Period-doubling as a limit to pulsation of short-period population II Cepheid models

The short-period limiting pulsation found by Fadeyev and Fokin (1985) in a short-period, Population II Cepheid model is examined by means of the Baker-von Sengbush-Stellingwerf (BSS) algorithm of limit cycles.It is shown that the model has a stable limit cycle of the fundamental mode and an unstable limit cycle of the first overtone mode. When the method is applied for pulsations spanning the time interval of twice the period of the fundamental mode, we find only the fundamental cycle repeated doubly or the first overtone limit cycle repeated three times, depending on initial conditions of the integration.We thus conclude that the period-doubling limiting pulsation found by Fadeyev and Fokin (1985) is a transient feature of the model.     

Clinopyroxene on the join CaMgSi2O6-CaFe3+AlSiO6-CaTiAl2O6 at low oxygen fugacity

Subsolidus phase relations on the join CaMgSi₂O₆-CaFe³⁺ AlSiO₆-CaTiAl₂O₆ were studied by the ordinary quenching method at \(f_{O_2 } = 10^{ - 11} \) atm and 1,100°C. Crystalline phases encountered are clinopyroxene_ss (ss:solid solution) (Cpx_ss), melilite (Mel), perovskite (Pv), spinel_ss (Sp_ss), magnetite_ss (Mt_ss) and anorthite (An). There is no Cpx_ss single phase field, and the following assemblages were found; Cpx_ss+Mel, Cpx_ss+Mel+Sp_ss, Cpx_ss+Mel+Pv, Cpx_ss+Mel+Sp_ss+Pv, Cpx_ss+Pv+Sp_ss+An, Sp_ss+Pv+Mel+An+Cpx_ss, Mel+Mt_ss+An+Sp_ss+Cpx_ss+liquid and Mel+Mt_ss+An+Sp_ss+Cpx_ss+Pv. Mössbauer spectral study revealed that Cpx_ss contains both Fe²⁺ and Fe³⁺ in the octahedral site, and it was confirmed that the CaFe³⁺ AlSiO₆ content in the Cpx_ss at low \(f_{O_2 } \) is considerably less than that in the Cpx_ss crystallized in air, whereas the CaFe²⁺Si₂O₆ component increases. The maximum solubility of CaTlAl₂O₆ component in the Cpx_ss at low \(f_{O_2 } \) is higher than that in air. The decrease of CaFe³⁺ AlSiO₆ in the Cpx_ss at low \(f_{O_2 } \) may cause increase of CaTial₂O₆ in the Cpx_ss.     

IR active orientation of OH bending mode in topaz

Infrared (IR) and nearinfrared (NIR) absorption spectra of hydrous and F-rich topazes were measured to assign an OH bending mode of topaz. Three absorption peaks at 1165, 3650, and 4803 cm⁻¹ are assigned to OH related absorption peaks. Since a peak at 4803 cm⁻¹ can be assigned to a combination mode of 1165 and 3650 cm⁻¹, the 1165 cm⁻¹ peak is harmonic with the 3650 cm⁻¹ peak. Polarized IR absorption spectra of (100), (010), and (001) planes of the hydrous topaz were measured to examine IR active orientation of the 1165 cm⁻¹ OH related mode. Three pleochroic distributions of the absorption peak at 1165 cm⁻¹ on (100), (010), and (001) planes indicate an active orientation of the 1165 cm⁻¹ OH related mode. The IR active orientation of the 1165 cm⁻¹ OH related mode in topaz is normal to the OH dipole. The orthogonality and harmonic combination mode indicate that the 1165 cm⁻¹ peak is OH bending mode. The active orientation of OH bending mode is polarized in the plane normal to the OH dipole. The polarization suggests that anisotropic thermal vibration of protons on the hydroxyl is maximum along the IR active orientation. Received: August 16, 1996 / Revised, accepted: April 20, 1997     

Correction to: El Niño-related sea surface elevation and ocean bottom pressure enhancement associated with the retreat of the Oyashio southeast of Hokkaido,Japan

Marine Geophysical Research - In the original publication, the Fig. 2 was published incorrectly. The correct version (Fig. 2) is given in this correction. The original article has been...     

Seasonal variations in the nitrogen isotopic composition of settling particles at station K2 in the western subarctic North Pacific

Intensive observations using hydrographical cruises and moored sediment trap deployments during 2010 and 2012 at station K2 in the North Pacific Western Subarctic Gyre (WSG) revealed seasonal changes in δ ¹⁵N of both suspended and settling particles. Suspended particles (SUS) were collected from depths between the surface and 200 m; settling particles by drifting sediment traps (DST; 100–200 m) and moored sediment traps (MST; 200 and 500 m). All particles showed higher δ ¹⁵N values in winter and lower in summer, contrary to the expected by isotopic fractionation during phytoplankton nitrate consumption. We suggest that these observed isotopic patterns are due to ammonium consumption via light-controlled nitrification, which could induce variations in δ ¹⁵N(SUS) of 0.4–3.1 ‰ in the euphotic zone (EZ). The δ ¹⁵N(SUS) signature was reflected by δ ¹⁵N(DST) despite modifications during biogenic transformation from suspended particles in the EZ. δ ¹⁵N enrichment (average: 3.6 ‰) and the increase in C:N ratio (by 1.6) in settling particles suggests year-round contributions of metabolites from herbivorous zooplankton as well as TEPs produced by diatoms. Accordingly, seasonal δ ¹⁵N(DST) variations of 2.4–7.0 ‰ showed a significant correlation with primary productivity (PP) at K2. By applying the observed δ ¹⁵N(DST) vs. PP regression to δ ¹⁵N(MST) of 1.9–8.0 ‰, we constructed the first annual time-series of PP changes in the WSG. This new approach to estimate productivity can be a powerful tool for further understanding of the biological pump in the WSG, even though its validity needs to be examined carefully.     

