Fixed-time observer-based tracking controller for a hysteretic piezoelectric deformable mirror of an adaptive optic system.

Piezoelectric deformable mirrors (DM) are benefited from the high accuracy and swift dynamics. The hysteresis phenomenon, which inherently exists in piezoelectric materials, degrades the capability and precision of the adaptive optics (AO) systems. Also, the dynamics of piezoelectric DMs make the controller design more complicated. This research aims to design a fixed-time observer-based tracking controller (FTOTC), which estimates the dynamics, compensates the hysteresis, and ensures tracking to the actuator displacement reference, in the fixed time. Unlike the existing inverse hysteresis operator-based methods, the proposed observer-based controller overcomes the computational burdens and estimates the hysteresis in real-time. The proposed controller tracks the reference displacements, while the tracking error converges in the fixed time. The stability proof is presented by two consecutive theorems. Numerical simulations demonstrate superior tracking and hysteresis compensation by the presented method, from a comparison viewpoint.

Clinical outcomes of subcutaneous implantable cardiac defibrillator implantation - Iran SICD registry.

BACKGROUND: The subcutaneous implantable-defibrillator (S-ICD) is a relatively new alternative to the transvenous ICD system to minimize intravascular lead-related complications. This paper presents outcome of SICD implantation in patients enrolled in Iran S-ICD registry. METHODS: Between October 2015 and June 2022, this prospective multicenter national registry included 223 patients with a standard indication for an ICD, who neither required bradycardia pacing nor needed cardiac resynchronization to evaluate the early post-implant complications and long-term follow-up results of the S-ICD system. RESULTS: The mean age of the patients was 45 ± 17 years. The majority (79.4%) were male. Ischemic cardiomyopathy (39.5%) was the most common underlying disorder among patients selected for S-ICD implant. Most study patients (68.6%) had ICD for primary prevention of sudden cardiac death. Seven patients (3.1%) were found to have suboptimal lead positions. Six patients (2.7%) developed a pocket hematoma; all were managed medically. During a mean follow-up of 2 years, the appropriate therapy was recorded in 13% of the patients and inappropriate ICD intervention mainly due to supraventricular tachycardia in 8.9%. Pocket infection was observed in four patients (1.8%) and five patients (2.2%) died mainly due to heart failure. CONCLUSION: S-ICDs were effective at detecting and treating both induced and spontaneous ventricular arrhythmias. Major clinical complications were rare.

Impact of hybrid plasmonic nanoparticles on the charge carrier mobility of P3HT:PCBM polymer solar cells.

The solution processable polymer solar cells have shown a great promise as a cost-effective photovoltaic technology. Here, the effect of carrier mobility changes has been comprehensively investigated on the performance of P3HT:PCBM polymer solar cells using electro-optical coupled simulation regimes, which may result from the embedding of SiO2@Ag@SiO2 plasmonic nanoparticles (NPs) in the active layer. Firstly, the active layer thickness, stemmed from the low mobility of the charge carriers, is optimized. The device with 80 nm thick active layer provided maximum power conversion efficiency (PCE) of 3.47%. Subsequently, the PCE has increased to 6.75% and 6.5%, respectively, along with the benefit of light scattering, near-fields and interparticle hotspots produced by embedded spherical and cubic nanoparticles. The PCE of the devices with incorporated plasmonic nanoparticles are remarkably enhanced up to 7.61% (for spherical NPs) and 7.35% (for cubic NPs) owing to the increase of the electron and hole mobilities to [Formula: see text] and [Formula: see text], respectively (in the optimum case). Furthermore, SiO2@Ag@SiO2 NPs have been successfully synthesized by introducing and utilizing a simple and eco-friendly approach based on electroless pre-treatment deposition and Stober methods. Our findings represent a new facile approach in the fabrication of novel plasmonic NPs for efficient polymer solar cells.

Group Refractive Index of Nanocrystalline Yttria-Stabilized Zirconia Transparent Cranial Implants.

Transparent "Window to the Brain" (WttB) cranial implants made from a biocompatible ceramic, nanocrystalline Yttria-Stabilized Zirconia (nc-YSZ), were recently reported. These reports demonstrated chronic brain imaging across the implants in mice using optical coherence tomography (OCT) and laser speckle imaging. However, optical properties of these transparent cranial implants are neither completely characterized nor completely understood. In this study, we measure optical properties of the implant using a swept source OCT system with a spectral range of 136 nm centered at 1,300 nm to characterize the group refractive index of the nc-YSZ window, over a narrow range of temperatures at which the implant may be used during imaging or therapy (20-43°C). Group refractive index was found to be 2.1-2.2 for OCT imaging over this temperature range. Chromatic dispersion for this spectral range was observed to vary over the sample, sometimes flipping signs between normal and anomalous dispersion. These properties of nc-YSZ should be considered when designing optical systems and procedures that propagate light through the window, and when interpreting OCT brain images acquired across the window.

Ultrahigh sensitive refractive index nanosensors based on nanoshells, nanocages and nanoframes: effects of plasmon hybridization and restoring force.

In this study, the effect of the plasmon hybridization mechanism on the performance and refractive index (RI) sensitivity of nanoshell, nanocage and nanoframe structures is investigated using the finite-difference time-domain simulation. To create nanocage structure, we textured the cubic nanoshell surfaces and examined the impact of its key parameters (such as array of cavities, size of cavities and wall thickness) on the nanocage's RI-sensitivity. Synthesis of the designed nanocages is a challenging process in practice, but here the goal is to understand the physics lied behind it and try to answer the question "Why nanoframes are more sensitive than nanocages?". Our obtained results show that the RI-sensitivity of nanocage structures increases continuously by decreasing the array of cavities. Transforming the nanocage to the nanoframe structure by reducing the array of cavities to a single cavity significantly increases the RI-sensitivity of the nanostructure. This phenomenon can be related to the simultaneous presence of symmetric and asymmetric plasmon oscillations in the nanocage structure and low restoring force of nanoframe compared to nanocage. As the optimized case shows, the proposed single nanoframe with aspect ratio (wall length/wall thickness) of 12.5 shows RI-sensitivity of 1460 nm/RIU, the sensitivity of which is ~ 5.5 times more than its solid counterpart.

Determination of nonlinear refractive index by an iterative phase retrieval method.

We present a simple and robust technique for measuring the nonlinear refractive index. The principle is based on an iterative phase retrieval algorithm with a pump-probe system. Different strong phase modulations are intentionally introduced into the probe beam, and corresponding diffraction intensity patterns are recorded. The recordings are used in the phase retrieval algorithm to reconstruct the pump-induced phase on the probe beam. The nonlinear refractive index is then extracted from the reconstructed phase. The reconstruction method offers a straightforward procedure and a simple lensless setup. Simulations validate the proposed method. The effects of different characteristics of the pump and probe beams on the quality of reconstructions are investigated. The obtained results demonstrate that the reconstructions are accurate even for the probe beams with complex-valued fields and non-Gaussian pump beams; it removes the requirement for smooth fields of the pump and probe beams. The validity of the method in noisy conditions is also shown.