Kobe, Japan
Kobe, Japan

Konan University is a university located on the slopes of Rokko Mountain in Higashinada-ku, Kobe, Japan. A private university with approximately 10,000 students, the university offers a wide variety of programs to Japanese students, as well as an international exchange program through the Konan International Exchange Centre. Wikipedia.

Time filter
Source Type

Nomoto K.,University of Tokyo | Kobayashi C.,University of Hertfordshire | Tominaga N.,Konan University
Annual Review of Astronomy and Astrophysics | Year: 2013

After the Big Bang, production of heavy elements in the early Universe takes place starting from the formation of the first stars, their evolution, and explosion. The first supernova explosions have strong dynamical, thermal, and chemical feedback on the formation of subsequent stars and evolution of galaxies. However, the nature of the Universe's first stars and supernova explosions has not been well clarified. The signature of the nucleosynthesis yields of the first stars can be seen in the elemental abundance patterns observed in extremely metal-poor stars. Interestingly, those patterns show some peculiarities relative to the solar abundance pattern, which should provide important clues to understanding the nature of early generations of stars. We thus review the recent results of the nucleosynthesis yields of mainly massive stars for a wide range of stellar masses, metallicities, and explosion energies. We also provide yields tables and examine how those yields are affected by some hydrodynamical effects during supernova explosions, namely, explosion energies from those of hypernovae to faint supernovae, mixing and fallback of processed materials, asphericity, etc. Those parameters in the supernova nucleosynthesis models are constrained from observational data of supernovae and metal-poor stars. Nucleosynthesis yields are then applied to the chemical evolution model of our Galaxy and other types of galaxies to discuss how the chemical enrichment process occurred during evolution. Copyright © 2013 by Annual Reviews. All rights reserved.

Machida M.N.,Kyushu University | Doi K.,Konan University
Monthly Notices of the Royal Astronomical Society | Year: 2013

The formation of Population III stars is investigated using resistive magnetohydrodynamic simulations. Starting from a magnetized primordial prestellar cloud, we calculate the cloud evolution several hundreds of years after first protostar formation, resolving the protostellar radius. When the natal minihalo field strength is weaker than B {less-than and not approximate } 10-13(n/1 cm-3)-2/3 G (n is the hydrogen number density), magnetic effects can be ignored. In this case, fragmentation occurs frequently and a stellar cluster forms, in which stellar mergers and mass exchange between protostars contribute to the mass growth of these protostars. During the early gas accretion phase, the most massive protostar remains near the cloud centre, whereas some of the less massive protostars are ejected. The magnetic field significantly affects Population III star formation when B {greater-than and not approximate } 10-12(n/1 cm-3)-2/3 G. In this case, because the angular momentum around the protostar is effectively transferred by both magnetic braking and protostellar jets, the gas falls directly on to the protostar without forming a disc, and only a single massive star forms. In addition, a massive binary stellar system appears when 10-13(n/1 cm-3)-2/3 {less-than and not approximate } B {less-than and not approximate } 10-12(n/1 cm-3)-2/3 G. Therefore, the magnetic field determines the end result of the formation process (cluster, binary or single star) for Population III stars. Moreover, no persistent circumstellar disc appears around the protostar regardless of the magnetic field strength, which may influence the further evolution of Population III stars. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Nakano S.-I.,Konan University | Miyoshi D.,Konan University | Sugimoto N.,Konan University
Chemical Reviews | Year: 2014

A study was conducted to investigate the effects of molecular crowding on the structures, interactions, and functions of nucleic acids. The study introduced the features of the behavior of nucleic acids inside living cells and those immobilized on material surfaces where molecules were highly crowded. Living cells consisted of a large number of macromolecules of proteins, nucleic acids, and carbohydrates. These in a small volume provided the excluded volume effect. These steric effects changed the thermodynamic activities of dissolved molecules and affected the thermodynamics and kinetics of cellular reactions. The large cellular components also caused interference with the movements and dynamics of molecules, which affected the rate of molecular diffusion and the efficiency of molecular collisions.

Tateishi-Karimata H.,Konan University | Sugimoto N.,Konan University
Angewandte Chemie - International Edition | Year: 2012

A green solvent: Quantitative thermodynamic analyses shows that A-T base pairs are more stable than G-C base pairs in the hydrated ionic-liquid choline dihydrogenphosphate because of specific interactions between DNA bases and choline ions. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sugimoto N.,Konan University
International Review of Cell and Molecular Biology | Year: 2014

How does molecular crowding affect the stability of nucleic acid structures inside cellsα Water is the major solvent component in living cells, and the properties of water in the highly crowded media inside cells differ from that in buffered solution. As it is difficult to measure the thermodynamic behavior of nucleic acids in cells directly and quantitatively, we recently developed a cell-mimicking system using cosolutes as crowding reagents. The influences of molecular crowding on the structures and thermodynamics of various nucleic acid sequences have been reported. In this chapter, we discuss how the structures and thermodynamic properties of nucleic acids differ under various conditions such as highly crowded environments, compartment environments, and in the presence of ionic liquids, and the major determinants of the crowding effects on nucleic acids are discussed. The effects of molecular crowding on the activities of ribozymes and riboswitches on noncanonical structures of DNA- and RNA-like quadruplexes that play important roles in transcription and translation are also described. © 2014 Elsevier Inc.

