Pmma-XO (X = C, Si, Ge) monolayer as promising anchoring materials for lithium-sulfur battery: a first-principles study.

Lithium-sulfur (Li-S) batteries hold great promise for the next-generation lithium-ion energy storage devices. A key issue in the Li-S batteries is, however, the dissolving and migrating of the soluble polysulfides during the charge and discharge processes and introducing anchoring materials (AM) in the batteries effectively prevent the problem and improve the cycling stability of the Li-S batteries. Herein, Pmma-XO (X = C, Si, Ge, Sn) monolayers are introduced as AM to confine the lithium polysulfides and their anchoring properties are studied with the density functional theory methods. Particularly, Pmma-SiO and GeO monolayers are studied for the first time, and our calculations show that these two materials are stable semiconductive monolayers with direct-band-gaps and moderate binding with lithium polysulfides Li2S n (n = 8, 6, 4, 2 and 1). The Pmma-SiO and GeO trap Li2S n species on their surfaces and keep them intact during the charge and discharge, and the adsorption of Li2S n species leads to the enhanced conductivity of Pmma-SiO and GeO monolayers. Our study suggests that the Pmma-SiO and GeO monolayers are the promising AM for highly efficient Li-S batteries.

3-Fold-Periodic Size-Dependence in Electronic Properties of Monolayer-TMDC Nanotriangles.

Stable nanotriangles of monolayer transitional metal dichalcogenides (referred herein as MS2 mNTs) grown via ordinary deposition conditions, where M = Mo or W, exhibit a peculiar 3-fold periodic size-dependence in electronic and chemical properties. For " k" being the number of M atoms per edge, mNTs are (a) intrinsic-semiconducting when k = 3 i + 1, such as k = 7, 10, 13, 16; (b) metallic-like with no bandgap when k = 3 i; (c) n+ semiconducting when k = 3 i - 1. Besides changes in electronic properties, the catalytic properties for hydrogen evolution reaction also switch from active for k = 3 i and 3 i - 1 to inactive for k = 3 i + 1. The peculiar periodic size-dependence roots from the chemistry of edge-reconstruction and the consequential evolution of band structure. Further, such chemistry and thereby the size-dependence can be manipulated by adding or depleting the atomic concentration of sulfur atoms along the mNT edges.

Nanopolygons of Monolayer MS2: Best Morphology and Size for HER Catalysis.

With first-principles calculations, we find a new strategy for developing high-performance catalysts for hydrogen evolution reaction (HER) via controlling the morphology and size of nanopolygons of monolayer transition-metal dichalcogenides (npm-MS2, with M = Mo, W, or V). Particularly, through devising a quantitative method to measure HER-active sites per unit mass and using such HER site density to comparatively gauge npm-MS2 performance, we identify three keys in making npm-MS2 with optimal HER performance: (a) npm-MS2 should be triangular with each edge being M-terminated and each edge-M atom passivated by one S atom; (b) each edge of npm-MoS2 and WS2 should have 5-6 metal atoms as HER site density drops below/above these sizes optimal both for HER and practical npm growth; and (c) npm-VS2 is immune to this overly fastidious size dependence. Known experimental data on npm-MoS2 indeed support the plausibility of practicing these design rules. We expect that raising the nucleation density and controlling the growth time to favor the production of our proposed ultrasmall npm-MS2 are critical but practical. Research on npm-VS2 would bear the highest impact because of its size-forgiving HER performance and relatively high abundance and low cost.

Clinical significance of HOTAIR expression in colon cancer.

AIM: To detect the expression of the long noncoding RNA HOTAIR in colon cancer and analyze its relationship with clinicopathological parameters of colon cancer. METHODS: Total RNA was extracted from 80 colon cancer tissues and matched tumor-adjacent normal colon tissues and reverse transcribed. Quantitative polymerase chain reaction was used to detect the expression of HOTAIR. The relationship between the expression of HOTAIR and clinicopathological parameters of colon cancer was analyzed. RESULTS: The expression of HOTAIR was significantly higher in colon cancer tissues than in matched tumor-adjacent normal colon tissues (P < 0.05). HOTAIR expression was significantly higher in cases with lymph node metastasis than in those without metastasis; in lowly differentiated and undifferentiated cases than in highly and moderately differentiated cases; and in stages III + IV cases than in stages I + II cases (P < 0.05). CONCLUSION: HOTAIR expression is upregulated in colon cancer, suggesting that HOTAIR plays an important role in the tumorigenesis, development and metastasis of colon cancer. HOTAIR may act as an oncogene and represents a new molecular target for the treatment of colon cancer.

[Effects of hydroxycamptothecin and teniposide on proliferation and apoptosis of gastric cancer cell line BGC-823].

BACKGROUND & OBJECTIVE: Some studies have showed that topoisomerase (Topo)I and II inhibitors have synergistic effects in tumor therapy, but the combinations have seldom been used in gastric cancer. This study was to investigate the effects of Topo I inhibitor hydroxycamptothecin (HCPT) and Topo II inhibitor teniposide (VM-26) on the proliferation and apoptosis of gastric cancer cell line BGC-823. METHODS: MTT assay was used to examine the inhibitory effects of VM-26 and HCPT, used alone or in combination, on the proliferation of BGC-823 cells. Cell apoptosis was examined by flow cytometry (FCM). RESULTS: The inhibition rates of BGC-823 cell proliferation were 15.99%-80.83% when treated with 1.963-31.413 micromol/L VM-26; the apoptosis rates were 3.90%, 4.42%, 7.36%, 17.07% when exposed to 1.963 micromol/L VM-26 for 0, 12, 24, 48 h, respectively. The inhibition rates of BGC-823 cell proliferation were 7.89%-70.32% when treated with 8.577-137.227 micromol/L HCPT; the apoptosis rates were 2.80%, 8.50%, 10.50%, 13.30% when exposed to 8.577 micromol/L HCPT for 0, 12, 24, 48 h, respectively. When treated with 1.963 micromol/L VM-26 and 3.125 microg/ml HCPT for 0, 12, 24, 48 h, the inhibition rates of BGC-823 cell proliferation were 21.32%-87.74%, and the apoptosis rates were 2.80%, 15.50%, 15.70%, 20.20%, respectively. The combination index (CI) was 1.293. CONCLUSION: HCPT and VM-26 used alone could inhibit the proliferation and induce the apoptosis of BGC-823 cells, and they have antagonistic effect on gastric cancer BGC-823 cells.