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Search Results: 1 - 10 of 2120 matches for " Koji Matsuura "
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Theoretical Study on the Detection of Tilted Lipid Bilayers Using Surface Plasmon Resonance Techniques
Koyo Watanabe,Koji Matsuura
Journal of Sensors , 2012, DOI: 10.1155/2012/640780
Abstract: Effective refractive indices detected using surface plasmon resonance techniques are calculated as a function of the tilt angle of lipid bilayers in a multilayered model. The changes in the effective refractive indices are derived from the shift of an excitation angle of surface plasmon. To obtain effective refractive index plots, we determined refractive index changes in the lipid bilayers with 3 and 5?nm thicknesses as a function of tilt angle and obtained a relationship between the effective refractive index and tilt angle. We also showed that the effective refractive index depended on the lipid bilayers thickness and anisotropic permittivities, which vary with interchain distance. 1. Introduction Mechanical stimuli (MS) such as osmotic stress, membrane stretch, and shear force are activators for cellular functions including signaling, proliferation, impulse propagation, and gene expression [1]. MS are believed to induce formation changes in the cell membrane, leading to conformational changes in membrane proteins [2, 3]. For instance, in the cardiovascular system, transient receptor potential membrane proteins, which act as mechanosensitive ion channels, are activated by blood pressure [4]. Furthermore, in the field of mammalian reproduction, it has been confirmed that reproductive cells can be activated by shear stress caused by embryo and/or fluid motions [5]. Although unique relationships between MS and cellular activation have been reported, no study has yet provided a clear understanding of the mechanism at the molecular level. In lipid bilayer deformations, it is difficult to unravel the complex mechanisms as the ion channel functions are sensitive to the properties of the surrounding lipid bilayers [6]. If deformation of the lipid bilayers is experimentally observed after applying MS, especially shear forces or compression, the stresses on the lipid bilayer and the ion channels can be estimated and related to the function of the involved molecules. By these MS, tilt of the average molecular orientation with respect to the layer was induced [7]. It is desired that the relationship between the angle of the lipid tilting and the ion channel activity could be surveyed when the lipid tilts. To obtain greater understanding of these mechanisms, measurement technologies to evaluate the deformations of lipid layers induced by physical and MS need to be developed. Reconstructed systems of lipid bilayers are useful for investigating MS and the molecular functions because physiological molecular systems are too complex to clearly demonstrate the
Application of the Modified Force-Coupling Method of Tracing the Trajectories of Spherical Bubbles with Solid-Like and Slip Surfaces  [PDF]
Chao Guan, Shinichiro Yanase, Koji Matsuura, Toshinori Kouchi, Yasunori Nagata
Open Journal of Fluid Dynamics (OJFD) , 2017, DOI: 10.4236/ojfd.2017.74043
The force-coupling method (FCM) developed by Maxey and Patel (2001) was modified and applied to trace the trajectories of spherical bubbles with solid-like and slip surfaces. Careful comparison was made to the experimental results of Takemura et al. (2000, 2002a, 2002b). First, the result obtained by use of the original version of the FCM was compared to the experimental results. It was found that the original FCM was not feasible for tracing spherical bubble trajectories. Then, a correction was made to the FCM calculation of the bubble velocity by renormalization in terms of the bubble Reynolds number, which could very well trace the trajectory of the bubble with a solid-like, no-slip surface, but not that of a bubble with a slip surface. Finally, a substantial correction was made to the monopole term of the FCM, which could trace the trajectory of a bubble with a solid-like or slip surface very well even for the Reynolds number up to 20.
Application of matrix product states to the Hubbard model in one spatial dimension
Yukihiro Shimizu,Koji Matsuura,Hikaru Yahagi
Physics , 2013,
Abstract: We investigate the application of matrix product states to the Hubbard model in one spatial dimension with both of open and periodic boundary conditions. We develop the variatinal method that the optimization of the variational parameters is carried out locally and sequentially in the framework of matrix product operators (MPO) by including the sign, due to the anti-commutation relation of fermion operators, in the matrix element of MPO. The numerical accuracy of the ground state energy is examined.
