Introducing the discussion paper by Sz\'{e}kely and Rizzo

Introducing the discussion paper by Sz\'{e}kely and RizzoComment: Published in at http://dx.doi.org/10.1214/09-AOAS34INTRO the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Gamma-based clustering via ordered means with application to gene-expression analysis

Discrete mixture models provide a well-known basis for effective clustering algorithms, although technical challenges have limited their scope. In the context of gene-expression data analysis, a model is presented that mixes over a finite catalog of structures, each one representing equality and inequality constraints among latent expected values. Computations depend on the probability that independent gamma-distributed variables attain each of their possible orderings. Each ordering event is equivalent to an event in independent negative-binomial random variables, and this finding guides a dynamic-programming calculation. The structuring of mixture-model components according to constraints among latent means leads to strict concavity of the mixture log likelihood. In addition to its beneficial numerical properties, the clustering method shows promising results in an empirical study.Comment: Published in at http://dx.doi.org/10.1214/10-AOS805 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Magnetic cylindrical colloids at liquid interfaces exhibit non-volatile switching of their orientation in an external field

We study the orientation of magnetic cylindrical particles adsorbed at a liquid interface in an external field using analytical theory and high resolution finite element simulations. Cylindrical particles are interesting since they possess multiple locally stable orientations at the liquid interface so that the orientational transitions induced by an external field will not disappear when the external field is removed, i.e., the switching effect is \emph{non-volatile}. We show that, in the absence of an external field, as we reduce the aspect ratio $\alpha$ of the cylinders below a critical value ($\alpha_c \approx 2$) the particles undergo spontaneous symmetry breaking from a stable side-on state to one of two equivalent stable tilted states, similar to the spontaneous magnetisation of a ferromagnet going through the Curie point. By tuning both the aspect ratio and contact angle of the cylinders, we show that it is possible to engineer particles that have one, two, three or four locally stable orientations. We also find that the magnetic responses of cylinders with one or two stable states are similar to that of paramagnets and ferromagnets respectively, while the magnetic response of systems with three or four stable states are even more complex and have no analogs in simple magnetic systems. Magnetic cylinders at liquid interfaces therefore provide a facile method for creating switchable functional monolayers where we can use an external field to induce multiple non-volatile changes in particle orientation and self-assembled structure

Biodiversity and ecosystem services in the Frome catchment, Purbeck district, United Kingdom

A map for valuing ecosystem services in the 480 km2 Frome catchment, to investigate scenarios of change in land use, was internet crowd-sourced. Scouts mapped deer habitats in 15% of the 30 km2 Arne Parish, while 143 residents volunteered data on deer sightings in the 5-year community survey

Bird Population Changes Following the Establishment of a Diverse Stand of Woody Plants in a Former Crop Field in North Dakota, 1975– 2015

Changes in the coverage of trees and shrubs on the North Dakota landscape since Euro- American settlement have likely had a pronounced impact on bird species that favor woody vegetation. Long- term data sets on breeding bird populations in wooded habitats in North Dakota or in the Great Plains are scarce. In 1975 a wildlife habitat plot was established in a 10.5 ha cropland field with a long history of small- grain production. Th e objective of this article is to evaluate the successional changes in bird populations as the habitat at this site became more biologically and structurally complex aft er the establishment of a diverse stand of shrubs and trees. Between 1975 and 2015, 103 species or varieties of native and non- native trees, shrubs, or vines were planted in this wildlife habitat plot (hereaft er woodlot); 58.2% of those species were still present in 2016. Th e avian community in the woodlot increased in abundance and diversity as the woody vegetation increased in complexity and maturity, but the changes in abundance varied among ecological bird groups. Grassland bird abundance remained relatively constant but uncommon throughout the four decades aft er woody vegetation was first established. Bird species associated with shrublands and open woodlands and edges responded positively and showed the greatest increases in abundance during the 41- year period. Th e abundance of bird species associated with open areas with scattered trees or shrubs (i.e., savanna habitat) increased during the first half of the study but declined during the second half. Bird species associated with forest habitats were rare throughout the 41- year period, but their abundance increased during the most recent two decades. Results of this study are important for informing decisions about restoration efforts of riparian forests and other native wooded areas in the Great Plains and setting expectations for the time- scale required for the return of assemblages of species of woodland birds