Uncertainty principles for the continuous wavelet transform in the Hankel setting

Shapiro’s dispersion and Umbrella theorems are proved for the continuous Hankel wavelet transform. As a side results, we extend local uncertainty principles for set of finite measure to the latter transform.     

Synthesis and chemistry of new spiro‐Δ1‐pyrazoline

In explorations of syntheses and chemistry of spiroheterocycles, we found that the reaction of 2‐diazopropane with (E)‐α‐arylidenepyrrolin‐2‐one, (E)‐α‐arylidene‐γ‐butyrolactone, and (E)‐arylidene‐N‐arylsuccinimide derivatives produced spiro‐Δ¹‐pyrazolines. The photolysis of Δ¹‐pyrazolines has led to cyclopropanes. The structures of the obtained adducts have been assigned by means of spectroscopic measurements. J. Heterocyclic Chem., (2011).     

Probing PAH formation chemical kinetics from benzene and toluene pyrolysis in a single-pulse shock tube

Benzene and toluene were pyrolyzed under highly argon-diluted conditions at a nominal pressure of 20 bar in a single-pulse shock tube coupled to gas chromatography/gas chromatography–mass spectrometry (GC/GC–MS) diagnostics. Concentration evolutions of polycyclic aromatic hydrocarbon (PAH) intermediates were measured in a temperature range of 1100–1800 K by analyzing the post-shock gas mixtures. Different PAH speciation behaviors, regarding types, concentrations and formation temperature windows, were observed in the two reaction systems. A kinetic model was proposed to predict and interpret the measurements. Through a combination of experimental and modeling efforts, PAH formation patterns from species pools of benzene and toluene pyrolysis were illustrated. In both cases, channels leading to PAHs basically originate from the respective fuel radicals, phenyl and benzyl. Due to the higher thermal stability of benzene, the production of phenyl, and thus most PAH species, occur in higher temperature windows, in comparison to the case of toluene. In benzene pyrolysis, benzyne participates in the formation of crucial PAH species such as naphthalene and acenaphthylene. Phenyl self-recombination takes considerable carbon flux into biphenyl, which serves as an important intermediate leading to acenaphthylene through hydrogen loss and ring closure. The resonantly-stabilized benzyl is abundant in toluene pyrolysis, and its decomposition further produces other resonantly-stabilized radicals such as fulvenallenyl and propargyl. Barrierless addition reactions among these radicals are found to be important sources of PAHs. Fuel-specific pathways have pronounced effects on PAH speciation behaviors, particularly at lower temperatures where fuel depletion is not completed within the reaction time of 4.0 ms. Contributions from the commonly existing Hydrogen-Abstraction-Carbon-Addition (HACA) routes increase with the temperature in both cases.     

Facile and efficient synthesis of functionalized iminothiopyran and isothiochromen via one-pot multicomponent reactions

An efficient synthesis of 6H-6-iminothiopyran-2,3-dicarboxylate and 1H-isothiochromene-3,4-dicarboxylate derivatives via one-pot reactions between acetylenic esters, aryl isothiocyanates and enaminones in dichloromethane at room temperature is described. The mild reaction condition, high yields and the new products are advantages of our method.     

Effect of doping by Bi and Ca on ferroelectric properties and relaxor character in the (Ba1−xCax)1−3y/2BiyTiO3 solid solution

The temperature dependence of the real and imaginary parts of dielectric permittivity for (Ba_1?xCa_x)_1?3y/2Bi_yTiO₃ solid solution prepared using the solid-state reaction technique, suggests that the relaxor character in this solid solution depends strongly on the Bi than on the Ca doping percent.X-ray diffraction analysis show that Bi doping can be fully incorporated into the perovskite lattice of (Ba_1?xCa_x)TiO₃. Doping with Bi causes remarkable shift of the maximum of dielectric permittivity (T_m) at low temperatures and the evolution of ε′_r exhibiting strong frequency dispersion. For some compositions, we have observed a typical behavior of a well-known relaxors. On the other hand, we pointed out that the relaxor character is linked principally to the nature of the substituting element and not to the heterogeneity in general. So the Ca element does not have the same effect as the Bi one.     

