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Metal–organic framework (MOF)-derived composites have gained wide attention due to their specific structures and enhanced performance. In this work, we prepared carbon nanotubes with Fe nanoparticles connected to two-dimensional (2D) hierarchical carbon network composites via a low-pressure gas–solid reaction strategy. Specifically, the three-dimensional (3D) networks derived from ZIF-8 exploited the carbon nanotubes with the function of charge modulation. Meanwhile, we utilized the interconnected 2D nanostructures to optimize impedance matching and facilitate multiple scattering, ultimately improving the overall microwave absorption performance. Furthermore, based on the well-designed structures, the composites prepared at 800 °C (Fe-N-C@CNTs-800) achieved the best reflection loss (RL) of −58.5 dB, thereby obtaining superior microwave absorption performance. Overall, this study provides a good groundwork for further investigation into the modification and dimension design of novel hierarchical microwave absorbers. [ABSTRACT FROM AUTHOR]

The design and fabrication of high-performance electrode devices are highly important for the practical application of electrochemical sensors. In this study, flexible three-dimensional porous graphene electrode devices were first facilely fabricated using common laser ablation technique at room temperature. After then, hydrophilic two-dimensional MXene (Ti 3 C 2 T x) nanosheet was decorated on the surface of the laser-induced graphene (LIG), resulting in disposable Ti 3 C 2 T x /LIG electrode devices. After introducing Ti 3 C 2 T x nanosheet, the electrochemical active area, electron transfer ability of LIG electrode device and its adsorption efficiency toward organic pesticide benomyl was significantly boosted. As a result, the fabricated Ti 3 C 2 T x /LIG electrode device exhibited significantly enhanced electrocatalytic activity toward benomyl oxidation. Based on this, a novel and ultra-sensitive electrochemical platform for micro-droplet detection of benomyl was achieved in the range of 10 nM–6000 nM with detection sensitivity of 169.9 μA μM−1 cm−2 and detection limit of 5.8 nM. Considering the low-cost Ti 3 C 2 T x /LIG electrode devices are rarely used for electrochemical analysis, we believed this research work will contribute to exploring the broader application of MXene/LIG electrode devices in the field of electrochemical sensing. [Display omitted] • Disposable and low-cost Ti 3 C 2 T x /LIG-based electrode devices were facilely prepared. • Hydrophilic Ti 3 C 2 T x nanosheets and LIG displayed obvious synergistic effect. • Ti 3 C 2 T x /LIG-based electrode devices exhibited superior electro-activity toward benomyl oxidation. • Rapid and sensitive detection of benomyl can be finished in a micro-droplet. [ABSTRACT FROM AUTHOR]

Highly n-doped silicon nanowires (SiNWs) exhibit excellent hydrogen generation. Our results indicate three hydrogen generation possibilities, i.e. SiNWs oxidation, photocatalysis and the cleavage of dangling H bonds, are jointly responsible for the efficient hydrogen generation. Oxidation accounts for about 80% of total hydrogen, photocatalysis contributes less than 20% of total hydrogen, and about 0.1% of total hydrogen is from cleavage of dangling H bonds. SiNWs were oxidized in water and form SiO x (0 < X < 2) thin layer. Furthermore, the ratio of photo-generated hydrogen to photo-generated oxygen is about 2.4:1. It suggests that photocatalysis appears to be a process of water splitting. This study is significant to reveal the mechanism of hydrogen production on SiNWs prepared by Metal-Assisted Wet Chemical Etching (MAWC). [Display omitted] • SiNWs were reported to produce H 2 in water as photocatalyst. However, the mechanism of hydrogen generation on SiNWs has not been clarified. Is it real water splitting? As far as We know, there is no clear conclusion on this issue at present. A accurate numerical computation of hydrogen and oxygen generation was given in the manuscript. Our results indicate SiNWs oxidation, photocatalysis and the cleavage of dangling H bonds, are jointly responsible for the efficient hydrogen generation. The ratio of photo-generated hydrogen to photo-generated oxygen is about 2.4:1, it is close to the theoretical ration of water splitting. [ABSTRACT FROM AUTHOR]

Matroid theory is a useful tool for the combinatorial optimization issue in data mining, machine learning and knowledge discovery. Recently, combining matroid theory with rough sets is becoming interesting. In this paper, rough set approaches are used to investigate an important class of matroids, transversal matroids. We first extend the concept of upper approximation number functions in rough set theory and propose the notion of generalized upper approximation number functions on a set system. By means of the new notion, we give some necessary and sufficient conditions for a subset to be a partial transversal of a set system. Furthermore, we obtain a new description of a transversal matroid by the generalized upper approximation number function. We show that a transversal matroid can be induced by the generalized upper approximation number function which can be decomposed into the sum of some elementary generalized upper approximation number functions. Conversely, we also prove that a generalized upper approximation number function can induce a transversal matroid. Finally, we apply the generalized upper approximation number function to study the relationship among transversal matroids. [ABSTRACT FROM AUTHOR]

