Mount Fuji Research Institute

The occurrence patterns of important words found in six texts (one historical pamphlet and five renowned academic books) are analyzed using both univariate and multivariate Hawkes processes. By treating the occurrence patterns as binary time-series data along the texts, we investigate how effectively univariate and multivariate Hawkes processes capture the characteristics of these word occurrence signals. Through maximum likelihood estimation and subsequent simulations, we found that the multivariate Hawkes process clearly outperforms the univariate Hawkes process in modeling word occurrence signals. Moreover, we found that the multivariate Hawkes process can provide a Hawkes graph, which serves as an intuitive representation of the relationships between concepts appearing in the analyzed text. Furthermore, our study demonstrates that the importance of concepts within a given text can be quantitatively estimated based on the optimized parameter values of the multivariate Hawkes process.

Significant mental health issues are already plaguing students at universities, and research on artificial intelligence (AI) and its impact on students' mental health is progressing quickly as an important contributor to psychological well-being. Therefore, by employing bibliometric methods, this study aims to analyze the role of AI in university student mental health. Publications on AI and university student mental health were obtained from the Scopus, Web of Science, and PubMed databases. VOS Viewer was used to analyse data on nations, authors, journals, and keywords, revealing collaboration patterns, research hotspots, and trends. Encompassing all papers up to February 2025, the investigation included 173 papers and produced several noteworthy findings: (1) a slow increase in yearly publications, which peaked in 2024; (2) the Frontiers in Psychology Journal appears as the most frequently publishing journal in this area, based on the current dataset, with major contributions from China, the Philippines, the United States, and their affiliated universities; (3) depression and anxiety were the main mental health issues, and machine learning and deep learning had the most applications; (4) a need for improved international and interdisciplinary cooperation. To enhance a more general comprehension of the possible application of AI in the student mental health, this paper offers an overview of the topic in the everyday life of the students in all its simplicity. Professionals are provided with further insights to assess benefits, risks and consequences of AI in this important domain.

SUMMARY Although asexual populations and species have been frequently reported in seaweeds, their nature (e.g. origins and distribution patterns relative to closely related sexual counterparts) remains largely unknown. This is likely because determining the species identity, sex, and phase of individual organisms is often troublesome, making it difficult to comprehensively survey reproductive modes across many populations within a single species. In this study, we demonstrated that reduced‐representation sequencing (RRS), a method of sequencing a fraction of the genome using high‐throughput DNA sequencing platforms, is a simple and effective tool to investigate the reproductive modes of populations. To uncover the evolutionary trajectory of asexuals in S. promiscuus , which is known to include both sexual and asexual populations, we performed an RRS approach, MIG‐seq. By applying MIG‐seq to 122 individuals from 20 localities, mainly across Japan, we were able to: (i) estimate genetic diversity and phylogenetic relationships of populations; (ii) detect possible cryptic species ( spro1 and spro2 ); (iii) develop a pair of polymerase chain reaction‐based sex markers to identify the sex and ploidy of individuals; and (iv) discover polyploid populations in spro1 and female‐dominant populations in spro2 , both of which appear to be maintained asexually. By subsequently conducting crossing experiments and phylogenetic analysis using the mitochondrial gene cox1 and nuclear gene cetn‐int2 , we confirmed that spro1 and spro2 are reproductively isolated. We also uncovered that polyploid populations have emerged multiple times in spro1 , and one of these populations originated from hybridization between S. promiscuus and S. shibazakiorum , while the other populations originated from intraspecies crossing within S. promiscuus . It is surprising that multiple pathways to asexuality were found within such a narrow phylogenetic scope.

