4,360 research outputs found

    High Frequency of Extra-Pair Paternity in Eastern Kingbirds

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    Genetic parentage in the socially monogamous and territorial Eastern Kingbird( Tyrannust tyrannus) was examined in a central New York population by multilocus DNA fingerprinting. Extra-pair young were identified in 60% (12 of 20) of nests. Of the 64 nestlings profiled, 42% were sired by extra-pair males, but no cases of conspecific brood parasitism were detected. These results are markedly different from a previous electrophoretic study of the same species in a Michigan population, which reported 39% of nestlings were unrelated to one (typically the mother, quasiparasitismo)r both (conspecificb roodp arasitism) of the putative parents. In the New York population, extra-pairp aternityw as most common among females that returned to breed on a former territory. Among females that were new to a breeding territory, extrapair paternity increased directly with breeding density. Although the power of the tests was low, neither breeding synchrony nor male experience with a breeding territory appeared to be associated with the occurrence of extra-pair young

    Ultrafast Spin Density Wave Transition in Chromium Governed by Thermalized Electron Gas

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    The energy and momentum selectivity of time- and angle-resolved photoemission spectroscopy is exploited to address the ultrafast dynamics of the antiferromagnetic spin density wave (SDW) transition photoexcited in epitaxial thin films of chromium. We are able to quantitatively extract the evolution of the SDW order parameter Δ through the ultrafast phase transition and show that Δ is governed by the transient temperature of the thermalized electron gas, in a mean field description. The complete destruction of SDW order on a sub-100 fs time scale is observed, much faster than for conventional charge density wave materials. Our results reveal that equilibrium concepts for phase transitions such as the order parameter may be utilized even in the strongly nonadiabatic regime of ultrafast photoexcitation

    Efficient Synthesis of Geminal-Dialkyl Dienes for Olefin Metathesis Polymerization

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    A robust synthesis of gem-dialkyl acyclic diene monomers has been developed. This route is scalable, flexible, and biorenewable, allowing for the production of a wide range of diene monomers of different lengths and different gem-dialkyl substitutions starting from unsaturated esters derived from seed oils. The metathesis polymerization of these monomers and the hydrogenation of the resulting polyolefins lead to telechelic gem-dialkyl polyethylenes, which can be used as elastomers in the synthesis of polyurethanes and other block polymers

    Efficient Synthesis of Geminal-Dialkyl Dienes for Olefin Metathesis Polymerization

    Get PDF
    A robust synthesis of gem-dialkyl acyclic diene monomers has been developed. This route is scalable, flexible, and biorenewable, allowing for the production of a wide range of diene monomers of different lengths and different gem-dialkyl substitutions starting from unsaturated esters derived from seed oils. The metathesis polymerization of these monomers and the hydrogenation of the resulting polyolefins lead to telechelic gem-dialkyl polyethylenes, which can be used as elastomers in the synthesis of polyurethanes and other block polymers

    A Spitzer IRAC Census of the Asymptotic Giant Branch Populations in Local Group Dwarfs. II. IC 1613

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    We present Spitzer Space Telescope IRAC photometry of the Local Group dwarf irregular galaxy IC 1613. We compare our 3.6, 4.5, 5.8, and 8.0 micron photometry with broadband optical photometry and find that the optical data do not detect 43% and misidentify an additional 11% of the total AGB population, likely because of extinction caused by circumstellar material. Further, we find that a narrowband optical carbon star study of IC 1613 detects 50% of the total AGB population and only considers 18% of this population in calculating the carbon to M-type AGB ratio. We derive an integrated mass-loss rate from the AGB stars of 0.2-1.0 x 10^(-3) solar masses per year and find that the distribution of bolometric luminosities and mass-loss rates are consistent with those for other nearby metal-poor galaxies. Both the optical completeness fractions and mass-loss rates in IC 1613 are very similar to those in the Local Group dwarf irregular, WLM, which is expected given their similar characteristics and evolutionary histories.Comment: Accepted by ApJ, 26 pages, 10 figures, version with high-resolution figures available at: http://webusers.astro.umn.edu/~djackson

