Relationships between textural and photoluminescence spectral features of carbonado (natural polycrystalline diamond) and implications for its origin     

Hidemi Ishibashi  Hiroyuki Kagi  Shoko Odake  Hiroyuki Ohfuji  Hiroshi Kitawaki 《Geochemistry International》2016,54(10):882-889

Field Emission SEM (FESEM) textural observations, crystal size distribution (CSD) analyses, UV-excited luminescence imaging, and photoluminescence (PL) microspectroscopy excited by 488 nm laser were conducted on two texturally contrasting samples of carbonado, a kind of natural polycrystalline diamond from the Central African Republic (CAR). The investigated carbonado samples A and B show extremely different textures: sample A is made up of faceted crystals accompanied by abundant, small rectangular pores, whereas sample B has a granular texture with coarser crystals and scarce, large pores. Diamond crystals smaller than 2–3 µm are enriched in sample A but depleted in sample B. These textural features indicate that sample B diamonds were annealed under thermodynamically stable P–T conditions. The pore characteristics indicate that fluid permeability was higher for sample A than sample B. Photoluminescence (PL) spectra indicate that samples A and B correspond to Group A and B carbonados in the classification of Kagi et al. (1994), respectively, so that sample A reveals emissions from the H3 center without any N–V⁰ derived emission at 575 nm, whereas sample B shows emissions from the 3H center and the N–V⁰ defect. In addition, UV-excited luminescence images and photoluminescence spectra for sample B indicate that the rims of diamond crystals within several microns of a pore show luminescence features similar to those of Group AB carbonados (Kagi et al., 1994), indicating that this Group AB material was formed from Group B by irradiation from pore-filling, radioactive-element-bearing materials at a low temperature. The extent of the low-temperature irradiation is considered to depend on fluid permeability, and the Group A material was strongly irradiated due to its permeable texture whereas the Group B material was not significantly irradiated due to its less permeable granular texture. These results indicate that Group B carbonados have retained their original PL spectral features produced under high pressures and temperatures at mantle depths.  相似文献   

Seasonal variations of dissolved organic matter and nutrients in sediment pore water in the inner part of Tokyo Bay     

Saori Yasui  Jota Kanda  Toshihiro Usui  Hiroshi Ogawa 《Journal of Oceanography》2016,72(6):851-866

At four stations in Tokyo Bay, pore water profiles of dissolved organic carbon (DOC), nitrogen (DON), phosphorus (DOP), and inorganic nutrients were determined at 3-month intervals over 6 years. Concentrations of dissolved organic matter (DOM) and nutrients were significantly higher in pore waters than in the overlying waters. Pore water DOC, DON, and DOP concentrations in the upper most sediment layer (0–1 cm) ranged from 246 to 888 μM, from 14.6 to 75.9 μM, and from 0.02 to 9.83 μM, respectively. Concentrations of DOM and nutrients in pore waters occasionally showed clear seasonal trends and were highest in the summer and lowest in the winter. The seasonal trends in the pore water DOM concentrations were coupled with trends in the overlying water temperature and dissolved oxygen concentration. Benthic effluxes of DON and DOP were low compared with those of inorganic nutrients, accounting for only 1.0 and 1.5 % of the total benthic effluxes of nitrogen and phosphorus, respectively; thus benthic DOM fluxes were quantitatively insignificant to the inorganic nutrient fluxes in Tokyo Bay. The DOM fluxes represented about 7, 3, and 10 % of the riverine discharge of DOC, DON, and DOP to Tokyo Bay, respectively.  相似文献   

Numerical study for specifying the major origin of low salinity water associated with <Emphasis Type="Italic">Chattonella</Emphasis> (Raphidophyceae) blooms in Tachibana Bay,Japan     

Kazuhiro?AokiEmail author  Manabu?Shimizu  Hiroshi?Kuroda  Toshifumi?Yamatogi  Naoya?Ishida  Shigeru?Kitahara  Keiji?Hirano 《Journal of Oceanography》2016,72(5):811-816

In both 2009 and 2010, massive Chattonella blooms occurred in Tachibana Bay. Observation results show that high cell densities of Chattonella were distributed in the central area of Tachibana Bay with low salinity water. Model results indicate that the low salinity water originated from the Ariake Sea and intruded into Tachibana Bay during the northerly or weak winds. It is suggested that low salinity water was mainly discharged from the northern area of the Ariake Sea. Northerly wind enhanced the horizontal advection of the low salinity water intruding into Tachibana Bay originating from the northern area of the Ariake Sea.  相似文献   

Effects of temperature elevation and glucose addition on prokaryotic production and respiration in the mesopelagic layer of the western North Pacific     

Mario Uchimiya  Hiroshi Ogawa  Toshi Nagata 《Journal of Oceanography》2016,72(3):419-426

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Effect of Fetch on a Mechanism for Pollutant Removal from a Two-Dimensional Street Canyon     

Takenobu Michioka  Hiroshi Takimoto  Hiroki Ono  Ayumu Sato 《Boundary-Layer Meteorology》2016,160(1):185-199

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Intraannual variability of sea level around Tosa Bay     

Hiroshi Kuroda  Manabu Shimizu  Yuuichi Hirota  Hideki Akiyama 《Journal of Oceanography》2007,63(5):849-862

