Low Cr Research Articles

Evidence from Cr-spinel chemistry for magma contamination by country rocks during formation of the northern lobe of the Bushveld Complex, South Africa

Although Cr-spinels from the Bushveld Complex have been studied for several decades, those from the northern lobe haven't received as much attention as Cr-spinels from other lobes of the intrusion. Disseminated Cr-spinels from the Flatreef of the northern lobe have chromium numbers (Cr# = 100•Cr/(Cr+Al)), which vary widely, from low values of ∼-32 hosted in altered olivines to high values of ∼55-82 hosted in orthopyroxenes and plagioclase. Few Cr-spinel crystals have almost identical Cr# from rim to core. Almost all Cr-spinels, irrespective of their host silicate types, display slight decreases in Cr# from the core to the rim of Cr-spinels. These Cr-spinels, however, are characterized by highly variable magnesium numbers (Mg# = 100•Mg/(Mg 2 + Fe 2+ )), ranging from 37-51 for Cr-spinels in olivines to 1-13 for Cr-spinels in pyroxenes and olivines. The chemistry of the Flatreef Cr-spinels in this study suggests the involvement of crustal contamination and re-equilibration. Plots of oxides such as aluminum, magnesium, and titanium, for example, are consistent with contamination of the Platreef by floor rocks to the intrusion such as dolomites and argillaceous shales. The low Cr# (<∼20) and enriched Al 2 O 3 (>32 wt.%) Cr-spinel chemistry signatures reported in this work appear not to have been previously documented in the Bushveld Complex.

Mesozoic lithospheric mantle evolution in South China: Evidence from Ar-Ar dating, geochemistry and Sr-Nd-Pb isotopes of lamprophyres

Understanding the Mesozoic lithospheric mantle beneath South China is challenging, primarily because mantle-derived magmatic rocks are rare, whereas granitic magmatism is far more abundant. In this study, we present new 40Ar/39Ar geochronology, major and trace elemental composition, and Sr-Nd-Pb isotopic data for lamprophyres from northern and central Guangxi Province, South China. Our results reveal two intrusion phases: an earlier phase at 207.7 ± 1.2 Ma, and a later phase between 95.6 ± 0.6 Ma and 102.3 ± 0.7 Ma. The earlier phase, represented by the Danyang lamprophyres, is marked by low Cr (330–355 ppm) and Ni (241–258 ppm) contents and strongly fractionated REE patterns with (La/Yb)n ratios of 57.5 to 62.8. The later phase, represented by the Leidong, Nongchang, and Longchang lamprophyres, shows higher Cr (490–781 ppm) and Ni (237–377 ppm) contents, with less fractionated REE patterns and (La/Yb)n ratios of 20.2 to 27.8. Despite their temporal differences, the lamprophyres share similar isotopic characteristics, including high initial 87Sr/86Sr (0.707940–0.721310), negative εNd(t) (−9.19 to −5.31), and radiogenic Pb isotopic compositions (206Pb/204Pb: 18.200–18.331, 207Pb/204Pb: 15.62–15.72, 208Pb/204Pb: 38.53–38.84). These features suggest derivation from low-degree partial melting of a phlogopite-bearing, refractory peridotite lithospheric mantle, modified by olivine and clinopyroxene fractionation. This refractory mantle was metasomatically enriched by Proterozoic subduction processes beneath the Yangtze Craton. By synthesizing published Sr-Nd-Pb isotopic data, we propose that the lithospheric mantle beneath South China shifted from enriched to depleted mantle between ∼220 Ma and ∼ 100 Ma, possibly due to extension associated with the subduction and rollback of the Paleo-Pacific Plate.

