the growth rate and uniformity of carbon nano tubes (cnts) based on chemical vapor deposition (cvd) technique is investigated by using a numerical model. in this reactor, inlet gas mixture, including xylene as carbon source and mixture of argon and hydrogen as  carrier gas enters into a horizontal cvd reactor at atmospheric pressure. based on the gas phase and surface reactions, released carbon...

chemical vapor deposition (cvd) is one of the most popular methods for producing carbon nanotubes (cnts). the growth rate of cnts based on cvd technique is investigated by using a numerical model based on finite volume method. inlet gas mixture, including xylene as carbon source and mixture of argon and hydrogen as carrier gas enters into a horizontal cvd reactor at atmospheric pressure. in thi...

Carbon compounds account for a large fraction of airborne particulate matter (‘carbonaceous aerosols’). Their presence raises a number of scientific questions dealing with climate issues and possible effects on human health. This review describes the current state of knowledge with respect to the ambient concentrations levels (elemental carbon, organic carbon and organic matter) and the various...

δCO2 measured in Antarctic ice cores provides constraints on oceanic and terrestrial carbon cycle processes linked with millennial-scale changes in atmospheric CO2. However, the interpretation of δCO2 is not straightforward. Using carbon isotope-enabled versions of the LOVECLIM and Bern3D models, we perform a set of sensitivity experiments in which the formation rates of North Atlantic Deep Wat...

Terrestrial ecosystems play a significant role in the global carbon cycle and offset a large fraction of anthropogenic CO2 emissions. The terrestrial carbon sink is increasing, yet the mechanisms responsible for its enhancement, and implications for the growth rate of atmospheric CO2, remain unclear. Here using global carbon budget estimates, ground, atmospheric and satellite observations, and ...

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Part of the puzzle of greenhouse gases and climate change is determining where carbon dioxide (CO2) is absorbed, and what causes a region to become a "carbon sink". Analyses of atmospheric CO2 concentration changes indicate a carbon sink of about 1 to 2 billion tons on land in the northerly regions. Elsewhere the land is suggested to be neutral, which implies that emissions of another 1.5 billi...

BACKGROUND The amount of carbon dioxide in the atmosphere steadily increases as a consequence of anthropogenic emissions but with large interannual variability caused by the terrestrial biosphere. These variations in the CO2 growth rate are caused by large-scale climate anomalies but the relative contributions of vegetation growth and soil decomposition is uncertain. We use a biogeochemical mod...

Soil moisture supply and atmospheric demand for water independently limit—and profoundly a ect—vegetation productivity and water use during periods of hydrologic stress1–4. Disentangling the impact of these two drivers on ecosystem carbon and water cycling is di cult because they are often correlated, and experimental tools for manipulating atmospheric demand in the field are lacking. Consequen...

The concentration of atmospheric methane is strongly linked to variations in Earth’s climate. Currently, we can directly reconstruct the total atmospheric concentration of methane, but not individual terms of the methane cycle. Northern wetlands, dominated by Sphagnum, are an important contributor of atmospheric methane, and we seek to understand the methane cycle in these systems. We present a...