Search

Background: Peri-extubation cough is an undesirable event during extubation, prevention of which has been studied with multiple drugs, amongst which intravenous dexmedetomidine has emerged as one of the favourable drugs. Intratracheal route is attractive because of its ease of administration, provided it avoids the hypotension and bradycardia that occurs during intravenous bolus administration. There is a paucity of data exploring the utility, doses, and adverse effect of intratracheal dexmedetomidine. Methods: After obtaining ethical committee approval, 60 eligible, consenting adult patients undergoing surgery under general anesthesia in a tertiary teaching hospital were recruited and randomised into three groups--DEX0.3, DEX0.5, and NS. The plan of general anesthesia was standardized. Half an hour prior to extubation, study drug was instilled intratracheally-- dexmedetomidine 0.3 mic/kg, 0.5 mic/kg, and NS in groups DEX0.3, DEX0.5, and NS, respectively. 4-point cough score was used to assess extubation response. Hemodynamic response and time to Ramsay sedation score 3 was also recorded. Results: Majority of patients in DEX0.3 (60%) and DEX0.5 (85%) group had no cough (cough score 0), while majority of the patients in the NS group (70%) had either mild or moderate cough (cough score 1, 2). Kruskal Wallis test followed by post-hoc pairwise comparison showed statistically significant difference in 4-point cough score between GroupDEX0.3 and GroupNS (P< 0.001) and between GroupDEX0.5 and GroupNS (P= 0.038). DEX0.5 group, compared to DEX0.3 group, had significantly higher time from reversal to extubation (P< 0.001) and time to achieve Ramsay sedation score of 3 (P< 0.001). Conclusion: We conclude that both 0.3 mic/kg and 0.5 mic/kg of dexmedetomidine when given intratracheally are effective in preventing peri-extubation cough. Further, 0.3 mic/kg dexmedetomidine showed a better recovery profile compared to 0.5 mic/kg dexmedetomidine when administered intratracheally. [ABSTRACT FROM AUTHOR]

The amplitude and the phase information are both important for damage localization in Lamb wave–based structural health monitoring and non-destructive testing. Most previous studies in Lamb wave imaging are only based on either the amplitude or phase of the signal at the time of flight. In this study, a post-processing technique for Lamb wave phased array imaging is proposed for isotropic plates, which simultaneously utilizes both the amplitude and phase information within a small neighborhood centered at the time of flight. In the proposed imaging algorithm, a modified virtual time reversal is firstly implemented to compensate for dispersion and the amplitude decrease caused by wave diffusion. Then the waveform covariance between any two processed wave packets, which contains information of both amplitude and phase, is used as the indicator of the presence of damage. Finally, adaptive weights based on minimum variance are introduced to weight and sum the waveform covariance for damage imaging. Based on a uniform circular array, experimental results on an aluminum plate with three defects verify that the proposed algorithm is capable of localizing multiple defects, suppressing background noise and main lobe width. [ABSTRACT FROM AUTHOR]

We introduce the implementation of a global climatological model of the equatorial ionospheric F-region zonal drifts (EZDrifts) that is made available to the public. The model uses the analytic description of the zonal plasma drifts presented by Haerendel et al. (1992) [J Geophys Res97(A2): 1209–1223] and is driven by climatological models of the ionosphere and thermosphere under a realistic geomagnetic field configuration. EZDrifts is an expansion of the model of the zonal drifts first presented by Shidler & Rodrigues (2021) [Prog Earth Planet Sci8: 26] which was only valid for the Jicamarca longitude sector and two specific solar flux conditions. EZDrifts now uses vertical equatorial plasma drifts from Scherliess & Fejer (1999) [J Geophys Res104(A4): 6829–6842] model which allows it to provide zonal drifts for any day of the year, longitude, and solar flux condition. We show that the model can reproduce the main results of the Shidler & Rodrigues (2021) [Prog Earth Planet Sci8: 26] model for the Peruvian sector. We also illustrate an application of EZDrifts by presenting and discussing longitudinal variabilities produced by the model. We show that the model predicts longitudinal variations in the reversal times of the drifts that are in good agreement with observations made by C/NOFS. EZDrifts also predicts longitudinal variations in the magnitude of the drifts that can be identified in the June solstice observations made by C/NOFS. We also point out data-model differences observed during Equinox and December solstice. Finally, we explain that the longitudinal variations in the zonal plasma drifts are caused by longitudinal variations in the latitude of the magnetic equator and, consequently, in the wind dynamo contributing to the resulting drifts. EZDrifts is distributed to the community through a public repository and can be used in applications requiring an estimate of the overall behavior of the equatorial zonal drifts. [ABSTRACT FROM AUTHOR]

In this paper I argue that the concept of time-reversal invariance in physics suffers from metaphysical underdetermination, that is, that the concept may be understood differently depending on one’s metaphysics about time, laws, and a theory’s basic properties. This metaphysical under-determinacy also affects subsidiary debates in philosophy of physics that rely on the concept of time-reversal invariance, paradigmatically the problem of the arrow of time. I bring up three cases that, I believe, fairly illustrate my point. I conclude, on the one hand, that any formal representation of time reversal should be explicit about the metaphysical assumptions of the concept that it intends to represent; on the other, that philosophical arguments that rely on time reversal to argue against a direction of time require additional premises. [ABSTRACT FROM AUTHOR]

Bolted spherical joints are widely used in space grid structures. However, the preload loss, which may arise from fabrication error, insufficient twist of the screw and some other unknown reasons can undermine the structural integrity and even lead to the collapse of the whole structure. Therefore, a method for evaluating the preload status of bolted spherical joints is vital to the structural health monitoring of the space grid structures. To this end, a non-destructive evaluation of the preload loss of bolted spherical joints based on time reversal acoustics (TRA) is presented. In this method, an excited signal generated by a lead zirconate titanate (PZT) patch at the bolted sphere is reconstructed after the signal recorded by another PZT patch at the bar is time-reversed and re-emitted. The deviation of the reconstructed signal from the initial signal allows identification of preload loss of the bolted spherical joint. This method is demonstrated to be effective by a finite element simulation. Furthermore, the effect of preload loss of the bolted spherical joint on its ultimate flexural capacity is studied, which highlights the necessity for the non-destructive evaluation. [ABSTRACT FROM AUTHOR]

