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41.
Hutchinson IH 《Physical review letters》2011,107(9):095001
The transverse force on a spherical charged grain lying in the plasma wake of another grain is analyzed to assess the importance of ion-drag perturbation, in addition to the wake-potential-gradient. The ion-drag perturbation is intrinsically one order smaller than the wake-potential force in the ratio of grain size (r(p)) to Debye length (λ(De)). So ion-drag perturbation is important only in nonlinear wakes. Rigorous particle-in-cell calculations of the force are performed in the nonlinear regime with two interacting grains. It is found that even for quite large grains, r(p)/λ(De)=0.1, the force is dominated by the wake-potential gradient. The wake-potential structure can then help explain the preferred alignment of floating dust grains. 相似文献
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Using the approach of Rulla (1996 SIAM J. Numer. Anal. 33, 68-87)for analysing the time discretization error and assuming moreregularity on the initial data, we improve on the error boundderived by Barrett and Blowey (1996 IMA J. Numer. Anal. 16,257-287) for a fully practical piecewise linear finite elementapproximation with a backward Euler time discretization of amodel for phase separation of a multi-component alloy. 相似文献
44.
Selective Alkylation of C‐Rich Bulge Motifs in Nucleic Acids by Quinone Methide Derivatives
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Dr. Tuomas Lönnberg Mark Hutchinson Prof. Dr. Steven Rokita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(37):13127-13136
A quinone methide precursor featuring a bis‐cyclen anchoring moiety has been synthesized and its capacity to alkylate oligonucleotide targets quantified in the presence and absence of divalent metal ions (Zn2+, Ni2+ and Cd2+). The oligonucleotides were designed for testing the sequence and secondary structure specificity of the reaction. Gel electrophoretic analysis revealed predominant alkylation of C‐rich bulges, regardless of the presence of divalent metal ions or even the bis‐cyclen anchor. This C‐selectivity appears to be an intrinsic property of the quinone methide electrophile as reflected by its reaction with an equimolar mixture of the 2′‐deoxynucleosides. Only dA‐N1 and dC‐N3 alkylation products were detected initially and only the dC adduct persisted for detection under conditions of the gel electrophoretic analysis. 相似文献
45.
This paper shows that repetitive, infinite structures cannot be simultaneously statically, and kinematically, determinate. 相似文献
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Analyses of the regiochemistry of [13C]acetate incorporation into fulvic acid () by Penicillium brefeldianum indicates that the metabolite is biosynthesized via a heptaketide intermediate assembled as a single chain of seven C2, units rather than from two smaller polyketide chains. This information favours a route leading through common C14 intermediates to the three fungal metabolites, citromycetin, fulvic acid and fusarubin. 相似文献
48.
Propagation of a neck along the length of a tensile specimen as occurs in certain polymeric materials and in a few metals is studied. Two material models are considered: a nonlinear elastic solid, and an inelastic flow theory solid with both rate-dependent and rate-independent behaviors. For the elastic solid the states ahead and behind the neck transition can be obtained fairly simply from just the jump conditions governing continuity of mass, momentum and energy. For the inelastic solid a full three-dimensional analysis must be performed to obtain the same information, and an analysis of axisymmetric neck propagation is carried out. 相似文献
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Several levels of approximation are investigated to account for the effect of small fatigue cracks on the residual strength of aircraft sheet materials and fuselage lap joints containing major cracks. A version of the Dugdale model is proposed which accounts for strain hardening of the sheet in an approximate way and which incorporates a criterion for crack advance leading to crack growth resistance. This model builds upon the model proposed by Nilsson and Hutchinson [1] and accounts for the detailed interaction between the major crack and the small damage cracks. A simpler version of the model uses the damage-reduced local strength of the sheet or joint in assessing the effect of the major crack on residual strength. The simpler approach thus bypasses the necessity of a direct determination of the highly complicated details of the interaction of the small cracks in a lap joint with a major crack. 相似文献