The impact of ultrasound and steam blanching pre-treatments on the drying kinetics,energy consumption and selected properties of parsley leaves

In current study the influence of ultrasound pre-treatment and drying conditions (microwave power, air temperature) was analysed by the means of drying kinetics, energy consumption and selected quality properties of dried parsley leaves. Ultrasound treatment (US) was compared with conventional treatment – steam blanching. In comparison to untreated material, ultrasound applied at 21 kHz, 12 W/g, contributed to significant reduction of the drying time up to 29.8%. Moreover, the energy expenditures were reduced maximally by 33.6% for parsley dried at 30 °C and 300 W. For this sample the colour retention was the highest, as well. In turn, steam treated parsley was dried maximally by 28.9% faster and thus specific energy consumption decreased to 72.0% of the value for intact leaves when 20 °C and 300 W were set. The influence of pre-drying treatment on the quality properties depended on the drying conditions. Pre-drying treatment (US, blanching) did not affect the lutein content significantly, whereas the most considerable increase of chlorophyll a and b resistance and their relative concentration (Chl a/b ratio) was achieved in US-treated leaves dried at 30 °C and 100 W. The utilisation of drying pre-treatment and dehydration parameters should be considered with respect to further utilisation of dried parsley leaves. Nonetheless, sonication is worth to be taken into account due to a significant reduction of energy expenditures and an improvement of resistance of bioactive components.     

Compatible rate-of-convergence bounds for the grid method in the eigenvalue problem for the Helmholtz equation in a right triangle

An O(h) accurate difference scheme is constructed for the eigenvalue problem for the Helmholtz operator in a right triangle. The convergence of the difference scheme is analyzed under conditions ensuring that the eigenfunctions of the differential problem are in the space W ₂ ¹ ().Translated from Vychislitel'naya i Prikladnaya Matematika, No. 63, pp. 50–57, 1987.     

Polyelectrolyte Hydrogels Based on Hydrolyzed Polyacrylonitrile Fiber

Cross-linking of hydrolyzed Nitron D polyacrylonitrile fiber on exposure to ionizing radiation was studied as influenced by its concentration in the solution, dose rate, and the presence of oxygen in the system. Preparation conditions of polyelectrolyte hydrogel with maximal water absorption by radiochemical cross-linking at the minimal dose were determined.     

Investigation of the shape and stability of a liquid drop on a rotating substrate

The shape and stability of a capillary-sized water drop sitting on a rotating substrate are studied both theoretically and experimentally. The theoretical and experimental data are found to be in good agreement. The results of the study may be used in fabricating self-assembled thin films by means of spin coating technology.     

Erd?l

Ohne Zusammenfassung     

Alkaline earth imidazolate coordination polymers by solvent free melt synthesis as potential host lattices for rare earth photoluminescence: (x)(∞)[AE(Im)2(ImH)(2-3)], Mg, Ca, Sr, Ba, x = 1-2

The series of alkaline earth elements magnesium, calcium, strontium and barium yields single crystalline imidazolate coordination polymers by reactions of the metals with a melt of 1H-imidazole: (1)(∞)[Mg(Im)(2)(ImH)(3)] (1), (2)(∞)[AE(Im)(2)(ImH)(2)], AE = Ca (2), Sr (3), and (1)(∞)[Ba(Im)(2)(ImH)(2)] (4). No additional solvents were used for the reactions. Co-doping experiments by addition of the rare earth elements cerium, europium and terbium were carried out. They indicate (2)(∞)[Sr(Im)(2)(ImH)(2)] as a possible host lattice for cerium(III) photoluminescence showing a blue emission and thus a novel blue emitting hybrid material phosphor 3:Ce(3+). Co-doping with europium and terbium is also possible but resulted in formation of (3)(∞)[Sr(Im)(2)]:Ln, Ln = Eu and Tb (5), with both exhibiting green emission of either Eu(2+) or Tb(3+). The other alkaline earth elements do not show acceptance of the rare earth ions investigated and a different structural chemistry. For magnesium and barium one-dimensional strand structures are observed whereas calcium and strontium give two-dimensional network structures. Combined with an increase of the ionic radii of AE(2+) the coordinative demand is also increasing from Mg(2+) to Ba(2+), reflected by four different crystal structures for the four elements Mg, Ca, Sr, Ba in 1-4. Different linkages of the imidazolate ligands result in a change from complete σ-N coordination in 1 to additional η(5)-π coordination in 4. The success of co-doping with different lanthanide ions is based on a match in the chemical behaviour and cationic radii. The use of strontium for host lattices with imidazole is a rare example in coordination chemistry of co-doping with small amounts of luminescence centers and successfully reduces the amount of high price rare earth elements in hybrid materials while maintaining the properties. All compounds are examples of pure N-coordinated coordination polymers of the alkaline earth metals and were identified by single crystal X-ray analysis and powder diffraction. The degree of co-doping was determined by SEM/EDX. Mid IR, Far IR and Raman spectroscopy and micro analyses as well as simultaneous DTA/TG were also carried out to characterize the products in addition to the photoluminescence studies of the co-doped samples.