Showing papers by "Waseda University published in 1994"

The Effects of Simplified and Elaborated Texts on Foreign Language Reading Comprehension

Abstract: Linguistic simplification of written texts can increase their comprehensibility for nonnative speakers but reduce their utility for language learning in other ways, for example, through the removal of linguistic items that learners do not know but need to learn. This study was conducted to test the hypothesis that elaborative modification observed in oral foreigner talk discourse, where redundancy and explicitness compensate for unknown linguistic items, offers a potential alternative approach to written text modification. We randomly presented 13 reading passages to 483 Japanese college students in one of three forms: (a) native baseline, (b) simplified, or (c) elaborated. Comprehension, assessed by 30 multiple-choice test items, was highest among learners reading the simplified version, but not significantly different from those reading the elaborated version. The type of modifications to the texts interacted significantly with the kind of test item used to, assess comprehension—replication, synthesis or inference—suggesting that different kinds of text modification facilitate different levels of comprehension.

Electronic states of the pristine and alkali-metal-intercalated monolayer graphite/Ni(111) systems

Abstract: The electronic states of the pristine and alkali-metal-intercalated monolayer graphite (MG)/Ni(111) systems are investigated by using angle-resolved ultraviolet photoelectron spectroscopy and x-ray-photoelectron spectroscopy (XPS). The electronic structure of the MG is modified largely by hybridization of the \ensuremath{\pi} orbitals of the graphite layer with the d orbitals of the substrate. The deposition of alkali-metal atoms onto the graphite overlayer at room temperature results in the penetration of the adsorbates into the interface between the MG and the Ni(111) surface. This intercalation causes the change in the band structure of the system because of the dilation of the MG-Ni interlayer distance. The intercalation of the alkali-metal atoms also shows the broadening of the XPS peak of the C 1s core level of the MG.

Neutron-scattering study of the spin-state transition and magnetic correlations in La1-xSrxCoO3 (x=0 and 0.08)

Abstract: ${\mathrm{LaCoO}}_{3}$ exhibits two magnetic-electronic transitions, one near 90 K and a second near 500 K. A previous study of the paramagnetic scattering using polarized neutrons demonstrated that the low-temperature transition is associated with the thermal excitation of ${\mathrm{Co}}^{3+}$ ions from the low-spin to the high-spin state. In the present work, we extend the paramagnetic-scattering measurements up to a temperature of 700 K. We find that the magnetic-scattering intensity decreases monotonically for temperatures above 300 K, indicating that the high-temperature transition is not dominantly magnetic in origin. Furthermore, the anomalous thermal expansion associated with the low-temperature transition is measured and shown to be consistent with a simple theoretical model for the spin-state transition. For comparison, paramagnetic-scattering measurements for ${\mathrm{La}}_{0.92}$${\mathrm{Sr}}_{0.08}$${\mathrm{CoO}}_{3}$ are also presented. In this material the ferromagnetic correlations are substantially stronger than in the undoped compound, and no transition to the low-spin state is observed. Instead, the paramagnetic scattering increases steadily with decreasing temperature until saturating below 24 K, the same temperature at which the magnetization of the zero-field-cooled specimen shows a sharp cusp. These results suggest that the magnetic moments in the doped compound freeze into a spin-glass state at low temperature.

An efficient maximum-likelihood-decoding algorithm for linear block codes with algebraic decoder

Abstract: A new soft decoding algorithm for linear block codes is proposed. The decoding algorithm works with any algebraic decoder and its performance is strictly the same as that of maximum-likelihood-decoding (MLD). Since our decoding algorithm generates sets of different candidate codewords corresponding to the received sequence, its decoding complexity depends on the received sequence. We compare our decoding algorithm with Chase (1972) algorithm 2 and the Tanaka-Kakigahara (1983) algorithm in which a similar method for generating candidate codewords is used. Computer simulation results indicate, for some signal-to-noise ratios (SNR), that our decoding algorithm requires less average complexity than those of the other two algorithms, but the performance of ours is always superior to those of the other two. >

Decreased synaptic density in aged brains and its prevention by rearing under enriched environment as revealed by synaptophysin contents

Abstract: Changes in synaptic density in various brain regions were assessed among different age groups of rats maintained in ordinary small cages, as determined by synaptophysin assay. The synaptophysin content in hippocampus decreases as early as in the adult stage. The most remarkable decrement occurs in occipital cortex. In other regions, synaptophysin contents decrease in senescence to 60–77% of the respective peak values during young and adult stages. The other rat group reared under enriched environment in a large cage until 30 months of age was examined for synaptic density, and was revealed to maintain the similar levels as in young, or even higher levels in frontal, temporal, entorhinal cortices and hippocampus. These results indicate that the synaptic density in cerebrum decreases in senescence and this decrease can be prevented by rearing under enriched environment. © 1994 Wiley-Liss, Inc.

