Confidence bands for Horvitz-Thompson estimators using sampled noisy functional data

When collections of functional data are too large to be exhaustively observed, survey sampling techniques provide an effective way to estimate global quantities such as the population mean function. Assuming functional data are collected from a finite population according to a probabilistic sampling scheme, with the measurements being discrete in time and noisy, we propose to first smooth the sampled trajectories with local polynomials and then estimate the mean function with a Horvitz-Thompson estimator. Under mild conditions on the population size, observation times, regularity of the trajectories, sampling scheme, and smoothing bandwidth, we prove a Central Limit theorem in the space of continuous functions. We also establish the uniform consistency of a covariance function estimator and apply the former results to build confidence bands for the mean function. The bands attain nominal coverage and are obtained through Gaussian process simulations conditional on the estimated covariance function. To select the bandwidth, we propose a cross-validation method that accounts for the sampling weights. A simulation study assesses the performance of our approach and highlights the influence of the sampling scheme and bandwidth choice.Comment: Published in at http://dx.doi.org/10.3150/12-BEJ443 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

Local Social Capital and Geographical Mobility: Some Empirics and a Conjecture on the Nature of European Unemployment

European labor markets are characterized by the low geographical mobility of workers. The absence of mobility is a factor behind high unemployment when jobless people prefer to remain in their home region rather than to go prospecting in more dynamic areas. In this paper, we attempt to understand the determinants of mobility by introducing the concept of local social capital. Using data from a European household panel (ECHP), we provide various measures of social capital, which appears to be a strong factor of immobility. It is also a fairly large factor of unemployment when social capital is clearly local, while other types of social capital are found to have a positive effect on employability. We also find evidence of the reciprocal causality, that is, individuals born in another region have accumulated less local social capital. Finally, observing that individuals in the South of Europe appear to accumulate more local social capital, while in Northern Europe they tend to invest in more general types of social capital, we argue that part of the European unemployment puzzle can be better understood thanks to the concept of local social capital.European unemployment, geographical mobility, social capital

Asynchronous Variational Contact Mechanics

An asynchronous, variational method for simulating elastica in complex contact and impact scenarios is developed. Asynchronous Variational Integrators (AVIs) are extended to handle contact forces by associating different time steps to forces instead of to spatial elements. By discretizing a barrier potential by an infinite sum of nested quadratic potentials, these extended AVIs are used to resolve contact while obeying momentum- and energy-conservation laws. A series of two- and three-dimensional examples illustrate the robustness and good energy behavior of the method

Local social capital and geographical mobility .

In the North of Europe, club membership is higher than in the South, but the frequency of contacts with friends, relatives and neighbors is lower. We link this fact to another one: the low geographical mobility rates in the South of Europe relative to the North. To interpret these facts, we build a model of local social capital and mobility. Investing in local ties is rational when workers do not expect to move to another region. We find that observationally close individuals may take different paths characterized by high local social capital, low mobility and high unemployment, vs. low social capital, high propensity to move and higher employment probability. Employment protection reinforces the accumulation of local social capital and thus reduces mobility. European data supports the theory: within a country and at the individual level, more social capital is associated with lower mobility.

Relation between obesity and the oestrogen receptor status of breast cancer

Introduction: Obesity is a growing problem in the Western world. Correlations have been found between increasing body mass index (BMI) and breast cancer. The objectives were to establish whether a relationship exists between BMI and breast cancer and to investigate any association between BMI and tumour oestrogen receptor expression. Method: Clinical and socio-demographic details (age, menopausal status, height and weight) of a sample of women with breast cancer operated in 2010 were collected, dividing the group into oestrogen receptor positive (ER+) and negative (ER–) subgroups. The average BMI of each subgroup was compared to the mean BMI of a sample of the general Maltese female population obtained from the European Health Examination Survey 2010 Report (Pilot Study) by virtue of an ANOVA test. Subsequently, the relations between oestrogen receptor expression and each of menopausal status, age and BMI were statistically analysed using chi-squared analysis and two-sample t-tests. Results: A total of 103 patients were studied. 72 patients (age range: 40 – 90 years) had ER+ malignancy and 31 patients (29 – 81 years) had ER- malignancy. The mean BMI’s of the ER+ and ER- subgroups were 30.1 and 27.1 respectively, while that of the female general population (29 – 90 years) was 28.4. Analysis revealed a significant difference between the BMI’s of the ER+ and ER- subgroups (p<0.05) but no difference between each receptor subgroup and the general population. Neither menopausal status nor age was found to correlate with positive oestrogen receptor expression. Conclusions: Women with ER+ malignancy tended to be significantly more obese than those with ER- breast cancer. However, neither subgroup had a mean BMI significantly different from that of the general population.peer-reviewe

A new algorithm for point spread function subtraction in high-contrast imaging: a demonstration with angular differential imaging

Direct imaging of exoplanets is limited by bright quasi-static speckles in the point spread function (PSF) of the central star. This limitation can be reduced by subtraction of reference PSF images. We have developed an algorithm to construct an optimized reference PSF image from a set of reference images. This image is built as a linear combination of the reference images available and the coefficients of the combination are optimized inside multiple subsections of the image independently to minimize the residual noise within each subsection. The algorithm developed can be used with many high-contrast imaging observing strategies relying on PSF subtraction, such as angular differential imaging (ADI), roll subtraction, spectral differential imaging, reference star observations, etc. The performance of the algorithm is demonstrated for ADI data. It is shown that for this type of data the new algorithm provides a gain in sensitivity by up to a factor 3 at small separation over the algorithm used in Marois et al. (2006).Comment: 7 pages, 11 figures, to appear in May 10, 2007 issue of Ap

Identifying research priorities for the competitiveness of arable crops

EU agriculture and arable crops in particular are suffering from competitiveness deficits compared to other producers in the world economy. One potential strategy to cope with competitiveness challenges is to focus on research and technological innovation. The objective of this paper is to present the results of the project EUROCROP (Agricultural research for improving arable crop competitiveness – EUROCROP - http://www.eurocrop.cetiom.fr/), aimed at the identification of research priorities for arable crop competitiveness. The project adopts a definition of competitiveness based on a combination of economic competitiveness and social/environmental sustainability. Furthermore, the project utilises both a crop chain and a horizontal issue perspective, and develops research priorities through the interaction of the scientific level (expert group approach) and the stakeholder level (scenario analysis). The main result of the project is the elaboration of approximately eighty research topics. Among these, the main areas for research identified are A: Risk management and adaptation of arable farming; B: Innovation in cropping systems for high environmental and economic performances; C: Limiting the impact of arable crop cropping systems on green-house gas emissions; D: Better understanding of public concern about arable crop production and products and communication with global and local societies. The project confirms that a number of well established research topics retain their importance (e.g. yield improvement, plant protection). However, they require cautious coordination with an increasingly complex system of short term priorities.Arable crops, crop chain, competitiveness, research priorities, foresight, Agricultural and Food Policy,