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551.
Ayush K. Narsaria Julian D. Ruijter Trevor A. Hamlin Andreas W. Ehlers Célia Fonseca Guerra Koop Lammertsma F. Matthias Bickelhaupt 《Journal of computational chemistry》2020,41(15):1448-1455
We have evaluated the performance of various density functionals, covering generalized gradient approximation (GGA), global hybrid (GH) and range-separated hybrid (RSH), using time dependent density functional theory (TDDFT) for computing vertical excitation energies against experimental absorption maximum (λmax) for a set of 10 different core-substituted naphthalene diimides (cNDI) recorded in dichloromethane. The computed excitation in case of GH PBE0 is most accurate while the trend is most systematic with RSH LCY-BLYP compared to λmax. We highlight the importance of including solvent effects for optimal agreement with the λmax. Increasing the basis set size from TZ2P to QZ4P has a negligible influence on the computed excitation energies. Notably, RSH CAMY-B3LYP gave the least error for charge-transfer excitation. The poorest agreement with λmax is obtained with semi-local GGA functionals. Use of the optimally-tuned RSH LCY-BLYP* is not recommended because of the high computational cost and marginal improvement in results. 相似文献
552.
Guerra M Thode AM Blackwell SB Michael Macrander A 《The Journal of the Acoustical Society of America》2011,130(5):3046-3058
Shallow-water airgun survey activities off the North Slope of Alaska generate impulsive sounds that are the focus of much regulatory attention. Reverberation from repetitive airgun shots, however, can also increase background noise levels, which can decrease the detection range of nearby passive acoustic monitoring (PAM) systems. Typical acoustic metrics for impulsive signals provide no quantitative information about reverberation or its relative effect on the ambient acoustic environment. Here, two conservative metrics are defined for quantifying reverberation: a minimum level metric measures reverberation levels that exist between airgun pulse arrivals, while a reverberation metric estimates the relative magnitude of reverberation vs expected ambient levels in the hypothetical absence of airgun activity, using satellite-measured wind data. The metrics are applied to acoustic data measured by autonomous recorders in the Alaskan Beaufort Sea in 2008 and demonstrate how seismic surveys can increase the background noise over natural ambient levels by 30-45 dB within 1 km of the activity, by 10-25 dB within 15 km of the activity, and by a few dB at 128 km range. These results suggest that shallow-water reverberation would reduce the performance of nearby PAM systems when monitoring for marine mammals within a few kilometers of shallow-water seismic surveys. 相似文献
553.
Sousa A Barros e Silva AE Cuadrado A Loarce Y Alves MV Guerra M 《Micron (Oxford, England : 1993)》2011,42(6):625-631
Secondary constrictions or 45S rDNA sites are commonly reported to be located mainly in the terminal regions of the chromosomes. This distribution has been assumed to be related to the existence of a "chromosome field" lying between the centromere and the telomere, an area in which certain cytogenetic events may predominantly occur. If this hypothesis is true this distribution should not be observed in holokinetic chromosomes, as they do not have a localized centromere. In order to evaluate this hypothesis, a comparative study was made of the distributions of 5S and 45S rDNA sites using fluorescence in situ hybridization in representatives of the genera Eleocharis, Diplacrum, Fimbristylis, Kyllinga and Rhynchospora, all of which belong to the family Cyperaceae. The numbers of sites per diploid chromosome complement varied from 2 to ~10 for 5S rDNA, and from 2 to ~45 for 45S rDNA. All of the 11 species analyzed had terminally located 45S rDNA sites on the chromosomes whereas the 5S rDNA sites also generally had terminal distributions, except for the Rhynchospora species, where their position was almost always interstitial. These results, together with other previously published data, suggest that the variation in the number and position of the rDNA sites in species with holokinetic chromosomes is non-random and similar to that reported for species with monocentric chromosomes. Therefore, the predominant terminal position of the 45S rDNA sites does not appear to be influenced by the centromere-telomere polarization as suggested by the "chromosome field" hypothesis. Additionally, the hybridization of 5S and 45S rDNA sites provides interesting markers to distinguish several chromosomes on the rather symmetrical karyotypes of Cyperaceae. 相似文献
554.
Elias Brito Aliliane Freitas Thiago Silva Thiago Guerra Sergio Azevedo 《The European Physical Journal B - Condensed Matter and Complex Systems》2015,88(6):153
We have applied first-principles calculations, based on the density functional theory, toinvestigate the stability and electronic properties of double-walled carbon nanocones,60°60°, 120°120° and 60°120° with different rotation anglesbetween the walls. We have shown that the most favorable double-walled nanocone studiedhere is that of angles of 60°60°, with rotation angle of 36° and distance between apexes of 4.22 Å.We have found that, the interaction between the walls of rotated double-walled nanoconesintroduce geometric distortion in gap states, such as in Fermi level. These results shouldhave consequences on the field emission properties of double-walled carbon nanocones.Additionally, we also investigated the spin polarization of such structures, and we havefound unpaired electrons, which induces a total spin from 1 and 1/2 for 60°60° and 60°120° double cones, respectively. 相似文献
555.
Denis Lima Guerra Claudio Airoldi Kaline S. de Sousa 《Applied Surface Science》2008,254(16):5157-5163
Kaolinite-bearing clay samples from Perus, São Paulo state, Brazil, were used for chemical modification process with dimethyl sulfoxide and organofunctionalized with the silyating agent (RO)3Si(CH2)3NH(CH2)2NH2 in the present study. The resulting material and natural kaolinite were subjected adsorpion process with Cu(II) and Zn(II) from aqueous solution at pH 6.0 and controlated temperature of 298 K. The Langmuir adsorption isotherm model has been applied to fit the experimental data. The results showed that the chemical modification process increases the basal spacing of the natural kaolinite from 0.711 to 0.955 nm. The energetic effects caused by Cu(II) and Zn(II) interactions were determined through calorimetric titration at the solid–liquid interface and gave a net thermal effect that enabled the calculation of the exothermic values and the equilibrium constant. 相似文献
556.
557.
Finizia Auriemma Paolo Corradini Gaetano Guerra Michele Vacatello 《Macromolecular theory and simulations》1995,4(1):165-176
The conformational disorder compatible with the highly extended chains found in mesomorphic poly(ethylene terephthalate) has been studied by Monte Carlo calculations on model oligomers confined inside cylindrical tubes. The distribution of torsional angles for such extended chains is characterized by O C C O bonds being always in the trans domain, while the C O C C bonds show an approximately similar probability of being found in trans and gauche states, the probability maxima being centered at 90° and −90° in the latter cases. At variance with the torsional angles of the O C C O and the ester bonds, always very close to 180°, the distributions for all other torsional angles show flat and broad probability maxima, indicating the possibility of substantial deviations from the average value inside each domain. This is also true for the fictitious O C˙˙˙C O bonds across the phenylene rings, for which a nearly trans geometry is preferred in extended conformations. 相似文献
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