Showing papers by "Tokyo Institute of Technology published in 2000"

Light-driven motion of liquids on a photoresponsive surface

Abstract: The macroscopic motion of liquids on a flat solid surface was manipulated reversibly by photoirradiation of a photoisomerizable monolayer covering the surface. When a liquid droplet several millimeters in diameter was placed on a substrate surface modified with a calix[4]resorcinarene derivative having photochromic azobenzene units, asymmetrical photoirradiation caused a gradient in surface free energy due to the photoisomerization of surface azobenzenes, leading to the directional motion of the droplet. The direction and velocity of the motion were tunable by varying the direction and steepness of the gradient in light intensity. The light-driven motion of a fluid substance in a surface-modified glass tube suggests potential applicability to microscale chemical process systems.

Speech parameter generation algorithms for HMM-based speech synthesis

Abstract: This paper derives a speech parameter generation algorithm for HMM-based speech synthesis, in which the speech parameter sequence is generated from HMMs whose observation vector consists of a spectral parameter vector and its dynamic feature vectors. In the algorithm, we assume that the state sequence (state and mixture sequence for the multi-mixture case) or a part of the state sequence is unobservable (i.e., hidden or latent). As a result, the algorithm iterates the forward-backward algorithm and the parameter generation algorithm for the case where the state sequence is given. Experimental results show that by using the algorithm, we can reproduce clear formant structure from multi-mixture HMMs as compared with that produced from single-mixture HMMs.

Synthesis and characterization of helical multi-shell gold nanowires

Abstract: Suspended gold nanowires were made in an ultra-high vacuum. The finest of them was 0.6 nanometer in diameter and 6 nanometers in length. By high-resolution electron microscopy, they were shown to have a multi-shell structure composed of coaxial tubes. Each tube consists of helical atom rows coiled round the wire axis. The difference between the numbers of atom rows in outer and inner shells is seven, resulting in magic shell-closing numbers.

Surface-emitting laser-its birth and generation of new optoelectronics field

Abstract: The surface-emitting laser (SEL) is considered one of the most important devices for optical interconnects and LANs, enabling ultra parallel information transmission in lightwave and computer systems. We introduce its history, fabrication technology, and discuss the advantages. Then, we review the progress of the surface emitting laser and the vertical-cavity surface-emitting laser (VCSEL), covering the spectral band from infrared to ultraviolet by featuring its physics, materials, fabrication technology, and performances, such as threshold, output powers, polarizations, line-width, modulation, reliability, and so on.

Q-Chem 2.0: a high-performance ab initio electronic structure program package

Abstract: Q-Chem 2.0 is a new release of an electronic structure programpackage, capable of performing first principles calculations on the ground andexcited states of molecules using both density functional theory and wavefunction-based methods. A review of the technical features contained withinQ-Chem 2.0 is presented. This article contains brief descriptive discussions of thekey physical features of all new algorithms and theoretical models, together withsample calculations that illustrate their performance. c 2000 John Wiley S electronic structure; density functional theory;computer program; computational chemistry Introduction A reader glancing casually at this article mightsuspect on the basis of its title that it is a thinlydisguised piece of marketing for a program pack-age. This is not the case. Rather, it is an attemptto document the key methodologies and algorithmsof our electronic structure program package, Q-Chem 2.0, in a complete and scientifically accurateway, with full references to the original literature.This is important for two principal reasons. First,while the use of electronic structure programs isburgeoning, many users of such programs do nothave much feel for the underlying algorithms thatmake large-scale calculations routine even on suchreadily available hardware as personal computers.Therefore, a link between the program package andthe original literature that is written at the level ofan introductory overview can be a useful bridge.Second, while citations of large-scale commercialprograms in published applications are tradition-ally part of the conditions of use of such codes, they

Tau neutrinos favored over sterile neutrinos in atmospheric muon neutrino oscillations.

Abstract: The previously published atmospheric neutrino data did not distinguish whether muon neutrinos were oscillating into tau neutrinos or sterile neutrinos, as both hypotheses fit the data. Using data recorded in 1100 live days of the Super-Kamiokande detector, we use three complementary data samples to study the difference in zenith angle distribution due to neutral currents and matter effects. We find no evidence favoring sterile neutrinos, and reject the hypothesis at the $99%$ confidence level. On the other hand, we find that oscillation between muon and tau neutrinos suffices to explain all the results in hand.

