Delay Interval Research Articles

A Novel Method for Stability Analysis of Time-Varying Delay Systems

The Lyapunov–Krasovskii functional (LKF) method is an effective tool to obtain delay-dependent stability criteria of time-varying delay systems. However, in the method, the requirement that there must exist an appropriate LKF for a system with a delay varying in a delay interval is too strict and may lead to considerable conservativeness. In order to get less conservative stability criteria, a novel stability analysis method called a delay-mode-based LKF (DMBLKF) method is first presented for nonlinear delay systems. Compared with the LKF method, the main advantage of the DMBLKF method lies in relaxing the aforementioned requirement and leading to a less conservative criterion in stability analysis. Then, with the help of the novel method, new stability criteria of linear delay systems are derived. Finally, the effectiveness of the proposed method and the obtained criteria is illustrated through two numerical examples.

Retention of Value Representations Across Time in People With Schizophrenia and Healthy Control Subjects

BackgroundThe current study aimed to further etiological understanding of the psychological mechanisms underlying negative symptoms in people with schizophrenia. Specifically, we tested whether negative symptom severity is associated with reduced retention of reward-related information over time and thus a degraded ability to utilize such information to guide future action selection. MethodsForty-four patients with a diagnosis of schizophrenia or schizoaffective disorder and 28 healthy control volunteers performed a probabilistic reinforcement-learning task involving stimulus pairs in which choices resulted in reward or in loss avoidance. Following training, participants indicated their valuation of learned stimuli in a test/transfer phase. The test/transfer phase was administered immediately following training and 1 week later. Percent retention was defined as accuracy at week-long delay divided by accuracy at immediate delay. ResultsHealthy control subjects and people with schizophrenia showed similarly robust retention of reinforcement learning over a 1-week delay interval. However, in the schizophrenia group, negative symptom severity was associated with reduced retention of information regarding the value of actions across a week-long interval. This pattern was particularly notable for stimuli associated with reward compared with loss avoidance. ConclusionsOur results show that although individuals with schizophrenia may initially learn about rewarding aspects of their environment, such learning decays at a more rapid rate in patients with severe negative symptoms. Thus, previously learned reward-related information may be more difficult to access to guide future decision making and to motivate action selection.

Ion energy distributions at substrate in bipolar HiPIMS: effect of positive pulse delay, length and amplitude

A bipolar HiPIMS discharge with a rectangular positive voltage pulse (with controllable amplitude, delay after the main negative pulse and positive pulse length) was systematically investigated by mass spectroscopy. The time-averaged spectra of ions measured at the substrate position exhibit a prominent high-energy peak. It is shown that the position of the peak can be varied by the positive pulse amplitude, its magnitude scales with the pulse length and its width can be slightly influenced by the length of the delay interval. Measurements of the plasma potential at the mass spectrometer position and time-resolved mass spectroscopy clearly show that the high-energy peak is formed by ions accelerated by the elevated plasma potential during the positive pulse. In addition, fine details of the ion energy distribution functions related to the plasma potential transients at the start of the positive pulse are identified. The presented results are beneficial for the optimisation of the parameters of the positive pulse in experiments implementing the bipolar HiPIMS technology.

The Cost-Effectiveness of Platelet-Rich Plasma Injections for Knee Osteoarthritis: A Markov Decision Analysis.

