Magnetic relaxation and memory effects in interacting nanoparticle manganites and iron oxides

Iako je razumevanje neravnotežnih relaksacionih fenomena u spinskim staklima sličnim (SSG) sistemima od velikog interesa kako sa teorijskog, tako i sa stanovišta mogućih primena, osnovni fizički mehanizmi još uvek nisu u potpunosti shvaćeni. Iz tog razloga se u fokusu eksperimentalnog istraživanja predstavljenog u ovoj doktorskoj disertaciji nalaze magnetni relaksacioni fenomeni, koji su proučavani u dve grupe nanočestičnih materijala, manganitima i oksidima gvožđa. Posebna pažnja posvećena je ispitivanju uticaja međučestičnih interakcija na pojavu niskotemperaturskog kolektivnog stanja, kao i na magnetne osobine sistema jednodomenskih čestica. Sistematsko proučavanje kompleksne neravnotežne dinamike kroz ispitivanje magnetnih relaksacija, starenja i memorijskih efekata izvedeno je na osnovu sveobuhvatnih merenja magnetizacije u magnetnom polju jednosmerne (DC) i naizmenične (AC) struje...Although the understanding of nonequillibrium relaxation phenomena in super spin glass (SSG) nanoparticle systems is of the great importance from both fundamental and technological point of view, the underlying physical processes are still not explained. For that reason, the experimental research presented in this thesis is focused on magnetic relaxation in two strongly interacting nanoparticle systems, manganites and iron oxides. The main goal of the study was to investigate the effect of interparticle interaction on the magnetic properties of single domain magnetic particles as well as to determine its importance on the formation of low temperature collective state. The complex nonequillibrium dynamics was revealed through the systematic investigations of magnetic relaxations, aging and memory effects by means of DC and AC magnetization measurements..

Cytogenetic alterations in rheumatoid arthritis patients treated with methotrexate and dry olive leaf extract

Oxidative stress and inflammation are DNA instability factors for rheumatoid arthritis (RA) patients. The aims of this study were to evaluate cytogenetic alterations in Peripheral Blood Lymphocytes (PBL) in two groups of RA patients: the early and the long-term RA group; and to examine potential of concomitant treatment with Methotrexate (MTX) and Dry olive leaf extract (DOLE) against cytogenetic damage in RA patients after a 3-weeks treatment. A total of 32 RA patients and 10 healthy individuals were included. RA patients were equally divided into four groups: two groups with early phase RA (one treated with MTX alone, the other in combination with DOLE); and two long-term phase RA groups (group with active disease and group with low disease activity)-both treated with MTX and DOLE combination. PBL cultures were screened for chromosome aberrations and micronuclei frequencies. Significantly increased frequencies of micronuclei were shown in active phase RA disease (both early and long-term) but not in the group with low disease activity, as compared to controls. Chromosome aberrations were detected for all 4 RA groups. The highest frequencies of micronuclei and chromosome aberrations were found in the long-term active RA group. After 3 weeks-treatment, there were no significant decrease of the micronuclei frequencies compared to baseline, although they were reduced in all RA groups, except for the group with the long-term active disease. High level of cytogenetic damage in RA patients was concordant with duration and activity of the RA disease. At 3 weeks of therapy, neither the combined treatment (MTX+DOLE), nor MTX alone did not affect the frequency of micronuclei formation

Spin Glass Dynamics of Nanoparticle La0 7Ca0 3Mn0 7Fe0 3O3 Obtained by a Mechanochemical Milling

Spin dynamics of nanoparticle La0 7Ca0 3Mn0 7Fe0 3O3 system was studied through the set of diverse magnetic measurements Analysis of the data obtained from magnetic relaxation measurements, memory effect and AC susceptibility experiments pointed to a spin glass like behavior of interacting nanoparticle system14th Czech and Slovak Conference on Magnetism, Jun 06-09, 2010, Kosice, Slovaki

