Month: July 2024

Abstract

In 3D modelling, a surface mesh is a collection of vertices, edges, and faces that define the shape of a 3D object. The surface mesh is typically used to represent the outer surface of an object, as opposed to the internal structure. A surface mesh is usually defined as a polygon mesh, which is a collection of polygons (triangles or quadrilaterals are the most common) that are connected at their vertices. The vertices of the mesh define the shape of the object, and the edges and faces provide the topological information that describes how the vertices are connected. Surface meshes are often used in 3D modelling software to create 3D objects for animation, video games, and other purposes. Although triangular meshes are the most widely used in various fields, they have a series of disadvantages that quad meshes solve in most cases. This article presents a set of algorithms capable of generating quad meshes from any type of input triangular mesh, preserving the geometric characteristics of the initial model. This process is known as ‘remeshing’. The results obtained by these algorithms on a large number of models related to the footwear industry have been compared, as well as analysing the advantages and disadvantages of each one of them applied to geometric models commonly used in footwear industry.

Abstract

Laser powder bed fusion (LPBF) is one of the most popular metal additive manufacturing technologies, which has found its applications in high-value sectors such as aerospace and biomedical devices. Some recent studies on the LPBF of stents have demonstrated its feasibility in the fabrication in thin strut structures including heart valve frames, as used in transcatheter aortic valve implantation (TAVI) for the treatment of severe aortic stenosis. The state of the art method of laser cutting TAVI frame limits the scope for novel concepts which are made possible by additive manufacturing. However, the surface quality and dimensional accuracy of LPBF parts are lower than that produced by laser cutting. To start the development of new TAVI concepts, the feasibility of manufacturing thin frames by LPBF has been investigated based on the SAPIEN 3 frame by Edwards Lifesciences. In this study, simplified frames with strut size from 0.3 to 0.5 mm have been successfully manufactured. The effects of strut size, strut angle, laser power and scan speed on the dimensional accuracy and surface quality were systemically studied. In addition, a representative SAPIEN 3 frame was manufactured and assessed with high-resolution X-ray CT scans. Good overall dimensional accuracy and low porosity were obtained for the SAPIEN 3 frame. However, inclined struts were found to have relatively low dimensional accuracy and poor surface quality.

Abstract

Additive manufacturing of copper enables enhanced design freedom which allows for improved performance of components in thermal management and electrical applications. Joining via soldering provides ideal electrical and thermal connections, but the solderability of complex additively manufactured surfaces is poorly understood. In the present work, the solderability of nominally pure copper coupons manufactured by three additive manufacturing techniques (laser powder bed fusion, laser engineered net shaping, and bound powder extrusion) was experimentally assessed using the wetting balance technique and pin pull testing. Coupons produced by each method were tested as built and after surface modification by dry electropolishing. Contact angles and wetting times were calculated from wettability testing. Peak tensile loads required to remove pins soldered to coupons were also recorded for each surface condition. The dipped coupons and solder joint fracture surfaces were examined with optical and scanning electron microscopes. It was found that nonuniform wetting and excessive wicking of solder can result in weak joints, and surface modification positively affected overall solderability in all cases. All surfaces were shown to be wettable, but bound powder extrusion was found to produce the most solderable copper surfaces among the additive manufacturing methods tested.

Abstract

Purpose

Historical French fleet of Nuclear Power Plants (NPP) is near end-of-life, with 14 NPPs planned to begin decommissioning by 2035. Despite decade-old calls for more research regarding these activities’ environmental impact, very few if any studies were conducted since. Due to the French fleet high-degree of standardization, a prospective investigation regarding the Fessenheim NPP—first large-scale plant to be decommissioned in France, starting 2026—is conducted to identify results of interest beyond this case study.

Methods

A life cycle assessment is realized, following ISO 14040/44, with a functional unit defined as “the decommissioning of the Fessenheim NPP.” The system boundaries encompass four unit-processes: dismantling of electromechanical equipment, clean-up of the structures, demolition of plant buildings, and transport of conventional and radioactive waste (RW). This last unit-process is investigated separately to make a clear comparison of conventional and radioactive waste. Pre-decommissioning activities, soil rehabilitation, and RW final storage are excluded. Primary data were obtained from the decommissioning public report of EDF (Electricity of France), with scaling based on the literature and third-party reports/documents. Background processes were modeled with the ecoinvent 3.8 database. Environmental impacts are estimated using the CML-IA baseline methodology to allow comparison with previous works based on CML2001.

