Semaine d'Etude Mathématiques et Entreprises 5 : Sélection de variables statistiquement représentatives pour la production électrique photovoltaïque

La production électrique des panneaux photovoltaïques dépend de nombreux paramètres météorologiques : rayonnement du soleil, présence ou absence de nuages, température, ... La problématique que nous a soumise l'entreprise RTE et à laquelle nous réfléchissons dans ce document est de sélectionner les variables les plus influentes sur cette production au moyen d'une étude statistique, et de proposer un modèle descriptif de cette production qui adhère le mieux possible à la réalité. Dans cet objectif, nous faisons dans un premier temps un tour d'horizon des modèles statistiques existants. Nous étudions ensuite un modèle additif pour analyser les données fournies par RTE et effectuer une première sélection de variables grâce au modèle GAM. Enfin, on reprend cette étude avec le modèle MARS dans l'objectif de pouvoir regrouper des variables entre elles pour pouvoir transformer notre modèle additif très restrictif en un modèle plus adapté à la situation considérée

Analyse canonique généralisée de données séquentielles d'espérance fixe ou variable dans le temps

International audienceHigh dimensional data of a generalized canonical correlation analysis (gCCA) are supposed first to be i.i.d. observations of a random vector Z which are taken sequentially. After defining a stochastic approximation process of the Robbins-Monro type to estimate sequentially the inverse of a covariance matrix, a recursive method of sequential estimation of direction vectors of the principal axes of gCCA is defined. Next, the case where the expectation of the nth observation varies with time n is studied. Finally, simulation results are given.On suppose que des vecteurs de données pouvant être de grande dimension et arrivant séquentiellement dans le temps sont des observations i.i.d. d'un vecteur aléatoire. Après avoir défini un processus d'approximation stochastique de type Robbins-Monro de l'inverse d'une matrice de covariance, on définit une méthode récursive d'estimation séquentielle de vecteurs directeurs des r premiers axes principaux de l'analyse canonique généralisée de ce vecteur aléatoire. On 'etudie ensuite le cas où l'espérance des observations varie dans le temps. On donne finalement des résultats de simulation

Analyse en composantes principales partielle de données séquentielles d'espérance et de matrice de covariance variables dans le temps

National audienceHigh dimensional batch data are supposed to be independent observations of a random vector Z, expectation and covariance matrix of which vary with time n. A recursive method of on-line estimation of direction vectors of the r first principal axes of a partial principal components analysis (PCA) of Z is defined. This is applied next to the particular case of a partial generalized canonical correlation analysis (gCCA) after defining a stochastic approximation process of the Robbins-Monro type to estimate recursively the inverse of a covariance matrix.On suppose que des vecteurs de données pouvant être de grande dimension et arrivant séquentiellement dans le temps sont des observations indépendantes d'un vecteur aléatoire d'espérance mathématique et de matrice de covariance variables dans le temps. On définit alors une méthode récursive d'estimation en ligne de vecteurs directeurs des r premiers axes principaux d'une analyse en composantes principales (ACP) partielle de ce vecteur aléatoire. On applique ensuite ce résultat au cas particulier de l'analyse canonique généralisée (ACG) partielle après avoir défini un processus d'approximation stochastique de type Robbins-Monro de l'inverse d'une matrice de covariance

Analyse Canonique Généralisée de données séquentielles

On suppose que des vecteurs de données pouvant être de grande dimension et arrivant séquentiellement dans le temps sont des observations i.i.d. d'un vecteur aléatoire. Après avoir défini un processus d'approximation stochastique de type Robbins-Monro de l'inverse d'une matrice de covariance, on définit une méthode récursive d'estimation séquentielle de vecteurs directeurs des r premiers axes principaux de l'analyse canonique généralisée de ce vecteur aléatoire. On étudie ensuite le cas où l'espérance des observations varie dans le temps. On donne finalement des résultats de simulation

Analyse canonique généralisée d'un flux de données d'espérance variable dans le temps

