle tenderness (P < .001), absent ankle Doppler signals (P = .008), neutrophilia (P = .011), and increased CK (P < .001) were significantly associated with major amputation. If CK was normal, the risk of major amputation was 4.6% (95% confidence interval, 0.0%-9.7%). If CK was increased, the risk was 56.2% (95% CI, 39.1%-73.4%).ConclusionsSpecific clinical findings were significantly associated with major amputation. Of these, only CK had a positive predictive value greater than 50%. Plasma CK can assist operative management of acute lower limb ischemia by quantifying prospectively the risk of major amputation or limb preservation on admission

What can ecosystem models tell us about the risk of eutrophication in the North Sea?

Eutrophication is a process resulting from an increase in anthropogenic nutrient inputs from rivers and other sources, the consequences of which can include enhanced algal biomass, changes in plankton community composition and oxygen depletion near the seabed. Within the context of the Marine Strategy Framework Directive, indicators (and associated threshold) have been identified to assess the eutrophication status of an ecosystem. Large databases of observations (in situ) are required to properly assess the eutrophication status. Marine hydrodynamic/ecosystem models provide continuous fields of a wide range of ecosystem characteristics. Using such models in this context could help to overcome the lack of in situ data, and provide a powerful tool for ecosystem-based management and policy makers. Here we demonstrate a methodology that uses a combination of model outputs and in situ data to assess the risk of eutrophication in the coastal domain of the North Sea. The risk of eutrophication is computed for the past and present time as well as for different future scenarios. This allows us to assess both the current risk and its sensitivity to anthropogenic pressure and climate change. Model sensitivity studies suggest that the coastal waters of the North Sea may be more sensitive to anthropogenic rivers loads than climate change in the near future (to 2040)

Air–sea CO2 exchange and ocean acidification in UK seas and adjacent waters

Ongoing anthropogenic emissions of carbon dioxide (CO2) into the atmosphere are driving a net flux of CO2 into the ocean globally, resulting in a decline in pH called ‘ocean acidification’. Here, we discuss the consequences of this for the seas surrounding the UK from a chemical perspective, focussing on studies published since the previous MCCIP review of ocean acidification research (Williamson et al., 2017). In this reporting cycle, the biological, ecological, and socio-economic impacts of ocean acidification are considered in more detail in separate accompanying MCCIP reviews The atmospheric CO2 concentration continues to increase due to human activities (Le Quéré et al., 2018), increasing the net flux of CO2 into the global ocean, including the North Atlantic and UK continental shelf seas. Such CO2 uptake has the desirable effect of reducing the rate of climate change, but the undesirable result of ocean acidification. Our understanding of the factors that drive high spatial and temporal variability in air-sea CO2 fluxes and seawater pH in UK waters has continued to improve, thanks to observational campaigns both across the entire North-West European continental shelf sea and at specific time–series sites. Key challenges for the future include sustaining time–series observations of near-surface marine carbonate system variables, and of the auxiliary parameters required for their interpretation (e.g. temperature, salinity, and nutrients); developing and deploying new sensor technology for full water-column profiles and pore waters in seafloor sediments; and increasing the spatial and temporal resolution of models sufficiently to capture the complex processes that dominate the marine carbonate system in coastal and shelf sea environments, along with improving how those processes are themselves simulated

Carbon dioxide and ocean acidification observations in UK waters. Synthesis report with a focus on 2010–2015

Key messages: 1.1 The process of ocean acidification is now relatively well-documented at the global scale as a long-term trend in the open ocean. However, short-term and spatial variability can be high. 1.2 New datasets made available since Charting Progress 2 make it possible to greatly improve the characterisation of CO2 and ocean acidification in UK waters. 3.1 Recent UK cruise data contribute to large gaps in national and global datasets. 3.2 The new UK measurements confirm that pH is highly variable, therefore it is important to measure consistently to determine any long term trends. 3.3 Over the past 30 years, North Sea pH has decreased at 0.0035±0.0014 pH units per year. 3.4 Upper ocean pH values are highest in spring, lowest in autumn. These changes reflect the seasonal cycles in photosynthesis, respiration (decomposition) and water mixing. 3.5 Carbonate saturation states are minimal in the winter, and lower in 7 more northerly, colder waters. This temperature-dependence could have implications for future warming of the seas. 3.6 Over the annual cycle, North-west European seas are net sinks of CO2. However, during late summer to autumn months, some coastal waters may be significant sources. 3.7 In seasonally-stratified waters, sea-floor organisms naturally experience lower pH and saturation states; they may therefore be more vulnerable to threshold changes. 3.8 Large pH changes (0.5 - 1.0 units) can occur in the top 1 cm of sediment; however, such effects are not well-documented. 3.9 A coupled forecast model estimates the decrease in pH trend within the North Sea to be -0.0036±0.00034 pH units per year, under a high greenhouse gas emissions scenario (RCP 8.5). 3.10 Seasonal estimates from the forecast model demonstrate areas of the North Sea that are particularly vulnerable to aragonite undersaturation

Multi-model comparison of trends and controls of near-bed oxygen concentration on the northwest European continental shelf under climate change

We present an analysis of the evolution of near-bed oxygen in the next century in the northwest European continental shelf in a three-member ensemble of coupled physics–biogeochemistry models. The comparison between model results helps highlight the biogeochemical mechanisms responsible for the observed deoxygenation trends and their response to climate drivers. While all models predict a decrease in near-bed oxygen proportional to climate change intensity, the response is spatially heterogeneous, with hotspots of oxygen decline (up to −1 mg L−1) developing along the Norwegian trench in the members with the most intense change, as well as areas where compensating mechanisms mitigate change. We separate the components of oxygen change associated with the warming effect on oxygen solubility from those due to the effects of changes in transport and biological processes. We find that while warming is responsible for a mostly uniform decline throughout the shelf (−0.30 mg L−1 averaged across ensemble members), changes in transport and biological processes account for the detected heterogeneity. Hotspots of deoxygenation are associated with enhanced stratification that greatly reduces vertical transport. A major change in circulation in the North Sea is responsible for the onset of one such hotspot that develops along the Norwegian trench and adjacent areas in the members characterised by intense climate change. Conversely, relatively shallow and well-mixed coastal areas like the southern North Sea, Irish Sea and English Channel experience an increase in net primary production that partially mitigates oxygen decline in all members. This work represents the first multi-model comparison addressing deoxygenation in the northwest European shelf and contributes to characterising the possible trajectories of near-bed oxygen and the processes that drive deoxygenation in this region. As our downscaled members factor in riverine inputs and small- and medium-scale circulation, which are not usually well represented in earth system models, results are relevant for the understanding of deoxygenation in coastal and shelf systems