| extinction coefficient | <chemistry> A constant used in the Beer-Lambert Law which relates the concentration of the substance being measured (in moles) to the absorbance of the substance in solution (how well the substance in solution blocks light beamed through it from getting out on the other side). (09 Oct 1997) |
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| extinction factor | <microscopy> In a polarizing or Differential Interference Contrast microscope, the ratio of the amount of light that is transmitted with the axes of the polars parallel over the amount transmitted with their axes crossed. Unless the lenses are rectified, the extinction factor drops exponentially as the numerical aperture is increased. Acronym: EF (26 Mar 1998) |
| extinction oblique | <microscopy> Vibration directions oblique to the long direction of the crystal or fibre. (05 Aug 1998) |
| extinction symmetrical | <microscopy> Vibration directions bisecting a prominent crystal profile angle. (05 Aug 1998) |
| undulose extinction | <microscopy> Nonuniform extinction of a substance between crossed polars. The areas of complete extinction move progressively with a fanlike motion across the surface of the substance as the stage is rotated. (05 Aug 1998) |
| first parallel pelvic plane | The upper opening of the true pelvis, bounded anteriorly by the pubic symphysis and the pubic crest on either side, laterally by the iliopectineal lines, and posteriorly by the promontory of the sacrum. Synonym: apertura pelvis superior, aditus pelvis, first parallel pelvic plane, pelvic brim, pelvic inlet, pelvic plane of inlet, plane of inlet. (05 Mar 2000) |
| fourth parallel pelvic plane | The lower opening of the true pelvis, bounded anteriorly by the pubic arch, laterally by the rami of the ischium and the sacrotuberous ligament on either side, and posteriorly by these ligaments and the tip of the coccyx. Synonym: apertura pelvis inferior, apertura pelvis minoris, fourth parallel pelvic plane, pelvic outlet, pelvic plane of outlet, plane of outlet. (05 Mar 2000) |