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Multidirectionally distributed feedback photonic crystal lasers

Physical Review B 2002年第19期65卷 195306-195306页

作者： Masahiro Imada Alongkarn Chutinan Susumu Noda Masamitsu Mochizuki Core Research for Evolutional Science and Technology Japan Science and Technology Corporation Kyoto 606-8501 Japan

The lasing mode of a two-dimensional (2D) photonic crystal laser with in-plane multidirectionally distributed feedback effect is analyzed theoretically and experimentally. From an investigation of the Bragg diffraction conditions at several points in the photonic band diagram where lasing is expected, we identify a particular Γ point at which lasing occurs due to the coupling of lightwaves propagating in six equivalent Γ-X directions and diffraction normal to the substrate surface. In order to investigate the lasing mode in detail, the distribution of the electromagnetic field at the band edges at the Γ point is calculated, and each band edge is found to have a different field pattern. The lasing characteristics of the 2D photonic crystal laser at the lasing wavelength corresponding to the Γ point are measured. Single-mode lasing over a broad circular area is observed by microelectroluminescence measurements under pulsed conditions at room temperature. We also demonstrate the correspondence between the measured lasing wavelengths and calculated band edges by comparing the polarization characteristics with the calculated distribution of the electromagnetic field. The results indicate that 2D coherent lasing oscillation does, in fact, occur due to the multidirectional coupling effect in the 2D photonic crystal. From the theoretical calculation, we show that the polarization patterns of the lasers can be controlled by introducing artificial lattice defects.

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Control system for talking robot to replicate articulatory movement of natural speech 7

Control system for talking robot to replicate articulatory m...

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7th International Conference on Spoken Language Processing, ICSLP 2002

作者： Mochida, Takemi Honda, Masaaki Hayashi, Kouki Kuwae, Toshiharu Tanahashi, Kunihiro Nishikawa, Kazufumi Takanishi, Atsuo Communication Science Laboratories Nippon Telegraph and Telephone Kanagawa Japan Department of Mechanical Engineering Waseda University Tokyo Japan Humanoid Robotics Institute Waseda University Tokyo Japan Advanced Research Institute for Science and Engineering Waseda University Tokyo Japan Core Research for Evolutional Science and Technology Japan Science and Technology Japan

The ultimate goal of our study is to create a new speech production system, in which an anthropomorphic hardware talking robot is handled so as to imitate human articulatory movement. We have developed a software motion simulator, which generates control parameter sequences for the talking robot Waseda Talker No. 2 (WT-2) using the trajectories of human articulatory organs during continuous utterances measured by an electromagnetic articulograph. This paper mainly describes the motion simulator. In addition to its main function as a generator of control parameters for WT-2, the motion simulator also simulates the resultant acoustic characteristics related to WT-2's vocal tract shape at each instance during the motion. The hardware structure of WT-2 is also described briefly. This comprehensive approach will enable us to study speech production using the features of the vocal tract shape as speech motor tasks, instead of using acoustic features.

关键词： Anthropomorphic robots

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Exciton-biexciton dynamics in an organic-inorganic hybrid quantum-well material

Exciton-biexciton dynamics in an organic-inorganic hybrid qu...

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Quantum Electronics and Laser science Conference (QELS)

作者： Kato Ichii Ohashi Kunugita Ema Tanaka Takahashi Kondo Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Corporation (JST) Department of Physics Sophia University Tokyo Japan Core Research for Evolutional Science and Technology (CREST) Japan Science and Technology Corporation (JST) Japan Department of Material Science The University of Tokyo Tokyo Japan

Summary form only given. Excitonic optical properties have been extensively studied in a large variety of semiconductors, and it has been found that biexciton formation and relaxation play an important role in the nonlinear optical processes. The binding energies of biexcitons in typical semiconductors, however, are less than 10 meV so that it is difficult in femtosecond spectroscopy to distinguish the biexciton process from a single exciton process. In order to study the exciton-biexciton system in detail, a large binding energy of the biexciton is required. In this paper we report on the biexcitons with extremely large binding energy (= 66 meV) in an organic-inorganic hybrid quantum-well material, (C/sub 4/H/sub 9/NH/sub 3/)/sub 2/PbBr/sub 4/. This material belongs to the layered perovskite-type quantum-well materials (C/sub n/H/sub 2n+1/NH/sub 3/)/sub 2/PbX/sub 4/ which have excitons with large binding energy. We investigate the dynamics of such a stable exciton-biexciton system.

