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.

First observation of the Greisen-Zatsepin-Kuzmin suppression.

Abstract: The High Resolution Fly's Eye (HiRes) experiment has observed the Greisen-Zatsepin-Kuzmin suppression (called the GZK cutoff) with a statistical significance of five standard deviations. HiRes' measurement of the flux of ultrahigh energy cosmic rays shows a sharp suppression at an energy of $6\ifmmode\times\else\texttimes\fi{}{10}^{19}\text{ }\text{ }\mathrm{eV}$, consistent with the expected cutoff energy. We observe the ankle of the cosmic-ray energy spectrum as well, at an energy of $4\ifmmode\times\else\texttimes\fi{}{10}^{18}\text{ }\text{ }\mathrm{eV}$. We describe the experiment, data collection, and analysis and estimate the systematic uncertainties. The results are presented and the calculation of the statistical significance of our observation is described.

An efflux transporter of silicon in rice

Abstract: Silicon is an important nutrient for the optimal growth and sustainable production of rice. Rice accumulates up to 10% silicon in the shoot, and this high accumulation is required to protect the plant from multiple abiotic and biotic stresses. A gene, Lsi1, that encodes a silicon influx transporter has been identified in rice. Here we describe a previously uncharacterized gene, low silicon rice 2 (Lsi2), which has no similarity to Lsi1. This gene is constitutively expressed in the roots. The protein encoded by this gene is localized, like Lsi1, on the plasma membrane of cells in both the exodermis and the endodermis, but in contrast to Lsi1, which is localized on the distal side, Lsi2 is localized on the proximal side of the same cells. Expression of Lsi2 in Xenopus oocytes did not result in influx transport activity for silicon, but preloading of the oocytes with silicon resulted in a release of silicon, indicating that Lsi2 is a silicon efflux transporter. The identification of this silicon transporter revealed a unique mechanism of nutrient transport in plants: having an influx transporter on one side and an efflux transporter on the other side of the cell to permit the effective transcellular transport of the nutrients.

Transport properties of nonequilibrium systems under the application of light: Photoinduced quantum Hall insulators without Landau levels

Abstract: In this paper, we study transport properties of nonequilibrium systems under the application of light in many-terminal measurements, using the Floquet picture. We propose and demonstrate that the quantum transport properties can be controlled in materials such as graphene and topological insulators, via the application of light. Remarkably, under the application of off-resonant light, topological transport properties can be induced; these systems exhibit quantum Hall effects in the absence of a magnetic field with a near quantization of the Hall conductance, realizing so-called quantum Hall systems without Landau levels first proposed by Haldane.

Circadian oscillation of a mammalian homologue of the Drosophila period gene.

Abstract: Many biochemical, physiological and behavioural processes in organisms ranging from microorganisms to vertebrates exhibit circadian rhythms1. In Drosophila, the gene period (per) is required for the circadian rhythms of locomotor activity and eclosion behaviour2. Oscillation in the levels of per mRNA and Period (dPer) protein in the fly brain is thought to be responsible for the rhythmicity3,4. However, no per homologues in animals other than insects have been identified. Here we identify the human and mouse genes (hPER and mPer, respectively) encoding PAS-domain (PAS, a dimerization domain present in Per, Amt and Sim)-containing polypeptides that are highly homologous to dPer. Besides this structural resemblance, mPer shows autonomous circadian oscillation in its expression in the suprachiasmatic nucleus, which is the primary circadian pacemaker in the mammalian brain5,6. Clock, a mammalian clock gene encoding a PAS-containing polypeptide7,8, has now been cloned: it is likely that the Per homologues dimerize with other molecule(s) such as Clock through PAS–PAS interaction in the circadian clock system.