Tribological Studies on Al-SiC composite and Al-Si alloy

Among the materials of tribological importance, Aluminium-silicon composites have received extensive attention for practical as well as fundamental reasons. This investigation describes about the wear characteristics of Al-Si alloys and Al-SiC composite using particle erosion test and pin-on-disc wear test at room temperature. Here Si and SiC, having 10% and 5% (weight percentages) are taken with Aluminium by stir casting method. It is found that addition of silicon/ silicon carbide improves the wear resistance, machinability, and corrosion resistance. It has been found that the wear rate is strongly dependent on impact angle of erodent, impact pressure and velocity (in case of particle erosion); and applied load, sliding speed, alloy composition (in case of sliding wear). Erosion wear behavior is also been affected with the hardness. It is observed, Al-SiC particulate composite bears higher hardness than that of Al-10%Si alloy. Maximum erosion has taken place at 90° angle of impingement and the erosion amount is less with Al-SiCp than that of Al-10%Si alloy. From experiment it is conclude that Al-Si alloys and Al-SiC composite can use as a potential structural material

Bulk Utilization of Red Mud in Geopolymer Based Products

Red Mud is the solid residue generated from Alumina refinery during the process of bauxite ore processing through Bayer’s process. Typical generation of red mud is 1.5 tons of red mud per ton of alumina produced. The disposal and storage of red mud has been a concern for the alumina industry since its inception, more than a hundred years ago. With the increase in alumina production, the magnitude of the problem is getting multiplied. Its alkaline nature (Na2O ~ 3-7%) and fine size make red mud unsuitable for many applications; a limited utilization is reported in cement industries as one of the raw mix components for cement. The present work deals with the utilization of red mud in geopolymer based paving blocks. Alumina, silica and alkali are the essential items required for geopolymer preparation. Having all these in red mud, the current study attempted to use the same in geopolymer based products. The focus has been on bulk utilization of red mud; target strength of 20 MPa after 28 days of curing (M20 grade) has been the goal as this strength is sufficient for many applications. The study focused on optimizing the red mud content, alkali concentration, fly ash content, etc. The samples are tested for its compressive strength and leachability. The study reveals that significant amount of red mud incorporation is possible with products conforming to USEPA 1311 norms

UVIT study of UV bright stars in the globular cluster NGC 4147

We present far ultraviolet (FUV) observations of globular cluster NGC 4147 using three FUV filters, BaF2 (F154W), sapphire (F169M), and silica (F172M) of Ultra-Violet Imaging Telescope (UVIT) on-board the AstroSat satellite. We confirmed the cluster membership of the UVIT observed sources using proper motions from Gaia data release 2 (GAIA DR2). We identified 37 blue horizontal branch stars (BHBs), one blue straggler star (BSS) and 15 variable stars using UV-optical color magnitude diagrams (CMDs). We find that all the FUV bright BHBs are second generation population stars. Using UV-optical CMDs, we identify two sub-populations, BHB1 and BHB2, among the UV-bright BHBs in the cluster with stars count ratio of 24:13 for BHB1 and BHB2. The effective temperatures (Teff) of BHB1 and BHB2 were derived using color-temperature relation of BaSTI-IAC zero-age horizontal branch (ZAHB). We found that BHB1 stars are more centrally concentrated than BHB2 stars. We also derive physical parameters of the detected FUV bright BSS by fitting younger age BaSTI-IAC isochrones on optical and UV-optical CMDs

PKS 1413+135: OH and H i at z = 0.247 with MeerKAT

The BL Lac object PKS 1413+135 was observed by the Large Survey Project MeerKAT Absorption Line Survey (MALS) in the L-band, at 1139 MHz and 12931379 MHz, targeting the HI and OH lines in absorption at z=0.24671. The radio continuum might come from the nucleus of the absorbing galaxy or from a background object at redshift lower than 0.5, as suggested by the absence of gravitational images. The HI absorption line is detected at a high signal-To-noise ratio, with a narrow central component, and with a red wing, confirming previous results. The OH 1720 MHz line is clearly detected in (maser) emission, peaking at a velocity shifted by-10 to-15 km s-1 with respect to the HI peak. The 1612 MHz line is lost due to radio frequency interference. The OH 1667 MHz main line is tentatively detected in absorption, but not the 1665 MHz line. Over 30 years a high variability is observed in optical depths, due to the rapid changes of the line of sight caused by the superluminal motions of the radio knots. The HI line has varied by 20% in depth, while the OH-1720 MHz depth has varied by a factor of ∼3. The position of the central velocity and the widths also varied. The absorbing galaxy is an early-Type spiral (maybe S0) seen edge-on, with a prominent dust lane, covering the whole disk. Given the measured mass concentration and the radio continuum size at centimeter wavelengths (100 mas corresponding to 400 pc at z=0.25), the width of the absorption lines from the nuclear regions are expected up to 250 km s-1. The narrowness of the observed lines (< 15 km s-1) suggests that the absorption comes from an outer gas ring, as frequently observed in S0 galaxies. The millimetric lines are even narrower (< 1 km s-1), which corresponds to the continuum size restricted to the core. The radio core is covered by individual 1 pc molecular clouds, whose column density is a few 1022 cm-2, which is compatible with the gas screen detected in X-rays

