Search

We present a comprehensive analysis of the X-ray spectral properties of 198 newly identified active galactic nuclei (AGNs), leveraging archival data from the Chandra X-ray Observatory. All these AGNs exhibit a power-law spectral signature spanning a broad energy range of |$0.5{\!-\!}7.0$| keV, characterized by the photon index (⁠|$\Gamma$|⁠) values ranging from |$0.3^{+0.16}_{-0.14}$| to |$2.54^{+0.14}_{-0.13}$|⁠. Particularly, 76 of these AGNs display discernible levels of intrinsic absorption, after considering the Galactic absorption. The column densities associated with this local absorption (⁠|$n_{\rm H}^{\rm local}$|⁠) are within a range of |${\sim} 10^{19}{\!-\!}10^{22}\ {\rm cm^{-2}}$|⁠. We study the cosmological evolution of AGNs using the variation of |$n_{\rm H}^{\rm local}$| and |$\Gamma$| with their estimated redshift. The intrinsic spectral signature did not reveal any significant cosmological evolution; however, a deficit of hard sources at high redshift is possibly intrinsic. Our sample covers several orders of broad-band intrinsic luminosity (⁠|$L_{\rm B}^{\rm intr}$|⁠) ranging from |$4.59^{+0.41}_{-0.41} \times 10^{42}$| to |$2.4^{+0.12}_{-0.12} \times 10^{46}\, {\rm erg~s}^{-1}$| with peak at 1.84 redshift. We also investigate the hardness–luminosity diagram to further probe the AGNs. We conduct a sanity check by applying our findings to known AGNs, and the results are consistent with our observations. [ABSTRACT FROM AUTHOR]

Consider the ring C c (X) F comprising real-valued functions exhibiting discontinuity on finite sets with a countable range. Within this context, we explore the ( c) F -filters on X and ( c) F -ideals in C c (X) F . We establish an adaptation of the Gelfand–Kolmogoroff theorem within this framework and present various equivalent conditions when C c (X) F conforms to the properties of a Baer-ring or a regular ring. Additionally, we delve into the zero divisor graph analysis within C c (X) F . [ABSTRACT FROM AUTHOR]

ASASSN-20hx, a.k.a AT2020ohl, is an ambiguous nuclear transient, which was discovered in the nearby galaxy NGC6297 by the All-Sky Automated Survey for Supernovae. We have investigated the evolution of AT2020ohl using a multiwavelength data set to explain the geometry of the system and the energy radiated by it between X-ray and radio wavelengths. Our X-ray, UV/optical, and radio observations of the object jointly clarify the association of AT2020ohl with the nuclear activity of NGC6297. We detected radio counterpart of AT2020ohl 111 and 313 d after the discovery in Jansky Very Large Array X-band with flux densities 47 ± 14 and 34 ± 3 |$\mu$| Jy, respectively. Using multiwavelength data analysis, we nullify the possibility of associating any stellar disruption process with this event. We found some evidence showing that the host galaxy is a merger remnant, so the possibility of a binary supermassive black hole (SMBH) system cannot be ruled out. The central SMBH has a mass of ∼1.2 × 107 M⊙. We propose the accretion disc activity as the origin of AT2020ohl – it is either due to disc accretion event on to the central SMBH or due to the sudden accretion activity in a pre-existing accretion disc of the system during the interaction of two SMBHs which became gravitationally bound during a merger process. However, we also admit that with the existing data set, it is impossible to say definitively, among these two probabilities, which one is the origin of this nuclear transient. [ABSTRACT FROM AUTHOR]

