Showing papers by "Tokyo Institute of Technology published in 1999"

Percolative phase separation underlies colossal magnetoresistance in mixed-valent manganites

Abstract: Colossal magnetoresistance1—an unusually large change of resistivity observed in certain materials following application of magnetic field—has been extensively researched in ferromagnetic perovskite manganites. But it remains unclear why the magnetoresistive response increases dramatically when the Curie temperature (T C) is reduced. In these materials, T C varies sensitively with changing chemical pressure; this can be achieved by introducing trivalent rare-earth ions of differing size into the perovskite structure2,3,4, without affecting the valency of the Mn ions. The chemical pressure modifies local structural parameters such as the Mn–O bond distance and Mn–O–Mn bond angle, which directly influence the case of electron hopping between Mn ions (that is, the electronic bandwidth). But these effects cannot satisfactorily explain the dependence of magnetoresistance on T C. Here we demonstrate, using electron microscopy data, that the prototypical (La,Pr,Ca)MnO3 system is electronically phase-separated into a sub-micrometre-scale mixture of insulating regions (with a particular type of charge-ordering) and metallic, ferromagnetic domains. We find that the colossal magnetoresistive effect in low-T C systems can be explained by percolative transport through the ferromagnetic domains; this depends sensitively on the relative spin orientation of adjacent ferromagnetic domains which can be controlled by applied magnetic fields.

Teddy: a sketching interface for 3D freeform design

Abstract: We present a sketching interface for quickly and easily designing freeform models such as stuffed animals and other rotund objects. The user draws several 2D freeform strokes interactively on the screen and the system automatically constructs plausible 3D polygonal surfaces. Our system supports several modeling operations, including the operation to construct a 3D polygonal surface from a 2D silhouette drawn by the user: it inflates the region surrounded by the silhouette making wide areas fat, and narrow areas thin. Teddy, our prototype system, is implemented as a Java™ program, and the mesh construction is done in real-time on a standard PC. Our informal user study showed that a first-time user typically masters the operations within 10 minutes, and can construct interesting 3D models within minutes.

Identification and characterization of a novel protein, periostin, with restricted expression to periosteum and periodontal ligament and increased expression by transforming growth factor β

Abstract: We had previously identified the cDNA for a novel protein called osteoblast-specific factor 2 (OSF-2) from an MC3T3-E1 cDNA library using subtraction hybridization and differential screening techniques. Here we describe the localization, regulation, and potential function of this protein. Immunohistochemistry using specific antiserum revealed that in adult mice, the protein is preferentially expressed in periosteum and periodontal ligament, indicating its tissue specificity and a potential role in bone and tooth formation and maintenance of structure. Based on this observation and the fact that other proteins have been called OSF-2, the protein was renamed "periostin." Western blot analysis showed that periostin is a disulfide linked 90 kDa protein secreted by osteoblasts and osteoblast-like cell lines. Nucleotide sequence revealed four periostin transcripts that differ in the length of the C-terminal domain, possibly caused by alternative splicing events. Reverse transcription- polymerase chain reaction analysis revealed that these isoforms are not expressed uniformly but are differentially expressed in various cell lines. Both purified periostin protein and the periostin-Fc recombinant protein supported attachment and spreading of MC3T3-E1 cells, and this effect was impaired by antiperiostin antiserum, suggesting that periostin is involved in cell adhesion. The protein is highly homologous to betaig-h3, a molecule induced by transforming growth factor beta (TGF-beta) that promotes the adhesion and spreading of fibroblasts. Because TGF-beta has dramatic effects on periosteal expansion and the recruitment of osteoblast precursors, this factor was tested for its effects on periostin expression. By Western blot analysis, TGF-beta increased periostin expression in primary osteoblast cells. Together, these data suggest that periostin may play a role in the recruitment and attachment of osteoblast precursors in the periosteum.

Homogeneous Catalysis in Supercritical Fluids.

