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Search Results: 1 - 10 of 298597 matches for " J. Maeda "
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A Dip after the Early Emission of Super-Luminous Supernovae: A Signature of Shock Breakout within Dense Circumstellar Media
Takashi J. Moriya,Keiichi Maeda
Physics , 2012, DOI: 10.1088/2041-8205/756/1/L22
Abstract: The origin of super-luminous supernovae (SLSNe), especially the source of their huge luminosities, has not been clarified yet. While a strong interaction between SN ejecta and dense circumstellar media (CSM) is a leading scenario, alternative models have been proposed. In this Letter, we suggest new diagnostics to discriminate the strong SN-CSM interaction scenario from the others: a decline in the luminosity ('dip') before the main peak of the light curve. This dip is an unavoidable consequence of having a dense CSM within which the shock breakout occurs. If a dense CSM shell is located far at large radii from the progenitor inside, it takes time for the SN ejecta to reach it and the early light curve can be powered by the SN ejecta before the collision. Once the SN ejecta collides with the dense CSM, the electron density and thus the Thomson scattering opacity suddenly increase. Photons become unable to go out of the shock even if there is a source of emission inside, which results in the dip in the light curve. This dip is a solid prediction from the strong interaction scenario irrespective of a power source for the early emission. Eventually the forward shock breaks out from within the dense CSM, and the luminosity increases by the continuous strong SN-CSM interaction, resulting in an SLSN. The possible dip observed in the hydrogen-poor SLSN, 2006oz, could be the first example of this signature and give support to the SN-CSM interaction as the power source of SLSN 2006oz.
Constraining Physical Properties of Type IIn Supernovae through Rise Times and Peak Luminosities
Takashi J. Moriya,Keiichi Maeda
Physics , 2014, DOI: 10.1088/2041-8205/790/2/L16
Abstract: We investigate the diversity in the wind density, supernova ejecta energy, and ejecta mass in Type IIn supernovae based on their rise times and peak luminosities. We show that the wind density and supernova ejecta properties can be estimated independently if both the rise time and peak luminosity are observed. The peak luminosity is mostly determined by the supernova properties and the rise time can be used to estimate the wind density. We find that the ejecta energy of Type IIn supernovae needs to vary by factors of 0.2-5 from the average if their ejecta mass is similar. The diversity in the observed rise times indicates that their wind density varies by factors of 0.2-2 from the average. We show that Type IIn superluminous supernovae should have not only large wind density but also large ejecta energy and/or small ejecta mass to explain their large luminosities and the rise times at the same time. We also note that the shock breakout does not necessarily occur in the wind even if it is optically thick, except for the case of superluminous supernovae, and we analyze the observational data both with and without assuming that the shock breakout occurs in the dense wind of Type IIn supernovae.
Automatic & Safe Oxytocin Induction of Labor  [PDF]
Kazuo Maeda
Open Journal of Obstetrics and Gynecology (OJOG) , 2018, DOI: 10.4236/ojog.2018.89084
Abstract: Aims: To prevent fetal damage by excess oxytocin administration of manually controlled infusion, by automatic and safe increasing infusion setting with monitoring uterine contraction and fetal heart rate. Methods: Starting infusion level was 2 milliU/ml, as oxytocin sensitivity of a pregnant uterus is unknown, to avoid hyper contraction and fetal bradycardia caused by unexpected excess oxytocin sensitivity. The infusion automatically increased with automatic monitoring of uterine contraction curve, then the increasing stopped when contraction reached to normal labor level, where the infusion level maintained, which continued until delivery, if there is no trouble. However, the infusion continued until expiring all fluid in case of insensitive uterus, where the induction was performed in another day. The infusion stopped automatically when contraction was too strong, or fetal heart rate is abnormal. Thus, oxytocin sensitive case is protected from excess contraction and fetal asphyxia. Results: Normal vaginal delivery was achieved in 28/33 cases (85%), which was more than manually controlled infusion. No case was abnormal in successful oxytocin infusion. Conclusion: The automated technique will be applied to oxytocin labor induction.
