WorldWideScience

Sample records for bump-in-tail instability

  1. Shoulder Instability

    Science.gov (United States)

    ... Causes & Risk FactorsIs shoulder instability the same as shoulder dislocation?No. The signs of dislocation and instability might ... the same to you–weakness and pain. However, dislocation occurs when your shoulder goes completely out of place. The shoulder ligaments ...

  2. Shoulder instability

    African Journals Online (AJOL)

    2011-09-02

    Sep 2, 2011 ... Honorary Consultant, Shoulder and Elbow Unit, Department of Orthopaedic Surgery, University of Cape Town. Basil Vrettos is a shoulder ... Head, Shoulder and Elbow Unit, Princess Alice Orthopaedic Unit, Groote Schuur Hospital. Steve Roche heads ..... tidirectional instability is physiotherapy. • Surgery for ...

  3. Electron heat flux instability

    Science.gov (United States)

    Saeed, Sundas; Sarfraz, M.; Yoon, P. H.; Lazar, M.; Qureshi, M. N. S.

    2017-02-01

    The heat flux instability is an electromagnetic mode excited by a relative drift between the protons and two-component core-halo electrons. The most prominent application may be in association with the solar wind where drifting electron velocity distributions are observed. The heat flux instability is somewhat analogous to the electrostatic Buneman or ion-acoustic instability driven by the net drift between the protons and bulk electrons, except that the heat flux instability operates in magnetized plasmas and possesses transverse electromagnetic polarization. The heat flux instability is also distinct from the electrostatic counterpart in that it requires two electron species with relative drifts with each other. In the literature, the heat flux instability is often called the 'whistler' heat flux instability, but it is actually polarized in the opposite sense to the whistler wave. This paper elucidates all of these fundamental plasma physical properties associated with the heat flux instability starting from a simple model, and gradually building up more complexity towards a solar wind-like distribution functions. It is found that the essential properties of the instability are already present in the cold counter-streaming electron model, and that the instability is absent if the protons are ignored. These instability characteristics are highly reminiscent of the electron firehose instability driven by excessive parallel temperature anisotropy, propagating in parallel direction with respect to the ambient magnetic field, except that the free energy source for the heat flux instability resides in the effective parallel pressure provided by the counter-streaming electrons.

  4. Evaluating shoulder instability treatment

    NARCIS (Netherlands)

    van der Linde, J.A.

    2016-01-01

    Shoulder instability common occurs. When treated nonoperatively, the resulting societal costs based on health care utilization and productivity losses are significant. Shoulder function can be evaluated using patient reported outcome measurements (PROMs). For shoulder instability, these include the

  5. Shoulder instability; Schulterinstabilitaeten

    Energy Technology Data Exchange (ETDEWEB)

    Kreitner, Karl-Friedrich [Mainiz Univ. (Germany). Klinik und Poliklinik fuer Diagnostische und Interventionelle Radiologie

    2014-06-15

    In the shoulder, the advantages of range of motion are traded for the disadvantages of vulnerability to injury and the development of instability. Shoulder instability and the lesion it produces represent one of the main causes of shoulder discomfort and pain. Shoulder instability is defined as a symptomatic abnormal motion of the humeral head relative to the glenoid during active shoulder motion. Glenohumeral instabilities are classified according to their causative factors as the pathogenesis of instability plays an important role with respect to treatment options: instabilities are classified in traumatic and atraumatic instabilities as part of a multidirectional instability syndrome, and in microtraumatic instabilities. Plain radiographs ('trauma series') are performed to document shoulder dislocation and its successful reposition. Direct MR arthrography is the most important imaging modality for delineation the different injury patterns on the labral-ligamentous complex and bony structures. Monocontrast CT-arthrography with use of multidetector CT scanners may be an alternative imaging modality, however, regarding the younger patient age, MR imaging should be preferred in the diagnostic work-up of shoulder instabilities. (orig.)

  6. Elbow joint instability

    DEFF Research Database (Denmark)

    Olsen, Bo Sanderhoff; Henriksen, M G; Søjbjerg, Jens Ole

    1994-01-01

    The effect of simultaneous ulnar and radial collateral ligament division on the kinematics of the elbow joint is studied in a cadaveric model. Severance of the anterior part of the ulnar collateral ligament and the annular ligament led to significant elbow joint instability in valgus and varus...... of the specimens was recorded. The reproducibility of the instability pattern suggests that this model is suitable for evaluating stabilizing procedures aimed at correction of elbow joint instability before these procedures are introduced into patient care....

  7. Lecture on beam instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Chao, A.

    1999-12-21

    These lectures treat some of the common collective beam instability effects encountered in accelerators. In choosing the material for these lectures, it is attempted to introduce this subject with a more practical approach, instead of a more theoretical approach starting with first principles. After introducing the terminologies, emphasis will be placed on how to apply the lecture material to perform calculations and to make estimates of various instability effects. In the first half of the lectures, after briefly introducing the concepts of impedance and wake field, the authors will discuss a selected list of formulas for the impedances of various accelerator components. Detailed derivations are omitted, allowing time for the students to think through the process of how to apply the knowledge learned. The list of impedances to be covered include: space charge, resistive wall, resonator, wall roughness, and small perturbation on the vacuum chamber wall. Assuming impedances are known, the second half of the lectures addresses the question of how to calculate the power of beam heating, the growth rates, and the thresholds for a list of selected beam instability effects. Again with minimal detailed derivations, the aim is to introduce a collection of formulas, and apply them to linear as well as circular accelerators. The list of beam instability effects to be covered include: loss factor, beam break-up, BNS damping, bunch lengthening, resistive wall instability, head-tail instability, longitudinal head-tail instability, Landau damping, microwave instability, and mode coupling instability.

  8. Imaging of shoulder instability

    Science.gov (United States)

    Martínez Martínez, Alberto; Tomás Muñoz, Pablo; Pozo Sánchez, José; Zarza Pérez, Antonio

    2017-01-01

    This extended review tries to cover the imaging findings of the wide range of shoulder injuries secondary to shoulder joint instability. Usefulness of the different imaging methods is stressed, including radiography, computed tomography (CT) and magnetic resonance. The main topics to be covered include traumatic, atraumatic and minor instability syndromes. Radiography may show bone abnormalities associated to instability, including developmental and post-traumatic changes. CT is the best technique depicting and quantifying skeletal changes. MR-arthrography is the main tool in diagnosing the shoulder instability injuries. PMID:28932699

  9. Neutrino beam plasma instability

    Indian Academy of Sciences (India)

    We derive relativistic fluid set of equations for neutrinos and electrons from relativistic Vlasov equations with Fermi weak interaction force. Using these fluid equations, we obtain a dispersion relation describing neutrino beam plasma instability, which is little different from normal dispersion relation of streaming instability.

  10. Posterior Shoulder Instability.

    Science.gov (United States)

    Antosh, Ivan J; Tokish, John M; Owens, Brett D

    Posterior shoulder instability has become more frequently recognized and treated as a unique subset of shoulder instability, especially in the military. Posterior shoulder pathology may be more difficult to accurately diagnose than its anterior counterpart, and commonly, patients present with complaints of pain rather than instability. "Posterior instability" may encompass both dislocation and subluxation, and the most common presentation is recurrent posterior subluxation. Arthroscopic and open treatment techniques have improved as understanding of posterior shoulder instability has evolved. Electronic databases including PubMed and MEDLINE were queried for articles relating to posterior shoulder instability. Clinical review. Level 4. In low-demand patients, nonoperative treatment of posterior shoulder instability should be considered a first line of treatment and is typically successful. Conservative treatment, however, is commonly unsuccessful in active patients, such as military members. Those patients with persistent shoulder pain, instability, or functional limitations after a trial of conservative treatment may be considered surgical candidates. Arthroscopic posterior shoulder stabilization has demonstrated excellent clinical outcomes, high patient satisfaction, and low complication rates. Advanced techniques may be required in select cases to address bone loss, glenoid dysplasia, or revision. Posterior instability represents about 10% of shoulder instability and has become increasingly recognized and treated in military members. Nonoperative treatment is commonly unsuccessful in active patients, and surgical stabilization can be considered in patients who do not respond. Isolated posterior labral repairs constitute up to 24% of operatively treated labral repairs in a military population. Arthroscopic posterior stabilization is typically considered as first-line surgical treatment, while open techniques may be required in complex or revision settings.

  11. Bacterial Genome Instability

    Science.gov (United States)

    Darmon, Elise

    2014-01-01

    SUMMARY Bacterial genomes are remarkably stable from one generation to the next but are plastic on an evolutionary time scale, substantially shaped by horizontal gene transfer, genome rearrangement, and the activities of mobile DNA elements. This implies the existence of a delicate balance between the maintenance of genome stability and the tolerance of genome instability. In this review, we describe the specialized genetic elements and the endogenous processes that contribute to genome instability. We then discuss the consequences of genome instability at the physiological level, where cells have harnessed instability to mediate phase and antigenic variation, and at the evolutionary level, where horizontal gene transfer has played an important role. Indeed, this ability to share DNA sequences has played a major part in the evolution of life on Earth. The evolutionary plasticity of bacterial genomes, coupled with the vast numbers of bacteria on the planet, substantially limits our ability to control disease. PMID:24600039

  12. Spondylolisthesis and Posterior Instability

    Energy Technology Data Exchange (ETDEWEB)

    Niggemann, P.; Beyer, H.K.; Frey, H.; Grosskurth, D. (Privatpraxis fuer Upright MRT, Koeln (Germany)); Simons, P.; Kuchta, J. (Media Park Klinik, Koeln (Germany))

    2009-04-15

    We present the case of a patient with a spondylolisthesis of L5 on S1 due to spondylolysis at the level L5/S1. The vertebral slip was fixed and no anterior instability was found. Using functional magnetic resonance imaging (MRI) in an upright MRI scanner, posterior instability at the level of the spondylolytic defect of L5 was demonstrated. A structure, probably the hypertrophic ligament flava, arising from the spondylolytic defect was displaced toward the L5 nerve root, and a bilateral contact of the displaced structure with the L5 nerve root was shown in extension of the spine. To our knowledge, this is the first case described of posterior instability in patients with spondylolisthesis. The clinical implications of posterior instability are unknown; however, it is thought that this disorder is common and that it can only be diagnosed using upright MRI.

  13. Propagating Instabilities in Solids

    Science.gov (United States)

    Kyriakides, Stelios

    1998-03-01

    Instability is one of the factors which limit the extent to which solids can be loaded or deformed and plays a pivotal role in the design of many structures. Such instabilities often result in localized deformation which precipitates catastrophic failure. Some materials have the capacity to recover their stiffness following a certain amount of localized deformation. This local recovery in stiffness arrests further local deformation and spreading of the instability to neighboring material becomes preferred. Under displacement controlled loading the propagation of the transition fronts can be achieved in a steady-state manner at a constant stress level known as the propagation stress. The stresses in the transition fronts joining the highly deformed zone to the intact material overcome the instability nucleation stresses and, as a result, the propagation stress is usually much lower than the stress required to nucleate the instability. The classical example of this class of material instabilities is L/"uders bands which tend to affect mild steels and other metals. Recent work has demonstrated that propagating instabilities occur in several other materials. Experimental and analytical results from four examples will be used to illustrate this point: First the evolution of L=FCders bands in mild steel strips will be revisited. The second example involves the evolution of stress induced phase transformations (austenite to martensite phases and the reverse) in a shape memory alloy under displacement controlled stretching. The third example is the crushing behavior of cellular materials such as honeycombs and foams made from metals and polymers. The fourth example involves the axial broadening/propagation of kink bands in aligned fiber/matrix composites under compression. The microstructure and, as a result, the micromechanisms governing the onset, localization, local arrest and propagation of instabilities in each of the four materials are vastly different. Despite this

  14. Handbook on plasma instabilities

    CERN Document Server

    Cap, Ferdinand F

    1982-01-01

    Handbook on Plasma Instabilities, Volume 3, is primarily intended to serve as a sourcebook for obtaining quick information and literature references pertaining to a specific topic. Such a handbook has to be formulated in a way that enables understanding of any one section without requiring full understanding of any other section. Volume 1 (Chapters 1-13) presents the fundamental concepts of plasma physics with applications, and has more the nature of a textbook treating basic plasma physics, containment, waves, and macroscopic instabilities. Volume 2 (Chapters 14-17) covers various aspects of

  15. Causes of genome instability

    DEFF Research Database (Denmark)

    Langie, Sabine A S; Koppen, Gudrun; Desaulniers, Daniel

    2015-01-01

    Genome instability is a prerequisite for the development of cancer. It occurs when genome maintenance systems fail to safeguard the genome's integrity, whether as a consequence of inherited defects or induced via exposure to environmental agents (chemicals, biological agents and radiation). Thus,...

  16. Neutrino beam plasma instability

    Indian Academy of Sciences (India)

    Abstract. We derive relativistic fluid set of equations for neutrinos and electrons from relativistic. Vlasov equations with Fermi weak interaction force. Using these fluid equations, we obtain a dis- persion relation describing neutrino beam plasma instability, which is little different from normal dispersion relation of streaming ...

  17. Chronic Ankle Instability

    Science.gov (United States)

    ... was not rehabilitated completely. When you sprain your ankle, the connective tissues (ligaments) are stretched or torn. The ability to balance ... Repeated ankle sprains often cause—and perpetuate—chronic ankle ... of the ligaments, resulting in greater instability and the likelihood of ...

  18. Posterolateral elbow joint instability

    DEFF Research Database (Denmark)

    Olsen, Bo Sanderhoff; Søjbjerg, Jens Ole; Nielsen, K K

    1998-01-01

    Thirty-five osteoligamentous elbows were included in a study on the kinematics of posterolateral elbow joint instability during the pivot shift test (PST) before and after separate ligament cuttings in the lateral collateral ligament complex (LCLC). Division of the annular ligament or the lateral...

  19. Instability and internet design

    Directory of Open Access Journals (Sweden)

    Sandra Braman

    2016-09-01

    Full Text Available Instability - unpredictable but constant change in one’s environment and the means with which one deals with it - has replaced convergence as the focal problem for telecommunications policy in general and internet policy in particular. Those who designed what we now call the internet during the first decade of the effort (1969-1979, who in essence served simultaneously as its policy-makers, developed techniques for coping with instability of value for network designers today and for those involved with any kind of large-scale sociotechnical infrastructure. Analysis of the technical document series that was medium for and record of that design process reveals coping techniques that began with defining the problem and went on to include conceptual labour, social practices, and technical approaches.

  20. Beam-beam instability

    Energy Technology Data Exchange (ETDEWEB)

    Chao, A.W.

    1983-08-01

    The subject of beam-beam instability has been studied since the invention of the colliding beam storage rings. Today, with several colliding beam storage rings in operation, it is not yet fully understood and remains an outstanding problem for the storage ring designers. No doubt that good progress has been made over the years, but what we have at present is still rather primitive. It is perhaps possible to divide the beam-beam subject into two areas: one on luminosity optimization and another on the dynamics of the beam-beam interaction. The former area concerns mostly the design and operational features of a colliding beam storage ring, while the later concentrates on the experimental and theoretical aspects of the beam-beam interaction. Although both areas are of interest, our emphasis is on the second area only. In particular, we are most interested in the various possible mechanisms that cause the beam-beam instability.

  1. Evaporation and Antievaporation instabilities

    OpenAIRE

    Addazi, Andrea; Marciano, Antonino

    2017-01-01

    We review (anti)evaporation phenomena within the context of quantum gravity and extended theories of gravity. The (anti)evaporation effect is an instability of the black hole horizon discovered in many different scenarios: quantum dilaton-gravity, $f(R)$-gravity, $f(T)$-gravity, string inspired black holes and brane-world cosmology. Evaporating and antievaporating black holes seem to have completely different thermodynamical features compared to standard semiclassical black holes. The purpose...

  2. Instability of warped discs

    Science.gov (United States)

    Doǧan, S.; Nixon, C. J.; King, A. R.; Pringle, J. E.

    2018-01-01

    Accretion discs are generally warped. If a warp in a disc is too large, the disc can `break' apart into two or more distinct planes, with only tenuous connections between them. Further if an initially planar disc is subject to a strong differential precession, then it can be torn apart into discrete annuli that precess effectively independently. In previous investigations, torque-balance formulae have been used to predict where and when the disc breaks into distinct parts. In this work, focusing on discs with Keplerian rotation and where the shearing motions driving the radial communication of the warp are damped locally by turbulence (the `diffusive' regime), we investigate the stability of warped discs to determine the precise criterion for an isolated warped disc to break. We find and solve the dispersion relation, which in general yields three roots. We provide a comprehensive analysis of this viscous-warp instability and the emergent growth rates and their dependence on disc parameters. The physics of the instability can be understood as a combination of (1) a term which would generally encapsulate the classical Lightman-Eardley instability in planar discs (given by ∂(νΣ)/∂Σ condition acting on the diffusion of the warp amplitude given in simplified form by ∂(ν2|ψ|)/∂|ψ| < 0. We discuss our findings in the context of discs with an imposed precession, and comment on the implications for different astrophysical systems.

  3. Radiation Induced Genomic Instability

    Energy Technology Data Exchange (ETDEWEB)

    Morgan, William F.

    2011-03-01

    Radiation induced genomic instability can be observed in the progeny of irradiated cells multiple generations after irradiation of parental cells. The phenotype is well established both in vivo (Morgan 2003) and in vitro (Morgan 2003), and may be critical in radiation carcinogenesis (Little 2000, Huang et al. 2003). Instability can be induced by both the deposition of energy in irradiated cells as well as by signals transmitted by irradiated (targeted) cells to non-irradiated (non-targeted) cells (Kadhim et al. 1992, Lorimore et al. 1998). Thus both targeted and non-targeted cells can pass on the legacy of radiation to their progeny. However the radiation induced events and cellular processes that respond to both targeted and non-targeted radiation effects that lead to the unstable phenotype remain elusive. The cell system we have used to study radiation induced genomic instability utilizes human hamster GM10115 cells. These cells have a single copy of human chromosome 4 in a background of hamster chromosomes. Instability is evaluated in the clonal progeny of irradiated cells and a clone is considered unstable if it contains three or more metaphase sub-populations involving unique rearrangements of the human chromosome (Marder and Morgan 1993). Many of these unstable clones have been maintained in culture for many years and have been extensively characterized. As initially described by Clutton et al., (Clutton et al. 1996) many of our unstable clones exhibit persistently elevated levels of reactive oxygen species (Limoli et al. 2003), which appear to be due dysfunctional mitochondria (Kim et al. 2006, Kim et al. 2006). Interestingly, but perhaps not surprisingly, our unstable clones do not demonstrate a “mutator phenotype” (Limoli et al. 1997), but they do continue to rearrange their genomes for many years. The limiting factor with this system is the target – the human chromosome. While some clones demonstrate amplification of this chromosome and thus lend

  4. Evaporation and Antievaporation Instabilities

    Directory of Open Access Journals (Sweden)

    Andrea Addazi

    2017-10-01

    Full Text Available We review (antievaporation phenomena within the context of quantum gravity and extended theories of gravity. The (antievaporation effect is an instability of the black hole horizon discovered in many different scenarios: quantum dilaton-gravity, f ( R -gravity, f ( T -gravity, string-inspired black holes, and brane-world cosmology. Evaporating and antievaporating black holes seem to have completely different thermodynamical features compared to standard semiclassical black holes. The purpose of this review is to provide an introduction to conceptual and technical aspects of (antievaporation effects, while discussing problems that are still open.

  5. Size effects on cavitation instabilities

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Tvergaard, Viggo

    2006-01-01

    In metal-ceramic systems the constraint on plastic flow leads to so high stress triaxialities that cavitation instabilities may occur. If the void radius is on the order of magnitude of a characteristic length for the metal, the rate of void growth is reduced, and the possibility of unstable cavity...... triaxiality, where cavitation instabilities are predicted by conventional plasticity theory, such instabilities are also found for the nonlocal theory, but the effects of gradient hardening delay the onset of the instability. Furthermore, in some cases the cavitation stress reaches a maximum and then decays...

  6. Instability of enclosed horizons

    CERN Document Server

    Kay, Bernard S

    2013-01-01

    We study the classical massless scalar wave equation on the region of 1+1-dimensional Minkowski space between the two branches of the hyperbola $x^2-t^2=1$ with vanishing boundary conditions on it. We point out that there are initially finite-energy initially, say, right-going waves for which the stress-energy tensor becomes singular on the null-line $t+x=0$. We also construct the quantum theory of this system and show that, while there is a regular Hartle-Hawking-Israel-like state, there are coherent states built on this for which there is a similar singularity in the expectation value of the renormalized stress-energy tensor. We conjecture that in 1+3-dimensional situations with 'enclosed horizons' such as a (maximally extended) Schwarzschild black hole in equilibrium in a stationary box or the (maximally extended) Schwarzschild-AdS spacetime, there will be a similar singularity at the horizon and that would signal an instability when matter perturbations and/or gravity are switched on. Such an instability ...

  7. Instability and Information

    CERN Document Server

    Patzelt, Felix

    2015-01-01

    Many complex systems exhibit extreme events far more often than expected for a normal distribution. This work examines how self-similar bursts of activity across several orders of magnitude can emerge from first principles in systems that adapt to information. Surprising connections are found between two apparently unrelated research topics: hand-eye coordination in balancing tasks and speculative trading in financial markets. Seemingly paradoxically, locally minimising fluctuations can increase a dynamical system's sensitivity to unpredictable perturbations and thereby facilitate global catastrophes. This general principle is studied in several domain-specific models and in behavioural experiments. It explains many findings in both fields and resolves an apparent antinomy: the coexistence of stabilising control or market efficiency and perpetual instabilities resembling critical phenomena in physical systems.

  8. Saturation of equatorial inertial instability

    NARCIS (Netherlands)

    Kloosterziel, R.C.; Orlandi, P.; Carnevale, G.F.

    2015-01-01

    Inertial instability in parallel shear flows and circular vortices in a uniformly rotating system ( $f$f-plane) redistributes absolute linear momentum or absolute angular momentum in such a way as to neutralize the instability. In previous studies we showed that, in the absence of other

  9. Microsatellite instability in bladder cancer

    DEFF Research Database (Denmark)

    Gonzalez-Zulueta, M; Ruppert, J M; Tokino, K

    1993-01-01

    Somatic instability at microsatellite repeats was detected in 6 of 200 transitional cell carcinomas of the bladder. Instabilities were apparent as changes in (GT)n repeat lengths on human chromosome 9 for four tumors and as alterations in a (CAG)n repeat in the androgen receptor gene on the X chr...

  10. Liquid propellant rocket combustion instability

    Science.gov (United States)

    Harrje, D. T.

    1972-01-01

    The solution of problems of combustion instability for more effective communication between the various workers in this field is considered. The extent of combustion instability problems in liquid propellant rocket engines and recommendations for their solution are discussed. The most significant developments, both theoretical and experimental, are presented, with emphasis on fundamental principles and relationships between alternative approaches.

  11. Beam instability Workshop - plenary sessions

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2001-07-01

    The purpose of this workshop was to provide a review of the mechanisms of limiting beam instabilities, their cures, including feedback, and beam measurement for synchrotron radiation light sources. 12 plenary sessions took place whose titles are: 1) challenging brilliance and lifetime issues with increasing currents; 2) limiting instabilities in multibunch; 3) experience from high currents in B factories; 4) longitudinal dynamics in high intensity/bunch; 5) Transverse instabilities for high intensity/bunch; 6) working group introduction from ESRF experience; 7) impedance modelling: simulations, minimization; 8) report on the broadband impedance measurements and modelling workshop; 9) feedback systems for synchrotron light sources; 10) beam instabilities diagnostics; 11) harmonic cavities: the pros and cons; and 12) experimental study of fast beam-ion instabilities at PLS. This document gathers the 12 articles that were presented during these sessions.

  12. Simulations of Astrophysical fluid instabilities

    Science.gov (United States)

    Calder, A. C.; Fryxell, B.; Rosner, R.; Dursi, L. J.; Olson, K.; Ricker, P. M.; Timmes, F. X.; Zingale, M.; MacNeice, P.; Tufo, H. M.

    2001-10-01

    We present direct numerical simulations of mixing at Rayleigh-Taylor unstable interfaces performed with the FLASH code, developed at the ASCI/Alliances Center for Astrophysical Thermonuclear Flashes at the University of Chicago. We present initial results of single-mode studies in two and three dimensions. Our results indicate that three-dimensional instabilities grow significantly faster than two-dimensional instabilities and that grid resolution can have a significant effect on instability growth rates. We also find that unphysical diffusive mixing occurs at the fluid interface, particularly in poorly resolved simulations. .

  13. WELLBORE INSTABILITY: CAUSES AND CONSEQUENCES

    Directory of Open Access Journals (Sweden)

    Borivoje Pašić

    2007-12-01

    Full Text Available Wellbore instability is one of the main problems that engineers meet during drilling. The causes of wellbore instability are often classified into either mechanical (for example, failure of the rock around the hole because of high stresses, low rock strength, or inappropriate drilling practice or chemical effects which arise from damaging interaction between the rock, generally shale, and the drilling fluid. Often, field instances of instability are a result of a combination of both chemical and mechanical. This problem might cause serious complication in well and in some case can lead to expensive operational problems. The increasing demand for wellbore stability analyses during the planning stage of a field arise from economic considerations and the increasing use of deviated, extended reach and horizontal wells. This paper presents causes, indicators and diagnosing of wellbore instability as well as the wellbore stresses model.

  14. Edge instabilities of topological superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Hofmann, Johannes S. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg (Germany); Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany); Assaad, Fakher F. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg (Germany); Schnyder, Andreas P. [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany)

    2016-07-01

    Nodal topological superconductors display zero-energy Majorana flat bands at generic edges. The flatness of these edge bands, which is protected by time-reversal and translation symmetry, gives rise to an extensive ground state degeneracy and a diverging density of states. Therefore, even arbitrarily weak interactions lead to an instability of the flat-band edge states towards time-reversal and translation-symmetry broken phases, which lift the ground-state degeneracy. Here, we employ Monte Carlo simulations combined with mean-field considerations to examine the instabilities of the flat-band edge states of d{sub xy}-wave superconductors. We find that attractive interactions induce a complex s-wave pairing instability together with a density wave instability. Repulsive interactions, on the other hand, lead to ferromagnetism mixed with spin-triplet pairing at the edge. We discuss the implications of our findings for experiments on cuprate high-temperature superconductors.

  15. Beam Instabilities in Hadron Synchrotrons

    CERN Document Server

    Métral, E; Bartosik, H; Biancacci, N; Buffat, X; Esteban Muller, J F; Herr, W; Iadarola, G; Lasheen, A; Li, K; Oeftiger, A; Pieloni, T; Quartullo, D; Rumolo, G; Salvant, B; Schenk, M; Shaposhnikova, E; Tambasco, C; Timko, H; Zannini, C; Burov, A; Banfi, D; Barranco, J; Mounet, N; Boine-Frankenheim, O; Niedermayer, U; Kornilov, V; White, S

    2016-01-01

    Beam instabilities cover a wide range of effects in particle accelerators and they have been the subjects of intense research for several decades. As the machines performance was pushed new mechanisms were revealed and nowadays the challenge consists in studying the interplays between all these intricate phenomena, as it is very often not possible to treat the different effects separately. The aim of this paper is to review the main mechanisms, discussing in particular the recent developments of beam instability theories and simulations.

  16. Microsatellite instability in bladder cancer

    DEFF Research Database (Denmark)

    Gonzalez-Zulueta, M; Ruppert, J M; Tokino, K

    1993-01-01

    Somatic instability at microsatellite repeats was detected in 6 of 200 transitional cell carcinomas of the bladder. Instabilities were apparent as changes in (GT)n repeat lengths on human chromosome 9 for four tumors and as alterations in a (CAG)n repeat in the androgen receptor gene on the X...... or larger (> 2 base pairs) alterations in repeat length. All six tumors were low stage (Ta-T1), suggesting that these alterations can occur early in bladder tumorigenesis....

  17. Material Instabilities in Particulate Systems

    Science.gov (United States)

    Goddard, J. D.

    1999-01-01

    Following is a brief summary of a theoretical investigation of material (or constitutive) instability associated with shear induced particle migration in dense particulate suspensions or granular media. It is shown that one can obtain a fairly general linear-stability analysis, including the effects of shear-induced anisotropy in the base flow as well as Reynolds dilatancy. A criterion is presented here for simple shearing instability in the absence of inertia and dilatancy.

  18. History of shoulder instability surgery.

    Science.gov (United States)

    Randelli, Pietro; Cucchi, Davide; Butt, Usman

    2016-02-01

    The surgical management of shoulder instability is an expanding and increasingly complex area of study within orthopaedics. This article describes the history and evolution of shoulder instability surgery, examining the development of its key principles, the currently accepted concepts and available surgical interventions. A comprehensive review of the available literature was performed using PubMed. The reference lists of reviewed articles were also scrutinised to ensure relevant information was included. The various types of shoulder instability including anterior, posterior and multidirectional instability are discussed, focussing on the history of surgical management of these topics, the current concepts and the results of available surgical interventions. The last century has seen important advancements in the understanding and treatment of shoulder instability. The transition from open to arthroscopic surgery has allowed the discovery of previously unrecognised pathologic entities and facilitated techniques to treat these. Nevertheless, open surgery still produces comparable results in the treatment of many instability-related conditions and is often required in complex or revision cases, particularly in the presence of bone loss. More high-quality research is required to better understand and characterise this spectrum of conditions so that successful evidence-based management algorithms can be developed. IV.

  19. Radiation-induced chromosomal instability

    Energy Technology Data Exchange (ETDEWEB)

    Ritter, S. [GSI, Biophysics, Darmstadt (Germany)

    1999-03-01

    Recent studies on radiation-induced chromosomal instability in the progeny of exposed mammalian cells were briefly described as well as other related studies. For the analysis of chromosomal damage in clones, cells were seeded directly after exposure in cell well-dish to form single cell clones and post-irradiation chromosome aberrations were scored. Both exposure to isoeffective doses of X-ray or 270 MeV/u C-ions (13 keV/{mu}m) increased the number of clones with abnormal karyotype and the increase was similar for X-ray and for C-ions. Meanwhile, in the progeny of cells for mass cultures, there was no indication of a delayed expression of chromosomal damage up to 40 population doublings after the exposure. A high number of aberrant cells were only observed directly after exposure to 10.7 MeV/u O-ions, i.e. in the first cycle cells and decreased with subsequent cell divisions. The reason for these differences in the radiation-induced chromosomal instability between clonal isolates and mass culture has not been clarified. Recent studies indicated that genomic instability occurs at a high frequency in the progeny of cells irradiated with both sparsely and densely ionizing radiation. Such genomic instability is thought likely to increase the risk of carcinogenesis, but more data are required for a well understanding of the health risks resulting from radiation-induced delayed instability. (M.N.)

  20. Instability Prediction and Disruption Avoidance

    Science.gov (United States)

    Turnbull, A. D.; Liu, Y. Q.; Hanson, J. M.; Turco, F.; Ferraro, N. M.

    2017-10-01

    Disruption avoidance requires both a prediction of the instability proximity and an estimate of the `disruptability' - the likelihood that the instability will ultimately result in a disruptive event. MHD spectroscopy is a promising option for obtaining information on the proximity of instabilities. Both the direct response and the antenna impedance provide valuable information on the low frequency global normal modes corresponding to stabilized kink modes. Data from DIII-D experiments and available nonlinear simulations are used to define quantitative criteria that signify when instabilities ultimately disrupt and when they saturate or dissipate. The key distinction in this approach is the use of physical characteristics of the modes rather than more accessible operation parameters. Simple characteristics of the linear instability for example include the linear growth or damping rate and the mode spatial extent. Criteria can also involve identifying sources of free energy in the nonlinear evolution. Work supported in part by the US DOE under DE-FC02-04ER54698 & DE-FG02-95ER54309.

  1. Telomere dysfunction and chromosome instability

    Energy Technology Data Exchange (ETDEWEB)

    Murnane, John P., E-mail: jmurnane@radonc.ucsf.edu [Department of Radiation Oncology, University of California San Francisco, 2340 Sutter Street, San Francisco, CA 94143-1331 (United States)

    2012-02-01

    The ends of chromosomes are composed of a short repeat sequence and associated proteins that together form a cap, called a telomere, that keeps the ends from appearing as double-strand breaks (DSBs) and prevents chromosome fusion. The loss of telomeric repeat sequences or deficiencies in telomeric proteins can result in chromosome fusion and lead to chromosome instability. The similarity between chromosome rearrangements resulting from telomere loss and those found in cancer cells implicates telomere loss as an important mechanism for the chromosome instability contributing to human cancer. Telomere loss in cancer cells can occur through gradual shortening due to insufficient telomerase, the protein that maintains telomeres. However, cancer cells often have a high rate of spontaneous telomere loss despite the expression of telomerase, which has been proposed to result from a combination of oncogene-mediated replication stress and a deficiency in DSB repair in telomeric regions. Chromosome fusion in mammalian cells primarily involves nonhomologous end joining (NHEJ), which is the major form of DSB repair. Chromosome fusion initiates chromosome instability involving breakage-fusion-bridge (B/F/B) cycles, in which dicentric chromosomes form bridges and break as the cell attempts to divide, repeating the process in subsequent cell cycles. Fusion between sister chromatids results in large inverted repeats on the end of the chromosome, which amplify further following additional B/F/B cycles. B/F/B cycles continue until the chromosome acquires a new telomere, most often by translocation of the end of another chromosome. The instability is not confined to a chromosome that loses its telomere, because the instability is transferred to the chromosome donating a translocation. Moreover, the amplified regions are unstable and form extrachromosomal DNA that can reintegrate at new locations. Knowledge concerning the factors promoting telomere loss and its consequences is

  2. Political instability and illegal immigration.

    Science.gov (United States)

    Campos, J E; Lien, D

    1995-01-01

    "Economic theory suggests that transnational migration results from the push-pull effect of wage differentials between host and source countries. In this paper, we argue that political instability exacerbates the migration flow, with greater instability leading to relatively larger flows. We conclude then that an optimal solution to the illegal immigration problem requires proper coordination of immigration and foreign policies by the host country. A narrow preoccupation with tougher immigration laws is wasteful and may be marginally effective." Emphasis is on the United States as a host country. excerpt

  3. Stringy bounces and gradient instabilities

    CERN Document Server

    Giovannini, Massimo

    2017-01-01

    Bouncing solutions are obtained from a generally covariant action characterized by a potential which is a nonlocal functional of the dilaton field at two separated space-time points. Gradient instabilities are shown to arise in this context but they are argued to be nongeneric. After performing a gauge-invariant and frame-invariant derivation of the evolution equations of the fluctuations, a heuristic criterium for the avoidance of pathological instabilities is proposed and corroborated by a number of explicit examples that turn out to be compatible with a quasi-flat spectrum of curvature inhomogeneities for typical wavelengths larger than the Hubble radius.

  4. Helical instability in film blowing process: Analogy to buckling instability

    Science.gov (United States)

    Lee, Joo Sung; Kwon, Ilyoung; Jung, Hyun Wook; Hyun, Jae Chun

    2017-12-01

    The film blowing process is one of the most important polymer processing operations, widely used for producing bi-axially oriented film products in a single-step process. Among the instabilities observed in this film blowing process, i.e., draw resonance and helical motion occurring on the inflated film bubble, the helical instability is a unique phenomenon portraying the snake-like undulation motion of the bubble, having the period on the order of few seconds. This helical instability in the film blowing process is commonly found at the process conditions of a high blow-up ratio with too low a freezeline position and/or too high extrusion temperature. In this study, employing an analogy to the buckling instability for falling viscous threads, the compressive force caused by the pressure difference between inside and outside of the film bubble is introduced into the simulation model along with the scaling law derived from the force balance between viscous force and centripetal force of the film bubble. The simulation using this model reveals a close agreement with the experimental results of the film blowing process of polyethylene polymers such as low density polyethylene and linear low density polyethylene.

  5. Modulational instability of nematic phase

    Indian Academy of Sciences (India)

    2014-02-08

    Feb 8, 2014 ... Abstract. We numerically observe the effect of homogeneous magnetic field on the modulation- ally stable case of polar phase in F = 2 spinor Bose–Einstein condensates (BECs). Also we investigate the modulational instability of uniaxial and biaxial (BN) states of polar phase. Our observations show that ...

  6. Modulational instability of nematic phase

    Indian Academy of Sciences (India)

    2014-02-08

    Feb 8, 2014 ... We numerically observe the effect of homogeneous magnetic field on the modulationally stable case of polar phase in = 2 spinor Bose–Einstein condensates (BECs). Also we investigate the modulational instability of uniaxial and biaxial (BN) states of polar phase. Our observations show that the magnetic ...

  7. The Chemistry of Beer Instability

    Science.gov (United States)

    Stewart, Graham G.

    2004-01-01

    Brewing of beer, one of the oldest biotechnology industries was one of the earliest processes to be undertaken on commercial basis. Biological instability involves contamination of bacteria, yeast, or mycelia fungi and there is always a risk in brewing that beer can become contaminated by micro-organisms.

  8. Edge instabilities of topological superconductors

    Science.gov (United States)

    Hofmann, Johannes S.; Assaad, Fakher F.; Schnyder, Andreas P.

    2016-05-01

    Nodal topological superconductors display zero-energy Majorana flat bands at generic edges. The flatness of these edge bands, which is protected by time-reversal and translation symmetry, gives rise to an extensive ground-state degeneracy. Therefore, even arbitrarily weak interactions lead to an instability of the flat-band edge states towards time-reversal and translation-symmetry-broken phases, which lift the ground-state degeneracy. We examine the instabilities of the flat-band edge states of dx y-wave superconductors by performing a mean-field analysis in the Majorana basis of the edge states. The leading instabilities are Majorana mass terms, which correspond to coherent superpositions of particle-particle and particle-hole channels in the fermionic language. We find that attractive interactions induce three different mass terms. One is a coherent superposition of imaginary s -wave pairing and current order, and another combines a charge-density-wave and finite-momentum singlet pairing. Repulsive interactions, on the other hand, lead to ferromagnetism together with spin-triplet pairing at the edge. Our quantum Monte Carlo simulations confirm these findings and demonstrate that these instabilities occur even in the presence of strong quantum fluctuations. We discuss the implications of our results for experiments on cuprate high-temperature superconductors.

  9. Lending sociodynamics and economic instability

    Science.gov (United States)

    Hawkins, Raymond J.

    2011-11-01

    We show how the dynamics of economic instability and financial crises articulated by Keynes in the General Theory and developed by Minsky as the Financial Instability Hypothesis can be formalized using Weidlich’s sociodynamics of opinion formation. The model addresses both the lending sentiment of a lender in isolation as well as the impact on that lending sentiment of the behavior of other lenders. The risk associated with lending is incorporated through a stochastic treatment of loan dynamics that treats prepayment and default as competing risks. With this model we are able to generate endogenously the rapid changes in lending opinion that attend slow changes in lending profitability and find these dynamics to be consistent with the rise and collapse of the non-Agency mortgage-backed securities market in 2007/2008. As the parameters of this model correspond to well-known phenomena in cognitive and social psychology, we can both explain why economic instability has proved robust to advances in risk measurement and suggest how policy for reducing economic instability might be formulated in an experimentally sound manner.

  10. Arthroscopic Management of Scapholunate Instability

    Science.gov (United States)

    Geissler, William B.

    2013-01-01

    Wrist arthroscopy plays a valuable role in the management of scapholunate instability. A spectrum of injuries can occur to the scapholunate interosseous ligament, which may be difficult to detect with imaging studies. Wrist arthroscopy enables detection and management of injury to the scapholunate ligament under bright light and magnified conditions, in both acute and chronic situations. PMID:24436805

  11. Singlet and triplet instability theorems

    Science.gov (United States)

    Yamada, Tomonori; Hirata, So

    2015-09-01

    A useful definition of orbital degeneracy—form-degeneracy—is introduced, which is distinct from the usual energy-degeneracy: Two canonical spatial orbitals are form-degenerate when the energy expectation value in the restricted Hartree-Fock (RHF) wave function is unaltered upon a two-electron excitation from one of these orbitals to the other. Form-degenerate orbitals tend to have isomorphic electron densities and occur in the highest-occupied and lowest-unoccupied molecular orbitals (HOMOs and LUMOs) of strongly correlated systems. Here, we present a mathematical proof of the existence of a triplet instability in a real or complex RHF wave function of a finite system in the space of real or complex unrestricted Hartree-Fock wave functions when HOMO and LUMO are energy- or form-degenerate. We also show that a singlet instability always exists in a real RHF wave function of a finite system in the space of complex RHF wave functions, when HOMO and LUMO are form-degenerate, but have nonidentical electron densities, or are energy-degenerate. These theorems provide Hartree-Fock-theory-based explanations of Hund's rule, a singlet instability in Jahn-Teller systems, biradicaloid electronic structures, and a triplet instability during some covalent bond breaking. They also suggest (but not guarantee) the spontaneous formation of a spin density wave (SDW) in a metallic solid. The stability theory underlying these theorems extended to a continuous orbital-energy spectrum proves the existence of an oscillating (nonspiral) SDW instability in one- and three-dimensional homogeneous electron gases, but only at low densities or for strong interactions.

  12. Singlet and triplet instability theorems

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Tomonori; Hirata, So, E-mail: sohirata@illinois.edu [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan)

    2015-09-21

    A useful definition of orbital degeneracy—form-degeneracy—is introduced, which is distinct from the usual energy-degeneracy: Two canonical spatial orbitals are form-degenerate when the energy expectation value in the restricted Hartree–Fock (RHF) wave function is unaltered upon a two-electron excitation from one of these orbitals to the other. Form-degenerate orbitals tend to have isomorphic electron densities and occur in the highest-occupied and lowest-unoccupied molecular orbitals (HOMOs and LUMOs) of strongly correlated systems. Here, we present a mathematical proof of the existence of a triplet instability in a real or complex RHF wave function of a finite system in the space of real or complex unrestricted Hartree–Fock wave functions when HOMO and LUMO are energy- or form-degenerate. We also show that a singlet instability always exists in a real RHF wave function of a finite system in the space of complex RHF wave functions, when HOMO and LUMO are form-degenerate, but have nonidentical electron densities, or are energy-degenerate. These theorems provide Hartree–Fock-theory-based explanations of Hund’s rule, a singlet instability in Jahn–Teller systems, biradicaloid electronic structures, and a triplet instability during some covalent bond breaking. They also suggest (but not guarantee) the spontaneous formation of a spin density wave (SDW) in a metallic solid. The stability theory underlying these theorems extended to a continuous orbital-energy spectrum proves the existence of an oscillating (nonspiral) SDW instability in one- and three-dimensional homogeneous electron gases, but only at low densities or for strong interactions.

  13. Treatment of glenohumeral instability in rugby players

    OpenAIRE

    Funk, Lennard

    2016-01-01

    Rugby is a high-impact collision sport, with impact forces. Shoulder injuries are common and result in the longest time off sport for any joint injury in rugby. The most common injuries are to the glenohumeral joint with varying degrees of instability. The degree of instability can guide management. The three main types of instability presentations are: (1) frank dislocation, (2) subluxations and (3) subclinical instability with pain and clicking. Understanding the exact mechanism of injury c...

  14. Interface instability modes in freezing colloidal suspensions: revealed from onset of planar instability

    Science.gov (United States)

    Wang, Lilin; You, Jiaxue; Wang, Zhijun; Wang, Jincheng; Lin, Xin

    2016-03-01

    Freezing colloidal suspensions widely exists in nature and industry. Interface instability has attracted much attention for the understandings of the pattern formation in freezing colloidal suspensions. However, the interface instability modes, the origin of the ice banding or ice lamellae, are still unclear. In-situ experimental observation of the onset of interface instability remains absent up to now. Here, by directly imaging the initial transient stage of planar interface instability in directional freezing colloidal suspensions, we proposed three interface instability modes, Mullins-Sekerka instability, global split instability and local split instability. The intrinsic mechanism of the instability modes comes from the competition of the solute boundary layer and the particle boundary layer, which only can be revealed from the initial transient stage of planar instability in directional freezing.

  15. Fluctuations and Instability in Sedimentation

    KAUST Repository

    Guazzelli, Élisabeth

    2011-01-21

    This review concentrates on the fluctuations of the velocities of sedimenting spheres, and on the structural instability of a suspension of settling fibers. For many years, theoretical estimates and numerical simulations predicted the fluctuations of the velocities of spheres to increase with the size of the container, whereas experiments found no such variation. Two ideas have increased our understanding. First, the correlation length of the velocity fluctuations was found experimentally to be 20 interparticle separations. Second, in dilute suspensions, a vertical variation in the concentration due to the spreading of the front with the clear fluid can inhibit the velocity fluctuations. In a very dilute regime, a homogeneous suspension of fibers suffers a spontaneous instability in which fast descending fiber-rich columns are separated by rising fiber-sparse columns. In a semidilute regime, the settling is hindered, more so than for spheres. © 2011 by Annual Reviews. All rights reserved.

  16. Quad-Bike Operational Instability

    Directory of Open Access Journals (Sweden)

    Ross H. Macmillan

    2017-05-01

    Full Text Available The stake-holders in the quad-bike (QB industry in Australia have failed to reach a satisfactory resolution of the present impasse that exists with respect to the causes and mitigation of the trauma suffered by riders due to QB instability. In an effort to provide purchasers with data enabling them to discriminate between safer and less safe machines, static longitudinal and lateral tests have been conducted by various interested parties; quasi-static lateral tests have also been conducted under some operational conditions. It is argued that while these static tests are valid, under many operating conditions QBs will not reach such unstable slopes due to poor traction. Further, these tests do not include the quasi-static and dynamic factors which also influence the processes associated with operational instability. For these reasons, the static tests do not provide an adequate basis for discrimination between safer and less safe machines.

  17. Instability of ties in compression

    DEFF Research Database (Denmark)

    Buch-Hansen, Thomas Cornelius

    2013-01-01

    Masonry cavity walls are loaded by wind pressure and vertical load from upper floors. These loads results in bending moments and compression forces in the ties connecting the outer and the inner wall in a cavity wall. Large cavity walls are furthermore loaded by differential movements from...... the temperature gradient between the outer and the inner wall, which results in critical increase of the bending moments in the ties. Since the ties are loaded by combined compression and moment forces, the loadbearing capacity is derived from instability equilibrium equations. Most of them are iterative, since......-connectors in cavity walls was developed. The method takes into account constraint conditions limiting the free length of the wall tie, and the instability in case of pure compression which gives an optimal load bearing capacity. The model is illustrated with examples from praxis....

  18. Placing Marangoni instabilities under arrest

    CERN Document Server

    Bhamla, M Saad

    2016-01-01

    Soap bubbles occupy the rare position of delighting and fascinating both young children and scientific minds alike. Sir Isaac Newton, Joseph Plateau, Carlo Marangoni, and Pierre-Gilles de Gennes, not to mention countless others, have discovered remarkable results in optics, molecular forces and fluid dynamics from investigating this seemingly simple system. We present here a compilation of curiosity-driven experiments that systematically investigate the surface flows on a rising soap bubble. From childhood experience, we are familiar with the vibrant colors and mesmerizing display of chaotic flows on the surface of a soap bubble. These flows arise due to surface tension gradients, also known as Marangoni flows or instabilities. In Figure 1, we show the surprising effect of layering multiple instabilities on top of each other, highlighting that unexpected new phenomena are still waiting to be discovered, even in the simple soap bubble.

  19. Instability of colliding metastable strings

    Energy Technology Data Exchange (ETDEWEB)

    Hiramatsu, Takashi [Kyoto Univ. (Japan). Yukawa Inst. for Theoretical Physics; Eto, Minoru [Yamagata Univ. (Japan). Dept. of Physics; Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics; Ookouchi, Yutaka [Kyoto Univ. (Japan). Dept. of Physics; Kyoto Univ. (Japan). The Hakubi Center for Advanced Research

    2013-04-15

    We investigate the collision dynamics of two metastable strings which can be viewed as tube-like domain walls with winding numbers interpolating a false vacuum and a true vacuum. We find that depending on the relative angle and speed of two strings, instability of strings increases and the false vacuum is filled out by rapid expansion of the strings or of a remnant of the collision.

  20. Morphological instabilities of lamellar eutectics

    Energy Technology Data Exchange (ETDEWEB)

    Karma, A.; Sarkissian, A. [Northeastern Univ., Boston, MA (United States). Physics Dept.

    1996-03-01

    The authors present the results of a numerical study based on the boundary integral technique of interfacial pattern formation in directional solidification of thin-film lamellar eutectics at low velocity. Microstructure selection maps that identify the stability domains of various steady-state and nonsteady-state growth morphologies in the spacing-composition ({lambda} {minus} C{sub 0}) plane are constructed for the transparent organic alloy CBr{sub 4}-C{sub 2}Cl{sub 6} and for a model eutectic alloy with two solid phases of identical physical properties. In CBr{sub 4}-C{sub 2}Cl{sub 6}, the basic set of instabilities that limit steady-state growth is richer than expected. It consists of three primary instabilities, two of which are oscillatory, which bound the domain of the commonly observed axisymmetric lamellar morphology, and two secondary oscillatory instabilities, which bound the domain of the nonaxisymmetric (tilted) lamellar morphology. Four stable oscillatory microstructures, at least three of which have been seen experimentally, are predicted to occur in unstable regimes. In the model alloy, the structure is qualitatively similar, except that a stable domain of tilted steady-state growth is not found, in agreement with previous random-walk simulations. Furthermore, the composition range of stability of the axisymmetric morphology decreases sharply with increasing spacing away from minimum undercooling but extends further off-eutectic than predicted by the competitive growth criterion. In addition, oscillations with a wavelength equal to two {lambda} lead to lamella termination at a small distance above the onset of instability. The implications of these two features for the eutectic to dendrite transition are examined with the conclusion that in the absence of heterogeneous nucleation, this transition should be histeritic at small velocity and temperature gradient.

  1. Atlantoaxial instability in Down's synarome

    OpenAIRE

    Kafadar, Ali; Hanci, Murat; Tuysuz, Beyhan; Sarioglu, Ali Cetin; Erginel, Ayten; Cenani, Asim

    2004-01-01

    9-31 % of children with Down syndrome have atlantoaxial instability. These children might have the risk of atlantoaxial dislocation and spinal cord compression if they play sport or take part actively in daily Iife. The purpose of our study was to assess the presumed risk. We examined and followed up one year Iong 35 children with Down syndrome through a series of Iateral cervical spine x-ray and neurological examination. Those children with an atlantoaxial distance => 5mm were considered uns...

  2. Atlantoaxial instability in Down's synarome

    OpenAIRE

    Kafadar, Ali; Hanci, Murat; Tuysuz, Beyhan; Sarioglu, Ali; Erginel, Ayten; Cenani, Asim

    2004-01-01

    9-31 % of children with Down syndrome have atlantoaxial instability. These children might have the risk of atlantoaxial dislocation and spinal cord compression if they play sport or take part actively in daily Iife. The purpose of our study was to assess the presumed risk. We examined and followed up one year Iong 35 children with Down syndrome through a series of Iateral cervical spine x-ray and neurological examination. Those children with an atlantoaxial distance => 5mm were considered ...

  3. Hydrodynamic instabilities in miscible fluids

    Science.gov (United States)

    Truzzolillo, Domenico; Cipelletti, Luca

    2018-01-01

    Hydrodynamic instabilities in miscible fluids are ubiquitous, from natural phenomena up to geological scales, to industrial and technological applications, where they represent the only way to control and promote mixing at low Reynolds numbers, well below the transition from laminar to turbulent flow. As for immiscible fluids, the onset of hydrodynamic instabilities in miscible fluids is directly related to the physics of their interfaces. The focus of this review is therefore on the general mechanisms driving the growth of disturbances at the boundary between miscible fluids, under a variety of forcing conditions. In the absence of a regularizing mechanism, these disturbances would grow indefinitely. For immiscible fluids, interfacial tension provides such a regularizing mechanism, because of the energy cost associated to the creation of new interface by a growing disturbance. For miscible fluids, however, the very existence of interfacial stresses that mimic an effective surface tension is debated. Other mechanisms, however, may also be relevant, such as viscous dissipation. We shall review the stabilizing mechanisms that control the most common hydrodynamic instabilities, highlighting those cases for which the lack of an effective interfacial tension poses deep conceptual problems in the mathematical formulation of a linear stability analysis. Finally, we provide a short overview on the ongoing research on the effective, out of equilibrium interfacial tension between miscible fluids.

  4. instability

    Directory of Open Access Journals (Sweden)

    Magdalena Czubaszek

    2014-06-01

    Full Text Available The basic method for analyzing the degree of DNA fragmentation caused by genotoxic factors is gel electrophoresis of single cells (single cell gel electrophoresis, also called the comet assay. The comet assay enables the analysis of the level of several different DNA modifications. The basic testing procedure has been only slightly modified. This method helps identify single-strand and double-strand DNA cracks, as well as any chemical and enzymatic modifications that can potentially turn into cracks in DNA or chromatids. The comet assay makes it possible to detect DNA damage at the level of single cells. It can be employed in analyses of any tissues which provide cellular suspensions. Analysed cells are submerged in agarose on a microscope slide. DNA is what is left after proteins have been broken down. The slide is then subjected to electrophoresis and stained with a fluorescent dye. A “comet-like” image is obtained. The “head” is the cell fixation site prior to lysis; the “tail” represents damaged DNA fragments. The extent of DNA damage is reflected in the length of the tail and the amount of DNA contained in it. The assay finds research applications in the following fields: genetic toxicology, monitoring of DNA repair following chemotherapy and radiotherapy, ecotoxicology, animal and human nourishment, biomonitoring of genotoxicity, epidemiology and assessment of material deposited in sperm and blood banks.

  5. Modes of storage ring coherent instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J.M.

    1986-12-01

    Longitudinal impedance in a beam and various modes of longitudinal coherent instabilities are discussed. The coasting beam coherent instability, microwave instability, and single-bunch longitudinal coherent instabilities are considered. The Vlasov equation is formulated, and a method of solving it is developed. The synchrotron modes are treated, which take the possible bunch shape distortion fully into consideration. A method of treating the synchrotron mode coupling in the case of a small bunch is discussed which takes advantage of the fact that only a few of the synchrotron modes can contribute in such a case. The effect of many bunches on the coherent motion of the beam and the longitudinal symmetric coupled bunch modes are discussed. The transverse impedance is then introduced, and the transverse coasting beam instability is discussed. Various bunched beam instabilities are discussed, including both single bunch instabilities and coupled bunch instabilities. The Vlasov equation for transverse as well as longitudinal motion of particles is introduced as well as a method of solving it within a linear approximation. Head-tail modes and short bunch instabilities and strong coupling instabilities in the long bunch case are covered. (LEW)

  6. Microsatellite instability in prostate cancer

    Energy Technology Data Exchange (ETDEWEB)

    Shan, A.L.; Wick, M.J.; Persons, D.L. [Mayo Clinic and Foundation, Rochester, MN (United States)] [and others

    1994-09-01

    Microsatellite instability (MIN) has been documented in hereditary nonpolyposis colorectal cancer (HNPCC) as well as in sporadic forms of human cancers. Two of the genes which appear to be responsible for this particular tumor phenotype, hMSH2 and hMLH1, have now been identified. To determine the potential role of these mutator genes in prostate cancer, we have examined 95 prostate adenocarcinomas (40 paraffin embedded and 55 fresh frozen) for the presence of genetic instability at four microsatellite markers. The markers are localized to chromosome arms 5q(APC-CA1), 8p(Mfd 210Z), 15q(635/636), and 17q(p53-CA). Patients from whom paraffin embedded material was obtained were divided into short term (<3 years, n=18), and long term (>3 years, n=22) survivors. Of the 95 tumors examined, only four tumors (4%) demonstrated MIN: two tumors demonstrated MIN at 3 loci (p53-CA, APC-CA1, 635/636), one tumor demonstrated MIN at 2 loci (APC-CA1 and 635/636), and one tumor demonstrated instability at 635/636 only. All tumors exhibiting MIN had Gleason scores of {ge} 4+4. A correlation between MIN and survival was not observed. Information on family history was limited. However, of the two patients demonstrating MIN at three loci, one patient was diagnosed with a second malignancy (TCC of the ureter), but otherwise had a negative family history, while the second patient had one first degree relative with esophageal cancer. The patient demonstrating MIN at two loci had a negative family history, while the remaining patient had two first degree relatives with cancer (prostate and stomach). These results suggest that hMSH2 and hMLH1 (as reflected by the small percentage of tumors displaying MIN) do not play a prominent role in the process of prostate tumorigenesis.

  7. Transverse Instabilities in the Fermilab Recycler

    Energy Technology Data Exchange (ETDEWEB)

    Prost, L.R.; Burov, A.; Shemyakin, A.; Bhat, C.M.; Crisp, J.; Eddy, N.; /Fermilab

    2011-07-01

    Transverse instabilities of the antiproton beam have been observed in the Recycler ring soon after its commissioning. After installation of transverse dampers, the threshold for the instability limit increased significantly but the instability is still found to limit the brightness of the antiprotons extracted from the Recycler for Tevatron shots. In this paper, we describe observations of the instabilities during the extraction process as well as during dedicated studies. The measured instability threshold phase density agrees with the prediction of the rigid beam model within a factor of 2. Also, we conclude that the instability threshold can be significantly lowered for a bunch contained in a narrow and shallow potential well due to effective exclusion of the longitudinal tails from Landau damping.

  8. Mode-locking via dissipative Faraday instability.

    Science.gov (United States)

    Tarasov, Nikita; Perego, Auro M; Churkin, Dmitry V; Staliunas, Kestutis; Turitsyn, Sergei K

    2016-08-09

    Emergence of coherent structures and patterns at the nonlinear stage of modulation instability of a uniform state is an inherent feature of many biological, physical and engineering systems. There are several well-studied classical modulation instabilities, such as Benjamin-Feir, Turing and Faraday instability, which play a critical role in the self-organization of energy and matter in non-equilibrium physical, chemical and biological systems. Here we experimentally demonstrate the dissipative Faraday instability induced by spatially periodic zig-zag modulation of a dissipative parameter of the system-spectrally dependent losses-achieving generation of temporal patterns and high-harmonic mode-locking in a fibre laser. We demonstrate features of this instability that distinguish it from both the Benjamin-Feir and the purely dispersive Faraday instability. Our results open the possibilities for new designs of mode-locked lasers and can be extended to other fields of physics and engineering.

  9. Asymptotic Behavior of the Electron Cloud Instability

    Energy Technology Data Exchange (ETDEWEB)

    Heifets, Samuel; /SLAC

    2007-06-06

    The fast beam-ion instability and the single bunch electron-cloud instability are substantially nonlinear phenomena and can be analyzed in a similar way. The initial exponential growth of the amplitudes known for both instabilities takes place only in the linear approximation. Later, in the nonlinear regime, amplitudes grow according to a power law or even decrease. We analyze the nonlinear regime describing the growth of amplitudes in time and along the train of bunches. Analytic analysis is compared with simulations.

  10. Evaluation and Management of Posterior Shoulder Instability

    Science.gov (United States)

    Tannenbaum, Eric; Sekiya, Jon K.

