Global burden and strength of evidence for 88 risk factors in 204 countries and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

Background: Understanding the health consequences associated with exposure to risk factors is necessary to inform public health policy and practice. To systematically quantify the contributions of risk factor exposures to specific health outcomes, the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 aims to provide comprehensive estimates of exposure levels, relative health risks, and attributable burden of disease for 88 risk factors in 204 countries and territories and 811 subnational locations, from 1990 to 2021. Methods: The GBD 2021 risk factor analysis used data from 54 561 total distinct sources to produce epidemiological estimates for 88 risk factors and their associated health outcomes for a total of 631 risk–outcome pairs. Pairs were included on the basis of data-driven determination of a risk–outcome association. Age-sex-location-year-specific estimates were generated at global, regional, and national levels. Our approach followed the comparative risk assessment framework predicated on a causal web of hierarchically organised, potentially combinative, modifiable risks. Relative risks (RRs) of a given outcome occurring as a function of risk factor exposure were estimated separately for each risk–outcome pair, and summary exposure values (SEVs), representing risk-weighted exposure prevalence, and theoretical minimum risk exposure levels (TMRELs) were estimated for each risk factor. These estimates were used to calculate the population attributable fraction (PAF; ie, the proportional change in health risk that would occur if exposure to a risk factor were reduced to the TMREL). The product of PAFs and disease burden associated with a given outcome, measured in disability-adjusted life-years (DALYs), yielded measures of attributable burden (ie, the proportion of total disease burden attributable to a particular risk factor or combination of risk factors). Adjustments for mediation were applied to account for relationships involving risk factors that act indirectly on outcomes via intermediate risks. Attributable burden estimates were stratified by Socio-demographic Index (SDI) quintile and presented as counts, age-standardised rates, and rankings. To complement estimates of RR and attributable burden, newly developed burden of proof risk function (BPRF) methods were applied to yield supplementary, conservative interpretations of risk–outcome associations based on the consistency of underlying evidence, accounting for unexplained heterogeneity between input data from different studies. Estimates reported represent the mean value across 500 draws from the estimate's distribution, with 95% uncertainty intervals (UIs) calculated as the 2·5th and 97·5th percentile values across the draws. Findings: Among the specific risk factors analysed for this study, particulate matter air pollution was the leading contributor to the global disease burden in 2021, contributing 8·0% (95% UI 6·7–9·4) of total DALYs, followed by high systolic blood pressure (SBP; 7·8% [6·4–9·2]), smoking (5·7% [4·7–6·8]), low birthweight and short gestation (5·6% [4·8–6·3]), and high fasting plasma glucose (FPG; 5·4% [4·8–6·0]). For younger demographics (ie, those aged 0–4 years and 5–14 years), risks such as low birthweight and short gestation and unsafe water, sanitation, and handwashing (WaSH) were among the leading risk factors, while for older age groups, metabolic risks such as high SBP, high body-mass index (BMI), high FPG, and high LDL cholesterol had a greater impact. From 2000 to 2021, there was an observable shift in global health challenges, marked by a decline in the number of all-age DALYs broadly attributable to behavioural risks (decrease of 20·7% [13·9–27·7]) and environmental and occupational risks (decrease of 22·0% [15·5–28·8]), coupled with a 49·4% (42·3–56·9) increase in DALYs attributable to metabolic risks, all reflecting ageing populations and changing lifestyles on a global scale. Age-standardised global DALY rates attributable to high BMI and high FPG rose considerably (15·7% [9·9–21·7] for high BMI and 7·9% [3·3–12·9] for high FPG) over this period, with exposure to these risks increasing annually at rates of 1·8% (1·6–1·9) for high BMI and 1·3% (1·1–1·5) for high FPG. By contrast, the global risk-attributable burden and exposure to many other risk factors declined, notably for risks such as child growth failure and unsafe water source, with age-standardised attributable DALYs decreasing by 71·5% (64·4–78·8) for child growth failure and 66·3% (60·2–72·0) for unsafe water source. We separated risk factors into three groups according to trajectory over time: those with a decreasing attributable burden, due largely to declining risk exposure (eg, diet high in trans-fat and household air pollution) but also to proportionally smaller child and youth populations (eg, child and maternal malnutrition); those for which the burden increased moderately in spite of declining risk exposure, due largely to population ageing (eg, smoking); and those for which the burden increased considerably due to both increasing risk exposure and population ageing (eg, ambient particulate matter air pollution, high BMI, high FPG, and high SBP). Interpretation: Substantial progress has been made in reducing the global disease burden attributable to a range of risk factors, particularly those related to maternal and child health, WaSH, and household air pollution. Maintaining efforts to minimise the impact of these risk factors, especially in low SDI locations, is necessary to sustain progress. Successes in moderating the smoking-related burden by reducing risk exposure highlight the need to advance policies that reduce exposure to other leading risk factors such as ambient particulate matter air pollution and high SBP. Troubling increases in high FPG, high BMI, and other risk factors related to obesity and metabolic syndrome indicate an urgent need to identify and implement interventions

