Taxonomy,location of origin and health status of proboscideans from Western Canada investigated using stable isotope analysis          下载免费PDF全文

Jessica Z. Metcalfe  Fred J. Longstaffe  Christopher N. Jass  Grant D. Zazula  Grant Keddie 《第四纪科学杂志》2016,31(2):126-142

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Correlations between re and PGE concentrations in rocks,ores, and minerals of mafic-ultramafic associations     

F. P. Lesnov  G. N. Anoshin 《Doklady Earth Sciences》2011,437(1):387-392

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Effects of forest roads on the hydrological response of a small‐scale mountain watershed in Greece          下载免费PDF全文

K. X. Soulis  N. Dercas  CH. Papadaki 《水文研究》2015,29(7):1772-1782

The effects of land use changes on the ecology and hydrology of natural watersheds have long been debated. However, less attention has been given to the hydrological effects of forest roads. Although less studied, several researchers have claimed that streamflow changes related to forest roads can cause a persistent and pervasive effect on hillslope hydrology and the functioning of the channel system. The main potential direct effects of forest roads on natural watersheds hydrologic response are runoff production on roads surfaces due to reduced infiltration rates, interruption of subsurface flow by road cutslopes and rapid transfer of the produced runoff to the stream network through roadside ditches. The aforementioned effects may significantly modify the total volume and timing of the hillslope flow to the stream network. This study uses detailed field data, spatial data, hydro‐meteorological records, as well as numerical simulation to investigate the effects of forest roads on the hydrological response of a small‐scale mountain experimental watershed, which is situated in the east side of Penteli Mountain, Attica, Greece. The results of this study highlight the possible effects of forest roads on the watersheds hydrological response that may significantly influence direct runoff depths and peak flow rates. It is demonstrated that these effects can be very important in permeable watersheds and that more emphasis should be given on the impact of roads on the watersheds hydrological response. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

射电望远镜远场区域强干扰源规避方法研究          下载免费PDF全文

李欢  刘奇  王娜  蔡明辉  王玥  朱春花  苏晓明 《天文学报》2021,62(6):61

随着频率使用率的提高, 射电天文台址地面或空间存在强电磁干扰致使望远镜接收机系统处于非线性状态. 为减少强电磁干扰的影响、提高天文观测效率, 提出了一种基于望远镜远场区域的强干扰源规避方法. 首先, 通过仿真分析确定的射电望远镜远场方向图, 结合望远镜与干扰源之间的位置关系, 分析了强电磁干扰到达射电望远镜焦点处的功率响应, 并依据接收机第2阶中频放大器性能参数, 确定射电望远镜处于非饱和状态的规避角度计算方法. 其次, 采用该方法计算分析了民航飞机对射电望远镜的影响, 若民航飞机上有主动发射的干扰源, 且不经过反射等传播现象, 当射电望远镜主波束轴偏开一定方向后, 可有效降低对射电望远镜的干扰强度.  相似文献   

Geomorphological Analysis of ExoMars Candidate Landing Site Oxia Planum     

Ivanov  M. A.  Slyuta  E. N.  Grishakina  E. A.  Dmitrovskii  A. A. 《Solar System Research》2020,54(1):1-14

Solar System Research - The article is devoted to a detailed photogeological and topographic analysis of the surface in the region of Oxia Planum, which is the most likely landing site for the...  相似文献   

A refractory inclusion with solar oxygen isotopes and the rarity of such objects in the meteorite record     

Levke Kp  Kazuhide Nagashima  Andrew M. Davis  Alexander N. Krot 《Meteoritics & planetary science》2020,55(3):524-534

NASA's Genesis mission revealed that the Sun is enriched in ¹⁶O compared to the Earth and Mars (the Sun's Δ¹⁷O, defined as δ¹⁷O–0.52×δ¹⁸O, is –28.4 ± 3.6‰; McKeegan et al. 2011). Materials as ¹⁶O‐rich as the Sun are extremely rare in the meteorite record. Here, we describe a Ca‐Al‐rich inclusion (CAI) from a CM chondrite that is as ¹⁶O‐enriched as the Sun (Δ¹⁷O = –29.1 ± 0.7‰). This CAI also has large nucleosynthetic anomalies in ⁴⁸Ca and ⁵⁰Ti (δ‐values are –8.1 ± 3.3 and –11.7 ± 2.4‰, respectively) and shows no clear evidence for incorporation of live ²⁶Al; (²⁶Al/²⁷Al)₀ = (0.03 ± 0.11) × 10^–5. Due to their anomalous isotopic characteristics, the rare CAIs consistent with the Genesis value could be among the first materials that formed in the solar system. In contrast to the CAI studied here, the majority of CAIs formed in or interacted with a reservoir characterized by a Δ¹⁷O value near –23.5‰. Combined with ²⁶Al‐²⁶Mg systematics, the oxygen isotopic compositions of FUN (fractionation and unidentified nuclear effects), UN, and normal CAIs suggest that nebular conditions were favorable for solids to inherit this value for an extended period of time. Many later‐formed materials, such as chondrules, planetesimals, and terrestrial planets, formed in reservoirs with Δ¹⁷O near 0‰. The distribution could be easier to explain if the common CAI value of –23.5‰, which is consistent with the Genesis value within 3σ, represented the average composition of the protoplanetary disk.  相似文献   

Influx of Streaming Methane into Anoxic Waters of the Black Sea Basin     

Artemov  Yu. G.  Egorov  V. N.  Gulin  S. B. 《Oceanology》2019,59(6):860-870

Oceanology - Based on long-term data on the spatial distribution and fluxes of streaming (bubbling) methane in the Black Sea, the study considers various types of streaming gas emissions...  相似文献   

Oceanographic Studies in the Northwest Pacific and Seas of Japan and Okhotsk on Cruise 73 of the R/V Professor Gagarinskiy and Cruise 53 of the R/V Akademik Oparin     

Karnaukh  V. N.  Sergeev  A. F.  Lobanov  V. B.  Tishcenko  P. Ya. 《Oceanology》2019,59(6):995-998

Oceanology - During cruise 73 of the R/V Professor Gagarinskiy and cruise 53 of the R/V Akademik Oparin, oceanographic studies of the Sea of Japan and Sea of Okhotsk and the Northwest Pacific were...  相似文献   

Heterotrophic Nanoflagellates in the Pelagic Zone and Sediments of the Eastern Laptev Sea     

Kosolapova  N. G.  Kosolapov  D. B.  Kopylov  A. I.  Romanenko  A. V. 《Oceanology》2019,59(6):881-892

Oceanology - For the first time, the species composition of heterotrophic nanoflagellates, their quantitative characteristics, and abundance and biomass of their main food objects—bacteria...  相似文献   

Variability of Ice Conditions of the Bering Sea and Assessment of Their Possible Modeling     

Plotnikov  V. V.  Vakulskaya  N. M.  Dubina  V. A. 《Oceanology》2019,59(6):829-835

Oceanology - Various aspects of the seasonal and interannual variability of the sea ice cover are estimated based on all available Bering Sea ice data from 1960 to 2017. The possibility of...  相似文献