Orbital contribution to the magnetic properties of nanowires: Is the orbital polarization ansatz justified?

We show that considerable orbital magnetic moments and magneto-crystalline anisotropy energies are obtained for a Fe monatomic wire described in a tight-binding method with intra-atomic electronic interactions treated in a full Hartree Fock (HF) decoupling scheme. Even-though the use of the orbital polarization ansatz with simplified Hamiltonians leads to fairly good results when the spin magnetization is saturated this is not the case of unsaturated systems. We conclude that the full HF scheme is necessary to investigate low dimensional systems

Entanglement and transport through correlated quantum dot

We study quantum entanglement in a single-level quantum dot in the linear-response regime. The results show, that the maximal quantum value of the conductance 2e^2/h not always match the maximal entanglement. The pairwise entanglement between the quantum dot and the nearest atom of the lead is also analyzed by utilizing the Wootters formula for charge and spin degrees of freedom separately. The coexistence of zero concurrence and the maximal conductance is observed for low values of the dot-lead hybridization. Moreover, the pairwise concurrence vanish simultaneously for charge and spin degrees of freedom, when the Kondo resonance is present in the system. The values of a Kondo temperature, corresponding to the zero-concurrence boundary, are also provided.Comment: Presented on the International Conference "Nanoelectronics '06", 7-8 January 2006, Lancaster, U

Nancy Bukey

36-1Private Land ClaimsOn the relief of N. Bukey. [1069] Indian wars in 1790 or 1792.1860-10

Giant Anisotropic Magneto-Resistance in ferromagnetic atomic contacts

Magneto-resistance is a physical effect of great fundamental and industrial interest since it is the basis for the magnetic field sensors used in computer read-heads and Magnetic Random Access Memories. As device dimensions are reduced, some important physical length scales for magnetism and electrical transport will soon be attained. Ultimately, there is a strong need to know if the physical phenomena responsible for magneto-resistance still hold at the atomic scale. Here, we show that the anisotropy of magneto-resistance is greatly enhanced in atomic size constrictions. We explain this physical effect by a change in the electronic density of states in the junction when the magnetization is rotated, as supported by our ab-initio calculations. This stems from the "spin-orbit coupling" mechanism linking the shape of the orbitals with the spin direction. This sensitively affects the conductance of atomic contacts which is determined by the overlap of the valence orbitals.Comment: latex AAMR.tex, 6 files, 5 figures, 4 pages (http://www-drecam.cea.fr/spec/articles/S06/011

Nitrogen nutrient status induces sexual differences in responses to cadmium in Populus yunnanensis

Populus yunnanensis was employed as a model species to detect sexual differences in growth, physiological, biochemical, and ultrastructural responses to cadmium (Cd) stress, nitrogen (N) deposition, and their combination. Compared with the control conditions, Cd decreased plant biomass, damaged the photosynthetic apparatus, visible as a decreased maximum efficiency of photosystem II (PSII; Fv/Fm) and effective quantum yield of PSII (Yield), depressed gas exchange capacity, and induced oxidative stress, visible as the disruption of antioxidative enzymes and accumulation of reactive oxygen species (ROS), in both sexes. On the other hand, Cd toxicity was mitigated by the recovery of gas exchange capacity, a decrease in ROS, and improvement of the redox imbalance in both sexes when N deposition was applied. However, males showed a higher gas exchange capacity, lower enzyme inhibition and ROS accumulation, stronger abilities to maintain cellular redox homeostasis, and a better maintenance of chloroplast ultrastructure than did females when exposed to Cd stress alone. Although males exhibited a higher Cd content in leaves than did females, males also accumulated higher levels of non-protein thiols (NP-SHs) and free amino acids (FAAs) for detoxification than did females. Sexual differences induced by Cd, visible, for example, in Fv/Fm, Yield, net photosynthesis rate (A), and stomatal conductance (gs), decreased under N deposition, as no significant differences between the sexes existed in these parameters under the combined treatment. The results indicated that females are more sensitive to Cd stress and suffer more injuries than do males. Moreover, N deposition can mitigate Cd toxicity and decrease sexual differences in Cd sensitivity

Ardisinones A-E, novel diarylundecanones from Ardisia arborescens

A phytochemical study on an ethanol extract of Ardisia arborescens resulted in the isolation of five new diarylundecanones, named ardisinones A-E (1-5). The structures were established by HRESIMS and NMR (H-1, C-13, DEPT, HSQC, HMBC) as 11-(2-acetoxy-6-hydroxyphenyl)-1-(2,4,6-trihydroxyphenyl)undecan-1-one (1), 11-(2-acetoxy-6-hydroxyphenyl)-1-(2,6-dihydroxy-4-methoxyphenyl)undecan- 1-one (2), 1-(2,6-dihydroxy-4-methoxyphenyl)-11-(2,6-dihydroxyphenyl)undecan-1-one (3), 1-(2,4,6-trihydroxyphenyl)-11-(2,6-dihydroxyphenyl)undecan-1-one (4), and 1-(2,4,6-trihydroxyphenyl)-11-(2-hydroxyphenyl)undecan-1-one (5). In our in vitro disk diffusion assay, compounds 1 and 4 showed some slight inhibition of three bacteria, while 2 and 3 did not show antimicrobial activity