Photoreductive Dissolution of Iron Oxides Trapped in Ice and Its Environmental Implications

The availability of iron has been thought to be a main limiting factor for the productivity of phytoplankton and related with the uptake of atmospheric CO_2 and algal blooms in fresh and sea waters. In this work, the formation of bioavailable iron (Fe(II)_(aq)) from the dissolution of iron oxide particles was investigated in the ice phase under both UV and visible light irradiation. The photoreductive dissolution of iron oxides proceeded slowly in aqueous solution (pH 3.5) but was significantly accelerated in polycrystalline ice, subsequently releasing more bioavailable ferrous iron upon thawing. The enhanced photogeneration of Fe(II)_(aq) in ice was confirmed regardless of the type of iron oxides [hematite, maghemite (γ-Fe_2O_3), goethite (α-FeOOH)] and the kind of electron donors. The ice-enhanced dissolution of iron oxides was also observed under visible light irradiation, although the dissolution rate was much slower compared with the case of UV radiation. The iron oxide particles and organic electron donors (if any) in ice are concentrated and aggregated in the liquid-like grain boundary region (freeze concentration effect) where protons are also highly concentrated (lower pH). The enhanced photodissolution of iron oxides should occur in this confined boundary region. We hypothesized that electron hopping through the interconnected grain boundaries of iron oxide particles facilitates the separation of photoinduced charge pairs. The outdoor experiments carried out under ambient solar radiation of Ny-Ålesund (Svalbard, 78°55′N) also showed that the generation of dissolved Fe(II)_(aq) via photoreductive dissolution is enhanced when iron oxides are trapped in ice. Our results imply that the ice(snow)-covered surfaces and ice-cloud particles containing iron-rich mineral dusts in the polar and cold environments provide a source of bioavailable iron when they thaw

The Meme Stock Frenzy: Origins and Implications

In 2021, several publicly traded companies, such as GameStop and AMC, became “meme stocks,” experiencing a sharp rise in their stock prices through a dramatic influx of retail investors into their shareholder base. Analyses of the meme stock surge and its implications for corporate governance have focused on the idiosyncratic creation of online communities around particular stocks during the COVID-19 pandemic. In this Article, we argue that the emergence of meme stocks is part of longer-running digital transformations in trading, investing, and governance. On the trading front, the sudden abolition of commissions by major online brokerages in 2019 reduced entry costs for retail investors. Zero-commission trading represents a modification of the payment for order flow (PFOF) system, which is itself a product of technological disruptions in the financial markets in the 1980s. With respect to investing, the emergence of social media communication amplified retail investors’ pre-existing dependence on social networks to make decisions regarding stock market entry and portfolio construction. It also allowed them to coordinate their investing activities and affect the market price while expressing their non-financial interests. Finally, while some startups have attempted to bring the shareholder experience into the digital age and help retail investors participate in governance, these developments have been relatively modest. After tracing the meme stock phenomenon, we sketch a research agenda for law and finance scholars to explore the concrete effects of meme investing on corporate governance outcomes. First, we ask whether retail traders can transform into enthusiastic retail shareholders engaged in corporate governance. Second, we propose a broader metric for “meme-ness”: future scholarship can use modern advances in data science to better identify which companies are vulnerable to meme surges and social media-driven investing unrelated to their financial fundamentals

