Memory Effect Research Articles

A comprehensive solid-state NMR and theoretical modeling study to reveal the structural evolution of layered yttrium hydroxide upon calcination

Layered rare earth hydroxides (LREHs) are a new family of ion-exchangeable layered metal hydroxides, which have extensive applications in various fields due to the unique properties of rare earth cations in the layered structure and the anion exchange capacity. The transformation of layered metal hydroxides to new layered phases that can be restored through the memory effect is critical for their chemistry and applications. However, the structure details of these new phases such as the coordination environments of rare earth cations/counterions and their evolution as a function of calcination temperature remain unclear to date. Herein, a comprehensive 89Y/35Cl solid-state NMR (ssNMR) and theoretical modeling approach was used to reveal the structural evolution of a representative LREH, namely LYH-Cl, upon calcination. We first identified partial decomposition products of Y3O(OH)5Cl2 and Y(OH)3 during the dehydration stage, then uncovered the preferential removal of hydroxide ions on yttrium sites coordinated with chlorine during the dehydroxylation stage, and finally determined the preferential removal of chlorine exposed to the surface of layers during the dechlorination stage. The coordination environments of Y3+ and Cl− undergo significant changes upon calcination, revealed by ssNMR experiments. These findings thus help us to overcome the obstacles impeding the rational design and synthesis of LREH-based functional materials via memory effect, underscoring the vast potential of ssNMR in deepening the understanding of layered metal hydroxides and related materials.

Rejuvenation and memory effects in active glasses induced by thermal and active cycling

Rejuvenation and memory effects in active glasses induced by thermal and active cycling

A new pavement crack repair sealant with two-way shape memory effect

To address the challenge of sealant debonding due to cyclic temperature variations, a new pavement crack repair sealant which can achieve two-way shape memory deformation is developed. The developed crack sealant is a shape memory liquid crystal elastomer (SMLCE), designed to exhibit the deformation characteristics of heat contraction and cold expansion. First, the material composition and preparation process of the developed SMLCE are given. Thermodynamic properties, phase transition temperatures and molecular structures are analyzed based on DSC and FITR. The effects of the crosslinker and chain extender ratios and the key preparation processes on the two-way shape memory deformation and mechanical performance of SMLCE are systematically analyzed. Based on the analysis, the optimum ratio of SMLCE is determined to be 1:15 and the optimum secondary crosslinking preparation process is 150% orientation stretching. Under the optimal solution, the developed SMLCE can achieve the multiple two-way shape memory reversible deformation with a maximum 46% deformation in the temperature range of -20°C∼120°C. At the same time, the developed SMLCE has excellent mechanical properties, with a tensile strength of 20.7Mpa and an elongation at break of 322%. It also exhibits good low-temperature deformation capabilities at -10°C and above. Finally, the suitability and application potential of the developed two-way SMLCE as a pavement crack sealant are assessed. The developed SMLCE has good adaptability in most climate zones, which indicates its great potential as a pavement crack sealant. This research provides a new way for the pavement crack repair.

Gravitational wave displacement and velocity memory effects

In this article, we compare in detail the linear and nonlinear approach to the Gravitational Waves Displacement and Velocity Memory (GWDM and GWVM) effects. We consider astrophysical situations that give rise to gravitational waves with GWVM effect, i.e. with a residual velocity (the so-called ‘velocity-coded memory’) and discuss the possibility of future detection of the GWVM effect.

Coexistance of the Negative Photoconductance Effect and Analogue Switching Memory in the CuPc Organic Memristor for Neuromorphic Vision Computing.

A bioinspired in-sensing computing paradigm using emerging photoelectronic memristors pursues multifunctionality with low power consumption and high efficiency for processing large amounts of sensing information. An organic semiconductor memristor strategy based on the CuPc functional layer integrates a negative photoconductance (NPC) effect and an analogue switching memory (ASM) effect in the same pixel. The NPC effect, present in the pure capacitance state at low bias voltage, provides high-performance short/long-term synaptic plasticity modulable by light pulse parameters. The interface charge effect along with defeat site trapping and detrapping is responsible for the pure capacitance effect and the NPC effect, with electron tunneling and electric-field-driven band dynamics responsible for ASM. This work reveals an organic memristor approach for hardware implementation of a neuromorphic vision computing system, emulating retinal bipolar cells via light-dominated NPC and electrically induced ASM with stable, tunable conductance states.

