Escano M.C.S.,University of Fukui
Nano Research | Year: 2015
The degradation of Pt nanoparticles (NPs) in fuel cell cathodes leads to the loss of the precious metal catalyst. While the effect of NP size on Pt dissolution has been studied extensively, the influence of NP shape is largely unexplored. Because of the recent development of experimental methods to control the shape of metal NPs, rational guidelines/insights on the shape effects on NP stability are imperative. In this study, first-principles calculations based on density functional theory were conducted to determine the stability of 1–2 nm Pt NPs against Pt dissolution and coalescence with respect to NP shape. Toward dissolution, the stability of the Pt NPs increases in the following order: Hexagonal close-packed < icosahedral < cuboctahedral < truncated octahedral. This trend is attributed to the synergy of the oxygen adsorption strength and the local coordination of the Pt atoms. With respect to coalescence, the size of a NP is related to its propensity to coalesce or detach/migrate to form larger particles. The stability of the Pt NPs was found to increase in the following order: Hexagonal close-packed < truncated octahedral < cuboctahedral < icosahedral, and was correlated with the cohesive energies of the particles. By combining the characteristic stabilities of the shapes, new “metal-interfaced” Pt-based coreshell architectures were proposed that should be more stable than pure Pt nanoparticles with respect to both dissolution and coalescence. © 2014, Tsinghua University Press and Springer-Verlag Berlin Heidelberg.
Ohshima Y.,University of Fukui
Allergology International | Year: 2013
Mucosal barriers encounter an environment that is rich in pathogens that possess mechanisms for invading mucosal tissues. These barriers also encounter innocuous antigens, such as foods, airborne antigens, and microbiota. The mucosa has developed a sophisticated immune system that can mount robust immune responses against pathogenic antigens, while maintaining mucosal tolerance against non-pathogenic antigens. Accumulating evidence indicates that the mucosal epithelium, dendritic cells, and a subtype of T cells with regulatory properties play important roles in the development and maintenance of mucosal tolerance. Moreover, the micribiota also contribute to regulating the mucosal immune system. A failure to develop or the breakdown of mucosal tolerance can result in allergic diseases, such as food allergy and asthma. By taking advantage of the unique characteristics of the mucosal immune system, strategies that induce regulatory cells in vivo and, thereby, reconstitute mucosal tolerance may be used to develop novel therapies that are suitable for treating or preventing of allergic diseases. © 2013 Japanese Society of Allergology.
Tamai Y.,University of Fukui
ACS Macro Letters | Year: 2013
This work demonstrates the possibility of rearranging nanoporous cavity structures in crystalline syndiotactic polystyrene (s-PS) by applying external stresses. A molecular dynamics (MD) simulation was performed for the s-PS crystal with increasing or decreasing of each stress tensor component, starting from the nanoporous ε form. Upon uniaxial compression along the b-axis, the ε form was transformed into a lower density porous form, accompanied by significant elongation of the a-axis. The new form, named the S-I form, was stable only under the stress and was transformed into the γ form after release of the stress. The cavity structure was drastically changed by the transition. The straight cylindrical channels in the ε form, which may be used for the separation of organic solvents, were rearranged to narrower zigzag channels in the S-I form, which is suitable for the precise separation of gases. The molecular cavities disappeared after release of the stress, associated with the transition to the γ form. © 2013 American Chemical Society.
Mochizuki H.,University of Fukui
Nuclear Engineering and Design | Year: 2010
The present paper describes the one-dimensional thermal-hydraulic network code NETFLOW++ which can simulate the plant transients of various types of nuclear reactors and facilities consisting of various components like pumps, valves, and heat exchangers connected by piping. Numerical proportional-integral-derivative (PID) control systems are also incorporated to control velocity of pumps, throttling of valves, vanes for an air cooler, etc. The newly developed code consists of the NETFLOW code which can simulate the nuclear steam supply system and the PLUS code which can simulate the turbine and the feed-water system. Thermal-hydraulics and neutronics of the coupled system of the core, heat transport systems and the turbine system can be calculated by this code. Moreover, the code can simulate various fluids such as water, heavy water, liquid sodium, lead and lead-bismuth in the heat transport systems. The main point of this paper is a description of the basic equations used in this code for the liquid metal cooled reactor. A steady state of the liquid metal cooled reactor is calculated using a full model of the code to check the capability of the models incorporated into the code. Then, the turbine trip transient conducted at the 'Monju' reactor was calculated with the same model. Good agreement was obtained in steady state and transient state between the test and the calculation. However, the calculation of the turbine system in the steady state was sensitive due to phase change of extracted vapor and drain water from single-phase to two-phase and vice versa. © 2009 Elsevier B.V. All rights reserved.
Konoshita T.,University of Fukui
Current Hypertension Reports | Year: 2011
The concept of "pharmacogenomics" or "pharmacogenetics" promises to offer the ultimate in personalized medicine, and the renin-angiotensin system (RAS) is one of the most plausible candidates for the application of this approach in the area of hypertension. For the past two decades, genetic variants of the RAS have been tested for association with blood pressure response, but the results have been inconsistent. The problems have been attributed to many issues, but the most fundamental concern is thought to be the statistical power of the studies. Therefore, we have tried to put together a new systematic review using a database search including only recent reports with adequate numbers of subjects, and 11 reports were identified. From the results, we were able to draw conclusions with nearly consistent findings that the conventional genetic variants of the system (i.e., the ACE I/D, AGT M235T, AT1 A1166C, and AT2 variant) are not associated with antihypertensive effects by RAS blockade, at least by one individual SNP. By contrast, significant associations have been reported (by one report each) for AGT rs7079, AT1 haplotype, REN, and ACE2. For these variants, further evaluations and confirmation are anticipated. © 2011 Springer Science+Business Media, LLC.