Showing papers by "National Institute of Advanced Industrial Science and Technology published in 2002"
Colorado State University1, Commonwealth Scientific and Industrial Research Organisation2, National Center for Atmospheric Research3, National Oceanic and Atmospheric Administration4, Massachusetts Institute of Technology5, Princeton University6, University of California, Berkeley7, Max Planck Society8, Meteorological Service of Canada9, Japan Meteorological Agency10, University of California, Irvine11, California Institute of Technology12, National Institute of Advanced Industrial Science and Technology13, Lamont–Doherty Earth Observatory14
TL;DR: An uptake of CO2 in the southern extratropical ocean less than that estimated from ocean measurements is found, a result that is not sensitive to transport models or methodological approaches, and carbon fluxes integrated over latitudinal zones are strongly constrained by observations in the middle to high latitudes.
Abstract: Information about regional carbon sources and sinks can be derived from variations in observed atmospheric CO2 concentrations via inverse modelling with atmospheric tracer transport models. A consensus has not yet been reached regarding the size and distribution of regional carbon fluxes obtained using this approach, partly owing to the use of several different atmospheric transport models. Here we report estimates of surface-atmosphere CO2 fluxes from an intercomparison of atmospheric CO2 inversion models (the TransCom 3 project), which includes 16 transport models and model variants. We find an uptake of CO2 in the southern extratropical ocean less than that estimated from ocean measurements, a result that is not sensitive to transport models or methodological approaches. We also find a northern land carbon sink that is distributed relatively evenly among the continents of the Northern Hemisphere, but these results show some sensitivity to transport differences among models, especially in how they respond to seasonal terrestrial exchange of CO2. Overall, carbon fluxes integrated over latitudinal zones are strongly constrained by observations in the middle to high latitudes. Further significant constraints to our understanding of regional carbon fluxes will therefore require improvements in transport models and expansion of the CO2 observation network within the tropics.
1,110 citations
TL;DR: The catalytic performance of Au nanoparticles is defined by three major factors: contact structure, support selection, and particle size, the first being the most important because the perimeter interfaces around Au particles act as the site for reaction as discussed by the authors.
Abstract: Gold in bulk is chemically inert and has often been regarded to be poorly active as a catalyst. However, when gold is small enough—with particle diameters below 10 nm—it turns out to be surprisingly active for many reactions, such as CO oxidation and propylene epoxidation. This is especially so at low temperatures. Here, a summary of the catalysis of Au nanoparticles deposited on base metal oxides is presented. The catalytic performance of Au is defined by three major factors: contact structure, support selection, and particle size, the first of which being the most important because the perimeter interfaces around Au particles act as the site for reaction.
1,042 citations
TL;DR: In this article, a simple catalytic chemical vapor deposition technique was used to synthesize high-purity single-walled carbon nanotubes at low temperature using alcohol as the carbon source.
986 citations
TL;DR: The dispersion interaction is found to be the major source of attraction in the benzene dimer and the orientation dependence of the dimer interaction is mainly controlled by long-range interactions.
Abstract: A model chemistry for the evaluation of intermolecular interaction between aromatic molecules (AIMI Model) has been developed. The CCSD(T) interaction energy at the basis set limit has been estimated from the MP2 interaction energy near the basis set limit and the CCSD(T) correction term obtained by using a medium size basis set. The calculated interaction energies of the parallel, T-shaped,and slipped-parallel benzene dimers are -1.48, -2.46, and -2.48 kcal/mol, respectively. The substantial attractive interaction in benzene dimer, even where the molecules are well separated, shows that the major source of attraction is not short-range interactions such as charge-transfer but long-range interactions such as electrostatic and dispersion. The inclusion of electron correlation increases attraction significantly. The dispersion interaction is found to be the major source of attraction in the benzene dimer. The orientation dependence of the dimer interaction is mainly controlled by long-range interactions. Although electrostatic interaction is considerably weaker than dispersion interaction, it is highly orientation dependent. Dispersion and electrostatic interactions are both important for the directionality of the benzene dimer interaction.
963 citations
TL;DR: A vector-based siRNA expression system that can induce RNAi in mammalian cells is reported, which might allow therapeutic applications by means of vector-mediated RNAi and facilitate a wide range of functional analysis of mammalian genes.