Knowledge based data boosting exposition on CNT-engineered carbon composites for machine learning

Machine Learning (ML) is useful in predictive analytic or prognostic modeling for materials and engineering. It is, however, challenging to gather sufficient and representative data. Experiments are possible only in small numbers due to specialty materials, manufacturing, infrastructure, and testing involved. Simulation and numerical models need skills and appropriate validation. If the dataset at hand is too small in size to train ML, professionals tend to create synthetic data, which may not necessarily meet the quality required of the new data. A Knowledge-based Data Boosting (KDB) process, named COMPOSITES, that rationally addresses data sparsity without losing data quality is systematically discussed in this paper. A study on inter-ply fracture toughness of carbon nanotube (CNT) engineered carbon fibre reinforced polymer (CFRP) composite laminates is used to demonstrate the KDB process. This involved strengthening of inter-ply interfaces using CNT advocated for improving delamination resistance of the CFRP composites. It is demonstrated that the KDB process helped augment the dataset reliably and improved the best fit regression lines. The process also made it possible to define boundaries and limitations of the augmented dataset. Such sanitised dataset is certainly valuable for prognostic modeling.Accepted versio

Enhancement Studies on Manufacturing and Properties of Novel Silica Aerogel Composites

Silica Aerogel composites are ultra-low density, highly porous foam-like materials that exhibit excellent thermal insulation and high strain recovery characteristics. In the present work, environment-friendly silica aerogel composites are fabricated using silica aerogel granules with bio based porcine-gelatin as the binding agent dissolved in water and by further drying the mix at sub-zero condition. This article focuses on improvement studies carried on the mold design and the manufacturing process to achieve better geometric compliance for the silica aerogel composites. It also presents contact angle measurements, compressive behavior under different cycles of loading, time dependent behavior and flexural response of the composites. The influence of additives, such as fumed silica and carbon nanotubes on mechanical properties of the composites is also deliberated. Water droplet contact angle experiments confirmed the ultra-hydrophobic nature of the composites. The mechanical properties were characterized under cyclic loading-unloading compression and three-point flexure tests. On successive compression in three consecutive load cycles, the strain and thickness recovery were found to decrease by around 30%. The flexural properties of the aerogel composites were investigated using it as the core covered by thin carbon composite face sheets. It was found that the flexural strength and the failure strain of this aerogel sandwich composites is approximately half of the conventional nomex honeycomb sandwich equivalent

