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991.
以叶绿素降解产物脱镁叶绿酸-a甲酯为起始原料,利用空气氧化反应在12-位上引进甲酰基,再通过氧化、还原、Grignard、Knoevenagel、Cannizzaro和1,3-偶极环加成等经典反应进行官能团转换,并对五元外接E-环实施结构改造,在C(12)-位上分别建立了能与大环色基形成不同共轭程度的酰基、酯基和取代烃基,完成了一系列未见报道的叶绿素类二氢卟吩衍生物的合成,其化学结构均经UV,IR,1H NMR及元素分析予以证实,同时也讨论了C(12)-位非甲基化对叶绿素类四吡咯大环分子所形成的各种影响. 相似文献
992.
In this study, a fast, low‐cost, and facile spray method was proposed. This method deposits highly sensitive surface‐enhanced Raman scattering (SERS) silver nanoparticles (AgNPs) on the paper‐microfluidic scheme. The procedures for substrate preparation were studied including different strategies to synthesize AgNPs and the optimization of spray cycles. In addition, the morphologies of the different kinds of paper substrates were characterized by SEM and investigated by their SERS signals. The established method was found to be favorable for obtaining good sensitivity and reproducible results. The RSDs of Raman intensity of randomly analyzing 20 spots on the same paper or different filter papers depositing AgNPs are both below 15%. The SERS enhancement factor is approximately 2 × 107. The whole fabrication is very rapid, robust, and does not require specific instruments. Furthermore, the total cost for 1000 pieces of chip is less than $20. These advantages demonstrated the potential for growing SERS applications in the area of environmental monitoring, food safety, and bioanalysis in the future. 相似文献
993.
This paper reviews the progress of two-dimensional mesoporous materials including their synthesis strategy,mesostructure,composition,surface property,flexibility,and potential applications.During the past two decades,research on two-dimensional mesoporous materials has experienced an evolution from fragile coatings to flexible membranes.Aiming at practical applications,it is significant to support mesoporous materials with proper matrices for example porous membranes especially flexible ones to form mesoporous composite membranes with designed pore size and chemistry. 相似文献
994.
以乙二醇单苯醚-甲醛负载三乙烯四胺螯合树脂(PB-TETA)为前驱体,经氨基与二硫化碳反应,得到含二硫代氨基甲酸基酚醛型螯合树脂(PB-TETA-CS2)。对所制备的新型螯合树脂进行了红外光谱和元素分析等表征,研究了树脂对Ag+、Hg2+、Cu2+、Pb2+和Ni2+等金属离子的静态饱和吸附量及树脂对Ag+的动力学及热力学吸附性能。结果表明,该树脂对Ag+的吸附量最高;pH=4时的最大吸附量为0.18mmol/g。树脂对Ag+的吸附受液膜扩散控制,等温吸附过程符合Langmuir单分子吸附模型。 相似文献
995.
996.
This paper is concerned with exact boundary behavior of large solutions to semilinear elliptic equations △u=b(x)f(u)(C0+|▽u|q),x∈Ω,where Ω is a bounded domain with a smooth boundary in RN,C0≥0,q E [0,2),b∈Clocα(Ω) is positive in but may be vanishing or appropriately singular on the boundary,f∈C[0,∞),f(0)=0,and f is strictly increasing on [0,∞)(or f∈C(R),f(s)> 0,■s∈R,f is strictly increasing on R).We show unified boundary behavior of such solutions to the problem under a new structure condition on f. 相似文献
997.
Existence of Positive Solutions for a Nonlinear
Second Order Periodic Boundary Value Problem 下载免费PDF全文
By using the first eigenvalue corresponding to the relevant linear
operator and the topological degree theorem, sufficient conditions for the existence of positive solutions for a nonlinear second order periodic boundary
value problem are given. Our results improve and generalize some preliminary
works. 相似文献
998.
Ye Cheng Bao Shi Wenfei Zhao Liangliang Ding 《Journal of Applied Analysis & Computation》2019,9(5):1927-1939
This paper presents a new class of protocols to solve finite-time consensus for multi-agent systems. The protocols are induced from the classical finite-time consensus algorithm by using the so-called protocol function. Sufficient conditions are established for networked agents to experience finite-time consensus under time-varying undirected and fixed directed topologies. Numerical simulations show that the proposed protocols can provide more flexibility to improve convergence rate. 相似文献
999.
1000.
Five interesting experiments have been done for a class of chaos synchronization systems with unknown parameters and unknown control directions. And three important conclusions about parameters identification have been made. First, a necessary and sufficient condition for parameters identification is obtained. Second, a Nussbaum method is proposed to solve the problem of unknown control direction. Third, the adaptive method is not infinitely effective considered for our current ability of computation and simulation algorithm. 相似文献