Cleanup date April 2008 Microsatellite genetics Microsatellites are repeated sequences of DNA. Although the length of these microsatellites is highly variable from person to person, each individual has microsatellites of a set length. These repeated sequences are common, and normal. The most common microsatellite in humans is a dinucleotide repeat of CA, which occurs tens of thousands of times across the genome. Image MicrosatelliteInstability in GeneMarker.jpg thumb 400px Example of MicrosatelliteInstability in a DNA Electropherogram Trace In cells with mutations in DNA repair genes, however, some of these sequences accumulate errors and become longer or shorter. The appearance of abnormally long or short microsatellites in an individual s DNA is referred to as microsatelliteinstability. Microsatelliteinstability MSI is a condition manifested by damaged DNA due to defects in the normal DNA repair process. ref MeshName MicrosatelliteInstability ref Sections of DNA called Microsatellite genetics microsatellite s, which consist of a DNA sequence sequence of repeating units of 1 6 base pair s in length, become unstable and can shorten or lengthen. Microsatellites are also known as simple sequence repeats SSRs . Clinical significance MSI is a key factor in several cancers including colorectal, endometrial, ovarian and gastric cancers. Colorectal cancer studies have demonstrated two mechanisms for MSI occurrence. The first is in hereditary nonpolyposis colorectal cancer HNPCC or Lynch Syndrome, where an inherited mutation in a mismatch repair gene causes a microsatellite repeat replication error to go unfixed. Most cases result in changes in the lengths of dinucleotide repeats of the nucleobase s cytosine and adenine sequence CACACACACA... . ref cite pmid 10321739 ref The replication ... mismatch repair gene. In both cases, microsatellite insertions and deletions within tumor suppressor ... or high probability of MSI MSI H . See also Adenomatous polyposis coli , or APC Chromosome instability ... more details
is an unstable situation. In numerous fields of study, the component of instability within a system ... stability . Atmospheric instability is a major component of all weather system s on Earth. Fluid ... instability ref Shengtai Li, Hui Li Parallel AMR Code for Compressible MHD or HD Equations Los Alamos ... Ballooning mode instability some analogy to the Rayleigh Taylor instability found in the magnetosphere Atmospheric instability Hydrodynamic instability or dynamic instability atmospheric dynamics Inertial instability baroclinic instability symmetric instability , conditional symmetric instability conditional symmetric or conditional symmetric instability convective symmetric instability barotropic instability Helmholtz instability Helmholtz or Helmholtz instability shearing instability rotational instability Hydrostatic instability or static instability static instability vertical instability static instability parcel instability , thermodynamic instability atmospheric thermodynamics Conditional instability Conditional or static instability , buoyant instability , latent instability , nonlocal static instability , conditional symmetric instability convective instability convective , convective instability potential , or convective instability thermal instability , convective instability of the first kind convective instability of the first and convective instability of the second kind second kind absolute instability absolute or absolute instability mechanical instability B nard cells B nard instability Drift mirror instability Kelvin Helmholtz instability similar, but different from the diocotron instability in plasmas Rayleigh Taylor instability Plateau Rayleigh instability similar to the Rayleigh Taylor instability Richtmyer Meshkov instability similar to the Rayleigh Taylor instability shock wave Shock Wave Instability clear Plasma instabilities Main Plasma stability ... is not smeared out by random motions. After the instability has run its course, the system is typically ... more details
Unreferenced date October 2006 Orphan date November 2009 The Instability is a science fiction short story by Isaac Asimov that was first published in the 1 January 1989 issue of The Observer and reprinted in the collection Gold Asimov Gold 1995 . Plot summary A professor tells his colleague he has made time travel possible. He also tells him that according to his calculations, there will be another star in the Sun s place in 27 million years. The professor makes a trip with his colleague through time to observe the dark star. After making some notes, they decide to return home. When they time travel back, the colleague notices that there is black space outside. The professor explains that time and space move, so their universe has moved in an upper dimensional level. This means they are in primeval Chaos cosmogony chaos . His colleague points out that since they are here this is not primeval chaos anymore. The professor states that his partner is right and that they have introduced an instability, but he never finishes the sentence. They are all wiped out by a Big Bang as a new universe is created. DEFAULTSORT Instability, The Category Short stories by Isaac Asimov Category 1989 short stories Category Works originally published in The Observer ... more details
