共查询到20条相似文献,搜索用时 31 毫秒
1.
用原子吸收光谱法测定延边地区317名65~108岁老人头发中锌、铜、铁、锰、镁含量,观察不同民族、性别、年龄老人这些元素的差异。结果表明:1.朝鲜旗发锌低于汉族,满族发铜低于汉族、朝鲜族,汉族发镁高于朝鲜族、满族,发铁、发锰在汉、朝、满民族之间无区别。2.汉族、朝鲜族男发锌高于女性,汉族女性发铜高于男性,发铁、发锰、发镁在性别之间无区别。3、90岁组朝鲜族发锰、发镁低于65岁、76岁组,朝鲜族发锌、发铜、发铁在65~108岁之间无统计学意义。 相似文献
2.
T. S. Kiran D. C. Hiremath S. T. Nandibewoor 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(12):2070-2077
The kinetics of oxidation of L-lysine by diperiodatocuprate (III) (DPC) in alkaline medium at a constant ionic strength of
0.15 mol/dm3 was studied spectrophotometrically. The reaction between DPC and L-lysine in an alkaline medium had a 1: 2 stoichiometry
(L-lysine: DPC). The reaction was first order in [DPC] and less than first order in [L-lysine] and [alkali]. The addition
of periodate had no effect on the rate of the reaction. The intervention of free radicals was observed in the reaction. The
oxidation reaction in alkaline medium was shown to proceed via a DPC-L-lysine complex. The main products were identified by
spot test and spectral studies. The reaction constants involved in different steps of the mechanism were calculated. The activation
parameters with respect to the slow step of the mechanism were computed and discussed, and thermodynamic values were also
determined.
The article is published in the original. 相似文献
3.
小波包分析用于重叠分析化学信号的处理 总被引:9,自引:1,他引:8
对小波包分析的算法进行了改进,并将此算法成功地应用于多组分重叠色谱信号的解析.结果表明,本文提出的算法解决了MRSD算法的不足,更适合处理分析化学信号,用于重叠信号的解析时不需重构(逆变换),简化了数据处理步骤,加快了数据解析速度,具有较强的解析能力.对于重叠色谱信号的解析,小波包分析比小波分析具有更强的解析能力. 相似文献
4.
5.
6.
先锋褐煤在水热处理过程中的结构演绎 《燃料化学学报》2016,44(2):129-137
以先锋褐煤(XF)为原料,在高压反应釜中考察了水热处理过程中褐煤的结构变化,通过13C固体核磁共振(NM R)和傅里叶变换红外光谱进行了分析表征。结果表明,在低于240℃的水热处理条件下,煤有机分子结构中的弱化学键有一定断裂,含氧官能团逐步减少;水中氢以离子形态迁移至褐煤中,处理后褐煤结构中甲基比例先增加后减少,次甲基比例由原煤的4.80%增加至XF-240的13.16%;释放的气体中主要是CO_2,烃类气体组分随处理温度的升高略有增加。当水热处理温度高于240℃时,褐煤中部分共价键开始断裂,释放的烃类气体(C1-4)由240℃时的2.13%增加至300℃时的8.59%,脂肪碳比例由XF-240的44.83%降低至XF-300的39.49%,与氧连接的碳比例由XF-240的12.57%降低至XF-300的1.49%。水热处理对褐煤的脱氧提质效果显著,300℃时氧含量降低约30%,芳香碳比例增加至60.50%,比原煤提高19%。 相似文献
7.
癫痫与微量元素 总被引:4,自引:1,他引:3
周清潮 《广东微量元素科学》1999,6(10):7-9
评论了微量元素锌,铜,铁,锰与癫痫的关系。癫痫患者血浆中锌、铜、铁含量比正常对照组增高,锰含量降低。锌/铜比值较正常对照组明显降低。而癫痫患者发锌,铁含量比正常人对照组升高,发铜,锰含量降低。 相似文献
8.
冷原子荧光法测定水中汞 总被引:9,自引:0,他引:9
研究了以高锰酸钾消化,冷原子荧光法测定水质中汞的最佳测定条件。汞含量在0.0025~0.075μg范围内呈线性关系,相关系数为0.99993,检出限为0.026μg.L-1。方法应用于水样中汞的测定,样品加标回收率在97.6%~117.0%之间,相对标准偏差在1.7%~5.7%之间。 相似文献
9.
马来酸酐与环氧丙烷开环共聚,所得聚酯具有功能团(C=C),可以通过接技、交联待方法改变其性能,马来酸杆与环氧化物开环共聚合成聚酯,所用催化剂通用有有机金属化合物和稀土 事物等,我们在铁系催化丁二聚合和马来酸酐与苯乙烯共聚的基础上,首次将Fe(acac)3-Al(i-Bu)3-α,α′-联吡啶催化剂用于马来酸酐与环氧化物开环共聚,发现该催化剂催化共聚反应具有时间短、收率高、共聚物交替度高等优点,并测定了共聚合反应动力学的参数。 相似文献
10.
11.
12.
13.