This paper empirically studies the reversal pattern following the formation of trend‐following signals in the time series context. This reversal pattern is statistically significant and usually occurs between 12 and 24 months after the formation of trend‐following signals. Employing a universe of 55 liquid futures, we find that instruments with sell signals in the trend‐following portfolio ('losers') contribute to this type of reversal, even if their profits are not realised. The instruments with buy signals in the trend‐following portfolio ('winners') contribute much less. A double‐sorted investment strategy based on both return continuation and reversal yields to portfolio gains which are significantly higher than that of the corresponding trend‐following strategy. [ABSTRACT FROM AUTHOR]

In this paper, we calculate the Andreev bound state spectrum in a half-infinite superconducting wire with an arbitrary number of bands crossing the chemical potential. Electrons in the wire are affected by the asymmetric (Rashba) spin–orbit coupling due to the presence of a substrate. The normal state of the wire is assumed to have an antiunitary symmetry (time reversal or its combination with a point group operation), which may be broken by the superconducting order parameter and/or the boundary. The bound state spectrum is calculated without relying on any particular microscopic model, using the semiclassical approach with the boundary conditions described by a phenomenological scattering matrix. [ABSTRACT FROM AUTHOR]

It has been argued that measurement-induced collapses in Orthodox Quantum Mechanics generates an intrinsic (or built-in) quantum arrow of time. In this paper, I critically assess this proposal. I begin by distinguishing between an intrinsic and non-intrinsic arrow of time. After presenting the proposal of a collapse-based arrow of time in some detail, I argue, first, that any quantum arrow of time in Orthodox Quantum Mechanics is non-intrinsic since it depends on external information about the measurement context, and second, that it cannot be global, but just local. I complement these arguments by assessing some criticisms and considerations about the implementation of time reversal in contexts wherein measurement-induced collapses work. I conclude that the quantum arrow of time delivered by Orthodox Quantum Mechanics is much weaker than usually thought. [ABSTRACT FROM AUTHOR]

We theoretically analyze spin filtering in two‐terminal systems, induced by the spin‐orbit interaction (SOI), as a possible origin of the "chirality‐induced spin selectivity" (CISS) effect observed experimentally in chiral molecules, such as DNA. Due to Bardarson's theorem, spin filtering cannot be realized in a molecule containing one orbital‐channel. However, when two orbitals are involved, SOI can induce spin filtering in a molecule coupled to two terminals without braking time‐reversal symmetry. In particular, we provide an example of a 4×4 ${4\times 4}$ reflection matrix for a spinful electron passing through a molecule containing two orbital‐channels, which complies with Bardarson's theorem and produces a finite spin conductance. As a microscopic toy model realizing a single strand of DNA, we consider a p‐orbital helical atomic chain with intra‐atomic SOI's and a strong crystalline field along the helix. This model exhibits two‐orbital spin filtering: For various parameters preserving the helical symmetry, the model hosts spin asymmetric states carrying pairs of up and down spins propagating in opposite directions. The typical energy scale of the helical states is the product of the intra‐atomic SOI and the curvature. The spin filtering mechanism is associated with the intra‐atomic SOI, which would be larger than the inter‐atomic SOI. In this respect, the present model may be a more likely candidate for the CISS in organic material than other models associated with the inter‐atomic SOI. [ABSTRACT FROM AUTHOR]

The time reversal method is based on the backpropagation of seismic waveforms recorded at a set of receivers. When this set forms a closed surface and the elastic properties of the medium are correct, the seismic energy focuses at the source location, creating a focal spot. Such a spot is smooth in space, whereas the original wavefield usually shows a displacement discontinuity at the source. The goal of this paper is to discuss the link between the focal spot and the original source using the concept of homogenized point source. We show that the backpropagated wavefield is equivalent to the sum of two low-wavenumber fields resulting from the homogenization of the original point source. In other words, the homogenized point source is the equivalent force for producing the focal spot. In addition to the demonstration in the general 3-D heterogeneous case, we present some numerical examples in 2-D. [ABSTRACT FROM AUTHOR]

This paper claims that, to the extent that temporal direction figures in physics at all, it is found there as part of the extra-scientific language science employs. The asymmetry between "before" and "after" is not captured by the mathematics of any theory, nor can it be derived from the laws of any theory. This, I argue, is true even of theories whose laws are not time reversal invariant. Recognizing that physics does not yield temporal direction but receives it from the background in which physics develops and operates does not, however, expose any hitherto unknown limitations or deficiencies of physics. The claim is not about physics, but about metaphysical stances regarding physics, specifically, physicalism, which requires from physics to deliver more than it does, or should. Once the place of temporal direction in physics is understood, infamous difficulties can be addressed in a novel way. Issues emerging from the 2nd law of thermodynamics, such as the minimum problem, and the worry that the law generates outlandish predictions, are removed. A side benefit is the recognition that the past hypothesis is superfluous. A final conclusion of the paper is that the relationship between physics and everyday language, far from being a source of difficulties, is healthy and beneficial to both. [ABSTRACT FROM AUTHOR]

Measurements of angular correlations in nuclear beta decay are important tests of the Standard Model (SM). Among those, the so-called D correlation parameter occupies a particular place because it is odd under time reversal, and because the experimental sensitivity is at the 10 - 4 level, with plans of further improvement in the near future. Using effective field theory (EFT) techniques, we reassess its potential to discover or constrain new physics beyond the SM. We provide a comprehensive classification of CP-violating EFT scenarios which generate a shift of the D parameter away from the SM prediction. We show that, in each scenario, a shift larger than 10 - 5 is in serious tension with the existing experimental data, where bounds coming from electric dipole moments and LHC observables play a decisive role. The tension can only be avoided by fine tuning of the parameters in the UV completion of the EFT. We illustrate this using examples of leptoquark UV completions. Finally, we comment on the possibility to probe CP-conserving new physics via the D parameter. [ABSTRACT FROM AUTHOR]

In rectal cancer surgery the formation of a defunctioning stoma is common in order to reduce the consequences of an anastomotic leakage. The role of a defunctioning stoma and time to stoma reversal, in relation to major Low Anterior Resection Syndrome (LARS) in the long-term perspective, is still unclear. The aim of the study was to investigate the association between a defunctioning stoma and long-term bowel function. Patients who underwent curative rectal cancer surgery between 2007 and 2013 in Stockholm county, Sweden, who had no history of anastomotic leakage, without a remaining stoma, free of cancer and alive in April 2017 were eligible for the study. The exposures were (i) use of defunctioning stoma at cancer surgery and (ii) time to stoma reversal. Main outcome was major LARS with information retrieved from the LARS score questionnaire. Multivariable logistic regression model was used to calculate odds ratios (OR) primary comparing major LARS to no LARS. A total of 430 patients were included in analysis. The mean follow-up time was 6.7 years after surgery (range 3.4–10.7 years). The use of a defunctioning stoma was associated to major LARS with an adjusted OR of 2.43 (95% CI 1.14–5.20) when compared to no stoma. There were no evident associations between time to stoma reversal and the risk of major LARS. This study indicates that the presence of a defunctioning stoma is associated with impaired bowel function in the long-term perspective, while failing to show any clear association to time to stoma reversal. [ABSTRACT FROM AUTHOR]

