Showing papers by "Kyoto University published in 1985"

Manipulability of robotic mechanisms

Abstract: This paper discusses the manipulating ability of robotic mechanisms in positioning and orienting end-effectors and proposes a measure of manipulability. Some properties of this measure are obtained, the best postures of various types of manipulators are given, and a four-degree-of-freedom finger is considered from the viewpoint of the measure. The pos tures somewhat resemble those of human arms and fingers.

Codon usage and tRNA content in unicellular and multicellular organisms.

Abstract: Choices of synonymous codons in unicellular organisms are here reviewed, and differences in synonymous codon usages between Escherichia coli and the yeast Saccharomyces cerevisiae are attributed to differences in the actual populations of isoaccepting tRNAs. There exists a strong positive correlation between codon usage and tRNA content in both organisms, and the extent of this correlation relates to the protein production levels of individual genes. Codon-choice patterns are believed to have been well conserved during the course of evolution. Examination of silent substitutions and tRNA populations in Enterobacteriaceae revealed that the evolutionary constraint imposed by tRNA content on codon usage decelerated rather than accelerated the silent-substitution rate, at least insofar as pairs of taxonomically related organisms were examined. Codon-choice patterns of multicellular organisms are briefly reviewed, and diversity in G+C percentage at the third position of codons in vertebrate genes--as well as a possible causative factor in the production of this diversity--is discussed.

Is the ρ Meson a Dynamical Gauge Boson of Hidden Local Symmetry

Abstract: We suggest that the $\ensuremath{\rho}$ meson is a dynamical gauge boson of a hidden local symmetry in the non-linear chiral Lagrangian. The origin of the $\ensuremath{\rho}$-meson mass is understood as the Higgs mechanism of the hidden local symmetry. The low-energy dynamics of $\ensuremath{\rho}$, $\ensuremath{\pi}$, and matter fields, including the Kawarabayashi-Suzuki-Riazuddin-Fayyazuddin relation and $\ensuremath{\rho}$-coupling universality, is consistently described in this new framework. The electromagnetic interaction can be introduced in a unique manner, which gives a successful explanation of $\ensuremath{\rho}$ dominance of the photon coupling.

Dynamic manipulability of robot manipulators

Abstract: The concept of dynamic manipulability measure of robot arms is proposed as a quantitative measure of their manipulating ability in positioning and orienting the end-effectors, which takes the arm dynamics into consideration. This measure is defined on the basis of the relation between the joint driving force and the acceleration of the end-effector. Some properties of the measure are established. A two-joint link mechanism is analyzed and its best posture is obtained under certain condition from the viewpoint of this measure. A numerical example is also given to illustrate the utilization of this concept for the design of robot manipulators.

A new glass-ceramic for bone replacement: Evaluation of its bonding to bone tissue

Abstract: Glass powders (350 mesh) of the composition MgO, 4.6; CaO, 44.9; SiO, 34.2; PO, 16.3; CaF, 0.5 in weight ratio were compacted, heated to 1050 degrees C at a rate of 5 degrees C/min and kept at 1050 degrees C for 2 h. The resultant glass-ceramic having oxyapatite, fluoroapatite, and wollastonite crystals showed high bending and compressive strengths of 157 and 1060 MPa, respectively. The biocompatibility and bonding ability of this new glass-ceramic to the bone tissue was evaluated using rabbit tibial bones, and the failure load to break the bonding of several ceramics (the new glass-ceramic, dense hydroxyapatite, 45S5 Bioglass, alumina-ceramic) to bone tissues was measured. The new glass-ceramic showed tight bonding to bone comparable with dense hydroxyapatite, and in 25 weeks its load was 70% of that of bone tissue.

Location of functional regions of acetylcholine receptor α-subunit by site-directed mutagenesis

Abstract: The availability of cloned cDNAs encoding the four subunits of the Torpedo acetylcholine receptor, which can be expressed to make functional receptors in Xenopus oocytes, has made possible a detailed investigation of the functions of the different structural components of the receptor. The functional analysis of receptors with α-subunits altered at specific sites by site-directed mutagenesis of the cDNA has allowed the location of specific regions of the α-subunit molecule involved in acetylcholine binding and forming a transmembrane ionic channel.