Charge Trapping and Defect Dynamics as Origin of Memory Effects in Metal Halide Perovskite Memlumors.

Large language models for artificial intelligence applications require energy-efficient computing. Neuromorphic photonics has the potential to reach significantly lower energy consumption in comparison with classical electronics. A recently proposed memlumor device uses photoluminescence output that carries information about its excitation history via the excited state dynamics of the material. Solution-processed metal halide perovskites can be used as efficient memlumors. We show that trapping of photogenerated charge carriers modulated by photoinduced dynamics of the trapping states themselves explains the memory response of perovskite memlumors on time scales from nanoseconds to minutes. The memlumor concept shifts the paradigm of the detrimental role of charge traps and their dynamics in metal halide perovskite semiconductors by enabling new applications based on these trap states. The appropriate control of defect dynamics in perovskites allows these materials to enter the field of energy-efficient photonic neuromorphic computing, which we illustrate by proposing several possible realizations of such systems.

Interference Management for a Wireless Communication Network Using a Recurrent Neural Network Approach

Wireless communication technologies have profoundly impacted the interconnectivity of mobile users and terminals. Nevertheless, the exponential increase in the number of users poses significant challenges, particularly in interference management, which is a major concern in wireless communication. Machine learning (ML) approaches have emerged as powerful tools for solving various problems in this domain. However, existing studies have not fully addressed the problem of interference management for wireless communication using ML techniques. In this paper, we explore the application of recurrent neural network (RNN) approaches to address co-channel interference in wireless communication. Specifically, we investigate the effectiveness of long short-term memory (LSTM), bidirectional LSTM (Bi-LSTM), and gated recurrent unit (GRU) network architectures in two different network settings. The first network comprises 10 connected devices, while the second network involves 20 devices. Our experimental results demonstrate that Bi-LSTM outperforms LSTM and GRU in terms of mean squared error, normalized mean squared error, and sum rate. While LSTM and GRU produce similar results, LSTM exhibits a marginal advantage over GRU. In addition, a combined RNN approach is also studied, and it can provide better results in dense networks.

Different phase transformation behaviors of B2-CuZr crystalline phase and their associated mechanical properties by molecular dynamics using different potentials

Metastable CuZr-based alloys have attracted much attention due to their high glass-forming ability and shape memory effect. Many experiments have underscored the pivotal role of the B2-CuZr phase as an effective inclusion to improve both the strength and ductility of metallic glass matrix composites. The improved ductility can be attributed to the dilatation induced by martensitic transformation, while the strengthening effect is owed to the higher strength and hardness of the martensite phase compared to the austenite phase. Well-designed atomistic simulations can predict the mechanical behavior of materials before experiments and offer sufficient information on the atomic scale. The selection of an appropriate interatomic potential is a primary concern in any atomistic simulation and needs to be carefully considered to ensure reliable results. The uniaxial tensile behavior of B2-CuZr crystalline phase is investigated by molecular dynamics simulations using five typical potentials, namely the potentials developed by Mendelev-2007, Mendelev-2009, Mendelev-2016, Mendelev-2019 and Cheng-2009. The phase transformation behavior during tension, Young’s modulus, and yield strength of the simulated samples exhibit variations when different potentials are employed. Notably, only by employing Mendelev-2019 and Cheng-2009 potentials, the strength and Young’s modulus of the transformed phase are higher than the untransformed austenite phase, corresponding well with experimental results. This work emphasizes the impact of different interatomic potentials on phase transformation behaviors within a specific simulation context.

Exploring the Reconfigurable Memory Effect in Electroforming-Free YMnO3-Based Resistive Switches: Towards a Tunable Frequency Response.

