Posts Tagged ‘Composition’

Plant diversity and community composition of rice agroecosystems in Vietnam and the Philippines

18 May 2017A new LEGATO-funded article looks into the links between plant diversity and community composition of rice agroecosystems in Vietnam and the Philippines.

Abstract:

Aims: The knowledge of rice weed communities, their diversity, composit…

Intramolecular interactions that control voltage sensitivity in the jShak1 potassium channel from Polyorchis penicillatus [RESEARCH ARTICLE]

Nazlee Sharmin and Warren J. GallinVoltage-gated potassium ion (Kv) channel proteins respond to changes in membrane potential by changing the probability of K+ flux through an ion-selective pore. Kv channels from different paralogous and orthologous fa…

Epigenetics: Organisms’ diet affects their DNA sequence

From ScienceDaily: In a study on two groups of parasites, the team detected differences in DNA sequences that could be attributed to the composition of their food. … ‘We found that different levels of nitrogen in a parasite’s diet contributed to changes in its DNA. Specifically, parasites with low-nitrogen, high-sugar diets had DNA sequences that […]

Implications for metal and volatile cycles from the pH of subduction zone fluids

The chemistry of aqueous fluids controls the transport and exchange—the cycles—of metals and volatile elements on Earth. Subduction zones, where oceanic plates sink into the Earth’s interior, are the most important geodynamic setting for this fluid-mediated chemical exchange. Characterizing the ionic speciation and pH of fluids equilibrated with rocks at subduction zone conditions has long been a major challenge in Earth science. Here we report thermodynamic predictions of fluid–rock equilibria that tie together models of the thermal structure, mineralogy and fluid speciation of subduction zones. We find that the pH of fluids in subducted crustal lithologies is confined to a mildly alkaline range, modulated by rock volatile and chlorine contents. Cold subduction typical of the Phanerozoic eon favours the preservation of oxidized carbon in subducting slabs. In contrast, the pH of mantle wedge fluids is very sensitive to minor variations in rock composition. These variations may be caused by intramantle differentiation, or by infiltration of fluids enriched in alkali components extracted from the subducted crust. The sensitivity of pH to soluble elements in low abundance in the host rocks, such as carbon, alkali metals and halogens, illustrates a feedback between the chemistry of the Earth’s atmosphere–ocean system and the speciation of subduction zone fluids via the composition of the seawater-altered oceanic lithosphere. Our findings provide a perspective on the controlling reactions that have coupled metal and volatile cycles in subduction zones for more than 3 billion years7.

Saturn’s C ring formed when dinosaurs walked the Earth, study finds

Scientists have largely agreed that Saturn’s rings are billions of years old, a conclusion based on 10 years of data gathered by NASA’s Cassini probe, which has been orbiting the planet since 2004. However, new research published in the journal Icarus has indicated that the C ring, one of Saturn’s inner rings, may have formed […]

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