Showing papers by "University of Tsukuba published in 1994"

Dentatorubral and pallidoluysian atrophy expansion of an unstable CAG trinucleotide on chromosome 12p.

Abstract: Dentatorubral and pallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disorder characterized by combined systemic degeneration of the dentatofugal and pallidofugal pathways. We investigated a candidate gene and found that DRPLA patients had an expanded CAG trinucleotide repeat in a gene on the short arm of chromosome 12. The repeat size varied from 7–23 in normal individuals. In patients one allele was expanded to between 49–75 repeats or occasionally even more. Expansion was usually associated with paternal transmission and only occasionally with maternal transmission. Repeat size showed a close correlation with age of onset of symptoms and disease severity. We conclude that DRPLA is the seventh genetic disorder known to be associated with expansion of an unstable trinucleotide repeat.

A truncated bone morphogenetic protein receptor affects dorsal-ventral patterning in the early Xenopus embryo

Abstract: Bone morphogenetic proteins (BMPs), which are members of the transforming growth factor beta (TGF-beta) superfamily, have been implicated in bone formation and the regulation of early development. To better understand the roles of BMPs in Xenopus laevis embryogenesis, we have cloned a cDNA coding for a serine/threonine kinase receptor that binds BMP-2 and BMP-4. To analyze its function, we attempted to block the BMP signaling pathway in Xenopus embryos by using a dominant-negative mutant of the BMP receptor. When the mutant receptor lacking the putative serine/threonine kinase domain was expressed in ventral blastomeres of Xenopus embryos, these blastomeres were respecified to dorsal mesoderm, eventually resulting in the formation of a secondary body axis. These findings suggest that endogenous BMP-2 and BMP-4 are involved in the dorsal-ventral specification in the embryo and that ventral fate requires induction rather than resulting from an absence of dorsal specification.

Vector autoregression and causality: a theoretical overview and simulation study

Abstract: This paper provides a theoretical overview of Wald tests for Granger causality in levels vector autoregressions (VAR's) and Johansen-type error correction models (ECM's). The theory is based on results in Toda and Phillips (1991a) and allows for stochastic and deterministic trends as well as arbitrary degrees of cointegration. We recommend some operational procedures for conducting Granger causality tests that are based on the Gaussian maximum likelihood estimation of ECM's. These procedures are applicable in the important practical case of testing the causal effects of one variable on another group of variables and vice versa. This paper also investigates the sampling properties of these testing procedures through simulation exercises. Three sequential causality tests in ECM's are compared with conventional causality tests in levels and differences VAR's.

Podiform chromitites of the Tari-Misaka ultramafic complex, Southwestern Japan, as mantle-melt interaction products.

Abstract: Petrological and geochemical data for chromian spinel from the Tari-Misaka ultramafic complex, southwest Japan, are discussed. In this complex, the spinels form a chromitite pod coated by a dunite envelope and are collectively enclosed by clinopyroxene-bearing harzburgite. Chromitite and its dunite envelope are distinctly different from the surrounding harzburgite in terms of the chromian spinel chemistry. The Ti content is five to ten times higher in spinels of the enveloped chromitite than in those of the harzburgite, although the Cr ratio (Cr/(Cr + Al, the atomic ratio) for both is almost constant or varies only slightly (0.4-0.5). This eliminates a comagmatic origin for the harzburgite-dunite-chromitite association. Spinel chemistry for both major and trace elements is almost the same in the chromitite and its dunite envelope, except for the Mg ratio and the Co and Mn contents which have a changed subsolidus as a function of the spinel mode. Thus, the dunite and chromitite could be comagmatic, but fractional crystallization of the dunite after or before chromitite deposition is not possible. The chemistry of the chromian spinel and the mode of occurrence of the dunite-chromitite association are consistent with an origin by interaction of an exotic melt with wall-rock harzburgite. The dunite may be of replacive origin: the exotic melt would react with the harzburgite at the new contact to form dunite and a secondary Si-rich melt. The melt thus formed could mix with a successive inflow of a more primitive melt; the mixed melt would be expected to have chromite (chromian spinel) as the only liquidus phase, precipitating chromitite next to the replacive dunite (the dunite envelope).Podiform chromitite is most commonly formed in the mantle beneath island arcs. The spread in Cr ratios of spinel in podiform chromitites is almost comparable with that of spinel in primitive arc-related magmas. The presence of chromitite in the upper mantle beneath the Japan arcs is consistent with this interpretation.

