Next Generation Orthopaedic Implants by Additive Manufacturing Using Electron Beam Melting

This paper presents some examples of knee and hip implant components containing porous structures and fabricated in monolithic forms utilizing electron beam melting (EBM). In addition, utilizing stiffness or relative stiffness versus relative density design plots for open-cellular structures (mesh and foam components) of Ti-6Al-4V and Co-29Cr-6Mo alloy fabricated by EBM, it is demonstrated that stiffness-compatible implants can be fabricated for optimal stress shielding for bone regimes as well as bone cell ingrowth. Implications for the fabrication of patient-specific, monolithic, multifunctional orthopaedic implants using EBM are described along with microstructures and mechanical properties characteristic of both Ti-6Al-4V and Co-29Cr-6Mo alloy prototypes, including both solid and open-cellular prototypes manufactured by additive manufacturing (AM) using EBM

Fabrication of Metal and Alloy Components by Additive Manufacturing: Examples of 3D Materials Science

ObjectiveThis paper provides a brief review of relatively new additive manufacturing technologies for the fabrication of unusual and complex metal and alloy products by laser and electron beam melting. A number of process features and product microstructures are illustrated utilizing 3D optical and transmission electron microscope image compositions representing examples of 3D materials science.MethodsProcessing methods involving electron beam melting (EBM) and a process referred to as direct metal laser sintering (DMLS), often called selective laser melting (SLM) are described along with the use of light (optical) microscopy (OM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) to elucidate microstructural phenomena.ResultsExamples of EBM and SLM studies are presented in 3D image compositions. These include EBM of Ti-6Al-4V, Cu, Co-base superalloy and Inconel 625; and SLM of 17-4 PH stainless steel, Inconel 718 and Inconel 625.Conclusions3D image compositions constituting 3D materials science provide effective visualization for directional solidification-related phenomena associated with the EBM and SLM fabrication of a range of metals and alloys, especially microstructures and microstructural architectures

A breakthrough on Amanita phalloides poisoning: an effective antidotal effect by polymyxin B

Amanita phalloides is responsible for more than 90 % of mushroom-related fatalities, and no effective antidote is available. a-Amanitin, the main toxin of A. phalloides, inhibits RNA polymerase II (RNAP II), causing hepatic and kidney failure. In silico studies included docking and molecular dynamics simulation coupled to molecular mechanics with generalized Born and surface area method energy decomposition on RNAP II. They were performed with a clinical drug that shares chemical similarities to a-amanitin, polymyxin B. The results show that polymyxin B potentially binds to RNAP II in the same interface of a-amanitin, preventing the toxin from binding to RNAP II. In vivo, the inhibition of the mRNA transcripts elicited by a-amanitin was efficiently reverted by polymyxin B in the kidneys. Moreover, polymyxin B significantly decreased the hepatic and renal a-amanitin-induced injury as seen by the histology and hepatic aminotransferases plasma data. In the survival assay, all animals exposed to a-amanitin died within 5 days, whereas 50 % survived up to 30 days when polymyxin B was administered 4, 8, and 12 h post-a-amanitin. Moreover, a single dose of polymyxin B administered concomitantly with a-amanitin was able to guarantee 100 % survival. Polymyxin B protects RNAP II from inactivation leading to an effective prevention of organ damage and increasing survival in a-amanitin-treated animals. The present use of clinically relevant concentrations of an already human-use-approved drug prompts the use of polymyxin B as an antidote for A. phalloides poisoning in humans.Juliana Garcia, Vera Marisa Costa, Ricardo Dinis-Oliveira and Ricardo Silvestre thank FCT-Foundation for Science and Technology-for their PhD grant (SFRH/BD/74979/2010), Post-doc grants (SFRH/BPD/63746/2009 and SFRH/BPD/110001/2015) and Investigator grants (IF/01147/2013) and (IF/00021/2014), respectively. This work was supported by the Fundacao para a Ciencia e Tecnologia (FCT) - project PTDC/DTPFTO/4973/2014 - and the European Union (FEDER funds through COMPETE) and National Funds (FCT, Fundacao para a Ciencia e Tecnologia) through project Pest-C/EQB/LA0006/2013

