1,271 research outputs found

    Feeding Ecology of Red Snapper (Lutjanus Campechanus) and Vermilion Snapper (Rhomboplites Aurorubens) Coexisting at the Louisiana Shelf-edge Banks

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    Niche partitioning, the process by which competing species use different subsets of the available resources, is commonly used to explain the coexistence of closely related species. In the northwest Gulf of Mexico on the shelf-edge banks, red snapper (Lutjanus campechanus) and vermilion snapper (Rhomboplites aurorubens) are two coexisting closely related species. Yet, little is known about how these species partition resources. In this study, niche partitioning of red snapper and vermilion snapper was investigated using gut contents and stable isotopes. While dietary niche partitioning was apparent, the species relied upon similar prey and displayed isotopic niche overlap, supporting the notion that their resource use overlaps. Red snapper and vermilion snapper shared five of the seven broad prey categories. Isotope niche overlap between the species was approximately 10%, with the greatest overlap occurring between the largest vermilion snappers (≄300 mm) and red snappers species’ diets was the predominance of fish and zooplankton. Red snapper specialized on fish, whereas vermilion snapper specialized on zooplankton. Vermilion snapper exhibited lower ∆13C and ∆15N values relative to red snapper, which is indicative of greater pelagic feeding on lower trophic level prey. The degree of niche partitioning was similar across different locations; however, size-related niche shifts were not consistent. It is possible that niche partitioning is the result of long-standing competition occurring between red snapper and vermilion snapper. In addition, size-related niche shifts might reduce intraspecific competition. However, competition is unlikely to occur unless shared food resources are limited. Further research is required to determine the existence of competition. Understanding interactions among coexisting species can provide a framework for a multispecies management approach

    Probing EWSB Naturalness in Unified SUSY Models with Dark Matter

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    We have studied Electroweak Symmetry Breaking (EWSB) fine-tuning in the context of two unified Supersymmetry scenarios: the Constrained Minimal Supersymmetric Model (CMSSM) and models with Non-Universal Higgs Masses (NUHM), in light of current and upcoming direct detection dark matter experiments. We consider both those models that satisfy a one-sided bound on the relic density of neutralinos, Ωχh2<0.12\Omega_{\chi} h^2 < 0.12, and also the subset that satisfy the two-sided bound in which the relic density is within the 2 sigma best fit of WMAP7 + BAO + H0 data. We find that current direct detection searches for dark matter probe the least fine-tuned regions of parameter-space, or equivalently those of lowest Higgs mass parameter ÎŒ\mu, and will tend to probe progressively more and more fine-tuned models, though the trend is more pronounced in the CMSSM than in the NUHM. Additionally, we examine several subsets of model points, categorized by common mass hierarchies; M_{\chi_0} \sim M_{\chi^\pm}, M_{\chi_0} \sim M_{\stau}, M_{\chi_0} \sim M_{\stop_1}, the light and heavy Higgs poles, and any additional models classified as "other"; the relevance of these mass hierarchies is their connection to the preferred neutralino annihilation channel that determines the relic abundance. For each of these subsets of models we investigated the degree of fine-tuning and discoverability in current and next generation direct detection experiments.Comment: 26 pages, 10 figures. v2: references added. v3: matches published versio

    Rare behavior of growth processes via umbrella sampling of trajectories

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    We compute probability distributions of trajectory observables for reversible and irreversible growth processes. These results reveal a correspondence between reversible and irreversible processes, at particular points in parameter space, in terms of their typical and atypical trajectories. Thus key features of growth processes can be insensitive to the precise form of the rate constants used to generate them, recalling the insensitivity to microscopic details of certain equilibrium behavior. We obtained these results using a sampling method, inspired by the “s-ensemble” large-deviation formalism, that amounts to umbrella sampling in trajectory space. The method is a simple variant of existing approaches, and applies to ensembles of trajectories controlled by the total number of events. It can be used to determine large-deviation rate functions for trajectory observables in or out of equilibrium

    Effects of Deepwater Horizon oil on feather structure and thermoregulation in gulls: Does rehabilitation work?

