42,928 research outputs found

    Factors limiting sand dune restoration in Northwest Beach, Point Pelee National Park, Canada

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    Known as home to rare species of flora and fauna, and their critical habitats, Northwest beach of Point Pelee National Park has undergone significant ecological and infrastructural changes in the past decades. A number of important management challenges have emerged, including conservation of endangered Five-lined Skink (Plestiodon fasciatus) which inhabit the extensive dune system within the park. This research investigates key factors for sand dune ecosystem restoration in Northwest beach of Point Pelee with particular attention to the conservation of Skink habitat. Random stratified sampling method was used to collect sand and vegetation samples from the disturbed and natural areas. Sand samples were also collected from the sand piles, which is a part of dune restoration process initiated by the Parks Canada. Three aspects were considered: grain size distribution of dune sediments, vegetation assemblage and character of the dune associated species, land use and land cover change. Grain size distribution indicated that samples from most of the sand piles contained some amounts of clay/silt and pebble sized grains making it unfavourable for wind action, resulting in no significant contribution to dune formation. Most of the sand samples collected along the foredunes and water edge were appropriate for sediment transport. Shannon and Simpson’s Diversity Index was calculated as 1.48 and 0.67 for natural area as compared to 0.71 and 0.35 for the disturbed area, which indicate unfavourable species diversity for dune restoration in disturbed areas. The research also focused on the spatial and temporal changes in land use and land cover in NW beach area of Point Pelee using aerial photos for 1959, 1977, 2006 and 2015. Different time series of the aerial photos were chosen based on their availability. The Ecological land classification system for Southern Ontario were used to classify the aerial photos for land use and land cover (LULC). LULC classes included Shoreline vegetation, Deciduous thicket, Sand Barren and Dune Type, and Infrastructures (includes Transportation and services) for the entire Northwest Beach area. Segmentation and classification tools was used to classify four different time series of aerial photos. Grain size distribution and vegetation assemblage for dune associated species were calculated to determine the factors limiting habitat restoration process. Based on the results alternate management strategies for dune restoration in Point Pelee were recommended. The study offers key insights on the importance of timely detection, analysis and visualisation of dynamic changes for habitat restoration and maintaining ecological integrity of the Northwest beach area of Point Pelee

    Book Review: Materialien zur Geschichte der Ramanuja-Schule II

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    A review of Materialien zur Geschichte der Ramanuja-Schule II by Gerhard Oberhammer

    Book Review: Die Symbolik von Gift und Nektar in der klassischen indischen Literatur

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    A review of Die Symbolik von Gift und Nektar in der klassischen indischen Literatur by Ira Stubbe-Diarra

    The Douglas Lemma for von Neumann Algebras and Some Applications

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    In this article, we discuss the well-known Douglas lemma on the relationship between majorization and factorization of operators, in the context of von Neumann algebras. We give a proof of the Douglas lemma for von Neumann algebras which is essential for some of our applications. We discuss several applications of the Douglas lemma and prove some new results about left (or, one-sided) ideals of von Neumann algebras. A result by Loebl-Paulsen characterizes C∗C^*-convex subsets of B(H)\mathcal{B}(\mathscr{H}) as those subsets which contain C∗C^*-segments generated from operators in the subset (B(H)\mathcal{B}(\mathscr{H}) denotes the set of bounded operators on a complex Hilbert space H\mathscr{H}.) We define the notion of pseudo C∗C^*-convexity for a subset of a Hilbert C∗C^*-bimodule over a C∗C^*-algebra with the aspiration of it being a practical technical tool in establishing C∗C^*-convexity of a subset. For a von Neumann algebra R\mathscr{R}, we prove the equivalence of the notions of C∗C^*-convexity and pseudo C∗C^*-convexity in Hilbert R\mathscr{R}-bimodules. This generalizes the aforementioned Loebl-Paulsen result which may be formulated in a straightforward manner in the setting of C∗C^*-convexity in Hilbert B(H)\mathcal{B}(\mathscr{H})-bimodules.Comment: 16 page

    Herman rings of meromorphic maps with an omitted value

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    We investigate the existence and distribution of Herman rings of transcendental meromorphic functions which have at least one omitted value. If all the poles of such a function are multiple then it has no Herman ring. Herman rings of period one or two do not exist. Functions with a single pole or with at least two poles one of which is an omitted value have no Herman ring. Every doubly connected periodic Fatou component is a Herman ring.Comment: 12 page

    A characterization of finite dimensional nilpotent Lie superalgebras

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    Let LL be a nilpotent Lie superalgebras of dimension (m∣n)(m\mid n) for some non-negative integers mm and nn and put s(L)=12[(m+n−1)(m+n−2)]+n+1−dim⁡M(L)s(L) = \frac{1}{2}[(m + n - 1)(m + n -2)]+ n+ 1 - \dim \mathcal{M}(L), where M(L)\mathcal{M}(L) denotes the Schur multiplier of LL. Recently, the author has shown that s(L)≥0s(L) \geq 0 and the structure of all nilpotent Lie superalgebras has been determined when s(L)=0s(L) = 0 \cite{Nayak2018}. The aim of this paper is to classify all nilpotent Lie superalgebras LL for which s(L)=1s(L) = 1 and 22.Comment: 19 page

    Density Wave States of Non-Zero Angular Momentum

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    We study the properties of states in which particle-hole pairs of non-zero angular momentum condense. These states generalize charge- and spin-density-wave states, in which s-wave particle-hole pairs condense. We show that the p-wave spin-singlet state of this type has Peierls ordering, while the d-wave spin-singlet state is the staggered flux state. We discuss model Hamiltonians which favor p-wave and d-wave density wave order. There are analogous orderings for pure spin models, which generalize spin-Peierls order. The spin-triplet density wave states are accompanied by spin-1 Goldstone bosons, but these excitations do not contribute to the spin-spin correlation function. Hence, they must be detected with NQR or Raman scattering experiments. Depending on the geometry and topology of the Fermi surface, these states may admit gapless fermionic excitations. As the Fermi surface geometry is changed, these excitations disappear at a transition which is third-order in mean-field theory. The singlet d-wave and triplet p-wave density wave states are separated from the corresponding superconducting states by zero-temperature O(4)-symmetric critical point
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