Memristors, since their inception, have demonstrated remarkable characteristics, notably the exceptional reconfigurability of their memory. This study delves into electroforming-free YMnO3 (YMO)-based resistive switches, emphasizing the reconfigurable memory effect in multiferroic YMO thin films with metallically conducting electrodes and their pivotal role in achieving adaptable frequency responses in impedance circuits consisting of reconfigurable YMO-based resistive switches and no reconfigurable passive elements, e.g., inductors and capacitors. The multiferroic YMO possesses a network of charged domain walls which can be reconfigured by a time-dependent voltage applied between the metallically conducting electrodes. Through experimental demonstrations, this study scrutinizes the impedance response not only for individual switch devices but also for impedance circuitry based on YMO resistive switches in both low- and high-resistance states, interfacing with capacitors and inductors in parallel and series configurations. Scrutinized Nyquist plots visually capture the intricate dynamics of impedance circuitry, revealing the potential of electroforming-free YMO resistive switches in finely tuning frequency responses within impedance circuits. This adaptability, rooted in the unique properties of YMO, signifies a paradigm shift heralding the advent of advanced and flexible electronic technologies.

Next-to-eikonal corrected double graviton dressing and gravitational wave observables at OG2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O}\\left({G}^2\\right) $$\\end{document}

Following a recent proposal to describe inelastic eikonal scattering processes in terms of gravitationally dressed elastic eikonal amplitudes, we motivate a collinear double graviton dressing and investigate its properties. This is derived from a generalized Wilson line operator in the worldline formalism by integrating over fluctuations of the eikonal trajectories of external particles in gravitationally interacting theories. The dressing can be expressed as a product of exponential terms — a coherent piece with contributions to all odd orders in the gravitational coupling constant and a term quadratic in graviton modes, with the former providing classical gravitational wave observables. In particular, the coherent dressing involves Oκ3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O}\\left({\\kappa}^3\\right) $$\\end{document} subleading double graviton corrections to the Weinberg soft factor. We use this dressing to derive expressions for the waveform, radiative momentum spectrum and angular momentum. In a limiting case of the waveform, we derive the nonlinear memory effect resulting from the emission of nearly soft gravitons from a scattering process.

Relevance of Specific Surface of Mixed Oxide Derived from Layered Double Hydroxides on the Rheological Properties and Porosity of Cement Pastes.

Cement-based products are the synthetic materials most used by humans, with consequent environmental impacts. One strategy that can assist in mitigating the adverse environmental effects of these materials involves the incorporation of multifunctional nanostructured additives. The objective of this work was to demonstrate the efficacy of incorporating mixed oxides (MO) derived from layered double hydroxides (LDH) to control the rheology and porosity of cement-based matrices. Thermal aging of LDH enabled the preparation of MO with different specific surface areas (SSA) for incorporation in different amounts in Portland cement. A low proportion of MO and low SSA increased workability by 22%. In contrast, a high proportion of MO and high SSA led to a 2.4-fold acceleration of cement consolidation and a 36.9% decrease of the porosity of the composite. These features could be attributed to additive-matrix interactions, with the LDH memory effect playing key roles in the cement crystal seed process and in competition for the absorption of free water within the cement paste. Therefore, the unprecedent results obtained suggest that the quantity and SSA of MO are key parameters to fine-tune the paste rheology and structure of hidrated cement. The MO materials showed easy adaptability and excellent potential for use as multifunctional additives in the production of eco-friendly, high-performance cement paste formulations with controllable properties according to the desired application.

Opposing effects of pre-existing antibody and memory T cell help on the dynamics of recall germinal centers

Re-exposure to an antigen generates abundant antibody responses and drives the formation of secondary germinal centers (GCs). Recall GCs in mice consist almost entirely of naïve B cells, whereas recall antibodies derive overwhelmingly from memory B cells. Here, we examine this division between cellular and serum compartments. After repeated immunization with the same antigen, tetramer analyses of recall GCs revealed a marked decrease in the ability of B cells in these structures to bind the antigen. Boosting with viral variant proteins restored antigen binding in recall GCs, as did genetic ablation of primary-derived antibody-secreting cells through conditional deletion of Prdm1, demonstrating suppression of GC recall responses by pre-existing antibodies. In hapten-carrier experiments in which B and Tcell specificities were uncoupled, memory Tcell help allowed B cells with undetectable antigen binding to access GCs. Thus, antibody-mediated feedback steers recall GC B cells away from previously targeted epitopes and enables specific targeting of variant epitopes, with implications for vaccination protocols.

Fully 3D-Printed Miniature Soft Hydraulic Actuators with Shape Memory Effect for Morphing and Manipulation.

