helicoid


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Related to helicoid: Catenoid, helicoid cyme

helicoid

[′hel·ə‚kȯid]
(invertebrate zoology)
Of a gastropod shell, shaped like a flat coil or flattened spiral.
(mathematics)
A surface generated by a curve which is rotated about a straight line and also is translated in the direction of the line at a rate that is a constant multiple of its rate of rotation.
References in periodicals archive ?
VTA adjustment is made via a helicoid thread knob with lock.
For centuries, the plane and the helicoid were the only known examples of infinite, unbounded minimal surfaces that don't fold back to intersect themselves.
A roof prism design, it sports central focusing, click stops on the eyepiece diopter, and helicoid eyecups.
Further notes on Helicoid Land Shells from Japan, The Loo-Choo, and Bonin Islands, with descriptions of seven new species.
A type of inflorescence in which there is a single terminal flower, and below this a single branch bearing one or more younger flowers; variations of coiled and zigzag patterns include helicoid, cincinnus, bostryx, and scorpioid.
A coiled inflorescence has several variations called helicoid, cincinnus, and bostryx.
A particular form of inflorescence typifies some plant families, such as the compound umbel of Apiaceae (Umbelliferae), the ultimate spike of Gramineae, the capitulum or head of Asteraceae, the helicoid cyme of Boraginaceae, and the spadix of Araceae.
Typically, the compound flows into a helicoid, a cylinder that deflects and distributes the flow of compound around a core tube, which slides into the helicoid and holds the mandrel.
Rather, there is growing support for viewing limpets as a divergent group (Ponder and Lindberg, 1996) whose ancestors may have had internal fertilization with introsperm, a helicoid larval shell (Page, 1994), and primitive ctenidia.
From the illustrations one can see, with some effort, that the helicoid is deformable to a plane, whereas the catenoid is deformable to a cylinder.
Descriptions of new helicoid shells from Cape Colony.