The “Chunnel” Fire. I: Chemoplastic Softening in Rapidly Heated Concrete

This paper and its companion paper present the main results of an assessment of the fire in the Channel Tunnel (the “Chunnel”), which destroyed a part of the concrete tunnel rings by thermal spalling. The study seeks (1) to evaluate the effect of thermal damage (loss of elastic stiffness) and thermal decohesion (loss of material strength) upon the stress state and cracking at a structural level; and (2) to check whether restrained thermal dilatation can explain the thermal spalling observed during the fire. In the present paper, a macroscopic material model for rapidly heated concrete is developed. It accounts explicitly for the dehydration of concrete and its cross-effects with deformation (chemomechanical couplings) and temperature (chemothermal couplings). The thermal decohesion is considered as chemoplastic softening within the theoretical framework of chemoplasticity. Furthermore, kinetics of dehydration, dimensional analysis, and thermodynamic equilibrium considerations show that a unique thermal dehydration function exists that relates the hydration degree to the temperature rise, provided that the characteristic time of dehydration is much inferior to the characteristic time of structural heat conduction. The experimental determination of the thermal dehydration function from in-situ measurements of the elastic modulus versus furnace temperature rise is shown from experimental data available from the chunnel concrete. Finally, by way of an example, the proposed constitutive model for rapidly heated concrete is combined with the three-parameter William-Warnke criterion extended to isotropic chemoplastic softening.     

Network Analysis of Commuting Flows: A Comparative Static Approach to German Data

The analysis of complex networks has recently received considerable attention. The work by Albert and Barabási presented a research challenge to network analysis, that is, growth of the network. The present paper offers a network analysis of the spatial commuting network in Germany. First, we study the spatial evolution of the commuting network over time. Secondly, we compare two spatial interaction model (SIM) specifications, in order to replicate the actual network structure. Our findings suggest that the commuting network appeared to become more dense and clustered, while the SIMs seem to require more sophisticated specifications, in order to replicate such a connectivity structure.     

Does microstructure matter for statistical nanoindentation techniques?

In their paper, Trtik et al. (2009) identify spurious peaks in the application of statistical nanoindentation technique as a critical obstacle for mechanical phase identification. In this discussion, we show that Trtik et al.’s finding is a consequence of an unrealistic virtual 3-D checkerboard microstructure considered by the authors. These peaks are not a general feature of indentation on multiphase materials, nor can the presence of such peaks be attributed to an intrinsic shortcoming of the grid-indentation technique. We also show that the authors’ assertion of the absence of homogeneous material regions extending beyond 3 μm in cementitious materials is groundless.     

Mean residence time analysis for twin screw extruders

This paper presents and experimentally validates a physically motivated model for predicting the mean residence time in twin screw extruders. Accurate estimation of the mean residence time and the propagation delay through a plasticating extruder is critical for implementing feedback control schemes employing sensors mounted along the extruder. Experiments were carried out on a 30 mm Krupp Werner and Pfleiderer co‐rotating twin screw extruder equipped with reflectance optical probes over the melting section and mixing section and at the die. The residence time distributions for twelve operating conditions and two screw geometries are compared. The mean residence times predicted by our model are in good agreement with the experimentally measured mean residence times.     

The production and application of cuprous oxide and cupric hydroxide

Copper compounds are crucial for major areas of application, basically due to the biological impact of small amounts of copper. Thus, on the one hand, copper is used in the form of cuprous oxide as a coating for the hulls of ships to prevent algae growth or as cupric hydroxide as a fungicide in wine or coffe plantations; on the other hand, it is indispensable as a trace element in animal foodstuffs. Other applications (e.g., the manufacture of catalysts or pigments) are presently quantitatively small. Adalbert Lossin earned his Ph.D. in incorganic chemistry at the University of Hannover in 1993. He is currently the head of research and development at Norddeutsche Affinerie. Franz-Josef Westhoff earned his Dr. Ing. in nonferrous metallurgy at Tu Clansthal-Zellerfeld in 1990. He is currently a general superinterdent at the Metais and Chemicals Division of Norddeutsche Affinerie.     

The role of cysteine oxidation in the thermal inactivation of T4 lysozyme

Wild-type T4 lysozyme contains unpaired cysteine residues atpositions 54 and 97. To investigate the role these residuesplay in the thermal inactivation of the wild-type, we constructeda double mutant with these cysteines replaced with valine andserine. This molecule, T4 lysozyme (C54V/C97S), is more stablethan the wild-type to inactivation at 70°C at pH 6.5 and8.0. Guanidine hydrochloride reactivation experiments and SDS-PAGEon the inactivated products show that the wild-type is susceptibleto varying degrees of oxidative damage, depending on bufferconditions, while the cysteine-minus mutant inactivates onlyby other pathways. The products of thermal, oxidative inactivationof the wild-type are disulfide-linked oligomers. The dependenceof inactivation rate on temperature suggests that the formationof these aggregates depends on prior thermal unfolding of theT4 lysozyme molecule.     

Mikrofiltration von Fermenterbrühen

Microfiltration of fermentation broths . Crossflow microfiltration is a modern process for the work-up of fermentation broths. In the case of intracellular components, the cells can be enriched by this technique prior to disintegration of the cells. Extracellular products can be separated from the cells by the microfiltration membrane, and also from solids originating from the nutrient. The approach adopted in isolation of dissolved products by crossflow microfiltration is illustrated for alkaline protease, particular attention being directed to the dependence of the flow of permeate and the retention of the membrane material, the mean pore size of the membrane, the operating conditions, the physical data of the fermentation broth, and the addition of solids, which are discussed and quantified.     

Preferences as expectation-driven inferences: Effects of affective expectations on affective experience.

Presents a model arguing that affect and emotion are often formed in an expectation-driven fashion. A pilot study and 2 experiments manipulated undergraduate Ss' affective expectations (e.g., how funny they expected a set of cartoons to be) and whether Ss' expectations were confirmed (e.g., whether the cartoons really were funny). When the value of a stimulus was consistent with an affective expectation, people formed evaluations relatively quickly. Even when the value of a stimulus was discrepant from an affective expectation, people sometimes assimilated the value of the stimulus to their expectations. Other times, such as when making a more fine-grained evaluation of the cartoons, people noticed that they were discrepant from their affective expectations. Under these conditions, people appeared to have more difficulty forming preferences. They took longer to evaluate and spent more time thinking about the cartoons. (PsycINFO Database Record (c) 2010 APA, all rights reserved)