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21.
Theoretical investigations of atomic charges, conformers, frontier molecular orbitals, molecular geometries, thermodynamic
properties, hyperpolarizabilities and harmonic vibrational frequencies of 6-methyluracil (6MU) have been carried out using
ab initio Hartree-Fock (HF), density functional theory (DFT) and second order M?ller-Plesset (MP2) methods. All calculations were performed
using the GAMESS-US program package with the basis sets 6-31G(d,p) and 6-311G(d,p). FT-IR and Raman spectra of 6MU were recorded
in the regions 50–4000 cm−1 and 60–4000 cm−1 respectively. Optimized geometries were obtained using the global optimization procedure. The calculated structural parameters
for two conformers of 6MU have been compared with experimentally observed values. The energy barrier (ΔE=ELUMO-EHOMO) between
the HOMO and LUMO is predicted on the basis of theoretical calculations. The simulated TD-DFT spectrum has been compared with
experimental electronic spectrum for 6MU. The calculated potential energy distribution (PED) values have been utilized to
perform vibrational assignment of the infrared and Raman spectra. 相似文献
22.
A phase conjugation algorithm for localizing the spatial support of an extended radiating current source from boundary measurements of the electric field over a finite set of frequencies is presented. An imaging function using a full frequency bandwidth is established and analyzed. It is subsequently adopted to the case of finite frequency measurements. Finally, the algorithm is blended with l1-regularization in order to deal with the artifacts associated with finite frequency data. 相似文献
23.
Nisha Preschilla A. S. Abdul Rasheed Swayajith Sahadevan Amit Biswas Jayesh R. Bellare Subarna Shyamroy 《Journal of Polymer Science.Polymer Physics》2010,48(16):1786-1794
Effect of very small quantities of organically modified layered silicate clay on the nucleation of polypropylene (PP), as an additive at ppm levels dosage was investigated, in combination with two of the most commercially exploited organic nucleating agents, one of which is a cyclic aromatic phosphinate salt and the other is bis(3,4‐dimethylbenzylidene) sorbitol, each representing a separate class of nucleating molecules by itself. Substitution of a considerable fraction of either of these organic nucleating agents with organically modified inorganic nanoclay was seen to result in a unique synergy between the two in nucleating PP. Polarized light microscopy studies of these synergistic formulations with organoclay to nucleating agent ratios of 1:1 and 1:3 totaling 0.2 weight percent in PP showed significant reduction in spherulite size from that of non‐nucleated PP, and compared with the samples containing exclusive organic nucleating agent at similar loading. Differential scanning calorimetric studies provided evidence and insight into such synergistic behavior. Crystallization and supercooling temperatures for the synergistic formulations were comparable for those formulations containing only organic nucleating agents, indicating comparable nucleation efficiency, whereas organoclay alone, although showing some extent of nucleation, was clearly poorer in efficiency. Wide and small angle X‐ray scattering studies further explained these observations. An increase in the gamma polytype fraction was seen in samples that contained both organoclay and nucleating agent, pointing to the role of organoclay as a gamma nucleator. Organoclay was found to be completely exfoliated in these synergistic formulations and was seen as well‐dispersed, single platelets in the PP matrix. A hybrid network consisting of exfoliated organoclay platelets and organic nucleating agent molecules was proposed, which is more stable and stiffer than the network formed by nucleating agent alone. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1786–1794, 2010 相似文献
24.
M. Yamaga Y. Gao F. Rasheed K. P. O'Donnell B. Henderson B. Cockayne 《Applied physics. B, Lasers and optics》1990,51(5):329-335
The fluorescence spectra of Ti3+ in Y3Al5O12 (YAG), Al2O3 (sapphire), YAlO3 (YAP) observed at 10 K are composed of zero-phonon lines accompanied by the broad vibronic sidebands. The temperature dependence of the fluorescence lifetime and of the total intensity of the broadband measured in YAG and Al2O3 indicate that the radiative decay times from the excited states are nearly constant in the range 10–300 K. This demonstrates that the broadband radiative emissions in Ti3+:YAG and Ti3+:Al2O3 are due to magnetic dipole transitions or to electric dipole transitions induced by static odd-parity distortion, respectively. The decrease of the fluorescence lifetime with increasing temperature in Ti3+:YAG and Ti3+:Al2O3 is due to non-radiative decay from the excited state which occurs through phonon-assisted tunnelling between the excited and ground states. The radiative decay of Ti3+:YAP is enhanced with increasing temperature, indicating that radiative decay rate contains a term associated with odd-parity phonons. Nevertheless, a non-radiative decay rate of 3.6 × 104 s–1 observed in the temperature range 10–300 K is due to excited state absorption, which depopulates the excited state and quenches the fluorescence at the laser wavelength. 相似文献
25.
