# Random positioning machine
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{{Infobox laboratory equipment
|name = Random Positioning Machine
|image = File:Random Positioning Machine.png
|alt =
|other_names = 3D clinostat
|uses = The RPM rotates biological samples around two independent axes to eliminate the effect of gravity.
|related = [clinostat](/source/clinostat), [free fall machine](/source/free_fall_machine)
}}
A '''random positioning machine''' ('''RPM''') is a mechanism that rotates biological samples along two independent axes to change their orientation in space in complex ways in order to eliminate the effect of [gravity](/source/gravity).[Jack J.W.A. van Loon (2007). Some history and use of the random positioning machine, RPM, in gravity related research. Advances in Space Research 39: 1161-1165] RPMs are often used as an alternative to [sub-orbital flights](/source/Sub-orbital_spaceflight) or [drop towers](/source/Drop_tube) in research studying the effects of [weightlessness](/source/weightlessness) or microgravity on biological systems.[{{Cite journal |last1=Wuest |first1=Simon L. |last2=Richard |first2=Stéphane |last3=Kopp |first3=Sascha |last4=Grimm |first4=Daniela |last5=Egli |first5=Marcel |date=2015 |title=Simulated Microgravity: Critical Review on the Use of Random Positioning Machines for Mammalian Cell Culture |journal=BioMed Research International |language=en |volume=2015 |pages=1–8 |doi=10.1155/2015/971474 |issn=2314-6133 |pmc=4310317 |pmid=25649075 |doi-access=free}}]
==Description==
The RPM is a more sophisticated development of the single-axis [clinostat](/source/clinostat). RPMs usually consist of two independently rotating frames. One frame is positioned inside the other giving a very complex net change of orientation to a biological sample mounted in the middle. The RPM is sometimes wrongly referred to as the "3-D clinostat" (which rotates both axes in the same direction, i.e. both clockwise). It is a microweight ('[micro-gravity](/source/Micro-g_environment)') simulator that is based on the principle of 'gravity-vector-averaging'. RPM provides a functional volume which is 'exposed' to simulated microweight.[A. G. Borst, J.J.W. A. van Loon. Technology and Developments for the Random Positioning Machine, RPM. Microgravity Sci. Technol., 2008. DOI 10.1007/s12217-008-9043-2]
== Simulated micro-, partial, and hyper gravity ==
The concept of 'random' positioning has been used to simulate a micro-gravity environment through the nullification of gravity. This is accomplished by disorientating the target model, or as "vector-averaging". Through the use of a centrifuge, a '[hyper-gravity](/source/Hypergravity)' gravity can be simulated, as the model will get exposed to a continued accelerated force.[{{Cite journal|last1=van Loon|first1=Jack J. W. A.|last2=Krausse|first2=Jutta|last3=Cunha|first3=Humberto|last4=Goncalves|first4=Joao|last5=Almeida|first5=Hugo|last6=Schiller|first6=Peter|date=June 2008|title=The Large Diameter Centrifuge, LDC, for Life and Physical Sciences and Technology|url=https://ui.adsabs.harvard.edu/abs/2008ESASP.663E..92V/abstract|journal=Life in Space for Life on Earth|language=en|volume=553|page=92|bibcode=2008ESASP.663E..92V|issn=1609-042X}}] In the circumstances of hyper-gravity within a micro-gravity environment, a partial 'Earth' gravity is created. Hyper-gravity simulation is also achieved through the use of larger centrifuges, such as the [Large diameter Centrifuge (LDC)](/source/ESTEC_Large_Diameter_Centrifuge) at the [European Space Agency](/source/European_Space_Agency). The LDC is able to simulate up to twenty times the Earth's gravitational strength. A system developed by Airbus uses an algorithm to simulate partial-gravity through a not fully randomly vector-averaging. The vector-averaging by Airbus' algorithm doesn't average out the vector to null but to a percentage representing simulated partial-gravity.