SOME ANALYTICS OF WHY CONDITIONAL IRRs CAN CONTAIN GROWTH RATE RELATED MEASUREMENT ERROR

This paper investigates the consequences of incorrectly modelling the investment outflow/benefit inflow relationship on estimates of the internal rate of return (IRR) prepared by using cash recovery rates (CRRs). The main result of this paper is that CRR-based estimates of the IRR will contain such bias if and only if either the duration of the assumed shape of the investment outflow/benefit inflow relationship is less than the duration of the true investment outflow/benefit inflow relationship for all rates of interest or the duration of the assumed shape of the investment outflowlbenefit inflow relationship is greater than the duration of the true investment outflowlbenefit inflow relationship for all rates of interest. This result is then applied to the case where both the true and the assumed shape of the investment outflow/benefit inflow relationships have benefit inflows that change exponentially over time. It is shown that if the exponential rate of change is mis-specified the resulting CRR-based estimate of the IRR will contain systematic bias monotonically related to the rate of growth.     

Toxicity of Detroit River Sediment-Bound Contaminants to Ultraplankton

Four sites in the Detroit River/Lake Erie western basin were evaluated for their toxicity. The evaluation was based on 1) bulk chemical characterization of the sediments, 2) chemical composition of the sediment elutriates, and 3) toxicity of the elutriates to ultraplankton and microplankton/net plankton. A sequence of decreasing contamination was determined from the chemical composition of the elutriates based on the elutriation release of metals such as Zn, Mn, Cd, Ni, and Co. Bioassessment of elutriate toxicity was determined by carbon-14 Algal Fractionation Bioassays (AFB's) which were conducted with various dilutions of standard and Chelex-100 treated elutriates. Site A (near Windsor, Ontario) and Site D (western Lake Erie) were found to be toxic to ultraplankton. The observed toxicity was attributed to the bioavailability and synergistic impact of elutriated metals on ultraplankton production. A direct relationship between the water soluble metal fraction and toxicity was observed. These results confirmed that sediment toxicity should not be evaluated solely on bulk chemical composition of the sediments. The AFB's have been proven useful in the bioassessment of sediments due to their rapidity/sensitivity and hence could be routinely used for the screening and early detection of contaminants affecting fast growing organisms which form the basis of the aquatic food chain.     

Integrated modelling under uncertainty in watershed-level assessment and management.

Uncertainty in water quality model predictions is inevitably high due to natural stochasticity, model uncertainty, and parameter uncertainty. An integrated modelling system (modified-BASINS) under uncertainty is described and demonstrated for use in receiving-water quality prediction and watershed management. A Monte Carlo simulation was used to investigate the effect of various uncertainty types on output prediction. Without pollution control measures in the watershed, the concentrations of total nitrogen (T-N) and total phosphorus (T-P) in the Hwaong Reservoir, considering three uncertainty types, would be less than about 4.4 and 0.23 mg L(-1), respectively, in 2012, with 90% confidence. The effects of two watershed management practices, wastewater treatment plants (WWTP) and constructed wetlands (WETLAND), were evaluated. The combined scenario (WWTP + WETLAND) was the most effective at improving reservoir water quality, bringing concentrations of T-N and T-P in the Hwaong Reservoir to less than 3.4 and 0.14 mg L(-1), 24 and 41% improvements, respectively, with 90% confidence. Overall, the Monte Carlo simulation in the integrated modelling system was practical for estimating uncertainty and reliable in water quality prediction. The approach described here may allow decisions to be made based on the probability and level of risk, and its application is recommended.     

Pilot experiments with electrodialysis and ozonation for the production of a fertiliser from urine.

Pilot tests were performed with a process combination of electrodialysis and ozonation for the removal of micropollutants and the concentration of nutrients in urine. In continuous and batch experiments, maximum concentration factors up to 3.5 and 4.1 were obtained, respectively. The desalination capacity did not decrease significantly during continuous operation periods of several weeks. Membrane cleaning after 195 days resulted in approximately 35% increase in desalination rate. The Yeast Estrogen Screen (YES), a bioassay that selectively detects oestrogenic compounds, confirmed that about 90% of the oestrogenic activity was removed by electrodialysis. HPLC analysis showed that ibuprofen was removed to a high extent, while other micropollutants were below the detection limit. In view of the fact that ibuprofen is among the most rapidly transported micropollutants in electrodialysis processes, this result indicates that electrodialysis provides an effective barrier for micropollutants. Standardised plant growth tests were performed in the field with the salt solution resulting from the treatment by electrodialysis and subsequent ozonation. The results show that the plant height is comparable to synthetic fertilisers, but the crop yield is slightly lower. The latter is probably caused by volatilisation losses during field application, which can be prevented by improved application technologies.     

