Comparison between tungsten carbide and molybdenum carbide for the hydrodenitrogenation of carbazole

The activity of molybdenum and tungsten carbides in hydrodenitrogenation (HDN) of carbazole was studied. Transition metal carbides (Mo₂C and W₂C) were synthesized using the temperature-programmed reaction of the appropriate oxide precursor (MoO₃ and WO₃) with the following gas mixture: 10 vol.% CH₄/H₂. The structure of the catalysts was characterized using X-ray diffraction, CO chemisorption, high resolution transmission electron microscopy (HRTEM) and BET surface area measurements. From the HRTEM analysis, it could be concluded that the tungsten carbide was thioresistant in our operating conditions (50 ppm of S, pressure = 6 MPa, 553 < T < 653 K, H₂/feed volumic ratio = 600). In the case of Mo₂C, molybdenum sulphide was observed as single slabs. The activity of catalysts was determined during the hydrodenitrogenation of carbazole at the wide range of temperature (553–653 K) and under a 6 MPa total pressure of H₂. The comparison of tungsten carbide and molybdenum carbide has shown higher activity of Mo₂C than W₂C at the same condition. However, W₂C leads to higher amount of isomers of main products, and have higher hydrogenation activity.     

Structure‐Based Virtual Screening for Dopamine D2 Receptor Ligands as Potential Antipsychotics

Structure‐based virtual screening using a D₂ receptor homology model was performed to identify dopamine D₂ receptor ligands as potential antipsychotics. From screening a library of 6.5 million compounds, 21 were selected and were subjected to experimental validation. From these 21 compounds tested, ten D₂ ligands were identified (47.6 % success rate, among them D₂ receptor antagonists, as expected) that have additional affinity for other receptors tested, in particular 5‐HT_2A receptors. The affinity (K_i values) of the compounds ranged from 58 nm to about 24 μm . Similarity and fragment analysis indicated a significant degree of structural novelty among the identified compounds. We found one D₂ receptor antagonist that did not have a protonatable nitrogen atom, which is a key structural element of the classical D₂ pharmacophore model necessary for interaction with the conserved Asp(3.32) residue. This compound exhibited greater than 20‐fold binding selectivity for the D₂ receptor over the D₃ receptor. We provide additional evidence that the amide hydrogen atom of this compound forms a hydrogen bond with Asp(3.32), as determined by tests of its derivatives that cannot maintain this interaction.     

Kinetic analysis of Li|Li+ interphase in an ionic liquid electrolyte

Kinetic analysis of the Li|Li⁺ interphase in an electrolyte based on N-metyl-N-propylpyrrolidinium bis(trifluoromethanesulfon)imide ionic liquid (MPPyrrTFSI) and lithium bis(trifluoromethanesulfon)imide salt (LiTFSI) was performed. Li|electrolyte|Li and LiC₆|electrolyte|Li cells were galvanostatically charged/discharged in order to form solid electrolyte interphase (SEI) protecting layer. SEM images showed that the surface of both Li and LiC₆ anodes was covered with small particles. The fitting procedure of electrochemical impedance data taken at different temperatures gave three resistances (R _el, R _SEI, R _ct) and hence, three lnR = f(T ^?1) straight lines of different slopes. Specific conductivity and activation energy of the conduction process of the liquid electrolyte, were ca. σ = 2.5 mS cm^?1 (at T = 25.0 °C) and $ E_{\text{el}}^{\# } $  = 15 kJ mol^?1. Activation energy for the conduction process in the SEI layer was ca. 56 kJ mol^?1 in the case of the metallic lithium and 62 kJ mol^?1 for the graphite anode. Activation energy of the charge transfer process, $ E_{\text{ct}}^{\# } $ , for Li and LiC₆ anodes was 71 and 65 kJ mol^?1, respectively. Analysis of literature data for different electrolytes suggests that the $ E_{\text{ct}}^{\# } $ value for Li⁺ reduction may be approximated by 57 ± 5 kJ mol^?1. Activation energy for the diffusion processes in the graphite electrode, detected from the Warburg coefficient, was ca 74 kJ mol^?1.     

