Fundamental insights into the stabilisation and chemical degradation of the corrosion product scales

Carbonate stability plays a crucial role in clarifying the evolution and protection of the naturally formed corrosion scales on the steel surface in the application of geothermal production. In this paper, the stability of the corrosion scales from both micro and atomic level are studied via a combination of electrochemistry, surface analysis and first-principle calculation. The chemical and physical characterisation of various iron–calcium mixed carbonates are experimentally analysed and results are compared with the first-principle calculation. In the presence of Ca2+, the preferential loss of Ca during the dissolution experiments was observed, the interactions within the crystal weaken where Ca2+ co-precipitation, confirmed by a faster degradation rate for Ca0.51Fe0.49CO3 than FeCO3. This work reveals the degradation and protection performance of the naturally formed carbonate layers and provides insights into understanding the corrosion product stability and chemical breakdown of the corrosion scales.

The Effects of Temperature and Ethanol on Proanthocyanidin Adsorption to Grape Cell Wall Material in the Presence of Anthocyanins

The quantitative and qualitative impacts of anthocyanins on proanthocyanidin adsorption to grape-derived cell wall material were investigated in fifteen unique systems of varying temperatures, ethanol concentrations, and proanthocyanidin concentrations. Proanthocyanidin solutions were exposed to cell wall material and monitored for changes in concentration over 24 h. Increases in both temperature and ethanol resulted in a larger retention of proanthocyanidins in solution and typically faster adsorption kinetics. Analysis of the solution after exposure to cell wall revealed a significant reduction in the molecular weight of proanthocyanidins present in solution, suggesting that anthocyanins do not alter a previously described mechanism of preferentially binding large molecular weight molecules. Additionally, a reduction in polymeric pigment abundance was noted in most conditions, suggesting rapid formation of polymeric pigment in the model solution and preferential adsorption of the polymeric pigment to cell wall material. Compared to a previous study of proanthocyanidin adsorption in the absence of anthocyanins, a significantly larger percentage of proanthocyanidin material was lost via adsorption—up to 70% of available material. In a winemaking context, this may suggest a preferential loss of polymeric pigment via adsorption to cap cell wall material compared to non-pigmented proanthocyanidins and free anthocyanins.

Maintenance of sarcomeric integrity in adult muscle cells crucially depends on Z-disc anchored titin

The giant protein titin is thought to be required for sarcomeric integrity in mature myocytes, but direct evidence for this hypothesis is limited. Here, we describe a mouse model in which Z-disc-anchored TTN is depleted in adult skeletal muscles. Inactivation of TTN causes sarcomere disassembly and Z-disc deformations, force impairment, myocyte de-stiffening, upregulation of TTN-binding mechanosensitive proteins and activation of protein quality-control pathways, concomitant with preferential loss of thick-filament proteins. Interestingly, expression of the myosin-bound Cronos-isoform of TTN, generated from an alternative promoter not affected by the targeting strategy, does not prevent deterioration of sarcomere formation and maintenance. Finally, we demonstrate that loss of Z-disc-anchored TTN recapitulates muscle remodeling in critical illness ‘myosinopathy’ patients, characterized by TTN-depletion and loss of thick filaments. We conclude that full-length TTN is required to integrate Z-disc and A-band proteins into the mature sarcomere, a function that is lost when TTN expression is pathologically lowered.

Geochemistry of the chromitite stringer at the contact of the mafic sequence and the ultramafic sequence in the Unki Mine area, Shurugwi Subchamber of the Great Dyke, Zimbabwe

ABSTRACT Several models have been proposed to explain the origin of a chromitite stringer located at the contact between the Mafic and Ultramafic Sequences in the Unki Mine area of the Shurugwi Subchamber of the Great Dyke, Zimbabwe. A petrographic and geochemical study of this chromitite stringer was undertaken with the aim of constraining its origin. Forty-three chromite compositions were obtained from the studied chromitite stringer, which is characterized by a chromium number between 59.9 and 62.8 and a magnesium number which ranges from 37.8 to 46.4. The chromites at the contact zone in the Unki Mine commonly contains inclusions of sulfides, orthopyroxene, plagioclase, and/or amphiboles. The chromites likely formed early in the crystallization history of the Mafic Sequence, as they are commonly partially rimmed by sulfides and they occur as inclusions in plagioclase crystals. Unlike chromites from underlying Ultramafic Sequence chromitite layers, chromites at the contact zone contain low Cr2O3 contents which range from 39.4 to 42.6 wt.%. Furthermore, these chromites are enriched in Fe compared to most Great Dyke chromitites, which is interpreted to be a consequence of subsolidus exchange of Mg into orthopyroxene and Fe into the chromite. The absence of zoning in the chromites at this contact zone, and their low Mn, Fe contents, is consistent with attainment of equilibrium because the altered chromites often contain Cr-bearing magnetite rims. Two possible models for the formation of this chromitite stringer are mixing of relatively primitive and evolved magmas (i.e., ultramafic and anorthositic magma), possibly of different oxygen fugacities, and chemical diffusion across the contact between the Mafic and the Ultramafic sequences which resulted in melting at and below this boundary. The latter would have caused preferential loss of orthopyroxene from the underlying P1 Pyroxenite Layer, accompanied by re-precipitation of chromite at this contact.

Improving Compositional Accuracy in APT Analysis of Carbides Using a Decreased Detection Efficiency

The composition of carbides in steel, measured by atom probe tomography, can be influenced by limitations in the ion detector system. When carbides are analyzed, many ions tend to field evaporate from the same region of the specimen during the same laser or voltage pulse. This results in a so-called multiple event, meaning that several ions impact the detector in close proximity both in time and space. Due to a finite detector dead-time not all ions can be detected, a phenomenon known as detector pile-up. The evaporation behavior of carbon is often different than the evaporation behavior of metals when analyzing alloy carbides, leading to preferential loss of carbon ions, and a measured carbon concentration below the expected value. This effect becomes stronger as the overall detection efficiency gets higher. Here, the detection efficiency was deliberately reduced by inserting a grid into the flight-path, which resulted in a higher and more correct carbon concentration, accompanied by an increase in the statistical uncertainty.

Mammalian CST averts replication failure by preventing G-quadruplex accumulation

Human CST (CTC1-STN1-TEN1) is an RPA-like complex that associates with G-rich single-strand DNA and helps resolve replication problems both at telomeres and genome-wide. We previously showed that CST binds and disrupts G-quadruplex (G4) DNA in vitro, suggesting that CST may prevent in vivo blocks to replication by resolving G4 structures. Here, we demonstrate that CST binds and unfolds G4 with similar efficiency to RPA. In cells, CST is recruited to telomeric and non-telomeric chromatin upon G4 stabilization. STN1 depletion increases G4 accumulation and slows bulk genomic DNA replication. At telomeres, combined STN1 depletion and G4 stabilization causes multi-telomere FISH signals and telomere loss, hallmarks of deficient telomere duplex replication. Strand-specific telomere FISH indicates preferential loss of C-strand DNA while analysis of BrdU uptake during leading and lagging-strand telomere replication shows preferential under-replication of lagging telomeres. Together these results indicate a block to Okazaki fragment synthesis. Overall, our findings indicate a novel role for CST in maintaining genome integrity through resolution of G4 structures both ahead of the replication fork and on the lagging strand template.