Iron substitution in PrAlO3 perovskite leading to structural transformation and multiferroicity

Recognizing the crucial properties exhibited by FeAlO₃ perovskite, its stabilization with the inclusion of bigger sized Pr³⁺ (f-block ion) in place of Fe³⁺ (d-block ion) is examined by preparing the samples employing an epoxide mediated sol-gel route and characterizing them extensively. Up to 40 mol % substitution of iron, hexagonal PrAlO₃ with rhombohedral symmetry (R-3c spacegroup) was retained. At 50 mol % of iron substitution, it transformed into orthorhombic symmetry (Pnma spacegroup). At 80 mol % substitution of iron, X-ray pattern was amorphous. The metal-oxide bonding and symmetries were further verified by FTIR and Raman measurements. EPR and XPS measurements, performed at room temperature, confirmed the presence of Fe²⁺ and Fe³⁺ in the samples. Besides, praseodymium existed in III and IV oxidation states in these samples. Both field and temperature-dependent measurements showed ferromagnetic/ferrimagnetic behavior in the iron substituted samples. The ferrimagnetic transition occurred above room temperature (321 K) in 70 mol % iron substituted PrAlO₃. Such a high T_F is not reported till now among the available polymorphs of PrAlO₃ or FeAlO₃. 50 and 70 mol % iron substituted PrAlO₃ samples showed ferroelectric behavior at room temperature, qualifying them to be multiferroics.     

Fish consumption and bioindicators of inorganic mercury exposure

BACKGROUND: The direct and close relationship between fish consumption and blood and hair mercury (Hg) levels is well known, but the influence of fish consumption on inorganic mercury in blood (B-IHg) and in urine (U-Hg) is unclear. OBJECTIVE: Examine the relationship between fish consumption, total, inorganic and organic blood Hg levels and urinary Hg concentration. METHODS: A cross-sectional study was carried out on 171 persons from 7 riparian communities on the Tapajós River (Brazilian Amazon), with no history of inorganic Hg exposure from occupation or dental amalgams. During the rising water season in 2004, participants responded to a dietary survey, based on a seven-day recall of fish and fruit consumption frequency, and socio-demographic information was recorded. Blood and urine samples were collected. Total, organic and inorganic Hg in blood as well as U-Hg were determined by Atomic Absorption Spectrometry. RESULTS: On average, participants consumed 7.4 fish meals/week and 8.8 fruits/week. Blood total Hg averaged 38.6+/-21.7 microg/L, and the average percentage of B-IHg was 13.8%. Average organic Hg (MeHg) was 33.6+/-19.4 microg/L, B-IHg was 5.0+/-2.6 microg/L, while average U-Hg was 7.5+/-6.9 microg/L, with 19.9% of participants presenting U-Hg levels above 10 microg/L. B-IHg was highly significantly related to the number of meals of carnivorous fish, but no relation was observed with non-carnivorous fish; it was negatively related to fruit consumption, increased with age, was higher among those who were born in the Tapajós region, and varied with community. U-Hg was also significantly related to carnivorous but not non-carnivorous fish consumption, showed a tendency towards a negative relation with fruit consumption, was higher among men compared to women and higher among those born in the region. U-Hg was strongly related to I-Hg, blood methyl Hg (B-MeHg) and blood total Hg (B-THg). The Odds Ratio (OR) for U-Hg above 10 microg/L for those who ate >4 carnivorous fish meals/week was 4.00 [1.83-9.20]. CONCLUSION: This study adds further evidence to a positive relation between fish consumption and IHg in both blood and urine, which may result from absorption of IHg from fish or from demethylation of MeHg. The findings support the importance of assessing IHg exposure in fish-eating communities. Further studies should examine the potential toxicity of IHg in heavy fish consumers.     

Significance of 8-oxoG in the spectrum of DNA damages caused by ionising radiation of different quality

The yields and composition of DNA damages caused by ionising radiation depends on radiation quality. With increasing light energy transfer (LET), the proportion of isolated DNA damages with respect to cluster damaged sites decreases. Non-double strand break complex damages are induced by gamma radiation in mammalian cells at least four times more frequently that prompt DSB. The most important product of oxidative damage to DNA bases is 8-oxo-7,8-dihydroguanine (8-oxoG). The modelling of DNA damage induced by ionising radiation of different qualities was performed to assess frequencies and composition of complex damages containing 8-oxoG. The occurrence of clusters containing 8-oxoG increases from 6 to 11% for LET in the range 0.4-160 keV microm(-1). Distributions of single strand break (SSB) on opposite DNA strand around induced 8-oxoG have similar shape for different ionising radiations, but differ in their occurrence in the whole spectrum of DNA damages. The most probable configuration is a strand break localised at position +/-3 bases from 8-oxoG.     

Theoretical modelling of radiolytic damage of free DNA bases and within DNA macromolecule

The base damages in living cell are the most frequent product of deleterious effect of ionizing radiation. Experimental yields of modified bases determined in free bases and in the double stranded DNA show significant differences in the yields of stable products of radiolytic attack. An attempt to explain these differences is made with the help of theoretical calculations. The relative probabilities of reactions of the most important radiolytic product, OH(*) radical, with individual nucleobases, nucleosides and short DNA oligomers are calculated and compared to available experimental yields of base damages.     

