199 research outputs found

    Crossing Disciplinary Boundaries to Understand Human Drivers of Environmental Threats

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    A wide range of ecological studies affirms the cumulative damage to ecosystem capital and services around the globe. They also point to the overwhelming role that anthropogenic or human drivers play in global ecological damage. The MAHB is intended to combine what we know about human drivers of environmental threats with what the social sciences know about changing human behavior and institutions. A variety of social sciences have taken up the first task of identifying the key human activities—at both the local, cumulative level and at the systemic level—most responsible for global environmental change. Considerable progress has been made in our understanding of land use and land cover change, of vulnerability, resilience, and adaptation, of the governance of common pool resources, and of demographic and economic factors. Each of these advances is the result of integrating ecological principals and findings into disciplined social science research. This presentation highlights one of these integrating approaches, the STIRPAT approach, that adds social and political variables and statistical sophistication from the social sciences to the widely adopted IPAT formula.
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    Bringing "The Moth" to Light: A Planet-Sculpting Scenario for the HD 61005 Debris Disk

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    The HD 61005 debris disk ("The Moth") stands out from the growing collection of spatially resolved circumstellar disks by virtue of its unusual swept-back morphology, brightness asymmetries, and dust ring offset. Despite several suggestions for the physical mechanisms creating these features, no definitive answer has been found. In this work, we demonstrate the plausibility of a scenario in which the disk material is shaped dynamically by an eccentric, inclined planet. We present new Keck NIRC2 scattered-light angular differential imaging of the disk at 1.2-2.3 microns that further constrains its outer morphology (projected separations of 27-135 AU). We also present complementary Gemini Planet Imager 1.6 micron total intensity and polarized light detections that probe down to projected separations less than 10 AU. To test our planet-sculpting hypothesis, we employed secular perturbation theory to construct parent body and dust distributions that informed scattered-light models. We found that this method produced models with morphological and photometric features similar to those seen in the data, supporting the premise of a planet-perturbed disk. Briefly, our results indicate a disk parent body population with a semimajor axis of 40-52 AU and an interior planet with an eccentricity of at least 0.2. Many permutations of planet mass and semimajor axis are allowed, ranging from an Earth mass at 35 AU to a Jupiter mass at 5 AU.Comment: Accepted to AJ; added Figure 5 and minor text edit

    The Gemini Planet Imager Exoplanet Survey: Giant Planet and Brown Dwarf Demographics From 10-100 AU

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    We present a statistical analysis of the first 300 stars observed by the Gemini Planet Imager Exoplanet Survey (GPIES). This subsample includes six detected planets and three brown dwarfs; from these detections and our contrast curves we infer the underlying distributions of substellar companions with respect to their mass, semi-major axis, and host stellar mass. We uncover a strong correlation between planet occurrence rate and host star mass, with stars M >> 1.5 MM_\odot more likely to host planets with masses between 2-13 MJup_{\rm Jup} and semi-major axes of 3-100 au at 99.92% confidence. We fit a double power-law model in planet mass (m) and semi-major axis (a) for planet populations around high-mass stars (M >> 1.5M_\odot) of the form d2Ndmdamαaβ\frac{d^2 N}{dm da} \propto m^\alpha a^\beta, finding α\alpha = -2.4 ±\pm 0.8 and β\beta = -2.0 ±\pm 0.5, and an integrated occurrence rate of 94+59^{+5}_{-4}% between 5-13 MJup_{\rm Jup} and 10-100 au. A significantly lower occurrence rate is obtained for brown dwarfs around all stars, with 0.80.5+0.8^{+0.8}_{-0.5}% of stars hosting a brown dwarf companion between 13-80 MJup_{\rm Jup} and 10-100 au. Brown dwarfs also appear to be distributed differently in mass and semi-major axis compared to giant planets; whereas giant planets follow a bottom-heavy mass distribution and favor smaller semi-major axes, brown dwarfs exhibit just the opposite behaviors. Comparing to studies of short-period giant planets from the RV method, our results are consistent with a peak in occurrence of giant planets between ~1-10 au. We discuss how these trends, including the preference of giant planets for high-mass host stars, point to formation of giant planets by core/pebble accretion, and formation of brown dwarfs by gravitational instability.Comment: 52 pages, 18 figures. AJ in pres

    Biodiversity and ecosystem services science for a sustainable planet: the DIVERSITAS vision for 2012–20