为了分析烤烟中游离氨基酸含量与烤烟香型、产地的关系,以国内14个烟草种植省份的138个调制后的烤烟中部叶片为材料,采用柱前衍生-超高效液相色谱-单重四极杆质谱法对烤烟中的20种游离氨基酸进行分析。方法表征结果显示该方法满足分析要求,适合烤烟中游离氨基酸的检测。对调制后烤烟中部叶片的游离氨基酸分析结果显示,烤烟的游离氨基酸含量在产地间差异很大(28.50%~94.20%),其中天冬酰胺、谷氨酰胺含量的相对标准偏差(RSD)超过80%;在3种典型香型(浓香型、清香型和中间香型)烤烟中,浓香型烤烟游离氨基酸含量的RSD大于其他两种香型。对同一香型的不同种植省份和同一省份不同香型的烤烟游离氨基酸分析结果显示,其含量呈现一定的规律。 相似文献
14.
Abstract— The base composition of messenger RNA in Escherichia coli B/r and B 8–1 irradiated with ultraviolet (u.v.) light has been examined. The experimental results are as follows: (1) the synthesis of rapidly labeled RNA does not stop in ultraviolet irradiated bacteria. (2) The rapidly labeled RNA in irradiated cells shows a change in base composition corresponding to the formation of pyrimidine dimers in DNA molecules. The mole per cent of adenine component is increased with ultraviolet dose. The ratio of purine/pyrimidine becomes larger and the GC content smaller. (3) The base composition of the rapidly labeled RNA in irradiated bacteria reversed to that in unirradiated cells, when the irradiated cells were reactivated by experimental procedures for photoreactivation or dark reactivation. The reversion in the base composition corresponds well to the decrease in the amount of thymine dimers in DNA molecules. (4) The mechanism of the change in the base composition of rapidly labeled RNA caused by ultraviolet irradiation is discussed. 相似文献
15.
The absorption and emission spectral properties of thioflavin T (TFT+) in Nafion (Nf) and cellulose matrices have been studied. Formation of the emittive dimer is observed in both matrices. The monomer TFT+ emission is blueshifted in Nafion membrane (Nf), whereas it is red-shifted in cellulose membrane when compared with the emission in aqueous solution. The dimer emission of TFT+ in the Na+-Nf membrane undergoes off-on switching with acids and alkalis. The TFT+ molecule undergoes protonation in the H+-Nf and the protonated dye is fluorescent. The dimer emission of TFT+ is not observed in the dry H+-Nf membrane because of the protonation of the TFT+ molecule. The diffusion coefficient and the free energy of hydrophobic interaction for the TFT+ molecule in the Nf membrane are calculated. The TFT+ molecule experiences hydrophobic and electrostatic interactions in the Nf matrix, whereas it experiences a polar environment in the cellulose membrane. The 3D emission spectral studies support the formation of the emittive dimer in both Nf and cellulose matrices. 相似文献
16.
The micelle formation of Tyr-Phe dipeptide and Val-Tyr-Val tripeptide has been studied for the first time. The aggregation numbers were determined for both the peptides in aqueous solution and in the presence of SDS and PEO-PPO-PEO triblock copolymer additive environments. The results obtained by steady state and time-resolved fluorescence spectroscopic techniques are in good agreement with each other. The higher value of aggregation number confirms the formation of mixed micelles. The fluorescence lifetime of tyrosine in various micellar and mixed micellar systems were also determined. The decreased lifetime values with the quencher suggested the dynamic nature of the quenching process. However, the possibility of static quenching cannot be ruled out. The accessibility of DPC quencher was found to be more in dipeptide than tripeptide. 相似文献
17.
18.
Issa RM El-Baradie KY El-Wakiel NA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(12):2883-2889
The electronic absorption spectra of some bisazo-dianils are studied in organic solvents of different polarity and in buffer solutions of varied pH. The different absorption bands are assigned to the corresponding electronic transitions, the solvent effect on the CT band energy is also discussed. The spectral study in buffer solutions is utilized for the determination of the pKa of the phenolic OH-groups. The important bands in the IR spectra as well as the signals of the 1H NMR spectra are assigned and discussed in relation to molecular structure. The fluorescence spectra of the compounds are recorded. The fluorescence quantum yield and pK in the ground and excited states are determined. 相似文献
19.
The rates of ring-opening of propylene oxide (PO) and propylene sulfide (PS) with dibutylamine (DBA) were measured in the range 40°–70°. The PO-DBA reaction in toluene (Tol) was too slow to be studied in detail. The PO-DBA reaction in DMSO-benzene mixtures was quicker and found to be competitive between the second-order dependent on the first order both in the PO concentration and in the DBA concentration, and the third-order by the participation of reaction products. The PS-DBA reactions both in Tol and in DMSO-Tol mixtures were found to obey the same kinetics as the PO-DBA reaction. The order of reactivity is PSPO. The PS-DBA reaction in DMSO-Tol mixtures was accelerated and the increase in reactivity of PS was based on the selective solvation of thiolate anion by DMSO in the transition state. The pull process was shown to be an important factor in the base-catalyzed ring-opening. 相似文献