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排序方式: 共有266条查询结果,搜索用时 421 毫秒
21.
Nano-TiO2 as an eco-friendly and efficient nanocatalyst was applied for quinoxaline preparation with improved yield.In this protocol,diketones and 1,2-diamines were condensed in the presence of catalyst at room temperature. 相似文献
22.
A PVC membrane vanadyl (VO2+) ion-selective electrode was constructed using 1,8-diaminonaphthalen (DAN) as a neutral carrier. The electrode shows good Nernstian response for VO2+ ions over a wide concentration range (1.0×10−1-1.0×10−5 M). The optimum composition of the membrane was 55 wt.% poly(vinylchloride), 35 wt.% 2-nitrophenyl octyl ether (NPOE), 5 wt.% ionophore, and 5 wt.% potassium tetrakis(p-chlorophenyl)borate (KTpClPB). It has relatively fast response time and can be used at least for 5 weeks without any considerable divergence in potentials. The proposed electrode revealed relatively good selectivity for VO2+ over wide variety of other metal ions. The electrode was used for the potentiometric titration of VO2+ ions with EDTA. 相似文献
23.
Jafar Akbari Akbar Heydari Leila Ma’mani Seyed Hassan Hosseini 《Comptes Rendus Chimie》2010,13(5):544-547
An efficient and practical protocol for the chemoselective N-Boc protection of various structurally different aryl, aliphatic and heterocyclic amines was carried out with (Boc)2O using protic 1, 1, 3, 3-tetra-methylguanidinium acetate (10 mol%) as recyclable catalyst under solvent free condition at ambient temperature. No competitive side reactions (isocyanate, urea and N, N-di-Boc) were observed. α-Amino alcohols afforded the N-Boc-derivative without oxazolidinone formation. 相似文献
24.
F. Moatar S. R. Shadizadeh A. R. Karbassi E. Ardalani R. Akbari Derakhshi M. Asadi 《Journal of Radioanalytical and Nuclear Chemistry》2010,283(1):3-7
The present study is conducted, in order to contribute to a future waste management policy related to the presence of technologically
enhanced natural occurring radioactive material (TENORM) in Iran petroleum industry. Samples were collected from offshore
oil company for analysis of 238U, 235U, and 232Th series in produced waters. The activities of samples were determined by high-purity germanium detector, well for lowlevel
activity γ-spectrometry. The results have shown that, 226Ra concentration ranges from 5.26 Bq/L to 27.93 Bq/L. Also the total activity in produced water is in the range of 16–840 Bq/L
were mainly due to enhanced levels of dissolved 226Ra, 214Pb, 214Bi ions. Also, enhanced dissolution of elements such as radium by increasing of salinity, result in higher concentration of
NORM in old oil region. Measured values are above EPA regulation (40 CFR 141055) & aqueous Derived Release Limit (DRL) of
Canadian guideline for the management of (NORM). Therefore produced water has to dispose in pits which have to design for
decrease the environmental effects. Also according to this study, re-injection of produced water in to abandon well of Iran
Offshore Oil Company in Persian Gulf, have preference over discharging to the pits. 相似文献
25.
26.
Let G be a graph. The core of G, denoted by G Δ, is the subgraph of G induced by the vertices of degree Δ(G), where Δ(G) denotes the maximum degree of G. A k -edge coloring of G is a function f : E(G) → L such that |L| = k and f (e 1) ≠ f (e 2) for all two adjacent edges e 1 and e 2 of G. The chromatic index of G, denoted by χ′(G), is the minimum number k for which G has a k-edge coloring. A graph G is said to be Class 1 if χ′(G) = Δ(G) and Class 2 if χ′(G) = Δ(G) + 1. In this paper it is shown that every connected graph G of even order whose core is a cycle of order at most 13 is Class 1. 相似文献
27.
M. Hosseinpour P. Nikdel M.A. Akbari 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2013,19(3):250-262
This article proposes a Takagi–Sugeno (T-S) fuzzy model of single-link rotary flexible joint robot. The proposed control method is based on parallel distributed control. The parameters of T-S controller are improved by distributed population genetic algorithm (GA) with chaos GA. Using Hermite–Biehler theorem in distributed population, GA is made to have a fast convergence. Dividing search space into several sub-spaces causes a better response, and chaos disturbance helps the whole algorithm to reach a best answer. The stability of the controller is analysed via the sum of squares programming, and finally, it is implemented on the plant. 相似文献
28.
S. Akbari 《Linear algebra and its applications》2007,421(1):3-15
We study graphs whose adjacency matrices have determinant equal to 1 or −1, and characterize certain subclasses of these graphs. Graphs whose adjacency matrices are totally unimodular are also characterized. For bipartite graphs having a unique perfect matching, we provide a formula for the inverse of the corresponding adjacency matrix, and address the problem of when that inverse is diagonally similar to a nonnegative matrix. Special attention is paid to the case that such a graph is unicyclic. 相似文献
29.
Nanomolar Determination of Methyldopa in the Presence of Large Amounts of Hydrochlorothiazide Using a Carbon Paste Electrode Modified with Graphene Oxide Nanosheets and 3‐(4′‐Amino‐3′‐hydroxy‐biphenyl‐4‐yl)‐acrylic Acid
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A novel electrochemical sensor for sensitive detection of methyldopa at physiological pH was developed by the bulk modification of carbon paste electrode (CPE) with graphene oxide nanosheets and 3‐(4′‐amino‐3′‐hydroxy‐biphenyl‐4‐yl)‐acrylic acid (3,′AA). Applying square wave voltammetry (SWV), in phosphate buffer solution (PBS) of pH 7.0, the oxidation current increased linearly with two concentration intervals of methyldopa, one is 1.0×10?8–1.0×10?6 M and the other is 1.0×10?6–4.5×10?5 M. The detection limit (3σ) obtained by SWV was 9.0 nM. The modified electrode was successfully applied for simultaneous determination of methyldopa and hydrochlorothiazide. Finally, the proposed method was applied to the determination of methyldopa and hydrochlorothiazide in some real samples. 相似文献
30.
S.A. Mirkhani M. Vossoughi G.R. Pazuki A.A. Safekordi A. Heydari J. Akbari M. Yavari 《The Journal of chemical thermodynamics》2011,43(10):1530-1534
(Liquid + liquid) equilibrium (LLE) data for the ternary systems (heptane + toluene + 1-ethyl-3-methylpyridinium ethylsulfate) and (heptane + benzene + 1-ethyl-3-methylpyridinium ethylsulfate) were measured at T = 298.15 K and atmospheric pressure. The selectivity and aromatic distribution coefficients, calculated from the equilibrium data, were used to determine if this ionic liquid can be used as a potential extracting solvent for the separation of aromatic compounds from heptane. The consistency of tie-line data was ascertained by applying the Othmer–Tobias and Hand equations. 相似文献