Fatty acid in colorectal cancer in adult and aged patients of both sexes

Purpose: Colorectal cancer represents the second most common type of cancer in Serbia. Alteration of lipid metabolism begins early, and can represent a central hallmark in cancer evolution. Fatty acids have various important functions as building components of cell membranes, as signaling molecules in immune responses and also manage the general cancer signaling network. The purpose of this study was to investigate the difference of various fatty acids content between colorectal cancer and adjacent healthy intestinal tissue in adult and aged patients of both sexes. Methods: 52 subjects participated in this study. Healthy colon mucosa and tumor tissue samples were obtained from patients previously diagnosed with colorectal carcinoma. Simplified method of Berstad et al was used for direct transesterification of total lipids in tumor and healthy mucosa tissue samples and separations of the methyl esters was carried out using a gas chromatograph equipped with a split/ splitless injector and a flame ionization detector. Results: 18 0, 18 1 n7, 20 3, 20 4, 20 5, 22 4, 22 5 22 6, SFA, PUFA, n6, n3 and AA/EPA were significantly higher in tumor tissue. On the other hand, 18 1 n9, 18 2, 18 3 n3, MUFA, n6/ n3 were significantly higher in healthy tissue. Conclusions: Saturation index (SI) could be a valuable tool to delineate robust immune response and worse prognosis in patients with colorectal cancer. Our study demonstrated significant differences in fatty acid profiles between tumor tissue and healthy mucosa. Parameters, such as gender, age, stage and mucinous component didn't influence altered fatty acid content

Crystal Structure and Magnetocaloric Effect of La0.80Ag0.15MnO3 Nanoparticles

Annealing of_ non stoichiometric La0.80Ag0.15MnO3 nanoparticles leads to the change of the crystal symmetry from Pnma to R3c and to almost doubling of its Curie temperature from 117 K to 317 K. This effect is due to the releasing of lattice distortions and strengthening of double exchange interaction. The large values of the magnetocaloric entropy of the order of ∆S = 6.19 J/(kg K) were observedat ∆µ0H = 5 T and T = 315 K.Proceedings of the 17th Czech and Slovak Conference on Magnetism, Košice, Slovakia, June 3–7, 2019

Magnetism of Nanoparticle La0 7Ca0 3Mn0 7Fe0 3O3 under Applied Hydrostatic Pressure

Nanoparticle La0 7Ca0 3Mn0 7Fe0 3O3 with the average particle size of 10 nm was mechanochemically synthesized in the single-step procedure Temperature and field dependences of magnetization were recorded under both ambient and applied hydrostatic pressure up to 0 47 GPa At ambient pressure, two magnetic transition points were observed one of the spin-glass like type at the temperature T-f approximate to 34 K, and ferro-to-paramagnet transition at T-C approximate to 51 K Under the applied pressure magnetic parameters gradually changed (i) both T-C and T-f were lowered with the increase in pressure, (ii) both high field magnetization M-5T and remanent magnetization M-Rem decreased with pressure, (iii) coercivity H increased with pressure The obtained results show that magnetism of a nanoparticle system with high degree of Intrinsic disorder diminishes with the applied pressure that is in compliance with the effect of the increased cationic disorder (internal pressure) in bulk manganites14th Czech and Slovak Conference on Magnetism, Jun 06-09, 2010, Kosice, Slovaki

An ac susceptibility study of spin dynamics in a super spin glass nanoparticle La0.7Ca0.3MnO3 system: simultaneous relaxation processes

In this paper, we present the results of a systematic study of nonequilibrium dynamics in a strongly interacting super spin glass (SSG) nanoparticle La0.7Ca0.3MnO3 system by alternating current (ac) susceptibility measurements. Cole-Cole analysis of the obtained data revealed the simultaneous existence of two separated relaxation processes, which can be assigned to the relaxation of different magnetic entities. Along with the expected relaxation of the collective SSG phase, the existence of individual, nonagglomerated particles, which do not take part in the collective phase and relax independently, was proposed. A full dynamical scaling analysis was performed in order to elucidate the nature of the transition to a low-temperature SSG state in the interacting La0.7Ca0.3MnO3 nanoparticle sample

Applicability of Construction and Demolition Waste in Geopolymers – A Screening Test

