Al–Mg and Pb–Pb systematics of Allende CAIs: Canonical solar initial Al/Al ratio reinstated     

Benjamin Jacobsen  Qing-zhu Yin  Frederic Moynier  Yuri Amelin  Alexander N. Krot  Kazuhide Nagashima  Ian D. Hutcheon  Herbert Palme 《Earth and Planetary Science Letters》2008,272(1-2):353-364

The precise knowledge of the initial ²⁶Al/²⁷Al ratio [(²⁶Al/²⁷Al)₀] is crucial if we are to use the very first solid objects formed in our Solar System, calcium–aluminum-rich inclusions (CAIs) as the “time zero” age-anchor and guide future work with other short-lived radio-chronometers in the early Solar System, as well as determining the inventory of heat budgets from radioactivities for early planetary differentiation. New high-precision multi-collector inductively-coupled plasma mass spectrometry (MC-ICP-MS) measurements of ²⁷Al/²⁴Mg ratios and Mg-isotopic compositions of nine whole-rock CAIs (six mineralogically characterized fragments and three micro-drilled inclusions) from the CV carbonaceous chondrite, Allende yield a well-defined ²⁶Al–²⁶Mg fossil isochron with an (²⁶Al/²⁷Al)₀ of (5.23 ± 0.13) × 10^− 5. Internal mineral isochrons obtained for three of these CAIs (A44A, AJEF, and A43) are consistent with the whole-rock CAI isochron. The mineral isochron of AJEF with (²⁶Al/²⁷Al)₀ = (4.96 ± 0.25) × 10^− 5, anchored to our precisely determined absolute ²⁰⁷Pb–²⁰⁶Pb age of 4567.60 ± 0.36 Ma for the same mineral separates, reinstate the “canonical” (²⁶Al/²⁷Al)₀ of 5 × 10^− 5 for the early Solar System. The uncertainty in (²⁶Al/²⁷Al)₀ corresponds to a maximum time span of ± 20 Ka (thousand years), suggesting that the Allende CAI formation events were culminated within this time span. Although all Allende CAIs studied experienced multistage formation history, including melting and evaporation in the solar nebula and post-crystallization alteration likely on the asteroidal parent body, the ²⁶Al–²⁶Mg and U–Pb-isotopic systematics of the mineral separates and bulk CAIs behaved largely as closed-system since their formation. Our data do not support the “supra-canonical” ²⁶Al/²⁷Al ratio of individual minerals or their mixtures in CV CAIs, suggesting that the supra-canonical ²⁶Al/²⁷Al ratio in the CV CAIs may have resulted from post-crystallization inter-mineral redistribution of Mg isotopes within an individual inclusion. This redistribution must be volumetrically minor in order to satisfy the mass balance of the precisely defined bulk CAI and bulk mineral data obtained by MC-ICP-MS.The radiogenic ²⁰⁸Pb/²⁰⁶Pb ratio obtained as a by-product from the Pb–Pb age dating is used to estimate time-integrated ²³²Th/²³⁸U ratio (κ value) of CAIs. Limited κ variations among the minerals within a single CAI, contrasted by much larger variations among the bulk CAIs, suggest Th/U fractionation occurred prior to crystallization of igneous CAIs. If interpreted as primordial heterogeneity, the κ value can be used to calculate the mean age of the interstellar dust from which the CAIs condensed.  相似文献   

Alkalinization and acidification of stream water with changes in atmospheric deposition in a tropical dry evergreen forest of northeastern Thailand          下载免费PDF全文

Hiroyuki Sase  Jesada Luangjame  Hathairatana Garivait  Bopit Kietvuttinon  Thiti Visaratana  Masato Kamisako  Ryo Kobayashi  Seiichi Ohta  Junko Shindo  Kentaro Hayashi  Hideshige Toda  Kazuhide Matsuda 《水文研究》2017,31(4):836-846