Results and discussion

The “Metal cutting” sub-process is found to be the major contributor to environmental impacts during dismantling, clean-up, and demolition, results varying from 62.6 to 99.5% depending on the impact category. A sensitivity analysis explores the effect of variation in shares of thermal and mechanical cutting. It demonstrates the huge potential of impact reduction for the total system under study if thermal cutting use is limited as much as possible. Despite representing only 5% of the total mass of waste, RW scores 1.8–6.6 times higher than conventional waste during transport, due to much higher distances to cover and specific conditioning. Previous explorations of results transferability are found to be methodologically uncertain, and the NPP total power installed is evaluated as an unpromising transferability factor.

Conclusions

Decommissioning of nuclear power plants is still in need of thorough studies based on exhaustive and transparent datasets. Until then, state-of-the-art prospective assessments and transferability of LCA results to future studies are severely limited. Restraint in use of oxy-acetylene cutting is nevertheless highly recommended. French unique policy regarding very low-level waste needs further consideration, and decentralized storage sites are a promising research lead.

Abstract

Purpose

Mediastinal nodal staging is crucial for surgical candidate selection in non-small cell lung cancer (NSCLC), but conventional imaging has limitations often necessitating invasive staging. We investigated the additive clinical value of fibroblast activation protein inhibitor (FAPI) PET/CT, an imaging technique targeting fibroblast activation protein, for mediastinal nodal staging of NSCLC.

Methods

In this prospective pilot study, we enrolled patients scheduled for surgical resection of NSCLC based on specific criteria designed to align with indications for invasive staging procedures. Patients were included when meeting at least one of the following: (1) presence of FDG-positive N2 lymph nodes, (2) clinical N1 stage, (3) central tumor location or tumor diameter of ≥ 3 cm, and (4) adenocarcinoma exhibiting high FDG uptake. [⁶⁸Ga]FAPI-46 PET/CT was performed before surgery after a staging workup including [¹⁸F]FDG PET/CT. The diagnostic accuracy of [⁶⁸Ga]FAPI-46 PET/CT for “N2” nodes was assessed through per-patient visual assessment and per-station quantitative analysis using histopathologic results as reference standards.

Results

Twenty-three patients with 75 nodal stations were analyzed. Histopathologic examination confirmed that nine patients (39.1%) were N2-positive. In per-patient assessment, [⁶⁸Ga]FAPI-46 PET/CT successfully identified metastasis in eight patients (sensitivity 0.89 (0.52–1.00)), upstaging three patients compared to [¹⁸F]FDG PET/CT. [¹⁸F]FDG PET/CT detected FDG-avid nodes in six (42.8%) of 14 N2-negative patients. Among them, five were considered non-metastatic based on calcification and distribution pattern, and one was considered metastatic. In contrast, [⁶⁸Ga]FAPI-46 PET/CT correctly identified all non-metastatic patients solely based on tracer avidity. In per-station analysis, [⁶⁸Ga]FAPI-46 PET/CT discriminated metastasis more effectively compared to [¹⁸F]FDG PET/CT-based (AUC of ROC curve 0.96 (0.88–0.99) vs. 0.68 (0.56–0.78), P < 0.001).

Conclusion

[⁶⁸Ga]FAPI-46 PET/CT holds promise as an imaging tool for preoperative mediastinal nodal staging in NSCLC, with improved sensitivity and the potential to reduce false-positive results, optimizing the need for invasive staging procedures.

Abstract

The cat primary visual cortex (V1) is a cortical area for which we have one of the most detailed estimates of the connection ‘weights’ (expressed as number of synapses) between different neural populations in different layers (Binzegger et al in J Neurosci 24:8441–8453, 2004). Nevertheless, the majority of excitatory input sources to layer 6, the deepest layer in a local translaminar excitatory feedforward loop, was not accounted for by the known neuron types used to generate the quantitative Binzegger diagram. We aimed to fill this gap by using a retrograde tracer that would label neural cell bodies in and outside V1 that directly connect to layer 6 of V1. We found that more than 80% of labeled neurons projecting to layer 6 were within V1 itself. Our data indicate that a substantial fraction of the missing input is provided by a previously unidentified population of layer 3/4 border neurons, laterally distributed and connecting more strongly to layer 6 than the typical superficial layer pyramidal neurons considered by Binzegger et al. (Binzegger et al in J Neurosci 24:8441–8453, 2004). This layer 3/4 to layer 6 connection may be a parallel route to the layer 3 – layer 5 – layer 6 feedforward pathway, be associated with the fast-conducting, movement-related Y pathway and provide convergent input from distant (5–10 degrees) regions of the visual field.