Identification and characterization of the new osteoclast progenitor with macrophage phenotypes being able to differentiate into mature osteoclasts

Abstract: Osteoclasts are thought to belong to a macrophage lineage. However, the nature of common precursors of osteoclasts and macrophages remains to be investigated. We have characterized the differentiation potential of mouse bone marrow macrophages into mature osteoclasts. Monocyte macrophage-colony-stimulating factor (M-CSF) stimulated the proliferation of bone marrow macrophages in a dose-dependent manner and these M-CSF-dependent bone marrow macrophage (MDBM) cells efficiently differentiated into the tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts in the presence of soluble RANKL (sRANKL) and M-CSF in the in vitro culture. The macrophage-like cell line TMC16 was established from tsA58 (temperature-sensitive SV40 large T-antigen) transgenic mice in the same manner to the preparation of MDBM cells and also differentiated into mature osteoclasts. During this differentiation in vitro, the morphology of the cells changed from spindle to round and smaller (termed pOC) on day 2 and to multinuclear (termed multinucleated cells [MNCs]) on day 4. The surface expression of macrophage marker CD14 was down-regulated and that of CD43 was up-regulated on pOC, analyzed by flow cytometry. RNA analysis revealed that osteoclast marker genes such as calcitonin receptor (CTR), carbonic anhydrase II (CAII), cathepsin K (cath K), MMP9, and TRAP were strongly expressed in MNCs and weakly in pOC whereas MDBM cells did not express these genes. However, the osteopontin (OPN) gene was strongly expressed in MDBM cells and this expression became weakened after differentiation into pOC. The TMC16 cell line weakly expressed cath K, TRAP, and OPN, suggesting that the TMC16 cell line is immortalized at a stage slightly differentiated from MDBM cells. Furthermore, cell sorting analysis revealed that osteoclast early progenitors in bone marrow cells are preferentially present in the Mac-1- F4/80dull population, which differentiated into MDBM cells (the osteoclast progenitor) expressing Mac-1+ F4/80int, suggesting that M-CSF plays roles of a differentiation factor as well as a growth factor for osteoclast early progenitors. These results showed the transition of morphology, surface markers, and gene expression from the early to mature stage in osteoclast differentiation. We propose three differentiation stages in the osteoclast lineage: the pro-osteoclast (spindle-shaped macrophage cells), the pre-osteoclast (small round mononucleated TRAP-positive cells), and the mature osteoclast (multinucleated TRAP-positive cells) stage.

Bose-Einstein condensation of dilute magnons in TlCuCl3.

Abstract: The recent observation [A. Oosawa et al., J. Phys. Condens. Matter 11, 265 (1999)] of the field-induced N\'eel ordering in the spin-gap magnetic compound ${\mathrm{TlCuCl}}_{3}$ is interpreted as a Bose-Einstein condensation of magnons. A Hartree--Fock-type calculation based on this picture is shown to describe the temperature dependence of the magnetization well.

Formation of Giant Planets: Dependences on Core Accretion Rate and Grain Opacity

Abstract: We have investigated the formation of gaseous envelopes of giant planets with wide ranges of parameters through quasi-static evolutionary simulations. In the nucleated instability model, rapid gas accretion is triggered when the solid core mass exceeds a critical mass. The gas accretion should be regulated essentially by core accretion rate and grain opacity in the outermost envelope. The conventional critical core mass ~5-20 M⊕ (M⊕: Earth's mass), however, is based on some nominal values of these quantities. The discovery of extrasolar giant planets requires investigation of the gas accretion processes under various circumstances. Furthermore, the current planetary accretion theory points out that the cores of Jupiter and Saturn would have been isolated from planetesimals and the core accretion would have almost stopped in their later stage of formation before their masses reached the conventional critical core mass. Through numerical simulations of quasi-static evolution of the gaseous envelope, we have investigated the characteristic growth times of the envelope mass for wide ranges of core accretion rate and grain opacity. We also studied the case where core accretion stops before onset of rapid gas accretion. Our main results are (1) the growth time of the envelope mass τg depends strongly on the core mass, moderately on the grain opacity, and weakly on the past core accretion process, and (2) τg is expressed approximately as τg ~ 108(Mcore /M⊕)-2.5(κ gr/1 cm 2 g-1) yr, where Mcore is the core mass and κgr is the grain opacity. Our results combined with the recent planetary accretion theory suggest surface density of solid materials twice as massive as that of the minimum-mass solar nebula model and the longer lifetime of the nebula than the 108 yr needed to form Jupiter and Saturn; otherwise migration of protoplanets may have to be considered. Our extensive parametric study not only confirms the difficulty in the formation of the giant planets quantitatively and rigorously, it also gives essential information in considering the problem of the formation, which is quite useful in applications.

The gamete fusion process is defective in eggs of Cd9-deficient mice.

