Complex Structure of the Eastern Lobe of the Pictor A Radio Galaxy: Spectral Analysis and X-ray/Radio Correlations

Here we present detailed analysis of the distinct X-ray emission features present within the Eastern radio lobe of the Pictor A galaxy, around the jet termination region, utilising the data obtained from the Chandra X-ray Observatory. Various emission features have been selected for the study based on their enhanced X-ray surface brightness, including five sources that appear point-like, as well as three extended regions, one characterised by a filamentary morphology. For those, we perform a basic spectral analysis within the 0.5-7keV range. We also investigate various correlations between the X-ray emission features and the non-thermal radio emission, utilising the high-resolution radio maps from the Very Large Array at GHz frequencies. The main novel findings following from our analysis, regard the newly recognized bright X-ray filament located upstream of the jet termination region, extending for at least thirty kiloparsec (projected), and inclined with respect to the jet axis. For this feature, we observe a clear anti-correlation between the X-ray surface brightness and the polarized radio intensity, as well as a decrease in the radio rotation measure with respect to the surroundings. We speculate on the nature of the filament, in particular addressing a possibility that it is related to the presence of a hot X-ray emitting thermal gas, only partly mixed with the non-thermal radio/X-ray emitting electrons within the lobe, combined with the reversals in the lobe's net magnetic field.Comment: Final version, accepted for publication in The Astrophysical Journa

Comparative evaluation of three noninvasive gingival displacement systems: An in vivo study

Aim: An attempt is made to investigate clinical efficacy of cord, paste system, and a strip gingival retractile materials. This study aims to evaluate and compare the gingival retraction efficacy of retraction strip along with conventional retraction cord and paste system. Material and Methods: This in vivo experimental study was carried out on 30 patients. Three different gingival retraction systems were used to evaluate the amount of vertical and lateral displacement. Based on selection criteria, 30 individuals requiring fixed dental prosthesis with respect to mandibular first molar were selected. Tooth preparation for metal ceramic restoration with subgingival finish line was performed. Gingival displacement was accomplished with ultrapak cord, merocel strip, and magic foam cord immediately, 7 and 14 days after the tooth preparation, respectively. The amount of gingival displacement in vertical and lateral directions was measured at mesiobuccal, midbuccal, and distobuccal regions of the prepared tooth. The vertical retraction was measured intraorally by using digital vernier caliper, and postgingival displacement impression was used to measure lateral gingival retraction. Stereomicroscopic images of impression under ×10 resolution were transferred to image analyzer to measure the lateral displacement. The obtained data analyzed in one-way ANOVA and Bonferroni test were used to determine the significant difference at P < 0.05 level. Results: ANOVA test showed the significant difference between the materials tested with respect to the mean vertical and lateral gingival retraction (P = 0.001). Multiple comparisons by Bonferroni test revealed a significant difference in vertical and lateral displacement among the materials tested. Conclusions: Merocel strip provided the maximum amount of vertical and lateral tissue displacement, followed by ultrapak cord and least with magic foam cord which was statistically significant

A hybrid electrochemical-thermal method for the preparation of large ZnO nanoparticles

A simple and efficient two-step hybrid electrochemical-thermal route was developed for the synthesis of large quantity of ZnO nanoparticles using aqueous sodium bicarbonate electrolyte and sacrificial Zn anode and cathode in an undivided cell under galvanostatic mode at room temperature. The bath concentration and current density were varied from 30 to 120 mmol and 0.05 to 1.5 A/dm(2). The electrochemically generated precursor was calcined for an hour at different range of temperature from 140 to 600 A degrees C. The calcined samples were characterized by XRD, SEM/EDX, TEM, TG-DTA, FT-IR, and UV-Vis spectral methods. Rietveld refinement of X-ray data indicates that the calcined compound exhibits hexagonal (Wurtzite) structure with space group of P63mc (No. 186). The crystallite sizes were in the range of 22-75 nm based on Debye-Scherrer equation. The TEM results reveal that the particle sizes were in the order of 30-40 nm. The blue shift was noticed in UV-Vis absorption spectra, the band gaps were found to be 5.40-5.11 eV. Scanning electron micrographs suggest that all the samples were randomly oriented granular morphology

