Search

The diffusive properties in amorphous systems are studied by Monte Carlo simulations of a continuous time random walk on a one dimensional lattice. When the probability distribution for the time interval between jump events satisfies the power law t−1−α, the relaxation becomes anomalous of a stretched-exponential type when α 1. Scaling properties both in real and reciprocal space are ascertained.

The purpose of the current study is to establish the dynamic close-mouth view radiograph method. Seven healthy volunteers were enrolled. Dynamic open-mouth and close-mouth view radiographs were obtained. The odontoid lateral mass interval and the dynamic atlantodental lateral shift (ADLS) were measured. The ADLS was 9.4+/-5.3% by the close-mouth view, showing a significantly greater percentage than that of 5.3+/-4.0% by the open-mouth view. The dynamic close-mouth view can be useful for diagnosis of atlantoaxial lateral instability.

The micelle formation and the dynamic coexistence in amphiphilic solution are investigated by molecular dynamics simulation of coarse-grained rigid amphiphilic molecules with explicit solvent molecules. Our simulations show that three kinds of isolated micelles (disk, cylindrical, and spherical micelles) are observed at a lower temperature by quenching from a random configuration of amphiphilic molecules in solution at a higher temperature. The micellar shape changes from a disk into a cylinder, and then into a sphere as the hydrophilic interaction increases whereas it is not so sensitive to the variation of the hydrophobic interaction. This fact indicates that the hydrophilic interaction plays an important role in determining the micellar shape in the range of the interaction parameters used. It is also found that in a certain interaction parameter range, two kinds of micellar shapes coexist dynamically. From the detailed analyses of the dynamic coexistence, it is ascertained that the dynamic coexistence of a cylindrical micelle and a spherical micelle accompanies the coalescence and fragmentation of micelles while that of a disk micelle and a cylindrical micelle does not, but exhibits the continuous change between them.

A method for the selection of appropriate test case, an important issue for conformance testing of protocol implementations as well as software engineering, is presented. Called the partial W-method, it is shown to have general applicability, full fault-detection power, and yields shorter test suites than the W-method. Various other issues that have an impact on the selection of a suitable test suite including the consideration of interaction parameters, various test architectures for protocol testing and the fact that many specifications do not satisfy the assumptions made by most test selection methods (such as complete definition, a correctly implemented reset function, a limited number of states in the implementation, and determinism), are discussed. >

The phase behavior of bolaamphiphilic solutions is studied by coarse-grained molecular dynamics simulations of semiflexible bolaamphiphilic molecules with explicit solvent molecules. Our simulations show that six kinds of self-assembled structures (spherical micelles, worm-like micelles, bicontinuous structure, hexagonal structure, plate-like micelles, and lamellar structure) are obtained. It is established that, at low concentrations, a plate-like micelle changes to worm-like micelles, and then to spherical micelles as the hydrophilic interaction increases. Conversely, at intermediate concentrations, a lamellar structure changes to a bicontinuous structure; it then changes to worm-like micelles or a hexagonal structure as the hydrophilic interaction increases. It is also observed that the global orientational order parameter for the end bonds of bolaamphiphilic molecules can be used to clearly distinguish between the randomly-oriented structures (the spherical micelles, the worm-like micelles, and the bicontinuous structure), the lamellar structure, the hexagonal structure, and the plate-like micelles.

This paper describes an innovative technique, the gradient pattern analysis (GPA), for analysing spatially extended dynamics. The measures obtained from GPA are based on the spatio-temporal correlations between large and small amplitude fluctuations of the structure represented as a dynamical gradient pattern. By means of four gradient moments it is possible to quantify the relative fluctuations and scaling coherence at a dynamical numerical lattice and this is a set of proper measures of the pattern complexity and equilibrium. The GPA technique is applied for the first time in 3D-simulated molecular chains with the objective of characterizing small symmetry breaking, amplitude and phase disorder due to spatio-temporal fluctuations driven by the spatially extended dynamics of a relaxation regime.

