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261.
Renu Chadha Poonam Arora Sushma Gupta Dharamvir Singh Jain 《Journal of Thermal Analysis and Calorimetry》2011,105(3):1049-1059
The work is undertaken to evaluate the effect of Tween 80 on the complexing ability of β-cyclodextrins to encapsulate the
poorly soluble antiretroviral agent, nevirapine. The phase solubility diagram indicates 1:1 stoichiometry and is supported
by electronspray ionization mass spectrometry. The complexes were characterized by DSC, FT-IR, and XRD in the solid state.
The ternary systems were autoclaved before being lyophilized for the best results. Proton NMR suggests that the methyl pyridine
ring of the drug is involved in inclusion and enters from the wider side of the cavity which was confirmed by COESY NMR. Solution
calorimetry, a direct method to determine the thermodynamic parameters, was used to determine the complexation constant (K) and other thermodynamic properties. The process is associated with negative ∆H and positive ∆S indicating a stable inclusion complex. The value of K follows the order β-CD < HP-β-CD < M-β-CD. The molar enthalpy of solution in autoclaved solid formulation is less endothermic
as compared to additive molar enthalpy of solution obtained by summation of enthalpy of solution of individual components
suggesting synergistic interaction between the drug and its constituents. A threefold increase of the in vitro permeability
flux was observed for binary systems which was elevated to fourfold for autoclaved ternary complexes. 相似文献
262.
263.
Renu Sharma Meena Nagar 《Phosphorus, sulfur, and silicon and the related elements》2013,188(7):1526-1535
A series of new mixed ligand complexes of Zn(II), Cd(II), and Hg(II) with citronellal thiosemicarbazone [3,7-dimethyl-6-octene-1-a1 thiosemicarbazone (LH)] and N-phthaloyl amino acids (AH) have been synthesized by the reaction of metal(II) chloride with ligands citronellal thiosemicarbazone (DOTSC) and N-phthaloyl glycine [1,3-dihydro-1,3-dioxo-2H-isoindole-2-acetic acid (A1H)] or N-phthaloyl alanine [1,3-dihydro-1,3-dioxo-α(methyl)-2H-isoindole-2-acetic acid (A2H)] in 1:1:1 molar ratio in dry refluxing ethanol. All the complexes have been characterized by elemental analyses, molar conductance measurement, molecular weight measurement, IR, and multinuclear NMR (1H and 13C{1H}) spectral studies. IR, 1H, and 13C{1H} NMR spectral studies suggest the involvement of azomethine-N, thiol-S atoms of the thiosemicarbazone moiety and both carboxylate-O of N-phthaloyl amino acid moiety in coordination with central metal(II) ion, and four coordinated geometries have been assigned to these complexes. The free ligands and metal complexes have been screened for their antifungal activity against two fungal strains, Fusarium moniliformae and Macrophomina phaseolina, using the the radial growth method. The results of antifungal activity show that metal complexes show enhanced higher activity than the free ligands. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
264.
Gunasekar Ramachandran Munusamy Sathishkumar Ravindranath S. Rathore Periyasamy Giridharan 《合成通讯》2013,43(19):2227-2239
A simple and efficient approach was developed to synthesize symmetrical/unsymmetrical bis[1,3]oxazines using ammonium acetate with controllable substitution patterns in a one-pot fashion. In a representative crystal structure, the [1,3]oxazine ring is in a distorted semichair conformation with C2-carbon and nitrogen atoms residing above and below the naphthalene plane, leading to strain in the ring that allows ring-opening polymerization to take place. A few of the derivatives were found to possess anticancer activity. This current modest protocol affords numerous advantages such as mild reaction condition, shorter reaction time, operational simplicity, and excellent yield. 相似文献
265.
Among various high-temperature organic polymers, the aromatic polyamides have shown excellent thermal stability due to the stiffness of the polymer chain and hydrogen bonding of the amide groups, but had limited solubility in most organic solvents [1-3]. 相似文献
266.
