Aoyama Gakuin University

About: Aoyama Gakuin University is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Superconductivity & Thin film. The organization has 3494 authors who have published 6419 publications receiving 115648 citations. The organization is also known as: Aoyama gakuin daigaku.

Do Ultraluminous X-Ray Sources Really Contain Intermediate-Mass Black Holes?

Abstract: An open question remains whether Ultraluminous X-ray Sources (ULXs) really contain intermediate-mass black holes (IMBHs). We carefully investigated the XMM-Newton EPIC spectra of four ULXs that were claimed to be strong candidates of IMBHs by several authors. Wefirst triedfitting by the standard spectral model of disk blackbody (DBB) + power-law (PL), finding good fits to all of the data, in agreement with others. We, however, found that the PL component dominates the DBB component at ∼ 0.3 to 10keV. Thus, the black hole parameters derived solely from the minor DBB component are questionable. Next, we tried to fit the same data by the “p-free disk model” without the PL component, assuming an effective temperature profile of Teff ∝ r −p ,w herer is the disk radius. Interestingly, in spite of one less free-model parameter, we obtained similarly good fits with much higher innermost disk temperatures, 1.8

The Effects of Using Corpora on Revision Tasks in L2 Writing with Coded Error Feedback.

Abstract: This study reports on the results of classroom research investigating the effects of corpus use in the process of revising compositions in English as a foreign language. Our primary aim was to investigate the relationship between the information extracted from corpus data and how that information actually helped in revising different types of errors in the essays. In ‘data-driven learning’, previous research has often failed to provide rigorous criteria for choosing the words or phrases suitable for correction with corpus data. By investigating the above relationship, this study aims to clarify what should be corrected by looking at corpus data. 93 undergraduate students from two universities in Tokyo wrote a short essay in 20 minutes without a dictionary, and the instructors gave coded error feedback for two lexical or grammatical errors. They deliberately selected one error which should be appropriate for checking against corpus data and one that was more likely to be corrected without using any reference resource. Three weeks later, a short hands-on instruction of the corpus query tool was given, followed by revision activities in which the participants were instructed to revise their first drafts, with or without the tool depending on the codes given to each error. 188 errors were automatically classified into three different categories (omission, addition and misformation) using natural language processing techniques. All words and phrases tagged for errors were further annotated for part-of-speech (POS) information. The results show that there was a significant difference in the accuracy rate among the three error types when the students consulted the corpus: omission and addition errors were easily identified and corrected, whereas misformation errors were low in correction accuracy. This reveals that certain errors are more suitable for checking against corpus data than others.

Broken time-reversal symmetry probed by muon spin relaxation in the caged type superconductor Lu5Rh6Sn18

Abstract: The superconducting state of the caged type compound ${\mathrm{Lu}}_{5}{\mathrm{Rh}}_{6}{\mathrm{Sn}}_{18}$ has been investigated by using magnetization, heat capacity, and muon spin relaxation or rotation $(\ensuremath{\mu}\mathrm{SR})$ measurements, and the results interpreted on the basis of the group theoretical classifications of the possible pairing symmetries and a simple model of the resulting quasiparticle spectra. Our zero-field $\ensuremath{\mu}\mathrm{SR}$ measurements clearly reveal the spontaneous appearance of an internal magnetic field below the transition temperature, which indicates that the superconducting state in this material is characterized by broken time-reversal symmetry. Further, the analysis of the temperature dependence of the magnetic penetration depth measured using the transverse-field $\ensuremath{\mu}\mathrm{SR}$ measurements suggests an isotropic $s\ensuremath{-}\text{wave}$ character for the superconducting gap. This is in agreement with the heat capacity behavior, and we show that it can be interpreted in terms of a nonunitary triplet state with point nodes and an open Fermi surface.

Can we explain AMS-02 antiproton and positron excesses simultaneously by nearby supernovae without pulsars or dark matter?

Abstract: We explain the excess of the antiproton fraction recently reported by the AMS-02 experiment by considering collisions between cosmic-ray protons accelerated by a local supernova remnant and the surrounding dense cloud. The same “$pp$ collisions” provide the right ratio of daughter particles to fit the observed positron excess simultaneously in the natural model parameters. The supernova happened in relatively lower metallicity than the major cosmic-ray sources. The cutoff energy of electrons marks the supernova age of ${\sim }10^{5}$ years, while the antiproton excess may extend to higher energy. Both antiproton and positron fluxes are completely consistent with our predictions in an earlier paper [Y. Fujita et al., Phys. Rev. D 80, 063003 (2009) [arXiv:0903.5298 [astro-ph.HE]]].

Ba 2 IrO 4 : A spin-orbit Mott insulating quasi-two-dimensional antiferromagnet

Abstract: A layered iridate Ba${}_{2}$IrO${}_{4}$ was synthesized using a high-pressure synthesis technique. Its electronic state was studied through electrical resistivity, magnetic susceptibility, and \ensuremath{\mu}SR experiments. It was found that Ba${}_{2}$IrO${}_{4}$ crystallizes in a ${\mathrm{K}}_{2}$NiF${}_{4}$-type structure (space group $I$4/mmm) with lattice parameters $a$ $=$4.030(1) \AA{} and $c$ $=$13.333(4) \AA{}. The structure includes flat IrO${}_{2}$ square planar lattices with straight Ir-O-Ir bonds. Ba${}_{2}$IrO${}_{4}$ is a Mott insulator (activation energy $\ensuremath{\Delta}{E}_{a}$ \ensuremath{\sim} 0.07 eV) driven by a spin-orbit interaction. The magnetic susceptibility and \ensuremath{\mu}SR studies revealed that the magnetic ground state is antiferromagnetic long-range order (${T}_{N}$ \ensuremath{\sim} 240 K) in which the magnetic moment (\ensuremath{\sim}0.34${\ensuremath{\mu}}_{B}$/Ir atom) is significantly reduced by a low-dimensional quantum spin fluctuation with a large intraplane correlation |$J$|. The behavior is similar to that in parent materials of high-${T}_{C}$ cuprate superconductors such as La${}_{2}$CuO${}_{4}$.