Spatial Pattern Formation During Aggregation of the Slime Mould Dictyostelium discoideum

Stream formation and spiral wave behaviour during the aggregation of Dictyostelium discoideum (Dd) are studied in a model based on the Martiel-Goldbeter equations for cAMP relay, combined with chemotactic motion of Dd cells. The results show that stream formation occurs if the turnover rate of intracellular cAMP is increased. This increase in the turnover rate of cAMP[in] leads to a dependence of the speed of the cAMP wave on the cell density. We propose that this dependence of wave speed on cell density is the underlying mechanism for stream formation. Besides stream formation, increasing the turnover rate of cAMP[in] also results in a spiral wave period that decreases during aggregation, a phenomenon that is commonly observed in situ. Furthermore, the dependence of wave speed on cell density is measured empirically[ The speed of the cAMP wave is found to decrease as the wave travels from high to low cell density. This indicates that in situ, wave speed does depend on cell density

The Applicability of Remote Sensing in the Field of Air Pollution

This report prepared by KNMI and JRC is the final result of a study on the applicability of remote sensing in the field of air pollution requested by the DG Environment. The objectives of this study were to: Have an assessment of presently available scientific information on the feasibility of utilising remote sensing techniques in the implementation of existing legislation, and describe opportunities for realistic streamlining of monitoring in air quality and emissions, based on greater use of remote sensing. Have recommendations for the next policy cycle on the use of remote sensing through development of appropriate provisions and new concepts, including, if appropriate, new environmental objectives, more suited to the use of remote sensing. Have guidance on how to effectively engage with GMES and other initiatives in the air policy field projects Satellite remote sensing of the troposphere is a rapidly developing field. Today several satellite sensors are in orbit that measure trace gases and aerosol properties relevant to air quality. Satellite remote sensing data have the following unique properties: Near-simultaneous view over a large area; Global coverage; Good spatial resolution. The properties of satellite data are highly complementary to ground-based in-situ networks, which provide detailed measurements at specific locations with a high temporal resolution. Although satellite data have distinct benefits, the interpretation is often less straightforward as compared to traditional in-situ measurements. Maps of air pollution measured from space are widespread in the scientific community as well as in the media, and have had a strong impact on the general public and the policy makers. The next step is to make use of satellite data in a quantitative way. Applications based solely on satellite data are foreseen, however an integrated approach using satellite data, ground-based data and models combined with data assimilation, will make the best use of the satellite remote-sensing potential, as well as of the synergy with ground-based observations.JRC.H.4-Transport and air qualit

Studying colours with a smartphone

We show how a low-cost spectrometer, based on the use of inexpensive diffraction transmission gratings coupled with a smartphone photo camera, can be assembled and employed to obtain quantitative measurements of spectra from different sources. The analysis of spectra emitted by different light sources (incandescent bulb, fluorescent lamp, gas lamps, LEDs) helps students understand the different physical mechanisms which govern the production of light. Measurements of emission and transmission spectra allow students to focus on the differences between additive and subtractive models of colour formation. For this purpose the spectra of RGB colours emitted from an LCD screen and the transmission spectra of CMY pigments of a laser printer have been studied, using our low-cost spectroscope. A sequence of experimental activities was designed, and proposed to undergraduate students and secondary school teachers in order to study the feasibility and educational potential

Adhesion of <i>Pseudomonas fluorescens</i> biofilms to glass, stainless steel and cellulose

Objectives: The adhesion of colloidal probes of stainless steel, glass and cellulose to Pseudomonas fluorescens biofilms was examined using atomic force microscopy (AFM) to allow comparisons between surfaces to which biofilms might adhere. Results: Biofilm was grown on a stainless steel substrate and covered most of the surface after 96 h. AFM approach and retraction curves were obtained when the biofilm was immersed in a tryptone/soy medium. On approach, all the colloidal probes experienced a long non-contact phase more than 100 nm in length, possibly due to the steric repulsion by extracellular polymers from the biofilm and hydrophobic effects. Retraction data showed that the adhesion varied from position to position on the biofilm. The mean value of adhesion of glass to the biofilm (48 ± 7 nN) was the greatest, followed by stainless steel (30 ± 7 nN) and cellulose (7.8 ± 0.4 nN). Conclusion: The method allows understanding of adhesion between the three materials and biofilm, and development of a better strategy to remove the biofilm from these surfaces relevant to different industrial applications

The nucleotide and partial amino acid sequences of rat fetuin

Fetuins are among the major plasma proteins, yet their biological role has remained elusive. Here we report the molecular cloning of rat fetuin and the sequence analysis of a full-length clone, RF619 of 1456 bp with an open reading frame of 1056 bp encoding 352 amino acid residues. The coding part of RF619 was identical with the cDNA sequence of the natural inhibitor of the insulin receptor tyrosine kinase from rat (pp63) except for four substitutions and a single base insertion causing divergence of the predicted protein sequences. Partial amino acid sequences of rat plasma fetuin were in agreement with the predictions based on the RF619 cDNA. Purified rat fetuin inhibited the insulin receptor tyrosine kinase in vitro. Therefore, we conclude that RF619 and pp63 cDNA encode the same protein, i.e. authentic rat fetuin which is a functional tyrosine kinase inhibitor

Models of Dictyostelium discoideum aggregation

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Surface free energy of polyurethane coatings with improved hydrophobicity

The polarity of polyurethane coats was studied on the basis of the goniometric method for determination of wetting angle values, on the basis of calculated surface free energy (SFE) values by the van Oss–Good and Owens–Wendt methods, and on the basis of polarity measurements with the use of the 1H NMR spectra. Test polyurethanes were synthesised in the reaction of methylene diphenyl 4,4′-diisocyanate (MDI) or 3-izocyanatomethyl –3,5,5- trimethylcyclohexyl isocyanate (IPDI) and polyoxyethylene glycols or polyesters poly(ε-caprolactone) diols and poly(ethyleneadipate) diol with different molecular weights, and some diols as chain extenders, in dioxane. The type of raw material was found to significantly affect the phase structure of the obtained polyurethane elastomers and to control physical interactions within those structures, thus influencing the SFE values. Fundamental reduction in the SFE value of a coating below 28 mJ/m2 was achieved by the use of 2,2,3,3-tetrafluoro-1,4-butanediol as the urethane prepolymer chain extender