Growth inhibition in Japanese medaka (Oryzias latipes) fish exposed to tetrachloroethylene

A recent study in our laboratory has demonstrated that tetrachloroethylene (TCE) is acutely toxic to Japanese medaka (Oryzias latipes) larvae with a 96 hr-LC50 of 18 (17-19) mg/mL (Spencer et al., 2002). In the present study we hypothesize that TCE exposure induces a developmental effect in Japanese medaka. Growth and age specific sensitivity of Japanese medaka larvae were studied with four age groups (7, 14, 21 and 28 days old) to determine tetrachloroethylene effects on these parameters. The medaka larvae were exposed for 96 hours in a single concentration (10 mg/mL) of TCE. The toxic endpoints evaluated were larvae weight, length, water content and protein concentration. The study revealed that exposure of medaka larvae to this sub-acute concentration of TCE significantly reduced length and weight in the treated group. The difference in growth between control and treated groups was more obvious in age versus length, than in age versus weight. The dry weight-fresh weight ratio (dw/fw) was shown to be higher in the control group. Water content in TCE-treated medaka was higher than in the control group, and younger fry had more water content than older ones. A higher protein concentration was also observed in TCE-treated medaka compared to the control group. These results indicate that TCE has a profound effect on the growth and development of Japanese medaka larvae.     

The structure of turbulence near a tall forest edge: the backward-facing step flow analogy revisited

Flow disturbances near tall forest edges are receiving significant attention in diverse disciplines including ecology, forest management, meteorology, and fluid mechanics. Current theories suggest that near a forest edge, when the flow originates from a forest into a large clearing, the flow retains its forest canopy turbulence structure at the exit point. Here, we propose that this framework is not sufficiently general for dense forested edges and suggest that the flow shares several attributes with backward-facing step (BFS) flow. Similar analogies, such as rotor-like circulations, have been proposed by a number of investigators, though the consequences of such circulations on the primary terms in the mean momentum balance at the forest clearing edge have rarely been studied in the field. Using an array of three triaxial sonic anemometers positioned to measure horizontal and vertical gradients of the velocity statistics near a forest edge, we show that the flow structure is more consistent with an intermittent recirculation pattern, rather than a continuous rotor, whose genesis resembles the BFS flow. We also show that the lateral velocity variance, v'2, is the moment that adjusts most slowly with downwind distance as the flow exits from the forest into the clearing. Surprisingly, the longitudinal and vertical velocity variances (u'2 and w'2) at the forest edge were comparable in magnitude to their respective values at the center of a large grass-covered forest clearing, suggesting rapid adjustment at the edge. Discussions on how the forest edge modifies the spectra and co-spectra of momentum fluxes, effective mixing length, and static pressure are also presented.     

Persistence models for mark-recapture

The stable of models available for analyzing mark-recapture data (Otis et al. Wild Momogr 66:135, 1978) includes those having behavioral characteristics, time variation, heterogeneity, along with combinations of those characteristics. This paper proposes use of a series of models based on the persistence model of Ramsey and Usner (Biometrics 59:331–339, 2003). We show that persistence can be modeled in combination with behavior and with time variation. We apply the persistence model to situations in which capture occasions are not equally-spaced in time. Two case studies illustrate the use of these extended persistence models.     

Evaluation of fast atmospheric dispersion models in a regular street network

Environmental Fluid Mechanics - The need to balance computational speed and simulation accuracy is a key challenge in designing atmospheric dispersion models that can be used in scenarios where...