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在对渤海滨州贝壳堤岛的自由生活海洋线虫进行分类和多样性研究中,发现2个我国新纪录种并进行了描述。其中,澳洲深咽线虫Bathylaimus australis Cobb,1894主要特征为:头刚毛长约20μm,分为4节,顶端膨大;前口腔大,无齿,后口腔小,具小齿;化感器双环形,位于口腔中部位置;交接刺细长,稍向腹面弯曲,近端膨大呈头状,长32-37μm;引带宽大,肾形,长36-40μm,末端角质化,渐尖。古氏努朵拉线虫Nudora gourbaultae Vincx,1989主要特征为:体表具12列纵向排列的V型装饰;第二体环较宽,头刚毛11-15μm(为头颈的67%-81%);化感器圆形,直径4-6μm(为相应体径的29%-38%),位于第二体环上;具双咽球;交接刺细长,弯曲呈S型,长为肛径的1.3-1.5倍;引带等于或长于交接刺,镰刀型,无肛前辅器。 相似文献
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《Chinese Astronomy and Astrophysics》2022,46(1):109-136
Near-Earth asteroids (10302) 1989 ML and (4660) Nereus have attracted much attention as candidates for the next generation of deep space explorations. In the study, the maximum Lyapunov exponent (MLE) and MEGNO (Mean Exponential Growth factor of Nearby Orbits) index are calculated after considering the effects of major objects in the Solar system, and the stabilities of these two asteroids are discussed. For each asteroid, 1000 clonal particles consistent with the observational uncertainties are generated from a multivariate normal distribution. Statistical results display probably emerging regions of each asteroid within 0.1 million years, and provide distributions of occurrence times in the phase space of semi-major axis versus eccentricity. We estimate the probability of close encounters and collisions between the asteroid and Earth or other planets. Furthermore, secular resonances, Kozai resonance, and mean motion resonances are analyzed for nominal orbits of the two asteroids. We conclude that 1989 ML is in the region dominated by mean motion resonances with terrestrial planets. The probability of close encounters with them is relatively small, therefore its orbit is relatively stable. Nereus is located in a region that can have close-encounters with the Earth, and it has an extremely unstable orbit. 相似文献
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David L. Lambert N. Kameswara Rao Sunetra Giridhar 《Journal of Astrophysics and Astronomy》1990,11(4):475-490
Moderate-resolution spectra of the C2 Swan 0-1 bandhead, the Na I D lines and the KI resonance lines near 7660 Å obtained at minimum light during the 1988–1989 decline of R CrB are discussed and interpreted in terms of a popular model for R CrB declines. High-resolution spectra obtained at maximum light show blue-shifted chromospheric emission in the cores of the Na I D and the Sc π 4246.8 Å lines 相似文献
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近地小行星(10302) 1989 ML和(4660) Nereus作为下一代深空探测的候选目标一直备受关注. 在考虑太阳系主要天体的动力学背景下, 通过计算最大Lyapunov指数(MLE)及MEGNO (Mean Exponential Growth factor of Nearby Orbits)指数讨论它们的稳定性. 同时, 对每个小行星, 在其观测误差范围内按多元正态分布各选取1000个克隆粒子, 通过统计分析显示这两个小行星在10万年内可能的运动范围, 给出半长径-偏心率空间中的出现次数分布图, 并统计小行星与地球或其他大行星之间的密近交汇及碰撞的概率. 此外还对这两个小行星的标称轨道进行长期共振、Kozai共振及平运动共振的动力学分析. 综上得出结论, 1989 ML处在平运动共振主导的区域, 发生密近交汇的概率较小, 从而其轨道相对较稳定; 而Nereus处在地球的密近交汇区域, 轨道极不稳定. 相似文献
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On the basis of a numerical simulation, Klose [Earth Planet. Sci. Lett. 256: 547–553 (2007)] proposed that the MW = 5.2–5.6 earthquake that nucleated beneath Newcastle (New South Wales, Australia) at 10.30 AM December 28, 1989 (AEST), was the result of 200yr of coal mining in the region. We argue here that Klose's [Earth Planet. Sci. Lett. 256: 547–553 (2007)] ultimate conclusion is not supported by his own model or by available geological and seismic data. In particular, the 1989 Newcastle earthquake was not anomalous with respect to regional seismic activity. 相似文献
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