System for measuring transients in fluid flow

When test valve is actuated, piston is moved by pressurized fluid, and displacement is monitored by electro-optical tracking system and recorded by oscilloscope camera. Electro-optical monitor produces output voltage proportional to displacement of piston

Is the Short Rate Drift Actually Nonlinear?

Virtually all existing continuous-time, single-factor term structure models are based on a short rate process that has a linear drift function. However, there is no strong a priori argument in favor of linearity, and Stanton (1997) and Ait-Sahalia (1996) employ nonparametric estimation techniques to conclude that the drift function of the short rate contains important nonlinearities. Comparatively little is known about the finite-sample properties of these estimators, particularly when they are applied to frequent sampling of a very persistent process, like short term interest rates. In this paper, we apply these estimators to simulated sample paths of a square-root diffusion. Although the drift function is linear, both estimators suggest nonlinearities of the type and magnitude reported in by Stanton (1997) and Ait-Sahalia (1996). These results, along with the results of a simple GMM estimation procedure applied to the Stanton and Ait-Sahalia data sets, imply that nonlinearity of the short rate drift is not a robust stylized fact.term structure, continuous-time

Risk measurement: an introduction to value at risk

This paper is a self-contained introduction to the concept and methodology of "value at risk," which is a new tool for measuring an entity's exposure to market risk. We explain the concept of value at risk, and then describe in detail the three methods for computing it: historical simulation; the variance-covariance method; and Monte Carlo or stochastic simulation. We then discuss the advantages and disadvantages of the three methods for computing value at risk. Finally, we briefly describe some alternative measures of market risk.Risk and Uncertainty,

Fishes of the Ohio River

Author Institution: Water Resources Laboratory, University of Louisville and Biology Department, Spalding UniversityTo date, 159 species of fishes (14 of them introduced by humans) have been reported from the Ohio River. Three native fishes {Acipenser fulvescens, Alosa alabamae, and Ammocrypta asprella) have apparently been eliminated from the river. The Ohio River fish community was severely affected by the siltation of clean gravel substrates, and the inundation of those substrates by the canalization of the river before 1927. In the past 20-30 years, populations of many species have increased, particularly in the upper third of the river. Some pollution-intolerant species which had disappeared from the upper reaches of the river between 1900 and 1950 have been returning since 1970 (e.g. Polyodon spathula, Hiodon tergisus, and Carpiodes velifer). A few pollution-tolerant species have declined in abundance since 1970 (e.g. bullheads and Ictalurus catus). The most abundant fishes in the lock chamber samples of 1957-87 were Notropis atherinoides, Dorosoma cepedianum, Aplodinotus grunniens, Notropis volucellus, and Ictalurus punctatus. The ongoing recovery of the Ohio River fish community should encourage us to take additional steps to protect the river from catastrophic spills of toxic materials and to reintroduce eliminated native fishes

Erratum: A yellow ‘Hippolais’ warbler trapped at Ngulia re-identified as Eastern Olivaceous Warbler Iduna pallida

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