Multiple Delays Research Articles

A CASE REPORT ON WOLCOTT RALLISON SYNDROME

A Case Report of Wolcott–Rallison syndrome, it is a rare, autosomal recessive disorder with infancy-onset diabetes mellitus, multiple epiphyseal dysplasia, osteopenia, mental retardation or developmental delay, and hepatic and renal dysfunction as main clinical findings. Patients have most common history of consanguineous marriage. Patients with WRS have mutations in the EIF2AK3 gene, which encodes the eukaryotic translation initiation factor 2-alpha kinase 3. Most common cause of death is fulminant hepatitis in early childhood.The EIKF2AK3 gene codes for PERK (pancreatic endoplasmic reticulum kinase),an explanation for the spectrum of symptoms.PERK is associated with the activity of beta cells in the pancreas.A broad range of bodily systems is affected, including pancreas, kidney, liver,bone, and nervous system, because of deficient stress response to improperly folded proteins inside the endoplasmic reticulum. A two months old male child born out of non-consanguineous marriage, Hindu by religion, presented with complain of fever since 4 days, respiratory distress since 12 hours. Patient was admitted and on regular blood sugar screening on arrival was high. Repeat random blood sugar was also elevated.Arterial blood gas was done which was suggested metabolic acidosis.Due to persistent high blood sugar,insulin drip was started and HbA1c was done which was 11 gm% and other investigations done. Diagnosis of neonatal diabetes mellitus was kept and managed accordingly. Studies for other endocrinopathies and autoimmune disease done which was negative. Child was having normal growth and development according to age. Genetic studies for neonatal diabetes was planned and EIKF2AK3 gene mutation was found homozygous. Both the parents were heterozygous for the mutation. So diagnosis was kept and regular follow up was advised.Key-words:Infant,Neonatal Diabetes,Endocrinopathy

Non-contrast assessment of blood-brain barrier permeability to water in mice: An arterial spin labeling study at cerebral veins

Blood-brain barrier (BBB) plays a critical role in protecting the brain from toxins and pathogens. However, in vivo tools to assess BBB permeability are scarce and often require the use of exogenous contrast agents. In this study, we aimed to develop a non-contrast arterial-spin-labeling (ASL) based MRI technique to estimate BBB permeability to water in mice. By determining the relative fraction of labeled water spins that were exchanged into the brain tissue as opposed to those that remained in the cerebral veins, we estimated indices of global BBB permeability to water including water extraction fraction (E) and permeability surface-area product (PS). First, using multiple post-labeling delay ASL experiments, we estimated the bolus arrival time (BAT) of the labeled spins to reach the great vein of Galen (VG) to be 691.2 ± 14.5 ms (N = 5). Next, we investigated the dependence of the VG ASL signal on labeling duration and identified an optimal imaging protocol with a labeling duration of 1200 ms and a PLD of 100 ms. Quantitative E and PS values in wild-type mice were found to be 59.9 ± 3.2% and 260.9 ± 18.9 ml/100 g/min, respectively. In contrast, mice with Huntington's disease (HD) revealed a significantly higher E (69.7 ± 2.4%, P = 0.026) and PS (318.1 ± 17.1 ml/100 g/min, P = 0.040), suggesting BBB breakdown in this mouse model. Reproducibility studies revealed a coefficient-of-variation (CoV) of 4.9 ± 1.7% and 6.1 ± 1.2% for E and PS, respectively. The proposed method may open new avenues for preclinical research on pathophysiological mechanisms of brain diseases and therapeutic trials in animal models.

Stability analysis of a digital hierarchical steering controller of autonomous vehicles with multiple time delays

This study investigates the lane-keeping control of autonomous vehicles with an emphasis on the digital delayed nature of the system. The vehicle dynamics are represented using a kinematic bicycle model, and a hierarchical lane-keeping controller is introduced with multiple delays in the feedback loop. An extension of the semidiscretization method is presented, in order to perform the stability analysis of the digitally controlled vehicle with multiple discrete time delays. The differences between the continuous approximation and the exact consideration of discrete time delays are highlighted. We show that in certain cases, neglecting the effects of quantization can lead to significant inaccuracies, especially when tuning the lower-level controller. The results are verified using a series of small-scale laboratory experiments.

