Influence of CuO addition to BaSm2Ti4O12 microwave ceramics on sintering behavior and dielectric properties

Microwave dielectric ceramics of tungsten–bronze-type BaSm₂Ti₄O₁₂ were prepared by doping CuO (up to 2 wt.%) as the liquid-phase sintering aid. The effects of CuO additive on the densification, micro structure and dielectric properties were investigated. Due to the liquid-phase effect, the sintering temperature of BaSm₂Ti₄O₁₂ ceramics with 1 wt.% CuO addition can be effectively reduced to 1160 °C, about 200 °C lower than that of pure BaSm₂Ti₄O₁₂ ceramics, while good microwave dielectric properties of ɛ_r = 75.8, Q*f = 4914.6 GHz and τ_f = −7.65 ppm/°C were still achieved.     

不同地域边销茯砖茶感官特征及香气成分比较

为研究我国不同地域边销茯砖茶的香气品质特点,试验选取具有代表性的陕西、湖南和浙江三主产区的边销茯砖茶为研究对象,采用同时蒸馏萃取法结合气质联用(GC-MS:Gas Chromatography-Mass Spectrometer)对其香气成分进行了分析,并结合感官审评初步探明了不同主产区边销茯砖茶的香气特征。三产区边销茯砖茶香气以纯正为主要特点,但陕西茯砖茶带高火香,湖南茯砖茶"菌花香"较明显,浙江茯砖茶略带青气。GC-MS分析结果表明:从陕、湘和浙三产区的边销茯砖茶样品中分别检测出46、56和53种香气成分,共有香气成分45种,主要以醇类、醛类和酮类物质为主,分别占陕、湘和浙边销茯砖茶检出香气总量的65.22%、69.01%和73.22%;含量较高的共有组分有:棕榈酸、植醇、橙花叔醇、6,10,14-三甲基-2-十五烷酮、(E,E)-2,4-庚二烯醛、香叶基丙酮、β-紫罗酮等,其中具高火香的杂环类化合物在陕西茯砖茶中含量较高,与"菌花香"紧密相关的烯醛类物质在湖南茯砖茶中含量最高,具青气味的低级脂肪醛在浙江茯砖茶中含量较高,与感官审评结果一致。     

Retro-analysis of liquid bio-ethanol and bio-diesel in New Zealand

This paper uses a new approach of retro-analysis. Typically policy is informed by forward-looking analysis of potential for alternative energy technologies. But historical knowledge of energy and processing requirements and greenhouse effects is more reliable for engineering evaluation of biofuel production systems. This study calculates energy inputs and greenhouse gas emissions for the most efficient biomass feedstocks in New Zealand if the policy had been implemented to maximize liquid biofuel production in the year 2004/2005. The study uses existing processing technologies and agricultural statistics. Bioethanol production is calculated from putrescible wastes and starch crops, and biodiesel production from rapeseed, tallow, wood and waste paper. Each production system is further evaluated using measures of land use, energy input, crop production related to the energy product, plus relative measures of efficiency and renewability. The research findings are that maximum biofuel production in 2004/2005 would have provided only a few per cent of demand, and would not have reduced dependence on foreign imported oil or exposure to fuel price rise. Finally, we conclude that demand management and efficiency are more effective means of meeting policy objectives.     

做青程度对信阳茶品质及其抗氧化活性的影响

该研究采用一芽三四叶的鲜叶原料,比较了信阳绿茶、信阳红茶和3个不同做青程度的信阳茶的品质及其抗氧化活性,以期为江北茶区小叶种茶树品种的鲜叶进一步开发利用提供理论依据。通过分光光度计、液相色谱和气相色谱-质谱联用仪检测5种茶主要生化成分和挥发性成分,利用1,1-二苯基-2-三硝基苯肼（1,1-Diphenyl-2-Picrylhydrazyl,DPPH）法检测此5种茶的抗氧化活性,最后进行感官审评。结果发现：不同做青程度的信阳茶中所含主要成分的含量及组成存在差异,随着做青程度加深,茶多酚由21.17%降到18.90%（P<0.05）,氨基酸由3.43%增加到3.73%（P<0.05）,黄酮由5.63 mg/g增加到6.55 mg/g（P<0.05）,香气成分呈递增的趋势,尤其单帖类物质增加明显,如β-蒎烯由0.13 μg/g增加到0.37 μg/g、E-β-罗勒烯0.05 μg/g增加到0.15 μg/g（P<0.05）。感官审评发现,轻度做青处理所制的茶叶品质相对较优。通过计算不同做青处理所制茶叶清除DPPH自由基半抑制浓度IC50值（Half Maximal Inhibitory Concentration,IC50）,发现随着做青程度加深,IC50值在增大,1/IC50值与茶多酚含量呈极显著正相关（P<0.01）,与氨基酸和黄酮含量呈极显著负相关（P<0.01）,与19种挥发性成分呈显著负相关（P<0.05）,说明适当的做青工艺可以改善一芽三四叶所制信阳绿茶的品质。     

