1,100 research outputs found
The Judicial Expansion of American Exceptionalism
The percolation theory is established as a useful tool in the field of pharmaceutical materials science.It is shown that percolation theory, developed for analyzing insulator–conductor transitions, can beapplied to describe imperfect dc conduction in pharmaceutical microcrystalline cellulose duringdensification. The system, in fact, exactly reproduces the values of the percolation threshold andexponent estimated for a three-dimensional random continuum. Our data clearly show a crossoverfrom a power-law percolation theory region to a linear effective medium theory region at a celluloseporosity of ;0.7
Piercing the Veil: William J. Brennan\u27s Account of Regents of the University of California v. Bakke
Porous nickel oxide films were deposited onto unheated indium tin oxide coated glass substrates by reactive dc magnetron sputtering. These films had a cubic NiO structure. Electrochromic properties were evaluated in 1 M potassium hydroxide (KOH) and in 1 M lithium perchlorate in propylene carbonate (Li-PC). Large optical modulation was obtained for similar to 500-nm-thick films both in KOH and in Li-PC (similar to 70% and similar to 50% at 550 nm, respectively). In KOH, tensile and compressive stresses, due to the expansion and contraction of the lattice, were found for films in their bleached and colored state, respectively. In Li-PC, compressive stress was seen both in colored and bleached films. Durability tests with voltage sweeps between -0.5 and 0.65 V vs Ag/AgCl in KOH showed good durability for 10,000 cycles, whereas voltage sweeps between 2.0 and 4.7 V vs Li/Li+ in Li-PC yielded significant degradation after 1000 cycles.EU GRINDOO
Extinction calculations of multi-sphere polycrystalline graphitic clusters - A comparison with the 2175 AA peak and between a rigorous solution and discrete-dipole approximations
Certain dust particles in space are expected to appear as clusters of
individual grains. The morphology of these clusters could be fractal or
compact. In this paper we study the light scattering by compact and fractal
polycrystalline graphitic clusters consisting of touching identical spheres. We
compare three general methods for computing the extinction of the clusters in
the wavelength range 0.1 - 100 micron, namely, a rigorous solution (Gerardy &
Ausloos 1982) and two different discrete-dipole approximation methods --
MarCODES (Markel 1998) and DDSCAT (Draine & Flatau 1994). We consider clusters
of N = 4, 7, 8, 27,32, 49, 108 and 343 particles of radii either 10 nm or 50
nm, arranged in three different geometries: open fractal (dimension D = 1.77),
simple cubic and face-centred cubic. The rigorous solution shows that the
extinction of the fractal clusters, with N < 50 and particle radii 10 nm,
displays a peak within 2% of the location of the observed interstellar
extinction peak at ~4.6 inverse micron; the smaller the cluster, the closer its
peak gets to this value. By contrast, the peak in the extinction of the more
compact clusters lie more than 4% from 4.6 inverse micron. At short wavelengths
(0.1 - 0.5 micron), all the methods show that fractal clusters have markedly
different extinction from those of non-fractal clusters. At wavelengths > 5
micron, the rigorous solution indicates that the extinction from fractal and
compact clusters are of the same order of magnitude. It was only possible to
compute fully converged results of the rigorous solution for the smaller
clusters, due to computational limitations, however, we find that both
discrete-dipole approximation methods overestimate the computed extinction of
the smaller fractal clusters.Comment: Corrections added in accordance with suggestions by the referee. 12
pages, 12 figures. Accepted for publication in Astronomy & Astrophysic
Giant magnetic enhancement in Fe/Pd films and its influence on the magnetic interlayer coupling
The magnetic properties of thin Pd fcc(001) films with embedded monolayers of
Fe are investigated by means of first principles density functional theory. The
induced spin polarization in Pd is calculated and analyzed in terms of quantum
interference within the Fe/Pd/Fe bilayer system. An investigation of the
magnetic enhancement effects on the spin polarization is carried out and its
consequences for the magnetic interlayer coupling are discussed. In contrast to
{\it e.g.} the Co/Cu fcc(001) system we find a large effect on the magnetic
interlayer coupling due to magnetic enhancement in the spacer material. In the
case of a single embedded Fe monolayer we find aninduced Pd magnetization
decaying with distance from the magnetic layer as ~ with
. For the bilayer system we find a giant magnetic
enhancement (GME) that oscillates strongly due to interference effects. This
