Environmental Factors Associated With Triploid Aspen Occurrence in Intermountain West Landscapes

Polyploidy is common among plants and can contribute to physiological and morphological differences, altering how plants respond to environmental changes, promoting genetic diversification and even species radiation. Quaking aspen (Populus tremuloides), a keystone species associated with high plant and animal diversity is frequently found in mixed diploid/triploid populations in the Intermountain West. Triploid aspen carries an extra chromosomal copy, whereas the diploid type contains two chromosomal copies. High mortality rates and widespread population declines in aspen are of increasing concern in the Intermountain West, and often ascribed to changing climates and drought stress events. The goal of this study was to better understand environmental factors influencing the distribution of triploid aspen population in the Intermountain West. Using restriction-site associated DNA sequencing (RAD-seq), a method used to identify thousands of genetic markers from a group of individuals, we examined the occurrence of diploid and triploid aspen populations at various spatial scales in relation to environmental variables associated with soil moisture content. Our results suggest that triploidy in aspen on the landscape is associated with environmental variables related to soil moisture and may be influenced by specific local variations in topography, climate, and precipitation patterns. Overall, we found that conditions associated with low soil moisture were associated with lower frequencies of triploid aspen. Our results suggest that triploid aspen clones may be more susceptible to mortality than diploid clones in the warmer, drier climates expected with climate change. We acknowledge, however, that there are many knowledge gaps regarding the generation and persistence of triploid aspen clones. Understanding the causes and consequences of triploidy in aspen will be important in predicting and managing aspen persistence in landscapes of the western U. S. under changing climate conditions

System model development for nuclear thermal propulsion

A critical enabling technology in the evolutionary development of nuclear thermal propulsion (NTP) is the ability to predict the system performance under a variety of operating conditions. This is crucial for mission analysis and for control subsystem testing as well as for the modeling of various failure modes. Performance must be accurately predicted during steady-state and transient operation, including startup, shutdown, and post operation cooling. The development and application of verified and validated system models has the potential to reduce the design, testing, and cost and time required for the technology to reach flight-ready status. Since Oct. 1991, the U.S. Department of Energy (DOE), Department of Defense (DOD), and NASA have initiated critical technology development efforts for NTP systems to be used on Space Exploration Initiative (SEI) missions to the Moon and Mars. This paper presents the strategy and progress of an interagency NASA/DOE/DOD team for NTP system modeling. It is the intent of the interagency team to develop several levels of computer programs to simulate various NTP systems. The first level will provide rapid, parameterized calculations of overall system performance. Succeeding computer programs will provide analysis of each component in sufficient detail to guide the design teams and experimental efforts. The computer programs will allow simulation of the entire system to allow prediction of the integrated performance. An interagency team was formed for this task to use the best capabilities available and to assure appropriate peer review

Evaluating Mixed-Initiative Procedural Level Design Tools using a Triple-Blind Mixed-Method User Study

Results from a triple-blind mixed-method user study into the effectiveness of mixed-initiative tools for the procedural generation of game levels are presented. A tool which generates levels using interactive evolutionary optimisation was designed for this study which (a) is focused on supporting the designer to explore the design space and (b) only requires the designer to interact with it by designing levels. The tool identifies level design patterns in an initial hand-designed map and uses that information to drive an interactive optimisation algorithm. A rigorous user study was designed which compared the experiences of designers using the mixed-initiative tool to designers who were given a tool which provided completely random level suggestions. The designers using the mixed-initiative tool showed an increased engagement in the level design task, reporting that it was effective in inspiring new ideas and design directions. This provides significant evidence that procedural content generation can be used as a powerful tool to support the human design process

Ce(OH)2Cl and lanthanide-substituted variants as precursors to redox-active CeO2 materials

The cerium(III) hydroxide chloride Ce(OH)2Cl crystallises directly as a polycrystalline powder from a solution of CeCl3·7H2O in poly(ethylene) glycol (Mn = 400) heated at 240 °C and is found to be isostructural with La(OH)2Cl, as determined from high-resolution synchrotron powder X-ray diffraction (P21/m, a = 6.2868(2) Å, b = 3.94950(3) Å, c = 6.8740(3) Å, β = 113.5120(5)°). Replacement of a proportion of the cerium chloride in synthesis by a second lanthanide chloride yields a set of materials Ce1−xLnx(OH)2Cl for Ln = La, Pr, Gd, Tb. For La the maximum value of x is 0.2, with an isotropic expansion of the unit cell, but for the other lanthanides a wider composition range is possible, and the lattice parameters show an isotropic contraction with increasing x. Thermal decomposition of the hydroxide chlorides at 700 °C yields mixed-oxides Ce1−xLnxO2−δ that all have cubic fluorite structures with either expanded (Ln = La, Gd) or contracted (Ln = Pr, Tb) unit cells compared to CeO2. Scanning electron microscopy shows a shape memory effect in crystal morphology upon decomposition, with clusters of anisotropic sub-micron crystallites being seen in the precursor and oxide products. The Pr- and Tb-substituted oxides contain the substituent in a mixture of +3 and +4 oxidation states, as seen by X-ray absorption near edge structure spectroscopy at the lanthanide LIII edges. The mixed oxide materials are examined using temperature programmed reduction in 10%H2 in N2, which reveals redox properties suitable for heterogeneous catalysis, with the Pr-substituted materials showing the greatest reducibility at lower temperature

