A tiered approach to estimate inventory data and impacts of chemical products and mixtures

Purpose: Mixtures of organic chemicals are a part of virtually all life cycles, but LCI data exist for only relatively few chemicals. Thus, estimation methods are required. However, these are often either very time-consuming or deliver results of low quality. This article compares existing and new methods in two scenarios and recommends a tiered approach of different methods for an efficient estimation of the production impacts of chemical mixtures. Methods: Four approaches to estimate impacts of a large number of chemicals are compared in this article: extrapolation from existing data, substitution with generic datasets on chemicals, molecular structure-based models (MSMs, in this case the Finechem tool), and using process-based estimation methods. Two scenarios were analyzed as case studies: soft PVC plastic and a tobacco flavor, a mixture of 20 chemicals. Results: Process models have the potential to deliver the best estimations, as existing information on production processes can be integrated. However, their estimation quality suffers when such data are not available and they are time-consuming to apply, which is problematic when estimating large numbers of chemicals. Extrapolation from known to unknown components and use of generic datasets are generally not recommended. In both case studies, these two approaches significantly underestimated the impacts of the chemicals compared to the process models. MSMs were generally able to estimate impacts on the same level as the more complex process models. A tiered approach using MSMs to determine the relevance of individual components in mixtures and applying process models to the most relevant components offered a simpler and faster estimation process while delivering results on the level of most process models. Conclusions: The application of the tiered combination of MSMs and process models allows LCA practitioners a relatively fast and simple estimation of the LCIA results of chemicals, even for mixtures with a large number of components. Such mixtures previously presented a problem, as the application of process models for all components was very time-consuming, while the existing, simple approaches were shown to be inadequate in this study. We recommend the tiered approach as a significant improvement over previous approaches for estimating LCA results of chemical mixture

Composite likelihood methods for large Bayesian VARs with stochastic volatility

© 2020 John Wiley & Sons, Ltd. Adding multivariate stochastic volatility of a flexible form to large vector autoregressions (VARs) involving over 100 variables has proved challenging owing to computational considerations and overparametrization concerns. The existing literature works with either homoskedastic models or smaller models with restrictive forms for the stochastic volatility. In this paper, we develop composite likelihood methods for large VARs with multivariate stochastic volatility. These involve estimating large numbers of parsimonious models and then taking a weighted average across these models. We discuss various schemes for choosing the weights. In our empirical work involving VARs of up to 196 variables, we show that composite likelihood methods forecast much better than the most popular large VAR approach, which is computationally practical in very high dimensions: the homoskedastic VAR with Minnesota prior. We also compare our methods to various popular approaches that allow for stochastic volatility using medium and small VARs involving up to 20 variables. We find our methods to forecast appreciably better than these as well

Factors affecting breeding status of wading birds in the Everglades.

This goals of this research and monitoring effort are to document nesting effort and roughly categorize success of nesting by wading birds in the central Everglades of Florida, and to investigate the causes of nonbreeding in a high proportion of the adult wading birds in the ecosystem The latter goal has focused on breeding of White Ibises (Eudocimus albus) and has been approached through 1) understanding the nutritional, behavioral, and hormonal aspects of normal breeding in a captive colony ofScarlet Ibises (considered conspecific to White Ibises) in central Florida, and 2) comparing breeding and nonbreeding wild White Ibises in the Everglades, in their physiology, nutritional state, breeding phenology, contaminant load, and hormonal status. This report covers work on this project between January and November, 2000. (81 page docoument

Spatial Expressions and Consumer Perceptions of Quantity

Marketplaces and media sources frequently present consumers with information or measurements that involve “extreme” quantities (e.g., the size of the national debt or the number of pounds of plastic in the Earth’s oceans). Often, communicators express these quantities in spatial terms in an effort to influence the perceptual impact of the information (e.g., expressing the national debt in terms of the number of miles it would extend if laid out in paper currency form). Across three experiments, we find evidence that perceptual impact diminishes with spatial dimensionality (e.g., expressing a quantity as a length makes it seem larger than expressing it as a volume)

Powers of the Universe: Empowering primary school students with the powers of ten notation

Numbers, both very large and very small, are crucially important for understanding the modern world. This paper assesses trials of a mathematics and physics module called Powers of the Universe in which arithmetic with extreme numbers (large and small) is developed through early learning of the powers of ten notation. We trialled a 6-hour progression of lessons based on activities and group learning with students aged 7-13 years. We measured students' ability to estimate, compare, and calculate extreme numbers using pre and post-tests to evaluate the program. Results demonstrated students' strong enthusiasm and positive learning outcomes in areas normally assumed to be beyond the capability of students in this age group. We discuss the age dependence of some results and suggest an optimum strategy for enhancing primary school mathematics. The module has been delivered, as part of a broader five-module program called Maths for Einstein's Universe, that aims to reduce maths anxiety through programs with direct relevance to the modern world and reduced emphasis on exactness.Comment: 30 pages, 10 figure

Pathogen removal and use of biosand water filters in the Region Autonoma Atlantico Sur of Nicaragua

This study examined usage of biosand filters amongst 86 families in three different communities in the Región Autónoma Atlántico Sur (RAAS) of Nicaragua. 75% of the families in the study were actively using their filter whilst the remaining 25% no longer used their filter. Pathogen levels (thermotolerant coliforms) were examined in samples of the unfiltered source water, the filtrate and the stored water post-filtration. Average pathogen removal efficiency was 89% and was not significantly higher amongst families who followed the recommended patterns of use of the filter. While the filters in the study typically produced water that was considered safe to drink, recontamination of the stored, filtered water was a significant problem that occurred in 66% of the families. This study affirms the effectiveness of biosand water filters in the field and highlights the need for a focus on prevention of recontamination of the stored, filtered water

Using mental transformation strategies for spatial scaling: Evidence from a discrimination task

Spatial scaling, or an understanding of how distances in different-sized spaces relate to each other, is fundamental for many spatial tasks and relevant for success in numerous professions. Previous research has suggested that adults use mental transformation strategies to mentally scale spatial input, as indicated by linear increases in response times and accuracies with larger scaling magnitudes. However, prior research has not accounted for possible difficulties in encoding spatial information within smaller spaces. Thus, the present study used a discrimination task in which we systematically pitted absolute size of the spaces against scaling magnitude. Adults (N = 48) were presented with 2 pictures, side-by-side on a computer display, each of which contained a target. Adults were asked to decide whether the targets were in the same position or not, by pressing the respective computer key. In the constant-large condition, the constant space was kept large, whereas the size of the other space was variable and smaller. In the constant-small condition, the constant space was small, whereas the size of the other space was variable and larger. Irrespective of condition, adults’ discrimination performance (d- primes) and response times were linear functions of scaling magnitude, supporting the notion that analog imagery strategies are used in spatial scaling