Primary structure of the α-subunit of Torpedo californica (Na+ + K+)ATPase deduced from cDNA sequence

Abstract: Sodium- and potassium-dependent ATPase [(Na+ + K+)ATPase], which is responsible for the active transport of Na+ and K+, is distributed universally among animal cell membranes and consists of two types of subunits, α and β (refs 1–4). The larger α-subunit with a relative molecular mass (Mr) of 84,000–120,000 is thought to have the catalytic role. We have now cloned and sequenced DNA complementary to the Torpedo californica electroplax messenger RNA encoding the α-subunit of (Na+ + K+)ATPase and have deduced the complete ammo-acid sequence of the polypeptide. Some structural features of the α-subunit molecule related to the function of this active-transport protein are discussed.

Asymptotic Stability of Traveling Wave Solutions of Systems for One-dimensional Gas Motion

Abstract: The asymptotic stability of traveling wave solutions with shock profile is investigated for several systems in gas dynamics. 1) The solution of a scalar conservation law with viscosity approaches the traveling wave solution at the ratet−γ (for someγ>0) ast→∞, provided that the initial disturbance is small and of integral zero, and in addition decays at an algebraic rate for |x|→∞. 2) The traveling wave solution with Nishida and Smoller's condition of the system of a viscous heat-conductive ideal gas is asymptotically stable, provided the initial disturbance is small and of integral zero. 3) The traveling wave solution with weak shock profile of the Broadwell model system of the Boltzmann equation is asymptotically stable, provided the initial disturbance is small and its hydrodynamical moments are of integral zero. Each proof is given by applying an elementary energy method to the integrated system of the conservation form of the original one. The property of integral zero of the initial disturbance plays a crucial role in this procedure.

High-Speed VLSI Multiplication Algorithm with a Redundant Binary Addition Tree

Abstract: A high-speed VLSI multiplication algorithm internally using redundant binary representation is proposed. In n bit binary integer multiplication, n partial products are first generated and then added up pairwise by means of a binary tree of redundant binary adders. Since parallel addition of two n-digit redundant binary numbers can be performed in a constant time independent of n without carry propagation, n bit multiplication can be performed in a time proportional to log2 n. The computation time is almost the same as that by a multiplier with a Wallace tree, in which three partial products will be converted into two, in contrast to our two-to-one conversion, and is much shorter than that by an array multiplier for longer operands. The number of computation elements of an n bit multiplier based on the algorithm is proportional to n2. It is almost the same as those of conventional ones. Furthermore, since the multiplier has a regular cellular array structure similar to an array multiplier, it is suitable for VLSI implementation. Thus, the multiplier is excellent in both computation speed and regularity in layout. It can be implemented on a VLSI chip with an area proportional to n2 log2 n. The algorithm can be directly applied to both unsigned and 2's complement binary integer multiplication.

Statistical analysis of the physical properties of the 20 naturally occurring amino acids

Abstract: In order to describe the conformational and other physical properties of the 20 naturally occurring amino acid residues with a minimum number of parameters, several multivariate statistical analyses were applied to 188 of their physical properties and ten orthogonal properties (factors) were obtained for the 20 amino acids without losing the information contained in the original physical properties. The analysis consisted of three main steps. First, 72 of the physical properties were eliminated from further consideration because they did not pass statistical tests that they follow a normal distribution. Second, the remaining 116 physical properties of the amino acids were classified by a cluster analysis to eliminate duplications of highly correlated physical properties. This led to nine clusters, each of which was characterized by an average characteristic property, namely bulk, two hydrophobicity indices for free amino acids, one hydrophobicity index for amino acid residues in a protein, two types of β-structure preference, α-helix preference, and two types of bend-structure preference. The physical properties within a given cluster were highly correlated with each other, but the correlation between clusters was low. Third, a factor analysis was applied to the nine average classified properties and 16 additional physical properties to obtain a small number of orthogonal properties (ten factors). Four of these factors arise from the nine characteristic properties, and the remaining six factors were obtained from the 16 physical properties not included in the nine characteristic properties. Finally, most of the 188 physical properties could be expressed as a sum of these ten orthogonal factors, with appropriate weighting factors. Since these factors contain information relating almost all properties of all 20 amino acids, it is possible to estimate the numerical values of a property for one or two amino acids for which experimental data for this property are not available. For example, the estimated values for the Zimm-Bragg parameters at 20°C are 0.66 and 0.92 for proline and cysteine, respectively, computed from the first four factors.

