Characterization of prenylflavonoids and hop bitter acids in various classes of Czech beers and hop extracts using high-performance liquid chromatography–mass spectrometry

Hops contain a wide range of polyphenolic compounds with antioxidant properties divided in various chemical classes. These compounds are detected in hop extracts and also in beer as its main product. Based on the careful optimization of column type, column packing, mobile phase composition and gradient steepness, two high-performance liquid chromatography–mass spectrometry (HPLC/MS) methods have been developed. The first method using Purospher Star RP-8e column and the gradient of aqueous acetonitrile containing 0.3% formic acid is optimized for the separation of low polar polyphenolic compounds, while the second one with Zorbax SB-CN column is used for more polar hops and beer components. In this work, more compounds are detected in comparison to previous reports. In total, 49 low polar and 37 polar compounds are detected in studied samples and their molecular weights are determined based on atmospheric pressure chemical ionization (APCI) mass spectra. Some compounds are identified based on the interpretation of their full scan and tandem APCI mass spectra, retention behavior and UV spectra, while the full structure elucidation of other species still requires further research. The quantitation of xanthohumol related prenylflavonoids and bitter acids is done with two detection techniques (APCI-MS and UV detection) providing comparable results. Both compound classes (i.e., prenylflavonoids and bitter acids) are separated and quantitated in a single HPLC run, where numerous other polyphenolics are detected as well.     

Chirooptical and photooptical properties of a novel side-chain azobenzene-containing LC polymer

Abstract  A novel chiral–photochromic side-chain polyacrylate with azobenzene fragments in the side groups has been synthesised. It was shown that the polymer forms a smectic phase and a cholesteric supramolecular helical structure with selective light reflection in IR spectral range. Thin spin-coated films of the polymer were prepared and their photooptical and chirooptical properties were studied in detail. It was found that UV irradiation of the films led to E–Z isomerization of the azobenzene moieties with high conversion, which is dependent on thermal prehistory of the films. Subsequent action of visible light results in partial recovery of the E-isomer content, whereas annealing leads to the full back conversion. Circular dichroism (CD) measurements revealed formation of the helical supramolecular structure even in the initial spin-coated polymer films. The E–Z isomerization induces complete disruption of helical order in non-annealed films of the polymer, whereas in the smectic phase of the annealed film only a significant decrease in CD values was found. In addition, the photoorientation phenomena induced by polarized light were studied. It was shown that polarized light induces linear dichroism in the films provided by azobenzene group orientation and the dichroism is stable at room temperature for a prolonged time. These combined chirooptical and photooptical features of this novel polymer enable one to consider this multifunctional compound as a promising material for photonics and for optical applications. Graphical abstract  

Deposition of NiO onto MoO3/γ-Al2O3 extrudates by slurry impregnation method

NiO-MoO₃/γ-Al₂O₃ catalysts were prepared by the reaction of γ-Al₂O₃ extrudates with an aqueous slurry of MoO₃, followed by the reaction of the MoO₃/γ-Al₂O₃ catalyst with an aqueous slurry of NiO, Ni(OH)₂, NiCO₃·2Ni(OH)₂·xH₂O, or 2NiCO₃·3Ni(OH)₂·4H₂O and by subsequent drying. The NiO deposition was examined with electron probe microanalysis. The deposited Ni efficiently increased the activity in benzothiophene hydrodesulfurization.     

Global optimization for parameter estimation of differential-algebraic systems

The estimation of parameters in semi-empirical models is essential in numerous areas of engineering and applied science. In many cases, these models are described by a set of ordinary-differential equations or by a set of differential-algebraic equations. Due to the presence of non-convexities of functions participating in these equations, current gradient-based optimization methods can guarantee only locally optimal solutions. This deficiency can have a marked impact on the operation of chemical processes from the economical, environmental and safety points of view and it thus motivates the development of global optimization algorithms. This paper presents a global optimization method which guarantees ɛ-convergence to the global solution. The approach consists in the transformation of the dynamic optimization problem into a nonlinear programming problem (NLP) using the method of orthogonal collocation on finite elements. Rigorous convex underestimators of the nonconvex NLP problem are employed within the spatial branch-and-bound method and solved to global optimality. The proposed method was applied to two example problems dealing with parameter estimation from time series data.     

Shape Optimization for Navier–Stokes Equations with Algebraic Turbulence Model: Existence Analysis

We study a shape optimization problem for the paper machine headbox which distributes a mixture of water and wood fibers in the paper making process. The aim is to find a shape which a priori ensures the given velocity profile on the outlet part. The mathematical formulation leads to an optimal control problem in which the control variable is the shape of the domain representing the header, the state problem is represented by a generalized stationary Navier–Stokes system with nontrivial mixed boundary conditions. In this paper we prove the existence of solutions both to the generalized Navier–Stokes system and to the shape optimization problem.     

Defects in Ce-doped LuAG and YAG scintillation layers grown by liquid phase epitaxy

The single crystalline Lu₃Al₅O₁₂ (LuAG) and Y₃Al₅O₁₂ (YAG) garnet layers doped by Ce³⁺ ions were grown by the liquid phase epitaxy from the flux. The effect of the flux composition, growth conditions, and substrate polishing on the layer morphology, creation of defects, and on optical and emission properties of layers was studied. The defects typical of the epitaxial growth are discussed.     

Two-Slit and Aharonov-Bohm Experiments in Magnetic Field

We discuss the two-slit experiment and the Aharonov-Bohm (AB) experiment in the magnetic field. In such a case the electron moving in the magnetic field produces so called synchrotron radiation. In other words the photons are emitted from the points of the electron trajectory and it means that the trajectory of electron is visible in the synchrotron radiation spectrum. The axiomatic system of quantum mechanics does not enable to define the trajectory of the elementary particle. The two-slit experiment and AB experiment in a magnetic field was never performed and it means that they are the missing experiments of quantum mechanics. The extension of the discussion to the cosmical rays moving in the magnetic field of the Saturn magnetosphere and its rings is mentioned. It is related to the probe CASSINI. The solution of the problem in the framework of the hydrodynamical model of quantum mechanics and the nonlinear quantum mechanics is also mentioned.     

On the Libera operator

We show that the Libera operator, L, on some spaces of analytic functions is a continuous extension of the conjugate of the Cesàro operator. Results on L acting on various spaces are obtained. In particular, L maps the Bloch space into BMOA. We also prove some results on the best approximation by polynomials in Hardy and Bergman spaces.     

Gagliardo–Nirenberg inequalities in regular Orlicz spaces involving nonlinear expressions

We consider a triple of N-functions (M,H,J) that satisfy the Δ^′-condition, and suppose that an additive variant of interpolation inequality holds

where , is an arbitrary set invariant with respect to external and internal dilations. We show that the above inequality implies its certain nonlinear variant involving the expressions and . Various generalizations of this inequality to the more general class of N-functions, measures and to higher order derivatives are also discussed and the examples are presented.