Eine kritische Analyse von Vernetzungsmaßen in sozialen Netzwerken

Social networks are currently gaining increasing impact in the light of the ongoing growth of web-based services like facebook.com. One major challenge for the economically successful implementation of selected management activities such as viral marketing is the identification of key persons with an outstanding structural position within the network. For this purpose, social network analysis provides a lot of measures for quantifying a member’s interconnectedness within social networks. In this context, our paper shows the state of the art with regard to centrality measures for social networks. Due to strongly differing results with respect to the quality of different centrality measures, this paper also aims at illustrating the tremendous importance of a reflected utilization of existing centrality measures. For this purpose, the paper analyzes five centrality measures commonly discussed in literature on the basis of three simple requirements for the behavior of centrality measures.     

Preservation of primer and probes on “ready-to-use” 96-well microtiter plates: A step forward towards enhancing throughput and harmonization of real-time PCR applications in food and feed control

Three different agents, trehalose (TRH), gelatine (GEL) and polyethylene glycol (PEG) were investigated regarding their capability to preserve oligonucleotides, such as primer and probes or double-stranded plasmid DNA, pre-coated in 96-wells microtiter plates. The evaluation of the retained efficiency of selected multi-copy and two single-copy PCR (polymerase chain reaction) systems revealed best-suited final concentrations in the preservation mix of 1.5% (w/v) for PEG, 0.17% (w/v) for GEL and 0.07% (w/v) - 20/1 (TRH/nucleic acid w/w) - for TRH, respectively. Under these conditions PCR efficiencies did not deviate significantly from non-coated, freshly pipetted control reactions even after three months of storage at room temperature or under thermal stress at constantly 50 °C simulating an ageing effect. Among the three reagents TRH showed best performance since not only the most labile component - the fluorescent probe - is protected from degradation but also double-stranded plasmid DNA which can be used as reference material and in quantitative real-time PCR.     

RNA Aminoacylation Mediated by Sequential Action of Two Ribozymes and a Nonactivated Amino Acid

In the transition from the RNA world to the modern DNA/protein world, RNA‐catalyzed aminoacylation might have been a key step towards early translation. A number of ribozymes capable of aminoacylating their own 3′ termini have been developed by in vitro selection. However, all of those catalysts require a previously activated amino acid—typically an aminoacyl‐AMP—as substrate. Here we present two ribozymes connected by intermolecular base pairing and carrying out the two steps of aminoacylation: ribozyme 1 loads nonactivated phenylalanine onto its phosphorylated 5′ terminus, thereby forming a high‐energy mixed anhydride. Thereafter, a complex of ribozymes 1 and 2 is formed by intermolecular base pairing, and the “activated” phenylalanine is transferred from the 5′ terminus of ribozyme 1 to the 3′ terminus of ribozyme 2. This kind of simple RNA aminoacylase complex was engineered from previously selected ribozymes possessing the two required activities. RNA aminoacylation with a nonactivated amino acid as described here is advantageous to RNA world scenarios because initial amino acid activation by an additional reagent (in most cases, ATP) and an additional ribozyme would not be necessary.     

Analytical prediction of roll coating with counter-rotating deformable rolls

Roll coating is a common technique for applying thin coating films on continuous substrates, e.g., papers and foils. Key advantages are the comparatively simple technology and the possibility of coating thin films using highly viscous fluids. Since roll coating is a self-metered process, the prediction of film thicknesses is of fundamental interest for industrial process control. In the present work, a new analytical approach for the prediction of the film thickness in roll coating with deformable rolls and negative gaps is developed. This method is based on the fluid dynamic theory of lubrication approximation. The film thickness is calculated depending on the geometry of the rolls (including the elasticity of the rubber), the fluid properties of the applied film and the roll velocities. This is gained by using boundary conditions for pressure and—in contrast to former literature—for force. The quality of the predicted results is validated with experimental data from literature. The comparison shows good agreement and thus the derived analytical model offers new possibilities for predicting film thickness and understanding of the associated influence parameters.     

Use of Cascaded Option Trees in Chemical‐Engineering Process Development

Fast and efficient procedures are increasingly important in process development since the time frame between development and market entry is reduced. The evaluation of alternatives is time consuming, but especially important to assure the choice of the optimal process. A simple and fast method to speed up process development while considering numerous alternatives has been developed using option trees. The option trees allow for easy and comprehensible evaluation of alternatives. Here the method of cascaded option trees is illustrated for the development of a biocompatible separation process.     

Advanced solar assisted desiccant and evaporative cooling system equipped with wet heat exchangers

This work concerns an innovative solar assisted desiccant and evaporative cooling (DEC) system for building air conditioning. In this system, air-to-air packaged wet heat exchangers are used to maximize the exploitation of the evaporative cooling potential associated with the exhaust air stream.The thermodynamic cycle is first theoretically described, and then an example of a real application is shown.The system presented is an experimental DEC system originally installed at the beginning of 2008 at the Solar Laboratory of the University of Palermo and recently modified and updated. These modifications have been implemented with the aim to foster some problems related to the conventional indirect evaporative process and to increase the overall performance of the process.Different energy performance figures, such as thermal and electrical COP, are presented and discussed.The obtained results are very positive, showing that DEC systems can benefit from the use of wet heat exchangers to efficiently cool the air stream after the adsorption process in the desiccant wheel without any change in moisture content.     

Geographic origin of meat—elements of an analytical approach to its authentication

This review article discusses recent analytical developments with respect to the determination of the geographic origin of raw meat. The main emphasis is laid on lamb, beef and poultry. So far, some methods have shown quite promising potential (e.g. stable isotope ratios, trace elements), others have remained unsatisfactory in their discriminating power to authenticate the geographic origin of meat (e.g. microbiological profile, sensory traits, volatile compounds). Other methods (e.g. animal genotype, gross chemical composition) could be auxiliary criteria as they help to determine related indicators such as feeding or housing conditions but not directly the origin. The complexity of this question is large. An integrated approach simultaneously addressing various species and production characteristics such as environment, animal husbandry conditions, breed, feeding and drinking water has to be developed. Strategies have to be different for global and micro-regional scales.