Complex formation of 2,2-diphenyl-2H-benzo[f]chromene containing the aza-18-crown-6-ether fragment in the polymeric layer

The synthesis of 2,2-diphenyl-2H-benzo[f]chromene containing the aza-18-crown-6-ether fragment was described. Its complex formation with alkaline-earth metal ions in dibutyl phthalate and the polymeric gelatin film was investigated. The treatment of the layers containing the ionophore mentioned with aqueous solutions of the corresponding salts in the presence of NaBPh₄ as the phase transfer catalyst results in the extraction of the metal cation into the polymeric layer due to complex formation with crown-containing benzo[f]chromene. The complex formation is accompanied by changes in the spectroscopic characteristics of chromene in the closed and open forms and an increase in the lifetime of the merocyanine form. The effects obtained depend on the metal cation concentration in a solution and the time of layer treatment.     

Dynamics of Null Hypersurfaces in General Relativity

This paper shows how the structure and dynamics of a lightlike thin shell in general relativity can be obtained from a distributional approach.     

Chain length effect on the crystal thermal stability of oligoesters crystallized in thin layers

Specific heat of two fractions of oligomeric ethylene adipates (EA-2 with molecular weight <M _n>=1700 and EA-4 <M _n>=4000) containing up to 85 weight parts of untreated Aerosil-175, was measured in the temperature range 150–400 K. Detailed analysis of experimental data in terms of equations (1) and (2) led to the conclusion that significantly higher rate of decrease of both crystalline melting point as well as true (i. e., corrected for crystallinity) enthalpy of fusion with inverse value of distance between filler particles for EA-2 reflects higher affinity of end hydroxyl groups of oligomer chains in extended conformation towards polar Aerosil surface, as compared to that for middle-chain segments of EA-4 molecules which presumably are in a coiled conformation in the melt, and fold back on themselves on crystallization. On the other hand, sudden drop of experimental heats of fusion and crystallinities for both oligomers at filler contents above 50 weight parts is attributed to drastic jump of nucleation barrier for crystallization due to severe loss of conformational entropy of oligomer chains which either form ties between filler particles, with end groups anchored on the latter (as in the case of EA-2), or are squeezed in coiled conformation, with middle-chain segments on the periphery of coils interacting with neighboring filler particles (EA-4).     

Advanced boundary conditions for eigenmode expansion models

In order to realise the full potential of eigenmode expansion models, advanced boundary conditions are required that can absorb the radiation impinging on the walls of the discretisation volume. In this paper, we will discuss and compare a number of these boundary conditions, like perfectly matched layers (PMLs), open (leaky mode) boundary conditions and transparent boundary conditions (TBCs). We will also introduce the case of PMLs with infinite absorption and discuss its relation to leaky mode expansion, leading to a deeper insight into the physics of PML.     

A finite element method for a three-dimensional second-order closure model of turbulent diffusion in a convective boundary layer

A three-dimensional second-order closure dispersion model is used to simulate the plume behaviour of a passive contaminant in a convective boundary layer. A time-splitting finite element method together with a non-linear filtering scheme is used to solve the three-dimensional second-order closure transport equations. The model results show good agreement with laboratory data for a ground level source.     

Modelling fluid flow in cross-bedded sections

Beadpack experiments and numerical simulations have been carried out to study flow displacements, effluent profiles and streamline patterns for layered systems with flow not parallel to the layers. The effects of layer thickness, permeability contrast, angle of layer to flow direction, mobility ratio and flood rate have been examined. Each of these parameters influence the displacement profiles, and disperse the flood front. Such real effects must be considered when subsuming reservoir heterogeneities in average reservoir parameters in simulation studies, or interpreting core tests.     

The Enskog repeated ring equations for tagged molecule motion and variational solutions

The Enskog repeated ring equations (ERRE) for tagged molecule motion are derived from the BBGKY hierarchy. The hierarchical deviation demonstrates the problem associated with using naive truncations for complex fluid systems. A moment-variational solution is suggested for the ERRE. The moment-variational method is applied to the ERRE for the two- and three-dimensional overlapping Lorentz gas (LG). Both self-consistent and non-self-consistent equations for the diffusion constant are solved. The results compare favorably with previous calculations and molecular dynamics (MD).     

Low-frequency relaxation modes in ferroelectric liquid crystal/gold nanoparticle dispersion: impact of nanoparticle shape

Low-frequency (1 mHz–100 Hz) dielectric relaxation modes were experimentally studied in ferroelectric liquid crystal (FLC)/gold nanoparticles (nanospheres and nanorods) dispersion. It was demonstrated that the dielectric spectra of nanodispersion are strongly influenced by the shape of nanoparticles. Using different formalisms of the impedance spectroscopy, three possible low-frequency relaxation processes were found in the dispersions and the pure FLC. Due to the electrical double layers (EDLs) near nanoparticles and the alignment layers, one can observe the relaxation of the EDL polarisation around the nanoparticles (Schwarz’s relaxation) and near the driving indium tin oxide (ITO) electrodes (electrode polarisation). The other possible relaxation process is interfacial polarisation (Maxwell–Wagner mode) in which the frequency is unaffected by the nanoparticles. It was shown that Schwarz’s relaxation frequency strongly depended on the shape and size of the nanoparticles. Moreover, dispersion of nanoparticles significantly reduced direct current conductivity of the FLC mixture.     

Patterned alignment of nematic liquid crystals generated by inkjet printing of gold nanoparticles and emissive carbon dots on both flexible polymer and rigid glass substrates

Patterned homeotropic alignment using nanoparticles (NPs) was achieved using inkjet printing. Two types of gold NPs, one smaller and one larger in core diameter (2 and 5 nm) capped with a monolayer of dodecanethiol, and emissive carbon dots with a core diameter of 2.5 nm featuring a mixed ligand shell of carboxylic acid groups and aliphatic hydrocarbon chains were tested on both rigid glass and flexible polycarbonate substrates. To define the director across the entire cell and not just in the NP-printed areas, alignment ‘underlayers’ were tested, and 30° obliquely evaporated SiO_x as alignment ‘underlayer’ generally provided the best results with the highest quality of the homeotropic alignment as well as the best contrast at the boundary between printed and non-printed (i.e. homeotropic and planar) domains of the fabricated cells. We also report that the chemical nature of the nematic liquid crystal (LC) used, the number of layers printed and the composition of the nano-ink need to be adjusted to obtain pattern alignment devices that positively benefit from both the properties of the LC and the nanomaterial printed.     

Dielectric relaxation in a novel tapered chiral photochromatic liquid crystalline dendrimer

Temperature-dependent dielectric spectroscopic measurements of newly synthesised ribbon-shaped chiral liquid crystalline dendrimer with photochromic azobenzene mesogens and an isosorbide chiral centre on planar anchoring cell have been performed in the frequency range of 1.0 Hz to 5.5 MHz. Three dielectric dispersions in the relaxation frequency range of 10–80 Hz, 80–130 kHz and ~3.5 MHz have been observed not only in chiral smectic phase but also in isotropic phase in which two lower-frequency processes are retarded while the other one remained at same relaxation rate from isotropic to chiral smectic phase. Based on the dielectric and optical polarising microscopic results, the chiral smectic phase has been identified as SmC* phase. The relaxation mode observed at low-frequency region in the SmC* phase followed the dielectric characteristics of pinned Goldstone mode. Whereas the dielectric dispersions observed at high-frequency region have been analysed in the framework of the model given by Maier and Meier.