Investigation of heating rate effect on solid-phase interaction in Li[2]CO[3]-Fe[2]O[3] reaction mixture

The influence of heating rate on solid-phase interaction in Li[2]CO[3]-Fe[2]O[3] reaction mixture was investigated by thermal analysis method. The powder mixture components were in the ratio corresponding to LiFe[5]O[8] ferrite. The ferrite synthesis was performed by thermal heating of mixture reagents in thermal analyzer up to 800 °С in air at various heating rates in the ranges (5-50) °С/min. The results showed that the heating rate affects the solid-phase interaction in Li[2]CO[3] - Fe[2]O[3] reaction mixture. The reaction phase formation is accompanied by heat endothermic effect, which was observed in the DSC curve in the form of a complex broad peak. For all samples, this complex peaks were decomposed into simpler peaks, and thereby, the enthalpies of the individual phase transitions were determined. It was shown that the heating rate affects the values of enthalpy and temperatures of heat endothermic effects, so that the high heating rate shifts the proceeding of reaction to higher temperatures

Electrical properties of lithium ferrite with addition of ZrO[2]

The study of electrical properties of composite ceramics based on lithium ferrite LiFe[5]O[8] with the addition of ZrO[2] (1 and 2 wt%) was carried out. The samples were prepared by standard ceramic technology. Synthesis of lithium ferrite was conducted at 800°С for 120 minutes. The zirconium dioxide was added to synthesized powder by mixing in planetary ball mill, and then the composite powders were sintered at temperatures of 1100°С and 1050°С. The electrical conductivity of the samples was studied using two-probe spreading resistance method. It was found that addition of ZrO[2] and an increase of its up to 2 wt% leads to increase in the activation energy and electrical resistivity

TG study of the Li[0.4]Fe[2.4]Zn[0.2]O[4] ferrite synthesis

In this paper, the kinetic analysis of Li-Zn ferrite synthesis was studied using thermogravimetry (TG) method through the simultaneous application of non-linear regression to several measurements run at different heating rates (multivariate non-linear regression). Using TG-curves obtained for the four heating rates and Netzsch Thermokinetics software package, the kinetic models with minimal adjustable parameters were selected to quantitatively describe the reaction of Li-Zn ferrite synthesis. It was shown that the experimental TG-curves clearly suggest a two-step process for the ferrite synthesis and therefore a model-fitting kinetic analysis based on multivariate non-linear regressions was conducted. The complex reaction was described by a two-step reaction scheme consisting of sequential reaction steps. It is established that the best results were obtained using the Yander three-dimensional diffusion model at the first stage and Ginstling-Bronstein model at the second step. The kinetic parameters for lithium-zinc ferrite synthesis reaction were found and discussed

Influence of mechanical milling conditions on the dispersity of lithium ferrite

The effect of mechanical milling in a planetary ball mills on dispersity of the synthesized lithium ferrite powder was investigated by laser diffraction technique. The mechanical milling of powder was carried out by two planetary ball mills: SPEX 8000М and Fritsch Pulverisette 5 with different time period. The lithium ferrite powder was milled for 30, 60 and 120 minutes in the first ball mill. The powder milled for 60 minutes in the second ball mill was performed. The results showed that an increase in the milling time slightly decreases the average particle size of the ferrite powder in case both ball mills. However, only milling in a SPEX planetary mill increases homogeneity of the ferrite powder, while the milling in Fritsch causes intensive processes of particle aggregation

Estimation of thermomagnetometry method sensitivity for magnetic phase determination

In this article, the sensitivity of thermomagnetometry method for magnetic phase determination in lithium substituted ferrites was estimated by thermogravimetric analysis in magnetic field of lithium-zinc ferrite and iron dioxide (Li[0.4]Fe[2.4]Zn[0.2]O[4]+[alpha]-Fe[2]O[3]) components mixture with different mass proportions: 2, 4, 6, and 100 mass% Li[0.4]Fe[2.4]Zn[0.2]O[4] phase in total mixture. Thereby, analyzed samples are mixture of magnetic and nonmagnetic phases. Results of thermomagnetometric analysis were supplemented with the X-Ray diffraction analysis data. It was shown that the thermomagnetometry method allows to determine a magnetic phases with mass content not less than 2 mass% in analyzed mixture. In this case, we can clearly estimate the position and intensity of the peak on derivative thermogravimetric curve, which connected with a magnetic phase transition in ferrite at Curie temperature

