Anna Z. Szeremeta

Bio: Anna Z. Szeremeta is an academic researcher from University of Silesia in Katowice. The author has contributed to research in topics: Dielectric & Manganite. The author has an hindex of 7, co-authored 25 publications receiving 124 citations.

Electric relaxation and Mn3+/Mn4+ charge transfer in Fe-doped Bi12MnO20–BiMn2O5 structural self-composite

Abstract: Fe-doped Bi12MnO20–BiMn2O5 ceramics was sintered at 1130 K for 6 h in ambient air. Two centro-symmetric phases formed thermodynamically stable self-composite material that was deduced from X-ray pattern analysis. The lattice parameters were a = 10.147(8) A—for the cubic I23 Bi12MnO20 phase; and a = 7.545(4) A, b = 8.538(1) A, c = 5.758(3) A—for the orthorhombic Pbam BiMn2O5 phase. The 57Fe Mossbauer spectrum, recorded at room temperature, has shown pure electronic quadrupolar split. The major doublets reflected the occurrence of Fe3+ ions distributed in two sites, i.e., octahedral Fe4+O6 and square pyramidal Fe3+O5, with preferential occupation of the pyramidal sites, that was consistent with the Pbam phase symmetry. The third doublet resulted from the presence of iron Fe3+ in tetrahedral Fe3+O4 coordination and corresponded to a small admixture of the I23 phase. The DC resistivity ρ DC(T) dependence on temperature has shown thermally activated features, and the value of E a,DC varied in the range of 0.22–0.37 eV. The electric impedance was measured in the f = 20 Hz–1 MHz and 100–690 K range. Two electrical relaxations were determined using the electric modulus formalism M″(T). Low-temperature relaxation has shown the temperature-dependent activation energy E A,1 = 0.14–0.20 eV and characteristic time values of τ 01 = 10−10–10−12 s in 100–200 K range. It was attributed to the charge transfer between Mn4+/Mn3+ sites. The other relaxation occurred in the 170–220 K range, and it exhibited the following values: τ 02 = 10−11 s, and E A,2 = 0.27 eV. A disorder-related VRH polaron model was proposed for ρ DC(T) and for electric relaxation processes.

Electric Current Relaxation and Resistance Switching in Non-Homogeneous Bismuth Manganite

Abstract: Bismuth manganite ceramics has been obtained by high temperature sintering in air. It was found from the X-ray diffraction pattern analysis that the ceramics consists of two centrosymmetric phases: the cubic I23 and the orthorhombic Pbam. Impedance has been measured at radiofrequencies in 85–500 K range. Two relaxation processes have been discerned. One process, which shows characteristic time value τ0 ≈ 10−12 s, occurs in 120–230 K range and it has been assigned to polaronic conductivity. The other process occurs in 270–310 K range and it exhibits longer characteristic time value τ0 ≈ 10−8 s. The resistance Rdc(T) temperature dependence shows semiconductor features with activation energy Ea = 0.28–0.40 eV for the as-sintered samples. The semiconductor to metallic-type transition has been induced after electroformation procedure carried out at 790 K in ambient air. We propose that extended defects, related to occurrence of the two phases, facilitate resistive switching.

Electric features of PZT 70/30–BiMnO3 solid solution ceramics

Abstract: We sintered the new (1 − x )Pb(Zr 0.70 Ti 0.30 )O 3 – x BiMnO 3 ( x = 0, 0.055, and 0.11) ceramics. The XRD test has shown the rhombohedral R3m symmetry for the PZT sample. The (1 − x )PZT– x BiMnO 3 samples show the existence of two phases, the one with R3m and the second with orthorhombic Pbam symmetry. Scanning electron microscopy test have shown a lack of bismuth oxide and manganese oxides precipitation. The density of states was calculated for a 40-atom supercell which corresponds to (Pb 7 Bi)(Zr 4 Ti 3 Mn)O 24 and (Pb 7 Bi)(Zr 3 MnTi 4 )O 24 ceramic compositions. The dielectric spectroscopy was conducted for f = 100 Hz–1 MHz in the 85–705 K range. The electric permittivity test indicated the existence of PZT phase within the PZT–BiMnO 3 ceramics. The addition of BiMnO 3 caused dispersion of electric conductivity in the low temperature range and induced a relaxor state in the high temperature range.

Phenyl Ring: A Steric Hindrance or a Source of Different Hydrogen Bonding Patterns in Self-Organizing Systems?

Abstract: A series of five alcohols (3-methyl-2-butanol, 1-cyclopropylethanol, 1-cyclopentylethanol, 1-cyclohexylethanol, and 1-phenylethanol) was used to study the impact of the size of steric hindrance and its aromaticity on self-assembling phenomena in the liquid phase. In this Letter, we have explicitly shown that the phenyl ring exerts a much stronger effect on the self-organization of molecules via the O-H···O scheme than any other type of steric hindrance, leading to a significant decline in the size and concentration of the H-bonded clusters. Given the combination of calorimetric, dielectric, infrared, and diffraction studies, this phenomenon was ascribed to its additional proton-acceptor function for the competitive intermolecular O-H···π interactions. The consequence of this is a different packing of molecules on the short- and medium-range scale.

