In this study, 364 first-year physics students were randomly assigned to one of four online multimedia treatments on Newton's First and Second Laws of Motion: (1) the 'Exposition', a concise lecture-style presentation; (2) the 'Extended Exposition', the Exposition with additional interesting information; (3) the 'Refutation', the Exposition with common misconceptions explicitly stated and refuted; or (4) the 'Dialogue', a student-tutor discussion of the same material as in the Refutation. Students were tested using questions from mechanics conceptual inventories before and after watching the multimedia treatments. Results show the Refutation and Dialogue produced the greatest learning gains, with effect sizes of 0.79 and 0.83, respectively, compared with the Exposition. Students with low prior knowledge benefited most, however high prior knowledge learners were not disadvantaged by the misconception-based approach. The findings suggest that online multimedia can be greatly improved, promoting conceptual change in students with all levels of experience, by including a discussion of misconceptions.

Intensity-modulated radiation therapy (IMRT) achieves optimal dose conformity to the tumor through the use of spatially and temporally modulated radiation fields. In particular, average dose rate and instantaneous dose rate (pulse amplitude) are highly variable within a single IMRT fraction. In this study we isolate these variables and determine their impact on cell survival. Survival was assessed using a clonogenic assay. Two cell lines of differing radiosensitivity were examined: melanoma (MM576) and non-small cell lung cancer (NCI-H460). The survival fraction was observed to be independent of instantaneous dose rate. A statistically significant trend to increased survival was observed as the average dose rate was decreased, for a constant total dose. The results are relevant to IMRT practice, where average treatment times can be significantly extended to allow for movement of the multi-leaf collimator (MLC). Our in vitro study adds to the pool of theoretical evidence for the consequences of protracted treatments. We find that extended delivery times can substantially increase the cell survival. This also suggests that regional variation in the dose-rate history across a tumor, which is inherent to IMRT, will affect radiation dose efficacy.

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We present an automated cell colony counting method that is flexible, robust and capable of providing more in-depth clonogenic analysis than existing manual and automated approaches. The full form of the Hough transform without approximation has been implemented, for the first time. Improvements in computing speed have facilitated this approach. Colony identification was achieved by pre-processing the raw images of the colonies in situ in the flask, including images of the flask edges, by erosion, dilation and Gaussian smoothing processes. Colony edges were then identified by intensity gradient field discrimination. Our technique eliminates the need for specialized hardware for image capture and enables the use of a standard desktop scanner for distortion-free image acquisition. Additional parameters evaluated included regional colony counts, average colony area, nearest neighbour distances and radial distribution. This spatial and qualitative information extends the utility of the clonogenic assay, allowing analysis of spatially-variant cytotoxic effects. To test the automated system, two flask types and three cell lines with different morphology, cell size and plating density were examined. A novel Monte Carlo method of simulating cell colony images, as well as manual counting, were used to quantify algorithm accuracy. The method was able to identify colonies with unusual morphology, to successfully resolve merged colonies and to correctly count colonies adjacent to flask edges.