HAPEE, a statistical approach for ionospheric scintillation prediction in the polar region

International audienceThrough several studies, CNES, ONERA, NSC and NMA have sought to define a prediction model for ionospheric variations that can disturb e.g. GNSS-based systems. The studies have focused on the high-latitude region, with a particular focus on the auroral oval. A first model was proposed in 2014. The model was a simple empirical model driven by the Kp geomagnetic index, and where the main output was the instantaneous mean Rate-of-TEC Index (ROTI) value. The model was found to not be sufficiently reliable to be used as an operational prediction model. In 2019, an updated model is proposed, where the main inputs are now the solar wind parameters pressure (the solar wind pressure p) and B z (the z component of the solar wind magnetic field). Moreover, a distribution of predicted ROTI or σ φ index is provided instead of a mean value. Thus, the model allows estimating the percentage of time of occurrence for a level of ROTI (or σ φ) to be exceeded in the next 5 minutes or 1 hour, or the exceeded ROTI (or σ φ) for a corresponding percentage of time. This empirical approach is based on 10 years of GNSS/scintillation data collected by more than 15 GNSS stations in Norway

A duct mapping method using least squares support vector machines

International audienceThis paper introduces a “refractivity from clutter” (RFC) approach with an inversion method based on a pregenerated database. The RFC method exploits the information contained in the radar sea clutter return to estimate the refractive index profile. Whereas initial efforts are based on algorithms giving a good accuracy involving high computational needs, the present method is based on a learning machine algorithm in order to obtain a real-time system. This paper shows the feasibility of a RFC technique based on the least squares support vector machine inversion method by comparing it to a genetic algorithm on simulated and noise-free data, at 1 and 5 GHz. These data are simulated in the presence of ideal trilinear surface-based ducts. The learning machine is based on a pregenerated database computed using Latin hypercube sampling to improve the efficiency of the learning. The results show that little accuracy is lost compared to a genetic algorithm approach. The computational time of a genetic algorithm is very high, whereas the learning machine approach is real time. The advantage of a real-time RFC system is that it could work on several azimuths in near real time

Caractérisation de films d'huile de la bande X à la bande K, expérimentation en bassin à vagues

This paper depicts an experiment conducted in a wind-wave pool in Brest, France, to characterize oil films when observed at moderate incidence from a X-to-K-band radar. Simultaneous measurements of surface elevation and radar backscattered field were carried out for various sea water surface states and incident angles. From this meaningful dataset (mainly lying in simultaneous acquisitions in X-, Ku-and K-band), an inversion method is proposed to characterize some properties of the oil film: its origin (mineral or biogenic) and its fractional coverage indicator. This process is based on the minimization of the cost function correlating the values given by a physical model of the wave damping ratio and the measured ones. The resulting oil parameters are found in overall good agreement with the three different released oils (two mineral and one biogenic) and it is observed that the fractional filling indicator of the oil slick decreases with increasing the roughness surface state whatever the considered oil.Ce papier décrit une expérimentation menée dans un bassin à vagues à Brest, France. L'objectif est de caractériser les films d'huile observés au moyen d'un système radar à des angles d'incidence modérée de la bande X à la bande K. Des mesures simultanées de l'élévation de la surface et du champ électromagnétique rétro-diffusé furent réalisées pour différents états de surface et divers angles d'incidence. A partir de cette base de données, une méthode d'inversion est proposée pour caractériser plusieurs propriétés du film d'huile: son origine (minérale ou biogénique) ainsi que sa fraction de couverture surfacique. Ce processus repose sur la minimisation d'une fonction coût liant la modélisation physique du coefficient d'atténuation des vagues avec la mesure. Les paramètres estimés sont en accord avec les trois huiles différentes déversées (deux minérales et une biogénique). Il est également observé que la fraction de couverture surfacique de la nappe d'huile décroît avec l'augmentation de la rugosité de surface et ce, quelle que soit l'huile considérée

