cluster

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cluster,

in astronomy: see star clusterstar cluster,
a group of stars near each other in space and resembling each other in certain characteristics that suggest a common origin for the group. Stars in the same cluster move at the same rate and in the same direction.
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; galaxygalaxy,
large aggregation of stars, gas, and dust, typically containing billions of stars. Recognition that galaxies are independent star systems outside the Milky Way came from a study of the Andromeda Galaxy (1926–29) by Edwin P.
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.

cluster

A group of stars whose members are sufficiently close to each other to be physically associated. Clusters range from dense congregations of many thousands of stars to loose groups of only a few stars. Current theories of stellar evolution suggest that stars form in associations, whose densest groupings remain bound as clusters while the other stars disperse; this view is supported by the relatively well-defined Hertzsprung–Russell diagrams of clusters, which indicate that cluster members are of essentially the same composition and age (see also turnoff point). Because the stars in a cluster are all at approximately the same distance, the observed differences in appearance are believed to be due mainly to differences in mass. An estimate of distance is obtained from the technique of main-sequence fitting. See globular cluster; open cluster.

Cluster

An ESA mission to study in three dimensions the shape and dynamic behavior of small-scale structures in the Earth's plasma environment. In effect, Cluster is examining ‘space weather’ – that is, the interaction between the particles of the solar wind and the Earth's magnetosphere. The mission consists of four identical 500-kg satellites, carrying the same 10 instruments. The satellites were carried into space in two pairs by Russian-made Soyuz rockets during the summer of 2000. The first pair, nicknamed Salsa and Samba, were launched July 16, followed by the second pair, Rumba and Tango, launched Aug. 9. The Cluster craft were scheduled to operate until 2005. The mission, which was designated Cluster II, was the replacement for an earlier failed mission. The original Cluster satellites were to have been sent into space together in June 1996, on an Ariane-5 rocket, but were destroyed when the rocket unexpectedly tilted and broke up soon after liftoff.

Cluster

Any configuration of elements that are grouped or gathered closely together.

cluster

[′kləs·tər]
(astronomy)
(computer science)
In a clustered file, one of the classes into which records with similar sets of content identifiers are grouped.
A grouping of hardware devices in a distributed processing system.
A group of disk sectors that is treated as a single entity by the operating system
(engineering)
A pyrotechnic signal consisting of a group of stars or fireballs.
A grouping of rocket motors fastened together.
(ordnance)
A collection of small bombs held together by an adapter for dropping.

cluster

i. Several bomblets forming part of a bomb as in cluster bomb. Once a bomb is released from the aircraft, individual bomblets are dispensed by the bomb.
ii. Two or more parachutes linked to support a single load.
iii. Several engines controlled by a single throttle.

cluster

1. Astronomy an aggregation of stars or galaxies moving together through space
2. Chem
a. a chemical compound or molecule containing groups of metal atoms joined by metal-to-metal bonds
b. the group of linked metal atoms present

cluster

(architecture)
Multiple servers providing the same service. The term may imply resilience to failure and/or some kind of load balancing between the servers. Compare RAIS.

cluster

(file system)
An elementary unit of allocation of a disk made up of one or more physical blocks.

A file is made up of a whole number of possibly non-contiguous clusters. The cluster size is a tradeoff between space efficiency (the bigger is the cluster, the bigger is on the average the wasted space at the end of each file) and the length of the FAT.

cluster

(1) Two or more systems working together. See clustering.

(2) Also called an "allocation unit" or "file allocation unit," it is a number of disk sectors treated as a unit. A cluster is the smallest unit of storage the operating system's file system can manage. That means if a 1KB file is stored in a system with a 32KB cluster (see table below), the 1KB file takes up 32KB of disk space.

Following are the cluster sizes for the FAT file systems for hard drives. When FAT32 came out, drive sizes were minuscule by today's standards, and the reduction of cluster size from 16KB and 32KB to 4KB** saved a lot of disk space for small files. See FAT, FAT32 and lost cluster.

                      Cluster Size                      FAT16   FAT32   Drive Size         (1984)  (1996)

        0-128MB         2KB
      128-256MB         4KB
      256-512MB         8KB
    512MB-1GB          16KB    4KB**
        1-2GB          32KB    4KB**
        1-8GB                  4KB**
        8-16GB                 8KB
       16-32GB                16KB
          32GB +              32KB
References in periodicals archive ?
Although every investigation has unique challenges that require some flexibility to account for intricacies of the particular health outcome of concern or the amount of resources and information available, the CDC guidelines (17) suggest a 4-stage systematic approach, portrayed in the Figure, when managing an investigation of a possible cancer cluster.
14) This assessment effectively ruled out the possibility of a cancer cluster with straightforward calculations.
The probability of a cancer cluster due to chance alone.
A confirmed cancer cluster could be the result of chance, miscalculation of the expected number of cancer cases (e.
Rather than call for a new analysis, Kuehl said she is considering holding a hearing to determine whether oversight is needed on how the Department of Public Health and California Cancer Registry conduct studies of cancer clusters.
Physicist Dr John Walker, 76, claimed that cancer clusters could be blamed on the 27-metre mast at St Edward's Primary School after being contacted by resident Jackie Slater.
In another part of the country, New York's Westchester and Suffolk counties and the state of New Jersey have appropriated funds to study areas near nuclear plants where cancer clusters are suspected.
My failure to unambiguously identify both of PGC 24284's members is softened by their stupendous distances: along with NGC 2624, NGC 2625, and UCG 4526, they lie about 200 million light-years from Earth, on the outskirts of the so-called Cancer Cluster.
NIE has also written to the chief executive of Dungannon District Council to request a meeting with elected representatives - but not with residents at the centre of a cancer cluster alert.
Close to 20% of all cases of colorectal cancer cluster in families, and the disorders for which genetic tests are available account for only about 3% of all colorectal cancers in the United States.
Case studies and examples range from the relationship between a nuclear reactor and a possible cancer cluster in Ames, IA, to Ansel Adams' idealizing photo graphs of western landscapes, to arguments over how to classify the almost extinct red wolf.
Notwithstanding, cancer cluster investigations can be useful for educating the public on known risk factors and preventive steps needed for the disease in question.