Mechanical reinforcement and water repellency induced to cellulose sheets by a polymer treatment

The present study reports a simple method to control the mechanical and surface properties of cellulose fiber networks and to protect them from humidity, without altering their initial morphology. This is achieved by dip coating the fiber networks in solutions containing different amounts of ethyl cyanoacrylate monomer (ECA). Under ambient humidity and due to the presence of the -OH groups of the cellulose, the ECA polymerizes around each individual cellulosic fiber forming a thin poly(ethyl cyanoacrylate) (PECA) shell. PECA was found to interact with the cellulose surface via hydrogen bonding as evidenced by Fourier transform infrared spectroscopy and thermogravimetric analysis measurements. The detailed surface characterization reveals that only 3.5 wt% of ECA in solution is sufficient to form compact PECA cladding around every cellulose fiber. After the proposed treatment the cellulose sheets become hydrophobic, well protected from the environmental humidity and with increased Young’s modulus.     

Weak versus strong harmonic-expansion analyses of self-pulsing lasers: I—the Laser Lorenz model

We apply a simple harmonic expansion method to the single-mode laser equations to analyze their dynamic properties. First, we extend the well-known small signal analysis to predict the transient pulsations of the relaxation oscillations. Such transients are characteristic of the laser signal relaxing towards its long-term solution, at any level of excitation, both beyond and below the instability threshold. Secondly, we extend the method to a strong harmonic expansion to analyze the properties of the long-term solutions. These properties are derived for typical examples, extending well beyond the boundary region of the instability domain, for which the laser field amplitude undergoes regular pulsations around zero-mean values.     

Uniform Existence of the Integrated Density of States for Randomly Weighted Hamiltonians on Long-Range Percolation Graphs

We consider random Hamiltonians defined on long-range percolation graphs over $\mathbb {Z}^{d}$ . The Hamiltonian consists of a randomly weighted Laplacian plus a random potential. We prove uniform existence of the integrated density of states and express the IDS using a Pastur-Shubin trace formula.     

In vivo quantitative NMR imaging of fruit tissues during growth using Spoiled Gradient Echo sequence

Nondestructive studies of physiological processes in agronomic products require increasingly higher spatial and temporal resolutions. Nuclear Magnetic Resonance (NMR) imaging is a non-invasive technique providing physiological and morphological information on biological tissues. The aim of this study was to design a robust and accurate quantitative measurement method based on NMR imaging combined with contrast agent (CA) for mapping and quantifying water transport in growing cherry tomato fruits. A multiple flip-angle Spoiled Gradient Echo (SGE) imaging sequence was used to evaluate the intrinsic parameters maps M₀ and T₁ of the fruit tissues. Water transport and paths flow were monitored using Gd^3 +/[Fe(CN)₆]^3 −/D − mannitol nanoparticles as a tracer. This dynamic study was carried out using a compartmental modeling. The CA was preferentially accumulated in the surrounding tissues of columella and in the seed envelopes. The total quantities and the average volume flow of water estimated are: 198 mg, 1.76 mm³/h for the columella and 326 mg, 2.91 mm³/h for the seed envelopes. We demonstrate in this paper that the NMR imaging technique coupled with efficient and biocompatible CA in physiological medium has the potential to become a major tool in plant physiology research.     

Molecular Imprints Frozen by Strong Intermolecular Interactions in Place of Cross-Linking

A new way to freeze molecular imprints in a polymer material is reported. So far, molecular imprinted polymers (MIP) involve copolymerization of a functional monomer and large amounts of cross-linking agent, which keeps the template shape memory in rigid molecular imprints. MIP materials are prepared herein without cross-linking agent. Stiff chains of polyaniline grafted on a solid support as a brush-like material achieve the necessary rigidity. Differential adsorption to imprinted and non-imprinted materials provides evidence of molecular imprints. A correct adsorption isotherm for mobile adsorbed layers (Volmer isotherm) is introduced instead of the popular but inadequate Langmuir isotherm. Non-selective adsorption is entropic, whereas adsorption to molecular imprints has an enthalpic contribution coming from specific interactions. Fast adsorption kinetics are a definite benefit with regards to applications such as chromatographic separations and chemical sensors.     

Stochastic multi-site supply chain planning in textile and apparel industry under demand and price uncertainties with risk aversion

A multi-product, multi-period, multi-site supply chain production and transportation planning problem, in the textile and apparel industry, under demand and price uncertainties is considered in this paper. The problem is formulated using a two-stage stochastic programming model taking into account the production amount, the inventory and backorder levels as well as the amounts of products to be transported between the different plants and customers in each period. Risk management is addressed by incorporating a risk measure into the stochastic programming model as a second objective function, which leads to a multi-objective optimization model. The objectives aim to simultaneously maximize the expected net profit and minimize the financial risk measured. Two risk measures are compared: the conditional-value-at-risk and the downside risk. As the considered objective functions conflict with each other’s, the problem solution is a front of Pareto optimal robust alternatives, which represents the trade-off among the different objective functions. A case study using real data from textile and apparel industry in Tunisia is presented to illustrate the effectiveness of the proposed model and the robustness of the obtained solutions.     

Weak versus strong harmonic-expansion analyses of self-pulsing lasers: II—the inhomogeneously broadened system

A simple harmonic expansion method is applied to investigate some aspects of the dynamic properties of the integro-differential ‘Maxwell-Bloch’ equations that describe the self-pulsing regime of a single-mode inhomogeneously broadened laser. First, we show that the usual small perturbative methods only describe the transient relaxation oscillations, characteristic of the signal relaxing towards its permanent state, either stable or unstable. Second, we show that an adapted strong harmonic expansion analysis applied to the permanent pulsing solutions yields an accurate evaluation of the pulsing frequencies.     

Formulation DNLR intégrale des lois de comportement : généralisation du principe de superposition de BoltzmannDNLR integral formulation of behaviour laws: generalisation of Boltzmann's superposition principle.

A thermodynamic approach of relaxation phenomena called DNLR (Distribution of Non Linear Relaxations) has been employed for about fifteen years to describe the behaviour of materials. In this Note, we show that different DNLR constitutive equations, initially written in a rate formulation, can be put in a time-integrated (hereditary) form which generalises the superposition principle to non linear fields like viscoplasticity or damage behaviours. To cite this article: B. Martin et al., C. R. Mecanique 332 (2004).     

Investigation of Pr0.2Ce0.8O2-δ@Li2CO3 nanocomposite electrolytes as intermediate temperature ionic conductors: a thermal,structural, and morphological insight

Journal of Solid State Electrochemistry - Pr0.2Ce0.8O2-δ@Li2CO3 (PDC-LC) nanocomposite electrolytes were prepared through the co-precipitation of Pr-doped cerium/lithium complex carbonate and...