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排序方式: 共有272条查询结果,搜索用时 15 毫秒
31.
This paper analyses the effects of investment in information technologies (IT) in the banking sector using bank-level data from a panel of 68 US banks over the period 1986–2005. Although IT can improve bank's performance by reducing operational cost (supply side), it can bring in competition among banks in order to embrace new technology (demand side). Since most empirical studies have adopted the production function approach, it is difficult to identify which effect has dominated. In a differentiated model with network effects, this paper characterizes the conditions to identify these two effects. The results suggest that (at individual firm levels) the bank profits can decline due to adoption and diffusion of IT investment, reflecting negative network competition effects in this industry. Using panel cointegration tests, we confirm that the estimated profit equation is indeed a long-run equilibrium relation. 相似文献
32.
Shubham Dutta Rajendra K. Mallick Rangu Prasad Vincent Gandon Akhila K. Sahoo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(8):2311-2316
Ynamides are typically more reactive than simple alkynes and olefins. However, a serendipitous observation revealed a rare case where the reactivity of simple alkynes exceeds that of ynamides. This led to the development of a unique sulfur‐radical‐triggered cyclization of yne‐tethered ynamides, which involves attack of the alkyne by a thiyl radical followed by cyclization with the ynamide. A wide range of novel 4‐thioaryl pyrroles that could tolerate common functional moieties and N‐protecting groups were expediently constructed by this strategy. The current method contrasts with the typical cyclization of yne‐ynamides, which involves the attack of the alkyne moiety by the ynamide core. Control experiments and DFT calculations supported the participation of the sulfur radical in the reaction and the regioselective cyclization. The synthetic potential of the substituted pyrroles is also discussed. 相似文献
33.
Gold(I)/Chiral Brønsted Acid Catalyzed Enantioselective Hydroamination–Hydroarylation of Alkynes: The Effect of a Remote Hydroxyl Group on the Reactivity and Enantioselectivity 下载免费PDF全文
Valmik S. Shinde Manoj V. Mane Dr. Kumar Vanka Arijit Mallick Dr. Nitin T. Patil 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):975-979
The catalytic enantioselective hydroamination–hydroarylation of alkynes under the catalysis of (R3P)AuMe/(S)‐3,3′‐bis(2,4,6‐triisopropylphenyl)‐1,1′‐binaphthyl‐2,2′‐diyl hydrogenphosphate ((S)‐TRIP) is reported. The alkyne was reacted with a range of pyrrole‐based aromatic amines to give pyrrole‐embedded aza‐heterocyclic scaffolds bearing a quaternary carbon center. The presence of a hydroxyl group in the alkyne tether turned out to be very crucial for obtaining products in high yields and enantioselectivities. The mechanism of enantioinduction was established by carefully performing experimental and computational studies. 相似文献
34.
Dr. Shubham Dutta Dr. Rajendra K. Mallick Prof. Dr. Akhila K. Sahoo 《Angewandte Chemie (International ed. in English)》2023,62(30):e202300816
The use of ynamides in organic synthesis has gained significant attention due to their ability to provide access to complex molecular structures through transformations such as 1,2-difunctionalization and annulation reactions. These reactions enable the formation of highly functionalized N-bearing olefins and unusual N-bearing heterocycles. In this minireview, we present a systematic overview of the regioselective difunctionalization and annulation reactions of ynamides. We discuss the multi-component reactions, and radical-triggered functionalizations across the ynamides carbon–carbon multiple bonds and the use of bifunctional reagents in annulation of ynamides, highlighting their potential in expanding the substrate scope. Furthermore, we provide insights into the mechanistic breakthroughs that have been achieved in recent years in the development of these reactions. Finally, we emphasize the promising future prospects of ynamides as versatile building blocks for the synthesis of complex molecular architectures. 相似文献
35.
36.
Möbius Aromatic Core‐Modified Heterocyclic [20] Macrocycles (4.1.1) with a Protruding N‐Methyl Pyrrole Ring 下载免费PDF全文
Herein, we report the first synthesis of an unorthodox tripyrrane moiety from the regioselective β‐benzoylation of pyrrole and the acid‐catalyzed condensation of the desired precursors. A [3+1] Mac Donald type condensation strategy for this tripyrrane has led to the exclusive isolation of two hitherto‐unknown aromatic [20] heterocyclic macrocycles (4.1.1). 相似文献
37.
The layered compound LiCoO2 belonging to the ABO2 class exhibits a variety of interesting behaviors, and substitution adds a twist to the properties. Hence, the effect of partial substitution of Co+3 with Fe+3 on the high-temperature thermoelectric properties has been studied in detail. The X-ray diffraction patterns together with Rietveld refinement indicate formation of a single phase conforming to R\( \overset{-}{3} \)m space group in all the three cases, LiCo1?x Fe x O2 with x = 0.01, 0.02, and 0.08. The electrical resistivity in all the compounds decreases by four orders of magnitude with increasing temperature from 300 to 1000 K, a semiconducting behavior. The Seebeck coefficient is found to be very high, >700 μV K?1 in all the cases, and increases with increasing temperature and Fe+3 substitution. The thermal conductivity, on the other hand, has been found to decrease with temperature in all the compounds from 3.5 W m?1 K?1 at room temperature to 1 W m?1 K?1 at 973 K, a consequence of phonon-phonon scattering. High resistivity of the compounds limits power factor indicating that carrier concentration and mobility need to be increased to realize a high figure-of-merit. 相似文献
38.
In this work we construct the stationary measure of the N species totally asymmetric simple exclusion process in a matrix product formulation. We make the connection between the matrix
product formulation and the queueing theory picture of Ferrari and Martin. In particular, in the standard representation,
the matrices act on the space of queue lengths. For N>2 the matrices in fact become tensor products of elements of quadratic algebras. This enables us to give a purely algebraic
proof of the stationary measure which we present for N=3. 相似文献
39.
Some copolymers of 2,4-dichlorophenyl acrylate (2,4-DCPA) with styrene (St) of different teed compositions were prepared by tree radical polymerization technique using 2,2′-azobisisobutyronitrile (AIBN) as an initiator,and the copolymers were characterized by IR spectroscopy.The copolymer composition obtained by UV-spectra led to determination of reactivity ratio by employing Fineman-Ross (F-R) and Kelen-Tudos (K-T) methods.Average molecular weight,as well as intrinsic viscosity,was obtained by vapor pre... 相似文献
40.
S.?Basavaraja A.?VenkataramanEmail author Arabinda?Ray 《Journal of Thermal Analysis and Calorimetry》2009,96(2):419-425
Partial dehydration of Dy2(SO4)3·8H2O was studied employing TG, DSC, D.C. electrical conductivity and spectroscopic techniques. The possible mechanism for the
loss of water molecules (partial dehydration) was found to be random nucleation obeying Mapel equation based on TG trace.
The DSC traces are supports the results of TG traces and are also utilized to understand the enthalpy changes accompanying
the partial dehydration and phase transition accompanying the dehydrated samples. D.C. electrical conductivity studies are
attempted to supplement these TG studies. Attempts are made to explain the structural changes accompanying dehydration on
the basis of infrared spectra and X-ray diffraction and scanning electron microscopic studies. 相似文献