Showing papers by "University of Tokyo published in 1991"
TL;DR: In this paper, a rhombohedral (Fα)-tetragonal (Fβ) morphotropic phase boundary (MPB) is shown to exist at x=0.06~0.07 by X-ray data, and dielectric and piezoelectric properties are investigated.
Abstract: One of the (Bi1/2Na1/2)TiO3 (BNT)-based solid solutions, Ba-modified bismuth sodium titanate, (Bi1/2Na1/2)1-xBaxTiO3 (BNBT), is studied for its dielectric and piezoelectric properties as a new group of lead-free piezoelectric ceramics. A rhombohedral (Fα)-tetragonal (Fβ) morphotropic phase boundary (MPB) is shown to exist at x=0.06~0.07 by X-ray data, and dielectric and piezoelectric properties. BNBT ceramics with the MPB composition are superior as piezoelectric ceramics in high-frequency ultrasonic applications or as piezoelectric actuator materials because of a lower free permittivity, e33T/e0, and a high electromechanical coupling factor, kt or k33, along with high mechanical strength.
1,897 citations
TL;DR: It is found that apo E immunoreactivity was associated with amyloid in both senile plaques and cerebral vessels and neurofibrillary tangles in Creutzfeldt-Jakob disease.
1,170 citations
TL;DR: This transgenic animal model appears ideal for defining the molecular events that follow the expression of the viral HBx gene and are responsible for the development of liver cancer.
Abstract: The exact role of hepatitis B virus in the development of liver cancer is not known The recent identification of a viral regulatory gene HBx suggests a possible direct involvement of the virus whereby the HBx protein, acting as a transcriptional transactivator of viral genes, may alter host gene expression and lead to the development of hepatocellular carcinoma We have tested this possibility of placing the entire HBx gene under its own regulatory elements directly into the germline of mice Transgenic animals harbouring this viral gene succumbed to progressive histopathological changes specifically in the liver, beginning with multifocal areas of altered hepatocytes, followed by the appearance of benign adenomas, and proceeding to the development of malignant carcinomas Male mice developed disease and died much earlier than females This transgenic animal model appears ideal for defining the molecular events that follow the expression of the viral HBx gene and are responsible for the development of liver cancer
1,118 citations
TL;DR: A new principle of sensorimotor control of legged locomotion in an unpredictable environment is proposed on the basis of neurophysiological knowledge and a theory of nonlinear dynamics by investigating the performance of a bipedal model investigated by computer simulation.
Abstract: A new principle of sensorimotor control of legged locomotion in an unpredictable environment is proposed on the basis of neurophysiological knowledge and a theory of nonlinear dynamics. Stable and flexible locomotion is realized as a global limit cycle generated by a global entrainment between the rhythmic activities of a nervous system composed of coupled neural oscillators and the rhythmic movements of a musculo-skeletal system including interaction with its environment. Coordinated movements are generated not by slaving to an explicit representation of the precise trajectories of the movement of each part but by dynamic interactions among the nervous system, the musculo-skeletal system and the environment. The performance of a bipedal model based on the above principle was investigated by computer simulation. Walking movements stable to mechanical perturbations and to environmental changes were obtained. Moreover, the model generated not only the walking movement but also the running movement by changing a single parameter nonspecific to the movement. The transitions between the gait patterns occurred with hysteresis.
1,042 citations
TL;DR: The Soft X-ray Telescope (SXT) of the SOLAR-A mission is designed to produce images of solar flares with excellent angular and time resolution as well as full-disk images for general studies.
Abstract: The Soft X-ray Telescope (SXT) of the SOLAR-A mission is designed to produce X-ray movies of flares with excellent angular and time resolution as well as full-disk X-ray images for general studies. A selection of thin metal filters provide a measure of temperature discrimination and aid in obtaining the wide dynamic range required for solar observing. The co-aligned SXT aspect telescope will yield optical images for aspect reference, white-light flare and sunspot studies, and, possibly, helioseismology. This paper describes the capabilities and characteristics of the SXT for scientific observing.
1,009 citations
TL;DR: Established parental tumors could be cured by the systemic immune response generated by injection of the genetically engineered tumors by providing a rationale for the use of lymphokine gene-transfected tumor cells as a modality for cancer therapy.
