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Geometry and thermal regime of the southern outlet glaciers of Qaanaaq Ice Cap, NW Greenland
No full textGlaciers and ice caps surrounding the Greenland Ice Sheet are found to be sensitive to warming climate thus the knowledge of their thickness and internal structure is substantial to determine their future impact on sea level and local environment. Still, in situ glaciological measurements of such glaciers are very scarce. Here, we present the results of ground penetrating radar (GPR) and uncrewed aerial vehicle surveys conducted on the two southern outlet glaciers of Qaanaaq Ice Cap in NW Greenland. GPR measurements reveal up to 170 m thick ice and the lack of englacial hyperbolae indicating no developed en/subglacial drainage system. The glaciers consist mainly of radar transparent facies characteristic for cold ice, while limited scattering facies appear closer to the glacier's terminus beneath the thinnest ice and are attributed to debris inside the ice. Results show that the glaciers flow into narrow V-shaped valleys suggesting spatio-temporally limited subglacial erosion and restricted possible distribution of temperate ice in the past. The comparison of the ice thickness measurement data with global ice thickness model estimates shows considerable discrepancies emphasising the need of modelling improvements in the case of narrow valley and outlet glaciers
Prevalence of repeat expansions causing autosomal dominant spinocerebellar ataxias in Hokkaido, the northernmost island of Japan
No full textIn Japan, approximately 30% of spinocerebellar degeneration (SCD) is hereditary, and more than 90% of hereditary SCD is autosomal dominant SCD (AD-SCD). We have previously reported the types of AD-SCD in Hokkaido, twice. In this study, we investigated the status of AD-SCD mainly due to repeat expansions, covering the period since the last report. We performed genetic analysis for 312 patients with a clinical diagnosis of SCD, except for multiple system atrophy at medical institutions in Hokkaido between January 2007 and December 2020. The median age at the time of analysis was 58 (1-86) years. Pathogenic variants causing AD-SCD due to repeat expansion were found in 61.5% (192 cases). Spinocerebellar ataxia (SCA) 6 was the most common type in 25.3% (79 cases), followed by Machado-Joseph disease (MJD)/SCA3 in 13.8% (43), SCA1 in 6.4% (20), SCA2 in 5.1% (16), SCA31 in 4.8% (15), dentatorubral-pallidoluysian atrophy in 4.8% (15), SCA7 in 0.6% (2), and SCA8 in 0.6% (2). SCA17, 27B, 36, and 37 were not found. Compared to previous reports, this study found a higher prevalence of SCA6 and a lower prevalence of MJD/SCA3. An increasing number of cases identified by genetic testing, including cases with no apparent family history, accurately revealed the distribution of disease types in Hokkaido
Study on the lower urinary tract dysfunction using animal models of Parkinson’s disease
No full text配架番号：284
Function of Bubble for Recovery from Cryptobiosis in Tardigrade Milnesium tardigradum
No full textTardigrades enter a cryptobiotic state (barrel-shaped form) to persist in extreme environments, but there are few experimental observations to examine how complete recovery from this state occurs. Here, we directly observed the tardigrade Milnesium tardigradum in the cryptobiotic and active states under the microscope with a video system. Rates of complete recovery of cryptobiotic organisms with or without cover glasses were 71.4% and 73.3%, respectively, suggesting no effect of the cover glass on the recovery success in this species. More than 50% of organisms showed bubbles in the mouth canal during the recovery process regardless of the recovery success. Since these bubbles disappeared just before the recovery at the end of the mouth canal, but did not flow into the pharynx, bubbles might flow into the body cavity and regulate the intracorporeal pressure during recovery. Bubbles were also observed in the mouth canal of active organisms entering the cryptobiotic state. Bubbles therefore occurred in both cryptobiotic-to-recovery and active-to-cryptobiotic processes. The end of the mouth canal in M. tardigradum might function as a barrier between the external and internal environment and contribute to the regulation of hydrostatic pressure in the body cavity
A new parasitic barnacle (Crustacea, Cirripedia, Rhizocephala, Mycetomorpha) from the abyssal zone in the northwestern Pacific
No full textI describe the parasitic barnacle Mycetomorpha abyssalis sp. nov. from the crangonid shrimp Sclerocrangon zenkevitchi collected from 3893–3890 m depth off the eastern coast of Iwate, Japan, northwestern Pacific. This is the first Mycetomorpha rhizocephalan from the abyssal zone and the third species in Mycetomorpha. Mycetomorpha abyssalis sp. nov. differs from its congeners M. vancouverensis and M. albatrossi in (1) triangular shield lacking, (2) stalk one-quarter of length from posterior end of externa, (3) mantle opening clearly anterior to stalk, (4) different host genus, and (5) depth range much deeper. I determined partial sequences for the mitochondrial cytochrome c oxidase subunit I (COI) and 16S rRNA genes and nuclear 18S rRNA and 28S rRNA genes from M. abyssalis sp. nov. for future DNA barcoding and phylogeny. Kimura 2-parameter distances between M. abyssalis sp. nov. and M. vancouverensis were 21.2% (16S), 0.6% (18S), and 1.5% (28S)
Double-Q and quadruple-Q instabilities at low-symmetry ordering wave vectors under tetragonal symmetry
No full textMultiple-Q states are expressed as a superposition of spin density waves at multiple ordering wave vectors, which results in unconventional complicated spin textures, such as skyrmions, hedgehogs, and vortexes. We investigate the multiple-Q instability by focusing on the low-symmetry ordering wave vectors in momentum space. By systematically performing the simulated annealing for effective spin models with various ordering wave vectors on a two-dimensional square lattice, we classify the magnetic phase diagram into four types according to the position of the ordering wave vectors. Three out of four cases lead to a plethora of isotropic multiple-Q instabilities yielding collinear, coplanar, and noncoplanar double-Q and quadruple-Q magnetic phases, while the remaining case leads to an anisotropic double-Q instability when the multiple-spin interaction is introduced. Our results indicate that exotic multiple-Q phases distinct from the skyrmion crystal phase are expected when the ordering wave vectors lie on the low-symmetry positions in the Brillouin zone
Dynamical generation of skyrmion and bimeron crystals by a circularly polarized electric field in frustrated magnets
No full textThe skyrmion crystal (SkX) has attracted much attention in condensed matter physics since topologically nontrivial structures induce fascinating physical phenomena. The SkXs have been experimentally observed in a variety of materials, where the Zeeman coupling to the static magnetic field plays an important role in the formation of the SkXs. In this study, we theoretically propose another route to generate the SkXs by using a circularly polarized electric field. We investigate a nonequilibrium steady state in a classical frustrated Heisenberg magnet under the circularly polarized electric field, where the electric field is coupled to the electric polarization via the spin-current mechanism. By numerically solving the Landau-Lifshitz-Gilbert equation at zero temperature, we show that the electric field radiation generates a SkX with a high topological number in the high-frequency regime, where the sign of the skyrmion number is fixed to be negative (positive) under the left (right) circularly polarized field. The intense electric field melts these SkXs and generates isolated skyrmions. We clarify that the microscopic origin is effective electric-field-induced three-spin interactions by adopting the high-frequency expansion in the Floquet formalism. Furthermore, we find that the electric field radiation generates another type of SkXs, a bimeron crystal, in the low-frequency regime. Our results provide a way to generate the SkXs and control the topology by the circularly polarized electric field