Global exponential periodicity of nonlinear neural networks with multiple time-varying delays

<abstract><p>Global exponential periodicity of nonlinear neural networks with multiple time-varying delays is investigated. Such neural networks cannot be written in the vector-matrix form because of the existence of the multiple delays. It is noted that although the neural network with multiple time-varying delays has been investigated by Lyapunov-Krasovskii functional method in the literature, the sufficient conditions in the linear matrix inequality form have not been obtained. Two sets of sufficient conditions in the linear matrix inequality form are established by Lyapunov-Krasovskii functional and linear matrix inequality to ensure that two arbitrary solutions of the neural network with multiple delays attract each other exponentially. This is a key prerequisite to prove the existence, uniqueness, and global exponential stability of periodic solutions. Some examples are provided to demonstrate the effectiveness of the established results. We compare the established theoretical results with the previous results and show that the previous results are not applicable to the systems in these examples.</p></abstract>

Small-Signal Stability Analysis and Lead-Lag Compensation Control for DC Networked-Microgrid Under Multiple Time Delays

Networked microgrid (NMG) system is an effective solution to enhance the power system's reliability and resilience. The distributed control is promising for NMG system due to its high reliability, scalability and low computational burden. The distributed control relies on the information exchange among distributed generators and sub-microgrids (sub-MGs), which inevitably contain heterogenous time delays that can deteriorate system stability. This paper focuses on the multiple time-delays small-signal stability analysis of a DC NMG with a distributed layered control architecture. Firstly, a generalized time-delayed DC NMG small-signal model with a typical two-layer distributed control framework is developed. Then, stability analysis is conducted considering multiple time delays from communication and measurement stages in NMG layer and MG layer. The impact of multiple time delays on NMG stability is quantified. We reveal that both the electrical coupling among MGs and different kinds of time delays in distributed control loops will impact the NMG stability. Subsequently, based on the detailed analytical results, the critical eigenvalue is identified, and a new lead-lag compensation controller is proposed to enhance the system stability by compensating for the phase lag of the critical eigenvalue. Lastly, the effectiveness of the proposed method and the accuracy of the analytical findings are verified by OPAL-RT-based real-time tests.

Adaptive Compensation of Unmatched Disturbances in Unstable MIMO LTI Plants with Distinct Input Delays

The paper concerns the problem of adaptive compensation of unmatched disturbances in linear time-invariant (LTI) multi-input multi-output (MIMO) unstable plants with multiple distinct input delays. The external disturbances affect both the input and the output of the plant and are represented by multi-harmonic signals with unknown parameters (frequencies, phases, and amplitudes). The paper extends results of the paper Nikiforov et al. (2021) on adaptive compensation of unmatched disturbances to the case of distinct input delays. To overcome the problem of multiple distinct input delays, a special scheme of the disturbance prediction is proposed and used for design of the adaptive control law.

Exponential stability of Cohen-Grossberg neural networks with multiple time-varying delays and distributed delays

<abstract><p>Maybe because Cohen-Grossberg neural networks with multiple time-varying delays and distributed delays cannot be converted into the vector-matrix forms, the stability results of such networks are relatively few and the stability conditions in the linear matrix inequality forms have not been established. So this paper investigates the exponential stability of the networks and gives the sufficient condition in the linear matrix inequality forms. Two examples are provided to demonstrate the effectiveness of the theoretical results.</p></abstract>

State Estimation for a Class of Discrete-Time BAM Neural Networks With Multiple Time-Varying Delays

For a class of discrete-time bidirectional associative memory neural networks (DTBAMNNs) with multiple time-varying delays, the issue of state estimation is studied. By propose a mathematical induction method, we first investigate novel delay-dependent and -independent global exponential stability (GES) criteria of the error system. The obtained GES criteria are described by linear scalar inequalities. Then, a state observer is derived via the theory of generalized matrix inverses. These exponential stability conditions are very simple, which is convenient to verify based on the standard software tools (for example, YALMIP). Finally, we present two illustrative examples to present the effectiveness of the theoretical results.

Discretization of the Functionals With Prescribed Derivative for Linear Systems With Multiple Delays

This work aims to derive a sufficient stability condition for linear systems with multiple delays based on a discretization procedure of Lyapunov – Krasovskii functionals. This procedure relies on a piecewise constant approximation of matrix kernels of the functionals with prescribed derivatives. The approximation error is explicitly bounded, and the resulting stability test is expressed in terms of nonnegative definiteness of a block matrix that depends on the values of delay Lyapunov matrix at discretization points and the system matrices.

