Flow over a profile in a channel with dynamical effects

The work deals with a numerical solution of 2D inviscid incompressible flow over the profile NACA 0012 in a channel. The finite volume method in a form of cell‐centered scheme at quadrilateral C‐mesh is used. Governing system of equations is the system of Euler equations. Numerical results are partially compared with experimental data. Steady state solutions of the flow as well unsteady flows caused by prescribed oscillation of the profile were computed. The method of artificial compressibility and the time dependent method are used for computation of the steady state solution. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and NMR characterization of the cis and trans isomers of [Pt(II)(N9-adeH)2(pz)2] and X-ray crystallography of the trans isomer

The reaction of tetrapyrazine Pt(II) with adenine under basic conditions yielded two products both disubstituted by adenine and bound in all cases to the N-9 nitrogen of adenine. Crystals amenable to X-crystallographic analysis were obtained for one product which was consequently identified as trans-[Pt(II)(N9-adeH)2(pz)2](NO3)(4).H2O. The other product, though, was identified as the cis isomer based on extensive and comparative NMR structural studies whereby the two compounds were examined as both neutral and tetraprotonated species in solution. The major product of the reaction was unexpectedly the cis isomer, thus obtained in contrast to the trans effect, and the reason for this result is speculated on. Computational calculations using DFT at the B3LYP/TZVP-MARI-J level of theory provided the head-to-tail conformer as the overwhelmingly more stable species over the head-to-head conformer for both compounds whilst the trans product was found to be more stable than the cis. Thus the reaction does not follow a thermodynamic course and rather is kinetically controlled in concert with the speculated mode of reaction.     

Synthesis,Characterization and Biological Investigations of Half-Sandwich Ruthenium(II) Complexes Containing Benzimidazole Moiety

Half-sandwich Ru(II) complexes belong to group of biologically active metallo-compounds with promising antimicrobial and anticancer activity. Herein, we report the synthesis and characterization of arene ruthenium complexes containing benzimidazole moiety, namely, [(η⁶-p-cymene)RuCl(bimCOO)] (1) and [(η⁶-p-cymene)RuCl₂(bim)] (2) (where bimCOO = benzimidazole-2-carboxylate and bim = 1-H-benzimidazole). The compounds were characterized by ¹H NMR, ¹³C NMR, IR, UV–vis and CV. Molecular structures of the complexes were determined by SC-XRD analysis, and the results indicated the presence of a pseudo-tetrahedral (piano stool) geometry. Interactions in the crystals of the Ru complexes using the Hirshfeld surface analysis were also examined. In addition, the biological studies of the complexes, such as antimicrobial assays (against planktonic and adherent microbes), cytotoxicity and lipophilicity, were performed. Antibacterial activity of the complexes was evaluated against S. aureus, E. coli, P. aeruginosa PAO1 and LES B58. Cytotoxic activity was tested against primary human fibroblasts and adenocarcinoma human alveolar basal epithelial cells. Obtained biological results show that the ruthenium compounds have bacteriostatic activity toward Pseudomonas aeruginosa PAO1 strain and are not toxic to normal cells. A molecular docking study was applied as a predictive source of information about the plausibility of examined structures binding with HSA as a transporting system.     

Electromagnetic waves propagation in real multimode waveguide structures

A power flow equation describing the power flow of electromagnetic waves in a real multimode waveguide represented by a linear multichannel trasmission system exhibiting an attenuation, dispersion, and an interchannel interaction is solved in three iterative ways. In the case of constant attenuation and constant propagation velocities in all channels and for the convolution interchannel interaction, a closed analytical solution of the problem is presented. Interesting forms of the solution, transfer function, and impulse response of the system which enable us to separate and compare the attenuation, dispersion, and coupling effects independently of each other are derived. The transfer function, the impulse response, and excitation conditions for their measurements are further discussed. Relations which make it possible to compare different experimental data obtained under specific excitation conditions in various laboratories are determined. Finally, a linear system with memory in time is studied and it is shown that the real multimode waveguide as a linear multichannel transmission system can be considered as a general linear system with memory in space.     

Numerical Analysis of the Rebellious Voter Model

The rebellious voter model, introduced by Sturm and Swart (2008), is a variation of the standard, one-dimensional voter model, in which types that are locally in the minority have an advantage. It is related, both through duality and through the evolution of its interfaces, to a system of branching annihilating random walks that is believed to belong to the ‘parity-conservation’ universality class. This paper presents numerical data for the rebellious voter model and for a closely related one-sided version of the model. Both models appear to exhibit a phase transition between noncoexistence and coexistence as the advantage for minority types is increased. For the one-sided model (but not for the original, two-sided rebellious voter model), it appears that the critical point is exactly a half and two important functions of the process are given by simple, explicit formulas, a fact for which we have no explanation.     

Determination of arsenic at a gold-plated carbon paste electrode using constant current stripping analysis

A new stripping method for the determination of arsenic in water samples with a gold film-plated carbon paste electrode has been developed for the use in constant current stripping analysis (CCSA). In the novelized procedure, differentiation between As(III) and chemically pre-reduced As(V), the effect of Cu(II) on the response of arsenic, and the stability of sample solutions were studied in detail. Compared to the voltammetric approach, the method utilizing CCSA offers a more rapid procedure with improved analytical characteristics such as reproducibility, selectivity over the Cu(II) ions, or lower detection limit (3 ppb for As(III) and 0.5 ppb for As(V), respectively). The possibilities of the optimized method are demonstrated by determinations of As(III), As(V), and total arsenic in samples of polluted river water.     

2-Alkylsulphanyl-4-pyridinecarbothioamides — inhibitors of oxygen evolution in freshwater alga Chlorella vulgaris

The inhibition of the oxygen evolution rate (OER) in Chlorella vulgaris by 2-alkylsulphanyl-4-pyridinecarbothioamides (APCTs; alkyl = methyl up to hexadecyl) was studied. APCTs were found to inhibit photosynthetic electron transport (PET) which resulted in the inhibition of OER in algae. The inhibitory activity of APCTs was highly dependent on the alkyl chain length of the 2-alkylsulphanyl substituent and the corresponding dependence showed a bilinear course with the decyl derivative as being the most active inhibitor. Using EPR spectroscopy, the site of APCT action in the algal photosynthetic apparatus was determined. It was confirmed that APCT interacted mainly with the D. intermediate, i.e. with tyrosine radical (Tyr_D) occurring at the 161st position in D2 protein which is situated on the donor side of photosystem 2.     

Macroporous antimony film electrodes for stripping analysis of trace heavy metals

We report on the elaboration of macroporous antimony film electrodes. The strategy to create macroporous electrodes is based on the replication of colloidal crystal templates. These electrodes of controlled porosity show an increased internal electroactive area and a significantly improved electrochemical performance. The application of this novel electrochemical sensor for the sensitive quantification of traces of heavy metals has been demonstrated in combination with differential pulse anodic stripping voltammetry in model solutions.     

Full analogy of Sharkovsky's theorem for lower semicontinuous maps

A full analogy of the celebrated Sharkovsky cycle coexistence theorem is established for lower semicontinuous (multivalued) maps on metrizable linear continua. This result is further extended to triangular maps.