In the era of big data, the memory wall between the processor and the memory as well as leakage current have become major bottlenecks of the traditional CMOS-based Von-Neumann computer architecture. Computing-in-memory (CiM) based on non-volatile memories (NVMs) is considered a promising method to solve the above-mentioned issues in computing systems. In this article, we propose a CiM platform based on spin-transfer torque magnetic random access memory (STT-MRAM). On the basis of the conventional CiM with AND/OR logic functions, the full-adder (FA) arithmetic operation is achieved with slight circuits modification by exploiting majority logic. Due to the parallel processing of carry and sum operations in multi-bit FA operation, the latency overhead caused by the two-step scheme is acceptable. The hybrid spintronic/CMOS simulations on the 40 nm technology node prove the functionality and performance of the proposed CiM platform. [ABSTRACT FROM AUTHOR]

Uncertainty measures are important tools for analyzing various data. However, there are relatively few studies on the uncertainty measures for covering rough set models. In this paper, from the viewpoint of the lower and upper approximations, we propose new uncertainty measures, the lower rough entropy and the upper rough entropy, for covering rough set models. Then, we define the concepts of the joint entropy and the conditional entropy in the covering rough set models. Some important properties of these measures are obtained, and their relationships are investigated. Furthermore, we provide a certain characterization of reducible element of a covering by means of the proposed measures, and apply the proposed rough entropy to evaluate the significance of covering granules of a covering. Finally, we apply these rough entropies to measure a dual degree between covering lower and upper approximations. The theoretical analysis and examples show that the proposed uncertainty measures for covering rough set models are reasonable and useful. [ABSTRACT FROM AUTHOR]

Recent progress has demonstrated that current-induced domain wall motion (CIDWM) is able to achieve efficient and ultrafast magnetic switching in the case of spin–orbit torque (SOT) and Dzyaloshinskii–Moriya interaction (DMI). CIDWM-based devices are taken as promising candidates for the next-generation nonvolatile artificial neurons and synapses due to its excellent programmability, fast operation speed, low write power, and so on. In this article, we present a physics-based model of CIDWM magnetic tunnel junction (MTJ), which exhibits high performance based on experimental results. The proposed model integrates the CIDWM dynamics and nanowire MTJ resistance, showing great agreement with extensive physical simulation. A learning circuit based on CIDWM-MTJ, as a hybrid MTJ/CMOS circuit example, has been designed and simulated to validate its functionality. The proposed SPICE-compatible compact model will be useful for high-performance circuit and system evaluation and is expected to promote the research and development of CIDWM-based spintronics devices. [ABSTRACT FROM AUTHOR]

A double-interface CoFeB/MgO magnetic tunnel junction (MTJ) has a high thermal stability barrier (E) and high-efficiency magnetization switching with the scaling of device dimensions. However, compared to a single-interface CoFeB/MgO MTJ, its more complicated film stacks and interfaces are more vulnerable to irradiation-induced swift heavy ions. We have studied the irradiation effects of Ta/Kr ions on double-interface CoFeB/MgO MTJs. Structural and physical analyses are performed through transmission electron microscopy, energy dispersive x-ray spectroscopy, and vibrating sample magnetometry. 1907 MeV Ta-ion irradiation damages the interfaces of the double-interface MTJ, resulting in the irreversible decrease in coercivity, while 2060 MeV Kr-ion irradiation damages the bulk properties of the MTJ, leading to the decrease in saturation magnetization. However, the electronic properties of the double-interface MTJ are almost immune to Kr-ion irradiation. [ABSTRACT FROM AUTHOR]

Covering rough set model is an important extension of Pawlak rough set model, and its structure is the foundation of covering rough set theory. This paper considers four covering approximations and studies the structures of the families of their covering upper (or lower) definable sets by means of lattice theory. We provide some conditions under which the families of covering upper (or lower) definable sets with respect to these covering approximations are lattices of sets, or distributive lattices, or geometric lattices, or Boolean lattices. Furthermore, based on these results, we give the relationship among the four covering approximations and establish the connection between matroids and covering rough sets from the viewpoint of lattice theory. [ABSTRACT FROM AUTHOR]

Covering rough set model is an important extension of Pawlak rough set model, and its structure is the foundation of covering rough set theory. This paper considers four covering approximations and studies the structures of the families of their covering upper (or lower) definable sets by means of lattice theory. We provide some conditions under which the families of covering upper (or lower) definable sets with respect to these covering approximations are lattices of sets, or distributive lattices, or geometric lattices, or Boolean lattices. Furthermore, based on these results, we give the relationship among the four covering approximations and establish the connection between matroids and covering rough sets from the viewpoint of lattice theory. [ABSTRACT FROM AUTHOR]

Uncertainty measures are an important tool for analyzing data. There is the uncertainty of a rough set caused by its boundary region in rough set models. Thus the uncertainty measurement issue is also an important topic for rough set theory. Shannon entropy has been introduced into rough set theory. However, there are relatively few studies on the uncertainty measure in generalized rough set models. We know that the boundary region of a rough set is closely related to the upper and lower approximations in rough set models. In this paper, from the viewpoint of the upper and lower approximations, we propose new uncertainty measures, the upper rough entropy and the lower rough entropy, in generalized rough set models. Then we focus on the investigations of the upper rough entropy, and give the concepts of the upper joint entropy, the upper conditional entropy and the mutual information with respect to a general binary relation. Some important properties of these measures are obtained. The connections among these measures are given. Furthermore, comparing with the existing uncertainty measures, the upper rough entropy has high distinguishing degree. Theoretical analysis and experimental results show that the proposed entropy is better effective than some existing measures. [ABSTRACT FROM AUTHOR]