Stability and Hopf Bifurcation Control for Fractional-Order Two-Gene Regulatory Network With Multiple Delays

Stability and Hopf Bifurcation Control for Fractional-Order Two-Gene Regulatory Network With Multiple Delays

Improved results for testing the oscillation of functional differential equations with multiple delays

<abstract><p>In this article, we test whether solutions of second-order delay functional differential equations oscillate. The considered equation is a general case of several important equations, such as the linear, half-linear, and Emden-Fowler equations. We can construct strict criteria by inferring new qualities from the positive solutions to the problem under study. Furthermore, we can incrementally enhance these characteristics. We can use the criteria more than once if they are unsuccessful the first time thanks to their iterative nature. Sharp criteria were obtained with only one condition that guarantees the oscillation of the equation in the canonical and noncanonical forms. Our oscillation results effectively extend, complete, and simplify several related ones in the literature. An example was given to show the significance of the main results.</p></abstract>

On the rate of convergence of Euler–Maruyama approximate solutions of stochastic differential equations with multiple delays and their confidence interval estimations

<abstract><p>In this paper, we investigate Euler–Maruyama approximate solutions of stochastic differential equations (SDEs) with multiple delay functions. Stochastic differential delay equations (SDDEs) are generalizations of SDEs. Solutions of SDDEs are influenced by both the present and past states. Because these solutions may include past information, they are not necessarily Markov processes. This makes representations of solutions complicated; therefore, approximate solutions are practical. We estimate the rate of convergence of approximate solutions of SDDEs to the exact solutions in the $ L^p $-mean for $ p \geq 2 $ and apply the result to obtain confidence interval estimations for the approximate solutions.</p></abstract>

Comparison between 1.5-Tesla pseudocontinuous and pulsed arterial spin labeling in visualizing peri-ictal hyperperfusion: A case report

Arterial spin labeling (ASL) imaging with multiple postlabeling delays (PLD) can demonstrate the hemodynamics of peri-ictal hyperperfusion. Labeling methods include pulsed ASL (PASL) and pseudocontinuous ASL (pCASL). Although PASL is more widely used in daily clinical practice, it has several disadvantages because of lower delivery of labeled magnetization. We compared pCASL and PASL images acquired after a 24-h interval, using a 1.5-Tesla machine, in a 62-year-old man with non-convulsive status epilepticus. The pCASL during electrographic status epilepticus clearly demonstrated that ASL signals in the grey matter of the right hemisphere, particularly in the posteromedial part of the right temporal lobe, increased at PLDs of 1.5 s and 1.75 s and were almost washed out at 2.0 s. Although PASL, which was obtained during the ictal-interictal continuum when there were no changes in ictal findings on diffusion-weighted images, showed a similar trend, the increased signals were less pronounced than those of pCASL, with more contamination of arte-rial transit artifact in the subarachnoid space. Although the electroencephalographic findings were not the same when both ASLs were performed, the present study confirms that PASL is somewhat inferior to pCASL in detecting peri-ictal hyperperfusion because of the greater effect of arterial transient artifacts.

Cerebral blood flow quantification with multi-delay arterial spin labeling in ischemic stroke and the association with early neurological outcome

Restoring blood flow to brain tissue at risk of infarction is essential for tissue survival and clinical outcome. We used cerebral blood flow (CBF) quantified with multiple post-labeling delay (PLD) pseudocontinuous arterial spin labeling (ASL) MRI after ischemic stroke and assessed the association between CBF and early neurological outcome. We acquired ASL with 7 PLDs at 3.0 T in large vessel occlusion stroke patients at 24 h. We quantified CBF relative to the contralateral hemisphere (rCBF) and defined hyperperfusion as a ≥30% increase and hypoperfusion as a ≥40% decrease in rCBF. We included 44 patients (median age: 70 years, median NIHSS: 13, 40 treated with endovascular thrombectomy) of whom 37 were recanalized. Hyperperfusion in ischemic core occurred in recanalized but not in non-recanalized patients (65.8% vs 0%, p = 0.006). Hypoperfusion occurred only in the latter group (0% vs 85.7%, p < 0.001). In recanalized patients, hyperperfusion was also seen in salvaged penumbra (38.9%). Higher rCBF in ischemic core (aβ, −2.75 [95% CI: −4.11 to −1.40]) and salvaged penumbra (aβ, −5.62 [95% CI: −9.57 to −1.68]) was associated with lower NIHSS scores at 24 h. In conclusion, hyperperfusion frequently occurs in infarcted and salvaged brain tissue following successful recanalization and early neurological outcome is positively associated with the level of reperfusion.

