نتایج جستجو برای: microfossils

تعداد نتایج: 531  

2016
Bettina E. Schirrmeister Patricia Sanchez-Baracaldo David Wacey

Life on Earth has existed for at least 3.5 billion years. Yet, relatively little is known of its evolution during the first two billion years, due to the scarceness and generally poor preservation of fossilized biological material. Cyanobacteria, formerly known as blue green algae were among the first crown Eubacteria to evolve and for more than 2.5 billion years they have strongly influenced E...

Journal: :The Science of the total environment 2013
Indu Karthic Richard B Brugam William Retzlaff Kevin Johnson

Anthropogenic nitrogen contamination has increased in ecosystems around the world (frequently termed the "nitrogen cascade"). Coke production for steel manufacturing is often overlooked as a source of nitrogen to natural ecosystems. We examined sediment cores from a Horseshoe Lake, a floodplain lake located just East of St. Louis Missouri (USA) to test whether a coking plant effluent could be t...

Journal: :Rapid communications in mass spectrometry : RCM 2014
Sierra V Petersen Daniel P Schrag

RATIONALE The measurement of multiply substituted isotopologues of CO2 derived from carbonate has allowed the reconstruction of paleotemperatures from a single phase (CaCO3 ), circumventing uncertainty inherent in other isotopic paleothermometers. Traditional analytical techniques require relatively large amounts of carbonate (3-8 mg per replicate), which limits the applicability of the clumped...

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