Dual functional states of working memory realized by memristor-based neural network

Working memory refers to the brain's ability to store and manipulate information for a short period. It is disputably considered to rely on two mechanisms: sustained neuronal firing, and “activity-silent” working memory. To develop a highly biologically plausible neuromorphic computing system, it is anticipated to physically realize working memory that corresponds to both of these mechanisms. In this study, we propose a memristor-based neural network to realize the sustained neural firing and activity-silent working memory, which are reflected as dual functional states within memory. Memristor-based synapses and two types of artificial neurons are designed for the Winner-Takes-All learning rule. During the cognitive task, state transformation between the “focused” state and the “unfocused” state of working memory is demonstrated. This work paves the way for further emulating the complex working memory functions with distinct neural activities in our brains

Extracellular Signal-regulated Kinase (ERK) Phosphorylates Histone Deacetylase 6 (HDAC6) at Serine 1035 to Stimulate Cell Migration

Histone deacetylase 6 (HDAC6) is well known for its ability to promote cell migration through deacetylation of its cytoplasmic substrates such as α-tubulin. However, how HDAC6 itself is regulated to control cell motility remains elusive. Previous studies have shown that one third of extracellular signal-regulated kinase (ERK) is associated with the microtubule cytoskeleton in cells. Yet, no connection between HDAC6 and ERK has been discovered. Here, for the first time, we reveal that ERK binds to and phosphorylates HDAC6 to promote cell migration via deacetylation of α-tubulin. We have identified two novel ERK-mediated phosphorylation sites: threonine 1031 and serine 1035 in HDAC6. Both sites were phosphorylated by ERK1 in vitro, whereas Ser-1035 was phosphorylated in response to the activation of EGFR-Ras-Raf-MEK-ERK signaling pathway in vivo. HDAC6-null mouse embryonic fibroblasts rescued by the nonphosphorylation mimicking mutant displayed significantly reduced cell migration compared with those rescued by the wild type. Consistently, the nonphosphorylation mimicking mutant exerted lower tubulin deacetylase activity in vivo compared with the wild type. These data indicate that ERK/HDAC6-mediated cell motility is through deacetylation of α-tubulin. Overall, our results suggest that HDAC6-mediated cell migration could be governed by EGFR-Ras-Raf-MEK-ERK signaling

Experimental study on the influence of recycled aggregates on the mechanical properties of concrete

Construction solid waste has become an important environmental pollution source in the city, and the treatment and application of construction solid waste has become the focus of attention. Construction waste recycled aggregates have defects such as high water absorption and micro cracks, which affect its extensive application. In order to improve the utilization rate of recycled aggregates, the influence of different replacement rates of recycled aggregates on the mechanical properties of concrete is studied in this paper. The results show that with the increase of replacement rate of recycled aggregates, the 3-day, 7-day and 28-day compressive strength, splitting strength and cohesive force of concrete decrease gradually, but the mechanical properties of concrete decrease slowly at 3 days and 7 days, and decrease obviously at 28 days. Moreover, with the increase of replacement rate of recycled aggregates, the decline trend of mechanical properties is not obvious. Compared with natural aggregate concrete, the 28-day compressive strength, splitting strength and cohesive force of 100% recycled aggregate concrete are reduced by 16.1%, 20.1% and 18.1% respectively, but the mechanical properties meet the requirements of C30 concrete, which provides a reference for engineering application

Directional-sensitive differential laser Doppler vibrometry for in-plane motion measurement of specular surface

A new method for measuring in-plane vibration velocity of glossy and specular surface using differential laser Doppler vibrometer (LDV) is proposed in this work. A standard tangential LDV using similar differential configuration is only able to measure in-plane velocity of objects with rough surface, due to its inherent on-axis optical design that collects backscatter light along its optical axis. The proposed method adopts an off-axis detection scheme, in which the photodetector is decoupled from LDV, and placed along the dominant direction of the scattered light. For optimal placement, the bidirectional reflectance distribution function (BRDF) of the sample must be considered ideally, but in our measurement tests, the off-axis detection along the direction of specular reflection is sufficient to obtain good measurement results. Another advantage with this setup is that it also works with the objects with rough surface. Experimental works using the standard tangential LDV and a prototype of this method were conducted to measure the in-plane motion of four different samples representing rough, glossy and mirror-like surface. An electrodynamic shaker was used to provide the in-plane motion of the samples at three different frequencies. A single point axial vibrometer was used to validate the in-plane velocity of the measurement from both in-plane LDVs. Some preliminary results showed that the in-plane motion of the object with glossy and specular surface can be measured using the proposed method.Published versio

