TLC and HPLC Analysis of the Phenolic Acids in Silphium perfoliatum L. Leaves,Inflorescences and Rhizomes

JPC – Journal of Planar Chromatography – Modern TLC - TLC and HPLC have been used for preliminary evaluation of the phenolic acids occurring in the leaves, inflorescences, and rhizomes...     

H-bonding dependent structures of (NH4+)3H+(SO4 2-)2. Mechanisms of phase transitions

The role of different H-bonds in phases II, III, IV, and V of triammonium hydrogen disulfate, (NH(4)(+))(3)H(+)(SO(4)(2)(-))(2), has been studied by X-ray diffraction and (1)H solid-state MAS NMR. The proper space group for phase II is C2/c, for phases III and IV is P2/n, and for phase V is P onemacr;. The structures of phases III and IV seem to be the same. The hydrogen atom participating in the O(-)-H(+).O(-) H-bond in phase II of (NH(4)(+))(3)H(+)(SO(4)(2)(-))(2) at room temperature is split at two positions around the center of the crucial O(-)-H(+).O(-) H-bonding, joining two SO(4)(2)(-) tetrahedra. With decreasing temperature, it becomes localized at one of the oxygen atoms. Further cooling causes additional differentiation of possibly equivalent sulfate dimers. The NH(4)(+) ions participate mainly in bifurcated H-bonds with two oxygen atoms from sulfate anions. On cooling, the major contribution of the bifurcated H-bond becomes stronger, whereas the minor one becomes weaker. This is coupled with rotation of sulfate ions. In all the phases of (NH(4)(+))(3)H(+)(SO(4)(2)(-))(2), some additional, weak but significant, reflections are observed. They are located between the layers of the reciprocal lattice, suggesting possible modulation of the host (NH(4)(+))(3)H(+)(SO(4)(2)(-))(2) structure(s). According to (1)H MAS NMR obtained for phases II and III, the nature of the acidic proton disorder is dynamic, and localization of the proton takes place in a broader range of temperatures, as can be expected from the X-ray diffraction data.     

Mathematical model of aerobic stabilization of old landfills

A short-term aerobic stabilization of digested waste in the final methane phase was studied. The effect of aeration rate on the reduction of leachate parameters and on the rate of CO₂ production and O₂ assimilation was investigated. Experimental simulation of aerobic landfill stabilization was carried out using lysimeters. When testing the effect of aeration rate on the reduction of leachate indices (BOD₅, COD, N-NH₄⁺), it was reported that the most significant reduction was obtained at the highest rate of aeration and the smallest reduction of leachate indices was attained not at the lowest but at medium aeration rates. Both the rate of CO₂ production and the O₂ assimilation reached their highest values in the lysimeters aerated at a high rate of aeration. The proposed mathematical model which consists of a system of five differential equations describing CO₂ production, O₂ assimilation and the changes of organic carbon content in the leachate correspond well with the experimental data.     

Reaction of Phenolic Mannich Base with Trialkyl Phosphite

Dialkyl [2-hydroxy-5-(phenylazo)benzyl]phosphonates were prepared by a convenient procedure in good yield from Mannich base and trialkyl phosphite in benzene with the elimination of ammonium or morpholinium cation. 2-[(Dialkylamino)methyl]-4-(phenylazo)phenol methiodide is a new reagent in the Michaelis-Arbuzov reaction.     

A New Phosphonium Calix[4]arene for Selective Anion Recognition: Synthesis and Studies in Solution and in Ion Selective Electrodes

The synthesis and characterization of a new tetra (triphenylphosphonium) p-tert-butylcalix[4]arene 2 is presented. Its interactions with anions were studied by ¹H and ³¹P NMR and UV absorption spectrophotometry, showing the biggest interaction with ClO₄ ^? , I^?  and SCN^? . Anion selectivity in ion-selective PVC-membrane electrodes (ISEs) plasticized with o-NPOE containing ionophore 2 was also investigated. Compound 2 shows a potentiometric response for various anions with the following selectivity pattern: ClO₄ ^?  > SCN^?  > I^?  > Cr₂O₇ ^2 ?  > NO₃ ^?  > Br^?  > Cl^? .     

Promoted ternary CuO-ZrO2-Al2O3 catalysts for methanol synthesis

Ternary CuO-ZrO₂-Al₂O₃ catalysts promoted by palladium or gold were prepared and tested in CO hydrogenation reaction at 260°C under elevated pressure (4.8 MPa). The promotion effect of palladium or gold addition on the physicochemical and catalytical properties of CuO-ZrO₂-Al₂O₃ catalysts in methanol synthesis (MS) was studied. The catalysts were characterized by BET, XRD, TPR-H₂, TPD-NH₃ methods. The BET results showed that the ternary system CuO-ZrO₂-Al₂O₃ had the largest specific surface area, cumulative pore volume and average pore size in comparison with the promoted catalysts. The yield of methanol can be given through the following sequence: 5%Pd/CuO-ZrO₂-Al₂O₃ > CuO-ZrO₂-Al₂O₃ > 2%Au/CuO-ZrO₂-Al₂O₃. We also found that the presence of gold or palladium on catalyst surface has strong influence on the reaction selectivity. The high selectivity of gold doped ternary catalyst is explained by the gold-oxide interface sites created on the catalyst surface and the acidity of those systems. The higher selectivity to methanol in the case of the palladium catalyst is explained by the spillover effect between Pd and CuO.      

1/f Flux noise in Josephson phase qubits

We present a new method to measure 1/f noise in Josephson quantum bits (qubits) that yields low-frequency spectra below 1 Hz. A comparison of the noise taken at positive and negative bias of a phase qubit shows the dominant noise source to be flux noise and not junction critical-current noise, with a magnitude similar to that measured previously in other systems. Theoretical calculations show that the level of flux noise is not compatible with the standard model of noise from two-level state defects in the surface oxides of the films.