Abstract: The first evidence for gene disruption by double-stranded RNA (dsRNA) came from careful analysis in Caenorhabditis elegans. This phenomenon, called RNA interference (RNAi), was observed subsequently in various organisms, including plants, nematodes, Drosophila, and protozoans. Very recently, it has been reported that in mammalian cells, 21- or 22-nucleotide (nt) RNAs with 2-nt 3' overhangs (small inhibitory RNAs, siRNAs) exhibit an RNAi effect. This is because siRNAs are not recognized by the well-characterized host defense system against viral infections, involving dsRNA-dependent inhibition of protein synthesis. However, the current method for introducing synthetic siRNA into cells by lipofection restricts the range of applications of RNAi as a result of the low transfection efficiencies in some cell types and/or short-term persistence of silencing effects. Here, we report a vector-based siRNA expression system that can induce RNAi in mammalian cells. This technical advance for silencing gene expression not only facilitates a wide range of functional analysis of mammalian genes but might also allow therapeutic applications by means of vector-mediated RNAi.
897 citations
TL;DR: It is demonstrated that exposure of HCT116 human colon carcinoma cells to IGF-1 induces the expression of HIF-1α, the regulated subunit of hypoxia-inducible factor 1, a known transactivator of the VEGF gene.
781 citations
TL;DR: The structural model suggests that water molecules, which were observed in the vicinity of highly conserved residues and in the retinal pocket, regulate the activity of rhodopsin-like GPCRs and spectral tuning in visual pigments, respectively.
Abstract: Activation of G protein-coupled receptors (GPCRs) is triggered and regulated by structural rearrangement of the transmembrane heptahelical bundle containing a number of highly conserved residues. In rhodopsin, a prototypical GPCR, the helical bundle accommodates an intrinsic inverse-agonist 11-cis-retinal, which undergoes photo-isomerization to the all-trans form upon light absorption. Such a trigger by the chromophore corresponds to binding of a diffusible ligand to other GPCRs. Here we have explored the functional role of water molecules in the transmembrane region of bovine rhodopsin by using x-ray diffraction to 2.6 A. The structural model suggests that water molecules, which were observed in the vicinity of highly conserved residues and in the retinal pocket, regulate the activity of rhodopsin-like GPCRs and spectral tuning in visual pigments, respectively. To confirm the physiological relevance of the structural findings, we conducted single-crystal microspectrophotometry on rhodopsin packed in our three-dimensional crystals and show that its spectroscopic properties are similar to those previously found by using bovine rhodopsin in suspension or membrane environment.
675 citations
TL;DR: Some of the advances in scaffold design focusing on the hybrid scaffolds recently developed in the authors' laboratory are reviewed, including three-dimensional porous scaffolds fabricated from various kinds of biodegradable materials.
Abstract: Tissue engineering has emerged as a promising alternative approach in the treatment of malfunctioning or lost organs. In this approach, a temporary scaffold is needed to serve as an adhesive substrate for the implanted cells and a physical support to guide the formation of the new organs. In addition to facilitating cell adhesion, promoting cell growth, and allowing the retention of differentiated cell functions, the scaffold should be biocompatible, biodegradable, highly porous with a large surface/volume ratio, mechanically strong, and malleable. A number of three-dimensional porous scaffolds fabricated from various kinds of biodegradable materials have been developed. This paper reviews some of the advances in scaffold design focusing on the hybrid scaffolds recently developed in the authors' laboratory.
632 citations
TL;DR: Experimental results of in vitro, uniaxial tension of swine brain tissue in finite deformation as well as a new hyper-viscoelastic constitutive model for the brain tissue, which accounts well for brain tissue deformation behaviour in both tension and compression.
613 citations
TL;DR: A novel robotic system called modular transformer (M-TRAN) is proposed, a distributed, self-reconfigurable system composed of homogeneous robotic modules that is able to metamorphose into robotic configurations such as a legged machine and generate coordinated walking motion without any human intervention.
Abstract: In this paper, a novel robotic system called modular transformer (M-TRAN) is proposed. M-TRAN is a distributed, self-reconfigurable system composed of homogeneous robotic modules. The system can change its configuration by changing each module's position and connection. Each module is equipped with an onboard microprocessor, actuators, intermodule communication/power transmission devices and intermodule connection mechanisms. The special design of M-TRAN module realizes both reliable and quick self-reconfiguration and versatile robotic motion. For instance, M-TRAN is able to metamorphose into robotic configurations such as a legged machine and hereby generate coordinated walking motion without any human intervention. An actual system with ten modules was built and basic operations of self-reconfiguration and motion generation were examined through experiments. A series of software programs has also been developed to drive M-TRAN hardware, including a simulator of M-TRAN kinematics, a user interface to design appropriate configurations and motion sequences for given tasks, and an automatic motion planner for a regular cluster of M-TRAN modules. These software programs are integrated into the M-TRAN system supervised by a host computer. Several demonstrations have proven its capability as a self-reconfigurable robot.
