Management of localized energy in discrete nonlinear transmission lines

The manipulation of locked intrinsic localized modes/discrete breathers is studied experimentally in nonlinear electric transmission line arrays. Introducing a static lattice impurity in the form of a capacitor, resistor or inductor has been used both to seed or destroy and attract or repel these localized excitations. In a nonlinear di-element array counter propagating short electrical pulses traveling in the acoustic branch are used to generate a stationary intrinsic localized mode in the optic branch at any particular lattice site. By changing the pulse polarity the same localized excitation can be eliminated demonstrating that the dynamical impurity associated with the propagating electrical pulse in the acoustic branch can trigger optical localized mode behavior.Comment: submitte

Regional and scale-specific effects of land use on amphibian diversity [poster]

Background/Question/Methods Habitat loss and degradation influence amphibian distributions and are important drivers of population declines. Our previous research demonstrated that road disturbance, development and wetland area consistently influence amphibian richness across regions of the U.S. Here, we examined the relative importance of these factors in different regions and at multiple spatial scales. Understanding the scales at which habitat disturbance may be affecting amphibian distributions is important for conservation planning. Specifically, we asked: 1) Over what spatial scales do distinct landscape features affect amphibian richness? and 2) Do road types (non-rural and rural) have similar effects on amphibian richness? This is the second year of a collaborative, nationwide project involving 11 U.S. colleges integrated within undergraduate biology curricula. We summarized North American Amphibian Monitoring Program data in 13 Eastern and Central U.S states and used geographic information systems to extract landscape data for 471 survey locations. We developed models to quantify the influence of landscape variables on amphibian species richness and site occupancy across five concentric buffers ranging from 300m to 10,000m. Results/Conclusions Across spatial scales, development, road density and agriculture were the best predictors of amphibian richness and site occupancy by individual species. Across regions, we found that scale did not exert a large influence on how landscape features influenced amphibian richness as effects were largely comparable across buffers. However, development and percent impervious surface had stronger influence on richness at smaller spatial scales. Richness was lower at survey locations with higher densities of non-rural and rural roads, and non-rural road density had a larger negative effect at smaller scales. Within regions, landscape features driving patterns of species richness varied. The scales at which these factors were associated with richness were highly variable within regions, suggesting the scale effects may be region specific. Our project demonstrates that networks of undergraduate students can collaborate to compile and analyze large ecological data sets, while engaging students in authentic and inquiry-based learning in landscape-scale ecology

Understanding tunneling magnetoresistance during thermal annealing in MgO-based junctions with CoFeB electrodes

The competition between the interface crystallization and diffusion processes, their influence on the onset of symmetry-filtering coherent tunneling of Δ1 band electrons in the MgO-based magnetic tunnel junctions is investigated. Systematic study of the transport and magnetoresistance during thermal annealing of these junctions shows a unique behavior of the tunneling conductance in the parallel state. The optimal annealing time for achieving giant tunneling magnetoresistance at different temperatures is determined. The evolution of magnetoresistance consists of three distinct regions, responsible by different contributions from CoFeB electrodes and the MgO barrier. The whole phenomenon can be understood through an empirical model based on the Landauer tunneling picture.United States. Dept. of Energy (Grant No. DE-FG02-07ER46374)National Science Foundation (U.S.) (DMR0827249)National Science Foundation (U.S.) (Grant No. DMR0504158)United States. Office of Naval Research (Grant No. N00014-09-1-0177)United States. Dept. of Energy. Office of Science (No. DE-AC02- 98CH10886

Land use data and anuran species richness for North American Amphibian Monitoring Program survey sites

Data from 587 NAAMP survey sites. NAAMP survey locations are organized as "stops" within "routes," each of which has a unique SiteID. Land use variables were measured within buffers of 300m, 600m, 1000m, 5km, and 10km. Variables include "wet_prop" (proportion of area covered by wetland), "imperv" (proportion of area covered by impervious surface), "PROP_FOR" (proportion of area covered by forest), "PROP_DEV" (proportion of area covered by developed land uses, and "PROP_AGR" (proportion of area covered by row crop agriculture. Road-related variables are given as linear lengths (meters) within each buffer. Variables are T_ROAD_LEN (total road length), P_ROAD_LEN (primary (divided) roads), S_ROAD_LEN (secondary roads), O_ROAD_LEN (other roads, i.e. not P or S), and PS_ROAD_LEN (the sum of primary and secondary road lengths). Data also show the number of NAAMP surveys of each stop (Num.Surv), the number of years covered (Num.Years), mean car count during surveys (Car.Count), number of surveys with ambient noise (Noise.Num), and proportion of surveys that noted noise (NOISE_LEV = Noise.Num/Num.Surv). Amphibian presence/absence over all surveys are given for the species ANFO, HYCI, HYSQ, LICA, LICL, LIPA, LIPI, LISP, LISY, HYCV, PSTR (full scientific names are provided in the associated paper). NAs indicate sites outside the known range of each species. Richness is shown as the sum of all species detected at each stop, and NPP represents estimated Net Primary Productivity at that set (which provided a geographic expectation of anuran species richness)

Effects of Road and Land Use on Frog Distributions Across Spatial Scales and Regions in the Eastern and Central United States

Understanding the scales over which land use affects animal populations is critical for conservation planning, and it can provide information about the mechanisms that underlie correlations between species distributions and land use. We used a citizen science database of anuran surveys to examine the relationship between road density, land use and the distribution of frogs and toads across spatial scales and regions of the United States

Data from: Effects of roads and land use on frog distributions across spatial scales and regions in the eastern and central United States

Aim: Understanding the scales over which land use affects animal populations is critical for conservation planning, and it can provide information about the mechanisms that underlie correlations between species distributions and land use. We used a citizen-science database of anuran surveys to examine the relationship between road density, land use, and the distribution of frogs and toads across spatial scales and regions of the United States. Location: Eastern and Central United States Methods: We compiled data on anuran occupancy collected from 1999-2013 across 13 states in the North American Amphibian Monitoring Program, a citizen science survey of calling frogs. These data were indexed to measures of land use within buffers ranging from 300 m to 10 km. Results: The negative effects of road density and development on anuran richness were strongest at the smallest scales (300 – 1000 m), and this pattern was consistent across regions. In contrast, the relationships of anuran richness to agriculture and forest cover were similar across local scales but varied among regions. Richness had a negative relationship with agriculture/ forest loss in the Midwest but a positive relationship with agriculture in the Northeast. Anuran richness was more closely related to primary/secondary road density than to rural road density, and the negative effects of larger roads increased at smaller scales. Individual species differed in the scales over which roads and development affected their distributions, but these differences were not closely related to either body size or movement ability. Main conclusions: This study further refines our understanding of the relationship between roads and amphibian populations and highlights the need for research into the specific mechanisms by which roads affect amphibians. Additionally, we find that relationships between land use and species richness can differ substantially across regions, demonstrating that one should use caution in generalizing from one region to another, even when species composition is similar