Abstract
Accretion disks around black holes power some of the most luminous objects in the universe. Disks that are misaligned to the black hole spin can become warped over time by Lense–Thirring ...precession. Recent work has shown that strongly warped disks can become unstable, causing the disk to break into discrete rings producing a more dynamic and variable accretion flow. In a companion paper, we present numerical simulations of this instability and the resulting dynamics. In this paper, we discuss the implications of this dynamics for accreting black hole systems, with particular focus on the variability of active galactic nuclei (AGN). We discuss the timescales on which variability might manifest, as well as the impact of the observer orientation with respect to the black hole spin axis. When the disk warp is unstable near the inner edge of the disk, we find quasi-periodic behavior of the inner disk, which may explain the recent quasi-periodic eruptions observed in, for example, the Seyfert 2 galaxy GSN 069 and in the galactic nucleus of RX J1301.9+2747. These eruptions are thought to be similar to the “heartbeat” modes observed in some X-ray binaries (e.g., GRS 1915+105 and IGR J17091-3624). When the instability manifests at larger radii in the disk, we find that the central accretion rate can vary on timescales that may be commensurate with, e.g., changing-look AGN. We therefore suggest that some of the variability properties of accreting black hole systems may be explained by the disk being significantly warped, leading to disk tearing.
The present research work focuses on preparing 3D transition metal doped copper oxide nanostructures through sonication method and to investigate the effect of doping different transition metal into ...copper oxide (CuO) on the basic properties of CuO nanoparticles and, to study the photocatalytic behaviour of the doped CuO samples. The morphological studies performed with the help of SEM revealed the formation of flower like CuO 3D nanostructures for all the doped samples. The slight shift in the position of peaks in the x-ray diffraction (XRD) pattern confirms that doping has been successfully done into CuO. Also, the sharp diffraction peaks suggest the polycrystalline nature of the sample with monoclinic structure. The UV–vis absorption analysis reveals a bandgap of 2.26, 2.12 and 2.15 eV for the CuO samples doped with nickel, zinc, and iron respectively via Tauc plot. The photocatalytic performance of the samples tested through the degradation of methylene blue (MB) dye suggests that samples doped with Zn shows better degradation. Thus, it is evident that the morphology and the optical properties of the CuO can be tailored by doping transition metal into it.
•Flower-like 3D CuO nanostructures doped with transition metals (Ni, Fe and Zn).•As the atomic radius of Cu, Ni, Zn and Fe are 0.73 Å, 0.69 Å, 0.70 Å and 0.74 Å.•Fe doped samples reveal a bandgap of 2.12 eV and 2.15 eV respectively.•Efficiency of photo-degradation of the Ni −52 %, Zn-63 %, and Fe-62 % doped samples.•After exposing the test solution for 60 min a very good degradation result.
Bearing faults of rotating machinery are observed as impulses in the vibration signal, but it is mostly immersed in noise. In order to effectively remove this noise and detect the impulses, a novel ...technique with morphological operators and fuzzy inference is proposed in this paper. The effectiveness of the morphological operators lies with the correct selection of structuring elements (SEs). This paper also proposes a new algorithm for this SE selection based on kurtosis, thereby making the analysis free of empirical methods. When analyzed with three different sets of faults, the results show that this method is effective and robust in bringing out the impulses. With fuzzy inference being coupled to this new technique, it makes the algorithm to be able to detect early faults also.
In this work, the ternary hybrid structure VSe2/SWCNTs/rGO is reported for supercapacitor applications. The ternary composite exhibits a high specific capacitance of 450 F g−1 in a symmetric cell ...configuration, with maximum energy density of 131.4 Wh kg−1 and power density of 27.49 kW kg−1. The ternary hybrid also shows a cyclic stability of 91 % after 5000 cycles. Extensive density functional theory (DFT) simulations on the structure as well as on the electronic properties of the binary hybrid structure VSe2/SWCNTs and the ternary hybrid structure VSe2/SWCNTs/rGO have been carried out. Due to a synergic effect, there are enhanced density of states near the Fermi level and higher quantum capacitance for the hybrid ternary structure compared to VSe2/SWCNTs, leading to higher energy and power density for VSe2/SWCNTs/rGO, supporting our experimental observation. Computed diffusion energy barrier of electrolyte ions (K+) predicts that ions move faster in the ternary structure, providing higher charge storage performance.
A ternary hybrid structure VSe2/SWCNTs/rGO is reported for supercapacitor applications. The ternary composite exhibits a high specific capacitance of 450 F g−1 in a symmetric cell configuration, with maximum energy density of 131.4 Wh kg−1 and power density of 27.49 kW kg−1. The ternary hybrid also shows a cyclic stability of 91 % after 5000 cycles. DFT simulations on the material have been also carried out.
