Synthetic, Crystallographic, and Computational Study of Copper(II) Complexes of Ethylenediaminetetracarboxylate Ligands

Copper(II) complexes of hexadentate ethylenediaminetetracarboxylic acid type ligands H4eda3p and H4eddadp (H4eda3p = ethylenediamine-N-acetic-N,N′,N′-tri-3-propionic acid; H4eddadp = ethylenediamine-N,N′-diacetic-N,N′-di-3-propionic acid) have been prepared. An octahedral trans(O6) geometry (two propionate ligands coordinated in axial positions) has been established crystallographically for the Ba[Cu(eda3p)]·8H2O compound, while Ba[Cu(eddadp)]·8H2O is proposed to adopt a trans(O5) geometry (two axial acetates) on the basis of density functional theory calculations and comparisons of IR and UV−vis spectral data. Experimental and computed structural data correlating similar copper(II) chelate complexes have been used to better understand the isomerism and departure from regular octahedral geometry within the series. The in-plane O−Cu−N chelate angles show the smallest deviation from the ideal octahedral value of 90°, and hence the lowest strain, for the eddadp complex with two equatorial β-propionate rings. A linear dependence between tetragonality and the number of five-membered rings has been established. A natural bonding orbital analysis of the series of complexes is also presented.

Agricultural monopolistic competitor and the Pigovian tax

A monopolistically competitive agricultural market structure has some features of competition and some features of monopoly. Monopolistic competition has the following attributes: (a) many sellers; (b) product differentiation; and (c) free entry. In the long-run equilibrium, price equals average total cost, and the agricultural firm earns zero economic profit. The aim of this paper is to construct a relatively simple chaotic long-run monopolistic competitor’s agricultural output growth model that is capable of generating stable equilibria, cycles or chaos. A key hypothesis of this work is based on the idea that the coefficient plays a crucial role in explaining local stability of the monopolistic competitor’s agricultural output, where d is the coefficient of the marginal cost function of the agricultural monopolistic competitor; b is the coefficient of the inverse demand function; a is the coefficient of average cost growth; m is the Pigovian tax rate; and e is the coefficient of the price elasticity of demand

Frequency domain analysis of lightning protection using four lightning protection rods

In this paper the lightning discharge channel is modeled as a vertical monopole antenna excited by a pulse generator at its base. The lightning electromagnetic field of a nearby lightning discharge in the case of lightning protection using four vertical lightning protection rods was determined in the frequency domain. Unknown current distributions were determined by numerical solving of a system of integral equations of two potentials using the Point Matching Method and polynomial approximation of the current distributions. The influence of the real ground, treated as homogeneous loss half-space of known electrical parameters, expressed through a Sommerfeld integral kernel, was modeled using a new Two-image approximation which gives good results in both near and far fields

Genetic algorithms and smoothing filters in solving the geophysical inversion problem

The combination of genetic algorithms, smoothing filters and geophysical tomography is used in solving the geophysical inversion problem. This hybrid technique is developed to improve the results obtained by using genetic algorithm sonly. The application of smoothing filters can improve the performance of GA implementation for solving the geophysical inversion problem. Some test-examples and the obtained comparative results are presented

Rare Earth‐Doped Anatase TiO2 Nanoparticles

Titanium dioxide is a wide band‐gap semiconductor of high chemical stability, nontoxicity and large refractive index. Because of the high photocatalytic activity, anatase is a preferred TiO2 form in many applications such as for air and water splitting and purification. Doping of TiO2 with various ions can increase the photocatalytic activity by enhancing light absorption in visible region and can alter structure, surface area and morphology. Also, by doping TiO2 with optically active ions, visible light via up‐ or downconversion luminescence can be produced. It is a challenge to optimize the synthesis procedure to incorporate rare earth RE3+ ions into the TiO2 structure due to large mismatch in ionic radii between the Ti4+ and RE3+ and because of the charge imbalance. Visible (VIS) and ultraviolet (UV) luminescence of several RE3+ ions can be obtained when incorporated into anatase TiO2, also affecting microstructural characteristics of TiO2. It is of great importance to summarize publications on rare earth‐doped anatase TiO2 nanoparticles to find correct TiO2-RE combination to sensitize trivalent rare earths luminescence, as well as to predict or tune structural and morphological properties. A better understanding on these topics may progress the desired design of this kind of material towards specific applications

Kinetic Determination of Arsenic(III) as Inhibitor of Victoria Blue 4R Oxidation in Strong Acid Solution

A new selective, sensitive and simple kinetic method was developed for the determination of As3+ traces in solution on the basis of their inhibiting effect on Victoria blue 4R (VB) oxidation by KBrO3 in the presence of HCl. The reaction was followed spectrophotometrically at 596.3 nm. The detection limit was 50.00 ng cm–3. The relative error vas 4.2 % to 1.5 % for As3+ in the concentration range from 80.00 to 350.00 ng cm–3. Also, appropriate kinetic equations were formulated and the influence of different ions upon the reaction rate was studied. The developed procedure was successfully applied to the determination of As3+ in various model and real samples

Introduction of the interdependence between the glutathione half-cell reduction potential and thermodynamic parameters during accelerated aging of maize seeds

