The N-terminal His-tag affects the enantioselectivity of staphylococcal lipases: a monolayer study

In order to check the influence of the polyhistidine tag at the N-terminus of recombinant lipases, a comparative study on the interfacial properties of native and recombinant Staphylococcus simulans (SSL and rSSL) or Staphylococcus xylosus lipase (SXL and rSXL) was investigated using the monomolecular film technique. No phospholipase activity was detected with rSSL or rSXL when using different phospholipids spread as monomolecular films maintained at various surface pressures, suggesting that the His-tag in the N-terminus of the recombinant proteins, do not affect the substrate recognition. The critical surface pressure measured with monomolecular films of egg-PC was slightly lowered with the two recombinant proteins compared to the native SSL or SXL one. A kinetic study on the surface pressure dependency, stereoselectivity and regioselectivity of native and recombinant SSL or SXL was performed using three dicaprin isomers spread as monomolecular films at the air-water interface. Our results show clearly that the presence of polyhistidine tag at the N-terminus of SSL or SXL changes their stereo- and regioselectivity.     

The rapid cooling of a hot gas discharge by liquid sprays

The cooling effect of liquid droplets introduced into a hot gas stream flowing in an adiabatic duct is analysed. The coupled interaction between the changes in the droplets and in the surrounding gas conditions is examined as a result of droplets vaporization. It was found that the use of liquid sprays as a rapid cooling process for a hot gas discharge is quite effective.     

Improvement of thermal and spectroscopic behavior of Er<Superscript>3+</Superscript>/Ce<Superscript>3+</Superscript> co-doped tellurite glass for lasing materials

Tellurite glasses (TeO₂–ZnO–Nb₂O₅) mono-doped Er³⁺ and co-doped Er³⁺/Ce³⁺ have been prepared using the melt-quenching technique. To evaluate the effect of Ce³⁺ on the structural, thermal stability of glass hosts and fluorescence properties of Er³⁺, X-ray diffraction patterns, Ftir spectra, differential scanning calorimeter curves, absorption spectra, fluorescence emission spectra, fluorescence lifetimes, up-conversion emission spectra of glass samples were measured and investigated. Using Judd–Ofelt theory, we calculated intensity parameters (Ω₂, Ω₄ and Ω₆), spontaneous emission probabilities, the radiative lifetime, luminescence branching factors and the quantum yield of luminescence for ⁴I_13/2 → ⁴I_15/2 transition. The co-doping with Ce³⁺ was effective on the suppression of up-conversion emission of Er³⁺ owing to the phonon-assisted energy transfer: Er³⁺:⁴I_11/2 + Ce³⁺:²F_5/2 → Er³⁺:⁴I_13/2 + Ce³⁺:²F_7/2 which contributed the effective enhancement of 1.53 µm fluorescence emission. The change in optical properties with the addition of Ce³⁺ ions have been discussed and compared with other glasses. Using the Mc Cumber method for the ⁴I_13/2 → ⁴I_15/2 transition, absorption cross-section, calculated emission cross-section, and gain cross-section values support that TZNEr1Ce1 glass is a potential material for developing broad-band and high-gain erbium-doped fiber amplifiers applied for 1.53 µm.     

Vibration testing for anomaly detection

In this paper we propose an efficient method to reconstruct a small inclusion buried inside a body using the perturbation of modal parameters measured on the boundary of the body. We design a reconstruction algorithm based on the asymptotic expansions of the eigenvalue perturbations obtained by Ammari and Moskow (Math. Meth. Appl. Sci. 2003; 26 :67–75). We then implement this algorithm and demonstrate its viability and limitations. Copyright © 2008 John Wiley & Sons, Ltd.     

Gross Laplacian Acting on Operators

In this paper, we introduce a noncommutative extension of the Gross Laplacian, called quantum Gross Laplacian, acting on some analytical operators. For this purpose, we use a characterization theorem between this class of operators and their symbols. Applying the quantum Gross Laplacian to the particular case where the operator is the multiplication one, we establishes a relation between the classical and the quantum Gross Laplacians.      

Bifurcation analysis of a two-DoF mechanical system subject to digital position control. Part II. Effects of asymmetry and transition to chaos

Considering a two DoF system subject to digital position control, of interest for robotic application, we analyze the dynamics of the system at the intersection of two loci of Neimark–Sacker bifurcations, where a double Neimark–Sacker bifurcation is taking place. In the system, the saturation of the control force is the only nonlinear term considered, other than this, the system is piecewise linear. Starting from the analytical investigation already performed in Part I (Habib et al. in Nonlin. Dyn., under review, 2013), in this paper the effects of an asymmetry of the saturation of the control force are investigated, both analytically and numerically. The results show the increasing complexity of the dynamics for a more and more asymmetric system. First, the asymmetry is making the bifurcation transit from supercritical to subcritical, then it generates a stable torus that breaks down into a strange attractor, associated with a chaotic motion. In the last part of the paper, the torus breakdown and the onset of chaos are investigated, furthermore the evolution of complex dynamics through regions of phase locking and higher-dimensional chaos is outlined.