We present an integrated stand-alone software package named KaKs_Calculator 2.0 as an updated version. It incorporates 17 methods for the calculation of nonsynonymous and synonymous substitution rates; among them, we ...We present an integrated stand-alone software package named KaKs_Calculator 2.0 as an updated version. It incorporates 17 methods for the calculation of nonsynonymous and synonymous substitution rates; among them, we added our modified versions of several widely used methods as the gamma series including y-NG, y-LWL, ）,-MLWL, y-LPB, y-MLPB, y-YN and y-MYN, which have been demonstrated to perform better under certain conditions than their original forms and are not implemented in the previous version. The package is readily used for the identification of positively selected sites based on a sliding window across the sequences of interests in 5＇ to 3＇ direction of protein-coding sequences, and have improved the overall performance on sequence analysis for evolution studies. A toolbox, including C＋＋ and Java source code and executable files on both Windows and Linux platforms together with a user instruction, is downloadable from the website for academic purpose at https：//sourceforge.net/projects/kakscalculator2/.展开更多
AIM: To select the optimal antisense accessible sites of survivin, a highly expressed gene in tumor tissues, in order to explore a novel approach to improve biological therapy of gastric cancer. METHODS: The 20 mer ra...AIM: To select the optimal antisense accessible sites of survivin, a highly expressed gene in tumor tissues, in order to explore a novel approach to improve biological therapy of gastric cancer. METHODS: The 20 mer random oligonucleotide library was synthesized, hybridized with in vitro transcribed total survivin cRNA, then digested by RNase H. After primer extension and autoradiography, the antisense accessible sites (AAS) of survivin were selected. Then RNADraw software was used to analyze and choose the AAS with obvious stem-loop structures, according to which the complementary antisense oligonucleotides (AS-ODNs) were synthesized and transferred into survivin highly- expressing gastric cancer cell line MKN-45. Survivin expression was detected by RT-PCR and Western Blotting. Cellular growth activities were assayed by tetrazolium bromide (MTT) colorimetry. Cellular ultrastructure was observed by electronic microscopy, while apoptosis was detected by annexin V-FITC and propidium iodide staining flow cytometry. RESULTS: Thirteen AAS of survivin were selected In vitro. Four AAS with stem-loop structures were chosen, locating at 207-226 bp, 187-206 bp, 126-145 bp and 44-63 bp of survivin cDNA respectively. When compared with non-tranfection controls, their corresponding AS-ODNs (AS-ODN1, AS-ODN2, AS-ODN3 and AS-ODN4) could reduce Survivin mRNA levels in MKN-45 cells by 54.3±±1.1% (t= 6.12, P<0.01), 86.1±±1.0% (t= 5.27, P<0.01), 32.2±±1.3% (t= 7.34, P<0.01) and 56.2±±0.9% (t = 6.45, P<0.01) respectively, while survivin protein levels were decreased by 42.2±±2.5% (t = 6.26, P<0.01), 75.4±±3.1% (t= 7.11, P<0.01), 28.3±±2.0% (t= 6.04, P<0.01) and 45.8±±1.2% (t = 6.38,P<0.01) respectively. After transfection with 600 nmol/L AS-ODN1-AS-ODN4for 24 h, cell growth was inhibited by 28.12±±1.54% (t= 7.62, P<0.01), 38.42±±3.12% (t= 7.75, P<0.01), 21.46±±2.63% (t= 5.94, P<0.01) and 32.12±1.77% (t = 6.17, P<0.01) respectively. Partial cancer cells presented the characteristic morphological changes of apopt展开更多
An investigation of gaseous elemental mercury concentration in atmosphere was conducted at Beijing and Guangzhou urban, Yangtze Delta regional sites and China Global Atmosphere Watch Baseline Observatory （CGAWBO） in...An investigation of gaseous elemental mercury concentration in atmosphere was conducted at Beijing and Guangzhou urban, Yangtze Delta regional sites and China Global Atmosphere Watch Baseline Observatory （CGAWBO） in Mt. Waliguan of remote continental area of China. High temporal resolved data were obtained using automated mercury analyzer RA-915^＋. Results showed that the overall hourly mean Hg^0 concentrations