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Search Results: 1 - 10 of 72 matches for " Takefumi Ishidao "
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Alternative Stable States Generated by Ontogenetic Niche Shift in the Presence of Multiple Resource Use
Takefumi Nakazawa
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0014667
Abstract: It has been suggested that when juveniles and adults use different resources or habitats, alternative stable states (ASS) may exist in systems coupled by an ontogenetic niche shift. However, mainly the simplest system, i.e., the one-consumer–two-resource system, has been studied previously, and little is known about the development of ASS existing in more complex systems. Here, I theoretically investigated the development of ASS caused by an ontogenetic niche shift in the presence of multiple resource use. I considered three independent scenarios; (i) additional resources, (ii) multiple habitats, and (iii) interstage resource sharing. The model analyses illustrate that relative balance between the total resource availability in the juvenile and adult habitats is crucial for the development of ASS. This balance is determined by factors such as local habitat productivity, subsidy inputs, colonization area, and foraging mobility. Furthermore, it is also shown that interstage resource sharing generally suppresses ASS. These results suggest that the anthropogenic impacts of habitat modifications (e.g., fragmentation and destruction) or interaction modifications (e.g., changes in ontogeny and foraging behavior) propagate through space and may cause or prevent regime shifts in the regional community structure.
Oxytocin and mutual communication in mother-infant bonding
Takefumi Kikusui
Frontiers in Human Neuroscience , 2012, DOI: 10.3389/fnhum.2012.00031
Abstract: Mother-infant bonding is universal to all mammalian species. In this review, we describe the manner in which reciprocal communication between the mother and infant leads to mother-infant bonding in rodents. In rats and mice, mother-infant bond formation is reinforced by various social stimuli, such as tactile stimuli and ultrasonic vocalizations (USVs) from the pups to the mother, and feeding and tactile stimulation from the mother to the pups. Some evidence suggests that mother and infant can develop a cross-modal sensory recognition of their counterpart during this bonding process. Neurochemically, oxytocin in the neural system plays a pivotal role in each side of the mother-infant bonding process, although the mechanisms underlying bond formation in the brains of infants has not yet been clarified. Impairment of mother-infant bonding, that is, deprivation of social stimuli from the mother, strongly influences offspring sociality, including maternal behavior toward their own offspring in their adulthood, implying a “non-genomic transmission of maternal environment,” even in rodents. The comparative understanding of cognitive functions between mother and infants, and the biological mechanisms involved in mother-infant bonding may help us understand psychiatric disorders associated with mother-infant relationships.
Quandle homotopy invariants of knotted surfaces
Takefumi Nosaka
Mathematics , 2010,
Abstract: Given a finite quandle, we introduce a quandle homotopy invariant of knotted surfaces in the 4-sphere, modifying that of classical links. This invariant is valued in the third homotopy group of the quandle space, and is universal among the (generalized) quandle cocycle invariants. We compute the second and third homotopy groups, with respect to "regular Alexander quandles". As a corollary, any quandle cocycle invariant using the dihedral quandle of prime order is a scalar multiple of the Mochizuki 3-cocycle invariant. As another result, we determine the third quandle homology group of the dihedral quandle of odd order.
Quandle cocycle invariants of links using Mochizuki's 3-cocycles and Dijkgraaf-Witten invariants of 3-manifolds
Takefumi Nosaka
Mathematics , 2011,
Abstract: T. Mochizuki determined all 3-cocycles of the third quandle cohomologies of Alexander quandles on finite fields. We show that all the 3-cocycles, except those of 2-cocycle forms, are derived from group 3-cocycles of a meta-abelian group. Further, the quandle cocycle invariant of a link using Mochizuki's 3-cocycle is equivalent to a $\Z$-equivariant part of the Dijkgraaf-Witten invariant of a cyclic covering of $S^3$ branched over the link using the group. We compute some Massey triple products via the former invariant.
Homotopical interpretation of link invariants from finite quandles
Takefumi Nosaka
Mathematics , 2012,
Abstract: This paper demonstrates a topological meaning of quandle cocycle invariants of links with respect to finite connected quandles $X$, from a perspective of homotopy theory: Specifically, for any prime $\ell$ which does not divide the type of $X$, the $\ell$-torsion of this invariants is equal to a sum of the colouring polynomial and a $\Z$-equivariant part of the Dijkgraaf-Witten invariant of a cyclic branched covering space. Moreover, our homotopical approach involves application of computing some third homology groups and second homotopy groups of the classifying spaces of quandles, from results of group cohomology.
On third homologies of groups and of quandles via the Dijkgraaf-Witten invariant and Inoue-Kabaya map
Takefumi Nosaka
Mathematics , 2012,
Abstract: We propose a simple method to produce quandle cocycles from group cocycles, as a modification of Inoue-Kabaya chain map. We further show that, in respect to "universal central extended quandles", the chain map induces an isomorphism between their third homologies. For example, all Mochizuki's quandle 3-cocycles are shown to be derived from group cocycles of some non-abelian group. As an application, we calculate some $\Z$-equivariant parts of the Dijkgraaf-Witten invariants of some cyclic branched covering spaces, via some cocycle invariant of links.
