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Search Results: 1 - 10 of 71 matches for " Youki Fukasawa "
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Dispersal Ability and Genetic Structure in Mytilid Mussels of Whale-Fall Communities  [PDF]
Youki Fukasawa, Haruna Kobayashi-Iwatani, Masaru Kawato, Hideki Kobayashi, Yoshihiro Fujiwara, Jun-Ichi Miyazaki
Open Journal of Marine Science (OJMS) , 2015, DOI: 10.4236/ojms.2015.53025
Abstract: Since organic falls are ephemeral and distributed sporadically, organisms in organic-fall communities must acquire high dispersal ability to migrate from one organic fall to another. However, the dispersal ability of obligate organic-fall organisms has not been investigated thoroughly and the stability of the genetic structure of their communities is unknown. In this study, in order to elucidate the dispersal ability and genetic structure in the organic-fall communities, we carried out population genetic analyses based on sequences of mitochondrial NADH dehydrogenase subunit 4 in two mytilid mussels.?Adipicola pacifica was obtained from whale and cow bones artificially settled in Japanese waters off Cape Noma (CN) and in the Nansei-Shoto Trench (NS) and Sagami Bay (SB), and Benthomodiolus geikotsucola from natural whale bones in the Torishima Seamount (TS); both species are symbiotic with chemoautotrophic bacteria. Genetic differentiation (Fst) indicated almost no annual change in genetic structure between 2003, 2004, 2005, and 2007 collections of A. pacificafrom CN (depth 225 - 229 m), although the 2010 collection had somewhat different genetic structure from the others.
Molecular Phylogenetic Analysis of Chemosymbiotic Solemyidae and Thyasiridae  [PDF]
Youki Fukasawa, Hiroto Matsumoto, Saori Beppu, Yoshihiro Fujiwara, Masaru Kawato, Jun-Ichi Miyazaki
Open Journal of Marine Science (OJMS) , 2017, DOI: 10.4236/ojms.2017.71010
Abstract: In order to invade and adapt to deep-sea environments, shallow-water organisms have to acquire tolerance to high hydrostatic pressure, low water temperature, toxic methane and hydrogen sulfide, and feeding strategies not relying on photosynthetic products. Our previous study showed that the “evolutionary stepping stone hypothe-sis”, which assumes that organic falls can act as stepping-stones to connect shallow sea with deep sea, was supported in Mytilidae. However, it is not known whether other bivalves constituting chemosynthetic communities experienced the same evolutionary process or different processes from mytilid mussels. Therefore, here, we performed phylogenetic analyses by sequencing the nuclear 18S rRNA and mitochondrial COI genes of solemyid and thyasirid bivalves. In Solemyidae, the two genera Solemya and Acharax formed each clade, the latter of which was divided into three subgroups. The Solemya clade and one of the Acharax subgroups diverged in the order of shallow-sea residents, whale-bone residents, and deep-sea vent/seep residents, which supported the “evolutionary stepping stone hypothesis”. Furthermore, in Thyasiridae, the two genera Thyasira and Maorithyas formed a paraphyletic group and the other genera, Adontorhina, Axinopsis, Axinulus, Leptaxinus, and Mendicula, formed a clade. The “evolu-tionary stepping stone hypothesis” was not seemingly supported in the other lineages of Solemyidae and Thyasiridae.
Intraspecific Relationships and Variation of Two Lefua Species (Balitoridae, Cypriniformes) in the Tokai Region, Honshu, Japan  [PDF]
Jun-Ichi Miyazaki, Seiya Hida, Takurou Ozaki, Yuichirou Tabata, Misaki Iwata, Masashi Nakazawa, Youki Fukasawa, Tomonari Asaka
Journal of Water Resource and Protection (JWARP) , 2017, DOI: 10.4236/jwarp.2017.92016
Abstract: Two species Lefua echigonia and Lefua sp. 2 of the eight-barbel loach inhabit the Tokai region of Honshu, Japan. We determined sequences of the mitochondrial D-loop region to elucidate intraspecific phylogenetic relationships and variation in these two species. Lefua sp. 2 represented high intraspecific genetic similarity and complicated haplotype network, but three assemblages were recognized, including specimens mainly from Yahagi, Toyo, and Tenryu River systems, respectively, and named Groups 1 to 3. Divergence of Group 1 from the others was marginally supported, but Group 2 was paraphyletic to Group 3, suggesting the existence of two populations, i.e. Yahagi River population and Toyo-Tenryu River population. Lefua echigonia also represented high intraspecific genetic similarity, and two assemblages with slight genetic differentiation were discernible, including specimens from Shizuoka and southeastern Aichi prefectures and those from northwestern Aichi, Gifu, and Mie prefectures, respectively, and named Groups A and B. Star-like relationships of haplotypes suggested the dispersal origin located in eastern Aichi prefecture. The two species are threatened to extinction and thus we proposed evolutionary significant units for conservation.