Positive periodic solutions for discrete Nicholson system with multiple time-varying delays

&lt;abstract&gt;&lt;p&gt;Fly communities exhibit rich ecological dynamics, and one of the important influencing factors is the interaction between species. A discrete Nicholson-type system with multiple time varying delays which considers the mutualism relationship between two fly species is investigated in this paper. Sufficient conditions for the existence of positive periodic solutions are elucidated. The result is obtained by the well-known continuation theorem of coincidence degree theory. An example is attached to illustrate our result. Moreover, the actual biological descriptions obtained from our main result are explained.&lt;/p&gt;&lt;/abstract&gt;

Distributed Low-Effort Load Balancing in the Presence of Time-Delays

In this paper, we investigate the problem of distributed load balancing under network capacity constraints, where the participating agents cooperate with the aim of jointly minimizing both the workload disparity among them as well as the overall workload transfer. Classical approaches for asymptotic convergence to the global optimum in a distributed fashion typically assume timely exchange of information between neighboring agents of a given multi-agent system. This assumption is not necessarily valid in practical settings due to non-commensurate (heterogeneous) communication and processing delays that might affect transmissions at different times. More specifically, we consider what effect multiple heterogeneous time-varying delays, among the agents can have on the distributed load balancing problem. We show that the distributed load balancing problem under bounded heterogeneous time-varying delays is globally asymptotically stable, but the rate of convergence is affected. Bounds on the convergence rate are provided with respect to an upper bound on the delays. Simulation examples are provided to show the validity and performance of our theoretical results.

Ethical Approaches to Public Policy for Health: A Focus on Principles and Working Together

News about the healthcare crisis, including strikes in multiple countries, workforce shortages, ambulance diversion and delays on entry to emergency rooms, closing floors while demand for beds increases, long waits for appointments in primary and specialty care, and shortages of supplies and medications all lead to proposed solutions for each issue. The point must be noted that these also point to some basic questions. This Commentary calls for a “back to basics” approach that requires dialogue (not just talking but listening) and a focus on some of our primary principles.

Stability switches, periodic oscillations and global stability in an infectious disease model with multiple time delays.

A delay differential equation model of an infectious disease is considered and analyzed. In this model, the impact of information due to the presence of infection is considered explicitly. As information propagation is dependent on the prevalence of the disease, the delay in reporting the prevalence is an important factor. Further, the time lag in waning immunity related to protective measures (such as vaccination, self-protection, responsive behaviour etc.) is also accounted. Qualitative analysis of the equilibrium points of the model is executed and it is observed that when the basic reproduction number is less unity, the local stability of the disease free equilibrium (DFE) depends on the rate of immunity loss as well as on the time delay for the waning of immunity. If the delay in immunity loss is less than a threshold quantity, the DFE is stable, whereas, it loses its stability when the delay parameter crosses the threshold value. When, the basic reproduction number is greater than unity, the unique endemic equilibrium point is found locally stable irrespective of the delay effect under certain parametric conditions. Further, we have analyzed the model system for different scenarios of both delays (i.e., no delay, only one delay, and both delay present). Due to these delays, oscillatory nature of the population is obtained with the help of Hopf bifurcation analysis in each scenario. Moreover, at two different time delays (delay in information's propagation), the emergence of multiple stability switches is investigated for the model system which is termed as Hopf-Hopf (double) bifurcation. Also, the global stability of the endemic equilibrium point is established under some parametric conditions by constructing a suitable Lyapunov function irrespective of time lags. In order to support and explore qualitative results, exhaustive numerical experimentations are carried out which lead to important biological insights and also, these results are compared with existing results.

Longitudinal alterations in cerebral perfusion following a season of adolescent contact sport participation compared to non-contact athletes

BackgroundCerebral blood flow (CBF) change, a non-invasive marker of head injury, has yet to be thoroughly investigated as a potential consequence of repetitive head impacts (RHI) via contact sport participation in youth athletes. We examined pre-to post-season differences in relative CBF (rCBF), arterial transit time (ATT), and neurocognition between adolescent contact sport (CS; 79.4% of which were football players) and non-contact sport (NCS) athletes. MethodsAdolescent athletes (N = 57; age = 14.70 ± 1.97) completed pre- and post-season clinical assessments and neuroimaging. Brain perfusion was evaluated using an advanced 3D pseudo-continuous ASL sequence with Hadamard encoded multiple post-labeling delays. Mixed-effect models tested group-by-time interactions for rCBF, ATT, and neurocognition. ResultsA significant group-by-time interaction was observed for rCBF in a cluster consisting primarily of frontal and parietal lobe regions, with regional rCBF increasing in CS and decreasing among NCS athletes. No significant interaction was observed for ATT. A significant group-by-time interaction was observed for verbal memory and visual motor speed, with NCS athletes improving and CS athletes exhibiting lower performance from pre-to post-season in comparison. ConclusionsAlterations in rCBF and variability in cognition, not purported neurovasculature changes (measured by ATT), were observed following one season of CS participation. Further study surrounding the clinical meaningfulness of these findings, as they related to adverse long-term outcomes, is needed.

Stability and persistence of a SEIRS model with multiple ages and delay

Stability and persistence of a SEIRS model with multiple ages and delay