18063. Hammock, E. A. D. and Young, L. J. 2005. Microsatelliteinstability generates diversity in brain ... disorders and cancer. Introduction One common example of a microsatellite is a CA sub n ... at a microsatellite locus, genotype s within Pedigree chart pedigree s are often fully informative ... year 1995 title An Evaluation of Genetic Distances for Use With Microsatellite Loci journal ... microsatellites have an increased or decreased density of SNPs depending on the microsatellite sequence ..., M.S., Parsons, M., Lacaille, V. & Lotz, S. year 1996 title Use of microsatellite loci to classify ... through the microsatellite. This process results in production of enough DNA to be visible on Agarose ... Freeman, New York ref With the abundance of PCR technology, primers that flank microsatellite loci are simple ... sequence repeat SSR, a.k.a. microsatellite locus. Samples have been run on a 5 polyacrylamide gel and visualized using silver staining. Creation of microsatellite primers If searching for microsatellite ... can be designed manually. This involves searching the genomic DNA sequence for microsatellite repeats ... oligonucleotide primers which will amplify the specific microsatellite repeat in a PCR reaction. Random microsatellite primers can be developed by cloning random segments of DNA from the focal species ... labelled oligonucleotide sequences that will hybridize to a microsatellite repeat, if present ... locus . This process involves significant trial and error on the part of researchers, as microsatellite ... and Evolution volume 11 pages 424 429 doi 10.1016 0169 5347 96 10049 5 ref Microsatellite loci are widely ... involve using oligonucleotide sequences consisting of repeats complementary to repeats in the microsatellite to enrich the DNA extracted Microsatellite enrichment . The oligonucleotide probe hybridizes with the repeat in the microsatellite, and the probe microsatellite complex is then pulled ... KJ, and Miller KM year 2004 title Enrichment of tetranucleotide microsatellite loci from invertebrate ... more details
Orphan date April 2012 Microsatellite enrichment is a method in molecular biology used for enriching the amount of Microsatellite genetics microsatellite sequences in a DNA sample. This can be achieved by designing oligonucleotide probes that hybridize with the repeats in the microsatellites and then pull out the probe microsatellite complexes from the solution. ref cite journal author Kaukinen KH, Supernault KJ, and Miller KM year 2004 title Enrichment of tetranucleotide microsatellite loci from invertebrate species journal Journal of Shellfish Research volume 23 issue 2 page 621 ref This has been shown to be a cost effective method to sample the genetic diversity in non model organisms. ref name pmid21676207 cite journal last Jennings first TN coauthors Knaus, BJ, Mullins, TD, Haig, SM, Cronn, RC title Multiplexed microsatellite recovery using massively parallel sequencing. journal Molecular ecology resources date 2011 06 16 pmid 21676207 ref References Reflist Category Molecular biology techniques ... more details
The ballooning instability , or ballooning mode , is a form of plasma instability seen in tokamak fusion power reactors. The name refers to the shape and action of the instability, which acts like the elongations formed in a balloon when it is squeezed. Category Plasma physics Category Stability theory phys stub ... more details
A diocotron instability is a Plasma physics plasma instability created by two sheets of charge slipping past each other. Energy is dissipated in the form of two surface waves propagating in opposite directions, with one flowing over the other. This instability is the plasma analog of the Kelvin Helmholtz instability in fluid mechanics . References cite journal doi 10.1063 1.1708223 title Diocotron Instability in Plasmas and Gas Discharges month February year 1966 author Knauer, W. journal Journal of Applied Physics volume 37 issue 2 pages 602 611 bibcode 1966JAP....37..602K Category Plasma physics physics stub ... more details
File Crow instability contrail 1 9 08.JPG The Crow instability is responsible for the shape of this contrail thumb 200px File Contrail with crow instability.jpg The Crow instability is also responsible for this different shape of contrail thumb 200px In aerodynamics , the Crow Instability is an Inviscid flow inviscid line vortex instability, named after its discoverer S. C. Crow. The Crow instability is most commonly observed in the skies behind large aircraft, when the wingtip vortices interact with contrail s from the engines, producing visible distortions in the shape of the contrail. Instability development The Crow Instability is a vortex pair instability, and typically goes through several stages A pair of counter rotating vortices act upon each other to amplify small sinusoidal distortions in their vortex shapes Normally created by some initial