Spectroscopic study of a bis(imidazole)(octaethylporphyrinato)iron(III) complex

Low-spin ferric octaethylporphyrinatoiron complex with two imidazole axial ligands [Fe(III)(OEP)(Im)_{2}]^{+} has been investigated by electron paramagnetic resonance (EPR) and Mossbauer spectroscopies. It was found that the ground spin state corresponds to the electron configuration (dxy)^{2} (dxz, dyz)^{3} and planes of the imidazole axial ligands have a parallel mutual orientation. Ethyl groups bonded to pyrrole rings, as peripheral substituents, effect on the ground electron spin state of the complex studied and the relative orientation of the the imidazole axial ligands in a similar way like the phenyl substituents bonded to meso-carbon atoms of the porphyrin macrocycle. The temperature dependence of the Mossbauer spectra is discussed in terms of magnetic relaxation processes

Mössbauer study of a tetrakis (pentafluorophenyl) porphyrin iron (III) chloride in comparison with the fluorine unsubstituted analogue

Mossbauer investigations, in association with density functional theory (DFT) calculations, have been conducted for the molecular and electronic structures of iron (III) [tetrakis (pentafluorophenyl)] porphyrin chloride [(F_{20}TPP)Fe:Cl], as a Fe(III)-tetraphenylporphyrin complex containing chloride axial ligand and substituted hydrogen atoms by fluorine ones in the four phenyl rings, in comparison with its fluorine unsubstituted analogue [(TPP)Fe:Cl]. It was found that the parameters of Mossbauer spectra of both complexes are close to one another, and correspond to the high-spin state of Fe(III) ions, but they show the different temperature dependence and the quadrupole doublets in Mossbauer spectra show different asymmetry at low temperatures. Results of DFT calculations are analyzed in the light of catalytic activity of the halogenated complex

6-year old children with special educational needs at the beginning of school. A study of gender in the context of education reform

Initiators of the most socially negotiated changes under the current reform of the education system, including the lowering of school age to 6, indicate “bridging the education gap” as one of the advantages of an earlier education. In fact, there is no critical refl ection and discussion on how the education system responds to the diversity of children’s needs and identifi ed areas and risk factors of educational failures on the threshold of school. In the text we pay special attention to two important issues overlooked in the ministerial discourse: a risk factor for school failure defi ned as special educational needs (SEN) and the problem of differentiation of the level of preparedness, experience and school achievements of children based on gender, with particular regard to socioemotional development

Elucidation of role of graphene in catalytic designs for electroreduction of oxygen

Graphene is, in principle, a promising material for consideration as component (support, active site) of electrocatalytic materials, particularly with respect to reduction of oxygen, an electrode reaction of importance to low-temperature fuel cell technology. Different concepts of utilization, including nanostructuring, doping, admixing, preconditioning, modification or functionalization of various graphene-based systems for catalytic electroreduction of oxygen are elucidated, as well as important strategies to enhance the systems' overall activity and stability are discussed

Leptin concentrations in patients with polycystic ovary syndrome before and after met-formin treatment depending on insulin resistance, body mass index and androgen con-centrations--introductory report.

Polycystic ovary syndrome (PCOS) is an endocrinological and metabolic disorder which may concern about 3-8% of women. Some PCOS women have the increased leptin concentration in blood serum. Leptin concentration is higher in patients with high body mass index (BMI) and impaired tissue sensitivity to insulin. The aim of this study was to determine leptin concentrations in PCOS patients before and after metformin treatment depending on BMI, insulin resistance calculated on the basis of the Homeostasis Model Assessment (HOMA) index, as well as concentrations of androgens: testosterone and androstendion. Such values as BMI, insulin resistance according to the HOMA index, and concentrations of androstendion, testosterone and leptin were determined in 35 patients with PCOS before and after 3-month metformin treatment administered in daily doses of 2 x 850 mg. Increased leptin levels before the therapy were observed in 91.3% (21 out of 23) of obese patients, in 75% (9 out of 12) non-obese patients, in 100% (8 patients) insulin resistance women, in 81.5% (22 out of 27) insulin sensitive patients, in 94.7% (18 out of 19) women with elevated androstendion concentration and in 75% (12 out of 16) with normal androstendion concentration, in 93.7% (15 out of 16) patients with increased testosterone concentration and in 78.9% (15 out of 19) patients with testosterone concentrations within the normal range. After treatment statistically significant decrease in leptin concentration was obtained in the patients with BM

Evaluation of Reduced-Graphene-Oxide Aligned with WO3-Nanorods as Support for Pt Nanoparticles during Oxygen Electroreduction in Acid Medium

Hybrid supports composed of chemically-reduced graphene-oxide-aligned with tungsten oxide nanowires are considered here as active carriers for dispersed platinum with an ultimate goal of producing improved catalysts for electroreduction of oxygen in acid medium. Here WO3 nanostructures are expected to be attached mainly to the edges of graphene thus making the hybrid structure not only highly porous but also capable of preventing graphene stacking and creating numerous sites for the deposition of Pt nanoparticles. Comparison has been made to the analogous systems utilizing neither reduced graphene oxide nor tungsten oxide component. By over-coating the reduced-graphene-oxide support with WO3 nanorods, the electrocatalytic activity of the system toward the reduction of oxygen in acid medium has been enhanced even at the low Pt loading of 30 microg cm-2. The RRDE data are consistent with decreased formation of hydrogen peroxide in the presence of WO3. Among important issues are such features of the oxide as porosity, large population of hydroxyl groups, high Broensted acidity, as well as fast electron transfers coupled to unimpeded proton displacements. The conclusions are supported with mechanistic and kinetic studies involving double-potential-step chronocoulometry as an alternative diagnostic tool to rotating ring-disk voltammetry.Comment: arXiv admin note: text overlap with arXiv:1805.0315

A formalism to compare electrocatalysts for the oxygen reduction reaction by cyclic voltammetry with the thin-film rotating ring-disk electrode measurements

This report describes a general method to correlate the features determining the performance of an electrocatalyst (EC), including the accessibility of O2 to the active sites and the kinetic activation barrier, with the outcome of conventional electrochemical experiments. The method has been implemented for oxygen reduction reaction ECs by cyclic voltammetry with the thin-film rotating ring-disk electrode setup. The method (i) does not rely on the simplifications associated with the Butler-Volmer kinetic description of electrochemical processes and (ii) does not make assumptions on the specific features of the EC, allowing to compare accurately the kinetic performance of oxygen reduction reaction ECs with completely different chemistry. Finally, with respect to other widespread figures of merit (e.g. the half-wave potential E1/2), the figure of merit here proposed, for example, E(jPt[5%]), allows for much more accurate comparisons of the kinetic performance of ECs