Green Synthesis of Poly(aminomethylenephosphonic) Acids

The reaction of polyamines with phosphorous acid and formaldehyde in water under focused microwave irradiation provides a facile and rapid synthesis of poly(aminomethylenephosphonic) acids.     

Constant Mean Curvature Foliations of Globally Hyperbolic Spacetimes Locally Modelled on <Emphasis Type="Italic">AdS</Emphasis><Subscript>3</Subscript>

We prove that every three-dimensional maximal globally hyperbolic spacetime, locally modelled on the anti-de Sitter space AdS ₃, with closed orientable Cauchy surfaces, admits a unique CMC time function.     

Aqueous solution behavior of p(N-isopropyl acrylamide) in the presence of water-soluble macromolecular species

We report here the polymerization of N-isopropyl acrylamide (NIPAM) via the reversible addition fragmentation chain transfer (RAFT) process. Two trithiocarbonates (S,S′-bis(α,α′-dimethyl-α″-acetic acid)-trithiocarbonate and 2-dodecylsulfanylthiocarbonylsulfanyl-2-methyl propionic acid) were used as the chain transfer agents in conjunction with 4,4′-azobis(4-cyanovaleric acid) and 2,2′azobis(2-methylpropionamidine) dihydrochloride as the initiating species. Poly(NIPAM) is a thermo-responsive polymer that has a sharp lower critical solution temperature (LCST). Herein, we investigated the aqueous solution behaviour of well defined p(NIPAM) prepared by the RAFT process as a function of molecular weight (degree of polymerization: 50, 100 and 200) and temperature. Furthermore, we examine the influence of varying concentrations of macromolecular species (neutral polyethylene glycol (M_n - 3400 g/mol) and ionic bovine serum albumin (M_n - 63 000 g/mol)) on the LCST of p(NIPAM). The aqueous solution behaviour was assessed by spectrophotometry, dynamic light scattering and surface tensiometry. The macromolecular additives was found to have a significant effect on the coil to globular transition of the lower molecular weight p(NIPAM).     

Fabrication and Properties of Doped Porous Polysiloxane Sol-Gel Layers on Optical Fibers

Polysiloxane porous layers doped with TiO- and phenyl-groups were fabricated by the sol-gel method. Starting sols were prepared from alkoxides using catalysis by HCl or HF. Stable SiO-TiO-sols were obtained by using HF. Porous gel layers with thicknesses of 0.3–1.1 m were coated on fiber surfaces or silicon wafers. Layers with the refractive index of 1.38–1.48 were prepared. The fractional porosity of the layers was estimated to be 0.1–0.35. The interactions of the layers with vapor or liquid chlorinated hydrocarbons, alcohols or aromatic hydrocarbons have been studied in immersing experiments by measuring the output light intensity from the fibers. The observed changes of the output intensity could be correlated to changes of the refractive index of the layer caused by the penetration of the tested chemicals into the layer pores.     

On rigidity of generalized conformal structures

The classical Liouville Theorem on conformal transformations determines local conformal transformations on the Euclidean space of dimension \({\ge }3\) . Its natural adaptation to the general framework of Riemannian structures is the 2-rigidity of conformal transformations, that is such a transformation is fully determined by its 2-jet at any point. We prove here a similar rigidity for generalized conformal structures defined by giving a one parameter family of metrics (instead of scalar multiples of a given one) on each tangent space.     

Boosting COVID-19 Image Classification Using MobileNetV3 and Aquila Optimizer Algorithm

Currently, the world is still facing a COVID-19 (coronavirus disease 2019) classified as a highly infectious disease due to its rapid spreading. The shortage of X-ray machines may lead to critical situations and delay the diagnosis results, increasing the number of deaths. Therefore, the exploitation of deep learning (DL) and optimization algorithms can be advantageous in early diagnosis and COVID-19 detection. In this paper, we propose a framework for COVID-19 images classification using hybridization of DL and swarm-based algorithms. The MobileNetV3 is used as a backbone feature extraction to learn and extract relevant image representations as a DL model. As a swarm-based algorithm, the Aquila Optimizer (Aqu) is used as a feature selector to reduce the dimensionality of the image representations and improve the classification accuracy using only the most essential selected features. To validate the proposed framework, two datasets with X-ray and CT COVID-19 images are used. The obtained results from the experiments show a good performance of the proposed framework in terms of classification accuracy and dimensionality reduction during the feature extraction and selection phases. The Aqu feature selection algorithm achieves accuracy better than other methods in terms of performance metrics.     

Study of EAS Registered by the PRISMA-32 Array and the Cherenkov Water Calorimeter NEVOD

Two installations that allow to detect the EAS hadron component in a continuous mode, the Cherenkov water calorimeter (CWC) NEVOD and PRISMA-32 are operated in MEPhI. The comparison of the characteristics of EAS simultaneously registered by CWC NEVOD and PRISMA-32 are presented. Groups of events with different positions of the shower axis are considered.

     

Optimisation de la forme de la trochoïde dans un engrenage droitOptimization of the trochoid form in spur wheels

Generally, mechanical damage in gear wheels results from either cracks at the base of the tooth or from high contact pressure between the teeth.Starting from the principle of mass minimization, this Note develops a new formulation in terms of displacement, calling on a new, more resistant and less voluminous form for the base of the teeth. As a result, the first cause of the breakages which happen at this point because of a concentration of constraints are limited. To cite this article: M.E.H. Bouanane, M. Bouchama, C. R. Mecanique 331 (2003).     

Effects of Fine Particles on the Suffusion of Cohesionless Soils. Experiments and Modeling

Internal erosion has long been a major problem associated with earthen structures, and its field investigation has been limited because of its complexity. Laboratory experiments provide a potential insight into the induced processes. Soils suitable to suffusion involve an easy movement of fine particles between the coarse ones. In this study, suffusion experiments were performed on a laboratory column packed with different sand–fines mixtures and subjected to controlled flow conditions. The mixtures are made of Fontainebleau sand (NE34) and fines (kaolinite or illite or silt). The initiation and the progression of soil suffusion were investigated for soil mixtures, and the hydraulic conductivity variation was derived from pressure measurements. Attempts are made to assess the influence of the type and content of fine particles on mixtures suffusion. The results show that among the tested fine particles, illite exhibits a great resistance against suffusion. Fine content increase involves less suitability to suffusion till a threshold value. Recorded pressures indicate that detachment of fines may be followed by clogging in the soil matrix, leading to a decrease of hydraulic conductivity. Furthermore, analytical solutions of simplified mathematical model based on the mass conservation of eroded particles (Govindaraju et al., J Hydrol 172:331–350, 1995) were used to simulate the recorded soil suffusion curves, and the model performance was evaluated. Comparisons between numerical and experimental results indicated a quite good agreement, and allowed the estimation of the model parameters.     

Kinetic models of chemotaxis towards the diffusive limit: asymptotic analysis

The paper is devoted to the study of the asymptotic behavior of the solutions of a kinetic model describing chemotaxis phenomena. Our interest focuses on the case, where the diffusion part dominates the chemotaxis part in the limit. More in detail, we prove that the solution of kinetic model exists globally and converges to a solution of diffusive limit. Copyright © 2015 John Wiley & Sons, Ltd.