Electronic structure of crystalline binary and ternary Cd-Te-O compounds

The electronic structure of crystalline CdTe, CdO, $\alpha$-TeO$_2$, CdTeO$_3$ and Cd$_3$TeO$_6$ is studied by means of first principles calculations. The band structure, total and partial density of states, and charge densities are presented. For $\alpha$-TeO$_2$ and CdTeO$_3$, Density Functional Theory within the Local Density Approximation (LDA) correctly describes the insulating character of these compounds. In the first four compounds, LDA underestimates the optical bandgap by roughly 1 eV. Based on this trend, we predict an optical bandgap of 1.7 eV for Cd$_3$TeO$_6$. This material shows an isolated conduction band with a low effective mass, thus explaining its semiconducting character observed recently. In all these oxides, the top valence bands are formed mainly from the O 2p electrons. On the other hand, the binding energy of the Cd 4d band, relative to the valence band maximum, in the ternary compounds is smaller than in CdTe and CdO.Comment: 13 pages, 15 figures, 2 tables. Accepted in Phys Rev

GaN and InN nanowires grown by MBE: a comparison

Morphological, optical and transport properties of GaN and InN nanowires grown by molecular beam epitaxy (MBE) have been studied. The differences between the two materials in respect to growth parameters and optimization procedure was stressed. The nanowires crystalline quality has been investigated by means of their optical properties. A comparison of the transport characteristics was given. For each material a band schema was shown, which takes into account transport and optical features and is based on Fermi level pinning at the surface.Comment: 5 pages, 5 figure

Toward a first-principles integrated simulation of tokamak edge plasmas

Performance of the ITER is anticipated to be highly sensitive to the edge plasma condition. The edge pedestal in ITER needs to be predicted from an integrated simulation of the necessary first-principles, multi-scale physics codes. The mission of the SciDAC Fusion Simulation Project (FSP) Prototype Center for Plasma Edge Simulation (CPES) is to deliver such a code integration framework by (1) building new kinetic codes XGC0 and XGC1, which can simulate the edge pedestal buildup; (2) using and improving the existing MHD codes ELITE, M3D-OMP, M3D-MPP and NIMROD, for study of large-scale edge instabilities called Edge Localized Modes (ELMs); and (3) integrating the codes into a framework using cutting-edge computer science technology. Collaborative effort among physics, computer science, and applied mathematics within CPES has created the first working version of the End-to-end Framework for Fusion Integrated Simulation (EFFIS), which can be used to study the pedestal-ELM cycles

Two-dimensional turbulence in magnetised plasmas

In an inhomogeneous magnetised plasma the transport of energy and particles perpendicular to the magnetic field is in general mainly caused by quasi two-dimensional turbulent fluid mixing. The physics of turbulence and structure formation is of ubiquitous importance to every magnetically confined laboratory plasma for experimental or industrial application. Specifically, high temperature plasmas for fusion energy research are also dominated by the properties of this turbulent transport. Self-organisation of turbulent vortices to mesoscopic structures like zonal flows is related to the formation of transport barriers that can significantly enhance the confinement of a fusion plasma. This subject of great importance in research is rarely touched on in introductory plasma physics or continuum dynamics courses. Here a brief tutorial on 2D fluid and plasma turbulence is presented as an introduction to the field, appropriate for inclusion in undergraduate and graduate courses.Comment: This is an author-created, un-copyedited version of an article published in European Journal of Physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher authenticated version is available online at doi: 10.1088/0143-0807/29/5/00

Benefits and risks of the hormetic effects of dietary isothiocyanates on cancer prevention

The isothiocyanate (ITC) sulforaphane (SFN) was shown at low levels (1-5 µM) to promote cell proliferation to 120-143% of the controls in a number of human cell lines, whilst at high levels (10-40 µM) it inhibited such cell proliferation. Similar dose responses were observed for cell migration, i.e. SFN at 2.5 µM increased cell migration in bladder cancer T24 cells to 128% whilst high levels inhibited cell migration. This hormetic action was also found in an angiogenesis assay where SFN at 2.5 µM promoted endothelial tube formation (118% of the control), whereas at 10-20 µM it caused significant inhibition. The precise mechanism by which SFN influences promotion of cell growth and migration is not known, but probably involves activation of autophagy since an autophagy inhibitor, 3-methyladenine, abolished the effect of SFN on cell migration. Moreover, low doses of SFN offered a protective effect against free-radical mediated cell death, an effect that was enhanced by co-treatment with selenium. These results suggest that SFN may either prevent or promote tumour cell growth depending on the dose and the nature of the target cells. In normal cells, the promotion of cell growth may be of benefit, but in transformed or cancer cells it may be an undesirable risk factor. In summary, ITCs have a biphasic effect on cell growth and migration. The benefits and risks of ITCs are not only determined by the doses, but are affected by interactions with Se and the measured endpoint

Depression and the vision-related quality of life in patients with retinitis pigmentosa