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    Impacts of large-scale oil spills on avian species are far-reaching.While media attention often focuses on lethal impacts, sub-lethal effects and the impacts of rehabilitation receive less attention. The objective of our study was to characterize effects of moderate external oiling and subsequent rehabilitation on feather structure and thermoregulation in gulls. We captured 30 wild ring-billed gulls (Larus delawarensis) and randomly assigned each individual to an experimental group: 1) controls, 2) rehabilitated birds (externally oiled, rehabilitated by washing), or 3) oiled birds (externally oiled, not rehabilitated). We externally oiled birds with weathered MC252 Deepwater Horizon oil (water for controls) and collected feathers and thermography imagery (FLIR) approximately weekly for four weeks to investigate feather structure (quantified using a barbule clumping index) and thermoregulatory ability (characterized by internal body temperature and external surface temperature). Post-oiling feather clumping was significantly higher in oiled and rehabilitated birds compared to controls, but steadily declined over time in both groups. However, feather microstructure in rehabilitated birds was indistinguishable from controls within three weeks of washing whereas the feathers of oiled birds were still significantly clumped a month post oiling. Internal body temperatures didn\u27t differ in any of the groups, suggesting birds maintain thermoregulatory homeostasis in spite of moderate external oiling. External temperatures for rehabilitated birds didn\u27t differ from controls within a week of rehabilitation. Overall, rehabilitation procedures were effective and washed birds were in better condition compared to non-rehabilitated, oiled birds. This study provides evidence that the benefits of rehabilitation for moderately oiled birds likely outweigh the costs with regard to feather structure and thermoregulation.While feather preening and time were insufficient to reestablish baseline fine scale feather structure in moderately oiled birds, the significant clumping reduction over time may indicate that rehabilitation of lightly oiled birds may not be necessary and deserves further study

    Soil resources, microbial activity, and primary production across an agricultural ecosystem

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    Includes bibliographical references (pages 169-170).The degree to which soil resource availability is linked to patterns of microbial activity and plant productivity within ecosystems has important consequences for our understanding of how ecosystems are structured and for the management of systems for agricultural production. We studied this linkage in a 48-ha site in southwest Michigan, USA, that had been cultivated and planted to row crops for decades. Prior to seeding the site to genetically identical soybean plants (Glycine max) in early spring, we removed soil samples from ≈600 locations; plant biomass was harvested from these same locations later in the season. Soil samples were analyzed for physical properties (texture, bulk density), chemical properties (moisture, pH, total C, total N, inorganic N), and biological attributes (microbial biomass, microbial population size, respiration potential, and nitrification and N-mineralization potentials). Plant analyses included biomass and C and N contents. Soil resource variability across this long-cultivated site was remarkably high, as was variability in microbial activity and primary productivity. In almost all cases variability exhibited a strong spatially explicit structure: for most properties and processes > 50% of sample variance was spatially dependent at a scale of 5–60 m. Exceptions included microtopography, soil pH, and inorganic P, which were spatially dependent across the entire 1–1200 m range of separation distances examined in this study, and the culturable-bacteria population, which was not spatially autocorrelated at any scale examined. Both topographic relief and soil pH exhibited strongly nested structures, with autocorrelation occurring within two (topography) or more (pH) distinct ranges. Multiple regression analysis showed surprisingly little correlation between biological processes (soybean productivity, soil N turnover, soil respiration), and static soil properties. The best predictor of soybean biomass at late reproductive stages (r2 = 0.42) was a combination of nitrate N, bulk density, inorganic P, N-mineralization rates, and pH. Overall, results suggest a remarkable degree of spatial variability for a pedogenically homogeneous site that has been plowed and cropped mostly as a single field for > 100 yr. Such variability is likely to be generic to most ecosystems and should be carefully evaluated when making inferences about ecological relationships in these systems and when considering alternative sampling and management strategies

    Effect of method of drying piglets at birth on rectal temperature over the first 24 h after birth

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    Piglets are born wet, and evaporation of that moisture decreases body temperature, increasing the risk of mortality. The objective of this study was to compare the effect of two commercially applicable methods for drying piglets at birth on piglet rectal temperature over 24 h after birth. The study was carried out in standard commercial farrowing facilities with 52 litters, using a completely randomized design with three Drying Treatments: Control (not dried); Desiccant (dried at birth using a cellulose-based desiccant); Paper Towel (dried at birth using paper towels). Litters were randomly allotted to treatments at the birth of the first piglet. At birth, piglets were individually identified, and the treatment was applied. Rectal temperature was measured at 0, 10, 20, 30, 45, 60, 120, and 1,440 min (24 h) after birth. Data were analyzed using a repeated measures model with PROC MIXED of SAS, with litter as the experimental unit and piglet a subsample of the litter. The model included the fixed effects of treatment and time (as a repeated measure), and the interaction. There was no effect (P\u3e 0.05) of treatment on temperature at birth, or 10 or 1,440 min after birth. Piglet temperatures between 20 and 120 min after birth were similar (P \u3e 0.05) for the Desiccant and Paper Towel treatments, but were greater (P ≀ 0.05) than the Control. The effect of birth weight on the response to Drying Treatment was evaluated by dividing the data into Light (\u3c1.0 kg), Medium (1.0 to 1.5 kg), or Heavy (\u3e1.5 kg) piglet Birth Weight Categories. Piglet rectal temperature data at each measurement time were analyzed using a model that included the fixed effects of Birth Weight Category, Drying Treatment, and the interaction. Temperatures of Light piglets were lower (P ≀ 0.05) than those of Heavy piglets between 20 and 120 min after birth, with Medium piglets being intermediate and generally different to the other two weight categories at these times. The difference in temperature between Light as compared with Medium or Heavy piglets was greater for the Control than the other two Drying Treatments at 60 min after birth. These results suggest that drying piglets at birth is an effective method to reduce rectal temperature decline in the early postnatal period, especially for low birth weight piglets

