Macalester College

Lunar mare basalts are often rich in titanium, hosted predominantly within the mineral ilmenite (Fe2+Ti4+O3). Here, we examine ilmenite in a ~ 3.8 billion-year-old mare basalt (Apollo rock 75035) using high-resolution electron microscopy and electron energy loss spectroscopy. A key finding is that 75035 ilmenite is itself enriched in Ti, beyond the end member of the conventional solid solution series. Using energy loss near-edge spectroscopy, we determine that the excess Ti is trivalent, with Ti3+ accounting for 13% of the total Ti content. This discovery confirms the presence of trivalent Ti in lunar ilmenite, long hypothesized based on the Moon’s reducing environment. Accounting for the change in implied stoichiometry, a review of literature data suggests that Ti3+ may be present in ilmenite across a wide range of lunar samples. We extrapolate known relationships from the literature to connect Ti3+ to redox conditions, estimating the oxygen fugacity during crystallization of 75035 to be below the iron-wüstite buffer, ΔIW≤ − 1.6. Further quantifying the relationship between Ti valence state and oxygen fugacity would allow Ti3+-bearing ilmenite to serve as an oxybarometer able to access the reducing conditions found on many planetary bodies.

Parallel and Distributed Computing (PDC) has increased in importance in recent years, with ABET requiring exposure to PDC topics, and CS2023 recommending at least 9 hours of coverage in required CS courses. However, injecting PDC topics quickly into a course is difficult due to time and expense to set up requisite hardware and lack of readily available materials to adopt for the classroom. In this demo, we -- the CSinParallel project -- present free, web-based, interactive textbooks for learning and practicing various forms of PDC. We developed the backend system and wrote the material based on decades of experience integrating these topics into courses throughout the computer science curriculum. Currently we have two books that educators can readily use: Parallel Computing for Beginners, and Intermediate Parallel and Distributed Computing, along with some additional materials. With just a laptop in class, students can edit and run PDC code examples on remote hardware that is professionally maintained, eliminating the need for instructors to prepare hardware and software. The material spans a range of PDC technology (OpenMP, MPI, CUDA, OpenACC), provides mini assessments as readers work, and is designed so that instructors can add brief modules into existing courses or can be used comprehensively for a course dedicated to PDC. All materials are available on learnpdc.org and the code used in the books is on https://github.com/csinparallel/csinparallel. Additional assignments for a PDC course can be found on https://github.com/csinparallel/pdc-assignments.

In postwar Peru, the censorship of artwork addressing memories of the war remains a persistent reality, ranging from silencing to the application of the Law of Defense of Terrorism, and further intensified through terruqueo —a stigmatizing practice used by conservative politicians to label dissenting voices as terrorists. Drawing on the 2017 accusation of alleged “defense of terrorism” against the art collection Piraq Causa (Who Is Still to Blame?), I argue that censorship extended beyond terruqueo to include the very strategies employed in the artists’ defense—what I term desterruqueo —which themselves enacted forms of silencing. These acts of censorship were shaped by the privileging of specific discourses: the historical reductionism that cast Andean peasants as passive victims caught in the crossfire between the Shining Path and the armed forces, and the recognition of Sarhua art as both intangible cultural heritage and contemporary art. As a result, these dynamics inadvertently fostered self-censorship, constraining more nuanced representations of the war and contributing to the depoliticization of Piraq Causa . Interestingly, the recent work of contemporary Sarhua artists demonstrates that their art continues to serve as a platform for social denunciation and collective action that resists depoliticization.

The scientific literature has seen a resurgence of interest in genetic influences on human behaviour and socioeconomic outcomes. Such studies face the central difficulty of distinguishing possible causal influences, in particular genetic and non-genetic ones. When confounding between possible influences is not rigorously addressed, it invites over- and misinterpretation of data. We illustrate the breadth of this problem through a discussion of the literature and a reanalysis of two examples. The first paper we discuss suggested that patterns of similarity in social status between relatives indicate that social status is largely determined by one’s DNA. Our reanalysis shows that the paper’s conclusions are based on the conflation of genetic and non-genetic transmission (for example, of wealth) within families. The second paper we discuss posited that genetic variants underlying bisexual behaviour are maintained in the population because they also affect risk-taking behaviour and thereby confer an evolutionary fitness advantage through increased sexual promiscuity. In this case, too, our reanalysis shows that, though possible explanations cannot be distinguished, only one is chosen and presented as a conclusion. We discuss how issues of confounding apply more broadly to studies that claim to establish genetic underpinnings to human behaviour and societal outcomes.

Tropical forests are a dominant regulator of the global carbon cycle, exchanging more carbon dioxide with the atmosphere than any other terrestrial biome. Climate models predict unprecedented climatic warming in tropical regions in the coming decades; however, in situ field warming studies are severely lacking in tropical forests. Here we present results from an in situ warming experiment in Puerto Rico, where soil respiration responses to +4 oC warming were assessed half-hourly for a year. Soil respiration rates were 42-204% higher in warmed relative to ambient plots, representing some of the highest soil respiration rates reported for any terrestrial ecosystem. While respiration rates were significantly higher in the warmed plots, the temperature sensitivity (Q10) was 71.7% lower, pointing to a mechanistic shift. Even with reduced Q10, if observed soil respiration rates persist in a warmer world, the feedback to future climate could be considerably greater than previously predicted or observed.

Abstract Lunar mare basalts are often rich in titanium, hosted predominantly within the mineral ilmenite (Fe2+Ti4+O3). Of all Apollo samples returned from the Moon, only two are olivine-free basalts, making them of interest for their potential to constrain models of lunar evolution. Here, we use electron microscopy and electron energy loss spectroscopy (EELS) to investigate ilmenite in one of these samples: Apollo rock 75035. A key finding is that 75035 ilmenite is itself enriched in Ti, beyond the end member of the conventional solid solution series. Using energy loss near-edge spectroscopy (ELNES), we determine that the excess Ti is reduced to trivalent Ti, with Ti3+ mole fraction ~ 0.07. This discovery confirms a longstanding hypothesis based on the Moon's reducing environment. Its impact for lunar models comes through the implied oxygen fugacity during crystallization of 75035, which we estimate to be below the iron-wüstite buffer (IW): ∆IW ≤ −1.5. Our research also suggests that Ti3+ -bearing ilmenite could serve as a single-phase oxybarometer for the reducing conditions found on many planetary bodies.