in Mt. Waliguan were 1.7±1.1 ng/m3 in summer and 0.6±0.08 ng/m^3 in winter. The concentration in Yangtze Delta regional site was 5.4±4.1 ng/m^3, which was much higher than those in Waliguan continental background area and also higher than that found in North America and Europe rural areas. In Beijing urban area the overall hourly mean Hg^0 concentrations were 8.3±3.6 ng/m^3 in winter, 6.5±5.2 ng/m^3 in spring, 4.9±3.3 ng/m^3 in summer, and 6.7±3.5 ng/m^3 in autumn, respectively, and the concentration was 13.5±7.1 ng/m^3 in Guangzhou site. The mean concentration reached the lowest value at 14：00 and the highest at 02：00 or 20：00 in all monitoring campaigns in Beijing and Guangzhou urban areas, which contrasted with the results measured in Yangtze Delta regional site and Mr. Waliguan. The features of concentration and diurnal variation of Hg^0 in Beijing and Guangzhou implied the importance of local anthropogenic sources in contributing to the high Hg^0 concentration in urban areas of China. Contrary seasonal variation patterns of Hg^0 concentration were found between urban and remote sites. In Beijing the highest Hg^0 concentration was in winter and the lowest in summer, while in Mt. Waliguan the Hg^0 concentration in summer was higher than that in winter. These indicated that different processes and factors controlled Hg^0 concentration in urban, regional and remote areas.展开更多
Tremendous efforts have been devoted to explore energy-efficient strategies of ammonia synthesis to replace Haber-Bosch process which accounts for 1.4% of the annual energy consumption. In this study, atomically dispe...Tremendous efforts have been devoted to explore energy-efficient strategies of ammonia synthesis to replace Haber-Bosch process which accounts for 1.4% of the annual energy consumption. In this study, atomically dispersed Au_1 catalyst is synthesized and applied in electrochemical synthesis of ammonia under ambient conditions. A high NH＋4 Faradaic efficiency of 11.1 % achieved by our Au_1 catalyst surpasses most of reported catalysts under comparable conditions. Benefiting from efficient atom utilization, an NH＋4 yield rate of 1,305 μg h-1 mg-1Au has been reached, which is roughly 22.5 times as high as that by sup- ported Au nanoparticles. We also demonstrate that by employing our Au_1 catalyst, NH＋4 can be electro- chemically produced directly from N_2 and H_2 with an energy utilization rate of 4.02 mmol kJ-1. Our study provides a possibility of replacing the Haber-Bosch process with environmentally benign and energy-efficient electrochemical strategies.展开更多
CO oxidation has been performed on Co_(3)O_(4) nanobelts and nanocubes as model catalysts.The Co_(3)O_(4) nanobelts which have a predominance of exposed{011}planes are more active than Co_(3)O_(4) nanocubes with expos...CO oxidation has been performed on Co_(3)O_(4) nanobelts and nanocubes as model catalysts.The Co_(3)O_(4) nanobelts which have a predominance of exposed{011}planes are more active than Co_(3)O_(4) nanocubes with exposed{001}planes.Temperature programmed reduction of CO shows that Co_(3)O_(4) nanobelts have stronger reducing properties than Co_(3)O_(4) nanocubes.The essence of shape and crystal plane effect is revealed by the fact that turnover frequency of Co3+sites of{011}planes on Co_(3)O_(4) nanobelts is far higher than that of{001}planes on Co_(3)O_(4) nanocubes.展开更多
In this work, the effectiveness of V2O5-WO3/TiO2 catalysts modified with different CeO2 contents by impregnation and co-precipitation methods on the selective catalytic reduction of NOxby NH3 have been studied compara...In this work, the effectiveness of V2O5-WO3/TiO2 catalysts modified with different CeO2 contents by impregnation and co-precipitation methods on the selective catalytic reduction of NOxby NH3 have been studied comparatively by various experimental techniques. The results showed that the NO conversion of V2O5-WO3/CeO2-TiO2 catalysts modified by co-precipitation method obviously increased with the Ce doping contents in the studied range below 20%（All Ce contents are in mass fractions）, but the NO conversion of V2O5-WO3/CeO2/TiO2 catalysts modified by impregnation methods was lower than V2O5-WO3/CeO2-TiO2 catalysts especially beyond 2.5% Ce doping contents. The V2O5-WO3/CeO2-TiO2 catalysts showed better SCR activity, wider reaction window, and higher sulfur and water resistance. The characterization results elucidated that the modified catalysts by co-precipitation method exhibited higher specific surface area, much better dispersity of Ce component, more Ce^（3＋）species and more Br？