Wirkungsschwellen für chemische Stoffe in Biosystemen Eine theoretische Betrachtung

Die aus der chemischen Umsetzung mit endogenen Molekülen resultierende biologische Wirkung von Fremdstoffen wird diskutiert, ausgehend von den Grunds?tzen der Thermodynamik und Kinetik. Dabei führt ein unter vereinfachenden Annahmen durchgeführter Vergleich der thermischen Energieverteilung von Molekülen mit typischen biochemischen Aktivierungsenergien zu dem Ergebnis, da? aus statistischen Gründen für jede mit stofflichen Umsetzungen zusammenh?ngende biologische Wirkung ein Schwellenwert existieren sollte.     

Modelling piloted ignition of wood and plastics

To gain insight in the startup of an incinerator, this article deals with piloted ignition. A newly developed model is described to predict the piloted ignition times of wood, PMMA and PVC. The model is based on the lower flammability limit and the adiabatic flame temperature at this limit. The incoming radiative heat flux, sample thickness and moisture content are some of the used variables. Not only the ignition time can be calculated with the model, but also the mass flux and surface temperature at ignition. The ignition times for softwoods and PMMA are mainly under-predicted. For hardwoods and PVC the predicted ignition times agree well with experimental results. Due to a significant scatter in the experimental data the mass flux and surface temperature calculated with the model are hard to validate. The model is applied on the startup of a municipal waste incineration plant. For this process a maximum allowable primary air flow is derived. When the primary air flow is above this maximum air flow, no ignition can be obtained.     

?kotoxikologie soll endlich wissenschaftliches Fach werden

Ohne Zusammenfassung     

A CART technique to adjust production from longwall coal operations under ventilation constraints

Methane emissions in longwall coal mines can arise from a variety of geologic and production factors, where ventilation and degasification are primary control measures to prevent excessive methane levels. However, poor ventilation practices or inadequate ventilation may result in accumulation of dangerous methane-air mixtures. The need exists for a set of rules and a model to be used as guidelines to adjust coal production according to expected methane emissions and current ventilation conditions.In this paper, hierarchical classification and regression tree (CART) analyses are performed as nonparametric modeling efforts to predict methane emissions that can arise during extraction of a longwall panel. These emissions are predicted for a range of coal productivities while considering specific operational, panel design and geologic parameters such as gas content, proximate composition of coal, seam height, panel width, cut height, cut depth, and panel size. Analyses are conducted for longwall mines with and without degasification of the longwall panel. These models define a range of coal productivities that can be achieved without exceeding specified emissions rates under given operating and geological conditions.Finally, the technique was applied to longwall mines that operate with and without degasification system to demonstrate its use and predictive capability. The predicted results proved to be close to the actual measurements to estimate ventilation requirements. Thus, the CART-based model that is given in this paper can be used to predict methane emission rates and to adjust operation parameters under ventilation constrains in longwall mining.     

Neue Kooperation in den Umweltwissenschaften — Assoziation zwischen GDCh und UWSF

Ohne Zusammenfassung