Fractionation of lead in soil by isotopic dilution and sequential extraction

‘Reactivity’ or ‘lability’ of lead is difficult to measure using traditional methods. We investigated the use of isotopic dilution with 204Pb to determine metal reactivity in four soils historically contaminated with contrasting sources of Pb, including (i) petrol-derived Pb, (ii) Pb/Zn minespoil, (iii) long-term sewage sludge application and (iv) 19th century urban waste disposal; total soil Pb concentrations ranged from 217 to 13 600 mg kg–1. A post-spike equilibration period of 3 days and suspension in 5.0 × 10–4 M ethylenediaminetetraacetic acid provided reasonably robust conditions for measuring isotopically exchangeable Pb. However, in acidic organic soils a dilute Ca(NO3)2 electrolyte may be preferable to avoid mobilisation of ‘non-labile’ Pb. Results showed that the reactive pool of soil Pb can be a large proportion of the total soil lead content but varies with the original Pb source. A comparison of isotopic exchangeability with the results of a sequential extraction procedure showed that (isotopically) ‘non-labile’ Pb may be broadly equated with ‘residual’ Pb in organic soils. However, in mineral soils the ‘carbonate’ and ‘oxide-bound’ Pb fractions included non-labile forms of Pb. The individual isotopic signatures of labile and non-labile Pb pools suggested that, despite prolonged contact with soil, differences between the lability of the original contaminant and the native soil Pb may remain

Sorting Via Screening Versus Signaling: A Theoretic and Experimental Comparison

Similar to Kübler et al. (2008, GEB 64, p. 219-236), we compare sorting in games with asymmetric incomplete information theoretically and experimentally. Rather than distinguishing two very different sequential games, we use the same game format and capture the structural difference of screening and signaling only via their payoff specification. The experiment thus relies on the same verbal instructions. Although the equilibrium outcomes coincide, greater efficiency losses off the equilibrium play due to sorting under signaling, compared to screening, is predicted and confirmed experimentally

Quantum Theory and Time Asymmetry

The relation between quantum measurement and thermodynamically irreversible processes is investigated. The reduction of the state vector is fundamentally asymmetric in time and shows an observer-relatedness which may explain the double interpretation of the state vector as a representation of physical states as well as of information about them. The concept of relevance being used in all statistical theories of irreversible thermodynamics is shown to be based on the same observer-relatedness. Quantum theories of irreversible processes implicitly use an objectivized process of state vector reduction. The conditions for the reduction are discussed, and I speculate that the final (subjective) observer system might even be carried by a spacetime point.Comment: Latex version of a paper published in 1979 (with minor revisions), 18 page

Firm heterogeneity and wages under different bargaining regimes : does a centralised union care for low-productivity firms?

This paper studies the relationship between wages and the degree of firm heterogeneity in a given industry under different wage setting structures. To derive testable hypotheses, we set up a theoretical model that analyses the sensitivity of wages to the variability in productivity conditions in a unionsised oligopoly framework. The model distinguishes centralised and decentralised wage determination. The theoretical results predict wages to be negatively associated with the degree of firm heterogeneity under centralised wage-setting, as unions internalise negative externalities of a wage increase for low-productivity firms. We test this prediction using a linked employeremployee panel data set from the German mining and manufacturing sector. Consistent with our hypotheses, the empirical results suggest that under industry-level bargaining workers in more heterogeneous sectors receive lower wages than workers in more homogeneous sectors. In contrast, the degree of firm heterogeneity is found to have no negative impact on wages in uncovered firms and under firm-level contracts

Technological Change in Economic Models of Environmental Policy: A Survey

This paper provides an overview of the treatment of technological change in economic models of environmental policy. Numerous economic modeling studies have confirmed the sensitivity of mid- and long-run climate change mitigation cost and benefit projections to assumptions about technology costs. In general, technical progress is considered to be a noneconomic, exogenous variable in global climate change modeling. However, there is overwhelming evidence that technological change is not an exogenous variable but to an important degree endogenous, induced by needs and pressures. Hence, some environmenteconomy models treat technological change as endogenous, responding to socio-economic variables. Three main elements in models of technological innovation are: (i) corporate investment in research and development, (ii) spillovers from R&D, and (iii) technology learning, especially learning-by-doing. The incorporation of induced technological change in different types of environmental-economic models tends to reduce the costs of environmental policy, accelerates abatement and may lead to positive spillover and negative leakage

Beyond the mean gender wage gap : decomposition of differences in wage distributions using quantile regression

Using linked employer-employee data, this study measures and decomposes the differences in the earnings distribution between male and female employees in Germany. I extend the traditional decomposition to disentangle the effect of human capital characteristics and the effect of firm characteristics in explaining the gender wage gap. Furthermore, I implement the decomposition across the whole wage distribution with the method proposed by Machado and Mata (2005). Thereby, I take into account the dependence between the human capital endowment of individuals and workplace characteristics. The selection of women into less successful and productive firms explains a sizeable part of the gap. This selection is more pronounced in the lower part of the wage distribution than in the upper tail. In addition, women also benefit from the success of firms by rent-sharing to a lesser extent than their male colleagues. This is the source of the largest part of the pay gap. Gender differences in human capital endowment as well s differences in returns to human capital are less responsible for the wage differential

Control of sympathetic vasomotor tone by catecholaminergic C1 neurones of the rostral ventrolateral medulla oblongata

C1 - Journal Articles RefereedAIMS: Increased sympathetic tone in obstructive sleep apnoea results from recurrent episodes of systemic hypoxia and hypercapnia and might be an important contributor to the development of cardiovascular disease. In this study, we re-evaluated the role of a specific population of sympathoexcitatory catecholaminergic C1 neurones of the rostral ventrolateral medulla oblongata in the control of sympathetic vasomotor tone, arterial blood pressure, and hypercapnia-evoked sympathetic and cardiovascular responses. METHODS AND RESULTS: In anaesthetized rats in vivo and perfused rat working heart brainstem preparations in situ, C1 neurones were acutely silenced by application of the insect peptide allatostatin following cell-specific targeting with a lentiviral vector to express the inhibitory Drosophila allatostatin receptor. In anaesthetized rats with denervated peripheral chemoreceptors, acute inhibition of 50% of the C1 neuronal population resulted in ∼50% reduction in renal sympathetic nerve activity and a profound fall in arterial blood pressure (by ∼25 mmHg). However, under these conditions systemic hypercapnia still evoked vigorous sympathetic activation and the slopes of the CO(2)-evoked sympathoexcitatory and cardiovascular responses were not affected by inhibition of C1 neurones. Inhibition of C1 neurones in situ resulted in a reversible fall in perfusion pressure and the amplitude of respiratory-related bursts of thoracic sympathetic nerve activity. CONCLUSION: These data confirm a fundamental physiological role of medullary catecholaminergic C1 neurones in maintaining resting sympathetic vasomotor tone and arterial blood pressure. However, C1 neurones do not appear to mediate sympathoexcitation evoked by central actions of CO(2)

Reassessing the Impact of High Performance Workplaces

High performance workplace practices were extolled as an efficient means to increase firm productivity. The empirical evidence is disputed, however. To assess the productivity effects of a broad variety of measures, we simultaneously account for both unobserved heterogeneity and endogeneity using establishment panel data for Germany. We show that increasing employee participation enhances firm productivity in Germany, whereas incentive systems do not foster productivity. Our results further indicate that firms with structural productivity problems tend to introduce organisational changes that increase employee participation whereas well performing firms are more likely to offer incentives