841 research outputs found

    Responses of soil carbon, nitrogen and cations to the frequency and seasonality of prescribed burning in a Cape Cod oak-pine forest

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    Author Posting. © The Author(s), 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Forest Ecology and Management 250 (2007): 234-243, doi:10.1016/j.foreco.2007.05.023.Fire is an important component of the historic disturbance regime of oak and pine forests that occupy sandy soils of the coastal outwash plain of the northeastern U.S. Today prescribed fire is used for fuel reduction and for restoration and maintenance of habitat for rare plant, animal and insect species. We evaluated the effects of the frequency and seasonality of prescribed burning on the soils of a Cape Cod, Massachusetts coastal oak-pine forest. We compared soil bulk density, pH and acidity, total extractable cations and total soil C and N in unburned plots and in plots burned over a 12-year period, along a gradient of frequency (every 1-to-4 years), in either spring (March/April) or summer (July/August). Summer burning decreased soil organic horizon thickness more than spring burning, but only summer burning every 1 to 2 years reduced organic horizons compared with controls. Burning increased soil bulk density of the organic horizon only in the annual summer burns and did not affect bulk density of mineral soil. Burn frequency had no effect on pH in organic soil, but burning every year in summer increased pH of organic soil from 4.01 to 4.95 and of mineral soil from 4.20 to 4.79. Burning had no significant effect on organic or mineral soil percent C, percent N, C:N, soil exchangeable Ca2+, Mg2+, K+ or total soil C or N. Overall effects of burning on soil chemistry were minor. Our results suggest that annual summer burns may be required to reduce soil organic matter thickness to produce conditions that would regularly allow seed germination for oak and for grassland species that are conservation targets. Managers may have to look to other measures, such as combinations of fire with mechanical treatments (e.g., soil scarification) to further promote grasses and forbs in forests where establishment of these plants is a high priority.Funding was provided by the National Park Service, The Nature Conservancy via a grant from the Mellon Foundation, the Joint Fire Science Program, and a grant from the Mellon Foundation to MBL

    The First Orbital Period for a Dwarf Nova in a Globular Cluster: V101 in M5

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    We report the first orbital period determination for a Dwarf Nova (DN) in a glubular cluster: V101 in M5 has a period of 5.796 +- 0.036 hours. We derived this period from I-band photometry acquired with the Calypso Observatory High Resolution Camera operating with tip-tilt adaptive optics correction. Observations from the South African Astronomical Observatory in the V-band were also analyzed and exhibit a periodic signal of the same period. This orbital period suggests that V101 has a secondary of mid to late K spectral type with Mv = +8.2 +- 0.5. The predicted spectral type is consistent with previous spectral observations in quiescence which show a fairly red continuum. From the observed minimum brightness of V = 22.5, we derive a distance modulus of (m - M)v = 14.3 +- 0.5 to the DN which supports V101's membership in the globular cluster M5. Measurement of the ellipsoidality effect indicates that the orbital plane of the V101 system is moderately inclined, but not enough to exhibit eclipses.Comment: 28 pages, 12 figures, 3 table

    Substellar Companions to Main Sequence Stars: No Brown Dwarf Desert at Wide Separations

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    We use three field L and T dwarfs which were discovered to be wide companions to known stars by the Two Micron All-Sky Survey (2MASS) to derive a preliminary brown dwarf companion frequency. Observed L and T dwarfs indicate that brown dwarfs are not unusually rare as wide (Delta >1000 A.U.) systems to F-M0 main-sequence stars (M>0.5M_sun, M_V<9.5), even though they are rare at close separation (Delta <3 A.U.), the ``brown dwarf desert.'' Stellar companions in these separation ranges are equally frequent, but brown dwarfs are >~ 10 times as frequent for wide than close separations. A brown dwarf wide-companion frequency as low as the 0.5% seen in the brown dwarf desert is ruled out by currently-available observations.Comment: ApJL, in pres

    An Ethnographic Study of Palliative and End-of-Life Care in a Nigerian Hospital:Impact of Education on Care Provision and Utilization