nsted acid sites than that by impregnation. The vacancies caused by more Ce^（3＋）species were favorable for more NO oxidation to NO2, and the interaction between Ce species and WOxspecies generated more Br？nsted acid sites. It could be supposed that dispersed Ce Oxspecies and WOxspecies offered more second active centers respectively to adsorb oxygen and activate ammonia as co-catalysis to the primary active center of V ions, thus facilitated the better SCR activity of modified V2O5-WO3/CeO2-TiO2 catalysts by coprecipitation methods. The co-precipitation methods with Ce component were more suitable for production of modified commercial V2O5-WO3/TiO2 catalysts.展开更多
The Longquansi site, Wayaobu site and Paomadi tombs of the Han period at Ninggu Town of Anshun City, Guizhou Province, were excavated in 1990-1996. At Longquansi, 13 ash-pits,four trenches and three post-holes were re...The Longquansi site, Wayaobu site and Paomadi tombs of the Han period at Ninggu Town of Anshun City, Guizhou Province, were excavated in 1990-1996. At Longquansi, 13 ash-pits,four trenches and three post-holes were revealed in the excavation area of 150 sq m, and pottery, bronze,iron and wooden objects were unearthed from the site. At Wayaobu, excavation covered an area of 46 sq m, where archaeologists discovered a pottery-making kiln and a number of bricks and tiles. The Paomadi tombs are brick-chambered graves, and yielded pottery, bronze and iron articles. The excavation of these sites and tombs provided important data for studying the politics, economy and culture of Han period Zangke Prefecture.展开更多
The Ca2+-sensing receptor(the Ca SR),a G-protein-coupled receptor,regulates Ca2+ homeostasis in the body by monitoring extracellular levels of Ca2+([Ca2+]o) and responding to a diverse array of stimuli.Mutations in th...The Ca2+-sensing receptor(the Ca SR),a G-protein-coupled receptor,regulates Ca2+ homeostasis in the body by monitoring extracellular levels of Ca2+([Ca2+]o) and responding to a diverse array of stimuli.Mutations in the Ca2+-sensing receptor result in hypercalcemic or hypocalcemic disorders,such as familial hypocalciuric hypercalcemia,neonatal severe primary hyperparathyroidism,and autosomal dominant hypocalcemic hypercalciuria.Compelling evidence suggests that the Ca SR plays multiple roles extending well beyond not only regulating the level of extracellular Ca2+ in the human body,but also controlling a diverse range of biological processes.In this review,we focus on the structural biology of the Ca SR,the ligand interaction sites as well as their relevance to the disease associated mutations.This systematic summary will provide a comprehensive exploration of how the Ca SR integrates extracellular Ca2+ into intracellular Ca2+ signaling.展开更多
Cu/ZSM-5 and CeO_2-modified Cu/ZSM-5 catalysts were prepared by a wetness impregnation method. The addition of CeO_2 was found to enhance the NO_x selective catalytic reduction（SCR） activity of the catalyst at low t...Cu/ZSM-5 and CeO_2-modified Cu/ZSM-5 catalysts were prepared by a wetness impregnation method. The addition of CeO_2 was found to enhance the NO_x selective catalytic reduction（SCR） activity of the catalyst at low temperatures, but the high-temperature activity was weakened. The catalysts were characterized by X-ray diffraction（XRD）, nitrogen physisorption, inductively coupled plasma optical emission spectrometry（ICP-OES）, X-ray photoelectron spectroscopy（XPS）, electron paramagnetic resonance（EPR）, H_2 temperature-programmed reduction（TPR） and NH_3 temperature-programmed desorption（TPD）. The results showed that more CuO clusters instead of isolated Cu^（2＋） species were obtained on the modified catalyst. These active CuO clusters, as well as the Cu-Ce synergistic effect, improved the redox property of the catalyst and low-temperatures SCR activity via promoting the oxidation of NO to NO_2 and fast SCR reaction. The loss in high-temperatures activity was attributed to the enhanced competitive oxidation of NH_3 by O_2 and decreased surface acidity of the catalyst.展开更多