Abstract: The generation of antigen-specific antitumor immunity is the ultimate goal in cancer immunotherapy. When cells from a spontaneously arising murine renal cell tumor were engineered to secrete large doses of interleukin-4 (IL-4) locally, they were rejected in a predominantly T cell-independent manner. However, animals that rejected the IL-4-transfected tumors developed T cell-dependent systemic immunity to the parental tumor. This systemic immunity was tumor-specific and primarily mediated by CD8+ T cells. Established parental tumors could be cured by the systemic immune response generated by injection of the genetically engineered tumors. These results provide a rationale for the use of lymphokine gene-transfected tumor cells as a modality for cancer therapy.
764 citations
TL;DR: Two types of task-related neurons in the anterior temporal cortex are found, which provide new evidence that single neurons acquire selectivity for visual patterns through associative learning and indicate neural mechanisms for storage and retrieval in the long-term memory of paired associates.
Abstract: Most of our long-term memories of episodes or objects are organized so that we can retrieve them by association. Clinical neuropsychologists assess human memory by the paired-associate learning test, in which a series of paired words or figures is presented and the subject is then asked to retrieve the other pair member associated with each cue. Patients with lesions of the temporal lobe show marked impairment in this test. In our study, we trained monkeys in a pair-association task using a set of computer-generated paired patterns. We found two types of task-related neurons in the anterior temporal cortex. One type selectively responded to both pictures of the paired associates. The other type, which had the strongest response to one picture during the cue presentation, exhibited increasing activity during the delay period when the associate of that picture was used as a cue. These results provide new evidence that single neurons acquire selectivity for visual patterns through associative learning. They also indicate neural mechanisms for storage and retrieval in the long-term memory of paired associates.
735 citations
TL;DR: In this paper, a robust speed control system for DC servomotors based on the parametrization of two-degree-of-freedom controllers is proposed, which can dramatically improve the characteristics of the closed loop systems, i.e., the disturbance torque suppression performance and the robustness to system parameter variations, without changing the command input response.
Abstract: The authors propose a robust speed control system for DC servomotors based on the parametrization of two-degree-of-freedom controllers. The servosystems can dramatically improve the characteristics of the closed loop systems, i.e. the disturbance torque suppression performance and the robustness to system parameter variations, without changing the command input response. The excellent control performances obtained during laboratory experiments by using a microprocessor-based controller are shown. >
701 citations
TL;DR: The purified and characterized growth inhibitory factor (GIF) revealed a distinct subset of astrocytes in the gray matter that appears to be closely associated with neuronal perikarya and dendrites during AD, suggesting that GIF is down-regulated in the subset of Astrocytes during AD.
673 citations
TL;DR: The resulting spectrum in the high-{ital T}{sub {ital c}} regime is suggestive of a strongly itinerant character of the state in the moderately doped CuO{sub 2} plane while appreciable weight remains in the charge-transfer energy region.
Abstract: Optical reflectivity spectra are studied for single crystals of the prototypical high-${\mathit{T}}_{\mathit{c}}$ system ${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_{4}$ over a wide compositional range 0\ensuremath{\le}x\ensuremath{\le}0.34, which covers insulating, superconducting, and normal metallic phases. The measurements are made at room temperature over an energy range from 0.004 to 35 eV for the polarization parallel to the ${\mathrm{CuO}}_{2}$ planes. They are also extended to the perpendicular polarization to study anisotropy and to discriminate the contribution from the ${\mathrm{CuO}}_{2}$ plane. The present study focuses on the x dependence of the optical spectrum, which makes it possible to sort out the features of the excitations in the ${\mathrm{CuO}}_{2}$ plane and thus to characterize the electronic structure of the ${\mathrm{CuO}}_{2}$ plane in the respective phase. Upon doping into the parent insulator ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$ with a charge-transfer energy gap of about 2 eV the spectral weight is rapidly transferred from the charge-transfer excitation to low-energy excitations below 1.5 eV. The low-energy spectrum is apparently composed of two contributions; a Drude-type one peaked at \ensuremath{\omega}=0 and a broad continuum centered in the midinfrared range. The high-${\mathit{T}}_{\mathit{c}}$ superconductivity is realized as doping proceeds and when the transfer of the spectrum weight is saturated. The resulting spectrum in the high-${\mathit{T}}_{\mathit{c}}$ regime is suggestive of a strongly itinerant character of the state in the moderately doped ${\mathrm{CuO}}_{2}$ plane while appreciable weight remains in the charge-transfer energy region. The spectrum exhibits a second drastic change for heavy doping (x\ensuremath{\sim}0.25) corresponding to the superconductor-to-normal-metal transition and becomes close to that of a Fermi liquid. The results are universal for all the known cuprate superconductors including the electron-doped compounds, and they reconcile the dc transport properties with the high-energy spectroscopic results.
