Delivery of Dark Material to Vesta via Carbonaceous Chondritic Impacts

NASA's Dawn spacecraft observations of asteroid (4) Vesta reveal a surface with the highest albedo and color variation of any asteroid we have observed so far. Terrains rich in low albedo dark material (DM) have been identified using Dawn Framing Camera (FC) 0.75 {\mu}m filter images in several geologic settings: associated with impact craters (in the ejecta blanket material and/or on the crater walls and rims); as flow-like deposits or rays commonly associated with topographic highs; and as dark spots (likely secondary impacts) nearby impact craters. This DM could be a relic of ancient volcanic activity or exogenic in origin. We report that the majority of the spectra of DM are similar to carbonaceous chondrite meteorites mixed with materials indigenous to Vesta. Using high-resolution seven color images we compared DM color properties (albedo, band depth) with laboratory measurements of possible analog materials. Band depth and albedo of DM are identical to those of carbonaceous chondrite xenolith-rich howardite Mt. Pratt (PRA) 04401. Laboratory mixtures of Murchison CM2 carbonaceous chondrite and basaltic eucrite Millbillillie also show band depth and albedo affinity to DM. Modeling of carbonaceous chondrite abundance in DM (1-6 vol%) is consistent with howardite meteorites. We find no evidence for large-scale volcanism (exposed dikes/pyroclastic falls) as the source of DM. Our modeling efforts using impact crater scaling laws and numerical models of ejecta reaccretion suggest the delivery and emplacement of this DM on Vesta during the formation of the ~400 km Veneneia basin by a low-velocity (<2 km/sec) carbonaceous impactor. This discovery is important because it strengthens the long-held idea that primitive bodies are the source of carbon and probably volatiles in the early Solar System.Comment: Icarus (Accepted) Pages: 58 Figures: 15 Tables:

Evidence-based Toxicology for the 21st Century: Opportunities and Challenges

The Evidence-based Toxicology Collaboration (EBTC) was established recently to translate evidence-based approaches from medicine and health care to toxicology in an organized and sustained effort. The EBTC held a workshop on “Evidence-based Toxicology for the 21st Century: Opportunities and Challenges” in Research Triangle Park, North Carolina, USA on January 24-25, 2012. The presentations largely reflected two EBTC priorities: to apply evidence-based methods to assessing the performance of emerging pathwaybased testing methods consistent with the 2007 National Research Council report on “Toxicity Testing in the 21st Century” as well as to adopt a governance structure and work processes to move that effort forward. The workshop served to clarify evidence-based approaches and to provide food for thought on substantive and administrative activities for the EBTC. Priority activities include conducting pilot studies to demonstrate the value of evidence-based approaches to toxicology, as well as conducting educational outreach on these approaches

Evidence-based Toxicology for the 21st Century: Opportunities and Challenges

The Evidence-based Toxicology Collaboration (EBTC) was established recently to translate evidence-based approaches from medicine and health care to toxicology in an organized and sustained effort. The EBTC held a workshop on “Evidence-based Toxicology for the 21st Century: Opportunities and Challenges” in Research Triangle Park, North Carolina, USA on January 24-25, 2012. The presentations largely reflected two EBTC priorities: to apply evidence-based methods to assessing the performance of emerging pathwaybased testing methods consistent with the 2007 National Research Council report on “Toxicity Testing in the 21st Century” as well as to adopt a governance structure and work processes to move that effort forward. The workshop served to clarify evidence-based approaches and to provide food for thought on substantive and administrative activities for the EBTC. Priority activities include conducting pilot studies to demonstrate the value of evidence-based approaches to toxicology, as well as conducting educational outreach on these approaches

Nanoindenting the Chelyabinsk meteorite to learn about impact deflection effects in asteroids

The Chelyabinsk meteorite is a highly shocked, low porosity, ordinary chondrite, probably similar to S- or Q-type asteroids. Therefore, nanoindentation experiments on this meteorite allow us to obtain key data to understand the physical properties of near-Earth asteroids (NEAs). Tests at different length scales provide information about the local mechanical properties of the minerals forming this meteorite: reduced Young's modulus, hardness, elastic recovery, and fracture toughness. Those tests are also useful to understand the potential to deflect threatening asteroids using a kinetic projectile. We found that the differences in mechanical properties between regions of the meteorite, which increase or reduce the efficiency of impacts, are not a result of compositional differences. A low mean particle size, attributed to repetitive shock, can increase hardness, while low porosity promotes a higher momentum multiplication. Momentum multiplication is the ratio between the change in momentum of a target due to an impact, and the momentum of the projectile, and therefore higher values imply more efficient impacts. In the Chelyabinsk meteorite the properties of the light-colored lithology materials facilitate obtaining higher momentum multiplication values, compared to the other regions described for this meteorite. Also, we found a low value of fracture toughness in the shock-melt veins of Chelyabinsk, which would promote the ejection of material after an impact and therefore increase the momentum multiplication. These results are relevant in the context of a future mission to test asteroid deflection, currently being studied by ESA and NASA: the Asteroid Impact and Deflection Assessment (AIDA) mission

