Multi-scale habitat associations of shorebirds during spring migration in southwestern Louisiana rice fields

Rice is the most common wetland crop in the world, and important for waterbirds and shorebirds worldwide, including the United States. In Louisiana, shorebirds use rice fields during spring migration, and are an important for foraging and refueling during migration. However, competing land uses and restoration projects may reduce the availability of rice fields, and impact the landscape that shorebirds use during migration. To determine how shorebirds use the landscape, I evaluated local and landscape factors affecting shorebird use of rice fields during spring migration in southwestern Louisiana. Using five habitat suitability zones (HSZs) based on rice density and canopy cover, I performed stratified random surveys at rice fields within each of the 5 HSZs. I surveyed 94 fields in 2008 and 85 fields in 2009. I quantified all habitat types within 3 km of each field, recorded habitat conditions during each visit, and recorded all shorebirds observed. Mixed modeling analyses indicated that shorebird density was primarily influenced by local field conditions: flooding extent (p\u3c00001), the percent of the field perimeter bordered by trees (p=0.0075), surveyed rice field area (p\u3c0.0001), and rice height (p\u3c0.0001). Shorebirds responded positively to flooding extent, and negatively to tree border, field area, and rice height. Overall shorebird density was not influenced by any landscape variables at any scale (1, 1.5, 2, 2.5, or 3 km). The percent of non-rice crop (p=0.0437) and fallow land (p=0.0400) immediately adjacent to surveyed fields was a positive influence on density of the seven most common species, and HSZ was a positive influence on shorebird habitat use for 3 of the most common species or species groupings: Dowitchers (2 spp), Peeps (3 spp), and Yellowlegs (2 spp). These species comprised \u3e 50 % of all birds observed, indicating the importance of HSZ for individual species. Rice density was significantly higher in HSZ4 and HSZ5, and the percent of forest (an alternate measurement of canopy cover) was significantly lower in HSZs 4 and 5. These results support the validity of the habitat suitability model. By maintaining rice production in the higher HSZs, suitable local habitat conditions would be provided for shorebirds

Structure, Scaling and Phase Transition in the Optimal Transport Network

We minimize the dissipation rate of an electrical network under a global constraint on the sum of powers of the conductances. We construct the explicit scaling relation between currents and conductances, and show equivalence to a a previous model [J. R. Banavar {\it et al} Phys. Rev. Lett. {\bf 84}, 004745 (2000)] optimizing a power-law cost function in an abstract network. We show the currents derive from a potential, and the scaling of the conductances depends only locally on the currents. A numerical study reveals that the transition in the topology of the optimal network corresponds to a discontinuity in the slope of the power dissipation.Comment: 4 pages, 3 figure

Interpolative Approach for Solving the Anderson Impurity Model

A rational representation for the self--energy is explored to interpolate the solution of the Anderson impurity model in general orbitally degenerate case. Several constrains such as the Friedel's sum rule, positions of the Hubbard bands as well as the value of quasiparticle residue are used to establish the equations for the coefficients of the interpolation. We employ two fast techniques, the slave--boson mean--field and the Hubbard I approximations to determine the functional dependence of the coefficients on doping, degeneracy and the strength of the interaction. The obtained spectral functions and self--energies are in good agreement with the results of numerically exact quantum Monte Carlo method.Comment: 15 pages, 9 figure

Results and recommendations from an intercomparison of six Hygroscopicity-TDMA systems

The performance of six custom-built Hygrocopicity-Tandem Differential Mobility Analyser (H-TDMA) systems was investigated in the frame of an international calibration and intercomparison workshop held in Leipzig, February 2006. The goal of the workshop was to harmonise H-TDMA measurements and develop recommendations for atmospheric measurements and their data evaluation. The H-TDMA systems were compared in terms of the sizing of dry particles, relative humidity (RH) uncertainty, and consistency in determination of number fractions of different hygroscopic particle groups. The experiments were performed in an air-conditioned laboratory using ammonium sulphate particles or an external mixture of ammonium sulphate and soot particles. The sizing of dry particles of the six H-TDMA systems was within 0.2 to 4.2% of the selected particle diameter depending on investigated size and individual system. Measurements of ammonium sulphate aerosol found deviations equivalent to 4.5% RH from the set point of 90% RH compared to results from previous experiments in the literature. Evaluation of the number fraction of particles within the clearly separated growth factor modes of a laboratory generated externally mixed aerosol was done. The data from the H-TDMAs was analysed with a single fitting routine to investigate differences caused by the different data evaluation procedures used for each H-TDMA. The differences between the H-TDMAs were reduced from +12/-13% to +8/-6% when the same analysis routine was applied. We conclude that a common data evaluation procedure to determine number fractions of externally mixed aerosols will improve the comparability of H-TDMA measurements. It is recommended to ensure proper calibration of all flow, temperature and RH sensors in the systems. It is most important to thermally insulate the aerosol humidification unit and the second DMA and to monitor these temperatures to an accuracy of 0.2 degrees C. For the correct determination of external mixtures, it is necessary to take into account size-dependent losses due to diffusion in the plumbing between the DMAs and in the aerosol humidification unit.Peer reviewe

Variational method and duality in the 2D square Potts model

The ferromagnetic q-state Potts model on a square lattice is analyzed, for q>4, through an elaborate version of the operatorial variational method. In the variational approach proposed in the paper, the duality relations are exactly satisfied, involving at a more fundamental level, a duality relationship between variational parameters. Besides some exact predictions, the approach is very effective in the numerical estimates over the whole range of temperature and can be systematically improved.Comment: 20 pages, 5 EPS figure

Bohmian Mechanics as a Practical Tool

In this chapter, we will take a trip around several hot-spots where Bohmian mechanics and its capacity to describe the microscopic reality, even in the absence of measurements, can be harnessed as computational tools, in order to help in the prediction of phenomenologically accessible information (also useful for the followers of the Copenhagen theory). As a first example, we will see how a Stochastic Schr\"odinger Equation, when used to compute the reduced density matrix of a non-Markovian open quantum system, necessarily seems to employ the Bohmian concept of a conditional wavefunction. We will see that by dressing these conditional wavefunctions with an interpretation, the Bohmian theory can prove to be a useful tool to build general quantum frameworks, like a high-frequency electron transport model. As a second example, we will introduce how a Copenhagen "observable operator" can be derived from numerical properties of the Bohmian trajectories, which within Bohmian mechanics, are well-defined even for an "unmeasured" system. Most importantly in practice, even if these numbers are given no ontological meaning, not only we will be able to simulate (thus, predict and talk about) them, but we will see that they can be operationally determined in a weak value experiment. Therefore, they will be practical numbers to characterize a quantum system irrespective of the followed quantum theory.Comment: 13 pages, 1 figure, to be published as a Chapter in the book "Physics and the Nature of Reality: Essays in Memory of Detlef D\"urr". Accepted version, integrating comments by refere

Diffeomorphic random sampling using optimal information transport

In this article we explore an algorithm for diffeomorphic random sampling of nonuniform probability distributions on Riemannian manifolds. The algorithm is based on optimal information transport (OIT)---an analogue of optimal mass transport (OMT). Our framework uses the deep geometric connections between the Fisher-Rao metric on the space of probability densities and the right-invariant information metric on the group of diffeomorphisms. The resulting sampling algorithm is a promising alternative to OMT, in particular as our formulation is semi-explicit, free of the nonlinear Monge--Ampere equation. Compared to Markov Chain Monte Carlo methods, we expect our algorithm to stand up well when a large number of samples from a low dimensional nonuniform distribution is needed.Comment: 8 pages, 3 figure