Effect of Aggressive Anions on the Stress Corrosion Cracking of Stainless Steel in Hot-Pressurized Alkaline Water

U-bend stress-corrosion cracking (SCC) testing of low Cr ferritic (Type 409) and austenitic (Type 304L) stainless steel was conducted in a hot-pressured alkaline water to study the effect of aggressive anions (Cl− and HS−) on the relative susceptibility. SCC was only observed in Type 304L when immersed in the solution that contained both aggressive anions. Critical factors were identified based on a cross-section examination of the U bends after exposure using complementary electron microscopy techniques. These factors include (i) preferential oxidation of deformation bands (arising from cold working), (ii) Ni-S compound formation at the oxide/metal interface and (iii) S and Cl incorporation into the inward-growing Cr-rich oxide. These critical factors were considered within an overall slip dissolution-type mechanism to account for the SCC observed.

Selective electro-induced reduction using bionic BC@SA-Nafion particle electrodes in 3D systems and phytotoxicity assessment

Three-dimensional electrode technology (3D technology), featuring dispersed particulate electrodes is rapidly advancing in the separation of pollutants. However, in contrast to the electrochemical oxidation performance, the design of particulate electrodes for electrochemical reduction remains relatively underexplored. This study introduced a bionic particle electrode (BC@SA-Nafion) with high reducibility and selectivity, and integrated it into a 3D system. Specifically, the selective electro-induced reduction capacity of BC@SA-Nafion was examined using Cr(Ⅵ) as a model pollutant. The electrochemical reactivity of BC@SA-Nafion was found to be dependent on the amount of biochar (BC) incorporated. Furthermore, the selectivity for Cr(Ⅵ) could be fine-tuned by adjusting the Nafion content, thereby addressing the efficiency decline at lower Cr(Ⅵ) concentrations. In the 3D system, the Cr(Ⅵ) removal rate reached up to 99 % under optimal conditions (pH 2, 2 V cm−1, 30 min). The density functional theory calculations indicated that the selectivity of BC@SA-Nafion for Cr(Ⅵ) was dependent on the presence of fluorine bonds. The reduction of Cr(Ⅵ) mainly relied on direct electron transfer provided, with superoxide (·O- 2) also playing a role. Post-treatment with the 3D technology resulted in negligible phytotoxicity of the wastewater. This study introduced a novel strategy for enhancing the selectivity of particle electrodes, thereby expanding the application of the particle electrode and advancing sustainable water treatment technologies.

Resilience and coping during protracted conflict: a comparative analysis of general and evacuees populations

BackgroundOn October 7th, 2023, Hamas launched a surprise attack on Israel, triggering a conflict with Israel in the Gaza Strip. This ongoing war, now six months old, has also seen threats from Hezbollah in Lebanon, as well as from Yemen and Iran. The precarious security situation along Israel’s southern and northern borders led to extensive evacuations, with residents relocating within Israel under uncertain conditions concerning their return and property safety. This study compares resilience (societal, SR; community, CR; and individual, IR), hope, morale, distress symptoms (anxiety and depression symptoms), and perceived danger between general Hebrew-speaking adults and evacuee adults a few months post-conflict initiation.MethodsData was collected using structured self-reported questionnaires focusing on resilience and coping strategies, administered through two online panel companies. The general population data was collected from January 14–21, 2024 (N = 1,360), and the evacuees’ data from March 1–9, 2024 (N = 372; 133 from the north, 239 from the south).ResultsEvacuees reported lower SR and CR, hope, and morale, and higher distress symptoms and perceived danger compared to the general population. No differences in IR were found. Regression analyses identified different primary predictors of SR for each group: hope for the general population and governmental support for evacuees. Additionally, IR significantly predicted outcomes only among evacuees, whereas age, religiosity, and education were significant predictors solely in the general population. One notable similarity emerged: CR served as the second most influential predictor in both samples.ConclusionsThe entire population of Israel is affected by the ongoing war, yet evacuees endure a disproportionately severe impact, with potential for increased harm as the conflict persists. The adjustment to a new wartime emergency routine is more complex for evacuees than for the general population. It is crucial for policy and decision-makers to address the distinct differences between evacuees and the general populace to effectively meet their specific needs. Yet, it should be acknowledged that the evacuees represent a heterogenic group, necessitating a detailed subdivision into subgroups to accurately assess and address their unique challenges.

