4,367 research outputs found
Fock space relativistic coupled-Cluster calculations of Two-Valence Atoms
We have developed an all particle Fock-space relativistic coupled-cluster
method for two-valence atomic systems. We then describe a scheme to employ the
coupled-cluster wave function to calculate atomic properties. Based on these
developments we calculate the excitation energies, magnetic hyperfine constants
and electric dipole matrix elements of Sr, Ba and Yb. Further more, we
calculate the electric quadrupole HFS constants and the electric dipole matrix
elements of Sr, Ba and Yb. For these we use the one-valence
coupled-cluster wave functions obtained as an intermediate in the two-valence
calculations. We also calculate the magnetic dipole hyperfine constants of
Yb.Comment: 23 pages, 12 figures, 10 tables typos are corrected and some minor
modifications in some of the section
Chiral surfaces self-assembling in one-component systems with isotropic interactions
We show that chiral symmetry can be broken spontaneously in one-component
systems with isotropic interactions, i.e. many-particle systems having maximal
a priori symmetry. This is achieved by designing isotropic potentials that lead
to self-assembly of chiral surfaces. We demonstrate the principle on a simple
chiral lattice and on a more complex lattice with chiral super-cells. In
addition we show that the complex lattice has interesting melting behavior with
multiple morphologically distinct phases that we argue can be qualitatively
predicted from the design of the interaction.Comment: 4 pages, 4 figure
Novel self-assembled morphologies from isotropic interactions
We present results from particle simulations with isotropic medium range
interactions in two dimensions. At low temperature novel types of aggregated
structures appear. We show that these structures can be explained by
spontaneous symmetry breaking in analytic solutions to an adaptation of the
spherical spin model. We predict the critical particle number where the
symmetry breaking occurs and show that the resulting phase diagram agrees well
with results from particle simulations.Comment: 4 pages, 4 figure
Using the uncertainty principle to design simple interactions for targeted self-assembly
We present a method that systematically simplifies isotropic interactions designed for targeted self-assembly. The uncertainty principle is used to show that an optimal simplification is achieved by a combination of heat kernel smoothing and Gaussian screening of the interaction potential in real and reciprocal space. We use this method to analytically design isotropic interactions for self-assembly of complex lattices and of materials with functional properties. The derived interactions are simple enough to narrow the gap between theory and experimental implementation of theory based designed self-assembling materials
Using the local density approximation and the LYP, BLYP, and B3LYP functionals within Reference--State One--Particle Density--Matrix Theory
For closed-shell systems, the local density approximation (LDA) and the LYP,
BLYP, and B3LYP functionals are shown to be compatible with reference-state
one-particle density-matrix theory, where this recently introduced formalism is
based on Brueckner-orbital theory and an energy functional that includes exact
exchange and a non-universal correlation-energy functional. The method is
demonstrated to reduce to a density functional theory when the
exchange-correlation energy-functional has a simplified form, i.e., its
integrand contains only the coordinates of two electron, say r1 and r2, and it
has a Dirac delta function -- delta(r1 - r2) -- as a factor. Since Brueckner
and Hartree--Fock orbitals are often very similar, any local exchange
functional that works well with Hartree--Fock theory is a reasonable
approximation with reference-state one-particle density-matrix theory. The LDA
approximation is also a reasonable approximation. However, the Colle--Salvetti
correlation-energy functional, and the LYP variant, are not ideal for the
method, since these are universal functionals. Nevertheless, they appear to
provide reasonable approximations. The B3LYP functional is derived using a
linear combination of two functionals: One is the BLYP functional; the other
uses exact exchange and a correlation-energy functional from the LDA.Comment: 26 Pages, 0 figures, RevTeX 4, Submitted to Mol. Phy
A Survey of Proper Motion Stars. XVII. A Deficiency of Binary Stars on Retrograde Galactic Orbits and the Possibility that omega Centauri is Related to the Effect
We find a deficiency of binary stars moving on strongly retrograde Galactic
orbits. No binary deficiencies are seen for U or W velocities, however. From
theoretical analyses, we rule out preferential disruption of pre-existing
