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71.
A mild and practically convenient one-pot procedure for the Mannich reaction via condensation of amines, aldehydes and malonates, β-ketoesters, or β-dicarbonyl compounds has been carried out without using any organic solvent, metallic catalyst, or Lewis acids or bases at room temperature. The present protocol offers several advantages, such as goods yields, simple procedure with easy workup, and the absence of any volatile, hazardous organic solvents and metallic catalyst. 相似文献
72.
Water was a suitable medium for Paal–Knorr pyrrole cyclocondensation. Hexa-2,5-dione was reacted with several aliphatic and aromatic primary amines, affording N-substituted 2,5-dimethyl pyrrole derivatives in good to excellent yields. An efficient, green method using water either as environmentally friendly solvent or catalyst was presented. 相似文献
73.
Image processing, in particular image enhancement techniques have been the focal point of considerable research activity in the last decade. With the aid of an existing image enhancement technique, adaptive unsharp masking (AUM), we propose a novel kernel to be used in AUM filtering in order to enhance discontinuities which occur on the edges of targets of interest in infrared (IR) images. The proposed method uses an adaptive filter approach where an objective function is minimized by using descent algorithms. The output IR image has better sharpness and contrast adjustment for the detection of targets in terms of objective quality metrics. Hence, the proposed method ensures that the edges of the targets in IR images are sharper and that the quality of contrast adjustment has its optimum level in terms of peak signal-to-noise ratios. 相似文献
74.
We demonstrate a Raman laser using cold (87)Rb atoms as the gain medium in a high-finesse optical cavity. We observe robust continuous wave lasing in the atypical regime where single atoms can considerably affect the cavity field. Consequently, we discover unusual lasing threshold behavior in the system causing jumps in lasing power, and propose a model to explain the effect. We also measure the intermode laser linewidth, and observe values as low as 80 Hz. The tunable gain properties of this laser suggest multiple directions for future research. 相似文献
75.
Elemental‐Sulfur‐Mediated Facile Synthesis of a Covalent Triazine Framework for High‐Performance Lithium–Sulfur Batteries 下载免费PDF全文
Dr. Siddulu Naidu Talapaneni Tae Hoon Hwang Sang Hyun Je Dr. Onur Buyukcakir Prof. Jang Wook Choi Prof. Ali Coskun 《Angewandte Chemie (International ed. in English)》2016,55(9):3106-3111
A covalent triazine framework (CTF) with embedded polymeric sulfur and a high sulfur content of 62 wt % was synthesized under catalyst‐ and solvent‐free reaction conditions from 1,4‐dicyanobenzene and elemental sulfur. Our synthetic approach introduces a new way of preparing CTFs under environmentally benign conditions by the direct utilization of elemental sulfur. The homogeneous sulfur distribution is due to the in situ formation of the framework structure, and chemical sulfur impregnation within the micropores of CTF effectively suppresses the dissolution of polysulfides into the electrolyte. Furthermore, the triazine framework facilitates electron and ion transport, which leads to a high‐performance lithium–sulfur battery. 相似文献
76.
Michelle M. H. Şeref Onur Şeref Aydın Alptekinoğlu S. Selçuk Erengüç 《Computational Management Science》2016,13(4):597-626
Advance selling of goods and services is a form of separating purchase from consumption. It is often employed when consumers are uncertain about their consumption utilities until a short time period before consumption. A book to be released, a concert to attend, or a cruise to take are some examples. Invariably, in consumers’ mind inventory availability (of copies, seats, or rooms) is a concern. In this paper we study a retailer’s inventory and pricing decisions in an advance selling scenario that involves consumers who are strategic. Some consumers not only consider advance and spot prices, but also the uncertainty in future availability of the product (during the spot period) and in their consumption utility from it. We characterize the optimal inventory management and pricing policies, and discuss several interesting aspects of the solution. For example, it can be optimal for the retailer to limit advance sales even if there is more demand for it, and it can be optimal for the retailer to limit its inventory even though there is more capacity to keep it, but not both. 相似文献
77.
Onur ahin Orhan Büyükgüngr Dursun Ali Kse Hacali Necefoglu 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(10):m317-m320
The title compound, [Co(C7H5O3)2(C6H6N2O)2(H2O)2], forms a three‐dimensional hydrogen‐bonded supramolecular structure. The CoII ion is in an octahedral coordination environment comprising two pyridyl N atoms, two carboxylate O atoms and two O atoms from water molecules. Intermolecular N—H...O and O—H...O hydrogen bonds produce R22(8), R22(12) and R22(14) rings, which lead to two‐dimensional chains. An extensive three‐dimensional supramolecular network of C—H...O, N—H...O and O—H...O hydrogen bonds and C—H...π interactions is responsible for crystal structure stabilization. This study is an example of the construction of a supramolecular assembly based on hydrogen bonds in mixed‐ligand metal complexes. 相似文献
78.
Hacer Azak Firat Baris Barlas Huseyin Bekir Yildiz Kadri Gulec Bilal Demir Dilek Odaci Demirkol Suna Timur 《Macromolecular bioscience》2016,16(4):545-552
Here, postfunctionalization and bioapplication of a π‐conjugated polymer named 4‐[4H‐dithieno(3,2‐b:2′,3′‐d)pyrrol‐4‐yl]aniline (DTP‐aryl‐NH2) are reported, which is successfully synthesized via electropolymerization onto the glassy carbon electrode. Folic acid (FA) is used to modify the amino functional polymer via N‐(3‐dimethylaminopropyl)‐N′‐ethylcarbodiimide hydrochloride/N‐hydroxysuccinimide chemistry for the further steps. The selective adhesion of folate receptor positive cells on the surface is followed by the electrochemical methods. Cyclic voltammetry and electrochemical impedance spectroscopy have been used to characterize stepwise modification of the electroactive surface. After optimization studies such as scan rate during the polymer deposition, FA amount for the efficient surface targeting, incubation time with the cells etc., analytical characterization is carried out. The surface morphologies at each step are imaged by using fluorescence microscopy.
79.
Hadi Naslhajian S. Morteza F. Farnia Ayda Sheykhi Onur Şahin Okan Zafer Yeşilel 《Journal of Coordination Chemistry》2017,70(17):2940-2949
A new decavanadate polyoxovanadate nanocluster, [2-ampH]6[V10O28]?2H2O (1), was synthesized through reaction between ammonium vanadate and 2-aminopyridine at pH = 2. Nanocluster 1 was characterized by IR, elemental analysis, and X-ray crystallography. 1 was found to adsorb and desorb dyes and may have widespread application in wastewater treatment. The utility of 1 for adsorption of methylene blue was studied. The adsorbed dyes can be easily desorbed, and 1 has full efficiency after five cycles. 相似文献
80.
In this research, we present a new approach based on variational iteration method for solving nonlinear time-fractional partial differential equations in large domains. The convergence of the method is shown with the aid of Banach fixed point theorem. The maximum error bound is specified. The optimal value of auxiliary parameter is obtained by use of residual error function. The fractional derivatives are taken in the Caputo sense. Numerical examples that involve the time-fractional Burgers equation, the time-fractional fifth-order Korteweg–de Vries equation and the time-fractional Fornberg–Whitham equation are examined to show the appropriate properties of the method. The results reveal that a new approach is very effective and convenient. 相似文献