A Global Newton Method for the Nonsmooth Vector Fields on Riemannian Manifolds

Journal of Optimization Theory and Applications - This paper proposes and analyzes a globalized version of the Newton method for finding a singularity of the nonsmooth vector fields. Basically, the...     

The effectiveness of the organosolv process in wheat straw delignification optimizing temperature and time reaction

Cellulose - The present study investigates the organosolv treatment of wheat straw, for the optimization of cellulose delignification, which will serve as raw material for the paper industry. The...     

Coends of Higher Arity

Applied Categorical Structures - We specialise a recently introduced notion of generalised dinaturality for functors $$T : (\mathcal {C}^\mathsf {op})^p \times \mathcal {C}^q \rightarrow \mathcal...     

Crystallization of the mesomorphic form and control of the molecular structure for tailoring the mechanical properties of isotactic polypropylene

The combination of the control of the concentration of stereodefects in isotactic polypropylene using metallocene catalysts and the crystallization via the mesophase is a strategy to tailor the mechanical properties. Stiff materials, flexible materials, and thermoplastic elastomers can be produced depending only on the concentration of rr stereodefects. Modulus, ductility, and strength can be modulated through the crystallization of α and γ forms or of the mesophase. Different morphologies are observed depending on the stereoregularity and conditions of crystallization. Crystals of the mesomorphic form always exhibit a nodular morphology, accounting for the similar good deformability of all quenched samples, whatever the concentration of stereodefects. The mesophase transforms by thermal treatments into the α form preserving the nodular morphology, with increase of strength while maintaining the ductility typical of the mesophase. Annealing of the mesophase permits a precise adjustment of crystallinity and size of nodular crystals offering additional options to modify the mechanical properties. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 677–699     

Degradation of a polyester‐urethane coating: Physical properties

In this article we studied the evolution of thermomechanical properties of a polyester‐urethane coating during degradation under different degradation conditions, i.e., aerobic and anaerobic conditions with and without dry/wet cycling during degradation. Dynamic mechanical and thermal analyses show that under aerobic conditions the coatings become stiffer and more brittle in the glassy state. This stiffening is probably due to the increase in the amount of hydrogen bonding and the formation of oxidized groups which increase the polarity of the material and enhance the interactions of the polymer segments. However, oxidation reactions result in a considerable decrease in cross‐link density and stiffness in the rubbery state. Both changes, in the glassy and rubbery states, give rise to development of internal stresses. These stresses increase as the degradation process proceeds. Nevertheless, for samples exposed to anaerobic conditions, the stiffness remains constant in the glassy state and the cross‐link density slightly increases as a result of degradation. This reconfirms the dominance of the effect of oxidation reactions on the mechanical failure of the coatings. Oxygen permeation measurements show a more‐or‐less time‐independent diffusion coefficient and a gradual decrease in solubility of oxygen as a function of exposure time. This results in a slight decrease in oxygen permeation (mainly in the early stage of the degradation) as degradation proceeds. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 659–671     

Surfactant effect on electrochemical-induced synthesis of α-Ni(OH)2

Nickel hydroxide films were electrosynthesized in the presence of different diluted surfactant solutions by galvanostatic electroprecipitation. Lamellar α-Ni(OH)₂ films are obtained using cationic surfactant cetyltrimethylammonium bromide (CTAB), anionic surfactant sodium dodecyl sulfate (SDS), and also neutral surfactant Tween® 80. The films were structurally and morphologically characterized by X-ray diffraction, thermal gravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy, and electrochemically by cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM). The results evidenced that SDS remains intercalated between the lamellae of α-Ni(OH)₂. Albeit the presence of CTAB and Tween® 80, it was noticed in FTIR spectra that the surfactants did not intercalate. The morphology was affected by the presence of different surfactants. All studied surfactants displaced the oxidation potential (E _O) of Ni²⁺/Ni³⁺ process to less positive values. Also, the presence of surfactants improved the electrode charge efficiency and the charge response for the same number of moles of nickel ions deposited. The ratio of the charge and frequency change is 4.4 times bigger for films deposited with SDS when compared with pure α-Ni(OH)₂ films.     

Synthesis of the bicyclo[6.2.1]undecane ring system by a solvent-free Diels–Alder reaction

A bicyclo[6.2.1]undecane model compound of the core structure of the biologically active furanoheliangolide sesquiterpene was synthesized. This new and short route was developed by using a solvent-free Diels–Alder reaction between cyclopentadiene and 3-nitro-2-cyclohexenone, followed by simple transformations. Theoretical calculations were performed in order to understand reactivity aspects of the cycloaddition.