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Both high-beam-quality and high-power operation of InGaN laser array are realized by lateral-corrugated waveguides (LCWG) with reduced higher-order transverse modes. In our proposed structure, the number of higher-order modes supported by the waveguide and scattered by the LCWG is smaller than that of a conventional LCWG, which suppresses the deterioration of quantum efficiency. This contributes to high-power operation for laser processing, since the maximum output power of an array is sensitive to the efficiency. Even at 55 W from a single InGaN array chip, averaged lateral beam-quality factor of 4.9 is successfully obtained for individual emissions in the array.

The aerosol oxidative potential (OP) is considered to better represent the acute health hazards of aerosols than the mass concentration of fine particulate matter (PM2.5). The proposed major contributors to OP are water soluble transition metals and organic compounds, but the relative magnitudes of these compounds to the total OP are not yet fully understood. In this study, as the first step toward the numerical prediction of OP, the cumulative OP (OPtm*) based on the top five key transition metals, namely, Cu, Mn, Fe, V, and Ni, was defined. The solubilities of metals were assumed constant over time and space based on measurements. Then, the feasibility of its prediction was verified by comparing OPtm* values based on simulated metals to that based on observed metals in East Asia. PM2.5 typically consists of primary and secondary species, while OPtm* only represents primary species. This disparity caused differences in the domestic contributions of PM2.5 and OPtm*, especially in large cities in western Japan. The annual mean domestic contributions of PM2.5 were 40%, while those of OPtm* ranged from 50 to 55%. Sector contributions to the OPtm* emissions in Japan were also assessed. The main important sectors were the road brake and iron–steel industry sectors, followed by power plants, road exhaust, and railways., 我が国における金属由来の粒子酸化能の大気中濃度について、初めて予測に成功、発生源別の寄与率を評価 --健康影響の低減に効果的な大気汚染物質の削減に向けて--. 京都大学プレスリリース. 2021-04-22.

Both high-beam-quality and high-power operation of InGaN laser diodes are realized by lateral corrugated waveguides with reduced higher-order transverse modes. As a result, lateral beam-quality factor is reduced from 8.8 (straight waveguide) to 3.8 even at a continuous-wave output power of 2.1 W.

A smile-suppressed high-power InGaN laser array has been developed for a high beam quality material processing light source. The smile effect becomes apparent especially in InGaN laser array with large chip curvature due to lattice mismatch of epitaxial growth layers. To reduce the smile, periodic grooves are introduced to the epitaxial layers for removing the origin of strain. It also enables a two-dimensional strain management of remaining epitaxial layers. This technology improves the chip curvature within micron range, i.e. as small as 0.3 μm in a 9 mm-width InGaN laser array. We have successfully realized reducing the smile to 0.4 μm without degrading the laser light output characteristics.

The simultaneous multi-element isotope ratio measurement by inductively coupled plasma time of flight mass spectrometry (ICP-TOFMS) was examined to evaluate the possibility of simultaneous multi-element determination by isotope dilution mass spectrometry (IDMS). Output from the two different ICP-TOFMS instruments (icpTOF and Optimass 9500) were examined and the figures of merit between them were determined from the analytical results of intensity ratios as isotope ratio measurements for 10 elements (137Ba/135Ba, 111Cd/112Cd, 63Cu/65Cu, 69Ga/71Ga, 60Ni/62Ni, 208Pb/206Pb, 107Ag/109Ag, 205Tl/203Tl, 238U/235U and 66Zn/68Zn). For the results, linear calibration curves for all elements, except for 235U obtained by icpTOF, with coefficient of determination (r2) of more than 0.999 could be obtained for both ICP-TOFMS instruments in the range of concentration from 1 ng mL−1 to 100 ng mL−1, even though the sensitivities of elements were slightly different. However, the trends of intensity ratios of elements observed were different between two ICP-TOFMS instruments, especially for heavier elements such as Pb, Tl and U. The icpTOF provided consistent isotope ratios at the concentrations from 1 ng mL−1 to 100 ng mL−1 for most of elements examined, although Optimass 9500 did not provide consistent isotope ratios except for Ba, Ga and Ag. From these analytical results, icpTOF appears to be the better instrument for simultaneous multi-element determination by IDMS compared to Optimass 9500. Consequently, the simultaneous IDMS of Cd, Hg and Pb by icpTOF was demonstrated to examine the possibility of simultaneous multi-element IDMS by ICP-TOFMS and the consistent analytical results with respect to the certified values could be obtained. From these results, it was expected that icpTOF could be used for simultaneous multi-element IDMS to obtain accurate and precise analytical results since it provided consistent isotope ratios of elements.

