电感耦合等离子体—质谱法测定成人脏器样品中痕量稀土元素的研究

本文采用ＩＣＰ－ＭＳ法对成人脏器样品中痕量稀土元素进行了研究，选择了测定的最佳仪器参数，检查了测定中的各种干扰和影响；用铼（Ｒｅ）为内标元素补偿基体抑制效应和灵敏度的漂移。方法对稀土元素各分量的检出限为０．００５－０．０２６ｎｇ．ｍ１＾－１，标准回收率为９２．９－１１１．３％，精密度为０．９６－３．０７％。在严格分析质量控制的基础上用混合酸消解样品，不须分离富集，直接对成人的心、脾、肝、肾、肺肉中     

Small sample estimation for Taylor's power law

An analysis of counts of sample size N=2 arising from a survey of the grass Bromus commutatus identified several factors which might seriously affect the estimation of parameters of Taylor's power law for such small sample sizes. The small sample estimation of Taylor's power law was studied by simulation. For each of five small sample sizes, N=2, 3, 5, 15 and 30, samples were simulated from populations for which the underlying known relationship between variance and mean was given by ² = c^d. One thousand samples generated from the negative binomial distribution were simulated for each of the six combinations of c=1,2 and 11, and d=1, 2, at each of four mean densities, =0.5, 1, 10 and 100, giving 4000 samples for each combination. Estimates of Taylor's power law parameters were obtained for each combination by regressing log₁₀ s ² on log₁₀ m, where s ² and m are the sample variance and mean, respectively. Bias in the parameter estimates, b and log₁₀ a, reduced as N increased and increased with c for both values of d and these relationships were described well by quadratic response surfaces. The factors which affect small-sample estimation are: (i) exclusion of samples for which m = s ² = 0; (ii) exclusion of samples for which s ² = 0, but m > 0; (iii) correlation between log₁₀ s ² and log₁₀ m; (iv) restriction on the maximum variance expressible in a sample; (v) restriction on the minimum variance expressible in a sample; (vi) underestimation of log₁₀ s ² for skew distributions; and (vii) the limited set of possible values of m and s ². These factors and their effect on the parameter estimates are discussed in relation to the simulated samples. The effects of maximum variance restriction and underestimation of log₁₀ s ² were found to be the most severe. We conclude that Taylor's power law should be used with caution if the majority of samples from which s ² and m are calculated have size, N, less than 15. An example is given of the estimated effect of bias when Taylor's power law is used to derive an efficient sampling scheme.     

Nonparametric estimation of Shannon’s index of diversity when there are unseen species in sample

A biological community usually has a large number of species with relatively small abundances. When a random sample of individuals is selected and each individual is classified according to species identity, some rare species may not be discovered. This paper is concerned with the estimation of Shannons index of diversity when the number of species and the species abundances are unknown. The traditional estimator that ignores the missing species underestimates when there is a non-negligible number of unseen species. We provide a different approach based on unequal probability sampling theory because species have different probabilities of being discovered in the sample. No parametric forms are assumed for the species abundances. The proposed estimation procedure combines the Horvitz–Thompson (1952) adjustment for missing species and the concept of sample coverage, which is used to properly estimate the relative abundances of species discovered in the sample. Simulation results show that the proposed estimator works well under various abundance models even when a relatively large fraction of the species is missing. Three real data sets, two from biology and the other one from numismatics, are given for illustration.     

雷州半岛桉树人工林地的生物改良研究

研究雷州半岛桉树人工林地的生物改良途径。结果表明；桉树林下间种绿肥、牧草或菠萝，可以提高林地覆盖度，增加林地枯落物，提高土壤肥力，促进桉树的生长。筛选出比较适宜于桉树人工林下间种的植物品种，并对间种的经济效益作了初步分析。     

桉树人工林生态系统养分循环与平衡研究Ⅰ. 桉树人工林生态系统的养分贮存

采用田间试验和定位方法，在标准样地中研究养分的输入、输出和贮存。桉树人工林生态系统的养分贮存，包括土壤、桉树林分和凋落物三者贮存的养分。在田间试验的基础上，获得了大量的分析数据。论述了刚果W5桉树人工林生态系统土壤养分的贮存量、林分的养分贮存量和凋落物层的养分贮存量以及上述分系统内大、中量元素的含量比例。土壤养分的贮存量，全量养分以K最多，其次为N、P；有效养分贮存量大小的顺序为N，K，Ca，P，Mg，Mn，Zn，Cu，B。桉树林分的总养分贮存量，是逐年增加的，但以第2年的增量最大；各元素贮量大小，则每年不同。凋落物层的养分贮存量，总体上逐年增长，但以第4年最多；各元素贮存量大小的顺序为N，Ca，Mg，K，P。这些结果，对于指导桉树施肥，有重要的参考价值。     

