VisChem: Building mental models of the molecular world using interactive multimedia

Understanding chemistry involves being able to link what one sees substances doing in the laboratory, to what one imagines is happening within these substances at the invisible molecular level. Only then can these ideas be communicated using abstract symbolism (e.g. chemical formulas), terminology and mathematics. The VisChem multimedia resources (QuickTime animations and video) explicitly link these three levels – the molecular, laboratory and symbolic. Research in chemical education over the last 20 years has revealed that many students have unacceptable, incomplete or non-existent mental models of chemical substances and processes at the molecular level. This problem is considered a major cause of misconceptions in chemistry, and is one reason why many students do not engage with the subject. In this poster session we will demonstrate some of the VisChem molecular-level animations (see http://vischem.cadre.com.au/). However, multimedia resources that promote meaningful learning should require ‘cognitive struggle’, facilitated through engagement, rather than by passive reception. We will describe how the animations are presented in live teaching contexts, and incorporated into interactive multimedia resources, to build mental models of the molecular world through meaningful ‘cognitive struggle’

Research into practice: Using molecular representations as a learning strategy in chemistry

Research in chemical education over the last 20 years has revealed that many students have unacceptable, incomplete or non-existent mental models of chemical substances and processes at the molecular level. Multimedia resources produced in the VisChem project (see http://vischem.cadre.com.au/) have been designed to address this problem. This paper investigates the effectiveness of VisChem molecular-level animations in enhancing student’ images of substances and processes in first year university chemistry. The effectiveness of these animations, and the way they were presented, were evaluated using a pre- and post-test format, with follow-up interviews of selected students. The pre- and post-test showed the sophistication and scientific acceptability of students’ images of molecular and ionic substances, before and after instruction. A comparison of pre- and post-data reveals significant improvements in students’ mental models of these chemical phenomena. In addition to this, data on self-perceptions of students’ confidence in their responses, and the vividness of their images, reveal a significant increase in both aspects following instruction. Interviews were used to probe what students believed to be the main sources of any changes in imagery or confidence. Without prompting, the molecular-level animations were commonly identified as a contributing factor

Global burden of 288 causes of death and life expectancy decomposition in 204 countries and territories and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BACKGROUND Regular, detailed reporting on population health by underlying cause of death is fundamental for public health decision making. Cause-specific estimates of mortality and the subsequent effects on life expectancy worldwide are valuable metrics to gauge progress in reducing mortality rates. These estimates are particularly important following large-scale mortality spikes, such as the COVID-19 pandemic. When systematically analysed, mortality rates and life expectancy allow comparisons of the consequences of causes of death globally and over time, providing a nuanced understanding of the effect of these causes on global populations. METHODS The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 cause-of-death analysis estimated mortality and years of life lost (YLLs) from 288 causes of death by age-sex-location-year in 204 countries and territories and 811 subnational locations for each year from 1990 until 2021. The analysis used 56 604 data sources, including data from vital registration and verbal autopsy as well as surveys, censuses, surveillance systems, and cancer registries, among others. As with previous GBD rounds, cause-specific death rates for most causes were estimated using the Cause of Death Ensemble model-a modelling tool developed for GBD to assess the out-of-sample predictive validity of different statistical models and covariate permutations and combine those results to produce cause-specific mortality estimates-with alternative strategies adapted to model causes with insufficient data, substantial changes in reporting over the study period, or unusual epidemiology. YLLs were computed as the product of the number of deaths for each cause-age-sex-location-year and the standard life expectancy at each age. As part of the modelling process, uncertainty intervals (UIs) were generated using the 2·5th and 97·5th percentiles from a 1000-draw distribution for each metric. We decomposed life expectancy by cause of death, location, and year to show cause-specific effects on life expectancy from 1990 to 2021. We also used the coefficient of variation and the fraction of population affected by 90% of deaths to highlight concentrations of mortality. Findings are reported in counts and age-standardised rates. Methodological improvements for cause-of-death estimates in GBD 2021 include the expansion of under-5-years age group to include four new age groups, enhanced methods to account for stochastic variation of sparse data, and the inclusion of COVID-19 and other pandemic-related mortality-which includes excess mortality associated with the pandemic, excluding COVID-19, lower respiratory infections, measles, malaria, and pertussis. For this analysis, 199 new country-years of vital registration cause-of-death data, 5 country-years of surveillance data, 21 country-years of verbal autopsy data, and 94 country-years of other data types were added to those used in previous GBD rounds. FINDINGS The leading causes of age-standardised deaths globally were the same in 2019 as they were in 1990; in descending order, these were, ischaemic heart disease, stroke, chronic obstructive pulmonary disease, and lower respiratory infections. In 2021, however, COVID-19 replaced stroke as the second-leading age-standardised cause of death, with 94·0 deaths (95% UI 89·2-100·0) per 100 000 population. The COVID-19 pandemic shifted the rankings of the leading five causes, lowering stroke to the third-leading and chronic obstructive pulmonary disease to the fourth-leading position. In 2021, the highest age-standardised death rates from COVID-19 occurred in sub-Saharan Africa (271·0 deaths [250·1-290·7] per 100 000 population) and Latin America and the Caribbean (195·4 deaths [182·1-211·4] per 100 000 population). The lowest age-standardised death rates from COVID-19 were in the high-income super-region (48·1 deaths [47·4-48·8] per 100 000 population) and southeast Asia, east Asia, and Oceania (23·2 deaths [16·3-37·2] per 100 000 population). Globally, life expectancy steadily improved between 1990 and 2019 for 18 of the 22 investigated causes. Decomposition of global and regional life expectancy showed the positive effect that reductions in deaths from enteric infections, lower respiratory infections, stroke, and neonatal deaths, among others have contributed to improved survival over the study period. However, a net reduction of 1·6 years occurred in global life expectancy between 2019 and 2021, primarily due to increased death rates from COVID-19 and other pandemic-related mortality. Life expectancy was highly variable between super-regions over the study period, with southeast Asia, east Asia, and Oceania gaining 8·3 years (6·7-9·9) overall, while having the smallest reduction in life expectancy due to COVID-19 (0·4 years). The largest reduction in life expectancy due to COVID-19 occurred in Latin America and the Caribbean (3·6 years). Additionally, 53 of the 288 causes of death were highly concentrated in locations with less than 50% of the global population as of 2021, and these causes of death became progressively more concentrated since 1990, when only 44 causes showed this pattern. The concentration phenomenon is discussed heuristically with respect to enteric and lower respiratory infections, malaria, HIV/AIDS, neonatal disorders, tuberculosis, and measles. INTERPRETATION Long-standing gains in life expectancy and reductions in many of the leading causes of death have been disrupted by the COVID-19 pandemic, the adverse effects of which were spread unevenly among populations. Despite the pandemic, there has been continued progress in combatting several notable causes of death, leading to improved global life expectancy over the study period. Each of the seven GBD super-regions showed an overall improvement from 1990 and 2021, obscuring the negative effect in the years of the pandemic. Additionally, our findings regarding regional variation in causes of death driving increases in life expectancy hold clear policy utility. Analyses of shifting mortality trends reveal that several causes, once widespread globally, are now increasingly concentrated geographically. These changes in mortality concentration, alongside further investigation of changing risks, interventions, and relevant policy, present an important opportunity to deepen our understanding of mortality-reduction strategies. Examining patterns in mortality concentration might reveal areas where successful public health interventions have been implemented. Translating these successes to locations where certain causes of death remain entrenched can inform policies that work to improve life expectancy for people everywhere. FUNDING Bill & Melinda Gates Foundation