672 citations
TL;DR: 1. PERSPECTIVES and SUMMARy .
Abstract: 1. PERSPECTIVES AND SUMMARy . . . . . . . . . . 350 II . INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 1 III. GENERAL CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354 Tra nslational Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... . . . . . . . . . . 354 Heterotrimeric G Protein s . . . . . . . . . . ... . . ... . ... . . . .... . . .. . . . . . . . . . . . . . . . . . . . . . . . 356 Ras Protein s . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . ... . . . . . . . . . . .. 357 Structu ral Simi/aritie s Be t ween Vari ou s G TP-Binding Protein s. . . . . . . . . . . . . . . . . 359 IV . MAMMALIAN G PRO TEINS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363 M olecular Entitie s and Gene Organizations of G P rotein s . . . . . . . . . . .... . . . . . . . . . . . ... 363 O verall Stru ctu re of G P rotein a-Su bunits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368 Structu re -Function Relation s hip of G P rotein a-Subunits . . . . . . . . . . . . . . . ... . . .. . . . .. . . . 368 Structure of fly-Subunits of G Protein . . . . . . . . . . . .. . . . ... ..... . ... . . . . . . ... . . . ... . . . . . . . . 376
TL;DR: DUK-1 was designated as the alpha subunit of the hIL-3R, indicating that different alpha subunits compete for a common beta subunit in human interleukin-3 cells.
TL;DR: As a first approach to cloning lipid autacoid receptors, isolated complementary DNA for the PAF receptors is isolated and Sequence analysis indicates that the receptor belongs to the superfamily of G protein-coupled receptors.
Abstract: PLATELET-activating factor (PAF), a unique phospholipid mediator, possesses potent proinflammatory, smooth-muscle contractile and hypotensive activities, and appears to be crucial in the pathogenesis of bronchial asthma and in the lethality of endotoxin and anaphylactic shock1–3. Despite this, little is known of the molecular properties of the PAF receptor and related signal transduction systems. Although several lines of evidence suggest that activation of the PAF receptor stimulates phospholipase C and subsequent inositol trisphosphate formation through G protein(s)4,5, the PAF receptor and calcium channel are reported to show a close relation2,6. As a first approach to cloning lipid autacoid receptors, we have isolated complementary DNA for the PAF receptors. Our strategy involved gene expression in Xenopus laevis oocytes and electrophysiological detection of PAF-induced responses. Sequence analysis indicates that the receptor belongs to the superfamily of G protein-coupled receptors.
TL;DR: In this paper, the transition to a ferromagnetic long-range ordered state was found at 0.60 K in the orthorhombic β-phase crystal of p-nitrophenyl nitronyl nitroxide.
TL;DR: A method is described for the numerical calculations of the ballistic conductance in mesoscopic structures in magnetic fields within a lattice model that quantizes the conductance even when the confinement is not adiabatic and interchannel scatterings are still appreciable.
Abstract: A method is described for the numerical calculations of the ballistic conductance in mesoscopic structures in magnetic fields within a lattice model. Examples of calculated results are given for the conductance across a single quantum point contact and a series of two quantum point contacts. The conductance is quantized even when the confinement is not adiabatic and interchannel scatterings are still appreciable. The quantization becomes better in magnetic fields. In a series of two quantum point contacts, the magnetic field dependence of the conductance is strongly dependent on the channel number of both emitter and collector contacts.
TL;DR: Ascorbic acid may act as a prooxidant in vitro in the presence of metal, but this effect is unlikely to be important in vivo where metal ions are sequestered and other reductants are present.
