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  • 1
    Publication Date: 2015-11-25
    Description: We report constraints on the three-dimensional orbital architecture for all four planets known to orbit the nearby M dwarf Gliese 876 based solely on Doppler measurements and demanding long-term orbital stability. Our data set incorporates publicly available radial velocities taken with the ELODIE and CORALIE spectrographs, High Accuracy Radial velocity Planet Searcher (HARPS), and Keck HIgh Resolution Echelle Spectrometer (HIRES) as well as previously unpublished HIRES velocities. We first quantitatively assess the validity of the planets thought to orbit GJ 876 by computing the Bayes factors for a variety of different coplanar models using an importance sampling algorithm. We find that a four-planet model is preferred over a three-planet model. Next, we apply a Newtonian Markov chain Monte Carlo algorithm to perform a Bayesian analysis of the planet masses and orbits using an N -body model in three-dimensional space. Based on the radial velocities alone, we find that a 99 per cent credible interval provides upper limits on the mutual inclinations for the three resonant planets ( cb  〈 6 $_{.}^{\circ}$ 20 for the ${c}$ and ${b}$ pair and be  〈 28 $_{.}^{\circ}$ 5 for the ${b}$ and ${e}$ pair). Subsequent dynamical integrations of our posterior sample find that the GJ 876 planets must be roughly coplanar ( cb  〈 2 $_{.}^{\circ}$ 60 and be  〈 7 $_{.}^{\circ}$ 87), suggesting that the amount of planet–planet scattering in the system has been low. We investigate the distribution of the respective resonant arguments of each planet pair and find that at least one argument for each planet pair and the Laplace argument librate. The libration amplitudes in our three-dimensional orbital model support the idea of the outer three planets having undergone significant past disc migration.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 2
    Publication Date: 2014-12-14
    Description: Langmuir DOI: 10.1021/la503690t
    Print ISSN: 0743-7463
    Electronic ISSN: 1520-5827
    Topics: Chemistry and Pharmacology
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  • 3
    Publication Date: 2019
    Description: People possess a creative set of strategies based on their local knowledge (LK) that allow them to stay in flood-prone areas. Stakeholders involved with local level flood risk management (FRM) often overlook and underutilise this LK. There is thus an increasing need for its identification, documentation and assessment. Based on qualitative research, this paper critically explores the notion of LK in Malawi. Data was collected through 15 focus group discussions, 36 interviews and field observation, and analysed using thematic analysis. Findings indicate that local communities have a complex knowledge system that cuts across different stages of the FRM cycle and forms a component of community resilience. LK is not homogenous within a community, and is highly dependent on the social and political contexts. Access to LK is not equally available to everyone, conditioned by the access to resources and underlying causes of vulnerability that are outside communities’ influence. There are also limits to LK; it is impacted by exogenous processes (e.g., environmental degradation, climate change) that are changing the nature of flooding at local levels, rendering LK, which is based on historical observations, less relevant. It is dynamic and informally triangulated with scientific knowledge brought about by development partners. This paper offers valuable insights for FRM stakeholders as to how to consider LK in their approaches.
    Electronic ISSN: 2071-1050
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI
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  • 4
    Publication Date: 2016-07-06
    Description: We invite readers to dig for ganguri (yams) at and with Bawaka, an Indigenous Homeland in northern Australia, and, in doing so, consider an Indigenous-led understanding of relational space/place. We draw on the concept of gurrutu to illustrate the limits of western ontologies, open up possibilities for other ways of thinking and theorizing, and give detail and depth to the notion of space/place as emergent co-becoming. With Bawaka as lead author, we look to Country for what it can teach us about how all views of space are situated, and for the insights it offers about co-becoming in a relational world.
