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Search Results: 1 - 10 of 3259 matches for " Yasutaka Yamamoto "
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Assessment of Carbon Dioxide Emissions from Biodiversity-Conscious Farming: A Case of Stork-Friendly Farming in Japan  [PDF]
Daisuke Sawauchi, Yasutaka Yamamoto
Low Carbon Economy (LCE) , 2015, DOI: 10.4236/lce.2015.61002
Abstract: Although agriculture can contribute to ecosystem services, it can also be a source of disservices, including loss of biodiversity and emissions of greenhouse gases and pollutants. In this study, we evaluate the biodiversity-conscious farming method in terms of the impact on global warming by using the life cycle assessment (LCA) taking stork-friendly farming in Japan as a case of farming method. The results show that efforts for biodiversity conservation and countermeasures against global warming may be in a trade-off relationship. The results suggest that expansion of the farming scale and switch from low-agrichemical to agrichemical-free farming may be two possible paths towards a lower carbon dioxide emission than the current level.
Carbon Dioxide Emissions and Energy Self-Sufficiency of Woody Biomass Utilization for Residential Heating: A Case Study of Nishiwaga, Japan  [PDF]
Daisuke Sawauchi, Daisuke Kunii, Yasutaka Yamamoto
Journal of Environmental Protection (JEP) , 2015, DOI: 10.4236/jep.2015.64032
Abstract: Renewable energy sources, including bioenergy, are presently attracting considerable attention as possible substitutes for fossil fuels. Among the various sources of bioenergy, biomass can arguably play a significant role in the reduction of greenhouse gases and the provision of a stable energy supply. However, the use of fossil fuels continues in the production of bioenergy. Consequently, the overall extent to which biomass utilization for energy can reduce carbon dioxide emissions as a substitute for fossil fuels and whether this can improve the energy self-sufficiency rate remains largely unknown. This study responds to these questions using a case of a Japanese rural community using firewood for residential heating. The results showed that woody biomass utilization for energy is able to both reduce the dependence on fossil fuels and mitigate climate change. These findings offer new insights into the development of sustainability in rural communities.
The Regional Comprehensive Economic Partnership and Its Potential Impact on Greenhouse Gas Emissions  [PDF]
Hirokazu Akahori, Daisuke Sawauchi, Yasutaka Yamamoto
Journal of Environmental Protection (JEP) , 2016, DOI: 10.4236/jep.2016.79105
Abstract: Whether trade liberalization resulting from mega free trade agreements, such as the Regional Comprehensive Economic Partnership (RCEP), will have an impact on the environment is the subject of ongoing debate and remains an empirical matter. In this paper, we contribute to the debate on the relation between trade and the environment by considering the case of the RCEP and examining whether it will increase or decrease greenhouse gas (GHG) emissions. We measure the impact of the RCEP on GHG emissions using the Global Trade Analysis Project (GTAP) model and the GTAP CO2 and non-CO2 emissions databases. Our results suggest that the RCEP is likely to “increase” the total amount of GHG emissions in the 16 RCEP members and the world.
Endovascular Treatment of Brachiocephalic and Subclavian Arterial Disease  [PDF]
Yasutaka Baba, Sadao Hayashi, Hiroyuki Yamamoto, Yutaka Imoto, Masayuki Nakajo
Open Journal of Radiology (OJRad) , 2013, DOI: 10.4236/ojrad.2013.31002
Abstract:

Objectives: To review our experience of stentgraft deployment for vascular aneurysm or pseudoaneurysm of the brachiocephalic or subclavian artery. Methods: Participants comprised 7 patients (4 men, 3 women; mean age, 61 years; range, 47 - 76 years) who underwent endovascular repair of brachiocephalic or subclavian arterial vascular lesions between July 2001 and November 2008. Causes of vascular lesions were: traffic accident, n = 4; infection, n = 2; and post-irradiation state of esophageal cancer, n = 1. Safety, technical success, and clinical follow-up were evaluated. Results: Stentgraft deployment was successful in all cases. No complications related to stent fracture were encountered during follow-up (up to 2308 days). One male patient with esophageal cancer died of rebleeding from the tracheostomy hole 13 days after treatment with size mismatch between the stentgraft and brachiocephalic artery. Conclusion: Stentgraft deployment represents acceptable treatment for the injured brachiocephalic artery or proximal side of the subclavian artery.

