A modular testbed for mechanized spreading of powder layers for additive manufacturing.

Powder bed additive manufacturing (AM) processes, including binder jetting (BJAM) and powder bed fusion (PBF), can manufacture complex three-dimensional components from a variety of materials. A fundamental understanding of the spreading of thin powder layers is essential to develop robust process parameters for powder bed AM and to assess the influence of powder feedstock characteristics on the subsequent process outcomes. Toward meeting these needs, this work presents the design, fabrication, and qualification of a testbed for modular, mechanized, multi-layer powder spreading. The testbed is designed to replicate the operating conditions of commercial AM equipment, yet features full control over motion parameters including the translation and rotation of a roller spreading tool and precision motion of a feed piston and the build platform. The powder spreading mechanism is interchangeable and therefore can be customized, including the capability for dispensing of fine, cohesive powders using a vibrating hopper. Validation of the resolution and accuracy of the machine and its subsystems, as well as the spreading of exemplary layers from a range of powder sizes typical of BJAM and PBF processes, are described. The precision engineered testbed can therefore enable the optimization of powder spreading parameters for AM and correlation to build process parameters in future work, as well as exploration of spreading of specialized powders for AM and other techniques.

[Hepatic fascioliasis: a diagnosis problem?]. / Faciolasis hepática: Un problema diagnóstico?

Human fasciolasis is an infection caused by the liver fluke Fasciola hepatica that predominantly affects cattle and sheep, man being an accidental host. The epidemiological situation has changed in the last few years, reporting an increase in the number of new cases in different countries around the world. In the majority of cases, diagnosis of infection in the acute or invasive phase or in chronic or state phase, is difficult because the symptoms of both phases overlap or due to the lack of symptoms or the intermittent elimination of eggs by the adult worm. Determining the phase will depend on clinical suspicion and on the selection of adequate serological and coprological methods in the acute or chronic stages, respectively, as well as determining whether the patient comes from an endemic area. In this study, we reported six cases of patients that were hospitalized at the Arzobispo Loayza Hospital in Lima, Peru, from 1990 to 1999, whose diagnoses were different from the final ones and which evidenced diagnosing problems. The important correlation between the place of origin, the physical and laboratory findings to diagnose this parasitic disease were emphasized.