The Structure and Dynamics of Sodium Disilicate

We investigate the structure and dynamics of sodium disilicate by means of molecular dynamics computer simulation. We show that the structure is described by a partially destroyed tetrahedral SiO_4 network and a spherical super structure formed by the silicon and sodium atoms. The static structure factor of our simulation is in very good agreement with one from a neutron scattering experiment. For 1008 particles we find strong finite size effects in the dynamics which are due to the missing of modes contributing to the boson peak.Comment: 7 pages of Latex, 3 figure

The Dynamics of Supercooled Silica: Acoustic modes and Boson peak

Using molecular dynamics computer simulations we investigate the dynamics of supercooled silica in the frequency range 0.5-20~THz and the wave-vector range 0.13-1.1\AA^{-1}. We find that for small wave-vectors the dispersion relations are in very good agreement with the ones found in experiments and that the frequency at which the boson-peak is observed shows a maximum at around 0.39\AA^{-1}.Comment: 4 pages of RevTex, 3 figure

Slow Dynamics in Ion-Conducting Sodium Silicate Melts: Simulation and Mode-Coupling Theory

A combination of molecular-dynamics (MD) computer simulation and mode-coupling theory (MCT) is used to elucidate the structure-dynamics relation in sodium-silicate melts (NSx) of varying sodium concentration. Using only the partial static structure factors from the MD as an input, MCT reproduces the large separation in relaxation time scales of the sodium and the silicon/oxygen components. This confirms the idea of sodium diffusion channels which are reflected by a prepeak in the static structure factors around 0.95 A^-1, and shows that it is possible to explain the fast sodium-ion dynamics peculiar to these mixtures using a microscopic theory.Comment: 4 pages, 4 figure

Employment and Innovations in the Environmental Sector: Determinants and Econometrical Results for Germany

Besides other determinants environmental regulation, institutions like environmental agencies and social customs lead to a demand for environmental goods and services. On the basis of the public choice theory it can be shown that environmental regulation is endogenous and can be influenced by the environmental awareness of voters and interest groups. Following the so-called Porter hypothesis early developed environmental legislation induces environmental innovations and creates first mover advantages connected with a high international competitiveness of the environmental industry. An empirical analysis based on the establishment panel of the Institute for Employment Research (IAB) shows that more than 900,000 persons are employed in the environmental sector in Germany. Following the results of an econometrical analysis of employment perspectives and innovation behaviour integrated environmental technologies will become more relevant whereas employment in “traditional” end-of-pipe fields like the prevention of waste water pollution or air pollution will be reduced.Employment, Environmental sector, Innovation behaviour

Determinants of Environmental Innovation – New Evidence from German Panel Data Sources

In most cases, empirical analyses of environmental innovations based on firm-level data relied on survey data for one point in time. These surveys, especially designed for the analysis of environmental innovations, are useful because they allow for the inclusion of many explanatory variables such as different policy instruments or the influence of stake-holders and pressure groups. On the other hand, it is not possible to address the dynamic character of the environmental innovation process. This paper uses two German panel data bases, the establishment panel of the Institute for Employment Research (IAB) and the Mannheim Innovation Panel (MIP) of the Centre for European Economic Research (ZEW), to explore the determinants of environmental innovations. These data bases were not specifically collected to analyze environmental issues, but they contain questions that allow the identification of environmental innovations. We use discrete choice models for each of the data bases to analyze hypotheses derived from the theoretical (environmental) innovation literature. The econometric estimations show that the improvement of the technological capabilities (“knowledge capital”) by R&D or further education measures triggers environmental innovations – this result is confirmed by both data bases and both methods to measure environmental innovation. The hypothesis that “Innovation breeds innovation” is confirmed by the analysis of the MIP data. General and environmental innovative firms in the past are more likely to innovate in the present. Environmental regulation, environmental management tools and general organizational changes and improvements trigger environmental innovation, a result that has also been postulated by the famous Porter-hypothesis. Environmental management tools especially help to detect cost-savings (specifically material and energy savings). Following our econometric results, cost-savings are an important driving force of environmental innovation.Environmental innovation, Panel data analysis, Discrete choice models

The impact of innovation activities on employment in the environmental sector : empirical results for Germany at the firm level

"The paper explores employment effects of environmental product innovations at the firm level. The empirical analysis is based on the establishment panel of the Institute for Employment Research (Nuremberg). A descriptive analysis shows that more than 50% of the firms in the environmental sector developed new products or improved existing products or services. The most dynamic environmental fields were analytics, consulting, measurement technology, waste disposal and recycling. A firm specialised in environmental research and development seems to have the best employment perspectives in the short and in the long run. Our econometric analysis had to address a simultaneity problem because the decision of a firm on the realisation of innovations and on the enlargement or reduction of employment is mutually dependant. Therefore, we apply a bivariate probit model that allows estimating the two variables simultaneously. The econometric results show that the influence of environmental innovation activities on the employment development is significantly positive. Furthermore, the quantitative importance of the new products with regard to the whole turnover of the firm is also important for employment growth. Within the bivariate probit model, the determinants of environmental innovation activities are also explored. They may be interpreted as indirect influences on the employment development of the firm. The results show that the improvement of the innovative capacities by R&D and further education measures and the existence of a high qualified human capital are significantly important for the development of new products in the environmental sector. A good strategy to improve the innovativeness of a firm seems to be a diversification of environmental product lines offered by the firm." (Author's abstract, IAB-Doku) ((en))Produktinnovation, Beschäftigungseffekte, Umweltschutzindustrie, IAB-Betriebspanel, Umweltforschung, Technik, Umweltverträglichkeit, Umwelttechnik, Recycling, Forschungsaufwand, Forschung und Entwicklung, Abfallbeseitigung, Umweltberatung, Innovationsfähigkeit