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    Most clinicians receive little or no palliative care (PC) education. Similarly, patients and their families receive little or no information on PC. Our study explored education in PC, while examining for its impacts on service delivery and utilization from the perspective of health care professionals (HCPs), patients, and their families. An ethnographic approach was utilized to gather data from 41 participants. Spradley’s ethnographic analytical framework guided data analysis. Two themes identified were inadequate HCPs’ knowledge base and impact of service-users’ inadequate health education. The findings show that most HCPs had no formal education in PC, attributed to the lack of PC residency programs and the absence of educational institutions that provide such education. Patients and families also conveyed poor understandings of their illness and palliation, rooted in the HCP culture of partial disclosure of information about their diagnosis, care, and prognosis. Findings suggest a cultural shift that supports PC education for professionals is required to promote realist medical approach in the care for patients with life-limiting illnesses. </jats:p

    Our Nearest 15 Million Neighbors: The Field Low-Mass Stellar Luminosity and Mass Functions

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    We report on a new measurement of the luminosity function (LF) and mass function (MF) of field low-mass dwarfs using Sloan Digital Sky Survey (SDSS) photometry. The final catalog is composed of ~15 million low-mass stars (0.1 Msun < M < 0.8 Msun), spread over 8,400 square degrees. Distances to the stars are estimated using new photometric parallax relations, constructed from ugriz photometry of nearby low-mass stars with trigonometric parallaxes. The LF is measured with a novel technique, which simultaneously measures Galactic structure and the stellar LF. The resulting LF is compared to previous studies and converted to a MF. The MF is well-described by a log-normal distribution, with Mo = 0.27 Msun.Comment: 4 pages, 3 figures. Included in the proceedings of Cool Stars 1

    Development of antigen-specific ELISA for circulating autoantibodies to extracellular matrix protein 1 in lichen sclerosus

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    Lichen sclerosus is a common, acquired chronic inflammatory skin disease of unknown etiology, although circulating autoantibodies to the glycoprotein extracellular matrix protein 1 (ECM1) have been detected in most patients’ sera. We have examined the nature of ECM1 epitopes in lichen sclerosus sera, developed an ELISA system for serologic diagnosis, and assessed clinicopathological correlation between ELISA titer and disease. Epitope-mapping studies revealed that lichen sclerosus sera most frequently recognized the distal second tandem repeat domain and carboxyl-terminus of ECM1. We analyzed serum autoantibody reactivity against this immunodominant epitope in 413 individuals (95 subjects with lichen sclerosus, 161 normal control subjects, and 157 subjects with other autoimmune basement membrane or sclerosing diseases). The ELISA assay was highly sensitive; 76 of 95 lichen sclerosus patients (80.0%) exhibited IgG reactivity. It was also highly specific (93.7%) in discriminating between lichen sclerosus and other disease/control sera. Higher anti-ECM1 titers also correlated with more longstanding and refractory disease and cases complicated by squamous cell carcinoma. Furthermore, passive transfer of affinity-purified patient IgG reproduced some histologic and immunopathologic features of lichen sclerosus skin. This new ELISA is valuable for the accurate detection and quantification of anti-ECM1 autoantibodies. Moreover, the values may have clinical significance in patients with lichen sclerosus

    The wave and tidal resource of Scotland

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    As the marine renewable energy industry evolves, in parallel with an increase in the quantity of available data and improvements in validated numerical simulations, it is occasionally appropriate to re-assess the wave and tidal resource of a region. This is particularly true for Scotland - a leading nation that the international community monitors for developments in the marine renewable energy industry, and which has witnessed much progress in the sector over the last decade. With 7 leased wave and 17 leased tidal sites, Scotland is well poised to generate significant levels of electricity from its abundant natural marine resources. In this state-of-the-art review of Scotland's wave and tidal resource, we examine the theoretical and technical resource, and provide an overview of commercial progress. We also discuss issues that affect future development of the marine energy seascape in Scotland, applicable to other regions of the world, including the potential for developing lower energy sites, and grid connectivity
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