Merging KK-means with hierarchical clustering for identifying general-shaped groups

Clustering partitions a dataset such that observations placed together in a group are similar but different from those in other groups. Hierarchical and $K$-means clustering are two approaches but have different strengths and weaknesses. For instance, hierarchical clustering identifies groups in a tree-like structure but suffers from computational complexity in large datasets while $K$-means clustering is efficient but designed to identify homogeneous spherically-shaped clusters. We present a hybrid non-parametric clustering approach that amalgamates the two methods to identify general-shaped clusters and that can be applied to larger datasets. Specifically, we first partition the dataset into spherical groups using $K$-means. We next merge these groups using hierarchical methods with a data-driven distance measure as a stopping criterion. Our proposal has the potential to reveal groups with general shapes and structure in a dataset. We demonstrate good performance on several simulated and real datasets.Comment: 16 pages, 1 table, 9 figures; accepted for publication in Sta

The role of heavy fermions

Heavy dynamical fermions with masses around the cut-off do not change the low energy physics apart from a finite renormalization of the gauge coupling. In this paper we study how light the heavy fermions have to be to cause more than this trivial renormalization.Comment: uuencoded 3 page postscript contribution to Lattice 93, COLO-HEP-33

Cost Sharing for Biodiversity Conservation: A Conceptual Framework

„h Many resource users undertake actions that conserve biodiversity. If, however, there were public demand for more conservation than would be provided voluntarily by the private sector alone, there are two broad principles for determining who should bear the costs ¡X ¡¥impacter pays¡¦ or ¡¥beneficiary pays¡¦. The two principles have different efficiency and distributional effects. „h A fundamental step in determining which cost sharing principle to apply is the clarification of the rights and responsibilities implied by existing property rights. This is an important issue that requires further work. „h If property rights effectively require resource users to meet an environmental standard, resource users who fail to achieve this may be considered to generate external costs. In these circumstances, on efficiency grounds, the impacter pays principle should generally be adopted to internalise external costs. This effectively amounts to enforcement of an individual¡¦s existing legal responsibilities. However, if the costs of implementing the impacter pays principle were to outweigh its efficiency advantages, the beneficiary pays principle may be considered.environment, conservation, biodiversity

Vikings across the Atlantic: Emigration and the Building of a Greater Norway, 1860-1945

Review of: "Vikings across the Atlantic: Emigration and the Building of a Greater Norway, 1860-1945," by Anna M. Peterson

Scandinavians in the State House: How Nordic Immigrants Shaped Minnesota Politics

Review of: "Scandinavians in the State House: How Nordic Immigrants Shaped Minnesota Politics" by Klas Bergma

Rodent assemblages and rodent associated pathogens in a counter-urbanizing landscape

Human population declines in urban centers (also known as counter-urbanization) can result in increased levels of vacancy and infrastructure loss, though relatively little is known regarding the ecological outcomes of this type of landscape change. The abundance and diversity of pest and zoonotic pathogen hosts are predicted to increase in counter-urbanizing environments, giving rise to a novel human-animal interface. Furthermore, the human-animal interface is a key location for zoonotic pathogen emergence, thus, understanding how host communities shift in regard to counter-urbanization can lend insight into risk of zoonotic pathogens in these areas.In this dissertation, I investigate the abundance and diversity of rodent hosts across a counter-urbanizing environment in the city of New Orleans, Louisiana, USA to understand how features of the urban environment shape rodent assemblages and the risk of zoonotic pathogens. I demonstrate that rodent abundance and diversity increase in areas with higher levels of vacancy, and that increased rodent abundance and diversity also translate to increased risk from some zoonotic pathogens. However, this work also indicates that not all zoonotic pathogens show similar patterns across the landscape. In this work I provide practical insight into specific environmental and sociological risk factors associated with rodent abundance and zoonotic pathogens, while also leveraging the gradient of rodent abundance and diversity present in the counter-urbanizing environment of New Orleans to test predictions regarding relationships between host diversity, host abundance, pathogen prevalence, and diversity