We carried out the heat capacity calculation of the magnetoresistance compounds EuMnO3 and Eu0.7A0.3MnO3 (where A=Ca and Sr) as a function of temperature from 5 to 100 K, using the Rigid Ion Model (RIM). The results on heat capacity for EuMnO3 and Eu0.7A0.3MnO3 (A=Ca and Sr) obtained by us are in good agreement with the measured values. Although strong electron–phonon interactions are present in these compounds but the lattice part of the specific heat also deserves proper attention. The parent compound EuMnO3 exhibits two magnetic transitions at 35 and 47 K due to weak ferromagnetic (FM) component and antiferromagnetic (AF) ordering. In addition, we have reported cohesive energy (φ), molecular force constant (f), compressibility (β), Restrahalen frequency (υ0), Debye temperature (θD) and Gruneisen parameter (γ) in the temperature range 5 K?T?100 K. 相似文献
267.
We report on the specific heat C(T) of doped manganites Nd0.5Sr0.5MnO3, Nd0.5Ca0.5MnO3, Sm0.5Ca0.5MnO3, Dy0.5Ca0.5MnO3 and Ho0.5Ca0.5MnO3 in the temperature range 2?T?300 K using modified rigid ion model (MRIM). The present specific heat results are in general satisfactory agreement with experimental data except at very low temperatures (i.e. T?12 K). Also a sharp peak observed in the experimental results for these compounds around 5 K could not be revealed by our computed results as they arise due to Schottky-like anomaly. Besides, we have reported the cohesive and the thermal properties of these compounds. The results obtained by us are discussed in detail. 相似文献
268.
Santosh Kumar Kudtarkar Renu Dhadwal 《Journal of magnetism and magnetic materials》2010,322(16):2287-2292
We determine the induced voltage generated by spatial and temporal magnetisation textures (inhomogeneities) in metallic ferromagnets due to the spin diffusion of non-equilibrium electrons. Using time dependent semi-classical theory as formulated in Zhang and Li [1] and the drift-diffusion model of transport it is shown that the voltage generated depends critically on the difference in the diffusion constants of up and down spins. Including spin relaxation results in a crucial contribution to the induced voltage. We also show that the presence of magnetisation textures results in the modification of the conductivity of the system. As an illustration, we calculate the voltage generated due to a time dependent field driven helimagnet by solving the Landau-Lifshitz equation with Gilbert damping and explicitly calculate the dependence on the relaxation and damping parameters. 相似文献
269.
Sanket?Chougale Dhammaraj?Rokade Tanushree?Bhattacharjee Harshawardhan?PolEmail author Renu?DhadwalEmail author 《Rheologica Acta》2018,57(6-7):493-503
Extrusion film casting (EFC) is an industrially important process which produces thousands of tons of polymer films, sheets, and coating used for various industrial as well as household applications. In this paper, we focus on an instability which occurs during certain polymer processing operations operating under predominantly elongational flow, such as extrusion film casting and fiber spinning. This instability, called the draw resonance, occurs in the form of sustained periodic fluctuations in the film dimensions. It appears when the process goes beyond the critical line speed of the EFC process. In this work, a conventional linear stability analysis is carried out for nonisothermal EFC process to determine the onset of the draw resonance. The polymer rheology is modeled by the Phan-Thien Tanner (PTT) multi-mode constitutive equation. For the implementation, a conventional shooting method approach is used. Extrusion film casting experiments were also carried out using a conventional linear low-density polyethylene (LLDPE) by varying process parameters such as draw ratio and aspect ratio, to observe the effect on the stability of the process. Linear stability analysis results under non-isothermal conditions are compared and validated with existing results from literature and with our own experimental data. This work displays the effect of multiple relaxation modes as well as the temperature influence on the stability of EFC process. Finally, results also indicate that the temperature highly affects the stability of the EFC process and cannot be ignored from modeling of EFC process. 相似文献