Enceladus and possibly Europa spew materials from their internal ocean into their exosphere, some of which are deposited back onto the surface of those Ocean Worlds. This setting provides a unique ...opportunity to seek traces of past or extant life in ice plume deposits on their surfaces. However, the design of lander missions and surface sampling techniques and the choice of sampling locations rely heavily on strength expectations. Here we present an experimental investigation of the evolution in strength of ice plume deposit analogs at several temperatures, as well as a model that predicts first‐order estimates of the strength of evolved ice plume deposits under geologic timescales relevant to Enceladus and Europa. These results suggest that plume deposits remain weak and poorly consolidated on Enceladus, while they may develop substantial strength (comparable to solid ice) within <100 Myr on Europa.
Plain Language Summary
Enceladus and Europa are Ocean Worlds; they harbor an internal ocean beneath their ice shells. There is proof that a plume emits ocean materials out of Enceladus, similar to geysers on Earth, and some evidence for similar activity on Europa. Based on the composition of the plumes and the surface, both Enceladus and Europa are the leading outer solar system candidates for possibly harboring life. Areas where fresh plume materials are deposited would be the best location to search for traces of life on the surface. A major challenge in preparing mission concepts to explore these locations arises from the need to collect samples of the surface ice, while little is known at present about the mechanical properties of the surface. In this study, we prepared icy plume deposit analogs and let them evolve in the laboratory over extended periods of time to investigate the evolution of their strength. We find that plume deposits are likely to remain loose and exhibit a low strength over geologic timescales under Enceladus's conditions, suggesting that they would be relatively easy to sample. Conversely, under Europa's surface conditions, such plume deposits appear likely to develop a substantial strength.
Key Points
The cone penetration resistance of fine‐grained porous ice held under isothermal conditions increases linearly over time
The temperature dependence of the strengthening rate yields an activation energy similar to self‐diffusion at the surface of ice grains
Plume deposits would remain weak on Enceladus, while they may develop substantial strength within a few million years on Europa
Laboratory evidence supports the notion that dehydration degrades exercise performance and impairs certain cognitive processes. The purpose of this study is to examine the effect of a voluntary ...versus a dictated drinking condition on exercise and cognitive performance. The study used a double-blind and paired design. Twenty male and female college students (10 women, 10 men) participated in an exercise protocol consisting of 1 hr of treadmill running followed by a high intensity portion continuing until voluntary exhaustion. The dictated drinking condition consisted of 900 ml of water equally distributed in 4 pre-prepared opaque bottles. At 15 min intervals the subject was instructed to drink the entire contents until the end of the 1 hr treadmill protocol. The voluntary drinking condition consisted of 225 ml of water within arm's reach of the subjects while on the treadmill. Exercise performance was significantly better (longer duration and faster speed) in the voluntary condition compared with the dictated condition. Cognitive test outcomes were not significantly different between drinking conditions. A difference in fluid absorption is a potential source of exercise impairment seen in the dictated fluid condition. The higher fluid consumption rate presumably would cause greater gastric and esophageal distention resulting in the diversion of blood flow from working muscles to the gastrointestinal system. In situations where dehydration is likely, drinking to recommended guidelines may protect individuals from dehydration and its negative effects. However, when dehydration is not likely, allowing an individual to follow voluntary drinking behavior is preferable for exercise performance.
High-quality early care and education for children from birth to kindergarten entry is critical to positive child development and has the potential to generate economic returns, which benefit not ...only children and their families but society at large. Despite the great promise of early care and education, it has been financed in such a way that high-quality early care and education have only been available to a fraction of the families needing and desiring it and does little to further develop the early-care-and-education (ECE) workforce. It is neither sustainable nor adequate to provide the quality of care and learning that children and families need?a shortfall that further perpetuates and drives inequality.
Transforming the Financing of Early Care and Education outlines a framework for a funding strategy that will provide reliable, accessible high-quality early care and education for young children from birth to kindergarten entry, including a highly qualified and adequately compensated workforce that is consistent with the vision outlined in the 2015 report, Transforming the Workforce for Children Birth Through Age 8: A Unifying Foundation . The recommendations of this report are based on essential features of child development and early learning, and on principles for high-quality professional practice at the levels of individual practitioners, practice environments, leadership, systems, policies, and resource allocation.
The delivery of high quality and equitable care for both mothers and newborns is complex and requires efforts across many sectors. The United States spends more on childbirth than any other country ...in the world, yet outcomes are worse than other high-resource countries, and even worse for Black and Native American women. There are a variety of factors that influence childbirth, including social determinants such as income, educational levels, access to care, financing, transportation, structural racism and geographic variability in birth settings. It is important to reevaluate the United States' approach to maternal and newborn care through the lens of these factors across multiple disciplines.