Asymptotic stability of traveling waves for scalar viscous conservation laws with non-convex nonlinearity

Abstract: The asymptotic stability of traveling wave solutions with shock profile is considered for scalar viscous conservation lawsu t +f(u) x =μu xx with the initial datau 0 which tend to the constant statesu ± asx→±∞. Stability theorems are obtained in the absence of the convexity off and in the allowance ofs (shock speed)=f′(u ±). Moreover, the rate of asymptotics in time is investigated. For the casef′(u+)

Decay kinetics of the 4.4-eV photoluminescence associated with the two states of oxygen-deficient-type defect in amorphous SiO2.

Abstract: We present the first observation of 4.4 eV photoluminescence (PL) decay in an oxygen-deficient-type silica excited with ultraviolet and vacuum ultraviolet photons from synchrotron radiation. The lifetime of the 4.4 eV PL is 4.2, 4.3, and 2.1 ns for the 5.0, 6.9, and 7.6 eV excitations, respectively, indicating the presence of multiple decay channels. This can be explained by an energy diagram involving the interconversion between two states of the oxygen-deficient-type defect.

Interaction of PbTiO3 Films with Si Substrate

Abstract: An investigation was made of the reasons why ferroelectric PbTiO3 films are hard to grow on single-crystal Si substrates. PbTiO3 films were formed on Si(100) and MgO(100) single-crystal substrates, and X-ray photoelectron spectroscopy (XPS) was used to analyze the composition, chemical structure and oxidation state at the interface between the substrate and the film. It was found that lead, oxygen and silicon diffused markedly at the interface and that the PbTiO3 film experienced both a lead deficiency and Si diffusion. These phenomena are thought to be the reasons why it is difficult to form good PbTiO3 films on silicon substrates by chemical vapor deposition (CVD). It was observed that the addition of TiO2 and ZrO2 films at the interface with the silicon substrate reduced the diffusion of Si to the PbTiO3 film.

Formation of Polyelectrolyte Complexes and Their Structures

Abstract: When a polycation and a polyanion are mixed together in an aqueous solution, a polyelectrolyte complex is formed. In general, an equimolar complex is formed by mixing oppositely charged strong polyelectrolytes. However, integral-type polycations provide nonstoichiometric complexes. In the case of the complexation of polycations with weak polyacids, the composition and the structure of the polyelectrolyte complexes obtained depend on the degree of neutralization of the polyacid, polymer structure, hydrophobicity, the concentration of the complex, pH, ionic strength, and so on. Complex formation proceeds cooperatively, and the stability constant increases with the degree of polymerization, i.e., the charge number on one chain. When a polyelectrolyte is added to the polymer complex, a cooperative interpolymer substitution occurs if the adding polymer can interact more strongly with the constituent of the complex. The process of polyelectrolyte complex leading to the supermolecular structure can be d...

A beat tracking system for acoustic signals of music

Abstract: This paper presents a beat tracking system that processes acoustic signals of music and recognizes temporal positions of beats in time. Musical beat tracking is needed by various multimedia applications such as video editing, audio editing, and stage lighting control. Previous systems were not able to deal with acoustic signals that contained sounds of various instruments, especially drums. They dealt with either MIDI signals or acoustic signals played on a few instruments, and in the latter case, did not work in real time. Our system deals with popular music in which drums maintain the beat. Because our system examines multiple hypotheses in parallel, it can follow beats without losing track of them, even if some hypotheses become wrong. Our system has been implemented on a parallel computer, the Fujitsu AP1000. In our experiment, the system correctly tracked beats in 27 out of 30 commercially distributed popular songs.

A Synthetic Hydrogel with Thermoreversible Gelation. I. Preparation and Rheological Properties

Abstract: Block copolymers composed of poly(N-isopropylacrylamide-co-n-butyl methacrylate) [poly(NIPAAm-co-BMA)] and poly(ethylene glycol) (PEG) were prepared. Aqueous solutions of the block copolymers were characterized by dynamic viscoelastic measurement as a function of temperature. The fluid solutions turned into hydrogels upon heating while keeping their transparency and without syneresis. The hydrogels turned back into solutions upon cooling. The thermoreversible sol-gel transition was observed with no hysteresis. The sol-gel transition temperatures were closely correlated to the lower critical solution temperature of the poly(NIPAAm-co-BMA) in the block copolymers. Gelation is believed to be caused by thermoreversible crosslinkages between intermolecular poly(NIPAAm-co-BMA) blocks due to hydrophobic interaction.