Ore and Skarn Mineralogy of the Yamato Mine,Yamaguchi Prefecture,Japan, with Emphasis on Silver‐, Bismuth‐, Cobalt‐, and Tin‐bearing Sulfides

Assemblages and chemical compositions of ore minerals from the Yamato mine, Yamaguchi Prefecture, Japan, were investigated in detail to clarify its characteristics as a skarn deposit. Special attention was paid to silver‐, bismuth‐, cobalt‐, and tin‐bearing sulfide minerals and native gold at the mine, which are described here for the first time. Samples of arsenopyrite‐dominant massive ore, and garnet‐rich, clinopyroxene‐garnet‐rich, and wollastonite‐bearing skarn ores were collected from the mine dump. Arsenopyrite is the most abundant ore mineral (>80 vol.%) in the massive ore, in association with both As‐poor/free and As‐bearing pyrite. The major ore minerals in the skarn specimens are pyrite, pyrrhotite, arsenopyrite, chalcopyrite, galena, and sphalerite, along with minor argentite, Ag‐Pb‐Bi sulfate, matildite, bismuthinite, native bismuth, molybdenite, scheelite, stannite, stannoidite, cassiterite, cobaltite, gersdorffite, and Co‐rich violarite. In addition, native gold is observed in the interstices of gangue minerals. Based on the mineral assemblages and textures of the specimens examined, the major ore minerals formed in the early stage of mineralization, and the Bi‐, Ag‐, Co‐, Ni‐, As‐ and Sn‐mineralization occurred in the middle stage. Native gold was deposited in the late stage. The estimated formation temperature of the middle mineralization stage was 312±5 °C, according to iron and zinc partitioning between stannite and coexisting sphalerite. The mineralogical properties and mineralization process of the Yamato mine are consistent with those of common skarn‐ and vein‐type ore deposits associated with ilmenite‐series granitoids in the San‐yo and San‐in districts.     

Pressure effect on the divalent cation distribution in nonideal solid solution of forsterite and fayalite

The divalent cation distribution in olivine (Mg, Fe)₂SiO₄ under high pressure and temperature was studied to clarify the detailed state of olivine in the mantle. Single crystal samples were heated for a sufficient period of time for the cations to migrate and quenched fast enough to preserve the equilibrated state under high pressures, and the crystal structure was determined with X-ray method. The pressure effect on the distribution coefficient K _D[= (Fe/Mg) _M1/(Fe/Mg) _M2] was determined for the first time; dK _D/dP?0.02 GPa^?1. A set of five thermodynamic parameters required to describe the regular solution model was determined from data concerning the pressure dependence and the known temperature and compositional effects. As a result we have shown how K _D depends on pressure, temperature, and composition. The notable feature clarified is the very large contribution of nonideality in the olivine solid solution. The K _D of olivine crystals in the mantle is predicted; K _D increases to ～ 2.2 at the depth of 400 km, in contrast to 0.9 ～ 1.2 of natural samples available at the surface of the Earth.     

The distribution of Fe3+ and Ga3+ between two tetrahedral sites in melilites,Ca2(Mg,Fe3+, Ga,Si)3O7

The distribution of Fe³⁺ and Ga³⁺ between the two tetrahedral sites in three synthetic melilites has been studied by using ⁵⁷Fe Mössbauer spectroscopy. In the melilite, (Ca₂Ga₂SiO₇)₅₀ (Ca₂Fe³⁺GaSiO₇)₅₀ (mol %), the distribution of Fe³⁺ and Ga³⁺ in T1 and T2 sites is apparently random, which can be explained in terms of the electrostatic valence rule. However in the melilites, (Ca₂MgSi₂O₇)₅₂ (Ca₂Fe³⁺GaSiO₇)₄₂ (Ca₂Ga₂SiO₇)₆ and (Ca₂MgSi₂O₇)₆₂ (Ca₂Fe³⁺GaSiO₇)₃₆ (Ca₂Ga₂SiO₇)₂ (mol %), Fe³⁺ shows preference for the more ionic T1 site and Ga³⁺ for the more covalent T2 site. If the electronegativity of Ga³⁺ is assumed to be larger than that of Fe³⁺, the mode of distribution of Fe³⁺ and Ga³⁺ can be explained in terms of our previous hypothesis that a large electronegativity induces a stronger preference for the more covalent T2 site.