Cross-code comparison of the edge codes SOLPS-ITER, SOLEDGE2D and UEDGE in modelling a low-power scenario in the DTT

As reactor-level nuclear fusion experiments are approaching, a solution to the power exhaust issue in future fusion reactors is still missing. The maximum steady-state heat load that can be exhausted by the present technology is around 10 MW/m2. Different promising strategies aiming at successfully managing the power exhaust in reactor-relevant conditions such that the limit is not exceeded are under investigation, and will be tested in the Divertor Tokamak Test (DTT) experiment. Meanwhile, the design of tokamaks beyond the DTT, e.g. EU-DEMO/ARC, is progressing at a high pace. A strategy to work around the present lack of reactor-relevant data consists of exploiting modelling to reduce the uncertainty in the extrapolation in the design phase. Different simulation tools, with their own capabilities and limitations, can be employed for this purpose. In this work, we compare SOLPS-ITER, SOLEDGE2D and UEDGE, three state-of-the-art edge codes heavily used in power exhaust studies, in modelling the same DTT low-power, pure-deuterium, narrow heat-flux-width scenario. This simplified, although still reactor-relevant, testbed eases the cross-comparison and the interpretation of the code predictions, to identify areas where results differ and develop understanding of the underlying causes. Under the conditions investigated, the codes show encouraging agreement in terms of key parameters at both targets, including peak parallel heat flux (1-45%), ion temperature (2-19%), and inner target plasma density (1-23%) when run with similar input. However, strong disagreement is observed for the remaining quantities, from 30% at outer mid-plane up to a factor 4-5 at the targets. The results primarily reflect limitations of the codes: the SOLPS-ITER plasma mesh not reaching the first wall, SOLEDGE2D not including ion-neutral temperature equilibration, and UEDGE enforcing a common ion-neutral temperature. Potential improvements that could help enhance the accuracy of the code models for future applications are also discussed.

Ionic Equilibria and pH

Ionic Equilibria and pH reviews the quantitative aspects of aqueous acid-base chemistry. Definitions and concepts are presented and appropriate worked examples illustrate calculations of concentration, pH and ionization constants. Acid-base properties of salts (salt hydrolysis) is introduced and explained along with the common-ion effect and calculation of hydrolysis constants. Equilibria of acid-base buffers with respect to buffer preparation, calculating the pH of a buffer solution and application of the Henderson-Hasselbalch equation, buffer range and buffer capacity is discussed. Determining the pH during acid-base titrations, selecting the appropriate acid-base indicators, and generating pH titration curves are explained.

Formation and Transformation Trends of Metal Carbonates With Cation Ratio and Ion Interaction in Post-treatment Process of Desalination Brine

BackgroundTo address the negative effects of desalination plants, CO2 emissions, and discharge of desalination brine, we studied the carbon capture utilization (CCU) process based on metal carbonation via the reuse of desalination brine. In this study, we converted CO2 and simulated desalination brine into metal carbonate using monoethanolamine as an aqueous absorbent. The produced metal carbonate varied according to the cation component of the simulated desalination brine. We focused on ion interactions in the aqueous system, occurred by cation ratio, and other phenomena caused by the interactions.ResultsWe determined that the common ion effect, which occurred owing to the ion interactions of the system, was the main reason for the various carbonation trends. Ionic atmospheres that were changed by the ionic components significantly affected the trends. The high salinity of the desalination brine also affected the metal carbonation. We further deduced that the variation in the results was derived from interactions between the abovementioned effects. And we also found that Na+, which was overlooked in former studies about polymorph transformation, also affects polymorph transformation.ConclusionsAll the phenomena in the metal carbonation interrupt desalination brine post-treatment because of their unpredictability. However, we suggest ambient estimation of its cation components, which would help future studies and demonstrate desalination brine post-treatment.

Novel amiloride derivatives that inhibit bacterial motility across multiple strains and stator types

The bacterial flagellar motor (BFM) is a protein complex that confers motility to cells and contributes to survival and virulence. The BFM consists of stators that are ion-selective membrane protein complexes and a rotor that directly connects to a large filament, acting as a propeller. The stator complexes couple ion transit across the membrane to torque that drives rotation of the motor. The most common ion gradients that drive BFM rotation are protons (H + ) and sodium ions (Na + ). The sodium-powered stators, like those in the PomAPomB stator complex of Vibrio spp, can be inhibited by sodium channel inhibitors, in particular, by phenamil, a potent and widely used inhibitor. However, relatively few new sodium-motility inhibitors have been described since the discovery of phenamil. In this study, we characterised two possible motility inhibitors HM2-16F and BB2-50F from a small library of previously reported amiloride derivatives. We used three approaches: effect on rotation of tethered cells, effect on free swimming bacteria and effect on rotation of marker beads. We showed that both HM2-16F and BB2-50F stopped rotation of tethered cells driven by Na + motors comparable to phenamil at matching concentrations, and could also stop rotation of tethered cells driven by H + motors. Bead measurements in presence and absence of stators confirmed that the compounds did not inhibit rotation via direct association with the stator, in contrast to the established mode of action of phenamil. Overall, HM2-16F and BB2-50F stopped swimming in both Na + and H + stator types, and in pathogenic and non-pathogenic strains. Importance: Here we characterised two novel amiloride derivatives in the search for antimicrobial compounds that target bacterial motility. Our two compounds were shown to inhibit flagellar motility at 10 μM across multiple strains, from non-pathogenic E. coli with flagellar rotation driven by proton or chimeric sodium-powered stators, to proton-powered pathogenic E. coli (EHEC/UPEC) and lastly in sodium-powered Vibrio alginolyticus . Broad anti-motility compounds such as these are important tools in our efforts control virulence of pathogens in health and agricultural settings.

