Polarization measurements using the Bragg crystal spectrometers on Hinotori     

Kyo Akita  Katsuo Tanaka  Tetsuya Watanabe 《Solar physics》1983,86(1-2):101-105

The two Bragg crystal spectrometers on board Hinotori provide a new technique for measuring linear polarization of the soft X-ray line emission from solar flares. The results of the measurements of large (X class) flares are given in this paper, and the polarization degree averaged over the soft X-ray maximum phases is estimated to be less than 4%.  相似文献   

Specific affinity for phosphate uptake and specific alkaline phosphatase activity as diagnostic tools for detecting phosphorus-limited phytoplankton and bacteria     

Tsuneo Tanaka  Peter Henriksen  Risto Lignell  Kalle Olli  Jukka Seppälä  Timo Tamminen  T. Frede Thingstad 《Estuaries and Coasts》2006,29(6):1226-1241

We analyzed responses of soluble reactive phosphorus (SRP), bioavailable phosphate (PO₄), particulate phosphorus, turnover time of orthophosphate (T_t), and alkaline phosphatase activity (APA) to varying degrees of nutrient stress. The nutrient stress was evoked by different treatments in concentration and combination of inorganic nitrogen (N) and phosphorus (P), and labile organic carbon (glucose) to mesocosms in experiments carried out in eutrophic southern (Odense Fjord, Denmark) and northern (Tvärminne Archipelago, Finland) coastal zones of the Baltic Sea. Despite seasonal and geographical differences, similar responses were observed in both experiments. Low SRP (<100 nmol l^?1), shortT _t (<10 h), and increased levels of APA were observed in both N+P balanced and P deficient treatments, while the opposite trend was observed in P replete treatments. The shortestT _t and the highest APA were found when glucose was combined with N treatment. Bioavailable PO₄ was estimated usingT _t and P uptake rates as derived from stoichiometric conversion of carbon based primary and bacterial production. With shorterT _t, the PO₄ pool declined to <1 nmol-P l^?1, whereas the SRP background pool (difference between SRP and PO₄) remained relatively constant (c. 50 nmol l^?1). APA was inversely related to PO₄ but not to SRP. Responses of specific APA and specific affinity for PO₄ uptake, which are APA and PO₄ uptake rates (inverse ofT _t), respectively, normalized to the summed P biomass of phytoplankton and bacteria, responded consistently to the pattern and magnitude of nutrient limitation evoked in our experiments. Our results, together with a literature survey, suggest that both parameters can be useful in examining PO₄ availability for the natural phytoplankton and bacteria community in P starved aquatic systems.  相似文献   

Evaluation of Genetic Diversity in Zostera japonica (Aschers. et Graebn.) for Seagrass Conservation in Brackish Lower Reaches of the Hii River System, Japan     

Yoshikuni Hodoki  Kako Ohbayashi  Norio Tanaka  Hidenobu Kunii 《Estuaries and Coasts》2013,36(1):127-134

This study examined the genetic diversity and composition of 15 populations of Zostera japonica in the Hii River system, Japan. Genetic and genotypic diversity were consistently higher in populations in the Ohashi River than those in Lake Nakaumi, and the local tidal movements may explain the observed patterns of genetic diversity. Pairwise fixation index values among the populations in Lake Nakaumi were higher than among those in the Ohashi River, even though the ranges of the distances among the populations in the two locations were almost the same. The gene flow from the Ohashi River populations was important for some populations in Lake Nakaumi. The low genotypic diversity and gene flow in Lake Nakaumi seemed similar to those of marginal populations. If this low genotypic diversity and genetic differentiation were partly caused by human activities, the promotion of gene flow should be taken into account in conserving the populations in Lake Nakaumi.  相似文献   

Impacts of pollution on coastal and marine ecosystems including coastal and marine fisheries and approach for management: a review and synthesis   总被引：2，自引：0，他引：2  

Shahidul Islam M  Tanaka M 《Marine pollution bulletin》2004,48(7-8):624-649

The history of aquatic environmental pollution goes back to the very beginning of the history of human civilization. However, aquatic pollution did not receive much attention until a threshold level was reached with adverse consequences on the ecosystems and organisms. Aquatic pollution has become a global concern, but even so, most developing nations are still producing huge pollution loads and the trends are expected to increase. Knowledge of the pollution sources and impacts on ecosystems is important not only for a better understanding on the ecosystem responses to pollutants but also to formulate prevention measures. Many of the sources of aquatic pollutions are generally well known and huge effort has been devoted to the issue. However, new concepts and ideas on environmental pollution are emerging (e.g., biological pollution) with a corresponding need for an update of the knowledge. The present paper attempts to provide an easy-to-follow depiction on the various forms of aquatic pollutions and their impacts on the ecosystem and organisms.  相似文献   

Efficiency of neutrino-induced radio measurements to inspect local areas of Enceladus     

D. Shoji  K. Kurita  H.K.M. Tanaka 《Icarus》2012,218(1):555-560

The Cassini probe observed a young and smooth surface around the south pole of Enceladus, while around the north pole the surface was found to be relatively old and inactive (Porco, C.C. et al. [2006]. Science 311, 1393–1401). This heterogeneous surface implies that the ice thickness of Enceladus is not uniform between the north and south polar regions. Determining the thickness of the icy layer is important to confirm the existence of an internal ocean as well as to reveal the heating mechanism of Enceladus. We show that the measurement of radio waves induced by cosmic neutrinos can be an effective method to constrain the ice thickness of a localized area where conventional gravity or electromagnetic field measurements cannot be used. This method could be used to constrain the thickness of the icy layer on Enceladus even if the ice is a few tens of kilometers thick, measuring over a period of several years, which greatly exceeds the ability of radar sounding, and hence could be used in future orbiter missions.  相似文献   

