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The paper presents the experimental characterization, the formulation of a numerical model, and the evaluation, by means of non-linear analyses, of a new friction damper conceived for the seismic upgrade of existing building frames. The damper dissipates seismic energy through the friction force triggered between a steel shaft and a lead core prestressed within a rigid steel chamber. The friction force is adjusted by controlling the prestress of the core, allowing the achievement of high forces with small dimensions, and reducing the architectural invasiveness of the device. The damper has no mechanical parts subjected to cyclic strain above their yield limit, thereby avoiding any risk of low-cycle fatigue. The constitutive behavior of the damper was assessed experimentally, demonstrating a rectangular hysteresis loop with an equivalent damping ratio of more than 55%, a stable behavior over repeated cycles, and a low dependency of the axial force on the rate of displacement. A numerical model of the damper was formulated in the OpenSees software by means of a rheological model comprising an in-parallel system of a non-linear spring element and a Maxwell element, and the model was calibrated on the experimental data. To assess the viability of the damper for the seismic rehabilitation of buildings, a numerical investigation was conducted by performing non-linear dynamic analyses on two case-study structures. The results highlight the benefits of the PS-LED in dissipating the largest part of seismic energy, limiting the lateral deformation of the frames, and controlling the increase in structural accelerations and internal forces at the same time.

Purpose: To describe the multimodal imaging characteristics of benign foveal depigmentation., Methods: The study was designed as prospective observational case series. Patients with benign foveal depigmentation were prospectively investigated by means of multimodal imaging, including blue-light and near-infrared fundus autofluorescence, optical coherence tomography (OCT), OCT angiography, color testing, microperimetry, and electrophysiology. The main outcome measures were vessel density and retinal pigment epithelium (RPE)/photoreceptor complex OCT reflectivity., Results: Overall, 4 patients were identified, with bilateral and unilateral involvement in 1 case and 3 cases, respectively. Fundus autofluorescence provided variable results, showing more impairment on near-infrared fundus autofluorescence. Structural OCT revealed slight attenuation of the outer retinal bands in the area affected by benign foveal depigmentation, associated with choroidal hypertransmission, whereas enface OCT better delineated the attenuation of the reflectivity signal. The mean reflectivity intensity of RPE/photoreceptor complex was statistically significantly reduced in patients with respect to control subjects in the benign foveal depigmentation area. Optical coherence tomography angiography, color testing, microperimetry, electrooculogram, and electroretinogram findings were normal., Conclusion: Benign foveal depigmentation may represent a focal RPE disease. The limited alterations within the RPE band, as visualized on enface OCT and confirmed on near-infrared fundus autofluorescence, suggest an impairment in melanin production or distribution within the RPE cells.

Introduction: Full-arch, implant-supported hybrid restorations, employing tilted implants, can offer an efficient way of treating edentulous patients. Several factors, such as the timing of implant placement and the inclination of the fixture, can have a detrimental effect on their stability. This retrospective study is aimed at discerning the role played by those factors., Materials and Methods: Patients treated with full-arch, implant supported restorations were selected for this study; cone-beam computed tomography (CBCT) images, taken 3 months and 3 years after delivery of the final restoration, as well as peri-implant values, were obtained and compared; bone loss was measured on four sites for each implant and then averaged. These patients were recalled, and the OHIP-5 questionnaire was administered., Results: 21 patients, with a mean age of 53 years, were included in the present analysis. 108 implants were placed, and 25 Toronto prostheses were delivered. According to a mixed-model analysis, tilted implants (0.51, p < 0.001) had a higher rate of bone loss, while implants placed in a healed ridge suffered less bone loss than immediate implants (-0.21, p < 0.001). Patient-level variables have a significant effect on this variable, as implants coming from the same subject share a similar risk of bone loss. The mean response to the self-administered OHIP-5 questionnaire was 1.53 ± 0.29; other variables did not have a statistically significant effect on this outcome. Discussion/Conclusions . The results of the present study show that Toronto bridges prostheses are an efficient procedure for treating edentulous patients, as their oral-related quality of life is reported as satisfactory even 7 years after delivery of the restoration. Tilted and immediate implants are more at risk of bone loss. Implants coming from the same subject share a similar risk of bone loss., Competing Interests: The authors declare that they have no competing interests., (Copyright © 2022 Ernesto Bruschi et al.)