GLOBAL EXISTENCE OF CLASSICAL SOLUTION FOR A VISCOUS LIQUID-GAS TWO-PHASE MODEL WITH MASS-DEPENDENT VISCOSITY AND VACUUM

In this work, we obtain the global existence and uniqueness of classical solu-tions to a viscous liquid-gas two-phase model with mass-dependent viscosity and vacuum in one dimension, where the initial vacuum is allowed. We get the upper and lower bounds of gas and liquid masses n and m by the continuity methods which we use to study the compressible Navier-Stokes equations.

QCD One-Loop Effective Coupling Constant and Quark Mass Given in a Mass-Dependent Renormalization

The QCD one-loop renormalization is restudied in a mass-dependent subtraction scheme in which the quark mass is not set to vanish and the renormalization point is chosen to be an arbitrary time-like momentum. The correctness of the subtraction is ensured by the Ward identities which are respected in all the processes of subtraction.By considering the mass effect, the effective coupling constant and the effective quark masses derived by solving the renormalization group equations are given in improved expressions which are different from the previous results.PACS numbers: 11.10.Gh, 11.10.Hi, 12.38.-t, 12.38.

Mercury accumulation,distribution,and isotopic composition in tissues of the Collared Scops Owl(Otus lettia)

Mercury is a ubiquitous contaminant known to accumulate in wildlife,particularly bird species at higher trophic levels.Knowledge of tissue-specific Hg distributions aids our understanding of Hg bioaccumulation in organisms.In this study,one adult and three juvenile Collared Scops Owls(Otus lettia)were studied to elucidate the bioaccumulation of Hg in body tissues.Six tissues and organs(feathers,nails,heart,liver,gizzard,and muscle),as well as gastric contents,were examined for total Hg(THg)and methylmercury(MeHg)contents,Hg isotopic compositions including mass-dependent fractionation(MDF;δ202Hg)and mass-independent fractionation(MIF;Δ199Hg andΔ201Hg),and C(δ13C)and N(δ15N)isotopic compositions.Tissue-specific THg and MeHg concentrations in the adult were in the ranges of 150–1360 ng/g and17–1060 ng/g,and lower in the juveniles at 91–419 ng/g and 67–350 ng/g,respectively.Theδ^(202)Hg values in the adult were strongly negative at-1.75‰±0.17‰compared with the juveniles at-0.99‰±0.25‰.The adult exhibited lower MIF values than the juveniles,at0.23‰±0.07‰forΔ^(199)Hg and 0.2‰±0.11‰forΔ^(201)Hg,comparedwith0.81‰±0.09‰and0.66‰±0.07‰,respectively.The lower adult MDF and MIF values suggest that the adult tended to accumulate negative Hg isotopes but the juvenile's positive Hg isotopes.Differences between adult and juvenile tissue Hg concentrations indicate that metabolic processes play an important role in Hg accumulation.

On the Enigma of Nb-Ta and Zr-Hf Fractionation——A Critical Review

Elemental ratios Zr/Hf and Nb/Ta are expected to be constant and of chondritic value （-36.30 and -17.57, respectively） in mantle and mantle-derived rocks. Studies in recent years have shown, however, that these two ratios do vary in some of these rocks. For example, MORB-like seamount lavas from flanks of the East Pacific Rise （EPR） show a correlated Zr/Hf （-25-50） and Nb/Ta （-9-18） variation. These two ratios are also correlated with ratios of more incompatible over less incompatible elements （e.g., La/Sm, Rb/Cs, Th/U, Nb/U, Sm/Yb） and with radiogenic isotope ratios （e.g., 87 Sr/86Sr, 143Nd/144Nd）. Furthermore, abyssal peridotites, which are melting residues for MORB, also show a huge correlated variation between Zr/Hf （-2.5-335） and Nb/Ta （-1-170）. All these observations plus a correlated variation between Zr/Hf （-22-48） and Nb/Ta （-10-23） in lunar rocks are consistent with the Zr-Hf and Nb-Ta fractionation being of magmatic origin. This contrasts with the common view that geochemical processes cannot readily fractionate them. As charges and ionic radii are the principal factors in the general theory of elemental fractionation, this theory cannot explain the fractionation of these two element pairs with the same charges （i.e., 5＋ for Nb and Ta, and 4＋ for Zr and Hf） and essentially the same ionic size （i.e., RNb/RTa=1.000, Rzr/RHf=1.006 to -1.026 for coordination numbers of 6, 7, 8 and 12）. We explore the possibilities of other factors and processes （e.g., mass-dependent fractionation during magmatism） that may cause the observed Nb-Ta and Zr-Hf fractionation. We emphasize that understanding the correlated Nb-Ta and Zr-Hf fractionation ＂known＂ to take place during magmatism is fundamental for improved understanding of elemental fractionations through other earth processes in various tectonic environments, including the origin and evolution of continental crust, which has a characteristic subchondritic Nb/Ta value of -11-12.