An analytical approach to engineer multistability in the oscillatory response of a pulse-driven ReRAM.

A nonlinear system, exhibiting a unique asymptotic behaviour, while being continuously subject to a stimulus from a certain class, is said to suffer from fading memory. This interesting phenomenon was first uncovered in a non-volatile tantalum oxide-based memristor from Hewlett Packard Labs back in 2016 out of a deep numerical investigation of a predictive mathematical description, known as the Strachan model, later corroborated by experimental validation. It was then found out that fading memory is ubiquitous in non-volatile resistance switching memories. A nonlinear system may however also exhibit a local form of fading memory, in case, under an excitation from a given family, it may approach one of a number of distinct attractors, depending upon the initial condition. A recent bifurcation study of the Strachan model revealed how, under specific train stimuli, composed of two square pulses of opposite polarity per cycle, the simplest form of local fading memory affects the transient dynamics of the aforementioned Resistive Random Access Memory cell, which, would asymptotically act as a bistable oscillator. In this manuscript we propose an analytical methodology, based on the application of analysis tools from Nonlinear System Theory to the Strachan model, to craft the properties of a generalised pulse train stimulus in such a way to induce the emergence of complex local fading memory effects in the nano-device, which would consequently display an interesting tuneable multistable oscillatory response, around desired resistance states. The last part of the manuscript discusses a case study, shedding light on a potential application of the local history erase effects, induced in the device via pulse train stimulation, for compensating the unwanted yet unavoidable drifts in its resistance state under power off conditions.

Recent Advances and Future Prospects for Memristive Materials, Devices, and Systems.

Memristive technology has been rapidly emerging as a potential alternative to traditional CMOS technology, which is facing fundamental limitations in its development. Since oxide-based resistive switches were demonstrated as memristors in 2008, memristive devices have garnered significant attention due to their biomimetic memory properties, which promise to significantly improve power consumption in computing applications. Here, we provide a comprehensive overview of recent advances in memristive technology, including memristive devices, theory, algorithms, architectures, and systems. In addition, we discuss research directions for various applications of memristive technology including hardware accelerators for artificial intelligence, in-sensor computing, and probabilistic computing. Finally, we provide a forward-looking perspective on the future of memristive technology, outlining the challenges and opportunities for further research and innovation in this field. By providing an up-to-date overview of the state-of-the-art in memristive technology, this review aims to inform and inspire further research in this field.

On Local Activity and Edge of Chaos in a NaMLab Memristor.

Local activity is the capability of a system to amplify infinitesimal fluctuations in energy. Complex phenomena, including the generation of action potentials in neuronal axon membranes, may never emerge in an open system unless some of its constitutive elements operate in a locally active regime. As a result, the recent discovery of solid-state volatile memory devices, which, biased through appropriate DC sources, may enter a local activity domain, and, most importantly, the associated stable yet excitable sub-domain, referred to as edge of chaos, which is where the seed of complexity is actually planted, is of great appeal to the neuromorphic engineering community. This paper applies fundamentals from the theory of local activity to an accurate model of a niobium oxide volatile resistance switching memory to derive the conditions necessary to bias the device in the local activity regime. This allows to partition the entire design parameter space into three domains, where the threshold switch is locally passive (LP), locally active but unstable, and both locally active and stable, respectively. The final part of the article is devoted to point out the extent by which the response of the volatile memristor to quasi-static excitations may differ from its dynamics under DC stress. Reporting experimental measurements, which validate the theoretical predictions, this work clearly demonstrates how invaluable is non-linear system theory for the acquirement of a comprehensive picture of the dynamics of highly non-linear devices, which is an essential prerequisite for a conscious and systematic approach to the design of robust neuromorphic electronics. Given that, as recently proved, the potassium and sodium ion channels in biological axon membranes are locally active memristors, the physical realization of novel artificial neural networks, capable to reproduce the functionalities of the human brain more closely than state-of-the-art purely CMOS hardware architectures, should not leave aside the adoption of resistance switching memories, which, under the appropriate provision of energy, are capable to amplify the small signal, such as the niobium dioxide micro-scale device from NaMLab, chosen as object of theoretical and experimental study in this work.

Total oxidative stress and antioxidant status in patients with carpal tunnel syndrome.

OBJECTIVES: Studies in the carpal tunnel syndrome (CTS) are supported ischemia-induced changes rather than inflammation of the flexor tenosynovium. In this study, total antioxidant status (TAS), total oxidative stress (TOS) and oxidative stress index (OSI) in patients with CTS has been investigated. METHODS: Forty-three patients (38 female and 5 male, 81 hands in total) diagnosed as CTS after the physical examination and electrophysiological findings included in study. The mean age of patients was 43.30 ± 10.49 years. RESULTS: Bilateral CTS in 38 (88%) patients and unilateral CTS in five patients were detected. Dominant hand was involved in all patients. The mean symptoms duration was 30.9 months (range, 5-67 months). TAS in patients with CTS was significantly lower compared with control (1.01 ± 0.14 versus 1.11 ± 0.20 mmol Trolox equiv./l), (P = 0.008). TOS and OSI in patients with CTS were significant higher compared with control (15.60 ± 7.03 versus 11.86 ± 2.18 µmol H2O2 equiv./l and 1.57 ± 0.72 versus 1.09 ± 0.28), (respectively P = 0.002 and <0.001). CONCLUSION: This study shows that there is a change in the oxidative stress and antioxidant defences in patients with CTS. Increased TOS and OSI and decreased TAS might be stimulate fibrosis through disturbed signaling pattern in the tenosynovium and median nerve. These processes might play a role in occurrence and progression of CTS.