NICER/NuSTAR Characterization of 4U 1957+11: A Near Maximally Spinning Black Hole Potentially in the Mass Gap

© 2023. The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the Creative Commons Attribution License, to view a copy of the license, see: https://creativecommons.org/licenses/by/4.0/4U 1957+11 is a black hole candidate system that has been in a soft X-ray spectral state since its discovery. We present analyses of recent joint NICER and NuSTAR spectra, which are extremely well described by a highly inclined disk accreting into a near maximally spinning black hole. Owing to the broad X-ray coverage of NuSTAR, the fitted spin and inclination are strongly constrained for our hypothesized disk models. The faintest spectra are observed out to 20 keV, even though their hard tail components are almost absent when described with a simple corona. The hard tail increases with luminosity, but shows clear two-track behavior with one track having appreciably stronger tails. The disk spectrum color-correction factor is anticorrelated with the strength of the hard tail (e.g., as measured by the Compton y parameter). Although the spin and inclination parameters are strongly constrained for our chosen model, the mass and distance are degenerate parameters. We use our spectral fits, along with a theoretical prior on color-correction, an observational prior on likely fractional Eddington luminosity, and an observational prior on distance obtained from Gaia studies, to present mass and distance contours for this system. The most likely parameters, given our presumed disk model, suggest a 4.6 M ⊙ black hole at 7.8 kpc observed at luminosities ranging from ≈1.7% to 9% of Eddington. This would place 4U 1957+11 as one of the few actively accreting sources within the mass gap of ≈2–5 M ⊙ where there are few known massive neutron stars or low-mass black holes. Higher mass and distance, however, remain viable.Peer reviewe

The Soft-Excess in Mrk 509: Warm Corona or Relativistic Reflection?

We present the analysis of the first NuSTAR observations ($\sim 220$ ks), simultaneous with the last SUZAKU observations ($\sim 50$ ks), of the active galactic nucleus of the bright Seyfert 1 galaxy Mrk 509. The time-averaged spectrum in the $1-79$ keV X-ray band is dominated by a power-law continuum ($\Gamma\sim 1.8-1.9$), a strong soft excess around 1 keV, and signatures of X-ray reflection in the form of Fe K emission ($\sim 6.4$ keV), an Fe K absorption edge ($\sim 7.1$ keV), and a Compton hump due to electron scattering ($\sim 20-30$ keV). We show that these data can be described by two very different prescriptions for the soft excess: a warm ($kT\sim 0.5-1$ keV) and optically thick ($\tau\sim10-20$) Comptonizing corona, or a relativistically blurred ionized reflection spectrum from the inner regions of the accretion disk. While these two scenarios cannot be distinguished based on their fit statistics, we argue that the parameters required by the warm corona model are physically incompatible with the conditions of standard coronae. Detailed photoionization calculations show that even in the most favorable conditions, the warm corona should produce strong absorption in the observed spectrum. On the other hand, while the relativistic reflection model provides a satisfactory description of the data, it also requires extreme parameters, such as maximum black hole spin, a very low and compact hot corona, and a very high density for the inner accretion disk. Deeper observations of this source are thus necessary to confirm the presence of relativistic reflection, and to further understand the nature of its soft excess.Comment: Accepted for publication in ApJ, 18 pages, 7 figure

Further Examination of the Geographic Range of Eriogonum corymbosum var. nilesii (Polygonaceae, Eriogoneae)

The wild buckwheat Eriogonum corymbosum is widely distributed throughout the southwestern United States, forming a complex of eight varieties. E. corymbosum var. nilesii is a predominantly yellow-flowered variant reported primarily from Clark Co., Nevada. A previous genetic study by our research group found that var. nilesii is genetically distinct from other E. corymbosum varieties, based on a limited number of populations. Here, we assess genetic variation in 14 newly sampled yellow-flowered populations from southern Nevada, southern Utah, and northern Arizona, and compare them to genetic variation in six populations of previously determined E. corymbosum varieties. Of the new populations, we identified four as var. nilesii, four as var. aureum, three as var. glutinosum, two as apparent hybrids involving vars. aureum and nilesii, and one as a more distantly related admixture involving E. thompsoniae. Our results extend the range and area of E. corymbosum var. nilesii considerably from that traditionally stated in the literature. However, this extended range is confined to the Mojave Desert region of southern Nevada, and the number of known populations remains limited

Adoption and Abandonment of Precision Soil Sampling in Cotton Production

Technology adoption in precision agriculture has received considerable attention, while abandonment has received little. Our objective was to identify factors motivating adoption and abandonment of precision soil sampling in cotton. Results indicate younger producers who farmed more cotton area, owned more of their cropland, planted more non-cotton area, used a computer, or used a Personal Digital Assistant (PDA) were more likely to adopt precision soil sampling. Those with more cotton area or who owned livestock were more likely to abandon, while those who used precision soil sampling longer, used a PDA, or used variable-rate fertilizer application were less likely to abandon.Crop Production/Industries,