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"He, B."
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High dislocation density–induced large ductility in deformed and partitioned steels
A wide variety of industrial applications require materials with high strength and ductility. Unfortunately, the strategies for increasing material strength, such as processing to create line defects (dislocations), tend to decrease ductility. We developed a strategy to circumvent this in inexpensive, medium manganese steel. Cold rolling followed by low-temperature tempering developed steel with metastable austenite grains embedded in a highly dislocated martensite matrix. This deformed and partitioned (D and P) process produced dislocation hardening but retained high ductility, both through the glide of intensive mobile dislocations and by allowing us to control martensitic transformation. The D and P strategy should apply to any other alloy with deformation-induced martensitic transformation and provides a pathway for the development of high-strength, high-ductility materials.
Journal Article
Prevalence and Risk Factors for Frailty Among Community-Dwelling Older People in China: A Systematic Review and Meta-Analysis
To systematically assess the prevalence of frailty, including prefrailty, stratified prevalence according to frailty criteria, gender, age, and region, and the risk factors for frailty in China.
We conducted a systematic literature review and meta-analysis using articles available in 8 databases including PubMed, Cochrane Library, Web of Science, CINAHL Plus, China Knowledge Resource Integrated Database (CNKI), Wanfang Database, Chinese Biomedical Database (CBM), and Weipu Database (VIP).
Crosssectional and cohort data from Chinese community.
Community-dwelling adults aged 65 and older.
Two authors independently extracted data based upon predefined criteria. Where data were available we conducted a meta-analysis of frailty parameters using a random-effects model.
We screened 915 different articles, and 14 studies (81258 participants) were ultimately included in this analysis. The prevalence of frailty and prefrailty in individual studies varied from 5.9% to 17.4% and from 26.8% to 62.8%, respectively. The pooled prevalence of frailty and prefrailty were 10% (95% CI: 8% to 12%, I2 = 97.4%, P = 0.000) and 43% (95% CI: 37% to 50%, I2 = 98.0%, P = 0.000), respectively. The pooled frailty prevalence was 8% for the Fried frailty phenotype, 12% for the frail index, and 15% for the FRAIL scale. Age-stratified meta-analyses showed the pooled prevalence of frailty to be 6%, 15%, and 25% for those aged 65–74, 75–84, and ≥85 years old, respectively. The pooled prevalence of frailty was 8% for males and 11% for females. The pooled prevalence of frailty in Mainland China, Taiwan, and Hong Kong was 12%, 8%, and 14%, respectively. The pooled frailty prevalence was 10% in urban areas and 7% in rural areas. After controlling for confounding variables, increasing age (OR = 1.28, 95% CI: 1.2 to 1.36, I2 = 98.0%, P = 0.000), being female (OR = 1.29, 95% CI: 1.16 to 1.43, I2 =92.7%, P=0.000), activities of daily living (ADL) disability (OR = 1.72, 95% CI: 1.57 to 1.90, I2 = 99.7%, P = 0.000), and having three or more chronic diseases (OR = 1.97, 95% CI: 1.78 to 2.18, I2 = 97.5%, P = 0.000) were associated with frailty.
These findings of this review indicate an overall pooled prevalence of frailty among Chinese community-dwelling older people of 10%. Increasing age, being female, ADL disability, and having three or more chronic diseases were all risk factors for frailty. Further research will be needed to identify additional frailty risk factors in order to better treat and prevent frailty in the community.
Journal Article
Viruses, endoplasmic reticulum stress, and interferon responses
Viral infection induces endoplasmic reticulum (ER) stress and interferon responses. While viral double-stranded RNA intermediates trigger interferon responses, viral polypeptides synthesized during infection stimulate ER stress. Among the interferon-regulated gene products, the double-stranded RNA-dependent protein kinase (PKR) plays a key role in limiting viral replication. Thus, to establish productive infection, viruses have evolved mechanisms to overcome the deleterious effects of PKR. It has become clear that ER stress causes translational attenuation and transcriptional upregulation of genes encoding proteins that facilitate folding or degradation of proteins. Notably, prolonged ER stress triggers apoptosis. Therefore, viruses are confronted with the consequences of ER stress. Emerging evidence suggests that viruses not only interfere with the interferon system involving PKR but also manipulate the programs emanating from the ER in a complex way, which may facilitate viral replication or pathogenesis. This review highlights recent progress in these areas.
