Comparison between flexural and uniaxial compression tests to measure the elastic modulus of silica aerogel

The Young’s moduli of a set of silica aerogels have been measured by two techniques: 3-point bending and uniaxial compression. The data found by the two methods differ strongly. The uniaxial compression test gives generally underestimated values of Young’s modulus, because of geometrical effects. The appropriate gauge lengths were estimated based on the discussion of Euler buckling and nonuniform stress distribution. The measured compressive moduli were analyzed to correct for machine compliance and possible misalignment under compression of the aerogels. Similarly, moduli obtained by 3-point bending depend on the length/thickness ratio of the sample, reaching equilibrium only for ratios above about 10. The corrected compressive moduli were comparable to those measured by 3-point bending on samples of sufficient length.     

Insecticidal effect of <Emphasis Type="Italic">Mentha pulegium</Emphasis> L. and <Emphasis Type="Italic">Mentha suaveolens</Emphasis> Ehrh. hydrosols against a pest of citrus, <Emphasis Type="Italic">Toxoptera aurantii</Emphasis> (Aphididae)

Essential oils proved their efficiency as natural insecticides to fight many pests of stored products and crops whereas the hydrosols have not been evaluated yet. The objective of this work is to assess the insecticidal effect of hydrosols extracted from Mentha suaveolens Ehrh. and Mentha pulegium L. toward an insect pest of citrus, Toxoptera aurantii (Homoptera, Aphididae). The extraction of hydrosols was carried out by hydro-distillation using Clevenger apparatus and then the chemical composition was identified by gas chromatography coupled with mass spectrometry. The chemical composition of two hydrosols revealed the abundance of hydrophilic and oxygenated compounds as piperitenone oxide and carvacrol. Different concentrations of each hydrosol were separately diluted in distilled water and applied topically to aphids. The results of this investigation have shown a high insecticidal effect, and the M. suaveolens hydrosol is more effective against citrus pests than that of M. pulegium L. Consequently, these natural compounds can be used in the management of aphids on citrus.     

A new 1D hybrid fluoroaluminate templated by an original tetramine

An original polyamine, 2,3 di-2-aminomethyl 1,4 diaminobut-2-ene (ten), characterized by single-crystal XRD analysis, has been synthesised and leads to a new hybrid fluoroaluminate [H₄ten] · (AlF₅)₂ by microwave heating assisted hydrothermal synthesis. The structure of [H₄ten] · (AlF₅)₂ is ab initio determined from powder data.     

Identification of twenty amino acids by circular thin-layer chromatography

Summary A method has been developed for the separation and identification of 20 common amino acids by circular thin-layer chromatography. The amino acids are separated to neutral, acid, and basic groups by electrolysis and then identified by circular TLC. The method is simple and development of a chromatoplate is complete in about 3 minutes. The application of the method is illustrated by the analysis of amino acids in foods and in urine.

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Zusammenfassung Zur Trennung und Identifizierung 20 gewöhnlicher Aminosäuren wurde ein chromatographisches Verfahren entwickelt. Die Aminosäuren werden elektrolytisch in neutrale, basische und saure getrennt und dann auf kreisförmiger Dünnschichte chromatographiert. Die Entwicklung des Chromatogramms ist in 3 Minuten beendet. Die Anwendung zur Analyse von Lebensmitteln und Harn wird beschrieben.

     

Oxyradical-mediated Clastogenic Plasma Factors in Psoriasis: Increase in Clastogenic Activity after PUVA

Abstract— Psoriasis is a common skin disorder characterized by hyperproliferation and incomplete differentiation of epidermal keratinocytes. Psoralen plus UVA (PUVA) is one of the treatments proposed for this disease. We had reported previously that exposure of regular blood cultures from healthy donors to PUVA leads to chromosomal breakage via the formation of transferable clastogenic materials, a phenomenon inhibitable by superoxide dismutase. In the present paper we show that these clastogenic factors (CF) are also formed in vivo. The CF were found in about 50% of the psoriasis patients studied (14 out of 31). In PUVA-treated psoriasis patients, the clastogenic activity of the plasma increased significantly between the first and the last (16th) exposure to PUVA. We hypothesize that CF formation in psoriasis is similar to that in other diseases accompanied by oxidative stress, in particular chronic inflammatory diseases with autoimmune reactions such as lupus erythematosus, progressive systemic sclerosis, rheumatoid arthritis and others. Increased superoxide production by phagocytes, formation of lipid peroxidation products and release of cytokines are considered to be responsible for the superoxide-stimulating and chromosome-damaging properties of patients' plasma. During PUVA therapy, superoxide generated via the interaction of psoralen with UVA may contribute to CF formation in addition to superoxide from inflammatory cells. An increased risk of cancer and leukemia is observed in diseases accompanied by CF formation. Therefore CF may contribute to the well-known risk of photocarcinogenesis by PUVA therapy. This additional risk may be preventable by antioxidants and superoxide scavengers.     

A new synthesis of vitamin C

l-Arabinose was reduced to l-arabinitol and condensed with formaldehyde to give two bis(di-0-methylene-l-arabityloxymethane and two di-O-methylene-l-arabinitol derivatives. Cis-fused 1,3:2,4-Di-O-methylene-l-arabinitol and trans-fused 2,4:3,5-Di-O-methylene-l-arabinitol were also isolated; only the former was affected by the oxidation to give the corresponding aldehyde, which was converted successively to the hydroxy amide, the ethyl hydroxy ester, the corresponding keto ester and vitamin C.     

