Showing papers by "Aoyama Gakuin University published in 2005"

Discovery of the short |[gamma]|-ray burst GRB 050709

Abstract: Gamma-ray bursts (GRBs) are either ‘long and soft’, or ‘short and hard’. The long-duration type leave a strong afterglow and have been extensively studied. So we have a good idea of what causes them: explosions of massive stars in distant star-forming galaxies. Short GRBs, with no strong afterglow, were harder to pin down. The Swift satellite, launched last November, is designed to study bursts as soon as they happen. Having shown its worth with long GRBs (reported in the 18 August issue of Nature), Swift has now bagged a short burst, GRB 050509B, precisely measured its location and detected the X-ray afterglow. Four papers this week report on this and another recent short burst. Now, over 20 years after they were first recognized, the likely origin of the short GRBs is revealed as a merger between neutron stars of a binary system and the instantaneous production of a black hole. Gamma-ray bursts (GRBs) fall into two classes: short-hard and long-soft bursts1,2,3. The latter are now known to have X-ray4 and optical5 afterglows, to occur at cosmological distances6 in star-forming galaxies7, and to be associated with the explosion of massive stars8,9. In contrast, the distance scale, the energy scale and the progenitors of the short bursts have remained a mystery. Here we report the discovery of a short-hard burst whose accurate localization has led to follow-up observations that have identified the X-ray afterglow10 and (for the first time) the optical afterglow10,11 of a short-hard burst; this in turn led to the identification of the host galaxy of the burst as a late-type galaxy at z = 0.16 (ref. 10). These results show that at least some short-hard bursts occur at cosmological distances in the outskirts of galaxies, and are likely to be caused by the merging of compact binaries.

Global characteristics of x-ray flashes and x-ray-rich gamma-ray bursts observed by hete-2

Abstract: We describe and discuss the global properties of 45 gamma-ray bursts (GRBs) observed by HETE-2 during the first 3 years of its mission, focusing on the properties of X-ray flashes (XRFs) and X-ray-rich GRBs (XRRs). We find that the numbers of XRFs, XRRs, and GRBs are comparable, and that the durations and the sky distributions of XRFs and XRRs are similar to those of GRBs. We also find that the spectral properties of XRFs and XRRs are similar to those of GRBs, except that the values of the peak energy E of the burst spectrum in νFν, the peak energy flux Fpeak, and the energy fluence SE of XRFs are much smaller (and those of XRRs are smaller) than those of GRBs. Finally, we find that the distributions of all three kinds of bursts form a continuum in the [SE(2-30 keV), SE(30-400) keV] plane, the [SE(2-400 keV), Epeak] plane, and the [Fpeak(50-300 keV), Epeak] plane. These results provide strong evidence that all three kinds of bursts arise from the same phenomenon.

Néel temperature of quasi-low-dimensional Heisenberg antiferromagnets.

Abstract: The Neel temperature T(N) of quasi-one- and quasi-two-dimensional antiferromagnetic Heisenberg models on a cubic lattice is calculated by Monte Carlo simulations as a function of interchain (interlayer) to intrachain (intralayer) coupling J(')/J down to J(')/J approximately = 10(-3). We find that T(N) obeys a modified random-phase approximationlike relation for small J(')/J with an effective universal renormalized coordination number, independent of the size of the spin. Empirical formulas describing T(N) for a wide range of J(') and useful for the analysis of experimental measurements are presented.

Repeated injections of energy in the first 600 ms of the giant flare of SGR 1806–20

Abstract: The massive flare of 27 December 2004 from the soft gamma-ray repeater SGR 1806-20, a possible magnetar, saturated almost all gamma-ray detectors, meaning that the profile of the pulse was poorly characterized. An accurate profile is essential to determine physically what was happening at the source. Here we report the unsaturated gamma-ray profile for the first 600 ms of the flare, with a time resolution of 5.48 ms. The peak of the profile (of the order of 10(7) photons cm(-2) s(-1)) was reached approximately 50 ms after the onset of the flare, and was then followed by a gradual decrease with superposed oscillatory modulations possibly representing repeated energy injections with approximately 60-ms intervals. The implied total energy is comparable to the stored magnetic energy in a magnetar (approximately 10(47) erg) based on the dipole magnetic field intensity (approximately 10(15) G), suggesting either that the energy release mechanism was extremely efficient or that the interior magnetic field is much stronger than the external dipole field.

