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"Cheng, Y."
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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 mu g 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
Highly efficient photocathodes for dye-sensitized tandem solar cells
Thin-film dye-sensitized solar cells (DSCs) based on mesoporous semiconductor electrodes are low-cost alternatives to conventional silicon devices. High-efficiency DSCs typically operate as photoanodes (n-DSCs), where photocurrents result from dye-sensitized electron injection into n-type semiconductors. Dye-sensitized photocathodes (p-DSCs) operate in an inverse mode, where dye-excitation is followed by rapid electron transfer from a p-type semiconductor to the dye (dye-sensitized hole injection). Such p-DSCs and n-DSCs can be combined to construct tandem solar cells (pn-DSCs) with a theoretical efficiency limitation well beyond that of single-junction DSCs (ref. 4). Nevertheless, the efficiencies of such tandem pn-DSCs have so far been hampered by the poor performance of the available p-DSCs (refs 3, 5-15). Here we show for the first time that p-DSCs can convert absorbed photons to electrons with yields of up to 96%, resulting in a sevenfold increase in energy conversion efficiency compared with previously reported photocathodes. The donor-acceptor dyes, studied as photocathodic sensitizers, comprise a variable-length oligothiophene bridge, which provides control over the spatial separation of the photogenerated charge carriers. As a result, charge recombination is decelerated by several orders of magnitude and tandem pn-DSCs can be constructed that exceed the efficiency of their individual components.
Journal Article
The rising incidence of Acanthamoeba keratitis: A 7-year nationwide survey and clinical assessment of risk factors and functional outcomes
To evaluate the incidence of Acanthamoeba keratitis in the Netherlands between 2009 and 2015 and to analyse predicting factors for treatment outcome.
Patient characteristics, diagnostic methods, diagnostic delay, therapy prior to and after diagnosis, and visual outcome were obtained from medical files of all patients diagnosed with Acanthamoeba keratitis in the Netherlands between 2009 and 2015. A logistic regression analysis on treatment failure, defined as a best corrected visual acuity of less than 20/40 Snellen decimals (i.e. >0.3 logMAR or an approximate loss of three lines of visual acuity) and/or the need for keratoplasty, was performed to determine predicting factors.
Two hundred and twenty-four eyes of 224 patients were included. Ninety-five percent of the patients were contact lens wearers, of whom 74% wore soft contact lenses. The number of cases increased from 16 in 2009 to 49 in 2015. This resulted in an estimated incidence of 1 in 21,000 for soft contact lens wearers in 2015. Eighty-seven eyes (39%) met the criteria for treatment failure. In a multivariable regression analysis, higher age at presentation, a higher severity stage and corticosteroid use before diagnosis were positively correlated with treatment failure. Early referral to a cornea specialist was associated with better clinical outcomes.
Although Acanthamoeba keratitis is still a relatively uncommon disease, the incidence in soft contact lens wearers has increased to reach 1 in 21,000 in 2015. Treatment failure occurred in 39% of cases, with age, higher severity stage, corticosteroid use before diagnosis and indirect referral to a cornea specialist as important risks factors.
Journal Article
Pembrolizumab plus Chemotherapy in Metastatic Non–Small-Cell Lung Cancer
The addition of pembrolizumab to chemotherapy for metastatic lung cancer without
EGFR
or
ALK
mutations resulted in better progression-free and overall survival than chemotherapy alone. Immune-related adverse effects were more common with the combination.
Journal Article
Stress Corrosion Cracking of Pipelines
This book describes the scientific, technical and practical aspects of stress corrosion cracking (SCC) occurring on pipelines. It summarizes the phenomena, mechanisms and management of pipeline SCC from in-service experiences and laboratory experiments to the range of modeling prediction for SCC initiation and propagation, and the remaining uncertainties that affect the understanding of pipeline SCC. For completeness, the book also includes fundamentals of SCC as well as the author's recent research results on pipeline SCC of high-strength pipeline steel.
eBook
Increased expression of programmed cell death protein 1 on NK cells inhibits NK-cell-mediated anti-tumor function and indicates poor prognosis in digestive cancers
Abnormal expression of activating/inhibitory receptors leads to natural killer (NK) cells dysfunction in tumor. Here we show that programmed cell death protein 1 (PD-1), a well-known immune checkpoint of T cells, is highly expressed on peripheral and tumor-infiltrating NK cells from patients with digestive cancers including esophageal, liver, colorectal, gastric and biliary cancer. The increased PD-1 expression on NK cells indicates poorer survival in esophageal and liver cancers. Blocking PD-1/PD-L1 signaling markedly enhances cytokines production and degranulation and suppresses apoptosis of NK cells in vitro. PD-1/PD-L1 exerts inhibitory effect through repressing the activation of PI3K/AKT signaling in NK cells. More importantly, a PD-1 blocking antibody was found to significantly suppress the growth of xenografts in nude mice, and this inhibition of tumor growth was completely abrogated by NK depletion. These findings strongly suggested that PD-1 is an inhibitory regulator of NK cells in digestive cancers. PD-1 blockade might be an efficient strategy in NK cell-based tumor immunotherapy.
