Heterogeneous

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Heterogeneous means that something (an object or system) consists of a diverse range of opposite items. It is the antonym of homogeneous, which means that an object or system consists of many identical items. Matters of a quantum can exist in homogenous or in heterogeneous or in combined distributions. The term is often used in a scientific (such as a kind of catalyst), mathematical, sociological or statistical context.

A heterogeneous compound, mixture, reaction or other such object is one that consists of many different items, which are often not easily sorted or separated, though they are clearly distinct.

A heterogeneous mixture is a mixture of two or more compounds. In chemical kinetics, a heterogeneous reaction is one that takes place at the interface of two or more i.e. between a solid and a gas, a liquid and a gas, or a solid and a liquid.

Statistics

In meta analysis the term refers to the presence of multiple non-random intercepts in a dataset. In Meta-analysis of clinical studies which involves comparing and quantifying the effects of separate studies, heterogeneity refers to the differences in study populations or in methodologies used to study them that may have the effect of reaching differing conclusions. This is a problem as it calls into question conclusions that are drawn from studies and reduces their comparability. The following concepts are important in understanding the importance of heterogeneity in meta-analytical research.

Clinical Heterogeneity:

Heterogeneity resulting from differences in clinical features of a population that is being studied or treated.

Methodological Heterogeneity:

Heterogeneity resulting from the differential use of study methodology. These may lead to different conclusions in different studies, despite their clinical characteristics being the same.

Statistical Heterogeneity:

Heterogeneity resulting from either clinical or statistical heterogeneity, which leads to a difference in expected results, more than which can be accounted for by chance.

Systems

In the world of enterprise computing, heterogeneous data is a mix of data from two or more sources, often of two or more formats, e.g., SQL and XML.

Distributed systems are called heterogeneous if they contain many different types of hardware and software.

See also

Distributed computing

Social and human science

Homogeneity and heterogeneity are terms used to describe variety in many aspects of human groups, communities and populations, including cultural, demographic, ethnic and socio-political. In Economics and Social Sciences, 'heterogeneous agents' refers to a set of agents with different properties. The opposite of 'heterogeneous agents' in economic terminology is 'representative agent'.

General

In taxonomy, a heterogeneous taxon is a taxon that contains a great variety of individuals or sub-taxa; usually this implies that the taxon is an artificial grouping.

Genetics

In genetics, heterogeneity refers to multiple origins causing the same disorder in different individuals.

Allelic heterogeneity

If a number of different mutations occurring the same locus of a gene produce same disorder, such disorder is said to manifest allelic heterogeneity.

Example diseases:

  • Beta-Thalessemia can be caused by a number of different mutations in beta-globin gene.
  • Cystic fibrosis is cause by greater than 900 different mutant alleles.

Locus (Non-allelic) Heterogeneity

If mutations at a number of different loci of the same gene, or mutations involving different genes, all result in the same disorder, such disorder is said to manifest locus heterogeneity.

Example Disease:

  • Retinitis Pigmentosa has autosomal dominant, autosomal recessive, and x-linked origins.
  • Sickle cell anemia

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