Air pollution constitutes the major threat to human health, whereas their adverse impacts and underlying mechanisms of different particular matters are not clearly defined.
Ultrafine particles (UFPs) ...are high related to the anthropogenic emission sources, i.e. combustion engines and power plants. Their composition, source, typical characters, oxidative effects, potential exposure routes and health risks were thoroughly reviewed.
UFPs play a major role in adverse impacts on human health and require further investigations in future toxicological research of air pollution.
Unlike PM2.5, UFPs may have much more impacts on human health considering loads of evidences emerging from particulate matters and nanotoxicology research fields. The knowledge of nanotoxicology contributes to the understanding of toxicity mechanisms of airborne UFPs in air pollution. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu.
•High concentration ultrafine particles in urban area constitute realistic health impacts.•Extremely small size and large particle number of UFPs dominate the high toxicity in PM2.5.•Knowledge from nanotoxicology provides insights to understand toxic effects of UFPs.•Airway mucosa constitutes the first barrier to UFPs exposure in respiratory system.
Hydrogenated amorphous carbon (a-C:H) is subjected to abnormal high friction in ambient air, and the possibility to retain an ultra-low friction state remains as a great challenge. Here, nanodiamond ...and graphene were used as solid lubricants to improve the tribological properties of two representative types of a-C:H films with 20 at.% and 40 at.% hydrogen contents, respectively. The results emphasize the exceptionally synergetic lubrication effect of nanodiamond + graphene composite with a mass ratio of 1:1 and a solution-processed concentration of 0.1 mg/mL. An ultra-low friction coefficient of ∼0.02 was achieved for a-C:H (20 at.% H) film, and more strikingly, a dramatic reduction in COF from 0.52 to 0.07 was realized in a-C:H (40 at.% H) film. Meanwhile, the wear rates of the counterparts in both cases are significantly reduced in the presence of nano-lubricants. The lubricity mechanisms are mainly based on the in-situ growth of nanostructured tribolayers. The roles of a-C:H film bonding characteristic and the tribo-induced structural evolution of nano-lubricants in the build-up of anti-friction and wear-resistant tribolayers are discussed. These findings can enrich the understanding of surface modification pathways to a-C:H films via low-dimensional nano-lubricants and help to develop more adaptive and robust solid carbon films.
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Nanocarbon materials have received considerable attention due to their unique structure and properties, which make them promising candidate materials for use in biomedical applications. In this ...review, we discuss the therapeutic applications of spherical nanocarbon materials, including fullerene nanoparticles, carbon nanohorn aggregates, nanodiamonds and porous carbon nanospheres, and their toxicology in biological systems. We put special emphasis on the antitumor effects of these multifunctional nanoparticles, which operate via novel mechanisms in a highly efficient manner. The low toxicities of these spherical nanocarbon materials as well as the possible effects of shape on toxicity are discussed.
Graphene has many excellent optical, electrical and mechanical properties due to its unique two-dimensional structure. High-efficiency preparation of large area graphene film is the key to achieve ...its industrial applications. In this paper, an ultrafast quenching method was firstly carried out to flow a single pulse current through the surface of a Si wafer with a size of 10 mm × 10 mm for growing fully covered graphene film. The wafer surface was firstly coated with a 5-nm-thick carbon layer and then a 25-nm-thick nickel layer by magnetron sputtering. The optimum quenching conditions are a pulse current of 10 A and a pulse width of 2 s. The thus-prepared few-layered graphene film was proved to cover the substrate fully, showing a high conductivity. Our method is simple and highly efficient and does not need any high-power equipment. It is not limited by the size of the heating facility due to its self-heating feature, providing the potential to scale up the size of the substrates easily. Furthermore, this method can be applied to a variety of dielectric substrates, such as glass and quartz.
Graphene has emerged as one of the most promising solid lubricants owing to their exceptional lubricity. The atomically thin nature and its ability to conformally adsorb on the sliding surfaces ...provide unprecedented pathways for modifying the friction and wear behaviors of the mechanical moving parts. Here, the tribological responses of several representative tribo-couples including bare steel, diamond-like carbon and ceramic materials are investigated to explore the potentials of graphene as surface modifier. Specific emphasis is devoted to the graphene-induced reconstruction of the sliding interface and the growth mechanism of nanostructured tribofilms formed on the contact surface using high-resolution microscopic technique. The results reveal the unique properties of graphene regarding the friction reduction and wear protection irrespective of the types of counterpart materials, graphene-processed methods, dry or humid tests environments. Nevertheless, the interfacial features and the bonding characteristics of the tribofilms are diversified in each specific rubbing case, demonstrating the distinguished adaption capacity of graphene to the tribo-testing conditions. The present findings shed light on the lubrication phenomenon of graphene at the microscale and may provide useful design criterion for 2D-based solid lubricants.
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•Graphene-processed lubricants with effective friction-reducing effects are achieved.•The lubricity depends strongly on the material characteristics of the tribo-couple.•The anti-friction tribofilms formed on the contact areas are analyzed to reveal the lubricating mechanisms.•The present findings show the promising application of graphene-based lubricants in engineering fields.
Carbon nanohorn (CNH) aggregates are spherical with a diameter of ∼80
nm. There are thousands of protruding nanohorns at the periphery of each CNH aggregate. However, the interior structure of CNH ...aggregates remains a question. In this work, we used focused ion beam (FIB) to cut CNH aggregates followed by electron microscopy observations. It was revealed that the interior consists of disordered single-layered graphene sheets with a lateral size of up to 10
nm and an interlayer distance of approximately 4–5
Å. The growth mechanism of CNH aggregates was discussed on the basis of this new finding.
In this article, experiments and finite-element (FE) analyses have been conducted in order to study the effects of open-hole and reinforcement on the buckling and failure of the plain-woven fabric ...(PWF) composite I-section beams under shear load. With the shear experiments, the buckling and failure characteristics of the PWF composite beams have been obtained, and experimental results of the beams in perfect conditions are compared with the results from the specimens with open-hole and reinforcement in the web region. FE analyses for the composite beams are then carried out with the assistance of the multi-scale method proposed for the PWF composites. With the comparison between the experimental and numerical results, the composite beams’ FE models and the utilized calculation methods are proved to be feasible. According to the parametric study based on the validated models and the multi-scale methods, it is found that the existence of the open-hole decreases the flexural rigidity of the beams’ web region and introduces the stress concentration, which further reduces the structural stability and the shear carrying capacity of the composite beams. With the effects of restraining the structural off-plane deformation and relieving the hole-edge stress concentration, the intercalation reinforcement could effectively improve the bearing performance of the PWF composite beams with open-holes.
Serine/threonine kinase 11 (STK11) is one member of the serine/threonine kinase family, which is involved in regulating cell polarity, apoptosis, and DNA damage repair. In lung adenocarcinoma (LUAD), ...it can play as one tumor suppressor and always be mutated. In this study, we aimed to assess the relevance of STK11 mutations in LUAD, in which we also studied the correlation among immune cell infiltration, drug sensitivity, and cellular processes. By performing the bioinformatics analysis of the Cancer Genome Atlas (TCGA) about LUAD patients, we found that the mutation efficiency of STK11 mutations is about 19%. Additionally, the differentially expressed gene analysis showed that there were 746 differentially expressed genes (DEGs) between LUAD patients with and without STK11 mutations. Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analysis showed that the DEGs were enriched in various tumorigenesis signaling pathways and metabolic processes. Among these DEGs, the top ranking 21 genes were found that they were more frequently mutated in the STK11 mutation group than in the wild-type group (p-value<0.01). Finally, the LUAD patients with STK11 mutations suffered the worse immune cell infiltration levels than the LUAD patients with wild-type. The STK11 gene copy number was correlated with immune cell infiltration. Aiming to develop the therapeutic drugs, we performed Genomics of Drug Sensitivity in Cancer (GDSC) data to identify the potential therapeutic candidate and the results showed that Nutlin-3a(-) may be a sensitive drug for LUAD cases harboring STK11 mutations. The specific genes and pathways shown to be associated with LUAD cases involving STK11 mutations may serve as targets for individualized LUAD treatment.
Hydrogenated amorphous carbon (a-C:H) films are capable of providing excellent superlubricating properties, which have great potential serving as self-lubricating protective layer for mechanical ...systems in extreme working conditions. However, it is still a huge challenge to develop a-C:H films capable of achieving robust superlubricity state in vacuum. The main obstacle derives from the lack of knowledge on the influencing mechanism of deposition parameters on the films bonding structure and its relation to their self-lubrication performance. Aiming at finding the optimized deposition energy and revealing its influencing mechanism on superlubricity, a series of highly-hydrogenated a-C:H films were synthesized with appropriate ion energy, and systematic tribological experiments and structural characterization were conducted. The results highlight the pivotal role of ion energy on film composition, nanoclustering structure, and bonding state, which determine mechanical properties of highly-hydrogenated a-C:H films and surface passivation ability and hence their superlubricity performance in vacuum. The optimized superlubricity performance with the lowest friction coefficient of 0.006 coupled with the lowest wear rate emerges when the carbon ion energy is just beyond the penetration threshold of subplantation. The combined growth process of surface chemisorption and subsurface implantation is the key for a-C:H films to acquire stiff nanoclustering network and high volume of hydrogen incorporation, which enables a robust near-frictionless sliding surface. These findings can provide a guidance towards a more effective manipulation of self-lubricating a-C:H films for space application.
This study investigated the frictional properties of HPMC under different load and concentration conditions through friction experiments and surface characterization. The study aimed to explore and ...reveal the influence of load and concentration on the frictional properties of HPMC, as well as its anti−wear mechanism. The results of the study indicated that under the same solution concentration, the effect of load on the friction coefficient of HPMC was not significant. Specifically, for samples with low concentration (C−0.2), the wear ratio of HPMC under a 4 N load (1.01 × 10−11 mm3·N−1·m−1) was significantly lower than the wear ratio under a 2 N load (1.71 × 10−10 mm3·N−1·m−1). The orientation−driven formation of graphite−like carbon nanosheets, initiated by the decomposition of HPMC short chains, created a tribofilm−containing organic−chain mixed nanosheet on the sliding contact surface, which prevented direct contact between the upper and lower friction pairs. This achieved the anti−wear mechanism of two−body wear (tribo−film of an mDLC−coated ball and tribo−film of a GLC−coated Si wafer), ultimately leading to a state of ultra−low wear at the interface. The excellent anti−wear performance of HPMC suggests its potential as a candidate for the next generation of environmentally friendly bio−based solid lubricants.
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