255. Additional bufadienolides from Ch'an Su. Toad venoms. 39

From the toad venom Ch'an Su the bufadienolides 1, 4, 9, 10, 12, 15, 17, 20, 22, 25 and 18 , the latter as diacetate 19 were isolated and their structure elucidated.     

Vacuum structure in gauge theories. The problem of strong CP violation and cosmology

An interplay between vacuum structure in gauge theories and cosmology is discussed and a possible solution of the strong CP violation problem in gauge theories is suggested.     

Small Deviations of Riemann-Liouville Processes In lq Spaces With Respect To Fractal Measures

We investigate Riemann–Liouville processes R_H, with H> 0, and fractional Brownian motions B_H, for 0 < H <1, and study their small deviation properties in the spacesL_q([0, 1], µ). Of special interest here are thin (fractal)measures µ, that is, those that are singular with respectto the Lebesgue measure. We describe the behavior of small deviationprobabilities by numerical quantities of µ, called mixedentropy numbers, characterizing size and regularity of the underlyingmeasure. For the particularly interesting case of self-similarmeasures, the asymptotic behavior of the mixed entropy is evaluatedexplicitly. We also provide two-sided estimates for this quantityin the case of random measures generated by subordinators. While the upper asymptotic bound for the small deviation probabilityis proved by purely probabilistic methods, the lower bound isverified by analytic tools concerning entropy and Kolmogorovnumbers of Riemann–Liouville operators. 2000 MathematicsSubject Classification 60G15 (primary), 47B06, 47G10, 28A80(secondary).     

Essential oil and fractions isolated of Laurel to control adults and larvae of cattle ticks

Abstract

This study, was to evaluate the acaricidal effect of the essential oil (EO) and fractions (FR) obtained from Laurus nobilis leaves on Rhipicephalus (Boophilus) microplus. Eight fractions were obtained, however FR1: sabinene (37.83%), β-pinene (13.50%), 1,8-cineole (12.66%), α-pinene (12.56%) and FR8: α-terpineol (79.19%) were highlighted as to the larvicidal potential when submitted by Larval Packet Test. The EO was tested by the Adult Immersion Test, at concentrations of 200.00; 100.00 and 50.00?µL/mL caused mortality of engorged females, egg mass reduction and hatching inhibition. Two fractions are shown to be efficient in controlling larvae FR8 (LC₅₀?=?0.13?µL/mL, LC₉₉?=?0.51?µL/mL) and FR1 (LC₅₀?=?0.20?µL/mL, LC₉₉?=?0.56?µL/mL). The fractionation of EO was determinant to elucidate which compounds were responsible for the larvicidal potential. This study opens new perspectives to direct new bioassays with the compounds obtained in the fractionation, since they present high potential on cattle tick larvae.     

Verschiedene Lebensmittel-Untersuchungsmethoden

Ohne Zusammenfassung     

Approximation of Gaussian Random Fields: General Results and Optimal Wavelet Representation of the Lévy Fractional Motion

We investigate the approximation rate for certain centered Gaussian fields by a general approach. Upper estimates are proved in the context of so–called Hölder operators and lower estimates follow from the eigenvalue behavior of some related self–adjoint integral operator in a suitable L ₂(μ)–space. In particular, we determine the approximation rate for the Lévy fractional Brownian motion X _H with Hurst parameter H∈(0,1), indexed by a self–similar set T?? ^N of Hausdorff dimension D. This rate turns out to be of order n ^?H/D (log?n)^1/2. In the case T=[0,1] ^N we present a concrete wavelet representation of X _H leading to an approximation of X _H with the optimal rate n ^?H/N (log?n)^1/2.     

Electrons Mediate the Gas‐Phase Oxidation of Formic Acid with Ozone

Gas‐phase reactions of CO₃^.? with formic acid are studied using Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometry. Signal loss indicates the release of a free electron, with the formation of neutral reaction products. This is corroborated by adding traces of SF₆ to the reaction gas, which scavenges 38 % of the electrons. Quantum chemical calculations of the reaction potential energy surface provide a reaction path for the formation of neutral carbon dioxide and water as the thermochemically favored products. From the literature, it is known that free electrons in the troposphere attach to O₂, which in turn transfer the electron to O₃. O₃^.? reacts with CO₂ to form CO₃^.?. The reaction reported here formally closes the catalytic cycle for the oxidation of formic acid with ozone, catalyzed by free electrons.     

Dynamical gain saturation in Kerr-lens mode-locked CW solid- state lasers

It is shown that dynamical gain saturation, usually neglected for solid-state lasers, can contribute significantly to the pulse-shaping mechanism in Kerr-lens mode-locked lasers. In particular, in combination with self-phase modulation it can cause red shifts and blue shifts of the laser spectrum. A control of the reciprocal gain and loss saturation rates using these shifts leads to improved mode- locking stability.     

Dual-cure processes: towards deformable crosslinked coatings

Two dual-cure processes consisting of a UV-initiated radical polymerization followed by either a UV-induced cationic polymerisation, or a thermal addition reaction, were investigated. The feasibility of the processes was studied using an acrylate-oxetane monomer for the UV/UV combination, and an acrylated oligoester for the UV/Heat combination. It was shown by FTIR and Tg measurements, that both steps of each process could be performed efficiently and separately. This allowed the production of a deformable partially cured coating, whose cure can then be completed, leading to the required final properties. Furthermore, it was demonstrated that the increase of the functionality of the reactive diluent led to a decrease of the thermal crosslinking extent. This is probably due to the reduced mobility of the reactive species that is caused by an enhanced UV crosslinking taking place during the first step.     

Selective adsorption, bound states, and potential parameters for He, Ne, and Ar interacting with a Cu(110) surface

Using nozzle beams of He, Ne, and Ar, we have measured diffractive selective adsorption resonances from a Cu(110) surface kept at 20 K. Bound state energies of the atom-surface potentials have been determined from plots of the measured resonance energies versus incident angle and their fits to calculated kinematical dispersion relations. For 3He and 4He we have found a unique level assignment that is compatible with a single gas-surface potential curve with a well depth of 6.05 meV of the He-Cu(110) potential. This value is about 10% larger than the prediction of 5.55 meV from the current physisorption theory. The Ne and Ar data reveal a large number of closely spaced levels with level separations and estimated van der Waals coefficients that are compatible with available theoretical data.