Echoes from the Abyss: A Status Update

Gravitational wave echoes provide our most direct and surprising observational window into quantum nature of black holes. Three years ago, the first search for echoes from Planck-scale modifications of general relativity near black hole event horizons led to tentative evidence at false detection probability of 1\% arXiv:1612.00266 . The study introduced a naive phenomenological model and used the public data release by the Advanced LIGO gravitational wave observatory for the first observing run O1 (GW150914, GW151226, and LVT151012, now GW151012). Here, we provide a status update on various observational searches for echoes by independent groups, and argue that they can all be consistent if echoes are most prominent at lower frequencies and/or in binary mergers of more extreme mass ratio. We also point out that the only reported "detection" of echoes (with $>4\sigma$ confidence) at 1.0 second after the binary neutron star merger GW170817 arXiv:1803.10454 is coincident with the formation time of the black hole inferred from electromagnetic observations

GW190521: First Measurement of Stimulated Hawking Radiation from Black Holes

Being the most massive binary black hole merger event observed to date, GW190521 is in a class of its own. The exceptionally loud ringdown of this merger makes it an ideal candidate to search for gravitational wave echoes, a proposed smoking gun for the quantum structure of black hole horizons. We perform an unprecedented multi-pronged search for echoes via two well-established and independent pipelines: a template-based search for stimulated emission of Hawking radiation, or Boltzmann echoes, and the model-agnostic coherent WaveBurst (cWB) search. Stimulated Hawking radiation from the merger is expected to lead to post-merger echoes at horizon mode frequency of $\sim 50$ Hz (for quadrupolar gravitational radiation), repeating at intervals of $\sim 1$ second, due to partial reflection off Planckian quantum structure of the horizon. A careful analysis using dynamic nested sampling yields a Bayesian evidence of $7\pm 2$ (90% confidence level) for this signal following GW190521, carrying an excess of $10^{+9}_{-7}\%$ in gravitational wave energy, relative to the main event. Similarly, the reconstructed waveform of the first echo in cWB carries an energy excess of $13^{+16}_{-7}\%$. Accounting for the "look-elsewhere" effects, we estimate a p-value for false detection probability of $5.1 \times 10^{-3}$ (or 2.6$\sigma$) using cWB pipeline, although the verdict on the co-localization of the post-merger echo and the main event in the sky is inconclusive. While the current evidence for stimulated Hawking radiation does not reach the gold standard of $5\sigma$, our findings are in line with expectations for stimulated Hawking radiation at current detector sensitivities. The next generation of gravitational wave observatories can thus draw a definitive conclusion on the quantum nature of black hole horizons

Quantum Black Holes in the Sky

Black Holes are possibly the most enigmatic objects in our Universe. From their detection in gravitational waves upon their mergers, to their snapshot eating at the centres of galaxies, black hole astrophysics has undergone an observational renaissance in the past 4 years. Nevertheless, they remain active playgrounds for strong gravity and quantum effects, where novel aspects of the elusive theory of quantum gravity may be hard at work. In this review article, we provide an overview of the strong motivations for why "Quantum Black Holes" may be radically different from their classical counterparts in Einstein's General Relativity. We then discuss the observational signatures of quantum black holes, focusing on gravitational wave echoes as smoking guns for quantum horizons (or exotic compact objects), which have led to significant recent excitement and activity. We review the theoretical underpinning of gravitational wave echoes and critically examine the seemingly contradictory observational claims regarding their (non-)existence. Finally, we discuss the future theoretical and observational landscape for unraveling the "Quantum Black Holes in the Sky"

Optimal placement of fuses and switches in active distribution networks using value-based MINLP

Contingency conditions in distribution networks create financial losses for different parts of the system including electricity customers, electricity retailers, distributed generation (DG) units, etc. Therefore, protective device allocation methods have been introduced in recent years to enhance the reliability of the power system. In this study, a new formulation is proposed to find the optimal places of sectionalizing switches and fuses while taking the financial loss of both electricity customers and DG units into account. The current method has the flexibility to consider DG effect on any location of the network and its islanded operation in case of contingencies. Moreover, the uncertainty in load and renewable generation is taken into account using stochastic programming. The results demonstrate that the DG units and their financial loss can change the results of switch and fuse placement dramatically when there are no tie switches in the network. Furthermore, it is found that this method can decrease the total reliability costs by 3.86% when high penetration of DG units is introduced into a modified Roy Billinton test system (RBTS). The problem is modeled as a mixed-integer nonlinear (MINLP) formulation and is handled using BARON solver in GAMS environment

