Qualitative behaviour of incompressible two-phase flows with phase transitions: The isothermal case

A thermodynamically consistent model for incompressible two-phase flows with phase transitions is considered mathematically. The model is based on first principles, i.e., balance of mass, momentum and energy. In the isothermal case, this problem is analysed to obtain local well-posedness, stability of non-degenerate equilibria, and global existence and convergence to equilibria of solutions which do not develop singularities.     

On second-order elliptic operators with complete first-order boundary degeneration and strong outward drift

Second order elliptic operators and their parabolic counterparts are studied in the case of complete boundary degeneration of the leading order coefficients in the presence of a strong outward pointing drift. It is shown that the problem generates a positive analytic \(C_0\)-semigroup with maximal \(L_p\)-regularity in \(L_q\)-spaces. This result is based on hard analysis estimates for integral operators in combination with modern functional analytic tools like \({\mathcal R}\)-boundedness and the operator-valued functional calculus.     

A computational two scaled model for the simulation of micro-heterogeneous low-alloyed TRIP steels

In transformation induced plasticity (TRIP) steel a diffusionless austenitic-martensitic phase transformation induced by plastic deformation can be observed, resulting in excellent macroscopic properties. In particular low-alloyed TRIP steels, which can be obtained at lower production costs than high-alloyed TRIP steel, combine this mechanism with a heterogeneous arrangement of different phases at the microscale, namely ferrite, bainite, and retained austenite. The macroscopic behavior is governed by a complex interaction of the phases at the micro-level and the inelastic phase transformation from retained austenite to martensite. A reliable model for low-alloyed TRIP steel should therefore account for these microstructural processes to achieve an accurate macroscopic prediction. To enable this, we focus on a multiscale method often referred to as FE² approach, see [6]. In order to obtain a reasonable representative volume element, a three-dimensional statistically similar representative volume element (SSRVE) [1] can be used. Thereby, also computational costs associated with FE² calculations can be significantly reduced at a comparable prediction quality. The material model used here to capture the above mentioned microstructural phase transformation is based on [3] which was proposed for high alloyed TRIP steels, see also e.g. [8]. Computations based on the proposed two-scale approach are presented here for a three dimensional boundary value problem to show the evolution of phase transformation at the microscale and its effects on the macroscopic properties. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Continuum modeling of the swelling behavior of concrete when modified through superabsorbent polymers

The main purpose of our investigation is to model the physical solidification process of a concrete mixture, involving water absorbing constituents, i. e. Superabsorbent Polymers (SAP). In order to model the chemo-mechanical swelling process, the system is described within the framework of the Theory of Porous Media (TPM). The swelling process is accounted for by including mass exchange terms between free and absorbed water. The chemo-mechanical driving forces are deduced from non-equilibrium thermodynamics while constitutive relations are motivated by appropriate micro-models of the swelling process. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Kinetic analysis of the estrogen receptor alpha using RIfS

The label-free time-resolved reflectometric interference spectroscopy has been used to study the interaction of the human estrogen receptor alpha (ERa) and different types of ligands. Different possible sensor surface coatings including various estrogen derivatives were evaluated for their suitability for detection of ERa. The determination of the kinetic and thermodynamic constants was carried out for the interaction in the heterogeneous phase as well as for the interaction in homogeneous phase. In addition, the affinity of 11 ligands ranging from natural hormones and pharmaceuticals to endocrine disrupting chemicals (EDCs) has been determined with this label-free assay format.     

An ylide-like phosphasilene and striking formation of a 4π-electron, resonance-stabilized 2,4-disila-1,3-diphosphacyclobutadiene

The first N-donor-stabilized phosphasilene LSi(SiMe(3))═PSiMe(3) (L = PhC(NtBu)(2)) has been synthesized in 87% yield through 1,2-silyl migration of the (Me(3)Si)(2)P-substituted, N-heterocyclic silylene [LSi-P(SiMe(3))(2)]. Remarkably, the latter reacts with dichlorotriphenylphosphorane Ph(3)PCl(2) to give the unprecedented 4π-electron Si(2)P(2)-cycloheterobutadiene [(LSi)(2)P(2)] with two-coordinate phosphorus atoms. The striking molecular structures as well as the (29)Si and (31)P NMR spectroscopic features of both products indicate the presence of zwitterionic Si═P bonds which is also in accordance with results by DFT calculations.     