关键词： Excitons Quantum wells Photoluminescence

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Semiconductor photonic crystals and devices

Semiconductor photonic crystals and devices

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Indium Phosphide and Related Materials Conference

作者： S. Noda T. Asano M. Imada Department of Electronic Science and Engineering Japan Science and Technology Corporation Kyoto University Core Research for Evolutional Science and Technology Kyoto Japan

Recent progresses in photonic crystals including both three-dimensional (3D) and two-dimensional (2D) crystals are reviewed. On 3D photonic crystals, we at first explain our approach to create full 3D bandgap crystals at near-infrared wavelengths, and then the introduction of the light-emitters into 3D crystals. On 2D crystals, two types of devices are explained. One is channel-add-drop-filtering devices, which utilize line- and single-defects introduced in 2D photonic crystal slab structure. The other is the 2D photonic crystal laser, which utilizes multi-directional distributed feedback effects.

关键词： Photonic crystals Photonic band gap Distributed feedback devices Photonic integrated circuits Crystallization Optical control Surface emitting lasers Slabs Laser feedback Lighting control

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Two-dimensional excitons in a layered-perovskite-type crystal (C/sub 6/H/sub 13/NH/sub 3/)/sub 2/PbI/sub 4/

Two-dimensional excitons in a layered-perovskite-type crysta...

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Quantum Electronics and Laser science Conference (QELS)

作者： Tanaka Sano Takahashi Kondo Department of Materials Science University of Tokyo Bunkyo Tokyo Japan Core Research for Evolutional Science and Technology Japan Science and Technology Corporation Japan

Summary form only given. It has been found that the lowest-energy exciton in (C/sub 6/H/sub 13/NH/sub 3/)/sub 2/PbI/sub 4/ is so stable that the excitonic absorption peaks are clearly observable even at room temperature. It has been shown by four-wave-mixing (FWM) spectroscopy that it has large /spl chi//sup (3)/ value (10/sup -6/ esu) and fast response time (<7 ps) at the exciton resonance, and that the exciton-exciton interactions play an important role in the FWM processes.

关键词： Organic compounds Excitons Optical mixing Electroabsorption Optical films Optical spectroscopy

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Crystal structure of lipocalin-type prostaglandin D synthase

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International Congress Series 2002年第C期1233卷 453-459页

作者： Irikura, Daisuke Kumasaka, Takashi Yamamoto, Masaki Hayaishi, Osamu Urade, Yoshihiro Core Research for Evolutional Science and Technology Science and Technology Corporation c/o Osaka Bioscience Institute Osaka 565-0874 Japan Department of Molecular Behavioral Biology Osaka Bioscience Institute Osaka 565-0874 6-2-4 Furuedai Suita Japan RIKEN Harima Institute Hyogo 679-5148 Mikazuki Sayo Japan

Lipocalin-type prostaglandin (PG) D synthase (L-PGDS) is responsible for the biosynthesis of PGD2, a potent endogenous sleep-inducing substance found in the central nervous system. In this study, we crystallized recom... 详细信息

Lipocalin-type prostaglandin (PG) D synthase (L-PGDS) is responsible for the biosynthesis of PGD₂, a potent endogenous sleep-inducing substance found in the central nervous system. In this study, we crystallized recombinant mouse L-PGDS from a sodium citrate solution by the hanging drop vapor-diffusion method. The crystal structure of the selenomethionyl Cys⁶⁵Ala-substituted L-PGDS was determined at 2.5 Å resolution by using the multiwavelength anomalous diffraction method. The crystals belonged to the orthorhombic space group C222₁ with lattice constants a=45.5, b=66.8, c=104.5 Å. The overall architecture of L-PGDS had an eight-stranded β-barrel with a hydrophobic cavity, in which the Cys⁶⁵ residue, an active site for the catalysis, was identified. © 2002 Elsevier science B.V.

关键词： Crystal structure Lipocalin Multiwavelength anomalous diffraction method Prostaglandin D synthase Prostaglandin D2

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Experimental and theoretical studies on nonlinear propagation of a-few-optical-cycle pulses in a photoniccrystal fiber -beyond the slowly-varying-envelope approximation-

Experimental and theoretical studies on nonlinear propagatio...

