Induced Binary Submatroids

The notion of induced subgraphs is extensively studied in graph theory. An example is the famous Gy\'{a}rf\'{a}s-Sumner conjecture, which asserts that given a tree $T$ and a clique $K$, there exists a constant $c$ such that the graphs that omit both $T$ and $K$ as induced subgraphs have chromatic number at most $c$. This thesis aims to prove natural matroidal analogues of such graph-theoretic problems

Tuza's conjecture for binary geometries

Tuza (A conjecture, in Proceedings of the Colloquia Mathematica Societatis Janos Bolyai, 1981) conjectured that $\tau(G) \le 2\nu(G)$ for all graphs $G$, where $\tau(G)$ is the minimum size of an edge set whose removal makes $G$ triangle-free, and $\nu(G)$ is the maximum size of a collection of pairwise edge-disjoint triangles. Here, we generalise Tuza's conjecture to simple binary matroids that do not contain the Fano plane as a restriction. We prove that the geometric version of the conjecture holds for cographic matroids.Comment: 9 pages. Changes since v1: fixed some typos, added reference to a related conjectur

Origin of scarlet gynogenetic triploid Carassius fish: Implications for conservation of the sexual–gynogenetic complex

天然記念物ヒブナの起源を解明 --クローン繁殖のはずなのにキンギョと交雑--. 京都大学プレスリリース. 2022-10-21.Conservation of sperm-dependent asexual (gynogenetic) species is challenging due to their complicated ecological dynamics, which requires the stable coexistence with their sperm-providing sexual relatives, who often share similar niches. A symbolic but vulnerable gynogenetic animal is the scarlet Carassius fish, or Hibuna, which is mainly found in Lake Harutori on Hokkaido, Japan. Although Hibuna in Lake Harutori has been protected as a symbol of the Natural Monument of Japan, it has recently suffered population decline. To establish an effective conservation strategy for Hibuna, we investigated its origin, reproductive mode, and genetic diversity, with reference to the surrounding wild populations, using nuclear microsatellites and mitochondrial gene sequences. Our genetic analyses revealed that the main ploidy of Hibuna was triploid or tetraploid, and it reproduces gynogenetically. However, no co-existing sexual diploid Carassius was detected among our samples, suggesting that the sexual diploids and the gynogenetic population including Hibuna would be at risk of co-extirpation. In addition, Hibuna showed high genetic/clonal diversity and most Hibuna had nonindigenous mitochondrial haplotypes that are mostly identical to those reported from goldfish. These results indicate that Hibuna most probably originated from hybridization between indigenous gynogenetic triploids and goldfish introduced about 100 years ago, involving rare sexual reproduction. This spontaneous long-term field experiment exemplifies the recently documented diversification process of gynogenetic Carassius via complex interploidy gene flow. Although the priority to be placed on the conservation of Hibuna is controversial, the maintenance of gynogenetic Carassius, including Hibuna, requires strategic conservation of sexual populations

Deficiency in Galectin-3 Promotes Hepatic Injury in CDAA Diet-Induced Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is increasingly recognized as a condition in which excess fat accumulates in hepatocytes. Nonalcoholic steatohepatitis (NASH), a severe form of NAFLD in which inflammation and fibrosis in the liver are noted, may eventually progress to end-stage liver disease. Galectin-3, a β-galactoside-binding animal lectin, is a multifunctional protein. This protein is involved in inflammatory responses and carcinogenesis. We investigated whether galectin-3 is involved in the development of NASH by comparing galectin-3 knockout (gal3−/−) mice and wild-type (gal3+/+) mice with choline-deficient L-amino-acid-defined (CDAA) diet-induced NAFLD/NASH. Hepatic injury was significantly more severe in the gal3−/− male mice, as compared to the gal3+/+ mice. Data generated by microarray analysis of gene expression suggested that galectin-3 deficiency causes alterations in the expression of various genes associated with carcinogenesis and lipid metabolism. Through canonical pathway analysis, involvement of PDGF and IL-6 signaling pathways was suggested in galectin-3 deficiency. Significant increase of CD14, Fos, and Jun, those that were related to lipopolysaccharide-mediated signaling, was candidate to promote hepatocellular damages in galectin-3 deficiency. In conclusion, galectin-3 deficiency in CDAA diet promotes NAFLD features. It may be caused by alterations in the expression profiles of various hepatic genes including lipopolysaccharide-mediated inflammation

Conductor and joint test results of JT-60SA CS and EF coils using the NIFS test facility

In 2007, JAEA and NIFS launched the test project to evaluate the performance of cable-in-conduit (CIC) conductors and conductor joints for the JT-60SA CS and EF coils. In this project, conductor tests for four types of coil conductor and joint tests for seven types of conductor joint have been conducted for the past eight years using the NIFS test facility. As a result, the test project indicated that the CIC conductors and conductor joints fulfill the design requirement for the CS and EF coils. In addition, the NIFS test facility is expected to be utilized as the test facility for the development of a conductor and conductor joint for the purpose of the DEMO nuclear fusion power plant, provided that the required magnetic field strength is within 9 T

No reduction of hatching rates among F1 hybrids of naturally hybridizing three Far Eastern daces, genus Tribolodon (Cypriniformes, Cyprinidae)

Egg hatching rates of F1 hybrids among three fishes, Japanese dace Tribolodon hakonensis, Pacific redfin T. brandtii, and rosyface dace T. sachalinensis, were compared with pure crosses. They are highly divergent (diverged 10-20 million years ago) but naturally hybridizing. Although crosses involving female rosyface dace were not available, hatching success was high among all combinations of hybrids (76 +/- 23%) and comparable to pure crosses (86 +/- 8%), implying ecological or genetic isolation mechanisms maintaining each species in later life stages