12,537 research outputs found

    First Nesting Record and Status Review of the Glossy Ibis in Nebraska

    Get PDF
    Glossy Ibis (Plegadis falcinellus) is believed to be a recent colonist from the Old World whose numbers have increased and range has expanded in North America over the past two centuries (Patten and Lasley 2000). Glossy Ibis range expansion has been described as involving periods of relative stability followed by periods of rapid increase (Patten and Lasley 2000). Prior to the 1980s, Glossy Ibis were primarily found in the southeastern United States and along the Atlantic Coast (Patten and Lasley 2000). In the mid to late 1980s, Glossy Ibis began to rapidly increase and expand into Texas. By the early 1990s they were increasingly reported in the Great Plains (Thompson et a1. 20 11), particularly along the front range of Colorado and New Mexico (Patten and Lasley 2000). In Nebraska, the first documented occurrence of Glossy Ibis was a single adult with 28 White-faced Ibis (Plegadis chihi) at Wilkins Waterfowl Production Area (WPA), Fillmore County, 24 April 1999 (Jorgensen 2001). Since the initial record, the number of reports of Glossy Ibis has increased. Glossy Ibis status was elevated from accidental to casual by the Nebraska Ornithologists’ Union Records Committee (NOURC) in 2005 (Brogie 2005). Only a few years later in 2014, its status was elevated again from casual to regular and NOURC no longer sought documentation for sightings (Brogie 2014). In 2015, Jorgensen observed this species nesting in the Rainwater Basin. Given the recent observation of nesting, the rapid increase in annual observations, along with field identification challenges as a result of similarity to and hybridization with the White-faced Ibis, the status of the Glossy Ibis in Nebraska is in need of clarification. Here, we provide observational details about the first confirmed nesting by the species in Nebraska, review all reports of Glossy Ibis and apparent Glossy × White-faced Ibis hybrids, and comment on this species’ overall status in the state

    The Measure of a Measurement

    Full text link
    While finite non-commutative operator systems lie at the foundation of quantum measurement, they are also tools for understanding geometric iterations as used in the theory of iterated function systems (IFSs) and in wavelet analysis. Key is a certain splitting of the total Hilbert space and its recursive iterations to further iterated subdivisions. This paper explores some implications for associated probability measures (in the classical sense of measure theory), specifically their fractal components. We identify a fractal scale ss in a family of Borel probability measures μ\mu on the unit interval which arises independently in quantum information theory and in wavelet analysis. The scales ss we find satisfy s∈R+s\in \mathbb{R}_{+} and s≠1s\not =1, some s1s 1. We identify these scales ss by considering the asymptotic properties of μ(J)/∣J∣s\mu(J) /| J| ^{s} where JJ are dyadic subintervals, and ∣J∣→0| J| \to0.Comment: 18 pages, 3 figures, and reference

    Spectral asymptotics of periodic elliptic operators

    Full text link
    We demonstrate that the structure of complex second-order strongly elliptic operators HH on Rd{\bf R}^d with coefficients invariant under translation by Zd{\bf Z}^d can be analyzed through decomposition in terms of versions HzH_z, z∈Tdz\in{\bf T}^d, of HH with zz-periodic boundary conditions acting on L2(Id)L_2({\bf I}^d) where I=[0,1>{\bf I}=[0,1>. If the semigroup SS generated by HH has a H\"older continuous integral kernel satisfying Gaussian bounds then the semigroups SzS^z generated by the HzH_z have kernels with similar properties and z↦Szz\mapsto S^z extends to a function on Cd∖{0}{\bf C}^d\setminus\{0\} which is analytic with respect to the trace norm. The sequence of semigroups S(m),zS^{(m),z} obtained by rescaling the coefficients of HzH_z by c(x)→c(mx)c(x)\to c(mx) converges in trace norm to the semigroup S^z\hat{S}^z generated by the homogenization H^z\hat{H}_z of HzH_z. These convergence properties allow asymptotic analysis of the spectrum of HH.Comment: 27 pages, LaTeX article styl

    Commuting self-adjoint extensions of symmetric operators defined from the partial derivatives

    Get PDF
    We consider the problem of finding commuting self-adjoint extensions of the partial derivatives {(1/i)(\partial/\partial x_j):j=1,...,d} with domain C_c^\infty(\Omega) where the self-adjointness is defined relative to L^2(\Omega), and \Omega is a given open subset of R^d. The measure on \Omega is Lebesgue measure on R^d restricted to \Omega. The problem originates with I.E. Segal and B. Fuglede, and is difficult in general. In this paper, we provide a representation-theoretic answer in the special case when \Omega=I\times\Omega_2 and I is an open interval. We then apply the results to the case when \Omega is a d-cube, I^d, and we describe possible subsets \Lambda of R^d such that {e^(i2\pi\lambda \dot x) restricted to I^d:\lambda\in\Lambda} is an orthonormal basis in L^2(I^d).Comment: LaTeX2e amsart class, 18 pages, 2 figures; PACS numbers 02.20.Km, 02.30.Nw, 02.30.Tb, 02.60.-x, 03.65.-w, 03.65.Bz, 03.65.Db, 61.12.Bt, 61.44.B

    A statistical study of the global structure of the ring current

    Get PDF
    [1] In this paper we derive the average configuration of the ring current as a function of the state of the magnetosphere as indicated by the Dst index. We sort magnetic field data from the Combined Release and Radiation Effects Satellite (CRRES) by spatial location and by the Dst index in order to produce magnetic field maps. From these maps we calculate local current systems by taking the curl of the magnetic field. We find both the westward (outer) and the eastward (inner) components of the ring current. We find that the ring current intensity varies linearly with Dst as expected and that the ring current is asymmetric for all Dst values. The azimuthal peak of the ring current is located in the afternoon sector for quiet conditions and near midnight for disturbed conditions. The ring current also moves closer to the Earth during disturbed conditions. We attempt to recreate the Dst index by integrating the magnetic perturbations caused by the ring current. We find that we need to multiply our computed disturbance by a factor of 1.88 ± 0.27 and add an offset of 3.84 ± 4.33 nT in order to get optimal agreement with Dst. When taking into account a tail current contribution of roughly 25%, this agrees well with our expectation of a factor of 1.3 to 1.5 based on a partially conducting Earth. The offset that we have to add does not agree well with an expected offset of approximately 20 nT based on solar wind pressure
    • …
    corecore