Herein, a scalable method was adopted for hosting membrane reusability via a technique in which a covalent adaptable network was installed in the membrane by covalently anchoring an interpenetrating polymeric network membrane with a Diels–Alder adduct. The membrane was then used for water treatment applications. The presence of the laterally large GO sheets in the membrane matrix helped to control the pore size and contributed towards significant separation performance. The fabricated membrane was characterized by high water flux and nearly 97% rejection of stringent contaminants, including dyes and ions. The hydrophilic membrane surface helped in exhibiting antifouling characteristics and assisted in hitting the age-old selectivity–permeability offset. The cytocompatibility of the designed membranes added required leverage in terms of real-time deployment. The recyclability of the membranes enabled by the dynamic bonds augmented the retention of mechanical properties and satisfactory water-remediating features. This study has the potential to buffer the ill effects of microplastic pollution generated by the deplorable management of membrane disposal and provide a quick remedy in terms of cleaner and greener membranes. [ABSTRACT FROM AUTHOR]

Host–guest chemistry, although historically developed in organic and aqueous solutions, recently has gained interest in designing systems assembled on solid surfaces. Following this unique chemistry, structural complexes consisting of copper-based molecular metal oxide clusters soldered onto a sequential interpenetrating polymer network (IPN) were designed to host carbon nanotubes constructed via electrostatic assembly designed to absorb millimeter waves. Such unique structures offer myriad solutions in this era of 5G and IoT (internet of things) wherein lightweight, ultrathin, and multifunctional properties have become a prerequisite to protect precise electronics from stray signals. This strategy offers to trigger and tune the surface charge of the host (Keggin type Cu-POM-soldered IPN), which allows the guest (positively charged CNTs) to self-assemble. The resulting construct (thickness ∼56 μm) demonstrated synergistic enhancement in millimeter wave absorption (>90% absorption in X-band, 8.2–12.4 GHz) through this unique host–guest assembly with a remarkable green index (gs ≈ 1.7). This study opens new avenues in designing lightweight constructs for millimeter wave absorption that are not possible via conventional routes of dispersing nanoflakes in composites. [ABSTRACT FROM AUTHOR]

Temperature downshifts are the gold standard when setting up control strategies for mammalian cell culture processes. These shifts are performed to prolong production phases and attain heightened levels of productivity. For the development of biosimilars, however, the bottleneck is in achieving a prespecified product quality. In a late-stage development project, we investigated the impact of temperature shifts and other process parameters with the aim of optimizing the glycosylation profile of a monoclonal antibody (mAb). We applied a design of experiments approach on a 3 L scale. The optimal glycosylation profile was achieved when performing a temperature upshift from 35.8 °C to 37 °C. Total afucosylated glycan (TAF) decreased by 1.2%, and galactosylated glycan species (GAL) increased by up to 4.5%. The optimized control strategy was then successfully taken to the manufacturing scale (1000 L). By testing two sets of set points at the manufacturing scale, we demonstrated that the statistical models predicting TAF and GAL trained with small-scale data are representative of the manufacturing scale. We hope this study encourages researchers to widen the screening ranges in process development and investigate whether temperature upshifts are also beneficial for other mAbs. [ABSTRACT FROM AUTHOR]

Polymer nanocomposites with exceptionally high mechanical properties owing to strong interfacial attraction have garnered tremendous interest in the research community. In general, tough and robust polymer nanocomposites are usually obtained via dispersing a nano‐flaky filler in the polymer matrix, although the strategy is only sometimes practically viable. To this end, in this work, a facile strategy has been adopted to achieve a strong and tough polymer nanocomposite. A novel mussel‐inspired full interpenetrating polymeric network (IPN) consisting of polyvinylalcohol and polydopamine was prepared. This technique helped integrate the advantages of dopamine chemistry with forming a full IPN using Borax as a common crosslinker. The infusion of 1 wt% acid‐modified carbon nanotubes (ACNT) in the IPN matrix helped greatly improve the current state‐of‐the‐art. The synergistic effect of nano‐reinforcement and formation of ester linkage through a substantial amount of di‐diol complexation dominated and accounted for the significant enhancement of mechanical properties. This is further supported by decreased intensity of free OH groups in the FTIR investigations, viscosity enhancement from rheological behavior, and temperature‐dependent dynamic mechanical property analysis. Such an IPN structure is a promising way to enhance mechanical properties. [ABSTRACT FROM AUTHOR]

