Extended Hydrodynamics from Enskog’s Equation for a Two-Dimensional System General Formalism

Balance equations are derived from Enskog’s kinetic equation for a two-dimensional system of hard disks using Grad’s moment expansion method. This set of equations constitute an extended hydrodynamics for moderately dense bi-dimensional fluids. The set of independent hydrodynamic fields in the present formulations are: density, velocity, temperature and also—following Grad’s original idea—the symmetric and traceless pressure tensor p _ij and the heat flux vector q ^k . An approximation scheme similar in spirit to one made by Grad in his original work is made. Once the hydrodynamics is derived it is used to discuss the nature of a simple one-dimensional heat conduction problem. It is shown that, not too far from equilibrium, the nonequilibrium pressure in this case only depends on the density, temperature and heat flux vector. PACS: 51.10.+y, 05.20.Jj, 44.10.+i, 05.70.Ln     

Polarized proton target for RI Beam experiments

We have constructed a polarized proton solid target system for radioactive nuclear beam experiments at the Center for Nuclear Study, the University of Tokyo. The proton polarization is based on an electron population difference in a photo-excited triplet state of pentacene molecule. The target system was completed in 2003 and applied to a RI beam experiment in 2003 and 2005 by using the projectile fragment separator, RIPS at RIKEN. The maximum polarization reached 20% under the condition of T=100 K and B=0.09 T. Overview of the polarized target and its application in physics experiments at RIPS and RIBF of RIKEN are presented.     

Precision measurement of vector and tensor analyzing powers in elastic deuteron-proton scattering

High-precision vector and tensor analyzing powers of elastic deuteron-proton ( d + p) scattering have been measured at intermediate energies to investigate effects of three-nucleon forces. Angular distributions in the range of 70^°-120^° in the center-of mass frame for incident-deuteron energies E _d ^lab = 130 and 180 MeV were obtained using the RIKEN facility. The beam polarization was unambiguously determined by measuring the ^12C (d, α)^10B(2⁺) reaction at 0^°. Results of the measurements are compared with state-of-the-art three-nucleon calculations. The present modeling of nucleon-nucleon forces and its extension to the three-nucleon system is not sufficient to describe the high-precision data consistently and requires, therefore, further investigation.     

The conformal status of o = ‐3/2 Brans‐Dicke cosmology

Following recent fit of supernovae data to Brans‐Dicke theory which favours the model with o = ‐ 3/2 [1] we discuss the status of this special case of Brans‐Dicke cosmology in both isotropic and anisotropic framework. It emerges that the limit o = ‐3/2 is consistent only with the vacuum field equations and it makes such a Brans‐Dicke theory conformally invariant. Then it is an example of the conformal relativity theory which allows the invariance with respect to conformal transformations of the metric. Besides, Brans‐Dicke theory with o = ‐3/2 gives a border between a standard scalar field model and a ghost/phantom model. In this paper we show that in o = ‐3/2 Brans‐Dicke theory, i.e., in the conformal relativity there are no isotropic Friedmann solutions of non‐zero spatial curvature except for k=‐1 case. Further we show that this k=‐1 case, after the conformal transformation into the Einstein frame, is just the Milne universe and, as such, it is equivalent to Minkowski spacetime. It generally means that only flat models are fully consistent with the field equations. On the other hand, it is shown explicitly that the anisotropic non‐zero spatial curvature models of Kantowski‐Sachs type are admissible in o = ‐3/2 Brans‐Dicke theory. It then seems that an additional scale factor which appears in anisotropic models gives an extra deegre of freedom and makes it less restrictive than in an isotropic Friedmann case.     

Development of highly potent chiral discrimination methods that solve the problems of the diastereomer method

The development of highly potent chiral discrimination methods that solve the problems of the diastereomer method, in which it is impossible to discriminate the diastereomers having chiral centers separated by more than four bonds, is described. On the basis of the results obtained, a new hypothesis, Induced Chiral Fields that the achiral reversed phase can provide chiral fields depending on the structures of the eluents, is proposed to explain the significant results of separation of the diastereomers derived from newly developed chiral and fluorescent labeling reagents and optical isomers by reversed-phase HPLC, which was hitherto impossible.     

Empirical analysis of the evolution of a scientific collaboration network

We present an analysis of the temporal evolution of a scientific coauthorship network, the genetic programming network. We find evidence that the network grows according to preferential attachment, with a slightly sublinear rate. We empirically find how a giant component forms and develops, and we characterize the network by several other time-varying quantities: the mean degree, the clustering coefficient, the average path length, and the degree distribution. We find that the first three statistics increase over time in the growing network; the degree distribution tends to stabilize toward an exponentially truncated power-law. We finally suggest an effective network interpretation that takes into account the aging of collaboration relationships.     

Enhanced ferroelectric properties of (Pb0.90La0.10)Ti0.975O3 multilayered thin films prepared by RF magnetron sputtering

The (Pb_0.90La_0.10)Ti_0.975O₃/PbTiO₃ (PLT/PT), PbTiO₃/(Pb_0.90La_0.10)Ti_0.975O₃/PbTiO₃ (PT/PLT/PT) multilayered thin films with a PbO_x buffer layer were in situ deposited by RF magnetron sputtering at the substrate temperature of 600 °C. With this method, highly (1 0 0)-oriented PLT/PT and PT/PLT/PT multilayered thin films were obtained. The PbO_x buffer layer leads to the (1 0 0) orientation of the films. The dielectric, ferroelectric and pyroelectric properties of the PLT multilayered thin films were investigated. It is found that highly (1 0 0)-oriented PT/PLT/PT multilayered thin films possess higher remnant polarization 2P_r (44.1 μC/cm²) and better pyroelectric coefficient at room temperature p (p = 2.425 × 10⁻⁸ C/cm² K) than these of PLT and PLT/PT thin films. These results indicate that the design of the PT/PLT/PT multilayered thin films with a PbO_x buffer layer should be an effective way to enhance the dielectric, ferroelectric and pyroelectric properties. The mechanism of the enhanced ferroelectric properties was also discussed.     

Stability analysis of a Maxwell fluid in a porous medium heated from below

Based on a modified-Darcy–Brinkman–Maxwell model, stability analysis of a horizontal layer of Maxwell fluid in a porous medium heated from below is performed. By solving the eigenvalue problems, the critical Rayleigh number, wave number and frequency for overstability are determined. It is found that the critical Rayleigh number for overstability decreases as the relaxation time increases and the elasticity of a Maxwell fluid has a destabilizing effect on the fluid layer in porous media. On the other hand, the critical Rayleigh number for overstability increases by increasing the porous parameter which acts to stabilize the system. In limiting cases, some previous results for viscoelastic fluids in nonporous media are recovered from our results.     

Effects of atomic-scale contacts on transport properties through single molecules - ab initio study

Using the RTM/NEGF method, which is a first-principles calculation tool for the quantum transport through nanostructures between electrodes, we study the effects of atomic-scale contacts on the transport properties through single molecules. Electronic states and current-voltage (I-V) characteristics are investigated in various contact conditions with and without single molecules between electrodes. We find that similar nonlinear behaviors appear in the I-V characteristics. Such nonlinear behaviors are determined not only by the HOMO-LUMO electronic states of single molecules between electrodes, but also by the atomic-scale contact conditions. We show that the transitions from tunneling to ballistic regimes affect the I-V characteristics significantly.