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91.
Occurrence and seasonal variations of algal toxins in water, phytoplankton and shellfish from North Stradbroke Island, Queensland, Australia 总被引:4,自引:0,他引:4
Takahashi E Yu Q Eaglesham G Connell DW McBroom J Costanzo S Shaw GR 《Marine environmental research》2007,64(4):429-442
A number of marine microalgae are known to produce toxins that can accumulate in shellfish and when eaten, lead to toxic and potentially fatal reactions in humans. This paper reports on the occurrence and seasonal variations of algal toxins in the waters, phytoplankton and shellfish of Southeast Queensland, Australia. These algal toxins include okadaic acid (OA), domoic acid (DA), gymnodimine (GD), pectenotoxin-2 (PTX-2) and pectenotoxin-2-seco acid (PTX-2-SA), which were detected in the sampled shellfish and phytoplankton, via HPLC-MS/MS. Dissolved OA, PTX-2 and GD were also detected in the samples collected from the water column. This was the first occasion that DA and GD have been reported in shellfish, phytoplankton and the water column in Queensland waters. Phytoplankton tows contained both the toxic Dinophysis and Pseudo-nitzschia algae species, and are suspected of being the most likely producers of the OA, PTX-2s and DA found in shellfish of this area. The number of cells, however, did not correlate with the amount of toxins present in either shellfish or phytoplankton. This indicates that toxin production by algae varies with time and the species present and that number of cells alone cannot be used as an indicator for the presence of toxins. The presence of OA and PTX-2s were more frequently seen in the summer, while DA and GD were detected throughout the year and without any obvious seasonal patterns. 相似文献
92.
M. Chernyakova A. Neronov F. Aharonian Y. Uchiyama T. Takahashi 《Monthly notices of the Royal Astronomical Society》2009,397(4):2123-2132
PSR B1259−63 is a 48-ms radio pulsar in a highly eccentric 3.4-yr orbit with a Be star SS 2883. Unpulsed γ-ray, X-ray and radio emission components are observed from the binary system. It is likely that the collision of the pulsar wind with the anisotropic wind of the Be star plays a crucial role in the generation of the observed non-thermal emission. The 2007 periastron passage was observed in unprecedented details with Suzaku , Swift , XMM–Newton and Chandra missions. We present here the results of this campaign and compare them with previous observations. With these data we are able, for the first time, to study the details of the spectral evolution of the source over a 2-month period of the passage of the pulsar close to the Be star. New data confirm the pre-periastron spectral hardening, with the photon index reaching a value smaller than 1.5, observed during a local flux minimum. If the observed X-ray emission is due to the inverse Compton (IC) losses of the 10-MeV electrons, then such a hard spectrum can be a result of Coulomb losses, or can be related to the existence of the low-energy cut-off in the electron spectrum. Alternatively, if the X-ray emission is a synchrotron emission of very high-energy electrons, the observed hard spectrum can be explained if the high-energy electrons are cooled by IC emission in Klein–Nishina regime. Unfortunately, the lack of simultaneous data in the TeV energy band prevents us from making a definite conclusion on the nature of the observed spectral hardening and, therefore, on the origin of the X-ray emission. 相似文献
93.
94.
95.
Kazuya Tanaka Yoshio Takahashi Kenji Horie Hiroshi Shimizu Takashi Murakami 《Physics and Chemistry of Minerals》2010,37(4):249-254
We examined the LIII-edge Pb X-ray absorption near-edge structure (XANES) of three natural zircon samples with different amounts of radiation
doses (1.9 × 1015 to 6.8 × 1015 α-decay events/mg). The results suggest that the oxidation state of radiogenic Pb in the zircon sample with the highest radiation
dose is divalent. The XANES spectra of the two other samples with lower radiation doses suggest that radiogenic Pb(II) is
present, and further that some Pb may be tetravalent. This is the first work on the determination of the oxidation state of
radiogenic Pb in natural zircon using XANES. 相似文献
96.
Runup data in Biak Island and itsnearby islets are described with discussions oftsunami magnitude and a few characteristics such aswitnessed arrival times, wave periods and wavenumbers. From an engineering viewpoint, a relationbetween inundation depth and current velocity on landis also described with relations between inundationdepth and degree of damage to houses and between sanderosion depth and current velocity in backshoreregion, based on data collected from the present andpast tsunamis. 相似文献
97.
98.
Numerical simulation of the 1992 Flores tsunami: Interpretation of tsunami phenomena in northeastern Flores Island and damage at Babi Island 总被引:2,自引:0,他引:2
Fumihiko Imamura Edison Gica Tomoyuki Takahashi Nobuo Shuto 《Pure and Applied Geophysics》1995,144(3-4):555-568
Numerical analysis of the 1992 Flores Island, Indonesia earthquake tsunami is carried out with the composite fault model consisting of two different slip values. Computed results show good agreement with the measured runup heights in the northeastern part of Flores Island, except for those in the southern shore of Hading Bay and at Riangkroko. The landslides in the southern part of Hading Bay could generate local tsunamis of more than 10 m. The circular-arc slip model proposed in this study for wave generation due to landslides shows better results than the subsidence model, It is, however, difficult to reproduce the tsunami runup height of 26.2 m at Riangkroko, which was extraordinarily high compared to other places. The wave propagation process on a sea bottom with a steep slope, as well as landslides, may be the cause of the amplification of tsunami at Riangkroko. The simulation model demonstrates that the reflected wave along the northeastern shore of Flores Island, accompanying a high hydraulic pressure, could be the main cause of severe damage in the southern coast of Babi Island. 相似文献
99.
Takuji Kobori Motoichi Takahashi Tadashi Nasu Naoki Niwa Katsura Ogasawara 《地震工程与结构动力学》1993,22(11):925-941
The Active Variable Stiffness (AVS) system is proposed as a seismic response control system. It actively controls structural characteristics, such as stiffness of a building, to establish a non-resonant state against earthquake excitations, thus suppressing the building's response. It consumes a relatively small amount of energy and maintains the safety of the building in moderate to severe earthquakes. In order to accumulate practical data and investigate them, a building has been constructed as a trial. This paper describes the applied system, the control algorithm, verification of stiffness selection, results of tests for verifying system characteristics, some observed earthquake records and simulation analyses. Responses in controlled and uncontrolled states have been compared to show the effectiveness of the proposed system. 相似文献
100.
Taro Takahashi Peter Kaiteris Wallace S. Broecker Arnold E. Bainbridge 《Earth and Planetary Science Letters》1976,32(2):458-467
The internal consistency of five sets of apparent dissociation constants of carbonic acid in seawater obtained by Buch (1951), Lyman (1956), Edmond and Gieskes (1970), Hansson (1973) and Mehrbach et al. (1973) have been tested using the GEOSECS Atlantic data for the total alkalinity, the total CO2 concentration and the partial pressure of CO2. As a measure of the consistency for each of the five sets of the dissociation constants with the data, the 77 measured values of the partial pressure of CO2 have been compared with those calculated from the alkalinity and total CO2 values determined for these samples. It has been found that: (1) the apparent dissociation constants of Lyman (1956), Hansson (1973) and Mehrbach et al. (1973) appear to be internally consistent with the data, whereas those of Buch (1951) and of Edmond and Gieskes (1970) appear to be markedly inconsistent with the GEOSECS data; and (2) on the basis of a statistical analysis of the data grouped in three temperature ranges, the dissociation constants of Lyman (1956) and of Mehrbach et al. (1973) appear to be most satisfactory. 相似文献