552 citations
TL;DR: In this article, the authors investigated the capacity of single wall carbon nanotubes as a host material for hydrogen storage and found that the capacity depends linearly on the tube diameter and starts at 1.5 mass% for a 0.671 nm single wall nanotube.
TL;DR: As monkeys perform schedules containing several trials with a visual cue indicating reward proximity, their error rates decrease as the number of remaining trials decreases, suggesting that their motivation and/or reward expectancy increases as the reward approaches.
Abstract: As monkeys perform schedules containing several trials with a visual cue indicating reward proximity, their error rates decrease as the number of remaining trials decreases, suggesting that their motivation and/or reward expectancy increases as the reward approaches. About one-third of single neurons recorded in the anterior cingulate cortex of monkeys during these reward schedules had responses that progressively changed strength with reward expectancy, an effect that disappeared when the cue was random. Alterations of this progression could be the basis for the changes from normal that are reported in anterior cingulate population activity for obsessive-compulsive disorder and drug abuse, conditions characterized by disturbances in reward expectancy.
TL;DR: In this article, the authors review recent progress made in the field of semiconductor spintronics, a branch of the semiconductor electronics where both charge and spin degrees of freedom play an important role in realizing unique functionalities.
Abstract: We review recent progress made in the field of semiconductor spintronics, a branch of semiconductor electronics where both charge and spin degrees of freedom play an important role in realizing unique functionalities. We first describe the new spin-dependent phenomena found in semiconductors including carrier-induced ferromagnetism in III-V compounds, followed by an account of our current understanding of such spin-dependent phenomena. Then we summarize the challenges the semiconductor spintronics has to meet in order for it to be a success as "electronics".
TL;DR: An efficient process using a shell-and-tube reactor, in which a gaseous mixture of benzene and oxygen is fed into a porous alumina tube coated with a palladium thin layer, attained phenol formation selectivities of 80 to 97% at benzene conversions of 2 to 16% below 250°C.
Abstract: Existing phenol production processes tend to be energy-consuming and produce unwanted by-products. We report an efficient process using a shell-and-tube reactor, in which a gaseous mixture of benzene and oxygen is fed into a porous alumina tube coated with a palladium thin layer and hydrogen is fed into the shell. Hydrogen dissociated on the palladium layer surface permeates onto the back and reacts with oxygen to give active oxygen species, which attack benzene to produce phenol. This one-step process attained phenol formation selectivities of 80 to 97% at benzene conversions of 2 to 16% below 250°C (phenol yield: 1.5 kilograms per kilogram of catalyst per hour at 150°C).
TL;DR: MEL, which are glycolipid BS produced by a yeast Candida antarctrica, exhibit not only excellent interfacial properties but also remarkable differentiation-inducing activities against human leukemia cells, and should broaden its applications in new advanced technologies.
TL;DR: The fragment molecular orbital (FMO) method as discussed by the authors has been proposed to reproduce ab initio total energies and geometries of molecules in good accuracy, but the most time consuming part in the method, the calculations of environmental electrostatic potentials, were speeded up by employing the Mulliken approximation for two-electron integrals and a fractional point charge approximation.
TL;DR: The double-layered nanotubular structures of the titanium dioxide were created by sol−gel polymerization of Ti(OiPr)4] using 1 as a template in 1-butanol.
Abstract: The helical ribbon and double-layered nanotubular structures of the titanium dioxide were created by sol−gel polymerization of Ti(OiPr)4] using 1 as a template in 1-butanol. All TiO2 nanotubes consist of two layers, 8−9 nm of nanospace between layers. In addition, the helicity of the helical ribbon titanium dioxide showed a right-handed motif.
TL;DR: It is found that the seismicity rate is proportional to the calculated stressing rate, and that the duration of aftershock sequences is inversely proportional to a laboratory-based rate/state constitutive law, suggesting an explanation for the occurrence of earthquake swarms.
Abstract: Magma intrusions and eruptions commonly produce abrupt changes in seismicity far from magma conduits that cannot be associated with the diffusion of pore fluids or heat. Such 'swarm' seismicity also migrates with time, and often exhibits a 'dog-bone'-shaped distribution. The largest earthquakes in swarms produce aftershocks that obey an Omori-type (exponential) temporal decay, but the duration of the aftershock sequences is drastically reduced, relative to normal earthquake activity. Here we use one of the most energetic swarms ever recorded to study the dependence of these properties on the stress imparted by a magma intrusion. A 1,000-fold increase in seismicity rate and a 1,000-fold decrease in aftershock duration occurred during the two-month-long dyke intrusion. We find that the seismicity rate is proportional to the calculated stressing rate, and that the duration of aftershock sequences is inversely proportional to the stressing rate. This behaviour is in accord with a laboratory-based rate/state constitutive law, suggesting an explanation for the occurrence of earthquake swarms. Any sustained increase in stressing rate--whether due to an intrusion, extrusion or creep event--should produce such seismological behaviour.
