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Search Results: 1 - 10 of 163 matches for " AKICHIKA MIKAMI "
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Basic Level of Categorization in Macaca fascicularis
HAYATI Journal of Biosciences , 2011,
Abstract: Human brain posseses the ability to create a concept to assist the process of grouping individual object or events into different classes or categories. We call this grouping process as categorization. In addition to humans, the ability to categorize has also been proposed for animals. Being able to identify, visually or otherwise, a new object as a member of a category is an advantage for animals. Present experiment aims to test the categorization ability in discriminating species by Macaca fascicularis. Using match-to-sample task with photographs of monkeys and human as stimuli, we tested whether monkeys able to categorize monkey individuals as a class against human individuals as another class. We found that monkeys categorized humans differently from monkeys. The monkeys used physical characteristic such as shape and colors from the photographs to create different concepts of human and monkeys.
Gene conversion and purifying selection shape nucleotide variation in gibbon L/M opsin genes
Tomohide Hiwatashi, Akichika Mikami, Takafumi Katsumura, Bambang Suryobroto, Dyah Perwitasari-Farajallah, Suchinda Malaivijitnond, Boripat Siriaroonrat, Hiroki Oota, Shunji Goto, Shoji Kawamura
BMC Evolutionary Biology , 2011, DOI: 10.1186/1471-2148-11-312
Abstract: Among 152 individuals representing three genera (Hylobates, Nomascus and Symphalangus), all had both L and M opsin genes and no L/M hybrid genes. Among 94 individuals subjected to the detailed DNA sequencing, the nucleotide divergence between L and M opsin genes in the exons was significantly higher than the divergence in introns in each species. The ratio of the inter-LM divergence to the intra-L/M polymorphism was significantly lower in the introns than that in synonymous sites. When we reconstructed the phylogenetic tree using the exon sequences, the L/M gene duplication was placed in the common ancestor of catarrhines, whereas when intron sequences were used, the gene duplications appeared multiple times in different species. Using the GENECONV program, we also detected that tracts of gene conversions between L and M opsin genes occurred mostly within the intron regions.These results indicate the historical accumulation of gene conversions between L and M opsin genes in the introns in gibbons. Our study provides further support for the homogenizing role of gene conversion between the L and M opsin genes and for the purifying selection against such homogenization in the central exons to maintain the spectral difference between L and M opsins in non-human catarrhines.In catarrhine primates (humans, apes and Old World monkeys) the L and M opsin genes are closely juxtaposed on the X chromosome and, in combination with the autosomal S opsin gene, enable routinely trichromatic color vision [1,2]. The L and M opsin genes have a close evolutionary relationship and are highly similar in nucleotide sequence (~96% identity). Among 15 amino acid differences between the human L and M opsin genes, three account for the main shifts in spectral sensitivities and tuning [3-9].The organization of the L and M opsin genes among humans is known to be variable and includes the absence of an L or M opsin gene or the presence of L/M hybrid genes with an intermediate spectral sensitivit
Reduction of the Optical Loss in the Multi-Cathode Structure Organic Light Emitting Device Using a Long Range Surface Plasmon  [PDF]
Akiyoshi Mikami
Optics and Photonics Journal (OPJ) , 2016, DOI: 10.4236/opj.2016.68B038
Light extraction efficiency of organic light-emitting devices has improved by using a nano-sized multi-cathode structure consisting of semi-transparent metal and an optical compensation layer. From the detail optical calculation based on the multi-scale analysis including near-field optics, it was found that surface plasmon loss in the metal cathode is suppressed to less than 10% due to long range and short range surface plasmon coupling between both sides of metal cathode. Not less than 90% of optical power in the dipole emission can be successfully utilized as propagation light. Light extraction efficiency in a phosphorescent device has improved about twice by using the multi-cathode structure.
Phototropism in the Marine Red Macroalga Pyropia yezoensis  [PDF]
Megumu Takahashi, Koji Mikami
American Journal of Plant Sciences (AJPS) , 2016, DOI: 10.4236/ajps.2016.717211
Abstract: Phototropism is a response to the direction of light that guides growth orientation and determines the shape of plants to optimize photosynthetic activity. The phototropic response is present not only in terrestrial plants but also in water-living algae. However, knowledge about phototropism in Bangiophycean seaweeds is limited. Here, we examined the phototropic response of the red alga Pyropia yezoensis to elucidate the regulatory mechanism of phototropism in Bangiophyceae. When leafy gametophytes and filamentous sporophytes of P. yezoensis were cultured under directional light, phototropism was observed in the gametophytes. Conchosporangia on the sporophytes also exhibited phototropism. Phototropism was positive in the majority of gametophytes and conchosporangia but in some cases was negative. In addition, a strong phototropic response occurred under white light, whereas blue and red light elicited minor and no responses, respectively. This observation is in contrast with the phototropic response in terrestrial plants and several algae, in which blue light is responsible for positive phototropism. Surprisingly, the genome of P. yezoensis has no homologues of the photoreceptors for blue and red light, revealing differences in the regulation of phototropism between terrestrial plants and P. yezoensis . Studies on the phototropism in P. yezoensis could shed light on the evolutional divergence of phototropic responses in plants.