Integrated collaborative tools for precast supply chain management

Precast construction projects are associated with many activities, numerous parties, enormous effort, and different processes. For effective communication, this requires delivering appropriate and up-to-date information to enhance collaboration and improve integration. The purpose of this paper is to develop the system architecture and prototype of Context-Aware Cloud Computing Building Information Modelling (CACCBIM) for precast supply chain management. The findings of this research are grounded on the literature of cloud computing, context-awareness, building information modelling, and, ultimately, the analysis of interviews with stakeholders in precast construction. Findings determine that lack of integration, improper planning and scheduling, poor production timing, poor coordination, lack of good communication among parties, wrong deliveries, and poor control and supervision are the major issues within the precast supply chain. These issues could result in adverse consequences for the objectives and success of the precast project. Eventually, to reduce and eliminate these issues, the proposed prototype will support appropriate deliveries, efficient monitoring, facilitation of coordination, and collaboration with improved communication. It is anticipated that this research will establish a unique perception in the precast construction industry, which will finally enhance its productivity, improve its efficiency, and maximise its effectiveness

Chronic effects of hydro-alcoholic artemisia absinthium extract on the liver enzymes and tissue changes of adult mal rat

Artemisia absinthium has many pharmacological effects, but toxic effects of it, were seen on nervous system and liver. Therefore, the aim of this study was to evaluate the chronic effects of different doses of Artemisia absinthium extract on the enzymes and histopathological changes of the liver tissue of adult normal male rat. Method and materials: In this experimental study, forty eight male Wistar rats were randomly divided into 6 groups of 8 as follows: Control, sham (recipient of distilled water) and 4 experimental groups that received Artemisia absinthium hydro- alcoholic extract at doses of 125, 250, 500 and 1000 mg/kg intraperitoneally.The data were analyzed using one-way ANOVA and Duncan post hoc tests. P≤0.05 was considered statistically significant. Results: After 8 weeks, doses of 125, 250 and 500 mg/kg could significantly reduce amount of ALT, AST and ALP. Dose of 1000 mg/kg increased ALT, AST and ALP. From the standpoint of histopathological study, doses of 125, 250 and 500 Artemisia absinthium had no significant side effect on liver tissue, but 1000 mg/kg caused destruction of liver cell membranes, enlargement of sinusoidal space, sporadic leukocyte infiltration, Kupffer cells hypertrophy, and vascular congestion.Conclusion: Maximum dose of Artemisia absinthium extract (1000 mg/kg) increased liver enzymes and destroy liver tissues of normal male rats.Keywords: Artemisia Absinthium, Enzymes, Histopathology, Liver, Ra

The effect of tactile-kinesthetic stimulation on growth indices of healthy neonates

Abstract Therapeutic touch is emphasized by healthcare professionals for improvement of neonates' growth and development. However, inconsistencies exist regarding effects and methods of massage in neonates. The purpose of this clinical trial is to assess and comprise intervention and control groups regarding the effects of tactile-kinesthetic stimulation (TKS) by mothers on growth indices of healthy term neonates. Sixty healthy term neonates were randomly assigned into intervention and control groups. Mothers of neonates in the experimental group were trained to perform TKS for their newborns at home before feeding for at least 28 consecutive days, two times a day, and 15 min each time. Neonates in the control group were not required to receive this intervention. The neonates’ growth indices were measured within 24 h after birth, and then at days 14 and 28. During the study and the three consecutive measurements, no significant difference was found between the mean weights, heights, and head circumferences of the neonates in the two groups (p > 0.05). Keywords: Tactile-kinesthetic stimulation Growth indices Neonates Mother's touc

Removal of Cationic Tolonium Chloride Dye Using Fe3O4 Nanoparticles Modified with Sodium Dodecyl Sulfate

In this study, Fe3O4 nanoparticles modified with sodium dodecyl sulfate (Fe3O4-SDS) were used for the adsorption of cationic tolonium chloride (TC) dye from aqueous solution. The effects of temperature, pH, amount of nanoparticles and SDS concentration, stirring time, and interfering ions on dye adsorption were investigated. For TC, the maximum removal was 98 % in the best conditions (pH = 6; 0.6 g Fe3O4-SDS; 30 °C temperature, and 3 min stirring time). Data from the sorption kinetic studies showed the best fitting of the pseudo-second-order model for adsorption of the dye. The Langmuir isotherm showed better fitting of the data for TC adsorption by Fe3O4-SDS compared with the other models. The Fe3O4-SDS nanoparticles are easily synthesizable, magnetically recoverable, and regenerable, which increases their practical applications. Additionally, NaCl showed no significant impact on the dye removal up to 0.8 molar concentration, which increases the industrial application of the process