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Search Results: 1 - 10 of 1225 matches for " Yuki Kawahara "
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Simulation of Human Phonation with Vocal Nodules  [PDF]
Shinji Deguchi, Yuki Kawahara
American Journal of Computational Mathematics (AJCM) , 2011, DOI: 10.4236/ajcm.2011.13022
Abstract: The geometric and biomechanical properties of the larynx strongly influence voice quality and efficiency. A physical understanding of phonation natures in pathological conditions is important for predictions of how voice disorders can be treated using therapy and rehabilitation. Here, we present a continuum-based numerical model of phonation that considers complex fluid-structure interactions occurring in the airway. This model considers a three-dimensional geometry of vocal folds, muscle contractions, and viscoelastic properties to provide a realistic framework of phonation. The vocal fold motion is coupled to an unsteady compressible respiratory flow, allowing numerical simulations of normal and diseased phonations to derive clear relationships between actual laryngeal structures and model parameters such as muscle activity. As a pilot analysis of diseased phonation, we model vocal nodules, the mass lesions that can appear bilaterally on both sides of the vocal folds. Comparison of simulations with and without the nodules demonstrates how the lesions affect vocal fold motion, consequently restricting voice quality. Furthermore, we found that the minimum lung pressure required for voice production increases as nodules move closer to the center of the vocal fold. Thus, simulations using the developed model may provide essential insight into complex phonation phenomena and further elucidate the etiologic mechanisms of voice disorders.
Examination of Treatment Methods for a PEDOT:PSS Transparent Conductive Film Produced Using an Inkjet Method  [PDF]
Atsushi Nitta, Yuki Imamura, Kazuya Kawahara, Kazuhiro Takeda
Advances in Materials Physics and Chemistry (AMPC) , 2017, DOI: 10.4236/ampc.2017.78024
Abstract: Flexible devices manufactured using printed electronics have attracted the attention of many researchers. A high-performance transparent conductive film exhibiting high flexibility and elasticity is expected to be developed because of its need for the creation of flexible devices. An indium tin oxide (ITO) thin film, which has generally been used, has weaknesses such as fragility to bending stress and depletion of the resource. This study focused on poly (3, 4-ethy-lenedioxythiophene)/poly (styrenesulfonate) (PEDOT:PSS), a conductive polymer material, and examined improvement in the resistivity and transmittance of the transparent conductive film produced using an inkjet method. The present study improved the electrical and optical characteristics of the thin film by examining the annealing temperature between printing operations and the application method of a polar solvent. As a result, the resistivity and transmittance of a PEDOT:PSS thin film were 1.49 × 10-3 Ω·cm and 89.2%, respectively. This film was obtained by annealing at 90°C for 30 min and applying a polar solvent, using an inkjet printer, between printing operations. The printing was performed three times.
Relationships of youth risk behaviors with norm-consciousness and resilience among Japanese high school students  [PDF]
Chie Kataoka, Yuji Nozu, Shiori Kawahara, Hiroko Kuroiwa, Masako Kudo, Yuki Sato, Motoyoshi Kubo, Motoi Watanabe
Open Journal of Preventive Medicine (OJPM) , 2012, DOI: 10.4236/ojpm.2012.23044
Abstract: The purpose of this study was to examine the influences of norm-consciousness and resilience on the prevention of youth risk behaviors among Japanese high school students. Data of a national survey, Japan Youth Risk Behavior Survey 2011, was used for this analysis. The subjects were 9778 students (5027 males, 4751 females) in grades 10-12 in 102 schools randomly selected from among high schools throughout Japan. When multiple regression analysis was carried out using four subdomains of norm-consciousness and three subdomains of resilience as the independent variables and nine risk behaviors as the dependent variables, the subdomains of norm-consciousness showed significant positive standardized partial regression coefficients for eight risk behaviors for both males and females. In particular, “current alcohol use” and “ever had sexual intercourse” showed the largest standardized partial regression coefficients for the norm-consciousness in school, and “current cigarette use” showed that for the norm-consciousness in community. The subdomains of resilience showed significant positive standardized partial regression coefficients for five risk behaviors for males and for six those for females. The results of this study suggest that the norm-consciousness is an important protective factor to comprehensively prevent risk behaviors among Japanese adolescents. It is expected to be effective to enhance the norm-consciousness particularly in school and community. In addition, resilience should also be emphasized as a factor to prevent specific risk behaviors.
