763 research outputs found
An assessment of ground-based techniques for detecting other planetary systems. Volume 1: An overview
The feasibility and limitations of ground-based techniques for detecting other planetary systems are discussed as well as the level of accuracy at which these limitations would occur and the extent to which they can be overcome by new technology and instrumenation. Workshop conclusions and recommendations are summarized and a proposed high priority program is considered
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An Assessment of Ground-Based Techniques for Detecting Other Planetary Systems. Volume 2: Position papers
The capabilities of several astronomical interferomenter system concepts are assessed and the effects of the Earth's atmosphere on astrometric precision are examined in detail. Included is an examination of the use of small aperture interferometry to detect planets in binary star systems. It is estimated that, for differential astrometric observation, an amplitude interferometer having two separate telescopes should permit observations of stars as faint as 14th magnitude and a positional accuracy of 0.00005 arc-sec. Instrumental, atmospheric, and photon noise errors that apply to interferometric observation are examined. It is suggested that the effects of atmospheric turbulence may be eliminated with the use of two color refractometer systems. Several sites for future telescopes dedicated to the search for planetary systems are identified
A large-scale proteogenomics study of apicomplexan pathogens-Toxoplasma gondii and Neospora caninum
Proteomics data can supplement genome annotation efforts, for example being used to confirm gene models or correct gene annotation errors. Here, we present a large‐scale proteogenomics study of two important apicomplexan pathogens: Toxoplasma gondii and Neospora caninum. We queried proteomics data against a panel of official and alternate gene models generated directly from RNASeq data, using several newly generated and some previously published MS datasets for this meta‐analysis. We identified a total of 201 996 and 39 953 peptide‐spectrum matches for T. gondii and N. caninum, respectively, at a 1% peptide FDR threshold. This equated to the identification of 30 494 distinct peptide sequences and 2921 proteins (matches to official gene models) for T. gondii, and 8911 peptides/1273 proteins for N. caninum following stringent protein‐level thresholding. We have also identified 289 and 140 loci for T. gondii and N. caninum, respectively, which mapped to RNA‐Seq‐derived gene models used in our analysis and apparently absent from the official annotation (release 10 from EuPathDB) of these species. We present several examples in our study where the RNA‐Seq evidence can help in correction of the current gene model and can help in discovery of potential new genes
Systematic derivation of hydrodynamic equations for viscoelastic phase separation
(abridged) We present a detailed derivation of a simple hydrodynamic
two-fluid model, which aims at the description of the phase separation of
non-entangled polymer solutions, where viscoelastic effects play a role. It is
directly based upon the coarse-graining of a well-defined molecular model, such
that all degrees of freedom have a clear and unambiguous molecular
interpretation. The considerations are based upon a free-energy functional, and
the dynamics is split into a conservative and a dissipative part, where the
latter satisfies the Onsager relations and the Second Law of thermodynamics.
The model is therefore fully consistent with both equilibrium and
non-equilibrium thermodynamics. The derivation proceeds in two steps: Firstly,
we derive an extended model comprising two scalar and four vector fields, such
that inertial dynamics of the macromolecules and of the relative motion of the
two fluids is taken into account. In the second step, we eliminate these
inertial contributions and, as a replacement, introduce phenomenological
dissipative terms, which can be modeled easily by taking into account the
principles of non-equilibrium thermodynamics. The final simplified model
comprises the momentum conservation equation, which includes both interfacial
and elastic stresses, a convection-diffusion equation where interfacial and
elastic contributions occur as well, and a suitably convected relaxation
equation for the end-to-end vector field. In contrast to the traditional
two-scale description that is used to derive rheological equations of motion,
we here treat the hydrodynamic and the macromolecular degrees of freedom on the
same basis. Nevertheless, the resulting model is fairly similar, though not
fully identical, to models that have been discussed previously. Notably, we
find a rheological constitutive equation that differs from the standard
Oldroyd-B model. ...Comment: Submitted to Journal of Physics Condensed Matte
Patterns of richness across forest beetle communities—A methodological comparison of observed and estimated species numbers
Abstract Species richness is a frequently used measure of biodiversity. The compilation of a complete species list is an often unattainable goal. Estimators of species richness have been developed to overcome this problem. While the use of these estimators is becoming increasingly popular, working with the observed number of species is still common practice. To assess whether patterns of beetle communities based on observed numbers may be compared among each other, we compared patterns from observed and estimated numbers of species for beetle communities in the canopy of the Leipzig floodplain forest. These patterns were species richness and the number of shared species among three tree species and two canopy strata. We tested the applicability of the asymptotic Chao1 estimator and the estimate provided by the nonasymptotic rarefaction–extrapolation method for all tree species and both upper canopy and lower canopy. In the majority of cases, the ranking patterns of species richness for host tree species and strata were the same for the observed and estimated number of species. The ranking patterns of the number of species shared among host tree species and strata, however, were significantly different between observed and estimated values. Our results indicate that the observed number of species under‐represents species richness and the number of shared species. However, ranking comparisons of published patterns based on the number of observed species may be acceptable for species richness but likely not reliable for the number of shared species. Further studies are needed to corroborate this conclusion. We encourage to use estimators and to provide open access to data to allow comparative assessments
Companion: a web server for annotation and analysis of parasite genomes
Currently available sequencing technologies enable quick and economical sequencing of many new eukaryotic parasite (apicomplexan or kinetoplastid) species or strains. Compared to SNP calling approaches, de novo assembly of these genomes enables researchers to additionally determine insertion, deletion and recombination events as well as to detect complex sequence diversity, such as that seen in variable multigene families. However, there currently are no automated eukaryotic annotation pipelines offering the required range of results to facilitate such analyses. A suitable pipeline needs to perform evidence-supported gene finding as well as functional annotation and pseudogene detection up to the generation of output ready to be submitted to a public database. Moreover, no current tool includes quick yet informative comparative analyses and a first pass visualization of both annotation and analysis results. To overcome those needs we have developed the Companion web server (http://companion.sanger.ac.uk) providing parasite genome annotation as a service using a reference-based approach. We demonstrate the use and performance of Companion by annotating two Leishmania and Plasmodium genomes as typical parasite cases and evaluate the results compared to manually annotated references
Bionovelty and ecological restoration
Anthropogenic activity has irreparably altered the ecological fabric of Earth. The emergence of ecological novelty from diverse drivers of change is an increasingly challenging dimension of ecosystem restoration. At the same time, the restorationist's tool kit continues to grow, including a variety of powerful and increasingly prevalent technologies. Thus, ecosystem restoration finds itself at the center of intersecting challenges. How should we respond to increasingly common emergence of environmental system states with little or no historical precedent, whilst considering the appropriate deployment of potentially consequential and largely untested interventions that may give rise to organisms, system states, and/or processes that are likewise without historical precedent? We use the term bionovelty to encapsulate these intersecting themes and examine the implications of bionovelty for ecological restoration
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