Ionospheric scintillation models: An inter-comparison study using GNSS data

Existing climatological ionosphere models, for example, GISM, SCIONAV, WBMOD, and STIPEE, have known limitations that prevent their wide use. In the framework of ESA study “Radio Climatology Models of the Ionosphere: Status and Way Forward” their performance was assessed using experimental observations of ionospheric scintillation collected over the past years to evaluate their ability to properly support future missions, and eventually indicate their weaknesses for future improvements. Model limitations are more important in terms of the intensity scintillation parameter (S4). To improve them, the COSMIC model has been fit (scaling factor and offset) to the measured data, and it became the one better predicting the intensity scintillation in a statistical sense.This research was funded by the project “Radio Climatology Models of the Ionosphere: Status and Way Forward,” ESA/ESTEC, grant number 4000120868/17/NL/AF [https://nebula.esa.int/content/radio-climatology-models-ionosphere-status-and-way-forward]. Article processing charges were funded by the project “GENESIS: GNSS Environmental and Societal Missions – Subproject UPC,” AEI Grant PID2021-126436OB-C21.Peer ReviewedPostprint (published version

A Network Analysis Approach to fMRI Condition-Specific Functional Connectivity

In this work we focus on examination and comparison of whole-brain functional connectivity patterns measured with fMRI across experimental conditions. Direct examination and comparison of condition-specific matrices is challenging due to the large number of elements in a connectivity matrix. We present a framework that uses network analysis to describe condition-specific functional connectivity. Treating the brain as a complex system in terms of a network, we extract the most relevant connectivity information by partitioning each network into clusters representing functionally connected brain regions. Extracted clusters are used as features for predicting experimental condition in a new data set. The approach is illustrated on fMRI data examining functional connectivity patterns during processing of abstract and concrete concepts. Topological (brain regions) and functional (level of connectivity and information flow) systematic differences in the ROI-based functional networks were identified across participants for concrete and abstract concepts. These differences were sufficient for classification of previously unseen connectivity matrices as abstract or concrete based on training data derived from other people

Orbital effects of a monochromatic plane gravitational wave with ultra-low frequency incident on a gravitationally bound two-body system

We analytically compute the long-term orbital variations of a test particle orbiting a central body acted upon by an incident monochromatic plane gravitational wave. We assume that the characteristic size of the perturbed two-body system is much smaller than the wavelength of the wave. Moreover, we also suppose that the wave's frequency is much smaller than the particle's orbital one. We make neither a priori assumptions about the direction of the wavevector nor on the orbital geometry of the planet. We find that, while the semi-major axis is left unaffected, the eccentricity, the inclination, the longitude of the ascending node, the longitude of pericenter and the mean anomaly undergo non-vanishing long-term changes. They are not secular trends because of the slow modulation introduced by the tidal matrix coefficients and by the orbital elements themselves. They could be useful to indepenedently constrain the ultra-low frequency waves which may have been indirectly detected in the BICEP2 experiment. Our calculation holds, in general, for any gravitationally bound two-body system whose characteristic frequency is much larger than the frequency of the external wave. It is also valid for a generic perturbation of tidal type with constant coefficients over timescales of the order of the orbital period of the perturbed particle.Comment: LaTex2e, 24 pages, no figures, no tables. Changes suggested by the referees include

The Concise Guide to PHARMACOLOGY 2023/24:Introduction and Other Protein Targets

The Concise Guide to PHARMACOLOGY 2023/24 is the sixth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of approximately 1800 drug targets, and about 6000 interactions with about 3900 ligands. There is an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes almost 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.16176. In addition to this overview, in which are identified 'Other protein targets' which fall outside of the subsequent categorisation, there are six areas of focus: G protein-coupled receptors, ion channels, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2023, and supersedes data presented in the 2021/22, 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.</p

Energy Resolution Performance of the CMS Electromagnetic Calorimeter

The energy resolution performance of the CMS lead tungstate crystal electromagnetic calorimeter is presented. Measurements were made with an electron beam using a fully equipped supermodule of the calorimeter barrel. Results are given both for electrons incident on the centre of crystals and for electrons distributed uniformly over the calorimeter surface. The electron energy is reconstructed in matrices of 3 times 3 or 5 times 5 crystals centred on the crystal containing the maximum energy. Corrections for variations in the shower containment are applied in the case of uniform incidence. The resolution measured is consistent with the design goals

Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV

Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio