University of Tokyo

About: University of Tokyo is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Population & Gene. The organization has 134564 authors who have published 337567 publications receiving 10178620 citations. The organization is also known as: Todai & Universitas Tociensis.

Success-history based parameter adaptation for Differential Evolution

Abstract: Differential Evolution is a simple, but effective approach for numerical optimization. Since the search efficiency of DE depends significantly on its control parameter settings, there has been much recent work on developing self-adaptive mechanisms for DE. We propose a new, parameter adaptation technique for DE which uses a historical memory of successful control parameter settings to guide the selection of future control parameter values. The proposed method is evaluated by comparison on 28 problems from the CEC2013 benchmark set, as well as CEC2005 benchmarks and the set of 13 classical benchmark problems. The experimental results show that a DE using our success-history based parameter adaptation method is competitive with the state-of-the-art DE algorithms.

A ribonucleotide reductase gene involved in a p53-dependent cell-cycle checkpoint for DNA damage

Abstract: The p53 gene is frequently inactivated in human cancers. Here we have isolated a p53-inducible gene, p53R2, by using differential display to examine messenger RNAs in a cancer-derived human cell line carrying a highly regulated wild-type p53 expression system. p53R2 contains a p53-binding sequence in intron 1 and encodes a 351-amino-acid peptide with striking similarity to the ribonucleotide reductase small subunit (R2), which is important in DNA synthesis during cell division. Expression of p53R2, but not R2, was induced by ultraviolet and γ-irradiation and adriamycin treatment in a wild-type p53-dependent manner. Induction of p53R2 in p53-deficient cells caused G2/M arrest and prevented cells from death in response to adriamycin. Inhibition of endogenous p53R2 expression in cells that have an intact p53-dependent DNA damage checkpoint reduced ribonucleotide reductase activity, DNA repair and cell survival after exposure to various genotoxins. Our results indicate that p53R2 encodes a ribonucleotide reductase that is directly involved in the p53 checkpoint for repair of damaged DNA. The discovery of p53R2 clarifies a relationship between a ribonucleotide reductase activity involved in repair of damaged DNA and tumour suppression by p53.

Carbon-doped Anatase TiO2 Powders as a Visible-light Sensitive Photocatalyst

Abstract: Carbon-doped TiO2 powders in an anatase phase colored yellow were fabricated by oxidative annealing of TiC Carbons were located at oxygen sites The carbon substitution caused the absorbance edge of TiO2 to be shifted to the higher wavelength region Carbon-doped TiO2 showed photocatalytic activities for the decomposition of IPA to CO2 via acetone under visible light (400–530 nm) irradiation

Evidence for reionization at z ∼ 6: Detection of a gunn-peterson trough in a z = 6.28 quasar

Abstract: We present moderate-resolution Keck spectroscopy of quasars at z = 5.82, 5.99, and 6.28, discovered by the Sloan Digital Sky Survey (SDSS). We find that the Ly? absorption in the spectra of these quasars evolves strongly with redshift. To z ~ 5.7, the Ly? absorption evolves as expected from an extrapolation from lower redshifts. However, in the highest-redshift object, SDSSp J103027.10+052455.0 (z = 6.28), the average transmitted flux is 0.0038 ? 0.0026 times that of the continuum level over 8450 ? 20, on the optical depth to Ly? absorption at z = 6. This is a clear detection of a complete Gunn-Peterson trough, caused by neutral hydrogen in the intergalactic medium. Even a small neutral hydrogen fraction in the intergalactic medium would result in an undetectable flux in the Ly? forest region. Therefore, the existence of the Gunn-Peterson trough by itself does not indicate that the quasar is observed prior to the reionization epoch. However, the fast evolution of the mean absorption in these high-redshift quasars suggests that the mean ionizing background along the line of sight to this quasar has declined significantly from z ~ 5 to 6, and the universe is approaching the reionization epoch at z ~ 6.