DLS measurements of the apparent diameter of 70 nm PSL particles obtained in pure water at NMIJ, dapp (○, Δ, +, ×, and ◊) and NIST, ZAVE (filled squares). The concentrations (× 1011 particles mL−1) at NMIJ are 24 (○), 19 (Δ), 15 (+), 10 (×), and 4.9 (◊). The concentrations (× 1011 particles mL−1) at NIST are 31, 20, 13, 10, 7.5, 5.2, and 2.6. Error bars as in Fig. 1.