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Quantum mechanics is counterintuitive, difficult to visualize, mathematically challenging, and abstract. The Physics Education Technology (PhET) Project now includes 18 simulations on quantum mechanics designed to improve the learning of this subject. These simulations include several key features to help students build mental models and intuition about quantum mechanics: visual representations of abstract concepts and microscopic processes that cannot be directly observed, interactive environments that directly couple students' actions to animations, connections to everyday life, and efficient calculations so that students can focus on the concepts rather than the mathematics. Like all PhET simulations, these are developed using the results of research and feedback from educators, and are tested in student interviews and classroom studies. This article provides an overview of the PhET quantum simulations and their development. We also describe research demonstrating their effectiveness and discuss some insights about student thinking. [DOI: 10.1119/1.2885199]

The impact of 27 volatile organic compounds (VOCs) on the regional O3 increment was investigated using measurements made at the UK EMEP supersites Harwell (1999-2001 and 2010-2012) and Auchencorth (2012). Ozone at these sites is representative of rural O3 in southeast England and northern UK, respectively. The monthlydiurnal regional O3 increment was defined as the difference between the regional and hemispheric background O3 concentrations, respectively, derived from oxidant vs. NOx correlation plots, and cluster analysis of back trajectories arriving at Mace Head, Ireland. At Harwell, which had substantially greater regional O3 increments than Auchencorth, variation in the regional O3 increment mirrored afternoon depletion of anthropogenic VOCs due to photochemistry (after accounting for diurnal changes in boundary layer mixing depth, and weighting VOC concentrations according to their photochemical ozone creation potential). A positive regional O3 increment occurred consistently during the summer, during which time afternoon photochemical depletion was calculated for the majority of measured VOCs, and to the greatest extent for ethene and mCp-xylene. This indicates that, of the measured VOCs, ethene and mCp-xylene emissions reduction would be most effective in reducing the regional O3 increment but that reductions in a larger number of VOCs would be required for further improvement. The VOC diurnal photochemical depletion was linked to anthropogenic sources of the VOC emissions through the integration of gridded anthropogenic VOC emission estimates over 96 h air-mass back trajectories. This demonstrated that one factor limiting the effectiveness of VOC gridded emissions for use in measurement and modelling studies is the highly aggregated nature of the 11 SNAP (Selected Nomenclature for Air Pollution) source sectors in which they are reported, as monthly variation in speciated VOC trajectory emissions did not reflect monthly changes in individual VOC diurnal photochemical depletion. Additionally, the major VOC emission source sectors during elevated regional O3 increment at Harwell were more narrowly defined through disaggregation of the SNAP emissions to 91 NFR (Nomenclature for Reporting) codes (i.e. sectors 3D2 (domestic solvent use), 3D3 (other product use) and 2D2 (food and drink)). However, spatial variation in the contribution of NFR sectors to parent SNAP emissions could only be accounted for at the country level. Hence, the future reporting of gridded VOC emissions in source sectors more highly disaggregated than currently (e.g. to NFR codes) would facilitate a more precise identification of those VOC sources most important for mitigation of the impact of VOCs on O3 formation. In summary, this work presents a clear methodology for achieving a coherent VOC, regional-O3-impact chemical climate using measurement data and explores the effect of limited emission and measurement species on the understanding of the regional VOC contribution to O3 concentrations. [ABSTRACT FROM AUTHOR]

Analyses have been undertaken of the trends and drivers of the distributions of ground-level O3 concentrations associated with potential impacts on human health and vegetation using measurements at the two UK EMEP supersites of Harwell and Auchencorth. These two sites provide representation of rural O3 over the wider geographic areas of south-east England and northern UK, respectively. The O3 exposures associated with health and vegetation impacts were quantified, respectively, by the SOMO10 and SOMO35 metrics, and by the flux-based PODγ metrics for wheat, potato, beech and Scots pine. Statistical analyses of measured O3 and NOx concentrations was supplemented by analyses of meteorological data and NOx emissions along air-mass back trajectories. The findings highlight the differing responses of impact metrics to the decreasing contribution of regional O3 episodes in determining O3 concentrations at Harwell between 1990 and 2013, associated with European NOx emission reductions. An improvement in human health-relevant O3 exposure observed when calculated by SOMO35, which decreased significantly, was not observed when quantified by SOMO10. The decrease in SOMO35 is driven by decreases in regionally-produced O3 which makes a larger contribution to SOMO35 than to SOMO10. For the O3 vegetation impacts at Harwell, no significant trend was observed for the PODγ metrics of the four species, in contrast to the decreasing trend in vegetation-relevant O3 exposure perceived when calculated using the crop AOT40 metric. The decreases in regional O3 production have not decreased PODγ as climatic and plant conditions reduced stomatal conductance and uptake of O3 during regional O3 production. Ozone concentrations at Auchencorth (2007-2013) were more influenced by hemispheric background concentrations than at Harwell. For health-related O3 exposures this resulted in lower SOMO35 but similar SOMO10 compared with Harwell; for vegetation PODγ values, this resulted in greater impacts at Auchencorth for vegetation types with lower exceedance ("Y") thresholds and longer growing seasons (i.e. beech and Scots pine). Additionally, during periods influenced by regional O3 production, a greater prevalence of plant conditions which enhance O3 uptake (such as higher soil water potential) at Auchencorth compared to Harwell resulted in exacerbation of vegetation impacts at Auchencorth, despite being further from O3 precursor emissions sources. These analyses indicate that quantifications of future improvement in health-relevant O3 exposure achievable from pan-European O3 mitigation strategies is highly dependent on the choice of O3 concentration cut-off threshold, and reduction in potential health impact associated with more modest O3 concentrations requires reductions in O3 precursors on a larger (hemispheric) spatial scale. Additionally, while further reduction in regional O3 is more likely to decrease O3 vegetation impacts within the spatial domains of Auchencorth compared to Harwell, larger reductions in vegetation impact could be achieved across the UK from reduction of hemispheric background O3 concentrations. [ABSTRACT FROM AUTHOR]

The use of symbolic calculators such as MATHEMATICA is becoming more commonplace among upper level physics students. The presence of such powerful calculators can couple strongly to the type of mathematical reasoning students employ. These tools do not merely offer students a convenient way to perform the calculations they would have otherwise done by hand. We present examples from the work of upper level physics majors where MATHEMATICA plays an active role in focusing and sustaining their thoughts around calculation. These students still engage in powerful mathematical reasoning while they calculate, but struggle because of the narrowed breadth of their thinking. We model MATHEMATICA'S influence as an integral part of the constant feedback that occurs in how students frame, and hence focus, their work. [ABSTRACT FROM AUTHOR]