Two genes that encode Ca(2+)-dependent protein kinases are induced by drought and high-salt stresses in Arabidopsis thaliana.

Abstract: Two cDNA clones, AATCDPK1 and cATCDPK2, encoding Ca2+-dependent, calmodulin-independent protein kinases (CDPK) were cloned from Arabidopsis thaliana and their nucleotide sequences were determined. Northern blot analysis indicated that the mRNAs corresponding to the ATCDPK1 and ATCDPK2 genes are rapidly induced by drought and high-salt stress but not by low-temperature stress or heat stress. Treatment of Arabidopsis plants with exogenous abscisic acid (ABA) had no effect on the induction of ATCDPK1 or ATCDPK2. These findings suggest that a change in the osmotic potential of the environment can serve as a trigger for the induction of ATCDPK1 and ATCDPK2. Putative proteins encoded by ATCDPK1 and ATCDPK2 which contain open reading frames of 1479 and 1488 bp, respectively, are designated ATCDPK1 and ATCDPK2 and show 52% identity at the amino acid sequence level. ATCDPK1 and ATCDPK2 exhibit significant similarity to a soybean CDPK (51 % and 73%, respectively). Both proteins contain a catalytic domain that is typical of serine/threonine protein kinases and a regulatory domain that is homologous to the Ca2+-binding sites of calmodulin. Genomic Southern blot analysis suggests the existence of a few additional genes that are related to ATCDPK1 and ATCDPK2 in the Arabidopsis genome. The ATCDPK2 protein expressed in Escherichia coli was found to phosphorylate casein and myelin basic protein preferentially, relative to a histone substrate, and required Ca2+ for activation.

A signal design without co-channel interference for approximately synchronized CDMA systems

Abstract: A signal design is proposed for a CDMA system that is approximately synchronized. The signals are called pseudoperiodic sequences. The set of pseudoperiodic polyphase sequences are introduced from a set of periodic polyphase sequences with ideal autocorrelation for small shifts and zero cross correlation for all shifts. The system works without cochannel interference, even when the signals are modulated by data. >

Effect of fungal to bacterial biomass ratio on the relationship between CO2 evolution and total soil microbial biomass

Abstract: The relationship between the fungal: bacterial biomass ratio and the metabolic quotient (qCO2) was studied in three different soils. In addition, the effect of the fungal: bacterial biomass ratio on the relationship between CO2 evolution and the size of the soil microbial biomass was examined. Soil samples were collected from three experimental fields amended with various organic materials (Yatsugatake, Ibaraki, and Tochigi fields). The range of the fungal:bacterial biomass ratio in the Yatsugatake and Ibaraki fields was small (1.54–2.24 and 1.11–1.71, respectively), but it was large in the Tochigi field (1.18–3.75). We found a high negative correlation between this ratio and the metabolic quotient (qCO2=2.10−0.361 (fungal:bacterial biomass ratio), R=−0.851, P<0.01) in the Tochigi field. Therefore, we suggest tha qCO2 decreases with an increase in the fungal:bacterial biomass ratio, which may be due to a higher efficiency of substrate C use by fungal flora in comparison with bacterial flora. In the Yatsugatake and Ibaraki fields, there was a high positive correlation between CO2 evolution and total microbial biomass. In contrast, no correlation was observed between these two parameters in the Tochigi field, probably reflecting the wide range of values for the fungal:bacterial biomass ratio. From the results obtained, we suggest that the fungal: bacterial biomass ratio is an important factor regulating the relationship between CO2 evolution and the size of the microbial biomass.

Characterization of two cDNAs that encode MAP kinase homologues in Arabidopsis thaliana and analysis of the possible role of auxin in activating such kinase activities in cultured cells.

