用硅胶柱色谱及重结晶等方法,并根据理化性质和光谱数据从一株红树林共生真菌Paecilomycessp.Tree 1-7中分离鉴定了四个化合物,分别为secalon ic ac id A(1),tenellic ac id A(2),大黄素(3),大黄酚(4)。并首次对化合物1和2进行了抗人的...用硅胶柱色谱及重结晶等方法,并根据理化性质和光谱数据从一株红树林共生真菌Paecilomycessp.Tree 1-7中分离鉴定了四个化合物,分别为secalon ic ac id A(1),tenellic ac id A(2),大黄素(3),大黄酚(4)。并首次对化合物1和2进行了抗人的肝癌细胞hepG2的活性测试。结果显示,化合物1有很强的抗肿瘤活性,IC50=2.0μg/m l,化合物2的抗肿瘤活性IC50=62.1μg/m l。展开更多
文章首先对Sql Server 2008商业智能平台及决策树技术相关理论作了介绍,然后对挖掘数据源数据进行了一系列预处理。利用Sql Server 2008商业智能平台下的决策树技术并采用数据挖掘扩展语言即DMX语言创建了CET-4成绩分析决策树模型。分...文章首先对Sql Server 2008商业智能平台及决策树技术相关理论作了介绍,然后对挖掘数据源数据进行了一系列预处理。利用Sql Server 2008商业智能平台下的决策树技术并采用数据挖掘扩展语言即DMX语言创建了CET-4成绩分析决策树模型。分类矩阵和挖掘提升图分别对该模型的评估结果表明了模型具有较高的可靠性和分类准确度,同时模型对应的一些规则可作为英语教学管理和改革的重要参考依据。展开更多
Background： Many tree species in tropical forests have distributions tracking local ridge-slope-valley topography. Previous work in a 50-ha plot in Korup National Park, Cameroon, demonstrated that 272 species, or 63%...Background： Many tree species in tropical forests have distributions tracking local ridge-slope-valley topography. Previous work in a 50-ha plot in Korup National Park, Cameroon, demonstrated that 272 species, or 63% of those tested, were significantly associated with topography. Methods： We used two censuses of 329,000 trees ≥1 cm dbh to examine demographic variation at this site that would account for those observed habitat preferences. We tested two predictions. First, within a given topographic habitat, species specializing on that habitat （＇residents＇） should outperform species that are specialists of other habitats （＇foreigners＇）. Second, across different topographic habitats, species should perform best in the habitat on which they specialize （＇home＇） compared to other habitats （＇away＇）. Species＇ performance was estimated using growth and mortality rates. Results： In hierarchical models with species identity as a random effect, we found no evidence of a demographic advantage to resident species. Indeed, growth rates were most often higher for foreign species. Similarly, comparisons of species on their home vs. away habitats revealed no sign of a performance advantage on the home habitat. Conclusions＂ We reject the hypothesis that species distributions along a ridge-valley catena at Korup are caused by species differences in trees _〉1 cm dbh. Since there must be a demographic cause for habitat specialization, we offer three alternatives. First, the demographic advantage specialists have at home occurs at the reproductive or seedling stage, in sizes smaller than we census in the forest plot. Second, species may have higher performance on their preferred habitat when density is low, but when population builds up, there are negative density-dependent feedbacks that reduce performance. Third, demographic filtering may be produced by extreme environmental conditions that we did not observe during the census interval.展开更多
The thermoelectric properties of Sr0.61Ba0.39Nb2O6-δ ceramics, reduced in different conditions, are investigated in the temperature range from 323 K to 1073 K. The electrical transport behaviors of the samples are do...The thermoelectric properties of Sr0.61Ba0.39Nb2O6-δ ceramics, reduced in different conditions, are investigated in the temperature range from 323 K to 1073 K. The electrical transport behaviors of the samples are dominated by the thermal-activated polaron hopping in the low temperature range, the Fermi glass behavior in the middle temperature range, and the Anderson localized behavior in the high temperature range. The thermal conductivity presents a plateau at high- temperatures, indicating a glass-like thermal conduction behavior. Both the thermoelectric power factor and the thermal conductivity increase with the increase of the degree of oxygen-reduction. Taking these two factors into account, the oxygen-reduction can still contribute to promoting the thermoelectric figure of merit. The highest ZT value is obtained to be -0.19 at 1073 K in the heaviest oxygen reduced sample.展开更多