Carotid intima-media thickness and paraoxonase activity in patients with ankylosing spondylitis.

PURPOSE: The risk of atherosclerosis is increased in several rheumatological disorders, but any such risk remains unproven for ankylosing spondylitis. Since carotid intima-media thickness is an indicator of early atherosclerosis, and the paraoxonase (PON1) enzyme has antioxidant activity to prevent LDL oxidation, we aimed to identify: 1) the relationship between carotid intima-media thickness (CIMT) and serum paraoxonase (PON1) activity in ankylosing spondylitis (AS) patients; and 2) the possible differences in CIMT in AS patients versus age-matched, healthy controls. METHODS: Forty-five AS patients (36.8±9.8 years, 36 males, 9 females) and 30 controls (35.9±10.2 years, 23 males, 7 females) were recruited consecutively. Serum PON1 activity and CIMT were measured. The Bath Ankylosing Spondylitis Metrology Index (BASMI), Bath Ankylosing Spondylitis Functional Index (BASFI), Bath Ankylosing Spondylitis Radiologic Index (BASRI) and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) were used to identify relationships between these clinical indices and levels of CIMT and PON1. RESULTS: Mean CIMT was significantly increased in AS patients relative to controls (0.49±0.06 mm vs. 0.59±0.07 mm; p < 0.0001). Conversely, serum PON1 activity was decreased (199.1±60.3 U/L vs. 96.7±29 U/L; p < 0.0001). PON1 activity was negatively correlated with CIMT (r = -0.557, p = 0.0001). Disease duration was positively correlated with CIMT (r = 0.542, p = 0.0001) and negatively correlated with PON1 (r = -0.649, p = 0.0001). On multivariate analysis, disease duration and serum PON1 activity were found to be independent predictors of CIMT (R2 = 0.687, p = 0.0001). CONCLUSIONS: In conclusion, significantly increased CIMT and decreased PON1 activity suggest a relationship between atherosclerosis and AS: a relationship that is strongly correlated with disease duration.

The medial plantar and medial peroneal cutaneous nerve conduction studies for diabetic polyneuropathy.

Objective of this study was to determine which nerve conduction is more sensitive electrophysiologically in the diagnosis of polyneuropathy in diabetics by evaluating the sensory conduction in medial plantar nerve and medial peroneal (dorsal) cutaneous nerves. Additionally to investigate the relation between Neuropathy Symptom Score (NSS) and Neuropathy Disability Score (NDS) values used in the diagnosis of these conduction studies. Forty patients with diagnosis diabetic neuropathy were included into this study. In diabetic polyneuropathic patient group, both medial plantar and medial dorsal cutaneous nerve sensory action potential were not bilaterally obtained in 19 patients (47.5%). Sensitivity and specificity of medial dorsal cutaneous nerve and medial plantar nerve sensory conduction abnormalities in diagnosis of diabetic polyneuropathy were higher compared to sural nerve conduction abnormalities. This study showed that both medial plantar and medial dorsal cutaneous nerve conduction study performed bilaterally was a highly sensitive and specific method in diagnosis of diabetic neuropathy.

Experimental verification of rank 1 chaos in switch-controlled Chua circuit.

In this paper, we provide the first experimental proof for the existence of rank 1 chaos in the switch-controlled Chua circuit by following a step-by-step procedure given by the theory of rank 1 maps. At the center of this procedure is a periodically kicked limit cycle obtained from the unforced system. Then, this limit cycle is subjected to periodic kicks by adding externally controlled switches to the original circuit. Both the smooth nonlinearity and the piecewise linear cases are considered in this experimental investigation. Experimental results are found to be in concordance with the conclusions of the theory.

Assessment of paraoxonase activities in patients with knee osteoarthritis.

The objective of this study was to investigate serum paraoxonase and arylesterase activities, and lipid hydroperoxide (LOOH) and total thiol (total free sulfhydryl groups, -SH) levels along with lipid parameters in patients with knee osteoarthritis. Thirty-six patients with knee osteoarthritis and 30 healthy individuals were enrolled in the study. Serum paraoxonase and arylesterase activities were measured spectrophotometrically. LOOH levels were measured by ferrous oxidation with xylenol orange assay (FOX-2). Serum high-density lipoprotein-cholesterol (HDL-C), -SH levels, paraoxonase and arylesterase activities were significantly lower in the patient group than those in the controls (P < 0.05, for all), while LOOH and low-density lipoprotein (LDL) levels were significantly higher. In conclusion, paraoxonase and arylesterase activities were decreased significantly in patients with knee osteoarthritis. Lower serum paraoxonase-1 activity and lower level of HDL-C seem to be related to increased oxidative stress and inflammatory condition in these patients. It is known that paraoxonases reduce oxidative stress in serum and tissues thereby protecting against cardiovascular disease, particularly atherosclerosis. Thus, decreased paraoxonase and arylesterase activities play a role in the pathogenesis of atherosclerosis through increased susceptibility to lipid peroxidation in patients with osteoarthritis.