989 research outputs found
Maps of the Southern Millimeter-wave Sky from Combined 2500 deg^2 SPT-SZ and Planck Temperature Data
We present three maps of the millimeter-wave sky created by combining data from the South Pole Telescope (SPT) and the Planck satellite. We use data from the SPT-SZ survey, a survey of 2540 deg^2 of the the sky with arcminute resolution in three bands centered at 95, 150, and 220 GHz, and the full-mission Planck temperature data in the 100, 143, and 217 GHz bands. A linear combination of the SPT-SZ and Planck data is computed in spherical harmonic space, with weights derived from the noise of both instruments. This weighting scheme results in Planck data providing most of the large-angular-scale information in the combined maps, with the smaller-scale information coming from SPT-SZ data. A number of tests have been done on the maps. We find their angular power spectra to agree very well with theoretically predicted spectra and previously published results
Rates of species introduction to a remote oceanic island
The introduction of species to areas beyond the limits of their natural distributions has a major homogenizing influence, making previously distinct biotas more similar. The scale of introductions has frequently been commented on, but their rate and spatial pervasiveness have been less well quantified. Here, we report the findings of a detailed study of pterygote insect introductions to Gough Island, one of the most remote and supposedly pristine temperate oceanic islands, and estimate the rate at which introduced species have successfully established.
Out of 99 species recorded from Gough Island, 71 are established introductions, the highest proportion documented for any Southern Ocean island. Estimating a total of approximately 233 landings on Gough Island since first human landfall, this equates to one successful establishment for every three to four landings. Generalizations drawn from other areas suggest that this may be only one-tenth of the number of pterygote species that have arrived at the island, implying that most landings may lead to the arrival of at least one alien. These rates of introduction of new species are estimated to be two to three orders of magnitude greater than background levels for Gough Island, an increase comparable to that estimated for global species extinctions (many of which occur on islands) as a consequence of human activities
Photon rockets and gravitational radiation
The absence of gravitational radiation in Kinnersley's ``photon rocket''
solution of Einstein's equations is clarified by studying the mathematically
well-defined problem of point-like photon rockets in Minkowski space (i.e.
massive particles emitting null fluid anisotro\-pically and accelerating
because of the recoil). We explicitly compute the (uniquely defined) {\it
linearized} retarded gravitational waves emitted by such objects, which are the
coherent superposition of the gravitational waves generated by the motion of
the massive point-like rocket and of those generated by the energy-momentum
distribution of the photon fluid. In the special case (corresponding to
Kinnersley's solution) where the anisotropy of the photon emission is purely
dipolar we find that the gravitational wave amplitude generated by the
energy-momentum of the photons exactly cancels the usual gravitational
wave amplitude generated by the accelerated motion of the rocket. More general
photon anisotropies would, however, generate genuine gravitational radiation at
infinity. Our explicit calculations show the compatibility between the
non-radiative character of Kinnersley's solution and the currently used
gravitational wave generation formalisms based on post-Minkowskian perturbation
theory.Comment: 21 pages, LATEX, submitted to Class. Quant. Gra
Maps of the Southern Millimeter-wave Sky from Combined 2500 deg^2 SPT-SZ and Planck Temperature Data
We present three maps of the millimeter-wave sky created by combining data from the South Pole Telescope (SPT) and the Planck satellite. We use data from the SPT-SZ survey, a survey of 2540 deg^2 of the the sky with arcminute resolution in three bands centered at 95, 150, and 220 GHz, and the full-mission Planck temperature data in the 100, 143, and 217 GHz bands. A linear combination of the SPT-SZ and Planck data is computed in spherical harmonic space, with weights derived from the noise of both instruments. This weighting scheme results in Planck data providing most of the large-angular-scale information in the combined maps, with the smaller-scale information coming from SPT-SZ data. A number of tests have been done on the maps. We find their angular power spectra to agree very well with theoretically predicted spectra and previously published results
Afshar's Experiment does not show a Violation of Complementarity
A recent experiment performed by S. Afshar [first reported by M. Chown, New
Scientist {\bf 183}, 30 (2004)] is analyzed. It was claimed that this
experiment could be interpreted as a demonstration of a violation of the
principle of complementarity in quantum mechanics. Instead, it is shown here
