A result in asymmetric Euclidean Ramsey theory

It is proved that if the points of the three-dimensional Euclidean space are coloured with red and blue, then there exist either two red points at unit distance, or six collinear blue points with distance one between any two consecutive points.     

The alignment of nematic liquid crystal by the Ti layer processed by nonlinear laser lithography

It is well known that the alignment of liquid crystals (LCs) can be realised by rubbing or photoalignment technologies. Recently, nonlinear laser lithography (NLL) was introduced as a fast, relatively low-cost method for large area nano-grating fabrication based on laser-induced periodic surface structuring. In this letter for the first time, the usage of the NLL as a perspective method of the alignment of nematics was presented. By NLL, nanogrooves with about 0.92 μm period were formed on Ti layer. The nanostructured Ti layer (NSTL) was coated with oxidianiline-polyimide film with annealing of the polymer followed without any further processing. Aligning properties of NSTLs were examined with combined twist LC cell. The dependencies of the twist angle of LC cells and azimuthal anchoring energy (AE) of layers on scanning speed and power of laser beam during processing of the Ti layer were the focus of our studies as well. The maximum azimuthal AE, obtained for pure NSTL, is comparable with photoalignment technology. It was found that the deposition of polyimide film on NSTL leads to the gain effect of the azimuthal AE. Also, atomic force microscopy (AFM) study of aligning surfaces was carried out.     

Electronic structure and solvatochromism of merocyanines NMR spectroscopic point of view

(1)H and (13)C NMR spectra of two series of malononitrile-based merocyanines, which possess positive and negative solvatochromism have been in detail investigated in low polar chloroform and polar dimethyl sulfoxide (DMSO). Careful attribution of signals in spectra has been made with the help of two-dimensional NMR experiments (COSY, NOESY, HMBC, and HMQC). Hence, the dependence of merocyanines electronic structure on their chemical structure and solvent nature has been studied by this powerful method. It has been shown that there exists a good correlation between the calculated charges on carbon atoms of a polymethine chain and their chemical shifts in (13)C NMR spectra. The influence of solvent polarity on bond orders for dyes with positive and negative solvatochromism is also observed. The comparison of (13)C NMR spectra of merocyanines and corresponding parent ionic dyes allows to determine their sign of solvatochromism irrespectively of electronic spectra, and also to find the key atoms of chromophore whose signals in (13)C NMR spectra are most informative.     

Wine Storage at Cellar vs. Room Conditions: Changes in the Aroma Composition of Riesling Wine

Storage temperature is one of the most important factors affecting wine aging. Along with bottling parameters (type of stopper, SO₂ level and dissolved O₂ in wine), they determine how fast wine will evolve, reach its optimum and decline in sensory quality. At the same time, lowering of the SO₂ level in wine has been a hot topic in recent years. In the current work, we investigated how Riesling wine evolved on the molecular level in warm (~25 °C) and cool (~15 °C) conditions depending on the SO₂ level in the wine (low, medium and high), flushing of the bottle’s headspace with CO₂ and three types of stoppers (Diam 30, Diam 30 origin and Diam 5) with different OIR levels (0.8–1.3 mg) and OTR levels (0.3–0.4 mg/year). It was demonstrated that the evolution of primary and secondary aromas, wine color and low molecular weight sulfur compounds (LMWSCs) during the two years of aging mainly depended on the storage temperature. Variation in the SO₂ level and CO₂ in the headspace affected mostly certain LMWSCs (H₂S, MeSH) and β-damascenone. New aspects of C₁₃-norisprenoids and monoterpenoids behavior in Riesling wine with different levels of SO₂ and O₂ were discussed. All three types of stoppers showed very close wine preservation properties during the two years of storage. The sensory analysis revealed that, after only six months, the warm stored wines with a low SO₂ level were more oxidized and different from the samples with medium and high SO₂ levels. A similar tendency was also observed for the cool stored samples.     

Stable Carbenes as Structural Components of Partially Saturated Sulfur-Containing Heterocycles

Recently, an unusual elongation of the C-S bond was observed experimentally for some sulfur-containing heterocycles. Using a superior ab initio (SCS-MP2/cc-pVTZ) level of theory, we showed that the phenomenon can be explained by a contribution of a donor–acceptor adduct of a carbene with an unsaturated ligand. One may achieve further elongation of the C-S bond, eventually turning it to a coordinate one, by increasing the stability of each part of the system as, e.g., in the utmost case of spiro adducts with Arduengo carbenes. The effect of carbene stability was quantified by employing the isodesmic reactions of carbene exchange.