Modeling Aerial Gamma-Ray Backgrounds using Non-negative Matrix Factorization

Airborne gamma-ray surveys are useful for many applications, ranging from geology and mining to public health and nuclear security. In all these contexts, the ability to decompose a measured spectrum into a linear combination of background source terms can provide useful insights into the data and lead to improvements over techniques that use spectral energy windows. Multiple methods for the linear decomposition of spectra exist but are subject to various drawbacks, such as allowing negative photon fluxes or requiring detailed Monte Carlo modeling. We propose using Non-negative Matrix Factorization (NMF) as a data-driven approach to spectral decomposition. Using aerial surveys that include flights over water, we demonstrate that the mathematical approach of NMF finds physically relevant structure in aerial gamma-ray background, namely that measured spectra can be expressed as the sum of nearby terrestrial emission, distant terrestrial emission, and radon and cosmic emission. These NMF background components are compared to the background components obtained using Noise-Adjusted Singular Value Decomposition (NASVD), which contain negative photon fluxes and thus do not represent emission spectra in as straightforward a way. Finally, we comment on potential areas of research that are enabled by NMF decompositions, such as new approaches to spectral anomaly detection and data fusion.Comment: 14 pages, 12 figures, accepted for publication in IEEE Transactions on Nuclear Scienc

Evaluating Functional Diversity as Potential Early-Warning Indicator of Rangeland Degradation

Droughts and overgrazing play a crucial role in the degradation of semi-arid rangelands. This is evident in the loss of palatable long-lived grass species and bush encroachment. Early warning indicators are needed to mitigate long-term degradation and decline in essential forage provision. Functional diversity provides valuable information on ecosystem health. However, functional diversity indices have not yet been tested regarding their applicability as early warning indicators, revealing non-linear threshold behaviour. We therefore examined the following questions: (1) How do functional diversity indices respond to grazing pressure? (2) Does land tenure affect the relationship between functional diversity and grazing pressure? (3) Are functional diversity indices suitable early-warning indicators? To answer these questions, we conducted a space-for-time substitution of land use intensity of semi-arid rangelands in Namibia. Some 16 grazing gradients were selected, each starting at a cattle watering point where grazing pressure was highest. Gradients were located in four communal and four freehold farms. Communal farms were characterised by continuous grazing, while freehold farms by rotational grazing. In each transect we recorded plant species composition of the grass layer in 9 plots of 10 × 10 m each (N = 162 plots). Within each transect, these plots were logarithmically distributed. Various plant functional traits—all relating to plant life history or resource acquisition strategy—were measured for 142 dominant species, accounting for more than 80 % of the biomass, and indices of functional diversity were calculated. We found potential threshold behaviour in functional richness on freehold farms. Certain functional diversity indices revealed non-linear patterns in rangelands but are currently not a user-friendly early-warning indicator. To harness functional diversity, we need a more standardized method of calculation, and more functional trait databases for sub-Saharan species

Seeking structural repetitivity in systems with interaction interference: crystal engineering in the gem-alkynol family

Synthon repetitivity has been demonstrated in a pair of gem-alkynols, despite the high degree of interaction interference typical of this family of compounds

When is a polymorph not a polymorph? Helical trimeric O-H···O synthons in trans-1,4-diethynylcyclohexane-1,4-diol

Two polymorphs (A and B) of trans-1,4-diethynylcyclohexane-1,4-diol represent a unique example of the simultaneous occurrence of both conformational polymorphism and conformational isomorphism, while a pseudopolymorphic monohydrate is closely related

The distribution of pond snail communities across a landscape: separating out the influence of spatial position from local habitat quality for ponds in south-east Northumberland, UK

Ponds support a rich biodiversity because the heterogeneity of individual ponds creates, at the landscape scale, a diversity of habitats for wildlife. The distribution of pond animals and plants will be influenced by both the local conditions within a pond and the spatial distribution of ponds across the landscape. Separating out the local from the spatial is difficult because the two are often linked. Pond snails are likely to be affected by both local conditions, e.g. water hardness, and spatial patterns, e.g. distance between ponds, but studies of snail communities struggle distinguishing between the two. In this study, communities of snails were recorded from 52 ponds in a biogeographically coherent landscape in north-east England. The distribution of snail communities was compared to local environments characterised by the macrophyte communities within each pond and to the spatial pattern of ponds throughout the landscape. Mantel tests were used to partial out the local versus the landscape respective influences. Snail communities became more similar in ponds that were closer together and in ponds with similar macrophyte communities as both the local and the landscape scale were important for this group of animals. Data were collected from several types of ponds, including those created on nature reserves specifically for wildlife, old field ponds (at least 150 years old) primarily created for watering livestock and subsidence ponds outside protected areas or amongst coastal dunes. No one pond type supported all the species. Larger, deeper ponds on nature reserves had the highest numbers of species within individual ponds but shallow, temporary sites on farm land supported a distinct temporary water fauna. The conservation of pond snails in this region requires a diversity of pond types rather than one idealised type and ponds scattered throughout the area at a variety of sites, not just concentrated on nature reserves

The type and frequency of interactions that occur between staff and children outside in Early Years Foundation Stage settings during a fixed playtime period when there are tricycles available

This study reports on an investigation into adult and child interactions observed in the outdoor play environment in four Local Authority early years foundation stage settings in England. In this instance the common two features across the settings were the presence of tricycles and a timetabled outdoor play period. In total, across the four schools, there were 204 children. The study aimed to gain an understanding of the nature of the dialogues between staff and children, that is, the types of exchange that occurred when either the child approached an adult or the adult approached a child. The most frequent type of utterance was also analysed. The study concludes that adults in these settings spoke more than children and the greatest type of utterance was that of the adult about domestic matters. When the child initiated the conversation there were more extended child utterances than domestic utterances. This may suggest that children wish to be involved in conversations of depth and meaning and that staff need to become aware of how to develop this conversational language with children

Babies and toddlers outdoors: a narrative review of the literature on provision for under twos in ECEC settings

This paper reports the findings of a narrative review of international research literature about babies’ and toddlers’ engagement with the outdoor environment whilst attending ECEC (Early Childhood Education and Care) settings. Based on the in-depth review of 21 papers, it identifies four dominant themes in the literature: the outdoors as a space to be physically active, the outdoors as a risky space, the challenge of creating an appropriate outdoor environment and the significance of the practitioner outdoors. The article argues that there is a need to re-conceive the ways in which the youngest children engage with the outdoors and to move beyond possible narratives of exclusion