Spin-orbit interaction in symmetric wells with two subbands

We investigate the spin-orbit (SO) interaction in two-dimensional electron gases in quantum wells with two subbands. From the 8x8 Kane model, we derive a new intersubband-induced SO term which resembles the functional form of the Rashba SO but is nonzero even in symmetric structures. This follows from the distinct parity of the confined states (even or odd) which obliterates the need for asymmetric potentials. We self-consistently calculate the new SO coupling strength for realistic wells and find it comparable to the usual Rashba constant. Our new SO term gives rise to a nonzero ballistic spin-Hall conductivity, which changes sign as a function of the Fermi energy (epsilonF) and can induce an unusual Zitterbewegung with cycloidal trajectories without magnetic fields.     

Josephson effect through an isotropic magnetic molecule

We study the Josephson effect through a quantum dot magnet whose spin is isotropic and which is coupled to the dot electron spin via exchange coupling. We calculate the Andreev levels and the supercurrent and examine the intertwined effect of the exchange coupling, Kondo correlation, and superconductivity. The former suppresses Kondo correlations, which triggers phase transitions from the 0 to the pi state, but strong antiferromagnetic coupling restores the 0 state. The asymmetric phase diagram in the exchange coupling suggests that the coupling sign could be determined in experiments.     

Direct writing of a conducting polymer with molecular-level control of physical dimensions and orientation

Polymer nanostructures composed of poly(3-dodecylthiophene) (PDDT) have been directly written with control of polymer strand alignment and monolayer-by-monolayer thickness down to a single molecular monolayer (2.6 nm). The molecularly ordered nanostructures were written on silicon oxide surfaces using thermal dip-pen nanolithography, where an atomic force microscope cantilever with integrated tip heater was precoated with solid PDDT. The PDDT was precisely deposited onto the surface when the tip temperature was set close to PDDT's melting temperature.     

Electrochemically induced and controlled one-step covalent coupling reaction on self-assembled monolayers

We report on a novel covalent coupling method using electrochemical activation of hydroquinone monoester self-assembled monolayers. The reaction generates benzoquinone as a good leaving group, followed by nucleophilic acyl substitution with a primary amine to form an amide in high yield. The method allows the site-selective and the reaction-controlled positioning of biotin on the individually addressable microelectrode array and, subsequently, density-differentiated patterning of streptavidin on the biotin surfaces. Because the electrochemical coupling method provides a very rapid, mild, and quantitatively controllable reaction pathway for covalent bond formation on organic surfaces, it will be used as a versatile molecular anchoring tool in fields such as molecular electronics and biochip technology.     

Effects of Majorana bound states on dissipation and charging in a quantum resistor-capacitor circuit

We investigate the effects of Majorana bound states on the ac response of a quantum resistor-capacitor circuit which is composed of a topological superconducting wire whose two ends are tunnel-coupled to a lead and a spinless quantum dot, respectively. The Majorana states formed at the two ends of the wire are found to suppress completely or enhance greatly the dissipation, depending on the strength of the overlap between two Majorana modes and/or the dot level. We compare the relaxation resistance and the quantum capacitance of the system with those of non-Majorana counterparts to find that the effects of the Majorana state on the ac response are genuine and cannot be reproduced in ordinary fermionic systems.     

Structure and growth of thin films of aniline on silver: nucleation and premelting of nanocrystallites, porosity, and crystallization