We have studied the superexchange interaction J i j in doped 2 D cuprates. The AFM interaction strongly depends on the state of the lattice of a CuO 2 layer surrounded by two LaO rock salt layers. In a static U and D stripe nanostructure, the homogeneous AFM interaction is impossible due to the U / D / U ... periodic stripe sequence and T N = 0 . In a dynamic stripe nanostructure, the ideal CuO 2 layer with nonlocal effects and the homogeneous AFM interaction are restored. However, the interaction J i j decreases by the exponential factor due to partial dynamic quenching. The meaning of the transition from the dynamic to the static cases lies in the spontaneous θ -symmetry breaking with respect to the rotation of all the tilted CuO 6 octahedra by an orientation angle δ θ = n · 45 ° (where n = 1 ÷ 4 ) in the U and D stripe nanostructure of the CuO 2 layer. Moreover, the structural features help to study various experimental data on the charge inhomogeneity, Fermi level pinning in the p type cuprates only and time reversal symmetry breaking from a unified point of view. [ABSTRACT FROM AUTHOR]

The authors report the use of the dressed chopped random basis optimal control algorithm to realize time‐reversal procedures. The latter are aimed for the implementation of quantum undo operations in quantum technology contexts as quantum computing and quantum communications. The last performed operation can be time‐reversed via the undo command so as to perfectly restore a condition in which any new operation, chosen by the external user, can be applied. By generalizing this concept, the undo command can also allow for the reversing of a quantum operation in a generic time instant of the past. Here, thanks to optimal time‐reversal routines, all these functionalities are experimentally implemented on the fivefold F=2$F=2$ Hilbert space of a Bose–Einstein condensate of non‐interacting 87Rb atoms in the ground state, realized with an atom chip. Each time‐reversal transformation is attained by designing an optimal modulated radio frequency field, achieving on average an accuracy of around 92% in any performed test. The experimental results are accompanied by a thermodynamic interpretation based on the Loschmidt echo. These findings are expected to promote the implementation of time‐reversal operations in a real scenario of gate‐based quantum computing with a more complex structure than the five‐level system considered here. [ABSTRACT FROM AUTHOR]

Of rising concern is the consecutive occurrence of contrasting precipitation extremes such as droughts followed by severe floods, which tips a precarious balance with lasting impacts on human and natural systems. However, it is not clear how the risk of such precipitation reversals may change over time at the global scale. Using precipitation data from the Community Earth System Model Version 1 (CESM1) Large Ensemble Simulations (LENS), we examined changes in the likelihood and spatial distribution of low‐intensity dry‐to‐wet fluctuations and more severe shifts from meteorological droughts to pluvials over global land areas via a conditional statistical framework. Our analysis of CESM1‐LENS leads to the conclusion that the worst‐case climate change scenario, that is, RCP8.5 can increase the percent of global land areas susceptible to both low‐intensity and more severe precipitation reversals by the end of the twenty‐first century, while inducing disproportionate impacts at regional scales depending on the severity of precipitation reversals. Particularly, we find 13.6% of global land areas may be depressed by interannual dry‐to‐wet events with a transition probability of greater than 0.5 in the twenty‐first century, quintupling the figure in the past century. The increase in the susceptible global land areas further indicates that new local hotspots with low‐frequency drought‐pluvial seesaws are more likely to emerge under the effects of enhancing anthropogenic greenhouse gases. Collectively, the study is expected to provide useful information for policy makers and infrastructure operators to prioritize actions that affect water resource objectives of flood control, drought mitigation, and water quality protection. Plain Language Summary: By probing changes in the likelihood and spatial distribution of precipitation reversal over time at the global land areas, this study provides new compelling evidence for the impact of anthropogenic climate change on low‐intensity dry‐to‐wet fluctuations and more severe shifts from meteorological droughts to floods. Presented is a new and robust analysis based on applying advances in statistical methods to a large set of Community Earth System Model simulations and observations. We find the worst‐case climate change scenario can increase the percent of global land areas susceptible to precipitation reversal (also known as precipitation whiplash) by the end of the twenty‐first century, while inducing disproportionate impacts at regional scales depending on the severity of precipitation reversal. Additionally, our results indicate that new local hotspots with low‐frequency drought‐flood seesaws are more likely to emerge under the effects of enhancing anthropogenic greenhouse gases. This study may broaden the scope of research related to compound events which describe multiple climate drivers and/or hazards occurring simultaneously or successively to contribute to societal or environmental risk. Key Points: The worst‐case climate change scenario can increase the percent of global land areas susceptible to precipitation reversal in the futureAbout 13.6% of global lands may be depressed by interannual dry‐to‐wet events with a transition probability above 0.5 in the 21st centuryNew local hotspots with low‐frequency drought‐pluvial seesaws are more likely to emerge under enhancing anthropogenic greenhouse gases [ABSTRACT FROM AUTHOR]

Time reversal (TR) transmission technology can focus the power of a signal in both time and space domains and reduce signal energy leakage to unintended receivers, making it suitable for physical layer security systems. By adding a pre-equalizer to the transmitter and optimizing it, the performance of multi-antenna TR transmission system can be improved obviously with an acceptable optimization complexity. In this paper, the pre-equalizer and artificial noise (AN) are jointly optimized to improve the security performance of pre-equalized TR (ETR) systems when eavesdropping channel state information (ECSI) is unknown or known. When ECSI is unknown, null-space AN is adopted, and the pre-equalizer is optimized to minimize the signal power under the constraint of the minimum signal-to-interference-plus-noise ratio (SINR) of the legitimate receiver, so the AN power and the interference with the eavesdropper are maximized. The optimization problem is transformed into the problem of finding the maximum generalized eigenvalue of a matrix pencil. When ECSI is known, under the minimum SINR constraint of the legitimate receiver, the pre-equalizer and AN's covariance matrix are jointly optimized to minimize the SINR of the eavesdropper. The optimization problem is non-convex and is transformed into a convex problem, which can be solved using the CVX toolbox. The optimization complexity is independent of the number of transmit antennas. Simulation results demonstrate that compared with TR systems, by optimizing the pre-equalizer, the security performance of ETR multi-antenna systems can be significantly improved, and the optimization complexity is acceptable. [ABSTRACT FROM AUTHOR]

