The Evolution of the Plateau, an Optical Coherence Tomography Signature Seen in Geographic Atrophy

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Microstructure and Residual Stress Evolution of Laser Powder Bed Fused Inconel 718 under Heat Treatments

AbstractThe current work aimed to study the influence of various heat treatments on the microstructure, hardness, and residual stresses of Inconel 718 processed by laser powder bed fusion process. The reduction in residual stresses is crucial to avoid the deformation of the component during its removal from the building platform. Among the different heat treatments, 800 °C kept almost unaltered the original microstructure, reducing the residual stresses. Heat treatments at 900, 980, and 1065 °C gradually triggered the melt pool and dendritic structures dissolution, drastically reducing the residual stresses. Heat treatments at 900 and 980 °C involved the formation of δ phases, whereas 1065 °C generated carbides. These heat treatments were also performed on components with narrow internal channels revealing that heat treatments up to 900 °C did not trigger sintering mechanisms allowing to remove the powder from the inner channels

Nanosatellite-5G Integration in the Millimeter Wave Domain: A Full Top-Down Approach

This paper presents a novel network architecture for an integrated nanosatellite (nSAT)-5G system operating in the millimeter-wave (mmWave) domain. The architecture is realized adopting a delay/disruption tolerant networking (DTN) approach allowing end users to adopt standard devices. A buffer aware contact graph routing algorithm is designed to account for the buffer occupancy of the nSATs and for the connection planning derived from their visibility periods. At the terrestrial uplink, a coded random access is employed to realize a high-capacity interface for the typically irregular traffic of 5G users, while, at the space uplink, the DTN architecture is combined with the contention resolution diversity slotted Aloha protocol to match the recent update of the DVB-RCS2 standard. To achieve a reliable testing of the introduced functionalities, an accurate analysis of the statistic of the signal to interference-plus-noise ratio and of the capture probability at each mmWave link is developed by including interference, shadowing, fading, and noise. The application of the designed architecture to data transfer services in conjunction with possible delay reduction strategies, and an extension to inter-satellite communication, are finally presented by estimating the resulting loss/delay performance through a discrete-time discrete-event platform based on the integration of Matlab with Network Simulator 3

The impact of age on prevalence of positive skin prick tests and specific IgE tests

SummaryAging is associated with modifications of the immune system, defined as immunosenescence. This could contribute to a reduced prevalence of allergic disease in the elderly population. In this regard, atopy has rarely been considered in the clinical assessment of the geriatric respiratory patient. This article is a review of the available literature assessing the impact of age on atopy. In the majority of papers, we found a lower prevalence of atopy in the most advanced ages, both in healthy subjects and in individuals affected by allergic respiratory diseases. Unfortunately, no large, longitudinal studies performed in the general population have been conducted to further explore this observation. Although available data seem to favor the decline of allergen sensitization with age, the prevalence of allergic sensitizations in the elderly population with respiratory symptoms is substantial enough to warrant evaluation of the atopic condition. From a clinical perspective, allergic reactions in older adults can have the same or even worse manifestations compared to young people. For this reasons, the evaluation of the atopic condition also in the geriatric patient is recommended. Thus, the role of atopy as it pertains to the diagnosis, therapy (adoption of preventive measure such as removal of environmental allergen or immunotherapy), and prognosis (influence on morbidity and mortality) of chronic respiratory illnesses in the elderly is addressed

Macular perfusion parameters in different angiocube sizes: does the size matter in quantitative optical coherence tomography angiography?

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SRtP 2.0 \u2014 The Evolution of the Safe Return to Port Concept

In 2010 IMO (International Maritime Organisation) introduced new rules in SOLAS with the aim of intrinsically increase the safety of passenger ships. This requirement is achieved by providing safe areas for passengers and essential services for allowing ship to Safely Return to Port (SRtP). The entry into force of these rules has changed the way to design passenger ships. In this respect big effort in the research has been done by industry to address design issues related to the impact on failure analysis of the complex interactions among systems. Today the research activity is working to bring operational matters in the design stage. This change of research focus was necessary because human factor and the way to operate the ship itself after a casualty on board may have a big impact in the design of the ship/systems. Also the management of the passengers after a casualty is becoming a major topic for safety. This paper presents the state of the art of Italian knowledge in the field of system engineering applied to passenger ship address to safety improvement and design reliability. An overview of present tools and methodologies will be offered together with future focuses in the research activity

