Jan Rose Sørensen

Denitrification and oxygen respiration in biofilms studied with a microsensor for nitrous oxide and oxygen

Depth distributions of O2 respiration and denitrification activity were studied in 1- to 2-mm thick biofilms from nutrient-rich Danish streams. Acetylene was added to block the reduction of N2O, and micro-profiles of O2 and N2O in the biofilm were measured simultaneously with a polarographic microsensor. The specific activities of the two respiratory processes were calculated from the microprofiles using a one-dimensional diffusion-reaction model. Denitrification only occurred in layers where O2 was absent or present at low concentrations (of a fewμM). Introduction of O2 into deeper layers inhibited denitrification, but the process started immediately after anoxic conditions were reestablished. Denitrification activity was present at greater depth in the biofilm when the NO3− concentration in the overlying water was elevated, and the deepest occurrence of denitrification was apparently determined by the depth penetration of NO3−. The denitrification rate within each specific layer was not affected by an increase in NO3− concentration, and the half-saturation concentration (Km) for NO3− therefore considered to be low (<25μM). Addition of 0.2% yeast extract stimulated denitrification only in the uppermost 0.2 mm of the denitrification zone indicating a very efficient utilization of the dissolved organic matter within the upper layers of the biofilm.

Denitrification in a trickling filter biofilm studied by a microsensor for oxygen and nitrous oxide

Abstract A newly developed microsensor for O2 and N2O was used to study denitrification in a trickling filter biofilm where the reduction of the denitrification intermediate N2O was inhibited with acetylene. The experimentally obtained N2O profiles and a diffusion-reaction model were used to obtain microprofiles of denitrification. Denitrification was restricted to deeper anaerobic layers of the biofilm. Both the total intensity and the thickness of the denitrifying zone increased when the NO3− concentration in the bulk waterphase was elevated from 200 to 750 μM. Addition of 5 mM acetate plus 0.2% yeast extract resulted in a considerable stimulation of the total activity, but the thickness of the denitrification zone decreased. Photosynthetic activity inhibited denitrification by introduction of O2 into the deeper layers.

Trade union behaviour, pay-bargaining, and economic performance

Part 1 Can political models predict union behaviour?, Robert J. Flanagan: trade unions - models and institutions classical voting models and union behaviour the descriptive power of the median voter model institutional structure and voting outcomes union leaders and union members a stocktaking comment, Alistair Ulph comment, Assar Lindbeck. Part 2 Bargaining structure and economic performance, Karl Ove Moene et al: wage demands by unions and employers bargaining models of wage-setting conflicts over the level of bargaining comment, Assar Lindbeck comment, Lars Calmfors.

Exchange rate variability and wage formation in open economies

Abstract Exchange rate variability is shown to influence wage formation in open economies with strong unions. Increased exchange rate variability may thus increase real- and product wages and lower employment. Hence, a stable and predictable exchange rate policy may have some gain.

On the effects of firing costs when investment is endogenous: An extension of a model by Bertola

Abstract This paper analyses how job security policies, which in practice result in higher firing costs, affect employment in a model that recognizes that these policies also affect profitability and investment. The results show that the effects depend crucially on the exact assumption about goods demand. If goods demand is very elastic, firing costs have large negative effects on trend employment and investment, whereas the effects are small when demand is inelastic or not very elastic. The paper also analyses the relationship between trend employment, investment and firing costs under alternative assumptions about the substitution elasticity between labour and capital.

Unemployment and fiscal policy in an economic and monetary union

Abstract We consider the need and room for demand management policies as a way to control unemployment in an Economic and Monetary Union. The set up is a general equilibrium model with imperfectly competitive product and labour markets. Balanced budget demand management policies are shown to affect employment, but they involve a beggar-thyneighbour element since gains in employment are matched by employment losses in other countries in the Union. Uncoordinated polices are too expansionary, and optimal policies require constraints on the size of the public sector in the participating countries.

Schooling, Training, Growth and Minimum Wages

We examine how the long-run growth performance of an economy is affected by a labor market distortion. In our model, growth occurs through skill formation, and skills are generated through schooling and training of unskilled workers. We analyze how a minimum wage legislation affects long-run growth. In general, the effects are ambiguous. The reason is that while a minimum wage discourages training, it also encourages schooling. The net effect then depends on whether training or schooling dominates the long-run increases in labor productivity. Copyright 1999 by The editors of the Scandinavian Journal of Economics.

Optimal fiscal policy in open economies with labour market distortions

Abstract We set up a general equilibrium model with unemployment owing to distortions in the labour market. It is shown that a public expansion, financed by a distortionary income tax, may give rise to a decrease in unemployment. Even if public goods are pure waste, such an expansion may give rise to an increase in welfare if it is associated with a decrease in unemployment. Since part of the gain from a fiscal expansion is achieved at the expense of welfare in other countries, non-cooperative policies tend to be too expansionary.

Uncertainty and Monetary Policy in a Wage Bargaining Model

In a wage bargaining model, increased uncertainty concerning monetary and real aggregates is shown to give rise to a higher equilibrium unemployment rate. Moreover, the equilibrium unemployment rate is found to depend on the choice of monetary policy regime, as this choice affects the uncertainty wagesetters face when setting the nominal wage rate. It is also shown that the equilibrium inflation rate may depend on uncertainty in such a way that increased uncertainty gives rise to a higher equilibrium unemployment rate as well as a higher equilibrium inflation rate--or what has been called stagflation. Copyright 1992 by The editors of the Scandinavian Journal of Economics.

Profit-sharing in a unionized cournot duopoly

The main purpose of this paper is to analyze when it is optimal for firms in a unionized duopoly to introduce profit-sharing. It is shown that a firm only prefers a profit-sharing system if its own union does not have “too much” bargaining power, and if the union in the other firm does not have “too much” bargaining power. However, if a firm introduces profit-sharing, the employment increases, and the price in the goods market decreases. Hence, even if it is not in the own interest of a firm to introduce profit-sharing, it may be in the interest of the society.