Perpendicular-anisotropy magnetic tunnel junction (p-MTJ), a type of magnetic storage element, has shown outstanding performances in terms of high density, good scalability, and low power. In particular, the double-interface CoFeB/MgO p-MTJ with W spacer and bridging layers was recently demonstrated. This device shows a large tunnel magnetoresistance ratio, low junction resistance, and high robustness against high-temperature annealing. To consider this type of p-MTJ for the space environment, the gamma irradiation effects need to be evaluated. In this paper, the double-interface CoFeB/MgO multifilms are exposed to the gamma irradiation at different doses. The gamma irradiation effects on double-interface CoFeB/MgO multifilms are experimentally evaluated based on the comparison between the results of prerad and postrad magnetic properties. In the case of a low irradiation dose, the coercivity gradually increases with the increasing dose, whereas no variation is observed for the saturation magnetization. However, the magnetism is destroyed if the irradiation dose is sufficiently high. Some possible mechanisms are discussed to explain the experimental results. [ABSTRACT FROM AUTHOR]

Ultrahigh-speed magnetization switching mechanism is strongly pursued, as it can improve the write performance of the magnetic random access memory (MRAM) and further extend the application area of spintronics. Currently, a well-studied switching mechanism is the spin transfer torque (STT), whose speed, however, is limited by an intrinsic incubation delay. Recently, spin–orbit torque (SOT) was proposed to solve the speed bottleneck of the STT. In this paper, we evaluate the potential of two types of SOT-MRAMs, whose data can be ultrafast written based on the recently discovered field-free SOT mechanisms, respectively. A cross-layer analysis is presented involving device modeling, circuit-level optimization, and architecture-level evaluation. First, the principle of the magnetization switching is analyzed with the macrospin simulation. Then, the optimization strategies at the circuit level are generalized through the SPICE-type simulation. Finally, we build up the memory architecture with the SOT-MRAMs, STT-MRAM, and static RAM. Their read/write performances are evaluated with NVSim software. It is demonstrated that one of the studied SOT-MRAMs shows the promising prospect in the non-volatile memory, especially suitable for high-capacity cache. [ABSTRACT FROM AUTHOR]

The conductivity of spin field-effect transistor (spin-FET) can be modulated by controlling the spin degree of freedom; therefore, emerging low-power applications can be explored. In this paper, we propose a novel device called multi-gate spin-FET where multi-gate voltages can successively modulate the spin of the electrons. Various logic functions can be implemented with multi-gate spin-FET by setting the appropriate channel lengths. First, we present an electrical model of the multi-gate spin-FET which considers the physical mechanisms and the fitting of experimental results. The availability of the electrical model is validated by the dc simulation. Afterward, typical logic circuits are designed with the multi-gate spin-FET, including NAND gate, XOR gate, full adder, and a representative three-input logic gate. Transient simulation results validate the functional behaviors of these logic circuits. Finally, based on an analysis of power consumption, we conclude that the multi-gate spin-FET is a more energy-efficient device compared with the conventional CMOS FET. [ABSTRACT FROM AUTHOR]

Magnetic random access memory (MRAM) is experimentally proved intrinsically immune to radiation effects including heavy-ion irradiation and total ion dose as the data are represented by the spin instead of charges. Hence, it is considered as a promising candidate for aerospace and avionic electronics. However, its CMOS peripheral read/write circuits are much more vulnerable to radiation-induced single-event upset (SEU) and double-node upset (DNU) induced by charge sharing. This paper presents a novel radiation-hardening design of the peripheral circuitry for spin orbit torque (SOT)-MRAM to address abovementioned issues effectively. Transient simulations are performed based on a physics-based SOT-magnetic tunnel junction compact model and a 65 nm CMOS design kit. Simulation results validate that the proposed hardening read/write circuits are strongly robust against SEUs and DNUs. Furthermore, the proposed hardening read circuit shows the improvement of hardware area and reliability compared with the previous works. [ABSTRACT FROM AUTHOR]

Spintronics-based devices and circuits attract massive research interest from both academia and industry. A number of the devices and logic circuits have been proposed such as spin-based magnetic tunnel junction and all spin logic gate. A fundamental spin-based device, spin field-effect transistor (spin-FET) is one of the most interesting spin-based devices to address the power issue of semiconductor transistors which is still a research focus. In this paper, we first present an electrical model for the spin-FET based on both theoretical and experimental results. The theories of spin injection and detection are considered by a current driver of the spin-FET. Gate voltage modulation following Datta–Das theory is combined with the experimental results from several works of literature. Afterward, through the dc analysis of two spin-FETs with different channel materials, we demonstrate that the channel using InAs is a better choice to make a feasible spin-FET. The channel length is also optimized by the comparison of simulation results. Finally, a local geometry spin-FET model suitable for logic design is implemented with Verilog-A language and integrated on Cadence platform. Using our model, a low-power inverter is designed based on the concept of complementary spin-FET, and a logic circuit is proposed to implement AND and NOR logic functions. Simulation results validate the behaviors of the logic circuits and availability of our model. [ABSTRACT FROM AUTHOR]

