Research Center for Advanced Science and Technology

Meguro-ku, Japan

Research Center for Advanced Science and Technology

Meguro-ku, Japan
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Morioka Y.,Application LaboratoryJAMSTECYokohama Japan | Taguchi B.,Research Center for Advanced Science and Technology | Behera S.K.,Application LaboratoryJAMSTECYokohama Japan
Journal of Geophysical Research: Oceans | Year: 2017

The origin and structure of eastward propagating decadal temperature variability in the South Atlantic and Indian Oceans are investigated by using long-term output of coupled general circulation model. Composite analysis during the warm Southwest Indian Ocean (SWIO) years shows that decadal temperature anomalies in the SWIO region originate in the South Atlantic and are associated with density anomalies. Since the density anomalies propagate at the speed of a few cm s-1, slower than the speed of the background eastward Antarctic Circumpolar Current, and exhibit a surface-intensified equivalent barotropic structure, the eastward propagation of the density anomalies may be attributed to quasi-stationary oceanic Rossby waves. The density anomalies are also accompanied with anomalous Ekman pumping, indicating an important contribution from the overlying atmospheric variability. The role of atmospheric variability is further examined by evaluating the mixed-layer heat balance. It is found that the warm temperature anomalies in the South Atlantic are due to anomalous entrainment and meridional advection. These results suggest that the atmospheric variability plays an important role through the ocean mixed layer in generating the eastward propagation of decadal temperature variability from the South Atlantic besides the internal ocean variability as suggested in previous studies. © 2017. American Geophysical Union.

Koshino K.,Tokyo Medical and Dental University | Nakamura Y.,NEC Corp | Nakamura Y.,RIKEN | Nakamura Y.,Research Center for Advanced Science and Technology
New Journal of Physics | Year: 2012

We investigate the dynamics of a superconducting qubit strongly coupled to a semi-infinite one-dimensional microwave field having a variable boundary condition. The radiative level shift and linewidth of the qubit are controllable through the boundary condition of the field, and the spectral properties of the output microwave are modified accordingly. The current scheme provides a compact method for controlling the radiative characteristics of quantum few-level systems that is useful in single-photon engineering. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Julian A.,Tokyo University of Science | Julian A.,Research Center for Advanced Science and Technology | Jehl Z.,Tokyo University of Science | Jehl Z.,Research Center for Advanced Science and Technology | And 6 more authors.
Superlattices and Microstructures | Year: 2016

Energy selective electrical contacts have been proposed as a way to approach ultimate efficiencies both for thermoelectric and photovoltaic devices as they allow a reduction of the entropy production during the energy conversion process. A self-consistent numerical model based on the transfer matrix approach in the effective mass and envelope function approximation has been developed to calculate the electronic properties of double resonant tunneling barriers used as energy selective contacts in hot carrier solar cells. It is found that the application of an external electric bias significantly degrades the electronic transmission of the structure, and thus the tunneling current in the current-voltage characteristic. This is due to a symmetry breaking which can be offset using finely tuned asymmetric double resonant tunneling barriers, leading to a full recovery of the tunneling current in our model. Moreover, we model the heterostructure using electrons temperature in the emitter higher than that of the lattice, providing insights on the interpretation of experimental devices functioning in hot carrier conditions, especially regarding the previously reported shift of the resonance peak (negative differential resistance), which we interpret as related to a shift in the hot electron distribution while the maximum remains at the conduction band edge of the emitter. Finally, experimental results are presented using asymmetric structure showing significantly improved resonant properties at room temperature with very sharp negative differential resistance. © 2016 Elsevier Ltd

PubMed | Laboratory of Cellular Biochemistry, University of Tokyo, Keio University, Japan Science and Technology Agency and 2 more.
Type: Journal Article | Journal: Journal of the American Society of Nephrology : JASN | Year: 2015