disturbance in the system . The waves develop into either symmetric or anti symmetric modes, depending on the nature of the initial disturbance. These distortions grow, both through interaction from one vortex on another, and also Self Induction of a vortex with itself. This leads to an exponential growth in the vortex wave amplitude. The vortex amplitudes reach a critical value and reconnect, forming a chain of vortex ring s. References Crow, S. C., Stability theory for a pair of trailing vortices , AIAA J., 8 , 2172 2179 1970 . Philip Saffman Saffman, P. G. , Vortex Dynamics , Cambridge Uni. Press, New York 1992 . External links http www.scientificamerican.com article.cfm?id why do jets leave a white Scientific American The Crow Instability http www.extrospection.com archives 2004 01 the crow instability.html Photos The Crow Instability Category Basic meteorological concepts and phenomena climate stub ... more details
The Weibel instability is a plasma instability present in homogeneous or nearly homogeneous electromagnetic Plasma physics plasmas which possess an anisotropy in momentum velocity space. This anisotropy is most generally understood as two temperatures in different directions. Burton Fried showed that this instability can be understood more simply as the superposition of many counter streaming beams. In this sense, it is like the two stream instability except that the perturbations are electromagnetic and result in filamentation as opposed to electrostatic perturbations which would result in charge bunching. In the linear limit the instability causes exponential growth of electromagnetic fields in the plasma which help restore momentum space isotropy. In other words, when this effect is pronounced, it creates electrostatic waves which fight the electrons from all moving in one direction. In very extreme cases, the Weibel instability is related to one or two dimensional Two stream instability stream instabilities . Consider an electron ion plasma in which the ions are fixed and the electrons are hotter in the y direction than in x or z direction. To see how magnetic field perturbation would grow, suppose a field B Bzz cos kx spontaneously arises from noise. The Lorentz force then bends the electron trajectories with the result that upward moving ev x B electrons congregate at B and downward moving ones at A. The resulting current j eni ve sheets generate magnetic field that enhances the original field and thus perturbation grows. References E.S. Weibel, Phys. Rev. Lett. 2, 83 1959 http prola.aps.org abstract PRL v2 i3 p83 1 B.D. Fried, Phys. Fluids 2, 337 1959 See also Chromo Weibel instability Chromo Weibel Instability DEFAULTSORT Weibel Instability Category Plasma physics Category Particle physics physics stub ... more details
Expert subject Physics date November 2008 File Kink instability at Aldermaston.jpg thumb right One of the earliest photos of the kink instability in action the 3 by 25 cm pyrex tube at Aldermaston. A kink instability , also oscillation or mode , is a class of magnetohydrodynamic instabilities which sometimes develop in a thin Plasma physics plasma column carrying a strong axial current. If a kink begins to develop in a column the magnetic force s on the inside of the kink become larger than those on the outside, which leads to growth of the perturbation. ref http plasmadictionary.llnl.gov terms.lasso? MaxRecords 1& SkipRecords 1& SortField Term& SortOrder ascending&ABC K&page detail Plasma Dictionary ref As it develops at fixed areas in the plasma, kinks belong to the class of absolute plasma instabilities , as opposed to convective processes. The kink instability was first widely explored in the Z pinch fusion power machines in the 1950s. References reflist physics stub Category Plasma physics ... more details
polyploidy to aneuploidy, genome instability and cancer year 2004 journal Nat Rev Mol Cell Biol ... The role of chromosomal instability in tumor initiation. year 2002 journal Proc. Natl Acad. Sci ... Genetic instability can originate due to individual mutations on a specific gene, or due to loss ... that can be selected by the environment. ref Citation title Genetic instability and darwinian ... more details
The Instability index is a measure of protein s, used to determine whether it will be stable in a test tube . If the index is less than 40, then it is probably stable in the test tube. If it is greater for example, enaptin then it is probably not stable. References cite journal author Guruprasad K, Reddy BV, Pandit MW title Correlation between stability of a protein and its dipeptide composition a novel approach for predicting in vivo stability of a protein from its primary sequence journal Protein Eng. volume 4 issue 2 pages 155 61 year 1990 pmid 2075190 doi 10.1093 protein 4.2.155 The instability index is also used to calculate risk in agriculture. External links http www.expasy.org tools protparam doc.html Expasy.org part of UniProt Category Proteomics protein stub chem stub ... more details
