apical angle


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apical angle

[′ap·i·kəl ′aŋ·gəl]
(mechanics)
The angle between the tangents to the curve outlining the contour of a projectile at its tip.
(optics)
The dihedral angle between the refracting faces of a prism. Also known as refracting angle.
References in periodicals archive ?
(iii) The ventral convexity K of the shell outline is strongly increasing with both the apical angle [alpha] and the differential-growth index [rho] and more weakly decreasing with the growth-dissymmetry index [delta].
One particular, unexpected feature emerging from this study is a negative covariance occurring between the differential growth index [rho] and the apical angle [alpha] (Figure 3).
The two species differ in teleoconch rib spacing, coiling tightness, width of the apical whorls, apical angle, proportional aperture and body whorl size, and whorl convexity.
Small, cylindrical shell of 5 to 6 whorls; protoconch smooth, depressed; ultimate whorl three times length of spire, tapering convexly to base; whorls gradate, sharply shouldered with flat to slightly inclined ramps; surface smooth; apical angle of 80 degrees.
Area between lateral carinae of pronotum mostly yellow; two branches of outer apical angle of genital styles unequal; aedeagus with one small tooth situated near middle, directed right M.
Hindwing wider than forewing, brownish black, apical angle acute, outer margin oblique, fringe scales yellow, area between costal margin and forewing yellow.
Head dark brownish orange, with 2 black maculae on posterior third of interocular space; tylus pale orange; most of juga and margin near eyes cover with a whitish cerumen; antennal segment I pale orange, segments II and III bright yellow with base and apex slightly darker, segment IV dark brown or reddish brown with base yellow; anterior lobe of pronotum dark brownish orange, posterior lobe yellowish orange with punctures slightly darker; scutellum with basal third yellowish orange and the rest reddish brown; clavus ochraceus with brownish orange punctures; corium hyaline, with punctures, a macula situated near middle third of endocorium, and a rectangular macula situated in the apical angle pale orange in color; membrane ambar.
Forewings with acute apical angle, outer margin approximately straight, oblique, posterior margin sinuate, with irregular markings at apical half (Figs.
Macropterous, extending beyond apex of last abdominal segment; costal margin emarginated, shallowly concave near midpoint; apical margin long, oblique, almost straight; apical angle subacute to truncate.
Structure: body oblong, parallel-sided; head with vertex slightly convex; eyes simple, barely pedunculate; buccula low, short, scarcely extended backward as far as the antenniferous tubercles, and apically rounded; rostrum reaching middle third of metasternum; pronotum with collar wide; frontal angles obtuse, rounded; anterolateral margins narrowly but distinctly carinate; humeral angles rounded, not exposed; fore femur with two subapical spines; middle and hind femora unarmed; macropterous, hemelytral membrane extending beyond the apex of last abdominal segment; costal margin slightly emarginate; apical margin straight; apical angle subacute; abdomen parallel, not dilated.
Dorsal coloration: Head yellowish hazel except for 2 short reddish brown irregular transverse marks restricted to the interocellar space; antennal segments I to IV reddish brown; pronotum yellowish orange with 2 large, irregular pale to dark brown spots at posterior lobe and transverse line; scutellum reddish brown to dark brown, middle third of apical half yellowish orange; clavus dark brown, claval commissure yellow; corium dark brown, costal margin and apical angle yellow; hemelytral membrane ocher, and apical margin widely hyaline.