Abstract: Supercritical fluids (SCFs), compounds heated and pressurized beyond the critical point, have many unusual properties. Homogeneous molecular catalysts, which have far greater control over selectivity than heterogeneous solid catalysts, are now being tested in SCFs, and early results show that high rates, improved selectivity, and elimination of masstransfer problems can be achieved. As industry moves away from toxic or environmentally damaging solvents, supercritical carbon dioxide may be an ideal replacement medium for nonpolar or weakly polar chemical processes. More than simply substitutes for nonpolar solvents, SCFs can radically change the observed chemistry. Supercritical carbon dioxide is also an excellent medium for its own fixation, as demonstrated by studies of its hydrogenation.

Regulation of maternal behavior and offspring growth by paternally expressed Peg3.

Abstract: Imprinted genes display parent-of-origin–dependent monoallelic expression that apparently regulates complex mammalian traits, including growth and behavior. The Peg3 gene is expressed in embryos and the adult brain from the paternal allele only. A mutation in the Peg3 gene resulted in growth retardation, as well as a striking impairment of maternal behavior that frequently resulted in death of the offspring. This result may be partly due to defective neuronal connectivity, as well as reduced oxytocin neurons in the hypothalamus, because mutant mothers were deficient in milk ejection. This study provides further insights on the evolution of epigenetic regulation of imprinted gene dosage in modulating mammalian growth and behavior.

Ferroelectricity Induced by Oxygen Isotope Exchange in Strontium Titanate Perovskite

Abstract: Ferroelectricity was induced in $\mathrm{SrTiO}{}_{3}$ by the isotope exchange of ${}^{18}\mathrm{O}$ for ${}^{16}\mathrm{O}$. Dielectric measurements confirmed the ferroelectricity of $\mathrm{SrTi}{}^{18}\mathrm{O}{}_{3}$, showing a peak at 23 K. A hysteresis loop in the $D$ vs $E$ measurement and TO phonon observed in the Raman spectra supported the evolution of ferroelectricity in $\mathrm{SrTi}{}^{18}\mathrm{O}{}_{3}$. This is the first demonstration of $\mathrm{SrTi}\mathrm{O}{}_{3}$ becoming ferroelectric without the application of external fields or the introduction of a random field through cation substitution.

Small-Scale Anisotropy of Cosmic Rays above 1019 eV Observed with the Akeno Giant Air Shower Array

Abstract: With the Akeno Giant Air Shower Array, 581 cosmic rays above 1019 eV, 47 above 4 ) 1019 eV, and seven above 1020 eV were observed until 1998 August. The arrival direction distribution of these extremely high energy cosmic rays has been studied. While no signi—cant large-scale anisotropy is found on the celestial sphere, some interesting clusters of cosmic rays are observed. Above 4 ) 1019 eV, there are one triplet and three doublets within a separation angle of and the probability of observing 2i.5, these clusters by a chance coincidence under an isotropic distribution is smaller than 1%. The triplet is especially observed against expected 0.05 events. The distribution expected from the dark cos (h GC ) matter halo model —ts the data as well as an isotropic distribution above 2 ) 1019 and 4 ) 1019 eV, but the —t with the dark matter halo model is poorer than the isotropic distribution above 1019 eV. The arrival direction distribution of seven 1020 eV cosmic rays is consistent with that of lower energy cosmic rays and is uniform. Three of the seven are members of doublets above about 4 ) 1019 eV. Subject headings: cosmic raysgalaxies: generalGalaxy: halolarge-scale structure of universe

The fate of subducted basaltic crust in the Earth's lower mantle

Abstract: The subduction of oceanic lithosphere into the Earth's deep interior is thought to drive convection and create chemical heterogeneity in the mantle. The oceanic lithosphere as a whole, however, might not subduct uniformly: the fate of basaltic crust may differ from that of the underlying peridotite layer because of differences in chemistry, density and melting temperature. It has been suggested that subducted basaltic crust may in fact become buoyant at the mantle's 660-km discontinuity, remaining buoyant to depths of at least 800 km, and therefore might be gravitationally trapped at this boundary to form a garnetite layer1, 2. Here we report the phase relations and melting temperatures of natural mid-ocean ridge basalt at pressures up to 64 GPa (corresponding to ∼1,500 km depth). We find that the former basaltic crust is no longer buoyant when it transforms to a perovskitite lithology at about 720 km depth, and that this transition boundary has a positive pressure–temperature slope, in contrast to the negative slope of the transition boundary in peridotite. We therefore predict that basaltic crust with perovskitite lithology would gravitationally sink into the deep mantle. Our melting data suggest that, at the base of the lower mantle, the former basaltic crust would be partially molten if temperatures there were to exceed 4,000 K.