Self-similar cosmological solutions with dark energy. II: black holes, naked singularities and wormholes
Hideki Maeda,Tomohiro Harada,B. J. Carr
Physics , 2007, DOI: 10.1103/PhysRevD.77.024023
Abstract: We use a combination of numerical and analytical methods, exploiting the equations derived in a preceding paper, to classify all spherically symmetric self-similar solutions which are asymptotically Friedmann at large distances and contain a perfect fluid with equation of state $p=(\gamma -1)\mu$ with $0<\gamma<2/3$. The expansion of the Friedmann universe is accelerated in this case. We find a one-parameter family of self-similar solutions representing a black hole embedded in a Friedmann background. This suggests that, in contrast to the positive pressure case, black holes in a universe with dark energy can grow as fast as the Hubble horizon if they are not too large. There are also self-similar solutions which contain a central naked singularity with negative mass and solutions which represent a Friedmann universe connected to either another Friedmann universe or some other cosmological model. The latter are interpreted as self-similar cosmological white hole or wormhole solutions. The throats of these wormholes are defined as two-dimensional spheres with minimal area on a spacelike hypersurface and they are all non-traversable because of the absence of a past null infinity.
Self-similar cosmological solutions with dark energy. I: formulation and asymptotic analysis
Tomohiro Harada,Hideki Maeda,B. J. Carr
Physics , 2007, DOI: 10.1103/PhysRevD.77.024022
Abstract: Based on the asymptotic analysis of ordinary differential equations, we classify all spherically symmetric self-similar solutions to the Einstein equations which are asymptotically Friedmann at large distances and contain a perfect fluid with equation of state $p=(\gamma -1)\mu$ with $0<\gamma<2/3$. This corresponds to a ``dark energy'' fluid and the Friedmann solution is accelerated in this case due to anti-gravity. This extends the previous analysis of spherically symmetric self-similar solutions for fluids with positive pressure ($\gamma>1$). However, in the latter case there is an additional parameter associated with the weak discontinuity at the sonic point and the solutions are only asymptotically ``quasi-Friedmann'', in the sense that they exhibit an angle deficit at large distances. In the $0<\gamma<2/3$ case, there is no sonic point and there exists a one-parameter family of solutions which are {\it genuinely} asymptotically Friedmann at large distances. We find eight classes of asymptotic behavior: Friedmann or quasi-Friedmann or quasi-static or constant-velocity at large distances, quasi-Friedmann or positive-mass singular or negative-mass singular at small distances, and quasi-Kantowski-Sachs at intermediate distances. The self-similar asymptotically quasi-static and quasi-Kantowski-Sachs solutions are analytically extendible and of great cosmological interest. We also investigate their conformal diagrams. The results of the present analysis are utilized in an accompanying paper to obtain and physically interpret numerical solutions.
Can a primordial black hole or wormhole grow as fast as the universe?
B. J. Carr,Tomohiro Harada,Hideki Maeda
Physics , 2010, DOI: 10.1088/0264-9381/27/18/183101
Abstract: This review addresses the issue of whether there are physically realistic self-similar solutions in which a primordial black hole is attached to an exact or asymptotically Friedmann model for an equation of state of the form $p=(\gamma-1)\rho c^2$. In the positive pressure case ($1 < \gamma < 2$), there is no such solution when the black hole is attached to an exact Friedmann background via a sonic point. However, it has been claimed that there is a one-parameter family of asymptotically Friedmann black hole solutions providing the ratio of the black hole size to the cosmological horizon size is in a narrow range above some critical value. There are also "universal" black holes in which the black hole has an apparent horizon but no event horizon. It turns out that both these types of solution are only asymptotically {\it quasi}-Friedmann, because they contain a solid angle deficit at large distances, but they are not necessarily excluded observationally. We also consider the possibility of self-similar black hole solutions in a universe dominated by a scalar field. If the field is massless, the situation resembles the stiff fluid case, so any black hole solution is again contrived, although there may still be universal black hole solutions. The situation is less clear if the scalar field is rolling down a potential and therefore massive, as in the quintessence scenario. Although no explicit asymptotically Friedmann black hole solutions of this kind are known, they are not excluded and comparison with the $0 < \gamma < 2/3$ perfect fluid case suggests that they should exist if the black hole is not too large. This implies that a black hole might grow as fast as the cosmological horizon in a quintessence-dominated universe in some circumstances, supporting the proposal that accretion onto primordial black holes may have played a role in the production of the supermassive black holes in galactic nuclei.
