Synthesis of some vinyl-substituted pyrylium salts and their intermediates

The preparation of vinyl-substituted pyrylium salts and their intermediates is described. These monomers and intermediates have been derived from syntheses based on p-2-hydroxyethoxybenzaldehyde and 4-methoxypyrylium salts. Treatment of the hydroxybenzaldehyde with acetophenone gives a hydroxypyrylium intermediate which, when methacrylated, gives a pyrylium methacrylate. Methacrylation of the hydroxy-benzyldehyde followed by condensation with methylpyrylium salts gives styryl-pyrylium methacrylates. Displacement of the methoxy group in methoxypyrylium salts with ethanolamine derivatives followed by methacrylation yields a series of aminopyrylium methacrylates. The preparation of a divinylpyrylium urethane and a pyrylium-type copolymer is also described.     

Novel Copolymers of Styrene. 7. Chlorine Ring-Substituted 2-Cyano-3-phenyl-2-propenamides

Novel trisubstituted ethylenes, chlorine ring-substituted 2-cyano-3-phenyl-2-propenamides, RC₆H₃CH?C(CN)CONH₂ (where R is 2,3-dichloro, 2,4-dichloro, 2,6-dichloro, 3,4-dichloro, 2-chloro-5-nitro, 4-chloro-3-nitro, 5-chloro-2-nitro) were synthesized by potassium hydroxide catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and cyanoacetamide and characterized by CHN elemental analysis, IR, ¹H- and ¹³C-NMR. Novel copolymers of the ethylenes and styrene were prepared at equimolar monomer feed composition by solution in the presence of a radical initiation (AIBN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H- and ¹³C-NMR, GPC, DSC, and TGA. Thus, the order of relative reactivity (1/r1) and the tendency toward alternation of monomer units in the copolymer for the monomers is 2-Cl-5-NO₂ (3.09) > 5-Cl-2-NO₂ (1.88) > 4-Cl-3-NO₂ (0.97) > 2,6-Cl₂ (0.93) > 3,4-Cl₂ (0.31) > 2,4-Cl₂ (0.30) > 2,3-Cl₂ (0.22). High T_g of the copolymers in comparison with that of polystyrene indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500°C range with residue (3.5–5.0 wt%), which then decomposed in the 500–800°C range.     

Heterotic strings on homogeneous spaces

We construct heterotic string backgrounds corresponding to families of homogeneous spaces as exact conformal field theories. They contain left cosets of compact groups by their maximal tori supported by NS‐NS 2‐forms and gauge field fluxes. We give the general formalism and modular‐invariant partition functions, then we consider some examples such as SU (2)/U (1) ~ S² (already described in a previous paper) and the SU (3)/U(1)² flag space. As an application we construct new supersymmetric string vacua with magnetic fluxes and a linear dilaton.     

Comparative Evaluation of Different Targeted and Untargeted Analytical Approaches to Assess Greek Extra Virgin Olive Oil Quality and Authentication

Extra virgin olive oil (EVOO) is a key component of the Mediterranean diet, with several health benefits derived from its consumption. Moreover, due to its eminent market position, EVOO has been thoroughly studied over the last several years, aiming at its authentication, but also to reveal the chemical profile inherent to its beneficial properties. In the present work, a comparative study was conducted to assess Greek EVOOs’ quality and authentication utilizing different analytical approaches, both targeted and untargeted. 173 monovarietal EVOOs from three emblematic Greek cultivars (Koroneiki, Kolovi and Adramytiani), obtained during the harvesting years of 2018–2020, were analyzed and quantified as per their fatty acids methyl esters (FAMEs) composition via the official method (EEC) No 2568/91, as well as their bioactive content through liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS) methodology. In addition to FAMEs analysis, EVOO samples were also analyzed via HRMS-untargeted metabolomics and optical spectroscopy techniques (visible absorption, fluorescence and Raman). The data retrieved from all applied techniques were analyzed with Machine Learning methods for the authentication of the EVOOs’ variety. The models’ predictive performance was calculated through test samples, while for further evaluation 30 commercially available EVOO samples were also examined in terms of variety. To the best of our knowledge, this is the first study where different techniques from the fields of standard analysis, spectrometry and optical spectroscopy are applied to the same EVOO samples, providing strong insight into EVOOs chemical profile and a comparative evaluation through the different platforms.     

AC and DC conductivity correlation: The coefficient of Barton–Nakajima–Namikawa relation

It has been some time since an empirical relation, which correlates DC with AC conductivity and contains a loosely defined coefficient thought to be of order one, was introduced by Barton, Nakajima and Namikawa. In this work, we derived this relation assuming that the conductive response consists of a superposition of DC conductivity and an AC conductivity term which materialized through a Havriliak–Negami dielectric function. The coefficient was found to depend on the Havriliak–Negami shape parameters as well as on the ratio of two characteristic time scales of ions motion which are related to ionic polarization mechanism and the onset of AC conductivity. The results are discussed in relation to other relevant publications, and they also applied to a polymeric material. Both theoretical predictions and experimental evaluations of the BNN coefficient are in an excellent agreement, while this coefficient shows a gradual reduction as the temperature increases.     

The photocurrent response of human cones is fast and monophasic

Background  

The precise form of the light response of human cone photoreceptors in vivo has not been established with certainty. To investigate the response shape we compare the predictions of a recent model of transduction in primate cone photoreceptors with measurements extracted from human cones using the paired-flash electroretinogram method. As a check, we also compare the predictions with previous single-cell measurements of ground squirrel cone responses.     

A comparative study of approaches applied to the permeability of binary composite polymeric materials

A study has been made of various approaches to the problem of evaluating the permeability of a binary composite polymeric material on the basis of certain fundamental theoretical assumptions. In particular, it is assumed that the component phases form well-defined microscopic domains and do not interact with each other or with the penetrant. The main characteristics and relative merits of these treatments are considered in detail, and it is shown that considerable information can be obtained about the range of validity and physical significance of certain well-known formulas, which were previously applied in a largely empirical way. These results indicate specific fields of application (which include filled or semicrystalline polymers, foams, block and graft copolymers, and nonhomogeneous polymer blends) for each of the formulas in question and lead to a deeper understanding of the relation between permeability or analogous properties (such as thermal or electrical conductivity, electrical permittivity, elastic modulus, etc.) and the structural characteristics of composite polymeric (and other) materials.