Electromechanical effect in an antiferroelectric liquid crystal

Abstract

The electromechanical properties of a compound exhibiting an antiferroelectric phase were investigated. An electric field induced antiferroelectric-ferroelectric transition could be detected by vibration analysis. In the antiferroelectric state the vibrations almost vanish while in the ferroelectric state the electromechanical effect has the same magnitude as in the chiral smectic C* phase.     

Detection of stress whitening in plastics with the help of X-ray dark field imaging

The processing of thermoplastics can induce a wide range of defects such as stress whitening, cavitation and porosity, which can adversely affect the reliability of the final products. Hence, fast and effective non-destructive detection methods for such defects are highly important for quality assurance on production lines. In this paper, X-ray dark field imaging is presented as a new non-destructive testing method that allows the visualization of stress whitening or cavitation efficiently. The performance of the method is demonstrated for the case of an injection-moulded polyvinylidene fluoride part that exhibits stress whitening. Whereas the stress whitening could not be detected by conventional X-ray imaging, it was localized by an X-ray dark field image acquired within a few minutes. Once the precise location of the stress whitening was known, it was possible to verify the result by local micro X-ray computed tomography and by a micro section image.     

Screening methods and recent developments in the detection of anticoccidials

This article presents a review of the current trends in the analysis of coccidiostats in various matrices, focusing principally on screening and rapid methods. Coccidiosis is an infectious disease having a high negative impact on the animal industry. Drugs are therefore necessary to prevent and/or to combat this disease. However, it is also of crucial importance that these veterinary drugs do not enter the human food chain. European legislation has therefore established the boundaries for the use of coccidiosats and has also addressed the unavoidable problem of cross-contamination of the feed, mainly caused by the use of the same production lines. Consequently there is a need for analytical methods and/or analytical strategies for the monitoring and control of the residues of anticoccidials, both in feed and in the resulting matrices for human consumption. In the frame of the European collaborative project CONffIDENCE, such attempts to establish the required analytical tools were made, which required beforehand a review of the state of the art in this domain. Aiming at this objective, in this review we consider the most interesting publications since 2000. In essence, both a rapid approach with mainly immunoassays and chromatographic methods were developed. To date, the obstacle to routine use of the first approach has been its inability to detect more than two compounds simultaneously, but recent developments in flow cytometry have made it possible to detect six coccidiostats at once. On the other hand, an increasingly popular approach for detecting multiple coccidiostats simultaneously is liquid chromatography coupled with tandem mass spectrometry. There remains a need to adapt these analytical methods to legislative requirements.     

Lanthanide Identity Governs Guest-Induced Dimerization in LnIII[15-MC N(L-pheHA)-5])3+ Metallacrowns

Series of lanthanide-containing metallic coordination complexes are frequently presented as structurally analogous, due to the similar chemical and coordinative properties of the lanthanides. In the case of chiral (Ln^III[15-MC _N(L-pheHA)-5])³⁺ metallacrowns (MCs), which are well established supramolecular hosts, the formation of dimers templated by a dicarboxylate guest (muconate) in solution of neutral pH is herein shown to have a unique dependence on the identity of the MC's central lanthanide. Calorimetric data and nuclear magnetic resonance diffusion studies demonstrate that MCs containing larger or smaller lanthanides as the central metal only form monomeric host-guest complexes whereas analogues with intermediate lanthanides (for example, Eu, Gd, Dy) participate in formation of dimeric host-guest-host compartments. The driving force for the dimerization event across the series is thought to be a competition between formation of highly stable MCs (larger lanthanides) and optimally linked bridging guests (smaller lanthanides).     

Genotoxicity and Cytotoxicity of 4-Nonylphenol Ethoxylate on Lymphocytes as Assessed by the Comet Assay

Surfactants, which are prevalent at industrial sites and in the environment generally, are potential risk factors in human carcinogenesis. The widespread industrial use of surfactants such as 4-alkylphenol ethoxylates and their prevalence in many cleaning products have provoked studies about surfactant concentrations in water and their toxicity levels. Up to now, these substances have mainly been tested on aquatic organisms. Though tests on human cell lines are rare. The alkaline Comet assay was performed to evaluate the genotoxicity of 4-nonylphenol ethoxylate, a biodegradable product of 4-alkylphenol ethoxylate, in human lymphocytes. Concentrations tested ranged from 0.15 to 150 µg/mL. Test concentrations of 10 to 15 µg/mL caused an increase level of DNA migration in human cells, but without inducing excessive toxicity (viability > 80%). Though induced levels of DNA migration starting at concentrations of 30 µg/mL may have been due to excessive levels of cytotoxicity (viability < 70%). Based on these data, 4-nonylphenol ethoxylate can induce DNA damage in human lymphocytes but at higher concentrations than are normally found in river or drinking water. However, considering the prevalence of surfactants, the measured genotoxicity of these substances is of concern. Further investigations on human target cells are necessary to evaluate the carcinogenic impact of surfactants and reconsider their environmental acceptance.     

Comparison of model predictions with measured proton-induced production of nickel and iridium isotopes

Journal of Radioanalytical and Nuclear Chemistry - Calculations were performed to support method development for simultaneous production of Ni and Ir isotopes. The work scope included development...