Measurement of the Flux and Zenith-Angle Distribution of Upward Throughgoing Muons by Super-Kamiokande

Abstract: A total of 614 upward throughgoing muons of minimum energy 1.6thinspthinspGeV are observed by Super-Kamiokande during 537 detector live days. The measured muon flux is [1.74{plus_minus}0.07(stat){plus_minus} 0.02(sys)]{times}10{sup {minus}13} cm{sup {minus}2}thinsps{sup {minus}1}thinspsr{sup {minus}1} compared to an expected flux of [1.97{plus_minus}0.44(theor)]{times} 10{sup {minus}13} cm{sup {minus}2}thinsps{sup {minus}1}thinspsr{sup {minus}1} . The absolute measured flux is in agreement with the prediction within the errors. However, the zenith-angle dependence of the observed upward throughgoing muon flux does not agree with no-oscillation predictions. The observed distortion in shape is consistent with the {nu}{sub {mu}}{leftrightarrow}{nu}{sub {tau}} oscillation hypothesis with sin{sup 2}thinsp2{theta} {gt}0.4 and 1{times}10{sup {minus}3}{lt}{Delta}m{sup 2}{lt}1{times}1 0{sup {minus}1} eV{sup 2} at 90{percent} confidence level. {copyright} {ital 1999} {ital The American Physical Society}

Phylogenetic relationships among cetartiodactyls based on insertions of short and long interpersed elements: hippopotamuses are the closest extant relatives of whales.

Abstract: Insertion analysis of short and long interspersed elements is a powerful method for phylogenetic inference. In a previous study of short interspersed element data, it was found that cetaceans, hippopotamuses, and ruminants form a monophyletic group. To further resolve the relationships among these taxa, we now have isolated and characterized 10 additional loci. A phylogenetic analysis of these data was able to resolve relationships among the major cetartiodactyl groups, thereby shedding light on the origin of whales. The results indicated (i) that cetaceans are deeply nested within Artiodactyla, (ii) that cetaceans and hippopotamuses form a monophyletic group, (iii) that pigs and peccaries form a monophyletic group to the exclusion of hippopotamuses, (iv) that chevrotains diverged first among ruminants, and (v) that camels diverged first among cetartiodactyls. These findings lead us to conclude that cetaceans evolved from an immediate artiodactyl, not mesonychian, ancestor.

Multi-parent recombination with simplex crossover in real coded genetic algorithms

Abstract: In this paper, we proposed simplex crossover (SPX), a multi-parent recombination operator for real-coded genetic algorithms. SPX generates offspring vector values by uniformly sampling values from simplex formed by m (2 ≤ m ≤ number of parameters + 1) parent vectors. The SPX features an independence from of coordinate systems. Experimental results using test functions, which are commonly used in studies of evolutionary algorithms, showed SPX works well on functions having multimodality and/or epistasis with a medium number of parents: 3-parent on a low dimensional function or 4 parents on high dimensional functions.

On stability of fuzzy systems expressed by fuzzy rules with singleton consequents

Abstract: Addresses the issue of stability of a fuzzy system described by fuzzy rules with singleton consequents. It first presents two canonical forms of a fuzzy system: a parametric expression and a state-space expression. A fuzzy system with singleton consequents is found to be a piecewise-polytopic-affine system. Then the paper gives stability theorems for a discrete-time system as well as for a continuous time system. It also gives a brief survey on the stability issues of fuzzy control systems.