    2011-01-01

    Context: Posterior shoulder instability is a commonly misdiagnosed disorder in many competitive athletes. Type of Study: Clinical review. Evidence Acquisition: Relevant studies on posterior shoulder instability from 1950 to 2010 in PubMed and Cochrane databases were reviewed. Results: A total of 107 studies were reviewed. Conclusion: Patients who have undergone at least 6 months of physical therapy and still experience instability symptoms should be considered for surgical stabilization directed at their underlying pathology. PMID:23016015

  11. Instabilities of flows and transition to turbulence

    CERN Document Server

    Sengupta, Tapan K

    2012-01-01

    Introduction to Instability and TransitionIntroductionWhat Is Instability?Temporal and Spatial InstabilitySome Instability MechanismsComputing Transitional and Turbulent FlowsFluid Dynamical EquationsSome Equilibrium Solutions of the Basic EquationBoundary Layer TheoryControl Volume Analysis of Boundary LayersNumerical Solution of the Thin Shear Layer (TSL) EquationLaminar Mixing LayerPlane Laminar JetIssues of Computing Space-Time Dependent FlowsWave Interaction: Group Velocity and Energy FluxIssues of Space-Time Scale Resolution of FlowsTemporal Scales in Turbulent FlowsComputing Time-Averag

  12. Size-effects on cavitation instabilities

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Tvergaard, Viggo

    2005-01-01

    In metal-ceramic systems the constraint on plastic flow leads to so high stress triaxialities that cavitation instabilities may occur. If the void radius is on the order of magnitude of a characteristic length for the metal, the rate of void growth is reduced, and the possibility of unstable cavity...... triaxiality, where cavitation instabilities are predicted by conventional plasticity theory, such instabilities are also found for the nonlocal theory, but the effects of gradient hardening delay the onset of the instability. Furthermore, in some cases the cavitation stress reaches a maximum and then decays...

  13. Review of two-phase instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Han Ok; Seo, Han Ok; Kang, Hyung Suk; Cho, Bong Hyun; Lee, Doo Jeong

    1997-06-01

    KAERI is carrying out a development of the design for a new type of integral reactors. The once-through helical steam generator is important design features. The study on designs and operating conditions which prevent flow instability should precede the introduction of one-through steam generator. Experiments are currently scheduled to understand two-phase instability, evaluate the effect of each design parameter on the critical point, and determine proper inlet throttling for the prevention of instability. This report covers general two-phase instability with review of existing studies on this topics. The general classification of two phase flow instability and the characteristics of each type of instability are first described. Special attention is paid to BWR core flow instability and once-through steam generator instability. The reactivity feedback and the effect of system parameters are treated mainly for BWR. With relation to once-through steam generators, the characteristics of convective heating and dryout point oscillation are first investigated and then the existing experimental studies are summarized. Finally chapter summarized the proposed correlations for instability boundary conditions. (author). 231 refs., 5 tabs., 47 figs

  14. Two-Beam Instability in Electron Cooling

    Energy Technology Data Exchange (ETDEWEB)

    Burov, Alexey V.; /Fermilab

    2006-04-01

    The drift motion of cooling electrons makes them able to respond to transverse perturbations of a cooled ion beam. This response may lead to dipole or quadrupole transverse instabilities at specific longitudinal wave numbers. While the dipole instabilities can be suppressed by a combination of the Landau damping, machine impedance, and the active damper, the quadrupole and higher order modes can lead to either emittance growth, or a lifetime degradation, or both. The growth rates of these instabilities are strongly determined by the machine x-y coupling. Thus, tuning out of the coupling resonance and/or reduction of the machine coupling can be an efficient remedy for these instabilities.

  15. Systems and methods for controlling flame instability

    KAUST Repository

    Cha, Min Suk

    2016-07-21

    A system (62) for controlling flame instability comprising: a nozzle (66) coupled to a fuel supply line (70), an insulation housing (74) coupled to the nozzle, a combustor (78) coupled to the nozzle via the insulation housing, where the combustor is grounded (80), a pressure sensor (82) coupled to the combustor and configured to detect pressure in the combustor, and an instability controlling assembly coupled to the pressure sensor and to an alternating current power supply (86), where, the instability controlling assembly can control flame instability of a flame in the system based on pressure detected by the pressure sensor.

  16. Combustion instability modeling and analysis

    Energy Technology Data Exchange (ETDEWEB)

    Santoro, R.J.; Yang, V.; Santavicca, D.A. [Pennsylvania State Univ., University Park, PA (United States)] [and others

    1995-10-01

    It is well known that the two key elements for achieving low emissions and high performance in a gas turbine combustor are to simultaneously establish (1) a lean combustion zone for maintaining low NO{sub x} emissions and (2) rapid mixing for good ignition and flame stability. However, these requirements, when coupled with the short combustor lengths used to limit the residence time for NO formation typical of advanced gas turbine combustors, can lead to problems regarding unburned hydrocarbons (UHC) and carbon monoxide (CO) emissions, as well as the occurrence of combustion instabilities. Clearly, the key to successful gas turbine development is based on understanding the effects of geometry and operating conditions on combustion instability, emissions (including UHC, CO and NO{sub x}) and performance. The concurrent development of suitable analytical and numerical models that are validated with experimental studies is important for achieving this objective. A major benefit of the present research will be to provide for the first time an experimentally verified model of emissions and performance of gas turbine combustors.

  17. Option price and market instability

    Science.gov (United States)

    Baaquie, Belal E.; Yu, Miao

    2017-04-01

    An option pricing formula, for which the price of an option depends on both the value of the underlying security as well as the velocity of the security, has been proposed in Baaquie and Yang (2014). The FX (foreign exchange) options price was empirically studied in Baaquie et al., (2014), and it was found that the model in general provides an excellent fit for all strike prices with a fixed model parameters-unlike the Black-Scholes option price Hull and White (1987) that requires the empirically determined implied volatility surface to fit the option data. The option price proposed in Baaquie and Cao Yang (2014) did not fit the data during the crisis of 2007-2008. We make a hypothesis that the failure of the option price to fit data is an indication of the market's large deviation from its near equilibrium behavior due to the market's instability. Furthermore, our indicator of market's instability is shown to be more accurate than the option's observed volatility. The market prices of the FX option for various currencies are studied in the light of our hypothesis.

  18. Manual testing for ankle instability.

    Science.gov (United States)

    Wilkin, Emily Jane; Hunt, Adrienne; Nightingale, Elizabeth Jean; Munn, Joanne; Kilbreath, Sharon Lynne; Refshauge, Kathryn Margaret

    2012-12-01

    To assess inter-rater reliability of ankle manual tests. We also correlated the manual tests with the Cumberland Ankle Instability Tool (CAIT). One ankle from each of 60 participants was assessed using four different manual tests (anterior drawer in supine and crook lying, talar tilt, inversion tilt). Three different raters, varying in experience, tested each participant. The CAIT questionnaire was also administered. The study received ethics approval from the University of Sydney Human Research Ethics Committee. Intraclass correlation coefficients (ICC), standard error of the mean (SEM) and percent close agreement (PCA) were used to determine reliability of the four tests. Pearson's correlation coefficients were used to determine relationships between the manual tests and CAIT scores. Inter-rater reliability for the four manual tests was poor regardless of therapist's experience (ICC([1,1]) -0.12 to 0.33; SEM 0.93-1.69). Correlations between the CAIT and manual tests were also low varying between r = -0.12 and -0.42. Inter-rater reliability was poor for manual tests of ankle stability. Reliability may be improved by using a grading scale with fewer intervals. The CAIT scores and manual tests correlated poorly, potentially reflecting the variety of conditions leading to ankle instability. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

  19. Adhesional instabilities and gecko locomotion

    Science.gov (United States)

    Williams, John A.

    2015-01-01

    Geckos possess a remarkable ability to run rapidly on both walls and ceilings and in recent years the mechanisms that underlie this facility have come under close scrutiny. It is now generally agreed that one of the principal mechanisms of adhesion relies on the action of van der Waal forces acting between the final extremely fine structure of the gecko toe and the underlying substrate. High speed video analysis shows that adhesive contact is both made and broken in intervals of less than 20 ms and this suggests that the mechanism of detachment is one of adhesive instability rather than steady-state peeling. By considering the gecko seta/spatula as a Euler-Bernoulli cantilever it is possible to model this instability in non-dimensional terms and thus to test the analysis at a much larger scale with more conventional engineering materials. When applied to the scale and material combination appropriate to a gecko spatula, the predicted critical load, of around 10 nN, is close to values that have been observed using and AFM cantilever and a single detached spatula.

  20. Hydrodynamic instability of meandering channels

    Science.gov (United States)

    Ali, Sk Zeeshan; Dey, Subhasish

    2017-12-01

    In this paper, we explore the hydrodynamic instability of meandering channels driven by the turbulent flow. The governing equations of channel dynamics with suitable boundary conditions are closed with the fluid and granular constitutive relationships. A regular expansion of the fundamental variables is employed to linearize the parent equations by superimposing the perturbations on the basic unperturbed flow. The channel dynamics reveal a resonance phenomenon which occurs when the key variables fall in the vicinity of the distinct critical values. The resonance phenomenon preserves its distinctive signature in different flow regimes which are guided by the characteristic values of the shear Reynolds number. The hydrodynamic analysis indicates that the fluid friction and the volumetric sediment flux play a decisive role to characterize the channel instability in different flow regimes. The growths of azimuthal velocity perturbation in phase with curvature, bed topography perturbation, bend amplification rate, and meander propagation speed in different flow regimes are investigated by varying the meander wavenumber, Shields number, channel aspect ratio, and relative roughness number. The analysis is capable to capture the effects of grain size on azimuthal velocity perturbation, bed topography perturbation, bend amplification rate, and meandering propagation speed over a wide range of shear Reynolds numbers. The variations of resonant wavenumbers in different flow regimes with the Shields number, channel aspect ratio, and relative roughness number are addressed. For a specific flow regime, the upstream and downstream migrations of meandering channels are typically governed by the Shields number, channel aspect ratio, and relative roughness number.

  1. Interface instability modes in freezing colloidal suspensions - revealed from onset of planar instability

    OpenAIRE

    Lilin Wang; Jiaxue You; Zhijun Wang; Jincheng Wang; Xin Lin

    2015-01-01

    Freezing colloidal suspensions widely exists in nature and industry. Interface instability has attracted much attention for the understandings of the pattern formation in freezing colloidal suspensions. However, the interface instability modes, the origin of the ice banding or ice lamellae, are still unclear. In-situ experimental observation of the onset of interface instability remains absent up to now. Here, by directly imaging the initial transient stage of planar interface instability in ...

  2. Instability of vortex pair leapfrogging

    DEFF Research Database (Denmark)

    Tophøj, Laust; Aref, Hassan

    2013-01-01

    Leapfrogging is a periodic solution of the four-vortex problem with two positive and two negative point vortices all of the same absolute circulation arranged as co-axial vortex pairs. The set of co-axial motions can be parameterized by the ratio 0 vortex pair sizes at the time when one...... pair passes through the other. Leapfrogging occurs for α > σ2, where is the silver ratio. The motion is known in full analytical detail since the 1877 thesis of Gröbli and a well known 1894 paper by Love. Acheson ["Instability of vortex leapfrogging," Eur. J. Phys.21, 269-273 (2000...... pairs fly off to infinity, and a "walkabout" mode, where the vortices depart from leapfrogging but still remain within a finite distance of one another. We show numerically that this transition is more gradual, a result that we relate to earlier investigations of chaotic scattering of vortex pairs [L...

  3. Instability Threshold “Hysteresis”

    Directory of Open Access Journals (Sweden)

    Agnes Muszynska

    1999-01-01

    Full Text Available The transient process which starts at the instability threshold of a rotor rotating in a fluid environment, and ends up in the limit cycle of self-excited vibrations known as fluid whirl or fluid whip, is discussed in this paper. A one-lateral-mode, isotropic, nonlinear model of the rotor with fluid interaction allows for exact particular solutions and an estimation of the transient process. The fluid interacting with the rotor is contained in a small radial clearance area, such as in bearings, seals, or rotor-to-stator clearances, and its effects are represented by fluid film radial stiffness, damping, and fluid inertia rotating at a different angular velocities.

  4. Instabilities in coaxial rotating jets

    Science.gov (United States)

    Ivanic, Tanja; Foucault, Eric; Pecheux, Jean; Gilard, Virginie

    2000-12-01

    The aim of this study is the characterization of the cylindrical mixing layer resulting from the interaction of two coaxial swirling jets. The experimental part of this study was performed in a cylindrical water tunnel, permitting an independent rotation of two coaxial jets. The rotations are generated by means of 2×36 blades localized in two swirling chambers. As expected, the evolution of the main instability modes presents certain differences compared to the plane-mixing-layer case. Experimental results obtained by tomography showed the existence of vortex rings and streamwise vortex pairs in the near field region. This method also permitted the observation of the evolution and interaction of different modes. PIV velocity measurements realized in the meridian plans and the plans perpendicular to the jet axis show that rotation distorts the typical top-hat axial velocity profile. The transition of the axial velocity profile from jet-like into wake-like is also observed.

  5. Plasma instabilities in high electric fields

    DEFF Research Database (Denmark)

    Morawetz, K.; Jauho, Antti-Pekka

    1994-01-01

    expression is derived for the nonequilibrium dielectric function epsilon(K, omega). For certain values of momenta K and frequency omega, Imepsilon(K, omega) becomes negative, implying a plasma instability. This new instability exists only for strong electric fields, underlining its nonequilibrium origin....

  6. Cultural diversity, economic development and societal instability.

    Science.gov (United States)

    Nettle, Daniel; Grace, James B; Choisy, Marc; Cornell, Howard V; Guégan, Jean-François; Hochberg, Michael E

    2007-09-26

    Social scientists have suggested that cultural diversity in a nation leads to societal instability. However, societal instability may be affected not only by within-nation or alpha diversity, but also diversity between a nation and its neighbours or beta diversity. It is also necessary to distinguish different domains of diversity, namely linguistic, ethnic and religious, and to distinguish between the direct effects of diversity on societal instability, and effects that are mediated by economic conditions. We assembled a large cross-national dataset with information on alpha and beta cultural diversity, economic conditions, and indices of societal instability. Structural equation modeling was used to evaluate the direct and indirect effects of cultural diversity on economics and societal stability. Results show that different types and domains of diversity have interacting effects. As previously documented, linguistic alpha diversity has a negative effect on economic performance, and we show that it is largely through this economic mechanism that it affects societal instability. For beta diversity, the higher the linguistic diversity among nations in a region, the less stable the nation. But, religious beta diversity has the opposite effect, reducing instability, particularly in the presence of high linguistic diversity. Within-nation linguistic diversity is associated with reduced economic performance, which, in turn, increases societal instability. Nations which differ linguistically from their neighbors are also less stable. However, religious diversity between neighboring nations has the opposite effect, decreasing societal instability.

  7. Recurrent Shoulder Instability After Primary Bankart Repair.

    Science.gov (United States)

    Donohue, Michael A; Mauntel, Timothy C; Dickens, Jonathan F

    2017-09-01

    The glenohumeral joint is one of the most frequently dislocated joints and occurs with increasing frequency in collision and contact athletes, especially those in sports that repeatedly place the glenohumeral joint in a position of vulnerability. Nonoperative management of shoulder instability especially in young contact athletes results in unacceptably high recurrence rates; thus, early surgical stabilization has become commonplace. Surgical stabilization typically yields acceptable outcomes. However, recurrent anterior instability may occur following a previous stabilization procedure at rates of 7% to 12%. Recurrent glenohumeral instability represents a treatment challenge for orthopedic surgeons as it not only has the potential to result in subsequent surgery, therapy, and missed activity time, but also has been associated with long-term degenerative joint changes. Thus, recurrent instability requires close examination to determine underlying pathology leading to failure. Evaluation of underlying pathology requires consideration of patient activity-related factors, hyperlaxity and multidirectional instability, glenoid bone loss, glenoid track lesions, and other pathologic lesions. Revision surgical stabilization approaches include arthroscopic and open stabilization, as well as glenoid osseous augmentation procedures. Postoperative rehabilitation and release to sports and activity must be tailored to protect the shoulder from continued instability. Understanding that risk of recurrent glenohumeral instability and the risk factors associated with it are essential so that these factors may be mitigated and recurrent instability prevented.

  8. Energetic particle instabilities in fusion plasmas

    NARCIS (Netherlands)

    Sharapov, S. E.; Alper, B.; Berk, H. L.; Borba, D. N.; Breizman, B. N.; Challis, C. D.; Classen, I.G.J.; Edlund, E. M.; Eriksson, J.; Fasoli, A.; Fredrickson, E. D.; Fu, G. Y.; M. García-Muñoz,; Gassner, T.; Ghantous, K.; Goloborodko, V.; Gorelenkov, N. N.; Gryaznevich, M. P.; Hacquin, S.; Heidbrink, W. W.; Hellesen, C.; Kiptily, V. G.; Kramer, G. J.; Lauber, P.; Lilley, M. K.; Lisak, M.; Nabais, F.; Nazikian, R.; Nyqvist, R.; Osakabe, M.; C. Perez von Thun,; Pinches, S. D.; Podesta, M.; Porkolab, M.; Shinohara, K.; Schoepf, K.; Todo, Y.; Toi, K.; VanZeeland, M. A.; Voitsekhovich, I.; White, R. B.; Yavorskij, V.; ITPA EP TG Contributors,; JET-EFDA Contributors,

    2013-01-01

    Remarkable progress has been made in diagnosing energetic particle instabilities on present-day machines and in establishing a theoretical framework for describing them. This overview describes the much improved diagnostics of Alfvén instabilities and modelling tools developed world-wide, and

  9. The short circuit instability in protoplanetary disks

    DEFF Research Database (Denmark)

    Hubbard, A.; McNally, C.P.; Mac Low, M.M.

    2013-01-01

    We introduce a magneto-hydrodynamic instability which occurs, among other locations, in the inner, hot regions of protoplanetary disks, and which alters the way in which resistive dissipation of magnetic energy into heat proceeds. This instability can be likened to both an electrical short circui...

  10. Instabilities and transition in boundary layers

    Indian Academy of Sciences (India)

    Abstract. Some recent developments in boundary layer instabilities and transition are reviewed. Background disturbance levels determine the instability mechanism that ulti- mately leads to turbulence. At low noise levels, the traditional Tollmien–Schlichting route is followed, while at high levels, a 'by-pass' route is more ...

  11. Gravitational Instability of Cylindrical Viscoelastic Medium ...

    Indian Academy of Sciences (India)

    field on the gravitational instability of strongly coupled plasma and observed that instability criterion gets modified due to the presence of non uniform magnetic field in transverse mode of wave propagation under both the kinetic and hydrodynamic limits, when the viscoelastic medium is infinitely electrically conducting.

  12. Genetically determined chromosome instability syndromes.

    Science.gov (United States)

    Schroeder, T M

    1982-01-01

    Spontaneously increased chromosomal instability is well documented in the three autosomal recessive diseases, Fanconi's anemia (FA), Bloom's syndrome (BS), and ataxia telangiectasia (AT). Other conditions have been reported to be associated with chromosomal breakage. Some are still single observations: in Werner's syndrome only fibroblasts are affected, and systemic sclerosis may not be an inherited disease. Various aspects of FA, BS, and AT are discussed which have emerged since recent reviews have been published. The differential diagnosis in FA has become more important than it was in the past. Proven heterogeneity in FA demands definition of what to name FA and FA variants. The analysis of cancer frequencies and types in FA and AT lacks important clues. This should stimulate all of us to mutual exchange of data and creation of registries not only of patients and follow-ups, but also of characterized cell strains. A synopsis of results from cell and cytogenetic studies demonstrates similarities and differences in detail of the general phenomenon of chromosomal instability which FA, BS, and AT share. Results from biochemical studies at the DNA level together with cytogenetic findings indicate different but still undefined failures in DNA metabolism or DNA repair mechanisms due to the different genes. A new approach to analyzing the impairment of DNA repair in FA is briefly described. DNA related enzymes are produced in the cytoplasm and have to be transported to the nucleus. The subcellular distribution of topoisomerase activity was found to be unusual in three placentas of FA patients. Other DNA enzymes were distributed normally. Thus, a specific mechanism for movement of the enzyme through the nuclear membrane seems to be defective.

  13. Surface instabilities during straining of anisotropic materials

    DEFF Research Database (Denmark)

    Legarth, Brian Nyvang; Richelsen, Ann Bettina

    2006-01-01

    The development of instabilities in traction-free surfaces is investigated numerically using a unit cell model. Full finite strain analyses are conducted using isotropic as well as anisotropic yield criteria and both plane strain tension and compression are considered. In the load range of tension...... of principal overall strain. For other orientations surface instabilities are seen when non-associated plastic flow is taken into account. Compared to tension, smaller compressive deformations are needed in order to initiate a surface instability....... investigated, it is found that isotropic plasticity can only predict surface instabilities if non-associated plastic flow is accounted for. However, for anisotropic plasticity a surface instability is observed for associated plastic flow if the principal axes of anisotropy coincide with the directions...

  14. Role of microsatellite instability in colon cancer

    Directory of Open Access Journals (Sweden)

    M. Yu. Fedyanin

    2012-01-01

    Full Text Available Coloncancer is among leading causes of cancer morbidity and mortality both inRussiaand worldwide. Development of molecular biology lead to decoding of carcinogenesis and tumor progression mechanisms. These processes require accumulation of genetic and epigenetic alterations in a tumor cell.Coloncancer carcinogenesis is characterized by mutations cumulation in genes controlling growth and differentiation of epithelial cells, which leads to their genetic instability. Microsatellite instability is a type of genetic instability characterized by deterioration of mismatch DNA repair. This leads to faster accumulation of mutations in DNA. Loss of mismatch repair mechanism can easily be diagnosed by length of DNA microsatellites. These alterations are termed microsatellite instability. They can be found both in hereditary and sporadic colon cancers. This review covers the questions of microsatellite instability, its prognostic and predictive value in colon cancer.

  15. Taming contact line instability for pattern formation

    Science.gov (United States)

    Deblais, A.; Harich, R.; Colin, A.; Kellay, H.

    2016-08-01

    Coating surfaces with different fluids is prone to instability producing inhomogeneous films and patterns. The contact line between the coating fluid and the surface to be coated is host to different instabilities, limiting the use of a variety of coating techniques. Here we take advantage of the instability of a receding contact line towards cusp and droplet formation to produce linear patterns of variable spacings. We stabilize the instability of the cusps towards droplet formation by using polymer solutions that inhibit this secondary instability and give rise to long slender cylindrical filaments. We vary the speed of deposition to change the spacing between these filaments. The combination of the two gives rise to linear patterns into which different colloidal particles can be embedded, long DNA molecules can be stretched and particles filtered by size. The technique is therefore suitable to prepare anisotropic structures with variable properties.

  16. Tensile Instability in a Thick Elastic Body

    Science.gov (United States)

    Overvelde, Johannes; Dykstra, David; de Rooij, Rijk; Bertoldi, Katia

    A range of instabilities can occur in soft bodies that undergo large deformation. While most of them arise under compressive forces, it has previously been shown analytically that a tensile instability can occur in an elastic block subjected to equitriaxial tension. Guided by this result, we conducted centimeter-scale experiments on thick elastomeric samples under generalized plane strain conditions and observed for the first time this elastic tensile instability. We found that equibiaxial stretching leads to the formation of a wavy pattern, as regions of the sample alternatively flatten and extend in the out-of-plane direction. Our work uncovers a new type of instability that can be triggered in elastic bodies, enlarging the design space for smart structures that harness instabilities to enhance their functionality.

  17. Plasma electron hole oscillatory velocity instability

    Science.gov (United States)

    Zhou, Chuteng; Hutchinson, Ian H.

    2017-10-01

    In this paper, we report a new type of instability of electron holes (EHs) interacting with passing ions. The nonlinear interaction of EHs and ions is investigated using a new theory of hole kinematics. It is shown that the oscillation in the velocity of the EH parallel to the magnetic field direction becomes unstable when the hole velocity in the ion frame is slower than a few times the cold ion sound speed. This instability leads to the emission of ion-acoustic waves from the solitary hole and decay in its magnitude. The instability mechanism can drive significant perturbations in the ion density. The instability threshold, oscillation frequency and instability growth rate derived from the theory yield quantitative agreement with the observations from a novel high-fidelity hole-tracking particle-in-cell code.

  18. Anterior Shoulder Instability in the Military Athlete.

    Science.gov (United States)

    Waterman, Brian; Owens, Brett D; Tokish, John M

    Given its young, predominately male demographics and intense physical demands, the US military remains an ideal cohort for the study of anterior shoulder instability. A literature search of PubMed, MEDLINE, and the Cochrane Database was performed to identify all peer-reviewed publications from 1950 to 2016 from US military orthopaedic surgeons focusing on the management of anterior shoulder instability. Clinical review. Level 4. The incidence of anterior shoulder instability events in the military occurs at an order of magnitude greater than in civilian populations, with rates as high as 3% per year among high-risk groups. With more than 90% risk of a Bankart lesion and high risk for instability recurrence, the military has advocated for early intervention of first-time shoulder instability while documenting up to 76% relative risk reduction versus nonoperative treatment. Preoperative evaluation with advanced radiographic imaging should be used to evaluate for attritional bone loss or "off-track" engaging defects to guide comprehensive surgical management. With complex recurrent shoulder instability and/or cases of clinically significant osseous lesions, potential options such as remplissage, anterior open capsular procedures, or bone augmentation procedures may be preferentially considered. Careful risk stratification, clinical evaluation, and selective surgical management for at-risk military patients with anterior shoulder instability can optimize the recurrence risk and functional outcome in this population.

  19. Serum Cartilage Biomarkers and Shoulder Instability.

    Science.gov (United States)

    Owens, Brett D; Cameron, Kenneth L; Bokshan, Steven L; Clifton, Kari B; Svoboda, Steven J; Wolf, Jennifer Moriatis

    2017-01-01

    Differences in cartilage biomarkers have been noted in patients with anterior cruciate ligament tears, but little is known about any similar relationship with shoulder instability. This study evaluated the relationship between serum cartilage biomarkers and shoulder instability. The authors present a prospective cohort study of young athletes followed from 2006 to 2010. A nested case-control analysis was conducted within this cohort to evaluate the association between preinjury collagen type II cleavage (a marker for type II collagen cleavage) and procollagen II carboxy propeptide (a marker of cartilage synthesis) and the subsequent likelihood of shoulder instability during the 4-year follow-up period. Preinjury collagen type II cleavage and procollagen II carboxy propeptide levels in 51 subjects who had shoulder instability were compared with levels in 210 subjects without documented anterior cruciate ligament or shoulder instability (control group) with commercially available enzyme-linked immunosorbent assay kits. Mean preinjury collagen type II cleavage levels in patients who subsequently had shoulder instability were significantly lower than those in the control group (73.91 vs 79.24 pg/mL, P=.03). No significant difference was found in preinjury procollagen II carboxy propeptide levels compared with the control group (359.94 vs 396.37, P=.24). This study is the first to examine the relationship between baseline collagen biomarkers and subsequent shoulder instability. The finding of lower baseline collagen type II cleavage levels in patients with subsequent shoulder instability may represent a genetic predisposition or a compensatory mechanism by which cartilage degradation is decreased in those who are more likely to have instability. [Orthopedics. 2017; 40(1):34-36.]. Copyright 2016, SLACK Incorporated.

  20. New instability strip for hot degenerates

    Energy Technology Data Exchange (ETDEWEB)

    Starrfield, S.G.; Cox, A.N.; Hodson, S.W.

    1980-01-01

    A new kind of variable star, designated as PG1159-035 is distinguished not only by the complete lack of hydrogen in its spectrum but also by an effective temperature that exceeds 8 x 10/sup 4/ K. The star does not fall near any of the known regions of instability in the HR diagram which suggests that the instability mechanism will not be helium and hydrogen ionization as in the Cepheid variables. The more unusual compositions are examined in order to discover the cause of the instability in PG1159-035. (GHT)

  1. Analyses of cavitation instabilities in ductile metals

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2007-01-01

    Cavitation instabilities have been predicted for a single void in a ductile metal stressed under high triaxiality conditions. In experiments for a ceramic reinforced by metal particles a single dominant void has been observed on the fracture surface of some of the metal particles bridging a crack...... for the influence of such size-effects on cavitation instabilities are presented. When a metal contains a distribution of micro voids, and the void spacing compared to void size is not extremely large, the surrounding voids may affect the occurrence of a cavitation instability at one of the voids. This has been...

  2. Two stream instabilities in degenerate quantum plasmas

    CERN Document Server

    Son, S

    2013-01-01

    The quantum mechanical effect on the plasma two-stream instability is studied based on the dielectric function approach. The analysis suggests that the degenerate plasma relevant to the inertial confinement fusion behaves differently from classical plasmas when the electron drift velocity is comparable to the Fermi velocity. For high wave vector comparable to the Fermi wave vector, the degenerate quantum plasma has larger regime of the two-stream instabilities than the classical plasma. A regime, where the plasma waves with the frequency larger than 1.5 times of the Langmuir wave frequency become unstable to the two-stream instabilities, is identified.

  3. Turing instability in reaction-subdiffusion systems.

    Science.gov (United States)

    Yadav, A; Milu, Shane M; Horsthemke, Werner

    2008-08-01

    We determine the conditions for the occurrence of Turing instabilities in activator-inhibitor systems, where one component undergoes subdiffusion and the other normal diffusion. If the subdiffusing species has a nonlinear death rate, then coupling between the nonlinear kinetics and the memory effects of the non-Markovian transport process advances the Turing instability if the inhibitor subdiffuses and delays the Turing instability if the activator subdiffuses. We apply the results of our analysis to the Schnakenberg model, the Gray-Scott model, the Oregonator model of the Belousov-Zhabotinsky reaction, and the Lengyel-Epstein model of the chlorine dioxide-iodine-malonic acid reaction.

  4. Careers in conditions of instability

    Directory of Open Access Journals (Sweden)

    Hohlova Valentina Vasil'evna

    2016-04-01

    Full Text Available The purpose of this work is the research of the social-economic phenomenon of a career as a result of conscious human position and behaviour in the field of employment, which is connected with job and professional growth, as a chain of events which are components of life, the sequence of professional activities and other biographical roles, which all together express the commitment of a person’s activity according to his generalized model of self-development. On the basis of the theoretical analysis the dependence of making a career in the condition of instability and indefiniteness on job market flexibility, erosion and even the destruction of the usual way of life and labor relations. The career concepts under the conditions of flexible capitalism and of career policy as the typology of empiric differences of job biographic models are considered. The peculiarity of the proposed career policy concept is that its individual alternatives of career making oppose to organization management and personal demands: the difference between a professional’s wishes and a specific strategy of the development phases are quite noticeable. According to the results of empiric research carried out through the methods of interview, polling, expert assessment, the analysis of the received results, the mathematical data processing the basic types of the career policy and its connection with the organization’s personal development are revealed.

  5. Parametric Instabilities of Electromagnetic Waves in Plasmas,

    Science.gov (United States)

    A simple formalism for the parametric decay of an intense, coherent electromagnetic wave into an electrostatic wave and scattered electromagnetic ... waves in a homogeneous plasma is developed. Various instabilities including Brillouin and Raman backscattering, Compton scattering, filamentation and

  6. Two-beam instability in electron cooling

    Directory of Open Access Journals (Sweden)

    A. Burov

    2006-12-01

    Full Text Available The drift motion of cooling electrons makes them able to respond to transverse perturbations of a cooled ion beam. This response may lead to dipole or quadrupole transverse instabilities at specific longitudinal wave numbers. While the dipole instabilities can be suppressed by a combination of the Landau damping, machine impedance, and the active damper, the quadrupole and higher order modes can lead to either emittance growth, or a lifetime degradation, or both. The growth rates of these instabilities are strongly determined by the machine x-y coupling. Thus, tuning out of the coupling resonance and/or reduction of the machine coupling can be an efficient remedy for these instabilities.

  7. Kelvin-Helmholtz instability in solar spicules

    Directory of Open Access Journals (Sweden)

    H Ebadi

    2016-12-01

    Full Text Available Magneto hydrodynamic waves, propagating along spicules, may become unstable and the expected instability is of Kelvin-Helmholtz type. Such instability can trigger the onset of wave turbulence leading to an effective plasma heating and particle acceleration. In present study, two-dimensional magneto hydrodynamic simulations performed on a Cartesian grid is presented in spicules with different densities, moving at various speeds depending on their environment. Simulations being applied in this study show the onset of Kelvin-Helmholtz type instability and transition to turbulent flow in spicules. Development of Kelvin-Helmholtz instability leads to momentum and energy transport, dissipation, and mixing of fluids. When magnetic fields are involved, field amplification is also possible to take place

  8. Cultural diversity, economic development and societal instability

    National Research Council Canada - National Science Library

    Nettle, Daniel; Grace, James B; Choisy, Marc; Cornell, Howard V; Guégan, Jean-François; Hochberg, Michael E

    2007-01-01

    ..., and effects that are mediated by economic conditions. We assembled a large cross-national dataset with information on alpha and beta cultural diversity, economic conditions, and indices of societal instability...

  9. Overview of Rayleigh-Taylor instability

    Energy Technology Data Exchange (ETDEWEB)

    Sharp, D.H.

    1983-01-01

    The aim of this talk is to survey Rayleigh-Taylor instability, describing the phenomenology that occurs at a Taylor unstable interface, and reviewing attempts to understand these phenomena quantitatively.

  10. Stepper motor instabilities in an aerospace application

    Science.gov (United States)

    Kackley, Russell; Mccully, Sean

    1992-01-01

    Stepper motors are frequently used in positioning mechanisms because they have several advantages over ordinary DC motors. However, there is frequently no feedback loop and the motor may exhibit instabilities under some conditions. A stepper motor in an aerospace positioning mechanism was investigated. During testing, the motor exhibited unstable behavior, such as backrunning and forward running. The instability was dependent on voltage pulse characteristics, temperature, positioning angle, step rate, and interaction between the two motors in the system. Both testing and analysis results verified the instability. A special purpose FORTRAN code was written to simulate the system. This code was combined with another simpler code to show the performance of the system in the phase plane so that instability boundaries could be displayed along with the motor performance. The analysis was performed to verify that proposed modifications would produce stable performance before implementation in the hardware. Subsequent testing verified the analytic stability predictions.

  11. Single-mode coherent synchrotron radiation instability

    Directory of Open Access Journals (Sweden)

    S. Heifets

    2003-06-01

    Full Text Available The microwave instability driven by the coherent synchrotron radiation (CSR has been previously studied [S. Heifets and G. V. Stupakov, Phys. Rev. ST Accel. Beams 5, 054402 (2002] neglecting effect of the shielding caused by the finite beam pipe aperture. In practice, the unstable mode can be close to the shielding threshold where the spectrum of the radiation in a toroidal beam pipe is discrete. In this paper, the CSR instability is studied in the case when it is driven by a single synchronous mode. A system of equations for the beam-wave interaction is derived and its similarity to the 1D free-electron laser theory is demonstrated. In the linear regime, the growth rate of the instability is obtained and a transition to the case of continuous spectrum is discussed. The nonlinear evolution of the single-mode instability, both with and without synchrotron damping and quantum diffusion, is also studied.

  12. Anisotropic instability of a stretching film

    Science.gov (United States)

    Xu, Bingrui; Li, Minhao; Deng, Daosheng

    2017-11-01

    Instability of a thin liquid film, such as dewetting arising from Van der Waals force, has been well studied, and is typically characterized by formation of many droplets. Interestingly, a thin liquid film subjected to an applied stretching during a process of thermal drawing is evolved into an array of filaments, i.e., continuity is preserved along the direction of stretching while breakup occurs exclusively in the plane of cross section. Here, to understand this anisotropic instability, we build a physical model by considering both Van der Waals force and the effect of stretching. By using the linear instability analysis method and then performing a numerical calculation, we find that the growth rate of perturbations at the cross section is larger than that along the direction of stretching, resulting in the anisotropic instability of the stretching film. These results may provide theoretical guidance to achieve more diverse structures for nanotechnology.

  13. [Cervical spine instability in the surgical patient].

    Science.gov (United States)

    Barbeito, A; Guerri-Guttenberg, R A

    2014-03-01

    Many congenital and acquired diseases, including trauma, may result in cervical spine instability. Given that airway management is closely related to the movement of the cervical spine, it is important that the anesthesiologist has detailed knowledge of the anatomy, the mechanisms of cervical spine instability, and of the effects that the different airway maneuvers have on the cervical spine. We first review the normal anatomy and biomechanics of the cervical spine in the context of airway management and the concept of cervical spine instability. In the second part, we review the protocols for the management of cervical spine instability in trauma victims and some of the airway management options for these patients. Copyright © 2013 Sociedad Española de Anestesiología, Reanimación y Terapéutica del Dolor. All rights reserved.

  14. Mirror Instability in the Turbulent Solar Wind

    Czech Academy of Sciences Publication Activity Database

    Hellinger, Petr; Landi, S.; Matteini, L.; Verdini, A.; Franci, L.

    2017-01-01

    Roč. 838, č. 2 (2017), 158/1-158/7 ISSN 0004-637X Institutional support: RVO:67985815 Keywords : instabilities * solar wind * waves Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 5.533, year: 2016

  15. On viscoelastic instability in polymeric filaments

    DEFF Research Database (Denmark)

    Rasmussen, Henrik Koblitz; Hassager, Ole

    1999-01-01

    The 3D Lagrangian Integral Method is used to simulate the effects of surface tension on the viscoelastic end-plate instability, occuring in the rapid extension of some polymeric filaments between parallel plates. It is shovn that the surface tension delays the onset of the instability. Furthermore...... it is demonstrated that surface tension plays a key role in the selection of the most unstable mode...

  16. Systematics of shoulder instability; Systematik der Schulterinstabilitaet

    Energy Technology Data Exchange (ETDEWEB)

    Kreitner, K.F.; Maehringer-Kunz, A. [Johannes-Gutenberg-Universitaet Mainz, Klinik und Poliklinik fuer Diagnostische und Interventionelle Radiologie, Mainz (Germany)

    2015-03-01

    Shoulder instability is defined as a symptomatic abnormal motion of the humeral head relative to the glenoid during active shoulder motion. Glenohumeral instabilities are classified according to the causative factors as the pathogenesis of instability plays an important role with respect to treatment options. Instabilities are classified into traumatic and atraumatic instabilities as part of a multidirectional instability syndrome and into microtraumatic instabilities. For diagnostics plain radiographs (''trauma series'') are performed to document shoulder dislocation and its successful repositioning. Direct magnetic resonance (MR) arthrography is the most important imaging modality for delineation of the different injury patterns of the labral-ligamentous complex and bony structures. Monocontrast computed tomography (CT) arthrography with the use of multidetector CT scanners represents an alternative imaging modality; however, MR imaging should be preferred in the work-up of shoulder instabilities due to the mostly younger age of patients. (orig.) [German] Unter einer Schulterinstabilitaet versteht man jede zu Beschwerden fuehrende Translation des Humeruskopfs in Relation zur Gelenkpfanne waehrend einer aktiven Bewegung der Schulter. Glenohumerale Instabilitaeten werden heute nach ihrer Aetiologie eingeteilt, da bei der Wahl der Therapie der Entstehungsmechanismus der Instabilitaet eine wichtige Rolle spielt. Danach unterscheidet man primaer traumatisch von atraumatisch entstandenen Instabilitaeten sowie Mikroinstabilitaeten. Bei der Diagnostik dienen konventionelle Roentgenuebersichtsaufnahmen nur noch zur Dokumentation einer Luxation und zur Beurteilung der Reposition. Die durch eine Instabilitaet hervorgerufenen Verletzungsfolgen am labroligamentaeren Komplex und den knoechernen Strukturen werden heute bevorzugt mit der direkten MR-Arthrographie dargestellt. Hierbei koennen unterschiedliche Verletzungsmuster dargestellt werden. Nach

  17. Elastic flow instability in nanotube suspensions.

    Science.gov (United States)

    Lin-Gibson, S; Pathak, J A; Grulke, E A; Wang, H; Hobbie, E K

    2004-01-30

    We report an elastic instability associated with flow-induced clustering in semidilute non-Brownian colloidal nanotubes. Rheo-optical measurements are compared with simulations of mechanical flocculation in sheared fiber suspensions, and the evolving structure is characterized as a function of confinement and shear stress. The transient rheology is correlated with the evolution of highly elastic vorticity-aligned aggregates, with the underlying instability being somewhat ubiquitous in complex fluids.

  18. Beam Instabilities in Circular Particle Accelerators

    CERN Document Server

    AUTHOR|(CDS)2067185

    2017-01-01

    The theory of impedance-induced bunched-beam coherent instabilities is reviewed following Laclare's formalism, adding the effect of an electronic damper in the transverse plane. Both single-bunch and coupled-bunch instabilities are discussed, both low-intensity and high-intensity regimes are analysed, both longitudinal and transverse planes are studied, and both short-bunch and long-bunch regimes are considered. Observables and mitigation measures are also examined.

  19. Computational methods for probability of instability calculations

    Science.gov (United States)

    Wu, Y.-T.; Burnside, O. H.

    1990-01-01

    This paper summarizes the development of the methods and a computer program to compute the probability of instability of a dynamic system than can be represented by a system of second-order ordinary linear differential equations. Two instability criteria based upon the roots of the characteristics equation or Routh-Hurwitz test functions are investigated. Computational methods based on system reliability analysis methods and importance sampling concepts are proposed to perform efficient probabilistic analysis. Numerical examples are provided to demonstrate the methods.

  20. Topographic-driven instabilities in terrestrial bodies

    Science.gov (United States)

    Vantieghem, S.; Cebron, D.; Herreman, W.; Lacaze, L.

    2013-12-01

    Models of internal planetary fluid layers (core flows, subsurface oceans) commonly assume that these fluid envelopes have a spherical shape. This approximation however entails a serious restriction from the fluid dynamics point of view. Indeed, in the presence of mechanical forcings (precession, libration, nutation or tides) due to gravitational interaction with orbiting partners, boundary topography (e.g. of the core-mantle boundary) may excite flow instabilities and space-filling turbulence. These phenomena may affect heat transport and dissipation at the main order. Here, we focus on instabilities driven by longitudinal libration. Using a suite of theoretical tools and numerical simulations, we are able to discern a parameter range for which instability may be excited. We thereby consider deformations of different azimuthal order. This study gives the first numerical evidence of the tripolar instability. Furthermore, we explore the non-linear regime and investigate the amplitude as well as the dissipation of the saturated instability. Indeed, these two quantities control the torques on the solid layers and the thermal transport. Furthermore, based on this results, we address the issue of magnetic field generation associated with these flows (by induction or by dynamo process). This instability mechanism applies to both synchronized as non-synchronized bodies. As such, our results show that a tripolar instability might be present in various terrestrial bodies (Early Moon, Gallilean moons, asteroids, etc.), where it could participate in dynamo action. Simulation of a libration-driven tripolar instability in a deformed spherical fluid layer: snapshot of the velocity magnitude, where a complex 3D flow pattern is established.

  1. Energetic particle instabilities in fusion plasmas

    Science.gov (United States)

    Sharapov, S. E.; Alper, B.; Berk, H. L.; Borba, D. N.; Breizman, B. N.; Challis, C. D.; Classen, I. G. J.; Edlund, E. M.; Eriksson, J.; Fasoli, A.; Fredrickson, E. D.; Fu, G. Y.; Garcia-Munoz, M.; Gassner, T.; Ghantous, K.; Goloborodko, V.; Gorelenkov, N. N.; Gryaznevich, M. P.; Hacquin, S.; Heidbrink, W. W.; Hellesen, C.; Kiptily, V. G.; Kramer, G. J.; Lauber, P.; Lilley, M. K.; Lisak, M.; Nabais, F.; Nazikian, R.; Nyqvist, R.; Osakabe, M.; Perez von Thun, C.; Pinches, S. D.; Podesta, M.; Porkolab, M.; Shinohara, K.; Schoepf, K.; Todo, Y.; Toi, K.; Van Zeeland, M. A.; Voitsekhovich, I.; White, R. B.; Yavorskij, V.; TG, ITPA EP; Contributors, JET-EFDA

    2013-10-01

    Remarkable progress has been made in diagnosing energetic particle instabilities on present-day machines and in establishing a theoretical framework for describing them. This overview describes the much improved diagnostics of Alfvén instabilities and modelling tools developed world-wide, and discusses progress in interpreting the observed phenomena. A multi-machine comparison is presented giving information on the performance of both diagnostics and modelling tools for different plasma conditions outlining expectations for ITER based on our present knowledge.

  2. Arthroscopic Findings in Anterior Shoulder Instability

    OpenAIRE

    Hantes, Michael; Raoulis, Vasilios

    2017-01-01

    Background: In the last years, basic research and arthroscopic surgery, have improved our understanding of shoulder anatomy and pathology. It is a fact that arthroscopic treatment of shoulder instability has evolved considerably over the past decades. The aim of this paper is to present the variety of pathologies that should be identified and treated during shoulder arthroscopy when dealing with anterior shoulder instability cases. Methods: A review of the current literature regarding arthros...

  3. Energetic particle instabilities in fusion plasmas

    CERN Document Server

    Sharapov, S E; Berk, H L; Borba, D N; Breizman, B N; Challis, C D; Classen, I G J; Edlund, E M; Eriksson, J; Fasoli, A; Fredrickson, E D; Fu, G Y; Garcia-Munoz, M; Gassner, T; Ghantous, K; Goloborodko, V; Gorelenkov, N N; Gryaznevich, M P; Hacquin, S; Heidbrink, W W; Hellesen, C; Kiptily, V G; Kramer, G J; Lauber, P; Lilley, M K; Lisak, M; Nabais, F; Nazikian, R; Nyqvist, R; Osakabe, M; von Thun, C Perez; Pinches, S D; Podesta, M; Porkolab, M; Shinohara, K; Schoepf, K; Todo, Y; Toi, K; Van Zeeland, M A; Voitsekhovich, I; White, R B; Yavorskij, V; TG, ITPA EP; Contributors, JET-EFDA

    2013-01-01

    Remarkable progress has been made in diagnosing energetic particle instabilities on present-day machines and in establishing a theoretical framework for describing them. This overview describes the much improved diagnostics of Alfven instabilities and modelling tools developed world-wide, and discusses progress in interpreting the observed phenomena. A multi-machine comparison is presented giving information on the performance of both diagnostics and modelling tools for different plasma conditions outlining expectations for ITER based on our present knowledge.

  4. Studies of elastic-plastic instabilities

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    1999-01-01

    Analyses of plastic instabilities are reviewed, with focus on results in structural mechanics as well as continuum mechanics. First the basic theories for bifurcation and post-bifurcation behavior are briefly presented. Then, localization of plastic flow is discussed, including shear band formation...... in solids, localized necking in biaxially stretched metal sheets, and the analogous phenomenon of buckling localization in structures. Also some recent results for cavitation instabilities in elastic-plastic solids are reviewed....

  5. Gigayear Instabilities in Planetary Systems

    Science.gov (United States)

    Fabrycky, Daniel

    One of the biggest modern discoveries about the Solar System is that it is chaotic (Laskar 1989, 1994). On million-year timescales, nearby trajectories exponentially diverge; on billion-year timescales, planets can develop large eccentricities and even collide. This is possible because our planets interact with enough energy and with the right (secular) timescales. This has the potential to put the planet Mercury on an unstable orbit in the future, before the Sun exhausts its fuel. Currently, as a standard step in the analysis, exoplanet observing teams check whether the planetary systems they are discovering are stable. This usually involves a few-Megayear numerical integration, and the system usually passes that test. However, the signatures of continuing instability have not been looked for in the exoplanet population, nor has its implications for planetary formation and evolution been fully recognized. We will study several specific evolutionary scenarios in which instability may manifest only on gigayear timescales, i.e. midway through the lives of the host stars. This is relevant to the solicitation in that it characterizes the dynamics of exoplanetary systems. In the first project, we will compare N-body, numerically-calculated secular, and Fourier-expansion secular theories to determine what essential ingredients go into the conclusion that a general planetary system is chaotic. We will apply these tools to specific realizations of Kepler-discovered close-in planetary systems consisting of three or more Neptunes or super-Earths, which is the most populous known exoplanet population. We will thus find the common ailments afflicting middle-age planetary systems. In the second project, we will consider how planets might get stranded in their Kuiper and Oort clouds during early system evolution, only to destabilize the inner system later on. Various investigators have wondered whether the Solar System is accompanied by a massive planetary companion, including a

  6. Interface instability modes in freezing colloidal suspensions: revealed from onset of planar instability

    National Research Council Canada - National Science Library

    Wang, Lilin; You, Jiaxue; Wang, Zhijun; Wang, Jincheng; Lin, Xin

    2016-01-01

    Freezing colloidal suspensions widely exists in nature and industry. Interface instability has attracted much attention for the understandings of the pattern formation in freezing colloidal suspensions...

  7. [Capsular retensioning in anterior unidirectional glenohumeral instability].

    Science.gov (United States)

    Benítez Pozos, Leonel; Martínez Molina, Oscar; Castañeda Landa, Ezequiel

    2007-01-01

    To present the experience of the Orthopedics Service PEMEX South Central Hospital in the management of anterior unidirectional shoulder instability with an arthroscopic technique consisting of capsular retensioning either combined with other anatomical repair procedures or alone. Thirty-one patients with anterior unidirectional shoulder instability operated-on between January 1999 and December 2005 were included. Fourteen patients underwent capsular retensioning and radiofrequency, and in 17 patients, capsular retensioning was combined with suture anchors. Patients with a history of relapsing glenohumeral dislocations and subluxations, with anterior instability with or without associated Bankart lesions were selected; all of them were young. The results were assessed considering basically the occurrence of instability during the postoperative follow-up. No cases of recurring instability occurred. Two cases had neuroma and one experienced irritation of the suture site. Six patients had residual limitation of combined lateral rotation and abduction movements, of a mean of 10 degrees compared with the healthy contralateral side. The most frequent incident was the leak of solutions to the soft tissues. Capsular retensioning, whether combined or not with other anatomical repair techniques, has proven to result in a highly satisfactory rate of glenohumeral stabilization in cases of anterior unidirectional instabilities. The arthroscopic approach offers the well-known advantages of causing less damage to the soft tissues, and a shorter time to starting rehabilitation therapy and exercises.

  8. Instabilities in Interacting Binary Stars

    Science.gov (United States)

    Andronov, I. L.; Andrych, K. D.; Antoniuk, K. A.; Baklanov, A. V.; Beringer, P.; Breus, V. V.; Burwitz, V.; Chinarova, L. L.; Chochol, D.; Cook, L. M.; Cook, M.; Dubovský, P.; Godlowski, W.; Hegedüs, T.; Hoňková, K.; Hric, L.; Jeon, Y.-B.; Juryšek, J.; Kim, C.-H.; Kim, Y.; Kim, Y.-H.; Kolesnikov, S. V.; Kudashkina, L. S.; Kusakin, A. V.; Marsakova, V. I.; Mason, P. A.; Mašek, M.; Mishevskiy, N.; Nelson, R. H.; Oksanen, A.; Parimucha, S.; Park, J.-W.; Petrík, K.; Quiñones, C.; Reinsch, K.; Robertson, J. W.; Sergey, I. M.; Szpanko, M.; Tkachenko, M. G.; Tkachuk, L. G.; Traulsen, I.; Tremko, J.; Tsehmeystrenko, V. S.; Yoon, J.-N.; Zola, S.; Shakhovskoy, N. M.

    2017-07-01

    The types of instability in the interacting binary stars are briefly reviewed. The project “Inter-Longitude Astronomy” is a series of smaller projects on concrete stars or groups of stars. It has no special funds, and is supported from resources and grants of participating organizations, when informal working groups are created. This “ILA” project is in some kind similar and complementary to other projects like WET, CBA, UkrVO, VSOLJ, BRNO, MEDUZA, AstroStatistics, where many of us collaborate. Totally we studied 1900+ variable stars of different types, including newly discovered variables. The characteristic timescale is from seconds to decades and (extrapolating) even more. The monitoring of the first star of our sample AM Her was initiated by Prof. V.P. Tsesevich (1907-1983). Since more than 358 ADS papers were published. In this short review, we present some highlights of our photometric and photo-polarimetric monitoring and mathematical modeling of interacting binary stars of different types: classical (AM Her, QQ Vul, V808 Aur = CSS 081231:071126+440405, FL Cet), asynchronous (BY Cam, V1432 Aql), intermediate (V405 Aql, BG CMi, MU Cam, V1343 Her, FO Aqr, AO Psc, RXJ 2123, 2133, 0636, 0704) polars and magnetic dwarf novae (DO Dra) with 25 timescales corresponding to different physical mechanisms and their combinations (part “Polar”); negative and positive superhumpers in nova-like (TT Ari, MV Lyr, V603 Aql, V795 Her) and many dwarf novae stars (“Superhumper”); eclipsing “non-magnetic” cataclysmic variables(BH Lyn, DW UMa, EM Cyg; PX And); symbiotic systems (“Symbiosis”); super-soft sources (SSS, QR And); spotted (and not spotted) eclipsing variables with (and without) evidence for a current mass transfer (“Eclipser”) with a special emphasis on systems with a direct impact of the stream into the gainer star's atmosphere, which we propose to call “Impactor” (short from “Extreme Direct Impactor”), or V361 Lyr-type stars. Other

  9. Measurement properties of the Western Ontario Shoulder Instability Index in Dutch patients with shoulder instability

    NARCIS (Netherlands)

    van der Linde, J.A.; Willems, W.J.; van Kampen, D.A.; van Beers, L.W.A.H.; van Deurzen, D.F.P.; Terwee, C.B.

    2014-01-01

    Background: The Western Ontario Shoulder Instability index (WOSI) is a patient-reported outcome measure for patients with shoulder instability. The purpose of this study was to validate the WOSI in a Dutch population by evaluating its structural validity, internal consistency, measurement error,

  10. The temporal interplay of self-esteem instability and affective instability in borderline personality disorder patients' everyday lives.

    Science.gov (United States)

    Santangelo, Philip S; Reinhard, Iris; Koudela-Hamila, Susanne; Bohus, Martin; Holtmann, Jana; Eid, Michael; Ebner-Priemer, Ulrich W

    2017-11-01

    Borderline personality disorder (BPD) is defined by a pervasive pattern of instability. Although there is ample empirical evidence that unstable self-esteem is associated with a myriad of BPD-like symptoms, self-esteem instability and its temporal dynamics have received little empirical attention in patients with BPD. Even worse, the temporal interplay of affective instability and self-esteem instability has been neglected completely, although it has been hypothesized recently that the lack of specificity of affective instability in association with BPD might be explained by the highly intertwined temporal relationship between affective and self-esteem instability. To investigate self-esteem instability, its temporal interplay with affective instability, and its association with psychopathology, 60 patients with BPD and 60 healthy controls (HCs) completed electronic diaries for 4 consecutive days during their everyday lives. Participants reported their current self-esteem, valence, and tense arousal levels 12 times a day in approximately one-hr intervals. We used multiple state-of-the-art statistical techniques and graphical approaches to reveal patterns of instability, clarify group differences, and examine the temporal interplay of self-esteem instability and affective instability. As hypothesized, instability in both self-esteem and affect was clearly elevated in the patients with BPD. In addition, self-esteem instability and affective instability were highly correlated. Both types of instability were related to general psychopathology. Because self-esteem instability could not fully explain affective instability and vice versa and neither affective instability nor self-esteem instability was able to explain psychopathology completely, our findings suggest that these types of instability represent unique facets of BPD. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  11. Active Suppression of Instabilities in Engine Combustors

    Science.gov (United States)

    Kopasakis, George

    2004-01-01

    A method of feedback control has been proposed as a means of suppressing thermo-acoustic instabilities in a liquid- fueled combustor of a type used in an aircraft engine. The basic principle of the method is one of (1) sensing combustor pressure oscillations associated with instabilities and (2) modulating the rate of flow of fuel to the combustor with a control phase that is chosen adaptively so that the pressure oscillations caused by the modulation oppose the sensed pressure oscillations. The need for this method arises because of the planned introduction of advanced, lean-burning aircraft gas turbine engines, which promise to operate with higher efficiencies and to emit smaller quantities of nitrogen oxides, relative to those of present aircraft engines. Unfortunately, the advanced engines are more susceptible to thermoacoustic instabilities. These instabilities are hard to control because they include large dead-time phase shifts, wide-band noise characterized by amplitudes that are large relative to those of the instabilities, exponential growth of the instabilities, random net phase walks, and amplitude fluctuations. In this method (see figure), the output of a combustion-pressure sensor would be wide-band-pass filtered and then further processed to generate a control signal that would be applied to a fast-actuation valve to modulate the flow of fuel. Initially, the controller would rapidly take large phase steps in order to home in, within a fraction of a second, to a favorable phase region within which the instability would be reduced. Then the controller would restrict itself to operate within this phase region and would further restrict itself to operate within a region of stability, as long as the power in the instability signal was decreasing. In the phase-shifting scheme of this method, the phase of the control vector would be made to continuously bounce back and forth from one boundary of an effective stability region to the other. Computationally

  12. Inertioelastic Flow Instability at a Stagnation Point

    Science.gov (United States)

    Burshtein, Noa; Zografos, Konstantinos; Shen, Amy Q.; Poole, Robert J.; Haward, Simon J.

    2017-10-01

    A number of important industrial applications exploit the ability of small quantities of high molecular weight polymer to suppress instabilities that arise in the equivalent flow of Newtonian fluids, a particular example being turbulent drag reduction. However, it can be extremely difficult to probe exactly how the polymer acts to, e.g., modify the streamwise near-wall eddies in a fully turbulent flow. Using a novel cross-slot flow configuration, we exploit a flow instability in order to create and study a single steady-state streamwise vortex. By quantitative experiment, we show how the addition of small quantities (parts per million) of a flexible polymer to a Newtonian solvent dramatically affects both the onset conditions for this instability and the subsequent growth of the axial vorticity. Complementary numerical simulations with a finitely extensible nonlinear elastic dumbbell model show that these modifications are due to the growth of polymeric stress within specific regions of the flow domain. Our data fill a significant gap in the literature between the previously reported purely inertial and purely elastic flow regimes and provide a link between the two by showing how the instability mode is transformed as the fluid elasticity is varied. Our results and novel methods are relevant to understanding the mechanisms underlying industrial uses of weakly elastic fluids and also to understanding inertioelastic instabilities in more confined flows through channels with intersections and stagnation points.

  13. Bilateral, atraumatic, proximal tibiofibular joint instability.

    Science.gov (United States)

    Morrison, Troy D; Shaer, James A; Little, Jill E

    2011-01-01

    Dislocation of the tibiofibular joint is rare and usually results from a traumatic event. Only 1 case of atraumatic proximal tibiofibular joint instability in a 14-year-old girl has been reported in the literature, however this condition might occur more frequently than once thought. A wide range of treatment options exist for tibiofibular dislocations. Currently, the first choice is a conservative approach, and when this fails, surgical means such as resection of the fibula head, arthrodesis, and reconstruction are considered. However, no consensus exists on the most effective treatment. This article reports a unique case of bilateral, atraumatic, proximal tibia and fibular joint instability involving a 30-year-old man with a 20-year history of pain and laxity in the right knee. The patient had no trauma to his knees; he reported 2 immediate family members with similar complaints, which suggests that this case is likely congenital. After conservative approaches proved to be ineffective, the patient underwent capsular reconstruction using free autologous gracilis tendon. At 6-month postoperative follow-up, the patient was pain free with no locking and instability. He then underwent surgery on the left knee. At 1-year follow-up after the second surgery, the patient had no symptoms or restrictions in mobility. We provide an alternative surgical approach to arthrodesis and resection for the treatment of chronic proximal tibiofibular instability. In the treatment of chronic tibiofibular instability, we believe that reconstruction of the tibiofibular joint is a safe and effective choice. Copyright 2011, SLACK Incorporated.

