Rate of Dimer Formation in Stable Colloidal Solutions Quantified Using an Attractive Interparticle Force.

We describe an optomagnetic cluster experiment to understand and control the interactions between particles over a wide range of time scales. Aggregation is studied by magnetically attracting particles into dimers and by quantifying the number of dimers that become chemically bound within a certain time interval. An optomagnetic readout based on light scattering of rotating clusters is used to measure dimer formation rates. Magnetic field settings, that is, field rotation frequency, field amplitude, and on- and off-times, have been optimized to independently measure both the magnetically induced dimers and chemically bound dimers. The chemical aggregation rate is quantified in solutions with different pH and ionic strengths. The measured rates are extrapolated to effective dimer formation rates in the absence of force, showing that aggregation rates can be quantified over several orders of magnitude, including conditions of very low chemical reactivity.

Appropriateness of different pedagogical approaches to road safety education for children with Developmental Coordination Disorder (DCD).

BACKGROUND: In 2016, 29% of pedestrians killed or seriously injured on the roads in Great Britain were under 15 years of age. Children with Developmental Coordination Disorder (DCD), a chronic disorder affecting the acquisition and execution of motor skills, may be more vulnerable at the roadside than typically developing (TD) children. Current methods used to teach road safety are typically knowledge-based and do not necessarily improve behaviour in real traffic situations. Virtual reality road crossing tasks may be a viable alternative. AIMS/METHODS: The present study aimed to test the road crossing accuracy of children with and without DCD in virtual reality tasks that varied the viewpoint to simulate the teaching methods currently used in road safety educational programmes. Twenty-one children with DCD and twenty-one age and gender matched TD peers were required to locate the safest road crossing sites in two conditions: allocentric (aerial viewpoint) and egocentric (first-person viewpoint). PROCEDURES/OUTCOMES: All children completed both conditions and were required to navigate either themselves or an avatar across the road using the safest crossing route. The primary outcome was accuracy defined as the number of trials, out of 10, on which the child successfully identified and used the safest crossing route. RESULTS/CONCLUSIONS: Children with DCD performed equally poorly in both conditions, while TD children were significantly more accurate in the egocentric condition. This difference cannot be explained by self-reported prior road crossing education, practice or confidence. IMPLICATIONS: While TD children may benefit from the development of an egocentric virtual reality road crossing task, multimodal methods may be needed to effectively teach road safety to children with DCD.