Abstract: The cell-surface molecule Cd9, a member of the transmembrane-4 superfamily, interacts with the integrin family and other membrane proteins. and is postulated to participate in cell migration and adhesion. Expression of Cd9 enhances membrane fusion between muscle cells and promotes viral infection in some cells. Fertilization also involves membrane fusion, between gametes. In mammals, the sperm binds to microvilli on the egg surface, and sperm-egg membrane fusion first occurs around the equatorial region of the sperm head12. The fused membrane is then disrupted, and the sperm nucleus as well as the cytoplasm is incorporated into the egg. Cd9 is expressed on the plasma membrane of the mouse egg, and an anti-Cd9 monoclonal antibody inhibits sperm-egg surface interactions. We generated Cd9 mice and found that homozygous mutant females were infertile. Sperm-egg binding was normal, but sperm-egg fusion was almost entirely inhibited in eggs from Cd9 females. Intracellular Ca2 oscillations, which signal fertilization, were absent in almost all mutant eggs; in rare cases, a response occurred after a long time period. In normal animals, Cd9 molecules were expressed on the egg microvilli and became densely concentrated at the sperm attachment site. Thus, our results show that Cd9 is important in the gamete fusion process at fertilization.

Glasses for Photonics

Abstract: 1 Glass properties 2 Gradient index glass 3 Laser glass 4 Nonlinear optical glass 5 Magneto-optical glass

SINE insertions: powerful tools for molecular systematics.

Abstract: Short interspersed repetitive elements, or SINEs, are tRNA-derived retroposons that are dispersed throughout eukaryotic genomes and can be present in well over 10(4) total copies. The enormous volume of SINE amplifications per organism makes them important evolutionary agents for shaping the diversity of genomes, and the irreversible, independent nature of their insertion allows them to be used for diagnosing common ancestry among host taxa with extreme confidence. As such, they represent a powerful new tool for systematic biology that can be strategically integrated with other conventional phylogenetic characters, most notably morphology and DNA sequences. This review covers the basic aspects of SINE evolution that are especially relevant to their use as systematic characters and describes the practical methods of characterizing SINEs for cladogram construction. It also discusses the limits of their systematic utility, clarifies some recently published misunderstandings, and illustrates the effective application of SINEs for vertebrate phylogenetics with results from selected case studies. BioEssays 22:148-160, 2000.

Exploiting Sparsity in Semidefinite Programming via Matrix Completion I: General Framework

Abstract: A critical disadvantage of primal-dual interior-point methods compared to dual interior-point methods for large scale semidefinite programs (SDPs) has been that the primal positive semidefinite matrix variable becomes fully dense in general even when all data matrices are sparse. Based on some fundamental results about positive semidefinite matrix completion, this article proposes a general method of exploiting the aggregate sparsity pattern over all data matrices to overcome this disadvantage. Our method is used in two ways. One is a conversion of a sparse SDP having a large scale positive semidefinite matrix variable into an SDP having multiple but smaller positive semidefinite matrix variables to which we can effectively apply any interior-point method for SDPs employing a standard block-diagonal matrix data structure. The other way is an incorporation of our method into primal-dual interior-point methods which we can apply directly to a given SDP. In Part II of this article, we will investigate an implementation of such a primal-dual interior-point method based on positive definite matrix completion, and report some numerical results.

Photocrosslinkable chitosan as a biological adhesive.

Abstract: A photocrosslinkable chitosan to which both azide and lactose moieties were introduced (Az-CH-LA) was prepared as a biological adhesive for soft tissues and its effectiveness was compared with that of fibrin glue. Introduction of the lactose moieties resulted in a much more water-soluble chitosan at neutral pH. Application of ultraviolet light (UV) irradiation to photocrosslinkable Az-CH-LA produced an insoluble hydrogel within 60 s. This hydrogel firmly adhered two pieces of sliced ham with each other, depending upon the Az-CH-LA concentration. The binding strength of the chitosan hydrogel prepared from 30-50 mg/mL of Az-CH-LA was similar to that of fibrin glue. Compared to the fibrin glue, the chitosan hydrogel more effectively sealed air leakage from pinholes on isolated small intestine and aorta and from incisions on isolated trachea. Neither Az-CH-LA nor its hydrogel showed any cytotoxicity in cell culture tests of human skin fibroblasts, coronary endothelial cells, and smooth muscle cells. Furthermore, all mice studied survived for at least 1 month after implantation of 200 microL of photocrosslinked chitosan gel and intraperitoneal administration of up to 1 mL of 30 mg/mL of Az-CH-LA solution. These results suggest that the photocrosslinkable chitosan developed here has the potential of serving as a new tissue adhesive in medical use.

Identification of an imprinted gene, Meg3/Gtl2 and its human homologue MEG3, first mapped on mouse distal chromosome 12 and human chromosome 14q.