A Micromixer Using the Chaos of Secondary Flow: Rotation Effect of Channel on the Chaos of Secondary Flow  [PDF]
Yasutaka Hayamizu, Shinichiro Yanase, Shinichi Morita, Shigeru Ohtsuka, Takeshi Gonda, Kazunori Nishida, Kyoji Yamamoto
Open Journal of Fluid Dynamics (OJFD) , 2012, DOI: 10.4236/ojfd.2012.24A021
Abstract: The micromixer, which has a rotor with a curved channel, is studied experimentally. The secondary flow in a curved channel of rectangular cross-section is investigated using PIV (Particle Image Velocimetry) and LIF (Laser Induced Fluorescence) methods. Two walls of the channel (the inner and top walls) rotate around the center of curvature and a pressure gradient is imposed in the direction of the exit of the channel. The non-dimensional channel curvature δ=a/R is taken to be about 0.1, where 2a is the width of the channel, R the curvature radius of the channel. Other non-dimensional parameters concerned are the Dean number De=Reδ1/2, the Reynolds number Re=qdh/v, where q is the mean flow velocity in the channel axis direction, ν the kinematic viscosity, dh the hydraulic diameter of the channel, and the Taylor number Tr=2(2δ)1/2Ωa2/(δv), where Ω is the angular velocity of the rotor. Photographs of the flow in a cross-section at 180° downstream from the curved channel entrance are taken by changing the flux (De) at a constant rotational speed (Tr) of the channel walls. It is found that good mixing performance is obtained in the case of De≤0.1|Tr| and for that case secondary flows show chaotic behaviors. And then we have confirmed the occurrence of reversal of the mean axial flow.
A Micromixer Using the Taylor-Dean Flow: Effect of Inflow Conditions on the Mixing  [PDF]
Toshihiko Kawabe, Yasutaka Hayamizu, Shinichiro Yanase, Takeshi Gonda, Shinichi Morita, Shigeru Ohtsuka, Kyoji Yamamoto
Open Journal of Fluid Dynamics (OJFD) , 2014, DOI: 10.4236/ojfd.2014.45037
Abstract: Chaotic mixing in a curved-square channel flow is studied experimentally and numerically. Two walls of the channel (inner and top walls) rotate around the center of curvature and a pressure gradient is imposed in the direction toward the exit of the channel. This flow is a kind of Taylor-Dean flows. There are two parameters dominating the flow, the Dean number De (∝ the pressure gradient or the Reynolds number) and the Taylor number Tr (∝ the angular velocity of the wall rotation). In the present paper, we analyze the physical mechanism of chaotic mixing in the Taylor-Dean flow by comparing experimental and numerical results. We produced a micromixer model of the curved channel several centimeters long with square cross section of a few millimeters side. The secondary flow was measured using laser induced fluorescence (LIF) method to examine secondary flow characteristics. We also performed three-dimensional numerical simulations for the exactly same configuration as the experimental system to study the mechanism of chaotic mixing. It is found that good mixing performance is achieved for the case of De ≤ 0.1Tr, and that mixing efficiency changes according to the difference in inflow conditions. The flow is studied both experimentally and numerically, and both results agree with each other very well.
A Micromixer Using the Taylor-Dean Flow: Effects of Aspect Ratio and Inflow Condition on the Mixing  [PDF]
Yasutaka Hayamizu, Toshihiko Kawabe, Shinichiro Yanase, Takeshi Gonda, Shinichi Morita, Shigeru Ohtsuka, Kyoji Yamamoto
Open Journal of Fluid Dynamics (OJFD) , 2015, DOI: 10.4236/ojfd.2015.53027
Abstract: Chaotic mixing in three different types of curved-rectangular channels flow has been studied experimentally and numerically. Two walls of the channel (inner and top walls) rotate around the center of curvature and a pressure gradient are imposed in the direction toward the exit of the channel. This flow is a kind of Taylor-Dean flow. There are two parameters dominating the flow, the Dean number De (∝ the pressure gradient or the Reynolds number) and the Taylor number Tr (∝ the angular velocity of the wall rotation). In this paper, we analyze the physical mechanism of chaotic mixing in the Taylor-Dean flow by comparing experimental results and numerical ones. We produced three micromixer models of the curved channel, several centimeters long, with rectangular cross-section of a few millimeters side. The secondary flow is measured using laser induced fluorescence (LIF) method to examine secondary flow characteristics. Also we performed three-dimensional numerical simulations with the open source CFD solver, OpenFOAM, for the same configuration as the experimental system to study the mechanism of chaotic mixing. It is found that good mixing performance is obtained in the case of De ≤ 0.1 Tr, and it becomes more remarkable when the aspect ratio tends to large. And it is found that the mixing efficiency changes according to the aspect ratio and inflow condition.
