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Selenium (Se) is an important element for assessing the safety of high-level waste disposal. Se is redox-sensitive, and its oxidation state varies from -2 to 6 depending on the redox conditions and pH of the solution. Large quantities of ferrous ions formed in bentonite due to corrosion of carbon steel overpack after the closure of a repository are expected to maintain a reducing environment near the repository. Therefore, the migration behavior of Se in the presence of Fe in bentonite was investigated by electrochemical experiments. Na2SeO3 solution was used as tracer solution. Dry density range of bentonite was from 0.8 to 1.4 ×103 kg/m3.
Results indicated that Se was strongly retained by the processes such as precipitation reaction with ferrous ions in bentonite. Se K-edge X-ray absorption near-edge structure (XANES) measurements were performed at the BL-11 beamline at SAGA Light Source, and the results revealed that the oxidation state of Se in the bentonite remained Se(IV).
We review emission processes within the supernova (SN) ejecta. Examples of the application of the theory to observational data are presented. The emission processes and thermal condition within the SN ejecta change as a function of time, and multi-epoch observations are important to obtain comprehensive views. Through the analyses, we can constrain the progenitor radius, compositions as a function of depth, ejecta properties, explosion asymmetry and so on. Multi-frequency follow-up is also important, including radio synchrotron emissions and the inverse Compton effect, γ-ray emissions from radioactive decay of newly synthesized materials. The optical data are essential to make the best use of the multi-frequency data.
Visible-light photocatalytic property of TiO2 / WO3 / FTO multi-layer structure was investigated. In this structure, the visible-light absorption takes place in the WO3 layer, and generated electrons and holes diffuse into the FTO and TiO2 layers, respectively. The holes diffused into the valence band of the TiO2 layer produce the hydroxyl radicals due to oxidation of H2O and/or OH− adsorbed on the TiO2 surface. The FTO bottom layer, which acts as a scavenger of electrons, contributes to an effective charge separation. As a result, the visible-light photocatalysis is enhanced in this structure.
Changes in critical current properties depending on growth temperature (Ts) were clarified for Ba-Nb-O-doped YBa2Cu3Oy (Y123) films deposited by YAG- and excimer-PLD. Due to the introduction of Ba-Nb-O-nanorods, a vortex-Bose-glass-like behavior emerged as irreversibility lines and in-field critical current densities (Jcs) were improved. Crossover magnetic fields (Bcr) and in-field Jcs increased with the increase in Ts for the Y123 films with nanorods. These Ts-dependent critical current properties were attributable to the changes in morphology of the nanorods with Ts and were independent of laser source in PLD apparatuses. For the fabrication of RE123 coated conductors containing nanorods, optimization of Ts with taking both materials of RE123 matrix and nanorod into account is necessary to achieve higher in-field Jc.
The surface potential (SP) undulation on the surfaces of tris(8-hydroxyquinolinato) aluminum (III) (Alq3) films has been investigated with Kelvin probe force microscopy (KFM) and scanning near-field optical microscope (SNOM)-KFM. The SP undulation observed on the amorphous Alq3 films with thicknesses of up to 300 nm showed a cloud-like morphology of 200–300 nm in lateral size. The temporal change of SP undulation was traced through cyclic measurement with KFM observation with intermittent photoexposure, as well as in situ localized photoexcitation with SNOM-KFM. We concluded that the origin of the SP undulation is the nonuniform distribution of charged traps and drift mobility in the Alq3 films.
The focus of this present work is concerned with a novel and facile method for obtaining colored Ag nanoparticle films using a sulfide as a coloring agent. The Ag nanoparticle films change their colors depending on the dipping time in a solution of a sulfide and the dipping time is at most on the second time scale. The color of the films, initially sliver (shiny white), changes to shiny yellow, red, and blue. Our scanning electron microscopy studies indicate that the color of the Ag nanoparticle films depend on the particle size of the Ag nanoparticle films.
Microfluidic mixing was applied to conventional acid pasting process to re-crystallize organic nanocrystals of Titanyl phthalocyanine (TiOPc). TiOPc nanocrystals were re-crystallized in a two step process. Seed particles were prepared by mixing TiOPc, dissolved in concentrated sulfuric acid with deionized water using high speed microchannel mixers. Seed particles were then subjected to post-precipitation treatment to achieve final crystalline product. Effects of seed preparation conditions, such as mixing efficiency (mixer type) and mixing temperature on the structure of final product were studied. Time evolution of optical absorption spectra was examined with a view to elucidate structure evolution during early stages of seed formation process.