The influence of frying medium degradation on fat uptake and texture of French fries

The purpose of the present investigation was to study the influence of the degree of degradation of different kinds of oils used as a frying medium on fat uptake and texture of frozen pre‐fried French fries. As has been found, the degradation degree of the frying medium depends on the kind of oil and processing time. Liquid hydrogenated rapeseed oil exhibited the best thermo‐oxidative stability among the oils under investigation. The kind of oil influenced fat uptake and the texture of French fries. The lowest fat uptake was observed with French fries fried in solid oil. Some correlations between fat uptake and changes in fatty acid content were found in the frying medium during frying. Fat absorption increased with increasing unsaturated fatty acids and decreasing saturated fatty acid content. The texture of French fries fried in hydrogenated oils was harder than that exhibited by French fries fried in liquid rapeseed oil. The hardness of French fries fried in liquid oils decreased during frying while the hardness of French fries fried in solid oil increased. Some correlations between the texture of French fries and iodine value and fatty acids content of frying media were found. The hardness of French fries increased with increasing content of saturated fatty acids and decreasing unsaturated fatty acids and trans isomer fatty acid content. Copyright © 2005 Society of Chemical Industry     

The influence of French fries processing on the glycoalkaloid content in coloured-fleshed potatoes

French fries made from coloured-fleshed potatoes may be interesting alternative to the traditional snacks for consumers. However, potatoes contain glycoalkaloids (TGA), so potato tubers and obtained fried snacks should be subjected to comprehensive examination. The aim of this study was to determine the effect of different stages of French fries processing on the content of TGA (α-solanine and α-chaconine) in the red- and blue-fleshed potatoes, in semi-products and ready-to-eat products. It was stated that during the processing of French fries prepared from coloured-flesh potato varieties significantly decreased the content of TGA (α-solanine and α-chaconine) in the samples obtained at different stages of the process compared to the raw material. Potatoes with blue-fleshed of Vitelotte variety and red-fleshed of Highland Burgundy Red variety can be used to French fries processing due to their low content of TGA (in unpeeled and peeled potatoes). However, Blue Congo variety with blue-fleshed should not be applied to French fries processing, because of high TGA content in raw material and first of all in peeled potatoes flesh. The peeling process of coloured-fleshed potatoes decreased in TGA content on average by about 50 %, cutting process on average by about 53 %, whereas blanching on average by about 58 % compared with the raw material. The highest decrease in TGA content was caused by frying process. The mean values were about 97.5 % in ready-to-eat French fries. In French fries after I and II steps of frying, the ratio α-solanine to α-chaconine was lower (1.0:2.0) than in unpeeled potatoes (1.0:2.3).     

Influence of cabbage juices on oxidative changes of rapeseed oil and lard

The influence of white cabbage on oxidative and thermooxidative changes of plant fats (rapeseed oil) and animal fats (lard) was determined by an array of standard tests. The fats were heated at 100 °C for 6 h in a model system mimicking normal cooking conditions in the presence or absence of fresh cabbage juice (FCJ) or sauerkraut juice (SJ). After thermal processing of fats in the presence of cabbage juices, regardless of the kind, the formation of oxidized triacylglycerols (TAG) was decreased by about 40% compared to fats heated alone. Juices also inhibited the formation of TAG dimers and polymers. Such parameters as peroxide value, extinction coefficient at 232 nm (E^1%_1cm), and losses of polyene fatty acids revealed the protective effect of cabbage juices as well; however, in this case FCJ displayed a much stronger antioxidant effect than SJ. The protection was more visible for lard which contains much lower amounts of natural antioxidants.     

Liquid-crystalline phases formed by symmetrical azines with different terminal chains: Thermal,optical and electrical study

One series of symmetrical azine-type liquid crystals were synthesized and their chemical structure identified by FTIR, NMR, high resolution mass spectrometry-electro spray ionization (MS-ESI) and elemental analysis. The absorption (UV–vis), photoluminescence (PL) and thermoluminescence (TL) features of the compounds are documented. X-ray diffraction was employed to evaluate their phase transitional behaviour. Their mesomorphic properties were investigated by polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). Terminal groups of the liquid crystals had an effect on their mesomorphic properties. Azine with alkoxysemiperfluorinated end-groups (A1) exhibited smectic C (SmC) phase, whereas azine with octadecyloxy end chains (A3) showed SmC and SmA phases. Azine with 5″-octyl-2,2′:5′,2″-terthiophene groups (A2) exhibited only nematic phase. Different types of N and SmC textures were found and investigated by POM technique. Azine with thiophene groups (A2) has an absorption band about 138 nm batochromically shifted compared to the analogous band of other compounds. The lowest optical band gap value (2.34 eV) was detected for A2. Azines emitted violet or green light. The thermoluminescence emission of azines occurred at about 390–440 nm wavelengths. Current–voltage measurements were performed on ITO/compound/Alq₃/Al and ITO/TiO₂/compound/Alq₃/Al devices before and after light irradiation. To prepare TiO₂ layer, sol–gel technique was applied.     

