浅谈新闻背景的交待

每一条新闻都是在一定的环境和历史条件下形成的。新闻报道要正确反映新闻事实,常常需要介绍与新闻相关的背景。新闻背景也是一种事实,它可以用来说明、映衬新闻事实。本文从新闻背景的作用,运用新闻背景的方法,介绍背景材料应注意的问题三个方面对新闻背景的交待进行了研究和探讨。     

Blood zinc protoporphyrin, serum total protein, and total cholesterol levels in automobile workshop workers in relation to lead toxicity: Our experience

Blood zinc protoporphyrin (ZPP), serum total protein (TP), and total cholesterol (TC) levels in automobile workshop workers in relation to lead toxicity were analysed. In the present study, automobile workshop workers (healthy male workers at an age between 28 and 35 from four major automobile workshops in Kottayam, Kerala State, India) and the control (male healthy adults at an age between 28 and 35 residing at Aymanam, a distant village at Kottayam District, Kerala having reduced or no chance of lead exposure) displayed significant difference in blood lead (BPb) and blood ZZP (BZPP) level. The mean value of BPb in automobile workshop workers was 15.76±0.33 μg/dl, while in the control it was 8.20±0.15 μg/dl. In automobile workshop workers, the mean value of BZPP was 34.2±0.62 μg/dl. The control group exhibited a mean of 11.5±0.22 μg/dl. Automobile workshop workers exhibited significant increase in BZPP was corresponding to the increase in BPb level. The total protein levels estimated in automobile workshop workers showed significant decrease compared to control individuals, but was within the reference range of healthy individuals. The mean value of TP level in automobile workshop workers and control was 6.9±0.13 g/dl and 7.71±0.18 g/dl, respectively. There was no significant difference in blood haemoglobin (BHb) level among the automobile workshop workers and control. The serum TC level in automobile workshop workers showed significant decrease compared to the control individuals, but was with in the reference range of healthy individuals. The mean level of serum TC in automobile workshop workers was 162.00±3.44 mg/dl and the same in control was 172.86±4.32 mg/dl. The present study affirms occupational lead toxicity in automobile workshop workers and its effect on serum protein and cholesterol levels.     

Insecticidal activity of the medicinal plant, <Emphasis Type="Italic">Alstonia boonei</Emphasis> De Wild,against <Emphasis Type="Italic">Sesamia calamistis</Emphasis> Hampson

The bioactivity of the aqueous extracts of the leaf and stem bark of the medicinal plant, Alstonia boonei De Wild (Apocyanaceae), against the pink stalk borer, Sesamia calamistis Hampson (Lepidoptera: Noctuidae) was studied in a laboratory bioassay. The extracts were incorporated into artificial diet at a rate of 0.0% (control), 1.0%, 2.5%, 5.0%, and 10.0% (w/w). Both extracts significantly (P<0.01) reduced larval survival and weight in a dose dependent manner. The concentrations that killed 50% of the larvae (LC50) for the stem bark extract were 2.8% and 2.1% at 10 and 20 DAI (days after introduction), respectively, while those for the leaves extract were 5.6% and 3.5%. The weights of the larvae also varied significantly (P<0.05) between the treatments in a dose dependent manner. We conclude that both leaf and stem bark extracts of A. boonei are toxic, used as growth inhibitors to S. calamistis larvae, and hold good promise for use as alternative crop protectants against S. calamistis.     

萃取技术和联用技术在铅的形态分析中的应用

铅是环境生物体系和食物中存在的污染元素,其毒性与化学形态密切相关。文章重点概述了国内外近年来萃取技术和联用技术在食品等物质中铅形态分析上的应用进展。     

Microanalytical identification of Pb-Sb-Sn yellow pigment in historical European paintings and its differentiation from lead tin and Naples yellows

The work is focused on identification of lead tin yellow types I and II, Naples yellow, and also on discrimination of a less common, distinct yellow pigment, the ternary Pb-Sb-Sn oxide.The knowledge about all those Pb-based yellows was in fact forgotten after introduction of modern synthetic yellows in 19th century. As late as in the last decade of the 20th century, the existence of Pb-Sb-Sn yellow and its production have been rediscovered, and only then it has been identified in colour layer of artworks.Pb-Sb-Sn yellow has recently been identified in colour layer of 17th century Italian paintings by Sandalinas and Ruiz-Moreno [C. Sandalinas, S. Ruiz-Moreno, Lead tin-antimony yellow, historical manufacture, molecular characterization and identification in seventeenth-century Italian paintings, Stud. Conserv. 49 (2003) 41–52], and here we report the finding of this pigment in Mid-European painting of the 18th and 19th centuries. Lead tin yellows, lead antimony yellow (Naples yellow), and lead antimony tin yellow were synthesized in laboratory following historical recipes, their colour was analyzed, and their structure was confirmed to provide a basis for their routine identification in microsamples of artworks by X-ray microdiffraction. Unequivocal identification of Pb-based yellows could help in authentication of traditional European paintings, because their use was temporally and also geographically specific. Combination of elemental microanalysis (X-ray fluorescence electron microanalysis) and X-ray powder microdiffraction were found very efficient in the microanalysis of colour layers of artworks with Pb-based yellows and their unequivocal identification.     

火焰原子吸收光度法测废水中的铅和铬

本法采用了火焰原子吸收法测定废水中的铅和铬含量,经过查阅比较,发现样品前处理简便、快捷,克服了消化法繁琐、耗时以及直接进样法的易堵塞燃烧头、基线漂移等缺点,测定结果准确,方法线性良好,样品加标回收率为88.6%和91.4%。     

整体浇注在铅锑冶炼中的应用

随着新型复合材料的研究与发展,多种新型的高温耐腐蚀材料在各类工业上面得到了广泛的应用。文章介绍了鑫华公司自把整体浇注应用到铅锑冶炼的筑炉工艺上后,采用新型耐火材料取代传统定型耐火材料以浇注方式对冶炼炉子的下料圈、炉墙进行整体浇注的实践。     

Chinese archaeological artefacts: Microstructure and corrosion behaviour of high-leaded bronzes

Metallographic features of ancient bronze artefacts often hide peculiar micro-chemical processes and corrosion behaviours, which are worth to be studied as they can provide conservators and archaeologists with valuable tools and information. It is widely documented that Chinese bronzes were cast and the way to adjust their properties was to change the alloy composition. In particular, addition of lead, which is insoluble in the bronze matrix, results in the formation of inclusions or globules, which undergo oxidation processes leading to their conversion into corrosion products. The mechanisms through which this occurs were still poorly investigated. The present work was conducted to further study the corrosion behaviour of high-leaded bronze, especially focusing on the behaviour of lead globules. To this aim, a collection of Chinese archaeological bronzes, showing intermediate steps of degradation, were selected and investigated. The use of combined microscopy-based, molecular and elemental, analytical techniques allowed the characterization as well as the precise location of corrosion products, thus enabling us to propose a degradation pathway basing on thermodynamic data provided by Pourbaix diagram. The achieved results will be useful for researchers involved in these kinds of studies to better interpret data obtained.     

原料乳及其成品乳中重金属污染的研究

为了给消费者提供乳制品质量参考,对山东省某乳制品企业的原料乳和成品乳随机抽样,用原子吸收光谱法和原子荧光光谱法测定了其中铅、铬、汞和砷等重金属的含量．结果表明,该企业的原料乳和成品乳都存在不同程度的铅、铬、汞和砷等重金属污染,其中,部分原料乳铅含量严重超出国家食品质量安全标准,成品乳铅含量轻微超标．