Measurements of the $D_{sJ}$ resonance properties
Y. Mikami
Physics , 2003, DOI: 10.1103/PhysRevLett.92.012002
Abstract: We report measurements of the properties of the $D_{sJ}^+(2317)$ and $D_{sJ}^+(2457)$ resonances produced in continuum $e^+ e^-$ annihilation near $\sqrt{s}=10.6 \mathrm{GeV}$. The analysis is based on an $86.9 \mathrm{fb^{-1}}$ data sample collected %at and 60 MeV below the $\Upsilon(4S)$ resonance with with the Belle detector at KEKB. We determine the masses to be $M(D_{sJ}^+(2317)) = 2317.2 \pm 0.5(\mathrm{stat}) \pm 0.9(\mathrm{syst}) \mathrm{MeV}/c^2$ and $M(D_{sJ}^+(2457))=2456.5 \pm 1.3(\mathrm{stat}) \pm 1.3(\mathrm{syst}) \mathrm{MeV}/c^2$. We observe the radiative decay mode $D_{sJ}^+(2457) \to D_s^+ \gamma$ and the dipion decay mode $D_{sJ}^+(2457) \to D_s^+ \pi^+ \pi^-$, and determine their branching fractions. No corresponding decays are observed for the $D_{sJ}(2317)$ state. These results are consistent with the spin-parity assignments of $0^+$ for the $D_{sJ}(2317)$ and $1^+$ for the $D_{sJ}(2457)$.
An affirmative answer to a conjecture for Metoki class
Kentaro Mikami
Mathematics , 2014,
Abstract: In "The {G}el'fand-{K}alinin-{F}uks class and characteristic classes of transversely symplectic foliations" arXiv:0910.3414, Kotschick and Morita showed that the Gel'fand-Kalinin-Fuks class in $\ds\HGF{7}{2}{}{8}$ is decomposed as a product $\eta\wedge \omega$ of some leaf cohomology class $\eta$ and a transverse symplectic class $\omega$. We show that the same formula holds for Metoki class, which is a non-trivial element in $\ds \HGF{9}{2}{}{14}$. The result was conjectured by Kotschick and Morita, where they studied characteristic classes of symplectic foliations due to Kontsevich. Our proof depends on Groebner Basis theory using computer calculations.
Another proof to Kotschick-Morita's Theorem of Kontsevich homomorphism
Kentaro Mikami
Mathematics , 2014,
Abstract: In \cite{KOT:MORITA}, Kotschick and Morita showed that the Gel'fand-Kalinin-Fuks class in $\ds \HGF{7}{2}{}{8}$ is decomposed as a product $\eta\wedge \omega $ of some leaf cohomology class $\eta$ and a transverse symplectic class $\omega$. In other words, the Kontsevich homomorphism $\ds\omega\wedge :\HGF{5}{2}{0}{10} \rightarrow\HGF{7}{2}{}{8}$ is isomorphic. In this paper, we give proof for the Kotschick and Morita's theorem by using the Gr\"obner Basis theory and computer symbol calculations.
The relative Gel'fand-Kalinin-Fuks cohomology groups of the formal Hamiltonian vector fields on 6-dimensional plane
Kentaro Mikami
Mathematics , 2014,
Abstract: Using Crystal basis theory, we study the relative Gel'fand-Kalinin-Fuks cohomology groups of the formal Hamiltonian vector fields on 6-dimensional plane with weight =2,4,6.
Photosynthesis-Dependent Extracellular Ca2+ Influx Triggers an Asexual Reproductive Cycle in the Marine Red Macroalga Porphyra yezoensis  [PDF]
Megumu Takahashi, Naotsune Saga, Koji Mikami
American Journal of Plant Sciences (AJPS) , 2010, DOI: 10.4236/ajps.2010.11001
Abstract: Asexual propagation to increase the number of gametophytic clones via the growth of asexual haploid spores is a unique survival strategy found in marine multicellular algae. However, the mechanisms regulating the asexual life cycle are largely unknown. Here, factors involved in the regulation of production and discharge of asexual spores, so-called monospores, are identified in the marine red macroalga Porphyra yezoensis. First, enhanced discharge of monospores was found by incubation of gametophytes in ASPMT1, a modified version of the previously established synthetic medium ASP12. Comparison of the compositions of ASPMT1 and our standard medium, ESL, indicated that the Ca2+ concentration in ASPMT1 was three times lower than that in ESL medium. Thus, we modified ASPMT1 by increasing its Ca2+ concentration, resulting in reduction of monospore discharge. These findings demonstrate the role of reduced Ca2+ concentrations in enhancing monospore production and release. Moreover, it was also observed that initiation of asexual life cycle required illumination, was repressed by DCMU, and was induced by a Ca2+ ionophore in the dark. Taken together, these results indicate that photosynthesis-dependent Ca2+ influx triggers the asexual life cycle by promoting the production and discharge of monospores in P. yezoensis.
Effect of Heterogeneity of Porous Media on Gas Permeation and Entrapment  [PDF]
Yohei Mikami, Yoshihiro Deguchi, Tetsuya Suekane
Journal of Flow Control, Measurement & Visualization (JFCMV) , 2014, DOI: 10.4236/jfcmv.2014.23013
Abstract: Capillary trapping prevents the migration of CO2 in reservoirs due to buoyancy. The residual gas saturation is strongly influenced by the gas saturation after gas injection. In this study, we have investigated the effect of stratified structure of heterogeneous porous media on gas permeation and entrapment. Experiments were carried out at a laboratory condition for a nitrogen-water system with the packed beds of glass beads with various diameters which modeled stratified porous media. In the case of parallel structure, the injected gas selectively percolated into permeable layers. The gas permeation can hardly occur for the less permeable layers because of the capillary entrance pressure. In the case of serial structure, the interface of porous structure hindered the migration of gas across it, because of the capillary entrance pressure. When the gas percolated in the permeable layers, capillary fingering was developed in the layers. However, when the tip of finger reached the interface, fingers grew in tangential directions until the pressure built up to overcome the capillary entrance pressure. As a result, high gas saturation was achieved in the permeable layers of both upward and downward gas injections.
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