Molecular Design of Sexiphenyl-Based Liquid Crystals: Towards Temperature-Stable, Nematic Phases with Enhanced Optical Properties

This research introduces a novel liquid crystal molecular design approach based on the para-sexiphenyl (6P) structure. Six new liquid crystalline materials were synthesized, incorporating an alkyl terminal and lateral substitutions of the sexiphenyl core to achieve temperature-stable and broad nematic phases. The synthetic pathway involved cross-coupling, resulting in derivatives with strong nematogenic characteristics. Optical investigations demonstrated that the tested material had high birefringence values, making it promising for optical and electronic applications. These results open up new avenues of research and offer potential practical applications in electronics, photonics, optoelectronics and beyond

Interplay of climate-human-vegetation on the north-eastern edge of the Carpathians (Western Ukraine) between 7500 and 3500 calibrated years BP

The area of Ukrainian Carpathians is still poorly investigated in the context of vegetation history and human activity during the Holocene. The present study was carried out on deposits collected from the former oxbow lake. The study aimed to examine (1) whether various tendencies for occupation of valley terraces by different Neolithic and Early Bronze cultures led to a discrepant records of human impact in palaeo-proxies and (2) whether forest vegetation in the Dniester River valley (Carpathian foreland, Western Ukraine) reacted to global climatic events during the period 7500 to 3500 calibrated years BP (cal BP). We reconstructed vegetation changes with special attention being paid to human and climate impact, applying palaeobotanical and faecal bacteria ancient DNA (aDNA) analyses combined with radiocarbon dating. The results revealed that aDNA and palaeobotanical proxies recorded human impacts of differing intensities in the deposits analyzed. The Linear Pottery culture (Early Neolithic) occupied lower terraces close to the lake and so high concentrations of aDNA were detected, although with the irregular presence of the pollen of cultivated plants. Subsequently, the Malicka culture (Lengyel-Polgar cycle) still inhabited lower terraces of the valley, although its representatives probably exploited higher terraces (fluctuations of aDNA, still with an irregular record of cultivated plants). Humans of the Funnel Beaker culture preferred the highest terrace levels and watersheds (more scattered aDNA distribution) and they extensively used fire for deforestation (an increase in the accumulation of microcharcoal); however, their activity only had a slight effect on the woodlands on the lowest terraces of the valley. During occupation by Late Neolithic and Early Bronze cultures, the pasturelands on the lowest terraces were probably (at least partly) transformed into mown meadows (spread of Plantago lanceolata). The advance of Picea abies in the Dniester valley approximately 6110-5240 cal BP and an increase in the water table dated at approximately 3975-3900 cal BP in the mire occurred during the global cold period at 6500-5900 cal BP and ‘4.2 ka’ cooling event

Synthesis and mesomorphic properties of laterally substituted 4,4′′′-dialkyl-p-quaterphenyls

Over 20 laterally substituted, mainly by fluorine and other more bulky substituents like chlorine and methyl group, 4,4 '''-dialkyl-p-quaterphenyls have been synthesised and mesomorphic properties, phase transition temperatures and enthalpies were measured. The influence of the number of lateral substituents and their type along with their position in the molecular core have been analysed and compared with similarly substituted terphenyl analogues. The example of the eutectic mixture composed of synthesised quaterphenyl derivatives has been formulated and characterised

Ochratoxin A—The Current Knowledge Concerning Hepatotoxicity, Mode of Action and Possible Prevention

Ochratoxin A (OTA) is considered as the most toxic of the other ochratoxins synthesized by various fungal species belonging to the Aspergillus and Penicillium families. OTA commonly contaminates food and beverages, resulting in animal and human health issues. The toxicity of OTA is known to cause liver damage and is still being researched. However, current findings do not provide clear insights into the toxin mechanism of action. The current studies focusing on the use of potentially protective compounds against the effects of the toxin are insufficient as they are mainly conducted on animals. Further research is required to fill the existing gaps in both fields (namely the exact OTA molecular mechanism and the prevention of its toxicity in the human liver). This review article is a summary of the so far obtained results of studies focusing on the OTA hepatotoxicity, its mode of action, and the known approaches of liver cells protection, which may be the base for expanding other research in near future

Synthesis, Mesomorphism and the Optical Properties of Alkyl-deuterated Nematogenic 4-[(2,6-Difluorophenyl)ethynyl]biphenyls

The synthesis and characterization of new deuterated liquid crystal (LC) compounds based on phenyl tolane core is described in this paper. The work presents an alternative molecular approach to the conventional LC design. Correlations between molecular structure and mesomorphic and optical properties for compounds which are alkyl-hydrogen terminated and alkyl-deuterium, have been drawn. The compounds are characterized by mass spectrometry (electron ionization) analysis and infrared spectroscopy. They show enantiotropic nematic behavior in a broad temperature range, confirmed by a polarizing thermomicroscopy and differential scanning calorimetry. Detailed synthetic procedures are attached. Synthesized compounds show a significantly reduced absorption in the near-infrared (NIR) and medium-wavelength infrared (MWIR) radiation range, and stand as promising components of medium to highly birefringent liquid crystalline mixtures