The paper studies the electronic current in a one-dimensional lead under the effect of spin–orbit coupling and its injection into a metallic conductor through two contacts, forming a closed loop. When an external potential is applied, the time reversal symmetry is broken and the wave vector k of the circulating electrons that contribute to the current is spin-dependent. As the wave function phase depends upon the vector k, the closed path in the circuit produces spin-dependent current interference. This creates a physical scenario in which a spin-polarized current emerges, even in the absence of external magnetic fields or magnetic materials. It is possible to find points in the system's parameter space and, depending upon its geometry, the value of the Fermi energy and the spin–orbit intensities, for which the electronic states participating in the current have only one spin, creating a high and totally spin-polarized conductance. For a potential of a few tens of meV, it is possible to obtain a spin-polarized current of the order of μ A. The properties of the obtained electronic current qualify the proposed device as a potentially important tool for spintronics applications. [ABSTRACT FROM AUTHOR]

Optical non‐reciprocity that allows unidirectional flow of optical field is pivoted on time reversal symmetry breaking, which originates from radiation pressure because of light–matter interaction in cavity optomechanical systems. Here, the non‐reciprocal transport of optical signals across two ports via three optical modes optomechanically coupled to the mechanical excitations of two nanomechanical resonators (NMRs) is studied under the influence of strong classical drive fields and weak probe fields. It is found that there exists the conversion of reciprocal to non‐reciprocal signal transmission via tuning the drive fields and perfect non‐reciprocal transmission of output fields is realized when the effective cavity detuning parameters are near resonant to the NMRs' frequencies. The unidirectional non‐reciprocal transport is robust to the optomechanical couplings around resonance conditions. Moreover, the loss rates of cavities play an inevitable role in the unidirectional flow of signal across the two ports. Bidirectional transmission can also be controlled by the phase changes associated with the probe and drive fields along with their relative phase. This scheme may provide a foundation for the compact non‐reciprocal communication and quantum information processing, thus enabling novel devices that route photons in unconventional ways such as all‐optical diodes, optical transistors, and optical switches. [ABSTRACT FROM AUTHOR]

Most biochemical reactions in living cells are open systems interacting with environment through chemostats to exchange both energy and materials. At a mesoscopic scale, the number of each species in those biochemical reactions can be modeled by a random time-changed Poisson processes. To characterize macroscopic behaviors in the large number limit, the law of large numbers in the path space determines a mean-field limit nonlinear reaction rate equation describing the dynamics of the concentration of species, while the WKB expansion for the chemical master equation yields a Hamilton–Jacobi equation and the Legendre transform of the corresponding Hamiltonian gives the good rate function (action functional) in the large deviation principle. In this paper, we decompose a general macroscopic reaction rate equation into a conservative part and a dissipative part in terms of the stationary solution to the Hamilton–Jacobi equation. This stationary solution is used to determine the energy landscape and thermodynamics for general chemical reactions, which particularly maintains a positive entropy production rate at a non-equilibrium steady state. The associated energy dissipation law at both the mesoscopic and macroscopic levels is proved together with a passage from the mesoscopic to macroscopic one. A non-convex energy landscape emerges from the convex mesoscopic relative entropy functional in the large number limit, which picks up the non-equilibrium features. The existence of this stationary solution is ensured by the optimal control representation at an undetermined time horizon for the weak KAM solution to the stationary Hamilton–Jacobi equation. Furthermore, we use a symmetric Hamiltonian to study a class of non-equilibrium enzyme reactions, which leads to nonconvex energy landscape due to flux grouping degeneracy and reduces the conservative–dissipative decomposition to an Onsager-type strong gradient flow. This symmetric Hamiltonian implies that the transition paths between multiple steady states (rare events in biochemical reactions) is a modified time reversed least action path with associated path affinities and energy barriers. We illustrate this idea through a bistable catalysis reaction and compute the energy barrier for the transition path connecting two steady states via its energy landscape. [ABSTRACT FROM AUTHOR]

Motivated by the quest to curtail the high mortality rate of breast cancer, the manuscript proposes the sensitivity enhancement of monopole antenna for hyperthermia application by using electromagnetic time reversal (EMTR) technique with transformation structures for early treatment of multi-focal breast tumors. The EMTR technique is characterized with temporal and spatial focusing, hence enhancing the visibility of tumors embedded in the breast medium. In this study, we aim at the non-invasive power deposition on sub-wavelength-sized tumors at sub-wavelength separation incorporation with sub-wavelength scatterers. The paper is focused on enhancing the sensitivity of scattering reception in TR algorithm for hyperthermia application using sub-wavelength sized scatterers. The proposed applicator is an ultra-wideband (UWB) monopole antenna designed with sub-wavelength-sized split ring embedded square patch (SRESP) on a grounded substrate placed below it at some distance to serve as near field scatterer. Another plate of sub-wavelength scatterers but without the ground plate is placed in close proximity to the unhealthy breast in-conjunction with four ultra-wideband antenna time reversal mirrors (UWB-TRM). The proposed method shows promising potential for the selective power deposition for hyperthermia of sub-wavelength-sized tumors at sub-wavelength separations. This technique of enhancing front-end sensor sensitivity can also be extended to other optimization techniques for selective power deposition in hyperthermia of breast cancer. [ABSTRACT FROM AUTHOR]

Multi-layer metal spherical shell structure is widely used as the core component of pressure-bearing equipment, deep-sea exploration equipment and other critical areas due to its plane stress uniformity and high specific strength. Its long-term service in complex and harsh environments will inevitably produce a variety of defects and damages, which will affect the safety of the equipment in service. Ultrasonic guided wave inspection is a potential non-destructive testing method, but the multilayer metal bonding structure between the metal and non-metal bonding layer impedance difference is large, resulting in defects located in the internal reflection signal is difficult to propagate to the outer layer with a sensor, the multilayer spherical shell structure itself leads to the complexity of the guided wave propagation characteristics, it is difficult to extract the individual modes of the time information for the defects of the detection and localization. Therefore, in this paper, we propose a probabilistic damage existence imaging method for spherical shell structures and combine it with the virtual time reversal technique to detect and localize the defects on the inner and outer surfaces of multilayered metallic spherical shell structures without benchmarks. The results show that the newly proposed method can realize the accurate localization imaging of internal/external defects of multilayer metal spherical shell structures. [ABSTRACT FROM AUTHOR]