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International Conference on Ultrafast Phenomena, UP 2002

作者： Fang, Xiaojun Hirasawa, Masakatsu Morita, Ryuji Yamashita, Mikio Windeler, Robert S. Department of Applied Physics Hokkaido University Core Research for Evolutional Science and Technology Japan Science and Technology Corporation Kita-13 Nishi-8 Kita-ku Sapporo060-8628 Japan Bell Laboratories Lucent Technologies 700 Mountain Avenue Murray HillNJ070974 United States

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Experimental and Theoretical Investigation on Nonlinear 4.5-Optlcal-cycle-pulse Propagation in Photonlc Crystal Abers

Experimental and Theoretical Investigation on Nonlinear 4.5-...

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Conference on Lasers and Electro-Optics, CLEO 2002

作者： Fang, Xiaojun Adachi, Muneyuki Karasawa, Naoki Morita, Ryuji Yamashita, Mikio Windeler, Robert S. Department of Applied Physics Hokkaido University Core Research for Evolutional Science and Technology Japan Science and Technology Corporation Kita-13 Nishi-8 Kita-ku Sapporo060-8628 Japan Bell Laboratories Lucent Technologies 700 Mountain Avenue Murray HillNJ070974 United States

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Bayesian on-line learning: a sequential Monte Carlo with Rao-Blackwellization

Bayesian on-line learning: a sequential Monte Carlo with Rao...

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IEEE Workshop on Neural Networks for Signal Processing

作者： K. Yosui T. Kurihara K. Wada T. Souma T. Matsumoto The Core Research for Evolutional Science and Technology Japan Science and Technology Agency-CREST Japan Department of Electrical Waseda University Shinjuku Tokyo Japan

ISBN: (纸本)0780376161

This paper proposes a Rao-Blackwellised sequential Monte Carlo (RBSMC) scheme for on-line learning with feedforward neural nets. The proposed algorithm is tested against an example and the performance is compared with those of the conventional sequential Monte Carlo as well as the extended Kalman filter (EKF). The proposed scheme outperforms those conventional algorithms.

关键词： Bayesian methods Monte Carlo methods Sampling methods Nonlinear filters Feeds Neural networks Sequential analysis Kalman filters Training data Uncertainty

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Lipocalin-type prostaglandin D synthase in cerebrospinal fluid of patients with aneurysmal subarachnoid hemorrhage scavenges bile pigments

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International Congress Series 2002年第C期1233卷 447-451页

作者： Inui, Takashi Mase, Mitsuhito Emi, Maiko Nakau, Hiroya Seiki, Kousuke Oda, Hiroshi Yamada, Kazuo Urade, Yoshihiro Core Research for Evolutional Science and Technology Japan Science and Technology Corporation Japan Department of Molecular Behavioral Biology Osaka Bioscience institute Suita Osaka 565-0874 6-2-4 Furuedai Japan Department of Neurosurgery Nagoya City University Medical School Nagoya 467-8602 Japan Department of Biological Chemistry Central Research institute Maruha Corporation Tsukuba 300-4295 Japan

Lipocalin-type prostaglandin D synthase (L-PGDS) is one of the major proteins in human cerebrospinal fluid (CSF) and binds various small lipophilic substances, such as bilirubin and biliverdin. The L-PGDS concentration increased in the CSF of patients with aneurysmal subarachnoid hemorrhage (SAH) from day 1 (10.5 μg/ml) to day 5 (25.6) and returned to the basal level after 2 months (12.9). L-PGDS purified from the CSF of SAH patients showed an absorbance spectrum with a peak at 392 nm in the visible range. The absorbance at 392 nm of the purified L-PGDS increased from day 1 (0.16/mg protein) to day 5 (0.44) and almost disappeared 2 months after SAH (0.11). Conversely, the enzyme activity of the purified L-PGDS decreased from day 1 (0.71 μmol/min/mg protein) to day 5 (0.28) and recovered 2 months after SAH (0.76). These results indicate that L-PGDS binds and scavenges bile pigments that accumulate in the CSF after SAH. © 2002 Elsevier science B.V.

关键词： Bile pigments Cerebrospinal fluid Lipocalin superfamily Prostaglandin D synthase Subarachnoid hemorrhage

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