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Search Results: 1 - 10 of 1125 matches for " Tadahiro Nakajima "
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Testing for Rational Bubbles in the Commodity Market
Tadahiro Nakajima,Shigeyuki Hamori
Accounting and Finance Research , 2012, DOI: 10.5430/afr.v1n2p101
Abstract: In order to hedge price-fluctuation risks, to derive fair prices, and to operate fundsas a new asset class, both expectations and concerns about commodity markets have been increasing.This paper proposes a sufficient condition for the absence of rational bubbles in the commodity market: that the first differences of real prices are stationary. This condition is proposed on the assumption that products of the convenience yield and the real prices are stationary. By applying this approach to the US crude oil and natural gas marketsfrom 3 January 2007, to 30 December 2011, the absence of rational bubbles in both markets can be verified.One should interpretthese large price fluctuations as caused by much larger income elasticity than price elasticity.These prices reflect thefundamental values of these commodities.
Cabergoline, Dopamine D2 Receptor Agonist, Prevents Neuronal Cell Death under Oxidative Stress via Reducing Excitotoxicity
Haruki Odaka, Tadahiro Numakawa, Naoki Adachi, Yoshiko Ooshima, Shingo Nakajima, Yusuke Katanuma, Takafumi Inoue, Hiroshi Kunugi
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0099271
Abstract: Several lines of evidence demonstrate that oxidative stress is involved in the pathogenesis of neurodegenerative diseases, including Parkinson's disease. Potent antioxidants may therefore be effective in the treatment of such diseases. Cabergoline, a dopamine D2 receptor agonist and antiparkinson drug, has been studied using several cell types including mesencephalic neurons, and is recognized as a potent radical scavenger. Here, we examined whether cabergoline exerts neuroprotective effects against oxidative stress through a receptor-mediated mechanism in cultured cortical neurons. We found that neuronal death induced by H2O2 exposure was inhibited by pretreatment with cabergoline, while this protective effect was eliminated in the presence of a dopamine D2 receptor inhibitor, spiperone. Activation of ERK1/2 by H2O2 was suppressed by cabergoline, and an ERK signaling pathway inhibitor, U0126, similarly protected cortical neurons from cell death. This suggested the ERK signaling pathway has a critical role in cabergoline-mediated neuroprotection. Furthermore, increased extracellular levels of glutamate induced by H2O2, which might contribute to ERK activation, were reduced by cabergoline, while inhibitors for NMDA receptor or L-type Ca2+ channel demonstrated a survival effect against H2O2. Interestingly, we found that cabergoline increased expression levels of glutamate transporters such as EAAC1. Taken together, these results suggest that cabergoline has a protective effect on cortical neurons via a receptor-mediated mechanism including repression of ERK1/2 activation and extracellular glutamate accumulation induced by H2O2.
Effects of Improving Public Services for Tourism Developments in Islands: The Case of Remote Islands in Nagasaki, Japan  [PDF]
Tadahiro Okuyama, Hayato Ishihara
Open Journal of Social Sciences (JSS) , 2015, DOI: 10.4236/jss.2015.36018
Abstract: Growths of numbers of tourists who stay long-term in tourism sites are an important policy for local governments in islands due to their locations that are far from urban areas. However, many tourists hesitate to stay long-term in islands owing to not only the expensive travel costs but also the lack of public services in islands. The purpose of this study is to examine effects of improving public services in islands for tourists’ willingness to pays (WTPs) and non-tourists’ attitudes for long-term stays. Data on tourism activity for islands, Nagasaki, Japan were used. Respondents were asked about their WTPs for long-term stays and their needs for public services of islands; reductions of costs for rent or purchasing houses for long-term stays and travel costs, easy to take a vacation, to enhance medical services, educational services and job search services. The logit model was used for estimations. Median and mean values of WTPs (per year) were calculated JPY 151,629 (USD 1184) and JPY 242,110 (USD 3008). Positive effects on five public services (without travel costs) were confirmed. For example, the median values of WTPs were increased to JPY 478,369 (USD 5943) when the medical services were improved, and JPY 1,484,704 (USD 18,446) when all public services were improved. The results showed that improvement of public services have the effect 1) to improve tourists’ benefits and 2) to change many non-tourists’ attitudes from the rejection of staying long term in islands to the acceptance. Thus, results indicate that it would be better for central and/or local governments in islands to enhance islands’ public services.
