Recalibration of mutually consistent garnet–biotite and garnet–cordierite geothermometers

Garnet–biotite and garnet–cordierite geothermometers have been consistently calibrated, using the results of Fe²⁺–Mg cation exchange experiments and utilizing recently evaluated nonideal mixing properties of garnet. Nonideal mixing parameters of biotite (including Fe, Mg, Al^VI, and Ti) and of cordierite (involving Fe and Mg) are evaluated in terms of iterative multiple least-square regressions of the experimental results. Assuming the presence of ferric Fe in biotite in relation to the coexisting Fe-oxide phases (Case A), and assuming the absence of ferric Fe in biotite (Case B), two formulae of garnet–biotite thermometer have been derived. The garnet–cordierite geothermometer was constructed using Margules parameters of garnet adopted in the garnet–biotite geothermometers. The newly calibrated garnet–biotite and garnet–cordierite thermometers clearly show improved conformity in the calculated temperatures. The thermometers give temperatures that are consistent with each other using natural garnet–biotite–cordierite assemblages within ±50 °C. The effects of ferric Fe in biotite on garnet–biotite thermometry have been evaluated comparing the two calibrations of the thermometer. The effects are significant; it is clarified that taking ferric Fe content in biotite into account leads to less dispersion of thermometric results.     

On the vertical structure of tidal currents in a homogeneous sea

Summary. The vertical variation of tidal currents caused by friction at the sea-bed is investigated in both qualitative and quantitative ways with the Coriolis force being taken into account. The simple model with the assumption of constant eddy viscosity is employed to study the effects of friction on the vertical structure of tidal currents. The model explains these effects in vertical change of the maximum velocity, the ellipticity (the ratio of the minor to the major axis) of current ellipse, the time and the direction of the maximum velocity, and the ratio of diurnal current to semidiurnal current.
To reach a quantitative agreement with the data observed by Bowden & Fairbairn in the Irish Sea, the mixing length theory is applied to numerical calculation of the vertical distribution of tidal currents with a finite difference scheme. A fair agreement with the observations is obtained in the calculation. The results show the following features: (1) the vertical profile of amplitude of the main component for the current is almost logarithmic throughout the depth; (2) the corresponding profde for the shearing stress is almost linear with depth; (3) the maximum stress lags the maximum velocity with the delay increasing with elevation; (4) the eddy viscosity coefficient has its maximum around the mid-depth; and (5) the vertically averaged viscosity lags the velocity magnitude.
The dependence of the quadratic resistance coefficient and the coefficient k defined by Bowden's formula = k hū(h — depth, and ū — depth-averaged eddy viscosity and velocity) on the roughness length is given for a steady flow in a non-rotating system. The numerical solution shows that these relations can be approximately applied to the tidal currents in shallow waters.     

Weak lensing predictions at intermediate scales

As pointed out in previous studies, the measurement of the skewness of the convergence field κ will be useful in breaking the degeneracy among the cosmological parameters constrained from weak lensing observations. The combination of shot noise and finite survey volume implies that such a measurement is likely to be performed in a range of intermediate scales (0.5 to 20 arcmin) where neither perturbation theory nor the hierarchical ansatz applies. Here we explore the behaviour of the skewness of κ at these intermediate scales, based on results for the non-linear evolution of the mass bispectrum. We combined different ray-tracing simulations to test our predictions, and we find that our calculations describe accurately the transition from the weakly non-linear to the strongly non-linear regime. We show that the single lens-plane approximation remains accurate even in the non-linear regime, and we explicitly calculate the corrections to this approximation. We also discuss the prospects of measuring the skewness in upcoming weak lensing surveys.     

Double layer formation due to current injection

It is shown by numerical simulations that enhanced current density can generate double layers, even when the electron drift speed is significantly below the electron thermal speed. The double layer potential is spontaneously produced by the space charge self-consistently developed inside the simulation domain. The particle influxes from the low-potential boundary of our simulation domain are independent of the outfluxes. The potential difference φ₀ is shown increase with increasing number density of the injection current. Strong double layers with potential energy eφ₀ ? kT₀ (the electron thermal energy) are stably formed when the injection electron current much exceeds the thermal current of ambient electrons. The backscattered and mirrored electrons are found to have stabilizing effects on the current-driven double layers.     

Placental transfer of arsenic to fetus of Dall's porpoises (Phocoenoides dalli)

Concentrations of total arsenic and individual arsenic compounds were determined in liver, muscle, kidney and blubber of mother and fetus of Dall’s porpoises collected from off Sanriku, Japan, in the year 2000 to characterize the placental transfer of arsenic to fetus in cetaceans. Arsenic was detected in all the tissues of Dall’s porpoises. Total arsenic concentrations in liver, kidney, muscle and blubber were 0.76, 0.69, 0.35 and 0.55 μg/g wet wt, respectively, for mother and 0.28, 0.23, 0.26 and 0.07 μg/g wet wt, respectively, for fetus. In all the tissues, concentrations of total arsenic in mother Dall’s porpoise were higher than in fetus. Arsenic speciation revealed that arsenobetaine was the major arsenic compound in liver, kidney and muscle of both mother and fetus. The percentage of arsenobetaine to total arsenic ranged from 76.0 to 91.0% in the tissues. Dimethylarsinic acid, arsenocholine, methylarsonic acid and an unidentified arsenic compound were also detected in tissues of both mother and fetus as minor constituents, whereas tetramethylarsonium ion was not detected in tissues of the fetus. These results suggest that arsenobetaine, dimethylarsinic acid, arsenocholine and methylarsonic acid are transferable from mother to fetus in Dall’s porpoises. To our knowledge, this is the first report on placental transfer of arsenic compounds to fetus in marine mammals.     

