Taxonomic analysis of the Quaternary archaeofauna found at The Lapa do Santo site,Lagoa Santa region,Brazil     

Artur Chahud  Gisele Ferreira Figueiredo  Gabriela Sartori Mingatos  Mercedes Okumura 《第四纪科学杂志》2021,36(7):1268-1278

The Lapa do Santo archaeological site, located in the Lagoa Santa region, Brazil, represents an important hunter-gatherer occupation dated from the Early and Middle Holocene. Prior studies of archaeofauna dating to this period are few and most of them only provide basic faunal identification with limited information on taphonomic processes. The main goal of this study is to identify the archaeofauna, record the taphonomic processes, and make inferences about its natural (interpreted as the death of the animal in the rockshelter area due to natural causes or due to predation) or anthropic origins. No extinct species (including megamastofauna) were identified. Taxonomic analysis indicated that most faunal remains consist of taxa that may be of mixed origin (natural or anthropic), such as microvertebrates and carnivorous mammals. The Cervidae are the main vertebrate family found in the studied material and these are likely the result of hunting. The Cervidae Ozotoceros support the presence of a fauna that is typical of savannah environments, although the assemblage contains mostly generalist fauna that can thrive in a variety of environments. Very few remains showed clear evidence for taphonomic processes related to human interaction, such as burnt bones.  相似文献   

Seasonal and spatial variation in the denitrifying activity in estuarine and lagoonal sediments     

Yukiko Senga  Minoru Okumura  Yasushi Seike 《Journal of Oceanography》2010,66(1):155-160

We have elucidated the seasonal and spatial variation in the potential denitrifying activity in estuarine and coastal lagoonal sediments in Lakes Shinji and Nakaumi, Japan. The denitrifying activity increased from summer through autumn and was positively correlated with the temperature of the overlying water at all sites except one, where the bottom was always more reductive than at the other sites and there was no NO₃ ⁻ as a substrate for denitrification from spring to autumn. Moreover, the relationship between the denitrifying activity and the distance from the sea showed different trends in estuarine and lagoonal sediments. These spatial differences indicate that different factors regulate the denitrification in estuarine and lagoonal sediments. Denitrifying activity in estuarine sediment was regulated by the discharge of freshwater containing NO₃ ⁻ or organic matter, while in the lagoonal sediments the occurrence of nitrification via the intrusion of oxic seawater into the reductive sediment appears to be a key requirement for the process of denitrification. Therefore, the denitrifying activity in the lagoonal sediment appears to be greater near the sea. Water intrusion is one of the key factors controlling denitrification in coastal marine ecosystems by affecting the supply of substrate available for denitrification.  相似文献   

Publisher’s Erratum to: The Herschel PACS photometer calibration     

Markus Nielbock  Thomas Müller  Ulrich Klaas  Bruno Altieri  Zoltán Balog  Nicolas Billot  Hendrik Linz  Koryo Okumura  Miguel Sánchez-Portal  Marc Sauvage 《Experimental Astronomy》2014,37(2):127-127

  相似文献   

Strong motion uncertainty determined from observed records by dense network in Japan   总被引：2，自引：1，他引：1  

Nobuyuki Morikawa  Tatsuo Kanno  Akira Narita  Hiroyuki Fujiwara  Toshihiko Okumura  Yoshimitsu Fukushima  Aybars Guerpinar 《Journal of Seismology》2008,12(4):529-546

The variation of ground motions at specific stations from events in six narrow areas was inspected by using K-NET and KiK-net records. A source-area factor for individual observation stations was calculated by averaging ratios between observed values for horizontal peak acceleration and velocity, as well as acceleration response spectra for 5% damping, and predicted values using a ground-motion model (usually known as an attenuation relation) by Kanno et al. (Bull Seismol Soc Am, 96:879–897, 2006). Standard deviations between observed and predicted amplitudes after the correction factor are less than 0.2 on the logarithmic scale and decrease down to around 0.15 in the short-period range. Intra-event standard deviation clearly increases with decreasing distance due to differing paths around near source area. Standard deviations may increase with amplitude or decrease with magnitude; however, both amplitude and magnitude of the data are strongly correlated with distance. The standard deviation calculated in this study is obviously much smaller than that of the original ground-motion model, as epistemic uncertainties are minimized by grouping ground motions at specific stations. This result indicates that the accuracy of strong ground motion prediction could be improved if ground-motion models for specified region are determined individually. For this to be possible, it is necessary to have dense strong-motion networks in high-seismicity regions, such as K-NET and KiK-net.  相似文献   