National audienceConsider a data stream and suppose that each multidimensional data $z_n$ is a realization of a random vector $Z_n$ whose expectation $\theta_n$ varies with time. Let $\tilde{Z}_n=Z_n-\theta_n$ and suppose that the vectors $\tilde{Z}_n$ form an i.i.d. sample of a random vector $\tilde{Z}$. Stochastic approximation processes using data blocks are used to estimate on-line direction vectors of the principal axes of the generalized canonical correlation analysis of $\tilde{Z}$.On suppose que des vecteurs de données $z_n$ arrivant séquentiellement dans le temps sont les observations respectives d'un vecteur $Z_n$ dont l'espérance $\theta_n$ varie dans le temps. On note $\tilde{Z}_n=Z_n-\theta_n$ et on suppose que les vecteurs $\tilde{Z}_n$ forment un échantillon i.i.d. d'un vecteur aléatoire $\tilde{Z}$. On définit des processus d'approximation stochastique utilisant des blocs de données pour estimer des vecteurs directeurs des axes principaux de l'analyse canonique généralisée (ACG) de $\tilde{Z}$

Universal evaluation of MLC models in treatment planning systems based on a common set of dynamic tests

Reference standards; Commission on professional and hospital activities; Radiotherapy, Intensity-ModulatedEstándares de referencia; Comisión sobre actividades profesionales y hospitalarias; Radioterapia de intensidad moduladaEstàndards de referència; Comissió sobre activitats professionals i hospitalàries; Radioteràpia d'intensitat moduladaPurpose: To demonstrate the feasibility of characterising MLCs and MLC models implemented in TPSs using a common set of dynamic beams. Materials and methods: A set of tests containing synchronous (SG) and asynchronous sweeping gaps (aSG) was distributed among twenty-five participating centres. Doses were measured with a Farmer-type ion chamber and computed in TPSs, which provided a dosimetric characterisation of the leaf tip, tongue-and-groove, and MLC transmission of each MLC, as well as an assessment of the MLC model in each TPS. Five MLC types and four TPSs were evaluated, covering the most frequent combinations used in radiotherapy departments. Results: Measured differences within each MLC type were minimal, while large differences were found between MLC models implemented in clinical TPSs. This resulted in some concerning discrepancies, especially for the HD120 and Agility MLCs, for which differences between measured and calculated doses for some MLC-TPS combinations exceeded 10%. These large differences were particularly evident for small gap sizes (5 and 10 mm), as well as for larger gaps in the presence of tongue-and-groove effects. A much better agreement was found for the Millennium120 and Halcyon MLCs, differences being within ± 5% and ± 2.5%, respectively. Conclusions: The feasibility of using a common set of tests to assess MLC models in TPSs was demonstrated. Measurements within MLC types were very similar, but TPS dose calculations showed large variations. Standardisation of the MLC configuration in TPSs is necessary. The proposed procedure can be readily applied in radiotherapy departments and can be a valuable tool in IMRT and credentialing audits

Production of Embryonic and Fetal-Like Red Blood Cells from Human Induced Pluripotent Stem Cells

We have previously shown that human embryonic stem cells can be differentiated into embryonic and fetal type of red blood cells that sequentially express three types of hemoglobins recapitulating early human erythropoiesis. We report here that we have produced iPS from three somatic cell types: adult skin fibroblasts as well as embryonic and fetal mesenchymal stem cells. We show that regardless of the age of the donor cells, the iPS produced are fully reprogrammed into a pluripotent state that is undistinguishable from that of hESCs by low and high-throughput expression and detailed analysis of globin expression patterns by HPLC. This suggests that reprogramming with the four original Yamanaka pluripotency factors leads to complete erasure of all functionally important epigenetic marks associated with erythroid differentiation regardless of the age or the tissue type of the donor cells, at least as detected in these assays. The ability to produce large number of erythroid cells with embryonic and fetal-like characteristics is likely to have many translational applications

Albumin Counteracts Immune-Suppressive Effects of Lipid Mediators in Patients With Advanced Liver Disease.