Inversion of phase velocity of long-period microtremors to the S-wave-velocity structure down to the basement in urbanized areas.

Abstract: Engineering seismology now requires a convenient and easy survey method for S-wave-velocity structures which enables exploration down to the basement even in urbanized areas. We have attempted an application of long-period (0.5Hz to 3.0Hz) microtremors to answer this demand. The method consists of three steps: (1) microtremors are observed using an array of seismometers; (2) their phase velocities are determined by the frequency-wavenumber-spectral analysis of array data; and (3) the S-wave-velocity structure is determined from the obtained phase velocities by the generalized inversion method. As an exploration method, this procedure has several advantages: (1) microtremors can be observed at any time and location; (2) observation is much easier than with other exploration methods; (3) it causes no environmental problems; and (4) geological conditions down to a depth of more than 100m can be inverted, as far as microtremors of required frequency range are observed. The method was applied at two sites located in and near urban areas, and the whole S-velocity structure above the basement was determined. This method proves to be a useful and practical tool for determining S-wave-velocity structures especially in urbanized areas.

Manipulability and redundancy control of robotic mechanisms

Abstract: The concept of manipulability measure of robotic mechanisms is discussed. This is a measure of manipulating ability of robotic mechanisms in positioning and orienting the end-effectors. Some properties of this measure are established and the best postures of various types of manipulators from the viewpoint of this measure are given. A four-joint wrist mechanism is also analyzed with respect to its manipulability, and a control algorithm for this redundant mechanism is developed.

On the structure of self-similar sets

Abstract: We shall investigate topological properties of a uniquely determined compact setK such thatK = Σ λ ∈Λ f λ (K), where eachf λ is a weak contraction of a complete metric space andΛ = {1,2,...,m} orΛ =N. Such a setK is said to be self-similar. Many classical peculiar sets can be represented in this form. We shall also discuss the interesting problem presented by R. F. Williams.

Effects of adrenalectomy and dexamethasone administration on the level of prepro-corticotropin-releasing factor messenger ribonucleic acid (mRNA) in the hypothalamus and adrenocorticotropin/beta-lipotropin precursor mRNA in the pituitary in rats.

Abstract: RNA blot hybridization analysis with cloned rat CRF precursor (prepro-CRF) cDNA as a probe showed that prepro-CRF mRNA existed in rat hypothalamic and extrahypothalamic brain tissue, whereas it was undetectable in the pituitary and adrenal. To study the effect of glucocorticoid on the level of prepro-CRF mRNA in the hypothalmus and that of ACTH/beta-lipotropin (beta LPH) precursor mRNA in the pituitary, effects of adrenalectomy and dexamethasone administration were studied in rats. Adrenalectomy markedly raised mRNA coding for ACTH/beta LPH precursor in the anterior pituitary, but not in the neurointermediate pituitary lobe. Hypothalamic pre-pro-CRF mRNA increased only to 152% of the control value, 7 days after adrenalectomy. The administration of dexamethasone (200 micrograms/day for 7 days) started immediately after adrenalectomy lowered the ACTH/beta LPH precursor mRNA level in the anterior pituitary to 19% of the intact control value, whereas the level of prepro-CRF mRNA in the hypothalamus decreased only to 102%. These results suggest that glucocorticoids exert their feedback effect at the level of gene expression on both hypothalamic CRF neurons and pituitary corticotropes. Although the possibility that CRF neurons insensitive to glucocorticoid in the hypothalamus might blunt the change in the prepro-CRF mRNA could not be ruled out, it is also possible that the effect of glucocorticoids on the pituitary is dominant.