about the bending instability in galaxies the firehose instability in magnetized plasmas Instability Image FirehoseNbody.png thumb right 300px Fig. 1. The firehose instability in an N body simulation of a prolate ..., the long to short axis ratio of the galaxy is 10 1. After the instability has run its course, the axis ... spiral galaxy bars observed in many spiral galaxy spiral galaxies . The firehose instability or hose pipe instability is a dynamical instability of thin or elongated galaxies . The instability causes the galaxy to buckle or bend in a direction perpendicular to its long axis. After the instability ... streaming motions as opposed to rotation , is subject to the instability. The firehose instability ... ratios more extreme than about 3 1, since this is roughly the axis ratio at which the instability ... James first3 R. A. last4 Kahn first4 F. A. title A dynamical instability of bars in disk galaxies .....411R issue 6334 ref The firehose instability derives its name from a similar instability in magnetized ... title Dynamical Instability in an Anisotropic Ionized Gas of Low Density journal The Physical Review ... ref However, from a dynamical point of view, a better analogy is with the Kelvin Helmholtz instability ... Instability year 1966 pages 111&ndash 114 ref or with beads sliding along an oscillating string. ref In spite of its name, the firehose instability is not related dynamically to the oscillatory ... instability can be analyzed exactly in the case of an infinitely thin, self gravitating sheet of stars ... instability is precisely complementary, in this sense, to the Jeans instability in the plane ... Kulsrud first1 R. M. last2 Mark first2 J. W. K. last3 Caruso first3 A. title The Hose Pipe Instability .... Importance The firehose instability is believed to play an important role in determining the structure ... ratio of about math math 3 1. The firehose instability is probably responsible for this fact, since ... have elongations greater than about 3 1. This is probably also a consequence of the firehose instability ... more details
Refimprove date November 2009 Image HR diag instability strip.svg right 350px The Instability strip is a nearly vertical region in the Hertzsprung Russell diagram which is occupied by pulsating variable stars including RR Lyrae variable , Cepheid variable , W Virginis variable , ZZ Ceti variable , RV Tauri variable , Delta Scuti variable , SX Phoenicis variable and rapidly oscillating Ap stars . ref cite web first last title Cepheid instability strip work A Dictionary of Astronomy url http www.encyclopedia.com doc 1O80 Cepheidinstabilitystrip.html publisher encyclopedia.com accessdate 2010 03 28 ref The instability strip intersects the main sequence in the region of A and F stars 1 2 Sun solar mass and extends upwards almost vertically slightly inclined to the right to the highest luminosity luminosities . The lower part of instability strip appears as the Hertzsprung gap on the Hertzsprung Russell diagram. Pulsations Stars in the instability strip pulsate due to Helium He III doubly Ionization ionized helium . In normal A F G stars He is neutral in the stellar photosphere . Deeper below the photosphere, at about 25,000 30,000K, begins the He II layer first He ionization . Second ionization He III starts at about 35,000 50,000K. When the star contracts, the density and temperature of the He II layer increase. He II starts to transform to He III second ionization . Opacity optics Opacity increases and the energy flux from the interior of the star is effectively absorbed. The temperature of the layer increases and it starts to expand. After expansion, density and temperature decrease and He III begins to recombine into He II. The outer layers contract and the cycle starts from the beginning. The phase shift between a star s radial velocity pulsations and Apparent magnitude brightness variability depends on the distance of He II zone from the stellar surface in the stellar atmosphere . References Reflist 2 Star DEFAULTSORT Instability Strip Category Hertzsprung Russell ... more details
In the field of nonlinear optics , modulational instability is a phenomenon whereby deviations from an optical waveform are reinforced by nonlinearity, leading to the generation of Frequency spectrum spectral sidebands and the eventual breakup of the waveform into a train of pulses. ref name agrawal cite book last Agrawal first Govind P. year 1995 title Nonlinear fiber optics place San Diego California publisher Academic Press edition 2nd isbn 0 12 045142 5 ref Initial instability and gain Modulation instability only happens under certain circumstances. The most important condition is anomalous group velocity dispersion , whereby pulses with shorter wavelengths travel with higher group velocity than pulses with longer wavelength. ref name agrawal This condition assumes a focussing Kerr nonlinearity , whereby refractive index increases with optical intensity. There is also a threshold power, below which no instability will be seen. ref name agrawal The instability is strongly dependent on the frequency of the perturbation. At certain frequencies, a perturbation will have little effect, whilst at other frequencies, a perturbation will