  14. Inertioelastic Flow Instability at a Stagnation Point

    Directory of Open Access Journals (Sweden)

    Noa Burshtein

    2017-11-01

    Full Text Available A number of important industrial applications exploit the ability of small quantities of high molecular weight polymer to suppress instabilities that arise in the equivalent flow of Newtonian fluids, a particular example being turbulent drag reduction. However, it can be extremely difficult to probe exactly how the polymer acts to, e.g., modify the streamwise near-wall eddies in a fully turbulent flow. Using a novel cross-slot flow configuration, we exploit a flow instability in order to create and study a single steady-state streamwise vortex. By quantitative experiment, we show how the addition of small quantities (parts per million of a flexible polymer to a Newtonian solvent dramatically affects both the onset conditions for this instability and the subsequent growth of the axial vorticity. Complementary numerical simulations with a finitely extensible nonlinear elastic dumbbell model show that these modifications are due to the growth of polymeric stress within specific regions of the flow domain. Our data fill a significant gap in the literature between the previously reported purely inertial and purely elastic flow regimes and provide a link between the two by showing how the instability mode is transformed as the fluid elasticity is varied. Our results and novel methods are relevant to understanding the mechanisms underlying industrial uses of weakly elastic fluids and also to understanding inertioelastic instabilities in more confined flows through channels with intersections and stagnation points.

  15. Transverse mode coupling instability of colliding beams

    Directory of Open Access Journals (Sweden)

    S. White

    2014-04-01

    Full Text Available In high brightness circular colliders, coherent and incoherent beam dynamics are dominated by beam-beam interactions. It is generally assumed that the incoherent tune spread introduced by the beam-beam interactions is sufficiently large to cure any instabilities originating from impedance. However, as the two counterrotating beams interact they can give rise to coherent dipole modes and therefore modify the coherent beam dynamics and stability conditions. In this case, coherent beam-beam effects and impedance cannot be treated independently and their interplay should be taken into account in any realistic attempt to study the beam stability of colliding beams. Due to the complexity of these physics processes, numerical simulations become an important tool for the analysis of this system. Two approaches are proposed in this paper: a fully self-consistent multiparticle tracking including particle-in-cell Poisson solver for the beam-beam interactions and a linearized model taking into account finite bunch length effects. To ensure the validity of the results a detailed benchmarking of these models was performed. It will be shown that under certain conditions coherent beam-beam dipole modes can couple with higher order headtail modes and lead to strong instabilities with characteristics similar to the classical transverse mode coupling instability originating from impedance alone. Possible cures for this instability are explored both for single bunch and multibunch interactions. Simulation results and experimental evidences of the existence of this instability at the LHC will be presented for the specific case of offset collisions.

  16. Microsatellite Instability Markers Status in Colorectal Cancer

    Directory of Open Access Journals (Sweden)

    Giti Esmailnia

    2014-12-01

    Full Text Available Background: Colorectal cancer (CRC is the third most prevalent and the third leading cause of cancer-related deaths in Iran. Our aim was to investigate five mononucleotide statuses among Iranian patients with sporadic colorectal cancer. Materials and Methods: In this experimental study 80 sporadic CRC patients were evaluated for microsatellite instability (MSI. The pentaplex panel including 5 quasi mononucleotide microsatellite markers (NR-21, BAT-26, BAT-25, NR-27 and NR-24 was used. The MSI analysis was performed on paired tumoral DNA from cancerous tissues and genomic DNA from whole blood. MSI carriers were identified by analysis of tumor tissue using polymerase chain reaction. Results: Our findings showed that microsatellite instability was detected in 36 of 80 cases (45% with colorectal cancer. MSI analysis revealed that 17 cases of MSI-H (21%, 19 MSI-L (23% and 44 microsatellite stable tumors (55%. Instability is observed in the tumoral DNA compared to the DNA from the normal DNA sample. The most instable markers were NR-21, NR-24 in which instability was detected in 45% of patients. Conclusion: Using a panel including 3 mentioned MSI markers should be more promising markers for identifying MSI status in patients with sporadic colorectal cancer.

  17. Tidal instability in exoplanetary systems evolution

    Directory of Open Access Journals (Sweden)

    Le Gal P.

    2011-02-01

    Full Text Available A new element is proposed to play a role in the evolution of extrasolar planetary systems: the tidal (or elliptical instability. It comes from a parametric resonance and takes place in any rotating fluid whose streamlines are (even slightly elliptically deformed. Based on theoretical, experimental and numerical works, we estimate the growth rate of the instability for hot-jupiter systems, when the rotation period of the star is known. We present the physical process, its application to stars, and preliminary results obtained on a few dozen systems, summarized in the form of a stability diagram. Most of the systems are trapped in the so-called "forbidden zone", where the instability cannot grow. In some systems, the tidal instability is able to grow, at short timescales compared to the system evolution. Implications are discussed in the framework of misaligned transiting systems, as the rotational axis of the star would be unstable in systems where this elliptical instability grows.

  18. Capillary instability on a hydrophilic stripe

    Energy Technology Data Exchange (ETDEWEB)

    Speth, Raymond L [Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Lauga, Eric [Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Dr, La Jolla, CA 92093-0411 (United States)], E-mail: elauga@ucsd.edu

    2009-07-15

    A recent experiment showed that cylindrical segments of water filling a hydrophilic stripe on an otherwise hydrophobic surface display a capillary instability when their volume is increased beyond the critical volume at which their apparent contact angle on the surface reaches 90 deg. (Gau et al 1999 Science 283 46-9). Surprisingly, the fluid segments did not break up into droplets-as would be expected for a classical Rayleigh-Plateau instability-but instead displayed a long-wavelength instability where all excess fluid gathered in a single bulge along each stripe. We consider here the dynamics of the flow instability associated with this setup. We perform a linear stability analysis of the capillary flow problem in the inviscid limit. We first confirm previous work showing that all cylindrical segments are linearly unstable if (and only if) their apparent contact angle is larger than 90 deg. We then demonstrate that the most unstable wavenumber for the surface perturbation decreases to zero as the apparent contact angle of the fluid on the surface approaches 90 deg, allowing us to re-interpret the creation of bulges in the experiment as a zero-wavenumber capillary instability. A variation of the stability calculation is also considered for the case of a hydrophilic stripe located on a wedge-like geometry.

  19. Electromagnetic instability induced by neutrino interaction

    Science.gov (United States)

    Bhatt, Jitesh R.; George, Manu

    We consider the generation and evolution of magnetic field in a primordial plasma at temperature T ≤ 1MeV in the presence of asymmetric neutrino background, i.e. the number densities of right-handed and left-handed neutrinos are not the same. Semi-classical equations of motion of a charged fermion are derived using the effective low-energy Lagrangian. We show that the spin degree of freedom of the charged fermion couples with the neutrino background. Using this kinetic equation, we study the collective modes of the plasma. We find that there exist an unstable mode. This instability is closely related with the instability induced by chiral-anomaly in high temperature T ≥ 80TeV plasma where right and left-handed electrons are out of equilibrium. We find that at the temperatures below the neutrino decoupling this instability can produce magnetic field in the universe. We discuss cosmological implications of the results.

  20. Early Prevention Method for Power Systems Instability

    DEFF Research Database (Denmark)

    Dmitrova, Evgenia

    . The predicted effect of the suggested countermeasure application is in a good agreement with the results obtained by RMS dynamic simulation. Developed method enables adaptive preventive control for near real-time stability maintenance. The achieved results are opening promising perspective for power system......In the scope of this work, a method capable of fast identification of the proper countermeasure, that prevents emerging instability, has been developed. The focus is placed on the prevention of aperiodic small signal angular instability by means of manipulations applied to load nodes (nodes...... containing no voltage sources). The main functionality of the early prevention method is to deliver control solution allowing escape from instability on the basis of data obtained by PMU measurements. The developed algorithm performs identification of the optimal node for countermeasure application...

  1. Plasma instabilities of a charge breeder ECRIS

    Science.gov (United States)

    Tarvainen, O.; Angot, J.; Izotov, I.; Skalyga, V.; Koivisto, H.; Thuillier, T.; Kalvas, T.; Lamy, T.

    2017-10-01

    Experimental observation of plasma instabilities in a charge breeder electron cyclotron resonance ion source (CB-ECRIS) is reported. It is demonstrated that the injection of 133Cs+ or 85Rb+ ion beam into the oxygen discharge of the CB-ECRIS can trigger electron cyclotron instabilities, which restricts the parameter space available for the optimization of the charge breeding efficiency. It is concluded that the transition from a stable to unstable plasma regime is caused by gradual accumulation and ionization of Cs/Rb and simultaneous change of the discharge parameters in 10-100 ms time scale, not by a prompt interaction between the incident ion beam and the ECRIS plasma. The instabilities lead to loss of ion confinement, which results in the sputtering of the surfaces in contact with the plasma, followed by up to an order of magnitude increase of impurity currents in the extracted n+ ion beam.

  2. Genome instabilities arising from ribonucleotides in DNA.

    Science.gov (United States)

    Klein, Hannah L

    2017-08-01

    Genomic DNA is transiently contaminated with ribonucleotide residues during the process of DNA replication through misincorporation by the replicative DNA polymerases α, δ and ε, and by the normal replication process on the lagging strand, which uses RNA primers. These ribonucleotides are efficiently removed during replication by RNase H enzymes and the lagging strand synthesis machinery. However, when ribonucleotides remain in DNA they can distort the DNA helix, affect machineries for DNA replication, transcription and repair, and can stimulate genomic instabilities which are manifest as increased mutation, recombination and chromosome alterations. The genomic instabilities associated with embedded ribonucleotides are considered here, along with a discussion of the origin of the lesions that stimulate particular classes of instabilities. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Nonlinear saturation of Weibel-type instabilities

    Science.gov (United States)

    Srinivasan, Bhuvana; Cagas, Petr; Hakim, Ammar

    2017-10-01

    Weibel-type instabilities, which grow in plasmas with anisotropic velocity distribution, have been studied for many years and drawn recent interest due to their broad applicability spanning from laboratory laser plasmas to origins of intergalactic magnetic fields in astrophysical plasmas. Magnetic particle trapping has been considered as the main mechanism of the nonlinear saturation of these instabilities. However, novel continuum kinetic and two-fluid five moment simulations show that there are additional effects - the transverse flow introduced by the magnetic field creates a secondary electrostatic two-stream instability which alters the saturation and is responsible for a quasi-periodic behavior in the nonlinear phase. This research was supported by the Air Force Office of Scientific Research under Grant Number FA9550-15-1-0193.

  4. Edge instability in incompressible planar active fluids

    Science.gov (United States)

    Nesbitt, David; Pruessner, Gunnar; Lee, Chiu Fan

    2017-12-01

    Interfacial instability is highly relevant to many important biological processes. A key example arises in wound healing experiments, which observe that an epithelial layer with an initially straight edge does not heal uniformly. We consider the phenomenon in the context of active fluids. Improving upon the approximation used by Zimmermann, Basan, and Levine [Eur. Phys. J.: Spec. Top. 223, 1259 (2014), 10.1140/epjst/e2014-02189-7], we perform a linear stability analysis on a two-dimensional incompressible hydrodynamic model of an active fluid with an open interface. We categorize the stability of the model and find that for experimentally relevant parameters, fingering instability is always absent in this minimal model. Our results point to the crucial role of density variation in the fingering instability in tissue regeneration.

  5. Pathways towards instability in financial networks

    Science.gov (United States)

    Bardoscia, Marco; Battiston, Stefano; Caccioli, Fabio; Caldarelli, Guido

    2017-02-01

    Following the financial crisis of 2007-2008, a deep analogy between the origins of instability in financial systems and complex ecosystems has been pointed out: in both cases, topological features of network structures influence how easily distress can spread within the system. However, in financial network models, the details of how financial institutions interact typically play a decisive role, and a general understanding of precisely how network topology creates instability remains lacking. Here we show how processes that are widely believed to stabilize the financial system, that is, market integration and diversification, can actually drive it towards instability, as they contribute to create cyclical structures which tend to amplify financial distress, thereby undermining systemic stability and making large crises more likely. This result holds irrespective of the details of how institutions interact, showing that policy-relevant analysis of the factors affecting financial stability can be carried out while abstracting away from such details.

  6. Control and simulation of thermoacoustic instabilities

    Science.gov (United States)

    Poinsot, Thierry

    2014-11-01

    Combustion instabilities (CI), due to thermoacoustic coupling between acoustic waves and chemical reaction, constitute a major danger for all combustion systems. They can drive the system to unstable states where the whole combustor can oscillate, vibrate, quench or in extreme cases explode or burn. Such phenomena are commonly observed in the final phases of development programs, leading to major difficulties and significant additional costs. One of the most famous examples of combustion instabilities is the F1 engine of the Apollo program which required more than 1000 engine tests to obtain a stable regime satisfying all other constraints (performance, ignition, etc). CIs constitute one of the most challenging problems in fluid mechanics: they combine turbulence, acoustics, chemistry, unsteady two-phase flow in complex geometries. Since combustion instabilities have been identified (more than hundred years ago), the combustion community has followed two paths: (1) improve our understanding of the phenomena controlling stability to build engines which would be ``stable by design'' and (2) give up on a detailed understanding of mechanisms and add control systems either in open or closed loop devices to inhibit unstable modes. Of course, understanding phenomena driving combustion instabilities to suppress them would be the most satisfying approach but there is no fully reliable theory or numerical method today which can predict whether a combustor will be stable or not before it is fired. This talk will present an overview of combustion instabilities phenomenology before focusing on: (1) active control methods for combustion instabilities and (2) recent methods to predict unstable modes in combustors. These methods are based on recent Large Eddy Simulation codes for compressible reacting flows on HPC systems but we will also describe recent fully analytical methods which provide new insights into unstable modes in annular combustion chambers. Support: European

  7. Arthroscopic Findings in Anterior Shoulder Instability.

    Science.gov (United States)

    Hantes, Michael; Raoulis, Vasilios

    2017-01-01

    In the last years, basic research and arthroscopic surgery, have improved our understanding of shoulder anatomy and pathology. It is a fact that arthroscopic treatment of shoulder instability has evolved considerably over the past decades. The aim of this paper is to present the variety of pathologies that should be identified and treated during shoulder arthroscopy when dealing with anterior shoulder instability cases. A review of the current literature regarding arthroscopic shoulder anatomy, anatomic variants, and arthroscopic findings in anterior shoulder instability, is presented. In addition, correlation of arthroscopic findings with physical examination and advanced imaging (CT and MRI) in order to improve our understanding in anterior shoulder instability pathology is discussed. Shoulder instability represents a broad spectrum of disease and a thorough understanding of the pathoanatomy is the key for a successful treatment of the unstable shoulder. Patients can have a variety of pathologies concomitant with a traditional Bankart lesion, such as injuries of the glenoid (bony Bankart), injuries of the glenoid labrum, superiorly (SLAP) or anteroinferiorly ( e.g . anterior labroligamentous periosteal sleeve avulsion, and Perthes), capsular lesions (humeral avulsion of the glenohumeral ligament), and accompanying osseous-cartilage lesions (Hill-Sachs, glenolabral articular disruption). Shoulder arthroscopy allows for a detailed visualization and a dynamic examination of all anatomic structures, identification of pathologic findings, and treatment of all concomitant lesions. Surgeons must be well prepared and understanding the normal anatomy of the glenohumeral joint, including its anatomic variants to seek for the possible pathologic lesions in anterior shoulder instability during shoulder arthroscopy. Patient selection criteria, improved surgical techniques, and implants available have contributed to the enhancement of clinical and functional outcomes to the

  8. Nucleation versus instability race in strained films

    Science.gov (United States)

    Liu, Kailang; Berbezier, Isabelle; David, Thomas; Favre, Luc; Ronda, Antoine; Abbarchi, Marco; Voorhees, Peter; Aqua, Jean-Noël

    2017-10-01

    Under the generic term "Stranski-Krastanov" are grouped two different growth mechanisms of SiGe quantum dots. They result from the self-organized Asaro-Tiller-Grinfel'd (ATG) instability at low strain, while at high strain, from a stochastic nucleation. While these regimes are well known, we elucidate here the origin of the transition between these two pathways thanks to a joint theoretical and experimental work. Nucleation is described within the master equation framework. By comparing the time scales for ATG instability development and three-dimensional (3D) nucleation onset, we demonstrate that the transition between these two regimes is simply explained by the crossover between their divergent evolutions. Nucleation exhibits a strong exponential deviation at low strain while ATG behaves only algebraically. The associated time scale varies with exp(1 /x4) for nucleation, while it only behaves as 1 /x8 for the ATG instability. Consequently, at high (low) strain, nucleation (instability) occurs faster and inhibits the alternate evolution. It is then this different kinetic evolution which explains the transition from one regime to the other. Such a kinetic view of the transition between these two 3D growth regimes was not provided before. The crossover between nucleation and ATG instability is found to occur both experimentally and theoretically at a Ge composition around 50% in the experimental conditions used here. Varying the experimental conditions and/or the system parameters does not allow us to suppress the transition. This means that the SiGe quantum dots always grow via ATG instability at low strain and nucleation at high strain. This result is important for the self-organization of quantum dots.

  9. Combustion instability mitigation by magnetic fields

    Science.gov (United States)

    Jocher, Agnes; Pitsch, Heinz; Gomez, Thomas; Bonnety, Jérôme; Legros, Guillaume

    2017-06-01

    The present interdisciplinary study combines electromagnetics and combustion to unveil an original and basic experiment displaying a spontaneous flame instability that is mitigated as the non-premixed sooting flame experiences a magnetic perturbation. This magnetic instability mitigation is reproduced by direct numerical simulations to be further elucidated by a flow stability analysis. A key role in the stabilization process is attributed to the momentum and thermochemistry coupling that the magnetic force, acting mainly on paramagnetic oxygen, contributes to sustain. The spatial local stability analysis based on the numerical simulations shows that the magnetic field tends to reduce the growth rates of small flame perturbations.

  10. A fast beam-ion instability

    Energy Technology Data Exchange (ETDEWEB)

    Stupakov, G.V. [Stanford Linear Accelerator Center, Menlo Park, CA (United States)

    1996-08-01

    The ionization of residual gas by an electron beam in an accelerator generates ions that can resonantly couple to the beam through a wave propagating in the beam-ion system. Results of the study of a beam-ion instability are presented for a multi-bunch train taking into account the decoherence of ion oscillations due to the ion frequency spread and spatial variation of the ion frequency. It is shown that the combination of both effects can substantially reduce the growth rate of the instability. (author)

  11. Aeroelastic instability problems for wind turbines

    DEFF Research Database (Denmark)

    Hansen, Morten Hartvig

    2007-01-01

    This paper deals with the aeroelostic instabilities that have occurred and may still occur for modem commercial wind turbines: stall-induced vibrations for stall-turbines, and classical flutter for pitch-regulated turbines. A review of previous works is combined with derivations of analytical...... stability limits for typical blade sections that show the fundamental mechanisms of these instabilities. The risk of stall-induced vibrations is mainly related to blade airfoil characteristics, effective direction of blade vibrations and structural damping, whereas the blade tip speed, torsional blade...

  12. MHD thermal instabilities in cool inhomogeneous atmospheres

    Science.gov (United States)

    Bodo, G.; Ferrari, A.; Massaglia, S.; Rosner, R.

    1983-01-01

    The formation of a coronal state in a stellar atmosphere is investigated. A numerical code is used to study the effects of atmospheric gradients and finite loop dimension on the scale of unstable perturbations, solving for oscillatory perturbations as eigenfunctions of a boundary value problem. The atmosphere is considered as initially isothermal, with density and pressure having scale heights fixed by the hydrostatic equations. Joule mode instability is found to be an efficient mechanism for current filamentation and subsequent heating in initially cool atmospheres. This instability is mainly effective at the top of magnetic loops and is not suppressed by thermal conduction.

  13. Theory of electrohydrodynamic instabilities in electrolytic cells

    Science.gov (United States)

    Bruinsma, R.; Alexander, S.

    1990-01-01

    The paper develops the theory of the hydrodynamic stability of an electrolytic cell as a function of the imposed electric current. A new electrohydrodynamic instability is encountered when the current is forced to exceed the Nernst limit. The convection is driven by the volume force exerted by the electric field on space charges in the electrolyte. This intrinsic instability is found to be easily masked by extrinsic convection sources such as gravity or stirring. A linear stability analysis is performed and a dimensionless number Le is derived whose value determines the convection pattern.

  14. On cavitation instabilities with interacting voids

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2012-01-01

    When a single void grows in an elastic–plastic material a cavitation instability may occur, if the stress triaxiality is sufficiently high. The effect of neighbouring voids on such unstable cavity growth is studied here by comparing two different models. The first model considers a periodic array...... voids so far apart that the radius of the plastic zone around each void is less than 1% of the current spacing between the voids, can still affect each others at the occurrence of a cavitation instability such that one void stops growing while the other grows in an unstable manner. On the other hand...

  15. IS POLARIS LEAVING THE CEPHEID INSTABILITY STRIP?

    OpenAIRE

    Turner, D. G.

    2017-01-01

    Although Polaris is generally regarded as an overtone pulsator that may soon switch to pulsation in the fundamental mode, it is argued that the variable is actually crossing the instability strip for the first time and is in the process of leaving the instability strip altogether. The luminosity of Polaris inferred from its optical F3 V companion, as well as from A, F, and G-type stars lying within a few degrees of it and populating a group main sequence coincident with that for Polaris B...

  16. Methods for Simulating the Heavy Core Instability

    Directory of Open Access Journals (Sweden)

    Chang Philip

    2013-04-01

    Full Text Available Vortices have been proposed as the sites of planet formation, where dust collects and grows into planetesimals, the building blocks of planets. However, for very small dust particles that can be treated as a pressure-less fluid, we have recently discovered the “heavy core” instability, driven by the density gradient in the vortex. In order to understand the eventual outcome of this instability, we need to study its non-linear development. Here, we describe our ongoing work to develop highly accurate numerical models of a vortex with a density gradient embedded within a protoplanetary disk.

  17. Heuristic explanation of journal bearing instability

    Science.gov (United States)

    Crandall, S. H.

    1982-01-01

    A fluid-filled journal bearing is viewed as a powerful pump circulating fluid around the annular space between the journal and the bearing. A small whirling motion of the journal generates a wave of thickness variation progressing around the channel. The hypothesis that the fluid flow drives the whirl whenever the mean of the pumped fluid velocity is greater than the peripheral speed of the thickness variation wave is discussed and compared with other simple explanations of journal bearing instability. It is shown that for non-cavitation long bearings the hypothesis predicts instability onset correctly for unloaded bearings but gradually overpredicts the onset speed as the load is increased.

  18. Efficiency Versus Instability in Plasma Accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Lebedev, Valeri [Fermilab; Burov, Alexey [Fermilab; Nagaitsev, Sergei [Fermilab

    2017-01-05

    Plasma wake-field acceleration in a strongly nonlinear (a.k.a. the blowout) regime is one of the main candidates for future high-energy colliders. For this case, we derive a universal efficiency-instability relation, between the power efficiency and the key instability parameter of the witness bunch. We also show that in order to stabilize the witness bunch in a regime with high power efficiency, the bunch needs to have high energy spread, which is not presently compatible with collider-quality beam properties. It is unclear how such limitations could be overcome for high-luminosity linear colliders.

  19. Modulational instability in periodic quadratic nonlinear materials

    DEFF Research Database (Denmark)

    Corney, Joel Frederick; Bang, Ole

    2001-01-01

    We investigate the modulational instability of plane waves in quadratic nonlinear materials with linear and nonlinear quasi-phase-matching gratings. Exact Floquet calculations, confirmed by numerical simulations, show that the periodicity can drastically alter the gain spectrum but never completely...... removes the instability. The low-frequency part of the gain spectrum is accurately predicted by an averaged theory and disappears for certain gratings. The high-frequency part is related to the inherent gain of the homogeneous non-phase-matched material and is a consistent spectral feature....

  20. The Rossby wave instability in protoplanetary disks

    Directory of Open Access Journals (Sweden)

    Meheut H.

    2013-04-01

    Full Text Available The Rossby wave instability has been proposed as a mechanism to transport angular momentum in the dead zone of protoplanetary disks and to form vortices. These vortices are of particular interest to concentrate solids in their centres and eventually to form planetesimals. Here we summarize some recent results concerning the growth and structure of this instability in radially and vertically stratified disks, its saturation and non-linear evolution. We also discuss the concentration of solids in the Rossby vortices including vertical settling.

  1. Plasma wave instabilities in nonequilibrium graphene

    DEFF Research Database (Denmark)

    Aryal, Chinta M.; Hu, Ben Yu-Kuang; Jauho, Antti-Pekka

    2016-01-01

    We study two-stream instabilities in a nonequilibrium system in which a stream of electrons is injected into doped graphene. As with equivalent nonequilibrium parabolic band systems, we find that the graphene systems can support unstable charge-density waves whose amplitudes grow with time. We...... determine the range of wave vectors q that are unstable, and their growth rates. We find no instability for waves with wave vectors parallel or perpendicular to the direction of the injected carriers. We find that, within the small-wave-vector approximation, the angle between q and the direction...

  2. Shape instability of a magnetic elastomer membrane

    Energy Technology Data Exchange (ETDEWEB)

    Raikher, Yu L; Stolbov, O V [Institute of Continuous Media Mechanics, Ural Branch of RAS, 614013 Perm (Russian Federation); Stepanov, G V [State Scientific Center ' Institute of Chemistry and Technology of Organoelement Compounds' , 11123 Moscow (Russian Federation)], E-mail: raikher@icmm.ru

    2008-08-07

    Shape instability occurring in a thin plate (membrane) made of a soft magnetoelastic material under a uniform magnetic field is predicted and analysed. The instability onset is shown to be similar to the second-order transition; the dependence of the threshold field on the magnetic and geometric parameters of the membrane is derived analytically; the membrane shapes (domes) are evaluated with the aid of numerical simulation. The theory proposed is in general agreement with experiments performed on a siloxane rubber/iron carbonyl composite. (fast track communication)

  3. Computing Instability In Combustion Of Liquid Propellants

    Science.gov (United States)

    Chen, Yen-Sen; Shang, Huan-Min

    1995-01-01

    Computational fluid dynamics (CFD) code developed for use in design analyses of flow instabilities associated with combustion of sprayed liquid propellants in rocket engines. Code also contributes to design of improved commercial sprayed-fuel combustors in furnaces and jet engines. Proves robust, user-friendly software tool with comprehensive analysis capability. Enables characterization of stability or instability of engine in terms of such physically meaningful parameters as initial conditions of spray, spatial distribution of ratio between concentrations of fuel and oxidizer at injector faces, geometry of combustor, and configurations of baffles.

  4. STRUCTURAL STRESS RELAXATION IN STAINLESS INSTABILITY STEEL

    Directory of Open Access Journals (Sweden)

    S. Lyabuk

    2017-06-01

    Full Text Available The approach to the description of conditions of martensitic transformation in austenitic steel is advanced. Transformation induced hardening is the result of Le Chatelier principle in instability alloys. The phase transformation in austenitic instability stainless steel is the cause of reduction of grain refining and increase of strength. It was experimentally shown that physical-mechanical characteristics of the prepared materials were defined by the structure and inhomogeneous distribution of the hardening phase within a grain. The reasons for high thermal stability of inverse austenitic were established. The factors determining the inverse austenitic relaxation resistibility and resources for its increasing were revealed.

  5. Composition driven structural instability in perovskite ferroelectrics

    Directory of Open Access Journals (Sweden)

    Chao Xu

    2017-04-01

    Full Text Available Ferroelectric solid solutions usually exhibit enhanced functional properties at the morphotropic phase boundary separating two ferroelectric phases with different orientations of polarization. The underlying mechanism is generally associated with polarization rotational instability and the flattened free energy profile. In this work we show that the polarization extensional instability can also be induced at the morphotropic phase boundary beyond the reported polar-nonpolar phase boundary. The piezoelectricity enhanced by this mechanism exhibits excellent thermal stability, which helps to develop high performance piezoelectric materials with good temperature stability.

  6. White-light parametric instabilities in plasmas.

    Science.gov (United States)

    Santos, J E; Silva, L O; Bingham, R

    2007-06-08

    Parametric instabilities driven by partially coherent radiation in plasmas are described by a generalized statistical Wigner-Moyal set of equations, formally equivalent to the full wave equation, coupled to the plasma fluid equations. A generalized dispersion relation for stimulated Raman scattering driven by a partially coherent pump field is derived, revealing a growth rate dependence, with the coherence width sigma of the radiation field, scaling with 1/sigma for backscattering (three-wave process), and with 1/sigma1/2 for direct forward scattering (four-wave process). Our results demonstrate the possibility to control the growth rates of these instabilities by properly using broadband pump radiation fields.

  7. Role of intrinsic flame instability in the excitation of combustion chamber instability

    Science.gov (United States)

    Akkerman, V'yacheslav; Law, Chung K.

    2011-11-01

    While considerable progress was made on understanding the various modes of flame instability at the fundamental level, and substantial empirical information and phenomenological descriptions was also accumulated on combustion instability within combustion chambers such as those of rocket engines, few attempts were made to explore the possible macro-scale excitation of the latter through the micro-scale manifestation of the former. Here we present an initial attempt towards identifying such a possibility and the associated coupling mechanisms. We shall incorporate the flame parameters into the classical theories of liquid-propellant rocket engines, and then implement the rocket dynamics into the analyses of premixed and diffusion flame segments. The analyses are conducted for the various instability modes, including the diffusional-thermal, Darrieus-Landau, and Rayleigh-Taylor (body-force) instabilities for premixed flames, and the Kelvin-Helmholtz and body-force instabilities for diffusion flames. The role of chamber-generated sound on stabilizing the inherent flame instabilities and triggering the parametric instability is also considered.

  8. MHD instabilities in astrophysical plasmas: very different from MHD instabilities in tokamaks!

    Science.gov (United States)

    Goedbloed, J. P.

    2018-01-01

    The extensive studies of MHD instabilities in thermonuclear magnetic confinement experiments, in particular of the tokamak as the most promising candidate for a future energy producing machine, have led to an ‘intuitive’ description based on the energy principle that is very misleading for most astrophysical plasmas. The ‘intuitive’ picture almost directly singles out the dominant stabilizing field line bending energy of the Alfvén waves and, consequently, concentrates on expansion schemes that minimize that contribution. This happens when the wave vector {{k}}0 of the perturbations, on average, is perpendicular to the magnetic field {B}. Hence, all macroscopic instabilities of tokamaks (kinks, interchanges, ballooning modes, ELMs, neoclassical tearing modes, etc) are characterized by satisfying the condition {{k}}0 \\perp {B}, or nearly so. In contrast, some of the major macroscopic instabilities of astrophysical plasmas (the Parker instability and the magneto-rotational instability) occur when precisely the opposite condition is satisfied: {{k}}0 \\parallel {B}. How do those instabilities escape from the dominance of the stabilizing Alfvén wave? The answer to that question involves, foremost, the recognition that MHD spectral theory of waves and instabilities of laboratory plasmas could be developed to such great depth since those plasmas are assumed to be in static equilibrium. This assumption is invalid for astrophysical plasmas where rotational and gravitational accelerations produce equilibria that are at best stationary, and the associated spectral theory is widely, and incorrectly, believed to be non-self adjoint. These complications are addressed, and cured, in the theory of the Spectral Web, recently developed by the author. Using this method, an extensive survey of instabilities of astrophysical plasmas demonstrates how the Alfvén wave is pushed into insignificance under these conditions to give rise to a host of instabilities that do not

  9. Aspects of electrohydrodynamic instabilities at polymer interfaces

    NARCIS (Netherlands)

    Russell, TP; Lin, ZQ; Schaffer, E; Steiner, U

    Electrospinning is emerging as a simple means of producing fibers with diameters ranging from 0.02 mum to many microns. Electrospinning, however, relies on the force generated by an electric field on the surface of a polymer solution to either enhance instabilities in a thinning jet or to rapidly

  10. Neutrino signal from pair-instability supernovae

    Science.gov (United States)

    Wright, Warren P.; Gilmer, Matthew S.; Fröhlich, Carla; Kneller, James P.

    2017-11-01

    A very massive star with a carbon-oxygen core in the range of 64M ⊙evolution at the extreme of stellar masses. Much will be sought within the electromagnetic radiation we detect from such a supernova but we should not forget that the neutrinos from a pair-instability supernova contain unique signatures of the event that unambiguously identify this type of explosion. We calculate the expected neutrino flux at Earth from two, one-dimensional pair-instability supernova simulations which bracket the mass range of stars which explode by this mechanism taking into account the full time and energy dependence of the neutrino emission and the flavor evolution through the outer layers of the star. We calculate the neutrino signals in five different detectors chosen to represent present or near future designs. We find the more massive progenitors explode as pair-instability supernova which can easily be detected in multiple different neutrino detectors at the "standard" supernova distance of 10 kpc producing several events in DUNE, JUNO, and Super-Kamiokande, while the lightest progenitors produce only a handful of events (if any) in the same detectors. The proposed Hyper-Kamiokande detector would detect neutrinos from a large pair-instability supernova as far as ˜50 kpc allowing it to reach the Megallanic Clouds and the several very high mass stars known to exist there.

  11. Pattern formation - Instabilities in sand ripples

    DEFF Research Database (Denmark)

    Hansen, J. L.; v. Hecke, M.; Haaning, A.

    2001-01-01

    Sand ripples are seen below shallow wavy water and are formed whenever water oscillates over a bed of sand. Here we analyse the instabilities that can upset this perfect patterning when the ripples are subjected to large changes in driving amplitude or frequency, causing them to deform both...

  12. Control of Coherent Instabilities by Linear Coupling

    CERN Document Server

    Cappi, R; Möhl, D

    2001-01-01

    One of the main challenges in the design of high-energy colliders is the very high luminosity necessary to provide significant event rates. This imposes strong constraints to achieve and preserve beams of high brightness, i.e. intensity to emittance ratio, all along the injector chain. Amongst the phenomena that can blow up and even destroy the beam are transverse coherent instabilities. Two methods are widely used to damp these instabilities. The first one is Landau damping by non-linearities. The second consists in using an electronic feedback system. However, non-linearities are harmful to single-particle motion due to resonance phenomena, and powerful wideband feedback systems are expensive. It is shown in this paper that linear coupling is a further method that can be used to damp transverse coherent instabilities. The theory of collective motion is outlined, including the coupling of instability rise and damping rates, chromaticity and Landau damping. Experimental results obtained at the CERN PS are rep...

  13. Understanding financial instability through complex systems

    NARCIS (Netherlands)

    in 't Veld, D.

    2011-01-01

    This article presents an outline and some early results of the research project Understanding inancial instability through complex systems, supported by the Dutch Science Foundation NWO. The project is carried out by the Center for Nonlinear Dynamics in Economics and Finance (CeNDEF) at the

  14. Plasmoid Instability in Forming Current Sheets

    Science.gov (United States)

    Comisso, L.; Lingam, M.; Huang, Y.-M.; Bhattacharjee, A.

    2017-12-01

    The plasmoid instability has revolutionized our understanding of magnetic reconnection in astrophysical environments. By preventing the formation of highly elongated reconnection layers, it is crucial in enabling the rapid energy conversion rates that are characteristic of many astrophysical phenomena. Most previous studies have focused on Sweet-Parker current sheets, which are unattainable in typical astrophysical systems. Here we derive a general set of scaling laws for the plasmoid instability in resistive and visco-resistive current sheets that evolve over time. Our method relies on a principle of least time that enables us to determine the properties of the reconnecting current sheet (aspect ratio and elapsed time) and the plasmoid instability (growth rate, wavenumber, inner layer width) at the end of the linear phase. After this phase the reconnecting current sheet is disrupted and fast reconnection can occur. The scaling laws of the plasmoid instability are not simple power laws, and they depend on the Lundquist number (S), the magnetic Prandtl number (P m ), the noise of the system ({\\psi }0), the characteristic rate of current sheet evolution (1/τ ), and the thinning process. We also demonstrate that previous scalings are inapplicable to the vast majority of astrophysical systems. We explore the implications of the new scaling relations in astrophysical systems such as the solar corona and the interstellar medium. In both of these systems, we show that our scaling laws yield values for the growth rate, wavenumber, and aspect ratio that are much smaller than the Sweet-Parker-based scalings.

  15. Instabilities in power law gradient hardening materials

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Tvergaard, Viggo

    2005-01-01

    Tension and compression instabilities are investigated for specimens with dimensions in the micron range. A finite strain generalization of a higher order strain gradient plasticity theory is implemented in a finite element scheme capable of modeling power law hardening materials. Effects...

  16. Greenscreen Teaching: Institutional Instability and Classroom Innovation

    Science.gov (United States)

    Perkins, Miriam Y.

    2017-01-01

    "Greenscreen Teaching" explores how the stresses of institutional and social change impact teaching and learning, and the creative resourcefulness born out of instability. In precarious institutions and social contexts, relevant outcomes for theological learning include developing attentiveness, robust moral discernment, and courageous…

  17. Treatment of glenohumeral instability in rugby players.

    Science.gov (United States)

    Funk, Lennard

    2016-02-01

    Rugby is a high-impact collision sport, with impact forces. Shoulder injuries are common and result in the longest time off sport for any joint injury in rugby. The most common injuries are to the glenohumeral joint with varying degrees of instability. The degree of instability can guide management. The three main types of instability presentations are: (1) frank dislocation, (2) subluxations and (3) subclinical instability with pain and clicking. Understanding the exact mechanism of injury can guide diagnosis with classical patterns of structural injuries. The standard clinical examination in a large, muscular athlete may be normal, so specific tests and techniques are needed to unearth signs of pathology. Taking these factors into consideration, along with the imaging, allows a treatment strategy. However, patient and sport factors need to be also considered, particularly the time of the season and stage of sporting career. Surgery to repair the structural damage should include all lesions found. In chronic, recurrent dislocations with major structural lesions, reconstruction procedures such as the Latarjet procedure yields better outcomes. Rehabilitation should be safe, goal-driven and athlete-specific. Return to sport is dependent on a number of factors, driven by the healing process, sport requirements and extrinsic pressures. Level of evidence V.

  18. Rodeo athletes: management of shoulder instability.

    Science.gov (United States)

    Figueiredo, Eduardo A; Belangero, Paulo S; Cohen, Carina; Louchard, Rafael L; Terra, Bernardo B; Pochini, Alberto C; Andreoli, Carlos V; Cohen, Moisés; Ejnisman, Benno

    2016-05-01

    The aim of this study was to describe epidemiological data and evaluate the clinical results of traumatic anterior glenohumeral instability in rodeo athletes. Thirteen patients, all male, with a mean age of 23.2 (18-31) years old, with anterior glenohumeral instability were include in this study. In 9 patients, the right side was affected. The mean time elapsed between injury and undergoing surgery was 56 months (24-120 months). The surgical technique used (arthroscopic or open bone block procedure) was chosen based on the ISIS (Instability Severity Index Score). Only professional athletes who had been in the sport for at least 60 months were included. Functional evaluation was conducted using the UCLA scale, after a 24-month follow-up period. The number of dislocation episodes varied from 10 to 100 (mean 27 episodes). All of the patients were submitted a surgical treatment open bone block procedure, due to their degree of sport participation, type of sport (forced overhead and collision) and the presence of associated bone defect lesions. According to UCLA criteria, the results were excellent in 12 patients and good in one. The mean time elapsed before returning to the sport was five months, varying between two and ten months. Complications included one patient developing axillary neuropraxia, which was completely resolved six months after the operation, and another patient developed a superficial skin infection. The rodeo athletes with anterior shoulder instability had serious associated bony lesions and has good outcome after bone block procedure.

  19. Corruption, Governance and Political Instability in Nigeria ...

    African Journals Online (AJOL)

    The Nigerian State is a victim of high-level corruption, bad governance, political instability and cyclical legitimacy crisis. In the absence of support from civil society, the effective power of government was eroded and patron-client relationships took a prime role over the formal aspects of politics, such as the rule of law, ...

  20. Nonlinear Instabilities on an Axisymmetric Ferrofluid Jet

    Science.gov (United States)

    Cornish, Michael; Papageorgiou, Demetrios

    2017-11-01

    The stability properties of an inviscid axisymmetric ferrofluid jet running over a current carrying rod are investigated. The rod generates an azimuthal magnetic field which can fully stabilize the Rayleigh-plateau instability for a sufficiently large magnetic field. However, long wave instability can occur when the magnetic field is below critical; this regime has not been studied nonlinearly unlike the above critical regime where the magnetic stabilization property has led to theoretical and experimental discoveries of solitary waves on the ferrofluid jet. We study the flow asymptotically near the critical value of the magnetic field. In the stable regime, we derive the Boussinesq equation. Our interest is in the unstable regime, where magnetic forces are slightly smaller than capillary forces. The Rayleigh-plateau instability is no longer suppressed and a weakly nonlinear long wave model is derived and studied analytically and computationally. The final part of the study follows the nonlinear evolution of the free surface for magnetic fields away from the critical level. A fully nonlinear long-wave theory will be used to derive reduced model equations to evaluate the nonlinear competition between capillary instability of the liquid jet and the stabilizing magnetic field.

  1. Parametric instabilities in picosecond time scales

    Energy Technology Data Exchange (ETDEWEB)

    Baldis, H.A. [Lawrence Livermore National Lab., CA (United States); Rozmus, W. [Alberta Univ., Edmonton, AB (Canada). Dept. of Physics; Labaune, C.; Mounaix, Ph.; Pesme, D.; Baton, S. [Ecole Polytechnique, Palaiseau (France); Tikhonchuk, V.T. [P.N. Lebedev Physics Inst., Moscow (Russian Federation)

    1993-03-01

    The coupling of intense laser light with plasmas is a rich field of plasma physics, with many applications. Among these are inertial confinement fusion (ICF), x-ray lasers, particle acceleration, and x-ray sources. Parametric instabilities have been studied for many years because of their importance to ICF; with laser pulses with duration of approximately a nanosecond, and laser intensities in the range 10{sup 14}--10{sup 15}W/cm{sup 2} these instabilities are of crucial concern because of a number of detrimental effects. Although the laser pulse duration of interest for these studies are relatively long, it has been evident in the past years that to reach an understanding of these instabilities requires their characterization and analysis in picosecond time scales. At the laser intensities of interest, the growth rate for stimulated Brillouin scattering (SBS) is of the order of picoseconds, and of an order of magnitude shorter for stimulated Raman scattering (SRS). In this paper the authors discuss SBS and SRS in the context of their evolution in picosecond time scales. They describe the fundamental concepts associated with their growth and saturation, and recent work on the nonlinear treatment required for the modeling of these instabilities at high laser intensities.

  2. Nonlinear parametric instability of wind turbine wings

    DEFF Research Database (Denmark)

    Larsen, Jesper Winther; Nielsen, Søren R.K.

    2006-01-01

    Nonlinear rotor dynamic is characterized by parametric excitation of both linear and nonlinear terms caused by centrifugal and Coriolis forces when formulated in a moving frame of reference. Assuming harmonically varying support point motions from the tower, the nonlinear parametric instability...

  3. Genome organization, instabilities, stem cells, and cancer

    Directory of Open Access Journals (Sweden)

    Senthil Kumar Pazhanisamy

    2009-01-01

    Full Text Available It is now widely recognized that advances in exploring genome organization provide remarkable insights on the induction and progression of chromosome abnormalities. Much of what we know about how mutations evolve and consequently transform into genome instabilities has been characterized in the spatial organization context of chromatin. Nevertheless, many underlying concepts of impact of the chromatin organization on perpetuation of multiple mutations and on propagation of chromosomal aberrations remain to be investigated in detail. Genesis of genome instabilities from accumulation of multiple mutations that drive tumorigenesis is increasingly becoming a focal theme in cancer studies. This review focuses on structural alterations evolve to raise a variety of genome instabilities that are manifested at the nucleotide, gene or sub-chromosomal, and whole chromosome level of genome. Here we explore an underlying connection between genome instability and cancer in the light of genome architecture. This review is limited to studies directed towards spatial organizational aspects of origin and propagation of aberrations into genetically unstable tumors.

  4. Suppression of instability in rotatory hydromagnetic convection

    Indian Academy of Sciences (India)

    Recently discovered hydrodynamic instability [1], in a simple Bénard configuration in the parameter regime 02 > 1 under the action of a nonadverse temperature gradient, is shown to be suppressed by the simultaneous action of a uniform rotation and a uniform magnetic field both acting parallel to gravity for oscillatory ...

  5. The disruptive instability in Tokamak plasmas

    NARCIS (Netherlands)

    Salzedas, F.J.B.

    2000-01-01

    Studies performed in RTP (Rijnhuizen Tokamak Project) of the most violent and dangerous instability in tokamak plasmas, the major disruption, are presented. A particular class of disruptions is analyzed, namely the density limit disruption, which occur in high density plasmas. The radiative

  6. Theory and Experiments on Chemical Instabilities.

    Science.gov (United States)

    1983-12-31

    following institutions and conferences: 1981 Jan. 8 X Reunion de Fisica Estadistica , Cocoyoc, Mexico, Resonances and Control Features Feb. 13 Michigan State...Aeronautics and Astronautics, Invited Remarks, Palo Alto, CA 1982 Feb. 25,26 Industrial Affiliates Program ": .’ Hydrodynamic and Chemical Instabilities

  7. Mechanisms of cadmium induced genomic instability

    Energy Technology Data Exchange (ETDEWEB)

    Filipic, Metka, E-mail: metka.filipic@nib.si [National Institute of Biology, Department for Genetic Toxicology and Cancer Biology, Ljubljana (Slovenia)

    2012-05-01

    Cadmium is an ubiquitous environmental contaminant that represents hazard to humans and wildlife. It is found in the air, soil and water and, due to its extremely long half-life, accumulates in plants and animals. The main source of cadmium exposure for non-smoking human population is food. Cadmium is primarily toxic to the kidney, but has been also classified as carcinogenic to humans by several regulatory agencies. Current evidence suggests that exposure to cadmium induces genomic instability through complex and multifactorial mechanisms. Cadmium dose not induce direct DNA damage, however it induces increase in reactive oxygen species (ROS) formation, which in turn induce DNA damage and can also interfere with cell signalling. More important seems to be cadmium interaction with DNA repair mechanisms, cell cycle checkpoints and apoptosis as well as with epigenetic mechanisms of gene expression control. Cadmium mediated inhibition of DNA repair mechanisms and apoptosis leads to accumulation of cells with unrepaired DNA damage, which in turn increases the mutation rate and thus genomic instability. This increases the probability of developing not only cancer but also other diseases associated with genomic instability. In the in vitro experiments cadmium induced effects leading to genomic instability have been observed at low concentrations that were comparable to those observed in target organs and tissues of humans that were non-occupationally exposed to cadmium. Therefore, further studies aiming to clarify the relevance of these observations for human health risks due to cadmium exposure are needed.

  8. Capillary instability on a hydrophilic stripe

    Science.gov (United States)

    Speth, Raymond L.; Lauga, Eric

    2009-07-01

    A recent experiment showed that cylindrical segments of water filling a hydrophilic stripe on an otherwise hydrophobic surface display a capillary instability when their volume is increased beyond the critical volume at which their apparent contact angle on the surface reaches 90° (Gau et al 1999 Science 283 46-9). Surprisingly, the fluid segments did not break up into droplets—as would be expected for a classical Rayleigh-Plateau instability—but instead displayed a long-wavelength instability where all excess fluid gathered in a single bulge along each stripe. We consider here the dynamics of the flow instability associated with this setup. We perform a linear stability analysis of the capillary flow problem in the inviscid limit. We first confirm previous work showing that all cylindrical segments are linearly unstable if (and only if) their apparent contact angle is larger than 90°. We then demonstrate that the most unstable wavenumber for the surface perturbation decreases to zero as the apparent contact angle of the fluid on the surface approaches 90°, allowing us to re-interpret the creation of bulges in the experiment as a zero-wavenumber capillary instability. A variation of the stability calculation is also considered for the case of a hydrophilic stripe located on a wedge-like geometry.

  9. Upstream and Downstream Influence in STBLI Instability

    Science.gov (United States)

    Martin, Pino; Priebe, Stephan; Helm, Clara

    2016-11-01

    Priebe and Martín (JFM, 2012) show that the low-frequency unsteadiness in shockwave and turbulent boundary layer interactions (STBLI) is governed by an inviscid instability. Priebe, Tu, Martín and Rowley (JFM, 2016) show that the instability is an inviscid centrifugal one, i.e Görtlerlike vortices. Previous works had given differing conclusions as to whether the low-frequency unsteadiness in STBLI is caused by an upstream or downstream mechanism. In this paper, we reconcile these opposite views and show that upstream and downstream correlations co-exist in the context of the nature of Görtler vortices. We find that the instability is similar to that in separated subsonic and laminar flows. Since the turbulence is modulated but passive to the global mode, the turbulent separated flows are amenable to linear global analysis. As such, the characteristic length and time scales, and the receptivity of the global mode might be determined, and low-order models that represent the low-frequency dynamics in STBLI might be developed. The centrifugal instability persists even under hypersonic conditions. This work is funded by the AFOSR Grant Number AF9550-15-1-0284 with Dr. Ivett Leyva.

  10. Mix and hydrodynamic instabilities on NIF

    Science.gov (United States)

    Smalyuk, V. A.; Robey, H. F.; Casey, D. T.; Clark, D. S.; Döppner, T.; Haan, S. W.; Hammel, B. A.; MacPhee, A. G.; Martinez, D.; Milovich, J. L.; Peterson, J. L.; Pickworth, L.; Pino, J. E.; Raman, K.; Tipton, R.; Weber, C. R.; Baker, K. L.; Bachmann, B.; Berzak Hopkins, L. F.; Bond, E.; Caggiano, J. A.; Callahan, D. A.; Celliers, P. M.; Cerjan, C.; Dixit, S. N.; Edwards, M. J.; Felker, S.; Field, J. E.; Fittinghoff, D. N.; Gharibyan, N.; Grim, G. P.; Hamza, A. V.; Hatarik, R.; Hohenberger, M.; Hsing, W. W.; Hurricane, O. A.; Jancaitis, K. S.; Jones, O. S.; Khan, S.; Kroll, J. J.; Lafortune, K. N.; Landen, O. L.; Ma, T.; MacGowan, B. J.; Masse, L.; Moore, A. S.; Nagel, S. R.; Nikroo, A.; Pak, A.; Patel, P. K.; Remington, B. A.; Sayre, D. B.; Spears, B. K.; Stadermann, M.; Tommasini, R.; Widmayer, C. C.; Yeamans, C. B.; Crippen, J.; Farrell, M.; Giraldez, E.; Rice, N.; Wilde, C. H.; Volegov, P. L.; Gatu Johnson, M.

    2017-06-01

    Several new platforms have been developed to experimentally measure hydrodynamic instabilities in all phases of indirect-drive, inertial confinement fusion implosions on National Ignition Facility. At the ablation front, instability growth of pre-imposed modulations was measured with a face-on, x-ray radiography platform in the linear regime using the Hydrodynamic Growth Radiography (HGR) platform. Modulation growth of "native roughness" modulations and engineering features (fill tubes and capsule support membranes) were measured in conditions relevant to layered DT implosions. A new experimental platform was developed to measure instability growth at the ablator-ice interface. In the deceleration phase of implosions, several experimental platforms were developed to measure both low-mode asymmetries and high-mode perturbations near peak compression with x-ray and nuclear techniques. In one innovative technique, the self-emission from the hot spot was enhanced with argon dopant to "self-backlight" the shell in-flight. To stabilize instability growth, new "adiabat-shaping" techniques were developed using the HGR platform and applied in layered DT implosions.

  11. On Hydrodynamic Instabilities in Cylindrical Geometry

    Science.gov (United States)

    Proano, Erik; Rollin, Bertrand

    2017-11-01

    Recent research has suggested that hydrodynamic instabilities induced mixing is one of the last major hurdles toward achieving optimum conditions for ignition in confined fusion approaches for energy production. We leave aside the complexities of multiple interacting physics that lead to a fusion target ignition to be able to focus on understanding the development of these hydrodynamic instabilities, namely Richtmyer-Meshkov and Rayleigh-Taylor, in the context of a converging geometry. The problem is reformulated into the cleaner case of a cylindrical shock wave imploding onto a pocket of Sulfur Hexafluoride immersed in air. This numerical experiment aims at characterizing qualitatively and quantitatively the relation between the instabilities initial conditions and their development until late time. Starting from carefully designed single- and multimode disturbances at the initial density interface, our simulations track the evolution of the mixing layer through successive occurrences of the Richtmyer-Meshkov and Rayleigh-Taylor instabilities. Evolution of the mixing zone width and growth rate are presented for selected initial conditions, along with a quantification of mixing. Also, the effect of the converging shock strength is discussed.

  12. Snake venom instability | Willemse | African Zoology

    African Journals Online (AJOL)

    Egyptian cobra Naja haje haje) and puffadder (Bills arietans). Considerable differences in electrophoretic characteristics were found between fresh venom and commercial venom samples from the same species of snake. These differences could be attributed partly to the instability of snake venom under conditions of drying ...

  13. Galloping instability to chaos of cables

    CERN Document Server

    Luo, Albert C J

    2017-01-01

    This book provides students and researchers with a systematic solution for fluid-induced structural vibrations, galloping instability and the chaos of cables. They will also gain a better understanding of stable and unstable periodic motions and chaos in fluid-induced structural vibrations. Further, the results presented here will help engineers effectively design and analyze fluid-induced vibrations.

  14. Remittances, spending, and political instability in Ukraine

    Czech Academy of Sciences Publication Activity Database

    Kuntsevych, Iuliia

    2016-01-01

    Roč. 64, č. 1 (2016), s. 42-57 ISSN 0722-480X Institutional support: PRVOUK-P23 Keywords : Ukraine * remittances * political instability Subject RIV: AH - Economics http://www.degruyter.com/view/j/soeu.2016.64.issue-1/soeu-2016-0004/soeu-2016-0004.xml

  15. Transport Properties of the Azimuthal Magnetorotational Instability

    Science.gov (United States)

    Guseva, Anna; Willis, Ashley P.; Hollerbach, Rainer; Avila, Marc

    2017-11-01

    The magnetorotational instability (MRI) is thought to be a powerful source of turbulence in Keplerian accretion disks. Motivated by recent laboratory experiments, we study the MRI driven by an azimuthal magnetic field in an electrically conducting fluid sheared between two concentric rotating cylinders. By adjusting the rotation rates of the cylinders, we approximate angular velocity profiles {ω }\\propto {r}q. We perform direct numerical simulations of a steep profile close to the Rayleigh line q≳ -2 and a quasi-Keplerian profile q≈ -3/2 and cover wide ranges of Reynolds ({{Re}} ≤slant 4× {10}4) and magnetic Prandtl numbers (0≤slant {{Pm}}≤slant 1). In the quasi-Keplerian case, the onset of instability depends on the magnetic Reynolds number, with {{{Rm}}}c≈ 50, and angular momentum transport scales as \\sqrt{{{Pm}}}{{{Re}}}2 in the turbulent regime. The ratio of Maxwell to Reynolds stresses is set by Rm. At the onset of instability both stresses have similar magnitude, whereas the Reynolds stress vanishes or becomes even negative as Rm increases. For the profile close to the Rayleigh line, the instability shares these properties as long as {{Pm}}≳ 0.1 but exhibits a markedly different character if {{Pm}}\\to 0, where the onset of instability is governed by the Reynolds number, with {{{Re}}}c ≈ 1250, and transport is via Reynolds stresses and scales as Re2. At intermediate Pm = 0.01 we observe a continuous transition from one regime to the other, with a crossover at {{Rm}}={ O }(100). Our results give a comprehensive picture of angular momentum transport of the MRI with an imposed azimuthal field.

  16. Prevalence of knee instability in relation to sports activity

    DEFF Research Database (Denmark)

    Hahn, Thomas; Foldspang, Anders; Hansen, Thorsten Ingemann

    2001-01-01

    The objective was to estimate the prevalence of knee instability among active athletes and to investigate potential associations to type, amount and duration of sports participation. Based on a questionnaire, 339 athletes provided information about different features of occupation, sports activity...... and knee instability. The 12-month period prevalence of knee instability and constant or recurrent knee instability, and absence from sport and absence from work due to knee instability, was 22%, 14%, 5% and 1%, respectively. Knee instability as such, and constant or recurrent knee instability were found...... to be positively associated with female gender and different features of occupational work. In conclusion, knee instability is a commonly reported phenomenon among active athletes. It was found to be independent of the type and the amount of sports activity but highly dependent on female gender, type and amount...

  17. Study of Electron Cloud Instability in Fermilab Main Injector

    Energy Technology Data Exchange (ETDEWEB)

    Zwaska, R. M. [Fermilab; Ohmi, K. [KEK, Tsukuba

    2012-05-01

    Electron cloud has been observed in Fermilab main injector. Electron signal is enhanced near the transition. The slippage factor which suppress instabilities approach to zero at the transition. Instabilities must be most serious near the trans ition. The instability caused by the electron cloud is an important issue for high intensity operation and the future toward Project-X. Simulations of electron cloud instability near the transition is presented.

  18. Helicobacter pylori infection generates genetic instability in gastric cells

    DEFF Research Database (Denmark)

    Machado, Ana Manuel; Figueiredo, C.; Seruca, R.

    2010-01-01

    The discovery that Helicobacter pylori is associated with gastric cancer has led to numerous studies that investigate the mechanisms by which H. pylori induces carcinogenesis. Gastric cancer shows genetic instability both in nuclear and mitochondrial DNA, besides impairment of important DNA repair...... of the host, such as oxidative damage, methylation, chromosomal instability, microsatellite instability, and mutations. Interestingly, H. pylori infection generates genetic instability in nuclear and mitochondrial DNA. Based on the reviewed literature we conclude that H. pylori infection promotes gastric...

  19. A Computational Study of Transverse Combustion Instability Mechanisms

    Science.gov (United States)

    2014-07-01

    Marshall Space Flight Center. References 1. Smith, D. A., Zukoski, E. E., “Combustion Instability Sustained by Unsteady Vortex Combustion,” 21st JPC ...Prediction in a Model Rocket Combustor,” 47th JPC , AIAA 2011-6030. 10. Harvazinski, M. E., Modeling Self-Excited Combustion Instabilities Using A...Instabilities,” 49th JPC , AIAA 2013-3992. 13. Smith, R., Xia, G., Anderson, W., Merkle, C. L., “Extraction of Combustion Instability Mechanisms form Detailed

  20. Current-Driven Filament Instabilities in Relativistic Plasmas. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Chuang

    2013-02-13

    This grant has supported a study of some fundamental problems in current- and flow-driven instabilities in plasmas and their applications in inertial confinement fusion (ICF) and astrophysics. It addressed current-driven instabilities and their roles in fast ignition, and flow-driven instabilities and their applications in astrophysics.

  1. On the measurement of political instability and its impact on economic growth

    NARCIS (Netherlands)

    Jong-A-Pin, R.

    We examine the multidimensionality of political instability using 25 political instability indicators in an Exploratory Factor Analysis. We find that political instability has four dimensions: politically motivated violence, mass civil protest. instability within the political regime. and

  2. Simulation of liquid propellant rocket engine combustion instabilities

    Science.gov (United States)

    Ventrice, M. B.; Fang, J. C.; Purdy, K. R.

    1979-01-01

    A simulation technique for studying the high frequency combustion instabilities of liquid propellant rocket engines has been developed and used to investigate various aspects of instability phenomena. Of importance was investigation of the significance of the method of coupling the combustion and the gas dynamics of the system. Two coupling processes were studied: linear response of the combustion process to pressure fluctuations, and the nature of the resulting instabilities; and nonlinear response of the combustion process to velocity fluctuations, and the nature of the resulting instabilities. For the combustion model studied, nonlinear (velocity) coupling was found to more closely characterize liquid propellant instabilities.