Nod1 signaling overcomes resistance of S. pneumoniae to opsonophagocytic killing

Airway infection by the Gram-positive pathogen Streptococcus pneumoniae (Sp) leads to recruitment of neutrophils but limited bacterial killing by these cells. Co-colonization by Sp and a Gram-negative species, Haemophilus influenzae (Hi), provides sufficient stimulus to induce neutrophil and complement-mediated clearance of Sp from the mucosal surface in a murine model. Products from Hi, but not Sp, also promote killing of Sp by ex vivo neutrophil-enriched peritoneal exudate cells. Here we identify the stimulus from Hi as its peptidoglycan. Enhancement of opsonophagocytic killing was facilitated by signaling through nucleotide-binding oligomerization domain-1 (Nod1), which is involved in recognition of γ-D-glutamyl-meso-diaminopimelic acid (meso-DAP) contained in cell walls of Hi but not Sp. Neutrophils from mice treated with Hi or compounds containing meso-DAP, including synthetic peptidoglycan fragments, showed increased Sp killing in a Nod1-dependent manner. Moreover, Nod1-/- mice showed reduced Hi-induced clearance of Sp during co-colonization. These observations offer insight into mechanisms of microbial competition and demonstrate the importance of Nod1 in neutrophil-mediated clearance of bacteria in vivo

ORGANIZATIONAL AND METHODOLOGICAL ASPECTS OF INTERNAL AUDIT IN PUBLIC ADMINISTRATION

Background: This article traces the transformation of internal financial audits into internal audits within public organizations in the Russian Federation. The need for such a transformation became apparent after Russia’s higher external audit bodies assessed the achievements of federal executive authorities in internal financial auditing and its impact on the efficiency and effectiveness of budgetary funding. Objective: The study aims to examine both organizational and methodological aspects of this transformation. The study focuses on establishing a comprehensive model integrating internal financial audit, internal financial control, departmental control, and founder’s control systems within the framework of sustainable development concepts. Methods: The research presents the architecture of the internal audit system in public organizations and emphasizes a wide range of activities to ensure its continuous improvement. This approach is based on the principles of cyclicality and ongoing development. The model considers the subject of internal audit to encompass not only the financial activities of public sector entities and assessment of internal control systems but also the achievement of current and strategic development goals, minimization of financial crime risks, and risk-laden business processes under uncertain external and internal conditions. Results: The study introduces a comprehensive model that proposes to harmonize the systems of internal financial audit systems, internal financial control, departmental control, and founder’s control. It extends the scope of internal audit beyond financial analysis to include evaluating the achievement of operational and strategic objectives, minimizing financial risks, and managing risky business processes amid uncertainties. Conclusions: The research conclusions could be useful for public organizations in developing an effective internal audit system. The proposed model not only enhances financial auditing and control but also aligns these processes with the broader objectives of sustainable development and strategic risk management

Investigation of oxidation process of mechanically activated ultrafine iron powders

The oxidation of mechanically activated ultrafine iron powders was studied using X-ray powder diffraction and thermogravimetric analyzes. The powders with average particles size of 100 nm were made by the electric explosion of wire, and were subjected to mechanical activation in planetary ball mill for 15 and 40 minutes. It was shown that a certain amount of FeO phase is formed during mechanical activation of ultrafine iron powders. According to thermogravimetric analysis, the oxidation process of non-milled ultrafine iron powders is a complex process and occurs in three stages. The preliminary mechanical activation of powders considerably changes the nature of the iron powders oxidation, leads to increasing in the temperature of oxidation onset and shifts the reaction to higher temperatures. For the milled powders, the oxidation is more simple process and occurs in a single step

Transfer of trace metals by trophic chain of plankton - filter-feeding bivalves in the brackish-water lagoon lakes on the Japan Sea coast

Content of the metals Fe, Mn, Ni, Pb, Zn, Cd, and Cu was determined in the water, suspended matter, plankton organisms and bivalves collected in the brackish-water lagoon lakes on the coast of the Japan Sea in July 2011-2012, August 2013, and July 2014. The lakes are located in the sparsely populated area of eastern Sikhote-Alin including the Sikhote-Alin biosphere nature reserve. The content of Fe, Mn, Ni, and Pb has a tendency to decrease along the trophic chain that is conditioned by prevalence of their suspended forms over dissolved ones in the water and decreasing of the surface : weight ratio with size of living organisms. On the contrary, the content of Cu, Zn and Cd is rather stable along the food chain because of prevalence of their dissolved forms and low content in the suspended organic matter