Perpendicular-anisotropy magnetic tunnel junction (MTJ) is one of the most promising candidates to build hybrid logic-in-memory architecture, because of its nonvolatility, infinite endurance, and 3-D integration with a CMOS technology. A novel magnetic full-adder (MFA) based on this architecture is proposed, with MTJs switched by spin-Hall-assisted spin-transfer torque (STT). Owing to the assistance of spin-Hall effect (SHE), MTJ switching time can significantly be reduced, and high operation frequency can be achieved. Moreover, the endurance of oxide barrier is largely enhanced as the requirement of lower write voltage. Using an industrial CMOS 28 nm design kit and a physics-based three-terminal spin-Hall-assisted STT-MTJ model, functionality and performance of the proposed MFA have been simulated and validated. A 1 ns STT current pulse assisted by 0.35 ns SHE current pulse is sufficient to switch the MTJ configuration. When compared with the previous MFAs based on STT-MTJ, the proposed MFA achieves 38% less operation time and 31% less power consumption to perform read and write operations. [ABSTRACT FROM AUTHOR]

A novel multi-bit non-volatile flip-flop (NVFF) written by spin-Hall-assisted spin-transfer torque (STT) is proposed. This NVFF employs perpendicular-anisotropy MTJs and requires an STT current combined with a spin-Hall current to write the data. Thanks to the assistance of spin-Hall effect (SHE), the incubation delay required by the conventional STT switching can be eliminated to achieve fast operation. Our proposed NVFF uses multi-bit architecture and shows high-density and low-energy advantages over hybrid NV/volatile FFs in the application of the NV register file. Sim-ulation results show that the proposed spin-Hall-assisted NVFF saves ∼31% storage density and ∼32% energy dissipation compared with the conventional STT-NVFF. Moreover, the reliability of MTJ barrier is enhanced due to the reduction of the write voltage. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Thanks to the progress in nonvolatile (NV) devices, such as magnetic tunnel junctions and phase change memories, various NV logic blocks have recently been proposed to overcome energy/delay bottlenecks caused by von Neumann computing architecture. The ferroelectric tunnel memristor (FTM) is an emerging NV multilevel device and was recently reported to show excellent performance. In this paper, we demonstrated that the short-circuit effect in an FTM provides the opportunity to design a novel FTM-based Boolean logic block. This block is composed of an FTM and a load resistor. Unlike classical schemes, where at least two cells are required as operands, our FTM-based block implements logic operation inside a single memristor. With a compact model of an FTM, transient simulation is performed to validate NAND and NOR logic functions. Finally, we provide the method of performance optimization and discuss the advantages/disadvantages of the proposed logic block to summarize our work. [ABSTRACT FROM AUTHOR]

Ferroelectric tunnel junction (FTJ) is able to store non-volatile data in the spontaneous polarization direction of ferroelectric tunnel barrier. Recent progress has demonstrated its great potential to build up the next generation non-volatile memory and logic (NVM and NVL) thanks to the high OFF/ON resistance ratio, fast operation speed, low write power, non-destructive readout and so on. In this paper, we present the first physics-based compact model for Co/BTO/LSMO FTJ nanopillar, which was reported experimentally to exhibit excellent NVM performance. This model integrates related physical models of tunnel resistance, static switching voltage and dynamic switching delay. Its accuracy is shown by the good agreement between numerical model simulation and experimental measurements. This compact model has been developed in Verilog-A language and validated by single-cell simulation on Cadence Virtuoso Platform. Hybrid simulations based on 40 nm-technology node of FTJ memory arrays and non-volatile full adder were performed to demonstrate the efficiency of our compact model for the simulation and analysis of CMOS/FTJ integrated circuits. [ABSTRACT FROM AUTHOR]

Rough set theory is an important technique in knowledge discovery in databases. In covering-based rough sets, seven types of rough set models were established in recent years. This paper defines the concept of maximal description of an element, and further explores the properties and structures of several types by means of the concepts of maximal description and minimal description. Finally, we study the relationship between covering-based rough sets and the generalized rough sets based on binary relation. [ABSTRACT FROM AUTHOR]

