A comparison of runoff- and spray-drift-related pesticide contamination in agricultural surface waters : exposure, effects and mitigation

Includes bibliographical references.Runoff and spray-drift-related pesticide input are important sources of non pointsource pesticide pollution in surface waters but few studies have directly compared these routes in a risk assessment scenario. Accordingly a risk assessment approach was instituted to determine differences between runoff and spray-drift based on exposure, effect and mitigation. An exposure assessment using predictive modelling that was validated by fieldbased sampling was used to compare relative pesticide inputs associated with runoff and spray-drift at the catchment level

Use of Erythrocyte Measurements to Identify Triploid Saugeyes

The use of erythrocyte size measurements as a possible alternative to flow cytometry for identifying triploid saugeyes (female walleye Stizostedion vitreum X male sauger S. canadense) was evaluated. Blood smear preparations were made from 32 heat-shocked saugeyes (1.0-42.7 g; 52-185 mm total length), which consisted of 12 diploids and 20 triploids, as determined by flow cytometry after blood cells were stained with propidium iodide. The length, width, surface area, and volume of the cell and nucleus of 100 erythrocytes were determined for each fish. The cell and nuclear dimensions were measured at 1,000X magnification with a calibrated ocular micrometer. Discriminant analysis was used to distinguish diploids and triploids based on their score profiles. Results showed that triploid saugeyes had significantly larger erythrocyte cell and nucleus measurements than their diploid counterparts (N = 32; P < 0.0001). Erythrocyte measurements correctly distinguished 93.8% of fish samples as diploids or triploids, but measurements require about 1 h/fish. The potential applications of this technique for fisheries management and aquaculture are discussed.This research was funded by the Ohio Division of Wildlife under Federal Aid in Sport Fish Restoration, project F-69-P-5, Fish Management in Ohio

Blowing-induced boundary-layer separation of shear-thinning fluids

PP Dabrowski & JP Denie

Born-Infeld Quantum Condensate as Dark Energy in the Universe

Some cosmological implications of ultraviolet quantum effects leading to a condensation of Born-Infeld matter are considered. It is shown that under very general conditions the quantum condensate can not act as phantom matter if its energy density is positive. On the other hand, it behaves as an effective cosmological constant in the limit where quantum induced contributions to the energy-momentum tensor dominate over the classical effects.Comment: 9 pages, no figures. Extended discussion, In Press, Physics Letters

Bayesian Physics Informed Neural Networks for Data Assimilation and Spatio-Temporal Modelling of Wildfires

We apply the Physics Informed Neural Network (PINN) to the problem of wildfire fire-front modelling. We use the PINN to solve the level-set equation, which is a partial differential equation that models a fire-front through the zero-level-set of a level-set function. The result is a PINN that simulates a fire-front as it propagates through the spatio-temporal domain. We show that popular optimisation cost functions used in the literature can result in PINNs that fail to maintain temporal continuity in modelled fire-fronts when there are extreme changes in exogenous forcing variables such as wind direction. We thus propose novel additions to the optimisation cost function that improves temporal continuity under these extreme changes. Furthermore, we develop an approach to perform data assimilation within the PINN such that the PINN predictions are drawn towards observations of the fire-front. Finally, we incorporate our novel approaches into a Bayesian PINN (B-PINN) to provide uncertainty quantification in the fire-front predictions. This is significant as the standard solver, the level-set method, does not naturally offer the capability for data assimilation and uncertainty quantification. Our results show that, with our novel approaches, the B-PINN can produce accurate predictions with high quality uncertainty quantification on real-world data.Comment: Accepted for publication in Spatial Statistic

XMM-EPIC observation of MCG-6-30-15: Direct evidence for the extraction of energy from aspinning black hole?

We present XMM-Newton European Photon Imaging Camera (EPIC) observations of the bright Seyfert 1 galaxy MCG-6-30-15, focusing on the broad Fe K$\alpha$ line at ~6keV and the associated reflection continuum, which is believed to originate from the inner accretion disk. We find these reflection features to be extremely broad and red-shifted, indicating its origin from the very most central regions of the accretion disk. It seems likely that we have caught this source in the ``deep minimum'' state first observed by Iwasawa et al. (1996). The implied central concentration of X-ray illumination is difficult to understand in any pure accretion disk model. We suggest that we are witnessing the extraction and dissipation of rotational energy from a spinning black hole by magnetic fields connecting the black hole or plunging region to the disk.Comment: 6 pages and one postscript figure. Accepted for publication in MNRAS letter

Validation of the AGDISP model for predicting airborne atrazine spray drift : a South African ground application case study

Air dispersion software models for evaluating pesticide spray drift during application have been developed that can potentially serve as a cheaper convenient alternative to field monitoring campaigns. Such models require validation against field monitoring data in order for them to be employed with confidence, especially when they are used to implement regulatory measures or to evaluate potential human exposure levels. In this case study, off‐target pesticide drift was monitored during ground application of a pesticide mixture to a sorghum field in South Africa. Atrazine was used as a drift tracer. High volume air sampling onto polyurethane foam (PUF) was conducted at six downwind locations and at four heights at each sampling point. Additional data, including meteorological information, required to simulate the spray drift with the AGDISP® air dispersion model was collected. The PUF plugs were extracted by a plunger method utilising a hexane:acetone mixture with analysis by GC‐NPD (94.5% recovery, 3.3% RSD, and LOD 8.7 pg). Atrazine concentrations ranged from 4.55 ng L‐1 adjacent to the field to 186 pg L‐1 at 400 m downwind. These results compared favourably with modeled output data, resulting in the validation of the model up to 400 m from the application site for the first time.Sensitivity studies showed the importance of droplet size distribution on spray drift, which highlighted the need for good nozzle maintenance. Results of this case study indicate that the model may provide meaningful input into environmental and human health risk assessment studies in South Africa and other developing countries.http://www.elsevier.com/locate/chemospherehb2017Chemistr

Origins of the Highly Ionized Gas along the Line of Sight towards HD 116852

We present Hubble Space Telescope Imaging Spectrograph (HST/STIS) and Far Ultraviolet Spectroscopic Explorer (FUSE) observations of high ion interstellar absorption along the sight line to HD 116852. At a distance of 4.8 kpc, HD 116852 is an O9 III star lying in the low Galactic halo, -1.3 kpc from the plane of the Galaxy in the direction l = 304.9, b = -16.1. The STIS E140H grating observations provide high-resolution (FWHM = 2.7 km/s) spectra of the resonance doublets of Si IV, C IV, and N V. These data are complemented by medium-resolution (FWHM = 20 km/s) FUSE spectra of O VI. We find evidence for three distinct types of highly ionized gas present in the data. First, two narrow absorption components are resolved in the Si IV and C IV profiles, at approximate LSR velocities of -36 and -10 km/s. These narrow components appear to be produced in gas associated with the Norma and Sagittarius spiral arms, at approximate z-distances of -1.0 and -0.5 kpc, respectively. Second, we detect an intermediate-width component in C IV and Si IV, at 17 km/s, which we propose could arise at the conductive interface at the boundary between a low column density neutral or weakly ionized cloud and the surrounding hot medium. Finally, a broad collisionally ionized component of gas responsible for producing the smooth N V and O VI profiles is observed; such absorption is also present to a lesser degree in the profiles of Si IV and C IV. The broad O VI absorption is observed at a velocity displaced from the broad C IV component by almost 20 km/s, an amount large enough to suggest that the two ions may not co-exist in the same physical location.Comment: 39 pages, 6 figures; accepted for publication in January 10, 2003 edition of The Astrophysical Journa