Estimating the Scale Parameter of a Lévy-stable Distribution via the Extreme Value Approach

The characteristic exponent α of a Lévy-stable law S _α (σ, β, μ) was thoroughly studied as the extreme value index of a heavy tailed distribution. For 1 < α < 2, Peng (Statist. Probab. Lett. 52: 255–264, 2001) has proposed, via the extreme value approach, an asymptotically normal estimator for the location parameter μ. In this paper, we derive by the same approach, an estimator for the scale parameter σ and we discuss its limiting behavior.      

Quark mass effects toO(α s ) ine + e −→hadrons asymmetries and precision tests of electroweak physics

We estimate, to first order in α _s , quark mass effects on a number of fully integrated and “two-jet” asymmetries for the processe ⁺ e ^?→ \(q\bar q \to q\bar qg\) . We find that the effects of strong interactions are appreciably decreased, especially in the case of theb quark, with respect to the massless case. For the fully integrated asymmetries these effects are sizeable. Concentrating on the “two-jet” asymmetries, we find that for small values of the parameters ε and δ defining a ”two-jet” event all the asymmetries are α _s independent. For larger values of these parameters this is no longer true. However it is still possible to define regions in the (ε, δ) plane where the strong interaction effects can be made arbitrarily small. These important features enhance the role of “two-jet” asymmetries as specially convenient candidates for high precision tests of Electroweak Physics.     

Investigation on corrosion inhibition and adsorption mechanism of azomethine derivatives at mild steel/0.5 ​M ​H2SO4 solution interface: Gravimetric,electrochemical, SEM and EDX studies

The inhibition performance of five azomethine derivatives such as: 1-(4-Methyloxy phenylimino)-1-(phenylhydrazono)-propan-2-one (SB₁), 1-(4-Methylphenylimino)-1-(phenylhydrazono) propan-2-one (SB₂), 1-(phenylimino)-1(phenylhydrazono)-propan-2-one (SB₃), 1-(4-Bromo phenylimino)-1(phenylhydrazono)-propan-2-one (SB₄) and 1-(4-Chlorophenylimino)-1(phenylhydrazono) -propan-2-on (SB₅) as corrosion inhibitors for mild steel in sulfuric acid 0.5 ?M were investigated using different methods. All experimental results demonstrate that these compounds are eficients inhibitors. The inhibition efficiencies ($IE$) increase with inhibitors concentration. At 7.5 $\times$ 10^?5 ?M, the $IE$ was 97.27%, 96.31%, 94.23%, 93.19 and 91.64% for SB₁, SB₂, SB₃, SB₄ and SB₅, respectively. The potentiodynamic polarization results indicated that all the studied inhibitors act as mixed type. The adsorption process on mild steel surface obeyed Langmuir isotherm. The associated activation parameters and thermodynamic have been calculated and discussed. The adsorbed film formed on the metal surface was characterized by SEM and EDX.     

Low-temperature formation and characterization of Cu2O nanoparticles in the binary gold alloys

Thermal analyses, using differential scanning calorimetry (DSC) and dilatometry, reveal an important anomaly at low temperature for Au-25 wt.% Cu composition after homogenization at 700°C during 2 hours under vacuum followed by heating up to 160°C before water quenching. This anomaly has been already observed and not explained. Surface characterization, using scanning electron microscopy (SEM), atomic force microscopy (AFM), and scanning tunneling microscopy (STM), exhibits a specific topography, consisting of a nanostructured surface. The precipitates of nanostructured particles are homogeneously scattered all over the surface for this 18-carat gold alloy. Moreover, X-ray photoelectron spectroscopy (XPS) shows that the composition of the observed particles corresponds to cuprous oxide phase (Cu₂O). The formation of such material can be explained by the diffusion of copper atoms from the lattice to the surface at 160°C. Pulsed radio-frequency glow discharge optical emission spectroscopy (RF GD-OES) further proves the proposed Cu₂O formation through a diffusion process. The appearance of such cuprous oxide nanoparticles on the Au-Cu alloy surface explains the low-temperature DSC and dilatometry anomaly and affects directly the surface electrical resistance at low temperature. These results might open a large gate for new ideas to investigate in catalytic, electronic, and antimicrobial activities.     

Topology change from quantum instability of gauge theory on fuzzy CP

Many gauge theory models on fuzzy complex projective spaces will contain a strong instability in the quantum field theory leading to topology change. This can be thought of as due to the interaction between space–time via its noncommutativity and the fields (matrices) and it is related to the perturbative UV–IR mixing. We work out in detail the example of fuzzy CP²${\mathbf{CP}}^2$ and discuss at the level of the phase diagram the quantum transitions between the 3 spaces (space–times) CP²${\mathbf{CP}}^2$, S²${\mathbf{S}}^2$ and the 0-dimensional space consisting of a single point {0}$\{0\}$.     

A numerical dispersion compensation technique for time recompression of Lamb wave signals

A Fourier domain numerical reconstruction technique has been created in order to eliminate the time spread of Lamb wave signals caused by their dispersive nature. This method allows a good time compaction of the echoes obtained from a Lamb wave inspection. In a pulse-echo setup, reflection peaks coming from targets located close one from each other that could not be separated or seen within raw signals are identified using this procedure. The utility of this new technique goes from simple signal analysis to imaging purposes such as the improvement of B-scan images or SAFT processing. It has been tested in three different situations with the S0 mode generated in a frequency bandwidth where it is highly dispersive. The reconstruction of a pure reflection coming from the edge of a plate, the separation of the echoes resulting from reflections on two targets near one each other and the effects of the presence of an obstacle between the emitter and the receiver are treated. Good results are obtained for every case studied.