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Can Invasive Snails Reduce Parasitism in Native Snails? An Evaluation of the Dilution Effect Hypothesis
No full textThe dilution effect hypothesis states that any non-target host species can act as a decoy or resistant host to disease or parasite transmission stages, thereby reducing the negative effects of the diseases or parasites on the coevolved host (Prenter et al. 2004, Johnson and Thieltges 2010). Invasive species are often resistant to parasites in the new ecosystem because native parasites have not evolved to be able to successfully infect them (Prenter et al. 2004). In laboratory experiments, Kopp and Jokela (2007) found the presence of the invasive snail, Lymnaea stagnalis, acted as a resistant host for trematode infection resulting in reduced infection rates in the native snail. Similarly, the presence of the invasive American slipper limpet, Crepidula foricata, and invasive Pacific oysters, Crassostrea gigas, reduced trematode infection load on native mussels, Mytilus edulis, in both single species and mixed species (both invasive species present) treatments (Thieltges et al. 2009). However, both of these experiments were conducted in mesocosms with simplified biotic interactions (Kopp and Jokela 2007, Thieltges et al. 2009)
River Reach Delineations and Beaver Movement in Grand Teton National Park
No full textThis project had two components, with the first component providing a background for the second component. Water resources in Grand Teton National Park (GTNP) are both unregulated and regulated by human management. The Jackson Lake Dam and the ponds scattered across the park influence the flow of water. In the process of managing the water it is important to have knowledge of the different components of the streams through which the water flows. One component of this project was to examine the different segments of the major rivers in GTNP and identify the river forms that are displayed by the different reaches of the Snake River above and below Jackson Lake, Buffalo Fork and Pacific Creek. The river form can be segregated into three main categories; the single channel, the meandering channel and the braided channel (Knighton 1984). The different river forms are part of the overall structural composition of the river and can be used to delineate the segments or reaches of the river. The river continuum concept presented by Vannote et al. (1980) provides a theoretical background upon which to construct the river reach system. In 2007, Nelson (2007) completed a reach system project while investigating the fluvial geomorphology of the Snake River below Jackson Lake Dam (Figure 1.). His 20 river reaches provided a zonation of the river that incorporated a range of geomorphic features. This same type of system can be used throughout the GTNP so that researchers have a common spatial unit designation when referencing portions of the Snake River and its tributaries. Ackers (1988) in his work on alluvial channel hydraulics identified three dimensions of meanders that should be considered; width, depth and slope. He further agreed with Hey (1978) that there are nine factors that define river geometry and that these should be considered as well: average bank full velocity, hydraulic mean depth, maximum bank full depth, slope, wave length of bed forms, their mean height, bank full wetted perimeter, channel sinuousity and arc length of meanders. Nelsonâs work (Nelson 2007) added another parameter by including a braiding index into the representation of river reach designations. In a more recent work, the Livers and Wohl (2014) study confirmed Nelsonâs approach by comparing reach characteristics between glacial and fluvial process domains using similar reach designation characteristics to determine reach differences
Methods in Geoscience Field Instruction: University of Nebraska-Lincoln
No full textEight in-service teachers, one pre-service education student, three observers from other universities, and two instructors from the University of Nebraska-Lincoln engaged in an inquiry-based geology field course from June 13 to 28, 2015 through Wyoming, South Dakota, and Nebraska. This commnity of learners spent three days working in the Grand Teton National Park area. Geological features and history present in Grand Teton National Park are an important part of the course curriculum. Large-scale extensional features of the Teton Range and Jackson Hole, and the glacial geomorphology and related climate changes of this area are some of the unique features examined here
Square roots of doubly regular tournament matrices
No full textFletcher asked whether there is a (0, 1)-matrix of order greater than 3 whose square is a regular tournament matrix. We give a negative answer for a special class of regular tournament matrices: There is no (0, 1)-matrix of order greater than 3 whose square is a doubly regular tournament matrix
On the sensitivity analysis of eigenvalues
No full textLet \lam be a simple eigenvalue of an -by- matrix Let and be left and right eigenvectors of corresponding to \lam, respectively. Then, for the spectral norm, the condition number \cond(\lam, A) := \|x\|_2\, \|y\|_2 /{|y^*x|} measures the sensitivity of \lam to small perturbations in and plays an important role in the accuracy assessment of computed eigenvalues. R. A. Smith [Numer. Math., 10(1967), pp.232-240] proved that \cond(\lam, A) = \|x\|_2\|y\|_2/{|y^*x|} = \|\adj(\lam I -A)\|_2/{|p'(\lam)|}, where \adj(A) is the ``adjugate" of and p'(\lam) is the derivative of at \lam. We extend Smith's condition number to any matrix norm and show that \cond(\lam, A) = \frac{\|yx^*\|_*}{|y^*x|} = \frac{\|\adj(\lam I - A)^*\|_*}{|p'(\lam)|} measures the sensitivity of \lam to small perturbations in where \norm_* is the dual norm of The {\sc matlab} command {\tt roots} computes roots of a polynomial by computing the eigenvalues of a companion matrix associated with We analyze the sensitivity of \lam as a root of as well as the sensitivity of \lam as an eigenvalue of and compare their condition numbers
Generalization of Gracia's Results
No full textLet α be a linear transformation of the m à n-dimensional vector space M_{mÃn}(C) over the complex field C such that α(X) = AX âXB, where A and B are mÃm and nÃn complex matrices, respectively. In this paper, the dimension formulas for the kernels of the linear transformations α^2 and α^3 are given, which generalizes the work of Gracia in [J.M. Gracia. Dimension of the solution spaces of the matrix equations [A, [A, X]] = 0 and [A[A, [A, X]]] = 0. Linear and Multilinear Algebra, 9:195â200, 1980.]
Factorization of Permutations
No full textThe problem of factoring a permutation as a product of special types of transpositions, namely, those transpositions involving two positions with bounded distances, is considered. In particular, the minimum number, δ, such that every permutation can be factored into no more than δ special transpositions is investigated. This study is related to sorting algorithms, Cayley graphs, and genomics
Evaluation of a family of binomial determinants
No full textMotivated by a recent work about finite sequences where the n-th term is bounded by n^2, some classes of determinants are evaluated such as the (n â 2) Ã (n â 2) determinant â_n=\det [ (x_i+j \choose i-1)] for n \geq 1, where n, k, h, i, j are integers, (x_k) is a sequence of indeterminates over C and ( A \choose B ) is the usual binomial coefficient. It is proven that D_n=1 and â_n=(-1)^{ (n-2)(n-3)/2}
Wave Packet Transform over Finite Fields
No full textIn this article we introduce the notion of finite wave packet groups over finite fields as the finite group of dilations, translations, and modulations. Then we will present a unified theoretical linear algebra approach to the theory of wave packet transform (WPT) over finite fields. It is shown that each vector defined over a finite field can be represented as a coherent sum of finite wave packet group elements as well
On the invertibility of length two elementary operators
No full textLet X be a complex Banach space and L(X) be the algebra of all bounded linear operators on X. For a given elementary operator P of length 2 on L(X), we determine necessary and sufficient conditions for the existence of a solution of the equation YP=0 in the algebra of all elementary operators on L(X). Our approach allows us to characterize some invertible elementary operators of length 2 whose inverses are elementary operators