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121.
2,4-二氯苯酚低浓度长期暴露对鲫鱼肝脏抗氧化系统的影响 总被引:18,自引:2,他引:16
在室内模拟条件下,研究了低浓度2,4-二氯苯酚(2,4-DCP)长期暴露(40d)对鲫鱼(Carassius auratus)幼体肝脏抗氧化系统的影响结果表明:过氧化氢酶(CAT)活性、谷胱甘肽过氧化物酶(Se-GPx)活性、氧化型谷胱甘肽(GSSG)含量可被显著诱导;超氧化物歧化酶(SOD)活性在0.005mg·L-1 2,4-DCP污染胁迫下即被显著诱导;还原型谷胱甘肽(GSH)含量几乎持续受到抑制;谷胱甘肽还原酶(GR)活性则先受到抑制后逐渐回升;谷胱甘肽硫转移酶(GST)的活性变化较小,仅在2个低浓度组中有轻微诱导.GR、GSH,尤其是SOD,对2,4-DCP较为敏感,可以作为水生生态系统中2,4-DCP污染的一项早期监测指标. 相似文献
122.
A novel spectrophotometric method for the determination of molybdenum(VI) by using a natural reagent, water extract of slippery elm tree leaves, is developed. Molybdenum(VI) reacts with this natural reagent to form an orange colored product. The formed product shows maximum absorbance at 418 nm with a molar absorptivity value of 0.57 × 104 L mol?1 cm?1, and this method is linear in the 0.4–10 mg L?1 concentration range. The detection limit value was found to be 0.0350 mg L?1. The proposed method is simple, clean, low cost, selective, and sensitive. It was applied to the analytic samples with satisfactory results. 相似文献
123.
A sensitive, accurate and reproducible method for the analysis of metoclopramide, a gastrointestinal drug, has been described. An isocratic HPLC elution method was employed which requires about 10 minutes to be performed. The concentration of metoclopramide hydrochloride preparations was found to be 95.1 ±0.3% and 94.21 ±0.25% in tablet and injection formulations, respectively. 相似文献
124.
P. Van Der Sluis G. W. H. Moes H. Behm C. Smykalla P. T. Beurskens A. T. H. Lenstra 《毒物与环境化学》2013,95(2-3):121-127
A method for the preparation of single crystals of PCB 35 suitable for single crystal X‐ray structure determination was developed. This method has already been proven suitable for 2,4'‐dichlorobiphenyl and may prove useful for other PCBs or related compounds. The crystals of PCB 35 are orthorhombic, spacegroup P21221 (a= 10.665(8), 6 = 3.825(3), c= 14.086(9) Å) and the structure was refined to R = 0.094 for 156 unique observed reflections and 43 parameters. Although the crystals were of poor quality, the structure determination unequivocally confirmed the substitution pattern of the biphenyl moiety by Cl atoms inferred previously from spectroscopic methods. The dihedral angle between the planes of the two phenyl rings is 33(2)°. 相似文献
125.
高效液相色谱-荧光检测法同时测定畜禽粪便中4种磺胺类药物残留 总被引:4,自引:0,他引:4
建立了高效液相色谱-荧光检测法测定畜禽粪便中4种磺胺药物(磺胺甲基嘧啶(SM1)、磺胺氯哒嗪(SCP)、磺胺邻二甲氧嘧啶(SDM’)、磺胺喹噁啉(SQ))的方法.样品用25 mL甲醇提取3次,合并提取液,浓缩干燥,用0.1 mol.L-1的HCL溶解残渣,经荧光胺衍生化后,用反相C18柱为分离柱,以乙腈∶0.5%乙酸=40∶60(V/V)为流动相进行洗脱,20 min内分离4种药物.在0.05—5.00μg.mL-1范围内,4种磺胺类药物的峰面积与质量浓度的线性关系良好(R2≥0.999),SM1、SCP、SDM’、SQ的定量限(LOQ)分别为2.3、6.3、4.3和9.6μg.kg-1;添加水平为50、100、1000μg.kg-1时,SM1、SCP、SDM’、SQ的回收率分别为74.91%—81.82%、78.45%—91.43%和86.10%—92.88%,RSD小于8.82%. 相似文献
126.
We formulate a two-sex model of temperature-dependent sex determination (TSD) for a freshwater turtle (C. picta) population. The aim is to understand how environmental temperature variations and nest heat conduction properties affect the long term dynamics of the population. This is a key to understanding how global temperature changes may affect their survival. With stochastic inputs of ambient temperature and solar radiation, the model uses the heat equation to determine the temperature in the egg layer in the nest; in turn, this determines the sex ratio in the egg clutch using a variable degree-day model. Finally, a nonlinear Leslie type, stage-based, two-sex model, is used to determine the long term male and female populations. A two-sex model is required because of different development rates for males and females. The model is flexible enough to enable other researchers to examine the effects of temperature variation variations on other species with TSD, e.g., crocodilians, reptilians, as well as other turtle species. It can be adapted to study effects of nest location, soil type, rain events, different incubation periods, and density effects, for example, the dependence of the mating function on the ratio of males to females and each’s contribution to the sex of hatchlings. Modifications can be easily made to fit a specific life history traits. The model is a beginning step in understanding the long term, high fitness shown by many reptile species with TSD, and it may suggest to experimentalists what data may be relevant to these issues; it can also be useful to wildlife managers in developing strategies for intervention if needed. Among the principal findings are that temperature variability and detailed nest heat conduction properties may buffer projected negative effects on a population. 相似文献
127.
128.
A continuously expanding group of commodities are being priced on commodity exchanges. This paper explains the causes to the increasing preference of exchanges as pricing instruments. It also provides the detail of the shift in the 1970s and 1980s from producer determined prices to prices set by commodity exchanges for three major commodities—aluminum, nickel and petroleum. 相似文献
129.
高锰酸盐指数测定的影响因素研究 总被引:1,自引:0,他引:1
采用正交实验设计法L9(34)考察高锰酸盐指数测定的影响因素,确定各因素的主次关系及最佳测定条件。结果表明,高锰酸钾浓度对高锰酸盐指数测定的影响程度最大,其次是加热时间及滴定时间,影响较小的是溶液的酸度。在最佳测定条件下:1+3硫酸、加热8min、60s内滴定、高锰酸钾浓度为0.0100mol/L,加标回收率为101%。 相似文献
130.