Scanning Space Analysis in Selective Laser Melting for CoCrMo Powder

AbstractSelective Laser Melting has been one of the last generation technologies of additive manufacturing. So far, one of the major problems confronted by researchers and designers has been the standardization of the optimal parameters. The setting of the appropriate parameters can lead to the acquisition of the desired characteristics in terms of morphology, porosity, hardness, and mechanical properties of the final piece. Therefore, the objective of this work is to study the scanning space that allows the formation of a continuous layer of material through the modification of the process parameters. Experiments were carried out in a self-develop SLM machine using CoCrMo powder as material. The experimental results showed that small separation between tracks provided a good overlapping while with higher separations, such as 750μm, isolated tracks were produced. Furthermore, other process parameters involved in the morphology of the tracks were identified and the overlapping estimated

Spectrum Transmission Measurement of a Fiber Laser Beam in Polymethyl Metacrylate for Laser Sintering Processing

AbstractA novel procedure is applied to evaluate the performance of Polymethyl Metacrylate (PMMA) plates as a pass through window for laser beam transmission, as a part of laser sintering machine construction. The method for laser beam spectrum transmission measurement consists basically in the exposure of a Kapton polyamide film, with the laser in a pulsed mode, in order to obtain variance diameter measurements. Measurements were analyzed in matched paired experiment levels in order to evaluate the effect of the laser beam transmission through the plates.A negligible effect of the presence of PMMA during the process was found. Selection of this polymer was then validated in performance, besides it owns transparency for purposes of process control and stable properties under harsh environmental conditions. Nevertheless, optical state of the material needs to be preserved in order to ensure consistent results in a long term

Designing and Prototyping of New Device for Scapholunate Ligament Repair

AbstractScapholunate instability, caused mainly due to tears in the scapholunate interosseous ligament (SLIL), may result in chronic pain, hand weakness, and lack of motion. Several open surgery procedures are used to repair it however long recovery time, widespread scarring and movement limitations are associated. Focusing on arthroscopy surgery, the combination of arthroscopy techniques and a prosthesis could be a good solution to manage it. A new prosthesis to substitute the SLIL was designed and manufactured. The design process was assessed by expert surgeons in wrist arthroscopy and the prototype manufactured allowed to analyze advantages and drawbacks of the adopted solution

Activation of glycogen synthase kinase-3 beta mediates β-amyloid induced neuritic damage in Alzheimer's disease

β-Amyloid (Aβ) plaques in Alzheimer (AD) brains are surrounded by severe dendritic and axonal changes, including local spine loss, axonal swellings and distorted neurite trajectories. Whether and how plaques induce these neuropil abnormalities remains unknown. We tested the hypothesis that oligomeric assemblies of Aβ, seen in the periphery of plaques, mediate the neurodegenerative phenotype of AD by triggering activation of the enzyme GSK-3β, which in turn appears to inhibit a transcriptional program mediated by CREB. We detect increased activity of GSK-3β after exposure to oligomeric Aβ in neurons in culture, in the brain of double transgenic APP/tau mice and in AD brains. Activation of GSK-3β, even in the absence of Aβ, is sufficient to produce a phenocopy of Aβ-induced dendritic spine loss in neurons in culture, while pharmacological inhibition of GSK-3β prevents spine loss and increases expression of CREB-target genes like BDNF. Of note, in transgenic mice GSK-3β inhibition ameliorated plaque-related neuritic changes and increased CREB-mediated gene expression. Moreover, GSK-3β inhibition robustly decreased the oligomeric Aβ load in the mouse brain. All these findings support the idea that GSK3β is aberrantly activated by the presence of Aβ, and contributes, at least in part, to the neuronal anatomical derangement associated with Aβ plaques in AD brains and to Aβ pathology itself

Activation of glycogen synthase kinase-3 beta mediates β-amyloid induced neuritic damage in Alzheimer's disease

β-Amyloid (Aβ) plaques in Alzheimer (AD) brains are surrounded by severe dendritic and axonal changes, including local spine loss, axonal swellings and distorted neurite trajectories. Whether and how plaques induce these neuropil abnormalities remains unknown. We tested the hypothesis that oligomeric assemblies of Aβ, seen in the periphery of plaques, mediate the neurodegenerative phenotype of AD by triggering activation of the enzyme GSK-3β, which in turn appears to inhibit a transcriptional program mediated by CREB. We detect increased activity of GSK-3β after exposure to oligomeric Aβ in neurons in culture, in the brain of double transgenic APP/tau mice and in AD brains. Activation of GSK-3β, even in the absence of Aβ, is sufficient to produce a phenocopy of Aβ-induced dendritic spine loss in neurons in culture, while pharmacological inhibition of GSK-3β prevents spine loss and increases expression of CREB-target genes like BDNF. Of note, in transgenic mice GSK-3β inhibition ameliorated plaque-related neuritic changes and increased CREB-mediated gene expression. Moreover, GSK-3β inhibition robustly decreased the oligomeric Aβ load in the mouse brain. All these findings support the idea that GSK3β is aberrantly activated by the presence of Aβ, and contributes, at least in part, to the neuronal anatomical derangement associated with Aβ plaques in AD brains and to Aβ pathology itself