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排序方式: 共有199条查询结果,搜索用时 31 毫秒
131.
The present account aims at amassing and recounting on our series of spectroscopic studies with a potential excited state intramolecular proton transfer (ESIPT) probe 1-hydroxy-2-naphthaldehyde (HN12). After a detailed investigation from experimental as well as theoretical viewpoints, a deeper insight into the photophysics of the selected molecular system is provided from thorough spectral deciphering of the effects of solvent, medium pH and temperature. In the following sections, the ESIPT emission of HN12 has been documented to be a potential avenue wherefrom characterization of a wide variety of biological, biomimetic and supramolecular assemblies has been executed to commendable fruition. Efforts are also invested to delineate the location, distribution and strength of interaction of the probe with various microheterogeneous environments. 相似文献
132.
Aram Rezaei Hamideh Ahankar Bijan Ganjeie 《Phosphorus, sulfur, and silicon and the related elements》2016,191(6):952-957
A novel application in the field of N-isocyaniminotriphenylphosphorane (Ph3PNNC) chemistry has been introduced in this work. A series of substituted isoindolin-1-one ring systems has been successfully synthesized through a novel and efficient multicomponent reaction of methyl 2-formylbenzoate and primary amines in the presence of N-isocyaniminotriphenylphosphorane (Ph3PNNC) as a catalyst. This one-pot three component reaction (3-CR) gives high yield using N-isocyaniminotriphenylphosphorane (Ph3PNNC) as a metal-free catalyst under mild conditions. 相似文献
133.
Combustion of hydrocarbon fuel is accompanied with the formation of nitric oxide (NO) amongst other harmful emissions. In this work, a numerical investigation has been made for understanding the effect of radiative heat transfer on temperature distribution and formation of thermal NO in a methane–air diffusion flame under different reduced gravity environments. Conservation equations of overall mass, species concentration, momentum and energy for the reactive flows have been numerically solved with the use of finite difference scheme. In addition to that a semi-empirical soot model and an optically thin radiation model have been incorporated in the simulation. Gravity level is varied by the changed values of acceleration due to gravity. A thermal NO model incorporated accounts for the NO formation process which is decoupled from the hydrocarbon combustion. The relevant conservation equations have been solved as a post combustion reaction process. The flame height drops marginally with the reduction of gravity. Temperature becomes more uniformly distributed at lower gravity. NO formation boosts up with the fall of gravity below normal level when no radiation effect is considered. However, when radiation is considered, NO formation declines marginally with the reduction of gravity levels. Also in this case, concentration values of NO compare substantially lower with those without radiation. The upsurge of NO formation due to decline in gravity; and on the other hand, a shrinkage in concentration values of NO due to radiation effect can be attributed mainly to the rise and fall of temperature respectively in the computational zone. 相似文献
134.
Among major components of LiBr–H2O absorption chillers is the absorber, which has a direct effect on the chillier size and whose characteristics have significant
effects on the overall efficiency of absorption machines. In this article, heat and mass transfer process in absorption of
refrigerant vapor into a lithium bromide solution of water-cooled incline plate absorber in the Reynolds number range of 5 < Re < 150 is performed numerically. The boundary layer assumptions are used for the mass, momentum and energy transport equations
and the fully implicit finite difference method is employed to solve the governing equations. Dependence of lithium bromide
aqueous properties to the temperature and concentration is employed as well as dependence of film thickness to vapor absorption.
An analysis for linear distribution of wall temperature condition carries out to investigate the reliability of the present
numerical method through comparing with previous investigation. The effect of plate angle on heat and mass transfer parameters
is investigated and the results show that absorption mass flux and heat and mass transfer coefficient increase as the angle
of the plate increase. The main parameters of absorber design, namely Nusselt and Sherwood numbers, are correlated as a function
of Reynolds Number and the plate angle. 相似文献
135.
Kowsari MH Alavi S Najafi B Gholizadeh K Dehghanpisheh E Ranjbar F 《Physical chemistry chemical physics : PCCP》2011,13(19):8826-8837
Systematic molecular dynamics simulations are used to study the structure, dynamics and transport properties of the ionic liquids composed of the tetra-butylphosphonium ([TBP](+), or [P(C(4)H(9))(4)](+)) cation with six amino acid ([AA](-)) anions. The structural features of these ionic liquids were characterized by calculating the partial site-site radial distribution functions, g(r), and computing the dihedral angle distribution of n-butyl side chains in the [TBP](+) cations. The dynamics of the ionic liquids are described by studying the velocity autocorrelation function (VACF) and the mean-square displacement (MSD) for the centers of mass of the ions at different temperatures. The ionic diffusion coefficients and the electrical conductivities were evaluated from both the Einstein and Green-Kubo methods. The cross-correlation terms in the electric-current autocorrelation functions, which are an indication of the ion pair correlations, are investigated. The cationic transference numbers were also estimated to study the contributions of the anions and cations to the transport of charge in these ionic liquids. We determined the role of the amino acid anion structures on the dynamical behavior and the transport coefficients of this family of ionic liquids. In general, the MSD and self-diffusion coefficients of the relatively heavier non-planar [TBP](+) cations are smaller than those of the lighter amino acid anions. Introducing polar functional groups (acid or amide) in the side chain of [AA](-) decreases the diffusion coefficient and electrical conductivity of AAILs. The major factors for determining the magnitude of the transport coefficients are the chemical functionality and the length of the alkyl side chain of the [AA](-) anion of these [TBP][AA] ionic liquids. 相似文献
136.
