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81.
Sekharan S Katayama K Kandori H Morokuma K 《Journal of the American Chemical Society》2012,134(25):10706-10712
Eyes gather information, and color forms an extremely important component of the information, more so in the case of animals to forage and navigate within their immediate environment. By using the ONIOM (QM/MM) (ONIOM = our own N-layer integrated molecular orbital plus molecular mechanics) method, we report a comprehensive theoretical analysis of the structure and molecular mechanism of spectral tuning of monkey red- and green-sensitive visual pigments. We show that interaction of retinal with three hydroxyl-bearing amino acids near the β-ionone ring part of the retinal in opsin, A164S, F261Y, and A269T, increases the electron delocalization, decreases the bond length alternation, and leads to variation in the wavelength of maximal absorbance of the retinal in the red- and green-sensitive visual pigments. On the basis of the analysis, we propose the "OH-site" rule for seeing red and green. This rule is also shown to account for the spectral shifts obtained from hydroxyl-bearing amino acids near the Schiff base in different visual pigments: at site 292 (A292S, A292Y, and A292T) in bovine and at site 111 (Y111) in squid opsins. Therefore, the OH-site rule is shown to be site-specific and not pigment-specific and thus can be used for tracking spectral shifts in any visual pigment. 相似文献
82.
Single crystals of the nonlinear material γ-glycine have been grown in the presence of lithium nitrate by slow-evaporation method. Structural characterization of the grown crystals was carried out by powder and single crystal X-ray diffraction (XRD) methods and it is observed that the samples crystallize in hexagonal system with non-centrosymmetric space groups. The modes of vibrations of different molecular groups present in glycine have been identified by spectral analyses. UV–visible transmittance study was performed to analyze optical transparency of γ-glycine crystals and found that the crystal was transparent in the entire visible-NIR region. Second harmonic generation (SHG) conversion efficiency has been estimated as 62 mV and the output power by the crystal was 1.72 times that of potassium dihydrogen phosphate (KDP) crystal. The thermal stability and decomposition of the sample have been studied by thermal analysis and it is observed that the γ-glycine crystal have good thermal stability. 相似文献
83.
The authors revisit the notion of a row monotone matrix and obtain new results that establish relationships with certain specific types of splittings of the matrix concerned. Among other results, analogous results for range monotone matrices are also obtained. 相似文献
84.
P. Sivakumar S. Meenakshi R. V. Subba Rao 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(2):603-608
A new process for the partitioning of plutonium and uranium during the reprocessing of spent fuel discharged from fast reactor
was optimised using hydroxyurea (HU) as a reductant. Stoichiometric ratio of HU required for the reduction of Pu(IV) was studied.
The effect of concentration of uranium, plutonium and acidity on the distribution ratio (Kd) of Pu in the presence of HU was
studied. The effect of HU in further purification of Pu such as solvent extraction and precipitation of plutonium as oxalate
was also studied. The results of the study indicate that Pu and U can be separated from each other using HU as reductant. 相似文献
85.
P. Sivakumar S. Meenakshi R. V. Subba Rao 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(3):763-767
Spent fuel discharged from Fast Breeder Test Reactor (FBTR) in Kalpakkam is being reprocessed by modified plutonium uranium
reduction extraction (PUREX) process using 30% TBP (tributylphosphate) as extractant in the presence of heavy normal paraffin
(HNP) as diluent. Partitioning of uranium (U) and plutonium (Pu) is carried out using oxalate precipitation method. Uranium
oxide product obtained by this method contains appreciable amount of plutonium which has to be recovered. Recovery of plutonium
from this uranium oxide product is carried out by reducing Pu to inextractable Pu(III) using hydroxyurea (HU) and then uranium
is extracted into 30% TBP. A small amount of Pu which is extracted in the organic phase is stripped back to aqueous phase
by scrubbing with scrubbing agent containing 0.1 M HU in 4 M nitric acid. Similarly U and Pu are co-extracted into 30% TBP
and then Pu is removed by scrubbing with 0.1 M HU in 4 M nitric acid. Further decontamination from Pu is obtained in the stripping
stages. By this method Pu contamination in the uranium oxide is brought from 7300 ppm to 0.4–3 ppm (wt/wt). This uranium product
obtained can be handled on table top. 相似文献
86.