Outgassing studies on thermal control coatings for micro‐satellites

Purpose – With the advent of micro‐satellites technology, passive thermal controls in the form of surface coatings have become important for onboard thermal management. The thermal coatings, however, suffer outgassing and mass loss due to their direct exposure to harsh thermal environment and high vacuum in space. The purpose of this paper is to discuss testing and evaluation on outgassing of AA6061‐T6 specimen surfaces treated with various types of anodized coatings of different thicknesses and the related mass loss before and after thermal exposure. Design/methodology/approach – Samples of chromic acid, polytetrafluroethylene polymer, and black‐ and brown‐colour anodized aluminum coupons were subjected to high vacuum (∼1×10−6 mbar), before and after thermal baking at 120°C. Spectrum analysis of the outgassed material to know their quantities and proportion was conducted subsequently using a Quadrupole mass analyzer. Findings – The surface coatings under study complied with the spacecraft requirements for the mass loss of less than 1 percent of the total mass of the coating material used for that surface. The mass spectrum analysis of the outgassed material indicated that the majority of the coating mass loss was on account of water vapours and organic solvents like ethylene. Practical implications – These results provided a good insight into the reliability of the coating materials studied and the bonding between the aluminum substrates and the coatings. Originality/value – The coatings and the technology needed for their application on aluminum are readily available. The present work on outgassing and mass loss in a simulated space environment will provide useful insight on their usage for micro‐satellites.Accepted versio

Enhancement in fatigue performance of FRP composites with various fillers: a review

Engineering structures are often subjected to fluctuating loads, which onset materials' fatigue and deleteriously affect their service life. This becomes crucial for fiber reinforced polymer (FRP) composite structures because their fatigue response is different from metals, complex, and can lead to catastrophic consequences. The desire and need to improve fatigue performance have been progressive and have led to the use of fillers as secondary reinforcement in matrix. In fact, ceramic, carbonaceous, clay, and polymer fillers have been extensively studied to enhance mechanical performance, but very limited study is available on the fatigue performance of FRP composites modified with fillers. Therefore, this work includes an extensive review on the use of fillers reinforcement to improve the fatigue performance of FRP composites, especially with thermoset and thermoplastic matrices. The various fatigue improvement mechanisms contributed by fillers are identified and explained. A comparison is made among the available literature to map the enhancement in the fatigue life of carbon and glass reinforced composites and the filler content used therein. This review shows that carbonaceous and polymer fillers have a positive reinforcing effect and provide maximum improvement in fatigue life by a factor of 11 and 100, respectively. There is enough evidence that the addition of fillers enhances the fatigue strength of thermosets composites, whereas not enough data is available yet to understand the fatigue performance of thermoplastic composites with fillers in entirety. In the end, the future potential and the likely challenges are summarized and discussed

Impact damage resistance of CFRP prepreg laminates with dispersed CSP particles into ply interfaces

The effects of incorporating core shell polymer (CSP) particles within interply interfaces on the impact response of CFRP prepreg laminates are investigated. The impact tests were conducted on samples without and with CSP particles into the ply interfaces. The loads versus time curves were examined to determine the impact response and the associated energy absorption by the laminates were studied. The results indicate that both, the peak load of the laminates improved by 41% and damping index (DI) reduced by 90% with the dispersion of 51 g/m2 of CSP particles within the prepreg ply interfaces of the laminates. It was noted that the CSP particles shielded the composites from the initial severity of impact. The energy absorbing mechanisms altered the supercritical response of the laminate to subcritical due to increase in the elastic energy stored within the laminates with CSP particles thereby changing the energy absorption modes. It was observed from macroscopic observations and SEM images of the damage sites that the damage mechanism and patterns changed and the extent of damage reduced with the addition of CSP particles

High strain recovery with improved mechanical properties of gelatin–silica aerogel composites post-binding treatment