Effect of Aging and Cooling Path on the Super β-Transus Heat-Treated Ti-6Al-4V Alloy Produced via Electron Beam Melting (EBM)

This work focuses on the effect of different heat treatments on the Ti-6Al-4V alloy processed by means of electron beam melting (EBM). Super beta-transus annealing was conducted at 1050 degrees C for 1 h on Ti-6Al-4V samples, considering two different cooling paths (furnace cooling and water quenching). This heat treatment induces microstructural recrystallization, thus reducing the anisotropy generated by the EBM process (columnar prior-beta grains). Subsequently, the annealed furnace-cooled and water-quenched samples were aged at 540 degrees C for 4 h. The results showed the influence of the aging treatment on the microstructure and the mechanical properties of the annealed EBM-produced Ti-6Al-4V. A comparison with the traditional processed heat-treated material was also conducted. In the furnace-cooled specimens consisting of lamellar alpha+beta, the aging treatment improved ductility and strength by inducing microstructural thickening of the alpha laths and reducing the beta fraction. The effect of the aging treatment was also more marked in the water-quenched samples, characterized by high tensile strengths but limited ductility due to the presence of martensite. In fact, the aging treatment was effective in the recovery of the ductility loss, maintaining high tensile strength properties due to the variation in the relative number of alpha/alpha' interfaces resulting from alpha' decomposition. This study, therefore, offers an in-depth investigation of the potential beneficial effects of the aging treatment on the microstructure and mechanical properties of the EBM-processed super beta-transus heat-treated Ti-6Al-4V alloy under different cooling conditions

Laser Powder Bed Fusion of Inconel 718: Residual Stress Analysis Before and After Heat Treatment

Residual stresses (RS) of great magnitude are usually present in parts produced by Laser Powder Bed Fusion (PBF-LB), mainly owing to the extreme temperature gradients and high cooling rates involved in the process. Those “hidden” stresses can be detrimental to a part’s mechanical properties and fatigue life; therefore, it is crucial to know their magnitude and orientation. The hole-drilling strain-gage method was used to determine the RS magnitude and direction-depth profiles. Cuboid specimens in the as-built state, and after standard solution annealing and ageing heat treatment conditions, were prepared to study the RS evolution throughout the heat treatment stages. Measurements were performed on the top and lateral surfaces. In the as-built specimens, tensile stresses of ~400 MPa on the top and above 600 MPa on the lateral surface were obtained. On the lateral surface, RS anisotropy was noticed, with the horizontally aligned stresses being three times lower than the vertically aligned. RS decreased markedly after the first heat treatment. On heat-treated specimens, magnitude oscillations were observed. By microstructure analysis, the presence of carbides was verified, which is a probable root for the oscillations. Furthermore, compressive stresses immediate to the surface were obtained in heat-treated specimens, which is not in agreement with the typical characteristics of parts fabricated by PBF-LB, i.e., tensile stresses at the surface and compressive stresses in the part’s core.info:eu-repo/semantics/publishedVersio

A workflow to generate physical 3D models of cerebral aneurysms applying open source freeware for CAD modeling and 3D printing

Objectives: 3D anatomical models are becoming a new frontier in surgery for planning and simulation on an individualized patient specific basis. Since 1999, 3D cerebral aneurysms models for neurosurgery have been proposed. The possibility of reproducing in a realistic 3D fashion the malformation with the surrounding vascular structures, provides important preoperative information for the treatment strategy. The same models can be used for training and teaching.Unfortunately stereolitography is often burdened by high costs and long times of production. These factors limit the possibility to use 3D models to plan surgeries in an easy daily fashion. Patients and methods: Our study enrolled 5 patients harboring cerebral aneurysms. DICOM data of each aneurysm were elaborated by an open source freeware to obtain CAD molds. Afterwards, the 3D models were produced using a fused deposition or a stereolitography printer. Results: Models were evaluated by Neurosurgeons in terms of quality and usefulness for surgical planning. Costs and times of production were recorded. Conclusions: Models were reliable, economically affordable and quick to produce. Keywords: Stereolitography, Cerebral aneurysms, 3D printing, Surgical planning, Aneurysm model