Metagenome-wide association study of gut microbiome revealed novel aetiology of rheumatoid arthritis in the Japanese population

Abstract: Objective The causality and pathogenic mechanism of microbiome composition remain elusive in many diseases, including autoimmune diseases such as rheumatoid arthritis (RA). This study aimed to elucidate gut microbiome’s role in RA pathology by a comprehensive metagenome-wide association study (MWAS). Methods We conducted MWAS of the RA gut microbiome in the Japanese population (ncase=82, ncontrol=42) by using whole-genome shotgun sequencing of high depth (average 13 Gb per sample). Our MWAS consisted of three major bioinformatic analytic pipelines (phylogenetic analysis, functional gene analysis and pathway analysis). Results Phylogenetic case–control association tests showed high abundance of multiple species belonging to the genus Prevotella (e.g., Prevotella denticola) in the RA case metagenome. The non-linear machine learning method efficiently deconvoluted the case–control phylogenetic discrepancy. Gene functional assessments showed that the abundance of one redox reaction-related gene (R6FCZ7) was significantly decreased in the RA metagenome compared with controls. A variety of biological pathways including those related to metabolism (e.g., fatty acid biosynthesis and glycosaminoglycan degradation) were enriched in the case–control comparison. A population-specific link between the metagenome and host genome was identified by comparing biological pathway enrichment between the RA metagenome and the RA genome-wide association study results. No apparent discrepancy in alpha or beta diversities of metagenome was found between RA cases and controls. Conclusion Our shotgun sequencing-based MWAS highlights a novel link among the gut microbiome, host genome and pathology of RA, which contributes to our understanding of the microbiome’s role in RA aetiology.

IGF1 receptor and thyroid-associated ophthalmopathy.

Abstract: Thyroid-associated ophthalmopathy (TAO) is a vexing and poorly understood autoimmune process involving the upper face and tissues surrounding the eyes In TAO, the orbit can become inflamed and undergo substantial remodeling that is disfiguring and can lead to loss of vision There are currently no approved medical therapies for TAO, the consequence of its uncertain pathogenic nature It usually presents as a component of the syndrome known as Graves' disease where loss of immune tolerance to the thyrotropin receptor (TSHR) results in the generation of activating antibodies against that protein and hyperthyroidism The role for TSHR and these antibodies in the development of TAO is considerably less well established We have reported over the past 2 decades evidence that the insulin-like growth factorI receptor (IGF1R) may also participate in the pathogenesis of TAO Activating antibodies against IGF1R have been detected in patients with GD The actions of these antibodies initiate signaling in orbital fibroblasts from patients with the disease Further, we have identified a functional and physical interaction between TSHR and IGF1R Importantly, it appears that signaling initiated from either receptor can be attenuated by inhibiting the activity of IGF1R These findings underpin the rationale for therapeutically targeting IGF1R in active TAO A recently completed therapeutic trial of teprotumumab, a human IGF1R inhibiting antibody, in patients with moderate to severe, active TAO, indicates the potential effectiveness and safety of the drug It is possible that other autoimmune diseases might also benefit from this treatment strategy

Genomics, transcriptomics and proteomics to elucidate the pathogenesis of rheumatoid arthritis

Abstract: Rheumatoid arthritis is an autoimmune disease that affects several organs and tissues, predominantly the synovial joints. The pathogenesis of this disease is not completely understood, which maybe involved in the genomic variations, gene expression, protein translation and post-translational modifications. These system variations in genomics, transcriptomics and proteomics are dynamic in nature and their crosstalk is overwhelmingly complex, thus analyzing them separately may not be very informative. However, various ‘-omics’ techniques developed in recent years have opened up new possibilities for clarifying disease pathways and thereby facilitating early diagnosis and specific therapies. This review examines how recent advances in the fields of genomics, transcriptomics and proteomics have contributed to our understanding of rheumatoid arthritis.

Dielectric, impedance and piezoelectric properties of (K0.5Nd0.5)TiO3-doped 0.67BiFeO3-0.33BaTiO3 ceramics

Abstract: A novel (0.67-x)BiFeO3-0.33BaTiO3-x(K0.5Nd0.5)TiO3 (KNT100x, x = 0.0, 0.02, 0.04, 0.06, 0.08 mol%) ceramics were fabricated and their microstructure and electrical properties were studied. All samples displayed a pseudo-cubic symmetry, and adding of KNT had little effect on grain size. The dielectric analysis displayed the dispersion increases with the addition of KNT compositions, showing strong relaxor properties. Besides, high dielectric constant (e’) of 23000 and dielectric peak temperature (Tm) of 390 °C remain at 1 kHz in the x = 0.02 sample while the dielectric loss (tanδ) dropped below 0.5 in the range of 30–400 °C, showing excellent electrical insulation performance. In addition, doping of KNT had obvious influence on the strain, and a large strain (Smax) of 0.26% was obtained at x = 0.02 due to the increase of electrical insulation. More importantly, the strain at 50 kV cm−1 enhanced significantly with temperature increasing, reaching a maximum strain of 0.75% with a small hysteresis coefficient of 30% at 110 °C. Particularly, KNT02 exhibited excellent fatigue resistance within 105 fatigue cycles. Presumably these results are attributed to the coexistence of ferroelectric and non-ergodic relaxor domains and the thermally activated domain wall motion.