PURPOSE. Light-emitting diodes that emit high-intensity blue light are associated with blue-light hazard. Here, we report that blue light disturbs circadian rhythms by interfering with the clock gene in the suprachiasmatic nucleus (SCN) and that suppression of blue light at night ameliorates metabolic abnormalities by controlling circadian rhythms. METHODS. C57BL/6J mice were exposed to 10-lux light for 30 minutes at Zeitgeber time 14 for light pulse with blue light or blue-light cut light to induce phase shift of circadian rhythms. Phase shift, clock gene expression in SCN, and metabolic parameters were analyzed. In the clinical study, healthy participants wore blue-light shield eyewear for 2 to 3 hours before bed. Anthropometric data analyses, laboratory tests, and sleep quality questionnaires were performed before and after the study. RESULTS. In mice, phase shift induced with a blue-light cut light pulse was significantly shorter than that induced with a white light pulse. The phase of Per2 expression in the SCN was also delayed after a white light pulse. Moreover, blood glucose levels 48 hours after the white light pulse were higher than those after the blue-cut light pulse. Irs2 expression in the liver was decreased with white light but significantly recovered with the blue-cut light pulse. In a clinical study, after 1 month of wearing blue-light shield eyeglasses, there were improvements in fasting plasma glucose levels, insulin resistance, and sleep quality. CONCLUSIONS. Our results suggest that suppression of blue light at night effectively maintains circadian rhythms and metabolism.
The development of sensors using surface acoustic wave (SAW) devices has been attracting attention. A shear horizontal SAW (SH-SAW) sensor can detect the properties and chemical reactions in liquids. To realize practical applications of the SAW sensor, it is necessary to discuss its properties. In this paper, SH-SAW sensors with a floating electrode unidirectional transducer (FEUDT) or an interdigital transducer (IDT) are compared and the insertion loss and phase characteristics are measured. Also, the phase shift between sample and reference liquids is evaluated. The results indicate that the SH-SAW sensor with the FEUDT is suitable for liquid measurements. The SH-SAW sensor with the FEUDT is then mounted in a newly developed SH-SAW sensing system. The system configuration is the same as that of a vector voltmeter measurement system. However, circuits have been developed that reduce its size. Using this system, several liquids are measured. The obtained results agree well with the theoretical values.
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