Use of platelet-rich-plasma (PRP) injections for treating knee osteoarthritis has increased over the past decade. We used cost-effectiveness analysis to evaluate the value of PRP in delaying the need for total knee arthroplasty (TKA). We developed a Markov model to analyze the baseline case: a 55-year-old patient with Kellgren-Lawrence grade-II or III knee osteoarthritis undergoing a series of 3 PRP injections with a 1-year delay to TKA versus a TKA from the outset. Both health-care payer and societal perspectives were included. Transition probabilities were derived from systematic review of 72 studies, quality-of-life (QOL) values from the Tufts University Cost-Effectiveness Analysis Registry, and individual costs from Medicare reimbursement schedules. Primary outcome measures were total costs and quality-adjusted life years (QALYs), organized into incremental cost-effectiveness ratios (ICERs) and evaluated against willingness-to-pay thresholds of $50,000 and $100,000. One and 2-way sensitivity analyses were performed as well as a probabilistic analysis varying PRP-injection cost, TKA delay intervals, and TKA outcomes over 10,000 different simulations. From a health-care payer perspective, PRP resulted in 14.55 QALYs compared with 14.63 for TKA from the outset, with total health-care costs of $26,619 and $26,235, respectively. TKA from the outset produced a higher number of QALYs at a lower cost, so it dominated. From a societal perspective, PRP cost $49,090 versus $49,424 for TKA from the outset. The ICER for TKA from the outset was $4,175 per QALY, below the $50,000 willingness-to-pay threshold. Assuming the $728 published cost of a PRP injection, no delay time that was <10 years produced a cost-effective course. When the QOL value was increased from the published value of 0.788 to >0.89, PRP therapy was cost-effective with even a 1-year delay to TKA. When considering direct and unpaid indirect costs, PRP injections are not cost-effective. The primary factor preventing PRP from being cost-effective is not the price per injection but rather a lack of established clinical efficacy in relieving pain and improving function and in delaying TKA. PRP may have value for higher-risk patients with high perioperative complication rates, higher TKA revision rates, or poorer postoperative outcomes. Economic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Refining the Empirical Constraints on Computational Models of Spatial Working Memory in Schizophrenia

BackgroundImpairments in spatial working memory (sWM) have been well documented in schizophrenia. Here we provide a comprehensive test of a microcircuit model of WM performance in schizophrenia that predicts enhanced effects of increasing delay duration and distractors based on a hypothesized imbalance of excitatory and inhibitory processes. MethodsModel predictions were tested in 41 people with schizophrenia (PSZ) and 32 healthy control subjects (HCS) performing an sWM task. In one condition, a single target location was followed by delays of 0, 2, 4, or 8 seconds. In a second condition, distractors were presented during the 4-second delay interval at 20°, 30°, 40°, 50°, or 90° from the original target location. ResultsPSZ showed less precise sWM representations than HCS, and the rate of memory drift over time was greater in PSZ than in HCS. Relative to HCS, the spatial recall responses of PSZ were more repelled by distractors presented close to the target location and more attracted by distractors presented far from the target location. The degree of attraction to distant distractors was correlated with the rate of memory drift in the absence of distractors. ConclusionsConsistent with the microcircuit model, PSZ exhibited both a greater rate of drift and greater attraction to distant distractors relative to HCS. These two effects were correlated, consistent with the proposal that they arise from a single underlying mechanism. However, the repulsion effects produced by nearby distractors were not predicted by the model and thus require an updated modeling framework.

Off-line learning in a rhythmic bimanual task: early feedback dependency is reduced over wakefulness.

Research has supported two distinct forms of motor skill consolidation that can occur between practice sessions: (1) off-line learning, and (2) memory stabilization. Off-line learning describes performance improvement between practice sessions that is above the gain observed at the end of practice, while memory stabilization describes a gain in performance that is maintained between practice sessions. This study used a Lissajous plot to provide concurrent feedback to train participants to produce a 90° relative phase between the index fingers (flexion/extension motion). Significant improvements in performance emerged after ten trials (5min) of practice. At the end of training, participants were divided into two delay interval groups before retesting, 2-h and 6-h. The retesting session started with participants performing an interference task (10 trials, 5min) that required training on a 45° relative phase between the fingers with concurrent feedback from the Lissajous plot. When training with the interference task was completed participants were retested with the 90° relative phase without the Lissajous plot feedback. In the retest of the 90° pattern, a performance loss was found in the 2-h delay group, whereas the 6-h delay group maintained the end of practice performance level. Maintenance of the same level of performance without the Lissajous plot represents memory stabilization of the initially trained 90° pattern. The findings are discussed within the context of current positions regarding procedural consolidation and the coordination dynamics framework wherein action and perception are linked through the informational nature of relative phase.

