Compact and power-efficient plastic electronic synapses are of fundamental importance to overcoming the bottlenecks of developing a neuromorphic chip. Memristor is a strong contender among the various electronic synapses in existence today. However, the speeds of synaptic events are relatively slow in most attempts at emulating synapses due to the material-related mechanism. Here we revealed the intrinsic memristance of stoichiometric crystalline Ge2Sb2Te5 that originates from the charge trapping and releasing by the defects. The device resistance states, representing synaptic weights, were precisely modulated by 30 ns potentiating/depressing electrical pulses. We demonstrated four spike-timing-dependent plasticity (STDP) forms by applying programmed pre- and postsynaptic spiking pulse pairs in different time windows ranging from 50 ms down to 500 ns, the latter of which is 105 times faster than the speed of STDP in human brain. This study provides new opportunities for building ultrafast neuromorphic computing systems and surpassing Von Neumann architecture.
A chalcogenide material with Ag/Ag5In5Sb60Te30/Ag structure was proposed as a memristor. Reproducible gradual resistance tuning in bipolar/unipolar modes was demonstrated. The resistance variation was tuned more precisely by controlling the polarity, the amplitude, the width, and the number of applied voltage pulses. The bipolar memristive switch was attributed to the coexistence of intrinsic space charge limited conduction and extrinsic electrochemical metallization effect. Moreover, the unipolar gradual resistance tuning reconfirmed the electrochemical metallization effect. The gradual resistance tuning characteristics will promote this memristor to potential application in mimicking biological plastic synapses.
In this paper we present the results of research aimed at the development of a 'smart' bed to non-intrusively monitor patient respiration, heart rate and movement using spatially distributed integrating multimode fibre optic sensors. The research is focused upon allowing more automation of patient care, an especially important matter for the elder population, which is a rapidly growing fraction of much of the world population today. Two spatially integrating fibre optic sensors were investigated, one of which was based on inter-modal interference and the other on mode conversion. The sensing fibre was integrated into a bed and test subjects were monitored in different positions. The sensor outputs were then correlated with subject movement, respiration rate and heart rate. The results indicated that the inter-modal sensor could detect patient movement and respiration rate while the mode conversion sensor could detect patient movement, respiration rate and heart rate. Results and analysis of the research are presented and future research activities discussed.
Severe acute pancreatitis (SAP) is a challenging disease with high morbidity and mortality, often complicated by multiple organ dysfunction syndrome (MODS). The intestine, a major organ involved in MODS, correlates strongly with the evolution of the disease. In this study, we demonstrated that the DPP4 inhibitor, sitagliptin, protects SAP-associated intestinal injury both in vitro and in vivo. These beneficial effects were achieved by suppressing oxidative stress and inflammatory responses. Moreover, in sitagliptin-treated SAP mice, expression of Nrf2 was induced and that of NF-κB was reduced, compared to the control SAP mice. In addition, we used Nrf2−/− mice to test the protective effect of Nrf2 during sitagliptin treatment of SAP; our results indicated that Nrf2−/− mice had greater pancreatic and intestinal injury than wild-type mice. Taken together, high levels of ROS induced by SAP may be inhibited by sitagliptin, possibly by inactivating the Nrf2-NF-κB pathway.
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