Journal Article
Mapping Asian anthropogenic emissions of non-methane volatile organic compounds to multiple chemical mechanisms
An accurate speciation mapping of non-methane volatile organic compounds (NMVOC) emissions has an important impact on the performance of chemical transport models (CTMs) in simulating ozone mixing ratios and secondary organic aerosols. Taking the INTEX-B Asian NMVOC emission inventory as the case, we developed an improved speciation framework to generate model-ready anthropogenic NMVOC emissions for various gas-phase chemical mechanisms commonly used in CTMs in this work, by using an explicit assignment approach and updated NMVOC profiles. NMVOC profiles were selected and aggregated from a wide range of new measurements and the SPECIATE database v.4.2. To reduce potential uncertainty from individual measurements, composite profiles were developed by grouping and averaging source profiles from the same category. The fractions of oxygenated volatile organic compounds (OVOC) were corrected during the compositing process for those profiles which used improper sampling and analyzing methods. Emissions of individual species were then lumped into species in different chemical mechanisms used in CTMs by applying mechanism-dependent species mapping tables, which overcomes the weakness of inaccurate mapping in previous studies. Emission estimates for individual NMVOC species differ between one and three orders of magnitude for some species when different sets of profiles are used, indicating that source profile is the most important source of uncertainties of individual species emissions. However, those differences are diminished in lumped species as a result of the lumping in the chemical mechanisms. Gridded emissions for eight chemical mechanisms at 30 min × 30 min resolution as well as the auxiliary data are available at http://mic.greenresource.cn/intex-b2006. The framework proposed in this work can be also used to develop speciated NMVOC emissions for other regions.
Journal Article
c-Myc suppresses microRNA-29b to promote tumor aggressiveness and poor outcomes in non-small cell lung cancer by targeting FHIT
The dual role of the microRNA-29 (miR-29) family in tumor progression and metastasis in solid tumors has been reported. Evidence for the role of miR-29 in tumor malignancy and its prognostic value in overall survival (OS) and relapse-free survival (RFS) in non-small cell lung cancer (NSCLC) remains conflicting. Mechanistic studies presented herein demonstrated that c-Myc suppressed the expression of miR-29b, promoting soft agar growth and invasion capability in lung cancer cells. Interestingly, the decrease in the expression of miR-29b by c-Myc is responsible for soft agar growth and invasiveness mediated by FHIT loss due to promoter methylation. Among patients, low expression of miR-29b and FHIT was more common in tumors with high c-Myc expression than in tumors with low c-Myc expression. Kaplan-Meier and Cox regression analysis showed that tumors with high c-Myc, low miR-29b and low FHIT expression had shorter OS and RFS periods than their counterparts. In conclusion, the decrease in the expression of miR-29b by c-Myc may be responsible for FHIT loss-mediated tumor aggressiveness and for poor outcome in NSCLC. Therefore, we suggest that restoration of the miR-29b expression using the c-Myc inhibitor might be helpful in suppressing tumor aggressiveness mediated by FHIT loss and consequently improving outcomes in NSCLC patients with tumors with low expression of FHIT.
Journal Article
Ultra-sparse metasurface for high reflection of low-frequency sound based on artificial Mie resonances
Acoustic metamaterials offer great flexibility for manipulating sound waves and promise unprecedented functionality, ranging from transformation acoustics, super-resolution imaging to acoustic cloaking. However, the design of acoustic metamaterials with exciting functionality remains challenging with traditional approaches using classic acoustic elements such as Helmholtz resonators and membranes. Here we demonstrate an ultraslow-fluid-like particle with intense artificial Mie resonances for low-frequency airborne sound. Eigenstate analysis and effective parameter retrieval show two individual negative bands in the single-size unit cell, one of which exhibits a negative bulk modulus supported by the monopolar Mie resonance, whereas the other exhibits a negative mass density induced by the dipolar Mie resonance. The unique single-negative nature is used to develop an ultra-sparse subwavelength metasurface with high reflectance for low-frequency sound. We demonstrate a 0.15λ-thick, 15%-filling ratio metasurface with an insertion loss over 93.4%. The designed Mie resonators provide diverse routes to construct novel acoustic devices with versatile applications.
Journal Article