Contrasting diurnal variations in fossil and nonfossil secondary organic aerosol in urban outflow, Japan

Diurnal variations of fossil secondary organic carbon (SOC) and nonfossil SOC were determined for the first time using a combination of several carbonaceous aerosol measurement techniques, including radiocarbon (1?C) determinations by accelerator mass spectrometry, and a receptor model (chemical mass balance, CMB) at a site downwind of Tokyo during the summer of 2007. Fossil SOC showed distinct diurnal variation with a maximum during daytime, whereas diurnal variation of nonfossil SOC was relatively small. This behavior was reproduced by a chemical transport model (CTM). However, the CTM underestimated the concentration of anthropogenic secondary organic aerosol (ASOA) by a factor of 4-7, suggesting that ASOA enhancement during daytime is not explained by production from volatile organic compounds that are traditionally considered major ASOA precursors. This result suggests that unidentified semivolatile organic compounds or multiphase chemistry may contribute largely to ASOA production. As our knowledge of production pathways of secondary organic aerosol (SOA) is still limited, diurnal variations of fossil and nonfossil SOC in our estimate give an important experimental constraint for future development of SOA models.     

Wavelength Tailorability of Broadband Near‐Infrared Luminescence in Cr4+‐Activated Transparent Glass‐Ceramics

Four Cr⁴⁺‐activated transparent glass‐ceramics containing different species of silicate nano‐crystals (Zn₂SiO₄, Mg₂SiO₄, Li₂ZnSiO₄, and Li₂MgSiO₄) were successfully prepared. Absorption spectra, photoluminescence spectra, lifetime decay curves, and quantum yield of these transparent glass‐ceramics were measured. According to the crystal field strength of Cr⁴⁺‐incorporated tetrahedral sites, the broadband near‐infrared (NIR) luminescence of Cr⁴⁺ can be tailored from 1130 to 1350 nm and the lifetime of Cr⁴⁺ luminescence can be prolonged from 6 to 100 μs. Quantum yield in the transparent glass‐ceramics containing Li₂ZnSiO₄ nano‐crystals reached at 17%, which is the highest value of NIR luminescence in transition‐metal‐activated glass materials.     

Catalytic cycle of cytochrome-c3 hydrogenase,a [NiFe]-enzyme,deduced from the structures of the enzyme and the enzyme mimic

Hydrogenases catalyze uptake and production of H₂. Heterolytic cleavage of H₂ bound on [NiFe]-hydrogenase (E) produces two unequal H species to form E:H_aH_b, where H_a and H_b behave differently. The structures of various states of the enzyme established by crystallography and spectroscopy were used to construct a catalytic cycle of the enzyme. The Ni–Fe center of the active enzyme has the Ni–Fe bridging site vacant. The enzyme is suggested to bind H₂ either at Ni or Fe atom. In E:H_aH_b, H_a is considered to be a protein-bound hydron (proton or deuteron) at the entrance to the hydrophobic gas tunnel. The structure of a synthetic hydrogenase-mimic suggests H_b to be the 6th ligand to Fe. Two successive one-electron processes from E:H_aH_b complete the catalytic cycle of H₂ uptake. The reverse of the cycle operates in the H₂ production. The proposed catalytic cycle is consistent with the kinetic, crystallographic and spectroscopic studies.     

Fabrication of 80 mm diameter-sized solid oxide fuel cells using a water-based NiO–YSZ slurry

Solid oxide fuel cells (SOFCs) are very attractive for their high energy conversion efficiency and low emissions. Generally, a supported layer of SOFCs is fabricated by tape casting, using an organic solvent. Recently, a slurry based on water instead of an organic solvent has been sought in order to avoid environmental pollution. In this study, the anode of SOFCs was fabricated by aqueous tape casting, and the electrolyte and the cathode were deposited by screen printing. The I–V characteristics of the cell thus obtained were evaluated. As a result, an 80 mm diameter-sized cell with a power density of 0.33 W/cm² at 800 °C was successfully fabricated by controlling sintering conditions.     

