ICP-OES法同时测定果蔬中铅、砷、镉、铬、铜、锡含量

果蔬样品经混酸消化后,控制一定的酸度,定容后应用等离子体发射光谱法(ICP-OES)对果蔬中铅、砷、镉、铬、铜、锡六种有害重金属进行测定,研究了分析测定条件,方法简单快速。测定结果表明,五种元素的加标平均回收率在91.0%~107%之间。其RSD均小于3.5%。按该方法进行处理及测定铅、砷、镉、铬、铜、锡,在选择的测定条件下最低检出限分别为0.0006 mg/kg、0.0003 mg/kg、0.00003 mg/kg、0.00005 mg/kg、0.00003 mg/kg、0.0006 mg/kg。     

我国主要砖茶中FAl等元素含量及其影响因素分析

为了解全国茶叶主产区砖茶中F、Al、Ca、Mg、Cu、Zn、Fe、Mn等主要元素的含量水平，在内蒙、甘肃、新疆、青海、四川等习惯饮用砖茶的地区收集了33份茶叶主产区砖茶样品，用燃烧水解-氟离子选择电极法对其进行氟含量的测定，同时用ICP-AES测定了砖茶中Al、Ca、Mg、Cu、Zn、Fe、Mn等生命元素的含量，并探讨了砖茶中F与其他元素的关系及其影响因素。结果表明，33份砖茶的F含量均值为431.92mg·kg^-1，Al、Ca、Mg、Cu、Zn、Fe、Mn含量分别是2237.88、6126.36、2163.01、19.00、29.73、633.88、1075.70mg·kg^-1;不同产地砖茶氟含量的差异比较明显，其中氟含量最低为74.1mg·kg^-1出现在云南省，最高为991.2mg·kg^-1出现在四川省;不同品种的砖茶氟含量也存在较大的差异，其中沱茶氟最低，其后依次为普洱茶、饼茶、茯砖、米砖、黑砖、青砖，最高的为康砖。多元回归分析表明砖茶中F与Al、Mn含量呈显著正相关（P〈0.05），与Zn呈显著负相关（P〈0.05），提示砖茶中的这些元素可能会影响氟中毒病情。     

一串红N、P、K、Ca、Mg、Fe缺素症状研究

以‘展望红’为材料,研究N、P、K、Ca、Mg、Fe缺乏对其生长发育的影响,并总结缺素症状,研究结果表明:N缺乏时植株矮小,叶发黄;P缺乏时叶色暗绿,且影响开花;K缺乏时基部叶枯黄,并易落叶;缺Fe症状较为明显,但能正常开花;Ca、Mg未表现出缺素症状,且各项指标要优于全素处理;N、P显著影响一串红的生长发育,K对开花品质的影响较大。     

重金属稀土元素污染在水生物体内的生物富集

对铅、镉、汞以及镧、铈在鲤鱼体内的生物富集作用进行了室内试验和讨论。结果表明,重金属及稀土元素在鱼体各部位均有较强的富集作用,其中肌肉部分富集能力较弱,内脏富集能力最强;鱼体各部位对重金属及稀土元素的富集作用随时间的增加而增加,在一定的时间后趋于平衡;并且,鱼体中各部位对重金属及稀土元素的生物富集作用存在较大差异。     

Alternatives, traditions, and diversity in agriculture

This review essay examines several recentbooks about agriculture, including two books on thelinks between cultural and biological diversity intraditional agriculture, two books on the US farmcrisis, and a collected volume examining globalaspects of agricultural restructuring andsustainability. Finally, a history of ``alternative'agriculture provides a framework for thinking aboutthe ways the different cases shed light on the complexrelations between tradition and innovation inagriculture. A historical perspective highlights theextent to which ``alternative' is a relative term. Themonocrop, ``factory' mode that dominate US agriculturetoday certainly differs from what has characterizedfarming for most of history and in most of the world.Small-scale, more or less organic, diversified farms,which appear so ``alternative' in the present context,have until lately counted as the norm, here andelsewhere. These books also highlight both the dangersof the currently dominant industrial agriculture andthe potential for genuine alternatives.     

Gallium, germanium, indium, and iridium in lunar samples

Neutron activation analyses of gallium, germanium, indium, and iridium in eight lunar samples and in meteorites and rocks (including four calciulnrich achondrites and five terrestrial basalts) with similar bulk compositions are reported. Lunar gallium concentrations are remarkably constant at about 5 parts per million, three times higher and four times lower than those in eucritic (calcium-rich) achondrites and terrestrial basalts, respectively. Lunar germanium concentrations range from 相似文献   

StKU80, a component in the NHEJ repair pathway,is involved in mycelial morphogenesis,conidiation, appressorium development,and oxidative stress reactions in Exserohilum turcicum

Homologous recombination(HR) and nonhomologous end joining(NHEJ) are considered the two main double-strand break(DSB) repair approaches in eukaryotes. Inhibiting the activities of the key component in NHEJ commonly enhances the efficiency of targeted gene knockouts or affects growth and development in higher eukaryotes. However, little is known about the roles of the NHEJ pathway in foliar pathogens. Here we identified a gene designated St KU80, which encodes a putative DNA end-binding protein homologous to yeast Ku80, in the foliar pathogen Exserohilum turcicum. Conserved domain analysis showed that the typical domains VWA, Ku78 and Ku-PK-bind are usually present in Ku70/80 proteins in eukaryotes and are also present in St Ku80. Phylogenetic analysis indicated that St Ku80 is most closely related to Ku80(XP_001802136.1) from Parastagonospora nodorum, followed by Ku80(AGF90044.1) from Monascus ruber. Furthermore, the gene knockout mutants ΔSt KU80-1 and ΔSt KU80-2 were obtained. These mutants displayed longer septas, thinner cell walls, smaller amounts of substances on cell wall surfaces, and more mitochondria per cell than the wild-type(WT) strain but similar HT-toxin activity. The mutants did not produce conidia and mature appressoria. On the other hand, the mutants were highly sensitive to H_2O_2, but not to ultraviolet radiation. In summary, the St KU80 plays devious roles in regulating the development of E. turcicum.     

