Efficacy and safety of enteral supplementation with high-dose vitamin D in critically ill patients with vitamin D deficiency.

BACKGROUND: Vitamin D deficiency is associated with mortality and morbidity in critically ill patients. This study investigated the safety and effectiveness of enteral high-dose vitamin D supplementation in intensive care unit (ICU) patients in Asia. METHODS: This was a multicenter, prospective, randomized-controlled study. Eligible participants with vitamin D deficiency were randomly assigned to the control or vitamin D supplementation group. In the vitamin D supplementation group, the patients received 569,600 IU vitamin D. The primary outcome was the serum 25(OH)D level on day 7. RESULTS: 41 and 20 patients were included in the vitamin D supplementation and control groups, respectively. On day 7, the serum 25(OH)D level was significantly higher in the vitamin D supplementation group compared to the control group (28.5 [IQR: 20.2-52.6] ng/mL and 13.9 [IQR: 11.6-18.8] ng/mL, p < 0.001). Only 41.5% of the patients achieved serum 25(OH)D levels higher than 30 ng/mL in the supplementation group. This increased level was sustained in the supplementation group on both day 14 and day 28. There were no significant adverse effects noted in the supplementation group. Patients who reached a serum 25(OH)D level of >30 ng/mL on day 7 had a significantly lower 30-day mortality rate than did those who did not (5.9% vs 37.5%, p < 0.05). CONCLUSIONS: In our study, less than half of the patients reached adequate vitamin D levels after the enteral administration of high-dose vitamin D. A reduction in 30-day mortality was noted in the patients who achieved adequate vitamin D levels. TRIAL REGISTRATION CLINICALTRIALS. GOV ID: NCT04292873, Registered, March 1, 2020.

Optimal Timing of Targeted Temperature Management for Post-Cardiac Arrest Syndrome: Is Sooner Better?

Targeted temperature management (TTM) is often considered to improve post-cardiac arrest patients' outcomes. However, the optimal timing to initiate cooling remained uncertain. This retrospective analysis enrolled all non-traumatic post-cardiac arrest adult patients with either out-of-hospital cardiac arrest (OHCA) or in-hospital cardiac arrest (IHCA) who received TTM from July 2015 to July 2021 at our hospital. The values of time delay before TTM and time to target temperature were divided into three periods according to optimal cut-off values identified using receiver operating characteristic curve analysis. A total of 177 patients were enrolled. A shorter time delay before TTM (pre-induction time) was associated with a lower survival chance at 28 days (32.00% vs. 54.00%, p = 0.0279). Patients with a longer cooling induction time (>440 minis) had better neurological outcomes (1.58% vs. 1.05%; p = 0.001) and survival at 28 days (58.06% vs. 29.25%; p = 0.006). After COX regression analysis, the influence of pre-induction time on survival became insignificant, but patients who cooled slowest still had a better chance of survival at 28 days. In conclusion, a shorter delay before TTM was not associated with better clinical outcomes. However, patients who took longer to reach the target temperature had better hospital survival and neurological outcomes than those who were cooled more rapidly. A further prospective study was warranted to evaluate the appropriate time window of TTM.

Duration of varenicline prescription and efficacy of smoking cessation treatment: an observational study in Taiwan.

Although varenicline has had a significant effect on smoking cessation in randomized clinical trials, the dose-effect of varenicline treatment for smoking cessation in real-world settings remains unclear. This study aimed to evaluate the association between the duration of varenicline prescription and smoking cessation in Taiwan after adjusting for potential confounding effects and endogeneity bias. A total of 5106 Taiwanese participants received varenicline monotherapy for smoking cessation between March 2012 and September 2016. Multinomial logistic regression (MLR) was used to analyze the association between varenicline prescription duration and smoking cessation, stratified by the frequency of smoking clinic visits and propensity scores of early stopping of smoking cessation treatment. Compared to the reference of nonquitting, longer durations of varenicline prescription were associated with the greater likelihood of immediate and complete quitting (OR = 1.08, 95% CI = 1.02-1.14) and late quitting (OR = 1.14, 95% CI = 1.07-1.20). Among those who were more likely to continue visiting smoking clinics, longer use of varenicline was significantly associated with an increase in immediate-and-complete quitting (OR = 1.19, 95% CI = 1.15-1.23) and late quitting (OR = 1.24, 95% CI = 1.20-1.28). Varenicline prescription duration was not associated with smoking cessation among smokers who visited smoking clinics once. The relationship between varenicline prescription duration and smoking cessation was modified by the frequency of smoking clinic visits and was dependent on quitting process patterns. Encouraging smokers to continue visiting the smoking cessation clinic and use medication will help smoking cessation efforts in Taiwan.