Field surveys on atmospheric deposition and stream water chemistry were conducted in an evergreen forest in northeastern Thailand characterized by a tropical savanna climate with distinct dry and wet seasons. Atmospheric deposition of ion constituents by throughfall and stemflow was shown to increase in the beginning and end of the wet season, reflecting the precipitation pattern. The pH and electrical conductivity of stream water increased with alkalinity and base cation concentrations due to mineralization of organic matter by the first rain and retention of anions in soil during the start of the wet season. After initial alkalinization, the pH and alkalinity declined rapidly with the highest SO₄^2? concentration displayed in the middle towards the end of the wet season. The magnitude of peaks in SO₄^2? concentration (13.5–60.6 μmol_c/L) reflects deposition during the first 2 months of the wet season (March and April) in respective years (60.8–170 mol_c/ha). Release of SO₄^2? with H⁺, which is retained in soil during the early wet season, may cause acidification later in the season. The deposition and concentration of SO₄^2? declined over 6 years. However, the pH of stream water declined with increasing concentrations of SO₄^2? and other major ions. The release of materials accumulated in the ecosystem was facilitated by the decrease in SO₄^2? concentration/deposition and increased precipitation in the middle–late wet season. The retention‐release cycle of SO₄^2? largely contributed to both seasonal and interannual variations in stream water chemistry in the tropical savanna climate studied.  相似文献   

Enhanced reduced model for elastic earthquake response analysis of a class of mono-symmetric shear building structures with constant eccentricity     

Fuyuki Adachi  Shinta YoshitomiMasaaki Tsuji  Izuru Takewaki 《Soil Dynamics and Earthquake Engineering》2011

An enhanced reduced model is proposed for elastic earthquake response analysis of a class of mono-symmetric shear building structures with constant eccentricity. The proposed reduction method consists of two parts. The first stage is the construction of a reduced structural model with the degrees of freedom at representative floor levels only. In this stage, an inverse eigenmode-problem formulation is used to guarantee the limited equivalence between the original model and the reduced model. The reduced model is constructed so as to have the same fundamental natural frequency and the same lowest-mode component ratios at the representative floor levels as those of the original model. The second stage is the transformation of earthquake input forces into a set of reduced input forces. This transformation utilizes the static equivalence of lateral-torsional stiffness between these two models and is introduced to enhance the accuracy level of the reduced model. Several examples of a three-dimensional mono-symmetric ten-story shear building model with constant eccentricity are presented to demonstrate the validity and accuracy of the proposed reduction method for earthquake response analysis.  相似文献   

53Mn‐53Cr dating of aqueously formed carbonates in the CM2 lithology of the Sutter's Mill carbonaceous chondrite     

Christine E. Jilly  Gary R. Huss  Alexander N. Krot  Kazuhide Nagashima  Qing‐Zhu Yin  Naoji Sugiura 《Meteoritics & planetary science》2014,49(11):2104-2117

Radiometric dating of secondary minerals can be used to constrain the timing of aqueous alteration on meteoritic parent bodies. Dolomite is a well‐documented secondary mineral in CM chondrites, and is thought to have formed by precipitation from an aqueous fluid on the CM parent body within several million years of accretion. The petrographic context of crosscutting dolomite veins indicates that aqueous alteration occurred in situ, rather than in the nebular setting. Here, we present ⁵³Mn‐⁵³Cr systematics for dolomite grains in Sutter's Mill section SM51‐1. The Mn‐Cr isotope data show well‐resolved excesses of ⁵³Cr correlated with ⁵⁵Mn/⁵²Cr ratio, which we interpret as evidence for the in situ decay of radioactive ⁵³Mn. After correcting for the relative sensitivities of Mn and Cr using a synthetic Mn‐ and Cr‐bearing calcite standard, the data yield an isochron with slope corresponding to an initial ⁵³Mn/⁵⁵Mn ratio of 3.42 ± 0.86 × 10^?6. The reported error includes systematic uncertainty from the relative sensitivity factor. When calculated relative to the U‐corrected Pb‐Pb absolute age of the D'Orbigny angrite, Sutter's Mill dolomites give a formation age between 4564.8 and 4562.2 Ma (2.4–5.0 Myr after the birth of the solar system). This age is contemporaneous with previously reported ages for secondary carbonates in CM and CI chondrites. Consistent carbonate precipitation ages between the carbonaceous chondrite groups suggest that aqueous alteration was a common process during the early stages of parent body formation, probably occurring via heating from internal ²⁶Al decay. The high‐precision isochron for Sutter's Mill dolomite indicates that late‐stage processing did not reach temperatures that were high enough to further disturb the Mn‐Cr isochron.  相似文献   

