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Wang K.,Tsinghua University | Ma L.,Tsinghua University | Xu X.,Beijing Forestry UniversityBeijing | Wen S.,Tsinghua University | Zhang Y.,Tsinghua University
Langmuir | Year: 2015

Triboluminescence (TL) has gained increasing attention in the past two decades due to its potential for many applications such as an in situ damage sensor, X-ray source, spectroscopic probe, and optical switch. So far the mechanisms by which TL is excited are not well understood. We have investigated the TL emitted during the sliding contact between silica wafer and YSZ (yttria-stabilized zirconia) wafers in CO2 gas, ambient air, and vacuum. We discovered that the mean intensity of photons emitted in CO2 gas is nearly a hundred times stronger than that in air. TL induced in the sliding experiment is proposed to be due to a combination of chemical luminescence, impurities and vacancies luminescence. In addition, the intensity of the light emission of YSZ may be controlled by changing the concentration of CO2 gas. © 2015 American Chemical Society. Source


Wang X.,Tsinghua University | Wang X.,Beijing Forestry UniversityBeijing | Shi G.,Tsinghua University
Physical Chemistry Chemical Physics | Year: 2015

Pristine graphene and chemically modified graphenes (CMGs, e.g., graphene oxide, reduced graphene oxide and their derivatives) can react with a variety of chemical substances. These reactions have been applied to modulate the structures and properties of graphene materials, and to extend their functions and practical applications. This perspective outlines the chemistry of graphene, including functionalization, doping, photochemistry, catalytic chemistry, and supramolecular chemistry. The mechanisms of graphene related reactions will be introduced, and the challenges in controlling the chemical reactions of graphene will be discussed. This journal is © the Owner Societies. Source


Yan H.,Beijing Forestry UniversityBeijing | Yan H.,Zhejiang Agriculture And forestry University | Dong L.,Beijing Forestry UniversityBeijing
Journal of Environmental Health Science and Engineering | Year: 2015

Abstract Background: This study investigated the microclimatic behavior of different land cover types in urban parks and, the correlation between air temperature and land cover composition to understand how land cover affects outdoor thermal environment during hot summer. Methods: To address this issue, air temperatures were measured on four different land cover types at four observation sites inside an urban park in Beijing, China, meanwhile, the land cover composition of each site was quantified with CAD, by drawing corresponding areas on the aerial photographs. Results: The results showed that the average air temperature difference among four land cover types was large during the day and small during the night. At noon, the average air temperature differed significantly among four land cover types, whereas on night, there was no significant difference among different land cover types. Results of the linear regression indicated that during daytime, there was a strong negative correlation between air temperature and percent tree cover; while at nighttime, a significant negative correlation was observed between air temperature and percent lawn cover. It was shown that as the percent tree cover increased by 10 %, the air temperature decreased by 0.26 °C during daytime, while as the percent lawn cover increased by 10 %, the air temperature decreased by 0.56 °C during nighttime. Conclusions: Results of this study help to clarify the effects of land cover on urban outdoor thermal environment, and can provide assistance to urban planner and designer for improving green space planning and design in the future. © 2015 Yan and Dong; licensee BioMed Central. Source


Xue Z.,Beijing Forestry UniversityBeijing | Sun X.,Renmin University of China | Li Z.,Shandong University | Mu T.,Renmin University of China
Chemical Communications | Year: 2015

A controllable synthetic route has been developed for the preparation of chitosan supported Pd catalysts in an ionic liquid, 1-butyl-3-methylimidazolium acetate ([Bmim]OAc), by using compressed CO2 as the anti-solvent and regulator. It was found that the dispersion of Pd particles on chitosan and the catalytic activity of the as-prepared catalysts for the hydrogenation of styrene could be tuned by changing the pressure of CO2. This journal is © The Royal Society of Chemistry. Source


Zhang D.,Beijing Forestry UniversityBeijing | Yan L.,Beijing Forestry UniversityBeijing | Zhang M.,Beijing Forestry UniversityBeijing | Chu H.,Wildlife Conservation Office of Altay Prefecture | And 4 more authors.
International Journal of Biological Sciences | Year: 2016

The complete mitogenome of the horse stomach bot fly Gasterophilus pecorum (Fabricius) and a near-complete mitogenome of Wohlfahrt’s wound myiasis fly Wohlfahrtia magnifica (Schiner) were sequenced. The mitogenomes contain the typical 37 mitogenes found in metazoans, organized in the same order and orientation as in other cyclorrhaphan Diptera. Phylogenetic analyses of mitogenomes from 38 calyptrate taxa with and without two non-calyptrate outgroups were performed using Bayesian Inference and Maximum Likelihood. Three sub-analyses were performed on the concatenated data: (1) not partitioned; (2) partitioned by gene; (3) 3rd codon positions of protein-coding genes omitted. We estimated the contribution of each of the mitochondrial genes for phylogenetic analysis, as well as the effect of some popular methodologies on calyptrate phylogeny reconstruction. In the favoured trees, the Oestroidea are nested within the muscoid grade. Relationships at the family level within Oestroidea are (remaining Calliphoridae (Sarcophagidae (Oestridae, Pollenia + Tachinidae))). Our mito-phylogenetic reconstruction of the Calyptratae presents the most extensive taxon coverage so far, and the risk of long-branch attraction is reduced by an appropriate selection of outgroups. We find that in the Calyptratae the ND2, ND5, ND1, COIII, and COI genes are more phylogenetically informative compared with other mitochondrial protein-coding genes. Our study provides evidence that data partitioning and the inclusion of conserved tRNA genes have little influence on calyptrate phylogeny reconstruction, and that the 3rd codon positions of protein-coding genes are not saturated and therefore should be included. © Ivyspring International Publisher. Source

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