Voltage-Time Transformation Model for Threshold Switching Spiking Neuron Based on Nucleation Theory.

In this study, we constructed a voltage-time transformation model (V-t Model) to predict and simulate the spiking behavior of threshold-switching selector-based neurons (TS neurons). The V-t Model combines the physical nucleation theory and the resistor-capacitor (RC) equivalent circuit and successfully depicts the history-dependent threshold voltage of TS selectors, which has not yet been modeled in TS neurons. Moreover, based on our model, we analyzed the currently reported TS devices, including ovonic threshold switching (OTS), insulator-metal transition, and silver- (Ag-) based selectors, and compared the behaviors of the predicted neurons. The results suggest that the OTS neuron is the most promising and potentially achieves the highest spike frequency of GHz and the lowest operating voltage and area overhead. The proposed V-t Model provides an engineering pathway toward the future development of TS neurons for neuromorphic computing applications.

Device quantization policy in variation-aware in-memory computing design.

Device quantization of in-memory computing (IMC) that considers the non-negligible variation and finite dynamic range of practical memory technology is investigated, aiming for quantitatively co-optimizing system performance on accuracy, power, and area. Architecture- and algorithm-level solutions are taken into consideration. Weight-separate mapping, VGG-like algorithm, multiple cells per weight, and fine-tuning of the classifier layer are effective for suppressing inference accuracy loss due to variation and allow for the lowest possible weight precision to improve area and energy efficiency. Higher priority should be given to developing low-conductance and low-variability memory devices that are essential for energy and area-efficiency IMC whereas low bit precision (< 3b) and memory window (< 10) are less concerned.

Maxacalcitol Pharmacokinetic-Pharmacodynamic Modeling and Simulation for Secondary Hyperparathyroidism in Patients Receiving Maintenance Hemodialysis.

BACKGROUND: Maxacalcitol was approved in Taiwan in 2018 as the first active vitamin D3 injection for secondary hyperparathyroidism (SHPT) in patients on maintenance hemodialysis. However, no data from any clinical study with maxacalcitol in Taiwanese patients is available. OBJECTIVES: This analysis aimed to evaluate the profiles of parathyroid hormone (PTH) and calcium (Ca) concentrations in Taiwanese SHPT patients on hemodialysis and maxacalcitol. METHODS: We developed population pharmacokinetic (PK) and pharmacodynamic (PD) models using a modeling and simulation approach. The data for these analyses were obtained from two studies: a clinical pharmacology study in Japanese patients and an ethnic comparison study in healthy Japanese and -Taiwanese volunteers. We then conducted a simulation study with a PK-PD model comprising the PK and PD models developed here. RESULTS: Serum maxacalcitol concentration profile was modeled using a two-compartment model that took into consideration the distribution of concentrations below the lower limit of quantification. An ethnic difference in clearance was included in the PK model as a covariate. A PD model that used a PTH/Ca feedback loop best described the observed data. There were no significant differences in Ca or PTH concentrations between Taiwanese and Japanese based on the simulation results from our PK-PD model, even though maxacalcitol exposure was approximately 40% higher in Taiwanese than in Japanese. CONCLUSIONS: On the basis of these population PK and PD analyses and the clinical study conducted in Japan, there is no clinically relevant difference between Taiwanese and Japanese in terms of serum Ca or PTH levels.

Does One Size Fit All? External Validation of the rCAST Score to Predict the Hospital Outcomes of Post-Cardiac Arrest Patients Receiving Targeted Temperature Management.

The revised post-Cardiac Arrest Syndrome for Therapeutic hypothermia (rCAST) score was proposed to predict neurologic outcomes and mortality among out-of-hospital cardiac arrest (OHCA) patients. However, it has rarely been validated outside Japan. Therefore, this study aimed to investigate this issue. All adult patients admitted to our medical intensive care unit for targeted temperature management (TTM) between July 2015 and July 2021 were enrolled. Their medical records were retrieved, and rCAST scores were calculated. A total of 108 post-cardiac arrest syndrome (PCAS) patients who received TTM were analyzed. According to the rCAST score, 49.1%, 50.0%, and 0.9% of the patients were classified as low, moderate, and high severity, respectively. The areas under the curves for the rCAST score were 0.806 (95% confidence interval [CI]: 0.719-0.876) and 0.794 (95% CI: 0.706-0.866) to predict poor neurologic outcomes and mortality at day 28, respectively. In contrast to the original report, only low-severity patients had favorable neurologic outcomes. The rCAST score showed moderate accuracy in our OHCA patients with PCAS who received TTM to predict poor neurologic outcomes and mortality at day 28.

