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111.
This paper introduces a mathematical model which makes it possible both to determine the concentration of photosynthetic herbicides and to obtain a quantitative parameter in order to compare their activity using a previously described sensing system. The working principle involves the changes in absorption properties at 860 nm of the reaction centre (RC) isolated from the bacteria Rhodobacter sphaeroides when photosynthetic herbicides are present. The method has been used for the determination and activity comparison of five photosynthetic herbicides: diuron, atrazine, terbutryn, terbuthylazine and simazine. Detection limits obtained were 2.2, 0.75, 0.046, 0.25, and 1.4 μM, respectively. The resulting order for the different herbicides according to their action on RC was: terbutryn > terbuthylazine > atrazine > simazine > diuron. 相似文献
112.
论述了激光拉曼光谱对高分子结构、结晶形态和表征,反应动力学过程和取向的研究,还介绍了纵向声学模、共振、高温高压、光波导和付里叶拉曼光谱在高分子研究中的最新进展。 相似文献
113.
114.
将高能Zn2+注入到CaF2介电基质中,在CaF2的表面下注入Zn2+浓度呈近似高斯分布,通过氧气氛后经热退火形成ZnO量子点.采用MaterialsStudio和Gaussian98W程序,结合实验结果计算分析了CaF2基质中ZnO纳米粒子的电子结构和光学性质.选取由4个ZnO原胞组成的超晶胞模型计算了ZnO纳米粒子的吸收光谱,理论结果与实验结果相符.对ZnO纳米粒子电子结构的研究结果表明,ZnO纳米粒子与CaF2基质的相互作用主要是ZnO表面的O与基质中Ca之间的作用,这种作用使ZnO纳米晶体的Fermi能级变窄,带隙相应减小;ZnO纳米粒子表面构型的变化对其本征吸收光谱没有影响,理论计算结果与实验值一致. 相似文献
115.
116.
Anilkumar Appajaiah Volker Wachtendorf Werner Daum 《Polymer Degradation and Stability》2006,91(11):2605-2613
The thermo-oxidative stability of commercially available polymer optical fibers (POFs) and their components (cores and claddings) was investigated. All the bare POFs (core and cladding only) studied here were based on poly(methyl methacrylate) (PMMA) core. The fibers were exposed to 100 °C/low humidity for about 4200 h. Chemiluminescence (CL) technique was applied to investigate the thermo-oxidative stability and for measuring the transmission loss during exposure a prototype device called multiplexer was used. POFs exhibited variation in thermo-oxidative stability although they possessed identical core material PMMA. This was due to difference in the chemical compositions of claddings. Claddings were more susceptible to the thermo-oxidative degradation compared to cores. The thermo-oxidative degradation of both the cladding and the core was found in POFs as a result of climatic exposure. POFs showed an early drop-off followed by a slow decline of transmission. The early drop-off of transmission was attributed to physical changes like thermal expansion and the slow decline of transmission to chemical changes like oxidative degradation of POFs. A good linear relationship between optical transmission stability and thermo-oxidative stability of POFs was established from these studies. 相似文献
117.
The plasma polymerization of 4-phenylbenzonitrile was carried out with the objective of synthesizing a novel conjugated polynitrile thin film with a better optical property. The structure, compositions and morphology of the plasma-polymerized 4-phenylbenzonitrile (PPBPCN) thin films were investigated by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). A fine, homogenous PPBPCN film with a large π-conjugated system and a high retention of the aromatic ring structure of the starting monomer in the deposited plasma films is obtained when a low discharge power of 30 W was used during film formation. For the first time, a blue emission with relatively high photoluminescence intensity for PPBPCN thin films was observed. 相似文献
118.
Kenji Maeda Ross A. Miller Ali Shafiee Joseph D. Armstrong III 《Tetrahedron letters》2005,46(9):1545-1549
Highly diastereoselective (>20:1) bromo-lactonization of N-sulfonyl-2-allyl-2-phenylglycine methyl ester (11) was observed. Successive treatment of the chiral lactone with MeONa gave the desired (2S,4R)-4-hydroxy-2-phenylproline derivative in high yield without erosion of the diastereoselectivity. The starting chiral non-racemic compound (5) was prepared from the racemic 2-phenylglycine using a classical kinetic resolution (crystallization), an asymmetric phase transfer alkylation, and an enzyme-catalyzed kinetic resolution. 相似文献
119.
Monitoring nitrite with optical sensing films 总被引:1,自引:0,他引:1
Ali A. EnsafiA. Kazemzadeh 《Microchemical Journal》2002,72(2):193-199
A new, low-cost nitrite sensor was developed by immobilizing a direct indicator dye in an optical sensing film for food and environmental monitoring. This sensor was fabricated by binding Safranine O to a cellulose acetate film that had previously been subjected to an exhaustive base hydrolysis. The membrane has good durability (>12 months) and a short response time (<8 s). Nitrite can be determined for the range of 0.005-2.00 μg ml−1 with 3δ detection limits of 0.001 μg ml−1. The method is easy to perform and uses acetylcellulose as a carrier. The reagents used for the activity of the cellulose support are inexpensive, non-toxic and widely available. 相似文献
120.