Satoru Yamamoto

A dissipative particle dynamics (DPD) simulation has been used to study the spontaneous vesicle formation of amphiphilic molecules in aqueous solution. The amphiphilic molecule is represented by a coarse-grained model, which contains a hydrophilic head group and a hydrophobic tail. Water is also modeled by the same size particle as adopted in the amphiphile model, corresponding to a group of several H2O molecules. In the DPD simulation, from both a randomly dispersed system and a bilayer structu

A method is proposed for simulating the dynamic behavior of rigid and flexible fibers in a flow field. The fiber is regarded as made up of spheres that are lined up and bonded to each neighbor. Each pair of bonded spheres can stretch, bend, and twist, by changing bond distance, bond angle, and torsion angle between spheres, respectively. The strength of bonding, or flexibility of the fiber model, is defined by three parameters of stretching, bending, and twisting constants. By altering these par

We studied the shape deformation induced by the phase separation of two-component vesicles using a dissipative particle dynamics simulation. Two types of amphiphiles, which have the same architecture but segregate from each other, are modeled by connecting particles representing the hydrophilic head and hydrophobic tail groups. After vesicle formation using a single component system, some of the amphiphiles are replaced by a second component, and then phase separation on the vesicle is simulated

A new method is presented to simulate the motion of concentrated fiber suspensions in shear flow at low Reynolds numbers without Brownian motion. The hydrodynamic interaction among fibers is considered in a particle simulation method (PSM), in which a fiber is modeled by arrays of spheres. The motion of each constituent sphere of a fiber, which are dispersed into a unit cell with periodic boundaries, is followed to predict the microstructure and the rheological properties. The hydrodynamic inter

The recently developed simulation method, named as the particle simulation method (PSM), is extended to predict the viscosity of dilute suspensions of rodlike particles. In this method a rodlike particle is modeled by bonded spheres. Each bond has three types of springs for stretching, bending, and twisting deformation. The rod model can therefore deform by changing the bond distance, bond angle, and torsion angle between paired spheres. The rod model can represent a variety of rigidity by modif

Epoxy is a class of thermosetting resins and has been widely used as a representative example of structural adhesives. Nevertheless, it remains unclear how the epoxy resin and curing agent are present on the adherend surface and how they move around dynamically and react with each other to form a three-dimensional network. We here adopt a fully atomistic molecular dynamics (MD) simulation to study molecular events of an epoxy resin composed of hydrogenated bisphenol A diglycidyl ether and 1,4-cy

Two forms of cytochrome P-450, designated as cytochrome P-450p-1 and cytochrome P-450p-2, were separated and purified to specific contents of 8.2 and 8.9 nmol/mg of protein, respectively, from lung microsomes of rabbits treated with progesterone. Cytochrome P-450p-1 and cytochrome P-450p-2 migrated as single polypeptide bands with molecular weights of 49,000 and 52,000, respectively, on SDS-polyacrylamide gel. Their CO-reduced difference spectral peaks were at 451.5 and 450 nm, respectively. Cyt

The crossing dynamics at an entanglement point of surfactant threadlike micelles in an aqueous solution was studied using a mesoscopic simulation method, dissipative particle dynamics, with a coarse-grained surfactant model. The possibility of a phantom crossing, which is the relaxation mechanism for the pronounced viscoelastic behavior of surfactant threadlike micellar solution, was investigated. When two threadlike micelles were encountered at an entanglement point under the condition close to

The composition of an epoxy resin at the interface with the adherend is usually different from that in the bulk due to the enrichment of a specific constituent, a characteristic called interfacial segregation. For better adhesion, it should be precisely understood how epoxy and amine molecules exist on the adherend surface and react with each other to form a three-dimensional network. In this study, the entropic factor of the segregation in a mixture of epoxy and amine at the copper interface be

In general, the network structure formed in epoxy resins is heterogeneous, and its extent is dependent on the curing temperature. Based on Fourier-transform infrared spectroscopy in conjunction with coarse-grained molecular dynamics simulations, we herein discuss the origin of mesoscopic heterogeneity in an epoxy resin composed of a typical epoxy base and diamine hardener, which react with each other in two steps. The rate balance of the first and second step reactions, which led to chain extens

Abstract A numerical simulation method has been developed to predict the motion of fiber suspensions in various flows by using the particle simulation method (PSM), in which a fiber is modeled by an array of spheres. The hydrodynamic interaction among fibers is considered by decomposing into intra‐fiber and inter‐fiber interactions. For the intra‐fiber case, the many‐body problem is solved by calculating the mobility matrix for each fiber to obtain the hydrodynamic force and torque exerted on ea

The adhesive strength of epoxy resins is generally dependent on the surface chemistry of an adherend. Although the free space, or the nanoscopic void space, formed at the adhered interface due to the curing shrinkage is expected to have a significant impact on the adhesive strength, the molecular picture is not yet well understood. In this study, all-atom molecular dynamics simulations were used to investigate how the curing reaction and thereby adhesive strength of an epoxy resin differed on hy

Electron microscopic observation on the precipitation sequence in Cu–Be alloys was carried out. Clear images of G. P. zones on {100} planes, the ordered phase, the intermediate γ′-phase, the equilibrium γ-phase and then the informations about the size, shape and distribution in each stage were obtained more clearly than before. Strains associated with precipitates in the early stages of aging and some lattice defects such as dislocations, twins and stacking faults were observed, and these mean t

A molecular spin quantum computer (MSQC) requires electron spin qubits, which pulse-based electron spin/magnetic resonance (ESR/MR) techniques can afford to manipulate for implementing quantum gate operations in open shell molecular entities. Importantly, nuclear spins, which are topologically connected, particularly in organic molecular spin systems, are client qubits, while electron spins play a role of bus qubits. Here, we introduce the implementation for an adiabatic quantum algorithm, sugge