Seasonal Abundance, Movement and Diversity of Fishes in an Ozark Stream

Seasonal fluctuations in fish abundance in Mud Creek occurred throughout the year at all sampling stations. At the two upper stations abundance was high and unstable during winter and early spring and decreased after heavy rainfall in mid-April. Abundance was low throughout the summer months, increasing in the fall due to large numbers of young-of-the-year. However, a different seasonal cycle occurred at the lower station which included deeper pools. Numbers were low and stable throughout the winter and early spring but high and unstable during the summer. Bigeye shiners (Notropis boops) and bluntnose minnows (Pimephales notatus) were the most mobile species marked. Populations of brook silversides (Labidesthes sicculus) remained fairly isolated, stable, and showed little mobility. Mean species diversity fluctuated during the winter, spring, and fall; diversity values were highest and most stable during summer months when high and relatively stable numbers were collected. The main difference in mean species diversity between stations was the greater stability throughout the year at the upper station

Loss of Larval Fish by Epilimnial Discharge From DeGray Lake, Arkansas

Weekly samples of larval fish were collected from water discharged from the epilimnion of DeGray Lake into the tailwaters, for power generation, from April through August, 1976 and 1977. Peak rates of loss measured were 1.4 larvae/m³ in May, 1976 and 2.7/m³ in April, 1977. Sunfish, shad and crappie made up 97% of an estimated 83.3 million fish lost in 1976, and 98% of 122.4 million lost in 1977. The most critical period for larval fish loss extended from the last week of April to the first week of June. No definite relationships were noted between length of the power generation period or power generation rate, and rate of larval fish discharge. Diel collections showed the rate of larval fish discharge to be lower and more uniform during darkness than during daylight

Fishes of the Caddo River, Arkansas, After Impoundment of DeGray Lake

Fifty-five collections of fishes were made with small-mesh seines and electrofishing gear in the Caddo River and four of its tributaries during 1974-75. Eighty-two species representing 17 families were collected; 14 of the species had not previously been reported from the Caddo River

XMM-Newton observations of SNR 1987A. II. The still increasing X-ray light curve and the properties of Fe K lines

Aims. We report on the recent observations of the supernova remnant SNR 1987A in the Large Magellanic Cloud with XMM-Newton. Carefully monitoring the evolution of the X-ray light curve allows to probe the complex circumstellar medium structure observed around the supernova progenitor star. Methods. We analyse all XMM-Newton observations of SNR 1987A from January 2007 to December 2011, using data from the EPIC-pn camera. Spectra from all epochs are extracted and analysed in a homogeneous way. Using a multi-shock model to fit the spectra across the 0.2-10 keV band we measure soft and hard X-ray fluxes with high accuracy. In the hard X-ray band we examine the presence and properties of Fe K ines. Our findings are interpreted in the framework of a hydrodynamics-based model. Results. The soft X-ray flux of SNR 1987A continuously increased in the recent years. Although the light curve shows a mild flattening, there is no sudden break as reported in an earlier work, a picture echoed by a revision of the Chandra light curve. We therefore conclude that material in the equatorial ring and out-of-plane HII regions are still being swept-up. We estimate the thickness of the equatorial ring to be at least 4.5x10^16 cm (0.0146 pc). This lower limit will increase as long as the soft X-ray flux has not reached a turn-over. We detect a broad Fe K line in all spectra from 2007 to 2011. The widths and centroid energies of the lines indicate the presence of a collection of iron ionisation stages. Thermal emission from the hydrodynamic model does not reproduce the low-energy part of the line (6.4-6.5 keV), suggesting that fluorescence from neutral and/or low ionisation Fe might be present.Comment: 4 pages, 3 figures, 2 tables. Accepted for publication in Astronomy and Astrophysic

A weak Hamiltonian finite element method for optimal control problems

A temporal finite element method based on a mixed form of the Hamiltonian weak principle is developed for dynamics and optimal control problems. The mixed form of Hamilton's weak principle contains both displacements and momenta as primary variables that are expanded in terms of nodal values and simple polynomial shape functions. Unlike other forms of Hamilton's principle, however, time derivatives of the momenta and displacements do not appear therein; instead, only the virtual momenta and virtual displacements are differentiated with respect to time. Based on the duality that is observed to exist between the mixed form of Hamilton's weak principle and variational principles governing classical optimal control problems, a temporal finite element formulation of the latter can be developed in a rather straightforward manner. Several well-known problems in dynamics and optimal control are illustrated. The example dynamics problem involves a time-marching problem. As optimal control examples, elementary trajectory optimization problems are treated

Effects of static equilibrium and higher-order nonlinearities on rotor blade stability in hover

The equilibrium and stability of the coupled elastic lead/lag, flap, and torsion motion of a cantilever rotor blade in hover are addressed, and the influence of several higher-order terms in the equations of motion of the blade is determined for a range of values of collective pitch. The blade is assumed to be untwisted and to have uniform properties along its span. In addition, chordwise offsets between its elastic, tension, mass, and aerodynamic centers are assumed to be negligible for simplicity. The aerodynamic forces acting on the blade are modeled using a quasi-steady, strip-theory approximation

Gene tree reconciliation: new developments in Bayesian concordance analysis with BUCKy

When phylogenetic trees inferred from different genes are incongruent, several methods are available to reconcile gene trees and extract the shared phylogenetic information from the sequence data. Bayesian Concordance Analysis, implemented in BUCKy, aims to extract the vertical signal and to infer clusters of genes that share the same tree topology. The new version of BUCKy includes a quartet-based estimate of the species tree with branch lengths in coalescent units

Inheritance Studies of a Wheat Cross to Six Races of Covered Smut

Covered smut is a fungus disease that has caused serious losses of wheat for centuries. Its origin is not known, but it was well known to early Romans as evidenced by the fact that they had a god, Robigus, whose special work was to watch over crops to avert the mildew . It is often referred to as bunt or stinking smut of wheat . Throughout this paper the term\u27 bunt will be used to designate this disease in order to avoid confusing it with other smuts of wheat

How do Kentucky Educators\u27 Opinions of Single Sex Classrooms differ between those with Experience in Sex Classes and those with no Experience in Single Sex Classes?

An applied project submitted in partial fulfillment of the requirements for the degree of Education Specialist at Morehead State University by Dewey Ray Ward on May 7, 2009

A finite element based method for solution of optimal control problems

A temporal finite element based on a mixed form of the Hamiltonian weak principle is presented for optimal control problems. The mixed form of this principle contains both states and costates as primary variables that are expanded in terms of elemental values and simple shape functions. Unlike other variational approaches to optimal control problems, however, time derivatives of the states and costates do not appear in the governing variational equation. Instead, the only quantities whose time derivatives appear therein are virtual states and virtual costates. Also noteworthy among characteristics of the finite element formulation is the fact that in the algebraic equations which contain costates, they appear linearly. Thus, the remaining equations can be solved iteratively without initial guesses for the costates; this reduces the size of the problem by about a factor of two. Numerical results are presented herein for an elementary trajectory optimization problem which show very good agreement with the exact solution along with excellent computational efficiency and self-starting capability. The goal is to evaluate the feasibility of this approach for real-time guidance applications. To this end, a simplified two-stage, four-state model for an advanced launch vehicle application is presented which is suitable for finite element solution