Selective Laser Melting and Mechanical Properties of Stainless Steels.

Metal additive manufacturing (AM) has been evolving in response to industrial and social challenges. However, new materials are hindered in these technologies due to the complexity of direct additive manufacturing technologies, particularly selective laser melting (SLM). Stainless steel (SS) 316L, due to its very low carbon content, has been used as a standard powder in SLM, highlighting the role of alloying elements present in steels.

Searching New Solutions for NiTi Sensors through Indirect Additive Manufacturing.

Shape Memory Alloys (SMAs) can play an essential role in developing novel active sensors for self-healing, including aeronautical systems. However, the NiTi SMAs available in the market are almost limited to wires, small sheets, and coatings. This restriction is mainly due to the difficulty in processing NiTi through conventional processes.

The Study of New NiTi Actuators to Reinforce the Wing Movement of Aircraft Systems.

Actuators using Shape Memory Alloy (SMA) springs could operate in different mechanical systems requiring geometric flexibility and high performance. The aim of the present study is to highlight the potential of these actuators, using their dimensional variations resulting from the phase transformations of NiTi springs (SMA) to make the movements of the system's mobile components reversible. This reversibility is due to thermal-induced martensitic transformation of NiTi springs.

Joining of Ti6Al4V to AlO Using Nanomultilayers.

Diffusion bonding of Ti6Al4V to AlO using Ni/Ti reactive nanomultilayers as interlayer material was investigated. For this purpose, Ni/Ti multilayer thin films with 12, 25, and 60 nm modulation periods (bilayer thickness) were deposited by d.c.

Development of Actuators for Repairing Cracks by Coating W Wires with Reactive Multilayers.

The aim of this research work was to optimize the coating of tungsten wires with reactive multilayer thin films and promote an exothermic self-propagating reaction. The ultimate goal is to use this heat to liquify low melting temperature materials, and thus block crack propagation in metallic materials. Ni/Me (Me = Al, Ti) multilayers were deposited by a DC (direct current) magnetron sputtering onto tungsten wires with diameters of 0.

Influence of Metallic Powder Characteristics on Extruded Feedstock Performance for Indirect Additive Manufacturing.

Material extrusion (MEX) of metallic powder-based filaments has shown great potential as an additive manufacturing (AM) technology. MEX provides an easy solution as an alternative to direct additive manufacturing technologies (e.g.

Experimental Analysis of NiTi Alloy during Strain-Controlled Low-Cycle Fatigue.

The interaction between the stress-induced martensitic transformation and resistivity behavior of superelastic NiTi shape memory alloy (SMA) was studied. Strain-controlled low-cycle fatigue up to 6% was monitored by in situ electrical resistivity measurements. The experimental results show that a great motion of martensite fronts results in a significant accumulation of defects, as evidenced by transmission electron microscopy (TEM), before and after the tensile cycles.

In Search of the Optimal Conditions to Process Shape Memory Alloys (NiTi) Using Fused Filament Fabrication (FFF).

This research was performed so as to investigate the additive manufacturing of NiTi shape memory alloys, which is associated with direct processes, such as selective laser melting. In addition to its expensive production costs, NiTi readily undergoes chemical and phase modifications, mainly as a result of Ni loss during processing as a result of high temperatures. This research explores the potential usefulness of NiTi as well as its limitations using indirect additive processes, such as fused filament fabrication (FFF).

Living Conditions as a Driving Factor in Persistent Methicillin-resistant Staphylococcus aureus Colonization Among HIV-infected Youth.

Background: Methicillin-resistant Staphylococcus aureus (MRSA) colonization has been linked to HIV-related sexual and social behaviors. MRSA risk factors may be different for HIV-infected children, adolescents and young adults. We investigated the association of MRSA colonization, persistent colonization and genotypes with potential risk factors among HIV-infected youth.

TEM and HRTEM characterization of TiAl diffusion bonds using Ni/Al nanolayers.

Diffusion bonding of TiAl alloys can be enhanced by the use of reactive nanolayer thin films as interlayers. Using these interlayers, it is possible to reduce the conventional bonding conditions (temperature, time, and pressure) and obtain sound and reliable joints. The microstructural characterization of the diffusion bond interfaces is a fundamental step toward understanding and identifying the bonding mechanisms and relating them to the strength of the joints.

Determination of airborne nanoparticles from welding operations.

The aim of this study is to assess the levels of airborne ultrafine particles emitted in welding processes (tungsten inert gas [TIG], metal active gas [MAG] of carbon steel, and friction stir welding [FSW] of aluminum) in terms of deposited area in pulmonary alveolar tract using a nanoparticle surface area monitor (NSAM) analyzer. The obtained results showed the dependence of process parameters on emitted ultrafine particles and demonstrated the presence of ultrafine particles compared to background levels. Data indicated that the process that resulted in the lowest levels of alveolar deposited surface area (ADSA) was FSW, followed by TIG and MAG.

Photorejuvenation with topical methyl aminolevulinate and red light: a randomized, prospective, clinical, histopathologic, and morphometric study.

Background: Photodynamic therapy (PDT) is an option for skin rejuvenation. Although many studies report clinical improvement with PDT in photodamaged skin, histologic and morphometric evidence is not documented in most cases.

Objective: To evaluate clinical and histopathologic changes induced by methyl aminolevulinate (MAL)-PDT and to morphometrically quantify collagen and elastic fibers in skin remodeling induced by MAL-PDT in photodamaged skin.

Coronary-subclavian steal syndrome. A case report.

Coronary-subclavian steal is an unusual clinical syndrome after successful internal mammary-coronary artery bypass grafting. Proximal subclavian artery (SA) stenosis is present and atherosclerotic disease is the underlying pathophysiologic mechanism in the majority of cases. The authors report a case of a sixty-two-year old man with angina and ventricular fibrillation soon after myocardial revascularization with left internal mammary artery (LIMA) to left anterior descending coronary (LAD).

[Factors associated with necrotizing enterocolitis].

Objective: To evaluate the features of clinical presentation of neonatal necrotizing enterocolitis and its associated factors.

Methods: Retrospective study of the cases of neonatal necrotizing enterocolitis (n = 56) diagnosed at Neonatal Intensive Care Unit Lagoa (NICU), between December 1986 and July 1992. Diagnosis and stages of the disease followed the modified Bell's criteria.