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Search Results: 1 - 10 of 612 matches for " Naoto Utsuyama "
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Surface Roughness of SiGe/Si(110) Formed by Stress-Induced Twins and the Solution to Produce Smooth Surface  [PDF]
Junji Yamanaka, Mai Shirakura, Chiaya Yamamoto, Naoto Utsuyama, Kei Sato, Takane Yamada, Kosuke O. Hara, Keisuke Arimoto, Kiyokazu Nakagawa
Journal of Materials Science and Chemical Engineering (MSCE) , 2018, DOI: 10.4236/msce.2018.61004
Abstract:
Lattice-strained Si thin films grown onto SiGe(110)/Si(110) are attracting because of their potential to realize high-speed transistors. In this study we observe surface morphology of Si/SiGe/Si(110) using scanning electron microscopy and we also observe microstructure of the identical position using cross-sectional transmission electron microscopy. These results reveal that crossing of stress-induced twins causes remarkable surface roughness. We propose using vicinal substrate to avoid this phenomenon and our successive experimental results are shown in this paper.
A 100% Water Mobile Phase HPLC-PDA Analysis of Meamine and Related Analogues  [PDF]
Naoto Furusawa
American Journal of Analytical Chemistry (AJAC) , 2012, DOI: 10.4236/ajac.2012.34040
Abstract: This paper describes a reserved-phase high performance liquid chromatographic method for detecting melamine (MEL) and related analogues, cyanuric acid (CYA), ammeline (AML), and ammelide (AMD), using a 100% water mobile phase. Chromatographic separation was performed an Inertsil? ODS-4 (250 × 4.6 mm, 5 μm) with a water mobile phase and a photodiode-array detector. The monitoring wavelength was adjusted to 210 nm which represents an average maximum for all the analytes. The total run time was < 8 min. The method shows high stability, significant linearity and satisfactory sensitivity. The detection limits were established in the range 23 - 46 ng.mL–1. An inexpensive and harmless method for the simultaneous detection of MEL, CYA, AML, and AMD was developed and may be further applied to the quantification in foods.
Organic Solvent-Free and Simple Method for Determining Cyromazine and Its Metabolite, Melamine, in Cow’s Milk  [PDF]
Naoto Furusawa
Journal of Analytical Sciences, Methods and Instrumentation (JASMI) , 2012, DOI: 10.4236/jasmi.2012.22013
Abstract: This paper described an organic solvent-free, rapid, simple, and space-saving method of sample preparation followed by HPLC coupled photo-diode array (PDA) detector for simultaneous quantification of cyromazine (CYR) and its decy-cropropylated metabolite, melamine (MEL), in milk. The HPLC-PDA was performed on an Inertsil? HILIC column with an isocratic aqueous mobile phase. Analytes were extracted from the sample using water, and purified by Mono-Spin?-C18, a centrifugal monolithic silica spin mini-columns, and quantified within 20 min. The method, performed under 100% aqueous conditions, obtained average recoveries for CYR and MEL in the range of 93.2% - 99.1% with relative standard deviations ≤ 2.8%. The quantitation limits were 8.5 ng/mL for CYR and 10 ng/mL for MEL, respectively. No organic solvents were used at any stage of the analysis.
Discrete Differential Geometry of n-Simplices and Protein Structure Analysis  [PDF]
Naoto Morikawa
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.516237
Abstract:

This paper proposes a novel discrete differential geometry of n-simplices. It was originally developed for protein structure analysis. Unlike previous works, we consider connection between space-filling n-simplices. Using cones of an integer lattice, we introduce tangent bundle-like structure on a collection of n-simplices naturally. We have applied the mathematical framework to analysis of protein structures. In this paper, we propose a simple encoding method which translates the conformation of a protein backbone into a 16-valued sequence.

