Graph kernels between point clouds

Point clouds are sets of points in two or three dimensions. Most kernel methods for learning on sets of points have not yet dealt with the specific geometrical invariances and practical constraints associated with point clouds in computer vision and graphics. In this paper, we present extensions of graph kernels for point clouds, which allow to use kernel methods for such ob jects as shapes, line drawings, or any three-dimensional point clouds. In order to design rich and numerically efficient kernels with as few free parameters as possible, we use kernels between covariance matrices and their factorizations on graphical models. We derive polynomial time dynamic programming recursions and present applications to recognition of handwritten digits and Chinese characters from few training examples

Poverty Lines as Context Deflators in the DRC. A methodology to account for contextual differences

In this paper we present a specific methodology to make spatial well-being and poverty assessments based on expenditure data to some extent sensitive to contextual aspects other than price differentials. The rationale behind this method coincides with the view expressed by the advocates of human development pointing to the irrelevance of (real) income levels for well-being measurement compared to an analysis of people?s ability to deploy this purchasing power in a very specific time and setting. Yet, in order to operationalize this principle, we opted to employ the ordinary technique of deflating nominal incomes, but in such a way that genuine comparability over different geographical entities comes within reach. Of course, the extent to which our methodology is able to achieve this goal, largely depend on the exact content and construction of the underlying deflators used. Given our research agenda to analyze the distribution of poverty and well-being in the Democratic Republic of Congo (DRC), we decided to construct 56 regional poverty lines whose pair wise ratios in turn were used as a set of context deflators. The challenge of this exercise essentially boiled down to reconciling the two seemingly discordant –but highly appreciated– poverty line characteristics of „specificity? and „consistency?: i.e. how to give due attention to the myriad of local living conditions while still ensuring sufficient comparability. Although this theoretical discordance has been settled some time ago, methodological problems to align both features still remain cumbersome in practice. Therefore, the main contribution of this paper needs to be understood in addressing these methodological issues within the framework of a household and expenditure survey. As a natural starting point to deal with these issues, we screened the validity of the major criticisms raised against the Food Energy Intake (FEI) method. Indeed, this context-sensitive methodology for setting poverty lines is often condemned for generating inconsistent results, but –after closer scrutiny– not for every reason put forward in the literature. On the basis of these insights, we started to mould our own specific poverty line methodology in which we tried to accommodate the remaining pieces of critique. This resulted in a three-step FEI-like procedure where the anchoring device to ensure consistency between all 56 localities, was built upon the basic human functionings of being adequately nourished and sheltered. Finally, we applied this procedure to our data in order to discern the impact of our own methodology vis-à-vis other internally and externally computed approaches.

Estimating the Economic Impact of Acas Services

The main focus of this report is on the economic value of a year of Acas services delivered during the 2014/15 operational year. The starting point for the analysis in this report is the prior review of the economic impact of Acas in 2007 (Meadows), which is based on Acas activities delivered in 2005/06. This has been updated in line with key principles of cost-benefit analysis and tackles a number of issues flagged in subsequent reviews with a particular focus on questions of the counterfactual, impacts beyond the first year of Acas intervention, and of displacement and substitution. In addition, new estimates have been provided in service areas that were not included in the 2007 study as well as in new areas of Acas activity, such as new digital channels of service delivery. Whereas previous economic impact analyses were estimated to account for around 70 per cent of Acas service delivery, this report considers approximately 90 per cent of Acas activitie

Estimating the Economic Impact of Acas Services

The main focus of this report is on the economic value of a year of Acas services delivered during the 2014/15 operational year. The starting point for the analysis in this report is the prior review of the economic impact of Acas in 2007 (Meadows), which is based on Acas activities delivered in 2005/06. This has been updated in line with key principles of cost-benefit analysis and tackles a number of issues flagged in subsequent reviews with a particular focus on questions of the counterfactual, impacts beyond the first year of Acas intervention, and of displacement and substitution. In addition, new estimates have been provided in service areas that were not included in the 2007 study as well as in new areas of Acas activity, such as new digital channels of service delivery. Whereas previous economic impact analyses were estimated to account for around 70 per cent of Acas service delivery, this report considers approximately 90 per cent of Acas activitie

Part-to-whole Registration of Histology and MRI using Shape Elements

Image registration between histology and magnetic resonance imaging (MRI) is a challenging task due to differences in structural content and contrast. Too thick and wide specimens cannot be processed all at once and must be cut into smaller pieces. This dramatically increases the complexity of the problem, since each piece should be individually and manually pre-aligned. To the best of our knowledge, no automatic method can reliably locate such piece of tissue within its respective whole in the MRI slice, and align it without any prior information. We propose here a novel automatic approach to the joint problem of multimodal registration between histology and MRI, when only a fraction of tissue is available from histology. The approach relies on the representation of images using their level lines so as to reach contrast invariance. Shape elements obtained via the extraction of bitangents are encoded in a projective-invariant manner, which permits the identification of common pieces of curves between two images. We evaluated the approach on human brain histology and compared resulting alignments against manually annotated ground truths. Considering the complexity of the brain folding patterns, preliminary results are promising and suggest the use of characteristic and meaningful shape elements for improved robustness and efficiency.Comment: Paper accepted at ICCV Workshop (Bio-Image Computing

Feature Lines for Illustrating Medical Surface Models: Mathematical Background and Survey

This paper provides a tutorial and survey for a specific kind of illustrative visualization technique: feature lines. We examine different feature line methods. For this, we provide the differential geometry behind these concepts and adapt this mathematical field to the discrete differential geometry. All discrete differential geometry terms are explained for triangulated surface meshes. These utilities serve as basis for the feature line methods. We provide the reader with all knowledge to re-implement every feature line method. Furthermore, we summarize the methods and suggest a guideline for which kind of surface which feature line algorithm is best suited. Our work is motivated by, but not restricted to, medical and biological surface models.Comment: 33 page

Critical Casimir effect in classical binary liquid mixtures

If a fluctuating medium is confined, the ensuing perturbation of its fluctuation spectrum generates Casimir-like effective forces acting on its confining surfaces. Near a continuous phase transition of such a medium the corresponding order parameter fluctuations occur on all length scales and therefore close to the critical point this effect acquires a universal character, i.e., to a large extent it is independent of the microscopic details of the actual system. Accordingly it can be calculated theoretically by studying suitable representative model systems. We report on the direct measurement of critical Casimir forces by total internal reflection microscopy (TIRM), with femto-Newton resolution. The corresponding potentials are determined for individual colloidal particles floating above a substrate under the action of the critical thermal noise in the solvent medium, constituted by a binary liquid mixture of water and 2,6-lutidine near its lower consolute point. Depending on the relative adsorption preferences of the colloid and substrate surfaces with respect to the two components of the binary liquid mixture, we observe that, upon approaching the critical point of the solvent, attractive or repulsive forces emerge and supersede those prevailing away from it. Based on the knowledge of the critical Casimir forces acting in film geometries within the Ising universality class and with equal or opposing boundary conditions, we provide the corresponding theoretical predictions for the sphere-planar wall geometry of the experiment. The experimental data for the effective potential can be interpreted consistently in terms of these predictions and a remarkable quantitative agreement is observed.Comment: 30 pages, 17 figure