  3. Selected Topics in Microwave Instabilities and Linacs

    Energy Technology Data Exchange (ETDEWEB)

    Ng, K. Y. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2013-06-01

    The Shanghai Institute of Applied Physics (SINAP) is embarking on its first X-ray free-electron laser (FEL) project. It is a cascading high-gain harmonic generation FEL. Microwave instabilities driven by various effects, especially the space-charge force, will degrade the qual- ity of the electron beam before entering into the undulator. However, inside the undulator, the occurrence of microbunching becomes an ut- most important ingredient for the generation of coherent radiation. In short, controlled and uncontrolled microwave instabilities must be fully understood in such a project. These are the slides of a series of eight-hour lectures given at the SINAP in June of 2013, with the intention of a fully understanding of the microbunching phenomenon. The sections of wake field and impedance theory are added as an in- troduction for those who are not familiar with the subject.

  4. Coulomb center instability in bilayer graphene

    Science.gov (United States)

    Oriekhov, D. O.; Sobol, O. O.; Gorbar, E. V.; Gusynin, V. P.

    2017-10-01

    In the low-energy two-band as well as four-band continuum models, we study the supercritical charge instability in gapped bilayer graphene in the field of an impurity charge when the lowest-energy bound state dives into the hole continuum. It is found that the screening effects are crucially important in bilayer graphene. If they are neglected, then the critical value for the impurity charge tends to zero as the gap Δ vanishes. If the screened Coulomb interaction is considered, then the critical charge tends to a finite value for Δ →0 . The different scalings of the kinetic energy of quasiparticles and the Coulomb interaction with respect to the distance to the charged impurity ensure that the wave function of the electron bound state does not shrink toward the impurity as its charge increases. This results in the absence of the fall-to-center phenomenon in bilayer graphene although the supercritical charge instability is realized.

  5. Instability in electromagnetically driven flows Part I

    CERN Document Server

    Gissinger, Christophe; Fauve, Stephan

    2016-01-01

    The MHD flow driven by a travelling magnetic field (TMF) in an annular channel is investigated numerically. For sufficiently large magnetic Reynolds number Rm, or if a large enough pressure gradient is externally applied, the system undergoes an instability in which the flow rate in the channel dramatically drops from synchronism with the wave to much smaller velocities. This transition takes the form of a saddle-node bifurcation for the time-averaged quantities. In this first paper, we characterize the bifurcation, and study the stability of the flow as a function of several parameters. We show that the bifurcation of the flow involves a bistability between Poiseuille-like and Hartman-like regimes, and relies on magnetic flux expulsion. Based on this observation, new predictions are made for the occurrence of this stalling instability.

  6. Microwave instability in electron storage rings

    CERN Document Server

    Mosnier, A

    1999-01-01

    Tracking simulations, with the aim of studying the microwave regime with short and intense bunches, suggest different instability mechanisms, according to the impedance model. In order to get a better insight of the source of the instability, i.e. azimuthal or radial mode coupling, we choose to follow the Sacherer (IEEE Trans. Nucl. Sci. NS-24, 1977 1393) approach to investigate the stability of the stationary solution. The generalized Sacherer's integral, including mode coupling and potential well distortion, is then solved by using the 'step function technique' for the expansion of the radial function, as proposed by Oide and Yokoya (KEK Preprint-90-10, April, 1990). For illustration, the effect of the resonant frequency of a broadband resonator in the SOLEIL storage ring is studied. When the resonator frequency is much higher than the bunch spectrum width, azimuthal mode coupling can occur before radial mode coupling. When the resonator frequency is lower, radial mode coupling comes usually first, but two ...

  7. Elastic instability in stratified core annular flow.

    Science.gov (United States)

    Bonhomme, Oriane; Morozov, Alexander; Leng, Jacques; Colin, Annie

    2011-06-01

    We study experimentally the interfacial instability between a layer of dilute polymer solution and water flowing in a thin capillary. The use of microfluidic devices allows us to observe and quantify in great detail the features of the flow. At low velocities, the flow takes the form of a straight jet, while at high velocities, steady or advected wavy jets are produced. We demonstrate that the transition between these flow regimes is purely elastic--it is caused by the viscoelasticity of the polymer solution only. The linear stability analysis of the flow in the short-wave approximation supplemented with a kinematic criterion captures quantitatively the flow diagram. Surprisingly, unstable flows are observed for strong velocities, whereas convected flows are observed for low velocities. We demonstrate that this instability can be used to measure the rheological properties of dilute polymer solutions that are difficult to assess otherwise.

  8. Rehabilitation for Shoulder Instability - Current Approaches.

    Science.gov (United States)

    Jaggi, Anju; Alexander, Susan

    2017-01-01

    The shoulder relies predominantly on dynamic muscular control to provide stability. Successful treatment is highly dependent upon the correct clinical diagnosis, identification of anatomical structural defects and abnormal movement patterns so that rehabilitation programs can be designed accordingly and individualised to the patient. A systematic outline is provided to guide the clinician on how to identify muscular insufficiencies both local to the shoulder joint and global muscles that can influence shoulder instability. Management is based on expert experience and current literature. The Stanmore classification helps to correctly diagnose the type of instability and prioritise management. Symptom modification tests can help to guide management, however assessing individual muscle groups local to glenohumeral control is also recommended. Physical and psychosocial factors can influence motor control in the presence of pain and injury. A multi-disciplinary approach is required to avoid recurrence of symptoms with rehabilitation focusing on kinetic chain, scapular and gleno-humeral control.

  9. Nanoemulsion Through Stretching-Folding Instability

    Science.gov (United States)

    Ohl, Claus-Dieter; Chan, Chon U.

    2009-11-01

    A new kind of instability sets in when a oil filament is focused by surrounding water-flow through a thin constriction commonly used in fluid focusing devices. At sufficiently high flow rates the oil filament is forced into harmonic oscillations through interfacial forces. Past the constriction the liquid is suddenly slowed down which leads to rapid shortening of the filament's wavelength. At sufficiently high amplitudes the co-flowing water stream breaks up and pinches off micrometer and sub-micrometer sized droplets in a very repeatable manner, thus producing a water-in-oil emulsion. This pinch off is caused by a stretching and folding instability when the oscillating flow impinges into the quasi stagnant reservoir past the constriction. We will present high-speed movies at up to 300,000 frames per second resolving details of the very fast events. A simple model based on restoring interfacial forces is able to predict the kilohertz oscillation frequency observed.

  10. Electrostatic instabilities in a mirror trap revisited

    Science.gov (United States)

    Kotelnikov, Igor A.; Chernoshtanov, Ivan S.; Prikhodko, Vadim V.

    2017-12-01

    The conditions for the stabilization of the Drift-Cyclotron Loss-Cone (DCLC) and Double-Humped (DH) microinstabilities in a mirror trap are critically revisited assuming the plasma is confined in the kinetic regime, which is characterized by an empty loss cone. The temperature of warm ions, necessary for stabilization of the DH instability, is calculated. The fraction of warm ions necessary to stabilize the DCLC instability at a given radial density gradient is calculated. Assuming the wavelength is much shorter than the Larmor radius, a simple criterion for the stability of drift-cyclotron loss-cone oscillations is derived whose accuracy is verified by comparison with the solution of the exact dispersion equation and with known experimental data obtained in the past decades in PR-6, 2XII, 2XIIB, TMX, and TMX-U devices for plasma confinement.

  11. Patellofemoral Pain and Instability in Adolescent Athletes.

    Science.gov (United States)

    Bessette, Matthew; Saluan, Paul

    2016-12-01

    Injuries and disorders of the patellofemoral joint in the adolescent athlete can encompass a wide spectrum of symptomatology and pathology. Anterior knee pain is a common presenting symptom in sports medicine clinics, and can have numerous underlying etiologies. This activity-related pain may be the manifestation of enthesopathy, tendinopathy, fat pad impingement, or numerous other conditions, but is more commonly related to more subtle skeletal and muscular imbalances. Treatment is typically nonoperative in nature, and excellent results are reported with physical therapy. Patellofemoral instability usually has a more dramatic onset in the form of dislocation or subluxation events, commonly experienced during athletics. Concomitant injuries to the patellofemoral articular cartilage are common. Again, treatment is typically nonoperative initially, but recurrent or recalcitrant instability may necessitate reconstructive or realignment procedures. Skeletal maturity often dictates what procedures can be safely attempted.

  12. Thermal instability in the interstellar medium

    Directory of Open Access Journals (Sweden)

    J. Ghanbari

    2000-06-01

    Full Text Available   This study demonstrates how thermal structures in the interstellar medium can emerge as a result of thermal instability. For a two-dimensional case, the steady state thermal structures was investigeted and it was shown that a large class of solutions exist. For a one –dimensional case the conductivity was found to be negligible. The effects of to cal cooling on the thermal instability were explored in some depth. In this case analytical results for time-dependent cooling function were presented, too. We studied nonlinear wave phenomena in thermal fluid systems, with a particular emphasis on presenting analytical results. When conductivity is proportional to temperature, the beliavior of thermal waves is soliton like. For slow thermal waves, approximate analytical results were presented. Extensions of this work are discussed briefly, together with possible astrophysical applications.

  13. Dissipative drift instability in dusty plasma

    Directory of Open Access Journals (Sweden)

    Nilakshi Das

    2012-03-01

    Full Text Available An investigation has been done on the very low-frequency electrostatic drift waves in a collisional dusty plasma. The dust density gradient is taken perpendicular to the magnetic field B0⃗, which causes the drift wave. In this case, low-frequency drift instabilities can be driven by E1⃗×B0⃗ and diamagnetic drifts, where E1⃗ is the perturbed electric field. Dust charge fluctuation is also taken into consideration for our study. The dust- neutral and ion-neutral collision terms have been included in equations of motion. It is seen that the low-frequency drift instability gets damped in such a system. Both dust charging and collision of plasma particles with the neutrals may be responsible for the damping of the wave. Both analytical and numerical techniques have been used while developing the theory.

  14. Rehabilitation for Shoulder Instability – Current Approaches

    Science.gov (United States)

    Jaggi, Anju; Alexander, Susan

    2017-01-01

    Background: The shoulder relies predominantly on dynamic muscular control to provide stability. Successful treatment is highly dependent upon the correct clinical diagnosis, identification of anatomical structural defects and abnormal movement patterns so that rehabilitation programs can be designed accordingly and individualised to the patient. Method: A systematic outline is provided to guide the clinician on how to identify muscular insufficiencies both local to the shoulder joint and global muscles that can influence shoulder instability. Management is based on expert experience and current literature. Results: The Stanmore classification helps to correctly diagnose the type of instability and prioritise management. Symptom modification tests can help to guide management, however assessing individual muscle groups local to glenohumeral control is also recommended. Conclusion: Physical and psychosocial factors can influence motor control in the presence of pain and injury. A multi-disciplinary approach is required to avoid recurrence of symptoms with rehabilitation focusing on kinetic chain, scapular and gleno-humeral control. PMID:28979601

  15. Longwave instabilities and patterns in fluids

    CERN Document Server

    Shklyaev, Sergey

    2017-01-01

    This book summarizes the main advances in the field of nonlinear evolution and pattern formation caused by longwave instabilities in fluids. It will allow readers to master the multiscale asymptotic methods and become familiar with applications of these methods in a variety of physical problems.  Longwave instabilities are inherent to a variety of systems in fluid dynamics, geophysics, electrodynamics, biophysics, and many others. The techniques of the derivation of longwave amplitude equations, as well as the analysis of numerous nonlinear equations, are discussed throughout. This book will be of value to researchers and graduate students in applied mathematics, physics, and engineering, in particular within the fields of fluid mechanics, heat and mass transfer theory, and nonlinear dynamics. .

  16. Magnetically Induced Rotating Rayleigh-Taylor Instability.

    Science.gov (United States)

    Scase, Matthew M; Baldwin, Kyle A; Hill, Richard J A

    2017-03-03

    Classical techniques for investigating the Rayleigh-Taylor instability include using compressed gasses1, rocketry2 or linear electric motors3 to reverse the effective direction of gravity, and accelerate the lighter fluid toward the denser fluid. Other authorse.g.4,5,6 have separated a gravitationally unstable stratification with a barrier that is removed to initiate the flow. However, the parabolic initial interface in the case of a rotating stratification imposes significant technical difficulties experimentally. We wish to be able to spin-up the stratification into solid-body rotation and only then initiate the flow in order to investigate the effects of rotation upon the Rayleigh-Taylor instability. The approach we have adopted here is to use the magnetic field of a superconducting magnet to manipulate the effective weight of the two liquids to initiate the flow. We create a gravitationally stable two-layer stratification using standard flotation techniques. The upper layer is less dense than the lower layer and so the system is Rayleigh-Taylor stable. This stratification is then spun-up until both layers are in solid-body rotation and a parabolic interface is observed. These experiments use fluids with low magnetic susceptibility, |χ| ~ 10-6 - 10-5, compared to a ferrofluids. The dominant effect of the magnetic field applies a body-force to each layer changing the effective weight. The upper layer is weakly paramagnetic while the lower layer is weakly diamagnetic. When the magnetic field is applied, the lower layer is repelled from the magnet while the upper layer is attracted towards the magnet. A Rayleigh-Taylor instability is achieved with application of a high gradient magnetic field. We further observed that increasing the dynamic viscosity of the fluid in each layer, increases the length-scale of the instability.

  17. Coherent instabilities of a relativistic bunched beam

    Energy Technology Data Exchange (ETDEWEB)

    Chao, A.W.

    1982-06-01

    A charge-particle beam contained in an accelerator vacuum chamber interacts electromagnetically with its environment to create a wake field. This field than acts back on the beam, perturbing the particle motion. If the beam intensity is high enough, this beam-environment interaction may lead to an instability and to subsequent beam loss. The beam and its environment form a dynamical system, and it is this system that will be studied. 84 references.

  18. Joint venture instability: a life cycle approach

    OpenAIRE

    Roy Chowdhury, Prabal; Roy Chowdhury, Indrani

    2001-01-01

    Joint ventures represent one of the most fascinating developments in international business. In the last few decades, the rate of joint venture formation has accelerated dramatically. Nowadays joint ventures are much more widespread and occur in industries like telecommunications, biotechnology etc. At the same time, however, it must be noted that joint ventures are very unstable. In this paper we survey the phenomenon of joint venture instability. We draw on the relative recent theoretical l...

  19. Beam instability studies for the SSC

    Energy Technology Data Exchange (ETDEWEB)

    Chou, W.

    1994-09-01

    Beam instability studies of the Superconducting Super Collider (SSC) during the period 1989--1993 are briefly reviewed in this paper. Various topics are covered: single bunch and multi-bunch, single beam and beam-beam, parasitic heating and active feedback, etc. Although the SSC will not be built, many of the results obtained from these studies remain as useful references to the accelerator community.

  20. Basic biomechanic principles of knee instability

    OpenAIRE

    Zlotnicki, Jason P.; Naendrup, Jan-Hendrik; Ferrer, Gerald A.; Debski, Richard E.

    2016-01-01

    Motion at the knee joint is a complex mechanical phenomenon. Stability is provided by a combination of static and dynamic structures that work in concert to prevent excessive movement or instability that is inherent in various knee injuries. The anterior cruciate ligament (ACL) is a main stabilizer of the knee, providing both translational and rotatory constraint. Despite the high volume of research directed at native ACL function, pathogenesis and surgical reconstruction of this structure, a...

  1. The Farley Instability: A Laboratory Test

    DEFF Research Database (Denmark)

    D'Angelo, N.; Pécseli, Hans; Petersen, P. I.

    1974-01-01

    An experiment is described that was performed in an alkali plasma (Cs) device in order to test the theory of the Farley instability. With υ E×B > Cs (the speed of sound) and νι ≳ ω cι (ν e ≪ ω ce ) wave excitation occurs, the waves traveling normal to the magnetic field B at the υ E×B speed. The ...

  2. Traumatic anterior instability of the shoulder

    Directory of Open Access Journals (Sweden)

    João Roberto Polydoro Rosa

    Full Text Available ABSTRACT The shoulder is the most unstable joint in the human body. Traumatic anterior instability of the shoulder is a common condition, which, especially in young patients, is associated with high recurrence rates. The effectiveness of non-surgical treatments when compared to surgical ones is still controversial. The purpose of this study was to review the literature for current concepts and updates regarding the treatment of this condition.

  3. Instability in flow boiling in microchannels

    CERN Document Server

    Saha, Sujoy Kumar

    2016-01-01

    This Brief addresses the phenomena of instability in flow boiling in microchannels occurring in high heat flux electronic cooling. A companion edition in the SpringerBrief Subseries on Thermal Engineering and Applied Science to “Critical Heat Flux in Flow Boiling in Microchannels,” and "Heat Transfer and Pressure Drop in Flow Boiling in Microchannels,"by the same author team, this volume is idea for professionals, researchers, and graduate students concerned with electronic cooling.

  4. Mirror Instability in the Turbulent Solar Wind

    Czech Academy of Sciences Publication Activity Database

    Hellinger, Petr; Landi, S.; Matteini, L.; Verdini, A.; Franci, L.

    2017-01-01

    Roč. 838, č. 2 (2017), č. článku 158. ISSN 0004-637X Institutional support: RVO:68378289 Keywords : instabilities * solar wind * turbulence * waves Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 5.533, year: 2016 http://iopscience.iop.org/article/10.3847/1538-4357/aa67e0

  5. Instability resistance training for health and performance.

    Science.gov (United States)

    Zemková, Erika

    2017-04-01

    Recently, resistance exercises performed on an unstable surface have become part of athletic training and rehabilitation. Accordingly, their role in performance and health-oriented strength training has increasingly emerged as a matter of interest to researchers and conditioning specialists. A more pronounced activation of stabilizing muscles is assumed to be the main feature of instability resistance exercises. This assumption has been proven by EMG studies, which have highlighted significantly greater electromyographic activity of trunk-stabilizing muscles during exercises under unstable as compared to stable conditions. Intervention studies also demonstrated an enhanced improvement of trunk stability after training programs utilizing unstable devices as compared to floor exercises. Findings indicate that instability resistance training may facilitate the neural adaptation of trunk-stabilizing muscles, resulting in an improvement in trunk stability. However, both acute and long-term responses of primarily activated muscles to exercises performed on an unstable surface remain a matter of debate. It has been established that there is a significantly lower peak isometric force and rate of force development during resistance exercises under unstable as compared to stable conditions. In addition, the power output was compromised when exercises were performed on unstable surfaces. However, we have demonstrated that this effect depends on the type of exercise, instability device used, weight lifted, subject's training background, and so forth. Our findings on muscular power in the concentric phase of resistance exercises with different weights under stable and unstable conditions complement this review. Applications of instability resistance exercises for the improvement of neuromuscular functions in the physically active, plus for those following anterior cruciate ligament reconstructions, are also presented.

  6. Envelope instability and the fourth order resonance

    Directory of Open Access Journals (Sweden)

    Chao Li

    2014-12-01

    Full Text Available The well-known envelope instability or the second order even collective mode [I. Hofmann, Phys. Rev. E 57, 4 (1998] and the fourth order resonance 4σ=360° due to the nonlinear space charge effect in high intensity beams have been studied previously. A wide stop band around 15° is found in a pure periodic focusing channel. In addition, it is illustrated that the fourth order resonance dominates over the envelope instability and practically replaces it in the stop band [D. Jeon et al., Phys. Rev. ST Accel. Beams 12, 054204 (2009]. In this paper, for a continuous beam with remarkable space charge, our 2D self-consistent particle-in-cell simulation work with the code topopic shows these two kinds of effects respectively in a periodic focusing defocusing (FD channel. For a fixed tune depression η=0.8, a stop band with a width of almost 15° is also demonstrated. Moreover, it is confirmed that analytical results of the rms envelope instability diagram are a valid tool to interpret the width of the stop band. Emittance growth rates in stop band are also well explained. It is found that, for a nearly rms matched beam, the emittance growth in the stop band is almost proportional to the saturation time of the nonlinear instability of the envelope, which happens in a quick manner and takes only a few FD cells. In contrast, the fourth order resonance is independent of rms matching and will be accompanied by beam evolution as “a long term effect” once the related mechanism is excited.

  7. Nonconservative higher-order hydrodynamic modulation instability

    Science.gov (United States)

    Kimmoun, O.; Hsu, H. C.; Kibler, B.; Chabchoub, A.

    2017-08-01

    The modulation instability (MI) is a universal mechanism that is responsible for the disintegration of weakly nonlinear narrow-banded wave fields and the emergence of localized extreme events in dispersive media. The instability dynamics is naturally triggered, when unstable energy sidebands located around the main energy peak are excited and then follow an exponential growth law. As a consequence of four wave mixing effect, these primary sidebands generate an infinite number of additional sidebands, forming a triangular sideband cascade. After saturation, it is expected that the system experiences a return to initial conditions followed by a spectral recurrence dynamics. Much complex nonlinear wave field motion is expected, when the secondary or successive sideband pair that is created is also located in the finite instability gain range around the main carrier frequency peak. This latter process is referred to as higher-order MI. We report a numerical and experimental study that confirms observation of higher-order MI dynamics in water waves. Furthermore, we show that the presence of weak dissipation may counterintuitively enhance wave focusing in the second recurrent cycle of wave amplification. The interdisciplinary weakly nonlinear approach in addressing the evolution of unstable nonlinear waves dynamics may find significant resonance in other nonlinear dispersive media in physics, such as optics, solids, superfluids, and plasma.

  8. Thermoelectrokinetic instability in micro/nanoscales

    Science.gov (United States)

    Ganchenko, Georgy; Ganchenko, Natalia

    2016-11-01

    A novel sophisticated type of electro-hydrodynamic instability in an electrolyte solution near ion-selective surfaces in an external electric field is discovered theoretically. The key mechanism of the instability is caused by Joule heating but dramatically differs from the well-known Raleigh-Benard convection. The investigation is based on the Nernst-Planck-Poisson-Navier-Stokes system along with the energy equation and corresponding BCs. The 1D quiescent steady state in microscales can be unstable with respect to either short-wave Rubinstein-Zaltzman or long-wave thermoelectokinenetic instability. The last one prevails in long microchannels and good enough thermal insulation of the system. In addition to the linear stability analysis a direct numerical simulation of the full 3D nonlinear system is fulfilled using a parallel computing. In the final coherent structures salt concentration, temperature and electric current are localized in narrow long fingers normal to the ion-selective surface while space charge forms crown-like micro-patterns. The investigation results can be useful in desalination problem.

  9. Magnetohydrodynamic thermal instabilities in cool inhomogeneous atmospheres

    Science.gov (United States)

    Bodo, G.; Ferrari, A.; Massaglia, S.; Rosner, R.; Vaiana, G. S.

    1985-01-01

    The stability of magnetic loops to current-driven filamentation instabilities is investigated. The unperturbed atmosphere is assumed to be composed of an (upper) isothermal optically thin low-density portion and a (lower) higher-density portion which is in radiative equilibrium; in both cases, the atmosphere is in hydrostatic equilibrium, so that gravitational stratification is taken into account. In order to provide specific equilibrium conditions for evaluation of the dispersion relation, conditions appropriate for the surface of a solar-type star are adopted; i.e., a fairly low temperature (T = 5000 K) appropriate for a 'precoronal' state associated, for example, with magnetic flux emerging from photospheric levels under the action of magnetic buoyancy. A linear stability analysis is performed, and numerical results show that physically plausible current densities, which would be generated by typical loop-footpoint motions, are effective in driving MHD instabilities in such a plasma. The instability growth rates are strongly dependent on the assumed current density distribution and on the density scale height.

  10. Astrophysically Relevant Instabilities at a Decelerating Interface.

    Science.gov (United States)

    Calder, A. C.; Fryxell, B.; Rosner, R.; Kane, J.; Remington, B. A.; Robey, H.; Keiter, P.; Drake, R. P.; Knauer, J.; Dursi, L. J.; Olson, K.; Ricker, P. M.; Timmes, F. X.; Zingale, M.; Tufo, H.; MacNeice, P.

    2000-10-01

    Hydrodynamic instabilities play an important role in many astrophysical phenomena, and modern intense lasers offer the chance to experimentally investigate these instabilities in similar environments in a laboratory. In this poster, we report on experimental and theoretical progress in ongoing research in laser astrophysics. We presents results of simulations of experiments performed using the University of Rochester's Omega laser facility. These experiments involve shock propagation through multi-layer targets, and are designed to replicate the complex hydrodynamic instabilities thought to arise during supernovae explosions. The simulations were performed with the FLASH code, developed by the ASCI/ASAP Center for Astrophysical Thermonuclear Flashes at the University of Chicago, and we are planning on a study making use of a realistic equation of state. We present results of an experimental study of 2-D vs. 3-D perturbation growth rates also performed at the Omega laser facility. Data from experiments with nominally identical two-layer targets, but 2-D or 3-D perturbations, show clear differences between the evolution of 2-D vs. 3-D perturbations. We also present simulations showing qualitatively similar features for comparison. This work is supported by the US Department of Energy.

  11. Planetesimals Born Big by Clustering Instability?

    Science.gov (United States)

    Cuzzi, Jeffrey N.; Hartlep, Thomas; Simon, Justin I.; Estrada, Paul R.

    2017-01-01

    Roughly 100km diameter primitive bodies (today's asteroids and TNOs; [1]) are thought to be the end product of so-called "primary accretion". They dominated the initial mass function of planetesimals, and precipitated the onset of a subsequent stage, characterized by runaway gravitational effects, which proceeded onwards to planetary mass objects, some of which accreted massive gas envelopes. Asteroids are the parents of primitive meteorites; meteorite data suggest that asteroids initially formed directly from freelyfloating nebula particles in the mm-size range. Unfortunately, the process by which these primary 100km diameter planetesimals formed remains problematic. We review the most diagnostic primitive parent body observations, highlight critical aspects of the nebula context, and describe the issues facing various primary accretion models. We suggest a path forward that combines current scenarios of "turbulent concentration" (TC) and "streaming instabilities" (SI) into a triggered formation process we call clustering instability (CI). Under expected conditions of nebula turbulence, the success of these processes at forming terrestrial region (mostly silicate) planetesimals requires growth by sticking into aggregates in the several cm size range, at least, which is orders of magnitude more massive than allowed by current growth-by-sticking models using current experimental sticking parameters [2-4]. The situation is not as dire in the ice-rich outer solar system; however, growth outside of the snowline has important effects on growth inside of it [4] and at least one aspect of outer solar system planetesimals (high binary fraction) supports some kind of clustering instability

  12. Glenohumeral arthropathy following stabilization for recurrent instability.

    Science.gov (United States)

    Papalia, Rocco; Osti, Leonardo; Del Buono, Angelo; Denaro, Vincenzo; Maffulli, Nicola

    2010-01-01

    Little attention has been focused on the most common risk factors for post-operative glenohumeral arthropathy in patients undergoing open and arthroscopic stabilization. We performed a literature search using Medline, Cochrane and Google Scholar using the keywords: 'Shoulder instability surgery' in combination with 'glenohumeral osteoarthrosis', 'recurrent shoulder dislocation' in combination with 'surgery' and 'complications'. We identified 33 published studies. There is evidence of long-term postoperative glenohumeral arthropathy in patients undergoing surgical management for shoulder instability. The Coleman methodology score showed great heterogeneity in terms of study design, patient characteristics, management methods and outcome assessment and generally low methodological quality. Follow-up length, age at first dislocation episode and limited external rotation have been shown to be strongly associated with shoulder arthropathy. There is no univocal outcome assessment available. To define the risk factors responsible for development of postoperative glenohumeral arthropathy, controversial findings have been detected. A common validated scale for clinical and imaging measurements for shoulder arthropathy is needed, so as to allow easier and more reliable comparison of outcomes in different studies. Patients should receive controlled imaging assessment (MR and radiographs) in addition to clinical examination. There is a need to perform appropriately powered randomized clinical trials comparing clinical and imaging related outcomes in patients undergoing open, arthroscopic and conservative management for shoulder instability. Standard diagnostic assessment, common and validated clinical and imaging scoring systems are needed.

  13. Baroclinic instability in the solar tachocline

    Energy Technology Data Exchange (ETDEWEB)

    Gilman, Peter; Dikpati, Mausumi, E-mail: gilman@ucar.edu, E-mail: dikpati@ucar.edu [High Altitude Observatory, National Center for Atmospheric Research, 3080 Center Green, Boulder, CO 80307-3000 (United States)

    2014-05-20

    The solar tachocline is likely to be close to a geostrophic 'thermal wind', for which the Coriolis force associated with differential rotation is closely balanced by a latitudinal pressure gradient, leading to a tight relation between the vertical gradient of rotation and the latitudinal entropy gradient. Using a hydrostatic but nongeostrophic spherical shell model, we examine baroclinic instability of the tachocline thermal wind. We find that both the overshoot and radiative parts of the tachocline should be baroclinicly unstable at most latitudes. Growth rates are roughly five times higher in middle and high latitudes compared to low latitudes, and much higher in the overshoot than in the radiative tachocline. They range in e-folding amplification from 10 days in the high latitude overshoot tachocline, down to 20 yr for the low latitude radiative tachocline. In the radiative tachocline only, longitudinal wavenumbers m = 1, 2 are unstable, while in the overshoot tachocline a much broader range of m are unstable. At all latitudes and with all stratifications, the longitudinal scale of the most unstable mode is comparable to the Rossby deformation radius, while the growth rate is set by the local latitudinal entropy gradient. Baroclinic instability in the tachocline competing with instability of the latitude rotation gradient established in earlier studies should be important for the workings of the solar dynamo and should be expected to be found in most stars that contain an interface between radiative and convective domains.

  14. Instability resistance training across the exercise continuum.

    Science.gov (United States)

    Behm, David G; Colado, Juan C; Colado, Juan C

    2013-11-01

    Instability resistance training (IRT; unstable surfaces and devices to strengthen the core or trunk muscles) is popular in fitness training facilities. To examine contradictory IRT recommendations for health enthusiasts and rehabilitation. A literature search was performed using MEDLINE, SPORT Discus, ScienceDirect, Web of Science, and Google Scholar databases from 1990 to 2012. Databases were searched using key terms, including "balance," "stability," "instability," "resistance training," "core," "trunk," and "functional performance." Additionally, relevant articles were extracted from reference lists. To be included, research questions addressed the effect of balance or IRT on performance, healthy and active participants, and physiologic or performance outcome measures and had to be published in English in a peer-reviewed journal. There is a dichotomy of opinions on the effectiveness and application of instability devices and conditions for health and performance training. Balance training without resistance has been shown to improve not only balance but functional performance as well. IRT studies document similar training adaptations as stable resistance training programs with recreationally active individuals. Similar progressions with lower resistance may improve balance and stability, increase core activation, and improve motor control. IRT is highly recommended for youth, elderly, recreationally active individuals, and highly trained enthusiasts.

  15. Dynamic instability of collective myosin II motors

    Science.gov (United States)

    Li, Jin-Fang; Wang, Zi-Qing; Li, Qi-Kun; Xing, Jian-Jun; Wang, Guo-Dong

    2016-11-01

    Some kinds of muscles can oscillate spontaneously, which is related to the dynamic instability of the collective motors. Based on the two-state ratchet model and with consideration of the motor stiffness, the dynamics of collective myosin II motors are studied. It is shown that when the motor stiffness is small, the velocity of the collective motors decreases monotonically with load increasing. When the motor stiffness becomes large, dynamic instability appears in the force-velocity relationship of the collective-motor transport. For a large enough motor stiffness, the zero-velocity point lies in the unstable range of the force-velocity curve, and the motor system becomes unstable before the motion is stopped, so spontaneous oscillations can be generated if the system is elastically coupled to its environment via a spring. The oscillation frequency is related to the motor stiffness, motor binding rate, spring stiffness, and the width of the ATP excitation interval. For a medium motor stiffness, the zero-velocity point lies outside the unstable range of the force-velocity curve, and the motion will be stopped before the instability occurs. Project supported by the National Natural Science Foundation of China (Grant No. 11205123).

  16. Role of chromosomal instability in cancer progression.

    Science.gov (United States)

    McClelland, Sarah E

    2017-09-01

    Cancer cells often display chromosomal instability (CIN), a defect that involves loss or rearrangement of the cell's genetic material - chromosomes - during cell division. This process results in the generation of aneuploidy, a deviation from the haploid number of chromosomes, and structural alterations of chromosomes in over 90% of solid tumours and many haematological cancers. This trait is unique to cancer cells as normal cells in the body generally strictly maintain the correct number and structure of chromosomes. This key difference between cancer and normal cells has led to two important hypotheses: (i) cancer cells have had to overcome inherent barriers to changes in chromosomes that are not tolerated in non-cancer cells and (ii) CIN represents a cancer-specific target to allow the specific elimination of cancer cells from the body. To exploit these hypotheses and design novel approaches to treat cancer, a full understanding of the mechanisms driving CIN and how CIN contributes to cancer progression is required. Here, we will discuss the possible mechanisms driving chromosomal instability, how CIN may contribute to the progression at multiple stages of tumour evolution and possible future therapeutic directions based on targeting cancer chromosomal instability. © 2017 Society for Endocrinology.

  17. Influence of Ion Streaming Instabilities on Transport Near Plasma Boundaries

    CERN Document Server

    Baalrud, Scott D

    2015-01-01

    Plasma boundary layers are susceptible to electrostatic instabilities driven by ion flows in presheaths and, when present, these instabilities can influence transport. In plasmas with a single species of positive ion, ion-acoustic instabilities are expected under conditions of low pressure and large electron-to-ion temperature ratio ($T_e/T_i \\gg 1$). In plasmas with two species of positive ions, ion-ion two-stream instabilities can also be excited. The stability phase-space is characterized using the Penrose criterion and approximate linear dispersion relations. Predictions for how these instabilities affect ion and electron transport in presheaths, including rapid thermalization due to instability-enhanced collisions and an instability-enhanced ion-ion friction force, are also briefly reviewed. Recent experimental tests of these predictions are discussed along with research needs required for further validation. The calculated stability boundaries provide a guide to determine the experimental conditions at ...

  18. 3D Relativistic Magnetohydrodynamic Simulations of Current-Driven Instability. 1; Instability of a Static Column

    Science.gov (United States)

    Mizuno, Yosuke; Lyubarsky, Yuri; ishikawa, Ken-Ichi; Hardee, Philip E.

    2010-01-01

    We have investigated the development of current-driven (CD) kink instability through three-dimensional relativistic MHD simulations. A static force-free equilibrium helical magnetic configuration is considered in order to study the influence of the initial configuration on the linear and nonlinear evolution of the instability. We found that the initial configuration is strongly distorted but not disrupted by the kink instability. The instability develops as predicted by linear theory. In the non-linear regime the kink amplitude continues to increase up to the terminal simulation time, albeit at different rates, for all but one simulation. The growth rate and nonlinear evolution of the CD kink instability depends moderately on the density profile and strongly on the magnetic pitch profile. The growth rate of the kink mode is reduced in the linear regime by an increase in the magnetic pitch with radius and the non-linear regime is reached at a later time than for constant helical pitch. On the other hand, the growth rate of the kink mode is increased in the linear regime by a decrease in the magnetic pitch with radius and reaches the non-linear regime sooner than the case with constant magnetic pitch. Kink amplitude growth in the non-linear regime for decreasing magnetic pitch leads to a slender helically twisted column wrapped by magnetic field. On the other hand, kink amplitude growth in the non-linear regime nearly ceases for increasing magnetic pitch.

  19. Muscle activation patterns in patients with recurrent shoulder instability

    Science.gov (United States)

    Jaggi, Anju; Noorani, Ali; Malone, Alex; Cowan, Joseph; Lambert, Simon; Bayley, Ian

    2012-01-01

    Purpose: The aim of this study is to present muscle patterns observed with the direction of instability in a series of patients presenting with recurrent shoulder instability. Materials and Methods: A retrospective review was carried out on shoulder instability cases referred for fine wire dynamic electromyography (DEMG) studies at a specialist upper limb centre between 1981 and 2003. An experienced consultant clinical neurophysiologist performed dual needle insertion into four muscles (pectoralis major (PM), latissimus dorsi (LD), anterior deltoid (AD) and infraspinatus (IS)) in shoulders that were suspected to have increased or suppressed activation of muscles that could be contributing to the instability. Raw EMG signals were obtained while subjects performed simple uniplanar movements of the shoulder. The presence or absence of muscle activation was noted and compared to clinical diagnosis and direction of instability. Results: A total of 140 (26.6%) shoulders were referred for fine wire EMG, and 131 studies were completed. Of the shoulders tested, 122 shoulders (93%) were identified as having abnormal patterns and nine had normal patterns. PM was found to be more active in 60% of shoulders presenting with anterior instability. LD was found to be more active in 81% of shoulders with anterior instability and 80% with posterior instability. AD was found to be more active in 22% of shoulders with anterior instability and 18% with posterior instability. IS was found to be inappropriately inactive in only 3% of shoulders with anterior instability but in 25% with posterior instability. Clinical assessment identified 93% of cases suspected to have muscle patterning, but the specificity of the clinical assessment was only correct in 11% of cases. Conclusion: The DEMG results suggest that increased activation of LD may play a role in both anterior and posterior shoulder instability; increased activation of PM may play a role in anterior instability. PMID:23493512

  20. Direct-Drive Hydrodynamic Instability Experiments

    Science.gov (United States)

    Azechi, Hiroshi

    1996-11-01

    As is well known, hydrodynamic instabilities play an important role in inertial-confinement-fusion implosions. Target surface perturbations are imposed, in addition to the original surface roughness, by imprint of laser irradiation nonuniformity. These perturbations may be amplified by rippled shock propagation before the shock transit through the pusher; and will grow due to the Rayleigh-Taylor (R-T) instability after the shock transit. Subsequent feed-through seeds the perturbations in the fuel-pusher interface. These together with the initial inner surface perturbations will grow again due to the R-T instability during the deceleration phase, resulting in fuel-pusher mixing which may degrade the implosion performance significantly. Good understandings of the instabilities are therefore necessary to tolerate the mixing. At the GEKKO XII laser facility, we have conducted an extensive series of direct-drive experiments on the imprint^1 and its reduction in pre-formed pl! asmas, rippled shock propagation^2, and R-T instability in linear regime^3. The partially-coherent-light^4 for the target drive performs the state-of-art uniformity and allows well controlled experiments. For the imprint experiments, we introduced a single-mode perturbation only on the foot pulse for the imprint followed by uniform main pulse for R-T amplification. We have also initiated investigation of the imprint by moving single-mode non-uniformity, which is generated by interference of two different laser wavelengths. The time for the interference fringe to move one perturbation wavelength is equivalent to the smoothing time of laser irradiation. The experimental R-T growth rate was significantly reduced from the classical growth rate. This and recently accumulated database of laser intensity, and target thickness dependences support the conclusion that non-local energy transport play an important role in these experiments. Experimental results and compari! sons with theory and simulations

  1. The electrostatic ion-cyclotron instability-a two-dimensional potential relaxation instability

    DEFF Research Database (Denmark)

    Popa, G.; Schrittwieser, R.; Juul Rasmussen, Jens

    1985-01-01

    An experimental investigation shows that the electrostatic ion-cyclotron instability, driven by an electron current to a positively biased collector, is accompanied by strong coherent two-dimensional fluctuations of the plasma potential in front of the collector. These results suggest that this i......An experimental investigation shows that the electrostatic ion-cyclotron instability, driven by an electron current to a positively biased collector, is accompanied by strong coherent two-dimensional fluctuations of the plasma potential in front of the collector. These results suggest...

  2. Segregation induced fingering instabilities in granular avalanches

    Science.gov (United States)

    Woodhouse, Mark; Thornton, Anthony; Johnson, Chris; Kokelaar, Pete; Gray, Nico

    2013-04-01

    It is important to be able to predict the distance to which a hazardous natural granular flows (e.g. snow slab avalanches, debris-flows and pyroclastic flows) might travel, as this information is vital for accurate assessment of the risks posed by such events. In the high solids fraction regions of these flows the large particles commonly segregate to the surface, where they are transported to the margins to form bouldery flow fronts. In many natural flows these bouldery margins experience a much greater frictional force, leading to frontal instabilities. These instabilities create levees that channelize the flow vastly increasing the run-out distance. A similar effect can be observed in dry granular experiments, which use a combination of small round and large rough particles. When this mixture is poured down an inclined plane, particle size segregation causes the large particles to accumulate near the margins. Being rougher, the large particles experience a greater friction force and this configuration (rougher material in front of smoother) can be unstable. The instability causes the uniform flow front to break up into a series of fingers. A recent model for particle size-segregation has been coupled to existing avalanche models through a particle concentration dependent friction law. In this talk numerical solutions of this coupled system are presented and compared to both large scale experiments carried out at the USGS flume and more controlled small scale laboratory experiments. The coupled depth-averaged model captures the accumulation of large particles at the flow front. We show this large particle accumulation at the head of the flow can lead to the break-up of the initially uniform front into a series of fingers. However, we are unable to obtain a fully grid-resolved numerical solution; the width of the fingers decreases as the grid is refined. By considering the linear stability of a steady, fully-developed, bidisperse granular layer it is shown that

  3. Neurodegeneration-associated instability of ribosomal DNA.

    Science.gov (United States)

    Hallgren, Justin; Pietrzak, Maciej; Rempala, Grzegorz; Nelson, Peter T; Hetman, Michal

    2014-06-01

    Homologous recombination (HR)-mediated instability of the repetitively organized ribosomal DNA (rDNA) has been proposed as a mediator of cell senescence in yeast triggering the DNA damage response. High individual variability in the content of human rDNA suggests that this genomic region remained relatively unstable throughout evolution. Therefore, quantitative real-time polymerase chain reaction was used to determine the genomic content of rDNA in post mortem samples of parietal cortex from 14 young and 9 elderly individuals with no diagnosis of a chronic neurodegenerative/neurological disease. In addition, rDNA content in that brain region was compared between 10 age-matched control individuals and 10 patients with dementia with Lewy bodies (DLB) which involves neurodegeneration of the cerebral cortex. Probing rRNA-coding regions of rDNA revealed no effects of aging on the rDNA content. Elevated rDNA content was observed in DLB. Conversely, in the DLB pathology-free cerebellum, lower genomic content of rDNA was present in the DLB group. In the parietal cortex, such a DLB-associated instability of rDNA was not accompanied by any major changes of cytosine-phosphate-guanine methylation of the rDNA promoter. As increased cerebro-cortical rDNA content was previously reported in Alzheimer's disease, neurodegeneration appears to be associated with instability of rDNA. The hypothetical origins and consequences of this phenomenon are discussed including possibilities that the DNA damage-induced recombination destabilizes rDNA and that differential content of rDNA affects heterochromatin formation, gene expression and/or DNA damage response. This article is part of a Special Issue entitled: Role of the Nucleolus in Human Disease. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Jets instabilities producing the slot-tone

    OpenAIRE

    Billon, Alexis; Valeau, Vincent; Sakout, Anas

    2004-01-01

    The nature of the instability governing the self-sustained tones produced by a low Mach number free plane jet impinging on a slotted plate, known as slot-tone, is identified experimentally. The experimental apparatus permits to control the Reynolds number and the distance from the jet outlet to the plate. For a Reynolds number, the shear-layer natural frequency and the jet column mode frequency of the free jet without the obstacle are estimated and compared to the minimal and maximal frequenc...

  5. Stochastic stability and instability of model ecosystems

    Science.gov (United States)

    Ladde, G. S.; Siljak, D. D.

    1975-01-01

    In this work, we initiate a stability study of multispecies communities in stochastic environment by using Ito's differential equations as community models. By applying the direct method of Liapunov, we obtain sufficient conditions for stability and instability in the mean of the equilibrium populations. The conditions are expressed in terms of the dominant diagonal property of community matrices, which is a suitable mechanism for resolving the central problem of 'complexity vs stability' in model ecosystems. As a by-product of this analysis we exhibit important structural properties of the stochastic density-dependent models, and establish tolerance of community stability to a broad class of nonlinear time-varying perturbations.

  6. Wake fields and instabilities in linear accelerators

    CERN Document Server

    Ferrario, M; Palumbo, L

    2006-01-01

    A charged particle beam travelling across perfectly conducting structures whose boundaries do not have constant cross section, such as an RF cavity or bellows, generates longitudinal and transverse wake fields. We discuss in this lecture the general features of wake fields, and show a few simple examples in cylindrical geometry: perfectly conducting pipe and the resonant modes of an RF cavity. We then study the effect of wake fields on the dynamics of a beam in a linac, such as beam break-up instabilities and how to cure them.

  7. Numerical parametric studies of spray combustion instability

    Science.gov (United States)

    Pindera, M. Z.

    1993-01-01

    A coupled numerical algorithm has been developed for studies of combustion instabilities in spray-driven liquid rocket engines. The model couples gas and liquid phase physics using the method of fractional steps. Also introduced is a novel, efficient methodology for accounting for spray formation through direct solution of liquid phase equations. Preliminary parametric studies show marked sensitivity of spray penetration and geometry to droplet diameter, considerations of liquid core, and acoustic interactions. Less sensitivity was shown to the combustion model type although more rigorous (multi-step) formulations may be needed for the differences to become apparent.

  8. Numerical simulation of instability and transition physics

    Science.gov (United States)

    Streett, C. L.

    1990-01-01

    The study deals with the algorithm technology used in instability and transition simulations. Discretization methods are outlined, and attention is focused on high-order finite-difference methods and high-order centered-difference formulas. One advantage of finite-difference methods over spectral methods is thought to be in implementation of nonrigorous boundary conditions. It is suggested that the next significant advances in the understanding of transition physics and the ability to predict transition will come with more physically-realistic simulations. Compressible-flow algorithms are discussed, and it is noted that with further development, exploration of bypass mechanism on simple bodies at high speed would be possible.

  9. A Thermal Oscillating Two-Stream Instability

    DEFF Research Database (Denmark)

    Dysthe, K. B.; Mjølhus, E.; Pécseli, H. L.

    1983-01-01

    A theory for the oscillating two‐stream instability, in which the Ohmic heating of the electrons constitutes the nonlinearity, is developed for an inhomogeneous and magnetized plasma. Its possible role in explaining short‐scale, field‐aligned irregularities observed in ionospheric heating...... experiments is emphasized. The theory predicts that the initial growth of such irregularities is centered around the level of upper hybrid resonance. Furthermore, plane disturbances nearly parallel to the magnetic meridian plane have the largest growth rates. Expressions for threshold, growth rate...

  10. How Do Cytokines Trigger Genomic Instability?

    Directory of Open Access Journals (Sweden)

    Ioannis L. Aivaliotis

    2012-01-01

    Full Text Available Inflammation is a double-edged sword presenting a dual effect on cancer development, from one hand promoting tumor initiation and progression and from the other hand protecting against cancer through immunosurveillance mechanisms. Cytokines are crucial components of inflammation, participating in the interaction between the cells of tumor microenvironment. A comprehensive study of the role of cytokines in the context of the inflammation-tumorigenesis interplay helps us to shed light in the pathogenesis of cancer. In this paper we focus on the role of cytokines in the development of genomic instability, an evolving hallmark of cancer.

  11. Diagnostic Role of Chromosomal Instability in Melanoma

    Directory of Open Access Journals (Sweden)

    Nitika Dabas

    2012-01-01

    Full Text Available Early diagnosis gives melanoma patients the best chance for long term survival. However discrimination of an early melanoma from an unusual/atypical benign nevus can represent a significant challenge. There are no current pathological markers to definitively define malignant potential in these indeterminate lesions. Thus, there is a need for improved diagnostic tools. Chromosomal instability (CIN is a hallmark of cancer and is markedly prevalent in melanoma. Advances in genomics have opened the door for the development of molecular tools to better segregate benign and malignant lesions. This paper focuses on CIN in melanoma and the role of current diagnostic approaches.

  12. Instability of Bucket Foundations during Installation

    DEFF Research Database (Denmark)

    Madsen, Søren; Andersen, Lars Vabbersgaard; Ibsen, Lars Bo

    The bucket foundation is an upcoming technology for offshore wind turbines. The bucket foundation is a large cylindrical monopod foundation constructed as a thin steel shell structure. A bucket foundation does not require heavy installation equipment since it is installed by suction forces....... The combination of a thin shell structure and suction forces leads to the fact that instability, in form of buckling, becomes a crucial issue during installation. The hydrostatic buckling pressure of the bucket foundation is addressed using three-dimensional, non-linear finite element analysis. The results...

  13. Molecular Dissection of Microsatellite Instable Colorectal Cancer

    Science.gov (United States)

    Vilar, Eduardo; Tabernero, Josep

    2013-01-01

    Colorectal cancer was one of the first solid tumors to be classified based on molecular profiling. Microsatellite instability has allowed researchers to distinguish a specific subtype of colorectal cancer that has a clearly identified molecular origin (mismatch repair deficiency), arises on a hereditary and sporadic basis, is linked to a clear clinicopathological profile and has prognostic implications. Inconclusive predictive data along with a paucity of targeted drug development have prevented this molecular classification system from being implemented in the clinical setting. New high-throughput genomic data have validated it, thus stressing the fact that it is ready to be applied clinically. PMID:23454900

  14. MODEL OF ELECTRON CLOUD INSTABILITY IN FERMILAB RECYCLER

    Energy Technology Data Exchange (ETDEWEB)

    Antipov, Sergey A. [Chicago U.; Burov, A. [Fermilab; Nagaitsev, S. [Fermilab

    2016-10-04

    An electron cloud instability might limit the intensity in the Fermilab Recycler after the PIP-II upgrade. A multibunch instability typically develops in the horizontal plane within a hundred turns and, in certain conditions, leads to beam loss. Recent studies have indicated that the instability is caused by an electron cloud, trapped in the Recycler index dipole magnets. We developed an analytical model of an electron cloud driven instability with the electrons trapped in combined function dipoles. The resulting instability growth rate of about 30 revolutions is consistent with experimental observations and qualitatively agrees with the simulation in the PEI code. The model allows an estimation of the instability rate for the future intensity upgrades.

  15. Experimental study on modulational instability and evolution of crescent waves

    Directory of Open Access Journals (Sweden)

    Ya-long Zhou

    2012-12-01

    Full Text Available A series of experiments on the instability of steep water wave trains in water with finite water depths and infinite water depths in a wide wave basin were performed. It was found that under the coupled development of modulational instability and class-II instability, the initial two-dimensional steep wave trains evolved into three-dimensional crescent waves, followed by the occurrence of disordered water surfaces, and that the wave energy transferred to sidebands in the amplitude spectrum of the water surface elevation. The results also show that water depth has a significant effect on the growth of modulational instability and the evolution of crescent waves. The larger the water depth, the more quickly the modulational instability suppresses class-II instability.

  16. Spectrum of magnetic resonance imaging findings in clinical glenohumeral instability

    Directory of Open Access Journals (Sweden)

    Manisha Jana

    2011-01-01

    Full Text Available The glenohumeral joint is the most commonly dislocated joint in the body, and anterior instability is the most common type of shoulder instability. Depending on the etiology and the age of the patient, there may be associated injuries, for example, to the anterior-inferior labro-ligamentous structures (in young individuals with traumatic instability or to the bony components (commoner in the elderly, which are best visualized using MRI and MR arthrography. Anterior instability is associated with a Bankart lesion and its variants and abnormalities of the anterior band of the inferior glenohumeral ligament (IGHL, whereas posterior instability is associated with reverse Bankart and reverse Hill-Sachs lesions. Cases of multidirectional instability often have no labral pathology on imaging but show specific osseous changes including increased chondrolabral retroversion. This article reviews the relevant anatomy in brief and describes the MRI findings in each type, with the imaging features of the common abnormalities.

  17. MR imaging in sports-related glenohumeral instability

    Energy Technology Data Exchange (ETDEWEB)

    Woertler, Klaus; Waldt, Simone [Technische Universitaet Muenchen, Klinikum rechts der Isar, Department of Radiology, Munich (Germany)

    2006-12-15

    Sports-related shoulder pain and injuries represent a common problem. In this context, glenohumeral instability is currently believed to play a central role either as a recognized or as an unrecognized condition. Shoulder instabilities can roughly be divided into traumatic, atraumatic, and microtraumatic glenohumeral instabilities. In athletes, atraumatic and microtraumatic instabilities can lead to secondary impingement syndromes and chronic damage to intraarticular structures. Magnetic resonance (MR) arthrography is superior to conventional MR imaging in the diagnosis of labro-ligamentous injuries, intrinsic impingement, and SLAP (superior labral anteroposterior) lesions, and thus represents the most informative imaging modality in the overall assessment of glenohumeral instability. This article reviews the imaging criteria for the detection and classification of instability-related injuries in athletes with special emphasis on the influence of MR findings on therapeutic decisions. (orig.)

  18. The Electric Honeycomb; an investigation of the Rose window instability

    Science.gov (United States)

    Niazi, Muhammad Shaheer

    2017-10-01

    The Rose window instability is a little-explored electrohydrodynamic instability that manifests when a layer of low-conducting oil is placed in an electric field generated by corona discharge in a point-to-plane configuration. Above a critical voltage, the instability starts as a single dimple in the oil layer right below the point electrode and subsequently evolves into a characteristic pattern of polygonal cells. In this study, we experimentally explore governing parameters that guide the instability and document geometric attributes of the characteristic cellular pattern. The driving force for the instability has been attributed to the buildup of charged ions which in turn apply an electric pressure on the oil surface. We confirm the charged surface distribution using thermal imaging and demonstrate that the instability can be locally inhibited by preventing charge buildup under an ion shadow.

  19. Simulation and quasilinear theory of aperiodic ordinary mode instability

    Energy Technology Data Exchange (ETDEWEB)

    Seough, Jungjoon [Faculty of Human Development, University of Toyama, 3190, Gofuku, Toyama City, Toyama 930-8555 (Japan); International Research Fellow of the Japan Society for the Promotion of Science, Tokyo (Japan); Yoon, Peter H. [Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States); School of Space Research, Kyung Hee University, Yongin-Si, Gyeonggi-Do 446-701 (Korea, Republic of); Hwang, Junga [Korea Astronomy and Space Science Institute, Daejeon (Korea, Republic of); Department of Astronomy and Space Science, University of Science and Technology, Daejeon (Korea, Republic of); Nariyuki, Yasuhiro [Faculty of Human Development, University of Toyama, 3190, Gofuku, Toyama City, Toyama 930-8555 (Japan)

    2015-08-15

    The purely growing ordinary (O) mode instability driven by excessive parallel temperature anisotropy for high-beta plasmas was first discovered in the 1970s. This instability receives renewed attention because it may be applicable to the solar wind plasma. The electrons in the solar wind feature temperature anisotropies whose upper values are apparently limited by plasma instabilities. The O-mode instability may be important in this regard. Previous studies of O mode instability have been based on linear theory, but the actual solar wind electrons may be in saturated state. The present paper investigates the nonlinear saturation behavior of the O mode instability by means of one-dimensional particle-in-cell simulation and quasilinear theory. It is shown that the quasilinear method accurately reproduces the simulation results.

  20. [Instability pattern of acromioclavicular joint dislocations type Rockwood III: relevance of horizontal instability].

    Science.gov (United States)

    Wellmann, M; da Silva, G; Lichtenberg, S; Magosch, P; Habermeyer, P

    2013-04-01

    There is no evidence-based treatment algorithm established for acromioclavicular joint (AC joint) dislocation classified as type Rockwood III injury. Recent meta-analyses revealed no advantage of surgical treatment compared to the non-operative approach. Both surgical and non-surgical approaches have been reported with inconsistent results. Therefore, the hypothesis of the current study was that patients classified as having Rockwood grade III injury may have different degrees of horizontal AC joint instability. A total of 18 consecutive patients who had sustained a dislocation of the AC joint classified as Rockwood III were evaluated radiologically to quantify the horizontal instability of the AC joint. The specific radiological investigation included lateral stress x-rays (Alexander view) und axial stress x-rays with the affected arm in a horizontal adduction position. The dynamic horizontal instability of the AC joint was found to be independent of the vertical dislocation measured in the Rockwood classification. For further treatment studies Rockwood III injuries should be distinguished in patients presenting with or without a substantial horizontal AC joint instability.

  1. Transverse mode coupling instability for leptons in the CERN SPS

    Energy Technology Data Exchange (ETDEWEB)

    Linnecar, T.; Shaposhnikova, E.N. [European Organization for Nuclear Research, Geneva (Switzerland)

    1996-08-01

    The intensity of leptons accelerated in the SPS machine is limited by a vertical transverse instability. The results of measurements of the thresholds for this transverse instability are compared with theoretical predictions for different broad band impedance models of the SPS. The threshold intensities found for the transverse instability and the position of the losses in the cycle enable the parameters of the broadband resonant impedance to be specified. (author)

  2. Singular divergence instability thresholds of kinematically constrained circulatory systems

    Energy Technology Data Exchange (ETDEWEB)

    Kirillov, O.N., E-mail: o.kirillov@hzdr.de [Magnetohydrodynamics Division, Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, D-01314 Dresden (Germany); Challamel, N. [University of South Brittany, LIMATB, Lorient (France); Darve, F. [Laboratoire Sols Solides Structures, UJF-INPG-CNRS, Grenoble (France); Lerbet, J. [IBISC, Universite d' Evry Val d' Essone, 40 Rue Pelvoux, CE 1455 Courcouronnes, 91020 Evry Cedex (France); Nicot, F. [Cemagref, Unite de Recherche Erosion Torrentielle Neige et Avalanches, Grenoble (France)

    2014-01-10

    Static instability or divergence threshold of both potential and circulatory systems with kinematic constraints depends singularly on the constraints' coefficients. Particularly, the critical buckling load of the kinematically constrained Ziegler's pendulum as a function of two coefficients of the constraint is given by the Plücker conoid of degree n=2. This simple mechanical model exhibits a structural instability similar to that responsible for the Velikhov–Chandrasekhar paradox in the theory of magnetorotational instability.

  3. Magnetic field generation via parametric instabilities in collisional plasmas

    Science.gov (United States)

    Katoh, K.

    1982-06-01

    A formalism for the parametric instability with low-frequency magnetic field generation in a collisional plasma is developed. The spontaneous low-frequency magnetic field results from a resonant decay instability of an intense pump wave into a magneto-static wave which appears only in a collisional plasma. The growth rate for a resonant decay instability of an intense electromagnetic wave into a Langmuir wave and a magneto-static wave is obtained.

  4. Formation of matter-wave soliton trains by modulational instability

    OpenAIRE

    Nguyen, Jason H. V.; Luo MR; Hulet, Randall G.

    2017-01-01

    Nonlinear systems can exhibit a rich set of dynamics that are inherently sensitive to their initial conditions. One such example is modulational instability, which is believed to be one of the most prevalent instabilities in nature. By exploiting a shallow zero-crossing of a Feshbach resonance, we characterize modulational instability and its role in the formation of matter-wave soliton trains from a Bose-Einstein condensate. We examine the universal scaling laws exhibited by the system, and ...

  5. Magnetic field induced by elliptical instability in a rotating spheroid

    OpenAIRE

    Lacaze, Laurent; Herreman, Wietze; Le Bars, Michael; Le Dizès, Stéphane; Le Gal, Patrice

    2006-01-01

    International audience; The tidal or elliptical instability of rotating fluid flows is generated by the resonant interaction of inertial waves. In a slightly elliptically deformed rotating sphere, the most unstable linear mode is called the spin-over mode and is a solid body rotation versus an axis aligned with the maximum strain direction. In the non viscous case, this instability corresponds to the median moment of inertia instability of solid rotating bodies. This analogy is furthermore il...

  6. Flow-Induced Instabilities in Pump-Turbines in China

    Directory of Open Access Journals (Sweden)

    Zhigang Zuo

    2017-08-01

    Full Text Available The stability of pump-turbines is of great importance to the operation of pumped storage power (PSP stations. Both hydraulic instabilities and operational instabilities have been reported in PSP stations in China. In order to provide a reference to the engineers and scientists working on pump-turbines, this paper summarizes the hydraulic instabilities and performance characteristics that promote the operational instabilities encountered in pump-turbine operations in China. Definitions, analytical methods, numerical and experimental studies, and main results are clarified. Precautions and countermeasures are also provided based on a literature review. The gaps between present studies and the need for engineering practice are pointed out.