Objectives: We previously reported that Golgi phosphoprotein 3 (GOLPH3) promotes glioma progression by inhibiting EGFR endocytosis and degradation, leading to EGFR accumulation and PI3K‐AKT pathway over‐activation. In the current study, we examine whether GOLPH3 affects the response of glioma cells to gefitinib, an EGFR selective inhibitor. Materials and Methods: The expression of GOLPH3 and EGFR in glioma cells was detected by immunofluorescence and immunoblotting. The cell viability or growth in vitro was determined by CCK‐8, EdU incorporation and clonogenic assays. The primary glioma cells were cultured by trypsin and mechanical digestion. The transwell invasion assay was used to examine the primary glioma cell motility. Intracranial glioma model in nude mice were established to explore the sensitivity of gefitinib to GOLPH3 high cancer cells in vivo. Results: Both the immortalized and primary glioma cells with GOLPH3 over‐expression hold higher EGFR protein levels on the cell membrane and exhibited higher sensitivity to gefitinib. In addition, primary glioma cells with higher GOLPH3 level exhibited stronger proliferation behaviour. Importantly, GOLPH3 enhanced the anti‐tumour effect of gefitinib in vivo. Consistently, after gefitinib treatment, tumours derived from GOLPH3 over‐expression cells exhibited lower Ki67‐positive and higher cleaved caspase‐3–positive cells than control tumours. Conclusions: Our results demonstrate that GOLPH3 increases the sensitivity of glioma cells to gefitinib. Our study provides foundation for further exploring whether GOLPH3 high gliomas will be more sensitive to anti‐EGFR therapy in clinic and give ideas for developing new possible treatments for individual glioma patients. [ABSTRACT FROM AUTHOR]

Spin-transfer torque magnetic random access memory (STT-MRAM) offers nonvolatility, good scalability, high speed, and low-power benefits. Multilevel cell (MLC) is an efficient technology to boost the storage density of the STT-MRAM. However, the conventional MLC structure is not suitable for more than 2-b storage due to inefficient multistep read/write operations. In this article, combining the emerging spin-orbit torque (SOT) and STT mechanisms, we propose a novel STT/SOT hybrid triple-level cell (TLC) MRAM cell structure. Corresponding write and read schemes are designed for this hybrid bit-cell to achieve low-cost operations. Unlike the regular stacked TLC, 3-b data can be written in two steps in the proposed cell structure, and be read in parallel with the assistance of SOT. Simulation results show that the proposed structure achieves 32% and 43% savings on write delay and energy consumption, respectively. Monte Carlo statistic simulation results indicate 1.4 × improvement in sensing margin as well. [ABSTRACT FROM AUTHOR]

Approximation is an important issue in rough set theory. In this study, we consider approximation by the matroidal approach. First, we study three lattices induced by an information system. Two of the three lattices are selected as the macrostructure and microstructure for approximation, respectively. Second, based on the two lattices, we define double-matroid lattices, where the upper and lower approximations with respect to an information system are depicted. Since the two lattices are geometric, we actually present approximation by the matroidal approach. Finally, we study the connection between our double-matroid lattices and granular partition lattices. Specifically, the comparison of these two structures is presented in both micro-level and macro-level. [ABSTRACT FROM AUTHOR]

In the current big data era, the memory wall issue between the processor and the memory becomes one of the most critical bottlenecks for conventional Von-Newman computer architecture. In-memory processing (IMP) or near-memory processing (NMP) paradigms have been proposed to address this problem by adding a small amount of processing units inside/near the memory. Unfortunately, although intensively studied, prior IMP/NMP platforms are practically unsuccessful because of the fabrication complexity and cost efficiency by integrating the processing units and memory on the same chip. Recently, emerging nonvolatile memories provide new possibility for efficiently implementing the IMP/NMP paradigm. In this paper, we propose a cost-efficient IMP/NMP solution in spin-transfer torque magnetic random access memory (STT–MRAM) without adding any processing units on the memory chip. The key idea behind the proposed IMP/NMP solution is to exploit the peripheral circuitry already existing inside memory (or with minimal changes) to perform bitwise logic operations. Such an IMP/NMP platform enables rather fast logic operations as the logic results can be obtained immediately through just a memory-like readout operation. Memory read and logics not, and/nand, and or/nor operations can be achieved and dynamically configured within the same STT–MRAM chip. Functionality and performance are evaluated with hybrid simulations under the 40 nm technology node. [ABSTRACT FROM AUTHOR]

With the rapid increase of leakage currents, non-volatile memories have become competitive candidates in the next-generation computer architecture. Among them, STT-MRAM shows great promise in working memory with high density, high speed and tremendous endurance, etc. However, based on our investigations, the dynamic write power and read reliability are two critical challenges of STT-MRAM. In this work, we propose a synergistic pseudo-differential sensing (PDS) framework that employs device, circuit and architectural techniques to address these challenges. In specific, three design techniques, including cell cluster, asymmetric sensing amplifier and self-error-detection-correction, are proposed to implement the PDS framework. We show that the holistic device-circuit-architecture cross-layer co-design enables STT-MRAM to be utilized in the cache memory, benefiting from the improved density, reliability and energy-efficiency. Our experimental results show that the proposed PDS scheme improves the read margin by ∼35.6 percent, reduces the area, read latency, read energy, write latency and write power by ∼46.7, ∼9.8, ∼30.3, ∼2.3 and ∼31.1 percent respectively, compared with the typical 1T1MTJ cell structure for the cache capacity of 8 MB. In addition, the proposed PDS scheme reduces the dynamic energy by ∼32.9 percent and leakage energy by ∼830 percent, improves the IPC by ∼1.3 percent and miss rate by ∼36.9 percent respectively, compared with conventional SRAM based cache. [ABSTRACT FROM AUTHOR]