Stability Analysis for Delayed Neural Networks via Some Switching Methods

In this paper, the stability problem of delayed neural networks is investigated by adopting some switching methods. First, the delay interval is divided into many smaller variable intervals, and when the smaller variable interval is regarded as a mode of the delay, delayed neural networks are modeled as switched systems. Then, by using some switching methods, less conservative stability criteria are derived to ensure the stability of delayed neural networks. Finally, one example is provided to show the effectiveness of the obtained criteria.

An Investigation to Assess the Cause of Accident due to Flyrock in an Opencast Coal Mine: A Case Study

The paper deals with the investigation carried out to find out the possible reason of the flyrock incident causing fatality of one person at Bhurkunda ‘Á’ Colliery of Central Coalfields Limited (CCL). The flying fragment travelled up to 280 m from the blasting source causing the accidental death. The blasts were conducted in overburden rock strata consisting of medium grained sandstone and shale. The blasthole diameter used in the blast was 160 mm, and the average hole depth was 6.0 m. Site mixed emulsion (SME) explosive was used in the blast, and explosive charge per hole was 50.00 kg. Non-electric initiation systems were used for in-hole explosive and surface hole-to-hole initiations. The design parameters used in the blast were thoroughly analyzed using blast simulation software to check any anomaly in the blast design viz. sequence of hole firing, success rate of burden movement, maximum charge per delay fired within 8 ms windows, etc. The different flyrock fragments prediction models were used to assess the maximum possible travel distance of the flying in the blast. A synonymous blast was also conducted in the mines to replicate the blast where flyrock accident occurred. All the blasting events were recorded and monitored using a digital video camera. The simulation results of the blast showed the success rate of burden relief more than 80% with sufficient delay intervals for the rock movement during the blast. The maximum possible travel distance of flying fragments based on different flyrock prediction models was 227 m. In the synonymous blast, only vertical throws of the flying fragments up to 70 m (approximate) height were observed. It was difficult to find out the exact cause of flyrock incident. However, based on the detailed investigation, it was concluded that the possible cause of flying fragments travelling up to a distance of 280 m could be due to the presence of a weak zone in the rock strata.

Epidemiological characteristics of the first 53 laboratory-confirmed cases of COVID-19 epidemic in Hong Kong, 13 February 2020.

BackgroundCOVID-19, caused by SARS-CoV-2, first appeared in China and subsequently developed into an ongoing epidemic. Understanding epidemiological factors characterising the transmission dynamics of this disease is of fundamental importance.AimsThis study aimed to describe key epidemiological parameters of COVID-19 in Hong Kong.MethodsWe extracted data of confirmed COVID-19 cases and their close contacts from the publicly available information released by the Hong Kong Centre for Health Protection. We used doubly interval censored likelihood to estimate containment delay and serial interval, by fitting gamma, lognormal and Weibull distributions to respective empirical values using Bayesian framework with right truncation. A generalised linear regression model was employed to identify factors associated with containment delay. Secondary attack rate was also estimated.ResultsThe empirical containment delay was 6.39 days; whereas after adjusting for right truncation with the best-fit Weibull distribution, it was 10.4 days (95% CrI: 7.15 to 19.81). Containment delay increased significantly over time. Local source of infection and number of doctor consultations before isolation were associated with longer containment delay. The empirical serial interval was 4.58–6.06 days; whereas the best-fit lognormal distribution to 26 certain-and-probable infector–infectee paired data gave an estimate of 4.77 days (95% CrI: 3.47 to 6.90) with right-truncation. The secondary attack rate among close contacts was 11.7%.ConclusionWith a considerable containment delay and short serial interval, contact-tracing effectiveness may not be optimised to halt the transmission with rapid generations replacement. Our study highlights the transmission risk of social interaction and pivotal role of physical distancing in suppressing the epidemic.

Motor and spatial representations of action: corticospinal excitability in M1 after training with a bimanual skill.