    Effect of drying and/or warming piglets at birth on rectal temperature over the first 24 h after birth

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    Piglets experience a rapid decrease in body temperature immediately after birth, increasing the risk of mortality. The objective of this study was to determine the effect of drying and/or warming piglets at birth on rectal temperature over the first 24 h after birth. The study was carried out at a commercial sow facility using a completely randomized design with four treatments (applied to piglets at birth): Control (no drying or warming), Desiccant (dried using a desiccant), Warming Box (placed in a box under a heat lamp for 30 min), and Desiccant + Warming Box (both dried and warmed as above). Farrowing pens had one heat lamp, temperatures under which were similar to the warming box (35 °C). A total of 68 litters (866 piglets) were randomly allotted to a treatment at the birth of the first piglet. At birth, each piglet was identified with a numbered ear tag and weighed; rectal temperature was measured at 0, 10, 20, 30, 45, 60, 120, and 1,440 min after birth. Data were analyzed using a repeated-measures model using PROC MIXED of SAS. Litter was the experimental unit, piglet was a subsample of the litter; and the model included the fixed effects of treatment, time (the repeated measure), and the interaction. Rectal temperatures at birth and 1,440 min after birth were similar (P \u3e 0.05) for all treatments. At all times between 10 and 120 min after birth, Control piglets had lower (P ≀ 0.05) temperatures than the other three treatments. The Desiccant and Warming Box treatments had similar (P \u3e 0.05) temperatures at most measurement times, but the Desiccant + Warming Box treatment had the highest (P ≀ 0.05) rectal temperatures at most times between 10 and 60 min. In addition, for all treatments, light (\u3c1.0 kg) birth weight piglets had lower (P ≀ 0.05) temperatures than medium (1.0–1.5 kg) or heavy (\u3e1.5 kg) piglets at all times between 10 and 120 min. In addition, at these measurement times, the deviation in temperature between the Control and the other three treatments was greater for light than medium or heavy piglets. In conclusion, both drying and warming piglets at birth significantly increased rectal temperatures between 10 and 120 min after birth, with the combination of the two interventions having the greatest effect, especially for low birth weight piglets

    ‘They’re more like ordinary stroppy British women’: Attitudes and expectations of maternity care professionals to UK-born ethnic minority women

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    Objective To explore the attitudes and expectations of maternity care professionals to UK-born ethnic minority mothers. Methods Qualitative in-depth interviews with 30 professionals from eight NHS maternity units in England that provide services for large proportions of women of black Caribbean, black African, Indian, Pakistani and Irish descent. Results All the professionals reported providing care to both UK-born and migrant mothers from ethnic minorities. Most of them felt that they could differentiate between UK-born and migrant mothers based mainly on language fluency and accent. ‘Westernized dress’ and ‘freedom’ were also cited as indicators. Overall, professionals found it easier to provide services to UK-born mothers and felt that their needs were more like those of white English mothers than those of migrant mothers. UK-born mothers were generally thought to be assertive and expressive, and in control of care-related decision-making whereas some South Asian Muslim women were thought to be constrained by family influences. Preconceived ideas about ethnic minority mothers' tolerance of pain in labour, use of pharmacological pain relief measures and mode of delivery were recurring themes. Women's education and social class were felt to be major influences on the uptake of maternity care, regardless of ethnicity. Conclusions Professionals appeared to equate the needs of UK-born ethnic minority women with those of white English women. Overall, this has positive implications for care provision. Despite this, specific behavioural expectations and unconscious stereotypical views were evident and have the potential to affect clinical practice
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