Polar surface engineering in ultra-thin MgO(111)/Ag(111) -- possibility of metal-insulator transition and magnetism

A recent report [Kiguchi {\it et al.}, Phys. Rev. B {\bf 68}, 115402 (2003)] that the (111) surface of 5 MgO layers grown epitaxially on Ag(111) becomes metallic to reduce the electric dipole moment raises a question of what will happen when we have fewer MgO layers. Here we have revealed, first experimentally with electron energy-loss spectroscopy, that MgO(111) remains metallic even when one-layer thick, and theoretically with the density functional theory that the metallization should depend on the nature of the substrate. We further show, with a spin-density functional calculation, that a ferromagnetic instability may be expected for thicker films.Comment: 5 pages, 7 figure

Signatures of the excitonic memory effects in four-wave mixing processes in cavity polaritons

We report the signatures of the exciton correlation effects with finite memory time in frequency domain degenerate four-wave mixing (DFWM) in semiconductor microcavity. By utilizing the polarization selection rules, we discriminate instantaneous, mean field interactions between excitons with the same spins, long-living correlation due to the formation of biexciton state by excitons with opposite spins, and short-memory correlation effects in the continuum of unbound two-exciton states. The DFWM spectra give us the relative contributions of these effects and the upper limit for the time of the exciton-exciton correlation in the unbound two-exciton continuum. The obtained results reveal the basis of the cavity polariton scattering model for the DFWM processes in high-Q GaAs microcavity.Comment: 11 pages, 1 figur

Micronucleus formation induced by biomass burning particles derived from biomass burning induce high micronucleus frequency in Tradescantia pallida assay (TRAD-MN)

Manual harvesting is usually done after to sugar cane burning which is responsible for seasonal emission of air pollutants in Brazil and it is believed to be responsible for deleterious health effects in exposed populations. The mutagenic potential of sugar cane burning harvesting particulate and particle surrogates of residual oil fly ash (ROFA) were evaluated in assays measuring micronuclei (MN) in the pollen mother cells of Tradescantia pallida (TRAD-MN). Micronuclei frequencies in TRAD-MN to sugar cane burning residues (SCBR) at doses 0.3 and 0.03 mg/mL were respectively 2.18 ± 0.35 and 5.53 ± 1.04, whereas to ROFA from incinerator and ROFA from an electrostatic precipitator installed in one of the chimneys of a steel plant, MN frequencies were, respectively, 3.43 ± 0.7 and 4.90 ± 1.07. Significant differences were detected among the groups (p < 0.001), demonstrating that SCBR was at least as genotoxic as the fossil fuel derived particles. The results suggest that the burning process to harvest sugar cane should be better controlled. Keywords: pollution, burning particles, micronuclei, Tradescantia pallida . Partículas derivadas da queima de biomassa induzem alta frequência de micronúcleos no ensaio de Tradescantia pallida (TRAD-MN) Resumo A coleta de cana-de-açúcar manual é geralmente realizada após a queima, a qual é responsável pela emissão sazonal de poluentes atmosféricos no Brasil e acredita-se que este seja responsável pelos efeitos deletérios a saúde da população exposta. O potencial mutagênico da queima de cana-de-açúcar e partículas oriundas de resíduos em cinza de óleo queimado (ROFA) foi avaliado em ensaio que mede a freqüência de micronúcleos (MN) em células mãe de grão de pólen de Tradescantia pallida (TRAD-MN). A freqüência de TRAD-MN em resíduos de queima de cana de açúcar (SCBR) nas doses de 0.3 e 0,03mg/mL foi, respectivamente de 2,18 ± 0,35 e 5,53 ± 1,04, enquanto para ROFA de incinerador e ROFA de um precipitador eletrostático instalado em uma chaminé de uma indústria siderúrgica, a freqüência de MN foi, respectivamente, 3,43 ± 0,7 e 4,90 ± 1,07. Diferença significante foi observada entre os grupos (p<0,001), demonstrando que SCBR foi ao menos tão genotóxico quanto às partículas derivadas de combustíveis fósseis. Os resultados sugerem que o processo de queima de cana-de-açúcar no período da safra deveria ser mais bem controlado. Palavras-Chave: poluição, partículas de queimadas, micronúcleos, Tradescantia pallida

Nuclear spin qubits in a pseudo-spin quantum chain

We analyze a quantum computer (QC) design based on nuclear spin qubits in a quasi-one-dimensional (1D) chain of non-Kramers doublet atoms. We explore the use of spatial symmetry breaking to obtain control over the local dynamics of a qubit. We also study the decoherence mechanisms at the single qubit level and the interactions mediated by the magnetic media. The design can be realized in $\textrm{PrBr}_{\textrm{3}-x}\textrm{F}_{x}$ with nuclear magnetic resonance (NMR) techniques.Comment: 7 pages, 3 figure

Surgical repair for aortic dissection accompanying a right-sided aortic arch

Aortic anomaly in which a right-sided aortic arch associated with Kommerell's diverticulum and aberrant left subclavian artery is rare. The present report describes a patient with type-B aortic dissection accompanying aortic anomalies consisting of right-sided aortic arch and the left common carotid and left subclavian artery arising from Kommerell's diverticulum. As dissecting aortic aneurysm diameter increased rapidly, Single-stage surgical repair of extensive thoracic aorta was performed through median sternotomy and right posterolateral fifth intercostal thoracotomy, yielding favorable results. Our surgical procedures are discussed

Distribution of particulate matter and tissue remodeling in the human lung.

We examined the relationship between intrapulmonary particle distribution of carbonaceous and mineral dusts and remodeling of the airways along anatomically distinct airway paths in the lungs of Hispanic males from the central valley of California. Lung autopsy specimens from the Fresno County Coroner's Office were prepared by intratracheal instillation of 2% glutaraldehyde at 30 cm H(2)O pressure. Two distinct airway paths into the apico-posterior and apico-anterior portions of the left upper lung lobe were followed. Tissue samples for histologic analysis were generally taken from the intrapulmonary second, fourth, sixth, and ninth airway generations. Parenchymal tissues beyond the 12th airway generation of each airway path were also analyzed. There was little evidence of visible particle accumulation in the larger conducting airways (generations 2-6), except in bronchial-associated lymphoid tissues and within peribronchial connective tissue. In contrast, terminal and respiratory bronchioles arising from each pathway revealed varying degrees of wall thickening and remodeling. Walls with marked thickening contained moderate to heavy amounts of carbonaceous and mineral dusts. Wall thickening was associated with increases in collagen and interstitial inflammatory cells, including dust-laden macrophages. These changes were significantly greater in first-generation respiratory bronchioles compared to second- and third-generation respiratory bronchioles. These findings suggest that accumulation of carbonaceous and mineral dust in the lungs is significantly affected by lung anatomy with the greatest retention in centers of lung acini. Furthermore, there is significant remodeling of this transitional zone in humans exposed to ambient particulate matter