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排序方式: 共有919条查询结果,搜索用时 15 毫秒
901.
Lucas R. Salviano Heibbe C.B. de Oliveira Luciano Ribeiro Ricardo Gargano 《Physica A》2010,389(17):3604-3612
In this work, we introduce a new analytical form based on the q-exponential function to build three-dimensional reactive surfaces. The quality of this new function is tested by fitting the ab initio potential energy surface (PES) to the ground state Na+HF reaction. The thermal rate constant and reactive probabilities were determined considering this new PES. The obtained properties agree with those found for other PES available in literature. 相似文献
902.
An axiomatization of the so‐called Teleparallel Equivalent to General Relativity is presented. A set of formal and semantic postulates are elaborated from where the physical meaning of various key concepts of the theory are clarified. These concepts include those of inertia, Lorentz and diffeomorphism invariance, and reference frame. It is shown that Teleparallel Gravity admits a wider representation of space‐time than General Relativity, allowing to define properties of the gravitational field such as energy and momentum that are usually considered problematic. In this sense, although the dynamical equations of both theories are equivalent, their inequivalence from a physical point of view is demonstrated. Finally, the axiomatic formulation is used to compare Teleparallel Gravity with other theories of gravity based on absolute parallelism such as non‐local and f(T) gravity. 相似文献
903.
The masonry assemblage composed of two piers connected by a spandrel can be considered a repetitive unit in large masonry walls with openings, occurring in masonry buildings. In this work, the collapse load of the above-mentioned masonry assemblage is predicted by solving a system of nonlinear equations, where the normal force in the spandrel is a root of an equilibrium equation of fourth degree. Piers and spandrel are assumed rigid and nonlinearity (crushing and no tensile strength) is concentrated at the pier-foundation and pier–spandrel interfaces. The model also takes into account the effect of a timber lintel supporting the spandrel and anchored into the two adjacent piers. This approach valid for assemblages with one spandrel can be extended for the evaluation of the collapse load of structures composed of N piers connected by N ? 1 spandrels. The system of nonlinear equations is easily solved with an iterative method and the collapse load provided by the solution agrees well with the experimental result. 相似文献
904.
Rodrigo A. Lemos Silva Daniel F. Scalabrini Machado Núbia Maria Nunes Rodrigues Heibbe C. B. de Oliveira Luciano Ribeiro Demtrio A. da Silva Filho 《Molecules (Basel, Switzerland)》2022,27(9)
In this work, a theoretical investigation of the effects caused by the doping of C20 with silicon (Si) atom as well as the adsorption of CO, CO2 and N2 gases to C20 and C19Si fullerenes was carried out. In concordance with previous studies, it was found that the choice of the doping site can control the structural, electronic, and energetic characteristics of the C19Si system. The ability of C20 and C19Si to adsorb CO, CO2 and N2 gas molecules was evaluated. In order to modulate the process of adsorption of these chemical species to C19Si, an externally oriented electric field was included in the theoretical calculations. It was observed that C19Si is highly selective with respect to CO adsorption. Upon the increase of the electric field intensity the adsorption energy was magnified correspondingly and that the interaction between CO and C19Si changes in nature from a physical adsorption to a partial covalent character interaction. 相似文献
905.
906.
Luciano Telesca Anh Tuan Thai Michele Lovallo Dinh Trong Cao 《Entropy (Basel, Switzerland)》2022,24(11)
In this study, the visibility graph analysis of seismicity triggered by Song Tranh 2 hydropower (Vietnam) is performed. The relationship between the seismic (the Gutenberg–Richter b-value) and topological (the k–M slope) parameters of seismicity is analysed. Our findings indicate that the relationship between the Gutenberg–Richter b-value and the k–M slope of the investigated seismicity is in agreement with that characterising the tectonic seismicity. The results obtained from analysing the reservoir-triggered seismicity of Song Tranh 2 area could contribute to better characterisation of the relationship between the seismological and topological parameters of seismicity, strengthening the universal character of the relationship between the b-value and the k–M slope. 相似文献
907.
Emmanoel V. Costa Csar A. S. de Souza Alexandre F. C. Galvo Valdenizia R. Silva Luciano de S. Santos Rosane B. Dias Clarissa A. Gurgel Rocha Milena B. P. Soares Felipe M. A. da Silva Hector H. F. Koolen Daniel P. Bezerra 《Molecules (Basel, Switzerland)》2022,27(17)
Duguetia pycnastera Sandwith (Annonaceae) is a tropical tree that can be found in the Guyanas, Bolivia, Venezuela, and Brazil. In Brazil, it is popularly known as “ata”, “envira”, “envira-preta”, and “envira-surucucu”. In the present work, we investigated the in vitro and in vivo HepG2 cell growth inhibition capacity of D. pycnastera leaf essential oil (EO). The chemical composition of the EO was determined by GC–MS and GC–FID analyses. The alamar blue assay was used to examine the in vitro cytotoxicity of EO in cancer cell lines and non-cancerous cells. In EO-treated HepG2 cells, DNA fragmentation was measured by flow cytometry. The in vivo antitumor activity of the EO was assessed in C.B-17 SCID mice xenografted with HepG2 cells treated with the EO at a dosage of 40 mg/kg. Chemical composition analysis displayed the sesquiterpenes α-gurjunene (26.83%), bicyclogermacrene (24.90%), germacrene D (15.35%), and spathulenol (12.97%) as the main EO constituents. The EO exhibited cytotoxicity, with IC50 values ranging from 3.28 to 39.39 μg/mL in the cancer cell lines SCC4 and CAL27, respectively. The cytotoxic activity of the EO in non-cancerous cells revealed IC50 values of 16.57, 21.28, and >50 μg/mL for MRC-5, PBMC, and BJ cells, respectively. An increase of the fragmented DNA content was observed in EO-treated HepG2 cells. In vivo, EO displayed tumor mass inhibition activity by 47.76%. These findings imply that D. pycnastera leaf EO may have anti-liver cancer properties. 相似文献
908.
Rosa Sparaco Antonia Scognamiglio Angela Corvino Giuseppe Caliendo Ferdinando Fiorino Elisa Magli Elisa Perissutti Vincenzo Santagada Beatrice Severino Paolo Luciano Marcello Casertano Anna Aiello Gilberto De Nucci Francesco Frecentese 《Molecules (Basel, Switzerland)》2023,28(1)
We recently identified 6-nitrodopamine and other nitro-catecholamines (6-nitrodopa, 6-nitroadrenaline), indicating that the endothelium has the ability to nitrate the classical catecholamines (dopamine, noradrenaline, and adrenaline). In order to investigate whether drugs could be subject to the same nitration process, we synthesized 4-nitro- and 7-nitropropranolol as probes to evaluate the possible nitration of the propranolol by the endothelium. The separation of the enantiomers in very high yields and excellent enantiopurity was achieved by chiral HPLC. Finally, we used Riguera’s method to determine the absolute configuration of the enantiomers, through double derivatization with MPA and NMR studies. 相似文献
909.
Rui Ba Michele Lovallo Weiguo Song Hui Zhang Luciano Telesca 《Entropy (Basel, Switzerland)》2022,24(12)
The MODIS Aqua and Terra Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) time series acquired during nearly two decades (2000 to 2020) covering the area burned by the Camp Fire (California) in 2018 is investigated in this study by using the multifractal detrended fluctuation analysis in relation to the recovery process of vegetation after fire. In 2008, the same area was partially burned by two wildfires, the BTU Lightning Complex Fire and the Humboldt Fire. Our results indicate that all vegetation index time series are featured by six- and twelve-month modulating periodicities, with a larger spectral content at longer periods for two-fire-affected sites. Furthermore, two fires cause an increase of the persistence of the NDVI and EVI time series and an increase of the complexity, suggesting that the recovery process of vegetation dynamics of fire-affected sites is characterized by positive feedback mechanisms, driving the growth-generating phenomena, which become even more effective in those sites affected by two fires. 相似文献
910.