To measure driving-distance-based mass emission factors for airborne brake wear particulate matter (PM; i.e., brake wear particles) related to the non-asbestos organic friction of brake assembly materials (pads and lining), and to characterize the components of brake wear particles, a brake wear dynamometer with a constant-volume sampling system was developed. Only a limited number of studies have investigated brake emissions under urban city driving cycles that correspond to the tailpipe emission test (i.e., JC08 or JE05 mode of Japanese tailpipe emission test cycles). The tests were performed using two passenger cars and one middle-class truck. The observed airborne brake wear particle emissions ranged from 0.04 to 1.4 mg/km/vehicle for PM10 (particles up to 10 μm (in size), and from 0.04 to 1.2 mg/km/vehicle for PM2.5. The proportion of brake wear debris emitted as airborne brake wear particles was 2–21% of the mass of wear. Oxygenated carbonaceous components were included in the airborne PM but not in the original friction material, which indicates that changes in carbon composition occurred during the abrasion process. Furthermore, this study identified the key tracers of brake wear particles (e.g., Fe, Cu, Ba, and Sb) at emission levels comparable to traffic-related atmospheric environments.

The emission of airborne brake wear particles due to non-asbestos organic friction material was studied for two passenger cars and a middle class truck. The emission of airborne brake particulates was tested with a brake dynamometer with a constant volume sampling system and real-time mass measurements were made. The particles emissions under constant driving were calculated in terms of initial wheel speed and deceleration. Time series mass emissions were obtained by real-time dust monitors for PM2.5 and PM10 (i.e., particles with a 50% cutoff aerodynamic diameter of 2.5 and 10 μm, respectively). The airborne brake wear particles emission occurred at deceleration and acceleration, suggesting resuspension of wear particles from friction on the surface of brakes and grooves at acceleration. The resuspended brake wear particles, whose emission during acceleration tended to increase with the initial speed, significantly contributed to the total emission. Therefore, they must be included in emission measurements of PM2.5 and PM10 during brake abrasion tests. Further measurements under a wide range of driving conditions, such as tailpipe emission test cycles, are required to obtain national and regional specific emission parameters for the development of inventories.

This article presents a cylindrical counter-current flow diffusion denuder with high efficiency penetration of nanoparticles, for non-specific removal of trace gases from an air flow. The denuder was designed to exchange gases in the sample flow by diffusion to the purge flow across a cylindrical microporous glass tube. Laboratory test results indicated that removal efficiencies of gases increased with a lower sample flow rate and a higher sample to purge flow rate ratio. Additionally, the pore size of the microporous glass did not affect gas removal efficiency and particle penetration following optimization of sample and purge flow rate conditions. Significantly high particle penetration was obtained for the counter flow denuder technique (94% penetration for 20 nm of polystyrene latex particle [PSL]) that agreed with theoretical estimation attributed to diffusion loss.Copyright © 2017 American Association for Aerosol Research

Reactive nitrogen species emission from the exhausts of gasoline and diesel vehicles, including nitrogen oxides (NOPhotolysis of HONO is a dominant source of morning OH radicals. Conventional traffic-induced HONO/NO

We propose optical-loss suppressed thick-optical-waveguide (TOW) InGaN laser diodes (LDs) without operatingvoltage increase. A record high continuous-wave (CW) output of 7.2W for a single-emitting InGaN LD is achieved without thermal peak-out in the light-current curve. The TOW enables to confine major part of the propagating light into a transparent undoped region, and thus significantly reduces the optical-loss. An electron-overflow-suppression (EOS) layer placed between the waveguide layer and a p-cladding layer plays an important role to reduce the operating voltage after introduction of the undoped TOW layer. We executed a self-consisted calculation of voltage-current characteristics taking into account Schrodinger and Poisson equations in conjunction with a carrier continuity equation. The calculation result indicates possible presence of conductivity-modulation in the waveguide filled with electrons reflected backward by the EOS layer and holes injected from the p-type cladding layer. We successfully demonstrated the optical-loss suppressed operation resulting in the slope efficiency (SE) increase from 2.0W/A to 2.5W/A. It is noted that the operating voltage of the TOW LD is nearly identical to the conventional LD thanks to the above conductivitymodulation phenomenon. The presented result suggests that our TOW structure can overcome the optical-loss drawback of the InGaN LDs, and hence will lead them to the applications requiring high wattage light sources.