Straightforward Synthesis of Mn3O4/ZnO/Eu2O3-Based Ternary Heterostructure Nano-Photocatalyst and Its Application for the Photodegradation of Methyl Orange and Methylene Blue Dyes

Zinc oxide-ternary heterostructure Mn₃O₄/ZnO/Eu₂O₃ nanocomposites were successfully prepared via waste curd as fuel by a facile one-pot combustion procedure. The fabricated heterostructures were characterized utilizing XRD, UV–Visible, FT-IR, FE-SEM, HRTEM and EDX analysis. The photocatalytic degradation efficacy of the synthesized ternary nanocomposite was evaluated utilizing model organic pollutants of methylene blue (MB) and methyl orange (MO) in water as examples of cationic dyes and anionic dyes, respectively, under natural solar irradiation. The effect of various experimental factors, viz. the effect of a light source, catalyst dosage, irradiation time, pH of dye solution and dye concentration on the photodegradation activity, was systematically studied. The ternary Mn₃O₄/ZnO/Eu₂O₃ photocatalyst exhibited excellent MB and MO degradation activity of 98% and 96%, respectively, at 150 min under natural sunlight irradiation. Experiments further conclude that the fabricated nanocomposite exhibits pH-dependent photocatalytic efficacy, and for best results, concentrations of dye and catalysts have to be maintained in a specific range. The prepared photocatalysts are exemplary and could be employed for wastewater handling and several ecological applications.     

PTFE/EP Reinforced MOF/SiO2 Composite as a Superior Mechanically Robust Superhydrophobic Agent towards Corrosion Protection,Self-Cleaning and Anti-Icing

Organic resin cross-linking ZIF-67/SiO₂ superhydrophobic (SHPB) multilayer coating was successfully fabricated on metal substrate. The perfluoro-octyl-triethoxy silane (POTS) modified ZIF-67 and SiO₂ coating was applied on primary coated polytetrafluoroethylene (PTFE) and epoxy resin (EP) via spray coating method. Here, we present that the robust superhydrophobicity can be realized by structuring surfaces at two different length scales, with a nanostructure design to provide water repellence and a microstructure design to provide durability. The as-fabricated multilayer coating displayed superior water-repellence (CA=167.4°), chemical robustness (pH=1–14) and mechanical durability undergoing 120th linear abrasion or 35th rotatory abrasion cycle. By applying different acidic and basic corrosive media and various weathering conditions, it can still maintain superior-hydrophobicity. To get a better insight of interaction between inhibitor molecules and metal surface, density functional theory (DFT) calculations were performed, showing lower energy gap and increased binding energy of ZPS/SiO₂/PTFE/EP (ZPS=ZIF-67+POTS) multilayer coating compared to the ZIF-67/SiO₂/PTFE/EP, thereby supporting the experimental findings. Additionally, such coatings may be useful for applications such as anti-corrosion, self-cleaning, and anti-icing multi-functionalities.     

K2M(H2P2O7)2·2H2O (M = Ni,Cu, Zn): ortho­rhom­bic forms and Raman spectra

The crystal structures of three isotypic ortho­rhom­bic dihydrogendiphosphates, namely dipotassium copper(II)/nickel(II)/zinc(II) bis­(dihydrogendiphosphate) dihydrate, K₂M(H₂P₂O₇)₂·2H₂O (M = Cu, Ni and Zn), have been refined from single‐crystal data. The M²⁺ and K⁺ cations are located at sites of m symmetry, and the P atoms occupy general positions. These compounds also exist in triclinic forms with very similar structural features. The structures of both forms are compared, as well as the geometry of the MO₆ octa­hedron, which is considerably elongated towards the water mol­ecules for M = Ni and Cu. Such elongation has not been observed among the other representatives of the family. A Raman study of the whole series K₂M(H₂P₂O₇)₂·2H₂O (M = Mn, Co, Ni, Cu, Zn and Mg) is reported.     

Ultrasound assisted pseudo-digestion of street dust samples prior to determination by atomic absorption spectrometry

A sample preparation method based on ultrasound assisted pseudo-digestion of Pb, Cu, Zn and Ni from street dust samples under ultrasonic effect has been described. Parameters influencing pseudo-digestion, such as sonication time, sample mass, particle size and solvent system were fully optimized. Final solutions obtained upon sonication were analyzed by atomic absorption spectrometry. The best conditions for metal pseudo-digestion were as follows: a 25 min sonication time, a 0.3 g sample mass (in 25 ml solvent), a particle size <63 μm and a mixture of concentrated HNO₃-HClO₄-HF (2:1:1, v/v/v). Analytical results for the four metals by ultrasound assisted pseudo-digestion, acid bomb and conventional wet digestion methods showed a good agreement, thus indicating the possibility of using mild conditions for sample preparation instead of intensive treatments inherent with the digestion methods. In addition, this method reduces the time required for all treatments (pseudo-digestion or digestion, heating to dryness, cooling and separation) with acid bomb and conventional wet digestion methods approximately from 9 to 1 h. The accuracy of the method was tested either by comparing obtained results with those of acid bomb and conventional wet digestion methods or by application on two standard reference materials. The average relative standard deviation of ultrasound assisted pseudo-digestion method varied between 0.9 and 1.8% for N = 12, depending on the analyte.