MnOx-TiO2, CeO2-MnOx-TiO2 and V2O5-MnOx-TiO2 catalysts for low-temperature NH3-SCR were prepared by sol-gel method. The results showed that both cerium and vanadium prevented the transformation ofanatase TiO2 to the m...MnOx-TiO2, CeO2-MnOx-TiO2 and V2O5-MnOx-TiO2 catalysts for low-temperature NH3-SCR were prepared by sol-gel method. The results showed that both cerium and vanadium prevented the transformation ofanatase TiO2 to the mille phase. The addition of vanadium oxide induced the segregation of crystalline Mn2O3, which contributed little to low-temperature SCR and ammonia oxidation, from the MnOx-TiO2 solid solutions. However, the selectivity of the V-containing catalyst was almost 100% due to the decreased ammonia consumption and enhanced adsorption capacity of ammonia on Bronsted acid sites at relatively high temperatures. The electron-donating effect of cerium reduced the Mn^4＋/Mn^3- ratio to some extent, resulting in a decreased activity for ammonia oxidation. This, in combination with the enhanced ammonia adsorption capacity by Ce^n＋ as additional Lewis acid sites, endowed the Ce-doped catalyst a higher N2 selectivity than MnOx-TiO2 despite the slightly elevated light-offtemperamre for NO conversion.展开更多
Metal-nitrogen-carbon(M-N-C)single-atom catalysts exhibit desirable electrochemical catalytic properties.However,the replacement of N atoms by heteroatoms(B,P,S,etc.)has been regarded as a useful method for regulating...Metal-nitrogen-carbon(M-N-C)single-atom catalysts exhibit desirable electrochemical catalytic properties.However,the replacement of N atoms by heteroatoms(B,P,S,etc.)has been regarded as a useful method for regulating the coordination environment.The structure engineered M-N-C sites via doping heteroatoms play an important role to the adsorption and activation of the oxygen intermediate.Herein,we develop an efficient strategy to construct dual atomic site catalysts via the formation of a Co_(1)-PN and Ni1-PN planar configuration.The developed Co_(1)-PNC/Ni1-PNC catalyst exhibits excellent bifunctional electrocatalytic performance in alkaline solution.Both experimental and theoretical results demonstrated that the N/P coordinated Co/Ni sites moderately reduced the binding interaction of oxygen intermediates.The Co_(1)-PNC/Ni1-PNC endows a rechargeable Zn-air battery with excellent power density and cycling stability as an air-cathode,which is superior to that of the benchmark Pt/C+IrO_(2).This work paves an avenue for design of dual single-atomic sites and regulation of the atomic configuration on carbon-based materials to achieve high-performance electrocatalysts.展开更多
Heavy metal(loid)s contamination is a constant issue at smelting sites.It is essential to investigate the spatial distribution and migration characteristics of heavy metal(loid)s in the soil for environmental manageme...Heavy metal(loid)s contamination is a constant issue at smelting sites.It is essential to investigate the spatial distribution and migration characteristics of heavy metal(loid)s in the soil for environmental management and remediation strategies of non-ferrous smelting sites.In this study,203 soil samples from 57 sites were collected in a typical lead smelting site.The findings demonstrated that there were significant Pb,Zn,Cd,and As contamination in soil samples.The spatial distribution of heavy metal(loid)s showed strong spatial heterogeneity,the contaminated soil areas of Pb,As,Cd,and Zn were 99.5%,98.9%,85.3%,and 72.4%,respectively.Pb,Cd,and As contamination of the soil reached a depth of 5 m,which migrated from the surface to deep soil layers.The leaching contents of Zn,Pb,and As decreased obviously in 3-4 m soil layer,but the leaching content of Cd was still high,which indicated the high migration of Cd.With the increase of depth,the proportion of acid soluble fraction of heavy metal(loid)s decreased,and the residual fraction increased.The acid soluble fraction of Cd accounted for a higher proportion,and As mainly existed in reducible and residual fractions in soil.According to the calculation of the migration factor,the migration of heavy metal(loid)s in soils were ordered as Cd>Zn>Pb>As.The outcomes are advantageous for risk reduction and site remediation for non-ferrous metal smelting sites.展开更多