Endoh T.,Konan University | Kawasaki Y.,Konan University | Sugimoto N.,Konan University
Angewandte Chemie - International Edition | Year: 2013

Suppressing the urge to translate: Sequences with the potential to form G-quadruplexes were identified in the open reading frames of E.coli genes. These sequences were found to form parallel G-quadruplexes and to suppress translation (see picture) of the mRNAs into proteins both invitro and in cells. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tateishi-Karimata H.,Konan University | Sugimoto N.,Konan University
Nucleic Acids Research | Year: 2014

Nucleic acids have become a powerful tool in nanotechnology because of their conformational polymorphism. However, lack of a medium in which nucleic acid structures exhibit long-term stability has been a bottleneck. Ionic liquids (ILs) are potential solvents in the nanotechnology field. Hydrated ILs, such as choline dihydrogen phosphate (choline dhp) and deep eutectic solvent (DES) prepared from choline chloride and urea, are 'green' solvents that ensure long-term stability of biomolecules. An understanding of the behaviour of nucleic acids in hydrated ILs is necessary for developing DNA materials. We here review current knowledge about the structures and stabilities of nucleic acids in choline dhp and DES. Interestingly, in choline dhp, A-T base pairs are more stable than G-C base pairs, the reverse of the situation in buffered NaCl solution. Moreover, DNA triplex formation is markedly stabilized in hydrated ILs compared with aqueous solution. In choline dhp, the stability of Hoogsteen base pairs is comparable to that of Watson-Crick base pairs. Moreover, the parallel form of the G-quadruplex is stabilized in DES compared with aqueous solution. The behaviours of various DNA molecules in ILs detailed here should be useful for designing oligonucleotides for the development of nanomaterials and nanodevices. © The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.

Susa H.,Konan University
Astrophysical Journal | Year: 2013

We perform a three-dimensional radiation hydrodynamics simulation to investigate the formation of the first stars from the initial collapse of a primordial gas cloud to the formation and growth of protostars. The simulation is integrated until ∼0.1 Myr after the formation of the primary protostar, by which time the protostars have already settled onto the main sequence. This work represents the first attempt at simulating the first episodes of star formation, taking into account the ultraviolet radiative feedback effect from multiple protostars as well as the three-dimensional effects of the fragmentation of the accretion disk. We find that the mass accretion onto Population III protostars is significantly suppressed by their radiative feedback. As a result, we find five stars formed in this particular simulation. The final masses of the stars are ≲ 60 M ⊙, including a star of 4.4 M ⊙. Formation of such a star hints at the existence of even lower-mass stars that would live today. © 2013. The American Astronomical Society. All rights reserved.

Takahashi S.,Konan University | Sugimoto N.,Konan University
Angewandte Chemie - International Edition | Year: 2013

Under pressure: A DNA G-quadruplex was unfolded under high pressure, but crowding conditions repressed this effect owing to enthalpic contributions. Volumetric analysis showed that ethylene glycol or poly(ethylene glycol) decreased the volume change of the transition by more than fourfold owing to the alteration of the number and/or radii of hydrating water molecules. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Kajino F.,Konan University
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2010

Accommodated on the Japanese Experiment Module (JEM) of the International Space Station (ISS), the Extreme Universe Space Observatory JEM-EUSO will utilize the Earth's atmosphere as a giant detector of the extreme energy cosmic rays; the most energetic particles coming from the Universe. Looking downward the Earth from Space, JEM-EUSO will detect such particles by observing the fluorescence and Cherenkov photons produced during their pass in the atmosphere. The main objective of JEM-EUSO is doing astronomy and astrophysics through the particle channel with extreme energies above several times 1019 eV with a significant statistics beyond the GreisenZatsepinKuzmin (GZK) cut-off. Moreover, JEM-EUSO could observe extremely high energy neutrinos. JEM-EUSO has been designed to operate for more than 3 years onboard the ISS orbiting around the Earth every 90 min at an altitude of about 400 km. JAXA has selected JEM-EUSO as one of the mission candidates of the second phase utilization of JEM/EF for the launch in mid 2010s. © 2010 Elsevier B.V. All rights reserved.

Loading Konan University collaborators
Loading Konan University collaborators