This article addresses analysis and control of the SIR model of infectious diseases in the framework of input-to-state stability (ISS) with respect to the net flow of susceptible individuals into a ...region in both disease-free and epidemic situations. The key development is the construction of a continuously differentiable strict Lyapunov function. First, this article clarifies that a continuously differentiable Lyapunov function whose derivative is nonpositive can deduce asymptotic stability on the whole state space. Second, it is demonstrated that a new idea of rendering the derivative strictly negative allows one to detect a margin proving ISS of the SIR model. The accomplishment is based on the pursuit of a Lyapunov function that is not entirely separable into components. It contrasts with previously studied and popular Lyapunov functions that are proven to be incapable of assessing robustness properties such as ISS. Third, two types of feedback control laws are proposed for mass vaccination of immigrants and inhabitants by making use of the strict Lyapunov functions. One type modifies the other type by focusing on the reduction of peaks of the infected population within the ISS guarantees.
This article pursues a new approach to the design of feedback control laws mitigating the spread of human infectious diseases. The control inputs of vaccination, isolation, and outing/gathering ...regulation are derived as the gradient of a positive definite function of all the population variables of the SIQR model. Lyapunov functions in which susceptible and infected populations are decoupled are known to be non‐self‐sufficient for proving stability of the SIQR model as well as other variants of the SIR model. This fact has been hampering Lyapunov‐based control design of infectious disease models. This article demonstrates that a popular decoupled function can still serve as a control Lyapunov function as long as isolation is made state‐dependent. Techniques realizing this novel idea are presented and shown to allow the Lyapunov function to establish a robustness guarantee in terms of input‐to‐state stability with respect to immigration and newborn perturbation on an arbitrarily large domain. The effectiveness of the proposed simultaneous controller is illustrated through numerical simulations performed with a parameter set of COVID‐19.
Left atrial appendage (LAA) size is crucial for determining the indication of transcatheter LAA closure. The aim of this study was to evaluate the differences in LAA morphology according to the types ...of atrial fibrillation (AF). A total of 299 patients (mean age: 67 ± 13 years) who underwent transesophageal echocardiography (TEE) were included. Patients were classified into non-AF (n = 64), paroxysmal AF (n = 86), persistent AF (n = 87), or long-standing persistent AF (n = 62). LAA morphology, including LAA ostial diameter and depth, was assessed using TEE. Patients with long-standing persistent AF had larger LAA ostial diameter and depth and lower LAA flow velocity. The maximum LAA ostial diameter was 19 ± 4 mm in patients with non-AF, 21 ± 4 mm in patients with paroxysmal AF, 23 ± 5 mm in patients with persistent AF, and 26 ± 5 mm in patients with long-standing persistent AF. LAA ostial diameter was increased by 2 or 3 mm with the progression of AF. LAA ostial diameter was correlated with LA volume index (R = 0.37, P < 0.01) and the duration of continuous AF (R = 0.30, P < 0.01), but not with age or the period from the onset of AF. In conclusion, LAA size was increased with the progression of AF.
This paper aims to develop a system-theoretic approach to ordinary differential equations which deterministically describe dynamics of prevalence of epidemics. The equations are treated as ...interconnections in which component systems are connected by signals. The notions of integral input-to-state stability (iISS) and input-to-state stability (ISS) have been effective in addressing nonlinearities globally without domain restrictions in analysis and design of control systems. They provide useful tools of module-based methods integrating characteristics of component systems. This paper expresses fundamental properties of models of infectious diseases and vaccination through the language of iISS and ISS of components and whole systems. The systematic treatment is expected to facilitate development of effective schemes of controlling the disease spread via non-conventional Lyapunov functions.
•Arterial stiffness is a determinant of cardiovascular health and organ damage.•Cardio–Ankle Vascular Index (CAVI) is a marker of arterial stiffness from the origin of the aorta to the ankle.•CAVI is ...independent of blood pressure changes at the time of measurement.•Treatment of cardiovascular risk factors and lifestyle modifications reduce CAVI.•A cut-off value of 9.0 can predict patients at a high risk of cardiovascular events.
