Crossword clues for annulus
The Collaborative International Dictionary
Annulus \An"nu*lus\, n.; pl. Annuli. [L.]
A ring; a ringlike part or space.
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(Geom.)
A space contained between the circumferences of two circles, one within the other.
The solid formed by a circle revolving around a line which is the plane of the circle but does not cut it.
(Zo["o]l.) Ring-shaped structures or markings, found in, or upon, various animals.
Douglas Harper's Etymology Dictionary
1560s, medical, from misspelling of Latin anulus "little ring, finger ring," a diminutive of anus (see anus).
Wiktionary
n. 1 A ring- or donut-shaped area or structure. 2 (context geometry English) The region in a plane between two concentric circles of different radius. 3 (context topology English) Any topological space homeomorphic to the region in a plane between two concentric circles of different radius. 4 (context astronomy English) The ring of the sun not covered by the moon in an annular eclipse. 5 (context botany English) Structure in a fern that consists of differentially thick-walled cells on a sporangium that bend and distort as a result of drying. 6 (context mycology English) The membranous remnants of a partial veil which leaves a ring on the stem of a mushroom. 7 (context oil and gas production English) The space contained between the centre well bore and any external tubing. Sometimes used for separated gas flow.
WordNet
Wikipedia
In mathematics, an annulus (the Latin word for "little ring" is anulus, with plural anuli) is a ring-shaped object — a region bounded by two concentric circles. The adjectival form is annular (as in annular eclipse).
The open annulus is topologically equivalent to both the open cylinder and the punctured plane. Informally, it has the shape of a hardware washer.
The area of an annulus is the difference in the areas of the larger circle of radius and the smaller one of radius :
A = πR − πr = π(R − r).
The area of an annulus can be obtained from the length of the longest line segment that can lie completely inside the annulus, 2d in the accompanying diagram. This can be proven by the Pythagorean theorem; the interval of greatest length that can lie completely inside the annulus will be tangent to the smaller circle and form a right angle with its radius at that point. Therefore, d and r are the sides of a right-angled triangle with hypotenuse R, and the area of the annulus is given by
A = π(R − r) = πd.
Thus the area depends solely on the length of the chord tangent to the inner circle, regardless of the radii of the circles.
The area can also be obtained via calculus by dividing the annulus up into an infinite number of annuli of infinitesimal width and area and then integrating from ρ = r to ρ = R:
A = ∫2πρ dρ = π(R − r).
The area of an annulus sector of angle , with measured in radians, is given by
$$A = \frac{\theta}{2} \left(R^2 - r^2\right).$$
Annulus (or anulus) or annular may refer to:
An annulus is the ring-like structure sometimes found on the stipe of some species of mushrooms. The annulus represents the remaining part of the partial veil, after it has ruptured to expose the gills or other spore-producing surface. An annulus may be thick and membranous, or it may be cobweb-like. An annulus may be persistent and be a noticeable feature of a mature mushroom, or it may disappear soon after the emergence of the mushroom, perhaps leaving a few remnants on the stipe as an "annular zone".
Annuli come in various shapes, which can be important features for identification of the mushroom. Common shapes include:
- pendant - drooping or skirt-like
- flaring - spreading outward from the stipe
- sheathing - opening upwards around the stipe
In zoology, an annulus is an external circular ring. Annuli are commonly found in segmented animals such as earthworms and leeches. The bodies of these annelids are externally marked by annuli that are arranged in series with each other.
An annulus may also be an indication of growth in certain species, similar to dendrochronology. For example, in fish, it is a series of concentric rings (or annuli) formed in the scales of bony fish. In bivalve mollusks, annuli are concentric growth rings in their shells.
The annulus of an oil well is any void between any piping, tubing or casing and the piping, tubing, or casing immediately surrounding it. It is named after the corresponding geometric concept. The presence of an annulus gives the ability to circulate fluid in the well, provided that excess drill cuttings have not accumulated in the annulus, preventing fluid movement and possibly sticking the pipe in the borehole.
