A systematic study on the extractability of arsenic species from algal certified reference material IAEA-140/TM (Fucus sp., Sea Plant Homogenate) using methanol/water extractant mixtures

Using methanol/water mixtures (from pure water to pure methanol), with different desorption and solubility parameters, and varying extractant volume to algal mass (V/m) ratios, the extractability of arsenic species from CRM IAEA-140/TM was investigated. A linear sorption isotherm-based model was developed to process the data obtained with variable volume extraction, allowing the unambiguous deduction of the maximal extractable species concentrations under the specific extraction conditions, even for more stable species.The maximal extractable arsenic fraction ranged from 41 to 68% of the total arsenic concentration in CRM IAEA-140/TM, depending on the extractant composition, with pure methanol giving the lowest extraction yield and pure water giving erratic extractability (probably due to bad wettability). The main arsenic species quantified in the methanol/water extracts were arsenosugars, with arsenosugars 1 (glycerol arsenosugar), 3 (sulfonate arsenosugar) and 4 (sulfate arsenosugar) making up ca. 90% of the maximal extractable arsenic. The rest accounts for DMA (dimethylarsinate), arsenosugar 2 (phosphate arsenosugar) and As(V). There is no clear extraction pattern emerging from the data although it may be seen that extraction of more polar species (e.g. arsenosugar 1) is favoured in pure methanol and less polar more ionic species (e.g. arsenosugar 2 and As(V)) in methanol extractants with a higher water percentage.The precise and highly accurate data may be used for quality control purposes under strictly followed extraction conditions since the extraction is operationally defined. Additionally, the variable volume extraction methodology presented may be applied to other elemental species in other matrices using other extractants. Although this approach does not maximise the absolute extractability but only that which is extractant-specific, experimentators are forewarned that in most cases only a fingerprint of the extractant-specific species is produced unless a quantitative extraction of all species is obtained.     

Photochromic liquid crystalline structures containing azobenzene moieties

Novel liquid crystalline photochromic materials of the type 4-R-C₆H₄-N=N-C₆H₄-O(CH₂)_n-N(CH₂CH₂OH)₂, where R is NO₂, H, CN, O-n-C₈H₁₇, phenyl, 4-O₂NC₆H₄, were prepared. Some of them are photoconductive. These materials were used for the preparation of light-sensitive polymers in which the photoactive moieties were attached to polyurethane chain. Photochromism of these compounds is based on trans-cis isomerization of azobenzene group. An example of the photochromic activity is presented on solid solution of one material (R = O-n-C₈H₁₇, n = 5) in poly(methyl methacrylate) matrix.     

MacNeille Completions of D-Posets and Effect Algebras

Our main result is stating and proving a necessary and sufficient condition forD-poset and effect algebras to have MacNeille completions.     

Screen-printing of microfibrillated cellulose for an improved moisture management,strength and abrasion resistant properties of flame-resistant fabrics

Cellulose - Low moisture absorbency of hydrophobically coated flame-resistant (FR) fabrics do not correlate well with the thermophysiological comfort. In this frame, we were the first to study the...     

DSC TOPEM® study of high-energy mechanical milling-driven amorphization in β-As4S4-based arsenicals

Journal of Thermal Analysis and Calorimetry - Temperature-modulated DSC TOPEM® method was applied to study amorphization in directly synthesized high-temperature polymorph of tetra-arsenic...     

Simulation of the first growth phase of single-walled carbon nanotubes using a model based on a cellular automaton

This paper presents a theoretical study on the first growth phase of single-walled carbon nanotubes. The model adopted is based on a cellular automaton containing as the elementary entities the metal particles and the carbon atoms. It uses an interaction based on phenomenological potentials to define the update function of the automaton. The purpose of this study is to establish the saturation condition of the metal particle with the carbon atoms when the formation of clusters of carbon begins. The results show that the first phase of formation of the carbon clusters can start with the particle partially saturated with carbon atoms.     

Microwave-assisted synthesis of new substituted anilides of quinaldic acid

In this study a one step method for the preparation of substituted anilides of quinoline-2-carboxylic acid was developed. This efficient innovative approach is based on the direct reaction of an acid or ester with substituted anilines using microwave irradiation. The optimized method was used for the synthesis of a series of eighteen substituted quinoline-2-carboxanilides. The molecular structure of N-(4-bromophenyl)quinoline-2-carboxamide as a model compound was determined by single-crystal X-ray diffraction. It crystallizes in the monoclinic space group with four molecules within the unit cell and the total structure of the compound can be described as "a slightly screwed boat".     

Phenolic compounds from Allium schoenoprasum, Tragopogon pratensis and Rumex acetosa and their antiproliferative effects

Experimental studies have shown that phenolic compounds have antiproliferative and tumour arresting effects. The aim of this original study was to investigate the content of phenolic compounds (PhC) in flowers of Allium schoenoprasum (chive), Tragopogon pratensis (meadow salsify) and Rumex acetosa (common sorrel) and their effect on proliferation of HaCaT cells. Antiproliferative effects were evaluated in vitro using the following concentrations of phenolic compounds in cultivation medium: 100, 75, 50 and 25 μg/mL. Phenolic composition was also determined by HPLC. The results indicate that even low concentrations of these flowers' phenolic compounds inhibited cell proliferation significantly and the possible use of the studied herb's flowers as sources of active phenolic compounds for human nutrition.     

Chemical evaluation of <Emphasis Type="Italic">Fallopia</Emphasis> species leaves and antioxidant properties of their non-cellulosic polysaccharides

Utilization of biomass from forest or agricultural crops for the production of energy or chemical products provides environmental advantages. Leaves of the knotweeds Fallopia japonica, Fallopia sachalinensis, and Fallopia × bohemica are rich sources of phenolics and polysaccharides. In view of their potential utilization before the disposal of these invasive plants, their gross composition was investigated. The content of extractives was the highest in F. sachalinensis. Extractive-free leaves of all species showed similar chemical composition. The content of ash, protein, lignin, uronic acids, and α-cellulose in the leaves of F. sachalinensis, F. × bohemica, and F. japonica was 63.3 %, 64.1 %, and 63.4 %, respectively. The rest comprised hemicelluloses and neutral carbohydrate components of pectic polysaccharides. Sequential extraction of F. sachalinensis with water, EDTA, DMSO, 1 % NaOH, and 5 % NaOH yielded fractions accounting together for 27.6 % of polysaccharides. Pectic polysaccharides predominated in the first three fractions, whereas the hemicellulose components — xylan and xyloglucan, prevailed in the two alkaline fractions. The polysaccharides displayed significant radical scavenging activities in the 1,1-diphenyl-2-picrylhydrazyl free radical assay thus indicating their potential application as novel natural antioxidants.     

Highly enantioselective nitroaldol reactions catalyzed by copper(II) complexes derived from substituted 2-(pyridin-2-yl)imidazolidin-4-one ligands

Ten optically pure substituted 2-(pyridin-2-yl)imidazolidin-4-ones, 1a-d, 2a-4a, and 2b-4b, were prepared and characterized. The absolute configurations of individual ligands were determined by X-ray analysis or NOESY experiments. The Cu(II) complexes of the respective ligands were studied as enantioselective catalysts of the nitroaldol (Henry) reaction of aldehydes with nitromethane, giving the corresponding substituted 2-nitroalkanols. In the case of an anti arrangement of the imidazolidin-4-one ring, the obtained result was 91-96% ee, whereas in the case of syn arrangement, a significant drop to 25-27% ee was observed.