Reconstructions of deltaic environments from Holocene palynological records in the Volga delta, northern Caspian Sea

This article was made available through open access by the Brunel Open Access Publishing Fund.New palynological and ostracod data are presented from the Holocene Volga delta, obtained from short cores and surface samples collected in the Damchik region, near Astrakhan, Russian Federation in the northern Caspian Sea. Four phases of delta deposition are recognized and constrained by accelerated mass spectrometry (AMS) radiocarbon ages. Palynological records show that erosive channels, dunes (Baer hills) and inter-dune lakes were present during the period 11,500–8900 cal. BP at the time of the Mangyshlak Caspian lowstand. The period 8900–3770 cal. BP was characterized regionally by extensive steppe vegetation, with forest present at times with warmer, more humid climates, and with halophytic and xerophytic vegetation present at times of drought. The period 3770–2080 cal. BP was a time of active delta deposition, with forest or woodland close to the delta, indicating relatively warm and humid climates and variable Caspian Sea levels. From 2080 cal. BP to the present-day, aquatic pollen is frequent in highstand intervals and herbaceous pollen and fungal hyphae frequent in lowstand intervals. Soils and incised valley sediments are associated with the regional Derbent regression and may be time-equivalent with the ‘Medieval Warm Period’. Fungal spores are an indicator of erosional or aeolian processes, whereas fungal hyphae are associated with soil formation. Freshwater algae, ostracods and dinocysts indicate mainly freshwater conditions during the Holocene with minor brackish influences. Dinocysts present include Spiniferites cruciformis, Caspidinium rugosum, Impagidinium caspienense and Pterocysta cruciformis, the latter a new record for the Caspian Sea. The Holocene Volga delta is a partial analogue for the much larger oil and gas bearing Mio-Pliocene palaeo-Volga delta.Funding for the data collection and field work was provided from the following sources: 1 – IGCP-UNESCO 2003–2008 (Project 481 CASPAGE, Dating Caspian Sea Level Change); 2 – NWO, Netherlands Science Foundation and RFFI, Russian Science Foundation 2005–2008 (Programme: ‘VHR Seismic Stratigraphy and Paleoecology of the Holocene Volga Delta’); and 3 – BP Exploration (Caspian Sea) Sea Ltd. (Azeri-Chirag-Gunashli) 2005–2008 (‘Unravelling the Small-Scale Stratigraphy and Sediment Dynamics of the Modern Volga Delta Using VHR Marine Geophysics’). The palynological work was funded jointly by BP Exploration (Caspian Sea) Ltd., Delft University of Technology and KrA Stratigraphic Ltd. Ostracod analyses were funded by StrataData Ltd. and funding for two additional radiocarbon dates provided by Deltares

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

Background Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide.Methods A multimethods analysis was performed as part of the GlobalSurg 3 study-a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital.Findings Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3.85 [95% CI 2.58-5.75]; p<0.0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63.0% vs 82.7%; OR 0.35 [0.23-0.53]; p<0.0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer.Interpretation Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised

К вопросу профилирования реактивного сопла ЖРД

As is known, the profiling of subsonic and supersonic parts of a liquid-propellant rocket engine (LPRE) nozzle is usually considered separately, which is one of the main drawbacks of modern design methods. Considering the nozzle in the form of joining two separate parts creates certain difficulties in the design of the liquid rocket engine chamber, which causes the necessity of a application of some other approach.In addition, the geometry of the nozzle contour for various settings doesn’t imply any preliminary distribution of the isentropic expansion degree, Mach number and other parameters along the nozzle axis.A preliminary analysis of existing researches shows to an approximate asymmetric sigmoidal velocity distribution of the gas flow along the axis of the LPRE chamber (along the nozzle axis). This means that in the initial design a velocity distribution (the end of the combustion chamber, the subsonic and supersonic part of the nozzle) can be described as a sigmoid function.Consequently, it becomes necessary to solve the nozzle gas dynamics equation in a new formulation. Taking into account the foregoing, we consider a dual scheme technique for determining the main parameters of 2D supersonic flow and the geometry of the LPRE nozzle.According to the first scheme for a supersonic and non-rotating 2D ideal gas flow, the application of the method of characteristics begins on the sonic line.An analysis of the studies shows that the nozzle axis can also be taken as the source line, taking into account the velocity distribution along the axis. In this case, the application of the method of characteristics is based on the data obtained from the thermodynamic calculation of the LPRE with using the new formula obtained. The method of characteristics in the C2 calculation scheme is applied parallel to the C1 design scheme. The dual scheme technique (C1 + C2) for determining the basic parameters of a planar supersonic flow and nozzle geometry can be performed with an unknown or known initial nozzle length.Thus, we proposed a dual scheme method for determining the optimal contour of the nozzle using the results of the thermodynamic calculation of the values of the parameters of a planar supersonic flow, which is covered by the internal curvilinear profile of the LPRE nozzle. The method is based on empirical formulas, which are obtained on the basis of numerical studies. The proposed technique allows performing combined thermodynamic, gas dynamic and geometric calculations of the nozzle, with the required error of the optimal contour. На основе результатов проведенных исследований определено характер распределения термогазодинамических параметров по длине камеры ракетного двигателя. Показано, что распределение скорости газового потока по оси сопла может быть представлено в виде асимметричного сигмоида. Предлагается метод профилирования сопла на основе распределения скорости газового потока по оси камеры двигателя. Уравнения газовой динамики решаются совместно с новым уравнением распределения скорости по оси сопла и с применением метода характеристик, что определил разработку двухсхемной методики профилирования.