Discrete Differential Geometry of Triangles and Escher-Style Trick Art  [PDF]
Naoto Morikawa
Open Journal of Discrete Mathematics (OJDM) , 2016, DOI: 10.4236/ojdm.2016.63013
Abstract: This paper shows the usefulness of discrete differential geometry in global analysis. Using the discrete differential geometry of triangles, we could consider the global structure of closed trajectories (of triangles) on a triangular mesh consisting of congruent isosceles triangles. As an example, we perform global analysis of an Escher-style trick art, i.e., a simpler version of “Ascending and Descending”. After defining the local structure on the trick art, we analyze its global structure and attribute its paradox to a singular point (i.e., a singular triangle) at the center. Then, the endless “Penrose stairs” is described as a closed trajectory around the isolated singular point. The approach fits well with graphical projection and gives a simple and intuitive example of the interaction between global and local structures. We could deal with higher dimensional objects as well by considering n-simplices (n > 2) instead of triangles.
Discrete Differential Geometry and the Structural Study of Protein Complexes  [PDF]
Naoto Morikawa
Open Journal of Discrete Mathematics (OJDM) , 2017, DOI: 10.4236/ojdm.2017.73014
Abstract: This paper proposes a novel four-dimensional approach to the structural study of protein complexes. In the approach, the surface of a protein molecule is to be described using the intersection of a pair of four-dimensional triangular cones (with multiple top vertexes). As a mathematical toy model of protein complexes, we consider complexes of closed trajectories of n-simplices (n=2,3,4...), where the design problem of protein complexes corresponds to an extended version of the Hamiltonian cycle problem. The problem is to find “a set of” closed trajectories of n-simplices which fills the n-dimensional region defined by a given pair of n+1 -dimensional triangular cones. Here we give a solution to the extended Hamiltonian cycle problem in the case of n=2 using the discrete differential geometry of triangles (i.e., 2-simplices).
Global Geometrical Constraints on the Shape of Proteins and Their Influence on Allosteric Regulation  [PDF]
Naoto Morikawa
Applied Mathematics (AM) , 2018, DOI: 10.4236/am.2018.910076
Abstract:
Proteins are the workhorse molecules of the cell, which are obtained by folding long chains of amino acids. Since not all shapes are obtained as a folded chain of amino acids, there should be global geometrical constraints on the shape. Moreover, since the function of a protein is largely determined by its shape, constraints on the shape should have some influence on its interaction with other proteins. In this paper, we consider global geometrical constraints on the shape of proteins. Using a mathematical toy model, in which proteins are represented as closed chains of tetrahedrons, we have identified not only global geometrical constraints on the shape of proteins, but also their influence on protein interactions. As an example, we show that a garlic-bulb like structure appears as a result of the constraints. Regarding the influence of global geometrical constraints on interactions, we consider their influence on the structural coupling of two distal sites in allosteric regulation. We then show the inseparable relationship between global geometrical constraints and protein interactions; i.e. they are different sides of the same coin. This finding could be important for the understanding of the basic mechanisms of allosteric regulation of protein functions.
EMTP Induction Motor Model from Modal Measurements for Inverter Surge Analysis  [PDF]
Asha Shendge, Naoto Nagaoka
Circuits and Systems (CS) , 2013, DOI: 10.4236/cs.2013.41004
Abstract:

The over-voltage phenomenon is usually described using the traveling wave and reflection phenomena in variable speed drive system. A voltage pulse, initiated at the inverter, being reflected at the motor terminals due to a mismatch between the surge impedance of the motor and the cable. In this paper, resistance, inductance and capacitance of the cable and the motor windings are obtained experimentally by modal measurements and suitable models are developed to match the experimental results by considering resonance in the motor winding. This paper emphasize on Induction motor model using the theory of natural modes of propagation. The developed model validity is investigated for inverter surge application.

Lyotropic Liquid Crystal Electrochemical Polymerization of Thiophene-Based Monomers: Polymerization in Cholesteric Liquid Crystal and Columnar Phase  [PDF]
Naoto Eguchi, Hiromasa Goto
Soft (Soft) , 2017, DOI: 10.4236/soft.2017.52002
Abstract: Synthesis of conductive polymer poly([thiophene]-[benzo[1,2,3]thiadiazole] [thiophene]) (abbreviated as P(T-Btdaz-T)) was achieved by electrochemical polymerization in hydroxypropyl cellulose (HPC)/N,N-dimethylformamide (DMF) in liquid crystal state. The polymer thus obtained shows fingerprint texture, which is derived from helical structure of the HPC in cholesteric liquid crystal state. Fourier transform infrared spectroscopy measurements revealed that the polymer film is P(T-Btdaz-T)/HPC composite. Circular dichroism optical absorption spectroscopy measurements show that the polymer has the optical activity. Next, electrochemical polymerization of 3,4-ethylene-dioxythiophene (EDOT) was carried out in columnar phase liquid crystal. The polymer transcribes the columnar structure and shows optical structure resembling columnar liquid crystal electrolyte solution.
Dynamical view of pair creation in uniform electric and magnetic fields
Tanji, Naoto
High Energy Physics - Phenomenology , 2008, DOI: 10.1016/j.aop.2009.03.012
Abstract: Pair creation in a uniform classical electromagnetic field (Schwinger mechanism) is studied focusing on the time evolution of the distribution of created particles. The time evolution of the distribution in time-dependent fields is also presented as well as effects of back reaction. Motivated by the Glasma flux tube, which may be formed at the initial stage of heavy-ion collisions, we investigate effects of a magnetic field parallel to an electric field, and find that the magnetic field makes the evolution of a fermion system faster.
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