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91.
A simple and efficient procedure for the preparation of silica-bound N-propyl triethylenetetramine sulfamic acid(SBPTETSA) by the reaction of silica-bound N-propyl triethylenetetramine(SBPTET) with chlorosulfonic acid in chloroform is described.Silica-bound N-propyl triethylenetetramine sulfamic acid was employed as a recyclable catalyst for the synthesis of 2-amino-4,6-diarylnicotinonitriles from the multi-component reaction of an acetophenone derivative,an aromatic aldehyde,malononitrile,and ammonium acetate under solvent-free conditions at 100 °C.The heterogeneous catalyst was recycled for five consecutive runs in the optimized multi-component reaction of 4-chloroacetophenone,4-chloroenzaldehyde,malononitrile,and ammonium acetate without significant loses to its catalytic activity. 相似文献
92.
In this numerical study, we present and demonstrate a compact, electrical plasmonic beam-steering device composed of anisotropic material. The splitting angle can be modulated by the external electric or magnetic field. The physical principle of this phenomenon is evaluated from the phase of surface plasmon polaritons and Fabry-Perot (F-P) resonance in slits. Our numerical simulations with finite-difference time-domain (FDTD) technique reveals that wide-angle (±27°) beam steering can be achieved. Moreover, the efficiency increases when increasing the steering angle. A special characteristic of the presented structure gives an opportunity to be used as an efficient element in a high integrated optical device for miniaturization and tuning purposes. 相似文献
93.
94.
A Roman dominating function on a graph G = (V, E) is a function f : V ? {0, 1, 2}f : V \rightarrow \{0, 1, 2\} satisfying the condition that every vertex v for which f(v) = 0 is adjacent to at least one vertex u for which f(u) = 2. The weight of a Roman dominating function is the value w(f) = ?v ? V f(v)w(f) = \sum_{v\in V} f(v). The Roman domination number of a graph G, denoted by gR(G)_{\gamma R}(G), equals the minimum weight of a Roman dominating function on G. The Roman domination subdivision number sdgR(G)sd_{\gamma R}(G) is the minimum number of edges that must be subdivided (each edge in G can be subdivided at most once) in order to increase the Roman domination number. In this paper, first we establish upper
bounds on the Roman domination subdivision number for arbitrary graphs in terms of vertex degree. Then we present several
different conditions on G which are sufficient to imply that $1 \leq sd_{\gamma R}(G)
\leq 3$1 \leq sd_{\gamma R}(G)
\leq 3. Finally, we show that the Roman domination subdivision number of a graph can be arbitrarily large. 相似文献
95.
An Expedient Synthesis of Novel Derivatives of Pyrido[2,3‐d]pyrimidines Using Magnetically Supported ZrO2 Nanocatalyst 下载免费PDF全文
Leila Kheirkhah Manouchehr Mamaghani Nosrat Ollah Mahmoodi Asieh Yahyazadeh Abdollah Fallah Shojaei Yaseman Rostamli 《中国化学会会志》2016,63(5):410-416
An efficient synthesis of pyrido[2,3‐d]pyrimidine derivatives via one‐pot multicomponent reactions of 6‐amino‐2‐(alkylthio)pyrimidin‐4(3H)‐one, 3‐cyanoacetylindole and arylaldehydes using [Fe3O4@ZrO2] as magnetically recyclable nanocatalyst is reported. This protocol furnished the desired products in good to excellent yields (70–93 %) and lower reaction times. The catalyst could be easily and efficiently separated from the final product solution by an external magnet and be reused in 5 consecutive runs without any significant activity decrease. 相似文献
96.