Effects of the ccd function of the F plasmid on bacterial growth

Abstract: The ccd segment of the mini F plasmid containing the ccdA and ccdB genes controls the coordination between plasmid proliferation and cell physiology and fate. When the DNA replication of a thermosensitive-replication plasmid carrying the ccd segment of mini F is blocked, plasmid DNA molecules are progressively diluted through cell division until the copy number reaches 1 per cell. From this time on, there is little increase in the number of viable cells, although cells continue to divide, resulting in a mixed population of viable cells (mostly plasmid containing), nonviable but residually dividing cells, and nonviable nondividing cells. Results are presented suggesting that plasmid-containing cells are viable and continue to divide, whereas plasmid-free segregants are nonviable and form filaments after a few residual divisions, with DNA synthesis reduced or arrested in the filaments. Although the ccd functions are known to induce the SOS response when plasmid replication is blocked, the production of nonviable plasmid-free segregants is independent of the SOS cell division inhibition mechanism determined by the sfiA and sfiC genes.

On the stability of travelling wave solutions of a one-dimensional model system for compressible viscous gas

Abstract: Travelling wave solutions with shock profile for a one-dimensional model system associated with compressible viscous gas are investigated in terms of asymptotic stability. The travelling wave solution is proved to be asymptotically stable, provided the initial disturbance is suitably small and of zero constant component. The proof is given by the elementalL 2 energy method.

Role of acetylcholine receptor subunits in gating of the channel.

Abstract: The Torpedo and calf acetylcholine receptors and hybrids composed of subunits from the two species have been produced in Xenopus oocytes by the use of the cloned complementary DNAs. Single-channel current measurements indicate that these receptors form channels of similar conductance but with different gating behaviour.

Mechanical properties of a new type of apatite-containing glass-ceramic for prosthetic application

Abstract: A new type of apatite-containing glass-ceramic in the system MgO-CaO-SiO2-P2O5 can form a tight chemical bond with bones and has a high mechanical strength. The cause for its high mechanical strength was examined by comparing mechanical properties of the glass-ceramics which have an identical chemical composition and different microstructures. It was found that the mechanical strength of the apatite-containing glass-ceramics is considerably increased by the precipitation ofβ-wollastonite crystals due to an increase in fracture surface energy resulting in an increase in fracture toughness.

Fluctuation effects in hot quark matter: Precursors of chiral transition at finite temperature.

Abstract: Fluctuations of the order parameter of chiral transition in a hot and dense quark gas are examined in the random-phase approximation with the use of a QCD-motivated effective Lagrangian. We show that there arise soft modes having a large strength and a narrow width above the critical temperature, which are analogous to the fluctuations of the order parameter in a superconductor above the critical point. It is argued that the modes contribute to the cooling of the quark-gluon plasma.

Primary structure of the alpha-subunit of transducin and its relationship to ras proteins.

Abstract: A group of membrane-associated guanine nucleotide binding proteins (G-proteins) are essential for transducing signals generated at cell-surface receptors into changes in cellular function and metabolism. These proteins are a complex of three subunits designated alpha, beta and gamma. The alpha-subunit is responsible for binding guanine nucleotides and seems to be characteristic of each protein. Transducin, a member of this protein family, mediates visual transduction by coupling the signal of photolysed rhodopsin with activation of a cyclic GMP phosphodiesterase. We have now cloned and sequenced the complementary DNA encoding the alpha-subunit of bovine retinal transducin and from this we have deduced the complete amino-acid sequence. The transducin alpha-subunit shares several homologous amino-acid sequences with ras gene products. The homologous segments correspond mostly to the regions thought to be involved in the guanine nucleotide binding and GTPase activity of ras proteins and to the ADP-ribosylation sites of the transducin alpha-subunit.

Non-Abelian Anomaly and Vector Mesons as Dynamical Gauge Bosons of Hidden Local Symmetries

Abstract: We present general solutions to the Wess-Zumino anomaly equation which incorporate vector mesons as dynamical gauge bosons of the hidden local symmetry in the nonlinear chiral Lagrangian. In contrast to the previous attempts to introduce the vector mesons, our formalism enables one to treat consistently and systematically various processes associated with pseudoscalar mesons (Nambu-Goldsone bosons) and vector mesons (dynamical gauge bosons); it is automatic in this framework that the on-shell amplitudes of photons and pseudoscalar mesons such as π^0 →2γ and γ→3 π which are fixed by the low energy theorems, are not affected no matter how the vector mesons participate in those processes. We further show that the “complete vector meson dominance” hypothesis of photon couplings is invalid in either π^0 →2γ or γ→3π process.