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排序方式: 共有275条查询结果,搜索用时 15 毫秒
51.
Vaisakh Mohan A. Nijamudheen Sudhir Kumar Das Prabhat K. Sahu Usha Pallabi Kar Dr. Abdur Rahaman Dr. Moloy Sarkar 《Chemphyschem》2012,13(17):3882-3892
A new multi‐component chemosensor system comprising a naphthalimide moiety as fluorophore is designed and developed to investigate receptor–analyte binding interactions in the presence of metal and non‐metal ions. A dimethylamino moiety is utilized as receptor for metal ions and a thiourea receptor, having acidic protons, for binding anions. The system is characterized by conventional analytical methods. The absorption and fluorescence spectra of the system consist of a broad band typical for an intramolecular charge transfer (ICT). The effects of various metal‐ion additives on the spectral behavior of the present sensor system are examined in acetonitrile. It is found that among the metal ions studied, alkali/alkaline earth‐metal ions and transition‐metal ions modulate the absorption and fluorescence spectra of the system. As an additional feature, the anion signaling behavior of the system in acetonitrile is studied. A decrease in fluorescence efficiency of the system is observed upon addition of fluoride and acetate anions. Fluorescence quenching is most effective in the case of fluoride ions. This is attributed to the enhancement of the photoinduced electron transfer from the anion receptor to the fluorophore moiety. Hydrogen‐bond interactions between the acidic NH protons of the thiourea moiety and the F? anions are primarily attributed to the fluoride‐selective signaling behavior. Interestingly, a negative cooperativity for the binding event is observed when the interactions of the system are studied in the presence of both Zn2+ and F? ions. NMR spectroscopy and theoretical calculations are also carried out to better understand the receptor–analyte binding. 相似文献
52.
Yoshinori Namihira Md. Anwar Hossain Taito Koga Md. Ashraful Islam S. M. Abdur Razzak Shubi F. Kaijage Yuki Hirako Hiroki Higa 《Optical Review》2012,19(2):78-81
In this paper, we propose a highly nonlinear dispersion flattened hexagonal photonic crystal fiber (HNDF-HPCF) with nonlinear
coefficients as large as 57.5W−1 km−1 at 1.31 μm wavelength for dental optical coherence tomography (OCT) applications. This HNDF-HPCF offers not only large nonlinear
coefficient but also very flat dispersion slope and very low confinement losses. Using these characteristics of our proposed
PCF, it is shown through simulations by using finite difference method with an anisotropic perfectly matched boundary layer
that this PCF offers the efficient supercontinuum (SC) generation for dental OCT applications at 1.31 μm wavelength using
a picosecond pulse easily produced by commercially available less expensive laser sources. Coherent length of light source
using SC is found 10 μm and the spatial resolutions in the depth direction for dental applications of OCT are found about
6.1 μm for enamel and 6.5 μm for dentin. 相似文献
53.
Nasim Ahmed Syed Alwee Aljunid R. Badlishah Ahmad Hilal A. Fadhil Mohd Abdur Rashid 《Optical Review》2012,19(1):1-6
The bit-error rate (BER) performance of the spectral amplitude coding-optical code division multiple access (SACOCDMA) system
has been investigated by using NAND subtraction detection technique with enhanced double weight (EDW) code. The EDW code is
the enhanced version of double weight (DW) code family where the code weight is any odd number and greater than one with ideal
cross-correlation. In order to evaluate the performance of the system, we used mathematical analysis extensively along with
the simulation experiment. The evaluation results obtained using the NAND subtraction detection technique was compared with
those obtained using the complementary detection technique for the same number of active users. The comparison results revealed
that the BER performance of the system using NAND subtraction detection technique has greatly been improved as compared to
the complementary technique. 相似文献
54.
We propose an implementable BFGS method for solving a nonsmooth convex optimization problem by converting the original objective function into a once continuously differentiable function by way of the Moreau–Yosida regularization. The proposed method makes use of approximate function and gradient values of the Moreau-Yosida regularization instead of the corresponding exact values. We prove the global convergence of the proposed method under the assumption of strong convexity of the objective function. 相似文献
55.
Rui Sang Peter Kucmierczyk Ricarda Dühren Rauf Razzaq Kaiwu Dong Jie Liu Robert Franke Ralf Jackstell Matthias Beller 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14503-14511
The synthesis of carboxylic acids is of fundamental importance in the chemical industry and the corresponding products find numerous applications for polymers, cosmetics, pharmaceuticals, agrochemicals, and other manufactured chemicals. Although hydroxycarbonylations of olefins have been known for more than 60 years, currently known catalyst systems for this transformation do not fulfill industrial requirements, for example, stability. Presented herein for the first time is an aqueous‐phase protocol that allows conversion of various olefins, including sterically hindered and demanding tetra‐, tri‐, and 1,1‐disubstituted systems, as well as terminal alkenes, into the corresponding carboxylic acids in excellent yields. The outstanding stability of the catalyst system (26 recycling runs in 32 days without measurable loss of activity), is showcased in the preparation of an industrially relevant fatty acid. Key‐to‐success is the use of a built‐in‐base ligand under acidic aqueous conditions. This catalytic system is expected to provide a basis for new cost‐competitive processes for the industrial production of carboxylic acids. 相似文献
56.
A Study on Oscillatory and Asymptotic Nature of Impulsive Neutral Differential Equations of Order Three
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Abdur Raheem Asma Afreen Areefa Khatoon 《Journal of Nonlinear Modeling and Analysis》2022,4(3):475-487
In this paper, we consider a class of third-order neutral impulsive differential equations. An equivalent class of neutral differential equations is obtained by using a suitable substitution. Some new oscillation results are proved. Moreover, we discuss the asymptotic behavior of the solution. The results presented here are illustrated via examples. 相似文献
57.
S. M. Hasany M. A. Rauf H. Rehman 《Journal of Radioanalytical and Nuclear Chemistry》1991,153(1):5-14
Gamma irradiation studies of morin (10–5M) in ethanol and dimethyl sulphoxide (DMSO) in the dose range of 149–895 Gy and of 4.5–45 Gy were carried out, respectively, in aerated and anoxic conditions purged with nitrogen and nitrous oxide. The decoloration yield of morin was studied as a function of dose. The relative radiation sensitivity was estimated under similar conditions. The effect of the concentration (10–5–10–4M) of iodine, succinic acid and acryl amide on radiolysis of morin was investigated at constant dose in both solvents and results were interpreted in terms of scavenging reactions. 相似文献
58.
Edward W. Abel A.Rauf Khan Kenneth Kite Keith G. Orrell Vladimir Šik 《Journal of organometallic chemistry》1978,145(2):C18-C20
Adducts of the type Me3PtXL (X = C1, Br, I; L = MeSCH2CH2SMe) exhibit pyramidal inversion at individual sulphur atoms, whereas the adducts (Me3PtX)2L′ (L′ = MeSCH2SMe, X = C1, Br, I) exhibit both ring inversion, and synchronous inversion about both sulphur atoms. 相似文献
59.
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