Falling from Rest: Particle Creation in a Dropped Cavity

We discuss the process of particle creation in the case of a scalar quantum field confined to a small cavity, initially at rest, which is suddenly dropped in a static gravitational field. We show that, due to the transition from a Schwarzschild to a Minkowski background, as perceived by a comoving observer, field particles are excited out of the quantum vacuum. The density of the created quanta depends on the proper gravitational acceleration as well as on a parameter α≃1/Δt, with Δt representing the typical time duration of the transition. For the specific acceleration profile considered, the energy spectrum of the created quanta roughly resembles a two-dimensional Planckian distribution, whose equivalent temperature mimics the Hawking-Unruh temperature, with the detector acceleration (or the black hole surface gravity) replaced by the parameter cα. We briefly comment on possible issues related to local Lorentz symmetry.

Seismic Reflection Analysis of AETA Electromagnetic Signals

Acoustic and electromagnetics to artificial intelligence (AETA) is a system used to predict seismic events through monitoring of electromagnetic and geoacoustic signals. It is widely deployed in the Sichuan–Yunnan region (22° N–34° N, 98° E–107° E) of China. Generally, the electromagnetic signals of AETA stations near the epicenter have abnormal disturbances before an earthquake. When a significant decrease or increase in the signal is observed, it is difficult to quantify this change using only visual observation and confirm that it is related to an upcoming large earthquake. Considering that the AETA data comprise a typical time series, current work has analyzed the anomalism of AETA electromagnetic signals using the long short-term memory (LSTM) autoencoder method to prove that the electromagnetic anomaly of the AETA station can be regarded as an earthquake precursor. The results show that there are 2–4% anomalous points and some outliers exceeding 0.7 (after normalization) in the AETA stations within 200 km of the epicenter of the Jiuzaigou earthquake (M. 7.0) and the Yibin earthquake (M. 6.0) half a month before the earthquakes. Therefore, the AETA electromagnetic disturbance signal can be used as an earthquake precursor and for further earthquake prediction.

Persistent Josephson Phase-Slip Memory with Topological Protection

Superconducting computing promises enhanced computational power in both classical and quantum approaches. Yet, efficient schemes for scalable and fast superconducting memories are still missing. On the one hand, the large inductance required in magnetic flux-controlled Josephson memories impedes device miniaturization and scalability. On the other hand, schemes based on the ferromagnetic order to store information often degrades superconductivity, and limits the operation speed to the magnetization switching rate of a few GHz. Here, we overcome these limitations with a fully superconducting memory cell based on the hysteretic phase-slip transition existing in long aluminum nanowire Josephson junctions. The memory logic state is codified in the topological index of the junction providing a robust protection against stocastic phase slips and magnetic flux noise. Our direct and non-destructive read-out schemes, based on local DC or AC tunneling spectroscopy, ensure reduced dissipation (≤ 40 fW) thereby yielding a very low energy per bit read-out power consumption as low as ~ 10-24 J as estimated from the typical time response of the structure (≤ 30 ps). The memory, measured over several days, showed no evidence of information degradation up to ~1.1 K, i.e., ~85% of the critical temperature of aluminum. The ease of operation combined with remarkable performance elects the Josephson phase-slip memory as an attractive storage cell to be exploited in advanced superconducting classical logic architectures or flux qubits.

The Suitability of Methylene Blue Discoloration (MB Method) to Investigate the Fe0/MnO2 System

The typical time-dependent decrease of the iron corrosion rate is often difficult to consider while designing Fe0-based remediation systems. One of the most promising approaches is the amendment with manganese dioxide (Fe0/MnO2 system). The resulting system is a very complex one where characterization is challenging. The present communication uses methylene blue discoloration (MB method) to characterize the Fe0/MnO2 system. Shaken batch experiments (75 rpm) for 7 days were used. The initial MB concentration was 10 mg L−1 with the following mass loading: [MnO2] = 2.3 g L−1, [sand] = 45 g L−1, and 0 < [Fe0] (g L−1) ≤ 45. The following systems where investigated: Fe0, MnO2, sand, Fe0/MnO2, Fe0/sand, and Fe0/MnO2/sand. Results demonstrated that MB discoloration is influenced by the diffusive transport of MB from the solution to the aggregates at the bottom of the test-tubes. Results confirm the complexity of the Fe0/MnO2/sand system, while establishing that both MnO2 and sand improve the efficiency of Fe0/H2O systems in the long-term. The mechanisms of water decontamination by amending Fe0-based systems with MnO2 is demonstrated by the MB method.

Implied Volatility Prediction Based on Different Term Structures: An Empirical Study of the SSE 50 ETF Options Market from High-Frequency Data

This article focuses on the implied volatility forecast of the SSE 50 ETF options market from June 1, 2017, to August 30, 2019, and constructs AR (1) model and ARMA-GARCH model based on liquidity characteristics to compare and analyze the prediction effect of implied volatility on different option types and term structures. The results show that, during the sample period of the SSE 50 ETF options market, the effect of model fitting of the ARMA-GARCH model is significantly better than the AR (1) model; the fitting sequences predicted by the two models have typical time-varying and synchronization characteristics, and the prediction effect of the ARMA-GARCH model in the whole period is significantly better than the AR (1) model.

