No abstract

The relation between semiclassical and density-functional approximations is clarified. Semiclassical approximations both explain and improve upon density-gradient expansions for finite systems. We derive highly accurate density and kinetic energy functionals of the potential in one dimension.

Most approximate density functionals do not bind small atomic anions because of large self-interaction errors. Yet atomic electron affinities are often calculated using finite basis sets with surprisingly good results, despite positive highest occupied molecular orbital (HOMO) energies. We show that excellent results (better than for ionization potentials) can be obtained using standard approximate functionals evaluated on Hartree−Fock or exact-exchange densities for which the extra electron is bound. Although these good results found with limited basis sets are not accidental, we argue that this method cannot be used in general. Thus a positive HOMO indicates that the total energy should not be disregarded, only treated with caution.

We study the asymptotic expansion of the neutral-atom energy as the atomic number Z → ∞, presenting a new method to extract the coefficients from oscillating numerical data. We find that recovery of the correct expansion is an exact condition on the Kohn-Sham kinetic energy that is important for the accuracy of approximate kinetic energy functionals for atoms, molecules and solids, when evaluated on a Kohn-Sham density. For example, this determines the small gradient limit of any generalized gradient approximation, and conflicts somewhat with the standard gradient expansion. Tests are performed on atoms, molecules, and jellium clusters. We also give a modern, highly accurate parametrization of the Thomas-Fermi density of neutral atoms.

Bio-based polymer materials from renewable resources have recently become a growing research focus. Herein, a novel thermoplastic elastomer is developed via controlled/living radical polymerization of plant-derived itaconic acid derivatives, which are some of the most abundant renewable acrylic monomers obtained via the fermentation of starch. The reversible addition-fragmentation chain-transfer (RAFT) polymerizations of itaconic acid imides, such as N-phenylitaconimide and N-(p-tolyl)itaconimide, and itaconic acid esters, such as di-n-butyl itaconate and bis(2-ethylhexyl) itaconate, are examined using a series of RAFT agents to afford well-defined polymers. The number-average molecular weights of these polymers increase with the monomer conversion while retaining relatively narrow molecular weight distributions. Based on the successful controlled/living polymerization, sequential block copolymerization is subsequently investigated using mono- and di-functional RAFT agents to produce block copolymers with soft poly(itaconate) and hard poly(itaconimide) segments. The properties of the obtained triblock copolymer are evaluated as bio-based acrylic thermoplastic elastomers.

For the kinetic energy of 1d model finite systems the leading corrections to local approximations as a functional of the potential are derived using semiclassical methods. The corrections are simple, non-local functionals of the potential. Turning points produce quantum oscillations leading to energy corrections, which are completely different from the gradient corrections that occur in bulk systems with slowly-varying densities. Approximations that include quantum corrections are typically much more accurate than their local analogs. The consequences for density functional theory are discussed

Interruption of the inferior vena cava (IVC) with azygos continuation is an uncommon vascular anomaly that results from aberrant development during embryogenesis. We report a rare case of this anomaly, presenting with massive pulmonary embolism. Subsequent evaluation with abdominal CT scan revealed the congenital absence of retrohepatic IVC. The patient was successfully treated with anticoagulation. When deep venous thrombosis (DVT) develops in patients with no apparent risk factors, the presence of congenital IVC anomalies should be considered.

These results suggest that immediate catheter removal (i.e., within 24 hours after the diagnosis of FP) is mandatory in PD patients with FP.