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181.
Mohd. Shakir S.K. KushwahaK.K. Maurya Manju AroraG. Bhagavannarayana 《Journal of Crystal Growth》2009,311(15):3871-3875
Remarkable second-harmonic generation (SHG) efficiency has been observed in the glycine picrate (GP) though it crystallizes in centrosymmetric structure. Bulk single crystals of GP with a good size of ~20×10×3 mm3 have been successfully grown by the slow cooling method in aqueous medium. Powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR) and FT-Raman studies have confirmed, respectively, the crystal structure and functional groups of the grown crystal. Crystalline perfection of single crystals has been evaluated by high-resolution X-ray diffractometry (HRXRD) using a multicrystal X-ray diffractometer and found that the grown crystals are nearly perfect. Nonlinear optical (NLO) behavior of glycine picrate crystals has been studied for the first time by Kurtz powder technique and its second-harmonic generation efficiency is found to be 2.34 times higher than that of KDP. Transparency of crystals in UV–vis–NIR region has also been studied. Dielectric measurements have been carried out using an impedance analyzer over a wide range of frequency (100 Hz–3 MHz) at room temperature. The slight decrease in dielectric constant has been observed as the frequency is increased and the dielectric loss is very low for the entire frequency range. The ac conductivity is almost constant up to 1 MHz and sudden increase has been observed above this frequency. 相似文献
182.
In this paper, finite element method (FEM) mode analyses of planar slab optical waveguide having complicated refractive index profile are presented. We try to estimate the dispersion graph, mode cut-off condition, group delay and waveguide dispersion for the case of α-power and chirped-type refractive index profile. In order to obtain the more accurate result, we have derived the higher-order polynomial, which establishes the suitable relationship between b and V for different profile of optical waveguide. On the basis of the derived polynomials, the waveguide dispersion is analyzed for different type of refractive index profile waveguide. Our study shows that the waveguide dispersion can be substantially reduced when we deployed the optical waveguide having linearly chirped-type refractive index profile. Earlier too, the arbitrary refractive index profile has been analyzed but to the best of our knowledge chirped-type refractive index profile has not been analyzed till date for the case of planar slab optical waveguide. 相似文献
183.
Kinetics of polymerization of acrylonitrile (AN) in presence of fullerene (C60) has been studied using p-acetyl benzylidine triphenyl arsonium ylide as initiator in dioxane at 60 ± 0.1°C under the blanket of nitrogen. The rate of polymerization (R p ) at low concentration of fullerene may be represented as R p ?? [Ylide]0.5[AN]1.0 [Full]?0.6, indicating inhibition effect of fullerene on the polymerization. The energy of activation for the polymerization was found to be 71.5 ± 0.5 kJ mol?1. Fourier transform infrared spectroscopic analysis (FTIR) confirmed the insertion of fullerene in to the final polymer. The mechanism for the polymerization has also been proposed. 相似文献
184.
Wu F Zhu H Sun L Rajendran C Wang M Ren X Panjikar S Cherkasov A Zou H Stöckigt J 《Journal of the American Chemical Society》2012,134(3):1498-1500
The Pictet-Spenglerase strictosidine synthase (STR1) has been recognized as a key enzyme in the biosynthesis of some 2000 indole alkaloids in plants, some with high therapeutic value. In this study, a novel function of STR1 has been detected which allows for the first time a simple enzymatic synthesis of the strictosidine analogue 3 harboring the piperazino[1,2-a]indole (PI) scaffold and to switch from the common tryptoline (hydrogenated carboline) to the rare PI skeleton. Insight into the reaction is provided by X-ray crystal analysis and modeling of STR1 ligand complexes. STR1 presently provides exclusively access to 3 and can act as a source to generate by chemoenzymatic approaches libraries of this novel class of alkaloids which may have new biological activities. Synthetic or natural monoterpenoid alkaloids with the PI core have not been reported before. 相似文献
185.
Singh SK Chauhan R Singh B Diwan K Kociok-Köhn G Bahadur L Singh N 《Dalton transactions (Cambridge, England : 2003)》2012,41(4):1373-1380
In this work, the photosensitizing properties of ferrocene (Fc)-based compounds FcCH(2)CS(3)CH(2)Fc (1) and FcCH(2)SSCH(2)Fc (2) were investigated and significant enhancement in the light harvesting efficiency was observed compared to those achieved with previously reported compounds from our lab. The compounds were fully characterized by spectroscopy and X-ray crystallography, and their electrochemical properties studied. DSSCs based on these dyes display efficiencies comparable to those of a standard cell based on N719 under similar experimental conditions. These studies demonstrate that ferrocenyl-based sulfur rich compounds with proper orientation of the Fc groups assisted via suitable linkers, together with desired redox properties and visible region electronic absorption features could constitute a new class of photosensitizers targeting light driven reactions. 相似文献
186.
We report the synthesis of a phospholipid-like platinous compound and its self-assembling into a liposome-like nanostructure, named Ptsome, as a new delivery system for platinum-based drugs. 相似文献
187.
Devkar Santosh T. Badhe Yogesh S. Jagtap Suresh D. Hegde Mahabaleshwar V. 《平面色谱法杂志一现代薄层色谱法》2012,25(4):290-294
JPC – Journal of Planar Chromatography – Modern TLC - The high-performance thin-layer chromatography (HPTLC) method has been developed for the simultaneous quantification of withaferine... 相似文献
188.
A new, highly stereoselective intramolecular cyclopropanation of vinylogous carbamates with carbenes in the presence of Cu(acac)(2) as the catalyst has been developed for the construction of cyclopropapyrrolidinones. The 'syn' isomer of N-DAC can be converted to the 'anti' isomer by simple silica gel treatment. Regioselective cleavage of each of the cyclopropane bonds of these two acceptor substituted N-DACs led to a diverse array of azacycles. 相似文献
189.
A set of three static fluid spheres once derived by Matese and Whitman (in Phys. Rev. D 22:1270, 1980) are charged by means of a particular electric intensity to obtain compact objects like white dwarfs, quark stars and neutron
stars etc. The charged objects so obtain and their neutral counterparts are analysed on astrophysical grounds. This revealed
that two of the charged spheres and one of the neutral seed solutions are well behaved. The corresponding red shift and adiabatic
index together with other physical entities like pressure, density and velocity of sound through the star models are studied
systematically. 相似文献
190.
S Mogurampelly S Panigrahi D Bhattacharyya AK Sood PK Maiti 《The Journal of chemical physics》2012,137(5):054903
Using all atom molecular dynamics simulations, we report spontaneous unzipping and strong binding of small interfering RNA (siRNA) on graphene. Our dispersion corrected density functional theory based calculations suggest that nucleosides of RNA have stronger attractive interactions with graphene as compared to DNA residues. These stronger interactions force the double stranded siRNA to spontaneously unzip and bind to the graphene surface. Unzipping always nucleates at one end of the siRNA and propagates to the other end after few base-pairs get unzipped. While both the ends get unzipped, the middle part remains in double stranded form because of torsional constraint. Unzipping probability distributions fitted to single exponential function give unzipping time (τ) of the order of few nanoseconds which decrease exponentially with temperature. From the temperature variation of unzipping time we estimate the energy barrier to unzipping. 相似文献