Ionic gels are attracting enormous attention due to their good conductivity and multifunctionality that are required for electronic devices. However, diverse applications require ionic gels whose mechanical properties can be adjusted to satisfy different demands. Herein, we designed and prepared conductive and self-healing ionic gels from deep eutectic monomers (DEMs) with adjustable mechanical properties via frontal polymerization (FP). FTIR and 1H-NMR spectra confirmed that there were the multiple hydrogen bonds in DEMs. The obtained DEMs were investigated for preparing self-healing ionic gels by FP. The FP experiments shown that higher molar ratio of AAc and AM caused a decrease in front velocity (Vf) and maximum front temperature (Tmax), while higher content of crosslinker led to an increase in Vf and Tmax. The mechanical properties of ionic gels can be adjusted by changing the molar ratio of AAc and AM. The tensile strength varied in the range from 0.11 to 0.85 MPa, and compression stress was different from 9.17 to 35.91 MPa (at a compression stress of 80%), respectively. The elongation rate became from 16.13 to 157.56%. The multiple hydrogen bonds in the ionic gels enabled them a rapid self-healing ability. In addition, the ion conductivities of ionic gels improved remarkably after water adsorption. The present study provides a rapid and green strategy to prepare conductive and self-healing ionic gels with turnable mechanical properties, which may inspire more future research studies for flexible electronic materials. [ABSTRACT FROM AUTHOR]

Spin-transfer torque magnetic random access memory (STT-MRAM) has emerged as a promising candidate for the next-generation high-speed, low-power, and scalable nonvolatile memory technology. Its advantageous features have attracted much attention in the area of research and development, and a number of preindustrial prototypes and small-scale products have been demonstrated. One expects to widely commercialize it in the next few years. One of the critical issues that blocks STT-MRAM’s wide commercialization is its low sensing reliability due to the relatively small tunnel magnetoresistance ratio of the magnetic tunnel junction (MTJ) and the continuously increasing process variations, especially as technology process scales down to the deep submicrometer nodes (e.g., 40 nm). In this paper, we present a variation-tolerant high-reliability sensing circuit for deep submicrometer STT-MRAM. This circuit, using triple-stage sensing and charge transfer amplification, is able to tolerate significantly the process variations and improve greatly the sensing margin by sacrificing some sensing time. Using a CMOS 40 nm design kit and a precise STT-MTJ compact model, transient and Monte Carlo simulations have been carried out to demonstrate its sensing performance. [ABSTRACT FROM AUTHOR]

Spin transfer torque-based magnetic random access memory (STT-MRAM) is considered as one of the most promising candidates for the next generation of nonvolatile memories; however, its storage density and reliability are currently uncompetitive compared with other nonvolatile memories (e.g., NAND flash). In this paper, a dual-functional memory cell structure, named DFSTT-MRAM, is proposed by stacking multiple magnetic tunnel junctions (MTJs) on top of the CMOS access transistor. In such a structure, the cell can be dynamically configured between two possible functional modes, i.e., high-reliability mode (HR-mode) and multilevel cell mode (MLC-mode), based on the data requirements of the addressed applications. The DFSTT-MRAM cell was electrically modeled based on the perpendicular magnetic anisotropy CoFeB/MgO/CoFeB MTJ integrating the STT stochastic switching behaviors. Transient and Monte Carlo simulations were then performed to evaluate its MLC functionality and reliability performance. Our evaluation results show that the DFSTT-MRAM cell can indeed realize MLC capability providing proper write/read control at the MLC-mode and enhance the intrinsic cell reliability by several orders of magnitude when operating at the HR-mode. This cell structure provides a flexible memory cell design for future advanced applications, such as high-density nonvolatile memory and neuromorphic circuits. [ABSTRACT FROM AUTHOR]

Highlights: [•] We analyse and model the reliability issue in STT-MRAM. [•] We present a low-cost OLSC circuit to improve STT-MRAM reliability. [•] Built-in-form implementation using STT-MRAM-based logic acts as an inner code. [•] Its simple codec provides very low area and high speed. [•] Modular codec structure enables adaptive error correction capability. [Copyright &y& Elsevier]

Spin–orbit torque magnetic tunnel junction (SOT-MTJ) is the memory cell of magnetic random access memory (MRAM), which is a promising candidate for upper level cache in the harsh environment due to nonvolatility, high speed, and high endurance. Therefore, it is significant to research the mechanism of irradiation effects on the SOT-MTJ before its integration onboard. This article investigates the ionization and displacement damage of in-plane magnetic anisotropy SOT-MTJ, including 1-MeV electron and 17.2-keV He+ and 60Co gamma irradiations with various fluences and doses, respectively. The devices are resilient to tunnel magnetoresistance (TMR), whereas the magnetic properties are changed after irradiation. The 100-Mrad (Si) gamma and 17.2-keV He+ irradiations generate similar damages on the device performances, in the aspects of the magnetic anisotropy and critical current density ($J_{\mathrm {c}}$). However, the displacement damage originating from the electron irradiation does not have a significant influence on $J_{\mathrm {c}}$. In addition, the saturation magnetization and exchange bias field are changed by irradiations without regularity. Some possible mechanisms are discussed to explain the experimental results through the simulation of stopping and range of ions in matter (SRIM) and microstructural tests. [ABSTRACT FROM AUTHOR]

