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21.
In the current contribution, we present a multi-scale constitutive model capturing macroscopic inelastic effects (like stress softening and permanent set) in soft tissues under cyclic loading. Soft biological tissues can be described as a biological composite material. The extracellular matrix is hereby reinforced by collagen fibers which themself are an assembly of collagen fibrils embedded in a proteoglycan (PG) rich matrix. Micro-damage induced by cyclic loading is treated by an interaction scenario between the fibrils and the PGs. At the low strain regime PGs promote sliding between fibrils [1] which leads to the yielding of statistical distributed overlapping segments. The breakage of the PG-bridges is defined by a decreasing PG-density. Due to the accumulated damage of the PG connections at high tissue strains, the strains at the fibril level increases. This finally drives the over-stretching of the fibrils, which is associated with a permanent rupture of the hydrogen bonds inside of the tropocollagen molecules [2]. The so obtained model is in line with recent experimental findings [1, 2] and was additionally validated against experimental data available in literature. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
22.
Van H. Vu 《Journal of Graph Theory》1996,22(2):137-149
A graph is called of type k if it is connected, regular, and has k distinct eigenvalues. For example graphs of type 2 are the complete graphs, while those of type 3 are the strongly regular graphs. We prove that for any positive integer n, every graph can be embedded in n cospectral, non-isomorphic graphs of type k for every k ≥ 3. Furthermore, in the case k ≥ 5 such a family of extensions can be found at every sufficiently large order. Some bounds for the extension will also be given. © 1996 John Wiley & Sons, Inc. 相似文献
23.
The gauge symmetry group of any slave boson representation allows to gauge away the phase of bosonic fields. One benefit of this radial field formulation is the elimination of spurious Bose condensations when saddle-point approximation is performed. Within the Kotliar–Ruckenstein representation, three of the four bosonic fields can be radial while the last one has to remain complex. In this work, the procedure to carry out the functional integration involving constrained fermionic fields, complex bosonic fields, and radial bosonic fields is presented. The correctness of the representation is verified by exactly evaluating the partition function and the Green's function of the Hubbard model in the atomic limit. 相似文献
24.
We present the first realisation of ferromagnetic Fe nanotips. Studies of the field emitted beams of electrons and metallic ions above and under the Curie temperature Tc were made. We have observed a reversible splitting of the electron beams when the temperature crossed through Tc and multiple spot patterns for the emitted metallic ion beams. These phenomena were not observed with Fe microtips or non-magnetic nanotips and thus were correlated to a strong magnetic interaction at the atomic scale apex of the nanotips. The Fe nanotips constitute an atomic scale beam-splitter. 相似文献
25.
We show here that field emission (FE) can be used to directly observe the vibration resonances nu(R) of carbon nanotubes (CNTs) and that the tension created by the applied field allows the tuning of these resonances by up to a factor of 10. The resonances are observable by the changes they create in the FE pattern or the emitted FE current. The tuning is shown to be linear in voltage and to follow from the basic physics of stretched strings. The method allows one to study the mechanical properties of individual multiwall carbon nanotubes within an ensemble and follow their evolution as the CNTs are modified. The tuning and detection should be useful for nanometric resonant devices. 相似文献
26.
As an extension of Polya’s classical result on random walks on the square grids (\({\mathbf {Z}}^d\)), we consider a random walk where the steps, while still have unit length, point to different directions. We show that in dimensions at least 4, the returning probability after n steps is at most \(n^{-d/2 - d/(d-2) +o(1) }\), which is sharp. The real surprise is in dimensions 2 and 3. In dimension 2, where the traditional grid walk is recurrent, our upper bound is \(n^{-\omega (1) }\), which is much worse than in higher dimensions. In dimension 3, we prove an upper bound of order \(n^{-4 +o(1) }\). We find a new conjecture concerning incidences between spheres and points in \({\mathbf {R}}^3\), which, if holds, would improve the bound to \(n^{-9/2 +o(1) }\), which is consistent to the \(d \ge 4\) case. This conjecture resembles Szemerédi-Trotter type results and is of independent interest. 相似文献
27.
Van H. Vu 《Combinatorica》1996,16(2):295-299
For every positive integern we show the construction of a strongly regular graph of order at most 2
n+2 which contains every graph of ordern as a subgraph. The estimation concerning the construction is best possible. 相似文献
28.
This paper gives lower estimates for the frequency modules of almost periodic solutions to equations of the form
, where A generates a strongly continuous semigroup in a Banach space
, F(t,x) is 2π-periodic in t and continuous in (t,x), and f is almost periodic. We show that the frequency module ℳ(u) of any almost periodic mild solution u of (*) and the frequency module ℳ(f) of f satisfy the estimate e
2π
iℳ(f)⊂e
2π
iℳ(u). If F is independent of t, then the estimate can be improved: ℳ(f)⊂ℳ(u). Applications to the nonexistence of quasi-periodic solutions are also given. 相似文献
29.
30.
Saturated aqueous solutions of 28 different salts have been studied as a potential mobile phases for salting-out thin-layer
chromatography, on silica gel, of a series of four mixed bis-aminocarboxylato cobalt(III) complexes. In addition, by linear
regression analysis of chromatographic data obtained for fifteen mixed aminocarboxylato Co(III) complexes (four series) with
solutions of ammonium chloride, three alkali metal chlorides, and four alkaline earth metal chlorides, four linear dependences
previously established on different adsorbents with (NH4)2SO4 solutions were confirmed. The qualities of the separations achieved with the salts were compared and Li+, Mg2+, and Ca2+ chlorides are proposed as the most suitable. 相似文献