A novel synthesis route to organic-capped and colloidal ZnO quantum dots (QDs) has been developed. Specifically, zinc-di-butoxide was hydrolyzed with very dilute water (100˜600 mass ppm) dissolved in hydrophilic benzylamine and polymerized to ZnO by dehydration condensation. After formation of ZnO QDs with 2˜3 nm in diameter, growth of the QDs and exchange the surface capping ligand from hydroxyl groups and/or benzylamine to oleylamine were developed by heating the colloidal solution with oleylamine. The size of the ZnO QDs finally obtained was in the range 3˜5 nm in diameter. The QDs show high dispersibility in various organic solvents. Clear UV emission due to exciton recombination was observed; and its energy was varied according to the quantum size effect from 3.39 to 3.54 eV. By using lithium-free zinc-di-butoxide as a starting material, the defect-related VIS emission was successfully decreased and the UV emission becomes dominant. The influence of water concentration in benzylamine and oleylamine on UV emission intensity was also investigated.
In the trough silicon via (TSV) structure for 3-dimensional integration (3DI), large thermal-mechanical stress acts in the TSV caused by the mismatch in thermal expansion coefficient (CTE) of the TSV materials. In this study, the stress of multi-stacked thin silicon wafers composed of copper TSV and copper/low-k BEOL structure was analyzed by the finite element method (FEM), aiming to reduce the stress of TSV of 3D-IC. The results of sensitivity analysis using design of experiment (DOE) indicated that the thickness of the silicon and adhesive layer are the key factors for the structural integration of TSV design.
We determined the genetic relationships and origin of the dengue virus (DENV) responsible for an outbreak of dengue fever (DF) in Guangdong province, China, in 2006. Five DENV type 1 (DENV-1) isolates were obtained from human serum samples collected from DF patients during the outbreak. The nucleotide sequences of the E (envelope) gene were compared with those of 48 previous DENV-1 isolates: 18 from Guangdong province, one from Fujian province, one from Zhejiang province, and 28 from other countries in the South Asian region. The results suggested that four DENV-1 isolates identified in Guangdong province in 2006 might be in general circulation there, although these DENV-1 viruses may have been originally introduced into the province from other countries. In contrast, one isolate from Guangzhou city in 2006, may have been introduced by a recently imported case from Cambodia.
Carbon nanotubes (CNTs) were grown by using a combination of ethanol and metallic Fe, which was not exposed to air before the growth. CNTs were also grown using intentionally oxidized Fe. The reaction products by these growths were analyzed by in situ photoelectron spectroscopy. We found that the oxidized Fe partially remained and did not completely reduce, resulting in low CNT yields. At higher growth temperature, oxide formation was found even when metallic Fe was used. These oxides induced a lowering of the decomposition efficiency of ethanol, resulting in difficulty of CNT growth by the combination of pure ethanol and Fe.
Local electronic structures of C60-Co hybrid films have been studied by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. XPS spectra of C 1s main and satellite peaks for the C60-Co films show binding-energy shifts and also line-broadening compared to those in a pure C60 film. In addition, XPS spectra in valence band region suggest an appearance of three new components at near Fermi level and HOMO level in the C60-Co film. These results are attributed to hybridizations between Co 3d band and C60 LUMO. The same effects have been observed in NEAXFS spectra at C 1s excitations.
Previous studies of rod photoreceptors in vivo have employed
a paired-flash electroretinographic (ERG) technique to determine rod
response properties. To test whether absence versus presence of
the ERG b-wave affects the photoreceptor response derived by the
paired-flash method, we examined paired-flash-derived responses obtained
from nob mice, a mutant strain with a defect in signal
transduction between photoreceptors and ON bipolar cells that causes a
lack of the b-wave. Normal littermates of the nob mice
served as controls. The normalized amplitude-intensity relation of the
derived response determined in nob mice at the near-peak time of
86 ms was similar to that determined for the controls. The full time
course of the derived rod response was obtained for test flash strengths
ranging from 0.11 to 17.38 scotopic cd s m−2 (sc cd s
m−2). Time-course data obtained from nob and
control mice exhibited significant but generally modest differences. With
saturating test flash strengths, half-recovery times for the derived
response of nobversus control mice differed by ∼60
ms or less about the combined (nob and control) average
respective values. Time course data also were obtained before
versus after intravitreal injection of
l-2-amino-4-phosphonobutyrate (APB) (which blocks transmission
from photoreceptors to depolarizing bipolar cells) and of cis
2,3-piperidine dicarboxylic acid (PDA) (which blocks transmission to OFF
bipolar cells, and to horizontal, amacrine and ganglion cells). Neither
APB nor PDA substantially affected derived responses obtained from
nob or control mice. The results provide quantitative information
on the effect of b-wave removal on the paired-flash-derived
response in mouse. They argue against a substantial skewing effect of the
b-wave on the paired-flash-derived response obtained in normal
mice and are consistent with the notion that, to good approximation, this
derived response represents the isolated flash response of the
photoreceptors in both nob and normal mice.
