Valence-band structures of layered oxychalcogenides, LaCuOCh (Ch=S, Se, and Te), studied by ultraviolet photoemission spectroscopy and energy-band calculations

To examine the electronic structure of the valence band, ultraviolet photoemission spectra of a series of layered oxychalcogenides, LaCuOCh (Ch=S, Se, and Te), were measured. The measurements were conducted using He II, He I, and Ne I excitation lines to observe the excitation energy dependence of the spectral shape. Energy-band calculations based on a full-potential linearized augmented plain-wave method were performed. The calculated density of states and partial density of states were compared to the observed photoemission spectra. Five bands were observed in the valence band of LaCuOCh, and Ne I radiation remarkably enhanced two of them. The energy dependence of the photoionization cross section of atomic orbitals indicated that the two enhanced bands were due to the Ch p states. Energy calculations were used to assign the remaining bands. The electronic structure of LaCuOCh was further discussed using molecular-orbital diagrams to visualize the (La2O2)2+ and (Cu2Ch2)2– layers as large donor-acceptor pairs. The energy-band calculation and molecular-orbital diagram analyses suggested that the main difference among the valence-band structures of LaCuOCh (Ch=S, Se, and Te) originates from the variations in the energy position of the Ch p bands. The observed spectra are consistent with the results of the band calculations and clearly show the energy variations in the Ch p bands with respect to spectral shape and excitation energy dependence

MicroRNA-194 inhibits epithelial to mesenchymal transition of endometrial cancer cells by targeting oncogene BMI-1

<p>Abstract</p> <p>Background</p> <p>Epithelial-mesenchymal transition (EMT) is the key process driving cancer metastasis. Oncogene/self renewal factor BMI-1 has been shown to induce EMT in cancer cells. Recent studies have implied that noncoding microRNAs (miRNAs) act as crucial modulators for EMT. The aims of this study was to determine the roles of BMI-1 in inducing EMT of endometrial cancer (EC) cells and the possible role of miRNA in controlling BMI-1 expression.</p> <p>Methods and results</p> <p>We evaluated the expression of BMI-1 gene in a panel of EC cell lines, and detected a strong association with invasive capability. Stable silencing of BMI-1 in invasive mesenchymal-type EC cells up-regulated the epithelial marker E-cadherin, down-regulated mesenchymal marker Vimentin, and significantly reduced cell invasion <it>in vitro</it>. Furthermore, we discovered that the expression of BMI-1 was suppressed by miR-194 via direct binding to the BMI-1 3'-untranslated region 3'-UTR). Ectopic expression of miR-194 in EC cells induced a mesenchymal to epithelial transition (MET) by restoring E-cadherin, reducing Vimentin expression, and inhibiting cell invasion <it>in vitro</it>. Moreover, BMI-1 knockdown inhibited <it>in vitro </it>EC cell proliferation and clone growth, correlated with either increased p16 expression or decreased expression of stem cell and chemoresistance markers (SOX-2, KLF4 and MRP-1).</p> <p>Conclusion</p> <p>These findings demonstrate the novel mechanism for BMI-1 in contributing to EC cell invasion and that repression of BMI-1 by miR-194 could have a therapeutic potential to suppress EC metastasis.</p

All-electron GW calculation based on the LAPW method: application to wurtzite ZnO

We present a new, all-electron implementation of the GW approximation and apply it to wurtzite ZnO. Eigenfunctions computed in the local-density approximation (LDA) by the full-potential linearized augmented-plane-wave (LAPW) or the linearized muffin-tin-orbital (LMTO) method supply the input for generating the Green function G and the screened Coulomb interaction W. A mixed basis is used for the expansion of W, consisting of plane waves in the interstitial region and augmented-wavefunction products in the augmentation-sphere regions. The frequency-dependence of the dielectric function is computed within the random-phase approximation (RPA), without a plasmon-pole approximation. The Zn 3d orbitals are treated as valence states within the LDA; both core and valence states are included in the self-energy calculation. The calculated bandgap is smaller than experiment by about 1eV, in contrast to previously reported GW results. Self-energy corrections are orbital-dependent, and push down the deep O 2s and Zn 3d levels by about 1eV relative to the LDA. The d level shifts closer to experiment but the size of shift is underestimated, suggesting that the RPA overscreens localized states.Comment: 10 pages, 3 figures, submitted to Phys. Rev.