    Print ISSN: 0309-1325
    Electronic ISSN: 1477-0288
    Topics: Geography
    Published by Sage
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  • 5
    Publication Date: 2015-04-21
    Description: We use picosecond ultrasonics to image animal cells in vitro —a bovine aortic endothelial cell and a mouse adipose cell—fixed to Ti-coated sapphire. Tightly focused ultrashort laser pulses generate and detect GHz acoustic pulses, allowing three-dimensional imaging ( x , y , and t ) of the ultrasonic propagation in the cells with ∼1  μ m lateral and ∼150 nm depth resolutions. Time-frequency representations of the continuous-wavelet-transform amplitude of the optical reflectivity variations inside and outside the cells show GHz Brillouin oscillations, allowing the average sound velocities of the cells and their ultrasonic attenuation to be obtained as well as the average bulk moduli.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 6
    Publication Date: 2015-06-25
    Description: We investigate surface phonon propagation in a triangular-lattice phononic crystal of microscopic holes in a gold-coated polymer by time-resolved two-dimensional imaging and by finite-element simulations at sub-gigahertz frequencies. The simulations allow the effects of exciting different points in the crystal lattice to be studied in real space, and also in k -space by spatiotemporal Fourier analysis. The acoustic field in a sub-surface plane below the reach of the holes is also revealed in real- and k -spaces. In addition, we demonstrate pitfalls in the analysis of k -space data when searching for the presence of band gaps. Applications include surface-acoustic wave filter quality control.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 7
    Publication Date: 2016-01-21
    Description: Author(s): Sam H. Lee and Oliver B. Wright This paper provides a warning to the acoustic metamaterials community to be careful not to mistake the sign or value of the effective parameters, i.e. the density and modulus, of acoustic metamaterials for want of an overall picture of the physics involved. The authors here provide a new picture of the functioning of acoustic metamaterials based on hidden forces and hidden sources of volume. The new ansatz is tested on some established acoustic metamaterials with elements based on membranes, Helmholtz resonators, springs, and masses. It should provide the basis for a clearer vision of acoustic metamaterials and a faster route to real-world applications. [Phys. Rev. B 93, 024302] Published Thu Jan 14, 2016
    Keywords: Dynamics, dynamical systems, lattice effects
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
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  • 8
    Publication Date: 2012-04-20
    Description: The objective of this study is to characterize the climatology of extreme rainfall and flash flooding in Atlanta, Georgia using high-resolution land surface, rainfall, and discharge datasets. We examine nine urban watersheds in the Atlanta area that range in size from 3.7 to 225 km2 and exhibit a range of urban development and land-use characteristics. We develop a high-resolution 15 min, 1 km2 radar rainfall data set for the 2002–2010 period using the Hydro-NEXRAD system with volume scan reflectivity observations from the Atlanta WSR-88D radar and rainfall observations from a dense network of 72 U.S. Geological Survey rain gauges. Bias-corrected radar rainfall fields accurately capture the spatial and temporal structure of heavy rainfall. There is enhancement of heavy rainfall within and east of the urban core, and a rainfall minimum north and northwest of the city. There has been an increase in variability of annual flood peaks in Atlanta since the 1960s associated with urban impacts on runoff production. Flood response is dependent on a combination of basin size, drainage network structure, spatial distribution of land use, and basin storage in urban soils and storm water detention ponds. Future studies of urban rainfall modification in Atlanta and elsewhere should consider the influence of regional topography and other geographic features on the storm environment.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
    Publication Date: 2012-04-25
    Description: To use lymphocytes as surrogate cells to investigate their in vitro sensitivities to ultraviolet (UV) treatment in different cancers and precancerous states by comparison with lymphocytes from healthy control individuals was the main aim of this research. UV light induces precise cellular and genomic mutations. In this study, the effect of ultraviolet A (UVA) (320–400 nm) was used as a generic mutagen to evaluate in vitro different sensitivities from lymphocytes of patients with suspected melanoma (SM), malignant melanoma (MM), polyposis coli (PC) and colorectal cancer (CRC). DNA damage was evaluated by two different methods: the micronucleus (MN) assay and the Comet assay. The baseline frequency of MNs was significantly increased in lymphocytes from all patients (SM, MM, PC and CRC) when compared to healthy individuals. After UV irradiation, MN frequencies were significantly increased in lymphocytes of all groups, both patients and healthy individuals. However, the MN frequency in all patient groups was significantly higher than in the healthy individual group. Similar results for the induction of genomic DNA damage were obtained for the Comet assay. Also for the Comet assay, UVA-induced DNA damage for all four patient groups was significantly increased when compared to healthy individuals (SM, MM, PC and CRC groups: P 〈 0.001). Conclusively, peripheral lymphocytes from patients with cancers MM and CRC or precancerous states SM and PC are more sensitive to a generic mutagen such as UVA than lymphocytes from healthy individuals. This feature may be used as an essential biomarker to screen and diagnose precancerous states and cancers in early stages.
    Print ISSN: 0267-8357
    Electronic ISSN: 1464-3804
    Topics: Biology , Medicine
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  • 10
    Publication Date: 2011-07-19
    Description: Author(s): Robert D. Guy, Toshiyuki Nakagaki, and Grady B. Wright A model is presented to explain the development of flow channels within the cytoplasm of the plasmodium of the giant amoeba Physarum polycephalum . The formation of channels is related to the development of a self-organizing tubular network in large cells. Experiments indicate that the flow of cytopl... [Phys. Rev. E 84, 016310] Published Mon Jul 18, 2011
    Keywords: Fluid dynamics
    Print ISSN: 1539-3755
    Electronic ISSN: 1550-2376
    Topics: Physics
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