X-ray Emission of the γ\gamma-ray Loud Young Radio Galaxy NGC 3894

The radio source 1146+596 is hosted by an elliptical/S0 galaxy NGC\,3894, with a low-luminosity active nucleus. The radio structure is compact, suggesting a very young age of the jets in the system. Recently, the source has been confirmed as a high-energy (HE, $>0.1$\,GeV) $\gamma$-ray emitter, in the most recent accumulation of the {\it Fermi} Large Area Telescope (LAT) data. Here we report on the analysis of the archival {\it Chandra} X-ray Observatory data for the central part of the galaxy, consisting of a single 40\,ksec-long exposure. We have found that the core spectrum is best fitted by a combination of an ionized thermal plasma with the temperature of $\simeq 0.8$\,keV, and a moderately absorbed power-law component (photon index $\Gamma = 1.4\pm 0.4$, hydrogen column density $N_{\rm H}/10^{22}$\,cm$^{-2}$\,$= 2.4\pm 0.7$). We have also detected the iron K$\alpha$ line at $6.5\pm 0.1$\,keV, with a large equivalent width of EW\,$= 1.0_{-0.5}^{+0.9}$\,keV. Based on the simulations of the {\it Chandra}'s Point Spread Function (PSF), we have concluded that, while the soft thermal component is extended on the scale of the galaxy host, the hard X-ray emission within the narrow photon energy range 6.0--7.0\,keV originates within the unresolved core (effectively the central kpc radius). The line is therefore indicative of the X-ray reflection from a cold neutral gas in the central regions of NGC\,3894. We discuss the implications of our findings in the context of the X-ray Baldwin effect. NGC\,3894 is the first young radio galaxy detected in HE $\gamma$-rays with the iron K$\alpha$ line.Comment: Revised version, accepted for publication in the Astrophysical Journa

Phase stability, hardness and oxidation behaviour of spark plasma sintered ZrB2-SiC-Si3N4 composites

Despite significant efforts to develop ultra-high temperature ceramics, the phase stability together with high hardness and oxidation resistance remains to be addressed in ZrB2-SiC based ceramics. ZrB2-20 vol% SiC (ZS20) ceramics with varying amounts of Si3N4 (2.5, 5 and 10 vol%) were processed by multi stage Spark Plasma Sintering (SPS) over a range of temperature (1800-1900 degrees C) for 3 min under 50 MPa. All the ZS20-Si3N4 composites could be densified to more than 98% theoretical density (rho th) after SPS at 1900 degrees C. The XRD, SEM-EDS analysis of the ZS20-Si3N4 composites revealed the presence of reaction product phases (ZrO2, BN, ZrN) along with SiC and ZrB2 major phases. Sintering reactions were proposed to explain the existence of such new phases and extinction of Si3N4. Thermo-Cale software was also used to further confirm the formation of these new phases in the ZS20-Si3N4 samples. The hardness of ZS20-Si3N4 composites varied between 25.50 and 30.56 GPa, in particular, ZrB2-20 vol% SiC-5 vol% Si(3)N(4 )measured with the maximum hardness. In fact, it is the highest ever reported hardness for the ZrB2 composites. Considering oxidation resistance, the weight gain of ZrB2-20 vol%SiC composites decreased (from 13.84 to 9.84 mg/cm(2)) and oxide layer thickness increased (64-128 mu m) after oxidation at 1500 degrees C for 10 h in air. The cross sectional microstructure of oxidized ZS20-Si3N4 composites consists of thick dense outer layer of SiO2, intermediate (ZrO2-SiO2) layer and unreacted bulk. The formation of dense SiO(2 )layer and absence of SiC depleted layer from the oxidized samples are signatures of improved oxidation resistance of Si3N4 reinforced ZrB2-20 vol% SiC