In this study, the applicability of construction and demolition waste (C&DW) in geopolymerization technology was investigated. The C&DW components, concrete and solid bricks, were collected from demolition sites in Belgrade, Republic of Serbia. The concrete sample came from a demolished fifty-year-old construction road, while the remains of solid bricks originated from a 1930s building. Prior to mechanical testing, the C&DW components were characterized by XRD analysis for their mineralogical composition. The results showed that the concrete waste consisted mainly of quartz (SiO2) and calcite (CaCO3), while the brick waste sample contained anorthite from the feldspar group (CaAl2Si2O8), wollastonite (Ca0.957Fe0.043O3Si) and mullite (Al2.4O4.8SiO6). The mechanical properties were examined using the screening method on three geopolymer mixtures, one of each mixture of concrete and brick powders and a mixture of both C&DW components. According to the standard SRPS EN 12390-3:2010 for cubic samples, the geopolymer samples were prepared with alkaline activators for testing the compressive strength as the dominant parameter in the mortar and concrete evaluation. The compressive strength values increased in the range of 2.4 MPa for concrete, 10.2 MPa for brick, and 10.8 MPa for the mixed geopolymer sample. The low compressive strength result of the concrete sample was the consequence of the mineral composition, i.e., the absence of aluminosilicate. However, the brick and the sample with a combination of both types of waste showed moderately satisfactory compressive strength, which could be the starting point for further investigations

Exchange Bias Effect in NdFeO3 System of Nanoparticles

We study the effect of nanometric size on the crystal structure, magnetic environment of iron and magnetization in NdFeO3 system of nanoparticles. The average particle size of NdFeO3 nanoparticles increases with annealing at 600 degrees C from about 15 nm to 40 nm, The smallest particles on annealed sample have size approximately 30 nm and typically have character of single crystalline samples. All samples adopt orthorhombic crystal structure, space group Prima with lattice parameters a = 5.5817 angstrom, b = 7.7663 angstrom and c = 5.456 angstrom for as prepared sample. The presence of superparamagnetic particles was indicated by the Mossbauer measurements. The reduction of dimensionality induces a decrease of T-N1 from 691 K to 544 K. The shift of magnetic hysteresis loop in vertical and horizontal direction was observed at low temperatures after cooling in magnetic field. We attribute such behaviour to exchange bias effect and discuss in the frame of core shellmodel.16th Czech and Slovak Conference on Magnetism (CSMAG), Jun 13-17, 2016, Kosice, Slovaki

Synthesis and Properties of Ni-doped Goethite and Ni-doped Hematite Nanorods

Ni-doped goethite (α-FeOOH) nanorods were synthesized from mixed Fe(III)-Ni(II) nitrate solutions with various Ni/(Ni+Fe) ratios (0, 5, 10, 20, 33 and 50 mol % Ni) by hydrothermal precipitation in a highly alkaline medium using the strong organic alkali, tetramethylammonium hydroxide (TMAH). Ni-doped hematite (α-Fe2O3) nanorods were obtained by calcination of Ni-doped goethite nanorods at 400 °C. The Ni 2+ -for-Fe 3+ substitution in goethite and hematite was confirmed by determination of the unit cell expansion (due to the difference in the ionic radii of Fe 3+ and Ni 2+ ) using XRPD and determination of the reduction of a hyperfine magnetic field (due to the difference in magnetic moments of Fe 3+ and Ni 2+ ) using Mössbauer spectroscopy. Single-phase goethite nanorods were found in samples containing 0 or 5 mol % Ni. A higher Ni content in the precipitation system (10 mol % or more) resulted in a higher Ni 2+ -for-Fe 3+ substitution in goethite, and larger Ni-doped goethite nanorods, though with the presence of low crystalline Ni-containing ferrihydrite and Ni ferrite (NiFe2O4) as additional phases. Significant changes in FT-IR and UV-Vis-NIR spectra of prepared samples were observed with increasing Ni content. Electrochemical measurements of samples showed a strong increase in oxygen evolution reaction (OER) electrocatalytic activity with increasing Ni content. © 2018 Croatian Chemical Society. All Rights Reserved