On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Scavenging of soluble and immobilized CCL21 by ACKR4 regulates peripheral dendritic cell emigration

Published April 19, 2021.Leukocyte homing driven by the chemokine CCL21 is pivotal for adaptive immunity because it controls dendritic cell (DC) and T cell migration through CCR7. ACKR4 scavenges CCL21 and has been shown to play an essential role in DC trafficking at the steady state and during immune responses to tumors and cutaneous inflammation. However, the mechanism by which ACKR4 regulates peripheral DC migration is unknown, and the extent to which it regulates CCL21 in steady-state skin and lymph nodes (LNs) is contested. Specifically, our previous findings that CCL21 levels are increased in LNs of ACKR4-deficient mice [I. Comerford et al., Blood 116, 4130–4140 (2010)] were refuted [M. H. Ulvmar et al., Nat. Immunol. 15, 623–630 (2014)], and no differences in CCL21 levels in steady-state skin of ACKR4-deficient mice were reported despite compromised CCR7-dependent DC egress in these animals [S. A. Bryce et al., J. Immunol. 196, 3341–3353 (2016)]. Here, we resolve these issues and reveal that two forms of CCL21, full-length immobilized and cleaved soluble CCL21, exist in steady-state barrier tissues, and both are regulated by ACKR4. Without ACKR4, extracellular CCL21 gradients in barrier sites are saturated and nonfunctional, DCs cannot home directly to lymphatic vessels, and excess soluble CCL21 from peripheral tissues pollutes downstream LNs. The results identify the mechanism by which ACKR4 controls DC migration in barrier tissues and reveal a complex mode of CCL21 regulation in vivo, which enhances understanding of functional chemokine gradient formation.Cameron R. Bastow, Mark D. Bunting, Ervin E. Kara, Duncan R. McKenzie, Adriana Caon, Sapna Devi, Lynn Tolley, Scott N. Mueller, Ian H. Frazer, Natasha Harvey, Mark R. Condina, Clifford Young, Peter Hoffmann, Shaun R. McColl, and Iain Comerfor

Quellen und Vorkommen kurzkettiger Alkylphenole (SCAP)

Aus der Literaturrecherche und eigenen Untersuchungen geht hervor, dass kurzkettige Alkylphenole (SCAP) während der Verarbeitungs- bzw. Veredelungsprozesse fester fossiler Brennstoffe ebenso in die Umwelt freigesetzt werden können, wie basierend auf Prozessen verschiedenster Industrien. Die große Bandbreite an Verwendungs- und Anwendungsmöglichkeiten von SCAP bringt viele Eintragsmöglichkeiten in die Umweltmedien mit sich. Prägnant sind die prozessbedingten SCAP-Muster (vorkommende Einzelsubstanzen) der verschiedenen Industrien und Produkte, wodurch Eintragsquellen und Fließpfade genauer quantifiziert werden können. Natürliche Eintragsquellen von SCAP mit Konzentrationen bis zu mehreren Tausend ppm sind ausschließlich Erdöle bzw. erdölführende Gesteine. Dieser Sachverhalt in Verbindung mit ihren chemisch-physikalischen Eigenschaften begründet die Verwendung der SCAP als Fluss- und Prozessindikatoren in der Erdöl-Reservoir-Erkundung und -Förderung. Anlehnend daran ist der oft noch fehlende Kenntnisstand der Umweltrelevanz und -akzeptanz von SCAP in Grundwasser-Schadensfällen in Deutschland nicht nachzuvollziehen. Es wird verdeutlicht, dass SCAP neben Erdölreservoiren auch für den Wasserkreislauf als Fluss- und Prozessindikatoren prädestiniert sind