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Search Results: 1 - 10 of 139119 matches for " K. Hirata "
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A Necessary Condition for existence of Lie Symmetries in Quasihomogeneous Systems of Ordinary Differential Equations
Y. Hirata,K. Imai
Physics , 2001, DOI: 10.1143/JPSJ.71.2396
Abstract: Lie symmetries for ordinary differential equations are studied. In systems of ordinary differential equations, there do not always exist non-trivial Lie symmetries around equilibrium points. We present a necessary condition for existence of Lie symmetries analytic in the neighbourhood of an equilibrium point. In addition, this result can be applied to a necessary condition for existence of a Lie symmetry in quasihomogeneous systems of ordinary differential equations. With the help of our main theorem, it is proved that several systems do not possess any analytic Lie symmetries.
A common developmental plan for neocortical gene-expressing neurons in the pallium of the domestic chicken Gallus gallus domesticus and the Chinese softshell turtle Pelodiscus sinensis
Ikuo K. Suzuki,Tatsumi Hirata
Frontiers in Neuroanatomy , 2014, DOI: 10.3389/fnana.2014.00020
Abstract: The six-layered neocortex is a unique characteristic of mammals and likely provides the neural basis of their sophisticated cognitive abilities. Although all mammalian species share the layered structure of the neocortex, the sauropsids exhibit an entirely different cytoarchitecture of the corresponding pallial region. Our previous gene expression study revealed that the chicken pallium possesses neural subtypes that express orthologs of layer-specific genes of the mammalian neocortex. To understand the evolutionary steps leading toward animal group-specific neuronal arrangements in the pallium in the course of amniote diversification, we examined expression patterns of the same orthologs and a few additional genes in the pallial development of the Chinese softshell turtle Pelodiscus sinensis, and compared these patterns to those of the chicken. Our analyses highlighted similarities in neuronal arrangements between the two species; the mammalian layer 5 marker orthologs are expressed in the medial domain and the layer 2/3 marker orthologs are expressed in the lateral domain in the pallia of both species. We hypothesize that the mediolateral arrangement of the neocortical layer-specific gene-expressing neurons originated in their common ancestor and is conserved among all sauropsid groups, whereas the neuronal arrangement within the pallium could have highly diversified independently in the mammalian lineage.
Focused-ion-beam-induced deposition of superconducting nanowires
E. S. Sadki,S. Ooi,K. Hirata
Physics , 2004, DOI: 10.1063/1.1842367
Abstract: Superconducting nanowires, with a critical temperature of 5.2 K, have been synthesized using an ion-beam-induced deposition, with a Gallium focused ion beam and Tungsten Carboxyl, W(CO)6, as precursor. The films are amorphous, with atomic concentrations of about 40, 40, and 20 % for W, C, and Ga, respectively. Zero Kelvin values of the upper critical field and coherence length of 9.5 T and 5.9 nm, respectively, are deduced from the resistivity data at different applied magnetic fields. The critical current density is Jc= 1.5 10^5 A/cm2 at 3 K. This technique can be used as a template-free fabrication method for superconducting devices.
Cooperative damping mechanism of the resonance in the nuclear photoabsorption
M. Hirata,K. Ochi,T. Takaki
Physics , 1997, DOI: 10.1103/PhysRevLett.80.5068
Abstract: We propose a resonance damping mechanism to explain the disappearance of the peaks around the position of the resonances higher than the $\Delta$ resonance in the nuclear photoabsorption. This phenomenon is understood by taking into account the cooperative effect of the collision broadening of $\Delta$ and $N^{*}$, the pion distortion and the interference in the two-pion photoproduction processes in the nuclear medium.
Effect of $ρN$ channel in the $γN \to ππN$ reactions
M. Hirata,K. Ochi,T. Takaki
Physics , 1997,
Abstract: A model for the two-pion photoproduction on the nucleon proposedearlier is modified to simultaneously explain the total cross sections and the invariant mass spectra. Using this model, we discuss the role of the $\rho $ meson in the $\gamma N \to \pi \pi N$ reaction.
Simulating carbon and water cycles of larch forests in East Asia by the BIOME-BGC model with AsiaFlux data
M. Ueyama,K. Ichii,R. Hirata,K. Takagi
Biogeosciences Discussions , 2009,
Abstract: Larch forests are widely distributed across many cool-temperate and boreal regions, and they are expected to play an important role in global carbon and water cycles. Model parameterizations for larch forests still contain large uncertainties owing to a lack of validation. In this study, a process-based terrestrial biosphere model, BIOME-BGC, was tested for larch forests at six AsiaFlux sites and used to identify important environmental factors that affect the carbon and water cycles at both temporal and spatial scales. The model simulation performed with the default deciduous conifer parameters produced results that had large differences from the observed net ecosystem exchange (NEE), gross primary productivity (GPP), ecosystem respiration (RE), and evapotranspiration (ET). Therefore, we adjusted several model parameters in order to reproduce the observed rates of carbon and water cycle processes. This model calibration, performed using the AsiaFlux data, significantly improved the model performance. The simulated annual GPP, RE, NEE, and ET from the calibrated model were highly consistent with observed values. The observed and simulated GPP and RE across the six sites are positively correlated with the annual mean air temperature and annual total precipitation. On the other hand, the simulated carbon budget is partly explained by the stand disturbance history in addition to the climate. The sensitivity study indicates that spring warming enhances the carbon sink, whereas summer warming decreases it across the larch forests. The summer radiation is the most important factor that controls the carbon fluxes in the temperate site, but the VPD and water conditions are the limiting factors in the boreal sites. One model parameter, the allocation ratio of carbon between aboveground and belowground, is site-specific, and it is negatively correlated with the annual climate of annual mean air temperature and total precipitation. Although this study significantly improves the model performance, the uncertainties that remain in terms of the sensitivity to water conditions should be examined in ongoing and long-term observations.