Effects of dry and mist saunas on circulatory and thermoregulatory functions in humans  [PDF]
Satoshi Iwase, Yuko Kawahara, Naoki Nishimura, Hiroki Takada, Mayumi Nagata, Yuki Niimi, Chihiro Miwa
Health (Health) , 2013, DOI: 10.4236/health.2013.52036

To test the hypothesis that mist sauna is a safer way of bathing than dry sauna, we compared changes in circulatory and thermoregulatory functions during 10 min sauna bathing in mist sauna at 40 with relative humidity of 100%, and in dry sauna by infrared ray at 70 with relative humidity of 15%. Subjects were seven healthy young men aged 29 ± 6 yrs (mean ± SD). We measured blood pressure, heart rate, skin temperatures at chest, forearm, thigh, and leg, tympanic temperature (Tty) by thermistors, skin blood flow at forearm by laser Doppler flowmetry, and sweat rate by ventilated capsule method at 1 min intervals throughout the experiment. Total sweating and change of hematocrit were also measured for dehydration analysis. Blood pressure was elevated more and changes in heart rate and total sweating were larger in dry sauna than mist. A significant hematocrit increase was observed in dry sauna bathing only. Mean skin temperature and Tty in dry sauna were elevated higher than those in mist. Heat stress of the dry sauna may be stronger than that of the mist, leading to dehydration and hypovolemia by sweating. Percent plasma volume loss was significantly larger in the dry than mist sauna. Changes in skin blood flow and sweat rate/\"\"Tty during mist sauna were significantly larger than those during dry sauna bathing despite heat stress of the mist sauna. The mist sauna bathing may thus be safer physiologically, and provide more effective vascular dilatation and sweating than the dry sauna bathing.

Characterization of Pancreatic Islets in Two Selectively Bred Mouse Lines with Different Susceptibilities to High-Fat Diet-Induced Glucose Intolerance
Mototsugu Nagao, Akira Asai, Wataru Inaba, Momoyo Kawahara, Yuki Shuto, Shunsuke Kobayashi, Daisuke Sanoyama, Hitoshi Sugihara, Soroku Yagihashi, Shinichi Oikawa
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0084725
Abstract: Hereditary predisposition to diet-induced type 2 diabetes has not yet been fully elucidated. We recently established 2 mouse lines with different susceptibilities (resistant and prone) to high-fat diet (HFD)-induced glucose intolerance by selective breeding (designated selectively bred diet-induced glucose intolerance-resistant [SDG-R] and -prone [SDG-P], respectively). To investigate the predisposition to HFD-induced glucose intolerance in pancreatic islets, we examined the islet morphological features and functions in these novel mouse lines. Male SDG-P and SDG-R mice were fed a HFD for 5 weeks. Before and after HFD feeding, glucose tolerance was evaluated by oral glucose tolerance test (OGTT). Morphometry and functional analyses of the pancreatic islets were also performed before and after the feeding period. Before HFD feeding, SDG-P mice showed modestly higher postchallenge blood glucose levels and lower insulin increments in OGTT than SDG-R mice. Although SDG-P mice showed greater β cell proliferation than SDG-R mice under HFD feeding, SDG-P mice developed overt glucose intolerance, whereas SDG-R mice maintained normal glucose tolerance. Regardless of whether it was before or after HFD feeding, the isolated islets from SDG-P mice showed impaired glucose- and KCl-stimulated insulin secretion relative to those from SDG-R mice; accordingly, the expression levels of the insulin secretion-related genes in SDG-P islets were significantly lower than those in SDG-R islets. These findings suggest that the innate predispositions in pancreatic islets may determine the susceptibility to diet-induced diabetes. SDG-R and SDG-P mice may therefore be useful polygenic animal models to study the gene–environment interactions in the development of type 2 diabetes.
The Phonetics of Multiple Vowel Lengthening in Japanese  [PDF]
Shigeto Kawahara, Aaron Braver
Open Journal of Modern Linguistics (OJML) , 2013, DOI: 10.4236/ojml.2013.32019
Abstract: Many languages exploit a short vs. long lexical contrast in vowels. In most, if not all of these languages, the contrast is binary. In Japanese, however, speakers can lengthen vowels to express emphasis, and multiple degrees of lengthening can be used to express different degrees of emphasis. This paper offers the first experimental documentation of this emphatic vowel lengthening phenomenon. The current results demonstrate that, among the seven speakers recorded, at least a few speakers show six-levels of distinction in duration, and all but one speaker showed a steady linear correlation between duration and level of emphasis. We conclude that Japanese speakers have articulatory control that allows them to make very fine-grained durational distinctions, which go beyond mere binary short vs. long distinctions.