We develop a stochastic formulation of cosmology in the early universe, after considering the scatter in the redshift-apparent
magnitude diagram in the early epochs as an observational evidence for the non-deterministic evolution of early universe.
We consider the stochastic evolution of density parameter in the early universe after the inflationary phase qualitatively,
under the assumption of fluctuating w factor in the equation of state, in the Fokker-Planck formalism. Since the scale factor for the universe depends on the energy
density, from the coupled Friedmann equations we calculated the two variable probability distribution function assuming a
flat space geometry. 相似文献
87.
R. V. Krishnakumar M. Subha Nandhini S. Natarajan K. Sivakumar Babu Varghese 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(10):1149-1150
The glycine molecule in the title compound, Na(NO3)·C2H5NO2, exists in the zwitterionic form. The Na atom exhibits eightfold coordination and the polyhedron may be visualized as a distorted hexagonal bipyramid. The glycine molecules are linked through head-to-tail hydrogen bonds and are found `sandwiched' between the Na(NO3) layers. 相似文献
88.
89.
A primitive-variable Riemann method for solution of the shallow water equations with wetting and drying 总被引:1,自引:0,他引:1
P. Sivakumar D.G. Hyams L.K. Taylor W.R. Briley 《Journal of computational physics》2009,228(19):7452-7472
A Riemann flux that uses primitive variables rather than conserved variables is developed for the shallow water equations with nonuniform bathymetry. This primitive-variable flux is both conservative and well behaved at zero depth. The unstructured finite-volume discretization used is suitable for highly nonuniform grids that provide resolution of complex geometries and localized flow structures. A source-term discretization is derived for nonuniform bottom that balances the discrete flux integral both for still water and in dry regions. This primitive-variable formulation is uniformly valid in wet and dry regions with embedded wetting and drying fronts. A fully nonlinear implicit scheme and both nonlinear and time-linearized explicit schemes are developed for the time integration. The implicit scheme is solved by a parallel Newton-iterative algorithm with numerically computed flux Jacobians. A concise treatment of characteristic-variable boundary conditions with source terms is also given. Computed results obtained for the one-dimensional dam break on wet and dry beds and for normal-mode oscillations in a circular parabolic basin are in very close agreement with the analytical solutions. Other results for a forced breaking wave with friction interacting with a sloped bottom demonstrate a complex wave motion with wetting, drying and multiple interacting wave fronts. Finally, a highly nonuniform, coastline-conforming unstructured grid is used to demonstrate an unsteady simulation that models an artificial coastal flooding due to a forced wave entering the Gulf of Mexico. 相似文献
90.
Cssio Luiz Coutinho Almeida-da-Silva Nallusamy Sivakumar Homer Asadi Anna Chang-Chien M. Walid Qoronfleh David M. Ojcius Musthafa Mohamed Essa 《Molecules (Basel, Switzerland)》2022,27(13)
Boswellia trees, found throughout the Middle East and parts of Africa and Asia, are the source of frankincense oil. Since antiquity, frankincense has been traded as a precious commodity, but it has also been used for the treatment of chronic disease, inflammation, oral health, and microbial infection. More recently, the bioactive components of Boswellia trees have been identified and characterized for their effects on cancer, microbial infection (especially infection by oral pathogens), and inflammation. Most studies have focused on cell lines, but more recent research has also investigated effects in animal models of disease. As natural products are considered to be safer than synthetic drugs, there is growing interest in further developing the use of substances such as frankincense oil for therapeutic treatment. 相似文献