Parameterization and Explicit Modeling of Cloud Microphysics: Approaches,Challenges, and Future Directions     

Yangang LIU  Man-Kong YAU  Shin-ichiro SHIMA  Chunsong LU  Sisi CHEN 《大气科学进展》2023,40(5):747-790

Cloud microphysical processes occur at the smallest end of scales among cloud-related processes and thus must be parameterized not only in large-scale global circulation models(GCMs) but also in various higher-resolution limited-area models such as cloud-resolving models(CRMs) and large-eddy simulation(LES) models. Instead of giving a comprehensive review of existing microphysical parameterizations that have been developed over the years, this study concentrates purposely on several topics that ...  相似文献   

Asperity Height and Aperture of an Artificial Tensile Fracture of Metric Size     

K. Sakaguchi  J. Tomono  K. Okumura  Y. Ogawa  K. Matsuki 《Rock Mechanics and Rock Engineering》2008,41(2):325-341

Summary  A tensile fracture of about 1 m in length was created by indenting wedges in a block of granite, and the heights of the two fracture surfaces were measured using a large, non-contact surface profile measurement system with a laser profilometer to determine the aperture distribution of the fracture. Based on the measured data, the frequency characteristics of the asperity heights, the initial aperture (the aperture when the surfaces are in contact at a single point), and the size effect on the statistical properties were analyzed. The results can be summarized as follows:

1.

The relation between the power spectral density of the fracture surface and the spatial frequency shows linearity on a log–log plot and thus the fracture surfaces can be assumed to be fractal object. On the other hand, the power spectral of the initial aperture becomes almost constant for wavelengths greater than about 100 mm. Thus, the matedness between the two surfaces of a fracture of 1 m monotonously increases with wavelength.

2.

The standard deviation of the initial aperture increases with fracture size until the fracture size is about 200 mm, beyond which the standard deviation is almost independent of the fracture size. On the other hand, the mean initial aperture still increases when the fracture size exceeds 200 mm, since the initial aperture depends on the minimum value of the aperture, which decreases with the number of data points.

Authors’ address: Dr. Kiyotoshi Sakaguchi, Graduate School of Environmental Studies, Tohoku University, 6-6-20 Aramaki-Aza-Aoba, Aoba-ku, Sendai 980-8579, Japan  相似文献   

Further study of synoptic variability in Wakasa Bay, Japan     

Shin-ichiro Umatani  Noriaki Masunaga  Toshio Yamagata 《Progress in Oceanography》1986,17(3-4)

Observations of synoptic variability from CTD and current meter measurements in Wakasa Bay, Japan in summer of 1980 and 1981 are compared with the results of 1979 reported by Yamagata, Umatani, Masunaga and Matsuura (1984). It is suggested that the speed and direction of propagation can basically be explained in terms of shelf wave dynamics.In the 1980 event, a dense (colder and more saline) water advanced eastward along the north coast at about 10 km day⁻¹. The lateral scale of the phenomenon was about 30 to 40 km, in agreement with the Rossby internal radius of deformation. The T-S and current data suggest that the 1980 cold event was dominated by phase propagation. In the 1981 event, a light (warmer and less saline) water area advanced eastward at the speed similar to the 1980 cold event, but the T-S and current data suggest that Lagrangian drift of water particles associated with strong eddy motions was not negligible.  相似文献   

Interannual variability of the Kuroshio Extension and its relation to the Southern Oscillation/El Niño     

Toshio Yamagata  Yoshiaki Shibao  Shin-ichiro Umatanit 《Journal of Oceanography》1985,41(4):274-281

