Effect of Serpentinite Dehydration in Subducting Slabs on Isotopic Diversity in Recycled Oceanic Crust and Its Role in Isotopic Heterogeneity of the Mantle

We conducted geochemical modeling of the isotopic evolution of subducted oceanic crust that takes into account the chemical variation produced at mid-ocean ridges and in subduction zones, and examined the suitability of our model for generating the high-μ (HIMU), focal zone (FOZO), and prevalent mantle (PREMA) mantle components. Chemical variation produced at mid-ocean ridges was represented by the chemical compositions of two groups of mid-ocean ridge basalts (depleted and enriched). Chemical variation produced in subduction zones was investigated with pressure-temperature paths of slabs of different ages (governing the physicochemical conditions of element exchanges), as determined using representative subduction zones involving young (hot), intermediate, and old (cold) slabs. The results suggest that dehydration of oceanic crust cannot alone produce isotopic variation beyond the bounds of PREMA compositions. Producing the wider range of isotopic diversity from PREMA to FOZO requires various degrees of element partitioning between subducted oceanic crust and fluids (aqueous or supercritical) released by dehydration of slab serpentinite. The extremely radiogenic Pb isotopic signature of HIMU can only be produced by extensive reaction between subducted oceanic crust and fluids derived from slab serpentinite along the specific geothermal gradient resulting from the relatively slow descent of moderately old slabs. The rarity of such tectonic conditions explains the scarcity of HIMU

Comparison of thread-cutting behaviour in three specialist predatory mites to cope with complex webs of Tetranychus spider mites

Anti-predator defenses provided by complex webs of Tetranychus mites can severely impede the performance of generalist predatory mites, whereas this may not be true for specialist predatory mites. Although some specialist predatory mites have developed morphological protection to reduce the adverse effects of complex webs, little is known about their behavioral abilities to cope with the webs. In this study, we compared thread-cutting behavior of three specialist predatory mites, Phytoseiulus persimilis, Neoseiulus womersleyi and N. californicus, exhibited inside the complex web of T. urticae. No major difference was observed among them in the basic pattern of this behavior, using chelicerae and palps, and in the number of silken threads severed while moving inside the web. These results and observations suggest that each predator species cut many sticky silken threads to move inside the complex web without suffering from serious obstructio

Temperature dependence of the ohmic conductivity and activation energy of Pb1+y(Zr0.3Ti0.7)O3 thin films

The ohmic conductivity of the sol-gel derived Pb1+y(Zr0.3Ti0.7)O3 thin films (with the excess lead y=0.0 to 0.4) are investigated using low frequency small signal alternate current (AC) and direct current (DC) methods. Its temperature dependence shows two activation energies of 0.26 and 0.12 eV depending on temperature range and excess Pb levels. The former is associated with Pb3+ acceptor centers, while the latter could be due to a different defect level yet to be identified.Comment: 13 pages, 3 figures, PostScript. Submitted to Applied Physics Letter

SUGGESTION TO ROWERS OBTAINED BY INVERSE DYNAMICS AND FUZZY MODELING

The aims of this study were to clarify the relationships between rower’s partial motions and the rowing performance, i.e. boat speed and efficiency, and to suggest the rower which part of the body he/she should concentrate on. Inverse dynamics found time-series patterns of joint torque power. The power patterns were parameterized to six parameters, amounts and timings of three partial motions, i.e. leg extension, trunk swing and arm pull, during the driving phase of rowing stroke. These parameters are easy for a rower to sense and control one by one. Fuzzy modeling identified the relationship between the parameters and the performance. The obtained linguistic fuzzy rules gave effective suggestion to each rower

Improved Coulomb Correction Formulae for Bose-Einstein Correlations

We present improved Coulomb correction formulae for Bose-Einstein correlations including also exchange term and use them to calculate appropriate correction factors for several source functions. It is found that Coulomb correction to the exchange function in the Bose-Einstein correlations cannot be neglected.Comment: LaTex file, 8 pages, hard copies of 6 (multiple) figures available on request to [email protected] or [email protected]