Kernel discriminant analysis and clustering with parsimonious Gaussian process models

This work presents a family of parsimonious Gaussian process models which allow to build, from a finite sample, a model-based classifier in an infinite dimensional space. The proposed parsimonious models are obtained by constraining the eigen-decomposition of the Gaussian processes modeling each class. This allows in particular to use non-linear mapping functions which project the observations into infinite dimensional spaces. It is also demonstrated that the building of the classifier can be directly done from the observation space through a kernel function. The proposed classification method is thus able to classify data of various types such as categorical data, functional data or networks. Furthermore, it is possible to classify mixed data by combining different kernels. The methodology is as well extended to the unsupervised classification case. Experimental results on various data sets demonstrate the effectiveness of the proposed method

MEASURING RACING WHEELCHAIR SPATIOTEMPORAL VARIABLES USING A PHONE CAMERA: A PRELIMINARY CONCURRENT VALIDITY STUDY

The purpose of this study was to assess the measurement agreement between a low-cost system (phone camera) and a reference optoelectronic system, to measure spatiotemporal variables that may be related to wheelchair racing performance: acceleration phase time, push time, backswing time, and maximal elbow height. Three regular wheelchair racers propelled at maximal velocity on a training roller. The temporal variables had a low disagreement between both systems (bias ± 1.96 std of less than 0.01 s ± 0.02 s), while for the maximal elbow height, a higher disagreement of 0.020 m ± 0.038 m was observed. Future improvements are required especially to measure the maximal elbow height. This method may have long term benefits both for the athletes and research, by including more wheelchair racing athletes in future biomechanics studies

Parsimonious Gaussian Process Models for the Classification of Multivariate Remote Sensing Images

International audienceA family of parsimonious Gaussian process models is presented. They allow to construct a Gaussian mixture model in a kernel feature space by assuming that the data of each class live in a specific subspace. The proposed models are used to build a kernel Markov random field (pGPMRF), which is applied to classify the pixels of a real multivariate remotely sensed image. In terms of classification accuracy, some of the proposed models perform equivalently to a SVM but they perform better than another kernel Gaussian mixture model previously defined in the literature. The pGPMRF provides the best classification accuracy thanks to the spatial regularization

Kernel discriminant analysis and clustering with parsimonious Gaussian process models

International audienceThis work presents a family of parsimonious Gaussian process models which allow to build, from a finite sample, a model-based classifier in an infinite dimensional space. The proposed parsimonious models are obtained by constraining the eigen-decomposition of the Gaussian processes modeling each class. This allows in particular to use non-linear mapping functions which project the observations into infinite dimensional spaces. It is also demonstrated that the building of the classifier can be directly done from the observation space through a kernel function. The proposed classification method is thus able to classify data of various types such as categorical data, functional data or networks. Furthermore, it is possible to classify mixed data by combining different kernels. The methodology is as well extended to the unsupervised classification case. Experimental results on various data sets demonstrate the effectiveness of the proposed method

Canagliflozin and renal outcomes in type 2 diabetes and nephropathy

BACKGROUND Type 2 diabetes mellitus is the leading cause of kidney failure worldwide, but few effective long-term treatments are available. In cardiovascular trials of inhibitors of sodium–glucose cotransporter 2 (SGLT2), exploratory results have suggested that such drugs may improve renal outcomes in patients with type 2 diabetes. METHODS In this double-blind, randomized trial, we assigned patients with type 2 diabetes and albuminuric chronic kidney disease to receive canagliflozin, an oral SGLT2 inhibitor, at a dose of 100 mg daily or placebo. All the patients had an estimated glomerular filtration rate (GFR) of 30 to <90 ml per minute per 1.73 m2 of body-surface area and albuminuria (ratio of albumin [mg] to creatinine [g], >300 to 5000) and were treated with renin–angiotensin system blockade. The primary outcome was a composite of end-stage kidney disease (dialysis, transplantation, or a sustained estimated GFR of <15 ml per minute per 1.73 m2), a doubling of the serum creatinine level, or death from renal or cardiovascular causes. Prespecified secondary outcomes were tested hierarchically. RESULTS The trial was stopped early after a planned interim analysis on the recommendation of the data and safety monitoring committee. At that time, 4401 patients had undergone randomization, with a median follow-up of 2.62 years. The relative risk of the primary outcome was 30% lower in the canagliflozin group than in the placebo group, with event rates of 43.2 and 61.2 per 1000 patient-years, respectively (hazard ratio, 0.70; 95% confidence interval [CI], 0.59 to 0.82; P=0.00001). The relative risk of the renal-specific composite of end-stage kidney disease, a doubling of the creatinine level, or death from renal causes was lower by 34% (hazard ratio, 0.66; 95% CI, 0.53 to 0.81; P<0.001), and the relative risk of end-stage kidney disease was lower by 32% (hazard ratio, 0.68; 95% CI, 0.54 to 0.86; P=0.002). The canagliflozin group also had a lower risk of cardiovascular death, myocardial infarction, or stroke (hazard ratio, 0.80; 95% CI, 0.67 to 0.95; P=0.01) and hospitalization for heart failure (hazard ratio, 0.61; 95% CI, 0.47 to 0.80; P<0.001). There were no significant differences in rates of amputation or fracture. CONCLUSIONS In patients with type 2 diabetes and kidney disease, the risk of kidney failure and cardiovascular events was lower in the canagliflozin group than in the placebo group at a median follow-up of 2.62 years

Apports de l'échocardiographie pour le suivi et la stratification du risque des patients porteurs d'hypertension artérielle pulmonaire