Birefringence analysis of segmented cladding fiber

We present a full-vectorial modal analysis of a segmented cladding fiber (SCF). The analysis is based on the H-field vectorial finite element method (VFEM) employing polar mesh geometry. Using this method, we have analyzed the circular SCF and the elliptical SCF. We have found that the birefringence of the circular SCF is very small (1.0×10(-8)). Birefringence of a highly elliptical SCF can be altered to some extent by the number of segments and duty cycle of segmentation in the segmented cladding. However, the change is not profound. The analysis shows that the circular SCF possesses low birefringence and that the segmented cladding does not add any significant birefringence in an elliptical fiber. This result strongly indicates that small deviations in the segmented cladding parameters arising from fabrication process do not significantly affect the birefringence of the fiber.     

Performance validation tests on 80 K bubble type of shields for SST-1

The 80 K thermal shields of Steady State Superconducting Tokamak (SST-1) minimize the steady state heat loads on the superconducting magnet system at 4.5 K from ambient. Uniform temperature, vacuum and cryo compatibility is desired for the 80 K shields. In order to meet these requirements, the bubble/embossed type of design concept is adopted. This design ensures lower pressure drop and better temperature uniformity within ±5 K. Special attention has been given for preventing direct radiation on the magnet system. As part of performance validation tests, a group of 80 K thermal shields have undergone rigorous testing protocols and procedures. The temperature distribution, helium leak tightness and insulation resistance tests have been carried out for SST-1 thermal shields before final assembly of the machine. The test design, procedures and results of the 80 K thermal shields will be discussed in this paper.     

Fast release of liquid antisolvent precipitated fenofibrate at high drug loading from biocompatible thin films

Motivated by recent papers on nano and micro-particle slurry casting of poorly water-soluble drugs forming biocompatible films with enhanced properties, this work explores incorporation of liquid antisolvent (LAS) precipitated suspensions of fenofibrate, a model poorly soluble drug using both semi-synthetic (HPMC E15 LV) and natural (sodium alginate, SA) polymer as film formers. Centrifugation and subsequent resuspension were employed to minimize residual solvent and increase drug loading (～20%) in the LAS suspensions and in the film. Film’s critical quality attributes (CQAs), including drug distribution and uniformity, mechanical properties, and dissolution were assessed. Crystalline nature of FNB was largely preserved in the film without any polymorphic changes confirmed by XRD, DSC, and Raman. The NIR chemical imaging, corroborated by SEM imaging and drug content relative standard deviation (RSD) indicates that the drug is uniformly distributed without any observable large agglomerates. The films with SA showed lower mechanical strength as compared to HPMC due to SA’s low molecular weight. All films exhibited immediate drug release as has been the case using FNB nano particles in previous papers. Interestingly, although addition of plasticizer improved film dissolution, HPMC-based films had a faster dissolution compared to SA-based films in spite of higher mechanical strength of the former.     

Ultra-fine dispersible powders coated with l-Leucine via two-step co-milling

Dispersion of ultrafine powders is difficult due to their high cohesion and consequent agglomeration. Dry coating with additives such as nano-silica, magnesium stearate (MgSt), or Leucine (Leu), an amino acid, may help mitigate this problem. Unfortunately, when the powders to be coated are very fine, the additives such as MgSt or Leu need to be of even finer size, requiring a separate milling process. Here, a two-step co-milling process is investigated to produce well dispersible inhalable size range (<5 µm) particles. The main advantage is that the powder to be coated and additives have starting size of several hundred microns and do not require separate pre-milling. In the first step, Potassium Chloride (KCl), used as a surrogate API, and Leu are pre-milled in a ball mill to achieve KCl coated with Leu of ～10?µm. In the second step, simultaneous co-milling via jet-milling of pre-coated KCl down to inhalable size KCl, coated with Leu is done. The dispersibility of coated KCl was assessed through laser diffraction of dry powder at low dispersion pressure (Sympatec Rodos-Helos), corroborated via scanning electron microscopy (SEM), and FT4 powder tester measuring flow function coefficient (FFC), conditioned bulk density, and aerated energy. This assessment revealed that about 2?wt% Leu was adequate to provide best overall dispersibility. The dispersibility of milled KCl after coating with Leu was found to be better compared with uncoated and MgSt or nano-silica coated KCl. Overall, this two-step co-milling of KCl with 2?wt% Leu yielded well-dispersible, <5?µm particles from starting particles of two orders of magnitude larger sizes.     

Hybrid Antibacterial Fabrics with Extremely High Aspect Ratio Ag/AgTCNQ Nanowires

This study reports the synthesis of extremely high aspect ratios (>3000) organic semiconductor nanowires of Ag–tetracyanoquinodimethane (AgTCNQ) on the surface of a flexible Ag fabric for the first time. These one‐dimensional (1D) hybrid Ag/AgTCNQ nanostructures are attained by a facile, solution‐based spontaneous reaction involving immersion of Ag fabrics in an acetonitrile solution of TCNQ. Further, it is discovered that these AgTCNQ nanowires show outstanding antibacterial performance against both Gram negative and Gram positive bacteria, which outperforms that of pristine Ag. The outcomes of this study also reflect upon a fundamentally important aspect that the antimicrobial performance of Ag‐based nanomaterials may not necessarily be solely due to the amount of Ag+ ions leached from these nanomaterials, but that the nanomaterial itself may also play a direct role in the antimicrobial action. Notably, the applications of metal‐organic semiconducting charge transfer complexes of metal‐7,7,8,8‐tetracyanoquinodimethane (TCNQ) have been predominantly restricted to electronic applications, except from our recent reports on their (photo)catalytic potential and the current case on antimicrobial prospects. This report on growth of these metal‐TCNQ complexes on a fabric not only widens the window of these interesting materials for new biological applications, it also opens the possibilities for developing large‐area flexible electronic devices by growing a range of metal‐organic semiconducting materials directly on a fabric surface.