exponential growth grow exponentially . The overall gain spectrum can be derived Analytical expression analytically , as is shown below. Random perturbations will generally contain a broad range of frequency components, and so will cause the generation ... to grow makes modulation instability a form of amplifier amplification . By tuning an input signal ... of modulation instability based upon the Nonlinear Schr dinger equation math frac partial A partial ... index , and the modified refractive index, as raised by the Kerr effect. The beginning of instability ... epsilon 2 approx 0 math . Instability can now be discovered by searching for solutions of the perturbation ... , corresponding to exponential growth and thus instability. Therefore, instability will occur ... references DEFAULTSORT Modulational Instability Category Nonlinear optics Category Photonics ... more details
Use dmy dates date September 2011 NOTOC The electrothermal instability also known as the ionization instability or Velikhov instability in the literature is a magnetohydrodynamics magnetohydrodynamic MHD instability appearing in Plasma physics Magnetization magnetized Plasma physics Temperatures non ... author E.P. Velikhov year 1962 title Hall instability of current carrying slightly ionized plasmas conference ... July 1963 title Plasma turbulence due to the ionization instability in a strong magnetic field conference ... year 1965 title Ionization instability of a plasma with hot electrons conference 7th International ... and characteristics Image electrothermal instability evolution.gif thumb 490px Evolution of the electrothermal instability in a Faraday MHD converter. Electric current lines. This instability is a turbulence ... instability is a kind of ionization wave system, almost frozen in the two temperature gas ..., some oblique grooves appear in the plasma, typical of the electrothermal instability. The electrothermal instability occurs extremely quickly, in a few microseconds. The plasma becomes non homogeneous ... is the strongest. Critical Hall parameter The electrothermal instability occurs in a plasma at a T sub ... volt s and k the Boltzmann constant . The growth rate of the instability is math g frac sigma ... But the unexpected large and quick drop of current density due to the electrothermal instability ruined ... energy conversion efficiencies over 60 with these devices. Whereas some studies were made about the instability ... studies about the growth rate of the electrothermal instability and the critical conditions showed ... coauthors J. Valensi date 1 September 1969 title Growth rate of electrothermal instability and critical ... to overtake the growth rate of the electrothermal instability where the Hall parameter decreases ... Instability in an MHD Generator journal Journal of the Physical Society of Japan volume 36 issue .... Another idea to control the instability would be to increase non thermal ionisation rate thanks ... more details
Geographical imbalance date May 2011 The Arc of Instability is a proposed, interconnected chain of politically unstable nation states in the Asia Pacific region. The term came into vogue in the late 1990s, proving especially popular with Australian politicians and journalists. The Arc is also sometimes to referred to as Balkanization balkanisation in a modern, Asia Pacific context. ref cite book last Moore first Clive authorlink Clive Moore title Happy Isles in Crisis publisher Asia Pacific Press date 2004 location Canberra pages 9 ref Definition and member states The term is used to suggest that the members of the Arc are interconnected to the point that destabilisation within one country can have major political, military and economic repercussions in neighbouring countries. For example, Australian media and politicians claimed the History of the Solomon Islands Civil war destabilisation of the Solomon Islands was the result of a copycat or domino effect of the 2000 Fijian coup d tat . In August 2006 Minister for Defence Australia Australian Defence Minister Brendan Nelson gave a speech to parliament on the topic of the Arc. Along with dropping Indonesia from the list of states in the Arc, he said blockquote We cannot afford to have failing states in our region. The so called arc of instability , which basically goes from East Timor through to the south west Pacific states, means that not only does Australia have a responsibility in preventing and indeed assisting with humanitarian and disaster relief, but also that we cannot allow any of these countries to become havens for transnational crime, nor indeed havens for terrorism. ref cite news last Dobell first Graeme title The Pacific arc of instability publisher Correspondent s Report date 2006 08 20 url http www.abc.net.au ... to the region s instability Fijian 2000 Fijian coup d tat coup d tat East Timor History ... DEFAULTSORT Arc Of Instability Category Melanesia Category Politics of Southeast Asia Category ... more details