热空气处理对荔枝生理特性和贮藏效果的影响

以黑叶荔枝为材料,以成熟季节的大气平均温度[θ=(30±1.5)℃]为基础,研究35℃、38℃热空气分别处理6 h、12 h和24 h对果实生理特性与贮藏效果的影响.与CK相比,温度升幅增大或处理时间延长,显著提高果皮多酚氧化酶(PPO)活性、果皮过氧化物酶(POD)活性、果实呼吸速率、果皮丙二醛(MDA)含量和果皮质膜相对透性,显著降低果肉可溶性固形物(SS)含量、果肉可滴定酸(TA)含量、果皮花色素苷含量和好果率.POD活性和MDA含量可作为果实生理活性的指标.图6表2参10     

The Contribution of Drinking Water towards Dental Fluorosis: A case study of Njoro Division, Nakuru District, Kenya

This study was carried out to measure the fluoride levels of water consumed in the Njoro division of Nakuru district, Kenya. The sources of drinking water, methods of water storage and utilisation, as well as the perceptions of the local community towards dental fluorosis and the percentage of children with moderate to severe dental fluorosis were also determined. Rainwater had mean fluoride levels of 0.5 mg L^-1, dams 2.4 mg L^-1, wells 4.1 mg L^-1, springs 5.5 mg L^-1, and boreholes 6.6 mg L^-1. Water stored in plastic and cement containers did not show appreciable reduction in fluoride content with storage time; water stored in metal containers reduced fluoride by up to 8.2%; water stored in clay pots had the highest reduction in fluoride content, ranging between 34.3 and 64.7%;. Forty eight point three percent of children observed in the area had moderate to severe dental fluorosis, even though most people in the area did not know the cause of the problem.There is need to educate the community on the causes of fluorosis, and to lay strategies for addressing the issue, such as encouraging more rainwater harvesting, treating drinking water with alum, or using clay pots for storage of drinking water.     

环境样品前处理技术及其进展（一）

本文讨论了环境分析化学中样品制备及前处理技术的现状及其进展。有关环境样品的特点、前处理的目的及其作用、选择前处理技术的依据等也做了阐述。重点评述了近年来在环境分析化学领域中发展最快、用得比较普遍的几种新方法，即超临界流体萃取、固定萃取、微波溶出和液膜萃取等。（一）介绍样品前处理的原则和有关的基础，以及超临界流体萃取法；（二）其它方法及今后的发展动向（将刊登在《环境化学》１９９４年第二期）。     

栽培水分对采摘后油菜硝酸盐与亚硝酸盐含量的影响

采用盆栽方法栽培油菜(Brassicaca mpestrisL.),研究了灌水水平对采摘后油菜植株体硝酸盐与亚硝酸盐含量随时间变化的影响。共设高(灌水控制上限为田间持水量)、中(灌水控制上限为田间持水量的75%)和低(灌水控制上限为田间持水量的50%)3个灌水水平。油菜采摘后恒温贮存,定期测定油菜植株体内硝酸盐、亚硝酸盐含量。研究结果表明:不同灌水水平和贮存时间以及两者的交互作用都能显著地影响油菜植株体硝酸盐和亚硝酸盐含量;在采摘后的8d时间里,低灌水水平处理(0.50θf处理)的油菜植株体硝酸盐含量一直高于其它两处理;采摘后当天测定高灌水水平处理(1.00θf处理)的油菜植株体硝酸盐含量最低,以后则以中等灌水水平处理(0.75θf处理)的油菜植株体硝酸盐含量为最低。采摘后当天测定油菜植株体亚硝酸盐含量,亦以高灌水水平处理(1.00θf处理)为最低。采摘后油菜植株体硝酸盐和亚硝酸盐含量都经历一个先降低、后升高、再降低的变化过程。因此,从对人体健康及卫生的角度出发,以较高灌水水平栽培油菜,采摘后在一两天内食用,有利于将其硝酸盐和亚硝酸含量控制在较低水平。     

水中总磷和溶解性磷酸盐的快速分光光度法

在H_2SO_4溶液介质中,磷钼钒三元杂多酸与孔雀绿反应形成有色络合物,在波长620nm处表观摩尔吸光系数为1.73×10~5L/mol·cm,线性范围是0～0.4(mg/L).检测下限为0.016mg/L,方法准确、稳定,操作简便、快速.能够用于水中总磷和溶解性磷酸盐的测定.