Interactions between sediment chemistry and frenulate pogonophores (Annelida) in the north-east Atlantic     

P.R. Dando  A.J. Southward  E.C. Southward  P. Lamont  R. Harvey 《Deep Sea Research Part I: Oceanographic Research Papers》2008,55(8):966-996

The small frenulate pogonophores (Annelida: Pogonophora a.k.a. Siboglinidae) typically inhabit muddy sediments on the continental slope, although a few species occur near hydrothermal vents and cold seeps. We present data on the distribution and habitat characteristics of several species on the European continental shelf and slope from 48°N to 75°N and show how the animals interact with the chemistry of the sediments. The environments inhabited include: shallow (30 m), organic-rich, fjord sediments; slope sediments (1000–2200 m) and methane seeps at 330 m depth. All the species studied obtain nutrition from endosymbiotic bacteria. They take up reduced sulphur species, or in one case, methane, through the posterior parts of their tubes buried in the anoxic sediment. We conclude that most species undertake sulphide ‘mining’, a mechanism previously demonstrated in the bivalves Lucinoma borealis and Thyasira sarsi. These pogonophores participate in the sulphur cycle and effectively lower the sulphide content of the sediments. Our results show that the abundance of frenulate pogonophores increases with increasing sedimentation and with decreasing abundance of other benthos, particularly bioturbating organisms. The maximum sustainable carrying capacity of non-seep sediments for frenulate pogonophores is limited by the rate of sulphate reduction.  相似文献   

Soldier crab (Dotilla myctiroides) distribution,food resources and subsequent role in organic matter fate in Ao Tang Khen,Phuket, Thailand     

Kimberly K. Takagi  Phaothep Cherdsukjai  Izumi Mimura  Yuka Yano  Kanjana Adulyanukosol  Makoto Tsuchiya 《Estuarine, Coastal and Shelf Science》2010

This study aimed to elucidate Dotilla myctiroides (H. Milne-Edwards) food resources and how the soldier crab influences the organic matter composition on the intertidal flat. A preliminary assessment of D. myctiroides size, sex, and population distribution was conducted to clarify the characteristics of the inhabiting population. Overall, D. myctiroides size and abundance was normal across the tidal flat area. Comparison of different sediment types from the soldier crab habitat (surface sediments, igloos, burrow lining, burrow pellets, feeding pellets, and feces) using the fatty acid (FA) analysis technique revealed D. myctiroides removes organic matter via the significantly lower contributions of polyunsaturated FAs, essential FAs, and dinoflagellates in the feeding pellets. Dotilla myctiroides tissue analysis of the hepatopancreas and hindgut in individuals that had been starved for 24 h confirmed not only the consumption of dinoflagellates, but diatoms and macroalgae as well. In addition, the FA metabolism within the digestive system implied the ability of the soldier crab to synthesize highly unsaturated FAs (HUFAs) such as 20:4n–6, 20:5n–3 and 22:6n–3.  相似文献   

Historical Evidence for the Birth of the Newly Discovered Pulsar PSR J1833-1034     

Zhen-Ru Wang  Min Li  Yi Zhao Astronomy Department  Nanjing University  Nanjing  Institute of Chinese Classics  Nanjing University  Nanjing 《中国天文和天体物理学报》2006,6(5)

Stimulated by the recent discovery of PSR J1833-1034 in SNR G21.5-0.9 and its age parameters presented by two groups of discovery, we demonstrate that the PSR J1833-1034 was born 2053 years ago from a supernova explosion, the BC 48 guest star observed in the Western Han (Early Han) Dynasty by ancient Chinese. Based on a detailed analysis of the Chinese ancient record of the BC 48 guest star and the new detected physical parameters of PSR J1833-1034, agreements on the visual position, age and distance between PSR J1833-1034 and the BC 48 guest star are obtained. The initial period P0 of PSR J1833-1034 is now derived from its historical and current observed data without any other extra assumption on P0 itself, except that the factor PP is a constant in its evolution until now.  相似文献   

Observations of the pulsating subdwarf B star Feige 48: Constraints on evolution and companions     

《Monthly notices of the Royal Astronomical Society》2004,348(4):1164-1174

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Outflowing material in the compact steep-spectrum source quasar 3C 48: evidence of jet–cloud interaction?     