Cognitive Abilities, Chunk-Strength, and Frequency Effects in Implicit Artificial Grammar and Incidental L2 Learning: Replications of Reber, Walkenfeld, and Hernstadt (1991) and Knowlton and Squire (1996) and Their Relevance for SLA.

Abstract: This paper reports replications of studies of implicit artificial grammar (AG) learning and explicit series-solution learning with experienced second language learners in order to examine their population and content generalizability. As found by Reber, Walkenfeld, and Hernstadt (1991), there was significantly greater variance in explicit compared to implicit learning. In contrast to Reber et al.'s findings, intelligence quotient (IQ) was significantly negatively related to implicit learning. As found by Knowlton and Squire (1996), chunks that appeared with high frequency (high chunk-strength) in AG training influenced incorrect acceptance of ungrammatical transfer test items containing them but did not affect the judgments of grammatical items. In a third experiment, learners semantically processed sentences in Samoan, a novel language for this population. This experiment found little evidence for the content generalizability of these AG findings to the incidental learning of Samoan. Implicit AG and incidental Samoan learning had different patterns of correlation with cognitive abilities (IQ, working memory, and aptitude) and differed in sensitivity to chunk-strength. As found for AG learning, high chunk-strength negatively affected correct rejection of ungrammatical Samoan transfer test items. Additionally, high chunk-strength negatively affected correct acceptance of grammatical items. For these grammatical items, the number of chunks they contained—not their frequency during training—positively influenced grammaticality judgments.I gratefully acknowledge the helpful comments and advice on this paper given by the editors of this special issue, Jan Hulstijn and Rod Ellis, and also by Nick Ellis, Barbara Knowlton, and two anonymous SSLA reviewers.

Cosmic-Ray Spectra and Composition in the Energy Range of 10-1000 TeV per Particle Obtained by the RUNJOB Experiment

Abstract: This is a full report on the cosmic-ray spectra and composition obtained by the emulsion chambers on board 10 long-duration balloons, launched from Kamchatka between 1995 and 1999. The total exposure of these campaigns amounts to 575 m2 hr, with an average flight altitude of ~32 km. We present final results on the energy spectra of two light elements, protons and helium nuclei, and on those of three heavy-element groups, CNO, NeMgSi, and Fe, covering the very high energy region of 10-1000 TeV particle-1. We additionally present the secondary/primary ratio, the all-particle spectrum, and the average mass of the primary cosmic rays. We find that our proton spectrum is in good agreement with other results, but the intensity of the helium component is nearly half that obtained by JACEE and SOKOL. The slopes of the spectra of these two elements obtained from RUNJOB data are almost parallel, with values of 2.7-2.8 in the energy range of 10-500 TeV nucleon-1. RUNJOB heavy-component spectra are in agreement with the extrapolation from those at lower energies obtained by CRN (Chicago group), monotonically decreasing with energy. We have also observed secondary components, such as the LiBeB group and the sub-Fe group, and present the secondary/primary ratio in the TeV nucleon-1 region. We determine the all-particle spectrum and the average mass of the primary cosmic rays in the energy region of 20-1000 TeV particle-1. The intensity of the RUNJOB all-particle spectrum is 40%-50% less than those obtained by JACEE and SOKOL, and the RUNJOB average mass remains almost constant up to ~1 PeV.

Previously Unknown Virus Infects Marine Diatom

Abstract: Diatoms are a major phytoplankton group that play important roles in maintaining oxygen levels in the atmosphere and sustaining the primary nutritional production of the aquatic environment. Among diatoms, the genus Chaetoceros is one of the most abundant and widespread. Temperature, climate, salinity, nutrients, and predators were regarded as important factors controlling the abundance and population dynamics of diatoms. Here we show that a viral infection can occur in the genus Chaetoceros and should therefore be considered as a potential mortality source. Chaetoceros salsugineum nuclear inclusion virus (CsNIV) is a 38-nm icosahedral virus that replicates within the nucleus of C. salsugineum. The latent period was estimated to be between 12 and 24 h, with a burst size of 325 infectious units per host cell. CsNIV has a genome structure unlike that of other viruses that have been described. It consists of a single molecule of covalently closed circular single-stranded DNA (ssDNA; 6,005 nucleotides), as well as a segment of linear ssDNA (997 nucleotides). The linear segment is complementary to a portion of the closed circle creating a partially double-stranded genome. Sequence analysis reveals a low but significant similarity to the replicase of circoviruses that have a covalently closed circular ssDNA genome. This new host-virus system will be useful for investigating the ecological relationships between bloom-forming diatoms and other viruses in the marine system. Our study supports the view that, given the diversity and abundance of plankton, the ocean is a treasury of undiscovered viruses.