• A modified virtual time reversal method for sensitive monitoring of bolt preloads. • Higher monitoring sensitivity than prevailing monitoring approaches. • A semi-analytical model to theoretically interpret the proposed method. Bolted joints are prone to loosening due to inaccurate initial preloads and time-varying service conditions. Real-time monitoring of bolt preloads is therefore an important means to warrant the reliability and safety of a bolted structure, though it remains a daunting task to implement precise monitoring of early bolt loosening. A modified virtual time reversal (MVTR) method is developed in this study, aimed at enhanced sensitivity of bolt preload monitoring. To begin with, the frequency response function (FRF) of an intact bolted structure is ascertained using the excitation wave and the received wave signal through the bolt. Then a received wave signal captured from the bolted structure under monitoring is time-reversed, and a refocused signal is calculated in virtue of the time-reversed signal and the FRF in the intact state. Bolt tightness indices are established by the peak amplitude or energy of the refocused wave packet. To facilitate interpretation of the principle of the proposed MVTR, a semi-analytic model is developed, which combines the waveform superposition method and finite element method. With the model, the effects of interface contact length, wave mode and signal frequency on the tightness indices are investigated. The effectiveness of the proposed MVTR is experimentally verified using three representative bolted lap structures featuring single bolt or multiple bolts. The results confirm the findings from the semi-analytic model, demonstrating that the MVTR enhances monitoring sensitivity compared to prevailing approaches using linear or nonlinear guided wave features. [ABSTRACT FROM AUTHOR]

The control of multiply-scattered light has greatly boosted the understanding of optics in complex photonic systems, leading to many applications including imaging, information processing, random lasing, to name just a few. Here, we demonstrate a real-time feedback approach to realize multiple focusing of multiply-scattered light, which is more robust to the inherent background field compared to the time reversal approach. Our method retrieves the optimized wavefront by aligning the high-dimensional vector of the measured pattern with that of the target pattern. Our theoretical simulations and experimental results show that the feedback approach is capable of constructing homogeneous diffraction-limited spots at predefined positions. Moreover, the peak-to-background ratio exhibits a sub- 1 / m decay with m being the number of focuses, indicating the excellent capability of the proposed approach to focus scattered light at multiple positions. This efficient approach provides a promising avenue toward complex control on scattered light in complex photonic media, and therefore would be useful in relevant applications such as optical imaging and optical manipulation. • A real-time feedback approach is developed for realizing diffraction-limited spots at a few predefined positions with multiply-scattered light. • The realized multiple focuses are robust to the random perturbation caused by inherent background light. • The peak-to-background ratio exhibits ∼ 1 / m 0. 62 decay (m: the number of focuses), slower than the well-known 1/m decay. [ABSTRACT FROM AUTHOR]

The photonic quantum spin Hall effect in time reversal invariant photonic system shows two pseudospin-up and-down photonic states preserved pseudo-time-reversal symmetry in C 6 v symmetry, and forms a typical of unidirectional helical edge modes within a topological bulk photonic bands gap. Here we demonstrate topological unidirectional helical edge states with robustness and pseudospin-locking in all-dielectric topological photonic crystals with honeycomb lattice. Based on intrinsic and local chirality of the topological helical edge modes, we calculate the directionality D to characterize directionality of topological unidirectional helical edge modes. The unidirectional excitation of topological helical edge states is position-dependent of chiral source, which is checked out by the full-wave simulations. A specific multifunctional waveguide with tunable cross-channel, V-splitting and four-channel in a waveguide structure with cross-like route is achieved by changing the location of chiral source based on chirality map. A reprogrammable system to recode information (pseudospin-polarized and location) of chiral source is presented by us, and realize multi-switching for integrated photonic via circuits external circuits control in computer. Our work has great potential for applications in on-chip optical circuits with recoding and modularized information processing using pseudospin-dependent one-way transport. • This research paper mainly works and highlights are as following: • The chirality map of topological helical edge modes is calculated and checked out. • A specific multifunctional waveguide with tunable cross-channel, V-splitting and four-channel in a waveguide structure with cross-like route is achieved. • A reprogrammable system to recode information (pseudospin-polarized and location) of chiral source is presented by us. [ABSTRACT FROM AUTHOR]

We introduce and study a non-oriented first passage percolation model having a property of statistical invariance by time reversal. This model is defined in a graph having directed edges and the passage times associated with each set of outgoing edges from a given vertex are distributed according to a generalized Bernoulli–Exponential law and i.i.d. among vertices. We derive the statistical invariance property by time reversal through a zero-temperature limit of the random walk in Dirichlet environment model. [ABSTRACT FROM AUTHOR]

This Letter aims to advance unexplored properties of a new class of Closed Timelike Curves recently discovered in scalar–tensor gravity, reported in Nguyen and Lobo (2023) [31] and Nguyen and Azreg-Aïnou (2023) [30]. Therein, it was shown that when the Weak Energy Condition is violated, the topology of spacetime in scalar–tensor gravity is altered and directly enables the formation of two-way traversable wormholes. Furthermore, each of these wormholes acts a gateway between two time-mirrored worlds, where the two asymptotically flat sheets in the Kruskal–Szekeres diagram are glued antipodally along three directions—time t and the polar and azimuth angles (θ , φ) of the 2-sphere—to form a wormhole throat. This contrasts with the standard embedding diagram which typically glues the sheets only along the θ and φ directions. Crucially, due to the 'gluing' along the t direction, the wormhole becomes a portal connecting the two spacetime sheets with opposite physical time flows, enabling the emergence of closed timelike loops which straddle the throat. In this Letter, we shall point out that this portal mathematically permits the possibility of backward propagation of information against time. This feature is ubiquitous for wormholes in scalar–tensor theories. In addition, we formulate the Feynman sum for transition amplitudes of microscopic particles in the proximity of a wormhole throat in which we account for timelike paths that experience time reversal. [ABSTRACT FROM AUTHOR]