Prevalence of Vitamin D Deficiency and Associated Factors in Critically Ill Patients: A Multicenter Observational Study.

Background: Vitamin D deficiency is common in the general population worldwide, and the prevalence and severity of vitamin D deficiency increase in critically ill patients. The prevalence of vitamin D deficiency in a community-based cohort in Northern Taiwan was 22.4%. This multicenter cohort study investigated the prevalence of vitamin D deficiency and associated factors in critically ill patients in Northern Taiwan. Methods: Critically ill patients were enrolled and divided into five groups according to their length of stay at intensive care units (ICUs) during enrolment as follows: group 1, <2 days with expected short ICU stay; group 2, <2 days with expected long ICU stay; group 3, 3-7 days; group 4, 8-14 days; and group 5, 15-28 days. Vitamin D deficiency was defined as a serum 25-hydroxyvitamin D (25(OH)D) level < 20 ng/ml, and severe vitamin D deficiency was defined as a 25(OH)D level < 12 ng/ml. The primary analysis was the prevalence of vitamin D deficiency. The exploratory analyses were serial follow-up vitamin D levels in group 2, associated factors for vitamin D deficiency, and the effect of vitamin D deficiency on clinical outcomes in critically ill patients. Results: The prevalence of vitamin D deficiency was 59% [95% confidence interval (CI) 55-62%], and the prevalence of severe vitamin D deficiency was 18% (95% CI 15-21%). The median vitamin D level for all enrolled critically ill patients was 18.3 (13.7-23.9) ng/ml. In group 2, the median vitamin D levels were <20 ng/ml during the serial follow-up. According to the multivariable analysis, young age, female gender, low albumin level, high parathyroid hormone (PTH) level, and high sequential organ failure assessment (SOFA) score were significantly associated risk factors for vitamin D deficiency. Patients with vitamin D deficiency had longer ventilator use duration and length of ICU stay. However, the 28- and 90-day mortality rate were not associated with vitamin D deficiency. Conclusions: This study demonstrated that the prevalence of vitamin D deficiency is high in critically ill patients. Age, gender, albumin level, PTH level, and SOFA score were significantly associated with vitamin D deficiency in these patients.

[Using Teamwork to Reduce the Incidence of Incontinence-Associated Dermatitis].

BACKGROUND & PROBLEMS: Dermatitis associated with incontinence was the cause of 55% of the total of 386 skin lesion cases in our unit between July and December 2016 and 40.3% of the skin lesion cases in our unit during March and April 2017, indicating the importance of this issue. Our survey showed that the nurses in our unit scored an average of 78.9% on knowledge related to the prevention of incontinence-associated dermatitis and only 58.2% on knowledge related to incontinence-associated dermatitis care. The main reasons for the high incidence of incontinence-associated dermatitis included: incorrect implementation of care, no discussion with the medical team, no incontinence care standards, no continue education, lack of related equipment for preventing incontinence-associated dermatitis, unit patient characteristics, and drugs used. PURPOSE: To reduce the incidence of incontinence-associated dermatitis from 40.3% to 32.0%. RESOLUTION: A care-bundle in treating incontinence-associated dermatitis was implemented by designing an assessment flow chart for evaluating incontinence-associated dermatitis, by setting standard guidelines for incontinence-associated dermatitis care, by distributing reminder cards, special toolboxes, and by changing how the little diapers were wrapped. In-service education lessons, inter-professional collaborative practice, and regular internal audit were also executed. RESULTS: After project implementation, the knowledge score of nurses increased from 78.9% to 95.7%; the correctness of care score, as retested in November 2017, increased from 58.2% to 91.5%; and the incidence of incontinence-associated dermatitis dropped to 18.5%. These improvements achieved the goals of this project. Furthermore, the sustained effect of the project measures was confirmed, with the incidence of incontinence-associated dermatitis determined as 17.9% at three months after completion of the project. CONCLUSIONS: Formulating care procedures and cooperating with medical team personnel to provide creative care measures were shown to effectively decrease the incidence of incontinence-associated dermatitis and improve overall quality of care. The findings of this project support the revision by hospitals of regulations and procedures related to adult incontinence-associated dermatitis to provide caregivers with basis-of-care standards and uniform care procedures and standards in support of effective patient skin care regimens.