Neeraj Gupta  R. Srianand  D. J. Saikia 《Monthly notices of the Royal Astronomical Society》2005,361(2):451-459

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The Qso Hosts I Zw 1 and 3C 48: Prototypes of a Merger-Driven Quasar Evolution?     

Julia Scharwächter  Andreas Eckart  Susanne Pfalzner  Jens Zuther  Melanie Krips  Eva Schinnerer  Johannes Staguhn 《Astrophysics and Space Science》2005,295(1-2):101-106

I Zw 1 and 3C 48 are two neighboring template objects at a later stage of the hypothesized merger-driven evolutionary sequence from ultra-luminous infrared galaxies (ULIRGs) to quasi-stellar objects (QSOs). Since galaxy mergers are assumed to trigger the evolution, it is important to confirm the merger properties of transitionary objects. Using multi-wavelength observations and N-body simulations, the merger histories of I Zw 1 and 3C 48 have been investigated in two separate case studies. Here, the results from both studies are compared and their relevance for the evolutionary hypothesis is discussed.This research is partly based on observations with ISAAC at the Very Large Telescope (VLT) of the European Southern Observatory (ESO) under projects 67.B-0009 and 67.B-0019.  相似文献   

The influence of political ideology on greenhouse gas emissions     

《Global Environmental Change》2022

This research tests the casual link from political ideology to national greenhouse gas emissions by utilizing multinational panel data covering 98 countries during the period 1990–2016. Overall, the baseline results and robustness tests show a political divide on national greenhouse gas emissions, whereby compared to right-wing governments, left-wing governments are more likely to exhibit less carbon dioxide emissions. We further explore this topic from the perspectives of energy efficiency and education. Three-stage OLS regressions suggest that leftist parties increase energy efficiency and spend more on secondary education, which lead to less greenhouse gas emissions. We also introduce the interaction between political ideology and economic performance as well as globalization to test the moderating effects of economic performance and globalization. The study further looks into the interaction effects of political ideology and democracies on greenhouse gas emissions by dividing the whole sample into two sub-samples. The results indicate that the ideology effect on greenhouse gas emissions varies among countries with different economic performances or different degrees of political globalization, as well as between democracies and non-democracies.  相似文献   

Short-term residence and movement patterns of the annular seabream Diplodus annularis in a temperate marine reserve     

David March  Josep Als  Amlia Grau  Miquel Palmer 《Estuarine, Coastal and Shelf Science》2011,92(4):251-587

The short-term movements of a small temperate fish, the annular seabream Diplodus annularis (Linnaeus 1758), were examined using standard tag-recapture and passive acoustic telemetry in Palma Bay (NW Mediterranean), a marine protected area (MPA). The study aimed to provide valuable information for assessing the recreational fishery and its results suggest that MPAs can be used to protect the adult stock of D. annularis. All the fish tagged with standard tags were recaptured near the release locations, with a maximum distance of ∼300 m. The maximum time between release and recapture was 185 d. Two different arrays of acoustic receivers were deployed, one in 2008 and another in 2009, within the MPA. Twenty adults were surgically tagged with acoustic transmitters. Fish monitored in 2008 (n = 12) were translocated from the point of capture to analyse the movement behaviour after artificial displacement. Upon release at displaced locations, 67% of the fish moved towards the original capture location using a time of return that ranged from 0.75 to 15.25 h. Fish monitored in 2009 (n = 8) were released at the point of capture. They showed high site fidelity with a maximum period of 27 d between the first time and the last time they were detected.  相似文献   

High Precision Determination of ⁴⁸Ca/⁴²Ca Ratio by TIMS for Ca Isotope Fractionation Studies     

Kunchithapadam Gopalan  J. Douglas Macdougall  Christopher Macisaac 《Geostandards and Geoanalytical Research》2007,31(3):227-236

