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1.
In this paper, the effect ofmaterial anisotropy on void nucleation and growth inincompressible nonlinearly elastic solids is examined. A bifurcation problem is considered for a solid sphere composed of an incompressible homogeneous nonlinearly elastic material which is transversely isotropic about the radial direction. Under a uniform radial tensile dead-load, a branch of radially symmetric configurations involving a traction-free internal cavity bifurcates from the undeformed configuration at sufficiently large loads. Closed form analytic solutions are obtained for a specific material model, which may be viewed as a generalization of the classic neo-Hookean model to anisotropic materials. In contrast to the situation for a neo-Hookean sphere, bifurcation here may occur locally either to the right (supercritical) or to the left (subcritical), depending on the degree of anisotropy. In the latter case, the cavity has finite radius on first appearance. Such a discontinuous change in stable equilibrium configurations is reminiscent of the snap-through buckling phenomenon of structural mechanics. Such dramatic cavitational instabilities were previously encountered by Antman and Negrón-Marrero [3] for anisotropiccompressible solids and by Horgan and Pence [17] forcomposite incompressible spheres. 相似文献
2.
Deformations possible (i.e., those satisfying the governing three-dimensional equations of equilibrium and the incompressibility
constraint) within a class of non-symmetric deformations for a neo-Hookean nonlinearly elastic body were determined in [1],
where it was found that only three special cases of the class of deformation fields considered could be solutions. One of
these is the trivial solution, one the solution describing radially symmetric deformation, and the other a (non-symmetric,
non-homogeneous) deformation contained within a family of universal deformations. In this paper, the results reported in [1]
are shown to hold for a substantially broadened deformation field.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Stephen R. Williams Denis J. Evans Debra J. Searles 《Journal of statistical physics》2011,145(4):831-840
We review the theoretical underpinning of nonequilibrium umbrella sampling. We provide its historical context and show how it relates to other important results in nonequilibrium statistical mechanics. Its relationships to the generalised Yamada-Kawasaki distribution function is explored. A new functional version of the Crooks Fluctuation Theorem is also presented. 相似文献
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Sudarsanan Varaprath Mark Seaton Debra McNett Lin Cao Kathleen P. Plotzke 《International journal of environmental analytical chemistry》2013,93(3):203-219
Abstract A method was developed and validated to measure octamethylcyclotetrasiloxane (D4)? quantitatively by gas chromatography-mass spectrometry (GC-MS) at low level in extracts of several biological matrices that include plasma, liver, lung, feces and fat from rats. The key to the successful determination lay in the use of extracts dried with anhydrous magnesium sulfate. This was necessary in view of the propensity of the methyl siloxane based GC-stationary phase to generate D4 by its reaction with water present in the extracts. To enable quantiiation of D4 at parts per billion (μg/L) levels, the base ion m/z 281 resulting from the loss of a methyl group from the parent molecule was selected for monitoring by SIM mode in GC-MS. The recovery of D4 from any of the biological matrices was determined to be greater than 90% in three extractions. The D4 response for the standards in GC-MS was linear (R2 > 0.9900) and reproducible at concentrations ranging from 1—16,000 ng D4/g solvent. Precision was less than 5%. 相似文献
8.
Thomas W. Gero Larry W. Jaques Richard P. Mays Debra H. Reid Dwight A. Shamblee Young S. Lo 《合成通讯》2013,43(3-4):553-559
A convenient method to prepare 5-halo-2-hydroxy-nicotinic acid is described. 相似文献
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Jian Dong Zhihao Zhuang Feng Song Debra Dunaway‐Mariano Paul R. Carey 《Journal of Raman spectroscopy : JRS》2012,43(1):65-71
4‐Hydroxybenzoyl‐CoA (4‐HB‐CoA) thioesterase from Arthrobacter is the final enzyme catalyzing the hydrolysis of 4‐HB‐CoA to produce coenzyme A and 4‐hydroxybenzoic acid in the bacterial 4‐chlorobenzoate dehalogenation pathway. Using a mutation E73A that blocks catalysis, stable complexes of the enzyme and its substrate can be analyzed by Raman difference spectroscopy. Here we have used Raman difference spectroscopy, in the non‐resonance regime, to characterize 4‐HB‐CoA bound in the active site of the E73A thioesterase. In addition, we have characterized complexes of the wild‐type enzyme complexed with the unreactive substrate analog 4‐hydroxyphenacyl‐CoA (4‐HP‐CoA). Both sets of complexes show evidence for two forms of the ligand in the active site: one population has the 4‐hydroxy group protonated, 4‐OH; while the second has the group as the hydroxide, 4‐O−. For bound 4‐HP‐CoA, X‐ray data show that glutamate 78 is close to the 4‐OH in the complex and it is likely that this is the proton acceptor for the 4‐OH proton. Although the pKa of the 4‐OH group on the free substrate in aqueous solution is 8.6, the relative populations of ionized and neutral 4‐HB‐CoA bound to E73A remain invariant between pH 7.3 and 9.8. The invariance with pH suggests that the 4‐OH and the ‐COO− of E78 constitute a tightly coupled pair where their separate pKa ‘s lose their individual qualities. Narrow band profiles are seen in the CO double bond and C‐S regions, suggesting that the hydrolyzable thioester group is rigidly bound in the active site in a syn gauche conformation. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献