Enhanced Piezoelectric Property of Barium Titanate Single Crystals with Engineered Domain Configurations

Abstract: Piezoelectric properties of barium titanate single crystals were investigated at room temperature as a function of crystallographic orientation. When a unipolar electric field was applied along [001], its strain vs electric-field curve showed a large hysteresis, and finally barium titanate crystal became to single-domain state with piezoelectric constant d33 of 125 pC/N over 20 kV/cm. On the other hand, electric-field exposure below 6 kV/cm along [111] resulted in a high d33 of 203 pC/N and a hysteresis-free strain vs electric-field behavior, which suggested the formation of an engineered domain configuration in a tetragonal barium titanate crystal. Moreover, when an electric field over 6 kV/cm was applied along [111], two discontinuous changes were observed in its strain vs electric-field curve. In situ domain observation and Raman measurement under an electric field suggested an electric-field-induced phase transition from tetragonal to monoclinic at around 10 kV/cm, and that from monoclinic to rhombohedral at around 30 kV/cm. Moreover, in a monoclinic barium titanate crystal, electric-field exposure along [111] resulted in the formation of another new engineered domain configuration with d33 of 295 pC/N.

Effect of A- and B-cation substitutions on the phase stability of PbTiO 3 ceramics

Abstract: Raman scattering studies of Nd-modified lead titanate ${\mathrm{Pb}}_{1\ensuremath{-}3y/2}{\mathrm{Nd}}_{y}{\mathrm{TiO}}_{3}$ (PNT), $y=0.02,$ 0.10, and $\mathrm{Pb}({\mathrm{Zr}}_{x}{\mathrm{Ti}}_{1\ensuremath{-}x}){\mathrm{O}}_{3}$ (PZT), $x=0.10,0.20,$ bulk ceramics were made at ambient temperatures between 4.2 and 297 K. Our measurements reveal splitting of the $E\ensuremath{\bigoplus}{B}_{1}$ symmetry peak at low temperatures in both the PNT and PZT samples. Some splitting of three $E(\mathrm{TO})\mathrm{}$ peaks in the PZT samples [except for the $E(2\mathrm{TO})$ peak in the sample with $x=0.10]$ and of the $E(3\mathrm{TO})$ peak in the PNT samples was also found. We discuss the phase stability of lead titanate based perovskites from the point of view of our experimental results and recent theoretical calculations. Raman results reveal that all ${A}_{1}(\mathrm{TO})$ symmetry modes in all samples are anharmonic down to the lowest measurement temperature.

Towards Resolving the Interordinal Relationships of Placental Mammals

Abstract: Here we show that progress towards a reliable phylogeny for placental mammals at the ordinal level continues apace. We draw especially upon insights from the recent “International Symposium on the Origin of Mammalian Orders” held at The Graduate University of Advanced Study, Hayama, Japan (21–25 July 1998), particularly work not incorporated in the remainder of this issue or published elsewhere. Abstracts to talks and posters presented at this meeting can be found at www.utexas.edu/ftp/depts/systbiol/. The talks fell into three main sections, which we will now consider, followed by a summary where we present our current best estimate of the tree for placental mammals.

Determination of Nitrogen Isotopomers of Nitrous Oxide on a Modified Isotope Ratio Mass Spectrometer

Abstract: A new method for the determination of the nitrogen isotopomers (intramolecular distribution of the nitrogen isotopes) of nitrous oxide has been developed. The method makes use of mass analyses of t...

Cloning of chlorophyllase, the key enzyme in chlorophyll degradation: finding of a lipase motif and the induction by methyl jasmonate.

Abstract: Chlorophyllase (Chlase) is the first enzyme involved in chlorophyll (Chl) degradation and catalyzes the hydrolysis of ester bond to yield chlorophyllide and phytol. In the present study, we isolated the Chlase cDNA. We synthesized degenerate oligo DNA probes based on the internal amino acid sequences of purified Chlase from Chenopodium album, screened the C. album cDNA library, and cloned a cDNA (CaCLH, C. album chlorophyll-chlorophyllido hydrolase). The deduced amino acid sequence (347 aa residues) had a lipase motif overlapping with an ATP/GTP-binding motif (P-loop). CaCLH possibly was localized in the extraplastidic part of the cell, because a putative signal sequence for endoplasmic reticulum is at the N terminus. The amino acid sequence shared 37% identity with a function-unknown gene whose mRNA is inducible by coronatine and methyl jasmonate (MeJA) in Arabidopsis thaliana (AtCLH1). We expressed the gene products of AtCLH1 and of CaCLH in Escherichia coli, and they similarly exhibited Chlase activity. Moreover, we isolated another full-length cDNA based on an Arabidopsis genomic fragment and expressed it in E. coli, demonstrating the presence of the second Arabidopsis CLH gene (AtCLH2). No typical feature of signal sequence was identified in AtCLH1, whereas AtCLH2 had a typical signal sequence for chloroplast. AtCLH1 mRNA was induced rapidly by a treatment of MeJA, which is known to promote senescence and Chl degradation in plants, and a high mRNA level was maintained up to 9 h. AtCLH2, however, did not respond to MeJA.

