In situ

In situ (pronEng|ɪn siːˈtuː) is a Latin phrase meaning "in the place". It is used in many different contexts.

Aerospace

In the aerospace industry, equipment on board aircraft must be tested "in situ", or in place, to confirm everything functions properly as a system. Individually, each piece may work but interference from nearby equipment may create problems not anticipated. Special test equipment is available for this "in situ" testing.

Archaeology

In archaeology, "in situ" refers to an artifact that has not been moved from its original place of deposition. In other words, it is stationary, meaning "Still". 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 'find-site' 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.

"In situ" only expresses that the object has not been "newly" moved. Thus, an archaeological in-situ-find may be an object that was historically looted from another place, an item of "booty" of a past war, a traded item, or otherwise of foreign origin. Consequently, the "in situ" find site may still "not" reveal its provenance but with further detective work may help uncover links that otherwise would remain unknown. It is also possible for archaeological layers to be reworked on purpose or by accident (by humans, natural forces or animals). For example, in a "tell-tell mound", where layers are not typically uniform or horizontal, or in land cleared or tilled for farming.

The term "In situ" is often used to discribe ancient sculpture that was carved in place such as the Sphinx or Petra. This destinguishes it from statues that were carved and moved like the Colossi of Memnon which was moved in ancient times.

Architecture

In architecture and building, "in situ" means construction which is carried out on the building site using raw materials. Compare that with "prefabricated" construction, in which building components are made in a factory and then transported to the building site for assembly. For example, concrete slabs may be "in situ" or "prefabricated".

"In situ" techniques are often more labour-intensive, and take longer, but the materials are cheaper, and the work is versatile and adaptable. "Prefabricated" techniques are usually much quicker, therefore saving money, but factory-made parts can be expensive. They are also inflexible, and must often be designed on a grid, with all details fully calculated in advance. Finished units may require special handling due to excessive dimensions.

Astronomy

Future space exploration or terraforming may rely on obtaining supplies "in situ", such as previous plans to power the Orion space vehicle with fuel minable on the moon.

Mars Direct mission concept is based primarily on the "in situ" fuel production using Sabatier reaction.

A fraction of the globular star clusters in our Galaxy, as well as those in other massive galaxies, might have formed "in situ". The rest might have been accreted from now defunct dwarf galaxies.

Biology

In biology, "in situ" means to examine the phenomenon exactly in place where it occurs (i.e. without moving it to some special medium). This usually means something intermediate between "in vivo" and "in vitro". For example, examining a within a whole organ intact and under perfusion may be "in situ" investigation. This would not be "in vivo" as the donor is sacrificed before experimentation, but it would not be the same as working with the cell alone (a common scenario in "in vitro" experiments).

In-vitro was the first of mankind’s attempts to qualitatively and quantitatively analyze natural occurrences in the lab [citation pending] . Eventually, the limitation of in-vitro experimentation was that they were not conducted in natural environments. To compensate for this problem, in-vivo experimentation allowed testing to occur in the originate organism or environment [citation pending] . To bridge the dichotomy of benefits associated with both methodologies, in-situ experimentation allowed the controlled aspects of in-vitro to become coalesced with the natural environmental compositions of in-vivo experimentation.

In oncology: for a carcinoma, "in situ" means that malignant cells are present as a tumor but has not metastasized, or invaded, beyond the original site where the tumor was discovered. This can happen anywhere in the body, such as the skin, breast tissue, or lung.

In conservation of genetic resources, "in-situ conservation" (also "on-site conservation") is the process of protecting an endangered plant or animal species in its natural habitat, as opposed to "ex-situ" conservation (also "off-site conservation").

Chemistry and chemical engineering

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.

In chemical engineering, in situ often refers to industrial plant "operations or procedures that are performed in place". For example, aged catalysts in industrial reactors may be regenerated in place (in situ) without being removed from the reactors.

Computer science

In computer science an "in situ" operation is one that occurs without interrupting the normal state of a system. For example, a file backup may be restored over a running system, without needing to take the system down to perform the restore. In the context of a database, a restore would allow the database system to continue to be available to users while a restore happened. An "in situ" upgrade would allow an operating system or application to be upgraded while the system was still running, perhaps without the need to reboot it, depending on the sophistication of the system.

An algorithm is said to be an in situ algorithm, or in-place algorithm, if the amount of memory required to execute the algorithm is O(1), that is, does not depend on the size of the input. For example, heapsort is an in situ sorting algorithm.

In designing user interfaces, the term "in situ" means that a particular user action can be performed without going to another window, for example, if a word processor displays an image and allows you to edit the image without launching a separate image editor, this is called "in situ editing."

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 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 Louvre Museum in Paris, France.

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" (see wh-movement): "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.

Petroleum production

In situ means "in place", and refers to recovery techniques which apply heat or solvents to heavy oil or bitumen reservoirs beneath the earth. There are several varieties of in situ technique, but the ones which work best in the oil sands use heat.

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".

ee also

*"carcinoma in situ"
*"ex vivo"
*"in silico"
*"in utero"
*"in vitro"
*"in vivo"
*In-situ conservation
*Ex-situ conservation
*List of Latin phrases

References