The purpose of the study was twofold: (1) determine if different time delays (30min or 6h) between training and a post-training test with a rhythmic bimanual pattern (90° relative phase) would be associated with different levels of consolidation for the motor and spatial representations of the pattern; and (2) determine if training with the rhythmic bimanual pattern would lead to enhanced corticospinal excitability in M1 linked to changes in motor and spatial performance measures. Coordination accuracy and stability of the 90° pattern improved over practice. Coordination accuracy and stability were the same after a 30-min or 6-h delay between training and the post-training test, indicating equivalent levels of consolidation in the motor representation. The 6-h delay interval resulted in shorter visual recognition times compared to the 30-min delay and was centered on the trained 90° pattern. These findings indicate the consolidation of the spatial representation was more time sensitive compared to the motor representation in the current task. Motor evoked potentials (MEPs) from the first dorsal interosseous muscle (FDI) generated by single-pulse transcranial magnetic stimulation (TMS) were measured at baseline (before training) and at 6-min and 21-min intervals post-training with the 90° pattern. Increased corticospinal excitability in M1 was evidenced by larger MEPs of the FDI muscle at the 6-min interval. This increased excitability after training is a novel finding after training with a difficult and initially unstable rhythmic bimanual pattern. No significant correlations were found between the MEP data and behavioral data; thus, the increased excitability in M1 may have been linked to the difficulty in performing the pattern, consolidation processes, or both.

Management of Explosive Crushing of Rock Mass in Quarries

The article deals with improving the quality of rock blast crushing due to increase in delay intervals. The recent decades change in understanding of the rock destruction mechanism under the blast loads influence is shown. The blast mechanical effect reveal itself in rock crushing as well as in the loss of strength away from a charge. The blast waves are acting as compressive and tensile loads in this area. Existing micro-defects and micro-cracks grow as a result. The rock mass strength properties changes. A new condition of the rock mass is called pre-destroyed. The blasts time delay increasing causes cracks merging and a gradual size decrease of the rocks structural elements.

An Electrophysiological Dissociation of Encoding vs. Maintenance Failures in Visual-Spatial Working Memory.

Working memory (WM) performance varies substantially among individuals but the precise contribution of different WM component processes to these functional limits remains unclear. By analyzing different types of responses in a spatial WM task, we recently demonstrated a functional dissociation between confident and not-confident errors reflecting failures of WM encoding and maintenance, respectively. Here, we use event-related brain potentials to further explore this dissociation. Healthy participants performed a delayed orientation-discrimination task and rated their response confidence for each trial. The encoding-related N2pc component was significantly reduced for confident errors compared to confident correct responses, which is indicative of an encoding failure. In contrast, the maintenance-related contra-lateral delay activity was similar for these response types indicating that in confident error trials, WM representations – potentially the wrong ones – were maintained accurately and with stability throughout the delay interval. However, contra-lateral delay activity measured during the early part of the delay period was decreased for not-confident errors, potentially reflecting compromised maintenance processes. These electrophysiological findings contribute to a refined understanding of the encoding and maintenance processes that contribute to limitations in WM performance and capacity.

Disruption of cholinergic neurotransmission, within a cognitive challenge paradigm, is indicative of A\u03b2-related cognitive impairment in preclinical Alzheimer\u2019s disease after a 27-month delay interval

BackgroundAbnormal beta-amyloid (Aβ) is associated with deleterious changes in central cholinergic tone in the very early stages of Alzheimer’s disease (AD), which may be unmasked by a cholinergic antagonist (J Prev Alzheimers Dis 1:1–4, 2017). Previously, we established the scopolamine challenge test (SCT) as a “cognitive stress test” screening measure to identify individuals at risk for AD (Alzheimer’s & Dementia 10(2):262–7, 2014) (Neurobiol. Aging 36(10):2709-15, 2015). Here we aim to demonstrate the potential of the SCT as an indicator of cognitive change and neocortical amyloid aggregation after a 27-month follow-up interval.MethodsOlder adults (N = 63, aged 55–75 years) with self-reported memory difficulties and first-degree family history of AD completed the SCT and PET amyloid imaging at baseline and were then seen for cognitive testing at 9, 18, and 27 months post-baseline. Repeat PET amyloid imaging was completed at the time of the 27-month exam.ResultsSignificant differences in both cognitive performance and in Aβ neocortical burden were observed between participants who either failed vs. passed the SCT at baseline, after a 27-month follow-up period.ConclusionsCognitive response to the SCT (Alzheimer’s & Dementia 10(2):262–7, 2014) at baseline is related to cognitive change and PET amyloid imaging results, over the course of 27 months, in preclinical AD. The SCT may be a clinically useful screening tool to identify individuals who are more likely to both have positive evidence of amyloidosis on PET imaging and to show measurable cognitive decline over several years.

