Structure refinement of quaternary spinel oxides experiments and modelling

Comprehensive studies have been undertaken, inclusive of experimental and computational techniques, on the structure and cation distribution of spinel solid solutions formed between the normal spinel LiMn2O4 and inverse LiFe5O8. Series of solid solutions of a composition (1 - x)LiMn2O4 x xLi0.5Fe2.5O4 are single phase products with spinel structure in the whole range of x, displaying a cubic structure. With increasing Fe3+ content, the tendency of ordering by lithium ions in octahedral spinel sites and a strongly marked preference of Li+ cations to occupy the octahedral positions is apparent. Modelling and refinement of crystal structure of such spinel solid solution series have been undertaken by the energy minimisation procedure, together with the interatomic potentials calculation, explaining some divergences of the experimental data.

Relationship of crystal structure to interionic interactions in the lithium-manganese spinel oxides

Lithium manganese oxides in the form of cubic spinel phases (space group Fd3m) are formed in a LixMn3-xO4 system for rather limited values of x. Structural investigations by X-ray powder diffraction, applied to the Li-Mn-O compounds, indicate the formation of a second crystalline phase, Li2MnO3 (space group C2/m), with the increasing lithium content. Total Li+ content per unit cell and the cation distribution over a spinel lattice in LixMn3-xO4 have been studied by measurements of integrated intensities of X-ray reflections, and by structure refinement using Rietveld profile analysis. In an attempt to understand the factors affecting cation distribution in the spinel lattice, we applied the computer modelling techniques and investigated the Li+, Mn3+ and Mn4+ ion distribution by calculating the lattice energy, combined with energy minimisation procedures, using the General Utility Lattice Program (GULP), a program designed for simulation of ionic and semi-ionic solids, based on interatomic potential models.

[The evaluation of goiter frequency and iodine prophylaxis efficiency in children population in Wielkopolska area from 1992 to 1998]. / Ocena czestosci wystepowania wola i skutecznosci profilaktyki jodowej u dzieci na terenie Wielkopolski w latach 1992-1998.

The aim of the study was to compare the current state and efficiency of iodine prophylaxis during the last six years. The study included 800 children from the rural and urban area (462 children in 1992 and 338 children in 1998) with the proportional sex and age (8-13 years) distribution, 24.936 newborns (9875 in 1992/1993 and 15.061 - mostly in the early part of 1998). The thyroid size (by USG), serum thyroglobulin (TG) concentration, urinary iodine (UI) concentration, %age of neonatal-TSH above 5 micro U/ml were evaluated using current ICCIDD and WHO criteria. The prevalence of goiter detected in children population in 1992 was 26% (recount by current criteria), in the early part of 1998 it was reduced to 21%. Parallelly, mean urinary iodine concentration increased from 49 micro g/l to 79 micro g/l. The reduction of goiter prevalence was associated with the reduction of mean serum thyroglobulin concentration from 26 ng/ml to 18 ng/ml. In the group of newborns the %age of TSH results above 5 micro U/ml decreased from 6 to 2.6%. Generally, the study proved significant increase of iodine prophylaxis efficiency in Wielkopolska Region in the period of the last six years, but it is still the area with mild iodine deficiency, which suggests the necessity of using other forms of iodine prophylaxis except for salt iodization. The obtained results suggest the necessity to extend the study on the role of other goitrogenic factors, which are probably present in the whole Wielkopolska Region.

[Bone marrow cellularity in acute lymphoblastic leukemia of children]. / Komórkowosc szpiku kostnego w ostrej bialaczce limfoblastycznej u dzieci.

The early response to therapy in childhood acute lymphoblastic leukemia (ALL) is typically assessed by bone marrow status. The clearance of blast cells in peripheral blood and bone marrow during induction therapy was analysed in 38 children (27 precursor-B-ALL and 11 precursor T-ALL) treated according to BFM90 or New York 93 protocols. Leukocyte count and peripheral blood smear taken at diagnosis, day 8, day 14 and day 33 as well as bone marrow cellularity and percentage of blasts on days: 0, 14, 33 were analysed. The number of blasts in bone marrow was correlated to bone marrow cellularity (Spearman's rho = 0.72, p = 0.001). Patients with T-ALL were more frequently resistant to steroids in vivo and reached remission later in comparison to precursor-B-ALL children (p = 0.019), however blasts reduction ratio was comparable in both lineages. Bone marrow cellularity on days 14 and 33 of induction therapy was similar.