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排序方式: 共有575条查询结果,搜索用时 15 毫秒
101.
Neogi A Majhi TP Mukhopadhyay R Chattopadhyay P 《The Journal of organic chemistry》2006,71(8):3291-3294
Pd-catalyzed intramolecular arylamination on sugar derivatives has been accomplished by using bulky biaryl phosphine ligands. An application of this methodology on a variety of D-glucose-derived substrates, 2a-f, led to the synthesis of highly functionalized cis-fused tricyclic oxazocines, 3a-e. The products could subsequently be transformed to the optically active benzoxazocine derivative 4 and tricyclic nucleoside 6. This is the first example of the synthesis of eight-membered rings via intramolecular cycloamination of furanose derivatives, which provides a very useful method for the catalytic synthesis of medium-ring heterocycles. 相似文献
102.
We obtain cosmological solutions which admit emergent universe (EU) scenario in the framework of Einstein Gauss–Bonnet (GB)
gravity coupled with a dilaton field in 4-dimensions. The coupling parameter of the GB terms and the dilaton in the theory
are determined for obtaining an EU scenario. The corresponding dilaton potential which admits such scenario is determined.
It is found that the GB terms coupled with a dilaton field plays an important role in describing the dynamics of the evolution
of the early as well as the late universe. We note an interesting case where the GB term dominates initially in the asymptotic
past regime, subsequently it decreases and thereafter its contribution in determining the dynamics of the evolution dominates
once again. We note that the Einstein’s static universe solution permitted here is unstable which the asymptotic EU might
follow. We also compare our EU model with supernova data. 相似文献
103.
An experimental study was conducted to characterize the dynamic wind loads and evolution of the unsteady vortex and turbulent
flow structures in the near wake of a horizontal axis wind turbine model placed in an atmospheric boundary layer wind tunnel.
In addition to measuring dynamic wind loads (i.e., aerodynamic forces and bending moments) acting on the wind turbine model
by using a high-sensitive force-moment sensor unit, a high-resolution digital particle image velocimetry (PIV) system was
used to achieve flow field measurements to quantify the characteristics of the turbulent vortex flow in the near wake of the
wind turbine model. Besides conducting “free-run” PIV measurements to determine the ensemble-averaged statistics of the flow
quantities such as mean velocity, Reynolds stress, and turbulence kinetic energy (TKE) distributions in the wake flow, “phase-locked”
PIV measurements were also performed to elucidate further details about evolution of the unsteady vortex structures in the
wake flow in relation to the position of the rotating turbine blades. The effects of the tip-speed-ratio of the wind turbine
model on the dynamic wind loads and wake flow characteristics were quantified in the terms of the variations of the aerodynamic
thrust and bending moment coefficients of the wind turbine model, the evolution of the helical tip vortices and the unsteady
vortices shedding from the blade roots and turbine nacelle, the deceleration of the incoming airflows after passing the rotation
disk of the turbine blades, the TKE and Reynolds stress distributions in the near wake of the wind turbine model. The detailed
flow field measurements were correlated with the dynamic wind load measurements to elucidate underlying physics in order to
gain further insight into the characteristics of the dynamic wind loads and turbulent vortex flows in the wakes of wind turbines
for the optimal design of the wind turbines operating in atmospheric boundary layer winds. 相似文献
104.
Kumar Abhinav Partha Guha 《The European Physical Journal B - Condensed Matter and Complex Systems》2018,91(3):52
Through the Hasimoto map, various dynamical systems can be mapped to different integrodifferential generalizations of Nonlinear Schrödinger (NLS) family of equations some of which are known to be integrable. Two such continuum limits, corresponding to the inhomogeneous XXX Heisenberg spin chain [J. Phys. C 15, L1305 (1982)] and that of a thin vortex filament moving in a superfluid with drag [Eur. Phys. J. B 86, 275 (2013) 86; Phys. Rev. E 91, 053201 (2015)], are shown to be particular non-holonomic deformations (NHDs) of the standard NLS system involving generalized parameterizations. Crucially, such NHDs of the NLS system are restricted to specific spectral orders that exactly complements NHDs of the original physical systems. The specific non-holonomic constraints associated with these integrodifferential generalizations additionally posses distinct semi-classical signature. 相似文献
105.
Tanima Bose Diane Latawiec Partha Pratim Mondal Subhra Mandal 《Journal of nanoparticle research》2014,16(8):1-25
The ever-increasing number of diseases worldwide requires comprehensive, efficient, and cost-effective modes of treatments. Among various strategies, nanomaterials fulfill most of these criteria. The unique physicochemical properties of nanoparticles have made them a premier choice as a drug or a drug delivery system for the purpose of treatment, and as bio-detectors for disease prognosis. However, the main challenge is the proper consideration of the physical properties of these nanomaterials, while developing them as potential tools for therapeutics and/or diagnostics. In this review, we focus mainly on the characteristics of nanoparticles to develop an effective and sensitive system for clinical purposes. This review will present an overview of the important properties of nanoparticles, through their journey from its route of administration until disposal from the human body after accomplishing targeted functionality. We have chosen cancer as our model disease to explain the potentiality of nano-systems for therapeutics and diagnostics in relation to several organs (intestine, lung, brain, etc.). Furthermore, we have discussed their biodegradability and accumulation probability which can cause unfavorable side effects in healthy human subjects. 相似文献
106.