Cosmological wormholes
Hideki Maeda,Tomohiro Harada,B. J. Carr
Physics , 2009, DOI: 10.1103/PhysRevD.79.044034
Abstract: Motivated by the cosmological wormhole solutions obtained from our recent numerical investigations, we provide a definition of a wormhole which applies to dynamical situations. Our numerical solutions do not have timelike trapping horizons but they are wormholes in the sense that they connect two or more asymptotic regions. Although the null energy condition must be violated for static wormholes, we find that it can still be satisfied in the dynamical context. Two analytic solutions for a cosmological wormhole connecting two Friedmann universes without trapping horizons are presented.
Non-existence of self-similar solutions containing a black hole in a universe with a stiff fluid or scalar field or quintessence
Tomohiro Harada,Hideki Maeda,B. J. Carr
Physics , 2006, DOI: 10.1103/PhysRevD.74.024024
Abstract: We consider the possible existence of self-similar solutions containing black holes in a Friedmann background with a stiff fluid or a scalar field. We carefully study the relationship between the self-similar equations in these two cases and emphasize the crucial role of the similarity horizon. We show that there is no self-similar black hole solution surrounded by an exact or asymptotically flat Friedmann background containing a massless scalar field. This result also applies for a scalar field with a potential, providing the universe is decelerating. However, if there is a potential and the universe is accelerating (as in the quintessence scenario), the result only applies for an exact Friedmann background. This extends the result previously found in the stiff fluid case and strongly suggests that accretion onto primordial black holes is ineffective even during scalar field domination. It also contradicts recent claims that such black holes can grow appreciably by accreting quintessence. Appreciable growth might be possible with very special matter fields but this requires {\it ad hoc} and probably unphysical conditions.
The Optimal Timing of the Transition to New Environmental Technology for Economic Growth  [PDF]
Akira Maeda, Makiko Nagaya
Modern Economy (ME) , 2012, DOI: 10.4236/me.2012.33036
Abstract: This study investigates the best timing for technological change affecting environmental quality in economic development. We develop a model that addresses the transition of environmental technology from an old system to a new one. Findings obtained are innovative in that they depict when as well as how transition to new environmental technology occurs. It demonstrates that the timing is endogenous and characterized by the properties of the economy: in particular, the optimal technology transition timing depends upon whether the economy is developing or developed.
Inhibitors of protein kinases affecting cAMP-dependent proteolysis of GATA-6  [PDF]
Hironori Ushijima, Masatomo Maeda
Advances in Biological Chemistry (ABC) , 2012, DOI: 10.4236/abc.2012.24051
Abstract: We screened 95 kinase inhibitors whether they affect cAMP-dependent proteolysis of GATA-6 or not. Among them 7 inhibitors inhibited the proteolysis at the concentration range of μM around their IC50. They are inhibitors for protein kinase A (H-89 and 4- cyano-3-methylisoquinoline), c-Jun N-terminal kinase (SP600125), phosphatidylinositol 3-kinase (Wort- mannin and LY-294002), casein kinase II (TBB) and cyclin dependent kinase (Cdk1/2 inhibitor III). It is of interest how these kinases play roles in the degradation process of GATA-6 since this transcription factor is essential for development and tissue-specific gene expression of mammals. Inhibitors identified in this study would be helpful to study molecular mechanisms of phenomena in which GATA-6 participates.
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