基金funded by the National Basic Research Program of China (973 Program) to JY (Grant No.2006CB910404)
文摘We present an integrated stand-alone software package named KaKs_Calculator 2.0 as an updated version. It incorporates 17 methods for the calculation of nonsynonymous and synonymous substitution rates; among them, we added our modified versions of several widely used methods as the gamma series including y-NG, y-LWL, ）,-MLWL, y-LPB, y-MLPB, y-YN and y-MYN, which have been demonstrated to perform better under certain conditions than their original forms and are not implemented in the previous version. The package is readily used for the identification of positively selected sites based on a sliding window across the sequences of interests in 5＇ to 3＇ direction of protein-coding sequences, and have improved the overall performance on sequence analysis for evolution studies. A toolbox, including C＋＋ and Java source code and executable files on both Windows and Linux platforms together with a user instruction, is downloadable from the website for academic purpose at https：//sourceforge.net/projects/kakscalculator2/.
基金Supported by National Natural Science Foundation of China, No.30200284Science Foundation of Huazhong University of Science and Technology
文摘AIM: To select the optimal antisense accessible sites of survivin, a highly expressed gene in tumor tissues, in order to explore a novel approach to improve biological therapy of gastric cancer. METHODS: The 20 mer random oligonucleotide library was synthesized, hybridized with in vitro transcribed total survivin cRNA, then digested by RNase H. After primer extension and autoradiography, the antisense accessible sites (AAS) of survivin were selected. Then RNADraw software was used to analyze and choose the AAS with obvious stem-loop structures, according to which the complementary antisense oligonucleotides (AS-ODNs) were synthesized and transferred into survivin highly- expressing gastric cancer cell line MKN-45. Survivin expression was detected by RT-PCR and Western Blotting. Cellular growth activities were assayed by tetrazolium bromide (MTT) colorimetry. Cellular ultrastructure was observed by electronic microscopy, while apoptosis was detected by annexin V-FITC and propidium iodide staining flow cytometry. RESULTS: Thirteen AAS of survivin were selected In vitro. Four AAS with stem-loop structures were chosen, locating at 207-226 bp, 187-206 bp, 126-145 bp and 44-63 bp of survivin cDNA respectively. When compared with non-tranfection controls, their corresponding AS-ODNs (AS-ODN1, AS-ODN2, AS-ODN3 and AS-ODN4) could reduce Survivin mRNA levels in MKN-45 cells by 54.3±±1.1% (t= 6.12, P<0.01), 86.1±±1.0% (t= 5.27, P<0.01), 32.2±±1.3% (t= 7.34, P<0.01) and 56.2±±0.9% (t = 6.45, P<0.01) respectively, while survivin protein levels were decreased by 42.2±±2.5% (t = 6.26, P<0.01), 75.4±±3.1% (t= 7.11, P<0.01), 28.3±±2.0% (t= 6.04, P<0.01) and 45.8±±1.2% (t = 6.38,P<0.01) respectively. After transfection with 600 nmol/L AS-ODN1-AS-ODN4for 24 h, cell growth was inhibited by 28.12±±1.54% (t= 7.62, P<0.01), 38.42±±3.12% (t= 7.75, P<0.01), 21.46±±2.63% (t= 5.94, P<0.01) and 32.12±1.77% (t = 6.17, P<0.01) respectively. Partial cancer cells presented the characteristic morphological changes of apopt
基金Project supported by the National Basic Research Program (973) of China (No. 2003CB415003)the Pilot Project of Knowledge Innovation Program of the Chinese Academy of Sciences (No. KZCX3-SW-443)the National Natural Science Foundation of China (No. 40473055).