酸性耕作土壤中Zn、Cd、Cu、Co、Ni和Pb的形态

采用连续提取法研究了福建省酸性耕作土壤中Zn、Cd、Cu、Co、Ni和Pb的形态分布及其影响因素.结果表明,各元素水溶态和交换态所占比例均很小,Zn、Co、Ni和Pb均以残渣态和铁锰氧化物结合态为主,Cu以残渣态和有机结合态为主,Cd以碳酸盐结合态与专性吸附态、铁锰氧化物结合态和交换态为主.相关分析表明,土壤理化性质对重金属形态有较大影响,但影响程度因元素而异.Zn、Ni和Co的形态受游离氧化铁、阳离子交换量和粘粒含量的影响较大;Cd和Pb的形态受土壤pH、游离氧化铁和粘粒含量的影响较大;Cu的形态与土壤粘粒含量呈较显著相关.     

Nonconversion of o,p'-DDT to p,p'-DDT in rats, sheep, chickens, and quail

The finding of appreciable quantities of p,p'-DDT after feeding o,p'-DDT to rats led to the proposal of a theory, that an isomeric metabolic conversion occurs. The presence of p,p'-DDT as an impurity in supposedly pure samples of o,p'-DDT is the correct explanation for the appearance of p,p'-DDT. Purified o,p'-DDT and (14)C-labeled o,p'-DDT yielded no data to support the idea that o,p'-DDT is converted to the p,p'-DDT isomer.     

Age, sex, density, winter weather, and population crashes in Soay sheep

Quantifying the impact of density, extrinsic climatic fluctuations, and demography on population fluctuations is a persistent challenge in ecology. We analyzed the effect of these processes on the irregular pattern of population crashes of Soay sheep on the St. Kilda archipelago, United Kingdom. Because the age and sex structure of the population fluctuates independently of population size, and because animals of different age and sex respond in different ways to density and weather, identical weather conditions can result in different dynamics in populations of equal size. In addition, the strength of density-dependent processes is a function of the distribution of weather events. Incorporating demographic heterogeneities into population models can influence dynamics and their response to climate change.     

Structure, dynamics, and reactivity in hemoglobin

The static structure of hemoglobin and its functional properties are very well characterized. It is still not known how energy is stored and used within the structure of the protein to promote function and functional diversity. An essential part of this question is understanding the mechanism through which the overall protein structure (quaternary structure) couples to the local environment about the oxygen binding sites. Time-resolved resonance Raman spectroscopy has been used to probe the vibrational degrees of the freedom of the binding site as a function of protein structure. Comparison of the spectra from both equilibrium and transient forms of deoxy hemoglobin from a variety of mammalian, reptilian, and fish hemoglobins reveals that for each quaternary structure there exist two tertiary states stabilized by the presence or absence of an iron-bound ligand. Pulse-probe Raman experiments show that for photodissociated, ligated hemoglobins the local tertiary structure relaxes at a solution-dependent rate extending from tens of nanoseconds to microseconds. In this local environment, the linkage between the iron and the proximal histidine proves to be the single observed structural feature that responds in a systematic and substantial manner to structural changes in the protein. The additional finding of a correlation between the frequency of the iron-proximal histidine stretching motion (nu Fe-His) and various parameters of ligand reactivity, including geminate recombination, implicates the associated localized structural element in the mechanism of protein control of ligand binding. On the basis of these and related finds, a model is presented to account for both coarse and fine control of ligand binding by the protein structure.     

饲料中4种硝基呋喃类药物的检测方法研究

建立了饲料中呋喃唑酮、呋喃它酮、呋喃西林和呋喃妥因4种药物的液相色谱分析方法。液相色谱柱为Waters SunfireTMC18(150 mm×2.1 mm,3.5μm),柱温30℃,流动相为乙腈和0.2%甲酸水溶液,检测波长365 nm,流速0.2 mL/min。此条件下硝基呋喃类药物的线性范围是0.1~10μg/mL,回收率为75%~90%,变异系数为3.24%~5.83%。检测限为0.5 mg/kg,定量限为1.0 mg/kg。     

铅.镉.砷.汞污染的治理研究进展

重金属污染问题是工业化和城市化活动导致的最有危害性环境问题之一,环境中重金属能通过食物链污染食品、危害人体健康。治理重金属污染已成为热点研究话题。分别对重金属铅、镉、砷、汞污染的治理现状进行了综述。     

Robots in agriculture: prospects,impacts, ethics,and policy

Agriculture is both the site of development of important new technologies and a key area of application of technologies developed elsewhere. It is little wonder, then, that many thinkers believe that progress in the science and engineering of robotics may soon change the face of farming. This paper surveys the prospects for agricultural robotics, discusses its likely impacts, and examines the ethical and policy questions it may raise. Along with the environmental and economic impacts of robots, political, social, cultural, and security implications of the introduction of robots that have received little attention in the larger literature on agricultural robotics are considered. Key policy choices necessary to meet the ethical challenges likely to arise as agricultural robots start to become used more widely, and to maximise the social, environmental, and economic benefits of robotics in agriculture, are highlighted.