Subsurface formation of oxidants on Mars and implications for the preservation of organic biosignatures     

Alfonso F. Davila  Alberto G. Fairn  Luis Gago-Duport  Carol Stoker  Ricardo Amils  Rosalba Bonaccorsi  Jhony Zavaleta  Darlene Lim  Dirk Schulze-Makuch  Christopher P. McKay 《Earth and Planetary Science Letters》2008,272(1-2):456-463

Hydrogen peroxide can form through the interaction of pyrite and anoxic water. The oxidation of pyrite results in the precipitation of sulfates and iron oxides, high redox potentials (~ 1000 mV) and acidic pH (3–4). The oxidative potential of the resultant solution may be responsible for the oxidation of organic compounds, as observed in the subsurface of the Rio Tinto Mars analog. On Mars subsurface migration of groundwater interacting with volcanogenic massive pyrite deposits would have mobilized acidic and oxidizing fluids through large portions of the crust, resulting in the widespread deposition of sulfates and iron oxides. This groundwater could have leached substantial volumes of aquifer material and crustal rocks, thereby erasing any organic compounds possibly down to depths of hundreds of meters. Therefore, the preservation of organic biosignatures must have been severely constrained in the portions of the ancient Martian crust that were exposed to aqueous processes, calling for a redefinition of the future targets in the search for biomolecular traces of life on Mars.  相似文献   

First Investigation of Microbial Community Composition in the Bridge (Gadeok Channel) between the Jinhae-Masan Bay and the South Sea of Korea     

Jiyoung Lee  Jae-Hyun Lim  Junhyung Park  Seok-Hyun Youn  Hyun-Ju Oh  Ju-Hyoung Kim  Myung Kyum Kim  Hyeyoun Cho  Joo-Eun Yoon  Soyeon Kim  Kesavan Markkandan  Ki-Tae Park  Il-Nam Kim 《Ocean Science Journal》2018,53(2):251-260

Microbial community composition varies based on seasonal dynamics (summer: strongly stratified water column; autumn: weakly stratified water column; winter: vertically homogeneous water column) and vertical distributions (surface, middle, and bottom depths) in the Gadeok Channel, which is the primary passage to exchange waters and materials between the Jinhae-Masan Bay and the South Sea waters. The microbial community composition was analyzed from June to December 2016 using 16S rRNA gene sequencing. The community was dominated by the phyla Proteobacteria (45%), Bacteroidetes (18%), Cyanobacteria (15%), Verrucomicrobia (6%), and Actinobacteria (6%). Alphaproteobacteria (29%) was the most abundant microbial class, followed by Flavobacteria (15%) and Gammaproteobacteria (15%) in all samples. The composition of the microbial communities was found to vary vertically and seasonally. The orders Flavobacteriales and Stramenopiles showed opposing seasonal patterns; Flavobacteriales was more abundant in August and December while Stramenopiles showed high abundance in June and October at all depths. The genus Synechococcus reached extremely high abundance (14%) in the June surface water column, but was much less abundant in December water columns. Clustering analysis showed that there was a difference in the microbial community composition pattern between the strongly stratified season and well-mixed season. These results indicate that the seasonal dynamics of physicochemical and hydrologic conditions throughout the water column are important parameters in shaping the microbial community composition in the Gadeok Channel.  相似文献   

Fluid—Structure Interaction Analysis of Flexible Plate with Partitioned Coupling Method     

Lim  W. Z.  Xiao  R. Y. 《中国海洋工程》2019,33(6):713-722

The development and rapid usage of numerical codes for fluid-structure interaction(FSI) problems are of great relevance to researchers in many engineering fields such as civil engineering and ocean engineering. This multidisciplinary field known as FSI has been expanded to engineering fields such as offshore structures, tall slender structures and other flexible structures applications. The motivation of this paper is to investigate the numerical model of two-way coupling FSI partitioned flexible plate structure under fluid flow. The adopted partitioned method and approach utilized the advantage of the existing numerical algorithms in solving the two-way coupling fluid and structural interactions. The flexible plate was subjected to a fluid flow which causes large deformation on the fluid domain from the oscillation of the flexible plate. Both fluid and flexible plate are subjected to the interaction of load transfer within two physics by using the strong and weak coupling methods of MFS and Load Transfer Physics Environment, respectively. The oscillation and deformation results have been validated which demonstrate the reliability of both strong and weak method in resolving the two-way coupling problem in contribution of knowledge to the feasibility field study of ocean engineering and civil engineering.  相似文献   

Description of feeding apparatus and mechanism innemopilema nomurai kishinouye (scyphozoa: rhizostomeae)     

Hye Eun Lee  Won Duk Yoon  Donghyun Lim 《Ocean Science Journal》2008,43(1):61-65

Feeding apparatus, mechanism and passage of ingested prey were described forNemopilema nomurai (Scyphozoa: Rhizostomeae).N. nomurai medusae without central mouths have developed complicated canal systems connecting the tip of the tentacle and oral arm to the gut cavity. The number of junctions in the canal system increases with the bell diameter. The prey is gathered by paralyzing nematocyst at the tentacles and by adhering cirri at the oral arms and scapulets. They are engulfed into the terminal pore located at the oral arms and scapulets, and entered into the gut cavity via the canal system. The estimated digestion time is 1 hour and 20 min. The diameter of terminal pore is always about 1 mm, implying that they could not eat prey larger than that pore size. On the other hand, ephyrae have central mouths and could swallow prey as large as adults could. Exploitation of the same size of food by adult and ephyra implies thatN. nomurai can affect seriously the whole food web, massively ingesting micro-and mesozoopl a n k t o n and cutting the energy transfer toward the higher level of carnivores.  相似文献   

