1,573 research outputs found
AMPHIBIAN RESPONSE TO A LARGE-SCALE HABITAT RESTORATION IN THE PRAIRIE POTHOLE REGION
Over the next half-century, scientists anticipate that nearly one third of the currently recognized 7,450 amphibian species will become extinct. Many organizations have responded to the challenge of conserving amphibian biodiversity, some indirectly. Under the auspices of the Iowa Great Lakes Management Plan, the United States Fish and Wildlife Service, Department of Natural Resources, and their partners have been implementing habitat restoration efforts designed to protect water quality, provide recreational opportunities, and benefit wildlife at the regional level. With this program, over 130 wetlands have been created in the past 30 years on recently purchased public lands—one of the largest wetland restoration projects conducted in the Prairie Pothole Region of the Great Plains. While amphibians were not the main target of these restorations, we show that in response, 121 new breeding populations of native Northern Leopard Frogs (Lithobates pipiens; n = 80) and Eastern Tiger Salamanders (Ambystoma tigrinum; n = 41) have been established; in addition, we found 19 populations of non-native American Bullfrogs (L. catesbeianus). Using the program PRESENCE, we show that leopard frog occupancy was greatest in newer (<18 years old), intermediate-sized wetlands, and that tiger salamander occupancy was greatest in small wetlands without fish and larval bullfrogs. These data imply that because native amphibians responded positively to these newly established wetlands, habitat availability has likely been a factor in limiting population numbers. Further, these data suggest the presence of fishes and introduced bullfrogs interferes with the ability of tiger salamanders to colonize restored wetlands
Macroalgae contribute to the diet of Patella vulgata from contrasting conditions of latitude and wave exposure in the UK
Analysis of gut contents and stable isotope composition of intertidal limpets (Patella vulgata) showed a major contribution of macroalgae to their diet, along with microalgae and invertebrates. Specimens were collected in areas with limited access to attached macroalgae, suggesting a major dietary component of drift algae. Gut contents of 480 animals from 2 moderately wave exposed and 2 sheltered rocky shores in each of 2 regions: western Scotland (55–56°N) and southwest England (50°N), were analysed in 2 years (n = 30 per site per year). The abundance of microalgae, macroalgae and invertebrates within the guts was quantified using categorical abundance scales. Gut content composition was compared among regions and wave exposure conditions, showing that the diet of P. vulgata changes with both wave exposure and latitude. Microalgae were most abundant in limpet gut contents in animals from southwest sites, whilst leathery/corticated macroalgae were more prevalent and abundant in limpets from sheltered and northern sites. P. vulgata appears to have a more flexible diet than previously appreciated and these keystone grazers consume not only microalgae, but also large quantities of macroalgae and small invertebrates. To date, limpet grazing studies have focussed on their role in controlling recruitment of macroalgae by feeding on microscopic propagules and germlings. Consumption of adult algae suggests P. vulgata may also directly control the biomass of attached macroalgae on the shore, whilst consumption of drift algae indicates the species may play important roles in coupling subtidal and intertidal production
Erupting Dwarf Novae in the Large Magellanic Cloud
We report the first likely detections of erupting Dwarf Novae (DN) in an
external galaxy: the Large Magellanic Cloud. Six candidates were isolated from
approximately a million stars observed every second night over 11 nights with
the CTIO 8K x 8K Mosaic2 CCD imager. Artificial dwarf nova and completeness
tests suggest that we are seeing only the brightest of the LMC DN, probably SS
Cygni-like CVs, but possibly SU UMa-type cataclysmics undergoing
superoutbursts. We derive crude but useful limits on the LMC DN surface
density, and on the number of DN in the LMC. Many thousands of cataclysmic
variables in the Magellanic Clouds can be discovered and characterized with 8
meter class telescopes.Comment: Accepted for publication in AJ, 28 pages, 9 figures total, Figures 1
and 8 are supplied separately in jpeg forma
Epidurals in Pancreatic Resection Outcomes (E-PRO) study: Protocol for a randomised controlled trial
Cardiovascular Magnetic Resonance and prognosis in cardiac amyloidosis