Arterial stiffness increases with age, as well as in various pathological states, including obesity, diabetes mellitus, smoking, and dyslipidemia, and it has important consequences for cardiovascular health. Arterial stiffness plays a central role in hemodynamic dysfunction characterized by excess pulsatility; specifically, it leads to heart failure, cerebrovascular disease, and renal failure. Among measures of arterial stiffness, carotid–femoral pulse wave velocity is considered as the reference standard; however, it has not been incorporated into routine clinical practice. Cardio–ankle vascular index (CAVI), which is a marker of arterial stiffness measured from the origin of the aorta to the ankle, was developed in 2004. CAVI is based on stiffness parameter β, which is theoretically independent of blood pressure at the time of measurement. CAVI applies stiffness parameter β to arterial segments between the heart and ankle. The measurement of CAVI is simple and well-standardized, and its reproducibility and accuracy are acceptable. Several studies have demonstrated that CAVI is high in patients with various atherosclerotic risk factors, and treatment of cardiovascular risk factors and lifestyle modifications improve CAVI. Several prospective studies have investigated the association between CAVI and future cardiovascular events in the general population and in patients with cardiovascular risk factors. A cut-off value of 9.0 is proposed for predicting patients at a high risk of cardiovascular events. From this review, it is clear that CAVI may be useful in the prevention of cardiovascular disease.
Display omitted
•Route planning requires the relationships between next movements and positions.•Place cells in the hippocampus represent an animal’s next position or trajectory.•Prospective coding in place cells ...requires prefrontal-hippocampal interactions.
Animals have the ability to navigate to a desired location by making use of information about environmental landmarks and their own movements. While decades of neuroscience research have identified neurons in the hippocampus and parahippocampal structures that represent an animal’s position in space, it is still largely unclear how an animal can choose the next movement direction to reach a desired goal. As the goal destination is typically located somewhere outside of the range of sensory perception, the animal is required to rely on the internal metric of space to estimate the direction and distance of the destination to plan a next action. Therefore, the hippocampal spatial map should interact with action-planning systems in other cortical regions. In accordance with this idea, several recent studies have indicated the importance of functional interactions between the hippocampus and the prefrontal cortex for goal-directed navigation. In this paper, I will review these studies and discuss how an animal can estimate its future positions correspond to a next movement. Investigation of the navigation problem may further provide general insights into internal models of the brain for action planning.
Unitraveling-Carrier Photodiodes for Terahertz Applications Ishibashi, Tadao; Muramoto, Yoshifumi; Yoshimatsu, Toshihide ...
IEEE journal of selected topics in quantum electronics,
2014-Nov.-Dec., 2014-11-00, 20141101, Letnik:
20, Številka:
6
Journal Article
Recenzirano
Device design for unitraveling-carrier photodiodes (UTC-PDs) and their derivative structures is reconsidered from the point of view of terahertz (THz) applications. A key design procedure for ...maximizing their bandwidth is optimization by incorporating hybrid absorbers. The effect of quasi-field in p-type absorber is carefully examined. It has been shown that the initial velocity transient must be taken into account to evaluate the effective average velocity. Photomixers integrating a hybrid-absorber UTC-PD and a bow-tie antenna were fabricated and characterized. THz-wave generation by the photomixers in a frequency range of up to around 2.5 THz was confirmed. The observed THz-wave output exhibits significant changes with bias voltage, where the decrease in the output with increasing negative bias voltage is more pronounced at higher frequencies. This output behavior is due to the change in electron velocity in the diode depletion layer associated with the overshoot effect. From the dependence of the output power on frequency, effective electron velocity is found to be as high as 6 \times 10^{7} cm/s at optimum bias voltage of -0.4 V.
PDF
