Alignment turning system for precision lens cells

In order to optimize turning processes, cutting forces need to be accurately predicted. This in turn requires accurate extraction of the geometry of tool-workpiece engagements (TWE) at critical points during machining. TWE extraction is challenging because the in-process workpiece geometry is continually changing as each tool pass is executed. This paper describes research on a hybrid analytical, solid modeler, and feature-based methodology for extracting TWEs generated during general turning. Although a pure solid modeler-based solution can be applied, it will be shown that because of the ability to capture different cutting tool inserts with similar geometry and to model the process in 2D, an analytical solution can be used instead of the solid modeler in many instances. This solution identifies features in the removal volumes, where the engagement conditions are not changing or changing predictably. This leads to significant reductions in the number of Boolean operations that are executed during the extraction of TWEs and associated parameters required for modeling a turning process. TWE extraction is a critical component of a virtual turning system currently under development.

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Overlapping positive and negative regulatory elements determine lens-specific activity of the delta 1-crystallin enhancer

Molecular and Cellular Biology ◽

10.1128/mcb.13.9.5206-5215.1993 ◽

1993 ◽

Vol 13 (9) ◽

pp. 5206-5215 ◽

Cited By ~ 1

Author(s):

Y Kamachi ◽

H Kondoh

Keyword(s):

Mutational Analysis ◽

Specific Activity ◽

Regulatory Elements ◽

Positive Element ◽

Specific Expression ◽

Enhancer Activity ◽

Negative Element ◽

Positive Elements ◽

Lens Cells ◽

Specific Regulation

Lens-specific expression of the delta 1-crystallin gene is governed by an enhancer in the third intron, and the 30-bp-long DC5 fragment was found to be responsible for eliciting the lens-specific activity. Mutational analysis of the DC5 fragment identified two contiguous, interdependent positive elements and a negative element which overlaps the 3'-located positive element. Previously identified ubiquitous factors delta EF1 bound to the negative element and repressed the enhancer activity in nonlens cells. Mutation and cotransfection analyses indicated the existence of an activator which counteracts the action of delta EF1 in lens cells, probably through binding site competition. We also found a group of nuclear factors, collectively called delta EF2, which bound to the 5'-located positive element. delta EF2a and -b were the major species in lens cells, whereas delta EF2c and -d predominated in nonlens cells. These delta EF2 proteins probably cooperate with factors bound to the 3'-located element in activation in lens cells and repression in nonlens cells. delta EF2 proteins also bound to a promoter sequence of the gamma F-crystallin gene, suggesting that delta EF2 proteins are involved in lens-specific regulation of various crystallin classes.

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