Apg10p, a novel protein‐conjugating enzyme essential for autophagy in yeast

Abstract: Autophagy is a cellular process for bulk degradation of cytoplasmic components. The attachment of Apg12p, a modifier with no significant similarity to ubiquitin, to Apg5p is crucial for autophagy in yeast. This reaction proceeds in a ubiquitination-like manner, and requires Apg7p and Apg10p. Apg7p exhibits a considerable similarity to ubiquitin-activating enzyme (E1) and is found to activate Apg12p with ATP hydrolysis. Apg10p, on the other hand, shows no significant similarity to other proteins whose functions are known. Here, we show that after activation by Apg7p, Apg12p is transferred to the Cys-133 residue of Apg10p to form an Apg12p-Apg10p thioester. Cells expressing Apg10p(C133S) do not generate the Apg12p-Apg5p conjugate, which leads to defects in autophagy and cytoplasm-to-vacuole targeting of aminopeptidase I. These findings indicate that Apg10p is a new type of protein-conjugating enzyme that functions in the Apg12p-Apg5p conjugation pathway.

Synthesis and characteristics of complex multicomponent oxides prepared by polymer complex method

Abstract: This account focuses on the synthesis and characteristics of ceramics prepared by the Pechini-type in-situ polymerizable complex (IPC) method The current status of the IPC method is reviewed, and the principle and underlying chemistry of the IPC method is illustrated with a special emphasis on its intrinsic advantage over other solution-based technologies The method has the ability to prepare complex multicomponent oxides with good homogeneity through mixing at the molecular level The importance of “polymerization” itself in the IPC route is demonstrated by comparing with the non-polymerizable so-called amorphous citrate method, which affords less compositional homogeneity The use of heterometallic complexes in the IPC processing is shown to be one of the most promising techniques to synthesize ceramics with exceptionally good homogeneity It is one function of this account to describe how Raman and 13C NMR spectroscopies can be effectively used for characterizing precursors in the IPC processing Fin

Hidden Markov models based on multi-space probability distribution for pitch pattern modeling

Abstract: This paper discusses a hidden Markov model (HMM) based on multi-space probability distribution (MSD). The HMMs are widely-used statistical models to characterize the sequence of speech spectra and have successfully been applied to speech recognition systems. From these facts, it is considered that the HMM is useful for modeling pitch patterns of speech. However, we cannot apply the conventional discrete or continuous HMMs to pitch pattern modeling since the observation sequence of the pitch pattern is composed of one-dimensional continuous values and a discrete symbol which represents "unvoiced". MSD-HMM includes discrete HMMs and continuous mixture HMMs as special cases, and further can model the sequence of observation vectors with variable dimension including zero-dimensional observations, i.e., discrete symbols. As a result, MSD-HMMs can model pitch patterns without heuristic assumption. We derive a reestimation algorithm for the extended HMM and show that it can find a critical point of the likelihood function.

Functional identification and reconstitution of an odorant receptor in single olfactory neurons

Abstract: The olfactory system is remarkable in its capacity to discriminate a wide range of odorants through a series of transduction events initiated in olfactory receptor neurons. Each olfactory neuron is expected to express only a single odorant receptor gene that belongs to the G protein coupled receptor family. The ligand–receptor interaction, however, has not been clearly characterized. This study demonstrates the functional identification of olfactory receptor(s) for specific odorant(s) from single olfactory neurons by a combination of Ca2+-imaging and reverse transcription–coupled PCR analysis. First, a candidate odorant receptor was cloned from a single tissue-printed olfactory neuron that displayed odorant-induced Ca2+ increase. Next, recombinant adenovirus-mediated expression of the isolated receptor gene was established in the olfactory epithelium by using green fluorescent protein as a marker. The infected neurons elicited external Ca2+ entry when exposed to the odorant that originally was used to identify the receptor gene. Experiments performed to determine ligand specificity revealed that the odorant receptor recognized specific structural motifs within odorant molecules. The odorant receptor-mediated signal transduction appears to be reconstituted by this two-step approach: the receptor screening for given odorant(s) from single neurons and the functional expression of the receptor via recombinant adenovirus. The present approach should enable us to examine not only ligand specificity of an odorant receptor but also receptor specificity and diversity for a particular odorant of interest.