Monitoring, removal and risk assessment of cytostatic drugs in hospital wastewater.

Cytostatic agents are applied in cancer therapy and subsequently excreted into hospital wastewater. As these substances are known to be carcinogenic, mutagenic and toxic for reproduction, they should be removed from wastewater at their source of origin.In this study the fate and effects of the cancerostatic platinum compounds (CPC) cisplatin, carboplatin, oxaliplatin, 5-fluorouracil (5-FU) and the anthracyclines doxorubicin, daunorubicin and epirubicin were investigated in hospital wastewater. Wastewater from the in-patient treatment ward of a hospital in Vienna was collected and monitored for the occurrence of the selected drugs. A calculation model was established to spot the correlation between administered dosage and measured concentrations. To investigate the fate of the selected substances during wastewater treatment, the oncologic wastewater was treated in a pilot membrane bioreactor system (MBR) and in downstream advanced wastewater treatment processes (adsorption to activated carbon and UV-treatment). Genotoxic effects of the oncologic wastewater were assessed before and after wastewater treatment followed by a risk assessment.Monitoring concentrations of the selected cytostatics in the oncologic wastewater were in line with calculated concentrations. Due to different mechanisms (adsorption, biodegradation) in the MBR-system 5 - FU and the anthracyclines were removed < LOD, whereas CPC were removed by 60%. In parallel, genotoxic effects could be reduced significantly by the MBR-system. The risk for humans, the aquatic and terrestrial environment by hospital wastewater containing cytostatic drugs was classified as small in a preliminary risk assessment.     

Employment,schooling and productivity growth

Summary This paper presents an empirical analysis of labour demand and labour productivity growth in The Netherlands. Assuming an aggregate production function with as factors capital and 3 types of labour, distinguished by educational attainment, cost minimization leads to a set of 3 labour demand relations to be estimated on time series data. Using the estimates and the implied elasticities, aggregate labour productivity growth is decomposed into factor substitution, autonomous factors, labour time shortening, economies of scale, utilization rates and the increased educational level of the working population. The contributions of substitution, utilization rates and education appear to be substantial, notably in the seventies.

List of symbols

Variables a _i Efficiency index of skill leveli - C production - h _i working-time index for skill leveli - g _i steady-state growth rate of skill leveli - K capital stock - L _i employment volume of skill leveli - L _i ^* desired level of labour skill leveli - p output price - p ^* desired output price - s _i ^* long-run static labour shares in the production value - p _k rental price of capital - P index of total factor productivity - P _l index of labour productivity - u _i utilization rate of skill leveli - u _k utilization rate of capital - w _i wage rate for skill leveli - y production volume - y _yij Hicks partial elasticities of complementarity - _i steady-state cost share of skill leveli - _k Bk steady-state cost share of capital - _f lf highest level price index in cost function nesting - _g 4 intermediate level price index in cost function nesting - _h 4 lowest level price index in cost function nesting - _i steady-state relative wage share of skill leveli - _ij Allen partial elasticities of substitution Parameters d _i l adjustment speed of skill leveli - d _p price adjustment speed - M mark-up on marginal costs - scale elasticity of production - _i distribution parameter in cost function,i = 3, g - _i distribution parameter in cost function,i = k, h - _i distribution parameter in cost function,i =1, 2 - _i autonomous labour productivity growth for skill leveli - _i cost share of skill level in base year - _f production cost index in base year - _i hours elasticity in labour efficiency index - group elasticity of substitution betweenL ₃ and (K, (L ₁,L ₂)) - _g Og group elasticity of substitution betweenK and (L ₁,L ₂) - _h 6h group elasticity of substitution betweenL ₁ andL ₂ We would like to thank B. Downey, G.M.M. Gelauff, A. Nieuwenhuis, J.M.M. Ritzen, J.C. Siebrand and an unknown referee for helpful comments on earlier drafts.     

A generalized maximum likelihood characterization of the normal distribution

LetP be a probability measure on ℝ andI _x be the set of alln-dimensional rectangles containingx. If for allx ∈ ℝⁿ and θ ∈ ℝ the inequality holds,P is a normal distributioin with mean 0 or the unit mass at 0. The result generalizes Teicher’s (1961) maximum likelihood characterization of the normal density to a characterization ofN(0, σ²) amongall distributions (including those without density). The m.l. principle used is that of Scholz (1980).     

Economic humidity control: an alternative to reheat

Heat pipe technology will have a significant impact on the power consumption of many manufacturing industries, the installation costs of new or replacement air conditioning systems, and on electric utility peak demands.