For studies of mass-dependent fractionation of calcium isotopes in natural materials, the ⁴⁸Ca/⁴²Ca ratio is a superior choice to the conventionally measured ⁴⁴Ca/⁴⁰Ca ratio for two important reasons. These are (1) mass-dependent fractionation can be determined free from the effects of inherited or ingrown radiogenic ⁴⁰Ca and (2) this ratio increases the spread of measured isotopic masses by 50%, resulting in statistically better resolution of fractionation, assuming similar precision. A third, though strictly technical, advantage is the inherent ability of a mass spectrometer to measure ratios close to unity (⁴⁸Ca/⁴²Ca) more precisely than very small or large ratios (⁴⁴Ca/⁴⁰Ca). However, because of the very low natural abundance of both ⁴⁸Ca and ⁴²Ca, their ratio has been very difficult to measure, the only attempt so far being on a high mass resolution MC-ICP-MS with a precision of 0.33%. We report here determination of the ⁴⁸Ca/⁴²Ca ratio by the more commonly available and user-friendly multi-collector TIMS using a ⁴³Ca-⁴⁶Ca double-spike, with a significantly better precision of 0.18% (2s). The ⁴⁸Ca/⁴⁰Ca or ⁴⁴Ca/⁴⁰Ca ratio can also be measured in the same mass spectrometer run to provide complementary information on any radiogenic component.  相似文献   

Identifying sources of groundwater in the lower Colorado River valley, USA, with δ18O, δD, and 3H: implications for river water accounting     

Bradley E. Guay  Christopher J. Eastoe  R. Bassett  Austin Long 《Hydrogeology Journal》2006,14(1-2):146-158

Isotope measurements (48v56mcn62386/xxlarge948.gif" alt="delta" align="BASELINE" BORDER="0">¹⁸O, 48v56mcn62386/xxlarge948.gif" alt="delta" align="BASELINE" BORDER="0">D, ³H) indicate groundwater origin in the Lower Colorado River Valley (LCRV) and provide an alternative, or supplement, to the US Bureau of Reclamation48v56mcn62386/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s proposed 48v56mcn62386/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">accounting surface48v56mcn62386/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> method. The accounting surface method uses a hydraulic criterion to identify certain wells away from the flood plain that will eventually yield mainstream Colorado River water. New isotope data for 5 surface-water and 18 groundwater sites around Topock Marsh, Arizona, are compared with river-water data (1974–2002) from 11 sites between Utah and Mexico and with groundwater data from previous LCRV studies. Three groundwater sources are repeatedly identified in the LCRV: (1) local recharge derived from precipitation, usually winter rain, plots slightly below the global meteoric water line (GMWL) and has 48v56mcn62386/xxlarge948.gif" alt="delta" align="BASELINE" BORDER="0">D values that are 2048v56mcn62386/xxlarge8240.gif" alt="permil" align="MIDDLE" BORDER="0"> greater than those of recent river water; (2) 48v56mcn62386/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">older48v56mcn62386/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> (pre-1950) upper basin river-water plots on or near the GMWL, distinct from local rainfall and recent river water; and (3) recent (post-1950) Colorado River water, including Topock Marsh samples, plots below the GMWL along an evaporation trend. Large floods, as in 1983, complicate interpretation by routing less evaporated upper basin water into the LCRV; however, tritium content can indicate the age of a water. River-water tritium has declined steadily from its peak of 716 TU in 1967 to about 11 TU in 2002. Mixtures of all three groundwater sources are common.

