Cellulose acetate deacetylation in benzene/acetic acid/water systems

An unconventional system for cellulose acetate hydrolysis, consisting of homogeneous mixtures of benzene/acetic acid/water of different compositions, was investigated from the perspective of kinetics and also with respect to the degradation of the cellulosic chains during the process. It was observed that the decrease of the degree of substitution of the polymer occurs with higher reaction rate than that in the reference system, free of benzene, and depends on the composition of the reaction medium. A pseudo–first‐order kinetic law satisfactorily describes the deacetylation process performed in the presence of benzene. Also, the degradation of the polymeric chain during the process is dependent on the presence of the hydrocarbon and on the composition of the reaction system used. A lower degradation rate was found to characterize the first period of the process, compared with that produced in a benzene‐free system. These peculiarities were explained by the influence of benzene on the composition of solvent shell in the vicinity of macromolecules. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1965–1968, 2004     

Influence of the substitution degrees on the optical properties of cellulose acetates

Cellulose acetates with different substitution degrees possess a set of properties that makes them highly suitable for optical applications. This article discusses some of these properties, namely refractivity, dielectric properties, and transmittance. The contribution of the ratio between the molar refraction, which is proportional to the induced dipole moment, and the molar volume for the different atoms present in the studied polymers to the optical properties was investigated. The study illustrates the importance of such structural and compositional characteristics in tailoring some specific optical applications. Furthermore, optical transmission has been investigated in the 200–1000 nm range. To obtain the optical parameters, the approach proposed by Tauc for amorphous semiconductors has been used because of the similarity of the absorption edges. The values of pseudogap energy ranged between 3.44 and 4.70 eV, whereas those of Urbach energy were modified in the 18–37 meV range. All parameters determined have been related to the influence of the substitution degrees and of the synthesis condition. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

New Potential Antitumor Pyrazole Derivatives: Synthesis and Cytotoxic Evaluation

New pyrazole derivatives were designed and synthesized as potential protein kinase inhibitors in the view to develop specific antitumor therapies. The structures of the compounds were elucidated using spectral and elemental analyses. The antitumor potential was estimated using wheat seeds and the general toxicity was evaluated by alternative methods, using invertebrate animals. One 3-aminopyrazole derivative emerged as a potential candidate for the development of future cytotoxic compounds.     

Hybrid modelling and constrained control of juggling systems

The goal of this article is to review the modelling framework for juggling systems by stressing the particularities of switching dynamics and to design a controller for the systems based on a reformulation of the model predictive control design. The main idea is to catch an impact during the prediction window at the desired level. One of the particularities is the on-line adaptation of the optimisation problem such that the receding prediction window assures the existence of an impact at a certain moment in absolute time. A constraints softening technique will be used to avoid the in-feasibility problems. In a first stage, the basic juggling system which consists of a ball and a juggling robot in one-dimensional case is detailed and subsequently the study is extended to the case of multiple balls juggling with two degrees of freedom. The simulation results demonstrate the performance of the presented approach.     

Explicit improved vertex control for uncertain,time‐varying linear discrete‐time systems with state and control constraints

A technique is presented to compute an explicit state feedback solution to the regulation problem for uncertain and/or time‐varying linear discrete‐time systems with state and control constraints. A piecewise affine control law is provided that not only guarantees recursive feasibility and robust asymptotic stability but is also optimal for a region of the state space containing the origin. Copyright © 2015 John Wiley & Sons, Ltd.     

Receding horizon flight control for trajectory tracking of autonomous aerial vehicles

This paper addresses the implementation of a predictive control strategy for Unmanned Air Vehicles in the presence of bounded disturbances. The goal is to prove the feasibility of such a real-time optimization-based control design and to demonstrate its tracking capabilities for the nonlinear dynamics with respect to a reference trajectory which is pre-specified via differential flatness. In order to benefit from the computational advantages of the linear predictive control formulations, an off-line linearization strategy of the nonlinear model of the vehicle along the flat trajectory is employed. The proposed method exhibits effective performance validated through software-in-the-loop simulations and real flight tests on different Unmanned Aerial Vehicles (UAVs).     

On the kinematic guidance of 3R-S open-loop robot manipulatorsSur le guidage cinematique des robots manipulateurs 3R-S a chaine ouverte

This paper develops the kinematic analysis procedure of open-loop robot manipulators with six degrees of mobility that contain in their structure three rotational pairs and one spherical joint. The equivalent closed-loop linkage approach suggested in some previous works of the author[2–5] is applied here for analyzing several dimensional and structural variants with different locations of the S-joint in the kinematic chain. For any prescribed position and orientation of the manipulating link, the expressions of all joint parameters are presented in an explicit form suitable for digital programming and computation. The algebraic noniterative procedure proposed for resolving the closed-form positional functions allows the accurate guidance of the free end along a programmed spatial path or through imposed discrete positions and favors the real-time CNC of the robot manipulator.     

Robust multi-model predictive control using LMIs

International Journal of Control, Automation and Systems - This paper proposes a novel synthesis technique for robust predictive control of constrained nonlinear systems based on linear matrix...     

Protective coatings based on silsesquioxane nanocomposite films for building limestones

The present paper reports on the evaluation of mineral composition of two porous limestones, i.e., a bioclastic limestone with large pore radii and grain size and a dolomitic one of small pore radii and grain size, used as monumental building stones, and on the influence of a new silicon-based hybrid polymer nanocomposite with silsesquioxane units (TMSPMA), used as protective coating material, on their composition and crystallographic properties. TMSPMA was obtained through radical polymerization of 3-(trimethoxysilyl)propyl methacrylate in the presence of a primary amine surfactant, via sol–gel technique. TMSPMA protective coating was proved to act as water repellent or as consolidant, function of stone composition, structure and porosity.     

Effects of Venlafaxine,Risperidone and Febuxostat on Cuprizone-Induced Demyelination,Behavioral Deficits and Oxidative Stress

Multiple sclerosis (MS) is a demyelinating, autoimmune disease that affects a large number of young adults. Novel therapies for MS are needed considering the efficiency and safety limitations of current treatments. In our study, we investigated the effects of venlafaxine (antidepressant, serotonin-norepinephrine reuptake inhibitor), risperidone (atypical antipsychotic) and febuxostat (gout medication, xanthine oxidase inhibitor) in the cuprizone mouse model of acute demyelination, hypothesizing an antagonistic effect on TRPA1 calcium channels. Cuprizone and drugs were administered to C57BL6/J mice for five weeks and locomotor activity, motor performance and cold sensitivity were assessed. Mice brains were harvested for histological staining and assessment of oxidative stress markers. Febuxostat and metabolites of venlafaxine (desvenlafaxine) and risperidone (paliperidone) were tested for TRPA1 antagonistic activity. Following treatment, venlafaxine and risperidone significantly improved motor performance and sensitivity to a cold stimulus. All administered drugs ameliorated the cuprizone-induced deficit of superoxide dismutase activity. Desvenlafaxine and paliperidone showed no activity on TRPA1, while febuxostat exhibited agonistic activity at high concentrations. Our findings indicated that all three drugs offered some protection against the effects of cuprizone-induced demyelination. The agonistic activity of febuxostat can be of potential use for discovering novel TRPA1 ligands.