Ichthyofaunal Diversification and Distribution in the Ozark Stream in Northcentral Arkansas

The distribution and diversity of the ichthyofauna of Arkansas are poorly known. This study is part of a continuing effort to elucidate the natural history of Arkansas. Big Creek is a relatively small, clear, cool-water stream in the Ozark Plateau of northcentral Arkansas. Big Creek and its tributaries drain into Lake Norfork, an impoundment on North Fork River. A total of 6,779 fish of 30 species was collected. Dominant pool species included Notropis boops, Fundulus catenatus, F. olivaceus, Labidesthes sicculus, and Campostoma anomalum; dominant riffle species included Etheostoma spectabile, E. caeruleum, Notropis boops, Fundulus catenatus, and Campostoma anomalum. The numerical standing crop ranged from 1.3 to 2.6 fish/m 2 in the pools and riffles, respectively. The relative uniformity of substrate and soil types throughout the watershed, and the absence of rooted aquatic plants, limited the diversity of species found. The concomitant reduction in competition and predation probably explains the relatively large numerical standing crop

Apparatus and method of capturing an orbiting spacecraft

Apparatus and a method of capturing an orbiting spacecraft by attaching a grapple fixture are discussed. A probe is inserted into an opening, such as a rocket nozzle, in the spacecraft until a stop on the prove mechanism contacts the spacecraft. A lever is actuated releasing a spring loaded rod which moves axially along the probe removing a covering sleeve to expose spring loaded toffle fingers which pivot open engaging the side of the opening. The probe is shortened and tensioned by turning a screw thread, pressing the fingers inside of the opening to compress the spacecraft between the toggle fingers and the stop. A grapple fixture attached to the probe, which is thus secured to the spacecraft, is engaged by appropriate retrieval means such as a remote manipulator arm

Application of nonlinear feedback control theory to supermaneuverable aircraft

Controlled flight at extremely high angles of attack, far exceeding the stall angle, and/or at high angular rates is sometimes referred to as supermaneuvering flight. The objective was to examine methods for design of control laws for aircraft performing supermaneuvers. Since the equations which govern the motion of aircraft during supermaneuvers are nonlinear, this study concentrated on nonlinear control law design procedures. The two nonlinear techniques considered were Nonlinear Quadratic Regulator (NLQR) theory and nonlinear dynamic inversion. A conventional gain scheduled proportional plus integral (P + I) controller was also developed to serve as a baseline design typical of current control laws used in aircraft. A mathematical model of a generic supermaneuverable aircraft was developed from data obtained from the literature. A detailed computer simulation of the aircraft was also developed. This simulation allowed the flying of proposed supermaneuvers and was used to evaluate the performance of the control law designs and to generate linearized models of the aircraft at different flight conditions

The Specification and Influence of Asset Markets

This paper is a chapter in the forthcoming Handbook of International Economics. It surveys the literature on the specification of models of asset markets and the implications of differences in specification for the macroeconomic adjustment process. Builders of portfolio balance models have generally employed "postulated" asset demand functions, rather than deriving these directly from micro foundations. The first major sec-tion of the paper lays out a postulated general specification of asset markets and summarizes the fundamental short-run results of portfolio balance models using a very basic specification of asset markets. Then,rudimentary specifications of a balance of payments equation and goods market equilibrium conditions are supplied, so that the dynamic distribution effects of the trade account under static and rational expectations with both fixed goods prices and flexible goods prices can be analyzed.The second major section of the paper surveys and analyzes microfoundation models of asset demands using stochastic calculus. The microeconomic theory of asset demands implies some but not all of the properties of the basic specification of postulated asset demands at the macrolevel. Since the conclusions of macroeconomic analysis depend crucially on the form of asset demand functions, it is important to continue to explore the implications of micro foundations for macro specification.

Exercise epigenetics and the foetal origins of disease

Exercise epigenetics is a nascent area of research with vast health implications (e.g., from the treatment of obesity-related diseases to beneficially decoupling epigenetic and chronological age). Evidence is accumulating [1] that exercise can acutely modify the epigenome (e.g., via DNA methylation) for short-term regulatory purposes (e.g., mRNA expression). More speculatively perhaps, maternal exercise during the pre and post–partum period could cause epigenetic changes in offspring. It is generally believed that there are benefits of regular moderate exercise during pregnancy [2]. The phenotypic benefits of maternal exercise notwithstanding, exercise can be viewed as a type of organismal stressor [1]. There are a myriad of ways in which environmental perturbations can affect foetal development. For example gestational stress could alter the epigenome and subsequent physical development. We suggest that maternal exercise -- like most gestational stressors -- will have a dose-response relationship on an offspring’s epigenome (i.e., negative effects at high doses), akin to the phenomenon of hormesis. Interestingly there is no research investigating the epigenetic effects of maternal exercise in humans. This editorial is a call for research on the subject

Interregional and International Competition in the Dairy Industry

International Relations/Trade, Livestock Production/Industries, Marketing,

Density Distribution Sunflower Plots

Density distribution sunflower plots are used to display high-density bivariate data. They are useful for data where a conventional scatter plot is difficult to read due to overstriking of the plot symbol. The x-y plane is subdivided into a lattice of regular hexagonal bins of width w specified by the user. The user also specifies the values of l, d, and k that affect the plot as follows. Individual observations are plotted when there are less than l observations per bin as in a conventional scatter plot. Each bin with from l to d observations contains a light sunflower. Other bins contain a dark sunflower. In a light sunflower each petal represents one observation. In a dark sunflower, each petal represents k observations. (A dark sunflower with p petals represents between /2-pk k and /2+pk k observations.) The user can control the sizes and colors of the sunflowers. By selecting appropriate colors and sizes for the light and dark sunflowers, plots can be obtained that give both the overall sense of the data density distribution as well as the number of data points in any given region. The use of this graphic is illustrated with data from the Framingham Heart Study. A documented Stata program, called sunflower, is available to draw these graphs. It can be downloaded from the Statistical Software Components archive at http://ideas.repec.org/c/boc/bocode/s430201.html . (Journal of Statistical Software 2003; 8 (3): 1-5. Posted at http://www.jstatsoft.org/index.php?vol=8 .)

Methods of determining loads and fiber orientations in anisotropic non-crystalline materials using energy flux deviation

An ultrasonic wave is applied to an anisotropic sample material in an initial direction and an angle of flux deviation of the ultrasonic wave front is measured from this initial direction. This flux deviation angle is induced by the unknown applied load. The flux shift is determined between this flux deviation angle and a previously determined angle of flux deviation of an ultrasonic wave applied to a similar anisotropic reference material under an initial known load condition. This determined flux shift is then compared to a plurality of flux shifts of a similarly tested, similar anisotropic reference material under a plurality of respective, known load conditions, whereby the load applied to the particular anisotropic sample material is determined. A related method is disclosed for determining the fiber orientation from known loads and a determined flux shift