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Published in Anton Sebastian, A Dictionary of the History of Medicine, 2018
Actinometer [Greek: actina, ray + meter, to measure] Instrument for measuring heat from the Sun. Invented by Sir John Herschel (1792–1871) in 1825 and improved by Robert Bunsen (1811–1899) and Henry Ruscoe in 1856.
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Published in Mario P. Iturralde, Dictionary and Handbook of Nuclear Medicine and Clinical Imaging, 1990
Actinometer. The general name for any instrument used to measure the intensity of radiant energy, particularly that of the sun. Actinometers may be classified, according to the quantities which they measure, in the following manner: (1) pyrheliometer, which measures the intensity of direct solar radiation; (2) pyranometer, which measures global radiation (the combined intensity of direct solar radiation and diffuse sky radiation); and (3) pyrgeometer, which measures the effective terrestrial radiation.
Photocatalytic activity of nanoparticles: the development of the standardized measurement for physiological conditions
Published in Nanotoxicology, 2022
Vytas Reipa, Nam Wong Song, Minjeong Kwak, Min Beom Heo, Tae Geol Lee, Paul Westerhoff, Yuqiang Bi, Blaza Toman, Vincent A. Hackley, Haruhisa Kato, Yosuke Tabei, Kanokwan Nontapot, Yonghyun Choi, Jonghoon Choi
Illumination intensity variation between the 96-well plate wells can result in uneven irradiance and NADH oxidation rates causing a variability in the measured catalytic activities. Previously, this issue was addressed by performing the measurement by loading a separate full 96-well plate with a fixed nano catalyst concentration (Lee et al. 2011) and using the measured NADH conversion rates to adjust for the inter-well light intensity variations. We have measured the irradiation of each well by means of UV actinometry with 2-nitrobenzaldehyde as a photo-reagent (Willett and Hites 2000). First, a separate 96-well plate is loaded with a solution of 2-nitrobenzaldehyde at pH = 12 containing phenolphthalein, serving as a colorimetric pH indicator. Next, the plate is exposed to a trans-illuminator light (λmax = 365 nm) for 10 min and absorbance at 540 nm is recorded with a plate reader. Absorbance variation between plate wells corresponds to the pH change due to the differences in the photochemical conversion of 2-nitrobenzaldehyde into benzoic acid, which is dependent on the difference in the photon flux in each well. This provides the light intensity correction factors for individual wells and a way to compensate for the inhomogeneity of the UVA light source profile. Plate position on the trans-illuminator is then fixed using a cutout to ensure a similar light intensity pattern during the calibration and subsequent exposure of NADH and test NP combination.