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331.
T. R. Nelson R. J. Gillies D. A. Powell M. C. Schrader D. K. Manchesters D. H. Pretorius 《黑龙江环境通报》1987,7(5):363-372
Human amniotic fluid (HAF) is a dynamic system whose characteristics depend on continuous interchanges between fetal and maternal circulations. HAF reflects not only the environment of the fetus but may also provide information about fetal development or pathology. The concentration of HAF constituents varies with gestational age and pathological states. The number of the compounds currently implicated in fetal developmental pathology are relatively few. Currently used assay methods are not adequate to totally explain or predict the complex biochemistry of the fetus. The purpose of this work was to investigate HAF with NMR spectroscopy. In the present study HAF was obtained from 47 women undergoing routine amniocentesis. Cells were separated for karyological analysis and the supernatant was acid-extracted, lyophilized and re-suspended in D20 resulting in a concentration increase over native fluid. 1H NMR spectra were obtained at 360 MHz and 60 MHz. Eighteen compounds including several amino acids, were identified using parallel reference and standard addition protocols. NMR spectroscopy detected compounds of known clinical importance including glucose, leucine, isoleucine, lactate and creatinine. In conclusion, we have demonstrated that a number of physiologically relevant compounds are readily observable in HAF using 1H NMR spectroscopy. This technique can currently provide valuable information regarding HAF composition and has the potential of being used in vivo in the future. 相似文献
332.
含磷污水淋滤条件下土壤中磷迁移转化模拟实验 总被引:11,自引:2,他引:11
以土柱实验为基础,结合磷在土壤中的化学转化机理,将磷在土壤中的形态分为可溶态磷、吸附态磷和沉淀态磷,根据磷在土壤中的迁移转化模拟实验,分析了这3种形态的磷在土壤中迁移转化的规律:可溶态磷进入土壤中,主要随水分作溶质迁移,在迁移的同时,不断转化为吸附态磷和各种沉淀态磷;吸附态磷由可溶态磷生成,并与可溶态磷一起发生沉淀反应生成沉淀态磷,但固着于土壤颗粒上,不发生迁移;沉淀态磷由可溶态磷和吸附态磷生成,在土壤中主要参与化学转化;沉淀态磷在土壤中有随水分迁移的现象。 相似文献
333.
红外分光光度法作为国家标准方法,具有灵敏度高、适用范围广等优点,目前得到普遍应用.但在测定过程中,还存在萃取过程烦琐、萃取剂毒性大、有时准确度偏低等同题,结合工作经验,本文对红外分光光度法测定石油类中的萃取剂的替代、萃取次数、脱水操作进行了改进试验.结果表明,采用四氯乙烯替代四氯化碳作为萃取剂,能够满足环境监测中油类测试的精度要求,一次萃取在样品浓度为100mg/L以下时能满足测定要求,萃取液放在瓶中以无水硫酸钠脱水后再在普通漏斗中经脱脂棉过滤后定量也可满足测试要求. 相似文献
334.
Wang Hong liang Department of Biology Lanzhou University Lanzhou China Zhao Zhen jie Li Fa shen Department of Physics Lanzhou University Lanzhou China 《环境科学学报(英文版)》1998,(4)
1IntroductionAlthoughfiltermethodisverytimeconsuming,ithasbeenemployedintheinvestigationsofaerosolsforalongtime(Kopcewicz,19... 相似文献
335.
This study investigates the mechanism of photosensitization and the recombination of excited electron–hole pairs affected by depositing platinum (Pt) on the surface of titanium dioxide (TiO2). A new catalyst of Pt–TiO2 was prepared by a photoreduction process. Being model reactions, the photocatalytic oxidation of methylene blue (MB) and methyl orange (MO) in aqueous solutions using the Pt–TiO2 catalyst was carried out under either UV or visible light irradiation. The experimental results indicate that an optimal content of 0.75%Pt–TiO2 achieves the best photocatalytic performance of MB and MO degradation and that the Pt–TiO2 catalyst can be sensitized by visible light. The interaction of Pt and TiO2 was investigated by means of UV–Vis absorption spectra, photoluminescence emission spectra, and X-ray photoelectron emission spectroscopy. The Pt0, Pt2+ and Pt4+ species existing on the surface of Pt–TiO2, and the Ti3+ species existing in its lattice may form a defect energy level. The Pt impurities, including Pt, Pt(OH)2, and PtO2, and the defect energy level absorb visible light more efficiently in comparison with the pure TiO2 and hinder the recombination rate of excited electron–hole pairs. 相似文献
336.