TL;DR: Several amino acid residues in fusion peptides and receptor-binding sites were shown to be conserved among the 13 HA serotypes, and results show that the amino acid residue at position 226 is not necessarily a determinant of receptor specificity for all serotypes.
TL;DR: In this paper, a reexamination is conducted as to whether or not AIC occurs for the new models of O + Ne + Mg white dwarfs and solid C + O white- dwarfs that can ignite nuclear burning at significantly lower central densities than in the previous models.
Abstract: Recent discovery of an unexpectedly large number of low-mass binary pulsars (LMBPs) in globular clusters has instigated active discussions on the evolutionary origin of binary pulsars. Prompted by the possibility that at least some of LMBPs originate from accretion-induced collapse (AIC) of white dwarfs, a reexamination is conducted as to whether or not AIC occurs for the new models of O + Ne + Mg white dwarfs and solid C + O white dwarfs that can ignite explosive nuclear burning at significantly lower central densities than in the previous models. Even with low critical densities, AIC is still much more likely than explosion for both types of white dwarfs. Possible regions for AIC are presented in a diagram of mass accretion rate vs initial mass of the white dwarfs.
TL;DR: The findings suggest that mechanical stimuli (myocyte stretching) might directly induce cardiac hypertrophy and specific gene expression possibly via protein kinase C activation.
TL;DR: The Lyn protein and its kinase activity could be coimmunoprecipitated with IgM from detergent lysates and is suggested to participate in antigen-mediated signal transduction.
Abstract: Antigen is thought to cross-link membrane-bound immunoglobulins (Igs) of B cells, causing proliferation and differentiation or the inhibition of growth. Protein tyrosine kinases are probably involved in signal transduction for cell proliferation and differentiation. The Src-like protein tyrosine kinase Lyn is expressed preferentially in B cells. The Lyn protein and its kinase activity could be coimmunoprecipitated with IgM from detergent lysates. Cross-linking of membrane-bound IgM induced a rapid increase in tyrosine phosphorylation of at least ten distinct proteins of B cells. Thus, Lyn is physically associated with membrane-bound IgM, and is suggested to participate in antigen-mediated signal transduction.
TL;DR: It is shown that a Xenopus kinase is phosphorylated and activated during M phase of meiotic and mitotic cell cycles, and that the interphase–metaphase transition of microtubule arrays can be induced by the addition of purified Xenopus M phase-activated MAP kinase or mammalian mitogen-activatedMAP kinase to interphase extracts in vitro.
Abstract: The protein kinase MAP kinase, also called MAP2 kinase, is a serine/threonine kinase whose activation and phosphorylation are induced by a variety of mitogens, and which is thought to have a critical role in a network of protein kinases in mitogenic signal transduction. A burst in kinase activation and protein phosphorylation may also be important in triggering the dramatic reorganization of the cell during the transition from interphase to mitosis. The interphase-metaphase transition of microtubule arrays is under the control of p34cdc2 kinase, a central control element in the G2-M transition of the cell cycle. Here we show that a Xenopus kinase, closely related to the mitogen-activated mammalian MAP kinase, is phosphorylated and activated during M phase of meiotic and mitotic cell cycles, and that the interphase-metaphase transition of microtubule arrays can be induced by the addition of purified Xenopus M phase-activated MAP kinase or mammalian mitogen-activated MAP kinase to interphase extracts in vitro.
28 Sep 1991
TL;DR: In this paper, a speed estimation method for an induction machine and its application to a flux observer-based field orientation (FOFO) control system is presented, where the motor speed is estimated on the basis of the difference between two flux estimators.
Abstract: A speed estimation method for an induction machine and its application to a flux observer-based field orientation (FOFO) control system proposed previously is presented. The motor speed is estimated on the basis of the difference between two flux estimators. The convergence of the method is analyzed, and a novel pole assignment method is proposed. The speed estimator is applied to the FOFO controller. The system has been implemented using a DSP, and some laboratory experiments showing that the speed-sensorless FOFO operates with enough stability and has a strong robustness to rotor resistance variation are reported. >
TL;DR: The Hard X-ray Telescope (HXT) as mentioned in this paper is a Fourier-synthesis imager that takes images of solar flares simultaneously in four energy bands, nominally 15 (or 19) −24, 24 −35, 35 −57, and 57 −100 keV, with an ultimate angular resolution as fine as ∼ 5 arc sec and a time resolution 0.5 s.
