Continuous-flow laboratory simulation of stream water quality changes downstream of an untreated wastewater discharge.

In regions of the world with poor provision of wastewater treatment, raw sewage is often discharged directly into surface waters. This paper describes an experimental evaluation of the fate of two organic chemicals under these conditions using an artificial channel cascade fed with a mix of settled sewage and river water at its upstream end and operated under continuous steady-state conditions. The experiments underpin an environmental risk assessment methodology based on the idea of an “impact zone” (IZ) – the zone downstream of wastewater emission in which water quality is severely impaired by high concentrations of unionised ammonia, nitrite and biochemical oxygen demand (BOD). Radiolabelled dodecane-6-benzene sulphonate (DOBS) and aniline hydrochloride were used as the model chemical and reference compound respectively. Rapid changes in 14C counts were observed with flow-time for both these materials. These changes were most likely to be due to complete mineralisation. A dissipation half-life of approximately 7.1 h was observed for the 14C label with DOBS. The end of the IZ was defined as the point at which the concentration of both unionised ammonia and nitrite fell below their respective predicted no-effect concentrations for salmonids. At these points in the cascade, approximately 83 and 90% of the initial concentration of 14C had been removed from the water column, respectively. A simple model of mineral nitrogen transformations based on Michaelis–Menten kinetics was fitted to observed concentrations of NH4, NO2 and NO3. The cascade is intended to provide a confirmatory methodology for assessing the ecological risks of chemicals under direct discharge co

Collective polarization exchanges in collisions of photon clouds

The one-loop "vacuum" Heisenberg-Euler coupling of four electromagnetic fields can lead to interesting collective effects in the collision of two photon clouds, on a time scale orders of magnitude faster than one estimates from the cross-section and density. We estimate the characteristic time for macroscopic transformation of positive to negative helicity in clouds that are initially totally polarized and for depolarization of a polarized beam traversing an unpolarized cloud.Comment: Recapitulates much that is in hep-ph/0402127, with new results in the last section, and the first section drastically reduced in view of the previous work of Kotkin and Serbo. Typo corrected in eq. 1

Beleidsboodschappen Natuurverkenning 2010-2040

Het natuurbeleid bevindt zich in een overgangsfase. Zowel rijk als provincies, maatschappelijke organisaties en het bedrijfsleven zijn op zoek naar verbetering van het bestaande natuurbeleid en hun positie daarbinnen. Het gaat daarbij niet alleen om natuurbeleid in de strikte zin, maar onder meer ook om het landschaps-, ruimtelijk, energie- en voedselbeleid. Dit artikel draagt bouwstenen voor die zoektocht aan op basis van vier kijkrichtingen die zijn ontwikkeld in de Natuurverkenning 2010-2040

Renormalizability of N=1\mathcal{N}=1 super Yang-Mills theory in Landau gauge with a Stueckelberg-like field

We construct a vector gauge invariant transverse field configuration $V^H$, consisting of the well-known superfield $V$ and of a Stueckelberg-like chiral superfield. The renormalizability of the Super Yang Mills action in the Landau gauge is analyzed in the presence of a gauge invariant mass term $m^2 \int dV \mathcal{M}(V^H)$, with $\mathcal{M}(V^H)$ a power series in $V^H$. Unlike the original Stueckelberg action, the resulting action turns out to be renormalizable to all orders.Comment: 19 page

A dynamic model of the eye nystagmus response to high magnetic fields

It was recently shown that high magnetic fields evoke nystagmus in human subjects with functioning vestibular systems. The proposed mechanism involves interaction between ionic currents in the endolymph of the vestibular labyrinth and the static magnetic field. This results in a Lorentz force that causes endolymph flow to deflect the cupulae of the semi-circular canals to evoke a vestibular-ocular reflex (VOR). This should be analogous to stimulation by angular acceleration or caloric irrigation. We made measurements of nystagmus slow-phase velocities in healthy adults experiencing variable magnetic field profiles of up to 7 Tesla while supine on a bed that could be moved smoothly into the bore of an MRI machine. The horizontal slow-phase velocity data were reliably modelled by a linear transfer function incorporating a low-pass term and a high-pass adaptation term. The adaptation time constant was estimated at 39.3 s from long-exposure trials. When constrained to this value, the low-pass time constant was estimated at 13.6 3.6 s (to 95% confidence) from both short and long exposure trials. This confidence interval overlaps with values obtained previously using angular acceleration and caloric stimulation. Hence it is compatible with endolymph flow causing a cupular deflection and therefore supports the hypothesis that the Lorentz force is a likely transduction mechanism of the magnetic-field evoked VOR