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21.
In this paper, an exact solution approach is described for solving a real-life school bus routing problem (SBRP) for transporting the students of an elementary school throughout central Ankara, Turkey. The problem is modelled as a capacitated and distance constrained open vehicle routing problem and an associated integer linear program is presented. The integer program borrows some well-known inequalities from the vehicle routing problem, which are also shown to be valid for the SBRP under consideration. The optimal solution of the problem is computed using the proposed formulation, resulting in a saving of up to 28.6% in total travelling cost as compared to the current implementation. 相似文献
22.
Enantiomerically pure α-chiral amines, have been commonly utilized as resolving agents and chiral auxiliaries and are currently found in 40% of active pharmaceutical ingredients. Hence, development of highly stereoselective metal-free protocols regarding atom-economy and large-scale applications becomes a major issue. In this respect, chiral bifunctional H-bonding squaramides have been successfully applied for both amine synthesis and functionalization of amines in the last decade. This survey summarizes asymmetric synthesis of chiral amines by various carbon-carbon and carbon-nitrogen bond formation with squaramide catalysis as a particular focus of interest. 相似文献
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A highly enantioselective synthesis of 3-amino-2-oxindoles by direct Mannich reaction between acetylacetone and N-carbamoyl isatin ketimine has been described herein. Corresponding chiral adducts were obtained in high yields (up to 98%) and with excellent enantioselectivities (up to?>99% ee) by very low (1?mol%) catalyst loading of 2-adamantyl substituted bifunctional cinchona-squaramide. 相似文献
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The first examples of insertion of a C(triple bond)C bond of an alkyne into a C(carbene)-Calpha single bond of a carbene complex (C-Calpha insertion) are reported. (prim-Alkyl)carbene complexes [(OC)(5)M=C(OEt)CH(2)R] (1 a-f; M=Cr, W; R=nPr, C(7)H(7), Ph) undergo C-Calpha insertion of electron-deficient alkynes [PhC(triple bond)CC(XEt)NMe(2)]BF(4) (5 a,b; X=O, S) to give zwitterionic carbiminium carbonylmetalates 3 a-g, which are thermally transformed into (CO)(4)M chelate carbene complexes 4 a-g by elimination of CO. The overall reaction is highly regio- and stereoselective. It involves an unprecedented metalla(di-pi-methane) rearrangement as the key step. 相似文献
25.
Kizilel S Pérez-Luna VH Teymour F 《Langmuir : the ACS journal of surfaces and colloids》2004,20(20):8652-8658
We describe a new method that allows photopolymerization of hydrogels to occur on surfaces functionalized with eosin. In this work, glass and silicon surfaces were derivatized with eosin and photopolymerization was carried out using visible light (514 nm). This mild condition may have advantages over methods that use ultraviolet (UV) light (e.g., for encapsulation of cells and proteins, in drug screening, or in biosensing applications). The hydrogel formed on the modified surface is remarkably stable for an extended period of time. The resultant hydrogel was hydrated for more than 18 months without suffering delamination from the substrate surface. This strongly suggests covalent attachment of the hydrogel to the surface. Contact angle titration measurements and X-ray photoelectron spectroscopy analysis of eosin surfaces before and after irradiation in the presence of triethanolamine suggest that the eosin radical is responsible for the covalent attachment of the gel onto the substrate surface. This method allows for 2-D patterning of hydrogels, which is demonstrated here using the microcontact printing technique. However, noncontact photolithography could be used to form similar patterns by directing light through a mask. This method can be easily implemented to form arrays of fluorophores and proteins in situ. 相似文献
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The phenyl‐substituted conduritol B 8 was prepared in racemic form in a five‐step sequence starting from 2‐phenyl‐1,4‐benzoquinone ( 10 ) (Scheme 1). The reaction mechanism of the key step 12b → 13 is discussed (Scheme 2). 相似文献
28.
Ylmaz Seda Kuyumcu zge Kerkez Bayazit ahika Sena Ayaz Rana Muhammad Zunain Akyz Duygu Koca Atf 《Journal of Solid State Electrochemistry》2022,26(1):245-255
Journal of Solid State Electrochemistry - Modified TiO2 nanocomposites have been recognized as attractive photocatalytic materials in solar energy conversion. The aim of this study is to enhance... 相似文献
29.
Ozlem Karahan Kinyas Aydin Seda Edizer Nihan Odabasi Duygu Avci 《Journal of polymer science. Part A, Polymer chemistry》2010,48(17):3787-3796
Six methacrylate monomers have been synthesized for use as reactive diluents in dental composites and evaluated to investigate the relationship between molecular structure and monomer reactivity. Four were synthesized by reactions of glycidyl methacrylate (GMA) with various acids, 2‐(2‐methoxyethoxy)acetic acid ( 1 ), 2‐(2‐(2‐methoxyethoxy)ethoxy)acetic acid ( 2 ), cyanoacetic acid ( 3 ), and benzoic acid ( 4 ); others were synthesized by reactions of GMA with diethyl hydrogen phosphate ( 5 ) or methanol ( 6 ). Monomers 1 and 2 are novel, 3 seems to be novel, 4 and 6 were synthesized via a novel method, and the synthesis of 5 was described in the literature. The monomers showed high crosslinking tendencies during thermal bulk polymerizations. The photo‐, homo‐, and copolymerization behavior of the monomers with 2,2‐bis[4‐(2‐hydroxy‐3‐methacryloyloxy)phenyl]propane (Bis‐GMA) were investigated. The maximum rate of polymerizations of monomers 2 – 6 was found to be greater than triethyleneglycol dimethacrylate, Bis‐GMA, 2‐hydroxyethyl methacrylate, and glycerol dimethacrylate. For the more reactive monomers ( 2 , 3 , and 4 ), the oxygen sensitivity of polymerization was found to be low due to a hydrogen abstraction/chain transfer reaction. The computationally calculated dipole moment and lowest unoccupied molecular orbital energies indicated that there seems to be a correlation between these quantities and reactivity for ester linked monomers ( 1 – 5 ), which was also supported by 13C NMR data. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3787–3796, 2010 相似文献
30.
Seda Kartal Dr. Guillaume Rogez Dr. Jérôme Robert Dr. Benoît Heinrich Dr. Athanassios K. Boudalis 《Chemphyschem》2022,23(12):e202200213
[Gd5(L)16(H2O)8](Tf2N)15 was obtained from reaction of Gd2O3 with 1-carboxymethyl-3-ethylimidazolium chloride (LHCl). The material was found to be an ionic liquid that freezes to glassy state on cooling to −30 °C. Variable-temperature magnetic studies reveal the presence of weak magnetic intramolecular interactions in the glass. Isothermal variable-field magnetization demonstrates a magnetocaloric effect (MCE), which is the first finding of such an effect in a molecular glass. This MCE is explainable by an uncoupled representation, with a magnetic entropy change of −11.36 J K−1 kg−1 at 1.8 K for a 0–7 T magnetic field change, and with a refrigerant capacity of 125.9 J kg−1, in the 1.8-50 K interval. 相似文献