Golabchifar AA Rouini MR Shafaghi B Rezaee S Foroumadi A Khoshayand MR 《Talanta》2011,85(5):2320-2329
A simple, rapid and specific HPLC method has been developed and validated for the simultaneous determination of imatinib, a tyrosine kinase inhibitor, and its major metabolite, CGP74588, in human plasma. The optimization of the HPLC procedure involved several variables, of which the influences of each was studied. After a series of preliminary-screening experiments, the composition of the mobile phase and the pH of the added buffer solution were set as the investigated variables, while the resolution between imatinib and CGP74588 peaks, the retention time and the imatinib peak width were chosen as the dependent variables. Applying D-optimal design, the optimal chromatographic conditions for the separation were defined. The method proved to show good agreement between the experimental data and predictive values throughout the studied parameter range.The optimum assay conditions were achieved with a Chromolith™ Performance RP-8e 100 mm × 4.6 mm column and a mixture of methanol/acetonitrile/triethylamine/diammonium hydrogen phosphate (pH 6.25, 0.048 mol L−1) (20:20:0.1:59.9, v/v/v/v) as the mobile phase at a flow rate of 2 mL min−1 and detection wavelength of 261 nm. The run time was less than 5 min, which is much shorter than the previously optimized methods. The optimized method was validated according to FDA guidelines to confirm specificity, linearity, accuracy and precision. 相似文献
137.
Mehdi Roopaei Mansoor Zolghadri Jahromi Bijan Ranjbar-Sahraei Tsung-Chih Lin 《Nonlinear dynamics》2011,66(4):667-680
In this paper, we use sliding mode control integrated with an interval type-2 fuzzy system for synchronization of two different
chaotic systems in presence of system unmodeling and external disturbances. To reduce the chattering and improve the robustness
of reaching phase of the Sliding Mode Control (SMC), an interval fuzzy type-2 logic controller is used. In addition, an adaptive
interval type-2 fuzzy inference approximator is proposed (as equivalent control part of SMC) to approximate the unknown parts
of the uncertain chaotic system. Using type-2 fuzzy systems makes more effective synchronization results in presence of system
uncertainty and disturbances in comparison with type-1 fuzzy approximators. The stability analysis for the proposed control
scheme is provided, and simulation results compare the performance of interval type-2 fuzzy and type-1 fuzzy controllers to
verify the effectiveness of the proposed method. 相似文献
138.
Bijan Kumar Paul 《Journal of luminescence》2011,131(9):1918-76
Here, we report a Density Functional Theoretical (DFT) study on the photophysics of a potent Excited-State Intramolecular Proton Transfer (ESIPT) molecular system, viz., 10-hydroxybenzo[h]quinoline (HBQ). Particular emphasis has been rendered on the assessment of the proton transfer reaction in HBQ in the ground and excited-states through elucidation and a careful perusal of the potential energy surfaces (PES). The non-viability of Ground-State Intramolecular Proton Transfer (GSIPT) process is dictated by a high-energy barrier coupled with no energy minimum for the proton transferred (K-form) form at the ground-state (S0) PES. Remarkable reduction of the barrier along with thermodynamic stability inversion between the enol (E-form) and the keto forms (K-form) of HBQ upon photoexcitation from S0 to the S1-state advocate for the operation of ESIPT process. These findings have been cross-validated on the lexicon of analysis of optimized geometry parameters, Mulliken’s charge distribution on the heavy atoms, and molecular orbitals (MO) of the E- and the K-forms of HBQ. Our computational results also corroborate to experimental observations. From the modulations in optimized geometry parameters in course of the PT process a critical assessment has been endeavoured to delve into the movement of the proton during the process. Additional stress has been placed on the analysis of the intramolecular hydrogen bonding (IMHB) interaction in HBQ. The IMHB interaction has been explored by calculation of electron density ρ(r) and the Laplacian ∇2ρ(r) at the bond critical point (BCP) using Atoms-In-Molecule (AIM) method and by calculation of interaction between σ? of OH with the lone pair of the nitrogen atom using Natural Bond Orbital (NBO) analysis. 相似文献
139.
Semiconductor optical amplifier (SOA) has already been established itself as a strong all-optical switching element for conducting super fast optical operations. Many all optical logic operations have been proposed by the use of SOA. Here in this paper the authors proposed a new method of implementing all-optical frequency encoded logic operations and half-adder by the use of SOA as well as Mach Zehnder interferometer. The advantage of frequency encoding has been strongly exploited here. 相似文献
140.
Prabir Nandi Ajaya Bhattarai Bijan Das 《Journal of Polymer Science.Polymer Physics》2007,45(14):1765-1770
Precise measurements on the viscosities of the solutions of sodium carboxymethylcellulose in water and in two acetonitrile–water mixtures containing 10 and 20 vol % of acetonitrile have been reported at 35, 40 and 50 °C. Isoionic dilutions were performed with the total ionic strengths of the solutions maintained with sodium chloride at ~4.20 × 10?4 and 1.45 × 10?3 mol dm?3 of NaCl to obtain the intrinsic viscosities. The Huggins constants were also obtained from the experimental results. The influences of the medium, the temperature, and the total ionic strength on the intrinsic viscosities as well as on the Huggins constants have been interpreted from the points of view of the solvodynamic and thermodynamic interactions prevailing in the polyelectrolyte solution under investigation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1765–1770, 2007 相似文献