Determination of free radicals and flavan-3-ols content in fermented and unfermented teas and properties of their infusions

The objective of this study was to analyse selected brands of fermented (red and black) and unfermented (white and green) teas for free radical content with the use of electron paramagnetic resonance (EPR) spectroscopy and for contents of flavan-3-ols by means of high-performance liquid chromatography. Analyses were also conducted for the polyphenolic profile of infusions of the analysed teas (with the Folin–Ciocalteu’s method) and their antioxidant activity (in reaction with a DPPH radical) at three brewing times (5, 10 and 15 min). The obtained results showed the possibility of using rapid spectroscopic method EPR to evaluate the oxidative changes in tea leaves caused by enzymatic fermentation. The number of free radicals in teas was negatively correlated with contents of flavan-3-ols, (?)-EGCG in particular. The main signals observed in EPR spectra of teas were attributed to semiquinone radicals; however, also signals attributed to carbohydrate radicals were detected. Regarding unfermented teas, it was ascertained that teas with the highest content of flavan-3-ols, (?)-EGCG in particular, were characterised by the lowest content of semiquinone radicals and a high content of carbohydrate radicals. The group of fermented teas demonstrated to contain mainly semiquinone radicals. The total phenolic content and antioxidant activity of the tea infusions were strongly diversified depending on the kind and brand of tea as well as on the extraction time. The predominating flavan-3-ol in the analysed teas was epigallocatechin gallate (?)-EGCG, the content of which was additionally highly correlated with the antioxidant activity of the tea infusions.     

A study of thermal,optical and electrical properties of new branched triphenylamine-based polyazomethines

A series of branched aromatic polyazomethines have been obtained by high temperature solution polycondensation of 4,4′,4″-triformyltriphenylamine with 3,3′-dimethoxybenzidine with different feed molar ratio. For three polymers additional condensation of chain end groups with monofunctional monomers such as 4-formyltriphenylamine or 2-naphthylamine was carried out. Moreover, two model compounds were prepared and investigated for comparison with branched polymers. The structures of polymers and models were characterized by means FTIR, ¹H, ¹³C NMR spectroscopy, elemental analysis and gel permeation chromatography (GPC). UV–vis properties of the thin films of the polymers and compounds were investigated on the glass substrate. Eg of the branched polymers was found about 2.47 eV. UV–vis and FTIR spectroscopy for iodine doped compounds were investigated. Doping decreased the value of Eg of the branched polyazomethines to about 1.71 eV. Refractive index (n) for branched polyazomethines was found about 1.97, while for the doped compounds was a little higher (～2.48). Absorption (UV–vis) properties of the doped with iodine branched imines were investigated additionally after heating in different temperatures from 50 to 200 °C. Intensity of photoluminescence of branched imines in relation to 9,10-diphenylanthracene was found in the range 0.2–1.0% and 2.7–43.7% in dependence on the excitation wavelengths. Current–voltage (I–V) measurements were performed on ITO/TiO₂/polymer/Al, ITO/polymer/Alq₃/Al and ITO/TiO₂/polymer/Alq₃/Al devices in the dark and during irradiation with light (under illumination 1000 W/m²). The sol–gel technique was applied to prepared TiO₂ layer. TiO₂ layers and devices were investigated by Atomic Force Microscopy (AFM). Moreover, properties of these branched polymers were compared with the linear polyazomethine based on 3,3′-dimethoxybenzidine and 4,4′-diformyltriphenylamine.     

Pressureless sintering of single-phase tantalum carbide and niobium carbide

This work presents the results of studies on the preparation of single-phase polycrystalline tantalum carbide and niobium carbide. It has been found that it is possible to obtain polycrystals with high density in the pressureless sintering process at temperatures up to 2000 °C and therefore relatively low temperatures such as for the compounds with one of the highest melting points; TaC – 3985 °C and NbC – 3600 °C. Only carbon as a sintering additive was used. The main role of carbon is to reduce of oxide contamination. It has been shown that the determination of the amount of carbon required to reduce oxide contamination is only possible through the experimental method.