Detonation propagation through a nonuniform layer of hydrogen-oxygen in a narrow channel

Experiments were carried out to study detonation propagation through a nonuniform layer of stoichiometric hydrogen-oxygen in a narrow channel. Premixed stoichiometric hydrogen-oxygen was injected through a series of 1.3 mm diameter, 4.8 mm spaced holes into a 7 mm wide optically accessible channel initially filled with an inert gas. A Chapman-Jouguet detonation wave was transmitted into the test section from a pre-detonator of equal height. The height of the layer was varied by changing the time of hydrogen-oxygen injection relative to the arrival-time of the detonation wave. Schlieren photography was used to record the progression of the detonation wave. Soot foils mounted to the back window, were used to record the detonation cellular structure and visualization of the soot incandescence provided tracking of the reaction zone. With the channel initially filled with argon, detonation propagation was only possible when the layer height accommodated at least 8–11 detonation cells. Detonation propagation was not possible when the channel initially contained nitrogen, or carbon dioxide, indicating strong mixing with the injected premixed hydrogen-oxygen. Numerical simulations confirmed the strong mixing between the injected premixed hydrogen-oxygen with the prefilled inert gas. The simplified mixing condition, i.e., injection of premixed hydrogen-oxygen, provides a unique data set for numerical code validation and verification for a linear RDE geometry.     

Computer-based engineering of thermostabilized antibody fragments

We used the molecular modeling program Rosetta to identify clusters of amino acid substitutions in antibody fragments (scFvs and scAbs) that improve global protein stability and resistance to thermal deactivation. Using this methodology, we increased the melting temperature (T_m) and resistance to heat treatment of an antibody fragment that binds to the Clostridium botulinum hemagglutinin protein (anti-HA33). Two designed antibody fragment variants with two amino acid replacement clusters, designed to stabilize local regions, were shown to have both higher T_m compared to the parental scFv and importantly to retain full antigen binding activity after 2 hr of incubation at 70°C. The crystal structure of one thermostabilized scFv variants was solved at 1.6 Å and shown to be in close agreement with the RosettaAntibody model prediction.     

Yield stress distribution in injection‐moulded glassy polymers

A methodology for structural analysis simulations is presented that incorporates the distribution of mechanical properties along the geometrical dimensions of injection‐moulded amorphous polymer products. It is based on a previously developed modelling approach, where the thermomechanical history experienced during processing was used to determine the yield stress at the end of an injection‐moulding cycle. Comparison between experimental data and simulation results showed an excellent quantitative agreement, both for short‐term tensile tests as well as long‐term creep experiments over a range of strain rates, applied stresses, and testing temperatures. Changes in mould temperature and component wall thickness, which directly affect the cooling profiles and, hence, the mechanical properties, were well captured by the methodology presented. Furthermore, it turns out that the distribution of the yield stress along a tensile bar is one of the triggers for the onset of the (strong) localization generally observed in experiments. © 2015 Society of Chemical Industry     

Mediated Electrochemistry to Mimic Biology's Oxidative Assembly of Functional Matrices

Biology uses diffusible oxidants to perform functions that range from signaling to matrix assembly, and these oxidation chemistries offer surprising selectivities. Here, it is reported that mediated electrochemistry can access the richness of such oxidation chemistries. Specifically, electrode‐imposed voltage inputs are used to locally generate oxidized mediators that can diffuse into polymer solutions and induce the formation of covalent bonds for the deposition and functionalization of hydrogels at the electrode surface. Depending on the mediator's redox potential (E⁰), it is possible to “gate” the voltage inputs to target specific residues (e.g., thiols or amines) and oxidation chemistries. Further, mediators of varying E⁰ offer different reactivities and thus allow control of reaction‐diffusion rates to modulate the hydrogel's crosslink density and mechanical properties. Importantly, this mediated oxidation can be performed under physiologically relevant conditions to preserve labile biological functionalities (e.g., cell viability and protein function). Finally, it is demonstrated that protein fusion tags can be engineered to have “targetable” amino acid residues that enable protein function to be oxidatively conjugated to electrodeposited hydrogels. In summary, mediated electrochemistry can engage orthogonal oxidation chemistries to create functionalized matrices and thus mediated electrochemistry should add important capabilities to the electrofabrication toolbox.     

Explicit versus implicit models: What are good languages for modeling?

Software and Systems Modeling -     

SoSyM significantly reduces its backlog

Software and Systems Modeling -     

On the relationship between models and ontologies

Software and Systems Modeling -     

Estimation of film accumulation in percolating filters: Comparison of methods

Estimation of film accumulation is necessary for the successful operational management of percolating filters. Prevention of ponding and loss of performance due to excessive film accumulation, and the optimization of the recirculation and alternating double filtration processes can only be achieved by regular monitoring of film growth. Five methods of determining film accumulation are compared; total film weight, total dry solids, volatile solids, percentage settlement of solids and the neutron scattering technique. The methods were used to monitor the film growth in pilot filters containing a mineral and a random plastics medium, over two twelve-month loading periods at 1.68 m³ m⁻³ day⁻¹ (0.28 kg BOD m⁻³ day⁻¹) and 3.37 m³ m⁻³ day⁻¹ (0.63 kg BOD m⁻³ day⁻¹).

Good correlations (P < 0.001) are found between all methods at the lower loading although the neutron scattering results are not significantly correlated (P > 0.10) with any of the gravimetric methods at the higher loading. Although the neutron scattering technique does provide a rapid and sensitive measure of hydrogen atoms in the filter, the results, expressed as percentage saturation of the voids, are not directly transferable to film weights and should be treated separately and not as a true measure of film accumulation.     

The effect of drinking water treatment on the spatial heterogeneity of micro-organisms: implications for assessment of treatment efficiency and health risk

The effect of drinking water treatment (ferric coagulation, floc blanket clarification, rapid sand filtration) on the spatial heterogeneity of five species of micro-organism was studied at pilot scale. It was found that the spatial heterogeneity of vegetative bacteria (namely total coliform and heterotrophic (22 degrees C; 3 d) bacteria) was little affected by treatment. Indeed, counts of total coliform bacteria within 500 l volumes of treated water were Poisson distributed (i.e. showed minimum variation). In contrast, treatment appeared to increase the spatial heterogeneity (or clustering) of both aerobic spores indigenous to the raw water and Bacillus subtilis var niger spores added to the raw water. Furthermore, B. subtilis var niger spores added to the raw water were detected in the treated water 25 h after termination of spiking to the raw water. The effect on C. parvum oocysts added to the raw water could not be determined because few oocysts broke through treatment into the treated water. Indeed oocyst removals of 5-6 logs were apparent. "Species-specific" differences in the removal ratios were also demonstrated. It is concluded that audits for treatment processes based on single 100 ml "spot" samples for spores will tend to over-estimate the net spore removal and hence underestimate the public health risk. Spatial heterogeneity of counts in treated water contributes to explaining why no "ideal" surrogate has been identified for treatment plant performance.