Development of the HXD-II wide-band all-sky monitor onboard Astro-E2

Abstract: The hard X-ray detector (HXD-II) is one of the three scientific instruments onboard Japanese X-ray astronomy satellite Astro-E2 scheduled to be launched in 2005. This mission is very unique in a point of having a lower background than any other past missions in the 10-600 keV range. In the HXD-II, the large and thick BGO crystals are used as active shields for particle and gamma-ray background to the main detector. They have a wide field of view of ~2pi and a large effective area of 400 cm2 even at 1 MeV. Hence, the BGO shields have been developed as a wide-band all-sky monitor (WAM) with a broadband coverage of 50-5000 keV. In this paper, overall design and performance of the HXD-II/WAM based on the results of preflight calibration tests carried out in June 2004 are described. By irradiating various radio isotopes with the WAM flight model, we verified that it had comparable capabilities with other gamma-ray burst detectors

Numerical study on three-dimensional C-J detonation waves: detailed propagating mechanism and existence of OH radical

Abstract: An unsteady three-dimensional simulation is performed for a hydrogen/air C–J detonation in a rectangular tube, where a detailed chemical reaction model is used to reveal the C–J detonation structure. In this simulation, detailed propagating detonation structures for a diagonal mode are described in three-dimensions. The detonation front structures, the line of triple points, and the strong explosions at the corners of the rectangular tube are revealed by using a three-dimensional numerical visualization. From the spatial isosurface profiles of H 2 mass fraction, it is confirmed that the triple point lines have a role of “shutter” to generate unburned gas pockets and become of a ring shape behind the detonation front due to its explosion. The explosion process and its influence on an induction delay are observed by visualizing the spatial isosurface profiles of OH mass fraction. Moreover, a high “peninsula-shaped” OH mass fraction area, which has been experimentally reported, is reproduced on the side wall of the rectangular tube.

An empirical study of TQM practices in Japanese‐owned manufacturers in China

Abstract: Purpose – The main purpose of this study is to explore the relationship between TQM practices and the business performance of Japanese‐owned manufacturers in China.Design/methodology/approach – In this study, 200 companies out of the universe 1000 were chosen by random sampling in June 2002.Findings – A total of 52 usable questionnaires were received and the overall response rate was 26 percent. The survey results show that TQM practices influence overall company performance significantly in Japanese‐owned manufacturers in China. This implies that TQM is an effective method to improve business performance regardless of where the company might be operating as long as the TQM practices are implemented appropriately. In addition to the research data, findings from a field study also provide supplementary evidence to support this conclusion.Originality/value – The findings based on the empirical research would be useful to both decision makers and researchers who are interested in this growing “factory of the...

A New Family of π-Conjugated Delocalized Biradicals: Electronic Structures of 1,4-Bis(2,5-diphenylimidazol-4-ylidene)cyclohexa-2,5-diene

Abstract: A new family of pi-conjugated delocalized biradical compound is developed. The solution of 1,4-bis(2,5-diphenylimidazol-4-ylidene)cyclohexa-2,5-diene shows the ESR signal consisting of a moderately broad unresolved line, Delta H(pp) approximately 1 mT, at room temperature. The presence of the thermal equilibrium between a triplet biradical state and a singlet state is confirmed by the ESR measurements, and the spin concentration is determined as 7.90 x 10(21) spin/mol at 300 K. The spin concentration can also be controlled by modifying the molecular planarity. Moreover, the unrestricted DFT/B3LYP calculations suggest the biradical character of the singlet ground state, and the modulation of the energy gap between the singlet state and the triplet state is investigated from the theoretical point of view. Controlling the equilibrium between a diamagnetic state and a paramagnetic state will provide significant progress in the field of biradical chemistry, and the materials with the biradical character in a ground state will lead to a novel development of molecular-based organic magnets.