Meme Corporate Governance

Can retail investors revolutionize corporate governance and make public companies more responsive to social concerns? The U.S. stock market offered an unusual experiment to test the impact of retail investors in 2021, when there was a dramatic influx of retail investors into the shareholder base of companies such as GameStop and AMC. The meme surge phenomenon elicited a variety of reactions from scholars and practitioners. While some worried that affected companies’ share prices were becoming disjointed from their financial fundamentals, others predicted that retail shareholders will reduce the power of large institutional investors and democratize corporate governance. This Article presents the first empirical analysis of the impact of retail investors on the governance of companies affected by the “meme stock surge.” The Article presents three principal findings. First, we show how the “meme stock” frenzy was affected by the introduction of the commission-free trading platform, such as Robinhood, in 2019. We show that the meme stock companies experienced higher abnormal stock returns when commission-free trading was widely introduced, and saw elevated trading volumes afterward. Second, we examine how the influx of retail shareholders has directly affected the governance outcomes at the meme stock companies. Notwithstanding the promise of a more active retail shareholder base, we show that meme stock companies have experienced a significant decrease in participation by their shareholders with respect to voting. Shareholder proposals under Rule 14a-8 have also been extremely limited, with most meme firms seeing no proposals brought after the rapid increase in retail ownership. Third, we examine whether the increase in retail shareholder base had any indirect effect on corporate governance and performance. While board gender diversity at these firms is broadly unchanged, their ESG scores have gotten worse subsequent to the meme surge. Examining meme firms’ use of corporate funds, we find decreases in research and development and capital expenditures after the meme surge. Collectively, our findings suggest that the influx of retail shareholders at these companies have not translated into more “democratic” governance regimes or reduced agency costs, even at firms the scholarly and popular commentary had highlighted as the cynosure of the retail investor storm

Ultraviolet photodepletion spectroscopy of dibenzo-18-crown-6-ether complexes with alkali metal cations

Ultraviolet photodepletion spectra of dibenzo-18-crown-6-ether complexes with alkali metal cations (M+-DB18C6, M = Cs, Rb, K, Na, and Li) were obtained in the gas phase using electrospray ionization quadrupole ion-trap reflectron time-of-flight mass spectrometry. The spectra exhibited a few distinct absorption bands in the wavenumber region of 35450−37800 cm^(−1). The lowest-energy band was tentatively assigned to be the origin of the S_0-S_1 transition, and the second band to a vibronic transition arising from the “benzene breathing” mode in conjunction with symmetric or asymmetric stretching vibration of the bonds between the metal cation and the oxygen atoms in DB18C6. The red shifts of the origin bands were observed in the spectra as the size of the metal cation in M^+-DB18C6 increased from Li^+ to Cs^+. We suggested that these red shifts arose mainly from the decrease in the binding energies of larger-sized metal cations to DB18C6 at the electronic ground state. These size effects of the metal cations on the geometric and electronic structures, and the binding properties of the complexes at the S_0 and S_1 states were further elucidated by theoretical calculations using density functional and time-dependent density functional theories

Effects of passive confinement on out-of-plane robustness of unreinforced masonry infill walls

Pradhan S., Sanada Y., Rokhyun Y., et al. Effects of passive confinement on out-of-plane robustness of unreinforced masonry infill walls. Structures 65, 106676 (2024); https://doi.org/10.1016/j.istruc.2024.106676.Unreinforced masonry (URM) walls are vulnerable to out-of-plane (OOP) collapse under lateral loads; however, URM structures are still popular in developing countries. Even in many countries classified as developed by the United Nations, URM walls are still commonly applied as exterior and interior infills in engineered buildings, resulting in severe OOP failure during strong earthquakes. The objectives of this study were: 1) to experimentally examine the OOP behavior and performance of URM infills with construction deficiencies commonly found in Asian countries, 2) to investigate the impact of construction quality on resistance to OOP collapse and 3) to propose a promising approach using passive confinement to improve the lateral resistance of URM infills and a method to evaluate their seismic performance. To attain these objectives, the study used two full-scale, single wythe, brick masonry specimens with specific boundary conditions at the top, a control specimen representing URM infills with construction flaws frequently found in Asian countries and a well-constructed specimen subjected to passive confinement under lateral excitation. A series of incremental dynamic shaking table tests was performed on both specimens under OOP unidirectional one-way bending. The test results revealed the positive effects of construction with passive confinement on OOP performance. The results indicated that the OOP robustness of infills can be improved without specific retrofit materials, leading to advantages such as simplicity, cost-effectiveness, and swift execution. Moreover, a theoretical method to evaluate the lateral resistance of infills was presented and verified for practical applications. This method can contribute to reducing the potential for earthquake damage in engineered buildings