文摘An investigation of gaseous elemental mercury concentration in atmosphere was conducted at Beijing and Guangzhou urban, Yangtze Delta regional sites and China Global Atmosphere Watch Baseline Observatory （CGAWBO） in Mt. Waliguan of remote continental area of China. High temporal resolved data were obtained using automated mercury analyzer RA-915^＋. Results showed that the overall hourly mean Hg^0 concentrations in Mt. Waliguan were 1.7±1.1 ng/m3 in summer and 0.6±0.08 ng/m^3 in winter. The concentration in Yangtze Delta regional site was 5.4±4.1 ng/m^3, which was much higher than those in Waliguan continental background area and also higher than that found in North America and Europe rural areas. In Beijing urban area the overall hourly mean Hg^0 concentrations were 8.3±3.6 ng/m^3 in winter, 6.5±5.2 ng/m^3 in spring, 4.9±3.3 ng/m^3 in summer, and 6.7±3.5 ng/m^3 in autumn, respectively, and the concentration was 13.5±7.1 ng/m^3 in Guangzhou site. The mean concentration reached the lowest value at 14：00 and the highest at 02：00 or 20：00 in all monitoring campaigns in Beijing and Guangzhou urban areas, which contrasted with the results measured in Yangtze Delta regional site and Mr. Waliguan. The features of concentration and diurnal variation of Hg^0 in Beijing and Guangzhou implied the importance of local anthropogenic sources in contributing to the high Hg^0 concentration in urban areas of China. Contrary seasonal variation patterns of Hg^0 concentration were found between urban and remote sites. In Beijing the highest Hg^0 concentration was in winter and the lowest in summer, while in Mt. Waliguan the Hg^0 concentration in summer was higher than that in winter. These indicated that different processes and factors controlled Hg^0 concentration in urban, regional and remote areas.
基金supported by the National Key R&D Program of China (2017YFA0208300)the National Natural Science Foundation of China (21522107, 21671180, 21521091, 21390393, U1463202, and 21522305)
文摘Tremendous efforts have been devoted to explore energy-efficient strategies of ammonia synthesis to replace Haber-Bosch process which accounts for 1.4% of the annual energy consumption. In this study, atomically dispersed Au_1 catalyst is synthesized and applied in electrochemical synthesis of ammonia under ambient conditions. A high NH＋4 Faradaic efficiency of 11.1 % achieved by our Au_1 catalyst surpasses most of reported catalysts under comparable conditions. Benefiting from efficient atom utilization, an NH＋4 yield rate of 1,305 μg h-1 mg-1Au has been reached, which is roughly 22.5 times as high as that by sup- ported Au nanoparticles. We also demonstrate that by employing our Au_1 catalyst, NH＋4 can be electro- chemically produced directly from N_2 and H_2 with an energy utilization rate of 4.02 mmol kJ-1. Our study provides a possibility of replacing the Haber-Bosch process with environmentally benign and energy-efficient electrochemical strategies.
基金This work was supported by National Natural Science Foundation of China(NSFC)(Nos.10979031,20921001,and 90606006)the“973”State Key Project(No.2006CB932303)and the China Postdoctoral Science Foundation(No.20080440361).
文摘CO oxidation has been performed on Co_(3)O_(4) nanobelts and nanocubes as model catalysts.The Co_(3)O_(4) nanobelts which have a predominance of exposed{011}planes are more active than Co_(3)O_(4) nanocubes with exposed{001}planes.Temperature programmed reduction of CO shows that Co_(3)O_(4) nanobelts have stronger reducing properties than Co_(3)O_(4) nanocubes.The essence of shape and crystal plane effect is revealed by the fact that turnover frequency of Co3+sites of{011}planes on Co_(3)O_(4) nanobelts is far higher than that of{001}planes on Co_(3)O_(4) nanocubes.
