Reduction of low voltage power cables electromagnetic field emission in MV/LV substations

In this paper a solution to reduce magnetic field emission levels generated by MV/LV substation power cables is proposed. The reduction is obtained by the arrangement of the phases in a proper way and by shielding the cables with magnetic or conductive materials. The effects introduced by these two options have been analyzed by means of simulations, using finite elements method calculation software, and by experimental measurements. The introduced results allow selecting an optimal arrangement and the best screening material in order to reduce the magnetic fields in those directions required to protect.     

Occurrence of major and trace elements in powdered milk from Argentina

The concentrations of major and trace elements in Argentinean commercial powdered milk samples were determined with inductively coupled plasma mass spectrometry. Also the daily intake (DI) was calculated for adults and infants. The concentrations of B, Mg, Na, K and Ca were significantly higher in skimmed milk. Cu, Mo, Fe, Mn and Zn were significantly higher in infant formula. All the DIs were below the tolerable upper intake levels. The mean As concentration (26.0 ± 8.6 ng/g) in the powdered skimmed milk samples was slightly higher than in the others. Mean Pb concentrations ranged from 4.1 ± 2.1 to 13.5 ± 8.2 ng/g. The highest mean U concentration was 7.8 ± 2.6 ng/g for whole milk. This study contributes to the knowledge of major and trace elements in powdered milk and its contribution to the diet in Argentina.     

柳河大米产地环境及其矿物元素分布特征的典范对应分析

为筛选稳定可靠的柳河大米产地确证元素,通过2 次典范对应分析研究影响吉林省柳河大米采样点分布的环境因子,分析大米产地确证元素在区域尺度内的影响关系及其稳定性。典范对应分析结果表明,2 个环境梯度轴分别解释大米矿物元素含量总方差的17.3%和23.4%,柳河大米矿物元素含量和环境变量之间存在较强的空间相关性,受产地环境变量影响最大的为Se元素,Ca、Zn、Mg含量受其影响最小,Mg、Ca、Na、Mn、Zn具有较好的稳定性和空间代表性,可作为柳河大米产地确证的指标元素。研究结果为建立柳河大米确证模型提供有效的理论依据。     

Trace metals supplementation enhanced microbiota and biohythane production by two-stage thermophilic fermentation

The effect of trace metals supplementation into palm oil mill effluent on biohythane production and responsible microbial communities in thermophilic two-stage anaerobic fermentation was investigated. High biohythane yields were linked to Ni/Co/Fe supplementation (10, 6 and 20 mg L⁻¹, respectively) with maximum H₂ and CH₄ yields of 139 mL H₂ gVS⁻¹ and 454 mL CH₄ gVS⁻¹, respectively. The Ni/Co/Fe supplementation resulted in higher numbers of Bacillus sp., Clostridium sp. and Thermoanaerobacterium sp. together with increasing hydrogenase expression level leading to increasing hydrogen yields of 90.4%. The numbers of Methanosarcina, Methanomassiliicoccus, and Methanoculleus were enhanced by Ni/Co/Fe addition, accompanied by 21.7% higher methane yields. No correlation between methyl coenzyme-M reductase expression level and methane yields was observed. The Ni/Co/Fe supplementation improved gas production in the two-stage biohythane process via enhancing a number of viable hydrogen-producing bacteria together with hydrogenase activity in H₂ stage and enhancing number methanogens in the CH₄ stage.     

基于ICP-MS/MS分析微量金属元素的原油产地溯源

建立电感耦合等离子体串联质谱(ICP-MS/MS)法测定原油中微量金属元素的分析方法,结合聚类分析(CA)建立判别模型,进行原油产地溯源研究。原油样品经微波消解处理后,采用ICP-MS/MS测定其中18种微量金属元素Mg、Al、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Rb、Sr、Mo、Ag、Cd、Ba、Pb的质量分数。在MS/MS模式下的碰撞反应池(CRC)中,应用O2或NH3/He为反应气可消除多原子离子对轻质量元素的干扰,采用国际标准物质燃油(NIST SRM 1634c)验证了分析方法准确可靠性,并利用多种微量金属元素质量分数的比值进行聚类分析。方法的检出限为0.43～59.2 ng/L,相对标准偏差(RSD)不大于4.82%;CA将18种原油聚为4大类,可实现原油产地的初步判别。通过微量金属元素的ICP-MS/MS分析,并结合CA能够对原油进行有效的产地溯源和判别。     

红枣中氨基酸和矿质元素含量的测定

采用高效液相色谱法对若羌红枣、哈密红枣和河南新郑中氨基酸进行分析,测定出了红枣中18种氨基酸的含量;用原子吸收方法对这三种红枣中所含的矿质元素Mn、Cu、Zn、Ca、Fe、Ni、Co、K、Na、Mg的含量进行测定.通过对实验数据进行方差分析,结果发现这三种红枣在氨基酸含量和微量元素、常量元素之间差异性不显著.     

火焰原子吸收分光光谱法测定玉米中铁、锰、铜、锌

采用HNO3-HClO4(4+1)湿法消解样品,用火焰原子吸收光谱法测定玉米中铁、锰、铜、锌的含量。测得铁、锰、铜、锌的回收率分别在97%～99%、95%～100%、95%～103%,100%～104%之间,平均回收率为95%～104%,RSD为0.1%～0.9%,表明该方法准确可靠。     

ICP - MS/ICP - AES法测定八角叶中的24种无机元素

八角是我国南方重要的经济树种,八角叶常用于生产八角茴香油及烹调佐料,本文采用电感耦合等离子体质谱、发射光谱(ICP - MS/ICP - AES)法同时测定八角叶中的Mg、Al、Ca、Mn、Fe、Co、Cu、Cd、Pb等24种元素,方法的准确度用国家一级标准物质GBW10015对比分析证实,结果表明该法快速简便、准确率高、精密度试验RSD在0.5％～7％之间,可以完全可以满足八角叶样品中无机元素测定要求.测定结果显示八角叶中含有较丰富的人体必需的宏量与微量元素,在所测定的24种元素中,含量最高为Al达8400μg·g-1,其后依次为K(7300μg·g-1)、Mg(3200μg·g-1)、Ca(3100μg·g-1)、P(1000μg·g-1)、Mn(728μg· g-1)、而Tl最少,仅0.011μg·g-1.     

发芽黑米中γ-氨基丁酸及矿物元素含量变化的研究

以黑米作为原料,研究黑米在发芽的过程中γ-氨基丁酸、矿物元素含量的变化规律。实验表明,黑米发芽过程中γ-氨基丁酸含量发生较大变化,呈上升趋势;黑米中的矿物元素也略有增加,本实验为开发发芽黑米提供了理论基础和参考依据。