An International Research Comparative Study of the Degree of Cooperation between disciplines within mathematics and mathematical sciences: proposal and application of new indices for identifying the specialized field of researchers

Behaviormetrika - Based on 10 years of data on academic papers from 2005 to 2014 available on the “Web of Science”, we conducted an in-depth review and analysis of...     

4032 ppi High‐resolution OLED microdisplay

A 0.5‐inch Ultra Extended Graphics Array (UXGA) organic light‐emitting diodes microdisplay has been developed with 6.3 μm pixel pitch. Not only 4032 ppi high resolution but high frame rate, low power consumption, wide viewing angle, and high luminance have been achieved. This newly developed organic light‐emitting diodes microdisplay is suitable for Near‐to‐Eye display applications, especially electronic viewfinders.     

An approach to the deep hydrodesulfurization of light cycle oil

Deep HDS of LCO to be <10 ppm was achieved by fractionating HDS. An LCO fraction having boiling point lower than 340 °C was easily hydrodesulfurized to be <10 ppmS under conventional HDS conditions because the hydrodesulfurization of the reactive sulfur species contained in the fraction was hardly inhibited by the aromatic compounds. In contrast, the heavier fraction was very hard to be hydrodesulfurized since its refractory sulfur species were strongly inhibited by large content of aromatic components. Dilution of the heavier fraction with common solvents showed higher reactivity over NiMo/Al₂O₃ catalyst than itself alone. Decalin, which showed the highest dilution effect, was believed to strip the strongly adsorbed aromatics off from the catalyst surface.     

High-Temperature Formation Phases and Crystal Structure of Hot-Pressed Thermoelectric CuGaTe<Subscript>2</Subscript> with Chalcopyrite-Type Structure

Polycrystalline CuGaTe₂ with a chalcopyrite-type structure consolidated by hot-pressing is a potential candidate as a medium-temperature thermoelectric (TE) material. However, its high-temperature formation phases have rarely been reported to date. Here, we investigated the temperature-dependent formation phases and crystal structure at 300–800 K of hot-pressed CuGaTe₂. From synchrotron x-ray diffraction data and crystal structure analysis of the heating and cooling processes, it was clarified that a certain amount of impurity phases, such as Te and CuTe, precipitated from the CuGaTe₂ matrix when the temperature was increased (to 500–650 K). This is the temperature range where CuGaTe₂ has been reported to show high TE performance. After CuGaTe₂ was heated to 800 K, such impurity phases remained, even when cooled to room temperature. They also affected the tetragonal distortion and the x-coordinate of Te in the CuGaTe₂ matrix, probably due to deficiencies of Cu and Te in the matrix. Our results reveal detailed information on the formation phases of CuGaTe₂ at high temperature and thus provide insight for evaluation of its high-temperature stability and transport properties.     

Effect of glass transition temperature on heat‐responsive gas bubbles formation from polymers containing tert‐butoxycarbonyl moiety

Various types of polymers containing tert‐butoxycarbonyl (BOC) moiety as the typical protecting group of functional moieties have been used for the design of stimuli‐responsive polymer materials. In this study, we investigated the heat‐responsive deprotection behavior of BOC‐containing polymers obtained by radical polymerization of 4‐(tert‐butoxycarbonyloxy)styrene (BSt) and copolymerizations of BSt with styrene and methyl acrylate. The deprotection of BOC groups accompanying the evolution of isobutene and carbon dioxide as gaseous products was monitored by thermogravimetric analyses at different temperature circumstances; that is, on heating at a rate of 10 °C/min and under isothermal conditions at various temperatures. The deprotection resulted in a significant decrease in the transmittance of visible light due to the formation of a large number of gas bubbles, that is, foaming, in the polymer films when a heating temperature was close to the glass transition temperature of the used polymer. The potential of BOC‐containing polymers was also evaluated as the heat‐responsive adhesive polymers for dismantlable adhesion. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46252.     

