8,386 research outputs found

    Soil Governance: Accessing Cross-Disciplinary Perspectives

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    Soil provides the foundation for agricultural and environmental systems, and are subject to a complex governance regime of property rights and secondary impacts from industry and domestic land use. Complex natural resource management issues require approaches to governance that acknowledge uncertainty and complexity. Theories of next generation environmental governance assume that inclusion of diverse perspectives will improve reform directions and encourage behaviour change. This paper reports on a qualitative survey of an international workshop that brought together cross-disciplinary perspectives to address the challenges of soil governance. Results reveal the challenges of communicating effectively across disciplines. The findings suggest that strategies for improved soils governance must focus on increasing communications with community stakeholders and engaging land managers in designing shared governance regimes. The need for more conscious articulation of the challenges of cross-disciplinary environments is discussed and strategies for increasing research collaboration in soils governance are suggested. The identified need for more systematic approaches to cross-disciplinary learning, including reporting back of cross-disciplinary initiatives to help practitioners learn from past experience, forms part of the rationale for this paper

    A Glimpse Inside the Coffers: Endowment Spending at Wealthy Colleges and Universities

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    Even as ongoing national conversations about income inequality intensify, wealth stratification is occurring not only among individuals but also among institutions of higher education, a study from theEducation Trust finds.The report, "A Glimpse Inside the Coffers", found that roughly 3.6 percent of the nation's colleges and universities held 75 percent of all postsecondary endowment wealth. Despite that wealth, however, few of the hundred and thirty-eight colleges and universities with at least 500millionintheirendowmentswerefoundtobeinvestingsignificantlyinstudentsfromlowincomefamilies,withnearlyhalfthoseinstitutionsrankinginthebottom5percentnationallyintermsoftheenrollmentoffirsttime,fulltimePellGrantrecipients.Theassetsoftheseinstitutionstotaled500 million in their endowments were found to be investing significantly in students from low-income families, with nearly half those institutions ranking in the bottom 5 percent nationally in terms of the enrollment of first-time, full-time Pell Grant recipients.The assets of these institutions totaled 149.5 billion at the beginning of 2010 and had grown to 202.3billionjustfouryearslater.Accordingtothereport,ifthethirtyfiveinstitutionsthatcurrentlyspendlessthan5percentoftheirendowmentsannuallyweretoincreasetheirspendoutratetothe5percentrequiredofprivatefoundations,anadditional202.3 billion just four years later. According to the report, if the thirty-five institutions that currently spend less than 5 percent of their endowments annually were to increase their spend-out rate to the 5 percent required of private foundations, an additional 418 million would become available for other things. And if those funds were allocated solely to financial aid, they could be used to enroll an additional 2,376 low-income students at the current net price for four years -- a nearly 67 percent increase from the enrollment numbers for first-time, full-time low-income students in 2012-13. Alternatively, the same 418millionalsocouldbeusedtoreducethenetpriceforlowincomestudentsattheseinstitutionsbyanaverageof418 million also could be used to reduce the net price for low-income students at these institutions by an average of 8,000 per year for four years."It's common for institutional leaders to say that endowment spending is all about preserving the excellence of their institutions for years to come. But our data show that most could easily afford to do more to educate more low-income students now without compromising their futures," said Andrew Nichols, director of higher education research and data analytics and co-author of the report. "By choosing to serve more low-income students, these wealthy institutions could be leaders -- not just in riches, but in extending opportunity.

    Astrophysical Insights into Radial Velocity Jitter from an Analysis of 600 Planet-search Stars

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    Radial velocity (RV) detection of planets is hampered by astrophysical processes on the surfaces of stars that induce a stochastic signal, or "jitter," which can drown out or even mimic planetary signals. Here, we empirically and carefully measure the RV jitter of more than 600 stars from the California Planet Search sample on a star by star basis. As part of this process, we explore the activity–RV correlation of stellar cycles and include appendices listing every ostensibly companion-induced signal we removed and every activity cycle we noted. We then use precise stellar properties from Brewer et al. to separate the sample into bins of stellar mass and examine trends with activity and with evolutionary state. We find that RV jitter tracks stellar evolution and that in general, stars evolve through different stages of RV jitter: the jitter in younger stars is driven by magnetic activity, while the jitter in older stars is convectively driven and dominated by granulation and oscillations. We identify the "jitter minimum"—where activity-driven and convectively driven jitter have similar amplitudes—for stars between 0.7 and 1.7 M⊙ and find that more-massive stars reach this jitter minimum later in their lifetime, in the subgiant or even giant phases. Finally, we comment on how these results can inform future RV efforts, from prioritization of follow-up targets from transit surveys like TESS to target selection of future RV surveys

    Radial velocities from the N2K Project: 6 new cold gas giant planets orbiting HD 55696, HD 98736, HD 148164, HD 203473, and HD 211810

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    The N2K planet search program was designed to exploit the planet-metallicity correlation by searching for gas giant planets orbiting metal-rich stars. Here, we present the radial velocity measurements for 378 N2K target stars that were observed with the HIRES spectrograph at Keck Observatory between 2004 and 2017. With this data set, we announce the discovery of six new gas giant exoplanets: a double-planet system orbiting HD 148164 (MsiniM \sin i of 1.23 and 5.16 MJUP_{\rm JUP}) and single planet detections around HD 55696 (MsiniM \sin i = 3.87 MJUP_{\rm JUP}), HD 98736 (MsiniM \sin i = 2.33 MJUP_{\rm JUP}), HD 203473 (MsiniM \sin i = 7.8 MJUP_{\rm JUP}), and HD 211810 (MsiniM \sin i = 0.67 MJUP_{\rm JUP}). These gas giant companions have orbital semi-major axes between 1.0 and 6.2 AU and eccentricities ranging from 0.13 to 0.71. We also report evidence for three gravitationally bound companions with MsiniM \sin i between 20 to 30 MJUP_{\rm JUP}, placing them in the mass range of brown dwarfs, around HD 148284, HD 214823, and HD 217850, and four low mass stellar companions orbiting HD 3404, HD 24505, HD 98630, and HD 103459. In addition, we present updated orbital parameters for 42 previously announced planets. We also report a nondetection of the putative companion HD 73256 b. Finally, we highlight the most promising candidates for direct imaging and astrometric detection, and find that many hot Jupiters from our sample could be detectable by state-of-the-art telescopes such as Gaia.Comment: Accepted by the Astronomical Journal. 75 pages, 49 figure

    Empirical Limits on Radial Velocity Planet Detection for Young Stars

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    We report initial results from our long term search using precision radial velocities for planetary-mass companions located within a few AU of stars younger than the Sun. Based on a sample of >150 stars, we define a floor in the radial velocity scatter, sigma_RV, as a function of the chromospheric activity level R'_{HK}. This lower bound to the jitter, which increases with increasing stellar activity, sets the minimum planet mass that could be detected. Adopting a median activity-age relationship reveals the astrophysical limits to planet masses discernable via radial velocity monitoring, as a function of stellar age. Considering solar-mass primaries having the mean jitter-activity level, when they are younger than 100 / 300 / 1000 Myr, the stochastic jitter component in radial velocity measurements restricts detectable companion masses to > 0.3 / 0.2 / 0.1 M_Jupiter. These numbers require a large number -- several tens -- of radial velocity observations taken over a time frame longer than the orbital period. Lower companion mass limits can be achieved for stars with less than the mean jitter and/or with an increased number of observations.Comment: 5 pages, to appear the 18th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun proceedings edited by G. van Belle & H. Harri
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