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Javier Sellanes Germán Zapata-Hernández Silvio Pantoja Gerdhard L. Jessen 《Estuarine, Coastal and Shelf Science》2011
We analyzed C and N stable isotope ratios of benthic fauna and their potential food sources at an intertidal methane seep site and a control site without emanation at Mocha Island (central Chile). The objective was to trace the origin of the main food sources used by the local heterotrophic fauna, based on the hypothesis that chemosynthetic production could be partially fueling the local food web at the seep site. Food sources sampled at both sites included macroalgae, particulate organic matter and bacteria-like filaments found growing over the red algae Gelidium lingulatum within the areas of active methane release. 相似文献
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Yun-Chun Jiang Yuan-Deng Shen Jing-Xiu Wang National Astronomical Observatories / Yunnan Observatory Chinese Academy of Sciences Kunming National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2007,7(1):129-140
1 INTRODUCTION Filaments are cool, dense material suspended in the hot, tenuous corona. It is widely accepted that the global magnetic field surrounding the filaments plays a key role in their formation, structure and stability (Tandberg-Hanssen1995). Fil… 相似文献
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Durgesh Tripathi 《Journal of Astrophysics and Astronomy》2006,27(2-3):193-200
The Large Angle Spectrometric Coronagraph (LASCO) and Extreme-ultraviolet Imaging Telescope (EIT) onboard Solar and Heliospheric
Observatory (SOHO) provide us with unprecedented multi-wavelength observations helping us to understand different dynamic
phenomena on the Sun and in the corona. In this paper we discuss the association between post-eruptive arcades (PEAs) detected
by EIT and white-light coronal mass ejections (CMEs) detected by LASCO/C2 telescope. 相似文献
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Marta Sebastin Javier Arístegui María F. Montero Jose Escanez F. Xavier Niell 《Progress in Oceanography》2004,62(2-4):131
The enzymatic activity of alkaline phosphatase (APA) was studied in the transition zone between the African upwelling system and the open ocean waters of the Canary Islands region. This region is recurrently dominated by the presence of upwelling filaments that may transport nutrient-enriched waters out into the open ocean before nutrients become exhausted by plankton. Turnover rates by APA were generally low in the whole region, but detectable in all the measurements carried out. On average, turnover rates were higher in the upwelling stations, and APA in those waters seemed to be mainly generated by heterotrophic bacteria to supply easily assimilable organic C. APA outside the upwelling area showed an inverse hyperbolic relationship with increasing phosphate, suggesting the presence of both constitutive and Pi-inducible APA. In these offshore waters, a threshold of 0.1 μM of phosphate could be defined for the regulatory function of Pi on APA. Thus, APA in nutrient-poor waters seemed to be induced to compensate for Pi-deficiency. Turnover rates in the filaments showed basal (probably constitutive) levels, whereas they increased in the surrounding waters, where phosphate concentration presumably did not satisfy plankton P-demands. The fertilising effect of the filaments and associated cyclonic eddies extended to at least 175 km offshore, where basal alkaline phosphatase activities were still found. The magnitude of this effect depends probably on the intensity of upwelling events and the degree of recirculation of filament water back to the coastal jet. 相似文献
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Makarov V. I. Stoyanova M. N. Sivaraman K. R. 《Journal of Astrophysics and Astronomy》1982,3(4):379-382
Ring-like filaments have been detected on the spectroheliograms in the H-alpha line. Inside these filaments the magnetic field
flux has a predominant polarity. Some of the dark filaments are connected by filament channels which can be seen at the limb
either as (a) weak prominences or (b) dense low chromospheric features or (c) multi-channel system of matter flow between
two prominences or (d) common quiescent prominences. The filament and the filament channel together form a continuous closed
contour and outline the region of thef polarity particularly at the beginning of the solar cycle. The change in sign of the polar field of the Sun is associated
with the drift of the filament band to high latitudes. 相似文献
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High-resolution Hαobservations indicate that filaments consist of an assembly of thin threads.In quiescent filaments,the threads are generally short,whereas in active region filaments,the threads are generally long.In order to explain these observational features,we performed one-dimensional radiative hydrodynamic simulations of filament formation along a dipped magnetic flux tube in the framework of the chromospheric evaporation-coronal condensation model.The geometry of a dipped magnetic flux tube is characterized by three parameters,i.e.,the depth(D),the half-width(w)and the altitude(h)of the magnetic dip.A survey of the parameters in numerical simulations shows that when allowing the filament thread to grow in 5 days,the maximum length(Lth)of the filament thread increases linearly with w,and decreases linearly with D and h.The dependence is fitted into a linear function Lth=0.84w-0.88D-2.78h+17.31(Mm).Such a relation can qualitatively explain why quiescent filaments have shorter threads and active region filaments have longer threads. 相似文献
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《New Astronomy》2014
The plasma from solar filament eruptions sometimes falls down to the lower solar atmosphere. These interesting events can help us to understand the properties of downflows, such as the temperature and the conversion between kinetic energy and thermal energy. We analyze the case of a filament eruption in active region NOAA 11283 and brightening caused by the return of filament material on September 7 and 8, 2011, observed by the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) aboard the Solar Dynamics Observatory (SDO). Magnetic flux cancellation was observed as a result of the eruption after the eruptive filament started to ascend. Another filament near the eruptive filament was disturbed by an extreme ultraviolet (EUV) wave that was triggered by the eruptive filament, causing it to oscillate. Based on coronal seismology, the mean magnetic field strength in the oscillatory filament was estimated to be approximately 18 ± 2 G. Some plasma separated from the filament and fell down to the solar northwest surface after the filament eruption. The velocities of the downflows increased at accelerations lower than the gravitational acceleration. The main characteristic temperature of the downflows was about 5 × 104 K. When the plasma blobs fell down to lower atmospheric heights, the high-speed downward-travelling plasma collided with plasma at lower atmospheric heights, causing the plasma to brighten. The brightening was observed in all 8 AIA channels, demonstrating that the temperature of the plasma in the brightening covered a wide range of values, from 105 K to 107 K. This brightening indicates the conversion between kinetic energy and thermal energy. 相似文献
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依据鲕粒的形态、结构及方解石组成,将豫西宜阳地区寒武系馒头组鲕粒灰岩中的鲕粒分为4种类型: 不规则放射状泥晶鲕粒、泥晶套亮晶表皮鲕粒、同心放射状泥晶鲕粒和规则放射状微亮晶鲕粒。这些鲕粒多由泥晶方解石组成,且泥晶方解石可出现在鲕粒的不同部位,从而与研究区张夏组的鲕粒明显不同,后者由亮晶方解石组成。在电子显微镜下,鲕粒中的泥晶方解石表现为六边形蜂格和片状壁,而这种结构被认为是细菌或蓝细菌的细胞结构,是由附着的微小晶粒呈切向围绕细菌或蓝细菌排列所致。构成蜂格结构的矿物主要为碳酸钙,其被认为是蓝细菌死亡后灰泥化的结果。由此可见,鲕粒中泥晶方解石的形成与微生物的生命活动密切相关,这对于阐明鲕粒在其形成过程中受到微生物的影响具有重要意义。 相似文献