Two Design Principles for the Design of Demonstrations to Enhance Structure–Property Reasoning

Structure–property reasoning (SPR) is one of the most important aims of chemistry education but is seldom explicitly taught, and students find structure–property reasoning difficult. This study assessed two design principles for the development of structure–property reasoning in the context of demonstrations: (1) use of a POE task (predict–observe–explain) and (2) use of the domain-specific particle perspective, both to increase student engagement and to scaffold micro-level modeling. The aim of the demonstration series was to teach structure–property reasoning more explicitly to pre-university students (aged 15–16). Demonstrations pertained to the properties of metals, salts and molecular compounds. The SPR instrument was used as a pretest and posttest in order to gain insight into the effects on structure–property reasoning. In addition, one student (Sally) was followed closely to see how her structure–property reasoning evolved throughout the demonstrations. Results show that after the demonstrations students were more aware of the structure models at the micro-level. The students also knew and understood more chemical concepts needed for structure–property reasoning. Sally’s qualitative data additionally showed how she made interesting progress in modeling micro-level chemical structures. As we used conventional demonstrations as a starting point for design, this could well serve as a practical tool for teachers to redesign their existing demonstrations.

Revisiting the Gage–Bidwell Law of Dilution in Relation to the Effectiveness of Swimming Pool Filtration and the Risk to Swimming Pool Users from Cryptosporidium

The transfer of water from a swimming pool to the treatment location is key in determining the effectiveness of water treatment by filtration in removing turbidity and managing the risk from particulate material, including microbial pathogens, such as Cryptosporidium spp. A key recommendation for pool operators when dealing with an accidental faecal release (the likely main source of high Cryptosporidium oocyst concentrations in pools) is that the pool water should be filtered for at least six turnover cycles prior to use. This paper briefly outlines the theoretical basis of what has become known as the Gage–Bidwell Law of Dilution, which provides a basis for this recommendation, and extends the idea to account for the impact of filter efficiency. The Gage–Bidwell Law reveals that for each pool turnover 63% of the water resident in the pool at the start of the turnover period will have been recirculated. Building on this, we demonstrate that both filter efficiency and water-turnover time are important in determining filtration effectiveness and can be combined through a single parameter we term ‘particle-turnover’. We consider the implications of the Gage–Bidwell Law (as referred to in the original 1926 paper) for the dynamics of the ‘dirt’ content of pool water, whether in terms of a specific particle size range (e.g., Cryptosporidium oocysts) or turbidity.

Statistical analysis of thermal conductivity experimentally measured in water-based nanofluids

Nanofluids are suspensions of nanoparticles in a base heat-transfer liquid. They have been widely investigated to boost heat transfer since they were proposed in the 1990s. We present a statistical correlation analysis of experimentally measured thermal conductivity of water-based nanofluids available in the literature. The influences of particle concentration, particle size, temperature and surfactants are investigated. For specific particle materials (alumina, titania, copper oxide, copper, silica and silicon carbide), separate analyses are performed. The conductivity increases with the concentration in qualitative agreement with Maxwell’s theory of homogeneous media. The conductivity also increases with the temperature (in addition to the improvement due to the increased conductivity of water). Surprisingly, only silica nanofluids exhibit a statistically significant effect of the particle size, whereby smaller particles lead to faster heat transfer. Overall, the large scatter in the experimental data prevents a compelling, unambiguous assessment of these effects. Taken together, the results of our analysis suggest that more comprehensive experimental characterizations of nanofluids are necessary to estimate their practical potential.

A whole lung in silico model to estimate age dependent particle dosimetry

Anatomical and physiological changes alter airflow characteristics and aerosol distribution in the developing lung. Correlation between age and aerosol dosimetry is needed, specifically because youth are more susceptible to medication side effects. In this study, we estimate aerosol dosages (particle diameters of 1, 3, and 5 $$\upmu$$ μ m) in a 3 month-old infant, a 6 year-old child, and a 36 year-old adult by performing whole lung subject-specific particle simulations throughout respiration. For 3 $$\upmu$$ μ m diameter particles we estimate total deposition as 88, 73, and $$66\%$$ 66 % and the conducting versus respiratory deposition ratios as 4.0, 0.5, and 0.4 for the infant, child, and adult, respectively. Due to their lower tidal volumes and functional residual capacities the deposited mass is smaller while the tissue concentrations are larger in the infant and child subjects, compared to the adult. Furthermore, we find that dose cannot be predicted by simply scaling by tidal volumes. These results highlight the need for additional clinical and computational studies that investigate the efficiency of treatment, while optimizing dosage levels in order to alleviate side effects, in youth.