The structure and growth of thin films of aniline vapor deposited on Ag(111) and Ag(110) surfaces have been examined using optical second harmonic generation (SHG) and linear optical differential reflectivity (DR). Aniline thin films deposited at 90 K give a detectable SH signal that arises from small polycrystallites with orientation anisotropy in the film. Upon annealing, the SH signal decreases, first due to premelting (at approximately 145 K) of the polycrystallites and then sublimation (at approximately 180 K) of the film. Quantitative analysis of the SH intensity change by a premelting model [J. Phys. Chem. 1988, 92, 7241] allows the determination of the average size of the crystallites as 1.1 nm in diameter and containing approximately 45 aniline molecules. The existence of the nanocrystalline structure and its premelting are confirmed by DR experiments. The DR signal around 145 K exhibits change corresponding to an order-disorder transition. Quantitative analysis of the DR data results in the same nanocrystallite size. Experimental observations indicate that films deposited at 90 K contain not only nanocrystallites but also approximately 30% porosity, which can be reduced by annealing. At temperatures above 195 K, micron-size crystallites start to form within the amorphous film, causing a large amount of light scattering while the film sublimates. It appears that, for molecules such as aniline with stronger intermolecular interactions, more enthalpy is released, upon adsorption to the local surrounding molecules, causing them to reorient into crystalline form. The low deposition temperature, on the other hand, prevents diffusion for further crystallization beyond nanocrystallites. The refractive index of the amorphous aniline solid can be determined as 1.68 +/- 0.03.     

Electric Double‐Layer Capacitor Based on an Ionic Clathrate Hydrate

Herein, we suggest a new approach to an electric double‐layer capacitor (EDLC) that is based on a proton‐conducting ionic clathrate hydrate (ICH). The ice‐like structures of clathrate hydrates, which are comprised of host water molecules and guest ions, make them suitable for applications in EDLC electrolytes, owing to their high proton conductivities and thermal stabilities. The carbon materials in the ICH Me₄NOH ? 5 H₂O show a high specific capacitance, reversible charge–discharge behavior, and a long cycle life. The ionic‐hydrate complex provides the following advantages in comparison with conventional aqueous and polymer electrolytes: 1) The ICH does not cause leakage problems under normal EDLC operating conditions. 2) The hydrate material can be utilized itself, without requiring any pre‐treatments or activation for proton conduction, thus shortening the preparation procedure of the EDLC. 3) The crystallization of the ICH makes it possible to tailor practical EDLC dimensions because of its fluidity as a liquid hydrate. 4) The hydrate solid electrolyte exhibits more‐favorable electrochemical stability than aqueous and polymer electrolytes. Therefore, ICH materials are expected to find practical applications in versatile energy devices that incorporate electrochemical systems.     

Improvement of saccharification process for bioethanol production from Undaria sp. by gamma irradiation

Recently, many research works have reported on improvements to the saccharification process that increase bioethanol production from cellulosic materials. Gamma irradiation has been studied as an effective method for the depolymerization of complex polysaccharides. In this study, the effect of gamma irradiation on saccharification of Undaria biomass for bioethanol production was investigated. The Undaria biomass was irradiated at doses of 0, 10, 50, 100, 200 and 500 kGy and then hydrolyzed using sulfuric acid. The effects of gamma irradiation were measured through microscopic analysis to determine morphological changes and concentration of the reducing sugar of hydrolysates. Microscopic images show that gamma irradiation causes structure breakage of the Undaria cell wall. The concentration of reducing sugar of hydrolysates significantly increased as a result of gamma irradiation, with or without acid hydrolysis. These results indicate that the combined method of gamma irradiation with acid hydrolysis can significantly improve the saccharification process for bioethanol production from marine algae materials.     

Spirogyra varians mutant generated by high dose gamma-irradiation shows increased antioxidant properties

The aim of this study was to evaluate the antioxidant properties of a Spirogyra varians mutant (Mut) produced by gamma irradiation. Methanol extracts were prepared from Spirogyra varians wild-type and Mut plants, and their antioxidant activities and total phenolic content (TPC) were determined. Antioxidant parameters, including the 2-diphenyl-1-picrylhydrazyl radical-scavenging activity and ferric-reducing/antioxidant power, were higher in the Mut extract. Moreover, the TPC level was higher (P<0.05) in the Mut methanol extract. Therefore, these results suggest that gamma irradiation-induced S. varians Mut has superior antioxidant properties.     