Sediment and carbon storages in the Yahagi River Delta during the Holocene,central Japan     

Kiyoshi Fujimoto  Kumiko Kawase  Shigehiro Ishizuka  Koji Shichi  Akio Ohira  Hiroshi Adachi 《Quaternary Science Reviews》2009,28(15-16):1472-1480

We estimated stored sediment and carbon during the Holocene for each layer of the Yahagi River Delta, central Japan and discussed the provenance of stored carbon. To estimate the bulk density and the carbon content of each layer, we collected two 30 m deep undisturbed cores. The volume of each layer was calculated using ArcView 3D analyst. Although the volume ratio of each layer to the total volume was calculated to be 9.5% for the top mud layer, 34.9% for the upper sand layer, 32.8% for the middle mud layer and 22.9% for the lower sand layer, the mass ratio of each layer to the total mass was calculated to be 8.5, 40.9, 25.2 and 25.4%, respectively, and the stored carbon ratio in each layer to the total stored carbon was 20.4, 4.7, 55.9 and 18.9%, respectively. These results suggest that the top mud and middle mud layers have a significant role as a place for carbon sequestration during postglacial time. Total stored carbon in the study area of only 92.1 km² was estimated at 26 Tg C, which is equivalent to 0.003% of atmospheric carbon. This suggests that deltas on the globe have accumulated a massive amount of carbon during the evolution. The inorganic carbon ratio to total carbon reached more than 45% around the boundary between the middle mud and lower sand layers. The increasing trend in the C_org/N_total ratio accompanied with a decrease in δ¹³C from the bottom to the top horizon in the middle mud layer indicates a gradual increase in terrestrial organic matter contribution. The relative proportion of terrestrially derived materials decreases with increasing distance seaward.  相似文献   

Assessment of degradation of agricultural soils arising from brick burning in selected soil profiles     

H. R. Khan Ph.D.  K. Rahman Ph.D.  A. J. M. Abdur Rouf Ph.D.  G. S. Sattar  Y. Oki Ph.D.  T. Adachi 《International Journal of Environmental Science and Technology》2007,4(4):471-480

The study was conducted with the selected soil profile of burnt (soil around brick kilns) and unburnt (agricultural land) soils in the Dinajpur, Rangpur, Rajshahi, Khulna and Patuakhali districts at the western part of Bangladesh to evaluate the effects of brick kilns on soil degradation and environmental pollution. The pH values of the unburnt soils increased as a function of the soil depth for Rangpur, Khulna and Patuakhali, while decreased for the soil profiles in Dinajpur. Burning of soils significantly (p<0.05) decreased the average pH values of soils by 0.4 pH units (7 % increased over average content = IOAC), but strikingly increased the average EC values from 0.26 to 1.77 mS/cm (592 % IOAC) and the effect was pronounced with the depth function. The average sand content of the soil profiles increased by 330%, while the silt and clay contents decreased by 49 and 40 %, respectively. The average losses arising from the burning of agricultural soils were amounted to 63% for organic matter, 56 to 86 % and 23 to 88 % for available and total N, P, K and S, respectively. This huge loss through the burning of 1 m deep soil profile, i.e. almost 3/4^th of the deterioration of soil fertility is not only reducing the crop production but also polluting the associated environment and atmosphere. The burning of enormous C, N and S not only degrade the agricultural soils but also contributing to the changes in the global climate.  相似文献   

Merger of binary globular clusters: Case of unequal masses     

Junichiro Makino  Kazuhide Akiyama  Daiichiro Sugimoto 《Astrophysics and Space Science》1991,185(1):63-78

