Rayleigh scattering studies on inter-layer interactions in structure-defined individual double-wall carbon nanotubes

Although the inter-layer coupling in layered materials has attracted considerable interest due to its importance in determining physical properties of two-dimensional systems, studies on the inter-layer coupling in one-dimensional systems have so far been limited. Double-wall carbon nanotubes (DWCNTs) are one of the most fundamental and ideal model systems to study the inter-layer coupling in one-dimensional systems. In this work, Rayleigh scattering spectroscopy and transmission electron microscopy are used to characterize the electronic transition between inner-and outer-nanotubes of the exactly same individual DWCNT. We find that the inter-layer coupling is strong, leading to downshifts in most of the optical transition energies (up to ～0.2 eV) compared to isolated CNTs. We also find that the presence of metallic tubes lead to stronger shifts. The inter-layer screening of Coulomb interactions is one of the key factors in explaining the observed results.      

Efficient Photocarrier Transfer and Effective Photoluminescence Enhancement in Type I Monolayer MoTe2/WSe2 Heterostructure

Artificial van der Waals heterostructures of 2D layered materials are attractive from the viewpoint of the possible discovery of new physics together with improved functionalities. Stacking various combinations of atomically thin semiconducting transition metal dichalcogenides, MX₂ (M = Mo, W; X = S, Se, Te) with a hexagonal crystal structure, typically leads to the formation of a staggered Type II band alignment in the heterostructure, where electrons and holes are confined in different layers. Here, the comprehensive studies are performed on heterostructures prepared from monolayers of WSe₂ and MoTe₂ using differential reflectance, photoluminescence (PL), and PL excitation spectroscopy. The MoTe₂/WSe₂ heterostructure shows strong PL from the MoTe₂ layer at ≈1.1 eV, which is different from the quenched PL from the WSe₂ layer. Moreover, enhancement of PL intensity from the MoTe₂ layer is observed because of the near‐unity highly efficient photocarrier transfer from WSe₂ to MoTe₂. These experimental results suggest that the MoTe₂/WSe₂ heterostructure has a Type I band alignment where electrons and holes are confined in the MoTe₂ layer. The findings extend the diversity and usefulness of ultrathin layered heterostructures based on transition metal dichalcogenides, leading to possibilities toward future optoelectronic applications.     

Public perception on hydrogen infrastructure in Japan: Influence of rollout of commercial fuel cell vehicles

A public survey was conducted in March 2015 in Japan asking public awareness, knowledge, perception and acceptance regarding hydrogen, hydrogen infrastructure and fuel cell vehicle. Changes in answers were found by comparing results of current survey to those of the two previous surveys that were conducted six and seven years ago. We found a large increase in the awareness and relatively a small improvement on knowledge on hydrogen energy, hydrogen infrastructure and fuel cell vehicle from the previous surveys. In contrast we did not find much changes in perception of risk and benefit on hydrogen society and hydrogen station and public acceptance of hydrogen infrastructure. Through the regression analyses we found the small influence of time background as well as the influence of risk and benefit perception of hydrogen infrastructure on the acceptance. In conclusion, we find people have become a little more positive about hydrogen infrastructure in the baseline but more cautious about the risk and benefits. This can be interpreted as a change in the quality of perception and acceptance, that is, the favorable prejudice to hydrogen energy and fuel cell technologies has changed towards a slightly more rational support.     

Inelastic stress-strain response for notched specimen of Cr-1Mo steel at 600°C

Following a series of cooperative studies A-I and A-II (phase III) concerning the inelastic behaviour of high temperature materials under uniform state of stress, finite element analyses were carried out on circumferential notched cylinders subjected to plasticity-creep interaction conditions. Using an electric capacitance type extensometer “Strain-Pecker”, which is capable of measuring a local strain response with a gauge length of 0.5 mm under high temperature conditions, stress-strain responses for both global and local regions near the notch root were evaluated. Ten kinds of inelastic constitutive model were introduced into a finite element code, and the responses for four kinds of loading pattern were examined for two types of notch shape.     

Determination of genotoxic phenylhydrazine agaritine in mushrooms using liquid chromatography-electrospray ionization tandem mass spectrometry

A new method with good sensitivity and specificity for detecting and quantifying genotoxic hydrazines, agaritine and 4-(hydroxymethyl)phenylhydrazine (HMPH), was developed using liquid chromatography-electrospray tandem mass spectrometry (MS). Synthetic agaritine and HMPH were structurally assigned by ¹H-, ¹³C- and two-dimensional nuclear magnetic resonance (NMR) analysis (HMBC and HMQC), high-resolution fast-atom bombardment (HR-FAB) MS and time of flight (TOF) MS. The polar molecule agaritine was separated on an ODS column using 0.01% AcOH-MeOH (99:1, v/v) as an eluent with a simple solid-phase extraction cleanup. There were no interference peaks for any of the mushrooms. Agaricus spp. contained 1247 and 2017 µg g^-1 agaritine. Other species of mushroom had no agaritine. Recoveries of agaritine from spiked mushroom samples were 60.3-114%. Intra-day precision values were 5.5 and 4.2%, and the inter-day precision values were acceptable (15.0 and 23.0%), as agaritine is unstable. The limit of quantification was 0.003 µg g^-1. Even a trace amount of agaritine in mushrooms can, therefore, be determined using this method. We also directly analysed HMPH, an active free hydrazine form of genotoxic agaritine, and obtained direct evidence of its absence from mushrooms. A precursor ion scan confirmed that agaritine derivatives, which could exert similar toxicity, were absent. The results indicate that this specific and sensitive analytical method for detecting and quantifying agaritine and its derivatives could help evaluate the risk of mushroom hydrazines to humans.     