Abstract: Summary Two cDNA clones, cATMPK1 and CATMPK2, encoding MAP kinases (mitogen-activated protein kinases) have been cloned from Arabidopsis thaliana and their nucleotide sequences have been determined. Putative proteins encoded by ATMPK1 and ATMPK2 genes, designated ATMPK1 and ATMPK2, contain 370 and 376 amino acid residues, respectively, and are 88.7% identical at the amino acid sequence level. ATMPK1 and ATMPK2 exhibit significant similarity to rat ERK2 (49%) and Xenopus MAP kinase (50%). The amino acid residues corresponding to the sites of phosphorylation (Thr-Glu-Tyr) that are involved in the activation of MAP kinases are conserved in ATMPK1 and ATMPK2. Northern blot analysis indicates that the ATMPK1 and ATMPK2 mRNAs are significantly present in all the organs except seeds. Genomic Southern blot analysis suggests that there are a few additional genes that are related to ATMPK1 and ATMPK2 in the Arabidopsis genome. Purified Xenopus MAP kinase kinase (MAPK kinase) phosphorylates ATMPK1 and ATMPK2 proteins that have been expressed in Escherichia coli, activating these enzymes. A rapid and transient activation of 46-kDa protein kinase activity that phosphorylated myelin basic protein (MBP) was detected when auxinstarved tobacco BY-2 cells were treated with synthetic auxin, 2,4-dichlorophenoxyacetic acid (2,4-D). Protein kinase activities which phosphorylated the recombinant ATMPK2 protein also increased rapidly after auxin treatment in the auxin-starved BY-2 cells. These results suggest that auxin may function as an activator of plant MAP kinase homologues, as do various mitogens in animal systems.

Influence of Elaboration on the Framing of Decision

Abstract: Two experimental studies were conducted to examine the influence of elaboration on the framing of a medical decision. Subjects (N = 344) were undergraduate students randomly assigned to one cell of a 2 × 2 design (high- and low-elaboration conditions; positive and negative decision frame versions). In the low-elaboration condition, a framing effect (Tversky & Kahneman, 1981) was observed: Most of the subjects chose the riskless option when decision options were phrased positively in terms of gains, whereas most chose the risky option when options were phrased negatively in terms of losses. However, in the high-elaboration condition, the framing effect was not observed.

Role of support in reforming of CH4 with CO2 over Rh catalysts

Abstract: The reforming of CH4 with CO2 over supported Rh catalysts has been studied over a range of temperatures (550–1000 K). A significant effect of the support on the catalytic activity was observed, where the order was Rh/Al2O3>Rh/TiO2>Rh/SiO2. The catalytic activity of Rh/SiO2 was promoted markedly by physical mixing of Rh/SiO2 with metal oxides such as Al2O3, TiO2, and MgO, indicating a synergetic effect. The role of the metal oxides used as the support and the physical mixture may be ascribed to the promotion in dissociation of CO2 on the surface of Rh, since the CH4 + CO2 reaction is first order in the pressure of CO2, suggesting that CO2 dissociation is the rate-determining step. The possible model of the synergetic effect was proposed.

Trajectory Tracking Control for Navigation of the Inverse Pendulum Type Self-Contained Mobile Robot.

Abstract: In this paper, we discuss the trajectory control for a wheeled inverse pendulum type mobile robot. The robot has two independent driving wheels on the same axle, and a gyro type sensor to measure the inclination angular velocity of the body and rotary encoders to measure wheel rotation. The purpose of this work is to make a robot autonomously navigate in a plane while keeping its own balance. The control algorithm consists of three parts: balance and velocity control, steering control and straight line tracking control. We designed and implemented a vehicle command system for such robot to control using the proposed algorithm. Experiments of the navigation in a real indoor environment have been performed using our experimental robot “Yamabico Kurara”.

