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51.
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
52.
Maria Giorgia Cutrufello Italo Ferino Elisabetta Rombi Vincenzo Solinas Gerardo Colón José Antonio Navío 《Reaction Kinetics and Catalysis Letters》2003,79(1):93-99
A ceria-lanthana catalytic system prepared by the sol-gel technique proved to be active in 4-methylpentan-2-ol conversion,
mainly leading to 4-methylpent-1-ene, a monomer for manufacturing polymers of high technological properties. The product distribution
strongly depends on the acid-base features of the catalyst. The catalytic behavior of the samples was examined in the light
of their acid-base properties.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
53.
We study a class of degenerate elliptic second order differential operators acting on some polynomial weighted function spaces on [0,+[. We show that these operators are the generators of C
0-semigroups of positive operators which, in turn, are the transition semigroups associated with right-continuous normal Markov processes with state space [0,+]. Approximation and qualitative properties of both the semigroups and the Markov processes are investigated as well. Most of the results of the paper depend on a representation of the semigroups we give in terms of powers of particular positive operators of discrete type we introduced and studied in a previous paper. 相似文献
54.
This short note is a response to the comment on our recently published paper cited in the title. All points raised by the
author of the comment are discussed. It is shown that one of the remarks, concerning eigenflow solutions in the limiting case
of forced convection, does not have a sound physical basis. In fact, it refers to a circumstance, a fluid with a thermal expansion
coefficient greater than that of a perfect gas, of marginal or no interest in the framework of convection in porous media. 相似文献
55.
56.
In this paper we propose a continuous-time Markov chain to describe the spread of an infective and non-mortal disease into a community numerically limited and subjected to an external infection. We make a numerical simulation that shows tendencies for recurring epidemic outbreaks and for fade-out or extinction of the infection. 相似文献
57.
Elisabetta Brenna Claudio Fuganti Francesco G. Gatti Fabio Parmeggiani 《Tetrahedron: Asymmetry》2009,20(22):2594-2599
A new scaleable synthetic route to the title compounds has been developed. The reaction pathway is based on the α-chymotrypsin-catalysed hydrolysis of the racemic ethyl 2-ethoxy-3-(p-methoxyphenyl)propanoate or of the racemic ethyl 2-methoxy-3-(p-methoxyphenyl)propanoate to give the corresponding resolved (S)-esters with excellent ee. The acids were easily separated from the (S)-esters by a simple acid–base work-up. The overall yields of 1 and 2 were 16% and 17%, respectively. 相似文献
58.
This paper is devoted to the analysis of a one-dimensional model for phase transition phenomena in thermoviscoelastic materials.
The corresponding parabolic-hyperbolic PDE system features a strongly nonlinear internal energy balance equation, governing the evolution of the absolute temperature ϑ, an evolution equation for the phase change parameter χ, including constraints on the phase variable, and a hyperbolic stress-strain relation for the displacement variable u. The main novelty of the model is that the equations for χ and u are coupled in such a way as to take into account the fact that the properties of the viscous and of the elastic parts influence
the phase transition phenomenon in different ways. However, this brings about an elliptic degeneracy in the equation for u which needs to be carefully handled.
First, we prove a global well-posedness result for the related initial-boundary value problem. Secondly, we address the long-time
behavior of the solutions in a simplified situation. We prove that the ω-limit set of the solution trajectories is nonempty, connected and compact in a suitable topology, and that its elements solve
the steady state system associated with the evolution problem.
Dedicated to Jürgen Sprekels on the occasion of his 60th birthday 相似文献
59.
Elisabetta Tornatore Stefania Maria Buccellato Pasquale Vetro 《Rendiconti del Circolo Matematico di Palermo》2006,55(2):223-240
We propose a stochastic disease model where vaccination is included and such that the immunity isn’t permanent. The existence,
uniqueness and positivity of the solution and the stability of disease free equilibrium is studied. The numerical simulation
is done. 相似文献
60.
Anna Luise Grab Dirk Hose Patrick Horn Elisabetta Ada Cavalcanti-Adam Anja Seckinger Martin Müller 《Particle & Particle Systems Characterization》2021,38(3):2000263
In the malignant plasma cell disease multiple myeloma (MM), bone lesions and resulting fractures caused by MM cell (MMC) accumulation represent a major cause of morbidity and mortality. Despite recent advantages in systemic treatment, residual MMCs remain, especially in bone lesions. Therefore an interfacial delivery system for local treatment of MM and induced bone disease based on polyelectrolyte complex nanoparticles (PEC NP) loaded with bone morphogenetic protein 6 (BMP-6) inducing de-novo bone formation and MMC apoptosis is presented herein. BMP-6 loaded PEC NP are fabricated by defined mixing bio-related cationic and anionic polysaccharides and BMP-6 according to molar ratio of BMP-6/PEC-NP of 1/3. BMP-6/PEC NP bound to a model substrate releases 10% BMP-6 sustainably within two weeks as accessed by infrared spectroscopy. BMP-6 loaded PEC NP adheres to cell membranes of MMCs and MSCs and activated phosphorylation of Smad 1/5. Osteogenic differentiation (ALP-concentration) is enhanced in MSCs (p < 0.05). All patient samples (10/10) of MMCs show significant induction of apoptosis (median 84%, p < 0.05). Finally, BMP-6/PEC NP are successfully integrated in a commercial hyaluronic acid based hydrogel material revealing MMC death as principal proof for the local treatment of MM induced bone lesions. 相似文献