BACKGROUND & AIMS: Patients with acute decompensation and acute-on-chronic liver failure (AD/ACLF) have immune dysfunction, which increases their risk for infections; however, there are no effective treatments to restore their immune function. We investigated whether the potentially immune-restorative effects of albumin are mediated by its effects on prostaglandin E2 (PGE2) and other lipids. METHODS: We analyzed bloods samples from 45 of 79 patients with AD/ACLF and serum levels of albumin less than 30 g/L for whom infusion of 20% human albumin solution (HAS) increased serum levels of albumin 30 g/L or more in a feasibility study of effects of 20% HAS. Immune function was determined by comparison of macrophage function following addition of plasma samples. We also used samples from 12 healthy individuals. We measured binding of plasma proteins to PGE2 and serum levels of endotoxin (lipopolysaccharide) and cytokines; using 10 patients' samples, we investigated the effects of PGE2 inhibitors. We performed a comprehensive lipid metabolomic analysis using samples from 10 different patients, before and after HAS administration. RESULTS: At baseline, AD/ACLF patient plasma induced significantly lower production of tumor necrosis factor by healthy macrophages than plasma from healthy individuals (P < .0001). Plasma from patients after HAS infusion induced significantly higher levels of tumor necrosis factor production by macrophages (19.5 ± 4.8 ng/mL) compared with plasma collected before treatment (17.7 ± 4.5 ng/mL; P = .0013). There was a significantly lower proportion of plasma protein (albumin) binding to PGE2 from patients with AD/ACLF plasma (mean, 61.9%) compared with plasma from control subjects (77.1%; P = .0012). AD/ACLF plasma protein binding to PGE2 increased following HAS treatment compared with baseline (mean increase, 8.7%; P < .0001). Circulating levels of PGE2, lipopolysaccharide, and inflammatory or anti-inflammatory cytokines were higher in patients with AD/ACLF than healthy volunteers. Unexpectedly, HAS infusion had no effect on mediator levels. Principal component analysis of baseline levels of lipids that induce or resolve inflammation identified 2 distinct groups of patients that differed according to baseline plasma level of lipopolysaccharide. Sample analyses after HAS treatment indicated that albumin regulates circulating levels of lipid mediators, but this effect was distinct in each group. CONCLUSIONS: Analysis of blood samples from patients with AD/ACLF participating in a feasibility study of 20% HAS infusions has shown that infusions to raise serum albumin above 30 g/L reversed plasma-mediated immune dysfunction by binding and inactivating PGE2. We also describe a method to classify the inflammatory response in AD/ACLF, based on lipid profile, which could improve identification of patients most likely to respond to HAS treatment. A randomized controlled trial is needed to determine whether these effects of HAS reduce infections in AD/ACLF. Trial registered with European Medicines Agency (EudraCT 2014-002300-24) and adopted by NIHR (ISRCTN14174793).Health Innovation Challenge fund (Wellcome Trust and Department of Health) award number 164699. This publication presents independent research commissioned by the Health Innovation Challenge Fund, a parallel funding partnership between the Department of Health and Wellcome Trust

EuReCa ONE—27 Nations, ONE Europe, ONE Registry A prospective one month analysis of out-of-hospital cardiac arrest outcomes in 27 countries in Europe

AbstractIntroductionThe aim of the EuReCa ONE study was to determine the incidence, process, and outcome for out of hospital cardiac arrest (OHCA) throughout Europe.MethodsThis was an international, prospective, multi-centre one-month study. Patients who suffered an OHCA during October 2014 who were attended and/or treated by an Emergency Medical Service (EMS) were eligible for inclusion in the study. Data were extracted from national, regional or local registries.ResultsData on 10,682 confirmed OHCAs from 248 regions in 27 countries, covering an estimated population of 174 million. In 7146 (66%) cases, CPR was started by a bystander or by the EMS. The incidence of CPR attempts ranged from 19.0 to 104.0 per 100,000 population per year. 1735 had ROSC on arrival at hospital (25.2%), Overall, 662/6414 (10.3%) in all cases with CPR attempted survived for at least 30 days or to hospital discharge.ConclusionThe results of EuReCa ONE highlight that OHCA is still a major public health problem accounting for a substantial number of deaths in Europe.EuReCa ONE very clearly demonstrates marked differences in the processes for data collection and reported outcomes following OHCA all over Europe. Using these data and analyses, different countries, regions, systems, and concepts can benchmark themselves and may learn from each other to further improve survival following one of our major health care events