• A novel hybrid adaptive framework for the extraction of fetal ECG is proposed. • FastICA extracts the maternal part and enhances the fetal part in abdominal ECG. • AEFLN cancels maternal ECG without any time and amplitude alignment. • Finally, NWT determines the exact fetal R-peak envelopes for FHR calculation. • Proposed framework attains 95.29% of SE, 96.68% of PPV, and 95.92% of F1 score. Continuous monitoring of fetal health requires the accurate calculation of the Fetal Heart Rate (FHR) by efficiently isolating fetal Electrocardiogram (fECG) from non-invasive abdominal Electrocardiogram (aECG). There are numerous solutions proposed for this problem, having its own restrictions. This paper introduces a novel three-stage hybrid adaptive approach for fECG extraction and FHR determination from aECG. The proposed framework is an amalgamation of independent component analysis (ICA), adaptive exponential functional link network (AEFLN), and novel wavelet thresholding (NWT). The proposed work aims to determine the best quality fetal R-peaks for calculating fetal heart rate (FHR). ICA is a blind source separation technique that uses all the information from the multichannel inputs to determine the maternal Electrocardiogram (mECG) and enhanced aECG. In the next stage, a non-linear adaptive filter, AEFLN, is used for the extraction of fECG. This approach requires no additional algorithm for polarity reversal and time alignment before AEFLN. At last, NWT determines the fetal R-peak envelopes from the residual fECG. The R-peak envelopes are used to analyze FHR, and its accuracy was accessed using the FHR trace. So far, FastICA-AEFLN-NWT has not been used as a hybrid method for fECG extraction and fetal R-peak detection. The algorithm's effectiveness was tested on both real databases from Daisy and Physionet and synthetic databases from Physionet. The proposed hybrid method attains 95.29 % of sensitivity (SE), 96.68 % of Positive Predictive Value (PPV), 95.92 % of F1 score, and FHR measurement (FHRmeas) is 29.72 bpm2. The proposed methodology outperforms the state-of-art methods in fECG extraction. [ABSTRACT FROM AUTHOR]

Moving target detection plays a pivotal role in many applications, especially in radar systems. In addition, time-reversal (TR) technology can improve radar detection probability by effectively solving the problem of multipath signals. However, detection performance can be affected when clutter exists and target Doppler shifts are unknown. For this reason, we propose a novel moving target detection algorithm that leverages TR technology and a novel waveform optimization method in clutter and multipath signal environments. In this paper, we establish a TR signal model for a moving target in such environments and derive the TR average likelihood ratio test (TR-ALRT) detector. Additionally, we introduce a waveform optimization method that adapts to clutter and unknown Doppler information further to enhance the performance of the TR-ALRT detector. Consequently, a TR-ALRT waveform optimization (TR-ALRT-WO) detector is derived to adapt to the unknown Doppler and environment information, thereby improving the detection probability. Comparative analysis with other detectors under the same conditions validates the effectiveness of our proposed TR-ALRT-WO detector. Furthermore, numerical experiments demonstrate the superior performance of the proposed detection algorithm.

Photoacoustic tomography (PAT) provides high resolution optical images of tissue at depths of up to several centimetres. This modality has been of interest to researchers for at least 30 years and is still the subject of intensive research. However, PAT researchers lack access to a comprehensive open-source graphical simulation and reconstruction software package. In this article, we introduce PATLAB, an open-source MATLAB-based graphical software package that can perform both PAT simulation and image reconstruction. PATLAB is simple to use yet is capable of complex PAT data processing tasks and offers advanced users a framework to build and test new methods.

The photoelectron asymmetry parameter β, which characterizes the direction of electrons ejected from a randomly oriented molecular ensemble by linearly polarized light, is investigated for degenerate orbitals. We show that β is totally symmetric under the symmetry operation of the point group of a molecule, and it has mixed properties under time reversal. Therefore, all degenerate molecular orbitals, except for the case of degeneracy due to time reversal, have the same β (Wigner-Eckart theorem). The exceptions are e-type complex orbitals of the Cn, Sn, Cnh, T, and Th point groups, and calculations on boric acid (C3h symmetry) are performed as an example. However, including those point groups, all degenerate orbitals have the same β if those orbitals are real. We discuss the implications of this operator formalism for molecular alignment and photoelectron circular dichroism. [ABSTRACT FROM AUTHOR]

Twisted double bilayer graphene (tDBG) comprises two Bernal-stacked bilayer graphene sheets with a twist between them. Gate voltages applied to top and back gates of a tDBG device tune both the flatness and topology of the electronic bands, enabling an unusual level of experimental control. Metallic states with broken spin and valley symmetries have been observed in tDBG devices with twist angles in the range 1.2–1.3°, but the topologies and order parameters of these states have remained unclear. We report the observation of an anomalous Hall effect in the correlated metal state of tDBG, with hysteresis loops spanning hundreds of mT in out-of-plane magnetic field (B⊥) that demonstrate spontaneously broken time-reversal symmetry. The B⊥ hysteresis persists for in-plane fields up to several Tesla, suggesting valley (orbital) ferromagnetism. At the same time, the resistivity is strongly affected by even mT-scale values of in-plane magnetic field, pointing to spin-valley coupling or to a direct orbital coupling between in-plane field and the valley degree of freedom. Twisted double bilayer graphene (tDBG) comprises two Bernal-stacked bilayer graphene sheets with a twist between them. Here, the authors report a strong anomalous Hall effect in the correlated-metal regime of tDBG, indicating time reversal symmetry breaking from orbital ferromagnetism, likely associated with valley polarization. [ABSTRACT FROM AUTHOR]

Cognitive flexibility, the ability to adapt to unexpected changes, is critical for healthy environmental and social interactions, and thus to everyday functioning. In neuropsychiatric diseases, cognitive flexibility is often impaired and treatment options are lacking. Probabilistic reversal learning (PRL) is commonly used to measure cognitive flexibility in rodents and humans. In PRL tasks, subjects must sample choice options and, from probabilistic feedback, find the current best choice which then changes without warning. However, in rodents, pharmacological models of human cognitive impairment tend to disrupt only the first (or few) of several contingency reversals, making quantitative assessment of behavioral effects difficult. To address this limitation, we developed a novel rat PRL where reversals occur at relatively long intervals in time that demonstrates increased sensitivity to the non-competitive NMDA receptor antagonist MK-801. Here, we quantitively compare behavior in timebased PRL with a widely used task where reversals occur based on choice behavior. In time-based PRL, MK-801 induced sustained reversal learning deficits both in time and across reversal blocks but, at the same dose, only transient weak effects in performance-based PRL. Moreover, time-based PRL yielded better estimates of behavior and reinforcement learning model parameters, which opens meaningful pharmacological windows to efficiently test and develop novel drugs preclinically with the goal of improving cognitive impairment in human patients. [ABSTRACT FROM AUTHOR]