Treatment strategies with electrochemotherapy for limb in-transit melanoma: Real-world outcomes from a European, retrospective, cohort study

BackgroundThis study analysed treatment strategies with electrochemotherapy (ECT) in melanoma with limb in-transit metastases (ITM). MethodsWe audited AJCC v.8 stage IIIB-IIID patients treated across 22 centres (2006–2020) within the International Network for Sharing Practices of ECT (InspECT). Results452 patients were included, 58 % pre-treated (93 % had lower limb ITM, 44 % had ≤10 metastases [median size 1.5 cm]. Treatment strategies included first-line ECT (n = 145, 32 %), ECT with concurrent locoregional/systemic treatment (n = 163, 36 %), and salvage ECT (n = 144, 32 %). The objective response rate was 63 % (complete response [CR], 24 %), increasing to 74 % (CR, 39 %) following retreatment (median two ECT, range 1–8). CR rate in treatment-naïve and pre-treated patients was 50 % vs 32 % (p < 0.001). Bleomycin de-escalation was associated with lower CR (p = 0.004). Small tumour number and size, hexagonal electrode, retreatment, and post-ECT skin ulceration predicted response in multivariable analysis. At a median follow-up of 61 months, local and locoregional recurrence occurred in 55 % and 81 % of patients. Median local progression-free, new lesions-free, and regional recurrence-free survival were 32.9, 6.9, and 7.7 months. Grade-3 toxicity was 15 %. Concurrent treatment and CR correlated with improved regional control and survival. Concomitant checkpoint inhibition did not impact toxicity or survival outcomes. The median overall survival was 5.7 years. ConclusionsAmong patients with low-burden limb-only ITM, standard-dose bleomycin ECT results in durable local response. Treatment naivety, low tumour volume, hexagonal electrode application, retreatment, and post-ECT ulceration predict response. CR and concurrent treatment correlate with improved regional control and survival outcomes. Combination with checkpoint inhibitors is safe but lacks conclusive support.

Salvia officinalis L. resilience under chromium stress: An integrated study of growth, physiology, biochemical changes and rosmarinic acid production

Medicinal plants are increasingly challenged by rising chromium (Cr) levels in agricultural soil and water bodies due to industrialization and human activities. This research examines the impact of various chromium concentrations on Salvia officinalis L., a medicinal herb, over 3 specific time periods: 30, 60 and 90 days. As the duration of Cr exposure increases, various growth parameters showed an upward trend at the lowest concentrations, with the most robust growth observed in the 20 ppm Cr treatment group after 90 days. However, higher chromium concentrations resulted in reduced plant growth compared to untreated plants. Chromium primarily accumulates in the roots, stems and leaves, with the highest accumulation observed at 100 ppm. However, chlorophyll content declined with prolonged Cr exposure, particularly at higher concentrations. Carbohydrate levels initially increased at lower Cr concentrations but decreased with greater exposure, while protein content consistently decreased with elevated Cr levels. Proline levels exhibited mixed responses, rising at lower concentrations and declining at higher ones. Malondialdehyde (MDA) content increased with higher Cr levels and extended exposure. The enzymatic antioxidant system showed an initial increase followed by a decline with prolonged exposure. Rosmarinic acid content increased with chromium (Cr) exposure upto 60 ppm but subsequently decreased beyond that threshold. In the first 30 days, plants treated with Cr demonstrated a 17 % increase in rosmarinic acid production compared to the control (48.9 mg/g DW). However, with continued Cr exposure, there was a decline in rosmarinic acid production ranging from 10 % to 20 % compared to the control level (67.02 mg/g DW) at 90 days post-treatment. These findings underscore the complex and contrasting responses of Salvia officinalis to Cr toxicity, highlighting the necessity for extended study into the core mechanisms governing these responses and the development of strategies to alleviate heavy metal stress in plants.

