Resistive Transition Research Articles

The influence of in situ microfibrillation on the mechanical properties and warpage of low‐density polyethylene/polystyrene composite prepared by fused filament fabrication

AbstractFused filament fabrication (FFF) has been widely adopted due to its simplicity and cost‐effectiveness. But until now, its application materials are still limited. Polyolefin material is one of the most commonly used plastics. However, low‐density polyethylene (LDPE) is rarely used in FFF due to the inadequate strength of the filaments and the warpage of the printed parts. In this work, polystyrene (PS) is added to LDPE to obtain blend filaments. After that, the filaments are used to validate the possibility of in situ microfibrillation directly in the process. The results show that the addition of PS can significantly improve the bending strength, bending modulus, and hardness without affecting the heat resistance and crystal transition of the composite. Besides, the PS dispersed phase can form microfibers under the influence of the shear field. The formation of microfibers can significantly enhance the mechanical properties of composites. The tensile strength and Young's modulus increase by 140% and 221%, respectively. The warping deformation and surface morphology of printed parts are also improved. This study provides a new idea for utilizing low‐strength polyolefin in 3D printing and achieving performance enhancement.

Acquisition of Doxorubicin Resistance Induces Breast Cancer Cell Migration and Epithelial-Mesenchymal Transition that are Reversed by Shikonin-Metformin Synergy

Background: Drug resistance is a major challenge in cancer chemotherapy. Methods: By adopting an appropriately timed strategy, we generated MCF-7 cell sublines resistant to serial doses of doxorubicin (DOX). Our higher-dose sublines showed more stability in resistance and were, therefore, subjected to further analyses. We tested the consistency of drug resistance by comparing sublines with control groups for growth and migration capacities. Molecular analyses monitored expression changes, CD44/CD24 ratios, and DOX binding to key molecules. The reverting impact of shikonin (SHKN) and metformin (MTFN) on DOX resistance was examined. Results. The resistant sublines grew parallel to or even faster than WT MCF-7 cells and showed a larger and more rounded morphology. The consistency of their drug resistance and invasive potential was demonstrated over time using serial doses of DOX. Real-time PCR revealed upregulation of genes involved in cell growth and survival, drug resistance, migration/invasion, and epithelial-mesenchymal transition and, conversely, downregulation of pro-apoptotic, anti-chemoresistance, and tumor suppressor genes. SHKN-MTFN co-treated resistant cells showed significantly lower CD44/CD24 ratios, less aggressiveness, and reduced survival and migration rates but enhanced apoptosis. SHKN’s affinity to CYP1A and TOP2A demonstrated the importance of these interactions and the compounds’ capacity to compete with DOX. Conclusion: Acquisition of DOX resistance increases tumorigenic properties of cancer cells, whereas synergy between selective anti-tumorigenic compounds re-sensitizes resistant cells by reverting cellular pathways that favor or follow resistance. Our findings suggest that this reversal is supported by competing reactions that deprive DOX of binding to its target molecules.

Investigation of Cu-Sn-Sb Thin Film for Ultra-Speed and Phase High-Reliability Change Memory Applications

SnSb (SS), a vital phase-change thin film, has attracted attention due to its excellent phase-change properties, but the poor amorphous stability and crystalline speed of SS greatly limit its application in rapid phase-transition memories. Here, we propose a copper (Cu)-doped SS phase change films to achieve ultra-speed and high-reliability of SS. Resistance-temperature tests show Cu-Sn-Sb possesses ultra-low crystalline and amorphous resistivity, higher phase transition speed, and lower activation energy. X-ray diffraction measurements illustrate the introduction of Cu ions hinders the growth of grains and reduce grains size. Atomic force microscopy characterizes the surface morphology of as-deposited and annealed Cu-Sn-Sb films, and difference of root-mean-square roughness before and after annealing promote Cu-Sn-Sb film is more reliable to touch electrodes. In addition, the ultra-low resistivity and fast transition speed effectively reduce thermal loss in SET and RESET process. The results reveal that Cu-Sn-Sb is a promising material for ultra-rapid phase change and high-reliability storage applications.

Electronic and Structural Disorder of the Epitaxial La0.67Sr0.33MnO3 Surface.