CuInS2 (CIS) fluorescent nanocrystals (NCs) were obtained by heating organic metal complex. The photoluminescence (PL) originated from the donor-acceptor, and the quantum yield (QY) was achieved at 6%. Furthermore, we doped some metal ions (Zn2+, Cd2+ or Ag+) by the post heat-treatment in the organic coordinating solvent in order to tune the band gap of NCs. By this post treatment, the alteration of NCs structure was suggested, such as changing into an alloying and composite structure. In Zn-doping, the PL wavelength was widely tuned from 535 to 650 nm by alloying between CIS and ZnS. Moreover, PL intensity was increased with these structure alterations. In particular, the materials doped with Zn or Cd achieved respective QY of 25% and 40%.
We calculate evolution, collapse, explosion, and nucleosynthesis of Population III very massive stars with 500 M⊙ and 1000 M⊙. It was found that both 500 M⊙ and 1000 M⊙ models enter the region of pair-instability but continue to undergo core collapse to black holes. For moderately aspherical explosions, the patterns of nucleosynthesis match the observational data of intergalactic and intercluster medium and hot gases in M82, better than models involving hypernovae and pair instability supernovae.
Our results suggest that explosions of Population III core-collapse very massive stars contribute significantly to the chemical evolution of gases in clusters of galaxies. The final black hole masses are about 500 M⊙ for our most massive 1000 M⊙ models. This result may support the view that Population III very massive stars are responsible for the origin of intermediate mass black holes which were recently reported to be discovered.
YMnO3, which is one of hexagonal RMnO3 compounds, has antiferromagnetic and ferroelectric properties, simultaneously. Recently, it has been reported that cross-correlation in the magnetic dielectric properties on hexagonal YMnO3 single crystals. However, the cross-correlation in the magnetic-ferroelectric properties has not been understood yet. In this study, we investigated the cross correlation between magnetism and ferroelectricity on YMnO3 epitaxial films with excellent crystallinity. YMnO3 epitaxial films were deposited pulsed laser deposition. The YMnO3 epitaxial films show the dielectric anomalies at around Néel point of the films. It was suggested that the ferroelectric domain switching was suppressed by the magnetic ordering. The relationship between the magnetic structure and the ferroelectric properties are discussed in terms of the temperature dependences of magnetization and dielectric permittivity. Moreover, the ablation plume of YMnO3 was investigated by optical emission spectroscopy. The effect of the ablation conditions on the thin film growth and electrical properties was discussed.
We review experimental results—over the past 10–15 years and more recent theoretical modeling and computer simulations—on the effects of surface subnanoscale texture on adhesion and friction and the implications for certain mechanical properties of materials such as Mode I and Mode II failure. Examples and comparisons include surfaces that are adhesive or nonadhesive, rough or smooth, hard or soft (e.g., viscoelastic polymers), dry (unlubricated) or lubricated. One important conclusion is that the ultrafine picoscale details of a surface lattice or its roughness (“texture”) can be the most important factor in determining its friction and Mode II fracture, whereas such effects are less important for determining adhesion forces and Mode I fracture processes. Such studies are also clarifying the molecular and atomic basis of many well-established adhesion and tribological laws and empirical observations and are revealing new fundamental insights and relationships between nanoscale (molecular) and macroscale processes.
We examined atomic and electronic structures of Pt supported on graphene, using the first-principles calculations based on the density functional theory (DFT). First, we examined the interaction between graphene and a Pt(111) monolayer. The stable distance between graphene and the Pt-monolayer is 3.48Å and the adhesive energy is 0.09 eV/atom. The density of states (DOS) for the Pt(111)/graphene system is the same with the sum of respective DOS's of the graphene sheet and the Pt monolayer. These results indicate that the interaction between graphene and a Pt(111) monolayer is very weak. Second, we examined the interaction between graphene and a Pt atom. The Pt-C bond length is 2.31Å and the adsorption energy is 2.82 eV/adatom, which means the stronger interaction. Finally, we examined the interaction between graphene and a Pt cluster consisting of ten atoms. The distance between graphene and the bottom layer of the cluster is about 2.7Å, which is shorter than that between graphene and the Pt(111) monolayer. This shows that the interaction between the Pt10 cluster and graphene is stronger than the Pt-monolayer/graphene interaction. The center atom in the hexagonal bottom layer of the Pt cluster has the nearest distance with graphene of about 2.5Å. If there is a defect on graphene, the center atom of the hexagonal bottom layer strongly interacts with that.