AM-compactness of positive Dunford-Pettis operators on banach lattices

We characterize Banach lattices on which each positive Dunford-Pettis operator is AM-compact and we give some consequences.     

Mechanical behaviour of nano composite aerogels

In order to improve the mechanical properties of silica aerogels, we propose the synthesis of nano composite aerogels. Silica particles (20–100 nm) are added in the monomer solution, just before gelling and supercritical drying. The silica particles addition increases the mechanical properties, but also affects the aggregation process, the aerogel structure and the pore sizes. We discuss the different parameters which infer in the mechanical behaviour of silica aerogel such as: brittle behaviour, load bearing fraction of solid (pore volume), internal stresses (shrinkage), size and distribution of flaws, subcritical flaws propagation (chemical susceptibility). With silica particles addition, the mechanical properties rapidly increase, stiffening and strengthening the structure by a factor 4–8. Moreover, the mechanical strength distribution and the Weibull modulus characterizing the statistical nature of flaws size in brittle materials show a more homogeneous strength distribution. The composite structure is made of two imbricate networks, the polymeric silica and the particles silica networks. Ultra Small Angle X-ray Scattering experiments show that besides the fractal network usually built up by the organosiloxane, the silica particles is forming another fractal structure at a higher scale. The fractal structure could be related to the low Weibull parameter characteristic of a large flaws size distribution, pores being the critical flaws.     

Optimal intervention strategies for tuberculosis

This paper deals with the problem of optimal control of a deterministic model of tuberculosis (abbreviated as TB for tubercle bacillus). We first present and analyze an uncontrolled tuberculosis model which incorporates the essential biological and epidemiological features of the disease. The model is shown to exhibit the phenomenon of backward bifurcation, where a stable disease-free equilibrium co-exists with one or more stable endemic equilibria when the associated basic reproduction number is less than the unity. Based on this continuous model, the tuberculosis control is formulated and solved as an optimal control problem, indicating how control terms on the chemoprophylaxis and detection should be introduced in the population to reduce the number of individuals with active TB. Results provide a framework for designing the cost-effective strategies for TB with two intervention methods.     

K2M(H2P2O7)2·2H2O (M = Ni,Cu, Zn): ortho­rhom­bic forms and Raman spectra

The crystal structures of three isotypic ortho­rhom­bic dihydrogendiphosphates, namely dipotassium copper(II)/nickel(II)/zinc(II) bis­(dihydrogendiphosphate) dihydrate, K₂M(H₂P₂O₇)₂·2H₂O (M = Cu, Ni and Zn), have been refined from single‐crystal data. The M²⁺ and K⁺ cations are located at sites of m symmetry, and the P atoms occupy general positions. These compounds also exist in triclinic forms with very similar structural features. The structures of both forms are compared, as well as the geometry of the MO₆ octa­hedron, which is considerably elongated towards the water mol­ecules for M = Ni and Cu. Such elongation has not been observed among the other representatives of the family. A Raman study of the whole series K₂M(H₂P₂O₇)₂·2H₂O (M = Mn, Co, Ni, Cu, Zn and Mg) is reported.     

Excess enthalpies of ether + alcohol + hydrocarbon mixtures: Binary and ternary mixtures containing dibutyl ether (DBE), 1-butanol and benzene at 298.15 K and 313.15 K

Experimental excess molar enthalpies of the ternary systems dibutyl ether (DBE) + 1-butanol + benzene and the corresponding binary systems at T = 298.15 K and T = 313.15 K at atmospheric pressure are reported. A quasi-isothermal flow calorimeter has been used to make the measurements. All the binary and the ternary systems show endothermic character. The experimental data for the binary and ternary systems have been fitted using the Redlich-Kister equation and the NRTL and UNIQUAC models. The values of the standard deviation indicate good agreement between the experimental results and those calculated from the equations.     

Cellulose Acetate-g-Polycaprolactone Copolymerization Using Diisocyanate Intermediates and the Effect of Polymer Chain Length on Surface,Thermal, and Antibacterial Properties

The need for biodegradable and biocompatible polymers is growing quickly, particularly in the biomedical and environmental industries. Cellulose acetate, a natural polysaccharide, can be taken from plants and modified with polycaprolactone to improve its characteristics for a number of uses, including biomedical applications and food packaging. Cellulose acetate-g-polycaprolactone was prepared by a three-step reaction: First, polymerization of ε-caprolactone via ring-opening polymerization (ROP) reaction using 2-hydroxyethyl methacrylate (HEMA) and functionalization of polycaprolactone(PCL) by introducing NCO on the hydroxyl end of the HEMA-PCL using hexamethyl lenediisocyanate(HDI) were carried out. Then, the NCO–HEMA-PCL was grafted onto cellulose acetate (using the “grafting to” method). The polycaprolactone grafted cellulose acetate was confirmed by FTIR, the thermal characteristics of the copolymers were investigated by DSC and TGA, and the hydrophobicity was analyzed via water CA measurement. Introducing NCO-PCL to cellulose acetate increased the thermal stability. The contact angle of the unreacted PCL was higher than that of cellulose acetate-g-PCL, and it increased when the chain length increased. The CA-g-PCL50, CA-g-PCL100, and CA-g-PCL200 showed very high inhibition zones for all three bacteria tested (E. coli, S. aureus, and P. aeruginosa).     

On the class of disjoint limited completely continuous operators

We introduce and study new class of sets (almost L-limited sets). Also, we introduce new concept of property in Banach lattice (almost Gelfand–Phillips property) and we characterize this property using almost L-limited sets. On the other hand, we introduce the class of disjoint limited completely continuous operators which is a largest class than that of limited completely continuous operators, we characterize this class of operators and we study some of its properties.     

Assessment of mineral elements and heavy metals in leaves of indigenous cypress of High Atlas Mountains

An inductively coupled plasma mass spectrometry was developed to determine 20 mineral elements and heavy metals in leaves of Cupressus atlantica Gaussen, a traditional Moroccan medicinal herb from five environmentally different sites in N'Fis valley (High Atlas Mountains). The results showed in the leaves that Ca, K, P, Mg, Na and Fe were the most abundant of the elements in all samples of the studied locality. The concentrations of trace metals from the leaves of this plant were in the order Ca>K > P > Mg>Na>Fe. The results of the mineral composition were analysed by hierarchical cluster and principal component analysis that established three statistically significant clusters.     

Weibull analysis of the mechanical strength of silica gels

Since gels are typically brittle materials, reliable analyses are essential to determine the strength distribution. The mechanical strength of silica gels has been measured by the three point bending technique. Based on the Weibull function, the statistical analysis allows determination of the Weibull modulus (m), which characterizes the strength distribution and the flaw size effect.Two kinds of gels, alcogels and aerogels, have been investigated with respect to their different mechanical behaviour owing to the transformations occurring during the supercritical drying (SD). The toughness of the two materials has been also measured by the SENB technique. It appears that the strength increases by a factor greater than two during SD, the K_IC increases slightly. However, m is not greatly affected which would suggest that SD does not induce significant flaws or defects change in the network.