137 research outputs found
Sing Again That Sweet Refrain
https://digitalcommons.library.umaine.edu/mmb-vp/6766/thumbnail.jp
Beleidsevaluatie vandaag: Een voorzichtige balans
The politics and administration of institutional chang
Beleidsevaluatie vandaag: Een voorzichtige balans
The politics and administration of institutional chang
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Producing Crack-Free, High Density M2 HSS Parts by Selective Laser Melting: Pre-Heating the Baseplate
Cracks and delamination, resulting from residual stresses are a barrier in the world of Additive
Manufacturing and Selective Laser Melting (SLM) that prohibits the use of many metals in this field. By preheating the baseplate, thermal gradients are lowered and stresses can be reduced. In this work, some initial tests
were performed with M2 Tool Steel. Results show that pre-heating enables the production of dense M2 parts.
The influence of pre-heating on density and mechanical and physical properties is investigated. The paper
shows many promising results for the production of SLM parts in materials that are very sensitive to crack
formation and delamination. When using a pre-heating of 200°C, crack-free parts were produced with a relative
density of 99.8%.Mechanical Engineerin
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Design Enhancement of Biomedical Scaffolds Made By Selective Laser Melting
Selective laser melting (SLM) is increasingly used to fabricate biomedical scaffolds.
However, the intrinsic specifications of the process such as laser spot size, layer thickness,
and particle size limit the production accuracy, altering the geometrical characteristics and
mechanical properties of the scaffolds. This work attempts to assess and improve the
mechanical properties of TiAl6V4 biomedical scaffolds by eliminating/modifying the sharp
and thin nodes (as the main source of stress concentrations and lowering the mechanical
properties). This is carried out through a gradual increase of the beam (strut) thickness around
the nodes where corresponding struts meet. The compression performance of these scaffolds
was assessed and compared to common examples (unaltered struts) and to scaffolds designed
with thicker struts in the centre of the beams (demonstrating the largest contrast). The findings
prove that the thickening of the nodal points improves the strain distribution while maintains
the mechanical properties at an identical solid volume fraction. This can be used to improve
the scaffold design by a gradual strut thickness (in a comparable volume fraction) for an
improved bio-mechanical performance.Mechanical Engineerin
Rheological behavior of ÎČ-Ti and NiTi powders produced by atomization for SLM production of open porous orthopedic implants
The growing interest for Selective Laser Melting (SLM) in orthopedic implant manufacturing is accompanied by
the introduction of novel Ti alloys, in particular ÎČ-Ti for their excellent corrosion resistance as well as favorable
combination of high mechanical strength, fatigue resistance and relatively low elastic modulus. As part of the
SLM process for producing quality ÎČ-Ti parts powder flowability is essential to achieve uniform thickness of powder
layers. In this work the flowability of different gas atomized ÎČ-Ti, including NiTi, powders has been studied. Their
rheological properties were compared to those of commercially available plasma-atomized Tiâ6Alâ4V powder
using a newly developed semi-automatic experimental set-up. Not only the particle size, shape and size distribution
of the powders display a large influence on the powder flowability but also particle surface properties such as
roughness, chemical composition and the presence of liquid on the surface of the particles. It was found that plasma
or gas atomization production techniques for SLM powder have a considerable effect on the particle topography.
Among the powders studied regarding SLM applicability only rheological properties of the fine size fraction
(25â45 ÎŒm) of Tiâ45Nb didn't conform to SLM processing requirements. To improve flowability of the Tiâ45Nb
powder itwas annealed both in air and argon atmosphere at 600 °C during 1 h, resulting in an improved rheological
behavior suitable for SLM processing
AMBRA1 is able to induce mitophagy via LC3 binding, regardless of PARKIN and p62/SQSTM1
Damaged mitochondria are eliminated by mitophagy, a selective form of autophagy whose dysfunction associates with neurodegenerative diseases. PINK1, PARKIN and p62/SQTMS1 have been shown to regulate mitophagy, leaving hitherto ill-defined the contribution by key players in 'general' autophagy. In basal conditions, a pool of AMBRA1 - an upstream autophagy regulator and a PARKIN interactor - is present at the mitochondria, where its pro-autophagic activity is inhibited by Bcl-2. Here we show that, upon mitophagy induction, AMBRA1 binds the autophagosome adapter LC3 through a LIR (LC3 interacting region) motif, this interaction being crucial for regulating both canonical PARKIN-dependent and -independent mitochondrial clearance. Moreover, forcing AMBRA1 localization to the outer mitochondrial membrane unleashes a massive PARKIN- and p62-independent but LC3-dependent mitophagy. These results highlight a novel role for AMBRA1 as a powerful mitophagy regulator, through both canonical or noncanonical pathways
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