Photo-Assisted Ferroelectric Domain Control for α-In2Se3 Artificial Synapses Inspired by Spontaneous Internal Electric Fields.

α-In2Se3 semiconductor crystals realize artificial synapses by tuning in-plane and out-of-plane ferroelectricity with diverse avenues of electrical and optical pulses. While the electrically induced ferroelectricity of α-In2Se3 shows synaptic memory operation, the optically assisted synaptic plasticity in α-In2Se3 has also been preferred for polarization flipping enhancement. Here, the synaptic memory behavior of α-In2Se3 is demonstrated by applying electrical gate voltages under white light. As a result, the induced internal electric field is identified at a polarization flipped conductance channel in α-In2Se3/hexagonal boron nitride (hBN) heterostructure ferroelectric field effect transistors (FeFETs) under white light and discuss the contribution of this built-in electric field on synapse characterization. The biased dipoles in α-In2Se3 toward potentiation polarization direction by an enhanced internal built-in electric field under illumination of white light lead to improvement of linearity for long-term depression curves with proper electric spikes. Consequently, upon applying appropriate electric spikes to α-In2Se3/hBN FeFETs with illuminating white light, the recognition accuracy values significantly through the artificial learning simulation is elevated for discriminating hand-written digit number images.

Reliable synaptic plasticity of InGaZnO transistor with TiO2interlayer.

We demonstrate an InGaZnO (IGZO)-based synaptic transistor with a TiO2buffer layer. The structure of the synaptic transistor with TiO2inserted between the Ti metal electrode and an IGZO semiconductor channel O2trapping layer produces a large hysteresis window, which is crucial for achieving synaptic functionality. The Ti/TiO2/IGZO synaptic transistor exhibits reliable synaptic plasticity features such as excitatory post-synaptic current, paired-pulse facilitation, and potentiation and depression, originating from the reversible charge trapping and detrapping in the TiO2layer. Finally, the pattern recognition accuracy of Modified National Institute of Standards and Technology handwritten digit images was modeled using CrossSim simulation software. The simulation results present a high image recognition accuracy of ∼89%. Therefore, this simple approach using an oxide buffer layer can aid the implementation of high-performance synaptic devices for neuromorphic computing systems.

Reinforcing Synaptic Plasticity of Defect-Tolerant States in Alloyed 2D Artificial Transistors.

While two-dimensional (2D) materials possess the desirable future of neuromorphic computing platforms, unstable charging and de-trapping processes, which are inherited from uncontrollable states, such as the interface trap between nanocrystals and dielectric layers, can deteriorate the synaptic plasticity in field-effect transistors. Here, we report a facile and effective strategy to promote artificial synaptic devices by providing physical doping in 2D transition-metal dichalcogenide nanomaterials. Our experiments demonstrate that the introduction of niobium (Nb) into 2D WSe2 nanomaterials produces charge trap levels in the band gap and retards the decay of the trapped charges, thereby accelerating the artificial synaptic plasticity by encouraging improved short-/long-term plasticity, increased multilevel states, lower power consumption, and better symmetry and asymmetry ratios. Density functional theory calculations also proved that the addition of Nb to 2D WSe2 generates defect tolerance levels, thereby governing the charging and de-trapping mechanisms of the synaptic devices. Physically doped electronic synapses are expected to be a promising strategy for the development of bioinspired artificial electronic devices.

Robust 2D MoS2 Artificial Synapse Device Based on a Lithium Silicate Solid Electrolyte for High-Precision Analogue Neuromorphic Computing.