The use of mini-projects in an undergraduate laboratory course in chemistry

This paper reports the results of a three-year study of the effectiveness of mini-projects in a first year laboratory course in chemistry at a Scottish university. A mini-project is a short, practical problem which requires for its solution the application of the knowledge and skills developed in previously completed set experiments. A number of recommendations have been made about the most appropriate ways of introducing mini-projects into undergraduate laboratory course. The main hypothesis of this survey was concerned with the value of mini-projects in laboratory courses formulated within the context of Information Processing Theory

Ecological approaches to the prevention of unintentional injuries

Background: Injury as a cause of significant morbidity and mortality has remained fairly stable in countries\ud with developed economies. Although injury prevention often is conceptualised as a biomedical construct, such\ud a reductionist perspective overlooks the importance of the psychological, environmental, and sociocultural\ud conditions as contributing factors to injury and its consequences. This paper describes the potential of\ud the ecological model for understanding the antecedent causes of unintentional injuries and guiding injury\ud prevention approaches. We review the origins and conceptualise the elements of the ecological model and\ud conclude with some examples of applications of ecological approaches to the prevention of unintentional\ud injury and promotion of community safety.\ud Methods: A review of the English-language literature on the conceptualization of ecological models in public\ud health and injury prevention, including the application of the ecological model in the prevention of falls and\ud road traffic injuries and in the community safety promotion movement.\ud Results: Three dimensions are important in social-ecological systems that comprise key determinants of\ud injuries: 1) the individual and his or her behaviour, 2) the physical environment, and 3) the social environment.\ud Social and environmental determinants have profound impact on population health and in the causation of injuries.\ud Conclusions: Social and environmental determinants of injury should be studied with the same energy, urgency, and intellectual rigor as physical determinants. Application of the ecological model in injury prevention shows the most promise in falls injury prevention, road traffic injury prevention, and community safety promotion

Political economy of Ramsey taxation

We study the dynamic taxation of capital and labor in the Ramsey model under the assumption that taxes and public good provision are decided by a self-interested politician who cannot commit to policies. We show that, as long as the politician is as patient as the citizens, the Chamley–Judd result of zero long-run taxes holds. In contrast, if the politician is less patient than the citizens, the best (subgame perfect) equilibrium from the viewpoint of the citizens involves long-run capital taxation.National Science Foundation (U.S.