Suppression of vortex channeling in meandered YBa2Cu3O7-d grain boundaries

We report on the in-plane magnetic field (H) dependence of the critical current density (Jc) in meandered and planar single grain boundaries (GBs) isolated in YBa2Cu3O7-d (YBCO) coated conductors. The Jc(H)properties of the planar GB are consistent with those previously seen in single GBs of YBCO films grown on SrTiO3 bi-crystals. In the straight boundary a characteristic flux channeling regime when H is oriented near the GB plane, associated with a reduced Jc, is seen. The meandered GB does not show vortex channeling since it is not possible for a sufficient length of vortex line to lie within it.Comment: Submitted to AP

Bloch oscillations of Bose-Einstein condensates: Breakdown and revival

We investigate the dynamics of Bose-Einstein condensates (BEC) in a tilted one-dimensional periodic lattice within the mean-field (Gross-Pitaevskii) description. Unlike in the linear case the Bloch oscillations decay because of nonlinear dephasing. Pronounced revival phenomena are observed. These are analyzed in detail in terms of a simple integrable model constructed by an expansion in Wannier-Stark resonance states. We also briefly discuss the pulsed output of such systems for stronger static fields.Comment: RevTeX4, 9 pages, 14 figure

The mechanisms of arsenic bioremediation from water by the green microalgae Chlorella vulgaris

The presence of arsenic (As) in drinking water is a major global public health issue. Chlorella vulgaris (C.vulgaris) is a common green alga that tolerates high levels of As. Focused sonication was used to extract previously unidentified As-GS/PC complexes from C. vulgaris and their integrity was confirmed by HPLC online with simultaneous HR-ICP-MS and ES-MS/MS detection. The response of C. vulgaris when challenged with As(III), As(V) and dimethylarsinic acid (DMA) was assessed through experiments on toxicity, adsorption, efflux, speciation of arsenic (reduction, oxidation and chelation with GSH/PC) and compartmentalisation (flow cytometry). C. vulgaris cells did not produce any As-GS/PC complexes when exposed to As(V) which may indicate that a reduction step is needed for As(V) complexation with GSH/PC. Cells formed DMASV-GS upon exposure to DMA, but this is not part of a detoxification mechanism. It was found that As(III) triggers the formation of arsenic complexes with PC and homophytochelatins (hPC) and their compartmentalisation in vacuoles. The potential of C. vulgaris to bio-remediate arsenic from water is highly selective for the more toxic As(III) (for human life) without the potential hazard to reduce As(V) to As(III)

Enhanced determination of As-phytochelatin complexes in Chlorella vulgaris using focused sonication for extraction of water-soluble species

The most challenging areas in the analysis of As–GS/PC complexes are their extraction from small amounts of biological material and the maintenance of their stability during HPLC separation. Focused sonication was used to extract these complexes from Chlorella vulgaris and the integrity of such complexes was determined by HPLC online with simultaneous HR-ICP-MS and ES-MS/MS detection. Water soluble arsenic species were extracted with an improved 71.1% (SE 0.78) efficiency and much reduced extraction times (30 s) allowing the determination of unstable arsenic phytochelatin (PC) and glutathione (GS) species in small biomass making the method particularly well-suited for cell cultures. Here, it was found that C. vulgaris produces the following intact phytochelatins and homo-phytochelatins (with Ala and desGly instead of Gly) complexes when cells are exposed to As(III): As(III)–PC2, GS–As(III)–PC2, As(III)–(PC2)2, MMA(III)–PC2, As(III)–PC3, As(III)–PC4, As(III)–γ-(Glu–Cys)3–Ala, GS–As(III)–γ-(Glu–Cys)2–Ala, As(III)–γ-((Glu–Cys)2)2–Ala, MMA(III)–γ-(Glu–Cys)2–Ala, As(III)–γ-(Glu–Cys)2, GS–As(III)–γ-(Glu–Cys)2. When the alga was exposed to DMA, only DMASV–GS was found. In contrast, cells did not produce any complex when exposed to As(V). It is the first time that, as a result of the newly developed extraction method using sonication, such complexes have been identified in Chlorella vulgaris exposed to arsenic and their intact arsenic homo-phytochelatins have been reported in any organism

