Impedance spectroscopy studies of electroless Ni–P matrix,Ni–W–P,Ni–P–ZrO2, and Ni–W–P–ZrO2 coatings exposed to 3.5% NaCl solution

Ni–P matrix, ternary Ni–W–P and Ni–P–ZrO₂ coatings, and quaternary Ni–W–P–ZrO₂ coatings were deposited using electroless method from a glycine bath. Their corrosion resistance was evaluated by electrochemical impedance spectroscopy (EIS) for various immersion times in a 3.5% NaCl solution. From among the investigated coatings, the ternary Ni–W–P coatings show the highest resistance to corrosion in the first hour of exposure to the 3.5% NaCl medium. An addition of ZrO₂ adversely affects the performance of both the Ni–P coatings and the Ni–W–P coatings. For all the coatings, including the ones containing tungsten, a marked decrease in pore resistance (R_por) over time is observed. This means that their corrosion resistance and capacity to protect the substrate decline. On the other hand, after 24 h immersion in the 3.5% NaCl solution the Ni–W–P coating shows the highest low‐frequency impedance modulus (|Z|_{f = 0.01 Hz}). As regards corrosion resistance, the Ni–P coatings and the Ni–W–P coatings perform best.     

Stresses and strains in soldered joints

In this article, current thinking on stresses in soldered joints of different physical and mechanical properties was appraised, as well as the possibilities for decreasing them with the use of different techniques, from technological experiments to numerical methods. The influence of individual factors on the size of stresses was analysed, including the solder gap size, the thicknesses of joined elements, area and soldered surface roughness, spacers, and compensation inserts as well as joint geometry. The results of numerical calculations of 2D models of soldered joints for different sizes of surfaces soldered at a constant width of solder gap were also presented. Particular attention was paid to stresses occurring in joints with large soldering surfaces.     

Problems with welding steel T24 intended for membrane walls of boilers

We present the issues connected with the manufacture of waterwalls made of modern 7CrMoVTiB10-10 (T24) steel by submerged and TIG welding methods. We give the results of mechanical testing and structural examination of parent materials and welding consumables used for the manufacture of welded joints as well as the results of weldability and crack resistance testing for T24 steel. Possible reasons for cracking in welded joints as well as the usability of T24 steel for construction of responsible elements of waterwalls in advanced power boilers is discussed.     

A fast exact algorithm for the allocation of seats for the EU Parliament

In this paper, we analyse the problem of allocation of seats for the EU Parliament. To solve it, we propose a fast exact algorithm which overwhelms limitations of the existing methods. It allows us to examine all feasible allocations of seats within few minutes. On this basis, an in-depth analysis of the problem is provided and some of its properties are revealed (e.g., the number of feasible allocations of seats holding the Treaty of Lisbon), which have never been presented in the scientific literature. Furthermore, the proposed algorithm is not limited to dealing with the problem of allocation of seats for the EU Parliament, but it can be applied in the expert system for any other similar problem, especially under degressive proportionality constraints.     

Pharmacological Profile and Molecular Modeling of Cyclic Opioid Analogues Incorporating Various Phenylalanine Derivatives

Peptide-based agonists of the μ opioid receptor (μOR) are promising therapeutic candidates for pain relief with reduced side effects compared to morphine. A deep understanding of μOR–ligand interactions is necessary for future design of peptide-based opioid analgesics. To explore the requirements of the μOR binding pocket, eight new analogues of our cyclic peptide Tyr-c[d -Lys−Phe−Phe−Asp]NH₂ displaying high μOR affinity were synthesized, in which Phe in either the third or fourth position was replaced by various derivatives of this amino acid (β³-Phe, homoPhe, β³-homoPhe and PhGly). The aim of this research was to examine the structural effects of such modifications on the bioactivity, and both experimental and theoretical methods were used. The binding of the cyclic analogues to all three OR types (μ, δ, κ) was assessed by radioligand competitive binding assay, and their functional activity was determined in a calcium mobilization assay. In order to provide structural hypotheses explaining the obtained experimental affinities, the complexes of the cyclic peptides with μOR were subjected to molecular modeling.     

Phenolic compounds from winemaking waste and its antioxidant activity towards oxidation of rapeseed oil

The effects of extraction parameters on bioactive compound contents of winemaking waste extracts (WWE) and its effect on rapeseed oil oxidative stability were evaluated. Research showed that the total phenols and anthocyanin contents and antioxidant activity (AA) of WWE significantly depended on the extraction parameters. Increasing the temperature (60 °C) and time (5 h) of extraction and an addition of water to ethanol statistically improved the rate of active component extraction. HPLC analysis showed that procyanidin B_2, catechin, gallic acid, γ‐resorcylic acid and p‐coumaric acid were the major phenolic compounds of WWE. Important correlations between total phenolic compounds quantified by HPLC and both DPPH and (ferric reducing antioxidant power) (FRAP) values were found. WWE added to the oil at three different levels clearly slowed down the process of fatty acid oxidation, inhibiting hydroperoxide formation by about 86%, comparable with BHT, while it was more effective than that of α‐tocopherol. When using volatile compound formation as a marker of lipid oxidation, WWE at the level of 2000 ppm were the most effective inhibitors of the decomposition of hydroperoxides. The research showed that the WWE are a rich source of phenolic compounds with powerful antioxidant activities and are suitable for preventing rapeseed oil oxidation.     

Analog filter pair design on the basis of a gyrator–capacitor prototype circuit

The paper presents an algorithmic approach to a low‐sensitivity design strategy for analog filter pairs based on a gyrator–capacitor prototype circuit. The general structure of the prototype circuit is proposed. It assumed that the generic structure of the prototype circuit can evolve, with the use of additional gyrators, into a circuit with increased redundancy. It is shown that symbolic analysis of the prototype circuit, used to formulate a set of nonlinear algebraic equations, is necessary to achieve a sufficiently high algorithm operation speed. To find a solution to this specific system of nonlinear algebraic equations, different numerical methods are compared. The modified Hooke and Jeeves algorithm is found to be the most effective. The elaborated algorithms and programs are illustrated with the seventh‐order filter pair example. The obtained filter is better than the filter obtained using LC ladder structures with respect to chip area and power consumption, and these improvements are obtained without loss of sensitivity properties. Copyright © 2010 John Wiley & Sons, Ltd.