    Effects of gender and ethnicity on outcomes after aortic valve replacement

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    ObjectiveTo evaluate the clinical outcomes after aortic valve replacement or aortic valve replacement and coronary artery bypass grafting in a large contemporary population, and to determine if outcomes are associated with patient ethnicity and gender status.MethodsUsing the Massachusetts Cardiac Surgery Database, we identified 6809 adults aged 18 years or older who had undergone isolated aortic valve replacement or aortic valve replacement and coronary artery bypass grafting in all non-federal acute-care Massachusetts hospitals from 2002 to 2008. Univariate and multivariate logistic regression analyses were used to identify differences in patient characteristics, major morbidity, and 30-day and 1-year mortality between men (n = 4043) and women (n = 2766) and between whites (n = 6481) and nonwhites (n = 328).ResultsThe unadjusted 30-day mortality rate was 2.6% for the men and 3.1% for the women (P = .296) and 2.8% for whites and 3.7% for nonwhites (P = .342). In adjusted logistic regression models, the 30-day mortality was not different between the female and male patients (odds ratio, 0.88; 95% confidence interval, 0.26–3.02, P = .84) nor between the nonwhites and whites (odds ratio, 1.57; 95% confidence interval, 0.45–5.44; P = .48). The incidence of postoperative stroke was greater in women (3.0% women and 2.2% men, P = .031), and the incidence of postoperative myocardial infarction (10.9% women and 13.6% men; P = .001) and septicemia (1.2% women and 2.0% men; P = .009) was greater in men.ConclusionsEthnicity and gender were not associated with greater 30-day and 1-year mortality after aortic valve replacement or aortic valve replacement and coronary artery bypass grafting. Differences in postoperative outcomes were not observed between ethnic groups

    Reward System Dysfunction as a Neural Substrate of Symptom Expression Across the General Population and Patients With Schizophrenia

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    Dysfunctional patterns of activation in brain reward networks have been suggested as a core element in the pathophysiology of schizophrenia. However, it remains unclear whether this dysfunction is specific to schizophrenia or can be continuously observed across persons with different levels of nonclinical and clinical symptom expression. Therefore, we sought to investigate whether the pattern of reward system dysfunction is consistent with a dimensional or categorical model of psychosis-like symptom expression. 23 patients with schizophrenia and 37 healthy control participants with varying levels of psychosis-like symptoms, separated into 3 groups of low, medium, and high symptom expression underwent event-related functional magnetic resonance imaging while performing a Cued Reinforcement Reaction Time task. We observed lower activation in the ventral striatum during the expectation of high vs no reward to be associated with higher symptom expression across all participants. No significant difference between patients with schizophrenia and healthy participants with high symptom expression was found. However, connectivity between the ventral striatum and the medial orbitofrontal cortex was specifically reduced in patients with schizophrenia. Dysfunctional local activation of the ventral striatum depends less on diagnostic category than on the degree of symptom expression, therefore showing a pattern consistent with a psychosis continuum. In contrast, aberrant connectivity in the reward system is specific to patients with schizophrenia, thereby supporting a categorical view. Thus, the results of the present study provide evidence for both continuous and discontinuous neural substrates of symptom expression across patients with schizophrenia and the general populatio

    Variation in Vital-rate Sensitivity Between Populations of Texas Horned Lizards

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    Demographic studies of imperiled populations can aid managers in planning conservation actions. However, applicability of findings for a single population across a species’ range is sometimes questionable. We conducted long-term studies (8 and 9 years, respectively) of 2 populations of the lizard Phrynosoma cornutum separated by 1000 km within the historical distribution of the species. The sites were a 15-ha urban wildlife reserve on Tinker Air Force Base (TAFB) in central Oklahoma and a 6000-ha wildland site in southern Texas, the Chaparral Wildlife Management Area (CWMA). We predicted a trade-off between the effect of adult survival and fecundity on population growth rate (λ), leading to population-specific contributions of individual vital rates to λ and individualized strategies for conservation and management of this taxon. The CWMA population had lower adult survival and higher fecundity than TAFB. As predicted, there was a trade-off in the effects of adult survival and fecundity on λ between the two sites; fecundity affected λ more at CWMA than at TAFB. However, adult survival had the smallest effect on λ in both populations. We found that recruitment in P. cornutum most affected λ at both sites, with hatchling survival having the strongest influence on λ. Management strategies focusing on hatchling survival would strongly benefit both populations. As a consequence, within the constraint of the need to more accurately estimate hatchling survival, managers across the range of species such as P. cornutum could adopt similar management priorities with respect to stage classes, despite intra-population differences in population vital rates
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