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    DIVERSITAS, the international programme on biodiversity science, is releasing a strategic vision presenting scientific challenges for the next decade of research on biodiversity and ecosystem services: “Biodiversity and Ecosystem Services Science for a Sustainable Planet”. This new vision is a response of the biodiversity and ecosystem services scientific community to the accelerating loss of the components of biodiversity, as well as to changes in the biodiversity science-policy landscape (establishment of a Biodiversity Observing Network — GEO BON, of an Intergovernmental science-policy Platform on Biodiversity and Ecosystem Services — IPBES, of the new Future Earth initiative; and release of the Strategic Plan for Biodiversity 2011–2020). This article presents the vision and its core scientific challenges.Fil: Larigauderie, Anne. DIVERSITAS. Muséum National d’Histoire Naturelle; FranciaFil: Prieur Richard, Anne Helene. DIVERSITAS. Muséum National d’Histoire Naturelle; FranciaFil: Mace, Georgina. Imperial College London. Center for Population Biology; Reino UnidoFil: Londsdale, Mark. CSIRO Ecosystem Sciences; AustraliaFil: Mooney, Harold A.. Stanford University. Department of Biological Sciences; Estados UnidosFil: Brussaard, Lijbert. Wageningen University, Soil Quality Department; Países BajosFil: Cooper, David. Secretariat of the Convention on Biological Diversity; CanadáFil: Wolfgang, Cramer. Institut Méditerranéen de Biodiversité et d’Ecologie marine et continentale; FranciaFil: Daszak, Peter. EcoHealth Alliance. Wildlife Trust; Estados UnidosFil: Diaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Duraiappah, Anantha. International Human Dimensions Programme; AlemaniaFil: Elmqvist, Thomas. University of Stockholm. Department of Systems Ecology and Stockholm Resilience Center; SueciaFil: Faith, Daniel. The Australian Museum; AustraliaFil: Jackson, Louise. University of California; Estados UnidosFil: Krug, Cornelia. DIVERSITAS. Muséum National d’Histoire Naturelle; FranciaFil: Leadley, Paul. Université Paris. Laboratoire Ecologie Systématique Evolution, Ecologie des Populations et Communautés; FranciaFil: Le Prestre, Philippe. Laval University; CanadáFil: Matsuda, Hiroyuki. Yokohama National University; JapónFil: Palmer, Margaret. University of Maryland; Estados UnidosFil: Perrings, Charles. Arizona State University; Estados UnidosFil: Pulleman, Mirjam. Wageningen University; Países BajosFil: Reyers, Belinda. Natural Resources and Environment; SudáfricaFil: Rosa, Eugene A.. Washington State University; Estados UnidosFil: Scholes, Robert J.. Natural Resources and Environment; SudáfricaFil: Spehn, Eva. Universidad de Basilea; SuizaFil: Turner II, B. L.. Arizona State University; Estados UnidosFil: Yahara, Tetsukazu. Kyushu University; Japó

    XIPE: the X-ray Imaging Polarimetry Explorer

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    X-ray polarimetry, sometimes alone, and sometimes coupled to spectral and temporal variability measurements and to imaging, allows a wealth of physical phenomena in astrophysics to be studied. X-ray polarimetry investigates the acceleration process, for example, including those typical of magnetic reconnection in solar flares, but also emission in the strong magnetic fields of neutron stars and white dwarfs. It detects scattering in asymmetric structures such as accretion disks and columns, and in the so-called molecular torus and ionization cones. In addition, it allows fundamental physics in regimes of gravity and of magnetic field intensity not accessible to experiments on the Earth to be probed. Finally, models that describe fundamental interactions (e.g. quantum gravity and the extension of the Standard Model) can be tested. We describe in this paper the X-ray Imaging Polarimetry Explorer (XIPE), proposed in June 2012 to the first ESA call for a small mission with a launch in 2017 but not selected. XIPE is composed of two out of the three existing JET-X telescopes with two Gas Pixel Detectors (GPD) filled with a He-DME mixture at their focus and two additional GPDs filled with pressurized Ar-DME facing the sun. The Minimum Detectable Polarization is 14 % at 1 mCrab in 10E5 s (2-10 keV) and 0.6 % for an X10 class flare. The Half Energy Width, measured at PANTER X-ray test facility (MPE, Germany) with JET-X optics is 24 arcsec. XIPE takes advantage of a low-earth equatorial orbit with Malindi as down-link station and of a Mission Operation Center (MOC) at INPE (Brazil).Comment: 49 pages, 14 figures, 6 tables. Paper published in Experimental Astronomy http://link.springer.com/journal/1068

