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排序方式: 共有275条查询结果,搜索用时 15 毫秒
91.
92.
Nagao K Okazaki R Nakamura T Miura YN Osawa T Bajo K Matsuda S Ebihara M Ireland TR Kitajima F Naraoka H Noguchi T Tsuchiyama A Yurimoto H Zolensky ME Uesugi M Shirai K Abe M Yada T Ishibashi Y Fujimura A Mukai T Ueno M Okada T Yoshikawa M Kawaguchi J 《Science (New York, N.Y.)》2011,333(6046):1128-1131
Noble gas isotopes were measured in three rocky grains from asteroid Itokawa to elucidate a history of irradiation from cosmic rays and solar wind on its surface. Large amounts of solar helium (He), neon (Ne), and argon (Ar) trapped in various depths in the grains were observed, which can be explained by multiple implantations of solar wind particles into the grains, combined with preferential He loss caused by frictional wear of space-weathered rims on the grains. Short residence time of less than 8 million years was implied for the grains by an estimate on cosmic-ray-produced (21)Ne. Our results suggest that Itokawa is continuously losing its surface materials into space at a rate of tens of centimeters per million years. The lifetime of Itokawa should be much shorter than the age of our solar system. 相似文献
93.
Flood mitigation in irrigation tanks and paddy fields is their favorable aspect though its practical effect is not known very
well. A dynamic and systematic approach is presented to assess flood mitigation in a tank irrigated paddy fields area in the
worst case where no static buffer function is expected. Based on the linear control theory, transfer function models for runoff
process in catchments are identified. Hydraulic models are developed to represent flood dynamics in irrigation tanks, paddy
fields, and drainage channels. These models are integrated as an ordinary differential equations system. Then, using the perturbed
linear system, flood mitigation in each component of the system is examined in terms of frequency response. An application
example demonstrates that a tank irrigated paddy fields area has a significant flood mitigation effect as a low-pass filter.
This method has the advantage of assessing flood mitigation even in the case of an increase in the total runoff ratio. 相似文献
94.
95.
Makoto Shirai Shingo Arakawa Hiroaki Miida Takuya Matsuyama Junzo Kinoshita Toshihiko Makino Kiyonori Kai Munehiro Teranishi 《Journal of toxicologic pathology》2013,26(2):175-186
To assess modification of thioacetamide-induced hepatotoxicity in mice fed a high-fat
diet, male C57BL/6J mice were fed a normal rodent diet or a high-fat diet for 8 weeks and
then treated once intraperitoneally with thioacetamide at 50 mg/kg body weight. At 24 and
48 hours after administration, massive centrilobular hepatocellular necrosis was observed
in mice fed the normal rodent diet, while the necrosis was less severe in mice fed the
high-fat diet. In contrast, severe swelling of hepatocytes was observed in mice fed the
high-fat diet. In addition, mice fed the high-fat diet displayed more than a 4-fold higher
number of BrdU-positive hepatocytes compared with mice fed the normal rodent diet at 48
hours after thioacetamide treatment. To clarify the mechanisms by which the hepatic
necrosis was attenuated, we investigated exposure to thioacetamide and one of its
metabolites, the expression of CYP2E1, which converts thioacetamide to reactive
metabolites, and the content of glutathione S-transferases in the liver. However, the
reduced hepatocellular necrosis noted in mice fed the high-fat diet could not be explained
by the differences in exposure to thioacetamide or thioacetamide sulfoxide or by
differences in the expression of drug-metabolizing enzymes. On the other hand, at 8 hours
after thioacetamide administration, hepatic total glutathione in mice fed the high-fat
diet was significantly lower than that in mice fed the normal diet. Hence, decreased
hepatic glutathione amount is a candidate for the mechanism of the attenuated necrosis. In
conclusion, this study revealed that thioacetamide-induced hepatic necrosis was attenuated
in mice fed the high-fat diet. 相似文献
96.