Understanding and tuning epitaxial complex oxide films are crucial in controlling the behavior of devices and catalytic processes. Substrate-induced strain, doping, and layer growth are known to influence the electronic and magnetic properties of the bulk of the film. In this study, we demonstrate a clear distinction between the bulk and surface of thin films of La0.67Sr0.33MnO3 in terms of chemical composition, electronic disorder, and surface morphology. We use a combined experimental approach of X-ray-based characterization methods and scanning probe microscopy. Using X-ray diffraction and resonant X-ray reflectivity, we uncover surface nonstoichiometry in the strontium and lanthanum alongside an accumulation of oxygen vacancies. With scanning tunneling microscopy, we observed an electronic phase separation (EPS) on the surface related to this nonstoichiometry. The EPS is likely driving the temperature-dependent resistivity transition and is a cause of proposed mixed-phase ferromagnetic and paramagnetic states near room temperature in these thin films.

Semiconductor fibers for textile integrated electronic systems.

The near-room temperature resistance transition in the Lu-H-N compound is repeatedly reproduced, which is clarified to originate from a metal-to-semiconductor/insulator transition rather than superconductivity.

The jump-like PTCR effect in Ca1-xYxCu3Ti4O12 ceramics hot quenched under high-pressure

The PTCR effect is an important application phenomenon in the ferroelectric BaTiO3 electronic ceramic materials. In this work, the PTCR effect is also found in high pressure (HP) hot quenched Ca1-xYxCu3Ti4O12 (CYCTO) ceramics. Compared with the pure CaCu3Ti4O12 (CCTO) ceramic synthesized under ordinary pressure (OP), the low temperature resistivity of HP CYCTO samples is about 3 orders of magnitude lower than that of untreated CCTO samples, showing an obvious PTCR effect. The transition temperature is close to 178 K for x = 0.2 sample. The analysis of crystal and magnetic structures shows that the crystal and magnetic structures of HP CYCTO samples do not change before and after the resistance transition. X-ray photoelectron spectroscopy showed that the concentration of oxygen vacancy defects in HP CYCTO is higher than CCTO. By analyzing the conduction behaviors of HP CYCTO samples, it suggests that oxygen vacancies and Y3+ ions may be the important donors for the decrease of low temperature resistivity of HP CYCTO samples. The results in this work have important reference value for the application of the electrical conduction behaviors in CCTO.

Cu/MgO-based resistive random access memory for neuromorphic applications

Resistive Random Access Memory (ReRAM) is considered to be a suitable candidate for future memories due to its low operating voltage, fast access speed, and the potential to be scaled down to nanometer range for ultra-high-density storage. In addition, its ability to retain multi-level resistance states makes it suitable for neuromorphic computing applications. In this paper, we report the resistive switching performance of Cu/MgO/Pt ReRAM. Repetitive resistive switching transitions with low switching voltages (around 1 V), 102 storage windows, and multi-level memory capabilities have been obtained. Biological synaptic plasticity behavior, such as long-duration potentiation/depression and paired-pulse facilitation, has been realized by the Cu/MgO/Pt ReRAM. The simulation of convolutional neural network for handwritten digit recognition is carried out to evaluate its potential application in neuromorphic systems. Finally, the conduction mechanism of the device is studied, and a resistive switching model based on Cu conducting filaments is proposed according to the dependence of I–V results on temperature and electrode size as well as the element distribution in the device. These findings indicate the potential of Cu/MgO/Pt device as high-performance nonvolatile memories and its utilization in future computer systems and neuromorphic computing.

A ZTO-based memristor with tunable synaptic plasticity

It is an inevitable trend to use artificial neural networks based on neurons and synapses to deal with the bottleneck of von Neumann architectures, and memristor is one of the most potential artificial synapses. Here, Zinc oxide doped tin (ZTO), as a resistive material of memristor with a planar structure of Cu/ZTO/FTO, was prepared using sol-gel and spin-coating methods. Such devices exhibit stable resistive transition within scanning voltage 4 V. In particular, the device shows adjustable synaptic plasticity simulations, including the alternation between habituation and sensitization, which can be regulated by amplitude, rest time of stimulus pulse and the number of positive and negative pulse. Such remarkable plasticity performance of memristor based on ZTO might have promising applications for artificial synapse devices.