<strong class="journal-contentHeaderColor">Abstract.</strong> Understanding the spatial and temporal variations in mineral dust sources in Greenland ice cores during the Holocene is challenging due to low dust concentration. Here, we present the first continuous records of the size and composition, as well as the temporal variations in potential sources, of mineral dust preserved in a northeastern Greenland ice core (EGRIP) covering the period from 1910 to 2013. Using a multi-proxy provenance approach based on individual particle analysis, we reconstruct variations in ice-core dust sources. We apply a recently developed provenance tracing technique, namely scanning electron microscopy (SEM)-cathodoluminescence (CL) analysis of single quartz particles, and SEM energy-dispersive X-ray spectroscopy (EDS) analysis to the Greenland ice core. The SEM-CL/EDS results reveal that the primary dust sources in the EGRIP ice core are Asian (Gobi Desert) and African (Sahara Desert) deserts. Their relative contributions have shifted since the 1970s&ndash;1980s: the contribution from the Gobi Desert has decreased whereas that from the Sahara Desert has increased. Our findings demonstrate that SEM-CL analysis is a valuable tool for identifying ice-core dust sources and reconstructing their variations during periods of low dust concentration. Additionally, we compare the EGRIP ice-core dust records with those of a northwestern Greenland ice core (SIGMA-D) to determine spatial variations in potential dust sources within the Greenland Ice Sheet over the past 100 years. The results reveal that the variability and mineral composition of the EGRIP ice-core dust differs significantly from those of the SIGMA-D ice-core dust, indicating that the dust in these two ice cores was likely transported from different geological sources. The SIGMA-D ice-core dust exhibits multidecadal variations, reflecting increased dust from the Greenland coastal region during warmer periods. Conversely, the EGRIP ice-core dust shows low temporal variation, suggesting a smaller contribution from local sources.

Identifying the metabolic and genetic changes that confer evolutionary novelty is essential for understanding the factors facilitating or constraining the occurrence of traits. We show that dimethyl disulfide (DMDS), a volatile compound that attracts saprophilous pollinators, is produced by a disulfide synthase (DSS) in the plant genus Asarum (Aristolochiaceae). DSS is derived from methanethiol oxidase (MTOX), an enzyme conserved among animals and plants, and similar DSS enzymes have independently evolved in two other plant genera. Three amino acid changes shared among the DSSs of independent origins were sufficient to cause a functional switch between MTOX and DSS. The small number of amino acid changes and the co-option of a highly conserved enzyme may explain why DMDS-emitting flowers are widespread among floral mimics.

This study aims to compare Thalictrum (Ranunculaceae) plant species, tentatively identified as T. minus, from the Yambaru region of Okinawa Island, Japan, with closely related species using morphometric and molecular phylogenetic analyses. Morphological observations revealed that the unique plants from Okinawa Island had clavate filaments and thickened roots. These traits differed significantly from those of typical T. minus, which have filamentous filaments and slender roots. Molecular phylogenetic analyses revealed that the unique plant on Okinawa Island is sister to T. urbaini, endemic to Taiwan, and formed a separate clade from those containing T. minus. Based on current morphological comparisons and molecular phylogenetic analyses, the unique plant on Okinawa Island was concluded to be a previously undescribed species, newly named Thalictrum yambaruense. Furthermore, our molecular phylogenetic analyses of Thalictrum in Japan and Taiwan revealed that T. tuberiferum var. yakusimense, endemic to Yakushima Island, Japan, is phylogenetically distinct from T. tuberiferum var. tuberiferum. Therefore, we propose elevating the taxonomic status of T. tuberiferum var. yakusimense to the species level as T. yakusimense.

Abstract East Asia is a major source of dust accounting for 20% of the global dust emission. Work on reconstructing past changes in dust transport in East Asia is complicated by difficulties in distinguishing local sedimentation from aerial material and lack of suitable material for age determination. Here, we address these issues and present a new dust proxy record from Lake Motosu, located on the Pacific side of Japan. The record is anchored by a high‐quality tephra and radiocarbon chronology. Because Lake Motosu is situated in a quartz‐free basaltic volcanic province, all quartz deposited in the lake is likely to be aerially sourced, and variations in quartz content should reflect past changes in dust transport. Our new record detects a low dust deposition event from 3.0 to 2.0 ka. This event corresponds to elevated sea surface temperature in the Sea of Japan and climate conditions similar to a negative phase of the Arctic Oscillation, indicating an association with the weakened Westerlies and with less frequent dust storms in the source region. The increase in spatial resolution of past dust transport reconstructions will further improve our understanding of the mechanism related to dust emission from East Asia.