Noisy Independent Factor Analysis Model for Density Estimation and Classification

We consider the problem of multivariate density estimation when the unknown density is assumed to follow a particular form of dimensionality reduction, a noisy independent factor analysis (IFA) model. In this model the data are generated by a number of latent independent components having unknown distributions and are observed in Gaussian noise. We do not assume that either the number of components or the matrix mixing the components are known. We show that the densities of this form can be estimated with a fast rate. Using the mirror averaging aggregation algorithm, we construct a density estimator which achieves a nearly parametric rate (log1/4 n)/√n, independent of the dimensionality of the data, as the sample size n tends to infinity. This estimator is adaptive to the number of components, their distributions and the mixing matrix. We then apply this density estimator to construct nonparametric plug-in classifiers and show that they achieve the best obtainable rate of the excess Bayes risk, to within a logarithmic factor independent of the dimension of the data. Applications of this classifier to simulated data sets and to real data from a remote sensing experiment show promising results.Financial support from the IAP research network of the Belgian government (Belgian Federal Science Policy) is gratefully acknowledged. Research of A. Samarov was partially supported by NSF grant DMS- 0505561 and by a grant from Singapore-MIT Alliance (CSB). Research of A.B. Tsybakov was partially supported by the grant ANR-06-BLAN-0194 and by the PASCAL Network of Excellence

Liquid-liquid equilibrium in quarternary systems ethanol – ethylpropanoate – choline chloride –glycerol, propanol – propylpropanoate – choline chloride –glycerol, butanol – butylpropanoate – choline chloride – glycerol

This study was supported by the Russian Foundation for Basic Research (project № 16-33-60128 mol_a_dk). The experimental work was facilitated by the equipment of Magnetic Resonance Research Centre at St. Petersburg State University

Easily Vaporizable Ionic Liquids - No Contradiction!

Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. It was a big surprise to see crystals of an ionic liquid (IL) forming by sublimation at room temperature. ILs are generally accepted to have negligible vapour pressures at elevated temperatures, making their sublimation or distillation very difficult. ILs that sublime easily contain silylimidazolium-based cations. In order to establish the details of the unusual behaviour of this subclass of ILs, a combined spectroscopic, X-ray crystallographic, physicochemical and theoretical characterization was performed. The results are compared with those of other easily vaporizable compounds, like ammonium chloride and naphthalene. The single-crystal X-ray structure analysis of one of these compounds, N-methyl-N′-dimethyl(phenyl)silylimidazolium chloride (monoclinic, C2/c), clearly shows the existence of isolated ions, demonstrating that the compound is an ionic liquid. Ionic liquids (ILs) are commonly known as compounds with negligible vapour pressure, which makes them difficult to boil/distil or sublime. Surprisingly, ILs with imidazolium-based cations with the specialty of N-bonded silylorganic groups sublime very easily. The process of sublimation has been investigated thoroughly with physicochemical methods and theoretical calculations

Microbiome Responses to an Uncontrolled Short-Term Diet Intervention in the Frame of the Citizen Science Project

Personalized nutrition is of increasing interest to individuals actively monitoring their health. The relations between the duration of diet intervention and the effects on gut microbiota have yet to be elucidated. Here we examined the associations of short-term dietary changes, long-term dietary habits and lifestyle with gut microbiota. Stool samples from 248 citizen-science volunteers were collected before and after a self-reported 2-week personalized diet intervention, then analyzed using 16S rRNA sequencing. Considerable correlations between long-term dietary habits and gut community structure were detected. A higher intake of vegetables and fruits was associated with increased levels of butyrate-producing Clostridiales and higher community richness. A paired comparison of the metagenomes before and after the 2-week intervention showed that even a brief, uncontrolled intervention produced profound changes in community structure: resulting in decreased levels of Bacteroidaceae, Porphyromonadaceae and Rikenellaceae families and decreased alpha-diversity coupled with an increase of Methanobrevibacter, Bifidobacterium, Clostridium and butyrate-producing Lachnospiraceae- as well as the prevalence of a permatype (a bootstrapping-based variation of enterotype) associated with a higher diversity of diet. The response of microbiota to the intervention was dependent on the initial microbiota state. These findings pave the way for the development of an individualized diet.</p

ХИМИЧЕСКОЕ РАВНОВЕСИЕ В СИСТЕМЕ ПРОПИОНОВАЯ КИСЛОТА - ЭТИЛОВЫЙ СПИРТ - ЭТИЛПРОПИОНАТ - ВОДА И ЭКСТРАКЦИОННЫЕ ПРОЦЕССЫ С УЧАСТИЕМ ГЛУБОКИХ ЭВТЕКТИЧЕСКИХ РАСТВОРИТЕЛЕЙ

New experimental data on the chemical equilibrium in the propionic acid - ethanol - ethyl propionate - water system at 293.15 K and atmospheric pressure are presented. Chemically equilibrium compositions corresponding to the liquid-liquid equilibrium were obtained by gas chromatographic analysis. Using the method of nuclear magnetic resonance, homogeneous chemically equilibrium compositions were determined and the concentration equilibrium constant is calculated. The surface of chemical equilibrium and the region of splitting chemically equilibrium compositions are represented in the square of the transformed concentration variables. Comparison of the data obtained in the work with the literature was carried out at 303.15 and 313.15 K. It was found that the region of such compositions decreases with increasing temperature, while the surface of chemical equilibrium does not change the shape and position in the concentration space in the temperature range 293.15-313.15 K and atmospheric pressure. Liquid-liquid equilibrium compositions have also been obtained by gas chromatographic analysis for ethanol and ethyl propionate in the pseudo-ternary system using deep eutectic solvents (DES) based on choline chloride and glycerol / urea in whole range of concentration. The analysis of the extraction properties of DES showed the highest efficiency of DES based on choline chloride and urea. Experimental data on phase equilibrium are processed using Othmer-Tobias and Hand models. The calculated correlation coefficient (more than 0.99) indicates a high internal consistency of the experimental data obtained in this work.В работе приведены новые экспериментальные данные о химическом равновесии в системе пропионовая кислота - этиловый спирт - этилпропионат - вода при 293.15 К и атмосферном давлении. Методом газового хроматографического анализа найдены составы химически равновесных фаз, отвечающие фазовому равновесию жидкостьжидкость. С использованием метода 1H-ЯМР определены гомогенные химически равновесные составы, на основании которых рассчитана концентрационная константа равновесия. Поверхность химического равновесия и область расслаивающихся химически равновесных составов представлены в квадрате трансформированных концентрационных переменных. Проведено сравнение полученных в работе данных с литературными при 303.15 и 313.15 K. Экспериментально установлено, что область этих составов уменьшается с ростом температуры, при этом поверхность химического равновесия не меняет форму и положение в концентрационном пространстве в температурном интервале 293.15-313.15 К и атмосферном давлении. Получены также составы, отвечающие фазовому равновесию жидкость-жидкость, методом газохроматографического анализа для псевдотройной системы этиловый спирт и этилпропионат с участием глубоких эвтектических растворителей (deep eutectic solvents, DES) на основе хлорида холина и глицерина/мочевины во всем диапазоне концентраций. Анализ экстракционных свойств DES показал наибольшую эффективность DES на основе хлорида холина и мочевины. Экспериментальные данные о фазовом равновесии обработаны с использованием моделей Отмера-Тобиаса и Ханда. Рассчитанный коэффициент корреляции (выше 0.99) подтверждает высокую внутреннюю согласованность полученных в работе экспериментальных данных