A narrative review on the similarities and dissimilarities between myalgic encephalomyelitis/chronic fatigue syndrome (me/cfs) and sickness behavior

It is of importance whether myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a variant of sickness behavior. The latter is induced by acute infections/injury being principally mediated through proinflammatory cytokines. Sickness is a beneficial behavioral response that serves to enhance recovery, conserves energy and plays a role in the resolution of inflammation. There are behavioral/symptomatic similarities (for example, fatigue, malaise, hyperalgesia) and dissimilarities (gastrointestinal symptoms, anorexia and weight loss) between sickness and ME/CFS. While sickness is an adaptive response induced by proinflammatory cytokines, ME/CFS is a chronic, disabling disorder, where the pathophysiology is related to activation of immunoinflammatory and oxidative pathways and autoimmune responses. While sickness behavior is a state of energy conservation, which plays a role in combating pathogens, ME/CFS is a chronic disease underpinned by a state of energy depletion. While sickness is an acute response to infection/injury, the trigger factors in ME/CFS are less well defined and encompass acute and chronic infections, as well as inflammatory or autoimmune diseases. It is concluded that sickness behavior and ME/CFS are two different conditions

Characterization of Tool Wear and Weld Optimization in the Friction-Stir Welding of Cast Aluminum 359+2% SiC Metal Matrix Composite

Tool wear for threaded steel pin tools declines with decreasing rotation speed and increasing traverse or weld speeds for the friction-stir welding (FSW) of Al 359+20% SiC metal-matrix composite (MMC). Less than 10% tool wear occurs when the threaded tool erodes to a self-optimized shape resembling a pseudo-hour glass at weld traverse distances in excess of 3 m. There is only a 7% reduction in the SiC mean particle size in the weld zone for self-optimized pin tools with no threads as compared with a 25% variation for threaded tools wearing significantly at the start of welding. The weld zone becomes more homogeneous for efficient welding with self-optimized tools, and there is a reduction in the weld zone grain size due to dynamic recrystallization, which facilitates the solid-state flow. Transmission electron microscopy shows little difference in the dislocation density from the base material to the weld zone, but there is a propensity of dislocation loops in the weld zone. The weld zone is observed to harden by as much as 30%, in contrast to the base material, as a consequence of the recrystallized grain size reduction and the SiC particles distributed therein

Electron Microscope Comparisons of Fine and Ultra-Fine Carbonaceous and Non-Carbonaceous, Airborne Particulates

Particulate matter (PM) from a number of specific sources has been collected on carbon/formvar-coated 100-mesh nickel or copper grids for transmission electron microscopy (TEM) using a thermal precipitator. These sources included diesel truck exhaust, graphitic PM from brake-shop environments, jet engine exhaust streams, and a wide range of general airborne PM for comparison. Individual PM TEM images were compared with corresponding selected-area electron diffraction patterns and energy-dispersive (X-ray) spectra. Diesel PM was characterized by aggregate branching of carbonaceous spherules while graphitic PM consisted of layered carbon, crystalline carbon nanotubes and fullerene-related nanocrystals, and prominent mixtures of inorganic microcrystals. Essentially, all airborne PM collected was characterized by variations of cluster or aggregate morphologies and non-carbonaceous PM was mostly micro- or nanocrystalline. Mixtures of carbonaceous and nanocrystalline PM were also observed. Although tedious, individual PM analysis and comparison appears to be a necessary strategy to elucidate the apparent toxic effects increasingly identified with ultra-fine and nanoparticulates in the air

3D metal droplet printing development and advanced materials additive manufacturing

While commercial additive manufacturing processes involving direct metal wire or powder deposition along with powder bed fusion technologies using laser and electron beam melting have proliferated over the past decade, inkjet printing using molten metal droplets for direct, 3D printing has been elusive. In this paper we review the more than three decades of development of metal droplet generation for precision additive manufacturing applications utilizing advanced, high-temperature metals and alloys. Issues concerning process optimization, including product structure and properties affected by oxidation are discussed and some comparisons of related additive manufactured microstructures are presented