Oxidized multiwalled carbon nanotubes modified with 2-(2-hydroxy-5-nitrophenyl)-4,5-diphenyl imidazole for solid phase extraction and preconcentration of some metal ions

In this work, a new procedure for the enrichment of the trace amount of Cu²⁺, Ni²⁺, Co²⁺, Pb²⁺, Fe²⁺, and Zn²⁺ ions based on the utilization of multiwalled carbon nanotubes (MWCNT) modified with 2-(2-hydroxy-5-nitrophenyl)-4,5-diphenyl imidazole as chelating agent prior to their determination by flame atomic absorption spectrometry has been described. The influence of effective parameters including pH, amount of ligand and MWCNT, composition of eluent, and coexisting ions on recoveries of understudy metal ions was examined. At the optimum pH of 5.0, all metal ions were quantitatively sorbed onto the proposed solid phase and completely desorbed with 8?mL of 5.0?mol?L^?1 HNO₃. The detection limit of Cu²⁺, Co²⁺, Ni²⁺, Pb²⁺, Fe²⁺, and Zn²⁺ ions was 1.7, 2.4, 2.3, 2.9, 2.8, and 1.4?µg?L^?1, while the preconcentration factor was 63 for Cu²⁺ and 94 for the other metal ions and relative standard deviations between 1.8 less than 3.0%. The proposed procedure was applied for the analysis of various samples.     

BOD_5样品分析中稀释倍数的确定探讨

首先正确估计出样品ＢＯＤ５浓度范围，并测定稀释水的溶解氧，然后根据稀释倍数公式计算出三个适当的稀释倍数，与其它方法相比，本方法省时、可靠、适用性强、能够确保ＢＯＤ５样品分析一次成功，在ＢＯＤ５样品分析中具有广泛的应用价值．     

五日生化需氧量(BOD5)测定方法探讨

本文针对GB／T7488-1987《水质五日生化需氧量(BOD5)稀释与接种法》中BOD5的测定和计算时接种稀释水的空白扣除方法，提出了直接测接种液的BOD5值，按接种液的比例在水样中进行扣除的方法，提高了BOD5值的准确性。更能反应BOD5的真实性。     

SPOT5卫星数据融合和彩色合成的方法及应用

文章利用玛多县2005年5月22日SPOT5卫星多光谱和全色段数据的融合和彩色影像图的处理和制作,系统介绍了目前较为成熟的像元级融合技术和SPOT5模拟真彩色影像图制作方法。制作后的影像图能够满足测量和专业制图的需求,而且可以用于地物分类、目标识别等处理。     

提高水中BOD5测定质量的探讨

介绍了环境空气质量、分析用水、接种液加入量、曝气方法的选择等因素对BOD5测定的影响。提出测定过程中实验室空气质量、分析用水的选择、接种液的选择和加入量以及曝气方法应注意事项,以期得到较为准确的测定结果,提高废水中BOD5测定质量。     

珠芽魔芋种子5苗接力生长当年形成商品芋技术

首次提出珠芽魔芋种子具有5苗接力生长的生物学特性。种子能在一个不间断的生长周期中积累最大生物产量,避免魔芋需反复"换头"种植3—4年才能收获商品芋的低产生长模式,使魔芋的膨大系数由块茎的低于10倍提高到种子最高约7000倍,所获地下球茎重量平均达1560g。采用种子种植当年即可获用于加工的商品芋,消除了魔芋种植过程中固有的风险,使魔芋由低产作物变成高产作物,魔芋多糖总量将实现跨越式增长。     

Some observations on copper yields and ore grades

The paper examines trends in the average copper content of mined ores over the years. It has tended to decline over the long term, but by no means evenly. US averages are not typical of global averages, at least in the past four decades. Those have been both higher, and less volatile than in the US. One reason for falling averages is a change in the type of deposit mined, with a rise in the share of relatively low grade porphyry deposits. The different nature of their deposits is reflected in marked differences in grades between the different continents. African and Australian average grades are higher than the global average, and changes in the share of Central Africa in global output have affected the global average grade. Yields are have been consistently lower in North America than elsewhere, and Latin American average grades have trended downwards, reflecting both the ageing of mines and the rising share of production from porphyry deposits. Typically the yield of mines declines over time as mining proceeds. The average copper content of ore deposits is usually below the average yield of the ore accessed in the early years of production. The initial grades of new mines have not declined over the past forty years, and there has been no perceptible tendency for the average grade of porphyry deposits brought into production to decline over time. There is no apparent correlation between average grade and deposit size, but mine operators tend to exploit economies of scale to offset low grades. The relationship between the annual percentage yields (the head grade) and the reserve grades of deposits is not static. In recent years head grades have fallen closer to reserve grades. The relationship may be affected by movements in metal prices. Although the evidence about the influence of prices is not clear-cut, it does suggest that prices and cut-off grades may be inversely related. As many ores contain other valuable metals besides copper, copper yields will sometimes be subordinated to the extraction of these other metals. Copper equivalent grades have not moved in the same way as copper grades alone.     

Prenatal diagnosis of 5p deletion syndrome following abnormally low maternal serum human chorionic gonadotrophin

Prenatal diagnosis of 5p deletion syndrome, or cri du chat, following an abnormally low measurement of a screening of serum human chorionic gonadotrophin (hCG), is reported. Karyotyping following amniocentesis revealed a terminal deletion in the short arm of one chromosome 5. The pregnancy was electively terminated. 5p deletion syndrome has been described with abnormally high hCG levels and normal hCG levels. This is the first report of its association with abnormally low levels. The association between chromosomal abnormalities and hCG is discussed. Copyright © 2003 John Wiley & Sons, Ltd.