Actigraphy-based sleep estimation in adolescents and adults: a comparison with polysomnography using two scoring algorithms

Objectives: Actigraphy is widely used to estimate sleep–wake time, despite limited information regarding the comparability of different devices and algorithms. We compared estimates of sleep–wake times determined by two wrist actigraphs (GT3X+ versus Actiwatch Spectrum [AWS]) to in-home polysomnography (PSG), using two algorithms (Sadeh and Cole–Kripke) for the GT3X+ recordings. Subjects and methods Participants included a sample of 35 healthy volunteers (13 school children and 22 adults, 46% male) from Boston, MA, USA. Twenty-two adults wore the GT3X+ and AWS simultaneously for at least five consecutive days and nights. In addition, actigraphy and PSG were concurrently measured in 12 of these adults and another 13 children over a single night. We used intraclass correlation coefficients (ICCs), epoch-by-epoch comparisons, paired t-tests, and Bland–Altman plots to determine the level of agreement between actigraphy and PSG, and differences between devices and algorithms. Results: Each actigraph showed comparable accuracy (0.81–0.86) for sleep–wake estimation compared to PSG. When analyzing data from the GT3X+, the Cole–Kripke algorithm was more sensitive (0.88–0.96) to detect sleep, but less specific (0.35–0.64) to detect wake than the Sadeh algorithm (sensitivity: 0.82–0.91, specificity: 0.47–0.68). Total sleep time measured using the GT3X+ with both algorithms was similar to that obtained by PSG (ICC=0.64–0.88). In contrast, agreement between the GT3X+ and PSG wake after sleep onset was poor (ICC=0.00–0.10). In adults, the GT3X+ using the Cole–Kripke algorithm provided data comparable to the AWS (mean bias=3.7±19.7 minutes for total sleep time and 8.0±14.2 minutes for wake after sleep onset). Conclusion: The two actigraphs provided comparable and accurate data compared to PSG, although both poorly identified wake episodes (i.e., had low specificity). Use of actigraphy scoring algorithm influenced the mean bias and level of agreement in sleep–wake times estimates. The GT3X+, when analyzed by the Cole–Kripke, but not the Sadeh algorithm, provided comparable data to the AWS

A virtual chemical mechanism for prediction of NO emissions from flames

A reduced order kinetic model for NO (nitric oxide) prediction, based on the virtual chemistry methodology [M. Cailler, N. Darabiha, and B. Fiorina, Development of a virtual optimized chemistry method. Application to hydrocarbon/air combustion, Combust. Flame 211 (2020), pp. 281–302], is developed and applied. Virtual chemistry aims to optimise thermochemical properties and kinetic rate parameters of a network of virtual species and reactions. A virtual main chemical mechanism is dedicated to temperature and heat release prediction and is coupled with the flow governing equations, whereas satellite sub-mechanisms are designed to predict pollutants formation. Two virtual chemistry mechanisms are here employed: a main mechanism for calculating the temperature and heat release rate and a second mechanism dedicated to NO prediction. To recover the chemical structure of multi-mode combustion, both premixed and non-premixed flamelets are included in the learning database used to optimise the virtual NO mechanism. A multi-zone optimisation procedure is developed to accurately capture both fast and slow NO chemistry that include prompt, thermal and reburning pathways. The proposed NO sub-mechanism and optimisation methodology are applied to CH (Formula presented.) /air combustion. Laminar 1-D premixed and non-premixed flamelet configurations are first tested. The approach is then further assessed in 2-D CFD laminar flame simulations, by providing a direct comparison against detailed chemistry. 2-D premixed, non-premixed and partially premixed flame configurations are numerically investigated. For all cases, the virtual mechanism fairly captures temperature and (Formula presented.) chemistry with only 12 virtual species and 8 virtual reactions with a drastic CPU time reduction compared to detailed chemistry

Quelques aspects théoriques de l'émission électronique secondaire du cuivre, produite par bombardement d'électrons de faible énergie