Reactive nitrogen species emission from the exhausts of gasoline and diesel vehicles, including nitrogen oxides (NOx) and nitrous acid (HONO), contributes as a significant source of photochemical oxidant precursors in the ambient air. Multiple laboratory and on-road exhaust measurements have been performed to estimate the NOx emission factors from various vehicles and their contribution to atmospheric pollution. Meanwhile, HONO emission from vehicle exhaust has been under-measured despite the fact that HONO can contribute up to 60% of the total hydroxyl budget during daytime and its formation pathway is not fully understood. A profound traffic-induced HONO to NOx ratio of 0.8%, established by Kurtenbach et al. since 2001, has been widely applied in various simulation studies and possibly linked to under-estimation of HONO mixing ratios and OH radical budget in the morning. The HONO/NOx ratios from direct traffic emission have become debatable when it lacks measurements for direct HONO emission from vehicles upon the fast-changing emission reduction technology. Several recent studies have reported updated values for this ratio. This study has reported the measurement of HONO and NOx emission as well as the estimation of exhaust-induced HONO/NOx ratios from gasoline and diesel vehicles using different chassis dynamometer tests under various real-world driving cycles. For the tested gasoline vehicle, which was equipped with three-way catalyst after-treatment device, HONO/NOx ratios ranged from 0 to 0.95 % with very low average HONO concentrations. For the tested diesel vehicle equipped with diesel particulate active reduction device, HONO/NOx ratios varied from 0.16 to 1.00 %. The HONO/NOx ratios in diesel exhaust were inversely proportional to the average speeds of the tested vehicles. Implications: Photolysis of HONO is a dominant source of morning OH radicals. Conventional traffic-induced HONO/NOx ratio of 0.8% has possibly linked to underestimation of the total HONO budget and consequently underestimation of OH radical budget. The recently reported HONO/NOx ratio of ~1.6% was used to stimulate HONO emission, which resulted in increased HONO concentrations during morning peak hours and its impact of 14% OH increment in the morning. However, the results were still lower than the measured concentrations. More studies should be conducted to establish an updated traffic-induced HONO/NOx ratio.

High-power InGaN-based laser diodes (LDs) are expected as light-sources of various high-power applications. The catastrophic-optical-damage (COD) is a major failure mechanism to limit the output power, where optical absorption at a light-emitting facet causes an irreversible damage to the LDs. In this paper, a window structure in InGaN-based LDs to suppress the COD is demonstrated for the first time. The structure is formed by the metal organic chemical vapor deposition growth over a recess placed besides of the ridge-waveguide. The In composition in the quantum well which is corresponding to the bandgap energy is reduced by controlling the local tilt angle at the sidewall of the recess. Thus, the formed window structure eliminates undesired optical absorption at the cleaved facet so that extremely high light output power over 2 W in narrow-stripe ridge-waveguide InGaN-based blue-violet LDs is achieved without any CODs.

Enzymatic oxidative polymerization of methoxyphenols by a fungal laccase was investigated to synthesize polymethoxyphenols, which would be environmentally benign materials because they are degraded by lignin degrading fungi. An industrially produced thermostable laccase from Trametes sp. Ha1 polymerized o -methoxyphenol and 2,6-dimethoxyphenol in McIlvaine buffer (pH 4.5) both with and without organic solvents while the enzyme needed organic solvents to polymerize phenol, alkylphenols, and m - and p -methoxyphenols. The reaction rates correlated with the energies of the highest occupied molecular orbitals (HOMO) of the phenols. The poly( o -methoxyphenol) synthesized was soluble in N , N -dimethylformamide (DMF) while 80% of the poly(2,6-dimethoxyphenol) was insoluble in DMF. The weight-average molecular weight of the poly( o -methoxyphenol) was 7000–11,000. The reaction rate of polymerization in McIlvaine buffer without organic solvents increased until an o -methoxyphenol concentration of 500 mmol dm −3 although the Michaelis constant calculated from the oxygen consumption rate was 0.4 mmol dm −3 . The o -methoxyphenol and 2,6-dimethoxyphenol would be suitable for production of environmentally benign phenolic resins by enzymatic oxidative polymerization using laccase without formaldehyde, hydrogen peroxide, or organic solvent.