Mechanism and future risk of slope instability induced by extreme rainfall event in Izu Oshima Island,Japan     

Towhata  Ikuo  Goto  Satoshi  Goto  Shigeru  Akima  Takeshi  Tanaka  Junya  Uchimura  Taro  Wang  Gonghui  Yamaguchi  Hiroshi  Aoyama  Shogo 《Natural Hazards》2021,105(1):501-530

Natural Hazards - A volcanic slope in Izu Oshima Island in Japan experienced a profound rain-induced disaster in October 2013. Since this slope had been stable for centuries except for minor...  相似文献   

Decision-theoretic sensitivity analysis for reservoir development under uncertainty using multilevel quasi-Monte Carlo methods     

Takashi Goda  Daisuke Murakami  Kei Tanaka  Kozo Sato 《Computational Geosciences》2018,22(4):1009-1020

At various stages of petroleum reservoir development, we encounter a large degree of geological uncertainty under which a rational decision has to be made. In order to identify which parameter or group of parameters significantly affects the output of a decision model, we investigate decision-theoretic sensitivity analysis and its computational issues in this paper. In particular, we employ the so-called expected value of partial perfect information (EVPPI) as a sensitivity index and apply multilevel Monte Carlo (MLMC) methods to efficient estimation of EVPPI. In a recent paper by Giles and Goda, an antithetic MLMC estimator for EVPPI is proposed and its variance analysis is conducted under some assumptions on a decision model. In this paper, for an improvement on the performance of the MLMC estimator, we incorporate randomized quasi-Monte Carlo methods within the inner sampling, which results in an multilevel quasi-Monte Carlo (MLQMC) estimator. We apply both the antithetic MLMC and MLQMC estimators to a simple waterflooding decision problem under uncertainty on absolute permeability and relative permeability curves. Through numerical experiments, we compare the performances of the MLMC and MLQMC estimators and confirm a significant advantage of the MLQMC estimator.  相似文献   

On meteotsunamis around Tsushima Strait generated by the Baiu front     

Kenji Tanaka 《Natural Hazards》2012,63(2):805-822

On July 15, 2009, a meteotsunami occurred over Tsushima Strait and flood damage was recorded on the west coast of Tsushima Island. This study investigated the meteorological systems related to that meteotsunami event using surface observation data, grid-point value data, and a mesoscale meteorological model. The mid-latitude trough in the mid-troposphere approached the moist air of the Baiu precipitation system, and a cold downdraft occurred over a wide area of western Japan. In the western Tsushima Strait, the warm, moist air of the lower atmosphere kept the front of the cold downdraft stationary. Around this area, an atmospheric gravity wave was generated continuously with the wave-conditional instability of the second kind mechanism and propagated toward Tsushima Island. The atmospheric gravity wave generated a pressure disturbance at sea level, which produced the meteotsunami. The frequency of the pressure disturbance using the numerical model had a peak in the 5- to 20-min period range, which corresponded with the peak frequency range of the observed tidal records.  相似文献   

Redefinition of the crater-density and absolute-age boundaries for the chronostratigraphic system of Mars     

S.C. Werner  K.L. Tanaka 《Icarus》2011,215(2):603-607

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Effects of length and application rate of rice straw mulch on surface runoff and soil loss under laboratory simulated rainfall   总被引：3，自引：0，他引：3  

Misagh Parhizkar  Mahmood Shabanpour  Manuel Esteban Lucas-Borja  Demetrio Antonio Zema  Siyue Li  Nobuaki Tanaka  Artemio Cerdà 《国际泥沙研究》2021,36(4):468-478

Forest land affected by deforestation yields high soil and water losses.Suitable management practices need to be found that can reduce these losses and achieve ecological and hydrological sustainability of the deforested areas.Mulch has been found to be effective in reducing soil losses;straw mulch is easy to apply,contributes soil organic matter,and is efficient since the day of application.However,the complex effects of rice straw mulch with different application rates and lengths on surface runoff and soil loss have not been clarified in depth.The current paper evaluates the efficiency of rice straw mulch in reducing the hydrological response of a silty clay loam soil under high intensity and low frequency rainfall events(tap water with total depth of 49 mm and intensity of 98 mm/h)simulated in the laboratory.Surface runoff and soil loss at three lengths of the straw(10,30,and 200 mm)and three application rates(1,2,and 3 Mg/ha)were measured in 50 cm(width)×100 cm(length)×10 cm(depth)plots with disturbed soil samples(aggregate soil size<4 mm)collected in a deforested area.Bare soil was used as control experiment.Runoff volume and erosion were significantly(at p<0.05)lower in mulched soils compared to control plots.These reductions were ascribed to the water absorption capacity of the rice straw and the protection cover of the mulch layer.The minimum runoff was observed for a mulch layer of3 Mg/ha of straw with a length of 200 mm.The lowest soil losses were found with straw length of10 mm.The models developed predict runoff and erosion based on simple linear functions of mulch application rate and length,and can be used for a suitable hydrological management of soil.It is concluded that,thanks to rice straw mulch used as an organic soil conditioner,soil erosion and surface runoff are significantly(at p<0.05)reduced,and the mulch protection contributes to reduce the risk of soil degradation.Further research is,however,needed to analyze the upscaling of the hydrological effects of mulching from the plot to the hillslope scale.  相似文献