The micellar shape transition in amphiphilic solutions is studied by coarse-grained molecular dynamics simulations of rigid amphiphilic molecules with explicit solvent molecules. Our simulations show that the dominant micellar shape changes from disc to cylinder, and then to sphere as the hydrophilic interaction increases. We find that, as the hydrophilic interaction increases, the potential energy decreases monotonically even during the micellar shape transition, whereas the slope of the potential energy decreases in a stepwise manner in relation to the micellar shape transition. We also ascertained that there exists a wide coexistence region in the intensity of the hydrophilic interaction between a cylinder and a sphere, whereas the coexistence region between a cylinder and a disc is very narrow.

The present study examined the effect of nefiracetam on ischemic brain damage by monitoring population spikes (PSs) in the dentate gyrus of guinea pig hippocampal slices; assaying high-energy phosphates (ATP and CrP) in guinea pig hippocampal slices; and monitoring whole-cell membrane-currents and intracellular Ca(2+) levels in cultured hippocampal neurons. Twenty-minute ischemic insult to slices, i.e., deprivation of glucose and oxygen from artificial cerebrospinal fluid, abolished PSs. As compared with only 35% recovery of the PS amplitude for control, PS amplitude reversed to 65% of basal levels 40 min after returning normal conditions by treatment with nefiracetam (0.01 microM). Ischemic insult reduced the levels of adenosine triphosphate (ATP) and creatine phosphate (CrP) in slices, and when returned to normal conditions, recovering to 70 and 85% of basal values, respectively, 30 min after returning normal conditions. Nefiracetam (0.01 microM) facilitated the recovery of ATP and CrP, reaching 110 and 140% of basal values, respectively. Nefiracetam inhibited N-methyl-D-aspartate (NMDA)-evoked currents to 35% of basal amplitudes. Likewise, nefiracetam (0.01 microM) inhibited intracellular Ca(2+) rise through NMDA receptor channels to 30% of basal levels. The results of the present study, thus, suggest that nefiracetam has the potential to protect against ischemic brain damage, possibly in part by preventing from accumulation of intracellular calcium through NMDA receptor channels.

By molecular dynamics simulation, discovered is a strange rigid-like nature for a hexagonally packed domain of short chain molecules. In spite of the non-bonded short-range interaction potential (Lennard-Jones potential) among chain molecules, the packed domain gives rise to a resultant global moment of inertia. Accordingly, as two domains encounter obliquely, they rotate so as to be parallel to each other keeping their overall structures as if they were rigid bodies., Comment: 7 pages, 5 figures, and 2 tables

The shape transition of micelles in an amphiphilic solution is studied by a molecular dynamics simulation of coarse-grained rigid amphiphilic molecules with explicit solvent molecules. Our simulations show that the micellar shape changes from a disc into a cylinder, and then into a sphere as the hydrophilic interaction increases. We find that the potential energy decreases monotonically even during the micellar shape transition as the hydrophilic interaction increases. In contrast, it is ascertained that there exists a wide coexistence region in the intensity of the hydrophilic interaction between a cylinder and a sphere.

The purpose of this study is to calculate the relationship between the circular shape of a corrugated waveguide and its electrical transfer characteristics by the finite-difference time-domain (FDTD) method. To improve the waveguide to transport with a lower loss of energy than the previous design, we optimize the waveguide structure by the time evolution of the electromagnetic fields in the waveguide. However, the calculation in a 3D model is difficult because of the large data size and the long calculation run time. Therefore, we used a cylindrical symmetry model. As a result of this simulation, a correlation of the electromagnetic field in the input source position and the output position has been calculated.