Epigenetic mechanisms may underlie the progression of diabetic kidney disease. Because the kidney is a heterogeneous organ with different cell types, we investigated DNA methylation status of the kidney in a cell type-specific manner. We first identified genes specifically demethylated in the normal proximal tubules obtained from control db/m mice, and next delineated the candidate disease-modifying genes bearing aberrant DNA methylation induced by diabetes using db/db mice. Genes involved in glucose metabolism, including Sglt2, Pck1, and G6pc, were selectively hypomethylated in the proximal tubules in control mice. Hnf4a, a transcription factor regulating transporters for reabsorption, was also selectively demethylated. In diabetic mice, aberrant hypomethylation of Agt, Abcc4, Cyp4a10, Glut5, and Met and hypermethylation of Kif20b, Cldn18, and Slco1a1 were observed. Time-dependent demethylation of Agt, a marker of diabetic kidney disease, was accompanied by histone modification changes. Furthermore, inhibition of DNA methyltransferase or histone deacetylase increased Agt mRNA in cultured human proximal tubular cells. Aberrant DNA methylation and concomitant changes in histone modifications and mRNA expression in the diabetic kidney were resistant to antidiabetic treatment with pioglitazone. These results suggest that an epigenetic switch involving aberrant DNA methylation causes persistent mRNA expression of select genes that may lead to phenotype changes of the proximal tubules in diabetic kidney disease.

Nagae G.,Research Center for Advanced Science and Technology | Isagawa T.,Research Center for Advanced Science and Technology | Shiraki N.,Kumamoto University | Fujita T.,Research Center for Advanced Science and Technology | And 15 more authors.
Human Molecular Genetics | Year: 2011

Epigenetic regulation is essential in determining cellular phenotypes during differentiation. Although tissuespecific DNA methylation has been studied, the significance of methylation variance for tissue phenotypes remains unresolved, especially for CpG-poor promoters. Here, we comprehensively studied methylation levels of 27 578 CpG sites among 21 human normal tissues from 12 anatomically different regions using an epigenotyping beadarray system. Remarkable changes in tissue-specific DNA methylation were observed within CpG-poor promoters but not CpG-rich promoters. Of note, tissue-specific hypomethylation is accompanied by an increase in gene expression, which gives rise to specialized cellular functions. The hypomethylated regions were significantly enriched with recognition motifs for transcription factors that regulate cell-type-specific differentiation. To investigate the dynamics of hypomethylation events, we analyzed methylation levels of the entire APOA1 gene locus during in vitro differentiation of embryonic stem cells toward the hepatic lineage. A decrease in methylation was observed after day 13, coinciding with alpha-feto- protein detection, in the vicinity of its transcription start sites (TSSs), and extends up to ~200 bp region encompassing the TSS at day 21, equivalent to the hepatoblastic stage. This decrease is even more pro- nounced in the adult liver, where the entire APOA1 gene locus is hypomethylated. Furthermore, when we compared the methylation status of induced pluripotent stem (iPS) cells with their parental cell, IMR-90, we found that fibroblast-specific hypomethylation is restored to a fully methylated state in iPS cells after reprogramming. These results illuminate tissue-specific methylation dynamics in CpG-poor promoters and provide more comprehensive views on spatiotemporal gene regulation in terminal differentiation. © The Author 2011. Published by Oxford University Press. All rights reserved.

Fujii H.,University of Tokyo | Toprasertpong K.,University of Tokyo | Watanabe K.,Research Center for Advanced Science and Technology | Sugiyama M.,University of Tokyo | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

The present paper proposes Carrier Collection Efficiency (CCE) as a useful evaluation measure to investigate the carrier transport in quantum well solar cells. CCE is defined as the ratio of the carriers extracted as photocurrent to the total number of the carriers that are photo-excited in the p-n junction area, and can be easily calculated by normalizing the collected current, i.e. the difference between the current under light irradiation and that in the dark, to its saturation value at reverse bias. By measuring CCE as a function of the irradiation wavelength and the applied bias, we can directly and quantitatively evaluate the efficiency of the carrier extraction under operation of the cell, and clarify the underlying problem of the carrier transport. The proposed derivation procedure of CCE is based on the assumption that the saturation of the collected current at reverse bias indicates 100% collection of the photo-excited carriers. We validated this hypothesis by studying the balance between the number of the photo-excited carriers that can be collected at a sufficiently large reverse bias and the number of the photons absorbed in the wells. As a result, the absorption fraction in the MQW region well agreed with the saturated external quantum efficiency as we predicted, indicating CCE defined in this study is an appropriate approximation for the collection efficiency of the carrier generated in the active region of a solar cell device. © 2013 Copyright SPIE.

PubMed | Research Center for Advanced Science and Technology and University of Tokyo
Type: | Journal: Gynecologic oncology reports | Year: 2015

Primary vaginal clear cell adenocarcinoma (PVCCA) coexists with urinary tract anomalies without exposure to diethylstilbestrol in some cases.PVCCA in our case showed genetic alterations of well-known cancer related genes, including a mutation of PIK3CA.The genetic profile suggests that the carcinogenesis of PVCCA might have elements common with that of OCCA.