The time reversal symmetry of the wave equation allows wave refocusing back at the source. However, this symmetry does not hold in lossy media. We present a new strategy to compensate wave amplitude losses due to attenuation. The strategy leverages the instantaneous time mirror (ITM) which generates reversed waves by a sudden disruption of the medium properties. We create a heterogeneous ITM whose disruption is unequal throughout the space to create waves of different amplitude. The time-reversed waves can then cope with different attenuation paths as typically seen in heterogeneous and lossy environments. We consider an environment with biological tissues and apply the strategy to a 2-D digital human phantom from the abdomen. A stronger disruption is introduced where the forward waves suffer a history of higher attenuation, with a weaker disruption elsewhere. Computer simulations show heterogeneous ITM is a promising technique to improve time reversal refocusing in heterogeneous, lossy, and dispersive spaces. [ABSTRACT FROM AUTHOR]

In this paper, we introduce (at least formally) a diffusion effect that is based on an axiom postulated by Werner Heisenberg in the early days of quantum mechanics. His statement was that—in quantum mechanics—kinematical quantities such as velocity must be treated as complex matrices. In the hydrodynamic formulation of quantum mechanics according to Madelung, the complex Schrödinger equation is rewritten in terms of two real equations—a continuity equation and a modified Hamilton–Jacobi equation. Considering seriously Heisenberg's axiom, the velocity occurring in the continuity equation should be replaced by a complex one, thus introducing a diffusion term with an imaginary diffusion coefficient. Therefore, in quantum mechanics, there should be a diffusion effect showing up in the dynamics. This is the case in the time evolution of the free-motion wave packet under time reversal. The maximum returns to the initial position; however, the width of the wave packet does not shrink to its initial width. This effect is obvious but—as far as we know—it is not mentioned in any textbook. In our paper, we discuss this effect in detail and show the connection with a complex version of quantum hydrodynamics. [ABSTRACT FROM AUTHOR]

Millimeter-scale implants using ultrasound (US) for power and communication have been proposed for a range of deep-tissue applications, including neural recording and stimulation. However, published implementations have shown high sensitivity to misalignment with the external US transducer. Ultrasonic beamforming using a phased array to these implants can improve tolerance to misalignment, reduce implant volume, and allow multiple implants to be operated simultaneously in different locations. This article details the design of a custom planar phased array US system, which is capable of steering and focusing US power within a 3-D volume. Analysis and simulation is performed to determine the choice of array element pitch, with special attention given to maximizing the power available at the implant while meeting FDA limits for diagnostic US. Time reversal (TR) is proposed as a computationally simple approach to beamforming that is robust despite scattering and inhomogeneity of the acoustic medium. This technique is demonstrated both in active drive and pulse-echo modes, and it is experimentally compared with other beamforming techniques by measuring energy transfer efficiency. Simultaneous power delivery to multiple implants is also demonstrated. [ABSTRACT FROM AUTHOR]

Purpose: Despite the wide range of medical and interventional therapy options available, some patients with Crohn's disease (CD) need an ileostomy or colostomy. The aim of this study was to identify clinical, surgical and drug-related predictors of successful stoma reversal in CD patients. Methods: A retrospective medical record analysis of surgical department logs, hospital discharge letters and patient reports from outpatient departments was performed for all CD patients who underwent a first ostomy surgery. Results: Our study analysed a total of 149 patients (76 women, 73 men, median age at first stoma of 34 years after a median CD duration of 9 years), with a median follow-up of 78.4 (IQR 88.6) months after first ostomy surgery. Of these patients, 73 (49%) underwent stoma reversal after a median of 11.7 months (IQR 15.7 months) of whom 17 (23.3%) needed a second stoma. In multivariant analysis, Montreal A1 classification (HR 2.07; 95% confidence interval 1.23–3.47; p = 0.006), a primary laparotomy (HR 2.30; 95% confidence interval 1.20–4.41; p = 0.012) and the absence of perianal/rectal CD activity (HR 3.00; 95% confidence interval 1.86–4.86; p < 0.001) emerged as independent predictors of a shorter time to stoma reversal. Introduction or switch of biological therapy after first stoma was not associated with successful reversal of the stoma (OR 4.6 95% confidence interval 1.45–14.66; p = 0.01). Laboratory parameters had no influence. Conclusion: Clinical and surgical features—rather than medication or laboratory findings—were found to be predictors of successful stoma reversal in CD patients. Future studies focusing on the definition of a Standard Operation Procedure for emergency and elective CD surgery are warranted. [ABSTRACT FROM AUTHOR]

The classical electromagnetic time reversal (EMTR) fault location method in power systems requires multiple simula-tions in the backward step, assuming different guessed fault loca-tions along the line. This process can be time consuming especially when a high location accuracy is desired, as it may require a significant number of guessed fault locations. To cope with this issue, the concept of EMTR in mismatched media has recently been introduced, allowing reducing the backward simulations to a single run and, thus, substantially improving the computation efficiency of the EMTR-based fault location technique. In this paper, we present a detailed study of the mismatched-media-based mirrored minimum energy property. This property has been applied in a few recent studies but never been theoretically studied and rigorously demonstrated. First, we infer a transfer function that relates the fault source to the voltage along the line resulting from back-injecting the time-reversed transients measured at a given observation point. We present a theorem according to which, at the fault switching frequency and its odd harmonics, the mirror-image point of the fault location with respect to the line center corresponds to a local minimum of the squared modulus of the transfer function. Then, it is proved that the mirrored minimum energy property is a corollary of this theorem. Based on these theoretical findings, we propose an algorithm that utilizes the reversed-time voltage energy as a fault location metric in the frequency domain. We further advance a data-driven strategy to maximize the computation efficiency of the fault location procedure. The applicability and robustness of the proposed frequency-domain fault location metric are numerically and experimentally validated. [ABSTRACT FROM AUTHOR]

Why does time reversal involve two operations, a temporal reflection and the operation of complex conjugation? Why is it that time reversal preserves position and reverses momentum and spin? This puzzle of time reversal in quantum mechanics has been with us since Wigner’s first presentation. In this paper, I propose a new solution to this puzzle. First, it is shown that the standard account of time reversal can be derived based on the assumption that the probability current is reversed by the time reversal transformation. Next, this assumption is justified and the meaning of time reversal is clarified by analyzing the relationship between the rates of change and the instantaneous quantities which determine them. Finally, I explain how the new analysis help solve the puzzle of time reversal in quantum mechanics. [ABSTRACT FROM AUTHOR]