The magnetorotational instability or MRI is a fluid instability that arises when the angular velocity of a magnetized fluid decreases as the distance from the rotation center increases. It can also be known as the Velikhov Chandrasekhar instability or Balbus Hawley instability in the literature not to be confused with the Velikhov instability which is the electrothermal instability . The MRI is of particular relevance in astrophysics where it is an important part of the dynamics in accretion disc s. Balbus and Hawley were the first to realize the astrophysical importance of this instability and explain its physical mechanism. Their original discovery paper now has over 1,600 citations. A rotating hydrodynamic fluid disc e.g. a nonmagnetic accretion disc will remain in a laminar flow state as long as the angular momentum per unit mass increases outwards. This is also known as the Rayleigh stability criterion math frac partial r 2 Omega partial r 0 math where math Omega math is the angular velocity of a fluid element and math r math is its distance to the rotation center. Instabilities leading ultimately to turbulence occur if a magnetic field is present and the angular velocity decreases with radius math frac partial Omega partial r 0 math Most accretion discs will meet this criterion. The MRI was first noticed in a non astrophysical context by Evgeny Velikhov in 1959 when considering the stability of Couette flow of an ideal magnetohydrodynamics hydromagnetic fluid. ref name V1959 ... shear instability in weakly magnetized disks. I Linear analysis. II Nonlinear evolution periodical Astrophysical ... A simple model illustrates the main effect of the instability. Consider a rotating fluid disc in the presence ... Dynamo action is usually invoked to justify the existence of the magnetic field required for the instability ... Observation and Characterization of the Magnetorotational Instability periodical Physical ... Evidence for Magnetorotational Instability in a Taylor Couette Flow under the Influence ... more details
displaced air per vertical distance. Instability results from difference between the adiabatic ... and resists vertical movement, which leads to good and generally clear weather. The greatest instability ..., thunderstorms appear on a daily basis in these regions due to the instability of the surrounding ... links http amsglossary.allenpress.com glossary search?id conditional instability of the 1 Meteorological ... more details
File Iraqi Dust Devil.jpg thumb right A dust devil in Ramadi , Iraq . Atmospheric instability is a condition where the Earth s atmosphere is generally considered to be unstable and as a result the weather is subject to a high degree of variability through distance and time ref http www.ace.mmu.ac.uk ... dense and is prone to further ascent. In meteorology , instability can be described by various ... instability itself, involves temperature changes through the troposphere with height, or lapse rate . Effects of atmospheric instability in moist atmospheres include thunderstorm development ... instability ref http www.piercecollege.edu offices weather stability.html Explanation of Atmospheric Stability Instability by Steve W. Woodruff ref Convective instability Dynamic instability fluid mechanics Under convective instability thermal mixing through Atmospheric convection convection ... meteorology precipitation or convective storms . Dynamic instability is produced through the horizontal ... scale meteorology synoptic scale . Cause of instability See also Lapse rate Whether or not the atmosphere ... changes indicate instability. This lapse rate is known as the dry adiabatic lapse rate. ref cite book ... indicate instability. In the range between 6C and 9.8C temperature decreases per kilometer ascent ... and is an indicator of atmospheric instability, which makes it valuable in predicting severe weather. It is a form of fluid instability found in thermally stratified atmospheres in which a colder ... unstable and or weakly sheared natural environment environment s low values indicate weak instability ... instability book&source bl&ots HSZR9 W4Zj&sig xqERYV7ABopr2OpPOONcz fXD0o&hl en&sa X&ei fq5JT ... ref When winds are light, dust devils can develop on dry days within a region of instability at ground ... surface heat source, which would have significant instability in its vicinity. Those that occur near ... DEFAULTSORT Atmospheric Instability Category Atmospheric dynamics Category Atmospheric thermodynamics ... more details
Orphan date February 2009 Context date October 2009 The Ledinegg instability occurs in two phase flow , especially in a boiler boiler tube , when the boiling boundary is within the tube. For a given mass flux J though the tube, the pressure drop per unit length which typically varies as the square of the mass flux and inversely as the density ie as math J 2 rho math ,is much less when the flow is wholly of liquid, than when the flow is wholly of steam. Thus, as the boiling boundary moves up the tube, the total pressure drop falls, potentially increasing the flow in an unstable manner. Boiler tubes normally overcome this which is effectively a negative resistance regime by incorporating a narrow orifice at the entry, to give a stabilising pressure drop on entry. References http caltechbook.library.caltech.edu 51 01 chap15.pdf System Instabilities http caltechbook.library.caltech.edu 51 01 chap15.pdf http authors.library.caltech.edu 25021 1 chap15.pdf http authors.library.caltech.edu 25021 1 chap15.pdf Category Fluid dynamics physics stub ... more details