On the Delay Interval in Which the Control Delay Systems are Stabilizable

In this paper, we firstly derive some criteria for considered control delay systems to be stabilizable and then get the interval of the control delay, in which the stabilizability of the systems can be kept.

Interventions Addressing Barriers to Delayed Cancer Diagnosis in Low- and Middle-Income Countries: A Systematic Review.

Delays to cancer diagnosis exist, resulting in worse survival outcomes for many cancers. Interventions targeting delays and barriers to cancer diagnosis and treatment have been investigated, but mostly in high-income countries. We conducted a systematic literature review to identify and characterize the interventions studied across cancers, within low- and middle-income countries (LMICs). This systematic review forms part two of a wider study examining solutions to delays and barriers in cancer early diagnosis in LMICs. A comprehensive literature search was conducted on November 27, 2017, encompassing published studies from the preceding 15 years. We extracted study design, population, and intervention, and reported outcome measures from each study. Results were presented by target of interventions (general vs. health care professionals). A narrative synthesis was used to summarize intervention efficacy. Of 10,193 abstracts returned, 25 were included, consisting of studies across World Health Organization geographical regions, examining breast, cervix, childhood, prostate, head and neck, and gastric cancers. Altogether, 11 intervention studies targeted the general population, 12 targeted health care professionals, and 2 targeted both. The majority (17/25) of studies reported interventions focusing on patient and diagnosis-related barriers early in the cancer care pathway. Most studies reported knowledge score as primary outcome measure (17/25); few (6/25) reported on clinically relevant measures such as reducing disease stage at presentation or diagnostic time interval. Effectiveness of interventions was demonstrated for some cancers only. More interventions reporting clinically relevant measures and using standardized methods and outcomes are required to improve our ability to effectively improve cancer early diagnosis in LMICs. Prior to this study, the extent of intervention literature in cancer early diagnosis in low- and middle-income countries had not been characterized. This study aimed to outline and characterize interventions across all cancer types and across all countries. This systematic review demonstrated that interventions have been investigated targeting both the general population and health care professionals. Furthermore, this review demonstrates that the majority of studies report knowledge as an outcome measure, rather than clinically significant measures that improve cancer-related outcomes, such as delay intervals or downstaging of disease. Future interventions should address clinically relevant measures to better assess efficacy of interventions.

Dynamic Recovery from Depression Enables Rate Encoding in Inhibitory Synapses.

SummaryParvalbumin-expressing fast-spiking interneurons (PV-INs) control network firing and the gain of cortical response to sensory stimulation. Crucial for these functions, PV-INs can sustain high-frequency firing with no accommodation. However, PV-INs also exhibit short-term depression (STD) during sustained activation, largely due to the depletion of synaptic resources (vesicles). In most synapses the rate of replenishment of depleted vesicles is constant, determining an inverse relationship between depression levels and the activation rate, which theoretically, severely limits rate-coding capabilities. We examined STD of the PV-IN to pyramidal cell synapse in the mouse visual cortex and found that in these synapses the recovery from depression is not constant but increases linearly with the frequency of use. By combining modeling, dynamic clamp, and optogenetics, we demonstrated that this recovery enables PV-INs to reduce pyramidal cell firing in a linear manner, which theoretically is crucial for controlling the gain of cortical visual responses.