A large number of unidentified sources found by astronomical surveys and other observations necessitate the use of an automated classification technique based on machine learning (ML) methods. The aim of this paper is to find a suitable automated classifier to identify the point X-ray sources in the Chandra Source Catalogue (CSC) 2.0 in the categories of active galactic nuclei (AGN), X-ray emitting stars, young stellar objects (YSOs), high-mass X-ray binaries (HMXBs), low-mass X-ray binaries (LMXBs), ultra luminous X-ray sources (ULXs), cataclysmic variables (CVs), and pulsars. The catalogue consists of ≈317 000 sources, out of which we select 277 069 point sources based on the quality flags available in CSC 2.0. In order to identify unknown sources of CSC 2.0, we use MW features, such as magnitudes in optical/ultraviolet bands from Gaia-EDR3, Sloan Digital Sky Survey, and GALEX, and magnitudes in infrared bands from 2MASS, WISE, and MIPS-Spitzer, in addition to X-ray features (flux and variability) from CSC 2.0. We find the Light Gradient Boosted Machine, an advanced decision tree-based ML classification algorithm, suitable for our purpose and achieve 93  per  cent precision, 93  per  cent recall score, and 0.91 Mathew's Correlation coefficient score. With the trained classifier, we identified 54 770 (14 066) sources with more than 3σ (4σ) confidence, out of which there are 32 600 (8574) AGNs, 16,148 (5,166) stars, 5,184 (208) YSOs, 439 (46) HMXBs, 197 (71) LMXBs, 50 (0) ULXs, 89 (1) CVs, and 63 (0) pulsars. This method can also be useful for identifying sources of other catalogues reliably. [ABSTRACT FROM AUTHOR]

A comprehensive wideband spectral analysis of the brightest black hole X-ray binary 4U 1543−47 during its 2021 outburst is carried out for the first time using NICER, NuSTAR , and AstroSat observations by phenomenological and reflection modelling. The source attains a super-Eddington peak luminosity and remains in the soft state, with a small fraction (⁠|$\lt 3{{\ \rm per\ cent}}$|⁠) of the inverse-Comptonized photons. The spectral modelling reveals a steep photon index (Γ ∼ 2–2.6) and relatively high inner disc temperature (T in ∼ 0.9–1.27 keV). The line-of-sight column density varies between (0.45–0.54) × 1022 cm−2. Reflection modelling using the RELXILL model suggests that 4U 1543−47 is a low-inclination system (θ ∼ 32°–40°). The accretion disc is highly ionized (log ξ > 3) and has super solar abundance (3.6–10 A Fe,⊙) over the entire period of study. We detected a prominent dynamic absorption feature between ∼8 and 11 keV in the spectra throughout the outburst. This detection is the first of its kind for X-ray binaries. We infer that the absorption of the primary X-ray photons by the highly ionized, fast-moving disc winds can produce the observed absorption feature. The phenomenological spectral modelling also shows the presence of a neutral absorption feature ∼7.1–7.4 keV, and both ionized and neutral absorption components follow each other with a delay of a typical viscous time-scale of 10–15 d. [ABSTRACT FROM AUTHOR]

