Entropy Change through Rayleigh-B\'enard Convective Transition with Rigid Boundaries

The previous investigation on Rayleigh-B\'enard convection of a dilute classical gas [T. Kita: J. Phys. Soc. Jpn. {\bf 75} (2006) 124005] is extended to calculate entropy change of the convective transition with the rigid boundaries. We obtain results qualitatively similar to those of the stress-free boundaries. Above the critical Rayleigh number, the roll convection is realized among possible steady states with periodic structures, carrying the highest entropy as a function of macroscopic mechanical variables.Comment: 5 pages, 4 figure

How Do Gestures Influence Thinking and Speaking? The Gesture-for-Conceptualization Hypothesis.

Peer reviewedPostprin

Oxygen-isotope and trace element constraints on the origins of silica-rich melts in the subarc mantle

Peridotitic xenoliths in basaltic andesites from Batan island in the Luzon arc contain silica-rich (broadly dacitic) hydrous melt inclusions that were likely trapped when these rocks were within the upper mantle wedge underlying the arc. These melt inclusions have been previously interpreted to be slab-derived melts. We tested this hypothesis by analyzing the oxygen isotope compositions of these inclusions with an ion microprobe. The melt inclusions from Batan xenoliths have δ 18OVSMOW values of 6.45 ± 0.51‰. These values are consistent with the melts having been in oxygen isotope exchange equilibrium with average mantle peridotite at temperatures of ≥875°C. We suggest the δ 18O values of Batan inclusions, as well as their major and trace element compositions, can be explained if they are low-degree melts (or differentiation products of such melts) of peridotites in the mantle wedge that had previously undergone extensive melt extraction followed by metasomatism by small amounts (several percent or less) of slab-derived components. A model based on the trace element contents of Batan inclusions suggests that this metasomatic agent was an aqueous fluid extracted from subducted basalts and had many characteristics similar to slab-derived components of the sources of arc-related basalts at Batan and elsewhere. Batan inclusions bear similarities to “adakites,” a class of arc-related lava widely considered to be slab-derived melts. Our results suggest the alternative interpretation that at least some adakite-like liquids might be generated from low-degree melting of metasomatized peridotites

Theory of Flux-Flow Resistivity near Hc2H_{c2} for s-wave Type-II Superconductors

This paper presents a microscopic calculation of the flux-flow resistivity $\rho_{f}$ for s-wave type-II superconductors with arbitrary impurity concentrations near the upper critical field $H_{c2}$. It is found that, as the mean free path $l$ becomes longer, $\rho_{f}$ increases gradually from the dirty-limit result of Thompson [Phys. Rev. B{\bf 1}, 327 (1970)] and Takayama and Ebisawa [Prog. Theor. Phys. {\bf 44}, 1450 (1970)]. The limiting behaviors suggest that $\rho_{f}(H)$ at low temperatures may change from convex downward to upward as $l$ increases, thus deviating substantially from the linear dependence $\rho_{f}\propto H/H_{c2}$ predicted by the Bardeen-Stephen theory [Phys. Rev. {\bf 140}, A1197 (1965)]

Evidence from Polymict Ureilite Meteorites for a Single "Rubble-Pile" Ureilite Parent Asteroid Gardened by Several Distinct Impactors

Ureilites are ultramafic achondrite meteorites that have experienced igneous processing whilst retaining heterogeneity in mg# and oxygen isotope ratios. Polymict ureilites represent material derived from the surface of the ureilite parent asteroid(s). Electron microprobe analysis of more than 500 olivine and pyroxene clasts in six polymict ureilites reveals that they cover a statistically identical range of compositions to that shown by all known monomict ureilites. This is considered to be convincing evidence for derivation from a single parent asteroid. Many of the polymict ureilites also contain clasts that have identical compositions to the anomalously high Mn/Mg olivines and pyroxenes from the Hughes 009 monomict ureilite (here termed the Hughes cluster ). Four of the six samples also contain distinctive ferroan lithic clasts that have been derived from oxidized impactors. The presence of several common distinctive lithologies within the polymict ureilites is additional evidence that the ureilites were derived from a single parent asteroid. Olivine in a large lithic clast of augite-bearing ureilitic has an mg# of 97, extending the compositional range of known ureilite material. Our study confirms that ureilitic olivine clasts with mg#s 85, which also show more variable Mn contents, including the melt-inclusion bearing "Hughes cluster" ureilites. We interpret this to indicate that the parent ureilite asteroid was disrupted by a major impact at a time when melt was still present in regions with a bulk mg# > 85, giving rise to the two types of ureilites: common ferroan ones that were already residual after melting and less common magnesian ones that were still partially molten when disruption occurred, some of which are the result of interaction of melts with residual mantle during disruption. A single daughter asteroid re-accreted from the disrupted remnants of the mantle of the proto-ureilite asteroid, giving rise to a "rubble-pile" body that had material of a wide variety of compositions and shock states present on its surface. The analysed polymict ureilite meteorites represent regolith that subsequently formed on this asteroidal surface, including impact-derived material from at least six different meteoritic sources

Magnetic-Field Dependences of Thermodynamic Quantities in the Vortex State of Type-II Superconductors

We develop an alternative method to solve the Eilenberger equations numerically for the vortex-lattice states of type-II superconductors. Using it, we clarify the magnetic-field and impurity-concentration dependences of the magnetization, the entropy, the Pauli paramagnetism, and the mixing of higher Landau levels in the pair potential for two-dimensional $s$- and $d_{x^2-y^2}$-wave superconductors with the cylindrical Fermi surface.Comment: 8 pages, 6 figure

A theory of new type of heavy-electron superconductivity in PrOs_4Sb_12: quadrupolar-fluctuation mediated odd-parity pairings

It is shown that unconventional nature of superconducting state of PrOs_4Sb_12, a Pr-based heavy electron compound with the filled-Skutterudite structure, can be explained in a unified way by taking into account the structure of the crystalline-electric-field (CEF) level, the shape of the Fermi surface determined by the band structure calculation, and a picture of the quasiparticles in f$^{2}$-configuration with magnetically singlet CEF ground state. Possible types of pairing are narrowed down by consulting recent experimental results. In particular, the chiral "p"-wave states such as p_x+ip_y is favoured under the magnetic field due to the orbital Zeeman effect, while the "p"-wave states with two-fold symmetery such as p_x can be stabilized by a feedback effect without the magnetic field. It is also discussed that the double superconducting transition without the magnetic field is possible due to the spin-orbit coupling of the "triplet" Cooper pairs in the chiral state.Comment: 12 pages, 2 figures, submitted to J. Phys.: Condens. Matter Lette

Photochemical production of O3 in biomass burning plumes in the boundary layer over northern Australia

In situ aircraft measurements of ozone (O3) and its precursors were made over northern Australia in August-September 1999 during the Biomass Burning and Lightning Experiment Phase B (BIBLE-B). A clear positive correlation of O3 with carbon monoxide (CO) was found in biomass burning plumes in the boundary layer (<3 km). The ΔO3/ΔCO ratio (linear regression slope of O3-CO correlation) is found to be 0.12 ppbv/ppbv, which is comparable to the ratio of 0.15 ppbv/ppbv observed at 0-4 km over the Amazon and Africa in previous studies. The net flux of O3 exported from northern Australia during BIBLE-B is estimated to be 0.3 Gmol O3/day. In the biomass burning region, large enhancements of O3 were coincident with the locations of biomass burning hot spots, suggesting that major O3 production occurred near fires (horizontal scale <50 km)