Any distributed resource(DR)is generally connected to any near grid of which the voltage is 35 kv or below to supply directly electricity to loads,which is conducive to reduce the power capacity supplied from the majo...Any distributed resource(DR)is generally connected to any near grid of which the voltage is 35 kv or below to supply directly electricity to loads,which is conducive to reduce the power capacity supplied from the major network to the distribution network,reduce the outage of and delay upgrading of the distribution network.On the other hand,DR connection will change the previous onefold and radial network connection展开更多
Effective piezoelectric properties,electromechanical coupling factors(ECF)and figures of merit(FOM)are studied in leadfree 0-3-type composites based on novel ferroelectric 0.965(K_(0.48)Na_(0.52))(Nb_(0.96)Sb_(0.04))O...Effective piezoelectric properties,electromechanical coupling factors(ECF)and figures of merit(FOM)are studied in leadfree 0-3-type composites based on novel ferroelectric 0.965(K_(0.48)Na_(0.52))(Nb_(0.96)Sb_(0.04))O_(3)-0.035Bi_(0.5)Na_(0.5)Zr_(0.15)Hf_(0.75)O_(3) ceramic.Systems of prolate ceramic inclusions are surrounded by a large polymer matrix that can be either monolithic(in the 0-3 composite)or porous(in the 0-3-0 composite).Non-monotonic volume-fraction dependences of the effective piezoelectric coefficients g_(3j)^(*),ECF k_(3j)^(*),squared FOM d_(3j)^(*)g_(3j)^(*)and their modified analogs for stress-driven systems are analysed,and examples of the high longitudinal piezoelectric sensitivity(g33^(*)>100 mV.m/N)are considered.A role of microgeometrical factors,that promote the large effective parameters and anisotropy of properties in the 0-3-type composites,is highlighted.New“aspect ratio-volume fraction”diagrams are first built to describe conditions for high piezoelectric sensitivity,large modified FOM and their anisotropy in the studied composites.These advanced materials can be of value for piezoelectric sensor,energy-harvesting and related applications.展开更多
文摘用硅胶柱色谱及重结晶等方法,并根据理化性质和光谱数据从一株红树林共生真菌Paecilomycessp.Tree 1-7中分离鉴定了四个化合物,分别为secalon ic ac id A(1),tenellic ac id A(2),大黄素(3),大黄酚(4)。并首次对化合物1和2进行了抗人的肝癌细胞hepG2的活性测试。结果显示,化合物1有很强的抗肿瘤活性,IC50=2.0μg/m l,化合物2的抗肿瘤活性IC50=62.1μg/m l。
文摘文章首先对Sql Server 2008商业智能平台及决策树技术相关理论作了介绍,然后对挖掘数据源数据进行了一系列预处理。利用Sql Server 2008商业智能平台下的决策树技术并采用数据挖掘扩展语言即DMX语言创建了CET-4成绩分析决策树模型。分类矩阵和挖掘提升图分别对该模型的评估结果表明了模型具有较高的可靠性和分类准确度,同时模型对应的一些规则可作为英语教学管理和改革的重要参考依据。
基金the National Institutes of Health award U01 TW03004 under the NIH-NSF-USDA funded International Cooperative Biodiversity Groups programfinancial support from the U.S. Agency for International Development’s Central Africa Regional Program for the Environment and the Smithsonian Tropical Research Institute+3 种基金Financial support for the 2008 recensus was provided by the Frank Levinson Family Foundationsupported by U.S. National Science Foundation award DEB-9806828provided by the Bioresources Development and Conservation Programme-Cameroonthe WWF Korup Project
文摘Background： Many tree species in tropical forests have distributions tracking local ridge-slope-valley topography. Previous work in a 50-ha plot in Korup National Park, Cameroon, demonstrated that 272 species, or 63% of those tested, were significantly associated with topography. Methods： We used two censuses of 329,000 trees ≥1 cm dbh to examine demographic variation at this site that would account for those observed habitat preferences. We tested two predictions. First, within a given topographic habitat, species specializing on that habitat （＇residents＇） should outperform species that are specialists of other habitats （＇foreigners＇）. Second, across different topographic habitats, species should perform best in the habitat on