880 resultados para Rotation-invariant feature


Relevância:

20.00% 20.00%

Publicador:

Resumo:

Mode of access: Internet.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

"January 1985."

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Mode of access: Internet.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Thesis (Ph.D.)--University of Washington, 2016-06

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Let Q be a stable and conservative Q-matrix over a countable state space S consisting of an irreducible class C and a single absorbing state 0 that is accessible from C. Suppose that Q admits a finite mu-subinvariant measure in on C. We derive necessary and sufficient conditions for there to exist a Q-process for which m is mu-invariant on C, as well as a necessary condition for the uniqueness of such a process.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The present paper examines the optimal use of a site containing standing timber, taking account of both timber and non-timber values. Using a site in the southern forest of Tasmania for illustrative purposes, it calculates the relationships between age of stand, extent of timber and non-timber values and optimal cutting age. It finds that, for a stand with moderate potential environmental benefits, there is a period of its life during which it is optimal to log. This segment narrows, and eventually disappears, as potential environmental benefits increase.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Concepts of constant absolute risk aversion and constant relative risk aversion have proved useful in the analysis of choice under uncertainty, but are quite restrictive, particularly when they are imposed jointly. A generalization of constant risk aversion, referred to as invariant risk aversion is developed. Invariant risk aversion is closely related to the possibility of representing preferences over state-contingent income vectors in terms of two parameters, the mean and a linearly homogeneous, translation-invariant index of riskiness. The best-known index with such properties is the standard deviation. The properties of the capital asset pricing model, usually expressed in terms of the mean and standard deviation, may be extended to the case of general invariant preferences. (C) 2003 Elsevier Inc. All rights reserved.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Doped ceria (CeO2,) compounds are fluorite type oxides, which show oxide ionic conductivity higher than yttria stabilized zirconia (YSZ), in oxidizing atmospheres. As a consequence of this, considerable interest has been shown in application of these materials for 'low (500-650 degreesC)' or 'intermediate (650-800 degreesC)' temperature operation, solid oxide fuel cells (SOFCs). In this study, the authors prepared two kinds of nanosize Sm-doped CeO2 particles with different morphologies: one type was round and the other was elongated. Processing these powders with different morphology produced dense materials with very different ionic conducting properties and different nanoscale microstructures. Since both particles are very fine and well dispersed, sintered bodies with high density (relative density >95% of theoretical) could be prepared using both types of powder particles. The electrical conductivity of sintered bodies prepared from these powders with different starting morphologies was very different. Materials prepared from particles having a round shape were much higher than those produced using powders with an elongated morphology. Measured activation energies of the corresponding sintered samples showed a similar trend; round particles (60 kJ/mol), elongated particles (74 kJ/mol). While X-ray diffraction (XRD) profiles of these sintered materials were identical, diffuse scatter was observed in the back.-round of selected area electron diffraction pattern recorded from both sintered bodies. This indicated an underlying structure that appeared to have been influenced by the processing technology. Detailed observation using high-resolution transmission electron microscopy (HR-TEM) revealed that the size of microdomain with ordering of cations in the sintered body made from round shape particles was much smaller than that of the sintered body made from elongated particles. Accordingly, it is concluded that the morphology of doped CeO2 powders strongly influenced the microdomain size and electrolytic properties in the doped CeO2 sintered body. (C) 2004 Elsevier B.V. All rights reserved.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The alpha-defensin antimicrobial peptide family is defined by a unique tridisulfide array. To test whether this invariant structural feature determines alpha-defensin bactericidal activity, mouse cryptdin-4 (Crp4) tertiary structure was disrupted by pairs of site-directed Ala for Cys substitutions. In a series of Crp4 disulfide variants whose cysteine connectivities were confirmed using NMR spectroscopy and mass spectrometry, mutagenesis did not induce loss of function. To the contrary, the in vitro bactericidal activities of several Crp4 disulfide variants were equivalent to or greater than those of native Crp4. Mouse Paneth cell alpha-defensins require the proteolytic activation of precursors by matrix metalloproteinase-7 (MMP-7), prompting an analysis of the relative sensitivities of native and mutant Crp4 and proCrp4 molecules to degradation by MMP-7. Although native Crp4 and the alpha-defensin moiety of proCrp4 resisted proteolysis completely, all disulfide variants were degraded extensively by MMP-7. Crp4 bactericidal activity was eliminated by MMP-7 cleavage. Thus, rather than determining alpha-defensin bactericidal activity, the Crp4 disulfide arrangement confers essential protection from degradation by this critical activating proteinase.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Growth hormone is believed to activate the growth hormone receptor (GHR) by dimerizing two identical receptor subunits, leading to activation of JAK2 kinase associated with the cytoplasmic domain. However, we have reported previously that dimerization alone is insufficient to activate full-length GHR. By comparing the crystal structure of the liganded and unliganded human GHR extracellular domain, we show here that there is no substantial change in its conformation on ligand binding. However, the receptor can be activated by rotation without ligand by inserting a defined number of alanine residues within the transmembrane domain. Fluorescence resonance energy transfer ( FRET), bioluminescence resonance energy transfer (BRET) and coimmunoprecipitation studies suggest that receptor subunits undergo specific transmembrane interactions independent of hormone binding. We propose an activation mechanism involving a relative rotation of subunits within a dimeric receptor as a result of asymmetric placement of the receptor-binding sites on the ligand.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The energy surface connecting oxazinium olates 9, several possible conformers of ketenes 10 and 11, and the final cyclization products 12, 13 and 14, as well as the isomeric 1,3-oxazine-6-ones 15, ring opening of the latter to N-acylimidoylketenes 16, and subsequent rearrangement of 16 to oxoketenimines 17, azetinones 18, and the cyclization products 19 and 20 are evaluated computationally at the B3LYP/6-31G* and B3LYP/6-311+G*//B3LYP/6-31G* levels. The cyclizations of ketenes to oxazinium olates 9 and oxazines 15 have the characteristics of pseudopericyclic reactions. Plots of the energy vs internal reaction coordinate for the cyclization of transoid acylketenes such as 10 to 9 (via TS1) and 16 to 15 (via TS7) feature two inflection points and indicate that the part of the energy surface above the lower inflection points describe internal rotation of the acyl function in the ketene moiety, and the part below this point describes the cyclization of the cisoid ketene to the planar mesoionic oxazinium olate 9 or oxazinone 15. The 1,3-shifts of the OR group that interconvert ketenes 16 and ketenimines 17 via four-membered cyclic transition states TS8 behave similarly, the first portion (from the ketenimine side) of the activation barrier being due largely to internal rotation of substituents, and the top part being due to the 1,3-shift proper.