基金Project supported by the Guangxi Natural Science Foundation(2014GXNSFAA118057)Guangxi Science and Technology Planning Project(AB16380276)
文摘In this work, the effectiveness of V2O5-WO3/TiO2 catalysts modified with different CeO2 contents by impregnation and co-precipitation methods on the selective catalytic reduction of NOxby NH3 have been studied comparatively by various experimental techniques. The results showed that the NO conversion of V2O5-WO3/CeO2-TiO2 catalysts modified by co-precipitation method obviously increased with the Ce doping contents in the studied range below 20%（All Ce contents are in mass fractions）, but the NO conversion of V2O5-WO3/CeO2/TiO2 catalysts modified by impregnation methods was lower than V2O5-WO3/CeO2-TiO2 catalysts especially beyond 2.5% Ce doping contents. The V2O5-WO3/CeO2-TiO2 catalysts showed better SCR activity, wider reaction window, and higher sulfur and water resistance. The characterization results elucidated that the modified catalysts by co-precipitation method exhibited higher specific surface area, much better dispersity of Ce component, more Ce^（3＋）species and more Br？nsted acid sites than that by impregnation. The vacancies caused by more Ce^（3＋）species were favorable for more NO oxidation to NO2, and the interaction between Ce species and WOxspecies generated more Br？nsted acid sites. It could be supposed that dispersed Ce Oxspecies and WOxspecies offered more second active centers respectively to adsorb oxygen and activate ammonia as co-catalysis to the primary active center of V ions, thus facilitated the better SCR activity of modified V2O5-WO3/CeO2-TiO2 catalysts by coprecipitation methods. The co-precipitation methods with Ce component were more suitable for production of modified commercial V2O5-WO3/TiO2 catalysts.
文摘The Longquansi site, Wayaobu site and Paomadi tombs of the Han period at Ninggu Town of Anshun City, Guizhou Province, were excavated in 1990-1996. At Longquansi, 13 ash-pits,four trenches and three post-holes were revealed in the excavation area of 150 sq m, and pottery, bronze,iron and wooden objects were unearthed from the site. At Wayaobu, excavation covered an area of 46 sq m, where archaeologists discovered a pottery-making kiln and a number of bricks and tiles. The Paomadi tombs are brick-chambered graves, and yielded pottery, bronze and iron articles. The excavation of these sites and tombs provided important data for studying the politics, economy and culture of Han period Zangke Prefecture.
基金supported by the US National Institutes of Health(GM081749 and EB007268)a Center for Diagnostics and Therapeutics fellowship(to Zhang Chen)funds from the Georgia Research Alliance
文摘The Ca2+-sensing receptor(the Ca SR),a G-protein-coupled receptor,regulates Ca2+ homeostasis in the body by monitoring extracellular levels of Ca2+([Ca2+]o) and responding to a diverse array of stimuli.Mutations in the Ca2+-sensing receptor result in hypercalcemic or hypocalcemic disorders,such as familial hypocalciuric hypercalcemia,neonatal severe primary hyperparathyroidism,and autosomal dominant hypocalcemic hypercalciuria.Compelling evidence suggests that the Ca SR plays multiple roles extending well beyond not only regulating the level of extracellular Ca2+ in the human body,but also controlling a diverse range of biological processes.In this review,we focus on the structural biology of the Ca SR,the ligand interaction sites as well as their relevance to the disease associated mutations.This systematic summary will provide a comprehensive exploration of how the Ca SR integrates extracellular Ca2+ into intracellular Ca2+ signaling.
基金Project supported by the the National Natural Science Foundation of China(51372137)Ministry of Science and Technology,China(2015AA034603)
文摘Cu/ZSM-5 and CeO_2-modified Cu/ZSM-5 catalysts were prepared by a wetness impregnation method. The addition of CeO_2 was found to enhance the NO_x selective catalytic reduction（SCR） activity of the catalyst at low temperatures, but the high-temperature activity was weakened. The catalysts were characterized by X-ray diffraction（XRD）, nitrogen physisorption, inductively coupled plasma optical emission spectrometry（ICP-OES）, X-ray photoelectron spectroscopy（XPS）, electron paramagnetic resonance（EPR）, H_2 temperature-programmed reduction（TPR） and NH_3 temperature-programmed desorption（TPD）. The results showed that more CuO clusters instead of isolated Cu^（2＋） species were obtained on the modified catalyst. These active CuO clusters, as well as the Cu-Ce synergistic effect, improved the redox property of the catalyst and low-temperatures SCR activity via promoting the oxidation of NO to NO_2 and fast SCR reaction. The loss in high-temperatures activity was attributed to the enhanced competitive oxidation of NH_3 by O_2 and decreased surface acidity of the catalyst.
