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In situ is a Latin phrase meaning in the place. It is used in many different contexts.
Archaeology In archaeology, in situ refers to an artifact that has not been moved from its original place of deposition. An artifact being in situ is critical to the interpretation of that artifact and, consequently, to the culture which formed it. Once an artifact's provenance has been recorded, the artifact can then be moved for conservation, further interpretation and display. An artifact that is not discovered in situ is considered out of context and will not provide an accurate picture of the associated culture. However, the out of context artifact can provide scientists with an example of types and locations of in situ artifacts yet to be discovered. Biology In biology, in situ means to examine the phenomenon exactly in place where it occurs (without removing it in some special medium etc.). Usually means something intermediate between in vivo and in vitro. For example, examining a cell within a whole organ intact and under perfusion may mean in situ investigation. This is not obviously in vivo experimenting because an animal is sacrificed, but it is not the same as working with the cell alone (which may be a perfect case of an in vitro experiment). In oncology, for a carcinoma which is a cancer of an epithelium, in situ means that malignant cells are present in the epithelium but has not invaded beyond the basal lamina into deeper tissues. In genetics, in situ can also mean in the chromosome. For example, FISH can be done with chromosomes in cells or in a karyotype, such as with spectral karyotyping. In each case, we are observing the target sequence(s) where they are in the chromosome. In conservation of genetic resources, In-situ conservation or "on-site conservation" is the process of protecting an endangered plant or animal species in its natural habitat. As opposed to ex-situ conservation or "off-site conservation". Chemistry In chemistry, in situ typically means "in the reaction mixture" There are numerous unstable molecules which must be synthesized in situ (i.e. in the reaction mixture but cannot be isolated on their own) for use in various processes. Examples include the Corey-Chaykovsky reagent and adrenochrome. Earth and atmospheric sciences In physical geography and the Earth sciences, in situ typically describes natural material or processes prior to transport. For example, in situ is used in relation to the distinction between weathering and erosion, the difference being that erosion requires a transport medium (such as wind, ice, or water), whereas weathering occurs in situ. Geochemical processes are also often described as occurring to material in situ. In the atmospheric sciences, in situ refers to measurements obtained through direct contact with the respective subject, such as a radiosonde measuring a parcel of air or an anemometer measuring wind, as opposed to remote sensing such as weather radar or satellites. Environmental engineering In situ can refer to where a clean up or remediation of a polluted site is performed using and simulating the natural processes in the soil, contrary to ex situ where contaminated soil is excavated and cleaned elsewhere, off site. Literature In literature in situ is used to describe a condition. The Rosetta Stone, for example, was originally erected in a courtyard, for public viewing. Most pictures of the famous stone are not "in-situ" pictures of it erected, as it would have been originally. The stone was uncovered as part of building material, within a wall. Its in situ condition today is that it is erected, vertically, on public display at the British Museum. Linguistics In linguistics, specifically syntax, an element may be said to be in situ if it is pronounced in the position where it is interpreted. For example, questions in languages such as Chinese have in-situ wh-elements, with structures comparable to "John bought what?" while English wh-elements are not in-situ: "What did John buy?" Law In legal context, in situ is often used for its literal meaning. For example, in Hong Kong, in situ land exchange involves the government exchanging the original or expired lease of a piece of land with a new grant or re-grant with the same piece of land or a portion of that. RF Transmission In Radio Frequency (RF) Transmission Systems, in situ is often used to describe the location of various components while the system is in its standard transmission mode, rather than operation in a test mode. For example, if an in situ wattmeter is used in a commercial broadcast transmission system, the wattmeter can accurately measure power while the station is "on the air". See also | ||||||||
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