Finite presentations of centrally extended mapping class groups
Takefumi Nosaka
Mathematics , 2014,
Abstract: We describe a finite presentation of $ \mathcal{T}_{g,r} $ for $g \geq 3$. % or $(g,r)=(2,0)$. Here $\mathcal{T}_{g,r} $ is the universal central extension of the mapping class group of the surface of genus $g$ with $r$-boundaries. We also investigate the case $g=2$,
Central extensions of groups and adjoint groups of quandles
Takefumi Nosaka
Mathematics , 2015,
Abstract: This paper develops an approach for describing centrally extended groups, as determining the adjoint groups associated with quandles. Furthermore, we explicitly describe such groups of some quandles. As a corollary, we determine some second quandle homologies.
One-Step Detection of the 2009 Pandemic Influenza A(H1N1) Virus by the RT-SmartAmp Assay and Its Clinical Validation
Yuki Kawai, Yasumasa Kimura, Alexander Lezhava, Hajime Kanamori, Kengo Usui, Takeshi Hanami, Takahiro Soma, Jean-étienne Morlighem, Satomi Saga, Yuri Ishizu, Shintaro Aoki, Ryuta Endo, Atsuko Oguchi-Katayama, Yasushi Kogo, Yasumasa Mitani, Takefumi Ishidao, Chiharu Kawakami, Hideshi Kurata, Yumiko Furuya, Takayuki Saito, Norio Okazaki, Masatsugu Chikahira, Eiji Hayashi, Sei-ichi Tsuruoka, Tokumichi Toguchi, Yoshitomo Saito, Toshiaki Ban, Shinyu Izumi, Hideko Uryu, Koichiro Kudo, Yuko Sakai-Tagawa, Yoshihiro Kawaoka, Aizan Hirai, Yoshihide Hayashizaki, Toshihisa Ishikawa
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0030236
Abstract: Background In 2009, a pandemic (pdm) influenza A(H1N1) virus infection quickly circulated globally resulting in about 18,000 deaths around the world. In Japan, infected patients accounted for 16% of the total population. The possibility of human-to-human transmission of highly pathogenic novel influenza viruses is becoming a fear for human health and society. Methodology To address the clinical need for rapid diagnosis, we have developed a new method, the “RT-SmartAmp assay”, to rapidly detect the 2009 pandemic influenza A(H1N1) virus from patient swab samples. The RT-SmartAmp assay comprises both reverse transcriptase (RT) and isothermal DNA amplification reactions in one step, where RNA extraction and PCR reaction are not required. We used an exciton-controlled hybridization-sensitive fluorescent primer to specifically detect the HA segment of the 2009 pdm influenza A(H1N1) virus within 40 minutes without cross-reacting with the seasonal A(H1N1), A(H3N2), or B-type (Victoria) viruses. Results and Conclusions We evaluated the RT-SmartAmp method in clinical research carried out in Japan during a pandemic period of October 2009 to January 2010. A total of 255 swab samples were collected from outpatients with influenza-like illness at three hospitals and eleven clinics located in the Tokyo and Chiba areas in Japan. The 2009 pdm influenza A(H1N1) virus was detected by the RT-SmartAmp assay, and the detection results were subsequently compared with data of current influenza diagnostic tests (lateral flow immuno-chromatographic tests) and viral genome sequence analysis. In conclusion, by the RT-SmartAmp assay we could detect the 2009 pdm influenza A(H1N1) virus in patients' swab samples even in early stages after the initial onset of influenza symptoms. Thus, the RT-SmartAmp assay is considered to provide a simple and practical tool to rapidly detect the 2009 pdm influenza A(H1N1) virus.
An Effective Routing Algorithm with Chaotic Neurodynamics for Optimizing Communication Networks  [PDF]
Takayuki Kimura, Takefumi Hiraguri, Tohru Ikeguchi
American Journal of Operations Research (AJOR) , 2012, DOI: 10.4236/ajor.2012.23042
Abstract: In communication networks, the most significant impediment to reliable communication between end users is the congestion of packets. Many approaches have been tried to resolve the congestion problem. In this regard, we have proposed a routing algorithm with chaotic neurodynamics. By using a refractory effect, which is the most important effect of chaotic neurons, the routing algorithm shows better performance than the shortest path approach. In addition, we have further improved the routing algorithm by combining information of the shortest paths and the waiting times at adjacent nodes. We confirm that the routing algorithm using chaotic neurodynamics is the most effective approach to alleviate congestion of packets in a communication network. In previous works, the chaotic routing algorithm has been evaluated for ideal communication networks in which every node has the same transmission capability for routing the packets and the same buffer size for storing the packets. To check whether the chaotic routing algorithm is practically applicable, it is important to evaluate its performance under realistic conditions. In 2007, M. Hu et al. proposed a practicable communication network in which the largest storage capacity and processing capability were introduced. New-man et al. proposed scale-free networks with community structures; these networks effectively extract communities from the real complex network using the shortest path betweenness. In addition, the scale-free networks have common structures in real complex networks such as collaboration networks or communication networks. Thus, in this paper, we evaluate the chaotic routing algorithm for communication networks to which realistic conditions are introduced. Owing to the effective alleviation of packets, the proposed routing algorithm shows a higher arrival rate of packets than the conventional routing algorithms. Further, we confirmed that the chaotic routing algorithm can possibly be applied to real communication networks.
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