Crystal chemistry of volcanic allanites indicative of naturally induced oxidation-dehydrogenation

The crystal chemistry of volcanic allanites from both the Youngest Toba Tuff (YTT), Sumatra, Indonesia and SK100 volcanic ash beds (SK100-VAB), Niigata, Japan has been examined by electron microprobe analysis (EMPA), Fourier-transform infrared spectroscopic analysis (FTIR), and single-crystal structure analysis. In the FTIR study, based on the Diamond ATR accessory, YTT and SK100- VAB allanites were observed to have different OH contents, respectively: the former has 0.64 wt% H2O (OH: 0.40 apfu.), while the latter has 1.65 wt% H2O (OH: 1.00 apfu.). The crystal structures of these two allanites have been refined to individual R indices (3.64 and 4.25) based on 1350 observed reflections (Fo> 4sigFo) measured using a single-crystal diffractometer with MoKα X-radiation. The OH-poor YTT allanite has a shorter b axis, a longer c axis, and larger β value than the relatively OH-rich SK100-VAB one. The bond valence sums of O4 (accepter oxygen for H atom) and O10 (donor oxygen for H atom) are 1.962 and 1.709 v.u. for YTT allanite (valence sum: 3.671 v.u.) and 1.754 and 1.271 v.u. for SK100-VAB one (valence sum: 3.025 v.u.). The difference from the ideal total bond valence value (4.00 v.u.) of O4 and O10 in YTT allanite (0.33 v.u.) is smaller than that in SK100-VAB (0.98 v.u.). These difference values are also broadly consistent with the corresponding differences in OH content between the YTT (OH: 0.40 apfu.) and SK100-VAB allanites (OH: 1.00 apfu.) determined by FTIR- ATR. Chemical analyses, FTIR-ATR and crystal structure refinement of YTT and SK100-VAB allanites yielded the following crystal chemical formula: YTT: (Ca0.83Mn2+ 0.06Fe2+ 0.11)(La0.24Ce0.32Pr0.04Nd0.11Sm0.02Th0.04Ca0.21)(Al0.73Fe3+ 0.19Ti0.08)(Al0.89Fe3+ 0.11)(Fe2+ 0.22Fe3+ 0.62Mg0.16)(SiO4)Si2O7O1.6(OH)0.4, SK100-VAB: (Ca0.81Fe2+ 0.13Mn2+ 0.06)(La0.22Ce0.34Pr0.05Nd0.13Sm0.02Th0.02Ca0.22)(Al0.76Fe3+ 0.19Ti0.05)Al1.00(Fe2+ 0.73Fe3+ 0.17Mg0.10)(Si0.96Al0.04O4)Si2O7O(OH). Therefore, it is concluded that welding of the Youngest Toba Tuff caused the following post-crystallization changes to occur in YTT allanite: oxidation of Fe2+ to Fe3+, release of H2, and the concomitant replacement of OH− by O2−. These oxidation and dehydrogenation processes advanced during the welding to thereby produce oxyallanite. Oxyallanite had been reported only in laboratory studies where it was produced by heating natural allanite. Our report on natural oxyallanite suggests that it may be present in other welded silicic volcanic rocks as well

Another Major Question: The Department of Labor Should Retire the Tiebreaker Rule and Reemploy Pecuniary Language in ERISA

The Employee Retirement Income Security Act of 1974 (“ERISA”) soon turns 50. Instead of celebrating with cake, retirees and future retirees alike get to witness a new chapter in the debate over the consideration of Environmental, Social, or Governance (“ESG”) factors in investing with plan assets. As employees cross the bridge into retirement, they look to their 401(k)s and pension plans for peace of mind, for it is ERISA that has been working silently in the background establishing minimum standards, practices, and fiduciary duties to protect participants. In recent years, the U.S. Department of Labor (“DOL”) has passed three regulations—two in 2020 and one in 2022—through notice of proposed rulemaking (“NPRM”) procedures that purport to address whether ESG factors may be considered by ERISA plan fiduciaries when managing plan assets. ERISA’s fiduciary duties have historically been viewed as narrowing the scope of considerations a plan’s fiduciary may incorporate into his decision-making process, but the DOL’s 2022 regulation expanded the pool of factors to include non-pecuniary considerations in both making investment decisions and exercising shareholder rights. The 2022 Rule also expanded the application of the tiebreaker rule. Ultimately, while moral, social, or political merits of businesses weighing ESG factors are a matter of significant interest, this Note argues that the consideration of ESG and socially responsible investment (“SRI”) factors, for its non-pecuniary benefits to ERISA plan participants or its collateral benefits to third parties, is inconsistent with ERISA’s duty of loyalty—the sole interest and exclusive benefits rules—and duty of prudence. Such policy change risks sacrificing plan diversification and incurring additional administrative fees for plan participants. This Note further evaluates the merits of a major questions doctrine challenge to the DOL’s creation of the 1994 tiebreaker rule and incorporation of non-pecuniary factors into the plan fiduciary’s decision-making process