Miniature shape-morphing soft actuators driven by external stimuli and fluidic pressure hold great promise in morphing matter and small-scale soft robotics. However, it remains challenging to achieve both rich shape morphing and shape locking in a fast and controlled way due to the limitations of actuation reversibility and fabrication. Here, fully 3D-printed, sub-millimeter thin-plate-like miniature soft hydraulic actuators with shape memory effect (SME) for programable fast shape morphing and shape locking, are reported. It combines commercial high-resolution multi-material 3D printing of stiff shape memory polymers (SMPs) and soft elastomers and direct printing of microfluidic channels and 2D/3D channel networks embedded in elastomers in a single print run. Leveraging spatial patterning of hybrid compositions and expansion heterogeneity of microfluidic channel networks for versatile hydraulically actuated shape morphing, including circular, wavy, helical, saddle, and warping shapes with various curvatures, are demonstrated. The morphed shapes can be temporarily locked and recover to their original planar forms repeatedly by activating SME of the SMPs. Utilizing the fast shape morphing and locking in the miniature actuators, their potential applications in non-invasive manipulation of small-scale objects and fragile living organisms, multimodal entanglement grasping, and energy-saving manipulators, are demonstrated.

Hysteresis, Rectification, and Relaxation Times of Nanofluidic Pores for Neuromorphic Circuit Applications

AbstractBased on the emergence of iontronic fluidic components for brain‐inspired computation, the general dynamical behavior of nanopore channels is discussed. The main memory effects of fluidic nanopores are obtained by the combination of rectification and hysteresis. Rectification is imparted by an intrinsic charge asymmetry that affects the ionic current across the nanopores. It is accurately described by a background conductivity and a higher conduction branch that is activated by a state variable. Hysteresis produces self‐crossing diagrams, in which the high current side shows inductive hysteresis, and the low current side presents capacitive hysteresis. These properties are well captured by measurements of impedance spectroscopy that show the correspondent spectra in each voltage wing. The detailed properties of hysteresis and transient response are determined by the relaxation time of the gating variable, that is inspired in the Hodgkin‐Huxley neuron model. The classification of effects based on simple models provides a general guidance of the prospective application of artificial nanopore channels in neuromorphic computation according to the measurement of complementary techniques.

Designing Advanced Amorphous/Nanocrystalline Alloys by Controlling the Energy State.

Amorphous alloys, also known as metallic glasses, exhibit many advanced mechanical, physical, and chemical properties. Owing to the nonequilibrium nature, their energy states can vary over a wide range. However, the energy relaxation kinetics are very complex and composed of various types that are coupled with each other. This makes it challenging to control the energy state precisely and to study the energy-properties relationship. This brief review introduces the recent progresses on studying the enthalpy relaxation kinetics during isothermal annealing, for example, the observation of two-step relaxation phenomenon, the detection of relaxation unit (relaxun), the key role of large activation entropy in triggering memory effect, the influence of glass energy state on nanocrystallization. Based on the above knowledge, a new strategy is proposed to design a series of amorphous alloys and their composites consisting of nanocrystals and glass matrix with superior functional properties by precisely controlling the nonequilibrium energy states. As the typical examples, Fe-based amorphous alloys with both advanced soft magnetism and good plasticity, Gd-based amorphous/nanocrystalline composites with large magnetocaloric effect, and Fe-based amorphous alloys with high catalytic performance are specifically described.

Three-dimensional GRMHD simulations of rapidly rotating stellar core collapse

ABSTRACT We present results from fully general relativistic (GR), three-dimensional (3D), neutrino-radiation magneto-hydrodynamic (MHD) simulations of stellar core collapse of a 20 M⊙ star with spectral neutrino transport. Our focus is to study the gravitational-wave (GW) signatures from the magnetorotationally (MR)-driven models. By parametrically changing the initial angular velocity and the strength of the magnetic fields in the core, we compute four models. Among our models, only those with cores having an initial magnetic field strength of 1012 G and rotation rates of 1 or 2 rad s−1 produce MHD jets. Seen from the direction perpendicular to the rotational axis, a characteristic waveform is obtained exhibiting a monotonic time increase in the wave amplitude. As previously identified, this stems from the propagating MHD outflows along the axis. We show that the GW amplitude from anisotropic neutrino emission becomes more than one order-of-magnitude bigger than that from the matter contribution, whereas seen from the rotational axis, both of the two components are in the same order-of-magnitudes. Due to the memory effect, the frequency of the neutrino GW from our full-fledged 3D-MHD models is in the range less than ∼10 Hz. Toward the future GW detection for a Galactic core-collapse supernova, if driven by the MR mechanism, the planned next-generation detector as DECIGO is urgently needed to catch the low-frequency signals.