that it can be understood in terms of classical wave optics and the standard
interpretation of quantum mechanics. Its performance is quantified and it is
concluded that the experiment is suboptimal in the sense that it does not fully
exhaust the limits imposed by quantum mechanics.Comment: 6 pages, 6 figure
Synthetic Quantum Systems
So far proposed quantum computers use fragile and environmentally sensitive
natural quantum systems. Here we explore the new notion that synthetic quantum
systems suitable for quantum computation may be fabricated from smart
nanostructures using topological excitations of a stochastic neural-type
network that can mimic natural quantum systems. These developments are a
technological application of process physics which is an information theory of
reality in which space and quantum phenomena are emergent, and so indicates the
deep origins of quantum phenomena. Analogous complex stochastic dynamical
systems have recently been proposed within neurobiology to deal with the
emergent complexity of biosystems, particularly the biodynamics of higher brain
function. The reasons for analogous discoveries in fundamental physics and
neurobiology are discussed.Comment: 16 pages, Latex, 1 eps figure fil
Biological survey of the Prince Edward Islands, December 2008
A biological survey of the Prince Edward Islands took place in December 2008. The survey repeated an earlier survey of the populations of surface-nesting seabirds on both islands and of fur seals (Arctocephalus spp.) and alien plants on Prince Edward Island in December 2001. Observations on burrowing seabirds, macro-invertebrates and plant communities on Prince Edward Island and an oceanographic survey of surrounding waters were also included. The survey confirmed many of the observations made on the earlier survey and permitted an assessment of trends in the abundance and distribution of biota since 2001
Using nearâground leaf temperatures alters the projected climate change impacts on the historical range of a floristic biodiversity hotspot
This is the final version. Available from Wiley via the DOI in this record.âŻDATA AVAILABILITY STATEMENT:
All datasets used are third-party datasets available freely on public repositories. The occurrence data for plant species in the Cape
floristic Region are freely available from the Global Biodiversity
Information Facility (www.gbif.org), and the occurrence data used in
this study is available at: https://doi.org/10.5281/zenodo.6374097;
the hourly climate data are available from the ERA5 fifth-generation
ECMWF atmospheric reanalysis of the global climate (https://cds.
climate.copernicus.eu/cdsapp#!/home); hourly near-ground temperatures are fully reproducible using the microclimf package for R 4.0
(https://mrke.github.io); temperature data from the Cederberg used
for verification were sourced via the SOILTEMP global database of
soil temperatures (https://soiltemp.weebly.com/). All figures created
for this study are also available on Figshare (private link: https://
figshare.com/s/d40f9cb44441b252318c).Aim: Species distribution models (SDMs) have been used widely to predict the responses of species to climate change. However, the climate data used to drive these models typically represents ambient air temperatures, derived from measurements taken 1â2 m above the ground. Most plant species live near the ground where temperatures can differ significantly, owing to the effects of solar radiation and reduced wind speed. Here, we investigate differences in spatio-temporal patterns in near-ground leaf and ambient air temperatures and the implications this has on projected changes in species richness of a suite of Fynbos plant species. Location: Fynbos Biome, South Africa. Methods: For each individual plant species (n = 83), we constructed two types of SDMs: one using ambient air temperatures and one using near-ground leaf temperatures. Each of these models was fitted to species occurrence data for a recent time period and projected backwards into the past. Species richness projections for both time periods were then constructed using binarized projections. Results: We found that the impact of climate change on species richness â both the degree of suitable climate lost from the historical range and gained outside of the historical range â was greater using SDMs built with near-ground leaf temperatures. Independent validation of the hindcast projections revealed near-ground SDMs to be more accurate. Main Conclusions: Our study suggests that SDMs constructed using ambient air temperatures are likely overestimating the breadth of the speciesâ occupied thermal niche, thus underestimating the climate change-driven risk to species where near-ground leaf and ambient air temperatures are particularly decoupled from one another. Additionally, ambient air SDMs may be underestimating the ex-situ refugial potential of inland mountains. Ambient air temperatures should not be considered an effective surrogate for investigating climate change impacts on species living near the ground
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