Range-wide sources of variation in reproductive rates of northern spotted owls

We conducted a range-wide investigation of the dynamics of site-level reproductive rate of northern spotted owls using survey data from 11 study areas across the subspecies geographic range collected during 1993–2018. Our analytical approach accounted for imperfect detection of owl pairs and misclassification of successful reproduction (i.e., at least one young fledged) and contributed further insights into northern spotted owl population ecology and dynamics. Both nondetection and state misclassification were important, especially because factors affecting these sources of error also affected focal ecological parameters. Annual probabilities of site occupancy were greatest at sites with successful reproduction in the previous year and lowest for sites not occupied by a pair in the previous year. Site-specific occupancy transition probabilities declined over time and were negatively affected by barred owl presence. Overall, the site-specific probability of successful reproduction showed substantial year-to-year fluctuations and was similar for occupied sites that did or did not experience successful reproduction the previous year. Site-specific probabilities for successful reproduction were very small for sites that were unoccupied the previous year. Barred owl presence negatively affected the probability of successful reproduction by northern spotted owls in Washington and California, as predicted, but the effect in Oregon was mixed. The proportions of sites occupied by northern spotted owl pairs showed steep, near-monotonic declines over the study period, with all study areas showing the lowest observed levels of occupancy to date. If trends continue it is likely that northern spotted owls will become extirpated throughout large portions of their range in the coming decades

MAJOR REPOSITORY DESIGN ISSUES

The Yucca Mountain Project is focused on producing a four-part viability assessment in late FY98. Its four components (design, performance assessment, cost estimate, and licensing development plan) must be consistent. As a tool to compare design and performance assessment options, a series of repository pictures were developed for the sequential time phases of a repository. The boundaries of the time phases correspond to evolution in the engineered barrier system (EBS)

Circumventing Thermodynamics to Synthesize Highly Metastable Tin(II) Perovskites: Nano Eggshells of SnHfO3

Sn(II)-based perovskite oxides, being the subject of longstanding theoretical interest for the past two decades, have been synthesized for the first time with a nanoshell approach. All past reported synthetic attempts had been rendered impotent by the extremely high metastabilities, i.e., thermodynamic instability. Herein, a soft topotactic exchange of Sn(II) cations into Ba-containing perovskites is demonstrated to successfully yield ~20 nm thick shells of Sn(II) perovskites, i.e. SnHfO3. Additionally, highly pure SnHfO3 was obtained for the first time as nano-eggshell morphologies that circumvent the intrinsic ion-diffusion limits occurring at a low reaction temperature of 200 oC. In summary, the high metastability of the Sn(II) perovskites is shown to be overcome by leveraging the high cohesive energies of the reactants, the exothermic formation of a stable salt side product, and a shortened diffusion pathway for the Sn(II) cations. The new approach finally provides an effective solution to surmounting highly intractable synthetic barriers, and which can be the key to unlocking the door to many other new metastable oxides