Memristive Synapse Based on Single‐Crystalline LiNbO3 Thin Film with Bioinspired Microstructure for Experience‐Based Dynamic Image Mask Generation

Abstract One of the key steps toward constructing neuromorphic systems is to develop reliable bio‐realistic synaptic devices. Here, memristors based on single‐crystalline LiNbO3 (SC‐LNO) thin film are fabricated as artificial synapses. A reservoir of oxygen vacancies is induced by Ar+ irradiation to resemble synaptic vesicles containing neurotransmitters. Phenomena of saturation and adaptivity, short‐term plasticity, paired‐pulse facilitation, paired‐pulse depression, and long‐term potentiation are successfully mimicked. The dynamic transition from sensory memory to short‐term memory, and further to long‐term memory, is also successfully emulated for multipattern memorization. In addition, first, taking advantage of short‐ and long‐term synaptic plasticity is proposed, to realize experience‐based image mask generation with different stimuli schemes. During the experience‐based generation process, memristive multi‐value masks (MMVMs) are generated with different numbers of stimuli applied to the memristor at each pixel, which corresponds to the times the region occurred in the history image set. The experience‐based memristive multi‐value mask successfully extracts multiple regions of interest with different priorities. This work demonstrates that the memristor based on Ar+‐irradiated SC‐LNO thin film with bioinspired microstructure shows great potential in future neuromorphic systems for experience‐based intelligent image processing

Investigation of the Temperature Fluctuation of Single-Phase Fluid Based Microchannel Heat Sink

The temperature fluctuation in a single-phase microchannel heat sink (MCHS) is investigated using the integrated temperature sensors with deionized water as the coolant. Results show that the temperature fluctuation in single phase is not negligible. The causes of the temperature fluctuation are revealed based on both simulation and experiment. It is found that the inlet temperature fluctuation and the gas bubbles separated out from coolant are the main causes. The effect of the inlet temperature fluctuation is global, where the temperatures at different locations change simultaneously. Meanwhile, the gas bubble effect is localized where the temperature changes at different locations are not synchronized. In addition, the relation between temperature fluctuation and temperature gradient is established. The temperature fluctuation increases with the temperature gradient accordingly

Area Dependence of Effective Electromechanical Coupling Coefficient Induced by On-Chip Inductance in LiNbO₃-Based BAW Resonators

To solve the problem of filter bandwidth in 5G communication, it is urgent to develop an acoustic resonator with a large effective electromechanical coupling coefficient (Keff2). In this paper, the dependence between the resonance area and the performance of the bulk acoustic wave (BAW) resonator is studied. The solidly mounted resonators (SMRs) based on 43° Y cut lithium niobate (LN) were fabricated by the wafer transfer technique. The on-chip inductor was integrated with the BAW resonator through a pad electrode. Resonators with different resonant areas were fabricated and tested. Finite element modeling (FEM) simulation of acoustic resonators and electromagnetic (EM) simulation of layout were carried out, respectively. The Modified Butterworth Van Dyke (MBVD) model was used to analyze the results, and simulation of the Mason model was adopted. The results show that the dependency relationship between the resonant area and the effective electromechanical coupling coefficient can be induced by on-chip inductance. In the resonant area range of 20 × 20 μm2~160 × 160 μm2, the Keff2 increases from 11.97% to 43.28%

A Comprehensive Study of a Micro-Channel Heat Sink Using Integrated Thin-Film Temperature Sensors

A micro-channel heat sink is a promising cooling method for high power integrated circuits (IC). However, the understanding of such a micro-channel device is not sufficient, because the tools for studying it are very limited. The details inside the micro-channels are not readily available. In this letter, a micro-channel heat sink is comprehensively studied using the integrated temperature sensors. The highly sensitive thin film temperature sensors can accurately monitor the temperature change in the micro-channel in real time. The outstanding heat dissipation performance of the micro-channel heat sink is proven in terms of maximum temperature, cooling speed and heat resistance. The temperature profile along the micro-channel is extracted, and even small temperature perturbations can be detected. The heat source formed temperature peak shifts towards the flow direction with the increasing flow rate. However, the temperature non-uniformity is independent of flow rate, but solely dependent on the heating power. Specific designs for minimizing the temperature non-uniformity are necessary. In addition, the experimental results from the integrated temperature sensors match the simulation results well. This can be used to directly verify the modeling results, helping to build a convincing simulation model. The integrated sensor could be a powerful tool for studying the micro-channel based heat sink