New method for resolving the enantiomeric composition of 2-methyltetrols in atmospheric organic aerosols

In order to facilitate the determination of the primary and secondary origin of atmospheric organic aerosols, a novel method involving chiral capillary gas chromatography coupled with mass spectrometry has been developed and validated. The method was focused on the analysis of 2-methylerythritol and 2-methylthreitol, considered to be tracers of secondary organic aerosols from the oxidation of atmospheric isoprene. The method was validated by performing various tests using authentic standards, including pure enantiomeric standards. The result showed that the analytical method itself does not affect the enantiomeric composition of the samples analyzed. The method was applied on atmospheric aerosols from a boreal forest collected in Aspvreten, Sweden and on laboratory samples obtained from liquid phase oxidation of isoprene and smog chamber experiments. Aerosol samples contained one enantiomer of 2-methylerythritol in significantly larger quantities than the others. In contrast, the liquid-phase oxidation of isoprene and its gas-phase oxidation in the smog chamber produced all enantiomers in equal quantities. The results obtained where the enantiomer fraction, EF, is larger than 0.50 suggest that 2-methyltetrols in atmospheric aerosols may also have biological origin. Information about the differences between enantiomer fractions obtained using this method brings new insights in the area of atmospheric aerosols.     

Solubilisation of different medium chain esters in zwitterionic surfactant solutions--effects on phase behaviour and structure

We studied the effect of solubilisation of methyl esters with different chains of medium length into the binary surfactant system tetradecyldimethylamine oxide/water at constant surfactant concentration of 200 mM. As esters we employed valeric, capronic, enanthic, and pelargonic methyl ester, thereby decreasing the polarity. Always a phase sequence L(1)-L(α)-L(1) is observed with increasing ester concentration, where the L(α)-phase increases in extent and goes to much lower temperatures with increasing chain length of the ester. Viscosity measurements show a maximum at intermediate concentrations of additive that is independent of the type of ester. From SANS measurements detailed information about the structural changes occurring during the rod-to-sphere transition in the system of the shortest additive is deduced, which proceeds first through a pronounced rod growth. Interestingly, for the different esters an almost constant value of the volumic solubilisation capacity is observed, in agreement with the relatively constant interfacial tension. For the different esters no effect on the radius and the area requirement at the amphiphilic interface is observed at the solubilisation boundary. The microemulsions present here are spherical aggregates where the ester is partitioned between core and shell. From the SANS and interfacial tension data the effective bending constants of the surfactant monolayers were deduced and they show that the extension of the L(α)-phase is directly related to a corresponding increase in the bending constants of the surfactant/ester monolayers.     

Availability of Isoflavones (Genistin,Genistein and Daidzein) in Soybean ( Glycine Max ) Curd Treated under High Pressure

The article describes the concentration of isoflavones (genistin, genistein and daidzein) in a Spanish commercial tofu treated under high-pressure. The tofu was subjected to pressure of 400 MPa, in cycles of 10 min each with a total of 4 cycles with the progression of 10, 20, 30 and 40 min, and a temperature of about 10-12 °C. The isoflavones were extracted from tofu with aqueous methanol solution (80:20). The content of isoflavones went up directly proportional to the pressure applied for the first 30 minutes. Afterwards, at 40 min, the values dropped close to the control. Significant differences were found in genistein, genistin and daidzein treated for 20 and 30 min in comparison to control values. Finally, we came to the conclusion that, the isoflavones (genistin, genistein and daidzein) of treated tofu were not destroyed at 400 Mpa for 30 min and a major extraction was observed when compared with the untreated tofu.