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Resumen Mediciones isotópicas (48v56mcn62386/xxlarge948.gif" alt="delta" align="BASELINE" BORDER="0">¹⁸O, 48v56mcn62386/xxlarge948.gif" alt="delta" align="BASELINE" BORDER="0">D, ³H) indican cual es el origen del agua subterránea en el Valle Bajo del Río Colorado (LCRV) y aportan una alternativa, o complemento, para el método 48v56mcn62386/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">superficie de conteo48v56mcn62386/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> propuesto por el Buró de Reclamación de Estados Unidos. El método superficie de conteo utiliza un criterio hidráulico para identificar ciertos pozos alejados de la planicie de inundación que eventualmente producirán agua a partir de la corriente principal del Río Colorado. Los nuevos datos isotópicos para 18 sitios de agua subterránea y 5 sitios de agua superficial cerca de los Pantanos Topock, Arizona, se comparan con datos de agua de río (1974–2002) provenientes de 11 sitios localizados entre Utah y México, y con datos de aguas subterráneas de estudios previos realizados en el LCRV. Se identifican reiteradamente tres fuentes de aguas subterráneas en el LCRV: (1) recarga local derivada de precipitación, generalmente lluvia de invierno, cuya composición cae ligeramente por debajo de la línea de agua meteórica global (GMWL) y tiene valores 48v56mcn62386/xxlarge948.gif" alt="delta" align="BASELINE" BORDER="0">D que son 2048v56mcn62386/xxlarge8240.gif" alt="permil" align="MIDDLE" BORDER="0"> mayores que los reportados para agua de río reciente; (2) el agua de río 48v56mcn62386/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">más vieja48v56mcn62386/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> (pre-1950) de la cuenca alta cuya composición cae sobre o cerca de la GMWL, diferente de la lluvia local y del agua de río reciente; (3) agua reciente (post-1950) del Río Colorado, incluyendo muestras de los Pantanos Topock, con composición por debajo de la GMWL a lo largo de una tendencia a la evaporación. Inundaciones grandes, como en 1983, complican la interpretación al transmitir menos agua evaporada de la cuenca alta hacia el LCRV; sin embargo, el contenido de tritio puede indicar la edad del agua. El contenido de tritio en agua de río ha disminuido constantemente desde la concentración pico de 716 TU en 1967 a cerca de 11 TU en 2002. Es común que exista mezclas de las tres fuentes de agua subterránea.

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Résumé Les mesures isotopiques (d18O, dD, 3H) indiquent les origine de l48v56mcn62386/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">eaux souterraines dans la Vallée de la Rivière du Bas Colorado (LCRV) et sont une alternative, ou un supplément, à la méthode des bilans hydrologiques proposée par du «US Bureau of Reclamation». Cette méthode de bilan hydrologique utilise un critère hydraulique permettant d48v56mcn62386/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">identifier certains puits hors de la plaine d48v56mcn62386/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">inondation qui pomperaient une part non négligeable de leur eau dans la rivière Colorado. De nouvelles données isotopiques provenant de 5 sites d48v56mcn62386/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">eau de surface et 18 d48v56mcn62386/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">eaux souterraines autour de Topock Marsh en Arizona, sont comparées avec les données (1974–2000) de 11 sites localisés entre Utah et Mexico, ainsi que des données d48v56mcn62386/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">autres études sur la LCRV. Ces sources d48v56mcn62386/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">eaux souterraines sont identifiées à plusieurs reprises dans la LCRV: (1) la recharge locale dérivant des précipitations, généralement les pluies hivernales, se retrouvent légèrement sous la ligne d48v56mcn62386/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">eau météoritique globale (GMWL) et possède des valeurs de dD 20% supérieures aux valeurs des eaux récentes de la rivière; (2) les eaux vieilles (pre-1950) du bassin supérieur de la rivière possèdent une valeurs très proches de la GMWL, distinctes des valeurs de la pluie locale et des eaux récentes de la rivière; et (3) les eaux récentes (post-1950) de la Rivière Colorado, incluant les échantillons de Topock Marsh, se positionnent à côté de la GMWL sur une droite d48v56mcn62386/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">évaporation. Les grandes inondations, par exemple celle de 1983, compliquent l48v56mcn62386/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">interprétation en reprenant dans la LCRV moins d48v56mcn62386/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">eaux marquées comme évaporées et provenant du bassin supérieur; par ailleurs le pic de tritium est descendu de 716 TU en 1967 à 11 TU en 2002. Les mélanges de ces trois sources sont assez fréquentes.

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