The structural, optical, magnetic and electrical properties of cerium oxide (CeO
2
) nanoparticles prepared by hydrothermal route are analyzed by subjecting them to characterization techniques such ...as Powder X-ray diffraction (PXRD), High resolution scanning electron microscope (HRSEM), High resolution transmission electron microscope (HRTEM), Energy Dispersive X-ray Analysis (EDAX), Fourier transform infra red spectroscopy (FTIR), Raman spectroscopy, Ultraviolet–Visible analysis, Vibrating sample magnetometer (VSM) analysis and Dielectric measurements. The PXRD, FTIR, Raman and EDAX analyses confirm the formation of CeO
2
nanoparticles. The PXRD studies reveal that the cerium oxide nanoparticles have crystalline nature and have Face Centered Cubic structure. The average crystallite size, estimated using Scherrer formula, is 7 nm. The HRSEM and HRTEM images reveal that the CeO
2
nanoparticles have spherical morphology with an average particle size of 23 nm. The optical band gap energy of the cerium oxide nanoparticles, calculated from UV–Vis studies, is 3.4 eV which could be due to the substantial concentration of Ce
3+
ions in the ceria nanoparticles. The Ferromagnetic behavior of CeO
2
at room temperature is implied from VSM studies. The Dielectric analysis divulge that the dielectric constant of cerium oxide nanoparticles decreases as the frequency and temperature increases. The electrical behaviour, activation energy and relaxation time of electrons of CeO
2
nanoparticles are studied by plotting Nyquist plot, Arrhenius plot and Bode plot respectively.
A dental implant with three distinct layers, of titanium alloy at core, porous titanium alloy at the intermediate layer and titanium alloy hydroxyapatite composite at the outer layer, is designed to ...achieve low elastic modulus and adequate strength with bioactive surface. Artificial Neural Network (ANN) along with Rule of Mixture (ROM) is used to generate the objective functions for the Genetic Algorithm (GA) based multi-objective optimization for achieving the optimal designs, which are validated using Finite Element Analysis (FEA) simulations. The composition and processing parameters are correlated with the yield strength and elastic modulus of titanium alloy using ANN. The ANN models are generated to express the strength and effective modulus of the implant using ROM. To determine the optimal composition of titanium alloys, porous layers, and composite layers for a three-layer dental implant, multi-objective genetic algorithm is employed. The Pareto optimal solutions provide the guidelines for designing the implant. A few selected non-dominated solutions are used for studying the actual stress distribution at the bone-implant interface using FEA, and showed significant improvements compared to conventional implants.
Human cytomegalovirus (HCMV) is the most common cause of congenital infections and is an important pathogen in immunocompromised individuals. Despite a robust host immune system, HCMV able to ...replicate, evade host defenses, establish latency for life. A significant portion of HCMV genome dedicated to encode gene products for modulation of host immune response. Growing number of HCMV gene products are being recognized to play role in immune evasion. Information on viral immune evasion mechanisms by which HCMV persists in host will be useful in devising antiviral intervention strategies and development of new vaccines. This minireview provides a brief overview of immune evasion strategy adapted by HCMV by utilizing its gene products in modulation of host immune response.
Nano-sized photocatalyst cerium oxide (CeO
2
) particles and activated carbon–cerium oxide (AC–CeO
2
) composite are prepared by facile hydrothermal technique. Their properties are analyzed by ...subjecting them to characterization techniques such as powder X-ray diffraction (PXRD), high-resolution scanning electron microscopy (HRSEM), energy dispersive X-ray analysis (EDX), high-resolution transmission electron microscopy (HRTEM), Fourier transform infra-red spectroscopy (FTIR) and Raman spectroscopy. The photocatalytic activity of the prepared samples is monitored by UV–visible spectrophotometer. The PXRD, FTIR, Raman and EDX analyses confirm the formation of CeO
2
nanoparticles. The PXRD studies revealed that the CeO
2
nanoparticles and AC–CeO
2
nanocomposite have face centered cubic structure. The average crystallite size of CeO
2
nanoparticles and AC–CeO
2
nanocomposite, estimated using Scherrer formula, is found to be 21 nm and 7 nm. The HRSEM images show that the CeO
2
nanoparticles and AC–CeO
2
nanocomposite have spherical morphology and some agglomeration. The HRTEM images strongly confirm spherical morphology of both CeO
2
nanoparticles and AC–CeO
2
nanocomposite. The particle size of the CeO
2
nanoparticles and AC–CeO
2
nanocomposite are in the size range 20–30 nm and 7–15 nm, respectively. The selected area electron diffraction (SAED) patterns reveal that both samples are polycrystalline in nature. The photocatalytic activity of the synthesized CeO
2
nanoparticles and AC–CeO
2
nanocomposite is measured by degrading methylene blue dye under solar radiation. The photocatalytic activity study shows that the AC–CeO
2
nanocomposite has a degradation efficiency of 94% in 1 h for methylene blue, which is remarkably high when compared to that of CeO
2
nanoparticles.
Presently most of the applications in Wireless Body Sensor Network (WBAN) demand effective communication processes, which is used to monitor the data in a remote manner according to the demand and ...timely manner for wearable systems. The data have been transmitted through the sensor networks among smart wearable devices which help to analyze the various security threats. The data transmission using sensor networks of smart wearable patches may consumes more energy which leads to minimize the entire network lifetime as well as to reduce the data transmission quality. Even though the network transmits the data with effective manner, the data has been aggregated from different sources via common aggregators in the smart wearable patches. At the time of the aggregation process, network lifetime needs to be managed for further data analyzes process. So, in this research the lifetime of the network has been managed by applying the opportunistic energy-efficient routing with load balancing (OE2-LB) algorithm which eliminates the data aggregation delay as well as avoid routing loops with effective manner for the smart wearable patches. Then the efficiency of the system has been validated in terms of network lifetime, delay, error metrics, Energy efficiency and throughput of the network.
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