Coulomb Dissociation of B-8 and the Be-7(p, Gamma)b-8 Reaction At Low Energies

Abstract: The cross section for Coulomb dissociation of $^{8}\mathrm{B}$---the $^{208}\mathrm{Pb}(^{8}\mathrm{B}^{7}\mathrm{Be}p)^{208}\mathrm{Pb}$ reaction---was measured using a $^{8}\mathrm{B}$ radioactive beam of 46.5 MeV/nucleon energy, and the cross section for the $^{7}\mathrm{Be}(p,\ensuremath{\gamma})^{8}\mathrm{B}$ capture reaction was deduced at low energies; ${E}_{\mathrm{c}.\mathrm{m}.}=0.6\ensuremath{-}1.7$ MeV. The extracted astrophysical ${S}_{17}$ factors were found to be consistent with the values measured by Vaughn et al. and Filippone et al. This result encourages further experimental studies extended to lower relative energies for a new determination of the ${S}_{17}$ value relevant to the $^{8}\mathrm{B}$ solar neutrino flux.

Production of germline chimeric chickens, with high transmission rate of donor‐derived gametes, produced by transfer of primordial germ cells

Abstract: Germline chimeric chickens were produced by transfer of primordial germ cells from White Leghorn to Barred Plymouth Rock, and vice versa. Blood was collected from stage 13-15 embryos and primordial germ cells were concentrated by Ficoll density gradient centrifugation. Approximately 200 primordial germ cells were injected into the bloodstream through the dorsal aorta of stage 14-15 recipient embryos from which blood had been drawn via the dorsal aorta prior to the injection. Intact embryos were also prepared as recipients for White Leghorns only. The manipulated embryos were cultured in recipient eggshells until hatching. Germline chimerism of the chickens reaching maturity was examined by mating them with Barred Plymouth Rocks and donor-derived offspring were identified based on their feather color. The efficiency of production of germline chimeras was 95% (19/20). When primordial germ cells were transferred from White Leghorn to Barred Plymouth Rock, the average frequency of donor-derived offspring was 81% for three male chimeras (96% for one female chimera), and it was approximately 3.5 times higher for transfer in the opposite direction (23% for 6 male chimeras). Removing blood from recipient embryos prior to primordial germ cell injection enhanced the frequency of donor-derived offspring by 10% in resulting male chimeras. Male chimeras produced donor-derived offspring more frequently (approximately 3.8 times) than female chimeras. Increases, decreases, or no changes were observed in the frequency of donor-derived offspring from the germline chimeras with increasing age.(ABSTRACT TRUNCATED AT 250 WORDS)

Luminescence properties of nanometer-sized Si crystallites: Core and surface states.

Abstract: We have studied the mechanism of visible photoluminescence (PL) from surface-oxidized Si crystallites of 3.7 nm diameter. Under intense laser-pulse illumination, two PL bands are clearly observed: a fast-decay blue-green PL band and a slow-decay red PL band. Time-resolved PL-spectrum measurements indicate that carriers generated in the core state are rapidly localized into the lower-energy surface states. Spectroscopic analysis indicates that the slow-decay red PL is caused by the hopping-limited recombination process in the surface-localized state of the crystallite, while the blue-green PL is caused by the band-edge emission from the core state of the crystallite.

Spin fluctuations in frustrated kagomé lattice system SrCr8Ga4O19 studied by muon spin relaxation.

Abstract: We have performed muon spin relaxation measurements of the frustrated kagom\'e lattice spin system Sr${\mathrm{Cr}}_{8}$${\mathrm{Ga}}_{4}$${\mathrm{O}}_{19}$. Our results demonstrate the slowing down of the Cr spin fluctuations when cooling toward the susceptibility-cusp temperature ${T}_{g}\ensuremath{\sim}3.5$ K. The saturation of the relaxation rate below ${T}_{g}$, together with its weak dependence on longitudinal field (LF) between 0 and 2 kG, indicates the presence of dynamic spin fluctuations persisting even at $T\ensuremath{\sim}100$ mK without static order parameter. We propose a spin-liquid type ground state to explain an undecouplable Gaussian shape of the relaxation function observed at $T\ensuremath{\le}{T}_{g}$.

Coherent oscillation of zone-folded phonon modes in GaAs-AlAs superlattices.

