463 research outputs found
Consequences of a Distant Massive Planet on the Large Semi-major Axis Trans-Neptunian Objects
We explore the distant giant planet hypothesis by integrating the large
semi-major axis, large pericenter Trans-Neptunian Objects (TNOs) in the
presence of the giant planets and an external perturber whose orbit is
consistent with the proposed distant, eccentric, and inclined giant planet, so
called planet 9. We find that TNOs with semi-major axes greater than 250 au
experience some longitude of perihelion shepherding, but that a generic outcome
of such evolutions is that the TNOs evolve to larger pericenter orbits, and
commonly get raised to retrograde inclinations. This pericenter and inclination
evolution requires a massive disk of TNOs (tens of M_\Earth) in order to
explain the detection of the known sample today. Some of the highly inclined
orbits produced by the examined perturbers will be inside of the orbital
parameter space probed by prior surveys, implying a missing signature of the
9th planet scenario. The distant giant planet scenarios explored in this work
do not reproduce the observed signal of simultaneous clustering in argument of
pericenter, longitude of the ascending node, and longitude of perihelion in the
region of the known TNOs
OSSOS VI. Striking Biases in the detection of large semimajor axis Trans-Neptunian Objects
The accumulating, but small, set of large semi-major axis trans-Neptunian
objects (TNOs) shows an apparent clustering in the orientations of their
orbits. This clustering must either be representative of the intrinsic
distribution of these TNOs, or else arise as a result of observation biases
and/or statistically expected variations for such a small set of detected
objects. The clustered TNOs were detected across different and independent
surveys, which has led to claims that the detections are therefore free of
observational bias. This apparent clustering has led to the so-called "Planet
9" hypothesis that a super-Earth currently resides in the distant solar system
and causes this clustering. The Outer Solar System Origins Survey (OSSOS) is a
large program that ran on the Canada-France-Hawaii Telescope from 2013--2017,
discovering more than 800 new TNOs. One of the primary design goals of OSSOS
was the careful determination of observational biases that would manifest
within the detected sample. We demonstrate the striking and non-intuitive
biases that exist for the detection of TNOs with large semi-major axes. The
eight large semi-major axis OSSOS detections are an independent dataset, of
comparable size to the conglomerate samples used in previous studies. We
conclude that the orbital distribution of the OSSOS sample is consistent with
being detected from a uniform underlying angular distribution.Comment: Accepted for publicatio
The environmental impact of climate change adaptation on land use and water quality
Encouraging adaptation is an essential aspect of the policy response to climate change1. Adaptation seeks to reduce the harmful consequences and harness any beneficial opportunities arising from the changing climate. However, given that human activities are the main cause of environmental transformations worldwide2, it follows that adaptation itself also has the potential to generate further pressures, creating new threats for both local and global ecosystems. From this perspective, policies designed to encourage adaptation may conflict with regulation aimed at preserving or enhancing environmental quality. This aspect of adaptation has received relatively little consideration in either policy design or academic debate. To highlight this issue, we analyse the trade-offs between two fundamental ecosystem services that will be impacted by climate change: provisioning services derived from agriculture and regulating services in the form of freshwater quality. Results indicate that climate adaptation in the farming sector will generate fundamental changes in river water quality. In some areas, policies that encourage adaptation are expected to be in conflict with existing regulations aimed at improving freshwater ecosystems. These findings illustrate the importance of anticipating the wider impacts of human adaptation to climate change when designing environmental policies
Sign-reversal of the in-plane resistivity anisotropy in hole-doped iron pnictides
The in-plane anisotropy of the electrical resistivity across the coupled
orthorhombic and magnetic transitions of the iron pnictides has been
extensively studied in the parent and electron-doped compounds. All these
studies universally show that the resistivity across the long
orthorhombic axis - along which the spins couple antiferromagnetically
below the magnetic transition temperature - is smaller than the resistivity
of the short orthorhombic axis , i. e. .
Here we report that in the hole-doped compounds
BaKFeAs, as the doping level increases, the
resistivity anisotropy initially becomes vanishingly small, and eventually
changes sign for sufficiently large doping, i. e. . This
observation is in agreement with a recent theoretical prediction that considers
the anisotropic scattering of electrons by spin-fluctuations in the
orthorhombic/nematic state.Comment: This paper has been replaced by the new version offering new
explanation of the experimental results first reported her
Rotation and Spin in Physics
We delineate the role of rotation and spin in physics, discussing in order
Newtonian classical physics, special relativity, quantum mechanics, quantum
electrodynamics and general relativity. In the latter case, we discuss the
generalization of the Kepler formula to post-Newtonian order )
including spin effects and two-body effects. Experiments which verify the
theoretical results for general relativistic spin-orbit effects are discussed
as well as efforts being made to verify the spin-spin effects
Systematic Conservation Planning in the Face of Climate Change: Bet-Hedging on the Columbia Plateau
Systematic conservation planning efforts typically focus on protecting current patterns of biodiversity. Climate change is poised to shift species distributions, reshuffle communities, and alter ecosystem functioning. In such a dynamic environment, lands selected to protect today's biodiversity may fail to do so in the future. One proposed approach to designing reserve networks that are robust to climate change involves protecting the diversity of abiotic conditions that in part determine species distributions and ecological processes. A set of abiotically diverse areas will likely support a diversity of ecological systems both today and into the future, although those two sets of systems might be dramatically different. Here, we demonstrate a conservation planning approach based on representing unique combinations of abiotic factors. We prioritize sites that represent the diversity of soils, topographies, and current climates of the Columbia Plateau. We then compare these sites to sites prioritized to protect current biodiversity. This comparison highlights places that are important for protecting both today's biodiversity and the diversity of abiotic factors that will likely determine biodiversity patterns in the future. It also highlights places where a reserve network designed solely to protect today's biodiversity would fail to capture the diversity of abiotic conditions and where such a network could be augmented to be more robust to climate-change impacts
Nature and mental health: An ecosystem service perspective
This is the final version. Available on open access from American Association for the Advancement of Science via the DOI in this recordData and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Additional data related to this paper may be requested from the authors.A growing body of empirical evidence is revealing the value of nature experience for mental health. With rapid urbanization and declines in human contact with nature globally, crucial decisions must be made about how to preserve and enhance opportunities for nature experience. Here, we first provide points of consensus across the natural, social, and health sciences on the impacts of nature experience on cognitive functioning, emotional well-being, and other dimensions of mental health. We then show how ecosystem service assessments can be expanded to include mental health, and provide a heuristic, conceptual model for doing so.Doug Walker Endowed ProfessorshipCraig McKibben and Sarah MernerJohn MillerMarianne and Marcus Wallenberg FoundationWinslow FoundationGeorge Rudolf Fellowship FundVictoria and David Rogers FundMr. & Mrs. Dean A. McGee Fun
Invasive Predators Deplete Genetic Diversity of Island Lizards
Invasive species can dramatically impact natural populations, especially those living on islands. Though numerous examples illustrate the ecological impact of invasive predators, no study has examined the genetic consequences for native populations subject to invasion. Here we capitalize on a natural experiment in which a long-term study of the brown anole lizard (Anolis sagrei) was interrupted by rat invasion. An island population that was devastated by rats recovered numerically following rat extermination. However, population genetic analyses at six microsatellite loci suggested a possible loss of genetic diversity due to invasion when compared to an uninvaded island studied over the same time frame. Our results provide partial support for the hypothesis that invasive predators can impact the genetic diversity of resident island populations
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