Impact of meteorological anomalies in the 2003 summer on gross primary productivity in East Asia
N. Saigusa,K. Ichii,H. Murakami,R. Hirata
Biogeosciences Discussions , 2009,
Abstract: Northern Eurasia experienced anomalous weather conditions in the 2003 summer. We examined how forest ecosystems responded to the meteorological anomalies during the period using the dataset collected at flux monitoring sites in Asia, including a boreal forest in Mongolia, temperate forests in China and Japan, and a sub-tropical forest in China, as well as the dataset from satellite remote sensing. From July to August 2003, an active rain band stayed in the mid-latitude in East Asia for an unusually long period. Under the influence of the rain band, the gross primary production (GPP) of temperate forests was 20–30% lower in the 2003 summer than in other years due to significant reduction in the photosynthetic photon flux density (PPFD). The GPP of a cool-temperate forest in the north of the rain band was slightly enhanced by the higher PPFD; however, the GPP of a sub-tropical forest located in the south of the rain band was reduced by drought stress due to extremely hot and dry conditions. The correlation coefficients for the year-to-year changes in the PPFD and GPP during mid-summer were calculated, and the spatial distribution was examined. The spatial pattern of the PPFD was calculated by satellite data, and that of the GPP was estimated by a regression-type model, which was trained and tested by ground observation data. The correlation was positive in the mid- and high-latitudes since light was an essential factor of the summer GPP. On the other hand, a negative correlation appeared in the lower latitudes, suggesting that the water limitation was much more important than the PPFD in the region. Our study illustrated that the integration of flux data from wide areas by combining satellite remote sensing data can help us gain an understanding of the ecosystem responses to large-scale meteorological phenomena.
Journal of Central European Agriculture , 2002,
Abstract: In the present study the molecular basis and mechanism of pepper cytoplasmic male sterility (CMS) and its restoration system (Rf) has been characterized in detail. Pollen fertility of five CMSs (No. 201 to 205), four restorer lines (No. 206, 207, 209 and 210) and their F1, F2 generations were investigated during different growing seasons to study the response of male sterility to various environmental conditions. Restorer gene specific primers were applied to reveal the molecular genetic differences between the CMS and restorer lines. Bulk segregant” and individual analysis screened DNA markers linked to the fertility restorer (Rf) gene for cytoplasmic male sterility. By the application for conventional breeding and molecular genetic methods co-segregation of the restorer specific markers and pollen viability data were observed on hundred individuals of the F2 generation in order to construct a physical linkage map.
Intrasplenic Pancreatic Pseudocysts
Hokama A,Maeda K,Tomiyama R,Hirata T
JOP Journal of the Pancreas , 2004,
Low temperature specific heat of La_{3}Pd_{4}Ge_{4} with U_{3}Ni_{4}Si_{4}-type structure
S. Kasahara,H. Fujii,T. Mochiku,H. Takeya,K. Hirata
Physics , 2007, DOI: 10.1088/0953-8984/20/38/385204
Abstract: Low temperature specific heat has been investigated in a novel ternary superconductor La_{3}Pd_{4}Ge_{4} with an U_{3}Ni_{4}Si_{4}-type structure consisting of the alternating BaAl_{4} (ThCr_{2}Si_{2})- and AlB$_{2}$-type layers. A comparative study with the related ThCr_{2}Si_{2}-type superconductor LaPd_{2}Ge_{2}, one of the layers in La_{3}Pd_{4}Ge_{4}, is also presented. From the normal state specific heat, the Sommerfeld coefficient $\gamma_{n} = 27.0$ mJ/mol K^2 and the Debye temperature $\Theta_{\rm D}$ = 256 K are derived for the La_{3}Pd_{4}Ge_{4}, while those for the LaPd_{2}Ge_{2} are $\gamma_{n} =8.26$ mJ/mol K^2 and $\Theta_{\rm D}$ = 291 K. The La_{3}Pd_{4}Ge_{4} has moderately high electronic density of state at the Fermi level. Electronic contribution on the specific heat, $C_{\rm el}$, in each compound is well described by the BCS behavior, suggesting that both of the La_{3}Pd_{4}Ge_{4} and the LaPd_{2}Ge_{2} have fully opened isotropic gap in the superconducting state.
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