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Worldwide trends in underweight and obesity from 1990 to 2022: a pooled analysis of 3663 population-representative studies with 222 million children, adolescents, and adults
Background
Underweight and obesity are associated with adverse health outcomes throughout the life course. We estimated the individual and combined prevalence of underweight or thinness and obesity, and their changes, from 1990 to 2022 for adults and school-aged children and adolescents in 200 countries and territories.
Methods
We used data from 3663 population-based studies with 222 million participants that measured height and weight in representative samples of the general population. We used a Bayesian hierarchical model to estimate trends in the prevalence of different BMI categories, separately for adults (age ≥20 years) and school-aged children and adolescents (age 5–19 years), from 1990 to 2022 for 200 countries and territories. For adults, we report the individual and combined prevalence of underweight (BMI 2 SD above the median).
Findings
From 1990 to 2022, the combined prevalence of underweight and obesity in adults decreased in 11 countries (6%) for women and 17 (9%) for men with a posterior probability of at least 0·80 that the observed changes were true decreases. The combined prevalence increased in 162 countries (81%) for women and 140 countries (70%) for men with a posterior probability of at least 0·80. In 2022, the combined prevalence of underweight and obesity was highest in island nations in the Caribbean and Polynesia and Micronesia, and countries in the Middle East and north Africa. Obesity prevalence was higher than underweight with posterior probability of at least 0·80 in 177 countries (89%) for women and 145 (73%) for men in 2022, whereas the converse was true in 16 countries (8%) for women, and 39 (20%) for men. From 1990 to 2022, the combined prevalence of thinness and obesity decreased among girls in five countries (3%) and among boys in 15 countries (8%) with a posterior probability of at least 0·80, and increased among girls in 140 countries (70%) and boys in 137 countries (69%) with a posterior probability of at least 0·80. The countries with highest combined prevalence of thinness and obesity in school-aged children and adolescents in 2022 were in Polynesia and Micronesia and the Caribbean for both sexes, and Chile and Qatar for boys. Combined prevalence was also high in some countries in south Asia, such as India and Pakistan, where thinness remained prevalent despite having declined. In 2022, obesity in school-aged children and adolescents was more prevalent than thinness with a posterior probability of at least 0·80 among girls in 133 countries (67%) and boys in 125 countries (63%), whereas the converse was true in 35 countries (18%) and 42 countries (21%), respectively. In almost all countries for both adults and school-aged children and adolescents, the increases in double burden were driven by increases in obesity, and decreases in double burden by declining underweight or thinness.
Interpretation
The combined burden of underweight and obesity has increased in most countries, driven by an increase in obesity, while underweight and thinness remain prevalent in south Asia and parts of Africa. A healthy nutrition transition that enhances access to nutritious foods is needed to address the remaining burden of underweight while curbing and reversing the increase in obesity.
Funding
UK Medical Research Council, UK Research and Innovation (Research England), UK Research and Innovation (Innovate UK), and European Union
Surface Texture Manufacturing Techniques and Tribological Effect of Surface Texturing on Cutting Tool Performance: A Review
The tribological characteristics of sliding surfaces have been remarkably improved by surface texturing. Surface texturing can be beneficial in many ways; for example, it can reduce friction and wear, increase load carrying capacity, and increase fluid film stiffness. The design process for surface texturing is highly correlated to the particular functions of any application for which texturing is required. Texture quality is greatly affected by manufacturing methods, therefore, it is important to have a detailed understanding of the related parameters of any technique. The use of surface texturing to improve the cutting performance of tools is a relatively new application. These textures improve cutting performance by enhancing lubricant availability at the contact point, reducing the tool-chip contact area, and trapping wear debris. Reductions in crater and flank wear, friction force, cutting forces, and cutting temperature are the main benefits obtained by this technique. To date, surface texturing has been successfully used in drilling, milling, and turning operations. This article provides an overview of the techniques that have been used in industry and research platforms to manufacture micro-/nano-textures for tribological applications, and it examines the effects of surface textures on cutting tool performance
A review on bio-based lubricants and their applications