which they specialize （＇home＇） compared to other habitats （＇away＇）. Species＇ performance was estimated using growth and mortality rates. Results： In hierarchical models with species identity as a random effect, we found no evidence of a demographic advantage to resident species. Indeed, growth rates were most often higher for foreign species. Similarly, comparisons of species on their home vs. away habitats revealed no sign of a performance advantage on the home habitat. Conclusions＂ We reject the hypothesis that species distributions along a ridge-valley catena at Korup are caused by species differences in trees _〉1 cm dbh. Since there must be a demographic cause for habitat specialization, we offer three alternatives. First, the demographic advantage specialists have at home occurs at the reproductive or seedling stage, in sizes smaller than we census in the forest plot. Second, species may have higher performance on their preferred habitat when density is low, but when population builds up, there are negative density-dependent feedbacks that reduce performance. Third, demographic filtering may be produced by extreme environmental conditions that we did not observe during the census interval.
基金Project supported by the National Basic Research Program of China(Grant No.2013CB632506)the National Natural Science Foundation of China(Grant Nos.51202132 and 51002087)
文摘The thermoelectric properties of Sr0.61Ba0.39Nb2O6-δ ceramics, reduced in different conditions, are investigated in the temperature range from 323 K to 1073 K. The electrical transport behaviors of the samples are dominated by the thermal-activated polaron hopping in the low temperature range, the Fermi glass behavior in the middle temperature range, and the Anderson localized behavior in the high temperature range. The thermal conductivity presents a plateau at high- temperatures, indicating a glass-like thermal conduction behavior. Both the thermoelectric power factor and the thermal conductivity increase with the increase of the degree of oxygen-reduction. Taking these two factors into account, the oxygen-reduction can still contribute to promoting the thermoelectric figure of merit. The highest ZT value is obtained to be -0.19 at 1073 K in the heaviest oxygen reduced sample.
文摘Any distributed resource(DR)is generally connected to any near grid of which the voltage is 35 kv or below to supply directly electricity to loads,which is conducive to reduce the power capacity supplied from the major network to the distribution network,reduce the outage of and delay upgrading of the distribution network.On the other hand,DR connection will change the previous onefold and radial network connection
文摘Effective piezoelectric properties,electromechanical coupling factors(ECF)and figures of merit(FOM)are studied in leadfree 0-3-type composites based on novel ferroelectric 0.965(K_(0.48)Na_(0.52))(Nb_(0.96)Sb_(0.04))O_(3)-0.035Bi_(0.5)Na_(0.5)Zr_(0.15)Hf_(0.75)O_(3) ceramic.Systems of prolate ceramic inclusions are surrounded by a large polymer matrix that can be either monolithic(in the 0-3 composite)or porous(in the 0-3-0 composite).Non-monotonic volume-fraction dependences of the effective piezoelectric coefficients g_(3j)^(*),ECF k_(3j)^(*),squared FOM d_(3j)^(*)g_(3j)^(*)and their modified analogs for stress-driven systems are analysed,and examples of the high longitudinal piezoelectric sensitivity(g33^(*)>100 mV.m/N)are considered.A role of microgeometrical factors,that promote the large effective parameters and anisotropy of properties in the 0-3-type composites,is highlighted.New“aspect ratio-volume fraction”diagrams are first built to describe conditions for high piezoelectric sensitivity,large modified FOM and their anisotropy in the studied composites.These advanced materials can be of value for piezoelectric sensor,energy-harvesting and related applications.