Dynamical quantum Zeno effect

Abstract: A purely dynamical explanation for the quantum Zeno effect is proposed. It is argued that a quantum system undergoes a quantum-Zeno-type dynamics as a consequence of a particular type of evolution involving a series of frequent spectral decompositions. The role of quantum measurements and of the ``collapse of the wave function'' is investigated and it is clarified that, provided a final observation is performed, the dynamical quantum Zeno effect can be obtained without making use of von Neumann's projection postulate. The meaning of infinitely frequent measurements is critically discussed and it is argued that it should be regarded as a mathematical idealization, impossible to realize from a physical point of view.

Formation of Metal/Ferroelectric/Insulator/Semiconductor Structure with a CeO2 Buffer Layer

Abstract: Experimental results derived from the capacitance vs voltage (C-V) characteristics of metal/ferroelectric/insulator/semiconductor (MFIS) structures are described. PbTiO3 ferroelectric films of 600 A thickness were grown on CeO2/Si(100) substrate by digital chemical vapor deposition (digital CVD). As the buffer layer between ferroelectric and Si substrate, 150-A-thick CeO2 intermediate epitaxial layers were grown on a (100) silicon substrate by vacuum evaporation. The density of surface states at the CeO2/Si(100) interface was estimated from the C-V characteristics of Al/ CeO2/Si(100) samples to be ~1011/cm2 eV. Epitaxial CeO2 films on Si(100) would therefore be expected to function as the gate oxide for MFS-FET's. Furthermore, the MFIS structure has ferroelectric switching properties, as demonstrated by the roughly 1-V threshold hysleresis in C-V characteristics. This structure is thus a first step toward high-performance MFIS-FET's.

Development of a biped walking robot adapting to a horizontally uneven surface

Abstract: In this paper, as the first stage of biped walking adapting to an uneven surface using an anthropomorphic biped walking robot, the authors introduce a biped walking control method for adapting to a surface that is called a horizontally composed (HC) plane whose step height is unknown, and a special foot mechanism which is capable of shock absorbtion. The authors developed an anthropomorphic biped walking robot with a foot mechanism and performed walking experiments with the robot using the control method. As a result, adaptive dynamic biped walking over a step of unknown height was realized. The maximum walking speed was 0.96 sec per step with a 0.3 m step length, and the greatest step height was 12 mm. The authors believe that the adaptability is integral to an anthropomorphic robot that will support human living in the near future. The authors call the robot Humanoid. >

Spectral analysis of electromyogram in lumbar muscles: fatigue induced endurance contraction.

Abstract: In the last few years, epidemiological studies have shown correlations between the low endurance capacity of the erector spinae muscle and low back pain (LBP) In this study, the function of the erector spinae muscle and localized muscle fatigue in LBP were investigated in both LBP patients and control subjects without LBP, using surface multi-channel electromyograms (EMG) Four positions (L1, L2, L4, L5) were chosen as representative locations for the different functions of the erector spinae muscle Median frequency (fm) parameters of an EMG power density spectrum were monitored to quantify localized muscle fatigue This research indicated a statistically significant difference (P < 005) in fm, parameters between the LBP patients and the control subjects The integrated electromyogram (iEMG) signals of LBP patients were considerably higher than for the control subjects during endurance isometric contraction Our research suggested that human fatiguing erector spinae muscle, in submaximal voluntary contractions tests, induced a different firing order of motor unit spikes between two groups

Change in the electronic states of graphite overlayers depending on thickness

Abstract: Electronic states of graphite overlayers formed on the TaC(111) surface have been investigated with the use of scanning tunneling microscopy and photoelectron spectroscopy. The graphite film grows on the substrate layer by layer. The thickness of the overlayer has been adjusted precisely to be either one or two monolayers. The physical properties of the monolayer graphite film are modified by chemical bonding at the interface. This interfacial bonding becomes weak upon the formation of the second layer of graphite, which makes the properties of the double-layer graphite film similar to those of bulk graphite.