Conductivity relaxation parameters of some H and K conducting in the polycrystalline compound KDyHP3O10

Polycrystalline samples of KDyHP₃O₁₀ was obtained by heating for 12 hour at 553 K a mixture containing K₂CO₃, Dy₂O₃ and H₃PO₄. Samples were characterized through X-ray diffraction, examined by IR vibrational spectroscopy and impedance and modulus spectroscopy techniques. The conductivity relaxation parameters of some H⁺ and K⁺ conducting in this compound have been determined from an analysis of ac conductivity data measured in a wide temperature range. Transport properties in this material appears as due to H⁺ and K⁺ ions hopping mechanism. The stretched exponential function exp[−(t/τ_σ)^β] has been used to describe the conductivity relaxation. The relaxation parameters have been investigated as a function of the nature of mobile ions. The results obtained are shown to be in good agreement with the predictions of the Ngai coupling model.     

Ferroelectric (Na1/2Bi1/2)TiO3 thin films showing photoluminescence properties

Polycrystalline lead-free (Na_1/2Bi_1/2)TiO₃ (NBT) ferroelectric thin films doped with 1 mol% of rare earth (RE) elements are processed on Pt-terminated silicon substrates using a solution deposition method. The thin films that exhibit single-phase perovskite structure show photoluminescence properties with highest intensities in the wavelength range between 700 and 850 nm, depending on RE element. The ferroelectric properties of the pure NBT film (P _r: 20.5 µC cm^?2, E _c: 150 kV cm^?1) are somewhat decreased for the doped films, which is ascribed to decreasing of the number of Bi lone pairs through the substitution of Bi with RE elements in the perovskite lattice.     

Electrochemical properties of LaY2Ni9 hydrogen storage alloy,used as an anode in nickel-metal hydride batteries

The electrochemical properties of LaY₂Ni₉ alloy used as an anode in nickel-metal hydride batteries were investigated at ambient and at different temperatures. Several techniques, such as the galvanostatic charging and discharging, the constant potential discharge, and the potentiodynamic polarization, were applied to characterize these electrochemical properties. The discharge capacity of the LaY₂Ni₉ alloy increases to reach 258 mAh g^?1 after 5 cycles and decreases to 140 mAh g^?1 after 100 cycles then stabilizes around this same value indicating good cycling held. The hydrogen diffusion coefficient D _H in the bulky alloy is estimated to be (1.02?±?0.11)?×?10^?11 cm² s^?1 correlated with the good stability of electrochemical capacity after 100 cycles. The evolution of the ratio \( \frac{D_{\mathrm{H}}}{a^2} \) and the corrosion current density and potential are correlated with the evolution of the electrochemical capacity during the activation and for a long cycling. The enthalpy, the entropy, and the apparent activation energy of the LaY₂Ni₉ hydride formation are evaluated. The calculated results show that the enthalpy change, the entropy change, and the activation energy are (?42.64?±?1.08), (56.85?±?2.11), and (14.84?±?0.35)?kJ mol^?1, respectively.     

Investigations of molybdenum redox phenomenon in Li2O-MoO3-P2O5 phosphate glasses

Two series of glasses have been prepared and characterized. One with varying Li₂O/P₂O₅ ratio and the other with varying Mo/P ratio. The relationship between the formation of the reduced state of molybdenum in phosphate glasses and the type of gases released in heating batch materials has been investigated. Effect of temperature on the valence state of molybdenum is also studied. Oxidation-reduction (redox) equilibrium of Mo⁵⁺/Mo⁶⁺ and environment of molybdenum (V) in these series of lithium-molybdenum-phosphate glasses are related to the glass composition and the possible structural units formation in the glasses.     

Water behaviour in processed cheese spreads

The behaviour of water in two processed cheese spreads, either standard or cream-enriched, was studied by differential scanning calorimetry (DSC) in the −50 to 45 °C temperature range as a function of controlled dehydration. The results were analyzed and related to cheese microstructures observed by environmental scanning electron microscopy (ESEM). Water freezing and subsequent ice melting were found to be dependent on the cheese composition in hydrophilic components and on water confinement within the micro-domains delimited by the fat droplets. Both cheeses exhibited partial water freezing from supercooling state while ice nucleation process was shown to be tightly affected by water connectivity within the cheese matrices.