Iron-Based Heavy Quasiparticles in SrFe4_{4}Sb12_{12}: An Infrared Spectroscopic Study

Temperature-dependent infrared reflectivity spectra of SrFe$_{4}$Sb$_{12}$ has been measured. A renormalized Drude peak with a heavy effective mass and a pronounced pseudogap of 10 meV develops in the optical conductivity spectra at low temperatures. As the temperature decreases below 100 K, the effective mass ($m^{*}$) rapidly increases, and the scattering rate ($1/\tau$) is quenched. The temperature dependence of $m^{*}$ and $1/\tau$ indicates that the hybridization between the Fe 3d spins and the charge carriers plays an important role in determining the physical properties of SrFe$_{4}$Sb$_{12}$ at low temperatures. This result is the clear evidence of the iron-based heavy quasiparticles.Comment: 5 pages, 5 figure

Temporal Changes in a Tropical Nekton Assemblage and Performance of a Prawn Selective Gear

The temporal variation of components of a moderately diverse (H=1.46) tropical estuarine fish assemblage (long. 146°30'E, lat. 8°45'S) was directed by salinities that had been determined by local oceanographic and probably topographic conditions. For this assemblage, two types of intrayear component profiles are predicted. Pooled data (1988-91) reveal a large component of regular/resident species (43%) in an assemblage which has been under a narrow temperature regime «5T). These results facilitate a discussion on the relevance and usefulness of three hypotheses often cited in studies concerning species diversity and component characteristics of the subtropical/tropical coastal nonreef fish assemblages. Manifestations of the assemblage are reflected in catch composition and weights of 39 trials conducted for a selective prawning gear whose performance in bycatch reduction, mainly for finfishes, is judged by an index, E, we have previously proposed. This gear is capable of harvesting the prawn while conserving the demersal fish. Behavioral responses to netting of the prawns and the finfishes, especially the nearshore surface schoolers such as leiognathids, are discussed from several points of view. An adaptation in terms of group selection for leiognathids of their locking mechanism of median fin spines has been interpreted. For the purpose of bycatch reduction or E enhancement, suggestions for improvements in net design and trawl configuration by considering the behavioral features of fish are made. Our original formula of E is modified for general use. Bycatch problems in the regional prawn fisheries and their possible impacts on fishery planning and development in Papua New Guinea as a developing country are discussed. The gear tested may offer enormous ecological and economic benefits. The gear is multipurpose, extremely simple, and can also be used as a biological sampler

Breaking of B-L in superstring inspired E6 model

In the framework of the superstring inspired E6 model, low-energy extensions of the standard model compatible with leptogenesis are considered and masses of right-handed neutrinos in two scenarios allowed by long-lived protons are discussed. The presence of two additional generations allows breaking of B-L without generating nonzero vacuum expectation values of right-handed sneutrinos of the three known generations. After the symmetry breaking, right-handed neutrinos acquire Majorana masses of order of 10^11 GeV. Within the framework of a simple discrete symmetry, assumptions made to provide a large mass of right-handed neutrinos are shown to be self-consistent. Supersymmetric structure of the theory ensures that large corrections, associated with the presence of a (super)heavy gauge field, cancel out.Comment: 18 pages, 6 tables, axodraw use

Neutrino masses and μ\mu terms in a supersymmetric extra U(1) model

We propose a supersymmetric extra U(1) model, which can generate small neutrino masses and necessary $\mu$ terms, simultaneously. Fields including quarks and leptons are embedded in three ${\bf 27}$s of $E_6$ in a different way among generations. The model has an extra U(1) gauge symmetry at TeV regions, which has discriminating features from other models studied previously. Since a neutrino mass matrix induced in the model has a constrained texture with limited parameters, it can give a prediction. If we impose neutrino oscillation data to fix those parameters, a value of $\sin\theta_{13}$ can be determined. We also discuss several phenomenological features which are discriminated from the ones of the MSSM.Comment: 27 pages, 2 figures, final version for publicatio

Multiscale modeling and simulation for polymer melt flows between parallel plates

The flow behaviors of polymer melt composed of short chains with ten beads between parallel plates are simulated by using a hybrid method of molecular dynamics and computational fluid dynamics. Three problems are solved: creep motion under a constant shear stress and its recovery motion after removing the stress, pressure-driven flows, and the flows in rapidly oscillating plates. In the creep/recovery problem, the delayed elastic deformation in the creep motion and evident elastic behavior in the recovery motion are demonstrated. The velocity profiles of the melt in pressure-driven flows are quite different from those of Newtonian fluid due to shear thinning. Velocity gradients of the melt become steeper near the plates and flatter at the middle between the plates as the pressure gradient increases and the temperature decreases. In the rapidly oscillating plates, the viscous boundary layer of the melt is much thinner than that of Newtonian fluid due to the shear thinning of the melt. Three different rheological regimes, i.e., the viscous fluid, visco-elastic liquid, and visco-elastic solid regimes, form over the oscillating plate according to the local Deborah numbers. The melt behaves as a viscous fluid in a region for $\omega\tau^R\lesssim 1$, and the crossover between the liquid-like and solid-like regime takes place around $\omega\tau^\alpha\simeq 1$ (where $\omega$ is the angular frequency of the plate and $\tau^R$ and $\tau^\alpha$ are Rouse and $\alpha$ relaxation time, respectively).Comment: 13pages, 12figure