综合研究大学院大学

Urbanization influences not only free-living organisms, but also various pathogens, including those with limited visibility to humans. Although previous research on urban parasites has primarily focused on human-specific and zoonotic species, a comprehensive understanding of parasite ecology in urban settings requires attention to inconspicuous enzootic species. In this study, we investigated two flea species, Aenigmopsylla grodekovi and Ceratophyllus (Monopsyllus) indages indages, parasitizing Eurasian red squirrels Sciurus vulgaris orientis in and around Obihiro City, Hokkaido, Japan. These fleas, dislodged during the routine handling of host squirrels, were collected and quantified during spring and autumn surveys to assess seasonal and spatial patterns of infestation across urban and rural sites. Over the course of a four-year survey (2017–2020), 317 squirrels (168 males and 149 females) were examined, with 284 individuals of A. grodekovi and 214 of C. (M.) indages indages recovered. The former was rarely observed in spring but showed a pronounced increase in autumn, with rural areas exhibiting 14.06 times more dislodged individuals than urban areas, on average. In contrast, the latter was more prevalent in spring (2.50 times higher than in autumn) and displayed no consistent difference between urban and rural habitats. Our results revealed distinct dislodgement patterns in two flea species in response to habitat and seasonal variations, indicating species-specific responses to urbanization. While direct quantification of flea abundance remains ideal, the number of dislodged individuals may serve as a useful indicator for assessing the effect of urbanization on host-parasitic interactions and infrapopulation dynamics.

We have constructed collisional-radiative (CR) models for tungsten ions, Wq+, with q = 18–25, including ionizing and recombining processes as well as collisional excitation/deexcitation and radiative decay, and applied the models to analyze extreme ultraviolet (EUV) spectra measured in magnetically confined fusion plasmas with a tungsten pellet injection into the Large Helical Device (LHD). The CR models are constructed as hybrids with fine-structure levels for lower states and relativistic configuration-averaged levels for higher states to include autoionizing states. The dielectronic recombination process is treated as dielectronic capture to the autoionizing states and radiative decay from the autoionizing states in the CR model. We calculated EUV spectra of the tungsten ions for ionizing and recombining plasmas. Measured spectra at the 2–4 nm region were used to estimate the charge state distribution of tungsten ions in LHD plasmas by comparing calculated emission peaks of n = 4–5 transitions of Wq+ with q = 22–25. Using the estimated ion distribution, the synthesized spectral profile at 4.5–7 nm shows characteristic profiles similar to the measured so-called unresolved transition array (UTA) due to n = 4–4 transitions. We also synthesized the spectra at 10–35 nm, where the UTA due to n = 5–5 transitions appeared, and we partly reproduced the UTA with synthesized spectra. The CR models for the tungsten ions were validated with the measured spectra of LHD plasmas.

This study uses drone imagery and orthomosaic analysis to document three large-scale fortification complexes in Central Mongolia's Khangai range, located near a known 13th-century military encampment associated with Khubilai Khan. Building upon observations first recorded by Russian explorer P.K. Kozlov in the 1920s, we present detailed mapping of these features, revealing their scale, geometric properties, and spatial organization. The complexes, each covering areas between 198,000 and 720,000 square meters, exhibit distinct square layouts adapted to hilly terrain, with regularly spaced pit structures, stone-demarcated trenches, and varying entrance configurations suggesting sophisticated planning and construction. Our research contextualizes these findings within the broader framework of Inner Asian military architecture, drawing comparisons with fortified sites across Mongolia from multiple periods. The results offer a foundation for future investigations into the chronology, function, and regional significance of these complexes.

The formation of the first stars and galaxies marked the onset of chemical enrichment, yet direct observations of such primordial systems remain elusive. Here we present James Webb Space Telescope spectroscopic observations of LAP1-B, an ultra-faint galaxy at redshift zspec = 6.625 ± 0.001, corresponding to a cosmic age of 800 million years after the Big Bang. This galaxy is strongly magnified by gravitational lensing. LAP1-B exhibits a gas-phase oxygen abundance of (4.2 ± 1.8) × 10-3 times the solar value, making it the most chemically primitive star-forming galaxy discovered to date. The galaxy displays an exceptionally hard ionizing radiation field, which is inconsistent with chemically enriched stellar populations or accreting black holes but matches theoretical predictions for an exceptionally metal-deficient stellar population1. It also shows an elevated carbon-to-oxygen abundance ratio for its metallicity in the interstellar medium, consistent with nucleosynthetic yields from a stellar population formed in the absence of initial metals2-4. The lack of detectable stellar continuum constrains the stellar mass to below 3,300 M⊙, and the dynamical mass, derived from emission-line kinematics, exceeds the combined stellar and gas mass, which indicates a dominant dark matter halo. Our findings establish LAP1-B as a 'fossil in the making', a direct high-redshift progenitor of the ancient ultra-faint dwarf galaxies observed in the local Universe and offers a rare window into the earliest stages of galaxy formation.

The Galaxy's most common known planetary systems have several Earth-to-Neptune-size planets in compact orbits1. At small orbital separations, larger planets are less common than their smaller counterparts by an order of magnitude. The young star V1298 Tau hosts one such compact planetary system, albeit with four planets that are uncommonly large (5 to 10 Earth radii)2,3. The planets form a chain of near-resonances that result in transit-timing variations of several hours. Here we present a multi-year campaign to characterize this system with transit-timing variations, a method insensitive to the intense magnetic activity of the star. Through targeted observations, we first resolved the previously unknown orbital period of the outermost planet. The full 9-year baseline from these and archival data then enabled robust determination of the masses and orbital parameters for all four planets. We find the planets have low, sub-Neptune masses and nearly circular orbits, implying a dynamically tranquil history. Their low masses and large radii indicate that the inner planets underwent a period of rapid cooling immediately after dispersal of the protoplanetary disk. Still, they are much less dense than mature planets of comparable size. We predict the planets will contract to 1.5-4.0 Earth radii and join the population of super-Earths and sub-Neptunes that nature produces in abundance.