Developmental Change of Vegetative Plant Architecture of Annual-Form-Wild Rice (Oryza rufipogon Griff.) Elevates Competitive Ability during the Late Development under a Dense Condition  [PDF]
Hiroyuki Shimizu, Youki Itoh
American Journal of Plant Sciences (AJPS) , 2012, DOI: 10.4236/ajps.2012.35081
Abstract: Annual-form-wild (AFW) rice developmentally changes the vegetative plant architecture from flat to elect shape. The main objective of the present study is to suggest that the change might be related to competitive ability (CA). Recombinant inbred lines (RILs) derived from a cross between an AFW rice and a cultivar were grown under high-density (H) and low-density (L) conditions in a weedy paddy field. At two and three months after transplanting (MATs), we evaluated the two traits associated with utilization of light resource, tiller angle (TA) and actual plant height (APH), and amount of the growing weeds using an index, weed-denseness score (WDS). Then, DC-TA, DC-APH and SC-WDS was defined as the amount of change in TA, APH, and WDS from two to three MATs, respectively. Multiple regression analysis revealed that only DC-TA significantly affected SC-WDS specific under H condition that is relatively similar to habitats of AFW rice. Quantitative trait locus (QTL) analyses identified that one of the two QTLs associated with DC-TA shared a linked molecular marker with a QTL associated with SC-WDS only under H condition. Further, RILs with AFW-rice-derived allele on the QTL associated with DC-TA tended to show drastic changes of TA toward narrow angle as well as large decreases of weed amount. All the QTLs associated with DC-APH were not linked to the QTL associated with SC-WDS under H condition. Therefore, it is suggested that under the crowded conditions during the late plant development, AFW-rice plants might not survive through canopy domination but elevate CA through increases of efficiency of capturing light due to changes from wide to narrow tiller angle. Since flat-plant shape of AFW rice during the early development would have been evolved by trampling pressures, the present finding suggest that different selective pressures in life time might have cooperatively evolved the developmental change.
HumanBoost: Utilization of Users’ Past Trust Decision for Identifying Fraudulent Websites  [PDF]
Daisuke Miyamoto, Hiroaki Hazeyama, Youki Kadobayashi
Journal of Intelligent Learning Systems and Applications (JILSA) , 2010, DOI: 10.4236/jilsa.2010.24022
Abstract: This paper presents HumanBoost, an approach that aims at improving the accuracy of detecting so-called phishing sites by utilizing users’ past trust decisions (PTDs). Web users are generally required to make trust decisions whenever their personal information is requested by a website. We assume that a database of user PTDs would be transformed into a binary vector, representing phishing or not-phishing, and the binary vector can be used for detecting phishing sites, similar to the existing heuristics. For our pilot study, in November 2007, we invited 10 participants and performed a subject experiment. The participants browsed 14 simulated phishing sites and six legitimate sites, and judged whether or not the site appeared to be a phishing site. We utilize participants’ trust decisions as a new heuristic and we let AdaBoost incorporate it into eight existing heuristics. The results show that the average error rate for HumanBoost was 13.4%, whereas for participants it was 19.0% and for AdaBoost 20.0%. We also conducted two follow-up studies in March 2010 and July 2010, observed that the average error rate for HumanBoost was below the others. We therefore conclude that PTDs are available as new heuristics, and HumanBoost has the potential to improve detection accuracy for Web user.
Mezigenera ní komunikace a sport: Simmel v pohled Intergenerational communication and sport: From Simmel's perspective
Koyo Fukasawa
Acta Universitatis Palackianae Olomucensis : Gymnica , 2006,
Abstract: M e moderní sport p ispět k reaktivaci komunity v urbanizované spole nosti? V této eseji, tykající se urbanizace, uva ujeme o vyznamu mezigenera ní komunikace pro obnovu komunity a o povaze sportu umo ňující posilovat kontakty mezi r znymi generacemi. Tyto mo nosti nacházíme ve sportovních aktivitách, které jsou "formou spole enskosti". Spole enskost vy aduje vztah, díky němu se lze radovat z kontakt s ostatními, a tento p ístup také p edpokládá. Can modern sport contribute to reactivating community in urbanized society? This essay, referring to the feature of urbanization, considers the significance of intergenerational communication to the regeneration of community and the character of sports for promoting exchanges among different generations. In sport activities, we can find, for example "the form of sociability". Sociability implies the ability to enjoy and relish relationships with others and supposes such an attitude.
Complete determination of the number of Galois points for a smooth plane curve
Satoru Fukasawa
Mathematics , 2010,
Abstract: Let $C$ be a smooth plane curve. A point $P$ in the projective plane is said to be Galois with respect to $C$ if the function field extension induced from the point projection from $P$ is Galois. We denote by $\delta(C)$ (resp. $\delta'(C)$) the number of Galois points contained in $C$ (resp. in $\mathbb P^2 \setminus C$). In this article, we determine the numbers $\delta(C)$ and $\delta'(C)$ in any remaining open cases. Summarizing results obtained by now, we will have a complete classification theorem of smooth plane curves by the number $\delta(C)$ or $\delta'(C)$. In particular, we give new characterizations of Fermat curve and Klein quartic curve by the number $\delta'(C)$.
Characterization of a Hermitian curve by Galois point
Satoru Fukasawa
Mathematics , 2011,
Abstract: For a plane curve, a point in the projective plane is said to be Galois when the point projection induces a Galois extension of function fields. We give a new characterization of a Fermat curve whose degree minus one is a power of $p$ in characteristic $p>2$, which is sometimes called Hermitian, by the number of Galois points lying on the curve.
Rational points and Galois points for a plane curve over a finite field
Satoru Fukasawa
Mathematics , 2014,
Abstract: We study the relationship between rational points and Galois points for a plane curve over a finite field. It is known that the set of Galois points coincides with that of rational points of the projective plane if the curve is the Hermitian, Klein quartic or Ballico-Hefez curves. We propose a problem: Does the converse hold true? When the curve of genus at most one has a rational point, we will have an affirmative answer.
Bounds for the number of Galois points for plane curves
Satoru Fukasawa
Mathematics , 2014,
Abstract: A point on a plane curve is said to be Galois (for the curve) if the projection from the point as a map from the curve to a line induces a Galois extension of function fields. It is known that the number of Galois points is finite except for a certain explicit example. We establish upper bounds for the number of Galois points for all plane curves other than the example in terms of the genus, degree and the generic order of contact, and settle curves attaining the bounds.
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