Impact of Tetracationic Calix[4]arene Conformation—from Conic Structure to Expanded Bolaform—on Their Antibacterial and Antimycobacterial Activities

The four possible conformers of a new tetrakisguanidino calix[4]arene thought to interact deleteriously with bacterial membranes have been synthesized, characterized, and evaluated for their in vitro cytotoxicity and antibacterial activity against various reference Gram-negative and Gram-positive bacteria, as well as Mycobacterium tuberculosis. It appears that reversal of at least one phenolic unit results in clear increases in their activities. This can be attributed to the evolution towards bolaform structures, which are able to interact more deeply with the bacterial membrane. Indeed, the 1,3-alternate conformer 16 exhibits the best antibacterial activity (MIC<1.0 μg mL⁻¹ on Staphylococcus aureus). Moreover, 16 displays very good antibacterial activities against an isoniazid-resistant strain of M. tuberculosis (MIC=1.2 μg mL⁻¹), associated with the lowest cytotoxicity, thus making it the most potent compound of the series; this could open new ways of research in the field of anti-infective drug development to meet the huge current demand.     

Identification algorithm for fracture parameters by combining DIC and FEM approaches

This research program focuses on a hybrid experimental and numerical approach to identifying the mechanical state in the vicinity of a crack. The digital image correlation, as corrected by interpolating a theoretical displacement field, enables determining the crack opening intensity factors representative of the kinematic state of crack lips. A finite element model is introduced for calculating stress intensity factors. The parallelism derived from the DIC method and FEM approach is presented by means of a specific identification algorithm that allows computing the energy release rate within a common finite element mesh. This algorithm is then illustrated by testing the opening-mode configuration for a PVC sample.     

Experimental characterization of the stress–strain behaviour of cemented paste backfill in compression

It is of great interest for economical and security reasons to understand the compressive properties of underground cemented paste backfill. In this paper, the stress–strain behaviours of cemented paste backfill (CPB) subjected to uniaxial compression and conventional triaxial tests are presented and discussed. The effect of CPB basic components, strength, ageing and confining pressure on the deformation behaviour of CPB are evaluated and discussed. The results show that the stress–strain behaviour of CPB is strongly influenced by the confinement, the age and strength of CPB, and its components. The increase in confining pressure leads to a change in the mode of failure, in the stiffness, and an increase in the strength.     

Investigation on the Effect of Condensing Moisture before Heating Air on the Performance of a Batch Tray Dryer: Application to the Drying of Vanilla

This article presents the results of an investigation of the effect of pre-dehumidifying the drying air before it is heated and supplied into a batch tray dryer. Dehumidification is achieved through moisture condensation as the air flowing through a coil is cooled by chilled water from a cold source. As an example, this process is applied to the drying of vanilla and is based on a numerical method already validated by former results. Then, it is established through comparisons with a conventional batch tray dryer model that pre-dehumidification significantly reduces drying time. Furthermore, preheating air by an intermediate heating source reduces total energy consumption of the primary heating system to a level depending on the preset drying temperature. As regards batch tray dryer design and optimization purposes, these results open up particularly interesting heating and cooling sources utilization prospects.     

Thermodynamic Properties of Asphaltenes Through Computer Assisted Structure Elucidation and Atomistic Simulations. 1. Bulk Arabian Light Asphaltenes

This article describes a new method for estimating the thermodynamic properties of asphaltenes. To illustrate this methodology, we used a computer assisted structure elucidation software (SIGNATURE) to generate an ensemble of 10 isomers for Arabian Light (AL) asphaltenes compatible with (i) analytical data from elemental analysis, FT-IR spectroscopy, 1-D ¹H/¹³C solution NMR and vapor pressure osmometry and (ii) literature data on the molecular composition of asphaltenes. The 10 model isomers were packed into a 3-D periodic cell to form the condensed phase model for the fraction of bulk AL asphaltenes with a number average molar mass (M_n) approximately equal to 1280 Dalton. This cell was subsequently used in molecular dynamics (MD) simulations to estimate the molar volume, density, enthalpy, specific heat at constant pressure, solubility parameter, and isothermal compressibility of the AL asphaltene fraction. The results of the MD simulations compare favorably with the available experimental data.     