Discovery of Hydrogen Radio Recombination Lines at z = 0.89 toward PKS 1830-211

We report the detection of stimulated hydrogen radio recombination line (RRL) emission from ionized gas in a z = 0.89 galaxy using 580-1670 MHz observations from the MeerKAT Absorption Line Survey. The RRL emission originates in a galaxy that intercepts and strongly lenses the radio blazar PKS 1830−211 (z = 2.5). This is the second detection of RRLs outside of the local Universe and the first clearly associated with hydrogen. We detect effective H144α (and H163α) transitions at observed frequencies of 1156 (798) MHz by stacking 17 (27) RRLs with 21σ (14σ) significance. The RRL emission contains two main velocity components and is coincident in velocity with H i 21 cm and OH 18 cm absorption. We use the RRL spectral line energy distribution and a Bayesian analysis to constrain the density (n e ) and the volume-averaged path length (ℓ) of the ionized gas. We determine log ( n e ) = 2.0 − 0.7 + 1.0 cm−3 and log ( ℓ ) = − 0.7 − 1.1 + 1.1 pc toward the northeast (NE) lensed image, likely tracing the diffuse thermal phase of the ionized ISM in a thin disk. Toward the southwest (SW) lensed image, we determine log ( n e ) = 3.2 − 1.0 + 0.4 cm−3 and log ( ℓ ) = − 2.7 − 0.2 + 1.8 pc, tracing gas that is more reminiscent of H scii regions. We estimate a star formation (surface density) rate of ΣSFR ∼ 0.6 M ⊙ yr−1 kpc−2 or SFR ∼ 50 M ⊙ yr−1, consistent with a star-forming main-sequence galaxy of M ⋆ ∼ 1011 M ⊙. The discovery presented here opens up the possibility of studying ionized gas at high redshifts using RRL observations from current and future (e.g., SKA and ngVLA) radio facilities

Probing The Circumgalactic Medium With Quasar Absorption Lines

Quasars (QSOs), the most distant and intrinsically luminous objects in the Universe, provide a direct probe to the history of the Universe. The quasar absorption spectroscopy has been one of the most used sensitive tools to probe the physical conditions of several different astrophysical environments. In particular, absorption lines observed in the background distance quasar spectra are unique probes of intervening gas from very high density (H ∼ 105 cm−3) outflowing gas to the extremely low density (H ∼ 10−5 cm−3) intergalactic medium (IGM). Studying them in absorption at low and high redshifts reveals a plethora of information about the nature of the gaseous environments, chemical enrichment, formation, and evolution of galaxies. This thesis examines the absorbing gas traced by double ionized carbon (C III) metal line species using archival data of high resolution optical (groundbased) and ultraviolet (UV) (spacebased) quasar spectra. In the first part of the thesis, a detailed survey of high ( > 2) C III systems has been carried out using archival spectroscopic data of ground based observations made with UVVisual Echelle Spectrograph (UVES) onboard Very Large Telescope(VLT) and the high Resolution Echelle Spectrometer (HIRES) on Keck. Out of a plethora of C III systems identified in this survey, 53 optically thin C III systems in the redshift range, 2.1 −1.2) are found when they are divided appropriately in the vs. (C III) plane. Further studies of C III absorbers in the redshift range, 1.0 ≤ ≤ 2.0 are important to map the redshift evolution of these absorbers and gain insights into the time evolution physical conditions of the circumgalactic medium. Finally, for the future direction of this work, a new PYTHON code “Quasar AbsorptionGALaxy Survey (QAGALS) is developed to automatically search for photometric/spectroscopic data of galaxies within a userdefined impact parameter around the intervening absorbers. QAGALS have also implemented the SED fitting code for modeling galaxy spectra with spectroscopic and photometric observations to compute the observed galaxy properties such as redshift, age, mass, star formation rate (SFR) and specific star formation rate (sSFR). For demonstration, QAGALS is used to search for galaxies from the SDSS DR16 catalog and compute the galaxy properties associated with the low C III sample

Drug Utilisation Pattern and Adverse Events in Patients with Chronic Kidney Disease Undergoing Maintenance Haemodialysis at a Tertiary Care Hospital of Odisha

Introduction: The number of patients receiving renal replacement therapy in the form of dialysis or transplant has been increasing in recent years. Increased frequency of monitoring due to complex therapeutic regimen and inappropriate use of drugs may lead to increased Adverse Events (AEs), hospital stay, cost of treatment as well as increased morbidity and mortality. Aim: To analyse utilisation pattern of drugs and AEs in Chronic Kidney Disease (CKD) patients undergoing maintenance haemodialysis. Materials and Methods: This prospective, observational study was conducted in the Department of Pharmacology in collaboration with Department of Nephrology, SCB Medical College and Hospital, Cuttack, from 1st June to 31st December, 2015. Demographic, clinical and medicine details were collected from patients’ case sheet, matched with nursing case records and tabulated in a predesigned case study form. The data were analysed in a descriptive manner using percentage calculation and Spearman’s correlation, multiple logistic regression using trial version SPSS v24. Results: A total number of 115 cases were included in this study. Average number of drugs used, per prescription was 12.8 during the dialysis and non-dialysis days. Most frequently used drugs were antihypertensives, 25% dextrose and heparin (before dialysis and on dialysis days) were prescribed to all patients followed by haematinics in 90.43% of the patients and proton pump inhibitors were prescribed in 70.43% of the patients. Among 1472 drugs prescribed, 40.96% of the drugs were prescribed in generic name. It was observed that 72.62% of the prescribed drugs were from National List of Essential Medicine. AEs were observed with varying severity in all the patients. Frequently observed AEs as per the laboratory investigations were hyperphosphataemia, hyponatraemia, metabolic acidosis, hyperkalemia, hypoglycaemia, hypocalcaemia and hypokalemia. AEs were statistically significant with age group >45 years (p<0.001). Conclusion: This study provides an insight regarding utilisation pattern of a wide variety of drug classes in CKD patients undergoing maintenance haemodialysis in a tertiary care teaching hospital setting and suggests a possible improvement in medicine practices among patients suffering from CKD which may probably affect adherence patterns positively. Certain areas like potential drug interactions, adverse drug reactions and adherence are required to be explored further