Novel amiloride derivatives that inhibit bacterial motility across multiple strains and stator types

The bacterial flagellar motor (BFM) is a protein complex that confers motility to cells and contributes to survival and virulence. The BFM consists of stators that are ion-selective membrane protein complexes and a rotor that directly connects to a large filament, acting as a propeller. The stator complexes couple ion transit across the membrane to torque that drives rotation of the motor. The most common ion gradients that drive BFM rotation are protons (H+) and sodium ions (Na+). The sodium-powered stators, like those in the PomAPomB stator complex of Vibrio spp, can be inhibited by sodium channel inhibitors, in particular, by phenamil, a potent and widely used inhibitor. However, relatively few new sodium-motility inhibitors have been described since the discovery of phenamil. In this study, we discovered two motility inhibitors HM2-16F and BB2-50F from a small library of previously reported amiloride derivatives. Using a tethered cell assay, we showed that both HM2-16F and BB2-50F had inhibition comparable to that of phenamils on Na+ driven motors at matching concentrations, with an additional ability to inhibit rotation in H+ driven motors. The two compounds did not exhibit adverse effects on bacterial growth at the motility-inhibiting concentration of 10 uM, however toxicity was seen for BB2-50F at 100 uM. We performed higher resolution measurements to examine rotation inhibition at moderate (1 um polystyrene bead) and low loads (60 nm gold bead) and in both the presence and absence of stators. These measurements suggested that the compounds did not inhibit rotation via direct association with the stator, in contrast to the established mode of action of phenamil. Overall, HM2-16F and BB2-50F showed reversible inhibition of motility across a range of loads, in both Na+ and H+ stator types, and in pathogenic and non-pathogenic strains.

Construction of DNA Biosensors for Mercury (II) Ion Detection Based on Enzyme-Driven Signal Amplification Strategy

Mercury ion (Hg2+) is a well-known toxic heavy metal ion. It is harmful for human health even at low concentrations in the environment. Therefore, it is very important to measure the level of Hg2+. Many methods, reviewed in several papers, have been established on DNA biosensors for detecting Hg2+. However, few reviews on the strategy of enzyme-driven signal amplification have been reported. In this paper, we reviewed this topic by dividing the enzymes into nucleases and DNAzymes according to their chemical nature. Initially, we introduce the nucleases including Exo III, Exo I, Nickase, DSN, and DNase I. In this section, the Exo III-driven signal amplification strategy was described in detail. Because Hg2+ can help ssDNA fold into dsDNA by T-Hg-T, and the substrate of Exo III is dsDNA, Exo III can be used to design Hg2+ biosensor very flexibly. Then, the DNAzyme-assisted signal amplification strategies were reviewed in three categories, including UO22+-specific DNAzymes, Cu2+-specific DNAzymes and Mg2+-specific DNAzymes. In this section, the Mg2+-specific DNAzyme was introduced in detail, because this DNAzyme has highly catalytic activity, and Mg2+ is very common ion which is not harmful to the environment. Finally, the challenges and future perspectives were discussed.

Influence of Feeding and Organism Age on the Acute Toxicity of Sodium Bromide to Artemia salina

Bromide is a common ion found in freshwater and marine systems. Although normally at relatively low concentrations, higher levels may occur in point-released wastewaters as well as nonpoint runoff from agricultural or industrial locations where bromide compounds are used as biocides and disinfectants. In this study, the potential toxicity of NaBr in a saltwater environment was studied using the brine shrimp, Artemia salina. The confounding factors of organism age at test initiation and pre-test feeding were included in the test design. Survival of brine shrimp nauplii in several NaBr treatments up to 11,000 mg Br−/L (measured) was assessed after 24 h in both fed- and unfed-tests. In tests with unfed organisms, only the youngest (< 24 h old) nauplii had acceptable control survival (≥90%), while control survival for all of the tests with fed organisms (< 24 h old, < 48 h old, < 72 h old) was acceptable. There was also greater and more erratic mortality in the unfed tests. These data indicate feeding A. salina prior to initiating a short-term acute test improved performance. Not feeding the test organisms, especially in longer tests or when using > 24 h old organisms, may result in excessive control mortality and an invalid test. These studies show that, when healthy organisms are used in the toxicity tests, 11,000 mg/L of Br− (~ 14,200 mg/L NaBr) is not acutely toxic to Artemia salina.