Aerosol size confines climate response to volcanic super-eruptions

Extremely large volcanic eruptions have been linked to global climate change, biotic turnover, and, for the Younger Toba Tuff (YTT) eruption 74,000 years ago, near-extinction of modern humans. One of the largest uncertainties of the climate effects involves evolution and growth of aerosol particles. A huge atmospheric concentration of sulfate causes higher collision rates, larger particle sizes, and rapid fall out, which in turn greatly affects radiative feedbacks. We address this key process by incorporating the effects of aerosol microphysical processes into an Earth System Model. The temperature response is shorter (9–10 years) and three times weaker (−3.5 K at maximum globally) than estimated before, although cooling could still have reached −12 K in some midlatitude continental regions after one year. The smaller response, plus its geographic patchiness, suggests that most biota may have escaped threshold extinction pressures from the eruption

Redox control of sulfur degassing in silicic magmas

International audienceExplosive eruptions involve mainly silicic magmas in which sulfur solubility and diffusivity are low. This inhibits sulfur exsolution during magma uprise as compared to more mafic magmas such as basalts. Silicic magmas can nevertheless liberate large quantities of sulfur as shown by the monitoring of SO2 in recent explosive silicic eruptions in arc settings, which invariably have displayed an excess of sulfur relative to that calculated from melt degassing. If this excess sulfur is stored in a fluid phase, it implies a strong preference of sulfur for the fluid over the melt under oxidized conditions, with fluid/melt partition coefficients varying between 50 and 2612, depending on melt composition. Experimentally determined sulfur partition coefficients for a dacite bulk composition confirm this trend and show that in volcanic eruptions displaying excess gaseous sulfur, the magmas were probably fluid-saturated at depth. The experiments show that in more reduced silicic magmas, those coexisting only with pyrrhotite, the partition coefficient decreases dramatically to values around 1, because pyrrhotite locks up nearly all the sulfur of the magma. Reevaluation of the sulfur yields of some major historical eruptions in the light of these results shows that for oxidized magmas, the presence of 1-5 wt % fluid may indeed account for the differences observed between the petrologic estimate of the sulfur yield and that constrained from ice core data. Explosive eruptions of very large magnitude but involving reduced and cool silicic magmas, such as the Toba or the Bishop events, release only minor amounts of sulfur and could have consequently negligible long-term (years to centuries) atmospherical effects. This redox control on sulfur release diminishes as the melt composition becomes less silicic and as temperature increases, because both factors favor more efficient melt sulfur degassing owing to the increased diffusivity of sulfur in silicate melts under such conditions

Impact on P-12 Student Learning: Perspectives from Multiple Stakeholders

Statement of Research Problem It is essential for teacher preparation programs to be able to track teacher candidates’ impact on P-12 student learning in school sites in order to fulfill accreditation requirements and measure candidate and program success. Additionally, it is critical for us to understand how candidates’ opportunities to impact P-12 student learning are influenced by their host school sites, including their classroom cooperating teachers. Therefore, we conducted an exploratory study to collect qualitative input from multiple stakeholders, including teacher candidates, cooperating teachers, and school. The perspectives collected in this study has helped our program, the college, and the outreach office to discern the factors that may prevent or promote field training and teaching effectiveness, and allow us to work collaboratively with partner schools to provide relevant resources and support for our candidates in the area of impacting P-12 learners. Research Question What kind of framework, processes and cooperation are needed for schools and colleges of education to track pre-service candidates’ impact on P-12 student learning