Abstract: Background The paternal duplication of mouse distal chromosome 12 leads to late embryonal/neonatal lethality and growth promotion, whereas maternal duplication leads to late embryonal lethality and growth retardation. Human paternal or maternal uniparental disomies of chromosome 14q that are syntenic to mouse distal chromosome 12 have also been reported to show some imprinting effects on growth, mental activity and musculoskeletal morphology. For the isolation of imprinted genes in this region, a systematic screen of maternally expressed genes (Megs) was carried out by our subtraction-hybridization method using androgenetic and normally fertilized embryos. Results We have isolated seven candidate clones of the mouse Meg gene. Among them, we identified a novel maternally expressed imprinted gene, Meg3, on mouse distal chromosome 12 and showed that it was identical to the Gtl2 gene. We also found that the human homologue MEG3 on chromosome 14q was also monoallelically expressed. Conclusions This is the first identification of the imprinting gene, both on mouse distal chromosome 12 and on human chromosome 14q, respectively. Because there are no obvious open reading frames in either the mouse Meg3/Gtl2 or human MEG3, the function of these genes remains unclear. However, this result will provide a good basis for the further investigation of several important imprinted genes in this chromosomal region.

Constraining the atmospheric N 2 O budget from intramolecular site preference in N 2 O isotopomers

Abstract: Nitrous oxide (N2O) is an important trace gas in the atmosphere. It is an active greenhouse gas in the troposphere and it also controls ozone concentration in the stratosphere through nitric oxide production1. One way to trace the geochemical cycle of N2O is by measuring the natural abundance of stable isotopes, namely 15N and 18O (refs 2,3,4,5,6,7,8,9,10,11, 12,13,14,15). Here we report the intramolecular distribution of 15N within the linear NNO molecule, determined by measuring molecular and fragment ions of N2O on a modified mass spectrometer. This revealed a preference for 15N at the central N position, or α-site, within N2O isotopomers (isotope-containing molecules). Moreover, this preference varied significantly throughout the atmosphere. In the troposphere, low α-site preference indicates local emission of N2O from soils and fossil-fuel combustion, each with distinct isotopomer signatures, which then mixes with background N2O. In the stratosphere, on the other hand, loss of N2O is observed as enhanced α-site preference for 15N, due to fractionation during ultraviolet photolysis of N2O. We have constructed an atmospheric mass balance of N2O, incorporating isotopomer abundance, which shows that the intramolecular distribution of 15N is a parameter that has the potential to increase significantly the resolution with which sources and sinks of N2O can be identified and quantified in the atmosphere.

Selective Hydrogenation of Acetylene over Au/Al2O3 Catalyst

Abstract: The hydrogenation of acetylene and ethylene was studied on Au/Al2O3 catalyst. Acetylene and hydrogen reacted readily to produce ethylene, but not to ethane on the catalyst in the temperature range between 313 and 523 K. The hydrogenation of ethylene on the catalyst occurred only at much higher temperatures over 573 K. The activity of the selective hydrogenation of acetylene over Au/Al2O3 catalyst depends on the size of ultrafine gold particles of Au/Al2O3 catalyst, which showed a maximum at about 3.0 nm in diameter.

Disordered magnetism at the metal-insulator threshold in nano-graphite-based carbon materials

Abstract: The magnetism of activated carbon fibers composed of a disorder network of nanographites was investigated, where each nanographite has about 1 edge-inherited localized spin. The susceptibility, for samples situated around the metal-insulator threshold, shows a cusp around 4-7 K in addition to the presence of a field-cooling effect. These behaviors are explained in terms of disordered magnetism caused by random strengths of inter-nano-graphite antiferromagnetic interactions mediated by pi-conduction carriers.

Steady hydrogen evolution from water on Eosin Y-fixed TiO2 photocatalyst using a silane-coupling reagent under visible light irradiation

Abstract: A chemical fixation of xanthene dyes on platinized TiO 2 particles via silane-coupling reagent was attempted in order to construct a stable dye-sensitized photocatalyst system in water. The Eosin Y fixed Pt-TiO 2 (E.Y-TiO 2 ) exhibited steady H 2 production from aqueous triethanolamine solution (TEOA aq.) under visible light irradiation for long time, and the H 2 evolution reproduced even after the exchange of TEOA aq., while the H 2 evolution from the mixture of Eosin Y (E.Y) and Pt-TiO 2 ceased in 10 h. The turnover number of the dye molecule fixed on TiO 2 surface reached more than 10,000, and the quantum yield of the E.Y-TiO 2 at 520 nm was determined to be about 10%.

Topological approach to Luttinger's theorem and the fermi surface of a kondo lattice

Abstract: A nonperturbative proof of Luttinger's theorem, based on a topological argument, is given for Fermi liquids in arbitrary dimensions. Application to the Kondo lattice shows that even completely localized spins contribute to the Fermi sea volume as electrons, whenever the system can be described as a Fermi liquid.