# Center

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Related to Ossification center: secondary ossification center

## center,

in politics, a party following a middle course. The term was first used in France in 1789, when the moderates of the National Assembly sat in the center of the hall. It can refer to a separate party in a political system, e.g., the Catholic Center party of imperial and Weimar Germany, or to the middle group of a party consisting of several ideological factions.

## Center

in machine building, a device used to position a work-piece or mandrel on lathes, rotary grinders, and other machine tools, as well as on checking and measurement instruments.

One end of a center has a working conical surface with a vertex angle of 60° or 90°; the other has a shank with a shallow cone used to secure the center in the headstock spindle or tailstock spindle, which is an axially adjustable sleeve. If it is necessary to bore the end face of a workpiece, an opening is provided on the dead center so that a cutting tool may protrude. Machining of hollow workpieces calls for larger-diameter centers in the shape of truncated cones that fit into a conical, chamfered hole in the workpiece. Live centers, which are set in the spindle of the machine tool, have serrations on a conical working surface to transmit motion to the workpiece. In order to prevent slippage of the workpiece at higher machine speeds, the dead center may be replaced with a live center running on roller bearings. Centers are fabricated from hardened steel.

## Center

in mathematics. (1) A point O is said to be the center of symmetry of a geometric configuration if for every point A of the configuration there is another point A′ of the configuration such that O is the midpoint of the line joining A and A′. A curve or surface that has such a center is said to be central. The circle, ellipse, and hyperbola are the simplest examples of central curves, and the sphere, ellipsoid, and hyperboloid (of one or two sheets) are the simplest examples of central surfaces. It is possible for a configuration to have infinitely many centers of symmetry; for example, the centers of symmetry of a configuration consisting of two parallel lines lie on the line equidistant from the two given lines. (See alsoSYMMETRY.)

Figure 1

(2) The center of similitude of radially related configurations is the point S at which lines joining corresponding points of the configurations intersect (Figure 1).

Figure 2

(3) If all integral curves in the neighborhood of a singular point of a differential equation are closed and enclose the singular point, that point is said to be a center (Figure 2). Centers belong to the class of singular points whose character generally is not preserved when small changes are made in the right-hand side of the equation.

## center

[′sen·tər]
(industrial engineering)
A manufacturing unit containing a number of interconnected cells.
(mathematics)
The point that is equidistant from all the points on a circle or sphere.
The point (if it exists) about which a curve (such as a circle, ellipse, or hyperbola) is symmetrical.
The point (if it exists) about which a surface (such as a sphere, ellipsoid, or hyperboloid) is symmetrical.
For a regular polygon, the center of its circumscribed circle.
The subgroup consisting of all elements that commute with all other elements in a given group.
The subring consisting of all elements a such that ax = xa for all x in a given ring.
(optics)
To adjust the components of an optical system so that their centers of curvature lie on a common optical axis. Also known as square-on.
(statistics)
For a distribution, the expected value of any random variable which has the distribution.

## center

1. The center ply in plywood.
2. The core in a laminated construction.
3. Centering.
4. The center about which an arc of a circle is drawn, equidistant from all points on the arc.

## centre

(US), center
1. Geometry
a. the midpoint of any line or figure, esp the point within a circle or sphere that is equidistant from any point on the circumference or surface
b. the point within a body through which a specified force may be considered to act, such as the centre of gravity
2. the point, axis, or pivot about which a body rotates
3. Politics
a. a political party or group favouring moderation, esp the moderate members of a legislative assembly
b. (as modifier): a Centre-Left alliance
4. Physiol any part of the central nervous system that regulates a specific function
5. a bar with a conical point upon which a workpiece or part may be turned or ground
6. a punch mark or small conical hole in a part to be drilled, which enables the point of the drill to be located accurately
a. the position of a player who jumps for the ball at the start of play
b. the player in this position
8. Archery
a. the ring around the bull's eye
b. a shot that hits this ring
References in periodicals archive ?
The skull base sutures, synchondroses and ossification centers were all assessed by the author for normal appearance and degree of suture closure.
He speculated that the anomaly resulted from failed fusion of either the sclerotomal chondrification or ossification centers during fetal spinal development.
Beginning in the third trimester of pregnancy and continuing after birth, secondary ossification centers form.
Moose had earlier formation of thyroid and adrenal glands, thymus, ossification centers in the skeleton, and of characteristic structures in the organs of the alimentary tract in comparison with domestic animals.
Ossification centers and skeletal development in the postnatal Virginia opossum.
3) Age can be determined from a variety of factors like the appearance of ossification centers and their fusions during skeletal development, from height and weight which is applicable in early periods of life, dental development and changes occurring at puberty like appearance of hair and their growth and colour changes, development of breast in females, starting of menarche and from menopause.
Numerous studies are done about the forming of the ossification centers in birds before and after hatching.
Secondary ossification centers located on the ends of the long bones are named epiphyses and those at the insertion site of a muscle are named apophyses.
The postmortem radiograph (X-Ray) showed sacral agenesis, fused hypoplasticpelvis, single appearing femur shaft bone with two distal epiphyseal ossification centers, single small tibia.

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