Seasonal and spatial trends of suspended-particle associated polycyclic aromatic hydrocarbons in urban Shizuoka, Japan

We characterized the monthly variations of 21 polycyclic aromatic hydrocarbons (PAHs) associated with suspended particles in the city of Shizuoka, Japan, over 12 months during 2001 and 2002. The fraction of fine particles (less than 2.5 microm diameter (PM2.5)) ranged from 40 to 60% of total suspended particles over the 12 months of the study, and their concentrations ranged from 19.3 to 41.7 microg/m(3). Almost all the PAHs were found in the PM2.5 fraction, in which the summed concentration (sigma PAH) of the 21 PAHs ranged from 1.0 to 8.4 ng/m(3). PAH concentrations were elevated in the colder seasons, but the concentrations of the PM2.5 fraction of suspended particles were not. The composition of PAHs associated with PM2.5 changed little during the year of our study, indicating that seasonal sources such as heating have little effect. Factor analysis showed that three factors explain little of the seasonal variations in the sources of PAHs. Contour maps showed high concentrations of indicator PAHs for gasoline and diesel engine sources distributed along major roads and near factories on the outskirts of the city. We concluded that the contribution of vehicle exhausts to particle-associated PAHs is significant not only in the central city, but also in outer areas associated with major ring roads, and suggest that air pollution in outskirts of urban area also is concerned for health risk associated with the exposure.     

Bovine Induced Pluripotent Stem Cells Are More Resistant to Apoptosis than Testicular Cells in Response to Mono-(2-ethylhexyl) Phthalate

Although the androgen receptor (AR) has been implicated in the promotion of apoptosis in testicular cells (TSCs), the molecular pathway underlying AR-mediated apoptosis and its sensitivity to environmental hormones in TSCs and induced pluripotent stem cells (iPSCs) remain unclear. We generated the iPSCs from bovine TSCs via the electroporation of OCT4. The established iPSCs were supplemented with leukemia inhibitory factor and bone morphogenetic protein 4 to maintain and stabilize the expression of stemness genes and their pluripotency. Apoptosis signaling was assessed after exposure to mono-(2-ethylhexyl) phthalate (MEHP), the active metabolite of di-(2-ethylhexyl) phthalate. Here, we report that iPSCs were more resistant to MEHP-induced apoptosis than were original TSCs. MEHP also repressed the expression of AR and inactivated WNT signaling, and then led to the commitment of cells to apoptosis via the cyclin dependent kinase inhibitor p21^CIP1. The loss of the frizzed receptor 7 and the gain of p21^CIP were responsible for the stimulatory effect of MEHP on AR-mediated apoptosis. Our results suggest that testicular iPSCs can be used to study the signaling pathways involved in the response to environmental disruptors, and to assess the toxicity of environmental endocrine disruptors in terms of the maintenance of stemness and pluripotency.     

Removal of endocrine disruptors in milk by circulation through polydimethylsiloxane tubing

A simple circulating system was developed, in which an aqueous solution, cow milk, or human milk was circulated through hydrophobic polymeric tubing to remove the endocrine disruptors from the solution by sorption into the tubing. The effect of circulating parameters, such as tube length, circulating time, and flow rate, against the removal ratio (R) of endocrine disruptors was investigated. R of 1,2,3,4,5,6‐hexachlorocyclohexane (γ‐HCH, lindane) increased with the length of the hydrophobic polymeric tubing, circulating time, and flow rate when cow milk containing 1 ppm γ‐HCH was circulated through polydimethylsiloxane tubing. The R values of several endocrine disruptors with different octanol–water distribution coefficients (log P_ow) was investigated for γ‐HCH and dichlorodiphenyltrichloroethane in an aqueous solution, cow milk, and human milk. A similar trend for R versus log P_ow of the human milk to that of the aqueous solution and cow milk was observed. The R values of the endocrine disruptors decreased in the following order: Aqueous solution > Human milk > Cow milk. Stable micelles in cow milk disturbed the shift of the endocrine disruptors from the milk micelles into the hydrophobic tubing. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:3634–3640, 2006     

Solid-state source of atomic oxygen for low-temperature oxidation processes: application to pulsed laser deposition of TiO2:N films

An atomic oxygen (AO) source has been redesigned to coordinate with a pulsed laser deposition system and used to grow nitrogen-doped TiO(2) films by deposition of TiN and simultaneous irradiation of the substrate with AO. The AO source uses an incandescently heated thin tube of zirconia as an oxygen permeation media to generate pure AO of low kinetic energy. The emission flux is calibrated using a silver-coated quartz crystal microbalance. The thin shape of the probe and transverse emission geometry of this emission device allow the emission area to be positioned close to the substrate surface, enhancing the irradiation flux at the substrate. AO irradiation is crucial for formation of TiO(2) phases via oxidation of the deposited TiN laser plume, and is effective for decrease of the substrate temperature for crystallization of anatase phase to as low as around 200 °C.