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101.
Manjushree Senapati Narayan C. Samal Ranu Mishra Alaka Patnaik Lalit N. Patnaik Mahendra K. Rout 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(5-6):557-566
The kinetics of the mechanism of the polymerization of methyl methacrylate initiated by the glycerol/Mn(III) acetate redox system has been investigated in aqueous sulfuric acid medium in the temperature range of 40 to 50 °C. The effects of glycerol, methyl methacrylate, metal ion, acetic acid, and sulfuric acid on the rates of polymerization have been studied. One striking observation is that the increase in monomer concentration steadily decreases the rate of polymerization, contrary to what was observed in the case of acrylonitrile. On the basis of these observations, an appropriate kinetic scheme and rate expression have been developed. 相似文献
102.
103.
Vikas Porwal Mahendra Singh Deepika Chaturvedi Poonam Tandon Vishwambhar Dayal Gupta 《Journal of Polymer Science.Polymer Physics》2010,48(2):175-182
Poly(L ‐lactic acid) (PLLA) (? CH(CH3) ? COO? )n is a biodegradable polymer, which exhibits many applications in the biomedical field and where thermoplastics are employed. A comprehensive study of the normal modes and their dispersion in PLLA using Wilson′s GF matrix method as modified by Higgs is being reported. Assignments of calculated normal modes have been made and characteristic features of dispersion curves are discussed. Heat capacity has been calculated via density‐of‐states using Debye relation in the temperature range 10–250 K, which is in fairly good agreement with the experimental data. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 175–182, 2010 相似文献
104.
A facile method for the synthesis of 1,3,5-triarylbenzenes is developed via cyclotrimerization of acetophenones in the presence of 4-dodecylbenzenesulfonic acid (DBSA) as an efficient Bronsted acid catalyst under solvent-free conditions. This synthetic protocol has several advantages such as green reaction conditions, short reaction times, high atom economy and good to excellent yields of the target products. 相似文献
105.
Azizi Masitah Abdul Halim Isahak Wan Nor Roslam Wan Masdar Mohd Shahbudin Somalu Mahendra Rao Yarmo Mohd Ambar 《Research on Chemical Intermediates》2018,44(11):6787-6802
Research on Chemical Intermediates - Hydrogen is considered a promising energy carrier for the future, especially for clean energy generation via fuel cell technologies. Formic acid is one of the... 相似文献
106.
107.
Shin J Ikonen T Khandkar MD Ala-Nissila T Sung W 《The Journal of chemical physics》2010,133(18):184902
We study the dynamics of flexible, semiflexible, and self-avoiding polymer chains moving under a Kramers metastable potential. Due to thermal noise, the polymers, initially placed in the metastable well, can cross the potential barrier, but these events are extremely rare if the barrier is much larger than thermal energy. To speed up the slow rate processes in computer simulations, we extend the recently proposed path integral hyperdynamics method to the cases of polymers. We consider the cases where the polymers' radii of gyration are comparable to the distance between the well bottom and the barrier top. We find that, for a flexible polymers, the crossing rate (R) monotonically decreases with chain contour length (L), but with the magnitude much larger than the Kramers rate in the globular limit. For a semiflexible polymer, the crossing rate decreases with L but becomes nearly constant for large L. For a fixed L, the crossing rate becomes maximum at an intermediate bending stiffness. For the self-avoiding chain, the rate is a nonmonotonic function of L, first decreasing with L, and then, above a certain length, increasing with L. These findings can be instrumental for efficient separation of biopolymers. 相似文献
108.
Sajeli B Sahai M Suessmuth R Asai T Hara N Fujimoto Y 《Chemical & pharmaceutical bulletin》2006,54(4):538-541
Hyosgerin, a new optically active coumarinolignan, has been isolated and characterized along with three other coumarinolignans, venkatasin, cleomiscosin A and cleomiscosin B, from the seeds of Hyoscyamus niger L. The structure was determined on the basis of spectroscopic analysis and chemical conversion. The optical properties and absolute stereochemistry of these coumarinolignans have also been studied and discussed. 相似文献
109.
Ramgir NS Late DJ Bhise AB More MA Mulla IS Joag DS Vijayamohanan K 《The journal of physical chemistry. B》2006,110(37):18236-18242
A simple method of vapor deposition for the shape selective synthesis of ZnO structures, namely, multipods, submicron wires, and spheres, has been successfully demonstrated. A plausible growth mechanism based on the studies of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) is proposed. Our studies suggest that the growth of a multipod structure is governed by the screw dislocation propagation while the vapor-liquid-solid (VLS) mechanism is responsible for the formation of submicron wires and spheres. Moreover, the flow rate of the carrier gas plays a crucial role in governing the morphology. Further, these structures exhibit an enhanced field emission behavior. The nonlinearity in the Fowler-Nordheim (F-N) plot, a characteristic feature of electron emission from semiconductors, is explained by considering the contributions from both the conduction and the valence bands of ZnO. 相似文献
110.
In the present paper, we investigate the majorization properties for certain classes of multivalent analytic functions defined by the S?l?gean operator. Moreover, we point out some new and interesting consequences of our main result. 相似文献