By Monte Carlo simulations of random walks in percolating systems, we show that the anomalous relaxation observed in disordered systems can be ascribed to the restricted geometry allowed for diffusion. In the fractal region corresponding to the concentration ${p\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}p}_{c}$, the relaxation function has scaling properties and becomes the Cole-Cole type, while, in the nonfractal disordered region corresponding to $pg{p}_{c}$, the relaxation function becomes the stretched-exponential and Cole-Cole type, respectively, when $k\ensuremath{\ll}2\ensuremath{\pi}/\ensuremath{\xi}$ and $k\ensuremath{\gg}2\ensuremath{\pi}/\ensuremath{\xi}$. From detailed analyses, we give a microscopic explanation for these two types of relaxation functions known so far only as the empirical laws.

Micellar shape change in an amphiphilic solution is investigated by a molecular dynamics simulation of coarse-grained semiflexible amphiphilic molecules with explicit solvent molecules. Our simulations show that a cylindrical micelle is obtained at small molecular rigidity while a disc-shaped micelle appears at large molecular rigidity. We find that most chains are in an extended conformation at large molecular rigidity whereas the fraction of the chains in a bent conformation becomes large at small molecular rigidity. It is also ascertained that the micellar shape starts to change immediately after sudden increase of the molecular rigidity while an induction time is needed to change the micellar shape after sudden decrease of the molecular rigidity. This result can be qualitatively explained by considering the bond-bending potential energy and the conformational entropy of the amphiphilic molecules.

When we design and construct a large-scale device, it is very important to confirm the interference among its parts. We might need to confirm not only the interference among the parts that are designed at the start but also the interference with some parts that are added after construction. However, sometimes even on using 3D CAD, we cannot detect the interference or the collision among parts, particularly when these parts form a complex 3D shape. On the other hand, virtual reality devices have been used in various fields such as design support systems; however, real-time collision detection among complex parts has been difficult to achieve. We constructed a system that can detect collision and interference in real time in a virtual reality system. This engine can detect interference between polygons. This enables to calculate more accurately than voxel-based detection engine. Moreover, we propose a dynamic interference vector for removing interference. This vector is defined as a local minimum vector which removes the interference from the same edge where the contact starts. This method enables to prevent an object moves discontinuously, when the interference is removed. Finally, we introduced an example of using this system for assembling parts.

We study the phase behavior of bolaamphiphilic solution performing the dissipative particle dynamics simulations of coarse-grained bolaamphiphilic molecules with explicit solvent molecules. Our simulations show that there are six kinds of phases: isotropic micellar, micellar, rod-shaped micellar, hexagonal, network-structure and lamellar. The network-structure and the lamellar phases disappear when the restoring potential against the bending of bolaamphiphilic molecules in our simulation model is excluded; and the isotropic micellar and the hexagonal phases disappear when the restoring potential is included. This suggests that the bending potential is important in the formation of the higher-ordered structures by the bolaamphiphilic molecules.

Micelle formation in an amphiphilic solution is investigated by a molecular dynamics simulation of coarse-grained semiflexible amphiphilic molecules with explicit solvent molecules. Our simulations show that the micellar shape changes from a cylinder to a disc as the intensity of the molecular rigidity increases. We find that the radius of gyration of the cylindrical micelle is larger than that of the disc-shaped micelle for small molecular rigidity, although the radius of gyration is almost steady even during the transition between a cylinder and a disc for large molecular rigidity. This indicates that a cylindrical micelle formed at small molecular rigidity is more anisotropic than the one obtained at large molecular rigidity. We also ascertained that a cylindrical micelle and a disc-shaped micelle coexist dynamically over a certain molecular rigidity range.

By a classical molecular dynamics (CMD) simulation with a modified Brenner's reactive empirical bond-order (REBO) potential, we found that graphite with zigzag (1010) and armchair (1120) edge states is destroyed more easily than other structures, i.e., graphite with the (0001) surface, and diamond with the (100), (111), (120), and (110) surfaces. Experimental results indicated that graphite is eroded under hydrogen atom injection with Ein = 0.3 eV, and that diamond is not eroded under the same conditions. Our simulation results are consistent with these experimental results. We also reveal the temperature and saturation dependence of the surface structure of carbon crystals.