  7. Physics-Based Pneumatic Hammer Instability Model Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Florida Turbine Technologies (FTT) proposes to conduct research necessary to develop a physics-based pneumatic hammer instability model for hydrostatic bearings...

  8. A Rare Complication of Tuberculous Meningitis Pediatric Anterior Glenohumeral Instability

    Directory of Open Access Journals (Sweden)

    Kerem Bilsel

    2012-01-01

    Full Text Available Dislocation and instability of the shoulder joint are rare occurrences in childhood. Traumatic, infectious, congenital, and neuromuscular causes of pediatric recurrent shoulder dislocations are reported before. Central nervous system infection in infancy may be a reason for shoulder instability during childhood. This situation, which causes a disability for children, can be treated successfully with arthroscopic stabilization of the shoulder and postoperative effective rehabilitation protocols. Tuberculous meningitis may be a reason for neuromuscular shoulder instability. We describe a 12-year-old child with a recurrent anterior instability of the shoulder, which developed after tuberculous meningitis at 18 months of age. We applied arthroscopic treatment and stabilized the joint.

  9. NEW DIAGNOSTICS AND CURES FOR COUPLED-BUNCH INSTABILITIES

    Energy Technology Data Exchange (ETDEWEB)

    Teytelman, Dmitry

    2002-08-06

    As circular accelerators move towards larger numbers of bunches and higher beam currents, the task of diagnosing and curing coupled-bunch instabilities becomes ever harder. This paper describes the use of phase space tracking, i.e. reconstruction of bunch phase space trajectories, as a comprehensive instability diagnostic. A new instability cure is also presented, based on recent insights into the dynamics of unevenly-filled rings. Data is shown from PEP-II and the ALS, where ''optimally shaped'' uneven fills have yielded significant increases in instability thresholds.

  10. The single-mode CSR instability for a bunched beam

    Energy Technology Data Exchange (ETDEWEB)

    Heifets, Samuel A

    2003-03-19

    The coherent synchrotron radiation (CSR) instability at the shielding threshold may be driven by a single synchronous mode excited by the beam in the beam pipe. The instability in this case has been analyzed [1] in the coasting beam approximation neglecting synchrotron motion. The later becomes important at large time intervals in storage rings where it substantially affects the beam dynamics. The single-mode CSR instability of a bunched beam with the synchrotron motion taken into account is described in this paper both in linear and nonlinear regimes. Analysis is relevant to other instabilities where the interaction is dominated by a single mode.

  11. POSTTRAUMATIC SHOULDER INSTABILITY IN CHILDREN: CLINICAL PRESENTATION, DIAGNOSIS AND TREATMENT

    Directory of Open Access Journals (Sweden)

    Ярослав Николаевич Прощенко

    2014-09-01

    Full Text Available The article presents an analysis of the treatment of 15 patients with posttraumatic shoulder instability aged 11-17 years, as a result of primary traumatic dislocation and chronic instability. We identified the following causes of chronic shoulder instability: Bankart injury, SLAP-injury; Hill-Sachs defect; fracture of the glenoid, type 3 humeral head-glenoid relation, and retroversion of the humeral head, as well as defects in the treatment of primary shoulder dislocation. Surgical treatment is performed in 7 patients with chronic instability (7 joints. Unsatisfactory result was detected in 1 patient (1 joints, which is caused by a type 3 humeral head-glenoid relation.

  12. Midflexion instability in primary total knee replacement: a review

    Directory of Open Access Journals (Sweden)

    Ramappa Manjunath

    2015-01-01

    Full Text Available Introduction: Midflexion instability in primary total knee replacement (TKR is an evolving concept. Successful treatment of instability requires an understanding of the different types of instability. Methods: A literature review was performed to identify information pertinent to midflexion instability in primary total knee replacement, utilising PRISMA guidelines. Databases searched included Embase, Medline, All of the Cochrane Library, PubMed and cross references. Results: Three factors, i.e., elevated joint line, multiradii femoral component and medial collateral ligament (MCL laxity, were identified to influence midflexion instability. Literature suggested mediolateral instability at 30–60° of flexion as diagnostic of midflexion instability. Literature search also revealed paucity in clinical studies analysing midflexion instability. Most of the evidence was obtained from cadaveric studies for elevated joint line and MCL laxity. Clinical studies on multiradii femoral component were limited by their small study size and early followup period. Conclusion: Elevated joint line, multiradii femoral component and MCL laxity have been suggested to cause midflexion laxity in primary TKR. Due to limitations in available evidence, this review was unable to raise the strength of overall evidence. Future well-designed clinical studies are essential to make definitive conclusions. This review serves as a baseline for future researchers and creates awareness for routine assessment of midflexion instability in primary total knee replacement.

  13. Suppression of wake's instabilities by optimal streaks

    Science.gov (United States)

    Del Guercio, Gerardo; Cossu, Carlo; Pujals, Gregory

    2014-11-01

    Wakes can sustain large transient energy growth. Optimal perturbations are computed for the cases of parallel, weakly non-parallel and the circular cylinder wakes. Streaks are found to be the optimal amplified structures produced by the non normal energy amplification. The level of energy increases with the spanwise wavelength of the perturbations except in the circular cylinder wake where the optimal is reached for λz ~ 6 D . In parallel wakes these streaks are shown to suppress the absolute instability. Furthermore the global instability of the weakly non-parallel and the circular cylinder wakes can be completely annihilate with moderate streaks amplitudes. The comparison of these spanwise periodic (3D) optimal perturbations with the spanwise uniform (2D) control showed that the energy required to stabilize the wake is always smaller for the 3D control. Moreover the sensitivity of the global mode growth rate is discovered to be quadratic for 3D perturbations while being linear for 2D ones meaning that usual first order sensitivity analysis is unable to predict their larger efficiency.

  14. Theory of loop flows and instability

    Science.gov (United States)

    Priest, E. R.

    A preliminary theory for the steady and transient coronal loop flows in solar active regions and their magnetohydrodynamic instability is presented. Siphon flow is shown to be possible in the loops if a pressure difference is maintained between the footpoints, and to account for the presence of cool cores and appearances of only half a loop. The evolution of active region magnetic loops is found to lead to the continual evaporation and draining of the plasma contained within them, particularly as a result of an increase in heating rate. Consideration of static models for thermally isolated loops reveals them to be thermally unstable, implying that in the absence of some atmospheric stabilizing mechanism, the loops must be in a dynamic state of thermal activity. It is shown that kilogauss photospheric fields may be formed by an intense magnetic field instability, with an associated transient downflow which may induce coronal flows at enhanced velocities. Magnetohydrodynamic stability analysis suggests that the major cause of magnetic stability may be line-tying of loop footpoints in the dense photosphere.

  15. Formation of the solar system by instability

    Science.gov (United States)

    Griv, Evgeny; Gedalin, Michael

    2005-02-01

    The early gas and dust protosolar nebula of the solar composition is considered analytically. A simultaneous formation of the sun and all the planets around it (≈ 5 × 10(9) yr ago) through a local gravitational Jeans-type instability of small-amplitude gravity perturbations in the nebula disk is suggested. It is shown that a collective process, forming the basis of the disk instability hypothesis, solves with surprising simplicity the two main problems of the dynamical characteristics of the system, which are associated with its observed spacing and orbital momentum distribution, namely, Bode's law on planet spacing and the concentration of angular momentum in the planets and mass in the sun. Besides, the analysis is found to imply the existence of new planets or other Kuiper-type belts of comets at mean distances from the sun of 87 AU, 151 AU, 261 AU, 452 AU, 781 AU (Mercury, Venus, ..., Asteroid belt, ..., Neptune, Kuiper belt, new planets or other Kuiper-type belts).

  16. Bias temperature instability for devices and circuits

    CERN Document Server

    2014-01-01

    This book provides a single-source reference to one of the more challenging reliability issues plaguing modern semiconductor technologies, negative bias temperature instability.  Readers will benefit from state-of-the art coverage of research in topics such as time dependent defect spectroscopy, anomalous defect behavior, stochastic modeling with additional metastable states, multiphonon theory, compact modeling with RC ladders and implications on device reliability and lifetime.  ·         Enables readers to understand and model negative bias temperature instability, with an emphasis on dynamics; ·         Includes coverage of DC vs. AC stress, duty factor dependence and bias dependence; ·         Explains time dependent defect spectroscopy, as a measurement method that operates on nanoscale MOSFETs; ·         Introduces new defect model for metastable defect states, nonradiative multiphonon theory and stochastic behavior.

  17. Mixing in Rayleigh-Taylor Instabilities

    Science.gov (United States)

    Calder, A. C.; Fryxell, B.; Rosner, R.; Dursi, L. J.; Olson, K.; Ricker, P. M.; Timmes, F. X.; Zingale, M.; Tufo, H. M.; MacNeice, P.

    2000-12-01

    Fluid instabilities and subsequent mixing can play a fundamental role in many astrophysical processes, including the shock of a core-collapse supernova propagating through the outer layers of a massive star and the propagation of a burning front through a white dwarf in a thermonuclear runaway supernova. We present direct numerical simulations of mixing at Rayleigh-Taylor unstable interfaces performed with the Flash code, developed at the ASCI/Alliances Center for Astrophysical Thermonuclear Flashes at the University of Chicago. We present results of both single- and multi-mode studies in 2- and 3-dimensions. Our results indicate that 3-d perturbations grow significantly faster than 2-d perturbations and that grid resolution can have a significant effect on instability growth rates. We also find that unphysical diffusive mixing occurs at the fluid interface, particularly in poorly resolved simulations, making it difficult to maintain the purity of our fluids. This work was supported by the U.S Department of Energy under grant No. B341495.

  18. Cometary ion instabilities in the solar wind

    Science.gov (United States)

    Matteini, L.; Schwartz, S. J.; Hellinger, P.

    2015-12-01

    We review some of the processes that characterize the interaction of the solar wind with newborn cometary ions. Instabilities generated by the typical ring-beam velocity-space configuration of the pick-up ions in the solar wind frame are studied by means of one- and two-dimensional hybrid numerical simulations. In agreement with previous studies, we find that instabilities generated by the cometary ions play an important role in shaping the properties of the plasma. The resulting ion distributions are in good agreement with observations, showing the presence of energy shells in velocity space. Bi-spherical shells for the heavy oxygen ions are also observed in the late phase of the simulations. Moreover, we also investigate some new aspects of the dynamics, such as the generation of turbulent cascade from the initial spectra of unstable waves, and the related heating and back reaction of the solar wind plasma. We also consider the case of initial non-gyrotropic pick-up ion distributions, and we focus on the polarization of the associated waves, suggesting that linear polarization can be a signature of this configuration, possibly observed by the Rosetta spacecraft in orbit around comet 67P/CG.

  19. Opto-hydrodynamic instability of fluid interfaces

    Science.gov (United States)

    Delville, Jean-Pierre; Issenmann, Bruno; Wunenburger, Regis; Casner, Alexis

    2005-08-01

    The bending of fluid interfaces by the optical radiation pressure is now recognized as an appealing contactless tool to probe microscopic surface properties of soft materials. However, as the radiation pressure is intrinsically weak (typically of the order of a few Pascal), investigations are often limited to the regime of weak deformations. Non-linear behaviors can nevertheless be investigated using very soft fluid interfaces. Either a large stable tether is formed, or else a break-up of the interface occurs above a well-defined beam power threshold, depending on the direction of the beam propagation. This asymmetry originates from the occurrence of total reflection condition of light at deformed interface. Interface instability results in the formation of a stationary beam-centered liquid micro-jet that emits droplets. Radiation-induced jetting can also lead to giant tunable liquid columns with aspect ratio up to 100, i.e. well beyond the fundamental Rayleigh-Plateau limitation. Consequently, the applications range of the opto-hydrodynamic interface instability is wide, going from adaptative micro-optics (lensing and light guiding by the induced columns) to micro-fluidics and microspraying, as fluid transfer is optically monitored and directed in three dimensions.

  20. Order and instabilities in dense bacterial colonies

    Science.gov (United States)

    Tsimring, Lev

    2012-02-01

    The structure of cell colonies is governed by the interplay of many physical and biological factors, ranging from properties of surrounding media to cell-cell communication and gene expression in individual cells. The biomechanical interactions arising from the growth and division of individual cells in confined environments are ubiquitous, yet little work has focused on this fundamental aspect of colony formation. By combining experimental observations of growing monolayers of non-motile strain of bacteria Escherichia coli in a shallow microfluidic chemostat with discrete-element simulations and continuous theory, we demonstrate that expansion of a dense colony leads to rapid orientational alignment of rod-like cells. However, in larger colonies, anisotropic compression may lead to buckling instability which breaks perfect nematic order. Furthermore, we found that in shallow cavities feedback between cell growth and mobility in a confined environment leads to a novel cell streaming instability. Joint work with W. Mather, D. Volfson, O. Mondrag'on-Palomino, T. Danino, S. Cookson, and J. Hasty (UCSD) and D. Boyer, S. Orozco-Fuentes (UNAM, Mexico).

  1. Shoulder MRI after surgical treatment of instability

    Energy Technology Data Exchange (ETDEWEB)

    Vahlensieck, Martin [University of Bonn, Department of Radiology, Sigmund-Freud-Strasse 25, 53105 Bonn (Germany); Lang, Philipp [University of California San Francisco, Department of Radiology, 505 Pamassus Avenue, San Francisco, CA 94143 (United States); Wagner, Ulli [University of Bonn, Department of Orthopedic Surgery, Sigmund-Freud-Strasse 25, 53105 Bonn (Germany); Moeller, Frank [University of Bonn, Department of Orthopedic Surgery, Sigmund-Freud-Strasse 25, 53105 Bonn (Germany); Deimling, Urs van [University of Bonn, Department of Orthopedic Surgery, Sigmund-Freud-Strasse 25, 53105 Bonn (Germany); Genant, H.K. [University of California San Francisco, Department of Radiology, 505 Pamassus Avenue, San Francisco, CA 94143 (United States); Schild, Hans H. [University of Bonn, Department of Radiology, Sigmund-Freud-Strasse 25, 53105 Bonn (Germany)

    1999-04-01

    Objective: To analyze magnetic resonance imaging (MRI) findings of the shoulder after an instability operation. Materials and methods: Physical examinations, radiographs and MRI of 10 patients after anterior glenoid bone block insertion for ventral instability were compared. MRI included T{sub 1}-weighted spin-echo (TR=600, TE=20 ms) and T{sub 2}*-weighted gradient-echo sequences (TE=600, TE=18, Flip=30 deg.) in the axial, oblique-coronal and oblique-sagittal planes. Results: No patient suffered from recurrent subluxation. We found fusion of the bone block with the anterior glenoid in seven cases, dislocation of the bone block without contact to the glenoid in one case, and no visible bone block in two cases. On MRI, the bone block showed either signal intensity equivalent to fatty bone marrow (n=4) or was devoid of signal consistent with cortical bone or bone sclerosis (n=4). In all patients, a low signal intensity mass, 2-4 cm in diameter, was visible next to the glenoid insertion site. Conclusion: Insertion of a bone block onto the anterior glenoid induces formation of scar tissue, increasing the stability of the shoulder joint. This scar is well visible on MRI and forms independently of the behavior of the bone block itself. MRI is ideally suited for evaluating postoperative shoulder joints after bone-grafting procedures.

  2. Fermi Liquid Instabilities in the Spin Channel

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Congjun; /Santa Barbara, KITP; Sun, Kai; Fradkin, Eduardo; /Illinois U., Urbana; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-16

    We study the Fermi surface instabilities of the Pomeranchuk type in the spin triplet channel with high orbital partial waves (F{sub l}{sup a} (l > 0)). The ordered phases are classified into two classes, dubbed the {alpha} and {beta}-phases by analogy to the superfluid {sup 3}He-A and B-phases. The Fermi surfaces in the {alpha}-phases exhibit spontaneous anisotropic distortions, while those in the {beta}-phases remain circular or spherical with topologically non-trivial spin configurations in momentum space. In the {alpha}-phase, the Goldstone modes in the density channel exhibit anisotropic overdamping. The Goldstone modes in the spin channel have nearly isotropic underdamped dispersion relation at small propagating wavevectors. Due to the coupling to the Goldstone modes, the spin wave spectrum develops resonance peaks in both the {alpha} and {beta}-phases, which can be detected in inelastic neutron scattering experiments. In the p-wave channel {beta}-phase, a chiral ground state inhomogeneity is spontaneously generated due to a Lifshitz-like instability in the originally nonchiral systems. Possible experiments to detect these phases are discussed.

  3. Microsatellite Instability in Sarcoma: Fact or Fiction?

    Science.gov (United States)

    Monument, Michael J.; Lessnick, Stephen L.; Schiffman, Joshua D.; Randall, Rl. Tx.

    2012-01-01

    Microsatellite instability (MSI) is a unique molecular abnormality, indicative of a deficient DNA mismatch repair (MMR) system. Described and characterized in the colorectal cancer literature, the MSI-positive phenotype is predictive of disease susceptibility, pathogenesis, and prognosis. The clinical relevance of MSI in colorectal cancer has inspired similar inquisition within the sarcoma literature, although unfortunately, with very heterogeneous results. Evolving detection techniques, ill-defined sarcoma-specific microsatellite loci and small study numbers have hampered succinct conclusions. The literature does suggest that MSI in sarcoma is observed at a frequency similar to that of sporadic colorectal cancers, although there is little evidence to suggest that MSI-positive tumors share distinct biological attributes. Emerging evidence in Ewing sarcoma has demonstrated an intriguing mechanistic role of microsatellite DNA in the activation of key EWS/FLI-target genes. These findings provide an alternative perspective to the biological implications of microsatellite instability in sarcoma and warrant further investigation using sophisticated detection techniques, sensitive microsatellite loci, and appropriately powered study designs. PMID:23401795

  4. LOX/Hydrocarbon Combustion Instability Investigation

    Science.gov (United States)

    Jensen, R. J.; Dodson, H. C.; Claflin, S. E.

    1989-01-01

    The LOX/Hydrocarbon Combustion Instability Investigation Program was structured to determine if the use of light hydrocarbon combustion fuels with liquid oxygen (LOX) produces combustion performance and stability behavior similar to the LOX/hydrogen propellant combination. In particular methane was investigated to determine if that fuel can be rated for combustion instability using the same techniques as previously used for LOX/hydrogen. These techniques included fuel temperature ramping and stability bomb tests. The hot fire program probed the combustion behavior of methane from ambient to subambient temperatures. Very interesting results were obtained from this program that have potential importance to future LOX/methane development programs. A very thorough and carefully reasoned documentation of the experimental data obtained is contained. The hot fire test logic and the associated tests are discussed. Subscale performance and stability rating testing was accomplished using 40,000 lb. thrust class hardware. Stability rating tests used both bombs and fuel temperature ramping techniques. The test program was successful in generating data for the evaluation of the methane stability characteristics relative to hydrogen and to anchor stability models. Data correlations, performance analysis, stability analyses, and key stability margin enhancement parameters are discussed.

  5. CLIMATE INSTABILITY ON TIDALLY LOCKED EXOPLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Kite, Edwin S.; Manga, Michael [Department of Earth and Planetary Science, University of California at Berkeley, CA 94720 (United States); Gaidos, Eric, E-mail: edwin.kite@gmail.com [Department of Geology and Geophysics, University of Hawaii at Manoa, Honolulu, HI 96822 (United States)

    2011-12-10

    Feedbacks that can destabilize the climates of synchronously rotating rocky planets may arise on planets with strong day-night surface temperature contrasts. Earth-like habitable planets maintain stable surface liquid water over geologic time. This requires equilibrium between the temperature-dependent rate of greenhouse-gas consumption by weathering, and greenhouse-gas resupply by other processes. Detected small-radius exoplanets, and anticipated M-dwarf habitable-zone rocky planets, are expected to be in synchronous rotation (tidally locked). In this paper, we investigate two hypothetical feedbacks that can destabilize climate on planets in synchronous rotation. (1) If small changes in pressure alter the temperature distribution across a planet's surface such that the weathering rate goes up when the pressure goes down, a runaway positive feedback occurs involving increasing weathering rate near the substellar point, decreasing pressure, and increasing substellar surface temperature. We call this feedback enhanced substellar weathering instability (ESWI). (2) When decreases in pressure increase the fraction of surface area above the melting point (through reduced advective cooling of the substellar point), and the corresponding increase in volume of liquid causes net dissolution of the atmosphere, a further decrease in pressure will occur. This substellar dissolution feedback can also cause a runaway climate shift. We use an idealized energy balance model to map out the conditions under which these instabilities may occur. In this simplified model, the weathering runaway can shrink the habitable zone and cause geologically rapid 10{sup 3}-fold atmospheric pressure shifts within the habitable zone. Mars may have undergone a weathering runaway in the past. Substellar dissolution is usually a negative feedback or weak positive feedback on changes in atmospheric pressure. It can only cause runaway changes for small, deep oceans and highly soluble atmospheric

  6. The cosmological Higgstory of the vacuum instability

    CERN Document Server

    Espinosa, Jose R.; Morgante, Enrico; Riotto, Antonio; Senatore, Leonardo; Strumia, Alessandro; Tetradis, Nikolaos

    2015-01-01

    The Standard Model Higgs potential becomes unstable at large field values. After clarifying the issue of gauge dependence of the effective potential, we study the cosmological evolution of the Higgs field in presence of this instability throughout inflation, reheating and the present epoch. We conclude that anti-de Sitter patches in which the Higgs field lies at its true vacuum are lethal for our universe. From this result, we derive upper bounds on the Hubble constant during inflation, which depend on the reheating temperature and on the Higgs coupling to the scalar curvature or to the inflaton. Finally we study how a speculative link between Higgs meta-stability and consistence of quantum gravity leads to a sharp prediction for the Higgs and top masses, which is consistent with measured values.

  7. Coping with instabilities - lessons from Japanese architecture

    DEFF Research Database (Denmark)

    Greve, Anni

    , a Japanese idea about an ‘in-between’, place and occasion means an ‘in-between’, the Japanese term ma. The final part of the lecture considers ma in its quality as 1) a formula replicated in different cognitive domains, in language, visual perception, abstract ways of reasoning, emotions and actions, and 2......This paper offers insight into the role of architecture in coping with instabilities. At its centre is a second generation of Japanese architects who came to maturity after World War II. They questioned the International Style, and asked for a return to architecture in the image of the early...... capabilities in coping with eruptions and sudden changes. Transforming ruins into a city for the future, he argued, is not merely achieved by replicating the International Style it needs the inclusion of a rather stable formula for the construction of image schemes. This implies a particular Japanese motif...

  8. An inherent instability of efficient markets.

    Science.gov (United States)

    Patzelt, Felix; Pawelzik, Klaus

    2013-09-27

    Speculative markets are often described as "informationally efficient" such that predictable price changes are eliminated by traders exploiting them, leaving only residual unpredictable fluctuations. This classical view of markets operating close to an equilibrium is challenged by extreme price fluctuations which occur far more frequently than can be accounted for by external news. Here we show that speculative markets which absorb self-generated information can exhibit both: evolution towards efficient equilibrium states as well as their subsequent destabilisation. We introduce a minimal agent-based market model where the impacts of trading strategies naturally adapt according to their success. This implements a learning rule for the whole market minimising predictable price changes, and an extreme succeptibility at the point of perfect balance. The model quantitatively reproduces real heavy-tailed log return distributions and volatility clusters. Our results demonstrate that market instabilities can be a consequence of the very mechanisms that lead to market efficiency.

  9. Aqueous Instability of δ-Fluorobutylpiperidines

    DEFF Research Database (Denmark)

    Vorberg, Raffael; Carreira, Erick M; Müller, Klaus

    2017-01-01

    to an intramolecular ring-closing fluorine substitution reaction by the moderately basic piperidine unit, leading to a spiro-pyrrolidinium salt. The chemical lability of δ-monofluorinated or γ,δ-difluorinated N-butylpiperidine derivatives even under very mild biophysical assay conditions constitutes a caveat......In a series of partially fluorinated N-propyl- and N-butylpiperidine derivatives, three compounds were found to exhibit unexpected instability under mild biophysical assay conditions. These compounds carry a single terminal fluorine in the δ-position of an N-butyl group as a common structural...... feature. An adjacent fluorine substituent at the γ-position significantly slows down the reactivity. All other compounds, having either no or more than one fluorine substituent at the δ-position are chemically inert under all assay conditions. The reactivity of the labile compounds is traced...

  10. Semiconductor lasers stability, instability and chaos

    CERN Document Server

    Ohtsubo, Junji

    2017-01-01

    This book describes the fascinating recent advances made concerning the chaos, stability and instability of semiconductor lasers, and discusses their applications and future prospects in detail. It emphasizes the dynamics in semiconductor lasers by optical and electronic feedback, optical injection, and injection current modulation. Applications of semiconductor laser chaos, control and noise, and semiconductor lasers are also demonstrated. Semiconductor lasers with new structures, such as vertical-cavity surface-emitting lasers and broad-area semiconductor lasers, are intriguing and promising devices. Current topics include fast physical number generation using chaotic semiconductor lasers for secure communication, development of chaos, quantum-dot semiconductor lasers and quantum-cascade semiconductor lasers, and vertical-cavity surface-emitting lasers. This fourth edition has been significantly expanded to reflect the latest developments. The fundamental theory of laser chaos and the chaotic dynamics in se...

  11. Instability in electromagnetically driven flows Part II

    CERN Document Server

    Imazio, Paola Rodriguez

    2016-01-01

    In a previous paper, we have reported numerical simulations of the MHD flow driven by a travelling magnetic field (TMF) in an annular channel, at low Reynolds number. It was shown that the stalling of such induction pump is strongly related to magnetic flux expulsion. In the present article, we show that for larger hydrodynamic Reynolds number, and with more realistic boundary conditions, this instability takes the form of a large axisymmetric vortex flow in the (r,z)-plane, in which the fluid is locally pumped in the direction opposite to the one of the magnetic field. Close to the marginal stability of this vortex flow, a low-frequency pulsation is generated. Finally, these results are compared to theoretical predictions and are discussed within the framework of experimental annular linear induction electromagnetic pumps.

  12. The cosmological Higgstory of the vacuum instability

    Energy Technology Data Exchange (ETDEWEB)

    Espinosa, José R. [IFAE, Universitat Autónoma de Barcelona,08193 Bellaterra, Barcelona (Spain); ICREA, Institució Catalana de Recerca i Estudis Avançats,Barcelona (Spain); Giudice, Gian F. [CERN, Theory Division,CH-1211 Geneva 23 (Switzerland); Morgante, Enrico; Riotto, Antonio [Département de Physique Théorique and Centre for Astroparticle Physics (CAP),Université de Genève, 24 quai Ernest-Ansermet, CH-1211 Geneva 4 (Switzerland); Senatore, Leonardo [Stanford Institute for Theoretical Physicsand Kavli Institute for Particle Astrophysics and Cosmology,Physics Department and SLAC, Stanford, CA 94025 (United States); Strumia, Alessandro [Dipartimento di Fisica dell’Università di Pisa and INFN, Polo Fibonacci,Largo B. Pontecorvo 3, Pisa (Italy); National Institute of Chemical Physics and Biophysics,Ravala 10, Tallinn (Estonia); Tetradis, Nikolaos [Department of Physics, University of Athens,Zographou 157 84 (Greece)

    2015-09-24

    The Standard Model Higgs potential becomes unstable at large field values. After clarifying the issue of gauge dependence of the effective potential, we study the cosmological evolution of the Higgs field in presence of this instability throughout inflation, reheating and the present epoch. We conclude that anti-de Sitter patches in which the Higgs field lies at its true vacuum are lethal for our universe. From this result, we derive upper bounds on the Hubble constant during inflation, which depend on the reheating temperature and on the Higgs coupling to the scalar curvature or to the inflaton. Finally we study how a speculative link between Higgs meta-stability and consistence of quantum gravity leads to a sharp prediction for the Higgs and top masses, which is consistent with measured values.

  13. Bifurcation and instability problems in vortex wakes

    DEFF Research Database (Denmark)

    Aref, Hassan; Brøns, Morten; Stremler, Mark A.

    2007-01-01

    A number of instability and bifurcation problems related to the dynamics of vortex wake flows are addressed using various analytical tools and approaches. We discuss the bifurcations of the streamline pattern behind a bluff body as a vortex wake is produced, a theory of the universal Strouhal......-Reynolds number relation for vortex wakes, the bifurcation diagram for "exotic" wake patterns behind an oscillating cylinder first determined experimentally by Williamson & Roshko, and the bifurcations in topology of the streamlines pattern in point vortex streets. The Hamiltonian dynamics of point vortices...... in a periodic strip is considered. The classical results of von Kármán concerning the structure of the vortex street follow from the two-vortices-in-a-strip problem, while the stability results follow largely from a four-vortices-in-a-strip analysis. The three-vortices-in-a-strip problem is argued...

  14. Estimations of Coherent Instabilities for JLEIC

    Energy Technology Data Exchange (ETDEWEB)

    Li, Rui [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

    2017-05-01

    JLEIC is the medium energy electron-ion collider currently under active design at Jefferson Lab*. The design goals of JLEIC are both high luminosity (1033-1034 cm-2ses-1) and high polarization (>70%) for the electron and light ion beams, for a wide range of electron and ion beam energies and for a wide spectrum of ion species. The unprecedented luminosity goal for this electron-ion collider sets strong requirements for the understanding and management of potential collective effects in JLEIC. In this paper, we present preliminary estimations of single and coupled bunch coherent instabilities for the electron and proton beams at collision energies for the JLEIC design. Further improvement of the estimations and mitigation methods are discussed.

  15. One-hit wonders of genomic instability

    Directory of Open Access Journals (Sweden)

    Strunnikov Alexander V

    2010-05-01

    Full Text Available Abstract Recent data show that cells from many cancers exhibit massive chromosome instability. The traditional view is that the gradual accumulation of mutations in genes involved in transcriptional regulation and cell cycle controls results in tumor development. This, however, does not exclude the possibility that some mutations could be more potent than others in destabilizing the genome by targeting both chromosomal integrity and corresponding checkpoint mechanisms simultaneously. Three such examples of "single-hit" lesions potentially leading to heritable genome destabilization are discussed. They include: failure to release sister chromatid cohesion due to the incomplete proteolytic cleavage of cohesin; massive merotelic kinetochore misattachments upon condensin depletion; and chromosome under-replication. In all three cases, cells fail to detect potential chromosomal bridges before anaphase entry, indicating that there is a basic cell cycle requirement to maintain a degree of sister chromatid bridging that is not recognizable as chromosomal damage.

  16. Estimation of collective instabilities in RHIC

    Science.gov (United States)

    Mackay, W. W.; Blaskiewicz, M.; Deng, D.; Mane, V.; Peggs, S.; Ratti, A.; Rose, J.; Shea, T. J.; Wei, J.

    1995-05-01

    The authors have estimated the broadband impedance in RHIC to be absolute value of(Z/n) less than 1.2 Omega for frequencies above 100 MHz. The Z/n threshold is set for Au(79+) ions at transition with an estimated 10% growth in emittance for Z/n = 1.5 Omega. They summarize the sources of broad and narrow band impedances in RHIC and investigate the multibunch instability limits throughout the machine cycle. The largest contribution to the broadband impedance comes from the abort and injection kickers. Since RHIC is designed to accelerate fully stripped ions from H(+) up to Au(79+) they give results for both protons and gold ions; other ions should give results somewhere between these two extremes. All ion species are expected to be stable during storage. At lower energies damping systems and chromaticity corrections will limit any growth to acceptable levels during the short time it takes to inject and accelerate the beams.

  17. Explosive magnetorotational instability in Keplerian disks

    Energy Technology Data Exchange (ETDEWEB)

    Shtemler, Yu., E-mail: shtemler@bgu.ac.il; Liverts, E., E-mail: eliverts@bgu.ac.il; Mond, M., E-mail: mond@bgu.ac.il [Department of Mechanical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel)

    2016-06-15

    Differentially rotating disks under the effect of axial magnetic field are prone to a nonlinear explosive magnetorotational instability (EMRI). The dynamic equations that govern the temporal evolution of the amplitudes of three weakly detuned resonantly interacting modes are derived. As distinct from exponential growth in the strict resonance triads, EMRI occurs due to the resonant interactions of an MRI mode with stable Alfvén–Coriolis and magnetosonic modes. Numerical solutions of the dynamic equations for amplitudes of a triad indicate that two types of perturbations behavior can be excited for resonance conditions: (i) EMRI which leads to infinite values of the three amplitudes within a finite time, and (ii) bounded irregular oscillations of all three amplitudes. Asymptotic explicit solutions of the dynamic equations are obtained for EMRI regimes and are shown to match the numerical solutions near the explosion time.

  18. Instabilities of microstate geometries with antibranes

    Energy Technology Data Exchange (ETDEWEB)

    Bena, Iosif; Pasini, Giulio [Institut de physique théorique, Université Paris Saclay, CEA, CNRS,F-91191 Gif-sur-Yvette (France)

    2016-04-29

    One can obtain very large classes of horizonless microstate geometries corresponding to near-extremal black holes by placing probe supertubes whose action has metastable minima inside certain supersymmetric bubbling solutions http://dx.doi.org/10.1007/JHEP12(2012)014. We show that these minima can lower their energy when the bubbles move in certain directions in the moduli space, which implies that these near-extremal microstates are in fact unstable once one considers the dynamics of all their degrees of freedom. The decay of these solutions corresponds to Hawking radiation, and we compare the emission rate and frequency to those of the corresponding black hole. Our analysis supports the expectation that generic non-extremal black holes microstate geometries should be unstable. It also establishes the existence of a new type of instabilities for antibranes in highly-warped regions with charge dissolved in fluxes.

  19. Effects of antioxidants on drug-induced glutathione instability and ...

    African Journals Online (AJOL)

    Glutathione (GSH) instability leading to its depletion, and enhanced lipid peroxidation, are associated with the pathogenesis, progression and therapy of many diseases / disease conditions – including sickle cell disease. In this study, the effects of two antioxidants, ascorbic acid and á - tocopherol, on GSH instability and ...

  20. Impact of Export Instability on Economic Growth in Tanzania | Kweka ...

    African Journals Online (AJOL)

    This is consistent with the findings in most commodity-dependent developing countries that export instability is detrimental to economic growth. Reducing export instability is possible through diversification of the export basket and destination markets, with policy attention on resolving constraints to domestic production for ...

  1. Modulation instability of an intense laser beam in an unmagnetized ...

    Indian Academy of Sciences (India)

    The modulation instability of an intense circularly polarized laser beam propagating in an unmagnetized, cold electron–positron–ion plasma is investigated. Adopting a generalized Karpman method, a three-dimensional nonlinear equation is shown to govern the laser field. Then the conditions for modulation instability and ...

  2. Two scenarios of instability development in flow with strong swirling

    DEFF Research Database (Denmark)

    Naumov, Igor; Okulov, Valery; Sørensen, Jens Nørkær

    2007-01-01

    The development of instability in a flow generated in a cylindrical cavity with a rotating endwall has been studied. Both possible scenarios of the development of instability, according to which the amplitude of velocity pulsation grows or decays with increasing twist of the flow, have been...

  3. Jeans Instability of the Self-Gravitating Viscoelastic Ferromagnetic ...

    Indian Academy of Sciences (India)

    Joginder Singh Dhiman

    2017-11-27

    Nov 27, 2017 ... usual Jeans instability, they also observed that the sound waves suffer a new type of instability, which is due to the combined effects of the baryonic gas dynamics and self-gravitational field in both weakly and highly colli- sional regimes. Odenbach (2003) studied the magnetoviscous and viscoelastic effects ...

  4. Dynamical instability of a two-dimensional quantum black hole

    Science.gov (United States)

    Itoh, Y.; Hotta, M.; Morikawa, M.; Futamase, T.

    1998-04-01

    We investigate the dynamical instability of the two-dimensional quantum black hole model considered by Lowe in his study of Hawking evaporation. The model is supposed to express a black hole in equilibrium with a bath of Hawking radiation. It turns out that the model has at least one instability mode for a wide range of parameters, and thus it is unstable.

  5. Interplay of magnetism and valence instabilities in lanthanide systems

    Directory of Open Access Journals (Sweden)

    José Luiz Ferreira

    2016-06-01

    Full Text Available The valence instability in lanthanide systems is described within an extended periodic Anderson Hamiltonian (EPAM which includes Coulomb repulsion between f- and conduction- electrons, allowing to describe both discontinuous and continuous valence variations. We investigate the connection between valence and magnetism in this model and show that it can be applied to several lanthanide compounds showing both magnetic and valence instabilities.

  6. Manipulation of interfacial instabilities by using a soft, deformable ...

    Indian Academy of Sciences (India)

    Abstract. Multilayer flows are oftensusceptible to interfacial instabilities caused due to jump in viscosity/elasticity across thefluid–fluid interface. It is frequently required to manipulate and control these interfacial instabilities in various applications such as coating processes or polymer coextrusion. We demonstrate here the ...

  7. SPHYNX: SPH hydrocode for subsonic hydrodynamical instabilities and strong shocks

    Science.gov (United States)

    Cabezon, Ruben M.; Garcia-Senz, Domingo

    2017-09-01

    SPHYNX addresses subsonic hydrodynamical instabilities and strong shocks; it is Newtonian, grounded on the Euler-Lagrange formulation of the smoothed-particle hydrodynamics technique, and density based. SPHYNX uses an integral approach for estimating gradients, a flexible family of interpolators to suppress pairing instability, and incorporates volume elements to provides better partition of the unity.

  8. On the Saturation of the Magnetorotational Instability via Parasitic Modes

    DEFF Research Database (Denmark)

    Pessah, Martin Elias; Goodman, Jeremy

    2009-01-01

    We investigate the stability of incompressible, exact, non-ideal magnetorotational (MRI) modes against parasitic instabilities. Both Kelvin-Helmholtz and tearing-mode parasitic instabilities may occur in the dissipative regimes accessible to current numerical simulations. We suppose that a primar...

  9. Turbulent Instability of Anti-De Sitter Space-Time

    Science.gov (United States)

    Maliborski, Maciej; Rostworowski, Andrzej

    2013-09-01

    In these lecture notes, we discuss recently conjectured instability of anti-de Sitter space, resulting in gravitational collapse of a large class of arbitrarily small initial perturbations. We uncover the technical details used in the numerical study of spherically symmetric Einstein-massless scalar field system with negative cosmological constant that led to the conjectured instability.

  10. Maintaining sleep and physical activity alleviate mood instability.

    Science.gov (United States)

    Bowen, Rudy; Balbuena, Lloyd; Baetz, Marilyn; Schwartz, Laura

    2013-11-01

    Building on previous work indicating that mood instability is the hallmark of neuroticism, our aim was to examine whether changes in exercise, sleep duration and leisure predicted decreases in mood instability with time. We used data from 3374 participants of the British Health and Lifestyle Study who answered the Eysenck Personality Inventory-Neuroticism subscale (EPI-N) and the General Health Questionnaire on two occasions 7 years apart. We predicted mood instability scores derived from the EPI-N at follow-up using self-reported changes in exercise, sleep duration and leisure hours between the two time points as independent variables. We confirmed the observation that mood instability decreases with age. Maintaining one's exercise at baseline level decreased mood instability (beta=-0.21) while sleeping less increased mood instability (beta=0.14). Change in leisure time was not independently related to mood instability after accounting for the two other lifestyle factors. Personality, at least with regard to mood instability, can be modified by lifestyle factors. Exercise and sleep support mood stability and could be important components of preventative mental health (as well as physical health) benefits. © 2013.

  11. Prediction of Combustion Instability with Detailed Chemical Kinetics

    Science.gov (United States)

    2014-12-01

    Rendus Mecanique , 2013. 8 S. Srinivasan, R. Ranjan, and S. Menon. Flame Dynamics During Combustion Instability in a High- Pressure, Shear-Coaxial...Terms on Reliability of CFD Algorithms. Computers and Fluids , 39(10):1909–1922, 2010. 18 Harvazinski M.E. Modeling Self-Excited Combustion Instabilities

  12. Open capsular shift for multi directional shoulder instability.

    NARCIS (Netherlands)

    Tankeren, E. van; Waal Malefijt, M.C. de; Loon, C. van

    2002-01-01

    We evaluated the outcome of open antero-inferior capsular shift in 17 patients with multidirectional instability of the shoulder who failed to respond to conservative treatment. Six shoulders presented with secondary impingement syndrome and 11 with involuntary instability. The mean duration of

  13. The modelling of instabilities in liquid-liquid miscible displacement ...

    African Journals Online (AJOL)

    The propagation of instabilities can be achieved through the actions of viscous, gravity and heterogeneous forces, and iv. Heterogeneity in permeability introduces a macroscopic dispersion effect that attempts to stabilize the instabilities. Journal of the Nigerian Association of Mathematical Physics Vol. 8 2004: pp. 173-176 ...

  14. On the Raman instability in degenerate relativistic plasmas

    Science.gov (United States)

    Chanturia, G. T.; Berezhiani, V. I.; Mahajan, S. M.

    2017-07-01

    The stimulated Raman scattering instability in a fully degenerate electron plasma is studied applying relativistic hydrodynamic and Maxwell equations. We demonstrated that the instability develops for weakly and strongly relativistic degenerate plasmas. It is shown that in the field of strong radiation, a degenerate relativistic plasma effectively responses as in the case of weak degeneracy.

  15. Manipulation of interfacial instabilities by using a soft, deformable ...

    Indian Academy of Sciences (India)

    Multilayer flows are oftensusceptible to interfacial instabilities caused due to jump in viscosity/elasticity across thefluid–fluid interface. It is frequently required to manipulate and control these interfacial instabilities in various applications such as coating processes or polymer coextrusion. We demonstrate here the possibility ...

  16. Vortex-Surface Interactions: Vortex Dynamics and Instabilities

    Science.gov (United States)

    2015-10-16

    Crow instability (see for example Leweke & Williamson, 2012). (b) Short-wave cooperative elliptic instability (Leweke & Williamson 1998). (c...vortex generators. Of interest in such studies would be the formation of secondary vorticity from the surface, the downstream vortex trajectories , and

  17. Chronic ankle instability: Arthroscopic anatomical repair.

    Science.gov (United States)

    Arroyo-Hernández, M; Mellado-Romero, M; Páramo-Díaz, P; García-Lamas, L; Vilà-Rico, J

    Ankle sprains are one of the most common injuries. Despite appropriate conservative treatment, approximately 20-40% of patients continue to have chronic ankle instability and pain. In 75-80% of cases there is an isolated rupture of the anterior talofibular ligament. A retrospective observational study was conducted on 21 patients surgically treated for chronic ankle instability by means of an arthroscopic anatomical repair, between May 2012 and January 2013. There were 15 men and 6 women, with a mean age of 30.43 years (range 18-48). The mean follow-up was 29 months (range 25-33). All patients were treated by arthroscopic anatomical repair of anterior talofibular ligament. Four (19%) patients were found to have varus hindfoot deformity. Associated injuries were present in 13 (62%) patients. There were 6 cases of osteochondral lesions, 3 cases of posterior ankle impingement syndrome, and 6 cases of peroneal pathology. All these injuries were surgically treated in the same surgical time. A clinical-functional study was performed using the American Orthopaedic Foot and Ankle Society (AOFAS) score. The mean score before surgery was 66.12 (range 60-71), and after surgery it increased up to a mean of 96.95 (range 90-100). All patients were able to return to their previous sport activity within a mean of 21.5 weeks (range 17-28). Complications were found in 3 (14%) patients. Arthroscopic anatomical ligament repair technique has excellent clinical-functional results with a low percentage of complications, and enables patients to return to their previous sport activity within a short period of time. Copyright © 2016 SECOT. Publicado por Elsevier España, S.L.U. All rights reserved.

  18. Moral instability: the upsides for nursing practice.

    Science.gov (United States)

    McCarthy, Joan

    2010-04-01

    This article briefly outlines some of the key problems with the way in which the moral realm has traditionally been understood and analysed. I propose two alternative views of what is morally interesting and applicable to nursing practice and I indicate that instability has its upsides. I begin with a moral tale - a 'Good Samaritan' story - which raises fairly usual questions about the nature of morality but also the more philosophically fundamental question about the relationship between subjectivity and moral agency. I then consider this relationship from the perspectives of two twentieth century philosophers: Emmanuel Levinas and Michel Foucault. Levinas' basic point is that the experience of ethical subjectivity is made possible through others: the demand to respond to the existence of others is the basic social structure that precedes individual freedom. If Levinas posits intersubjectivity as a fundamental or primitive feature of the moral realm, Foucault poses an even more basic question: how have moral subjects and relations of obligation been constituted? The aim of ethical inquiry, for Foucault, is to describe the network of discourses, institutions, relations, and practices through which certain kinds of subjects are constituted and constitute themselves, e.g. as a kind of person who can act morally. Finally, I consider some recent research in philosophy of nursing which illustrates how Levinasian and/or Foucauldian perspectives can deepen understanding of nurses' moral practices, specifically, the work of Norwegian public health nurses, Canadian pediatric nurses, and Irish midwives. I suggest that in spite of the instability of morality in general and the particular ethical challenges that face nurses, there are grounds for hope and possible strategies for living in unstable times.

  19. Instability of a spatially developing liquid sheet

    Science.gov (United States)

    de Luca, Luigi; Costa, Michela

    1997-01-01

    The linear stability of an inviscid two-dimensional liquid sheet falling under gravity in a still gas is studied by analysing the asymptotic behaviour of a localized perturbation (wave-packet solution to the initial value problem). Unlike previous papers the effect of gravity is fully taken into account by introducing a slow length scale which allows the flow to be considered slightly non-parallel. A multiple-scale approach is developed and the dispersion relations for both the sinuous and varicose disturbances are obtained to the zeroth-order approximation. These exhibit a local character as they involve a local Weber number We[eta]. For sinuous disturbances a critical We[eta] equal to unity is found below which the sheet is locally absolutely unstable (with algebraic growth of disturbances) and above which it is locally convectively unstable. The transition from absolute to convective instability occurs at a critical location along the vertical direction where the flow Weber number equals the dimensionless sheet thickness. This critical distance, as measured from the nozzle exit section, increases with decreasing the flow Weber number, and hence, for instance, the liquid flow rate per unit length. If the region of absolute instability is relatively small it may be argued that the system behaves as a globally stable one. Beyond a critical size the flow receptivity is enhanced and self-sustained unstable global modes should arise. This agrees with the experimental evidence that the sheet breaks up as the flow rate is reduced. It is conjectured that liquid viscosity may act to remove the algebraic growth, but the time after which this occurs could be not sufficient to avoid possible nonlinear phenomena appearing and breaking up the sheet.

  20. Electron-ion hybrid instability experiment upgrades to the Auburn Linear Experiment for Instability Studies.

    Science.gov (United States)

    DuBois, A M; Arnold, I; Thomas, E; Tejero, E; Amatucci, W E

    2013-04-01

    The Auburn Linear EXperiment for Instability Studies (ALEXIS) is a laboratory plasma physics experiment used to study spatially inhomogeneous flows in a magnetized cylindrical plasma column that are driven by crossed electric (E) and magnetic (B) fields. ALEXIS was recently upgraded to include a small, secondary plasma source for a new dual source, interpenetrating plasma experiment. Using two plasma sources allows for highly localized electric fields to be made at the boundary of the two plasmas, inducing strong E × B velocity shear in the plasma, which can give rise to a regime of instabilities that have not previously been studied in ALEXIS. The dual plasma configuration makes it possible to have independent control over the velocity shear and the density gradient. This paper discusses the recent addition of the secondary plasma source to ALEXIS, as well as the plasma diagnostics used to measure electric fields and electron densities.

  1. Clinical and radiological instability following standard fenestration discectomy

    Directory of Open Access Journals (Sweden)

    Mascarenhas Amrithlal

    2009-01-01

    Full Text Available Background: Post-surgical lumbar instability is an established complication but there is limited evidence in the literature regarding the incidence of lumbar instability following fenestration and discectomy. We analyzed our results following fenestration discectomy with a special focus on instability. Materials and Methods: Eighty-three patients between the age of 17 and 52 years who had undergone fenestration discectomy for a single-level lumbar intervertebral disc prolapse were followed-up for a period of 1-5 years. The criteria for instability included "instability catch,", "painful catch," and "apprehension." The working capacity of the patient and the outcome score of the surgery were assessed by means of the Oswestry disability score and the Prolo economic and functional outcome score. Flexion-extension lateral radiographs were taken and analyzed for abnormal tilt and translation. Results: Of the 83 patients included, 70 were men and 13 were women, with an average age of 37.35 years (17-52 years at 5 years follow-up. Clinical instability was seen in 10 (12.04% patients. Radiological instability was noted in 29 (34.9% patients. Only six (60% of the 10 patients who demonstrated clinical instability had radiological evidence of instability. Twenty (68.96% patients with radiological instability were asymptomatic. Three (10.34% patients with only radiological instability had unsatisfactory outcome. The Oswestry scoring showed an average score of 19.8%. Mild disability was noted in 59 (71.08% patients and moderate disability was seen in 24 (28.91% patients. None of the patients had severe disability. These outcomes were compared with the outcomes in other studies in the literature for microdiscectomy and the results were found to be comparable. Conclusion: The favorable outcome of this study is in good agreement with other studies on microdiscectomy. Clinical instability in 12.04% of the patients is in agreement with other studies. Radiological

  2. Anisotropy-Driven Instability in Intense Charged Particle Beams

    CERN Document Server

    Startsev, Edward; Qin, Hong

    2005-01-01

    In electrically neutral plasmas with strongly anisotropic distribution functions, free energy is available to drive different collective instabilities such as the electrostatic Harris instability and the transverse electromagnetic Weibel instability. Such anisotropies develop naturally in particle accelerators and may lead to a detoriation of beam quality. We have generalized the analysis of the classical Harris and Weibel instabilities to the case of a one-component intense charged particle beam with anisotropic temperature including the important effects of finite transverse geometry and beam space-charge. For a long costing beam, the delta-f particle-in-cell code BEST and the eighenmode code bEASt have been used to determine detailed 3D stability properties over a wide range of temperature anisotropy and beam intensity. A theoretical model is developed which describes the essential features of the linear stage of these instabilities. Both, the simulations and analytical theory, clearly show that moderately...

  3. Laboratory experiments and numerical simulations on magnetic instabilities

    CERN Document Server

    Stefani, F; Kasprzyk, Ch; Paredes, A; Ruediger, G; Seilmayer, M

    2016-01-01

    Magnetic fields of planets, stars and galaxies are generated by self-excitation in moving electrically conducting fluids. Once produced, magnetic fields can play an active role in cosmic structure formation by destabilizing rotational flows that would be otherwise hydrodynamically stable. For a long time, both hydromagnetic dynamo action as well as magnetically triggered flow instabilities had been the subject of purely theoretical research. Meanwhile, however, the dynamo effect has been observed in large-scale liquid sodium experiments in Riga, Karlsruhe and Cadarache. In this paper, we summarize the results of some smaller liquid metal experiments devoted to various magnetic instabilities such as the helical and the azimuthal magnetorotational instability, the Tayler instability, and the different instabilities that appear in a magnetized spherical Couette flow. We conclude with an outlook on a large scale Tayler-Couette experiment using liquid sodium, and on the prospects to observe magnetically triggered ...

  4. Rayleigh-Taylor instability in accelerated solid media

    Science.gov (United States)

    Piriz, A. R.; Sun, Y. B.; Tahir, N. A.

    2017-01-01

    A linear study of the Rayleigh-Taylor instability based on momentum conservation and the consideration of an irrotational velocity field for incompressible perturbations is discussed. The theory allows for a very appealing physical picture and for a relatively simple description of the main features of the instability. As a result, it is suitable for the study of the very complex problem of the instability of accelerated solids with non-linear elastic-plastic constitutive properties, which cannot be studied by the usual normal modes approach. The elastic to plastic transition occurring early in the instability process determines the entire evolution and makes the instability exhibit behavior that cannot be captured by an asymptotic analysis.

  5. Electromagnetic ion/ion cyclotron instability - Theory and simulations

    Science.gov (United States)

    Winske, D.; Omidi, N.

    1992-01-01

    Linear theory and 1D and 2D hybrid simulations are employed to study electromagnetic ion/ion cyclotron (EMIIC) instability driven by the relative streaming of two field-aligned ion beams. The characteristics of the instability are studied as a function of beam density, propagation angle, electron-ion temperature ratios, and ion beta. When the propagation angle is near 90 deg the EMIIC instability has the characteristics of an electrostatic instability, while at smaller angles electromagnetic effects play a significant role as does strong beam coupling. The 2D simulations point to a narrowing of the wave spectrum and accompanying coherent effects during the linear growth stage of development. The EMIIC instability is an important effect where ion beta is low such as in the plasma-sheet boundary layer and upstream of slow shocks in the magnetotail.

  6. Cyclotron instabilities driven by temperature anisotropy in the solar wind

    Science.gov (United States)

    Noreen, N.; Yoon, P. H.; Zaheer, S.

    2017-10-01

    Kinetic plasma instabilities are important for regulating the temperature anisotropies of electrons and ions in solar wind. For the low beta regime, it is known that electromagnetic ion/electron cyclotron instabilities are important, but in the literature these unstable modes are discussed under the assumption of parallel propagation. The present paper extends the analysis to two (or with cylindrical symmetry, three) dimensions. The analysis is further extended to include quasilinear description with the assumption of the bi-Maxwellian velocity distribution function. Such an analysis lays the foundation for an eventual study in which cyclotron instabilities as well as obliquely propagating unstable modes such as the mirror instability are simultaneously taken into account. The present paper first lays down the basis for such future efforts in which the two- or three dimensional linear and quasilinear theories of cyclotron instabilities in the low beta regime are formulated.

  7. Simulations of electrothermal instability growth in solid aluminum rods

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, Kyle J.; Yu, Edmund P.; Sinars, Daniel B.; Cuneo, Michael E.; Slutz, Stephen A.; Nakhleh, Charles; Herrmann, Mark C. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185-1186 (United States); Koning, Joseph M.; Marinak, Michael M. [Lawrence Livermore National Laboratory, University of California, Livermore, California 94551 (United States)

    2013-05-15

    A recent publication [K. J. Peterson et al., Phys. Plasmas 19, 092701 (2012)] describes simulations and experiments of electrothermal instability growth on well characterized initially solid aluminum and copper rods driven with a 20 MA, 100 ns rise time current pulse on Sandia National Laboratories Z accelerator. Quantitative analysis of the high precision radiography data obtained in the experiments showed excellent agreement with simulations and demonstrated levels of instability growth in dense matter that could not be explained by magneto-Rayleigh-Taylor instabilities alone. This paper extends the previous one by examining the nature of the instability growth in 2D simulations in much greater detail. The initial instability growth in the simulations is shown via several considerations to be predominantly electrothermal in nature and provides a seed for subsequent magneto-Rayleigh-Taylor growth.

  8. Overturning instability in the mesosphere and lower thermosphere: analysis of instability conditions in lidar data

    Directory of Open Access Journals (Sweden)

    L. Hurd

    2009-07-01

    Full Text Available Resonant sodium lidar measurements from the transition region between the mesosphere and lower thermosphere have revealed frequently-occurring overturning events characterized by vertical scales of ~3–6 km and timescales of several hours. Larsen et al. (2004 proposed that a convective roll instability, similar to that found in the planetary boundary layer, is the likely mechanism responsible for the events. This type of instability requires an inflection point in the background winds near the center of the vortex roll with a low static stability region capped by an inversion. The earlier paper argued that the conditions required to support the instability are common in the altitude range where the features are found. In this paper, we use data from the University of Illinois sodium lidar that was located at the Starfire Optical Range near Albuquerque, New Mexico, and from the Maui/MALT Lidar Facility in Hawaii and present several cases that are used to examine the behavior of the inflection point in detail as a function of time during the evolution of the overturning event. In addition, we examine the background static stability conditions using the temperature data from the lidar.

  9. Mood instability underlies the relationship between impulsivity and internalizing psychopathology.

    Science.gov (United States)

    Peters, Evyn M; Balbuena, Lloyd; Baetz, Marilyn; Marwaha, Steven; Bowen, Rudy

    2015-10-01

    Impulsivity, the tendency to act without adequate forethought, has been associated with various internalizing disorders. Mood instability, the tendency to experience rapid and intense mood swings, relates to both internalizing disorders and impulsivity. We hypothesized that the association between mood instability and impulsivity accounts for the relationship between impulsivity and internalizing psychopathology. We conducted two studies to test our hypothesis. In Study 1 we used data from the 2007 Adult Psychiatric Morbidity Survey to examine mood instability in the relationship between depression and impulsivity. Mood instability and impulsivity were assessed with the Structured Clinical Interview for DSM-IV Axis-II Personality Disorders and depression was assessed with the revised Clinical Interview Schedule. In Study 2 we used data from the 1984 and 1991 British Health and Lifestyle Surveys to examine mood instability in the longitudinal relationship between impulsivity and internalizing symptoms. Mood instability and impulsivity were measured with the Eysenck Personality Inventory and internalizing symptoms were assessed with the General Health Questionnaire. In both studies we used a sequential regression analysis to test our hypothesis. Results from Study 1 showed that participants with depression were more likely to report impulsivity, but this effect became nonsignificant when mood instability was included in the same regression model. In Study 2 impulsivity predicted internalizing symptoms seven years in the future, but this effect became nonsignificant after mood instability was included in the same regression model. We conclude that impulsivity relates to internalizing psychopathology largely by being associated with mood instability. Research and therapy for internalizing conditions might be more productively directed at mood instability rather than impulsivity. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Return to play and recurrent instability after in-season anterior shoulder instability: a prospective multicenter study.

    Science.gov (United States)

    Dickens, Jonathan F; Owens, Brett D; Cameron, Kenneth L; Kilcoyne, Kelly; Allred, C Dain; Svoboda, Steven J; Sullivan, Robert; Tokish, John M; Peck, Karen Y; Rue, John-Paul

    2014-12-01

    There is no consensus on the optimal treatment of in-season athletes with anterior shoulder instability, and limited data are available to guide return to play. To examine the likelihood of return to sport and the recurrence of instability after an in-season anterior shoulder instability event based on the type of instability (subluxation vs dislocation). Additionally, injury factors and patient-reported outcome scores administered at the time of injury were evaluated to assess the predictability of eventual successful return to sport and time to return to sport during the competitive season. Cohort study (prognosis); Level of evidence, 2. Over 2 academic years, 45 contact intercollegiate athletes were prospectively enrolled in a multicenter observational study to assess return to play after in-season anterior glenohumeral instability. Baseline data collection included shoulder injury characteristics and shoulder-specific patient-reported outcome scores at the time of injury. All athletes underwent an accelerated rehabilitation program without shoulder immobilization and were followed during their competitive season to assess the success of return to play and recurrent instability. Thirty-three of 45 (73%) athletes returned to sport for either all or part of the season after a median 5 days lost from competition (interquartile range, 13). Twelve athletes (27%) successfully completed the season without recurrence. Twenty-one athletes (64%) returned to in-season play and had subsequent recurrent instability including 11 recurrent dislocations and 10 recurrent subluxations. Of the 33 athletes returning to in-season sport after an instability event, 67% (22/33) completed the season. Athletes with a subluxation were 5.3 times more likely (odds ratio [OR], 5.32; 95% CI, 1.00-28.07; P = .049) to return to sport during the same season when compared with those with dislocations. Logistic regression analysis suggests that the Western Ontario Shoulder Instability Index (OR, 1

  11. Investigation of Active Control of Combustion Instabilities in Liquid Propellant Rocket Motors

    National Research Council Canada - National Science Library

    Zinn, B

    1999-01-01

    This study investigated the feasibility of active control of combustion instabilities in liquid fueled combustors using a liquid fuel injector actuator and adaptive control of combustion instabilities...