Coconut Oil Alleviates the Oxidative Stress-Mediated Inflammatory Response via Regulating the MAPK Pathway in Particulate Matter-Stimulated Alveolar Macrophages

Exposure to particulate matter (PM) is related to various respiratory diseases, and this affects the respiratory immune system. Alveolar macrophages (AMs), which are defenders against pathogens, play a key role in respiratory inflammation through cytokine production and cellular interactions. Coconut oil demonstrates antioxidant and anti-inflammatory properties, and it is consumed worldwide for improved health. However, reports on the protective effects of coconut oil on the PM-induced respiratory immune system, especially in AMs, are limited. In this study, we generated artificial PM (APM) with a diameter approximately of 30 nm by controlling the temperature, and compared its cytotoxicity with diesel exhaust particles (DEP). We also investigated the antioxidant and anti-inflammatory effects of coconut oil in APM– and DEP–stimulated AMs, and the underlying molecular mechanisms. Our results showed that APM and DEP had high cytotoxicity in a dose-dependent manner in AMs. In particular, APM or DEP at 100 μg/mL significantly decreased cell viability (p < 0.05) and significantly increased oxidative stress markers such as reactive oxygen species (p < 0.01); the GSSH/GSH ratio (p < 0.01); and cytokine production, such as tumor necrosis factor-α (p < 0.001), interleukin (IL)-1β (p < 0.001), and IL-6 (p < 0.001). The expression of the genes for chemokine (C-X-C motif) ligand-1 (p < 0.05) and monocyte chemoattractant protein-1 (p < 0.001); and the proteins toll-like receptor (TLR) 4 (p < 0.01), mitogen-activated protein kinase (MAPK), and c-Jun N-terminal kinase (p < 0.001), p38 (p < 0.001); and extracellular receptor-activated kinase (p < 0.001), were also upregulated by PM. These parameters were reversed upon treatment with coconut oil in APM– or DEP–stimulated AMs. In conclusion, coconut oil can reduce APM– or DEP–induced inflammation by regulating the TLR4/MAPK pathway in AMs, and it may protect against adverse respiratory effects caused by PM exposure.Exposure to particulate matter (PM) is related to various respiratory diseases, and this affects the respiratory immune system. Alveolar macrophages (AMs), which are defenders against pathogens, play a key role in respiratory inflammation through cytokine production and cellular interactions. Coconut oil demonstrates antioxidant and anti-inflammatory properties, and it is consumed worldwide for improved health. However, reports on the protective effects of coconut oil on the PM-induced respiratory immune system, especially in AMs, are limited. In this study, we generated artificial PM (APM) with a diameter approximately of 30 nm by controlling the temperature, and compared its cytotoxicity with diesel exhaust particles (DEP). We also investigated the antioxidant and anti-inflammatory effects of coconut oil in APM– and DEP–stimulated AMs, and the underlying molecular mechanisms. Our results showed that APM and DEP had high cytotoxicity in a dose-dependent manner in AMs. In particular, APM or DEP at 100 μg/mL significantly decreased cell viability (p < 0.05) and significantly increased oxidative stress markers such as reactive oxygen species (p < 0.01); the GSSH/GSH ratio (p < 0.01); and cytokine production, such as tumor necrosis factor-α (p < 0.001), interleukin (IL)-1β (p < 0.001), and IL-6 (p < 0.001). The expression of the genes for chemokine (C-X-C motif) ligand-1 (p < 0.05) and monocyte chemoattractant protein-1 (p < 0.001); and the proteins toll-like receptor (TLR) 4 (p < 0.01), mitogen-activated protein kinase (MAPK), and c-Jun N-terminal kinase (p < 0.001), p38 (p < 0.001); and extracellular receptor-activated kinase (p < 0.001), were also upregulated by PM. These parameters were reversed upon treatment with coconut oil in APM– or DEP–stimulated AMs. In conclusion, coconut oil can reduce APM– or DEP–induced inflammation by regulating the TLR4/MAPK pathway in AMs, and it may protect against adverse respiratory effects caused by PM exposure.