On 29 June 2015, a small phreatic eruption occurred at Hakone volcano, Central Japan, forming several vents in the Owakudani geothermal area on the northern slope of the central cones. Intense earthquake swarm activity and geodetic signals corresponding to the 2015 eruption were also observed within the Hakone caldera. To complement these observations and to characterise the shallow resistivity structure of Hakone caldera, we carried out a threedimensional inversion of magnetotelluric measurement data acquired at 64 sites across the region. We utilised an unstructured tetrahedral mesh for the inversion code of the edge-based finite element method to account for the steep topography of the region during the inversion process. The main features of the best-fit three-dimensional model are a bell-shaped conductor, the bottom of which shows good agreement with the upper limit of seismicity, beneath the central cones and the Owakudani geothermal area, and several buried bowl-shaped conductive zones beneath the Gora and Kojiri areas. We infer that the main bell-shaped conductor represents a hydrothermally altered zone that acts as a cap or seal to resist the upwelling of volcanic fluids. Enhanced volcanic activity may cause volcanic fluids to pass through the resistive body surrounded by the altered zone and thus promote brittle failure within the resistive body. The overlapping locations of the bowl-shaped conductors, the buried caldera structures and the presence of sodium-chloride-rich hot springs indicate that the conductors represent porous media saturated by highsalinity hot spring waters. The linear clusters of earthquake swarms beneath the Kojiri area may indicate several weak zones that formed due to these structural contrasts.

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We have developed a real-time terahertz time-domain polarization analyzer by using 80-MHz repetition-rate femtosecond laser pulses. Our technique is based on the spinning electro-optic sensor method, which we recently proposed and demonstrated by using a regenerative amplifier laser system; here we improve the detection scheme in order to be able to use it with a femtosecond laser oscillator with laser pulses of a much higher repetition rate. This improvement brings great advantages for realizing broadband, compact and stable real-time terahertz time-domain polarization measurement systems for scientific and industrial applications.

Dogs with previously sectioned dorsal spinal roots (T11-L3) were used in experiments for collecting the adrenal venous blood without anesthetizing or evoking any pain. Intravenous injection of histamine in doses of 0.05–1.0 mg/kg body wt. was demonstrated to produce a marked acceleration of 17-hydroxycorticoid secretion. The time courses of changes in the secretion rate after injection of varying doses of histamine are compared.

In dogs with previously cut dorsal spinal roots (T11-L3), adrenal venous blood was collected without anesthetic or pain. Ether was then inhaled for 30–60 minutes. During and after ether inhalation, adrenal venous blood was again collected and the plasma was analyzed for 17-hydroxycorticosteroids (17-OHCS). The mean preinhalation control secretion rate of 17-OHCS by one adrenal was 0.10 (0.06–0.20) µg/kg/min. During ether inhalation it increased to 0.34–1.2 µg/kg/min. Thirty to sixty minutes after the end of ether inhalation the secretion rate increased to a maximum of 0.79–1.8 µg/kg/min. and then decreased.