Abstract: Graphene nanoplatelets have been applied as the support to electrodeposit monometallic Au and Pd nanoparticles as well as bimetallic Au–Pd nanoparticles. These nanoparticles have been characterized with scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, and electrochemical techniques. They are further utilized as the catalysts for electrochemical oxidation of hydrazine. The oxidation peak potential is −0.35 and 0.53V (vs. SCE) when monometallic Pd and Au nanoparticle are used as the catalysts. When bimetallic nanoparticles are applied as the catalyst, their composition affects the peak potential and peak current for the oxidation of hydrazine. Higher oxidation current is achieved when bimetallic Au–Pd nanoparticles with an atomic ratio of 3:1 are deposited on graphene nanoplatelets. Metal nanoparticle-loaded graphene nanoplatelets are thus novel platforms for electrocatalytic, electroanalytical, environmental, and related applications. [Copyright &y& Elsevier]

Abstract: This paper addresses the stability properties of switched linear positive systems in continuous-time as well as in discrete-time. In the discrete-time case, some sufficient and necessary conditions for asymptotic stability are derived for pairs of second order systems. Similar conditions are also established for a finite number of second order systems. Furthermore, for higher order systems, some results on stability are provided in a similar manner. In particular, in this case, a common linear Lyapunov function guaranteeing the stability of the switched positive systems can be easily located by means of geometry properties. In the continuous-time case, a finite number of second order systems are considered. Some equivalent conditions for stability of such systems are developed. [ABSTRACT FROM AUTHOR]

Magnetic anisotropy modulation is an effective method to simultaneously reduce the switching current and extend the data retention of magnetic tunnel junction (MTJ), which is promising to be used in the next-generation spin transfer torque (STT) magnetic random-access memory. However, to meet the requirements of high storage life and harsh environments, the improved perpendicular magnetic anisotropy of MTJ makes the conventional modulation methods suffer from high breakdown risk owing to the relatively low efficiency. In this paper, a method of phase-change controlled magnetic anisotropy (PCMA) is introduced to a physical model of VO2/CoFeB/MgO/CoFeB perpendicular MTJ with superior modulation capability proved by systematical simulation. The time sequence of phase change pulse and STT pulse is studied, proving that there exists a specific interval to achieve both rapid and low-power switching. With the joint effect of PCMA and STT, low-energy (68.2 fJ), low-error-rate (0.08), and fast (2 ns) write operation can be achieved in the MTJ accompanied by a high thermal stability factor (78). The results demonstrate that the PCMA-STT switching strategy is most suitable for MTJ with large perpendicular magnetic anisotropy, paving a promising way to replace NOR flash memories. [ABSTRACT FROM AUTHOR]

With the process node further scaling down, the bit cell of magnetic random access memory (MRAM) device suffers from severe failure and reliability problems due to its process variation. In this article, we explored the variability of a promising toggle spin torques MRAM (TST-MRAM) in detail, which achieves ultrafast switching speed and high endurance and is expected to be applied as upper-level caches. Our research is conducted with a 14 nm FinFET design kit, the basic performance of TST-MRAM and different pulse conditions are explored, and then the variation effect of device parameters is discussed and compared in detail as well as the write error rate (WER) under different voltages. The results demonstrate that the variation of access transistors dominates the variability, where the transistor in the spin–orbit torque (SOT) branch has a greater negative impact than the transistor in the spin transfer torque (STT) branch. To further reduce WER, a better structure with diodes of bit cell is proposed. [ABSTRACT FROM AUTHOR]

As the speed gap of the modern processor and the off-chip main memory enlarges, on-chip cache capacity increases to sustain the performance scaling. As a result, the cache power occupies a large portion of the total power budget. Spin transfer torque magnetic memory (STT-MRAM) is proposed as a promising solution for the low power cache design due to its high integration density and ultralow leakage power. Nevertheless, the high write power and latency of STT-MRAM become new barriers for the commercialization of this emerging technology. In this paper, we investigate the thermal effect on the access performance of STT-MRAM, and observe that the temperature can affect the write delay and energy significantly. Then, we explore the nonuniform cache access (NUCA) design of the chip-multiprocessors with STT-MRAM-based last level cache (LLC). A thermal aware data migration policy, called “Thermosiphon,” which takes advantage of the thermal property of STT-MRAM, is proposed to reduce the LLC write energy. This policy splits the LLC into different regions dynamically based on the thermal distribution monitored by thermal sensors available on-chip, and adaptively migrates write intensive data among different thermal regions considering the thermal gradient. Compared to the conventional NUCA design, our proposed design can save 41.2% write energy at most and 13.01% on average with negligible hardware overhead. [ABSTRACT FROM AUTHOR]