In this paper, we are interested to study zero-divisor properties of a 0-symmetric nearring of polynomials R0[x], when R is a commutative ring. We show that for a reduced ring R, the set of all zero-divisors of R0[x], namely Z(R0[x]), is an ideal of R0[x] if and only if Z(R) is an ideal of R and R has Property (A). For a non-reduced ring R, it is shown that Z(R0[x]) is an ideal of Z(R0[x]) if and only if annR({a, b}) ∩ N i?(R) ≠ 0, for each a, b ∈ Z(R). We also investigate the interplay between the algebraic properties of a 0-symmetric nearring of polynomials R0[x] and the graph-theoretic properties of its zero-divisor graph. The undirected zero-divisor graph of R0[x] is the graph Γ(R0[x]) such that the vertices of Γ(R0[x]) are all the non-zero zero-divisors of R0[x] and two distinct vertices f and g are connected by an edge if and only if f ? g = 0 or g ? f = 0. Among other results, we give a complete characterization of the possible diameters of Γ(R0[x]) in terms of the ideals of R. These results are somewhat surprising since, in contrast to the polynomial ring case, the near-ring of polynomials has substitution for its “multiplication” operation. 相似文献
97.
A two-step sol-gel technique was used here to prepare a carbon ceramic electrode modified with nafion and [Ru(bpy)(tpy)Cl]PF6. This involves two steps: first, forming a bulk-modified carbon ceramic electrode with nafion, and then immersing the electrode into a Ru-complex solution (electroless deposition) for a short period of time (5-25 s). Cyclic voltammograms of the resulting surface-modified carbon ceramic electrode show stable and a well-defined redox couple due to Ru(II)/Ru(III) system with surface-confined characteristic. l-Cysteine (CySH) has been chosen as a model to elucidate the electrocatalytic ability of Ru-complex nafion sol-gel composite electrode. Not only the modified electrode shows excellent catalytic activity toward l-cysteine electrooxidation in pH range 3-9, but the antifouling effect of nafion film also increases the reproducibility of results in comparison with CCE modified with homogeneous mixing of graphite powder and Ru-complex (one step sol-gel method). Under the optimized conditions in amperometry method, the concentration calibration range, detection limit and sensitivity were 0.1-100 μM, 20 nM and 50 nA/μM, respectively. The advantages of this modified electrode are good reproducibility, excellent catalytic activity, simplicity of preparation and especially its antifouling properties towards l-cysteine and its oxidation products. Additionally, it is promising as a detector in flow system or chromatography systems. 相似文献
98.
Babae Robabeh Ghezelbash Mahsa Majd Abdollah Eslami Darbani Seyyed Mohammad Reza 《Journal of Russian Laser Research》2022,43(2):162-168
Journal of Russian Laser Research - In this paper, we use laser-induced breakdown spectroscopy (LIBS) to investigate the laser-induced copper plasma with and without an external magnetic field,... 相似文献
99.
Application of multiwalled carbon nanotubes for the preconcentration and determination of organochlorine pesticides in water samples by gas chromatography with mass spectrometry 下载免费PDF全文
Abdollah Taghani Naaser Goudarzi Ghadamali Bagherian 《Journal of separation science》2016,39(21):4219-4226
A fast, sensitive, and convenient technique consisting of a miniaturized solid‐phase extraction method named microextraction in packed syringe coupled with gas chromatography and mass spectrometry was developed for the preconcentration and determination of some pesticides, including hexachlorobenzene, heptachlor, alachlor, aldrine, and metolachlore, in natural water samples. Carboxyl‐purified multiwalled carbon nanotubes were used as a sorbent in microextraction in packed syringe. Based on this technique, 6.0 mg of multiwalled carbon nanotubes was inserted in the syringe between two polypropylene frits. The analytes would be adsorbed on the solid phase, and would subsequently be eluted using organic solvents. The influence of some important parameters involved including the solution pH, type, and volume of the organic desorption solvent, and amount of the multiwalled carbon nanotubes sorbent on the extraction efficiency of the selected pesticides were investigated. The proposed method showed a good linearity in the range of 0.1–25.0 ng/mL and low limits of detection in the range of 0.02–0.19 ng/mL using the selected ion‐monitoring mode. Reproducibility of the method was in the range of 3.3–8.5% for the studied pesticides. Also to evaluate the matrix effect, the developed method was applied to the preconcentration and determination of the selected pesticides in different water samples. 相似文献
100.