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BackgroundTo increase the consultation rate of potential major depressive disorder (MDD) patients, we developed a contact-type fingertip photoplethysmography-based MDD screening system. With the outbreak of SARS-CoV-2, we developed an alternative to contact-type fingertip photoplethysmography: a novel web camera-based contact-free MDD screening system (WCF-MSS) for non-contact measurement of autonomic transient responses induced by a mental task.MethodsThe WCF-MSS measures time-series interbeat intervals (IBI) by monitoring color tone changes in the facial region of interest induced by arterial pulsation using a web camera (1920 × 1080 pixels, 30 frames/s). Artifacts caused by body movements and head shakes are reduced. The WCF-MSS evaluates autonomic nervous activation from time-series IBI by calculating LF (0.04–0.15 Hz) components of heart rate variability (HRV) corresponding to sympathetic and parasympathetic nervous activity and HF (0.15–0.4 Hz) components equivalent to parasympathetic activities. The clinical test procedure comprises a pre-rest period (Pre-R; 140 s), mental task period (MT; 100 s), and post-rest period (Post-R; 120 s). The WCF-MSS uses logistic regression analysis to discriminate MDD patients from healthy volunteers via an optimal combination of four explanatory variables determined by a minimum redundancy maximum relevance algorithm: HF during MT (HFMT), the percentage change of LF from pre-rest to MT (%ΔLF(Pre–R⇒MT)), the percentage change of HF from pre-rest to MT (%ΔHF(Pre–R⇒MT)), and the percentage change of HF from MT to post-rest (%ΔHF(MT⇒Post–R)). To clinically test the WCF-MSS, 26 MDD patients (16 males and 10 females, 20–58 years) were recruited from BESLI Clinic in Tokyo, and 27 healthy volunteers (15 males and 12 females, 18–60 years) were recruited from Tokyo Metropolitan University and RICOH Company, Ltd. Electrocardiography was used to calculate HRV variables as references.ResultThe WCF-MSS achieved 73% sensitivity and 85% specificity on 5-fold cross-validation. IBI correlated significantly with IBI from reference electrocardiography (r = 0.97, p < 0.0001). Logit scores and subjective self-rating depression scale scores correlated significantly (r = 0.43, p < 0.05).ConclusionThe WCF-MSS seems a promising contact-free MDD screening apparatus. This method enables web camera built-in smartphones to be used as MDD screening systems.

We have developed a physical random number generator in which radioactivity, i.e., one of the most random phenomena, is used. The long-lived radioactive nuclide 241 Am and a clock pulse generator are used for generating random pulses and regular pulses, respectively. A 1024 channel scaler counts clock pulses between two consecutive random pulses. This procedure is repeated and the counts are stored in a computer.The last digit of a count at the scaler gives a digit of uniform physical random number.We have tested our random numbers for randomness and uniformity, and stored 600 million random digits on each compact disc for users.

The 152Eu/Eu ratios were measured in a tombstone exposed to neutrons of the Hiroshima atomic bomb near the hypocenter. Measurements of 152Eu gamma rays were performed for europium samples chemically isolated from numerous rock specimens taken from the tombstone. A reliable attenuation curve of the 152Eu/Eu ratios was obtained. The curve suggests that the thermal neutron component was relatively small and the average incident angle of neutrons to the tombstone was roughly 45°C from the perpendicular downward direction. It revealed to us several important pieces of information concerning the energy and angular distributions near the Hiroshima bomb hypocenter.