binary stars due to encounters with massive perturbers. We also rule out
globular clusters as the source of the effect since prograde motions are more
likely to create such an effect. We search for star streams and find one
possible candidate, but it is not on a retrograde orbit and probably represents
the remains of a cluster that has passed too near the Galactic center. Based on
a very small number of stars, we find that about the right fraction of stars on
retrograde Galactic orbits share some chemical similarities to the cluster
omega Cen, suggesting that its parent galaxy could be the explanation.Comment: To appear in the Astronomical Journal (March 2005 issue
The Origin of Iddingsite Veins in Olivine from the Nakhlite Meteorites:New Insights from Analogy with CM Carbonaceous Chondrites and Terrestrial Basalts
The nakhlite meteorites are samples
of a ~1300 million year old martian clinopyroxenite
lava flow or sill [1, 2]. These rocks contain secondary
minerals including hydrous silicates, carbonates, sulphates
and Fe-(hydr)oxides that formed by watermediated
alteration of the igneous body [3, 4]. A prerequisite
for understanding the nature of the aqueous
system from which these minerals formed, including
water/rock ratio, the provenance of solutes and its longevity,
is knowing whether the secondary minerals
formed by replacement of primary igneous components
(minerals and glasses), or by cementation of pores that
were opened by fracturing. A replacive origin would
suggest low water/rock ratios with solutions being
close to saturation with respect to secondary minerals,
and does not require a pre-existing network of pores
for fluids to gain access to mineral grain interiors. An
origin by cementation would suggest that solutes had
been sourced by dissolution of other parts of the
nakhlite parent rock or the martian crust and were introduced
by fluid flow under relatively high water/rock
ratio conditions; a means of fracturing the rock is also
required.<p></p>
Here we have sought to answer the question of
whether olivine-hosted veins in the nakhlites formed by
cementation or replacement by comparing the microstructures
of veins in the nakhlite Lafayette with veins
in olivine grains from type I chondrules in Murchison
(CM2 carbonaceous chondrite). We also draw on previously
published work on ‘iddingsite’ veins in olivine
from terrestrial basalts.<p></p>
Prevalence and correlates of dementia and mild cognitive impairment classified with different versions of the modified Telephone Interview for Cognitive Status (TICS-m)
Objectives The modified Telephone Interview for Cognitive Status (TICS-m) is an efficient and cost-effective screening instrument of dementia, but there is less support for its utility in the detection of mild cognitive impairment (MCI). We undertook a comprehensive evaluation of the utility of different TICS-m versions with or without an education-adjusted scoring method to classify dementia and MCI in a large population-based sample. Methods Cross-sectional assessment of cognition (TICS-m), depressive symptoms (CES-D), and apolipoprotein E (APOE) epsilon 4 status was performed on 1772 older adults (aged 71-78 y, education 5-16 y, 50% female) from the population-based older Finnish Twin Cohort. TICS-m classification methods with and without education adjustment were used to classify individuals with normal cognition, MCI, or dementia. Results The prevalence of dementia and MCI varied between education-adjusted (dementia = 3.7%, MCI = 9.3%) and unadjusted classifications (dementia = 8.5%-11%, MCI = 22.3%-41.3%). APOE epsilon 4 status was associated with dementia irrespective of education adjustment, but with MCI only when education adjustment was used. Regardless of the version, poorer continuous TICS-m scores were associated with higher age, lower education, more depressive symptoms, male sex, and being an APOE epsilon 4 carrier. Conclusions We showed that demographic factors, APOE epsilon 4 status, and depressive symptoms were similarly related to continuous TICS-m scores and dementia classifications with different versions. However, education-adjusted classification resulted in a lower prevalence of dementia and MCI and in a higher proportion of APOE epsilon 4 allele carriers among those identified as having MCI. Our results support the use of education-adjusted classification especially in the context of MCI.Peer reviewe
Accuracy of Imputation for Apolipoprotein E epsilon Alleles in Genome-Wide Genotyping Data
This diagnostic study evaluates the association of reference panels with imputation quality for 2 single-nucleotide polymorphisms located on the apolipoprotein E (APOE) gene.Non peer reviewe
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