Thermal display, which is a type of haptic display, is effective in providing intuitive information of temperature. However, in many studies, the user has assumed a sitting position during the use of these devices. In contrast, the user generally watches 3D objects while standing and walking around in large-scale virtual reality system, In addition, in scientific visualization, the response time is very important for observing physical phenomena, especially for dynamic numerical simulation. One solution is to provide two types of thermal information: information about the rate of thermal change and information about the actual temperature. We propose a thermal display with two Peltier elements which can show above two pairs of information and the result (for example energy and temperature, as thermal information) of numerical simulation. Finally, we represent an example of visualizing and haptizing the result of molecular dynamics simulation.

A random walk model is formulated and examined which gives the correlated anomalous diffusion found in molecular dynamics simulations. The mean square displacement (MSD) shows a logarithmic behavior in one dimension. Corresponding Langevin equation is constructed by solving the inverse problem which gives a procedure to derive random impulse correlation from MSD function.

Vinylidene fluoride/trifluoroethylene (VDF/TrFE) copolymer crystals were grown from the dilute solution on cleaved (0001) surface of highly oriented pyrolytic graphite (HOPG). Using transmission electron microscopy, the orientational relation between the copolymer crystals and cleaved (0001) surface of HOPG is clarified, as well as the supperlattice matching. Electron diffraction (ED) patterns with 6-fold symmetry were observed for the copolymer crystals with VDF molar contents of 59, 65, and 71%. It suggests that a rectangular array of (20\bar1) plane for the high-temperature phase (HP) of the copolymer crystal faces HOPG(0001) plane, from which the molecular chains tilt by 46.7°. The ED pattern with such 6-fold symmetry is attributed to superposition of diffractions from the HP crystallites with three different orientations on HOPG. Such results suggest that epitaxial growth of HP occurred and it was frozen or stabilized even at room temperature due to epitaxial effect or interaction between copolymer m...

The micelle formation in amphiphilie solution is investigated by means of a a molecular dynamics simulation of coarse-grained amphipliilic molecules with explicit solvent molecules. A random configuration of amphiphilic molecules in solution at high temperature is quenched to a lower temperature. Our simulations show that the micella shapes change from a cylindrical micelle to a planar bilayer as the number density increases. At higher densities, we also find the following characteristic features. (1) The potential energy relaxes in a stepwise manner (2) The radius of gyration R g of the largest micelles increases with time in a stepwise fashion, (3) The sharp bumps in R g occur during coalescence of micelles.

The structure formation of a single polymer chain in solution with explicit solvent molecules is investigated by molecular dynamics simulation. The orientationally ordered structure is formed at a low temperature by quenching from a random conformation at a high temperature. The growth of the global and local orientational order proceeds in a stepwise manner at T ≥350 K, whereas it proceeds in a gradual manner at T =300 K. From the detailed analyses of the parallel ordering process, it is found that a conformational change of the polymer chain occurs at first, and then parallel ordering starts to take place. In comparison with the simulation results of an isolated polymer chain in vacuum, it is ascertained that the stem length of the orientationally ordered structure formed in solution becomes 2–3 times longer than that formed in vacuum.

A silencing apparatus for effectively reducing noises in the three dimension space which detects physical characteristics of the noise source by the laser doppler sensor unit during the noise source comes close to the telephone booth, and collects acoustic characteristics of the noise source by the sensor microphone array. The control portion generates an inverse-phased signal against the noise source so that the noises are decreased at the error sensor, and stores the noise source information ( physical characteristics and the acoustic characteristics) and the generated inverse-phased signal. When the same noise source come closely, the voice is generated from the speaker using the inverse-phased signal stored in the memory. The control portion generates an inverse-phased voice from the speaker when the collected noise by the sensor microphone is actually over a certain threshold level.