Search

NdxY1-xFeO3 polycrystalline samples with ‘x’ value ranging from 0.0 to 1.0 in steps of 0.2 are synthesized using sol–gel auto combustion method. The structural and magnetic properties of Neodymium (Nd) doped YFeO3 are presented in the present work. Experimental techniques like X-ray diffraction (XRD) and Raman spectroscopic studies are used for structural characterization of the prepared compounds. From XRD measurements, unit cell parameters and cell volume are calculated. XRD graphs indicate the presence of secondary phases in the studied samples. The Fe–O–Fe bond angles from XRD show no significant change with substitution. Magnetic measurements indicate the presence of weak ferromagnetic component for all the samples. Isomer shift value from 57Fe Mossbauer measurements indicate that iron ion is in Fe3+ionic state. Hyperfine field (Bhf) values increase with the increase in the Nd doping concentration. The important observation of the present work is the increase in electrical leakage current with Nd substitution. [ABSTRACT FROM AUTHOR]

PurposeMetabolic syndrome (MetS) is associated with several degenerative diseases, including retinal degeneration. Previously, we reported on progressive retinal degeneration in a spontaneous obese rat (WNIN/Ob) model. In this study, we investigated the additional effect of impaired glucose tolerance (IGT), an essential component of MetS, on retinal degeneration using the WNIN/GR-Ob rat model.MethodsThe retinal morphology and ultrastructure of WNIN/GR-Ob and age-matched littermate lean rats were studied by microscopy and immunohistochemistry. The retinal transcriptome of WNIN/GR-Ob was compared with the respective lean controls and with the WNIN/Ob model using microarray analysis. Expression of selected retinal marker genes was studied via real-time PCR.ResultsProgressive loss of photoreceptor cells was observed in WNIN/GR-Ob rats with an onset as early as 3 months. Similarly, thinning of the inner nuclear layer was observed from 6 months in these rats. Immunohistochemical analysis showed decreased levels of rhodopsin and postsynaptic density protein-95 (PSD-95) proteins and increased levels of glial fibrillary acidic protein (GFAP), vascular endothelial growth factor (VEGF), and calretinin in WNIN/GR-Ob rats compared with the age-matched lean controls, further supporting cellular stress/damage and retinal degeneration. The retinal transcriptome analysis indicated altered expression profiles in both the WNIN/GR-Ob and WNIN/Ob rat models compared to their respective lean controls; these pathways are associated with activation of pathways like cellular oxidative stress response, inflammation, apoptosis, and phototransduction, although the changes were more prominent in WNIN/GR-Ob than in WNIN/Ob animals.ConclusionsWNIN/GR-Ob rats with added glucose intolerance developed retinal degeneration similar to the parent line WNIN/Ob. The severity of retinal degeneration was greater in WNIN/GR-Ob rats compared to WNIN/Ob, suggesting a possible role for IGT in this model. Hence, the WNIN/GR-Ob model could be a valuable tool for investigating the impact of MetS on retinal degeneration pathology.

The Y-type hexaferrites, Ba0.5Sr1.5Me2Fe12O22 (where Me = Co, Zn and Ni), were synthesized by employing the solid-state technique. The prepared samples were examined using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM) with energy-dispersive X-ray analysis (EDAX) spectrometer, X-ray photoelectron spectroscopy (XPS), magnetic and room temperature Mössbauer spectroscopy techniques. The information from the XRD confirms the rhombohedral structure with space group R-3m for the samples under study. The average crystallite size varies between 75 and 80 nm. The morphology of the samples by FESEM reveals that the grains are interconnective, homogeneously distributed and the average grain size varies from 2.2 to 3.1 µm. The nominal composition of all elements and their oxidation state was established with XPS and confirms that the Fe ions are in + 3 state. The measured room temperature magnetization properties inveterate the soft ferrimagnetic character of the samples. The enhanced saturation magnetization is noticed for Zn Y-type hexaferrites, i.e., 31 emu/g. The room temperature Mössbauer spectra confirm the existence of magnetic ordering in all the compounds. The Mössbauer spectra confirm the coevality of Fe ions at six sub-lattices with dissimilar occupancy ratio. The isomer shift values confirm the Fe ions in Fe3+ state. [ABSTRACT FROM AUTHOR]

Familial Danish dementias (FDDs) are autosomal dominant neurodegenerative disorders that are associated with visual defects. In some aspects, FDD is similar to Alzheimer’s disease (AD)– the amyloid deposits in FDD and AD are made of short peptides: amyloid β (Aβ) in AD and ADan in FDD. Previously, we demonstrated an interaction between the dementia peptides and α-crystallin leading to lens opacification in organ culture due to impaired chaperone activity of α-crystallin. Herein, we report the in vivo effects of ADan and Aβ on the eye. ADan [reduced (ADan-red) and oxidized (ADan-oxi)] and Aβ (Aβ1-40 and Aβ1-42) were injected intravitreally in rats. The onset of cataract was seen after injection of all the peptides, but the cataract matured by 2 weeks in the case of ADan-red, 5 weeks for ADan-oxi and 6 weeks for Aβ1-40, while Aβ1-42 had minimal effect on cataract progression. The severity of cataract is associated with insolubilization and alterations in crystallins and loss of chaperone activity of α-crystallin. Further, disruption of the architecture of the retina was evident from a loss of rhodopsin, increased gliosis, and the thinning of the retina. These results provide a basis for the dominant heredo-otoophthalmo-encephalopathy (HOOE)/FDD syndrome and indicate that ADan peptides are more potent than Aβpeptides in inflicting visual impairment.