Creation of ventricular septal defects on the beating heart in a new pig model

Background/ Aims: So far, surgical and interventional therapies for muscular ventricular septal defects ( mVSDs) beyond the moderator band have had their limitations. Thus, alternative therapeutic strategies should be developed. We present a new animal model for the evaluation of such strategies. Methods: In a pig model ( n = 9), anterolateral thoracotomy was performed for exposure of the left ventricle. mVSDs were created under two- and three- dimensional echocardiography with a 7.5- mm sharp punch instrument, which was forwarded via a left ventricular puncture without extracorporeal circulation. Results: Creation of mVSDs was successful in all animals ( n = 9) confirmed by echocardiography, hemodynamic measurements and autopsy. The defects were located in the midmuscular ( n = 4), apical ( n = 1), inlet ( n = 2) and anterior part ( n = 2) of the muscular septum. All animals were hemodynamically stable for further procedures. The diameter and shunt volume of the mVSDs were 4.8 - 7.3 mm ( mean: 5.9 mm) and 12.9 - 41.3% ( mean: 22.1%), respectively. Autopsy confirmed in all animals the creation of a substantial defect. Conclusion: The described new technique for creation of an mVSD on the beating heart in a pig model is suitable for the evaluation of new therapeutic strategies for mVSD closure. Copyright (C) 2008 S. Karger AG, Basel

Selforganized 3-band structure of the doped fermionic Ising spin glass

The fermionic Ising spin glass is analyzed for arbitrary filling and for all temperatures. A selforganized 3-band structure of the model is obtained in the magnetically ordered phase. Deviation from half filling generates a central nonmagnetic band, which becomes sharply separated at T=0 by (pseudo)gaps from upper and lower magnetic bands. Replica symmetry breaking effects are derived for several observables and correlations. They determine the shape of the 3-band DoS, and, for given chemical potential, influence the fermion filling strongly in the low temperature regime.Comment: 13 page

The mechanisms of detoxification of As(III), dimethylarsinic acid (DMA) and As(V) in the microalga Chlorella vulgaris

The response of Chlorella vulgaris when challenged by As(III), As(V) and dimethylarsinic acid (DMA) was assessed through experiments on adsorption, efflux and speciation of arsenic (reduction, oxidation, methylation and chelation with glutathione/phytochelatin [GSH/PC]). Our study indicates that at high concentrations of phosphate (1.62 mM of HPO42−), upon exposure to As(V), cells are able to shift towards methylation of As(V) rather than PC formation. Treatment with As(V) caused a moderate decrease in intracellular pH and a strong increase in the concentration of free thiols (GSH). Passive surface adsorption was found to be negligible for living cells exposed to DMA and As(V). However, adsorption of As(III) was observed to be an active process in C. vulgaris, because it did not show saturation at any of the exposure periods. Chelation of As(III) with GS/PC and to a lesser extent hGS/hPC is a major detoxification mechanism employed by C. vulgaris cells when exposed to As(III). The increase of bound As-GS/PC complexes was found to be strongly related to an increase in concentration of As(III) in media. C. vulgaris cells did not produce any As-GS/PC complex when exposed to As(V). This may indicate that a reduction step is needed for As(V) complexation with GSH/PC. C. vulgaris cells formed DMASV-GS upon exposure to DMA independent of the exposure period. As(III) triggers the formation of arsenic complexes with PC and homophytochelatins (hPC) and their compartmentalisation to vacuoles. A conceptual model was devised to explain the mechanisms involving ABCC1/2 transport. The potential of C. vulgaris to bio-remediate arsenic from water appeared to be highly selective and effective without the potential hazard of reducing As(V) to As(III), which is more toxic to humans