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Less is more: information needs, information wants, and what makes causal models useful
No full textAbstractEach day people make decisions about complex topics such as health and personal finances. Causal models of these domains have been created to aid decisions, but the resulting models are often complex and it is not known whether people can use them successfully. We investigate the trade-off between simplicity and complexity in decision making, testing diagrams tailored to target choices (Experiments 1 and 2), and with relevant causal paths highlighted (Experiment 3), finding that simplicity or directing attention to simple causal paths leads to better decisions. We test the boundaries of this effect (Experiment 4), finding that including a small amount of information beyond that related to the target answer has a detrimental effect. Finally, we examine whether people know what information they need (Experiment 5). We find that simple, targeted, information still leads to the best decisions, while participants who believe they do not need information or seek out the most complex information performed worse.</jats:p
Statistically Modeling the Fatigue Life of Copper and Aluminum Wires Using Archival Data
No full textIt has been known for at least 150 years that fatigue life data exhibits a considerable amount of variability. Furthermore, statistically modeling fatigue life adequately is challenging. Different empirical approaches have been used, each of which has merit; however, none is appropriate universally. Even when a sufficiently robust database exists, the scatter in the fatigue lives may be extremely large and difficult to characterize. The purpose of this work is to review traditional and more modern empirically based methodologies for estimating the statistical behavior of fatigue data. The analyses are performed on two historic sets of data for annealed aluminum wire and annealed electrolytic copper wire tested in reverse torsion fatigue. These data are readily available In publications. Specifically, the review considers a traditional method for stress-cycle (S-N) analysis which includes linear regression through load dependent medians and mean square error (MSE) confidence bounds. Another approach that is used is Weibull distribution estimation for each loading condition, from which estimations for the median behavior and confidence bounds are determined. The preferred technique is the development of a cumulative distribution functions for fatigue life, which contains aspects of traditional reliability, classical S-N, and applied loading modeling. Again, confidence bounds are estimated for this technique. Even though it is an empirical technique, there are mechanistic aspects that underlie the empiricism. This approach is suggested because the method is very robust, and the estimation is more accurate than the other methods.</jats:p
Paths to adaptation under fluctuating nitrogen starvation: The spectrum of adaptive mutations in Saccharomyces cerevisiae is shaped by retrotransposons and microhomology-mediated recombination
No full textThere are many mechanisms that give rise to genomic change: while point mutations are often emphasized in genomic analyses, evolution acts upon many other types of genetic changes that can result in less subtle perturbations. Changes in chromosome structure, DNA copy number, and novel transposon insertions all create large genomic changes, which can have correspondingly large impacts on phenotypes and fitness. In this study we investigate the spectrum of adaptive mutations that arise in a population under consistently fluctuating nitrogen conditions. We specifically contrast these adaptive alleles and the mutational mechanisms that create them, with mechanisms of adaptation under batch glucose limitation and constant selection in low, non-fluctuating nitrogen conditions to address if and how selection dynamics influence the molecular mechanisms of evolutionary adaptation. We observe that retrotransposon activity accounts for a substantial number of adaptive events, along with microhomology-mediated mechanisms of insertion, deletion, and gene conversion. In addition to loss of function alleles, which are often exploited in genetic screens, we identify putative gain of function alleles and alleles acting through as-of-yet unclear mechanisms. Taken together, our findings emphasize that how selection (fluctuating vs. non-fluctuating) is applied also shapes adaptation, just as the selective pressure (nitrogen vs. glucose) does itself. Fluctuating environments can activate different mutational mechanisms, shaping adaptive events accordingly. Experimental evolution, which allows a wider array of adaptive events to be assessed, is thus a complementary approach to both classical genetic screens and natural variation studies to characterize the genotype-to-phenotype-to-fitness map.</jats:p
Mapping Fractional Vegetation Coverage across Wetland Classes of Sub-Arctic Peatlands Using Combined Partial Least Squares Regression and Multiple Endmember Spectral Unmixing
No full textVegetation communities play a key role in governing the atmospheric-terrestrial fluxes of water, carbon, nutrients, and energy. The expanse and heterogeneity of vegetation in sub-arctic peatland systems makes monitoring change at meaningful spatial resolutions and extents challenging. We use a field-collected spectral endmember reference library to unmix hyperspectral imagery and map vegetation coverage at the level of plant functional type (PFT), across three wetland sites in sub-arctic Alaska. This study explores the optimization and parametrization of multiple endmember spectral mixture analysis (MESMA) models to estimate coverage of PFTs across wetland classes. We use partial least squares regression (PLSR) to identify a parsimonious set of critical bands for unmixing and compare the reference and modeled coverage. Unmixing, using a full set of 110-bands and a smaller set of 4-bands, results in maps that effectively discriminate between PFTs, indicating a small investment in fieldwork results in maps mirroring the true ground cover. Both sets of spectral bands differentiate between PFTs, but the 4-band unmixing library results in more accurate predictive mapping with lower computational cost. Reducing the unmixing reference dataset by constraining the PFT endmembers to those identified in the field-site produces only a small advantage for mapping, suggesting extensive fieldwork may not be necessary for MESMA to have a high explanatory value in these remote environments.</jats:p