La place de l'échographie cardiaque (EU) dans la stratification du risque des hypertensions artérielle pulmonaire (HTAP) reste mal définie. L'objectif était d'étudier le rôle pronostique de l'ETT chez ses patients. Les patients porteurs d'une HTAP adressés au CHU de Rouen (01/01/2002-31/12/2019) ont été inclus puis un traitement vasodilatateur pulmonaire était débuté et les patients régulièrement suivis. Les paramètres échographiques ont été évalués via les méthodes statistiques "usuelles" (en prenant comme référence les seuils de la littérature) et par machine learning non supervisé ("arbres décisionnels"). Le critère de jugement principal composite était la survie sans décès ou transplantation à 3 ans. Les paramètres identifiés ont été combinés dans une définition pronostique du remodelage inverse ventriculaire droit (VD) puis l'apport de l'ETT dans la French Method non invasive à 3 paramètres a été étudié. Les résultats ont été confirmés dans une cohorte de validation (CHU Bicêtre, centre de référence national HTAP). 126 patients ont été inclus (63% femmes). Aucun paramètre ETT à l'inclusion n'était associé au critère de jugement principal. Au suivi, l'amélioration du TAPSE > 0 mm restait indépendant associé au critère de jugement principal (p=0.03). Les patients avec un remodelage inverse VD complet avaient une survie sans évènement à 1 an de 100%. L'ajout du TAPSE à la French Method non invasive permettait d'identifier un groupe de patient avec une survie à 3 ans de 100% (confirmé dans la cohorte de validation). L'UT via l'amélioration du TAPSE, le remodelage inverse VD, ou intégré à la French method non invasive, permet d'identifier les patients HTAP à bas risque

Parsimonious Gaussian process models for the classification of hyperspectral remote sensing images

International audienceA family of parsimonious Gaussian process models for classification is proposed in this letter. A subspace assumption is used to build these models in the kernel feature space. By constraining some parameters of the models to be common between classes, parsimony is controlled. Experimental results are given for three real hyperspectral data sets, and comparisons are done with three others classifiers. The proposed models show good results in terms of classification accuracy and processing time

Processus gaussiens parcimonieux pour la classification générative de données hétérogènes

International audienceNous proposons dans ce travail une famille de processus gaussiens parcimonieux permettant de construire, à partir d'un échantillon de taille finie, un classifieur génératif dans un espace de dimension (potentiellement) infinie. Ces modèles parcimonieux permettent en particulier d'utiliser des transformations non-linéaires des données projetant les observations dans un espace de dimension infinie. Nous montrons qu'il est possible de construire directement le classifieur depuis l'espace des observations au travers d'une fonction noyau. La méthode de classification proposée permet ainsi de classer des données de types variés (données qualitatives, données fonctionnelles, réseaux, ...). En particulier, il est possible de classer des données hétérogènes en combinant plusieurs fonctions noyaux. La méthodologie est également étendue au cas de la classification non supervisée (clustering)

Homologous ELISA procedure for the determination of penaeid shrimp vitellogenin

Vitellogenin (VTG) was isolated from the haemolymph of Penaeus vannamei by a three step procedure including ultracentrifugation, gel filtration and ion exchange chromatography. VTG was used to raise polyclonal antibodies that were purified by ion exchange chromatography. A two step competitive assay was developed in which VTG could be quantitated by its capacity to inhibit the binding of antibody to the VTG previously adsorbed onto a solid phase. Sensitivity from equilibrium and from non-equilibrium assays was 41 and 2.3 ng/ml respectively. Estimates of within-assay and between-assay variabilities of standard curves were 4.2 and 9.6% respectively. The inhibition curves for dilutions of haemolymph from vitellogenic females, egg yolk extracts and purified vitellin (VTL) were parallel to the standard VTG curve, haemolymph from immature females and males showed no cross-reactivity. The antibodies directed against VTG recognize but partially VTL as shown by displacement curves. Recovery tests were near 100%. Thus the procedure was considered to be suitable for the measurement of haemolymphatic VTG. The VTG enzyme-linked immunosorbent assay (ELISA) developed in this study was validated by detecting physiological VTG changes in female shrimps after being fed squid extracts.La vitellogénine (VTG) de Penaeus vannamei a été purifiée à partir d'hémolymphe par une procédure en trois étapes comprenant l'ultracentrifugation, la filtration sur gel et la chromatographie d'échange d'ions. Un essai compétitif en deux étapes a été développé par lequel la VTG peut être quantifiée en fonction de sa capacité d'inhiber la liaison de l'anticorps à la VTG préalablement adsorbée à une phase solide. La sensibilité pour des essais en équilibre et non-équilibre a été respectivement de 41 et de 2,3 ng/ml. Les coefficients de variation intra-essai et inter-essais ont été respectivement de 4,2 et 9,6 %. Les courbes d'inhibition pour des dilutions de I'hémolymphe de femelles en cours de vitellogenèse, d'homogénats d'ovaire de ces dernières et de vitelline (VTL) purifiée ont été parallèles à la courbe étalon de VTG; en revanche, l'hémolymphe de femelles sexuellement immatures et de mâles n'ont pas montrée de réactivité croisée. Les anticorps dirigés contre la VTG ne reconnaissent que partiellement la VTL comme l'ont montré les courbes de déplaccmcnt. Les épreuves de surcharge ont été approximativement de 100 %. Ainsi la procédure a été considérée comme adéquate pour mesurer la VTG hémolymphatique. Le test enzymatique immuno-adsorbant (ELISA) développé dans cette étude a été validé physiologiquement en détectant des variations de VTG chez des crevettes femelles nourries avec des extraits de calmar