Remarks on the Erroneous Dispersion Surfaces From a Pair of a Hyperbolic Branch and An Elliptical Arc of the Intersected Two Laue Spheres Based on the Usual Crude Approximation  [PDF]
Tetsuo Nakajima
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.23022
Abstract: In almost all previous works, the hyperbolic dispersion surfaces of the central proper quadrics have been crudely derived from the degree of reduction from the bi-quadratic equation by use of some roughly indefinable approximate relations. Moreover, neglecting the high symmetry of the hyperbola, both the branches have been approximated on the asymmetric surfaces composed of a pair of a branch of the hyperbola and a vertex of the ellipse without the presentation of reasonable evidence. Based upon the same dispersion surfaces equation, a new original gapless dispersion surfaces could be rigorously introduced without crude omission of even a term in the bi-quadratic equation based upon usual analogy with the extended band theory of solid as the close approximation to the truth.
Migration, Employment, and Industrial Development in Japan  [PDF]
Tetsuya Nakajima
Theoretical Economics Letters (TEL) , 2014, DOI: 10.4236/tel.2014.48083
Abstract: Industrial development in Japan is accompanied by massive migration from agricultural to industrial areas. In a modified Harrod-Domar model, this paper compares two steady states, the first and the second, which emerge before and after the termination of such migration, respectively. Then, the paper shows that employment rates must be lower in the second steady state. Further, by examining the effects of fiscal policy, the paper shows that the balanced budget multiplier exceeds unity, and fiscal policy raises households’ disposable income and consumption.
Design of Autonomous Underwater Vehicle
Tadahiro Hyakudome
International Journal of Advanced Robotic Systems , 2011,
Abstract: There are concerns about the impact that global warming will have on our environment, and which will inevitably result in expanding deserts and rising water levels. While a lot of underwater vehicles are utilized, AUVs (Autonomous Underwater Vehicle) were considered and chosen, as the most suitable tool for conduction survey concerning these global environmental problems. AUVs can comprehensive survey because the vehicle does not have to be connected to the support vessel by tether cable. When such underwater vehicles are made, it is necessary to consider about the following things. 1) Seawater and Water Pressure Environment, 2) Sink, 3) There are no Gas or Battery Charge Stations, 4) Global Positioning System cannot use, 5) Radio waves cannot use. In the paper, outline of above and how deal about it are explained.
Diophantine conditions in global well-posedness for coupled KdV-type systems
Tadahiro Oh
Electronic Journal of Differential Equations , 2009,
Abstract: We consider the global well-posedness problem of a one-parameter family of coupled KdV-type systems both in the periodic and non-periodic setting. When the coupling parameter $alpha = 1$, we prove the global well-posedness in $H^s(mathbb{R}) $ for $s > 3/4$ and $H^s(mathbb{T}) $ for $s geq -1/2$ via the I-method developed by Colliander-Keel-Staffilani-Takaoka-Tao [5]. When $alpha e 1$, as in the local theory [14], certain resonances occur, closely depending on the value of $alpha$. We use the Diophantine conditions to characterize the resonances. Then, via the second iteration of the I-method, we establish a global well-posedness result in $H^s(mathbb{T})$, $s geq widetilde{s}$, where $widetilde{s}= widetilde{s}(alpha) in (5/7, 1]$ is determined by the Diophantine characterization of certain constants derived from the coupling parameter $alpha$. We also show that the third iteration of the I-method fails in this case.
Some rigorous results on the Holstein-Hubbard model
Tadahiro Miyao
Physics , 2014,
Abstract: The Holstein model has been widely accepted as a model of electrons interacting with the phonons. Analysis of its ground states was accomplished decades ago. However obtained results did not completely take account of the repulsive Coulomb interactions. Recent progress has made it possible to treat such interactions rigorously. In this paper, we study the Holstein-Hubbard mdoel with the repulsive Coulomb interactions. Ground state properties of the model are investigated. Especially, the ground state of the Hamiltonian is proven to be unique for an even number of electrons on bipartite connected lattice. In addition, an infrared bound on the two-point function is given. The effects of the repulsive Coulomb interaction induce several technical difficulties.
Upper bounds on the charge susceptibility of many-electron systems coupled to the quantized radiation field
Tadahiro Miyao
Physics , 2014,
Abstract: We extend the Kubo-Kishi theorem concerning the charge susceptibility of the Hubbard model in the following way: (i) The electron-photon interaction is taken into account. (ii) Not only on-site but also general Coulomb repulsion is considered.
Reflection positivity and quantum Griffiths' inequalities
Tadahiro Miyao
Physics , 2015,
Abstract: We propose a new method of constructing the quantum Griffiths inequality. From a viewpoint of operator inequalities, we first study the quantum rotor model. This viewpoint clarifies important connections between the reflection positivity and the Griffiths inequality. Next we apply our method to the spin-$1/2$ quantum Heisenberg model. Finally we point out a model-independent structure which governs the correlation inequalities.
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