Interplay of air and sand: Faraday heaping unravelled

We report on numerical simulations of a vibrated granular bed including the effect of the ambient air, generating the famous Faraday heaps known from experiment. A detailed analysis of the forces shows that the heaps are formed and stabilized by the airflow through the bed while the gap between bed and vibrating bottom is growing, confirming the pressure gradient mechanism found experimentally by Thomas and Squires [Phys. Rev. Lett. 81, 574 (1998)], with the addition that the airflow is partly generated by isobars running parallel to the surface of the granular bed. Importantly, the simulations also explain the heaping instability of the initially flat surface and the experimentally observed coarsening of a number of small heaps into a larger one

National urban policy responses in the European Union: Towards a European urban policy?

"Europe's towns and cities remain its primary source of wealth creation and the centre of its social and cultural development. However there are rising problems relating to rapid economic adjustments. It is clear that new efforts are necessary to strenghten or restore the role of Europe's cities as places of social and cultural integration, as sources of economic prosperity and sustainable development, and as bases of democracy" ["Towards an urban agenda in the European Union", European Commission, 1997]. The environment of cities has become increasingly competitive and complex. Cities need to anticipate and respond quickly to opportunities and threats that influence their position structurally. Although city governments develop policies and strategies to meet the challenges, at the same time higher layers of government pursue policies that influence the position of cities. National governments draw up financial and policy frameworks and create conditions in which cities have to manoeuvre and design their own policies. At the European level the interest for the strategic position of cities within regional development policy is growing. This harmonises with a major objective of the association of large European cities ('Eurocities') to bring the position of the large cities as engines of economic growth and at the same time as concentrations of social problems to the attention of the Europan Commission. Although the Commission recognises the important role of cities for European regional development, until now European urban policy initiatives have been blocked by a majority of national governments, as a consequence of the principle of subsidiarity. The objective of our contribution is to compare current developments as far as explicit national urban policies in the member states are concerned. However the scope will not be limited to explicit policies alone. National policies with a substantial impact on urban development will be dealt with too. The framework for the investigation is made up of four parts. The first two parts compare national urban patterns and structures (the urbanisation pattern and the administrative structure), while the remaining parts deal with the questions: (1) what do national authorities consider to be main issues for, and challenges to their (larger) cities?; and (2) how do national governments respond to these issues and challenges by policies targeted to the role and function of cities? The results of our investigation into current national urban policies are for an important part based on fifteen national case studies produced by colleagues from each of the member states according to the framework mentioned before. This contribution summarises the results of the comparison. The results might give ingredients for a future urban policy at the European level.

Effect of two types of biosurfactants on phenanthrene availability to the bacterial bioreporter Burkholderia sartisoli strain RP037

Biosurfactants are tensio-active agents that have often been proposed as a means to enhance the aqueous solubility of hydrophobic organic contaminants, such as polycyclic aromatic hydrocarbons (PAHs). Biosurfactant-producing bacteria such as those belonging to the genus Pseudomonas might therefore enhance PAH availability to PAH-degrading bacteria. We tested the effects of two types of biosurfactants produced by Pseudomonas sp., cyclic lipopeptides and rhamnolipids, on phenanthrene bioavailability. Bioavailability was judged from growth rates on phenanthrene and from specific induction of a phenanthrene-responsive GFP-reporter in Burkholderia sartisoli strain RP037. Co-culturing of strain RP037 with the lipopeptide-producing bacterium Pseudomonas putida strain PCL1445 enhanced GFP expression compared to a single culture, but this effect was not significantly different when strain RP037 was co-cultivated with a non-lipopeptide-producing mutant of P. putida. The addition of partially purified supernatant extracts from the P. putida lipopeptide producer equally did not unequivocally enhance phenanthrene bioavailability to strain RP037 compared to controls. In contrast, a 0.1% rhamnolipid solution strongly augmented RP037 growth rates on phenanthrene and led to a significantly larger proportion of cells in culture with high GFP expression. Our data therefore suggest that biosurfactant effects may be strongly dependent on the strain and type of biosurfactan

Social revitalisation of urban regions

This paper aims to analyse how social revitalisation can contribute to an (economically) attractive urban region and how such policies can be made more effective and efficient. To stimulate re-urbanisation and attract new economic activities and residents, much attention is paid to the concept of ''the attractive city''. Cities are observed to switch their focus from hardware (tangible services) to software (image, quality of life) and orgware (organising capacity). To enhance the effectiveness of social policy is in that context often considered a spearhead for cities. In practice, social policy does not always seem to be carried out effectively. Much money may be spent on solving a problem without effective progress being accomplished. Moreover, the results of social policy are often hard to measure, so that a lack of purpose may not be easy to detect. The paper is based on a comparative research of eight European urban regions.

Development of bacteria-based bioassays for arsenic detection in natural waters

Arsenic contamination of natural waters is a worldwide concern, as the drinking water supplies for large populations can have high concentrations of arsenic. Traditional techniques to detect arsenic in natural water samples can be costly and time-consuming; therefore, robust and inexpensive methods to detect arsenic in water are highly desirable. Additionally, methods for detecting arsenic in the field have been greatly sought after. This article focuses on the use of bacteria-based assays as an emerging method that is both robust and inexpensive for the detection of arsenic in groundwater both in the field and in the laboratory. The arsenic detection elements in bacteria-based bioassays are biosensor-reporter strains; genetically modified strains of, e.g., Escherichia coli, Bacillus subtilis, Staphylococcus aureus, and Rhodopseudomonas palustris. In response to the presence of arsenic, such bacteria produce a reporter protein, the amount or activity of which is measured in the bioassay. Some of these bacterial biosensor-reporters have been successfully utilized for comparative in-field analyses through the use of simple solution-based assays, but future methods may concentrate on miniaturization using fiberoptics or microfluidics platforms. Additionally, there are other potential emerging bioassays for the detection of arsenic in natural waters including nematodes and clam

Mutation analysis of the different tfd genes for degradation of chloroaromatic compounds in Ralstonia eutropha JMP134

Ralstonia eutropha JMP134 possesses two sets of similar genes for degradation of chloroaromatic compounds, tfdCDEFB (in short: tfd I cluster) and tfdD II C II E II F II B II (tfd II cluster). The significance of two sets of tfd genes for the organism has long been elusive. Here, each of the tfd genes in the two clusters on the original plasmid pJP4 was replaced by double recombination with a gene fragment in which a kanamycin resistance gene was inserted into the respective tfd gene's reading frame. The insertion mutants were all tested for growth on 2,4-dichlorophenoxyacetic acid (2,4-D), 2-methyl-4-chlorophenoxyacetic acid (MCPA), and 3-chlorobenzoate (3-CBA). None of the tfdD II C II E II F II B II genes appeared to be essential for growth on 2,4-D or on 3-CBA. Mutations in tfdC, tfdD and tfdF also did not abolish but only retarded growth on 2,4-D, indicating that they were redundant to some extent as well. Of all tfd genes tested, only tfdE and tfdB were absolutely essential, and interruption of those two reading frames abolished growth on 2,4-D, 3-CBA (tfdE only), and MCPA completely. Interestingly, strains with insertion mutations in the tfd I cluster and those in tfdD II , tfdC II , tfdE II and tfdB II were severely effected in their growth on MCPA, compared to the wild-type. This indicated that not only the tfd I cluster but also the tfd II cluster has an essential function for R. eutropha during growth on MCPA. In contrast, insertion mutation of tfdD II resulted in better growth of R. eutropha JMP134 on 3-CBA, which is most likely due to the prevention of toxic metabolite production in the absence of TfdDII activit