Silica aerogels are very light and highly porous materials that are intriguingly and complexly networked with large internal surface area, high hydrophobicity with extremely low density and thermal conductivity. These features make them ideal choice for applications as thermal and acoustics insulators or as optical, electrical and energy storing devices. However, their exploitation for structural applications is primarily inhibited by their brittleness. The brittleness of the silica aerogels makes their processing and handling difficult. Volumetric shrinkage occurs, which becomes more apparent at elevated temperatures. While there are hybrid silica aerogels doped with materials such as polymer, ceramics, metals in the market, the improvements in the mechanical properties are compromised with tremendous increase in density and reduction in the insulation performance. Post synthesis binding treatment of silica aerogels composites are not extensively explored due to the chemically inert trimethylsilyl (TMS) terminal groups on the surface of the hydrophobic silica aerogels. This paper discusses a unique fabrication method of developing a ductile silica aerogel composite solid via post synthesis binding treatment. Gelatin silica aerogel (GSA) and GSA-sodium dodecyl sulfate (SDS) composite blocks were produced by mixing hydrophobic aerogel granulates in a gelatin-SDS foamed solution by frothing method. The entire fabrication process and grounds for using a controlled % of gelatin as the main binder and SDS as an additive are explained. The compression testing of the blocks is presented. The associated strain recovery, - an unusual phenomenon with brittle silica aerogels, observed upon unloading is highlighted and studied. The microstructure and surface characterization of these composites was examined via FESEM/EDX and XPS/ESCA respectively. The dependency of process variables involved were analyzed through Analysis of Variance (ANOVA) model. Empirical models that relate the composition of gelatin, aerogel and SDS to achieve the optimal strain recovery with the associated compressive modulus and strength and density are established. The transition from brittleness to ductility is measured in terms of compressive stress versus strain behavior for various mass fractions of gelatin and SDS. The test data presented indicate analogous behavior of these to creep-like behavior of a material typically identified as the primary, secondary and tertiary stages. The rationale and mechanisms behind such creep-like three stages are explained using schematic diagramsAccepter versio

Effect of roller pressure and base prepreg layer on tensile and flexural properties of CFRP laminates fabricated using automated fiber placement

Composites can be manufactured in numerous ways. Among the available methods, Automated Fiber Placement (AFP) is the most advanced and latest technology utilized by companies for aerospace and other projects. Although it offers many benefits, it has unique manufacturing challenges and quality issues. The presence of tow placement defects such as tow gaps, tow overlaps, twisted tows, incomplete tows, and missing tows in the AFP process are causes for concern as these lead to a decrease in the mechanical performance of the fabricated parts. Although it is not possible to completely avoid the occurrence of defects, optimizing key process parameters is a possible way to minimize them. Roller pressure is one such parameter. If it is too high, it can lead to wider and thinner tows and if it is too low, the towpreg may not stick properly to the substrate and hence, not conform to curvatures. In this work, test layups of different configurations using carbon (T700SC-24K-50C) towpreg with epoxy (UF 3376-100) as the matrix system were prepared at different compaction roller pressures (2 bar, 3.5 bar, and 5 bar), with and without the presence of base prepreg layers. Tensile and bending tests were respectively carried out according to ASTM D3039 and ASTM D7264 to study the effects of these process parameters on the layup defects. From the test results, it is found that using a compaction roller pressure of 3.5 bar and a base prepreg layer of the same material as the towpreg, leads to minimum defects, and hence, to the best tensile and bending properties.Published versio

Enhancing interlaminar fracture characteristics of woven CFRP prepreg composites through CNT dispersion

The inter-ply characteristics of polymeric prepreg composites influence their interlaminar fracture toughness and the overall performance. This article embarks on engineering the inter-ply interfaces of carbon fiber reinforced polymer (CFRP) composites. A novel and practical technique for dispersion of multi-walled carbon nanotubes (MWCNTs) onto woven CFRP prepreg is presented. The interlaminar fracture toughness of these CFRP lay-ups was evaluated experimentally and compared with the regular (without any CNTs) specimen. Double cantilever beam and end notch flexure tests were conducted for interlaminar fracture studies. It was observed that the addition of MWCNTs in between the CFRP prepreg plies helps in strengthening the interface. There existed an optimum percentage in which these nanofillers should be added. The presence of nanotubes increased fiber bridging within the ply interfaces, which in turn controlled the inter-ply crack propagation. The findings and the mechanisms are discussed using the test data, SEM pictures, schematics, and scans of the fractured surfaces