9,991 research outputs found
Coarse-Graining and Renormalization of Atomistic Binding Relations and Universal Macroscopic Cohesive Behavior
We present two approaches for coarse-graining interplanar potentials and
determining the corresponding macroscopic cohesive laws based on energy
relaxation and the renormalization group. We analyze the cohesive behavior of a
large---but finite---number of interatomic planes and find that the macroscopic
cohesive law adopts a universal asymptotic form. The universal form of the
macroscopic cohesive law is an attractive fixed point of a suitably-defined
renormalization-group transformation.Comment: 15 pages, 6 figures, submitted to the Journal of the Mechanics and
Physics of Solid
Physical Activity Health Communication for Adults with Mood Disorders in the United States
Using national representative data, this study sought to examine receipt of physical activity communication and counseling among adults with mood disorders in comparison to the general population in the United States. The sample consisted of adult primary-care visits in the National Hospital Ambulatory Medical Care and National Ambulatory Medical Care Surveys. Multivariable logistic regression was used to examine the relationship between mental health status and receipt of physical activity communication and counseling. Overall, less than 20% of visits included physical activity communication and counseling. Controlling for covariates, visits for adults with a mood disorder diagnosis were associated with an increased odds of including physical activity communication and counseling, odds ratio = 1.25, 95% confidence interval = [1.08, 1.45]. Although adults with mood disorders were more likely to receive physical activity communication and counseling, most primary-care visits for adults in the United States did not include physical activity communication and counseling
Data mining and accelerated electronic structure theory as a tool in the search for new functional materials
Data mining is a recognized predictive tool in a variety of areas ranging
from bioinformatics and drug design to crystal structure prediction. In the
present study, an electronic structure implementation has been combined with
structural data from the Inorganic Crystal Structure Database to generate
results for highly accelerated electronic structure calculations of about
22,000 inorganic compounds. It is shown how data mining algorithms employed on
the database can identify new functional materials with desired materials
properties, resulting in a prediction of 136 novel materials with potential for
use as detector materials for ionizing radiation. The methodology behind the
automatized ab-initio approach is presented, results are tabulated and a
version of the complete database is made available at the internet web site
http://gurka.fysik.uu.se/ESP/ (Ref.1).Comment: Project homepage: http://gurka.fysik.uu.se/ESP
Beyond conventional factorization: Non-Hermitian Hamiltonians with radial oscillator spectrum
The eigenvalue problem of the spherically symmetric oscillator Hamiltonian is
revisited in the context of canonical raising and lowering operators. The
Hamiltonian is then factorized in terms of two not mutually adjoint factorizing
operators which, in turn, give rise to a non-Hermitian radial Hamiltonian. The
set of eigenvalues of this new Hamiltonian is exactly the same as the energy
spectrum of the radial oscillator and the new square-integrable eigenfunctions
are complex Darboux-deformations of the associated Laguerre polynomials.Comment: 13 pages, 7 figure
Phonon engineering with superlattices: generalized nanomechanical potentials
Earlier implementations to simulate coherent wave propagation in
one-dimensional potentials using acoustic phonons with gigahertz-terahertz
frequencies were based on coupled nanoacoustic resonators. Here, we generalize
the concept of adiabatic tuning of periodic superlattices for the
implementation of effective one-dimensional potentials giving access to cases
that cannot be realized by previously reported phonon engineering approaches,
in particular the acoustic simulation of electrons and holes in a quantum well
or a double well potential. In addition, the resulting structures are much more
compact and hence experimentally feasible. We demonstrate that potential
landscapes can be tailored with great versatility in these multilayered
devices, apply this general method to the cases of parabolic, Morse and
double-well potentials and study the resulting stationary phonon modes. The
phonon cavities and potentials presented in this work could be probed by
all-optical techniques like pump-probe coherent phonon generation and Brillouin
scattering
- …