Metabolic tumor volume predicts overall survival in patients with primary pulmonary lymphoepithelioma-like carcinoma.

Pretreatment tumor metabolic burden, measured using fluorine-18 fluorodeoxyglucose positron emission tomography/computerized tomography (18F-FDG PET/CT), has been demonstrated to predict outcomes in various types of malignancies. Additionally, Epstein-Barr virus (EBV) serum titer is associated with stages of pulmonary lymphoepithelioma-like carcinoma (LELC). The present study aimed to investigate the prognostic value of the functional parameters of 18F-FDG PET/CT in pulmonary LELC and their association with serum EBV DNA. The present retrospective study analyzed data from 71 patients with pulmonary LELC; among these, 32 patients with pulmonary LELC underwent pretreatment 18F-FDG PET/CT staging between January 2008 and December 2016. EBV viral load and functional parameters of 18F-FDG PET/CT were used for survival analysis. Multivariate analysis identified tumor stage IV as a significant predictor of poor progression-free survival [hazard ratio (HR), 4.85; P=0.049], whereas elevated total metabolic tumor volume (MTV ≥72.6 ml) independently predicted worse overall survival (OS; HR, 12.59; P=0.024). Pretreatment serum EBV DNA titer was significantly positively associated with total MTV (P=0.0337) and total lesion glycolysis (TLG; P=0.0093), but could not predict outcomes. Total MTV was an independent predictor of OS, and may guide clinical management for pulmonary LELC.

Comparison of Clinical Manifestation, Diagnosis, and Outcomes of Invasive Pulmonary Aspergillosis and Pulmonary Mucormycosis.

OBJECTS: Invasive pulmonary mold infection usually has devastating outcomes. Timely differentiation between invasive pulmonary aspergillosis (IPA) from pulmonary mucormycosis (PM) is critical for treatment decision-making. However, information on IPA and PM differentiation is limited. METHODS: We conducted a retrospective, multicenter, observational study, with proven and probable IPA and PM patients from January 2004 to December 2017. Demographics, clinical manifestations, image reports, histopathological findings, and outcomes were analyzed. RESULTS: A total of 46 IPA (33 proven and 13 probable) and 19 PM (18 proven and one probable) cases were analyzed. The majority of tissues (81% in IPA and 61% in PM) were obtained using bronchoscopy. Prior influenza infection was a predisposing factor for IPA, and abscess formation in CT scan was associated with PM (p = 0.0491, p = 0.0454, respectively). The positive culture rate for PM was lower than that for IPA (37% vs. 67%, p = 0.0294). The galactomannan (GM) level from serum and bronchoalveolar lavage (BAL) fluid was significantly higher in IPA than in PM (3.3 ± 0.5 vs. 0.8 ± 0.6, p = 0.0361; 4.0 ± 0.6 vs. 0.59 ± 0.1, p = 0.0473, respectively). The overall mortality rate was 65%, which was similar among IPA and PM groups. Systemic steroid exposure and high Acute Physiology and Chronic Health Evaluation II (APACHE II) scores on admission were independently correlated to mortality in IPA (p = 0.027, p = 0.026, respectively). However, there was no predictor for mortality found in PM patients. CONCLUSIONS: Influenza infection, abscess formation in CT scan, and GM level may help physicians to differentiate IPA and PM. Bronchoscopy-guided biopsy and lavage specimen provide timely and definite diagnosis. The prognosis of IPA is associated with systemic steroid exposure and higher APACHE II scores on admission.

Altered NMDAR signaling underlies autistic-like features in mouse models of CDKL5 deficiency disorder.

CDKL5 deficiency disorder (CDD) is characterized by epilepsy, intellectual disability, and autistic features, and CDKL5-deficient mice exhibit a constellation of behavioral phenotypes reminiscent of the human disorder. We previously found that CDKL5 dysfunction in forebrain glutamatergic neurons results in deficits in learning and memory. However, the pathogenic origin of the autistic features of CDD remains unknown. Here, we find that selective loss of CDKL5 in GABAergic neurons leads to autistic-like phenotypes in mice accompanied by excessive glutamatergic transmission, hyperexcitability, and increased levels of postsynaptic NMDA receptors. Acute, low-dose inhibition of NMDAR signaling ameliorates autistic-like behaviors in GABAergic knockout mice, as well as a novel mouse model bearing a CDD-associated nonsense mutation, CDKL5 R59X, implicating the translational potential of this mechanism. Together, our findings suggest that enhanced NMDAR signaling and circuit hyperexcitability underlie autistic-like features in mouse models of CDD and provide a new therapeutic avenue to treat CDD-related symptoms.