For a new well in the process of being drilled, this would be the void between the drill string and the formation being drilled. An easy way to visualise this would be to stand a straw (purple in diagram) straight up in the center of a glass of water. All of the water in between the straw and the sides of the glass would be the annulus (yellow area in diagram), with the straw itself representing the drill string and the sides of the glass representing the formation. While drilling, drilling fluid is pumped down the inside of the drill string and pushes the drill cuttings up the annulus to the surface, where the cuttings are removed from the drilling fluid ( drilling mud) by the shale shakers.
In a completed well, there may be many annuli. The 'A' annulus is the void between the production tubing and the smallest casing string. The 'A' annulus can serve a number of crucial tasks, including gas lift and well kills. A normal well will also have a 'B' and frequently a 'C' annulus, between the different casing strings. These annuli do not normally have any connection to well bore fluids, but maintaining pressure in them is important in order to ensure integrity of the casing strings.
Though all annuli in a completed well are expected to be isolated from the production tubing and each other, connections allowing the flow of fluids between them may sometimes occur, due to either intervention or wear and tear. There is said to be "communication" between these connected annuli.
During coiled tubing interventions, the void between the coil and the production tubing can also be considered an annulus and be used for circulation.
The Annulus, or annular space, is the space between a penetrant and whatever surrounds it, such as the sides of an opening or a sleeve, as the case may be.
Sometimes an annulus can be "offset", meaning that the penetrant is not centred. If the firestop was tested only to a perfectly centred opening, an offset may disqualify it for use in the field.
In practical terms, an offset penetrant or annulus may very well present an added degree of difficulty for passing the fire test. A metallic sleeve as well as a metallic penetrant will conduct heat through the firestop. Insulation on the bottom of floor systems or in the middle of wall systems, as is the case with caulking or paint based (soft) systems, will encourage more heat to travel through the sleeve and the penetrant, which can put more stress on the seal on the unexposed side. In the case of a thin (below 4") firestop mortar, there is also more potential hazard from tight annular spacing because metal expands during the fire, thus squeezing the firestop - only to rapidly shrink when hit with the hose-stream test, which can let water through, thus failing the H rating in Canada or the entire rating in the US, where hose-stream testing is mandatory. Such a failure may no longer be visible once the test assembly has reached ambient temperatures again.
For all these considerations, the annular space is a critical aspect of field approvals.
An annulus in botany is a single row of specialized cells on the outer rim of a fern sporangium that serves in spore dispersal. It consists typically of a ring or belt of dead water-filled cells with differentially thickened cell walls that stretches about two-thirds around each sporangium in leptosporangiate ferns. The thinner walls on the outside allow water to evaporate quickly under dry conditions. This dehiscence causes the cells to shrink and a contraction and straightening of the annulus ring, eventually rupturing the sporangial wall by ripping apart thin-walled lip cells on the opposite side of the sporangium. As more water evaporates, air bubbles form in the cells causing the contracted annulus to snap forward again, thus dislodging and launching the spores away from the plant. The type and position of the annulus is variable (e.g. patch, apical, oblique, or vertical) and can be used to distinguish major groups of leptosporangiate ferns.
Usage examples of "annulus".
The annulus, the ring, between inner and outer hull is about fifteen feet on the top and bottom, about twenty-five feet on the sides.
The annulus was filled with tanks and air bottles and batteries and piping, all leaving more room inside the pressure hull.
Pendeen switched off the torch and straightened, looking down at the annulus of still-glowing metal.
And the Thing Below rose up from the white-hot annulus around its pit.
In an eye blink it became a broad annulus of scintillating light around a disk of blackness now bespecked with stars.
He was inclined to sit there for a few minutes with his buttocks cupped in the luxuriously polished wooden annulus of the shite-hole, and to savor this triumph, just as the late Samuel Pepys had taught him to do in the case of urination.
They grew legs, and around them sprang up an annulus of fire, which they survived, turning.
A distinct operculum is usually detached by the help of the annulus, and its removal may leave the mouth of the capsule widely open.
Its living-room was an immense annulus of glass from which, by merely moving along its circular length, any desired view could be had.
That part of the veil which breaks away from the cap, called the secondary veil, forms the annulus or ring.
The circular annulus on which the cut face of the donut half sits, as measured by Cst, represents the lunar surface where the shield intersects the ground.
The corresponding foundation for a communications satellite was essentially a thin steel annulus, a flat, sturdy donut that invariably looked too light for its job.