528 research outputs found

    Quantitative assessment of emergent biomass and species composition in tidal wetlands using remote sensing

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    Do We See Eye to Eye? Moderators of Correspondence Between Student and Faculty Evaluations of Day-to-Day Teaching

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    Students and instructors show moderate levels of agreement about the quality of day-to-day teaching. In the present study, we replicated and extended this finding by asking how correspondence between student and instructor ratings is moderated by time of semester and student demographic variables. Participants included 137 students and 5 instructors. On 10 separate days, students and instructors rated teaching effectiveness and challenge level of the material. Multilevel modeling indicated that student and instructor ratings of teaching effectiveness converged overall, but more advanced students and Caucasian students converged more closely with instructors. Student and instructor ratings of challenge converged early but diverged later in the semester. These results extend our knowledge about the connection between student and faculty judgments of teaching

    Scaling behavior of giant magnetotransport effects in Co/Cu superlattices

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    We have observed two forms of scaling in magnetotransport properties of (111) Co/Cu superlattices: (1) the extraoridnary Hall coefficient Rs correlates with the resistivity xx(0) in the form Rsxx2(0), and (2) the magnetothermopower S(H) correlates with the magnetoresistivity xx(H) in the form S(H)/Txx(0)/xx(H). The first effect relates to quantum mechanical side jump while the other relates to interfacial spin-dependent density of states (DOS). These results revel the different roles of bulklike spin-dependent scattering in Co layers and spin-dependent DOS of interfacial layers in causing the observed large positive extraodinary Hall effect and giant longitudinal magnetotransport

    Langevin-like giant magnetoresistance in Co-Cu superlattices

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    We present evidence for a new type of giant magnetoresistance in (111) cobalt-copper superlattices with atomically smooth interfaces. We propose that the lowered dimensionality of the structure leads to an enhancement of the scattering of conduction electrons from paramagnetic interfaces obeying a Langevin-like saturation at very high fields, well beyond the switching field of the Co layers. The findings help to explain similarities in magnetotransport behavior with recently reported granular systems as well as differences with antiferromagnetically coupled multilayers

    Energy loss of fast quarks in nuclei

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    We report an analysis of the nuclear dependence of the yield of Drell-Yan dimuons from the 800 GeV/c proton bombardment of 2H^2H, C, Ca, Fe, and W targets. Employing a new formulation of the Drell-Yan process in the rest frame of the nucleus, this analysis examines the effect of initial-state energy loss and shadowing on the nuclear-dependence ratios versus the incident proton's momentum fraction and dimuon effective mass. The resulting energy loss per unit path length is −dE/dz=2.32±0.52±0.5-dE/dz = 2.32 \pm 0.52\pm 0.5 GeV/fm. This is the first observation of a nonzero energy loss of partons traveling in nuclear environment.Comment: 5 pages, including 4 figure

    Inter-decadal variability of phytoplankton biomass along the coastal West Antarctic Peninsula

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    The West Antarctic Peninsula (WAP) is a climatically sensitive region where periods of strong warming have caused significant changes in the marine ecosystem and food-web processes. Tight coupling between phytoplankton and higher trophic levels implies that the coastal WAP is a bottom-up controlled system, where changes in phytoplankton dynamics may largely impact other food-web components. Here, we analysed the inter-decadal time series of year-round chlorophyll-a (Chl) collected from three stations along the coastal WAP: Carlini Station at Potter Cove (PC) on King George Island, Palmer Station on Anvers Island and Rothera Station on Adelaide Island. There were trends towards increased phytoplankton biomass at Carlini Station (PC) and Palmer Station, while phytoplankton biomass declined significantly at Rothera Station over the studied period. The impacts of two relevant climate modes to the WAP, the El Niño-Southern Oscillation and the Southern Annular Mode, on winter and spring phytoplankton biomass appear to be different among the three sampling stations, suggesting an important role of local-scale forcing than large-scale forcing on phytoplankton dynamics at each station. The inter-annual variability of seasonal bloom progression derived from considering all three stations together captured ecologically meaningful, seasonally co-occurring bloom patterns which were primarily constrained by water-column stability strength. Our findings highlight a coupled link between phytoplankton and physical and climate dynamics along the coastal WAP, which may improve our understanding of overall WAP food-web responses to climate change and variability
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