Abstract: We have observed a coherent oscillation of zone-folded acoustic phonons in GaAs-AlAs superlattices for the first time by means of a femtosecond time-resolved pump-probe technique. The oscillatory component in the time-resolved reflection signal corresponds to the upper branch (${B}_{2}$ symmetry) of the first-order doublet mode. Carriers were selectively excited in well layers and the ${B}_{2}$-symmetry phonon mode was selectively generated. The dephasing time of the ${B}_{2}$ mode was measured to be 70 ps from our experiments.

Mutation of K-ras protooncogene is associated with histological subtypes in human mucinous ovarian tumors.

Abstract: A series of 57 mucinous and 47 serous ovarian tumors (adenomas, tumors of borderline malignancy, and carcinomas) were examined by polymerase chain reaction-single strand conformation polymorphism analysis and direct sequencing for mutations in codons 12, 13, and 61 of K-ras gene. Higher incidence of K-ras mutations was observed in mucinous tumors compared to serous ones. Mutations were detected in 4 of 30 mucinous adenomas (13%), in 4 of 12 mucinous tumors of borderline malignancy (33%), and in 7 of 15 mucinous carcinomas (46%). Only 1 of 17 serous carcinomas (6%) had a mutation of K-ras in serous ovarian tumors. All mutations identified were in codon 12. Detailed analysis revealed that more K-ras mutations in mucinous adenomas were observed in intestinal type (identified in 4 of 13) than in endocervical type (identified in 0 of 17). Thus, K-ras gene codon 12 mutations in mucinous ovarian adenomas appear to be associated with the occurrence of intestinal type adenomas.

A metadatabase system for semantic image search by a mathematical model of meaning

Abstract: In the design of multimedia database systems, one of the most important issues is to extract images dynamically according to the user's impression and the image's contents In this paper, we present a metadatabase system which realizes the semantic associative search for images by giving keywords representing the user's impression and the image's contentsThis metadatabase system provides several functions for performing the semantic associative search for images by using the metadata representing the features of images These functions are realized by using our proposed mathematical model of meaning The mathematical model of meaning is extended to compute specific meanings of keywords which are used for retrieving images unambiguously and dynamically The main feature of this model is that the semantic associative search is performed in the orthogonal semantic space This space is created for dynamically computing semantic equivalence or similarity between the metadata items of the images and keywords

GestureCam: a video communication system for sympathetic remote collaboration

Abstract: An approach supporting spatial workspace collaboration via a video-mediated communication system is described. Based on experimental results, the following were determined to be the system requirements to support spatial workspace collaboration: independency of a field of view, predictability, confidence in transmission and sympathy toward the system. Additionally, a newly developed camera system, the GestureCam System, is introduced. A camera is mounted on an actuator with three degrees of freedom. It is controlled by master-slave method or by a touch-sensitive CRT. Also, a laser pointer is mounted to assist with remote pointing. Preliminary experiments were conducted and the results are described herein.

Derivation and implementation of a cone-beam reconstruction algorithm for nonplanar orbits

Abstract: B.D. Smith (ibid., vol.MI-4, p.15-25, 1985; Opt. Eng., vol.29, p.524-34, 1990) and P. Grangeat (These de doctorat, 1987; Lecture Notes in Mathematics 1497, p.66-97, 1991) derived a cone-beam inversion formula that can be applied when a nonplanar orbit satisfying the completeness condition is used. Although Grangeat's inversion formula is mathematically different from Smith's one, they have similar overall structures to each other. The contribution of the present paper is two-fold. First, based on the derivation of Smith, the authors point out that Grangeat's inversion formula and Smith's one can be conveniently described using a single formula (the Smith-Grangeat inversion formula) that is in the form of space-variant filtering followed by cone-beam backprojection. Furthermore, the resulting formula is reformulated for data acquisition systems with a planar detector to obtain a new reconstruction algorithm. Second, the authors make two significant modifications to the new algorithm to reduce artifacts and numerical errors encountered in direct implementation of the new algorithm. As for exactness of the new algorithm, the following fact can be stated. The algorithm based on Grangeat's intermediate function is exact for any complete orbit, whereas that based on Smith's intermediate function should be considered as an approximate inverse excepting the special case where almost every plane in 3D space meets the orbit. The validity of the new algorithm is demonstrated by simulation studies. >