Mode of Action in Relevance of Rodent Liver Tumors to Human Cancer Risk

Hazard identification and risk assessment paradigms depend on the presumption of the similarity of rodents to humans, yet species specific responses, and the extrapolation of high-dose effects to lowdose exposures can affect the estimation of human risk from rodent data. As a consequence, a human relevance framework concept was developed by the International Programme on Chemical Safety (IPCS) and International Life Sciences Institute (ILSI) Risk Science Institute (RSI) with the central tenet being the identification of a mode of action (MOA). To perform a MOA analysis, the key biochemical, cellular, and molecular events need to first be established, and the temporal and dose-dependent concordance of each of the key events in the MOA can then be determined. The key events can be used to bridge species and dose for a given MOA. The next step in the MOA analysis is the assessment of biological plausibility for determining the relevance of the specified MOA in an animal model for human cancer risk based on kinetic and dynamic parameters. Using the framework approach, a MOA in animals could not be defined for metal overload. The MOA for phenobarbital (PB)-like P450 inducers was determined to be unlikely in humans after kinetic and dynamic factors were considered. In contrast, after these factors were considered with reference to estrogen, the conclusion was drawn that estrogen-induced tumors were plausible in humans. Finally, it was concluded that the induction of rodent liver tumors by porphyrogenic compounds followed a cytotoxic MOA, and that liver tumors formed as a result of sustained cytotoxicity and regenerative proliferation are considered relevant for evaluating human cancer risk if appropriate metabolism occurs in the animal models and in humans

The Impact of COVID-19 Pandemic on Medical Doctors’ Work-Family Balance at German University Clinics

The measures taken to cope with the COVID-19 pandemic by governments worldwide have vast consequences on all areas of life. To assess the impact of the COVID-19 pandemic on long-term career development, we evaluated the work-family balance of medical doctors at nine German university clinics. The results indicate a severely disturbed work-family balance, which was mostly due to insufficient childcare, based on restrictions in school operations and childcare. Despite the newly created emergency childcare options, aiming to ensure the functioning of the “systematically important” professional groups, medical doctors feel that they are not sufficiently supported by the measures taken by local governments. Women, in particular, see their professional development at risk. Our results underline that proper and flexible childcare is essential for the career advancement of female medical doctors and is particularly important in times of crises such as the current COVID-19 pandemic. At university medicine clinics, increased work time flexibility and optimized schooling and childcare are needed to promote the career development of female as well as male medical doctors in the early stage of their careers

Accelerating the Development of 21st-Century Toxicology: Outcome of a Human Toxicology Project Consortium Workshop

The U.S. National Research Council (NRC) report on “Toxicity Testing in the 21st century” calls for a fundamental shift in the way that chemicals are tested for human health effects and evaluated in risk assessments. The new approach would move toward in vitro methods, typically using human cells in a high-throughput context. The in vitro methods would be designed to detect significant perturbations to “toxicity pathways,” i.e., key biological pathways that, when sufficiently perturbed, lead to adverse health outcomes. To explore progress on the report’s implementation, the Human Toxicology Project Consortium hosted a workshop on 9–10 November 2010 in Washington, DC. The Consortium is a coalition of several corporations, a research institute, and a non-governmental organization dedicated to accelerating the implementation of 21st-century Toxicology as aligned with the NRC vision. The goal of the workshop was to identify practical and scientific ways to accelerate implementation of the NRC vision. The workshop format consisted of plenary presentations, breakout group discussions, and concluding commentaries. The program faculty was drawn from industry, academia, government, and public interest organizations. Most presentations summarized ongoing efforts to modernize toxicology testing and approaches, each with some overlap with the NRC vision. In light of these efforts, the workshop identified recommendations for accelerating implementation of the NRC vision, including greater strategic coordination and planning across projects (facilitated by a steering group), the development of projects that test the proof of concept for implementation of the NRC vision, and greater outreach and communication across stakeholder communities