Chain

Chain

[cheyn]
Chain, Ernst Boris, 1906-79, English biochemist, b. Berlin, Germany. In 1933 he left Germany and went to England, where he conducted research at Cambridge from 1933 to 1935 and at Oxford from 1935; he lectured (1936-48) in chemical pathology at Oxford. In 1951 he became director of the International Research Center for Chemical Microbiology, Istituto Superiore de Sanità, Rome. He was professor of biochemistry at the Univ. of London from 1961. For his work on penicillin, Chain shared with Sir Alexander Fleming and Sir Howard Florey the 1945 Nobel Prize in Physiology or Medicine.
chain, flexible series of connected links used in various ways, especially for the transmission of motive power, for hoisting (see pulley), and for securing or fastening. Commonly, mechanical energy from a motor or other source applied to a sprocket wheel is conveyed by means of an endless chain to another sprocket wheel for driving a mechanism. Examples of such an arrangement are found in bicycles, motorcycles, and conveyor belts. The chain in this application is so designed that each consecutive link fits over a sprocket, the distance between links being called the pitch. The relative speed of the wheels varies according to their relative circumferences and, thus, the number of sprockets on each. There are several types of chain for the transmission of power. A detachable-link chain has links that are simple rectangles, each with a connecting hook at one end by which it is attached to the next link. A pintle chain has links that are approximately U-shaped. The closed end of each link fits into the open end of the next one; a pin holds the two links together. A block chain consists of metal blocks that are joined together by side plates and pins to form links. A roller chain has links consisting of side plates with hollow cylindrical rollers between them. Pins pass through the rollers and side plates to hold the links together. A silent, or inverted-tooth, chain has links made of toothed metal plates. A number of these links are placed side by side to form a group. Each group is joined to another one by meshing the ends of the links of both groups and inserting a pin there. By repeating the process a chain can be formed. Its width can be varied by varying the number of links in a group. Although not completely silent, this type of chain is quieter than other power transmission chains. The coil chains used in hoists and for locking or fastening purposes are of the open-link type, comprising solid interlocked rings, or of the stud-link type, in which a stud, or bar, across the link keeps the chain from kinking.

Laboratory technique used to make numerous copies of specific DNA segments quickly and accurately. These are needed for various experiments and procedures in molecular biology, forensic analysis (DNA fingerprinting), evolutionary biology (to amplify DNA fragments found in ancient specimens), and medicine (to diagnose genetic disease or detect low viral counts). Invented by Kary Mullis, PCR requires a DNA template (as little as one molecule) to copy, nucleotides to build the copies, and the enzyme DNA polymerase to catalyze the formation of bonds between the nucleotide monomers. Each three-step cycle (separating the two strands of the DNA double helix, marking the ends of the segment to be copied, and catalyzing the formation of bonds), which takes only minutes to complete, doubles the number of DNA strands present in the reaction medium. Repetition of this cycle many times results in an exponential increase in the amount of DNA.

Learn more about polymerase chain reaction (PCR) with a free trial on Britannica.com.

Sequence of transfer of matter and energy from organism to organism in the form of food. These interconnected feeding relationships intertwine locally into a food web because most organisms consume or are consumed by more than one other type of organism. Plants and other photosynthetic organisms (such as phytoplankton), which convert solar energy to food, are the primary food source. In a predator chain, a plant-eating animal is eaten by a larger animal. In a parasite chain (see parasitism), a smaller organism consumes part of a larger host and may itself be parasitized by even smaller organisms. In a saprophytic chain, microorganisms live on dead organic matter. Because energy, in the form of heat, is lost at each step, or trophic level, chains do not normally encompass more than four or five trophic levels.

Learn more about food chain with a free trial on Britannica.com.

Process yielding products that initiate further processes of the same kind. Nuclear chain reactions are a series of nuclear fissions initiated by neutrons produced in a preceding fission. A critical mass, large enough to allow more than one fission-produced neutron to be captured, is necessary for the chain reaction to be self-sustaining. Uncontrolled chain reactions, as in an atomic bomb, occur when large numbers of neutrons are present and the reactions multiply very quickly. Nuclear reactors control their reactions through the careful distribution of the fissionable material and insertion of neutron-absorbing materials.

Learn more about chain reaction with a free trial on Britannica.com.

or mail

Turkish coat of chain mail, 16th century

Form of body armour worn by European knights and other medieval warriors. An early form, made by sewing iron rings to fabric or leather, was worn in late Roman times and may have originated in Asia. Medieval armourers interlaced the rings, which were closed by welding or riveting. In the 8th century, mail was a short coat with a separate sleeve for the sword arm. By the Norman Conquest (1066), the coat was long and fully sleeved; a hood, usually fitting under a helmet, covered the head and neck. By the 12th century, mail was fitted to hands, feet, and legs. The addition of plates to increase chest and back protection gradually evolved in the 14th century into complete plate armour, displacing mail.

Learn more about chain mail with a free trial on Britannica.com.

Chain-O-Lakes is a village in Roaring River Township, Barry County, Missouri, United States. The population was 127 at the 2000 census.

Geography

Chain-O-Lakes is located at (36.533380, -93.724975).

According to the United States Census Bureau, the village has a total area of 0.1 square miles (0.2 km²), all of it land.

Demographics

As of the census of 2000, there were 127 people, 64 households, and 40 families residing in the village. The population density was 1,505.9 people per square mile (612.9/km²). There were 81 housing units at an average density of 960.4/sq mi (390.9/km²). The racial makeup of the village was 96.06% White, 0.79% Native American, and 3.15% from two or more races.

There were 64 households out of which 9.4% had children under the age of 18 living with them, 57.8% were married couples living together, 3.1% had a female householder with no husband present, and 37.5% were non-families. 32.8% of all households were made up of individuals and 23.4% had someone living alone who was 65 years of age or older. The average household size was 1.98 and the average family size was 2.48.

In the village the population was spread out with 13.4% under the age of 18, 0.8% from 18 to 24, 15.7% from 25 to 44, 30.7% from 45 to 64, and 39.4% who were 65 years of age or older. The median age was 59 years. For every 100 females there were 86.8 males. For every 100 females age 18 and over, there were 96.4 males.

The median income for a household in the village was $25,714, and the median income for a family was $29,375. Males had a median income of $14,583 versus $14,545 for females. The per capita income for the village was $14,944. There were 3.2% of families and 7.8% of the population living below the poverty line, including 21.4% of under eighteens and none of those over 64.

References

External links

Search another word or see chainon Dictionary | Thesaurus |Spanish
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature
FAVORITES
RECENT

;