Crosslinking of poly(vinyl alcohol) and poly(vinyl acetate) using poly(maleic anhydride‐alt−2,4‐dimethyl‐1,3‐pentadiene) as polyfunctional crosslinker and decrosslinking by ozone degradation

Crosslinking and decrosslinking reactions of poly(vinyl alcohol) (PVA) and poly(vinyl acetate) (PVAc) using an alternating copolymer of maleic anhydride and 2,4‐dimethyl‐1,3‐pentadiene (PMAD) as the polyfunctional crosslinker and subsequent ozone degradation are reported. PVA and PVAc are heated at 200 °C for 0.5 to 3 h in the presence of 5 to 30 wt % of PMAD in the solid state to obtain the corresponding crosslinked polymers. The reactions of a hydroxy group of PVA and an acetate group of PVAc with an anhydride group of PMAD slowly proceed to give insoluble polymers with a loose crosslinking structure. Almost no change in the thermal decomposition temperatures and the IR spectra is observed during the crosslinking reactions. The crosslinked PVA produces hydrogels with a high swelling ratio of 500 to 1700%, which are readily degradable during a reaction with ozone in water at 0 °C. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44229.     

Characteristics and Reactivity of Lignin in Acacia and Eucalyptus Woods

The chemical characteristics of lignin, including the Klason lignin content, acid-soluble lignin content, proportion of the aromatic ring types [syringyl ratio = syringyl/(syringyl + guaiacyl)], and proportion of the diastereomeric forms for the β-O-4 structure [erythro ratio = erythro/(erythro + threo)], and pulpability were investigated for 28 wood samples belonging to the genera Acacia and Eucalyptus. Although the lignin characteristics of these 28 woods varied widely, the chemical characteristics of the two genera could be categorized in two clearly distinguished groups on the basis of the syringyl ratio. Clear negative correlations were observed between both the syringyl and erythro ratios and the total lignin content (sum of the Klason and acid-soluble lignin contents) within each genus. In addition, the syringyl ratio correlated positively with the erythro ratio and acid-soluble lignin content, regardless of the genus. The existence of a clear, high correlation between the syringyl and erythro ratios supports the hypothesis that the aromatic ring type (syringyl ratio) is a decisive factor for controlling the diastereomeric forms of the β-O-4 structure (erythro ratio). Each of the wood samples was also subjected to Kraft pulping, and it was demonstrated that the woods with higher syringyl ratios were easier to delignify. This tendency is reasonably attributed to the high reactivity of the erythro-rich and syringyl-rich β-O-4 structures, and the low lignin content of these syringyl-rich woods.     

Construction of superconducting bulk magnet magnetron sputtering apparatus for fabrication of highly reflective optical mirrors

We have developed the two-cathode magnetron sputtering apparatus equipped with superconducting permanent magnet to produce Mo/Si multi-layer films, which would potentially serve as a high-quality optical mirror at extreme ultraviolet (EUV) wavelength of 13.5 nm. The best deposition condition was searched by analyzing the structure of the inter-diffusion layer formed in the Mo/Si bi-layer film prepared under different deposition conditions. It was found that (1) Xe gas should be used as inert gas species, (2) its pressure is lower than 4 × 10⁻² Pa, (3) a throw distance is longer than 250 mm and (4) discharge voltage around 2 kV. By making full use of these data, we synthesized Mo/Si multi-layer films and analyzed the structure and its effect on the reflectivity. The highest EUV-reflectivity so far obtained is 67% in the normal incident condition.     

Nanosurface-confined anisotropic growth and magnetism of ellipsoidal alpha-Fe nanogranules

We have investigated the nanosurface-confined anisotropic growth of ordered-ellipsoidal Fe nanogranules when an Fe plume was deposited at a slanting angle onto an anodized aluminum oxide (AAO) film. Layer-by-layer growth was also investigated. This growth is driven by two critical factors: (1) a new rhombic AAO cell and (2) the slanting deposition of the Fe plume. During slanting deposition, the rhombic AAO cell induces strong restrictions in the nucleation site, growth direction, and granular size; therefore, the degree of freedom during growth is restricted. The magnetic dipoles of the ordered Fe nanogranules are placed along the long axis of the ellipsoid at an angle of 180 degrees (antiparallel) due to the demagnetizing field, shape anisotropy, and magnetic dipole-to-dipole interactions.     

Insights on interfacial charge transfer across P3HT/fullerene photovoltaic heterojunction from Ab initio calculations

The interfacial charge-transfer mechanism of the P3HT/fullerene photovoltaic heterojunction is elucidated using density functional theory calculations. Our findings indicate that an efficient adiabatic electron transfer is highly probable due to the presence of an extended electronic state that has a significant probability distribution across the interface in the lowest excited state. Furthermore, efficient exciton dissociation is possible because this bridging state has significant overlap with near-degenerate unoccupied states that are localized on the fullerene.