Akihiro MATSUURA Mami IRIMAJIRI Kunihiro MATSUZAKI Yuko HIRAGURI Toshihiko NAKANOWATARI Atusi YAMAZAKI Koichi HODATE 《Animal Science Journal》2013,84(1):75-81
The aim of this study was to establish a method for estimating loading capacity for Japanese native horses by gait analysis using an accelerometer. Six mares of Japanese native horses were used. The acceleration of each horse was recorded during walking and trotting along a straight course at a sampling frequency of 200 Hz. Each horse performed 12 tests: one test with a loaded weight of 80 kg (First 80 kg) followed by 10 tests with random loaded weights between 85 kg and 130 kg and a final test with a loaded weight of 80 kg again. The time series of acceleration was subjected to fast Fourier transformation, and the autocorrelation coefficient was calculated. The first two peaks of the autocorrelation were defined as symmetry and regularity of the gait. At trot, symmetries in the 100, 110, and 125 kg tests were significantly lower than that in First 80 kg (P < 0.05, by analysis of covariance and Sidak's test). These results imply that the maximum permissible load weight is less than 100 kg, which is 29% of the body weight of Japanese native horses. Our method is a widely applicable and welfare‐friendly method for estimating maximum permissible load weights of horses. 相似文献
97.
Eradication of feral goats enhances expansion of the invasive shrub Leucaena leucocephala on Nakoudo‐jima,an oceanic island
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Many introduced species can co‐exist within the same ecosystem and sometimes interact with each other. Under such situations, eradication of one species may cause unexpected negative effects. Nakoudo‐jima in the Ogasawara (Bonin) Islands is an oceanic island that had feral goats that were introduced in the 1880s, but eradicated in 1999. Following their eradication, the alien invasive shrub Leucaena leucocephala (Fabaceae) was predicted to increase drastically. In this study, we tested the hypothesis that the eradication of feral goats enhanced the expansion of L. leucocephala using four time‐series aerial photographs and validation work based on current field surveys of Nakoudo‐jima. Our results showed that following feral goat elimination, bare ground areas decreased and forest cover increased. This was particularly true of areas dominated by L. leucocephala. Thus, feral goats appear to have limited the expansion of L. leucocephala on Nakoudo‐jima. Grassland cover also increased following feral goat elimination, but this may have occurred prior to L. leucocephala expansion. These results suggest that L. leucocephala‐dominated forest might invade grassland areas and that grasslands may have mediated the expansion of L. leucocephala after feral goat elimination. Future management of L. leucocephala should target the species in the high‐risk expansion zones adjacent to grasslands. 相似文献
98.
Matsunaga S Osawa T Geshi M Takahashi H Inumaru S Yokomizo Y Miyake YI 《Research in veterinary science》2012,93(1):381-385
This study tested the effect of recombinant bovine interferon-tau (rboIFN-τ) on the length of estrous cycle, luteal lifespan and side effects of rboIFN-τ in the cow. A normal estrous cycle in six non-lactating cycling Holstein cows was observed (non-treated cycle), and either 2.0 mg of liposomalized rboIFN-τ (treated cycle) or bovine serum albumin (BSA; placebo cycle) was infused in the uterus on day 7 of the estrous cycle (day 0=day of ovulation). Rectal temperature, heart rate and respiratory rate were recorded and blood samples were collected before and after the treatments. The length of the estrous cycle and corpus luteum lifespan in rboIFN-τ treated cycles were not significantly different from those of the non-treated and placebo cycles. In contrast, the rboIFN-τ treatment caused a transient increase in rectal temperature and a decrease in the number of peripheral lymphocytes and neutrophils after the treatment. 相似文献
99.
100.
Influence of riders’ skill on plasma cortisol levels of horses walking on forest and field trekking courses
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Ayaka Ono Akihiro Matsuura Yumi Yamazaki Wakako Sakai Kentaro Watanabe Toshihiko Nakanowatari Hiroshi Kobayashi Mami Irimajiri Koichi Hodate 《Animal Science Journal》2017,88(10):1629-1635
The aim of this study was to evaluate the influence of rider's skill on the plasma cortisol levels of trekking horses on two courses, walking on field and forest courses (about 4.5 to 5.1 km each). Three riders of different skills did horse trekking (HT) in a tandem line under a fixed order: advanced‐leading, beginner‐second and intermediate‐last. A total of six horses were used and they experienced all positions in both courses; a total of 12 experiments were done. Blood samples were obtained before HT, immediately after and 2 h after HT. As a control, additional blood samples were obtained from the same horses on non‐riding days. Irrespective of the course and the rider's skill, the cortisol level before HT was higher than that of control (P < 0.05). In both courses, the cortisol levels immediately after HT ridden by the advanced rider were higher than that of control (P < 0.05). However, in every case, the cortisol level 2 h after HT was closely similar to the level of the control. Thus, we concluded the stress of trekking horse was not sufficient to disturb the circadian rhythm of the cortisol level, irrespective of the course and the rider's skill. 相似文献