Two maize hybrids with a different ability to maintain seed germination were examined during the course of accelerated aging (AA). Initially, the similar seed reduction potential of the GSSG/2GSH half-cell increased in H1 (dent hybrid) without influencing the seed germination ability up to the 6th day of AA, while in H2 (sweet corn hybrid), it was not changed up to the 6th day of AA but with a significant later loss of seed germination ability. During the AA course, the amount of free thiol decreased in H1 and increased in H2. Irrespective of the continual increase of the differential Gibbs energy during AA, the characteristics of the examined hybrids are possibly connected to the different metabolic pathways of the seeds: H1 is characterized by higher entropy and positive enthalpy values, while H2 had negative entropy values and a decreasing trend of enthalpy, indicating a shift of the system from a relatively ordered to a disordered state. The different types of nanomolecular switches, resulting in a faster decrease of GSH in the H2 than in the H1 hybrids, indicate that a combination of the GSSG/2GSH half-cell potential and thermodynamics could be a useful tool to quantify plant stress.Proučavano je ubrzano starenje semena dva hibrida kukuruza koja imaju drugačiju sposobnost očuvanja klijavosti. Sličan početni redukcioni potencijal GSSG/2GSH para je kod H1(zuban) rastao bez uticaja na sposobnost klijanja do šestog dana ubrzanog starenja, dok se kod H2 (šećerac) nije menjao do šestog dana starenja, uz kasniji značajan pad klijavosti. Količina PSH se smanjivala kod H1, dok je rasla kod H2 tokom tretmana starenja. Bez obzira na kontinuiran pad slobodne energije tokom ubrzanog starenja, osobine semena ispitivanih hibrida su možda bile vezane za drugačije metaboličke puteve: H1 karakteriše visoka entropija i pozitivne vrednosti entalpije, dok je za H2 karakteristična relativno niska entropija, uz negativne vrednosti entalpije, ukazujući na pomeranje sistema iz relativno uređenog u neuređeno stanje. Drugačiji tipovi nanomolekulskih prekidača, utičući na brži pad GSH kod H2 u odnosu na H1, ističu da se kombinacija GSSG/2GSH ćelijskog potencijala i termodinamike mogu koristiti pri kvantifikaciji biljnog stresa.Projekat ministarstva br. TR-20007: Development of maize cropping technology with an ecological approac

The programme for professional development of chemistry teachers’ assessment competency

The aim of this paper is to investigate the effects of the programme for professional development of chemistry teachers on their competencies for conducting formative and summative assessment in chemistry teaching. The programme participants were 30 chemistry teachers from primary and secondary schools. Data were collected using a questionnaire at the beginning and at the end of the programme implementation. The programme included four workshops with the same structure: the introduction, group work and the discussion of the results obtained through group work. The workshops focused on: i) the assessment as a support for chemistry learning; ii) the harmonization of teaching and learning activities, formative and summative assessment, feedback from formative assessment and the criteria used to evaluate students in summative assessment; iii) the evaluation of the validity of tasks used for formative and summative assessment according to the curricula aims and the educational standards; iv) designing tasks for monitoring students’ progress towards certain educational standards. Teachers’ responses show the impact of the programme for the development of their competencies for assessment, particularly regarding formative and summative assessment and designing various kinds of assessment in accordance with the achievement standards

The effect of encapsulated amount of caffeine on the mechanism of its release from hydrogels based on poly(methacrylic) and casein

Researchers are making everyday efforts to develop new drugs or improve present ones in order to enhance therapies of various diseases, especially serious ones like cancer. Drug delivery systems (DDS) are one of the solutions for safer and more efficient therapy. Hydrogels based on poly(methacrylic acid) (PMAA) are extensively investigated as DDS due to their nontoxicity, biocompatibility and pH sensitivity. Many chemotherapeutics are poorly watersoluble, so it is quite challenging to encapsulate them into highly hydrophilic PMAA. In our previous study we overcome this limitation by modifying PMAA with amphiphilic casein and demonstrated that poorly water-soluble model drug – caffeine can be successfully encapsulated and released in control manner from these samples (H hydrogels). In present study we go step forward and investigated how the change in the amount of encapsulated caffeine affect the mechanism of caffeine release from the H hydrogels in medium with pH of 6.8 (which simulates the environment in human intestines). Commonly used models for the analysis of kinetics of drug release from hydrogels: Ritger-Peppas, Higuchi and Kopcha model are employed for the analysis of the mechanism of caffeine release. Presented results indicate that it is possible to adjust the manner and mechanism of drug release by changing the amount of encapsulated drug, due to which the H hydrogels can adapt to the unique requirements of the therapy

C − H···π interactions in the metal-porphyrin complexes with chelate ring as the h acceptor

Specific C − H···π interactions with the π-system of porphyrinato chelate ring were found in crystal structures of transition metal complexes from the CSD and statistical analysis of geometrical parameters for intramolecular and intermolecular interactions was done. DFT calculations on a model system show that energy of the interaction is 1.58 kcal/mol and that the strongest interaction occurs when the distance between hydrogen atom and the center of the chelate ring is 2.6 Å. This prediction is in good agreement with the distances for intermolecular interactions found in the crystal structures. In many cases the intramolecular interaction distances are much shorter than 2.6 Å, and these short distances appear to be caused by geometrical constrains. The C − H···π interactions with chelate ring of porphyrinato ligand can be important in biomolecules with porphyrin as they can influence the structure, contribute to the stability and play some role in function of biomolecules.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200