The interannual variability of the temperature structure of the Kuroshio Extension is studied by establishing time series for the period 1950 to 1970 and then comparing it with the time series of sea level differences across the North Equatorial Current obtained by Wyrtki (1975). First, the present analysis shows a significant correlation between the interannual fluctuation of the Kuroshio Extension and the eddy activity south of the Kuroshio axis, suggesting the importance of the eddy-driven mechanism. Secondly, spectral analysis shows close connections between the Kuroshio Extension and the North Equatorial Current with a reasonable time lag of about 1.5 years. This time lag of the mid-latitude variability is also supported by other independent data. In particular, the present preliminary study strongly suggests that the bimodal behavior of the Kuroshio path south of Japan and the intensity of the Kuroshio Countercurrent are closely connected with the Southern Oscillation/El Niño.  相似文献   

Climate impacts of recent multidecadal changes in Atlantic Ocean Sea Surface Temperature: a multimodel comparison   总被引：4，自引：4，他引：0  

Daniel L. R. Hodson  Rowan T. Sutton  Christophe Cassou  Noel Keenlyside  Yuko Okumura  Tianjun Zhou 《Climate Dynamics》2010,34(7-8):1041-1058

During the twentieth century sea surface temperatures in the Atlantic Ocean exhibited prominent multidecadal variations. The source of such variations has yet to be rigorously established—but the question of their impact on climate can be investigated. Here we report on a set of multimodel experiments to examine the impact of patterns of warming in the North Atlantic, and cooling in the South Atlantic, derived from observations, that is characteristic of the positive phase of the Atlantic Multidecadal Oscillation (AMO). The experiments were carried out with six atmospheric General Circulation Models (including two versions of one model), and a major goal was to assess the extent to which key climate impacts are consistent between the different models. The major climate impacts are found over North and South America, with the strongest impacts over land found over the United States and northern parts of South America. These responses appear to be driven by a combination of an off-equatorial Gill response to diabatic heating over the Caribbean due to increased rainfall within the region and a Northward shift in the Inter Tropical Convergence Zone (ITCZ) due to the anomalous cross-equatorial SST gradient. The majority of the models show warmer US land temperatures and reduced Mean Sea Level Pressure during summer (JJA) in response to a warmer North Atlantic and a cooler South Atlantic, in line with observations. However the majority of models show no significant impact on US rainfall during summer. Over northern South America, all models show reduced rainfall in southern hemisphere winter (JJA), whilst in Summer (DJF) there is a generally an increase in rainfall. However, there is a large spread amongst the models in the magnitude of the rainfall anomalies over land. Away from the Americas, there are no consistent significant modelled responses. In particular there are no significant changes in the North Atlantic Oscillation (NAO) over the North Atlantic and Europe in Winter (DJF). Additionally, the observed Sahel drying signal in African rainfall is not seen in the modelled responses. Suggesting that, in contrast to some studies, the Atlantic Multidecadal Oscillation was not the primary driver of recent reductions in Sahel rainfall.  相似文献   

Origin of a magnetic lineation on Kyushu Island, Japan     

Yasukuni  Okubo  Hiroshi  Kanaya  Akitsura  Shibuya Kimio  Okumura 《Island Arc》1997,6(4):386-395

Abstract Several linear magnetic anomalies over continental crust have been identified in and around the Japanese Islands. The anomalies are probably related to island arc tectonic structures, but identifying specific sources has been difficult. Several deep holes were drilled in and around Aso caldera, where a linear anomaly occurs along an active fault. One drillhole located on the linear anomaly encountered a zone of highly magnetized and altered basement rocks at least 100 m thick at a depth of ∼1000 m. The other hole was located away from the anomaly and did not encounter any high-magnetic zones. Rocks from the zone have exceptionally strong remanent magnetization (several tens of A/m) sub-parallel to the present field. AF demagnetization experiments indicated that the magnetization is hard and stable. Magnetic modeling indicates that the linear anomaly is caused mainly by this layer. Microscopic examination of core samples shows that the highly magnetized zone includes secondary magnetic minerals and abundant hydrothermal alterations. Temperatures determined by fluid inclusions and down-hole temperatures show that the temperature of the highly magnetized zone was elevated in the past relative to surrounding rocks. The high temperature could destroy primary magnetic minerals and replace them with secondary magnetic minerals. Thus, the past hydrothermal system may have enhanced thermo-chemical remanent magnetization. The results can produce a model indicating that there was a past hydrothermal system related to the tectonic structure.  相似文献