News Article | December 21, 2015

A research group at Osaka University has succeeded in observing at the intended timing two-phonon quantum interference by using two cold calcium ions in ion traps, which spatially confine charged particles. A phonon is a unit of vibrational energy that arises from oscillating particles within crystals. Two-particle quantum interference experiments using two photons or atoms have been previously reported, but this group's achievement is the world's first observation using two phonons. This group demonstrated that the phonon, a quantum mechanical description of an elementary vibrational motion in matter, and the photon, an elementary particle of light, share common properties. This group's research results will contribute to quantum information processing research, including quantum simulation using phonons and quantum interface research. Ion traps are an important technique in physically achieving quantum information processing including quantum computation, and research on ion traps is being carried out all over the world, with Dr. David J. Wineland of the United States, a leading expert in the field, winning the Nobel Prize in Physics in 2012. For this research, a team from Osaka University led by Shinji Urabe, Professor Emeritus, Kenji Toyoda, Assistant Professor, and Atsushi Noguchi (currently at the Research Center for Advanced Science and Technology, The University of Tokyo) used a laser to irradiate 2 calcium ions to completely remove almost any movement energy from the ions. After this, the team caused a single phonon to form at each of the ion sites. Since there is mutual interaction between the two ions, this causes the phonons to move and mutually interfere with each other. In the case of classical particles, there is a possibility that the particles will be detected individually at each of the sites. However, with phonons, since the effects of two-phonon interference eliminate the possibility of each particle being detected individually, it was predicted that the two phonons would be detected simultaneously at one of the two ion sites. Through experimentation, the two phonons were in fact detected at the same site, confirming that the probability of simultaneous detection of the phonons at individual ion sites is close to zero. This phenomenon is a distinctive interference effect in bosonic particles such as photons, elementary particles of light, and phonons, the quantum of vibrational energy; a typical phenomenon which indicates quantum characteristics. Since this phenomenon can only be observed when the quantum particles have been properly prepared simultaneously, the success rate when performed with photons is limited. However, with ion traps, individual phonons can be created with a high level of control, allowing for successful observation at specific timing on demand. Explore further: Quantum information motion control is now improved

Aiba Y.,Research Center for Advanced Science and Technology
Artificial DNA, PNA & XNA | Year: 2012

Peptide nucleic acid (PNA) is one of the most widely used synthetic DNA analogs. Conjugation of functional molecules to PNA is very effective to further widen its potential applications. For this purpose, here we report the synthesis of several ligand monomers and introduced them to PNA. These ligand-modified PNAs attract cerium ion and are useful for site-selective DNA hydrolysis. It should be noted that these ligands on PNA are also effective even under the conditions of invasion complex.

Maeda Y.,Research Center for Advanced Science and Technology | Tanaka T.,Research Center for Advanced Science and Technology | Nakajima Y.,Hokkaido Industrial Research Institute | Shimizu K.,Hokkaido University
Journal of Medical and Biological Engineering | Year: 2011

Base of support (BOS) influences the postural control of upright standing in humans. Since a narrowed BOS in the upright position makes postural control difficult, it is important to evaluate and practice balance with a narrowed BOS. We performed an experimental study to clarify the postural control mechanism in a feet-together position in response to dynamic perturbations. Subjects were 10 healthy young adults. Using an electrically operated platform, tilting perturbation was applied to subjects standing in feet-together position. Perturbation was in four directions: backward, forward, right, and left. Using a motion analysis system and electromyography (EMG), we simultaneously measured the three-dimensional postural change and EMG of seven muscles of the trunk and legs. We obtained joint angular change from the motion analysis and the integrated values of muscle activity and latency of the lower extremities from the EMG. In terms of pitch tilt, the ankle strategy was observed: this involved simultaneous contraction of the ankle muscles as usual in the upright position. In contrast, in terms of roll tilt, "counterweighting" was observed. We also observed a change in postural control to respond to the narrowed BOS. We found that, unlike the feet-apart position, the feet-together position, narrowing the BOS in the left-right direction causes a prominent change and makes postural control strategy difficult only in response to roll tilt perturbations. In the future, we need to investigate the effectiveness of balance training including roll tilting in the feet-together position in improving balance ability in the left-right direction.

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