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101.
Summary The behaviour and sign of the Reynolds stress for periodic perturbation of finite amplitude is studied in this paper for the plane Poiseuille flow. The case considered has Reynolds number 250 and wave number =1. The Reynolds stress that in the linear case was of opposite sign with respect to the viscosity, in the case considered becomes such for perturbation amplitudes which are still significant with respect to the dynamics of the mean flow. Some numerical results are given to characterize the phenomenon.
This work is part of a research program on hydrodynamics at the Istituto di Elaborazione dell'Informazione of the C.N.R., Pisa. The first Author has suggested and precisely formulated the problem, whereas the numerical work was carried out by the second Author. 相似文献
Sommario In questo lavoro si studia nel moto piano di Poiseuille il comportamento ed il segno dello stress di Reynolds per perturbazioni periodiche di ampiezza finita. E' trattato il caso del numero di Reynolds 250 e del numero d'onda =1. Si osserva che lo stress di Reynolds, che nel caso lineare era di segno opposto alla viscosità, diventa tale per ampiezza della perturbazione rilevante rispetto alla dinamica del moto medio. Sono dati alcuni risultati numerici che caratterizzano il fenomeno.
This work is part of a research program on hydrodynamics at the Istituto di Elaborazione dell'Informazione of the C.N.R., Pisa. The first Author has suggested and precisely formulated the problem, whereas the numerical work was carried out by the second Author. 相似文献
102.
The coupling of 2-(tributylstannyl)cyclopent-2-enone with several (π-allyl)palladium complexes derived from allylic electrophiles was investigated as the key step in the synthesis of jasmonoids. These compounds have an important role in plant development, triggering direct and indirect responses when harmed to induce pest resistance. Palladium-catalyzed coupling conditions to obtain a jasmonoid library are described. The retention of geometry of the olefin in the allyl group is not always observed due to syn-anti isomerization of the (π-allyl)palladium complex. The methodology was employed for the synthesis of a simplified jasmonic acid analog. 相似文献
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Lubomír Dostl Florencia Pratto Juan C. Alonso Heinz Welfle 《Journal of Raman spectroscopy : JRS》2007,38(2):166-175
pSM19035‐encoded dimeric regulator omega (ω2) belongs to the MetJ/Arc family of ribbon–helix–helix DNA binding proteins. ω2 binds to a set of unspaced 7‐base pair repeat units with sequence 5′‐A/TATCACA/T‐3′. Protein ω2 and its variant ω2ΔN18, lacking the first 18 N‐terminal amino acids, bind poorly to one heptad DNA, but the affinity to DNA markedly increases with two and more heptads organized in direct or inverted orientation. Raman difference spectra indicate that ω2 and ω2ΔN18 bind to operator DNA in the major groove and contact thymine, adenine and guanine residues. The mode of ω2 or ω2ΔN18 interaction with operator DNA is not affected by the orientation and number of heptads. The Raman data of ω2T29A, an ω2 variant with Ala instead of Thr at position 29 of the β‐sheet, show a sequence‐independent binding mode to DNA, which differs from the binding mode of wt ω2 protein to its cognate site. The Raman data strongly support the notion that the 18 N‐terminal amino acids are not required for ω2 activity, whereas Thr29 plays an essential role for operator DNA binding. The data suggest the formation of a hydrogen bond between Thr29 of wild‐type ω2 to one of the bases in the central 5′‐TCA‐3′/5′‐TGA‐3′ stretch of the 7‐bp binding site. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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Mariella Cecchi Zuzana Došlá Mauro Marini 《Central European Journal of Mathematics》2009,7(2):322-334
A characterization of oscillation and nonoscillation of the Emden-Fowler difference equation
is given, jointly with some asymptotic properties. The problem of the coexistence of all possible types of nonoscillatory
solutions is also considered and a comparison with recent analogous results, stated in the half-linear case, is made.
相似文献
108.
Inside Back Cover: Zinc Porphyrin Metal‐Center Exchange at the Solid–Liquid Interface (Chem. Eur. J. 25/2016)
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