Loss of CDKL5 in Glutamatergic Neurons Disrupts Hippocampal Microcircuitry and Leads to Memory Impairment in Mice.

Cyclin-dependent kinase-like 5 (CDKL5) deficiency is a neurodevelopmental disorder characterized by epileptic seizures, severe intellectual disability, and autistic features. Mice lacking CDKL5 display multiple behavioral abnormalities reminiscent of the disorder, but the cellular origins of these phenotypes remain unclear. Here, we find that ablating CDKL5 expression specifically from forebrain glutamatergic neurons impairs hippocampal-dependent memory in male conditional knock-out mice. Hippocampal pyramidal neurons lacking CDKL5 show decreased dendritic complexity but a trend toward increased spine density. This morphological change is accompanied by an increase in the frequency of spontaneous miniature EPSCs and interestingly, miniature IPSCs. Using voltage-sensitive dye imaging to interrogate the evoked response of the CA1 microcircuit, we find that CA1 pyramidal neurons lacking CDKL5 show hyperexcitability in their dendritic domain that is constrained by elevated inhibition in a spatially and temporally distinct manner. These results suggest a novel role for CDKL5 in the regulation of synaptic function and uncover an intriguing microcircuit mechanism underlying impaired learning and memory.SIGNIFICANCE STATEMENT Cyclin-dependent kinase-like 5 (CDKL5) deficiency is a severe neurodevelopmental disorder caused by mutations in the CDKL5 gene. Although Cdkl5 constitutive knock-out mice have recapitulated key aspects of human symptomatology, the cellular origins of CDKL5 deficiency-related phenotypes are unknown. Here, using conditional knock-out mice, we show that hippocampal-dependent learning and memory deficits in CDKL5 deficiency have origins in glutamatergic neurons of the forebrain and that loss of CDKL5 results in the enhancement of synaptic transmission and disruptions in neural circuit dynamics in a spatially and temporally specific manner. Our findings demonstrate that CDKL5 is an important regulator of synaptic function in glutamatergic neurons and serves a critical role in learning and memory.

Increased risk of avascular necrosis in patients with psoriatic disease: A nationwide population-based matched cohort study.

BACKGROUND: Avascular necrosis (AVN) and psoriasis have some pathogenic mechanisms and associated conditions in common. OBJECTIVE: To examine the association between psoriasis and AVN. METHODS: This study used data from the Taiwan National Health Insurance Research Database for the period 2004-2006 and identified 28,268 patients with psoriasis, who were then matched for age and sex with 113,072 controls without psoriasis from the Taiwan Longitudinal Health Insurance Database 2000. Multivariate Cox proportional hazards models were used for the analysis. RESULTS: The unadjusted risk of AVN was significantly higher for patients with psoriasis than for controls (hazard ratio [HR] 2.29) and remained significant after adjustment for other risk factors (adjusted HR 1.96; 95% confidence interval 1.62-2.38). The risk for AVN increased in relation to psoriasis severity and was higher for patients with psoriasis and arthritis than for patients without arthritis. The adjusted HRs were higher for male patients than for female patients and for patients younger than 30 years compared with older patients. LIMITATIONS: We lacked information on daily tobacco use, alcohol consumption, and physical activity. CONCLUSION: The risk for AVN increased with the disease severity of psoriasis.

3D Ta/TaO x /TiO2/Ti synaptic array and linearity tuning of weight update for hardware neural network applications.

The implementation of highly anticipated hardware neural networks (HNNs) hinges largely on the successful development of a low-power, high-density, and reliable analog electronic synaptic array. In this study, we demonstrate a two-layer Ta/TaO x /TiO2/Ti cross-point synaptic array that emulates the high-density three-dimensional network architecture of human brains. Excellent uniformity and reproducibility among intralayer and interlayer cells were realized. Moreover, at least 50 analog synaptic weight states could be precisely controlled with minimal drifting during a cycling endurance test of 5000 training pulses at an operating voltage of 3 V. We also propose a new state-independent bipolar-pulse-training scheme to improve the linearity of weight updates. The improved linearity considerably enhances the fault tolerance of HNNs, thus improving the training accuracy.

Fully parallel write/read in resistive synaptic array for accelerating on-chip learning.