MITSuME - Multicolor imaging telescopes for survey and monstrous explosions

Abstract: Development of MITSuME is reported. Two 50- cm optical telescopes have been built at Akeno in Yamanashi prefecture and at Okayama Astrophysical Observatory (OAO) in Okayama prefecture. Three CCD cameras for simultaneous g'RcIc photometry are to be mounted on each focal plane, covering a wide FOV of about 30" × 30". The limiting magnitude at V is fainter than 18. In addition to these two optical telescopes, a 91-cm IR telescope with a 1° × 1° field of view is being built at OAO, which performs photometry in Y JHK bands. These robotic telescopes can start the observation of counterparts of a GRB within a minute from an alert. We aim to obtain photometric redshifts exceeding 10 with these telescopes. The performance and the current construction status of the telescopes are presented.

Flat-Bands on Partial Line Graphs-Systematic Method for Generating Flat-Band Lattice Structures-

Abstract: We introduce a systematic method for constructing a class of lattice structures that we call “partial line graphs”. In tight-binding models on partial line graphs, energy bands with flat energy dispersions emerge. This method can be applied to two- and three-dimensional systems. We show examples of partial line graphs of square and cubic lattices. The method is useful in providing a guideline for synthesizing materials with flat energy bands, since the tight-binding models on the partial line graphs provide us a large room for modification, maintaining the flat energy dispersions.

Maximizing Weighted number of Just-in-Time Jobs on Unrelated Parallel Machines

Abstract: We are concerned with problems of scheduling jobs non-preemptively with the objective to maximize the weighted number of jobs that are completed exactly at their due dates. It has been shown that the problems for single machine and identical parallel machines are polynomial time solvable. The purpose of this paper is to establish the complexity status of the problem for unrelated parallel machine, which was left open. First, we present a polynomial time algorithm for solving the problem when the number of machine is fixed. Second, we show that when the number of machine is a part of input, the problem becomes NP-hard in the strong sense.

Disorder effect on spin excitation in double-exchange systems

Abstract: Spin excitation spectrum is studied in the double-exchange model in the presence of disorder. Spin wave approximation is applied in the lowest order of $1∕S$ expansion. The disorder causes anomalies in the spin excitation spectrum such as broadening, branching, anticrossing with gap opening. The origin of the anomalies is the Friedel oscillation, in which the perfectly polarized electrons form the charge density wave to screen the disorder effect. Near the zone center $q=0$, the linewidth has a $q$ linear component while the excitation energy scales to ${q}^{2}$, which indicates that the magnon excitation is incoherent. As $q$ increases, there appears a crossover from this incoherent behavior to the marginally coherent one in which both the linewidth and the excitation energy are proportional to ${q}^{2}$. The results are compared with experimental results in colossal magnetoresistance manganese oxides. Quantitative comparison of the linewidth suggests that spatially-correlated or mesoscopic-scale disorder is more relevant in real compounds than local or atomic-scale disorder. Comparison with other theoretical proposals is also discussed. Experimental tests are proposed for the relevance of disorder.

English Language Teaching in Japan Policy Plans and their Implementations

Abstract: This paper describes Japan's most recent attempts to improve English teaching and learning at all levels of the education system both for students and teachers as well as for the public in general....

Novel Wide-Band-Gap Ag(In1-xGax)Se2 Thin Film Solar Cells

Abstract: Ag(In1-xGax)Se2 thin films have been deposited on Mo-coated soda-lime glass substrates by the three-stage process using a molecular beam epitaxy (MBE) system. We found a remarkable decrease in the substrate temperature during the 2nd stage in which the film composition changes to a Ag excess. A single phase chalcopyrite AIGS thin film with a slightly Ag poor composition was obtained by using the temperature monitoring composition method. The cell performance of the AIGS thin film solar cell was found to strongly depend on the Ga/(In+Ga) and Ag/(In+Ga) atomic ratios. A high efficiency wide-gap (Eg=1.7eV) Ag(In0.2Ga0.8)Se2 thin film solar cell with a total-area efficiency of 9.3% (10.2% active area efficiency), Voc = 949mV, Jsc = 17.0 mA/cm2, FF = 0.577, and total area = 0.42 cm2 was achieved. The junction formation mechanism of AIGS devices is discussed based on electron beam induced current (EBIC) and scanning capacitance microscopy (SCM) analyses.