High-precision artificial synaptic devices compatible with existing CMOS technology are essential for realizing robust neuromorphic hardware systems with reliable parallel analogue computation beyond the von Neumann serial digital computing architecture. However, critical issues related to reliability and variability, such as nonlinearity and asymmetric weight updates, have been great challenges in the implementation of artificial synaptic devices in practical neuromorphic hardware systems. Herein, a robust three-terminal two-dimensional (2D) MoS2 artificial synaptic device combined with a lithium silicate (LSO) solid-state electrolyte thin film is proposed. The rationally designed synaptic device exhibits excellent linearity and symmetry upon electrical potentiation and depression, benefiting from the reversible intercalation of Li ions into the MoS2 channel. In particular, extremely low cycle-to-cycle variations (3.01%) during long-term potentiation and depression processes over 500 pulses are achieved, causing statistical analogue discrete states. Thus, a high classification accuracy of 96.77% (close to the software baseline of 98%) is demonstrated in the Modified National Institute of Standards and Technology (MNIST) simulations. These results provide a future perspective for robust synaptic device architecture of lithium solid-state electrolytes stacked with 2D van der Waals layered channels for high-precision analogue neuromorphic computing systems.

Highly Reproducible Heterosynaptic Plasticity Enabled by MoS2/ZrO2-x Heterostructure Memtransistor.

Electrically tunable resistive switching of a polycrystalline MoS2-based memtransistor has attracted a great deal of attention as an essential synaptic component of neuromorphic circuitry because its switching characteristics from the field-induced migration of sulfur defects in the MoS2 grain boundaries can realize multilevel conductance tunability and heterosynaptic functionality. However, reproducible switching properties in the memtransistor are usually disturbed by the considerable difficulty in controlling the concentration and distribution of the intrinsically existing sulfur defects. Herein, we demonstrate reliable heterosynaptic characteristics using a memtransistor device with a MoS2/ZrO2-x heterostructure. Compared to the control device with the MoS2 semiconducting channel, the Schottky barrier height was more effectively modulated by the insertion of the insulating ZrO2-x layer below the MoS2, confirmed by an ultraviolet photoelectron spectroscopy analysis and the corresponding energy-band structures. The MoS2/ZrO2-x memtransistor accomplishes dual-terminal (drain and gate electrode) stimulated multilevel conductance owing to the tunable resistive switching behavior under varying gate voltages. Furthermore, the memtransistor exhibits long-term potentiation/depression endurance cycling over 7000 pulses and stable pulse cycling behavior by the pulse stimulus from different terminal regions. The promising candidate as an essential synaptic component of the MoS2/ZrO2-x memtransistors for neuromorphic systems results from the high recognition accuracy (∼92%) of the deep neural network simulation test, based on the training and inference of handwritten numbers (0-9). The simple memtransistor structure facilitates the implementation of complex neural circuitry.

In-depth analysis on electrical parameters of floating gate IGZO synaptic transistor affecting pattern recognition accuracy.

The reliable conductance modulation of synaptic devices is key when implementing high-performance neuromorphic systems. Herein, we propose a floating gate indium gallium zinc oxide (IGZO) synaptic device with an aluminum trapping layer to investigate the correlation between its diverse electrical parameters and pattern recognition accuracy. Basic synaptic properties such as excitatory postsynaptic current, paired pulse facilitation, long/short term memory, and long-term potentiation/depression are demonstrated in the IGZO synaptic transistor. The effects of pulse tuning conditions associated with the pulse voltage magnitude, interval, duration, and cycling number of the applied pulses on the conductance update are systematically investigated. It is discovered that both the nonlinearity of the conductance update and cycle-to-cycle variation should be critically considered using an artificial neural network simulator to ensure the high pattern recognition accuracy of Modified National Institute of Standards and Technology (MNIST) handwritten digit images. The highest recognition rate of the MNIST handwritten dataset is 94.06% for the most optimized pulse condition. Finally, a systematic study regarding the synaptic parameters must be performed to optimize the developed synapse device.

In-depth analysis on electrical parameters of floating gate IGZO synaptic transistor affecting pattern recognition accuracy.