Background: Cardiac involvement is common in amyloidosis and associated with a variably adverse outcome. We have previously shown that cardiovascular magnetic resonance (CMR) can assess deposition of amyloid protein in the myocardial interstitium. In this study we assessed the prognostic value of late gadolinium enhancement (LGE) and gadolinium kinetics in cardiac amyloidosis in a prospective longitudinal study.Materials and methods: The pre-defined study end point was all-cause mortality. We prospectively followed a cohort of 29 patients with proven cardiac amyloidosis. All patients underwent biopsy, 2D-echocardiography and Doppler studies, I-123-SAP scintigraphy, serum NT pro BNP assay, and CMR with a T-1 mapping method and late gadolinium enhancement (LGE).Results: Patients with were followed for a median of 623 days (IQ range 221, 1436), during which 17 (58%) patients died. The presence of myocardial LGE by itself was not a significant predictor of mortality. However, death was predicted by gadolinium kinetics, with the 2 minute post-gadolinium intramyocardial T1 difference between subepicardium and subendocardium predicting mortality with 85% accuracy at a threshold value of 23 ms (the lower the difference the worse the prognosis). Intramyocardial T1 gradient was a better predictor of survival than FLC response to chemotherapy (Kaplan Meier analysis P = 0.049) or diastolic function (Kaplan-Meier analysis P = 0.205).Conclusion: In cardiac amyloidosis, CMR provides unique information relating to risk of mortality based on gadolinium kinetics which reflects the severity of the cardiac amyloid burden
APM 08279+5255: an ultraluminous BAL quasar at a redshift z=3.87
We report on the discovery of a highly luminous, broad absorption line quasar
at a redshift of which is positionally coincident, within one
arcsecond, with the IRAS FSC source F08279+5255. A chance alignment of the
quasar and the IRAS source is extremely unlikely and we argue that the optical
and FIR flux are different manifestations of the same object. With an R-band
magnitude of 15.2, and an IRAS 60\mum flux of 0.51\jy, APM 08279+5255 is
(apparently) easily the most intrinsically luminous object known, with
L_{Bol}\sim5\times10^{15}L_{\odot}}. Imaging suggests that gravitational
lensing may play a role in amplifying the intrinsic properties of the system.
The optical spectrum of the quasar clearly reveals the presence of three
potential lensing galaxies, \mg absorption systems at and ,
and a \ly absorption system at . We estimate the total amplification of
the optical component to be , but, due to the larger scale of the
emitting region, would expect the infrared amplification to be significantly
less. Even making the conservative assumption that all wavelengths are
amplified by a factor 40, APM 08279+5255 still possesses a phenomenal
luminosity of \simgt 10^{14L_{\odot}}, indicating that it belongs to a small,
but significant population of high--redshift, hyperluminous objects with
copious infrared emission.Comment: 15 Pages with Four figures. Accepted for publication in the
Astrophysical Journa
21-cm synthesis observations of VIRGOHI 21 - a possible dark galaxy in the Virgo Cluster
Many observations indicate that dark matter dominates the extra-galactic
Universe, yet no totally dark structure of galactic proportions has ever been
convincingly identified. Previously we have suggested that VIRGOHI 21, a 21-cm
source we found in the Virgo Cluster using Jodrell Bank, was a possible dark
galaxy because of its broad line-width (~200 km/s) unaccompanied by any visible
gravitational source to account for it. We have now imaged VIRGOHI 21 in the
neutral-hydrogen line and find what could be a dark, edge-on, spinning disk
with the mass and diameter of a typical spiral galaxy. Moreover, VIRGOHI 21 has
unquestionably been involved in an interaction with NGC 4254, a luminous spiral
with an odd one-armed morphology, but lacking the massive interactor normally
linked with such a feature. Numerical models of NGC 4254 call for a close
interaction ~10^8 years ago with a perturber of ~10^11 solar masses. This we
take as additional evidence for the massive nature of VIRGOHI 21 as there does
not appear to be any other viable candidate. We have also used the Hubble Space
Telescope to search for stars associated with the HI and find none down to an I
band surface brightness limit of 31.1 +/- 0.2 mag/sq. arcsec.Comment: 8 pages, accepted to ApJ, uses emulateapj.cls. Mpeg animation (Fig.
2) available at ftp://ftp.naic.edu/pub/publications/minchin/video2.mp
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