# chain

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Related to Respiratory chain: oxidative phosphorylation

## chain,

flexible series of connected links used in various ways, especially for the transmission of motive power, for hoisting (see pulleypulley,
simple machine consisting of a wheel over which a rope, belt, chain, or cable runs.

A grooved pulley wheel like that used for ropes is called a sheave. A single sheave mounted in a block and fixed in place simply changes the direction of force exerted on the rope

## Chain

in mathematics, a fundamental concept of combinatorial topology. A chain is a generalization, to the case of n dimensions, of the concept of an oriented polygonal line.

## Chain

a series of identical segments (links) joined together and movable relative to one another. It is known that chains were used for several millennia before the Common Era; for example, chains were used in simple mechanisms in the third century B.C. in Greece. In the first century B.C. the Roman architect Vitruvius described a water pump that used buckets attached to an endless pintle chain. Leonardo da Vinci left drawings of chains with link plates of approximately the same shape as those of modern chains. I. I. Polzunov developed a pintle chain for driving machines that was similar to the chain patented 65 years later (in 1829) by the French engraver A. Galle.

The chains used in technology may be classified according to their purpose in the following categories: drive chains (in drives for machines, used to transmit motion from a drive shaft to one or more driven shafts), hauling chains (in conveyors, elevators, escalators, paternosters, and similar machines in which the working members that directly move loads and people are attached to the chains), hoisting chains (in load-lifting machines and water-engineering works, used to suspend, raise, and lower loads), anchor chains (on ships, used to tie an anchor to the ship), chains used to bind groups of logs into rafts, antiskid chains (used to increase the grip of motor vehicle wheels on icy roads and in similar slippery conditions), saw chains (for motor-driven saws used in the lumber industry), and holing and cutting chains (used in machines for extracting and processing minerals and for digging trenches).

Chains are also classified according to the method used in fabricating the links. The categories include ordinary round-link chains with circular cross sections, which may be welded or cast; pintle chains with link plates connected by pins or bushings; open-hook chains having forged or cast links with hooks at one end; detachable chains with hot-forged or cold-forged links; and block chains with links in the form of thick bars.

Round-link chains are used for hauling, lifting, attaching anchors, and tying logs and as antiskid chains. Pintle chains are the most common type. Those used in hoists that operate only occasionally and for short periods at velocities up to 0.25 m per second and in slow-moving conveyors for removing manure or distributing feed are made with simple articulated chains with twin-plate or multiplate links. In order to reduce unit loads on the joints and joint wear, pintle chains used for driving and hauling are equipped with bushings. Rollers may be fitted over the bushings to reduce wear on the bushings and sprocket teeth. Such single-and multistrand roller chains represent the most developed designs and have been used extensively. For handling large dynamic loads that are applied in high-frequency cycles, as in the case of excavator mechanisms, the drive chains used have offset sidebars that reduce the dynamic load on the mechanisms and on the elements of the chain itself. In order to improve engagement with the sprockets, reduce noise, and increase reliability, inverted-tooth silent chains with multiplate links are supplied for high-power, high-speed drives. With the advent of precision, multistrand roller chains that are simpler and cheaper to fabricate, the use of inverted-tooth silent chains has declined and is now limited primarily to older types of machines.

In the 1970’s open-link twin-pin chains came to be used (together with round-link chains and detachable chains with open links) for operations in powdery, corrosive, and chemically-active media that cause a loss of mobility in the joints of roller chains and pintle chains equipped with bushings. The new design also differs from roller chains in having joint parts with better impact and fatigue resistance, in requiring less labor to produce, and in being lighter and cheaper. Open-hook and block chains are used for both driving and hauling. Detachable chains are widely used for hauling.

The ends of chains are connected by special links. In order to reduce wear on the joint parts or, in the case of round-link chains, on the chain as a whole, chains may be subjected to heat treatment or chemical case hardening; they may also be lubricated while in operation.

The primary geometric parameters of chains are the pitch (average length) and, for round-link chains, the gauge (cross-sectional diameter of the links). In order to achieve compact drives and mechanisms, the pitches of driving and hoisting chains are kept to a minimum (4–300 mm); hauling chains, which are very long, are designed with a large pitch (up to 1,400 mm), which permits substantial reductions in weight and cost.

The principal types of chains produced in the USSR are standardized, and their production is specialized.

### REFERENCES

Vorob’ev, N. V. Tsepnye peredachi, 4th ed. Moscow, 1968.
Reshetov, D. N. Detail mashin, 3rd ed. Moscow, 1974.