Interpreting other's actions is a very important ability not only in social life, but also in interactive sports. Previous experiments have demonstrated good estimation performances for the weight of lifted objects through point-light displays. The basis for these performances is commonly assigned to the concept of motor simulation regarding observed actions. In this study, we investigated the weak version of the motor simulation hypothesis which claims that the goal of an observed action strongly influences its understanding (Fogassi, Ferrari, Gesierich, Rozzi, Chersi, & Rizzolatti, 2005). Therefore, we conducted a weight judgement task with point-light displays and showed participants videos of a model lifting and lowering three different weights. The experimental manipulation consisted of a goal change of these actions by showing the videos normal and in a time-reversed order of sequence. The results show a systematic overestimation of weights for time-reversed lowering actions (thus looking like lifting actions) while weight estimations for time-reversed lifting actions did not differ from the original playback direction. The results are discussed in terms of motor simulation and different kinematic profiles of the presented actions. [ABSTRACT FROM AUTHOR]

Full sets of inequivalent elementary band co-representations (coEBRs) for spinless and spinful systems with grey line group (LG) symmetry are calculated and, together with recently reported elementary band representation (EBRs) for colorless single and double LGs by Milošević et al (2020 J. Phys. A: Math. Theor. 53 455204), the task of characterization of nonmagnetic quasi-one-dimensional (quasi-1D) topological crystals by means of the theory of topological quantum chemistry can be completed. Effects of additional time reversal symmetry on band topology and applicability of topological quantum chemistry is thoroughly analyzed. The main conclusions of the latter are illustrated on spinful Suâ€"Schriefferâ€"Heeger model (topological mirror chain). Technique of induction and decomposition of coEBRs is fully developed and presented in detail. Complete sets of coEBRs for all thirteen families of single and double grey LGs are tabulated. Quasi-1D structures with symmetry enforced hourglass fermions are singled out. [ABSTRACT FROM AUTHOR]

We discuss spectral properties of a periodic quantum graph consisting of an array of rings coupled either tightly or loosely through connecting links, assuming that the vertex coupling is manifestly non-invariant with respect to the time reversal and a homogeneous magnetic field perpendicular to the graph plane is present. It is shown that the vertex parity determines the spectral behavior at high energies and the Bandâ€"Berkolaiko universality holds whenever the edges are incommensurate. The magnetic field influences the probability that an energy belongs to the spectrum in the tight-chain case, and also it can turn some spectral bands into infinitely degenerate eigenvalues. [ABSTRACT FROM AUTHOR]

It is well-known that an iterative time-reversal (TR) process, applied via a distributed sensing system, can be used to produce a space-time waveform that maximizes the energy scattered from a stationary target back to the sensors. The TR process accomplishes this by automatically focusing energy, both spatially and spectrally, on the stationary target. When scatterers are moving, however, the TR focusing can break down. This article shows how to modify the TR process so that it automatically focuses energy on a moving target. This new TR process automatically generates a distributed beam that: 1) follows the target as it moves and 2) enhances the target resonances by concentrating the energy spectrally. This focusing occurs without a priori knowledge of the target’s location or spectral response. The new TR algorithm is derived through a careful analysis of the idealized case of a single isotropic moving point scatterer. This article includes simulations that compare the TR focus both with and without the new modification. Although the simulations are carried out for the electromagnetic case, the theory applies equally well to the acoustic case when the target speed is significantly less than the ambient sound speed. Appendices are included with details of the calculations and with analysis of the range of relative velocities for which the modified TR process should be used. [ABSTRACT FROM AUTHOR]

The paper falls into the category of computational methods for inverse scattering techniques for the identification of scatterers. We consider a linear elastodynamic problem and compare two popular methods for identifying a scatterer in the domain. Finite elements are employed with each of the two methods for spatial discretization. One method considered is Full Waveform Inversion using a gradient-based optimization and the adjoint method. In the adjoint procedure for calculating the gradient, we use the variant of discretizing the unknown parameters from the outset while all other variables remain continuous. Gradient optimization is performed in the examples using a quasi-Newton method. The other method compared is the computational Time Reversal technique, which is used in combination with an augmentation procedure to enhance performance. advantages and limitations of the two methods are outlined, and their performance is compared through an example from geophysics. [ABSTRACT FROM AUTHOR]

Many complex systems are characterized by interconnected units often difficult, or even impossible, to map through direct observations, while the dynamics of units is mostly easier to measure. The reconstruction of an unknown structure from the observed dynamics is a typical inverse problem in network‐based approaches to overcome such obstacles. However, this procedure is affected by the interplay between the structure and dynamics, as well as by the choice of the statistical method. In this study, collective behaviour of the Earth's climate system was investigated by focusing on three distinct climatological variables in monthly time step using a causality measure to separately construct climate networks through a robust statistical analysis. Multiplex network (MUX) was used to integrate the information obtained from collective dynamics and time reversal for better filtering spurious connectivity. In fact, the proposed approach mitigates undesired effects of pairwise statistical inference by adjusting for unphysical relationships in two layers of the constructed networks. The results indicate that the mere existence of statistical errors allowed by the hypothesis testing lead, inevitably, to reconstruct spurious connections in the null models even when the collective dynamics consists of white‐noise datasets from uncoupled units. The impact of spurious connections with the MUX dynamics is not remarkable to reconstruct the underlying plausible interactions; therefore, the concepts of MUX might be employed with the statistical analysis to unravel the backbone of climate networks. In this way that the inferred connections could distinguish highly connected regions for better understanding interconnected dynamical patterns, yielding deep insights into underlying physical interactions between the oceans and atmosphere. More specifically, edge directionality features provide a complementary tool for analysing topology of the networks with respect to the climatological variables, identifying relevant patterns in the climate system. [ABSTRACT FROM AUTHOR]

The influence of Dzyaloshinskiiâ€"Moriya interaction (DMI) on the vortex reversal driven by an out-of-plane spin-polarized current in an off-centered nanocontact structure is investigated. The simulation results show that DMI plays a vital role in vortex core reversal, including reversal current density, reversal velocity and reversal time. Under the influence of DMI, magnetic vortices still reverse polarity through the nucleation and annihilation of vortex and anti-vortex, with some peculiar characteristics. These results open up new possibilities for the application of magnetic vortex-based spin-transfer encryption nano-storage. [ABSTRACT FROM AUTHOR]