Layered Micro-Wall Structures from the Gas Phase

The use of3-D LCVD with volumetric rate feedback was investigated in the fabrication ofmicromechanical wall structures. These were constructed by recursive laser scanning and resulted in layered wall composed ofrecursive line deposition. Experiments were designed to uncover the relationship between scan rate, volumetric deposition rate, pressure and laser powerfor pyrolytic graphite from an ethylene precursor. Results point to a conduction dominated heat transfer which greatly limits the volumetric deposition rate at the wall. This also results in a highly unstable deposition process, since volumetric deposition increases by orders ofmagnitude as soon as rod growth is initiated. An unexpected results ofthis work is the ability to grow rods at an angle to the laser axis, with good control ofthe linear growth rate. This is achieved by adaptive laser scanning during rod growth.Mechanical Engineerin

Trussed Structures: FreeForm Fabrication without the Layers

Recent progress in 3D-LCVD have demonstrated the advantages ofrod micro-fabrication, both from the point of view of the range of volumetric deposition rates -from 1cl- to 109 cubic micron per second- andfrom the point ofview ofprocessable materials. A methodforfabricating trussed structures by LCVD ofethylene was tested, based upon scanning of the laserfocus perpendicular to the laser axis during rod growth. Control of the process is achieved though feedback ofthe laser power. A closed loop system was designed, which maintains a constant volumetric deposition rate during growth. Such capability, combined with previous results by the authors and other researchers in the field, open a new approach to free form fabrication without layers. Indeed, current results constitute a proofofconceptfor the fabrication oftruss structures akin to a finite element mesh.Mechanical Engineerin

Free and unfree labour in the colonial Andes in the sixteenth and seventeenth centuries

This article analyses free and unfree labour in mining centres in the Andes during early Spanish colonial times. It focuses on two themes: the condition of indigenous or "native" people as "free labourers", and the mita system of unfree labour. For that purpose I shall consider the cases of Potosí, the most important mining centre in the Andes, and San Antonio del Nuevo Mundo in southern Bolivia, a large mine unaffected by the mita system of labour obligations.Fil: Gil Montero, Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Estudios Sociales. Universidad Nacional de Tucumán. Instituto Superior de Estudios Sociales; Argentin

Proceedings Of The 23Rd Paediatric Rheumatology European Society Congress: Part Two

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