The dimeric form of the single-molecule magnet [Mn4O3Cl4(O2CEt)3(py)3]2 recently revealed interesting phenomena: no quantum tunneling at zero field and tunneling before magnetic field reversal. This is attributed to substantial antiferromagnetic exchange interaction between different monomers. The intermolecular exchange interaction, electronic structure and magnetic properties of this molecular magnet are calculated using density-functional theory within generalized-gradient approximation. Calculations are in good agreement with experiment.
The electronic structure, vibrational spectra, and thermodynamic stability of CCCN and HCCCN have been determined using ab initio molecular orbital theory. The heat of formation for HCCCN was determined using Gaussian-2 theory (G2) and was found to be 91.5±2 kcal mol−1. There is good agreement between the G2 value and that determined using an isodesmic reaction (i.e., one in which both the number and types of bonds are conserved), which yields 90.7±2 kcal mol−1. The heat of formation for the CCCN radical is 178.2±2 kcal mol−1. These data are used to compute the bond dissociation energies in HCCCN, D0(C–C) and D0(C–H), which are important in assessing the chemistry in Titan’s atmosphere, as well as in other interstellar media.
%'e demonstrate that both the empirical pseudopotential method (EPM) and the linear combination of atomiclike orbitals (LCAO) approach are capable of producing consistent electronic charge distributions in a compound semiconductor. Since the EPM approach is known to produce total valence electron charge densities which compare well with experimental x-ray data (e.g. , Si), this work serves as a further test for the LCAO method. In particular, the EPM scheme, which uses an extended plane-wave basis, and the LCAO scheme, which employs a localized Gaussian basis, are used, with the same empirical potential as input, to analyze both the total valence electron charge density and the charge density of the first conduction band at the I, L, and X k. points of the Brillouin zone. These charge densities are decomposed into their s-, p-, and d-orbital contributions, and this information is used to interpret the differences in the topologies of the conduction bands at I, L, and X. Such differences are crucial for a comprehensive understanding of interstitial impurities and the response of specific band states to perturbations in compound semiconductors.
We investigated the use of termite baiting, a proven system of targeted colony elimination, in an overall area-wide control strategy against subterranean termites. At two field sites, we used microsatellite markers to estimate the total number of Reticulitermes colonies, their spatial partitioning, and breeding structure. Termite pressure was recorded for two years before and after the introduction of Trelona® (active ingredient novaluron) to a large area of one of the sites. Roughly 70% of the colonies in the treatment site that were present at the time of baiting were not found in the site within two months after the introduction of novaluron. Feeding activity of the remaining colonies subsequently ceased over time and new invading colonies were unable to establish within this site. Our study provides novel field data on the efficacy of novaluron in colony elimination of Reticulitermes flavipes, as well as evidence that an area-wide baiting program is feasible to maintain a termite-free area within its native range.
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