Kajian Pustaka Karakterisasi Perekat Polivinil Asetat Berbasis Air dengan Variabel Surfaktan

Polyvinyl acetate (PVAc) is an applicative polymer used as an adhesive material for one to another. These polymers can be synthesized through an emulsion polymerization process. In the industrial world, the process of making adhesive still involves environmentally unfriendly organic compounds containing xylene, benzene, and toluene. Therefore, water-based adhesive was introduced as an alternative to the PVAc synthesis solution. The aim of this literature review is to identify the type of surfactants used and analyze the PVAc characterization. This literature study focuses on the characterization of water-based PVAc with non-ionic nonylphenol (NP) surfactants including: NP-06, NP-10, NP 10 + 30, NP-30 and NP-40. Another surfactant used in this literature study is anionic surfactant Sodium Lauryl Sulfate (SLS) in units of Critical Micelle Concentration (CMC) including 1 CMC, 3 CMC, 5 CMC, 10 CMC, and 15 CMC. The result is a similarity in phenomena between the two types of surfactants. There is an increase in viscosity and a decrease in the value of the particle size as the surfactant increasing concentration used. However, in terms of the particle size, there is an optimal value where the specific NP surfactant concentration produces specific particle size with grit and at the specific SLS surfactant concentration produces relatively similar particle size.

A Finite Element/Neural Network Framework for Modeling Suspensions of Non-spherical Particles

An accurate prediction of the translational and rotational motion of particles suspended in a fluid is only possible if a complete set of correlations for the force coefficients of fluid-particle interaction is known. The present study is thus devoted to the derivation and validation of a new framework to determine the drag, lift, rotational and pitching torque coefficients for different non-spherical particles in a fluid flow. The motivation for the study arises from medical applications, where particles may have an arbitrary and complex shape. Here, it is usually not possible to derive accurate analytical models for predicting the different hydrodynamic forces. The presented model is designed to be applicable to a broad range of shapes. Another important feature of the suspensions occurring in medical and biological applications is the high number of particles. The modelling approach we propose can be efficiently used for simulations of solid-liquid suspensions with numerous particles. Based on resolved numerical simulations of prototypical particles we generate data to train a neural network which allows us to quickly estimate the hydrodynamic forces experienced by a specific particle immersed in a fluid.

A New Method of Diatomaceous Earth Fractionation - A Bio-Raw Material Source for Epoxy-Based Composites

The authors of this paper use an original method of diatomaceous earth fractionation, which allows for obtaining a filler with a specific particle size distribution. The method makes it possible to separate small, disintegrated and broken diatom frustules from those which maintained their original form in diatomaceous earth. The study covers a range of tests conducted to prove that such a separated diatomic fraction shows features different from the base diatomite used as an epoxy resin filler. We have examined mechanical properties of a series of diatomite/resin composites considering the weight fraction of diatoms and the parameters of the composite production process. The studied composites of Epidian 601 epoxy resin cross-linked with amine-based curing agent Z-1 contained 0 to 70% vol. of diatoms or diatomaceous earth. Samples were produced by casting into silicone moulds in vacuum degassing conditions and, alternatively, without degassing. The results have shown that the size and morphology of the filler based on diatomaceous earth affects mechanical and rheological properties of systems based on epoxy resin.

Formulation of SiO2/oil nanolubricant for metal forming using hydrodynamic cavitation

A novel hydrodynamic cavitation–based dispensing process was developed to disperse SiO2 nanoparticles into the base oil, and the effects of process parameters on dispersity and tribological properties of SiO2/oil nanolubricants were studied using the dynamic laser scattering and ring compression tests. With this process, nanolubricants with fine nanoparticles (139–1240 nm) were formulated. A mean particle size reduction of 78% was achieved in 60 min. This process can be scaled up for mass production with relative ease. The formulated SiO2/oil nanolubricants exhibited better tribological performance over that of base oil. Lubrication mechanisms of the SiO2/oil nanolubricant in metal forming were ascertained through analysis of the dispersity of nanolubricants and characterization of dents appearing on the surface of the deforming material. The study revealed the importance of formulating nanolubricants with specific particle size distribution that relate to the surface morphology of the deforming material. In this study, a nanolubricant with particle size of 3.6 μm exhibited better lubrication on ring samples with dent depth of 4.7 μm, implying that most nanoparticles were encapsulated in the dents facilitating hydrostatic lubrication.