7 research outputs found
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Video Microscopy of Selective Laser Sintering
This paper presents the design and implementation
of a video microscopy system that enables real time observation
and archival of selective laser sintering of polymer
and metal materials. The design objectives and selection of
system components are discussed in the first section of this
paper. Experimental results from preliminary experiments
conducted on polycarbonate, wax and nylon powders are
also presented.Mechanical Engineerin
Incorporating New Technologies Into Toxicity Testing and Risk Assessment: Moving From 21st Century Vision to a Data-Driven Framework
Based on existing data and previous work, a series of studies is proposed as a basis toward a pragmatic early step in transforming toxicity testing. These studies were assembled into a data-driven framework that invokes successive tiers of testing with margin of exposure (MOE) as the primary metric. The first tier of the framework integrates data from high-throughput in vitro assays, in vitro-to-in vivo extrapolation (IVIVE) pharmacokinetic modeling, and exposure modeling. The in vitro assays are used to separate chemicals based on their relative selectivity in interacting with biological targets and identify the concentration at which these interactions occur. The IVIVE modeling converts in vitro concentrations into external dose for calculation of the point of departure (POD) and comparisons to human exposure estimates to yield a MOE. The second tier involves short-term in vivo studies, expanded pharmacokinetic evaluations, and refined human exposure estimates. The results from the second tier studies provide more accurate estimates of the POD and the MOE. The third tier contains the traditional animal studies currently used to assess chemical safety. In each tier, the POD for selective chemicals is based primarily on endpoints associated with a proposed mode of action, whereas the POD for nonselective chemicals is based on potential biological perturbation. Based on the MOE, a significant percentage of chemicals evaluated in the first 2 tiers could be eliminated from further testing. The framework provides a risk-based and animal-sparing approach to evaluate chemical safety, drawing broadly from previous experience but incorporating technological advances to increase efficiency
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The Electrostatic Application of Powder for Selective Laser Sintering
Mechanical Engineerin
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The Application of an Artificial Body Force to the Selective Laser Sintering Process
An artificial body force generated by a magnetic
field is applied to the green powder bed of a ferromagnetic
powder during the Selective Laser Sintering process.
Preliminary experiments and theory are formed to
determine whether the artificial body force is beneficial to
the Selective Laser Sintering process and if it is usable
within that process. Several applications are discussed
including microgravity situations and two phase sintering
processes. It is determined that the magnetic body force is
beneficial to the Selective Laser Sintering process.Mechanical Engineerin
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A Sieve Feed System for the Selective Laser Sintering Process
A sieve feed system has been designed for use with the Selective
Laser Sintering process. The sieve feed system uses
electrostatic charge to help apply polymer powder to a green
powder bed. The sieve feed system was found to help the
application of polymer powder as measured by a 10 to 15%
increase in final part density. The sieve feed system has
many potential applications, including material property design,
and material mixing during the sintering process.Mechanical Engineerin
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Nickel Applied for Selective Laser Sintering Using a Magnetic Field
Metal powder was applied for the Selective Laser Sintering
process using the sieve feed system and a magnetic field.
The magnetic field had a negative effect on final part quality
as measured by a reduction in final part density. This
negative effect is theorized to be due to the shape and orientation
ofthe magnetic field. It appears possible to change
the field to a benevolent orientation.Mechanical Engineerin
Incorporating New Technologies Into Toxicity Testing and Risk Assessment: Moving From 21st Century Vision to a Data-Driven Framework
Based on existing data and previous work, a series of studies is proposed as a basis toward a pragmatic early step in transforming toxicity testing. These studies were assembled into a data-driven framework that invokes successive tiers of testing with margin of exposure (MOE) as the primary metric. The first tier of the framework integrates data from high-throughput in vitro assays, in vitro-to-in vivo extrapolation (IVIVE) pharmacokinetic modeling, and exposure modeling. The in vitro assays are used to separate chemicals based on their relative selectivity in interacting with biological targets and identify the concentration at which these interactions occur. The IVIVE modeling converts in vitro concentrations into external dose for calculation of the point of departure (POD) and comparisons to human exposure estimates to yield a MOE. The second tier involves short-term in vivo studies, expanded pharmacokinetic evaluations, and refined human exposure estimates. The results from the second tier studies provide more accurate estimates of the POD and the MOE. The third tier contains the traditional animal studies currently used to assess chemical safety. In each tier, the POD for selective chemicals is based primarily on endpoints associated with a proposed mode of action, whereas the POD for nonselective chemicals is based on potential biological perturbation. Based on the MOE, a significant percentage of chemicals evaluated in the first 2 tiers could be eliminated from further testing. The framework provides a risk-based and animal-sparing approach to evaluate chemical safety, drawing broadly from previous experience but incorporating technological advances to increase efficiency