Chromium cycle in Red Soil Critical Zone constrained by chromium isotopes

Chromium (Cr) isotopic system has been used to trace Cr pollution in the modern surface environment and redox change in the paleoenvironment. However, the transformation mechanism of Cr in soil and the accompanied Cr isotopic fractionation have not been clarified clearly. Here we measured Cr isotopic compositions (δ53Cr) of two paddy field profiles from the Red Soil Critical Zone Observatory in South China. The δ53Cr values of the young paddy fields, which have been cultivated for about 20 years, range from −0.34 ‰ to −0.22 ‰. The old paddy fields have been cultivated for >100 years and have more positive Cr isotopic compositions than the young paddy fields, from −0.20 ‰ to −0.06 ‰. The results of three-step leaching experiments show that iron and manganese oxides are enriched in heavy Cr isotopes, while organic matters have much lower Cr isotopic compositions, likely resulting from back reduction of Cr(VI). Our results suggest that Cr isotopic fractionation during the oxidation of Cr(III) is not the only reason for the depletion of heavy isotopes during oxidative weathering, and the partial back-reduction of generated Cr(VI) by organic matter plays an important role in Cr isotopic fractionation during weathering. Comparison between the old and young paddy fields further indicates that cultivation can significantly affect the Cr cycle in red soils. Paddy fields could be a potential sink for the Cr(VI) contaminant, and soils with a long history of cultivation would be more susceptible.

Dissecting the Simultaneous Extracellular/Intracellular Contributions to Cr(VI) Reduction under Aerobic and Anaerobic Conditions Using the Newly Isolating Cr(VI)-Reducing Bacterium of Pseudomonas sp. HGB10.

Quantifying extracellular and intracellular contributions to Cr(VI) reduction is crucial for understanding bacterial Cr(VI)-reduction mechanisms. However, this contribution under different oxygen conditions remains largely unexplored. This study quantified the extracellular/intracellular contribution to aerobic and anaerobic Cr(VI) reduction using Pseudomonas sp. HGB10, an isolated Cr(VI)-reducing bacterium, as the experimental model. Interestingly, it was found that the lower anaerobic minimum inhibitory concentration (MIC) does not necessarily imply a lower anaerobic Cr(VI)-reduction rate for HGB10. For the initial Cr(VI) concentration of 20 mg L-1, the maximum anaerobic Cr(VI)-reducing rate reached 100%, while the aerobic counterpart was only 75%, even though the value of the aerobic MIC (400 mg L-1) is twice that of the anaerobic (200 mg L-1). Additionally, the calculated extracellular contributions to aerobic and anaerobic Cr(VI) reduction were 10.76% and 55.71%, respectively, while the intracellular contributions were 68.29% and 40.38%. The sum of extracellular and intracellular contributions to Cr(VI) reduction (79.05% and 96.09%) under aerobic and anaerobic conditions was nearly balanced with the corresponding maximum values despite minor relative errors. These results indicated that anaerobic Cr(VI) reduction mainly occurred extracellularly rather than intracellularly, which differs from the existing result. Overall, our findings provide new insights into bacterial Cr(VI) reduction.

Molecular dynamics simulation of friction in DLC films with different Cr doping levels

This study systematically investigates the impact of varying Cr doping levels on the friction properties of DLC films using molecular dynamics simulations. The results demonstrate that under identical friction velocities and load conditions, the friction force of DLC films significantly decreases when the Cr doping content reaches 16.5 %. High Cr doping levels lead to the formation of Cr atomic clusters at the interface, hindering contact and reducing the number of interface bonds. These clusters act as lubricants, filling the interface gaps and thereby reducing the friction force. Internal stress calculations indicate that Cr doping effectively reduces the average internal stress of DLC films. For DLC films with lower Cr doping levels, the friction force exhibits similar trends under different friction velocities, while films with higher Cr doping levels show a more pronounced response, with friction force increasing at higher velocities. Increasing the load significantly raises the friction force, especially for DLC films with higher Cr doping levels. Furthermore, high Cr doping levels under high loads lead to significant structural damage and adhesive wear. This study provides theoretical and technical references for optimizing the friction performance of DLC films.

