A decision-theoretic approach for segmental classification

This paper is concerned with statistical methods for the segmental classification of linear sequence data where the task is to segment and classify the data according to an underlying hidden discrete state sequence. Such analysis is commonplace in the empirical sciences including genomics, finance and speech processing. In particular, we are interested in answering the following question: given data $y$ and a statistical model $\pi(x,y)$ of the hidden states $x$, what should we report as the prediction $\hat{x}$ under the posterior distribution $\pi (x|y)$? That is, how should you make a prediction of the underlying states? We demonstrate that traditional approaches such as reporting the most probable state sequence or most probable set of marginal predictions can give undesirable classification artefacts and offer limited control over the properties of the prediction. We propose a decision theoretic approach using a novel class of Markov loss functions and report $\hat{x}$ via the principle of minimum expected loss (maximum expected utility). We demonstrate that the sequence of minimum expected loss under the Markov loss function can be enumerated exactly using dynamic programming methods and that it offers flexibility and performance improvements over existing techniques. The result is generic and applicable to any probabilistic model on a sequence, such as Hidden Markov models, change point or product partition models.Comment: Published in at http://dx.doi.org/10.1214/13-AOAS657 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

How changes in the former CMEA area may affect international trade in manufactures

The authors give a long-term perspective on how changes in the former CMEA areas will affect international trade in manufactures. They show that expanding Eastern European exports to the West should be viewed as a step toward normalizing the Eastern European countries'trade patterns. First, proportionally less of the Eastern European economies'trade will be with each other, especially with the former Soviet Union. Second, Western Europe will be their major trading partner but their trade with (especially imports from) Japan and North America may increase dramatically (from a small base). Their exports to and imports from developing countries may also change dramatically. The volume of Eastern European trade is in line with the low income of these economies. In the long run manufactures trade will increase four- to sixfold, once Eastern European income levels catch up with industrial country levels. Until incomes in Eastern European and former Soviet economies increase significantly, labor-intensive goods are likely to dominate their exports to market economies, and sophisticated goods their imports. The authors contend that, since the end of the Cold War, the West has successfully improved the Eastern European countries'access to Western trade, and that the Eastern European countries should now enjoy equal or favorable treatment. Czechoslovakia, Hungary, and Poland, in particular, may become the most favored outsiders in the European Economic Space, the largest single market in the world. One short-term effect of the Eastern European countries'improved outlook may be that developing countries that rely on manufactures for export revenues may have tougher times in major Western markets. But the emancipation of Eastern European and former Soviet economies - and the pent-up demand for consumer goods likely from deprived populations - should provide important opportunities for the dynamic developing countries. The former Soviet Union was not a large market for developing countries - except for India and Yugoslavia and to a lesser extent Algeria and Egypt. Countries such as India that did supply the former Soviet Union with manufactures may soon have to seek alternative markets.Economic Theory&Research,Environmental Economics&Policies,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Trade Policy,Transport and Trade Logistics

The restrictiveness of the multi-fibre arrangement on Eastern European trade

Historically, Eastern Europe has not been favorably treated in terms of quota growth in the European Community and U.S. markets - often quite the contrary. But the EC and U.S. treatment of these countries has already changed since their reform and can be expected to become even more favorable. Eastern Europe's exports of textiles and clothing have tended to be more capital-intensive and less specialized than those of other major suppliers, including Asia's newly industrialized economies. Erzan and Holmes argue that Eastern Europe's expansion of relatively labor-intensive products has probably been inhibited byquotas and by the weak adjustment mechanisms inherent in a centrally planned economic system. If so, given market reforms in Eastern Europe, exports of labor-intensive textiles and clothing should expand more than proportionately and the degree of specialization should increase if the Multi-Fibre Arrangement is abolished or its grip on Eastern Europe's exports is relaxed in the EC. Putting aside questions of the composition of exports, textile and clothing exports are to expand considerably because they make up a large part of labor-intensive manufacturers, where Eastern Europe's comparative advantage lies in the near future.Markets and Market Access,Economic Theory&Research,Environmental Economics&Policies,Economic Adjustment and Lending,Access to Markets

Dirichlet multinomial mixtures: generative models for microbial metagenomics

We introduce Dirichlet multinomial mixtures (DMM) for the probabilistic modelling of microbial metagenomics data. This data can be represented as a frequency matrix giving the number of times each taxa is observed in each sample. The samples have different size, and the matrix is sparse, as communities are diverse and skewed to rare taxa. Most methods used previously to classify or cluster samples have ignored these features. We describe each community by a vector of taxa probabilities. These vectors are generated from one of a finite number of Dirichlet mixture components each with different hyperparameters. Observed samples are generated through multinomial sampling. The mixture components cluster communities into distinct ‘metacommunities’, and, hence, determine envirotypes or enterotypes, groups of communities with a similar composition. The model can also deduce the impact of a treatment and be used for classification. We wrote software for the fitting of DMM models using the ‘evidence framework’ (http://code.google.com/p/microbedmm/). This includes the Laplace approximation of the model evidence. We applied the DMM model to human gut microbe genera frequencies from Obese and Lean twins. From the model evidence four clusters fit this data best. Two clusters were dominated by Bacteroides and were homogenous; two had a more variable community composition. We could not find a significant impact of body mass on community structure. However, Obese twins were more likely to derive from the high variance clusters. We propose that obesity is not associated with a distinct microbiota but increases the chance that an individual derives from a disturbed enterotype. This is an example of the ‘Anna Karenina principle (AKP)’ applied to microbial communities: disturbed states having many more configurations than undisturbed. We verify this by showing that in a study of inflammatory bowel disease (IBD) phenotypes, ileal Crohn's disease (ICD) is associated with a more variable community

Planar micromachined glass cantilevers utilising integrated Bragg Fabry-Perot cavities

Here we demonstrate a glass cantilever based on a unique micromachining and etching approach, combined with UV written Bragg gratings. We shall also discuss the increase in sensitivity by using two Bragg gratings to form Fabry-Pérot cavity. Cantilevers are in ultra sensitive force sensors used in applications such as Atomic Force Microscopy, mass sensing and acoustic transducers

Lateral groove geometry for planar UV written evanescent devices - new flexibility new devices

Conventional evanescent optical devices have made use of etched windows to allow access of an optical field to a material of interest. Such devices are a route to accurate refractive index sensors and to realising modulators, however, the geometry of etching the cladding to give the fluid access to a pre-defined core waveguide mode is limiting. In this work, we present an alternative approach in which a groove is cut using a polishing saw blade to give a vertical, high optical quality trench. Optical waveguides are then UV written to allow evanescent lateral access of the mode to a fluid placed in the trench. This seemingly subtle change in geometry provides greatly increased flexibility to tailor the interaction between the optical mode and the surrounding material, by, for example, changing the mode size and the allowing couplers or tapers to be used