The reliable conductance modulation of synaptic devices is key when implementing high-performance neuromorphic systems. Herein, we propose a floating gate IGZO synaptic device with an aluminum trapping layer to investigate the correlation between its diverse electrical parameters and pattern recognition accuracy. Basic synaptic properties such as excitatory postsynaptic current, paired pulse facilitation, long/short term memory, and long-term potentiation/depression are demonstrated in the IGZO synaptic transistor. The effects of pulse tuning conditions associated with the pulse voltage magnitude, interval, duration, and cycling number of the applied pulses on the conductance update are systematically investigated. It is discovered that both the nonlinearity of the conductance update and cycle-to-cycle variation should be critically considered using an artificial neural network simulator to ensure the high pattern recognition accuracy of Modified National Institute of Standards and Technology (MNIST) handwritten digit images. The highest recognition rate of the MNIST handwritten dataset is 94.06% for the most optimized pulse condition. Finally, a systematic study regarding the synaptic parameters must be performed to optimize the developed synapse device.

Accelerated Learning in Wide-Band-Gap AlN Artificial Photonic Synaptic Devices: Impact on Suppressed Shallow Trap Level.

Artificial synaptic platforms are promising for next-generation semiconductor computing devices; however, state-of-the-art optoelectronic approaches remain challenging, owing to their unstable charge trap states and limited integration. We demonstrate wide-band-gap (WBG) III-V materials for photoelectronic neural networks. Our experimental analysis shows that the enhanced crystallinity of WBG synapses promotes better synaptic characteristics, such as effective multilevel states, a wider dynamic range, and linearity, allowing the better power consumption, training, and recognition accuracy of artificial neural networks. Furthermore, light-frequency-dependent memory characteristics suggest that artificial optoelectronic synapses with improved crystallinity support the transition from short-term potentiation to long-term potentiation, implying a clear emulation of the psychological multistorage model. This is attributed to the charge trapping in deep-level states and suppresses fast decay and nonradiative recombination in shallow traps. We believe that the fingerprints of these WBG synaptic characteristics provide an effective strategy for establishing an artificial optoelectronic synaptic architecture for innovative neuromorphic computing.

Comparative study of the physicochemical, nutritional, and antioxidant properties of some commercial refined and non-centrifugal sugars.

Three refined and four unrefined branded commercial sugars available in Korea were investigated in terms of pH, soluble solids, moisture, ash content, turbidity, color values, microbial profile, reducing power, 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activities, cellular antioxidant activity, and total phytoconstituent (i.e. phenolic, flavonoid, mineral, sucrose, glucose, and fructose) contents using standard analytical protocols such as high-performance liquid chromatography, gas chromatography-flame ionization detector/mass spectrometry, and inductively coupled plasma atomic emission spectroscopy. All tested physicochemical parameters were within the recommended standard levels. Significantly high nutritional and antioxidant properties were observed for the unrefined sugars, especially AUNO® sugar, whereas a high sucrose content was detected for the refined sugars. Hence, this study revealed that the degree of purification affects the nutritional values and antioxidant potentials of sugars. The present findings also indicate that unrefined sugars can be used as sweeteners in sugar-based cuisine to obtain nutritional and antioxidant-rich foodstuff.

Potential effect of compounds isolated from Coffea arabica against UV-B induced skin damage by protecting fibroblast cells.

Ultraviolet (UV) radiation has adverse effects on extracellular matrix (ECM) proteins, leading to formation of wrinkles a hallmark of premature skin aging. The adverse effects of UV radiation are associated with induction of matrix metalloproteinases (MMPs) expression and degradation of collagen and elastin. The present study investigated anti-wrinkle effects of chlorogenic acid (CGA), pyrocatechol (PC) and 3,4,5-tricaffeoyl quinic acid (TCQ), isolated from beans of Coffea arabica, against UV-B stimulated mouse fibroblast cells (CCRF) by measuring expression levels of MMP-1, 3, 9, and type-I procollagen. The three compounds were isolated and purified from coffee grounds using column chromatography and structural examination was evaluated by nuclear magnetic resonance (NMR) analysis. Among the three isolated compounds, CGA effectively suppressed the expression of the MMP-1, 3, and 9 and increased synthesis of type-I procollagen as compared UV-B-stimulated CCRF cells. In addition, CGA dose-dependently inhibited intracellular reactive oxygen species (ROS) production in CCRF cells stimulated by UV radiation. Moreover, CGA displayed a good sun protection factor (SPF) and in vitro DNA damage protection together with inhibition of enzyme xanthine oxidase. The enzyme inhibitory kinetic behavior of CGA was determined by Lineweaver-Burk plot, displayed a mixed type enzyme inhibition with 260.3±4.5µM, Ki value. The results indicate that CGA has potential to be used as a preventive agent against premature skin aging induced by UV radiation.