Spin orbit torque magnetic random access memory (SOT-MRAM) has attracted massive research interests due to its promising application potential in high-speed computing systems (e.g. upper level caches). Here we propose an erasable spintronics memory based on a novel field-free SOT switching mechanism. The data writing is achieved through erase and subsequent program operations, both of which are implemented with unidirectional currents. For improving the storage density, the erase operation is shared by multiple bit-cells, meanwhile some access transistors could be replaced with diodes thanks to the use of unidirectional currents. The simulation results demonstrate that the proposed erasable spintronics memory is featured by sub-nanosecond write speed, femto-joule write energy and higher storage density than the conventional SOT-MRAMs. [ABSTRACT FROM AUTHOR]

Circuit obfuscation is a frequently used approach to conceal logic functionalities in order to prevent reverse engineering attacks on fabricated chips. Efficient obfuscation implementations are expected with lower design complexity and overhead but higher attack difficulties. In this paper, an emerging obfuscation approach is proposed by leveraging spin-orbit torque (SOT) devices-based look-up-tables as reconfigurable logic to replace the carefully selected gates. It is essentially impossible to identify the obfuscated gate with SOTs inside according to the physical geometry characteristics because the configured functionalities are represented by magnetization states. Such an obfuscation approach makes the circuit security further improved with high exponential attack complexities. Experiments on MCNC and ISCAS 85/89 benchmark suits show that the proposed approach could reduce the area overheads due to obfuscation by 10% averagely. [ABSTRACT FROM AUTHOR]

Surface coating of graphene nano platelets with gold-palladium nanoparticles (AuPd NPs) was conducted via potentiostatic electrodeposition from a mixture of HAuCl4 and H2PdCl4. AuPd NPs were characterized using SEM, TEM, XRD and energy dispersive X-ray spectroscopy. The AuPd NPs with the diameter of about 30-60 nm were alloyed and well-dispersed on the graphene surface. Electrochemistry of hydrazine on AuPd NPs was investigated using cyclic voltammetry and chronoamperometry, indicating high electrocatalytic ability of AuPd NPs towards oxidation of hydrazine. Under the optimized conditions, the oxidation current was linear to the hydrazine concentration in the range of 0.02-166.6 µM. The calculated detection limit was 5 nM (S/N=3). [ABSTRACT FROM AUTHOR]

Mesoporous silica has been functionalized with vanadium pentoxide (V2O5) and cerium oxide (CeO2). It was then immobilized with biocatalyst horseradish (HRP) to realize highly sensitive detection of H2O2. The electrode was characterized with SEM, cyclic voltammetry, and impedance measurements. A well-defined peak for HRP reduction was noticed at about −0.31 V with an apparent heterogeneous electron transfer rate constant of 1.01 s−1. The catalytic reduction of H2O2 was achieved. The Michaelis constant was calculated to be 0.018 mM. On this electrode, H2O2 was detectable in the range of 20 to 180 µM and the detection limit was 3.0 µM. [ABSTRACT FROM AUTHOR]

Protein kinase D2 (PKD2) has been demonstrated to promote tumorigenesis in many types of cancers. However, how PKD2 regulates cancer cell growth is largely unknown. In this study, we found that over-expression of PKD2 promoted glioma cell growth but down-regulation of PKD2 inhibited it. Further investigation indicated that PKD2 down-regulation decreased the protein level of Golgi phosphoprotein 3(GOLPH3) as well as p-AKT level. On the contrary, over-expression of PKD2 increased the protein level of GOLPH3 and p-AKT. In addition, GOLPH3 exhibited similar effect on glioma cell growth to that of PKD2. Importantly, GOLPH3 down-regulation partially abolished glioma cell proliferation induced by PKD2 over-expression, while over-expression of GOLPH3 also partially rescued the inhibition effect of PKD2 down-regulation on glioma cell growth. Interestingly, the level of PKD2 and GOLPH3 significantly increased and was positively correlated in a cohort of glioma patients, as well as in patients from TCGA database. Taken together, these results reveal that PKD2 promotes glioma cell proliferation by regulating GOLPH3 and then AKT activation. Our findings indicate that both PKD2 and GOLPH3 play important roles in the progression of human gliomas and PKD2-GOLPH3-AKT signaling pathway might be a potential glioma therapeutic target. [ABSTRACT FROM AUTHOR]

Abstract: In order to construct a three-dimensional electrode, in situ electrochemical deposition of gold nanoparticles onto a gold electrode coated with a self-assembled monolayer of 3-mercaptopropionic acid (Au NP/MPA/Au) was conducted. Horseradish peroxidase (HRP) was then immobilized into this three-dimensional electrode, leading to the realization of direct electron transfer of HRP. Scanning electron microscopy and electrochemical impedance spectroscopy were applied to characterize the electrode before and after HRP immobilization. The apparent Michaelis-Menten constant for immobilized HRP on a Au NP/MPA/Au electrode is 0.78mM, indicating high enzymatic activity of HRP. The HRP modified electrode was further utilized as a sensing platform for the electrocatalytic reduction and detection of hydrogen peroxide. For the detection of hydrogen peroxide on this electrode, the sensitivity is 311.72μAmM−1 cm−2, the detection limit is 0.16μM, and the dynamic range is from 0.48μM to 1.2mM. Therefore this electrode is a promising device for sensitive and reproducible detection of H2O2. [Copyright &y& Elsevier]