Comparison of the corrosion behavior of four Fe-Cr-Ni austenitic alloys in supercritical water

The corrosion behavior of four Fe-Cr-Ni austenitic alloys were investigated after exposure to deaerated supercritical water (SCW) at 650°C. Results show that the corrosion resistance follows the trend:Fe-29Cr-61Ni > Fe-16Cr-75Ni > Fe-25Cr-20Ni > Fe-21Cr-31Ni. The increase in Cr and Ni contents promote a transition from low-protective multilayer oxide scales to protective Cr2O3 scales. After surface grinding, the weight gains of all specimens dropped by one order of magnitude. Surface grinding induces the formation of ultrafine grains and a high density of dislocations, which enhances the corrosion resistance among all studied austenitic alloys. However, the beneficial effects of grinding diminish with increased Cr and Ni contents due to the pre-existing portion of Cr2O3 scales. The lower critical Cr content required to form Cr2O3 scales in high Ni austenitic alloys is primarily attributed to their lower solubility of O and the slower diffusion rates of Ni, which inhibit corrosion behavior.

Association between Cognitive Reserve Indicator and Chronic Disease-Free Survival: A Large Community-Based Longitudinal Study

BackgroundCognitive reserve (CR) has been linked to dementia and might be a predictor of aged-related outcomes. However, the association between CR and risk of other chronic diseases and mortality remains unclear.ObjectivesWe aimed to investigate the association of CR with survival free from major chronic diseases.Design, Setting and ParticipantsThis community-based longitudinal study used data from the UK Biobank. A total of 412,509 participants (mean age 55.71±8.10) free of major chronic disease (including dementia, diabetes, cardiovascular diseases, chronic obstructive pulmonary disease, and cancer) completed the baseline examination between 2006 to 2010 and were followed for changes in health status.MeasurementsLatent class analysis was used to generate an indicator of CR (categorized as low, moderate, or high) based on education, occupation, television viewing time, confiding, social connection, and leisure activities. Major chronic diseases and survival status were ascertained through self-reported history and/or linkages to medical and death records. Chronic disease-free survival was defined as survival without any of the aforementioned chronic diseases. Effect modifications and interactions between the CR indicator and sex, age, and lifestyle factors (including smoking status, alcohol consumption, physical activity, and body mass index) were explored.ResultsOver a median follow-up of 12.49 (interquartile range 11.42–13.41, range 0.01–15.87) years, 112,190 (27.2%) participants died or developed at least one chronic disease. High CR indicator was associated with lower risk of chronic disease/death (hazard ratio 0.82, 95% confidence interval: 0.80–0.83) compared to low CR indicator. Chronic disease-free survival was prolonged by 1.33 (1.21–1.44) years among participants with high CR compared to low CR indicator. Furthermore, the association between the CR indicator and chronic disease-free survival was strengthened among individuals aged <60 years and current smokers.ConclusionHigh CR indicator is associated with a lower risk of chronic disease/death and may prolong chronic disease-free survival. Our findings underscore the importance of CR-enhancing lifestyle and experiences in health longevity, especially for younger individuals and current smokers.

Thermal corrosion behavior of Inconel 693, Hastelloy N and 310S in ceramic waste forming reactions

The thermal corrosion behavior of Inconel 693, Hastelloy N, and 310S was investigated in the reaction environment of ceramic waste forming reactions. Due to the difference in Cr content and the effect of chlorides, the high Cr Inconel 693 and 310S alloys exhibit selective corrosion by Cr, while the low Cr Hastelloy N exhibits uniform corrosion and the volatilization of MoO3 caused high dimensional losses. The different behavior of the alloys in different corrosive environmental regions is also discussed. In the sintered product region, due to the encapsulation of the sintered product and the corrosion inhibiting role played by O2−, Hastelloy N alloy and 310S alloy experienced milder corrosion compared to alloy in the atmosphere region. And in the atmosphere region, the more abundant gas supply and the open environment caused Hastelloy N alloy and 310S alloy to experience more severe erosion. However, for Inconel 693 alloy, it formed a continuous spinel phase layer containing FeCr2O4 due to the higher partial pressure of O2 in the atmosphere region, resulting in more slight corrosion compared to the sintered product region.

