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11.
Akizumi Ishida Kouki Kitajima Ko Hashizume Michael J. Spicuzza Alexander Zaitsev Daniel J. Schulze John W. Valley 《Geostandards and Geoanalytical Research》2023,47(3):569-578
Simultaneous analysis of carbon and nitrogen isotope ratios by SIMS was applied for the first-time to a natural diamond from the Kelsey Lake kimberlite, State Line Distinct, Colorado (UWD-1). This in situ procedure is faster, reduces sample size for analysis, and measures both isotope ratios from a single ~ 10 μm diameter pit, a critical advantage for zoned diamonds. The carbon isotope ratio (expressed as δ13CVPDB) of the bulk UWD-1 crystal, determined by the conventional combustion method in the present study, is -5.9‰ ± 0.2‰ (VPDB, 2s). Nitrogen mass fraction ([N]) and isotope ratio (expressed as δ15NAir) were determined by stepwise combustion and gas-source mass-spectrometry, resulting in 553 ± 64 μg g-1 and -6.7‰ ± 1.1‰ (Air, 2s), respectively. Secondary ions of 12C2-, 12C13C-, 12C14N-, and 12C15N- were simultaneously measured by SIMS using three Faraday cups and one electron multiplier. The spot-to-spot reproducibility of δ13C and δ15N values for the UWD-1 (178 spots on sixteen chips, 10 μm spots), were 0.3‰ and 1.6‰, respectively (2s). While 12C14N-/12C2- ratios, which are an indicator for [N], varied up to 12% among these sixteen chips, such variation did not correlate with either δ13C or δ15N values. We propose that UWD-1 is a suitable reference sample for microscale in situ analysis of δ13C and δ15N values in diamond samples. 相似文献
12.
The second order theory of coupling is discussed regarding the radial pulsation of stellar models which are constructed ignoring convection. The formula including the nonadiabatic effect is presented. Numerical values given for model classical cepheids are considerably greater than the adiabatic values. 相似文献
13.
Kunimitsu Ishida Kay I. Ohshima Takashi Yamanouchi Hiroshi Kanzawa 《Journal of Oceanography》1999,55(3):417-426
Meso- or submeso-scale features of the Antarctic sea ice are investigated using the MOS-1/1b MESSR Images (spatial resolution of approximately 50 m) received at Syowa Station. Particular attention is paid to the ice bands and ice streamers in coastal polynyas. In the Antarctic Ocean, ice bands can be often seen not only at the ice edge but also in the ice interior zone throughout the year and they extend for hundreds of kilometers in the latitudinal direction. It is found that the width and spacing of ice bands tend to decrease from winter to summer. The width of ice band is about 2–6 km in August and September, and 0.1–0.7 km in December. The spacing of ice bands is about 3–10 km in August and September, and 0.1–2 km in December. In coastal polynyas, ice streamers, which are composed of new ice, are sometimes observed. In general, the row of the streamers is spaced at 0.5–2 km with a width of 0.1–1.0 km. 相似文献
14.
A numerical method has been developed for the dynamic analysis of a tall building structure with viscous dampers. Viscous dampers are installed between the top of an inverted V‐shaped brace and the upper beam on each storey to reduce vibrations during strong disturbances like earthquakes. Analytically, it is modelled as a multi‐degree‐of freedom (MDOF) system with the Maxwell models. First, the computational method is formulated in the time domain by introducing a finite element of the Maxwell model into the equation of motion in the discrete‐time system, which is based on the direct numerical integration. Next, analyses for numerical stability and accuracy of the proposed method are discussed. The results show its numerical stability. Finally, the proposed method is applied to the numerical analysis of a realistic building structure to demonstrate its practical validity. 相似文献
15.
Hiroshi Ishida Lars G. Golmen Julia West Martin Krüger Patricia Coombs John Arthur Berge Tastuo Fukuhara Michimasa Magi Jun Kita 《Marine pollution bulletin》2013
Carbon capture and storage (CCS) methods, either sub-seabed or in ocean depths, introduces risk of CO2 leakage and subsequent interaction with the ecosystem. It is therefore important to obtain information on possible effects of CO2. In situ CO2 exposure experiments were carried out twice for 10 days during 2005 using a Benthic Chamber system at 400 m depth in Storfjorden, Norway. pCO2 in the water above the sediment in the chambers was controlled at approximately 500, 5000 and 20,000 μatm, respectively. This article describes the experiment and the results from measured the biological responses within the chamber sediments. The results show effects of elevated CO2 concentrations on biological processes such as increased nanobenthos density. Methane production and sulphate reduction was enhanced in the approximately 5000 μatm chamber. 相似文献
16.
Insoluble particle concentration in ice cores is commonly analyzed as a proxy for varia-tions in atmospheric mineral dust (aerosol concentration). However, recent studies have revealed that the mineral dust is not only a constituent of the particles but that biogenic organic particles are also contained. We microscopically analyzed insoluble particles in a shallow ice core drilled on a mountain glacier, the ürümqi Glacier No. 1, in eastern Tienshan, China. We distinguished different morphologi-cal particles... 相似文献
17.