Bar AK Mohapatra S Zangrando E Mukherjee PS 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(31):9571-9579
Three new nanoscopic trigonal prisms, [(tmen)(6) Pd(6) (H(2)L)(3)](NO(3))(12) (1), [(Meen)(6) Pd(6)(H(2) L)(3)](NO(3))(12) (2), and [(2,2'-bipy)(6)Pd(6) (H(2)L)(3)](NO(3))(12) (3), have been synthesized in excellent yields through single-step metal-ligand-coordination-driven self-assembly using 5,10,15,20-tetrakis(3-pyridyl)porphyrin (H(2)L) as a donor and cis-blocked Pd(II) 90° acceptors. These complexes were fully characterized by spectroscopic studies and single-crystal X-ray diffraction. All of these barrels quantitatively bind Zn(II) ions in the N(4) pockets of the porphyrin walls at room temperature. Their corresponding zinc-embedded complexes, [(tmen)(6)Pd(6)(ZnL)(3)](NO(3))(12) (1?a), [(Meen)(6) Pd(6)(ZnL)(3)](NO(3))(12) (2?a), and [(2,2'-bipy)(6)Pd(6)(ZnL)(3)](NO(3))(12) (3?a), were synthesized under ambient conditions by the post-synthetic binding of Zn(II) ions into the H(2)N(4) pockets of the porphyrin walls of these complexes. These zinc-embedded complexes were characterized by electronic absorption, fluorescence emission, (1)H?NMR spectroscopy, as well as elemental analysis. Complexes 1-3 exhibited considerable microporosity in their solid state. Complex 1 was an efficient adsorbent for nitrogen gas and EtOH, MeOH, and water vapors. 相似文献
107.
An amperometric immunosensor for the specific detection of Ricinus communis is reported. Screen printed electrodes (SPEs) were modified with gold nanoparticles (GNPs) loaded multiwalled carbon nanotubes (MWCNTs)-chitosan (Ch) film. The ratio of MWCNT and GNP was optimised to get best electrochemically active electrode. Sandwich immunoassay format was used for the immunosensing of ricin. The revealing antibodies tagged with the enzyme alkaline phosphatase (ALP) converts the substrate 1-naphthyl phosphate into 1-naphthol that was determined with the amperometric technique. The amperometric current obtained was correlated with the concentration of ricin. The prepared GNP-MWCNT-Ch-SPE showed high stability due to the Ch film, short response time with good reproducibility and increased shelf life of the electrodes immobilised with antibodies. The electrochemical activity of the electrode improved because of optimization of composition of CNTs and gold nanoparticles. Under the optimal conditions, the modified electrode showed a wide linear response to the concentration of ricin in the range of 2.5-25 ng mL(-1) with a limit of detection of 2.1 ng mL(-1) and with a relative standard deviation of 5.1% and storage life of 32 days. 相似文献
108.
109.
Partha Guha A. Ghose Choudhury Barun Khanra 《Communications in Nonlinear Science & Numerical Simulation》2012,17(11):4053-4063
We introduce a new transformation (nonlocal) to find the general solutions of some equations belonging to the third and fourth-order time dependent Riccati class of equations. These are in turn related to the Chazy polynomial class and the time dependent F-XVI Bureau symbol PI equations respectively. 相似文献
110.
M. K. PARTHA 《应用数学和力学(英文版)》2010,31(5):565-574
In this paper, the natural convection in a non-Darcy porous medium is studied using a temperature-concentration-dependent density relation. The effect of the two parameters responsible for the nonlinear convection is analyzed for different values of the inertial parameter, dispersion parameters, Rayleigh number, Lewis number, Soret number, and Dufour number. In the aiding buoyancy, the tangential velocity increases steeply with an increase in the nonlinear temperature parameter and the nonlinear concentration parameter when the inertial effect is zero. However, when the inertial effect is non-zero, the effect of the nonlinear temperature parameter and the nonlinear concentration parameter on the tangential velocity is marginal. The concentration distribution varies appreciably and spreads in different ranges for different values of the double dispersion parameters, the inertial effect parameter, and also for the parameters which control the nonlinear temperature and the nonlinear concentration. Heat and mass transfer varies extensively with an increase in the nonlinear temperature parameter and the nonlinear concentration parameter depending on Dacry and non-Darcy porous media. The variation in heat and mass transfer when all the effects, i.e., the inertial effect, double dispersion ef- fects, and Soret and Dufour effects, are simultaneously zero and non-zero. The combined effects of the nonlinear temperature parameter, the nonlinear concentration parameter and buoyancy are analyzed. The effect of the nonlinear temperature parameter and the nonlinear concentration parameter and also the cross diffusion effects on heat and mass transfer are observed to be more in Darcy porous media compared with those in non- Darcy porous media. In the opposing buoyancy, the effect of the temperature parameter is to increase the heat and mass transfer rate, whereas that of the concentration parameter is to decrease. 相似文献