TL;DR: In this article, photoelectrochemical properties of nanoporous TiO2 electrodes sensitized by a series of benzothiazole merocyanine dyes, 3-carboxyalkyl-5-[2-(3-alkyl)-2-benzothiazolinyldene) ethylidene]-2-thioxo-4-thiazolidinone, having a different alkyl chain length.
Abstract: We studied the photoelectrochemical properties of nanoporous TiO2 electrodes sensitized by a series of benzothiazole merocyanine dyes, 3-carboxyalkyl-5-[2-(3-alkyl-2-benzothiazolinyldene) ethylidene]-2-thioxo-4-thiazolidinone, having a different alkyl chain length. Broadening of absorption spectra and a large red shift of the absorption threshold up to 680 nm were observed by adsorbing dyes on a porous TiO2 electrode, suggesting the formation of various kinds of J aggregates of the dye on the TiO2 surface. The dye was fixed by a chelate-like linkage of the carboxylate anchoring group on the TiO2 surface, rather than by an ester linkage. The solar light-to-power conversion efficiency (ηsun) and the incident photon-to-current conversion efficiency (IPCE) increased with increasing the length of alkyl chain attached to the benzothiazole ring. The maximum ηsun value was 4.5%, which is the second highest value among organic dye systems reported so far (AM-1.5, 100 mW/cm2). The J aggregates of the dyes having lo...
TL;DR: In this paper, the authors studied the water splitting into H2 and O2 using two different semiconductor photocatalysts and a redox mediator, mimicking the Z-scheme mechanism of the photosynthesis.
Abstract: We studied the water splitting into H2 and O2 using two different semiconductor photocatalysts and a redox mediator, mimicking the Z-scheme mechanism of the photosynthesis. It was found that the H2 evolution took place on a Pt–SrTiO3 (Cr–Ta-doped) photocatalyst using an I− electron donor under the visible light irradiation. The Pt–WO3 photocatalyst showed an excellent activity of the O2 evolution using an IO3− electron acceptor under visible light. Both H2 and O2 gases evolved in the stoichiometric ratio (H2/O2=2) for more than 250 h under visible light using a mixture of the Pt–WO3 and the Pt–SrTiO3 (Cr–Ta-doped) powders suspended in NaI aqueous solution. It is for the first time that the stoichiometric water splitting occurred over oxide semiconductor photocatalysts under the visible light irradiation. We proposed a two-step photo-excitation mechanism using a pair of I−/IO3− redox mediators. The quantum efficiency of the stoichiometric water splitting was ca. 0.1% at 420.7 nm.
07 Aug 2002
TL;DR: Geometric nature of trajectories under the 3D-LIPM is discussed, and an algorithm for walking pattern generation is presented, and the dynamics of a three-dimensional inverted pendulum whose motions are constrained onto an arbitrarily defined plane are analyzed.
Abstract: For real-time walking control of a biped robot, we analyze the dynamics of a three-dimensional inverted pendulum whose motions are constrained onto an arbitrarily defined plane. This analysis leads us a simple linear dynamics, the Three-Dimensional Linear Inverted Pendulum Mode (3D-LIPM). Geometric nature of trajectories under the 3D-LIPM is discussed, and an algorithm for walking pattern generation is presented. Experimental results of real-time walking control of a 12-DOF biped robot HRP-2L using an input device such as a game pad are also shown.
TL;DR: A database of amo gene sequences for pure cultures of ammonia-oxidizing bacteria representing both the β- and the γ-subdivision of Proteobacteria in the following genera is presented.