Object-Spatial Imagery Types of Japanese College Students  [PDF]
Masahiro Kawahara, Kazuo Matsuoka
Psychology (PSYCH) , 2013, DOI: 10.4236/psych.2013.43024

This study investigated the object-spatial imagery types found among Japanese college students. First, we examined the descriptive statistics of the Japanese version of the Object-Spatial Imagery Questionnaire object-spatial imagery scales, which measure respondents’ tendencies with respect to object-spatial imagery types. Although the means of these subscales were lower than those of the original versions, the raw score distributions and gender differences were similar to those obtained using the original version. Additionally, we compared imagery types among students in seven different academic departments. Specifically, the results showed specific patterns of imagery type among students in each department, indicating that the object-spatial imagery type model is applicable to Japanese college students and that individual imagery type data would be helpful for career guidance.

An Empirical Investigation of Common Sense of Land Use from a Statistical Approach  [PDF]
Yuki Hanashima
Journal of Geographic Information System (JGIS) , 2012, DOI: 10.4236/jgis.2012.42014
Abstract: Recently, ontological study has been one of the key concerns of geographic information science, a number of studies have been conducted in both of philosophical and knowledge engineering approach. Some studies pointed out the importance of human cognition and social context for development of ontologies. This paper presents empirical investigation of common sense of land use categories for development of suitable ontologies for each cultural or speech communities. Distinctions and characteristics in perceiving land use categories were described by a psychological method that was submitted to Japanese graduate and undergraduate students. In addition the results were analyzed using corresponddence analysis, a statistical technique for categorical data. This analysis serves to clarify the dominant determining factors for land use categories.
The Effect of Participants' Stress Manipulation on Experimenters’ Mood States  [PDF]
Hirotsune Sato, Jun I. Kawahara
Psychology (PSYCH) , 2017, DOI: 10.4236/psych.2017.88079
Abstract: This study examined whether experimenters’ mood states vary as a function of participants’ mood states. Thirty unacquainted “Experimenter”-“Participant” pairs participated. Participants delivered an unscripted speech in front of an experimenter while being videotaped. The stress levels of experimenters and participants were measured using a questionnaire and salivary cortisol measurements prior to and following the stress induction. A strong negative relationship was found between changes in the stress indices of the experimenters and those of the participants; a smaller increase in stress among participants was associated with a greater increase in stress among experimenters. This result suggests that stress induction can produce negative side effects among experimenters.
MicroRNAs in Neural Stem Cells and Neurogenesis
Hironori Kawahara
Frontiers in Neuroscience , 2012, DOI: 10.3389/fnins.2012.00030
Abstract: MicroRNA (miRNA) is a type of short-length (~22 nt) non-coding RNA. Most miRNAs are transcribed by RNA polymerase II and processed by Drosha-DGCR8 and Dicer complexes in the cropping and dicing steps, respectively. miRNAs are exported by exportin-5 from the nucleus to the cytoplasm after cropping. Trimmed mature miRNA is loaded and targets mRNA at the 3′ or 5′ untranslated region (UTR) by recognition of base-pairing in the miRNA-loaded RISC, where it is involved in gene silencing including translational repression and/or degradation along with deadenylation. Recent studies have shown that miRNA participates in various biological functions including cell fate decision, developmental timing regulation, apoptosis, and tumorigenesis. Analyses of miRNA expression profiles have demonstrated tissue- and stage-specific miRNAs including the let-7 family, miR-124, and miR-9, which regulate the differentiation of embryonic stem cells and/or neurogenesis. This review focuses on RNA-binding protein-mediated miRNA biogenesis during neurogenesis. These miRNA biogenesis-relating proteins have also been linked to human diseases because their mutations can cause several nervous system disorders. Moreover, defects in core proteins involved in miRNA biogenesis including Drosha, DGCR8, and Dicer promote tumorigenesis. Thus, the study of not only mature miRNA function but also miRNA biogenesis steps is likely to be important.
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