A neuro-inspired computing paradigm beyond the von Neumann architecture is emerging and it generally takes advantage of massive parallelism and is aimed at complex tasks that involve intelligence and learning. The cross-point array architecture with synaptic devices has been proposed for on-chip implementation of the weighted sum and weight update in the learning algorithms. In this work, forming-free, silicon-process-compatible Ta/TaOx/TiO2/Ti synaptic devices are fabricated, in which >200 levels of conductance states could be continuously tuned by identical programming pulses. In order to demonstrate the advantages of parallelism of the cross-point array architecture, a novel fully parallel write scheme is designed and experimentally demonstrated in a small-scale crossbar array to accelerate the weight update in the training process, at a speed that is independent of the array size. Compared to the conventional row-by-row write scheme, it achieves >30× speed-up and >30× improvement in energy efficiency as projected in a large-scale array. If realistic synaptic device characteristics such as device variations are taken into an array-level simulation, the proposed array architecture is able to achieve ∼95% recognition accuracy of MNIST handwritten digits, which is close to the accuracy achieved by software using the ideal sparse coding algorithm.

Characterization and Modeling of Nonfilamentary Ta/TaOx/TiO2/Ti Analog Synaptic Device.

A two-terminal analog synaptic device that precisely emulates biological synaptic features is expected to be a critical component for future hardware-based neuromorphic computing. Typical synaptic devices based on filamentary resistive switching face severe limitations on the implementation of concurrent inhibitory and excitatory synapses with low conductance and state fluctuation. For overcoming these limitations, we propose a Ta/TaOx/TiO2/Ti device with superior analog synaptic features. A physical simulation based on the homogeneous (nonfilamentary) barrier modulation induced by oxygen ion migration accurately reproduces various DC and AC evolutions of synaptic states, including the spike-timing-dependent plasticity and paired-pulse facilitation. Furthermore, a physics-based compact model for facilitating circuit-level design is proposed on the basis of the general definition of memristor devices. This comprehensive experimental and theoretical study of the promising electronic synapse can facilitate realizing large-scale neuromorphic systems.

Perceived environmental and personal factors associated with walking and cycling for transportation in Taiwanese adults.

This study examined perceived environmental and personal factors associated with walking and cycling as means of transportation for Taiwanese adults. A random-digit-dialing telephone-based cross-sectional survey was conducted with Taiwanese adults aged 20 to 64 years. Data on time spent walking and cycling for transportation and perceptions of neighborhood environment and personal characteristics were obtained from 1065 adults by using the International Physical Activity Questionnaire-long version and its environmental module. Adjusted binary logistic regression was performed. The results showed that, after adjusting potential confounders, common and different personal and perceived environmental factors were associated with walking and cycling for transportation. For common personal factors, adults who had employment were less likely to engage in 150 min of walking per week (odds ratio [OR] = 0.41; 95% confidence interval (CI): 0.27-0.62) and to use cycling as a means of transportation (OR = 0.51; 95% CI: 0.32-0.79). For common perceived environmental factors, adults who perceived good connectivity of streets were more likely to walk (OR = 1.95; 95% CI: 1.20-3.16) and cycle (OR = 2.02; 95% CI: 1.16-3.54) for transportation. Targeting employed adults and improving the connectivity of streets should be a priority for developing transport policies and intervention strategies to promote active transportation.

Homogeneous barrier modulation of TaOx/TiO2 bilayers for ultra-high endurance three-dimensional storage-class memory.

Three-dimensional vertical resistive-switching random access memory (VRRAM) is the most anticipated candidate for fulfilling the strict requirements of the disruptive storage-class memory technology, including low bit cost, fast access time, low-power nonvolatile storage,and excellent endurance. However, an essential self-selecting resistive-switching cell that satisfies these requirements has yet to be developed. In this study, we developed a TaOx/TiO2 double-layer V-RRAM containing numerous highly desired features, including: (1) a self-rectifying ratio of up to 10³ with a sub-µA operating current, (2) little cycle-to-cycle and layer-to-layer variation, (3) a steep vertical sidewall profile for high-density integration, (4) forming-free and self-compliance characteristics for a simple peripheral circuit design, and (5) an extrapolated endurance of over 10¹5 cycles at 100 °C. Furthermore, the switching and self-rectifying mechanisms were successfully modeled using oxygen ion migration and homogeneous barrier modulation. We also suggest the new possibility of monolithically integrating working and storage memory by exploiting a unique tradeoff between retention time and endurance.