  12. Two Stream Instability in an Inhomogeneous Magnetized Plasma

    Science.gov (United States)

    Jyoti, Jyoti; Malik, Hitendra

    2010-11-01

    A plasma can support several kinds of electrostatic and electromagnetic waves depending upon what the external perturbations are and how the plasma is generated or under what conditions the waves are excited. In the presence of magnetic field, more new kinds of the waves can evolve in the plasma. Moreover, if the free energy is available in the system, then these waves can grow at the cost of this free energy and hence instabilities can take place. In the present investigation, we make an analytical study of a two stream instability in an inhomogeneous magnetized plasma having drifting ions and electrons. We consider a general situation by taking an oblique propagation of the wave from the magnetic field and a constant ionization. Using normal mode analysis, we derive dispersion relation which is solved numerically for the growth rate of the instability. The behavior of growth rate with magnetic field and the propagation angle along with ionization constant has been studied for two different wavelengths of the oscillations. We observe two type of the instabilities out of which one grows at a faster rate and hence is named as fast growing instability. The growth rate of the other slowly growing instability is also examined. We find that the growth rates of both the instabilities attain higher magnitudes at smaller wavelength of the oscillations.

  13. Numerical Simulations of Instabilities in Single-Hole Office Elements

    Science.gov (United States)

    Ahuja, Vineet; Hosangadi, Ashvin; Hitt, Matthew A.; Lineberry, David M.

    2013-01-01

    An orifice element is commonly used in liquid rocket engine test facilities either as a flow metering device, a damper for acoustic resonance or to provide a large reduction in pressure over a very small distance in the piping system. While the orifice as a device is largely effective in stepping down pressure, it is also susceptible to a wake-vortex type instability that generates pressure fluctuations that propagate downstream and interact with other elements of the test facility resulting in structural vibrations. Furthermore in piping systems an unstable feedback loop can exist between the vortex shedding and acoustic perturbations from upstream components resulting in an amplification of the modes convecting downstream. Such was the case in several tests conducted at NASA as well as in the Ariane 5 strap-on P230 engine in a static firing test where pressure oscillations of 0.5% resulted in 5% thrust oscillations. Exacerbating the situation in cryogenic test facilities, is the possibility of the formation of vapor clouds when the pressure in the wake falls below the vapor pressure leading to a cavitation instability that has a lower frequency than the primary wake-vortex instability. The cavitation instability has the potential for high amplitude fluctuations that can cause catastrophic damage in the facility. In this paper high-fidelity multi-phase numerical simulations of an orifice element are used to characterize the different instabilities, understand the dominant instability mechanisms and identify the tonal content of the instabilities.

  14. Nonlinear Development and Secondary Instability of Traveling Crossflow Vortices

    Science.gov (United States)

    Li, Fei; Choudhari, Meelan M.; Duan, Lian; Chang, Chau-Lyan

    2014-01-01

    Transition research under NASA's Aeronautical Sciences Project seeks to develop a validated set of variable fidelity prediction tools with known strengths and limitations, so as to enable "sufficiently" accurate transition prediction and practical transition control for future vehicle concepts. This paper builds upon prior effort targeting the laminar breakdown mechanisms associated with stationary crossflow instability over a swept-wing configuration relevant to subsonic aircraft with laminar flow technology. Specifically, transition via secondary instability of traveling crossflow modes is investigated as an alternate scenario for transition. Results show that, for the parameter range investigated herein, secondary instability of traveling crossflow modes becomes insignificant in relation to the secondary instability of the stationary modes when the relative initial amplitudes of the traveling crossflow instability are lower than those of the stationary modes by approximately two orders of magnitudes or more. Linear growth predictions based on the secondary instability theory are found to agree well with those based on PSE and DNS, with the most significant discrepancies being limited to spatial regions of relatively weak secondary growth, i.e., regions where the primary disturbance amplitudes are smaller in comparison to its peak amplitude. Nonlinear effects on secondary instability evolution is also investigated and found to be initially stabilizing, prior to breakdown.

  15. On the shear instability in relativistic neutron stars

    Energy Technology Data Exchange (ETDEWEB)

    Corvino, Giovanni; Rezzolla, Luciano; Giacomazzo, Bruno [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Golm (Germany); Bernuzzi, Sebastiano [Theoretical Physics Institute, University of Jena, 07743 Jena (Germany); De Pietri, Roberto, E-mail: Giovanni.Corvino@roma1.infn.i [Physics Department, Parma University and INFN, Parma (Italy)

    2010-06-07

    We present new results on instabilities in rapidly and differentially rotating neutron stars. We model the stars in full general relativity and describe the stellar matter adopting a cold realistic equation of state based on the unified SLy prescription (Douchin and Haensel 2001 Astron. Astrophys. 380 151-67). We provide evidence that rapidly and differentially rotating stars that are below the expected threshold for the dynamical bar-mode instability, {beta}{sub c} {identical_to} T/|W| {approx_equal} 0.25, do nevertheless develop a shear instability on a dynamical timescale and for a wide range of values of {beta}. This class of instability, which has so far been found only for small values of {beta} and with very small growth rates, is therefore more generic than previously found and potentially more effective in producing strong sources of gravitational waves. Overall, our findings support the phenomenological predictions made by Watts et al (2005 Astrophys. J. 618 L37) on the nature of the low-T/|W| instability as the manifestation of a shear instability in a region where the latter is possible only for small values of {beta}. Furthermore, our results provide additional insight on shear instabilities and on the necessary conditions for their development.

  16. A Framework for Integrated Component and System Analyses of Instabilities

    Science.gov (United States)

    Ahuja, Vineet; Erwin, James; Arunajatesan, Srinivasan; Cattafesta, Lou; Liu, Fei

    2010-01-01

    Instabilities associated with fluid handling and operation in liquid rocket propulsion systems and test facilities usually manifest themselves as structural vibrations or some form of structural damage. While the source of the instability is directly related to the performance of a component such as a turbopump, valve or a flow control element, the associated pressure fluctuations as they propagate through the system have the potential to amplify and resonate with natural modes of the structural elements and components of the system. In this paper, the authors have developed an innovative multi-level approach that involves analysis at the component and systems level. The primary source of the unsteadiness is modeled with a high-fidelity hybrid RANS/LES based CFD methodology that has been previously used to study instabilities in feed systems. This high fidelity approach is used to quantify the instability and understand the physics associated with the instability. System response to the driving instability is determined through a transfer matrix approach wherein the incoming and outgoing pressure and velocity fluctuations are related through a transfer (or transmission) matrix. The coefficients of the transfer matrix for each component (i.e. valve, pipe, orifice etc.) are individually derived from the flow physics associated with the component. A demonstration case representing a test loop/test facility comprised of a network of elements is constructed with the transfer matrix approach and the amplification of modes analyzed as the instability propagates through the test loop.

  17. Generalized joint laxity and multidirectional instability of the shoulder

    Science.gov (United States)

    SACCOMANNO, MARISTELLA F.; FODALE, MARIO; CAPASSO, LUIGI; CAZZATO, GIAMPIERO; MILANO, GIUSEPPE

    2013-01-01

    Generalized joint laxity and shoulder instability are common conditions that exhibit a wide spectrum of different clinical forms and may coexist in the same patient. Generalized joint laxity can be congenital or acquired. It is fundamental to distinguish laxity from instability. Laxity is a physiological condition that may predispose to the development of shoulder instability. A high prevalence of generalized joint laxity has been identified in patients with multidirectional instability of the shoulder. Multidirectional instability is defined as symptomatic instability in two or more directions. The diagnosis and treatment of this condition are still challenging because of complexities in its classification and etiology. These complexities are compounded when multidirectional instability and laxity exist in the same patient. With an improved understanding of the clinical symptoms and physical examination findings, a successful strategy for conservative and/or surgical treatments can be developed. Conservative treatment is the first-line option. If it fails, different surgical options are available. Historically, open capsular shift has been considered the gold standard in the surgical management of these patients. Nowadays, advanced arthroscopic techniques offer several advantages over traditional open approaches and have shown similar outcomes. The correct approach to the management of failed stabilization procedures has not been yet defined. PMID:25606530

  18. Parametric Instability of Square Laminated Plates in Hygrothermal Environment

    Directory of Open Access Journals (Sweden)

    Manoj Kumar Rath

    2013-01-01

    Full Text Available The present paper investigates the parametric instability of square laminated plates subjected to periodic dynamic loadings in hygrothermal environment. The effects of various parameters like the increase in static load factor and the degree of orthotropy of simply supported composite plates at elevated temperatures and moisture concentrations on the principal instability regions are investigated using finite element method. The effects of transverse shear deformation and rotary inertia are used to study the antisymmetric angle-ply square plates. A simple laminated plate model is developed for the parametric instability of square laminated plates subjected to hygrothermal loading. A computer program based on FEM in MATLAB environment is developed to perform all necessary computations. The results show that instability of square laminated plates occurs for different parameters with an increase in temperature and moisture environment. The onset of instability occurs earlier, and the width of dynamic instability regions increases with a rise in temperature and moisture for different parameters. The effect of damping shows that there is a finite critical value of dynamic load factor for each instability region below which the square laminated plates cannot become unstable.

  19. Sleepwalking, a disorder of NREM sleep instability.

    Science.gov (United States)

    Guilleminault, Christian; Kirisoglu, Ceyda; da Rosa, Agostinho C; Lopes, Cecilia; Chan, Allison

    2006-03-01

    Thirty-two chronic sleepwalkers who were part of a larger, previously reported sleepwalking group all achieved control of sleepwalking after undergoing treatment for an associated sleep disorder. In the current study, all records were blindly scored to perform a cyclic alternating pattern (CAP) analysis. Thirty-two young adult chronic sleepwalkers had polysomnography (PSG) on initial nights without sleepwalking events, as did age-matched normal controls and patients with mild sleep-disordered breathing (SDB). More than 90% of these patients with mild SDB had upper airway resistance syndrome (UARS). Ten randomly selected PSGs for sleepwalkers and matched controls also had quantitative electroencephalographic (EEG) analysis using Fast Fourier Transformation (FFT) with determination of delta power for each non-rapid eye movement (NREM)-REM sleep cycle. Compared to normal controls, an investigation of CAP in sleepwalkers demonstrated the presence of an abnormal CAP rate with a decrease in phase A1 and an increase in phases A2 and A3 on non-sleepwalking nights. The results of CAP analysis in sleepwalkers were similar to those obtained in age-matched UARS patients. Furthermore, the analysis of the first four NREM-REM sleep cycles reconfirmed the presence of an important decrease in delta power in sleep cycles 1 and 2 during a non-sleepwalking night in sleepwalkers compared to normal controls. The presence of both 'hypersynchronous slow delta' and 'burst of delta waves' have been reported in sleepwalkers, but their significance is controversial. These EEG patterns are similar to phase A1 (and possibly A2) of the CAP. Proper analysis of the sleep EEG of sleepwalkers should integrate CAP analysis. Sleepwalkers on a non-sleepwalking night present instability of NREM sleep, as demonstrated by this analysis. This instability is similar to the one noted in UARS patients. Subtle sleep disorders associated with chronic sleepwalking constitute the unstable NREM sleep background on

  20. Instability of repeated DNAs during transformation in Escherichia coli.

    Science.gov (United States)

    Hashem, Vera I; Klysik, Elzbieta A; Rosche, William A; Sinden, Richard R

    2002-05-22

    Escherichia coli has provided an important model system for understanding the molecular basis for genetic instabilities associated with repeated DNA. Changes in triplet repeat length during growth following transformation in E. coli have been used as a measure of repeat instability. However, very little is known about the molecular and biological changes that may occur on transformation. Since only a small proportion of viable cells become competent, uncertainty exists regarding the nature of these transformed cells. To establish whether the process of transformation can be inherently mutagenic for certain DNA sequences, we used a genetic assay in E. coli to compare the frequency of genetic instabilities associated with transformation with those occurring in plasmid maintained in E. coli. Our results indicate that, for certain DNA sequences, bacterial transformation can be highly mutagenic. The deletion frequency of a 106 bp perfect inverted repeat is increased by as much as a factor of 2 x 10(5) following transformation. The high frequency of instability was not observed when cells stably harboring plasmid were rendered competent. Thus, the process of transformation was required to observe the instability. Instabilities of (CAG).(CTG) repeats are also dramatically elevated upon transformation. The magnitude of the instability is dependent on the nature and length of the repeat. Differences in the methylation status of plasmid used for transformation and the methylation and restriction/modification systems present in the bacterial strain used must also be considered in repeat instability measurements. Moreover, different E. coli genetic backgrounds show different levels of instability during transformation.

  1. CHF Enhancement by Surface Patterning based on Hydrodynamic Instability Model

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Han; Bang, In Cheol [UNIST, Ulsan (Korea, Republic of)

    2015-05-15

    If the power density of a device exceeds the CHF point, bubbles and vapor films will be covered on the whole heater surface. Because vapor films have much lower heat transfer capabilities compared to the liquid layer, the temperature of the heater surface will increase rapidly, and the device could be damaged due to the heater burnout. Therefore, the prediction and the enhancement of the CHF are essential to maximizing the efficient heat removal region. Numerous studies have been conducted to describe the CHF phenomenon, such as hydrodynamic instability theory, macrolayer dryout theory, hot/dry spot theory, and bubble interaction theory. The hydrodynamic instability model, proposed by Zuber, is the predominant CHF model that Helmholtz instability attributed to the CHF. Zuber assumed that the Rayleigh-Taylor (RT) instability wavelength is related to the Helmholtz wavelength. Lienhard and Dhir proposed a CHF model that Helmholtz instability wavelength is equal to the most dangerous RT wavelength. In addition, they showed the heater size effect using various heater surfaces. Lu et al. proposed a modified hydrodynamic theory that the Helmholtz instability was assumed to be the heater size and the area of the vapor column was used as a fitting factor. The modified hydrodynamic theories were based on the change of Helmholtz wavelength related to the RT instability wavelength. In the present study, the change of the RT instability wavelength, based on the heater surface modification, was conducted to show the CHF enhancement based on the heater surface patterning in a plate pool boiling. Sapphire glass was used as a base heater substrate, and the Pt film was used as a heating source. The patterning surface was based on the change of RT instability wavelength. In the present work the study of the CHF was conducted using bare Pt and patterned heating surfaces.

  2. Plastic instabilities in statically and dynamically loaded spherical vessels

    Energy Technology Data Exchange (ETDEWEB)

    Duffey, Thomas A [Los Alamos National Laboratory; Rodriguez, Edward A [Los Alamos National Laboratory

    2010-01-01

    Significant changes were made in design limits for pressurized vessels in the 2007 version of the ASME Code (Section VIII, Div. 3) and 2008 and 2009 Addenda. There is now a local damage-mechanics based strain-exhaustion limit as well as the well-known global plastic collapse limit. Moreover, Code Case 2564 (Section VIII, Div. 3) has recently been approved to address impulsively loaded vessels. It is the purpose of this paper to investigate the plastic collapse limit as it applies to dynamically loaded spherical vessels. Plastic instabilities that could potentially develop in spherical shells under symmetric loading conditions are examined for a variety of plastic constitutive relations. First, a literature survey of both static and dynamic instabilities associated with spherical shells is presented. Then, a general plastic instability condition for spherical shells subjected to displacement controlled and impulsive loading is given. This instability condition is evaluated for six plastic and visco-plastic constitutive relations. The role of strain-rate sensitivity on the instability point is investigated. Calculations for statically and dynamically loaded spherical shells are presented, illustrating the formation of instabilities as well as the role of imperfections. Conclusions of this work are that there are two fundamental types of instabilities associated with failure of spherical shells. In the case of impulsively loaded vessels, where the pulse duration is short compared to the fundamental period of the structure, one instability type is found not to occur in the absence of static internal pressure. Moreover, it is found that the specific role of strain-rate sensitivity on the instability strain depends on the form of the constitutive relation assumed.

  3. Instability Model of the Universe with De Sitter Beginning

    CERN Document Server

    Ignat'ev, Yurii

    2015-01-01

    The physical instability of the Universe model with de Sitter beginning is proved in this article. 1. It is shown that even a small addition of ultrarelativistic matter turns the de Sitter Universe into the Universe with finite past. 2. Constant solution of equation of model with constant scalar field is shown to be instable. 3. It is also shown that lateral gravitational perturbations of such model make it instable near of cosmological singularity. The conclusion is made that de Sitter stage of the Universe evolution most likely should be preceded by the ultrarelativistic stage.

  4. 3D analyses of cavitation instabilities accounting for plastic anisotropy

    DEFF Research Database (Denmark)

    Legarth, Brian Nyvang; Tvergaard, Viggo

    2010-01-01

    Full three dimensional cell model analyses are carried out for a solid containing a single small void, in order to determine the critical stress levels for the occurrence of cavitation instabilities. The material models applied are elastic‐viscoplastic, with a small rate‐hardening exponent...... that the quasi‐static solution is well approximated. A special procedure is used to strongly reduce the loading rate a little before the instability occurs. It is found that plastic anisotropy has a significant effect on the level of the critical stress for cavitation instabilities....

  5. Feedback techniques and SPS Ecloud instabilities - design estimates

    Energy Technology Data Exchange (ETDEWEB)

    Fox,J.D.; Mastorides, T.; Ndabashimiye, G.; Rivetta, C.; Van Winkle, D.; Byrd, J.; Vay, J-L.; Hofle, W.; Rumolo, G.; de Maria, R.

    2009-05-04

    The SPS at high intensities exhibits transverse single-bunch instabilities with signatures consistent with an Ecloud driven instability. While the SPS has a coupled-bunch transverse feedback system, control of Ecloud driven motion requires a much wider control bandwidth capable of sensing and controlling motion within each bunched beam. This paper draws beam dynamics data from the measurements and simulations of this SPS instability, and estimates system requirements for a feedback system with 2-4 GS/sec. sampling rates to damp Ecloud-driven transverse motion in the SPS at intensities desired for high-current LHC operation.

  6. Formation of matter-wave soliton trains by modulational instability

    Science.gov (United States)

    Nguyen, Jason H. V.; Luo, De; Hulet, Randall G.

    2017-04-01

    Nonlinear systems can exhibit a rich set of dynamics that are inherently sensitive to their initial conditions. One such example is modulational instability, which is believed to be one of the most prevalent instabilities in nature. By exploiting a shallow zero-crossing of a Feshbach resonance, we characterize modulational instability and its role in the formation of matter-wave soliton trains from a Bose-Einstein condensate. We examine the universal scaling laws exhibited by the system and, through real-time imaging, address a long-standing question of whether the solitons in trains are created with effectively repulsive nearest-neighbor interactions or rather evolve into such a structure.

  7. Rolie-Poly fluid flowing through constrictions: Two distinct instabilities

    KAUST Repository

    Reis, T.

    2013-05-01

    Elastic instabilities of entangled polymer melts are common in industrial processes but the physics responsible is not well understood. We present a numerical linear stability study of a molecular based constitutive model which grants us physical insight into the underlying mechanics involved. Two constriction flows are considered - one shear dominated, the other extension dominated - and two distinct instabilities are found. The influence of the molecular structure and the behaviour of the polymer dynamics are investigated and in both cases chain relaxation and orientation play a crucial role. This suggests a molecular-based physical interpretation of the underlying mechanisms responsible for flow instabilities. © 2013 Elsevier B.V.

  8. Current trends in the management of recurrent anterior shoulder instability.

    Science.gov (United States)

    Rossy, William H; Cieslak, Kristina; Uquillas, Carlos A; Rokito, Andrew

    2014-01-01

    The glenohumeral joint is innately complex and comprised of both static and dynamic stabilizers. Anterior glenohumeral instability has been estimated to have an incidence of 11.2 cases per 100,000 persons and typically follows a traumatic injury. Although there are specific instances when conservative management is advocated, a majority of these patients are treated with operative stabilization. Recent advancements in arthroscopy have created a shift from the traditional open stabilization procedures towards more minimally invasive arthroscopic stabilization procedures. This comprehensive review will summarize current concepts involved in evaluating patients with anterior glenohumeral instability and specifically focus on those patients who suffer from recurrent instability.

  9. Management of recurrent shoulder instability in patients with epilepsy.

    Science.gov (United States)

    Thangarajah, Tanujan; Lambert, Simon M

    2016-08-01

    Epileptic seizures can cause dislocation of the shoulder. Recurrent instability is common and occurs soon after the first dislocation. Significant bone loss from the humeral head and glenoid is thought to be responsible for this, and therefore the majority of surgical approaches focus on bone augmentation of the glenohumeral joint. Understanding of the current management strategies and the anatomic lesions associated with seizure-related shoulder instability will guide clinical decision-making. The purpose of this article was to review the pathoanatomy, treatment options, and clinical outcomes of seizure-related shoulder instability. Copyright © 2016 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  10. Assessing Spontaneous Combustion Instability with Recurrence Quantification Analysis

    Science.gov (United States)

    Eberhart, Chad J.; Casiano, Matthew J.

    2016-01-01

    Spontaneous instabilities can pose a significant challenge to verification of combustion stability, and characterizing its onset is an important avenue of improvement for stability assessments of liquid propellant rocket engines. Recurrence Quantification Analysis (RQA) is used here to explore nonlinear combustion dynamics that might give insight into instability. Multiple types of patterns representative of different dynamical states are identified within fluctuating chamber pressure data, and markers for impending instability are found. A class of metrics which describe these patterns is also calculated. RQA metrics are compared with and interpreted against another metric from nonlinear time series analysis, the Hurst exponent, to help better distinguish between stable and unstable operation.

  11. Suppression of electromechanical instability in fiber-reinforced dielectric elastomers

    Directory of Open Access Journals (Sweden)

    Rui Xiao

    2016-03-01

    Full Text Available The electromechanical instability of dielectric elastomers has been a major challenge for the application of this class of active materials. In this work, we demonstrate that dielectric elastomers filled with soft fiber can suppress the electromechanical instability and achieve large deformation. Specifically, we developed a constitutive model to describe the dielectric and mechanical behaviors of fiber-reinforced elastomers. The model was applied to study the influence of stiffness, nonlinearity properties and the distribution of fiber on the instability of dielectric membrane under an electric field. The results show that there exists an optimal fiber distribution condition to achieve the maximum deformation before failure.

  12. The LHC Transverse Coupled-Bunch Instability

    CERN Document Server

    Mounet, Nicolas; Métral, Elias

    In this thesis, the problem of the transverse coupled-bunch instabilities created by the Large Hadron Collider (LHC) beam-coupling impedance, that can possibly limit the machine operation, is addressed thanks to several new theories and tools. A rather complete vision of the problem is proposed here, going from the calculation of the impedances and wake functions of individual machine elements, to the beam dynamics study. Firstly, new results are obtained in the theory of the beam-coupling impedance for an axisymmetric two-dimensional structure, generalizing Zotter's theories, and a new general theory is derived for the impedance of an infinite flat two-dimensional structure. Then, a new approach has been found to compute the wake functions from such analytically obtained beam-coupling impedances, over-coming limitations that could be met with standard discrete Fourier transform procedures. Those results are then used to obtain an impedance and wake function model of the LHC, based on the (resistive-) wall im...

  13. Environmentally Triggered Instabilities in Origami Structures

    Science.gov (United States)

    Buskohl, Phil; Treml, Ben; Gillman, Andrew; Vaia, Richard

    Mechanically adaptive films and 3D structures that respond to environmental stimuli (light, heat, humidity) show promise as next-generation materials in devices, sensors, and regulators. The interplay between a material's response to an external environmental field and the deformation presents an opportunity for local material design to achieve targeted actuation. While response rates can be fast, the associated strains are often small and limit motion. To amplify the mechanical response, origami fold patterns are designed and embedded into environmentally responsive thin films. Design of these origami structures is accomplished through development of a topology optimization framework that discovers optimal fold patterns that achieve targeted metastable equilibrium positions through environmentally induced instabilities. These computationally designed patterns are experimentally realized through additive manufacturing of composite structures that exhibit active and inactive zones. These concepts are demonstrated for hygroscopic polymers subject to humidity gradient fields to illustrate how environmentally responsive materials with local patterning can amplify the mechanical response and enable enhanced functionalization for remote, autonomous locomotion. The authors acknowledge support from the Air Force Office of Scientific Research.

  14. Effect of Hecogenin on DNA instability

    Directory of Open Access Journals (Sweden)

    Marina Sampaio Cruz

    2016-01-01

    Full Text Available Hecogenin is a sapogenin found in Agave species in high quantities and is responsible for the many therapeutic effects of these medicinal plants. In addition, this compound is also widely used in the pharmaceutical industry as a precursor for the synthesis of steroidal hormones and anti-inflammatory drugs. Despite Hecogenin being widely used, little is known about its toxicological properties. Therefore, the present study aimed to investigate the cytotoxic, genotoxic and mutagenic effects of Hecogenin on HepG2 cells. Cytotoxicity was analyzed using the MTT test. Then, genotoxic and mutagenic potentials were assessed by comet assay and cytokinesis-block micronucleus assay, respectively. Cytotoxic effect was observed only when cells were exposed to concentrations of Hecogenin equal or higher than 100 μM. Although a lower concentration of Hecogenin caused DNA damage, a reduction on nuclear mutagenic markers in HepG2 cells was observed. The results indicated that Hecogenin treatment generated DNA damage, but in fact it would be repaired, avoiding dissemination of the damage throughout the cell division. Further studies need to be performed to confirm the observed protective effect of Hecogenin against genomic instability.

  15. Basic biomechanic principles of knee instability.

    Science.gov (United States)

    Zlotnicki, Jason P; Naendrup, Jan-Hendrik; Ferrer, Gerald A; Debski, Richard E

    2016-06-01

    Motion at the knee joint is a complex mechanical phenomenon. Stability is provided by a combination of static and dynamic structures that work in concert to prevent excessive movement or instability that is inherent in various knee injuries. The anterior cruciate ligament (ACL) is a main stabilizer of the knee, providing both translational and rotatory constraint. Despite the high volume of research directed at native ACL function, pathogenesis and surgical reconstruction of this structure, a gold standard for objective quantification of injury and subsequent repair, has not been demonstrated. Furthermore, recent studies have suggested that novel anatomic structures may play a significant role in knee stability. The use of biomechanical principles and testing techniques provides essential objective/quantitative information on the function of bone, ligaments, joint capsule, and other contributing soft tissues in response to various loading conditions. This review discusses the principles of biomechanics in relation to knee stability, with a focus on the objective quantification of knee stability, the individual contributions of specific knee structures to stability, and the most recent technological advances in the biomechanical evaluation of the knee joint.

  16. Instability and Turbulence of Propagating Particulate Flows

    Science.gov (United States)

    Balachandar, S.

    2015-11-01

    Propagation of particle-laden fluid into an ambient is a common fluid mechanical process that can be observed in many industrial and environmental applications. Sedimentation fronts, volcanic plumes, dust storms, powder snow avalanches, submarine turbidity currents, explosive powder dispersal and supernovae offer fascinating examples of advancing particulate fronts. The propagating interface can undergo Rayleigh-Taylor, Kelvin-Helmholtz and double-diffusive instabilities and result in the formation of lobes and clefts, spikes and bubbles, and particulate fingers. The interplay between suspended particles and turbulence is often complex due to interaction of competing mechanisms. In problems such as turbidity currents, turbulence controls sediment concentration through resuspension and settling of particles at the bed. Also, turbulent entrainment at the propagating front is observed to be influenced by the sediments. Stable stratification due to suspended sediment concentration can damp and even kill turbulence. This complex turbulence-sediment interaction offers possible explanation for massive sediment deposits observed in nature. The talk will also address challenges and recent advancements in the modeling and simulation of such particle-laden turbulent flows.

  17. MHD Ballooning Instability in the Plasma Sheet

    Energy Technology Data Exchange (ETDEWEB)

    C.Z. Cheng; S. Zaharia

    2003-10-20

    Based on the ideal-MHD model the stability of ballooning modes is investigated by employing realistic 3D magnetospheric equilibria, in particular for the substorm growth phase. Previous MHD ballooning stability calculations making use of approximations on the plasma compressibility can give rise to erroneous conclusions. Our results show that without making approximations on the plasma compressibility the MHD ballooning modes are unstable for the entire plasma sheet where beta (sub)eq is greater than or equal to 1, and the most unstable modes are located in the strong cross-tail current sheet region in the near-Earth plasma sheet, which maps to the initial brightening location of the breakup arc in the ionosphere. However, the MHD beq threshold is too low in comparison with observations by AMPTE/CCE at X = -(8 - 9)R(sub)E, which show that a low-frequency instability is excited only when beq increases over 50. The difficulty is mitigated by considering the kinetic effects of ion gyrorad ii and trapped electron dynamics, which can greatly increase the stabilizing effects of field line tension and thus enhance the beta(sub)eq threshold [Cheng and Lui, 1998]. The consequence is to reduce the equatorial region of the unstable ballooning modes to the strong cross-tail current sheet region where the free energy associated with the plasma pressure gradient and magnetic field curvature is maximum.

  18. Experimental Investigation of Current Sheet Instabilities

    Science.gov (United States)

    Markusic, Thomas E.; Choveiri, E. Y.; Schafer, Charles (Technical Monitor)

    2001-01-01

    Configuration space instabilities of propagating current sheets were studied in order to better understand acceleration mechanisms in pulsed plasma thrusters. Experiments were carried out in a parallel plate accelerator with argon as propellant. Propagating current sheets were visualized using fast framing cameras with inter-frame delays ranging between 0.05 - 2 microsecond. Schlieren photography using a pulse-burst Nd:YAG laser was used to image electron density gradients in the discharge. Magnetic field probes were used to map the magnetic field topology during the evolution of the discharge. Pressure probes were used to monitor axial pressure gradients. Emission spectroscopy was used to estimate the electron temperature in the arc. The motivation for applying all of these diagnostics was to gain an understanding of what parameters influence the macroscopic stability of a propagating current sheet. Since a stable current sheet is required for any effective snowplow-type of accelerator, an understanding of the processes which can cause current sheets to break apart into filaments is essential for the design of future pulsed plasma thrusters.

  19. Instabilities in electrically driven rotating MHD layers

    Science.gov (United States)

    Mistrangelo, C.; Bühler, L.

    2017-07-01

    Flows of electrically conducting fluids exposed to intense magnetic fields exhibit a common feature i.e. the formation of uniform cores in which electromagnetic forces are dominant. Cores are separated from each other by thin layers that extend along magnetic field lines. Across these parallel layers strong gradients of flow variables are present, which can lead to the onset of instabilities and non-linear flow transitions. In this work we investigate dynamics and stability issues of rotating parallel layers driven by electromagnetic forces caused by the interaction of injected electric currents with an applied magnetic field. The geometry considered consists of two coaxial circular electrodes used for current injection. They are placed in parallel electrically insulating planes perpendicular to a uniform magnetic field. The basic axisymmetric steady state flow, characterized by a rotating velocity jet confined in a parallel layer that connects the rims of the electrodes, is rather well understood. By increasing the driving current above a critical value the basic flow becomes unstable and undergoes a sequence of supercritical bifurcations.

  20. Mechanical instability of normal and aneurysmal arteries.

    Science.gov (United States)

    Lee, Avione Y; Sanyal, Arnav; Xiao, Yangming; Shadfan, Ramsey; Han, Hai-Chao

    2014-12-18

    Tortuous arteries associated with aneurysms have been observed in aged patients with atherosclerosis and hypertension. However, the underlying mechanism is poorly understood. The objective of this study was to determine the effect of aneurysms on arterial buckling instability and the effect of buckling on aneurysm wall stress. We investigated the mechanical buckling and post-buckling behavior of normal and aneurysmal carotid arteries and aorta's using computational simulations and experimental measurements to elucidate the interrelationship between artery buckling and aneurysms. Buckling tests were done in porcine carotid arteries with small aneurysms created using elastase treatment. Parametric studies were done for model aneurysms with orthotropic nonlinear elastic walls using finite element simulations. Our results demonstrated that arteries buckled at a critical buckling pressure and the post-buckling deflection increased nonlinearly with increasing pressure. The presence of an aneurysm can reduce the critical buckling pressure of arteries, although the effect depends on the aneurysm's dimensions. Buckled aneurysms demonstrated a higher peak wall stress compared to unbuckled aneurysms under the same lumen pressure. We conclude that aneurysmal arteries are vulnerable to mechanical buckling and mechanical buckling could lead to high stresses in the aneurysm wall. Buckling could be a possible mechanism for the development of tortuous aneurysmal arteries such as in the Loeys-Dietz syndrome. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Instability control in microwave-frequency microplasma

    Science.gov (United States)

    Miura, N.; Hopwood, J.

    2012-05-01

    Atmospheric argon microplasmas driven by 1.0 GHz power were studied by microwave circuit analyses and spatially-resolved optical diagnostics. These studies illuminate the mechanisms responsible for microplasma stability. A split-ring resonator (SRR) microplasma source is demonstrated to reflect excess microwave power, preventing the ionization overheating instability while limiting electron density to approximately 1 × 1014 cm-3 and OH rotational temperature to 760 K at 0.76 W. Providing the SRR microplasma with an electrical path to ground, however, allows the microplasma to transition from the SRR mode to the so-called transmission line mode (T-line). This transition is due to matching of the microplasma and transmission line impedances. The higher power T-line mode supports a more intense microplasma with electron density of 1 × 1015 cm-3 and OH rotational temperature of 1480 K with 15 W absorbed power. While the SRR mode is optimized for ignition and sustaining a stable nonequilibrium plasma, and T-line mode is better suited for driving a hot, high density microplasma. The estimated microwave discharge voltages were 15 V and 35 V in SRR mode and T-line mode, respectively, and the voltages are rather independent of input power. Microplasma stability is due to a combination of impedance mismatching and direct control of power, both inherent to microwave circuitry.

  2. Investigation of Microplasma Instabilities at 1 GHz

    Science.gov (United States)

    Wu, Chen; Hopwood, Jeffrey

    2013-09-01

    Microwave microplasmas have been operated stably in excess of 2000 hours using less than one watt of power. Plasmas at atmospheric pressure and high power density, however, are subject to ionization overheating instability followed by a destructive glow-to-arc transition. We describe steady-state atmospheric pressure microplasmas in non-flowing argon and air driven by up to 40 watts of microwave power. These discharges are supported by either a quarter-wave microstrip resonator or a microstrip transmission line. Models show that the resonator configuration rejects excess power and remains unconditionally stable. The transmission line, however, couples power efficiently to a plasma of ~100 Ω and produces a more intense discharge. Electrodes of copper, aluminum and lead-based solder are investigated on both polymer and alumina substrates. Copper and lead electrodes may be evaporated by a high power microdischarge as seen by optical emission. These conditions uniquely result in severe electrode damage. Microdischarges supported on polymer substrates show C2, CN and CH emission but alumina substrates are unaffected by the microplasma. These results show that steady-state microwave discharges can be stable at very high power density provided that copper microelectrodes and ceramic substrates are employed. This work supported by the US DOE Grant No. DE-SC0001923.

  3. Axial Flow Conditioning Device for Mitigating Instabilities

    Science.gov (United States)

    Ahuja, Vineet (Inventor); Birkbeck, Roger M. (Inventor); Hosangadi, Ashvin (Inventor)

    2017-01-01

    A flow conditioning device for incrementally stepping down pressure within a piping system is presented. The invention includes an outer annular housing, a center element, and at least one intermediate annular element. The outer annular housing includes an inlet end attachable to an inlet pipe and an outlet end attachable to an outlet pipe. The outer annular housing and the intermediate annular element(s) are concentrically disposed about the center element. The intermediate annular element(s) separates an axial flow within the outer annular housing into at least two axial flow paths. Each axial flow path includes at least two annular extensions that alternately and locally direct the axial flow radially outward and inward or radially inward and outward thereby inducing a pressure loss or a pressure gradient within the axial flow. The pressure within the axial flow paths is lower than the pressure at the inlet end and greater than the vapor pressure for the axial flow. The invention minimizes fluidic instabilities, pressure pulses, vortex formation and shedding, and/or cavitation during pressure step down to yield a stabilized flow within a piping system.

  4. The Correlation Between Self-Reported Instability, Balance and Health Status in Individuals with Chronic Functional Ankle Instability

    Directory of Open Access Journals (Sweden)

    Tara Azaran

    2016-12-01

    Full Text Available Background Functional ankle instability (FAI, characterized by feeling of “giving way” and instability of ankle, is the most prevalent problem following ankle sprains which causes deficits in balance and health status. However, little is known about the correlation between ankle instability measuring tools in individuals with FAI. Objectives The present study aimed at evaluating the correlation between self-reported instability with balance and health status in individuals with FAI. Methods Twenty-three patients with unilateral FAI and 23 healthy individuals participated in the present study. Ankle instability index and SF-36 questionnaire were completed by the participants; then balance error scoring system (BESS was used to measure static balance. To compare balance and health status between the 2 groups, independent sample and Mann-Whitney tests were used; moreover, Spearman correlation coefficient was used to determine the correlation between the main variables. Results BESS scores in FAI group was significantly more than the control group (P 0.05. However, no significant correlation was found between the balance tests scores and the instability index. Conclusions The results of the present study suggest that the individuals with FAI had greater activity limitations and participation restrictions compared with the control group. There were deficits in balance status in FAI group. Moreover, a significant correlation was observed between the ankle instability index and the subjective measures of health status.

  5. Physics-Based Pneumatic Hammer Instability Model Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of this project is to develop a physics-based pneumatic hammer instability model that accurately predicts the stability of hydrostatic bearings...

  6. Modes of electrokinetic instability for imperfect electric membranes

    Science.gov (United States)

    Ganchenko, G. S.; Kalaydin, E. N.; Schiffbauer, J.; Demekhin, E. A.

    2016-12-01

    The direct transition to overlimiting current bypassing the stage of limiting currents is considered for imperfect membranes. Instability of the quiescent steady-state one-dimensional solution, which is the result of a balance of diffusion and electromigration, is investigated on the basis of the full Nernst-Planck-Poisson-Stokes system and a simplified quasielectroneutral system. A three-layer geometry, electrolyte-porous membrane-electrolyte, is considered. The usual assumption of a constant electrochemical potential along the membrane surface is removed from consideration. The effect of bulk and surface effects on the instability and transition to the overlimiting currents is evaluated for a different membrane selectivity. It becomes clear that for sufficiently small fixed charge concentration (large ion concentration in the electrolyte), the monotonic instability is replaced by an oscillatory one. The dependence of instability on the membrane porosity is found to be weak.

  7. TIN: An R Package for Transcriptome Instability Analysis.

    Science.gov (United States)

    Johannessen, Bjarne; Sveen, Anita; Skotheim, Rolf I

    2015-01-01

    Alternative splicing is a key regulatory mechanism for gene expression, vital for the proper functioning of eukaryotic cells. Disruption of normal pre-mRNA splicing has the potential to cause and reinforce human disease. Owing to rapid advances in high-throughput technologies, it is now possible to identify novel mRNA isoforms and detect aberrant splicing patterns on a genome scale, across large data sets. Analogous to the genomic types of instability describing cancer genomes (eg, chromosomal instability and microsatellite instability), transcriptome instability (TIN) has recently been proposed as a splicing-related genome-wide characteristic of certain solid cancers. We present the R package TIN, available from Bioconductor, which implements a set of methods for TIN analysis based on exon-level microarray expression profiles. TIN provides tools for estimating aberrant exon usage across samples and for analyzing correlation patterns between TIN and splicing factor expression levels.

  8. Parametric instability of a nonuniform plasma near a linear focus

    Energy Technology Data Exchange (ETDEWEB)

    Arkhipenko, V.I.; Budnikov, V.N.; Gusakov, E.Z.; Romanchuk, I.A.; Simonchik, L.V.

    1985-02-01

    Parametric instability l ..-->.. l'+s resulting in anomalous reflection of oblique Langmuir waves in a two-dimensionally nonuniform plasma is studied experimentally and theoretically. The experimental results confirm the theoretical prediction that for low input powers, the instability consists in the spatial amplification of ion-sound noise. The scattered signal is found to rise abruptly for spatial gains s> or approx. =10/sup 4/ because the threshold for absolute instability l ..-->.. l'+s is approached. The absolute instability saturates due to depletion of the pump wave, which is almost completely reflected. A mechanism for the generation of cascade parametric turbulence spectra is identified which is specific to nonuniform plasmas.

  9. Modulational instability and solitons in nonlocal media with competing nonlinearities

    DEFF Research Database (Denmark)

    Esbensen, B. K.; Wlotzka, A.; Bache, Morten

    2011-01-01

    We investigate analytically and numerically propagation and spatial localization of light in nonlocal media with competing nonlinearities. In particular, we discuss conditions for the modulational instability of plane waves and formation of spatial solitons. We show that the competing focusing...

  10. Mechanical instability of monocrystalline and polycrystalline methane hydrates

    NARCIS (Netherlands)

    Wu, J.; Ning, F.; Trinh, T.T.; Kjelstrup, S.; Vlugt, T.J.H.; He, J.; Skallerud, B.H.; Zhang, Z.

    2015-01-01

    Despite observations of massive methane release and geohazards associated with gas hydrate instability in nature, as well as ductile flow accompanying hydrate dissociation in artificial polycrystalline methane hydrates in the laboratory, the destabilising mechanisms of gas hydrates under deformation

  11. Testing for parameter instability across different modeling frameworks

    NARCIS (Netherlands)

    Calvori, Francesco; Creal, Drew; Koopman, Siem Jan; Lucas, André

    2017-01-01

    We develop a new parameter instability test that generalizes the seminal ARCHLagrange Multiplier test of Engle (1982) for a constant variance against the alternative of autoregressive conditional heteroskedasticity to settings with nonlinear timevarying parameters and non-Gaussian distributions. We

  12. Cavitation instabilities between fibres in a metal matrix composite

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    2016-01-01

    Short fibre reinforced metal matrix composites (MMC) are studied here to investigate the possibility that a cavitation instability can develop in the metal matrix. The high stress levels needed for a cavitation instability may occur in metal–ceramic systems due to the constraint on plastic flow...... of transversely staggered fibres is here modelled by using an axisymmetric cell model analysis. First the critical stress level is determined for a cavitation instability in an infinite solid made of the Al matrix material. By studying composites with different distributions and aspect ratios of the fibres...... it is shown that regions between fibre ends may develop hydrostatic tensile stresses high enough to exceed the critical level for a cavitation instability. For cases where a void is located in such regions it is shown that unstable cavity growth develops when the void is initially much smaller than the highly...

  13. Unstable colloidal rollers: a new kind of fingering instability

    Science.gov (United States)

    Driscoll, Michelle; Delmotte, Blaise; Youssef, Mena; Sacanna, Stefano; Donev, Aleksandar; Chaikin, Paul

    When colloidal particles are rotated adjacent to nearby floor, strong advective flows are generated around them, even quite far away. When a group of these microrollers is driven, the strong hydrodynamic coupling between particles leads to formation of new structures: an initially uniform front of microrollers evolves first into a shock-like structure, which then quickly becomes unstable, emitting fingers of a well-defined wavelength. Our experiments and simulations confirm that this instability is quite different than typical fingering instabilities, where size scale selection is a consequence of competing stresses. Here, this instability arises only due to hydrodynamic interactions, and it is controlled by a single geometric parameter, the particle-floor height. Our measurements of the growth rate in both experiments and simulations agree with results from our continuum model. This instability is a direct consequence of the inward flows created by the interactions between the particles and the nearby solid surface.

  14. The pathological phenotype of colon cancer with microsatellite instability

    DEFF Research Database (Denmark)

    Andersen, Helene Schou; Bertelsen, Claus Anders; Henriksen, Rikke

    2016-01-01

    INTRODUCTION: Colorectal cancer is a common malignant disease, caused by different aetiologies and molecular pathways. Heterogeneous results have been published regarding the association of microsatellite instability and clinicopathological features. The aim of this study was to compare clinicopa...

  15. Transverse electron-scale instability in relativistic shear flows

    CERN Document Server

    Alves, E P; Fonseca, R A; Silva, L O

    2015-01-01

    Electron-scale surface waves are shown to be unstable in the transverse plane of a shear flow in an initially unmagnetized plasma, unlike in the (magneto)hydrodynamics case. It is found that these unstable modes have a higher growth rate than the closely related electron-scale Kelvin-Helmholtz instability in relativistic shears. Multidimensional particle-in-cell simulations verify the analytic results and further reveal the emergence of mushroom-like electron density structures in the nonlinear phase of the instability, similar to those observed in the Rayleigh Taylor instability despite the great disparity in scales and different underlying physics. Macroscopic ($\\gg c/\\omega_{pe}$) fields are shown to be generated by these microscopic shear instabilities, which are relevant for particle acceleration, radiation emission and to seed MHD processes at long time-scales.

  16. Kink instability suppression with stochastic cooling pickup and kicker

    Energy Technology Data Exchange (ETDEWEB)

    Hao Y.; Blaskiewicz, M.; Litvinenko, V.N.; Ptitsyn, V.

    2012-05-20

    The kink instability is one of the major beam dynamics issues of the linac-ring based electron ion collider. This head-tail type instability arises from the oscillation of the electron beam inside the opposing ion beam. It must be suppressed to achieve the desired luminosity. There are various ways to suppress the instability, such as tuning the chromaticity in the ion ring or by a dedicated feedback system of the electron beam position at IP, etc. However, each method has its own limitation. In this paper, we will discuss an alternative opportunity of suppressing the kink instability of the proposed eRHIC at BNL using the existing pickup-kicker system of the stochastic cooling system in RHIC.

  17. Determination Of Slope Instability Using Spatially Integrated Mapping Framework

    Science.gov (United States)

    Baharuddin, I. N. Z.; Omar, R. C.; Roslan, R.; Khalid, N. H. N.; Hanifah, M. I. M.

    2016-11-01

    The determination and identification of slope instability are often rely on data obtained from in-situ soil investigation work where it involves the logistic of machineries and manpower, thus these aspects may increase the cost especially for remote locations. Therefore a method, which is able to identify possible slope instability without frequent ground walkabout survey, is needed. This paper presents the method used in prediction of slope instability using spatial integrated mapping framework which applicable for remote areas such as tropical forest and natural hilly terrain. Spatial data such as geology, topography, land use map, slope angle and elevation were used in regional analysis during desktop study. Through this framework, the occurrence of slope instability was able to be identified and was validate using a confirmatory site- specific analysis.

  18. Multiparticle instability in a spin-imbalanced Fermi gas

    Science.gov (United States)

    Whitehead, T. M.; Conduit, G. J.

    2018-01-01

    Weak attractive interactions in a spin-imbalanced Fermi gas induce a multiparticle instability, binding multiple fermions together. The maximum binding energy per particle is achieved when the ratio of the number of up- and down-spin particles in the instability is equal to the ratio of the up- and down-spin densities of states in momentum at the Fermi surfaces, to utilize the variational freedom of all available momentum states. We derive this result using an analytical approach, and verify it using exact diagonalization. The multiparticle instability extends the Cooper pairing instability of balanced Fermi gases to the imbalanced case, and could form the basis of a many-body state, analogously to the construction of the Bardeen-Cooper-Schrieffer theory of superconductivity out of Cooper pairs.

  19. Helicobacter pylori infection generates genetic instability in gastric cells

    DEFF Research Database (Denmark)

    Machado, Ana Manuel Dantas; Figueiredo, Céu; Seruca, Raquel

    2010-01-01

    The discovery that Helicobacter pylori is associated with gastric cancer has led to numerous studies that investigate the mechanisms by which H. pylori induces carcinogenesis. Gastric cancer shows genetic instability both in nuclear and mitochondrial DNA, besides impairment of important DNA repair...... pathways. As such, this review highlights the consequences of H. pylori infection on the integrity of DNA in the host cells. By down-regulating major DNA repair pathways, H. pylori infection has the potential to generate mutations. In addition, H. pylori infection can induce direct changes on the DNA...... of the host, such as oxidative damage, methylation, chromosomal instability, microsatellite instability, and mutations. Interestingly, H. pylori infection generates genetic instability in nuclear and mitochondrial DNA. Based on the reviewed literature we conclude that H. pylori infection promotes gastric...

  20. Ulnar-sided perilunate instability: an anatomic and biomechanic study.

    Science.gov (United States)

    Viegas, S F; Patterson, R M; Peterson, P D; Pogue, D J; Jenkins, D K; Sweo, T D; Hokanson, J A

    1990-03-01

    A staging system for ulnar-sided perilunate instability is presented based on a series of cadaver dissections and load studies. Stage I: partial or complete disruption of the lunotriquetral interosseous ligament, without clinical and/or radiographic evidence of dynamic or static volar intercalated segment instability deformity; stage II: complete disruption of the lunotriquetral interosseous ligament and disruption of the palmar lunotriquetral ligament, with clinical and/or radiographic evidence of dynamic volar intercalated segment instability deformity; and stage III: complete disruption of the lunotriquetral interosseous and the palmar lunotriquetral ligaments, attenuation or disruption of the dorsal radiocarpal ligament, with clinical and/or radiographic evidence of static volar intercalated segment instability deformity.

  1. Fiber amplifiers under thermal loads leading to transverse mode instability

    DEFF Research Database (Denmark)

    Johansen, Mette Marie; Hansen, Kristian Rymann; Alkeskjold, Thomas Tanggaard

    2014-01-01

    Transverse mode instability (TMI) in rare-earth doped fiber amplifiers operating above an average power threshold is caused by intermodal stimulated thermal Rayleigh scattering due to quantum defect heating. We investigate thermally induced longitudinal waveguide perturbations causing power trans...

  2. Patella morphological alteration after patella instability in growing rabbits

    National Research Council Canada - National Science Library

    Jinghui Niu; Qi Qi; Yingzhen Niu; Conglei Dong; Zhenyue Dong; Peng Cui; Fei Wang

    2017-01-01

    Background The shape of the patella has been considered to be a predisposing factor resulting in patellar instability, but the effects of abnormal patella position during its development are unclear...

  3. A system close to a threshold of instability

    CERN Document Server

    Floriani, E; Lima, R

    2003-01-01

    We propose a probabilistic model for a system at a threshold of instability. The distribution of residence times below the threshold that characterizes the properties of the system is studied analytically in various cases.

  4. Quasilinear saturation of the aperiodic ordinary mode streaming instability

    Energy Technology Data Exchange (ETDEWEB)

    Stockem Novo, A., E-mail: anne@tp4.rub.de; Schlickeiser, R. [Institut für Theoretische Physik, Lehrstuhl IV: Weltraum-und Astrophysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Yoon, P. H. [Institute for Physical Science & Technology, University of Maryland, College Park, Maryland 20742 (United States); School of Space Research, Kyung Hee University, Yongin-Si, Gyeonggi-Do 446-701 (Korea, Republic of); Lazar, M. [Institut für Theoretische Physik, Lehrstuhl IV: Weltraum-und Astrophysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Centre for Mathematical Plasma Astrophysics, Celestijnenlaan 200B, 3001 Leuven (Belgium); Poedts, S. [Centre for Mathematical Plasma Astrophysics, Celestijnenlaan 200B, 3001 Leuven (Belgium); Seough, J. [Faculty of Human Development, University of Toyama, 3190, Gofuku, Toyama City, Toyama 930-8555 (Japan); International Research Fellow of the Japan Society for the Promotion of Science, Tokyo (Japan)

    2015-09-15

    In collisionless plasmas, only kinetic instabilities and fluctuations are effective in reducing the free energy and scatter plasma particles, preventing an increase of their anisotropy. Solar energetic outflows into the interplanetary plasma give rise to important thermal anisotropies and counterstreaming motions of plasma shells, and the resulting instabilities are expected to regulate the expansion of the solar wind. The present paper combines quasilinear theory and kinetic particle-in-cell simulations in order to study the weakly nonlinear saturation of the ordinary mode in hot counter-streaming plasmas with a temperature anisotropy as a follow-up of the paper by Seough et al. [Phys. Plasmas 22, 082122 (2015)]. This instability provides a plausible mechanism for the origin of dominating, two-dimensional spectrum of transverse magnetic fluctuations observed in the solar wind. Stimulated by the differential motion of electron counterstreams the O mode instability may convert their free large-scale energy by nonlinear collisionless dissipation on plasma particles.

  5. Faraday instability of crystallization waves in 4He

    Science.gov (United States)

    Abe, H.; Ueda, T.; Morikawa, M.; Saitoh, Y.; Nomura, R.; Okuda, Y.

    2007-12-01

    Periodic modulation of the gravity acceleration makes a flat surface of a fluid unstable and standing waves are parametrically excited on the surface. This phenomenon is called Faraday instability. Since a crystal-superfluid interface of 4He at low temperatures is very mobile and behaves like a fluid surface, Saarloos and Weeks predicted that Faraday instability of the crystallization waves exists in 4He and that the threshold excitation for the instability depends on the crystal growth coefficient. We successfully observed the Faraday instability of the crystal-liquid interface at 160 mK. Faraday waves were parametrically generated at one half of the driving frequency 90 Hz. Amplitude of the Faraday wave becomes smaller at higher temperature due to decrease of the crystal growth coefficient and disappears above 200 mK.

  6. Development instability of plants and radiation from Chernobyl

    Energy Technology Data Exchange (ETDEWEB)

    Moeller, A.P. [Univ. Pierre et Marie curie, Lab. d`Ecologie, Paris Cedex (France)

    1998-04-01

    Phenotypic measures of developmental instability were used to assess the hypothesis that radiation from Chernobyl in Ukraine directly affects the developmental processes of plants. Fluctuating asymmetry and the frequency of pheno-deviants in three species of plants. Robinia pseudoacacia. Sorbus aucuparia and Matricaria perforata, were assessed along a transect from the security zone of Chernobyl towards the largely uncontaminated area 225 km SE of Chernobyl. Measures of developmental instability decreased in a similar way for the three species with increasing distance from Chernobyl the level of developmental instability being three to four times as large near Chernobyl as in the control area. Developmental instability was positively related to the level of radiation by caesium-137 along the transect. In conclusion, radiation from Chernobyl has resulted in a reduced ability of plants to control the stability of their developmental processes. (au) 15 refs.

  7. Current Concepts in Rehabilitation for Traumatic Anterior Shoulder Instability.

    Science.gov (United States)

    Ma, Richard; Brimmo, Olubusola A; Li, Xinning; Colbert, Lindsey

    2017-12-01

    The objectives of this review are to evaluate the current evidence-based literature and concepts surrounding rehabilitation in patients with anterior shoulder instability injuries and surgical repair. The current literature evidence for shoulder rehabilitation for anterior shoulder instability and labral repair is limited. As a result, there are variations among surgeons and physical therapists in rehabilitation protocols after anterior shoulder instability injuries and repair. While general consensus on certain rehabilitation parameters exists, the evidence for the importance of rehabilitation and functional performance test for return to sport in future injury prevention is still lacking in literature. Rehabilitation after anterior shoulder instability injury and anterior labral repair is paramount in the injured or post-operative shoulder. Restoration of soft tissue mobility, dynamic glenohumeral joint stability, and balance and strength around the shoulder not only protect healing of injured or repaired soft tissues but also potentially minimizes future re-injury or recurrence risk.

  8. Joule Heating Effects on Electrokinetic Flow Instabilities in Ferrofluids

    Science.gov (United States)

    Brumme, Christian; Shaw, Ryan; Zhou, Yilong; Prabhakaran, Rama; Xuan, Xiangchun

    We have demonstrated in our earlier work that the application of a tangential electric field can draw fluid instabilities at the interface of a ferrofluid/water co-flow. These electrokinetic flow instabilities are produced primarily by the mismatch of electric conductivities of the two fluids. We demonstrate in this talk that the Joule heating induced fluid temperature rises and gradients can significantly suppress the electrokinetic flow instabilities. We also develop a two-dimensional depth-averaged numerical model to predict the fluid temperature, flow and concentration fields in the two-fluid system with the goal to understand the Joule heating effects on electric field-driven ferrofluid flow instabilities. This work was supported by the Honors and Creative Inquiry programs at Clemson University.

  9. Higher-order modulation instability in nonlinear fiber optics.

    Science.gov (United States)

    Erkintalo, Miro; Hammani, Kamal; Kibler, Bertrand; Finot, Christophe; Akhmediev, Nail; Dudley, John M; Genty, Goëry

    2011-12-16

    We report theoretical, numerical, and experimental studies of higher-order modulation instability in the focusing nonlinear Schrödinger equation. This higher-order instability arises from the nonlinear superposition of elementary instabilities, associated with initial single breather evolution followed by a regime of complex, yet deterministic, pulse splitting. We analytically describe the process using the Darboux transformation and compare with experiments in optical fiber. We show how a suitably low frequency modulation on a continuous wave field induces higher-order modulation instability splitting with the pulse characteristics at different phases of evolution related by a simple scaling relationship. We anticipate that similar processes are likely to be observed in many other systems including plasmas, Bose-Einstein condensates, and deep water waves. © 2011 American Physical Society

  10. Association Between Serum Relaxin and Subsequent Shoulder Instability.

    Science.gov (United States)

    Owens, Brett D; Cameron, Kenneth L; Clifton, Kari B; Svoboda, Steven J; Wolf, Jennifer Moriatis

    2016-07-01

    Ligamentous laxity correlates with shoulder instability. Relaxin is a hormone that has been linked to laxity in the knee and has been shown to be a risk factor for anterior cruciate ligament (ACL) injury. This study prospectively evaluated the association between relaxin and acute shoulder instability. A prospective cohort study of 1050 young athletes was performed between 2006 and 2010. The authors conducted a nested case-control analysis within this cohort to evaluate the association between preinjury serum relaxin concentration and the likelihood of subsequent shoulder instability. The study compared 53 patients who had shoulder instability and 53 control subjects who were matched for sex, age, height, and weight. The serum relaxin concentration in preinjury baseline samples was tested with enzyme-linked immunosorbent assay analysis in duplicate. Independent t tests were performed to identify differences in mean serum relaxin concentration between patients with shoulder instability and uninjured control subjects. Logistic regression was used to evaluate whether preinjury baseline serum relaxin concentration was associated with the subsequent likelihood of shoulder instability. Of the 53 patients with instability, 13 (25%) had a detectable serum relaxin concentration compared with 9 (17%) of uninjured control subjects (P=.34). Mean serum relaxin concentration in the injury group was 3.69±1.78 pg/mL and 2.20±0.97 pg/mL in uninjured control subjects (P=.02). Increased serum relaxin concentration was associated with the subsequent likelihood of acute shoulder instability. Subjects were 2.18 times (odds ratio, 2.18; 95% confidence interval, 1.01-4.76) more likely to have acute shoulder instability during the follow-up period for every 1-pg/mL increase in serum relaxin concentration at baseline. The findings suggest that serum relaxin concentration is associated with a risk of subsequent shoulder instability in young athletes. Further research on the role of relaxin

  11. Mini-Open Latarjet Procedure for Recurrent Anterior Shoulder Instability

    Science.gov (United States)

    Mercier, Numa; Saragaglia, Dominique

    2011-01-01

    Anterior shoulder instability is a common problem. The Latarjet procedure has been advocated as an option for the treatment of anteroinferior shoulder instability. The purpose of this paper is to explain our surgical procedure titled “Mini-open Latarjet Procedure.” We detailed patient positioning, skin incision, subscapularis approach, and coracoid fixation. Then, we reviewed the literature to evaluate the clinical outcomes of this procedure. PMID:22191039

  12. Electrokinetic instability in microchannel ferrofluid/water co-flows

    OpenAIRE

    Le Song; Liandong Yu; Yilong Zhou; Asher Reginald Antao; Rama Aravind Prabhakaran; Xiangchun Xuan

    2017-01-01

    Electrokinetic instability refers to unstable electric field-driven disturbance to fluid flows, which can be harnessed to promote mixing for various electrokinetic microfluidic applications. This work presents a combined numerical and experimental study of electrokinetic ferrofluid/water co-flows in microchannels of various depths. Instability waves are observed at the ferrofluid and water interface when the applied DC electric field is beyond a threshold value. They are generated by the elec...