We present the results on broad-band X-ray properties of persistent black hole binaries GRS 1758−258 and 1E 1740.7−2942 using AstroSat, NuSTAR , and Swift – XRT observations carried out during 2016–2022. We perform spectral modelling of both sources after eliminating the contamination in their LAXPC spectra from nearby X-ray sources. Preliminary spectral modelling using Comptonization and line emission (∼6.4 keV) models suggest that GRS 1758−258 occupies both dim-soft state (kT bb = 0.37 ± 0.01 keV, Γ ∼ 5.9, |$L_{bol}=1{{\ \rm per\ cent}}$| of Eddington luminosity L Edd) and hard state (Γ = 1.64–2.22, kT e = 4–45 keV, L bol = 1–5 per cent L Edd) that requires a multicolour disc blackbody model (kT in = 0.54 ± 0.01 keV) occasionally. 1E 1740.7−2942 instead is found only in hard state (Γ = 1.67–2.32, kT e = 5–16 keV, L bol = 1–2 per cent L Edd). Reflection properties of both sources are studied by applying relativistic reflection model RELXILL to the broad-band spectra. Our results from AstroSat and NuSTAR consistently unveiled the presence of a Comptonizing region along with an ionized reflection region (ionization parameter log ξ = 2.7–3.8 and 2.7–4.7 erg cm s−1 in GRS 1758−258 and 1E 1740.7−2942, respectively) in both sources. Reflection modelling revealed GRS 1758−258 to have a high metal abundance (⁠|$A_{fe}=3.9^{+0.4}_{-0.3}$| times solar metal abundance) and inclination angle (i) of 61 ± 2°. In case of 1E 1740.7−2942, i is constrained to be 55 ± 1°. Finally, we discuss the implication of our findings in the context of accretion dynamics by comparing our results with the previous studies. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced polymer composite (GFRP) encounter many practical situations during its application, exposed to different temperature fluctuation. Absorption of moisture and the fluctuated thermal environment cause mechanical degradation of GFRP. The current plan is to explore the mechanical and chemical behavior of pristine multiwall carbon nanotubes(pMWCNTs)‐glass fiber strengthens epoxy composites during thermal shock (TS). The laminates were prepared by the hand‐lay‐up process followed by compression molding. The thermal shock was performed at the temperature for the required samples was 135°C for 24 h, followed by −135°C for 24 h. A flexural test has been carried out at 1 mm/min loading speed. 0.2 wt% pMWCNTs filled nanocomposite appeared to have the highest flexural strength and modulus compared to ambient samples. The thermomechanical behavior of nanocomposites has been accomplished by analyzing the dynamic mechanical thermal analysis graph (DMTA). Field emission scanning electron microscope (FESEM) analyzed the fracture surface of in‐situ mechanical failure samples to find out the primary failure modes for strengthening and weakening mechanisms. The glass transition temperature (Tg) of the nanocomposite observed decreased due to homogeneous dispersion of pMWCNTs, imparting some effect on crosslink density and reinforcement up to 0.2 wt%. This study reveals that the uniform distribution of pMWCNTs and thermal shock treatment enhances the matrix stiffness and improves the mechanical properties. [ABSTRACT FROM AUTHOR]

We present a comprehensive spectral and temporal study of the black hole X-ray transient MAXI J1820+070 during its outbursts in 2018 using Swift/XRT, NICER, NuSTAR , and AstroSat observations. The Swift/XRT and NICER spectral study shows a plateau in the light curve with spectral softening (hardness changes from |$\sim \, 2.5$| to 2) followed by a gradual decline without spectral softening during the first outburst. Also, spectral modelling suggests that the first outburst is in the low/hard state throughout with a truncated disc, whereas the thermal disc emission dominates during the second outburst. During the entire outburst, strong reflection signature (reflection fraction varies in the range |$\sim \, 0.38\!-\!3.8$|⁠) is observed in the simultaneous wideband (NICER – NuSTAR, XRT – NuSTAR, AstroSat) data due to the presence of a dynamically evolving corona. The NICER timing analysis shows quasi-periodic oscillation signatures and the characteristic frequency increases (decreases) in the plateau (decline) phase with time during the first outburst. We understand that the reduction of the electron cooling time-scale in the corona due to spectral softening and the resonance oscillation with the local dynamical time-scale may explain the above behaviour of the source during the outburst. Also, we propose a possible scenario of outburst triggering and the associated accretion geometry of the source. [ABSTRACT FROM AUTHOR]