Journal Article
A review on deformation mechanisms of metastable β titanium alloys
Over the past few decades, titanium (Ti) alloys containing fully or mostly body-centred cubic
β
phase in metastable state have received considerable interest due to their elevated strength with remarkable ductility. Apart from dislocation slip, the plastic deformation of metastable
β
Ti alloys involves either twinning-induced plasticity (TWIP), transformation-induced plasticity (TRIP), or the complex coupling of both (TWIP/TRIP). The pursuance of better mechanical performance necessitates the fundamental understanding of these various deformation mechanisms and has driven substantial studies. Therefore, the present work reviews recent research on the mechanical behaviour of TWIP and/or TRIP metastable
β
Ti alloys, with special emphasis on the role of different plasticity modes in enhancing work hardening. The effective inhibition to dislocation slip produced by deformation-induced twins and phases which gives rise to the dynamic Hall–Petch effect is discussed in detail since it underpins the TWIP/TRIP engineering. In particular, the correlation between deformation twinning and stress-induced phase transformation is well addressed. It is expected that such review may shed light on the underlying physics of the intricate deformation behaviour of metastable
β
Ti alloys and inspire more studies in designing novel Ti alloys with superior mechanical properties.
Graphical Abstract
Journal Article
High-resolution inventory of technologies, activities, and emissions of coal-fired power plants in China from 1990 to 2010
This paper, which focuses on emissions from China's coal-fired power plants during 1990–2010, is the second in a series of papers that aims to develop a high-resolution emission inventory for China. This is the first time that emissions from China's coal-fired power plants were estimated at unit level for a 20-year period. This inventory is constructed from a unit-based database compiled in this study, named the China coal-fired Power plant Emissions Database (CPED), which includes detailed information on the technologies, activity data, operation situation, emission factors, and locations of individual units and supplements with aggregated data where unit-based information is not available. Between 1990 and 2010, compared to a 479 % growth in coal consumption, emissions from China's coal-fired power plants increased by 56, 335, and 442 % for SO2, NOx, and CO2, respectively, and decreased by 23 and 27 % for PM2.5 and PM10 respectively. Driven by the accelerated economic growth, large power plants were constructed throughout the country after 2000, resulting in a dramatic growth in emissions. The growth trend of emissions has been effectively curbed since 2005 due to strengthened emission control measures including the installation of flue gas desulfurization (FGD) systems and the optimization of the generation fleet mix by promoting large units and decommissioning small ones. Compared to previous emission inventories, CPED significantly improved the spatial resolution and temporal profile of the power plant emission inventory in China by extensive use of underlying data at unit level. The new inventory developed in this study will enable a close examination of temporal and spatial variations of power plant emissions in China and will help to improve the performances of chemical transport models by providing more accurate emission data.
Journal Article
Heterogeneous chemistry: a mechanism missing in current models to explain secondary inorganic aerosol formation during the January 2013 haze episode in North China
Severe regional haze pollution events occurred in eastern and central China in January 2013, which had adverse effects on the environment and public health. Extremely high levels of particulate matter with aerodynamic diameter of 2.5 μm or less (PM2.5) with dominant components of sulfate and nitrate are responsible for the haze pollution. Although heterogeneous chemistry is thought to play an important role in the production of sulfate and nitrate during haze episodes, few studies have comprehensively evaluated the effect of heterogeneous chemistry on haze formation in China by using the 3-D models due to of a lack of treatments for heterogeneous reactions in most climate and chemical transport models. In this work, the WRF-CMAQ model with newly added heterogeneous reactions is applied to East Asia to evaluate the impacts of heterogeneous chemistry and the meteorological anomaly during January 2013 on regional haze formation. As the parameterization of heterogeneous reactions on different types of particles is not well established yet, we arbitrarily selected the uptake coefficients from reactions on dust particles and then conducted several sensitivity runs to find the value that can best match observations. The revised CMAQ with heterogeneous chemistry not only captures the magnitude and temporal variation of sulfate and nitrate, but also reproduces the enhancement of relative contribution of sulfate and nitrate to PM2.5 mass from clean days to polluted haze days. These results indicate the significant role of heterogeneous chemistry in regional haze formation and improve the understanding of the haze formation mechanisms during the January 2013 episode.