The application of C/Sb composite multilayer films on fast flexible phase change memory

In this paper, the phase transformation properties of C/Sb composite multilayer films based on flexible substrates were studied. After different times of bending, the flexible films can still achieve amorphous to crystalline phase transition, but the crystalline resistance increases to different degrees. When the bending times are less than 15000 times, the deformation makes the grain fine, the surface of the film tends to be flat, the surface electric field effect is weakened, and the resistance drift is reduced. When the bending times are higher than 15000 times, cracks begin to appear in the film, and the cracks’ depth and width increase with the bending times. The distribution of C and Sb elements at the crack was analyzed by scanning electronic microscope energy spectrum. The phase change memory device of C/Sb composite multilayer film based on flexible PEEK substrate has been made, and the rapid reversible resistance transition (∼10 ns) in various complex states has been successfully achieved. This research provides a new idea for flexible information storage.

Asymmetric transition of electrical resistance in an all-solid-state redox device with Fe3O4 and Li-ion electrolyte thin films for physical reservoir computing

In recent years, ion-gating devices have been used in artificial neuromorphic computing and achieved high performance for time-series data processing. However, the origin of this performance still needs to be clarified. In this study, we fabricated an all-solid-state redox device with functional material Fe3O4 and Li-ion conducting solid electrolytes, and the transient response of the electrical resistance of the Fe3O4 thin film to time-series data input was investigated. The transition between high and low electrical resistance states was asymmetric, and residual Li-ion in the thin film led to a hysteresis effect. These unique features, which are induced by ion-electron dynamics coupling, contributes to the high performance of physical reservoir computing utilizing an ion-gating device.

The characteristics of Cu-doped lead apatite (LK-99) synthesized with the removal of Cu2S using ammonia solution: A diamagnetic semiconductor

This study evaluated the superconducting properties of Cu-doped lead apatite “LK-99” and synthesized LK-99 samples using the process proposed by a team from Korea, who first described the process. Additionally, whether the results of this Korean team were related to Cu2S was also examined using an ammonia solution (NH3·H2O) to remove Cu2S. Through x-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDX) analyses, a distinct Cu2S phase was identified in the LK-99 samples. This phase was effectively eliminated through a subsequent treatment using an ammonia solution. The appearance of blue Cu+2 ions in the solution and the elimination of the Cu2S peak in XRD supported the conclusion. The magnetic and electrical properties of LK-99 with and without Cu2S suggest that the superconductor-like behavior in LK-99 predominantly arises from a transition in resistivity due to the influence of Cu2S. As such, LK-99 is better classified as a diamagnetic semiconductor than a room-temperature superconductor. The room-temperature superconductors still require further research.

LncRNA CYTOR promotes lung adenocarcinoma gemcitabine resistance and epithelial-mesenchymal transition by sponging miR-125a-5p and upregulating ANLN and RRM2.

Lung adenocarcinoma (LUAD) is one of the most aggressive types of lung cancer. The prognosis of LUAD patients remains poor, and the overall efficacy of gemcitabine-based chemotherapy is still unsatisfactory. Long noncoding RNAs (lncRNAs) play important roles in several cancer types by interacting with multiple proteins, RNA, and DNA. However, the relationship between lncRNA dysregulation and gemcitabine resistance in LUAD has not been fully elucidated. In this study, lncRNA CYTOR expression and its association with the prognosis of LUAD patients are assessed by quantitative RT-PCR and Kaplan-Meier survival analysis. In vitro and in vivo functional studies are conducted to evaluate the biological functions of CYTOR in LUAD. The underlying mechanism regarding the tumor-promoting effects of CYTOR is explored using RNA immunoprecipitation, biotin-labelled RNA pulldown, luciferase reporter assays, and western blot analysis. We identify that CYTOR is an oncogenic lncRNA and is apparently upregulated in LUAD by analysing TCGA-LUAD data. High CYTOR expression is a poor prognostic factor for LUAD. Functional studies reveal that CYTOR confers LUAD cells with stronger resistance to gemcitabine treatment and upregulates the expression levels of epithelial-mesenchymal transition (EMT)-related proteins. Mechanically, CYTOR acts as a competitive endogenous RNA (ceRNA) to absorb miR-125a-5p, weakens the antitumor function of miR-125a-5p, and ultimately upregulates ANLN and RRM2 expressions. Taken together, this study explains the mechanism of lncRNA in the gemcitabine resistance of LUAD and formulates a theoretical framework for the in depth study of LUAD.

In-Plane Anisotropy of Electrical Transport in Y0.85Tb0.15Ba2Cu3O7-x Films.

