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11.
Kota Katsuki Yasushi Miyamoto Kazuyoshi Yamada Hiroyuki Takata Keiko Yamaguchi Daisuke Nakayama Hugo Coops Hidenobu Kunii Ritsuo Nomura Boo-Keun Khim 《Journal of Paleolimnology》2008,40(4):1115-1125
Lake Nakaumi, southwest Japan, is an enclosed lagoon characterized by polyhaline and halocline conditions. Since the last
century, its ecological state has been altered by eutrophication. We used a paleolimnological approach and studied multiple
proxies, including chemical compounds, diatoms, foraminifera and molluscs, to infer the eutrophication history of the ecosystem.
Eutrophication in Lake Nakaumi was associated with several factors, including increased nutrient loading, input of herbicides,
and dike building since the 1920s. The ecological condition of this lake was divided into several stages that reflect the
eutrophication process after the 1940s. A catastrophic “regime shift” from a clear state with aquatic vegetation to a turbid
one with phytoplankton occurred in the early 1950s. Environmental degradation in the Honjo area, a part of Lake Nakaumi, was
attributed primarily to physical changes caused by the construction of an enclosing dike. Eutrophication occurred almost simultaneously
with the physical changes to the Honjo area in the 1970s. Until recently, no regime shift was observed in this area, though
the core-top sediments show possible symptoms of incipient change. 相似文献
12.
A two-dimensional stress field of dislocation or fault is geometrically studied for an asymmetric continuum. For geometric surfaces of the stress and couple-stress functions, the mean and Gaussian curvatures are derived. The mean curvature of couple-stress function surface is connected with the asymmetric of stress tensor. Moreover, the Gaussian curvature of stress function surface is characterized by both the stress and couple-stress. On the other hand, the mean curvature of stress function surface is not affected by the asymmetry of stress. Based on these geometric expressions, the Coulomb’s failure criterion and the friction coefficient are expressed by the curvatures of couple-stress function surface. Moreover, geometric structures of stress and couple stress function surfaces are shown for edge and wedge dislocations as faults. The curvatures of these surfaces show that the effect of couple-stress is constrained around the dislocations only. 相似文献
13.
Kinya Hibino Toshisuke Kashiwagi Shoji Okuno Kaori Yajima Yukio Uchihori Hisashi Kitamura Takeshi Takashima Mamoru Yokota Kenji Yoshida 《Astrophysics and Space Science》2007,309(1-4):541-544
We have developed radiation detectors using the new synthetic diamonds. The diamond detector has an advantage for observations
of “low/medium” energy gamma rays as a Compton telescope. The primary advantage of the diamond detector can reduce the photoelectric
effect in the low energy range, which is background noise for tracking of the Compton recoil electron. A concept of the Diamond
Compton Telescope (DCT) consists of position sensitive layers of diamond-striped detector and calorimeter layer of CdTe detector.
The key part of the DCT is diamond-striped detectors with a higher positional resolution and a wider energy range from 10 keV
to 10 MeV. However, the diamond-striped detector is under development. We describe the performance of prototype diamond detector
and the design of a possible DCT evaluated by Monte Carlo simulations.
相似文献
14.
We considered the two-dimensional stress aspect of a fault from the viewpoint of differential geometry. For this analysis,
we concentrated on the curvatures of the Airy stress function surface. We found the following: (i) Because the principal stresses
are the principal curvatures of the stress function surface, the first and the second invariant quantities in the elasticity
correspond to invariant quantities in differential geometry; specifically, the mean and Gaussian curvatures, respectively;
(ii) Coulomb’s failure criterion shows that the coefficient of friction is the physical expression of the geometric energy
of the stress function surface; (iii) The differential geometric expression of the Goursat formula shows that the fault (dislocation)
type (strike-slip or dip-slip) corresponds to the stress function surface type (elliptic or hyperbolic). Finally, we discuss
the need to use non-biharmonic stress tensor theory to describe the stress aspect of multi-faults or an earthquake source
zone. 相似文献
15.
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