Birth Settings in America: Outcomes, Quality, Access, and Choice reviews and evaluates maternal and newborn care in the United States, the epidemiology of social and clinical risks in pregnancy and childbirth, birth settings research, and access to and choice of birth settings.
The objective of the study was to examine salivary biomarker response to fluid consumption in exercising athletes. Exercise induces stress on the body and salivary alpha amylase (sAA) and salivary ...cortisol are useful biomarkers for activity in the sympathoadrenal medullary system and the hypothalamic pituitary adrenal axis which are involved in the stress response. Fifteen college students were given 150 ml and 500 ml of water on different days and blinded to fluid condition. The exercise protocol was identical for both fluid conditions using absolute exercise intensities ranging from moderate to high. Saliva was collected prior to exercise, post moderate and post high intensities and analyzed by Salimetrics assays. Exercise was significant for sAA with values different between pre-exercise (85 ± 10 U · ml(-1)) and high intensity (284 ± 30 U · ml(-1)) as well as between moderate intensity (204 ± 32 U · ml(-1)) and high intensity. There was no difference in sAA values between fluid conditions at either intensity. Exercise intensity and fluid condition were each significant for cortisol. Cortisol values were different between pre-exercise (0.30 ± 0.03 ug · dL(-1)) and high intensity (0.45 ± 0.05 ug · dL(-1)) as well as between moderate intensity (0.33 ± 0.04 ug · dL(-1)) and high intensity. Moderate exercise intensity cortisol was lower in the 500 ml condition (0.33 ± 0.03 ug · dL(-1)) compared with the 150 ml condition (0.38 ± 0.03 ug · dL(-1)). This altered physiological response due to fluid consumption could influence sport performance and should be considered. In addition, future sport and exercise studies should control for fluid consumption.
Bonnie et al comment on the new report, The Promise of Adolescence: Realizing Opportunity for All Youth, released in May 2019, is particularly timely. Today's youth, representing approximately 25% of ...the US population, are more culturally and ethnically diverse than ever before. Unfortunately, however, inequalities in income, access to resources, and opportunity among youth continue to increase, with stark differences in poverty by race, ethnic group, and geography. The report highlights two overarching messages. The first is that adolescence is a period of extraordinary opportunity for learning and exploration and for laying a strong foundation for a successful life. The second message is that our nation needs to commit itself to a sustained plan for reversing the worsening inequities of childhood disadvantage, thereby enabling all adolescents to flourish.
Reactive oxygen species and nitrogen species have been implicated in the pathogenesis of coal dust-induced toxicity. The present study investigated several oxidative stress biomarkers (Contents of ...lipoperoxidation = TBARS, reduced = GSH, oxidized = GSSG and total glutathione = TG, α-tocopherol, and the activities of glutathione S-transferase = GST, glutathione reductase = GR, glutathione peroxidase = GPx, catalase = CAT and superoxide dismutase = SOD), in the blood of three different groups (n = 20 each) exposed to airborne contamination associated with coal mining activities: underground workers directly exposed, surface workers indirectly exposed, residents indirectly exposed (subjects living near the mines), and controls (non-exposed subjects). Plasma TBARS were increased and whole blood TG and GSH levels were decreased in all groups compared to controls. Plasma α-tocopherol contents showed approximately half the values in underground workers compared to controls. GST activity was induced in workers and also in residents at the vicinity of the mining plant, whilst CAT activity was induced only in mine workers. SOD activity was decreased in all groups examined, while GPx activity showed decreased values only in underground miners, and GR did not show any differences among the groups. The results showed that subjects directly and indirectly exposed to coal dusts face an oxidative stress condition. They also indicate that people living in the vicinity of the mine plant are in health risk regarding coal mining-related diseases.
We present a measurement of atmospheric tau neutrino appearance from oscillations with three years of data from the DeepCore subarray of the IceCube Neutrino Observatory. This analysis uses ...atmospheric neutrinos from the full sky with reconstructed energies between 5.6 and 56 GeV to search for a statistical excess of cascadelike neutrino events which are the signature of ντ interactions. For CC+NC (CC-only) interactions, we measure the tau neutrino normalization to be 0.73−0.24+0.30 (0.57−0.30+0.36) and exclude the absence of tau neutrino oscillations at a significance of 3.2σ (2.0σ) These results are consistent with, and of similar precision to, a confirmatory IceCube analysis also presented, as well as measurements performed by other experiments.
PDF