Glass-Ceramics and Solid-State Lighting

Yttrium aluminum garnet (YAG) doped with Ce³⁺ ion is known as an excellent phosphor for light-emitting diode (LED), usually used as a powder form dispersed in organic resins. We have developed translucent glass-ceramics (GC) of YAG: Ce³⁺ microcrystals in 2004. The GC sheet with half millimeter thick can work efficiently to make identical emission spectra with conventional white LED when combined with a blue LED. This report reviews the development history of the GC materials and impact for all inorganic solution for solid-state lighting.     

Glass and Rare-Earth Elements: A Personal Perspective

Light-based technologies are strongly supported by various glass materials in general. This article focuses on glasses containing rare-earth elements, doped fibers, as well as their photonic functions such as optical amplifications in fiber telecommunication. Scientific progress and applications of rare-earth spectroscopy and technologies of doped glasses and fibers in recent 60 years have been more than dramatic. Development of various laser diodes has been strongly linked with realization of novel devices of rare-earth-doped glasses. In addition to many milestones listed in the resolution of International Year of Light, we should notice that 2015 is also the 50th anniversary of the erbium-doped glass laser, which is later transformed into the optical fiber amplifier, the enabler of today's information society.     

On-off switching properties of one-dimensional photonic crystals consisting of azo-functionalized polymer liquid crystals having different methylene spacers and polyvinyl alcohol

In this paper, photoresponsive behavior of multi-bilayered films having precisely controlled layer thickness prepared by stacking an azo-functionalized polymer liquid crystal, PMAzXAc, and polyvinyl alcohol alternatively, PVA, is described. The multi-bilayered films were found to reflect a light of specific wavelength depending on the layer thickness and refractive index, and showed the reversible change in the reflection intensity by irradiation with visible and UV lights. The change in the reflection intensity was brought about by change in the molecular orientation of PMAzXAc between an out-of-plane orientation and a photo-induced isotropic state, and was strongly dependent on the number of methylene spacer of PMAzXAc linking the azobenzene side group with the acrylate polymer main chain. PMAz6Ac with hexa-methylene spacer showed the largest change in the reflection intensity, while smaller change in the reflection intensity was observed for PMAzXAc having shorter or longer methylene spacer than 6. The effect of the methylene spacers on the photochemical change in the molecular orientation of azobenzene chromophores in the multi-bilayered films will be discussed.     

Enhanced Light Storage of SrAl2O4 Glass‐Ceramics Controlled by Selective Europium Reduction

A luminescent Eu, Dy: SrAl₂O₄ glass‐ceramics with high transparency in the visible region was successfully synthesized using the frozen sorbet technique with the control of O₂ partial pressure () for the oxidation of Eu²⁺ ions. The glass‐ceramics include Eu²⁺, Eu³⁺, and Dy³⁺ ions, and thus exhibits three characteristic types of emission bands, 4f–5d at around 520 nm (Eu²⁺ ions), 4f–4f at 610 nm (Eu³⁺ ions), and 480 nm (Dy³⁺ ions). The Eu, Dy: SrAl₂O₄ glass‐ceramics provide remarkable long‐persistent luminescence under dark condition. The glass‐ceramics also exhibits color‐changing luminescence in the visible region based on their remarkable light storage properties. The luminescent Eu, Dy: SrAl₂O₄ glass‐ceramics using the frozen sorbet technique with control of are promising materials for application in novel photonic and light storage materials.     

A Fast and Accurate Method of Redesigning Analog Subcircuits for Technology Scaling

In this paper, we present an efficient approach for technology scaling of MOS analog circuits by using circuit optimization techniques. Our new method is based on matching equivalent circuit parameters between a previously designed circuit and the circuit undergoing redesign. This method has been applied to a MOS operational amplifier. We were able to produce a redesigned circuit with almost the same performance in under 4 h, making this method 5 times more efficient than conventional methods.