Yuki Kuruma

National Institute of Advanced Industrial Science and Technology

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Hiromu Sakurai

Hokkaido University of Science

Takayuki Sakaguchi

National Institute of Advanced Industrial Science and Technology

Yutaka Matsumi

Nagoya University

Tomoki Nakayama

Nagasaki University

Yosuke Sakamoto

Kyoto University

Michihiro Mochida

Nagoya University

Yoshihiro Nakashima

Tokyo University of Agriculture and Technology

Shuhei Ogawa

Maruho (Japan)

Maho Nakagawa

Université de Strasbourg

Yoshizumi Kajii

National Institute for Environmental Studies

Cooperative Institutions

The University of Tokyo

Nagoya University

Kyoto University

National Institute of Advanced Industrial Science and Technology

Osaka University

National Institute for Environmental Studies

Tokyo Metropolitan University

Hokkaido University

Earth and Space Research

Institute of Solar-Terrestrial Physics

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Assessment of the Sphericity of Submicrometer Particles Using a Single-particle Polar Nephelometer at an Urban Site in Japan

Aerosol and Air Quality Research (2020)

Maho Nakagawa Tomoki Nakayama Hiroshi Sasago Yuki Kuruma Hikari Yai

The sphericity of particles must be considered when evaluating their effects on the climate and human health. Thus, to examine this property and its controlling factors, this study measured the scattering angular distributions of both thermodenuded and non-thermodenuded individual particles with a diameter of 500 nm in real time using a home-made polar nephelometer in Nagoya, Japan. Estimating the sphericities based on the depths of the local minima in the scattering angular distributions, we found the ambient aerosols to be external mixtures of at least two types of particles, one with relatively high and the other with relatively low sphericity. Although most of the particles exhibiting high sphericity were removed as they passed through the thermodenuder, approximately one-third of the fraction exhibiting low sphericity remained. During the daytime, the proportion of the low-sphericity particles decreased, whereas the average sphericity of the high-sphericity particles increased, which can be attributed to photochemical formation and/or aging processes. On days with extremely high relative humidity, the diurnal variation in the average sphericity displayed another peak during the early morning, which may have been due to the secondary formation of nitrate.

Sphericity

Nephelometer

Particle (ecology)

10.4209/aaqr.2020.01.0023

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Development of an SI Traceable Measurement Method for the Number Concentration of Liquid-borne Particles

Journal of the Society of Powder Technology Japan (2023)

Yuki Kuruma Takayuki Sakaguchi Hiromu Sakurai

The number concentrations of liquid-borne particles are widely measured in various settings such as in semiconductor industries, clinical laboratory testing, pharmaceutical industries, and maintenance for industrial machineries. These industrial fields need quality control for the particle number concentration measurements by using reliable metrological standard. To establish the traceability in measurements of the particle number concentration from sub-micrometer to micrometer size range, we have developed an SI-traceable measurement method. We refer to this method as mass-measurement-type optical particle counting (M-OPC) method. The M-OPC method is based on single-particle optical particle counting method. Adopting two different type of optical particle counters having different measurable size ranges enables our calibration service to cover a wide range of particle diameters from sub-micrometer to micrometer level (600 nm–10 μm). This paper reviews the principle of the M-OPC method and the evaluation procedure of the particle number concentration including the uncertainty analysis. We also report the results of the verification tests for 600 nm, 2 μm, and 10 μm to confirm the validity of the M-OPC method in the above size range by using polystyrene latex (PSL) particles suspensions.

Micrometer

Particle (ecology)

Particle counter

Traceability

10.4164/sptj.60.414

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Measurement of ambient particles using a newly developed polar nephelometer -Relationship between scattering angular distributions and chemical compositions-

Japan Geoscience Union (2016)

Maho Nakagawa Tomoki Nakayama Hiroshi Sasago Yuki Kuruma Hikari Yai

Nephelometer

Polar coordinate system

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Missing ozone-induced potential aerosol formation in a suburban deciduous forest

Atmospheric Environment (2017)

Tomoki Nakayama Yuki Kuruma Yutaka Matsumi Yu Morino Kei Sato

Isoprene

Noon

Volatile organic compound

Particle (ecology)

Atmospheric chemistry

10.1016/j.atmosenv.2017.10.014

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Citations (3)

Development of primary standard for number concentration in liquid-borne particles by the optical particle counter for liquid with the method for simultaneous measurement of mass

The Japan Society of Applied Physics (2019)

Takayuki Sakaguchi Yuki Kuruma Hiromu Sakurai

Particle counter

Particle (ecology)

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Fluorescence particle counter for distinction of spurious counts

The Japan Society of Applied Physics (2021)

Yuki Kuruma Takayuki Sakaguchi Hiromu Sakurai

Spurious relationship

Particle (ecology)

Source

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Primary standard for the number concentration of liquid-borne particles: extension of the diameter range from the micrometer to the sub-micrometer level and reduction of the measurement uncertainty

Metrologia (2021)

Yuki Kuruma Takayuki Sakaguchi Hiromu Sakurai

Micrometer

Primary standard

Primary (astronomy)

10.1088/1681-7575/abff07

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Citations (6)

Mass-measurement-type optical particle counting method for determination of number concentration of liquid-borne particles

Advanced Powder Technology (2019)

Yuki Kuruma Takayuki Sakaguchi Hiromu Sakurai

Micrometer

Particle (ecology)

Particle counter

10.1016/j.apt.2019.12.003

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Citations (6)

Optimization of Flow Imaging Microscopy Setting Using Spherical Beads with Optical Properties Similar to Those of Biopharmaceuticals

Journal of Pharmaceutical Sciences (2023)

Takaaki Kurinomaru Kimitoshi Takeda Megumi Onaka Yuki Kuruma Keiji Takahata

Flow imaging microscopy (FIM) is widely used to characterize biopharmaceutical subvisible particles (SVPs). The segmentation threshold, which defines the boundary between the particle and the background based on pixel intensity, should be properly set for accurate SVP quantification. However, segmentation thresholds are often subjectively and empirically set, potentially leading to variations in measurements across instruments and operators. In the present study, we developed an objective method to optimize the FIM segmentation threshold using poly(methyl methacrylate) (PMMA) beads with a refractive index similar to that of biomolecules. Among several candidate particles that were evaluated, 2.5-µm PMMA beads were the most reliable in size and number, suggesting that the PMMA bead size analyzed by FIM could objectively be used to determine the segmentation threshold for SVP measurements. The PMMA bead concentrations measured by FIM were highly consistent with the indicative concentrations, whereas the PMMA bead size analyzed by FIM decreased with increasing segmentation threshold. The optimal segmentation threshold where the analyzed size was closest to the indicative size differed between an instrument with a black-and-white camera and that with a color camera. Inter-instrument differences in SVP concentrations in acid-stressed recombinant adeno-associated virus (AAV) and protein aggregates were successfully minimized by setting an optimized segmentation threshold specific to the instrument. These results reveal that PMMA beads can aid in determining a more appropriate segmentation threshold to evaluate biopharmaceutical SVPs using FIM.

Bead

Particle (ecology)

10.1016/j.xphs.2023.10.007

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Citations (2)

Determination of refractive index increments of PMMA particles dispersed in liquid phase

Advanced Powder Technology (2023)

Kayori Takahashi Yuki Kuruma Keiji Takahata Hiromu Sakurai

Refractometer

Refractometry

Normalized frequency (unit)

10.1016/j.apt.2023.104185

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Citations (1)