In transportation and industrial sectors, the world relies heavily on petroleum-based products which may cause grave concern related to future energy security. On certain cases, these products would end up back to the environment causing serious environmental pollution and hazards. Recognized as potential substitutes to mineral-based lubricants, bio-based lubricants have received growing interest as they play a significant role in overcoming above problems. Bio-based lubricants have been found to exhibit superior lubricant properties over the conventional mineral lubricants, with renewability and biodegradability being their strongest suit. There is a strong need to review the available literature to explore the potential of bio-based lubricants for various applications. In this regard, the goal of this paper is to highlight the potential of biolubricants for a broad range of applications based upon the published researches over the past decade. The correlation between molecular structures, physicochemical properties and lubrication performance of natural oil were reviewed which is essential for lubricant development and selection. This review also acknowledged some applications of which the potential use of bio-based lubricant has been explored. Based on the key findings, it can be concluded that bio-based lubricant is a promising substitute for various applications due to their availability in wide arrays of properties which are essential for some applications. However, for certain applications, prior chemical modification is required to overcome the limitations including substandard low temperature characteristics and oxidative stability. With proper base oil and additive packages formulation, bio-based lubricants can perform better than the conventional lubricants
Analysis of thermal stability and lubrication characteristics of: Millettia pinnata oil
Lubricants are mostly used to reduce the friction and wear between sliding and metal contact surfaces, allowing them to move smoothly over each other. Nowadays, due to the increase in oil prices and reduction of oil reserves, it is necessary to replace mineral oil, which will also protect the environment from hazards caused by these oils. It is essential to find an alternative oil for the replacement of mineral-oil-based lubricants, and vegetable oil already meets the necessary requirements. Vegetable-oil-based biolubricants are non-toxic, biodegradable, renewable and have a good lubricating performance compared to mineral-oil-based lubricants. This study analyzes the thermal stability and lubricating characteristics of different types of vegetable oil. The friction and wear characteristics of the oils were investigated using a four-ball tester, according to ASTM method 4172. Millettia pinnata oil has good oxidation stability due to the presence of higher percentages of oleic acid in its fatty acid composition. Millettia pinnata oil also shows a higher kinematic viscosity. Rice bran oil shows a higher viscosity index than other oils, and it is better for boundary lubrication. In thermogravimetric analysis, it was found that Millettia pinnata oil remains thermally stable at 391 °C. Millettia pinnata oil showed a lower coefficient of friction and rice bran oil showed a lower wear scar diameter compared to other vegetable oils and lube oils. A lower wear scar surface area was found with rice bran oil compared to other vegetable and commercial oils. Therefore, due to a better lubricating performance, Millettia pinnata oil has great potential to be used as a lubricating oil in industrial and automotive applications
Performance and emission characteristics of a spark ignition engine fuelled with butanol isomer-gasoline blends
The heavy reliance on petroleum-derived fuels such as gasoline in the transportation sector is one of the major causes of environmental pollution. For this reason, there is a critical need to develop cleaner alternative fuels. Butanol is an alcohol with four different isomers that can be blended with gasoline to produce cleaner alternative fuels because of their favourable physicochemical properties compared to ethanol. This study examined the effect of butanol isomer-gasoline blends on the performance and emission characteristics of a spark ignition engine. The butanol isomers; n-butanol, sec-butanol, tert-butanol and isobutanol are mixed with pure gasoline at a volume fraction of 20 vol%, and the physicochemical properties of these blends are measured. Tests are conducted on a SI engine at full throttle condition within an engine speed range of 1000–5000 rpm. The results show that there is a significant increase in the engine torque, brake power, brake specific fuel consumption and CO2 emissions with respect to those for pure gasoline. The butanol isomers-gasoline blends give slightly higher brake thermal efficiency and exhaust gas temperature than pure gasoline at higher engine speeds. The iBu20 blend (20 vol% of isobutanol in gasoline) gives the highest engine torque, brake power and brake thermal efficiency among all of the blends tested in this study. The isobutanol and n-butanol blend results in the lowest CO and HC emissions, respectively. In addition, all of the butanol isomer-gasoline blends yield lower NO emissions except for the isobutanol-gasoline blend