I. I. IVASHKOV and A. A. PARKHOMENKO

## chain

[chān]
(chemistry)
A structure in which similar atoms are linked by bonds.
(civil engineering)
(communications)
A network of radio, television, radar, navigation, or other similar stations connected by special telephone lines, coaxial cables, or radio relay links so all can operate as a group for broadcast purposes, communication purposes, or determination of position.
(computer science)
A series of data or other items linked together in some way.
A sequence of binary digits used to construct a code.
(design engineering)
A flexible series of metal links or rings fitted into one another; used for supporting, restraining, dragging, or lifting objects or transmitting power.
A mesh of rods or plates connected together, used to convey objects or transmit power.
(geology)
A series of interconnected or related natural features, such as lakes, islands, or seamounts, arranged in a longitudinal sequence.
(mathematics)

## chain

A land surveyor’s standard distance-measuring device. Also see Gunter’s chain.

## chain

1. a set of metal links that fit over the tyre of a motor vehicle to increase traction and reduce skidding on an icy surface
2.
a. a number of establishments such as hotels, shops, etc., having the same owner or management
b. (as modifier): a chain store
3. a series of deals in which each depends on a purchaser selling before being able to buy
4. Logic (of reasoning) a sequence of arguments each of which takes the conclusion of the preceding as a premise
5. a unit of length equal to 22 yards
6. a unit of length equal to 100 feet
7. Chem two or more atoms or groups bonded together so that the configuration of the resulting molecule, ion, or radical resembles a chain
8. Geography a series of natural features, esp approximately parallel mountain ranges

## Chain

Sir Ernst Boris. 1906--79, British biochemist, born in Germany: purified and adapted penicillin for clinical use; with Fleming and Florey shared the Nobel prize for physiology or medicine 1945

## chain

(operating system)
(From BASIC's "CHAIN" statement) To pass control to a child or successor without going through the operating system command interpreter that invoked you. The state of the parent program is lost and there is no returning to it. Though this facility used to be common on memory-limited microcomputers and is still widely supported for backward compatibility, the jargon usage is semi-obsolescent; in particular, Unix calls this exec.

Compare with the more modern "subshell".

## chain

(programming)
A series of linked data areas within an operating system or application program. "Chain rattling" is the process of repeatedly running through the linked data areas searching for one which is of interest. The implication is that there are many links in the chain.

## chain

(theory)
A possibly infinite, non-decreasing sequence of elements of some total ordering, S

x0 <= x1 <= x2 ...

A chain satisfies:

for all x,y in S, x <= y \/ y <= x.

I.e. any two elements of a chain are related.

("<=" is written in LaTeX as \sqsubseteq).
References in periodicals archive ?
In particular, protein levels of cytochrome B (CYT B), a component of respiratory chain complex III [25], and cytochrome C (CYT C), a small heme-protein involved in the transfer of electrons between complexes III and IV [26], were evaluated in the three different groups by ELISA.
Researchers describing the relationship between the proliferation of tumor cells and their respiratory activity demonstrated that the Q02 levels (Q02: 02 consumption in mg of tissue per hour), resulting from destruction of the respiratory chain, has an effect on the proliferation of tumor cells.
A recent study in mito-mice carrying different proportions of [DELTA]mt DNA showed respiratory chain defect that leads to meiotic arrest during spermatogenesis.
Alcohol has been shown to deplete GSH levels, particularly in the mitochondria, which normally are characterized by high levels of GSH needed to eliminate the ROS generated during activity of the respiratory chain.
Respiratory chain enzyme activities in lymphocytes from untreated patients with Parkinson disease.
Caption: Figure 2: (a) Original recording of the assessment of the respiratory chain function in myoblasts.
Clinically, the most important application of CoQ10 assay is detection of CoQ10 deficiency of the respiratory chain.
Oxygen free radicals, an important role in the pathogenesis of stroke, wreak havoc in mitochondrial membrane and respiratory chain complex, which results in mitochondrial dysfunction (Lin and Beal 2006).
When oxygen levels in cells are low, ATP production through the respiratory chain is greatly reduced, and most ATP is produced through glycolysis (as described in the following section).
SDH indicates succinate dehydrogenase; CK, creatine kinase; CM, respiratory chain complex; EMG, electromyogram; and MMP, idiopathic mitochondrial myopathy.
Development and implementation of standardized respiratory chain spectrophotometric assays for clinical diagnosis.
The ability to detect POLG mutations prospectively in muscle samples from 2 patients further supports the importance of qPCR analysis, given that the results of studies of respiratory chain enzymes in muscle tissue from MDDS patients may be negative or inconclusive (27, 28).

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