Structural and Optical Characterization of ZnO/Mg_<i>x</i>Zn_1–<i>x</i>O Multiple Quantum Wells Based Random Laser Diodes

Two kinds of laser diodes (LDs) comprised of ZnO/Mg_<i>x</i>Zn_1–<i>x</i>O (ZnO/MZO) multiple quantum wells (MQWs) grown on GaN (MQWs/GaN) and Si (MQWs/Si) substrates, respectively, have been constructed. The LD with MQWs/GaN exhibits ultraviolet random lasing under electrical excitation, while that with MQWs/Si does not. In the MQWs/Si, ZnO/MZO MQWs consist of nanoscaled crystallites, and the MZO layers undergo a phase separation of cubic MgO and hexagonal ZnO. Moreover, the Mg atom predominantly locates in the MZO layers along with a significant aggregation at the ZnO/MZO interfaces; in sharp contrast, the ZnO/MZO MQWs in the MQWs/GaN show a well-crystallized structure with epitaxial relationships among GaN, MZO, and ZnO. Notably, Mg is observed to diffuse into the ZnO well layers. The structure–optical property relationship of these two LDs is further discussed

Origin of the High Performance in GeTe-Based Thermoelectric Materials upon Bi₂Te₃ Doping

As a lead-free material, GeTe has drawn growing attention in thermoelectrics, and a figure of merit (<i>ZT</i>) close to unity was previously obtained via traditional doping/alloying, largely through hole carrier concentration tuning. In this report, we show that a remarkably high <i>ZT</i> of ∼1.9 can be achieved at 773 K in Ge_0.87Pb_0.13Te upon the introduction of 3 mol % Bi₂Te₃. Bismuth telluride promotes the solubility of PbTe in the GeTe matrix, thus leading to a significantly reduced thermal conductivity. At the same time, it enhances the thermopower by activating a much higher fraction of charge transport from the highly degenerate Σ valence band, as evidenced by density functional theory calculations. These mechanisms are incorporated and discussed in a three-band (L + Σ + C) model and are found to explain the experimental results well. Analysis of the detailed microstructure (including rhombohedral twin structures) in Ge_0.87Pb_0.13Te + 3 mol % Bi₂Te₃ was carried out using transmission electron microscopy and crystallographic group theory. The complex microstructure explains the reduced lattice thermal conductivity and electrical conductivity as well

Expression levels of miR-200a and validation for stable miR-200a knockdown in WB cells.

<p>(A) QRT-PCR analysis of the relative miR-200a levels in WB cells and three hepatoma cells (H-4-II-E, CBRH-7919, RH-35) compared with the normal liver cell line BRL. (B) Validation of miR-200a levels in WB cells lentivirally transfected with miR-200a antagomir (WB-anti-miR-200a) or negative control (WB-miR-NC) by qRT-PCR analysis. (C and D) Functional evaluation of down-regulated miR-200a on its validated target ZEB2 in WB cells using qRT-PCR (C) and western blot analysis (D). For A and B, data are normalized to U6 and represented as the mean ± SD; n = 5; **, p<0.01. For C, data are normalized to β-actin and presented as the mean ± SD; n = 4.</p

Downregulation of miR-200a confers tumorigenicity to WB cells in vivo.

<p>(A) Subcutaneous tumors developed by WB-miR-NC or WB-anti-miR-200a for 40 days post inoculation (left). Pictures of collected subcutaneous tumors were taken (middle) and tumor weights are shown (right). (B) Representative images of H&E staining of xenografted tumors are shown (left, magnification×200; right, magnification×400).</p

Sequences of qRT-PCR primers used for mRNA analysis.

<p>Sequences of qRT-PCR primers used for mRNA analysis.</p

Stable knockdown of miR-200a facilitates CSC-like phenotypes in WB cells.

<p>(A) Growth curve of WB-miR-NC and WB-anti-miR-200a cells determined by cell counting. Data are expressed as the mean ± SD; n = 3; *, p<0.05. (B) Representative images of spheroids formed by WB-miR-NC and WB-anti-miR-200a cells in the spheroid formation assay (left, magnification×100). Number of spheroids formed in the primary, secondary and tertiary generations of suspension cultured WB-miR-NC or WB-anti-miR-200a cells (right). Data represent means from four randomly selected fields under the microscope, and error bars represent SD. *, p<0.05; **, p<0.01. (C and D) Apoptosis of WB-miR-NC and WB-anti-miR-200a cells measured by caspase-3/7 assay and Annexin V and PI staining. Data are expressed as the mean ± SD (C) and representative dot plots of apoptosis tests are shown (D); n = 5. (E) Expression of EpCAM, CD133, ABCG2, CK19, AFP, ALB and c-myc in WB-anti-miR-200a cells measured by qRT-PCR. Data are normalized to β-actin, shown relative to the level in WB-miR-NC cells and expressed as the mean ± SD; n = 3; *, p<0.05; **, p<0.01. (F) WB-miR-NC and WB-anti-miR-200a cells were treated with 10 ng/ml paclitaxel or 30 ng/ml doxorubicin for 48 h and then subjected to FACS with Annexin V and PI staining, respectively. Representative dot plots (left) and the mean percentage of apoptotic cells (± SD) from three independent experiments (right) are shown; *, p<0.05; **, p<0.01.</p

Stable knockdown of miR-200a confers mesenchymal characteristics to WB cells.

<p>(A) Morphological changes in WB-miR-NC and WB-anti-miR-200a cells (magnification×200). (B) Evaluation of in vitro migration abilities of WB-miR-NC and WB-anti-miR-200a cells by transwell migration assay. Representative images (upper, magnification×200) and the mean number of migrated cells (± SD) in five randomly selected fields counted under the microscope (lower) are shown; **, p<0.01. (C) Western blot analysis of epithelial (E-cadherin) and mesenchymal (N-cadherin and vimentin) markers in WB-miR-NC and WB-anti-miR-200a cells.</p