Stability control for a mobile manipulator using a potential method

Abstract: Many future applications of robotic systems will require that manipulators perform operations while being carried by moving vehicles. However, such a vehicle mounted mobile manipulator can be unstable or even tip over. Previous work on stability control hardly considered the dynamics and environmental disturbances. The stability of a mobile manipulator has a close relation with the vehicle motion, manipulator motion and posture, and end-effector force. To evaluate the stability for a mobile manipulator, the concepts about stability, such as the stability degree and the valid stable region based on the zero moment point (ZMP) criterion have already been proposed. In this paper, as a control scheme for maintaining or recovering stability, the method of ZMP path planning by a stability potential field is presented, in which the concepts of the goal state and prohibitive state of stability are outlined. A motion planning algorithm is then formulated, which controls the manipulator in order to maintain the stability of the whole system while the vehicle is moving along a given trajectory. >

Dielectric Relaxation and Hopping of Electrons in ErFe2O4

Abstract: We report the frequency and the temperature dependence of the dielectric constant of polycrystalline ErFe 2 O 4-δ with different degrees of oxygen deficiency δ. A large dielectric relaxation, with the order of magnitude of 10 4 and nearly of the Debye type, is observed in the magnetically ordered states within the temperature and frequency ranges of 150 K to 290 K and 1 kHz to 3 MHz, respectively. The dispersion is larger in the sample with more oxygen deficiency. From the temperature dependence of the characteristic frequency, we conclude that the elementary process of the dispersion is related to electron hopping between Fe 2+ and Fe 3+ ions. A large value of the dielectric constant is consistent with the existence of spontaneous polarization in the magnetic phases of this oxide. We propose that the motion of the polarization domain boundaries is a determining factor of low-frequency dielectric constant.

Stepwise Motion of an Actin Filament over a Small Number of Heavy Meromyosin Molecules Is Revealed in an In Vitro Motility Assay.

Abstract: In order to determine the relative motions of an actin filament and a myosin molecule upon hydrolysis of one ATP, an in vitro motility assay, in which individual actin filaments slide over heavy meromyosin molecules bound to a substrate, was combined with an optical trapping technique. An actin filament, attached to a gelsolin-coated bead, was captured with an optical trap. The surface-bound heavy meromyosin molecules pulled the filament against the trapping force, which resulted in back and forth motions of the actin-bound bead. The number of heavy meromyosin molecules interacting with an actin filament (at most 1/micron filament) and the ATP concentration (< or = 0.5 microM) were chosen so as to facilitate detection of each "pull." Calculation of the centroid of the bead image revealed abrupt displacements of the actin filament. The frequency of such displacements was between 0.05 and 0.1 per 1 s per 1 micron actin filament, being consistent with calculated values based on the reported bimolecular binding constants of ATP and the actomyosin rigor complex. The distribution of the displacements peaked around 7 nm at a trapping force of 0.016 pN/nm, but it became broader, and some displacements were as large as 30 nm, when the trapping force was reduced to 0.0063 pN/nm, suggesting that the force generation due to the structural change of a myosin head may be insufficient to explain such displacements.

Preparation and Properties of Ru and RuO2 Thin Film Electrodes for Ferroelectric Thin Films

Abstract: Ru and RuO2 thin films were prepared by RF magnetron sputtering. The crystalline structure and electrical properties of these films were investigated. Reactive sputtering of a ruthenium metal target was carried out in a mixed gas of argon and oxygen at 580° C. Total pressure (P O2 +P Ar) was controlled to maintain a constant pressure of 1 Pa. The RuO2 single phase could be obtained when P O2 was 0.5 Pa and the deposition rate was about 30 nm/min. The resistivity of the 290 nm-thick RuO2 thin films deposited on SiO2(1000 nm)/Si was 54.9 µ Ω cm. However, the resistivity increased with decreasing film thickness. Fatigue resistance of (Pb, La)TiO3 thin films with RuO2 as top and bottom electrodes was improved compared to the films on Pt electrodes.

Synthesis and characterization of highly ordered mesoporous material; FSM-16, from a layered polysilicate

Abstract: Development of preparation conditions of highly ordered mesoporous SiO2materials(FSM-16) derived from a layered polysilicate has been summarized and a “folded sheets: mechanism for their formation has been presented. When Na ions in the interlayer region of kanemite were exchanged for alkyltrimethylammonium ions, organoammonium/silicate complexes were obtained and mesoporous silica materials were prepared by calcination of those complexes. When the exchange reaction was carried out at a relatively low pH(∼8.5), the exchange ratio was low and highly ordered pore structures of the mesoporous silica could not be confirmed although the formation of uniform pore size was realized. Increasing the pH(∼11.5) improved the exchange ratio and consequently realized highly porous materials with a regular hexagonal array of uniform channels. The condition of high pH(>11.5) increased a fraction of dissolved silica species. Removal of the dissolved species from the system was necessary to prepare pure FSM-16. The improvement of the reguarlity and purity of FSM-16 by increasing the pH and filtration supported the “folded sheets” mechanism for its formation. The Q4/Q3ratios of SiO4tetrahedra in the silicate/organic complexes prepared by the optimum procedure were in good agreement with those calculated by the folded sheets model and the observed N2absorption behavior suggested an uniform pore-size of FSM-16.