This paper reports the structural, electrical, 57Fe Mossbauer, and high temperature dielectric studies of Er1−x Gdx FeO3 (x = 0.0, 0.4, 0.8, and 1.0) orthoferrites. The XRD data confirm the prepared samples are stabilized in the orthorhombic crystal structure, and the FESEM images confirm all compositions are in nanosize regimes. The Raman spectroscopic studies indicate that the Gd doping at the Er site induces a significant change in the Raman shift of A1g and B2g vibrational modes. The leakage current density of the samples has increased with the doping of Gd at the Er site, which is correlated with morphological studies. Magnetization studies confirm weak DM interactions caused by Fe3+ spins with increasing Gd doping at the Er site. The Mossbauer study at room temperature confirms the +3 charge state of Fe ions and the magnetic ordering of all the samples. The dielectric properties within a high-temperature range (350–920 K) and a frequency range spanning from 1 to 700 kHz, revealed distinct phenomena in different temperature regimes. Below 500 K, we observed polaronic relaxation, while above 550 K, both Maxwell-Wagner and dipolar-type relaxation mechanisms were observed. All there relaxations are mainly due to presence of oxygen vacancies arising at high sintering, which is confirmed by XPS spectra of O1s.The observed results confirm the complex dielectric behavior exhibited by the material across varying temperature and frequency conditions. [ABSTRACT FROM AUTHOR]

Radon and thoron are significant contributors for radiological risk in indoors and are originating from decay chain of uranium and thorium, which are prevalent in the environment. These concentrations in indoors depends on the presence of uranium and thorium concentration, and lifestyle of the habitants. The village "Peddamula" is located in the neighbourhood area of proposed mining for exploration of uranium. The estimated concentration of radon and thoron is found in the range 14- 448 Bq.m-3 with an average value of 120 ± 82 Bq.m-3 (GM 100Bq.m-3), and vary from 7 to 452 Bq.m-3with an average value of 154 ± 111 Bq.m-3 (GM 112Bq.m-3), respectively. Computed the contribution to the effective dose per annum from, radon 3.02 mSv.y-1 and thoron is 4.32mSv.y-1. In this paper the seasonal variation and distribution of 222Rn and 220Rn levels in the dwellings of the study area will be discussed. [ABSTRACT FROM AUTHOR]

In the present work, polycrystalline Y-type Ba0.5Sr1.5Co2−xZnxFe12O22 (X = 0, 0.5, 1 & 2) hexa-ferrites prepared by the sol-gel auto combustion method are investigated by x-ray diffraction (XRD), 57Fe Mössbauer spectroscopy (MS) and magnetization measurements. XRD data confirms the single-phase formation for x = 0 and 0.5; however, with further increase in Zn concentration secondary phases are observed. The in-field Mössbauer data measured at low temperature (5K) indicates that there is a re-distribution of Fe3+ ions in the studied samples, with the substituted Zn2+ preferentially going to 6CIV, 6CIV ∗ sites. [ABSTRACT FROM AUTHOR]

The magnetic, Raman, ferroelectric, and in-field 57Fe Mössbauer studies of polycrystalline multiferroic Sr3Co2Fe24O41 are reported in this paper. From the magnetization studies, it is observed that the sample is soft magnetic in nature with low temperature magnetic spin transitions like longitudinal to transverse conical structure around 130K and change in magnetic crystalline anisotropy from conical to planar structure at 250K. Ferroelectric studies of the sample exhibit the spontaneous polarization at low temperature. Strong spin phonon and spin lattice coupling is observed through low temperature Raman spectroscopy. From the in-field 57Fe Mössbauer spectroscopy, spin up and spin down site occupations of Fe ions are calculated in the unit cell. [ABSTRACT FROM AUTHOR]

Electrical, magnetic and Mössbauer measurements have been carried out on La0.67-xEuxCa0.33MnO3 (x=0.21 and 0.29) for a comparative study of different grain size materials. The samples have been prepared through sol-gel method and sintered at 700, 800, and 900 °C to achieve nanosized materials. All the prepared samples are found to be single phase having orthorhombic structure. The particle sizes are estimated through x-ray diffraction (XRD) by using the Debye-Scherrer's formulae and these sizes are further confirmed by transmission electron microscopy (TEM) images. 151Eu Mössbauer studies reveal that Eu is in 3+ charge state. The isomer shift and full width at half maximum (FWHM) of the Mössbauer peak decrease with the increase in particle size. Reduction in the grain size leads to drastic increase in electrical resistivity in all the samples. The typical metal-insulator transition (MIT) observed in x=0.21 bulk sample disappears with decrease in grain size while an external magnetic field of 8T restores the MIT. For x=0.29, the sample with the lowest grain size does not show a field induced MIT whereas the samples with higher grain sizes show the field induced MIT. Hysteresis in field cooled cooling and warming cycles of magnetization measurements of x=0.21 system suggests that the decrease in grain size induces strong competition between the FM and AFM interaction. Interestingly, the combined effect of chemical pressure induced due to the additional rare earth doping and smaller grain size leads to a more stable AFM phase in x=0.29 system where no such hysteresis is observed in field cooled cooling and warming cycles of magnetization measurements. [ABSTRACT FROM AUTHOR]

Electrical, magnetic and Mossbauer measurements are performed on [La.sub.0.67-x][Eu.sub.x][Ca.sub.0.33]Mn[O.sub.3] in order to study different grain size materials. The combined effect of chemical pressure induced due to the additional rare earth doping and smaller grain size has led to a more stable AFM phase where no such hysteresis is observed in field cooled cooling and warming cycles of magnetization measurements.