Electron-Hole Asymmetry in Single-Walled Carbon Nanotubes Probed by Direct Observation of Transverse Quasi-Dark Excitons

We studied the asymmetry between valence and conduction bands in single-walled carbon nanotubes (SWNTs) through the direct observation of spin-singlet transverse dark excitons using polarized photoluminescence excitation spectroscopy. The intrinsic electron-hole (e-h) asymmetry lifts the degeneracy of the transverse exciton wavefunctions at two equivalent K and K' valleys in momentum space, which gives finite oscillator strength to transverse dark exciton states. Chirality-dependent spectral weight transfer to transverse dark states was clearly observed, indicating that the degree of the e-h asymmetry depends on the specific nanotube structure. Based on comparison between theoretical and experimental results, we evaluated the band asymmetry parameters in graphene and various carbon nanotube structures.Comment: 11 pages, 4 figure

Suppression of cell-spreading and phagocytic activity on nano-pillared surface: in vitro experiment using hemocytes of the colonial ascidian Botryllus schlosseri.

Nano-scale nipple array on the body surface has been described from various invertebrates including endoparasitic and mesoparasitic copepods, but the functions of the nipple array is not well understood. Using the hydrophilized nanopillar sheets made of polystyrene as a mimetic material of the nipple arrays on the parasites\u2019 body surface, we assayed the cell spreading and phagocytosis of the hemocytes of the colonial ascidian Botryllus schlosseri. On the pillared surface, the number of spreading amebocytes and the number of phagocytizing hemocytes per unit area were always smaller than those on the flat surface (Mann-Whitney test, p < 0.05 - 0.001), probably because the effective area for the cell attachment on the pillared surface is much smaller than the area on the flat sheet. The present results supports the idea that the nipple array on the parasites' body surface reduces the innate immune reaction from the host hemocytes

Financial Assessment Considered Weighting Factor Scenarios for the Optimal Combination of Power Plants on the Power System Operation

This paper presents an application of the novel evolutionary algorithm for assessing financially an economic power system operation throughout a combined economic and emission dispatch problem required by various technical limitations. In detail, this problem considers two dispatches for fuel and environmental aspects as a constrained objective function associated with weighting factor scenarios. Running out simulations show that minimum costs are depended on weighting factors, which implemented on the combination of the problem. Reducing the total fuel cost focused on the dispatching priority and the pollutant target based on the emission production have difference implications as its contribution to the economic operation, the increasing load demand leads to generated powers, costs and emission discharges associated with its parameters and power schedules

The Penetration of Pollutant Productions on Dynamic Generated Power Operations Optimized Using a Novel Evolutionary Algorithm

At Present, the environmental protection penetrates public awareness to decrease atmospheric emissions as important efforts for increasing living quality in air from various gaseous effects. Technically, it has forced industrial sectors to control pollutant productions while operating machineries of engineering processes to keep all materials for final products. It has also forced the power system operation to modify operational strategies of thermal power plants considered pollutant productions from combustions of fossil fuels for reducing emissions. Moreover, reasonable decisions are needed to schedule combinations of generating units for providing electric energy with less pollutant discharges and more economically operation. In particular, these strategies are required by operational conditions and technical constraints for optimizing the operating cost included decreasing pollutant productions. This paper demonstrates new approaches for measuring pollutant penetrations embedded in single priority function. Results obtained show that the computation has different performances for 24 hours of the operation. Moreover, emission discharges are dominated gradually by higher contributors associated with scheduled power plants as emission requirements

Formation of hydrogen peroxide and water from the reaction of cold hydrogen atoms with solid oxygen at 10K

The reactions of cold H atoms with solid O2 molecules were investigated at 10 K. The formation of H2O2 and H2O has been confirmed by in-situ infrared spectroscopy. We found that the reaction proceeds very efficiently and obtained the effective reaction rates. This is the first clear experimental evidence of the formation of water molecules under conditions mimicking those found in cold interstellar molecular clouds. Based on the experimental results, we discuss the reaction mechanism and astrophysical implications.Comment: 12 pages, 3 Postscript figures, use package amsmath, amssymb, graphic

Magnetic Brightening of Carbon Nanotube Photoluminescence through Symmetry Breaking

Often a modification of microscopic symmetry in a system can result in a dramatic change in its macroscopic properties. Here we report that symmetry breaking by a tube-threading magnetic field can drastically increase the photoluminescence quantum yield of semiconducting single-walled carbon nanotubes, by as much as a factor of six, at low temperatures. To explain this striking connection between seemingly unrelated properties, we have developed a comprehensive theoretical model based on magnetic-field-dependent one-dimensional exciton band structure and the interplay of strong Coulomb interactions and the Aharonov-Bohm effect. This conclusively explains our data as the first experimental observation of dark excitons 5-10 meV below the bright excitons in single-walled carbon nanotubes. We predict that this quantum yield increase can be made much larger in disorder-free samples