Metal-organic chemical vapor deposition of 2D van der Waals materials-The challenges and the extensive future opportunities

The last decade has witnessed significant progress in two-dimensional van der Waals (2D vdW) materials research; however, a number of challenges remain for their practical applications. The most significant challenge for 2D vdW materials is the control of the early stages of nucleation and growth of the material on preferred surfaces to eventually create large grains with digital thickness controllability, which will enable their incorporation into high-performance electronic and optoelectronic devices. This Perspective discusses the technical challenges to be overcome in the metal-organic chemical vapor deposition (MOCVD) growth of 2D group 6 transition metal dichalcogenide (TMD) atomic crystals and their heterostructures, as well as future research aspects in vdW epitaxy for 2D TMDs via MOCVD. In addition, we encourage the traditional MOCVD community to apply their expertise in the field of "2D vdW materials," which will continue to grow at an exponential rate

Two-dimensional heterogeneous photonic bandedge laser

We proposed and realized a two-dimensional (2D) photonic bandedge laser surrounded by the photonic bandgap. The heterogeneous photonic crystal structure consists of two triangular lattices of the same lattice constant with different air hole radii. The photonic crystal laser was realized by room-temperature optical pumping of air-bridge slabs of InGaAsP quantum wells emitting at 1.55 micrometer. The lasing mode was identified from its spectral positions and polarization directions. A low threshold incident pump power of 0.24mW was achieved. The measured characteristics of the photonic crystal lasers closely agree with the results of real space and Fourier space calculations based on the finite-difference time-domain method.Comment: 14 pages, 4 figure

Neuroprotective Effects of Astaxanthin in Oxygen-Glucose Deprivation in SH-SY5Y Cells and Global Cerebral Ischemia in Rat

Astaxanthin (ATX), a naturally occurring carotenoid pigment, is a powerful biological antioxidant. In the present study, we investigated whether ATX pharmacologically offers neuroprotection against oxidative stress by cerebral ischemia. We found that the neuroprotective efficacy of ATX at the dose of 30 mg/kg (n = 8) was 59.5% compared with the control group (n = 3). In order to make clear the mechanism of ATX neuroprotection, the up-regulation inducible nitric oxide synthase (iNOS) and heat shock proteins (HSPs) together with the oxygen glucose deprivation (OGD) in SH-SY5Y cells were also investigated. The induction of various factors involved in oxidative stress processes such as iNOS was suppressed by the treatment of ATX at 25 and 50 µM after OGD-induced oxidative stress. In addition, Western blots showed that ATX elevated of heme oxygenase-1 (HO-1; Hsp32) and Hsp70 protein levels in in vitro. These results suggest that the neuroprotective effects of ATX were related to anti-oxidant activities in global ischemia

Violet-light spontaneous and stimulated emission from ultrathin In-rich InGaN/GaN multiple quantum wells grown by metalorganic chemical vapor deposition

We investigated the spontaneous and stimulated emission properties of violet-light-emitting ultrathin In-rich InGaN/GaN multiple quantum wells (MQWs) with indium content of 60%-70%. The Stokes shift was smaller than that of In-poor InGaN MQWs, and the emission peak position at 3.196 eV was kept constant with increasing pumping power, indicating negligible quantum confined Stark effect in ultrathin In-rich InGaN MQWs despite of high indium content. Optically pumped stimulated emission performed at room temperature was observed at 3.21 eV, the high-energy side of spontaneous emission, when the pumping power density exceeds ???31 kW/ cm2.open6

Bacterial community analysis of sediment seep in Kagoshima Bay, Japan

1902-1906Microorganisms in the deep-sea environments such as hydrothermal vent and cold-seep regions are primary energy producers and an important community in these ecosystems. We have used 454-Pyrosequencing and 16S rDNA clone library methods to determine the diversity of bacteria in the sediment of the seep regions around the vestimentiferan tubeworm habitat at Kagoshima Bay. Taxonomic composition from both libraries suggested that 454-Pyrosequencing methods can represent more diverse groups than the conventional clone library methods. Most abundant taxa with higher folds were Proteobacteria and Bacteroidetes found in both methods. Through the 454-Pyrosequencing method, we were able to detect underrepresented taxa as well as non-detectable taxa. This analyses and comparison provide bacterial taxonomic group detection efficiency of both library types and emphasize the different uses and utilities for exploring the unknown microbial domain

N-(2,5-Dimeth­oxy­phen­yl)-N′-(4-hy­droxy­pheneth­yl)urea

In the title compound, C17H20N2O4, the 2,5-dimeth­oxy­phenyl unit is almost planar, with an r.m.s. deviation of 0.015 Å. The dihedral angle between the 2,5-dimeth­oxy­phenyl ring and the urea plane is 20.95 (8)°. The H atoms of the urea NH groups are positioned syn to each other. The mol­ecular structure is stabilized by a short intra­molecular N—H⋯O hydrogen bond. In the crystal, inter­molecular N—H⋯O and O—H⋯O hydrogen bonds link the mol­ecules into a three-dimensional network

Mutagenic activity of river water from a river near textile industrial complex in Korea

The mutagenic activity of XAD-2 adsorbates and water extracts recovered from nine locations of the Kumho River was tested on S. typhimurium TA98 strain to identify the source of the mutagenicity. A sampling site, receiving effluents from the textile industrial complex located in Daegu City, showed extraordinarily high mutagenic activity, especially in the presence of S9 mixture, at all sampling time in both XAD-2 adsorbates and dichloromethane extracts. This indicated the existence of the frame-shift mutagens in the Kumho River, same type of mutagens detected in previous studies by other researchers in the Nakdong River into which the Kumho River discharges. The fractionation study showed that the mutagenic chemicals in the river water are mid-polar. Furthermore, mean tail length obtained by single cell gel electrophoresis assay (Comet assay) showed consistent dose-dependent DNA damage, indicating that the chemicals in the river water not only act as frame-shift mutagens but also break human lymphocytes DNA strain. Chemical identification of the mutagens should be require

1-[3-(Hy­droxy­meth­yl)phen­yl]-3-phenyl­urea

In the title compound, C14H14N2O2, the dihedral angle between the benzene rings is 23.6 (1)°. The H atoms of the urea NH groups are positioned syn to each other. In the crystal, inter­molecular N—H⋯O and O—H⋯O hydrogen bonds link the mol­ecules into a three-dimensional network