广西降雨量时空变异规律

为揭示广西不同地区降雨量的时空变化规律,利用17个气象站点1957~2001年的降雨资料,通过年际极值比、变差系数、累积滤波器、Kendall秩次相关法、Mann Kendall非参数统计法,分析了广西单个站点和区域降雨量的年际变化特征、变化趋势及其突变点。结果表明,桂南降雨量年际变化最剧烈,桂北年际变化最小;非岩溶发育地区降雨量的年际变化比岩溶发育地区剧烈;17个单站点中,64.7%的降雨量呈上升趋势,35.3%呈下降趋势;桂北、桂南和桂西的降雨量主要呈增加趋势,桂中和桂东的降雨量主要呈下降趋势。     

3株拮抗烟草尖孢镰刀菌的木霉菌筛选鉴定及促生防病效果评价

  目的  为筛选对烟草镰刀菌根腐病菌具有较好拮抗效果的菌株。  方法  从河南省主要烟叶产区健康烟株根际土壤中,分离纯化对尖孢镰刀菌（Fusarium oxysporum）具有一定拮抗作用的真菌菌株,对筛选出的拮抗菌株进行形态学和分子生物学鉴定,并测定促生作用和防治效果。  结果  分离纯化得到的3株木霉菌分别为棘孢木霉（Trichoderma asperellum）Ta-0101、哈茨木霉（Trichoderma harzianum）Th-0201和毛簇木霉（Trichoderma velutinum）Tv-0207,具有较强的抑菌能力,对尖孢镰刀菌的抑菌率分别为91.24%、84.71%和82.48%。3株木霉菌对烟草种子根长和总长均有显著的促生效果,根长增长率分别为28.89%、25.92%和22.22%,根系活力也显著提高;对烟株最大叶面积和鲜重的促生作用明显,其中棘孢木霉Ta-0101促生效果最显著。3株木霉菌对尖孢镰刀菌的相对盆栽防效分别为78.95%、69.73%和69.73%,均高于70%甲基硫菌灵1000倍液处理的防效。  结论  3株拮抗木霉菌具有较好的抑菌效能和促生防病效果,应用前景良好。      

信阳产地不同茶类抗氧化活性的研究

目的 探讨信阳产地传统茶(信阳毛尖1、2和信阳红1、2)与新试制茶(奇岩、奇白和奇红)的抗氧化活性。方法 通过高效液相色谱仪和紫外分光光度计检测7种茶中6种儿茶素单体、茶多酚等13个指标;然后利用1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)法和糖尿病小鼠模型检测这些茶的体外和体内抗氧化活性。结果 不同茶中所含主要抗氧化成分含量及组成存在差异,受茶树品种、鲜叶采摘标准、季节和制作工艺等因素综合影响。通过计算7种茶清除DPPH自由基的半抑制浓度(half maximal inhibitory concentration, IC₅₀)值,得出抗氧化强弱为绿茶>乌龙茶>白茶>红茶。相关性分析, IC₅₀值与茶多酚、维生素C、儿茶素总量及其6个单体成显著负相关(P<0.05、P<0.01),与黄酮和没食子酸成极显著正相关(P<0.01)。体内抗氧化检测10个处理中,信阳毛尖2处理丙二醛(malonaldehyde, MDA)最低,信阳红2处理MDA最高。信阳毛...     

Controlled Release System by Active Gelatin Film Incorporated with β-Cyclodextrin-Thymol Inclusion Complexes

Essential oils such as thymol are added to food packaging film to obtain active films with antimicrobial and antioxidant properties. However, thymol is insoluble in water, and release rate of thymol is usually too fast. Therefore, a need exists to increase thymol solubility and to deliver thymol in a controlled manner from film matrix to food surface. In this study, spray dried inclusion complexes of β-cyclodextrin/thymol (1:1 molar ratio) was incorporated into gelatin solution to obtain active gelatin films. Both inclusion complexes and active films showed sustained release of thymol. Physical properties and thymol release kinetics were evaluated for active films. For gelatin films with 8.25% (mass ratio) inclusion complexes, complete thymol release took 235 h, compared with 38 h for thymol release from inclusion complexes. The diffusion coefficient reached 2.04?×?10^?15 m² s^?1.     

A general framework incorporating knowledge,risk perception and practices to eliminate pesticide residues in food: A Structural Equation Modelling analysis based on survey data of 986 Chinese farmers

Following a variety of incidents in China relating to food poisoning due to the presence of pesticide residues, it is crucial to correct for farmers’ unsafe and improper practices towards pesticide use. Although most studies have focused on the role of external stakeholders such as government extension agencies and pesticide retailers, the attention paid to farmers’ intrinsic motivations is limited. This paper applies Structural Equation Modelling to investigate psychological motivational concepts such as farmers’ knowledge and risk perception, their formation mechanisms and the underlying processes of these concepts that lead to farmers’ practices to eliminate pesticide residues, based on a representative survey conducted with 986 Chinese farmers from 20 counties selected from six provinces. We found both a direct and significant effect of farmers’ knowledge on pesticides residue on their safe pesticide practices and also an indirect effect, i.e. knowledge influences on risk perception which in turn enhances safe pesticide practices. It was also reported that government support strategies are more effective in promoting safe pesticide practices than government regulation.