Madhava Golla Subba Rao Devineni Rasheed Syed Bhanu Kiran Rayalacheru Rajasekhar Maram 《Phosphorus, sulfur, and silicon and the related elements》2017,192(7):794-798
The synthesis of a new series of P-heterocyclic compounds, substituted 2-aminomethyl-2-oxo-2λ5-perhydro-[1,3,2]oxazaphospholo[3,4-a]pyridine derivatives 8(a-j), was accomplished. A key intermediate, 2-(chloromethyl)-2-oxo-2λ5-perhydro-[1,3,2]oxazaphospholo[3,4-a]pyridine (6) was primarily synthesized by the condensation of (±)-2-piperidinemethanol (4) and chloromethylphosphonic dichloride (5); subsequently, it was treated with various heterocyclic amines/benzylamines/aminoacid esters, 7(a-j) to obtain the desired products. The structures of the newly synthesized compounds were elucidated by 1H, 13C, and 31P NMR spectroscopy, mass spectra and elemental analyses. The biological potency of title products was investigated by screening in vitro antimicrobial activity. The bio-screening data revealed that most of the synthesized derivatives showed potent growth of inhibition against fungi while compared with bacteria. Particularly, compounds 8c and 8i against bacterial strains, and 8a and 8f against fungi exhibited promising activity. 相似文献
26.
Syed Rasheed Devineni Subba Rao Chennamsettty Subramanyam Shaik Thaslim Basha 《合成通讯》2014,44(20):2988-2998
An expeditious, simple, and green method was developed for the synthesis of privileged aryl/heterocyclicphosphonates, 8(a–c) to 13(a–c) through Michaelis–Arbuzov reaction of aryl/heterocyclic halides (Br), 1–6, and trialkylphosphites, 7(a–c), in room-temperature ionic liquid [bbim]Br using heterogeneous Lewis catalyst, nano-silica-supported boron trifluoride (BF3-SiO2). The advantages of this protocol are simplicity, good yield of the products, less reaction time (20–38 min), mild reaction conditions, easy workup, and reusability of the catalyst and ionic liquid. It is demonstrated that nano-BF3-SiO2 is a recoverable and easy accessible catalyst for the formation of C(sp2)-P bond in an ionic liquid. 相似文献
27.
Abid OU Nawaz M Ibad MF Khera RA Iaroshenko V Langer P 《Organic & biomolecular chemistry》2011,9(7):2185-2191
Aryl-substituted pyridines and pyrimidines were prepared by [4+2] cycloadditions of alkynyl-substituted pyridines and -pyrimidines with electron-rich dienes. The reactions proceed by formation of a bridged cycloadduct and subsequent thermal extrusion of ethylene. The pyridine moiety plays a crucial role for the success of the reaction. 相似文献
28.
Caragisides A–C ( 1 – 3 , resp.), three new isoflavone glucosides, were isolated from the BuOH sub‐fraction of the EtOH extract of the whole plant of Caragana conferta, along with ononoside ( 4 ), reported for the first time from this species. The structures of the new compounds were elucidated by spectroscopic techniques including MS and 2D‐NMR spectroscopy. Compounds 1 – 3 showed significant inhibition of platelet aggregation. 相似文献
29.
Syed Ashfaq Nabi Rifaqat AliKhan Rao Ahsan Rasheed Siddiqui 《Fresenius' Journal of Analytical Chemistry》1982,311(5):503-506
Summary Stannic selenoarsenate samples have been prepared by adding a mixture which is 0.05 M in sodium arsenate and 0.05 M in sodium selenite to a 0.05 M solution of stannic chloride in different volume ratios at pH 1. Its ion-exchange properties, pH titration curves and X-ray pattern were studied. Adsorption behaviour of 24 metal ions in different solvent systems has been examined. The analytical importance of this material has been demonstrated by achieving the following binary and ternary separations: Hg2+-Cd2+, Co2+-Fe3+, Cu2+-Fe3+, Hg2+-Zn2+-Al3+, Hg2+-Cu2+-Al3+, Hg2+-Ni2+-Al3+, Hg2+-Zn2+-Fe3+ and Hg2+-Ni2+-Fe3+. A comparison of the ion-exchange properties of this material has also been made with some other tin(IV) based ion-exchangers.
Synthese, Ionenaustauscher-Eigenschaften und analytische Anwendungen von Zinn-Selenoarsenat: Vergleich mit anderen Heteropolysalzen
Zusammenfassung Zinn-Selenoarsenat wurde durch Mischen von 0,05 M Natriumarsenat-, 0,05 M Natriumselenitund 0,05 M Zinn(IV)-Chlorid-Lösungen bei pH 1 in verschiedenen Verhältnissen hergestellt. Die Ionenaustauscher-Eigenschaften, pH-Titrationskurven sowie Röntgendiagramme wurden untersucht und das Adsorptionsverhalten von 24 Metallionen in verschiedenen Lösungsmittelsystemen geprüft. Die analytische Verwertbarkeit wurde an Hand der folgenden Trennungsmöglichkeiten gezeigt: Hg2+-Cd2+, Co2+-Fe3+, Cu2+-Fe3+, Hg2+-Zn2+-Al3+, Hg2+-Cu2+-Al3+, Hg2+-Ni2+-Al3+, Hg2+-Zn2+-Fe3+, Hg2+-Ni2+-Fe3+. Vergleiche mit anderen Ionenaustauschern auf Zinn(IV)-Basis werden ebenfalls beschrieben.相似文献
30.
Selective extraction of metals from mixed oxide matrixes using choline-based ionic liquids 总被引:2,自引:0,他引:2
The solubility of a range of metal oxides in a eutectic mixture of urea/choline chloride is quantified, and it is shown that the dissolved metals can be reclaimed from a mixed metal oxide matrix using electrodeposition. 相似文献