Influence of surface plastic deformation on oxidation behavior for low Cr content nickel superalloy: Focus on the Cr diffusion

The surface plastic deformation induced by shot-peening on the oxidation behavior for GH3535 alloy was investigated. The variation in microstructure and mechanical property of GH3535 with different shot peening intensities was compared, followed by exposure to air at 950 °C for 200 h. The structure and elemental distribution of the oxide film were analyzed by combining SEM, EBSD and TEM. The result shows that shot peening significantly improves the oxidation resistance of GH3535 alloy. This treatment promotes the formation of fine grains on the surface of the alloy, and the grain boundaries act as fast diffusion channels of Cr leading to the Cr effective diffusivity of shot peening samples increase, the Cr effective diffusivity value is 0.235, 4.8 × 10−3, 3.8 × 10−3, 3.7 × 10−3, respectively. It promotes the formation of protective scales for the continuous Cr2O3 layer. Additionally, the effect of grain size on the diffusion of scale-forming elements (Cr, Si and Mn) in the GH3535 alloy was analyzed, with a particular focus on the diffusion of Cr and the synergistic effects of scale-forming element.

Nano-micrometer scale characterization of PWSCC crack tips in the transition zone of 52M overlay and the implication to intergranular cracking

This study examines the microstructural characteristics of the primary water stress corrosion cracking (PWSCC) crack tip in the transition zone (TZ) of the 52 M overlay and its implications for intergranular cracking. In the TZ, the Cr content at grain boundaries near the fusion boundary (FB) is lower than those farther from the FB. Additionally, residual strain at grain boundaries near the FB is higher than that farther away, with the fine-grained zone around the FB showing higher local deformation than the surrounding columnar grains. Stress corrosion cracking (SCC) crack growth rate (CGR) test results indicate that the TZ showed certain SCC sensitivity, and the closer to the FB, the lower the SCC resistance. Analysis of the SCC crack tip found that the distinctive composition distribution of the 52 M overlay TZ, characterized by low Cr and high Fe near the FB, is prone to intergranular oxidation, thereby reducing SCC resistance. Conversely, higher Cr and lower Fe content at grain boundaries in the TZ farther from the FB form dense, Cr-rich oxides ahead of the crack tip that slow SCC crack growth, resulting in the diffusion of oxidation along the dislocation structure into the grains and forming a fibrous oxidation zone.

Prolonged arc accretion during growth of juvenile crust in the Arabian Nubian Shield: Insights from the granitoids of northern Ethiopia

