1,398 research outputs found
Failure of classical elasticity in auxetic foams
A recent derivation [P.H. Mott and C.M. Roland, Phys. Rev. B 80, 132104
(2009).] of the bounds on Poisson's ratio, v, for linearly elastic materials
showed that the conventional lower limit, -1, is wrong, and that v cannot be
less than 0.2 for classical elasticity to be valid. This is a significant
result, since it is precisely for materials having small values of v that
direct measurements are not feasible, so that v must be calculated from other
elastic constants. Herein we measure directly Poisson's ratio for four
materials, two for which the more restrictive bounds on v apply, and two having
values below this limit of 0.2. We find that while the measured v for the
former are equivalent to values calculated from the shear and tensile moduli,
for two auxetic materials (v < 0), the equations of classical elasticity give
inaccurate values of v. This is experimental corroboration that the correct
lower limit on Poisson's ratio is 0.2 in order for classical elasticity to
apply.Comment: 9 pages, 2 figure
The high energy semiclassical asymptotics of loci of roots of fundamental solutions for polynomial potentials
In the case of polynomial potentials all solutions to 1-D Schroedinger
equation are entire functions totally determined by loci of their roots and
their behaviour at infinity. In this paper a description of the first of the
two properties is given for fundamental solutions for the high complex energy
limit when the energy is quantized or not. In particular due to the fact that
the limit considered is semiclassical it is shown that loci of roots of
fundamental solutions are collected of selected Stokes lines (called
exceptional) specific for the solution considered and are distributed along
these lines in a specific way. A stable asymptotic limit of loci of zeros of
fundamental solutions on their exceptional Stokes lines has island forms and
there are infintely many of such roots islands on exceptional Stokes lines
escaping to infinity and a finite number of them on exceptional Stokes lines
which connect pairs of turning points. The results obtained for asymptotic
roots distributions of fundamental solutions in the semiclassical high
(complex) energy limit are of a general nature for polynomial potentials.Comment: 41 pages, 14 figure
Murine cytomegalovirus genomic material in marrow cells; relation to altered leukocyte counts during sublethal infection of mice
Plans for interaction with the Tropical Legumes II project (TLII) and for seed increase on a country-by-country basis
Representation Theory of Quantized Poincare Algebra. Tensor Operators and Their Application to One-Partical Systems
A representation theory of the quantized Poincar\'e (-Poincar\'e)
algebra (QPA) is developed. We show that the representations of this algebra
are closely connected with the representations of the non-deformed Poincar\'e
algebra. A theory of tensor operators for QPA is considered in detail.
Necessary and sufficient conditions are found in order for scalars to be
invariants. Covariant components of the four-momenta and the Pauli-Lubanski
vector are explicitly constructed.These results are used for the construction
of some q-relativistic equations. The Wigner-Eckart theorem for QPA is proven.Comment: 18 page
Topological Expansion and Exponential Asymptotics in 1D Quantum Mechanics
Borel summable semiclassical expansions in 1D quantum mechanics are
considered. These are the Borel summable expansions of fundamental solutions
and of quantities constructed with their help. An expansion, called
topological,is constructed for the corresponding Borel functions. Its main
property is to order the singularity structure of the Borel plane in a
hierarchical way by an increasing complexity of this structure starting from
the analytic one. This allows us to study the Borel plane singularity structure
in a systematic way. Examples of such structures are considered for linear,
harmonic and anharmonic potentials. Together with the best approximation
provided by the semiclassical series the exponentially small contribution
completing the approximation are considered. A natural method of constructing
such an exponential asymptotics relied on the Borel plane singularity
structures provided by the topological expansion is developed. The method is
used to form the semiclassical series including exponential contributions for
the energy levels of the anharmonic oscillator.Comment: 46 pages, 22 EPS figure
Projective representation of k-Galilei group
The projective representations of k-Galilei group G_k are found by
contracting the relevant representations of k-Poincare group. The projective
multiplier is found. It is shown that it is not possible to replace the
projective representations of G_k by vector representations of some its
extension.Comment: 15 pages Latex fil
Universality of electron-positron distributions in extensive air showers
Using a large set of simulated extensive air showers, we investigate
universality features of electron and positron distributions in
very-high-energy cosmic-ray air showers. Most particle distributions depend
only on the depth of the shower maximum and the number of particles in the
cascade at this depth. We provide multi-dimensional parameterizations for the
electron-positron distributions in terms of particle energy, vertical and
horizontal momentum angle, lateral distance, and time distribution of the
shower front. These parameterizations can be used to obtain realistic
electron-positron distributions in extensive air showers for data analysis and
simulations of Cherenkov radiation, fluorescence signal, and radio emission.Comment: 13 pages, 22 figures, 1 tabl
CocoaSoils data interoperability vision
Data-generative approaches are becoming increasingly common in modern life science research. Agronomy, food, plant sciences, and biodiversity are examples of complementary scientific disciplines that can greatly benefit from the integration and re-sue of the data that they produce. For instance, at WENR ..
Unified order-disorder vortex phase transition in high-Tc superconductors
The diversity of vortex melting and solid-solid transition lines measured in
different high-T superconductors is explained, postulating a unified
order-disorder phase transition driven by both thermally- and disorder-induced
fluctuations. The temperature dependence of the transition line and the nature
of the disordered phase (solid, liquid, or pinned liquid) are determined by the
relative contributions of these fluctuations and by the pinning mechanism. By
varying the pinning mechanism and the pinning strength one obtains a spectrum
of monotonic and non-monotonic transition lines similar to those measured in
BiSrCaCuO, YBaCuO,
NdCeCuO,
BiPbSrCaCuO and (LaSr)CuOComment: To be published in Phys. Rev. B Rapid Com
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