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GUO LanLan FENG ZaoDong LI XinQing LIU LianYou WANG LiXia 《科学通报(英文版)》2007,52(7):959-966
A 5.3 m lake core was drilled in Baahar Nuur Lake in the Ordos Plateau, and measurements of meangrain size, organic δ 13C (δ 13Corg), organic carbon content (TOC), C/N, carbonate content, carbonate δ 13C(δ 13Ccar) and δ 18O (δ 18Ocar) were conducted for retrieving the Holocene chronosequence of climaticchanges based on 15 AMS 14C dates. The record documented four major stages of climate change inthe Ordos Plateau: (IV) a cold and dry condition before ~7.65 14C ka BP; (III) a warm and humid stagebetween ~7.65 and ~5.40 ka BP; (II) a generally drier and cooler climate since ~5.40 ka BP with twohumid events occurring from ~4.70 to ~4.60 ka BP and from ~4.20 to ~3.70 ka BP, and (I) a dry climatecharacterized by complete desiccation of the lake after 3.70 ka BP. Stage III can be further divided intothree sub-stages: (IIIa) a warm and humid episode from ~7.65 to ~6.70 ka BP, (IIIb) a warm and relativelydry episode from ~6.70 to ~6.20 ka BP, and (IIIc) the magthermal and maghumid episode of the Holo-cene from ~6.20 to ~5.40 ka BP. 相似文献
2.
XinQing Wang Liang Li Min Chen HongXiao Jin DingFeng Jin Min Peng HongLiang Ge 《科学通报(英文版)》2009,54(10):1801-1804
To optimize field emission (FE) property of carbon nanotube (CNT) array on a planar cathode surface, the Fowler-Nordheim formula has been used to discuss the maximum of the emission current density with the floating sphere model in this paper. The emission current density is dominating as the analytical Fowler-Nordheim function of the intertube distance, and the maximum of the emission current density is deduced and discussed. The results indicate that the intertube distance in CNT array critically affects the field enhancement factor and the emission current density, whose maximum occurs at the intertube distance approximating a tenth of the tube height. Considering the emission current density and the field enhancement factor, the FE can be optimized analytically when the intertube distance is about a tenth of the tube height. 相似文献
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ShuiHong Li ChangYu Wu XiaYi Lv Xiao Tang XinQing Zhao Hong Yan Hui Jiang XueMei Wang 《中国科学:化学(英文版)》2012,55(11):2388-2395
Antimicrobial resistance has now become a very serious global public health problem. New drug discovery and development are urgently needed to combat the growing threat of multidrug-resistant (MDR) bacteria. The aim of this study was to explore the potential application of three ferrocene-carborane derivatives as new promising agents to confront the problem of increasing antibiotic resistance. The results of agar diffusion bioassay, minimal inhibitory concentrations (MIC) testing and time-kill assay illustrate their broad-spectrum antimicrobial activities to both American Type Culture Collection (ATCC) control strains and MDR clinical isolates. It is evident that the relevant antimicrobial properties are all in a dose-dependent manner and gradually transform into a bactericidal effect from a bacteriostatic effect with the increasing of the drug concentration. Furthermore, these ferrocene-carborane derivatives have no/little toxic effect on normal cells like HELF cells and lead to little hemolysis at their MICs. This raises the possibility to develop novel antimicrobial drugs using these new ferrocene carborane derivants. 相似文献
4.
LEE XinQing 《科学通报(英文版)》2010,55(16):1667-1673
Low molecule weight carboxylic acids are ubiquitous and important chemical constituents in the troposphere.Seven carboxylic acids in the rainwater of Guiyang and Shangzhong were simultaneously determined by ion chromatography from April 2006 to April 2007.Formic, acetic and oxalic acids were found to be the predominant carboxylic acids.Their volume weighted average concentration (VWA) in the rainwater of Guiyang were 14.24 μmol/L, 9.35 μmol/L and 2.79 μmol/L, respectively;as compared to 4.95 μmol/L, 1.35 μm... 相似文献
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Preparation of polymer-supported hydrated ferric oxide based on Donnan membrane effect and its application for arsenic removal 总被引:2,自引:0,他引:2
QingJian Zhang BingCai Pan XinQing Chen WeiMing Zhang BingJun Pan QuanXing Zhang L. Lv X. S. Zhao 《中国科学B辑(英文版)》2008,51(4):379-385
In the present study a novel technique was proposed to prepare a polymer-supported hydrated ferric oxide (D201-HFO) based on Donnan membrane effect by using a strongly basic anion exchanger D201 as the host material and FeCl3-HCl-NaCl solution as the reaction environment. D201-HFO was found to exhibit higher capacity for arsenic removal than a commercial sorbent Purolite ArsenX. Furthermore, it presents favorable adsorption selectivity for arsenic removal from aqueous solution, as well as satis- factory kinetics. Fixed-bed column experiments showed that arsenic sorption on D201-HFO could re- sult in concentration of this toxic metalloid element below 10 μg/L, which was the new maximum con- centration limit set recently by the European Commission and imposed by the US EPA and China. Also, the spent D201-HFO is amenable to efficient regeneration by NaOH-NaCl solution. 相似文献
6.
Low molecular weight (LMW) organic acids are important and ubiquitous chemical constituents in the atmosphere. A comprehensive
study of the chemical composition of precipitation was carried out from June 2007 to June 2008 at a rural site in Anshun,
in the west of Guizhou Province, China. During this period, 118 rainwater samples were collected and the main LMW carboxylic
acids were determined using ion chromatography. The average pH of rainwater was 4.89 which is a typical acidic value. The
most abundant carboxylic acids were formic acid (volume weight mean concentration: 8.77 μmol L−1) and acetic acid (6.90 μmol L−1), followed by oxalic acid (2.05 μmol L−1). The seasonal variation of concentrations and wet deposition fluxes of organic acids indicated that direct vegetation emissions
were the main sources of the organic acids. Highest concentrations were observed in winter and were ascribed to the low winter
rainfall and the contribution of other air pollution sources northeast of the study area. The ratio of formic and acetic acids
in the precipitation ([F/A]
T
) was proposed as an indicator of pollution source. This suggested that the pollution resulted from direct emissions from
natural or anthropogenic sources. Comparison with acid precipitation in other urban and rural areas in Guizhou showed that
there was a decreasing contribution of LMW organic acids to free acidity and all anions in rainwater from urban to remote
rural areas. Consequently, it is necessary to control emissions of organic acids to reduce the frequency of acid rain, especially
in rural and remote areas. 相似文献
7.
ShuiHong Li ChangYu Wu Xiao Tang ShengPing Gao XinQing Zhao Hong Yan XueMei Wang 《中国科学:化学(英文版)》2013,56(5):595-603
Bacterial biofilms are inherently resistant to antimicrobial agents and are difficult to eradicate with conventional antimicrobial agents, resulting in many persistent and chronic bacterial infections. In this contribution, a new strategy for reversing the biofilm-associated antibiotic resistance has been explored by induction of a carborane ruthenium(II)-arene complex (FcRuSB). Our results demonstrate that the FcRuSB could be utilized as an inducer to efficiently reverse the biofilm-associated antibiotic resistance of multidrug-resistant (MDR) clinical isolates of Staphylococcus aureus and Pseudomonas aeruginosa. The induced effect of FcRuSB is correlated with a considerable decrease in the expression of extracellular matrix proteins (EMP) of the two strains. The considerable decrease of the EMP of induced cells, resulting in the reduction of adherence and biofilm formation ability of the two types of MDR pathogens, and then can cause significantly enhanced sensitivity of them to antibiotics. 相似文献
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