Geomorphological and seismostratigraphic evidence for multidirectional polyphase glaciation of the northern Celtic Sea     

Zsuzsanna Tóth  Stephen McCarron  Andrew J. Wheeler  Stefan Wenau  Stephen Davis  Aaron Lim  Volkhard Spiess 《第四纪科学杂志》2020,35(3):465-478

High-resolution seismic and bathymetric data offshore southeast Ireland and LIDaR data in County Waterford are presented that partially overlap previous studies. The observed Quaternary stratigraphic succession offshore southeast Ireland (between Dungarvan and Kilmore Quay) records a sequence of depositional and erosional events that supports regional glacial models derived from nearby coastal sediment stratigraphies and landforms. A regionally widespread, acoustically massive facies interpreted as the ‘Irish Sea Till’ infills an uneven, channelized bedrock surface overlying irregular mounds and deposits in bedrock lows that are probably earlier Pleistocene diamicts. The till is truncated and overlain by a thin, stratified facies, suggesting the development of a regional palaeolake following ice recession of the Irish Sea Ice Stream. A north–south oriented seabed ridge to the north is interpreted as an esker, representing southward flowing subglacial drainage associated with a restricted ice sheet advance of the Irish Ice Sheet onto the Celtic Sea shelf. Onshore topographic data reveal streamlined bedforms that corroborate a southerly advance of ice onto the shelf across County Waterford. The combined evidence supports previous palaeoglaciological models. Significantly, for the first time, this study defines a southern limit for a Late Midlandian Irish Ice Sheet advance onto the Celtic Sea shelf. © 2020 John Wiley & Sons, Ltd.  相似文献   

Comparison of Intestine Microbiota Between Wild and Farmed Korean Rockfish,Sebastes schlegelii     

Yu  Jihyun  Kang  Min Joo  Kim  Yun Jae  Park  Mi-Jeong  Lim  Jae Kyu  Noh  Choong Hwan  Kang  Sung Gyun  Lee  Hyun Sook  Lee  Jung-Hyun  Kwon  Kae Kyoung 《Ocean Science Journal》2021,56(3):297-306

Ocean Science Journal - The Korean rockfish, Sebastes schlegeli, is most commonly farmed in sea cages along the coast of Korea; however, detailed information on intestinal microbiota regarding this...  相似文献   

Geochemistry of Quaternary sediments of the Jeongokri archaeological site,Korea: implications for provenance and palaeoenvironments during the Late Pleistocene     

Jin Cheul Kim  Yong Il Lee  Hyoun Soo Lim  Seonbok Yi 《第四纪科学杂志》2012,27(3):260-268

The geochemical characteristics of an approximately 6‐m‐long sediment core collected from the Jeongokri archaeological site (Hantan River, Korea) were examined to determine the provenance of the sediments and to reconstruct the palaeoenvironment of the study area during the Late Pleistocene (200–127 ka). The core sediments were subdivided into two parts based on grain size: an upper (0–380 cm depth) and lower part (>380 cm depth). The lower part was deposited primarily by fluvial processes during an interglacial period [marine isotope stage (MIS) 7] with warm and humid conditions. Conversely, the upper part was mainly deposited by aeolian processes during a cold and dry glacial period (MIS 6). Geochemical characteristics, represented by major, trace and rare earth element (REE) compositions, and textures of the Jeongokri core sediments show distinct differences between the upper and lower parts. The mineralogy and major, trace and REE compositions indicate that the influence of felsic source rocks (e.g. granite) was dominant in the lower sediments, which were derived from the Hantan River. In contrast, increased quartz content and the very fine and homogeneous grain size in the upper sediments indicate an aeolian origin. REE ratios and distribution patterns, and geochemical signatures indicate that these sediments were derived predominantly from Chinese loess deposits and partially from local sediments from the Korean Peninsula; the possible source area of the upper sediments is the northern part of the Yellow Sea basin. The Yellow Sea basin, having mixed geochemical signatures between Chinese loess and Korean‐derived sediments, was exposed because of low sea levels during MIS 6. The exposed Yellow Sea basin was located in the path of winter‐monsoon winds, which may have carried a great deal of airborne sediments from the basin to the Jeongokri area. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Floods,false hope,and the future     

Alan D. Ziegler  Lim Han She  Chatchai Tantasarin  Nick R. Jachowski  Robert Wasson 《水文研究》2012,26(11):1748-1750

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The spatial exposure of the Chinese infrastructure system to flooding and drought hazards     

Xi Hu  Jim W. Hall  Peijun Shi  Wee Ho Lim 《Natural Hazards》2016,80(2):1083-1118

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Strong Blue Asymmetry in Hα$\upalpha$ Line as a Preflare Activity     

Kyuhyoun Cho  Jeongwoo Lee  Jongchul Chae  Haimin Wang  Kwangsu Ahn  Heesu Yang  Eun-kyung Lim  Ram Ajor Maurya 《Solar physics》2016,291(8):2391-2406

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