Abstract: The Hard X-ray Telescope (HXT) is a Fourier-synthesis imager; a set of spatially-modulated photon count data are taken from 64 independent subcollimators and are Fourier-transformed into an image by using procedures such as the maximum entropy method (MEM) or CLEAN. The HXT takes images of solar flares simultaneously in four energy bands, nominally 15 (or 19)–24, 24–35, 35–57, and 57–100 keV, with an ultimate angular resolution as fine as ∼ 5 arc sec and a time resolution 0.5 s. Each subcollimator has a field of view wider than the solar disk. The total effective area of the collimator/detector system reaches ∼ 70 cm2, about one order of magnitude larger than that of the HINOTORI hard X-ray imager. Thanks to these improvements, HXT will for the first time enable us to take images of flares at photon energies above ∼ 30 keV. These higher-energy images will be compared with lower-energy ones, giving clues to the understanding of nonthermal processes in solar flares, i.e., the acceleration and confinement of energetic electrons. It is of particular importance to specify the acceleration site with regard to the magnetic field figuration in a flaring region, which will be achieved by collaborative observations between HXT and the Soft X-ray Telescope on board the same mission.
TL;DR: In this paper, a Morse-based coding system for representing the hierarchical structure of contours is presented, and the resulting coding works interactively with a range of surface reconstruction systems.
Abstract: Coding system requirements are briefly discussed. Classical Morse theory, which was primarily motivated by the calculus of variations, is reviewed. The limits of the theory are examined, and an extension that enables 3-D surfaces to be accurately reconstructed from cross sections is presented. The resulting coding works interactively with a range of surface reconstruction systems. The prototype coding system is applied to representing the hierarchical structure of contours. >
TL;DR: In this paper, it was shown that a higher-order nonlinear Schrodinger equation which describes propagation of pulses in optical fiber is solvable by means of the inverse scattering transform, which possesses a remarkable property that it can propagate steadily with two peaks of the same height.
Abstract: It is shown that a higher-order nonlinear Schrodinger equation which describes propagation of pulses in optical fiber is solvable by means of the inverse scattering transform. The soliton solution possesses a remarkable property that it can propagate steadily with two peaks of the same height.
TL;DR: Mitochondrial nucleoids (mt-nucleoids) of the A2780 line of cultured human cells were stained with DAPI and observed using an epifluorescence microscope and appeared to be organized compactly in mitochondria.
TL;DR: In this paper, the continuum Schwinger-Dyson equations for nonperturbative two-dimensional quantum gravity coupled to various matter fields are explicitly derived and turn out to be a formal Virasoro condition on the square root of the partition function, which is conjectured to be the τ function of the KdV hierarchy.
Abstract: We study the continuum Schwinger-Dyson equations for nonperturbative two-dimensional quantum gravity coupled to various matter fields. The continuum Schwinger-Dyson equations for the one-matrix model are explicitly derived and turn out to be a formal Virasoro condition on the square root of the partition function, which is conjectured to be the τ function of the KdV hierarchy. Furthermore, we argue that general multi-matrix models are related to the W algebras and suitable reductions of KP hierarchy and its generalizations.
TL;DR: In this paper, a local deformation transducer (LDT) was developed to investigate stiffness of soils that can be measured in the laboratory for strain levels ranging from 10-6 to 10-2.
TL;DR: There is a possibility that HTLV-I is one of the etiologic agents of chronic arthritis in humans, as observed in mice that developed chronic arthritis resembling rheumatoid arthritis.
Abstract: Human T cell leukemia virus type-I (HTLV-I) is the etiologic agent of adult T cell leukemia and has also been suggested to be involved in other diseases such as chronic arthritis or myelopathy. To elucidate pathological roles of the virus in disease, transgenic mice were produced that carry the HTLV-I genome. At 2 to 3 months of age, many of the mice developed chronic arthritis resembling rheumatoid arthritis. Synovial and periarticular inflammation with articular erosion caused by invasion of granulation tissues were marked. These observations suggest a possibility that HTLV-I is one of the etiologic agents of chronic arthritis in humans.