The Arabian Nubian Shield (ANS) is one of the largest juvenile continental crust formed after the Archean. To determine the timing and understand the mechanism of its early crustal growth, we conducted geochronological and geochemical studies on granitoids from northern Ethiopia. A plagiogranite, dated at 929.7 ± 2.2 Ma, represents one of the early granitoids from the ANS. It shows low K2O, TiO2, and REE contents, flat REE pattern and absence of Eu anomaly. Moreover, it exhibits (87Sr/86Sr)i, ƐNd(t) and ƐHf(t) values of 0.70341, +5.0 and +8.4, respectively. Its zircon δ18O value is 4.8‰, lower than the mantle value. These characteristics suggest that it was derived from partial melting of altered oceanic crust. The oxygen fugacity obtained from zircon trace elements is ΔFMQ+1.3, consistent with a subduction setting.Other plutons have much younger ages ranging from 860 to 840 Ma and are mainly medium K, I-type granitoids. These granitoids show low MgO, Ni and Cr contents, low Sr/Y, (La/Yb)N, Nb/Ta and Zr/Sm ratios. They exhibit whole-rock (87Sr/86Sr)i values of 0.70236–0.70304, ƐNd(t) values of 4.2–5.2, ƐHf(t) values of 5.8–7.6 and zircon ƐHf(t) values of 5.5–10.4, slightly lower than coeval depleted mantle. Furthermore, they exhibit fractionated REE patterns, enrichments in LILE and depletion in HFSE. These geochemical features suggest that these granitoids were generated by remelting of arc crust. Compiled data show that the associated basaltic rocks are of arc affinity, which confirms the coeval development of arc magmatism in the southern ANS. Our results suggest that the growth of juvenile crust in the southern ANS started from the early Neoproterozoic and peaked at ca. 880 to 800 Ma, much earlier than those in the northern ANS. The prolonged history accounts for the growth of the vast juvenile crust in the ANS.

Clinical, Laboratory, and Demographic Factors Contributing to COVID-19 Mortality Risk

Background: This study aimed to identify COVID-19 mortality risk factors and relevant laboratory markers to inform prevention and treatment strategies. Methods: This cross-sectional study was conducted in Iran, involving 1561 patients diagnosed with COVID-19 between 2019 and 2021. Demographic, clinical, and laboratory data were collected from hospital records and analyzed using a logistic regression model. Results: The mortality rate attributed to COVID-19 in this study was 24.7%. Identified risk factors for mortality included intubation, multiple chronic conditions, liver or kidney disease or cancer, low RBC levels, and abnormal creatinine (Cr) levels. The adjusted odds ratios (adjOR) and 95% confidence intervals (CIs) for these factors were as follows: intubation (70.75, 14.07:355.84), concurrent chronic diseases (24.29, 3.25:181.24), liver or kidney disease or cancer (5.13, 1.21:21.81), low RBC levels (5.21, 1.24:21.79), and abnormal Cr levels (5.09, 1.21:21.43). Conclusion: The findings from this study indicated that several factors, including intubation, multiple chronic conditions, liver or kidney disease or cancer, and low Cr levels were associated with a higher risk of death from COVID-19. These results highlight the significance of continuous monitoring and specialized care for patients exhibiting these risk factors to reduce the risk of COVID-19 mortality.

Studying the effect of Cr content on microstructure and deformation behavior of (NiCo)88-xCrxAl10Ta2 medium-entropy alloy through L-DED gradient material

Optimization of Cr content is crucial for γ'-strengthened NiCoCr-based medium entropy alloys, influencing the stacking fault energy, deformation behavior and the precipitation of brittle σ phase. In this study, (NiCo)88-xCrxAl10Ta2 gradient materials were prepared by L-DED, and the influence of Cr content on the phase precipitation and tensile deformation behavior was investigated. As the Cr content decreases from 24.1 at% to 13.9 at%, the aging time for σ phase precipitation at the grain boundaries at 750°C increases from 100 hours to 215 hours. Meanwhile, the coarsening rate of γ' phase at 750°C are found to be 7.84×10−28 m3/s and 13.6×10−28 m3/s for the Cr content of 24.1 at% and 18.7 at%, respectively. It suggests that the reduction in Cr content notably suppresses the precipitation of σ phase, and accelerates the coarsening rate of γ' phase. Tensile testing of the gradient material reveals that the lower Cr content region exhibits fewer and shorter stacking faults during tensile deformation due to its higher stacking fault energy, leading to the rapid development of local strain, subsequent necking, and eventual fracture. Taking into account the evolution of microstructure, hardness, and deformation substructure with varying Cr content, the appropriate Cr content in (NiCo)88-xCrxAl10Ta2 medium entropy alloy is 17–24 at%.