Image elastic instability.png thumb Elastic instability of a rigid beam supported by an angular spring. Deleted image removed Image elastic instability curve.png thumb Deformation paths of a rigid beam supported by an angular spring. Elastic instability is a form of instability occurring in elastic systems, such as buckling of beams and plates subject to large compressive loads. Single degree of freedom systems Consider as a simple example a rigid beam of length L , hinged in one end and free in the other, and having an Spring device angular spring attached to the hinged end. The beam is loaded in the free end by a force F acting in the compressive axial direction of the beam, see the figure to the right. Moment equilibrium condition Assuming a clockwise angular deflection math theta math , the clockwise Moment physics moment exerted by the force becomes math M F F L sin theta math . The moment Mechanical equilibrium equilibrium equation is given by math F L sin theta k theta theta math where math k theta math is the spring constant of the angular spring Nm radian . Assuming math theta math is small enough, implementing the taylor expansion of the sine function and keeping the two first terms yields math F L Bigg theta frac 1 6 theta 3 Bigg approx k theta theta math which has three solutions, the trivial math theta 0 math , and math theta approx pm sqrt 6 Bigg 1 frac k theta F L Bigg math which is complex number imaginary i.e. not physical for math F L k theta math and complex number real otherwise. This implies that for small compressive forces, the only equilibrium state is given by math theta 0 math , while if the force exceeds the value math k theta L math there is suddenly another mode of deformation possible. Energy method The same result can be obtained by considering .... Hence, these solutions are stable. Multiple degrees of freedom systems Image Elastic instability 2DOF.png thumb Elastic instability, 2 degrees of freedom By attaching another rigid beam to the original ... more details
Mergefrom Jeans length date May 2009 Star formation In physics, the Jeans instability causes the collapse of interstellar gas clouds and subsequent star formation. It occurs when the internal gas pressure is not strong enough to prevent gravitational collapse of a region filled with matter. For stability, the cloud must be in hydrostatic equilibrium, which in case of a spherical cloud translates to math frac dp dr frac G rho r M enc r r 2 math , where math M enc r math is the enclosed mass, math p math is the pressure, math rho r math is the density of the gas at math r math , math G math is the gravitational constant and math r math is the radius. The equilibrium is stable if small perturbations are damped and unstable if they are amplified. In general, the cloud is unstable if it is either very massive at a given temperature or very cool at a given mass for gravity to overcome the gas pressure. Jeans mass The Jeans mass is named after the Great Britain British physics physicist Sir James Hopwood Jeans James Jeans , who considered the process of gravitational collapse within a gaseous cloud. He was able to show that, under appropriate conditions, a cloud, or part of one, would become unstable and begin to collapse when it lacked sufficient gaseous pressure support to balance the force of gravity . Remarkably, the cloud is stable for sufficiently small mass at a given temperature and radius , but once this critical mass is exceeded, it will begin a process of runaway contraction until some other force can impede the collapse. He derived a formula for calculating this critical ... region will in fact also be collapsing. As a result, the growth rate of the gravitational instability ... corrects for this effect. The Jeans instability likely determines when star formation occurs in molecular ... mass density. It is also the distance a sound wave would travel in the Jeans Instability collapse time . Fragmentation Jeans instability can also give rise to fragmentation in certain conditions. To derive ... more details
Chromosome instability syndromes are a group of inherited conditions associated with chromosomal instability and breakage. They often lead to an increased tendency to develop certain types of malignancies. ref cite journal author Taylor AM title Chromosome instability syndromes journal Best Pract Res Clin Haematol year 2001 pages 631 44 volume 14 issue 3 pmid 11640873 doi 10.1053 beha.2001.0158 ref The following chromosome instability syndromes are known Ataxia telangiectasia Ataxia telangiectasia like disorder Bloom syndrome Fanconi anaemia Nijmegen breakage syndrome References reflist DNA replication and repair deficiency disorder Category Chromosome instability syndromes pl Zespo y niestabilno ci chromosomalnych ... more details
Encyclopedia
top
