Structure formation mechanisms in consolidating pigment coatings—Simulation and visualisation

Microstructure development in consolidating pigment coating layers was studied in terms of particle flocculation and clustering mechanisms utilising a 3D particle dynamics model. The model includes hydrodynamic forces, colloidal interactions as well as the Brownian motion. The influence of colloidal interactions and drying strategy on the coating layer thickness development and internal solid concentration gradients, was investigated. A low particle surface potential resulted in the formation of porous particle networks, which impeded the shrinkage of the coating layer. At higher surface potentials particles arranged into denser structures, whereby the solids concentration profile could be controlled by the drying. Low electrostatic double layer thicknesses allowed sharp concentration gradients to form as result of the applied drying strategy. At high double layer thicknesses, the structure formation was similar regardless of drying strategy. This work elucidates the combined effect of drying conditions and colloidal suspension properties on coating microstructure development. Furthermore, the results aid in the understanding of how coating suspension additives may influence the structure development of the coating layer.     

Microwave assisted click chemistry on a conductive polymer film

Microwave (MW) irradiation has been used to accelerate the functionalization of an azide functional poly(3,4-ethylenedioxythiophene) film by click chemistry. The absorption of MW energy by the conductive polymer has been exploited for localized activation of the reaction on the polymer surface. By use of an alkyne modified fluorescein derivative the reaction conditions have been optimized in a conventional MW oven, enabling the use of different sizes of substrates. The optimization resulted in a reduction of reaction times of approximately 20 h to only 2 min for bulk film functionalization. The method has been applied for anchoring of the chelating agent nitrilotriacetic acid (NTA) on the conductive polymer. The chelating linkage ability of NTA on the surface was investigated through a sandwich ELISA study confirming the selective bonding of a histidine tagged protein.     

Swedish hunters’ safety behaviour and experience of firearm incidents

Since any firearm injury is potentially lethal, it is of great interest to prevent firearm incidents. This study investigated such incidents during hunting and Swedish hunters’ safety behaviour. A 48-item questionnaire was posted to a random sample of 1000 members of the Swedish Association for Hunting and Wildlife Management. The questions considered demographics, hunting experience/hunting habits/safety behaviour/attitudes and experience of careless weapon handling, hunters’ weapons and safety behaviour relating to weapons, health status, firearm incidents and their preventability, and personal comments on the questionnaire. The response rate was almost 50%. The mean age of the responders was 54 years; 5% were females. Almost none (1%) reported hunting under the influence of alcohol. Young age and male sex were positively associated with risk behaviour, although the presence of multiple risk behaviours in the same responder was not common. A very high degree of compliance with Swedish laws regarding weapon storage was reported. One-quarter of the responders had witnessed a firearm incident caused by another hunter, which in most situations did not result in human injury or death. An unsafetied weapon was the most common reported “cause” of these incidents. Experience of a firearm incident was not uncommon and the majority of the responders considered the incident in question to be preventable. This study provides a picture of the possible risk behaviour among hunters and the results suggest that future prevention work should target safer weapon handling.     

Dynamical systems and topology optimization

This paper uses a dynamical systems approach for studying the material distribution (density or SIMP) formulation of topology optimization of structures. Such an approach means that an ordinary differential equation, such that the objective function is decreasing along a solution trajectory of this equation, is constructed. For stiffness optimization two differential equations with this property are considered. By simple explicit Euler approximations of these equations, together with projection techniques to satisfy box constraints, we obtain different iteration formulas. One of these formulas turns out to be the classical optimality criteria algorithm, which, thus, is receiving a new interpretation and framework. Based on this finding we suggest extensions of the optimality criteria algorithm. A second important feature of the dynamical systems approach, besides the purely algorithmic one, is that it points at a connection between optimization problems and natural evolution problems such as bone remodeling and damage evolution. This connection has been hinted at previously but, in the opinion of the authors, not been clearly stated since the dynamical systems concept was missing. To give an explicit example of an evolution problem that is in this way connected to an optimization problem, we study a model of bone remodeling. Numerical examples, related to both the algorithmic issue and the issue of natural evolution represented as bone remodeling, are presented.     

Partitioning of organic biocides between wood and supercritical carbon dioxide

The degree of interaction between selected organic biocides (tebuconazole, propiconazole, and IPBC) and wood under supercritical conditions was investigated using a supercritical fluid chromatograph. The biocides were carried through a sawdust column by CO₂ at various conditions. Retention times differed markedly both between the examined biocides and between physical conditions. Tebuconazole showed a higher affinity for wood than the other biocides. For all biocides, wood affinity was highest and, thus, fluid affinity lowest, at lowest pressures.     

Effects of climate change on biomass production and substitution in north-central Sweden

In this study we estimate the effects of climate change on forest production in north-central Sweden, as well as the potential climate change mitigation feedback effects of the resulting increased carbon stock and forest product use. Our results show that an average regional temperature rise of 4 °C over the next 100 years may increase annual forest production by 33% and potential annual harvest by 32%, compared to a reference case without climate change. This increased biomass production, if used to substitute fossil fuels and energy-intensive materials, can result in a significant net carbon emission reduction. We find that carbon stock in forest biomass, forest soils, and wood products also increase, but this effect is less significant than biomass substitution. A total net reduction in carbon emissions of up to 104 Tg of carbon can occur over 100 years, depending on harvest level and reference fossil fuel.     

Social influence during the initial phase of a fire evacuation—Analysis of evacuation experiments in a cinema theatre

Unannounced evacuation experiments in a cinema theatre were analysed. The analysis focused on investigating if people are influenced by others during the initial phase of a fire evacuation. This type of influence is called social influence. Three separate behaviour types were identified and studied and the recognition and pre-movement time was measured. The results suggest that social influence is an important factor and that it becomes more important when the fire cue, e.g., the alarm, is unclear or uninformative. Results also indicate that social influence increases with decreasing distance between visitors. This result implies that individuals are influenced more by people who are close than by people who are further away.     

Low-voltage terahertz quantum-cascade lasers based on LO-phonon-assisted interminiband transitions

A report is presented on GaAs/(Al,Ga)As terahertz (THz) quantum-cascade lasers (QCLs) based on alternating photon and longitudinal optical (LO) phonon-assisted transitions between quasi-minibands. The design is optimised for low threshold current densities and low operating voltages, resulting in reduced ohmic heating during continuous-wave (CW) operation. The QCLs exhibit lasing over a broad range of frequencies from 2.91 to 3.21 THz. Using single-plasmon waveguides, pulsed operation up to 114 K and CW operation up to 65 K has been achieved.     

Plant fibre composites – porosity and stiffness

Plant fibre composites contain typically a relatively large amount of porosity which influences their performance. A model, based on a modified rule of mixtures, is presented to include the influence of porosity on the composite stiffness. The model integrates the volumetric composition of the composites with their mechanical properties. The fibre weight fraction is used as an independent parameter to calculate the complete volumetric composition. A maximum obtainable stiffness of the composites is calculated at a certain transition fibre weight fraction, which is characterised by a best possible combination of high fibre volume fraction and low porosity. The model is validated with experimental data from the literature on several types of composites. A stiffness diagram is presented to demonstrate that the calculations can be used for tailoring and design of composites with a given profile of properties.