Hiroshi Ishida Yutaka W. Watanabe Joji Ishizaka Toshiya Nakano Naoki Nagai Yuji Watanabe Akifumi Shimamoto Nobuhiro Maeda Michimasa Magi 《Journal of Oceanography》2009,65(2):179-186
Our analysis of the last three decades of retrospective data of vertical distributions and size composition of chlorophyll-a
(Chl-a) over the western North Pacific has revealed significant changes of three indices related to Chl-a during summer season,
as follows: (1) decreasing linear trend of the proportion of Chl-a in surface layer to that of the whole water column by 0.4
and 2.3% year−1 in the subtropical area along 137°E (STA137) during 1972 to 1997 and in the Kuroshio Extension area along 175°E (KEA175) during 1990 to 2001; (2) increasing linear trend of the depth of subsurface Chl-a maximum (DCM) by 0.4 and 2.6 m year−1 in STA137 and KEA175; and (3) decreasing linear trend of larger-size Chl-a (>3 μm) by 0.1 and 2.5% year−1 in STA137 and KEA175, respectively. Water density (σ
θ
) at 75 m depth had also decreased by 0.006 and 0.05 year−1 in STA137 and KEA175, respectively. The ratio of biogenic opal to biogenic CaCO3 in the sinking flux decreased by 0.015 year−1 in the subtropical region from 1997 to 2005. These findings may indicate that the subsurface chlorophyll maximum is deepening
and larger phytoplankton such as diatoms has been decreasing during the past decade, associated with the decreasing density
of surface water caused by warming in the western North Pacific, especially in the summer. 相似文献
18.
Observations of the North Equatorial Current,Mindanao Current,and Kuroshio current system during the 2006/07 El Niño and 2007/08 La Niña 总被引:1,自引:0,他引:1
Yuji Kashino Norievill España Fadli Syamsudin Kelvin J. Richards Tommy Jensen Pierre Dutrieux Akio Ishida 《Journal of Oceanography》2009,65(3):325-333
Two onboard observation campaigns were carried out in the western boundary region of the Philippine Sea in December 2006 and January 2008 during the 2006/07 El Niño and the 2007/08 La Niña to observe the North Equatorial Current (NEC), Mindanao Current (MC), and Kuroshio current system. The NEC and MC measured in late 2006 under El Niño conditions were stronger than those measured during early 2008 under La Niña conditions. The opposite was true for the current speed of the Kuroshio, which was stronger in early 2008 than in late 2006. The increase in dynamic height around 8°N, 130°E from December 2006 to January 2008 resulted in a weakening of the NEC and MC. Local wind variability in this region did not appear to contribute to changes in the current system. 相似文献
19.
Kei Ishida M. Levent Kavvas Z. Q. Richard Chen Alain Dib Andres J. Diaz Michael L. Anderson Toan Trinh 《水文研究》2018,32(20):3188-3201
Estimation of the extreme precipitation over a target watershed under a changing climate would be necessary to design safe large hydraulic structures. For this purpose, the maximum precipitation (MP) estimation approach was applied to the American River Watershed (ARW) in Northern California under several future climate conditions over 90 water years (2010–2099). These future climate conditions were obtained using 13 future climate projections from two general circulation models (ECHAM5 and CCSM3) based on four future climate scenarios (Special Report on Emissions Scenarios: A1B, A1FI, A2, and B1). A total of 1,170 future projected severe storm events (90 years × 13 projections) were selected with respect to the 72‐hr basin‐average precipitation over the ARW. The 72‐hr basin‐average precipitation for each of the selected severe storm events was maximized over the ARW by horizontally shifting the atmospheric boundary conditions of a regional atmospheric model in order to optimize the path of the storm system that corresponded to the particular event. After maximization, the MP estimates, which are the largest precipitation depths among the maximized results, were obtained as 836.7 mm for the early half‐century period (2010–2054) and 1,056.5 mm for the late half‐century period (2055–2099). 相似文献
20.
K. Asai Y. Ishida M. Kojima K. Maruyama H. Misawa N. Yoshimi 《Astrophysics and Space Science》1996,243(1):247-250
We have been carrying out solar wind measurements using the interplanetary scintillation (IPS) method. Our IPS observation system is operated at a frequency of 327MHz and consists of four stations located at Toyokawa, Fuji, Sugadaira and Kiso. The present system, however, has insufficient sensitivity to measure enough IPS sources for observing the solar wind with adequate spatial and temporal resolution. Therefore we have been excuting the upgrade project since 1994 in order to observe a larger number of compact radio sources. The Fuji system has been improved successfully and has achieved sensitivity by a factor over five compared with the previous system. The upgrade project is now in progress for the Toyokawa and Sugadaira station. 相似文献