Global, regional, and national incidence, prevalence, and mortality of HIV, 1980–2017, and forecasts to 2030, for 195 countries and territories: a systematic analysis for the Global Burden of Diseases, Injuries, and Risk Factors Study 2017

Background Understanding the patterns of HIV/AIDS epidemics is crucial to tracking and monitoring the progress of prevention and control efforts in countries. We provide a comprehensive assessment of the levels and trends of HIV/AIDS incidence, prevalence, mortality, and coverage of antiretroviral therapy (ART) for 1980–2017 and forecast these estimates to 2030 for 195 countries and territories. Methods We determined a modelling strategy for each country on the basis of the availability and quality of data. For countries and territories with data from population-based seroprevalence surveys or antenatal care clinics, we estimated prevalence and incidence using an open-source version of the Estimation and Projection Package—a natural history model originally developed by the UNAIDS Reference Group on Estimates, Modelling, and Projections. For countries with cause-specific vital registration data, we corrected data for garbage coding (ie, deaths coded to an intermediate, immediate, or poorly defined cause) and HIV misclassification. We developed a process of cohort incidence bias adjustment to use information on survival and deaths recorded in vital registration to back-calculate HIV incidence. For countries without any representative data on HIV, we produced incidence estimates by pulling information from observed bias in the geographical region. We used a re-coded version of the Spectrum model (a cohort component model that uses rates of disease progression and HIV mortality on and off ART) to produce age-sex-specific incidence, prevalence, and mortality, and treatment coverage results for all countries, and forecast these measures to 2030 using Spectrum with inputs that were extended on the basis of past trends in treatment scale-up and new infections. Findings Global HIV mortality peaked in 2006 with 1·95 million deaths (95% uncertainty interval 1·87–2·04) and has since decreased to 0·95 million deaths (0·91–1·01) in 2017. New cases of HIV globally peaked in 1999 (3·16 million, 2·79–3·67) and since then have gradually decreased to 1·94 million (1·63–2·29) in 2017. These trends, along with ART scale-up, have globally resulted in increased prevalence, with 36·8 million (34·8–39·2) people living with HIV in 2017. Prevalence of HIV was highest in southern sub-Saharan Africa in 2017, and countries in the region had ART coverage ranging from 65·7% in Lesotho to 85·7% in eSwatini. Our forecasts showed that 54 countries will meet the UNAIDS target of 81% ART coverage by 2020 and 12 countries are on track to meet 90% ART coverage by 2030. Forecasted results estimate that few countries will meet the UNAIDS 2020 and 2030 mortality and incidence targets. Interpretation Despite progress in reducing HIV-related mortality over the past decade, slow decreases in incidence, combined with the current context of stagnated funding for related interventions, mean that many countries are not on track to reach the 2020 and 2030 global targets for reduction in incidence and mortality. With a growing population of people living with HIV, it will continue to be a major threat to public health for years to come. The pace of progress needs to be hastened by continuing to expand access to ART and increasing investments in proven HIV prevention initiatives that can be scaled up to have population-level impact

Understanding the mechanical reinforcement of uniformly dispersed multiwalled carbon nanotubes in alumino-borosilicate glass ceramic

The improvement of mechanical properties of carbon nanotube-reinforced polycrystalline ceramic or glass matrix composites was limited in earlier studies by the difficulties in producing a good dispersion of carbon nanotubes. Additionally, a proper understanding of the reinforcing mechanisms, if any, affecting the mechanical properties of ceramics containing carbon nanotubes is still lacking. We report here the effects of a good dispersion of as much as 10 wt.% multiwalled carbon nanotubes (MWCNTs) on the mechanical properties of dense alumino-borosilicate glass ceramics (ABS) prepared by an ultrasonication-assisted sol-gel technique followed by hot pressing (950 °C; 2 h; Ar atmosphere). The fracture toughness and flexural strength of the nanocomposites increased with increasing MWCNT content up to 10 wt.%. The ABS-10 wt.% MWCNT nanocomposite possessed nearly double the strength of the unreinforced ABS, accompanied by ∼150% improvement in fracture toughness. However, a further increase in MWCNT content to 15 wt.% resulted in a modest deterioration of the mechanical properties due to agglomeration of the MWCNTs. The carbon nanotubes have been observed to bridge crack openings of the order of ∼100 nm and the experimental evidence, along with theoretical analysis, showed that crack bridging provided the major contribution towards the improvement in fracture toughness. Debonding between the MWCNTs and the matrix appeared to occur in the matrix, away from the actual interface. However, the absence of significant pull-out of broken sections of the MWCNTs during fracture, due to failure of the bridging CNTs being predominantly at the crack plane, indicates that further toughening may be available if this mechanism can be activated. © 2010 Acta Materialia Inc

Thermal and electrical properties of aluminoborosilicate glass-ceramics containing multiwalled carbon nanotubes

We report the effects of multiwalled carbon nanotube (MWCNT) dispersions (≤15 wt.%) on the electrical and thermal conductivities of an aluminoborosilicate glass-ceramic. The electrical conductivity was improved by a factor of ∼106 and the thermal conductivity by ∼70%. The uniform MWCNT distribution achieved with up to 10 wt.% MWCNT resulted in a relatively high electrical percolation threshold. Thermal conductivity was limited by the low thermal conductivities of the CVD MWCNTs, length reduction during processing and interfacial resistance. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Fabrication of carbon-nanotube-reinforced glass-ceramic nanocomposites by ultrasonic in situ sol-gel processing

The addition of carbon nanotubes (CNTs) to ceramic or glass matrices has the potential to provide composites with novel properties but composites with a uniform dispersion of undamaged CNTs have proved difficult to make. This paper reports a processing method that overcomes these problems by using a powderless sol-gel route to produce a low-melting point aluminoborosilicate glass matrix, in combination with a dispersion method for the CNTs that is compatible with the sol. Single-walled or multi-walled CNTs were first functionalized by treatment with nitric acid followed by an ammonia-ethanol solution and were then dispersed in a glass precursor sol via ultrasonic processing. After gelation and calcination, the powder was hot pressed to make dense, well dispersed CNT-borosilicate glass composites with CNT contents from 0.5 to 5 wt%. Raman spectroscopy showed that the CNTs had suffered little damage during processing. The formation of cristobalite initially lead to microcracking but this was successfully suppressed by further additions of alumina. The CNTs suppressed cracking around hardness indentations and substantial crack bridging by the CNTs was observed. © 2008 The Royal Society of Chemistry