Infrared light responsive shape memory tracheal stent based on TPU6/PCL4/PANI composites

3D printed tracheal stent based on light-responsive shape memory composites (SMC) has a good application prospect due to its remote, non-contact drive and the ability to adapt to complex environments. This paper detailed the fabrication, characterization, and infrared light (IR) actuating shape memory effects of the SMC based on the thermal polyurethane (TPU)/poly(caprolactone) (PCL)/polyaniline (PANI)/composites. Herein, the experiments have explored the preparation and process parameters and 3D printing properties (e.g., filament-molding temperature, 3D printing temperature, and speed) on the premise of smooth printing of the composites. The thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy analysis (FTIR), differential scanning calorimetry analysis (DSC), micro-morphology, and tensile testing was operated to characterize the properties of the TPU6/PCL4/PANI composites. Additionally, shape memory performance has shown that the shape memory fixation rate of the prepared IR-responsive SMC was about 99%, and the shape recovery ratio was approximately 95%. Therefore, this work customized the tracheal scaffold based on TPU6/PCL4/PANI composites by 3D printing technology (FDM), which possesses excellent IR-triggered remote-controlling structure deformation performance. Moreover, by collaborating with minimally invasive surgery, 3D printed IR-actuating SMC structures can expand the application scope in the biomedical field and provide a new way for personalized implantable medical devices.

Better source memory for remembered to-be-forgotten items than for remembered to-be-remembered items.

When participants study items one-by-one and are directed to either remember or forget the respective item directly after its presentation, retention of to-be-forgotten items is regularly worse than of to-be-remembered items. We tested whether this directed forgetting effect which is regularly observed for item memory generalizes to source memory. In three experiments, participants studied items in two different source colors (N = 101) or at two different source locations (N = 64; N = 81). Sources were manipulated orthogonally to item type (remember vs. forget). At test, we asked participants to recognize all studied items and also to identify their source. We used a multinomial processing tree model to disentangle item memory, source memory, and guessing. In all three experiments, we replicated the directed forgetting effect in item memory. Source memory for to-be-forgotten items that were recognized despite the intention to forget, however, tended to be even better than source memory for to-be-remembered items that were recognized. These results suggest that the directed forgetting effect does not simply translate from item to source memory. Rather source memory seems to be disproportionally increased in to-be-forgotten items that are remembered. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Kondo enabled transmutation between spinons and superconducting vortices: Origin of magnetic memory in 4Hb−TaS2

Recent experiments [Persky , ] demonstrate a magnetic memory effect in 4Hb−TaS2 above its superconducting transition temperature, where Abriokosov vortices are spontaneously generated by lowering the temperature at zero magnetic field after field training the normal state. Motivated by the experiment, we propose the chiral quantum spin liquid (QSL) stabilized in the constituent layers of 4Hb−TaS2 as a mechanism. We model 4Hb−TaS2 as coupled layers of the chiral QSL and the superconductor. Through the Kondo coupling between the localized moments and conduction electrons, there is mutual transmutation between spinons and vortices during the thermal-cycling process, which yields the magnetic memory effect observed in experiments. We also propose a mechanism to stabilize chiral and nematic superconductivity in 4Hb−TaS2 through the Kondo coupling of conduction electrons to the chiral QSL. Our picture suggests 4Hb−TaS2 as an exciting platform to explore the interplay between QSL and superconductivity through the Kondo effect. Published by the American Physical Society 2024

DESIGN, IMPLEMENTATION, AND TESTING OF A 3D-PRINTED GRIPPER ACTUATED BY NITINOL SPRINGS

This article explores the use of shape memory alloy (SMA) materials in the creation of robot effectors. Specifically, we focus on the design and implementation of a gripper powered by nitinol springs. Nitinol, an alloy of nickel and titanium, can return to a pre-set shape when heated - a phenomenon known as the shape memory effect - which we utilize to control the gripper. The article showcases the design, construction, and testing of the gripper, including its speed and reliability in grasping different objects. Our findings indicate that the gripper was reliable solution, but further research is necessary to optimize its functions and control for more efficient results in practical applications.