Investigating the Impact of an Exsolved H₂O CO₂ Phase on Magma Chamber Growth and Longevity: A Thermomechanical Model
No full textAbstractMagmatic volatiles drive pressure, temperature, and compositional changes in upper crustal magma chambers and alter the physical properties of stored magmas. Previous studies suggest that magmatic H2O content influences the growth and longevity of silicic chambers through regulating the size and frequency of eruptions and impacting the crystallinity‐temperature curve. However, there has been comparatively little exploration of how CO2 impacts the evolution of magma chambers despite the strong influence of CO2 on H2O solubility and the high concentrations of CO2 often present in mafic systems. In this study, we integrate the thermodynamic effects of dissolved and exsolved H2O and CO2 with the mechanics of open‐system magma chambers that interact thermally and mechanically with the crust. We applied this model to investigate how intrinsic variations in magmatic H2O‐CO2 content influence the growth and longevity of silicic and mafic magma chambers. Our findings indicate that even with a tenfold increase in CO2 content (up to 10,000 ppm), CO2 plays a minimal role in long‐term chamber growth and longevity. While CO2 content affects the magma compressibility, the resulting changes in eruption mass are balanced out by a commensurate change in eruption frequency so that the time‐averaged eruptive flux and long‐term chamber behavior remain similar. In contrast, H2O content strongly influences chamber growth and longevity. In silicic systems, high H2O contents hinder magma chamber growth by increasing the total eruptive flux and steepening the slope of the crystallinity‐temperature curve. In mafic systems, high H2O contents promote magma chamber growth by flattening the slope of the crystallinity‐temperature curve.</jats:p
Catalog of Integrated-light Star Cluster Light Curves in TESS
No full textAbstract
We present the first integrated-light, TESS-based light curves for star clusters in the Milky Way, Small Magellanic Cloud, and Large Magellanic Cloud. We explore the information encoded in these light curves, with particular emphasis on variability. We describe our publicly available package elk, which is designed to extract the light curves by applying principal component analysis to perform background light correction and incorporating corrections for TESS systematics, allowing us to detect variability on timescales shorter than ∼10 days. We perform a series of checks to ensure the quality of our light curves, removing observations where systematics are identified as dominant features, and deliver light curves for 348 previously cataloged open and globular clusters. Where TESS has observed a cluster in more than one observing sector, we provide separate light curves for each sector (for a total of 2204 light curves). We explore in detail the light curves of star clusters known to contain high-amplitude Cepheid and RR Lyrae variable stars, and we confirm that the variability of these known variables is still detectable when summed together with the light from thousands of other stars. We also demonstrate that even some low-amplitude stellar variability is preserved when integrating over a stellar population.</jats:p
Variations in climate drive behavior and survival of small desert tortoises
No full textIn the Mojave Desert, timing and amounts of precipitation profoundly affect the availability of water and annual plant foods necessary for the threatened Agassiz’s desert tortoise (Gopherus agassizii) to survive, especially during prolonged droughts. As part of recovery actions to increase declining populations, we translocated 83 juvenile and young desert tortoises raised in head-start pens for 4–10 years to a new location 15 km away during the fall of 2013 and 2014. We tracked them for 9 years during a megadrought, during multiple years of low rainfall, and a few years when precipitation neared or exceeded long-term norms. We evaluated behaviors and how precipitation and forage availability affected survival. At the end of the study, 21.6% of tortoises were alive, and six had grown to adulthood. Annual models of survival indicated that tortoise size was the driving variable in most years, followed by the number of repeatedly used burrows during periods of temperature extremes. Other variables affecting survival in ≥1 year were vegetation, movements during the first 2 years post-translocation, and condition index, a measure of health. Tortoises moved more, expanded home ranges, and grew rapidly in years when winter rainfall approached or exceeded long-term norms and annual plants were available to eat. During dry years, movements and growth were limited. Exceptions to this pattern occurred in the last year of study, a dry year: tortoises grew and moved more, and home ranges increased. The increase in size and approaching adulthood may have stimulated greater traveling. Some left the study area, indicating a need for large release areas. We may have aided survival by offering water twice yearly when handling because some tortoises drank and increased in mass up to 40%. Prolonged droughts and hotter temperatures can limit the recovery of populations, reduce the survival of young tortoises, and increase the time to maturity.</jats:p
Direct air capture (DAC) and sequestration of CO <sub>2</sub> : Dramatic effect of coordinated Cu(II) onto a chelating weak base ion exchanger
No full text
Direct air capture (DAC) is important for achieving net-zero greenhouse gas emissions by 2050. However, the ultradilute atmospheric CO
2
concentration (~400 parts per million) poses a formidable hurdle for high CO
2
capture capacities using sorption-desorption processes. Here, we present a Lewis acid-base interaction–derived hybrid sorbent with polyamine-Cu(II) complex enabling over 5.0 mol of CO
2
capture/kg sorbent, nearly two to three times greater capacity than most of the DAC sorbents reported to date. The hybrid sorbent, such as other amine-based sorbents, is amenable to thermal desorption at less than 90°C. In addition, seawater was validated as a viable regenerant, and the desorbed CO
2
is simultaneously sequestered as innocuous, chemically stable alkalinity (NaHCO
3
). The dual-mode regeneration offers unique flexibility and facilitates using oceans as decarbonizing sinks to widen DAC application opportunities.
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