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排序方式: 共有163条查询结果,搜索用时 15 毫秒
61.
S.K. Srivastava S.K. Sharma Pallavi Sinha 《Journal of Physics and Chemistry of Solids》2009,70(2):255-2191
In the present study, the compression dependence of αKT is analyzed using Anderson-Isaak equation along with Stacey's equation of state for ionic solids such as NaCl and MgO. It is found that the value of αKT decreases with increasing compression and attains a minimum, after which it increases with increasing compression along an isotherm. It is also found that αKT tends to infinity as P→∞ or V→0. The presented nature of αKT is valuable to understand the thermoelastic and thermodynamic properties of MgO and NaCl at high compressions and at high temperatures. 相似文献
62.
We present an analysis of the -prime equations of state (EOS) due to Keane and Stacey. It is found that the two EOS differ significantly from each other in some important respects. -prime represents the pressure derivative of the bulk modulus. It is shown that the volume dependence of -prime and higher derivative properties predicted from the Keane EOS are compatible with those predicted from Stacey’s reciprocal -prime EOS only when the Murnaghan approximation is valid. It has been emphasized that the Stacey EOS is more appropriate for describing the relationship between pressure and the bulk modulus and its pressure derivative. The results based on the two EOS have been compared and discussed. 相似文献
63.
Pallavi Raote 《Optics Communications》2008,281(8):2213-2217
We report here the reliable and efficient operation of a mini-TEA CO2 laser utilizing uniform field electrodes wherein the parallel spark channels of the preioniser, an integral part of the laser, functioned as a switch as well as a source of UV photons. The operation of the laser has been realized up to a maximum energy loading of ∼197 J/l atm under widely varying gas composition including helium lean as well as helium-free gas mixtures. Under most optimized conditions the laser operated with an efficiency of ∼7.1%. The spatially symmetric nature of the emission from the laser in spite of the one sided preionisation points to the effectiveness of the excitation circuit employed here to energise the laser. 相似文献
64.
65.
Experimental and computational studies of ring‐opening polymerization of ethylene brassylate macrolactone and copolymerization with ε‐caprolactone and TBD‐guanidine organic catalyst
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Ana Pascual Haritz Sardón Fernando Ruipérez Raquel Gracia Pallavi Sudam Antonio Veloso David Mecerreyes 《Journal of polymer science. Part A, Polymer chemistry》2015,53(4):552-561
The ring‐opening polymerization (ROP) of ethylene brassylate, catalyzed by the cyclic guanidine 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD) is reported. Several experimental parameters were evaluated for bulk ROP process and polyesters, resulting in molecular weights between 3 and 15 kg mol?1. End‐group analysis by 1H nuclear magnetic resonnance (NMR) and matrix assisted laser desorption ionization time of flight computational studies supports the dual behavior of TBD, which can act as both a catalyst and initiator of the polymerization process. Under optimum conditions, semicrystalline poly(ethylene brassylate‐co‐ε‐caprolactone) random copolymers were synthesized. Depending on the comonomer content, our results showed a range of melting temperatures between 39 and 69 °C. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 552–561 相似文献
66.
Kimberley J. Powell Joanna L. Richens Jonathan P. Bramble Li-Chen Han Pallavi Sharma Paul OShea John E. Moses 《Tetrahedron》2018,74(12):1191-1198
Marine organisms rely upon complex bio-chemical systems to manage photo-induced oxidative damage as part of a sophisticated chemical defense. Using a combination of synthetic chemistry and biophysical techniques, we provide evidence to support the notion that marine derived polyene γ-pyrone metabolites of sacoglossan molluscs become localised at cell membranes where they influence the total absorption of the harmful radiation by the lipid membrane, thereby functioning as sunscreen agents. We also report two new hyperperoxide analogues of the putative polyene biosynthetic precursors that themselves are likely candidate natural products. 相似文献
67.
68.
A total synthesis of the recently reported triquinane natural product dichomitol, isolated from the fermentation broth of Dichomitus squalens, has been accomplished from the commercially available 1,5-cyclooctadiene through a series of unambiguous synthetic steps. A complete mismatch between the spectral characteristics of the synthetic product and that of the natural product warrants a revision of the structure of dichomitol. 相似文献
69.
Subhash P. Chavan Cherukupally Praveen Pallavi Sharma U.R. Kalkote 《Tetrahedron letters》2005,46(3):439-441
A short synthetic route to (−)-and (+)-bulgecinine, the amino acid moiety of the bulgecins was achieved from the readily available nonchiral pool starting material cis-2-butene-1,4-diol in which a Claisen orthoester rearrangement and a Sharpless asymmetric dihydroxylation were used as the key steps. 相似文献
70.
Time-dependent fluctuations in the distance x(t) between two segments along a polymer are one measure of its overall conformational dynamics. The dynamics of x(t), modeled as the coordinate of a particle moving in a one-dimensional potential well in thermal contact with a reservoir, is treated with a generalized Langevin equation whose memory kernel K(t) can be calculated from the time-correlation function of distance fluctuations C(t) identical with x(0)x(t). We compute C(t) for a semiflexible continuum model of the polymer and use it to determine K(t) via the GLE. The calculations demonstrate that C(t) is well approximated by a Mittag-Leffler function and K(t) by a power-law decay on time scales of several decades. Both functions depend on a number of parameters characterizing the polymer, including chain length, degree of stiffness, and the number of intervening residues between the two segments. The calculations are compared with the recent observation of a nonexponential C(t) and a power law K(t) in the conformational dynamics within single molecule proteins [Min et al., Phys. Rev. Lett. 94, 198302 (2005)]. 相似文献