Branched polymeric media: boron-chelating resins from hyperbranched polyethylenimine

Extraction of boron from aqueous solutions using selective resins is important in a variety of applications including desalination, ultrapure water production, and nuclear power generation. Today's commercial boron-selective resins are exclusively prepared by functionalization of styrene-divinylbenzene (STY-DVB) beads with N-methylglucamine to produce resins with boron-chelating groups. However, such boron-selective resins have a limited binding capacity with a maximum free base content of 0.7 eq/L, which corresponds to a sorption capacity of 1.16 ± 0.03 mMol/g in aqueous solutions with equilibrium boron concentration of ～70 mM. In this article, we describe the synthesis and characterization of a new resin that can selectively extract boron from aqueous solutions. We show that branched polyethylenimine (PEI) beads obtained from an inverse suspension process can be reacted with glucono-1,5-d-lactone to afford a resin consisting of spherical beads with high density of boron-chelating groups. This resin has a sorption capacity of 1.93 ± 0.04 mMol/g in aqueous solution with equilibrium boron concentration of ～70 mM, which is 66% percent larger than that of standard commercial STY-DVB resins. Our new boron-selective resin also shows excellent regeneration efficiency using a standard acid wash with a 1.0 M HCl solution followed by neutralization with a 0.1 M NaOH solution.     

Statistical modeling of global geogenic fluoride contamination in groundwaters

The use of groundwater with high fluoride concentrations poses a health threat to millions of people around the world. This study aims at providing a global overview of potentially fluoride-rich groundwaters by modeling fluoride concentration. A large database of worldwide fluoride concentrations as well as available information on related environmental factors such as soil properties, geological settings, and climatic and topographical information on a global scale have all been used in the model. The modeling approach combines geochemical knowledge with statistical methods to devise a rule-based statistical procedure, which divides the world into 8 different "process regions". For each region a separate predictive model was constructed. The end result is a global probability map of fluoride concentration in the groundwater. Comparisons of the modeled and measured data indicate that 60-70% of the fluoride variation could be explained by the models in six process regions, while in two process regions only 30% of the variation in the measured data was explained. Furthermore, the global probability map corresponded well with fluorotic areas described in the international literature. Although the probability map should not replace fluoride testing, it can give a first indication of possible contamination and thus may support the planning process of new drinking water projects.     

Efficient approaches for ℓ2-ℓ0 regularization and applications to feature selection in SVM

For solving a class of ?₂- ?₀- regularized problems we convexify the nonconvex ?₂- ?₀ term with the help of its biconjugate function. The resulting convex program is explicitly given which possesses a very simple structure and can be handled by convex optimization tools and standard softwares. Furthermore, to exploit simultaneously the advantage of convex and nonconvex approximation approaches, we propose a two phases algorithm in which the convex relaxation is used for the first phase and in the second phase an efficient DCA (Difference of Convex functions Algorithm) based algorithm is performed from the solution given by Phase 1. Applications in the context of feature selection in support vector machine learning are presented with experiments on several synthetic and real-world datasets. Comparative numerical results with standard algorithms show the efficiency the potential of the proposed approaches.     

A GIS-based mapping of historical coastal cliff recession

This paper presents the results of a study on historical cliffs recessions using GIS. In this study, a GIS methodological approach was developed to model and analyse the development and spatial distribution of cliff recession on the coast at Dakar. Valuable information about the coastal erosion and the main causes of the instabilities was obtained. Finally, this research also suggests that important information regarding instability processes can be gathered from existing information sources, such as technical maps, aerial photographs, and written documents, thereby limiting the need for costly and time-consuming field and/or laboratory investigations.     

New accelerated charge methods using early destratification applied on flooded lead acid batteries

A traditional charge process for flooded lead acid batteries (FLABs) lasts generally from 8 to 14 h. Nowadays, many applications of FLABs require reduction of the charge duration, for instance, a 4 h-charge for FLABs in grid energy storage or 1 h-charge for FLABs in electric buses. These are called accelerated charge and fast charge. Such reductions of charge time imply the use of a new charge process. One way to reduce the charge duration is to perform an early destratification step without waiting for the end of charge. The new charge method proposed in this paper (early destratification method - ED) focuses on the reduction of the charge time for FLABs using early destratification, which is performed and controlled using charge acceptance measurement during the charge. Laboratory experiments presented here aim first to develop charge acceptance measurements followed by an ED charge method compared to an IUi traditional charge process.