arXiv subjects

Y. Naito

Publications and source records attributed to Y. Naito.

4 recordsLinked to original sources

arXiv2026

The Sunrise Chromospheric Infrared Spectro-Polarimeter SCIP: an instrument for SUNRISE III

The Sunrise balloon-borne solar observatory is equipped with a one-meter aperture optical telescope, offering a unique platform for uninterrupted seeing-free observations across ultraviolet, visible, and infrared wavelengths from altitudes higher than 33 km. For the third flight of the upgraded Sunrise observatory conducted in 2024, now called Sunrise III, a new spectro-polarimeter called the Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) was developed for observing near-infrared wavelength ranges around 770 nm and 850 nm. These wavelength ranges contain many spectral lines, including two of the Ca II infrared triplet, K I D1 and D2 lines, and multiple Fe I lines, that are sensitive to solar magnetic fields and velocities in the photosphere and chromosphere. SCIP consists of a grating spectrograph in which polarimetric measurements are conducted using a rotating waveplate as a modulator and polarizing beam splitters placed in front of the cameras. The spatial and spectral resolutions are 0.21" and 1x10^5, respectively, and a polarimetric sensitivity of 0.03% (1sigma) of the continuum intensity is achieved with a 10 s integration time per a resolution element. To achieve high-precision detection of small polarization signals, we carefully designed the optical and mechanical systems, polarization components, control electronics, and onboard data processing. Together with the other post-focus instrumentation developed for Sunrise III, the Sunrise Ultraviolet Spectropolarimeter and Imager (SUSI) and the visible imaging spectro-polarimeter Tunable Magnetograph (TuMag), SCIP provides novel observations that help elucidate energy transfer and time-dependent phenomena across the solar photosphere and chromosphere.

astro-ph.SR↗

arXiv2022

Pressure tuning of localization and superconductivity in LaOPbBiS$_{3}$ and La$_{2}$O$_{2}$Bi$_{3}$AgS$_{6}$

We report the effect of pressure on the electrical transport properties of the four-layer-type bismuth chalcogenide semiconductors LaOPbBiS$_{3}$ and La$_{2}$O$_{2}$Bi$_{3}$AgS$_{6}$ and present the discovery of a pressure-induced superconductivity. In both compounds, the semiconductorlike behavior concomitant with an anomaly in the more insulating state is gradually suppressed with increasing pressure while the superconductivity develops. The obtained phase diagrams, in sharp contrast with the interplay between the conventional charge density waves and superconductivity, suggest that the enhancement of the superconductivity is due to the disorder near the localization threshold. These results indicate that pressure tuning of the local disorder in four-layer-type bismuth chalcogenides provides an attractive opportunity to study the interplay between disorder and superconductivity.

cond-mat.supr-con↗

arXiv2007

Huddling behavior in emperor penguins : dynamics of huddling

Although huddling was shown to be the key by which emperor penguins (Aptenodytes forsteri) save energy and sustain their breeding fast during the Antarctic winter, the intricacies of this social behavior have been poorly studied. We recorded abiotic variables with data loggers glued to the feathers of eight individually marked emperor penguins to investigate their thermoregulatory behavior and to estimate their "huddling time budget" throughout the breeding season (pairing and incubation period). Contrary to the classic view, huddling episodes were discontinuous and of short and variable duration, lasting 1.6+/-1.7 (S.D.) h on average. Despite heterogeneous huddling groups, birds had equal access to the warmth of the huddles. Throughout the breeding season, males huddled for 38+/-18% (S.D.) of their time, which raised the ambient temperature that birds were exposed to above 0 degrees C (at average external temperatures of -17 degrees C). As a consequence of tight huddles, ambient temperatures were above 20 degrees C during 13+/-12% (S.D.) of their huddling time. Ambient temperatures increased up to 37.5 degrees C, close to birds' body temperature. This complex social behavior therefore enables all breeders to get a regular and equal access to an environment which allows them to save energy and successfully incubate their eggs during the Antarctic winter.

q-bio.PE↗

arXiv2006

Dispersal and dive patterns in gravid leatherback turtles during the nesting season in French Guiana

We present the first combined analysis of diving behaviour and dispersal patterns in gravid leatherback turtles during 3 consecutive nesting seasons in French Guiana. In total 23 turtles were fitted with Argos satellite transmitters and 16 individuals (including 6 concurrently satellite-tracked) were equipped with an electronic time-depth recorder for single inter-nesting intervals, i.e. between two consecutive ovi-positions. The leatherbacks dispersed over the continental shelf, ranging from the coastal zone to the shelf break and moved over 546.2 $\pm$ 154.1 km (mean $\pm$ SD) in waters of French Guiana and neighbouring Surinam. They mostly performed shallow (9.4 $\pm$ 9.2 m) and short (4.4 $\pm$ 3.4 min) dives with a slight diurnal pattern. They dived deeper as they moved away from the coast suggesting that they were predominantly following the seabed. Inter-nesting intervals could be divided into two phases: during the first 75% of the time turtles spent at sea, they dived on average 47 min h-1 before showing a lower and more variable diving effort as they came back to the shore. The extended movements of leatherbacks and the fine analysis of dive shapes suggest that in French Guiana leatherbacks may feed during the inter-nesting interval, probably to compensate for the energy costs associated with reproduction. This results in this endangered species being exposed to high risks of interactions with local fisheries throughout the continental shelf.

q-bio.PE↗