Among the synthetic polymers of commercial potential, poly-butadiene is an important rubbery material and it encompasses the bulk elastomers in use. To the best of our knowledge, a complete normal coordinate analysis with full phonon dispersion curves for cis 1,4 polybutadiene (CPBD) have not been reported so far. In the present communication, we report a complete normal coordinate analysis with full dispersion curves, density-of-states and calculation of heat capacity. The normal coordinate analysis has been carried out using the Urey-Bradley force field and the Wilson's GF matrix method as modified by Higgs. A comparison has been made with trans 1,4 polybutadiene (TPBD). The prominent features of the dispersion curves like crossing over and regions of zero-slope away from the zone centre are discussed. To check the validity of the force field used and the assignments, normal mode calculations are also performed for unsaturated C-deuterated and fully deuterated CPBD. 相似文献
A metal‐free, regioselective synthesis of trisubstituted pyrroles has been developed through a formal [3+2] cycloaddition reaction between 2H‐azirines and nitroalkenes under visible light/photoredox‐catalyzed conditions. The reaction proceeds through 2H‐azaallenyl radical addition on β‐nitrostyrenes in a Michael fashion followed by a base‐mediated denitration reaction. The directive group influence of the nitro group controls the regiochemistry of the reaction. 相似文献
Optical and Quantum Electronics - Arithmetic logic unit (ALU) is the core of any digital processing systems. For creating an all optical ALU one needs basic logic gates such as optical NOT, OR and... 相似文献
Effects of a new plasticizer, polysorbate 80, on the structural and electrochemical properties of PEO–NH4PF6 polymer electrolyte system have been investigated. X-ray diffraction studies show significant increase in amorphicity of the solid polymer electrolyte on introduction of the plasticizer, which is also supported by lesser-dense spherulites observed in the SEM micrographs. The room temperature ionic conductivity of the electrolyte shows an increase of about two orders of magnitude (σmax~10?5 S/cm) on plasticization. The frequency dependence of the conductivity has been found to obey the Jonscher’s power law and slower backward ion hopping on plasticization. The polymer electrolyte shows protonic conduction as confirmed using cyclic voltammetry study. The studies show that polysorbate 80 is a promising plasticizer for semicrystalline polymer electrolytes. 相似文献
We have studied the reaction of methylenedicarbonyl compounds with 4,6-disubstituted 2-hydrazinyl-1,3,5-triazine in order to obtain novel coupled biheterocyclic aromatic systems with potential bioactivity. Reaction conditions were studied and optimized, and a series of 4,6-disubstituted 2-(1H-pyrazolyl)-1,3,5-triazines were obtained with good yield. 相似文献
Bimodal polyethylenes comprising varying proportions of high‐ and low‐molecular‐weight fractions are synthesized in a single polymerization stage, via the co‐immobilization of a chromium and an iron catalyst on an MgCl2/AlEtn(OEt)3?n support. Changes observed in the viscoelastic response of the polymer melt with increasing content of the high‐molecular‐weight fraction indicate effective mixing in the bimodal blend. In flow, chains in the high‐molecular weight fraction tend to orient and stretch under shear. Due to the longer relaxation time of the high‐molecular‐weight component, X‐ray diffraction and scattering reveal that shear‐induced crystallization takes place at temperatures close to the equilibrium melting point of linear polyethylene. The so‐crystallized high‐molecular‐weight component suppresses the nucleation barrier for further crystallization, leading to the formation of a “shish‐kebab” polymer morphology.
The tunneling conductance for a device consisting of a metal–insulator–superconductor (MIS) junction is studied in presence of Rashba spin–orbit coupling (RSOC) via an extended Blonder–Tinkham–Klapwijk formalism. We find that the tunneling conductance as a function of an effective barrier potential that defines the insulating layer and lies intermediate to the metallic and superconducting electrodes, displays an oscillatory behavior. The tunneling conductance shows high sensitivity to the RSOC for certain ranges of this potential, while it is insensitive to the RSOC for others. Additionally, when the period of oscillations is an odd multiple of a certain value of the effective potential, the conductance spectrum as a function of the biasing energy demonstrates a contrasting trend with RSOC, compared to when it is not an odd multiple. The explanations for the observation can be found in terms of a competition between the normal and Andreev reflections. Similar oscillatory behavior of the conductance spectrum is also seen for other superconducting pairing symmetries, thereby emphasizing that the insulating layer plays a decisive role in the conductance oscillations of a MIS junction. For a tunable Rashba coupling, the current flowing through the junction can be controlled with precision. 相似文献
Prodigiosin, a metabolite isolated from Serratia bacteria, is a potent anti-cancer agent. The goal of this research was to determine if prodigiosin could bind to G-quadruplex DNA. We found by using UV–vis spectroscopy that the G-quadruplex K+√d[TG4T]4, but not the single-stranded Li+√d[TG4T], increased the water solubility of prodigiosin. In addition, we found that prodigiosin's fluorescence was strongly enhanced in the presence of K+√d[TG4T]4, further evidence for quadruplex-ligand binding. Using 1H and 31P NMR experiments, we confirmed that prodigiosin binds at the 3′-end of K+√d[TG4T]4. Saturation transfer difference NMR experiments, done by irradiating the G5 H8 signal in K+√d[TG4T]4, indicated specific interactions between the G-quadruplex and prodigiosin's A and B rings. This study raises the possibility that G-quadruplex DNA may well be a target for the anti-cancer agent prodigiosin. 相似文献
Raman spectrum of 2,4-dichlorobenzonitrile (2,4-DCBN) in powder form has been recorded in the region 50-4000 cm(-1) on a Jasco K-500 Raman spectrophotometer using the 488.0 nm radiation from an argon laser. FTIR spectra in the region 200-4000 cm(-1) have been recorded in KBr pellet and nujol mull on a Nicolet DX spectrometer. Using the observed Raman and IR frequencies, normal co-ordinate analysis has been carried out to support the vibrational analysis and to determine the planar and non-planar force fields. 相似文献