Non-diffusive transport in the tokamak edge pedestal

AbstractMetallic iron (Fe0) has shown outstanding performances for water decontamination and its efficiency has been improved by the presence of sand (Fe0/sand) and manganese oxide (Fe0/MnOx). In this study, a ternary Fe0/MnOx/sand system is characterized for its discoloration efficiency of methylene blue (MB) in quiescent batch studies for 7, 18, 25 and 47 days. The objective was to understand the fundamental mechanisms of water treatment in Fe0/H2O systems using MB as an operational tracer of reactivity. The premise was that, in the short term, both MnO2 and sand delay MB discoloration by avoiding the availability of free iron corrosion products (FeCPs). Results clearly demonstrate no monotonous increase in MB discoloration with increasing contact time. As a rule, the extent of MB discoloration is influenced by the diffusive transport of MB from the solution to the aggregates at the bottom of the vessels (test-tubes). The presence of MnOx and sand enabled the long-term generation of iron hydroxides for MB discoloration by adsorption and co-precipitation. Results clearly reveal the complexity of the Fe0/MnOx/sand system, while establishing that both MnOx and sand improve the efficiency of Fe0/H2O systems in the long-term. This study establishes the mechanisms of the promotion of water decontamination by amending Fe0-based systems with reactive MnOx.

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Water-Enhanced Flux Changes under Dynamic Temperatures in the Vertical Vapor-Phase Diffusive Transport of Volatile Organic Compounds in Near-Surface Soil Environments

Sustainability ◽

10.3390/su13126570 ◽

2021 ◽

Vol 13 (12) ◽

pp. 6570

Author(s):

Asma Akter Parlin ◽

Monami Kondo ◽

Noriaki Watanabe ◽

Kengo Nakamura ◽

Mizuki Yamada ◽

...

Keyword(s):

Air Quality ◽

Volatile Organic Compounds ◽

Organic Compounds ◽

Vapor Phase ◽

Inverse Correlation ◽

Diffusive Transport ◽

Near Surface ◽

Voc Emissions ◽

Transport Behavior ◽

Volatile Organic

The quantitative understanding of the transport behavior of volatile organic compounds (VOCs) in near-surface soils is highly important in light of the potential impacts of soil VOC emissions on the air quality and climate. Previous studies have suggested that temperature changes affect the transport behavior; however, the effects are not well understood. Indeed, much larger changes in the VOC flux under in situ dynamic temperatures than those expected from the temperature dependence of the diffusion coefficients of VOCs in the air have been suggested but rarely investigated experimentally. Here, we present the results of a set of experiments on the upward vertical vapor-phase diffusive transport of benzene and trichloroethylene (TCE) in sandy soils with water contents ranging from an air-dried value to 10 wt% during sinusoidal temperature variation between 20 and 30 °C. In all experiments, the flux from the soil surface was correlated with the temperature, as expected. However, the changes in flux under wet conditions were unexpectedly large and increased with increasing water content; they were also larger for TCE, the volatility of which depended more strongly on the temperature. Additionally, the larger flux changes were accompanied by a recently discovered water-induced inverse correlation between temperature and flux into the overlying soil. These results demonstrated that the flux changes of VOCs under dynamic temperatures could be increased by volatilization-dissolution interactions of VOCs with water. Future extensive studies on this newly discovered phenomenon would contribute to a better understanding of the impacts of soil VOC emissions on the air quality and climate.

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Diffusive transport in highly corrugated channels

Physics Letters A ◽

10.1016/j.physleta.2018.12.041 ◽

2019 ◽

Vol 383 (11) ◽

pp. 1084-1091

Author(s):

Fabio Cecconi ◽

Valon Blakaj ◽

Gabriele Gradoni ◽

Angelo Vulpiani

Keyword(s):

Diffusive Transport

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Alfvén wave forces, affecting the tokamak edge plasma in the presence of impurities or dust

Physics of Plasmas ◽

10.1063/1.872488 ◽

1997 ◽

Vol 4 (9) ◽

pp. 3436-3438 ◽

Cited By ~ 13

Author(s):

V. S. Tsypin ◽

S. V. Vladimirov ◽

A. G. Elfimov ◽

M. Tendler ◽

A. S. de Assis ◽

...

Keyword(s):

Edge Plasma ◽

Alfven Wave ◽

Wave Forces ◽

Tokamak Edge

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AC Electrokinetics for Biosensors

Fluids Engineering ◽

10.1115/imece2004-62013 ◽

2004 ◽

Author(s):

M. Sigurdson ◽

C. Meinhart ◽

D. Wang

Keyword(s):

Electric Fields ◽

Dna Hybridization ◽

Fluid Motion ◽

Diffusive Transport ◽

Analyte Concentration ◽

Ac Electrokinetics ◽

Ac Electric Fields ◽

Binding Rate ◽

Electrothermal Flow ◽

Biosensor Device

We develop here tools for speeding up binding in a biosensor device through augmenting diffusive transport, applicable to immunoassays as well as DNA hybridization, and to a variety of formats, from microfluidic to microarray. AC electric fields generate the fluid motion through the well documented but unexploited phenomenon, Electrothermal Flow, where the circulating flow redirects or stirs the fluid, providing more binding opportunities between suspended and wall-immobilized molecules. Numerical simulations predict a factor of up to 8 increase in binding rate for an immunoassay under reasonable conditions. Preliminary experiments show qualitatively higher binding after 15 minutes. In certain applications, dielectrophoretic capture of passing molecules, when combined with electrothermal flow, can increase local analyte concentration and further enhance binding.

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