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121.
Das P Mandal AK Kesharwani MK Suresh E Ganguly B Das A 《Chemical communications (Cambridge, England)》2011,47(26):7398-7400
A receptor with acidic methylene hydrogens is found to act as an efficient binding mode for F(-). This reagent could as well be used for selective and quantitative extraction of F(-) from the aqueous solution of NaF and sea water. 相似文献
122.
Tapas Mitra G. Sailakshmi A. Gnanamani A. B. Mandal 《Journal of Thermal Analysis and Calorimetry》2011,105(1):325-330
This study emphasizes, cross-linking potential of a simple di-carboxylic acid, namely, oxalic acid with type I collagen for
the preparation of collagen based biomaterial for clinical applications. Further the study discusses the characteristics features
of the cross-linked material in comparison with the standard cross-linker. In addition, the study also demonstrates the role
of ionic interactions in providing the thermal stability and tensile strength to the cross-linked biopolymer material. Type
I collagen from rat tail tendon treated with oxalic acid at optimized concentrations provided a biopolymer material without
changing the triple helical pattern of collagen (CD spectrum) and also with 6–7 fold increase in tensile strength than native
collagen. FTIR spectral details demonstrate the ionic interactions between collagen and oxalic acid. Thermal stability analyses
of oxalic acid cross-linked biopolymer revealed, high thermal stability compared to materials of glutaraldehyde cross-linked.
The results of the study suggest oxalic acid as a suitable cross-linker for collagen and it cross-link with collagen through
ionic interactions. 相似文献
123.
A method of construction of a new class of trees with reciprocal pairs of eigenvalues (λ, 1/λ) has been developed. They are derived from star graphs and can be symbolized as K 1, n ?1 + n(p) + mK 2 (1 ≤ m ≤ n ? 1 except for n = 1). The trees are minimally Kekulenoid and hence contain reciprocal pairs of eigenvalues in their eigenspectra. The characteristic polynomial coefficients of these trees with given values of n and m are shown to be obtainable by appropriate use of the Pascal's triangle. A general formula for this purpose has been developed. An analytical formula for the Wiener indices of such trees in terms of m and n has been derived and some consequences of this formula are presented. The relevance of these trees to real molecular structures is discussed. The trees have been shown to be useful in observing the subspectrallity of two series of IPR fullerenes of formulae C50+10 n and C60+12 n (n is a positive integer). 相似文献
124.
The effect of nanometric grain size modulation on the behavior of different kinds of chemically synthesized multiferroic ferrite–ferroelectric nanocomposites with cobalt zinc ferrite (Co0.65Zn0.35Fe2O4) as a ferrimagnetic component and lead zirconate titanate (PbZr0.52Ti0.48O3) as a ferroelectric component have been investigated in detail. Formation of two distinct pure phases of as-prepared nanocomposites was confirmed from recorded X-ray diffraction patterns at room temperature. The backscattered mode of a field emission scanning electron microscope micrograph has been used to study the microstructure, average grain size, and distribution of the two individual phases in the composites. Magnetization vs. magnetic field measurements clearly show the room temperature good hysteretic ferrimagnetic behavior of the composites having coercivity of 83–124 Oe and spontaneous magnetization of 20–24 emu/g. The dielectric constant is found to increase with increasing grain size of the nanocomposites from 124 to 687 at a frequency of 1 kHz. Investigation of temperature-dependent dielectric constant behavior reveals that the paraelectric–ferroelectric transition temperature decreases from 364 to 351 °C with decreasing particle size. A complex impedance spectroscopy study was carried out in the frequency range of 50 Hz–1 MHz and in the temperature range of 27–400 °C. The contribution of both grains and grain boundaries in the electrical properties of the composites has been confirmed from the complex impedance spectroscopy data. The activation energies estimated from the complex impedance spectroscopy and the ac conductivity spectrum are found to be nearly the same for the nanocomposites. The polarization vs. electric field measurement exhibits a typical ferroelectric hysteresis loop at room temperature and provides conclusive evidence of the presence of spontaneous polarization in the composites, confirming the presence of excellent ferroelectricity in the nanocomposites. At room temperature the multiferroic behavior of the composites is also confirmed from detailed magnetoelectric (ME) response studies. The optimal ME response is observed to be 0.6 % for higher temperature sintered composites. 相似文献
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129.
Atul D. Sontakke Kaushik Biswas Ashis K. Mandal Kalyandurg Annapurna 《Journal of fluorescence》2010,20(1):425-434
This paper reports on the preparation and systematic analysis of energy transfer mechanisms in Nd3+–Yb3+–Er3+ co-doped new series of barium-alumino-metaphosphate glasses. The time resolved fluorescence of Nd3+ in triply doped Ba–Al-metaphosphate glasses have revealed that, Yb3+ ions could function as quite efficient bridge for an energy transfer between Nd3+ and Er3+ ions. As a result, a fourfold emission enhancement at 1.54 μm of Er3+ ions has been achieved through an excitation of 4F5/2 level of Nd3+ at 806 nm for the glass having 3 mol% Yb3+ with an energy transfer efficiency reaching up to 94%. Decay of donor (Nd3+) ion fluorescence has been analyzed based on theoretical models such as direct energy transfer model (Inokuti–Hirayama) and
migration assisted energy transfer models (Burshtein’s hopping and Yokota–Tanimoto’s diffusion). The corresponding energy
transfer parameters have been evaluated and discussed. Primarily, electrostatic dipole–dipole (s ~ 6) interactions are found
to be responsible for the occurrence of energy transfer process in theses glasses. 相似文献
130.
Eighteen binary mixtures of 4-pentyloxy-4′-cyanobiphenyl (5OCB) and 4, 4′-di(alkoxy)azoxybenzenes (nOAB) with n = 5, 6, and
7 at different concentrations have been studied in detail. Over a wide concentration range, induced SmA phase was observed
in all the mixtures except in one. In most of the mixtures, the refractive indices no, ne, and Δn lie between the values of
pure components. The optical birefringence of the mixtures is found to decrease non-additively with concentration. The molecular
polarizability anisotropy and the orientational order parameter <P2> of the mixtures were calculated. Nature of variation of polarizability anisotropy with concentration is similar to that
of Δn. In allmixtures <P2> is more in smectic phase than in nematic phase and it also shows non-additive behaviour. Observed <P2> values of the mixtures were compared with McMillan’s and Maier-Saupe theoretical values and good agreement is found in some
mixtures. The transition temperatures obtained by fitting <P2> data to McMillan’s theory agree with the observed values within a few degrees. Ratio of elastic constants K33 and K11 is determined for mixtures having nematic phase and found to diverge at TNA transition point. 相似文献