  13. Mini-Open Latarjet Procedure for Recurrent Anterior Shoulder Instability

    Directory of Open Access Journals (Sweden)

    Numa Mercier

    2011-01-01

    Full Text Available Anterior shoulder instability is a common problem. The Latarjet procedure has been advocated as an option for the treatment of anteroinferior shoulder instability. The purpose of this paper is to explain our surgical procedure titled “Mini-open Latarjet Procedure.” We detailed patient positioning, skin incision, subscapularis approach, and coracoid fixation. Then, we reviewed the literature to evaluate the clinical outcomes of this procedure.

  14. Two phase flow instabilities in horizontal straight tube evaporator

    OpenAIRE

    2010-01-01

    Abstract It is essential to ensure the stability of a refrigeration system if the oscillation in evaporation process is the primary cause for the whole system instability. This paper is concerned with an experimental investigation of two phase flow instabilities in a horizontal straight tube evaporator of a refrigeration system. The relationship between pressure drop and mass flow with constant heat flux and evaporation pressure is measured and determined. It is found that there is...

  15. MIRMMR: binary classification of microsatellite instability using methylation and mutations.

    Science.gov (United States)

    Foltz, Steven; Liang, Wen-Wei; Xie, Mingchao; Ding, Li

    2017-08-17

    MIRMMR predicts microsatellite instability status in cancer samples using methylation and mutation information, in contrast to existing methods that rely on observed microsatellites. Additionally, MIRMMR highlights those genetic alterations contributing to microsatellite instability. Source code is freely available at https://github.com/ding-lab/MIRMMR under the MIT license, implemented in R, and supported on Unix/OS X operating systems. Supplementary data are available at Bioinformatics online.

  16. Snake instability of dark solitons in fermionic superfluids

    OpenAIRE

    Cetoli, A.; Brand, J.; Scott, R. G.; Dalfovo, F.; Pitaevskii, L. P.

    2013-01-01

    We present numerical calculations of the snake instability in a Fermi superfluid within the Bogoliubov-de Gennes theory of the BEC to BCS crossover using the random phase approximation complemented by time-dependent simulations. We examine the snaking behaviour across the crossover and quantify the timescale and lengthscale of the instability. While the dynamic shows extensive snaking before eventually producing vortices and sound on the BEC side of the crossover, the snaking dynamics is pree...

  17. Internal Gravity Wave Interactions with Double-Diffusive Instabilities

    Science.gov (United States)

    Brown, Justin; Radko, Timour

    2017-04-01

    In this study, we focus on the phenomenon of oscillatory double-diffusive convection, which occurs when cool fresh water is stratified above warm salty water, as commonly observed in the Arctic Ocean. In the Arctic, these regions are generally stable to the development of oscillatory double-diffusive instabilities; despite this, observations show the presence of staircases, i.e., the well-defined structures consisting of a series of homogeneous layers separated by thin high-gradient interfaces. Recent studies have shown that an instability can develop in such circumstances if weak static shear is present even when the shear and double-diffusion are themselves individually stable. However, the impact of oscillating shear, associated with the ubiquitous presence of internal gravity waves, has not yet been addressed for the diffusive case. Through two-dimensional simulations of diffusive convection, we have investigated the impact of magnitude and frequency of externally forced internal waves on the double-diffusive shear instability. The analysis is focused on the parameter regime in which the flow is individually stable with respect to double-diffusion and Kelvin-Helmholtz instabilities, but could be susceptible to the combined thermohaline-shear instability. We have illustrated that rapid oscillation inhibits the development of this instability if the dominant period is shorter than four hours for the oceanographically relevant parameters; otherwise, models with static shear adequately reproduce our results. If the dominant period is shorter than four hours but still significantly exceeds the buoyancy period, the instability range is much reduced to the low Richardson number regime. Some of these simulations show the saturated system developing into structures reminiscent of double-diffusive staircases whose thickness is given by the wavelength of the forced shear. Finally, preliminary three-dimensional simulations show no major differences in the growth rate of

  18. On brane instabilities in the large D limit

    Energy Technology Data Exchange (ETDEWEB)

    Rozali, Moshe; Vincart-Emard, Alexandre [Department of Physics and Astronomy, University of British Columbia,Vancover, BC V6T 1Z1 (Canada)

    2016-08-30

    Using an expansion in large number of dimensions, taken to subleading orders, we discuss several issues concerning the Gregory-Laflamme instabilities. We map out the phase diagram of neutral and charged black strings, and comment on the possible transition in the nature of the final state of the instability at higher order in the 1/D expansion. We also discuss unstable black membranes, and show that in certain limits the preferred shape of the non-uniform phase is a triangular lattice.

  19. Influence of flavor oscillations on neutrino beam instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Mendonça, J. T., E-mail: titomend@ist.utl.pt [Instituto de Física, Universidade de São Paulo, 05508-090 São Paulo SP (Brazil); Haas, F. [Instituto de Física, Universidade Federal do Rio Grande do Sul, 91501-970 Porto Alegre RS (Brazil); Bret, A. [ETSI Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain and Instituto de Investigaciones Energeticas y Aplicaciones Industriales, Campus Universitario de Ciudad Real, 13071 Ciudad Real (Spain)

    2014-09-15

    We consider the collective neutrino plasma interactions and study the electron plasma instabilities produced by a nearly mono-energetic neutrino beam in a plasma. We describe the mutual interaction between neutrino flavor oscillations and electron plasma waves. We show that the neutrino flavor oscillations are not only perturbed by electron plasmas waves but also contribute to the dispersion relation and the growth rates of neutrino beam instabilities.

  20. Instability Analysis of Vortex Systems in Lifting-Body Wakes

    OpenAIRE

    Tendero Ventanas, Juan Ángel

    2016-01-01

    The present work deals with vortical flow instabilities, in particular with those that appear in the wake left by aircraft, wind turbines or any other body surrounded by fluid, generating a force perpendicular to the flow, namely lift. The case of the aircraft wake destruction caused by the growth of vortex instabilities is of great importance, as the selection of safe distances between aircraft is in most of the cases very conservative due to the lack of knowledge of the phenomena involved i...

  1. Mini-Open Latarjet Procedure for Recurrent Anterior Shoulder Instability

    OpenAIRE

    Numa Mercier; Dominique Saragaglia

    2011-01-01

    Anterior shoulder instability is a common problem. The Latarjet procedure has been advocated as an option for the treatment of anteroinferior shoulder instability. The purpose of this paper is to explain our surgical procedure titled “Mini-open Latarjet Procedure.” We detailed patient positioning, skin incision, subscapularis approach, and coracoid fixation. Then, we reviewed the literature to evaluate the clinical outcomes of this procedure.

  2. Morphological Instability of Steps During Crystal Growth from Solution Flow

    OpenAIRE

    Potapenko, Serge Yu.

    1995-01-01

    It is shown that step moving to meet solution flow can be unstable against lateral perturbations. The instability of long-wavelength perturbations occurs at values of the solution flow intensity less than some critical value depending on the step velocity. At given intensity of the solution flow, the instability comes at the step velocity exceeding a critical velocity. Decay of short-wavelength fluctuations is conditioned by the line tension of the step. The step moving along the solution flo...

  3. Model of E-Cloud Instability in the Fermilab Recycler

    Energy Technology Data Exchange (ETDEWEB)

    Balbekov, V. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2015-06-24

    Simple model of electron cloud is developed in the paper to explain e-cloud instability of bunched proton beam in the Fermilab Recycler. The cloud is presented as an immobile snake in strong vertical magnetic field. The instability is treated as an amplification of the bunch injection errors from the batch head to its tail. Nonlinearity of the e-cloud field is taken into account. Results of calculations are compared with experimental data demonstrating good correlation.

  4. Critical fluctuations in cortical models near instability

    Directory of Open Access Journals (Sweden)

    Matthew J. Aburn

    2012-08-01

    Full Text Available Computational studies often proceed from the premise that cortical dynamics operate in a linearly stable domain, where fluctuations dissipate quickly and show only short memory. Studies of human EEG, however, have shown significant autocorrelation at time lags on the scale of minutes, indicating the need to consider regimes where nonlinearities influence the dynamics. Statistical properties such as increased autocorrelation length, increased variance, power-law scaling and bistable switching have been suggested as generic indicators of the approach to bifurcation in nonlinear dynamical systems. We study temporal fluctuations in a widely-employed computational model (the Jansen-Rit model of cortical activity, examining the statistical signatures that accompany bifurcations. Approaching supercritical Hopf bifurcations through tuning of the background excitatory input, we find a dramatic increase in the autocorrelation length that depends sensitively on the direction in phase space of the input fluctuations and hence on which neuronal subpopulation is stochastically perturbed. Similar dependence on the input direction is found in the distribution of fluctuation size and duration, which show power law scaling that extends over four orders of magnitude at the Hopf bifurcation. We conjecture that the alignment in phase space between the input noise vector and the center manifold of the Hopf bifurcation is directly linked to these changes. These results are consistent with the possibility of statistical indicators of linear instability being detectable in real EEG time series. However, even in a simple cortical model, we find that these indicators may not necessarily be visible even when bifurcations are present because their expression can depend sensitively on the neuronal pathway of incoming fluctuations.

  5. Jeans instability in a universe with dissipation

    Science.gov (United States)

    Kremer, Gilberto M.; Richarte, Martín G.; Teston, Felipe

    2018-01-01

    The problem of Jeans gravitational instability is investigated for static and expanding universes within the context of the five and thirteen field theories which account for viscous and thermal effects. For the five-field theory a general dispersion relation has been derived with the help of relevant linearized perturbation equations, showing that the shear viscosity parameter alters the propagating modes for large and small wavelengths. The behavior of density and temperature contrasts are analyzed for the hard-sphere model in detail. In the small wavelengths regime, increasing the amount of shear viscosity into the system forces the harmonic perturbations to damp faster, however, in the opposite limit larger values of shear viscosity lead to smaller values of density and temperature contrasts. We also consider the hyperbolic case associated with the thirteen-field theory which involves two related parameters, namely the shear viscosity and the collision frequency, the last one is due to the production terms which appear in the Grad method. The dispersion relation becomes a polynomial in the frequency with two orders higher in relation to the five-field theory, indicating that the effects associated with the shear viscosity and heat flux are nontrivial. The profile of Jeans mass in terms of the temperature and number density is explored by contrasting with several data of molecular clouds. Regarding the dynamical evolution of the density, temperature, stress and heat flux contrasts for a universe dominated by pressureless matter, we obtain also damped harmonic waves for small wavelengths. In the case of large wavelengths, the density and temperature contrasts grow with time (due to the Jeans mechanism) while the stress and heat flux contrasts heavily decay with time. For an expanding universe, the Jeans mass and Jeans length are obtained and their physical consequences are explored.

  6. The electrohydrodynamic instability in homeotropic nematic layers

    Science.gov (United States)

    Hertrich, A.; Decker, W.; Pesch, W.; Kramer, L.

    1992-11-01

    We calculate the threshold for electrohydrodynamic convection in homeotropically oriented nematic layers with negative dielectric anistropy that sets in after the bend-Fréedericksz transition to a quasi-planar alignment has taken place. Oblique rolls are found in a larger range than in the case of planar anchoring. The most interesting prediction is that in the weakly nonlinear analysis all roll solution are in fact unstable so that a direct transition to spatio-temporal chaos becomes possible. In the oblique-roll case this may be accompanied by a permanent local rotation of the director bend axis. Application of a planar magnetic field should stabilize the rolls. Nous calculons le seuil d'apparition de convection électrohydrodynamique dans des couches nématiques orientées homéotropiquement possédant une anisotropie diélectrique négative après que la transition de Fréedericksz de type courbure (bend) vers un alignement quasihorizontal ait eu lieu. Des rouleaux obliques sont observés dans un domaine plus grand que dans le cas de conditions aux limites planes. La prédiction la plus intéressante est que dans le cadre d'une analyse faiblement nonlinéaire toutes les solutions de rouleaux sont en fait instables et un passage direct vers un chaos spatio-temporel a lieu. Dans le cas de rouleaux obliques ceci peut être accompagné d'une rotation permanente locale de l'axe directeur de courbure. L'application d'un champ magnétique plan devrait stabiliser les rouleaux.

  7. Parametric Instability Rates in Periodically Driven Band Systems

    Science.gov (United States)

    Lellouch, S.; Bukov, M.; Demler, E.; Goldman, N.

    2017-04-01

    In this work, we analyze the dynamical properties of periodically driven band models. Focusing on the case of Bose-Einstein condensates, and using a mean-field approach to treat interparticle collisions, we identify the origin of dynamical instabilities arising from the interplay between the external drive and interactions. We present a widely applicable generic numerical method to extract instability rates and link parametric instabilities to uncontrolled energy absorption at short times. Based on the existence of parametric resonances, we then develop an analytical approach within Bogoliubov theory, which quantitatively captures the instability rates of the system and provides an intuitive picture of the relevant physical processes, including an understanding of how transverse modes affect the formation of parametric instabilities. Importantly, our calculations demonstrate an agreement between the instability rates determined from numerical simulations and those predicted by theory. To determine the validity regime of the mean-field analysis, we compare the latter to the weakly coupled conserving approximation. The tools developed and the results obtained in this work are directly relevant to present-day ultracold-atom experiments based on shaken optical lattices and are expected to provide an insightful guidance in the quest for Floquet engineering.

  8. R loops stimulate genetic instability of CTG.CAG repeats.

    Science.gov (United States)

    Lin, Yunfu; Dent, Sharon Y R; Wilson, John H; Wells, Robert D; Napierala, Marek

    2010-01-12

    Transcription stimulates the genetic instability of trinucleotide repeat sequences. However, the mechanisms leading to transcription-dependent repeat length variation are unclear. We demonstrate, using biochemical and genetic approaches, that the formation of stable RNA.DNA hybrids enhances the instability of CTG.CAG repeat tracts. In vitro transcribed CG-rich repeating sequences, unlike AT-rich repeats and nonrepeating sequences, form stable, ribonuclease A-resistant structures. These RNA.DNA hybrids are eliminated by ribonuclease H treatment. Mutation in the rnhA1 gene that decreases the activity of ribonuclease HI stimulates the instability of CTG.CAG repeats in E. coli. Importantly, the effect of ribonuclease HI depletion on repeat instability requires active transcription. We also showed that transcription-dependent CTG.CAG repeat instability in human cells is stimulated by siRNA knockdown of RNase H1 and H2. In addition, we used bisulfite modification, which detects single-stranded DNA, to demonstrate that the nontemplate DNA strand at transcribed CTG.CAG repeats remains partially single-stranded in human genomic DNA, thus indicating that it is displaced by an RNA.DNA hybrid. These studies demonstrate that persistent hybrids between the nascent RNA transcript and the template DNA strand at CTG.CAG tracts promote instability of DNA trinucleotide repeats.

  9. Pair-instability supernovae in the local universe

    Energy Technology Data Exchange (ETDEWEB)

    Whalen, Daniel J. [Zentrum für Astronomie, Institut für Theoretische Astrophysik, Universität Heidelberg, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Smidt, Joseph [CCS-2, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Heger, Alexander [Monash Centre for Astrophysics, Monash University, Victoria 3800 (Australia); Hirschi, Raphael [Astrophysics Group, EPSAM, University of Keele, Lennard-Jones Labs, Keele ST5 5BG (United Kingdom); Yusof, Norhasliza [Department of Physics, University of Malaysia, 50603 Kuala Lampur (Malaysia); Even, Wesley; Fryer, Chris L. [T-2, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Stiavelli, Massimo [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Chen, Ke-Jung [Department of Astronomy and Astrophysics, UCSC, Santa Cruz, CA 95064 (United States); Joggerst, Candace C. [XTD-3, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2014-12-10

    The discovery of 150-300 M {sub ☉} stars in the Local Group and pair-instability supernova candidates at low redshifts has excited interest in this exotic explosion mechanism. Realistic light curves for pair-instability supernovae at near-solar metallicities are key to identifying and properly interpreting these events as more are found. We have modeled pair-instability supernovae of 150-500 M {sub ☉} Z ∼ 0.1-0.4 Z {sub ☉} stars. These stars lose up to 80% of their mass to strong line-driven winds and explode as bare He cores. We find that their light curves and spectra are quite different from those of Population III pair-instability explosions, which therefore cannot be used as templates for low-redshift events. Although non-zero metallicity pair-instability supernovae are generally dimmer than their Population III counterparts, in some cases they will be bright enough to be detected at the earliest epochs at which they can occur, the formation of the first galaxies at z ∼ 10-15. Others can masquerade as dim, short duration supernovae that are only visible in the local universe and that under the right conditions could be hidden in a wide variety of supernova classes. We also report for the first time that some pair-instability explosions can create black holes with masses of ∼100 M {sub ☉}.

  10. Punctuating Instability of a 2D Dusty Plasma Colloidal Crystal

    Science.gov (United States)

    Gogia, Guram; Burton, Justin

    When placed in a weakly-ionized RF plasma, colloidal microparticles can be trapped in the narrow Debye sheath region above a capacitively-coupled electrode. Known as a ''dusty plasma'', the particles become negatively charged, leading to the formation of large, 2D crystalline monolayers. At low pressures the particles can experience vertical oscillations due to plasma density fluctuations in the sheath. As a result of these fluctuations, we have found that at low pressures and low bias voltage, the colloidal crystal experiences temporally reoccurring instabilities. Such ''punctuating'' instabilities are caused by the redistribution of kinetic energy from vertical vibrations to horizontal motion, essentially melting the crystal into a gas-like state. After the incipient instability, without changing any external parameters, the system loses kinetic energy to damping with the surrounding gas, then eventually recrystallizes and remains stable until next punctuating instability. The period of the instability ranges from seconds to minutes depending on the system parameters, and can vary significantly within a given system. Using simple simulations of 2D crystals driven by a vertical Langevian forcing, we are able to capture the salient features of the punctuating instability.

  11. Dynamical non-axisymmetric instabilities in rotating relativistic stars

    Energy Technology Data Exchange (ETDEWEB)

    Manca, Gian Mario [Dipartimento di Fisica, Universita di Parma and INFN, Parma (Italy); Baiotti, Luca [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Golm (Germany); Pietri, Roberto De [Dipartimento di Fisica, Universita di Parma and INFN, Parma (Italy); Rezzolla, Luciano [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Golm (Germany)

    2007-06-21

    We present new results on dynamical instabilities in rapidly rotating relativistic stars. In particular, using numerical simulations in full general relativity, we analyse the effects that the stellar compactness has on the threshold for the onset of the dynamical bar-mode instability, as well as on the appearance of other dynamical instabilities. By using an extrapolation technique developed and tested in our previous study (Baiotti L et al 2007 Phys. Rev. D 75 044023), we explicitly determine the threshold for a wide range of compactnesses using four sequences of models of constant baryonic mass comprising a total of 59 stellar models. Our calculation of the threshold is in good agreement with the Newtonian prediction and improves the previous post-Newtonian estimates. In addition, we find that for stars with sufficiently large mass and compactness, the m = 3 deformation is the fastest growing one. For all of the models considered, the non-axisymmetric instability is suppressed on a dynamical timescale with an m = 1 deformation dominating the final stages of the instability. These results, together with those presented in Baiotti L et al (2007 Phys. Rev. D 75 044023), suggest that an m = 1 deformation represents a general and late-time feature of non-axisymmetric dynamical instabilities both in full general relativity and in Newtonian gravity.

  12. Cervical instability in Sotos syndrome: a case report.

    Science.gov (United States)

    Carlo, Waldemar; Dormans, John P

    2004-04-01

    A case report on cervical instability detected in a patient with Sotos syndrome, along with a review of the literature on Sotos syndrome and associated spinal findings. To present the case of a patient with a C3-C4 anterolisthesis occurring in the setting of Sotos syndrome and explore a possible association between the two. Sotos syndrome, a rare overgrowth syndrome with slightly more than 300 cases reported in the English literature to date, is characterized by a unique constellation of symptoms and signs including musculoskeletal findings such as scoliosis, pes planus, generalized ligamentous laxity, and increased growth rates. Cervical instability as part of this syndrome is unreported and rarely presents as a C3-C4 anterolisthesis. A case report detailing the evaluation and treatment of a cervical instability in a 3-year-old with Sotos syndrome. A previously unreported cervical spine instability in Sotos syndrome is described. The patient underwent a posterior spinal fusion of C3 and C4 to avoid complications from the instability. The surgery achieved good results. We outline a possible connection between Sotos syndrome and cervical instability, which may be associated with the unique features of this syndrome including ligamentous laxity or macrosomia and/or with unrecognized injury. Awareness of this occurrence is important for enhancing early detection and correction of this condition.

  13. Current concepts in the management of shoulder instability

    Directory of Open Access Journals (Sweden)

    Suresh Srinivasan

    2017-01-01

    Full Text Available Shoulder instability ranges from subtle instability to frank dislocation. Our understanding on the subject is getting better. Patient lifestyle, increased awareness/expectations, better availability of information, improved imaging modalities, and increased awareness about the previously less known concepts in instability all add to the challenges of managing the problem. History and clinical examination without over reliance on imaging remain essential. We used Embase, PubMed, Medline, CINAHL, Cochrane Library, Scottish Intercollegiate Guidelines Network and Google Scholar search for published literature in English. We used various combinations of the keywords, namely, human shoulder instability, sports injuries, dislocation, surgery, latarjet, glenohumeral, glenoid, and arthroscopy from 1980 to March 2017. The systematic search captured 310 publications. After applying initial exclusion criteria, 41 abstracts were assessed for eligibility. Of these, we selected 20 full-text articles with the majority of focus primarily on surgical management of traumatic shoulder instability. A tailor-made approach for the management of the individual patient is essential and should involve shared decision making. In this article, we have tried to simplify and present the current evidence in the management of traumatic shoulder instability, particularly in sportsperson.

  14. Radiographic Evaluation of Patients with Anterior Shoulder Instability.

    Science.gov (United States)

    Kompel, Andrew J; Li, Xinning; Guermazi, Ali; Murakami, Akira M

    2017-12-01

    Injuries to the labrum, joint capsule (in particular the inferior glenohumeral ligament), cartilage, and glenoid periosteum are associated with anterior shoulder instability. The goal of this review is to provide common radiographic images and findings in patients with anterior shoulder instability. Furthermore, we will demonstrate the best methods for measuring anterior glenoid bone loss. Magnetic resonance (MR) imaging is highly relied upon for evaluating anterior shoulder instability and can diagnose soft tissue injuries with high sensitivity. While 3D computed tomography (CT) scan has been considered the optimal tool for evaluating osseous defects, certain MR imaging sequences have been shown to have similar diagnostic accuracy. Repair of Bankart lesions is critical to stabilizing the shoulder, and in the recent years, there has been an increasing focus on imaging to accurately characterize and measure glenoid bone loss to properly indicate patients for either arthroscopic repair or anterior bony reconstruction. Furthermore, Hill-Sachs lesions are commonly seen with shoulder instability, and importance must be placed on measuring the size and depth of these lesions along with possible engagement, as these factors will dictate management. The labral-ligamentous complex and rotator cuff are primary stabilizers of the shoulder. With anterior shoulder instability, the labrum is frequently injured. MRI with an arthrogram or provocative maneuvers is the gold standard for diagnosis. Various imaging modalities and methods can be performed to identify and measure Bankart and Hill-Sachs lesions, which can then be used for surgical planning and treating shoulder instability.

  15. Current Concepts in the Management of Shoulder Instability.

    Science.gov (United States)

    Srinivasan, Suresh; Pandey, Radhakant

    2017-01-01

    Shoulder instability ranges from subtle instability to frank dislocation. Our understanding on the subject is getting better. Patient lifestyle, increased awareness/expectations, better availability of information, improved imaging modalities, and increased awareness about the previously less known concepts in instability all add to the challenges of managing the problem. History and clinical examination without over reliance on imaging remain essential. We used Embase, PubMed, Medline, CINAHL, Cochrane Library, Scottish Intercollegiate Guidelines Network and Google Scholar search for published literature in English. We used various combinations of the keywords, namely, human shoulder instability, sports injuries, dislocation, surgery, latarjet, glenohumeral, glenoid, and arthroscopy from 1980 to March 2017. The systematic search captured 310 publications. After applying initial exclusion criteria, 41 abstracts were assessed for eligibility. Of these, we selected 20 full-text articles with the majority of focus primarily on surgical management of traumatic shoulder instability. A tailor-made approach for the management of the individual patient is essential and should involve shared decision making. In this article, we have tried to simplify and present the current evidence in the management of traumatic shoulder instability, particularly in sportsperson.

  16. Clinical forms of shoulder instability in pediatric patients

    Directory of Open Access Journals (Sweden)

    Yaroslav N. Proshchenko

    2016-12-01

    Full Text Available Background. The recurrence rate of adolescent chronic shoulder instability is approximately 56%–68%. However, this pathology is often missed in childhood and adolescence. Aim. To identify the clinical forms of shoulder joint instability in pediatric patients. Materials and methods. The authors present the data from 57 pediatric patients aged 3−17 years with a total of 61 unstable shoulder joints. All patients were divided into groups according to the form of instability. Traumatic chronic shoulder instability was identified in 40 patients (Bankart and Hill–Sachs injuries. Of these, non-traumatic shoulder instability was diagnose in 17, including five with recurrent dislocation, and spontaneous shoulder dislocation due to dysplasia of glenoid and labrum was diagnosed in 12. Of the 57 patients in the study cohort, 53 underwent surgery. Postoperatively, two patients developed recurrent shoulder dislocation (Andreev–Boichev technique due type III shoulder dysplasia in the first patient and multidirectional injury in the second. Conclusions. Shoulder joint instability should be considered as the traumatic or non-traumatic form. Treatment decisions should be based on anatomical characteristics that predispose to recurrent dislocation.

  17. Glenohumeral arthrodesis for recurrent types II and III shoulder instability.

    Science.gov (United States)

    Thangarajah, Tanujan; Higgs, Deborah; Bayley, J Ian L; Lambert, Simon M

    2017-04-01

    This study reports the clinical outcome after glenohumeral arthrodesis for recurrent type II (atraumatic structural) and type III (muscle patterning nonstructural disorder) shoulder instability. A retrospective review was conducted at a single facility. Eight consecutive patients (7 women and 1 man) with recurrent shoulder instability underwent arthrodesis and were monitored for a mean of 57 months (range, 24-123 months). Mean age at the time of surgery was 47 years (range, 21-73 years). Bony union was achieved in all patients at a mean time to fusion of 3 months (range, 1-11 months). No complications, such as routine removal of the metalwork or loosening, were noted. No residual perceived glenohumeral instability was reported, and no patient developed scapulothoracic instability or painful scapular dyskinesis. The mean Oxford Shoulder Instability Score improved from 8 preoperatively (range, 0-19) to 32 postoperatively (range, 16-41; P = .001). This was accompanied by an increase in the mean subjective shoulder value, which improved from 22 (range, 0-50) preoperatively to 73 (range, 50-100) postoperatively (P = .004). In our series, glenohumeral arthrodesis was associated with no complications and was able to reduce pain, eliminate instability, and improve functional outcome. It should therefore be considered in this patient population. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  18. Arthroscopic Soft Tissue Procedures for Anterior Shoulder Instability.

    Science.gov (United States)

    Brown, Mathew; Wallace, Andrew; Lachlan, Andrew; Alexander, Susan

    2017-01-01

    Arthroscopy has rapidly transformed the treatment of anterior shoulder instability over the past 30 years. Development of arthroscopic equipment has permitted the investigation and diagnosis of the unstable shoulder, and fixation methods have evolved to promote arthroscopy from an experimental procedure to one of first-line mainstream treatment. Key research papers were reviewed to identify the fundamental principles in patient diagnosis and appropriate selection for arthroscopic treatment. The evolution of arthroscopy is described in this article to facilitate the understanding of current treatment. Accurate diagnosis of the shoulder instability subtype is essential prior to selection for surgery. Different surgical techniques are described to address different pathology within the glenohumeral joint related to instability and the appropriate method should be selected accordingly to optimise outcome. Anterior shoulder instability can be treated successfully using arthroscopic surgery, but the surgeon must treat each patient as an individual case and recognise the different subtypes of instability, the associated pathological lesions and the limitations of arthroscopy. The article concludes with a suggested algorithm for the treatment of anterior shoulder instability.

  19. Correlations between three patient-assessed shoulder instability scales.

    Science.gov (United States)

    Taylor, David; Garewal, Devinder; Evans, Matthew C

    2015-08-01

    To evaluate the correlations between three patient-assessed shoulder instability scales before and after Latarjet stabilisation for traumatic anteroinferior glenohumeral instability. Records of 30 men and 2 women (mean age, 26.7 years) who had not undergone surgery for antero-inferior shoulder instability and records of 31 men and one woman (mean age, 27 years) who had undergone Latarjet stabilisation for anteroinferior shoulder instability and had been followed up for a mean period of 21.3 months were reviewed. Correlations between the Western Ontario Shoulder Instability Index (WOSI), the Melbourne Instability Shoulder Score (MISS), and the L'Insalata Shoulder Questionnaire (L'Insalata) were assessed. The mean score of each scale was significantly greater in the postoperative than preoperative group (p0.01, post-hoc analysis). Correlations of all scale pairs were significant (p<0.001). The WOSIMISS correlations in the pre- and post-operative groups were moderate. The L'Insalata-WOSI correlations in the pre- and post-operative groups were moderate and high, respectively. The L'Insalata-MISS correlations in the pre- and post-operative groups were high and moderate, respectively. The MISS and WOSI scales are moderately correlated. Correlation of the L'Insalata scale with other scales depends on the operative status of the patient. The use of the L'Insalata scale alone is not recommended.

  20. Magnetically-Driven Convergent Instability Growth platform on Z.

    Energy Technology Data Exchange (ETDEWEB)

    Knapp, Patrick [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Mattsson, Thomas [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Martin, Matthew [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Benage, John F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jenkins, James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Albright, Brian James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-09-01

    Hydrodynamic instability growth is a fundamentally limiting process in many applications. In High Energy Density Physics (HEDP) systems such as inertial confinement fusion implosions and stellar explosions, hydro instabilities can dominate the evolution of the object and largely determine the final state achievable. Of particular interest is the process by which instabilities cause perturbations at a density or material interface to grow nonlinearly, introducing vorticity and eventually causing the two species to mix across the interface. Although quantifying instabilities has been the subject of many investigations in planar geometry, few have been done in converging geometry. During FY17, the team executed six convergent geometry instability experiments. Based on earlier results, the platform was redesigned and improved with respect to load centering at installation making the installation reproducible and development of a new 7.2 keV, Co He-a backlighter system to better penetrate the liner. Together, the improvements yielded significantly improved experimental results. The results in FY17 demonstrate the viability of using experiments on Z to quantify instability growth in cylindrically convergent geometry. Going forward, we will continue the partnership with staff and management at LANL to analyze the past experiments, compare to hydrodynamics growth models, and design future experiments.

  1. The Instability of Astrophysics Witnessed in the Twentieth Century

    Science.gov (United States)

    Harwit, Martin

    2014-01-01

    Scientific progress entails instabilities that advance a field; but excessive instability, often arising from misunderstandings, thwarts planning and adds cost. The history of 20th century astronomy provides insight on several factors that make astronomy and astrophysics exceptionally unstable. A fundamental source of instability is astronomy’s inability, sometimes for decades at a time, to pursue discoveries of rare events systematically. Such delays inject levels of uncertainty in an observational science that are more readily avoided in the experimental sciences. Beneficial instabilities can arise through the import of novel theories and tools from sister sciences, industry or the military. Such imports, however, can also destabilize the field. Astronomy comprises many distinct disciplines, which need to interact coherently for a broader understanding of the Cosmos to emerge. As the complexity of these disciplines’ undertakings increases, and their respective uses of tools and vocabularies diverge, misunderstandings arise to threaten coherence. Misinformation can then cascade back and forth, with consequences similar to those of failures in electrical power grinds and financial meltdowns. A balance needs to be sought, which protects astrophysics against such failures, while permitting ready discourse so the whole field can benefit from genuine advances in its respective disciplines. I will discuss means by which the benefits of instabilities advancing the field may be retained while avoiding more damaging instabilities.

  2. Implication of microsatellite instability in human gastric cancers

    Science.gov (United States)

    Shokal, Upasana; Sharma, Prakash C.

    2012-01-01

    Microsatellite instability, one of the phenomena implicated in gastric cancer, is mainly associated with the expansion or contraction of microsatellite sequences due to replication errors caused most frequently by mutations in the mismatch repair (MMR) and tumour suppressor genes. Tumours exhibiting microsatellite instability are proven to have truncated products resulting from frequent mutations in mononucleotide or dinucleotide runs in coding and non-coding regions of the targeted genes. Epigenetic changes like hypermethylation of the promoter region of MMR genes as well as gene silencing are also responsible for the microsatellite instability phenotypes. Assessing microsatellite instability in tumours has proved to be an efficient tool for the prognosis of various cancers including colorectal and gastric cancers. Such tumours are characterized by distinct clinicopathological profiles. Biotic agents like Epstein Barr Virus and H. pylori along with other factors like family history, diet and geographical location also play an important role in the onset of gastric carcinogenesis. Instability of mitochondrial DNA has also been investigated and claimed to be involved in the occurrence of gastric cancers in humans. Development of simplified but robust and reproducible microsatellite instability based molecular tools promises efficient prognostic assessment of gastric tumours. PMID:22771588

  3. Arthroscopic Soft Tissue Procedures for Anterior Shoulder Instability

    Science.gov (United States)

    Brown, Mathew; Wallace, Andrew; Lachlan, Andrew; Alexander, Susan

    2017-01-01

    Background: Arthroscopy has rapidly transformed the treatment of anterior shoulder instability over the past 30 years. Development of arthroscopic equipment has permitted the investigation and diagnosis of the unstable shoulder, and fixation methods have evolved to promote arthroscopy from an experimental procedure to one of first-line mainstream treatment. Methods: Key research papers were reviewed to identify the fundamental principles in patient diagnosis and appropriate selection for arthroscopic treatment. The evolution of arthroscopy is described in this article to facilitate the understanding of current treatment. Results: Accurate diagnosis of the shoulder instability subtype is essential prior to selection for surgery. Different surgical techniques are described to address different pathology within the glenohumeral joint related to instability and the appropriate method should be selected accordingly to optimise outcome. Conclusion: Anterior shoulder instability can be treated successfully using arthroscopic surgery, but the surgeon must treat each patient as an individual case and recognise the different subtypes of instability, the associated pathological lesions and the limitations of arthroscopy. The article concludes with a suggested algorithm for the treatment of anterior shoulder instability. PMID:29114337

  4. The responsiveness and minimal important change of the western Ontario shoulder instability index and oxford shoulder instability score

    NARCIS (Netherlands)

    Van Der Linde, Just A.; Van Kampen, Derk A.; Van Beers, Loes W.A.H.; Van Deurzen, Derek F.P.; Saris, Daniël B.F.; Terwee, Caroline B.

    2017-01-01

    BACKGROUND: Patient-reported outcome measurements (PROMs) are widely used to evaluate functional limitations. Considering PROMs for shoulder instability, information is lacking with regard to what constitutes a relevant change from baseline scores. OBJECTIVES: To evaluate the responsiveness of the

  5. New diagnostics and cures for coupled-bunch instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Prabhakar, S.

    2000-02-14

    Electromagnetic interaction between a charged particle beam and its surroundings causes collective instabilities, which must be controlled if the new light sources and colliders are to meet their design goals. Control requires a combination of passive damping and fast active feedback on an unprecedented technological scale. Efficient instability diagnosis techniques are also needed for machines with large numbers of bunches. This thesis describes new methods of measuring and analyzing coupled-bunch instabilities in circular accelerators, and demonstrates the existence of a new cure. A new technique is demonstrated for simultaneous measurement of growth rates, damping rates and coherent tune shifts of all unstable coupled-bunch eigenmodes from a single 10-25-ms transient snapshot of beam motion. The technique has been used to locate and quantify beam impedance resonances at PEP-II, ALS and SPEAR. This method is faster than existing spectral scan methods by at least an order of magnitude, and has the added advantage of revealing coupled-bunch dynamics in the linear small-signal regime. A method is also presented for estimating beam impedance from multi-bunch fill shape and synchronous phase measurements. Phase space tracking of multi-bunch instabilities is introduced as a ``complete instability diagnostic.'' Digitized multi-bunch data is analyzed offline, to estimate the phase space trajectories of bunches and modes. Availability of phase space trajectories is shown to open up a variety of possibilities, including measurement of reactive impedance, and diagnosis of the fast beam-ion instability. Knowledge gained from longitudinal measurements (all made using a digital longitudinal feedback system) has been used to optimize cavity temperatures, tuner positions and feedback parameters, and also to identify sources of beam noise at the three machines. A matrix-based method is presented for analyzing the beneficial effect of bunch-to-bunch tune variation on

  6. Thermal preconditioning of mountain permafrost towards instability

    Science.gov (United States)

    Hauck, Christian; Etzelmüller, Bernd; Hilbich, Christin; Isaksen, Ketil; Mollaret, Coline; Pellet, Cécile; Westermann, Sebastian

    2017-04-01

    Warming permafrost has been detected worldwide in recent years and is projected to continue during the next century as shown in many modelling studies from the polar and mountain regions. In mountain regions, this can lead to potentially hazardous impacts on short time-scales by an increased tendency for slope instabilities. However, the time scale of permafrost thaw and the role of the ice content for determining the strength and rate of permafrost warming and degradation (= development of talik) are still unclear, especially in highly heterogeneous terrain. Observations of permafrost temperatures near the freezing point show complex inter-annual responses to climate forcing due to latent heat effects during thawing and the influence of the snow-cover, which is formed and modulated by highly non-linear processes itself. These effects are complicated by 3-dimensional hydrological processes and interactions between snow melt, infiltration and drainage which may also play an important role in the triggering of mass movements in steep permafrost slopes. In this contribution we demonstrate for the first time a preconditioning effect within near-surface layers in mountain permafrost that causes non-linear degradation and accelerates permafrost thaw. We hypothesise that an extreme regional or global temperature anomaly, such as the Central European summers 2003 and 2015 or the Northern European summers 2006 and 2014, will enhance permafrost degradation if the active layer and the top of the permafrost layer are already preconditioned, i.e. have reduced latent heat content. This preconditioning can already be effectuated by a singular warm year, leading to exceptionally strong melting of the ground ice in the near-surface layers. On sloping terrain and in a context of quasi-continuous atmospheric warming, this ice-loss can be considered as irreversible, as a large part of the melted water will drain/evaporate during the process, and the build-up of an equivalent amount of

  7. Trends in Surgical Management of Shoulder Instability

    Science.gov (United States)

    Bonazza, Nicholas A.; Liu, Guodong; Leslie, Douglas L.; Dhawan, Aman

    2017-01-01

    Background: Optimal surgical management of anterior shoulder instability remains controversial. There is a need to assess the most recent trends for primary and revision shoulder stabilization surgery using a national database significantly larger than those previously utilized. Hypothesis: Most shoulder stabilization procedures are performed arthroscopically. Examining revision procedures, we hypothesized that open procedures would result in decreased revision stabilizations compared with arthroscopic procedures and that most revision procedures would be open Bankart or bone transfer procedures regardless of the index procedure technique. Study Design: Descriptive epidemiology study. Methods: The MarketScan Database was searched using International Classification of Diseases–Ninth Revision (ICD-9) and Current Procedural Terminology (CPT) codes to identify patients who underwent any shoulder stabilization procedure between 2008 and 2012. Regression analysis was used to evaluate trends between patient groups. The Cochran-Armitage trend test was used to identify differences in trends seen yearly. Odds ratios (ORs) were calculated to compare the likelihood of undergoing a revision stabilization procedure. Results: A total of 66,564 shoulder stabilization procedures were identified from 2008 through 2012: 60,248 arthroscopic stabilization procedures (90.5%) and 6316 open stabilization procedures (9.5%), including 1623 bone block procedures. Arthroscopic stabilization procedures increased in total number and percentage of all procedures in each year of the study. Bone block procedures increased in number each year, although other open procedures decreased during the study period. Males underwent more stabilization procedures, while patients between the ages of 10 and 19 years were most likely to undergo any procedure. Patients who underwent bone block stabilization were significantly less likely to undergo a second stabilization procedure during the study period when

  8. The Hydrodynamics of Blast-Wave-Driven Instabilities

    Science.gov (United States)

    Miles, Aaron R.

    2010-05-01

    Supernova explosions are among the most dramatic in the universe. Type II supernovae follow core collapse of a massive star, while Type Ia supernovae are typically believed to be thermonuclear explosions of carbon-oxygen white dwarfs that have accreted enough material to initiate carbon burning. In both cases, the explosion dynamics are complicated by hydrodynamic instabilities that make spherical symmetry impossible. Non-planar interactions of shocks with steep density gradients result in vorticity deposition that drives Richtmyer-Meshkov (RM) instability growth. Deceleration of those same shock-accelerated interfaces drives the ubiquitous Rayleigh-Taylor (RT) instability. These processes yield highly nonlinear structures that are further modified by shear-driven Kelvin-Helmholtz (KH) instabilities, and provide elemental mixing on a wide range of scales. A broad spectrum of approaches can be applied to study the role of hydrodynamic mixing in SNe. These range from analytic treatments of the fundamental instability problems of classical RT and steady-shock RM, to complex (often multiphysics) computational and experimental systems, including numerical simulations of supernovae and laser-driven laboratory. Between these two extremes lies a third fundamental instability problem that is more relevant than either RT or RM in isolation and somewhat less complex than the full system. Namely, an idealized blast-wave-driven problem in which a localized source drives a divergent Taylor-Sedov blast wave that in turn drives a perturbed interface between heavier and lighter gamma-law fluids. Within this context, we use numerical simulations and simplified analytic models to consider the effect of the initial perturbation spectrum in determining the late-time asymptotic state of the mixing zone, the interaction of multiple unstable interfaces relevant to core-collapse supernovae, and the proximity of the forward shock to the developing instability. This work performed under the

  9. Biomechanics of the spine. Part II: spinal instability.

    Science.gov (United States)

    Izzo, Roberto; Guarnieri, Gianluigi; Guglielmi, Giuseppe; Muto, Mario

    2013-01-01

    Spine stability is the basic requirement to protect nervous structures and prevent the early deterioration of spinal components. All bony and soft spinal components contribute to stability, so any degenerative, traumatic or destructive lesion to any spinal structure gives rise to some degree of instability. Degenerative instability is considered a major cause of axial and radicular pain and is a frequent indication for surgery. Nevertheless the assessment of instability remains difficult in both clinical and imaging settings. All static imaging modalities, even conventional MR, the most accurate technique, are unreliable in assessing instability and chronic pain due to degenerative spine. Dynamic-positional MR is considered the most sophisticated imaging modality to evaluate abnormal spinal motion and instability. In spinal traumas, as multi-detector CT yields high-resolution reconstructions in every spatial plane, it will detect even the tiniest fractures revealing potentially unstable lesions, often avoid the routine use of MR. Nevertheless, MR remains the only modality that will directly and routinely assess soft tissue changes. Unfortunately the objectivity of MR in assessing the integrity of ligaments is not rigorously defined and its use in routine protocols to clear blunt spinal injuries remains controversial. There are no evidence-based guidelines currently available to assess the risk of spinal instability in the setting of neoplastic spinal disease, so predicting the risk of a pathological fracture or the timing of a collapse remains challenging even when the lesions are well-characterized by neuroimaging. Diagnostic difficulties lead to controversy in the choice of the best treatment in all forms of spinal instability. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  10. Biomechanics of the spine. Part II: Spinal instability

    Energy Technology Data Exchange (ETDEWEB)

    Izzo, Roberto, E-mail: roberto1766@interfree.it [Neuroradiology Department, “A.Cardarelli” Hospital, Napoli (Italy); Guarnieri, Gianluigi, E-mail: gianluigiguarnieri@hotmail.it [Neuroradiology Department, “A.Cardarelli” Hospital, Napoli (Italy); Guglielmi, Giuseppe, E-mail: g.gugliemi@unifg.it [Department of Radiology, University of Foggia, Foggia (Italy); Muto, Mario, E-mail: mutomar@tiscali.it [Neuroradiology Department, “A.Cardarelli” Hospital, Napoli (Italy)

    2013-01-15

    Spine stability is the basic requirement to protect nervous structures and prevent the early deterioration of spinal components. All bony and soft spinal components contribute to stability, so any degenerative, traumatic or destructive lesion to any spinal structure gives rise to some degree of instability. Degenerative instability is considered a major cause of axial and radicular pain and is a frequent indication for surgery. Nevertheless the assessment of instability remains difficult in both clinical and imaging settings. All static imaging modalities, even conventional MR, the most accurate technique, are unreliable in assessing instability and chronic pain due to degenerative spine. Dynamic-positional MR is considered the most sophisticated imaging modality to evaluate abnormal spinal motion and instability. In spinal traumas, as multi-detector CT yields high-resolution reconstructions in every spatial plane, it will detect even the tiniest fractures revealing potentially unstable lesions, often avoid the routine use of MR. Nevertheless, MR remains the only modality that will directly and routinely assess soft tissue changes. Unfortunately the objectivity of MR in assessing the integrity of ligaments is not rigorously defined and its use in routine protocols to clear blunt spinal injuries remains controversial. There are no evidence-based guidelines currently available to assess the risk of spinal instability in the setting of neoplastic spinal disease, so predicting the risk of a pathological fracture or the timing of a collapse remains challenging even when the lesions are well-characterized by neuroimaging. Diagnostic difficulties lead to controversy in the choice of the best treatment in all forms of spinal instability.

  11. Nonlinear Farley-Buneman instability with Dust Impurities.

    Science.gov (United States)

    Atamaniuk, B.; Volokitin, A. S.

    2009-04-01

    The regimes of nonlinear stabilization of instability of low frequency waves in magnetized, weakly ionized and inhomogeneous ionospheric dusty plasma are considered. In the lower ionosphere in the E--region, a complex process transforms wind energy into currents creating the E--region electrojet. If these currents exceed a certain critical amplitude, a streaming instability called the Farley--Buneman or a collisional two-stream instability develops. When the number of cooperating waves remains small due to a competition of processes of their instability and attenuation, the turbulence appears in the result of their stochastic behavior. Then even system with finite number of interacting waves can realize a turbulent state in active media. At conditions when electrons are magnetized and characteristic time of density oscillations exceed the rate of electron ion collisions and electron dust collision the drift of electrons perpendicular to magnetic field is the main motion. Consequently, the main nonlinearity appears in result of convection of a density perturbation in one wave by another wave in the perpendicular to magnetic field and mathematically is expressed in a specific vector form The strong collisional damping of waves allow to assume that a typical perturbed state of plasma can be described as finite set of interacting waves. This allow to avoid difficulties of 3D simulations and to make full study of nonlinear stabilization and influence of the dust component in the conditions when the number of interacting waves keeps small by the strong competition of processes wave damping and instabilities Keywords: Dusty Plasmas, Farley-Buneman Instability, Nonlinear Stabilization. REFERENCES 1. M. Oppenheim and N. Otani, Geophysical Research Letters, 22, pp. 353-356, 1995. 2. A.V. Volosevich and C.V. Meister, Int. Journal of Geomagnetism and aeronomy, 3 pp.151-156, 2002 3. A. S. Volokitin and B. Atamaniuk, Reduced nonlinear description of Farley-Buneman instability

  12. Instability in Thoracolumbar Trauma: Is a New Definition Warranted?

    Science.gov (United States)

    Abbasi Fard, Salman; Skoch, Jesse; Avila, Mauricio J; Patel, Apar S; Sattarov, Kamran V; Walter, Christina M; Baaj, Ali A

    2017-10-01

    Review of the articles. The objective of this study was to review all articles related to spinal instability to determine a consensus statement for a contemporary, practical definition applicable to thoracolumbar injuries. Traumatic fractures of the thoracolumbar spine are common. These injuries can result in neurological deficits, disability, deformity, pain, and represent a great economic burden to society. The determination of spinal instability is an important task for spine surgeons, as treatment strategies rely heavily on this assessment. However, a clinically applicable definition of spinal stability remains elusive. A review of the Medline database between 1930 and 2014 was performed limited to papers in English. Spinal instability, thoracolumbar, and spinal stability were used as search terms. Case reports were excluded. We reviewed listed references from pertinent search results and located relevant manuscripts from these lists as well. The search produced a total of 694 published articles. Twenty-five articles were eligible after abstract screening and underwent full review. A definition for spinal instability was described in only 4 of them. Definitions were primarily based on biomechanical and classification studies. No definitive parameters were outlined to define stability. Thirty-six years after White and Panjabi's original definition of instability, and many classification schemes later, there remains no practical and meaningful definition for spinal instability in thoracolumbar trauma. Surgeon expertise and experience remains an important factor in stability determination. We propose that, at an initial assessment, a distinction should be made between immediate and delayed instability. This designation should better guide surgeons in decision making and patient counseling.

  13. Smectite reactions and slip instabilities in subduction zones

    Science.gov (United States)

    Gadenne, Leslie; Raimbourg, Hugues; Champallier, Remi; Yamamoto, Yuzuru

    2015-04-01

    Though it is of prime importance in terms of seismic and tsunami risk, the mechanical behavior of the shallow (ztransformation of a soft sediment into a hard sedimentary rock, which modifies the rock potential to localize deformation and be involved in slip instabilities. While it is the major control on diagenetic reactions, the effect of temperature on the mechanical behavior is not well constrained experimentally. To address this question, we have designed triaxial deformation experiments in the Paterson rig either at ambient temperature or at 300 °C. The tested material includes siltstones from the Boso Peninsula in Japan (corresponding to the shallow domain of a paleo-accretionary prism), either as cylindrical cores or as ground powders as well as powders composed principally of smectite. For this material, the main consequence of the high temperature conditions is to trigger the smectite-to-illite reaction or the smectite interlayer space collapse. The first result is that at 300 °C, all tested samples show slip instabilities. These instabilities are apparent as a sudden (~ 4s) and large (~10 to 45 MPa depending on the starting material and the confining pressure) stress drop in the macroscopic stress-strain curve, in some cases followed by a rapid restrengthening of the material. In contrast, no instability was observed for the experiments at ambient temperature. As slip instabilities are activated by the temperature and occur as well in smectite powders, we attribute these instabilities to the diagenetic reactions of smectite. An additional experiment on a powder of smectite where the smectite-to-illite reaction has been inhibited by cationic exchanges does not show instabilities upon deformation at 300 °C. We propose therefore that catastrophic dehydration of smectite associated with the smectite-to-illite reaction may be responsible for triggering the instabilities. This catastrophic dehydration is potentially a major control on the genesis of

  14. Plasma instabilities and turbulence in non-Abelian gauge theories

    Energy Technology Data Exchange (ETDEWEB)

    Scheffler, Sebastian Herwig Juergen

    2010-02-17

    Several aspects of the thermalisation process in non-Abelian gauge theories are investigated. Both numerical simulations in the classical statistical approximation and analytical computations in the framework of the two-particle-irreducible effective action are carried out and their results are compared to each other. The physical quantities of central importance are the correlation functions of the gauge field in Coulomb and temporal axial gauge as well as the gauge invariant energy-momentum tensor. Following a general introduction, the theoretical framework of the ensuing investigations is outlined. In doing so, the range of validity of the employed approximation schemes is discussed as well. The first main part of the thesis is concerned with the early stage of the thermalisation process where particular emphasis is on the role of plasma instabilities. These investigations are relevant to the phenomenological understanding of present heavy ion collision experiments. First, an ensemble of initial conditions motivated by the ''colour glass condensate'' is developed which captures characteristic properties of the plasma created in heavy ion collisions. Here, the strong anisotropy and the large occupation numbers of low-momentum degrees of freedom are to be highlighted. Numerical calculations demonstrate the occurrence of two kinds of instabilities. Primary instabilities result from the specific initial conditions. Secondary instabilities are caused by nonlinear fluctuation effects of the preceding primary instabilities. The time scale associated with the instabilities is of order 1 fm/c. It is shown that the plasma instabilities isotropize the initially strongly anisotropic ensemble in the domain of low momenta (instabilities in an idealised setup is investigated. In the second part, the

  15. Self-similar evolution of the nonlinear magnetic buoyancy instability

    Science.gov (United States)

    Shibata, K.; Tajima, T.; Matsumoto, R.

    1990-01-01

    A new type of self-similar solution of ideal magnetohydrodynamics (MHD) in the nonlinear stage of the undular model (k parallel to B) of the magnetic buoyancy instability (the ballooning instability in fusion plasma physics or the Parker instability in astrophysics) is found through MHD simulation and theory. The linear theory developed agrees well with the simulation in the early (linear) stage. The nonlinear stages of the instability in the simulation show the self-similar evolution. One of the solutions obtained from the nonlinear analysis has the characteristics of nonlinear instability in Lagrangian coordinates; the fluid velocity and the Alfven speed on each magnetic loop increase exponentially with time, because the loop is evacuated by the field-aligned motion of matter resulting from gravitational acceleration. In the later stage of the nonlinear evolution, the solution property changes from exponential to power-law time dependence. The latter corresponds to a force-free expansion solution. The later saturation of the velocity increment is also discussed.

  16. Experimental Investigation of Cavitation Induced Feedline Instability from an Orifice

    Science.gov (United States)

    Hitt, Matthew A.; Lineberry, David M.; Ahuja, Vineet; Frederick, Robert A,

    2012-01-01

    This paper details the results of an experimental investigation into the cavitation instabilities created by a circular orifice conducted at the University of Alabama in Huntsville Propulsion Research Center. This experiment was conducted in concert with a computational simulation to serve as a reference point for the simulation. Testing was conducted using liquid nitrogen as a cryogenic propellant simulant. A 1.06 cm diameter thin orifice with a rounded inlet was tested in an approximately 1.25 kg/s flow with inlet pressures ranging from 504.1 kPa to 829.3 kPa. Pressure fluctuations generated by the orifice were measured using a high frequency pressure sensor located 0.64 tube diameters downstream of the orifice. Fast Fourier Transforms were performed on the high frequency data to determine the instability frequency. Shedding resulted in a primary frequency with a cavitation related subharmonic frequency. For this experiment, the cavitation instability ranged from 153 Hz to 275 Hz. Additionally, the strength of the cavitation occur red as a function of cavitation number. At lower cavitation numbers, the strength of the cavitation instability ranged from 2.4 % to 7 % of the inlet pressure. However, at higher cavitation numbers, the strength of the cavitation instability ranged from 0.6 % to 1 % of the inlet pressure.

  17. Isentropic thermal instability in atomic surface layers of photodissociation regions

    Science.gov (United States)

    Krasnobaev, K. V.; Tagirova, R. R.

    2017-08-01

    We consider the evolution of an isentropic thermal instability in the atomic zone of a photodissociation region (PDR). In this zone, gas heating and cooling are associated mainly with photoelectric emission from dust grains and fine-structure lines ([C II] 158, [O I] 63 and [O I] 146 μm), respectively. The instability criterion has a multi-parametric dependence on the conditions of the interstellar medium. We found that instability occurs when the intensity of the incident far-ultraviolet field G0 and gas density n are high. For example, we have 3 × 103 360 waves is L ˜ 10-3-5 × 10-2 pc. For objects that are older than tinst and have sizes of the atomic zone larger than L, we expect that instability influences the PDR structure significantly. The presence of multiple shock waves, turbulent velocities of several kilometres per second and inhomogeneities with higher density and temperature than the surrounding medium can characterize isentropic thermal instability in PDRs.

  18. Space-Charge Waves and Instabilities in Intense Beams

    Science.gov (United States)

    Wang, J. G.

    1997-11-01

    Advancced accelerator applications, such as drivers for heavy ion inertial fusion, high-intensity synchrotrons for spallation neutron sources, high energy boosters, free electron lasers, high-power microwave generators, etc., require ever-increasing beam intensity. An important beam dynamics issue in such beams is the collective behavior of charged particles due to their space charge effects. This includes the phenomena of space-charge waves and instabilities excited on beams by external perturbations. It is very crucial to fully understand these phenomena in order to develop advanced accelerators for various applications. At the University of Maryland we have been conducting experimental programs to study space-charge waves and longitudinal instabilities by employing low-energy, high-current, space-charge dominated electron beams. Localized perturbations on the beams are generated from a gridded electron gun. In a conducting transport channel focused by short solenoids, these perturbations evolve into space-charge waves propagating on the beams. The wave speed is measured and many beam parameters are determined with this technique. The reflection of space-charge waves at the shoulder of an initially rectangular beam bunch is also observed. In a resistive-wall channel focused by a uniform long solenoid, the space-charge waves suffer longitudinal instability. The properties of the instabilities are studied in detail in the long wavelength range. In this talk we review our experimental results on the waves and instabilities and compare with theory.

  19. Dehydration-induced instabilities at intermediate depths in subduction zones

    Science.gov (United States)

    Brantut, Nicolas; Stefanou, Ioannis; Sulem, Jean

    2017-08-01

    We formulate a model for coupled deformation and dehydration of antigorite, based on a porosity-dependent yield criterion and including shear-enhanced compaction. A pore pressure and compaction instability can develop when the net volume change associated with the reaction is negative, i.e., at intermediate depth in subduction zones. The instability criterion is derived in terms of the dependence of the yield criterion on porosity: if that dependence is strong, instabilities are more likely to occur. We also find that the instability is associated with strain localization, over characteristic length scales determined by the hydraulic diffusivity, the elasto-plastic parameters of the rock, and the reaction rate. Typical lower bounds for the localization length are of the order of 10 to 100 for antigorite dehydration and deformation at 3 GPa. The fluid pressure and deformation instability is expected to induce stress buildup in the surrounding rocks forming the subducted slab, which provides a mechanism for the nucleation and propagation of intermediate-depth earthquakes.

  20. Axial Instability Growth in Tungsten Wire Array Z-Pinches

    Science.gov (United States)

    Cahill, Adam; Knapp, Patrick; Greenly, John; Pikuz, Sergei; Shelkovenko, Tania; Hammer, David

    2010-11-01

    The individual exploding wires in wire array z-pinches have been shown to suffer from axially non-uniformity beginning from the moment of plasma formation. This non-uniformity grows in amplitude and wavelength until it reaches what appears to be a material dependent wavelength at the time array implosion begins. Previous work by Knapp et al. [1] studied the temporal evolution of this instability in aluminum wire arrays. We have extended that work to include the evolution of tungsten wire array instabilities. Time gated laser shadowgraphy is used to track wavelength and amplitude over a series of shots to develop a record of the instability's growth. We attempt to identify array parameters which significantly contribute to the growth of this instability. [4pt] [1] Knapp, P. F., J. B. Greenly, P. A. Gourdain, C. L. Hoyt, M. R. Martin, S. A. Pikuz, C. E. Seyler, T. A. Shelkovenko, and D. A. Hammer. ``Growth and Saturation of the Axial Instability in Low Wire Number Wire Array Z Pinches.'' Physics of Plasmas 17 (2010). Web.

  1. High-frequency instability of the sheath-plasma resonance

    Science.gov (United States)

    Stenzel, R. L.

