Sophia University

About: Sophia University is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Nonlinear system & Catalysis. The organization has 4986 authors who have published 7657 publications receiving 106567 citations. The organization is also known as: Jōchi Daigaku.

Perelman’s invariant, Ricci flow, and the Yamabe invariants of smooth manifolds

Abstract: In his study of Ricci flow, Perelman introduced a smooth-manifold invariant called \(\bar{\lambda}\). We show here that, for completely elementary reasons, this invariant simply equals the Yamabe invariant, alias the sigma constant, whenever the latter is non-positive. On the other hand, the Perelman invariant just equals +∞ whenever the Yamabe invariant is positive.

Characterization of vibrational and visual signals which elicit spawning behavior in the male himé salmon (landlocked red salmon, Oncorhynchus nerka)

Abstract: Hime salmon (landlocked red salmon, Oncorhynchus nerka) have an elaborate communication system, which ensures synchronous spawning by both sexes and successful fertilization. Both the vibrational and visual signals have been suggested to be involved in this communication system. To characterize these signals, vibrating or stationary three-dimensional models of various types were presented to the male, and male behavior elicited was examined. The results showed that the vibrating model mimicking certain aspects of the female behavior (‘prespawning act’) elicits the spawning in the male (Figs. 2, 3, 5). Furthermore, it was found that (1) the presence of both the vibrational and visual cues (Figs. 6, 7), and (2) spatial coincidence of these two cues (Fig. 8) are necessary for eliciting this behavior. Based on these results it was supposed that the vibrational and visual informations converge at the central nervous system where they are integrated to elicit the spawning.

Mechanism of egg envelope digestion by hatching enzymes, HCE and LCE in medaka, Oryzias latipes.

Abstract: Hatching of medaka embryos from the fertilized egg envelope involves two enzymes, HCE and LCE. HCE swells the envelope and then LCE completely dissolves it. We determined HCE and LCE cleavage sites on the egg envelope that are primarily constructed of two groups of subunit proteins, ZI-1,2 and ZI-3. HCE and LCE cleaved different target sequences on the egg envelope proteins but shared one common cleavage site. HCE cleaved the N-terminal region of ZI-1,2 and ZI-3, mainly the Pro-Xaa-Yaa repeat sequence of ZI-1,2 into hexapeptides, but not the site within a zona pellucida (ZP) domain that is considered to be the core structure of the egg envelope. The cleavage of these N-terminal regions results in swelling and softening of the envelope. LCE cleaved the middle of the ZP domain of ZI-1,2, in addition to the upstream of the trefoil domain of ZI-1,2 and the ZP domain of ZI-3. This middle site is in the intervening sequence connecting two subdomains of the ZP domain. Cleaving this site would result in the solubilization of the swollen egg envelope by the disruption of the filamentous structure that is thought to be formed by the non-covalent polymerization of ZP domains.

Crystallization of Ca + ions in a linear rf octupole ion trap

Abstract: A laser-cooling experiment with ${\mathrm{Ca}}^{+}$ ions trapped in a linear rf octupole ion trap is presented. The phase transition of the laser-cooled ${\mathrm{Ca}}^{+}$ ions from the cloud to the crystal state is observed by an abrupt dip of the laser-induced fluorescence spectrum and indicates that mK temperatures are obtained. We have also performed molecular dynamics simulations under various conditions to confirm this property by deducing axially symmetric structures of Coulomb crystals and by evaluating the translational temperatures of the laser-cooled ions. The simulation results show that for small numbers of ions novel ring-shaped crystals are produced. As the number of ions is increased, cylindrical layers in the ring crystal are sequentially formed. For more than 100 ions, also hexagonal and spiral structures emerge in parts of the large-size ion crystal, which has a length on the order of millimeters for the present geometrical arrangement and voltages. An advantage of the linear rf octupole trap is its large almost-field-free region in the middle of the trap, where the micromotion amplitude is small for trapped ions. These results demonstrate that such a multipole trap has attractive features for quantum computing and ultracold ion-atom collision studies.

Education system in acoustics of speech production using physical models of the human vocal tract

Abstract: In this paper, we present and discuss an educational system in the fields of acoustics and speech science using a series of physical models of the human vocal tract. Because education in acoustics is relevant for several fields related to speech communication, it hosts students from a variety of educational backgrounds. Moreover, we believe that an education in acoustics is important for students of different ages: college, high school, middle school, and even elementary school students. Because of the varied student populations, we develop an educational system that instructs students intuitively and effectively and consists of the following models: lung models, an artificial larynx, Arai's models (cylinder and plate type models), Umeda and Teranishi's model (a variable-shape model), and head-shaped models. These models effectively demonstrate several principal aspects of speech production, such as phonation, source-filter theory, the relationship between vocal-tract shape/ tongue movement and vowel quality, and nasalization of vowels. We have confirmed that combining the models in an effective way produces complete education in the acoustics of speech production. The examinations and questionnaire surveys conducted before and after using our proposed system revealed that the learners' understanding of what improves with the use of the system. The system is also effective for voice and articulatory training in speech pathology and language learning.