Development of a Monte Carlo Simulator for the Astro-E2 hard X-ray detector (HXD-II)

Abstract: The Hard X-ray Detector (HXD-II) is one of the scientific payloads on board the fifth Japanese cosmic X-ray satellite Astro-E2 , scheduled for launch in 2005. The HXD-II is designed to cover a wide energy range of 10-600 keV with a high sensitivity of about 10/sup -5/ cnt/s/cm/sup 2//keV. In order to derive the energy response of the sensor and to estimate the background, a Monte Carlo simulator based on the Geant4 toolkit is currently being developed. This paper describes the design concept of the HXD-II software package, including the analysis tools and the Monte Carlo simulator, and its verification through a comparison with actual data taken by pre-flight radio-isotope irradiation experiments, together with calculated outputs that can demonstrate the in-orbit performance of the HXD-II.

High-Energy Observations of XRF 030723: Evidence for an Off-Axis Gamma-Ray Burst?

Abstract: We report High Energy Transient Explorer 2 (HETE-2) Wide Field X-ray Monitor (WXM) and French Gamma Telescope observations of XRF 030723 along with observations of the XRF afterglow made using the 6.5 m Magellan Clay telescope and Chandra. The observed peak energy E of the νFν burst spectrum is found to lie within (or below) the WXM 2-25 keV passband at 98.5% confidence, and no counts are detected above 30 keV. Our best-fit value is E = 8.4 keV. The ratio of X-ray to γ-ray flux for the burst follows a correlation found for GRBs observed with HETE-2, and the duration of the burst is similar to that typical of long-duration GRBs. If we require that the burst isotropic equivalent energy Eiso and Epk satisfy the relation discovered by Amati et al. (2002), a redshift of z = 0.38 can be determined, in agreement with constraints determined from optical observations. We are able to fit the X-ray afterglow spectrum and to measure its temporal fade. Although the best-fit fade is shallower than the concurrent fade in the optical, the spectral similarity between the two bands indicates that the X-ray fade may actually trace the optical fade. If this is the case, the late-time rebrightening observed in the optical cannot be due to a supernova bump. We interpret the prompt and afterglow X-ray emission as arising from a jetted GRB observed off-axis and possibly viewed through a complex circumburst medium that is due to a progenitor wind.

Interaction of the ground state of quarter-filled one-dimensional strongly correlated electronic system with localized spins.

Abstract: We study numerically the ground-state properties of the one-dimensional quarter-filled strongly correlated electronic system interacting antiferromagnetically with localized $S=1/2$ spins. It is shown that the charge-ordered state is significantly stabilized by the introduction of relatively small coupling with the localized spins. When the coupling becomes large the spin and charge degrees of freedom behave quite independently and the ferromagnetism is realized. Moreover, the coexistence of ferromagnetism with charge order is seen in the strongly interacting region. The present theoretical results are to be compared with the experiments on phthalocyanine compounds.

"v-mics", advanced tps for strategic production administration: innovative maintenance combining db and cg

Abstract: To achieve worldwide high productivity and quality assurance of global production, the authors considered the necessity of including the above with strategic application of the TPS, and clarified the Advanced TPS as the global production by manufacturing technology for the strategic administration of production facilities. Nowadays, we have established manufacturing technology by innovative maintenance of Toyota, a most advanced automotive manufacturing enterprise. Therefore, we propose the V-MICS (utilizing Visualization-Maintenance Innovated Computer System) consisting of five steps (AML-1 to AML-5). Concretely for transfer of the maintenance skill, in particular we will accomplish a procedure combining DB (database) and CG (computer graphics). With regard to the former we will construct a DB for easier accumulation of know-how for parts replacement and other jobs. As regards to the latter, we will provide the instructions to enable even a person not familiarized with machine-drawings to carry out dairy inspection. As a result, we will not only attain considerable reduction of the maintenance cost, but also realize a lot of benefits such as more improved availability when we start up the global production in the world.

Design methodologies of planar duplexers and triplexers by manipulating attenuation poles

Abstract: Design methodologies of planar duplexer and triplexer consisting of bandpass filters (BPFs) using different tapped resonators are described. Firstly, we propose a planar duplexer consisting of BPFs using a tapped half-wavelength resonator and a tapped quarter-wavelength resonator. The duplexer is designed based on a classical filter design method with a narrow-band approximation and a tap-coupling method. The experimental duplexer is fabricated using coplanar-waveguide structures. Secondly, a planar triplexer consisting of three types of BPFs is described in a similar manner. The results of this study show that the design methodology is useful for realizing the high-performance planar duplexer and triplexer fabricated without increasing the number of elements.