We fabricated high-quality c-axis-oriented epitaxial YBa2Cu3O7-x films with 15% of the yttrium atoms replaced by terbium (YTBCO) and studied their electrical properties. The Tb substitution reduced the charge carrier density, resulting in increased resistivity and decreased critical current density compared to pure YBa2Cu3O7-x films. The electrical properties of the YTBCO films showed an in-plane anisotropy in both the superconducting and normal states that, together with the XRD data, provided evidence for, at least, a partially twin-free film. Unexpectedly, the resistive transition of the bridges also demonstrated the in-plane anisotropy that could be explained within the framework of Tinkham's model of resistive transition and the Berezinskii-Kosterlitz-Thouless (BKT) model, depending on the sample parameters. Measurements of the differential resistance in the temperature range of the resistive transition confirmed the occurrence of the BKT transition in the YTBCO bridges. Therefore, we consider the YTBCO films to be a promising platform for both the fabrication of devices with high kinetic inductance and fundamental research on the BKT transition in cuprate superconductors.

Magnetic-Field Response and Giant Electric-Field Modulation of Cu2S.

Cu2S likely plays an important role in the sharp resistivity transition of LK-99. Nevertheless, this immediately arouses an intriguing question of whether the extraordinary room-temperature colossal magnetoresistance in the initial reports, which has been less focused, originates from Cu2S as well. To resolve this issue, we have systematically investigated the electrical transport and magnetotransport properties of near-stoichiometric Cu2S pellets and thin films. Neither Cu2S nor LK-99 containing Cu2S in this study was found to exhibit the remarkable magnetoresistance effect implied by Lee et al. This implies that Cu2S could not account for all of the intriguing transport properties of the initially reported LK-99, and the initially reported LK-99 samples might contain magnetic impurities. Moreover, based on the crystal-structure-sensitive electrical properties of Cu2S, we have constructed a piezoelectric-strain-controlled device and obtained a giant and reversible resistance modulation of 2 orders of magnitude at room temperature, yielding a huge gauge factor of 160,000.

Origin of the near-room temperature resistance transition in lutetium with H2/N2 gas mixture under high pressure.

The recent report of room-temperature superconductivity at near-ambient pressure in nitrogen-doped lutetium hydride (Lu-H-N) by Dasenbrock-Gammon etal. [Nature 615, 244-250 (2023)] has attracted tremendous attention due to its anticipated great impact on technology. However, the results could not be independently reproduced by other groups worldwide in follow-up studies, which elicited intense controversy. Here, we develop a reliable experimental protocol to minimize the extensively concerned extrinsic influences on the sample by starting the reaction from pure lutetium loaded with an H2/N2 gas mixture in a diamond anvil cell under different pressures and temperatures and simultaneously monitoring the entire chemical reaction process using in situ four-probe resistance measurements. Therefore, we could repeatedly reproduce the near-room temperature upsurge of electrical resistance at a relatively early stage of the chemical reaction. However, the mechanism is suggested to be a metal-to-semiconductor/insulator transition associated with the structural modulation in the non-stoichiometric Lu-H-N, rather than superconductivity.

Magnetic ac susceptibility of superconducting Ta films for quantum computing

Recently, breakthroughs were reported in the long coherence time (>0.5 ms) transmon qubit using tantalum films (Ta). Identifying the loss mechanism in Ta films will help further improve the performance of Ta-based superconducting qubits. Here, we report a study of superconducting properties in two sets of Ta films grown on c-cut and a-cut sapphires respectively using contact transport and noncontact magnetic ac susceptibility measurements. Although the resistive transition appears to be similar in both films, we found strikingly different responses in their complex magnetic susceptibilities . in the c-cut films exhibits a sharp peak at superconducting transition T c and becomes featureless below T c indicating a strongly coupled superconducting state. In contrast, in the a-cut films exhibits a broad peak near T c and a second peak appears below T c, indicating granular superconductivity behavior. This second peak in is associated with the hysteresis loss at weak-link-type grain boundaries, which is believed to be a leading source of decoherence in the a-cut Ta films. The derived magnetic loss tangent in the a-cut films is about one order of magnitude higher than in the c-cut films. This study demonstrates that ac susceptibility is an excellent probe for characterizing bulk superconducting properties of the constituent superconducting materials used in qubits.

Dynamics of cascades in spatial interdependent networks.