[{{Cite journal|last1=Manzano|first1=Aránzazu|last2=Herranz|first2=Raúl|last3=den Toom|first3=Leonardus A.|last4=te Slaa|first4=Sjoerd|last5=Borst|first5=Guus|last6=Visser|first6=Martijn|last7=Medina|first7=F. Javier|last8=van Loon|first8=Jack J. W. A.|date=2018-04-04|title=Novel, Moon and Mars, partial gravity simulation paradigms and their effects on the balance between cell growth and cell proliferation during early plant development|journal=npj Microgravity|volume=4|page=9|doi=10.1038/s41526-018-0041-4|issn=2373-8065|pmc=5884789|pmid=29644337}}]
== Disadvantages ==
The simulated microgravity environment attained inside the RPM is not perfect. A secondary effect part of this is the shear forces created by the [fluid dynamics](/source/fluid_dynamics) of the [cell culture](/source/cell_culture) medium. They have been mathematically modeled by Wüest,[{{cite journal |last1=Wuest |first1=Simon L. |last2=Stern |first2=Philip |last3=Casartelli |first3=Ernesto |last4=Egli |first4=Marcel |title=Fluid Dynamics Appearing during Simulated Microgravity Using Random Positioning Machines |journal=PLOS ONE |date=30 January 2017 |volume=12 |issue=1 |article-number=e0170826 |doi=10.1371/journal.pone.0170826 |doi-access=free |pmid=28135286 |pmc=5279744 |bibcode=2017PLoSO..1270826W |language=en |issn=1932-6203}}] and according to the research by Hauslage,[{{cite journal |last1=Hauslage |first1=Jens |last2=Cevik |first2=Volkan |last3=Hemmersbach |first3=Ruth |title=Pyrocystis noctiluca represents an excellent bioassay for shear forces induced in ground-based microgravity simulators (clinostat and random positioning machine) |journal=npj Microgravity |date=24 April 2017 |volume=3 |issue=1 |pages=1–7 |doi=10.1038/s41526-017-0016-x |url=https://www.nature.com/articles/s41526-017-0016-x |language=en |issn=2373-8065|pmc=5460110 }}] they are of a magnitude enough to have biological implications. Also, Cortés-Sánchez showed these effects in mammalian cells cultured in the RPM.[{{cite journal |last1=Cortés-Sánchez |first1=José Luis |last2=Melnik |first2=Daniela |last3=Sandt |first3=Viviann |last4=Kahlert |first4=Stefan |last5=Marchal |first5=Shannon |last6=Johnson |first6=Ian R. D. |last7=Calvaruso |first7=Marco |last8=Liemersdorf |first8=Christian |last9=Wuest |first9=Simon L. |last10=Grimm |first10=Daniela |last11=Krüger |first11=Marcus |title=Fluid and Bubble Flow Detach Adherent Cancer Cells to Form Spheroids on a Random Positioning Machine |journal=Cells |date=January 2023 |volume=12 |issue=22 |page=2665 |doi=10.3390/cells12222665 |doi-access=free |pmid=37998400 |pmc=10670461 |language=en |issn=2073-4409}}]
==See also==
* [Drop tube](/source/Drop_tube)
* [Gravitropism](/source/Gravitropism)
* [Sub-orbital spaceflight](/source/Sub-orbital_spaceflight)
* [Weightlessness](/source/Weightlessness)
== References ==
==External links==
* ETH Space Biology [https://web.archive.org/web/20110610184940/http://www.spacebiol.ethz.ch/infra/equip_1 ''Random Positioning Machine'']
* DESC VU Amsterdam [http://www.descsite.nl/RPM_Frames.htm ''Standard and desktop Random Positioning Machines'']
*Manufacturer's Website: [https://yurigravity.com/ yuri GmbH]
Category:Laboratory equipment
Category:Gravitational instruments
Category:Positioning instruments
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Adapted from the Wikipedia article [Random positioning machine](https://en.wikipedia.org/wiki/Random_positioning_machine) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Random_positioning_machine?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.