Bestimmung der Wärmeleitfähigkeit im Untergrund durch Labor- und Feldversuche und anhand theoretischer Modelle

For the planning and design of borehole heat exchangers systems, the knowledge of the thermophysical ground parameters is essential. In this study, several methods for the determination of thermal conductivity were used on a borehole for a ground source heat pump system. Thermal conductivity was measured on core samples using laboratory tests and likewise a Thermal Response Test (TRT) was carried out. In addition, several ground parameters, such as water content and carbonate content, were determined by laboratory tests. With these parameters the thermal conductivity was then calculated using different theoretical models. The best agreement between measured and calculated values for thermal conductivities was obtained using the geometric mean. The mean error of these calculations in this study is about 12 %. Thus, the accuracy of the calculation of thermal conductivity is lower than the accuracy of the laboratory tests or TRTs, but it nevertheless represents a simple and more accurate method than parameter estimations based on published values.     

Photo‐electrochemical Bioanalysis of Guanosine Monophosphate Using Coupled Enzymatic Reactions at a CdS/ZnS Quantum Dot Electrode

A photo‐electrochemical sensor for the specific detection of guanosine monophosphate (GMP) is demonstrated, based on three enzymes combined in a coupled reaction assay. The first reaction involves the adenosine triphosphate (ATP)‐dependent conversion of GMP to guanosine diphosphate (GDP) by guanylate kinase, which warrants substrate specificity. The reaction products ADP and GDPare co‐substrates for the enzymatic conversion of phosphoenolpyruvate to pyruvate in a second reaction mediated by pyruvate kinase. Pyruvate in turn is the co‐substrate for lactate dehydrogenase that generates lactate via oxidation of nicotinamide adenine dinucleotide (reduced form) NADH to NAD⁺. This third enzymatic reaction is electrochemically detected. For this purpose a CdS/ZnS quantum dot (QD) electrode is illuminated and the photocurrent response under fixed potential conditions is evaluated. The sequential enzyme reactions are first evaluated in solution. Subsequently, a sensor for GMP is constructed using polyelectrolytes for enzyme immobilization.     

Influence of cement content and environmental humidity on asphalt emulsion and cement composites performance

Asphalt and cement concrete are the most popular materials used in the construction of roads, highways, bridge deck surface layers and pavements in airports and other areas with heavy wheel roads. Whereas asphalt possesses, compared to concrete, the advantages of a short curing period, high skid resistance and easy maintenance, it also shows lower fatigue durability, ravelling and rutting due to repeated concentrated loads and susceptibility to temperature changes and moisture. On the other hand, concrete pavements are initially more expensive, have lower driving comfort and are susceptible to cracking due to volume changes and to salt damage. A material with low-environmental impact and with advantages of both asphalt and concrete may be obtained by combining bitumen emulsions and a cementitious material. In this paper, cold asphalt mixtures with different amounts of cement were tested with Marshall stability tests. Selected mixtures were also cured at different environmental relative humidity (35, 70 and 90 % RH). By monitoring the mass of the specimens and estimating the water bound by the cement, the total water remaining in the mixtures was calculated. Details of the microstructure in the mixtures were examined with X-ray microtomography. According to the results of the present study, cement contributes to the hardening of cold asphalt mixtures both by creating cement paste bridges between the aggregates and by removing water from the mixtures through cement hydration. Asphalt and cement composites appear to be promising materials for implementation in real pavements, although their rate of hardening needs to be improved further.     

Surface‐Layer Lattices as Patterning Element for Multimeric Extremozymes

A promising new approach for the production of biocatalysts comprises the use of surface‐layer (S‐layer) lattices that present functional multimeric enzymes on their surface, thereby guaranteeing most accurate spatial distribution and orientation, as well as maximal effectiveness and stability of these enzymes. For proof of concept, a tetrameric and a trimeric extremozyme are chosen for the construction of S‐layer/extremozyme fusion proteins. By using a flexible peptide linker, either one monomer of the tetrameric xylose isomerase XylA from the thermophilic Thermoanaerobacterium strain JW/SL‐YS 489 or, in another approach, one monomer of the trimeric carbonic anhydrase from the methanogenic archaeon Methanosarcina thermophila are genetically linked to one monomer of the S‐layer protein SbpA of Lysinibacillus sphaericus CCM 2177. After isolation and purification, the self‐assembly properties of both S‐layer fusion proteins as well as the specific activity of the fused enzymes are confirmed, thus indicating that the S‐layer protein moiety does not influence the nature of the multimeric enzymes and vice versa. By recrystallization of the S‐layer/extremozyme fusion proteins on solid supports, the active enzyme multimers are exposed on the surface of the square S‐layer lattice with 13.1 nm spacing.     

Influence of S/B middle block composition on the morphology and the mechanical response of polystyrene-poly(styrene-co-butadiene)-polystyrene triblock copolymers

Polystyrene-poly(styrene-co-butadiene)-polystyrene triblock copolymers (PS-P(S-co-B)-PS) having different styrene contents (from 30 wt.% to 80 wt.%) in the statistical copolymer middle block and different block architectures (20-60-20 and 30-40-30) were characterised to study the influence of S/B middle block composition and segregation strength on the morphology and mechanical behaviour. The morphological investigations, i.e. TEM and SAXS, exhibited ordered lamellar and lamellar-like morphologies for both block architectures at low styrene contents between 30 wt.% and 50 wt.% in the S/B middle block. The increase in the styrene content in the middle block to 70 wt.% resulted in phase separated structures without long range order due to the enhanced miscibility between the PS and P(S-co-B) phase as observed from dynamic mechanical analysis. Further it was observed that the glass transition of the butadiene-rich phase is mainly determined by the S/B composition of the statistical copolymer block as confirmed by the Fox-equation. The alteration of the glass transition of the PS-rich phase and the observed PS-softening with raise in styrene content might be correlated to the increasing interphase width due to the enhanced miscibility as shown by calculations based on a simple model for diblock copolymers. Tensile testing revealed a transition from ductile to semi-ductile to brittle behaviour that strongly depends on the styrene content in the S/B middle block, chain architecture and the resulting morphology. Block copolymers (BCPs) with lamellar structure exhibited ductile behaviour with extensive strain hardening, whereas BCPs forming segregated structures without long range order were semi-ductile or brittle depending on the type of block architecture and on the hard-phase content. The transition in the mechanical behaviour was confirmed by fracture mechanical investigations based on the essential work of fracture approach and SEM-characterizations.     

Vapor–liquid equilibria of hydrogen chloride,phosgene, benzene,chlorobenzene, ortho‐dichlorobenzene,and toluene by molecular simulation

Vapor–liquid equilibria (VLE) of nine binary mixtures containing hydrogen chloride or phosgene in the solvents benzene, chlorobenzene, ortho‐dichlorobenzene, and toluene as well as the mixture hydrogen chloride + phosgene are predicted by molecular modeling and simulation. The underlying force fields for the pure substances are developed on the basis of quantum chemical information on molecular geometry and electrostatics. These are individually optimized to experimental pure fluid data on the vapor pressure and saturated liquid density, where the deviations are typically less than 5 and 0.5 %, respectively. The unlike dispersive interaction is optimized for seven of the nine studied binaries. Previously unpublished experimental binary VLE data, measured by BASF in the vicinity of ambient temperature, are predominantly used for these fits. VLE data, including dew point composition, saturated densities and enthalpy of vaporization, are predicted for a wide range of temperatures and compositions. © 2010 American Institute of Chemical Engineers AIChE J, 2011