An Analysis of the 3 May 2020 Low-Predictability Derecho Using a Convection-Allowing MPAS Ensemble

This study analyzes the low short-range predictability of the 3 May 2020 derecho using a 40-member convection-allowing Model for Prediction Across Scales (MPAS) ensemble. Elevated storms formed in south-central Kansas late at night and evolved into a progressive mesoscale convective system (MCS) during the morning while moving across southern Missouri and northern Arkansas, and affected western and middle Tennessee and southern Kentucky in the afternoon. The convective initiation (CI) in south-central Kansas, the organization of a dominant bow echo MCS and the MCS maintenance over Tennessee were identified as the three main predictability issues. These issues were explored using three MPAS ensemble members, observations and the Rapid Refresh analyses. The MPAS members were classified as successful or unsuccessful with regard to each predictability issue. CI in south-central Kansas was sensitive to the temperature and dewpoint profiles in low levels, which were associated with greater elevated thermodynamic instability and lower level of free convection in the successful member. The subsequent organization of a dominant bowing MCS was well predicted by the member that had more widespread convection in the early stages and no detrimental interaction with other simulated convective systems. Lastly, the inability of MPAS ensemble members to predict the MCS maintenance over western and middle Tennessee was linked to a dry bias in low levels and much lower thermodynamic instability ahead of the MCS compared to observations. This case demonstrates the challenges in operational forecasting of warm-season derecho-producing progressive MCSs, particularly when ensemble numerical weather prediction guidance solutions differ considerably.

Data Analysis of the Effect of Onion, Glycine and Cassava Additives on the Coating Performance of Zn Electrodeposition on Plain Carbon Steel

Data analysis of the coating performance of Zn electrodeposited plain carbon steel in 0.5 M HCl solution at specific volume addition (5 ml, 10 ml and 15 ml) of onion, glycine and cassava (ON, GY and CS) distillate additives, and at plating time of 15 and 18 mins with respect to 538 h of observation time was performed. Analytical outputs showed ON distillate most effectively improved the Zn electrodeposited by 14% at 10 ml volume and plating time of 15 mins. GY and CS distillate generally improved the Zn electrodeposited at all volumes and plating time with optimal values of 42.7% and 45.7% at 15 ml and plating times of 15 and 18 mins. Generally, coating performance varied significantly with observation time, but marginally with plating time and additive volume. The standard deviation values for onion additive showed significant variation from mean values due to relative thermodynamic instability of it coating performance with respect to observation time. This contrast the output observed for GY and CS additives which signifies thermodynamic equilibrium. The proportion of coating performance data above 10% improvement for the additives are (ON, GY and CS) are 32%, 85% and 78% at margin of error of 11.8%, 9.04% and 10.42%. Analysis of variance showed ON and GY additive volume only, influenced the coating performance output of the additives at 64.56% and 74.67% while CS additive volume and observation time influenced the coating performance output of CS at values of 91.18% and 3.27%.

Tracking slab surface temperatures with electrical conductivity of glaucophane

Slab surface temperature is one of the key parameters that incur first-order changes in subduction dynamics. However, the current thermal models are based on empirical thermal parameters and do not accurately capture the complex pressure–temperature paths of the subducting slab, prompting significant uncertainties on slab temperature estimations. In this study, we investigate whether the dehydration-melting of glaucophane can be used to benchmark the temperature in the slab. We observe that dehydration and melting of glaucophane occur at relatively low temperatures compared to the principal hydrous phases in the slab and produce highly conductive Na-rich melt. The electrical properties of glaucophane and its dehydration products are notably different from the hydrous minerals and silicate melts. Hence, we conclude that the thermodynamic instability of glaucophane in the slab provides a unique petrological criterion for tracking temperature in the present-day subduction systems through magnetotelluric profiles.

Gravimetric and Data Analysis of the Protection Performance of Plant Extracts on Plain Carbon Steel in Dilute H2SO4 Solution

Analysis of the protection performance of kolanut leaves (KL), kolanut fruits (KF), tobacco leaves (TL) and bitter leaves (BL) extracts at 30%, 60% and 80% concentration on plain carbon steel in 0.5 M H2SO4 solution was done by gravimetric measurement and statistical evaluation. Data output showed KF and TL extracts performed effectively at all concentrations studied with protection performance output generally above 80%. KL and BL extracts performed poorly at the lowest concentration while at higher concentrations optimal protection performance outputs are 74.41% and 83.53%. The protection performance outputs of KL, KF and TL extracts varied significantly with observation time due to thermodynamic instability and unstable inhibition behavior. BF extract exhibited stable inhibition behavior due to general stability of its protection performance outputs with respect to observation time. BF and KL exhibited the highest and lowest standard deviation due to the degree of variation of their protection performance outputs from mean value. Data showed 9.5%, 76.2%, 76.2% and 71.4% of the protection performance outputs of KL, KF, TL and BL extracts are above 80% inhibition performance at margin of error of 12.6%, 18.2%, 18.2% and 19.3%. Data from analysis of variance shows that observation time exerted more influence than extract concentration on the protection performance outputs of KL, KF and TL extracts with statistical relevance values of 91.24%, 91.93% and 93.61%. BL extract concentration exhibited significant influence on the protection performance outputs of BL compared to observation time with statistical relevance values of 81.43%.

Determinants of crystal structure transformation of ionic nanocrystals in cation exchange reactions

Changes in the crystal system of an ionic nanocrystal during a cation exchange reaction are unusual yet remain to be systematically investigated. In this study, chemical synthesis and computational modeling demonstrated that the height of hexagonal-prism roxbyite (Cu1.8S) nanocrystals with a distorted hexagonal close-packed sulfide anion (S2−) sublattice determines the final crystal phase of the cation-exchanged products with Co2+ [wurtzite cobalt sulfide (CoS) with hexagonal close-packed S2– and/or cobalt pentlandite (Co9S8) with cubic close-packed S2–]. Thermodynamic instability of exposed planes drives reconstruction of anion frameworks under mild reaction conditions. Other incoming cations (Mn2+, Zn2+, and Ni2+) modulate crystal structure transformation during cation exchange reactions by various means, such as volume, thermodynamic stability, and coordination environment.

Iridium-catalyzed Z-retentive asymmetric allylic substitution reactions

Z-Olefins are challenging synthetic targets owing to their relative thermodynamic instability. Transition metal–catalyzed asymmetric allylic substitution reactions are well known for installing stereocenters adjacent to branched or E-linear olefins. However, analogous reactions for the synthesis of optically active Z-olefin products are rare. Here we report iridium-catalyzed asymmetric allylic substitution reactions that retain Z-olefin geometries while establishing an adjacent quaternary stereocenter. The formation of transient anti-π-allyl-iridium intermediates and their capture by external nucleophiles before isomerization to the thermodynamically more stable syn-π-allyl-iridium counterparts have been observed. These results provide a promising method for preparing chiral Z-olefinic compounds.

Enhanced ozonation of pollutants by MgO nanoclusters/sewage sludge-derived hierarchal porous carbon: Experimental and theoretical study

Highly reactive nanoclusters of metal oxides are extremely difficult to be synthesized due to the thermodynamic instability. For the first time, MgO nanoclusters supported on sewage sludge-derived hierarchal porous carbon...