    Arrested spinodal decomposition in polymer brush collapsing in poor solvent

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    We study the Brownian dynamics of flexible and semiflexible polymer chains densely grafted on a flat substrate, upon rapid quenching of the system when the quality of solvent becomes poor and chains attempt collapse into a globular state. The collapse process of such a polymer brush differs from individual chains, both in its kinetics and its structural morphology. We find that the resulting collapsed brush does not form a homogeneous dense layer, in spite of all chain monomers equally attracting each other via a model Lennard-Jones potential. Instead, a very distinct inhomogeneous density distribution in the plane forms, with a characteristic length scale dependent on the quenching depth (or equivalently, the strength of monomer attraction) and the geometric parameters of the brush. This structure is identical to the spinodal-decomposition structure, however, due to the grafting constraint we find no subsequent coarsening: the established random bundling with characteristic periodicity remains as the apparently equilibrium structure. We compare this finding with a recent field-theoretical model of bundling in a semiflexible polymer brush.This work was funded by the Osk. Huttunen Foundation (Finland) and the Cambridge Theory of Condensed Matter Grant from EPSRC. Simulations were performed using the Darwin supercomputer of the University of Cambridge High Performance Computing Service provided by Dell Inc. using Strategic Research Infrastructure funding from the Higher Education Funding Council for England.This is the accepted manuscript. The final version is available at http://pubs.acs.org/doi/abs/10.1021/ma501985r

    Aqueous Tear Deficiency Increases Conjunctival Interferon-c (IFN-c) Expression and Goblet Cell Loss

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    PURPOSE. To investigate the hypothesis that increased interferon-c (IFN-c) expression is associated with conjunctival goblet cell loss in subjects with tear dysfunction. METHODS. Goblet cell density (GCD) was measured in impression cytology from the temporal bulbar conjunctiva, and gene expression was measured in cytology samples from the nasal bulbar conjunctiva obtained from 68 subjects, including normal control, meibomian gland disease (MGD), non-Sjögren syndrome (non-SSATD)-, and Sjögren syndrome (SSATD)-associated aqueous tear deficiency. Gene expression was evaluated by real-time PCR. Tear meniscus height (TMH) was measured by optical coherence tomography. Fluorescein and lissamine green dye staining evaluated corneal and conjunctival disease, respectively. Between-group mean differences and correlation coefficients were calculated. RESULTS. Compared to control, IFN-c expression was significantly higher in both ATD groups, and its receptor was higher in SSATD. Expression of IL-13 and its receptor was similar in all groups. Goblet cell density was lower in the SSATD group; expression of MUC5AC mucin was lower and cornified envelope precursor small proline-rich region (SPRR)-2G higher in both ATD groups. Interferon-c transcript number was inversely correlated with GCD (r ¼ À0.37, P < 0.04) and TMH (r ¼ À0.37, P ¼ 0.02), and directly correlated with lissamine green staining (r ¼ 0.51, P < 0.001) and SPRR-2G expression (r ¼ 0.32, P < 0.05). CONCLUSIONS. Interferon-c expression in the conjunctiva was higher in aqueous deficiency and correlated with goblet cell loss and severity of conjunctival disease. These results support findings of animal and culture studies showing that IFN-c reduces conjunctival goblet cell number and mucin production

    Can Emotional and Behavioral Dysregulation in Youth Be Decoded from Functional Neuroimaging?

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    High comorbidity among pediatric disorders characterized by behavioral and emotional dysregulation poses problems for diagnosis and treatment, and suggests that these disorders may be better conceptualized as dimensions of abnormal behaviors. Furthermore, identifying neuroimaging biomarkers related to dimensional measures of behavior may provide targets to guide individualized treatment. We aimed to use functional neuroimaging and pattern regression techniques to determine whether patterns of brain activity could accurately decode individual-level severity on a dimensional scale measuring behavioural and emotional dysregulation at two different time points

    The Gemini Planet Imager View of the HD 32297 Debris Disk

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    We present new H-band scattered light images of the HD 32297 edge-on debris disk obtained with the Gemini Planet Imager. The disk is detected in total and polarized intensity down to a projected angular separation of 0.?15, or 20 au. On the other hand, the large-scale swept-back halo remains undetected, likely a consequence of its markedly blue color relative to the parent body belt. We analyze the curvature of the disk spine and estimate a radius of ?100 au for the parent body belt, smaller than past scattered light studies but consistent with thermal emission maps of the system. We employ three different flux-preserving post-processing methods to suppress the residual starlight and evaluate the surface brightness and polarization profile along the disk spine. Unlike past studies of the system, our high-fidelity images reveal the disk to be highly symmetric and devoid of morphological and surface brightness perturbations. We find the dust scattering properties of the system to be consistent with those observed in other debris disks, with the exception of HR 4796. Finally, we find no direct evidence for the presence of a planetary-mass object in the system
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