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41.
V. Thiagarajan V.K. Indirapriyadharshini P. Ramamurthy 《Journal of inclusion phenomena and macrocyclic chemistry》2006,54(3-4):309-313
23Na NMR measurements were employed to monitor the stability of Na+ ion complexes with 18-crown-6 (18C6), dicycloxyl-18-crown-6 (DC18C6), dibenzo-18-crown-6 (DB18C6), 15-crown-5 (15C5) and benzo-15-crown-5 (B15C5) in binary acetonitrile–dimethylformamide mixtures of varying composition. In all cases, the variation of 23Na chemical shift with [crown]/[Na+] mole ratios indicated the formation of 1:1 complexes. The formation constants of the resulting complexes were evaluated from computer fitting of the mole ratio data to an equation which relates the observed chemical shifts to the formation constants. It was found that, in pure acetonitrile, the stabilities of the resulting 1:1 complexes vary in the order 15C5>DC18C6>B15C5>18C6>DB18C6, while in pure dimethylformamide the stability order is DC18C6>18C6>15C5>B15C5>DB18C6. The observed changes in the stability order could be related to the specific interactions between some crown ethers and acetonitrile. It was found that, in the case of all complexes, an increase in the percentage of dimethylformamide in the solvent mixtures would significantly decrease the stability of the complexes. 相似文献
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Suraj Ravindran Rajesh Langoju Abhijit Patil Pramod Rastogi 《Optics and Lasers in Engineering》2007,45(7):766-772
The effectiveness of phase-shifting interferometry (PSI) techniques employing piezoelectric device PZT in the estimation of phase depends largely on the accuracy with which the phase shifts are imparted to the device and the noise influencing the measurement. Several effective algorithms have been proposed to compute the phase shifts imparted to the device and subsequently obtain the phase using least-squares estimation technique. In this paper, we propose a generalized approach, which accurately estimates the phase shifts in the presence of noise. The method is based on the idea of linear prediction and explores the fact that sampling more data frames yields a reliable phase step estimate in a least-squares sense. We also compare our method with a commonly used generalized phase-shifting method based on histogram analysis and show that our proposed approach is highly effective. We also present simulation and experimental validations of our proposed method. 相似文献
45.
Nonlinear Dynamics - Analysis of electrostatic floating potential fluctuations associated with multiple anodic double layer revealed a complexity dynamic coexisting with chaotic behavior. These... 相似文献
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Damped transient dynamic elasto-plastic analysis of plate is investigated. A finite element model based on a C
0 higher order shear deformation theory has been developed. Nine noded Lagrangian elements with five degrees of freedom per
node are used. Selective Gauss integration is used to evaluate energy terms so as to avoid shear locking and spurious mechanisms.
Von Mises and Tresca yield criteria are incorporated along with associated flow rules. Explicit central difference time stepping
scheme is employed to integrate temporal equations. The mass matrix is diagonalized by using the efficient proportional mass
lumping scheme. A program is developed for damped transient dynamic finite element analysis of elasto-plastic plate. Several
numerical examples are studied to unfold different facets of damping of elasto-plastic plates. 相似文献
48.
Suraj P. Narula Sajeev Soni Meenu Puri Rishi D. Anand Jugal K. Puri 《Phosphorus, sulfur, and silicon and the related elements》2013,188(7):1647-1654
Si(NHC6H5-nFn)4.xTiCl4 [n = 2–5; x = 3,4] are obtained from the disproportionation reactions between (CF3CH2O)3SiNHC6H5-nFn (n = 2–5) and TiCl4 in petroleum ether (40–60°C) at 0°–10°C. These complexes are characterized by elemental analyses and IR, 1H, and 19F NMR spectroscopy. Unlike the reported5 complex Si(NHC6H4F-o)4.3TiCl4, these are non-ionic in nature. All complexes give double adducts with CH3NO2 and CH3CN within 24 h. 相似文献
49.
Geetha Thiagarajan Effendi Widjaja Jun Hyuk Heo Jason K. Cheung Busolo Wabuyele Xiaodun Mou Mohammed Shameem 《Journal of Raman spectroscopy : JRS》2015,46(6):531-536
Structural complexity of biological drug products presents an analytical challenge in terms of early detection of aggregation and/or degradation. In the present study, Raman and Raman optical activity (ROA) were evaluated for their sensitivity to detect heat‐induced molecular instability in an Immunoglobulin G4 subclass therapeutic monoclonal antibody present in its formulation matrix. The therapeutic antibody was subjected to heat stress at 50 °C and was analyzed at various time points up to 1 month. The current results suggest that Raman and ROA are sensitive to early‐stage detection of heat‐induced instability of the antibody, in which significant changes could be observed at 1 week of stress. ROA could provide early detection of the subtle differences at the tertiary structure level in a heat‐stressed monoclonal antibody and Raman/ROA spectra could provide early detection in secondary structural changes as well. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
50.
The electrochemical depositions of Pt microparticles and KI film were successfully carried out on glassy carbon electrodes (GCE), gold electrodes (GE), and indium tin oxide electrodes (ITO). The electrochemical studies of Pt micro/KI film on GCE show that the film was stable, active at pH 1.5 electrolyte solutions. The Pt microparticle/KI film modified ITO electrodes were examined by using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The SEM and AFM results show that the Pt particle sizes were in the range of 120 nm–1.4 μm, respectively. The proposed film on GCE shows efficient electrocatalysis for oxygen, Cr2O reduction by using cyclic voltammetry. Further the electrochemical oxidation of sodium meta‐arsenite (As(III)), H2O2 were successfully carried out and the detection of H2O2 in real samples has been validated. 相似文献