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338.
在实验室模拟培养条件下,研究Shewanella oneidensis MR-1和Shewanella putrefaciens在厌氧体系中对V(V)的耐性试验,探讨在不同的V(V)浓度、接菌量、pH值和不同蒽醌-2,6-二磺酸(AQDS)浓度下对V(V)还原的影响,并通过扫描电镜(SEM)和X射线光电子能谱(XPS)进行表征.结果表明V(V)浓度低于10mg/L时对S.oneidensis MR-1和S.putrefaciens的生长影响较小,V(V)浓度超过20mg/L则会抑制其生长和V(V)的还原;随着接菌量的增加,2种微生物对V(V)的还原能力逐渐增强;2种微生物最适生长pH值均为7.0左右,弱碱性环境下2种微生物对V(V)的还原率高于弱酸性环境;添加1mmol/L AQDS会加快2种微生物对V(V)的还原.菌株培养3d后通过SEM分析,S.oneidensis MR-1和S.putrefaciens进行V(V)还原的同时也伴有少量的吸附作用.利用XPS能谱分析表明S.oneidensis MR-1和S.putrefaciens将V(V)还原为V(IV). 相似文献
339.
Zhiyan Li Pinhua Xie Renzhi Hu Dan Wang Huawei Jin Hao Chen Chuan Lin Wenqing Liu 《环境科学学报(英文版)》2020,32(9):248-255
The nitrate radical (NO3) and dinitrogen pentoxide (N2O5) play an important role in the nocturnal atmosphere chemistry. Observations of NO3 radicals and N2O5 were performed in a semirural ground site at Tai'Zhou in polluted southern China using cavity ring down spectroscopy (CRDS) from 23 May to 15 June 2018. The observed NO3 and N2O5 concentrations were relatively low, with 1 min average value of 4.4 ± 2.2 and 26.0 ± 35.7 pptV, respectively. The N2O5 uptake coefficient was determined to be from 0.027 to 0.107 based on steady state lifetime method. Fast N2O5 hydrolysis was the largest contributor to the loss of NO3 and contributed to substantial nitrate formation, with an average value of 14.83 ± 6.01 µg/m3. Further analysis shows that the N2O5 heterogeneous reactions dominated the nocturnal NOx loss and the nocturnal NOx loss rate is 0.14 ± 0.02 over this region. 相似文献
340.
在实验室纯培养条件下,探讨厌氧体系中Shewanella oneidensis MR-1对Cr(VI)的还原能力,采用扫描电镜(SEM)-能谱(EDS)、X射线光电子能谱(XPS)等方法进行表征.结果表明,S.oneidensis MR-1介导下不同浓度Cr(VI)的生物转化与微生物对铬的耐受特性密切相关,低浓度Cr(VI)对其生长影响不大,高浓度时细菌生长则受到抑制,进而抑制Cr(VI)的还原率;菌株对Cr(VI)的还原作用随着接种菌悬液量的增加而增强;菌株最适生长pH值为中性,弱碱性环境比酸性环境更有利于菌株对Cr(VI)的还原;增加Fe(Ⅲ)的量会加快Cr(VI)完全还原的速率.通过SEM-EDS和XPS分析,在对Cr(VI)进行处理5d后,菌体表面有Cr(VI)和Cr(Ⅲ)两种形态存在,证实S.oneidensis MR-1在对Cr(VI)进行还原的同时也伴有少量的吸附作用.微生物还原为环境中Cr(VI)的去除以及解毒提供了一种有效的方法. 相似文献