Global, regional, and national burden of neurological disorders, 1990–2016 : a systematic analysis for the Global Burden of Disease Study 2016

Background: Neurological disorders are increasingly recognised as major causes of death and disability worldwide. The aim of this analysis from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2016 is to provide the most comprehensive and up-to-date estimates of the global, regional, and national burden from neurological disorders. Methods: We estimated prevalence, incidence, deaths, and disability-adjusted life-years (DALYs; the sum of years of life lost [YLLs] and years lived with disability [YLDs]) by age and sex for 15 neurological disorder categories (tetanus, meningitis, encephalitis, stroke, brain and other CNS cancers, traumatic brain injury, spinal cord injury, Alzheimer's disease and other dementias, Parkinson's disease, multiple sclerosis, motor neuron diseases, idiopathic epilepsy, migraine, tension-type headache, and a residual category for other less common neurological disorders) in 195 countries from 1990 to 2016. DisMod-MR 2.1, a Bayesian meta-regression tool, was the main method of estimation of prevalence and incidence, and the Cause of Death Ensemble model (CODEm) was used for mortality estimation. We quantified the contribution of 84 risks and combinations of risk to the disease estimates for the 15 neurological disorder categories using the GBD comparative risk assessment approach. Findings: Globally, in 2016, neurological disorders were the leading cause of DALYs (276 million [95% UI 247–308]) and second leading cause of deaths (9·0 million [8·8–9·4]). The absolute number of deaths and DALYs from all neurological disorders combined increased (deaths by 39% [34–44] and DALYs by 15% [9–21]) whereas their age-standardised rates decreased (deaths by 28% [26–30] and DALYs by 27% [24–31]) between 1990 and 2016. The only neurological disorders that had a decrease in rates and absolute numbers of deaths and DALYs were tetanus, meningitis, and encephalitis. The four largest contributors of neurological DALYs were stroke (42·2% [38·6–46·1]), migraine (16·3% [11·7–20·8]), Alzheimer's and other dementias (10·4% [9·0–12·1]), and meningitis (7·9% [6·6–10·4]). For the combined neurological disorders, age-standardised DALY rates were significantly higher in males than in females (male-to-female ratio 1·12 [1·05–1·20]), but migraine, multiple sclerosis, and tension-type headache were more common and caused more burden in females, with male-to-female ratios of less than 0·7. The 84 risks quantified in GBD explain less than 10% of neurological disorder DALY burdens, except stroke, for which 88·8% (86·5–90·9) of DALYs are attributable to risk factors, and to a lesser extent Alzheimer's disease and other dementias (22·3% [11·8–35·1] of DALYs are risk attributable) and idiopathic epilepsy (14·1% [10·8–17·5] of DALYs are risk attributable). Interpretation: Globally, the burden of neurological disorders, as measured by the absolute number of DALYs, continues to increase. As populations are growing and ageing, and the prevalence of major disabling neurological disorders steeply increases with age, governments will face increasing demand for treatment, rehabilitation, and support services for neurological disorders. The scarcity of established modifiable risks for most of the neurological burden demonstrates that new knowledge is required to develop effective prevention and treatment strategies. Funding: Bill & Melinda Gates Foundation

Stability of Partially Premixed Ammonia/Methane Flames in a Concentric Flow Conical Nozzle Burner

Ammonia, as a carbon-free fuel, holds promise as a potential alternative to fossil fuels. However, its practical implementation requires a comprehensive understanding of its combustion properties, particularly concerning flame stability. This study investigates the stability and flame appearance of partially premixed ammonia-methane flames in a concentric flow conical nozzle burner. The research explores the effects of varying the ammonia fraction in the inner stream, the outer stream velocity, and the degree of partial premixing (expressed as L/D). The findings indicate that flame stability is enhanced by increasing the outer stream equivalence ratio, while it is reduced by increasing the degree of premixing via higher L/D values. Notably, the case of L/D = 0 demonstrates a virtual improvement in flame stability, attributed to the absence of reaction between the inner mixture and the stable outer methane flame. This study provides valuable insights into the combustion characteristics of ammonia-methane blends under partially premixed conditions

Simultaneous line Raman/Rayleigh measurements for mixture fraction determination in turbulent, partially premixed slot burner flames

International audienc

Simultaneous line Raman/Rayleigh measurements for mixture fraction determination in turbulent, partially premixed slot burner flames

International audienc

Effect of Inner Swirl Angle on Flame Stability of a Double-Swirl Burner with Biogas-Methane Co-Firing

This paper studies how the inner swirl angle affects the flame stability of a double-swirl burner with biogas-methane co-firing. Biogas is a renewable fuel that is produced from organic waste by anaerobic digestion, it can be mixed with methane as an act to save methane fuel as well reduce CO_2 emissions. However, biogas has combustion challenges due to its high CO_2 content. The double-swirl burner is a technology that can improve combustion performance and reduce nitrogen oxide emissions. This study investigates different inner swirl angles with various CO_2 fractions in biogas and assesses their effects on flame stability and flame appearance. The paper finds that a higher CO_2 fraction and inner swirl angle make the flame less stable and requires more fuel, and also changes the flame shape. The paper gives insights into improving the double-swirl burner for biogas-methane co-firing

Simultaneous line Raman/Rayleigh measurements for mixture fraction determination in turbulent, partially premixed slot burner flames

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Auto-ignition and numerical analysis on high-pressure combustion of premixed methane-air mixtures in highly preheated and diluted environment

This work investigates both autoignition and combustion characteristics in highly preheated and diluted combustion of a laminar premixed stoichiometric CH4/O2/N2 mixture in a cylindrical combustor operating at elevated pressures. The analysis was carried out for a range of operating parameters, including reactant preheat temperatures of 1100–1500 K, combustor pressures of 1-10 atm, and in a highly diluted mixture, achieved by decreasing the oxygen content in the oxidizer from 21% to 3% on volume basis. Simulations were conducted using the laminar premixed adiabatic PFR (plug flow reactor) model of Ansys Chemkin Pro. Two-dimensional pictorial representation was performed using the finite volume-based CFD code Ansys Fluent 19.2. Finite-rate chemistry with the detailed chemical mechanism GRI Mech 3.0 was used for combustion analysis. Results showed that OH and HCO mole fractions decreased with increasing combustor pressure and N2 dilution (or decreased O2 content), while the mole fractions increased with reactant temperature. It was also found that, by reducing the oxygen content in the mixture, the flame stabilized far away from the combustor inlet. In contrast, an increase in combustor pressure and reactant temperature stabilized the flame toward the combustor inlet. These flame stabilization characteristics at different locations of the combustor are explained in terms of ignition delay time, which were calculated using the closed homogenous reactor (CHR) model available in the Ansys Chemkin Pro package. The flame peak temperature decreased with increased N2 dilution and increased by increasing the reactant temperature. Moreover, the peak temperature varied marginally when the combustor pressure was increased. Finally, a regime diagram was prepared to show the various combustion modes, such as HiTAC, MILD combustion, and the no ignition region as a function of O2 content and reactant temperature for different operating pressures. The CO and NO emission were reduced with an increase in pressure in the MILD combustion region

Evaluation of partially premixed flame stability from mixture fraction statistics in a turbulent slot burner

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