An investigation into the ameliorating effect of black soybean extract on learning and memory impairment with assessment of neuroprotective effects.

BACKGROUND: The physiological effects of the non-anthocyanin fraction (NAF) in a black soybean seed coat extract on Aß-induced oxidative stress were investigated to confirm neuroprotection. In addition, we examined the preventive effect of NAF on cognitive defects induced by the intracerebroventricular (ICV) injection of Aß. METHODS: Levels of cellular oxidative stress were measured using 2',7'-dichlorofluorescein diacetate (DCF-DA). Neuronal cell viability was investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assay. To investigate in vivo anti-amnesic effects of NAF by using Y-maze and passive avoidance tests, the learning and memory impairment in mice was induced by Aß. After in vivo assays, acetylcholinesterase (AChE) activity and level of malondialdehyde (MDA) in the mouse brain were determined to confirm the cognitive effect. Individual phenolics of NAF were qualitatively analyzed by using an ultra-performance liquid chromatography (UPLC) Accurate-Mass Quadrupole Time of-Flight (Q-TOF) UPLC/MS. RESULTS: A NAF showed cell protective effects against oxidative stress-induced cytotoxicity. Intracellular ROS accumulated through Aß1-40 treatment was significantly reduced in comparison to cells only treated with Aß1-40. In MTT and LDH assay, the NAF also presented neuroprotective effects on Aß1-40-treated cytotoxicity. Finally, the administration of this NAF in mice significantly reversed the Aß1-40-induced cognitive defects in in vivo behavioral tests. After behavioral tests, the mice brains were collected in order to examine lipid peroxidation and AChE activity. AChE, preparation was inhibited by NAF in a dose-dependent manner. MDA generation in the brain homogenate of mice treated with the NAF was decreased. Q-TOF UPLC/MS analyses revealed three major phenolics from the non-anthocyanin fraction; epicatechin, procyanidin B1, and procyanidin B2. CONCLUSIONS: The results suggest that the NAF in black soybean seed coat extracts may improve the cytotoxicity of Aß in PC12 cells, possibly by reducing oxidative stress, and also have an anti-amnesic effect on the in vivo learning and memory deficits caused by Aß. Q-TOF UPLC/MS analyses showed three major phenolics; (-)-epicatechin, procyanidin B1, and procyanidin B2. Above results suggest that (-)-epicatechins are the major components, and contributors to the anti-amnesic effect of the NAF from black soybean seed coat.

Hyperoside inhibits high-glucose-induced vascular inflammation in vitro and in vivo.

Hyperoside, an active compound from the genera of Hypericum and Crataegus, was reported to have antioxidant, antihyperglycemic, anticancer, anti-inflammatory, and anticoagulant activities. Vascular inflammatory process has been suggested to play a key role in initiation and progression of atherosclerosis, a major complication of diabetes mellitus. Thus, in this study, we attempted to determine whether hyperoside can suppress vascular inflammatory processes induced by high glucose (HG) in human umbilical vein endothelial cells (HUVECs) and mice. Data showed that HG induced markedly increased vascular permeability, monocyte adhesion, expressions of cell adhesion molecules (CAMs), formation of reactive oxygen species (ROS), and activation of nuclear factor (NF)-κB. Remarkably, all of the above-mentioned vascular inflammatory effects of HG were attenuated by pretreatment with hyperoside. Vascular inflammatory responses induced by HG are critical events underlying development of various diabetic complications; therefore, our results suggest that hyperoside may have significant therapeutic benefits against diabetic complications and atherosclerosis.

