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].
fruticicola, especially by its (slightly less) close-set teleoconch ribs, but this species has a smaller, less elongate shell with less rapidly expanding whorls, less sharp apical angle and spire angle, proportionally larger body whorl, and differs in protoconch sculpture.
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.
Marginal impression distinct, narrow near apical angle, broadly widened to the basal angles, ending in fairly deep dimple-like, basal impression which is situated near hind margin.
Area between lateral carinae of pronotum dark brown; two branches of outer apical angle of genital styles subequal; aedeagus with one small spine situated near basal third, directed caudally M.
Forewings broadening apically, cross veins located in apical half, with apical angle acute, 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.
This genus is closely related to Neobelocera Ding and Yang, 1986 (Chen & Liang 2005), which also feeds on bamboo, but differs in the following: the latter with the antennae markedly flattened, first segment subsagittate, a longitudinal carina down middle, with the apex unequally bifurcate, the inner apical angle much longer than outer apical angle, the postclypeus in profile, apical part of median carina bend at rounded, not angled, the rostrum very short, only reaching mesotrochanters, and the forewing often with snatchy blackish brown markings, in dark portion veins bear white spots.
5 cm in length with apical angles ranging from approximately 35-40 [degrees].