The OECD software tool for screening chemicals for persistence and long-range transport potential

We present the software implementation of The OECD P_OV & LRTP Screening Tool (The Tool) that is used to assess the environmental hazard of organic chemicals using metrics of overall persistence (P_OV) and long-range transport potential (LRTP). The Tool is designed to support decision making for chemical management and includes features that are recommended by the Organization for Economic Cooperation and Development (OECD) expert group on multimedia modeling. The Tool is useful for screening the environmental hazard potential of non-ionizing organic chemicals whose environmental partitioning can be described by absorptive capacities of environmental media estimated from partitioning between air, water and octanol in the laboratory. The software includes data storage functionality, and a user interface that is designed to facilitate simple data input and straightforward interpretation of the model results. The effect of uncertainties in input properties describing chemicals can be assessed with a Monte Carlo analysis. The software is evaluated and illustrated by comparing results from The Tool with those from other models and by evaluating four substances that are candidates for regulation or ban under the Stockholm Convention on Persistent Organic Pollutants.     

Vergleich von hydraulischen und chemischen Sedimenteigenschaften aus Spül- und Kernbohrungen im Raum Peine (Norddeutschland)

Comparison of hydraulic and chemical properties of sediments from flush- and core drillings in the area of Peine (Germany). Because of financial constraints, investigations of nitrate metabolism are often based on disturbed borehole samples. It is arguable, however, whether disturbed samples are suitable for these types of investigations. Disadvantages of disturbed samples in comparison to undisturbed core samples are well known and include possible contamination of the sample by mud additives, destruction of the sediment formation and the insecurity concerning the correct depth allocation. In this study, boreholes were drilled at three locations to a maximum depth of 50?m. The extracted samples, as intact sediment cores and drill cuttings, were studied with regard to chemical and hydraulic parameters of the aquifer sediments. The results show: 1. hydraulic parameters are not affected by clay-based mud; 2. disturbed samples contain less fine grain material relative to the core samples, and the hydraulic conductivity can only be estimated from catch samples; 3. catch samples contain fewer reducing agents (sulphides, organic carbon) than core samples in hydraulically passive zones (defined as K < 10^–6?m?·?s^–1); 4. the results of analyses of disturbed and undisturbed core samples are in good agreement for hydraulically active zones (K ≥ 10^–6?m?·?s^–1).     

Assay of ascorbic phosphates and in-vitro availability assay of ascorbic mono-and polyphosphates

A method was devised to assay ascorbic phosphate esters in biological materials by potassium bromoxide hydrolysis followed by determination of the liberated ascorbic acid. For the differential measurement of ascorbic acid and ascorbic phosphate, a spectrophotometric method was employed to screen out the interfering substances based on studies of absorbance curves of 2,4-dinitrophenyl hydrazine derivatives. A variety of vertebrate tissues were examined for phosphatase activity on ascorbic phosphate esters. The results suggest that pigeon kidney, rat liver and several tissues of fishes readily hydrolyse ascorbic monophosphate but not ascorbic polyphosphate. Hydrolysis of ascorbic monophosphate is completed by both phosphatases of intestine, kidney and liver acting at neutral pH and phosphatase of stomach acting at acid pH. Thus, ascorbic monophosphate has the potential to be a source of available vitamin C in vivo, and this explains its antiscorbutic activity in scurvy-prone animals.     

Calculating the steady-state polarizations of quantum cellular automata (QCA) circuits

We present on the use of well-known stochastic methods for computing the steady-state polarizations of quantum cellular automata (QCA) circuits. Typically, a Boltzmann distribution, which requires the exploration of the complete configuration space of an \(N\) -cell QCA circuit, is used to compute the \(2^N\) steady-states of the QCA circuit. However, the exponential growth in states as the circuit size grows makes computing the Boltzmann distribution infeasible for large circuits. Thus, we approximate the Boltzmann distribution of a QCA circuit by conducting a partial exploration of the complete configuration space by means of a Monte Carlo method, simulated annealing, and a genetic algorithm. The approximated Boltzmann distribution from each method was able to compute the steady-state polarizations with a very high degree of accuracy, with the simulated annealing algorithm producing the best results.     

Measures of overall persistence and the temporal remote state

The overall persistence, Pov, has been suggested as an indicator that integrates single media half-lives and phase partitioning. However, the application of this indicator is hindered by the fact that there are different definitions of Pov and that the most common measure of Pov, the residence time at steady state, depends heavily on the release pattern. Here, different measures are compared that can be used to compute Pov from the mass of a chemical in the environment as a function of time in a dynamic multimedia model. These measures include the equivalence width, which corresponds to the residence time at steady state, the mean value of the function of mass vs time ("mean time"), and the clearance time. The temporal remote state is defined as the state of the model system long after the stop of emissions; it is independent of the release pattern of a chemical. The mean time in the temporal remote state reflects the long-term removal rate of a chemical and is used as a persistence benchmark. Correlations of the three measures of Pov to the persistence benchmark are analyzed. The maximum equivalence width, which is obtained with release to one of the media air, water, or soil, is a good approximation of the mean time in the temporal remote state. Because the maximum equivalence width is identical to the maximum residence time at steady state, the mean time in the temporal remote state can be estimated with existing steady-state models.     

Railgun performance with a two-stage light-gas gun injector

Results obtained with the HELEOS (hypervelocity experimental launcher for equation of state) railgun, which uses a two-stage light-gas gun (2SLGG) as an injector, are presented. The high-velocity 2SLGG injector preaccelerates projectiles up to ~7 km/s. The high injection velocity reduces the exposure duration of the railgun barrel to the passing high temperature plasma armature, thereby reducing the ablation and subsequent armature growth. The 2SLGG also provides a column of cool, high-pressure hydrogen gas to insulate the rails behind the projectile, thereby eliminating restrike. A means to form an armature behind the injected projectile has been developed. In preliminary tests, the third-stage railgun has successfully increased the projectile velocity by 1.35 km/s. Extensive diagnostics have been used to determine the behavior of the armature and track the launcher's performance. Insome cases, velocity increases in the railgun section have been achieved, which are in close agreement with theoretical predictions, whereas in other experiments deviations from theoretical have been observed. The reasons for and implications of these results are addressed. Recent tests are reported     

Galerkin's method and the variational procedure

Galerkin's method and the variational procedure, when applied to most practical problems in electromagnetics, lead to matrix equations of the same form. Variational procedures for self-adjoint and nonself-adjoint operators also result in the same form of matrix equations for a large subclass of problems. However, the three cases may yield different matrix equations in general. This paper examines the subclass of problems for which these methods result in the same matrix equation and provides systematic ways for classification of problems for which two or all three of the cases lead to the same matrix equation. It also describes properties of the coefficient matrix in the matrix equation     

Anisotropic Filtering of Non-Linear Surface Features

A new method for noise removal of arbitrary surfaces meshes is presented which focuses on the preservation and sharpening of non‐linear geometric features such as curved surface regions and feature lines. Our method uses a prescribed mean curvature flow (PMC) for simplicial surfaces which is based on three new contributions: 1. the definition and efficient calculation of a discrete shape operator and principal curvature properties on simplicial surfaces that is fully consistent with the well‐known discrete mean curvature formula, 2. an anisotropic discrete mean curvature vector that combines the advantages of the mean curvature normal with the special anisotropic behaviour along feature lines of a surface, and 3. an anisotropic prescribed mean curvature flow which converges to surfaces with an estimated mean curvature distribution and with preserved non‐linear features. Additionally, the PMC flow prevents boundary shrinkage at constrained and free boundary segments.