A new statistical test based on the wavelet cross-spectrum to detect time–frequency dependence between non-stationary signals: Application to the analysis of cortico-muscular interactions

The study of the correlations that may exist between neurophysiological signals is at the heart of modern techniques for data analysis in neuroscience. Wavelet coherence is a popular method to construct a time-frequency map that can be used to analyze the time-frequency correlations be- tween two time series. Coherence is a normalized measure of dependence, for which it is possible to construct confidence intervals, and that is commonly considered as being more interpretable than the wavelet cross-spectrum (WCS). In this paper, we provide empirical and theoretical arguments to show that a significant level of wavelet coherence does not necessarily correspond to a significant level of dependence between random signals, especially when the number of trials is small. In such cases, we demonstrate that the WCS is a much better measure of statistical dependence, and a new statistical test to detect significant values of the cross-spectrum is proposed. This test clearly outperforms the limitations of coherence analysis while still allowing a consistent estimation of the time-frequency correlations between two non-stationary stochastic processes. Simulated data are used to investigate the advantages of this new approach over coherence analysis. The method is also applied to experimental data sets to analyze the time-frequency correlations that may exist between electroencephalogram (EEG) and surface electromyogram (EMG)

Villerouge-Termenès – Le château

Date de l'opération : 1992 - 1997 (SD) Inventeur(s) : Maso David Le château de Villerouge-Termenès, classé comme monument historique depuis 1976, a été progressivement acquis par la commune afin d'être ouvert aux visiteurs dans le cadre d'un programme de développement local. Cette initiative a entraîné la mise en place d'un programme de réhabilitation en collaboration avec le service des Monuments historiques (Fig. n°1 : Vue du château). En 1986, une première intervention a été consacrée à l..

RiBaSE : a pilot for testing the OGC web services integration of water-related information and models

The design of an interoperability experiment to demonstrate how current ICT-based tools and water data can work in combination with geospatial web services is presented. This solution is being tested in three transboundary river basins: Scheldt, Maritsa and Severn. The purpose of this experiment is to assess the effectiveness of OGC standards for describing status and dynamics of surface water in river basins, to demonstrate their applicability and finally to increase awareness of emerging hydrological standards as WaterML 2.0. Also, this pilot will help in identifying potential gaps in OGC standards in water domain applications, applied to a flooding scenario in present work

Reconstruction of material losses by perimeter penalization and phase-field methods

We treat the inverse problem of determining material losses, such as cavities, in a conducting body, by performing electrostatic measurements at the boundary. We develop a numerical approach, based on variational methods, to reconstruct the unknown material loss by a single boundary measurement of current and voltage type. The method is based on the use of phase-field functions to model the material losses and on a perimeter-like penalization to regularize the otherwise ill-posed problem.We justify the proposed approach by a convergence result, as the error on the measurement goes to zero.Comment: 28 page

The behaviour of charged particles (ions) during new particle formation events in urban Leipzig, Germany

Air ions are electrically charged particles in air. They are ubiquitous in the natural environment and affect the Earth's radiation budget by accelerating the formation and growth of new aerosol particles. Despite this, few datasets exist exploring these effects in the urban environment. A neutral cluster and air ion spectrometer was deployed in Leipzig, Germany, to measure the number size distribution of charged particles from 0.8 to 42 nm, between 27 July and 25 August 2022. Following previous analyses, charged particles were classified into small (0.8-1.6 nm), intermediate (1.6-7.5 nm), and large (7.5-22 nm) fractions by mass diameter, and their mean concentrations (sum of positive and negative polarities) during the campaign were 405, 71.6, and 415 cm-3, respectively. The largest peaks in intermediate and large ions were explained by new particle formation (NPF), with intermediate ions correlating well with sulfuric acid dimer. Smaller morning and evening peaks were coincident with black carbon concentrations and attributed to primary emissions. NPF events, observed on 30 % of days, coincided with intense solar radiation and elevated sulfuric acid dimer. Small charged particles were primarily associated with radioactive decay and highest during the early hours, and they are unrelated to primary emissions or NPF. The apparent contributions of charged particles to 3 and 7.5 nm particle formation rates were 5.7 % and 12.7 %, respectively, with mean growth rates of 4.0 nm h-1 between 3-7.5 nm and 5.2 nm h-1 between 7.5 and 22 nm. The ratio of charged to total particle formation rates at 3 nm suggests a minor role for charged particles in NPF. We conclude that NPF is a primary source of &gt; 3 nm ions in our data, with primary emissions being the major source in the absence of NPF.</p

