Determination of three major triterpenoids in epicuticular wax of cabbage (Brassica oleracea L.) by high-performance liquid chromatography with UV and mass spectrometric detection

Lupeol, together with alpha- and beta-amyrins in smaller quantities, has been found for the first time in the epicuticular wax of white cabbage (Brassica oleracea L. convar. capitata (L.) Alef. var. alba DC) leaf surface extract. The three triterpenoids were identified by a new high-performance liquid chromatographic (HPLC) method with UV and mass spectrometric (MS) detection using atmospheric pressure chemical ionization (APCI). All three isomeric compounds gave a parent ion peak at m/z 409 [M+H-18](+) and the relative intensities of some characteristic fragment ion peaks in tandem mass spectrometric (MS-MS) spectra of this parent ion enabled differentiation between the isomers. An additional peak at m/z 439 [M+H](+), which could be oleanonic or ursonic aldehyde, was detected by HPLC-APCI-MS. Saponification of cabbage leaf surface extract with 20% NaOH in methanol at 65 degrees C for 2h had no influence on lupeol, or alpha- or beta-amyrins, but lead to the formation of three additional compounds, which were not identified.     

Optimal Control in Autonomous Driving

Autonomous driving is no longer a subject of science fiction. Instead it has become a field of highly topical developments and has already reached numerous milestones. The Audi Autonomous Driving Cup provides a stage for students to participate in this development process. This competition, carried out in Germany, Austria and Switzerland, provides miniature vehicles of normed hardware to the participants which have the task of implementing algorithms for autonomous handling of problems such as lane tracking, obstacle detection, adaptive cruise control, overtaking, turning as well as entering and exiting parking spaces. To present the concept of optimal control based on a single track model in combination with image processing methods we focus in this paper on the parking manoeuvre only. Thereby we show that optimization and control techniques can play a key role in the design of autonomous vehicles. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Matrix semigroups whose ring commutators have real spectra are realizable

We introduce the numerical spectrum \(\sigma _n(A)\subseteq {\mathbb {C}}\) of an (unbounded) linear operator A on a Banach space X and study its properties. Our definition is closely related to the numerical range W(A) of A and always yields a superset of W(A). In the case of bounded operators on Hilbert spaces, the two notions coincide. However, unlike the numerical range, \(\sigma _n(A)\) is always closed, convex and contains the spectrum of A. In the paper we strongly emphasise the connection of our approach to the theory of \(C_0\)-semigroups.     

Comparison of mass transfer models for the numerical prediction of sheet cavitation around a hydrofoil

Cavitating flows, which can occur in a variety of practical cases, can be modelled with a wide range of methods. One strategy consists of using the RANS (Reynolds Averaged Navier Stokes) equations and an additional transport equation for the liquid volume fraction, where mass transfer rate due to cavitation is modelled by a mass transfer model. In this study, we compare three widespread mass transfer models available in literature for the prediction of sheet cavitation around a hydrofoil. These models share the common feature of employing empirical coefficients, to tune the models of condensation and evaporation processes, that can influence the accuracy and stability of the numerical predictions. In order to compare the different mass transfer models fairly and congruently, the empirical coefficients of the different models are first well tuned using an optimization strategy. The resulting well tuned mass transfer models are then compared considering the flow around the NACA66(MOD) and NACA009 hydrofoils. The numerical predictions based on the three different tuned mass transfer models are very close to each other and in agreement with the experimental data. Moreover, the optimization strategy seems to be stable and accurate, and could be extended to additional mass transfer models and further flow problems.     

Global invariant manifolds

The main result of our article is an analog of the local manifold theorem for a hyperbolic point. We give a set of sufficient conditions that ensure the existence of the global invariant manifold.

We will prove the existence of invariant curves which lie in the quaternionic Julia set of the map f_c(X)=X²+c.     

The controversy in theγγ →ρρ process: potential scattering or qq\bar q};\bar q}; resonance?; resonance?

Theγγ →ρ ⁰ ρ ⁰ → 4π reaction shows a broad peak at 1.5 GeV in the (J ^P ,J _z )=(2⁺,2) channel which has no counterpart in theρ ⁺ ρ ^? channel. This “resonance” is considered as a candidate for a qq $\bar q$ ; $\bar q$ state in the “s-channel”. We show, however, that it can also be explained by potential scattering ofρ ⁰ ρ ⁰ via theσ- exchange in the “t-channel”.     

Suppression of the exaggerated growth of barium ferrite nanoparticles from solution using a partial substitution of Sc<Superscript>3+</Superscript> for Fe<Superscript>3+</Superscript>

The effect of the substitution of Sc³⁺ for Fe³⁺ in barium ferrite on the size of the resulting nanoparticles was studied. These nanoparticles, with the nominal compositions BaFe₁₂O₁₉ and BaFe_11.5Sc_0.5O₁₉, were synthesized hydrothermally at 90–240 °C or by coprecipitation under reflux at 140 °C. The precursors were obtained using (co)precipitation at room temperature. The sizes and morphologies of the precursors and nanoparticles were inspected with transmission electron microscopy, while their structures were confirmed with a combination of X-ray powder and electron diffraction. The samples’ compositions were analyzed with energy-dispersive X-ray spectroscopy. The evolution of the particle size and its distribution with the synthesis temperature and time were studied in pure and Sc-substituted barium ferrite and correlated with the evolution of the magnetic properties. The Sc substitution in the barium ferrite results in the formation of magnetic nanoparticles with applicable magnetic properties and in a significant reduction of the exaggerated particle growth. This was explained on the basis of the reaction kinetics.