Abstract: Autotrophic ammonia-oxidizing bacteria use the essential enzyme ammonia monooxygenase (AMO) to transform ammonia to hydroxylamine. The amo operon consists of at least three genes, amoC, amoA, and amoB; amoA encodes the subunit containing the putative enzyme active site. The use of the amo genes as functional markers for ammonia-oxidizing bacteria in environmental applications requires knowledge of the diversity of the amo operon on several levels: (1) the copy number of the operon in the genome, (2) the arrangement of the three genes in an individual operon, and (3) the primary sequence of the individual genes. We present a database of amo gene sequences for pure cultures of ammonia-oxidizing bacteria representing both the β- and the γ-subdivision of Proteobacteria in the following genera: Nitrosospira (6 strains), Nitrosomonas (5 strains) and Nitrosococcus (2 strains). The amo operon was found in multiple (2–3) nearly identical copies in the β-subdivision representatives but in single copies in the γ-subdivision ammonia oxidizers. The analysis of the deduced amino acid sequence revealed strong conservation for all three Amo peptides in both primary and secondary structures. For the amoA gene within the β-subdivision, nucleotide identity values are approximately 85% within the Nitrosomonas or the Nitrosospira groups, but approximately 75% when comparing between these groups. Conserved regions in amoA and amoC were identified and used as primer sites for PCR amplification of amo genes from pure cultures, enrichments and the soil environment. The intergenic region between amoC and amoA is variable in length and may be used to profile the community of ammonia-oxidizing bacteria in environmental samples. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00203-001-0369-z.
TL;DR: It is shown that TRX‐2 is an essential gene and that Trx‐2‐deficient cells undergo apoptosis upon repression of the TRX•2 transgene, showing an accumulation of intracellular reactive oxygen species (ROS).
Abstract: Thioredoxin-2 (Trx-2) is a mitochondria-specific member of the thioredoxin superfamily. Mitochondria have a crucial role in the signal transduction for apoptosis. To investigate the biological significance of Trx-2, we cloned chicken TRX-2 cDNA and generated clones of the conditional Trx-2-deficient cells using chicken B-cell line, DT40. Here we show that TRX-2 is an essential gene and that Trx-2-deficient cells undergo apoptosis upon repression of the TRX-2 transgene, showing an accumulation of intracellular reactive oxygen species (ROS). Cytochrome c is released from mitochondria, while caspase-9 and caspase-3, but not caspase-8, are activated upon inhibition of the TRX-2 transgene. In addition, Trx-2 and cytochrome c are co-immunoprecipitated in an in vitro assay. These results suggest that mitochondrial Trx-2 is essential for cell viability, playing a crucial role in the scavenging ROS in mitochondria and regulating the mitochondrial apoptosis signaling pathway.
TL;DR: A novel procedure for characterizing the conformational flexibility of β2-microglobulin amyloid fibrils at single-residue resolution that uses H/D exchange of amide protons combined with NMR analysis indicates that most residues in the middle region of the molecule, including the loop regions in the native structure, form a rigid β-sheet core.
Abstract: Despite numerous efforts, the lack of detailed structural information on amyloid fibrils has hindered clarification of the mechanism of their formation. Here, we describe a novel procedure for characterizing the conformational flexibility of β2-microglobulin amyloid fibrils at single-residue resolution that uses H/D exchange of amide protons combined with NMR analysis. The results indicate that most residues in the middle region of the molecule, including the loop regions in the native structure, form a rigid β-sheet core, whereas the the N- and C-termini are excluded from this core. The extensively hydrogen-bonded β-sheet core explains the remarkable rigidity and stability of amyloid fibrils. The present method could be used to obtain residue-specific conformational information of various amyloid fibrils, even though it does not provide a high resolution three-dimensional structure.
TL;DR: The results indicate that the recombinant mPGE synthase is identical to the enzyme purified from the microsomal fraction of bovine heart, and is a novel type of mPGe synthase based on the primary structure, a broad specificity of thiol requirement, and tissue distribution.
TL;DR: In this article, a body-centered-cubic ordered structure in a Ni-Ga-Fe system has been developed for ferromagnetic shape memory alloys, which exhibit a thermoelastic martensitic transformation from a B2 and/or an L21 parent to a martensite phase.
Abstract: Ferromagnetic shape memory alloys with a body-centered-cubic ordered structure in a Ni–Ga–Fe system have been developed. The alloys with the composition range of Ni 27 at. % Ga (20–22 at. %)Fe exhibit a thermoelastic martensitic transformation from a B2 and/or an L21 parent to a martensite phase, with a seven-layer modulated (14M) and a five-layer modulated (10M) structure, in the ferromagnetic state. The parent phase transforms from the B2 to the L21 structure at about 970 K during cooling, and the degree of the L21 order in the parent phase is increased by annealing at 773 K, resulting in the increase of both the martensite starting and the Curie temperatures. The ductility of these alloys is improved by introducing of a small amount of a γ-phase solid solution. Consequently, we can conclude that the present alloys are promising for ferromagnetic shape memory alloys.
TL;DR: A series of high-activity supported nickel phosphide hydroprocessing catalysts (Ni2P/SiO2) was synthesized by means of temperature-programmed reduction (TPR), and the effect of phosphorus content on hydroprocessing performance and catalyst structure was studied as discussed by the authors.