Polarization-driven topological insulator transition in a GaN/InN/GaN quantum well

Topological insulator (TI) states have been demonstrated in materials with a narrow gap and large spin-orbit interactions (SOI). Here we demonstrate that nanoscale engineering can also give rise to a TI state, even in conventional semiconductors with a sizable gap and small SOI. Based on advanced first-principles calculations combined with an effective low-energy k · p Hamiltonian, we show that the intrinsic polarization of materials can be utilized to simultaneously reduce the energy gap and enhance the SOI, driving the system to a TI state. The proposed system consists of ultrathin InN layers embedded into GaN, a layer structure that is experimentally achievable.

Ages at different reproductive events, numbers of menstrual cycles in between and breast cancer risk

One hundred and seventy-five pathologically confirmed new cases of female breast cancer in National Taiwan University Hospital were selected as the case group. Four hundred and fifty-seven inpatient controls were individually matched for each case by age and date of admission. Information of reproductive factors and potential confounders were collected from questionnaire interview and medical records. Menstrual cycles before and after first fuIl-term pregnancy were estimated from the questionnaire. Conditional logistic regression was used to estimate the effects of reproductive risk factors and numbers of menstrual cycles before and after first full-term pregnancy. After adjusting for educational level, body mass index, family history of breast cancer and oral contraceptive use, age at menarche and menopause only showed borderline significance. Age at first full-term birth predicted breast cancer risk better. Parity was the most important protective factor. Number of menstrual cycles before first full-term pregnancy was also positively associated with breast cancer risk with linear trends.

H⁺-myo-inositol transporter SLC2A13 as a potential marker for cancer stem cells in an oral squamous cell carcinoma

Cancer Stem Cells (CSCs) from tumors of different phenotypes possess a marked capacity for proliferation, self-renewal, and differentiation. They also play a critical role in cancer recurrence. Although CSC has been regarded as a new target for cancer therapy, the fundamental questions in the CSC study have not been resolved mainly due to the lack of proper CSC markers. To find new CSC markers for oral squamous cell carcinoma (OSCC), we cultured the primary tumor cells from OSCC patients the regular culture condition and the sphere-forming culture condition to enrich primary tumor cells and potential CSCs. We compared gene expression profiles between sphere-forming and non-forming cells, thus identifying that 23 membrane protein-coding genes were over-expressed in the sphere-forming cells. Among them, 8 belonged to the solute carrier (SLC) protein family. H⁺-myo-inositol transporter SLC2A13 and monocarbohydrate transporter SLC16A6 genes that were consistently increased in the sphere-forming cells in the primary cultures of OSCC samples. Confocal microscopy revealed that SLC2A13-expressing cells were embedded in the limited areas of tumor tissue as a cluster, while SLC16A6 was uniformly detected in hyperplastic epithelium. Moreover, SLC2A13 an expression was induced in human breast adenocarcinoma MCF7 cells after serum starvation. Taken together, our results suggest that SLC2A13 can be a potential markers for CSC in various tumors.

The shear mode of multilayer graphene

The quest for materials capable of realizing the next generation of electronic and photonic devices continues to fuel research on the electronic, optical and vibrational properties of graphene. Few-layer graphene (FLG) flakes with less than ten layers each show a distinctive band structure. Thus, there is an increasing interest in the physics and applications of FLGs. Raman spectroscopy is one of the most useful and versatile tools to probe graphene samples. Here, we uncover the interlayer shear mode of FLGs, ranging from bilayer graphene (BLG) to bulk graphite, and suggest that the corresponding Raman peak measures the interlayer coupling. This peak scales from ~43 cm(-1) in bulk graphite to ~31 cm(-1) in BLG. Its low energy makes it sensitive to near-Dirac point quasiparticles. Similar shear modes are expected in all layered materials, providing a direct probe of interlayer interactions.