Cr-induced structural phase transformation in sputter deposited poly-AlN thin film from wurtzite to rocksalt structure and their effect on the optical properties

We report Cr doping-induced structural phase transformation (PT) in sputter-deposited polycrystalline-AlN thin film from wurtzite (w) to rocksalt (r) structure. Rietveld analysis shows that the steady substitution of Al ions by Cr ions in the w-AlN lattice distorts and compresses the wurtzite lattice along the c-axis. The chemical pressure exerted in the w-AlN lattice by the compression from the doped Cr ions causes the PT, similar to the high-pressure-induced PT in AlN. Post the PT, the r-Al1-xCrxN thin film continues to exhibit compressive residual stress, indicating that such sustained stress may also play a role in stabilizing the metastable r-Al1-xCrxN phase. The structural distortion and the PT also affected the optical absorption characteristics of the w-Al1-xCrxN thin films. The w-Al1-xCrxN exhibit a direct inter-band transition and the band gap (Eg) decreases from ∼ 6.06 eV for pure w-AlN to ∼ 4.15 eV for w-Al0.73Cr0.27N. After the PT, the r-Al0.61Cr0.39N thin film, on the other hand, exhibits an indirect inter-band transition with an Eg of ∼ 1.84 eV. In addition to the change in Eg, a prominent defect band appears at ∼ 4 eV at low Cr% and another band appears at ∼ 0.98 eV at higher Cr%.

Kyanite microstructural and microchemical characteristics reveal differences in growth, deformation and chemical modification: A case study from the Paleoproterozoic suture zone of South Harris, NW Scotland

Based on petrological association, cathodoluminescence (CL), trace element signatures and orientation relationships, two generations of kyanite are distinguished in a high temperature, high pressure garnet-biotite-aluminosilicate bearing migmatite of South Harris, NW Scotland. The migmatite shows a garnet and biotite rich domain (Grt-Bt domain) which is cut at a low angle by a dominantly coarse-grained plagioclase-quartz leucosome. In addition, a fine-grained plagioclase-quartz-kyanite domain (Plag-Qtz-Ky domain) is present intercalated with the Grt-Bt domain and subparallel to the plagioclase-quartz domain. Type 1 kyanite is coarse grained and associated with Bt clusters and garnet within the Grt-Bt domain. It grew relatively early, syn- to post-garnet growth, in a suprasolidus environment resulting in crystallographically determined oscillatory CL and trace element zoning. Grains record evidence of progressive deformation in the crystal plastic regime, where deformation is accommodated by dislocation glide, climb and deformation twinning. The dominant activated slip system is (100)<001> with minor component of <100>, while deformation twins show a ∼ 180° rotation around ∼<001> axis and a twin plane near (001). Grains appear to be impervious to deformation induced diffusion with all zoning remaining sharp despite crystal plastic deformation. Grains in direct contact with the Plag-Qtz-Ky domain show late modification of the CL and trace element signature suggesting melt-mediated interface-coupled dissolution-precipitation reaction. This modification resulted in crosscutting lobate high trace element regions and irregular rims with low Cr and V content. These rims show similar CL and trace element characteristics as Type 2 kyanite which are exclusively seen within the Plag-Qtz-Ky domain suggesting that Type 2 grains are cogenetic with Type 1 rims. Type 2 grains are finer grained than Type 1 grains and show near uniform CL and trace element distributions with rare oscillatory zoned and relatively higher Cr & V bright cores. Type 2 show either no or very localized internal deformation features. However, they exhibit a clear shape preferred orientation which coincides with a crystallographic preferred orientation where the longest shape axis is parallel to <001>. We propose that Type 2 kyanite grains underwent melt-present deformation by rigid body rotation in an externally derived melt with different trace element chemistry than the host rock. This melt thus interacted chemically by melt-mediated interface-coupled dissolution-precipitation reactions with the surrounding rocks forming the Type 1 rims.Our study shows detailed analysis of kyanite is an important tool for giving constraints on the deformation, P–T and melting history of high-grade metamorphic rocks and migmatites.