Detection of local ATP release from activated platelets using cell surface-attached firefly luciferase

Abstract: We have developed a method for measuring the local concentration of ATP at the extracellular surface of live cells. This method relies on the specific attachment to the cell surface of a chimeric protein that consists of the IgG-binding domain of Staphylococcus aureus protein A fused in-frame with the complete sequence for firefly luciferase (proA-luc). Expression of proA-luc in Escherichia coli and its one-step affinity purification are straightforward. Attachment to cells is demonstrated to be specific and antibody dependent using several suspended and adherent cell types. Light production by cell surface-attached luciferase is continuous, linearly related to ATP concentration, and sufficient to provide nanomolar sensitivity. The spatial resolution of this method enables the observation of strictly local changes in extracellular ATP during its secretion from activated platelets. Furthermore, the activity of cell-attached luciferase is relatively refractory to the inclusion of nucleotidases in the medium, arguing for its effectiveness in cell systems possessing potent ecto-ATPases.

Constraints on neutrino oscillation parameters from the measurement of day-night solar neutrino fluxes at super-kamiokande

Abstract: A search for day-night variations in the solar neutrino flux resulting from neutrino oscillations has been carried out using the 504 day sample of solar neutrino data obtained at Super-Kamiokande. The absence of a significant day-night variation has set an absolute flux independent exclusion region in the two neutrino oscillation parameter space.

Orbital-State-Mediated Phase-Control of Manganites

Abstract: Using the epitaxial strain, the magnetic and electronic phases can be controlled for thin films of the manganites, La1-xSrxMnO3, grown on perovskite substrates with various lattice parameters. The strain-induced orbital-ordering (disordering) via coupling

Purification and characterization of a novel peroxidase from Geotrichum candidum dec 1 involved in decolorization of dyes.

Abstract: The discharge to the environment of 10 to 15% of the synthetic dyes produced (42) causes environmental problems. These dyes are poorly biodegradable because of their structures, and treatment of wastewater containing dyes usually involves physical and/or chemical methods. Although these treatment methods are efficient, they may result in the production of toxic by-products and/or require high levels of energy. Microbial decolorization has been proposed as a less expensive and less environmentally intrusive alternative. Various bacteria and fungi have decolorizing abilities, and an extensive review of microbiological decolorization has been made (3); in many cases adsorption of dyes to the microbial cell surface is the primary mechanism of decolorization (22). Azo dyes may be microbially degraded under anaerobic (28, 52) or aerobic (8, 13, 30, 32, 42, 47) conditions or in aerobic and anaerobic two-stage systems (39). Enzymes, such as lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase, all of which are involved in lignin degradation, participate in the decolorization of the dyes (6–8, 13, 30, 47). Recently, another such peroxidase was purified from Pleurotus ostreatus that was found to be different from MnP, LiP, and horseradish peroxidase (HRP) (17, 41). However, few studies have been made of the enzymatic degradation of anthraquinone dyes, which are xenobiotic chemicals similar to azo dyes but different in structure (11, 22, 31, 47). Previously, we reported that Geotrichum candidum Dec 1, a newly isolated decolorizing fungus, decolorized 21 types of reactive dyes, including azo and anthraquinone dyes (18). The broad decolorization spectrum of this strain suggested the involvement of extracellular peroxidase-type enzymes. Our objectives in this study were to purify and characterize the novel peroxidase (DyP) that is responsible for the dye-decolorizing activity of G. candidum Dec 1.

Structural Genealogy of BEDT-TTF-Based Organic Conductors II. Inclined Molecules: θ, α, and κ Phases

Abstract: Overlap integrals between HOMO’s of two non-parallel BEDT-TTF (bis(ethylenedithio)tetrathiafulvalene) molecules have been calculated. As the dihedral angle between the molecular planes decreases fr...