Fine particles were collected at a suburban site in the inland Kanto plain, Japan, in the spring and winter of 2007, and the summer of 2008. Organic carbon (OC), water-soluble organic carbon (WSOC), elemental carbon (EC), inorganic ions, and water-soluble organic compounds (dicarboxylic acids and levoglucosan) were analyzed. The WSOC/OC ratio was the highest in summer, followed by in spring, suggesting that organic aerosols were influenced by aging. The concentrations of total diacids (C2–C9) in spring and summer were higher than in winter. In each season, WSOC showed a strong positive correlation with the total diacids. Levoglucosan, which is recognized as a biomass burning tracer, was observed in a considerably higher concentration in winter than in spring or summer. In winter, WSOC also showed a strong positive correlation with levoglucosan. These results indicate that secondary formation is important as a source of WSOC and OC especially in the warm seasons, although emissions from biomass burning also contribute to WSOC in winter. By using the combination of source profile for biomass burning emission and EC tracer method, OC derived from biomass combustion in winter was calculated to be 47% of OC and OC derived from secondary formation in summer was calculated to be 75% of OC.

The standard method for determining gaseous aldehydes involves the collection of the aldehydes on a 2,4-dinitrophenyl hydrazine (DNPH)-coated silica gel cartridge, followed by solvent extraction of the cartridge and analysis of the aldehyde derivatives using high-performance liquid chromatography (HPLC). However, acid catalysis is required for a fast and quantitative derivatization reaction, and the DNPH derivatives of α,β-unsaturated aldehydes, such as acrolein, disappear during storage of the acidified DNPH-coated cartridges. In this paper, we describe a new method that involves the collection of acrolein and other lower aldehydes on a non-acidified DNPH-coated silica-gel cartridge. Using this method, we were able to carry out highly sensitive simultaneous sampling, as indicated by the quantitative collection of acrolein and other lower aldehydes on the cartridge. The acrolein hydrazone was stable on the cartridge at room temperature, and the gaseous acrolein concentrations measured in a test atmosphere were in good agreement with those obtained by means of the traditional DNPH-solution method. In addition, the new method was tested on an ambient air sample. The operational procedure for the non-acidified DNPH-coated cartridge is nearly the same as that for the standard DNPH/HPLC method. This new method will permit the determination of acrolein, formaldehyde, and acetaldehyde in atmospheric environmental applications.

Real time secondary organic aerosol (SOA) density evolution for m-xylene photo-oxidation and α-pinene ozonolysis was obtained using an Aerosol Particle Mass Analyzer (APM)/Scanning Mobility Particle Spectrometer (SMPS) setup, which has been modified to achieve higher transmission of particles and improved sampling frequency. The aerosol density of SOA generated from α-pinene ozonolysis was found to be 1.24 ± 0.03 g/cm3 while the aerosol generated from m-xylene photo-oxidation was determined to be 1.35 ± 0.03 g/cm3. These results confirm the measurement approach from a combined SMPS and Aerodyne Aerosol Mass Spectrometer (AMS) system and are found to be within good agreement with the effective density measurements.