基金Project supported by 863 Project (2009AA06Z313,2010CB732304)
文摘MnOx-TiO2, CeO2-MnOx-TiO2 and V2O5-MnOx-TiO2 catalysts for low-temperature NH3-SCR were prepared by sol-gel method. The results showed that both cerium and vanadium prevented the transformation ofanatase TiO2 to the mille phase. The addition of vanadium oxide induced the segregation of crystalline Mn2O3, which contributed little to low-temperature SCR and ammonia oxidation, from the MnOx-TiO2 solid solutions. However, the selectivity of the V-containing catalyst was almost 100% due to the decreased ammonia consumption and enhanced adsorption capacity of ammonia on Bronsted acid sites at relatively high temperatures. The electron-donating effect of cerium reduced the Mn^4＋/Mn^3- ratio to some extent, resulting in a decreased activity for ammonia oxidation. This, in combination with the enhanced ammonia adsorption capacity by Ce^n＋ as additional Lewis acid sites, endowed the Ce-doped catalyst a higher N2 selectivity than MnOx-TiO2 despite the slightly elevated light-offtemperamre for NO conversion.
基金This work was supported by the National Natural Science Foundation of China(Nos.21971135,21925202,21872076,and 21590792)the National Key R&D Program of China(Nos.2017YFA0700101 and 2016YFA0202801)Beijing Natural Science Foundation(No.JQ18007).
文摘Metal-nitrogen-carbon(M-N-C)single-atom catalysts exhibit desirable electrochemical catalytic properties.However,the replacement of N atoms by heteroatoms(B,P,S,etc.)has been regarded as a useful method for regulating the coordination environment.The structure engineered M-N-C sites via doping heteroatoms play an important role to the adsorption and activation of the oxygen intermediate.Herein,we develop an efficient strategy to construct dual atomic site catalysts via the formation of a Co_(1)-PN and Ni1-PN planar configuration.The developed Co_(1)-PNC/Ni1-PNC catalyst exhibits excellent bifunctional electrocatalytic performance in alkaline solution.Both experimental and theoretical results demonstrated that the N/P coordinated Co/Ni sites moderately reduced the binding interaction of oxygen intermediates.The Co_(1)-PNC/Ni1-PNC endows a rechargeable Zn-air battery with excellent power density and cycling stability as an air-cathode,which is superior to that of the benchmark Pt/C+IrO_(2).This work paves an avenue for design of dual single-atomic sites and regulation of the atomic configuration on carbon-based materials to achieve high-performance electrocatalysts.
基金supported by the National Key Research and Development Program of China (No.2019YFC1803604)the National Natural Science Foundation of China (No.42177392).
文摘Heavy metal(loid)s contamination is a constant issue at smelting sites.It is essential to investigate the spatial distribution and migration characteristics of heavy metal(loid)s in the soil for environmental management and remediation strategies of non-ferrous smelting sites.In this study,203 soil samples from 57 sites were collected in a typical lead smelting site.The findings demonstrated that there were significant Pb,Zn,Cd,and As contamination in soil samples.The spatial distribution of heavy metal(loid)s showed strong spatial heterogeneity,the contaminated soil areas of Pb,As,Cd,and Zn were 99.5%,98.9%,85.3%,and 72.4%,respectively.Pb,Cd,and As contamination of the soil reached a depth of 5 m,which migrated from the surface to deep soil layers.The leaching contents of Zn,Pb,and As decreased obviously in 3-4 m soil layer,but the leaching content of Cd was still high,which indicated the high migration of Cd.With the increase of depth,the proportion of acid soluble fraction of heavy metal(loid)s decreased,and the residual fraction increased.The acid soluble fraction of Cd accounted for a higher proportion,and As mainly existed in reducible and residual fractions in soil.According to the calculation of the migration factor,the migration of heavy metal(loid)s in soils were ordered as Cd>Zn>Pb>As.The outcomes are advantageous for risk reduction and site remediation for non-ferrous metal smelting sites.