Behavior of Motile Sperm in Taylor-Couette Flow: Effect of Shear Stress on the Behavior of Motile Sperm  [PDF]
Yasutaka Hayamizu, Toru Hyakutake, Koji Matsuura, Shinichiro Yanase, Shinichi Morita, Shigeru Ohtsuka, Takeshi Gonda
Open Journal of Fluid Dynamics (OJFD) , 2013, DOI: 10.4236/ojfd.2013.32A002

Infertility is often cited as one of the causes of a declining birthrate, which has become a serious social problem in recent years. Processes by which motile sperm can be safely and easily sorted are therefore important for infertility treatment. Therefore, as a new sorting method, microfluidic sperm sorter using the microfluidic system has been developed. To improve more separation efficiency of this device, it is necessary to know the behaviors of motile sperm in the microchannel where the sperm undergo shear flow. The previous study implied the necessity of the modeling of motile sperm in the shear flow. In the present study, therefore, we experimentally investigated the behavior of the motile sperm in the Taylor-Couette flow using PTV (Particle Tracking Velocimetry) method. The experimental results showed that the ascent of the shear stress led to the increase in the sperm velocity, and the direction of the sperm velocity was opposite to that of the flow.

Detection of Micrococcus Luteus Biofilm Formation in Microfluidic Environments by pH Measurement Using an Ion-Sensitive Field-Effect Transistor
Koji Matsuura,Yuka Asano,Akira Yamada,Keiji Naruse
Sensors , 2013, DOI: 10.3390/s130202484
Abstract: Biofilm formation in microfluidic channels is difficult to detect because sampling volumes are too small for conventional turbidity measurements. To detect biofilm formation, we used an ion-sensitive field-effect transistor (ISFET) measurement system to measure pH changes in small volumes of bacterial suspension. Cells of Micrococcus luteus ( M. luteus) were cultured in polystyrene (PS) microtubes and polymethylmethacrylate (PMMA)-based microfluidic channels laminated with polyvinylidene chloride. In microtubes, concentrations of bacteria and pH in the suspension were analyzed by measuring turbidity and using an ISFET sensor, respectively. In microfluidic channels containing 20 μL of bacterial suspension, we measured pH changes using the ISFET sensor and monitored biofilm formation using a microscope. We detected acidification and alkalinization phases of M. luteus from the ISFET sensor signals in both microtubes and microfluidic channels. In the alkalinization phase, after 2 day culture, dense biofilm formation was observed at the bottom of the microfluidic channels. In this study, we used an ISFET sensor to detect biofilm formation in clinical and industrial microfluidic environments by detecting alkalinization of the culture medium.
The Unstable CCTG Repeat Responsible for Myotonic Dystrophy Type 2 Originates from an AluSx Element Insertion into an Early Primate Genome
Tatsuaki Kurosaki, Shintaroh Ueda, Takafumi Ishida, Koji Abe, Kinji Ohno, Tohru Matsuura
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0038379
Abstract: Myotonic dystrophy type 2 (DM2) is a subtype of the myotonic dystrophies, caused by expansion of a tetranucleotide CCTG repeat in intron 1 of the zinc finger protein 9 (ZNF9) gene. The expansions are extremely unstable and variable, ranging from 75–11,000 CCTG repeats. This unprecedented repeat size and somatic heterogeneity make molecular diagnosis of DM2 difficult, and yield variable clinical phenotypes. To better understand the mutational origin and instability of the ZNF9 CCTG repeat, we analyzed the repeat configuration and flanking regions in 26 primate species. The 3′-end of an AluSx element, flanked by target site duplications (5′-ACTRCCAR-3′or 5′-ACTRCCARTTA-3′), followed the CCTG repeat, suggesting that the repeat was originally derived from the Alu element insertion. In addition, our results revealed lineage-specific repetitive motifs: pyrimidine (CT)-rich repeat motifs in New World monkeys, dinucleotide (TG) repeat motifs in Old World monkeys and gibbons, and dinucleotide (TG) and tetranucleotide (TCTG and/or CCTG) repeat motifs in great apes and humans. Moreover, these di- and tetra-nucleotide repeat motifs arose from the poly (A) tail of the AluSx element, and evolved into unstable CCTG repeats during primate evolution. Alu elements are known to be the source of microsatellite repeats responsible for two other repeat expansion disorders: Friedreich ataxia and spinocerebellar ataxia type 10. Taken together, these findings raise questions as to the mechanism(s) by which Alu-mediated repeats developed into the large, extremely unstable expansions common to these three disorders.