The chemical composition and size distribution of submicron aerosols were analyzed at a suburban site at Saitama, Japan, in the winter of 2004/2005, using an Aerodyne aerosol mass spectrometer. Although organics and nitrate were the dominant species during the sampling period, a large fraction of sulfate was observed at the accumulation mode when mass loading was low and wind speed was high. The size distributions of m/z 44 (mostly CO 2 + ) and sulfate aerosols during periods of high wind speed showed remarkable similarities in the accumulation mode, indicating that oxygenated organics were aged aerosols and internally mixed with sulfate. Ozone concentrations were also increased during these high wind speed periods although nighttime (e.g., 12/17 2004), indicating that the oxygenated compounds were strongly influenced by transported and aged air masses. The diurnal profiles of ultrafine-mode organics and hydrocarbon-like organic aerosols (HOA) were similar to NO X derived from traffic and other combustion sources. The temporal variation of oxygenated organic aerosols (OOA) agreed well with that of nitrate as a secondary aerosol tracer, and the diurnal profile of the OOA fraction of organics increased during the day associated with higher UV light intensity. The result of time and size-resolved chemical composition of submicron particles indicated that the OOA is associated with both photochemical activity and transboundary pollution, and ultrafine-mode organic and HOA aerosols are mainly associated with combustion sources.

We have succeeded in fabricating a photonic crystal nanocavity with a photon lifetime of 2.1 ns, which corresponds to a quality factor of 2.5 x 10(6). This lifetime is the longest recorded thus far in photonic crystal cavities, and was brought about by improvements in the fabrication process. Comparing our experimental quality factor with the results of calculations shows that we have suppressed variations in the radii and positions of the air holes composing a nanocavity such that their standard deviations are less than 1 nm.

Low-molecular-weight carbonyl compounds, generated by photochemical reactions in the atmosphere and found in the exhaust of motor vehicles, have recently come to the attention of researchers because some of them are suspected carcinogens or mutagens. Six bifunctional carbonyl compounds were detected and measured in a suburban site 30 km northwest of the Tokyo metropolitan area. Samples were taken on five sunny days between 2 August and 11 August 2003 with a low-volume denuder and three-filter tandem system using O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) as a sorbent. Bifunctional carbonyls were measured by gas chromatography-mass spectrometry after two derivatization processes with PFBHA and N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA). The average total (gas plus particle) concentrations were 162.8 ng m -3 for pyruvic acid, 113.7 ng m -3 for methylglyoxal, 36.0 ng m -3 for glycolaldehyde and 58.6 ng m -3 for glyoxal.

We successfully demonstrated a multi-striped InGaN-based laser diode (LD) array with an optical output power of 6.3 W under continuous wave operation. The LD array was operated on a conventional metal package without any cooling system. The world highest power operation as InGaN LD array is attributed to thermally optimized layout design taking advantage of highly efficient wide-striped emitters.

A multi-striped InGaN-based laser diode (LD) array is demonstrated at a high power of 6.3W under continuous wave operation. The world highest power operation as InGaN LD array is attributed to thermally optimized layout design taking an advantage of highly efficient emitters.

High power over 2W free from catastrophic-optical-damage is achieved in InGaN-based lasers with epitaxially-formed window structure. Epitaxial growth over a recess reduces the In composition which eliminates the undesired optical absorption only at the facet.

We have investigated the localized design of heterostructure photonic crystal nanocavities in order to make them more suitable for integration. While retaining theoretical quality factors of more than ten million, the total length of the heterostructure nanocavity can be reduced to ~5 mum and the shifted air holes comprising the heterostructure can be restricted to the two rows nearest the nanocavity on each side. Though the area for the heterostructure nanocavity investigated thus far was larger than 10 x 10 microm(2) in the photonic crystal slab, heterostructure nanocavities of this new design have sizes of approximately 3 x 5 microm(2), thus allowing dense integration.

We investigate the influence of the nanometer-scale variations in the radii and positions of air holes on the optical characteristics for photonic crystal heterostructure nanocavities. The change in the quality factor, the resonant wavelength, the near-field image, and the polarization property are examined using three-dimensional finite difference time domain calculation with random fluctuation patterns. The variations with a standard deviation as small as 1 nm have a clear effect on these optical characteristics, whose magnitudes are strongly dependent on the fluctuation patterns. To prevent this deterioration, the accuracy of the 50 air holes nearest to the nanocavity is the most important.

We investigated the optical characteristics of higher-order resonant modes for a heterostructure nanocavity formed in a two-dimensional photonic-crystal silicon slab. Two kinds of resonant modes were observed, the nanocavity modes and the Fabry–Pérot modes. High quality factors of more than 1.0×106 were obtained not only for the nanocavity mode but also for the Fabry–Pérot modes.