results in a strongly modified magnetic interlayer coupling, both in phase and
magnitude, which may not be described in the pure
Ruderman-Kittel-Kasuya-Yoshida (RKKY) picture. No anti-ferromagnetic coupling
was found and by comparison with magnetically constrained calculations we show
that the overall ferromagnetic coupling can be understood from the strong
polarization of the Pd spacer
Law School Libraries 2007
The primary mission of the law school library is to meet the information needs of the faculty and students of the institution it supports. In addition to their role in educating future lawyers, law schools are the major producers of scholarly literature in law and rely on academic law libraries to provide the resources and support needed for research and publication. Beyond support for the core functions of legal education and research, the specific missions of law school libraries vary depending on the size and missions of law schools of different types. Differences among law schools result in differences among their libraries in collection size and composition, staffing and services offered, and additional clienteles served
Wavefunction extended Lagrangian Born-Oppenheimer molecular dynamics
Extended Lagrangian Born-Oppenheimer molecular dynamics [Niklasson, Phys.
Rev. Lett. 100 123004 (2008)] has been generalized to the propagation of the
electronic wavefunctions. The technique allows highly efficient first
principles molecular dynamics simulations using plane wave pseudopotential
electronic structure methods that are stable and energy conserving also under
incomplete and approximate self-consistency convergence. An implementation of
the method within the planewave basis set is presented and the accuracy and
efficiency is demonstrated both for semi-conductor and metallic materials.Comment: 6 pages, 3 figure
Ab initio linear scaling response theory: Electric polarizability by perturbed projection
A linear scaling method for calculation of the static {\em ab inito} response
within self-consistent field theory is developed and applied to calculation of
the static electric polarizability. The method is based on density matrix
perturbation theory [Niklasson and Challacombe, cond-mat/0311591], obtaining
response functions directly via a perturbative approach to spectral projection.
The accuracy and efficiency of the linear scaling method is demonstrated for a
series of three-dimensional water clusters at the RHF/6-31G** level of theory.
Locality of the response under a global electric field perturbation is
numerically demonstrated by approximate exponential decay of derivative density
matrix elements.Comment: 4.25 pages in PRL format, 2 figure
Shadow Energy Functionals and Potentials in Born-Oppenheimer Molecular Dynamics
In Born-Oppenheimer molecular dynamics (BOMD) simulations based on density
functional theory (DFT), the potential energy and the interatomic forces are
calculated from an electronic ground state density that is determined by an
iterative self-consistent field optimization procedure, which in practice never
is fully converged. The calculated energies and the forces are therefore only
approximate, which may lead to an unphysical energy drift and instabilities.
Here we discuss an alternative shadow BOMD approach that is based on a backward
error analysis. Instead of calculating approximate solutions for an underlying
exact regular BO potential, we do the opposite. Instead, we calculate the exact
electron density, energies, and forces, but for an underlying approximate
shadow BO potential. In this way the calculated forces are conservative with
respect to the shadow potential and generate accurate molecular trajectories
with long-term energy stability. We show how such shadow BO potentials can be
constructed at different levels of accuracy as a function of the integration
time step, dt, from the minimization of a sequence of systematically
improvable, but approximate, shadow energy density functionals. For each
functional there is a corresponding ground state BO potential. These pairs of
shadow energy functionals and potentials are higher-level generalizations of
the original "0th-level" shadow energy functionals and potentials used in
extended Lagrangian BOMD [Eur. Phys. J. B vol. 94, 164 (2021)]. The proposed
shadow energy functionals and potentials are useful only within this dynamical
framework, where also the electronic degrees of freedom are propagated together
with the atomic positions and velocities. The theory is general and can be
applied to MD simulations using approximate DFT, Hartree-Fock or semi-empirical
methods, as well as to coarse-grained flexible charge models.Comment: 16 pages, 3 figure
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