Preparation of Calcium- and Magnesium-Fortified Potato Starches with Altered Pasting Properties
Takahiro Noda,Shigenobu Takigawa,Chie Matsuura-Endo,Koji Ishiguro,Koichi Nagasawa,Masahiro Jinno
Molecules , 2014, DOI: 10.3390/molecules190914556
Abstract: Calcium- and magnesium-fortified potato starches were prepared by immersion in various concentrations of CaCl 2 and MgCl 2 aqueous solutions, respectively. The pasting properties, i.e., peak viscosity and breakdown, of all the starches obtained above were analyzed using a Rapid Visco Analyzer. Furthermore, the gelatinization properties and in vitro digestibility of the representative calcium- and magnesium-fortified starches were tested. The maximum calcium content of the fortified potato starches was as high as 686 ppm with the addition of a high-concentration CaCl 2 solution, while the calcium content of the control potato starch was 99 ppm. The magnesium content increased from 89 to 421 ppm by treatment of the potato starch with an MgCl 2 solution. Markedly lower values of peak viscosity and breakdown were observed in calcium- and magnesium-fortified potato starches than in the control potato starch. However, the gelatinization temperature and enthalpy as well as resistant starch content of calcium- and magnesium-fortified potato starches were similar to those of the control potato starch. It is concluded that potato starches with altered pasting properties can be easily manufactured by the use of solutions containing high levels of calcium and magnesium.
Novel Synthetic Method for the Vilsmeier-Haack Reagent and Green Routes to Acid Chlorides, Alkyl Formates, and Alkyl Chlorides  [PDF]
Yoshikazu Kimura, Daisuke Matsuura
International Journal of Organic Chemistry (IJOC) , 2013, DOI: 10.4236/ijoc.2013.33A001
Abstract: An environmentally benign and practical preparation method for the Vilsmeier-Haack reagent (VH) has been developed by using phthaloyl dichloride with DMF in toluene or 2-chlorotoluene. Phthalic anhydride as the byproduct was recovered in high yield by simple filtration. Some aromatic acids have been transformed into the corresponding acid chlorides in good yields by employing the isolated VH. Treatment of primary or secondary alcohols with VH gave alkyl formates or alkyl chlorides by depending on the reaction conditions.
Empirical Investigation of Threats to Loyalty Programs by Using Models Inspired by the Gordon-Loeb Formulation of Security Investment  [PDF]
Shiori Shinoda, Kanta Matsuura
Journal of Information Security (JIS) , 2016, DOI: 10.4236/jis.2016.72003
Abstract: Loyalty program (LP) is a popular marketing activity of enterprises. As a result of firms’ effort to increase customers’ loyalty, point exchange or redemption services are now available worldwide. These services attract not only customers but also attackers. In pioneering research, which first focused on this LP security problem, an empirical analysis based on Japanese data is shown to see the effects of LP-point liquidity on damages caused by security incidents. We revisit the empirical models in which the choice of variables is inspired by the Gordon-Loeb formulation of security investment: damage, investment, vulnerability, and threat. The liquidity of LP points corresponds to the threat in the formulation and plays an important role in the empirical study because it particularly captures the feature of LP networks. However, the actual proxy used in the former study is artificial. In this paper, we reconsider the liquidity definition based on a further observation of LP security incidents. By using newly defined proxies corresponding to the threat as well as other refined proxies, we test hypotheses to derive more implications that help LP operators to manage partnerships; the implications are consistent with recent changes in the LP network. Thus we can see the impacts of security investment models include a wider range of empirical studies.
Matrices and Division by Zero z/0 = 0  [PDF]
Tsutomu Matsuura, Saburou Saitoh
Advances in Linear Algebra & Matrix Theory (ALAMT) , 2016, DOI: 10.4236/alamt.2016.62007
Abstract: In this paper, a new viewpoint of the division by zero z/0 = 0 in matrices is introduced and the results will show that the division by zero is our elementary and fundamental mathematics. New and practical meanings for many mathematical and physical formulas for the denominator zero cases may be given. Furthermore, a new space idea for the point at infinity for the Eucleadian plane is also introduced.
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