Through analysis of monthly in situ hydrographic, tide gauge, altimetry and Kuroshio axis data for the years 1993–2001, the intraannual variability of sea level around Tosa Bay, Japan, with periods of 2–12 months is examined together with the intraannual variability of the Kuroshio south of the bay. It is shown that the intraannual variation of steric height on the slope in Tosa Bay can account for that of sea level at the coast around the bay as well as on this slope. It is found that the steric height (or sea level) variation on the slope in this bay is mainly controlled by the subsurface thermal variation correlated with the Kuroshio variation off Cape Ashizuri, the western edge of Tosa Bay. That is, when the nearshore Kuroshio velocity south of the cape is intensified [weakened] concurrently with the northward [southward] displacement of the current axis, temperature in an entire water column decreases [increases] simultaneously, mainly due to the upward [downward] displacement of isotherms, coincident with that of the main thermocline. It follows that the steric height (or sea level) decreases [increases].  相似文献   

Wind effects on sub-tidal currents in Puget Sound     

Hiroshi Matsuura  Glenn A. Cannon 《Journal of Oceanography》1997,53(1):53-66

Wind effects on sub-tidal currents are studied using current meter records obtained at six moorings across the main basin of Puget Sound. High correlations between wind speeds and currents are found near the surface and at mid-depths of about 100 m. Empirical Orthogonal Function analysis applied to the axial currents in 1984 and 1985 shows that mode 1, containing over 60% of the variance, is highly correlated with wind speed even without any near surface current records. When near surface stratification is strong, direct wind effects are limited to the upper 30 m with counter currents in the lower layer indicating a baroclinic response. The transport in the lower layer almost balances the transport in the upper layer. When near surface stratification is weak, direct wind effects on currents can be detected to about 100 m. In this case, there is no clear and consistent depth at which one can separate the upper from the lower layer. Time series show that the acceleration in the surface layer initially increases in the same direction as the wind when the wind starts blowing, but it reaches a maximum, starts decreasing, and eventually changes to the opposite direction (decelerates) while the wind continues to blow in one direction. Results of a continuously stratified normal mode model and estimations from the observations suggest that friction at solid boundaries is a major cause of these phenomena. The model shows that modal currents of normal modes 2 and 3 are as important as mode 1, although the resultant vertical structure of total current shows a two-layer type pattern with only one zero crossing. The effect of the baroclinic pressure gradient is only apparent at low frequencies and among lower modes.  相似文献   

Age and growth of John Dory, Zeus faber (Linnaeus, 1758), in the East China Sea     

Yoneda  Michio; Yamasaki  Shunji; Yamamoto  Keisuke; Horikawa  Hiroshi; Matsuyama  Michiya 《ICES Journal of Marine Science》2002,59(4):749-756

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Chemical studies of dissolved carbohydrates in seawater     

Hiroshi Sakugawa  Nobuhiko Handa 《Journal of Oceanography》1983,39(6):279-288

Charcoal column chromatography and a dialysis system using a Visking tube were used for the concentration and separation of dissolved carbohydrates in seawater. Recoveries of mono-, oligo-, and polysaccharides were 46–74, 61–89 and 70%, respectively, relative to the total amount of sugars initially submitted to analysis. The combined charcoal column chromatography and dialysis system was used to separate dissolved carbohydrates in seawater samples from Mikawa Bay into mono-, oligo- and polysaccharide fractions. The polysaccharides are separated into two fractions with molecular weights of <4,000 and >4,000 using Sephadex G-25 column chromatography. Monosaccharides, oligosaccharides, polysaccharides with M.W.<4,000 and polysaccharides with M.W. >4,000 accounted for 7–9, 15–26, 7–13 and 20–33% of total dissolved carbohydrates, respectively. However, 32–38% of dissolved carbohydrates were lost during the analytical procedures. Glucose, galactose, mannose, xylose, arabinose, ribose, fucose, and rhamnose were found upon acid hydrolysis of the oligo- and polysaccharide fractions, while fucose and rhamnose were not present in the monosaccharide fraction. Possible sources of the carbohydrates in these fractions are discussed with reference to the monosaccharide composition of cellular carbohydrate in marine algae.  相似文献   

Seasonal Variation of Space/Time Statistics of Short-Term Sea Surface Temperature Variability in the Kuroshio Region   总被引：1，自引：0，他引：1  

Kohtaro?HosodaEmail author  Hiroshi?Kawamura 《Journal of Oceanography》2005,61(4):709-720

Spatial and temporal scales of sea surface temperature (SST) variations in the Kuroshio region have been investigated using a satellite-based one-year merged SST product. Targeting short-term variations with temporal scales of less than a year, decorrelation scales, which are defined as the e-folding scale of SST variability, have been derived as functions of regional positions and calendar months. We assumed that the autocorrelation function of SST has anisotropic Gaussian characteristics in the space-time domain. Resultant spatial and temporal decorrelation scales range from 1 to 3° and 2 to 3 days, respectively. They are strongly inhomogeneous, anisotropic and time-dependent. These characteristics are attributed to the oceanic and atmospheric disturbances. Spatial decorrelation scales are determined mainly by strong atmospheric forcing in the study region. In the area with dominant atmospheric forcing, the spatial scales are larger than those in the other regions. Those in the regions with dynamical oceanographic disturbances are as small as 1°. Signal-to-noise ratios are also large where the atmospheric forcing is strong, while they are small where the oceanic signals are active.  相似文献