Secondary electron emission from thick metallic targets in a polycristalline state is studied from a theoretical point of view as they are bombarded by an electron beam of 200 eV energy. This analysis treats separately the processes of creation, transport and metal-vacuum interface crossing by excited electrons. Copper has been chosen as a check for our various assumptions. The source term makes use of a dielectric function given by optical measurements. A first treatment takes account of the different processes through a Boltzmann equation. When the maximum depth of penetration of primary electrons can no longer be considered as large as the excited electron mean free path, the former method may be doubtful. In such a case, by using a Monte Carlo simulation method, one can partially get rid of these difficulties. Results obtained by both methods are very similar. Thus one is allowed to think that a Boltzmann equation can give valuable information even beyond the domain of its validity. Agreement with experimental data is generally good. Influence of various parameters is studied in view of a more quantitative fitting.L'émission électronique secondaire de cibles métalliques polycristallines épaisses par bombardement électronique, est étudiée du point de vue théorique pour une énergie du faisceau primaire de 200 eV. Cette analyse distingue les processus de création, de transport et de franchissement de l'interface métal-vide par les électrons excités. Le cuivre a été choisi pour tester les différentes hypothèses. Le terme source utilise une fonction diélectrique issue de mesures optiques. Un premier traitement rend compte des divers processus au travers de l'équation de Boltzmann. Lorsque la profondeur maximale de pénétration des électrons primaires ne peut plus être considérée comme grande vis-à-vis du libre parcours moyen des électrons excités, la méthode précédente peut être contestable. Dans ces conditions, l'utilisation d'une méthode de simulation de Monte Carlo permet de s'affranchir partiellement de ces difficultés. Les résultats obtenus par les deux méthodes sont très voisins. Il est ainsi permis de penser que l'utilisation de l'équation de Boltzmann peut donner des indications appréciables même en dehors de son strict domaine de validité. L'accord avec l'expérience est bon en général. On étudie l'influence de divers paramètres en vue d'un ajustement plus quantitatif

Interaction individuelle d'un électron incident et d'un électron de conduction lors du bombardement électronique d'un métal

In order to determine the contribution of weakly bound electrons to the secondary electron emission yield induced by electron bombardment, we apply the OPW method for calculating the transition probability of Bloch electrons to excited states leading to electron emission.En vue de déterminer la contribution des électrons faiblement liés au rendement de l'émission électronique secondaire induite par bombardement électronique, on applique la méthode d'approximation OPW au calcul de la probabilité de transition des électrons de Bloch vers des états excités pouvant conduire à leur émission

Traitement unifié de l'émission électronique secondaire du cuivre par une méthode de Monte Carlo

The present theory of secondary electron emission intends to be a unified treatment both for penetration and back-scattering processes of primary electrons and for production and transport of secondary electrons excited inside a metal. It makes use of a Monte Carlo method. In the case of copper concerning low primary energies, it takes into account the energy distribution of emitted secondary electrons in a satisfactory way. Comparison with experiment is however somewhat difficult on account of disagreements with existing measurements. Selected angular models for a description of elastic and inelastic collisions and use of data related to characteristic energy losses allow us to obtain some very realistic values of secondary yields. We also study how the energy dissipation takes place inside the metal with respect to primary beam energy.La présente théorie de l'émission électronique secondaire se veut un traitement unifié tant des processus de pénétration et de rétrodiffusion des électrons primaires que de création et de transport des électrons secondaires excités dans un métal. Elle utilise pour cela une méthode de Monte Carlo. Appliquée au cuivre et concernant les faibles énergies primaires, elle rend compte de façon satisfaisante de la distribution énergétique des électrons secondaires émis. La comparaison avec l'expérience est cependant quelque peu malaisée compte tenu des désaccords entre les mesures existantes. Les modèles angulaires retenus pour décrire les collisions élastiques et inélastiques et l'utilisation de données relatives aux pertes d'énergies caractéristiques permettent d'atteindre des valeurs très raisonnables des rendements secondaires. On étudie par ailleurs comment s'effectue la dissipation d'énergie à l'intérieur du métal en fonction de l'énergie du faisceau primaire

Spurious effects of electron emission from the grids of a retarding field analyser on secondary electron emission measurements. results on a (111) copper single crystal

Spurious effects of a four grid retarding field analyser were studied for low energy secondary electron measurements. Their behaviour was investigated and two peaks in the energy spectrum were interpreted as resulting from tertiary electrons from the grids. It was shown that the true secondary electron peak has to be separated from these spurious peaks. The spectrum and the yields σ and η obtained for a Cu (111) crystal after a surface cleanness control by Auger spectroscopy are given