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11.
Giovanni Petrillo Cinzia Tavani Lara Bianchi Alice Benzi Maria Maddalena Cavalluzzi Lara Salvagno Laura Quintieri Annalisa De Palma Leonardo Caputo Antonio Rosato Giovanni Lentini 《Molecules (Basel, Switzerland)》2021,26(13)
Twenty-two novel, variously substituted nitroazetidines were designed as both sulfonamide and urethane vinylogs possibly endowed with antimicrobial activity. The compounds under study were obtained following a general procedure recently developed, starting from 4-nitropentadienoates deriving from a common β-nitrothiophenic precursor. While being devoid of any activity against fungi and Gram-negative bacteria, most of the title compounds performed as potent antibacterial agents on Gram-positive bacteria (E. faecalis and three strains of S. aureus), with the most potent congener being the 1-(4-chlorobenzyl)-3-nitro-4-(p-tolyl)azetidine 22, which displayed potency close to that of norfloxacin, the reference antibiotic (minimum inhibitory concentration values 4 and 1–2 μg/mL, respectively). Since 22 combines a relatively efficient activity against Gram-positive bacteria and a cytotoxicity on eucharyotic cells only at 4-times higher concentrations (inhibiting concentration on 50% of the cultured eukaryotic cells: 36 ± 10 μM, MIC: 8.6 μM), it may be considered as a promising hit compound for the development of a new series of antibacterials selectively active on Gram-positive pathogens. The relatively concise synthetic route described herein, based on widely available starting materials, could feed further structure–activity relationship studies, thus allowing for the fine investigation and optimization of the toxico-pharmacological profile. 相似文献
12.
Drag reduction by polymers in wall turbulence is bounded from above by a universal maximal drag reduction (MDR) velocity profile that is a log law, estimated experimentally by Virk as V+(y+) approximately 11.7logy+ - 17. Here V+(y+) and y+ are the mean streamwise velocity and the distance from the wall in "wall" units. In this Letter we propose that this MDR profile is an edge solution of the Navier-Stokes equations (with an effective viscosity profile) beyond which no turbulent solutions exist. This insight rationalizes the universality of the MDR and provides a maximum principle which allows an ab initio calculation of the parameters in this law without any viscoelastic experimental input. 相似文献
13.
We present the results of numerical experiments aimed at comparing two recently proposed sparse approximate inverse preconditioners
from the point of view of robustness, cost, and effectiveness. Results for a standard ILU preconditioner are also included.
The numerical experiments were carried out on a Cray C98 vector processor.
This work was partially supported by the GA AS CR under grant 2030706 and by the grant GA CR 205/96/0921. 相似文献
14.
Manfredotti C. Fizzotti F. Vittone E. Polesello P. Rizzi N. Cantelli V. Bruno P. Volpe P. Castiglioni M. Benzi P. Pallavidino P. Chiari G. Borghi A. 《Il Nuovo Cimento D》1994,16(10):1729-1734
Il Nuovo Cimento D - Metal-Organic Deposition (MOD) technique has been used for the first time, in the spray version, to obtain thin and thick films of BSCCO on substrates like MgO and Ag and, in... 相似文献
15.
Summary This paper concerns the Hamiltonian formulation of non-linear waves in a closed basin. Using the spectral representation of
the functional Hamiltonian, we transform our problem in continuous mechanics into a problem in classical mechanics. Truncating
the new Hamiltonian at the first order in the slope of the surface elevation and considering only two degrees of freedom,
we study the statistical behaviour of this system. We find that under a critical energy the motion in phase space appears
to be ordered, whereas above the critical value we have a random behaviour.
Research partially sponsored by C.N.R. ≪Progetti Finalizzati Oceanografia≫ 相似文献
Riassunto Questo lavoro tratta il problema delle onde non lineari in un bacino chiuso nella sua formulazine hamiltoniana. Usando la rappresentazione spettrale dell’hamiltoniana, si trasforma il problema di meccanica dei continui in problema di meccanica classica. Troncando la nuova hamiltoniana al primo ordine nello sviluppo in pendenza della superficie e considerando solo due gradi di libertà, si studia il comportamento statistico del sistema. Si trova che sotto una certa energia critica il moto nello spazio delle fasi è ordinato, mentre sopra il valore critico si ha un comportamento stocastico.
Резюме В этой статье рассматривается гамильтонова формулировка нелинейных волн в замкнутом резервуаре. Используя спектральное представление рункции Гамильтона, мы преобразуем нашу проблему в механике сплошных сред в проблему классической механики. Обрезая новый Гамильтониан на первом порядке по наклону поверхности возвышения и рассматривая только две степени свободы, мы исследем статическое поведение этой системы. Мы находим, что ниже критической энергии движение в фазовом пространстве оказывается упорядоченным, тогда как выце критической энергии мы имеем случайное поведение.
Research partially sponsored by C.N.R. ≪Progetti Finalizzati Oceanografia≫ 相似文献
16.
17.
Benzi R Biferale L Fisher RT Kadanoff LP Lamb DQ Toschi F 《Physical review letters》2008,100(23):234503
We perform high-resolution numerical simulations of homogenous and isotropic compressible turbulence, with an average 3D Mach number close to 0.3. We study the statistical properties of intermittency for velocity, density, and entropy. For the velocity field, which is the only quantity that can be compared to the isotropic incompressible case, we find no statistical differences in its behavior in the inertial range due either to the slight compressibility or to the different dissipative mechanism. For the density field, we find evidence of "frontlike" structures, although no shocks are produced by the simulation. 相似文献
18.
In this paper we discuss some theoretical aspects concerning the scaling laws of the Nusselt number versus the Rayleigh number in a Rayleigh–Bénard cell. We present a new set of numerical simulations and compare our findings against the predictions of existing models. We then propose a new theory which relies on the hypothesis of Bolgiano scaling. Our approach generalizes the one proposed by Kadanoff, Libchaber, and coworkers and solves some of the inconsistencies raised in the recent literature. 相似文献
19.
20.
Roberto Benzi Giovanni Jona-Lasinio Alfonso Sutera 《Journal of statistical physics》1989,55(3-4):505-522
We analyze several aspects of a reaction-diffusion equation in two space dimensions with cubic nonlinearity, stochastically perturbed by white noise in time and in space. This equation needs renormalization, and physical implications of this circumstance are discussed. In particular, for sufficiently large coupling constant the effective potential becomes a double well and rare transitions from one minimum to the other are possible. These, however, are revealed only by large-scale fluctuations which exhibit a bimodal distribution. Fluctuations below a critical scale have unimodal distribution and do not see the double well. This phenomenon is connected with the singular character of local fluctuations in two or more space dimensions. The theoretical results are confirmed by numerical simulations. The possible physical relevance of our results is illustrated in connection with the analysis of certain observations of atmospheric fields. 相似文献