Polarity reversals of remanent magnetization in a sedimentary core from Northwind Ridge, western Arctic Ocean

We studied the remanent magnetization of a sedimentary core PC2 (6.48m length) drilled during the MR99-K05 cruise of JAMSTEC in the western Arctic Ocean. Discrete specimens and u-channel samples were used in the study. In the discrete specimens, the change of remanent magnetization with depth show many clear polarity reversals in both inclination and declination. Furthermore, most reversals in discrete specimens correlated well with those in the u-channel samples. Core PC2 is characterized by distinct alternations of dark gray and brownish layers. Through comparison of lithostratigraphic cycles with glacial-interglacial cycles (referring to R.L. Phillips and A. Grantz, Geol. Soc. Am. Bull., 109, 1101, 1997), sedimentary cycles of core PC2 are correlated to marine isotope stages up to MIS-8. This indicates that polarity reversals of remanent magnetization in core PC2 are geomagnetic excursions in the Brunhes epoch. Comparison with the previously known geomagnetic excursions shows that the polarity reversals are clear and have long duration in core PC2. This feature may be related to characteristic geomagnetism around the western Arctic Ocean

Classifying microfossil radiolarians on fractal pre-trained vision transformers

While deep learning techniques, especially image classification using deep learning, continue to evolve, it has been noted that there is a large time gap in applying these techniques in geological studies. Recently, a new architecture called the vision transformer (ViT), which is an alternative to convolutional neural networks (CNN), has attracted considerable attention. In addition, it has been proposed that the pre-training of classification models using mathematically generated images instead of real images, called formula-driven supervised learning (FDSL), achieves a comparative or even higher performance in visual understanding. In this study, we applied these new techniques to the classification of microfossils (radiolarians). Compared with a previous CNN model, the ViT-based model achieved 6–8% higher average precision. On average, the precision of the FDSL pre-trained models was slightly higher than that of the models pre-trained on real images. Therefore, we propose that these techniques may be suitable for image classification in geological tasks

Spatiotemporal variations in the ice mass of East Antarctica during the Holocene revealed by sea-level observations and GIA modelling

The 14th Symposium on Polar Science/Ordinary sessions [OG] Polar geosciences, Wed. 15 Nov. / Entrance Hall (1st floor), National Institute of Polar Researchconference objec

Prokaryotic and eukaryotic community structures in surface sediments of the East Antarctic coastal region

The 14th Symposium on Polar Science/Ordinary sessions [OB] Polar biology, Wed. 15 Nov. / Entrance Hall (1st floor), National Institute of Polar Researchconference objec

Universal Money as the Unity of Hoard of Value and Means of Payment

吉信肅教授古稀記念特

Sensory analysis and acceptance of feijoa fruit

The southern region of Brazil is home of a myriad of native species which have high organoleptic potential, and among those species the feijoa fruit (Feijoa sellowiana) stands out. This species has an incipient production chain; however, the promotion of the species to the consumers can increase the fruit’s consumption, stimulate its production, in addition to its conservation. This study aims to perform sensory analysis and verify the preference for fruits of two cultivars and a selection of F. sellowiana. Fifty-seven tasters evaluated the fruits for sensory characteristics, taste and appearance. The evaluations included a questionnaire to characterize the taster’s profile. The tasters’ perception of the three samples did not differ in terms of sweetness, acidity, juiciness, pulp yield and overall impression. In general, the sensorial analysis showed that feijoa is a fruit with notorious acceptance by consumers. This result demonstrates the potential for promotion and use of the species, in order to make compatible the promotion of its cultivation and conservation

Genetic diversity in two sibling species of the Anopheles punctulatus group of mosquitoes on Guadalcanal in the Solomon Islands

<p>Abstract</p> <p>Background</p> <p>The mosquito <it>Anopheles irenicus</it>, a member of the <it>Anopheles punctulatus </it>group, is geographically restricted to Guadalcanal in the Solomon Islands. It shows remarkable morphological similarities to one of its sibling species, <it>An. farauti sensu stricto </it>(<it>An. farauti s.s</it>.), but is dissimilar in host and habitat preferences. To infer the genetic variations between these two species, we have analyzed mitochondrial <it>cytochrome oxidase subunit II </it>(<it>COII</it>) and nuclear ribosomal <it>internal transcribed spacer 2 </it>(<it>ITS2</it>) sequences from Guadalcanal and from one of its nearest neighbours, Malaita, in the Solomon Islands.</p> <p>Results</p> <p><it>An. farauti s.s</it>. was collected mostly from brackish water and by the human bait method on both islands, whereas <it>An. irenicus </it>was only collected from fresh water bodies on Guadalcanal Island. <it>An. irenicus </it>is distributed evenly with <it>An. farauti s.s</it>. (Φ_SC= 0.033, 0.38%) and its range overlaps in three of the seven sampling sites. However, there is a significant population genetic structure between the species (Φ_CT= 0.863, <it>P </it>< 0.01; Φ_ST= 0.865, <it>P </it>< 0.01 and <it>F</it>_ST= 0.878, <it>P </it>< 0.01). Phylogenetic analyses suggest that <it>An. irenicus </it>is a monophyletic species, not a hybrid, and is closely related to the <it>An. farauti s.s</it>. on Guadalcanal. The time estimator suggests that <it>An. irenicus </it>diverged from the ancestral <it>An. farauti s.s</it>. on Guadalcanal within 29,000 years before present (BP). <it>An. farauti s.s</it>. expanded much earlier on Malaita (<it>t</it>_exp= 24,600 BP) than the populations on Guadalcanal (<it>t</it>_exp= 16,800 BP for <it>An. farauti s.s</it>. and 14,000 BP for <it>An. irenicus</it>).</p> <p>Conclusion</p> <p>These findings suggest that <it>An. irenicus </it>and <it>An. farauti s.s</it>. are monophyletic sister species living in sympatry, and their populations on Guadalcanal have recently expanded. Consequently, the findings further suggest that <it>An. irenicus </it>diverged from the ancestral <it>An. farauti s.s</it>. on Guadalcanal.</p

Multiple episodes of ice loss from the Wilkes Subglacial Basin during the Last Interglacial

The Last Interglacial (LIG: 130,000–115,000 years ago) was a period of warmer global mean temperatures and higher and more variable sea levels than the Holocene (11,700–0 years ago). Therefore, a better understanding of Antarctic ice-sheet dynamics during this interval would provide valuable insights for projecting sea-level change in future warming scenarios. Here we present a high-resolution record constraining ice-sheet changes in the Wilkes Subglacial Basin (WSB) of East Antarctica during the LIG, based on analysis of sediment provenance and an ice melt proxy in a marine sediment core retrieved from the Wilkes Land margin. Our sedimentary records, together with existing ice-core records, reveal dynamic fluctuations of the ice sheet in the WSB, with thinning, melting, and potentially retreat leading to ice loss during both early and late stages of the LIG. We suggest that such changes along the East Antarctic Ice Sheet margin may have contributed to fluctuating global sea levels during the LIG