Merger process of binary globular cluster is discussed for a pair of unequal-mass components. We calculated the case of mass ratio 10.5 by means of anN-body code with 6144 particles in total. We have found the followings. The mass exchange between the components takes place through the Roche-lobe overflow. In the early stages, however, the dynamical evolution is mainly governed by escape of particles from the system. As the particles escape carrying angular momentum with them, the separation between the component cluster shrinks. The time-scale of this shrinkage depends upon the size of the clusters. When a critical separation is reached, the orbital angular momentum is transferred unstably to the spins of the component clusters. This is the process of the synchronization instability which was found in a previous study on binary cluster of equal masses. As a result the component clusters merge into a single cluster. The structures of the mergers are quite similar among different cases except for the central cores which retain their initial central concentrations. In particular, the ellipticity and the rotation curve are quite close each other among models of different initial radii and of different mass ratios.  相似文献   

Effect of estradiol-17β on pituitary-thyroidal axis of Japanese eel (Anguilla japonica)     

Qu Xiancheng  Masaki Nagae  Sinji Adachi  Kohei Yamauchi 《海洋学报(英文版)》2001,20(4):585-596

In teleost sPeCies, it is well accepted that estradiol--l75 (E2 )is generated from ovarian fOl-licles stimulated by pituitary gonadOtropins (GTH) (Nagahama, l987). FUrthermore, E2 canstimulate hepatic vitellngenesis and elevate plasrna yOlk protein precursor vite1lOgenin, totalCa and W levels in several teleosts (KorSgaard and Petersen, l976, l978; Whiteheadet al., l978; Elliott et al., l979; Pertersen et al., l983; Wallace, 1985; tapigliati etal., 1999). On the other hand, many stud…  相似文献   

Factors controlling the temporal variation of fatty acids in piculate matter during a phytoplankton bloom in a marine mesocosm     

Kazuhide Hayakawa  Nobuhiko Handa  Kyoko Kawanobe  Chi Shing Wong 《Marine Chemistry》1996,52(3-4)

Fatty acids present in suspended particles were examined following the onset of a phytoplankton bloom in an experimental marine mesocosm set up in Patricia Bay, Saanich Inlet, British Columbia, Canada. The predominantly diatom bloom, triggered by the addition of nutrients at the commencement of the experiment, was succeeded by several other phytoplankton forms, which in turn led to changes in particulate chl a, and organic carbon, and nitrogen within the experimental enclosure. An examination of individual fatty acids indicated that the variation of individual fatty acids can be classified into three groups, although the variation pattern of individual fatty acids differed from one another. An attempt was made to establish the factors controlling particulate fatty acid concentrations by principal component analysis. After Varimax rotation, six factors were extracted, of which four factors contributed to 83% of the data matrix. These were mainly dependent on the source of the particles i.e., diatoms, dinoflagellates, and bacteria.Fatty acid concentrations obtained by analysis of different lipid class fractions indicated that the production of fatty acids was distinctly related to the growth stage of the phytoplankton bloom. Fatty acids in triglycerides peaked during stationary phase, whereas fatty acids in polar lipids were high during the stage of an increase of phytoplankton biomass. However, fatty acid composition in both lipid classes changed under the influence of species succession of the phytoplankton population. This strongly suggested that species succession of the phytoplankton exerted the most significant control on fatty acid composition of particulate matter.  相似文献   

Application of microtremor measurements to the estimation of earthquake ground motions in Kushiro city during the Kushiro-Oki earthquake of 15 january 1993     

Takeyasu Suzuki  Yoshitaka Adachi  Minato Tanaka 《地震工程与结构动力学》1995,24(4):595-613

Microtremor measurements were conducted in Kushiro City, Hokkaido Island of Japan. The thickness of alluvial deposits in the central area of Kushiro City abruptly changes from 0 to 80 m. Predominant ground motion at a microtremor measuring site is represented by the spectral ratio, the ratio of Fourier amplitude spectrum of microtremor in the horizontal direction to that in the vertical direction. The peak frequency of the spectral ratio corresponds well to the predominant frequency estimated from the thickness of alluvial layer at each site. Based on a hypothesis that the spectral ratio can be regarded identical with a half of the amplification factor from diluvial bed rock to the ground surface, the strong ground motion due to the Kushiro-oki earthquake at each site is estimated. The method of estimation is verified by the comparison of the synthesized accelerogram with the recorded one at West Port of Kushiro. The results satisfactorily explain major damages and vibrations felt in Kushiro City during the earthquake.  相似文献