AIMS: To assess the relationship between depression and the vision-related quality of life in patients with retinitis pigmentosa (RP). METHODS: The study included 144 patients diagnosed as having RP. The mean age of the patients was 38.5 (SD 13.3) years, and 42% of the subjects were women. They answered the National Eye Institute Visual Function Questionnaire (NEI-VFQ) to assess the vision-related quality of life and the Beck Depression Inventory (BDI) to assess depressive symptoms. Patients were classified into groups with and without depression according to the BDI score. The NEI-VFQ composite and subscale scores were compared between groups. The correlations between the BDI and the NEI-VFQ, weighted visual acuity (WVA) and functional vision score (FVS) were investigated. RESULTS: The depressed group had significantly less subjective visual function compared with the non-depressed group. A negative correlation was observed between the BDI and the NEI-VFQ scores, while no correlation was found between the BDI score and WVA or FVS. CONCLUSION: The RP patients with depression had poorer vision-related functions compared with those patients without depression, which cannot be explained by the visual acuity. Interventions to diagnose and treat depression are necessary to enhance the overall quality of life in RP patients

Tumor Necrosis Factor-α and Muc2 Mucin Play Major Roles in Disease Onset and Progression in Dextran Sodium Sulphate-Induced Colitis

The sequential events and the inflammatory mediators that characterize disease onset and progression of ulcerative colitis (UC) are not well known. In this study, we evaluated the early pathologic events in the pathogenesis of colonic ulcers in rats treated with dextran sodium sulfate (DSS). Following a lag phase, day 5 of DSS treatment was found clinically most critical as disease activity index (DAI) exhibited an exponential rise with severe weight loss and rectal bleeding. Surprisingly, on days 1-2, colonic TNF-α expression (70-80-fold) and tissue protein (50-fold) were increased, whereas IL-1β only increased on days 7-9 (60-90-fold). Days 3-6 of DSS treatment were characterized by a prominent down regulation in the expression of regulatory cytokines (40-fold for IL-10 and TGFβ) and mucin genes (15-18 fold for Muc2 and Muc3) concomitant with depletion of goblet cell and adherent mucin. Remarkably, treatment with TNF-α neutralizing antibody markedly altered DSS injury with reduced DAI, restoration of the adherent and goblet cell mucin and IL-1β and mucin gene expression. We conclude that early onset colitis is dependent on TNF-α that preceded depletion of adherent and goblet cell mucin prior to epithelial cell damage and these biomarkers can be used as therapeutic targets for UC

Benzyl Isothiocyanate Causes FoxO1-Mediated Autophagic Death in Human Breast Cancer Cells

Benzyl isothiocyanate (BITC), a constituent of edible cruciferous vegetables, inhibits growth of breast cancer cells but the mechanisms underlying growth inhibitory effect of BITC are not fully understood. Here, we demonstrate that BITC treatment causes FoxO1-mediated autophagic death in cultured human breast cancer cells. The BITC-treated breast cancer cells (MDA-MB-231, MCF-7, MDA-MB-468, BT-474, and BRI-JM04) and MDA-MB-231 xenografts from BITC-treated mice exhibited several features characteristic of autophagy, including appearance of double-membrane vacuoles (transmission electron microscopy) and acidic vesicular organelles (acridine orange staining), cleavage of microtubule-associated protein 1 light chain 3 (LC3), and/or suppression of p62 (p62/SQSTM1 or sequestosome 1) expression. On the other hand, a normal human mammary epithelial cell line (MCF-10A) was resistant to BITC-induced autophagy. BITC-mediated inhibition of MDA-MB-231 and MCF-7 cell viability was partially but statistically significantly attenuated in the presence of autophagy inhibitors 3-methyl adenine and bafilomycin A1. Stable overexpression of Mn-superoxide dismutase, which was fully protective against apoptosis, conferred only partial protection against BITC-induced autophagy. BITC treatment decreased phosphorylation of mTOR and its downstream targets (P70s6k and 4E-BP1) in cultured MDA-MB-231 and MCF-7 cells and MDA-MB-231 xenografts, but activation of mTOR by transient overexpression of its positive regulator Rheb failed to confer protection against BITC-induced autophagy. Autophagy induction by BITC was associated with increased expression and acetylation of FoxO1. Furthermore, autophagy induction and cell growth inhibition resulting from BITC exposure were significantly attenuated by small interfering RNA knockdown of FoxO1. In conclusion, the present study provides novel insights into the molecular circuitry of BITC-induced cell death involving FoxO1-mediated autophagy

Size Scaling of Turbulent Transport in Magnetically Confined Plasmas

Transport scaling with respect to device size in magnetically confined plasmas is critically examined for electrostatic ion temperature gradient turbulence using global gyrokinetic particle simulations. It is found, by varying device size normalized by ion gyroradius while keeping other dimensionless plasma parameters fixed, that fluctuation scale length is microscopic in the presence of zonal flows. The local transport coefficient exhibits a gradual transition from a Bohm-like scaling for device sizes corresponding to present-day experiments to a gyro-Bohm scaling for future larger devices