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991.
994.
Wnt基因家族编码一类保守的分泌型糖蛋白,广泛参与细胞分化与增殖、细胞运动、凋亡、免疫调控以及色素生成等生物学过程。本研究鉴定了一个长牡蛎Wnt家族基因——CgWnt5b,比较了黑、白壳色长牡蛎中CgWnt5b转录水平的表达情况,并对其在调控黑色素生成方面的功能进行初步研究。研究结果显示,CgWnt5b编码序列全长1116 bp,编码371个氨基酸。生物信息学分析预测CgWnt5b蛋白相对分子量为42 KDa,等电点为9.28。对CgWnt5b与哺乳动物Wnt基因家族19个成员进行系统发育分析,确定了CgWnt5b为哺乳动物Wnt5a和Wnt5b的同源基因。荧光实时定量PCR检测长牡蛎外套膜、鳃、消化腺、闭壳肌、性腺、唇瓣以及血淋巴组织中CgWnt5b的mRNA分布,结果显示,CgWnt5b在外套膜、闭壳肌和唇瓣组织中的相对表达水平较高,在消化腺、鳃、血淋巴和性腺组织中相对表达量较低。黑壳长牡蛎中CgWnt5b mRNA表达量显著低于白壳长牡蛎,且siRNA敲降CgWnt5b的表达后,多个黑色素生成相关酪氨酸酶基因的表达显著上调。综上,本研究在长牡蛎中鉴定了一个Wnt家族成员CgWnt5b,可能通过抑制黑色素生成关键基因TYR的表达抑制长牡蛎中黑色素的生成。 相似文献
995.
水体吸收系数是评价水体环境质量和衡量海洋对全球气候影响的重要因子.水色遥感作为目前对大范围海洋进行长时间连续监测的唯一手段,可以借助于合适的反演模型从影像上获取水体吸收系数.然而现有模型多为经验模型,反演精度和水体适应性都较差.基于自建的全球水体光学原位测量数据集SeaBASS2020,通过选用412、443、490、... 相似文献
996.
越野环境下机动车辆的快速路径规划在野外搜救、应急抢险及军事作战等领域均具有重要意义,在以上场景中,随着空间维数的增加,传统路径搜索算法计算复杂性急剧增长,可能无法在既定时间内求解可靠路径。为解决上述不足,本文结合越野路径规划不受路网通行限制以及两点之间直线最短的特点,提出以方向指向作为搜索策略的启发式算法,该算法搜索效率大幅提升,却难以保证求解质量。为进一步提高求解质量,提出了带有方向指向的Dijkstra分段算法,该算法在较低精度环境模型下通过Dijkstra算法找到最优路径,并将该路径进行分段,各分段以方向指向作为搜索策略进行路径搜索,从而在长距离越野路径规划中快速规划通行方案。为验证该算法的有效性,本文利用山西省某市的数字高程模型数据进行实验,引入了窗口移动法对地形进行先期的坡度计算和通行性分析,构建越野环境模型,调用路径搜索算法进行规划。实验结果表明,本文所提算法相比Dijkstra算法计算效率得到了大幅提升,且规划路径的长度接近于最优解。 相似文献
997.
Gao Kai Liu Yanjie Ding Lin Huang Shuai Qiu Kaichi Wang Zhongpan Yang Yang Liu Xing Li Jiaxin 《地震工程与工程振动(英文版)》2021,20(4):1007-1019
The permafrost of Mohe County and its suburbs in the Daxing′an Mountains has been influenced by the urbanization. Remote sensing, GIS technology and numerical simulation was used to study the temperature variations of permafrost with the changes in surface vegetation that cover Mohe County and suburban areas, and the law of permafrost degradation on the study area was analyzed. The research results show that the urban area of the study area increased 114.42%from 2000 to 2016, and the urbanization process is continuing to accelerate. The Normalized Difference Vegetation Index map of 2017 in Mohe County and its suburbs was studied and the maximum proportion of vegetation coverage was different in the four seasons. The numerical calculation model results show that the permafrost temperature change in the study area cyclically fluctuates in a cosine form. The annual variation curve of permafrost temperature gradually decreased and its accompanying phase lag increased with depth. The annual temperature change value with the different depths of the town was greater than the natural ground. The maximum permafrost thawing depths of the town and natural ground were 4.2 m and 2.82 m in 50 a, and the degradation rates of the two permafrost are, respectively, 0.88 cm/a and 0.46 cm/a. These results show that urbanization has accelerated the degradation of permafrost. 相似文献
998.
Shiyang River streamflow since AD 1765, reconstructed by tree rings,contains far‐reaching hydro‐climatic signals over and beyond the mid‐latitude Asian continent
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Feng Chen Yu‐jiang Yuan Rui‐bo Zhang Hui‐qin Wang Hua‐ming Shang Tong‐wen Zhang Li Qin Zi‐ang Fan 《水文研究》2016,30(13):2211-2222
In this study, the regional tree‐ring chronology of Picea crassifolia was used to estimate annual (September to August) streamflow of the Shiyang River for the period from AD 1765 to 2010. The linear regression model was stable and could explain 41.5% of the variance for the calibration period of 1955–2005. According to the streamflow reconstruction, dry periods with below average streamflow occurred in AD 1775–1804, 1814–1823, 1831–1856, 1862–1867, 1877–1885, 1905–1910, 1926–1932, 1948–1951, 1960–1963 and 1989–2002. Periods of relatively wet years are identified for AD 1765–1774, 1805–1813, 1824–1830, 1857–1861, 1868–1876, 1886–1904, 1911–1925, 1933–1947, 1952–1959, 1964–1988 and 2003–2010. Comparisons with the precipitation reconstructions from surrounding areas supplied a high degree of confidence in our reconstruction. Our reconstructed streamflow is significantly correlated with sea surface temperature in the eastern equatorial Pacific Ocean and the North Atlantic Ocean. The Multitaper spectral and correlation analyses also suggested that the reconstructed streamflow variation in the Shiyang River could be associated with large‐scale atmospheric‐oceanic variability, such as El Niño‐Southern Oscillation (ENSO). The linkages among the streamflow reconstruction, NAO and ENSO suggest the connection of regional streamflow variations to the Asian monsoon and westerlies circulations. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
999.
Jinrong Wu Erchang Shang 《Oceanic Engineering, IEEE Journal of》2007,32(4):872-878
The integrated bottom scattering strength (ISS) and the modal backscattering matrix (MBSM) have been used to describe the bottom backscattering in shallow-water reverberation modeling, and both can be extracted from the reverberation data. The relationship between the ISS and the MBSM based on the same reverberation data in shallow water is discussed. It is shown that the ISS is an angular weighting average of the MBSM in mode space. The weighting factors are range-depth-frequency-dependent and also depend on the sound-speed profile (SSP) in the water column. Thus, the ISS has a complex variation. This complexity of the ISS causes it to be so variable that it provides little basic understanding of the scattering. Numerical examples are conducted to show this complexity. 相似文献
1000.
Qiusheng Gu Jiehao Huang Zhaohui Shang Hongjun Su Jin Zhu 《Astrophysics and Space Science》1995,229(2):317-323
We report our discovery of new active galaxies in a small sample of 23 sources with 2.16 m telescope at Beijing Astronomical Observatory. After wavelength and flux calibration, they are classified by their degree of nuclear activities: one Seyfert 1, three Seyfert 2s, six Seyfert 3s, Seven HII galaxies and one possible Seyfert 3. 相似文献