Ca2+ Dependence of Volume-Regulated VRAC/LRRC8 and TMEM16A Cl– Channels

All vertebrate cells activate Cl– currents (ICl,swell) when swollen by hypotonic bath solution. The volume-regulated anion channel VRAC has now been identified as LRRC8/SWELL1. However, apart from VRAC, the Ca2+-activated Cl– channel (CaCC) TMEM16A and the phospholipid scramblase and ion channel TMEM16F were suggested to contribute to cell swelling-activated whole-cell currents. Cell swelling was shown to induce Ca2+ release from the endoplasmic reticulum and to cause subsequent Ca2+ influx. It is suggested that TMEM16A/F support intracellular Ca2+ signaling and thus Ca2+-dependent activation of VRAC. In the present study, we tried to clarify the contribution of TMEM16A to ICl,swell. In HEK293 cells coexpressing LRRC8A and LRRC8C, we found that activation of ICl,swell by hypotonic bath solution (Hypo; 200 mosm/l) was Ca2+ dependent. TMEM16A augmented the activation of LRRC8A/C by enhancing swelling-induced local intracellular Ca2+ concentrations. In HT29 cells, knockdown of endogenous TMEM16A attenuated ICl,swell and changed time-independent swelling-activated currents to VRAC-typical time-dependent currents. Activation of ICl,swell by Hypo was attenuated by blocking receptors for inositol trisphosphate and ryanodine (IP3R; RyR), as well as by inhibiting Ca2+ influx. The data suggest that TMEM16A contributes directly to ICl,swell as it is activated through swelling-induced Ca2+ increase. As activation of VRAC is shown to be Ca2+-dependent, TMEM16A augments VRAC currents by facilitating Hypo-induced Ca2+ increase in submembraneous signaling compartments by means of ER tethering.

Active Tectonics And Active Faults: Why These Terms Still Lack Consensus On Definitions

The terms: Active tectonics and active faults have emerged as some of the most frequently used terms in geological literature, and traditionally, the main purpose of these definitions has historically remained devoted to either geological or engineering uses. However, most of the existing literature on the definitions has been gathered since >230 years that were spent on the understanding of the science of earthquakes, but a clear-cut consensus lacks on how to define active tectonics and active faults, for various reasons that are discussed at length here. Therefore, this paper presents a brief overview of the terms with a motivation to rekindle the discussion on what is considered active in tectonics. It also explores whether the traditional definitions are valid or not, and should we look for other alternatives. We present a brief historical background knowledge and understanding on the active faults, and particularly in some of the tectonically stable and presumably inactive portions of the Earth’s crust. The two major strike-slip faulting events (Mw 8.6 and Mw = 8.2) that have occurred in the Wharton Basin, Indian Ocean in 2012 are discussed in detail. The events are specially quoted to make a case for reactivation of old fracture systems as these earthquakes ruptured the ~30-90 Ma old Indian oceanic crust. This clearly demonstrates that much older geological structures could also be re-activated, thereby questioning the traditional definition of the typical time span that is used to define active tectonics and active faults.

The light/dark cycle of microalgae in a thin-layer photobioreactor

A numerical study of the motion of algal cells in a representative thin-layer-cascade (TLC) photobioreactor is presented. The goal is to determine the time scale associated with the light/dark (L/D) cycle seen by the cells during their turbulent motion in the liquid culture. Owing to the limited reliability of the available numerical results which deal with time-averaged quantities and thus lack time-resolved information, the present study is based upon the Direct Numerical Simulation of the Navier-Stokes equations, a reliable but consequently expensive numerical approach which does not incur in turbulence modelling errors. Indeed, the simulation is successfully validated in terms of averaged velocity with experimental data. The availability of full temporal information allows algae cells to be followed in time along their trajectories. A large number (up to a million) of tracers is placed in the flow to mimic the algae cell. Their trajectories are statistically studied and linked to the turbulent mixing. Results indicate that, in a typical TLC reactor designed to mimic an experimental setup, cells undergo an L/D cycle with a time scale in the range 0.1–2 s. Such time scale, albeit much longer than the typical time scale of the photosynthesis, significantly benefits the productivity of the algae compared to a steady illumination.

New Data Analysis Method for Time-Resolved Infrared Photoluminescence Spectroscopy

In this article, a new data treatment based on time-resolved photoluminescence is presented. It works as a streak camera for infrared. A time-resolved photoluminescence spectrum for the HgCd0.33Te0.67 sample at 120 K was performed and analyzed. Typical time-resolved photoluminescence measurements, to compare our results with literature, were conducted. An interpretation of the behavior for three different time constants found in the signal is proposed.