Production optimization and tribological characteristics of cottonseed oil methyl ester
This paper presented experimental results to evaluate the optimization of production parameters through response surface methodology. These parameters significantly affected the yield of cottonseed oil methyl ester (COME). The input variables for the production of methyl ester from cottonseed oil were methanol/oil molar ratio, concentration of catalyst, temperature, and stirring speed. The response or output variable was the yield of methyl ester. The fatty acid methyl ester composition of COME (biodiesel) was obtained using a gas chromatography (GC) analyzer. BS EN 14103:2011 was the standard used to analyze the fatty acid methyl ester. The derived mathematical model was statistically accurate to predict the optimum value of COME. The optimized values to obtain a 98.3% yield of methyl ester were as follows: methanol/oil molar ratio of 6:1, catalyst concentration of 0.97% (w/w), temperature of 63.8 °C, and speed of 797 rpm. The physicochemical properties of COME were measured in accordance with ASTM D6751. The friction and wear properties of COME and its blends with petroleum diesel were tested using a four-ball wear testing machine. The tribological characteristics of COME as a new biofuel were assessed. COME displayed good lubricity with a low coefficient of friction and wear scar diameter. The coefficient of friction of pure COME (COME100) was lower than that of pure petroleum diesel (DL100) and COME blends with petrol diesel (COME10, COME20, and COME50). The average coefficient of friction of COME 100 was lower than that of DL100, COME10, COME20, and COME50 by 28.06%, 19.49%, 7.49%, and 3.65%, respectively. The wear scar diameter of COME100 for the tested ball was lower than that of DL100, COME10, COME20, and COME50 by 47.6%, 33.3%, 32.1%, and 21.42%, respectively. The worn surfaces of the tested balls were examined by scanning electron microscopy, and the results were presented in this paper
Effect of gasoline-bioethanol blends on the properties and lubrication characteristics of commercial engine oil
Concerns over depleting fossil fuel reserves, energy security, and climate change have resulted in stringent legislation demanding that automobiles use more renewable fuels. Bioethanol is being given significant attention on a global scale and is being considered as a long-term gasoline replacement that helps reduce exhaust emissions. The piston ring and cylinder wall interface is generally the largest contributor to engine friction and these regions of the engine also suffer the highest levels of fuel dilution into the lubricant from unburned fuel, especially for bioethanol as it has a high heat of vaporization, which enhances the tendency of the fuel to enter the oil sump. As bioethanol is being blended with gasoline at increasingly higher concentrations and the accumulation of fuel in the crankcase is significant, it is crucial to study the effect of various bioethanol blends on the degradation of engine oil's properties and the friction and wear characteristics of engine oil. A fully synthetic oil was homogenously mixed with five formulated fuels such as gasoline blend (E0), gasoline-10% ethanol (E10), gasoline-20% ethanol (E20), gasoline-30% ethanol (E30), and gasoline-85% ethanol (E85). These mixtures were then tested in a four-ball wear tester according to the ASTM D4172 standard test. Under selected operating conditions, the results show that the addition of a gasoline-bioethanol blend decreases the oil viscosity, whereas the acid number increases because bioethanol is more reactive compared to gasoline, which enhances oil degradation and oxidation. Fuel dilution reduces the lubricating efficiency and the wear protection of the engine oil. All fuel-diluted oil samples have higher friction and wear losses, compared to the fresh synthetic oil. E10 has slight effects on the friction and wear behaviors of the engine oil. Thus, it still has a high potential to be widely used as a transportation fuel for existing gasoline engines
Investigation of laser texture density and diameter on the tribological behavior of hydrogenated DLC coating with line contact configuration
The technique of laser texturing has been gaining popularity in recent years because of its use in enhancement of tribological performance. In this paper, the effect of indirect laser texturing is analyzed on hydrogenated DLC coating under line contact configuration. Most previous research studies have been carried out for point contact configuration. The aim of this study is to investigate the effectiveness of indirect laser textured DLC for cam/tappet contact in an engine. For this reason, this study focuses on line contact. The tribological performance of textures is dependent on their geometric parameters. Therefore, textures' diameters and densities were varied. The results indicated that at a diameter of 50-ÎĽm and 20% density, tribological performance of a cylinder on a coated plate tribo-pair can be enhanced