Control of transmission error of high contact ratio spur gears with symmetric profile modifications

This paper presents a study on the influence on the quasi-static transmission error of symmetric long profile modifications on high contact ratio spur gears. A previously developed model for the load sharing ratio and quasi-static transmission error, based on the hypothesis of equal delay interval in all the teeth in simultaneous contact, has been used. The simple formulation of the model allows to obtain the equation of the required profile modification to ensure a preestablished function of load sharing ratio or quasi-static transmission error. From this model, the tip reliefs for minimum peak-to-peak amplitude of quasi-static transmission error and for minimum dynamic load, have been obtained. In both cases, the optimum length of modification has been expressed as a function of the contact ratio.

Robust H∞ performance for discrete time T-S fuzzy switched memristive stochasticneural networks with mixed time-varying delays

ABSTRACT In this paper, we study the robust H ∞ performance for discrete-time T-S fuzzy switched memristive stochastic neural networks with mixed time-varying delays and switching signal design. The neural network under consideration is subject to time-varying and norm bounded parameter uncertainties. Decomposing of the delay interval approach is employed in both the discrete delays and distributed delays. By constructing a proper Lyapunov-Krasovskii functional (LKF) with triple summation terms and using an improved summation inequality techniques. Sufficient conditions are derived in terms of linear matrix inequalities (LMIs) to guarantee the considered discrete-time neural networks to be exponentially stable. Finally, numerical examples with simulation results are given to illustrate the effectiveness of the developed theoretical results.

Investigation of Delayed Response during Real-Time Cursor Control Using Electroencephalography.

Error-related brain activation has been investigated for advanced brain-machine interfaces (BMI). However, how a delayed response of cursor control in BMI systems should be handled is not clear. Therefore, the purpose of this study was to investigate how participants responded to delayed cursor control. Six subjects participated in the experiment and performed a wrist-bending task. For three distinct delay intervals (an interval where participants could not perceive the delay, an interval where participants could not be sure whether there was a delay or not, and an interval where participants could perceive the delay), we assessed two types of binary classifications (“Yes + No” vs. “I don't know” and “Yes” vs. “No”) based on participants' responses and applied delay times (thus, four types of classification, overall). For most participants, the “Yes vs. No” classification had higher accuracy than “Yes + No” vs. “I don't know” classification. For the “Yes + No” vs. “I don't know” classification, most participants displayed higher accuracy based on response classification than delay classification. Our results demonstrate that a class only for “I don't know” largely contributed to these differences. Many independent components (ICs) that exhibited high accuracy in “Yes + No” vs. “I don't know” response classification were associated with activation of areas from the frontal to parietal lobes, while many ICs that showed high accuracy in the “Yes vs. No” classification were associated with activation of an area ranging from the parietal to the occipital lobes and were more broadly localized in cortical regions than was seen for the “Yes + No” vs. “I don't know” classification. Our results suggest that small and large delays in real-time cursor control differ not only in the magnitude of the delay but should be handled as distinct information in different ways and might involve differential processing in the brain.

Improved Delay-Range-Dependent Stability Condition for T–S Fuzzy Systems with Variable Delays Using New Extended Affine Wirtinger Inequality

In this paper, a new integral inequality lemma along with an appropriate Lyapunov–Krasovskii functional (LKF) is proposed for fuzzy time-delay system to enhance the delay upper bound estimate. The proposed lemma is referred to hereafter as Extended Affine Wirtinger inequality. The novelty of the lemma is twofold, it has the ability to integrate uncertain delay information utilizing the convex combination of certain and uncertain delay intervals involved in the proposed LKF, and it is compatible to derive delay-range-dependent (DRD) stability conditions for continuous time Takagi–Sugeno (T–S) fuzzy time-delay system. One noteworthy advantage of the proposed stability condition in a linear matrix inequality (LMI) framework is that it requires less number of matrix variables compared to the existing integral inequalities of the similar type, thus reducing the computational burden too. The efficacy of the proposed DRD stability condition over existing conditions is validated numerically by solving three examples related to fuzzy time-delay system.