Computed magnetic field structure of the flares observed by Hinotori hard X-ray telescope

Potential field computations have been carried out to study the location of hard X-ray sources observed by the HINOTORI hard X-ray imaging instrument, SXT. Of the two flares studied, the X-ray source of the 1981 May 13 event, a very unusual gradual flare, appears to lie at the top of an arcade of field lines. In the other event, the 1981 October 15 flare, the observed double source structure is not explained in the present computation, implying the existence of non-negligible electric currents in the flare region.     

Concentrations of trace elements in muscle of sturgeons in the Caspian Sea

Concentrations of 21 trace elements were determined in muscle of beluga (Huso huso), Persian sturgeon (Acipenser persicus), Russian sturgeon (Acipenser gueldenstaedtii), ship sturgeon (Acipenser nudiventris) and stellate sturgeon (Acipenser stellatus) collected from coastal regions of Azerbaijan, Iran, Kazakhstan and Turkmenistan, surrounding the Caspian Sea during 2000-2001. Concentrations of Mn, Co, Cu, Mo, Sn, Hg, Pb and Bi in the muscle were apparently different among the five species of sturgeons. Especially, beluga showed the highest concentrations of Hg, Pb and Mn in all the five species. In addition, more than half of the individuals of beluga exceeded the guideline level (0.3 microg/g wet wt.) of Hg for food in UK. However, V, Cr, Zn, Ga, Rb, Sr and Ba concentrations were similar among five sturgeons. Growth-dependent increase in Hg in beluga, Cu in Persian sturgeon, and Zn in Russian sturgeon were observed, whereas V, Mn, Co, Cu, Ga, Sr, Mo, Sn, Hg and Bi concentrations in Persian sturgeon, Pb in ship sturgeon, and Cr, Mn, and Rb in stellate sturgeon were negatively correlated with body length. All species of sturgeon in Azerbaijan showed the highest concentration of Sr and the lowest concentration of Rb, while the five sturgeons from Iran showed opposite trends. Concentration of V, which is present in oil, in sturgeons in the Caspian Sea was considerably lower than that of fish from Kuwait, but was comparable to that of Cambodia and the Gulf and Gulf of Oman. To our knowledge, this study provides the first extensive data on multielemental accumulation in sturgeons of the Caspian Sea.     

Outflow of water from Funka Bay,Hokkaido, during early spring

Observations were made to study the oceanographic structure of the dense water formation and its outflow from Funka Bay, Hokkaido, during early spring. The winter Funka Bay water, which was transformed from the warm water of the Tsugaru Current, due to cooling and deep convection during the winter, flowed from the bay, while forming a frontal structure. The width and inclination of the density front were about 3 n. miles and 1.4×10^?2, respectively, during the early spring of 1982. These values roughly coincided with calculated values of 2.6 n. miles and 1.7×10^?2 using the sill flow model proposed by Whiteheadet al. (1974). Observed current speeds and directions were also similar to those predicted by the model. The renewal time of bay water with this flow was estimated to be about 51 days, which is consistent with the results of previous studies.     

Retrieval of chlorophyll-a concentration via linear combination of ADEOS-II Global Imager data

Top-of-atmosphere reflectance measured above the ocean in the visible and near infrared, after correction for molecular scattering, may be linearly combined to retrieve surface chlorophyll-a abundance directly, without explicit correction for aerosol scattering and absorption. The coefficients of the linear combination minimize the perturbing effects, which are modeled by a polynomial, and they do not depend on geometry. The technique has been developed for Global Imager (GLI) spectral bands centered at 443, 565, 667, and 866 nm, but it is applicable to other sets of spectral bands. Theoretical performance is evaluated from radiation-transfer simulations for a wide range of geophysical and angular conditions. Using a polynomial with exponents of −2, −1, and 0 to determine the coefficients, the residual influence of the atmosphere on the linear combination is within ±0.001 in most cases, allowing chlorophyll-a abundance to be retrieved with a root-mean-squared (RMS) error of 8.4% in the range 0.03–3 mgm⁻³. Application of the method to simulated GLI imagery shows that estimated and actual chlorophyll-a abundance are in agreement, with an average RMS difference of 32.1% and an average bias of −2.2% (slightly lower estimated values). The advantage of the method resides in its simplicity, flexibility, and rapidity of execution. Knowledge of aerosol amount and type is avoided. There is no need for look-up tables of aerosol optical properties. Accuracy is adequate, but depends on the polynomial representation of the perturbing effects and on the bio-optical model selected to relate the linear combination to chlorophyll-a abundance. The sensitivity of the linear combination to chlorophyll-a abundance can be optimized, and the method can be extended to the retrieval of other bio-optical variables.