The behaviour of charged particles (ions) during new particle formation events in urban Leipzig, Germany

Air ions are electrically charged particles in air. They are ubiquitous in the natural environment and affect the Earth's radiation budget by accelerating the formation and growth of new aerosol particles. Despite this, few datasets exist exploring these effects in the urban environment. A neutral cluster and air ion spectrometer was deployed in Leipzig, Germany, to measure the number size distribution of charged particles from 0.8 to 42 nm, between 27 July and 25 August 2022. Following previous analyses, charged particles were classified into small (0.8-1.6 nm), intermediate (1.6-7.5 nm), and large (7.5-22 nm) fractions by mass diameter, and their mean concentrations (sum of positive and negative polarities) during the campaign were 405, 71.6, and 415 cm-3, respectively. The largest peaks in intermediate and large ions were explained by new particle formation (NPF), with intermediate ions correlating well with sulfuric acid dimer. Smaller morning and evening peaks were coincident with black carbon concentrations and attributed to primary emissions. NPF events, observed on 30 % of days, coincided with intense solar radiation and elevated sulfuric acid dimer. Small charged particles were primarily associated with radioactive decay and highest during the early hours, and they are unrelated to primary emissions or NPF. The apparent contributions of charged particles to 3 and 7.5 nm particle formation rates were 5.7 % and 12.7 %, respectively, with mean growth rates of 4.0 nm h-1 between 3-7.5 nm and 5.2 nm h-1 between 7.5 and 22 nm. The ratio of charged to total particle formation rates at 3 nm suggests a minor role for charged particles in NPF. We conclude that NPF is a primary source of &gt; 3 nm ions in our data, with primary emissions being the major source in the absence of NPF.</p

Road Traffic Emissions Lead to Much Enhanced New Particle Formation through Increased Growth Rates

New particle formation (NPF) is a major source of atmospheric aerosol particles, including cloud condensation nuclei (CCN), by number globally. Previous research has highlighted that NPF is less frequent but more intense at roadsides compared to urban background. Here, we closely examine NPF at both background and roadside sites in urban Central Europe. We show that the concentration of oxygenated organic molecules (OOMs) is greater at the roadside, and the condensation of OOMs along with sulfuric acid onto new particles is sufficient to explain the growth at both sites. We identify a hitherto unreported traffic-related OOM source contributing 29% and 16% to total OOMs at the roadside and background, respectively. Critically, this hitherto undiscovered OOM source is an essential component of urban NPF. Without their contribution to growth rates and the subsequent enhancements to particle survival, the number of &gt;50 nm particles produced by NPF would be reduced by a factor of 21 at the roadside site. Reductions to hydrocarbon emissions from road traffic may thereby reduce particle numbers and CCN counts.</p

Evaluating environmental risk assessment models for nanomaterials according to requirements along the product innovation Stage-Gate process

Nanomaterial risk governance requires models to estimate the material flow, fate and transport as well as uptake/bioavailability, hazard and risk in the environment. This study assesses the fit of such available models to different stages during the innovation of nano-enabled products. Through stakeholder consultations, criteria were identified for each innovation stage from idea conception to market launch and monitoring. In total, 38 models were scored against 41 criteria concerning model features, applicability, resource demands and outcome parameters. A scoring scheme was developed to determine how the models fit the criteria of each innovation stage. For each model, the individual criteria scores were added, yielding an overall fit score to each innovation stage. Three criteria were critical to stakeholders and incorporated as multipliers in the scoring scheme; the required time/costs and level of expertise needed to use the model, and for risk assessment models only, the option to compare PEC and PNEC. Regulatory compliance was also identified as critical, but could not be incorporated, as a nanomaterial risk assessment framework has yet to be developed and adopted by legislators. In conclusion, the scoring approach underlined similar scoring profiles across stages within model categories. As most models are research tools designed for use by experts, their score generally increased for later stages where most resources and expertise are committed. In contrast, stakeholders need relatively simple models to identify potential hazards and risk management measures at early product development stages to ensure safe use of nanomaterials without costs and resource needs hindering innovation