A comparison of plastic cable ties based on physical,chemical and stable isotopic measurements

Plastic cable ties can be utilised in a range of serious criminal activities and a comparison of cable ties, or fragments, may form part of the physical evidence presented to a Court of law. This research assessed the potential value of evidence based on the analysis of plastic cable ties. Twenty packets of black coloured plastic cable ties (nominally 200 mm × 4.8 mm) were purchased in pack sizes ranging from 25 to 100 individual cable ties (Brisbane, Australia, March 2015). Representative samples from each packet were visually examined, compared and tested to determine their physical dimensions, chemical compositions and stable isotopic compositions (δ²H, δ¹³C and δ¹⁵N).All of the individual cable ties from a given packet were found to be indistinguishable with respect to appearance, physical, chemical and isotopic measurements (within-batch variability). Individual cable ties were also found to be isotopically homogeneous with respect to hydrogen, carbon and nitrogen. All of the cable ties analysed were found to have very similar chemical compositions and to be manufactured predominantly from nylon 6,6. The elemental compositions of composite samples, prepared from each packet, were found to be highly variable and, as such, were of very limited value.Cable ties from ten of the twenty packets were uniquely characterised by physical appearance (between-batch variability). Physical measurements such as the width, thickness and tooth-count of the grip section did not provide additional discrimination. Cable ties from nineteen of the twenty packets were uniquely characterised by isotopic composition, based on δ²H and δ¹⁵N measurements. Samples from two packets of Crescent brand cable ties were found to be indistinguishable with respect to all of the tests applied in this study. These two packets were inadvertently purchased from the same retailer and had the same barcode and batch number. It was considered a reasonable assumption that these two packets originated from the same manufacturing batch.The authors reason that a likelihood ratio (that might be presented to a Court of law) can be derived from this type of discrete data based on a calculation of the possible combinations of distinguishable objects (unordered sampling with replacement) in a convenience sample collected from the background population. In this example, a database of 19 distinguishable objects can yield a likelihood ratio as high as 210, with a verbal equivalent of “moderately strong support” for a proposition that two cable ties have the same isotopic composition because they originate from the same batch rather than by random chance.     

Self-Regulation as Policy Process: The Multiple and Criss-Crossing Stages of Private Rule-Making

While there are many studies of self-regulation, they have not yet systematically analyzed the very process by which rules are developed and implemented. This article treats self-regulation as a process with sufficient autonomy and functional coherence to display identifiable stages, each of which deserves independent attention in turn. It draws from the literature on the stages of public policy processes and uses this as a template to identify and analyze the unique properties of private rule-making, while acknowledging the criticisms that have been made of excessive determinism and simplicity in some applications of the general idea of stages. The article shows that our understanding of self-regulation is significantly advanced by examining it as a process with stages but it emphasizes that the different stages of the self-regulatory policy process (agenda-setting, problem identification, decision, implementation and evaluation) are criss-crossed in numerous and interesting ways. It also shows that private rule-making often seeks to solve societal problems in domestic and international settings and is an important alternative to public regulation but self-regulation is rarely completely de-coupled from public authority. Instead, public authority is activated to solidify self-regulatory arrangements across the different stages of the policy process.     

On The Application of Fuzzy Clustering for Crime Hot Spot Detection

   One of the fundamental challenges in crime mapping and analysis is pattern recognition. Efforts and methods to detect crime hot-spots, or geographic areas of elevated criminal activity, are wide ranging. For aggregate data, such as total crime events in a census tract(s), measures of spatial autocorrelation have proven useful. For disaggregate data (i.e. individual crime events), kernel density smoothing and non-hierarchical cluster analysis (e.g. k-means), are widely used. Non-hierarchical techniques are particularly effective in delineating geographic space into areas of higher or lower crime concentrations, because each observation is assigned to one and only one cluster. The resulting set of partitions provides clear-cut spatial boundaries that can be used for hot-spot evaluation and interpretation. However, the strength of non-hierarchical methods can also be viewed as a weakness. Although the hard-clustering of observations into a set of discrete clusters is helpful, there are many cases where ambiguity exists in the data. In such cases, a more generalized approach for hot-spot detection would be helpful. The purpose of this paper is to explore the use of a generalized partitioning method known as fuzzy clustering for hot-spot detection. Functional and visual comparisons of fuzzy clustering and two hard-clustering approaches (medoid and k-means), across a range of cluster values are analyzed. The empirical results suggest that a fuzzy clustering approach is better equipped to handle intermediate cases and spatial outliers.

Small-scale irrigation in sub-Saharan Africa: Sparse lessons,big problems,any solutions?

This paper identifies from studies made of specific schemes the major social and administrative problems confronting the improvement and extension of small-scale irrigation in Africa. The first section reviews the studies and notes the conclusions to be drawn from each separate one. Underlying these separate conclusions six general problems are identified and in the second section of the article each of these six is elaborated and discussed: the relation between the direct producer'S benefit and wider social benefits: problems of control, commitment to hierarchy, the working of production units, and how to learn from farmers in respect of water use; and finally the general problem of how to plan for the further change that follows after irrigation is introduced.