Reactions of saturated hydrocarbons I. Oxidation of isoparaffins by chromic acid

Measurements of the rate of reduction of chromium(VI) oxide in acetic acid–acetic anhydride solution by 2-methyl-pentane, 3-methylpentane, 2,3-dimethylbutane and 2,4-dimethylpentane show that the initial rate depends on the number and nature of carbon atoms in the hydrocarbon. When steric or other interaction effects prevail between adjacent atoms or groups in the molecule, these effects also influence the rate. The values obtained for the oxidation rates agree with those calculated from a proposed expression (Rn_p+R'n_s+R'n_t)/(n_p+n_s+n_t) based on the formula of Chambers & Ubbelohde.     

Extraction of delta-lognormal parameters from handwriting strokes

In the context of the Kinematic Theory of Rapid Human Movement, handwriting strokes are considered to be primitives that reflect the intrinsic properties of the neuromuscular system of a writer as well as the basic control strategies that the writer uses to produce such strokes. The study of these strokes relies on the extraction of the different parameters that characterize a stroke velocity profile. In this paper, we present a new method for stroke parameter extraction. The algorithm is described and evaluated under various testing conditions.     

Borates in hydrolysis of ammonia borane

Ammonia borane NH₃BH₃ (19.5 wt% H) is able to release hydrogen by hydrolysis in the presence of a catalyst in ambient conditions. This reaction has received considerable attention since 2006, with special focus on the catalytic material. In comparison, important aspects like the nature of the hydrolysis by-product(s) have been much less investigated while a good identification of the borate(s) is required for approaching recyclability. In this context, we present a work based on a systematic approach that aims at characterizing the hydrolysate, its stability in time, and the borate(s) recovered after drying. It is shown that the hydrolysate consists in aqueous B(OH)₃ and that the solution (catalyst-free) is stable when stored 6 months under argon atmosphere at 30 °C. The extraction of the water from the hydrolysate was performed at different conditions (vacuum, or air; from −50 to 500 °C). It is observed that the higher the temperature, the lower the hydration degree of the borates. The total dehydration, with the formation of B₂O₃, can be obtained at heating at 500 °C. The main problem with the hydrolysate is the release of NH₃ during the drying stage. A solution is to remove NH₃ after hydrolysis and to dry the NH₃-free hydrolysate. By this way, H₃B₃O₆ forms. Hence, B₂O₃ and H₃B₃O₆ could be recovered and recycled into ammonia borane. Besides the identification of the borates, the suitability of ammonia borane for hydrogen production by hydrolysis is discussed, especially in comparison with sodium borohydride NaBH₄.     

Static Ferromagnetic Modulation Revealed by Neutron Scattering in La1?xCaxMnO3

Mn perovskites La_1–x Ca _x MnO₃ (0x0.1) have been studied by small angle neutron scattering (SANS) and elastic neutron scattering (ESANS). At low temperature, both experiments reveal a broad modulation centered at the same q _m whatever the q direction. This scattering pattern is typical of a liquid-like distribution of similar magnetic droplets, or large magnetic polarons.     

Estimation of nonlinear systems via a Chebyshev approximation approach

This paper proposes to decompose the nonlinear dynamic of a chaotic system with Chebyshev polynomials to improve performances of its estimator. More widely than synchronization of chaotic systems, this algorithm is compared to other nonlinear stochastic estimator such as Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF). Chebyshev polynomials orthogonality properties is used to fit a polynomial to a nonlinear function. This polynomial is then used in an Exact Polynomial Kalman Filter (ExPKF) to run real time state estimation. The ExPKF offers mean square error optimality because it can estimate exact statistics of transformed variables through the polynomial function. Analytical expressions of those statistics are derived so as to lower ExPKF algorithm computation complexity and allow real time applications. Simulations under the Additive White Gaussian Noise (AWGN) hypothesis, show relevant performances of this algorithm compared to classical nonlinear estimators.     

Static Ferromagnetic Modulation Revealed by Neutron Scattering in La1−xCaxMnO3

Mn perovskites La_1?x Ca _x MnO₃ (0≤x0.1) have been studied by small angle neutron scattering (SANS) and “elastic” neutron scattering (ESANS). At low temperature, both experiments reveal a broad modulation centered at the same q _m whatever the q direction. This scattering pattern is typical of a liquid-like distribution of similar magnetic droplets, or large magnetic polarons.