Comparative study of quality characteristics of Korean soy sauce made with soybeans germinated under dark and light conditions.

This study was conducted to evaluate the effects of germinating soybeans under dark and light conditions on the quality characteristics of Korean soy sauce made with germinated soybeans. The germination rate of soybeans germinated under dark conditions (GSD) was higher than that of soybeans germinated under light conditions (GSL), whereas the lengths of sprouts and relative weights of GSL did not differ from those of GSD. The L, a, b, and ΔT values of GSL were significantly lower than GSD. The color of GSD remained yellow, while GSL changed to a green color due to photosynthesis by chlorophyll. The total amino acid contents in soy sauce fermented with soybeans germinated under dark conditions (SSGD) and soy sauce fermented with soybeans germinated under light conditions (SSGL) were lower than in soy sauce fermented with non-germinated soybeans (SNGS). The levels of isoflavone content in SSGD and SSGL were significantly increased compared to the SNGS. In conclusion, the germination of soybeans under dark and light conditions is not only an increasing organoleptic preference, but also has implications for the health benefits of Korean soy sauce.

Functional comparison of esterified and free forms of conjugated linoleic acid in high-fat-diet-induced obese C57BL/6J mice.

This study investigated the effects of dietary conjugated linoleic acid (CLA), in the form of free fatty acid (FFA-CLA) or triacylglycerol (TG-CLA), on serum and liver lipid composition and gene expression associated with lipogenesis and ß-oxidation in high-fat-diet (HFD)-induced obese C57BL/6J mice. Animals were fed a control diet, HFD, HFD supplemented with 2% FFA-CLA, or HFD supplemented with 2% TG-CLA for 8 weeks. Supplementation with both forms of CLA significantly reduced the weights of whole body and adipose tissue and was positively associated with significant liver enlargement. Both forms of CLA significantly decreased serum TG concentration, but had no effect on total cholesterol levels, which were increased in mice fed HFD. There was a prominent increase in serum alanine aminotransferase (ALT) levels in mice that received either form of CLA. TG accumulation and lipogenic gene expression, including the expression of genes for fatty acid synthase (FAS), acetyl-coenzyme A carboxylase (ACC), and malic enzyme, were significantly lower in the livers of mice that received TG-CLA as compared to FFA-CLA. The gene expressions of sterol regulatory element binding protein-1c (SREBP-1c) in both liver and adipose tissue were suppressed in mice that were fed either form of CLA as compared to the mice fed HFD alone, whereas there were no increases in the levels of expression of ß-oxidation-related genes. These findings demonstrated that free and esterified forms of CLA have differing effects on liver and adipose tissue lipogenesis.

Variations in conjugated linoleic acid (CLA) content of processed cheese by lactation time, feeding regimen, and ripening.

Dairy products are major sources of conjugated linoleic acid (CLA); thus, an increase in CLA content can improve the quality value of dairy products. The objective of this work was to determine the effects of lactation time, feeding regimen, and ripening period on the level of CLA in processed cheese. CLA content in milk varied with the period of lactation; high in spring (April and May, about 6.8 mg CLA/g fat) and relatively low in mid summer and winter (about 4.3 mg CLA/g fat). The effects of dietary regimen and ripening period were determined in milk, which was obtained from March to May. After aging for 4 months, the cheese made from milk obtained from cows fed on pasture contained relatively higher levels of CLA compared to cheese made from milk obtained from cows fed indoors (8.12 mg CLA/g fat vs 6.76 mg CLA/g fat), but there was no difference in 7 month-aged cheeses. In both pasture and indoor feeding, 7 month-aged cheeses showed higher CLA content than 4 month-aged cheeses. The contents of stearic acid (C18:0) and linolenic acid (C18:3) were significantly higher in cheese from pasture fed cows compared to those in cows fed indoors. These findings should be helpful for the efficient production of functional dairy products with high CLA contents.