Alterations in the human epidermal growth factor receptor 2-phosphatidylinositol 3-kinase-v-Akt pathway in gastric cancer
Yasutaka Sukawa,Hiroyuki Yamamoto,Katsuhiko Nosho,Hiroaki Kunimoto
World Journal of Gastroenterology , 2012, DOI: 10.3748/wjg.v18.i45.6577
Abstract: AIM: To investigate human epidermal growth factor receptor 2 (HER2)-phosphatidylinositol 3-kinase (PI3K)-v-Akt murine thymoma viral oncogene homolog signaling pathway. METHODS: We analyzed 231 formalin-fixed, paraffin-embedded gastric cancer tissue specimens from Japanese patients who had undergone surgical treatment. The patients’ age, sex, tumor location, depth of invasion, pathological type, lymph node metastasis, and pathological stage were determined by a review of the medical records. Expression of HER2 was analyzed by immunohistochemistry (IHC) using the HercepTestTM kit. Standard criteria for HER2 positivity (0, 1+, 2+, and 3+) were used. Tumors that scored 3+ were considered HER2-positive. Expression of phospho Akt (pAkt) was also analyzed by IHC. Tumors were considered pAkt-positive when the percentage of positive tumor cells was 10% or more. PI3K, catalytic, alpha polypeptide (PIK3CA) mutations in exons 1, 9 and 20 were analyzed by pyrosequencing. Epstein-Barr virus (EBV) infection was analyzed by in situ hybridization targeting EBV-encoded small RNA (EBER) with an EBER-RNA probe. Microsatellite instability (MSI) was analyzed by polymerase chain reaction using the mononucleotide markers BAT25 and BAT26. RESULTS: HER2 expression levels of 0, 1+, 2+ and 3+ were found in 167 (72%), 32 (14%), 12 (5%) and 20 (8.7%) samples, respectively. HER2 overexpression (IHC 3+) significantly correlated with intestinal histological type (15/20 vs 98 /205, P = 0.05). PIK3CA mutations were present in 20 cases (8.7%) and significantly correlated with MSI (10/20 vs 9/211, P < 0.01). The mutation frequency was high (21%) in T4 cancers and very low (6%) in T2 cancers. Mutations in exons 1, 9 and 20 were detected in 5 (2%), 9 (4%) and 7 (3%) cases, respectively. Two new types of PIK3CA mutation, R88Q and R108H, were found in exon1. All PIK3CA mutations were heterozygous missense single-base substitutions, the most common being H1047R (6/20, 30%) in exon20. Eighteen cancers (8%) were EBV-positive and this positivity significantly correlated with a diffuse histological type (13/18 vs 93/198, P = 0.04). There were 7 cases of lymphoepithelioma-like carcinomas (LELC) and 6 of those cases were EBV-positive (percent/EBV: 6/18, 33%; percent/all LELC: 6/7, 86%). pAkt expression was positive in 119 (53%) cases but showed no correlation with clinicopathological characteristics. pAkt expression was significantly correlated with HER2 overexpression (16/20 vs 103/211, P < 0.01) but not with PIK3CA mutations (12/20 vs 107/211, P = 0.37) or EBV infection (8/18 vs 103/211, P = 0.69).
A Simple Method of Measuring Vaccine Effects on Infectiousness and Contagion  [PDF]
Yasutaka Chiba
Open Journal of Statistics (OJS) , 2013, DOI: 10.4236/ojs.2013.34A002
Abstract:

The vaccination of one person may prevent another from becoming infected, either because the vaccine may prevent the first person from acquiring the infection and thereby reduce the probability of transmission to the second, or because, if the first person is infected, the vaccine may impair the ability of the infectious agent to initiate new infections. The former mechanism is referred as a contagion effect and the latter is referred as an infectiousness effect. By applying a principal stratification approach, the conditional infectiousness effect has been defined, but the contagion effect is not defined using this approach. Recently, new definitions of unconditional infectiousness and contagion effects were provided by applying a mediation analysis approach. In addition, a simple relationship between conditional and unconditional infectiousness effects was found under a number of assumptions. These two infectiousness effects can be assessed by very simple estimation and sensitivity analysis methods under the assumptions. Nevertheless, such simple methods to assess the contagion effect have not been discussed. In this paper, we review the methods of assessing infectiousness effects, and apply them to the inference of the contagion effect. The methods provided here are illustrated with hypothetical vaccine trial data.

Sample Size Calculation of Exact Tests for the Weak Causal Null Hypothesis in Randomized Trials with a Binary Outcome  [PDF]
Yasutaka Chiba
Open Journal of Statistics (OJS) , 2016, DOI: 10.4236/ojs.2016.65063
Abstract: The main purpose in many randomized trials is to make an inference about the average causal effect of a treatment. Therefore, on a binary outcome, the null hypothesis for the hypothesis test should be that the causal risks are equal in the two groups. This null hypothesis is referred to as the weak causal null hypothesis. Nevertheless, at present, hypothesis tests applied in actual randomized trials are not for this null hypothesis; Fisher’s exact test is a test for the sharp causal null hypothesis that the causal effect of treatment is the same for all subjects. In general, the rejection of the sharp causal null hypothesis does not mean that the weak causal null hypothesis is rejected. Recently, Chiba developed new exact tests for the weak causal null hypothesis: a conditional exact test, which requires that a marginal total is fixed, and an unconditional exact test, which does not require that a marginal total is fixed and depends rather on the ratio of random assignment. To apply these exact tests in actual randomized trials, it is inevitable that the sample size calculation must be performed during the study design. In this paper, we present a sample size calculation procedure for these exact tests. Given the sample size, the procedure can derive the exact test power, because it examines all the patterns that can be obtained as observed data under the alternative hypothesis without large sample theories and any assumptions.
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