Effects Of Some Thermo-Physical Properties On Force Convective Stagnation Point On A Stretching Sheet With Convective Boundary Conditions In The Presence Of Thermal Radiation And Magnetic Field

Of concern in this paper is an investigation of force convective stagnation point on a stretching sheet with convective boundary conditions in the presence of thermal radiation and uniform magnetic field. Rosseland approximation is used to model the radiative heat transfer. The nonlinear partial differential equations arising from the flow modeling were transformed by similarity transformation. The resulting coupled nonlinear ordinary differential equations were then solved numerically by employing the Adaptive Runge-Kutta together with shooting technique. Finally the effects of the pertinent thermo-physical parameters are presented in graphs and tables. Keywords: Plane Stagnation Point, Thermal Radiation, Convective Boundary Conditions, Magnetic Field

The contribution of surface and submesoscale processes to turbulence in the open ocean surface boundary layer

The ocean surface boundary layer is a critical interface across which momentum, heat, and trace gases are exchanged between the oceans and atmosphere. Surface processes (winds, waves, and buoyancy forcing) are known to contribute significantly to fluxes within this layer. Recently, studies have suggested that submesoscale processes, which occur at small scales (0.1–10 km, hours to days) and therefore are not yet represented in most ocean models, may play critical roles in these turbulent exchanges. While observational support for such phenomena has been demonstrated in the vicinity of strong current systems and littoral regions, relatively few observations exist in the open‐ocean environment to warrant representation in Earth system models. We use novel observations and simulations to quantify the contributions of surface and submesoscale processes to turbulent kinetic energy (TKE) dissipation in the open‐ocean surface boundary layer. Our observations are derived from moorings in the North Atlantic, December 2012 to April 2013, and are complemented by atmospheric reanalysis. We develop a conceptual framework for dissipation rates due to surface and submesoscale processes. Using this framework and comparing with observed dissipation rates, we find that surface processes dominate TKE dissipation. A parameterization for symmetric instability is consistent with this result. We next employ simulations from an ocean front‐resolving model to reestablish that dissipation due to surface processes exceeds that of submesoscale processes by 1–2 orders of magnitude. Together, these results suggest submesoscale processes do not dramatically modify vertical TKE budgets, though such dynamics may be climatically important owing to their ability to remove energy from the ocean

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Momentum transport and mixing by internal lee waves and a vortical wake: laboratory and numerical experiments

International audienceThe Antarctic Circumpolar current is recognized as the main source of ocean mixing with strong impact on Earth climate. Field campaigns in the Southern Ocean have revealed that the interaction of this current (and of geostrophic eddies) with bottom topography can radiate internal gravity waves whose momentum transport contributes to dis-sipation and mixing in the ocean interior (Naveira-Garabato et al 2004). This process has been studied numerically and theoretically by a few authors, considering an idealised topography in a vertical plane (Nikurashin and Ferrari 2010) or a model of a realistic three-dimensional topography (Nikurashin et al 2013). Dossman et al (2016) addressed this problem with laboratory experiments, by studying the flow generated behind a ridge in a non rotating configuration. A three-dimensional topography behaves very differently from a two-dimensional one, because the fluid can flow horizontally around the topography as well as rise above it, thus possibly generating a vortical wake behind the topography and a lee wave field above it. The competition between the vortical wake and the lee wave field can be estimated by the concept of dividing streamline. We have reproduced this process in a linearly stratified fluid on the Coriolis rotating platform, 13 m in diameter, and with joint three-dimensional numerical experiments. An idealized topography is considered, made of either a single or multiple spherical caps. The objective of this work is to estimate the relative contribution of the turbulent wake and of lee wave breaking on fluid mixing, namely, from an oceanic view point, the relative amounts of local and interior mixing, depending on the flow parameters. The effect of rotation on the lee wave field appears to be an essential ingredient to promote interior mixing, as will be discussed during the talk among other results

A laboratory analogue of current-topography interaction in the Southern Ocean

International audienceThe Antarctic Circumpolar Current (ACC) is an active site of turbulent mixing in the circulation of Southern Ocean (SO). This is attributed to the instabilities of waves and eddies resulting from the interaction of geostrophic flow with bottom topography.For the first time, the dynamics of the Antarctic Circumpolar Current is reproduced in the laboratory using the rotating Coriolis platform with diameter 13m. The tank is filled with a 1m thick layer of uniformly stratified salt water. A uniform circular current around the tank is produced by a small change of tank rotation speed which persists by inertia for the duration of the experiment, during which the flow conditions can be considered quasi-steady. Spherical cap(s) was introduce as bottom topography in the flow configuration. The experimental module was divided into two cases: with Coriolis effect and without Coriolis effect. Several experiments with multiple caps to mimic rough topography features were conducted with various values of Froude and Rossby number.Waves and eddies resulting from the interaction of the flow with the topography were studied. It was re- alised that rotation greatly enhances vertical transport of momentum from the bottom. Inertial oscillations were observed and likely contribute to this transport. Turbulence generation was observed close the topography but also in the fluid interior far above it, which presumably results from wave breaking. Consistently, analysis of the density probes showed vertical mixing in the water column both at the bottom and in the interior. The link with the theoretical modelling by Nikurashin & Ferrari (2010) and Labreuche et al. (2016) will be discussed

Laboratory modelling of momentum transport by internal gravity waves and eddies in the Antarctic circumpolar current

International audienceThe Antarctic Circumpolar current is recognized as a key location for ocean mixing, and its interaction with the bottom topography is an important source of energy dissipation and mixing. We have reproduced this process in a linearly stratified fluid on the Coriolis rotating platform, 13 m in diameter. A uniform circular current around the tank is produced by a small change of tank rotation speed (spinup) which persists by inertia for the duration of the experiment. The wake of a single spherical cap is first investigated, involving wave emission and vortex shedding. Then a bottom roughness is introduced as a set of 18 spherical caps. In the absence of background rotation, the friction effect on the current is mainly confined to the wake located below the topography top, with a weak contribution of the radiated lee waves. By contrast, the background rotation favors the downward transport of momentum by mechanisms that we relate to the excitation of inertial waves and Ekman pumping enhanced by the rough bottom

On Energy Cascades in General Flows

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SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population