Repair of DNA-protein crosslinks in mammalian cells

University of Minnesota Ph.D. dissertation. 2018. Major: Pharmacology. Advisor: Colin Campbell. 1 computer file (PDF); 178 pages.The work below describes a new assay called strand-specific primer extension-quantitative polymerase chain reaction (SSPE-qPCR) used to study the repair of DNA-protein crosslinks in mammalian cells. DNA-protein crosslinks (DPCs) are bulky lesions which disrupt important cell processes such as transcription and replication. They are formed by endogenous molecules such as formaldehyde and exogenous damaging agents such as ionizing radiation. However, the repair mechanisms associated with their repair are still unclear. Chapter 1 of this document provides background information on the formation, biological consequences, current models, and methods used to study DPC repair. Chapter 2 describes the SSPE-qPCR assay and its uses/limitations for studying the repair of plasmids containing DPCs or other polymerase-blocking adducts transfected into mammalian cells. Chapter 3 describes results generated using this assay to assess the role of nucleotide excision repair in DPC repair and highlights the versatility of the SSPE-qPCR assay. Chapter 4 extends observations made in Chapter 3 by using SSPE-qPCR to examine repair of DPC-containing plasmids in the presence of a homologous donor. It also provides evidence for homologous recombinational repair of DPCs in mammalian mitochondria. Overall, this work provides additional insight into the mechanisms of DPC repair in the nucleus and mitochondria using a quantitative, flexible assay that has not been available previously

Effect of Social Isolation on Seizure Susceptibility through GABA-ergic Mechanisms

The ongoing Covid-19 pandemic has incited an array of social, psychological, and emotional burdens among adolescents and adults. The lockdowns, social distancing measures, and general anxiety surrounding the virus have produced an unprecedented and pervasive degree of social isolation, particularly amongst adolescents. Social isolation has deleterious effects on physical and mental well-being and is a critical risk factor for morbidity among adults. However, the neural and physiological underpinnings and consequences of social isolation have yet to be fully explored. Social isolation has been understood as a source of chronic and early stress, with various developmental consequences. In the past decade, researchers have found the stress associated with social isolation to worsen the development of epilepsy, among other neuropsychological disorders. There are various mechanisms and regions involved such as the GABAergic system, which is the neural system regulating GABA neurotransmission. There is a growing consensus in the scientific community that changes in the GABAergic system stemming from social isolation can lead to a lower seizure threshold. This leads us to not only ask whether the GABAergic system, and other systems involved with neurotransmitters, could be affected by social isolation, but also whether this corresponding change in neurophysiology leads to a lowered seizure threshold. Our objective is to better understand the effects of social isolation on epilepsy development. The broad, long-term objective of this work is to provide clinicians with a framework for how to properly intervene and target therapies for neuropsychological disorders that might arise from early life stress

JS/DH: Primary Sources and Open Data

Column on digital humanities and Jewish Studies, focusing on open data in digitized material

Building the Foundations of Scholarship at Home: Salo Baron and the Judaica Collections at Columbia University Libraries

Salo Baron’s impact on Judaic scholarship in the 20th century is hardly unknown. Moreover, his leadership of the Jewish Cultural Reconstruction Project solidly places him in the annals of the history of bibliography as well. Less well-known, however, is the outsized impact Baron had on the collections at his home institution. In this chapter, I will discuss how Salo Baron’s connections and advocacy for the Judaica collections at Columbia University ensured its place as a top primary source collection of Judaica in the United States

Capture of linear fragments at a double-strand break in yeast

Double-strand breaks (DSBs) are dangerous chromosomal lesions that must be efficiently repaired in order to avoid loss of genetic information or cell death. In all organisms studied to date, two different mechanisms are used to repair DSBs: homologous recombination (HR) and non-homologous end joining (NHEJ). Previous studies have shown that during DSB repair, non-homologous exogenous DNA (also termed ‘filler DNA’) can be incorporated at the site of a DSB. We have created a genetic system in the yeast Saccharomyces cerevisiae to study the mechanism of fragment capture. Our yeast strains carry recognition sites for the HO endonuclease at a unique chromosomal site, and plasmids in which a LEU2 gene is flanked by HO cut sites. Upon induction of the HO endonuclease, a linear extrachromosomal fragment is generated in each cell and its incorporation at the chromosomal DSB site can be genetically monitored. Our results show that linear fragments are captured at the repaired DSB site at frequencies of 10−6 to 10−4 per plated cell depending on strain background and specific end sequences. The mechanism of fragment capture depends on the NHEJ machinery, but only partially on the homologous recombination proteins. More than one fragment can be used during repair, by a mechanism that relies on the annealing of small complementary sequences. We present a model to explain the basis for fragment capture