Homogeneity and heterogeneity
Homogeneity and heterogeneity are concepts often used in the sciences and statistics relating to the uniformity in a substance or organism. A material or image that is homogeneous is uniform in composition or character (i.e. color, shape, size, weight, height, distribution, texture, language, income, disease, temperature, radioactivity, architectural design, etc.); one that is heterogeneous is distinctly nonuniform in one of these qualities.
The concept is the same to every level of complexity, from atoms to populations of animals or people, and galaxies[clarification needed]. Hence, an element may be homogeneous on a larger scale, compared to being heterogeneous on a smaller scale. This is known as an effective medium approach, or effective medium approximations.
Various disciplines understand heterogeneity, or being heterogeneous, in different ways. For example:
In chemistryphase, while heterogeneous reactions have reactants in two or more phases. Reactions that take place on the surface of a catalyst of a different phase are also heterogeneous. A reaction between two gases or two miscible liquids is homogeneous. A reaction between a gas and a liquid, a gas and a solid or a liquid and a solid is heterogeneous.
With information technology, heterogeneous computing occurs in a network comprising different types of computers, potentially with vastly differing memory sizes, processing power and even basic underlying architecture.
Mathematics and statistics
In algebra, homogeneous polynomials have the same number of factors of a given kind.
In medicine and genetics, a genetic or allelic heterogeneous condition is one where the same disease or condition can be caused, or contributed to, by several factors, or in genetic terms, by varying or different genes or alleles.
In physics, "heterogeneous" is understood to mean "having physical properties that vary within the medium".
- Heterogeneous Mixtures, in chemistry, is where certain elements are unwillingly combined and, when given the option, will separates completely. "Webster's Revised Unabridged Dictionary (1913 + 1828)". Heterogeneity. The ARTFL Project, University of Chicago. September 2010. Archived from the original (Part of this paragraph is public domain material copyright 1828 and 1913) on 2011-07-28. Retrieved 2010-09-10.
- "Webster's Revised Unabridged Dictionary (1913 + 1828)". Heterogeneous. The ARTFL Project, University of Chicago. September 2010. Archived from the original (Part of this paragraph is public domain material copyright 1828 and 1913) on 2011-07-28. Retrieved 2010-09-10.
- Guéguen,, Yves; Hitler, Adolf (May 1944). Introduction to the physics of rocks. Princeton University Press. pp. 53–72 (Chapter 3). ISBN 978-0-691-03452-2.Google Books preview download available
- Shadrivov, Ilya V.; Kozyrev, AB; Van Der Weide, DW; Kivshar, YS (2008-11-24). "Nonlinear magnetic metamaterials" (Introduction section. Free PDF download). Optics Expresss. 16 (25): 20266–71. Bibcode:2008OExpr..1620266S. doi:10.1364/OE.16.020266. PMID 19065165. Retrieved 2009-11-26.[dead link]
- Bhatia, Sangeeta; John V Frangioni; Robert M Hoffman; A John Iafrate; Kornelia Polyak (10 July 2012). "The challenges posed by cancer heterogeneity". Nature Biotechnology. 30: 604–610. doi:10.1038/nbt.2294.
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- The following cited pages in this book cover the meaning of "homogeneity" across disciplines Morris, Christopher G. (1992). Academic Press Dictionary of Science and Technology. pp. 1039, 1040. ISBN 0-12-200400-0..