The dynamics of cascading failures in spatial interdependent networks significantly depends on the interaction range of dependency couplings between layers. In particular, for an increasing range of dependency couplings, different types of phase transition accompanied by various cascade kinetics can be observed, including mixed-order transition characterized by critical branching phenomena, first-order transition with nucleation cascades, and continuous second-order transition with weak cascades. We also describe the dynamics of cascades at the mutual mixed-order resistive transition in interdependent superconductors and show its similarity to that of percolation of interdependent abstract networks. Finally, we lay out our perspectives for the experimental observation of these phenomena, their phase diagrams, and the underlying kinetics, in the context of physical interdependent networks. Our studies of interdependent networks shed light on the possible mechanisms of three known types of phase transitions, second order, first order, and mixed order as well as predicting a novel fourth type where a microscopic intervention will yield a macroscopic phase transition.

Resistance Transition of Pseudomonas aeruginosa in SARS-CoV-2-Uninfected Hospitalized Patients in the Pandemic.

To investigate the impact of coronavirus disease 2019 (COVID-19) specified preventive and control measures on the distribution and resistance transition of Pseudomonas aeruginosa (P. aeruginosa) in uninfected hospitalized patients during the pandemic. This retrospective study retrieved data from 316 P. aeruginosa isolates in the year pre-COVID-19 (n=131) pandemic and the year under COVID-19 specified preventive and control (post-pandemic year, n=185), compared the general characteristics, laboratory results, and antimicrobial susceptibility tests of P. aeruginosa between the two groups. Compared with the pre-pandemic year, the isolation rate of P. aeruginosa (14.35% vs 22.31%, P<0.001) increased, while the rate of drug resistant P. aeruginosa decreased significantly (29.77% vs 19.45%, P<0.001) in the post-pandemic year; Prescription of β-Lactams (30.5% vs 50.0%, P<0.01) also increased significantly. The resistance rates of P. aeruginosa isolates to ceftazidime (P<0.01), ciprofloxacin (P<0.01), and gentamicin (P<0.001) increased, whereas the resistance rates to piperacillin/tazobactam (P<0.01) and imipenem (P<0.05) decreased significantly. The COVID-19 specified preventive and control measures have influenced the distribution and resistance transition of P. aeruginosa, further verifications are needed in future research.

Encoding multistate charge order and chirality in endotaxial heterostructures

High-density phase change memory (PCM) storage is proposed for materials with multiple intermediate resistance states, which have been observed in 1T-TaS2 due to charge density wave (CDW) phase transitions. However, the metastability responsible for this behavior makes the presence of multistate switching unpredictable in TaS2 devices. Here, we demonstrate the fabrication of nanothick verti-lateral H-TaS2/1T-TaS2 heterostructures in which the number of endotaxial metallic H-TaS2 monolayers dictates the number of resistance transitions in 1T-TaS2 lamellae near room temperature. Further, we also observe optically active heterochirality in the CDW superlattice structure, which is modulated in concert with the resistivity steps, and we show how strain engineering can be used to nucleate these polytype conversions. This work positions the principle of endotaxial heterostructures as a promising conceptual framework for reliable, non-volatile, and multi-level switching of structure, chirality, and resistance.

Simultaneously low resistance drift and ultra‐fast phase change speed based on GeSb/Sb multilayer thin films

AbstractThermal stability and phase transition rate are two important issues that restrict the engineering applications of phase change memories. In this paper, GeSb/Sb multilayer films were prepared by multilayer stacking, and their phase transition properties were investigated. GeSb/Sb multilayer films had higher crystallization temperature, better data retention, and lower resistance drift than pure Sb films, which indicated that they had excellent thermal stability and accuracy of resistance identification. The test results of X‐ray diffraction and atomic force microscopy showed that GeSb spacer layers could inhibit grain growth of Sb film layers, thus reducing the roughness and potential fluctuation of the film surface. X‐ray reflectivity experiments showed that the GeSb/Sb multilayer films before and after crystallization had small volume changes. The devices based on [GeSb(7 nm)/Sb(3 nm)]8 multilayer films could achieve reversible resistive transition operation between SET and RESET at a pulse width of 10 ns, showing satisfactory transition rate and operational power consumption. The low resistance drift and ultra‐fast phase transition speed make GeSb/Sb multilayer films one of the promising choices for phase change memories.