Nitrogen management in reservoir catchments through constructed wetland systems.

In this study, nitrogen removal was investigated in pilot-scale subsurface flow (SSF) and in free water surface flow (FWS) constructed wetlands installed in the campus of TUBITAK-Marmara Research Center, Gebze, near Istanbul, Turkey. The main purposes of this study are to apply constructed wetlands for the protection of water reservoirs and to reuse wastewater. Experiments were carried out at continuous flow reactors. The effects of the type of plants on the removal were investigated by using emergent (Canna, Cyperus, Typhia spp., Phragmites spp., Juncus, Poaceae, Paspalum and Iris.), submerged (Elodea, Egeria) and floating (Pistia, Salvina and Lemna) marsh plants at different conditions. During the study period HLRs were 30, 50, 70, 80 and 120 L m(2)d(-1) respectively. The average annual NH4-N, NO(3)-N, organic N and TN treatment efficiencies in SSF and FWS wetlands are 81% and 68%, 37% and 49%, 75% and 68%, 47% and 53%, respectively. Nitrification, denitrification and ammonification rate constant (k20) values in SSF and FNS systems have been found as 0.898 d(-1) and 0.541 d(-1), 0.488 d(-1) and 0.502 d(-1), 0.986 d(-1) and 0.908 respectively. Two types of the models (first-order plug flow and multiple regression) were tried to estimate the system performances.     

Adjustment costs and time-to-build in factor demand in the U.S. manufacturing industry

In order to explain cyclical behavior of factor demand, the static neoclassical model of the firm has been extended to include either adjustment costs (e.g. Lucas (1967)) or time-to-build considerations as in Kydland and Prescott (1982). This paper presents an intertemporal factor demand model which accounts for adjustment costs and gestation lags. The closed form solution of the model is a highly restricted vector ARMA-process that is estimated using quarterly data for the manufacturing industry in the U.S., 1960–1988. The main conclusion is that both sources of dynamics of factor demand are identifiable and found to be empirically of importance.     

Stories from the Front‐line: How they Construct the Organization*

abstract Drawing on social constructionist theory this paper applies discourse analysis to ten narratives told by service delivery staff in one distribution network. The analysis looks at how the narratives construct the organization through their constructions of self (the narrator), customer and manufacturer and their constructions of the relationships linking these three sets of actors. The paper argues that the narrators construct the self either as an organizational customer or an organizational partner. The two constructions locate conflict either within the organization or at the customer–organizational boundary respectively. The implications of this are suggested. Contrasts between the manner in which organizational members construct the self as customer or partner and the construction of the organizational member in the internal customer literature are highlighted and briefly discussed.     

Are differences in firm size transitory or permanent?

An Erratum for this article has been published in Journal of Applied Econometrics 18(2) 2003, 249 Previous empirical work on corporate growth rates using cross‐section or short‐panel econometric techniques suggests that growth rates are random but that some degree of mean reversion exists. This means that size differences between firms are transitory. Another, more natural way to explore the long‐run distribution of firm sizes is to examine data on the growth of particular firms over long periods of time. Using a sample of 147 UK firms observed continually for more than 30 years, our conclusions are that growth rates are highly variable over time and that differences in growth rates between firms do not persist for very long. Further, firms show no tendency to converge to either a common size or to a pattern of stable size differences over time. These results are compared and contrasted with standard approaches that suggest that firms reach and maintain stable positions in a skewed size distribution. Copyright © 2002 John Wiley & Sons, Ltd.     

THE MORISHIMA ELASTICITY OF SUBSTITUTION FOR THE VARIABLE PROFIT FUNCTION AND THE DEMAND FOR IMPORTS IN THE UNITED STATES*

In this article, I derive expressions for the Morishima elasticities of substitution (MES) for the variable profit function and estimate these elasticities to shed some light on the substitutability between imports, capital services, and labor services. The results reveal that capital services and imports are Morishima substitutes, irrespective of whether the price of capital services or imports changes, and imports and labor services are also Morishima substitutes, irrespective of whether the price of imports or the wage rate changes. Thus, an increase in the price of U.S. imports (through tariffs or duties) will result in substitution (in the Morishima sense) into labor and capital services.     

Zero-valent iron treatment of RDX-containing and perchlorate-containing wastewaters from an ammunition-manufacturing plant at elevated temperatures.

The use of zero-valent iron for treating wastewaters containing RDX and perchlorate from an army ammunition plant (AAP) in the USA at elevated temperatures and moderately elevated temperature with chemical addition was evaluated through batch and column experiments. RDX in the wastewater was completely removed in an iron column after 6.4 minutes. Increasing the temperature to 75 degrees C decreased the required retention time to 2.1 minutes for complete RDX removal. Perchlorate in the wastewater was completely removed by iron at an elevated temperature of 150 degrees C in batch reactors in 6 hours without pH control. Significant reduction of perchlorate by zero-valent iron was also achieved at a more moderate temperature (75 degrees C) through use of a 0.2 M acetate buffer. Based on the evaluation results, we propose two innovative processes for treating RDX-containing and perchlorate-containing wastewaters: a temperature and pressure-controlled batch iron reactor and subsequent oxidation by existing industrial wastewater treatment plant; and reduction by consecutive iron columns with heating and acid addition capabilities and subsequent oxidation.     

Liquidity, Labels and Medium-Term Notes

We suggest that the medium-term note market provides an excellent laboratory for exploring the relationships between yield, liquidity, and the label affixed to a financial instrument. Crabbe and Turner (1995) examined the liquidity issue and uncovered the counter-intuitive result that issue size is unrelated to liquidity. Their study failed to examine a potential channel for a liquidity effect, however, in the form of multiple issues from a single, typically large, MTN registration filing. We find evidence that file size is significantly related to yield in a number of instances. Several other proxies for liquidity, such as frequency of issue, are also sometimes significantly related to yields. Contrary to Crabbe and Turner (1995) , we find that labeling a security an MTN can have an impact on its yield. The label "note" also appears to matter for yield in some instances.     

The Returns to Academic and Vocational Qualifications in Britain

This paper uses data from the 1991 sweep of the National Child Development Study (NCDS) and the 1998 Labour Force Survey (LFS) to provide a comprehensive analysis of the labour market returns to academic and vocational qualifications. The results show that the wage premia from academic qualifications are typically higher than from vocational qualifications. However, this gap is reduced somewhat, when we control for the amount of time taken to acquire different qualifications. This is particularly important for vocational courses, which generally take shorter time periods to complete. In the paper we also investigate how returns vary by gender, subsequent qualifications, and the natural ability of individuals. Finally, by comparing the NCDS results with those from the LFS, we estimate the bias that can result from not controlling for factors such as ability, family background and measurement error. The results reveal that the estimated returns in the NCDS equations controlling for ability, family background and measurement error are similar to the simple OLS estimates obtained with the LFS, which do not control for these factors. This suggests that the biases generally offset one another.