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In the present study, cellular lattice structures for implant applications are reported for the first-time incorporating copper directly by in-situ alloying in the laser powder bed fusion process. The aim to incorporate 3 at.% Cu into Ti6Al4V(ELI) is selected for improved antibacterial properties while maintaining appropriate mechanical properties. Previously, topologically optimized Ti6Al4V(ELI) lattice structures were successfully designed, manufactured and studied for implant applications. The development of a new alloy produced by in-situ alloying of elemental powder mixture of Ti6Al4V(ELI) and pure Cu powders was used here for the production of identical lattice structures with improved antibacterial properties. One of the same as-designed CAD models was used for the manufacturing of these lattices compared to previous work on pure Ti6Al4V(ELI) lattices, making direct comparison of mechanical properties possible. Similar manufacturability highlights the applicability of this alloying technique to other lattice designs. Microstructural characterization was performed by optical and electron microscopies, as well as microCT. Mechanical characterization was performed by means of compression tests and hardness measurements. Results showed that in-situ alloying with copper leads to the formation of localized Cu-rich regions, refinement of martensitic phase and the formation of CuTi2 intermetallic precipitates, which increased the hardness and strength of the material. Deviations in wall thickness between the as-designed and as-manufactured lattices led to anisotropy of the mechanical properties of the lattices. Higher compressive strength values were obtained when thicker walls were oriented along the loading direction. Nevertheless, alloying with Cu had a higher impact on the compressive strength of lattice structure than the wall thickness deviations. The direct in-situ alloying of copper in Ti6Al4V(ELI) is a promising mute for direct manufacturing of antibacterial

This study presents the attempt made to develop an ideal equivalent system for adiabatic expansion type thermal pumps found in the literature. The purpose of developing the ideal system is to investigate the maximum achievable performance of such systems irrespective of the system sizing and pump design adopted and obtain a characteristic efficiency. An ideal system was developed and analyzed. Then the system performance was compared with literature data, which was found to be reasonable. The comparison of the ideal performance of such systems with existing cycles revealed that the efficiency of such types of pumping systems is limited.

Biofunctionalization of Ti6Al4V alloy with metallic agents like Ag or Cu is a promising approach to add antibacterial properties and thus to reduce the risk of implant failure. This research investigates the in-situ alloying of Ti6Al4V(ELI) with 3 at.% Cu powders using Laser Powder Bed Fusion (L-PBF). The morphology and geometrical characteristics of the single tracks and layers were studied. Laser powers of 170 W and 340 W, and scanning speeds ranging from 0.4 to 1.4 m/s and 0.8-2.8 m/s were implemented. Single track results showed balling effect and humping at high scanning speeds, 1.4 m/s and 1.6 m/s, for each laser powder respectively. Conversely, keyhole formation occurred at lower scanning speeds of 0.4-0.6 m/s for 170 W laser power, and below and 0.8 m/s for 340 W laser power. For both laser powers, single layers resulted in smoother surfaces at lower scanning speeds. These results were used for the development of optimal process parameters for 3D cubes with 99.9 % density. Optimal process parameters were found for 170 W and 340W laser powders at 0.7-0.9 and 1.0-1.2 m/s scanning speeds, respectively. In-situ alloying by L-PBF was challenging and a homogeneous distribution of Cu within the alloy was hard to achieve. The increase in laser power from 170 to 340 W resulted in small increase in homogenization. Microstructural analyses after stress-relieving treatment showed the presence of alpha' and beta phases, as well as CuTi2 intermetallic precipitates. The finer microstructure together with CuTi2 intermetallic precipitates resulted in an increase in hardness. This study demonstrates the potential for printing in-situ alloyed Ti6Al4V(ELI)- 3 at.% Cu for biomedical applications. However, further studies are required to determine the effectiveness of antibacterial properties.

Contains fulltext : 219632.pdf (publisher's version ) (Open Access), Preclinical applications of resting-state functional magnetic resonance imaging (rsfMRI) offer the possibility to non-invasively probe whole-brain network dynamics and to investigate the determinants of altered network signatures observed in human studies. Mouse rsfMRI has been increasingly adopted by numerous laboratories worldwide. Here we describe a multi-centre comparison of 17 mouse rsfMRI datasets via a common image processing and analysis pipeline. Despite prominent cross-laboratory differences in equipment and imaging procedures, we report the reproducible identification of several large-scale resting-state networks (RSN), including a mouse default-mode network, in the majority of datasets. A combination of factors was associated with enhanced reproducibility in functional connectivity parameter estimation, including animal handling procedures and equipment performance. RSN spatial specificity was enhanced in datasets acquired at higher field strength, with cryoprobes, in ventilated animals, and under medetomidine-isoflurane combination sedation. Our work describes a set of representative RSNs in the mouse brain and highlights key experimental parameters that can critically guide the design and analysis of future rodent rsfMRI investigations.

Topology optimization approach was used for the design of Ti6A14V ELI lattice structures with stiffness and density close to the human bone for implant applications. Three lattice designs with volume densities of 350/0, 40 % and 45 % and corresponding elastic modulus of 18.6 GPa, 23.1 GPa 27.4 GPa close to the human bone were generated. Laser powder bed fusion (LPBF) technique was used for the manufacturing of the specimens. Physical measurements and mechanical characterization of specimens were assessed by microCT analyses and compression test, perpendicular and parallel to the building direction of the specimens. LPBF Ti6A14V ELI manufactured lattice structures showed deviations in wall thickness in comparison with the generated designs, leading to an increase in relative porosity but also a decrease in elastic modulus in comparison with the original designs. Horizontal walls of the lattice structures showed higher wall thickness in comparison with the vertical walls, leading to anisotropic behaviour of the lattice structures. Higher elastic modulus and compression strength were obtained when thicker walls were oriented along the loading direction of the compression test, showing a complete failure by dividing the specimens into two neighbouring halves. All specimens showed 45 degrees diagonal shear fracture along the structure. On the other hand, higher energy absorption at first maximum compression strength peak was observed when samples were tested parallel to the building direction (when thinner walls were oriented along the loading compression direction). Results showed that designed lattice structures can possess the levels of human bones' stiffness and therefore can reduce/avoid stress shielding on implant applications.