    1989-01-01

    Coherent high frequency oscillations near the electron plasma frequency (omega approx. less than omega sub p) are generated by electrodes with positive dc bias immersed in a uniform Maxwellian afterglow plasma. The instability occurs at the sheath-plasma resonance and is driven by a negative RF sheath resistance associated with the electron inertia in the diode-like electron-rich sheath. With increasing dc bias, i.e., electron transit time, the instability exhibits a hard threshold, downward frequency pulling, line broadening and copious harmonics. The fundamental instability is a bounded oscillation due to wave evanescence, but the harmonics are radiated as electromagnetic waves from the electrodes acting like antennas. Wavelength and polarization measurements confirm the emission process. Electromagnetic waves are excited by electrodes of various geometries (planes, cylinders, spheres) which excludes other radiation mechanisms such as orbitrons or beam-plasma instabilities. The line broadening mechanism was identified as a frequency modulation via the electron transit time by dynamic ions. Ion oscillations at the sheath edge give rise to burst-like RF emissions. These laboratory observations of a new instability are important for antennas in space plasmas, generation of coherent beams with diodes, and plasma diagnostics.

  2. Instability in strongly magnetized accretion discs: a global perspective

    Science.gov (United States)

    Das, Upasana; Begelman, Mitchell C.; Lesur, Geoffroy

    2018-01-01

    We examine the properties of strongly magnetized accretion discs in a global framework, with particular focus on the evolution of magnetohydrodynamic instabilities such as the magnetorotational instability (MRI). Work by Pessah & Psaltis showed that MRI is stabilized beyond a critical toroidal field in compressible, differentially rotating flows and, also, reported the appearance of two new instabilities beyond this field. Their results stemmed from considering geometric curvature effects due to the suprathermal background toroidal field, which had been previously ignored in weak-field studies. However, their calculations were performed under the local approximation, which poses the danger of introducing spurious behaviour due to the introduction of global geometric terms in an otherwise local framework. In order to avoid this, we perform a global eigenvalue analysis of the linearized MHD equations in cylindrical geometry. We confirm that MRI indeed tends to be highly suppressed when the background toroidal field attains the Pessah-Psaltis limit. We also observe the appearance of two new instabilities that emerge in the presence of highly suprathermal toroidal fields. These results were additionally verified using numerical simulations in PLUTO. There are, however, certain differences between the the local and global results, especially in the vertical wavenumber occupancies of the various instabilities, which we discuss in detail. We also study the global eigenfunctions of the most unstable modes in the suprathermal regime, which are inaccessible in the local analysis. Overall, our findings emphasize the necessity of a global treatment for accurately modelling strongly magnetized accretion discs.

  3. Snow instability patterns at the scale of a small basin

    Science.gov (United States)

    Reuter, Benjamin; Richter, Bettina; Schweizer, Jürg

    2016-02-01

    Spatial and temporal variations are inherent characteristics of the alpine snow cover. Spatial heterogeneity is supposed to control the avalanche release probability by either hindering extensive crack propagation or facilitating localized failure initiation. Though a link between spatial snow instability variations and meteorological forcing is anticipated, it has not been quantitatively shown yet. We recorded snow penetration resistance profiles with the snow micropenetrometer at an alpine field site during five field campaigns in Eastern Switzerland. For each of about 150 vertical profiles sampled per day a failure initiation criterion and the critical crack length were calculated. For both criteria we analyzed their spatial structure and predicted snow instability in the basin by external drift kriging. The regression models were based on terrain and snow depth data. Slope aspect was the most prominent driver, but significant covariates varied depending on the situation. Residual autocorrelation ranges were shorter than the ones of the terrain suggesting external influences possibly due to meteorological forcing. To explore the causes of the instability patterns we repeated the geostatistical analysis with snow cover model output as covariate data for one case. The observed variations of snow instability were related to variations in slab layer properties which were caused by preferential deposition of precipitation and differences in energy input at the snow surface during the formation period of the slab layers. Our results suggest that 3-D snow cover modeling allows reproducing some of the snow property variations related to snow instability, but in future work all relevant micrometeorological spatial interactions should be considered.

  4. Co-Extrusion Instabilities Modeled with a Single Fluid

    Science.gov (United States)

    Reis, T.; Sahin, M.; Wilson, H.

    2008-07-01

    Industrial processes involving co-extrusion of multiple fluids to produce multi-layered products are rife with instabilities. We consider a simple indicative instance of co-extrusion, in which there is only a single fluid involved in the flow, but two different channel branches impose differing flow histories on it. The channels merge and, ideally, a smooth film is extruded with two layers having different stress histories. In experimental studies a wavelike instability is observed with a well defined wavelength in the flow direction and a `zig-zag' like structure, indicating that the extra flow caused by the instability is three-dimensional. Suggested mechanisms for instabilities in co-extrusion include a jump in viscosity and/or first normal stress difference across a flat interface, and a coupling of normal stresses with streamline curvature in the region where the two streams merge. Using a numerical linear stability tool we investigate this instability (using a single mode fluid model throughout) and explore which of the known mechanisms is the most likely culprit here.

  5. A coupled "AB" system: Rogue waves and modulation instabilities.

    Science.gov (United States)

    Wu, C F; Grimshaw, R H J; Chow, K W; Chan, H N

    2015-10-01

    Rogue waves are unexpectedly large and localized displacements from an equilibrium position or an otherwise calm background. For the nonlinear Schrödinger (NLS) model widely used in fluid mechanics and optics, these waves can occur only when dispersion and nonlinearity are of the same sign, a regime of modulation instability. For coupled NLS equations, rogue waves will arise even if dispersion and nonlinearity are of opposite signs in each component as new regimes of modulation instability will appear in the coupled system. The same phenomenon will be demonstrated here for a coupled "AB" system, a wave-current interaction model describing baroclinic instability processes in geophysical flows. Indeed, the onset of modulation instability correlates precisely with the existence criterion for rogue waves for this system. Transitions from "elevation" rogue waves to "depression" rogue waves are elucidated analytically. The dispersion relation as a polynomial of the fourth order may possess double pairs of complex roots, leading to multiple configurations of rogue waves for a given set of input parameters. For special parameter regimes, the dispersion relation reduces to a cubic polynomial, allowing the existence criterion for rogue waves to be computed explicitly. Numerical tests correlating modulation instability and evolution of rogue waves were conducted.

  6. R-loops: targets for nuclease cleavage and repeat instability.

    Science.gov (United States)

    Freudenreich, Catherine H

    2018-01-11

    R-loops form when transcribed RNA remains bound to its DNA template to form a stable RNA:DNA hybrid. Stable R-loops form when the RNA is purine-rich, and are further stabilized by DNA secondary structures on the non-template strand. Interestingly, many expandable and disease-causing repeat sequences form stable R-loops, and R-loops can contribute to repeat instability. Repeat expansions are responsible for multiple neurodegenerative diseases, including Huntington's disease, myotonic dystrophy, and several types of ataxias. Recently, it was found that R-loops at an expanded CAG/CTG repeat tract cause DNA breaks as well as repeat instability (Su and Freudenreich, Proc Natl Acad Sci USA 114, E8392-E8401, 2017). Two factors were identified as causing R-loop-dependent breaks at CAG/CTG tracts: deamination of cytosines and the MutLγ (Mlh1-Mlh3) endonuclease, defining two new mechanisms for how R-loops can generate DNA breaks (Su and Freudenreich, Proc Natl Acad Sci USA 114, E8392-E8401, 2017). Following R-loop-dependent nicking, base excision repair resulted in repeat instability. These results have implications for human repeat expansion diseases and provide a paradigm for how RNA:DNA hybrids can cause genome instability at structure-forming DNA sequences. This perspective summarizes mechanisms of R-loop-induced fragility at G-rich repeats and new links between DNA breaks and repeat instability.

  7. Fast Transverse Instability and Electron Cloud Measurements in Fermilab Recycler

    Energy Technology Data Exchange (ETDEWEB)

    Eldred, Jeffery; Adamson, Philip; Capista, David; Eddy, Nathan; Kourbanis, Ioanis; Morris, Denton; Thangaraj, Jayakar; Yang, Ming-Jen; Zwaska, Robert; Ji, Yichen

    2015-03-01

    A new transverse instability is observed that may limit the proton intensity in the Fermilab Recycler. The instability is fast, leading to a beam-abort loss within two hundred turns. The instability primarily affects the first high-intensity batch from the Fermilab Booster in each Recycler cycle. This paper analyzes the dynamical features of the destabilized beam. The instability excites a horizontal betatron oscillation which couples into the vertical motion and also causes transverse emittance growth. This paper describes the feasibility of electron cloud as the mechanism for this instability and presents the first measurements of the electron cloud in the Fermilab Recycler. Direct measurements of the electron cloud are made using a retarding field analyzer (RFA) newly installed in the Fermilab Recycler. Indirect measurements of the electron cloud are made by propagating a microwave carrier signal through the beampipe and analyzing the phase modulation of the signal. The maximum betatron amplitude growth and the maximum electron cloud signal occur during minimums of the bunch length oscillation.

  8. Parametric Instability of a Leipholz Column Under Periodic Excitation

    Science.gov (United States)

    KANG, B.; TAN, C. A.

    2000-02-01

    In this paper, the parametric instability of a Leipholz column under four boundary conditions is examined. The study of this prototypical model is intended to provide a basic understanding of the disc brake pad instability. The distributed, follower-type axial load is assumed to be uniform and periodic. Instability regions are obtained and the existence of combination resonances of the sum and difference types is discussed for each set of boundary conditions. It is found that the combination resonance of the sum type exists in all the cases of boundary conditions considered, but the difference type exists only in the cases of clamped-simply supported and clamped-free boundary conditions. The combination resonance is shown to be as important as the simple parametric resonance. Results, when compared to a column under a periodic end load, show that the instability characteristics of these two columns are considerably different. The effect of a constant axial load is to shift the instability regions along the frequency axis.

  9. Faraday instability in a near-critical fluid under weightlessness.

    Science.gov (United States)

    Gandikota, G; Chatain, D; Amiroudine, S; Lyubimova, T; Beysens, D

    2014-01-01

    Experiments on near-critical hydrogen have been conducted under magnetic compensation of gravity to investigate the Faraday instability that arises at the liquid-vapor interface under zero-gravity conditions. We investigated such instability in the absence of stabilizing gravity. Under such conditions, vibration orients the interface and can destabilize it. The experiments confirm the existence of Faraday waves and demonstrate a transition from a square to a line pattern close to the critical point. They also show a transition very close to the critical point from Faraday to periodic layering of the vapor-liquid interface perpendicular to vibration. It was seen that the Faraday wave instability is favored when the liquid-vapor density difference is large enough (fluid far from the critical point), whereas periodic layering predominates for small difference in the liquid and vapor densities (close to the critical point). It was observed for the Faraday wave instability that the wavelength of the instability decreases as one approaches the critical point. The experimental results demonstrate good agreement to the dispersion relation for zero gravity except for temperatures very close to the critical point where a transition from a square pattern to a line pattern is detected, similarly to what is observed under 1g conditions.

  10. Two modes of microsatellite instability in human cancer: differential connection of defective DNA mismatch repair to dinucleotide repeat instability

    Science.gov (United States)

    Oda, Shinya; Maehara, Yoshihiko; Ikeda, Yoichi; Oki, Eiji; Egashira, Akinori; Okamura, Yoshikazu; Takahashi, Ikuo; Kakeji, Yoshihiro; Sumiyoshi, Yasushi; Miyashita, Kaname; Yamada, Yu; Zhao, Yan; Hattori, Hiroyoshi; Taguchi, Ken-ichi; Ikeuchi, Tatsuro; Tsuzuki, Teruhisa; Sekiguchi, Mutsuo; Karran, Peter; Yoshida, Mitsuaki A.

    2005-01-01

    Microsatellite instability (MSI) is associated with defective DNA mismatch repair in various human malignancies. Using a unique fluorescent technique, we have observed two distinct modes of dinucleotide microsatellite alterations in human colorectal cancer. Type A alterations are defined as length changes of ≤6 bp. Type B changes are more drastic and involve modifications of ≥8 bp. We show here that defective mismatch repair is necessary and sufficient for Type A changes. These changes were observed in cell lines and in tumours from mismatch repair gene-knockout mice. No Type B instability was seen in these cells or tumours. In a panel of human colorectal tumours, both Type A MSI and Type B instability were observed. Both types of MSI were associated with hMSH2 or hMLH1 mismatch repair gene alterations. Intriguingly, p53 mutations, which are generally regarded as uncommon in human tumours of the MSI+ phenotype, were frequently associated with Type A instability, whereas none was found in tumours with Type B instability, reflecting the prevailing viewpoint. Inspection of published data reveals that the microsatellite instability that has been observed in various malignancies, including those associated with Hereditary Non-Polyposis Colorectal Cancer (HNPCC), is predominantly Type B. Our findings indicate that Type B instability is not a simple reflection of a repair defect. We suggest that there are at least two qualitatively distinct modes of dinucleotide MSI in human colorectal cancer, and that different molecular mechanisms may underlie these modes of MSI. The relationship between MSI and defective mismatch repair may be more complex than hitherto suspected. PMID:15778432

  11. Mitigation of the Hose Instability in Plasma-Wakefield Accelerators.

    Science.gov (United States)

    Mehrling, T J; Fonseca, R A; Martinez de la Ossa, A; Vieira, J

    2017-04-28

    Current models predict the hose instability to crucially limit the applicability of plasma-wakefield accelerators. By developing an analytical model which incorporates the evolution of the hose instability over long propagation distances, this work demonstrates that the inherent drive-beam energy loss, along with an initial beam-energy spread, detunes the betatron oscillations of beam electrons and thereby mitigates the instability. It is also shown that tapered plasma profiles can strongly reduce initial hosing seeds. Hence, we demonstrate that the propagation of a drive beam can be stabilized over long propagation distances, paving the way for the acceleration of high-quality electron beams in plasma-wakefield accelerators. We find excellent agreement between our models and particle-in-cell simulations.

  12. Harmonic Instability Source Identification in Large Wind Farms

    DEFF Research Database (Denmark)

    Ebrahimzadeh, Esmaeil; Blaabjerg, Frede; Wang, Xiongfei

    2017-01-01

    A large-scale power electronics based power system like a wind farm introduces the passive and active impedances. The interactions between the active and passive impedances can lead to harmonic-frequency oscillations above the fundamental frequency, which can be called harmonic instability....... This paper presents an approach to identify which wind turbine and which bus has more contribution to the harmonic instability problems. In the approach, a wind farm is modeled as a Multi-Input Multi-Output (MIMO) dynamic system. The poles of the MIMO transfer matrix are used to predict the system...... instability and the eigenvalues sensitivity analysis in respect to the elements of the MIMO matrix locates the most influencing buses of the wind farm. Time-domain simulations in PSCAD software environment for a 400-MW wind farm validate that the presented approach is an effective tool to determine the main...

  13. Active control of magneto-hydrodynamic instabilities in hot plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Igochine, Valentin (ed.) [Max-Planck-Institut fuer Plasmaphysik, Garching (Germany)

    2015-04-01

    Written and edited by leading plasma physics researchers. Provides a toolkit for scientists and engineers aiming to optimize plasma performance. Comprehensive treatment of different plasma instabilities. During the past century, world-wide energy consumption has risen dramatically, which leads to a quest for new energy sources. Fusion of hydrogen atoms in hot plasmas is an attractive approach to solve the energy problem, with abundant fuel, inherent safety and no long-lived radioactivity. However, one of the limits on plasma performance is due to the various classes of magneto-hydrodynamic instabilities that may occur. The physics and control of these instabilities in modern magnetic confinement fusion devices is the subject of this book. Written by foremost experts, the contributions will provide valuable reference and up-to-date research reviews for ''old hands'' and newcomers alike.

  14. Neutrino signature of supernova hydrodynamical instabilities in three dimensions.

    Science.gov (United States)

    Tamborra, Irene; Hanke, Florian; Müller, Bernhard; Janka, Hans-Thomas; Raffelt, Georg

    2013-09-20

    The first full-scale three-dimensional core-collapse supernova (SN) simulations with sophisticated neutrino transport show pronounced effects of the standing accretion shock instability (SASI) for two high-mass progenitors (20 and 27 M([Symbol: see text])). In a low-mass progenitor (11.2 M([Symbol: see text])), large-scale convection is the dominant nonradial hydrodynamic instability in the postshock accretion layer. The SASI-associated modulation of the neutrino signal (80 Hz in our two examples) will be clearly detectable in IceCube or the future Hyper-Kamiokande detector, depending on progenitor properties, distance, and observer location relative to the main SASI sloshing direction. The neutrino signal from the next galactic SN can, therefore, diagnose the nature of the hydrodynamic instability.

  15. Solutal Marangoni instability in layered two-phase flows

    CERN Document Server

    Picardo, Jason R; Pushpavanam, S

    2015-01-01

    In this paper, the instability of layered two-phase flows caused by the presence of a soluble surfactant (or a surface active solute) is studied. The fluids have different viscosities, but are density matched to focus on Marangoni effects. The fluids flow between two flat plates, which are maintained at different solute concentrations. This establishes a constant flux of solute from one fluid to the other in the base state. A linear stability analysis is performed, using a combination of asymptotic and numerical methods. In the creeping flow regime, Marangoni stresses destabilize the flow, provided a concentration gradient is maintained across the fluids. One long wave and two short wave Marangoni instability modes arise, in different regions of parameter space. A well-defined condition for the long wave instability is determined in terms of the viscosity and thickness ratios of the fluids, and the direction of mass transfer. Energy budget calculations show that the Marangoni stresses that drive long and shor...

  16. Curvature instability of chiral colloidal membranes on crystallization.

    Science.gov (United States)

    Saikia, Lachit; Sarkar, Tanmoy; Thomas, Meera; Raghunathan, V A; Sain, Anirban; Sharma, Prerna

    2017-10-27

    Buckling and wrinkling instabilities are failure modes of elastic sheets that are avoided in the traditional material design. Recently, a new paradigm has appeared where these instabilities are instead being utilized for high-performance applications. Multiple approaches such as heterogeneous gelation, capillary stresses, and confinement have been used to shape thin macroscopic elastic sheets. However, it remains a challenge to shape two-dimensional self-assembled monolayers at colloidal or molecular length scales. Here, we show the existence of a curvature instability that arises during the crystallization of finite-sized monolayer membranes of chiral colloidal rods. While the bulk of the membrane crystallizes, its edge remains fluid like and exhibits chiral ordering. The resulting internal stresses cause the flat membrane to buckle macroscopically and wrinkle locally. Our results demonstrate an alternate pathway based on intrinsic stresses instead of the usual external ones to assemble non-Euclidean sheets at the colloidal length scale.

  17. Landau Damping of Beam Instabilities by Electron Lenses

    Energy Technology Data Exchange (ETDEWEB)

    Shiltsev, V. [Fermilab; Alexahin, Yuri; Burov, A. [Fermilab; Valishev, A. [Fermilab

    2017-06-26

    Modern and future particle accelerators employ increasingly higher intensity and brighter beams of charged particles and become operationally limited by coherent beam instabilities. Usual methods to control the instabilities, such as octupole magnets, beam feedback dampers and use of chromatic effects, become less effective and insufficient. We show that, in contrast, Lorentz forces of a low-energy, a magnetically stabilized electron beam, or "electron lens", easily introduces transverse nonlinear focusing sufficient for Landau damping of transverse beam instabilities in accelerators. It is also important that, unlike other nonlinear elements, the electron lens provides the frequency spread mainly at the beam core, thus allowing much higher frequency spread without lifetime degradation. For the parameters of the Future Circular Collider, a single conventional electron lens a few meters long would provide stabilization superior to tens of thousands of superconducting octupole magnets.

  18. Snake instability of dark solitons in fermionic superfluids

    Science.gov (United States)

    Cetoli, A.; Brand, J.; Scott, R. G.; Dalfovo, F.; Pitaevskii, L. P.

    2013-10-01

    We present numerical calculations of the snake instability in a Fermi superfluid within the Bogoliubov-de Gennes theory of the Bose-Einstein condensate (BEC) to BCS crossover using the random-phase approximation complemented by time-dependent simulations. We examine the snaking behavior across the crossover and quantify the time scale and length scale of the instability. While the dynamics shows extensive snaking before eventually producing vortices and sound on the BEC side of the crossover, the snaking dynamics is preempted by decay into sound due to pair breaking in the deep BCS regime. At the unitarity limit, hydrodynamic arguments allow us to link the rate of snaking to the experimentally observable ratio of inertial to physical mass of the soliton. In this limit we witness an unresolved discrepancy between our numerical estimates for the critical wave number of suppression of the snake instability and recent experimental observations with an ultracold Fermi gas.

  19. Unconventional fermi surface instabilities in the kagome Hubbard model.

    Science.gov (United States)

    Kiesel, Maximilian L; Platt, Christian; Thomale, Ronny

    2013-03-22

    We investigate the competing Fermi surface instabilities in the kagome tight-binding model. Specifically, we consider on-site and short-range Hubbard interactions in the vicinity of van Hove filling of the dispersive kagome bands where the fermiology promotes the joint effect of enlarged density of states and nesting. The sublattice interference mechanism devised by Kiesel and Thomale [Phys. Rev. B 86, 121105 (2012)] allows us to explain the intricate interplay between ferromagnetic fluctuations and other ordering tendencies. On the basis of the functional renormalization group used to obtain an adequate low-energy theory description, we discover finite angular momentum spin and charge density wave order, a twofold degenerate d-wave Pomeranchuk instability, and f-wave superconductivity away from van Hove filling. Together, this makes the kagome Hubbard model the prototypical scenario for several unconventional Fermi surface instabilities.

  20. Modeling and Identification of Harmonic Instability Problems In Wind Farms

    DEFF Research Database (Denmark)

    Ebrahimzadeh, Esmaeil; Blaabjerg, Frede; Wang, Xiongfei

    2016-01-01

    to identify harmonic instability problems in wind farms, where many wind turbines, cables, transformers, capacitor banks, shunt reactors, etc, typically are located. This methodology introduces the wind farm as a Multi-Input Multi-Outpur (MIMO) control system, where the linearized models of fast inner control...... loops of the grid-side converters are considered. Therefore, instability problems of the whole wind farm are predicted based on the poles of the introduced MIMO system. In order to confirm the effectiveness of the proposed analytical approach, time-domain simulations are performed in the PSCAD......In power electronics based power systems like wind farms, the interactions between the inner control systems of the power converters and the passive components may lead to high frequency oscillations, which can be called harmonic instability. In this paper, a simple methodology is presented...

  1. Charge-Induced Saffman-Taylor Instabilities in Toroidal Droplets

    Science.gov (United States)

    Fragkopoulos, A. A.; Aizenman, A.; Fernández-Nieves, A.

    2017-06-01

    We show that charged toroidal droplets can develop fingerlike structures as they expand due to Saffman-Taylor instabilities. While these are commonly observed in quasi-two-dimensional geometries when a fluid displaces another fluid of higher viscosity, we show that the toroidal confinement breaks the symmetry of the problem, effectively making it quasi-two-dimensional and enabling the instability to develop in this three-dimensional situation. We control the expansion speed of the torus with the imposed electric stress and show that fingers are observed provided the characteristic time scale associated with this instability is smaller than the characteristic time scale associated with Rayleigh-Plateau break-up. We confirm our interpretation of the results by showing that the number of fingers is consistent with expectations from linear stability analysis in radial Hele-Shaw cells.

  2. Fast Vertical Beam Instability in the CTF3 Combiner Ring

    CERN Document Server

    Corsini, R; Biscari, C; Ghigo, A; Schulte, D; Skowronski, P K; Tecker, F

    2008-01-01

    The CLIC Test Facility CTF3 is being built at CERN by an international collaboration, in order to demonstrate the main feasibility issues of the CLIC two-beam technology by 2010. The facility includes an 84 m combiner ring, which was installed and put into operation in 2007. High-current operation has shown a vertical beam break-up instability, leading to high beam losses over the four turns required for nominal operation of the CTF3 ring. Such instability is most likely due to the vertically polarized transverse mode in the RF deflectors used for beam injection and combination. In this paper we report the experimental data and compare them with simulations. Possible methods to eliminate the instability are also outlined.

  3. Experiments on the Richtmyer-Meshkov Instability of Incompressible Fluids

    Science.gov (United States)

    Jacobs, J.; Niederhaus, C.

    2000-01-01

    Richtmyer-Meshkov (R-M) instability occurs when two different density fluids are impulsively accelerated in the direction normal to their nearly planar interface. The instability causes small perturbations on the interface to grow and possibly become turbulent given the proper initial conditions. R-M instability is similar to the Rayleigh-Taylor (R-T) instability, which is generated when the two fluids undergo a constant acceleration. R-M instability is a fundamental fluid instability that is important to fields ranging from astrophysics to high-speed combustion. For example, R-M instability is currently the limiting factor in achieving a net positive yield with inertial confinement fusion. The experiments described here utilize a novel technique that circumvents many of the experimental difficulties previously limiting the study of the R-M instability. A Plexiglas tank contains two unequal density liquids and is gently oscillated horizontally to produce a controlled initial fluid interface shape. The tank is mounted to a sled on a high speed, low friction linear rail system, constraining the main motion to the vertical direction. The sled is released from an initial height and falls vertically until it bounces off of a movable spring, imparting an impulsive acceleration in the upward direction. As the sled travels up and down the rails, the spring retracts out of the way, allowing the instability to evolve in free-fall until impacting a shock absorber at the end of the rails. The impulsive acceleration provided to the system is measured by a piezoelectric accelerometer mounted on the tank, and a capacitive accelerometer measures the low-level drag of the bearings. Planar Laser-Induced Fluorescence is used for flow visualization, which uses an Argon ion laser to illuminate the flow and a CCD camera, mounted to the sled, to capture images of the interface. This experimental study investigates the instability of an interface between incompressible, miscible liquids

  4. On spatial instability of a swirling jet - Theory and experiment

    Science.gov (United States)

    Wu, C.; Farokhi, S.; Taghavi, R.

    1991-01-01

    The spatial instability of a swirling jet is investigated both experimentally and theoretically. A hydrodynamic stability analysis is applied to an inviscid incompressible top-hat jet, with a swirl distribution of solid-body rotation and free vortex in and outside the vortex core, respectively. Both plane and helical instability modes are examined. It is found that the top-hat jet with swirl distribution of Rankine vortex type is unstable in all the modes studied. The higher the positive helicity, the less spatially unstable the jet behavior; the higher the negative helicity, the more spatially unstable this behavior becomes. A comparison is made between theoretical results and experimental data on a low-intensity swirling jet. The trend of the initial growth of the instability waves in the near field is captured.

  5. Numerical Analysis for Dynamic Instability of Electrodynamic Maglev Systems

    Directory of Open Access Journals (Sweden)

    Y. Cai

    1995-01-01

    Full Text Available Suspension instabilities in an electrodynamic maglev system with three- and five-degrees-of-freedom DOF vehicles traveling on a double L-shaped set of guideway conductors were investigated with various experimentally measured magnetic force data incorporated into theoretical models. Divergence and flutter were obtained from both analytical and numerical solutions for coupled vibration of the three-DOF maglev vehicle model. Instabilities of five direction motion (heave, slip, roll, pitch, and yaw were observed for the five-DOF vehicle model. The results demonstrate that system parameters such as system damping, vehicle geometry, and coupling effects among five different motions play very important roles in the occurrence of dynamic instabilities of maglev vehicles.

  6. SPOP mutation leads to genomic instability in prostate cancer

    Science.gov (United States)

    Boysen, Gunther; Barbieri, Christopher E; Prandi, Davide; Blattner, Mirjam; Chae, Sung-Suk; Dahija, Arun; Nataraj, Srilakshmi; Huang, Dennis; Marotz, Clarisse; Xu, Limei; Huang, Julie; Lecca, Paola; Chhangawala, Sagar; Liu, Deli; Zhou, Pengbo; Sboner, Andrea; de Bono, Johann S

    2015-01-01

    Genomic instability is a fundamental feature of human cancer often resulting from impaired genome maintenance. In prostate cancer, structural genomic rearrangements are a common mechanism driving tumorigenesis. However, somatic alterations predisposing to chromosomal rearrangements in prostate cancer remain largely undefined. Here, we show that SPOP, the most commonly mutated gene in primary prostate cancer modulates DNA double strand break (DSB) repair, and that SPOP mutation is associated with genomic instability. In vivo, SPOP mutation results in a transcriptional response consistent with BRCA1 inactivation resulting in impaired homology-directed repair (HDR) of DSB. Furthermore, we found that SPOP mutation sensitizes to DNA damaging therapeutic agents such as PARP inhibitors. These results implicate SPOP as a novel participant in DSB repair, suggest that SPOP mutation drives prostate tumorigenesis in part through genomic instability, and indicate that mutant SPOP may increase response to DNA-damaging therapeutics. DOI: http://dx.doi.org/10.7554/eLife.09207.001 PMID:26374986

  7. E-P instability in the NSNS accumulator ring

    Energy Technology Data Exchange (ETDEWEB)

    Ruggiero, A.G.; Blaskiewicz, M.

    1997-08-01

    It has been speculated that the intensity limitation observed in the Los Alamos Proton Storage Ring (PSR) is caused by a coherent instability induced by the presence of pockets of electrons generated by scattering with the molecules of the vacuum residual gas. A theoretical explanation of the e-p instability of course does exist, and is similar to the one developed for the ion-induced instability in electron storage rings. Considering the large beam power (3 MW) involved in the NSNS Accumulator Ring, and the consequences caused by even a small amount of beam loss, we need to carefully assess the effects of electrons that may be generated in the vacuum chamber.

  8. The SOL width and the MHD interchange instability in tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Kerner, W. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Pogutse, O. [Kurchatov institute, Moscow (Russian Federation)

    1994-07-01

    Instabilities in the SOL plasma can strongly influence the SOL plasma behaviour and in particular the SOL width. The SOL stability analysis shows that there exists a critical ratio of the thermal energy and the magnetic energy. If the SOL beta is greater than this critical value, the magnetic field cannot prevent the plasma displacement and a strong MHD instability in the SOL occurs. In the opposite case only slower resistive instabilities can develop. A theoretical investigation of the SOL plasma stability is presented for JET single-null and double-null divertor configurations. The dependence of the stability threshold on the SOL beta and on the sheath resistance is established. Applying a simple mixing length argument gives the scaling of the SOL width. 5 refs., 2 figs.

  9. Rayleigh-Taylor instability in soft elastic layers.

    Science.gov (United States)

    Riccobelli, D; Ciarletta, P

    2017-05-13

    This work investigates the morphological stability of a soft body composed of two heavy elastic layers attached to a rigid surface and subjected only to the bulk gravity force. Using theoretical and computational tools, we characterize the selection of different patterns as well as their nonlinear evolution, unveiling the interplay between elastic and geometric effects for their formation. Unlike similar gravity-induced shape transitions in fluids, such as the Rayleigh-Taylor instability, we prove that the nonlinear elastic effects saturate the dynamic instability of the bifurcated solutions, displaying a rich morphological diagram where both digitations and stable wrinkling can emerge. The results of this work provide important guidelines for the design of novel soft systems with tunable shapes, with several applications in engineering sciences.This article is part of the themed issue 'Patterning through instabilities in complex media: theory and applications.' © 2017 The Author(s).

  10. Instabilities in passive dispersion oscillating fiber ring cavities

    Science.gov (United States)

    Copie, François; Conforti, Matteo; Kudlinski, Alexandre; Mussot, Arnaud; Biancalana, Fabio; Trillo, Stefano

    2017-05-01

    We investigate theoretically and experimentally the development of instabilities in passive ring cavities with stepwise longitudinal variation of the dispersion. We derive an extended version of the Lugiato-Lefever equation that permits to model dispersion oscillating cavities and we demonstrate that this equation is valid well beyond the mean field approximation. We review the theory of Turing (modulational) and Faraday (parametric) instability in inhomogeneous fiber cavities. We report the experimental demonstration of the generation of stable Turing and Faraday temporal patterns in the same device, which can be controlled by changing the detuning and/or the input power. Moreover, we experimentally record the round-trip-to-round-trip dynamics of the spectrum, which shows that Turing and Faraday instabilities not only differ by their characteristic frequency but also by their dynamical behavior. Contribution to the Topical Issue: "Theory and Applications of the Lugiato-Lefever Equation", edited by Yanne K. Chembo, Damia Gomila, Mustapha Tlidi, Curtis R. Menyuk.

  11. Suppression of microbunching instability in the linac coherent light source

    Directory of Open Access Journals (Sweden)

    Z. Huang

    2004-07-01

    Full Text Available A microbunching instability driven by longitudinal space charge, coherent synchrotron radiation, and linac wakefields is studied for the linac coherent light source (LCLS accelerator system. Since the uncorrelated (local energy spread of electron beams generated from a photocathode rf gun is very small, the microbunching gain may be large enough to significantly amplify rf-gun generated modulations or even shot-noise fluctuations of the electron beam. The uncorrelated energy spread can be increased by an order of magnitude to provide strong Landau damping against the instability without degrading the free-electron laser performance. We study different damping options in the LCLS and discuss an effective laser heater to minimize the impact of the instability on the quality of the electron beam.

  12. Linear growth of streaming instability in pressure bumps

    Science.gov (United States)

    Auffinger, Jérémy; Laibe, Guillaume

    2018-01-01

    Streaming instability is a powerful mechanism which concentrates dust grains in protoplanetary discs, eventually up to the stage where they collapse gravitationally and form planetesimals. Previous studies inferred that it should be ineffective in viscous discs, too efficient in inviscid discs and may not operate in local pressure maxima where solids accumulate. From a linear analysis of stability, we show that streaming instability behaves differently inside local pressure maxima. Under the action of the strong differential advection imposed by the bump, a novel unstable mode develops and grows even when gas viscosity is large. Hence, pressure bumps are found to be the only places where streaming instability occurs in viscous discs. This offers a promising way to conciliate models of planet formation with recent observations of young discs.

  13. [Cervical spine instability: point of view of the anesthesiologist].

    Science.gov (United States)

    Poveda Jaramillo, R; Paredes Sanín, P; Carvajal, H; Carrasquilla, R; Murillo Deluquez, M

    2014-01-01

    The experience in airway management permits the anesthesiologist to participate in cases of cervical spine instability in the operating room when the patient is subjected to surgical procedures, or in cases of difficulty to access or keep the airway open in emergencies. This article reviews the epidemiology, definition, etiology, diagnostic criteria, methods of approach to airway management, and current recommendations on handling cervical instability in different scenarios. There is no approach to the airway that ensures complete immobility of the cervical spine, but there are methods that are better adapted to specific contexts; at the end, the reader will be able to identify the virtues and defects of the various options that the anesthesiologists have to address the airway in cases of cervical instability. Copyright © 2012 Sociedad Española de Anestesiología, Reanimación y Terapéutica del Dolor. Published by Elsevier España. All rights reserved.

  14. f-Mode instability in relativistic neutron stars.

    Science.gov (United States)

    Gaertig, E; Glampedakis, K; Kokkotas, K D; Zink, B

    2011-09-02

    We present the first calculation of the basic properties of the f-mode instability in rapidly rotating relativistic neutron stars, adopting the Cowling approximation. By accounting for dissipation in neutron star matter, i.e., shear or bulk viscosity and superfluid mutual friction, we calculate the associated instability window. For our specific stellar model, a relativistic polytrope, we obtain a minimum gravitational growth time scale (for the dominant ℓ=m=4 mode) of the order of 10(3)-10(4)  s near the Kepler frequency Ω(K) while the instability is active above ∼0.92  Ω(K) and for temperatures ∼(10(9)-2×10(10))  K, characteristic of newborn neutron stars.

  15. Control authority over a combustion instability investigated in CFD

    Directory of Open Access Journals (Sweden)

    Roel AJ Müller

    2016-03-01

    Full Text Available Control authority is investigated for active damping of a combustion instability by modulation of the fuel flow. Two combustors, operating as quarter-wave thermo-acoustic oscillators, are modelled in ANSYS CFX. In experiments, active damping was applied successfully on one of these, but was not effective on the other. Active instability control is implemented in the model analogous to experiment. The goal of this research is to explain why the same implementation of active instability control, using the same controller, would be effective on one combustor geometry, but not on the other. Turbulent combustion is modelled by SAS-SST and the burning velocity model. The distribution of the convective time between fuel injector and flame is evaluated and used to estimate the response of the heat release to modulation of the fuel mass flow. The results can be used to predict the feasibility of this kind of active control.

  16. International Conference on Instability and Control of Massively Separated Flows

    CERN Document Server

    Soria, Julio

    2015-01-01

    This book contains the outcome of the international meeting on instability, control and noise generated by massive flow separation that was organized at the Monash Center, in Prato, Italy, September 4-6, 2013. The meeting served as the final review of the EU-FP7 Instability and Control of Massively Separated Flows Marie Curie travel grant and was supported by the European Office of Aerospace Research and Development. Fifty leading specialists from twelve countries reviewed the progress made since the 50s of the last century and discussed modern analysis techniques, advanced experimental flow diagnostics, and recent developments in active flow control techniques from the incompressible to the hypersonic regime. Applications involving massive flow separation and associated instability and noise generation mechanisms of interest to the aeronautical, naval and automotive industries have been addressed from a theoretical, numerical or experimental point of view, making this book a unique source containing the stat...

  17. Nontraumatic posterior atlantooccipital dislocation associated with atlantoaxial instability.

    Science.gov (United States)

    Wu, Tian-Long; Jia, Jing-Yu; Chen, Wei-Cai; He, Ding-Wen; Cheng, Xi-Gao

    2015-05-01

    Nontraumatic posterior atlantooccipital dislocation has only been rarely reported. In the current study, the authors reported an extremely rare case of nontraumatic posterior atlantooccipital dislocation associated with atlantoaxial instability. A 47-year-old female was referred with a history of neck pain for 5 years. The patient had no history of trauma. The axial rotation of range of motion of the cervical spine was severely restricted. Posterior atlantooccipital dislocation with atlantoaxial instability was confirmed through conventional radiography, computed tomography and magnetic resonance imaging. We performed realignment of the dislocation and posterior occipitocervical (C0-C2) fusion. After the surgery, the patient's symptoms improved significantly and she manifested neurological improvement. To our knowledge, this lesion has not been reported previously. Anomalies of upper cervical spine may have induced this instability.

  18. Real world ocean rogue waves explained without the modulational instability

    Science.gov (United States)

    Fedele, Francesco; Brennan, Joseph; Ponce de León, Sonia; Dudley, John; Dias, Frédéric

    2016-01-01

    Since the 1990s, the modulational instability has commonly been used to explain the occurrence of rogue waves that appear from nowhere in the open ocean. However, the importance of this instability in the context of ocean waves is not well established. This mechanism has been successfully studied in laboratory experiments and in mathematical studies, but there is no consensus on what actually takes place in the ocean. In this work, we question the oceanic relevance of this paradigm. In particular, we analyze several sets of field data in various European locations with various tools, and find that the main generation mechanism for rogue waves is the constructive interference of elementary waves enhanced by second-order bound nonlinearities and not the modulational instability. This implies that rogue waves are likely to be rare occurrences of weakly nonlinear random seas. PMID:27323897

  19. Effect of bone loss in anterior shoulder instability

    Science.gov (United States)

    Garcia, Grant H; Liu, Joseph N; Dines, David M; Dines, Joshua S

    2015-01-01

    Anterior shoulder instability with bone loss can be a difficult problem to treat. It usually involves a component of either glenoid deficiency or a Hill-Sachs lesion. Recent data shows that soft tissue procedures alone are typically not adequate to provide stability to the shoulder. As such, numerous surgical procedures have been described to directly address these bony deficits. For glenoid defects, coracoid transfer and iliac crest bone block procedures are popular and effective. For humeral head defects, both remplissage and osteochondral allografts have decreased the rates of recurrent instability. Our review provides an overview of current literature addressing these treatment options and others for addressing bone loss complicating anterior glenohumeral instability. PMID:26085984

  20. Affective instability in borderline personality disorder: experience sampling findings.

    Science.gov (United States)

    Nica, Elena Irina; Links, Paul S

    2009-02-01

    Affective instability, defined as repeated, rapid, and abrupt shifts in mood, is considered the core pathology in borderline personality disorder. The temporal pattern of affective instability can be best captured with the experience sampling method-longitudinal assessment of people's affective states as they occur in real time and in their natural environment. A review of the experience sampling studies published to date for borderline personality disorder suggests the following mood variability pattern: intense negative mood, more frequent and abrupt mood changes than healthy controls and patients with major depression, and partial triggering of affect by external events. The method also has great potential to investigate the links between affective instability and other psychological and behavioral correlates of the disorder, such as suicide, lack of self-esteem, and erratic behaviors. However, the method requires systematic study to determine best data collection designs and mathematical models of mood variability.

  1. Family Instability and Pathways to Adulthood in Urban South Africa

    Science.gov (United States)

    Goldberg, Rachel E.

    2014-01-01

    Social, political, epidemiological, and economic forces have produced family instability during childhood for many young people transitioning to adulthood in South Africa. This study identifies pathways to adulthood for youth in Cape Town that capture the timing and sequencing of role transitions across the life domains of school, work, and family formation. It then uses these pathways to investigate the relationship between childhood family instability and the way young people’s lives unfold during the transition to adulthood. Results indicate that changes in co-residence with parents are associated with following less advantageous pathways into adulthood, independent of particular family structure or orphan status. Overall, the findings suggest that family instability influences not only single transitions for youth, but also combinations of transitions. They also indicate the value of a multi-dimensional conceptualization of the transition to adulthood in empirical work. PMID:25067862

  2. Triadic instability of a non-resonant precessing fluid cylinder

    CERN Document Server

    Lagrange, R; Eloy, C

    2015-01-01

    Flows forced by a precessional motion can exhibit instabilities of crucial importance, whether they concern the fuel of a flying object or the liquid core of a telluric planet. So far, stability analyses of these flows have focused on the special case of a resonant forcing. Here, we address the instability of the flow inside a precessing cylinder in the general case. We first show that the base flow forced by the cylinder precession is a superposition of a vertical or horizontal shear flow and an infinite sum of forced modes. We then perform a linear stability analysis of this base flow by considering its triadic resonance with two free Kelvin modes. Finally, we derive the amplitude equations of the free Kelvin modes and obtain an expression of the instability threshold and growth rate.

  3. Single Bunch Longitudinal Instability in the CERN SPS

    CERN Document Server

    Lasheen, Alexandre; Hancock, Steven; Radvilas, Edgaras; Roggen, Toon; Shaposhnikova, Elena

    2016-01-01

    The longitudinal single bunch instability observed in the SPS leads to uncontrolled emittance blow-up and limits the quality of high intensity beams required for the High Luminosity LHC and AWAKE projects at CERN. The present SPS impedance model developed from a thorough survey of machine elements was used in macro-particle simulations (with the code BLonD) of the bunch behavior through the acceleration cycle. Comparison of simulations with measurements of the synchrotron frequency shift, performed on the SPS flat bottom to probe the impedance, show a reasonable agreement. During extensive experimental studies various beam and machine parameters (bunch intensity, longitudinal emittance, RF voltage, with single and double RF systems) were scanned in order to further benchmark the SPS impedance model with measurements and to better understand the mechanism behind the instability. It was found that the dependence of instability threshold on longitudinal emittance and beam energy has an unexpected non-monotonic b...

  4. Internal gravity waves: parametric instability and deep ocean mixing

    Science.gov (United States)

    Staquet, Chantal

    2007-09-01

    The Boussinesq approximation provides a convenient framework to describe the dynamics of stably-stratified fluids. A fundamental motion in these fluids consists of internal gravity waves, whatever the strength of the stratification. These waves may be unstable through parametric instability, which results in turbulence and mixing. After a brief review of the main properties of internal gravity waves, we show how the parametric instability of a monochromatic internal gravity wave organizes itself in space and time, using energetics arguments and a simple kinematic model. We provide an example, in the deep ocean, where such instability is likely to occur, as estimates of mixing from in situ measurements suggest. We eventually discuss the fundamental role of internal gravity wave mixing in the maintenance of the abyssal thermal stratification. To cite this article: C. Staquet, C. R. Mecanique 335 (2007).

  5. Instability of (CTGn•(CAGn trinucleotide repeats and DNA synthesis

    Directory of Open Access Journals (Sweden)

    Liu Guoqi

    2012-02-01

    Full Text Available Abstract Expansion of (CTGn•(CAGn trinucleotide repeat (TNR microsatellite sequences is the cause of more than a dozen human neurodegenerative diseases. (CTGn and (CAGn repeats form imperfectly base paired hairpins that tend to expand in vivo in a length-dependent manner. Yeast, mouse and human models confirm that (CTGn•(CAGn instability increases with repeat number, and implicate both DNA replication and DNA damage response mechanisms in (CTGn•(CAGn TNR expansion and contraction. Mutation and knockdown models that abrogate the expression of individual genes might also mask more subtle, cumulative effects of multiple additional pathways on (CTGn•(CAGn instability in whole animals. The identification of second site genetic modifiers may help to explain the variability of (CTGn•(CAGn TNR instability patterns between tissues and individuals, and offer opportunities for prognosis and treatment.

  6. Acquired atlantoaxial instability in children with spastic cerebral palsy.

    Science.gov (United States)

    Tsirikos, Athanasios I; Chang, Wei-Ning; Shah, Suken A; Miller, Freeman

    2003-01-01

    The development of nontraumatic atlantoaxial instability in children with spastic cerebral palsy has not been reported. The authors present three patients with severe spastic quadriplegia who developed C1-C2 instability and cervical myelopathy at mean age 12.6 years. These patients demonstrated a similar clinical picture with symptoms attributed to cervical myelopathy in varied severity including apneic episodes, opisthotonus, alteration in muscle tone, torticollis, respiratory problems, hyperreflexia, and bradycardia. Patient 1 was scheduled for surgery but died due to an apneic episode. Patient 2 refused surgery and has been followed for 3 years while his neurologic condition remains unchanged. Patient 3 underwent occipitocervical decompression and fusion, recovered neurologically, and resumed his previous functional skills. Patients demonstrating considerable functional deterioration or insidious change in their established neurologic status should undergo detailed screening to rule out developing upper cervical instability. Early surgical intervention consisting of spinal decompression and fusion may prevent the development of myelopathy.

  7. Pathways and Mechanisms that Prevent Genome Instability in Saccharomyces cerevisiae

    Science.gov (United States)

    Putnam, Christopher D.; Kolodner, Richard D.

    2017-01-01

    Genome rearrangements result in mutations that underlie many human diseases, and ongoing genome instability likely contributes to the development of many cancers. The tools for studying genome instability in mammalian cells are limited, whereas model organisms such as Saccharomyces cerevisiae are more amenable to these studies. Here, we discuss the many genetic assays developed to measure the rate of occurrence of Gross Chromosomal Rearrangements (called GCRs) in S. cerevisiae. These genetic assays have been used to identify many types of GCRs, including translocations, interstitial deletions, and broken chromosomes healed by de novo telomere addition, and have identified genes that act in the suppression and formation of GCRs. Insights from these studies have contributed to the understanding of pathways and mechanisms that suppress genome instability and how these pathways cooperate with each other. Integrated models for the formation and suppression of GCRs are discussed. PMID:28684602

  8. Sedimentation and gravitational instability of Escherichia coli Suspension

    Science.gov (United States)

    Salin, Dominique; Douarche, Carine

    2017-11-01

    The successive runs and tumbles of Escherichia coli bacteria provide an active matter suspension of rod-like particles with a large swimming, Brownian like, diffusion. As opposed to inactive elongated particles, this diffusion prevents clustering of the particles and hence instability in the gravity field. We measure the time dependent E . coli concentration profile during their sedimentation. After some hours, due to the dioxygen consumption, a motile / non-motile front forms leading to a Rayleigh-Taylor type gravitational instability. Analysing both sedimentation and instability in the framework of active particle suspensions, we can measure the relevant bacteria hydrodynamic characteristics such as its single particle sedimentation velocity and its hindrance volume. Comparing these quantities to the ones of equivalent passive particles (ellipsoid, rod) we tentatively infer the effective shape and size of the bacteria involved in its buoyancy induced advection and diffusion. Laboratoire FAST University Paris Saclay France.

  9. The plasmoid instability during asymmetric inflow magnetic reconnection

    CERN Document Server

    Murphy, Nicholas A; Shen, Chengcai; Lin, Jun; Ni, Lei

    2013-01-01

    Theoretical studies of the plasmoid instability generally assume that the reconnecting magnetic fields are symmetric. We relax this assumption by performing two-dimensional resistive magnetohydrodynamic simulations of the plasmoid instability during asymmetric inflow magnetic reconnection. Magnetic asymmetry modifies the onset, scaling, and dynamics of this instability. Magnetic islands develop preferentially into the weak magnetic field upstream region. Outflow jets from individual X-points impact plasmoids obliquely rather than directly as in the symmetric case. Consequently, deposition of momentum by the outflow jets into the plasmoids is less efficient, the plasmoids develop net vorticity, and shear flow slows down secondary merging between islands. Secondary merging events have asymmetry along both the inflow and outflow directions. Downstream plasma is more turbulent in cases with magnetic asymmetry because islands are able to roll around each other after exiting the current sheet. As in the symmetric c...

  10. Azimuthal magnetorotational instabilities to non-axisymmetric perturbations

    Science.gov (United States)

    Fukumoto, Yasuhide; Zou, Rong

    2014-11-01

    Short-wavelength stability analysis is made of axisymmetric rotating flows of a perfectly conducting fluid subjected to external azimuthal magnetic field, to non-axisymmetric as well as axisymmetric perturbations. The instability caused by the azimuthal magnetic field is referred to as the azimuthal magnetorotational instability (AMRI). We determine the range of unstable angular-velocity distribution and the overall maximum growth rate for the AMRI. Non-axisymmetric perturbations, when coupled to azimuthal magnetic field, widen the instability range of angular-velocity profiles of rotating flows. For strong external field, the maximum growth rate increases, beyond the Oort A-value, without bound in proportion to the strength of the external field. The effect of the electric resistivity is also considered in the limit of very low magnetic Prandtl number. Y.F. was supported in part by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (Grant No. 24540407).

  11. Microsatellite instability in cancer of the proximal colon

    Energy Technology Data Exchange (ETDEWEB)

    Thibodeau, S.N.; Bren, G.; Schaid, D. (Mayo Clinic and Foundation, Rochester, MN (United States))

    1993-05-07

    Colorectal tumor DNA was examined for somatic instability at (CA)[sub n] repeats on human chromosomes 5q, 15q, 17p, and 18q. Differences between tumor and normal DNA were detected in 25 of the 90 (28 percent) tumors examined. This instability appeared as either a substantial change in repeat length (often heterogeneous in nature) or a minor change (typically two base pairs). Microsatellite instability was significantly correlated with the tumor's location in the proximal colon (P = 0.003), with increased patient survival (P = 0.02), and, inversely, with loss of heterozygosity for chromosomes 5q, 17p, and 18q. These data suggest that some colorectal cancers may arise through a mechanism that does not necessarily involve loss of heterozygosity. 23 refs., 2 figs., 3 tabs.

  12. Performance of PROMIS Instruments in Patients With Shoulder Instability.

    Science.gov (United States)

    Anthony, Chris A; Glass, Natalie A; Hancock, Kyle; Bollier, Matt; Wolf, Brian R; Hettrich, Carolyn M

    2017-02-01

    Shoulder instability is a relatively common condition occurring in 2% of the population. PROMIS (Patient-Reported Outcome Measurement Information System) was developed by the National Institutes of Health in an effort to advance patient-reported outcome (PRO) instruments by developing question banks for major health domains. To compare PROMIS instruments to current PRO instruments in patients who would be undergoing operative intervention for recurrent shoulder instability. Cohort study (diagnosis); Level of evidence, 2. A total of 74 patients with a primary diagnosis of shoulder instability who would be undergoing surgery were asked to fill out the American Shoulder and Elbow Surgeons shoulder assessment form (ASES), Marx shoulder activity scale (Marx), Short Form-36 Health Survey Physical Function subscale (SF-36 PF), Western Ontario Shoulder Instability Index (WOSI), PROMIS physical function computer adaptive test (PF CAT), and PROMIS upper extremity item bank (UE). Correlation between PRO instruments was defined as excellent (>0.7), excellent-good (0.61-0.7), good (0.4-0.6), and poor (0.2-0.3). Utilization of the PROMIS UE demonstrated excellent correlation with the SF-36 PF ( r = 0.78, P shoulder and upper extremity PRO instruments as well as the SF-36 PF in patients with shoulder instability. In patients aged ≤21 years, there were significant ceiling effects utilizing the PROMIS UE. While the PROMIS PF CAT appears appropriate for use in adults of any age, our findings demonstrate that the PROMIS UE has significant ceiling effects in patients with shoulder instability who are ≤21 years old, and we do not recommend use of the PROMIS UE in this population.

  13. Arthroscopic "Remplissage" for shoulder instability: a systematic review.

    Science.gov (United States)

    Rashid, Mustafa S; Crichton, James; Butt, Usman; Akimau, Pavel I; Charalambous, Charalambos P

    2016-02-01

    Large Hill-Sachs lesions engaging the glenoid rim predispose to recurrent anterior instability and failure of isolated labrum repairs. In arthroscopic remplissage, the posterior capsule and infraspinatus are sutured into the humeral defect to limit such engagement. This systematic review assessed the outcomes and complications of arthroscopic remplissage for anterior shoulder instability. A search of the MEDLINE, EMBASE and evidence-based medicine Cochrane databases was conducted. Data were extracted by two reviewers in a standardised manner. Redislocation, instability and complication rates were calculated and expressed as percentages with 95 % confidence intervals. Of 4,284 studies identified, eight articles with a total of 207 patients were analysed. Mean redislocation rate was 4.2 ± 3.9 % (range 0-15 %), and mean recurrent instability rate 3.2 ± 3.8 % (0-15 %). Posterosuperior shoulder pain and stiffness were the only complications described. Overall, there was a mean reduction in external rotation in adduction of 5.6° (-40 to +30), reduction in external rotation in abduction of 11.3° (-50 to +7) and reduction in internal rotation of 0.9 (-4 to 0) vertebral levels. Arthroscopic remplissage alongside anterior labrum repair seems successful in treating recurrent shoulder instability in the presence of large or engaging Hill-Sachs lesion. However, the available literature consists mainly of heterogeneous case series. There is a need for a high-quality randomised trial to compare remplissage with other commonly used techniques for recurrent instability associated with substantial Hill-Sachs defects such as the Latarjet procedure. Systematic review, Level IV.

  14. Plasma blob generation due to cooperative elliptic instability.

    Science.gov (United States)

    Manz, P; Xu, M; Müller, S H; Fedorczak, N; Thakur, S C; Yu, J H; Tynan, G R

    2011-11-04

    Using fast-camera measurements the generation mechanism of plasma blobs is investigated in the linear device CSDX. During the ejection of plasma blobs the plasma is dominated by an m=1 mode, which is a counterrotating vortex pair. These flows are known to be subject to the cooperative elliptic instability, which is characterized by a cooperative disturbance of the vortex cores and results in a three-dimensional breakdown of two-dimensional flows. The first experimental evidence of a cooperative elliptic instability preceding the blob-ejection is provided in terms of the qualitative evolution of the vortex geometries and internal wave patterns.

  15. The dispersion equation of the induced Smith-Purcell instability

    Energy Technology Data Exchange (ETDEWEB)

    Klochkov, Dmitry N [Ap.49, Mesentsev St. 44-2, 300026 Tula (Russian Federation); Artemyev, Alexander I [General Physics Institute RAS, Vavilova 38, 119991 Moscow (Russian Federation); Oganesyan, Koryun B [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia); Rostovtsev, Yuri V; Scully, Marlan O [Department of Physics and Institute for Quantum Studies, Texas A and M University, College Station, TX 77843-4242 (United States); Hu, Chin-Kun, E-mail: bsk@yerphi.a [Institute of Physics, Academia Sinica, Taipei, Taiwan 1152 (China)

    2010-09-01

    The simplest model of a magnetized infinitely thin electron beam is considered. For the grating, where the depth of grooves is a small parameter, the dispersion equation of the induced Smith-Purcell instability was obtained. It was found that the condition of the Thompson or the Raman regimes of excitation does not depend on beam current but depends on the height of the beam above the grating surface. The growth rate of instability in both cases is proportional to the square root of the electron beam current.

  16. Instabilities in a nonlinear model of a passive damper

    Science.gov (United States)

    Tinker, Michael L.; Cutchins, Malcolm A.

    1991-01-01

    During a study of the dynamic characteristics of a wire rope vibration isolation system constructed with helical isolatoars, an interesting instability was observed. In addition to experimental investigation of this system, a semi-empirical model having nonlinear stiffness, nth-power velocity damping, and variable Coulomb-type friction damping was developed. Results obtained using ACSL compare well with experimental data. The primary emphasis of this paper, however, centers on the instabilities and largea-response behavior of this semi-empirical model. Stabilizing effects are discussed.

  17. Instability and Spatiotemporal Dynamics of Alternans in Paced Cardiac Tissue

    Science.gov (United States)

    Echebarria, Blas; Karma, Alain

    2002-05-01

    We derive an equation that governs the spatiotemporal dynamics of small amplitude alternans in paced cardiac tissue. We show that a pattern-forming linear instability leads to the spontaneous formation of stationary or traveling waves whose nodes divide the tissue into regions with opposite phase of oscillation of action potential duration. This instability is important because it creates dynamically a heterogeneous electrical substrate for the formation of conduction blocks and the induction of fibrillation if the tissue size exceeds a fraction of the pattern wavelength. We derive an analytical expression for this wavelength as a function of three basic length scales related to dispersion and intercellular electrical coupling.

  18. Instabilities, motion and deformation of active fluid droplets

    Science.gov (United States)

    Whitfield, Carl A.; Hawkins, Rhoda J.

    2016-12-01

    We consider two minimal models of active fluid droplets that exhibit complex dynamics including steady motion, deformation, rotation and oscillating motion. First we consider a droplet with a concentration of active contractile matter adsorbed to its boundary. We analytically predict activity driven instabilities in the concentration profile, and compare them to the dynamics we find from simulations. Secondly, we consider a droplet of active polar fluid of constant concentration. In this system we predict, motion and deformation of the droplets in certain activity ranges due to instabilities in the polarisation field. Both these systems show spontaneous transitions to motility and deformation which resemble dynamics of the cell cytoskeleton in animal cells.

  19. Jeans instability with exchange effects in quantum dusty magnetoplasmas

    Energy Technology Data Exchange (ETDEWEB)

    Jamil, M., E-mail: jamil.gcu@gmail.com [Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Rasheed, A. [Department of Physics, Government College University, Faisalabad 38000 (Pakistan); Rozina, Ch. [Department of Physics, Lahore College for Women University, Lahore 54000 (Pakistan); Jung, Y.-D. [Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of); Salimullah, M. [Department of Physics, Jahangirnagar University, Savar, Dhaka 1342 (Bangladesh)

    2015-08-15

    Jeans instability is examined in magnetized quantum dusty plasmas using the quantum hydrodynamic model. The quantum effects are considered via exchange-correlation potential, recoil effect, and Fermi degenerate pressure, in addition to thermal effects of plasma species. It is found that the electron exchange and correlation potential have significant effects over the threshold value of wave vector and Jeans instability. The presence of electron exchange and correlation effect shortens the time of dust sound that comparatively stabilizes the self gravitational collapse. The results at quantum scale are helpful in understanding the collapse of the self-gravitating dusty plasma systems.

  20. Filamentation instability of counter-streaming laser-driven plasmas

    CERN Document Server

    Fox, W; Bhattacharjee, A; Chang, P -Y; Germaschewski, K; Hu, S X; Nilson, P M

    2013-01-01

    Filamentation due to the growth of a Weibel-type instability was observed in the interaction of a pair of counter-streaming, ablatively-driven plasma flows, in a supersonic, collisionless regime relevant to astrophysical collisionless shocks. The flows were created by irradiating a pair of opposing plastic (CH) foils with 1.8 kJ, 2-ns laser pulses on the OMEGA EP laser system. Ultrafast laser-driven proton radiography was used to image the Weibel-generated electromagnetic fields. The experimental observations are in good agreement with the analytical theory of the Weibel instability and with particle-in-cell simulations.