Journal Article
Exploring the severe winter haze in Beijing: the impact of synoptic weather, regional transport and heterogeneous reactions
Extreme haze episodes repeatedly shrouded Beijing during the winter of 2012–2013, causing major environmental and health problems. To better understand these extreme events, we performed a model-assisted analysis of the hourly observation data of PM2.5 and its major chemical compositions. The synthetic analysis shows that (1) the severe winter haze was driven by stable synoptic meteorological conditions over northeastern China, and not by an abrupt increase in anthropogenic emissions. (2) Secondary species, including organics, sulfate, nitrate, and ammonium, were the major constituents of PM2.5 during this period. (3) Due to the dimming effect of high loading of aerosol particles, gaseous oxidant concentrations decreased significantly, suggesting a reduced production of secondary aerosols through gas-phase reactions. Surprisingly, the observational data reveals an enhanced production rate of secondary aerosols, suggesting an important contribution from other formation pathways, most likely heterogeneous reactions. These reactions appeared to be more efficient in producing secondary inorganics aerosols than organic aerosols resulting in a strongly elevated fraction of inorganics during heavily polluted periods. (4) Moreover, we found that high aerosol concentration was a regional phenomenon. The accumulation process of aerosol particles occurred successively from cities southeast of Beijing. The apparent sharp increase in PM2.5 concentration of up to several hundred μg m−3 per hour recorded in Beijing represented rapid recovery from an interruption to the continuous pollution accumulation over the region, rather than purely local chemical production. This suggests that regional transport of pollutants played an important role during these severe pollution events.
Journal Article
Three-component fermions with surface Fermi arcs in tungsten carbide
Topological Dirac and Weyl semimetals not only host quasiparticles analogous to the elementary fermionic particles in high-energy physics, but also have a non-trivial band topology manifested by gapless surface states, which induce exotic surface Fermi arcs1,2. Recent advances suggest new types of topological semimetal, in which spatial symmetries protect gapless electronic excitations without high-energy analogues3–11. Here, using angle-resolved photoemission spectroscopy, we observe triply degenerate nodal points near the Fermi level of tungsten carbide with space group \\[P\\bar{6}m2\\] (no. 187), in which the low-energy quasiparticles are described as three-component fermions distinct from Dirac and Weyl fermions. We further observe topological surface states, whose constant-energy contours constitute pairs of ‘Fermi arcs’ connecting to the surface projections of the triply degenerate nodal points, proving the non-trivial topology of the newly identified semimetal state.
Journal Article
High-resolution mapping of vehicle emissions in China in 2008
This study is the first in a series of papers that aim to develop high-resolution emission databases for different anthropogenic sources in China. Here we focus on on-road transportation. Because of the increasing impact of on-road transportation on regional air quality, developing an accurate and high-resolution vehicle emission inventory is important for both the research community and air quality management. This work proposes a new inventory methodology to improve the spatial and temporal accuracy and resolution of vehicle emissions in China. We calculate, for the first time, the monthly vehicle emissions for 2008 in 2364 counties (an administrative unit one level lower than city) by developing a set of approaches to estimate vehicle stock and monthly emission factors at county-level, and technology distribution at provincial level. We then introduce allocation weights for the vehicle kilometers traveled to assign the county-level emissions onto 0.05° × 0.05° grids based on the China Digital Road-network Map (CDRM). The new methodology overcomes the common shortcomings of previous inventory methods, including neglecting the geographical differences between key parameters and using surrogates that are weakly related to vehicle activities to allocate vehicle emissions. The new method has great advantages over previous methods in depicting the spatial distribution characteristics of vehicle activities and emissions. This work provides a better understanding of the spatial representation of vehicle emissions in China and can benefit both air quality modeling and management with improved spatial accuracy.
Journal Article