Natural Fe-bearing aluminous bridgmanite in the Katol L6 chondrite

Bridgmanite, the most abundant mineral of the Earth’s lower mantle, has been reported in only a few shocked chondritic meteorites; however, the compositions of these instances differ from that expected in the terrestrial bridgmanite. Here, we report the first natural occurrence of Fe-bearing aluminous bridgmanite in shock-induced melt veins within the Katol L6 chondrite with a composition that closely matches those synthesized in high-pressure and temperature experiments over the last three decades. The Katol bridgmanite coexists with majorite and metal-sulfide intergrowths. We found that the natural Fe-bearing aluminous bridgmanite in the Katol L6 chondrite has a significantly higher Fe3+/ΣFe ratio (0.69 ± 0.08) than coexisting majorite (0.37 ± 0.10), which agrees with experimental studies. The Katol bridgmanite is arguably the closest natural analog for the bridgmanite composition expected to be present in the Earth’s lower mantle. Textural observations and comparison with laboratory experiments suggest that the Katol bridgmanite formed at pressures of ∼23 to 25 gigapascals directly from the chondritic melt generated by the shock event. Thus, the Katol L6 sample may also serve as a unique analog for crystallization of bridgmanite during the final stages of magma ocean crystallization during Earth’s formation.

Evolution of Anand Parameters With Elevated Temperature Aging for SnAgCu Lead-free Alloys

Electronic components in downhole oil drilling and gas industry applications, automotive, and avionics may be exposed to high temperatures (>150 °C) and high strain rates (1–100 per sec) during storage, operation, and handling, which can contribute to the failures of electronic devices. Temperatures in these applications can exceed 200 °C, which is close to melting point for SnAgCu (SAC) alloys. Prior studies at low strain rates have shown property evolution even under moderate exposure to high temperature. In this paper, the evolution of Anand parameters for unaged and aged SAC (SAC105 and SAC-Q) lead-free solder alloys at high strain rates has been investigated induced under sustained periods of thermal aging. The thermal aged lead-free SAC solder alloys specimen has been tested at high strain rates (10–75 per sec) at elevated temperatures of (25 °C–200 °C). The SAC lead-free solder samples were subjected to isothermal aging at 50 °C up to 1-year before testing. To describe the material constitutive behavior, the Anand Viscoplastic model has been used. The effect of thermal aging on Anand parameters also has been investigated. In order to verify the accuracy of the model, the computed Anand parameters have been used to simulate the uni-axial tensile test. The material constitutive behavior has been implemented in a finite element framework to simulate the drop events using the Anand constitutive model and determine the plastic work per shock event. The plastic work per shock event is a measure of the damage progression in the solder interconnects. The constitutive model has been used to simulate the shock event of a ball-grid array package on printed circuit board assembly.

Impact shock origin of diamonds in ureilite meteorites

The origin of diamonds in ureilite meteorites is a timely topic in planetary geology as recent studies have proposed their formation at static pressures >20 GPa in a large planetary body, like diamonds formed deep within Earth’s mantle. We investigated fragments of three diamond-bearing ureilites (two from the Almahata Sitta polymict ureilite and one from the NWA 7983 main group ureilite). In NWA 7983 we found an intimate association of large monocrystalline diamonds (up to at least 100 µm), nanodiamonds, nanographite, and nanometric grains of metallic iron, cohenite, troilite, and likely schreibersite. The diamonds show a striking texture pseudomorphing inferred original graphite laths. The silicates in NWA 7983 record a high degree of shock metamorphism. The coexistence of large monocrystalline diamonds and nanodiamonds in a highly shocked ureilite can be explained by catalyzed transformation from graphite during an impact shock event characterized by peak pressures possibly as low as 15 GPa for relatively long duration (on the order of 4 to 5 s). The formation of “large” (as opposed to nano) diamond crystals could have been enhanced by the catalytic effect of metallic Fe-Ni-C liquid coexisting with graphite during this shock event. We found no evidence that formation of micrometer(s)-sized diamonds or associated Fe-S-P phases in ureilites require high static pressures and long growth times, which makes it unlikely that any of the diamonds in ureilites formed in bodies as large as Mars or Mercury.

Textural Identification of Polycrystalline Magmatic, Tectonically-Deformed, and Shock-Related Zircon Aggregates

Zircon with polycrystalline or polygranular appearance is either produced in the magmatic environment through crystallization, or due to deformation in metamorphic settings (including regional metamorphism and ductile shear zones), or as a result of shock-induced recrystallization. All three types can be easily confused and potentially lead to incorrect interpretations, especially if the crystallographic orientation analyses of zircon are not conducted. It is particularly important to establish the difference between tectonically-deformed polygranular zircon and shock-induced polygranular zircon because the latter serves as an indicator of shock event and is often used for dating asteroid impacts. In this paper, a series of polycrystalline zircon grains from ductile shear zones and metamorphic rocks are analyzed using a combination of techniques (BSE, CL, orientation contrast, EBSD, and microprobe mapping), and their properties are compared to reported polycrystalline zircons from magmatic and impact settings. This work shows how appearance, crystallographic orientation, and CL signature of “granules” differ between the different types of deformed zircon.

Bank Risks, Shock Event and Profitability in Islamic Banks: Adoption of Panel Data Approach

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Shock events and corporate announcements

Purpose – The purpose of this paper is to verify if, in case of a shock event, there are types of corporate announcement that may influence stock price behaviour better than others. The authors also try to determine if the communication strategy may be affected by the type of shock event. Design/methodology/approach – Using the event study analysis, the authors estimate the Cumulative Abnormal Returns associated to the stocks of the selected firms hit by a shock event, in order to visualise the effectiveness of different types of corporate announcements after the event. Findings – The research confirms the negative effect of shock events on corporate stocks’ value. Moreover, the study envisages that financial market rewards companies that assume consistent and reassuring announcements during the event window. The authors also find that the effectiveness of corporate announcements is related to the shock’s typology. Research limitations/implications – The study employs a small and unbalanced sample of shock events. Moreover, it does not exist a generally accepted criterion to define and classify corporate announcements and the authors cannot exclude the influence of the media in the categorisation process of the announcements. Practical implications – Since shock events may threat firms’ survival, by knowing which response strategy fits better a shock situation, a manager can assess the potential effect of his communication options and choose the right type of announcement. Originality/value – There is a lack of literature on this theme, in particular on the effects that the different corporate announcements following a shock event may have on shareholders’ value.

Energy Harvesting of Piezoelectric Stack Actuator From a Shock Event

The energy harvesting performance of a piezoelectric stack actuator under a shock event is theoretically and experimentally investigated. The first method is derived from the single degree of freedom constitutive equations, and then a correction factor is applied onto the resulting electromechanically coupled equations of motion. The second approach is deriving the coupled equations of motion with Hamilton's principle and the constitutive equations, and then formulating it with the finite element method. Two experimental cases matched well with the model predictions where the percent errors were 3.90% and 3.26% for the SDOF analysis and 1.52% and 1.42% for the FEM.